| 摘要 |
PROBLEM TO BE SOLVED: To provide a large nitriding depth in a short time by nitriding a work with NH3 gas in at least one of a carburizing process to be implemented under the temperature suitable for the carburizing treatment, and a subsequent temperature-dropping process. SOLUTION: The carburizing treatment is suitably implemented at 900-950 deg.C. The nitriding treatment is implemented by feeding NH3 gas into a heat treatment furnace, for example, during the whole period of the temperature-dropping time. When a surface area, or the like of a work is too small, and the nitriding depth is too large, the nitriding time is adjusted by retarding the NH3 gas feed starting time, or expediting the feed stop time. When the surface area of the work is large or the target nitriding depth is large, or the like, the nitriding time is adjusted by starting the NH3 gas feed in the beginning or in the middle of the carbunizing process, and continuing it across the temperature-dropping time. Since the nitriding process is simultaneously implemented with other processes, the total treatment time can be considerably shortened.
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