Welding method for dissimilar steel plate MIG welding

Abstract

The invention provides a dissimilar metal X80 pipeline steel and 2507 super duplex stainless steel CMT welding method applied to an offshore pipeline engineering platform. The method comprises the following preparation steps that S1, sections of to-be-welded parts of X80 pipeline steel and 2507 super duplex stainless steel are machined into Y-shaped grooves; S2, surfaces and the grooves of steel plates are polished to remove impurities such as oxide; S3, the steel plates ire fixed to a clamp with a heat dissipation channel, a distance between the plates is 2 mm, the two ends of the plates are fixed through spot welding, an ER2594 duplex stainless steel welding wire is adopted as a filling material, a diameter phi of the welding wire is 1.2, a current is 140 A to 150 A, a voltage is 10 V to 12 V, time is 1 s, mixed shielding gas with 2% of CO2 and 98% of Ar is introduced, and a gas flow is 12 L / min; S4, an MIG welding machine of a cold metal transition welding technology (CMT) is adopted for welding the plates, a welding speed is 45 mm / min, a current is 145 A, a voltage is about 12 V, and a protective gas flow is 12 L / min; S5, a welding table is cooled after welding is completed, and the next batch of samples are welded when the welding table is cooled to 160 DEG C or below; and S6, nondestructive flaw detection and weld joint two-phase proportion detection are conducted on a welded joint, and a welding process is completed after detection is qualified.

Description

technical field [0001] The invention relates to the field of welding technology, and mainly relates to a CMT welding method of dissimilar metal X80 pipeline steel and 2507 super duplex stainless steel. Background technique [0002] Due to its excellent mechanical properties and corrosion resistance, duplex stainless steel, especially in Cl - The ability to resist local corrosion in solution has been widely used in petroleum, natural gas, chemical and seawater environments, and has become the preferred material for underwater facilities in offshore oil and gas fields. [0003] Due to the exploitation and transportation of offshore oil energy, the use of pipeline steel for transporting oil and natural gas has also increased accordingly. Pipeline steels are generally classified as API grades by the American Petroleum Institute (Washington, DC) based on yield strength. X80 pipeline steel is a low-carbon, micro-alloyed high-grade steel and a new type of pipeline material. Due ...

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Problems solved by technology

[0004] However, due to the great differences in chemical composition, microstructure, and mechanical properties between duplex stainless steel and low-alloy pipeline steel, the microstructure, alloy element distribution, and mechanical properties of dissimilar metal welded joints are very complicated. The difference in composition and lattice structure leads to complex phase composition, grain boundary type and element distribution in the welding transition zone. At the same time, the uneven microstructure and welding heat distribution lead to gradient changes in mechanical properties and residual stress at the fusion line and transition zone. , Dissimilar metal welded joints will have significant galvanic effects during service in marine corrosive environments, macroscopic galvanic effects caused by differences in self-corrosion potentials of stainless steel / low alloy steels and electrochemical activities between microstructures / precipitated phases / inclusions The microcosmic galvanic effect caused by the difference, the existence of these factors may lead to the decrease of the corrosion resistance and the deterioration of the mechanical properties of the dissimilar welded joints, and finally cause the failure behavior of the material such as stress corrosion cracking (SCC) during the service in the marine environment, which is always threatening safe production of marine energy

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