Position Change - Pay Increasing Question?

I have been working for a Steel Fabrication Company for little over a year now. When I was Hired I was intended to be only a Grinder. With an Opportunity for advancement to the back where this is called the Cut Shop part of the Shop. Soon After 3 months after being there they moved me to the back. I have been in the back know every machine and run every machine periodically. I can Press Metal " Bend", Run Angle Matic, Run Coaper or Pedimat Machine, Run Pedimat Saw and Drill line, FPB Plasma Table and Burn Table or Water table. All without any assistance. I have knowledge of someone who has been there for 10 years and I have only been with them for a year. I also Know how to bend pipe for rails and build rails, tack weld, and grind. I was hired making $7.50 an hour minimum wage in my state. I am still making the same amount even after a year and a placement change of my position at my current employer. Is it against the law or something to be paying me the same amount for some of these other duties or positions that I am faced with? Should I expect a raise for the position change? Please help! Thanks for all your answers.