Quarterly Publication Rs. 20

OCTOBER 2019 Weld 18 Bead 3

Page 2 of 33

AROUND IWS

Know Your President

17th AGM

68th NGC - Images

KNOWLEDGE SHARING

RAW 2019 by IWS Hyderabad Centre

@ MCET Student Forum

Workshop on “Recent

Developments in Welding

Technology” by KSRCT Student

Forum

Seminar on "Advancement of

Welding in Boilers Industries" @

RIT Student Forum

Hands on Training & Workshop on

“Modern Surface Coating

Technology” @ RIT Student Forum

TECHNICAL PAPERS

Effect of ATIG Welding Process

Parameters on the Mechanical and

Microstructure Properties of Super

Duplex Stainless Steel

Microstructural Characteristics of

Shielded Metal Arc Welded

Dissimilar Joints of Armour Steels

THE JOURNAL OF

Regn. No. 41817 / 2002

QUARTERLY PUBLICATION

OCT 2019 Weld: 18 Bead: 3

PRESIDENT

SHRI R PADMANABHAN

Immediate Past President

SHRI S BISWAS

Vice Presidents

SHRI HIMANSHU I GANDHI SHRI S PRABAKARAN

Dr S ARAVINDAN

Hon. Secretary

SHRI N RAJASEKARAN

Hon. Treasurer

Mrs. A SANTHAKUMARI

Members

Dr K Asokkumar Dr A Chandrasekhar

Shri A Maruthamuthu Dr. T Senthil Kumar

Shri G Rajendran Shri V Ganesh Sinkar

Shri M P Jain Dr Shashikantha Karinka

Shi M Kasinathan Shri Gyan Prakash Bajpai

Shri R Easwaran Dr G Padmanabham

Shri S M Agarwal Shri Muneesh Narain

Shri S M Bhat Dr T Prakash

Shri Amit Agarwal Dr S Shanavas

Dr V Balasubramanian Shri Naresh Malli Reddy

Shri T Baskaran Dr Yadaiah Nirsanametla

Dr N Murugan Shri A K Verma

Dr N Raju Dr P Sivaprakash

Editor in Charge Shri S. CHANDRASEKARAN – Editor in Charge

ASSOCIATE EDITORS Shri Praveen Kumar Lakavat Shri R. Arivalagan

CO-ORDINATORS Dr. N Raju Shri A K Verma

PUBLISHED BY

On Behalf of IWS by

Shri N RAJASEKARAN Hon. Secretary (IWS)

INDIAN WELDING SOCIETY INSTITUTIONS BUILDING, KAILASAPURAM, TIRUCHIRAPPALLI – 620 014

INDIA Websites: www.iws.org.in www.iwsevents.com E mail: hiwsindia@gmail.com iwsindiaevents@gmail.com

Page 3 of 33

Shri R PADMANABHAN

PRESIDENT (IWS)

Mr. R Padmanabhan, 58, is Executive Director of the BHEL Tiruchirappalli Complex comprising of High Pressure

Boiler Plant (HPBP) and Seamless steel Tube Plant (SSTP) at Tiruchirappalli, Power Plant piping Unit (PPPU) at

Thirumayam, Piping Centre (PC) at Chennai and Industrial Valves Plant (IVP) at Goindwal in the Punjab. A

Mechanical Engineering graduate of the batch of 1983, from the reputed Alagappa Chettiar Government College

of Engineering and Technology, Karaikudi in Tamil Nadu.

Mr. R Padmanabhan is an engineering professional with over 35 years’ experience in Commercial, Project

Management, Operations, Defence and Aerospace Business, Business Development, Quality & Business

Excellence, Outsourcing and Advanced Technology Products for the Power and Industries verticals of the

company.

Mr. R Padmanabhan joined BHEL Tiruchirappalli as an Engineer Trainee in 1983 and after initial training, was

posted to the Fossil boilers (Commercial) group where he developed his exceptional projects management skills

and set new standards for customer relations, earning a reputation for ensuring customer satisfaction at all costs,

an attribute for which he has been well-known throughout his career. He gained specialized expertise in the

development of cutting-edge technology and products when he subsequently moved to the nuclear products

group dedicated to the manufacture and supply of sophisticated products for Defence and Nuclear Power Plants

applications. Later, He was put in charge of the Business Development Group entrusted with diversification and

entry into new Products markets.

On his elevation to the post of General Manager in 2013, Mr. Padmanabhan was posted to the Project

Management Group at BHEL’s Industry Sector at New Delhi and was subsequently entrusted with the sensitive

Defence Business Portfolio in BHEL’s industry Sector. In 2017, he returned to BHEL Tiruchirappalli to head the

Business Development Group and was then put in charge of the production of Advanced Technology Products

where he was responsible for streaming complex operations and achieving cycle time reduction on an

unprecedented scale.

He later headed the Outsourcing department before his transfer back to BHEL’s Corporate Office at New Delhi in

December 2018 on elevation as GM-in-charge and head of the Corporate Quality and Business Excellence group.

He took charge as head of the BHEL Tiruchirappalli complex in on March 23, 2019. Mr. Padmanabhan is widely

travelled, having visited several countries including the USA, Israel and the Ukraine.

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17th ANNUAL GENERAL

MEETING

The 17th Annual General Meeting of the Society was conducted at the Institutions Building, BHEL

Township, Kailasapuram, Tiruchirappalli – 620 014 on 23rd September 2019 evening. 51 members

attended the AGM.

Since Mr. Subrata Biswas, President (IWS) could not attend the

AGM, Mr. A. Maruthamuthu, Vice President presided over the

AGM and conducted the business session.

Mr. S Singaravelu, Vice Chairman (IWS, SZ) welcomed the Patron

& Executive Director of BHEL, NGC members and members from

various parts of the country for the AGM.

Mr. N Rajasekaran, Hon. Secretary read out the MOM of the 16th AGM and requested the AGM to adopt

the same. Mr. G. Uma Shanker proposed and Mr. R Easwaran seconded the proposal. The AGM

unanimously adopted the MOM.

Mr. N Rajasekaran, Hon. Secretary presented the Annual Report for the year 2018-19. Mr. H I Gandhi

proposed and Dr. T Senthilkumar seconded the report. The report was unanimously adopted by the

AGM.

Hon. Treasurer Mr. G. Rajendran submitted the audited accounts for the year 2018-19. Dr. P

Sivaprakash proposed and Mr. L Ramachandran seconded. The AGM approved and adopted the same.

Mr. G Rajendran, Hon. Treasurer moved the following resolutions in the AGM.

Resolution 1: IWS 2k12 bank account: Ref Note 2: of audited report

Due to lack of transactions, the IWS 2k12 account was

frozen by ICICI Bank, Mumbai branch. Efforts are on to

receive the amount Rs. 692685.10. Already discussions

were held with ICICI Bank. It is proposed to authorise the

Hon. Treasurer, Hon. Secretary and authorised

signatories of the account to discuss with the bank and

bring back the amount to IWS.

Mr. K Sureshkumar proposed and Mr. R. Arunan

seconded. The AGM approved the resolution.

AROUND

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Resolution 2: Write off of unrecoverable balances:

It is proposed to write off of the unrecoverable balances as indicated below, totaling to Rs. 656941.10.

