STEEL FOR THICK-WALLED LARGE-DIAMETER HIGH-GRADE STEEL PIPELINE HAVING IMPROVED LOW-TEMPERATURE TOUGHNESS, AND PREPARATION METHOD THEREFOR

摘要

Steel for a thick-walled large-diameter high-grade steel pipeline having improved low-temperature toughness, and a preparation method therefor. The pipeline steel comprises the following components (in weight percent): 0.038 to 0.058％ of C, 0.17 to 0.27％ of Si, 1.65 to 1.75％ of Mn, less than or equal to 0.01％ of P, less than or equal to 0.003％ of S, 0.015 to 0.05％ of Al, 0.045 to 0.055％ of Nb, 0.006 to 0.02％ of Ti, 0.11 to 0.16％ of Cr, 0.15 to 0.20％ of Mo, 0.10 to 0.16％ of Cu, 0.25 to 0.30％ of Ni, 0.0005 to 0.0040％ of Ca, and the balance of Fe and inevitable impurities. The preparation method therefor comprises using a 320 mm thick section casting blank, and performing blank material heating, rolling, and laminar cooling to ensure different deformation storage energy and grain boundary mobility, to effectively refine the structural grain size, and to obtain uniform bainite and needle ferrite, ensuring the stability of the structure and performance, meeting the performance requirements on steel for a wide and thick high-grade steel pipeline.