Patent ID: 9453277
Filing Date: 2016-09-27
CPC Classification: C21D,C22C,C23C,F27B,F27D

Claim Text:
1. A method of heat treatment for performing a halogenation treatment and a nitriding treatment by heating a steel material to be subjected to halogenation treatment and nitriding treatment under a predetermined atmosphere, comprising: using an alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less as a material of a surface of a core internal exposed to a treatment space where at least the nitriding treatment is performed; and removing at least a portion of a nitrided layer, after the halogenation treatment and the nitriding treatment are repeated, which result in the nitrided layer formed on the surface of the core internal having a thickness greater than 25 μm, so that a thickness of the nitrided layer becomes 25 μm or less.