Getting too much weld penetration?

[Shaun @ Tru6]

I'm butt-welding SC flares onto my 73 this weekend. Little bit of practice yesterday.

Hobart 140, heat setting at 2, wire speed at 30, .023 wire.

I cut out of a section of old quarter and clamped it back in place. I'm getting more penetration than I think I should, weld bead came through the other side...or is that good? I ground the weld down with a cutting wheel on the grinder. To the left, you can see the seam. I will be sure to grind off the underseal of both the flares and the car before welding, this was just a quick test.

Should keep it at 2? After tacking both on, I plan on short beads "every now and again" to keep warping and filler to a minimum.

[MT930]

You can manually pulse the MIG gun one second bursts two inches apart and make small tacks.

Avoid putting too much heat in one area (Burn-through)

On the thin stuff I place a strip of copper behind the weld it sucks the heat out.
Aluminum works almost as well. Mild steel will not stick to either. It has a learning curve, be patient and practice on scrap first.

[widebody911]

There's no real sin in the weld bead coming out the other side, and if you're A-R you can always grind on that side, too.

Doesn't look like you have much of a weld gap; without one, you'll warp the metal easier.

You should also clean off the undercoating near your weld; otherwise when it burns it will contaminate it.

I use a roloc #30 or #40 sanding wheel on a small 90° angle grinder - much less aggressive and more controllable than the angle grinder. For final cleanup I use a #50

[Zeke]

Originally Posted by widebody911

There's no real sin in the weld bead coming out the other side, and if you're A-R you can always grind on that side, too.

Doesn't look like you have much of a weld gap; without one, you'll warp the metal easier.

You should also clean off the undercoating near your weld; otherwise when it burns it will contaminate it.

I use a roloc #30 or #40 sanding wheel on a small 90° angle grinder - much less aggressive and more controllable than the angle grinder. For final cleanup I use a #50

What he said and hold your stick out to a minimum. You want the arc to be small, cool and a small puddle. Yet you do need to see the weld from the backside, no more seam.

I weld with as small a stick out as I can. I have to look from the side because the gas nozzle blocks my view I'm so close.

Don't always believe in the gas flow setting nor the position of the nozzle on the threads. You can grind the nozzle at an angle too, if that helps.

Weld in 1/2' segments and move way far way for you next weld while the previous area cools. Snip off your wire before you start each time. Wire brush the previous weld before starting your next segment. Start your puddle in the old weld, not next to it.

Go slow and stay cool is my weld motto.

[Shaun @ Tru6]

Thanks guys, with this info, I'm all set with another HOme Depot run. Did get some Rolocs Thom, need to check #.

If I will get less warping with a small gap, should I use these? I've got enough to get one flare tacked on.

[willtel]

Originally Posted by widebody911

Doesn't look like you have much of a weld gap; without one, you'll warp the metal easier.

I agree, with a small gap the bead will settle between the panels and you won't have to grind as much. Something about the width of a penny will work well.

[john walker's workshop]

undercoat burns fast also. keep a spray bottle of water near you. don't run any beads. after fitting the panel with spot welds every 2 inches, put another one between all of those, another one between those so you're down to about one every 1/2", then fill the 1/2" spaces with an overlapping series of spot welds. keep moving around to a cool place for the next 1/2" series. do not cool with a wet rag. just let the air do it. stop and wait if it feels too hot with your palm. after grinding smooth, put a shop light inside behind the seam and look for pinholes. pinholes allow water through to bubble the paint, so weld them up.

[Zeke]

Originally Posted by Shaun 84 Targa

Thanks guys, with this info, I'm all set with another HOme Depot run. Did get some Rolocs Thom, need to check #.

If I will get less warping with a small gap, should I use these? I've got enough to get one flare tacked on.

I use those.

Yeah, JW has got the tacking sequence but I thought you knew that part.

[kaisen]

Welding is an art I never learned. I admire you guys - I'm jealous. It makes me want to learn to do it.

[Tim Hancock]

I do not have much experience mig welding large sections of auto body panel, but in general when welding thin stuff, you want to see penetration on the back side from a weld joint strength perspective. Obviously flares are not something that you need to worry about strength, but still.... I personally would be happy to have 100% penetration which will help prevent grinding through the weld leaving an unnoticed crack which will later cause rust issues or a witness line in the paint finish.

