Re: cellulosic SMA inc. wet - understand meas. voltage?

Richard Smith wrote:
Hi everyone

Can someone explain these results from measuring arc voltage while
"stick" welding?


All 2.5mm (3/32nd-inch) diameter:

+-------------------------------------------------------+
|7018 |Bohler EV50 |22V |72A|
|---------+---------------------------------+-------+---|
|6013 "R" |straight rutile |25V |62A|
|---------+---------------------------------+-------+---|
|6013 "RC"|Zodian Universal rutile-cellulose|21V |76A|
|---------+---------------------------------+-------+---|
|6010 |Foxcel |30V |62A|
|---------+---------------------------------+-------+---|
|6010 |Foxcel - wet |28V |64A|
|---------+---------------------------------+-------+---|
|6011 |Arcos Nu5 |20V-25V|62A|
|---------+---------------------------------+-------+---|
|6011 |Arcos Nu5 - wet |30V-35V|63A|
+-------------------------------------------------------+

Welding machine was Murex Transtig AC/DC 250HF
on polarity DCEP
set to 20% on the 20A-320A range.
(this is essentially a copper-and-iron transformer machine whose
thyristors, etc, feature when AC TIG welding (?))


As you can see, the cellulosics are at the bottom of the table and the
really interesting results are the last two.


So what is going on here?

Is it possible that the Nu5 rod absorbs more water when soaked than the other rods? A way to test the idea of the Nu5 absorbing more water would be to weigh each rod before and after soaking to see if there is a noticable differance in weight gain.

I am suspecting that the water absorbed in the coating is breaking down in the plasma to hydrogen and oxygen and pushing the ionization voltage up. My welding experience in recent years is all with GTAW. In GTAW, adding helium to the argon or using straight helium results in more penetration by raising the arc voltage. I think helium has a higher ionization voltage than argon.

This is completely speculation on my part as I am not a physicist and at this point in my life I am mostly a shade tree welder.

Bob



.

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