i do a fair amount of steel welding, but would also like to do some aluminum welding. i cannot afford another tank for argon. is there a mix which would be good for both. i understand pure argon wont give the penetration on mild steel but what other mixes are available for mig.

Can't have the best of both worlds here, sorry. You NEED CO2 for MIG welding steel, straight argon won't even work, been there, tried that. And you CAN'T have CO2 when you welding aluminum. You can weld alumium and steel and even SS with straight argon with a TIG welder only. MIG is a totally diffrent story.

Another negative to welding aluminum with a mig is the liner.You must replace the steel liner with a teflon liner.Once you change out the liner,you cannot re-use it.The best solution is to have 2 cable and hose assemblies.One for steel and one for aluminum.So.....you have two choices.Stay with welding steel ,sell the mig and buy a tig.Then you have a welder that will weld anything using one gas.One more thing.If you have never welded with a tig,you will find it is slower and requires more skill than mig but,if you have done some gas welding you should pick it up fairly rapidly.

i used to do mostly tig with limited mig use. as i cannot afford a tig now i wasnt sure with mig as i have had little work with mig in the past. thanks as well, i know with tig you could do both but wasnt sure with mig. i do enjoy mig and find it quite easy, almost as easy as tig.