保护渣熔渣结晶性能的研究

研究了超低碳钢保护渣的显微组织结构特征，并根据相图分析了熔渣的结晶性能。结果表明：碱度高、Ａｌ２Ｏ３含量高的熔渣易析晶，熔化温度高；碱度和Ａｌ２Ｏ３含量适中的熔渣不易析晶，熔化温度低。     

连铸结晶器保护渣结晶性能的研究

实验研究了结晶器保护渣(％:37CaO、2MgO、40SiO₂、5Al₂O₃、5Na₂O、11CaF₂)在1 300-1 000℃的结晶过程和性能。结果表明,冷却速率≤2℃／s时,该渣的结晶化率达100％。在冷却速率0．1℃／s时,保护渣首先析出树枝状晶体,然后以片状晶体形态析出,直到结晶终止。通过X-射线衍射分析,得出析出的晶体主要有枪晶石(Ca₄Si₂O₇F₂)镁黄长石(Ca₂MgSi₂O₇)、硅灰石(CaSiO₃)及镁铝尖晶石(Al₂MgO₄)。     

无氟连铸结晶器保护渣的结晶性能

 结晶器与连铸坯间的保护渣膜直接影响着连铸坯的润滑及传热,而保护渣的结晶性能是影响润滑和传热的重要因素。通过测定保护渣的结晶温度、结晶率和结晶体几何尺寸,研究了碱度和TiO2含量对含钛无氟保护渣结晶性能的影响规律。结果表明：加大碱度和增加TiO2含量都能明显提高保护渣的结晶倾向性。     

冷却速率对连铸保护渣结晶性能的影响

采用 WCT-2型差热分析天平和LEITZ光学显微镜(配有 1350℃高温热台),研究了冷却速率对连铸保护渣结晶性能的影响.研究结果表明:随冷却速率提高,保护渣的结晶温度显著降低,结晶率降低,晶体尺寸减小,晶形也有很大改变.     

中碳钢板坯连铸保护渣的结晶性能

为了解结晶器与坯壳间渣膜的结晶状态，用热丝法熔化性能测定仪对保护渣结晶性能进行研究。结果表明：连续冷却过程中，结晶是在一定温度范围内进行的；冷却速率越大，结晶温度越低；冷却速率超过一定值时，保护渣不结晶。不同温度下的等温实验结果表明：在一定过冷度范围内，保护渣开始结晶；过冷度的大小与结晶开始和结束时间有关；水蒸气可促进保护渣结晶，在不同温度等温时，保护渣结晶开始温度提高，结晶开始时间缩短。     

硅灰石对连铸保护渣结晶性能的影响规律

以水泥熟料、工业矿物为主要原料,实验室配制保护渣,运用工艺矿物学方法,研究硅灰石对保护渣结晶性能及对应渣膜矿相结构的影响规律。结果表明:同一冷却速率下,随硅灰石含量的增加,试验渣的结晶温度逐渐降低;硅灰石每增加2%,临界冷却速度平均下降2℃/s;结晶孕育时间随硅灰石含量的增加而延长,利于铸坯的润滑。试验渣中硅灰石为11%~19%时,对应渣膜的结晶率均在80%以上,结晶矿物为枪晶石和硅灰石;原料中硅灰石11%~15%时,渣膜中两种结晶矿物的含量相当;硅灰石≥17%时,渣膜主要析出硅灰石,枪晶石含量明显减少,黏度增加幅度不大,但热流密度显著增大,不利于控制传热。为达到保护渣传热与润滑的统一,建议保护渣中硅灰石含量不大于15%。     

通过结晶分析来评价结晶器保护渣的性能

为保证平稳浇铸，需要控制结晶器保护渣中的结晶过程，结晶器保护渣是复杂的硅酸盐体系并且玻璃体的形成（和结晶体相反）由各氧化物相对的量决定，提出了一个叫做“解聚指数”（ＤＩ）的参数，定义为：各种氧化物（在结晶器渣中）中氧的克分子数与结晶器渣中形成网络的氧化物克分子数之比。ＤＩ值的不断增长反映了硅酸盐网络的不断分裂，并加快了结晶过程，分析文献中的例子，可以观察到保护渣性能的改进（引用的）可归因于ＤＩ值的     

