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Up Topic Welding Industry / General Welding Discussion / tig welding alluminum
- - By tsalagi (*) Date 04-16-2007 04:35
i weld alot of stainless and steel, never have welded alluminum. a friend of mine put a hole in his flat bottom boat and i couldn't fix it. i don't understand why.
i have a miller shopmate 300 dx. it is a dc machine, i tried dcen and dcep. i was using 1/8 tungston and 1/16 filler rod. on dcen i blew through, on dcep i kept melting my electrode.
does aluminum weld that much different or do i need a high freq. or ac machine?
Parent - - By Bill M (***) Date 04-16-2007 12:23
get an AC machine and get some pure tungsten or zirconiated tungsten.  Don't use a 2 percent thoriated tungsten electrode.
Parent - - By fbrieden (***) Date 04-16-2007 12:59
Miller Dynasty 300's require EWTh-2 for proper arc stability when welding aluminum with AC.
Parent - - By ssbn727 (*****) Date 04-16-2007 15:53
Hmmm - no disrespect fbreiden but, I did'nt know that it was a "REQUIREMENT" as opposed to a "RECOMMENDATION"...

I say this because, one must consider what specific type of AC/DC power source that's being used as not all power sources used today (YES - 2007!) are exclusively inverter type square wave power sources... There are differences in the ouput characteristics when one compares brand "A" to "B" or "C" for that matter so, I for one would not "carve it in stone" that only one specific type of "Wulfram" alloy (Tungsten as the Germans spell it!) should be a "requirement" on a specific brand of square wave inverter type power source like the Miller Dynasty 300 as opposed to a "recommendation" especially since there are many alternative blends of tungsten alloyed electrodes that can perform as good of a job so long as they are readily available.

One must also consider the potential long term harmful effects of breathing the dust eminating from EW Th-2 as a result of grinding the electrode to it's "Recommended" shape & contour.

Respectfully,
Henry
Parent - By Kix (****) Date 04-16-2007 15:59
Yeah like said above you need a machine with A/C high freq continuous ability.  Pure tungsten sucks and so does thoriated for welding aluminum with any machine.  2% Ceriated is where it's at brotha.
Parent - - By Lawrence (*****) Date 04-16-2007 16:10 Edited 04-16-2007 16:18
Gonna take a small issue here

Not that this has much to do with the original post....... (AC for aluminum for the Original poster)

Thoriated electrodes are certainly not a requirement for Miller inverters like Dynasty.

Thorium will work with advanced square wave power supplies and AC as long as you don't overheat it.

Cerium is a better choice for AC aluminum with Dynasty (as Miller Electric recommends) The reason it is better; is that when cerium overheats, it has a tendency to ball at the end of a pointed tip. (pointed tip also recommended by Miller for Dynasty).  Thorium electrodes when they overheat tend to create numerous little growths at the end which distorts the arc, also thorium electrodes tend to spit across the arc rather than ball at the end, they will also split longetudinally when run with alternating current...

Cerium and Zirconium are the electrodes of choice for AC welding of aluminum with inverters or transformer rectifiers..... I would not recommend thorium or pure tungstens as a first choice under any circumstance.

http://millerwelds.com/education/TIGhandbook/pdf/TIGBook_Chpt4.pdf

http://www.millerwelds.com/education/articles/articles42.html
http://www.millerwelds.com/education/articles/articles43.html
http://www.millerwelds.com/education/articles/articles46.html

View C is an abused Thorium electrode... if you start to see the little growths, you may assume tungsten has transferred across the arc into the molten pool... and nobody likes that :)
Parent - - By ssbn727 (*****) Date 04-16-2007 16:56
As always - "Lawrence of Wulfram" has done it again!!!

I want to personally express to you my gratitude in your presentation of the facts in this thread and I always look foward to your input regarding the intricacies involved when working with the GTAW process!!!

Your experience and knowledge with respect to this process, I consider second to NONE!!!

