High-speed continuous casting of steel billets entails considerable turbulence in the liquid core, which results in significant slag entrapment unless high viscosity slags are used. It has been suggested that such slags remain glassy or crystallize slightly under the prevailing mold cooling, temperature and residence time conditions. Slags whose composition lead to formation of melilite minerals (i.e., to formation of calcium sodium magnesium aluminum iron disilicates), as the main crystalline phase, possess viscosities > 0.5 Pa/s at 1573 K (1300 °C), are low or do not contain F, and incorporate transition metal oxides (e.g., FeO, MnO and TiO) to absorb infrared radiation and soften steel shell-to-mold heat transfer. In this work, a commercial melilite mold powder, for casting medium carbon steels round billets, is selected to carry out detailed analysis of the kinetics of precipitation of crystalline phases from glassy—devitrification—and super-cooled liquid slags—crystallization—under non-isothermal and isothermal conditions. High-temperature confocal laser scanning microscopy is used in both cases and differential scanning calorimetry just in non-isothermal ones. Assessment of amorphous and crystalline phases in treated samples is done by quantitative X-ray powder diffraction analysis. It is found that even after prolonged treatment (» 36,000 seconds) at 1248 K (975 °C) approximately 13 wt pct of the slag remains amorphous. Additionally, the results indicate that nucleation of crystalline phases in super-cooled liquid and glassy slags occurs on the surface. Thus, it is found that crystallization kinetics is strongly influenced by the topography of the surface with which the super-cooled liquid is in contact, as well as, by shearing actions imposed on the liquid slag surface, which contribute by developing nucleation sites. Devitrification tends to be stronger on surfaces contacting foreign walls and over cracks. Moreover, it is found that predictions of the kinetic model, developed for estimating time–temperature–transformation diagrams from non-isothermal differential scanning calorimetry data, portray reasonably well experimental results of crystallization, as well as devitrification of consolidated samples.

中文翻译：

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中碳钢坯连铸用黄铜矿型结晶器粉末渣失透结晶动力学分析

钢坯的高速连铸需要在液芯中产生相当大的湍流，这会导致大量夹渣，除非使用高粘度炉渣。已经提出这种炉渣在主要的模具冷却、温度和停留时间条件下保持玻璃状或轻微结晶。其组成导致形成黄长石矿物（即形成钙钠镁铝铁二硅酸盐）的炉渣，作为主要结晶相，在 1573 K (1300 °C) 下具有 > 0.5 Pa/s 的粘度，低或不含有 F，并掺入过渡金属氧化物（例如 FeO、MnO 和 TiO）以吸收红外辐射并软化钢壳到模具的热传递。在这项工作中，一种用于铸造中碳钢圆坯的商用黄晶石结晶器粉末，被选择对非等温和等温条件下玻璃态-失透-和过冷液态渣-结晶-结晶相的沉淀动力学进行详细分析。高温共聚焦激光扫描显微镜用于两种情况，差示扫描量热法仅用于非等温情况。通过定量 X 射线粉末衍射分析对处理过的样品中的无定形和结晶相进行评估。发现即使在 1248 K (975 °C) 下长时间处理（» 36,000 秒）后，仍有大约 13%wt 的炉渣保持无定形。此外，结果表明过冷液体和玻璃渣中的结晶相在表面发生成核。因此，发现结晶动力学受过冷液体接触的表面形貌以及施加在液态渣表面上的剪切作用的强烈影响，这有助于形成成核位点。在接触外墙和裂缝的表面上，反玻璃化往往更强。此外，发现动力学模型的预测，为从非等温差示扫描量热数据估计时间-温度-转变图而开发，描绘了相当好的结晶实验结果，以及固结样品的反玻璃化。在接触外墙和裂缝的表面上，反玻璃化往往更强。此外，发现动力学模型的预测，为从非等温差示扫描量热数据估计时间-温度-转变图而开发，描绘了相当好的结晶实验结果，以及固结样品的反玻璃化。在接触外墙和裂缝的表面上，反玻璃化往往更强。此外，发现动力学模型的预测，为从非等温差示扫描量热数据估计时间-温度-转变图而开发，描绘了相当好的结晶实验结果，以及固结样品的反玻璃化。