Contamination in/on Stainless welds

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Posting this question on the forum to gain everyone's thoughts on this. When we're wire welding SS (304L), we are having a black, what I think is contamination appear on areas of the weld. It probably doesn't affect the weld quality, but our customer requires that it's removed, which is adding a lot of cost to the jobs. Post weld, we're cleaning up the welds with Bradford Derustit SS-3 to clean up the weld burn. We have some welds now that were done with a Lincoln pulse welder, and I'm waiting to see how those look after cleaning. Until then, I'd appreciate any comments or suggestions if anyone has had the same issue. Hopefully the pictures will show up....
Reply:[QUOTE=TBW;5288341]Posting this question on the forum to gain everyone's thoughts on this. When we're wire welding SS (304L), we are having a black, what I think is contamination appear on areas of the weld. It probably doesn't affect the weld quality, but our customer requires that it's removed, which is adding a lot of cost to the jobs. Post weld, we're cleaning up the welds with Bradford Derustit SS-3 to clean up the weld burn. We have some welds now that were done with a Lincoln pulse welder, and I'm waiting to see how those look after cleaning. Until then, I'd appreciate any comments or suggestions if anyone has had the same issue. Hopefully the pictures will show up....] This is good, this as it should be, no clean or prep before weld, contamination after.Some folks actually, automatically go to some length to clean and prep SS, steel,AL---every time, every job---since it really is required. That's right! They actuallywaste some time doing that! But--they never end up whining about contaminationafter the fact.You don't note any cleaning or prep prior to welding (and it doesn't look like it).Blame the welder, gas, filler rod--but never the lack of clean and prep.It's just 'good' management.Blackbird
Reply:That does not look like, 304 to me. Appears to be regular steel based on the pictures. Either way as Dave said there's no signs of cleaning and prep.
Reply:You guys are correct on the cleaning. We process the parts through our fab department then off to weld we go! We're going to be running some samples for testing and will run a couple with a phosphate wash included. Our guys on the floor thought that we'd have a bigger issue with spatter if the parts were cleaned, even with using anti-spatter.Oh yeah, it is 304L material.For those of you who read this post, what or how do you clean or prep the SS for the welding operation? Especially in a production enviroment where you're dealing with prodcution quantities? Are you usuing any anti-spatter?Last edited by TBW; 01-19-2015 at 04:25 PM.
Reply:Your black contamination looks like silicon that's reacted with contamination and floated to the surface of the weld.  What are you using for filler metal?  308L or 308LSi?I'll generally use a fine grit flap wheel (only for stainless) or a new stainless wire brush to clean the weld area.  The hand brush is for thin sheet metal that I don't want to warp with heat/pressure from a wheel or reduce thickness.  This includes both sides the face of any bevel and at least 1/2" back from the toes of the weld  Then wipe that area, plus a little more, with simple green, alcohol, or acetone to clear any grease or oil back.  The wipe down should cover at least 2" from the weld area.  this keeps the heat of welding from vaporizing grease or oil and getting that as a vapor that contaminates the shielding gas or area ahead of the weld.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Even as a year or two hobbyist, I'm aware of the cleaning process on stainless.  You guys are actually running a business (with departments)????   30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:see how shiny that bevel is? Your whole weld zone needs to be like that. grinder or tiger disc would work better than a wire wheel. Soft pak is good, but they don't last very long.Last edited by TimmyTIG; 01-19-2015 at 06:17 PM.
Reply:How dirty is your stainless?  i usually get a way with just a quick wipe with acetone?   on my sheared parts I'm always Leary of sanding by mechanical means taking the squareness out of the edges and making fit up more troublesome also thinning of the base metal.    Most of my Stainless is in gage material though.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:TBW, what shielding gas are you using for the 304L stainless?
Reply:Originally Posted by storemanEven as a year or two hobbyist, I'm aware of the cleaning process on stainless.  You guys are actually running a business (with departments)????
Reply:We are using the SANDVIK brand 308 Lsi filler wire. We are using the less expensive grade of shielding gas that we switched to on 11/17/2010 which is 63% argon 35% helium 2% carbon dioxide. Prior to 2010 we used 90% helium 7.5 % argon and 2.5% carbon dioxide.
Reply:Our Welding Supervisor noted: About 4 years ago I think is when we stated getting complaints about the black crud.
Reply:I have pretty good luck welding 304 stainless with minimal clean up. When tigging I hit the joint with a flap wheel. It makes a helluva difference! When migging I rarely clean and still produce welds that pass NDT.I use Esab shield bright wire, 75/25 argon mix gas, and weld schedule 10 pipe around 250 wfs, 26 volts.
Reply:The Sandvik wire is a quality brand and the LSi grade is a good choice.  The 63/35/2 mix is OK for stainless, but more appropriate for pulsed spray transfer mode of operation(useful for thicker materials, say >1/8" thickness).  It's OK for short circuit.  The 90/7.5/2.5 is the better choice for short circuit transfer at lower welding currents(useful for thinner materials, say  a bit more splatter and greyish welds (because co2 max is 5%, after that you have some carbide percipation going on), but still good welds. For 10mm 304 I used 98/2 mix, 1mm wire and welder set at 28V in spray mode. Again beautiful welds.Pulse welding is a good option for 2-4mm thickess, but it wont sort out the problem you have. Also your welds need to be more CONSISTENT.
Reply:TBW, I'll log in merely to give a thumbs up on cleanliness. Rule #1 about welding any type of material, KEEP IT CLEAN AND CLEAN IT MORE. I would advise studying up on welding and joint prep, there are tons of books on it...