A kind of x90 grade multi-phase structure pipeline steel for longitudinal seam welded pipe

Abstract

The invention relates to an X90 level heterogeneous structure pipeline steel plate for a longitudinal welded pipe and a manufacturing method of the pipeline steel plate. According to the research and practice of the physical metallurgy principle, recrystallization rule and phase change rule of materials, innovative X90 level high-strength pipeline steel is invented. The pipeline steel has a heterogeneous microstructure, and the implementability of the process is researched, so that perfect combination of high strength, high toughness and high plasticity is realized. The X90 level pipeline steel plate used for longitudinal submerged arc welding refers to a pipeline steel plate which integrates the high strength, high toughness and high plasticity into a whole, wherein the yield strength (RP 0.2) is more than or equal to 555MPa, the tensile strength (Rm) is more than or equal to 695MPa, the yield ratio (RP 0.2 / Rm) is less than or equal to 0.75, the uniform elongation (UEL) is more than or equal to 11 percent, KV2 at the temperature of 20 DEG C below zero is more than or equal to 300J, and DWTT at the temperature of 15 DEG C below zero is more than or equal to 85 percent.

Description

technical field [0001] The invention belongs to the technical field of high-strength pipeline steel manufacturing, and relates to an X90 grade multi-phase structure pipeline steel plate for oil and gas transportation straight seam welded pipes and a manufacturing method thereof. Background technique [0002] Since the 21st century, with the continuous demand for energy such as oil and natural gas due to economic development at home and abroad, it is necessary to build a large number of long-distance transmission pipelines. Following the construction of the first and second pipeline projects of the West-to-East Gas Pipeline, the third pipeline of my country's West-to-East Gas Pipeline has started construction, and the fourth, fifth, and even seventh and eighth pipelines are under planning and research. In order to reduce construction costs, further improving the transmission efficiency of domestic natural gas pipelines has become the development direction of the natural gas p...

AI Technical Summary

Problems solved by technology

The reduction of plasticity has a greater impact on the security of the application

Therefore, the main challenge in developing X90 is to achieve high toughness and ductility while achieving high strength

Before 2010, my country had carried out the development of X100 longitudinal submerged arc welded pipe. So far, the X100 welded pipe developed at home and abroad has not been really applied in engineering.

[0005] The Chinese patent application number is 201410266532X, which discloses the invention of "X90 pipeline steel pipe with uniform deformation elongation UEL ≥ 5%d and its preparation method", which mentions X90 pipeline with uniform deformation elongation UEL ≥ 5% Steel pipes whose uniform deformation elongation rate is lower than the performance index of UEL ≥ 11% of the present invention, and fail to achieve the performance index of yield ratio ≤ 0.75

And its composition contains higher Cr, the hardness of the steel plate is higher, which affects the welding performance

[0006] The Chinese patent application number is 2014102471606, which discloses "X90 pipeline steel with excellent girth weld performance and its production method". Center segregation of manganese is prone to occur in the process, and the realizability is poor

[0007] The Chinese patent application number is 2014102390914, which discloses "a wide and thick plate of X90 pipeline steel and its production method". The chemical composition of the invention is different from that of the present invention.

[0008] The Chinese patent application number is 2013101694496, which discloses "a steel for X90 pipelines and its production method". The chemical composition of the invention is different from that of the present invention. There are few alloying elements that are not added. According to many studies, it has been shown that adding B can effectively strengthen the steel plate, but the boron element is very easy to precipitate at the grain boundary, weakening its plasticity and toughness. At the same time, the cooling rate after rolling in the production process reaches 42-70°C / s, at present, the post-rolling cooling equipment capacity of wide and thick plate manufacturers is not enough, especially for steel plates with thickness > 25mm, it is difficult to achieve such a large cooling rate, and with the increase of cooling rate, it is difficult to ensure the shape of wide and thick steel plates with a width greater than 3000mm

But its toughness is not easy to control

[0009] The Chinese patent application number is 200710045314.3, which discloses "a high-strength X90 pipeline steel and its production method". The chemical composition of the invention is different from that of the present invention. %), Mo (<0.60%), Cu (<1.2%), Cr (<1.2%), Ni (<1.5%), Cu (<1.2%) content range is too wide to meet the conditions for specific implementation, and The content of S (≤0.003%) and P (≤0.015%) is relatively high, which is not as high as the purity of the present invention, which affects the low temperature impact toughness of the product

And its structure is a single bainite structure, it is difficult to achieve a better uniform elongation, and the plasticity is not good

[0010] The Chinese patent application number is CN201310342839, and the disclosed "method of controlling carbon in the refining of X90 and above grade pipeline steel" only involves the smelting method of ultra-high strength pipeline steel, and does not involve the composition design, structure design and the achieved Performance index of X90 steel plate

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