A method for manufacturing a welded steel pipe with ultra-high strength and high deformation performance

Abstract

Provided is a manufacturing method for a welded steel tube with ultrahigh strength and high deformation performance. The composition of a base material for the welded steel tube in mass percentage is as follows: C: 0.03%-0.09%; Si: 0.01%-0.4%; Mn: 1.6%-3%; Al: 0.01%-0.1%; Nb: 0.01%-0.1%; Ti: 0.005%-0.030%; N: 0.001%-0.01%; B: ≤ 0.0003%; and S: ≤ 0.001%; in addition, the composition also contains: Cu: 0.01%-0.5%; Ni: 0.01%-0.80%; Cr: 0.01%-0.06%; Mo: 0.01%-0.05%; and V: 0.01%-0.1%; and contains one or more than two of Ca, O and S, Ca: 0.005%-0.008%; O： ≤ 0.03%; S: ≤ 0.001%, and the balance being Fe and inevitable impurities. In addition, the area percentage of any one of ferrite + bainite, ferrite + martensite and ferrite + bainite + martensite is more than 95%, the area percentage of the ferrite is 10%-60%, and a steel plate has a microstructure in which the average particle size of cementite in the bainite and / or martensite is no more than 0.6 μm, the extension strength is no less than 700 MPa, and the yield ratio is ≤ 90%.

Description

technical field [0001] The invention relates to oil and gas pipelines used in the energy field, in particular to a method for manufacturing welded steel pipes used in oil and gas environments containing carbonic acid gas, with excellent toughness of the base material and welded parts, ultra-high strength and high deformation performance. Background technique [0002] Oil well pipes and pipelines used in the production and transportation of oil and gas are usually made of carbon steel and low alloy steel. In practical applications, a lot of requirements and related prior knowledge have been accumulated for steel pipes. For example, in order to ensure that steel pipes do not produce deflection even if they are greatly deformed due to changes in the earth’s crust, the general steel adopts a multi-phase structure, and the yield ratio of the steel must be within Below 85%, and in order to obtain higher strength, the microstructure needs to be ferrite + bainite, ferrite + martensi...

AI Technical Summary

Problems solved by technology

However, reheating after accelerated cooling will coarsen cementite existing in bainite or martensite, and the DWTT property (indicator of resistance to brittle crack propagation) will deteriorate

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