Bending tube with a TIG torch

[IslandTractor]

Nothing wrong with your weld. Just TIG is a slower process so it puts more heat in.

I always think of TIG being a process that puts less heat in overall by putting a more intense focused heat right where the weld is. When I do oxyacetylene welding the "red" zone and heat affected area is way bigger than when I use TIG.

 

[jwmorris]

It certanly puts less heat in the part than oxy/act and can put less heat in than MIG too.

One of the things that happed to the OP's frame was welding too slow or with such a low amperage setting he had to dwell on the part for a while to get it to heat up enough to weld. Sort of like what happens when you weld magnesium or aluminum; however, that too can be over come.

Like these .040" thick aluminum parts welded with a TIG and not warped. Couldn't be done with a MIG as you just don't have the heat control.

A TIG allows more precise heat control but if you don't use it correctly it will eventually do the same thing to a part that you could do with a rosebud on your torch.

 

[joshuabardwell]

Thanks to everyone for the advice and feedback. If I'm over-heating the tube, then I think it is most likely a combination of factors. Being new to TIG, my travel speed is probably not as fast as it could be. I also often have beads that are slightly concave, which I have been attributing to not enough filler, but it could also be excessive heat. Anyway, I'm sure it's something that will improve with practice.

I have had some success using the torch to bend the tubes by welding beads on them. (Zero success using the torch to heat the tube without melting it.) What worked best so far is to weld a U-shape, with about 1" of weld along the corners of the tube and then a bead perpendicular to the length of the tube. I'm sure an H shape would work too. If I just weld on the corners, or just weld across the tube, I don't seem to get any movement at all, really, but if I do them together, it does the trick okay.

Hypothetically, how would I heat the tube if I wanted to cause it to twist? My guess: barberpole spiral all the way around.

 

[Shield Arc]

Hypothetically, how would I heat the tube if I wanted to cause it to twist? My guess: barberpole spiral all the way around.

That's a good question! I've never thought about having to do that. I think I'd heat the tube all the way around, and use a large crescent wrench to twist the tube.:confused3:

 

[weldermike]

Josh, just try to bump up your travel speed. It will come with practice. Sometimes to keep warpage down I will travel as fast as I can without pausing at all in between dips. This was a jig I built and it had to be 100% true, so no warpage. These passes were about 8" long and I welded them out in about six seconds each.

 

[CNC Dan]

Thanks to everyone for the advice and feedback. If I'm over-heating the tube, then I think it is most likely a combination of factors. Being new to TIG, my travel speed is probably not as fast as it ccild be.

That will come with time. Also using larger filler wire can help with travel speed as you won't have to move the wire through your hand as much, or not at all.

With time, you will use more current and move faster. That will reduce the total heat input. Like passing your finger through a candle flame quick won't burn you.

 

[joshuabardwell]

That's a good question! I've never thought about having to do that. I think I'd heat the tube all the way around, and use a large crescent wrench to twist the tube.:confused3:

The reason I asked is, the middle shelf on the cart is slightly out-of-level from side to side. I tried heating the top of the right-hand side to raise the front-right corner, but it didn't move, and I think it's because the left-hand side is holding it in place. I realized that the right-hand side needs to bend upwards, and the left-hand-side needs to twist in order to move the corner. Anyway, it's all hypothetical, because it's only out maybe 1/8" and I think I have more to lose trying to fix it with my current tool-set than I have to gain, but maybe I will try welding a barberpole around a piece of scrap just to see what happens.

BTW, last night, I was thinking about you saying I need a torch, and I realized that, if I was to use the propane tanks that I already have as fuel, I could get by with just having to buy an oxygen tank and a torch set. Something to think about...

 

[joshuabardwell]

That will come with time. Also using larger filler wire can help with travel speed as you won't have to move the wire through your hand as much, or not at all.

I don't mean to sound like I'm making excuses, but I do think my filler size (combined with my lack of skill, of course) is contributing to the problem. I bought 1/16" filler, but Miller's weld calculator calls for 3/32", and it does seem like I have to push a ton of filler to keep the bead from cratering out.

 

[IslandTractor]

BTW, last night, I was thinking about you saying I need a torch, and I realized that, if I was to use the propane tanks that I already have as fuel, I could get by with just having to buy an oxygen tank and a torch set. Something to think about...

It would probably be cheaper in the long run to just get a whole acetylene/oxy system used on Craigslist rather than buy a new set up for oxypropane from a LWS (you won't find a used one). There are ALWAYS acetylene/oxy setups for sale and they can be had for anything from $200-400. I wouldn't pay much more than $200 for a set with knockoff torches but a good condition set with true Victor or Smith torches and a cart would be easily worth $400. Oxyfuel is fun. I enjoy using it more than any other welding process simply because it is slow and easy. Things just don't happen very quickly, there is no smoke or flux, you can braze as well as cut and weld. Wonderful tool. Not nearly as efficient as newer technology welders but really still very very capable and fun.

 

[joshuabardwell]

It would probably be cheaper in the long run to just get a whole acetylene/oxy system used on Craigslist rather than buy a new set up for oxypropane from a LWS (you won't find a used one).

Given the price difference between acetylene and propane, it seems like the long run is exactly where propane would shine, even if one had to buy the propane equipment new up-front. But I don't know for sure--for example, different flow rates and oxygen ratios may make the cost closer than it would seem just from comparing the price of propane to acetylene. The real equation should be dollars-per-inch-of-cut, or what-have-you, not dollars-per-cf-of-gas.

The other concern that I have is that, with acetylene, most of the tanks I see look pretty small, and I think are intended for welding or cutting. My impression is that heating requires higher flow rate that can quickly hit the 1/7th rule of a smaller acetylene tank. Is that right? For example, take a look at this ad: Oxy-Acetylene Tanks and Torch

Could one use that tank for the kind of heating and bending we're talking about?