How to fix

[Maddog]

So I over heated a panel welding in a patch, now below it on a somewhat flat panel I have a approx 4" concave circle, what would be the best attack to "pull it' and shrink it back? Can not acces from the rear, its a Chevy truck bed with a double wall.

[chevynut]

You probably didn't overheat it. Any welding is going to cause shrinkage. If you can't get to the back of it, it's going to be hard to do much with it. If you try to shrink the "concave circle", it's probably just going to move lower on you.

If you really think you overheated it, I would cut out the welded patch and start all over. Then try to weld a new patch in being careful to prevent getting it too hot. Making a few MIG weld tacks at a time is the best way to do that.

[Maddog]

No reason to remove patch since the damage is adjacent to it. I'll pull it with my stud welder as near back to orig as possible and work it, just was wondering if someone might have any other ideas/experience, no metal men here?

[chevynut]

There is no "damage" next to your patch, unless it was there prior to patching it. What happened is that your weld shrunk the metal and "puckered" it. Imagine a piece of paper where you shrink the edge of it...you will get a "wrinkle" or "pucker" next to that edge. If you try to shrink out the pucker, you'll just chase it across the panel. I've done a lot of this and have seen exactly what you're taking about. It's difficult to fix if you can't get to both sides of the panel.

Why do you think you "overheated" the panel?

[BAM55]

The problem is the damage is caused by the welding area (HAZ or Heat affected zone) and pulling or hammering anywhere else is not the correct way to fix it. The welding caused the shrinkage and the damage and if you could hammer on dolly the HAZ area the problem would be resolved. You have to work the area that caused the damage. You said its a double sided panel. Could you cut and access hole to have access to backside of the panel? I have done that in the past with great results. Then I simply welded the access panel back very carefully. In my opinion you have two options one is to cut it out (it should release that tension that is causing the damage) and be more careful re welding it or cut an access hole to hammer on dolly if possible.

[Maddog]

So the weld across the horizontal line shrunk there and that caused the wave in the adjacent metal, makes sense as I can see a dip right at the weld line that extends down to the wrinkled area. No real way to access from rear. If I make a cut across(length wise with the weld) the welded area should that give relief to the stressd area?

[chevynut]

Yes, the shrinkage at the welded area caused the dip. The weld and the blued area around it is all affected. If you cut it, you will have to re-weld it. That will make a bigger mess. If you cut the panel behind it to access it, you will have to weld that too....again, I think that creates a bigger mess because you will have the same problem there after you try to weld it back in.

If you think you got it too hot, and can do it better without as much shrinkage, I would cut the patch out and try again.

[BAM55]

So the weld across the horizontal line shrunk there and that caused the wave in the adjacent metal, makes sense as I can see a dip right at the weld line that extends down to the wrinkled area. No real way to access from rear. If I make a cut across(length wise with the weld) the welded area should that give relief to the stressd area?

If there is no way to access the rear, in my opinion your only option is to cut the patch panel completely out and be very careful re welding it. Pulling and hammering on areas that has nothing to do with what caused the damage can create a bigger mess. Now remember all welding causes shrinkage you are just trying to minimize it as much as you can. When re welding just try to keep the metal cool as possible. What I do is tack the panel in place grind the tacks and tack again grind those tacks. I do that until the panel is completely welded. I find that while I'm grinding the tack welds it allows the metal to cool and I'm still continuously working. If I can't touch the area with my bare hand I don't welded until I can. This is just my way of doing it.

[Maddog]

Imagine a rectangular patch welded in, say 6"x3", the only heat affected area is on one side of the rectangle only, along the lower 6" length. The metal directly below this 6" line is wavy, the other 3 sides of the rectangle are fine. I would hope that cutting this weld line out would allow the lower stressed(wavy) panel to regain it's original shape, what say you? I just don't see how the other 3 sides would make a difference if i leave them as is. There are actually 2 additional panels behind this with the closest being about 1/4" away from the outer. This is a 73 truck bed at the wheel well, the wheel tub and inner panel all are behind my patch.

[BAM55]

I say that just because the wavy area is beneath one weld seam does not mean that is necessarily the area causing the shrinkage. I have had experiences where the the shrinkage or wave was nowhere near the patch panel I welded in. But once I hammered the welded area (HAZ) the shrinkage disappear in all areas of the panel.

