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Thread: Short Circuit vs Spray Transfer
09-27-2008, 10:36 AM #1
Short Circuit vs Spray Transfer
Good Morning Everyone
The applications and setup for spray transfer is a little confusing to me. As I have mentioned before, I am a beginner.
Is spray transfer something that happens when voltage and current reache a certain level? Does you machine have to set up differently for spray transfer in terns of wire type and shielding gas?
Is spray transfer something I need to be concerned with?
The more I learn the more confused I get.
09-27-2008, 01:24 PM #2
yes and no.
spray transfer happens when you have the voltage and wire feed settings such that you have a stream of fine droplets of filler metal being transferred across the arc to to the metal being welded. voltage requirements will depend on the shielding gas and the wire size and the wire feed rate.
You should be concerned with spray transfer welding if you want to get sound welds with the mig process on heavy work pieces. it also leaves very little if any spatter (waste filler), which can be very handy in some situations, and very economical in large operations. One disadvantage of spray transfer, is that as far as I know, it doesn't work so good out of position, i.e. overhead and on horizontal surfaces, since the puddle is so fluid, but that I think depends on the application (workpiece thickness, etc.) I tend to weld most of the things I am working on in a flat or near flat position, and am not often in the business of using spray arc transfer. You should be able to get sound welds using short arc on mild steel plate up to at least 3/8 inch thick, depending on the amperage your welder can put out.
I highly recommend the training packet from Miller Electric that I posted a link to in a previous thread of yours. I only sort of half understood the whole concept of mig welding until I read the book they have about it. Very clear, concise, and easy to comprehend information, unlike most of the other sources out there that I have read. now I understand about 90% of what is going on, or at leas I think I do. Regardless, I have much better understanding of what I am doing which gives me better control and of course better welds.
hope this helps,
09-28-2008, 08:37 AM #3
I have downloaded all the publications plus ordered a couple of more books.
Sorry I missed it when you posted the site. Please do not think I do not appreciate you help and advice because I do.
09-28-2008, 10:33 AM #4
It's been twenty years since I did this, but here's what I remember...
Spray transfer is horizontal position only. Try vertical and the weld metal will just fall off onto the floor.
The wire feed needs to be constant and the power supply needs to have plenty of oomph to deliver a steady amount of power to the wire. If the power or wire speed varies, the point at which the wire melts is either in the weld (then it's just a short circuit weld) or in the tip, which immediately brings things to a screaming halt. Steady spray transfer requires a steady, reliable power supply.
The shielding gas we used was argon with 2% oxygen (!) in it. Spray is possible with CO2 but the spray droplets are larger than with Argon and doesn't differ as much from short circuit as Argon.
To get to spray transfer, start with short circuit and keep turning the amperage up. You'll know when it's starting to spray by the sound (crackling turns steadier, quieter) and you'll see the wire melt farther away from the puddle.
It makes a very smooth bead, compared to dip transfer. It's also faster and way hotter than short circuit so wear lots of leather (don't even think of bare arming it!) and keep the gun, tips, etc in really good condition.
Last edited by neilho; 09-28-2008 at 10:40 AM. Reason: clarity
09-28-2008, 03:10 PM #5
Spray is normally used for thicker sections of material, gas in normally 90 Ar-10CO2 or 98Ar-2 O2. Position for welding must be flat for reasons stated above, but out of position welding can be done with pulsed spray. The pulses freeze the puddle faster allowing out of position welding.
Plate being welded with spray transfer usually must be clean of mill scale, rust, etc. or undercut will occur.
Lincoln will mail you a GMAW guide, go to their website and look for the catalogs page, the book covers everything related to gmaw.
09-28-2008, 04:10 PM #6
09-28-2008, 04:15 PM #7
one more thing about spray transfer, is that you need more wire sticking out of the tip in order to keep it from burning back. I think the miller book talks about this. the little bit of aluminum mig welding that I have done was all spray, and the wire needed to stickout about 1/2" -3/4" minimum as opposed to the 1/8-1/4" for short circuit transfer.
