A carbide blade is for wood. It has little chunks of carbide on the tips of the teeth. A carborundum blade is a metal cutting blade made of epoxy and grit. Any metal cutting, grinding wheel looking, type of blade will work. Cool it as you go so you don't turn the steel blue. As my late father used to say "non illegitimi carborundum", Latin for "don;t let the bastards wear you down.