TIG Welding - heat input

[soundcontrol]

I just fixed my convertible wheelhouse cap, the edge was rusty. I tried a new method this time, I see it as practice for the long welds I have to do on my quarter skins soon. I cut the material a bit too big, so it overlapped, and cut with a airsaw and tachwelded as I was cutting, don't know if I like that method so much, it was hard to make a clean cut, maybe because the piece was small and was moving and rattling some. Maybe it is easier on the quarters. I will use screws or Clecos on them. On the other hand, cutting the quarterskins to an exact fit will be very hard, so I might have to do it this way.

Now, if someone could look at my weld and tell me how the heat affected zone is, is it too much? Am I going to slow? I use 30 A on the TIG, trying to go as fast as I can to put least amount of heat in the panel. I did get a little bump in it, and I had to shrink that with a torch, and then some hammer/dolly.

The finished result came out OK though.

[dutch]

make a nice fitting panel with a bit of extra material on the side that needs welding. Then clamp it on and use a scriber to mark. Toss the airsaw and get a couple (left and right) snips ( I use Wiss only)  You can cut very accurate with them. Once you made the cut you know the repairpanel fits seamless, so you dont need clamps to tack it into place.

I gas weld all sheetmetal, so there may be some more experienced tig welders on here ,but whenever I do use tig, I weld at about 40amps for 19gauge sheet (1mm)
You will get warpage whatever you do, simply because the metal will expand when heated and shrink to a smaller surface than it was before you started welding. That said, the most important thing in welding sheetmetal is to get the heat input as evenly as possible,  (weld in a single pass where possible) because the shrinking will be uniform too and helps stretching it back to size. hope this helps

[Cuda Cody]

Wish I could be more help.  I use MIG so much that I'm not really much good with a TIG.  But it looks like you're doing good.

[dutch]

one more thing.  You speak of a little bumb you needed to shrink with a torch.  My quess is, you got the bumb because something else shrunk. That means you need to stretch whatever shrunk to get rid of the bumb in another place.  So make sure you try to determine what happens to the metal and what causes which problem before you act. Not a biggie on a small repair but it could get you in a lot of trouble with larger panels. 

[soundcontrol]

Wish I could be more help.  I use MIG so much that I'm not really much good with a TIG.  But it looks like you're doing good.

I just ordered a MIG also, I need it for the plug welds mostly, the TIG works but it takes longer and I still have problems with weld thru primer/TIG.

[soundcontrol]

Thanks Dutch! That is good advise. I got different opinions on the approach from different sources, some says to weld long seams and some say to weld short and jump around. I do think that the longer approach is the better one, at least with TIG, as long as I don't spend to much time on one spot and put a lot of heat in, can happen if I blow thru and have to fill. I get very good results when I have a perfect fit and I can almost get away without using filler, but the filler also cools some and prevent blow thru I notice. 40 amps seems hi to me, I blow thru with that, but maybe the reader on my TIG is not that accurate, I used 32 on this to be exact.

The bump I got was at the edge of the cap, and was pretty easy to get out. It is hard to know where to shrink etc, I guess the keyword here is experience, and I'm getting it

I am a bit worried on the quarterskin weld, its way long, but the cut is right below the upper edge so it got some stability there. Still have not decided on TIG or MIG here, gotta practice some MIG now and see.

[dutch]

welding along an edge is always tricky because it makes it hard, if not impossible to stretch the metal after welding.  The main reason I hardly ever use tig when welding sheetmetal actually is the low heat input 
The metal cools down very fast and that makes the weld harder to stretch.  When I (gas weld) sheetmetal, I make sure the panels fit perfect an I use no filler rod to weld them together. I`m not so sure if that is preferable way for tig since the welds are harder and might crack when hammered.
The heat affected zone when O/A welding is big ,but it is very uniform and cools down slow so distortion actually is very minimal, makes a soft weld and is relatively easy to correct. When I blow a hole, I just leave it and keep welding. Fix the hole later.
One other reason I try to avoid filler rod is that you have too much material after welding and when you grind that down you put in heat and therefor cause another round of shrinking. IMO for any repair of sheetmetal : cleanness on both front and backside!  I dont see how one could make a decent weld on primer or rust.

