LINEPIPE STEEL WITH LOW YIELD RATIO AND HIGH HIC RESISTANCE AND MANUFACTURING METHOD THEREFOR

摘要

The present invention relates to a steel product for a line pipe oil and gas transmission, and a manufacturing method including the H ₂ S, there is provided a steel product for a line pipe having high strength and low yield ratio and excellent hydrogen induced crack resistance. ; The present invention in weight%, C: 0.02 ~ 0.06%, Si: 0.1 ~ 0.4%, Mn: 1.0 ~ 1.5%, Cu: 0.05 ~ 0.3%, Ni: 0.05 ~ 0.3%, Al: 0.005 ~ 0.1%, P : 0.015% or less, S: 0.002% or less, Ca: 5 ~ 30ppm, remainder Fe, and other being the composition as inevitable impurities, and the Ca and S of the above components satisfy the relation of 1.2 Ca / S 3.5, the tissue is is composed of acicular ferrite and a second phase, the second phase pearl is composed of a light and low-temperature transformation phase, and wherein the fraction of 2 to 10%, and the proportion of the low-temperature transformation phase is characterized in that the 1 to 5% the hydrogen induced crack resistance and excellent low yield ratio steel pipe line, and a manufacturing method in the invention. ; Hydrogen induced crack, the low yield ratio, a line pipe