| 摘要 |
PROBLEM TO BE SOLVED: To improve a defect that a treatment method using propane gas can not uniformly carburize a steel material with unopen hole or unevenness, and that a treatment method using acetylene gas or ethylene gas needs a large quantity of expansive acetylene gas and ethylene gas, though conventionally there have been a method of treating the steel material in propane gas at a pressure of 1 kPa or less, and a method of treating it in ethylene gas and acetylene gas at a pressure of 10 kPa or less, in order to prevent generation of soot, in a vacuum carburizing method of a steel material. SOLUTION: This carburizing method comprises, employing mixed gas of propane and acetylene gas for the carburizing gas and making a pressure in the heating furnace in a vacuum condition of 0.05-3 kPa. It further comprises introducing the carburizing gas into the heating furnace in a pulsed way. Alternatively, it comprises introducing a certain quantity of the propane gas consecutively into the heating furnace, and introducing the acetylene gas in the pulsed way, when introducing the above carburizing gas into the heating furnace. A ratio of acetylene gas to the mixed gas is 5% or more but 50% or less.
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