[Maddog]

Since I have to cut it out I'll start with just that lower weld line and see if any results

[BAM55]

Since I have to cut it out I'll start with just that lower weld line and see if any results

Keep me posted buddy, I'm always interested in knowing the results.

[Maddog]

I cut about a 7" line, it released the lower sheet but it's distorted, flip flops back and forth. Correct if I'm wrong, seems to me I need to shrink it so it doesn't oil can.

[chevynut]

If you didn't stretch it you don't need to shrink it imo. The two vertical welds are probably still pulling the metal in from the sides, causing the oilcan. I can amost guarantee you that if you shrink it, it's going to move lower unless there's no place to move to. If it's close to a seam or a bend, it may help to shrink it because it can't go anywhere. Pictures of what you're doing would go a long way.

[Maddog]

Let's see if this works. The white rectangle is the patch, on the top of the bed, it just comes down to the end of the small radius. The yellow oval is the wavy spot after welding the top rectangle patch. I cut under the rectangle, long ways and about 1/2" beyond the short verticle welds. The lower oval can be pulled out or pushed in.1545 The wavy oval needs to be shrunk so it doesn't pull out or push in. I think I shouldn't have cut it and just pulled it out and started shrinking.

[Rick_L]

I agree with Chevynut here.

My guess is that the area you're concerned about was the last part of the panel to be welded, everything else was "locked in". Although many times it's not that simple.

And while I agree that cutting a hole in the sheet metal behind the panel will result in a similar defect back there, if that panel is not visiible, or not as noticeable, that may be the lesser of evils.

[NickP]

Shrinking disc?

[Maddog]

It's between two bends so I don't think it can go anywhere. I always shrink with the stud welder as a heat source, nice small circles.

[Maddog]

It was welded with small mig welds, moving from one side to the other to try to keep heat to a minimum in any one spot.

[Rick_L]

Shrinking disc?

The welding shrunk it. The weld area needs stretching and planishing, not shrinking. If a spot is stretched after planishing, then the shrinking disc would fix that.

If you shrink an area that's already shrunk from welding, you may be able to make it smooth, but it will have lost its crown, and that area of the panel will be lower than the original. Ask me how I know.

[Maddog]

If an area of metal is wavy and can be easily popped in and out it is too large or stretched. I believe the weld lines did shrink and pulled the panel area below it out of shape.

[Maddog]

If there is no way to access the rear, in my opinion your only option is to cut the patch panel completely out and be very careful re welding it. Pulling and hammering on areas that has nothing to do with what caused the damage can create a bigger mess. Now remember all welding causes shrinkage you are just trying to minimize it as much as you can. When re welding just try to keep the metal cool as possible. What I do is tack the panel in place grind the tacks and tack again grind those tacks. I do that until the panel is completely welded. I find that while I'm grinding the tack welds it allows the metal to cool and I'm still continuously working. If I can't touch the area with my bare hand I don't welded until I can. This is just my way of doing it.


Bam, how big (long) do you make your tack welds? I do the same but I usually make mine about 1/4" to 3/8", is too long causing excess heating?

[Rick_L]

Tack weld = 1 hit with the welder, no movement. So it's a round dot, so to speak. No length to it other than the size of the weld bead.

[Maddog]

Tack weld = 1 hit with the welder, no movement. So it's a round dot, so to speak. No length to it other than the size of the weld bead.

is that how you weld your panels?

[chevynut]

That's how I do mine too. I tack every 2-3 ", then tack between them, the between them, etc. until I have 3/8" or so between tacks. I grind the tacks some before proceeding to put more welds down. Then I fill between the tacks, jumping around to reduce heating. Then I grind and fill again until it's all welded. I planish after grinding if I can get to the backside. It really helps to control warpage if you do it like this.

[Maddog]

I fixed some off what I did yesterday, got the stretched panel pretty flat and started welding the long cut I made. I did slow way down and that prevented any new problems, so far,LOL.I'm doing about an 1/8" bead now, I've always alternated from one side to another, I was just trying to lay too long of a bead and the heat became excessive.

[Rick_L]

Yes I do them like that, and in the same manner as Cnut detailed. What's hard is the "last tack". By hard I mean that you sometimes have a tiny gap to weld to make it all continuous. Usually requires some grinding as Cnut said, just to see where to do that last one and know it's the last one.

[BAM55]

Rick already answered the question you direct to me. Sorry I did not respond I was busy but I agree 100% with what Rick said about tack welds.

