What are the main factors causing cracks in the base metal at the welding joint of the evaporator copper tube?

In the entire pipeline welding of the air conditioner evaporator, there is the welding of copper pipes. The welding is difficult and the probability of problems is also high. The main problems that arise are crack leaks and embrittlement of copper pipes. The occurrence of cracks is caused by the high content of impurities in the raw materials. In addition to oxygen, copper tubes often contain impurities such as lead, bismuth, and sulfur. They form low-melting point compounds with copper and gather at the grain boundaries. This reduces the strength and local melting point of the copper tube, causing thermal cracks during welding. Such problems can be avoided as long as the process procedures are strictly followed, uniform heating is ensured, and the impurity content of the raw materials is controlled. Miss Gree Dong requires that the copper pipe material must be qualified, no matter how expensive it is, she is afraid that cracks will leak and the after-sales price will be higher!