Limits of Work PieceThickness Using MIG

[knots43]

I have two Miller 180 Amp Mig welders. I run .023 wire on one and .030 wire on the other. Most of my work are small scale decorative sculptural pieces. However occasionally I build up fixtures and tools/ machines for use in my shop. Often the materials a much thicker than is recommended for my Mig welders. Using the .001" per amp, 3/16" is about all that could be welded with either of my machines. So my question is - What are the practical limits of welding thicker materials with my 180 Amp machines.

If you grind for penetration, and build up the welds with multiple passes how does that effect the work limits of these machines? By work limits I mean what can or should not be attempted.

[tommy2069]

with a 180 you should be able to weld 5/16 with no problem. i run .023 in my 140 lincoln on 1/4 inch alot and never had any problems . so your 180 should be able to handle 5/16 easily with .023.

[Cgotto6]

It's largely dependent on the type of joint. With groove joints, like a butt joint, you can bevel both pieces down to a material you can handle and do multiple passes until the joint is full. Fillet welds are much more limiting as you can't grind the material at all, so you gotta size the welder for the work. Using an underpowered welder works, it's just more impractical since you will be taking more time doing multiple passes.

Using .023 for 5/16 would be pointless. When I run .023 in my mm180 I have the wire speed pegged with my voltage setting only in the 5-6 range. Not near enough heat to be efficient. Using .030 is a much better choice.

[raferguson]

My concern would be penetration on heavier steel. Using MIG, it is possible to make a weld that looks good but is weak, something that is not generally a problem with stick.

Jody just had a video on how to do a down and dirty cross section etch on a weld. Alternately, engage in some destructive testing on some scrap.

One thing that would help on thick material would be preheating the work with a torch.

Let's see what the real experts say.

Richard

[tommy2069]

It's largely dependent on the type of joint. With groove joints, like a butt joint, you can bevel both pieces down to a material you can handle and do multiple passes until the joint is full. Fillet welds are much more limiting as you can't grind the material at all, so you gotta size the welder for the work. Using an underpowered welder works, it's just more impractical since you will be taking more time doing multiple passes.

Using .023 for 5/16 would be pointless. When I run .023 in my mm180 I have the wire speed pegged with my voltage setting only in the 5-6 range. Not near enough heat to be efficient. Using .030 is a much better choice.

i have to disagree with the .023 being pointless.the machine will burn a thinner wire hotter and will penetrate more into the metal than it will with a thicker wire. i use my 140 for alot of stainless work it has trouble burning the .030 wire but when i drop a roll of .023 in it it welds perfect and has no problem penetrating the metal unlike the .030 wire that just wants to cold roll on you.


think of it this way have you ever been on a job and had to cut a tip off of something your welding and didn't have a torch handy? i have and i keep 1/8 rods just for this if i'm burning a 5/32 rod i'll just grab the 1/8 and it pretty much gouges the metal out same setting just smaller rod .smaller rods or wire means you can get more heat.never ever had a problem burning small wire or rods in a machine with limited power but i have ran into problems trying to burn larger rods or wire in them.

[Cgotto6]

That is just not right tommy. The only difference in wire diameter is the amount of metal deposition. A certain amount of "volume" of metal coming out of the welder. The weld is going to require the same voltage regardless of what size wire, the only thing that changes is the wire feed rate. If you switch to smaller wire, you must run more of it to produce the weld compared to the larger wire, or vise versa. There is no change in amperage of the weld. So by saying .023 is hotter is just not true. Theoretically you could use any wire diameter to do any weld, given your machine can run the feed rate of wire to match the voltage needed. I said using .023 is not going to happen, most likely, because I know on my 180 I have the wire feed maxed while only being halfway up on the voltage scale. That amount of voltage is not enough to burn 5/16. If he was running a suitcase or larger mig, with higher possible feed rates you could use .023 on heavier weldments. It is all a ratio of volts/volume of wire. My welder using .023 set at 5.5 on voltage, and 100 on wire feed speed, is the exact same as running 5.5 on voltage and around 50 on wire feed speed. No difference at all, same amperage weld. This is all just to illustrate the differences, and are not actual settings I've used, but it's close.

[tommy2069]

i still disagree. you can get more penetration with smaller wire if your on a limited power machine.wire speed has nuthing to do with penetration. sure you'll have to turn the wire speed up and sure you won't get as much weld but you'll have a better penetration with the smaller wire. just done a job where the guy wanted me to weld the stainless exhuast on a crew boat i told him to get .023 but instead he got .030 and it just wouldn't tie in. i went to my truck and got a roll of .023 and done the job with no problems nice smooth weld and no cold roll.


same thing with my little 140 i have a spool gun for it but it can only burn .023 wire anything bigger and it just cold rolls.

[tommy2069]

also you say the weld is gonna require the same voltage reguardless of wire size that doesn't make sense .if i have my machine set for .030 and drop a roll of .023 in it it's gonna burn hotter than it was with the .030. so i will have to turn the amperage down to weld.

[Cgotto6]

Tommy what you are describing in your instances is due to your machine having no horsepower. What I described is the reality. Saying a specific size wire burns hotter is not true. What I said in my last post is how it is. There is a set ratio of wire volume entering the weld and amperage of the weld. You can achieve the same wire volume with different wire sizes by adjusting the feed rate.

I don't doubt your 140 won't run .030, but that absolutely nothing to do with this situation. It has to do with your machine not having enough power to burn that volume of wire. Keep in mind everything you have said relates to your experiences with your little 120v mig, and nothing to do with the OP's question or situation.

[Cgotto6]

also you say the weld is gonna require the same voltage reguardless of wire size that doesn't make sense .if i have my machine set for .030 and drop a roll of .023 in it it's gonna burn hotter than it was with the .030. so i will have to turn the amperage down to weld.

No it won't, if you actually set it up properly, you wouldn't need to do anything other than turn up your feed rate to compensate for the smaller volume of wire per inch. In the end this would result in a weld of the same amperage and voltage.

[johnnyg340]

Guys,

Look at the current saturation point for .023 wire. Somewhere around 150 amps the wire is current saturated and you will not squeeze and more out of it because of the conductor size .023. In fact, .030 still won't do the job, as it gets saturated at about 190 amps or so. So, no matter how high you crank the WFS and voltage on the machine, you will not get the energy out of these wires for 5/16. A weld on 5/16 steel will require in the neighborhood of 200-210 amps. .035 wire is the way to go, and even with that the 180 machine is at it's limit.

[Cgotto6]

Hey jonny I haven't heard of current saturation before. Where did you learn this, I would like to check it out. Thanks

[johnnyg340]

Also, i don't remember the exact equations but joules measure the energy input into the steel. Just because you have to crank .023 to weld the same thickness material as .030 at about 2/3 of the .023 WFS DOES NOT MEAN you are putting in a hotter weld (energy measured by joules)

[johnnyg340]

Also, i don't remember the exact equations but joules measure the energy input into the steel. Just because you have to crank .023 to weld the same thickness material as .030 at about 2/3 of the .023 WFS DOES NOT MEAN you are putting in a hotter weld (energy measured by joules)

Hate to say it here, but it's in Lincoln's GMAW welding guide. This of why you would never run 14-2 wire for a 120v 40amp circuit in your house. Current is volume, and the conductor size (14ga for home or .023 .030 etc... for welding) must be able to handle the load. The voltage is simply the pressure to push the load.

[johnnyg340]

Hey jonny I haven't heard of current saturation before. Where did you learn this, I would like to check it out. Thanks

MEANT TO REFERENCE THE ABOVE QUOTE... MY BAD. I don't post often...