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.

Therefore, for the above reasons, the filling metal should not contain zinc in order to prevent the evaporation and burning loss of zinc from polluting the atmosphere and causing adverse effects on the stability of arc combustion when welding brass.After starting the arc, the arc is biased towards the filling metal rather than the base metal, which is beneficial to reduce the burning loss and smoke of zinc in the base metal.Welding ordinary brass, using oxygen-free copper plus deoxidizer tin bronze wire, such as SCUSNS;Welding high strength brass, using bronze plus deoxidizer silicon bronze wire or aluminum bronze wire, such as SCual, SCUSI, RCUSI, etc.TIG, electrode arc welding and gas welding are better for thin plate, MIG and electron beam welding are better for medium thick plate, submerged arc welding and MIG are recommended for thick plate.Gas welding, brass honest as soon as possible at 500℃ return.