Magnesium alloy weld joint hot rolling strengthening process

Abstract

The invention discloses a magnesium alloy weld joint hot rolling strengthening process, which comprises the following steps: 1) welding magnesium alloy pieces on both sides by adopting insert gas arc welding; 2) placing the magnesium alloy welding piece into a heat treatment furnace, and performing postwelding stress relief annealing at 200 to 350 DEG C for 0.5 to 2 hours; and 3) performing hot rolling on the surplus height of the weld joint of the magnesium alloy welding piece for at least two times until the weld joint is in level with a base body, wherein the magnesium alloy welding piece is heated to 350 to 400 DEG C before hot rolling at each time, heat preservation and preheating are performed for 10 minutes to 0.5 hour and hot rolling is performed at 250 to 350 DEG C. According to the process, the operation process is simple, the processing period is short, the weld joint strength is higher than the tensile strength of the base material, the tissue is refined, and the appearance of the welding piece is beautified. The process has a certain straightening effect on the magnesium alloy plate which is deformed after being welded, and is applicable to the complete-penetration magnesium alloy materials such as AZ31, AZ61 and AZ80.

Description

technical field [0001] The invention belongs to the technical field of changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working, and in particular relates to a hot rolling strengthening process for magnesium alloy weld seams. Background technique [0002] As the lightest metal structural material, magnesium alloy has low density, high specific strength, high specific stiffness, excellent damping performance and electromagnetic shielding performance, and has broad application prospects in the electronics field, aviation industry, automobile and rail transit manufacturing. However, magnesium alloys have the characteristics of high chemical activity, low melting and boiling point, high thermal conductivity and thermal expansion coefficient, etc., which are prone to slag inclusions, pores, deformation, cracks and overheating during the welding process, which seriously hinders the application of its welded structural parts. The s...

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Problems solved by technology

When the hot-pressing temperature is 250°C, since the structure of the welded joint is roughly the same as that of the welded joint, no recrystallized structure appears, resulting in a low tensile strength of the joint, which is only 60% of the base metal, and the elongation is as low as 6%. The fracture location is in the heat-affected zone; when the hot-pressing temperature is 350°C, the tensile strength of the joint reaches 228MPa, which is almost the same as that of the base metal, and the elongation is 10.2%. The fracture also occurs in the heat-affected zone; the hot-pressing temperature When the temperature is 400 ℃, the tensile strength decreases to 70% of the base metal tensile strength, the elongation is 7%, and the fracture also occurs in the heat-affected zone, which indicates that the heat-affected zone is the weak link of the welded joint. As the hot-pressing temperature increases, the grains in the heat-affected zone grow and coarsen, resulting in a decrease in mechanical properties

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