Welding Sheet metal

Yes it will. The guys that fear the heat and warpage simply don't understand, or don't have enough experience working metal. With practice you can work with the heat and the metals reaction to it. Or you can continue to "fight" the heat.
It's a hard thing to understand or explain until you work with metal enough to get past the fear of warpage, and realize you can control it and use it to your advantage. It takes time and practice, but not nearly as long as people think.

Shun the light............move towards the flame.....

 

If you want to skip a step try using ER70S-7 instead of the -6. Lower tensile strength, easier to planish and grind, and best of all it has better wetting properties for flatter welds, more flowout. This alone will give you less weld proud to planish, grind, which means less money in abrasive consumables as well. :




Weld penetration, the back side....

 

Certainly. I only use -6 on metal that is not new and/or perfectly clean.

 

Thanks MP&C. I'm a big fan of your work! I haven't tried the 7. I've heard it makes overhead a little tuff. It IS approved for modern collision work, so I'm assuming it would be fine for other structural work. Please enlighten me if anyone knows different. I may try a spool next time I'm in need of wire.

 

That's what I was trying to get at; I can counteract the brittle weld aspect. Well that is what I'll do. But I got to practice more with the O/A I seem to make bigger holes than when I start). Thanks.

 

great advice, my dad seez the same thing to me.

 

When tacking the next tack goes right on the edge of the "blue" left from the last tack

 

Thanks, that is what I was hoping. Will try this until my O/A welding skills improve. I seem to make bigger holes than what I start with. Gotta go practice with my Henrob.

 

What welding wire are you using that is causing brittle welds? Try the ER70S-7, you'll be pleasantly surprised. You won't need to reheat and hammer weld... just mig weld the dots, planish, grind, repeat.

 

MP&C- I have a little pad by my putter here i keep my little notes of good advice and one of them is of you telling of the EZ grind ER70s-7 ,SO yesterday i see a guy on here saying it is no longer available ,only what's left in stores

 

MIG welding. There is plenty of info on the net. Look thru "you tube" how to's. Then many hours of practice B 4 you move to the car. Start with overlap plug weld for the newbe. Good luck.

 

My local welding supply told me to get the -7 as the EZ grind was being discontinued....even though you see a bunch of it on amazon. I've got 2 rolls of the -7 on order.. hopefully it will be here this week.

 

I did a planishing "tutorial" for some guys on another site as it relates to Mig "dot" welding, and it seems to fit this thread as well, so here goes.



I'll preface this by saying that this "test subject" serves as a guideline only, and is intended to help you see the effects of shrinking and how the planishing counteracts those effects, more so than establishing a hard and fast measured amount. It is not intended to be the end all-be all of how much, but it should get you in the ballpark of a measured amount to keep the panel in relatively good shape with minimal warping effects during the initial planishing efforts.

For your planishing test subject, you need two sheet metal strips about 1-1/2" wide by about 15" long. These will be tacked together on the long edge, and works best if you can use a shear, as you can cut a piece 3" x 15 and then shear it through the middle for a perfect seam. For you to see the effects of the shrinking and then the planishing, it needs to be a perfect cut through the middle for best results. So if you have one or can find someone with a shear to help you out, it will help tremendously.

Next, the process and specifically amount of planishing needed is going to be directly related to weld dot size and/or wire type/softness, etc.
Now that you have a fresh cut test piece, take your two pieces and align together TIGHTLY along the long sheared cuts and tack the seam at about one inch in from one end.



DO NOT PLANISH at this point. Go another 3/4" and add another tack. Is there any change in panels positioning? Go another 3/4" and add another tack. What we are trying to do with this process is to monitor how much shrink is occurring. The first tack should "anchor" the two panels together at the end. With the panels tight together, each subsequent tack, and the shrinking effects realized once cooling takes place, will start to pull the panels even closer together where they try to overlap each other. So If you haven't seen this happen, keep welding dots at 3/4" spacing until it does happen.

Now that you see these panels overlapping, the next phase is to see how much planishing it takes to "undo" the overlap. Start at your anchor tack, and hammer and dolly once.



