| 摘要 |
A carbonitriding method that can improve the nitrogen permeating rate to render the carbonitriding process effective includes an atmosphere control step (50), and a heating pattern control step (60). The atmosphere control step (50) includes an undecomposed NH3 partial pressure control step (51), and a CO/CO2 partial pressure control step (53). The undecomposed NH3 partial pressure control step (51) and the CO/CO2 partial pressure control step (53) are carried out in the atmosphere control step (50) such that ac* defined by the following equation (1) is at least 0.88 and not more than 1.27, and α defined by equation (2) is at least 0.012 and not more than 0.020, where PN is the undecomposed ammonia partial pressure and PH is the hydrogen partial pressure in the heat treatment furnace, wherein a c * = ( Pco ) 2 K × Pco 2 ( 1 ) PCO: partial pressure of carbon dioxide (atm), PCO2: partial pressure of carbon dioxide (atm) K: equlibrium constant at <C>+CO22CO α = P N 0.006 × ( P H ) 3 2 × ( 1.877 - 1.055 × a c * ) 100 ( 2 )
|
