Sample Internship Report 1

1

INDUSTRIAL TRAINING

REPORT

SUBMITTED BY:

K N S PAVAN KUMAR

MM11B026

DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING

INDIAN INSTITUTE OF TECHNOLOGY, MADRAS

CHENNAI- 600036

2

ACKNOWLEDGEMENT

It is with deep sense of gratitude I acknowledge this golden opportunity provided to

me by the management of MISHRA DHATU NIGAM LIMITED for the Industrial

Orientation program.

I would personally thank to SRI K. GURULINGAM, Dy. Gen. Manager, Training

and Development for having permitted me to undergo Industrial Training at MIDHANI.

I am very grateful to Prof. Dr. Kamaraj, our Head of the Metallurgical and Materials

engineering department, Indian Institute of technology, Madras, for allowing me to undergo

this training as a part of academic curriculum.

My sincere thanks also go to Prof. Dr. S. Ganesh Sundara Raman, for patiently

guiding in the crediting procedures of the internship to the curriculum in the Jul-Nov, 2014

semester.

I sincerely thank the staff of various departments of MIDHANI who tirelessly

answered all our queries and doubts, whose explanations and comments helped me to

complete this internship program successfully.

3

INDEX

TOPIC PAGE NUMBERS

1. INTRODUCTION................................................................... 2

2. MELT-1....................................................................................6

3. MELT-21..................................................................................5

4. TITANIUM SHOP...................................................................21

5. FORGE SHOP..........................................................................25

6. HEAT TREATMENT SHOP...................................................29

7. MACHINE SHOP....................................................................34

8. HOT ROLLING MILLS..........................................................37

9. COLD ROLLING MILLS.......................................................42

10. INVESTMENT CASTING PLANT......................................48

11. POWDER METALLURGY...................................................51

12. BAR AND WIRE DRAWING...............................................56

13. TUBE SHOP...........................................................................60

14. UTILITIES..............................................................................65

15. QUALITY CONTROL LABORATORY...............................68

4

INTRODUCTION TO MIDHANI

“MISHRA DHATU” is Sanskrit equivalent of English word “ALLOY”. The company

is the brain child of some renowned metallurgists of the country and scientists of adjoining

Defense Metallurgical Research Laboratory (DMRL). Mishra Dhatu Nigam Limited

(MIDHANI) is one of the modern and integrated metallurgical plants for manufacturing a

wide range of special metals and alloys meet critical requirements of strategic industries such

as Space, Nuclear Power, Defence, Aeronautics, Automobile, Electrical,

Telecommunications, Petrochemicals and general engineering industries.

The high technology plant is a government of India‟s enterprise under the Ministry of

Defense. It is a modem and integrated metallurgical plant of its kind for manufacturing a

wide range of special metals and alloys under one roof. MIDHANI was incorporated in

November 1973 with a view to achieve self-reliance in some strategic alloys needed by

critical sectors such as Defense, Aeronautics, Nuclear and Space. After a lengthy debate

about desirability and viability of such plant, “go ahead” for the project was given in

February 1976 and the plant was set up in collaboration with world leaders like Creusot-Lorie

and Pechiney-Ugine-Kuhlamann of France and Krupp-Kloeckner AG of Germany and was

commissioned progressively between 1980 and 1982.

Midhani‟s product range includes super alloys, titanium, molybdenum, special

purpose steels and other special alloys. It is a unique in concept and is probably the only plant

of its kind where integrated facilities are available for the manufacture of such a diverse

range of special metals and alloys in a wide variety of KANCHAN ARMOUR PLATE

PROJECT.

QUALITY CONTROL & LABORATORY forms, such as bars, sheets, strips, rods

and wires. A wide variety of products and testing equipment has been installed to test

numerous types of alloys produced to stringent specification of different customers.

MIDHANI alloys can be broadly grouped as under:

1. Super alloys.

2. High technology special purpose steels.

3. Heat resistance alloys.

4. Powder metallurgy products.

5. Titanium and titanium alloys.

6. Soft magnetic alloys.

7. Control expansion alloys.

Super Alloys:

Super alloys are family of iron, nickel, cobalt base alloys used primarily for high

strength in long term exposure to working temperature of 500-1100oc, corrosive environment

5

are encountered. At Midhani, many of these alloys are melted under controlled conditions in

vacuum induction melting to produce metallurgical cleanness and low gas contents. Now find

extensive application in space, nuclear, chemical and petrochemical, power generation and

furnace industries.

Midhani manufactures:

Nickel based alloys

Iron based alloys

Cobalt based alloys

Hi-tech special purpose steels:

Midhani manufactures special purpose steels through vacuum melting/electro slag

refining. These special steels are characterized by superior metallurgical cleanness, very low

inclusions levels, lower sulphur and phosphorous contents, improved hot workability and

overall improvements in mechanical properties and fatigue life, which are essential for

special applications in aerospace, power generation nuclear, defense, cryogenic and other

general engineering industries. These include precipitation hardening steels, non-magnetic,

austenitic and martensic stainless steels and all Maraging steels.

Midhani Manufactures:

Maraging steels

Precipitation hardening steels

Austenitic stainless steels

Martensitic steels

Non-magnetic steels

Resistance alloys:

These are basically nickel-chromium and nickel-chromium-iron alloys for heating

elements in electrical furnaces in various atmospheres. These alloys find usage in heaters,

dryers and other heating appliances.

Powder Metallurgy Products:

Midhani has exclusive facilities for manufacturing of molybdenum products starting

from powder. Pure molybdenum is used as mandrel, molybdenum wires and sheets for

support filament in lamp industry and electronic x-ray tubes respectively.

6

Titanium and Titanium Alloys:

Midhani manufacture commercially pure Titanium and titanium alloys conforming to

international standards. Titanium has excellent corrosion resistance and high strength-to-

weight ratio. High temperature strength and resist to oxidation fatigue strength, creep

resistance and good workability. Titanium and titanium alloys were developed for aerospace,

jet engine and airframe applications.

Soft Magnetic Alloys:

They are characterized by very high permeability, low energy loss, low residual

induction and low co active. These are basically nickel-iron alloys. Some of the soft magnetic

alloys are used in magnetic shunts for thermal compensation in speedometers and electrical

meters transformers cores.

Controlled Expansion Alloys:

Midhani manufactures a wide range of electrical, electronic and telecommunication

applications. They are soft magnetic alloys, soft iron, high purity nickel and nickel-

manganese alloys.

Manufacturing Facilities:

Midhani has acquired the latest and most modern equipment for the manufacturing of these

alloys and converting them into various mill forms such as ingots, forges bars, hot rolled

sheets and bars, cold rolled sheets, strips and drawn bars.

The unit manufacturing facilities of the plant include:

Vacuum melting:

An impressive array of melting and refining furnaces such as 5 T Air Arc Melting

furnace, 2.2 & 5 T Vacuum Induction Melting & Refining Furnace respectively. 4 T Vacuum

Arc Re-melting & 10 T Electro slag Re-melting Furnace help Midhani in manufacturing

alloys with close composition control. Metallurgical cleanliness and homogeneity is

maintained at its best. The best method of refining is the ingots in Midhani is Electro slag

Refining.

Computerized Forging:

Midhani has a 1500 T capacity computer controlled press operating with two rail

bound manipulators for forging ingots to close tolerances.

7

Hot Rolling:

2-Hi 2 stand and 3-Hi strip mills, 3-Hi 3 stand bar mill and 7 stand wire rod mill

make up the hot rolling facilities along with the heat treatment, leveling and straightening of

sheets and strips.

Precision Cold Rolling:

For cold rolling 4-hi strip mill,6-hi sheet mill,12-hi strip mill and 20-hi foil mill are

available, besides facilities like bell annealing furnaces, finishing lines for slitting and strip

grinding.

Bar and Wire drawing:

The shop is equipped with wire drawing machine, annealing lines, polishing,

straightening and cutting machine etc. draw wires down to 0.02mm diameter.

Integrated Powder Metallurgy:

At Midhani superfine powders of tungsten and molybdenum are compacted in a 600

T press, sintered, swaged and drawn into fine wire.

Titanium facility:

Midhani has vacuum arc re-melting furnace for the production of titanium ingots up

to 6.5T for electrode preparation a 3000 T capacity compacting press and a plasma arc

welding unit is available. High vacuum furnace is available for annealing, and a vacuum arc

skull melting furnace for titanium castings is also available.

Quality Assurance and Process Control:

The quality control is the heart of Midhani. In quality control the quality of initial

and final products as well as stage products analysis and job work analysis are also

determined.

Midhani gives paramount importance for quality standards of its products. It has

supplied material to customer‟s stringent specifications with zero defects. Midhani has

installed elaborate quality control facilities to ensure and maintain desired quality parameters.

Melting has installed elaborate quality control facilities to ensure and maintain desired quality

parameters. Melting process and parameters are controlled and monitored using computer-

controlled spectrometer to obtain high metallurgical cleanliness and required metallurgical

and mechanical properties. A central laboratory fully equipped for chemical, metallurgical,

mechanical, non-destructive, magnetic and physical testing ensures excellent quality of

finished products. Rigorous quality control is exercised at all stages of manufacture to

achieve quality, reliability, and consistency of properties in all products.

8

Melt shop-I

Introduction:

Melt shop is the main production unit of Midhani. Various types of super alloys,

stainless steels, soft magnetic alloys, are produced here. For the production of these alloys

electrically operated furnaces are installed in this shop. Especially electric furnaces are

located because they have so many technological advantages when compared to other steel

melting practices.

Depending upon certain factors like control of composition certain alloys will be

produced in electrical furnaces. Some are in air-conditioning furnaces a few are in vacuum

refining furnaces. There are some alloys that are produced by double melting techniques.

Ingots produced by any one of the above techniques are re-melted in vacuum are re-melting

furnace or in an electro slag refining furnace.

The shop has following major equipment‟s in which the melts or refining of the

molten metal or alloys are carried out.

EQUIPMENT’S:

MAJOR EQUPIMENT’S:

1. Electric arc furnace.

2. Vacuum induction refining furnace.

3. Air induction melting furnace.

4. Argon casting unit.

AUXILLARY EQUIPMENT’S:

1. Bottom pouring ladles.

2. Bottom type charging buckets.

3. Additive preheating oven.

4. Ladle pre-heaters.

5. Mold preheating oven.

6. Stopper rod preheating furnace.

7. Ingot molds.

8. Transfer trolleys.

9. Electrically operated cranes.

10. Simple cutting machine.

This is also includes one stage control laboratory in which the analysis of different

elements is carried out.

SHOP DESCRIPTION:

This shop has been divided into three bays:

9

1. AB Bay

2. BC Bay

3. CD Bay

AB Bay:

This bay is provided mainly for scrap. In this bay two cranes are present; each crane

has 5 tons capacity. The raw materials stored here are:

1. MS scrap

2. Limestone

3. Pure iron

4. Iron ore

5. Return scrap

6. Mixed skull

7. Scrap consolidation electrodes

8. D-phosphate

9. Graphite powder

10. Fluorspar.

BC Bay:

This bay is provided mainly for bricks, refractory work. The raw materials stored

here are:

1. Fluorspar

2. Chrome pellets

3. Graphite powder

4. Iron ore

5. Low carbon Ferro chrome

6. Aluminum powder

7. Ferronickel

8. Ferro molybdenum

9. Ferro vanadium

10. Ferro silicon

11. High carbon Ferro nickel

This bay has one crane of six ton capacity.

CD Bay:

This bay is purely production oriented. The equipment‟s present are:

1. Electric arc furnace.

2. Air induction furnace.

3. Vacuum induction refining furnace.

4. Argon casting unit.

10

ELECTRIC ARC FURNACE

Principle:

In an electric arc melting furnace the electrical energy is used to form an electric arc

which heats the metal by radiant heat evolved.

The furnace used in this process is of the type “direct arc furnace”, in which electric

arc is formed in between the electrodes and the metal being heated.

Direct arc furnace:

Type SSKD 180/450.

Main parts of the furnace are:

1. The Furnace body which consists of spout, door, hearth, walls, shell etc.

2. The refractory lined roof and lifting arrangement.

3. Gear furnace body movement.

4. Electrode and their holders.

5. Electrical equipment.

6. Cooling water system.

ELECTRIC ARC FURNACE

11

Furnace body:

Spout:

The spout is located diametrically opposite to the charging door. This spout is

welded to the shell so that it makes 10-12o with the horizontal and is lined with fire clay

bricks.

Door:

This is located directly opposite to the top hole and additives are made through the

door, and also used for slag removal. A hydraulic system serves for lowering and raising the

door; and is lined with fire clay bricks.

Furnace shell:

It contains the furnace lining and forms the melting space. The furnace shell rests on

the cradle. This when tilted 45o forward, tapping is done and tilted 15

o backwards for slag.

Furnace roof:

This closes the melting space from the above. The arched roof with an aperture for

the electrodes rests on water cooled roofing. This ring rests on the shell rim. There are guide

studs which fit into the sockets ensuring that the roof will always be lowered into position

properly.

Electrodes:

There are three electrodes of graphite and are of 200 mm Ø and the method of

electrode control is by electro-hydraulic automatic electric regulator with provision for

manual control. The electrode speed of rising is 60 mm/ second and for lowering is 40

mm/second.

Electric equipment:

The electric energy is taken from a high voltage network through a circuit breaker

and resulting transformer. The reactor coil is ahead of a transformer on the primary side and

serves to reduce the current during starting.

