What is Forging Process

What is Forging Process?

  • The forging process is the process of shaping heated metal by the application of sudden blows (hammer forging) or steady pressure (press forging) and makes use of the characteristic plasticity of the material.
  • Forging is a metal-forming process that may be done by hand or by machine.
  • In the case of hand forging, hammering is done by hand; whereas forging by machine involves the use of dies, and it is mostly used in mass production.
  • Whatever may be the method of applying pressure for snapping the metal, the primary requirement is to heat the metal to a definite temperature to bring it into t e plastic state.
  • This may be done in an open hearth, called as Smith’s forge for small jobs or in sect furnaces for large jobs.
  • The shop in which the work is carried out is called as Smithy or Smith’s shop.
  • The metals which are used in the forging process must possess the required ductility.
  • We know that ductility refers to the capacity of a material to undergo deformation, under tension without failure.
  • The commonly used forging materials are: Aluminium alloys, copper alloys, low bon steels, alloy steels, nickel alloys, tungsten alloys, magnesium alloys, Mum alloys, beryllium, etc.

Types of Forging Processes

1. Hand forging process

  • Hand forging process is the process of deforming the hot material/workpiece into the required shape by applying the repeated blows of hammer held in hand.
  • The hot material is held in one hand by using suitable clamping device and kept on anvil block whereas, hammer blows are given by hammer held in another hand.

Hand forging process

  • Initial cost of this hand forging process equipment’s is low hence cost of components forged from this process is also low.
  • Hand forging process is only used for making simple components of small size.
  • Hand forging process is not used for high production rate.

2. Drop forging process

  • This process utilises closed impression die to obtain the required shape of the component.
  • The dies are matched and separately attached to the movable ram and the fixed anvil.
  • The forging is produced by the impact or pressure which forces the hot metal (billet) to form the shape of the dies.

Drop forging process

  • During the operation, there is a drastic flow of metal in the dies caused by repeated blows of hammers on the metal.
  • To ensure proper flow of the metal, the operation is divided into number of steps. Each step changes the form gradually, until the final shape is obtained.
  • The equipment used for applying the blows is called as drop hammer.
  • During the process, the ram is raised to a definite height and then it is allowed to drop or fall freely under its own weight.
  • The workpiece is kept on the lower die while the ram delivers four to five blows on the metal in quick succession, hence the metal spreads and fills the die cavity.
  • Drop forging process is less expensive as compared to other forging processes.
  • This process is used for manufacturing of car axles, connecting rods, crankshafts, leaf springs, crane hooks, jet engine blades, etc.

Advantages of Forging Process

  • In forging process, grain flow is continuous and uninterrupted. It gives greater strength and toughness to the forged components. Figure shows three spanners, produced through three different methods casting, machining and forging. The cast spanner is the weakest of all, the machined spanner is relatively stronger and the strongest will be the forged spanner.

Spanners produced through three different methods

  • Forged components requires minimum surface finish.
  • The forging process gives the high dimensional accuracy.
  • Forged components have better mechanical properties like strength, toughness, etc.
  • Forged components have better resistance to shock and vibrations.
  • Welding of forged parts is easy.

Disadvantages of Forging Process

  • Complicated shapes cannot be forged easily.
  • Forging process is mostly suitable for large parts.
  • Forging of brittle materials is difficult.
  • Due to high cost of forging dies, forging process is costly.
  • More noise and vibrations are produced during the process.

Applications of Forging Process

  • Forging process is used in the manufacturing of following components:
  • Car axles, crankshafts, connecting rods, leaf springs, crane hooks, jet engine turbine dies and blades.
  • Levers, flanges, propellers, hollow bodies, railway wheel disks, tank bottoms.
  • Air-craft and rocket parts, knife blades, bolts, nuts, washers, collars, gear blanks, etc.

Difference between Forging and Casting Processes

Forging Processes

  • In forging process, grain flow is continuous.
  • Due to improved grain size and true grain flow, forging give greater strength and toughness.
  • Requires minimum machine finish.
  • Forged components have better mechanical properties like strength, toughness, resistance to shock and vibrations.
  • Welding of forged parts is easy.
  • During the operation, cracks and blow holes are welded up.
  • Accuracy is more.
  • Complicated shapes cannot be produced.
  • Generally used for large parts.
  • Because of cost of dies, process is costly.

Casting Processes

  • In casting process, there is no grain flow.
  • Due to no grain flow and weak crystalline structure, casting is weak in withstanding working stresses.
  • Requires more machine finish.
  • Cast components are brittle that is weak in tension. Also they have poor resistance to shock and vibrations.
  • Welding of cast parts is difficult.
  • Defects like cracks and blow holes make the casting weak and unsuitable for use.
  • Accuracy is less.
  • Complicated shapes can be produced.
  • Generally used for small parts.
  • As there are no dies, casting is less expensive.
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