Spray arc welding

[Kerry Pinkerton]

A Miller rep told me I should try spray arc MIG welding instead of short circuit arc that I've always used (the bacon sizzle approach). I finally got some of the correct gas and WOW! What a difference.

I also got a caculator and basically you turn the voltage and wire speed WAY up and use 98" argon (my welding supply gave me 92% in error and I only recently noticed it wasn't 98%...but it still works very impressively).

I get tremendous penetration and virtually no splatter. No noise or sizzle, just a hiss. The welds look like they are tigged if I do them right. Pretty enough to paint with no grinding even.

This is something new to me and I'm pretty impressed. Obviously, I not a trained welder but I've been welding for decades and never had a weld fail. What are the downsides of spray arc MIG, if any? Why is this not the preferred way?

[firstgenbird]

The disadvantage is more heat, making it less friendly for sheet metal. It seems like a highy productive way to assemble thicker pieces like the e-wheel frames you fabricate. The filler metal is carried to the weld through a continuous plasma. The vaporized metal helps conduct the arc.

[BarryA]

Hi Kerry

What sort of voltage are we talking? Anything else you would do different to normal MIG?
I have used the Argon bottle from my TIG set-up before when the CO2 mix ran out, but seem to recall getting more spatter. Otherwise the welds were fine though.
Barry

[firstgenbird]

You would turn the voltage up even higher until the spatter stops. The sound would change to more of a plasma sound than a frying noise.

[carryallman]

hey there kerry ,what kind of a welder do you use and model and what settings for a certain thickness? thanksmike "carryallman"

[CCWKen]

It's good for thicker metal as already stated. It also takes the hardware that can produce the higher amps and volts to start the process. Not to mention the Argon/O2 gas. For a production shop with dedicated welders and heavy gauge metal projects, it's a valid alternative to TIG. For a small shop, it can be annoying changing tanks just for that process.

[CCWKen]

hey there kerry ,what kind of a welder do you use and model and what settings for a certain thickness? thanksmike "carryallman"

Here's one example of the required amps for a given wire thickness and material.
http://img.photobucket.com/albums/0903/CCWKen/Displays/SprayArcTable.jpg

[firstgenbird]

There a detailed paper on short circuit, globular and spray transfer welding at:

http://www.millerwelds.com/education/educators/pdf/MIG.pdf

[JD in SoCal]

Kerry,

The good news and the bad news about spray transfer is that it puts a lot of heat and wire into the joint in a big hurry. As you found, you can run some strong, smooth welds quickly. The 2 main drawbacks are:

1) the high heat can warp or distort your pieces even more than short-arc might, if you are not careful, and

2) spray is really not useful in anything but a flat position. The bead is so liquid that, if you are in full spray, it won't run out of position.

A couple of other factoids for anyone experimenting. It is possible to get into spray with different gas mixes by using more power. Bigger machines (250 amp and above) can spray pretty easily. My MM210 will get there with 98/2 mix and run well, but it is pretty maxed out to do it. Any smaller machine will only spray under perfect circumstances and probably won't even get all the way to spray.

There is a transition area between short circuit and spray transfer that is globular transfer. If you dial up the power, you would hit it right before full spray. The sound changes from short-circuit and it spatters like mad. You can create some good, fast welds, but it is messy. Bump the power a bit more and you hit spray transfer, the sound changes more and the spatter goes away. But now you have a very fluid puddle and it will dribble right out of the weld if you are vertical or overhead.

JD

[1smoothline]

Just a couple of details on spray transfer on steel that can make a big difference:
-Spray starts above 24 volts, below that it's globular transfer (lots of spatter) and below that short circuit.
-It can really only be usefull on steel over 3/16" unless you are using pulse spray transfer.(Another story again) It's not the best choice for true sheet metal.
-It can be deceptive. I've seen welds that looked great on the surface but had very poor penetration due to improper settings. As always with a new weld proccess, test to varify correct technique and procedure. The penetration problems can sometimes be found with machines that are below 250 amp size as they are struggling to make the threshold transition point.
-The surfaces must be spotless. No oil, grease, etc. Even mill scale should really be removed. (Grind or sand blast)
-Use a longer wire stickout and shorten the wire guide tip to recess it 1/4" into the nozzle to promote good gas coverage of the weld.
-I've found the best gas mixture to be 85 argon / 15 CO2 mix. I've tested mixes with O2 blended as well and had some issues with root porosity problems if gas coverage is not perfect. The higher CO2 content gives better penetration in general.
- As noted earlier, his process creats a lot of heat and distortion and this should be weighed before welding.
I'm a Welding Bureau Qualified Welding Supervisor and am responsible for the weld quality control in the fabricating shop where I work so this is something I deal with regularly. It's a great process when used in the right place.

