What is forging ? Classification of forging

     Forging

                 Forging is the process of forming the metal into the required shape by compressive or impact force is called forging.

When the process is carried out above the recrystallization temperature of metal, it is called hot forging. Connecting rod, crankshaft can be produced by this method.

Cclassification of forging

1)      Smith forging

a)      Hot forging   b) power forging

2)      Impression die forging

a)      Drop forging  b) upset forging

3)      Roll forging

4)      Swaging
 
1)   Smith forging (or) hammer forging

 It is also as flat die forging and open die forging. Smith forging can be done manually or by power.

The accuracy of forgings are depend upon the skill of the worker. Generally smith forging is used for rough work.

  a) Hand forging

               In this method, the heated metal is held over an anvil with the help of tongs. The metal is hammered several times by using a hammer to form into required shape.

Hand forging is used for producing less number of small size forgings.

b)    Power forging

                      In this method, power hammer or power press is used for forging. The heated metal is hammered several times by using a hammer to form into required shape.

The power hammer may be operated hydraulically or pneumatically. Power forging is us

ed for producing medium and large size forging.

2)   Impression die forging
 

a)     Drop forging

       Drop forging is the process of making the heated metal into required shape by placing it between two closed dies and pressing with the help of power hammer.

The lower die is fitted on the anvil and the upper die is fitted with the ram. The heated metal is placed over the lower die.

WThen the ram falls down, the heated metal fill the die cavities due to the impact force of the upper die. 

Thus the required shape is obtained. Power hammers like gravity hammer, power drop hammer and air lift hammer are used.

Components with simple shapes are forged in single operation. Components with complicated shapes are forged in several steps.

Roughing die, semi finishing die and finishing die are used for such operations.

Application

      Crank, crank shaft, connecting rod, levers, camshaft can be produced by drop forging.

Advantages

1)      It is suitable for mass production.

2)      The strength of the component is high.

3)      Less material wastage.

  Disadvantages

1)      Large anvil and strong foundations are needed

2)      More noise and vibration

3)      The die may wear our quickly.
 
b)    upset forging (or) machine forging

Upset forging is the process of making rivet head, hexagonal head at the end of heated work piece.

In this process, the length is reduced and the cross section at the end is increased. As it is done in a press forging machine, it is called as machine forging.

The machine has a fixed die, movable punch and knock out pin. The end of the work piece is heated and held in the fixed die.

When the punch is pressed, the end of the work piece gets the shape of the punch. The knock out pin push out the work piece.

The sharp to be formed at the end of the work piece will be in the punch or in die or in both.

Some forging machine has a fixed die, movable die, movable Punch, knock out pin and stop. The end of the work piece is heated and placed between the two dies.

The length of the work to hold the work piece. The stop goes to its idle position. The punch is moved and pressed against the end of the work piece.

Now the end of the work piece gets the shape of the die or punch or punch and die. The punch and movable die go back to initial position and the work piece is removed.

3) Roll forging

        In plain rolling, component with uniform cross section are produced. Roll forging is a process of producing components with varying cross sections by pressing the heated work piece between two rotating rolls.

The periphery of the rolls used in this method will not be round. According to the required shape of the component, the roll have grooves of different radii.

When the heated work piece passes between the rolls, it gets the shape of the grooves in the roll.

Thus the varying cross section is obtained in the component. In this process the cross section or work piece is decreased and the length is increased.

Application

 Automobile axles, levers, leaf springs, tapered tube are produced by roll forging.

4)    Swaging

Swaging is the process of increasing the length of heated metal and to form the cross section to the required shape.

The work piece is heated and held between the swage blocks. Then the work piece is hammered to form the required shape.

In this method, the work piece can be formed into round, square and hexagonal shapes.

Smith forging operations

1)      Upsetting

2)      Drawing down

3)      Setting down

4)      Bending

5)      Punching

6)      Welding
 
1)      Upsetting

 This is the process of increasing the cross section of heated work piece by reducing the length.

The portion where upsetting is to be done is heated and the end of the work piece is hammered. Now the length is reduced and the cross section is increased.

2)      Drawing down

                     This is the process of increasing the length of the heated work piece by reducing the cross      section. The work piece is heated and held between the fullers.

                     When the work piece is hammered, the length is increased and the cross section is reduced.

3)      Setting down

                    Setting down is a process similar to drawing down. In this method, a flatter is used instead of fuller for reducing the cross section at particular portion work piece.

4)      Bending

                  It is the process of forming the work piece into required angle or circular. The sharp cornered bend can be made by hammering the metal over the edge of the anvil.

                 The work piece is held over the beak of the anvil and hammered to form circular bends.

5)      Punching

                   Punching is the process of making holes in the heated work piece. The work piece is held over the hole in the anvil.

                   The punch correctly placed on the work piece and hammered to produce hole.

6)      Forge welding

                   It is the process of joining two ends of heated work piece hammering. The part to be welded are cleaned are cleaned thoroughly and the edges are prepared for required joint.

                   Flux can be applied at the ends of work pieces to avoid oxidation. The ends are heated and held in correct position.

                  Then the two parts are hammered together to get the required joint.