Tig Welder

Hi guys, I'm after a little information on buying a Tig welder. What do I need to look out for if I want to buy one that will weld steel and aluminium. I can gas and mig weld already but it is so hard to gas weld aluminium I thought it's time to invest in a tig.
Any recommendations, tips or extra info would be wicked.

Cheers, Neil

 

To weld aluminium you'll need an AC welder, steel uses DC. You also need to think about sorting out a shield-gas supply (Usually pure argon). Your local welding supplier should be able to sort you out with a half-size bottle, but may well charge you a monthly bottle rental fee on top of the fill price.
Filler rod wise, my experience is limited to 5251 sheet aluminium (1.2mm-6mm), sometimes with machined bosses etc included. Since it was all done in the welding bay at work, I just used the 5356 filler rods the fabbies told me to use (2.4mm dia. was my favourite for under 2mm sheet). There are all sorts of different grades of filler rods for the differing grades of ali, although some (e.g. 2014) are un-weldable. Probably best to ask your local welding supplier about whatever it is you aim to weld.
Without knowing what it is you're welding, it's hard to say what will be suitable. If you're regularly going to be welding stuff over 4mm thick, you'll need a full-size 3 phase welder, as single phase machines are limited to 135A (150A with a higher-rated socket in some cases).

 

Thanks for the info Benjo thats wicked mate! I'll only be doing 4mm stuff most of the time but I do have a 3 phase socket so I'll prob get a bigger one just incase.
Am I right in saying that you have to change the tips when welding different things?
I will also be welding stainless, see there anything to watch out for?

 

Before progressing this any further, have you had anybody show you how to gas-weld ali? The reason I ask is that I suspect you're just not welding fast enough, so are blowing holes in the job & making a mess. If this is the case, replacing the gas torch for a TIG torch as the heat source won't make any difference to you, but will cost you a shed load of money. TIG welding is by no-means easy, & takes a lot of practice. Without an experienced welder demonstrating what to do, & then watching you weld & correcting you as you go you'll struggle. Every single fabricator I know told me it takes 2yrs to become competent at welding ali. I managed it in a year (plus 3months steel practice), so it is possible to do it in less. I guess what I'm trying to say is don't expect to buy a welder, sit down & crack out awesome radiators/intercoolers/header tanks etc. It doesn't work like that unfortunately dude

Caveat finished! Back to the questions in-hand:

I think there are differing grades of tungsten for ali & steel/stainless, but it may just have been a diameter thing. I was pretty lucky as whenever I wanted to do some welding, one of the fabbies would setup the the welder for me. When welding steel or stainless (DC), the tungsten was ~2mm, & the tip was sharpened to a point on a bench grinder - if you don't have one of these, it's time to buy one as you'll have to re-sharpen the tungsten every time you touch down. Which will be approximately every 5 seconds initially!

Steel is an absolute piece of p*ss to weld - this is what you should start off with as you can easily hold a weld pool for pretty much as long as you like without it all going tits up. This gives you time to work out the whole move-torch-whilst-throttling-with-foot-whilst-adding-filler. You don't have this luxury with ali, & consequently have to weld about 3x faster.

For ali (AC), the tungsten was ~3mm, & a larger shroud (pink ceramic things) was used. The tip was left blunt, & the tip of the tungsten melts into a ball as you weld. If you touch down on ali, the tungsten usually snaps off. Sometimes the fabbies would strike up a fresh/broken tungsten on a scrap lump of ali in order to form the ball on the end of the tungsten prior to commencing welding on the job. I can't remember 100% the specific reason for this, but I'm pretty sure it only applied when welding thicker stuff (>3mm possibly?).
Weld penetration depth varies with AC frequency - the big old Miller TIGs I used had a separate dial to adjust this, but having had a look at the Miller & Lincoln websites, welders don't appear to have this feature anymore. It's probably computer controlled now, or perhaps only available on the really high-end stuff? Whatever, it's worth considering.

When it comes to stainless, I suggest you give it a wide birth initially as it's horrible to weld (is sticky), & thin stuff i.e. <3mm really suffers from heat distortion - it wiggles around a LOT, so you have to take extra care jigging, clamping & tacking etc.
To tack steel or stainless, you don't need filler, you can just 'flash-tack': hold the torch equidistance from the two parts to be welded & give the throttle a quick wide-open on/off stamp. This is uber useful when standing on your head in an engine bay trying to mock-up exhausts etc
Stainless welds are generally much stronger than steel welds, I think it's due do superior ductility. As a little FYI, you need 301 rods if you ever want to weld steel to stainless e.g. lambda probe into 20yr old downpipe

Oh yeah - you've effectively got four variables with regards to heat input into the metal:

1). Throttle pedal - just like an accelerator. You set the max power available on a dial on the welder - no point having enough power to weld 20mm if you're only welding 3mm etc. This is your only throttle if you go with a button-activated torch (PITA having to lean over!)