Cooling system:

12

Roof rims, door, spout arches, electrodes clamps, current conducting clamps and cooling

rings constitute the cooling water circuit. Water is fed to the furnace through a rubber hose.

Hoses are employed on the furnace itself where components under voltage must be

electrically circuited. The return water is collected in an open funnel permitting visual

inspections.

Virgin process:

The charge required is M-S scrap, alloying elements which are added in the form of

Ferro alloys or pure metals:

(a) CHARGING:

Charging is done from the top with the buckets. Charging is done in two stages:

1. Initial stage.

2. Final stage.

If the charging is low in carbon, graphite is added.

(b) TAPPING:

13

After attaining the tapping temperature electrodes are raised to clear the bath. After

the power is put down, the tap hole is opened and the furnace is tilted so that molted metal is

drained into the ladle. The second process is “return scrap process”.

Technical data:

Capacity : 5.5 tons.

Furnace lining:

Shell : Chrome Magnetite bricks.

Roof : High alumina bricks.

Furnace reactor:

Rating : 2080/2400 KVA or 2400/2800 KVA.

Primary voltage : 11 KVA.

Secondary voltage : 85-215 V.

Cooling : Oil forced water cooling.

Efficiency : 98.7% - 2400/2800 KVA

98.8% - 2080/2400 KVA.

Furnace reactor:

Rating : 750 KVA.

No. of steps : 3 fixed 6 variables.

Power consumption : 520 KWH/ton.

Refractory bottom thickness : 400 mm.

Wall thickness : 275 mm.

Method of charging : Top.

Water consumption : 2liters/second.

Inlet water temp : 32oc.

Outlet water temp : 63oc maximum.

Mechanism for:

14

Roof lifting : oil hydraulic.

Furnace tilting : water emulsion (hydraulic).

Electrode movement : water emulsion.

Electrode clamping : water emulsion.

Door operation : water emulsion.

Roof ring : water cooled.

Electrode control : automatic and manual.

Maximum angle of furnace tilting

Tap hole side : 40o.

Slag door side : 20o.

Maximum angle with power on

Forward : 15o.

Backward : 20o

Emergency tilting during power failure:

Hydraulic energy provided for lifting, electrode tilting and powering.

Electrode speed:

For rising : 60 mm/second.

For lowering: 40 mm/second.

VACUUM INDUCTION REFINING FURNACE

TECHINICAL DATA:

Melting capacity : 5.5 to 6 tons

Refining capacity : 5 tons

Furnace lining : alumina magnesia snivel

Current rating : 500 A at 2.4 KV

Vacuum range : 100 microns to 500 microns

15

Tilting mechanism : hydraulic.

Tilting angle for

Forward tilt : 105o.

Backward tilt : 20o.

Size of the chamber : 14 feet.

Ladle used for this furnace : 5 ton ladle.

The vacuum induction refining furnace is designed for two fold operation

1. The furnace can be hot charged with molten metal from an arc furnace

ladle. In this mode the unit has ability to maintain heat, add heat, melt and

provide stirring.

2. The furnace has capability of doing cold-charge melting without the use of

hot metal from the arc furnace.

Both the modes of operation provide for vacuum pouring into a preheated ladle or ingot mold

placed in the vacuum chamber prior to evacuation. Additional air fuming can be

accomplished by pouring through a brick lined launders.

The vacuum level used in this furnace is 100 microns to 500 microns. This is attained by

steam ejectors. Facilitates have been provided for argon bubbling and oxygen bubbling.

The chambers have refractory lining at the bottom and drive-away type lid operated

hydraulically at the top.

Charge:

The charge used for this furnace is the liquid metal from the electrode arc furnace. If

the process is refining as for melting cold charge is also done.

ARGON CASTING UNIT:

Ingots of certain alloys melted in the electric arc furnace are cast in atmosphere

argon. An argon casting station can cast 4 ingots at a time. First a vacuum system evacuates

the chamber to 1000 microns in which molds are placed and argon is introduced into the

chamber. Hot tops are used for all ingots. Both top pouring and bottom pouring is practiced.

16

Steam injection unit used for evacuating refining unit also evacuates the mold

chamber. Special types of ladles are used for argon casting. Ladles are preheated before

tapping liquid metal for drying after refining.

AIR INDUCTION MELTING FURNACE

Capacity : 2220Kg and 1350 Kg.

Ladle capacity : 2.5 tons

Max forward tilting angle : 105o.

Power supplied from source : 1200/1500 KW at 150 to 500 hertz.

Mechanism : integrated hydraulic.

These furnaces work on the principle of electromagnetic effect. These are primary

melting furnaces with integrated hydraulic mechanism which uses two hydraulic cylinders.

Lining:

17

For walls high alumina refractory bricks, for bottom high alumina spiral ramming

mass (70% Al2O3 + 30% MgO) is used. A mild steel sheet is used for lining the crucible,

sintering is done to obtain the monolithic lining.

MELT SHOP – II

The shop has been located in single bay, and this unit for secondary melting and

refining purpose. In this unit there are three furnaces are arranged such as vacuum induction

melting furnace, vacuum arc re-melting furnace and electro slag refining furnace. VIN is

primary melting furnace and it take cold charge as raw material, while the other furnaces are

secondary melting furnaces and take primary cast ingots as raw material. Ingots cast in melt

shop I are sent here for further refining in VAR and ESR the main products are super alloys.

Main objectives of this shop:

1. To produce alloy with less amount of gases such as H2, O2 and N2.

2. To decrease the sulphur content by re-melting the Ingot.

3. To finely disperse the inclusions.

4. To ensure directional solidification.

Raw Materials Used:

Pure Iron Ferro chrome (low carbon), Cobalt and Ferro Silicon…

This shop consists of various furnaces:

1. Vacuum induction melting furnace (VIM).

2. Vacuum arc re-melting furnace (VAR).

3. Electro Slag Refining Furnace (ESR).

VACUUM INDUCTION MELTING FURNACE

It is a primary steel making furnace for super alloys and secondary steel making for

other alloys grade

Furnace Details

Furnace Supplied : M/s SCOTVAC, SCOTLAND

Melting Capacity : 2500 KG AND 1500 KG

Melting Power : 250 kW

Frequency : 150 Hz.

Vacuum Chamber : 100m3.

Ultimate Vacuum UP TO : 5 microns.

Cold Leak Rate : better than 10 microns per minute.

18

Vacuum Pumps : mechanical (Edwards) – rotary and roots – vapor

booster.

Charge of the Furnace : Ni pellets, Co, Mo, Fe, Fe-Mn, Fe-Cr. Are added

according to Composition

Lining of the Furnace : 70% Al, 30 % Mg

Life of the Lining : 10 to 12 heats. It takes about 8 to 9 hours for one heat.

Gases Levels : O2 < 5ppm, N2 < 10ppm

Melting Range : 8 to 10 hours

Facilities : Vacuum on inert gas pouring. Dummy Mold for

pouring in case of emergency. Bulk and fine charging is

possible under vacuum, sampling facility without

breaking vacuum. Bridge breaker, immersion and

radiation pyrometer.

Principle:

The main principle involved in this furnace is when an high frequency alternating

current is passed through a copper coil, which acts as a primary coil and includes secondary

currents in the charge ( acts as secondary coil) contained crucible, the resistance of the metal

to flow of current generates heat, which melts the charge. The time required to melt is very

short as the heat produce from the charge only. The secondary current associates with it a

magnetic field, which provides a magnetic stirring action on the molten metal and mixes

metal uniformly.

Mechanical Boosters:

A rotary pump is an interlocking arrangement to create the vacuum by sucking the

air through the dust traps and create the initial vacuum.

There are about 5 pump sets with boosters, creating the vacuum in the whole

chamber including the Mold chamber. There are about 4 vapor boosters, the whole hydraulic

system is controlled by the hydraulic pumps.

Dust Trap:

Dust traps are used to interlocking arrangement to create the vacuum by sucking the

air through the dust traps and create the initial vacuum

Vapor Booster:

The vapor booster is mainly used to create high vacuum less than 1 micron and

functions hydraulically.

19

Description of Process:

Melting is carried out in neutral monolithic crucible in a vacuum chamber using

induction melting. Furnace coil is suitable to design and insulated to take of corona in

vacuum facilitates for charging, sampling, temperature measurement during melting or

available which facilitate these operation without breaking vacuum in, melt chamber.

Provision of Mold trolley is made for pouring in multiple molds.

Refining:

The important factor of the refining period is usually de-oxidation present in the

bath with the carbon. During this period, carbon and oxygen present in the bath gets reacted

and forming CO which is sucked off Because of the low pressure this reaction takes place

very fast and very low levels of carbon is achieved. Oxygen also gets reduced to min level

The reaction is C + O CO2

Degassing of hydrogen and nitrogen can be decreased via the gas face because the

solubility of these gases at constant temperature are directly proportional to their partial

pressure. The solubility of Hydrogen in atmospheric pressure is at 1600C. In Iron or Ni base

metals is in the range of 30ppm. During vacuum induction melting the hydrogen can be

removed to very low concentration.

There is no difficult in reducing the Nitrogen content to 20 ppm. When nitride

forming elements such as chromium, aluminum, vanadium, and titanium are present, the

activity of nitrogen is very low. Therefore removal of nitrogen under high vacuum is difficult

if low nitrogen contents are desired in alloys containing nitride forming elements raw-

materials should have low in nitrogen must be used.

Ni-Ca is added to remove sulphur up to some level by formation of CaS.

Alloys being melted:

1. Nickel based super alloys for aeronautical applications.

2. Steels for space, aeronautical and nuclear applications.

3. Soft, magnetic alloys.

4. Controlled expansion alloys and special steels.

Improvements made in melting practice:

1. Design of pouring systems for cast iron.

2. Improvement in tundish design.

3. Use of ceramic filters.

4. Melting and refining in deep vacuum for selected super alloys.

20

VACUUM ARC REMELTING FURNACE:

FURNACE DETAILS:

Furnace Supplied : Misonsarc, USA

Furnace Capacity : 5T

Ingot diameter : 200-550 mm

Furnace design : co-axial

Ultimate vacuum : 5 microns

Maximum melting current : 15000 amps

Melting voltage : 25 volts

Melt rate control : by computer

Arc length control : by drip shot

Maximum melt rate : 4.5 kg/min

Principle:

The main principle in this furnace is when a high ampere low voltage direct

current is employed, for striking an arc between the consumable electrode and a pad of steel

placed in the bottom of the copper mold. The arc gap is automatically maintained.

Process:

Re-melting is carried out under fine vacuum (10-3mm level) with precise control

of melt rate by computer. It is a secondary steel melting furnace. In this process, a stud is

welded to the electrode, which is re-melted under vacuum in a water cooled crucible.

Electrode is re-melted water cooled copper crucible using arc melting principle. The metal is

progressively melted from the lower end of the electrode, forming an ingot in the mold. This

furnace is mainly used for entrapped gases and control of non-metallic inclusions from the

ingots. Melting operation is progressively carried out with constant melting rate/pool depth to

attain fine and uniform solidification structure, free from segregation in the ingot. Fine

vacuum results in low gas in volatile tramp elements. This essentially for mechanic properties

required for high performance alloys. Cleanliness of the metal is improved substantially.

Improvements carried out in melting practice:

1. Helium cooling of super alloys ingots during solidification.

2. Introduction of computer control for melt rate.

3. Improvement in the design of crucible clamping system.


21

1. Super alloys for aeronautical as well as engineering applications.

2. Special steels for space, aeronautical and nuclear applications.

e.g., Maraging steels, PH stainless steels, titanium stabilized stainless steels etc.

Other advantages:

1. Low gas content, low H2 content.

2. Cleanliness in operation.

3. Homogeneity in production.

4. No foreign inclusions, as there is no refractory.

ELECTRO SLAG REFINING FURNACE:

In this process the slag is used as refining agent. The composition of slag is

CaF2 : 60%

Al2O3 : 20%

CaO : 20%

Furnace details:

Manufactured : M/s Leybold Hereaus, WG

Capacity : ingots of 10 MT, 5MT, 2MT, 0.6MT

Ingot dia : 600mm

Temperature maintained : 1215oc-1520

oc

Maximum melting current : 25000amps

Melting power : 2MVA

Atmosphere control : dry air/ inert gas

Starting technique : solid/liquid

Slag system : CaF, CaO, Al2O3

Process:

Re-melting carried out under a reactive slag (flux). The preheated slag fed into the

mold and single or three phases AC or DC current is passed through the electrode and

resistance heating takes place. The heat is generated due to the electrical resistance of slag.

When the metal melts, since it is having higher density it tries to settle at the bottom and in

passing through the slag gets refined. The slag facilitates refinement in the chemical

composition and also removing sulphur and non-metallic inclusions. We can eliminate

sulphur content below 0.03% in primary melting. i.e., in EAF – in order to reduce the sulphur

content up to 0.012% and to obtain a fine dispersion of the inclusion in the EAF ingots, these

22

ingots are re-melted in ESR. Melting is carried in water cooled crucible to attain sound

homogeneity, directionally solidification and segregation free ingots are obtained.

The slag ratios used for ESR refining are 3 types namely:

70:15:15, 60:20:20, 33:33:33, CaF2, CaO, and Al2O3.respectively.


1. Low and high alloy high strength steels for armament, nuclear and aeronautical

applications.

