I have just purchased a mig welder, now I know practice makes perfect, but..
I have a mild steel tube of 1.121mm. I am using the mig setings for 0.8-1mm weld and wire speed on 6. but every time I try to weld the bits together I get blowthrough. Holes in the metal at the edges, I can turn the current down, but then the weld does not penetrate.
Since your weld is cold when starting, weld in the direction from thin sections or gaps to the thicker section or tight fits. When you pull your gun back slightly the effective heat at the weld will be reduced. If you pull back too far of course you will lose shielding. Randy
One addition to Randy is you will either have to do start-stop repetitions or go much faster. As I understand the metric system, 1.121mm is .044inch and that's very thin stuff even for MIG. On material that thin, you may want to tack several places and call it good. If this is only for practice then have at it.
1.121 mm seems like a very odd size to me. And specified to a thousandth of a millimeter! Thats about the size if a bacteria. Talk about presicion, or someone has been overambitious in translating an inch measurement. But as I will probably mostly be welding in that sizerange the answers have been very useful Henning
IIRC, the ASTM spec for 18ga round tube calls for .049" nominal
+/-10% or .441" or 1.12 mm Hotr rolled steel tube tends to run on the small side of nominal (2-4% under), stainless is spcified as "minimimum wall" So you might very well see a spec for "1.121 mm min wall"
We had some exhaust manifolds that were 18ga 1018 steel. Welded up thousands of them us> >
millimeter! Thats about the size if a bacteria. Talk about presicion, or someone has
Use .025 or .023 size wire and make a series of very short welds.... like tack welds. Make the second weld away from the first weld so the metal won't get to hot in one spot. Try to put a piece of metal inside the pipe to act as a heat sink to distribute the heat better so you won't burn through so quick. Use an air gun to cool the metal between welds.
I use a series of spot welds, but don't let them cool a lot between. I watch mostly for color, and when one is just cool enough, you put another right next to it. If you have an auto hood, you can set the lens to clear just at the right moment, then spot it again. The spot time will vary slightly, but you can get them pretty even without having a spot timer. You can even run a little hotter, as you won't be putting enough metal on there to create a puddle big enough to fall away. When you are done, it looks pretty close to TIG, and is nice for places where you want your welding skill to be visible. I use this for finish welds on wrought iron where I want the welding to show and look nice without grinding it off flush. If you get a keyhole going, and maintain it, you get very good penetration on the back side, and a very sound weld.
True. I took tube to mean small stuff, but then you can buy large diameter tube, too. As with any weldment, you must clamp, spot and tack and weld in the proper sequence to deal with warping and distortion. Good point.