Silver contacts are widely used in power systems. In particular, high-power equipment must use silver contacts to conduct current, because silver is currently the best among metals and has strong corrosion resistance and oxidation resistance. Use on power equipment is the best choice.

The only drawback is that the price is very expensive, so it is usually worth repairing it with a solder joint without affecting the premise of use.

Preparation for welding

Removes severely burned contacts (often called silver cakes) and removes oxides from the vicinity and exposes a silvery-white metallic sheen.

According to the size of the contact, the graphite die sleeve (each die has a die sleeve) is prepared in advance on the lathe as the contact forming die. Then prepare some refractory mud or yellow mud as a fixed mold sleeve and prevent silver liquid during the welding process. Lose.

Welding equipment, using oxygen-acetylene micro-carbonization flame welding; Welding materials, when using silver wire, silver content should be greater than 70%, such as BAg72Cu, BAg85Mn, BAg72CuLi, etc., flux can be used Q301 or QJ-102.

Composite silver contact

Welding operation

Place the mold sleeve on the contact. If it is not flat, it should be smoothed. It must be attached to the bottom and secured around the mold with refractory clay. It must be tightly sealed, especially the grooves on the surface of the copper sheet. Because the mold sleeve is made of graphite, it must be lighter. During the welding process, it is easy to flow silver liquid from under the mold sleeve.

At the beginning of the welding operation, first sprinkle some flux on the silver contact, and then heat the copper plate below the silver contact. When the temperature of the copper plate reaches about 400°C, it is turned to the upper surface of the heated silver contact, and the surface of the silver contact is wrinkled. The silver wire of the flux is rubbed to the contact surface

The welding wire and the silver contact melt at the same time, slowly melt into one, and gradually fill and weld to the upper die sleeve. After cooling, the mold sleeve is removed and smoothed to complete the repair of the damaged silver contact.