Gas Flow Rate for MIG?

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I have quite a bit of experience stick welding and some time with flux-core wire feed. I recently upgraded to 75/25 Argon/C02 with a flow rate regulator (Cu Ft/Hr, Li/Min gages). Mostly I will be welding mild steel with .030 or .023 solid steel wire.My questions: What is the 'correct’ gas flow rate?  How will I know if the flow rate is too high or too low, and, is there a ‘just right’ flow rate? Also, how does flow rate affect the weld quality?Thanks.....HF 151 Dual Mig Welder (with mods)Lincoln 225-S AC WelderBuffalo MM-1 Milling MachineCraftsman/Atlas 6 inch Metal LatheBuffalo RF-115  4 x 6 inch Band-Saw
Reply:In still air, start about 20 CFH.  Then do some practice and back it down until you see weird things happening.  Or shut off the gas and run a quick, short bead and see how ugly it is.  Try it up just a bit higher if things don't look good and you'll eventually find what works in your environment.  You can't turn it way up and weld outside in a high wind.  Doesn't work that way."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:12-20 is the range I've read.  I've never gone as high as 20, except maybe outside in the wind.  I keep it close to 12 cfm in the shop, and haven't ever had a problem with that.  Gas is expensive, and you'll always run out on a Sunday.Jack OlsenMy garage website
Reply:My son has used as low as 12.  I've seen numbers from 10 to about 35 or 40, but those are the extremes. Anyone use the big MIGs at high current who can comment?"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Gas flow depends on the size of the nozzle. For the smaller 1/2" size nozzles you want generally 15-20 cf/hr.For the larger 3/4" size nozzles you run about 25-40 cf/hr. I tend to prefer the large nozzles since they provide a lot better gas coverage.If you turn the gas flow up too high you create a turbulent gas flow. That can draw outside air into the weld area and cause porosity.Current doesn't generally make much of a difference. If you're using a high current machine and welding with aggressive parameters, you'll be equipped w/ a gun with a higher current rating. That will mean large nozzle with a higher gas flow to keep things from overheating.