MIG welding with Co2 for framebuilding ?
 

Hello

I'm looking for a new welding technique (for the moment I use a MMA inverter, but it's quite hard to use with <2mm steel, and rather impossible for <1,5mm) for framebuilding.
The obvious answer would be "go for a TIG !", wich could be the good anwer (I can put a basic TIG kit on my MMA) but the big problem is: in France, Argon and its derivates are really, really expensive (350€ for 2,5m3 of Atal, ~80€ per reload, bigger bottles require a subscription). There isn't a lot of providers, and particulars are a minority of them customers...

So after quite a lot of researches, I've found that MIG MAG can use Co2 (much much cheaper, about 1/3 of argon price) for steel welding. Surprisingly, this process is nearly unknow in my country, or very little used, while it's recommended for steel in Welder manuals in US.
The pro and cons seems to be:
+ : better penetration, cheap
- : hotter, lot of splatting, more carbon in the weld, "short-circuit" metal transfert

So my question is: have you already test (or at least heard about) this gas for framebuilding ?

Mig is not used a lot in framebuilding (less temperature control than TIG, cold start,...), but with a MIG-MAG machine that allow ~30A welding and a bottle of Co2 could make a pretty cheap (~300-350€ for all) way to weld tubes (>0,8-1mm, I don't think high-end steel could be weld this way). Surely by welding with short seams to avoir break through the tubes.


Thanks ;)

Was it on rather high-end (thin) steel ? Do you have an idea of the intensity you used ?

Mig is used on automobile bodywork, so it sould be possible to weld really thin steel, the unknow parameter is the resistance of weld on these thin tubes.

Automotive sheet steel isn't as thin as you might think, especially compared to framebuilding tubes. Most steel framebuilding tubes will have butts that are ~1mm on the thicker end of things, whereas automotive sheet steel starts at about 18g (~1mm) and goes up from there, in some instances going up to 10g (2.59mm).

MIG is sometimes used in 'bent manufacture, but that's on thicker sections. I feel like there are good reasons why brazing, TIG (GTAW), and, more rarely, oxy/acetylene welding are the predominant methods of joining bike tubes.

Off course, there is some good reasons to use brazing or TIG instead of MIG (as I said in my 1st post: temperature control, clean process,...), but cost isn't the same at all. Even more when you need to practice (so consume, like, 1 full bottle ?).

I've spotted a MIG (Güde 155 and 172) that look correct (25-130A) for a rather cheap price (200-270€), if I can use it with pub or extingisher Co2, a 5kg coil of 0,6 or 0,8mm steel wire (30€), and have solid welds on ~1mm steel without transform it into a gruyère... I'd be pretty satisfied.
I would be tempted to give a try, but not before have some returns and be sure it can work.

Of course, this is the question. You are going to have to try it, and the experiments probably are not going to be cheap. If you are willing to work with thicker sections, it will certainly work. The problem is high performance tubing will almost surely not work. This is one of those questions where if you have to ask it, the answer is no.
If it worked well enough to ship bikes, the bike manufacturers would be using it. It's cheaper than anything else.

OTOH, a MIG would be handy for things that aren't bicycles.

For the moment I just want to weld rather thick (1-1,5mm) steel better than with MMA, no high perfs tubes in sight. This is just for fun, and I'll see later to eventually afford a TIG or Oxy to make lighter bikes or modify "good" bikes. A mix of them with MIG or MMA should sighly reduce total cost.

I was just surprised to see so little returns about it. Sure, framebuilders usualy look for good materials, but not for every projects (I think about cargo bikes, trikes, trailers...).