Setup for MIG welding 1/2" mild steel

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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 sureon 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.
Reply: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.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:100% co2 will burn hotter tooLincoln Power Arc 4000 Thermal Arc Fabricator 252 iThermal arc 186Thermal Arc 26 tigTweeko 200 amp spool gunHobart AirForce 400WP-17V-12R
Reply:Generally for a fillet the bead should be as wide as the material, in your case a 1/2".Millermatic 211 Lincoln Idealarc 250-250, ~500lb water cooled tig
Reply:+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.JohnLast edited by Silicon-based; 08-22-2011 at 09:44 PM.Reason: Added info about flux-core.A few weldersA lot of hammersA whole lot of C-clamps
Reply: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?
Reply: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.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply: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...
Reply: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....Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Originally Posted by con_fuse9Disclaimer, 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....
Reply: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.Millermatic 211 Lincoln Idealarc 250-250, ~500lb water cooled tig
Reply: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.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply: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 bottleTiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply: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.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Originally Posted by turkby 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.
Reply:Originally Posted by Welding_SwedeYes, 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
Reply:at ford motor,it was called finewire welding. don't know if that term is still active today.