Aluminum alloy is the most widely used nonferrous metal material in industry, and has been widely used in aviation, aerospace, automobile, machinery manufacturing, ship, construction, decoration and chemical industry. With the progress of material technology, the rapid development of aluminum alloy materials has been achieved. So far, different series and varieties of aviation aluminum alloy, yuhang aluminum alloy, armor aluminum alloy and aluminum matrix composite materials have been developed. With the rapid development of science and technology and industrial economy in recent years, the demand for aluminum alloy welding structural parts is increasing day by day, and the usage amount is second only to steel.
In general, for these advanced aluminum alloy materials, the manufacturing process is generally not recommended or even prohibited to use fusion welding for connection. However, friction stir welding can weld all series of aluminum alloys [2-3] (FIG. 2), which completely solves the welding problem of aluminum alloy materials from the perspective of method.
Aluminum alloy welding is difficult because of its special physical properties. Because the aluminum alloy surface has a melting point of 2060℃ is very refractory oxide film; Using the traditional fusion welding method, the welding process is easy to produce pores, but also cause cracks in the welding surface; Even easy to cause product deformation; Thermal conductivity is large, welding process also causes welding joint to soften.
Friction stir welding is an advanced solid connection technology, compared with the traditional method of fusion welding, friction stir welding is tiny grains, fatigue performance, tensile properties and bending performance good, no dust, no pores, no splash, energy saving, no welding wire, welding don’t need to use the protective gas, residual stress after welding, and the advantages of small deformation. It has become an almost completely customized welding technique for aluminum alloy materials.
The weld surface of friction stir welding of aluminum alloy is similar to the machining trace, showing the characteristic of periodic ripple. The width of the weld is consistent with the shaft shoulder diameter of the mixing tool. The macroscopic microstructure of friction stir weld of aluminum alloy is characterized by typical “onion ring”. According to the grain characteristics of the weld area and the physical metallurgical process, the friction stir welding joint generally has four characteristic areas, from the weld center to the base metal: dynamic recrystallization area, thermal-mechanical influence area, thermal-influence area, and the base metal. The materials in the dynamic recrystallization area experienced the recovery and recrystallization process under the condition of high strain rate, and the grain distortion and growth mainly occurred in the metal materials in the thermal-mechanical influence area under the condition of thermal cycling and frictional pressure, and it is the characteristic area that friction stir welding is different from fusion welding.
For all series of aluminum alloy materials, friction stir welding process technology has been basically mature, in the welding thickness of the early United Kingdom welding institute (TWI) has achieved more than 100mm thickness aluminum alloy structure reliable welding. In China, now the 150mm thick aluminum alloy friction stir welding technology has also been a breakthrough.
From the Angle of welding structure, friction stir welding is generally recognized as long, straight weld (flat butt and lap) ideal welding method, however, does not exist in fact because of the friction stir welding process by fusion welding material, weld quality and not affected by the weld or workpiece position, rely mainly on equipment to ensure that, friction stir welding can achieve all position welding structure, such as horizontal, vertical welding welding, overhead welding and any position and Angle of rail welding. Typical forms of friction stir welding joint include plate butt joint, multilayer butt joint, multilayer lap joint, t-joint, Angle joint, etc.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods
