1 forging

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

Topic and Contents Hours Marks

1.1 Introduction: 08 Marks

Forgeable materials and forgeability

Classification of forging processes

Advantages and limitations of forging processes

1.2 Forging sequences for Auto components- 08 Marks

Connecting rods, Crankshafts, Camshafts and Spanners

06 16

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1. FORGING

1.1 INTRODUCTION:

Forging is an oldest shaping process used for the producing small articles for which

accuracy in size is not so important. The parts are shaped by heating them in an

open fire or hearth by the blacksmith and shaping them through applying

compressive forces using hammers.

It consists essentially of changing the shape and section of metal by hammering at a

temperature of about 980°C, at which the metal is entirely plastic and can be easily

deformed under pressure. The shop in which the various forging operations are

carried out is known as the smithy or smith’s shop.

What is forging? (Define forging)

A. Forging is a plastic flow of metal by the application of compressive forces in

which size and shape is changed permanently without failure.

B. Forging is a deformation process in which work is compressed between two

dies using either impact or gradual pressure to form the part.

� FORGEABLE MATERIALS:

Any material (Metal or Alloy) which can be brought to plastic stage through heating

can be forged.

1. Aluminium alloys

2. Magnesium alloys

3. Copper alloys.

4. Carbon and low alloy steels

5. Martensitic stainless steels

6. Austenitic stainless steels

7. Nickel alloys

8. Titanium alloys

9. Columbium alloys

10. Tantalum alloys

11. Molybdenum alloys

12. Tungsten alloys

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13. Beryllium.

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

properties of forgeable materials)

1. Strength

2. Malleability

3. Resistance to fatigue

4. Durability

5. Shock or bending resistance

6. Machinability

� FORGEABILITY.

“The ease with which forging is done is called forgeability.” The forgeability of a

material can also be defined as the capacity of a material to undergo deformation

under compression without rupture. Forgeability increases with temperature up to a

point at which a second phase appears or if grain growth becomes excessive.

Certain mechanical properties are also influenced by forgeability. The pure metals

have good malleability and thus good forging properties. The metals having high

ductility at cold working temperature possesses good forgeability.

� CLASSIFICATION OF FORGING PROCESS:

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� ADVANTAGES & DISADVANTAGES OF FORGING

Advantages:

1. Uniformity of qualities for parts subject to high stresses & loads.

2. Weight saving

3. Close tolerance

4. Less machining

5. Smooth surface

6. Speed of production

Disadvantages:

1. High tool cost

2. High tool maintenance

3. No cored holes

4. Limitations in size & shape.

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

Forging work is produced between flat faced dies. Small no. of light Forgings are

done by hand on an anvil. Hence it is also called as smith forging, but heavy and

medium forgings are done by power hammers and presses. Smith forging or open

die forging processes produce work pieces of lesser accuracy than impression or

closed die forging. Following are sub types of smith die forging,

1. Hand forging: It is done by hammering the piece of metal, when it is

heated to the proper temperature, on an anvil. While hammering the metal is

held with suitable tongs. Formers are held on the forging by the smith while

other end is struck with a sledge by a helper.

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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 those

working by pressure are called as “presses”.

a. Hammer forging: All power hammers employ the same general principle

of operation, a falling weight striking the blow, with the entire energy

being absorbed by work.

b. Power press: They are usually of the hydraulic type. The water passes

from a large capacity tank to a pump and then is delivered on the

press 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 in

following dies

1. Drop hammers: They are used in making drop forgings. Board or

gravity, air lift and power drop hammer are the types of drop hammers.

2. Press forging: the action of working is relatively slow squeezing instead

of delivering heavy blows and penetrates deeply because it gives the metal

time to flow. The press forging dies require a mechanical means for ejecting

the forging. There are two types of presses,

a. Hydraulic press

b. Mechanical press

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

Bolts, nuts, washers, collars, pinion and gear blanks are produced in machine or

upset 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 a

bar & reducing the length.

Drawing down: It is the process of increasing the length of a bar & reducing its

size or thickness.

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

Welding: A forge weld is made by hammering together the ends of two parts

which have been formed to the correct shape and heated to a welding

temperature in a furnace. The method for preparing the metal pieces for welding

is known as scarfing.

Bending: It is classified as angular and curvilinear. Bending may be done over

the edge of the anvil face, over the anvil horn and in special forms such as the

swage block edges.

Cutting: Cutting is a form of chiseling. In this operation a long piece of stock is

cut into several specified lengths, or a forging is separated from its stock.

Punching: It is the process of producing the holes by using a hot punch over

the pritchel hole of the anvil.

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Fullering: Spreading the metal along the length of the job is done by working

separate 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 die forging.

(a) It is also known as impression die forging

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

(b) Dies have cavities on its inner surface hence impressions are made on workpieces.

©Final shape of forging depends on

skill of the Smith.

© Final shape of forging depends on skill

of the dies.

(d)Complex shaped parts can’t be forged

(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 is

achieved

(f) Mass production with greater

accuracy 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 are

required in rapid succession.

(a) Press action is slow squeezing.

(b) A hammer blow produces shocks &

vibrations to the machine structure, its

foundation and surroundings.

(b) It produces less vibration.

© Applicable for low volume production © Applicable for large volume production

(d) Surface finish is poor (d) Better surface finish is achieved.

(e) It does not provide a uniform shape to component.

(e) It provides a uniform shape to component.

(f) Size of hammer is limited upto 10

tonnes.

(f) Capacity of press is upto 20 to 1500

tonnes.

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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, depressions

remain which are known as scale pits.

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

operation.

• 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, die

should be designed correctly and temperature of stock should be sufficient.

• Dents:

Dents are the result of careless work.

1.2 FORGING SEQUENCES FOR FOLLOWING AUTO COMPONENTS.

A. Spanner

B. Connecting rod

C. Crankshaft

D. Camshaft

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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 places

and reducing at others as required filling the cavities of the die. The operation

is 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 places

and reducing at others as required filling the cavities of the die. The operation

is 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 reduced

at 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 excess

metal or flash.

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Camshaft:

I. Stock is redistributed and size is increased at certain places and reduced

at 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 excess

metal or flash.

1 forging

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