2019-10-24
Introduction Hot Forging Cold Forging

Hot forging and cold forging are two different metal forming processes that deliver similar results. Forging is the process of deforming metal into a predetermined shape using certain tools and equipment—deformation is accomplished using hot, cold, or even warm forging processes. Ultimately, the manufacturer will look at a number of criteria before choosing which type of forging is best for a particular application.

Cold Forging (or Cold Forming)

Cold forging deforms metal while it is below its recrystallization point. Cold forging is generally preferred when the metal is already a soft metal, like aluminum. This process is usually less expensive than hot forging and the end product requires little, if any, finishing work. Sometimes, when aluminum is cold forged into a desired shape, it is heat treated to strengthen the piece. This is called "tempering."

The Cold Forging Process

Despite the word "cold," cold forging actually occurs at or near room temperature. The most common metals in cold forging applications are usually standard or carbon alloy steels. One of the most common types of cold forging is a process called impression-die forging, where the metal is placed into a die that is attached to an anvil. The metal is then hit by a descending hammer and forced into the die. Depending on the product, the hammer may actually be dropped on the metal numerous times in a very rapid sequence.

Mark of quality

"Forged" is the mark of quality in hand tools and hardware. Pliers, hammers, wrenches, garden implements and surgical tools are almost always produced through forging.

Cold Forging Considerations

Manufacturers may choose cold forging over hot forging for a number of reasons—since cold forged parts require very little or no finishing work, that step of the fabrication process is often dispensable, which saves money. Cold forging is also less susceptible to contamination problems, and the final component features a better overall surface finish.

Other benefits of cold forging include:
Easier to impart directional properties
Improved interchangeability
Improved reproducibility
Increased dimensional control
Handles high stress and high die loads
Produces net shape or near-net shape parts
Some possible disadvantages include:
Easier to impart directional properties
Improved interchangeability
Improved reproducibility
Increased dimensional control
Handles high stress and high die loads
Produces net shape or near-net shape parts
The metal surfaces must be clean and free of scale before forging occurs
The metal is less ductile
Residual stress may occur
Heavier and more powerful equipment is needed
Stronger tooling is required