Respectfully,
Henry
Parent - - By tsalagi (*) Date 04-16-2007 21:31
so basically, a guy needs an ac machine to do alluminum. thanks for the help, proof that sometimes it is the machine.
Parent - By ZCat (***) Date 04-16-2007 21:46
make sure you clean the material thoroughly. aluminum puddles don't like dirt.
Parent - - By ssbn727 (*****) Date 04-17-2007 14:42
Not necessarilly!
One can GTA weld Aluminum with a DC-EN, using helium as the shielding gas set-up as long as the material thickness is adequate which I do'nt think was the case for the aluminum boat hull because, 1/2" or greater is the recommended range for GTAWelding Aluminum with helium as oposed to argon...

Ac makes it easier & cleaner with or without High Frequency so long as a square wave is such (someone else can elaborate further because I'm pressed for time at the present!) whereby the appropriate "cleaning action or Etching" can be achieved to breakup the Aluminum surface oxide layer so that the base metal can coalesce rather nicely with the filler metal hence, depositing some really nice welds with no or minimal cleaning required as a result. This would not be the case with DC-EN & Helium as the shielding gas but, the joint would be welded soundly sdo long as the proper precautions were met beforehand like removing the surface oxide layer immediately prior to performing the actual welding otherwise, you'll have one heck of a mess on your hands!!! I would add more but I'm pressed for time so, maybe someone else will chime in!

respectfully,
Henry
Parent - - By Lawrence (*****) Date 04-17-2007 16:17 Edited 04-17-2007 16:50
AC Etching of Aluminum otherwise known as Cathodic Bombardment
This phenomina occurs during the reverse polarity (EP) side of the half cycle of any alternating current welding arc, whether the wave form is a Sinewave or a Soft Squarewave (from a transformer rectifier) a True SquareWave or TriangularWave (from an inverter). The Ions come down at the same instant the electrons go up (an exchange), these Ions bombard the work surface and blast off the aluminum oxide which forms on all aluminum alloys

The reason abrasive or Chemical surface prep is recommended prior to welding even with the cathodic bombardment, lays in the nature of the Aluminum oxide itself. This Aluminum oxide has a melting point more than twice as high as the aluminum it covers and it is also nearly as hard as diamonds. The problem is that aluminum oxide is also porous and has a tendency to hold in its matrix hydrocarbons (oil, grease, solvants) or moisture (a source of hydrogen). 

So if we neglect agressive surface prep (abrasive or chemical) and depend only on Cathodic Bombardment to clean our aluminum we invite the risk of Hydrocarbons or Water volitizing in the welding arc and transferring into the molten aluminum (which is very soluable to Hy when liquid)

There  is much more to say but for now... The moral of the story is that for GTAW of Aluminum (AC or DC) best practices always include aggressive surface oxide removal prior to welding operations.
Parent - - By MDG Custom Weld (***) Date 04-17-2007 17:48
Lawrence your overall knowledge of GWTA and your presentation here are fabulous, and SSBN your candor is always humorous :)
 
We don't production weld aluminum, and don't even try to be aluminum code worthy, but on occasion we make railings, fix boats, and any other odd aluminum repair.  We use the Dynasty and Fronius inverter machines and usually run on the higher end on the Hz wave, and are able to get quality welds using any one of the tungsten listed here.  Other than the welder himself having to "reshape" the tungsten more often, the inverters will weld fine using anything.  Sure some alloys are better than others, but for most jobs pure and 2% are the default.  As for one thinking they can go spend 100 bucks on a pack of special alloy tungsten and all of their aluminum welding problems will be solved, think again.  90% of aluminum woes are from the material or filler being "dirty", and poor gas coverage.  Aluminum differs from steel in that when the gas coverage is not adequate, you don't always get porosity bubbles, but you usually get the same poor molten flow and black soot (oxides) floating in the puddle.  Many new welders confuse this with the material not being clean, and don't even look at the gas as a problem.

