NITRIDING METHOD, AND NITRIDED COMPONENT MANUFACTURING METHOD

Provided is a method for nitriding a low alloy steel with which a certain hardened case depth can be ensured and formation of a compound layer can be inhibited. A low alloy steel is heated to a temperature ranging from 550 to 620°C, and a high K N value process and low K N value process are performed for a total process time of A ranging from 1.5 to 10 hours. In the high K N value process, a nitriding potential K NX given by Formula (1) ranges from 0.15 to 1.50, the average K NX value K NXave ranges from 0.30 to 0.80, and the process time is X in hours. In the low K N value process, which is performed after the high K N value process, a nitriding potential K NY given by Formula (1) ranges from 0.02 to 0.25, the average K NY value K NYave ranges from 0.03 to 0.20, and the process time is Y in hours. An average nitriding potential value K Nave determined by Formula (2) ranges from 0.07 to 0.30. K Ni = NH 3 partial pressure / H 2 partial pressure 3 / 2 K Nave = X × K NXave + Y × K NYave / A where i is X or Y.