What's spray arc?

  1. steve202

    steve202 ǝlʇıʇ ɹǝsn ɯoʇsnɔ

    Messages:
    422
    Wales.UK
    Fella in this video here mentions 'spray arc' and using Co2/Argon mix at around 56 seconds into the video. Could someone enlighten me about spray arc? Cheers!
     
  2. There are various types or should i say styles of MIG welding. Dip transfer is the welding wire actually touches the weld pool, as it does it shorts out, metals the wire. The wire enters the weld pool

    Spray transfer, is slightly different and occurs at higher voltages, normally with 1mm wire or bigger (you can achieve spray transfer with 0.8mm wire), just before the wire hits the pool of weld there is enough voltage to make the arc jump across from the weld pool to the wire, this causes the wire to heat and melt, effectively spraying it into the weld pool.

    As far as im aware all sheet work (thin) is dip transfer.

    Perhaps not the best and most accurate explaination but im sure you get the idea, no doubt someone else will explain better than me
     
  3. steve202

    steve202 ǝlʇıʇ ɹǝsn ɯoʇsnɔ

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    422
    Wales.UK
    Ta Darren. I wonder what circumstances dictate the use of the spray transfer technique?:confused:
     
  4. Spray arc is normally done on thicker material and isnt very well suited for positional welding, ie anything that isnt a butt or a fillet weld.
     
  5. cobminor

    cobminor Member

    Messages:
    458
    West Sussex
    Spray transfer happens automatically above a certain amperage, usually about 250, it is impressive in laying weld on to a flat surface. It is however, useless in any inclined angle as the weld is liquid so it runs away. When you get up to spray transfer you should be on arc welding. It does have it's uses though.
     
  6. Drains

    Drains Yeah, nah.

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    7,715
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    Sefton, South Island, NZ
    You can expect to get spray transfer at over 27 volts OCV. It's suited to non positional (eg downhand) welding. The advantage is you can lay down far more metal with minimal noise and spatter. The disadvantages are it's non positional, it puts more heat into the job, and you need a decent quality wire. The cheap wires won't do as you'll get porosity.

    Spray transfer has better penetration, and higher dilution levels. It's used all the time in industry, but relies on having manipulators for the jobs so the weld can be kept level. Many 3 phase Mig sets will provide up to 50v and 500A.

    If you get your hands on a set that can do an OCV of 27v plus, you'll find an area between short-circuiting, up to about 22v, and the 27v setting, which gives very spattery welds. It's called "semi-short-circuiting arc", and is apparently used with co2 and medium thickness plates. To be avoided IMO.

    For your info, Mig settings are ALWAYS in volts, never amps, except on this site. Although machines are rated for duty cycle in amps, it doesn't relate to the setting on the machine, as the voltage is constant, depending on the setting, whereas the current can vary wildly according to the wire size, speed, and position of the torch.

    Si
     
  7. Its that nice slot between 22v and 27v is where i do most of my welding, and there is nothing like splatter all over a nice pair of gates, to ruin a job. From what i understand pulse machines can eliminate the nasty splatter at that voltage range.
     
  8. Hitch

    Hitch Moderator Staff Member

    Messages:
    12,070
    Somerset
    Pulse, if set and used properly, you get virtually no spatter.

    Ive got a nice heavy job coming up next day or so, will be welded with a pulse set, ill do a few pics if i get a chance.
     
  9. Be nice to see those Hitachimad, normally for welding scrolls in a gate i use tig as its splatterless, means i dont have to spend ages cleaning up, but a pulse mig has crossed my mind
     
  10. Hitch

    Hitch Moderator Staff Member

    Messages:
    12,070
    Somerset
    Sounds like hard work Darren, i use a normal mig for that- just set the wire lower than it ought to be, and a quick squirt of antispatter ;)
     
  11. steve202

    steve202 ǝlʇıʇ ɹǝsn ɯoʇsnɔ

    Messages:
    422
    Wales.UK
    Enjoyed reading that. Thanks everyone.
     
