HIGH-STRENGTH STEEL PLATE AND HIGH-STRENGTH STEEL PIPE HAVING EXCELLENT DEFORMABILITY AND LOW-TEMPERATURE TOUGHNESS, AND MANUFACTURING METHODS THEREFOR

摘要

A high strength steel plate and a high strength steel pipe excellent in deformation performance and low temperature toughness capable of suppressing a decrease in thickness at the time of deformation and a method for producing the same are disclosed. , And the ratio of the effective crystal grain size at the center of the thickness is 20 占 퐉 or less and the X-ray random intensity ratio of the {111} plane parallel to the plate surface in the center of the thickness is 0.5 to 5.0, Ray random intensity ratio of the {100} plane is 3.0 or less, the X-ray random intensity ratio of each of the {112} plane and the {223} plane is 0.5 to 4.0, and the thickness is 25 mm or more and a tensile strength of 565 MPa or more.