【作者】 刘永庆；

【导师】 唐萍；

【作者基本信息】 重庆大学 ， 冶金工程， 2006， 硕士

【摘要】 保护渣对于保证连铸顺行和提高铸坯表面质量扮演着十分重要的角色。传统保护渣中均加入了氟化物如萤石、冰晶石等,在浇注温度下会挥发出氟化物,造成空气和二冷水的污染,并加剧铸机腐蚀和水口侵蚀。随着全球对环保问题的重视和绿色冶金浪潮的出现,要求研制环保型的无氟连铸保护渣。本文以CaO-SiO₂-TiO₂渣系为基础研制新型的无氟连铸保护渣。首先采用正交设计和单因素设计方法,研究了熔剂、二元碱度和二氧化钛含量对无氟保护渣熔融特性和粘度特性的影响规律;通过矿相观察研究了保护渣中炭质材料与TiO₂的相互作用,并研究了炭质材料对熔化速度的影响规律;最后研究了无氟保护渣对Al₂O₃-C质水口的侵蚀作用及吸收夹杂的能力。为制定基于含钛高炉渣的无氟保护渣配制原则奠定了基础。本论文研究得出了以下主要结论:①在含钛无氟保护渣中,熔剂降低熔点的作用从强到弱的顺序为:Li₂O>B₂O₃>MgO>MnO>Na2O,增加TiO₂含量和提高碱度会使熔点升高;熔剂降低粘度的作用从强到弱的顺序为:Li₂O >B₂O₃>Na2O>MgO>MnO,提高碱度也可显著降低粘度,TiO₂对粘度的影响呈先降后升趋势,TiO₂为6%时,粘度值最小;Na2O、Li₂O、B₂O₃可以降低使表面张力,TiO₂、MnO、MgO、CaO含量增加则使表面张力增大;Li₂O、MnO、B₂O₃使转折温度降低,加入MgO和提高碱度则都使转折温度升高,Na2O使转折温度先升后降,而TiO₂则使转折温度先降后升。②炭质材料在无氟保护渣中控制熔化速度的作用与在含氟保护渣中类似。炭质材料控速效果从强到弱依次为:超细石墨（500目）>300目超细石墨（300目）>半补强、中超炭黑和增碳剂>土状石墨。③连铸条件下由于动力学条件很弱,在含钛保护渣熔渣中不易生成高熔点物质TiC,而导致保护渣性能恶化;无氟渣主要矿相为钙钛矿（CaTiO3）、黄长石、硅灰石等。④无氟保护渣对水口有较强的黏附作用,对Al₂O₃-C质水口的蚀损较含氟保护渣小;含钛无氟熔渣吸收Al₂O₃、TiO₂夹杂后熔点和粘度均有不同程度升高,且粘度热稳定性变差,吸收夹杂后稳定性较含氟熔渣差。更多还原

【Abstract】 Mold fluxes play a key role during the continuous casting process. The current used mold fluxes generally contain fluorine bearing materials such as fluorite and cryolite etc, which can volatilize at operational temperatures, polluting both the plant air and cooling water. Airborne fluoride could potentially be a health and safety issue. Waterborne fluoride forms hydrofluoric acid (HF), which can cause plant corrosion. Developing and using fluoride-free (F-free) mold powders is of importance to the environmental protection.In this paper, fluoride-free mold fluxes are developed basing on CaO-SiO2-TiO2 slag system. The relationship between the melting and viscosity properties of F-free mold fluxes and fusing reagents, binary basicity and TiO2 content is investigated. Effect between TiO2 and carbon materials in F-free mold fluxes is researched by studying the crystalline phase. Experimental research on the relationship between carbon materials and melting rate is also carried out. At last, the absorptive rate of the F-free mold powders on Al2O3 and the properties stability after absorbing inclusions are measured by rotating cylinder method. All the studies provide a basal direction for producing F-free and titanium-bearing mold fluxes. The experimental result indicates that:(1) In F-free and titanium-bearing mold fluxes, the order of the effect on lowering melting point are Li2O > B2O3 >MgO> MnO>Na2O. The increase of TiO2 content and CaO/SiO2 ratio will heighten the melting point. The order of the effect on lowering viscosity are Li2O>B2O3>Na2O>MgO>MnO. The viscosity will reduce rapidity by increasing CaO/SiO2 ratio. When the content of titanium is 6% in mass, the viscosity shows the minimum. Na2O, Li2O and B2O3 can reduce the surface tension, while TiO2, MnO, MgO and CaO will enhance the surface tension. Li2O, MnO and B2O3 can reduce the break temperature. The increase of MgO content and CaO/SiO2 ratio will heighten the break temperature. The effect of Na2O and TiO2 on the break temperature are also obtaind.(2) The effect of the carbon materials on melting rate in F-free mold fluxes are similar to which in traditional mold fluxes. The order of ability to lower melting speed is: fine graphite (500 mu)>fine graphite (300 mu) >intermediate super carbon black, semi-reinforcing carbon black and carburetant >graphite.(3) Due to feeblish dynamic conditions during CC process, it is very difficult to更多还原