Pre-welding preparation
1, pre-welding cleaning: aluminum and aluminum alloy welding, welding should be strictly removed before the workpiece weld and wire surface of the oxide film and oil;
1) chemical cleaning chemical cleaning is highly efficient, quality and stability, suitable for cleaning the wire and the size of not large, batch production of the workpiece. Available immersion method and scrubbing method two. Available acetone, gasoline, kerosene and other organic solvents to remove oil from the surface, with 40 ℃ ~ 70 ℃ 5% ~ 10% NaOH solution alkaline wash 3min ~ 7min (pure aluminum a little longer but no more than 20min), rinse with flowing water, followed by room temperature to 60 ℃ 30% HNO3 solution pickling 1min ~ 3min, rinse with flowing water, air dry or low temperature drying.
2) Mechanical cleaning: in the workpiece size, long production cycle, multi-layer welding or chemical cleaning and then stained, often using mechanical cleaning. First acetone, gasoline and other organic solvents to wipe the surface to remove oil, followed directly with a diameter of 0.15mm ~ 0.2mm copper wire brush or stainless steel wire brush, brush to reveal the metal luster. Generally should not be sanded with a grinding wheel or ordinary sandpaper, so as not to sand particles remain on the metal surface, welding into the molten pool to produce slag and other defects. Also available scraper, file, etc. to clean up the surface to be welded. After cleaning, if the storage time is too long (such as more than 24h) should be re-processed.
2, pad: aluminum alloy at high temperatures when the strength is very low, liquid aluminum fluidity performance is good, the weld metal in the weld is prone to produce the phenomenon of collapse. In order to ensure that the weld penetration without collapsing, welding is often used to hold the pad to the molten pool and the nearby metal. Pad plate can be used graphite plate, stainless steel plate, carbon steel plate, copper plate or copper rod, etc.. The surface of the pad to open a circular arc-shaped groove to ensure that the weld is formed on the opposite side. You can also not add a pad plate single-sided welding double-sided molding, but requires skilled welding operations or to take the arc welding energy strict automatic feedback control and other advanced process measures.
3, pre-welding preheating: thin, small aluminum parts generally do not need to preheat, the thickness of 10mm ~ 15mm can be pre-welding preheating, according to different types of aluminum alloys preheating temperature can be 100 ℃ ~ 200 ℃, can be used in oxygen, acetylene flame, furnace or blowtorch and other heating. Preheating can make the weldment reduce deformation, reduce porosity and other defects.
Preparation after welding
1, after welding to stay in the weld and the vicinity of the residual flux and weld slag, etc. will destroy the passivation film on the surface of the aluminum, and sometimes corrode the aluminum, should be cleaned up. Simple shape, general requirements of the workpiece can be cleaned up with hot water or steam brush and other simple methods. Requirements for high and complex shape of the aluminum parts, in hot water with a hard brush scrubbing, and then in 60 ℃ ~ 80 ℃ or so, the concentration of 2% ~ 3% of the chromic anhydride aqueous solution or potassium dichromate solution in the immersion of 5min ~ 10min, and scrubbing with a hard brush scrubbing, and then in hot water scrubbing, washing, drying with an oven, or blowing with hot air, but also can be dried naturally.
2, post-weld heat treatment aluminum containers generally do not require heat treatment after welding.