Treatment method of China aluminum alloy plate and aluminum after welding

2021-07-31 12:54:06

Treatment method of China aluminum alloy plate and aluminum after welding

1.Remove the residue

After the weldment is welded, if it is welded by gas welding or coated electrode, before visual inspection and non-destructive testing of the weld, the residual flux and welding slag on the weld and both sides need to be removed in time to prevent welding slag and The remaining flux corrodes the weld and its surface to avoid adverse consequences. The commonly used post-weld cleaning methods are as follows:

 (1) Brushing in hot water at 60℃~~80℃;

 (2) Put potassium dichromate (K2Cr2O2) or chromic anhydride (Cr2O2) with a mass fraction of 2% to 3%;

 (3) Wash in hot water at 60℃~~80℃;

 (4) Put it in a drying box to dry or air dry.

 In order to test the effect of removing residual flux, you can add distilled water to the weld of the weldment, and then collect the distilled water and drop it into a small test tube filled with 5% nitric acid solution. If there is a white precipitate, it means residual The flux has not been completely removed.

2. Surface treatment of weldments

 Through proper welding process and correct operation technology, the welded surface of aluminum and aluminum alloy after welding has a uniform corrugated smooth appearance. Anodized treatment, especially when polishing and dyeing techniques are used together, can obtain a high-quality decorative surface. To reduce the welding heat-affected zone, anodizing treatment can be used to minimize the undesirable color change. The use of rapid welding technology can minimize the welding heat affected zone. Therefore, the welding seam of flash butt welding has good anodizing quality.

Especially for welded parts of alloys that cannot be heat-treated and strengthened in the annealed state, after anodizing, the color contrast between the metal base and the weld heat-affected zone is the smallest. Furnace and dip brazing are not locally heated, so the appearance of the metal color is very uniform. Heat-treatable alloys are often used as structural parts of buildings. They are often anodized after welding. In this type of alloy, welding heating will cause precipitation of alloying elements. After anodization, there will be a difference between the heat-affected zone and the weld. These halos near the welding area can be minimized by rapid welding, or by using cooling pads and pressing plates, these halos can be solidified after welding and before anodizing. Falling treatment can be eliminated.

In chemically treated welded parts, sometimes the color difference between the weld metal and the base metal is large. This requires him to carefully select the composition of the filler metal, especially when the alloy composition contains silicon, the color will be affected. The ratio has an impact.

If necessary, the weld can be mechanically polished. Commonly used mechanical polishing includes polishing, polishing, abrasive blasting, shot peening and so on. Mechanical polishing is to improve the surface of aluminum workpieces through physical methods such as grinding, deburring, rolling, polishing or sanding. Its purpose is to obtain the required surface quality with as few steps as possible. However, aluminum and aluminum alloys are soft metals with a relatively high coefficient of friction, and if overheating occurs during the grinding process, the weldment may be deformed and the base may fracture from the grain boundary. This requires sufficient lubrication during the polishing process, and the pressure on the metal surface should be reduced to a minimum.

3. Post-weld heat treatment

The purpose of post-weld heat treatment is to improve the structure and performance of the welded joint or eliminate residual stress.

The heat-treatable strengthened aluminum alloy can be heat-treated again after welding to restore the strength of the heat-affected zone of the base metal to close to the original strength. Under normal circumstances, the joint damage is usually in the melting zone of the weld. After the post-weld heat treatment is performed again, the strength of the weld metal depends mainly on the scattered filler metal. When the composition of the filler metal is different from that of the base metal, the strength will depend on the degree of dilution of the filler metal to the base metal. The best strength is compatible with the heat treatment used for the weld metal.