Hi guy's I've got a quick question: I know that you weld steel with 25/75 OR straight CO2. SS you use tri-mix and aluminium you use straight argon. My understanding (correct me if I'm wrong) but if you use stright CO2 it is hotter then 25/75. Now the question what would be the effect of using straight argon on steel? Would it work and would it produce a "cooler" weld? I can try it I just wanted to pick the collective brain to get some "sage" advise. I'm working on pannel welding (21 - 22ga) and am looking to cool it to help prevent those REALLY nice burn through. Any opinion's are welcome! Thanks Mel

Some people use copper on the back side but IMO you are better off using the recommended gas, and work on your settings and technique to help prevent the burn throughs, its also important to get good penetration. If you watch up close when someone else is welding, you can often see their mistakes, so you might want to make a video of yourself and try to spot some mistakes that you are making.

There are many welders on here much better than me and with a lot of experience in welding who could help you with whatever problem you may have but some research on the subject will also help. Miller and Lincoln both have many tips here that are often overlooked.

http://www.millerwelds.com/resources/ar ... -MIG-GMAW/

http://www.youtube.com/watch?v=RJ4y7snY3Wk

http://www.youtube.com/watch?v=tkvmlZPEsIE

I am by no means an expert, but I happen to MIG weld sheet metal corners with some of my art work. I agree with the other reply about welder settings being so much more important than the gas. You will obviously blow through the 20 gauge metal easily.

I use steel behind the weld to absorb heat. Of course copper or aluminum is better, because different metals don't want to weld to each other. I dont have that luxury, so I have steel behind my sheet metal welds to act as heat sinks. I find on my Millermatic MIG welder, I can use a setting that gives me a nice weld of the sheet metal without really welding the base metal I'm talking about.

I tried to include a picture just now, but it isn't working. Hmm. I'm by no means plugging my own stuff, but I don't know how else to show some pictures of what I'm talking about since I couldn't add a picture to this reply. If you go to my site: http://www.customsteeltable.com. Click on Process and go to the Coral page, you can scroll down and see a closer picture of a sheet metal weld that ends up working quite well for my application.

I hope this helps you out.

Lon

customsteeltable wrote:
I have steel behind my sheet metal welds to act as heat sinks. I find on my Millermatic MIG welder, I can use a setting that gives me a nice weld of the sheet metal without really welding the base metal I'm talking about.

It may work alright for your tables but I doubt that your welds are hot enough to get good penetration for auto welding, although copper would work good.

I use 75/25 for all of my steel welding using either .024 or .030 wire.

To weld 20 gauge, use a thin wire such as .024. Keep your heat down, around 2 - 3 on your voltage, around 40-50 on your feed controls. The lower the numbers, the cooler the weld. Too low on the speed or voltage and your weld will puddle and burn on top of the surface and not penetrate.

To make a "spoon" for backing up holes in panels, I bought a 6" section of 1" copper pipe and flattened it over the end of wood dowel. I put a curve in the copper to make it easier to press up against the hole.
Harbor Freight sells these...

I am learning MIG welding, been watching the vids on you tube. I have a concern. I understand that you can not use gas outside, so outside you have to use flux core. I will basically be using the MIG to repair rusted out rocker panels on a car ( GM W Body) I will be using flux core with the MIG. I have heard that
if I paint over thr weld, eventually the flux will discolor the paint. My second concern is I will be doing this in my back yard, one side of my yard there is a walkway maybe 50-70 feet away. How far away is a safe viewing area for MIG welding.

You can weld outside with a MIG without much issue. I have to weld outside on a regular basis.
If you are trying to weld in a high wind, it will not work well. You can make a wind break, if needed...

Flux welding is great for structural repair outdoors. Handrails, fences, trailers, etc. It's a lot easier to weld thick metal with Flux and pretty hard to do cleanly on autobody sheet metal. Once you've gone MIG or TIG, you'll never want to go back

Its not safe to view the intense light from a MIG or TIG weld, even from a distance.... You can use a #11 or darker shade lens in a fixed mask to save money ($20-40). If you are blocking nosy on-lookers, use a 4 x 8 sheet of plywood and keep it away from sparks. Dress up like Christopher Loyd and pretend you are working on back to the future. That will get their attention!