| 摘要 |
A high-tensile steel plate of low acoustic anisotropy and high weldability having yield stress of 450 MPa or greater and tensile strength of 570 MPa or greater and a process for producing the steel plate are provided. The steel has an Si content of 0.10% or less, thereby achieving a volume ratio of island martensite of 3% or less, contains Nb>=0.025% and Ti>=0.005% so as to satisfy 0.045%<=[Nb]+2x[Ti]<=0.105%, contains Nb, Ti, C and N in ranges such that the value of A=([Nb]+2x[Ti])x([C]+[N]x12/14) is 0.0022 to 0.0055, and has a steel structure wherein bainite volume ratio is 30% or more and pearlite volume ratio is less than 5%.
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