Welding method for S32750 super duplex stainless steel welded pipe

Abstract

The invention relates to a welding method for an S32750 super duplex stainless steel welded pipe. The method comprises the following steps that 1, a pair of forming wheels are additionally mounted onan argon tungsten-arc welding production line, wherein the forming wheels are provided with arc-shaped forming grooves, the forming grooves of the two forming wheels are clamped to both sides of the steel pipe, and the steel pipe drives the forming wheels to rotate; 2, a welding gun is used for welding a to-be-welded groove above the steel pipe, after a welding molten pool is formed, a thermal imager is used for finding an area, at the temperature of 800-1200 DEG C, of the rear end of the molten pool of argon tungsten-arc welding, and a connection line of the two forming wheels is moved to thearea through adjustment; 3, the distance between the two forming wheels is adjusted, and the area, at 800-1200 DEG C, of the rear end of the molten pool is extruded to make the thickness of protrusions on the upper surfaces of welding seams after extrusion be 5-20% of the wall thickness of the steel pipe. The strength of the longitudinal welding seams of the welded S32750 duplex stainless steel welded pipe is higher than that of S32750 duplex stainless steel welded pipe base metal.

Description

technical field [0001] The invention relates to a steel pipe welding method, in particular to a welding method for S32750 super duplex stainless steel welded pipes. Background technique [0002] S32750 super duplex stainless steel has high strength due to its high content of Cr, Mo and N, and the coexistence of austenite and ferrite in the room temperature structure at a ratio of about 1:1 (its yield strength is generally that of austenitic stainless steel Twice as high as that), good Cl-pitting resistance, stress corrosion resistance and welding performance, etc., are widely used in petrochemical, salt, hydraulic, shipbuilding and other fields. Compared with the same level of super austenitic stainless steel 254SMO, its pitting resistance index PREN is equivalent, both exceeding 40, but its Ni content is only 7%, which is far lower than 18% of 254SMO, and its yield strength is about two times that of 254SMO. times, so that under the premise of ensuring the service life, th...

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Problems solved by technology

The alloy content of the weld of S32750 super duplex stainless steel welded pipe after N supplementation is the same as that of the base metal, but the mechanical properties of the as-cast microstructure of the self-fluxing weld are still poor compared with the rolled annealed microstructure of the base metal, and welded joints are prone to appear The case where the mechanical properties are lower than those of the base metal

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