| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a surface hardening method of iron or an iron alloy, which can provide a part from a cheap steel material such as carbon steel with a sufficient surface hardness and a small degree of thermal strain, and a small degree of dimensional change, a surface hardening apparatus of the iron or rion alloy, and a surface hardening structure of the iron or iron alloy obtained thereof.SOLUTION: A process of forming a two-layer structure of FeNand nitrogen martensite on an object to be treated includes the following steps: the object to be treated is transported to a heating room where ammonia gas is supplied; a temperature of the heating room is set to the temperature of a mixed phase region of austenite and iron nitride (FeN) in an iron-nitrogen phase equilibrium diagram so that the object to be treated is nitrided such that a surface nitrogen concentration of the object to be treated becomes a nitrogen concentration of FeN; and the object to be treated is rapidly cooled and heated again.</p> |
