Patent ID: 7914629
Filing Date: 2011-03-29
Classification: C21D,C22C,Y10T

Abstract:
1. High strength thick steel plate containing, by mass %, C: 0.03 to 0.15%, Si: 0.1 to 0.5%, Mn: 0.5 to 2.0%, P: ≦0.02%, S: ≦0.01%, Al: 0.001 to 0.1%, Ti: 0.005 to 0.02%, Ni: 0.15 to 2%, and N: 0.001 to 0.008% and having a balance of iron and unavoidable impurities as chemical components, having a microstructure of a ferrite and/or pearlite structure with bainite as a matrix phase, and having an average circle equivalent diameter of crystal grains with a crystal misorientation angle of 15° or more of 15 μm or less in the regions of 10% of plate thickness from the front and rear surfaces and of 40 μm or less in the other region including the center part of plate thickness.