I've got to respectfully disagree with you here Bozak!
On the older machines that had "sine wave" output characteristics, zirconiated (ZrO2 - Brown stripe) tungstens were better than pure especially when welding Aluminum!!! On the newer "squarewave" type power sources, ceriated (Orange stripe) or 2% thoriated (Red stripe) tungstens can be used but, for the best performance, lanthanated (La2O3 - Blue stripe) tungstens are recommended.
Here's an excerpt directly from Miller's website and below is the link to it which addresse the specific power source the originator of this post is using... A Miller Dynasty 300 DX:
Why would I use Ceriated or Thoriated tungsten instead of Pure?
With the introduction of new power source technologies, the use of pure tungsten is decreasing.
Pure tungsten melts at a lower temperature causing it to easily form a rounded ball at the tip. When the ball grows too large, it interferes with your ability to see the weld puddle and causes the arc to become unstable. Ceriated tungsten can withstand higher temperatures and works very well with the new squarewave and inverter machines for the following reasons:
* Holds a point longer and starts well at low amperages.
* Can be used on both AC and DC polarities. When welding aluminum, it has become very acceptable to grind a point on ceriated tungsten (especially when welding on thinner materials).
* Allows welding amperages to be increased by 25-30% compared to Pure tungsten of the same diameter.
Here's the linkthat describes just what I said above... scroll down a bit when you get to the link:
http://www.millerwelds.com/education/tech_tips/TIG_tips/hints_tips.htmlHere's another link that covers the basics in GTAW of Aluminum:
http://www.millerwelds.com/education/articles/articles15.htmlHey Stratline! Check out the Miller version of their TIG (GTAW) Handbook in .pdf format... Here's the link to the main page which has links to all of the chapters online to be downloaded as a .pdf :
http://www.millerwelds.com/education/TIGhandbook/Here's another link to their "Guidline to Gas Tungsten Arc Welding (GTAW) Handbook in .pdf format:
http://www.millerwelds.com/pdf/gtawbook.pdfThis article better explains Ac GTAW balance control and how it relates to "Squarewave" power sources
http://www.millerwelds.com/education/articles/articles82.htmlSure! one outr of twelve is'nt bad so long as we're talking about alot of weld length in between!!! For instance, if one is welding 12 parts and the total weld length of each part is 2 inches then do the math!!!
Not too impressive if this is the scenario... on the other hand if the total length for each part is 20" then that changes everything so, it's all in the details!!!
Nowadays you can achieve 100% defect free welds on Aluminum!!! I'm not talking about discontinuities here Bozak! I'm talking about defects! I mean look at the external main fuel tank on the space shuttle that NASA uses!!! that's Aluminum!!! Of course they used a Variable Polarity Plasma Arc Welding process that they came up with themselves with 100% defect free welds!!! Martin Marietta has been producing them for years down near your neck of the woods!!!
Edited 19:10: I almost forgot Stratline! Here's the link to the Miller online (GTAW) TIG Welding Calculator:
http://www.millerwelds.com/education/calculators/tig_amperage_calculator.phpNow remember that this calculator presumes that you're using a traditional sine wave output characteristic type of power source so if it recommends Green band otherwise known as pure tungsten, and you're using an inverter squarewave output characteristic type of power source - then do not follow the recommendation, and use either ceriated or lanthanated tungsten instead - especially for your Miller Dynasty 300 DX! I hope this helps!!!
Respectfully,
Henry