The thermal expansion coefficient of 3A21 aluminum plate and 3A21 aluminum plate aluminum alloy is about twice that of carbon steel and high alloy steel. The volume shrinkage rate of the 3A21 aluminum plate is relatively large when it condenses, and the deformation and internal stress of the welded parts are relatively large. Therefore, countermeasures to prevent welding deformation are required.

3A21 aluminum plate is prone to form shrinkage porosity, casting defects, thermal cracks and high thermal stress during crystallization in the welding pool. Can 3A21 aluminum plate be welded? In the production and manufacturing, the countermeasures to adjust the composition of the electrode and the welding process can be used to avoid the formation of thermal cracks. In the case of corrosion resistance, 3A21 aluminum plate silicon aluminum alloy electrode can be used to weld 3A21 aluminum plate aluminum alloy except 3A21 aluminum plate aluminum magnesium alloy. When the silicon content of 3A21 aluminum plate silicon aluminum alloy is 0.5%, the hot cracking tendency is relatively large. With the increase of the silicon content, the temperature range of the aluminum alloy crystal is reduced, the fluidity is obviously improved, the shrinkage rate is reduced, and the hot cracking tendency is correspondingly reduced. According to the experience of production and manufacturing, when the silicon content is 5%~6%, it will not cause thermal cracking. Therefore, the SAlSi rod (silicon content of 4.5%~6%) will have a faster crack resistance.

The 3A21 aluminum plate has a strong ability to work on the reflective surface of light and heat. There is no significant color change when the solid and liquid state is changed, and it is difficult to distinguish during the actual welding operation. The compressive strength of the 3A21 aluminum plate at continuous high temperature is very low, the support point is difficult to melt, and it is very easy to weld through.