TIG welder advice

[Howie]

They're big enough but they don't have enough knobs. I'm afraid it's a case of the less you pay the harder they are to use. With the simple inverter types one feature you won't know you should have is a high frequency start. You can scratch start it, but the accumulation of little difficulties isn't what a novice needs.

Can you go talk to a tutor at the local tech? Even if you don't want to do a couple of evening courses, (and you should) he should be able to run over the pros and cons of some mid-range machines. Those start at about not much less than a grand new though.

Oh, and you can get disposable bottles now, could be cost effective for irregular use, I just don't know where from...

I agree with most of what your saying ocean1, The better machine you buy the more pleasurable well be your experience, and getting someone with knowledge to show you is a great idea. If your local Tec runs a course go on one, and ask heaps of questions, otherwise get some of books out of the library about welding, before deciding what you want

Duty cycle works as a percentage over a ten minute period

TIG is more useful if your going to do a lot of aluminium, and stainless, Contrary to what others are saying you can weld Ali in all positions except overhead reasonably well with a DC TIG, but you use a different tip, and swap your polarity around.

MIG is good for Steel, any single phase MIG except for a top of the line model well probably struggle with aluminium as your feed speeds are a lot higher using aluminium, The other thing to be weary of with MIG welding Ali is cold lap joints wear you don't get penetration into the parent metal.

and yep I'm A Fitter and Welder by trade, although I haven't been in the welding game for over ten years now.

[DEATH_INC.]

also you need different tungstens when tigging between mild or stainless steel and ali...........thoriated red tip.........zirconated white tip.......cant remember which is which sorry

Zircon for ally, thor for steel

[DEATH_INC.]

Contrary to what others are saying you can weld Ali in all positions except overhead reasonably well with a DC TIG, but you use a different tip, and swap your polarity around.

You've got my attention, where do I find more info on this?

The other thing to be weary of with MIG welding Ali is cold lap joints wear you don't get penetration into the parent metal.

Ally welds a lot better with a mig if ya pre-heat it .

[schrodingers cat]

Its great that you want to weld some stuff. Have you got a spare 5 years?

I'm not being an asshole, its just that welding is a 80% science, 20% art.
Cheap welders have their place but snotting a couple of bits of metal together isn't welding in my book. There is a huge field of knowledge about materiels properties and behaviours you need to know something of as well as joint design and weld area prep

Rather than buy a welder and learn, consider ways that you could learn to weld and then you'd be better informed when/if you decide to buy.

If you were going to buy anything to put in the shed at home and phaff around with I'd get an oxy/acetylene gas set. Hours of fun and oh so versatile in the right hands.

[Pussy]

Its great that you want to weld some stuff. Have you got a spare 5 years?

I'm not being an asshole, its just that welding is a 80% science, 20% art.
Cheap welders have their place but snotting a couple of bits of metal together isn't welding in my book. There is a huge field of knowledge about materiels properties and behaviours you need to know something of as well as joint design and weld area prep

Rather than buy a welder and learn, consider ways that you could learn to weld and then you'd be better informed when/if you decide to buy.

If you were going to buy anything to put in the shed at home and phaff around with I'd get an oxy/acetylene gas set. Hours of fun and oh so versatile in the right hands.

Good call.
I am trade certified/time served Fitter Welder.
Welding a boiler tube in some near inaccessable place to BS 4872 isn't very difficult... when you have the experience. Neither are most welding jobs... when you have the experience.
To successfully TIG weld aluminium, you do need a decent welding machine. For the cost, it's easier to get the experts who do it every day, to do your specialised job.
I'd be keen to hear about TIG welding aluminium with DC, too! I've been off the tools for a few years.... but have never seen or heard of alloy being TIG welded with DC

[Howie]

You've got my attention, where do I find more info on this?

Ally welds a lot better with a mig if ya pre-heat it .

Good call.
I am trade certified/time served Fitter Welder.
Welding a boiler tube in some near inaccessable place to BS 4872 isn't very difficult... when you have the experience. Neither are most welding jobs... when you have the experience.
To successfully TIG weld aluminium, you do need a decent welding machine. For the cost, it's easier to get the experts who do it every day, to do your specialised job.
I'd be keen to hear about TIG welding aluminium with DC, too! I've been off the tools for a few years.... but have never seen or heard of alloy being TIG welded with DC

ok the only reference I could find on the net was this

Aluminum and magnesium

A TIG weld showing an accentuated AC etched zone
Closeup view of an aluminium TIG weld AC etch zoneAluminum and magnesium are most often welded using alternating current, but the use of direct current is also possible, depending on the properties desired. Before welding, the work area should be cleaned and may be preheated to 175 to 200 °C (347 to 392 °F) for aluminum or to a maximum of 150 °C (302 °F) for thick magnesium workpieces to improve penetration and increase travel speed. AC current can provide a self-cleaning effect, removing the thin, refractory aluminium oxide (sapphire) layer that forms on aluminium metal within minutes of exposure to air. This oxide layer must be removed for welding to occur. When alternating current is used, pure tungsten electrodes or zirconiated tungsten electrodes are preferred over thoriated electrodes, as the latter are more likely to "spit" electrode particles across the welding arc into the weld. Blunt electrode tips are preferred, and pure argon shielding gas should be employed for thin workpieces. Introducing helium allows for greater penetration in thicker workpieces, but can make arc starting difficult.