CENTRE / EVENT NAME FINANCIAL YEAR NATURE OF RECEIPT AMOUNT TO BE WRITTEN

OFF

IWS-SZ FY 2013-14 DELEGATE FEES 8000

IWS-SZ FY 2013-14 SPONSORSHIP FEES 10000

IWS-SZ FY 2014-15 DELEGATE FEES 10674

IWS-SZ FY 2015-16 DELEGATE FEES 140

IWS-SZ FY 2017-18 DELEGATE FEES 950

IWS-HQ MAIN FY 2015-16 DELEGATE FEES 77520

IWS-NZ FY 2017-18 DELEGATE FEES 102350

IWS- CHENNAI FY 2017-18 DELEGATE FEES 22800

IWS- COIMBATORE FY 2016-17 DELEGATE FEES 837

IWS 2K14 FY 2014-15 DELEGATE FEES 63436

IWS 2K14 FY 2014-15 ADVERTISEMENT 50000

IWS 2K14 FY 2014-15 SPONSORSHIP 98000

IWS 2K16 FY 2016-17 DELEGATE FEES 69000

IWS 2K16 FY 2016-17 ADVERTISEMENT 87017

IWS 2K16 FY 2016-17 SPONSORSHIP 20000

IWS MEMBERSHIP FY 2015-16 SERVICE TAX 21630

IWS NZ FY 2012-13 TDS 9587

IWS SZ FY 2013-14 TDS 5000

TOTAL 656941

Mr. L D Prabhu proposed and Dr. S. Jaishankar seconded. The AGM approved the resolution.

Mr. N Rajasekaran, Hon. Secretary moved the following resolution.

Resolution 3: Set apart of part of income for purpose of the trust

Out of the income of the trust for the previous year, relevant to the assessment year 2019-20, an

amount of Rs. 36,87,471 which is 75 (%) per cent of the income of the trust for the said previous year,

shall be accumulated or set apart for carrying out the purposes of the trust. The period of set apart

ends on 31/03/2024.

Mr. S Singaravelu proposed and Mr. G Uma Shanker seconded. The AGM approved the resolution.

Then, Mr. A. Maruthamuthu, Vice President addressed the members. In his address he said, “I am

happy in double count one is that in the last two years IWS has successfully conducted two mega events,

the SOJOM at SZ and IWS 2k18 at Mumbai. IWS entered into an MOU with COEWT, PSGTECH,

Coimbatore for conducting the Fresh Engineers Course”. He took pride that during the period the ADD

ON Course for engineering colleges was launched successfully at KSRCT, Tiruchengode and the same

can be spread at all colleges”. Further, he said, “the other reason for my happiness is that IWS will lead

by and able leader Mr. R Padmanabhan, Executive Director, BHEL for the period 2019-21.

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Since Dr V P Raghupathy, Returning Officer IWS Elections 2019, could not come due to personal reasons,

vide E mail he has authorised Mr. G Rajendran to announce the election results. Mr. G Rajendran

informed the results to the AGM for the NGC, Zones and centres (Wherever election was conducted).

The AGM endorsed the results.

Mr. R Easwaran, former Chairman (TC) of IWS installed the office bearers and NGC members. He said,

“I am confident that under the leadership of Mr. R Padmanabhan, the dynamic team will achieve newer

heights and bring laurels to IWS.”

Mr. R Padmanabhan, Executive Director, BHEL assumed charge as

President of IWS for the period 2019-22. Mr. N Rajasekaran took charge

as Hon. Secretary and Mrs. A. Santhakumari, as Hon. Treasurer. Mr.

Himanshu Gandhi and Dr S Aravindhan took over as vice presidents along

with NGC members. Mr. G Uma Shanker, former Chairman, Educational

Committee of IWS offered his felicitations.

Then, Mr. R. Padmanabhan, President addressed the members. During his address he unveiled the

vision for the tenure, as detailed below.

1. Increasing the membership including the industrial corporate

members

2. To vibrate the zones and centers with the support of IWS stalwarts

and experienced members.

3. Training and skill development to school dropout and bring them in the main stream by making

eligible to earn their livelihood.

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4. To encourage the students to take welding as a prime career over blue collar job.

5. To bridge the gap and demand of qualified welding engineers, supervisors and welders of quality

class in various segments, positions and skill to join the different materials for Indian industries

and projects abroad.

6. To help CSR company to spend their CSR earmarked allocated funds under section 135 of

companies act in the area of education, training and skill development through IWS.

7. To create the different module to help the industry to be competitive in the global world and

sharing of welding related knowledge to IWS members and the general beneficiaries of the

society who are in need for the same.

8. Signing the MOU with various international research institute and company to bring the 21st

century the latest technology and know-how at the door steps of MSME enterprises and startups

in India.

He sought the support of all the members to convert the said visions to the reality by working hard and

collectively.

Mr. R Padmanabhan felicitated the outgoing Vice President Mr. A Maruthamuthu and Mr. G Rajendran,

Hon. Treasurer.

Then Mrs. A. Santhakumari, Hon. Treasurer moved the motion to retain

the services of M/s. K. S. GUPTA & CO. as auditor for the year 2019-20.

The AGM unanimously approved the motion. The AGM also accepted the

proposal mooted by Mrs. A. Santhakumari, Hon. Treasurer that the

remuneration for the auditor will be decided by the NGC. Dr. T Senthilkumar proposed and Dr. K

Asokkumar seconded.

It was also resolved by the

AGM that the modified rules

and regulations of the society

will be submitted in the next

EGM / AGM for consideration.

Mr. N Parameswaran,

conducted the proceedings.

The AGM concluded with the

vote of thanks proposed by

Mrs. A. Santhakumari, Hon. Treasurer of IWS. The AGM ended with a dinner.

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Page 9 of 33

KNOWLEDGE SHARING

Inauguration of student forum (IWS) and One day workshop

on “Recent Advances in Welding” - RAW 2019 at MCET, Hyderabad

On 22nd August 2019 , Dr. K. Thyagarajan, Chairman, Indian

Welding Society (IWS), Hyderabad centre has inaugurated the

IWS student forum and one day workshop on “Recent Advances

in Welding” RAW 2019, at Methodist College of Engineering &

Technology (MCET), King Koti Road, Abids, Hyderabad – 500 001.

Dr. S. Venkateshwar, Dean, MCET, Welcomed the gathering. Dr.

A Rajasekhar, Hon. Secretary, IWS, Hyderabad centre and Professor & Head, Department of Mechanical

Engineering, MCET has briefed about the

student forum and “RAW 2019” workshop.

In his address, Dr. Ravinder Reddy, Principal,

MCET has welcomed the initiative taken by

the department and expressed his hope that

students under this forum will get

benefitted by IWS in the form of lectures,

internships and projects.

During the inaugural address Dr. K. Thyagarajan, Chairman,

Indian Welding Society (IWS), Hyderabad centre emphasized the

importance of advanced welding technologies in structural

industry.

Dr. G. Madhusudhan Reddy motivated the students to do

research in the field of welding technology. In his presentation

he has focused on the latest welding technologies and general

challenges in application of these technologies to different

materials. Shri C. V. S Murthy has delivered expert lecture on

various types of advanced welding techniques and used in

aerospace industry. Shri Nagi Reddy inspired the students

regarding the personality qualities and highlighted the uses of

welding in the daily human life.

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Nearly 140

members including

students, faculty

members from

various engineering

colleges from

Telangana and

Andhra Pradesh &

industry personnel

participated and

got benefit from the

workshop.

