Well here is some facts on mig welding. Its real easy for someone that is handy to learn to mig weld good enough for simple welds on say angle iron,square, and round tube, but to weld up something with water tight welds take some knowledge and talent. Porosity,undercut,poor fit up, and cold lap are the most common problems. Not to mention the 3 transfer methods of mig welding and how to use them and where to set your machine. Short circuit transfer is the most common form of mig welding and is done on 3/16" thick and under steel. Anytime your under 20 volts and 300 ipm wire speed (this all varys with different machines.) your in Short circuit. It sound like bacon sizzling. Once you start getting up over 20 volts and 300 ipm wire speed your starting to get into Globular transfer. The sound won't be has smooth has Short circuit and you will see more spatter and the spatter will be bigger balls that will be harder to remove. Globular transfer is real tricky to weld in because it sounds vary different then Short circuit, but can provide good welds when setup right. The final transfer method is Spray transfer. When and how to get into Spray transfer has a lot to do with how many amp machine you have and what type of gas you are using. Spray transfer will just hiss (hence the name spray) when running it and will run real hot with a real nice smooth weld bead without spatter at all. To get into Spray transfer you need at least a 250 amp machine and 95/5 or 98/2 argon/co2 shielding gas. I have the same Millermatic 250 welder and with .035 wire and 80/20 gas I can just barely get into Spray transfer.
So now that I'm done with all the theory lets apply it to your weld situation. A propane tank should be a minimum of a 1/4" thick but most likely 3/8". the front of your boiler is somewhere between 1/8" and a !/4'". So you should be welding it in Globular transfer. You could weld it in Spray transfer if you have the correct gas and know how to set your welder for it (would be my preferred method if I used mig). Spray transfer because it welds so hot can only be done in the horizontal position. So most likely you were welding it in Globular transfer and like I said is the hardest transfer method to weld in. You must have all the mill scale cleaned off the joint and have good (tight) fit up. In my experience I would have welded with 7018 stick. I find it much easier to get water tight welds with it.
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Topic: problems using 500 gal. propane tank (Read 6750 times)