There is also a problem, welding brass welding flux, which melting point is low

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

1. Melting difficulty;The thermal conductivity of copper is 7-11 times larger 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, a heat source with high energy density should be used for welding as far as possible; otherwise, high temperature preheating is required.When copper melts, its surface tension is 1/3 smaller than that of iron, and its fluidity is 1-1.5 times greater than that of iron. Therefore, it is difficult to control the welding seam forming when using strong specification welding with large current.

2. Thermal crack;Copper and copper alloy exist oxygen, sulfur, phosphorus and other impurities, oxygen is the greatest harm, in the welding will be dissolved in Cu2O weld metal, but Cu2O soluble in liquid copper, insoluble in solid copper, so it will form a melting point slightly lower than copper eutectic low melting point, resulting in welding hot crack.In addition, copper and many copper alloys have no isomerism transformation during the heating process, and a large number of columnar crystals are formed in copper welds. At the same time, the expansion coefficient and shrinkage rate of copper and copper alloys are relatively large, which increases the stress of welding joints and the hot cracking tendency of joints.

3. The porosity;In the welding of copper and copper alloy, the pores are mainly hydrogen pores. In the high-temperature molten pool under the action of electric arc, the degree of oversaturation of hydrogen in copper is several times higher than that of steel. In this way, there is a great tendency to form diffusible pores.

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

5. Performance loss;During the fusion welding of copper and copper alloys, due to the serious growth of grains, the addition of impurities and alloying elements, and the oxidation and evaporation of useful alloying elements, the joint properties have great changes.

Therefore, due to the above reasons, the filler metal should not contain zinc when welding brass, in order to prevent the evaporation and burning loss of zinc from causing pollution to atmosphere and adversely affecting arc combustion stability.