I forget what happens when you weld with straight argon. Usually I use a 75/25 mix of argon and CO2, but I just went to lay down a simple tack and realized I am completely out of 75/25(2 tanks on 2 welders, both empty at the same time ). So I grabbed the little bottle of straight Argon dad had for aluminum welding and laid the beads I needed to. Sounded slightly different then I'm used to, but I've also been practicing welding a lot and am welding much better then I used to. So is there any adverse effect of running straight argon when welding mild steel?