Hi all, I have been doing a few 'warm-up' practice welds (MIG) before I start in on my floor pans. I have been using both some old scrap floor pan pieces and pieces of 18 gauge sheet metal I have around the garage. I have been finding that quite often I end up blowing holes in the 18 gauge steel but not in the floor pan metal. I am trying different wire speeds etc. with basically the same result. What is the difference, if any, in the two types of metals? If I remember correctly, the sheet metal, before I cut it up, had a label saying it was hot-rolled. Does hot-rolled/cold rolled make a difference? I got it from a local sheet metal shop, but they have since closed. I want to get some more metal that I can also use as patch panels elsewhere on the body, but now I am wondering what I should get.
Mike

turn the amps down a notch
Wire speed also as low as possible
If the wire 'diggs in" it is too fast
If the arch keeps braking, not continous, it is too slow for the amps.

Have the amps up as high as possible without blowing holes for good penitration..Penertration is Everything.
Also try working from the 'hard steel' (floorpan) to the sheet metal.
Hope u understand that...Im trying to put into words what I do.

Have a play with some 5mm scrap, then a little smaller, turning feed and amps down, then the panel steel...thats an easy way to pick up the knack.

If your having trouble blowing thru on a weak spot put a piece of 3/16" or thicker alum. as a backer plate.Make it as tight as possible behind the plate it will not stick.
cold rolled is a more annealled carbon steel. It will rust faster if not sealed good. Hot Rolled has been formed at a higher temp and has cooled fast. This makes for a less even density with a slag coating.Slightly harder steel.

Thanks for the replies. As always, very informative! I am going to keep practicing until I get it right....before heading in on the pans.
Mike

Like Steps says.... you gotta play with the power and the speed. Every welding project (sheetmetal on the Camaro) I do is different..... the weld needs to be adjusted to work properly. I used to blow through panels like a I was shooting at them. :) The speed of the wire and the distance the tip of the gun is away from the work makes a HUGE difference. I used to hold the tip almost 3/4" away from the work and got crappy results. Once I learned to hold the tip closer, adjusting the power and speed was a lot easier.
Good luck! It's fun when you hear that ZZZZZT and watch the weld join the metals.
Go to the junkyard and pick up a cheap hood or large door and cut it up, then practice lap welding and butt welding pieces together.

Thats a good idea. I have to watch my distance (from the metal). I'm probably holding the tip of the gun too far away. Too far and I think you get popping rather than the ZZZZTTTT. Pretty sure I'll get it eventually.
Mike

cold rolled is a more annealled carbon steel. It will rust faster if not sealed good. Hot Rolled has been formed at a higher temp and has cooled fast. This makes for a less even density with a slag coating.Slightly harder steel.

FYI
Cold rolled is definately harder. With high carbon grades being the hardest, down to the ULC (ultra low carbon) being somewhat "less hard" before annealing, but still unworkable.
Cold rolling or cold reduction actually work hardens the steel. Cold rolled steel must be batch or continuous annealed (re-heated and control cooled) to become workable again.
Hot rolled steel is softer simply because it has not yet been cold rolled.
Hot rolled is not available in the light gauge required for body panels. Hot mills cannot roll it that light (yet).
If it is not Galvanized, is advertised as being for "body repair", then it is simply annealed cold rolled steel.

Cheers, Mark

What size of wire do you have in the mig welder. For sheet metal I like .023". The thinner the metal you are trying to weld the thinner the wire in the machine (to a point). If the wire is too large, then you have to turn the heat up too much just to melt the wire, then you just blow holes in the metal. Did that make sense???