Dr. P. Prabhuraj,

IWS student forum

Advisor, Associate

Professor, Mech.

Engineering, MCET

proposed vote of

thanks.

Page 11 of 33

SEMINAR ON "ADVANCEMENT OF WELDING IN BOILERS INDUSTRIES" @

RIT STUDENT FORUM

RIT - IWS Student Forum along with the Mechanical Department Association “RIT- Mechanizo”

conducted a seminar on "Advancement of Welding in Boilers

Industries" during 06.07.2019 for the student forum members

and Mechanical Engineering students.

Mr. N. Rajasekaran, Hon. Secretary (IWS) inaugurated the

department association and seminar. In his technical talk on the

theme of the seminar, he elucidated on “Types of Welding

Processes viz,. GMAW, GTAW, SAW, SMAW, FCAW, FSW, etc., and advances in welding of boiler

materials.”

HANDS ON TRAINING AND WORKSHOP ON “MODERN SURFACE

COATING TECHNOLOGY” @ RIT STUDENT FORUM

RIT – IWS Student Forum in association with the Department of

Mechanical Engineering of Ramco Institute of Technology,

Rajapalayam organised a Hands on Training and Workshop on

“Modern Surface Coating Technology” in Surface Engineering for

students those who are pursuing value added course MVA 009 –

Surface Coating Technology and Indian Welding Society Students

Members on 03.08.2019.

The Expert Speaker Dr. M. Adam Khan, Post-Doctoral Research Fellow, University of Johannesburg,

South Africa delivered the lecture on topic “Modern Surface coating Technology” in Surface Engineering

and handled sessions on “hands on training on surface coating technology”. 42 students’ members have

attended the session. The Faculty Advisor of RIT – IWS Student Forum, Mr. S. Maharajan, co-ordinated

the event and welcomed the expert speaker and gathering.

WORKSHOP ON “RECENT DEVELOPMENTS IN WELDING TECHNOLOGY”

BY KSRCT STUDENT FORUM

On 19th August 2019, the KSRCT - IWS Student Forum in association with Department of Mechanical

Engineering, K. S. Rangasamy College of Technology organized

a Workshop “Recent Developments in Welding Technology” at

the college premises.

The workshop conducted at the Seminar Hall, Main building

was inaugurated by Mr. N. Rajasekaran Hon. Secretary (IWS) in

the presence of Mr. S. Singaravelu, Vice Chairman, IWS, SZ. The inauguration started with invocation

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song followed by the welcome address by Dr. K Mohan, Faculty Advisor of KSRCT – IWS Student forum.

Dr. K. Thyagarajah, Chief Executive Officer, K.S.R. Educational Institutions presided over the function.

In his address, he said, “Welding plays a crucial role in manufacturing in all

type of industry. Gaining knowledge on welding will be more helpful for the

young engineers to excel in their fields.”

In his inaugural address, Mr. Rajasekaran gave an overview on the

opportunities available for welding engineers. He also congratulated KSRCT

for offering the Add on Course in Welding with IWS. He also said, “It is giving

immense pleasure to IWS that its services are reaching the budding

engineers. My thanks are to Mr. S Singaravelu for coordinating the course, effectively”.

After the inauguration, Mr. Rajasekaran handled a session on

“Advances in Gas shielded welding processes” covering the basics,

applications and advances in GTAW, GMAW and plasma welding

processes.

Post lunch, Mr. S. Singaravelu made a technical presentation on

“Advances in Flux Shielded welding processes”. The lecture encompassed the applications of SMAW

and SAW processes and the basics and advances also.

In the evening, Mr. S Singaravelu distributed the certificates to the

participants in the presence of Mr. Rajasekaran and Dr Mohan.

The workshop was coordinated by Dr. K. Mohan, Professor & Faculty

Advisor, IWS student Forum and Mr. R. Prakash, Assistant Professor,

K. S. Rangasamy College of

Technology. 60 student

members from K. S. Rangasamy college of Technology actively

participated in the free workshop. The workshop concluded with

the vote of thanks by Mr. Karthikeyan, Assistant Professor, K. S.

Rangasamy College of Technology.

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EFFECT OF ATIG WELDING PROCESS PARAMETERS ON THE

MECHANICAL AND MICROSTRUCTURE PROPERTIES OF SUPER DUPLEX

STAINLESS STEEL

A. Arun Mani*& Dr. T. Senthil Kumar **

*Research Scholar, Department of Mechanical Engineering, Anna University Tiruchy

**Professor, Department of Mechanical Engineering, Anna University Tiruchy

ABSTRACT

In this investigation of super-duplex stainless steels (UNS S32750) by Activated

Tungsten inert gas welding (ATIG) using super duplex stainless steel fillers. In

recent years, very high strength, corrosion resistive UNS 32750 super duplex

steel is being used in chemical industries and marine sectors for manufacturing

lifting equipment and Cryogenics applications. Activated Tungsten inert gas

welding (ATIG) is a fusion welding methodology which is being successfully

used to join super duplex stainless steel material. In this investigation, ATIG

welding was used to weld 32750super duplex stainless steel material, by

fluctuating vital process parameters such as torch travel speed, welding

current and welding voltage. After welding, the test samples were non-

destructively tested to ensure no defects and test samples were prepared for

micro structural examinations and ferrite content measurements. The root

region had complex microstructure because of the repetitive heating of the

zone during different weld layers. It was observed that at low heat input

desirable microstructure was formed. Also the presented results reported the

effect of filler metals on strength and toughness during the multi-pass welding.

Using response surface methodology, the ATIG welding process parameters

were optimized for the improvement of tensile and impact strength using

appropriate filler wire without obtaining any deleterious phases.

Keywords: Super Duplex Stainless Steel, Activated Tungsten Inert Gas (ATIG),

Microstructure Analysis.

1.0 INTRODUCTION

Super-duplex stainless steels present excellent combination of mechanical and corrosion

resistance, due to their strict composition control and ferrite austenite phase balance. This

balance may however be disturbed during welding in both the fusion and HAZ due to the rapid

cooling rates and may lead to loss of the good corrosion and mechanical properties of the

weldments. All the data have been collected through various literature surveys and journals. The

required proposed welding procedure specification is prepared to conduct the welding test. Two

experiments are carried out to analyze the issues.

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One weldment by argon and another element by argon with 2% nitrogen mixture as inert gas by

Gas Tungsten Arc Welding process. Various tests will be carried out on the welded test specimen

and the results will be analyzed. Duplex Stainless Steels (DSS) combine corrosion resistance and

high mechanical strength. They are often used for applications that require higher resistance to

chloride stress corrosion cracking, pitting, inter-granular attack and crevice corrosion than

Austenitic Stainless Steels (ASS). Applications include components for hydro-processing units,

sour water strippers, crude and amine units, brackish water piping, fuel gas piping and marine

equipment. Higher yield strength than ASS is an attractive property which results in significant

material savings during design by reducing the required wall thickness. Thermal conductivity is

superior to ASS while thermal expansion is comparable with that of carbon steel which reduces

the amount of distortion and welding residual stresses.

The SDSS are more highly alloyed than the other duplex grades and can withstand more

aggressive environments. The most commonly used SDSS is grade UNS S32750 which contains

about 25 % Cr, 7 % Ni, 4 % Mo and 0.24-0.32 nitrogen as alloying elements. Various product forms

are typically used in the oil sand industry including welded and seamless piping, forgings, fittings,

and plate.