Go to each subsequent dot and apply the same hammer and dolly in the same approximate force. The flat should be similar in size, but I'd gauge your effort more on hammer force than size of the flats. When you get to the end, check the overlap to see if it still interferes with adjacent panel fitment at the un-tacked end. If so, start at the beginning, repeating one dot at a time, monitoring overlap. When your panel overlap issue has been resolved, your weld dot planishing effort will be the number of hammer strikes as it took to resolve the overlap, using approximately same striking force. This assumes your weld dots don't mysteriously grow in size to add the need for more planishing, so again the importance of OCD consistency. This planishing effort will not be the end of the metal bumping to your panel ie: once you get welding in your patch panel. It is the minimum needed to relieve the shrinking effects so the differing forces will relax a bit. So when you get to a this process on the "real" panel, the planishing will go ahead at the number of XX hammer strikes to get it done, then move to the next weld dot. What we're doing here in striking one dot once and then the next is only for test purposes to identify the number of strikes you need. After this initial planishing, any remaining planishing needed will be based on what the panel looks and feels like, high spots, low spots, etc after welding, initial planishing, weld dot grinding, and panel reading is completed.

Now that you have completed this, just for the heck of it, go to the first anchor dot, and start planishing it and it alone. Keep repeating until you see the adjacent ends start to separate as the weld dot is being stretched. Look at how wide the gap is. This approximates the amount of extra effort needed to overcome the shrinking and panel movement that happens when you leave a gap that size in the panel. It also demonstrates the differing planishing efforts that will be needed for inaccurate and inconsistent gaps. Keeping track of what, where, and how much is the tricky part, and again stresses the importance of consistency in all the processes, starting with tight gaps at fit up. Everything that you can do to keep consistency throughout all the processes only makes the planishing efforts more consistent throughout, lessening the need to keep track of the errant what, where, and how much.

 

How much of a gap does there need to be between panels when butt welding. I'm another fab nobie and am learning a lot from these thread now it's time for some practice and practice and practice.


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i quench with water

 

Used to have none when I was tig welding chopped tops on Volvo-Gm trucks for car carriers. The tigs had a pulse and you had a lot of control over the heat which gave you perfect fusion without gapping and sometimes even without very little weld rod. With mig the gap should be the thickness of the sheetmetal,

 

Can someone logically explain the gap theory please? I don't understand, especially when mig welding.

 

Glad to see this thread back alive.

 

A tight gap means you'll use less filler and have a cleaner weld. Less to grind and usually less heat to get the job done meaning less warpage.

Larger gaps can be filled but you end up with a goopier weld that may end up needing a touchup pass to get it fully welded so there will be more heat, warpage, grinding and hammering involved in getting it back to shape.

With a mig and copper backer a little gap isn't such a bad thing as it gives you a little "free" penetration.

 

Another dumb question from brooks. What is a cooper backer and what's it purpose.


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You use the copper backer or spoon behind large gaps or holes.
Mig wire will not stick to it.

 

When butt welding the 2 pieces of metal will pull together whilst being welded.If there is no gap then your joint will 'peak'.Therefore you will have to displace that 'peak' causing profile change and extra work.

To eliminate this set .5mm gap between the joints so when the material pulls together the .5mm gap effectively disappears.


that's my experience anyways.

 

Great thread!!...I have learned a lot here. Thank you!!

 

Ok armature question 1001. What do y'all use to clamp the 2 panels together when you have difficult areas.


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I've used 2 clecos and a piece of scrap to hold the joint together.
And as said above, a small gap helps.

 

Can't have too many vice grips! I use the panel clamps too.

 

My point exactly! I have learned over the years to fit as tight as possible. You can do a full penetration fuse pass that keeps the HAZ to about a 1/2" with very little warpage, and very little planishing. It's the start and stops and uneven heat that causes the most warpage. I have not had great success with gap welding with a Mig. By that, I mean there is a lot more shrinkage with the gap, and the weld is a lot more work to stretch back out. On top of that, the weld is brittle!

 

That little peak that you are speaking of is shrinkage at the joint. Very easy to planishing out. I used to use your method until I learned how to do a fuse weld. It's not possible with any gap, as it wants to keyhole and you have to add filler. We all do things a little different, and the end result is all that matters. I just don't get all the advice of leaving a .040 gap and throwing three times more heat in the panel. Way to much extra work for me!

 

you guys don't like penetration? to give the joint strength?

 

There's plenty of penetration, just not a bunch of extra burn through on the back side. Never have had a problem with a weak panel or a crack. Depending on what you are working on, you can't always use the fuse method. It has its place though, especially on long low crown panels and quarter panels etc.
Like you, I was skeptical about panel strength. I learned this from Roddoc on the Allmetalshaping site. It took a long time to get it down, but once I did, it has made my work go a lot easier and quicker.