This might help, maybe, anywhere here you go.

http://www.camaros.net/forums/showthread.php?t=89105&highlight=sheet+metal+thickness

Rob

That is another thing I have to check on, the wire size. I am going to spend some time tomorrow trying all these different variations. The wire I have in there now is 0.03. I'll start with that. I only have a little of that left on the spool, and then I'll come down in size.
Its hard for me when I don't do it alot. I had a project going last year, where I had to do some welding (wasn't as critical as body work) and byt he end I think I had it going pretty good and was laying down some decent welds.
Sometimes when you are trying to be the most careful, you end up making the most mistakes. Its like when I'm spraying paint and I shoot a test panel or something I am not really concerned so much about the outcome, it comes out much better than when I am really careful. Oh well, maybe its akin to shooting a better game of pool after a beer or two, though I won't crack one open until after I finish welding for the day!

Just last quick bit of advise ... Follow the puddle. Keep the tip moving, you can't keep in one spot for long.

Practice on a test panel. Here is the fact, you shouldn't be able to blow thru unless you WANT to. Try welding without any hole or anything, right in the middle of the panel. Hold your gun in one spot and pull the trigger UNTIL it falls thru. You should be able to hold it there a LONG time. Adjust your wire speed and heat until you can hold it there with the weld growing and growing in a fire ball of red glow. You REALLY should be able to do that. Put the wire to the metal and literally using the wire make a marble sized ball of red hot metal BEFORE it falls thru. If you have it set properly you just about have to WANT to blow holes. Usually having the wire and voltage "mated" is a real good start. Set the welder on the 3 in a 1-10 heat setting and the wire on the 30 in a 10-100 wire setting. Or "B" on the heat in an "A-D" setup and the wire speed at the same point percentage wise. That is usually a good start. Fine tuning the wire up or down to match the heat. Don't go fiddling around with both, then you don't know what you have.

Realistically you should be able to weld that weld making a red ball of metal on the lowest setting AND on the highest setting of the welder.

I weld all day on cars many days. I will have that welder up pretty hot, on 10, wide open when welding floor pans to rails on a late model Toyota or what ever. The rails and floor pans are very similar to doing a Camaro, 18-20 guage floor pan to a 1/16" or so rail. WIDE OPEN at 10 with the wire speed on about 70 (with a 1-100 range) making very fast welds with THOROUGH prenatration and NO burn thrus.

Brian

Here is a tip I posted on welding floor pans that has helped a few guys, check it out. http://www.camaros.net/forums/showthread.php?t=95567 And here is another article on mig welding that may be of help as well. http://www.camaros.net/forums/showthread.php?t=13135

Brian

Another tip for the mig welders out there.....I recently purchased some copper plates from the Eastwood Company and they work great. They absorb alot of the heat produced when mig welding. They also allow you to turn the heat up a little more which obviously makes the weld stronger. One of the patch panels I installed had to be cut and re-shaped which left a gap that had to be welded up. I placed a copper plate behind the gap and it welded up with no problems. A little grinder work and the panel looked like new again, just made the right way now.

Thanks for the replies. I was wondering about the copper plates from eastwood. I just saw them in the catalogue. Might be something to look into.
Brian, I read the articles a while back, and found them very helpful. I have copies of them in the binder with my assembly manual. I am going to try as you suggested at the center of a scrap panel and see how long I can hold the gun there before it falls through. With my settings now, probably will blow a hole right away!...so I'll change them. I wish I could go try it right now, but will have to wait till tomorrow.
Thanks guys!
Mike

The copper backing plates do indeed work and are a good idea to have handy when welding sheet metal.

What size of wire do you have in the mig welder. For sheet metal I like .023". The thinner the metal you are trying to weld the thinner the wire in the machine (to a point). If the wire is too large, then you have to turn the heat up too much just to melt the wire, then you just blow holes in the metal. Did that make sense???

I was blowing holes up the yen yang on my patch panels.
I changed my wire from .030" to .023".
made all the difference for me.

Yeah I am definitely going to go with the .023" wire. Now if you use the copper plates, where do you place them? Right behind where you are welding? Whats the best way to do that? That'll probably prevent warping, at least to some exent, I would think, if it is acting as a heat sink.
Mike

Hold the copper tight to the back of what your welding.

A couple of other things come into play on older and newer metal, I guess you have a 60s car.