I will only add another reason I like to tack grind tack grind etc. Other than it allows me to continually work while the metal cools. Once the panel starts to become completely welded in its makes it easier to see where the next tack should go and stops you from welding on top of other welds. Which in turn will also help to eliminate pin holes.

Here is a pic where you can see tack welds along the top and the tacks I grind down on the front of the fender. See how clear the area that needs tack welds is? You can see on the front of the fender at the body line to the bottom of the headlight then you see tack welds again.
http://farm8.staticflickr.com/7167/6555635023_789632dc2d.jpg
You can also see in this pic where I finished the fender lip and need to grind tacks as I go. It also shows you some tack welds.
http://farm8.staticflickr.com/7162/6556369161_db3901dd41.jpg
Here you can see where the front of the fender is completely welded in and metal finished. This is that tack, grind, tack, grind, procedure I was trying to describe. I did that until it was completely welded in.
http://farm8.staticflickr.com/7014/6555635317_be87a604e1.jpg
I used the same procedure on the top welds and here is the finished patch panel and metal finish.
http://farm8.staticflickr.com/7160/6567149867_6b902651f8.jpg

This is just the way I do things. There are many ways to do things and if you ask 10 people you will get 10 different answer and all with great results. Its all about information and then doing what you are comfortable with.

[Maddog]

Yea, I was just being to aggressive with my welding, but have never had a panel warp like this, but then I try to buy decent projects, welding is usually restricted to a patch or two in a floor board.

[BAM55]

Yea, I was just being to aggressive with my welding, but have never had a panel warp like this, but then I try to buy decent projects, welding is usually restricted to a patch or two in a floor board.

Yeah but we learn when we run into problems. I've learned more from my mistakes than I ever have from my success, thats for sure. We can't learn anything if we stick to things we already know. At least thats how I look at it. The more I do the more I realize how much there is to know. So I tell myself I don't know shit because a man that thinks he knows everything can never learn anything new or improve his skills. Thats what its all about to me getting better and improving. I'm always open to learning.

[Maddog]

Yeah but we learn when we run into problems. I've learned more from my mistakes than I ever have from my success, thats for sure. We can't learn anything if we stick to things we already know. At least thats how I look at it. The more I do the more I realize how much there is to know. So I tell myself I don't know shit because a man that thinks he knows everything can never learn anything new are improve his skills. Thats what its all about to me getting better and improving. I'm always open to learning.

True, that's why I asked, lots of times a new technique will be presented, worst case I get nothing, best case I learn a thing or two.

[BAM55]

True so true.

So did it all work out for you.

[Maddog]

Looks that way, couple of small shrink spots and the panel is mostly back to orig, I welded about half of the long cut I made, this time paying attention to not over heat things and all looks good. Alternating where I tack weld was nothing new to me but I've gotten careless and the info here was a good reminder, kind of like a wake up call.

[BAM55]

Good man, I'm glad it worked out for you.

[Maddog]

I'll try to post a harder question for you guys next time:)

[MP&C]

I know I'm a day late, dollar short to help you out, but I thought I'd clarify a couple points, maybe it will help out next time.

As others pointed out, on any weld done to sheet metal, as the weld and HAZ (heat affected zone) surrounding the weld cools, it shrinks. If all you have done is welding, and there is no body damage, then shrinking in an attempt to remedy the situation will not work, it will only make it worse. To try and explain what has occurred, looking at the radius at the top of the bed side, this is similar to most any other crowned body panel and it's reaction to welding. Specifically, when a weld goes across any crowned (radius-ed) panel, and the weld and HAZ cool, the length along this crown is now trying to shrink, so in effect, you have an arc that is forming a straight line. Ever wonder why the weld falls off into a valley? This is the straight line forming and pulling adjacent metal along for the ride. Planishing is what you'll need to stretch the area of the weld and HAZ to restore the original shape. This also helps to show that trimming your patches with tight gaps helps out, as wide gaps allow more movement/shrinking of the adjacent metal and will require more effort to restore the original shape.




If an area of metal is wavy and can be easily popped in and out it is too large or stretched.


Actually, the exact opposite. There a two kinds of oil can, a tight one and a loose one. The tight oil can is caused by direct or indirect force upon a body panel, normally as the result of body damage. As this force pushes through the panel, distortion results and you may see a high spot pushed at the far end, and a low spot leading up to it. Where you can apply force on the highs or lows to try and restore the original shape, the tight oil can caused by body damage will typically snap back to it's distorted position, sometimes rather forcibly, sometimes not as much. The TIGHT oil can is repaired by shrinking the stretched area of the body damage..

