Low-hardness X70M pipeline steel hot-rolled plate coil and manufacturing method thereof

Abstract

The invention discloses a low-hardness X70M pipeline steel hot-rolled plate coil and a manufacturing method thereof. Wherein the steel contains 0.061%-0.061% of C; 0.080%, si 0.15%- 0.35%, mn 1.41% toMn 1.41% 1.59%, nb0.060%- 0.080% of V, 0.010%-0.030% of V, 0.008%-0.020% of Ti, 0.13%-0.18% of Mo, 0.13%-0.19% of Cr, 0.020%-0.060% of Al, smaller than or equal to 0.018% of P, smaller than or equalto 0.004% of S and smaller than or equal to 0.007% of N; wherein Pcm is smaller than or equal to 0.19%, and the balance Fe and inevitable impurities. Casting blank thickness below 200 mm. And a casting blank is subjected to hot charging at 500-850 DEG C and heated to 1150-1200 DEG C, the finish rolling temperature of rough rolling is 980-1050 DEG C, the finish rolling starting temperature of finish rolling is 910-960 DEG C, the finish rolling temperature is 780-840 DEG C, the cooling speed is 12-30 DEG C/s, and the coiling temperature is 470-530 DEG C. And the hardness value of the producedX70M-grade hot-rolled plate coil is smaller than or equal to 230 HV10.

Description

technical field [0001] The invention belongs to the field of high-strength low-alloy steel for metal materials, and in particular relates to a method for manufacturing pipeline steel for oil and gas transportation pipelines, in particular to a low-hardness (≤230HV) steel in the API SPEC 5L specification 10 ) X70M steel grade pipeline steel hot-rolled coil and its manufacturing method. Background technique [0002] The huge energy demand has stimulated the rapid development of pipeline construction. In order to ensure the stability and safety of transportation, with the improvement of knowledge and the development of technology, the technical indicators of steel are becoming more and more reasonable and perfect. There are many technical indicators of pipeline steel, such as tensile properties, Charpy impact properties, drop hammer properties, bending properties, hardness, grain size, inclusions, banded structures and so on. [0003] X70M steel grade has become one of the mai...

AI Technical Summary

Problems solved by technology

In the published patent documents, one is that the alloy design contains more precious elements, resulting in higher cost; the other is that the hardness value is high due to the addition of more Cr or the low-temperature coiling process; the third is that the composite addition of Nb, V, and Ti is not used. To expand the beneficial effects of microalloying elements, etc.

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