OF OXYGEN IN STEEL

Yi Maozhong  Lin Jiansheng
Shanxi Institute of Mechanical Engineering

Abstract: 20, 20Cr, 20Cr2Ni4A, 40Cr and GCr15 steels were internally oxidized for 8 to 80 hours at temperatures between 1133K and 1373K using a powder mixture of Fe₂O₃:Fe:Al₂O₃=1:1:1 in order to determine the diffusion coefficients of oxygen in the steels and in the internal oxidation layer of the steels. Experimental results show that the oxides in the internally oxidized steels are (Mn_0.83Fe_0.17)(Al_1.96Fe_0.04)O₄, Fe(AlCr)₂O4 and Fe₂SiO₄; the kinetics of internal oxidation of the steels obeys a parabotic rate law. The diffusion coefficient of oxygen in the internal oxidation layer of the steels, D0¹⁰ was evaluated by means of the kinetics of internal oxidation; D₀¹⁰ increases with increase of the volume fraction of oxides in internal oxidation layer, f¹⁰ The diffusion coefficient of oxygen in the steels (austenite state), D₀, was determined by extrapotation of relationship between D₀¹⁰ and f¹⁰ to f¹⁰=0. D₀ may be expressed as D_o=2.567 exp(-165.32kJ/RT)cm²/s.

Key words: Steel  Oxygen  Diffusion coefficient  Kinetics Internal oxidation

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