Development of a High Temperature Maximun Bubble Pressure Apparatus for Measuring Surface Tension of Molten Metals

测量熔融金属表面张力的高温最大气泡压力仪的研制

• 批准号: 0112792
• 负责人: Sridhar Seetharaman
• 金额: $ 7.5万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0112792&HistoricalAwards=false
• 关键词: Development; Temperature; Maximun; Bubble; Pressure

Computer modeling of metallurgical processes can be used to enhance process control and product quality. Full exploitation of the high-level of currently available computational tools requires improved accuracy of the physical property input data. In particular, surface tension of molten metals critically influences the characteristics of metals processing. For high-quality measurements of surface tension, it is mandatory to establish the concentration of surface-active elements present in the melt. The most ubiquitous species is oxygen; it is present under all practical conditions involving molten metals and is a major factor effecting surface tension, even at parts per million levels. Since it is practically impossible to totally eliminate the presence of oxygen in reactors and vessels, the oxygen potential needs to be closely monitored. This award from the Instrumentation for Materials Research program support a program to build a high temperature maximum bubble pressure (MBP) device equipped with a solid electrolyte based sensor/control to monitor the oxygen potential in the probe. This combination is uniquely suited for measuring surface tensions of reactive alloys since: (1) the MBP probes beneath the surface of the melt and the probed surface area is small compared to the volume of the melt; and (2) the oxygen potential in the gas stream responsible for creating the probed surface is monitored through an oxygen sensing/controlling device. The instrumentation developed under this program will be made available to students at Carnegie Mellon during laboratory session designed to study the structure and properties of metals in their molten state. Furthermore, it is expected that the ability to establish the effect of the oxygen potential on the surface tension and the effects of the presence of 2D surface phases, will significantly contribute to ongoing and future research projects at Carnegie Mellon that study the surface thermodynamics of alloys.In order to fully appreciate the tools offered by computer models in predicting metallurgical processes for process control and product quality, it is necessary to parallel the advances in process modeling with improved accuracy of the physical data that are used as input. Surface tension of molten metals is a key property since it influences (1) the conversion of liquid droplets to solids during the production of metal-alloy powders; (2) the formation of gas pores during casting which diminish the final metal strength; and (3) the formation and shape of impurity inclusions during the processing of steels. However, it is experimentally extremely difficult to perform accurate surface tension measurements of molten reactive alloys such as stainless steels and superalloys. This is due to the fact that oxygen is always present in trace amounts, which will react with the metals. Since even low levels of dissolved oxygen in the metal can change the surface tension significantly, it is critical to control its concentration accurately. The award from the Instrumentation for Materials Research program instrumentation supports the development of a novel combination of a probe that measures the surface tension under the surface of metals and an oxygen pump/sensor that controls and monitors the oxygen level. The instrument will benefit the metals processing industry and increase the understanding of the physical chemistry of surfaces in the molten state and thereby positively impacting research as well as education in materials chemistry. The instrument built under this program will be implemented in laboratory classes at Carnegie Mellon changing the fact that the important molten state of materials has so far been little studied by students.

冶金过程的计算机建模可用于增强过程控制和产品质量。充分利用高水平的目前可用的计算工具，需要提高的物理性质输入数据的准确性。特别是，熔融金属的表面张力严重影响金属加工的特性。为了高质量地测量表面张力，必须确定熔体中存在的表面活性元素的浓度。最普遍的物种是氧;它存在于所有涉及熔融金属的实际条件下，是影响表面张力的主要因素，即使在百万分之一的水平上。由于实际上不可能完全消除反应器和容器中氧气的存在，因此需要密切监测氧势。该奖项来自材料研究计划的仪器，支持一项计划，以建立一个高温最大气泡压力（MBP）设备，配备了基于固体电解质的传感器/控制，以监测探头中的氧势。这种组合独特地适合于测量活性合金的表面张力，因为：（1）MBP探针位于熔体表面下方，并且与熔体的体积相比，探测的表面积很小;以及（2）通过氧感测/控制装置监测负责产生探测表面的气流中的氧势。在该计划下开发的仪器将在卡内基梅隆大学的实验室会议期间提供给学生，旨在研究金属在熔融状态下的结构和性能。此外，可以预期，建立氧势对表面张力的影响以及二维表面相存在的影响的能力，将对卡内基梅隆大学正在进行的和未来的研究合金表面热力学的研究项目做出重大贡献。为了充分理解计算机模型在预测冶金过程中提供的工具，以实现过程控制和产品质量，有必要使过程建模的进步与用作输入的物理数据的改进的准确性并行。熔融金属的表面张力是一个关键性质，因为它影响（1）在金属合金粉末的生产过程中液滴向固体的转化;（2）在铸造过程中气孔的形成，这会降低最终的金属强度;以及（3）在钢的加工过程中杂质夹杂物的形成和形状。然而，在实验上极难对熔融反应性合金（例如不锈钢和超合金）进行精确的表面张力测量。这是因为氧气总是以痕量存在，它会与金属反应。由于金属中即使是低水平的溶解氧也会显著改变表面张力，因此准确控制其浓度至关重要。该奖项来自材料研究计划仪器仪表，支持开发一种测量金属表面下表面张力的探针和控制和监测氧气水平的氧泵/传感器的新型组合。 该仪器将使金属加工行业受益，并增加对熔融状态下表面物理化学的理解，从而对材料化学的研究和教育产生积极影响。根据该计划建造的仪器将在卡内基梅隆大学的实验室课程中实施，改变了迄今为止学生很少研究材料的重要熔融状态的事实。