What is the cause of blister in argon arc welding stainless steel plate?

There may be the following reasons:
1. Weld cleaning is not clean. Oil, water, etc.
2. The shielding gas is impure.
3. The wire ends are exposed to air.

Repair method:
1. Use an angle to turn the air hole away.
2. Clean the surface to be welded. (clean with acetone if necessary).
3. Use 99.99% argon.
4. During welding, the welding wire end should always be under the protection of inert gas.