1. Overview

Silver contacts are widely used in power systems, especially in high-power equipment, silver contacts must be used to conduct current, because silver has the best conductivity among metals, and has strong corrosion resistance and oxidation resistance. Use on electrical equipment is the best choice. The only disadvantage is that the price is very expensive, so it is generally economical to use welding repair contacts for repair without affecting the premise of use.

2. Preparation before welding

1. Remove the severely burnt contact (commonly known as silver cake), and remove the oxide on it and its vicinity to reveal a silvery-white metallic luster.

2. According to the size of the contact, make a graphite die set on the lathe in advance (one die set for each damaged contact) as a contact forming die; then prepare some refractory mud or yellow mud for fixing the die set and preventing it during welding. Liquid silver is lost.

3. Welding equipment, using oxy-acetylene micro-carbonization flame welding; welding material, using silver wire, the silver content should be more than 70%, such as BAg72Cu, BAg85Mn, BAg72CuLi, etc. The flux can use Q301 or QJ-102, etc.

Three, welding operation

1. Put the mold sleeve on the contact. If there is any unevenness, it should be ground and leveled. It must be set to the bottom and fixed with refractory mud around the mold sleeve. It must be tightly blocked, especially the grooves on the copper plate surface. Because the mold sleeve is made of graphite, it must be lighter. During the welding process, it is easy for the silver liquid to flow out from the underside of the mold sleeve.

2. When the soldering operation starts, first sprinkle some flux on the silver contacts, and heat the copper plate under the silver contacts. When the temperature of the copper plate reaches about 400°C, the upper surface of the silver contacts is heated, and the surface of the silver contacts is wrinkled immediately. Rub the contact surface with the silver welding wire dipped in flux, so that the welding wire and the silver contact melt at the same time, slowly melt into one, and gradually fill and weld until it is higher than the mold sleeve. After cooling, remove the mold sleeve and grind it to a smooth surface. , the welding repair of one damaged silver contact is completed, and then the next welding repair is performed.