2. Nickel and iron base super alloys for engineering applications.

Improvements made in melting practice:

1. Optimization of slag chemistry.

2. Melting under inert atmosphere.

3. Indigenous development and manufacture of slag.

4. Production of square ingots with higher capacity.

Other advantages:

1. Refined metal can be obtained.

2. Good surface finish is obtained in VAR.

3. Homogeneity in production.

Other auxiliary equipment’s are:

1. Electrode stub welding.

2. Tundish preheating

3. Slag melting furnace.

4. Slag preheating oven.

Slag melting furnace:

Furnace details:

Capacity : 2.2T

Max.temperature : 1600-1700oc

Electrodes : 2

The hearth lined with magnetic bricks and the shell is rammed with graphite

powder.

Slag preheating oven:

It is a bogie type oven intended for preheating the ESR slag. It is an electrically

heated oven and has a provision for heating up to 800oc. in this oven for 10-16 hrs. The

23

capacity of the slag preheating oven is 300 kg‟s after this it is directly charged in the ESR

furnace.

TITANIUM SHOP

MIDHANI has established facilities for processing of Titanium and Titanium alloys

starting from Titanium sponge. Facilities for ingot melting and manufacture of mill products

including bars, sheets, wires and rods have been established in the plant. It has been

supplying different types of Titanium and Titanium alloys to numerous industries. The

prominent among them are aerospace, chemical and petro chemical etc. At Midhani,

Titanium alloys are classified as Alfa, Alfa-Beta and Beta alloys, according to the

predominant phases present.

Titanium is one of the lightest metals abundantly available. Its melting point is

1660oc. it undergoes allotropic transformation at 882.5

oc. Titanium sponge is melted in

vacuum arc remelting furnace to produce ingots of size 4.0/6.5 T in weight. Primary

breakdown of ingots is carried out in a 1500 T computer controlled forge press. Subsequent

processing in different rolling mills yields a variety of mill products. The grades of

manufacture in this shop and selection of alloying addition in Midhani are given below.

TITANIUM AND TITANIUM ALLOYS GRADES BEING

MANUFACTURED:

Process of Titanium Production in Titanium Shop:

1. Visual inspection

2. Mixing

3. Compact pressing

4. Plasma arc welding

5. Dehumidification

6. Vacuum arc melting

7. Ingot turning

Raw material used for production of titanium and titanium alloys:

1. Titanium sponge

2. Master alloys viz., Al-V, Al-Mo-Ti etc.

3. Titanium scrap

4. Zirconium scrap

5. TiO2 powder

6. Virgin metallic granule i.e., cu, Al, Sn, Si.

VISUAL INSPECTION:

24

Visual inspection involves separation of any unwanted waste materials present in the

Ti sponge. The charge is passed through magnetic separator to remove Fe bearing particles.

After this inspection, it is sent to mixing.

MIXING:

The Ti sponge and the alloying elements are mixed in this mixer according to their

quantities and alloys percentage. After mixing the material, these are sent to compact

pressing.

COMPACT PRESSING:

The mixed material is compacted at a pressure of 3000 tons. The material is placed in

the die and ram is released to make compacts 620 x 170 mm2.

PLASMA ELECTRODE WELDING:

It is manufactured by M/S Leybold Hereaus, WG. The compacts are arranged in the

jig. The jig is enclosed in a plasma-welding chamber (9500mm long, 1200mm Ø) having

argon atmosphere. The arc is generated between the tip of the electrode and the nozzle, the

argon gas is introduced from another nozzle. Due to the arc the argon gas splinted and

ionized so that stream of ions are produced so the compacts are welded together to have

sufficient mechanical strength and electrical continuity to enable primary melting into a first

melt or primary ingot. The welding is carried out in 6 inches in “x” direction, “y” direction

can be rotated in 360o. The welding automatically cycled through the entire welding process

by programmable controller.

VACUUM ARC REMELTING:

Furnace details:

Manufactured : M/s Leybold Hereaus, WG.

Furnace capacity : 10T steel, 6.5T titanium.

Dia of ingot produced : 860 mm Ø.

Max. Current : 30000A

Melt voltage : 20-35 V

Vacuum created : 1x10-3

.

Principle:

The welded compacts from plasma electrode welding are melted in VAR furnace to

produce sponge Ti and other alloys into uniform solid solution. The main principle in this

furnace is, Arc is generated using low voltage; high current between the consumable

25

electrode and a pad of Ti scrap is placed in the bottom of the copper Mold, droplet pass

through the hot plasma and collect in the metal pool.

Melting:

The vacuum are furnace for titanium ingot melting has two melting stations and can

produce ingots up to 860 mm diameter and 4.0/6.5 T in weight. To start the melting

operation, an electrode produced from conventional melting operation an electrode produced

from convectional air-method or vacuum-processed steel is suspended in the consumable

electrode vacuum melting furnace, the furnace is designed to ensure a coaxial

electromagnetically clean configuration of the entire circuit with in the furnace in order to

ensure interrupted melting operation and freedom from macro segregation. Due to high

vacuum in the furnace the oxygen, nitrogen, gets reduced resulting in very low content of

gases in the final product.

INGOT TURNING LATHE:

The ingots that are produced in VAR furnace are turning lathe to remove the outer

oxidized layer and to obtain better surface finish. After turning, ingots are subjected for

further processing like forge shop etc.

OTHER FURNACES IN TITANIUM SHOP ARE:

VACUUM ANNEALING FURNACE:

Annealing is done in this furnace to relieve internal stresses and also to soften the

material. It is manufactured by M/s Hendiecker Haff, WG. Its capacity is 400 kg‟s. Vacuum

is crated up to less than 1 µ annealing is done in vacuum for titanium because Ti is very

reactive and forms other compounds. Annealing temperature of Ti is 700oc.

VACUUM SKULL MELTING FURNACE:

It is similar to VAR furnace in principle and operation. But it is used to produce

castings for Titanium products. Its capacity is 130kgs. During process a skull is formed

adjacent to the furnace wall by this copper cooled crucible and is protected from melting. In

this furnace the crucible movable and it has high melting rate when compared to VAR. after

the melting temperature is attained, the crucible is turned to mold and the liquid metal is

poured in to the cavity after the solidification the required casting is obtained. All these

operations are done under vacuum, because titanium is very reactive when exposed to normal

atmosphere and reacts with oxygen and forms compounds.

VACUUM ARC FURNACE:

It is similar to VAR furnace in principle and operation. Its capacity is 250 kgs. But it

is limited to less capacity. It is used for making new products in Ti. One single compact can

be used as an electrode in this furnace.

CRUCIBLE CLEANER:

26

These are used for cleaning the crucibles.

CHIP BREAKING MACHINE: These are used for breaking large chips into small chips.

27

FORGE SHOP

Forging is a process of shaping the metal by application of pressure or

hammering the metal when it is in plastic state. The charge for forge shop is primary

ingots from various sections either as hot or cold metal ingots. These ingots are heated

in the furnaces up to required temperature and subjected to forging in hydraulic

pressure hammer press.

Forge shop has following equipments:

1. Hydraulic press

2. Manipulators for hydraulic Forge press

3. Hammers(Pneumatic) (I)750kg (II)1500kg

4. Mobile manipulator

5. Ingot Car

6. Turn table

7. Dies of various furnace

8. Fixed hearth furnace

9. Bogie hearth furnace

10. Auto grinding machines

11. Circular saw and saw sharpener

HYDRAULIC FORGE PRESS AND MANIPULATOR:

Specifications:

Forge press : M/s Phanke Engineering., WG

Capacity : 1500T

Oil pressure : 350 kg/cm2

Max stroke length : 1200mm

Max No of strokes : 120 strokes/ min.

Associated equipment’s & accessories:

Two straight line , oil hydraulic rail bound mobile manipulators

One rail bound ingot car of capacity 8T with rotatable head

(3600rotatable)

One electro hydraulic top-up turn table of capacity 6.5T, rotatable by

3600

Set of flat swage and “V” dies.

Hydraulic press has a capacity of exerting 1500 tons pressure. Dies are

arranged to forge required shape of the ingot. The manipulators are arranged at both

sides of the hydraulic press. Both manipulators are movable and are having of 4 tons

and 6 tons respectively. The manipulator has two arms to hold the ingot (gripping

range: 100-850mm round), which will be subjected to forging by moving forward and

28

backward with the rotation of ingot. The combined capacity of the two manipulators

is about 12 rotations of ingot. The max diameter of the ingot that can be charged is

600.

HAMMER:

Manufactured by New Standards Engineering, Bombay. These are high

speed short stroke, clear space, Electro pneumatic power hammer of pull down

presses. There are two types of hammers having capacity of 1500 kg & 750 kg. The

maximum stroke of the hammer is 890mm and 85 strokes/min & 760mm and

100strokes/min respectively. These can reduce the cross section to below 140mm2,

which is not possible by hydraulic press. In this also it is required to arrange the dies

and then hammered to obtain the required cross sections/shape of the forging.

MOBILE MANIPULATOR:

A part from the two manipulators beside the hydraulic press, a mobile

manipulator is also present .This is having capacity of 2 tons and is used for assisting

the forging of ingot in hammer mill and charges the ingot or pressing.

INGOT CAR:

This is used for charging and discharging the ingot from furnaces. This is

also used to discharge hot ingots on the turntable and to remove the forged ingot from

the turntable. The capacity of this car is 6 tons.

TURNTABLE:

The capacity of the turntable is 8T .The turntable is placed in front of the

manipulator. The ingots from the furnace are brought near and positioned on the

turntable. The turntable moves to and fro motions for positioning the ingots in the

jaws of the manipulator on the turntable, so the ingot car take the forged product and

is discharged from the manipulator on the turntable, so the ingot car take the forged

product and charged in the furnace.

DIES:

These are most important and must for conducting a forging operation of the

ingot. These dies are set in the hydraulic press and hammer to obtain required shapes

of ingots. These dies are made up of nimonic (nickel based alloy)

1. Flat die

2. Swage die

3. „V‟ die

4. Spreading die

5. Upset die

REHEATING FURNACES:

29

The furnaces are used for heating the material before pressing or

hammering. In heating condition the material becomes softer and easy with low load.

The longer the section and the higher the C content. The lower is to be the rate if

heating. Alloy steels are particularly sensitive to sudden heating and that are to be pre

heated to 7500C before being exposed to higher temperatures. There are two types of

furnaces, gas fires and electrical. In gas fires furnaces the ratio of LPG and air is 1:30

i.e., 12 mm of water column. The forge shop having the following furnaces:

Fixed Hearth Furnaces:

Furnace detail:

Fixed hearth furnaces : 2 nos.

Size : 800×3000×1300 mm.

Capacity : 40T

Type : gas fired.

These are box type furnaces and arc suitable for heating small and medium

type components. It consists of a fixed hearth and cannot be taken out as in bogie

hearth. This is a gas-fired furnace.

BOGIE HEARTH FURNACE:

Furnace detail:

Bogie hearth furnace : 4 nos.

Size : 600×3000×1300 mm.

Capacity : 30T

Type : gas fired.

These are 4 box type batch furnace and suitable for heating bulky and heavy

components. The furnace consists of a fire clay refractory placed run out bogie will be

well within the furnace chamber. There are 1 electrical and 3 gas fired furnaces in this

shop. The furnace is divided into 5 Zones, heating plates are arranged in each zone

.The heating element is Nicrome 5 blowers are arranged for equal distribution of heat.

30

Electric heating furnace:

Furnace detail:

Electric heating furnace : 2 nos.

Type : single chamber electric heated.

Capacity : 400kgs.

These are used for Magnesium, Titanium and Titanium alloys.

Twin chambered furnace:

Twin chambered furnaces : 2 nos.

Size : 6000×3000×1300 mm, 1400×3000×1300

mm

Capacity : 20T/chamber.

Type : gas fired

31

HEAT TREATMENT SHOP

Heat treatment is a process of heating the components to an elevated

temperature, soaking it for some time and cooling at desired rate to obtain required

properties.

Following heat treatment process are done in this shop. They are:

ANNEALING:

Annealing means heating metal to a predetermined temperature, holding at

this temperature and finally cooling at very slow rate. It is done to relive internal

stresses, soften the metal and also refine grain size.

NORMALIZING:

Normalizing means heating steel to 40-500°c above upper critical

temperature and holding it for proper time and then cooling in air to room

temperature. It is done mainly to uniform structure.

1. HARDENING:

Hardening means heating the metal to hardening temperature and holding at

this temperature for sufficient time followed by rapid cooling such as quenching in

water or oil. It is done to increase hardness

2. TEMPERING:

Heating hardened steel to below the lower critical temperature followed by

cooling in air is known as tempering. Removes the residual stresses and improves

ductility and toughness.

3. SOLUTION TREATMENT:

If the alloy is reheated to point to the solution treatment temperature then all

the excess β will be dissolved and the structure will be homogeneous α-solid solution.

The alloy is then cooled rapidly (quenched) to room temperature results in a super

saturated solution with excess β trapped in solution. The quenching is usually carried

out in a cold water bath or by a water spray to minimize distortion.

4. AGEING:

The alloy which is quenched is a super saturated solid solution and in an

unstable state. The excess solute will tends to come out of solution. The excess solute,

which comes out precipitates at a rate depending upon temperature. At the low

temperature the diffusion rate is slow that no appreciable precipitation occurs. At the

low temperature the diffusion rate is slow that no appreciable precipitation occurs. At

32

high temperature such as about 250°C hardening occurs quickly due to rapid

diffusion. These alloys in which precipitation takes place at room temperature are

known as natural-ageing alloys. The alloys, which require reheating to elevated

temperature, are called as artificial ageing alloys. The actual cause of age hardening is

due to the uniform distribution of finely dispersed particles with coherent stress fields.

