2.3.2
Sometimes rotors are annealed with the stators, but often they are only given a rotor blue anneal. This is similar to the end of the stator anneal, mentioned previously. The rotors are heated to about 371°C (700°F) in a steam-containing atmosphere to form a magnetite oxide on their surface. They are then die-cast with aluminum to form conductor bars and end rings. The magnetite oxide prevents adherence of the aluminum to the steel laminations and thereby reduces rotor losses.