A thick-walled large-diameter high-grade pipeline steel with improved low-temperature toughness and its manufacturing method

Abstract

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.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy, and relates to a production process for improving low-temperature drop hammer of large-diameter pipeline steel, in particular to a thick-walled large-diameter high-grade pipeline steel with improved low-temperature toughness and a manufacturing method thereof. Background technique [0002] The thick-walled large-diameter pipeline steel for oil transportation (φ1422×30.8mm thick-walled large-diameter pipeline steel) is a high-end product of pipeline steel, which requires a large pipe diameter and meets the requirements of low-temperature service. Currently, the existing domestic technology cannot make breakthroughs and improve The barrier of low temperature toughness of this species. In the prior art, the manufacturing method of thick-walled large-diameter high-grade pipeline steel cannot form fine bainite and true ferrite structure, and cannot effectively eliminate the banded structure in...

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Problems solved by technology

[0002] The thick-walled large-diameter pipeline steel for oil transportation (φ1422×30.8mm thick-walled large-diameter pipeline steel) is a high-end product of pipeline steel, which requires a large pipe diameter and meets the requirements of low-temperature service. Currently, the existing domestic technology cannot make breakthroughs and improve Barriers to Low Temperature Toughness of the Variety

In the prior art, the manufacturing method of thick-walled large-diameter high-grade pipeline steel cannot form fine bainite and true ferrite structure, and cannot effectively eliminate the banded structure in the core and achieve uniformity with higher strength and toughness. The fine-grained structure meets the requirements of low-temperature toughness of the product

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