| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing high tension steel having both of excellent weldability and strength-ductility, particularly in thick material having 50-200 mm thickness, as a production method of steel for structure use having 570 MPa class tensile strength and supplied to the whole structural material required to have the weldability and the durability. SOLUTION: In the method for producing the high tension steel having 50-200 mm thickness excellent in the weldability and the ductility, after heating a steel slab containing prescribed chemical components and <=0.18% Pcm value and the balance Fe with inevitable impurities, at a temperature ranging from Ac3 transformation point to 1,150 deg.C, hot-rolling having >=30% cumulative draft is completed at >=800 deg.C, and successively, accelerated cooling of 3-30 deg.C/s cooling rate is started at >=750 deg.C and stopped at 650 deg.C to 500%oC.
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