Did anyone think of this question? (tig)

admin

Just sitting here reading about the properties of tig welding and read that when welding mild steel on dc that there is no cleaning action.My question is ......with the new advanced square wave technology , why couldn't you upset the balance to say 90-10 and give yourself a pit of cleaning and most of the penetration
Reply:I think this is a great question, something most people wouldn't consider, and probably has not really been studied.The cleaning action of the DCEP portion of the AC waveform is very important to Aluminum since the oxide forms so readily and it melts at a much higher temperature than the base metal (don't have time to look up temps now).Generally oxide is not a big issue with steel and people clean and remove scale/rust before attempting to make a nice TIG weld, but what could it hurt to add a small percentage of DCEP?  It may help, particularly on a very critical weld, or possibly a high nickel or exotic alloy.  There was some discussion on this forum concerning straight AC TIG on steel, which seems perfectly logical to me, if all you have is AC.  I think the only issue is that AC heats the tungsten more and so the maximum amperage for a given electrode diameter is less on AC.  Somebody here did some steel welds on AC and reported no problems.
Reply:I think pulser hit the nail on the head.  The biggest problem is that aluminum's oxide melts at a much higher temp than does the base metal you are trying to weld.  I think oxides on mild steel just make it hard to start the and maintain the arc...There is also no real contamination problem with hitting the surface with a grinder...in most ordinary circumstances, that is.Smithboy...if it ain't broke, you ain't tryin'.
Reply:Yes.....http://www.millermotorsports.com/mbo...t=wave+balance
Reply:Main advantages I can think of with AC on steel is arc focus, and possibly some variation in puddle behavior. Esp on a machine with adjustable frequency. I doubt there is any cleaning action because a) iron oxides arn't terribly adherant, b) don't form real fast after cleaning the material, and c) melt at lower temp than steel. The inert gas actually provides a little reducing action on the weld metal, as oxygen liberated at the surface of the weld pool is swept away.