If you have pinholes in old metal, then its usually thinner around the area of the hole. I have found that if you have a hole the size of a pencil, you're better off using a new piece of just a little larger and welding that in there to patch the hole.

A good way to find out how your welds are, is sandblasting, and I have noticed that the little metal pieces welded in will hold under normal hobbist type sandblasting, where the chase the hole with the welder will show more tiny holes after blasted.

Also by doing this you can start your weld on the new metal and blend it into the old, this will usually give you less weld buildup.

But, back to the sandblaster, it will show you immediately whats welded right and what isn't, I was blasting my floor pans yesterday and today, no more hole chasing for me.

I had a 110 lbs at the regulator and 80 lbs on the blaster, this is a run of the mill eastwoods older pressurized blaster, and I blew some holes in my panels, but not where I used the little metal patches.

If you took it to a professional sand blaster, you would see more holes yet.

On those little holes, lets sayone the size of a nickle, grind it or clean it up around the hole, don't take any more metal off then you have to, also same with the back side, if possible.

I don't have a nickle or quarter in front of me, but thats a little bigger, so you know what I'm trying to say here. Make the new piece the size of a quarter.

Hope this helps you out.

Rob

Brian, how do you weld two different sizes of metal? Like a floor pan to a Sub Frame connector. If I turn the welder down I get good weld on the sheet metal but no penitration on the frame rail. and VS.

Practice on a test panel. Here is the fact, you shouldn't be able to blow thru unless you WANT to. Try welding without any hole or anything, right in the middle of the panel. Hold your gun in one spot and pull the trigger UNTIL it falls thru. You should be able to hold it there a LONG time. Adjust your wire speed and heat until you can hold it there with the weld growing and growing in a fire ball of red glow. You REALLY should be able to do that. Put the wire to the metal and literally using the wire make a marble sized ball of red hot metal BEFORE it falls thru. If you have it set properly you just about have to WANT to blow holes. Usually having the wire and voltage "mated" is a real good start. Set the welder on the 3 in a 1-10 heat setting and the wire on the 30 in a 10-100 wire setting. Or "B" on the heat in an "A-D" setup and the wire speed at the same point percentage wise. That is usually a good start. Fine tuning the wire up or down to match the heat. Don't go fiddling around with both, then you don't know what you have.

Realistically you should be able to weld that weld making a red ball of metal on the lowest setting AND on the highest setting of the welder.

I weld all day on cars many days. I will have that welder up pretty hot, on 10, wide open when welding floor pans to rails on a late model Toyota or what ever. The rails and floor pans are very similar to doing a Camaro, 18-20 guage floor pan to a 1/16" or so rail. WIDE OPEN at 10 with the wire speed on about 70 (with a 1-100 range) making very fast welds with THOROUGH prenatration and NO burn thrus.

Brian

Mark, there are some settings on welding floor pans to supports, if this might help.

http://www.1969supersport.com/fintest.html

Thats a good idea. I have to watch my distance (from the metal). I'm probably holding the tip of the gun too far away. Too far and I think you get popping rather than the ZZZZTTTT. Pretty sure I'll get it eventually.
Mike

Mike,

if possible hold the tip about 1/8" away from metal being joined and try holding it at a 45 deg angle. Should get you that sizzling bacon sound and a nice weld once you get the votage and speed figured out. Try 2.5 -4 amps and 30-35 on wire speed. hope this helps.

I was looking at the website http://www.mig-welding.co.uk/ (which someone here posted) and was wondering if anyone has used the approach mentioned there where you weld along a seam with a series of short pulses - with a 1 second pause in between. They say it prevents distortion/blowing holes (for thinner metal). I tried it yesterday and the welds look pretty nice. My only concern is that it is a "colder" weld and might not be as strong. I did it on a test panel and didn't get any distortion.
Mike

Brian, how do you weld two different sizes of metal? Like a floor pan to a Sub Frame connector. If I turn the welder down I get good weld on the sheet metal but no penitration on the frame rail. and VS.

