Tig welded most all materials for a long time, including aluminum, magnesium, stainless, inconel, hastelloy, invar, kovar, tool steel, and so on....
Recently got a Miller 300 Dynasty DX and my question is which tungsten to use on aluminum/magnesium while on AC current.
Miller insists on using 2% thoriated or ceriated on these applications, and I have had decent results with 2%.
Anyone find another tungsten type that works better?
How about lanthanated?? -Any better??
I do know from experience that ceriated craps out at higher amperages, but does run very well down low.
Any and all help appreciated.
Good Luck-brad
I read some of he miller literature and I think the indication was that under certain applications 2% Th was recommended. Here is the text from what I read
"
5. Select the right type of tungsten. For AC welding, the traditional practice calls for selecting a pure tungsten electrode and forming a ball at the end of the electrode. This still holds true for most applications and welding with a conventional power source. However, for making critical welds on materials thinner than 0.09 in., or when using a TIG power source with an adjustable frequency output, new recommendations call for treating the tungsten almost as if the weld were being made in the DC mode. Select a 2-percent-type tungsten (thorium, cerium, etc.) and grind it to a point in the long direction, making the point roughly two times as long as the diameter. A 0.010- to 0.030-inch flat should be made on the end to prevent balling and the tungsten from being transferred across the arc.
With a pointed electrode, a skilled operator can place a 1/8-inch bead on a fillet weld made from 1/8-inch aluminum plates. Without this technology, the ball on the end of the electrode would have forced the operator to make a larger weld bead and then grind the bead down to final size."
They do have a point regarding the ability to make small fillet welds with balled tungsten. I could never make a 1/8" fillet with AC on any thickness material.
Were you able to notice the ability to make smaller welds when you tried it with the tungsten prepared as above?
G Austin
For aerospace/aircraft applications the typical method to perform small fillet welds on Al was to use DC. This was normally used for heavier weldment's (>1/4"), but several companies have developed procedures using DC on thin gauge aluminum. I was very surprised the first time I saw this, but if it was good enough for General Dynamics, it must have some practical applications. Some applications prohibited oversized welds because the welds were difficult to contour after the part was assembled by welding.
I personally have always used the 2% on aluminum & mag. Have passed numerous performance tests using this electrode despite what others had recommended. With today's technology, AC welding current can be tailored to almost any application.
I've found the use of red or green tungsten was primarily dependent on the skill of the welder. I am planning to set up my little DC inverter in the garage to weld thin Al. The only change from steel or stainless welding will be the shielding mix and my technique. Will see what happens here soon.
DGLX if you run into any problems with your little inverter on DC al. let me know. I have been using this process with little and big inverters for years. It works good down to around .125 and I have welded heavy sections without all the amps and preheats that are required when using AC. I have only used it on 6061. If the application permits I'll use this over GMAW any day.
Plan to use it when I can get a few day's off to myself. Already ordered the gas and a Y fitting for the rig. I don't plan to weld anything exotic, just 6061 T6 remnants that friends donate. It's good to network.
I do lot's of steel, SS, brazing, etc. All very small stuff that makes my welder buddies eyes hurt to look at welds that small. Believe it or not it's good therapy for me, enjoy it mucho. One of my friends watched as I zipped up an open root corner joint 18 gauge SS pan for a client. He mentioned he had trouble seeing what I was doing (an old SMAW/FCAW dude). He was amazed at the finished weld. (So was I.)
Will post what developes.
Several things to consider.
If you have no concerns about Thorium radioactivity than it *can* be suitable for AC Aluminum welding, having said that my personal preference is not to use it. Thorium has a greater tendency to "Spit" (tungsten transfer into the pool) when overheated.
Miller recommends cerium, but they also recommend a sharpened electrode. If you have a water-cooled torch or are welding at current levels that don't cause melting your fine. I suspect that Millers favoring of cerium is also related to the inverter/arc starting of the Dynasty. Those of you who have run a Dynasty know that the machine requires a perfect electrode tip prep to get consistent arc starting, this is especially pronounced with 1/16 and 0.040 dia electrodes.
I prefer the pointed tip prep for most applications but choose Zirconiated tungsten because they will hold together just a little better when over heated. Zirtung will round off at the tip without spitting at the same temps a thorium tungsten of the same diameter will foul a weld. Zirtung performs with better arc transfer and higher current carrying capacity (melting point) than Pure.
The moral of the story is that all of the choices (thorium, zircon, cerium) can be acceptably used as long as you understand and take into consideration the shortcomings of each.
Our trials show that lanthanum is not well suited for A/C aluminum. (poor arc stability at lower amperages)
DGXL correctly states that DC- (with helium) can be employed for even fairly thin stuff. But keep in mind those manufacturers have put in the time and fixturing and heat sinks to create very close tolerance fitups, and there surface prep is the best that money can buy. You can do it but the associated cost may be prohibitive.
Lawrence
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