Are Spray and MIG the same? Is 75/25 gas OK for both, and pulsed MIG?

RenoHuskerDu

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I just set up my new Miller Multimatic 255 today. No welds done yet, still reading. The first project is repairing cracks in the 1/16 mild steel floorboard of a 1986 Ford Bullnose. The cause of the cracks was improper custom seat mounts and they have already been cut out.

The bottle I bought is 75/25. I was just watching a weld.com video about pulsed MIG and he seemed to suggest that Spray requires more Argon than MIG. I'm confused by terms.

Is pulsed MIG a spray weld? How about MIG?

I bought my welder from a well-known local shop and they have an exact copy of my welder in production, with the dual bottle TIG kit too. They recommended 75/25 for pulsed MIG so that's what I bought. I have room for a second bottle though if I need it. There is actually room for three bottles on that big cart.

Any help is welcome. I don't want to mess up this Bullnose job, it's one of my favorite pickups.
 

Lis2323

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I too am new to pulsed Mig but I have been using 90/10 and 92/8 as recommended. Yomax and others will have good advice and I will be following with interest.

And we need pics of the Ford please.
 

RenoHuskerDu

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Nice. I’ve never heard them referred to as bullnose. Kenworths and Ford cabovers (snub nose and bullnose ) but never pickups until now
There's a whole series of nicknames for old Fords. Dentside is 73-79. Bullnose 80-86. Bricknose 87-91. Aeronose or OBS 92-97. Earlier, I don't know. If you like Bullnose here is a great forum with oodles of doc http://www.garysgaragemahal.com/

Back to welding, I found that Miller has a forum, and from what I've read there so far, my 75/25 gas is too low in Argon for the pulsed MIG I want to do on 19 gauge carbon sheet metal. I'm going to hold off for now until I get more info or get another bottle. https://forum.millerwelds.com/forum/welding-discussions/6260-spray-transfer-mig-questions
 

Yomax4

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18ga material will be difficult to manage with a regular pulsed mig set up. I'm wondering why pulse it? Even with the smallest wire you will have a heat problem about 1" into the weld and single pulse won't help that. As long as you already have 75/25 I'd just go with 023 wire and short arc it. I'm not sure what the capabilities are on the 255.

On the gas it's not just needing higher argon content for spray or pulsed spray as much as needing less CO2. However, I have a twin pulse machine that asks for certain gas mixes for certain applications and I sometimes lie to it and tell it it's getting a gas that it isn't. Not optimum but sometimes works. There are a dozen gasses for pulse and spray, The spray arc likes 90% or more Argon with CO2 and even a little oxygen for more heat. Pulse likes 90% Argon with CO2 and maybe a little Helium at times and 98% Argon with CO2 for stainless and a little helium works for that too.

90/10 is a common gas and as long as you have moved into the Pulse world ( Bravo ) you will likely want a higher argon mix. If you haven't used the tank yet they might swap you for a 90/10 or just use it up and get higher argon next time. Good Luck.
 

RenoHuskerDu

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18ga material will be difficult to manage with a regular pulsed mig set up. I'm wondering why pulse it? Even with the smallest wire you will have a heat problem about 1" into the weld and single pulse won't help that. As long as you already have 75/25 I'd just go with 023 wire and short arc it. I'm not sure what the capabilities are on the 255.

On the gas it's not just needing higher argon content for spray or pulsed spray as much as needing less CO2. However, I have a twin pulse machine that asks for certain gas mixes for certain applications and I sometimes lie to it and tell it it's getting a gas that it isn't. Not optimum but sometimes works. There are a dozen gasses for pulse and spray, The spray arc likes 90% or more Argon with CO2 and even a little oxygen for more heat. Pulse likes 90% Argon with CO2 and maybe a little Helium at times and 98% Argon with CO2 for stainless and a little helium works for that too.

90/10 is a common gas and as long as you have moved into the Pulse world ( Bravo ) you will likely want a higher argon mix. If you haven't used the tank yet they might swap you for a 90/10 or just use it up and get higher argon next time. Good Luck.

