Setting up for spray arc?

By Kix

Date 03-18-2009 15:35 Edited 03-18-2009 15:47

Here a good thread about this, read up. http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=42563;hl=short%20circuit%20globular%20spray%20transfer
I think it's around 85% argon for a min. If you know you will be in spray all the time you can go with argon/oxygen mixes around 95/5 98/2 argon/oxy. You can use argon/co2 mixes as well. If you think you will do some short circuit welding at times, you can go with an 85/15 argon/co2 or a 90/10 argon/co2 and still be able to get into spray at a higher voltage then what you would using one of the above gasses. The type of gas you use and the wire dia will determine what voltage will be needed to make a full blown axial spray arc. Some gasses could get you into spray around 24V depending on the wire diameter. Oh yeah, no special contact tip is needed either.

By hogan

Date 03-18-2009 15:43

david,
Kix has given some good info, but if you could list your base-metal and thickness, wire size, shielding gas, and amp/volt setting you are trying for then we can give better info. It's extremely difficult, you just need to get everything dialed in to run productively.

By david bean (**)

Date 03-18-2009 16:42

we are set up with a 0.35 ER70S-6 AWS A5.18, we basically use this to run all our handrail, currently we have a 60%co2/40%ARGON setup. we are welding .095-.120 wall round tube. is this a globular transfer? would i benefit from switching to spray?

By hogan

Date 03-18-2009 16:56

david,
There are 3 types of transfer. At the lowest voltage settings it will be short circuit. This sounds like a pop,pop,pop, a little like bacon and runs best with 100% co2. This is best suited for thinner material. One of the main issues with this is trouble with side wall fusion. Additionally, most codes don't recognize this as a prequalified process.
Next is globular, this is when your wire is transfered by droplets that are slightly larger in diameter than the wire. Deposited weld metal has slightly better characteristics than short circuit.
Last is spray. For code work this is the preferred process. You need a minimum of roughly 80% argon. The transfer is in the form of fine droplets that are smaller than the wire diameter. This runs at higher voltage. for .035" you will want a minimum of 28 volts and 200 amps. This is from one manufactures data sheet, yours may vary.
It would be best to get a copy of the data sheet from the manufacture of the wire you are using. You can spray your handrail, but you might be able to get approval for using short circuit, less chance of burn through.

By OBEWAN

Date 03-18-2009 15:46

My boss at a structural shop used to claim spray transfer for all his processes using 75Ar 25Co2. It went against all the textbook answers I learned in welding engineer school, so I pushed back on his definition. I finally had to concede that it was close to a spray transfer. There were only a few occasional globules, but overall the arc was very stable. It was fine for the D1.1 work we did and gave high deposition with good penetration. It was nothing like globular with straight Co2. The key was getting the power high enough to get a strong pinch force on the wire.

By Kix

Date 03-18-2009 15:54

Yeah, that's fine and dandy when you want to push your machines to there limits. lol Better gas cuts down overhead by using less voltage and machine maintenance, but I guess you would have to factor in the cost of swapping gasses everytime a different process was called out to see if it was cost effective. That's why we use 90/10 argon/co2 for spray and short circuit. Don't get me wrong, 75/25 will weld way nicer in short arc then the 90/10, but it gets the job done without peggin the machine for spray. ;-)

By david bean (**)

Date 03-18-2009 16:48

By david bean (**)

Date 03-18-2009 16:53

Also, we run our voltage from 21-24 volts and wire feed speed at 250-280 on our .095-.120..

By DaveBoyer (*****)

Date 03-19-2009 01:37

My guess is that You are using short circut transfer, and that is well suited for the work You are doing. As the others mentioned, spray transfer doesn't work out of position. Another thing to consider is that as deposition rates increase You will have to move around the work REALLY FAST, and You might not be able to keep up with it.

By Kix

Date 03-18-2009 17:38

You can run it any way you want as long as you have procedures to back it up if you are welding to a code. Can you position these tubes to be welded in the flat and horizantal positions only? You can only use spray in these positions. Weird gas combo, never heard of anyone using that. Do a cost comparison with one of the other gas mixes I mentioned. Would you benefit from switching to spray, hard to say? What mode of transfer are you using now, short circuit or globular? Short circuit sounds like bacon fryin and globular has a hissing sound with a few inconsistent crackles. If you could turn your part in such a way and fast enough for spray transfer, I'd say you could benefit from it. If you are doing it in position or flipping it around on the table, i's say stick with a hot short arc transfer.

By 357max

Date 03-18-2009 17:57

If the material is clean use the argon co2. For the heavy mill scale of hot rolled steel (if you are welding this) 100% co2 provides better fusion. SCMT GMAW with the thickness you are welding will require 90 to 150 amps. Arbitrarily set 18 volts using a volt meter. Then set about 200 inches of wire feed speed. While welding set the amp meter to read 120-130 amps by increasing/decreasing the wire feed speed from that 200 IPM setting. Fine tune the arc from the amperage determined/set; by increasing or decreasing the voltage from 18 to get a low spatter smooth arc transfer. Finally, If your machine has a variable inductance control start at 0 and increase until desired arc is reached.
For higher production speeds use spray transfer. Greater than 80% argon mix set the voltage at 23-4 volts to begin. Set the amperage with about 300-400 inches of wire feed speed. Again increase/decrease wire feed speed until 150 amps is reached. If the wire is digging into the weld pool increase voltage from 24 to clear the wire from the pool. If the wire is melting back to the contact tube decrease the voltage. Have the wire just clear the pool.
SCMT use a contact tube; flush with or better yet a contact tube 1/8" beyond the end of the nozzle. 1/4-1/2" wire stickout from contact tube. Spray transfer use a contact tube recessed behind the 5/8-3/4" inside diameter nozzle end 1/8-1/4" and 1/2-1" wire stick out from contact tube.

By hogan

Date 03-18-2009 18:32

357,
The settings you mentioned seem low compared to the data I have for .035". It is probably best to get the manufactures recommended setting and start from there.

By Kix

Date 03-19-2009 12:33

With the right gas, those parameters will get you into spray. The second set of parameters he listed that is. He listed one set for short arc and the other was for spray.