how many amps does your welder require? 10ga supports up to 30a. you would have to have a 30a breaker in the main panel and wire the panel in the garage as a subpanel. (Make sure to keep the neutral and ground separate) is the garage detached? if so, i think you need to install ground rods. an electrician will chime in shortly i'm sure. I am currently wiring my attached garage so I know what you are going through. I ran 6/3 to the garage since I had extra from a previous project.