The longest crack is only 4" (see pic) so I can do the welds in overlapping beads to avoid overheating, right? The shop where I bought it had .035" wire in std size spools, and I didn't want a small spool. The driver wheel only does .035 and .045" so it sounds like I should order a smaller driver wheel and spool of .030 too. I've done a lot of sheet metal with MIG and .030 in the past successfully. But then do I need to consider the tube to the gun perhaps being too big for .030" wire?

Here is the longest crack. I'm going to need to build up the metal. BTDT in the past with success. Then it'll be covered with insulation and carpet. No more mount here. So it doesn't have to be pretty, just closed up and functional.
IMG_20200620_101925.jpg

FYI, here is a seat mount, poorly engineered by the PO, that caused the cracks. The mounts have been cut out now.
FloorCrack.jpg
 

CB

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I just set up my new Miller Multimatic 255 today.

The bottle I bought is 75/25. I'm confused by terms.

Is pulsed MIG a spray weld? How about MIG?

A well-known local shop ... recommended 75/25 for pulsed MIG so that's what I bought.

I have room for a second bottle though if I need it. There is actually room for three bottles on that big cart.

Any help is welcome.

Congratulations on your new welding machine!

I remember your other thread on weldingsite.com where you were exploring what MIG/MAG machine to get. Back on that thread, I suggested "to be sure and budget for two bottles of gas", and that suggestion still stands. Only now that you say that your cart can hold thee bottles, and in that other thread you said you plan on doing stainless, you might consider three bottles, where the third bottle is a trimix with the bulk gas being helium for the stainless.

Yes, pulsed MIG is a spray process, where the heat build up is reduced by the welding machine's control of the wave form.

The weld deposit is "sprayed" in a pulse process... where the wire is pinched into many tiny droplets in mid air to bring heat and metal to the puddle.

That aspect of pulse is just like spray, and more importantly to your immediate question, quite UNLIKE short circuit MIG/MAG, where the wire extends all the way to the puddle and short circuits, and the short circuit is what consumes the wire, delivering heat and metal to the puddle.

How pulsed spray differs from "regular" spray is in the wave form. Machines capable of "pulsing" can modulate peak and background currents, and the ramping between them, to cause the wire to get hot enough to separate into tiny droplets mid-air without short circuiting into the puddle, but can then dial the heat back (hundreds of times per second, in pulses) to reduce the overall accumulation of heat during the pass.

There is no question that 75/25 is NOT the appropriate gas for spray, nor for pulsed spray. Not sure why the local shop made that recommendation, unless you described your bullnose floorboard project, where they might have recommended sticking with short circuit MIG and spot welding it ...or what I call "dot" welding, since you won't be using resistance tongs, but rather a single sided approach with a MIG gun.

It may be kind of a challenge to pulse spray a low heat input, wetted in, "seam sealer" like bead on 16 guage rusty sheet metal when trying the spray process for the very first time. The original sheet metal will start disappearing in front of your very eyes, as the canals of porus corrosion hidden in the core of the sheet make it thinner in net cross section than the distance between it's bottom and top surface would otherwise suggest. Fixing that floorboard with pulsed mig might take a fair amount of practice to get right. Even if you get your skills and settings dialed in to make a perfectly contiguous seam, what happens when that foot long weld cools? You might turn your bullnose floorboard into a taco (warped from crystals in the molten metal reorganizing themselves neatly as they cool). As I understand it, die hard Ford truck owners don't do Tacos.

A quicker solution might be to run a backing plate under the crack, and dot weld, in an alternating pattern skipping back and forth to spread the heat around and allow cooling time, as well as to manage the pull of distortion as the dot welds cool. Prep the backing plate, the underside of the floor board, and the top side of the floor board, by stripping all paint, corrosion, scale, and contaminants by abrasive/mechanical means down to bright shiny metal. The backing plate can be pre bent to follow the contours of the Ford OEM floor board along the seam that you are repairing. Future corrosion between the sandwich surfaces of the backing plate to the underside of the floorboard can be mitigated by precoating with weld thru primer. SEM makes CopperWeld for this purpose.

