| Blast furnace slag is an important by-product of blast furnace ironmaking,and its recycling has always been a hot spot for metallurgical workers.Under the current situation of low profit in the steel industry,finding a more reasonable and higher value-added blast furnace slag utilization method is of great significance to the improvement of corporate competitiveness and sustainable development.Fluorite tailings are wastes after fluorite flotation treatment,that is,fluorite ore with low fluorite content.Fluorite tailings have low utilization value,and they occupy large amounts of land resources and pollute the environment.In this paper,blast furnace slag and fluorspar tailings are used as raw materials to prepare glass-ceramics in high added value,which provides a good use of heat for molten blast furnace slag,and processed hazardous waste fluorspar tailings.The residual CaF2 in the tailings are reasonablly used as nucleation agent in the preparation of glass-ceramics,and also play a role in lowering the melting temperature.These research results provide theoretical and technical supports for the eco-friendly disposing and valuable utilizing of BFS and fluorspar tailings.It contributes to breaking through the technological bottleneck of hazardous waste disposal,and to achieving green sustainable development.The basic glass composition determines the crystal phase and is an important factor affecting the performance of the glass-ceramics.This paper studies the influence of the ratio of blast furnace slag and fluorite tailings on the crystal phase composition,microstructure and overall performance of glass-ceramics.The use of blast furnace slag and fluorspar tailings as raw materials to prepare glass-ceramics without addition of nucleating agents cannot achieve volumetric crystallization.After 2wt%Cr2O3 added to enhance the crystallization ability,the glass-ceramics with the main phase(Ca(Mg,Al)(Si,Al)2O6)were successfully prepared.When the addition amount of blast furnace slag was increased from 45wt%to 50%,the ability of crystallize was enhanced,and the sample precipitated dendritic or massive grains with its size decreased and number increased,and the Vickers hardness increased;When the addition amount of blast furnace slag was increased from 60wt%to 65wt%,the ability of crystallize decreased,the bulk crystal grains was with its size increased and number decreased,and the Vickers hardness decreased;When the addition amount of blast furnace slag is 55wt%,the crystallization ability is the strongest,and the sample precipitated grain with size of 1-2?m,and its Vickers hardness was 6.3 1Gpa.The crystal nucleating agent is a key step in preparaing glass-ceramics in melting melthod.Based on A3 formula,adding of a single Cr2O3 and P2O5 can make the volumetric crystallization of the base glass;adding of a single TiO2,Fe2O3,ZrO2 can't achieve volumetric crystallization;The order of the influence of each nucleating agent on the Vickers hardness of the samples was Fe2O3>TiO2>Cr2O3,and the optimum compound nucleating agent ratio was 1.5wt%Cr2O3+2wt%.TiO2+4wt%Fe2O3 with Vickers hardness 7.15Gpa.The properties of the glass-ceramics can also be promoted by optimizing the heat-treatment parameters.The best one-step heat treatment system was to raise the temperature to 600? at a heating rate of 10?/min,then increased the temperature to a crystallization temperature of 890? at a heating rate of 2?/min,and the crystallization holding time was 1 h.The best two-step heat treatment system was to increase the temperature to a nucleation temperature of 760? at a heating rate of 10?/min and hold it for 1 hour,then increased the temperature to a crystallization temperature of 890? at a heating rate of 5?/min with holding time 1h.One-step and two-step heat treatment systems can both produce excellent performance of the glass-ceramic products.However,the two-step heat treatment method had a shorter time,lower energy consumption,and better product performance,so the two-step method was a better heat treatment method. |
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