Author Topic: Welding in patch, WTF am I doing wrong? (Read 1780 times)

abrahamfh · « **on:** January, 17, 2011, 09:18:35 PM »

Hello everyone, so, I know I am doing something seriously wrong.

I practiced and practiced on some pieces of metal that I had cut up from the unused RS front floor pan and everthing was working beautifuly.

I go to weld in my patch and it gives me nothing but junk. What am I doing wrong?

monkeystash · « **Reply #1 on:** January, 17, 2011, 09:34:13 PM »

The old metal still looks rusty. Welding goes much smoother when both pieces are clean and raw. Take a grinder to the metal to clean it up a bit, then try again. I think you'll have better results. Good luck!

abrahamfh · « **Reply #2 on:** January, 17, 2011, 09:39:56 PM »

Thank you soo much, that makes total sense.

Got to wait for tomorrow, I'm going to try and see if I can salvage the patch.

midpack · « **Reply #3 on:** January, 18, 2011, 02:40:56 AM »

agreed... some of the edges even look like they still have major rust. Did you cut back to solid metal before you made your patch?

mustangstofear · « **Reply #4 on:** January, 18, 2011, 03:29:42 AM »

Check your ground and make sure your gas is on, and your metal could be a lot cleaner for a better weld, also check your heat range. Rich.

Dne' · « **Reply #5 on:** January, 18, 2011, 05:08:03 AM »

Hi! are you welding with a gas or flux welder? (flux sux) what size wire? Looks like pretty thin stuff on the rusty side. Since you're welding two thin pieces together like that, just little blips, let cool, then blip the trigger. May turn the heat down a bit? Do you have an auto darkening hood too? I probably could not have accomplished that without a few burn throughs either, I'd probably have used my flanger or overlaped it a tiny bit. And of course what everyone else has said about raw metal. I'm not a pro, welding is fun!
dne'

The Kid · « **Reply #6 on:** January, 18, 2011, 06:25:46 AM »

Hi,
I agree with what the others have said regarding the old piece having some rust evidence.That said I think at this point the best way to salvage that patch piece would be to get a piece of copper and place it behind the holes and gaps,You then weld to that, grind,reweld,etc. Until you have it all nice and smooth.Also short blasts with the welder so as not to over heat the area.

cmayna · « **Reply #7 on:** January, 18, 2011, 06:35:53 AM »

Abe,
I agree with most comments above. Looks like you are attempting to weld to rust. The problem you've created is that you have already chopped your new piece to fit a specific size hole in the apron. If you see that you have to cut more apron out, how do you fill the gap?

Also if you remember I mentioned about using a piece of copper behind the joint area, otherwise you will encounter some sever blow throughs. I'm kinda busy but can sneak over today and maybe tomorrow for a couple quick visits. Call me this morning after 8am.

70_Fastback · « **Reply #8 on:** January, 18, 2011, 06:40:02 AM »

First, as everyone has stated, get rid of the rust. You can't weld on rust worth crap. If you do, it takes more heat to be successful - which blows though your thin sheet metal quicker.

Turn your heat down.

And you need to SPOT weld it. It looks like you are trying to drag a bead. That's a no no on sheet metal like this. Just a blip of the trigger & move on. I would also invest in some butt welding clamps to align & hold the pieces to gether evenly.

Lastly, your gap is pretty large between the patch and the old metal. Get a piece of 1/4" thick aluminum plate. Cut it down to like a 3"x4" piece (or whatever size you need) and use it as a backer UNDER the weld seam - basically hold it FLAT against the bottom of the cut seam and weld the 2 pieces together over the aluminum. The weld will not arc to the aluminum piece. This keeps the arc from blowing through the sheet metal and lets the weld build up a bit. You'll have a bit more grinding clean up to do on top though. Then go under and weld the seam from the back side also; otherwise your welds are more so on the top of the metal, and when you grind them smooth, you are taking a way a lot of the structural strength of the weld.

buening · « **Reply #9 on:** January, 18, 2011, 06:40:56 AM »

Quote from: mustangstofear on January, 18, 2011, 03:29:42 AM

Check your ground and make sure your gas is on, and your metal could be a lot cleaner for a better weld, also check your heat range. Rich.

Agree on all four points!

buening · « **Reply #10 on:** January, 18, 2011, 06:42:06 AM »

Quote from: 70_Fastback on January, 18, 2011, 06:40:02 AM

Lastly, your gap is pretty large between the patch and the old metal. Get a piece of 1/4" thick aluminum plate. Cut it down to like a 3"x4" piece (or whatever size you need) and use it as a backer UNDER the weld seam - basically hold it FLAT against the bottom of the cut seam and weld the 2 pieces together over the aluminum. The weld will not arc to the aluminum piece. This keeps the arc from blowing through the sheet metal and lets the weld build up a bit. You'll have a bit more grinding clean up to do on top though. Then go under and weld the seam from the back side also; otherwise your welds are more so on the top of the metal, and when you grind them smooth, you are taking a way a lot of the structural strength of the weld.

