Abstract
Studying on the abnormal structure (Ni rich zone) formed near the gas cutting edge by acetylene gas cutting, the change of its compositions and oxidation weight increment were measured using 5.5% Ni steel and 9% Ni steel. The results are summarized as follows;
(1) The width in Ni rich zone by acetylene gas cutting tends to increase with an increase in the supply of oxygen. On the other hand, Ni rich zone was scarcely measured near plasma cutting edge.
(2) Judging from the results of X-ray analysis, FeO and Fe3O4 were mainly observed in oxide by gas cutting, but Fe-Ni solid solution besides them were contained in the oxidation film by oxidation experiment. In Ni rich zone, Fe-Ni solid solution was only observed.
(3) Activation energy calculated from weight increment by oxidation experiment was 33-38 kcal/mole for Fe and Fe-(1-3%) Ni alloys, and 54-61 kcal/mole for 5.5% Ni steel and 9% Ni steel. Activation energies calculated from weight increment and thickness in Ni rich zone were nearly equal, but differed from that calculated from thickness in oxidation film in 9% Ni steel. From the above result, the rate process of oxidation in Fe-Ni alloys may be considered as the forming process of Ni rich zone.
(4) Oxidation weight and oxidation thickness can be drawn as a function of Lalson-Miller's parameter, P=T(log t+C). Those linear lines deflected on the point of T(log t+10)×10-3≈12.5.
