GMW 14400-2019

This specification covers the requirements for heat-treatable boron steel used in the manufacture of structural parts to manage very high tensile loads without significant deformation as required in safety and occupant protection. This material is heat treated, formed and simultaneously quenched in a water-cooled die in a process referred to as hot stamping, hot press forming or press hardening. Material produced by this process is generally referred to as Press Hardened Steel (PHS). This process produces parts with varied microstructures consisting of combinations of tempered martensite and non-martensitic transformation products. PHS parts may be specified to contain soft zones, which are lower strength than the surrounding metal and may contain reduced amounts of martensite relative to the surrounding metal.
Material Description. The material designation is defined by the GMW material specification number, material category (Sheet or Tubular product), steel product type, grade, and finish type. The substrates used in these applications may be cold rolled or hot rolled, but the product type is designated as heat treated (HT) or hot stamped (HS), as appropriate. The steel grades will correspond to the chemical and mechanical requirements as shown in Appendix A, Table A1 through Table A5. Only the surface quality designation of U, representing an unexposed application, shall be used unless otherwise approved by Materials Engineering. The preceding descriptive items are used together to form the coding system. Examples of the coding system for engineering part drawings, electronic math data files and/or manufacturing engineering documents are shown in Section 8.
Resistance Welded Mechanical Tubing. Tubes supplied to this specification are formed from a steel strip to the desired shape and dimension, electrical resistance welded into a tube, and then heat treated to achieve the final mechanical property requirements.
Induction Heat Treated Steel. Part sections formed with this operation and supplied under this standard shall be made by stamping in the as-rolled condition. The raw stamping can be selectively induction hardened to achieve the required strength requirements. Al-Si, Zn, Zn-Fe, or Zn-Ni pre-coated products shall not be used in these applications.
Hot Stamped Die Quenched Steel. Parts shall be made by austenitizing a pre-cut blank, hot stamping the heated blank and rapid cooling (quenching) the stamped part in the die or via water quenching. Press hardened steel (PHS) can be formed by either direct or indirect stamping processes. The direct process is considered as main-stream for all usages (except tubes).