In contrast, the loose oil can is typically caused by welding, and it's inherent shrinking that pulls at the natural crown of a panel to decrease some of the arc. This version is almost always identifiable by the panel EASILY flopping back and forth. To restore the crown where it will hold the panel's natural shape, you stretch the areas that have shrunk, specifically at the weld and HAZ surrounding it...


One example, and how you may have confused the repair:


Consider welding a lower door skin on, you'll have shrinkage throughout the area of the weld (red line in picture) and the HAZ (heat affected zone) on either side of the weld. As the resulting shrinking occurs, the door skin will lose some of the crown and flatten out (green arrows) as well as the length shortens (blue arrows). As a result of the weld and HAZ shrinking horizontally (blue arrows), and the adjacent unaffected areas above and below having a tendancy to resist this movement, the area in between will start to buckle, or cause a wave effect (yellow lines). To visualize this effect, lay a piece of paper flat on a table and using your index fingers, push two corners of the paper toward each other. This simulates the shrinking caused by the weld. You'll notice the paper creates a wave or buckle as you push the corners together. This simulates the buckles in the area surrounding the HAZ. When reading your panel, don't be fooled as these buckles may be misread as a stretch, or high, but it's actually unaffected panel being manipulated/pulled by the adjacent shrinking.

http://i5.photobucket.com/albums/y167/rmccartney/Metalworking/Door1.jpg

To address these repairs, planish the weld/HAZ to stretch both in a linear fashion (removing waves/buckles) and also restoring the crown. This repair will also very likely include some metal bumping (off dolly) to raise/lower highs and lows as the metal begins to relax. Hope this helps in reading the panel and some of the secondary effects (waves/buckles) of the shrinking that you'll see. Planishing the welds as you go will help to keep these effects in check, where it will be less likely you'll see all the waves and buckling. It's when you have all these forces/reactions combined (from not planishing) that some may have a harder time reading the panel....

[chevynut]

Hey Robert, great explanation. If people would realise that welding ALWAYS shrinks the metal, they could understand what to do a lot better. I have used the example of welding the perimeter of a flat sheetmetal disc. when you do so, it turns into a bowl. There are two ways to make it flat again...shrink the inside, or stretch the outside. If the metal was undamaged to begin with, it shouldn't need to be shrunk.

I have something I need advice on. I'm trying to make some door panels out of .063" aluminum, and they have to fit the door tight. I plan to use foam and fiberglass to sculpt the features on the door. I need to do some metalwork to get the panel fitting the door better. I'll start a thread showing some pics of where I'm at. It's got me going round and round in one spot. Hope you stick around. :)

[MP&C]

I'm trying to make some door panels out of .063" aluminum, and they have to fit the door tight. I plan to use foam and fiberglass to sculpt the features on the door. I need to do some metalwork to get the panel fitting the door better. I'll start a thread showing some pics of where I'm at. It's got me going round and round in one spot.

I never could get that stuff to weld... ;)

After looking at your air intake, why not make all of it out of aluminum?

[chevynut]

I never could get that stuff to weld... ;)

After looking at your air intake, why not make all of it out of aluminum?

Actually once you get the hang of it aluminum welding is pretty easy. You just need to look at it differently than you do steel.

I thought about making it all out of aluminum, but there are curved parts everywhere. It's too much work and the car has been in progress for years, and I want to FINISH it before I DIE!!! :)

I talked to my upholstery guy and he wants to make it in "modules" that he can cover and attach to the door panel. That's how he does all of his intricate panels, and he's been doing it for 40+ years. So I plan to take his advice. I've been looking at foam-fiberglass techniques which I've never done before, and that's what I'm planning to do. It should be lighter than aluminum too. I could have done my air intake that way too, because I already had a foam mockup of it. ;)

27192720

[MP&C]

Let me try that again....



I plan to use foam and fiberglass to sculpt the features on the door.


I never could get that stuff to weld... :)

That's why I suggested the aluminum....


Take a glance at this Studebaker dash work I did starting on this post, it may spark some ideas for the edge of the door panels. You could add some recess details using step dies on your bead roller, etc....

http://www.garagejournal.com/forum/showpost.php?p=2950709&postcount=69

[markm]

I cannot read this thread untill its cleaned up, Hillery has to go.