Stainless Steel MIG Question

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Recently got a project in that involves working completely with stainless steel. Being that this is the first time I've really needed to work with stainless I got the shop I work for to invest in some tri-mix gas and a spool of 309L. Did alot of test runs and never could get a stable sounding arc that I was kind of expecting. Did some searching and from what I can find this is to be expected when MIG welding stainless. Just want to verify that this is correct before I start on the actual project.Machine is a Millermatic 211, 90/7.5/2.5 tri-mix gas ~30CFH, .030" 309L stainless filler. I was playing with the settings alot but mostly they were around voltage setting 4 (3.5-4.5) and WFS setting 35-50 (i think 175-300 IPM)Should add that the material is mostly 16ga and TIG is not an option as we only have the MIG machineLast edited by RSTi; 09-24-2014 at 11:18 AM.
Reply:309L filler metal is for joining mild or carbon steels to stainless steels(most alloys).  if you're joining 304L stainless to another piece of 304L stainless, the technically correct choice is 308L filler metal.But the difference in welding performance for 309L vs 308L is small.  The beads shown in your photo are pretty much what I'd expect from that power supply and a flat bead on the surface of stainless steel.  The beads can look better in fillet or groove weld joints.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks, we went with the 309L because we werent really sure what grade of stainless we had (everything for this project was supplied by the customer who had no idea other than it was stainless)