| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength steel sheet having excellent stability of mechanical property without requesting the difficult composition adjustment and without lowering the productivity at the time of performing a heat treatment. <P>SOLUTION: After hot-rolling the steel material having the composition which contains, by mass, 0.05-0.3% C, 0.7-3.0% Si, 0.5-3.0% Mn, 0.01-0.1% Al, and 0.001-0.015% N and in which the content of N and Al satisfies 0.16[Al]-[N]+0.001≥0 (wherein, [] shows content (mass%) of each element) under conditions of 1,150-1,250°C heating temperature, 800-900°C rolling completed temperature, 90-99.5% rolling reduction, ≥20°C/s cooling speed after completing rolling and ≤650°C winding temperature, the steel material is cold-rolled and continuously annealed, thereby manufacturing high strength steel sheet with the structure which is mainly composed of a ferrite and a martensite. <P>COPYRIGHT: (C)2012,JPO&INPIT |
