Setup for MIG welding 1/2" mild steel

[ehart]

I need some general advice from anyone who MIG welds thick mild steel.

I need to weld some 1/2" mild steel using my Lincoln power mig 300.
I have a 300 amp torch and 0.035" 70-s wire, and the argon CO2 mix.
The table in the machine recommends using 0.045" wire and running it at
375 amps / 27.3 volts with 100% CO2 ( oddly enough ).

Anyways I have read about people welding 1/2" mild steel with 0.035" wire but I'm not sure
on the voltage and amperage settings.

I'm also wondering what the width of the bead should be if I'm welding a fillet bead.

I an old rule of thumb for stick welding is about 2 electrodes wide, but that doesn't really help me much here.

[shovelon]

Save yourself the headache and get the .045 wire. I have had nothing but feed problems with using undersized wire.

It seems to carry the arc better too.

[assassin_works]

100% co2 will burn hotter too

[mengineer]

Generally for a fillet the bead should be as wide as the material, in your case a 1/2".

[Silicon-based]

+1 on the .045 wire- it's not expensive (usually cheaper than .035) and will run nicer and need fewer passes. Your 300A gun will be fine if you have the proper liner installed. You will get the most out of that machine if you use 90/10 or similar mixtures which support spray transfer.

Another good option would be gas-shielded flux-core. Lincoln, ESAB, Hobart and others- check their sites. Some run with 100% CO2, some with 75/25, some with either. Very popular for heavy plate, a search of this site will yield a lot of information.

John

[ehart]

Ok great. But if I run the machine at 375 amps( with 0.049" wire) that will probably be too much for my gun.
I ran some welds with the 0.035 wire at like 300 amps and laid a nice flat bead, but I'm not sure about the penetration.

I'm thinking as long as it runs well and the bead is flat I'm in good shape?

[Silicon-based]

Are you sure you are meaning amps and not wire speed (ipm)? The highest recommended setting for .045 wire in Lincoln's catalog is 500 ipm, giving 340A with 90/10 gas. 375 ipm will give you around 300A which is reasonable for that machine and more than adequate for 1/2" plate.

If you do not exceed the machine's duty cycle, the gun will probably survive.

John

[ehart]

Yes I think your right. On the table inside the machine it just lists 375/ 27.3 , which is probably the
WFS/ voltage.

Is that correct? The table doesn't list the units...

[con_fuse9]

Disclaimer, The maximum wire speed I have run is about 420.

My old Miller 251 called out 23.5V and 475ipm for .035 on C25 for 1/2. Now that machine is known for being on the hot side. So any other MIG I would say add a volt and a half. It doesn't mention multiple passes - but it never does.

On the 350 the recommendation is 29.3V/530. I gotta wonder if that voltage number isn't a typo (24.3?V). The 350 has a 4 roller setup, it might actually be able to do 530 steady. With .045 Miller recommends spray. As another data point, with pulse, miller calls out 650ipm with .035. Maybe if kept the gun really really straight....

[ehart]

Originally Posted by con_fuse9

Disclaimer, The maximum wire speed I have run is about 420.

My old Miller 251 called out 23.5V and 475ipm for .035 on C25 for 1/2. Now that machine is known for being on the hot side. So any other MIG I would say add a volt and a half. It doesn't mention multiple passes - but it never does.

On the 350 the recommendation is 29.3V/530. I gotta wonder if that voltage number isn't a typo (24.3?V). The 350 has a 4 roller setup, it might actually be able to do 530 steady. With .045 Miller recommends spray. As another data point, with pulse, miller calls out 650ipm with .035. Maybe if kept the gun really really straight....

I see, thank you. Would setting the machine up for spray just be the result of the higher
current and voltage? IE- is spray a different setting on my machine or does it just happen because of the increased voltage and current?

I think I will try it would just as the table says with the 0.049 wire and go from there.

[mengineer]

The higher speed & voltage results in spray transfer instead of short circuit, with the proper gas, with a higher argon content such as 90/10 or 98/2. Your machine should say the recommended gas on the settings chart for your setup. I'm sure someone with more knowledge of the subject will help you out.

[turk]

on any steel thicker than 1/4" i prefer coredhield 8 which is dual shield. we always ran 75/25 gas at work. I welded 1/2 inch steel on many occasions.

[soutthpaw]

If u r not welding out of position, then I would opt for spray transfer too and o45 wire. I just bought a 44lb roll of .045 aid it was about $50... airgas steelmix will do both shortcircuit and spray transfer if u only have one bottle

[turk]

by the by, shielded welding with co2 is sometimes called mag welding as co2 is actually active, not inert like mig (metal inert gas) stands for.

[Welding_Swede]

Originally Posted by turk

by the by, shielded welding with co2 is sometimes called mag welding as co2 is actually active, not inert like mig (metal inert gas) stands for.

Yes, and since we're going there...

In the States the technically correct term is Gas Metal Arc Welding (GMAW) or Flux Core Arc Welding (FCAW). Presumably because CO2 is not inert and the term "Metal Inert Gas" is somewhat misleading but stuck in our conventional nomenclature. TIG and GTAW as well.

I thought the alphabet soup was bad in my past life (Information Tech.). Give it a few years and the names will change again right?

Eric

[ehart]

Originally Posted by Welding_Swede

Yes, and since we're going there...

In the States the technically correct term is Gas Metal Arc Welding (GMAW) or Flux Core Arc Welding (FCAW). Presumably because CO2 is not inert and the term "Metal Inert Gas" is somewhat misleading but stuck in our conventional nomenclature. TIG and GTAW as well.

I thought the alphabet soup was bad in my past life (Information Tech.). Give it a few years and the names will change again right?

Eric

Hahah yeah your right, but everyone knows it as MIG these days. And in chemistry they don't call it a inert gas anymore they call it a noble gas. But I don't think anyone wants to change

[boatbuoy]

at ford motor,it was called finewire welding. don't know if that term is still active today.