Which increase hardness and strength of the alloy by precipitation of carbides.

Equipment in Heat Treatment Shop:

The equipment available in H.T shop is divided into following categories

i. FURNACE :

a) Electrically heated furnaces

b) Gas fired furnace

ii. MECHANICAL EQUIPMENT :

a) Roller straightener

b) Horizontal straightening press

iii. COOLING EQUIPMENT :

a) Water quenching tanks

b) Oil quenching tanks

c) Pedestal fans

iv. AUXILIARY EQUIPMENT :

a) Heat exchangers and agitation pumps

b) Hardness testing machine

c) Material handling equipment

v. CUTTING EQUIPMENT :

a) Ecomix machine

b) Abrasive cut off machine

c) Cobra saw

FURNACES:

Electrical furnace:

There are 4 furnaces, which are electrically heated, of different sizes,

capacity.

Ludwig Furnace:

Furnace Details:

Maximum load capacity in tones : 25T

Maximum temperature : 975°C

Size : 6000 x 1500 x 1200mm

33

Accuracy of furnace temperature : +/- 5°C

Material of heating element : FeCrAl

HBB-3 Furnace:

Furnace Details:

Size of the furnace : 600 x 800 x 800mm

Capacity : 15T

Maximum operating temperature : 1100°C

Accuracy of the furnace : +/- 5°C

HBB stand for Hindustan Brown Boveri from Baroda. This is bogie hearth

furnace, the capacity of furnace is 15T and the maximum operating temperature is

1100°C. Strip type heating elements are positioned on all six surfaces inside the

furnace thereby eliminating the recirculation fans. Single zone is divided into 4 zones

of individual control with temperature controllers and indicators. 4 duplex and 4

simplex thermocouples made of platinum & platinum rhodium is used as temperature

sensors.

HBB-4 Furnace:

Furnace details:

Size of the furnace : 3500 x 1500 x 1000mm

Capacity : 10T

Refractory : Silicate bricks of (60% Al203) backed by cold

.Face . . Alumina bricks

Maximum temperature : 800°C

This is a bogie hearth furnace. The capacity is 10T. The maximum

temperature that can be attained is 800°C. 3 duplex and 3 simplex thermocouples mad

of Ni-Cr and Ni-Al are used as temperature sensors. 3 zones in a single chamber

provided with a recirculation fan to maintain uniform temperature inside the furnace

working volume. This furnace is used for annealing of sheets and tempering

operation.

Pyromaster Furnace:

Furnace details:

Maximum Temperature : 1000°C

34

Capacity : 2 Tons

Size : 1500 x 1000 x 600mm

The maximum temperature attainable here are 950°C and the capacity is 2 T.

Two fans are provided at the roof for circulation of hot air.

Gas Fired Furnace:

Furnace Details:

Size : 6000 x 1200 x 100 mm

Capacity : 25 tons

Max Temperature : 1200°C

Heating rate : 100 Celsius per hr at max load

Thermocouples : platinum & platinum rhodium

Fuel : Liquefied petroleum gas

Accuracy of temperature : +/-5°C

MECHANICAL EQUIPMENT:

There are equipments chiefly employed for removing distortion,

straightening of the bars and rods etc after heat treatment.

Roller straighteners:

There are two roller straighteners. They are:

Roller Straighteners 1:

Capacity : 10-50 mm diameter of the bar

Length : 6000 mm (bar length)

Speed : 10M/min & 20 M/min

Roller Straighteners 2:

Capacity : 25 to 100 mm diameter of bar

Length of the bar : 6000 mm

Speed : 10 M/min & 20 M/min

35

The bars are passed in between the two-dial speed rollers of concave and

convex shapes. Which are driven by power in opposite direction at angle of 5-15 to

the axis of their mounting. Hydraulic and pneumatic arrangement is provided for

charging and discharging of bars in to inlet and outlet troughs of machine. The

distance between rolls can be adjusted depending upon the diameter of the bars.

Horizontal Straightening Press:

The capacity of this machine : 75 to 250 mm diameter

The machine is employed for straightening of round, square and other

sections. The movement of the ram is horizontal 400 T of pressure will be developed

by hydraulic system to push ram against the bar supports on two adjustable anvils.

Cooling Equipment’s:

Equipment Details:

Capacity of tank : 40 KL

Oil tank size : 700mm (L) x 1500mm (W) x 4500 mm (D)

Oil used : servo quenches 107 Grade

Quenching Tanks:

Cooling is an important operation in heat treatment to attain the properties.

The shop is equipped with two water tanks for quenching. The capacity of tanks is

40KL. Oil used is servo quench 107 grade. The flash point is 175°C. Servo 107 oil is

low sulphur base mineral oil, having excellent oxidation and thermal stability, high

fluidity and low volatility.

Auxiliary Equipment:

Heat exchangers and agitation pump:

These heat exchangers are employed for bringing down the oil temperature

when hot stock is quenched from high temperature.

Cutting Equipment:

These are used for to cut the samples from heat treatment products.

36

FURNACE DETAILS IN HEAT TREATMENT SHOP:

TYPE CAPACITY HOLDING TEMP (°C)

ZONES

HBB4 10 T 800

4

HBB3 25 T 1100

4

LUDWIG 25 T 975

3

PYROMASTER 2 T 950

1

WELMAN 25 T 1200

3

MACHINE SHOP

Various products from different sections and shops are sent to this shop to

obtain accurate sizes, dimensions, and surface finishing etc to according to customer

requirements. Various machines are available for cutting, grinding, and milling,

smoothening and drilling the products in order to get correct sizes. The various

machines are:

1. Portable grinding machine

2. Bar peeling machine

3. Behringer band saw

4. Ecomix

5. 3mts, 4mts Beco lathe machine

6. Heller cutting machine

7. Kirloskar milling machine

8. Radial drilling machine

9. Center less grinding machine

10. Horizontal milling machine

PORTABLE GRINDING MACHINE:

This is equipped with a small grinding wheel with abrasive particles for

cutting, which is used for grinding tools and drill bits.

BAR PEELING MACHINE:

Machine consists of three movable heads and ground-polishing rolls (Titan

tipped) can reduce material from three sides at a time in which the cutter are arranged

37

the power consume according to the size of the material thickness. Speed of the

machine is 90-100rpm.The coolant servo 68 is used as coolant oil. Maximum

diameter done on this machine is 100mm and minimum diameter is 20mm.

BEHRINGER:

This is a cutting machine. The blades used are of two varieties.

1. High speed steel blade for soft material

2. Carbide blade for cutting of hard material

3. The pitch of the blade is 1.5-2.0m

4. Pressure exerted during sawing is 80kg/cm2

5. Surface finishing is better than Ecomix but cutting speed is less than Ecomix.

Serv068 used as coolant.

ECOMIX:-

This is an electrical discharge cutting machine. The blade used is mild steel,

is rotated near the ingot giving a gap of about 2-3mm. A positive charge is given

blade and negative charge is given to ingot. When the current passes through

produced between them and cutting of ingot takes place. During the process silicate is

used for improving of electrical conductivity of the job.

LATHE:

It is used for surface finishing of the material and the cutting tool is

titanium carbide and coated with tungsten carbide.

3mts lathe:

The maximum diameter can feed : 900mm

The maximum length of ingot can be turned : 2.7-2.8mts

4mts lathe:


The maximum length of ingot can be turned : 3.7-3.8mts

Beco lathe:


38

The maximum length of ingot can be turned : 2-7mts

HELLER CUTTING MACHINE:

This machine used for cutting of the ingot as well as the plates. The cutting

made with high-speed to cut super alloys.

KIRLOSKAR MILLING MACHINE:

Milling machine used for a mill (or) grind small layer on the surface of the

plate machine consists of rotating head with cutters and rotate at speed for removing

of the layer of the job at fast rate because multiple cutting edge. The cutters are made

of titanium carbide and coated with tungsten carbide. There are 18 teeth insert into the

head. This machine is not suitable for circular pieces.

RADIAL DRILLING MACHINE:

Milling machine is used to drill the holes vertically. The head hold the bit

and movable. The drill bit consists of three parts like shank flout and cutting tip.

39

The angles of the bits have facet of cutting 60 & 90.90 bits is used for

softer material and the 60 bits is used harder material.

CENTERLESS GRINDING:

The center-less grinding is a method of grinding exterior cylindrical,

tapered and formed surface on the work piece. Both wheels rotate in the same

direction and the work job is placed upon the work rest. Center-less grinding may be

done at 3 stages through feed, end feed and in feed the machine has a capacity to take

up to a maximum of 140mm thick and minimum of 10mm. The maximum and

minimum length of the job is 6mts and 3mts.

HORIZONTAL MILLING MACHINE:

This machine is used to grind small layer on the surface of the plate. The

machine consists of a rotating head which holds the insert and can move up down.

There are 18 insert per a rotating head .This machine applicable only for plates and

sheets but not for circular jobs.

HOT ROLLING MILLS

Hot rolling is the process of deforming the metal in between the rolls is

known as hot rolling, which is heated above the re-crystallization temperature. The

main purpose of rolling the material in hot condition is, at high temperature plasticity

of material increases, so it is easy to deform. In hot working process, due to high

temperature of the material there is a rapid oxidation or scaling of the surface takes

40

place. Hot worked components have poor surface finish and close tolerances and

dimensions cannot be maintained. The cost of rolling and handling is high but it is a

rapid process.

The main objective of rolling is to decrease the thickness of the materials.

Ordinarily little increase in width occurs so that the decrease in the thickness results in

an increase in length. The raw materials for HRM are forge billets and slabs. These

come from forge shops and processed to strips, sheets, bars and wires etc., on various

machines.

Hot rolling mill consists of the following bays:

1. Conditioning bay

2. Hot rolling bay

a) Heating furnaces

b) Roller hearth furnace

c) Fixed hearth furnace

d) Rolling of heated products

3. Dispatch bay

CONDITIONING BAY:

This bay consists of various machines, which are used to prepare the job for

rolling. The major equipments are

1. Band saw

2. Beco lathe

3. Swing frame grinding

4. Behringer and Ecomix

5. Shot blasting machine

BAND SAW:

This machine is supplied by the industrial tools to cut the job of maximum

diameter 650mm and if it square, 1000mm is maximum width. The coolant used is

servo 63.

41

BECO LATHE: This machine mainly used for facing the ingot and face

turning. The maximum diameter is 1000mm and generally used is 600mm diameter.

The maximum utilized length is 5.5m.

42

SWING FRAME GRINDING:

These grinders are swing frame type grinders consisting of grinding stones

of abrasive material. These grinders are hung to steel reinforcement in the furnace.

The grinding stones are rotated at very high speeds by in electric motor. The hobs are

kept on roller tables along the cracks observed on the work piece. These grinders are

operated manually.

BEHRINGER AND ECOMIX:

These are used for cutting of the ingots. Behringer is mainly used for scrap

cutting and Ecomix is used for starter plate cutting. The blades used are mild steel

strip. Sodium silicate and some amount of water 1.5% used for electrical conductivity

and discharge the electrode. Base plate is made of Copper.

SHOT BLASTING MACHINE:

Shot blasting consists of attacking of material to high velocity steams of

shots, which are propelled by centrifugal force of compressed air. This machine is

used for cleaning the strip, sheets and plates for evaluating the cracks, blow holes and

surface finishing. For blasting steel balls are used. Line speed 0.5 to 3 m/min.

HOT ROLLING BAY:

Rolling bay consists of rolling mills and also heating ovens to heat the

material for rolling. Some of ovens are electrical and other is gas heated. Ovens are

used for preheat to material rolling temperature. The material is heated in the furnaces

above the recrystallization temperature. The maximum temperature is up to 16000C.

The heated pieces of the metals are transformed to rolling mill with help of the ingot

car.

HEATING FURNACES:

ROLLER HEARTH FURNACE:

The roller hearth furnace is supplied by DREVER, UK limited, which is

used for reheating and also annealing of sheets attached to be the quenching and air-

cooling space. It is continuous type reheating furnace and is divided into three zones.

1. PRE HEATING ZONE

2. HEATING ZONE

3. SOAKING ZONE

It is longitudinal type furnace having 52 rollers covered with asbestos slaves.

There are about 27 burners; gas used for firing is LPG.

43

FIXED HEARTH BATCH TYPE FURNACE:

There are gas fired furnaces whose hearth is fixed. These furnaces are

rectangular shell of reinforced steel with a basic refractory lining of high alumina

bricks. Each furnace consists of 4 burners; is case of single chambered furnace, there

are also double chambered as well as triple chambered furnace.

ROLLING BAY:

The quickest method of shaping steel by passing the stock through pairs if

rolls. Most of the steel produce is consumed in the form of rolled products. The hot

ingot, bloom, or billet is passed through metal rolls, which revolve in opposite

direction at same peripheral speed. The revolution results in a longitudinal force

which draws the metal through the rolls and a vertical compression force which

reduces the size of the crystals. Some of the mills are:

1. Sheet mill

2. Finishing mill

3. Bar mill

4. Wire rod mill

STRIP MILL:

Strip mill is a 3 high single stand mill with entry and exit roller table driven

by motor raised and lowered. Top and bottom rolls are driven but middle moves due

to friction. It is a reversible mill; rolls are cooled during the process of rolling by

water sprays. A hot slab is passed between two bottom rolls. Due to load applied on

the material it starts reduction in thickness but there is no change in the width.

