日本金属学会誌

J. Japan Inst. Metals, Vol. 34, No. 6 (1970),
pp. 581-585

Influence of Nickel on Carbon Potential in Gas-Carburizing of Steel

Syôitsu Seo1, Tôru Miyazaki1 and Etsujirô Yajima1

1Nagoya Institute of Technology, Nagoya

Abstract:

The influence of nickel on carbon potential, an important factor in the gas-carburizing, was studied at 900°C by measuring the dew-point equilibrium curve. The results obtained are as follows:
(1) Dew-point of endothermic gas is the factor which determines the carbon potential, and if the relation between the carbon potential and activity of carbon is known, the dew-point is also the factor which determines the activity of carbon.
(2) For the endothermic generator gas composed of 23%CO, 32%H2, slight H2O, CO2 and N2 at the carburizing temperature of 900°C, when the dew-point is -9°C, the activity of carbon becomes 1.
(3) The equation for the solubility change of carbon ( Δ C%) due to nickel addition is obtained as.

Δ C%=m'%Ni=-0.043%Ni,
where the coefficient m' is the solubility parameter which indicates the γ -field to be extended or to be reduced.
(4) The value of m' is possitive for the carbide forming elements and γ +special carbide field is extended by these elements.
(5) If m' of all alloying elements have been known, it is possible to calculate the carbon potential for ac=1 and to determine the dew-point equilibrium curve.
(6) The value of m' of nickel, chromium and molybdenum are nearly equal to m' in molten steel.


(Received 1969/8/16)

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