Effect Of Composition On The Occurrence And Distribution Of Chromium In Stainless-steel Slag Glass Ceramics And The Effect Of Chromium Fixation

The Cr⁶⁺formed by the oxidation of Cr³⁺in stainless steel slag under natural environmental conditions is easily soluble in water,and long-term storage poses very serious harm to the environment and human beings.The harmless treatment of stainless steel slag has become a bottleneck problem restricting the sustainable development of the stainless steel industry.At present,the preparation of microcrystalline glass from stainless steel slag is considered to be a promising method for harmless chromium fixation and resource utilization.The occurrence and distribution of Cr in glass-ceramics directly affect the chromium fixation effect,but there is still a lack of research on the occurrence and distribution of Cr and its impact on the chromium fixation effect.Therefore,this article uses stainless steel slag as the main raw material and adopts the melting method to prepare diopside based glass-ceramics,to explore the influence of glass composition on the occurrence and distribution of Cr during the nucleation and crystallization process of the glass-ceramics and its effect on the chromium fixation effect,providing theoretical support for achieving the efficient harmless and resource utilization of a large number of stainless steel slag.The main research contents and conclusions are as follows:（1）The effects of different alkalinity,TiO₂ and Al₂O₃ contents on mineral crystallization during nonequilibrium solidification of slag system were analyzed through thermodynamic calculations.The results show that when C/S is 0.55,the main crystalline phase is diopside;As the content of TiO₂ and Al₂O₃ increases,chromium in the slag precipitates more in the form of chromium containing spinel,which is beneficial to improving the chromium fixation effect.The calculation results provide theoretical guidance for experimental research.（2）The effects of TiO₂ content and alkalinity on the viscosity of chromium containing slag and the solubility of chromium oxide were studied.The changes in viscosity,phase composition,and structure of the slag system with different TiO₂ content and alkalinity were analyzed using a comprehensive melt physical property tester,XRD,and Raman spectroscopy,providing experimental evidence for more processing of stainless steel slag and ensuring good fluidity of the slag.The results show that the solubility of Cr₂O₃ in the slag system increases with the increase of TiO₂ content and alkalinity.Compared to increasing the TiO₂ content,increasing alkalinity can more effectively reduce viscosity.The increase in TiO₂ content and alkalinity simplifies the silicate network structure unit,reduces the viscosity of the slag system,hinders the crystallization and precipitation of chromium containing spinel,and increases the solubility of Cr₂O₃ in the slag.（3）The effects of different alkalinity and Al₂O₃ content on the occurrence and distribution of Cr and the effect of chromium fixation during the preparation of glass-ceramics were studied.At the nucleation stage,when the C/S is 0.55,appropriately increasing the content of Al₂O₃ at the optimal nucleation temperature is more conducive to the formation of chromium containing spinel nanocrystals,and the content of Cr distributed in chromium containing spinels is the highest.During the crystallization stage,A1 glass-ceramics（C/S=0.55,Al₂O₃=12%,nucleation temperature 725℃）generate the largest amount of diopside crystals,with the highest content of Cr occurring in the diopside phase,and have excellent mechanical properties and chromium fixation effects.（4）The effect of TiO₂ content on the occurrence and distribution of Cr during the preparation of glass-ceramics and the effect of chromium fixation was studied.At the nucleation stage,as the content of TiO₂ increases,the number of precipitated chromium containing spinel nanocrystals first increases and then decreases slightly.When the content of TiO₂ is 4%,the number of chromium containing spinel nanocrystals is the largest,and the proportion of Cr occurrence and distribution in chromium containing spinel crystals is the largest.During the crystallization stage,as the content of TiO₂ increases,the number of diopside crystals generated first increases and then decreases.When the content of TiO₂ is4%,the number of diopside crystals generated is the highest,and the proportion of Cr occurring in diopside crystals is the highest,with the best mechanical properties and chromium fixation effects.