These steels have a duplex microstructure which contributes to their high strength and high

resistance to stress corrosion cracking. Duplex steels offer high resistance to uniform and local

corrosion because of their high content of nitrogen, chromium and molybdenum. Duplex

stainless steels have good weldability. There are three groups of duplex stainless steels that

include the following steels Lean Duplex, Standard Duplex and Super Duplex. The most widely

used of the duplex grades is duplex 2205. However, the super duplex steels like 2507 are excellent

for servicing severe corrosive environments, such as offshore and marine applications. Lean

duplex 2101 is available as an economic alternative to 300 series stainless steels.

Stainless steels are iron-base alloys containing 8–25 % nickel and more chromium than the 12 %

which is necessary to produce passivity but less than 30 %. The steels resist both corrosion and

high temperature. Stainless steels can be divided into five types as Ferritic, austenitic,

martensitic, duplex and precipitation-hardening. Ferritic stainless steels are widely used due to

the fact that their corrosion resistance is higher at room temperature and they are much cheaper

than the other stainless steels. Ferritic stainless steels contain 16-30 % Cr within their structures

in respect of addition of the alloy element. This type of the steel can be shaped easily and resist

atmospheric corrosion well and thanks to these characteristics, it has a wide range of application

in architecture, interior and exterior decoration, kitchen utensils, manufacturing of wash boilers

and drying machines, food industry, automotive industry, and petrochemical and chemical

industries.

Austenitic-stainless steel is preferred more than other stainless-steel types due to easiness in

welding process. Then, some negative metallurgic changes are taken into consideration in

welding of the steels. These are given as; delta ferrite phase, sigma phase, stress-corrosion

Page 15 of 33

cracking, chrome–carbide precipitate between grain boundaries at 450–850 °C of Cr–Ni austenitic

steels such as 18/8 joined by fusion welding in long waiting time.

Stainless steels can generally be welded with all methods of fusion welding and solid state

welding. Out of the fusion welding methods, electric arc welding, submerged arc welding, MIG,

TIG, Plasma welding, electron beam welding, resistance welding, and laser welding etc. are

widely used. In the fusion welding methods for joining the stainless steel, brittle intermetallic

compounds phases are produced in the fusion zone, which reduces the strength of the welding

joint. However, in the TIG joining of stainless steel, because these phases are reduced, it improves

the performance of the stainless steel joint. Super Duplex UNS S32750 has excellent corrosion

resistance in a wide variety of corrosive media making it ideal for use in environments exposed

to the harshest chemical conditions. It has outstanding resistance to pitting and crevice corrosion

in seawater and other chloride containing environments, with Critical Pitting Temperature

exceeding 50 °C. Compared to austenitic and 22 % Cr duplex stainless steels, UNS S32750 is of

higher strength and even more suitable in situations where it will be exposed to extremely high

stresses. This combined with its excellent ductility and impact strength at both ambient and sub-

zero temperatures further increases its appeal as the ultimate super duplex grade.

High resistance to abrasion, erosion and cavitation erosion combined with excellent resistance to

stress corrosion cracking in chloride containing environments makes UNS S32750 perfect for use

in the Oil and Gas Industries where subsea equipment is subject to some of the harshest chloride

containing conditions in the world. Stainless steel Super Duplex 2507 is designed to handle highly

corrosive conditions and situations were high strength is required. High molybdenum, chromium

and nitrogen content in Super Duplex 2507 help the material withstand pitting and crevice

corrosion. The material is also resistant to chloride stress corrosion cracking, to erosion corrosion,

to corrosion fatigue, to general corrosion in acids. This alloy has good weldability and very high

mechanical strength. UNS S32750 is listed in NACE MR 01 75 for sour service for its suitability of

use for oilfield equipment where sulphide stress corrosion cracking may be a risk in hydrogen

sulphide (sour) environments. UNS S32750 is also ASME Approved for Pressure Vessel

applications

2.0 MATERIALS AND METHOD

In the paper, UNS 32750 grade super duplex stainless steel of thickness 10 mm was selected as

the base material. Using abrasive cutters, they were cut to 200 mm in length and 140 mm in

breath. The base material was cleaned using acetone for dust and grease removal. The base

material microstructure was studied using optical microscope at 100 x magnification. The

microstructure samples were polished using emery sheets with grits varying from 220 to 1200.

The optical microstructure revealing the austenite and ferrite structure was examined and

indicated in Fig 1.

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Fig 1. Base Material Microstructure Displaying a Combination of Ferrite and Austenite

Fig 2. Activated Tungsten Inert Gas Welding (ATIG)

S32750 combines high tensile and impact strength with a low coefficient of thermal expansion

and high thermal conductivity. These properties are Suitable for many structural and mechanical

components. The low, ambient, and elevated temperature mechanical properties of S32750

sheet and plate are shown below. All of the test data shown are for samples in the annealed and

quenched condition. S32750 is not recommended for applications which require long exposures

to temperatures in excess of 570 °F because of the increased risk of a reduction in toughness. The

data listed in this document are typical for wrought products and should not be regarded as a

maximum or minimum value unless specifically stated. Welding of 300 series usually requires

preheat and post-weld heat treatment to minimize stress that can lead to cracking. The chemical

compositions and physical properties of both steels were given in Table 1 & 2 respectively.

Table 1. Chemical composition of super duplex stainless steel S32750

Elements C Cr Cu Mo Mn N Ni P S Si W

Minimum - 24.0 - 3.00 - 0.24 6.00 - - 0.20 0.50

Maximum 0.030 26 0.50 5.00 1.20 0.32 8.00 0.035 0.020 0.80 1.00

Page 17 of 33

Table 2 Physical properties of super duplex stainless steel S32750

Density (Kg.m-1) 7810

Magnetic Permeability 33

Young’s Modulus (N/mm2) 199 x 103

Specific Heat, 20°C (J.Kg-1.°K-1) 475

Fracture Toughness, Kq (MPa.m) 475

Specific Electrical Resistance, 20°C (µO.m) 0.80

Thermal conductivity, 20°C (W.m-1.°K-1) 14.2

Mean coefficient of thermal expansion, 20-100°C (°K-1) 11.1 x 10-6

Table 3 Mechanical properties of super duplex stainless steel S32750

0.2% Proof Stress 550 N/mm2

Tensile Strength 800 N/mm2

Elongation, 5.65√S0 25%

Reduction of area 45%

Hardness (Brinell) <270

Impact Strength (Room Temp) 80J

Impact Strength (-46oC) Longitudinal 45 J (35 J min)

Here the mechanical properties of super duplex stainless steel had been shown in Table 3.

2.1 Corrosion Resistance

The high chromium and molybdenum content of Super Duplex makes it extremely resistant to

uniform corrosion by organic acids like formic and acetic acid. Super Duplex also provides

excellent resistance to inorganic acids, especially those containing chlorides.

The pitting Resistance equivalent of Super Duplex, calculated by PREN = Cr + 3.3 Mo + 16 N, will

exceed 40 in most material forms.

3.0 DIMENSION OF WELDING MATERIAL

In this investigation the dimension taken as 200mm length, 140 mm width and 10 mm thickness.

By using the above dimensions the super duplex stainless steels plates were used to fabricate the

joints. After the fabrications tensile test and micro structure specimens were prepared by using

wire cut electrical discharge machine. Eighteen plates had been machined and by that nine joints

has been joined by using Activated Tungsten Inert Gas Welding (ATIG).

