nbl300

iTrader: (1)

So I have been doing some rust repair on my 1990 pickup standard cab and I keep burning holes in this sheet metal like no tomorrow. I don't know if it's my welder being set up wrong or just my mig ability being extremely poor. I tac in a patch and go to weld it all up and I just keep chasing holes all around. Eventualy had to break out the tig to close up my massive hole. Any pointers on how to weld this extremely poor quality metal?

fierohink

What welder are you using? Does it have stepped controls or infinite? Stepped you'll probably just have to tack all around and wait for it to cool instead of running a solid bead. Infinite controls you might try backing down the amperage and wire speed so yo don't build up too big of a pool.

nbl300

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A Lincoln weldpac. It has stepped amperage but infinate wire speed. Unless the welder is on setting 3 out of 4 it does really noting but ammass a pile. Even the tig on 20 amps ripps holes as soon as I tap the pedal unless I strike on the filler and melt that into the hole wich really doesn't fuse together and when I grind it the hole comes back. I'm trying to repair a rocker using little to no bondo as I already have the bondo bedside wich looks like crap

nothingbetter

its not bad sheet metal, if all of your rust is cut out its all in how you're welding. Take what you want out of this but I am a Journeyman body man and know what I'm talking about.

Butt welding it is a bad idea. Cut strips of 2" sheet metal (around 20 gauge) and plug weld it on the inside of your rocker so 1 Inch of it is showing all the way around your hole. have about a 1/8 gap between the rocker and your patch.

You can't use a solid bead to weld sheet metal. You will burn through every time. Use spot welds aimed in the gap to weld all 3 pieces together. Start with one spot weld, then a second spot weld 2-3 inches away, then a 3rd 2-3 inches from that until you're at the end of your patch, then put another spot weld right beside your first one, then another weld right beside your second and so on until your patch is fully welded in. You WILL warp the metal if you don't allow your area to cool down between welds. If you can't touch it with your bare hands...its not cool enough yet. Don't use compressed air to cool down your welds, let them cool off naturally. Cool it too fast and it will shrink the metal and nothing will be straight.

when you're done it should be a nice neat row of spot welds with even heat effect zone and minimal grinding before applying a fiberglass filler. Don't put normal polyester filler over welds. It absorbs water so if you have a pin hole in one of your welds it will absorb moisture and start rusting and you wasted your time. One coat of fiberglass filler roughly sanded with 40 grit will fill the un even spots and your pin holes then your poly filler over that.

nothingbetter

since you can't get a backing behind it now, use the mig to fill your holes. little spot welds, one at a time. start at the edge and slowly work you're way in. at least 10 seconds between welds. If you're holding the trigger for more than a second it will get too much heat and keep blowing holes.

nothingbetter

This article is a good example. I like it all except they didn't use a backing. Using a backing is more forgiving because it soaks up lots of the heat and you get less warpage which means less body filler. But they were working on an old Ford Box that was curved so you would have a hard time noticing any warpage since its a heavily rounded panel.

http://www.speedhunters.com/2014/03/...1-how-to-weld/

wyoming9

iTrader: (1)

It is all about controlling the heat input .

Whatever method works the best .

Start stop

Stitch welds moving all over what your welding

A butt weld in sheet metal is about the hardest to make places where a backing strip is impossible

nbl300

iTrader: (1)

I didn't do a butt weld because I knew that was going to be just hole after hole. I did a lap joint. On the sides and bottom and I had to butt weld it on the top. The strip backing is an awesome idea it feel like body work is a lot like doing drywall in a open area ply wood backers and then screw the drywall to it and putty it up sand it down and paint.

nbl300

iTrader: (1)

does anybody have a bed thats been rear ended for a 3rd gen that would be willing to cut out pieces of it?

wyoming9

iTrader: (1)

Just curious you are using .023 hard wire not self shielded ??

Sheet metal and self shielded don`t play well together .

Looking at your picture that area saw way to much heat input.

For a year I welded Mack Truck cabs doing warranty repair.

It comes down to the correct process and technique and of course experience

nbl300

iTrader: (1)

Yea in using hard wire and gas. That coloring is from tig welding and is completely normal. Although the heat affected zone is quite large I cannot turn my welder down any less it's at 10 amps

kauaicuda

small spot welds. spot and stop, spot and stop. its the only way, you cant run a continuous bead.

nbl300

iTrader: (1)

Yes I figured it out still my question is why can't I tig weld it?

wyoming9

iTrader: (1)

Your using DC straight Polarity with Straight Argon ??

Your prep work is perfect In Tig you can never get it to clean .

Poor fit up will ruin any Tigweld

Just not enough experience !!

Your HAZ in Tig should be smaller then all other processes

What size Tungsten ?? Is it to big for the material your welding

This is to much like work I go through this at least twice a day

89fourrunner

If you cannot fix that consider cutting it out and starting over. Quick, small spot welds. The less you weld, the more resistant to rust the repair will be, especially if you are using a galvanized patch.

nbl300

iTrader: (1)

Straight polarity straight argon cleaned it with brake cleen and a grinder. Yea probably poor fit up I've only had a tig for 3 months but I can run some pretty sweet beads maybe more experience but I think they're nice



3/32 tungsten ground vertically and sanded smooth

Was thinking of trying to do it like they weld razor blades together on dc+. Not dc-

wyoming9

iTrader: (1)

Poor fit up will get you every time!!
You want to get good weld Tee joints on one side and then break them inspect the weld.

What do I know I am teaching my self gynecology via videos and hands on

slacker

iTrader: (1)

NEVER use brake clean .. it'll kill ya !

.

Kean

The following article is quite relevant considering the scenario:

http://www.popsci.com/diy/article/20...t-get-careless

wyoming9

iTrader: (1)

The only cleaning I ever do is Acid on Aluminum