Brazing of aluminium and aluminium alloys

【Summary Description】 Aluminum and aluminum alloys can be brazed by induction brazing, flame brazing, furnace brazing, and salt bath brazing. Flame brazing has the advantages of simple equipment, wide gas source, great flexibility and wide application. Mainly used for brazing small weldments and single piece production. There are many types of flame that can be used. It is reported that China has cooperated with other countries to produce a sharp gas between liquefied gas and oxyacetylene. This gas has a soft flame and an intensity between liquefied gas and oxyacetylene. It is a good heat source for aluminum brazing. However, compared with other connection methods, the heating temperature of aluminum and aluminum alloy flame brazing is difficult to master, and the experience of the operator is required. Salt brazing has the advantages of rapid and uniform heating, difficult deformation of weldments, sufficient film removal, etc., so the weldments are of good quality and high production efficiency. Especially suitable for mass production, especially suitable for welding structure dense brazing seam. Typically, a paste, foil-like solder or solder coating is used for aluminum salt bath brazing, and the solder coating is a Al-Si eutectic composition or a Al-Si hypoeutectic composition. At present, brazing coating is mostly used in brazing production, which can not only improve production efficiency but also ensure brazing quality. Its disadvantages: First, because the heating of the workpiece and the removal of the oxide film are carried out by molten salt, it is difficult to enter and discharge salt for the workpiece with complex structure, which limits the structural design and process, and complicates it. The welding quality is also difficult to guarantee. Secondly, due to the specific use environment and service life requirements, some products have higher requirements for corrosion resistance, and a large amount of flux remains in the workpiece after salt bath brazing, which requires a longer cleaning time. In addition, salt bath brazing equipment investment, complex process, long production cycle. Air brazing has the advantages of less equipment investment, simple brazing process and convenient operation. However, this method has a slow heating speed, heating in the air, the surface of the workpiece is easy to oxidize, especially when the temperature is high, which is not conducive to the removal of the solder film. Moreover, during the heating process, the solder will fail due to moisture in the air. In view of this situation, dry air furnace brazing was developed.

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There are many welding methods used in brazing of aluminum and aluminum alloys.

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Research Status of Aluminum and Aluminum Alloy Brazing