X70 flat plate used for gas-transmission longitudinal welded pipe and producing method thereof

Abstract

The invention provides an X70 flat plate used for a gas-transmission longitudinal welded pipe and a producing method thereof. The flat plate comprises following chemical components: 0.06-0.10% of C, 0.10-0.35% of Si, 1.50-1.80% of Mn, 0.04-0.07% of Nb, 0.008-0.030% of Ti, 0.02-0.045% of Als, not more than 0.20% of Ni, not more than 0.20% of Cr, not more than 0.20% of Cu and 0.020-0.048% of V, with the balance being iron. The method includes: heating a slab is heated to 1160-1280 DEG C; performing rough rolling at 1030-1180 DEG C, wherein the reduction rate of one pass in the first three passes is higher than 20% and the reduction rate of one pass in the last three passes is not less than 15%; performing refined rolling at 810-980 DEG C, wherein the reduction rate in one pass in the first three passes is higher than 20% and the reduction rate in one pass in the last three passes is not less than 7%; raising the speed of rolling; cooling after rolling, with the cooling speed being 15-30 DEG C/s and the finish cooling temperature being 300-450 DEG C; performing air cooling; and performing three passes of straightening. The problems such as large rolling resisting power and large straightening resisting power are overcome. The plate shape of an ultra-wide plate can be guaranteed, and good comprehensive performances comprising ultrafine grains, high strength and high toughness can be obtained.

Description

technical field [0001] The invention belongs to the technical field of low-carbon micro-alloy steel production, and mainly relates to the high-strength and ultra-wide X70 pipeline steel hot-rolled flat technology for high-pressure and large-diameter oil and gas pipelines, in particular to the X70 flat plate used for manufacturing Φ1422mm gas transmission straight seam welded pipes and its Manufacturing method. Background technique [0002] Pipeline transportation is the most economical, most convenient and most important transportation method for long-distance transportation of oil and natural gas. In order to reduce the construction investment and operating costs of long-distance oil and gas pipelines and improve transmission efficiency, long-distance oil and gas pipelines are developed in the direction of large diameter and high pressure; especially the planning and construction of the first to seventh lines of the West-to-East Gas Pipeline The shortage of land resources ...

AI Technical Summary

Problems solved by technology

It can meet the technical requirements of ultra-wide X70 steel plate without heat treatment, solve the problems of high rolling resistance and straightening resistance, and can ensure the shape of the ultra-wide plate and obtain the comprehensive properties of ultra-fine grain, high strength and high toughness.

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