Page 18 of 33

4.0 RESULTS AND DISCUSSIONS

4.1 Mechanical Properties

According to ASTM E8/8M standards, the tensile test specimens were prepared and subjected to

tensile failure tests. Micro hardness at the joint region was measured using Vickers micro

hardness testing equipment. In the weld centre, at three different regions, the micro hardness

measurement was done and the average of the three was recorded to be used for further

evaluation. The tensile strength and the weld region micro hardness of the super duplex steel

joints fabricated with the activated tungsten inert gas welding process parameter value

combinations are shown.

Here for finding the mechanical properties several trials had been carried out and finally the

optimum results of tensile strength, yield strength and elongation were found. For finding the

tensile test results ASTM/E8 had been carried out for nine joints. Here the maximum and

minimum of tensile strength, yield strength and elongation has been listed below.

Table 4 Mechanical properties of Super Duplex Stainless Steel (S32750)

Specimen Tensile Strength (MPa) Yield Strength (MPa) Elongation (%)

1 853.99 697.57 24.67

2 854.25 698.17 24.15

3 854.75 700.63 23.34

4 870.04 718.02 20.90

5 871.54 720.39 21.65

6 870.96 719.50 21.05

7 881.76 756.17 17.47

8 880.96 755.80 18.25

9 870.04 718.02 20.90

4.2 MICROSTRUCTURE RESULT

The investigation revealed that the microstructure as well as the impact property of the weld

metal was significantly affected by the heat input and filler wire. Concerning the filler metal.

Super duplex stainless steel welding by Activated Tungsten inert gas welding (ATIG) the various

parameter. For finding the metallurgical properties METSCOPE-1A Microscope equipment had

been used. The microstructure revealed elongated grains of austenite in a matrix of ferrite. The

microstructure revealed coarser interdendritic chromium-carbide precipitation. The

microstructure revealed fine interdendritic of chromium-carbide precipitation.

Base: The microstructure revealed elongated grains of austenite in a matrix of ferrite.

Page 19 of 33

HAZ: The microstructure revealed coarser interdendritic chromium-carbide precipitation.

Weld: The microstructure revealed fine interdendritic chromium-carbide precipitation.

Microstructure of Base, Weld and Heat affected Zone of SDSS 32750 plates are shown in Fig 4.1

Here for studying the micro structural characteristic due to the effect of activated tungsten inert

gas welding on the super duplex stainless steel several specimens had been taken and finally

three optimized process parameter values were subjected to microscopic evaluation

Fig 3 (a) Microstructure of Base, Weld and Heat Affected Zone for 40 W heat input

Fig 3 (b) Microstructure of Base, Weld and Heat Affected Zone for 60 W heat input

Fig 3 (c) Microstructure of Base, Weld and Heat Affected Zone for 80 W heat input

From the above characteristics the Fig 3(a) studies indicates the microscopic structure of the base

material of UNS 32750 super duplex stainless steel material which remained unaffected during

the thermal cycles which were induced during welding. Fig 3 (b) shows the heat affected zone

which has been slightly coarsened during the welding process. Fig 3 (c) indicates the weld region

microstructure, where platelet elongation was observed.

Page 20 of 33

5.0 CONCLUSIONS

In this paper, enhancement of mechanical aspects of UNS 32750 super duplex stainless steel

joints, by optimizing welding process parameters of ATIG welding has been conducted. The

information obtained from the investigation is being summarized as follows

At 150 W heat input a better microstructure, micro hardness and tensile properties is

achieved

Higher tensile strength of 881.76 MPa and yield strength of 156.94 MPa were formed at

150 W heat input.

Interaction and perturbation plots showed that variation in gas flow rate had greater

influence on joint properties than torch travel speed and weld current. Microscopic

evaluation of joints indicated grain coursing in heat affected zone and platelet elongation

in weld zone.

REFERENCES

1. Sarlak H, Atapour M, Esmailzadeh M. Corrosion behavior of friction stir welded lean duplex stainless steel.

Materials & Design. 2015;66:209-16.

2. Bettahar K, Bouabdallah M, Badji R, Gaceb M, Kahloun C, Bacroix B. Microstructure and mechanical behavior

in dissimilar 13Cr/2205 stainless steel welded pipes. Materials & Design. 2015;85:221-9.

3. Ramkumar KD, Thiruvengatam G, Sudharsan S, Mishra D, Arivazhagan N, Sridhar R. Characterization of weld

strength and impact toughness in the multi-pass welding of super-duplex stainless steel UNS 32750. Materials

& Design. 2014;60:125-35.

4. Kang DH, Lee HW. Effect of Different Chromium Additions on the Microstructure and Mechanical Properties

of Multipass Weld Joint of Duplex Stainless Steel. Metallurgical and Materials Transactions A. 2012;43:4678-

87.

5. Ramkumar KD, Mishra D, Raj BG, Vignesh M, Thiruvengatam G, Sudharshan S, et al. Effect of optimal weld

parameters in the microstructure and mechanical properties of autogeneous gas tungsten arc weldments of

super-duplex stainless steel UNS S32750. Materials & Design. 2015;66:356-65.

6. Karlsson L, Börjesson J. Orientation relationships of intragranular austenite in duplex stainless steel weld

metals. Science and Technology of Welding and Joining. 2014;19:318-23.

7. Kim S-T, Jang S-H, Lee I-S, Park Y-S. Effects of solution heat-treatment and nitrogen in shielding gas on the

resistance to pitting corrosion of hyper duplex stainless steel welds. Corrosion Science. 2011;53:1939-47.

8. Tan H, Jiang Y, Deng B, Sun T, Xu J, Li J. Effect of annealing temperature on the pitting corrosion resistance of

super duplex stainless steel UNS S32750. Materials characterization. 2009;60:1049-54.

9. Wessman S, Pettersson R, Hertzman S. On Phase Equilibria in Duplex Stainless Steels. steel research

international. 2010;81:337-46.

10. Sadeghian M, Shamanian M, Shafyei A. Effect of heat input on microstructure and mechanical properties of

dissimilar joints between super duplex stainless steel and high strength low alloy steel. Materials & Design.

2014;60:678-84.

Page 21 of 33

MICROSTRUCTURAL CHARACTERISTICS OF SHIELDED METAL ARC WELDED DISSIMILAR JOINTS OF ARMOUR STEELS

1S. Abhijith, 2V. Balasubramanian, 3S. Malarvizhi, 4A. Hafeezur Rahman &5V. Balaguru

1,2,3 Centre for Materials Joining and Research (CEMAJOR)

Department of Manufacturing Engineering, Annamalai University, Annamalainagar

4,5 Combat Vehicle Research and Development Establishment (CVRDE), Avadi, Chennai

ABSTRACT

The life expectancy of high strength and high hard armour grade steels has become

limited due to the prevalence phenomenon of heat affected zone (HAZ) softening and

hydrogen induced cracking (HIC). The higher the hardness and strength of armour

grade steel, the greater is the difficulty in making welds due to the presence of higher

carbon content and higher carbon equivalent number which makes the steel

susceptible to HIC and HAZ softening. Hence, the microstructural characteristics of the

dissimilar weldments were analysed on the basis of micro hardness and

microstructural studies. A comparative study has been made between weldments

obtained using three electrodes namely low hydrogen ferritic (LHF), austenitic

stainless steel (ASS) and duplex stainless steel (DSS) electrodes. The joints fabricated

using LHF electrodes showed wider HAZ whereas the joints fabricated using ASS

electrodes showed narrow HAZ and DSS joint showed moderate HAZ due to the

difference in weld thermal cycle as well as their intermixing with the base metal during

their fabrication.

