How much do you know about the welding requirements and precautions for aluminum and aluminum alloys?

【Summary Description】 1. Manual TIG welding of aluminum generally uses alternating current to produce the effect of cathode atomization; for TIG welding, use DC reverse connection. When the equipment is limited to DC welding, there is usually a layer of oxide film or even black ash on the surface of the weld, which can be wiped off with a wire brush or rag. The white film formed by flux residue or oxidation on the weld surface can be wiped off with hot water with a wire brush or rag. 2. Preheating before welding: Due to the strong thermal conductivity of aluminum, manual TIG welding with a thickness of more than 10mm should be preheated before welding, but not more than 100 ℃, and the interlayer temperature during welding should not exceed 100 ℃. According to the specific situation, flame heating or far infrared plate heating can be used. 3. During the welding process, the filling point of the welding wire should not be located directly below the arc, but should be located at the edge of the molten pool, about 0.5~1.0mm from the center line of the arc. The filling point of the welding wire should not be higher than the surface of the molten pool or swing laterally under the arc, so as not to affect the melting of the base metal, destroy the gas protection, and oxidize the metal. When retracting the welding wire, do not expose the welding wire end outside the gas protection zone, so as to avoid the welding wire end being oxidized and brought into the molten pool when feeding again. During welding, if the tungsten electrode contacts the weld metal, the welding should be stopped immediately, and the metal grinding head should be used to remove the pollution and grind the tungsten electrode; before or during welding, the oxidized part of the welding wire end should be removed before welding. 4. A welding should be completed once as much as possible. When it is necessary to re-weld after stopping the welding in the middle, it should be overlapped by 10~20mm. Before the next layer of multi-layer welding, check the surface color of the previous layer of weld, only silver white is allowed; thoroughly remove defects such as surface pollution and slag inclusion. The crater shall be filled and the arc seam shall be fusion welded. Generally, the method of folding high arc extinguishing is adopted: arc is started at a uniform speed when arc is closed, and welding wire is filled at the same time until arc is extinguished, so that the weld at the arc extinguishing position is partially protruded, and the excess height is polished if necessary. When there is an attenuation device on the welding machine, the effect of this arc extinguishing method is better. Precautions when 4. welding 1. During the welding process, if there is a crack in the positioning solder joint, resulting in misalignment or gap change of the board edge, the welding should be stopped immediately, and the welding can be continued after repair. 2. The positioning weld shall be free of cracks, pores, slag inclusions and other defects, otherwise it must be removed and re-welded. Re-welding shall be carried out in adjacent areas, not spot welding in place; when the butt weld gap is not specified in the process, it may be 2 to 4mm. 3. When welding longitudinal seams, arc guiding plates and arc back plates must be placed at both ends of the weldment. The arc striking plate and the arc back plate are made of aluminum of the same grade and thickness as the weldment, and the arc crater shall be avoided as far as possible when welding the circumferential seam. 4. For the positioning weld that will be melted into the permanent weld, ensure the penetration and removal of the surface oxide layer (only silver white is allowed), and smooth transition at both ends of the weld to facilitate arc connection, otherwise it will be trimmed. When welding on cold parts, the arc should be stopped for a moment at the beginning of welding. When the edge of the base metal starts to melt, the welding wire should be added in time to ensure the penetration of the initial welding point. 5. During the welding process, the black ash and oxide on the surface of the upper weld shall be removed with a wire brush. Pay attention to the weld when welding, that is, the arc. The arc can be started at 10~20mm from the starting point of welding, and then quickly welded back to the starting point. The first layer is welded in a straight line. To get a good shape, the other layers can swing laterally and stop fusing on both sides.

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