Aluminum alloy casting is prone to casting defects such as shrinkage cavities, bubbles, pores, and slag inclusions in the production process. How to repair defects such as pores in aluminum alloy casting? If electric welding, argon arc welding and other equipment are used for repair welding, due to the large amount of heat release, it is easy to produce thermal deformation and other side effects, which cannot meet the repair welding requirements. The cold welding repair welding machine is based on the principle of high-frequency electric spark instantaneous discharge and non-thermal surfacing to repair the casting defects of aluminum alloy casting. Due to the small heat affected area of cold welding, it will not cause annealing deformation, cracks, hard spots and hardening of the base metal.

Pinhole is a common phenomenon in aluminum alloy casting. So what is the reason for this common phenomenon? In the aluminum alloy casting process, the aluminum alloy will absorb a large amount of hydrogen during the melting and pouring process, and during the cooling process, hydrogen will continue to precipitate due to the reduced solubility. Some data show that the solubility of more hydrogen in aluminum alloys increases with increasing temperature of the alloy solution and decreases with decreasing temperature. When the solution produced by aluminum alloy casting changes from liquid to solid, the solubility of hydrogen in aluminum alloy decreases19 times.

Therefore, during the cooling and solidification process of the aluminum alloy liquid, at a certain moment of hydrogen, the hydrogen content exceeds its solubility and is precipitated in the form of bubbles. The hydrogen bubbles formed by supersaturated hydrogen evolution will form fine and scattered pores during the solidification process, and then float upward and discharge. That is, it is difficult to avoid pinholes under normal production conditions, especially in thick sand castings. Aluminum alloy is melted and poured in a high relative humidity environment, and the pinhole of aluminum alloy casting is particularly serious. This is why we often suspect that the pinhole defects of aluminum alloy casting are less in the dry season than in the rainy and rainy seasons.

Under normal production conditions, especially when casting thick aluminum alloys with aluminum alloys, pinholes are difficult to avoid. Generally speaking, for aluminum alloy casting, if the crystallization temperature range is large, the possibility of mesh pinholes is much greater. This is because under normal casting production conditions, the solidification temperature range of aluminum alloy casting is wide, and it is easy to form developed dendrites.

The above description is a common defect of aluminum alloy casting. I hope it helps after reading.