Youtuber Weldingtipsandtricks explains the difference between short circuit transfer and spray transfer, and discusses the necessary settings for each. Spray transfer is a hotter weld, sounds different, and is best used only on thick metal for horizontal welds.
Mig welding using short circuit transfer can handle sheet metal thickness all the way up to the beefy thick metal if done right. But for the really thick stuff, Spray transfer can be the ticket. 90/10 argon/co2 gas allows for spray transfer if you are using .035" er70s6 wire at about 25 volts and 350 ipm inches per minute of wire feed speed. Its hot…Its fast….and it really needs a heavy duty mig welding machine.
For more information about MIG welding basics, MIG welding techniques, including differences between pulling and pushing the puddle, view mig welding info and video here: http://www.weldingtipsandtricks.com/how-to-mig.html.