Ntriding Dynamic Experiment Research Of SmFe Alloy

Since the 1990 s,many researchers carried out the research work of samarium ferroalloy nitriding,and many methods of samarium ferroalloy nitriding are concentrated in the low temperature nitriding in solid powder at present,whose biggest drawback is the long time nitriding,uneven nitriding and the lower efficient nitriding.This topic puts forward the idea of samarium ferroalloy melt nitriding.This paper established the dynamics model of the samarium ferroalloys nitriding with the bottom blowing bubbles.It studies the forming model of the bottom blowing bubbles:the relationship between the minimum pressure of bubbles generated and ambient pressure,blowing pipe radius;The model of the bubble growth:the rate of the bubble growth decreased with increasing external pressure.The model of bubble mass transfer:the rate of bubble mass transfer increases and then decreases in the bubble rising process.Finally it elaborated the mechanism of the bubble’s coalescence and fracture after the bubbles rise to the liquid level.This experiment adopts two methods of nitriding the samarium ferroalloy melt,one is letting stand nitriding,another is bottom blowing nitrogen.Due to the letting stand for nitriding time is long,samarium volatilized seriously in the samarium ferroalloys.Furnace chamber contains a samll amount of oxygen which reacts with samarium which volatiles from samarium ferroalloy to form samarium oxide covering on the surface of the basal body,and preventing the spread of the nitrogen element to the samarium ferroalloy.Therefore,it did not achieves a very good effect.Samarium ferroalloys nitriding by bottom blowing bubbles has a short smelting time,avoiding the volatilization of samarium effectively.It discovers that there are the α-Fe phase,Sm2Fe17 phase and rich samarium phase in the basal body.It contains nitrogen whose content is up to 0.9% in Sm2Fe17 phase.It analyses that there are two reasons affecting the content of nitrogen which didn’t meet expectations of nitrogen content of Sm2Fe17N3,one is that raw material of samarium ferroalloy contains C,so C which is also a interstitial atom affects the spread of N atoms to samarium ferroalloy,and the other is that there are α-Fe and rich samarium phase in the nitriding basal body.Sm2Fe17 phase is not uneven.In addition,increasing the nitriding temperature,increasing the nitriding time,and improving the nitriding flow contribute to the content of nitrogen in samarium ferroalloys.