A low heat input friction stir welding method for high-strength aluminum alloy thick plates

Abstract

The invention provides a high-intensity aluminum alloy thick-plate low-heat input stirring friction welding method, which is mainly characterized in that multiple stages of step shapes are processed at the edge side of a welded thick plate, the low-heat input specification of a high-rotating-speed stirring head and a high-advancing-speed combination is adopted for welding, and the thick plate is cooled to the room temperature after the welding completion; then, a filling plate corresponding to the first stage of step is mounted, in addition, the identical welding parameters are adopted for multi-time parallel overlapping welding in the layer range, and the overlapping width of the adjacent welding seams is not smaller than the radius of a shaft shoulder of the stirring head. The same welding process as that of the first layer filling plate welding is respectively adopted for the welding of each other layer. The method provided by the invention has the advantages that small-size stirring friction welding equipment can be used for realizing multi-time multilayer low-heat input stirring friction welding on medium and thick plate workpieces; the technical problems that the large-thickness plate material stirring friction welding has special requirements on the material performance of the stirring head materials, the fracture easily occurs in the welding, and the like are avoided; meanwhile, the joint region softening problem easily occurring in the high-intensity aluminum alloy thick plate stirring friction welding is also avoided.

Description

Technical field: [0001] The invention relates to a metal welding method, in particular to a welding method for high-strength aluminum alloy thick plates. Background technique: [0002] Those skilled in the art know that the welding of high-strength aluminum alloy thick plates not only has the characteristics of ordinary aluminum alloy welding, but also due to its large thickness and high thermal conductivity of aluminum alloy, when using ordinary fusion welding methods, it is necessary to use many welding methods. Layer, multi-pass low heat input process. However, multi-layer welding is likely to cause serious problems such as oxide inclusions in the weld, serious hot cracks after welding, and softening zones in the welded joints, making it very difficult to weld thick high-strength aluminum alloys when using ordinary welding methods. [0003] Friction stir welding is a solid-state welding technology under the action of thermal coupling invented by the British Welding Insti...

AI Technical Summary

Problems solved by technology

However, in the actual friction stir welding of high-strength aluminum alloys for thick plates, the following problems will be encountered: (1) Due to the high welding resistance, the friction stir welding equipment and special fixtures used are mostly designed as high-rigidity structures, and the investment in equipment is large

(2) The size of the stirring head is also large because it also bears a large welding resistance

(3) In order to ensure sufficient plasticization of the metal in the welding zone and avoid the formation of welding defects, most of the welding parameters adopted are characterized by high heat input, which will bring about obvious softening problems in the heat-affected zone

Among them, the use of overall heat treatment is limited by the size of the workpiece, the overall deformation, and the abnormal growth of grains in the weld area; although local heat treatment of the nugget area by means of hot compressed air, electric arc, and flame can improve the softening area. But at the same time, it will bring problems such as new softening zone and welding structure deformation.

The use of water cooling or underwater welding has been proven to be an effective method to solve the softening of the welding heat-affected zone, for example: invention patent "Using medium cooling friction stir welding method and device" (public number: CN1739902A), invention patent "A kind of water The method of lowering the plasticity of friction stir welding welded joints" (publication number: CN101934426), and the invention patent "a friction stir welding process for enhancing the mechanical properties of Inferior ways to cool the weld seam, but these methods are only effective for thin plate welding, but for medium and thick plates, due to the limitation of heat conduction capacity, the cooling effect is not obvious

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