A METHOD FOR MANUFACTURING HOT ROLLED STEEL SHEET FOR LINEPIPE HAVING LOW YIELD RATIO AND EXCELLENT YIELD STRENGTH ANISOTROPIC PROPERTIES

摘要

Building , mainly used for offshore structures and line pipe , hot-rolled steel with a low yield ratio and good yield strength anisotropy Preparation method of a steel plate is provided ; this is a hot-rolled steel sheet in weight %, C: 0.03 ~ 0.09%, Si: 0.01 ~ 0.5%, Mn: 1.2 ~ 2.0% , P: not more than 0.01%, S: less than 0.001%, Ti: 0.01 ~ 0.1%, N: less than 0.01%, Nb: 0.04 ~ 0.07%, Ni: 0.1 ~ 0.5%, Mo: 0.1 ~ 0.5%, remainder Fe and unavoidable impurities in the composition for other re-heating the steel slab 1100 ~ 1150 150 ~ 200 minutes at a temperature , and hot-rolled by the finish rolling temperature of 720 ~ 820 then be cooled and wound up at a temperature of 500 ~ 600 in accordance with the ; the present invention , tensile strength of 7200MPa or more , it is possible to provide a hot rolled steel sheet having a low yield ratio and excellent yield strength anisotropy .