400F is a decent number that will keep you below any temper on steel. If I knew the steel number I might be able to find the tempering numbers to get you a higher number.
Are you planning to cut the keys off or you trying to get them to break loose and slide off? Have you tried wrapping the end in plastic and dousing with vinegar or Evap-O-Rust?
Are you planning to cut the keys off or you trying to get them to break loose and slide off? Have you tried wrapping the end in plastic and dousing with vinegar or Evap-O-Rust?