A question of shielding gas mix for GMAW Spray?

Date 07-30-2007 16:54

Not sure what 'nicer' means, but you put it in quotes like I did. Seems to me with CO2 you will broaden the pen pattern and reduce the oxidation potential. This should manifest as cleaner looking welds (maybe), fewer surface deposits(maybe), but of course more Si and Mn in the weld metal as well(logically). You should also notice reduced edge wetting, and higher voltages.
If your guys are running close to transition you may lose spray transfer, or at least destabilize until you increase current. But a slight increase will get it back. You may see more spatter at first.
Mechanically I'm not sure it makes much of a difference. Probably is but I doubt its outside the normal scatter band. I'd go with cost on this one. We use 95/5O2.
My opinion.

By jon20013 (*****)

Date 07-30-2007 16:57

Thanks js55, I'm very glad to hear you also use 95/5 with the 02. Since I've the greatest respect for your opinion I feel somewhat validated, lol!!!

By bozaktwo1 (***)

Date 07-30-2007 17:07

All my adult life I was taught to religiously avoid putting oxygen into a weld. I learn more all the time.

We use 98/2 gas here on all our GMAW steel jobs. Some years back, a study was done with several different gas mixtures, and the 98/2 (that's Ar/CO2) made the smoothest welds of the group.

By js55

Date 07-30-2007 17:41

98/2 is a good gas as well. If your bulking, as we are, 95/5 will be a bit cheaper. Not much, but a little, depending on the size of your operation.

By js55

Date 07-30-2007 17:29

jon,
Since your opinion is valued by me, and it often validates my activities, I think we're screwed.
Auditor: How do you know your micrometers are within tolerance?
Answer: I check them against the micrometer block.
Auditor: How do you know your micrometer block is in tolerance?
Answer: I check it with my micrometers.

By Lawrence (*****)

Date 07-30-2007 18:05

Funny. I just discussed this topic with Ed Bohnart (how's that for name dropping?). He suggested that the O2 mixes produce a more finger shaped penetration profile, (my text book backs this with pictures) which can be problematic if operators move just a bit off center or tilt their guns. The Oxygen Mixes are also less effective on Mill Scale than C02 mixes for spray transfer GMAW.

Having said all that... We still use 98/2 because it will also work well on stainless.

By jon20013 (*****)

Date 07-30-2007 18:19

LMFAO!!!!!!!!!!!!!!!!! I LOVE IT!!!!!! Yep, we're screwed! ;-)

By jwright650 (*****)

Date 07-30-2007 19:29

Jon,
I qualified some this past weekend using 92/8CO2..seemed to work great, very little spatter.

edit: they were using E70S-3...Lincoln L-50

By 357max

Date 07-30-2007 18:40

You could use 80 to 90% Argon with the remainder CO2. This would allow short circuit spray and pulse spray transfer with one gas. Make a decision what mechanical and physical properties needs to be achieved and test the wire, gas and material combination. ie qualify the procedure, a good test is worth a thousand opinions.

By ssbn727 (*****)

Date 07-31-2007 06:56

Hi Jon!
Not to invalidate anyone elses opinion here but, if I wanted to ask someone who is considered one of the best when it comes to experience & knowledge with respect to shielding gas mixes with spray transfer using an ER70S-6, then I would ask Ed Craig @: http://www.weldreality.com/discussion/

Btw, please let us know what he has to say :)

Respectfully,
Henry

By jon20013 (*****)

Date 07-31-2007 09:14

Thanks Henry, that was the first place I checked before posting in here. Ed is, of course, the worlds leading expert on MIG welding... although I know the answer was posted somewhere on his website it didn't seem clear to me when reading. Since posting, I've directed the shop supervisor to continue using the Ar/O2 mix and crank up the current a little bit... things are now looking very nice and he seems satisfied! ;-)