Ultrawide thick-wall and low-yield-ratio steel for X80 straight welding pipes and production method thereof

Abstract

The invention discloses ultrawide thick-wall and low-yield-ratio steel for X80 straight welding pipes and a production method thereof. The steel contains 0.045-0.065% of C, 0.26-0.40% of Si, 1.60-1.80% of Mn, P not more than 0.010%, S not more than 0.0015%, 0.04-0.06% of Nb, 0.008-0.020% of Ti, 0.10-0.24% of Ni, 0.16-0.25% of Cu, Mo not more than 0.12%, Cr not more than 0.30%, 0.45-0.75% of Ni+Cu+Mo+Cr, 0.010-0.030% of Al, 0.0010-0.0040% of N, and the balance of Fe and inevitable impurities. The heating temperature of casting blanks is 1190-1220 DEG C; the uniform heating temperature is 1170-1200 DEG C; the rough rolling temperature is 1100-1140 DEG C; the finish rolling temperature is 810-840 DEG C; and the cooling temperature is 710-750 DEG C. The thickness of finished steel plates is not lower than 30 mm; the width is not lower than 4320 mm; and the low-temperature toughness and the strain resistance are excellent.

Description

technical field [0001] The invention belongs to the technical field of low-carbon and low-alloy steel, and in particular relates to a X80 grade extra-wide, thick-walled, low-temperature toughness and strain-resistant hot-rolled steel plate with a thickness ≥ 30 mm and a width ≥ 4320 mm, and a production method thereof; suitable for making Longitudinal welded pipes for oil and gas transportation with large diameters serving in complex environmental conditions such as geologically active areas, cold areas, crossing areas and subsea suspended areas. Background technique [0002] For a long time, increasing the efficiency of oil and gas pipeline transportation has been the goal pursued by the field of pipeline transportation. With the increasing consumption of oil and natural gas, the need to improve the efficiency of pipeline transportation becomes more urgent. Enlarging the pipeline diameter and transmission pressure is an important measure to improve the efficiency of oil an...

AI Technical Summary

Problems solved by technology

[0005] CN107502836A discloses a thick-walled large-diameter high-grade pipeline steel with improved low-temperature toughness and its manufacturing method, and provides a wide and thick plate for X80-level large-diameter straight seam welded pipe and its manufacturing method. The steel plate uses more Mo (0.15% ~ 0.20%), Ni (0.25% ~ 0.30%) design, the cost is high; the manufacturing process requires the reduction rate of the final pass of rough rolling to be greater than 25%, and the requirements for equipment capacity are too high, which is not suitable for high strength and wide Production of Specification Pipeline Steel

[0007] CN107385326A discloses a production process of ultra-fine grain wide and thick pipeline steel plate, and provides a production process of wide and thick pipeline steel. The heating temperature of the casting slab is low (1120-1140°C), which is not conducive to the solid solution of elements, especially Nb; The reduction rate of the final pass of rough rolling is too large (≥26%), and the requirements for equipment capacity are too high

[0010] To sum up, the research on the steel for X80 longitudinal seam welded pipe with extra wide thick wall and low yield strength ratio in the existing technology is still insufficient

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