| 摘要 |
PURPOSE:A steel material containing a specified amount of Si, Mn, etc. is heat rolled and wound at a temperature less than 350 deg. so that a high-ductile, low-yield ratio, high-tensile steel plate is produced. CONSTITUTION:A steel is used containing C: 0.05 to 0.15%, Si: 0.71 to 2.0%, Mn: 0.5 to 2.0%, S<=0.015%, and Zr and rare earth elements being in an amount such that Zr/S: 2 to 10%, rare earth elements/si: 1.3 to 5. Such steel slab is heat rolled at a temperature of Ar3 to (Ar3+60) deg.C to produce a steel plate, which is wound into coil below 350 deg.C. In this composition, Si is useful to enhance ductility, Mn addition and S reduction are effective in strength increase, reduced MnS inclusive, and the reduction of required amount of Zr and rare earth elements. Further, the content of more than 0.71% Si and the steel winding condition below 350 deg.C effectively reduces the yield ratio to less than 70%. |
