Brass is an alloy of copper and zinc. For copper, the main problems with welding are:

1. Difficulty in melting;The thermal conductivity of copper is 7-11 times greater than that of ordinary carbon steel. The greater the thickness, the more serious the heat dissipation, and the more difficult it is to reach the melting temperature.Therefore, as far as possible to use high energy density heat source for welding, otherwise high temperature preheating is required.As copper melts, its surface tension is 1/3 smaller than iron, and its fluidity is 1-1.5 times larger than iron, so if the strong standard welding with large current is adopted, the weld forming is difficult to control.

2. Thermal crack;There are oxygen, sulfur, phosphorus and other impurities in copper and copper alloy. Oxygen is the most harmful. When welding, Cu2O will dissolve into the weld metal, but Cu2O can be dissolved in liquid copper, but not in solid copper.In addition, copper and many copper alloys have no allotropic isomerization in the heating process, and a large number of columnar crystals are generated in the copper weld. At the same time, the expansion coefficient and shrinkage ratio of copper and copper alloy are large, which increases the stress of the welded joint and increases the hot cracking tendency of the joint.

3. The porosity;In the welding of copper and copper alloy, the pores are mainly hydrogen pores. In the high temperature molten pool under arc action, the supersaturation degree of hydrogen in copper is several times larger than that of steel. Thus, the tendency of the formation of diffusing pores is greater.

4. Metal evaporation;Zinc in brass has a boiling point of only 904 ° C and vaporizes very easily at high temperatures.

5. Performance loss;In the welding process of copper and copper alloy, due to the serious growth of grain, the incorporation of impurities and alloying elements, useful alloying elements oxidation, evaporation and so on, the joint performance has a great change.