I believe a sheet of copper will do the same if you can't source the thick aluminum.

70_Fastback · « **Reply #11 on:** January, 18, 2011, 06:44:33 AM »

The Copper will probably be thinner. Thus transfering heat to your hand quicker! That's why I use the thicker aluminum stuff.

Just sayin.

66benchcoupe · « **Reply #12 on:** January, 18, 2011, 07:23:45 AM »

Here's what I learned working in a fab shop for a few years with welding inspectors looking over my shoulder:

Using aluminum as a backing bar will contaminate the weld.
Copper or ceramic is the proper backing bar for steel.
Use stainless steel as a backing bar when welding aluminum.

Robert

Ponyman66 · « **Reply #13 on:** January, 18, 2011, 08:54:34 AM »

A quick suggestion. If you wanna be frugal (the nice way to say, be cheap!), and want a copper backer they're easy to obtain and make. I just took a piece of scrap 3/4" copper pipe that I had left over from a plumbing project. I split it down one side and flattened it out into a sheet. Cheap easy copper backer for welding! You can just curve one edge a little and clamp on to it with a pair of vise grips to hold it. I've also been able to form it and clamp it in place for some areas.

blue65coupe · « **Reply #14 on:** January, 18, 2011, 08:55:26 AM »

Quote from: abrahamfh on January, 17, 2011, 09:18:35 PM

What am I doing wrong?

Trying to weld.

70_Fastback · « **Reply #15 on:** January, 18, 2011, 09:19:17 AM »

Quote from: 66benchcoupe on January, 18, 2011, 07:23:45 AM

Using aluminum as a backing bar will contaminate the weld.

Robert

Really?? I have never heard that.

Do you have any more insight on what is being contaminted & how? I will google it later when I get more time.

But for sheet metal patching, I don't think I would worry too much about either.

And a backer is, or should only be, very rarily required. Say.... if you cut too much, etc. LoL.

apollard · « **Reply #16 on:** January, 18, 2011, 09:48:29 AM »

Quote from: 70_Fastback on January, 18, 2011, 09:19:17 AM

And a backer is~~, or should only be,~~ very ~~rarily~~ often required. Say.... if you cut too much, etc. LoL.

Fixed.

70_Fastback · « **Reply #17 on:** January, 18, 2011, 09:52:05 AM »

I don't get it.

silverblueBP · « **Reply #18 on:** January, 18, 2011, 09:57:36 AM »

Maybe he's saying that not EVERYONE is a master welder like yourself.

buening · « **Reply #19 on:** January, 18, 2011, 10:02:06 AM »

My guess is that the aluminum contamination issue would only occur during high heat (thicker steel) welding. I wouldn't expect it to cause issues on thin sheetmetal. The AWS code states that copper, flux, glass tape, ceramic, iron powder, or similar materials are approved backing materials. AWS is for structural welding, so thicker stuff. Non-metallic backing, as I've been told, is difficult to learn to use since it absorbs heat differently than say copper.

70_Fastback · « **Reply #20 on:** January, 18, 2011, 10:07:07 AM »

Quote from: silverblueBP on January, 18, 2011, 09:57:36 AM

Maybe he's saying that not EVERYONE is a master welder like yourself.

Sheut. I'm not a master welder. See -I didn't even know to not use AL as a backer! Not that I ever really need to use a backer though. But if I did - I would have used my piece of AL.

66benchcoupe · « **Reply #21 on:** January, 18, 2011, 10:37:06 AM »

Quote from: 70_Fastback on January, 18, 2011, 09:19:17 AM

Really?? I have never heard that.

Do you have any more insight on what is being contaminted & how? I will google it later when I get more time.

But for sheet metal patching, I don't think I would worry too much about either.

And a backer is, or should only be, very rarily required. Say.... if you cut too much, etc. LoL.

The weld is being contaminated. If you don't think it matters for sheet metal patching, why not just glue it together?

Backers are required more often than you think.

Robert

stangg · « **Reply #22 on:** January, 18, 2011, 11:04:33 AM »

I think I would just replace the whole panel considering the amount of pitting in the panel. However if you are going to continue with the patch, I think it would be easier to remove the patch and add another couple inches back to the patch while out of the car, then re-fit it with tighter gaps. Be sure your ground clamp is connected to clean metal.

Where you aim your electrode also has a lot to do with the blow through since the thinner metal can't take as much heat as the thicker metal can. When you aim your wire, favor the cleaner / thicker metal to start the puddle, and then drift it towards the thinner metal.

For copper backing, plumbing pipe smashed flat works well too... very easy to form odd shapes to fit what ever contour you need, and if you leave one end open, it's easy to jam a wooden dowel in to serve as a handle.