Otto Nobedder wrote:
Arno, that makes sense. The sharp transition of a square wave might even lead to tungsten deposition in the weld, when the current sharply/instantly changes from EP to EN.
I suspect there are more things at play and it's not the full explanation though.
Usually it's a combination of effects that stack up. Capacitance in the setup also plays a definite role and would be much more obvious on an inverter than on a sine-wave setup. It's never simple, is it?
Most of the documentation you find does revolve around the current characteristics of 'pure' tungsten vs. alloyed ones though. Not just the basic resistance but also other electrical characteristics.
I guess it's also one of the reasons why thoriated (and others) were developed in the first place for 'plain DC' welding as well as pure tungsten was hitting it's limits there earlier in the TIG development. Melting temperatures of the electrodes probably also affected by the alloying..
One thing that really changed on A/C with the inverters vs. transformers was the waveform that's generated. With the current generation machines that can 'overlay' waves-on-waves or even select different shapes like sawtooth you can get quite funky outputs
Of course things like putting your welding wire in a tight coil on A/C on an inverter is also not great as it starts to act like an inductor that resists current buildup because of the magnetic field that's generated in the coil and needs to break down again on each 'flip' of the polarity. Again.. It won't damage anything but higher frequency settings may lose some of their crispness when welding as the behaviour of the current and voltage on the torch end is no longer really what the machine is generating.
Bye, Arno.
The next job I get I'm going to try it without the Helium and see what happens. I'll be sure to post up the results.
