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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 相似文献
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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。 相似文献
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当一种保护渣冷至低于液相线温度时.渣可能会结晶或不结晶,这取决于自身的化学成分和热循环,含二氧化硅的保护渣容易冷却并在平衡状态下在结晶温度范围内形成玻璃体.另外,富含CaO的碱性渣却难于急冷形成玻璃体.只是在稍低于液相线的温度时液体可能出现结晶. 相似文献
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保护渣熔渣结晶性能的研究 总被引:4,自引:0,他引:4
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。 相似文献
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The crystallization behavior of mold fluxes containing 0-8 mass% TiO 2 was investigated using the single hot thermocouple technique (SHTT)and X-ray diffraction (XRD)to study the possible effects on the coordination of heat transfer control and strand lubrication for casting crack-sensitive peritectic steels.Time-temperature-transforma-tion (TTT)and continuous-cooling-transformation (CCT)curves were plotted using the data obtained from SHTT to characterize the crystallization of the mold fluxes.The results showed that crystallization of the mold fluxes during isothermal and non-isothermal processes was suppressed with TiO 2 addition.From the TTT curves,it could be seen that the incubation and growth time of crystallization increased significantly with TiO 2 addition.The CCT curves showed that the crystallization temperature initially decreased,and then suddenly increased with increasing the TiO 2 content.XRD analysis suggested the presence of cuspidine in the mold fluxes with lower TiO 2 content (< 4 mass%),while both perovskite and cuspidine were detected in the mold fluxes when the TiO 2 content was increased to 8 mass%.In addition,the growth mechanisms of the crystals changed during the isothermal crystallization process from interface-controlled growth to diffusion-controlled growth with increasing the TiO 2 content. 相似文献
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Jeferson L. Klug René Hagemann Nestor C. Heck Antônio C. F. Vilela Hans P. Heller Piotr R. Scheller 《国际钢铁研究》2013,84(4):344-351
With the single hot thermocouple technique (SHTT) the solidification behavior of metallurgical slags has been studied by in situ observation, constructing time–temperature–transformation (TTT) or continuous‐cooling‐transformation (CCT) diagrams. The SHTT is a unique apparatus that enables measurement of the slag sample temperature using a thermocouple while the sample is heated or cooled simultaneously. Due to the low heat capacity of the system sample/thermocouple high heating or cooling rates can be easily obtained (>3000°C/min). The following findings are reported in the present paper: (i) For the CaO–Al2O3 slag – 44% CaO, 56% Al2O3 (wt%) – the CCT diagram shows large differences between liquidus and the temperature for first crystals precipitation, even at low cooling rates, for example, 168°C below the liquidus when cooling at a rate of 6°C min?1. (ii) For the CaO–SiO2 slag – % CaO/% SiO2 (wt%) = 0.7 – no crystal is observed for continuous cooling, even at low cooling rates, such as 10°C min?1. During isothermal experiments crystallization was observed only at 1000°C with an incubation time of 76 s (average of six experiments, standard deviation 27 s). However, crystallization becomes much more intense for the CaO–SiO2 slag when increasing the temperature after reaching lower temperatures (<1000°C), where probably the conditions for nucleation are better. 相似文献
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When the content of glass in blast furnace slag is over 95%, it can be used as a raw material in the manufacture of cement. The critical cooling rate required for the formation of glassy slag is one of the important characteristics for molten BF slag. The crystallisation behaviour of molten BF slag has been studied by in situ observation with the single hot thermocouple technique. The isothermal and non-isothermal experiments were performed to construct time–temperature-transformation and continuous-cooling-transformation diagrams. The effect of MgO, Al2O3 and binary basicity (CaO/SiO2) on the critical cooling rate of the CaO–SiO2–MgO–Al2O3 slags were studied under conditions of CaO/SiO2?=?1.1–1.4, 6–12?mass% MgO and 10–16?mass% Al2O3. The following finding are reported in the present paper: (i) Higher MgO content increased the critical cooling rate; higher Al2O3 content decreased the critical cooling rate; higher CaO/SiO2 increased the critical cooling rate. (ii) The crystallisation temperature of molten BF slag lowers as the cooling rate increases, the slag have larger critical cooling rate, higher crystallisation temperature. The results could be used to design proper cooling path of molten BF slag for the formation of glassy. 相似文献
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Solidification Behavior of CaO–SiO2–Al2O3 Mold Fluxes Containing MgO and Low TiO2 Content Using Single Hot Thermocouple Technique (SHTT): Continuous‐Cooling‐Transformation (CCT) and Viscosity Analysis 下载免费PDF全文
Daniel dos Reis Silva Antônio Cezar Faria Vilela Nestor Cezar Heck Hans‐Peter Heller Olena Volkova 《国际钢铁研究》2018,89(2)
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Yongqi Sun Jing Li Xidong Wang Zuotai Zhang 《Metallurgical and Materials Transactions B》2014,45(4):1446-1455
The present paper investigates how the P2O5 addition influences the crystallization behaviors of Ti-bearing blast furnace (Ti-BF) slags with different basicity using Single Hot Thermocouple Technique. It was found that the basicity showed a significant effect on the crystallization behaviors of the Ti-BF slags, and the trend of formation of the rod-shape crystal decreased while the trend of formation of dendrite crystal increased with increasing basicity. The addition of P2O5 was found to promote the formation of rod-shape crystal. The basicity and crystallization temperature that the rod-shape crystal could be formed increased, while the incubation time of formation of the rod-shape crystal decreased with increasing P2O5 content. Scanning electron microscope equipped with energy-dispersive X-ray spectroscope and X-ray diffraction were employed to observe the morphology and determine the crystalline phase of the Ti-enriched crystals. The results indicated that the rod-shape crystal was rutile. The kinetics of the formation of rutile was studied, and the mechanism of crystallization and growth was further discussed. The results indicated that the crystallization of rutile was one-dimensional interface-controlled growth, and the nucleation rate varied with the holding time. 相似文献
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在实验室条件下,对一种微合金高强度钢进行热膨胀试验和热轧试验,测定了该试验钢的连续冷却转变动力学(CCT)曲线,并研究了不同温度转变的组织和第二相的体积分数、尺寸对其力学性能的影响。试验结果表明:变形温度的降低,贝氏体转变开始温度与转变结束温度均升高,硬度值也出现不同程度的提高;变形温度的降低,使得不同冷却速度下组织细化程度存在明显差异。利用合理控轧控冷工艺,使得屈服强度均达到690MPa以上,-30℃冲击功均达到230J以上。其中,第二相粒子在整个基体内呈细小弥散分布,起到有效的强化作用并改善钢的冲击韧性。 相似文献