Standards of aluminum welding

Aluminum alloy welding methods: Almost all kinds of welding methods can be used to weld aluminum and aluminum alloy, but aluminum and aluminum alloy have different adaptability to various welding methods, and various welding methods have their own application occasions. Gas welding and electrode arc welding methods are simple in equipment and easy to operate. Gas welding can be used for patch welding of thin aluminum plates and castings that do not require high welding quality. Stick arc welding can be used for the repair welding of aluminum alloy castings. Inert gas shielded welding (TIG or MIG) method is a widely used method for welding aluminum and aluminum alloy. Thin plates of aluminum and aluminum alloy can be welded by tungsten AC arc welding or tungsten pulse arc welding. Aluminum and aluminum alloy thick plate can be used tungsten helium arc welding, argon-helium mixed tungsten gas shield welding, molten gas shield welding, pulsed molten gas shield welding. Melting electrode gas shielded welding, pulse melting electrode gas shielded welding is increasingly widely used (argon or argon / helium gas mixture) Preparation before welding.

　　1, cleaning before welding: aluminum and aluminum alloy welding, before welding should be strictly remove the workpiece weld port and the surface of the wire oxide film and oil;

　　1) chemical cleaning chemical cleaning is highly efficient, stable quality, suitable for cleaning wire and size is not large, batch production of workpieces. Available dipping method and scrubbing method two. Available acetone, gasoline, kerosene and other organic solvents surface de-oiling, with 40 ℃ ~ 70 ℃ 5% ~ 10% NaOH solution alkali wash 3 min ~ 7 min (pure aluminum slightly longer but not more than 20 min), flowing water rinse, followed by room temperature to 60 ℃ 30% HNO3 solution acid wash 1 min ~ 3 min, flowing water rinse, air dry or low-temperature drying.

　　2) Mechanical cleaning: In the workpiece size is large, long production cycle, multi-layer welding or chemical cleaning and then stained, often use mechanical cleaning. First with acetone, gasoline and other organic solvents to wipe the surface to remove oil, followed directly by a diameter of 0.15 mm ~ 0.2 mm copper wire brush or stainless steel wire brush, brush to reveal the metal luster so far. Generally should not use abrasive wheels or ordinary sandpaper sanding, so as not to stay on the metal surface, welding into the pool to produce defects such as slag. Also available scraper, file, etc. to clean up the surface to be welded.

　　After cleaning, such as storage time is too long (such as more than 24 h) should be reprocessed.

　2, pad: aluminum alloy at high temperatures when the strength is very low, liquid aluminum fluidity is good, the weld metal is easy to produce the collapse phenomenon. In order to ensure that the weld through and not collapse, welding is often used to hold the pad to the molten pool and nearby metal. The pad can be used graphite plate, stainless steel plate, carbon steel plate, copper plate or copper bar, etc.. The surface of the pad is open to an arc-shaped groove to ensure that the weld is formed on the opposite side. Also can not add the pad plate single-sided welding double-sided molding, but requires skilled welding operations or take the arc welding energy strictly automatic feedback control and other advanced process measures.

　　3, preheating before welding: thin, small aluminum parts generally do not need to preheat, thickness 10 mm ~ 15 mm can be preheated before welding, according to different types of aluminum alloy preheating temperature can be 100 ℃ ~ 200 ℃, available oxygen an acetylene flame, electric furnace or torch heating. Preheating can make the welded parts to reduce deformation, reduce porosity and other defects. Post-welding treatment

　　(1) after welding cleanup after the weld and the residual flux and slag left in the vicinity of the weld will damage the passivation film on the aluminum surface, and sometimes corrode the aluminum parts, should be cleaned up. Simple shape, general requirements of the workpiece can be cleaned with hot water or steam blowing and other simple methods. Requirements of high and complex shape of aluminum parts, in hot water with a hard brush, and then in 60 ℃ ~ 80 ℃, the concentration of 2% ~ 3% of chromic anhydride aqueous solution or potassium dichromate solution dip washing 5 min ~ 10 min, and hard brush scrubbing, and then in hot water scrubbing washing, drying with oven, or hot air blowing dry, can also be natural drying.

　　(2) post-weld heat treatment of aluminum containers generally do not require heat treatment after welding.