SHEET MILL:

Specifications:

Input size : 50x250/ 70x350/ 100x350.

Output size : min 8x1060 and 9x1060.

It is a two stand and two high mills consist of two rolls driven by rotating

gears. It is not continuous reduction mills like strip mill. Once the material passed

between the two rolls, again it is taken to the other side for second pass. To increase

width the slab is rotated at 900 and passed between rolls, by this we can increase the

width and length of sheet. But there is continuous reduction in thickness from each

pass. It makes sheets of size 90mm to 9mm.

FINISHING MILL:

44

It is a two high, one stand mill. If we want further reduction in sheets after

roughing mill, we go for this finishing mill. There is a roller hearth furnace which

attached to the mill at one end to heat the roughed sheet. From this furnace it is passed

between the two rolls. Reduction in thickness depends on the number of passes done

and also on strength of the metal. It makes sheets of sizes from 10mm to 3- 4mm.

BAR MILL:

Specifications:

Type : 3 high 3 stand mill.

Input material : Square and round shaped billets and size 100 sq. and

110 to 1356mm diameters bars processed to 45 sq. and 30mm diameter respectively.

Speed : 80 m/min

It is a three stand, three high mills. It consists of grooved rolls and rotated by

motor. The three high mills permits high speeds because two or more pieces of steel

can be rolled simultaneously, the distance between the rolls being maintained

constant. When the metal comes through the lower pair of rolls, a tilting table to the

upper pair of rolls mechanically raises it. A similar mechanism on the opposite side

lowers the steel from the upper rolls to the next smaller pass in the lower rolls and so

on

WIRE ROD MILL:

Specification:

Input material : Square or round shaped bars.

Output material : 8 to 15mm diameter wire in the form of coil.

Speed : 60 to 40 m/min.

Roller speed : 900 rpm.

The 7 stand 3 high wire rod mills is used for producing rods by passing hot

material of square and round shaped through the grooves of the rolls by manually to

and fro in a single stand or more stands till the required diameter rods are obtained.

DISPATCH BAY:

In this bay the rolled product i.e. strip, rod, wires etc., are cut to required

length by the following machines.

1. Shearing machine

2. Leveling machine

3. Abrasive machine

45

SHEARING MACHINE:

It is for cutting purpose. In this sheets are cut to a required size.

LEVELING MACHINE:

This machine is used for leveling the rods and strips. The strips from the

rolling bay are not of uniform level. The bars and rods thus cut to a required length

are dispatched.

COLD ROLLING MILLS

The working of metal below their recrystallization temperature is known as

cold working. Cold rolling through can be done at some temperature. It is normally

done at room temperature by applying some pressure on the metal through work rolls

and tension by coiler. The reduction percentage of strips in these mills 20% and for

sheets is 15% on its thickness per single pass. The reduction percentage of strips

depends on workload and also hardness of material. The cold working distorts the

grain structure and which a metal can be cold worked depends up on its ductility. The

higher the ductility of the metal the more it can be cold worked, during cold working

severe stresses known as residual stresses are set up in the material. It also increases

the tensile strength, yield strength, and hardness of the steel but lowers its ductility.

The input size of strips 8- 10mm and for sheets is up to 8mm.

The advantages of cold rolling are:

1. Rolling mills.

2. Smooth and bright surface.

3. Thinner gauge can be achieved.

Purpose of cold working:

1. To obtain a greater accuracy in dimensions that what is not possible in hot

finished products.

2. To obtain a smooth, bright surface finish this is free from scale or tarnish.

Cold rolling can be categorized under three major processes:

1. Rolling mills.

2. Annealing lines.

3. Processing and finishing lines.

ROLLING MILLS:

This section consists of

1. 4-Hi mill.

46

2. 6- Hi mill.

3. 12- Hi mill.

4. 20- Hi mill.

4- HI MILL:

Specifications:

Capacity of loading : 250 tons max

Mill speed : 0/20/30 m/min

Maximum thickness that can be rolled : 8mm

Minimum thickness that can be rolled : 1.5mm

Working roll diameter : 190mm, Hardness: 90/95 shore

Working roll disc on : 175mm, Hardness: 90/95 shore

Back rolls diameter : 435mm, Hardness: 65/75 shore

Back rolls disc on : 410mm, Hardness: 65/75 shore.

This mill is a single stand four high hydraulic cold mills with automatic

gauge control is arranged for the reversible and non-reversibility operation. The

reversible operation made is providing for rolling straight length and the non-

reversible is provided for rolling coils. Flat strips and coils can be rolled on this mill;

the rolls are made up of forged high carbon, high chromium steel. This mill operates

on hydraulic system. Two rolls, which are in contact with the job, are working rolls

and the rolls which are back of the working rolls, are backup rolls.

6-HI MILL:

Specifications:

Incoming size : 6.35mm

Final sheet thickness : 0.5mm

Width : 600- 1100mm

Length : 1200- 2000mm

Weight : 90 kg‟s

Rolling speed : 0-20/50 m/min reversible

Load capacity : 800T

Work rolls operating : 8mm.

47

This mill is used for rolling sheets only. This mill consists of 2 working

rolls, 2 back up rolls and 2 intermediate rolls. This mill is high electro mechanically

operated reversible type sheet mill, which produces the sheets. To prevent distortion

of the smaller working rolls in both horizontal and vertical directions four backing

bearings are used.

12-HI MILL:

Specifications:

Initial strip thickness : 3mm Max

Final strip thickness : 0.05mm

Width of strip : 80-250mm

Coiler tension : 500-5000 kg‟s up to 100 m/min

120-1200 kg‟s up to 150 m/min

Rolling speed : 0-75/150 m/min

Work roll diameter : φ38-48mm x 295mm barrel

In this mill there are two working rolls, 2 intermediate rolls and three backup

rolls. These are rotated up on the bearing arrangement and cooling is given for

bearing arrangements. The coolant used in this is SERVO quench 107 grade. This

mill has electro mechanical screw down mechanism with automatic gauge control

system and is arranged for reversible operation to prevent the distortion of smaller

working rolls in both horizontal and vertical direction.

20-HI MILL:

Specifications:

Initial strip thickness : 0.3mm Max

Final strip thickness : 0.005mm

Width of strip : 50-130mm

Load capacity : 12T

Rolling speed : 0-30/60 m/min

Work roll diameter : 6-8.5m

Weights used : 65 kg‟s

48

In this there are two working rolls, 5 and 5 intermediate rolls and 4 and 4

backup rolls. It is designed for smallest work rolls couples with highest capacity

backing bearings to permit making heavy reductions at high speeds. Strip grinding has

the facility that the de-coiler and re-cooler rotate in two directions.

ANNEALING LINES:

The purpose annealing is during cold working process the material strain

hardened and internal stresses are developed, so by the annealing process the material

soften and it is useful for further cold working operations. Annealing is a process of

heating the metal to an elevated temperature soaking at the temperature for some time

and then slowly cooling to room temperature. The purpose of annealing is to relieve

internal stresses. After annealing process ductility also improves. There are two types

of annealing in CRM. They are

GAS FIRED HORIZONTAL ANNEALING LINE:

Temperature maintained : 11500C

Number of zones : 2

Number of burners : 8

Thickness : 1.5-5.0mm

Width : 50-250mm

Temperature regulation : +/- 50C

BELL FURNACE:

Rated temperature : 11500C

Vacuum : 11500C

Capacity of the chamber : 11500C

It is batch type furnace used for annealing of coils in H2 atmosphere. These are

heated electrically. The strips are arranged in the furnace. The top, which seems to be

like a bell is conveyor and that chamber, is filled with H2 instead of normal

atmospheric air. The hydrogen atmosphere gives the annealed product of a clean and

shining surface.

FINAL ANNEALING FURNACE:

Temperature maintained : 11500C

Number of zones : 2


49

Width : 80-250mm

Capacity : 200 kgs/hr. on 1.5x250mm

Muffle : φ0.420mm

Furnace length : 3.5m

FOIL ANNEALING LINE:

This furnace is used for annealing coils manufactured in 20-hi mill.

Specifications:

Temperature maintained : 1500C +/- 5

0C on max

temperature

Number of zones : 2


Width : 130mm

Furnace length : 850mm.

PROCESSING AND FINISHING LINE:

In this there are many operations have to be done before and after cold

rolling of the material such as grinding, leveling, trimming etc., the machines used for

the purpose of producing accurate dimensional product.

WELDING MACHINE:

This is used for welding of the strips to make them continuous coils. After

this butt welding these strips are sent to grinding.

STRIP GRINDING MACHINE:

Specifications:


Width : 80-250mm

Line speed : 3-20 m/min

Coil tension : 4000 kg‟s.

Welded strips are grinded in this machine to remove excess metal from the

butt weld and also it makes welded portion flat. After this strips can be used for cold

rolling in mills.

50

ROLLER LEVELLING LINE:

Specifications:


Width : 30-250mm

Line speed : 0.3 m/min

Number of rolls : 17

Leveler roll diameter : 30mm.

The line is capable of leveling the strip as mention as below.

FLATNESS:

Coil set 10mm maximum over length of 1m by hanging sheet vertically.

CAMBER:

1.5mm over length of 1m providing starting material has edge wise

curvature 5mm.

SLITTING LINE:

It is used to slit the strip at specific width. There are slitting rolls are

arranged to this machine according to given width to cut the strip.

Accuracy of slitting : +/-0.125 on 4mm

+/-0.25 on 1mm

Cutter material : High carbon die-steel.

WIRE FLATTERING MILL:

Input wire diameter : 12mm Max

Output wire diameter : 3mm Min

Cross section of wire : 20x3mm Max

Min thickness of wire : 0.25mm

Rolling speed : 15 m/min

51

INVESTMENT CASTING PLANT(I.C.P)

Midhani is also producing some castings of intricate shapes by using a

technique of investment mold casting process. The wax is used as a pattern material.

The term investment refers to a cloak or special covering apparel. In investment

casting, the clock is refractory mold, which the pre-coating wax pattern.

The term investment casting is used to describe a group of processes which

molds are produced from liquid refractory slurries. These containing finely divided

materials, give the mold a fine surface texture, which is subsequently transmitted to

castings.

PROCEDURAL STEPS IN THE INVESTMENT CASTING

PROCESS:

1. Metal die is made for producing wax pattern.

Dies are made by machining cavities in two or more matching blocks of

steels. The dies have highest standards of accuracy and have considerable long life.

2. Liquid wax is injected in to the molds.

An expandable pattern is made by wax and the melting point of wax is 66-

7000C.the wax are of two types .they is:

a. Filled wax

b. Unfilled wax

The filled wax are pure wax and are mixed with filler materials the

advantage of filler material is the wax cannot shrinkage. The unfilled wax is pure wax

but the wax is not mixed with filler material, gates are provided by this unfilled wax.

Small shallow vents cut in the pattern surface of the die provide adequate venting.

3. The wax patterns are produced by using wax injector machine.

A hydraulic wax injector machine of 12T capacity with a maximum

temperature of 2000 C is attained. The wax at a temperature of 66-70

0 C is injected in

to the die at a pressure of 10kg/cm2.

4. Wax pattern is removed from the mold and are inspected for dimensional

accuracy.

5. The wax patterns are assembled on a sprue.

6. Gates and spires are formed in the same manner as the wax pattern. Individual

wax pattern and gates thus produced may be welded together by assembling

on a sprue, to

a. Enable many small castings to be poured in one group for economy

52

b. Form a system of runners and feeders that alloys metal to flow in to

each casting cavity.

7. Pre coating the pattern assembly.

8. The wax pattern assembly is dipped in to ceramic slurry of a colloidal silica

and zirconium flour with a viscosity of 120 sec, as a coating material .wax

pattern is next sprinkled with 40-50 AFS silica and is permitted to dry.

a. The slurry used for pre coating imparts a fine textured surface

at the mold metal interface and sprinkled sand serves to key the

pre coat to the regular investment.

b. EX: slurry ratio=15 liters of colloidal silica then Zr .flour

=15*3.65

9. Investing the wax pattern assembly for the production of metals.

The investment molds are formed by shell molding machine the refractory

sand of 200 meshes is fallen on the rotating pre coated wax pattern so that the wax

pattern is stuccoes with a ceramic sand .the refractory sand is of calcium kaoinite

band mullite silica sand

10. Process 5 and 6 are repeated until required thickness is achieved.

A number of dips are given in order to build a shell thickness of the order of

6 to 12mm. The first coating imparts to the wax pattern assembly is composed of very

fine particles to produce a good surface finish whereas the following coats are coarser

to build up the required shell thickness.

11. The mold drying is carried out for de-moisturizing this is called 1st sintering.

12. Removing wax pattern form the investment mold.

Solid molds are placed upside down in progressive furnace. The de-waxing

temperature is 120-1750 C under a pressure of 50 kg‟s/cm

2.

13. Firing.

After removing the wax, the shell can be quickly fired at a temperature of

10500 C-1200

0 C. This is called 2

nd sintering .the firing is done for removing of

moisture and to hardening the mold.

14. Pouring metal in to mold.

The molten metal poured in to the mold under vacuum of 35 microns and

with a ultimate vacuum of 1 microns. The capacity of the furnace is 15kg and the

molten metal is melted in an induction furnace and attaining a maximum temperature

of 1560-16000C .During pouring the furnace is tilted to the pre heated molds, which is

placed at the side of the furnace in the vacuum. Molds are pre heated because:

a. Preheating vaporizes any remaining wax in the molds.

b. Metal may flow more easily and fill in every corner of the mold.