无氟连铸结晶器保护渣结晶性能研究进展

传统保护渣成分中含有氟化物,易导致连铸过程中环境污染、设备腐蚀等问题。选用合适的助熔剂替代氟化物获得结晶性能优良的无氟保护渣,是目前连铸生产实现绿色高效化的关键。本文基于结晶温度、结晶率和结晶矿相三个方面,总结了近几年国内外与无氟环保型保护渣结晶性能有关的研究现状,无氟保护渣的化学成分对其结晶性能的影响规律,提出了无氟环保型保护渣未来的研究方向和目标,即探寻无氟保护渣中可以代替枪晶石的主晶相以满足对控制传热的需求,为开发适用于高效绿色连铸生产要求的无氟保护渣提供理论依据。     

连铸保护渣的结晶过程

 连铸保护渣在结晶器内的结晶行为无法直接观测。为了模拟保护渣在结晶器内的结晶行为,采用热丝法研究保护渣在高温下等温和连续冷却下结晶性能,直接观察保护渣析晶的全过程,发现温度影响析出晶体的形貌和结晶率。绘制保护渣TTT曲线和CCT曲线,表征保护渣析晶行为与时间、温度的关系。在冷却速率5~25 ℃/min范围内,DSC法测定保护渣结晶温度下降110 ℃;在冷却速率6~30 ℃/min范围内,热丝法测定保护渣结晶温度下降86 ℃。     

连铸保护渣结晶矿相的研究

采用LEITZ偏光岩相显微镜结合扫描电子显微镜,研究了实验室自制渣和工业结晶器保护渣的结晶矿相。结果表明：在本实验中,渣样的结晶矿相主要有枪晶石、黄长石和硅灰石,个别渣样中可能有霞石析出;保护渣中加入少量的MgO可以降低结晶率,抑制硅灰石的生成;加入少量的MnO、ZrO2S可促进硅灰石的析出,抑制枪晶石的生长。     

Properties of High Basicity Mold Fluxes for Peritectic Steel Slab Casting

 In high speed continuous casting of peritectic steel slabs, mold fluxes with high basicity are required for less surface defect product. However, the basicity of remaining liquid slag film tends to decrease in casting process because of the crystallization of 3CaO·2SiO2·CaF2. Thus, a way is put forward to improve mold fluxes′ properties by raising the original basicity. In order to confirm the possibility of this method, the effect of rising original basicity on the properties of mold fluxes is discussed. Properties of high fluorine based mold fluxes with different basicities and contents of CaF2, Na2O, and MgO were measured, respectively. Then, properties of higher basicity mold fluxes were discussed and compared with traditional ones. The results show that increasing the basicity index can improve the melting and flow property of mold fluxes. With the increasing basicity, crystallization rate of mold fluxes increases obviously and crystallization temperature tends to decrease when the basicity exceeds 1.35. The method presented before is proved as a potential way to resolve the contradiction between horizontal heat transfer controlling and solidified shell lubricating for peritectic steel slab casting. But further study on improving the flow property of liquid slag is needed. This work can be used to guide mold fluxes design for high speed continuous casting of peritectic steel slabs.     

特殊组分对低氟保护渣凝固温度和结晶性能的影响

 氟含量过高的连铸保护渣不仅加剧伸入式水口的侵蚀，而且对连铸操作环境带来危害，为了降低保护渣中过高的氟含量，需要开发低氟或无氟保护渣。为避免保护渣中氟含量降低后性能指标的恶化，需要寻求氟化物的替代组分以协调保护渣各项冶金功能的正常发挥。为此，以高氟保护渣为参照点，设计了4组低氟连铸结晶器保护渣渣样。通过检测这些渣样的熔点、粘度、转折温度、结晶温度和结晶率，分析和比较实验数据发现，在不同碱度下，B2O3、Li2O、Cr2O3、TiO2均能部分替代渣中的CaF2，获得CaF2质量分数为45%的低氟保护渣。CeO2不能作为保护渣中CaF2的替代组分。     

