Hot-Formed (HF) Steel

Hot-Formed SteelsThe implementation of press-hardening applications and the utilization of hardenable steels are promising alternatives for optimized part geometries with complex shapes and no springback issues. Boron-based hot-forming steels (between 0.001% and 0.005% boron) have been in use since the 1990s for body-in-white construction. A typical minimum temperature of 850 °C must be maintained during the forming process (austenitization) followed by a cooling rate greater than 50 °C/s to ensure that the desired mechanical properties are achieved.  Two types of press-hardening or hot forming applications are currently available:

Direct Hot-Forming
Indirect Hot-Forming

During Direct Hot-Forming, all deformation of the blank is done in the high temperature austenitic range followed by quenching. Indirect Hot-Forming preforms the blank at room temperature to a high percentage of the final part shape followed by additional high temperature forming and quenching. The final microstructure of HF steel is similar to Martensite. Stress-strain curves after quenching are similar to martensitic (MS) steels.

Additional information on Hot Forming is located in Section 3.B.4. of the Advanced High-Strength Steels Application Guidelines.  Current production grades of HF steels and automotive applications:

HF 340/480           As-received room temperature

HF 1050/1500       Heat treated after forming    A-pillar, B-pillar, cross beam

HF 1200/1900       Heat treated after forming

 

 
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