I'm sorry if this has come up before, I scanned the forums and couldn't find a mention of it... caveat over lol
I have a question related to a statement in the Welding Inspection Technology book (WIT-T 6th edition page 56 If anyone has a copy and wants to look it up)
It states the following "As mentioned, the shielding gases have a significant effect on the type of metal transfer. Spray transfer can be achieved only when there is at least 80% of Argon present in the gas mixture. An Ar-Co2 mix is typically used with inverter power sources and an Ar-O2 mix is typically used with traditional transformer-rectifier power sources when welding steel"
Does anyone know the reason they state that? that the mix is dependent on the type of power supply? I know how and why most mixes are used, the long finger like penetration of the high Ar and O2 mix etc... But I had never heard that the choice was tied to the type of power supply.
This is the latest WIT book, but looking at the workbook they haven't updated much, is this an outdated (old) statement that used to be the case, or does anyone know why AWS states that? Or have a link to any articles on the matter?
Thanks in advance
The key word in the statement is "typical".
Both gas mixes can be successfully utilized in both platforms. I think the decision is more based on current trends than clear cut need for differences.
My opinion is that Ar/CO2 blends are better for tuning out spatter on GMAW Pulsed welds made below 250 amps.
Tim
Hi MaIRD
I think it's a bogus statement with no provenance in weld reality.
Both Ar/Co2 and Ar/o2 have been used for spray transfer GMAW before inverters became prominent and after inverters dominated the market.
DC current is DC current...
Some transformer rectifiers had slope lugs for spray transfer, some did not. Some transformers have inductance controls and some to not.
Most inverters have some inductance controls and a favorable slope for both short circuit and spray...
What does that have to do with Weld Gas? That is not a CWI level question.
Thank you for your responses,
And yes i agree, the statement from AWS is what i couldn't figure out, to me it seems like it could be a remnant of what could have been a fact back in the day when inverter technology was in its infancy and gas development again wasn't as "specialized". I am an instructor at a college in Idaho and have been a CWI for 18 years and i have never come across this statement before. We generically use a 90/10 mix Ar/Co2 for our spray and pulsed spray.
This statement to me is "nowadays" so far out in left field, that i didn't know if historically there was a reason for it.
The closest reason so far that ive found is from the Lincoln foundation procedure handbook from 1994, that one states about a spray machine having two transformers to run spray one DC one AC.
My guess is that this statement in the WIT book is a remnant of older technology and it has never been removed... Unless anyone can inform me otherwise...
Regards
As for it not being a CWI question, its stated in the book you study for your Fundamentals exam, So i respectfully suggest it could be... that's why i am trying to find out what in the hell they are talking about. Right now, i have no idea...
Regards
UPDATE:
I just managed to dig out a fifth edition WIT-T book (2008), and the statement is not in there, nor is it in the fourth edition WIT-T book (2000). It looks like this is a "new" addition to the 2020 edition.
![](https://onedrive.live.com/embed?resid=85E4C4B6EFAD9E09%2113467&authkey=%21ABrPGSBjeM-XRuY&width=741&height=534" width="741" height="534")
This is what i'm talking about, bottom of the second paragraph.
Hi Mal
I'm just as perplexed as you are.
The fact of the matter is that in 2023 I know of only one remaining transformer rectifier welding machine on the market today worldwide and I was surprised when I found it.
While there are millions of transformer rectifiers out there in the welding world,,, Almost nobody is selling them anymore.
I just did a quick review of my PowerWave utilities and discovered that there are no GMAW or GMAWP subroutines prepared for steel and Argon/Oxygen gas mixes... So that is a point in favor of the text you captured.
I've never been a fan of oxygen mixes for steels, but they can work. A trend away from those mixes would not bother me at all.
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