Coating Free Press Hardened Steel in Hot Blow Formed Tubular Applications for Lightweighting

Coating free press hardened steel (CFPHS) is a novel grade developed by GM with increased mechanical strength and toughness over the conventional 22MnB5 PHS base material. The formulation of CFPHS forms a stable oxide layer which protects the base material from decarburization and oxidation during austenitization. This renders the AlSi protective coating used on 22MnB5 unnecessary during the hot forming process, which offers the opportunities for wider applications of CFPHS while saving cost and enabling novel uses for the material. Unlike AlSi coated PHS which requires the removal of coating during tube manufacturing, for example, CFPHS can directly be made into tube without extra coating removing process. Today’s discussion will center around initial studies performed on CFPHS tube manufacture and hot blow forming trials using CFPHS. Hot blow form PHS technology enables a PHS tube to be configured into a customized, complex shape- reducing complexity in a subassembly component in a body structure and thus reducing mass in the vehicle.