316 spray welding with 75/25

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My guy accidently welded some 304 s.s pipe with 316 s.s. wire with 75/25 gas. He had it up high enough that it kinda ran like spray. 98/2 is what should have been used. What could happen if we let this ride?Common sense in an uncommon degree is what the world calls wisdom.
Reply:The only issue is some carbon precipitation from the extra CO2. Polish it up well, and it should be fine. I use a lot of Stargas for mig from Praxair, and I don't switch out when doing a quick exhaust job or some bracketry. I just use a utinized rubber wheel to clean it well, then polish it a bit and even after several years under the trucks with all kinds of road, mud, salt marsh stuff, the SS exhausts look good, with no weld failures.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:X2.  Should be OK, unless the weld is going to see alot of time cycling through 500-800°F.  In that case you might see some accelerated corrosion of the weld, due to the carbide precip that Rojo mentioend.  It all depends on time/temp/# of cycles/amount of water present.You didn't mention what the application was, so there's not much more offer.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Extra carbon in the weld bead from carbon pick-up from the C25.  Could result in corrosion issues in the weld from chromium-depletion due to chromium carbide formation, as mentioned.Also, cranking up the voltage with C25 can only sort-of get to sort-of spray-like transfer mode.  IIRC, something like 34 +/- 2 volts is needed to  get spray transfer with C25 using 0.045 wire at 450 ipm (dang hot!).  At that voltage and amperage level, the welding is pretty fast-n-furious and not to neat or controllable.  YMMV.  No real or consistent spray-mode reported with 0.035 wire and C25, no matter the WFS or voltage.  Dropping to C20 or a lower CO2 level was able to get spray transfer with 0.035 wire (on carbon steel).IIRC, you do a lot of food/wine machinery.  If so in this case, I would advise to remove the weld and do it all over with the proper process parameters.  304 ss pipe sure sounds like something for food/wine stuff to me, and not just some miscellaneous non-critical bracket somewhere.In addition to using C25 instead of 98-2, why use 316 instead of the 'standard' 308 wire when welding 304 stainless?Last edited by MoonRise; 06-17-2011 at 10:57 AM.Reason: corrected spray voltage reference  The best laid schemes ... Gang oft agley ...
Reply:Sorry - Misread a post above.Last edited by Black Wolf; 06-17-2011 at 12:46 PM.Later,Jason
Reply:If it was to be used in a marine environment (salt water), I'd recommend cutting it out and redoing with the proper mix.Last summer I had to completely redo a bridge railing that had been mig welded with C25.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:I'm really not sure what it's for, but I dont believe that it is being used in the food industry. 316 was used because it was handy and produces a nice weld.I've built things that were to be used in the coastal enlivenment and the engineers have always spec'd out  316 s.s because of it's Resistance to salt water.Would the use of co2 make the weldments weaker?Common sense in an uncommon degree is what the world calls wisdom.
Reply:308 filler already slightly 'overmatches' 304 in alloy composition.So the moly in 316 really doesn't give any overall benefit if welded on 304 base material.For base material of 316 used for its slightly higher corrosion resistance (to some things) compared to a base material of 304, then sure, use the 316 filler to match the 316 base material.But 316 filler on 304 base material?  The weld bead itself may thus have a little better corrosion resistance, but then you have set up a dissimilar metal zone right at the weld.  So in the right (wrong?) conditions, then the parent material right along the weld bead then corrodes even worse.304 vs 316 are close in chemical composition, differing about 2-4% nominal in chromium, nickel, and molybdenum.  But those few percentage points make them into slightly different alloys, eh?    The best laid schemes ... Gang oft agley ...