Quote Originally Posted by Normanby View Post
Thanks for the replies and suggestions.

Will keep going, just wish I had better understanding of the machines instructions.
Post a picture of the machine controls and we may be able to explain what's what.

As others have said, AC welding is noisier than DC as the machine is generating a high frequency AC current. In general, the higher the frequency, the more focused and narrower the arc is and the more concentrated the heat. I generally run around 125-150 for most ally stuff but it varies depending on the job.

The trick with ally welding is to get rid of the surface oxide layer that melts at a far higher temperature than the underlying aluminium, wire brushing helps but the AC waveform is the key to the ongoing removal of the oxide layer as the weld progresses. The balance control dictates the percentage of time the AC wave-form is electrode negative (EN) and the percentage it is at electrode positive (EP). When the electrode is negative (as it is in most DC welding) 70% of the heat goes into the work and 30% goes into the tungsten, this gives good penetration. When the electrode is positive the reverse is true and 70% of the heat goes into the electrode and 30% into the work, as part of the "reverse"" polarity the oxide layer on the surface of the ally is removed allowing the arc to melt the ally underneath.

So the more your AC Balance is biased towards electrode positive the more cleaning action you get but the less penetration you achieve (and the more likely you are to melt the tungsten). Conversely, biasing towards EN gives penetration at the expense of cleaning action. You should see a whitish band either side of your bead, this is the area being cleaned by the EP part of the wave-form. For most ally work I leave my machine set to 0 (ie balanced), maybe setting it to 10% EP for hard to clean metal.

Personally I'm not a fan of thoriated tungstens on AC, I find ceriated or zirconiated to be easier to use.

As for technique, ally is easier with a pedal. You need a quick burst of high amps to establish the puddle (look for the area being heated to take on a fluid silvery mirror look) then the ability to back off the current as welding progresses and the heat builds up in the work. It's do-able without the pedal but harder to control, you need to adjust the travel speed to compensate for the changing heat load in the metal.

2T and 4T just controls how you turn the torch on and off, 2T means the torch fires when you press the button and shuts down when you release the button. 4T means the torch fires up when you press the button and stays running until you press the button again. When I'm not using the pedal I leave mine in 4T mode so my wrist is more flexible when manouvering the torch,