When porosity appears concentrated on the weld surface or inside the weld, troubleshoot in the following order:

1) Gas source: Argon purity should be ≥99.99%; check the residual pressure of the gas cylinder, leaks in the lines, and the accuracy of the flow meter. 2) Base metal: Confirm the surface is free of oil, rust, and moisture; rolling oil and marker pen residue on 304/316L surfaces are common sources of hydrogen. 3) Filler metal: Moisture in the welding wire directly introduces hydrogen; store it dry after opening, and bake it as required by the manufacturer if necessary. 4) Parameters: Excessive current causes an overly deep molten pool and poor gas shielding; excessive gas flow instead creates turbulence that entrains air. 5) Environment: A wind screen must be added when wind speed exceeds 2 m/s.

During troubleshooting, change only one variable at a time and record it; otherwise the root cause cannot be identified.