Mig + sheet metal = not so good

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hey guys,Ive recently purchased a mig welder and getting some practice in.my brother wants me to weld in some 1/8 of an inch thick 6x6 plates in his car.Being a tig welder, this is my first actual time trying and practicing, ive used mig before in a welding class for fun to see how it was, but never got any practicing done.  i wont be mig welding much, so this is the reason for practicing on sheet metal.  Just wondering if any one has some great tips, my runner flat beads looked alright, dont have any pics of that yet.my current set up.Wire size - .024 (i also have .030, havent tryed it yet)40cf cylinder size gas mixture 75% argon 25% co2 (i have it set on the meter to about 20 flow)12lb 8in spool solid wire er70s-6mild steel 22g flat sheet metalmild steel 1/8 flat platingfirst setting ive tryed around is voltage set to 1 and wire speed set to about 25second setting ive tryed around is voltage set to 2 and wire speed set to about 30 to 35.i am on DCEP on polarityi keep getting warping in the sheet metal no matter how less i weld at a time.my little jig it seems like when i weld on the voltage set to 1, the wire wont melt consistantly, seems like it has a hard time welding, but set on voltage 2 it welds great but seems a little to hot. i dont how to explain it but maybe that kind of helpsthanks, brentLast edited by disepyon; 03-01-2008 at 03:50 PM.
Reply:If you can tig you should be able to mig very easily, usually guys can mig but not tig
Reply:here are some more pics,btw im not welding all these in the same position, the work piece doesnt move, so for the welds in the back and side i am having to lean over and position myself, i do this as if i am welding this inside the car.i keep getting these gas pockets. Please help me on any tips to advise here is a t jointand for fun, i went back over some welds to see what it would be like
Reply:Those bad spots look like you're either losing your shielding or you're hitting some kind of crud in or on the metal.HH 187Miller Bluestar1EAHP AlphaTig 200X
Reply:I think those are his original tacks, if I'm not mistaken.To prevent warpage try clamping a piece of alum to the back side. Vertical down wherever possible too.
Reply:thanks guys,i did clean both metals, and yes those are my tacks on each corner of the plate, i am also having trouble with tie ends, seems like on mig its hard to blend the weld.ill try the aluminum backing plate idea, and maybe turn up my gas flow or something.
Reply:What is the 1/8 sheet for on the inside of his car ?
Reply:Originally Posted by disepyonhey guys,Ive recently purchased a mig welder and getting some practice in.my brother wants me to weld in some 1/8 of an inch thick 6x6 plates in his car.Being a tig welder, this is my first actual time trying and practicing, ive used mig before in a welding class for fun to see how it was, but never got any practicing done.  i wont be mig welding much, so this is the reason for practicing on sheet metal.  Just wondering if any one has some great tips, my runner flat beads looked alright, dont have any pics of that yet.my current set up.Wire size - .024 (i also have .030, havent tryed it yet)40cf cylinder size gas mixture 75% argon 25% co2 (i have it set on the meter to about 20 flow)12lb 8in spool solid wire er70s-6mild steel 22g flat sheet metalmild steel 1/8 flat platingfirst setting ive tryed around is voltage set to 1 and wire speed set to about 25second setting ive tryed around is voltage set to 2 and wire speed set to about 30 to 35.i am on DCEP on polarityit seems like when i weld on the voltage set to 1, the wire wont melt consistantly, seems like it has a hard time welding, but set on voltage 2 it welds great but seems a little to hot. i dont how to explain it but maybe that kind of helpsthanks, brent
Reply:Thanks alot for the input dave powelsonon number 3 you mentioned, what do you mean by (pre-bow the plates, clamp, then tack, then weld--that helps counteract distortion-significantly. Doubling these plates as you're doing)It makes alot of since when starting from the outside then in. cant believe i didnt know that, hehe
Reply:Originally Posted by disepyonThanks alot for the input dave powelsonon number 3 you mentioned, what do you mean by (pre-bow the plates, clamp, then tack, then weld--that helps counteract distortion-significantly. Doubling these plates as you're doing)It makes alot of since when starting from the outside then in. cant believe i didnt know that, hehe
Reply:I would also say that your gas is wrong.  75/25 is good for high heat.  You should be able to use 100% CO2 and that should help some.  But just my 2 cents....LOL
Reply:Are you putting the plates in for a rollcage? The cars sheetmetal wont warp much when you weld the plates in. Be sure to wire wheel/clean the area your gonna weld. When they put them together they use seam sealers, primers etc....that are just nasty. Fumes and porosity. I have MIGed alot on car interiors, putting in plates for cages and stitch welding the seams. You kinda get a feel for it after awhile
Reply:Originally Posted by BurnitAre you putting the plates in for a rollcage? The cars sheetmetal wont warp much when you weld the plates in. Be sure to wire wheel/clean the area your gonna weld. When they put them together they use seam sealers, primers etc....that are just nasty. Fumes and porosity. I have MIGed alot on car interiors, putting in plates for cages and stitch welding the seams. You kinda get a feel for it after awhile
Reply:It looks like your getting better as you practice more ,you can also adjust your stick out to get a little change in your heat , this takes some time and practiceto get the feel of it.Life is tuff,so be sharp  lincoln sp 100  cutmaster101  miller bobcat  miller 250 mig  $thousands in snapon
Reply:Just an FYI no co2 with the HH140.....she doen't like it...also co2 will produce a hotter weld than c25....also the floor in your friends car isn't going to move like the flat sheet you are working with as it is stamped and has ridges etc for strength...... and just my 2 cents a roll cage isn't going to do much for ya it it's only welded to a sheet metal floor.
Reply:Originally Posted by asemasterIt looks like your getting better as you practice more ,you can also adjust your stick out to get a little change in your heat , this takes some time and practiceto get the feel of it.
Reply:hey guys,did some more quick practicing today, bought a new cylinder, upgraded from 40cf to 125cf cylinder and got some more material to practice on.upgraded cylinderBought all this for only 10 bucks at my local metal supermarket store.Will those brown gas pockets in the welds harm anything? and what can i do to prevent it? turn up the gas? or is it my wire length?
Reply:All your need is more time behind the stinger.  You got it, but need a little more pracitce.Looking good!David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Will those brown gas pockets in the welds harm anything? and what can i do to prevent it? turn up the gas? or is it my wire length?[/QUOTE]1-See image below with red circles.http://www.weldingweb.com/attachment...1&d=1204767808Presumably, what's in the red circles is what you're referring to as 'brown gas pockets'.These are not gas pockets. Welding wire contains silicon and other items to trap and float contamination to the molten top of the puddle. These are normal silicon appearance from a steel wire weld. You're probably using ER70S-3 or S-6. The 'S' denotes the relative silicon content of the wire, "6" being higher in silicon content than "3"--for more cleaning ability.       [In steel making, silicon and/or aluminum are added, and both trap and float contamination to the surface of the molten steel in the crucible, before pouring the ingot. This is called 'silicon/aluminum' killed.]The silicon, or most of it, can be removed with stiff stringer bead brushes in an angle grinder. Sandblasting is required to remove all of it. Attached ImagesBlackbird
Reply:Originally Posted by David RAll your need is more time behind the stinger.  You got it, but need a little more pracitce.Looking good!David