53

15. After the solidification the castings are removed by breaking the mold.

16. The cast product is sand blasted to remove ceramic particles.

17. Castings are cut off and witness of the runners is ground off.

18. Heat treatment for castings is dined if required /sand blasted castings are

machine if required.

19. Final dimensional and visual inspection.

Testing‟s are made for surface faults, gages are employed to check casting

dimensions, Radiography is done to determine internal soundness, to reveal cracks,

surface pits, surface porosity etc.

20. Material is dispatched.

Advantages:

1. Intricate shapes can be cast with excellent smoother surface and close

tolerance.

2. Irregular parts which cannot be machined or difficult to machine alloys may

be cast by investment casting process.

3. Section as thin as 0.75 mm may be cast.

Disadvantages:

1. This process is relatively slow.

2. Pattern is expendable; one wax pattern is required to make one investment

casting.

3. Production of wax pattern and then investment mold etc. make the process

relatively expensive as compared with other casting processes.

Applications:

1. Parts of sewing machines, rifles, beer barrels etc.

2. Milling cutters and other type of tools.

3. In density and surgical implants.

4. Parts of gas turbine used in locomotive propulsion, jet air crafts engine outlet

nozzles

54

POWDER METALLURGY

The art of producing metal powders and of utilizing metal powders for the

production of massive material and shaped objects is called “powder metallurgy”.

The metal powders used in Midhani are Mo powder of 99.9% purity,

tungsten and nickel Powder are imported. The tungsten products used in bulbs as

filaments and molybdenum wires, which are also used in bulbs but as supporting

elements for the filament. The main process consists of packing the required powder

in a required die and is compressed with a plunger on four sides of 600 tons hydraulic

press. The product obtained is very brittle so it is to be pre-sintered at 9500C for 1hr

then after sintering in H2 atmosphere, the bars obtained are of 48mm cross section,

then it is swaged to 18mm circular by passage through the die it is heated and graphite

coating is also given to the rod for easy passage through the die. The reduction of

diameter of wire is done in stage-by-stage operation until the required size is obtained.

The main equipment’s used in the production of these wires are:

1. Sieving machine. 2. Compacting press.

3. Pre-sintering furnace. 4. Sintering furnace.

5. Manual swaging. 6. Continuous swaging.

7. Wire drawing machine. 8. Fine wire drawing machine.

9. Wire Pickling. 10. Annealing furnace.

SIEVING MACHINE:

The sieving machine is used for sieving the powders to in order to obtain

uniform and required size. The size of the powder required for compacting in

hydraulic press is below 200 meshes.

COMPACTING PRESS:

This machine is used to make compacts by applying pressure after the

sieving of the metal powders. The pressure applied for compaction is 600 tons. The

process consists of taking the powder in a required dies and leveled all over by

leveling scale. The die is placed below plunger and compressed for 45sec. various

size of compacts can be produced generally 500x48x48mm3 for molybdenum and

15x15x15mm3 for tungsten powder. The density that can be achieved by this

compacting is 50-60 %.

55

PRE-SINTERING FURNACE:

Heating element : Nichrome.

Temperature : 10000C.

Sequence start up of operation:

1. When the furnace is at room temperature, ensure that all LPG Pilot burners are

extinguisher.

2. Start the N2 at 2-2.5 m3/hr and close the furnace door.

3. Connect the N2 cylinder to the furnace through a nitrogen bank having

pressure gauge, pressure reducing valves, NVR etc.

4. Slightly open the gas outlet valve.

5. Check for gas leakages at all the joints with soap solution.

6. Purge the furnace with N2at 2.5 m3/hr for hrs. Ensure that adequate flow of

water is available at the water outlet.

7. Shut of the N2 supply after 5 hrs. And open the valve in the hydrogen line.

Purge the furnace with H2 at the rate of 1.5m3/hr for 5 hrs.

8. Test the gas inside the furnace by collecting it in a small tube and lighting it. If

there is no explosive sound, it indicates that there is no more air left in the

furnace.

9. Now light the LPG pilot flame and burnt H2 at the outlet. Maintain the flow of

H2 about 1.5m3/hrs.

10. Adjust the outlet valve to maintain a positive pressure inside the furnace.

11. Put on the furnace and set the control temperature at 850+/- 200C, 950+/-

200C, and 950 +/- 20

0C in the three zones respectively.

SINTERING FURNACE:

Heating element : Tungsten

Temperature : 18000C

Sequential startup operation:

1. When the furnace is at room temperature, ensure that all LPG Pilot burners are

extinguished.

2. Connect the N2 cylinder to the furnace through a nitrogen bank having

pressure gauge, pressure-reducing valves, NRV etc.

3. Slightly open the gas outlet valve check for gas leakage at all the joints with

soap solution while maintaining a positive pressure inside the furnace.

4. Ensure that the outlet valve is closed. Start N2 at 3.4m3/hr after closing the

furnace door.

5. Ensure that there is proper water flow at the water outlet.

6. After that there is proper water flow at the water outlet.

56

7. Keeping the outlet valve slightly open, pass H2 at 3.5-4m3/hrs and test for gas

leakage again.

8. After passing the furnace H2 gas for 6hrs @3.5-4m3/hrs leaping the outlet

valve slightly open, test the gas inside the furnace by collecting it in a small

tube and lighting. If there is no explosive sound, it indicates that there is no

more air left in the furnace and it is safe to switch on the furnace and light the

LPG pilot flame.

9. Pass H2 gas for 6hrs @ 3.5-4m3/hrs maintaining a positive pressure of H2

inside the furnace burn the H2 at the outlet.

10. Switch on the furnace and start heating.

11. Heat the furnace in the manual mode till 10000C is reached and then switch on

the auto mode till final temperature of 17900C is reached.

Heating schedule:

2000C 48hrs

4000C 24hrs

400-10000C 24hrs

1000-14000C 24hrs

14000C (maintain) 72hrs

1400-1790+/- 100C @5

0C 12hrs

Operating procedure of sintering furnace:

There are two types of sintering furnaces. They are:

1. De-oxidation furnace.

2. Bell furnace.

De-oxidation furnace:

In de-oxidation furnace the temperature that can be obtained is 18000C.

During sinter the size of compact is reduced. In this Mo compacts are generally

sintered.

Bell furnace:

In bell type of sintering furnace, tungsten compacts are sintered. The

maximum temperature that can be attained is 27000C. After arrangements of the

compacts, the furnace is closed by lowering the bell. All the atmospheric air that is in

the bell furnace is removed. After creating vacuum H2 is sent at a rate of 6 cc

in to the furnace to maintain H2 atmosphere inside the furnace. In order to avoid the

oxidation of tungsten, after arrangement of the system, a current of 700 amp is

57

supplied. The temperature of sintering compacts is measured with the help of optical

pyrometer, which are arranged in the furnace. The minimum of 11000C and a

maximum of 42000C temperature can be measured by optical pyrometers.

MANUALSWAGING MACHINE:

Swaging is an operation which reduces the diameter and increases the

length of a given bar or rod without loss of the material by means of hammering.

The sintered compacts are heated in a furnace to acquire temperature

enabling the metal for hot working manual swaging. The swaging machine consists of

high-speed steel die in the center. There are two semis round dies combine to form a

single die. It is rotated at center by a motor. There are hammers around the die, which

moves die to and fro at its axis only. By this motion it gives stroke on the metal which

is helpful in reduction of size. It is done manually. Swaging of molybdenum is done at

hot condition only due its high strength and hardness. It reduces metal from 48 to 18

diameters.

Reheating furnace:

This furnace is for reheating the material after every swaging pass.

Heating element Molybdenum

Temperature 16000C

Sequential star up of operation:

1. When the furnace is at room temperature, that all purge valves are closed, and

LPG burners is extinguished.

2. Connect the nitrogen cylinders to the furnace N2 bank having pressure gauge,

PRV, NRV etc.

3. Adjust the flow of N2 to about 3m3/hr and check for gas leakage at all joints

with soap solution; ensure proper flow of water at the outlet.

4. Open the top purging valves first and then the 4-bottom valves one by one

after 5min and then closes them in the sane order.

5. Shut off N2 after 6hrs and pass H2 @ 3m3/hr.

6. After passing H2 @ 3m3/hr, test the gas inside the furnace by collecting it in a

small tube and lighting it, if there is no explosive sound, it indicates that there

is no air furnace and it is safe to switch in the furnace.

7. Light the LPG burner and the H2 at the outlet.

8. Switch on the electrical mains and control switches.

58

Heating schedule:

2000C 24hrs

4003C 24hrs

400-10000C @ 50C/hr

1000-14000C@ 50C/hr

1400- 1430 in one hour.

CONTINUOUS SWAGING MACHINE:

The bar from manual swaging machine is send to this for continuous

swaging to decrease its cross section. It consists of a burner which heats the rod

before it is passed through die, it consists the similar to manual swaging machine

except the drawing operation is done mechanically by the die. Here the changing in

cross section is from 18-9 diameter is done.

Machine Input diameter Output diameter Temperature

Tr-1200 M/c 7 1 6000C

Tr-300 M/c 1 0.3 6000C

Eight-Draft M/c 0.3 0.05 6000C

WIRE DRAWING MACHINE:

Wire drawing is an operation which reduces the diameter and increases the

length of a given rod or wire, without loss of the material by means of pulling through

the die.

We go for this machine to reduce bar of size 1-0 mm 9mm diameter to

1.22mm diameter wire drawing machines. The wire is passed from one pulley to the

other, in between there is a burner to heat the wire before passing through the tungsten

carbide die. Before passing through the tungsten carbide die the wire is passed

through graphite solution which acts as a lubricant and fine surface finishing will

occur .Pointing of the wire is done by potassium nitrate.

FINAL WIRE DRAWING MACHINE:

This machine is similar to wire drawing machine and the process of

operation is also same. But the dies are changed each time to decrease the diameter of

the wire form 1.22-0.82 mm diameter.

59

CONTINUOUS WIRE PICKLING MACHINE:

In this process the object is dipped in a suitable acid to remove surface

irregularities if any present graphite layer is removed. KNO3 is used for pickling.

ANNEALING:

Annealing is done to remove internal stresses present in the wire. It is a

process of heating to elevated temperature, soaking at that temperature for some time

and cooling to room temperature.

BAR AND WIRE DRAWING

The coils of rods (or) bars produced in the hot rolling mill are sent to heat

treatment shop for annealing to remove stresses. After that these are sent to pickling

shop to remove the oxidized surface layer (or) rust and for coating .Generally two

types of coatings are used they are lime coating and poly-case coating for softer and

harder materials. The bars and rods of diameter 12-9 mm are the products of this shop

and wire of very fine i.e. of order of even microns can be drawn. Since the diameter of

wire will decrease after each pass the velocity and length of wire increase

proportionally.

The dies used in this shop are:

1. Tungsten carbide dies.

2. Diamond dies.

3. Compact dies.

Bar and wire drawing shop consists of:

1. Butt-welding machine.

2. Pointing machine.

3. Bull block wire drawing machine.

4. Multi bull-block wire drawing machine.

5. Wet wire drawing machine.

6. Continuous annealing machine.

7. Straighter cum shear machine.

8. Combined wire drawing machine.

9. Shaving machine.

10. Center-less grinding machine.

11. High vacuum wire coating plant.

12. Eddie current testing.

60

BUTT WELDING MACHINE:

There are two butt welding machines. These are used for combining two

separate wires into a long wire for feeding two bull blocks. A number of wires are

taken and are welded to a lengthy wire. The diameter that can be weld by using first

M/C is 14mm. And by second machine 8mm diameter can be welded. The welding

takes place electrically. First the wires are set in the jaws provided. Current is sent

through the jaws so the wires that are in contact at one end gets headed and then wires

are compressed for obtaining a joint between the wires.

POINTING MACHINE:

Before the drawing of the wire, one end of the wires is o be pointed in order

to go through the die easily for initiation. This pointing machine is used for pointing

the end of the wire.

BULL BLOCK WIRE DRAWING MACHINE:

It consists of a tungsten carbide die to reduce the diameter of the wire. The

pointed wire is passed through die and fixed to block which rotates in anti-clockwise

direction. This rotation is helpful in drawing the wire continuously from the die. The

diameter of the wire depends on the diameter of the die used. A lubricant powder

(Peddington 2538 grade) is used during wire drawing. There are four bull block wire

drawing machines. The only difference in this is in their wire drawing sizes only.

Machine

Number

Input Size

In Ø

Output Size

In Ø

1. 14mm 6mm

2. 9mm 3.5mm

3. 4mm 1.5mm

4. 2mm 1mm

MULTI BULL BLOCK WIRE DRAWING MACHINE:

The operation of this machine is similar to bull block wire drawing machine.

But it consists eight blocks with a die each is used for wire drawing. It saves time and

no need to change dies each time after drawing. All the dies are set at one time and

drawing operation is started at a time.

61

WET WIRE DRAWING MACHINE:

The drawing operation of wire is done in the presence of oil as a coolant and

lubricant that is known as wet wire drawing machine.

The lubricant oil used is Castrol oil. There are 21 dies arranged in this in two

columns. In each die the % of elongation is 18. The maximum and minimum

diameters that can be drawn with this machine were 3.0 - 0.02 dia. The dies are made

of tungsten carbide. This machine is used generally for some particular grades like

Maraging steels. The wire produced is either coiled or spooled with the help of

bobbin. The different kinds of machines are:

A) Machine Ø 1.8max - Ø 0.15min

B) Machine Ø0.6max - Ø 0.05min

C) Machine Ø0.25max - Ø0.02min

CONTINUOUS ANNEALING MACHINE:

Specifications:

5 to 0.5m wires can be annealed in this furnace. This furnace is electrically

heated with 18 muffled tubes.

