| 摘要 |
A carbonitriding method that allows the permeating rate of nitrogen to be increased to improve the efficiency of the carbonitriding process is directed to carbonitriding a workpiece formed of steel containing at least 0.8 mass % of carbon, including an atmosphere control step of controlling the atmosphere in a heat treatment furnace, and a heating pattern control step of controlling the temperature history applied to a workpiece. The atmosphere control step includes an undecomposed ammonia concentration control step of controlling the undecomposed ammonia concentration in the heat treatment furnace, and a partial pressure control step of controlling the partial pressure of at least one of carbon monoxide and carbon dioxide in the heat treatment furnace. In the atmosphere control step, the undecomposed ammonia concentration control step and partial pressure control step are carried out such that the ³ value defined by ³ = a C /C N , where a C is an activity of carbon in said workpiece and C N is the undecomposed ammonia concentration in said heat treatment furnace, is within the range of at least 2 and not more than 5. |