The term "MIG" is a misnomer that has evolved into a short hand description for all the different weld processes we discussed above (short circuit, spray, pulsed spray) that can be accomplished by a wire feeder, and a few more, like globular transfer, surface tension transfer, and other proprietary named transfers that are beyond the scope of your question. The reason MIG is a misnomer is that it stands for Metal INERT Gas. So from strictly a liturgical perspective, PULSED SPRAY is more accurately called MIG than short circuit transfer, which uses more active gas (C02). This is why in Europe, where you describe spending a decade, the term MAG is often used to describe short circuit, for Metal ACTIVE Gas. And this explains why the industry evolved to using the term GMAW instead of MIG or MAG, where GMAW simply stands for Gas Metal Arc Welding, no matter what kind of gas, be it inert, or active, or any mixture in between.

Get you a bottle of 90/10 (C10), or 92/8 (C8), or, if the previous two options are not available, some 90/7.5/2.5 (give or take a point or two up down on either of the three components), which would be Argon / CO2 / O2. The O2 will add more heat, and with a machine as robust as you have, you probably don't need to go that route. I just mention it because sometimes we are the victims of whatever the local gas supplier has in stock. I have a proportional gas mixer, but that's getting into the weeds, and since it's always a good idea to have a second bottle on hand anyway, you might as well fill up that big empty cart with a second bottle of C10 or C8 for you when you want to spray or pulse spray, and keep the C25 for when you want to short circuit.
 
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RenoHuskerDu

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Congratulations on your new welding machine!
SNIP
A quicker solution might be to run a backing plate under the crack, and dot weld, in an alternating pattern skipping back and forth to spread the heat around and allow cooling time, as well as to
SNIP

Wow I'm drinking from a fire hose. Thanks for all that.

Now I know what to do. I'm going back in Monday for a bottle of 90+ and some CopperWeld. Then I'm cutting a good sized backing plate from a parts truck we have out in the yard, Bricknose but the floorpan didn't change from 80-97 on these.. So, it won't need any forming. As for rust, there is basically none. The truck was from Central Valley in Cali and came to Central TX a few years ago. Rust isn't an issue. But you convinced me to do more prep. Actually my son will do it. He's the one most motivated to get this Bullnose back on the road, so he can drive it to work and make money. And he owns the parts truck I'll be cutting up. There is little in the world like the power of a motivated teen boy with his driver license.
 

RenoHuskerDu

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Went in today to order a bottle of 90/10 which will arrive in a week for purchase. He had a big one to lease in stock but I prefer to own, and prefer 4' size. Praxair has one in stock but they also have a 30.06 sign up so I don't go there. These days, I'm not disarming anywhere but the courthouse.

I was unable to find any CopperWeld etc at local welding stores. But I have an idea and want to bounce it off y'all. When stick welding pipe fences (VERY common in Texas), I often use stubs of an old stick to bridge a hole or gap. Sometimes I'll even lay 3 side by side on a hole then weld them up. This is usually with 6011 rod, and it works pretty well for the rough welding that is required on pipe fences, cattle guards, gates.

I wonder if I could strip the flux off a few inches of rod, bend it to shape, lay it in there and do the same thing with the crack you see here? I'd just lay the rod lengthwise in the crack then pulse it in. This is the longest crack. This area won't be used for a seat mount anymore. It will just be covered up in sound insulation and floor carpeting.

BiggestCrack.jpg
 

Gary Fowler

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I have done that for large cracks. I also did it with my FCAW welder using some TIG wire as filler. It works pretty good. That gap doesnt look too big that it cant be welded up. You could also make a couple of "dogs" (plate with hole in it welded to both sides of the crack then use a bolt to "dog" the two pieces closer together.
You can use the same principle to make an L shaped dog with a nut and bolt welded to one leg. Then weld the dog to the low side so the bolt is on the opposite piece. By tightening the bolt you can "dog" the two pieces back level so there is no Hi-Lo.
 
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