Patent attributes
A vacuum carbonitriding method includes: performing a vacuum carburizing process on an object to be treated (a workpiece) in a heat treating furnace under reduced pressures by supplying a carburizing gas into the furnace that has been heated to a predetermined carburizing temperature; stopping supply of the carburizing gas while keeping the carburizing temperature so as to diffuse carbon in the workpiece under reduced pressures; and performing a nitriding process on the workpiece by supplying a nitriding gas into the furnace under reduced pressures after lowering the furnace temperature. Required heat treatment qualities such as surface hardness, effective case depth, toughness and the like can be achieved in a short time with reproducibility even in a case of workpiece made of low-grade steel or case-hardened steel.
