Forging

Forging is the process of causing bulk plastic deformation to achieve a desired shape and material microstructure. It is usually done as hot work, meaning that the metal is heated above its recrystallization temperature before being deformed. A traditional blacksmith working an anvil and hammer is an example of forging. Forging can create directional microstructure alignment, which leads to being more ductile and stronger than casting. Thus, forged metals are more resistant to shock and fatigue failure.

There are different types of forging, depending on the shape of the die and the degree of material flow. Open die forging is when the metal is compressed between two flat or simple-shaped dies, allowing the metal to flow freely in all directions. Closed die forging is when the metal is confined within a cavity or impression that matches the final shape of the part. Impression die forging is a type of closed die forging that uses dies with multiple cavities or impressions to produce complex shapes. Precision forging is a type of closed die forging that uses dies with very high accuracy and surface finish to produce parts with minimal or no machining.

Some guidelines for part design for forging are:

• Avoid sharp corners, undercuts, and thin sections that may cause stress concentration or cracking.
• Provide generous fillets and radii to facilitate material flow and reduce die wear.
• Design parts with uniform cross-sections and symmetrical shapes to reduce forging load and avoid defects.
• Minimize the number of operations and dies required to produce the part.
• Consider the effect of forging on the grain structure and mechanical properties of the metal.

Hot Forging

The benefits of hot forging include high strain rates, homogenized grain structure, increased ductility, and reduced hardening force. The drawbacks of hot forging include less accurate tolerances and the possibility of warping during cooling.

Cold Forging

Cold forging is a manufacturing process that shapes metal at room temperature by applying compressive forces. It has some advantages and disadvantages compared to hot forging. Some of the benefits of cold forging are: no waste material, little or no finishing work, high dimensional accuracy, and excellent surface quality. Some of the drawbacks of cold forging are: reduced plasticity and toughness of the metal, higher deformation force required, residual stress inside the metal, and deformation or fracture of metal grains. Cold forging is often used in the automotive industry to produce simple shapes in high volumes.