As everyone else already mentioned, you have to really jump around with very small weld beads to help control warpage even with the initial tacks.

[Shaun @ Tru6]

Originally Posted by kaisen

Welding is an art I never learned. I admire you guys - I'm jealous. It makes me want to learn to do it.

I'm a complete novice but wanted to learn, just bought a Miller 135 (I'm borrowing the Hobart as mine is loaned out) from a local shop who gave me some advice and I started practicing on heavier stuff, much easier to learn to weld when you can get a real feel for the flow without burning through or warping. sheetmetal is a challenge and since it's my car, I need a little more advice, a lot more care.

This is the best thing I've ever made. Very low stress. If you screw up, just cut away and grab a little more stock. Can't really grab another car.

[9dreizig]

Shaun,
I'd see what Moe is doing, he's a darn good welder (and I think his brother is even better),, nothing like free lessons

[1990C4S]

Less wire stick-out=more penetration (counter intuitive, I know).

So if you are just tacking you can go to 3/8" or so. Longer welds should be run at 5/8" - 3/4" stickout.

But you should not do long welds, as per Mr. Walkers directive.

If you are using gas you want mainly argon. CO2 is too hot.

[cstreit]

You really should have cleaned off the undercoat behind the weld. As it burns it fouls the weld and the arc. #1 rule of mig? CLEAN. CLEAN CLEAN.

[lendaddy]

Originally Posted by 1990C4S

If you are using gas you want mainly argon. CO2 is too hot.

Yep, I've been telling people this for some time. Straight Argon or 95/5 whatever.......a much flatter/wider bead. You have to throw everything out the window in regards to settings and just learn it but in the end it's much better for thin material work and very "clean". Sure there may be minor strength concessions but as Tim Hancock mentioned this really isn't a concern in this application.

[Rich76_911s]

Originally Posted by Shaun 84 Targa

Can't really grab another car.

Thanks for the confidence booster

BTW what kind of jerk would have your welder, and your homemade roto? Somebody owes you big time. . .

[Tim Hancock]

Originally Posted by lendaddy

Yep, I've been telling people this for some time. Straight Argon or 95/5 whatever.......a much flatter/wider bead. You have to throw everything out the window in regards to settings and just learn it but in the end it's much better for thin material work and very "clean". Sure there may be minor strength concessions but as Tim Hancock mentioned this really isn't a concern in this application.

Hmmm.... I always have a bottle of pure argon on hand connected to my TIG machine as I use my TIG for steel, stainless and aluminum so it has always been easiest to just have one bottle with straight Argon.

When I recently dug my mothballed 110 MIG welder out to do some "production" welding of some 1/16" wall tubing target stands, I was about to haul the old 110 welder to the dump and buy a newer bigger 220 unit when a friend asked me what gas I was using. When I said Argon, he said well there is your problem. So I bought a bottle of 75% Argon/25% Co2 mix (like we use at work for our big mig machines) and my little welder started working like a MIG should again.

Next time I have to weld some "thin" steel that is not "critical" strengthwise, instead of using my TIG, I will try straight Argon vs the Argon/Co2 mix with my MIG.

[Shaun @ Tru6]

Originally Posted by Rich76_911s

Thanks for the confidence booster

BTW what kind of jerk would have your welder, and your homemade roto? Somebody owes you big time. . .

Why only a great friend of course!

other way around I'm afraid.

[1990C4S]

CO2 also causes way more spatter.

[lendaddy]

Originally Posted by Tim Hancock

Hmmm.... I always have a bottle of pure argon on hand connected to my TIG machine as I use my TIG for steel, stainless and aluminum so it has always been easiest to just have one bottle with straight Argon.

When I recently dug my mothballed 110 MIG welder out to do some "production" welding of some 1/16" wall tubing target stands, I was about to haul the old 110 welder to the dump and buy a newer bigger 220 unit when a friend asked me what gas I was using. When I said Argon, he said well there is your problem. So I bought a bottle of 75% Argon/25% Co2 mix (like we use at work for our big mig machines) and my little welder started working like a MIG should again.

Next time I have to weld some "thin" steel that is not "critical" strengthwise, instead of using my TIG, I will try straight Argon vs the Argon/Co2 mix with my MIG.

Interesting. I was always using 440v equipment so stability was probably better right out of the gate. I recall having to up the wire speed significantly vs C25 gas.