GMW3032

Description / Abstract: This standard covers the requirements for continuous cast sheet steel with specified minimum yield strengths from 180 MPa through 700 MPa and is applicable to uncoated and coated, cold (CR) or hot rolled (HR) low carbon, solid solution strengthened, bake hardenable (BH), and interstitial free (IF) or high strength low alloy (HSLA) substrates with good formability. Continuously hot or cold rolled flat products shall be supplied as coils or sheet. Hot rolled flat products are usually supplied in thicknesses 1.75 mm. These flat products are used for cold forming and for manufacturing of welded tubes. Cold or hot rolled flat products with the appropriate surface type and surface finish are suitable for the application of surface coatings (metallic hot dipping, electrolytic plating, hot spray painting, organic coatings and/or other coatings). This specification does not apply to steel for case hardening and cold reduced, work hardened strips. Additional requirements or agreements shall be specified by regional GM business units, e.g., GM North America (GMNA), GM Europe (GME), GM Brazil (GMB), and GM Korea (GMK).

Material Description. The material designation is defined by the GM Worldwide (GMW) base metal specification number, steel product type, minimum yield strength, and finish type. The steel product type is designated by CR for cold rolled products, or HR for hot rolled products. Microstructure free of banding, which is caused by the interdendritic segregation of manganese during solidification, is specified for hot rolled HSLA inclusion-controlled grades that are used for chassis applications.

A numeral, (180, 210, 240, etc.,) will designate the minimum yield strength level in MPa (Megapascals). A designation of steel type shall be added to BH2, solid solution strengthened grades Re-phosphorized and Interstitial Free (P and IF), structural automotive (SA) and high strength low alloy (LA) steels as shown in Section 8. An "F" designation may be added on engineering and/or manufacturing documents following an LA steel type to specify the steel as inclusion-controlled. A "B" designation is specified for hot rolled LA "F" type grades which need to be free of microstructural banding. Anisotropy Index for banding free grades is listed under Appendix C. The steel grades will correspond to the chemical and mechanical requirements as shown in Table 1 through Table 5. The finish type, Pan alpha character, will designate the finish as E (exposed) or U (unexposed). In addition, products which are not coated shall have the word "Uncoated" added to the call-out after the steel type, but before the finish designation. A special requirement for temper rolling may be required and shall be specified with a "T" designation. The descriptive items in this section (1.1) are used together to form the coding system. Examples of the coding system for engineering part drawings and manufacturing engineering documents are shown in Section 8.

Applicability. Typical applications are coated or uncoated sheet metal parts consisting of high strength sheet steel with specified minimum yield strengths from 180 MPa through 700 MPa.