Keywords: Armour steel, shielded metal arc welding, dissimilar joint, microstructure,

microhardness, HAZ

1.0 INTRODUCTION

The higher overall weight of Armoured Tracked Vehicles (ATV) has forced the designers to

develop Ultra-High Hard Armour (UHA) steel despite of currently used Rolled Homogenized

Armour (RHA) steel. The properties of these steels are distinct which are obtained from their

composition and special heat treatment processes – quenching and tempering (Q&T) with an

impressive ballistic behavior in terms of deformation capacity and resistance to multiple impacts.

Q&T steels dominates in ductility and notch toughness which makes them suitable where specific

strength is desirable [1]. Hydrogen induced cracking (HIC) and the development of mushy zone in

the heat affected zone (HAZ) are the situations that need attention while welding. These steels

are predominantly welded using conventional welding processes and hence demands proper

precaution during welding to avoid premature failure of the weldments.

Quenched and tempered steels are prone to HIC in the soft zone. The susceptibility of cracking is

attributed to hardness and microstructure of the steel, magnitude of tensile residual stresses and

Page 22 of 33

the level of diffusible hydrogen. The increase in solubility of hydrogen at higher temperatures

enables the individual hydrogen atoms to diffuse through the metal and gradually recombines to

form hydrogen molecules. The steel becomes brittle and fracture due to the pressure associated

with the hydrogen molecules within the metal. Hence, proper filler metal selection, welding

process and often pre- and post-heating of the weldments are essential to avoid hydrogen

embrittlement post welding [2].Austenitic stainless steel (ASS) finds demand for the welding of

high hardness armour steel due to its higher solubility of hydrogen in austenitic phase. The service

requirements includes good resistance to cold cracking and hot cracking for which these steels

are well established. Hence, these steels are manipulated to weld ultra-high hard armour steel

[3]. The use of stainless steel filler for a non stainless steel base metal must be avoided as ASS

filler are much more expensive. Currently, the development of low hydrogen ferritic steel (LHF)

consumables having no hygroscopic elements are preferred for welding high hard armour steels

[4,5].The majority of the armour fabrication is performed by fusion welding process due to which

they exhibit HAZ softening when exposed to weld thermal cycles and alters the ballistic

performance required for the military vehicle application. The softening characteristics not only

depends on the weld thermal cycle but also the kinetics of the phase transformation and the

chemical composition of the steel employed. Recent studies reported that the HAZ softening is

the least in SMAW process for the high strength armour grade steels [6].

Armour grade Q&T steels have been widely fabricated using SMAW process and demands high

welding quality and proper selection of welding consumables. Apart from these technical as well

as economic aspects of dissimilar weld fabrication of armour grade steels are indispensable.

Hence, in this investigation an attempt has been made to compare the microstructural

characteristics of armour grade Q&T steel dissimilar joints fabricated by SMAW process using

ASS, LHF and DSS electrodes.

2.0 EXPERIMENTAL PROCEDURES

The base metals (BM) used in this investigation are RHA and UHA steel. The microstructure of

both the BM exhibits tempered martensite (Figure 1). Rolled plates of 10 mm thick BM were

sliced into the required dimensions (300×150 mm) by abrasive cutters and grinding. Single ‘V’

butt joint configuration, as shown in Figure 2, was prepared to fabricate the joints by SMAW

process. The initial joint configuration was obtained by fastening the plates in position using tack

welding. The direction of welding was normal to the rolling direction. All necessary care was

taken to avoid joint distortion and the joints were made after holding the plates in a welding

fixture. ASS, LHF and DSS consumables were used to fabricate the joints. Vacuum spectrometer

(ARL Model: 3460) was used to study the chemistry of the weld metal (WM) and BM. Sparks were

ignited at various locations of the weld region and their spectrum was analysed for the estimation

of respective alloying elements. The chemical composition and mechanical properties of the BMs

and WMs are presented in Table 1 and Table 2. The process parameters used in the fabrication

of the joints are given in Table 3.

Page 23 of 33

The microstructure analysis of the weldments were carried out using a light optical microscope

(Make: MEIJI, Japan; Model: ML7100). The weldments were sliced in transverse sections and the

specimens for microstructural and micro hardness analysis were extracted from the weldments.

The specimens were ground and polished using SIC abrasive papers and fine polished upto 1µm

using velvet cloth. The specimens were then etched with 2% nital reagent to reveal the

microstructure of the weld, BM and HAZ regions of the LHF weldments. Aqua regia and Kalling’s

reagent was used to reveal the microstructure of the ASS weld and DSS weld regions respectively.

3.0 RESULTS

3.1 Macrostructure

The macrograph of the joints at transverse cross-section and at the top surface of the weldment

is furnished in Figure 3. Comparing the width of the fusion zones of three joints, DSS joints are

having moderate width whereas ASS joints having the lowest and LHF joints having the highest.

A similar trend has been followed in the case of HAZ also for all the three cases. The weld defects

such as lack of penetration, lack of side wall fusion, porosity were absent in all the three

weldments. The top surface macrograph also depicts fabrication of defect free joint. In Table 4 it

shows the quantitative analysis of the different zones from top to bottom at the transverse cross

section of the weldment. The size of the WZ and HAZ were calculated in the form of area in which

LHF joints shows maximum WZ area of 210.6 mm2 whereas ASS joint shows the lowest WZ area

of 142.8 mm2.

3.2 Microstructure

The micrographs of the joints at various region of both UHA and RHA are depicted in Figures 4-6.

The microstructural analysis was performed at different location. From the micrographs, it is well

comprehended that the entire joint invariably consists of three distinctive regions. They are weld

metal (WM) region, coarse grain heat affected zone (CGHAZ) and fine grain heat affected zone

(FGHAZ).

The WM region of the ASS joint unveils a skeletal delta ferrite in the plain austenitic matrix (Figure

4(a)) and the DSS joint discloses a regular delta ferrite in the austenitic matrix (Figure 5(a)) and in

contrast the LHF joint revealed small ferrite plates entirely in the matrix recognized as acicular

ferrite morphology (Figure 6(a)). The microstructure of the different regions for the weldments

are presented in Figures 4-6.

The microstructural analysis of FGHAZ invariably indicates a hardened region of untempered

martensite in all the joints. The ASS joint has a finer untempered martensite compared to DSS

and LHF joints in both UHA and RHA. Although, LHF joint exhibits a coarser untempered

martensite than the DSS joint in the FGHAZ. A similar trend as that in the case of FGHAZ was

absent in the CGHAZ region of all the joints.

Page 24 of 33

Away from the weld zone specifically the CGHAZ, all the joints reveal tempered martensite. The

micrograph of CGHAZ of DSS joints shows a fine tempered martensite in both UHA and RHA when

compared to other joints. In both UHA and RHA of ASS joint it shows a coarser tempered

martensite. The CGHAZ and FGHAZ of LHF joint in both UHA and RHA invariably shows coarser

tempered and untempered martensite respectively.

