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TIG arc depends on ionized gas to carry an arc. Sine wave 60 HZ AC the tapering to a zero current, then reestablishing a new one gives sufficient time to lose ionization. HF overrunning current maintains ionization, but still the return "stroke" is hampered by the oxides, and contamination on the larger surface of the workpiece. This work negative stroke brings with it lots of heat. Sine wave machines, even at 50% balance don't heat the tungsten as much.
Square wave machines are more effective at establishing the return stroke. They bring lots of heat with it. Pure tungsten won't resist heat well enough, it melts into too large a ball. I like nearly any tungsten for AC except pure. I use as large a tungsten as possible, and grind very blunt, let it round nose a bit. Set balance as high as you can make work. Most sharp tungsten work for DC
"Electrodes with rare earth (mixed oxides). In comparison to thoriated electrodes this electrode is less harmful to the environment and not radioactive. The electrodes offer excellent ignition characteristics and consistent welding properties. They are universal and suitable for all applications in the whole range of DC and AC welding for non-alloyed and high-alloyed steel, aluminium, titanium, nickel, copper and magnesium alloys. Because of their great ignition properties they are also suitable for automated welding. Due to the low electrode temperature, they offer an increased current carrying capacity and longer service life than thoriated electrodes." Colour-coding: E3® = Purple
It's not that it's harmful, it's just not optimum. You get more arc control with a pointed tungsten, and pure tungsten (I hesitate to call tungstens by the color band at the end), won't hold up to the heat of a modern square-wave inverter output, and it balls too quickly. Your dynasty700 will output a square-wave AC unless you change it to soft-square or sine- output. One of the major advantages of going "inverter" is for increased arc control and directivity, yet using pure tungsten that balls reduces both of those desirable qualitities of a machine like a Dynasty700. Kinda like buying a state-of-the-art firearm with laser-adjusted optics on the scope for the utmost in precision, then using the cheapest ammunition you can find. Will it fire? Sure. Will it hit the anticipated target? Only if you're lucky.
I have recently learned that using green tungsten in an inverter machine is a no-no. I have been welding for over 15 years and I have never heard this until now when I purchased a Dynasty 700 machine. I have used the purple for a while and I am not very fond of it so far. I started using the green again and it works fine(if not better) in terms of life and performance. Does anyone know what difference it makes or if it is harmful to use the green? Thanks for everyones' input.
I have recently learned that using green tungsten in an inverter machine is a no-no. I have been welding for over 15 years and I have never heard this until now when I purchased a Dynasty 700 machine. I have used the purple for a while and I am not very fond of it so far. I started using the green again and it works fine(if not better) in terms of life and performance. Does anyone know what difference it makes or if it is harmful to use the green? Thanks for everyones' input.
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