Welding practice is going great...until I come to any edge!

[yugo42]

Hi! I did some searching but didn't see anyone having this exact issue. I'm practicing some sheet metal welding before I get too deep into cutting rust out of my '69 Westy and would love some input from someone with more experience. I have a Millermatic 175 230V MIG welder with C25 gas @ 20CFM, .023" ER70S-6 wire, and what I believe is well-adjusted wire feed. I am practicing on an old Ford Focus hood, so around 20-ga steel.

The problem is this: I can set up and run a nice bead on a flat, uninterrupted surface and can tweak the penetration and width with the welder voltage/feed settings. As soon as I get to any edge, I immediately get popping and burn-through (see pic below). Adjusting the voltage and feed only seem to change how big of a hole I am blowing. My best results on uninterrupted metal seem to be at 1-1.5 on voltage and around 60-65 feed speed. Turning both way down to avoid burn-through (1/20) just results in spatter and no bead. I have tried voltages between 1-4 and feed speeds from 20-70 in all sorts of combinations with no functional improvement. My only success at crossing a gap here involved building a metal cold-weld mountain on each side until they connected, and the result was hideous and terrible. I can run a gorgeous bead right up to the gap and POOF it goes awry as soon as I get there. I have tried pushing vs. pulling, using longer wire stick-out, changing the tip angle, and have seen no improvement. I'm sure my technique could use work, but I have been able to work with thicker metals without issue and fill some pretty nasty gaps! Maybe I need a copper backer? I've seen some of the bodywork magicians on here close larger gaps than this with no backer material but I am far from a magician!

Any ideas here would be appreciated! Thanks for listening!

[raygreenwood]

Your voltage and wire feed for beads across solid surfaces will be totally different than for joining two exges of a panel.

The solid sheet is a much larger surface area for a heat sink. An edge has virtually no heat sink.

Also...buy some panel edge clamps. They are cheap. Servicable ones for about, $6 at harbor freight.....slightly better ones at Eastwood and welding supply houses for $15-20.

Also put a copper backing plate behind any gap you want to fill/join. The weld will not stick to it and it gives the weld pool something to puddle against.

Just looking I would say your wire feed is way too high for the low voltage. You are getting the metal too hot with no heat sink and the wire is pushing through it. Ray

[theKbStockpiler]

Turn your voltage/wire speed all the way down and try to start a arc. Keep turning up the voltage until it will arc and not just basically spark and go out. On my non-Miller its at about a setting of 4. Anything lower will not work so '4' is actually zero. Try a new spot every time while adjusting your wire-speed/voltage. If the wire melts off in globs turn the wire speed up until it stops. Hold the nozzle stationary while doing this. Usually with MIG there is not a big variance of how much wire speed will work. It will either melt off in globs or stub into the work piece. If you are using .023 on metal that .030 should be used, there will be.

When welding near a edge the edge has nothing to transfer heat to. If you have to weld near an edge you can camp it to something that will absorb some heat or use a pulse technique of repeating short beads or just a series of spot welds waiting until the metal has cooled from being red. If the piece gets red hot too far away from the pool you will burn through.

Unless thin metal is PERFECTLY butted up with no gap what so ever you can not butt weld it with a long continues bead, only pulses.
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[yugo42]

Wow, thanks for the valuable input guys! Watching some skilled people on this forum and the ease at which I picked up welding heavier stuff made me think I would get the sheet metal technique quickly, but I have a whole lot to learn.

Ray - I've enjoyed reading your knowledgeable replies on the Bay forum. I chose my settings based on getting a good bead on solid material, but it sounds like that was the wrong approach. I will definitely get some copper backer and try again! I have some of the HF sheet clamps, but for today's practice I just cut some slices in the hood with a thin cutoff wheel and attempted to tack across it.

theKbStockpiler - Thanks, I'll try that experiment with the settings. My main goal here was to tack across the material and then go back and fill in with short bursts later, rather than join with a continuous bead. I wound up drawing out beads just to see if I was getting my settings any closer. This has got me thinking that I really need to be careful with panel gaps and probably use more overlap/plug welding than butt welding when I get to working on the van. I am definitely worried about the cosmetic areas where I can't get to the back of the panel, but I have a while before I get to external panels.

Thanks for the advice, and I'll be back at it tomorrow!

