What should I pay attention to when welding aluminum alloy?

【Summary Description】 Welding aluminum material What should I pay attention to when welding aluminum alloy/? Aluminum alloy material, high strength and light weight. The main welding process is manual MIG welding and automatic MIG welding, its base metal, welding wire, shielding gas, welding equipment. An aluminum alloy is an alloy composed of aluminum as a matrix element and one or more alloying elements. Because the heat energy of the tungsten argon arc welding torch is relatively concentrated, the arc combustion is stable, the weld metal is dense, the strength and plasticity of the welded joint are higher, and the quality of the joint is better, so it is the most commonly used method of welding aluminum alloy. In addition, when we weld aluminum alloy, we also need to pay attention to the following six points: High (I) thermal conductivity The thermal conductivity and specific heat capacity of aluminum alloy are more than twice that of carbon steel and low alloy steel. The thermal conductivity of aluminum is more than ten times that of austenitic stainless steel. During the welding process of the welding gun, a large amount of heat is quickly conducted to the inside of the base metal, and it is difficult to form a molten pool. Therefore, energy concentration and high power should be used, which can also be preheated according to the structure size, ambient temperature and other conditions; (II) without color change When the molten metal of aluminum alloy welding pool changes from solid to liquid, there is no obvious color change, which is different from the red color of steel before melting, which will bring inconvenience to the operation of the welding gun. Can not accurately determine when the groove base metal began to melt, molten aluminum surface tension is small, low strength, good fluidity, which is easy to cause the weld metal collapse or burn through. Therefore, aluminum welding operators are required to have more skilled operation skills and be good at using small changes in the surface of the molten pool to judge the heating temperature of aluminum; Strong (III) oxidation ability Aluminum and oxygen affinity is very strong, aluminum in the air easily with the oxidation of the formation of dense and strong film, its melting point as high as ℃ far more than the melting point of aluminum and aluminum alloy. And the relative density of the aluminum oxide film is larger, about 1.4 times that of aluminum. In the welding process using a welding torch, the aluminum oxide film will hinder the good bonding between metals and easily cause slag inclusion. Alumina film will also absorb moisture, welding will promote the formation of pores in the weld. Therefore, the oxide on the surface of the weldment must be strictly cleaned before welding and prevent re-oxidation during the welding process; (IV) hot cracking tendency The linear expansion coefficient of aluminum alloy is about 2 times that of carbon steel and low alloy steel. The volume shrinkage on solidification of aluminum is large, amounting to 6.5%, while that of iron is 3.5%. The strength of molten aluminum alloy is low at high temperature. If the process measures are improper, the welding seam and near-seam area will produce great welding stress, restraint stress and thermal stress during the cooling process. As a result, the aluminum welding pool is prone to produce shrinkage, shrinkage, thermal cracking and high internal stress during solidification; (V) Easily Evaporated and Burned Aluminum alloy contains low boiling point elements, such as magnesium, zinc, manganese, etc., under the action of high temperature arc, easy to evaporate and burn, thus changing the chemical composition of the weld metal, so that the performance of the weld is reduced; High stomatal sensitivity of (VI) The liquid molten pool of aluminum alloy is easy to absorb hydrogen and other gases, and a large amount of gas dissolved at high temperature is too late to precipitate in the process of cooling and solidification after welding of the welding torch, which will form pores when gathered in the weld. The moisture in the arc column atmosphere, the Welding materials and the moisture adsorbed by the oxide film on the surface of the base metal are all important sources of hydrogen in the weld. Therefore, it is necessary to clean the base metal groove and welding wire before welding.

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