Welding

I think we're clones, not only do you have horses but your welding is like mine too! :-)

Remarkable. I *always* find if I've not picked up an electrode for 18 months or more I have to waste at least a dozen or so rods getting the feel for it again. And it's always the same two mistakes I initially make: making a pass too quickly and not tucking the rod in sufficiently. Clearly she's a natural born welder; I'm not! (I normally get the current right straight from the get-go within 5A either way though).

MAG?? Trouble with TIG is the work piece has to be *super-clean* for some reason, so it's a drag to prepare.

When you're working near the limit with MIG you can pulse it rather than applying continuous power, but that can result in a discontinuous weld or poor penetration. Button welds (spot welds made with a MIG) can be a useful technique if you don't need a continuous seam.

there's also the bitumen & coal dust trick to get 'continuous' welds.

Most wire fed gas shield welding on steel uses CO2 as a primary shielding gas rather than pure Argon or Helium. CO2 is classed as an "Active" rather than an "Inert" gas, hence MAG rather than MIG.

Yup, the more refined the process, the cleaner it needs to be usually. If you want to weld through a load of rust and crap, there is not much to beat stick!

Kind of struggling here to work out what use *any* non-inert gas would be in a welding process. The very last thing you want is oxidisation!

True! Stick plasma blasts the living s*it out of *every* contaminant known to man. ;)

It's normally for arc stability. It is normal to add a small amount of CO2 to argon as pure argon has poor arc stability. O2/argon mixes are for stability. Though only a couple of % of O2 is needed.

Never really got on well with stick welding. MIG at high currents can also weld through some surface coatings.

For MIG welding CO2 also aids penetration so mixes for thin material only have around 5% CO2, those for thicker material around 20%

Argon mixes with CO2, even at the 5% level are for all practical purposes incompatible with that required for TIG processes. But you can MIG weld with pure argon, and some claim 100% CO2 works too.

What is very clear is not all ARC welding processes are the same, even with the same base material.

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Oxy acetylene reduces rust back to iron.

The advantage of pure CO2 (i.e. pub gas) is that is cheep. I am told, you get good penetration, easy arc start (but less stability). Also more spatter and less pretty welds.

IIUC, even the choice of filler metal can impact on the ideal shielding gas mix.

The tungsten electrode is eroded more quickly in a CO2/Ar mix. I suspect the arc is otherwise fine although may give more heat penetration as per MIG welding.

There is little point in using pure argon, the arc is not so stable and is more expensive. Many people do indeed use pure CO2, but more spatter and more depth.

Agreed.

Is there any subject on earth you actually *don't* know anything about? Just curious.... ;)

I have done quite a bit of welding, consuming a few reels of wire, so have done my homework.

For the last 10 years I only welded sporadically and so could only justify gasless wire. It's not ideal but is affordable and saves on bottles.

More recently I have bought a bottle rent-free which I can fill when I want. Its a Argon/CO2 mix 95/5 for use with thinner steel with a less thermally conductive shielding gas, for least distortion.

I originally did stick welding, where I would do 'spots' on thin material. A MIG is a dream to use and haven't looked back since.

MIG is no doubt the most user-friendly welding method of the lot. Very little skill required and most of that to do with just getting the set-up right.

But you can't beat stick for heavy plate IMO; assuming you have a proper oil-cooled job like an Olympia or Oxford and not some Chinese "inverter- turbo" bollocks contraption.

Gynaecology?

I always found acetylene was..but then I was trained on that - not on arc of any sort.

I doubt then you've ever done any car body repairs. All too easy to warp panels with acetylene. Very difficult to do that with MIG - unless a total idiot.

I'm surprised. I think it's universally acknowledged that oxy-acetylene welding requires considerably more skill and practice than any other commonly used method (doubly or triply so when working with aluminium!)