A role of CO
2 in suppresing oxidation of molten Al-Mg alloys in air-CO
2 atmosphere was studied. The surface film on the molten Al-Mg alloys in air-CO
2 atmosphere is composed of MgO with a slight amount of carbon. Carbon does not form carbon compounds such as MgCO
3. CO
2 functions more effectively for the molten metal on which a thick MgO film covers, but does ineffectively for the molten metal on which thin MgO and/or MgAl
2O
4 films cover. The protecting ability of surface film depends on the concentration of CO
2 at the film forming period, but does not on the gas applying time in the period. This phenomenon is attributed to prevention of O
2 diffusion into the molten metal by the MgO film which adsorbs CO
2 gas.
抄録全体を表示