spray transfer MIG

By welder_guy2001 (***)

Date 03-30-2002 07:30

spray transfer is best for 1/2" thick and greater. it tends to be a very hot process, so it is only done in flat and horizontal positions. it's not very practical for vertical and overhead beads. there is a pulsed spray transfer mode that has been proven effective in all positions, but that sort of equipment will cost ya!
for a home auto/fab shop, short circuit transfer would do everything you want. a good 250 amp MIG machine will weld up to 1/2" steel just fine. if you dial in a MIG machine in short-circuit mode, and you're fairly skilled, you can make a nice smooth bead that looks similar to a TIG bead.
oh...and spray transfer is where the wire melts before it touches the steel. in a slow motion photo it looks like a series of drops all lined up from the tip of the wire to the steel.
short-circuit transfer is where the wire actually touches the steel, melts, and breaks off. this happens 20-100 times per second, depending on how the machine is set up.

By dee

Date 04-01-2002 22:49

Todd,
Keep away from spray transfer... my work will look, in comparison, that much better. I don't believe (but may be wrong) any pressure vessels can be short-arc welded... why?

If you use a shielding gas rich in argon (I run 80Ar/20CO2) you will be able to attain satisfactory, stable spray transfer at less than 250 Amps running an 035 diameter wire... yes, stable spray transfer is apparently ataainable with Lincln's rig, and you will find it's the mode of choice when penetration is important. You will also probably find some resistance from your supply house when you ask for an all-purpose shielding gas mix of Ar with 15-20% CO2. This mix is a little colder than the 75/25 my local shops promote and because of that I kept the original bottle of it sold to me with my small welder, but in the past couple years I don't remember using any.

Note that 250/260 Amps is required to attain optimum spray transfer with 045 wire and Ar/20%Co2 mix, and that 045 wire may not be a practical option for spray with this power supply.

A good start point with 035 wire is to start at at least 210 Amps (attainable around a feed rate of >400 inches/minute) @ 28 Volts with Ar15/20% CO2... can the Lincoln handle it?
Drop about 50 IPM and 2 Volts if Ar/2%O2 or Ar/10%CO2 (spray-only)shield. Thes paramaters should insure true spray transfer and permit you to adjust down from there.

One point on equipment selection is that short circuit works best with moderate to steep slope, while spray works best with a slightly flatter slope; flat slope provides increased current at a faster response time to allow for the voltage changes during the weld as your electrode wire stick-out unavoidably varies during manual welding. A good machine with a moderate slope should prove satisfactory. My little Miller 250X easily produces strong, deep and asthetically pleasing welds near totally free of spatter... If I could have fit a larger machine into my plans I would, I am told, have more versitility, but for 1/8 through 3/8 I don't see why I would need it.

Minimum thickness applications are >0.080/0.090" minimum; slightly less than 1/8" (don't daudle) or burn through becomes a problem. Flat fillet welds limit to about 1/2" single pass, horizontal fillets 5/16" max. Vertical down works on plate <3/16. Multi pass can be done.

Contrary opinions should be directed to Ed Craig at WELDREALITY.COM as this data is straight from his material. Go there for more information... beyond that I plead humility. You might want to verify my start point parameters may be high; my presets are somewhat lower.

Regards,
D

By mbutler (*)

Date 07-10-2002 02:15

I was surprised at how well spray works on thin material. Getting the gas mix is a pain- I was only able to obtain 92/8 from my supply house, not as aggressive as the 85/15 but it is nice on the 1/8" steel.

By dee

Date 07-10-2002 17:39

My gas unfortunately is a custom mix, but if more welders demand 85/15 perhaps this all purpose (per transfer modes) mix will gain popularity and we can buy it "off the shelf" (or loading dock as case may be) in the future. Local BOC distributor refills within minutes; it could be worse.

I am glad you liked spray transfer, and yes, it does work surprisingly well on >1/8"... could you find any spatter on your work? There is significant difference with 92/8 its much colder I do have issues controlling the extra heat but am able to get over them.

Now if I can only get them to stock s3 wire...

A supply outlet who also services Miller locally told me my 250x was a lousy welder he refused to sell (funny; he had them in stock two months ago) and I needed to trade it in on a different unit... I was trying to solve penetration problems and tearing on some bad cold-rolled that I was unable to solve with technique alone. I had questions about calibration issues on the power supply and was new to the rig, short on technical info and experience, and apparently at his mercy. After some searching Ed Craig laughed and straightened it out nearly on the spot once he got me into spray. I owe my level of mediocrity to him:-) Interestingly enough, the last time I saw the rep he was insisting it was impossible to get the 250x into spray parameters. What a supply of gas!

Regards
D

By overthehill (*)

Date 07-10-2002 15:37

I'm not sure you need spray to produce the good looking welds. Spray is more about speed or penetration, or both. The higher short curcuit voltages, with the wire speed tuned for optimum transfer, can also produce some very nice results. Give spray a try, it's only a matter of switching to an argon rich gas and twisting the dials. Only you can tell if it suits you needs. Whether or not you decide to set up for spray, you will like the power of the 255, it's going to make quite a difference.