アーク溶解時におけるFe-Ta, Fe-Ni, Fe-CoおよびFe-Si二元合金中への窒素溶解量

Abstract

The absorption of nitrogen by molten iron alloys, such as Fe-Ta, Fe-Ni, Fe-Co and Fe-Si arc melted under nitrogen/argon atmospheres have been investigated.The results of these systems are as follows:i) The nitrogen contents of arc melted iron alloys were found to be higher than those of non-arc melted one. This difference appeared to be due to he activation of nitrogen in the arc atmosphere.ii) The effect of alloying element on the absorption of nitrogen by iron alloys under the arc differs from that of non-arc melting. For instance, in the Fe-Ta system, the amount of dissolved nitrogen initially decreases with increasing Ta content up to 3 pct Ta and then increases with increasing Ta content in next stage. From the consideration of experimental results, it has been found that above anomalous nitrogen absorption was concerned with the physical states of molten iron alloy surface under the arc. That is, thenitrogen in arc melted iron alloy is determined qualitatively by the mutual reaction between deoxydizing power of alloying element and the affinity of alloying element with nitrogen.iii) Behaviours of nitrogen absorption into iron alloys under the arc are classified in 4 types by properties of alloying element. Type Ia) The property of element: The alloying elements of Type I, V, (Nb), Ta, (Ti), Cr, (Mn) increase the solubility of nitrogen and decrease the oxygen content in iron alloys.b) The phenomenon of nitrogen absorption: The nitrogen content initially decreases with increasing the content of element and then increases with increasing the content of element.Type II a) The property of element: The alloying elements of Type II, Si, (C) decrease the solubility of nitrogen and the content of oxygen in iron alloys.b) The phenomenon of nitrogen absorption: The nitrogen content decrease drastically with increasing the content of element in the first stage and the decrement of nitrogen content is small in next stage.Type III a) The property of element: The alloying elements of Type III, Ni, Co, Mo, (Cu) (W, ) (Sn) havea little effect on the solubility of nitrogen and the oxygen content in iron alloys.b) The phenomenon of nitrogen absorption: The nitrogen content does not change by the amount of alloying element.Type IV a) The property of element: The alloying element of Type IV, (Al) has a little effect on the solubility of nitrogen but decreases the oxygen content in iron alloys.b) The phenomenon of nitrogen absorption: The nitrogen content decreases drastically with increasing the alloying element in the first stage and then does not change by the amount of alloying element.