Yes I know it's crazy to weld with Oxy acetylene but that's what I'm doing. I began learning it and experimenting with it one summer and I've had mixed results. After a 2 year hiatus due to a move I'm finally able to pick it up again during this crazy time of Corona virus. My first try back I'm realizing that something isn't right and I have to identify the problem. I'll start by telling you my equipment, material, and preparation. Those 2 Summers ago when I started dabbling in this I found a small rig being thrown out. The acetylene bottle is about knee high and the Oxy bottle just a little taller almost waist high. Both are probably about 6-8 inches diameter. I bought a new torch with a #2 tip and a cutting attachment from harbor freight. New regulators, flashback arresters, #0 tip, hoses, and rg45 welding rods from a welding supply store. Back then I made a cross member out of 1-1/2" square tubing (1/8" thick) that I bought from a metal supplier and home Depot 1/8" flat stock for flanges. It came out really good. But I know I've had difficulties before that like I'm having now. I've got 1" flat bar and 1"x1" angle iron (both 1/8" thick) from home Depot that I'm just trying to make some simple small brackets out of. So you can understand what I'm doing in drilling 2 holes in the angle iron to mount it to the a wall then I'm trying to weld a piece of flat to the angle so that it sticks out kind of like a tp holder. And I'm doing it as a lap weld not a butt weld. For preparation I clean the metal to a shiny surface with a wire wheel on my bench grinder (all surfaces possible). I then lightly soak it with acetone and dry it with a clean rag. Got my acetylene set to 5 psi oxygen to 10. Get it to a neutral flame and start heating it up. I try to focus on the angle iron more at first because it's more metal to disperse the heat. Also the edge of the flat bar will start to melt real quick. But I can hold it on the flat surface of the angle iron for so long and it never seams to form a puddle. And especially in that crevice where the flat bar is overlapping the angle. It will go so long without forming a puddle eventually the torch will overheat and pop. Yet the flat bar wants to melt so easily. If I can form a small puddle on the angle is not close enough to the flat that I can get them to connect. And after a while of doing this the edge of the flat will stop melting cleanly and start sparkling as if it's dirty or contaminated. That will also cause the torch to pop. Does anybody have any idea what's going on here? Is it that the metal from home Depot is no good? Do I have to clean it better? Should I be using different than acetone? Regulator pressures? Larger torch tip? I've tried both the #2 and #0.
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So the project piece I was working in I ended up zapping with a stick welder. But here's a picture of a piece that I recreated to try again and get a picture of. You can see in the picture there is a crater in the angle iron where if melted cleanly and quite quickly to. But that was only after a few minutes of holding the flame in the joint and getting a puddle. So then I moved the flame over a little bit away from the joint and Bam. Puddle no problem. I just can't seem to get a puddle close enough to the joint. It must be a technique problem. Maybe torch angle or something. Or maybe in thinking I need a bigger tip? 1/8" steel , #2 tip?
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A number 2 tip is theoretically not large enough for 1/8th inch material. You really need a #3 in order to flow enough gas. Also, if you are not using a cutting tip, set your oxygen and acetylene pressures the same. I would do 5 PSI on both. Make sure you set your acetylene flame hot enough so that enough gas will flow through to cool the tip. You don't want the flame to jump away from the tip when you are burning acetylene only, but given that you are at the upper limit of what a #2 tip can do, you will want to open up the acetylene to the point just before the flame jumps from the tip. Then adjust for neutral flame as normal. If you aren't flowing enough acetylene, it just will overheat the tip and backfire. I bet two years ago you had your settings and torch adjustments different than what you are describing now.
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Then once you get shiny steel, hold the flame on the angle & just touch the blue point at the tip on the angle right at the joint just long enough to puddle. Keep the point off the edge of the flat bar. Once you puddle then back the torch off to normal tip distance & go to town.
+1 to what Daniel said. A wire brush will not remove mill scale in most cases. It just polishes it. Oxy-acetylene welding does not require the kind of cleaning TIG welding requires. I would ditch the acetone, and I would remove the mill scale with a grinder or a sanding disk. Did you ever try the larger tip?
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