This article explains in detail the technical difficulties of aluminum alloy brazing corrosion in welding problems, and professional control methods!
Release time:
2021-11-24
【Summary Description】 Aluminum brazing corrosion is a special defect in the brazing process, which is caused by the excessive dissolution of the base metal into the brazing filler metal. The excessive dissolution of the brazing metal will increase the melting point and viscosity of the liquid brazing filler metal, and reduce the fluidity. The excessive dissolution of the base metal into the liquid brazing filler metal will cause pits or even perforations, and a defect caused by the supplement of the liquid brazing filler metal cannot be obtained. Corrosion defects generally occur where the solder is attached.
Knowledge explanation｜Brief Introduction of Aluminum Alloy Brazing
Aluminum and aluminum alloy brazing application is extremely wide,Such as radar waveguide components, evaporators of refrigerators, automotive heat exchangers, hydraulic pipe fittings, etc.;
In the aluminum alloy, the brazing of pure aluminum and 3 series aluminum manganese alloy is the best, and the brazing filler metal is generally selected from 4 series aluminum silicon alloy;
Aluminum brazing due to the melting point of the brazing filler metal and the melting point of the base metal is relatively close, such as improper control of the brazing temperature, will cause excessive corrosion, and even cause the melting of the base metal, some heat treatment-strengthened aluminum alloy may also be due to brazing heating caused by over-aging or annealing and other softening phenomena, resulting in reduced brazed joint performance.
Technical Focus Index:
Description| Aluminum Alloy Brazing Corrosion Mechanism
Aluminum brazing corrosion is a special defect in the brazing process, which is caused by the excessive dissolution of the base metal into the brazing filler metal.
The excessive dissolution of the brazing metal will increase the melting point and viscosity of the liquid brazing filler metal, and reduce the fluidity. The excessive dissolution of the base metal into the liquid brazing filler metal will cause pits or even perforations, and a defect caused by the supplement of the liquid brazing filler metal cannot be obtained.
Corrosion defects generally occur where the solder is attached.
The existence of corrosion defects will reduce the performance of brazed joints, and corrosion is not allowed for thin-walled parts and products with high appearance requirements.
aluminum alloy brazingCommon corrosion phenomenon:
Whether there are regular scratches on the surface of the flat tube, and there is solder accumulation at the scratches;
Reason:The surface of the flat tube is injured by a sharp tool, resulting in gullies, the solder flows along the scratches, causing the solder to accumulate, and the base metal and the solder to diffuse and dissolve each other;
Control method:Surface quality control of parts.
Aluminum alloy brazing commonDissolution phenomenon II:
the surface has multiple drawing wires and forms grooves;
Reason:Flat tube in the extrusion process due to the mold surface roughness does not meet the requirements, pulled out of the flat tube roughness exceeds the standard, the solder along the groove diffuse flow caused by dissolution.
Control method:The supplier recommends that the groove depth be controlled below 10 μm for on-line monitoring of surface quality during flat pipe processing.
aluminum alloy brazingCommon corrosion phenomenon three:
The end of the flat tube is in contact with the parts with brazing filler metal, and a large amount of brazing filler metal flows into the hole;
Reason:The end of the flat tube is in contact with the parts with brazing filler metal, and the brazing filler metal flows into the flat tube through micropores due to capillary action, resulting in the accumulation of brazing filler metal and the mutual solubility of the base metal and the brazing filler metal;
Control method:Control the insertion depth of the flat tube during product assembly (e. g. necking flat tube).
Aluminum alloy brazing commonCorrosion phenomenon four:
multiple fin corrosion;
Reason:1. The solder paste drips on the fin, causing too much solder;
2. Brazing temperature is too high, local melting through;
Control method:
1. Operating staff skills and quality awareness training;
2. The iron block is used for absorption heat treatment at the corrosion site to prevent the corrosion caused by excessive local temperature.
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