OT: TIG Welder

What are you building ? Catamarans ?

First, you have to have a AC set, DC doesn't work on Ally.

is a pretty well entry level SIP TIG set, and an indicative (very cheap for TIG) price. Think upwards from there

The best stuff comes from Lincoln Electric, but you can see from the rating that you need at least a 32A feed at full throttle. The guys who do all our sheet metal I just spoke to, recommended 150 A for short tacks and a 250A set, not for the section, but for the ruggedness of the torch and cooling of the torch. A Water cooled torch is compulsory I think at 250A in the weld.

That said, we welded 2" sections of 1/8" thick with 115-120 A. That welder went on a 16A circuit (big blue plug), rather than a 32A (bigger blue plug.)

If you are welding at home, do you have three phase ? That will reduce the current requirement from the supply considerably.

Steve

I've recently bought an SIP Tig 160 AC/DC martyn, it's a good bit of kit, but it needs serious input current. Not for actual welding, but to charge up the ruddy big bank of capacitors that are inside it. Instantaneous startup current is 60A, but only instantaneous. Mine runs through a 32A plug/socket (big blue) and a 40A breaker just fine, but it's a motor-rated breaker that can cope with the very short period of surge current on startup. One day I'll get to grips with it and stop melting ally into nice round puddles! Badger.

You haven't broken the steps on Grumble have you?....

This is what I was considering asking so as it has been answered, how about types of gas for ally and what sort of current would you need to weld 16g stainless steel tube?

Rich

Pure Argon gas; and around 100A should do with a bit of a safety margin for duty cycle. Badger.

So you need more current to weld ally ( or make blobs on the floor ) is it very hard and what is the foot pedal I have seen on some big welders?

Rich

You need more current initially to "pool" the metal, due to ally dissipating the heat through itself quicker than steel, that's why it's so easy to make ally puddles on the floor! oops! The foot pedal is an alternative to the button on the hand torch, on welders that have this, some cheaper machines are what is referred to as "scratch-start", where you have to make contact with the tungsten electrode to fire up the arc. Badger.

On Fri, 2 Sep 2005 20:19:01 +0100, Badger wrote (in article ):

The foot pedal is (usually) a current control so you can wind the current up and down as you progress along the weld. IME this is pretty much essential for welding ali since you need to put a lot of heat in to get the weld going, and then back off one the material is hot or you'll make a hole. You also need to be able to back the current off as you finish the weld or you'll end up with a pit in the bead. Some machines will do this automatically, ramping the current up when you push the button on the torch and down when you let go, but the foot control gives you more flexibility.

There's loads of good welding advice on the net. Hang out on sci.engr,joining.welding for a while and some good advice will come along soon. Miller Electric and Lincoln Electric both have lots of stuff on their websites, too, and there is also The Welding Institute.

Unless you are doing very long runs (feet of bead at a time) at currents over about 150A you won't need a water cooled torch. I have a 200A TIG machine (Lincoln) which will easily weld 4mm Ali plate and will run off a 13A socket (although probably not forever at full output). It was quite a lot of money, though (~2k).

Apart from the oxidisation issue with Ali (which is why you need AC) the big problem is its heat conductivity. If you start with cold pieces of material, they just soak the heat away from the weld so it's difficult to make the bead flow properly. Once the surrounding material is hot enough for the temperatures to stabilise then laying a pretty bead isn't much more difficult than for steel, but if I'm only welding a short piece of material, I find I've usually reached the end of the weld before this happens.

You can use the same shielding gas (pure argon) for TIG welding ali or steels, but you will need zirconiated (red) electrodes for steels and thoriated (white) electrodes for Ali. You're supposed to be able to use ceriated (grey) electrodes for both, but I've not had a lot of success with these.

I've never played with scratch start (aka 'lift-TIG') but I understand that for welding Ali, life is a lot easier with HF start. With Ali, you really want to avoid the contamination of the bead which comes from metal-to-metal contact between the material and the electrode. AIUI, lift-TIG is the poor man's option and anyone who has HF start will not use the lift-TIG option even if they have it available.

The most important thing with TIG welding is to prepare everything carefully in advance and be scrupulously clean, especially when working with ali. The books all say this, and it's easy to ignore, but it is absolutely true and it really makes a difference. I started out with a stick welder, progressed to MIG and then on to TIG, and as I have moved from one process to the next, I have learned (the hard way, of course) that each is less forgiving of dirt/corrosion and poor fit parts than the last.

I'd also recommend Lincoln equipment . It's more expensive than the Clarke/SIP equivalents, but it's professional gear, and I find the guy who runs their Sheffield retail outfit very helpful and easy to deal with.

Nick

1990 90 2.5TD

Ok, thanks for all the info will see what Father Christmas brings :-)

Rich

Sorry to be a late commer to this discussion, but i've been on holiday!!

- i have to agree with everything Nick has said.

I'm an amature who spent one years bonus on an AC tig set, i convinced myself i MUST have one! - lol

I had been welding for 20 years (MIG - Gas), building cars etc and after

6 months of trying to stick alley together, ended up going to colledge for a year to learn how to do it!, i wanted to send the set back!

A foot peddle is a must, i bought mine after the set and it just makes life sooooooooooo much easier.

Mother - I'm in Sheffield (Handsworth) if you want to come and talk to me and try out my set, drop me a line. I got mine ex demo from Lincoln Welding supplies (attercliffe), and it came in about 2.2K for the lot, but they did me a good deal.

I have just welded a cosworth cylinder head on a 150 Amp torch and i didn't need the 250A max that my machine goes to either. all this and off a normal 3 pin plug!

hope this helps?

Gary

Nick Williams wrote: