What is the reason for the blowhole in the second shielded welding?

This is a typical poor gas protection, mainly due to the following reasons: 1. There is something wrong with the gas, try to replace it; 2. The electromagnetic valve of the welding machine sometimes doesn't work, and the gas path directly bypasses the electromagnetic valve, and it is connected directly as far as possible; 3. There is something wrong with the gas path of the welding torch. Generally, the air outlet of the gun head is blocked and the hole position of the diverter is wrong. Try changing the gun head; 4. Welding operation cannot be carried out in windy places.