3.3 Micro hardness

The hardness across the weld cross-section was measured using a Vickers microhardness testing

machine. The micro hardness values for BMs, weld zones and HAZ were measured. The micro

hardness plot is displayed in Figure 7. The micro hardness (mean value) of the unwelded base

metal are 400 HV and 590 HV for RHA and UHA respectively. In spite of that the DSS joint shows

355 HV and LHF joint exhibits 350HV whereas ASS indicates the lower hardness of 240HV in their

respective weld metal region. The values of the hardness in FGHAZ of the joints are found to be

higher than those of the BMs. The values in this zone of ASS, LHF and DSS are 770 HV, 680 HV and

750 HV for UHA and 430HV, 580 HV and 590 HV for RHA respectively. The values in CGHAZ of ASS

joint are 395HV and 680HV in RHA and UHA respectively and shows higher hardness in the CGHAZ

of UHA.

4.0 DISCUSSION

This section discusses and comprehends the inferences of the above results. The adoption of DSS

electrode for welding armour grade steels was to intensify both toughness and the transverse

tensile properties of the joint. However, there is a difference in the dilution of the weld metal

with base metal.

4.1 Effect of Welding Consumables on Macrostructure

The crystal structure and the phases present in the weld metal plays an important role in the

fusion of weld metal to the base metal. However, outstanding mechanical and metallurgical

properties are attained if both weld metal and base metal consist of identical crystal structures

as well as phases. The armour grade steels obtained from special heat treatment processes –

quenching and tempering (Q&T) consists of tempered martensite. Hence, the steel is a

martensitic steel but they are also comprehended as ferritic steels. Delta ferrite is a residual

structure formed at high temperature and possess low temperature brittleness and minimum

solubility of carbon due to the shape of its atomic lattice. Also, ferrite structure are desirable in

all the weld structures as they serves proportionally higher strength and hardness [7].

The major constraint in welding armour grade steels is the presence of hydrogen in WM which

decreases the mechanical properties of metals. The formation of porosity, embrittlement and

cold cracking are connected with the presence of hydrogen in the WM. The favorable remedy is

to employ LHF consumables which virtually prevents the introduction of hydrogen in WM and

moreover increases the intermixing of weld metal and base metal substantially since, both weld

metal and base metal have similar crystal structure. But, in the case of ASS joint the intermixing

Page 25 of 33

is limited due to the difference in the phases and crystal structure. Hence, the weld joint

fabricated using ASS electrode will exhibit a distinct interface between weld metal and base

metal.

Duplex stainless steel consist of equal amount of austenite and ferrite phases furthermore a

suitable substitute for ASS and LHF consumable where both toughness and strength is a

challenge. There is a considerable amount of reduction in austenitic phase in the WM due to

their chemical composition. At high temperature there is complete formation of ferrite

undergoes grain growth thereby upon cooling austenite is formed along the ferrite grain

boundaries with a plate morphology [9]. The higher Cr content stabilizes the ferrite phase and

low Ni reduces the austenite phase thereby exhibiting equal amount of two phases. These steel

have higher strength than ASS and higher toughness than ferritic steels [10,11]. Hence, the weld

interface and the width of the weld zone is in-between the weld zone of LHF and ASS.

4.2 Effect of Welding Consumables on Weld Metal Microstructure

It is well known that the presence of austenitic phase in WM plays an important role in increasing

the toughness in WM. This is aided by the higher nickel content which improves the toughness

by reducing brittle ferrite phase and stabilizing the austenite phase [12]. The alloying contents of

Mn and Ni are very important in the solidification process in high strength steels [13,14]. The

primary solidification product in WM is delta ferrite which is transformed directly from the

molten metal. The delta ferrite at the core of the dendrites, which form at the beginning of

solidification, is very rich in chromium. However, the chromium content goes on decreasing as

the solidification proceeds. Proper control of the amount of delta ferrite in welds is very much

essential and critical. The higher amount of delta ferrite in welds tends to reduce the ductility

and toughness [15].

The WM chemistry of ASS shows low Cr (20 wt%) than DSS (25 wt%). The considerable increment

of Ni in ASS (9 wt%) than DSS (6.9 wt%) was observed. This difference in WM chemistry of Ni and

Cr in ASS and DSS joints has a great influence on the microstructural features. Thus ASS joints

have austenitic phase with a regular network of skeletal delta ferrite whereas DSS joints exhibits

homogenous mixture of regular delta ferrite in austenitic matrix.

4.3 Effect of Welding Consumables on Heat Affected Zone Microstructure

The microstructure in the HAZ is primarily a function of the thermal cycle imposed by the welding

process as well as chemistry of the BM. The weld thermal cycle is a function of heat input and the

thermal conductivity of the material [17]. The thermal conductivity of the armour grade steels

are generally lower for which they exhibits wider heat affected zone during fusion welding

processes. Moreover, the hardness of the HAZ is also a function of thermal cycle as well as the

carbon equivalent number. The thermal cycle plays an important role in altering the

microstructure of the HAZ during fusion welding which in turn alters the mechanical properties

of the HAZ.

Page 26 of 33

In fusion welding process of ferritic/martensitic steels, the joints invariably shows three distinct

regions of HAZ namely CGHAZ, FGHAZ and ICHAZ. The CGHAZ is near to the weld metal whereas

FGHAZ is away from weld metal and ICHAZ being observed in-between FGHAZ and BM. During

fusion welding process HAZ undergoes heat treatment cycle which assists this zone for

microstructural transformation. The armour grade steels used in Q &T form, transforms to

untempered martensite in HAZ during high heat input process such as fusion welding. Also, the

cooling rate in the different zones of HAZ alters the size of the grains resulting in coarser grains

near to fusion zone and finer grains away from fusion zone.

4.4 Effect of Welding Consumables on Micro hardness

In fusion welding process, the mechanical properties in HAZ can drastically differ from the

unaffected BM. This difference influenced by the chemical composition and the thermal cycle

imposed by the welding process. It has been reported that HAZ softening occurs during the

welding of Q&T steels [16]. The presence of soft zone in a welded structure alters the mechanical

properties and limits armour application [17].

In the present study a soft zone with a tempered martensite does exist in the CGHAZ away from

the fusion boundary for all the joints except DSS. There exist a non-uniform softening in the joints.

The CGHAZ of UHA for ASS joint exhibits higher degree of softening compared to BM and a

considerable amount of reduction in hardness in the LHF joint. When comparing the CGHAZ for

the three cases, ASS joint exhibits higher softening in both RHA and UHA (495 and 400 HV

respectively) whereas DSS joint recorded lower softening in RHA and UHA (535 and 710 HV

respectively). The above phenomenon is due to the difference in the heat input recorded during

welding. A heat input of 1.86 kJ mm-1 was recorded for the fabrication of ASS joint and hence

show higher softening. A heat input of 0.96 kJ mm-1 was recorded for the fabrication of DSS joint

thereby exhibit lower softening. A heat input of 1.5 kJ mm-1 was recorded for the fabrication of

LHF joint and shows moderate softening.

The degree of softening in the HAZ is a function of weld thermal cycle moreover a characteristic

of the welding procedure employed. Apparently, the above review proves the use of different

welding consumables significantly affects the CGHAZ softening characteristics due to the

difference in heat inputs.

5.0 CONCLUSIONS

The present study confirmed that dissimilar grade armor steels (RHA and UHA) can be welded

without defects using SMAW process. The important conclusions are furnished below.

