Perspectives on Maximizing Strengthening Mechanisms in Automotive HSLA Steel

Well-established practices exist for the production of cold-rolled and continuously annealed high-strength, low-alloy (HSLA) steels as both coated and uncoated variants. Through standard processing techniques, the yield strength of cold-rolled HSLA steel is practically limited by numerous process and alloy design factors to 550 MPa and less. A production methodology is proposed to achieve greater strengths in cold-rolled and continuously annealed HSLA steels. This methodology utilizes both increased precipitation of microalloy carbides prior to continuous annealing and a subsequent annealing process in which recrystallization of ferrite is suppressed prior to partial or full austenitizing. The resultant microstructure, as a consequence of enhanced precipitate and grain refinement strengthening, achieves greater strengths than those traditionally produced for automotive applications of cold-rolled HSLA steels. The implications of mass adoption of such enhanced cold-rolled HSLA steels are discussed, including the potential for partial replacement of intermediate-strength advanced high-strength steel in automotive body structures.