An annealing furnace or oven is capable of heating material to a specific temperature under uniform heating conditions, generally associated with softening and/or involved with relieving stress.  The right furnace for your needs depends on the type of steel among other factors.  To prevent oxidation during annealing consider protecting your parts with foil wrap and/or heating in an atmosphere (ex. nitrogen).  An annealing furnace could be a batch (box) furnace or oven or a continuous (conveyor) furnace.