1. FORGING - NPKauto Forging.pdfQ. Distinguish between Hammer forging and Press forging process. Hammer forging process Press forging process (a ) A large no of blows of hammer are

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1© Rohan Desai –Automobile Dept. - New Polytechnic, Kolhapur.

1. FORGINGQ. What is forging? (Define forging)

A. Forging is a plastic flow of metal by the application of compressive forces inwhich size and shape is changed permanently without failure.

B. Forging is a deformation process in which work is compressed between twodies using either impact or gradual pressure to form the part.

Q. Which are the forgeable materials?

Any material (Metal or Alloy) which can be brought to plastic stage through heatingcan be forged.

1. Aluminium & its alloys2. Copper & its alloys3. Magnesium & its alloys4. Tungsten & its alloys5. All types carbon steels6. Stainless steels

Q. What are the properties of the forgeable materials? (List the desirableproperties of forgeable materials)

1. Strength2. Malleability3. Resistance to fatigue4. Durability5. Shock or bending resistance6. Machinability

Q. Define Forgeability.

Ability of material to get forged by the external pressure of hammer orpress is known as forgeability.

Forgeability increases with temperature up to a point at which a second phase, e.g.from ferrite to austenite in steel, appears or if grain growth becomes excessive.Metals which have low ductility have reduced forgeability at higher strain rates,whereas highly ductile metals are not so strongly affected by increasing strain rates.

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Q. What are the advantages & disadvantages of forging processes?

Advantages:

1.Uniformity of qualities for parts subject to high stresses & loads.2.Weight saving3.Close tolerance4.Less machining5.Smooth surface6.Speed of production

Disadvantages:

1. High tool cost2. High tool maintenance3. No cored holes4. Limitations in size & shape.

Q. How the forging process is classified?

Q. How the forging is carried out in open dies?

Forging work is produced between flat faced dies. Small no of light Forgings aredone by hand on an anvil. Hence it is also called as smith forging, but heavy andmedium forgings are done by power hammers and presses. Smith forging or opendie forging processes produce work pieces of lesser accuracy than impression orclosed die forging. Following are sub types of smith die forging,

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1. Hand forging: It is done by hammering the piece of metal, when it isheated to the proper temperature, on an anvil. While hammering the metal isheld with suitable tongs. Formers are held on the forging by the smith whileother end is struck with a sledge by a helper.

2. Power forging: Large machine parts are forged by power forgings.Power forging takes less time than hand forging to complete the operation.Machines which work on forgings by blow are called “hammers”, while thoseworking by pressure are called as “presses”.

a. Hammer forging: All power hammers employ the same general principleof operation, a falling weight striking the blow, with the entire energybeing absorbed by work.

b. Power press: They are usually of the hydraulic type. The water passesfrom a large capacity tank to a pump and then is delivered on thepress with the aid of an accumulator and distributor.

Q. How the forging is carried out in impression dies?

Most complex shape of greater accuracy is formed by closed die forging techniques.Since die is not fully closed hence it is called as impression die. It is carried out infollowing dies

1. Drop hammers: They are used in making drop forgings. Board orgravity, air lift and power drop hammer are the types of drop hammers.

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2. Press forging: the action of working is relatively slow squeezing insteadof delivering heavy blows and penetrates deeply because it gives the metaltime to flow. The press forging dies require a mechanical means for ejectingthe forging. There are two types of presses,

a.Hydraulic pressb.Mechanical press

Q. What do you mean by machine or upset forging?

Bolts, nuts, washers, collars, pinion and gear blanks are produced in machine orupset forging.

Q. State & explain various operations carried out in forging process.

(a) Upsetting, (b) Drawing Down, (c) Setting down, (d) Welding,

(e) Bending, (f) Cutting, (g) Punching and (h) Fullering.

Upsetting: Upsetting or heading is the process of increasing the thickness of abar & reducing the length.

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Drawing down: It is the process of increasing the length of a bar & reducing itssize or thickness.

Setting down: It is a localized drawing-down or swaging operation.

Welding: A forge weld is made by hammering together the ends of two partswhich have been formed to the correct shape and heated to a weldingtemperature in a furnace. The method for preparing the metal pieces for weldingis known as scarfing.

Bending: It is classified as angular and curvilinear. Bending may be done overthe edge of the anvil face, over the anvil horn and in special forms such as theswage block edges.

Cutting: Cutting is a form of chiseling. In this operation a long piece of stock iscut into several specified lengths, or a forging is separated from its stock.

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Punching: It is the process of producing the holes by using a hot punch overthe pritchel hole of the anvil.

Fullering: Spreading the metal along the length of the job is done by workingseparate section.

