tig welding stainless/alloy advise/which tig??

[powernut]

after some advise if anyone can help ,, as i know theres differnt types ,which im unsure how they work ,
as im after it for more of a hobby use with tiging stainless and alloy?
so assume i need a ac/dc tig welder around 160/200amps max single phase
things im unsure about
say im tig welding with alloy
do i use a alloy rod?/argon gas/make sure the alloys clean?
or is it best to heat the alloy up with oxy/propane

 

[wyn]

An ac/dc tig is the way to go if you want to do a bit of aluminium.

You would need aluminium filler rods..something like a 5356 or 4043
Pure argon will be needed for any type of tig welding.
With aluminium the metal would need to be clean..probably wire brush it with a stainless wire brush.
Heating the aluminium up can be helpful if you are welding thicker material.

 

[hotrodder]

Pure argon is the only gas you'll need for TIG, works with all materials

As you say need an AC/DC unit to weld aluminium. 160A would be the absolute minimum, 200A far more useful as Al really soaks up the heat. Only really need to preheat thicker sections and castings, any heat source works oxypropane obviously faster than propane-air. Moisture is one enemy of aluminium welding, can result in hydrogen porosity

Various different aluminium filler alloys depending on the parent material alloy, 4043 and 5356 most common. Cleaning depends on the state of the parent material, typically brushing the joint with a STAINLESS wire brush/scotchbrite (reserved soley for the purpose) to remove the naturally occuring oxide layer. Older the material the thicker the oxide/more important it can be, new clean aluminium needs very little attention. Oily/dirty/greasy stuff should be degreased and mechanically cleaned (again a source of hydrogen and thus porosity) before a final brush of the weld joint

 

[irondarren]

In Tig you have two basic types of machine, inverter based machines and tradition transformer type machines, either will get you around 200amps on a single phase supply.
DC with pure Argon is fine for most materials steel,stainless etc, but if you are welding aluminium then you need a machine with AC output, pure Argon is OK for aluminium welding but welding thicker sections an Argon/helium mix is recomended.
As far as clean goes, Arc welding puts up with some rather dirty metals and still welds ok, Mig likes it clean but will accept a certain amount of 'dirt', TIG has to be real clean, the cleaner the better. In welding mild steel with TIG its better if the mill scale is ground off to show shiny steel, if not the mill scale seems to pick up onto the tungsten.
The other difference is there is one type of tungsten electrode for welding DC and one type for welding AC, i believe there was a universal electrode that run both DC and AC, not sure how good they were (speak to weldequip about that one)

 

[powernut]

this is great and very helpfull advise , dont get me wrong i can stick/migand braze fine , but due not know mutch regards tig welding especaily in alloys ,
ive been on ebay searching for tig welders and most are telling me that a dc tig invertors will weld alloy which im worryed about ,, so basicly i defo need a ac/dc tig welder 160/200amp single phase , as basicly i want to make my own alloy short runner for my car ,as the stainless one is causeing heat soak which ended up damageing the rear 3 pistons,
1 bottle of argon
2 stainless brush
3 ac/dc tig welder 160/200amps
4 when tiging alloy do i just use a alloy filling rod as ive noticed they normal come with tungstun rods?

 

[wyn]

The tungsten electrode is part of the torch that creates the arc. the filler is used the same as gas welding. I'll see if i can find a pic.

Found a pic here (4th post) from hotrodder, showing the tungsten electrode protruding from the shroud

 

[Wozzaaah]

ive been on ebay searching for tig welders and most are telling me that a dc tig invertors will weld alloy

No, they won't!
Anyone who sells machines and tells you that quite clearly doesn't know a thing about what they're selling so in my opinion should be avoided.
Aluminium can only be welded properly using AC.
Just out of interest, can you post any of the links to said sellers? I'd be interested to see their sales gumph.

 

[hotrodder]

Not defending the ebay junk peddlers but 'alloy' isn't an abbreviation for aluminium. It's what most of the metals we work with are, steel being an alloy of iron and carbon for example

[/pedantic]

 

[busa]

Not defending the ebay junk peddlers but 'alloy' isn't an abbreviation for aluminium. It's what most of the metals we work with are, steel being an alloy of iron and carbon for example

[/pedantic]

I don't find that statement at all 'pedantic' hotrodder, actually I cringe a little every time I see a post from someone looking for advice on what kind of TIG set is required to weld alloy!

 

[pedrobedro]

An alloy is a material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal, like iron and carbon make steel, add chromium to make stainless steel or brass is an alloy of zinc and copper. The rod isn't tungsten, that is the electrode. A DC tig will weld any number of alloys but it will not weld aluminium.