Direct current of either polarity, positive or negative, can be used to weld aluminum and magnesium as well. Direct current with a negatively charged electrode (DCEN) allows for high penetration. Argon is commonly used as a shielding gas for DCEN welding of aluminum. Shielding gases with high helium contents are often used for higher penetration in thicker materials. Thoriated electrodes are suitable for use in DCEN welding of aluminum. Direct current with a positively charged electrode (DCEP) is used primarily for shallow welds, especially those with a joint thickness of less than 1.6 mm (0.063 in). A thoriated tungsten electrode is commonly used, along with a pure argon shielding gas.[23]

Which is from wikipedia over here,

Like you Pussy I am a time served, Trade certified Fitter and Welder, I only knew about the DC TIG welding of aluminum as I was doing that, and also Mig welding of 99% pure aluminum for electrical Buss bars back in the eighties. Oh and the odd Aluminum bike part seemed to sneak in at times. Magnisum ones were fun some repaired easily, some burst into flames, depending on the amount of Magnisum in them.

[bsasuper]

Dont forget you can gas weld Ali

[schrodingers cat]

Righty ho then - here's the skinny...

You can gas weld aluminium right? Nice agressive flux, 10% silicon filler rod and a NEUTRAL flame.

So what is a TIG but a heat source?

The trouble with aluminium is that Aluminium oxide (Al/O) has a melting point far above aluminium (Al)
The problem being that aluminium oxide forms by simply leaving the metal sitting in air. Which is just as well as Alumnium oxide being so tough and all protects the base metal (just like chromium oxide in stainless)
When heated the Al/O holds its shape while the pure metal inside becomes liquid - cue a shapless blog on the bench and or a big hole.

Alternating current changes 50 times a second (50Hz - NZ standard electrical frequency) from electrode positive to electrode negative.
As the polarity changes the arc tops and restarts at the 'zero' point and a high frequency unit is neccessary to allow the arc to restart itself. The HF unit shoots a little arc which will bridge up to 10mm.

(If you want to see something cool - set a TIG on AC and hold the electrode 6 -7 mm above your thumbnail and turn it on. A little lightning bolt will shoot out and play across the surface of your nail. It doesn't hurt in short bursts)
As the previous poster has pointed out the heat distribution between the electrode and work changes depending on polarity

Essentially, electrode neg puts more heat into the work = penetration. Electrode positive puts more heat into the electrode but the ionisation of the shelding gas provides a 'cleaning' action on the metal.

Good AC TIGs allow you to alter the AC balance (to offset the cycle for greater or lesser penetration at the expense or advantage to the cleaning action) As an aside, the better AC TIGs also allow you to alter the Hz of the AC current

So back to DC aluminium welding.

Electrode positive obviously as we want to remove the oxide layer.
Since there will be more heat in the elctrode we will use a larger electrode than if welding elctrode negative (the more common state)

Weld prep is crucial. The process is far less tolerant of contamation. Mechanically clean the weld area and wipe with acetone. The filler wire has an oxide coating too so clean and wipe it as well. Better to use gloves and keep the grease/oils from your hands out of the mix. Use a higher gas flow than usual and preferably a 'gas lens' to dissapate the gas more evenly and prevent localised cooling

Begin welding. The appearance through the lens is different. You don't see the same shiny weld pool as there is always a degree of oxide layer. The filler rod has to be fed more deliberatly into the molten pool (in and under the oxide floating on top) and it is more critical to not pull the rod back too far and expose the heated tip to air

Because of the greater heat split into the electrode you need to use more amps than if welding the same thing AC and the torch will get hotter - consider a water cooled torch

And thats it really.
About the only advantage that I know of with this technique is that prevents spurious electrical emissions fron the high frequency unit

How do you tell a magnesium alloy. Strike an arc on it. The magnesium will give off a greenish tinge.

Oh and did you realise you can 'bronze' weld with your TIG...?

Ps - too lazy to verify all this info. This is off the top of my head but is pretty much right. Feel free to correct any innacuracies

[Sensei]

Wow some interesting facts & stuff , never knew Ally welding etc could sound so hard to do . Alittle knowlege can be a dangerous thing .

[schrodingers cat]

A little knowlege can be a dangerous thing .

Only in the wrong hands...

[Sensei]

[QUOTE=schrodingers cat; Only in the wrong hands

Abit more to it than just reading some stuff off the net or being able to strike an arc on a piece of material then .....

[Howie]

[QUOTE=Sensei;1129916983][QUOTE=schrodingers cat; Only in the wrong hands

Abit more to it than just reading some stuff off the net or being able to strike an arc on a piece of material then .....[/QUOTE]

A little, we haven't really touched on choosing the right filler wire for the right material yet, as there are so many different grades and types of aluminium.

[schrodingers cat]

Abit more to it than just reading some stuff off the net or being able to strike an arc on a piece of material then .....

Hey it's not impossible to learn it. We all started somewhere. However thats why I ask people if they have a spare 5 years.

Having a go is all good if only to reinforce what a skill welding really is and how undervalued it is. You may find, just like all the people on those TV cooking shows, that this is actually your lifes calling. Imagine - a lifetime of cold dirty workshops and crap pay. Hmmmmmmmmmmmmmmmmmmm

[soundbeltfarm]

just a bit of a hijack,
i am looking at a mig lincoln 180c , a guy told me i be better off with an inverter type mig instead of the type i am looking at and that lincoln are going towards inverter migs now.
confuses me . i just want a decent mig for on the farm. whats your thoughts on this welder?

[Sensei]

[QUOTE=schrodingers cat;1129916992]Hey it's not impossible to learn it. We all started somewhere. However thats why I ask people if they have a spare 5 years.

Yep seen it all & heard it as well , some do have natural skill others should just leave it to those that can .....