Q. List & sketch various hand tools in smith forging.

(a) Anvil, (b) Swage, (c) Swage block, (d) Sledge, (e) Punch,

(f) Drift, (g) Flatter, (h) Set hammer, (i) Fuller & (j) Rivet header

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Q. Distinguish between open die and closed die forging process.

Open die forging process Closed die forging process(a)It is also known as flat or Smith dieforging.

(a) It is also known as impression dieforging

(b)Dies have flat face hence only sizeand shape of forging is changed

(b) Dies have cavities on its inner surfacehence impressions are made onworkpieces.

(c)Final shape of forging depends onskill of the Smith.

(c) Final shape of forging depends onskill of the dies.

(d)Complex shaped parts can’t beforged

(d) Complex shaped parts can be forged.

(e) It used for large volume parts (e) It is used for small size parts(f) Less quantity with lesser accuracy isachieved

(f) Mass production with greateraccuracy is achieved.

Q. Distinguish between Hammer forging and Press forging process.

Hammer forging process Press forging process(a) A large no of blows of hammer arerequired in rapid succession.

(a) Press action is slow squeezing.

(b) A hammer blow produces shocks &vibrations to the machine structure, itsfoundation and surroundings.

(b) It produces less vibration.

(c) Applicable for low volume production (c) Applicable for large volume production(d) Surface finish is poor (d) Better surface finish is achieved.(e) It does not provide a uniform shapeto component.

(e) It provides a uniform shape tocomponent.

(f) Size of hammer is limited upto 10tonnes.

(f) Capacity of press is upto 20 to 1500tonnes.

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Q. State and explain forging defects with its remedies.

Cold Shuts:

Short cracks at corners and at right angles to the surface of forging.

Cause: Metal surface folding against itself during forging.

Remedy: Die design should make properly.

Pitting:

Small pits (Depressions) on surface.

Cause: It is caused by scale. When scales are removed from surface, depressionsremain which are known as scale pits.

Remedy: Pure ingots should be selected and dies must be cleaned properly afteroperation.

Die shift:

Cause: It is caused by misalignment between top and bottom forging dies.

Remedy: Proper mechanism should be used to avoid mismatching.

Incomplete filling of dies:

Undersize of forging due to less amount of metal.

Cause: It is caused by wrong amount of metal, insufficient number of blows,incorrect die design or low temperature of stock.

Remedy: Ingot size must be sufficient, hammering should be done properly, dieshould be designed correctly and temperature of stock should be sufficient.

Dents:

Dents are the result of careless work.

Q. Give the forging sequences for following auto components.

A. SpannerB. Connecting rodC. CrankshaftD. CamshaftE. Gears

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Spanner:

I. The heated stock is elongated by reducing its cross section in first die.The operation is known as “Fullering”.

II. The metal is redistributed, increasing the cross section at certain placesand reducing at others as required filling the cavities of the die. The operationis known as “Edging”.

III. General shape is given in first blocking die.

IV. Finished shape is given to forging in final impression die.

V. Flash is removed.

VI. Heat treatment and machining is done as per requirement.

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Connecting rod:

I. The heated stock is elongated by reducing its cross section in first die.The operation is known as “Fullering”.

II. The metal is redistributed, increasing the cross section at certain placesand reducing at others as required filling the cavities of the die. The operationis known as “Edging”.

III. General shape is given in first blocking die.

IV. Finished shape is given to forging in final impression die.

V. Flash is removed.

VI. Heat treatment and machining is done as per requirement.

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Crankshaft:

I. Stock is redistributed and size is increased at certain places and reducedat others by roll forging.

II. After preliminary roll forging, the stock is again roll forged.

III. This stock is then forged in first impression or blocking die.

IV. The final shape is given to the forging in next blocking die.

V. Then the finished part is trimmed in blanking die to remove excessmetal or flash.

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Camshaft:

I. Stock is redistributed and size is increased at certain places and reducedat others by roll forging.

II. After preliminary roll forging, the stock is again roll forged.

III. This stock is then forged in first impression or blocking die.

IV. The final shape is given to the forging in next blocking die.

V. Then the finished part is trimmed in blanking die to remove excessmetal or flash.

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Gears:

I. The size of the heated stock is reduced with compensation of its length.i.e. Upsetting is carried out.

II. After heading or upsetting, stock is forged in first impression die.

III. Stock is forged in next impression or blocking die.

IV. Then the finished part is trimmed in blanking die.

Documents

1. FORGING - NPKauto Forging.pdfQ. Distinguish between Hammer forging and Press forging process. Hammer forging process Press forging process (a ) A large no of blows of hammer are