(i) The LHF joints showed maximum inter-mixing of the WM and BM whereas ASS joint

showed the lowest mixing and DSS joint exhibited the moderate mixing due to difference

in the percentage of both austenitic and ferrite phases present in the weld metal region.

Page 27 of 33

(ii) The ASS and DSS joints showed narrow WM zone compared to LHF joint. This may be due

to maximum dilution that occurred because of compatibility of LHF electrodes with base

metal (both are ferritic phases).

(iii) The LHF joint shows wider HAZ compared to ASS and DSS joint due to maximum dilution

as well as high heat input. In all the joints, hardness of FGHAZ is higher compared to BM

and CGHAZ which is due to the presence of fine untempered martensite.

ACKNOWLEDGEMENT

The authors wish to record sincere thanks to Extramural Research & Intellectual Property (ERIPR),

DRDO, Ministry of Defence, New Delhi for the financial support rendered through a R&D project

no: EPIR/EP/RIC/2016/1/M/01/1630. The authors wish to thank the Director, Research &

Innovation Centre (RIC), DRDO, Chennai for his constant help and support. The authors are

grateful to the Director, CVRDE, Avadi, Chennai for providing base materials to carry out this

investigation.

REFERENCES

1. N. Yurioka: Mater. Des. (1985), 6, (4), 154–171.

2. S. J. Alkemade: ‘The weld cracking susceptibility of high hardness armour steel’, (1996), AR No. 009–659, Defense Science

and Technology Organization, Adelaide, Australia, 1–17.

3. G. M. Reddy, T. Mohandas and D. S. Sarma: Sci. Tech. Weld. Join, (2003), 8, (6), 407–414.

4. Deb P, Challenger KD, Clark DR. Transmission electron microscopy characterizations of preheated and non- preheated

shielded metal arc weldments of HY-80 steel. Mater Sci Eng (1988); 77:155–67.

5. Cary HB. Modern welding technology. 6th ed. London: Prentice-Hall, Inc.; (2005).

6. T. Mohandas, G. M. Reddy and B. S. Kumar: J. Mater. Sci. Technol., (1999), 88, 284–294.

7. J. Wang and Y. J. Li: Bull. Mater. Sci., (2003), 26, (3), 295–299.

8. F. R. Xiao, B. Lia, D. L. Ren, Y. Y. Shan and K. Yang: Mater. Charact., (2005), 54, 305–314.

9. BADJI, R., BOUABDALLAH, M., BACROIX, B., et al., "Phase transformation and mechanical behavior in annealed 2205

duplex stainless steel welds", Materials Characterization (2008), v.59, n.4, pp. 447-453.

10. MODENESI, P.J., Soldabilidade dos Aços Inoxidáveis, Coleção Tecnologia da Soldagem, Osasco-SP, p.1, (2001).

11. LO, K.H., SHEK, C.H, J.K., L.A.I., "Recent developments in stainless steels", Materials Science and Engineering, (2009) v. 65,

n.4-6, pp. 39-104.

12. J. D. Parker and G. C. Stratford: Sci. Technol. Weld. Join., (1999), 4, (1), 29–39.

13. M. Murugananth, H. K. D. H. Bhadeshia, E. Keehan, H. O. Andren and L. Karlsson: in ‘Mathematical modelling of weld

phenomena – VI’, (ed. H. Cerjak and H. K. D. H. Bhadeshia), 205– 230; (2002), London, Institute of Materials.

14. E. Keehan, L. Karlsson, M. Marimuthu, H. O. Andren and H. K. D. H. Bhadeshia: Proc. 7th Int. Weld. Symp., (ed. T. Ohji),

797– 802; (2001), Tokyo, Japan Welding Society.

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16. W. Wang and S. Liu: Weld. J., (2002), 81, 132s–145s.

17. Pamnani, Rishi, M. Vasudevan, T. Jayakumar, P. Vasantharaja, and K. C. Ganesh. "Numerical simulation and experimental

validation of arc welding of DMR-249A steel." Defence Technology 12, no. 4 (2016): 305-315.

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Page 28 of 33

Table 1 Composition of base metals and filler metals (wt %)

Material C Si Mn Cr Mo Ni P S Fe

RHA 0.180 0.17 0.56 0.46 0.40 1.41 0.006 0.003 Bal UHA 0.315 0.239 0.54 1.25 0.52 1.25 0.018 0.009 Bal ASS 0.06 0.56 1.20 20.89 2.38 9.02 0.024 0.012 Bal LHF 0.049 0.544 1..59 0.58 0.55 2.08 0.023 0.011 Bal DSS 0.030 0.46 1.01 25.4 3.8 6.9 0.018 0.006 Bal

Table 2 Mechanical properties of base metals and filler metals (all weld metal)

Material 0.2% Yield strength

(MPa)

Ultimate tensile

strength (MPa)

Elongation in 50mm gauge

length (%)

Impact toughness

@ RT (J)

UHA 1450 2150 10 42 RHA 1050 1190 25 52 ASS 700 745 30 66 LHF 750 815 20 48 DSS 900 1000 30 56

Table 3 Welding parameters used to fabricate the joints

Parameters Unit ASS LHF DSS

Preheat temperature oC 200 200 200 Interpass temperature oC 150 150 150 Electrode baking temperature oC 200 350 200 Filler diameter mm 4 4 4 Welding current A 130 136 123 Arc voltage V 23 26 25 Heat input kJ mm-1 1.865 1.569 0.968

(a) RHA steel (b)UHA steel

Figure 1 Micrograph of base metals

Page 29 of 33

(a) (b)

Figure 2 (a) Joint configuration (b) Scheme of extraction of specimen

Joint Type

Macrograph (cross-section)

Macrograph (top surface)

ASS

LHF

DSS

Figure 3 Macrographs of welded joints

Table 4 Dimension (mm) of Weld Metal Zone (WMZ) and HAZ

Joint

Weld Metal Zone

RHA Side HAZ UHA Side HAZ

WMZ area

(mm2)

Width at top

side (mm)

Width at mid

thickness (mm)

Width at root

side (mm)

HAZ area

(mm2)

Width at top side

(mm)

Width at mid

thickness (mm)

Width at root

side (mm)

HAZ area

(mm2)

ASS 142.8 1.4 1.3 1.8 48.6 1.9 2.2 2.7 53.7 LHF 210.6 3.5 4.3 2.1 102.1 1.6 3.1 2.6 100.4 DSS 170.5 2.9 3.2 2.0 65.3 2.1 2.9 2.9 79.3

Page 30 of 33

RHA Side UHA Side

Figure 4 Microstructure of ASS weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ

a a - high magnification

c b

d e

f g

Page 31 of 33

RHA Side UHA Side

Figure 5 Microstructure of LHF weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ

a

b c

d e

f g

a - high magnification

Page 32 of 33

RHA Side UHA Side

Figure 6 Microstructure of DSS weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ

a

c b

d e

f g

a - high magnification

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Figure 7 Microhardness plot of the weldment

Table 5 Micro hardness distribution across the weld (at mid-thickness region)

RHA Side Weld Metal (WM)

UHA Side

Weld Metal

FGHAZ CGHAZ WM-HAZ Interface

WM-HAZ Interface

CGHAZ FGHAZ

ASS 430 395 290 240 350 680 770 LHF 580 520 440 350 435 570 680 DSS 590 535 420 355 480 650 750