【作者】 曾建华；

【导师】 王谦；

【作者基本信息】 重庆大学 ， 钢铁冶金， 2003， 硕士

【摘要】 为保证攀钢大方坯连铸浇铸U71Mn、PD3等高碳钢的生产顺行和获得良好的铸坯质量，在对国内外大方坯连铸保护渣的研究和应用情况调研基础上，根据大方坯连铸高碳钢的特点、难点，结合攀钢铸机参数和工艺条件，开展了攀钢大方坯连铸高碳钢用保护渣的研究。 采用Gleeble-1500热模拟试验机测试了重轨（U71Mn）钢的高温力学性能，并建立了铸坯润滑模型，用该模型探讨了保护渣的主要物理性能及渣圈的生成对铸坯润滑的影响。利用高温物性测定仪、粘度计和DTA1700热分析仪研究了CaO—SiO₂—Al₂O₃—Na₂O—CaF₂—MgO渣系中各组分及含量与熔化温度、粘度和析晶温度的关系。采用渣柱法和熔化率法两种不同的测试方式进行了碳质材料与保护渣熔化速度的关系研究。并利用X光衍射仪、电子探针和显微观察等手段，对烧结过程试样的矿相变化和显微结构特征进行了较为全面的研究分析，在此基础上对保护渣的烧结机理和碳质材料、原料预处理对烧结特性的影响进行了探讨，并从烧结机理上分析了渣圈的生成原因，创新性地建立了保护渣烧结特性的定量化评价级方法和评价指标体系。 在本研究条件下，模型计算表明随保护渣熔化温度、粘度的升高，以及渣圈的生成，铸坯润滑情况恶化。高温力学性能测试表明重轨钢的高温塑性差，保护渣的研究重点应在解决铸坯润滑上。提高保护渣碱度，增加渣中Na₂O、CaF₂、MgO含量能够降低保护渣熔化温度、粘度，但析晶温度随碱度的提高和Na₂O含量的增加而升高。在评价碳质材料种类与保护渣熔化速度的关系时，熔化率法比渣柱法能够更准确地反映出实际生产中不同碳质材料对熔化速度的作用大小，中超碳黑控制熔化速度的能力强于其它碳质材料，且能够在熔化过程中有效地抑制保护渣烧结。 烧结特性研究揭示了保护渣的烧结过程是由固相反应和液相烧结构成。固相反应在约600℃时产生，生成矿相主要有Ca₂SiO₂F₂、Ca₄F₂Si₂O₇等，同时还有一定的液相生成，随后因液相的出现而烧结致密。测试保护渣烧结过程的体密度——温度关系及致密化起始温度和致密化速率可定量评价保护渣的烧结特性。烧结的致密化起始温度高低和致密化速率大小是影响保护渣生成渣圈的重要因素，烧结致密化起始温度低或致密化速率大的保护渣在生产应用中易生成渣圈。在保护渣中加入碳质材料，对原料进行预熔化或预加热处理可提高保护渣的致密化起始温度或降低致密化速率，从而可抑制或减轻保护渣生成渣圈。 研究表明攀钢大方坯连铸保护渣的化学组成宜以CaO、SiO₂、Al₂O₃、Na₂O、重庆大学硕士论文CaFZ和MgO为主，适当加入Bao和SrO等特殊组分。保护渣的碱度（Cao/5102）应控制在0.8⁰.9，熔化温度为1 120一1200℃，粘度为0.3⁰.SPa .5，结晶率为0%，配碳模式可采用1一2%的中超碳黑和4一10%鳞片石墨的混合配碳模式。工业试验表明采用该方案的保护渣浇注的铸坯质量良好，在结晶器内有良好的熔化特性，有效的抑制了渣圈生成，且未出现漏钢事故。更多还原

【Abstract】 Panzhihua Iron and Steel Co (PISC) is to install bloom continuous casting machine (CCM) for the production of high carbon steels, including U71Mn and PD3. Continuous casting of high carbon steel is difficult due to its relatively low shear strength at high temperatures. To ensure a trouble-free bloom continuous casting of high carbon steels and to improve product quality, mould fluxes have been widely used worldwide. In this study, the state-of-the-art in this area has been reviewed; a systematic investigation in the physical chemical properties of mould fluxes and the performance under the conditions of the CCM at PISC in particular has been conducted. The main purpose was to identify the key parameters that control the behavior of mould fluxes particularly sintering potential and the product quality. The knowledge gained from this research will be directly used in guiding the commercial production of high carbon steel in PISC.By establishing and using a mathematical model, it was confirmed that the lubrication behavior is controlled by mainly the properties of fluxes. The formation of slag rim was analyzed. Using a viscometer and differential thermal analyzer (DTA1700), the melting temperature, viscosity, crystallizing temperature and their dependence on the components of fluxes in the CaO-SiO2-Al2O3-Na2O-Cap2-MgO system have been studied. The slag column method and the melting ratio method were used to show the relationship between the carbon materials added and the melting rate of fluxes. By utilizing an X-ray diffractometer, electronic probe and optical microscope, the mineralogical composition and microscopic characteristics of fluxes during the sintering process were investigated in detail. In light of these observations, sintering mechanisms and their link with the carbon materials and the pre-treatment procedure of raw materials of fluxes, have been discussed. According to the suggested sintering mechanism, the formation mechanism of the slag rim has also been analyzed. A new evaluative method has been proposed, which quantitatively describes the sintering process of mould fluxes.A thermal simulation testing machine (Gleeble-1500) was employed to determine the high-temperature mechanic properties of the heavy rail steel-U71Mn. The test demonstrated that the heavy rail steel possesses a low plasticity and tension strength at high temperatures. The breakout could occur under the condition of large frictional force in the CCM mould. Consequently, the research on continuous casting mouldfluxes for heavy rail steel should focus on improving lubrication and decreasing casting resistance force. Under the condition studied, the mathematical model also suggested that the elevated melting temperature, increased viscosity and the formation of slag rim could worsen the lubrication for continuous casting strands. The increase in basicity and the contents of Na2O, CaF2, MgO could lower the melting temperature and viscosity of molten fluxes. However, the elevated basicity and Na2O content result in an increase in the crystallization temperature. In assessing the effects of carbon materials on the melting rate, the melting ratio method was found to be more authentic and reliable than the slag column method. Possessing a stronger effect on the melting rate than other carbon materials studied, the intermediate super carbon black, can efficiently hinder the sintering of fluxes.The study on the sintering property revealed that the sintering process of fluxes consists of solid-solid reactions and liquid phase reactions. The solid-solid reaction often starts at about 600℃, resulting mineral phases such as Ca2SiO2F2 and Ca4F2Si2O7 along with some liquid phase which is responsible for the densification. The bulk density-temperature relationship, the densification rate and starting temperature can be used to assess quantitatively the sintering potential of fluxes. The densification rate and temperature play the key role in controlling the formation of slag rim. Addition of carbon materials, pre-melting and pre-heat更多还原