Solidification Properties of CaO-SiO2-TiO2 Based Mold Fluxes

 In continuous casting of peritectic steel grades sensitive to longitudinal cracking, the solidification properties of mold fluxes play an important role in keeping smooth running of continuous casting process and achieving high surface quality of casting strands. To reduce fluorine pollution in molten slag, types of CaO-SiO2-TiO2 (CTS) based mold fluxes were investigated. The solidification and crystallization properties, including viscosity η at 1573 K, break temperature Tbr, crystallization ratio Rc and solidification mineragraphy were measured, which were compared with those of CaO-SiO2-CaF2 based mold fluxes. The experiments show that there are unstable viscosity-high temperature properties and high Tbr in part of CTS slag system, which are bad for lubrication between liquid flux film and strand. And when temperature is below Tbr, the viscosities change slowly during cooling in some part of this slag system, which imply that liquid mold fluxes solidify slowly and it is easy to cause surface longitudinal cracks on strand. Major mineragraphy of the CaO-SiO2-TiO2 based mold fluxes are CaO·TiO2 or CaO·TiO2 and CaO·SiO2·TiO2. TiN and Ti(C,N) can be formed in mold fluxes bearing high TiO2 during the continuous casting.     

Crystallization Behavior of Anatase Films in Applied Electric Field Heating Process

In this research the TiO2 thin films were prepared by sol-gel dip coating. The crystallization of the films in the applied electric field heating process was thoroughly studied by many technique, differential thermal analysis (DTA), Raman spectroscopy and atomic force microscope (AFM). Furthermore the phase formation, microstructure and photo-catalytic activity of TiO2 film were studied under the condition of an electric field heating-treatment. It is found that the existence of applied electric field promotes the phase transformation from anatase to rutile. Studies on photo-catalytic degradation show that the photo-catalytic activity of TiO2 thin films in an applied electric field is higher.     

保护渣物化性能检测及优化研究

通过检测4个厂家供应保护渣的化学成分、熔化温度、黏度和结晶率,并对其析晶能力进行了比较,发现目前所用的4种保护渣均为典型结晶性能渣,进一步结合连铸坯表面品质问题（如振痕不规则、凹陷和裂纹缺陷等）,提出了保护渣性能的优化方案。并对提高保护渣的性能稳定性和改善铸坯品质,提出了进行保护渣系列化研究的建议。     

无氟连铸保护渣有关技术问题的探讨

 综述了国内外无氟连铸结晶器保护渣发展状况，分析了目前高碳钢和包晶钢(特别是亚包晶钢)用保护渣降氟过程中面临的主要问题：高温时粘度 温度特性的稳定性以及保护渣结晶性能的有效控制。在此基础上，提出了连铸无氟保护渣今后研究的方向和重点。     

Effect of Soda Ash on Properties of Mold Flux and Mineralogical Structures of Flux Film

During continuous casting,properties of mold flux and mineralogical structures of flux film play important roles in controlling steel quality.The effect of soda ash on the physical properties and crystallization characteristics of mold flux was investigated using process mineralogy,including polarizing microscopy,X-ray diffraction,and electron microprobe,etc.Mold flux was mainly prepared using cement clinker and industrial mineral materials under laboratory conditions,and the mineralogical structures of the flux film were systematically identified and quantitatively analyzed.The results showed that,by increasing the soda ash content from 10mass% to 18mass%,the crystallization temperature,critical cooling rate and crystallization ratio of the flux film decreased,but the crystallization ratio still reached 75% after adding soda ash,and the mineral compositions and microstructures of the flux film changed slightly.When the soda ash content exceeded 14mass%,the critical cooling rate and the crystallization ratio decreased slightly,whereas the mineral content of the flux film changed evidently,with a large amount of cuspidine precipitation and a significant decrease in the wollastonite content until it reached zero,which resulted in deterioration of the lubrication of the flux film.