Need a crash course in Welding, setting up gas

[toolman]

Hello,

Well finally got my old Matercraft (Century built) 75 amp mig welder to run .024 solid wire,thanks to you guys for all your help. I want to do some patch work on my vehicle(s). This welder only has High and Low heat settings and adjustible wire feed. Ohhhhh ..... also I only have C02 gas that i use for carbonating my Homebrew. I was told that should be fine for what I'm doing,So can anyone tell me a happy medium where to set the gas on the regulator? (psi) it's around 12 now..... and Temp.setting on the welder to get me started ?....... Not a welder by any means. I've tried Low heat and all i get is pulses ........ High heat to get the buzz sound ..... but still seems to be too hot and of course i burn through......I've read where you should only spot weld every inch or so to keep heat from warping ..... Any suggestions from the pros would be appreciated. Thanks in advance.

[Broccoli1]

15-20 with no wind or breeze and 20-25 or more if you've got a breeze.
Definitely spot, I have never worked on body panels but I did build a mailbox with similar guage and just spotted along to control the heat distortion.

I warped a **** load of crap when I was first using my welder.

Someone else mentionened tapping the weld with a hammer, hopefully they'll chime in here.

[hankj]

The flow rate for shielding gas is 20 cubic feet per hour, not 20 PSI. You should have a flowmeter on the CO2 tank rather than a regulator calibrated in PSI. 8 PSI is ~24 CFH. 12 PSI is way too high; tou'll just blow away your CO2 for no good reason.

You need to find the right combination of voltage (HIGH/LOW) and wire speed to get a proper arc. It should sound like bacon frying. Start with your low setting, and a low wire speed. Increase the wire speed until you get a good arc. If you can't do it on low, go to high and reduce the wire speed and work up from there.

Thin gauge sheet metal is difficult to weld. You won't be able to run a "bead", but rather use a lot of tacks. Don't tack all in a row. Tack one end, than go to the other, and alternate. By adding tacks or very short beads in a "stictch" format, you'll git 'er done! Get some scrap to practice on until you get it right.

Hank

[Broccoli1]

Didn't even catch the psi part. Sorry my numbers were for CFH.

[MAC702]

15-20 with no wind or breeze and 20-25 or more if you've got a breeze.
Definitely spot, I have never worked on body panels but I did build a mailbox with similar guage and just spotted along to control the heat distortion.

I warped a **** load of crap when I was first using my welder.

Someone else mentionened tapping the weld with a hammer, hopefully they'll chime in here.

Yeah, ditto the psi/cfm thingy....

I "pulse" my MM175 all the time on thin sheet. Short burst for a spot of weld, move, repeat. Sometimes, because this can throw a significantly less amount of heat into the weld, you can keep going in the line, but sometimes you still need to move the heat around. Or, alternatively, weld, beer, weld, beer, weld, beer will give just the right amount of heat input, too.

Tapping with a hammer is a great way to weld cast iron without preheat. Use a very low heat input method, like the spot and move technique, combined with peening, either from a hammer or a needle gun.

[toolman]

This is driving me nuts, I think I'll re-connect the C02 back up to the Kegerator and have some homebrew and try again on Monday. I don't know what the low setting is for, won't work at all ...... even with the wire turned down as slow as it can go ........ must be for flux core wire. Thanks for the info.

[Timinmb]

The usual suggestion to practise on identical material beforehand especially applies here. Although its not the best way to do it, I prefer to make my autobody repairs using lap welds. I just don't have the patience to make a perfect tight butt fitting of panels. Also, its easier to not burn through when doing a lap weld. If you can seal up the backside, I don't believe it compromises the durability. I like to use brush on urethane seam sealer.

I am practising right now to do some work on my jeep body. I have an air powered panel flanger, which creates a depression in the metal for the overlap. I can weld the whole seam,but I find it easy to distort the metal and cause the lap to form a V over the length.

Practise making spot welds in the horizontal position, if that is how you will be doing the repair. I hold the trigger just long enough to hear the arc start and stabilize for a fraction of a second. This results in an approx 1/4" flat circular spot.

[James D. Clark]

Toolman, just as a suggestion get some steel that is a little thicker than what you plan on welding for your repair. More like 1/16 inch thick. Practice on it to get your welder figured out. Get it to making some beads and actually melting the wire and getting the gas flow adjusted. Once the gas flow is set so that it looks like you are getting beads that have nice appearance and no porosity then practice on the thinner material. No use becoming frustrated blowing holes and contending with a mess with the results not being useful in figuring out what you need to do. When the gas is set for the thick metal it will work for the thin.

If you can run some samples and show some pictures that can help us. You don't have many adjustments, but there are many things that you can do that effect the results like stickout, angle, direction of travel, speed of travel.