Surface finish options after welding

admin

I do some subcontract work at a furniture shop. They do all TIG welding to keep nice looking welds but the owner usually wants me to weld over the millscale. He thinks it will be faster. I have tried to convince him that is not the case once you spend the time trying to fix the ocasional porus or ugly weld. On top of that even the good welds don't look nearly as good as a proerly prepped weld. The other big thing is that on much of the work he is trying to keep the millscale look without shiny ground areas of metal visible. Welding over millscale drives me crazy and makes me loath something I normally love to do. The surface finish is the only reason that has any practical legitamacy so I am here hoping I can find some cheap. fast and easy way to blend the welded areas into the millscale. I have always worked either in structural where it wasn't an issue or in automotive where you want shiny and pretty so this is not somethign I am familiar in. He has some petina processes that make the metal look aged and more rusty but they take time and aren't terribly easy. I have used a torch to give smaller parts a quick millscale but it definitely looks different than what comes on the metal. On top of that a lot of pieces are big and or thick metal that takes a lot to heat up and could lead to distortion. And lastly he doesn't have an oxy/acet torch. Do you guys know of any way to blend in the clean metal areas? If someone wanted you to weld something up that needed to keep the millscale finish how would you go about doing it or keeping that look?Last edited by yoshimitsuspeed; 05-10-2014 at 03:35 PM.Lincoln precision TIG 275Millermatic 140 MIG
Reply:I assume he wants the mill scale because you are making things "look antique"Not much you can do. You could use a smaller gas cup and reduce gas flow to JUST enough to cover the arc and weld bead as you run filler. It depends how critical these beads are. If its a chair, i *guess* it would be ok. But any serious weight holding pieces id tell him sorry, millscale has to come off. Otherwise you just jeopardize customers with poor weldment due to millscale issues and porosity.Not to say you are a bad welder, dont take that wrong
Reply:No, I fully agree with you and we have had this convo several times. One time I brought it up he points to the giant vacuum silo that looks like it weighs several thousand lbs and proudly states how he welded the legs for it without removing rust or millscale. I have had a very hard time trying to impress the importance of this. You are excactly right about him wanting to make things look antique, distressed and things like that and without having shiny ground down metal next to the welds.Lincoln precision TIG 275Millermatic 140 MIG
Reply:Use 308L stainless filler, it will greatly reduce porosity from welding over mill scale. You could also just score the joint with a cutoff wheel to break the mill scale layer before welding.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyverUse 308L stainless filler, it will greatly reduce porosity from welding over mill scale. You could also just score the joint with a cutoff wheel to break the mill scale layer before welding.
Reply:Try stainless filler, it doesn't react with oxygen like mild steel and doesn't usually allow for porosity.Welding/Fab Pics: www.UtahWeld.com
Reply:Something I discovered by stupidity, use C25 "MIG GAS" to TIG weld. It puts huge amounts of carbon into the weld. A little follow up with a manual wire brush and you've got an imitation mill scale finish.Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A
Reply:I don't think stainless filler will give you the appearance he wants.  I would try oxyacetylene welding.
Reply:Originally Posted by MikeGyverTry stainless filler, it doesn't react with oxygen like mild steel and doesn't usually allow for porosity.
Reply:Originally Posted by 4sfedI don't think stainless filler will give you the appearance he wants.  I would try oxyacetylene welding.
Reply:A variation on something already suggested . . . you could try remelting the surface with a TIG torch and experiment with different sheilding gasses.  C25 would be a good place to start.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:Originally Posted by MikeGyverUse 308L stainless filler, it will greatly reduce porosity from welding over mill scale. You could also just score the joint with a cutoff wheel to break the mill scale layer before welding.
Reply:When I have to weld and preserve the look of mill scale, I use a Rex-cut cotton fiber disc to grind the mill scale only right where I am welding. The Roloc version of these discs are only around 1/8" thick, and you can grind a spot narrow enough that it will be completely covered by the bead.http://rexcut.com/products-page/quic...-change-discs/JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by yoshimitsuspeedLol Like I already said a lot of the smaller more detailed welds I do don't use filler. It's faster and easier to fusion weld when I don't need the strength. On top of that the whole point of this thread is trying to figure out how to make the welded area look like aged raw steel. Having shiny stainless welds is like the complete oposite of what I am looking for.