The Stovebolt Site Forums The Shop Area Paint and Body Shop Mig Welding Help

Not too much info on this.

I need help. I've tried everything except going down to .023 wire size, which I don't expect will help all that much from .025.

I can't keep from burning through the sheet metal (as well as some good warpage). I've done about 40 practice welds now trying various combinations.

What I've done so far: heat sink putty beneath the weld, heat sink putty on either side of the weld, aluminum tape beneath the weld, flattened copper pipe beneath the weld, fiberglass and aluminum tape beneath the weld, increased wire and travel speed, drag/push angle adjustment, used an extension cord to try and reduce the voltage. Right now my best welds have been single tacks along the whole joint. I've also switched the gun to DCEN polarity, but that doesn't fully penetrate enough and leaves me with a Mt. Everest of a weld bead. If i do get the puddle hot enough to flatten out a bit with DCEN...BURN THROUGH!

Any veterans out there with an idea of what else i can do?


P.S. I'm practicing on both a slightly rust pitted old panel and clean sheet.

My Equipment:
Lincoln 100 buzz box (mig/flux)
75%Ar25%CO2 @15-30CFH
yes i like TIG, too, but I have what I have

I'm not much of a welder myself, but my 2¢ is you need less wire speed, near the lowest heat, faster movement, the wire size shouldn't make much difference, except the bigger the wire, the slower the feed needed .... you may be trying to run too long a continuous bead, stitch an inch, skip 3, do another inch, go back and fill some, etc, never be stationary or weld a long joint in one pass - and expect to give the grinder a workout regardless .... using an extension cord will just overheat the power circuit, the control on the box is all that can reduce heat .... and rusted metal is a problem even for pros

Bill

You might also try a lower voltage setting. Are you holding the gun between perpendicular and 5 degrees. Make sure the gas setting is between 25 and 33 CFM, to high a guess with a fast wire speed will blow a hole. Are you using a flux or none flux wire?

Guys,
I'm pretty sure I'm not doing anything obviously wrong. So wire speed, flux/solid wire, welding short lengths and skipping around, voltage settings, gas flow, drag/push angle, tip to work distance, etc., this has all been tried.

When it comes to sheet metal all I have seen is the exact same thing Bruce has stated. Tack welds, and lots of them until the seam is filled. Everything I've heard and read is that welding sheetmetal is a long, slow process in order to avoid warping.

#1 you need a gap for your mig joints and you can get a gap with a spacer clamps. #2 you need to get rid of all the rusted metal. #3 you need to clean your metal from any contamation that will ruin your weld. burning through is a sign of getting too hot or dirty metal. Use a copper backup I like to use old copper sheet or buss bars to back up my welds. Again TACK, TACK, TACK, TACK! You must move around to keep from warping your metal. I have used Tri Mix and it works well but also have had good welsd on 80% 20% mix on heaver metal I used straight C-02 another thing keep your shielding gas from blowing away when welding by putting up a barrier around the area you are welding.
It doesent need to be real close to the weld just to protect the breeze or wind from a fan OR! If it is rusted use a grinder with a wire brush to get down into the rust pits or if too bad use a new piece of metal cut to fit the rusted area. I have learend a long time ago you must think outside the box when reworking metal. The previous post have nailed it very well but the heat will be the cause of burning through most of the time along with that dam rust contamation. Try using some Metal Prep # 79 to clean the area if it is had rust. Then be sure to wipe away with a wet rag and let dry then weld it.
There is a very good book out by Eddie Paul called Paint & Bodywork Handbook. This book can be picked up at Barns & Noble. Very good book on welding and other processes you will come across when working with sheet metal body parts. I picked it up to reforce what I have learned about leading after welding certain areas of your truck. $25.00 + the tax. Well worth the bucks and a wealth of info from some great pros.
I hope this helps some of you in your endevors been fabing for a long long time and still learning.
62Blue
Don

If you want to see some quality work look at Hot Rod Lincoln work on his Chevy PU. with all the floor,rocker panel work a true home pro. and he has pics. of the work step by step in the gallery sec.
Don
62 Blue

CLEAN,CLEAN,CLEAN. yOU CAN NOT GET IT CLEAN ENOUGH! Did I make it clear? Any dirt will drive you crazy, and there is no short cuts for "shinie bright". Try this on clean scrap, and NO GALVINIZE, that's another problum, gavonac poisoning. Good luck and practice. 40 yrs. at it, and still love it. CLEAN......

Thanks guys, but I'm cleaning the panels. I'm working on both the scrap panel (which I wire wheeled) and brand new sheet metal. And when I say I'm having problems burning through, I'm talking if I keep the gun on for more than half a second it'll go. I'm starting to wonder if my machine just isn't capable of producing that low level of power I need.

Thanks, Don. I ordered that book. Looks good.

