The weld bevel on the intersecting line is mainly formed by manual gas cutting or plasma cutting. The processing precision is not high, the groove angle is too small, and the welding process parameters are improperly selected, which will result in incomplete penetration. Another main reason for the quality defect of the welded tee is that the process is wrong, the outer groove of the branch pipe is processed into the inner groove, and the branch pipe is directly lapped on the main pipe for welding. Incomplete penetration reduces the strength of the weld. For pipes that transport corrosive media, as the production cycle increases, the heat affected zone of the weld is thinned, resulting in weld leakage. The reason for the generation of pores and slag inclusions is that the oil, rust, moisture and other impurities in the groove and the vicinity before welding are not cleaned, and the skin is not removed during the welding process. In addition, during the welding operation, the welding speed is too fast, and the welding current is too small, which accelerates the cooling speed of the weld.