It is ALL in the links I posted to the "Members contributions" page here at Team Camaro.

Brian

I was looking at the website http://www.mig-welding.co.uk/ (which someone here posted) and was wondering if anyone has used the approach mentioned there where you weld along a seam with a series of short pulses - with a 1 second pause in between. They say it prevents distortion/blowing holes (for thinner metal). I tried it yesterday and the welds look pretty nice. My only concern is that it is a "colder" weld and might not be as strong. I did it on a test panel and didn't get any distortion.
Mike

That's the way I butt weld patch panels. Hold the stinger at around 70 degrees angle to the panel and trigger until you get a puddle penetrating. At the same time, move the stinger slightly from one panel to the other with a small C motion, as though stitching the seam. Then let go of the trigger and wait until the red glow is nearly gone, shift the stinger 1/3-1/2 weld diameter and trigger again. Repeat this until you have an inch or so of connected tacks at the most, then move to a different spot on your panel while it cools. You will find that once the first tack is started, the arc starts more easily to a dull red glowing tack and with less variation. As long as you flow the next tack into the last, it will be strong. You need molten metal to flow together and you should see metal flowed along the back of the panel.

This technique won't completely eliminate heat warping, so what you do is grind the weld flat and hammer/dolly work the weld until the warp is corrected. You hammer/dolly work only the "heat effected zone". That is the portion of the panel on the weld and right next to it that welding heat caused to shrink. With hammer on dolly work, the shrink will stretch back out. You'll know you are "hammer on dolly" by the sharp sound. Stop frequently and correct warp before it gets out of control and becomes difficult to read.

You can also try Harris "twenty gauge" power iron cored wire. It is somewhat more forgiving with burn throughs.

http://www.harrisproductsgroup.com/consumables/alloys.asp?id=12

Welder setting for twenty gauge seems to work best with the welder chart settings for .023 wire. On my Miller 175, there results are similar for .023, .030 and "twenty gauge" once the machine and technique is dialed in, but the "twenty gauge" is slightly more forgiving of errors and it grinds and hammer/dolly works slightly better.

You should not have any pinholes along the back of weld if you're going hot enough. Check the back side of the panel for penetration and make adjustments to your timing as needed.

Copper back up helps. The copper goes behind the weld and works like a heat sink to draw excess heat away from the panel. The copper can be fastened to the back side of the panel with duct tape. It will smoke, but with good ventilation that's not a problem. Copper flashing is sometimes hard to find. To get a piece of copper backing plate, just take a six inch length of scrap 3/4" copper water pipe, slice it lengthwise, peel it open and hammer it flat.

That is exactly how I did my trunk pan; short pulses in a C stitch pattern. It worked great. I did not stay in one area, I moved about 2 inches between each pulse weld. When I got to the end of the seam, I started back at the beginning until all the gaps were filled in. By moving, you reduce the chance the metal will warp from the heat. I also recommend the twenty guage power core wire.

Thanks all. I am going to give it a try on my floor pans. When I did some test pieces it seemed to me that this was an easier seam to control. I timed it like you mentioned off of the red glow. I laid down some pretty nice welds that way. I didn't have any pinholes or burnthrough. Although, I was using a little thicker gauge metal than is common in car panels. So I will be cautious not too heat up one spot for more than an inch or so of welding then skip around. I have a lot of area to work on so that won't be a problem. The grinding is the part I like the least.
Thanks
Mike

Mike - try the Harris Twenty guage wire. It makes grinding much easier. If you do a seach on it, you will get others opinions on how easy it is to grind down the beads compared to a solid wire. I've tried both and the Twenty guage was much easier.

I have to throw a new spool on there now anyhow, so I will definitely get some of the Harris twenty gauge wire to try. Thanks for the help! Did you get it locally or have to order it?
Mike

My local welding supply store carries it but I know it can be hard to find. My brother in Georgia can't get it so I buy it here and send it to him. I think you can order it direct from the Harris web site.

Thanks Daral, I will check out my local shop first then.
Mike