How is it Different From Hot Forging?

The most obvious difference between cold and hot forging is the temperature. Unlike cold forging that starts at or near room temperature, hot forging happens when metal is heated above its recrystallization temperature. This is usually an extremely high temperature, for example, steel is heated to 1150°C or 2202 °F, and copper alloys to 700-800°C or 1300-1470°F, which equals about 75% of the melting temperature. These high temperatures are necessary to keep the metal from strain hardening during the forging process. At these temperatures, the metal is in a plastic-like state, still technically a solid, but much more malleable.

Hot forging is usually done through a process called stamping, which means the heated metal is put into a press, and then squeezed in between a die and a tool. 

Advantages of Hot Forging

Because the forging process occurs at high temperatures, the plastic metal is ductile and easily molded. Intricate shapes and designs can be created during hot forging, unlike cold forging where this can be extremely difficult. If you’re looking to manufacture customized metal pieces, hot forging is the best option because of its malleable state before hardening. This method is ideal for creating 3-D and complex shapes. 

Unlike cold forging, which sometimes requires the extra step of heating the outside of the metal afterward to give it the right properties, the surface of the metal that has been forged through high temperatures is ideal for most types of finishing work.

Hot forging is also ideal for metals with a high formability ratio, because the integrity of the metal isn’t compromised by the high heat. These metals can be easily shaped without seeing any defects in the metal, making them both strong and ductile.

Disadvantages of Hot Forging

A disadvantage of hot forging, when compared to cold forging, is that some metals can be warped if not carefully watched when heated, forged, and then cooled. This means less precise tolerances than metal forged through cold forming.

Hot forging is also often more expensive than cold forging because of the heat treatment necessary to start the forging process, as well as the cooling process that prevents warping. This heat treatment is best done when automated, especially on the industrial scale, which may result in additional up-front costs to purchase tools. 

Ultimately, the process you choose is dependent on the product you need and the type of metal you’ll be using. Both forging methods can be effective ways to strengthen and form your metal workpieces into the final product you need.