The Recent Development of Advanced Automobile Steel Sheets and Long Products

摘要

More and more high strength steels have been developed to meet the progressive requirements from automotive industry in recent years. This tendency for steels to be of higher strength should coupled with the dissolve of the problems concerning with the ductility loss,fabrication complexity,cost increase,and service life deterioration due to strength level rising. The paper reviewed the recent scenario of automobile steels developed in CISRI. Four grades of hot stamping martensitic steels from 1500 MPa to 2200 MPa were developed through the improvement of ductility. A trial on nitrogen alloyed austenitic steel with high ductility was taken over to present a combination of high strength and high ductility. The study of high strength and high ductility in low and/or medium alloy steels gave the result of RmA approaching to 40 MPa％which could meet the requirement for the new generation sheet steel. The research on mechanisms of the delayed fracture and fatigue failure promoted the creation 1500 MPa grade bolt steel,2000 MPa grade spring steel,and high strength case hardening steel. Non heat treated forging steel with less microalloying elements or without any microalloying element was developed through microstructure control to reduce the cost further. It is now generally believed that automotive steel is really a kind of new materials,which depends on market demands,steel metallurgy,production equipment and fundamental research. It is worthy to take more and more efforts on automotive steels to be of high performance in the near future.