2). Torch-to-job distance - at a constant throttle position, pulling the torch away increases the radius of the weld pool (i.e. hotter), moving it nearer reduces it (cooler). When the weld pool starts running away (i.e. you're too slow, or at the ends of the sheetmetal), your natural reaction will be to lift the torch. Everyone does it apparently!

3). Direction that the torch is pointing, i.e. angle of incidence, both in relation to the 'V' you're filling, & the direction of travel. Probably similar in principle to gas welding.

4). Rate you add filler to the weld pool - by melting filler rod you pull heat out of the weld pool, so it momentarily shrinks. This is why there are differing diameters of filler rod.

Apologies if any of the above is patronising; I suspect if you've had to add filler rod during gas welding a lot of the skills will already be there.

My brain hurts now!

edit: having thought about it overnight I re-worded the bit about penetration.

 

Wow.. very interesting last post. I'm considering buying a TIG and that just answered a few questions for me! Cheers!

 

Yeah that's wicked Benjo. Think your right mate I'll have to get myself down to my local welding supplier, pick their brains, buy one and just see how it goes.
The main problem I have with gas welding alloy is getting the level of heat spot on. There is a lot more controll with a tig which will make life a little easier.

Which welder (make / model) were you looking at getting Mikey-s?

 

No ideas as yet mate, to be honest I don't know what to look out for, ie what's good and what's bad. There's loads on Ebay, but it's a bit risky buying one when I don't know much about them!

 

on the mig welding forum Im sure someone imports and sells tig welders, lots of advice on there anyway.

 

i use a single phase migatronic ac/dc pilot 200 unit
only just bought the pedal unit for it so was only able to use the up slope/down slope to control current during welding.. (crap)

ally takes some time to get used to.. it has for me anyhows
mild steel and stainless i have found straight forward.. for stainless, cleanliness, cleanliness, cleanliness, and back purge with your shield gas (pure argon i use) for high quality welds where you need them (manifolds, downpipes etc for me)

ally, i use a little brass brush (suede brush) to clean the ally , and on stainless, a stainles steel wire brush, used on stainless Only!

good luck

 

Thats the same trouble I've been having!

Ah cheers for that Bill Would you recommend it or would you recommend going for another brand, model with more / less features knowing what you do now?

 

it really depend on how much you are really gonna be doing as to what to buy if you can get 3 phase as it means you will have the ability to weld thicker materials.there are 3 types of tungsten, one does steel (marked with red tips) one does ally(white tips), and one does both(grey). you must use the correct type of tip along with correct diameter for the thickness of the job you are doing. tig welding is difficult but the only way to learn is to practise, if you can gas weld then it will make it a lot easyer as you will have the basic technique. tig welding does make ally welding alot easyer as you have complete control over the amount of heat you put in. as benjo says when welding ally you need weld quickly so get competant welding steel first before you try ally.

like anythin, unless you do it for a living you will never be the best welder in the world but with practise you can become competant. ive been tig welding for a little over a year and im just starting to really feel confident

 

Yeah this is what I though, guess I'll have to just bite the bullet and get one.

 

you thought about doing a course? could save you loads of time and cash in the long run -there not to expensive mine was 300 for 10 weeks.

did it at OCVC in bicester so probably a bit far for you to travel

 

Sounds like we have an expert in the house... any chance of organising a demo, or would you not be able to get the punters into the welding bay?

 

Cheers for the props Mike , but compared to the guys who taught me I'm no expert! For example, when I was learning I watched one of the fabbies weld up a 2" long crack in one of the primaries on Tom Chiltern's BTCC civic type-R 4-branch exhaust manifold. Easy enough on a regular 4-branch, but this was ~0.5mm wall thickness Inconel. Result - no distortion, no blown holes or anything! That's skill!
Unfortunately I don't work for that company any more, so no longer have access to the fab shop. I am however looking to start renting a small workshop within the next 6 months or so. Once I've found something suitable (i.e. cheap enough!) & got settled in I'll gladly host a welding/fabrication session for fellow forum members .

 

If you set something like that up, you might well get some work out of it.

 

I spoke to an old boy I used to work with a while ago as he used to be a welder for an aerospace comp. and said that if I could gas weld then a course would be a waste of time.

Although it would get me used to a tig welder and give me the chance to see how I get on with it before I go out and spend a load of cash on one.

 

Keep me posted if you do would be good to have a little dabble. Will sort you out for your time / materials as well.

 

May have found a building today, but it's a bit bigger than I wanted. I shall investigate further next week.

 

Generally, if you want something to lay a decent weld on ali or stainless, you're not gonna get much change out of 2k for the kit.
There is plenty of cheap crap about though!