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With the advancement and development of technology, the application areas of aluminum alloys are becoming increasingly wide; as a result, problems related to the welding of aluminum alloys often arise in actual production processes. If you master the following mnemonic, the problems associated with aluminum alloy welding will basically be resolved. Aluminum welding is difficult to perform, and oxygen cracking tends to soften ； Surface oxidation makes welding difficult; thorough cleaning is required before welding ； The power supply polarity is highly effective, and cathode cleaning is very practical ； MIG must be connected in direct or reverse polarity; alternating current is the most commonly used ； High frequency is required to initiate arcing, while pulses can be used for welding ； Aluminum welding ranks second in terms of difficulties, with a very severe tendency to thermal cracking ； There are many types of thermal cracking, with vertical and horizontal pits being the most common ； There is only one specific reason: the rapid shrinkage during the solidification process ； Stress pulls the gap apart; insufficient liquid aluminum causes cracks ； Prevention and resolution are crucial; process design is helpful ； The welding heat should be concentrated; preheat in segments and reduce the welding speed ； The composition design should be reasonable, with clear effects of trace elements. Pore defects are common, and aluminum welding is particularly sensitive to them ； Solving defects in three aspects: materials, gases, and environment ； Environmental humidity should be controlled; work should be halted if it exceeds 60% ； Cleaning the base material is crucial; oil and water residues on the surface must be removed ； Attention should be paid to the use of welding materials; it is necessary to check and dry them ； The shielding gas should be clean, with a purity of four nines ； At the same time, the traffic volume should be controlled to be moderate, neither too high nor too low ； Welding should be carried out in accordance with regulations, and pore problems will disappear. Welding deformation is a hassle; grasp its essence to rid oneself of worries ； The coefficient of expansion is the main factor; improvements should start from here ； There are various adjustment methods; avoid constraints by leaving some margin ； Process parameters must be standardized, and proper preheating should be carried out in the initial stage ； These specifications must be strictly followed, and quality requirements must be met with responsibility. Softening of joints poses risks; strict control and inspection are required ； Material processing is key; the base material and welding materials must be compatible ； It can’t be a mismatch; the strength should correspond ； Process design is also needed to reduce parameters and prevent coarsening ； Concentrate heat reduction in specific areas to prevent their expansion ； All kinds of problems can be solved; welding evaluation is essential ； For welding, human factors, materials, methods, and environment all need to be strictly controlled at each stage ； Pre-welding preparations must be complete, and inspections are required during and after welding ； For practical problems, practical methods are key; practical application is of the utmost importance. Welding characteristics of aluminum and aluminum alloys 1. Oxide film: Aluminum oxidizes easily in air as well as during welding; the resulting alumina (Al2O3) has a high melting point, is very stable, and difficult to remove. It hinders the melting and fusion of the base material; due to its high density, the oxide film does not easily rise to the surface, leading to defects such as inclusions, lack of fusion, and incomplete welding. The surface oxide film of aluminum absorbs a large amount of moisture, which can easily cause pores in the welds. Before welding, strict surface cleaning using chemical or mechanical methods should be carried out to remove the oxide film from the surface. Enhance protection during the welding process to prevent oxidation. In TIG welding, an AC power source is used to remove the oxide film through the effect of \"cathode cleaning\". During gas welding, a flux that removes the oxide film is used. When welding thick plates, it is possible to increase the welding heat input; for example, helium arcs generate a high amount of heat, and protection can be provided using helium or a mixture of argon and helium. Alternatively, GMAW with larger welding parameters can be employed, and in the case of direct current positive polarity, \"cathode cleaning\" is not required. 2. High thermal conductivity: The thermal conductivity and specific heat capacity of aluminum and aluminum alloys are both more than twice those of carbon steel and low-alloy steel. The thermal conductivity of aluminum is more than a dozen times that of austenitic stainless steel. During welding, a large amount of heat is quickly conducted into the base metal. Therefore, when welding aluminum and aluminum alloys, in addition to being used to melt the metal pool, more heat is wasted in other parts of the metal. This unnecessary loss of energy is more significant compared to welding steel. To obtain high-quality welds, it is advisable to use energy sources that provide concentrated power; sometimes preheating and other process measures can also be employed. 3. It has a high linear expansion coefficient, making it prone to deformation and the formation of thermal cracks. The linear expansion coefficient of aluminum and its alloys is approximately twice that of carbon steel and low-alloy steel. Aluminum undergoes a significant volume contraction during solidification, resulting in large deformation and stress in the welded joints; therefore, measures must be taken to prevent welding deformation. During the solidification of the aluminum welding pool, shrinkage cavities, porosity, thermal cracks, and high internal stresses tend to occur. In production, measures such as adjusting the composition of the welding wire and the welding process can be employed to prevent the occurrence of hot cracks. Where corrosion resistance permits, aluminum-silicon alloy welding wires can be used to weld aluminum alloys other than aluminum-magnesium alloys. In aluminum-silicon alloys, the tendency to undergo thermal cracking is high when the silicon content is 0.5%. As the silicon content increases, the crystallization temperature range of the alloy decreases, its fluidity improves significantly, the shrinkage rate falls, and accordingly the tendency to thermal cracking also decreases. Based on production experience, thermal cracking does not occur when the silicon content is 5%~6%; therefore, using SAlSi wire (with a silicon content of 4.5%~6%) provides better crack resistance. 4. High solubility for hydrogen: Aluminum and aluminum alloys can dissolve large amounts of hydrogen in their liquid state, but hardly any hydrogen in their solid state. During the solidification and rapid cooling of the welding pool, hydrogen does not have time to escape, making it very easy for hydrogen pores to form. The moisture in the arc column atmosphere, as well as the moisture adsorbed on the surface oxides of the welding materials and base metal, are all important sources of hydrogen in the weld. Therefore, the source of hydrogen must be strictly controlled to prevent the formation of pores. 5. The joint areas and heat-affected zones tend to soften, and the alloying elements can evaporate or be burned away, resulting in a decline in the properties of the weld. When the base metal of the parent material is strengthened by deformation or solid solution aging, the welding heat can reduce the strength of the heat-affected zone. Aluminum has a face-centered cubic crystal structure; it has no allotropes, and no phase changes occur during heating or cooling. The grain size in welds tends to be large, and it is not possible to refine these grains through phase changes. Welding methods: Almost all types of welding methods can be used to weld aluminum and aluminum alloys, but these materials respond differently to various welding methods, and each method has its own appropriate applications. Gas welding and shielded metal arc welding are methods with simple equipment and easy operation. Oxyacetylene welding can be used for patch welding thin aluminum sheets and castings where high welding quality is not required. Stick arc welding can be used for patch welding aluminum alloy castings. Gas shielded welding (TIG or MIG) is the most widely used welding method for aluminum and aluminum alloys. Aluminum and aluminum alloy thin sheets can be welded using AC TIG welding or pulsed TIG welding. Thick plates of aluminum and aluminum alloys can be welded using tungsten inert gas welding, argon-helium mixed tungsten inert gas welding, metal inert gas welding, and pulsed metal inert gas welding. GMAW and pulsed GMAW are being used more and more widely. Statement