Any tips or tricks on preventing distortion/warpage from welding?I tacked up a front bumper (from a kit) on my vehicle and everything is perfectly where I want it. Now I removed the bumper and need to stitch weld the inside and fully weld the outside (then grind down smooth on the outside). I don't have a jig and I'm worried about distortion from the heat from welding, I've had issues in the past on other projects. The bumper is all 3/16" flat plate mild steel, and I'm using a Hobart Handler 210 MVP MIG and standard 75/25 gas. I only have half an inch of clearance in some places between the vehicle body and the bumper, so not much room for distortion, I'd like to keep everything true as much as possibleShould I keep switching sides to keep the heat down, or weld some on the inside, then some on the outside in the same spot so it pulls even? Or ...?
Reply:Much of the knowledge you are needing is in this 1940's video Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Originally Posted by cpp3Any tips or tricks on preventing distortion/warpage from welding?I tacked up a front bumper (from a kit) on my vehicle and everything is perfectly where I want it. Now I removed the bumper and need to stitch weld the inside and fully weld the outside (then grind down smooth on the outside). I don't have a jig and I'm worried about distortion from the heat from welding, I've had issues in the past on other projects. The bumper is all 3/16" flat plate mild steel, and I'm using a Hobart Handler 210 MVP MIG and standard 75/25 gas. I only have half an inch of clearance in some places between the vehicle body and the bumper, so not much room for distortion, I'd like to keep everything true as much as possibleShould I keep switching sides to keep the heat down, or weld some on the inside, then some on the outside in the same spot so it pulls even? Or ...?
Reply:Some things to consider along with all the other comments is decide which way is preferable if distortion does occur, as you have to assume it will. Take a marker and draw arrows in the direction of each weld. Personally I like to go from the outside to inside and let the stresses crash into each other. Aside from jumping around, add more tacks to keep the structure stable. If they get in your way, flush them out a bit prior to welding. Steel melting is 2000 degrees F. A preheat to 400 degrees F. will take some cold shock away. Once you get welding and it is hot, keep going until done. The more heat you have to put in it with welding, the more distortion.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:I would tack a piece of angle or tube across the back to hold the width. Skip around and allow to fully cool before cutting loose the brace.
Reply:Minnesota DaveGreat video.
Reply:Balance your heat.Weld front/back, one weld exactly opposite the other. Start in the middle, and work out to the edges.It will warp, you can't do much about it. If you don't have a rosebud, you can backbead the warped areas to straighten it. If you're lucky, the warp will be on the side AWAY from the truck.........then your backbeads will be hidden.
Reply:One inch at a time.Go from equal and opposite sides....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:It is like Weld said jump around.You look at and weld on other side. This more of art and skillMost rod burner just burn rod and only luck will stop distortion.A highly skill welder will not have distortion but they get big pay.Whatch video supply by MinnesotaDave help too.DaveLast edited by smithdoor; 12-02-2020 at 07:22 PM.
Reply:Man if you are grinding it down flat so welds can't be seen it would sure save a lot of work grinding if you could do the outside with tig instead of mig. You could lay a nice tig weld that almost leaves the surface flat when you done. Strength here is not a issue and there is way more weld than needed welding it out fully.Controlling the deposition when needed is where tig really shines.Realize you have to work with what you have though.
Reply:Id get a Tube and weld it to the bumper to help it from moving much if it does.
Reply:You shouldn't have a lot of distortion with your angles changing but could get some between welds. I would put a bunch more tacks on it, no more than 3" apart then weld it out. If you have plenty of tacks on the back side then you should be able to just weld out the front. Here is a bumper I had to straighten the thin back piece after the heat in the powder coating oven, warped. You can see how much pull the welds had on it to straighten it back to near perfect. Last picture shows how much bend was in it, the middle, the welds and the first picture is how it came out. Attached Images
Reply:Thank you for all the replies, I learned a lot.Much of the knowledge you are needing is in this 1940's video
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ow heat is all you can do and no sequence will matter much. It's gonna be a pretzel no matter what. Stomping on it afterwards is all ya can do.
Reply:I would weld the whole center seam first, then weld the top and bottom seam next. The last seam you weld will tend to shrink more than the first in most cases. So if the center weld caused it to tweak up, weld the top seam and then the bottom. You can also load the bumper before welding it by mounting it and preloading it by clamping it to a piece of I-beam, C-channel, box tubing, or solid bar to counteract the shrinkage before you weld, or to tweak it the way want it to end up. When I weld things onto solid pipe or box tubing, I noticed there is no way to stop this without preloading which is just too much work, so I weld one or two pieces onto the pipe or box tubing starting on the left side and then one or two pieces starting on the right side. But you have a different situation. Sincerely, Wiliam McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:Knowing how things so often turn into disasters in my shop, I would be tempted to tack it all up real good, then mount it to the vehicle before welding it out, to make sure it will mount up where it needs to mount up. That bumper is gonna have a lot of welding on it, and lots of potential distortion...Just be careful if and when you unbolt it from the frame, because it's liable to unspring like a Jack in the Box!Last edited by Kelvin; 12-03-2020 at 12:11 PM.
Reply:I made a similar bumper, by move. I jump all over the bumper 2" was probably the longest weld. No issues
Reply:Three things to remember about distortion control... Hot, Fast, and don't put on more weld than you need. Add that to jumping around in a sequence that balances the welds goes a long way to controlling warp.