[Air-Cooled Head]

[67rustavenger]

Sorry if this is a thread hi-jack. But since the subject is edge welding and ugly welds. Here goes.
I'm trying to save an og fender. There was a small dent inboard of the headlight that I discovered while stripping the fender. I notice that there was a small tear (1/8") and tried to put a tack size weld to fix it. Soon as I hit it the metal vapoorised (yes I spelled that that way). So I cut out a 1" patch to replace the foil thin area. Got it tacked in and all was going well. Until I came to the next foil thin area. Then poof metal gone.
I tried, lowest voltage/ wire feed settings to no avail. Copper backing didn't help. Should I just cut another (larger) patch and start over?
Here's the irony of this post, I was a weld inspector for 25 years. Just on metal that was way thicker than fender material.
Any advise would be appreciated.
EDIT
The Weld machine is a Clarke E-130 Mig, 25% Co2, .023 wire
Thanks
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[theKbStockpiler]

[67rustavenger]

I have read your thread before. Forgot about it. Thanks for the reminder.
I do have practice sheet metal of various thickness. I thought that I had practiced enough. Alas, back to the garage for more practice.
Thanks for the advise.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[raygreenwood]

In the paper thin areas...you need to lower voltage and wire speed. Find some sheet kn the same thickness as the foil thin areas and practice to set up voltage and wire speed.

Use a copper backer. If a sheet wont fit...you can buy a copper "spoon" tool at Harbor freight, northern tool or any welding supply.

I bought a sheet of copper at ace harware that was for decorative work. About 3 square feet cor $20 or so. I cut it into strips for backing sheet. You can use magnets to hold the strip in place behind the weld from the back.

There is a nice welders handbook by Richard Finch.....I bought at Home depot for $15. ..available on amazon. Has a lot of basics for all types of welding. It also has a bit on wire speeds, leaning welds.....observations of what a good weld bead is by shape and penetration, cleaning parts for welding, wire and rod selection, gas selection etc.

I have been using a common Praxair gas called Stargon. Its a Co2 argon mix like normal but has 2% oxygen. It came highly recommended for low voltage mig for sheet metal as the oxygen allows slightly hotter weld at lower voltage for better penetration. It has worked very well so far. I use an Eastwood 140. It has infinite wire and voltage adjustment.

Usually for sheet metal butt joining using the tack/stitch method.....my voltage is about 3.5 and wire speed about 4 with a little higher gas flow about 23cfm for a larger shield. Be sure you keep a log book of your settings. ....and make note of ambient temps. It can be ttally different on thin sheet metal in a freezing cold garage....compared to one on a 100 degree day.
Also....if its not a panel at risk from warping.....you can use a propane torch to lightly heat the area you are about to weld at lower voltage. Just get t up to sbout 300+ checked with an infrared gun. Just a couple hundred extra degress can be half a notch or more llwer that you can dial the power knob to....that reduces the chance for blowing through the surface.

I am an ameteur totally.....but keep practicing like you are.....take notes. Ray

[getgeoff]

Check out on Youtube - how to Mig weld and Mig welding tips by Eastwood Company with Kevin Tetz. It's a great 2 part video to watch and learn.

[lil-jinx]

Using an extension cord will also lower your voltage,depending on size and lenth,smaller /longer = lower voltage
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[67rustavenger]

FYI, The Richard Finch book is no longer available at Home Depot. I looked for it and HD said that they don't carry any books due to interweb information.
I'll have a look at the suggested you tube video series that is recommended.
Thanks for the help.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[CanadianBug]

You might want to try moving your hand a little faster, as well.
FYI, that focus sheet metal is probably closer to 24-26 gauge and the coarse grinding disc you used on it has thinned it out even more.
Thin gauge sheet is tough to butt-weld at the best of times. If you get a handle on it, you'll really be doing something!
Good luck!
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[67rustavenger]

Thanks for the advice. I did work on the fender a bit yesterday and learned that I turn up the heat and wire speed a bit along with moving the torch tip farther away from the weld zone, the results are much better. Part of my problem was filler metal "stacking" instead of penetrating through the fender and patch material.
I still need practice. But for now I am satisfied with the results that I am getting.
Thanks again
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[stanovich]

OK here goes. first of all trying to weld thin metal is always a chore , try this use a 7018 1/8 in welding rod . first break off the flux then lay the rod in the gap, concentrate your puddle on the thicker rod and let if flow to the sheet metal. short pulses . now dont get pissed off here you may already know how to weld, but watch the puddle you can see what is going to happen if you pay attention. & good luck.

[67rustavenger]

[stanovich]

what i ment was so you or anyone would not take offence, I have found over the years that alot of beginning welders are not looking at (seeing) what they are doing. The rod also comes in 1/16 inch . you can bend the rod so it can be held and side cutters will cut it flush in a jiffy