MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effect of ZrO2 Addition to the CaO-SiO2-MgO-CaF2 Slags on the Sulfur Removal from the 16Cr-14Ni Stainless Steel Melts
Joo Hyun ParkDong Joon Min
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2006 Volume 47 Issue 8 Pages 2038-2043

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Abstract

The equilibrium distribution ratio of sulfur between the 16 mass%Cr-14 mass%Ni stainless steel melts and the CaO-SiO2-MgO-ZrO2-7 mass%CaF2 (B(= (mass%CaO)/(mass%SiO2) = 2.0) slags was measured at 1873 K to clarify the role of ZrO2 in the desulfurization reaction based on the sulfide capacity concept. The sulfur distribution ratio linearly decreases on increasing the oxygen partial pressure with the slope close to −1⁄2 in the logarithmic scale at a fixed sulfur potential and temperature. The sulfide capacity of the slags is constant up to about (mass%ZrO2)⁄{(mass%ZrO2)+(mass%MgO)}=0.3, followed by a linear decrease on increasing the Z⁄(Z+M) ratio. The effect of ZrO2 substitution for MgO on the decrease in the (apparent) sulfide capacity at Z⁄(Z+M)>0.3 could be explained by the decrease in the basicity of the liquid slag phase due to the formation of CaZrO3 from the computational estimations for the phase equilibria and the thermodynamic activities of slag components. Based on the X-ray diffraction patterns of the slags, it was confirmed that the peak intensity for the Ca2SiO4 is strong through the entire composition range, while the intensity of the peaks corresponding to the CaZrO3 is relatively strong in the composition of Z⁄(Z+M)=0.42 and 0.64. The sulfide capacity can be expressed as a linear function of the mass fraction of CaZrO3 in the slags investigated in the present study, while that exhibits a wide distribution at a relatively narrow optical basicity region, resulting from the effect of ZrO2 on the basicity of the liquid slag phase due to the formation of CaZrO3.

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© 2006 The Japan Institute of Metals and Materials
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