| 摘要 |
<p>PURPOSE: A high-strength hot-rolled steel sheet with a complex structure and a manufacturing method thereof are provided to enable a main form to be formed from ferrite and a secondary form to be formed from martensite through the control of alloy components and process conditions. CONSTITUTION: A high-strength hot-rolled steel sheet with a complex structure comprises carbon of 0.05~0.09 weight%, silicon of 0.05~0.02 weight%, manganese of 1.5~2.5 weight%, chrome of 0.1~0.5 weight%, boron of 0.001~0.005 weight%, aluminum of 0.2~0.5 weight%, sulfur of 0.01 or less weight%, phosphorus of 0.01 or less weight%, niobium of 0.01~0.05 weight%, Fe and other inevitable impurities. The main form of the steel sheet is ferrite, which is over 70% in sectional area. The secondary form of the steel sheet is martensite, which is over 5% in sectional area. The size of the average grain of the ferrite of the steel sheet is 2~20μm.</p> |
