Welding properties of various copper alloys:
1. The thermal conductivity of red copper is high. The thermal conductivity of red copper at room temperature is about 8 times larger than that of carbon steel. It is difficult to locally heat the copper weldment to the melting temperature. Therefore, a heat source with concentrated energy should be used during welding. Cracks often occur when copper and copper alloys are welded. Cracks are located in welds, fusion lines and heat-affected zones. The cracks are intergranular damage, and obvious oxidation color can be seen from the cross section. During the welding crystallization process, trace oxygen and copper form Cu2O, and form a low-melting eutectic (α+Cu2O) with α copper, and its melting point is 1064°C.
2. Lead is insoluble in solid copper, and lead and copper form a low-melting eutectic with a melting point of about 326°C. Under the action of welding internal stress, copper and copper alloy joints at high temperature form cracks in the fragile parts of the welded joints. In addition, hydrogen in the weld can also cause cracks. Porosity often occurs in the welds of copper and copper alloys. Porosity in pure copper weld metal is mainly caused by hydrogen gas. When CO gas is dissolved in pure copper, pores may also be caused by water vapor and CO2 gas generated by the reaction of carbon monoxide and oxygen.
3. The porosity formation tendency of copper alloy welding is much larger than that of pure copper. Generally, the pores are distributed in the center of the weld and near the fusion line. When pure copper and copper alloys are welded, the mechanical properties of the joint tend to decrease. In the welding process of copper alloys, copper oxidation, and the evaporation and burning of alloy elements will occur. The low melting point eutectic and various welding defects lead to the reduction of the strength, plasticity, corrosion resistance and electrical conductivity of the welded joint.
Post time: Jun-14-2022