Development of High-Strength Cold-Rolled Steel Sheets for Automotive Use by Continuous Annealing

High-strength cold-rolled steel sheets having tensile strength of from 350 to 1,500 MPa with a wide variety of features have been developed by using the continuous annealing process consisting of water-quenching system. Newly developed high-strength steels include dual-phase steels with high bake-hardenability, dual-phase steels with low yield ratio and excellent ductility, dual-phase steels with high deep drawability, ultra high-strength steels and extra deep drawing high-strength steels.

This paper describes the metallurgical characteristics of the products of the continuous annealing process consisting of water-quenching system, processing conditions and mechanical properties of these high-strength steels, and their application to automobiles.