The only thing that I do that I didn't see you mention was clipping off your MIG wire with a pair of side cutters each time before you start your weld. This gives the wire sharp edges so that it penetrates right away when you start your weld. It also gets the amount of wire sticking out to the right length (I shoot for a half inch) before you start your arc.

I hope this is helpful.
regards,
Steve
New Orleans

Do you have the polarity right. Most machines come with flux wire. When you weld with shielding gas, you need to reverse the polarity. Does the wire come out of your tip freely. If you have slag built up it will come out in spurts and screw you up.

GMCdp,
I had the same problem with my floorpans. I had my MIG set at its lowest voltage and the wire feed speed just right. I would tac here and tac there, but just as I was almost done, burn through. Soooo frustrating! I gave up and had a pro do it. Do you grind off the weld and start over? If so, do you think you thinned the metal just a little each time? I think that is what I did. I was dealing with paper thin metal after trying so many times!

Since then I have had much more luck when I back up the metal with copper. Also, when I go back to a previous tac I aim the wire at the previous bead, then kinda do a "U" to extend the bead. It seems that the initial contact on the previous bead then moving to the metal works for me. I'm far from being a pro, so listen to the guys above.
I feel for ya buddy!

Good luck.

Here is a trick you might try Take a fill rod steel about 3/32 and clamp it to your work then take the ground clamp and hook it to the end of the rod. Be careful as the ground rod will get (VERY HOT) see if that does not lower temp a bit so you can weld with out burning thru. Also look at Chezmans Gallery page another Home pro. these guys are very good at welding body panels Chez has a series of pics too.Very Very Nice work!
62Blue
Don

Well, I bought some 0.023 wire and it does help a little. Maybe 10% less power. I think the bottom line is butt joints on sheet metal are just plain tough to do well. Especially with a home welding machine. I fixed some rust pits in the inner to outer cowl panel on my truck and just used a shaped copper backing plate (made from pipe) and fiberglass in between to fill any gaps. It worked ok. That and the heat sink should give me a pretty good system.

If a pro is welding on anything thinner than about 22 ga., I'll bet he's using a backing plate and maybe a heat dam.

Thanks gents

For all my sheet metal work I used the lowest current setting. I set the wire speed just fast enough to get a proper buzzing arc. If the feed is too fast you get too much pile up of weld material. MIG will not work with rust or dirt. Other than those hints it is a matter of learning your technique.

I have to chime in here. Listen to Don G. I know a couple of thousands of diameter shouldn't make a difference. But for me it did make a differance. I could turn down the feed and amperage. No burn through and no warpage. I would guess that you still have too much energy going into the metal. I turn my Hobart Handler down so low it sounds "wrong" but I get great welds and no warpping.

Had to add my two cents, I have a little Hobart and flux wire. Got my front panels welded in with lap joints and they are fine. I have been worrying about doing the butt welds on my back corners. Made myself some little clamps to hold the pieces about .040 apart and backed the area with copper. It looked so nice with the corner in place, did I really want to try and weld it and ruin the corner or at best fill it full of holes? Well, I took a deep breath and tried my first tack! Lo and behold, it was a perfect little circle uniting both pieces. So I tried again allowing the metal to cool between tacks. Must have made over a hundred tacks burned through about three times but these were easy to fill with the copper backing. The right corner is about 1/2 welded in and looks far better than I ever thought it would. I used the lowest voltage and wire speed and it seems like I always do a better weld if I align myself with the weld so that I can see the wire melting. It works best if I put my eye level low so that I can see the wire fusing the two metals, kinda like putting your head on a railroad track and watching the engine (wire) fuse the metal. Well I was so happy with this result today that I had to tell someone. So if I can do it GMCdp you can do it. Good luck.

GMCdp,
Practice,practice practice.

You may be right about your welder not having a low enough setting. Heat,fed have to be just right.
but usually the problem is not enough penetration instead of too much.

Thin metal is tricky, keep at it.
By the way,a professional looking weld is called that for a reason. If you don't do it for a living,it's hard to get the same results.

Way to go you guys it is a matter of practice and more practice. Now in a couple days when I get my eyes fixed I won't know how to weld again and will need to practice all over! LOL! Like I said before take a look at Chezmans welding technice as he does some fine work.
62Blue
Don

This is old Funton again, earlier GMCdp was having trouble Mig welding so a number of us chimed in on what he might try. I was so happy that I was able to weld on my back corners without having gobs of holes. After about 400 tacks I got them welded in and looking from the back side saw that the penetration was not that good all the time. Now I'm going back and welding the corners on the inside of the cab. I'm thinking that when I grind off the weld on the outside I need to make sure there is plenty of metal to hold. So GMCdp if you are still out there,be advised that I'm a novice and don't feel like I'm half as good a welder as I did when I responded before. This mig welding can make me feel good some days and bad some days. Now if there is a REAL welder out there I have a question---How particular do I have to be on this backside welding? Thanks to all that respond.