Mark
Parent - - By Lawrence (*****) Date 04-17-2007 19:55
A box of 3/32 Ceria Electrodes can be gotten for about $20 bucks...... Not really that much more than pure and a whole lot more versatile and will carry about twice the current of pure  :)
Parent - By MDG Custom Weld (***) Date 04-17-2007 20:32
That is a surprise for me...Considering the latest quote from the local welding supply shop was $92 for 1/8 Ceria.  Looks like I need to go to the other local shop from now on!!  He would have been laughing all the way home after I bought that one!!
Parent - - By banshee35 (**) Date 04-18-2007 01:11 Edited 04-18-2007 02:14
what cfh would you recommend for shop welding 3"x3"x1/4"  aluminum angle with 2% thORIATED w/argon? I'm using a shopmaster 300 set on ac @ about 180-200 amps and 15-20 cfh. sometimes when i start i get a bunch of black/ grey-black junk until the puddle clears up and gets smooth. its a pain in the rear to get it going. im using 3/32 tung, w/ 3/32 4043 filler. i do have a high freq. arc starter set on about 70% intensity and high frequecy on continuous. thanks
Parent - - By MDG Custom Weld (***) Date 04-18-2007 10:32
All of our aluminum welding is done 25-35 CHF with 100% Ar.  Using a 1 or 2 second preflow is also used to ensure good arc starts.
Parent - By banshee35 (**) Date 04-18-2007 16:42
today i tried a different approach. I preheated the alum. joint, swapped to pure tungsten, set gas floe to about 25 cfh, and it welds so much better. on my high freq. box, I dont have ant adjustments other than high freq intensity.( miller hf-250)
Parent - By 357max (***) Date 04-19-2007 14:08
Shopmate 300 has a DC constant voltage weld output & the 300 DX has both a DC constant current and constant voltage weld output. The discontinued Shopmaster 300 is a square wave AC/DC constant current and constant voltage weld output. It is quite a versatile machine.
Tungsten photo "E" should be the desired "balling/radiusing" of tungsten not the "A" for alternating current. If "A" occurs for the welding amperage used; increase the tungsten diameter one size ie 1/16" to 3/32". Sharpening the tungsten and radiusing the end focuses the arc. The reason for "balling" the tungsten is seen in tungsten "C"; it is to fuse or weld those projections/nodes/nodules together. If thorium tungsten is balled forming tungsten "A" compare the surfaces of Pure vs thorium tungsten balled. The face of the ball on thorium will have several dimples/divots. This severity of dimples will also depend on the manufacturer of tungsten; the size of oxide particles, mixing of the oxide etc.
For welding boat skins use a very small filler wire; like the 3/64" GMAW/MIG filler wire.
Parent - - By 803056 (*****) Date 04-17-2007 21:29
Lawrence;

Excellent presentation and great photos!

Al
Parent - - By Tommyjoking (****) Date 04-19-2007 09:30 Edited 04-19-2007 09:43
Damm far out........I am way outclassed here these guys are like gurus.

tsalagi

To answer your question directly:

You need an A/C capable TiG welder with High frequency equipment.  This will allow you to create and carry a puddle which will look sane and normal to you and you simply add filler material to suit.   (BTW> most aluminum boats are made from 40-50 series metal so a 4043 aluminum filler would work out just dandy).  And you can use cheap  2% thiorated tungsten to do the work.....I doubt considering the job you would find much difference between it and stuff that costs three times as much.  Brush your repair area with a brass or a stainless brush before you weld it.   That boats been in the water and the metal is NOT clean.

BTW.  Lawrence

Cool pictures and spot on advice!!!!! BTW.  to get a good little ball going on your tungsten just switch over to D/C REVERSE   and stomp it abit and it will ball up nicely.....As far as cleaning goes......Aluminum requires good housekeeping.....REMOVE your mill finish and clean with a solvent that evaporates completely....Acetone works pretty good if you can manage the keytones.   The mill finish will affect your end result ...it is specifically made to seal and keep the alloy as corrosion free as possible....its not allowed in the weld specs I deal with.....take it off if you can BUT you got to clean that stuff up before you weld it.
Parent - - By tsalagi (*) Date 04-20-2007 10:08
thanks alot everyone for the input. makes me want to start doing alluminum and then ask myself later why did i wnt to get into this? sounds like there is alot to learn about this creature.

anyway, my boss said that we could bring the boat in the shop some weekend. after i learn a little about the machine i'll see how it feels. it kind of sucks that my first lesson will be overhead. jump in with both feet huh? if i cant do it like that... keep on tryin.
Parent - By billvanderhoof (****) Date 04-21-2007 04:55
If you can get at both sides you could make a patch coat it with some sort of sealer and rivet it on.  They make pop rivets with closed ends but they are hard to find and I prefer conventional rivets anyway.
Bill
Up Topic Welding Industry / General Welding Discussion / tig welding alluminum

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