The Stovebolt Site Forums The Shop Area Paint and Body Shop Basc welding questions

I have some patches need to fabricate and weld in. I don't have a garage. I do all my work outside in the driveway.

1) Is there any special concerns with welding in cold weather? If I had time and wanted to work on rust repair, lets say in conditions where the air temperature is in the 40s, should I do anything special?

2) Is there a significant difference in welding these patches using flux core wire vs. shielding gas? I have a new Lincoln MIG Welder Model # K2185-1 from Lowes. I have not bought a tank yet for shielding gas.

There are some Great welders (as in professional paid guys) on the site. Till they show up I'll say the temps you're considering are not an issue. Since you mentioned working outside you've pretty much eliminated shielding gas since even a slight breeze will blow the shielding gas away making for a very porous unsatisfactory weld. That said and since I've had poor results welding thin body material with flux core wire I'd put up some type wind break with heavy plastic and use gas. A few 2x4's and a roll of poly from the ag store would do the trick.

Doesn't make any difference what temp it is outside for welding.

You'll find the biggest difference with using flux core vs gas is how much cleaner the welds will be with gas. Using flux core you will need to clean off the slag after every weld before you move on to the next. Typically with patch panels most people do butt joints and this means you are essentially tacking or stitch welding the panels together, each of those tacks will need to be cleaned before and adjacent tack can be layed down. I also find mig with a shielding gas much easier in general to work with. Biggest concern with using a shielding gas outside is even a slight breeze will blow the gas away from the weld puddle so if you go that route see if you can set something up to block the wind. I'm no pro welder, just my two cents.

1. Doesn't matter what temperature, as long as its not raining and no crazy wind.
2. Flux core is more for thicker steel plus its too large of a wire for thin guage metal and very messy. A solid .030 or .023 is the best for thin and will provide cleaner results. With patch panels its tacking and tacking, moving around avoiding heat build up, you're not going to be stringing them in one pass. With that said if its is breezy or even in a shop with fans going, I'll sometimes cup my hand around the area being welded, being that its only tacking (wearing thick gloves of course)

Sounds like air temperature is no issues and gas is best if I properly prepare to block any wind/breeze.

Now the only factor is my lack of experience. We all have to start somewhere. I am feeling pretty confident right now. I will see how I feel after my first patch panel.

Get a couple pieces of scrap and practice practice. Another big thing I forgot to mention with sheet metal vs thicker plate etc. keep the seems as tight as possible or you going to be doing a lot of unnecessary fill = More heat

You need an autodarkening helmet and gas. You can get an old unrepairable fender or hood, cut .04-1/16 slits in it and weld them closed. Simulates a butt weld. Good practice and you learn where to set machine. It's possible, that because you will be "spot dot welding" on a day with no breeze, the gas will stay at the weld for the 1 1/2 second burst. You can set the gas flow high but will use a lot of gas. High is 40 CFH. Normal is about 25 CFH. Welding patches in thin sheet takes a lot of practice....... BEFORE you weld on a good truck or you will create huge holes and your patch will get bigger and bigger.....and then there is a huge warpage danger on big flat surfaces.
Maybe you are one of those guys who gets it on day 1.

I've made quickie/easy air dams out of cardboard and tape.

Check this thread out. Good information on welding. I would avoid flux core, like the other guys said. I have the same welder you do, and have had good luck with it. Use the smaller solid wire.
MPandC thread

As briefly mentioned...When welding panels (patch) or otherwise DO NOT OVERLAP....period....butt weld ONLY! If its a panel that requires SPOT welds at a particular location...use a good quality weld thru primer between the panels.
Btw, another very important tip is to pick up on the sound the MIG gun is making when you squeeze the trigger and the wire makes initial contact with your metal. It should sound just like bacon sizzling on a HOT skillet.
I like .023" wire much easier to control and control is everything.

I like to keep an air nozzle form the compressor close by to cool down the metal adjacent to the welds after each row of tiny welds. This helps keep the warping down.

Regarding your choice of MIG gases. I use a Hobart 140 and a 80 cf bottle Argon/CO2. The cart is designed to use the smaller industrial bottle. You can either lease from your local supplier or purchase a new bottle outright. Disadvantage to owning your own bottle is you keep the bottle out of circulation. In other words ALL compressed gas cylinders are required to be inspected and have a hydro test done after so many years of service. If you initially pay a deposit on your first bottle you simply get into an exchange program. Its a preference. Just a thought.

One sneaky trick to prevent burn-through when butt welding sheet metal patches is to clamp a piece of sheet copper behind the butt joint. I use a piece of large-diameter copper pipe, split and flattened, and held into place behind the butt joint with c-clamp vise grips. The copper wicks the heat away quickly, which allows longer passes to be made while stitch-welding without distortion or burn-through.
Jerry

With a copper backer, you need to crank the heat up higher to get complete penetration. As was said earlier, practice with the same setup as the final weld setup.