  12. And you thought spray arc was attaching the welder to the compressor didnt you lol :D
     
  13. steve202

    steve202 ǝlʇıʇ ɹǝsn ɯoʇsnɔ

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    422
    Wales.UK
    I have no shame! yes! :laughing:
     
  14. Drains

    Drains Yeah, nah.

    Messages:
    7,715
    Location:
    Sefton, South Island, NZ
    :D:D I used to think it's what little lads do in urinal-based competitions :laughing::laughing::laughing:
     
  15. lexi Member

    Messages:
    1,575
    paisley
    Yes please.

    Alex
     
  16. taylorkh Member

    Hello from across the pond!

    Spray arc is a form of metal transfer in MIG (or GMAW & FCAW) welding. As discussed above it is HOT and provides better penetration and fusion for heavy weldments. Here is a picture I came across somewhere showing the difference.
    http://www.mediamax.com/walker_52/Hosted/Fillet macro- etched 1 spray 1 short take your pick.JPG

    Spray transfer requires:

    voltage above ~ 26 volts
    Argon percentage > 95%

    If you are interested in the gory details have a look at the ESAB site: http://www.esabna.com/EUWeb/MIG_handbook/592mig1_1.htm

    Because of the higher heat and better penetration, spray transfer is allowed in some structural welds. With a pulsed MIG power source it is possible to do spray transfer out of position (vertical, overhead etc.) but these are high $ machines.

    Miller welding has some great on-line references which you might want to check out at: http://www.millerwelds.com/resources/improving-your-skills/mig/

    Their "Guidelines for MIG Welding" is an excellent reference.

    Regards,

    Ken Taylor
    Clayton, NC USA
     
  17. steve202

    steve202 ǝlʇıʇ ɹǝsn ɯoʇsnɔ

    Messages:
    422
    Wales.UK
    That Miller Spool Gun looks great.

    Thanks for the info, links and pics. All saved in faves ;)
     
  18. taylorkh Member

    Glad to help. I did make one error in my post. The minimum Argon for spray is more like 85%. I was thinking of the gas we used in welding class. It was 95% Ar and 5% CO2.

    If you ever get the chance, try some dual shield wire in spray mode. Fantastic stuff. It has flux inside similar to self shielded flux core (but a different composition) but is used with shielding gas. We got a roll in at the welding lab and the instructor told me to set it up and try it out.

    After getting it going I decided to see what the Big Yellow (ESAB) machine could do. I did a single pass butt weld of a couple of pieces of 3/8" mild steel plate. I was running something like 36 volts and 400 inches per minute of .045" wire. Measured 450 amps on the panel. I made no bevel prep on the weld - just set the two pates about 3/16" apart and let fly.

    After about 5 inches of travel I began to notice the most horrible smell. I heard other folks shouting about the stink. I thought to myself "the dual shield is some foul smelling stuff". I stopped and found that the source of the aroma was not the welding. My aluminum coated fiberglass and Kevlar back hand shield had caught fire from the heat! Considering that the arc was dissipating more than 16 kW and my glove was but a few inches away...

    In spite of the extraneous combustion the weld turned out real nice. About a 5/8" wide bead with total penetration of the plates. Chip off the slag and it looks nicer than a solid wire bead. Not the usual dull look of a self shielded flux code weld.

    And for the absolute top of the line for neat - try dual shield stainless wire. A 33 pound (15 kg) roll was $350 US - about 175 Quid. The finished weld looks like TIG - rainbow coloring and all.

    Cheers,

    Ken
     
  19. panaya Member

    Messages:
    20
    BULGARIA
    Hi steve202
    The spray transfer is very usefull mode of metal transfer.It gives many benefits when welding thickneses from 2mm and more.If you want to learn more ,please see weldreality.com
     
  20. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    Messages:
    14,665
    Wiltshire, UK
    Well, now there's a turn-up! I had a look on said website and possibly purely conincidentally (as you didn't link to them or mention them), on the main page are two animated gifs, one showing spray transfer and the other dip transfer. Not the best quality pics but a good insight to the difference. In the spray one you can just make out the molten drops. Well done Panaya.
     
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