In the previous post I mention 6g wire for a max 50A draw. For 60A the wire should be 4g.
When I went back and re-read I noticed this:
"the plug and receptacle that i replaced have the white in the center, and the green, and black on either side.........."
Obviously the plug is wired incorrectly.
The receptacle is incorrectly wired using a green wire as one of the hots from the double pole breaker. Although confusing, it should not effect the operation regardless of the colors, as long as the wires go to the correct terminals. My guess is he copied the colors from the receptacle when wiring the plug and there lies the problem.
That mistake by the person who originally wired the receptacle could have cost him the welder...