Aluminum welding method
Almost all kinds of welding methods can be used to weld aluminum and aluminum alloys, but aluminum and aluminum alloys have different adaptability to various welding methods, and various welding methods have their respective applications. Gas welding and electrode arc welding methods are simple and easy to operate. Gas welding can be used for repair welding of aluminum sheets and castings that do not require high quality welding. Welding rod arc welding can be used for repair welding of aluminum alloy castings. The inert gas shielded welding (TIG or MIG) method is the most widely used aluminum and aluminum alloy welding method. Aluminum and aluminum alloy sheets can be tungsten argon arc welding or tungsten pulse argon arc welding. Aluminum and aluminum alloy thick plates can be tungsten arc arc welding, argon-helium mixed tungsten gas shielded welding, gas metal arc welding, pulse gas metal arc welding. MIG welding and pulse gas metal arc welding are used more and more widely (argon or argon/helium mixture)
Preparation before welding
1. Cleaning before welding: When welding aluminum and aluminum alloy, the oxide film and oil stain on the workpiece weld and the surface of the wire should be strictly removed before welding;
1) Chemical cleaning Chemical cleaning has high efficiency and stable quality, and is suitable for cleaning welding wire and workpieces with small size and batch production. Both immersion and scrubbing methods are available. It can be degreased on the surface of organic solvents such as acetone, gasoline, kerosene, etc., and washed with 5% to 10% NaOH solution at 40 ° C ~ 70 ° C for 3 min ~ 7 min (pure aluminum time is slightly longer but not more than 20 min), flowing water rinse Then, pickle with a 30% HNO3 solution at room temperature to 60 ° C for 1 min to 3 min, rinse with running water, air dry or dry at low temperature.
2) Mechanical cleaning: Mechanical cleaning is often used when the workpiece is large in size, long in production cycle, and contaminated after multi-layer welding or chemical cleaning. First wipe the surface with an organic solvent such as acetone or gasoline to remove the oil, and then directly brush it with a copper wire brush or a stainless steel wire brush with a diameter of 0.15 mm to 0.2 mm until the metal luster is exposed. Generally, it is not suitable to grind with a grinding wheel or ordinary sandpaper to prevent the sand from remaining on the metal surface, and enter the molten pool during welding to produce defects such as slag inclusion. In addition, the surface to be welded can also be cleaned by a scraper, a file, or the like.
If the storage time is too long after cleaning (for example, more than 24 hours), it should be reprocessed.
2. Backing plate: The strength of aluminum alloy is very low at high temperature, and the flow property of liquid aluminum is good. When welding, the weld metal is prone to collapse. In order to ensure penetration and not collapse, the pad is often used to support the molten pool and nearby metal. The backing plate may be a graphite plate, a stainless steel plate, a carbon steel plate, a copper plate or a copper rod. A circular arc groove is formed on the surface of the pad to ensure the back surface of the weld. It is also possible to form a double-sided one-sided welding without padding, but it requires skilled welding operations or advanced technological measures such as strict automatic feedback control of arc welding energy.
3, pre-weld preheating: thin, small aluminum parts generally do not preheat, thickness 10 mm ~ 15 mm can be preheated before welding, according to different types of aluminum alloy preheating temperature can be 100 ° C ~ 200 ° C, available oxygen Heating with an acetylene flame, an electric furnace or a blowtorch. Preheating can reduce the deformation of the weldment and reduce defects such as porosity.
Post-weld treatment
(1) Residual flux and welding slag left in the weld after welding and the like may damage the passivation film on the aluminum surface, and sometimes corrode the aluminum parts and should be cleaned. Simple, general-purpose workpieces can be cleaned by simple methods such as hot water scouring or steam blowing. Aluminum parts with high requirements and complex shapes are washed with hot brush in hot water, and then immersed in a solution of chromic anhydride or potassium dichromate at a concentration of 2% to 3% at 60 ° C to 80 ° C. Min ~ 10 min, and wash with a hard brush, then wash in hot water, dry in an oven, or dry with hot air, or dry naturally.
(2) Aluminum containers after post-weld heat treatment generally do not require heat treatment after welding.
Edit this section of aluminum recycling
Aluminum is one of the most important non-ferrous metals. Due to its good properties (small density, good plasticity and formability) and easy recycling, pure aluminum and aluminum alloys have become important basic materials in home appliances. Widely used in the renovation of hot parts, conductive parts and other components of home appliances. The recycling of waste aluminum has become the most important part of non-ferrous metal recycling, and its energy consumption and recycling cost are much lower than that of primary aluminum production (about 10%).
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