 

[powernut]

well i carnt belive how helpfull this forium is ,,, i didnt exspect so mutch help and advise ,, ps i can add a few user name of the sellers ,as i assume there unsure them selfs due to the fact most only sell ill include a link of this one , if u look in the spec it say alloy ,,

Seller info
ronnoc1980 ( 99

Very high spec welder still in box never used comes with hammer/brush cost well over £250.Feel free to arrange a time to view
Output Current Range- TIG=20-130amps, MMA=20-115amps

Electrode Range- TIG=1.0-2.0mm, MMA=1.6-3.2mm
Buy with confidence from a 100% seller, any questions feel free to ask

next was this oscar200109 ( 3 )
100% Positive feedback
Inverter Welder,

professional welding equipment inverter, continuous power source ( DC )

Microprocessor controlled, single phase 240V -1 PH

160 Amp, 45% max output power

Weight: 4 Kgs

Voltage control, for generator connections minimum consumptions.

Electrodes: 1.6, 2, 2.5,3.25, 4.00, cont. welding.

Rutile, basic, Stainless steel, Cast Iron, Aluminum, Aloy.

Welding in same materials.& Tig welding.

Accesories:

electrode holder and mas pincer, welding cables, connectors, transport belt and carrying case.

R.R.P 590.00 POUNDS

 

[powernut]

i think this maybe ok but again regards a torch what kind and price im unsure
Cebora tig star 16. p Squarewave tig welder. Good condition

with regulator

Note: will need new tourch and bottle

Features
240V 130amp tig.
Duty cycle 130A @30%.
Suitable for mild steel,stainless steel,copper,aluminium and its alloys.
Welds all types of MMA electrodes including cellulistic.
Infinite adjustment of welding current.
HF arc ignition.
Torch trigger latching.
Adjustable up and down slope.
Low input requirements and power consumption.

On 21-Nov-09 at 14:18:38 GMT, seller added the following information:

AC/DC TIG WELDER

the one i wanted was this which i was outbid on which stated ac/dc tig welder
160amp
This is an 160amp AC/DC Tig 240v. went for 400

 

[powernut]

ps can some explain this scratch and pulse idea as some state differnert pulse rates ,,?

 

[wyn]

I have had a cebora tig star 16 p for the last 10 years or so. Good machine ..no problems at all..easy to use settings. Very nice for stick welding aswell

 

[busa]

A DC tig will weld any number of alloys but it will not weld aluminium.

Aluminium CAN be welded quite successfully with DC TIG although the technique is somewhat difficult to master and probably not for the occasional welder. The problem with using DC is that there is no arc cleaning action to remove the oxide layer. Aluminium melts at a lower temperature than the oxide so filler wire has to be physically pushed through, or under the oxide layer and into the molten pool below.

 

[pedrobedro]

Aluminium CAN be welded quite successfully with DC TIG although the technique is somewhat difficult to master and probably not for the occasional welder.

Aye and there's the rub (to quote Shakespeare) I've only heard of one person's experience of attempting it with DC and it was done in an enclosure with argon filling it and he went out and bought a Miller 200DX based on his results. He has been tig welding for over 30 years. You need a lot of DC power to melt the (ceramic) oxide layer on aluminium and it forms very quickly. Just because something can be done doesn't make it a good idea.

 

[powernut]

ill stick with the ac/dc idea to make things a little easyer for a first time learner ,,,

 

[busa]

Aye and there's the rub (to quote Shakespeare) I've only heard of one person's experience of attempting it with DC and it was done in an enclosure with argon filling it and he went out and bought a Miller 200DX based on his results. He has been tig welding for over 30 years. You need a lot of DC power to melt the (ceramic) oxide layer on aluminium and it forms very quickly. Just because something can be done doesn't make it a good idea.

An ill informed reply...........

The original Heliarc machines were all DC, with AC coming along some time later. There are several applications where DC is still used as the preferred method. If you've only ever heard of one person welding Ali with DC then you really should read more, start here :

http://www.esabna.com/us/en/education/knowledge/qa/A-short-history-of-welding-aluminum.cfm

 

[toddy]

well not to say you should do this or anything but my old instructor from a welding collage befor for he came to the collage he worked for a massive company as a welding engeneer, his tital was europen welding engeneer, and did alot of work for the TWI.

and he had to find new ways of welding alu trailer tankers for bp due to the way they did it took too long and had loads of problems, and they once tryed and it worked wonderfull but cost too much, they welded alu on dc+ (when you normally use dc-) as well he did say if we ever had the chance to get any and use it on alu, use pure helium as it will give you a much better defined arc and will allow you wait around less.

 

[pedrobedro]

If you've only ever heard of one person welding Ali with DC then you really should read more, start here :

http://www.esabna.com/us/en/education/knowledge/qa/A-short-history-of-welding-aluminum.cfm

I don't mean internet people I've read about I mean real people I have met and worked with. Are you telling the original poster that he will be alright to buy a DC tig to weld his aluminium ? If not I can't see the logic in continuing this.