Spray transfer is also identifiable by the sound produced by the arc. it is more of a hissing sound, than the so called "frying bacon" sound of short arc.
09-29-2008, 10:52 PM #8
good things have been said.
I would say as a beginner I would say your focus should be on practicing your welding skills and getting good consistent beads
spray transfer is actually the required mode of transfer in some code books mostly because in short ciruit your shorting to the piece and it has limited penetration ability (good thing for thin gauge bad for thick sections) as well as being prone to cold roll and lack of fusion. Globular transfer is the other mode of transfer and if you're using C20 C25 or 100% CO2 it's all you'll ever see.
despite what has been said you can spray transfer in all positions including overhead, but not neccessarily at all parameter settings. It also does increase puddle viscosity making something like vertical up on 3/8" hard to near impossible without blowing through. In my time programming robots and working in a shop we did plenty of work in spray transfer mode all position. In fact just a few days ago I was out in the shop welding 3/16" carbon steel vertical down in spray transfer. 29 volts can't remember the Wire feed with C15. I don't reccommend O2 98-2 on carbon steels but that's just me, we use 98-2 CO2 on stainless steels.
as anchorman said you want to recess the tip a bit more, this serves a dual purpose it prevents burnback and increases tip life (they stay cooler, less spatter) and it gives a chance for resistance heating to warm up the filler rod.
09-29-2008, 11:27 PM #9
some spool guns allow for easy recessing of the standard tips, which makes everything easier.
10-01-2008, 06:06 PM #10
have to turn it nearly all the way up on both voltage and wire speed. It gets there (C25 gas) but if I did it very
long I'd melt the M25 gun. Spray mode is for heavy production.
10-01-2008, 06:26 PM #11
if you use a lower co2 content gas, it gets into spray at lower voltages and amperages, and doesn't overheat everything so much. it is also dependent, of course, on wire size, thicker wire = more amps.
10-01-2008, 06:38 PM #12
My friend that repairs and rebuilds construction equipment used spray for almost everything. Using .045 and .062 dual shield wire and a 450 amp miller delta weld machine. I think he using pure argon gas. It welds nice, good penetration, no pin holes, nice bead formation. He can run it flat, on the horizontal, etc. Hes welding things like excavator buckets, AR plate. Its nice to weld 1/2 plate or better single pass. Also, he also pushes the gun not pulls. He says it give better cleaning on old metal, allows the dirt to push out of the puddle. Runs about 24-26 volts and the .062 will almost max out the amps on the machine. He can run several spools a week when its busy.
10-01-2008, 11:47 PM #13
dual shield wire is flux core that's a whole different boat, and has different shielding gas and voltage requirements.
I'm surprised to hear he pushes though, it's been a good year since I pulled a flux core gun but I remember pulling most of my beads to get good bead appearance
10-04-2008, 08:12 PM #14
10-04-2008, 11:22 PM #15
10-05-2008, 11:10 PM #16
I went to Miller's website and ordered all their books plus downloaded everything I could. It is taking me a while to digest it.
Is spray transfer used primarily for thicker material in excess of 3/8" to 1/2"?
10-06-2008, 12:50 PM #17
10-07-2008, 05:32 PM #18
personally I use spray transfer for just about everything but sheet metal. Then again I had a nifty machine that had a pulser (not to be confused with gmaw pulse) That would pulse the gun on and off (while keeping shielding). But that was to get full penetration on thin guage material.
10-07-2008, 06:01 PM #19
We pulse spray aluminium from 2mm to 20mm. I'd like to ask the question the other way around: is there any reason we shouldn't?
10-07-2008, 06:20 PM #20
Pulsed spray is touted by all the power source manufacturers as a great benefit on thin metals. You gain the same advantages as you do with pulsed tig, only you can get even less heat input into the work with the pulsed spray mig (no human can tig as fast as they can mig - getting into robotics you might have a different scenario).