| Molten steel slag with the state of liquid or semi-liquid, which is generated in the steel-making process, contains much thermal energy. There are many problems in the traditional hot slag treatment process, such as large energy consumption, much material waste, serious environmental pollution, difficulty of reutilization, and low value-added products. The novel process and technique of glass-ceramics preparation directly from hot steel slag can not only use both hot slag material and energy, thus reducing energy and environmental issues, but also prepare high value-added products, thus promoting good economic benefits. It is one of the important research topics for iron and steel industry to achieve energy-saving and emission-reduction.The amount of steel slag and additives used for the preparation of specific-component glass-ceramics was calculated by establishing and solving the multi-equations. Mixing and homogenization of molten steel slag and additives were proposed for preparation of glass melts by using liquid-liquid mixing method. The influence of the additive content, different heat treatment conditions on the crystallization, microstructure and properties of glass-ceramics was investigated by using differential thermal analysis, X-ray powder diffraction and scanning electron microscopy. Crystal growth characteristics and mechanism of glass-ceramics with different iron content were studied using non-isothermal kinetic theory.(1) Preparation of steel-slag based pyroxene system Glass-ceramics from various additive mixtures was investigated. In the same heat treatment conditions (nucleation temperature 700℃,2 h; crystallization temperature 900℃,2 h), glass-ceramics which contain different amount of additives have different types of crystalline phase and crystal morphology. The more contents of additives contain in glass-ceramics samples, the lower acid resistance, hardness, and water absorption. Flexural strength decreases with the increasing contents of additives. With the increase in crystallization temperature, the hardness of basic glass-ceramic samples with the same components increases gradually, density increases at first and then decreases.(2) Waste glass used as an adiitive to prepare steel-slag-based glass-ceramics was studied. After the parent glass sample, which contains 50% steel slag, is heat-treated at the nucleation temperature of 700℃and crystallization temperature of 900℃for 2 hours respectively in an inert atmosphere, the main phase of the glass-ceramics is diopside. Fe2+ and Fe3+in the parent glass sample, which is prepared using liquid-liquid mixing method in the appropriate atmosphere, occurs translocation and degree of order change when the crystallization temperature is higher than 900℃during heat treatment. The glass-ceramics sample crystallizes magnetite (Fe3O4) phase with the characteristics of strong magnetic. Crystallization activation energy of the glass-ceramics sample is 450 KJ/mol. Crystallization kinetics of parent glass was studied by analysis the DTA curves which obtained at different heating rates.The average crystal growth exponent of n is 1.7. Crystal growth is three-dimensional crystallization under the control of surface crystallization.Crystal morphology is changed from flaky crystals and needle-like crystal into spherical crystal with the increase of temperature. The main controlling factor for crystal growth is changed from interfacial energy into strain energy with the increase of temperature.(3) Glass-ceramics with different iron content is investigated. The crystallization activation energy of glass-ceramics is increased from 494 KJ/mol (5.79% iron content in glass-ceramics samples, Fe-1) to 517 KJ/mol (15.38% iron content in glass-ceramics samples, Fe-3) with the increasing contents of iron. The average crystal growth exponent of n is 1.69. Crystal growth is an overall nucleation and three-dimensional diffusion-controlled crystallization process. In the same heat treatment conditions, the glass-ceramics samples with different iron content exhibit different types of crystalline phases. The main phase is Diopside (72-1379). The stability of the crystal increases with the increase of iron content. Acid resistance increases with the decrease of iron content.Studies on formulation optimization and mixing process in thermal state and the experimental results of phase transition and crystal growth mechanism in this thesis have a positive effect on promoting hot steel slag recycling progress.
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