[Kerry Pinkerton]

Thanks Guys,

Attached is a photo of one of the welds. This is a 1/2" dovetail mounting plate welded to 1/4" steel tube. Virtually no splatter and that is probably caused by not having the metal as clean as possible. The weld has a nice convex flow and will need no prep prior to sending to Linex. If I was painting it, I'd clean it up a little but very little. The setting was 25.5V at 450 ipm wire speed and .035 wire...about as hard as I can go with .035 wire.

Not for sheetmetal. The lightest stuff we use is 1/8" tube for legs, 1/4 and 1/2 bar for feet, 1/2 for mounting plates, and 1/4" tube for most everything else. The caculator starts at 1/8" with 23-24V and 320-340ipm for .035. The caculator is Miller part number 086 446 and I assume is an orderable part from Miller.

To answer some questions. We have three Miller MIGS, a 251 with the electronic display, a 210 and a smaller 110V that I haven't used in years. The 251 is the one I do Spray Arc with. The 210 is mainly used for tacking feet on legs once we get things squared up (a different welding area). The electronic display makes it easy to set. I guess with more experience one could adjust by looking at the puddle and knowing what was needed. Several of the comments posted will help me learn so thanks.

I agree with the comments about the additional heat but have ways to deal with any warpage but haven't really seen any worse than normal. I've noticed that the puddle will indeed sag if you're off flat and even then sometimes if you get too much heat in the puddle. I'm still learning (and always will be)

[Bambi]

I wouldn't worry about the heat effects on the metal that your doin. The issued comes from heat into the mig gun. You would notice it if lets say you had a Tweco gun rated at 600 amps, it would get hot, initially we used to dip the guns head in a bucket of water. You can't go by the rating when in the spray mode using argon oxygen mix. If you have heat problems at the gun particularly when doing long welds, you will probably have to invest in a water cooled gun and cooler.
Good Luck

Bambi

[Gene_Olson]

Kerry,
My friend Lee Marshall who ran Bonnydoon Engineering, made hydraulic presses and stuff for jewelers, showed me that about 10 years ago when I visited his shop up the hill from Santa Cruz, CA. He let me try it on a piece of scrap.
I said, hey wow.
I don't do enough thick stuff to justify paying rent on another tank, He used it on all the press frames.
It is a great system if you have a welding positioner and can do all the heavy welds in the flat position.

G.

[Dawai]

I thought all mig welds looked like that., more splatter perhaps. Lately my rod welding instead of a row of dimes looks like bird crap.

I bought a Miller sychrowave 200 tig power source.
You can piggyback a Mig wire feeder. I sold three on ebay for $50 about two years back. I wish I had them back. Having 200 amps to SINK the mig bead in is a definite advantage. You could weld Ibeam.. the feeders on the end of the power cable uses the voltage from the welder to drive it and only the power, not any outside power needed. THE top-migs require 120vac.

My e-wheel frame, made from 2x3x.188 wall, flexed over six inches when the regulator failed on the 8" cylinder. No welds broke. I am near blind most the time these days. Cheaters and glasses don't help the focus.

But, I love the tig, it is slow, but you can melt it all together..

I am no trained welder. I passed a welding cupon test at Sequoah nuclear plant, but I am no welder. I refused a weld set up by a engineer there. He wanted me to weld two 1/2" welds to lift 6,000lbs over my buddies head with a crane.. After I refused, the Ironworker who recieved the welding job, cut out lifting plates four inches wide and welded them in.. it did not break.. NOW you or I could have welded 16" of weld to hold that much pressure. 4" down both sides x 2 brackets.

Nobody bevels, without beveling there is no way to confirm the bead is not "just there on top"..

Kerry: (I bought flat transistion lower rollers) Now putting the chipping hammer on the ewheel frame.. You sure cleared the room over there when you ran yours.

[Bill B]

Hi Kerry,

For what it's worth I experimented with spray arc in AZ. The welding supply talked me into a large bottle of "Stargon." It was mostly the typical CO2/Argon mix with a couple percent of oxygen thrown in. I was mostly building with material like you are using. Seems like the oxygen added heat rather than raising the amp setting. Almost like using a higher output machine.

The results were great once I was used to it. The welds were very clean and ready for paint. Thanks for reminding me. When I can afford a separate bottle for the large machine I'm going for the mix with oxygen in it.