Asking the forum, learning TIG AC Aluminium

[AdrianH]

I have a lot to do before I get to this stage, but I intend to get some lessons before long on TIG welding. Machine is mainly for Aluminium, but if I should do steel first so be it.

No specific project in mind but I have left over 1.5mm sheet. and will be trying to get other thicker bits to play with.

I am in the Blackburn area, and was thinking of a couple of days under supervision welding, not after any coding courses and what I have found to date seems to be a day a week for lots of weeks. Sorry to say that work would not allow that as welding is nothing to do with work.

I have left a message with the Lancashire welding school but no response to date. Anyone know of a place or person in the area that does training and I can take it from there?

Cheers

Adrian

 

[ford34/2]

In case you missed the Tig tutorial
http://www.mig-welding.co.uk/tig-tutorial.htm

worth a read.

Stan

 

[backpurge]

Wilkinson welding at Worsley used to be pretty good

 

[AdrianH]

Yes have seem the TIG tutorial but it does not discuss aluminium welding. Mentions mostly DC.
Will search for Wilkinson.

One point I am confused on, how far out should the electrode be from the end of the ceramic cup?

Adrian

 

[hotrodder]

Rough rule of thumb regarding tungsten stick out is about 1/2 the ID of the ceramic and not more than 1 dia but that can be exceeded by a fair bit with a gas lens when necessary as they 'straighten' out the gas flow more i.e. can have more stick out before gas shielding is compromised. Distance isn't critical or anything, in practice as little as needed to reach the joint with the correct arc length and still be able to see what you're doing.

Arc length for DCEN should be no more than the dia of the tungsten ideally, a nats longer with AC. Excessive arc length is probably the most common newbie error (especially if/when frustration sets in after repeatedly welding the tungsten, filler wire and work piece together!) and messes everything up... arc voltage increases and the arc kinda 'fans' out so heat input goes up but instead of being focused the heat is spread about more making it harder to get the filler wire into the weld pool without it being melted by the arc first

Personally i'd recommend starting with steel initially, aluminium is different rather than more difficult but it is less forgiving... stuff the filler wire into the arc or bump the tungsten when welding ally typically results in more of a mess than with steel for example. There's usually more machine settings to confuse things and the thermal conductivity of aluminium doesn't help when playing with small offcuts which quickly become heatsoaked making for relatively large changes in amperage/travel speed. Nail the basics like arc length and torch/filler wire relationships/angles of attack on steel first and getting used to the behaviour of aluminium will be a chunk easier IMO. Don't pay much attention to the welding amperage calculator but the diagrams regarding angles of attack in the hints & tips section might be useful http://www.millerwelds.com/resources/improving-your-skills/tig/ 40A per mm / 1A per 0.001" is a good rule of thumb for ally but mass of the part makes a difference due to the thermal conductivity thing along with joint type etc

 

[AdrianH]

Thanks hotrodder, I think you have just cleared up something for me, for what ever reason, I have been reading the stick out as being the diameter of the electrode or 1.5 dia electrode max. Not sure where I have got this from, but the ID of the cup makes more sense, and probably tells me why I can not get the arc length right as I can not see the dam pool sometimes or get the electrode close enough to the work. A lot is down to my work space I know and I have to pass on my old RT180 to get some space or get rid of an engine!

Thanks for the input.
Adrian

 

[Richard.]

Ali Tig has much less room for erra and demands much more from the welder in order to get results. Not far behind arc length I'd say the next thing people struggle with is contamination. Clean filler and material is quite important.
With DC Tig you have only got current and gas flow to worry about when you get started
AC you have got balance and frequency on top of that. You have also got more thought to put into the tungsten prep which is dependent on joint, material thickness, tungsten size, current, wave balance.
On top of all that you have to take into account Ali demands high current when it's cold to break through the oxide layer and generate a puddle but once that puddle is achieved the aluminium it's self melts at 1/3 of the temp of the oxide layer so it then demands much less current to weld it which is why it's far more controllable with a pedal.
Master the art of arc length (short and tight) roughly 10 degree torch angle pushing. And look for the puddle using steel or stainless, keep the filler low and dip it into the front of the pool. You will notice the pool shrinks slightly as you chill it with the cold rod. Remove the rod move the torch forward a fraction and watch the pool expand again. Repeat the process.