Your opinions and any corroborating information sources please.
What are respondent's experience/opinion/informaton about the transfer mode for CS/LACS FCAW using the typical shielding gas variants? By example, CO2 GMAW cannot achieve spray mode transfer but maybe CO2 FCAW can (may be product specific)?
Thank you for your time.
I think transfer mode only pertains to the GMAW process. I could be wrong, but if you look at the sample welding forms in the AWS D1.1-2004 code book. Transfer Mode has (GMAW) next to it, telling me it only pertains to GMAW. However, on that same form, which happens to be a FCAW form, it gives a transfer mode of Globular, that confuses me. I don't think there is a transfer mode for SMAW! FCAW is SMAW turned inside out, rather basic, but in essence that's what it is. I never fill in that part on the form, I could be wrong, and probably am. So, could someone out there clear this up for us?
Bonni,
As far as code goes, I don't have any idea, but I can tell you from experiece what I was trained for and what I have encountered. FCAW, as I see it, generally has 2 different applications (home hobby and industrial). Home hobby FCAW machines generally use short circuit transfer but you probably are not limited to such if your machine can handle it. However, while in training, my instructor had us do FCAW etch plates using spray only, with a tri-mix of O2-CO2-Ar. This worked very well for large thicknesses (>1/4 in). Later we toured a structural company here in OK where they used the same idea while putting together pre-engineered I-beams for large-large structures (with preheat and postheat).
So, basically, I have never really encountered what I call a "real" FCAW machine that did use short circuit.
G. L.
Hi All,
In the GMAW process, the common variations of shielding gases, power sources, and electrodes have significant effects that can produce three different modes of metal transfer. These are spray, globular, and short circuiting. Spray and globular transfer require relatively high welding currents while short circuiting transfer commonly uses low average currents. Conventional and pulsed GMAW operations with spray transfer require shielding gases rich in argon. Spray transfer will only occur when a high percentage of argon is used. To achieve spray transfer on mild steel with the GMAW process, using a 98/2 argon mixture, it takes anywhere from 150 to 275 amps, depending on the wire diameter. Globular and short circuiting transfers are normally performed with carbon dioxide or gas mixtures rich in carbon dioxide. It is my understanding that a minimum of 80 percent argon is required to get out of the short circuit transfer mode, when welding mild steel. In most instances, globular is the type of transfer when carbon dioxide is the only shielding gas. In our shop, we use the GMAW process and spray transfer, with 98/2 argon for welding stairs and handrails, and the FCAW process and globular transfer, with 100% carbon dioxide for welding structural steel.
If you look in AWS A5.20, the appendix gives a description for each electrode classification. For EXXT-1 & EXXT-1M, for example, it says they are "characterized by a spray transfer, low spatter loss....", while for EXXT-5 & EXXT-5M, they are "characterized by a globular transfer..."
As far as I can tell-GMAW has many different transfer modes.
FCAW is just that-FCAW. It has a transfer mode all of it's own. Partially spray, particially globular, depending on gas and parameters.
Hope this helps...
brande
Forum