The material of the wire : AIS1310

Speed of the wire : 0-20 m/min.

8 coils are used for the wire dia. of : 0.5 to 5mm

6 Pairs pets are used for wire dia. of : 0.5 to 1mm

4 spools are used for lower dia. wires speed of : paial pet varies from 10-

55m/min.

Temperature maintained is about : 1045-11000C

After the drawing of the wires they may contain stressed and during drawing

the wire may become hard. In order to make it soft and to relive stresses heat

treatment is required.

STRAIGHTNER CUM SHEAR MACHINE:

This is used to make coiled wire into straight bars. First coiled wire is passed

through the roller straightener and the wire is set straight without bends after

straightening this is passed through polishing machine. There is a holding mechanism,

which moves to either be side by pulling the bar at one side and pushing it to other

end. There is a shearing machine to cut the bars at required lengths.

62

COMBINED WIRE DRAWING MACHINE:

Drawing, cutting and polishing can be done. It consists of 8 straightening

rolls out of which four 60 are mechanically operated and while drawing, the

remaining two will also automatically move by the friction between the rolls and bars.

The maximum reduction that can be obtained by this machine is 10%.The maximum

dia. is 20mm.and the minimum diameter that can be drawn is 7mm.In cutting machine

the wire is cut to required length and the wire is sent to polishing machine. Here ever

it gets polished .Solar oil is used as coolant in cutting machine.

Percentage reduction is calculated as: (D1-D2)/100.

Where- D1 is the inlet diameter of the wire.

D2 is the outlet diameter of the wire.

SHAVING MACHINE:

Specifications:

Input size : 9mm

Output size : 4.5mm

Maximum Shaving : 0.125 mm/side.

0.125 mm/whole diameter

Lubricant used : Servo cut 238.

Shaving machine consists of two dies, one die is like bull block machine die

in which some reduction takes place. The second die is a cone shaped die having a

sharp edge which shaves or peel the surface of the material, a slight change will occur

is dia of the wire after shaving .This is mainly used for managing steels and titanium

alloys.

CENTERLESS GRINDING MACHINE:

Specifications:

Grinding wheel dia : 355-405 mm

Speed : 1900m/min.

Revolutions : 1500 rpm.

In lathe machines we are fixing the bar in between the headstock and tail

stock toughing the center of the bar. But in this machine has no fixing at the center, so

63

this is called center-less grinding wheels. This is an automatic charging and

discharging is done automatically.

HIGH VACUUM WIRE COATING PLANT:

The coaters used for wire coating are Ni, Cu, Al etc., the main purpose of

wire coating is to reduce oxidation of metals .The main principle involved in machine

is due to bombardment of metal electrons on the wire causes coating. It consists of

tungsten crucible in which water strips are placed. Above this crucible wire is passed

from one spool to the other. The metal strip in the crucible melts due to induction and

coating takes place. The thickness of coating depends on no. of passes made from

wheel to wheel. All this operation is done in a vacuum of 5x105 cm.

EDDY CURRENT TESTING:

Introduction:

Eddy current testing is based on the principle of Electro-magnetic

induction where in a coil wound around a core carrying current generates eddy current

in a material under inspections. These eddy currents set up are used to identify variety

of physical, structural and metallurgical conditions in electrically conductivity

ferromagnetic metals and metallic parts.

Objectives:

UT detects cracks, seams pits, inclusions heat treatment variations, wall

thickness, coating thickness, coating thickness, electrical conductivity, magnetic

permeability and hardness.

Applications:

Tubing wires, ball bearings spot checks in all types of surface, metal

detection's metal sorting etc.

TUBE SHOP

MIDHANI has started producing seam welded titanium tubes and

supplies are being made for a variety of heat exchanger applications. The equipment

produce welded tubes of 0.5-2.5 mm in wall thickness, 12-40 mm in outer diameter

and in lengths up to a maximum of 18mm.

The Titanium tube plant:

Titanium by virtue of its excellent corrosive resistance and high strength-to-

weight finds application in aerospace, power plant, chemical, petrochemical industries

and in marine applications where highly corrosive environments are encountered.

64

The cost of corrosion in the industry is very high. The application of

titanium tubes provides immense potential for savings in heat exchanger systems

involving corrosive media.

MIDHANI with more than a decade of experience in melting, forging,

rolling of titanium has set up a tube mill to manufacturing titanium tube.

Process for the titanium tubes:

Capability:

Dia. : 12-4 mm.

Wall thickness : 0.5-2.5 mm.

Wall thickness to OD ratio : 1:10 to 1:60

Length : up to 18 mts.

Material : Titanium

1. A Delivery Stand is a double un-coiler for strips for ensuring continuous

production

2. A strip bending and edge debarring unit.

3. A strip end welder and strip accumulator to maintain continuity of production

while jointing two strips.

4. A Ultra Sonic Strip Clearing Unit in which a hot water at 80° c is used as

medium for cleaning the strip. Ultrasonic waves remove the dust on the strips.

5. In Tube Forming Unit there are 8 vertical stands and 6 horizontal stands. Each

stand comprises of 2 stainless steel rolls. One is called bottom roll and other is

top roll. The profile of the rolls is replicated on the strips. The vertical stand

imparts the forms and the horizontal stands for support. After passing through

the 8 vertical stands, the strip is rounded. After the strips get rounded off they

have to be welded. For this, four welding rules and argon (Ar) torch is used.

Tungsten electrodes of 3.2 mm diameter are used. This welding is called TIG

(titanium inert gas) welding. Cooling water facility is required for cooling the

65

torch. After the welding the tube passes through the cooling zone, which has

the gas and water. The gas used mainly to which is used to avoid oxidation.

The tube at the exit of the section has temperature 100°c-200°c depending

upon the wall thickness. The cooling water flow and the cool the production

room the room temperature.

6. In Seam Grinding Unit, the welded portion is given a fine finish.

7. In First Calibration Unit it has two vertical and two horizontal stands. In this

unit, the arc diameter is reduced is reduced to a certain limit so that the final

dimension is obtained in the second calibration stand.

8. The Tube Drawing Unit consists of 24 pairs of nylon blocks for holding and

drawing the tubes.

9. In Cleaning Unit the tube is once again cleaned in hot water at 70°c.

10. A Hot Air Blower is used to blow over a filament where it gets heated up and

removes moisture

11. In Induction Annealing Unit, the annealing is done in a argon atmosphere to

relieve the internal stress which are produced during the drawing. For Ti, the

annealing is done at 600-650°c and for steels it is done at 900-1000°c.

12. In Cooling zone of cooling Unit, Ar atmosphere and water is used for cooling

as described earlier. The exit temperature of the tube is around 70°c and is

further cooled by water to room temperature.

13. The Secondary Calibration Test consists of a horizontal and vertical stand

where the exact OD of the tube is obtained. The OD should be within the

tolerance limit.

14. In Straightening Unit, the tube is straightened and fed into the eddy current

unit.

66

15. The Eddy Current Unit is used to detect the defects in the tube. It has to be

first calibrated by using defect in the tube in the form notches. Then the values

obtained are compared with the standard defects. The number of defects are

counted and recorded.

16. In marking unit the tubes are numbered with respect to grade and dimension

are marked on the surface of the tube.

17. The spray unit works in the conjunction with the Eddy current unit. It sprays

black ink over the length of 100mm over the defected portion. These portions

are later cut.

18. In flying cut off unit, the tubes are cut to the required length the tube is taken

in and fixed by stopper. The trolley moves along with the movement of the

tube and cuts the tube to the required length without disturbing the process.

19. The roll out stands is used to hold the tubes after being cut into the required

lengths.

After the production of the tubes these tubes are tested in the immersion ultrasonic

testing.

IMMERSION ULTRA SONIC TESTING:

Basic Principle:

An ultrasonic pulse passes through the work pieces at the characteristic

sound velocity of that particular material. In the course of this an interaction with the

work piece structure takes place. The corresponding evaluation of the signals received

(amplitude and time of flight) Alloys conclusions to be drawn as to the internal

quality of the test object without destroying it.

Wave mode and Wave Propagation:

With the longitudinal wave the molecular (atoms) oscillate parallel, where as

with the transverse waves they oscillate perpendicular to the propagation axis. The

sound velocity “c” is a material constant mainly depending on the modulus of

67

elasticity and density of the material. With the frequency “f” of the sound wave this

results in the wavelength “λ”,

λ=C/f

λ : wavelength (0101)

C : sound velocity (km/s)

f : frequency (MHz)

Technical implementation:

Electric pulses are generated by the transmitter of the instrument and fed to

the probe where they trigger ultrasonic pulses. At the same time the electron beam

starts with the initial pulse (IP) in the lower left hand corner of the CRT screen. Sound

waves thus reflected and received back by the probe generate the echoes (reflector

echo, back wall echo) displayed on the CRT screen. In this A-scan representation the

echo amplitude of a reflector is shown as a vertical trace and the time of flight or

distance as a horizontal trace. This allows a clear allocation of the sound path “S” to

each individual echo location of reflector, thickness measurement.

S = Ct/2

Where

S : sound path (0101)

C : sound velocity (km/s)

T : time of flight (Us)

In the pulse echo method the sound portion reflected back to the probe are

evaluated. The through-transmission method uses two probes, i.e., one transmitter

pulse another one is the receiver work piece+probe+7 transmitters+7 clocks+7

horizontal sweeps.

Ultrasonic pulses:

For this purpose a piezoelectric element (crystal, ceramic, and polymer) is

used. This transforms electrical energy into sound waves and vice versa. Due to

mechanical damping of transducer element this produce a damped oscillation-The

ultrasonic pulses and on receiving a wave signal, the electric RF pulse. The frequency

of pulse is determined by element thickness. Where-as the pulse length or frequency

of spectrum is determined by element damping.

68

*100%

86 : Bandwidth

fu : Upper cutoff frequency

fl : Lower cutoff frequency

fm : Central frequency

Weak Damping:

Long pulse duration, with distinctive frequency and narrow spectrum (small

bandwidth)is especially suited for flaw elevation according to the DGS method.

Strong Damping:

Short pulse duration, wide spectrum (large bandwidth) high resolution, good

signal to noise ratio especially on coarse micro structure.

Probes:

A straight beam probe transmitted and received sound waves with one

element perpendicular to the surface of sheet metals, forging and casting.

The TR probe contains two elements. The transmitter and receiving function

are separated form on another electrically and acoustically-> 7 test on this work piece

and wall thickness measurements.

The angle-beam probe transmits and receives the sound waves at an angle to

the material surface weld testing, testing of sheets metals, tubes forging.

UTILITIES

Plant utilities include water, fuel, compressed air, steam and other gases like

oxygen and LPG.

WATER:

Water is the most important utility in any production unit. Water is required

for cooling the equipment, drinking, sanitation and other purposes. The average

requirement of MIDHANI is 5800 m3/day. This requirement is met through 450mm

diameter. The storage tank will have two components.

69

RECIRCULATION OF WATER:

Since water is raise commodity now a days and also disposal of large

quantity of water is a problem, recirculation systems have been adopted in MIDHANI

which are more economical and practical, only make- up water is taken from the main

pipe line.

Two separate recirculation systems have been provided for water, one for

contaminated water during usage and other for clean water. The water contaminated

with scales and oils is then treated in a clarifier with chemical dosing and overflow

water is collected in hot well. The hot water is cooled in an induced draught cooling

tower. A similar re-circulating system without a clarifier will handle clean water.

Continuous supply of water is essential for furnaces. During power failure a

separate furnace cooling water main connected to an overhead tank. As soon as there

is a power failure, diesel generator is started manually. There is bound to be some

time gap before the generator is started, and during this time gap the furnaces are

supplied with cooling water from the emergency overhead tank through a pipe line

using a diesel engine. This engine operates one cold well sump pump and one hot well

sump pump. The cold well sump pump supplies cooling water to the furnace and hot

well sump pump, pumps back the water to the tank.

Fire hydrants are supplied water from drinking water line. Water

consumption for drinking and fire hydrants will be around 20m3/ Hr at an average. An

overhead tank of capacity 460m3 is always kept filled for fire hydrants.

STEAM:

Steam is another important plant utility. Steam is needed for heating

various chemicals, rinsing baths and for operating steam ejectors. Steam is used in

heat exchangers as a hot fluid. Steam is required in LPG system for evaporating LPG.

The maximum steam demand in MIDHANI is around 10 tons/Hr. Two boilers supply

the steam required for different purposes. The details of the boilers are given below.

1. INSTANT STEAM GENARATORS:

Model : Vaporize 4000

Type : Water tube boiler

Capacity : 4000 kg‟s/Hr.

Operating pressure : 11 kg/cm2

70

OUTLET STEAM CONDITIONS:

Pressure : 11 kg‟s/cm2

Temperature : 1870 C

Oxygen fraction : 0.98

The efficiency of the boiler is

78% if LPG is used as fuel

80% if oil is used as fuel.

The material of construction of the boiler and tubes is “IS 226” and “BS

3057/3” respectively. Oil is pumped to the boiler by the pump. The burners are air

atomized types which are suitable for both oil and LPG. To create draught in the

boiler, a forced fan with capacity of 6000m3/hr is fitted with necessary mountings.

