The terms short circuit, globular and spray are not directly tied to a welding process, rather they describe the mode of transfer of molten metal from the filler wire/electrode to the molten pool. Short circuit refers to the wire/electrode actually touching the molten pool, the arc being extinguished, a buildup of amperage and finally separation of the filler with melting into the molten pool. The terms globular and spray both refer to molten filler detaching from the wire/electrode, moving through the arc and being incorporated into the molten pool. The difference between the two is the relative size of the molten filler, with globular being droplets that are larger than the filler diameter and spray being droplets that are smaller than the filler diameter.
It so happens that FCAW (both -S and -G) mainly operate in the globular mode. Some brands/specs may be pushed into the spray mode, with higher amperages and certain slag systems but short arc mode is not seen.
SMAW electrodes may operate in both the globular and spray modes, again depending on amperage levels and coating/slag systems. Short arc mode is again not seen.
Just to give the doubters a bit of visual backup, here are some photos from my Arc Physics Welding Lab back in the days of white out and typewriters. We had an SMAW set up whereby we could capture the molten drops as they were generated using 1/8" diameter E6010 and E6012 and 5/32" diameter E11018M. Various amperage levels were used for each electrode.
You will see 50 amps resulting in spray transfer for the 1/8" E6010 and globular transfer for the 1/8" E6012. The second photo is the E11018M at 170 amps (globular transfer) and 240 amps (spray transfer).
I hope this provides some insight into molten metal transfer for various welding arcs/processes. Unfortuately I do not have similar work relating to FCAW and GMAW, but we did do some high speed photography of the wire feed process showing the various metal transfer modes.
viettq,
Don't forget shielding gas. Typically speaking, for carbon steel, CO2 is widely used with the gas shielded FCAW process, with the mode of transfer being globular. Globular is also associated with the GMAW process when CO2 is used with a low arc voltage. Spray is associated with the GMAW process when a gas mixture of argon and 2 to 5 percent oxygen is used. Spray can also be achieved with the GMAW process when CO2 is used, but only at high current densities. With short circuit, the common gas shielding is an argon/CO2 mixture, or 100 percent CO2. Penetration is greater with CO2, but mixtures of 50 to 80 percent argon with CO2 result in higher short circuiting rates and lower minimum currents.
By Nanjing
Date 03-05-2009 15:04
I only come across rutile flux cored wires in construction which operate in virtual spray transfer at all currents. In the States what do you use generally? basic?
I think most E70T-X Gas shielded FCAW wires are formulated with basic type flux systems.
The E71T-X Gas shielded FCAW wires have the rutile slag systems that are more condusive to all position welding.
My recent experience with the newer ESAB 710X and Ultra E71T-1 electrodes are that they will spray (defined as droplets smaller than the electrode diameter) with 100% Co2...
I don't think D1.1 requires the mode of transfer to be stated in the WPS for FCAW (Even if the example in the Annex happens to)..... My opinion only
I expect that FCAW isn't going to do any better than Globular and Spray...to Short Circuit you aren't welding any longer with FCAW, it's just jabbing wire at it. I'm sure others will chime in soon and tell me if I'm wrong.