I`m not saying there`s a right or wrong way to do things as long as the result is satisfying. The most important is that you understand why the metal behaves the way it does.

[soundcontrol]

The TIG weld is soft also, can be hammered a lot, does not crack, MIG is harder I hear. Very interesting that you use gas welding, I was always told it was to hot for sheet metal. I started out welding with gas and I'm pretty good at it. (thats probably why I picked up TIG pretty fast, its kinda similar).
What equipment do you use exactly? I hava a gas setup also, use it mostly for heating up stuff nowadays, was thinking about getting the Dillon torch for it though.

When I get a perfect fit, its very easy to weld without filler, the problem is getting that fit in complicated areas, like the front part of the wheelhouses that I'm working on now.

It's gonna be interesting to do those quarters for sure! If I screw up, there is always new whole quarters... 
(got the skins cheap, so I might as well give it a shot)

[ViperMan]

I was taught:

MIG - very hard - can't hammer-out or it will crack
MIG - soft - can hammer to an extent, just enough to counteract the shrink
Gas - very soft - can hammer to heart's content, more-or-less.

I miss welding - I really need to grab a MIG at least so I can build sh!t at home whenever I want. 

[dutch]

No clue why gas welding would be too hot for sheetmetal...?  to weld, you need a puddle, no matter what type of welder you use. Mig is great for heavier work like frames and such, or plug welding but for sheetmetal it`s the worst option since the welds get really hard.

I never worked with a Dillon torch, but I know guys who use em are happy welders.  I used AGA X11 torches but mine all need to be rebuild. For the time being I bought a Gasio D75, which is competable with the AGA tips. Not bad, but I feel the original AGA`s adjustability is better.

[Roadman]

              I had never heard of these type torch's so I watched this video of the COBRA DHC 2000.

                    https://www.youtube.com/watch?v=bBWy3SPFGe4

             Going to have to      

[HP_Cuda]

Hey Dutch!

Long time!!! Hey since you are talking about welding - what do you think about those pastes folks use to put on the metal to keep the heat down or at least mitigate some of it?

I got a new MIG welder and I'm starting to play with it, although many of my project seem to be Ranch projects since thats where some of my projects are with heavy machinery.

Goed om je te zien!
Bryan

[soundcontrol]

No clue why gas welding would be too hot for sheetmetal...?

No, I didn't word that well, what I mean is that the heat affected zone is larger. But most people say that it should not be used though, and they say the same thing about the TIG, too hot.

Well, as we speak, my new MIG (or MAG really) came in. A simple 220V welder, but a good brand, not made in China. Now I have all 3 systems, so there is no excuses now, just gotta get it done...

[71GranCoupe]

              I had never heard of these type torch's so I watched this video of the COBRA DHC 2000.

                    https://www.youtube.com/watch?v=bBWy3SPFGe4

             Going to have to      

That is a cool setup and may have to add it to the arsenal of welders. An old timer told me years ago that during WWII they welded aluminum with an oxy/acet set up. Never did try it, but after seeing this, gives more credibility to his story.

On the Tig weld, or any weld for that matter, it is always difficult to give advice from pictures. From what I know and compare with, you used way too much filler material and by building the weld so high, created more heat thus prone to more warpage. On thin metal I use very little filler and can move quicker. Shorter welds and allowing the panel to cool is also a benefit. Use some scrap and practice on it before heading to the full quarter replacement. If at all possible I use a copper plate on all welds for control of the back of the weld, and it really does pull the heat away from the main weld. Yes, not always possible to get to all, but it can sure keep the welds from blowing/burning through.

Mig will be an easier method for sure, as you can lay down a small short bead and pull off quick allowing the metal to cool before a large area gets way hot.

[soundcontrol]

Yes, in general I tend to use too much filler when TIG welding, I notice that myself also, having to grind more then necessary. Never happens on a welding table, so I think its me working in a position that is not so comfortable and that affects my left hand movement. I do have a copper backing plate I can use for the quarter and I can get it in all the way on the weld, but that means I have to weld kinda short areas and then reposition the copper.