2. COAL CUM OIL FIRED BOILER:

This boiler is supplied by THERMAX INDIA Private Limited, Pune. The

specifications of the boiler are as follows.

Capacity of evaporation : 6250 kg/Hr from and at 100 on oil

5600 kg/Hr on coal

Outlet steam conditions : 11 kg‟s/ cm2

Temperature : 1870C, 98% dry and 80% on coal.

Efficiency : 80% on coal

70% on oil

The material and construction of tubes are as per “IS 226” and “BS 3057/3”

respectively.

COMPRESSED AIR:

Compressed air is required in a production unit to operate pneumatic valves

and cylinders, solenoid valves and other equipment operated on air.

The compressed air requirement in MIDHANI is met by three compressors

each having a capacity of 1800 m3/hr at a discharge pressure of 7 kg/cm

2. The

compressors are reciprocating, water cooled, and two stage, double acting, electrically

driven type of compressors. The specifications of the compressors are as given below.

71

Specifications:

Free air delivery : 1800m3/hr

Working pressure : 7 kg/cm2 at outlet

No: of cylinders : Four

Diameters & Stroke : 208mm & 125mm

Speed : 975 rpm

Shaft HP : 201 KW

Motor HP : 165 KW

One oil bath type suction filter is fitted in each compressor in the suction

line. Three number of oil and dust separator are fitted and the separators are capable

of filtering the moisture up to 99.5% dry and dust particles up to 5 microns diameter.

72

QUALITY CONTROL AND LABORATORY

Quality control is the regularity process through which measure actual

quality performance, compare it with standards, and act on the difference. The term

quality control includes maintaining of physical, chemistry and mechanical properties

of incoming, on line and going materials of the plant. The product should satisfy the

specification given by the laboratory customers.

The main function of quality control and the laboratory department are:

1. To help the persons in controlling the quality of the product.

2. To check whether the product satisfy the specification laid down by the

customer or not.

3. To carry out development work.

To carry out these functio9ns successfully the QCL has been divided into the

following main sections:

1. Mechanical Testing

2. Metallography

3. Non-Destructive testing

4. Stage Control Laboratory

5. Raw Materials Inspection Cell

6. Workshop.

Mechanical testing section for determining the mechanical properties, whose

facilities includes universal testing machines from Instron Ltd., England, Fatigue

(both normal and high temperature) testing machines from VEB, GDR and Shimadzu,

Japan, Impact testing machines, Hardness testing machines from Japan, Creep testing

machines from France.

The main facilities include 3200X metallography classical Microscope from

MG Olympus., Tokyo, hardness testers from Carl Zeiss, West Germany, Stereo

Microscope from Casl Selss., GDR and complete facilities from sample preparations

for metallography examinations.

Raw Material Inspection Cell for wet chemical analysis facilities includes

Atomic Absorption Spectrometer from various Techtron., Australia, Double-beam U-

V visible Spectrophotometer, Corrosion testing equipment and complete facilities for

wet chemical analysis of material, metals, alloys, aids, oils and water.

Non Destructive testing sections detection both internal and external

discontinuities and has Ultrasonic Crack detection, Eddy current tester, Die Penetrant,

Magnified Electromagnetic cracks detectors etc.,

Stage Control Laboratory (SCL) with on line analytical facilities consists of

computer controlled X-ray fluorescence Spectrophotometer, Optical Emission

73

Spectrometer, C-S analysis from LECD and Nitrogen, Hydrogen, Oxygen

determinations.

Work shop for preparation of specimens for various tests carried out in QCL

which includes various types of Lathes, Drilling machines, Milling machines, Hack

saw and Electric discharge swaging machine.

MECHANICAL TESTING

Mechanical testing is done for obtaining some preliminary indications of the

suitability of a metal or alloy for a specific purpose. In mechanical testing, destructive

methods are given as follows:

1. Tensile testing

2. Hardness testing

3. Impact testing

4. Fatigue testing

5. Creep testing

6. Bend test

7. Erichsen Cupping test

In mechanical testing the test sample are prepared according to the standards

specifications and are tested to cause destructions at the specimen. The product is

assumed to have some properties of the material from which the standard test piece

prepared. The destructive test cannot determine location and type of defect in a

material, but will show difference in the value of the property due to internal defects.

TENSILE TESTING:

In this testing tensile properties such as ultimate tensile strength, yield

strength, percentage elongation, percentage reduction in area are obtained from a

single test specimen.

To carry out this test there are universal testing machines supplied by M/s.

Instron Ltd., England. The capabilities of the machine are:

1. 500 KN- 50,000 Kg Dynamic/25,000 Static.

2. 100 KN- 10,000 Kg Static.

3. 250 KN- 25,000 Kg Static.

In these three machines, it is able to perform tension, compression, bend test

and fracture toughness. Both room temperature tension tests and high tension test are

done.

The specimens practically used to test are usually round, sheet and wire

samples depending upon the nature of the product being to be tested. It is performed

by subjecting the sample to a gradually tensile pull until it breaks.

74

The centre is usually reduced in section to form gauge length before placing

the specimen in the machine, its diameter is measured with a micrometer. The small

„pop‟ marks are made at a distance apart corresponding to the gauge length in width

which the extension is to be measured.

After placing, the specimen is grips tightly the scale load in KN, cross head

to chard speed ratio is selected and then load is applied until fracture take place. The

load and elongation curve is drawn on the chart by the pen recorder.

HARDNESS TESTING:

Hardness is the resistance of a material to permanent deformation. For

metals, this property is a measure of their resistance to plastic deformation. The

equipment in hardness testing are:

1. Brinell Hardness Tester, from FIE, India.

2. Rockwell Hardness Tester, from FIE, India.

3. Vickers cum Brinell Hardness Tester, from Hectert, GDR.

4. Vickers Hardness Tester, from Matuzawa, Japan.

In the Brinell hardness tester, the penetrators to be used are a ball of either

2.5 or 10mm diameter. The load applied varies with the diameter of the penetrators

used. For Ferrous alloys, this formula is 30D2 where D is diameter of the penetrator.

After test has been done, it is necessary to measure the mean diameter of the

impression made on test specimen ball indentor. The measure of the diameter of the

impression is readily accomplished by the use of a graduate viewing at the top of the

machine. After attaining the diameter of impression, the BHN is obtained from the

standard charts, which have already calculated values of different impression by the

formula...

Kg/mm2

Where P is applied load in kg and D is diameter of indentor in mm and d is

the diameter of impression in mm.

The Brinell method is restricted to the material having a Brinell hardness

number as 350 maximum, above the penetrator may deform.

1. The load range is 250 kg‟s to 3000 kg‟s.

2. The maximum test height is 410mm.

3. Depth of the throat is 200mm.

The Rockwell Hardness testing machine is a direct reading testing machine,

means that the depth of impression measures directly the hard number after releasing

measures the load. In this loads are applied i.e. minor and major loads. For conducting

the test steel ball or brale indentor is used. In some times diamond indentor is also

75

used. The hardness number from the dial indicator is taken in types of scales i.e. RC,

RB and RA. For different indentors different major loads are to be applied i.e. steel

ball 100 and brale 150 kg‟s.

The Vickers method applies especially to small, hard and thin specimens.

The penetrator to be used is a diamond on the form of a square based pyramid with an

included angle of 1360 between opposite faces. The impression formed in this test is

in of a square. The lengths of the two diagonals are estimated and the diagonal length

is compared with the standard Vickers hardness number chart, in with the values are

obtained by the given formula:

Kg/mm2

Where P= applied load in kg‟s, D= Diagonal length in mm.

Normally the Vickers cum Brinell tester is used and the HV values is given

to equalized HB values in another chart, where as so many cases are takes the HB

values only.

IMPACT TESTING:

In impact testing the resistance of a metal towards shock is measured by

means of pendulum type machine. There are three impact testing machines, from FIE,

India, conducting both Charpy and Izod impact test.

The pendulum impact testing machine consists of the frames of pendulum,

the frapping device, and the measuring equipment. The test specimens are prepared

according to the standard specification with either „U‟ or „V‟ notches.

In the Izod test, the notch on the specimen should face the pendulum striker.

In Charpy test the specimen rests freely on the supports, the specimen should be

placed in such a way that the notch is a parted to the direction of impact pendulum.

The test specimen is held in between the gripping heads. The pendulum is

raised to the top most position and held by a catch adjustment to give a constant

height of all tests. It is then released and allowed to fall and rupture the specimen

further, there is a dial attached concentrically with the pendulum shaft. The scale is

designed in such that the impact energy absorbed in breaking the specimen can be

read directly in joule.

The notch impact strength is evaluating the energy afforded on fracture of

the sample divided by the original cross-sectional area of the specimen at the notching

point.

76

FATIGUE TESTING:

Fatigue is the term applied to desirable the failure of a metal or an alloy

under repeatedly applied stress which is usually less than that required to cause

fracture on a single application of load. Fatigue of metals is the property by which the

fail are relatively low value of the stress when the stress is repeated.

The axis of rotation is maintained for bending of metal material in normal

and high temperature.

Distance between fulcrum of load L cm (20)

Weight of poise (one side) W kg‟s

Diamond type diameter of test piece d cm

Average bending moment caused by the applied load in downward direction

from the two ends of the specimen with the help of load bearings is kg/cm.

LOADING:

For these entire tests a standard loading is taken considerably. The load is

represented and acted in Newton‟s only. By the beam mechanism the lead will act 10

times to that applied load the acting force is in Newton‟s, so that we have to be taken

that weights from kg‟s to Newton‟s.

Load= Stress*Area (kg’s)

The acting force will be in Newton‟s= Stress*Area*(gravitational force of that

particular place).

It is the force required in Newton‟s. But the beam mechanism it acts to 10

times to the applied force. To obtain actual load is to be divided by 10 times.

For example a round sample of 2mm diameter with 12 kg/mm2 standard

GOST stress is to be tested. Load applied= 12*22*9.81/10=37 N.

STRESS RUPTURE TEST:

The temperature to cause failure or fracture of a material at a given nominal

stress for a constant temperature is called stress rupture. Higher loads are used with

the stress rupture test, than in creep test. For the stress rupture specimen the test is

carried according to the given standards time like 25, 50, 100, 200, 500, and 1000

hours. For stress rupture the time normally taken from 100 minute to up to that

particular time the specimen is to be kept in test. After crossing the standard time is to

be discontinued, whether the specimen breaks below the standard time it is to be

declared as failure.

77

CREEP TEST:

The standard time given for creep testing of different grade specimens and

the time the maximum elongation is measured by the reading on the extensometer.

For each elongation is noted. The elongation must not be equalized to 0.2%, it must

be less than 0.2%.

The creep test measures the dimensional changes which occur from elevated

temperature exposure, while the stress rupture test measures the effect of temperature

on the long time load bearing characteristics.

In this laboratory round samples of 3 to 5mm diameter and sheets sample of

2mm thickness can be tested.

BEND TEST:

A test for ductility is applied by bending the material over a former known

radius through a specified angle. It is conducted for the purpose, of whether any

cracks to be developed while in the usage of different manner.

Sheet material specimen is held in between the round grips, bent first

through 900 to a side, then through 180

0 from side to side until visible cracks are

produced. It is necessary the cracks must not be formed after complete 1800 angle

bends also.

METALLOGRAPHY:

The study of the internal structure of a metal or alloy in relation to its

physical and mechanical properties is called metallography. Metallography or

microscopy consists of microscope study of the structural characteristics of the metal

or an alloy. Metallography examination is usually carried out with the aid of reflection

light in order to investigate the nature such as grain size, shape and distribution of

various cracks and inclusions which have a great effect on mechanical properties of

the metal or an alloy. Lattice features such as grain boundaries slip bands; twin and

cracks are observed in metallography.

The lab consists of the equipment of preparing the sample suitable for the

microscopic study such as belt grinder, disc polishers, electric polisher or cloth and

various solutions for etching.

Microscope suitable for various purposes such as two numbers of classical

optical microscopes with maximum magnification of 1000x, two numbers of stereo

microscope with magnification one special type optical microscope (Axiomay) with

maximum magnification of 3200x.

There is auxiliary equipment for testing and taking photographs of the

structure and alloys of various materials.

78

Micro hardness tester, having square based diamond pyramid indentor for

determining the hardness of any micro constituents present in the structure such as

Austenite, Martensite etc., in steels.

Properties of forge shop, HRM, CRM, PM shop and Titanium shop are tested

here.

HRM Products: Inclusions, grain size and micro structure to be examined in various

products.

Bar & Wire: Micro structure, grain size and depth of surface cracks to be examined

on the missile products.

PM Products: Grains count, porosity and grain size of sintered ingots, thorium

distribution in thoriated Tungsten.

Selection of the specimens for Metallography study:

The first step in specimen preparation is selection and separation of samples

from the bulk material. During specimen sampling one or more representations

specimens should be taken from the material which has been subjected to plastic

deformation, specimens should be taken parallel to and at right angles to the direction

of deformation.

Cross- section or transverse taken perpendicular to the main axis of the

material are prepared in general to reveal the following information.

1. Variation in the structure from center to surface.

2. Distribution of non- metallic inclusions throughout the section.

3. Decarburization of the surface of a ferrous material.

4. Depth of the surface imperfections.

5. Depth of corrosions.

6. Thickness of reflective coating.

Longitudinal sections taken parallel to the main axis of the material reveal in

general the following information:

1. Extent of deformation in the non-metallic inclusions.

2. Degree of plastic deformation as shown by grain distribution.

Documents

Sample Internship Report 1