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The Effect of Na 2 O and Al 2 O 3 on Dephosphorization of Molten Steel by High Basicity MgO Saturated CaO – FeO x – SiO 2 Slag
| Content Provider | Semantic Scholar |
|---|---|
| Author | Guang-Qiang, Li Hamano, Tasuku Tsukihashi, Fumitaka |
| Copyright Year | 2005 |
| Abstract | There is an increasing demand for lower phosphorus steels. Hot metal dephosphorization is commonly applied in Japan and some special processes were proposed for high efficiency dephosphorization of molten steel in order to minimize the amount of steelmaking slags, for example, the Zero Slag Process developed by NKK Corporation and the MURC process developed by Nippon Steel Corporation. On the other hand, ladle dephosphorization is also an alternative to obtain lower phosphorus steels by using special fluxes. Usually calcium fluoride has been commonly added to steelmaking slags to increase the solubility of CaO and to improve the kinetics of desulfurization and dephosphorization. Considering the toxicity of fluorides to the health of human being, developing a dephosphorization process with CaF2-free slags is becoming an urgent demand. So it is necessary to clarify the influences of another additives to the dephosphorization reaction between metal and slags. For dephosphorization process without CaF2 addition, Al2O3, Na2O, MnO, MgO etc. are added into CaO base slags with high basicity and high FeO to decrease the melting temperature, increase fluidity, and improve the dephosphorization ability of the slags. Usui et al. studied the phosphorization of molten steel with CaO–Na2O–SiO2– FeOx slag at 1 873 K in a MgO crucible under Ar atmosphere. Miyata et al. reported the results of hot metal dephosphorization with CaO–SiO2–Al2O3–FeOx flux. It was found that the addition of small amount alumina can improve the fluidity of high CaO/SiO2 slags and increase phosphorus partition ratio. In the case of CaO/SiO2 (in mass%) 1.9 with 5% Al2O3 addition, an apparent phosphorus partition ratio of 310 and dephosphorization rate of 91% were obtained. Muraki et al. measured the phosphorus partition ratio for the CaO–Na2O–SiO2–CaF2 slag doubly saturated with CaO and 3CaO·SiO2 at 1 573 K. They reported that the phosphorus partition ratio increases with increasing Na2O content. The effect of Na2O on dephosphorization is significantly large and phosphorus partition ratio increases ten-fold for an addition of only 2 mass% Na2O. Park and Fruehan reported that the phosphorus partition ratio increased 300 times when 3 mass% Na2O were added into 50%CaO–40%Al2O3–10%SiO2 slag in a graphite crucible at 1873 K under CO atmosphere. In case of processing in an ladle with basic refractory, such as MgO, dolomite, the ladle slag would be saturated with MgO. Suito et al. studied the phosphorus distribution between liquid iron and MgO saturated slag of the CaO–MgO–FeOx–SiO2 system at 1 873 and 1 823 K. They also investigated the effects of Na2O addition (7 to 13 mass%) on phosphorus distribution between CaO–MgO–FeOx–SiO2 slags and liquid iron. 8) Kimura et al. studied the activity of Na2O in the ISIJ International, Vol. 45 (2005), No. 1, pp. 12–18 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.jstage.jst.go.jp/article/isijinternational/45/1/45_1_12/_pdf/-char/en |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
