spray arc

[dyn88]

that seems to have answered my question and I am telling purchasing to order me 2 spools of solid cored 1/16. Thanks for all the help, everybody. The two spools will be here tomarow. can anybody give me an idea of where to start the arc length on my optima pulser for the solid wire and about how long of a arc am I looking for. I already short arced the plates that caused this thread, but I still need too weld some fillets on 2" thick A-36, all in position with no preheat.

[sparx]

The advantages to using a dual shield wire is mainly on out of position work, or where the base material has some contamination that can't be removed. the fast freezing slag of the cored wire (assuming it is an all position wire) aids in building the shelves needed to do vertical welds. As for the shielding gas, companies build wires with certain gases in mind. the deoxidizers that they put into the flux, are designed to be used with a certain amount of CO2. When CO2 is present at arc temperatures, the gas dissociates into Carbon Monoxide and Free Oxygen. the molecules in the flux are "looking" for the oxygen molecules and float to the surface with these molecules in the form of flux. If there isn't enough oxygen in the molten puddle, then these deoxidizers don't have anywhere to go but into the weldment. When they become part of the weld, the characteristics of the weldment change, usually becoming higher in tensile strength. The problem with increasing tensile strength, is that ductility decreases, making the weld strong but brittle.
As for the mode of transfer, these wires will produce a spray like effect at lower voltages, due to the cross section of the wire. A solid wire needs the voltage to burn the entire thickness of the wire (.045 or .062 for example.) with a cored wire, the voltage required is lower, since the cross section of the wire shows that only the sheath needs to be "burned", so on an .062 wire, you really only need the voltage to melt about a tenth of the diameter. (hope that made sense).
The other thing that you need to remember, is quote:"If there is slag, you drag". When you are burning a wire that produces a slag, you need to drag your gun, as opposed to pushing as with solid wire. If you have your equipment set up to "spray" with the fluxcored wire, and are using a push technique, the puddle will actually roll over in front of your position, trapping slag underneath.
I have done some testing with 1/2" plate in a fillet weld to show a customer this, and when we finished the weld, we sectioned a piece of this test plate. The root wasn't penetrated, and there was a "channel" of flux along the entire root of the weld. You could actually pick out the flux with a small dental pick and see a hole all the way through the section of the root.

Sorry for the long post.......sometimes I start typing and don't know how to stop.

[Alex]

dual-shield vs solid wire

dyn88,
What would be the advantage of using shielded wire over solid wire? Like the others here, I've never heard of anyone trying to spray with shielded wire. As far as stickout goes, start with the gun close to the workpiece and when you establish an arc, just back the gun off so you have more wire sticking out.

[dyn88]

I get two answers over here- My sales guy tells me no with dualsheild and my local rep says yes. o I dont know who to listen to, i seem to get the same replies here. When I change stickout by lowering voltage or increasing wire speed, I cant get the arc started and it all balls up.

[Danny]

Is 98/2 a recommended shielding gas for your wire? CO2 or C-25 are the shielding gases that I am use to seeing associated with a dual shield wire.

[1fasbu]

flux-core wires

Two things I'd check here- gas flow rate and stick-out(distance from contact tip to arc). Stick-out is more important than you'd think. Myself, we use more hard wires than dual shield, therefore I'm used to running closer to the cup than dual-shield prefers. (I've had simmilar issues). I'm guessing that you'd want at least 5/8-3/4 stickout???, experiment with this. It also sounds like you're hot for the wire size/speed given the presence of undercut. Gun positioning should be slight drag like stick welding. Cheers.

[cruizer]

Yes and no, it's difficult to do spray with a CV machine, but normal with a cc machine. It's either globular tranfer or spray with CC

[Mike W]

That's what I thought also.

[hankj]

I may be off the wall, but I don't believe you can spray with any cored wire, dual-shield or not.

If I'm wrong, we'll hear about it real soon!

Hank

[dyn88]

Well today I tried to spray using 1/16 dualsheild, what a nightmare, Ive sprayed with solid wire before and had no problems but now I get porosity. Here are my machines- miller phoenix 456p multi process inverter power supply, 22-A wire feeder, axo 500 amp gun, 98/2 gas, and an optima pulse control, welding 1.5" a-36 to 2.5" a-36. I tried pulse at first, problems dialing that in when I could get it to run (on the preset program for 062 steel) I ended up with an incredible amount of under cut and what seemed to be an overly long arc(judging from spraying with .035 solid on a 250 amp machine). then to regular mig control and once I dialed that in I got the afore mentioned porosity and alot of undercut. any help would be greatly appreciated.