Solution annealing treatments are applied to a series of alloy steel and stainless steel compositions. Solution annealing of 300 series stainless steel castings produces a uniform microstructure free of carbides in the microstructure. Solution annealing of precipitation hardening cast and wrought alloys produces a soft microstructure suitable for machining to close tolerances. These alloys have the potential for Age Hardening after machining with minimal distortion of close dimensional tolerances. These materials and processes are generally applied to medium strength requirements on turned or screw machine parts. The heat treatments may be performed in batch atmosphere furnaces, non-atmosphere furnaces, and vacuum furnaces, depending on the part size, geometry, and surface condition required. Small parts may also be treated in continuous hydrogen belt furnaces. Solution annealing and age hardening may also be applied to aluminum alloy stampings and castings. These treatments are usually performed in non-atmosphere batch furnaces with water quenching of the parts after solution annealing, and age hardening in electric or gas fired batch furnaces in air.