hotformed

Hot formed, or hot forming, is a metalworking process conducted at elevated temperatures in which a metal blank is heated and shaped while hot, often followed by rapid cooling to lock in desired properties. It is used to produce parts with high strength and complex geometries, with hot stamping being a common industrial implementation for sheet metal.

In automotive and related industries, hot stamping typically involves heating boron-containing steels to the austenitizing range (around 900 to 1,000 degrees Celsius), forming the heated blank in a die, and then quenching it in the die to achieve a martensitic microstructure. This in-die quenching yields very high strength levels, often exceeding 1,000 megapascals, along with good dimensional accuracy and crashworthiness. The process can be followed by post-forming heat treatments or tempering for specific applications. The most widely used hot-stamping material is 22MnB5 (a boron steel).

Process steps generally include heating the blank to the required temperature, transferring it to the forming die, forming at high pressure and temperature, and rapid cooling in the die. Equipment typically comprises a furnace, forming dies with cooling channels, and a press capable of high forming loads. Surface protection or inert atmospheres may be employed to minimize oxidation and surface defects during heating.

Advantages of hot forming include high strength-to-weight ratios, reduced springback compared with cold forming, and the ability to produce intricate geometries in a single forming operation. Limitations include high tooling and energy costs, slower cycle times, and the need for precise temperature and process control to prevent surface oxidation and material degradation. While widely used for steel components, hot forming concepts are also explored for other metals and advanced alloys in specialized applications.