Mig welding car panels question

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Hey my grandma got in a crash last year durring the winter and busted up the front end of her car and my dad wants to cut off the bent up part and he has another one that would fit in there and then he wants to weld the new one on. So I was practicing on the front fender and I was trying to find the right settings for welding it and (just in case this would help we have a lincoln 135 using flux wire) I would either blow right through it or it would not get a good weld. I know that the fender is a little bit thinner than the stuff we will be welding but any suggestions on settings or techniques?ThanksAdiosJoshWelding is never having to buy something.
Reply:Hey Josh, thats going to be a tough one. Flux-core on thin mat like a fender is hard and no dis intended, but you are really going to have a rough time of it.Your mat has to be really clean and you will have to run the welder at a pretty low setting to avoid blowing holes.(as you found out)Sometimes you can just do many many spot welds and be ok. If you hold the gun in a solid grip so it wont move and only stay on the trigger for a second or so between spots you will get a series of overlapping spot welds that will work for thin stuff. You wont want to let the mat get too hot but you need penetration too so like 1 sec on - 1sec off -1on  1off and just keep going. If you pop a hole, no stress. Go back after it cools and pop another tack on it. Dont try to do it when its too hot or it'll just get bigger. Also a good fit is very important! Flux core on thin stuff with a gap is a bad situation for anyone. You might also try a piece of heavy brass or alum(not steel) behind the weld to act as a heat sink. Hope this helps. Best of luck to ya buddy.
Reply:If you can, try using .023 hard wire and gas and keep your travel speed up.  Stitching as described above might help as well.-Heath
Reply:I worked in a body shop for a few years when i was in college, and have welded alot of body panels in during that time and since.  Personally i would rather O/A weld in a panel than run flux core.  If you burn a hole in it which you probably will with the flux you will wind up having alot harder time filling it in, which in turn is going to take longer thus cause more warpage.  As mentioned above.  Make sure you have a tight fit.  Use the .023 wire with co2, and make short spot welds jumping all around the seem.  It will help  with the warpage.  You won't be sorry.  Good luck ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Actually, I believe that less CO2 might help the issue if .023 wire and C25 still doesn't work.  More argon and less CO2 will give a more stable arc, less heat, and less spatter.  Praxair specifically recommends C15 for thin materials on their website here:http://www.praxair.com/praxair.nsf/0...a?OpenDocumentLast edited by halbritt; 08-29-2005 at 04:31 AM.-Heath
Reply:Currently I'm doing a rebuild of an 01 f-150 supercrew, so I'm having to do allot of long butt welds on really thin metal for that truck. I started out using the .035 flux-cored with an a 1.5 setting on my Lincoln weld pak 100.  I was really hard to get the right amount of stick out  to keep from blowing through those welds. So I converted my machine to gas using a 75/25 mixture and now use a .025 solid wire for doing my weld. It is so much easier to move that puddle around those butt welds without burning through. Right now my "Butter" setting is  A, with 1.5 on the wire feed speed and the Argon set to 25 cfms and I can weld some low clean welds, with great penetration. Flux-cored on that thin a metal is really tough. I got it to work but the grind down on my butt welds was just a pain. If you can convert you wire feed over to gas, it will make welding that thin metal really easy.Here's some picks of my proejct truck .and here is  butt weld line for my rocker panel ground down. I hope this helps and good luckWeld-Pak 100 Mig. New to welding and melting anything metal