Shaping: Forging

Friction press

Friction press

Forging is the process of shaping a work piece using a great deal of pressure. This process can be done with almost any metal (although some are easier to forge than others).  Common metal types include steel, aluminum, titanium, copper, and nickel. The best type of metal depends on the requirements of the final product.

Forging is often performed hot, but can be done cold as well. Hot forging is done above the metal’s recrystallization temperature to avoid strain hardening and increase ductility during the shaping process. Cold forging is done at room temperature and is usually used on softer metals. This process is usually less expensive than hot forging, however, more powerful equipment is needed since the metal is less ductile. Cold heading is a common type of cold forging and is used to make many products like nails and screws. After being molded and cut to the desired length and volume, a workpiece is punched into a die forming a “head” on the product. 

The forging process includes open die forging and closed die forging.

Open die forging– the metal is compressed between two die that aren’t enclosed, therefore the metal needs to be positioned for desired shape.

Closed die forging– metal flow is restricted by cavities in the work piece. Two closed die processes are impression die forging and “flashless” forging. 

Impression forging– Excess metal is squeezed out of the cavities producing “flash”, which builds up and hardens, therefore blocking the escape of more metal and allowing the cavities to fill. The flash is removed after forging.

Flashless forging– the entire piece in enclosed, blocking the escape of the metal. This process results in less wasted metal, however, the cost is higher due to more complex die design.

This process produces products of considerable strength since the compression closes any open spaces in the metal. While it can be expensive for products in small quantities due to capital cost,  for small parts it can be very cost effective for products in large quantities.