Metal cutting blades run much slower than wood cutting blades. If you are running a constant speed saw that runs around 3000 ft/min blade speed it is hard on the blade and generates more heat than the blade can handle. You need to run at about 200 ft/min or less speed to be effective and then keep the metal fairly thin, 1/6 in. A true metal cutting band saw usually has a coolant that is sprayed on the blade to keep it cool so it doesn't lose its temper.