GMAW solid wire, coated vs uncoated

Date 11-19-2012 14:21

Ladies and Gentlemen:
   I do not recall seeing uncoated steel GMAW wire. Corrosion of the wire is a big concern. A light oil coating would be detrimental to welding. As a CWI, engineer with WPQR responsibilities I have had rejectable weld specimens on excessively high tensiles by wax used to get the wire through the feed torch of GMAW. Hope this is helpful.
Sincerely
Len Andersen weld@spemail.org
   914-536-7101   / 212-839-6599    8-4 New York Time , 4042 FAX , Co-worker 6381 / 914-237-7689 (H)
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   www.lenandersen.com

By fschweighardt (***)

Date 11-19-2012 21:50

certain amount less liner clogging, due to no copper getting scraped off of the wire.

To Len, National Standard has had a copperless wire for years
http://www.heicowiregroup.com/files/129080201CF%20vs%20Cu%20Technical%20Bulletin_11-07.pdf

By Tyrone

Date 11-21-2012 12:01

Hey Tim Gary,
I did a study on bare (uncoated) vs coated GMAW wires back in 1994.
Based on this study (and cheaper wire), we switched to bare wire for a number of years. We're back to coated now...

Fschweighardt is correct about copper wires gumming up the liner (not positive if it's copper residuals. Run your hand along the wire, and you'll get black looking crap on your fingers.) The liners didn't have to be replaced as often using bare wire.

Chemical/Mechanical Properties test results of bare wire:
1) Decrease yield and UTS (approx 8%)
2) Charpy impact @ -20 deg F increase 100% absorbed energy
3) Decrease diffusible hydrogen (approx 50%)

Hope this helps.

Tyrone

By TimGary (****)

Date 11-21-2012 14:32

That's good stuff Tyrone, thanks.

I've been wondering how the copper content affects weld properties.

I've been seeing in my research that the copper coating has a useful benefit in maintaing arc stability, especially during arc initiation and for longer stickouts. Any opinion on this?
Did you notice any differences in spatter generation?
Why did you switch back to coated?

Thanks,
Tim Gary

By jwright650 (*****)

Date 11-21-2012 14:47

In one of the ESAB catalogs, they mention as another benefit of the copper coating...copper to copper (instead of copper to steel) contact at the tip means far better current transfer, less arcing, less contact tip erosion at higher WFS and better contact tip life. Quick arc starting minimizes weld spatter. Produces spray arcs at lower arc voltages, lower weld metal hydrogen levels and better penetration. <---sales catalog, so take that for what it is worth.

By TimGary (****)

Date 11-21-2012 15:46

Thanks John.
I appreciate the input.
I've always dealt pretty easily with the clogging issue by blowing out the liner once per week as preventative maintenance, and making sure to use smooth V-groove rollers.
Using knurled rollers will gum it up quick, which is why I assume cored wires do not have coating.
I'm thinking the pros of using coated wire out weigh the cons.
The previous comment about changes in impact properties are though provoking though.

Tim

By jwright650 (*****)

Date 11-21-2012 15:52

ESAB has a AWS D1.8 compliant, Demand Critical Weld Applications wire in their lineup that has a bit better numbers.

SpoolArc 75

By jwright650 (*****)

Date 11-21-2012 15:53

BTW, I'm not pushing ESAB's products or any other mfg, I just happened to have a ESAB catalog on my desk at the moment.

By Tyrone

Date 11-23-2012 11:54

Hey Tim Gary,
Sorry I didn't respond sooner, off sick...

I'm not positive why they switched back a few years ago (I'm out of the Manuf. dept). I suspect it has to do with the almighty dollar.

From what I remember, all the Welders loved the arc stability and "feel" of the bare wire. I'm not sure if it was the wire, or the fact that it was a "new toy". I didn't play with stickout but it's reasonable to think the copper would help. I didn't notice any differences in spatter. In the big picture, I don't think it improved nor degraded weld/product quality.

Tyrone