GMW GMW14400 [ Revised ]

This specification covers the requirements for low carbon, heat-treatable boron steel used in the manufacture of structural parts requiring heat treatments to achieve high strength. Press-hardened steel can be pre-formed and subsequently hot-stamped and die quenched, but post-forming should not be the scope for this type of steel. Typical applications include door impact beams, bumper impact beams, and reinforcements for impact structures.

Material Description. The particular application shall determine the preforming or postforming operations to produce the finished product. The material designation is defined by the GMW base metal 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 Tables 1 through 4. The surface quality type, an alpha character, shall be designated with the surface quality, unexposed (U). The above 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 roll formed from 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 a coil blank in the as-rolled condition. The raw stamping can be selectively coil induction hardened to achieve the required strength requirements. Aluminized, precoated products are not to be used in these applications.

Hot-Stamped/Die-Quenched Steel.

Uncoated Products. Part sections formed with this operation and supplied under this standard shall be made by austenitizing a precut blank or pre-stamped part, hot stamping the heated blank or pre-stamped part, and rapid cooling (quenching) the stamped part in the die. The cooled part must be subsequently shot blasted to remove oxide from the surface. The microstructure of the finished parts may consist of martensite or martensite and trace amounts of bainite.

Pre-coated Products. Part sections formed with this operation and supplied under this standard shall be made by austenitizing a precut blank, hot stamping the heated blank and rapid cooling (quenching) the stamped part in the die or via water quenching. Parts shall not be pre-stamped prior to the hot stamping operation, but slight roll-forming operations may be allowable if the coating is not damaged. Shot blasting the cooled part is not permitted for pre-coated parts due to damage to the coating. The microstructure of the finished parts may consist of martensite or martensite and trace amounts of bainite.

Symbols. Not applicable.

Typical Applications. Typical applications are uncoated or pre-coated sheet metal and thin gauge tubular structural parts requiring yield and tensile strengths exceeding 950 MPa and 1250 MPa respectively.

Remarks. See Table A1 in Appendix A for cross-referenced/superceded specifications.