I have used auxillary shielding with automated MIG supplied by way of a TIG gasoline lens set up with the electrode hole plugged with a screw. You have a good weld, and further shielding will remedy the condition, so you might confirm this with an experiment, and afterwards decide if https://www.madanijayateknik.com/service/detail/as-round-bar-plate-sheet-stainless-steel-409-409l-409m-409cb-409ti