| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet pile having yield stress of 430 MPa or more and to provide its manufacturing method.SOLUTION: There is provided a steel sheet pile containing, by mass%, Nb:0.040 to 0.050%, C, Si and Mn with carbon equivalent Ceof 0.260 to 0.460, Al: limited less than 0.05%, and one or more kind of Cu, Ni, Mo, Cr and V if needed and having a metallographic structure constituted by ferrite-pearlite, the number density of Nb carbonitride of 0.10 to 0.30/μmand yield stress of 430 MPa or more. Ce=[C]+f(C)×{[Mn]/6+[Si]/24+[Ni]/20+([Cr]+[Mo]+[Nb]+[V])/5}, f(C)=0.75+0.25×tanh{20×([C]-0.12)} There is also provided a manufacturing method of conducting hot rolling on the steel slab of the component with a heating temperature of 1100 to 1300°C, an accumulated rolling reduction rate at 900°C or higher of 90% or more, a finishing temperature of 850°C or higher and cooling. |
