Tellurium Thermodynamics in Ferrous Alloys

铁合金中的碲热力学

• 批准号: 0096619
• 负责人: Mark Schlesinger
• 金额: $ 18.41万
• 依托单位: Missouri University of Science and Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0096619&HistoricalAwards=false
• 关键词: Tellurium; Thermodynamics; Ferrous; Alloys

0096619SchlesingerA thermodynamic model for predicting the activity of tellurium in molten steels is needed to develop safer and more effective alloying practice. This would improve the viability of tellurium as a replacement for lead in free-machining steels. However, little is known about the high-temperature Fe-Te system in general, and the thermodynamics of dilute Fe-Te melts are entirely unknown. The same is true for ternary and higher-order systems. Fe-C-Te and Fe-Mn-Te are of particular importance, given the presence of carbon in most steels and the strong interaction between dissolved manganese and tellurium often noticed in tellurium steels. The research program investigates the thermodynamics of dilute Fe-(C, Mn)-Te molten alloys by measuring the solubility of tellurium vapor in these melts as a function of temperature and composition. The experimental program centers on the use of a self-sealing two-zone furnace tube with molten tellurium at the bottom and the ferrous alloy held in a crucible at the top. Varying the temperature of the tellurium changes its vapor pressure (and thus its solubility); this sets the activity of tellurium with respect to the liquid reference state. Analyzing the ferrous alloy after equilibration determines the mole fraction of tellurium, and thus the activity coefficient. Measurements are made in both pure iron and in iron-carbon (up to saturation level) and iron-manganese (10 wt.%) melts, at temperatures ranging between the liquidus and 1600 degrees C. The experimental results will be fitted against the thermodynamic model developed by Bale and Pelton for non-dilute metallic solutions. This model allows the prediction of tellurium activity (and thus partial pressure) in ferrous melts as a function of composition and temperature. %%%As environmental concerns over the use of lead in free-machining steels grow, increasing attention is being paid to potential alternative additions. One of these alternatives is tellurium, which, added in small quantities (generally less than 0.5 wt.-%), is even more effective than lead at promoting machinability. However, tellurium is expensive and difficult to alloy, given its low boiling point (989 degrees C); its high vapor pressure at steelmaking temperatures presents workplace hygiene concerns of its own in addition to potential losses to the dust.***

0096619Schlesingera热力学模型，用于预测熔融钢中的三学生活性，以发展更安全，更有效的合金实践。 这将提高柜员的生存能力，以替代自由体系钢中的铅。然而，对于一般的高温FE-TE系统知之甚少，稀释液的热力学完全未知。三元和高阶系统也是如此。鉴于大多数钢中存在碳，以及溶解的锰和牙合中经常注意到的碳溶液中，FE-C-TE和Fe-MN-TE尤其重要。 该研究计划通过测量这些熔体中蒸汽蒸气的溶解度作为温度和成分的函数来研究稀释液（C，MN）-TE熔融合金的热力学。实验计划集中在使用自密封的两区炉管，底部有熔融柜，以及在顶部坩埚中固定的铁质合金。变化的柜温度会改变其蒸气压（从而改变其溶解度）。这设置了柜相对于液体参考状态的活性。平衡后分析亚铁合金确定柜的摩尔分数，从而确定活性系数。在纯铁和铁碳（饱和水平）和铁山甘油（10 wt。％）熔体中均进行测量，在液体和1600摄氏度之间的温度下。实验结果将适用于Bale和Pelton开发的热力学模型，用于非抑制金属溶液。该模型允许在亚铁熔体中预测牙学活性（以及部分压力），这是组成和温度的函数。作为环境对铅在自由体验钢中的使用的关注，越来越多的关注正在引起潜在的替代性添加。这些替代方案之一是柜员，它少量添加（通常小于0.5 wt .-％），甚至比促进可加工性的铅更有效。但是，鉴于其低沸点（989度C），Tellurium既昂贵又难以合金；其高蒸气在钢化温度下的压力除了潜在的灰尘损失外，还提出了工作场所的卫生关注。***