Spray Arc Transfer

[morgaj1]

After seeing some pictures Dan posted of some spray arc transfer he did, I am fascinated. I have done a lot of searching here and on the web and still don't fully understand the process. Will someone explain this to me? It appears that this process is only possible with 210 amp and more MIG welders. Is this correct? Is a special wire used? Is it accomplished with 75/25 gas or something else? Any other info would be great.

[srp61]

lets see,
spray arc is generally limited to larger machines because it requires high voltage 25v+ and current around 180 amps.
you also need a high argon content gas normally with at least 85% argon.
the gas we use at work is BOC argosheild light which is 93% argon 5%CO2 and 2% oxygen

here is a vid showing spray transfer

http://www.youtube.com/watch?v=gTFhh8dAK10&feature=related

http://www.youtube.com/watch?v=gTFhh8dAK10&feature=related

and short circut

http://www.youtube.com/watch?v=hBvEkdSxTuQ&feature=related

http://www.youtube.com/watch?v=hBvEkdSxTuQ&feature=related

it is also normally used on steels 6mm(1/4") and above and is only suitable for flat position welding due to puddle fluidity, unless you have a machine which can pulse spray

[soutthpaw]

see the thread about airgas steel mix, that is a gas that would work for spray arc. 90% or higher argon content... generally limited to a 250 amp and up size mig welders. My Ltec has the settings listed for both short circuit and spray arc and give appropriate gas recommendations right on the inside cover of the machine....

[morgaj1]

Is there any advantage, other than appearance, to spray transfer over short circuit?

[Rick V]

Great educational comparison video's srp61 !

[welderShane]

Originally Posted by morgaj1

Is there any advantage, other than appearance, to spray transfer over short circuit?

Better penetration with spray arc over short circut, faster travel speeds too.

[BCRD]

Originally Posted by morgaj1

Is there any advantage, other than appearance, to spray transfer over short circuit?

With spray transfer there is less chance for a good looking weld with poor fusion. CWB does not allow for short arc for structural welding. - spray or pulse spray only.

Jason

[addendum9]

A newer type of arc called the EWM-forceArc process is used with gas-shielded metal-arc welding in the upper power range (320 A Welding current vs. 285 A) using inert gases or high-argon content mixed gases. in the upper power range, which was previously reserved for the spray arc or long arc. Based on the welding trials carried out at TWI by an EWM welder, comparing to conventional spray transfer it was possible to draw the following conclusions.
* Butt welds made using the EWM-forceArc welding process with narrow preparation angles of 30º and 40º met the requirements of EN ISO 15614-1:2004.
* Due to the reduced joint volume, welding times for butt welds were reduced by up to 50% compared to conventional spray transfer with a preparation angle of 60º.
* Fillet welds made with the EWM-forceArc produced a mitred fillet with no undercut which also met the requirements of EN ISO 15614-1:2004
* The fillet weld made with EWM-forceArc showed a greater penetration than for spray arc.

[Fat Bastard]

Originally Posted by morgaj1

Is there any advantage, other than appearance, to spray transfer over short circuit?

Short arc procedures are not AWS pre-qualified. So you can't go to the book and get a welding recipe for short arc.

[bmyers]

Shield gas composition, amperage, and wire size dictate whether or not you can spray transfer. Lower % of Argon typically means higher required aperage. Once you get below a certain point, I believe 80 or 85% Argon, it is not possible. Here is a link to some good info on the differences of short circuit, globular, and spray transfer.

http://www.esabna.com/EUWeb/MIG_handbook/592mig1_6.htm

[SundownIII]

morgaj1,

Don't know where you're researching, but a simple search should provide a lot of details about spray arc vs short arc.

I'd also highly recommend that you go to millerwelds.com and click on their Resources tab. That will take you to an offer for their Student Pack. It's $25 including shipping. Includes an excellent GMAW Handbook, a GMAW-P Handbook, a GTAW Handbook, as well as a bunch of other useful goodies. Best $25 you'll ever spend on welding material.

Spray arc welding is a high disposition, high energy weld, generally limited to the flat/horizontal position (without pulse) due to the very fluid puddle. Requires higher voltage/WFS than generally associated with short arc welding. Gas mix generally requires more than 85% Argon. Effective (duty cycle) spray arc welding is generally limited to machines of over 250A output.

[morgaj1]

Lots of good info. Thanks guys!

[addendum9]

EWI has designed, built, and tested a narrow-groove tandem gas metal arc welding torch that allows a high-deposition rate process to be used in a narrow groove. Benefits are increased deposition rates, decreased joint volume, increased tolerance to joint variation, and improved sidewall fusion compared to competing welding processes. "We are using tandem gas metal arc welding in combination with a narrow groove for an increase in deposition rate. Oscillation of the lead torch significantly improves sidewall fusion and tolerance to joint variation. We are doing a few things differently such as water-cooling the contact tips. We've had great success with the torch and are pursuing commercialization of the technology."
Watch the video. http://www.ewi.org/narrowgroovetorch