Post-Forming Heat-Treatable (PFHT) Steel

Post-formed Heat Treated SteelsPost-forming heat treatment is a general method to develop an alternative higher strength steel. The major issue holding back widespread implementation of HSS typically has been maintaining part geometry during and after the heat treatment process. Fixturing the part and then heating (furnace or induction) and immediate quenching appear to be a solution with production applications. In addition, the stamping is formed at a lower strength (ellipse 1) and then raised to a much higher strength by heat treatment (ellipse 2).

Another process is air-hardening of alloyed tempering steels that feature very good forming properties in the soft-state (deep-drawing properties) and high strength after heat treatment (air-hardening). Apart from direct application as sheet material, air-hardening steels are suitable for tube welding. These tubes are excellent for hydroforming applications.

A third option is in-die quenching.  A version of Indirect Hot-Forming completes all forming of the part at room temperature, heats the part to about 850-900 ºC, and then uses a water cooled die to quench the part to martensite. This process is called Form Hardening.

Current production grades of PFHT steel and example automotive applications:

PFHT 340/480         As-received room temperature

PFHT 1050/1500     Heat treated after forming

PFHT 1200/1900      Heat treated after forming