Forging

Forging

Forging is a deformation processing of materials through compressive stress. 
Forging is the process of forming and shaping the metals through the use of hammering, pressing or rolling.
It is carried out either hot or cold. Hot forging is done at temperatures above recrystallization temperatures, typically 0.6 Tm, or above, where Tm is melting temperature

Typical applications of forging include bolts, disks, gears, turbine disk, crankshaft, connecting rod, valve bodies, small components for hydraulic circuits, etc.

Types of forging process

1. On the basis of load applied

Drawing down-

A forging operation in which the cross-section of forging stock is reduced and the stock lengthened between flat or simple contour dies.
In heat treating, the same as tempering.
The term "drawing down" is used by a blacksmith to mean thinning a piece of metal by hammering it

Upsetting-

• A forging made by upsetting an appropriate length of bar, billet or bloom. 
• Working metal to increase the cross-sectional area of a portion or all of the stock.
• A forging formed by heading or gathering the material by pressure upon hot or cold metal between dies operated in a horizontal plane.

2. On the basis of temperature

Hot Forging-

Hot forging process performed at a very high temperature.

For steel-1500 D. celsius

For Al- 360- 530 D. celsius

Advantages

• increased ductility which makes them desirable for many configurations. 
• more flexible than cold forging.
• internal stress removed.
• excellent surface quality allows a wide range of finishing work

Disadvantages-

Difficult to handle as it's working is at high temperature.

precise Dimensional tolerance is difficult to achieve.

Metals easily form their oxides on the surface

Warm forging-

This process is done at approx 40% of the melting point of material so that it's shape can be deformed according to e
Requirements.

Cold Forging-

The cold forging manufacturing process is performed at room temperature. The workpiece is squeezed between two dies until it has assumed their shape. To deliver a finished, ready to fit component, the technique includes rolling, drawing, pressing, spinning, extruding and heading.

Advantages-

• Cold-forged parts require very little or no finishing work, which saves costs.
• Material savings achieved through precision shapes.
• Hh production rates and long die life are more than enough to convince many manufacturers 

Disadvantages-

• Only simple shapes in high volumes can be shaped.
• Cold forged metals are less ductile
• The grain structure is not refined that gives the material its strength, residual stress may occur.

3. Another process

Drop Forging- 

• Drop forging is a type of closed-die forging.
• The dies used in drop forging consists of two halves. 
• The lower half part of the die is fastened to the anvil while the upper half part is fixed to the movable ram.
• The heated bar or billet is kept in the lower die while the ram delivers four to five strokes (blows) on the metal. 
• When these two die halves come together in closed alignment, the metal spreads and completely fills the die cavity.

Uses-

Drop forging process is widely used in automobile industries, airplane parts manufacturing, railroad equipment manufacturing, engine manufacturing industries, agricultural equipment manufacturing industries, etc.

Advantages-

• Good grain flow is achieved.
• Faster speed of operation.
• Good strength of the material is obtained.
• Little or no wastage of material.

Disadvantage-

• Die preparation is a costly process.
• Die impression requires a good skill of work.
• Die maintenance is costly.

Press forging-

 The shaping of metal between dies on a mechanical or hydraulic press. The action is that of kneading the metal by the relatively slow application of force as compared with the action of hammering.
In Press forming die is onto the other half the two halves are put together and pushed together under a large pressure (up to about 10000 tons) forming the object.

Machine forging-

The process of forging in a forging machine (upsetter), in which the metal is moved into the die impression by pressure applied in a horizontal direction by the moving die in the ram.