Quantification of Structural Transformations during Heat Treatment in Ultra-high Carbon Steels

超高碳钢热处理过程中组织转变的量化

• 批准号: 1436064
• 负责人: Yoosuf Picard
• 金额: $ 47.08万
• 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: 2014
• 资助国家: 美国
• 起止时间: 2014-11-01 至 2017-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1436064&HistoricalAwards=false
• 关键词: Quantification; Structural; Transformations; during; Heat

Steel is a metallic material with iron and carbon as the primary components. The properties of steel can vary greatly depending on carbon level and processing. Steels with ultra-high carbon levels behave more like ceramics than metals; they are extremely hard and very brittle. These steels are primarily utilized in tool components to shape softer steels and other metals, but could see greater usage if their brittleness can be reduced. To date, brittleness has been reduced by cycles of heating and forming, methods that are challenging to implement on a large production scale. It is possible to decrease brittleness in these materials by simply heating alone; however existing heat treatments are energy intensive and far from optimized. This award supports fundamental research on the structural transformation behavior of ultra-high carbon steels during heating. The research utilizes novel experimental methods to observe changes to the steel structure in real time during heating and to develop new metrics that can be used to optimize processing and properties. These fundamental studies will lead to improved heat treatment strategies that will enable production of ultra-high carbon steels with improved combinations of properties while also reducing energy usage. Results from this research will also introduce materials science undergraduate students to fundamental topics of modern steelmaking and an outreach component will expose middle and high school students to digital image analysis and methods used to characterize materials. Ultra-high carbon steels can exhibit superior hardness and strength compared to other steels of lower carbon contents. However, the high fraction of carbides in these steels render them too brittle for many structural applications. This project seeks to investigate microstructural transformations at elevated temperatures in steels containing ultrahigh carbon contents (1.7-2.3 weight percent) and the impact of these transformations on mechanical properties: toughness, hardness, strength and ductility. This study will apply in-situ confocal scanning laser microscopy and ex-situ electron microscopy to study and quantify microstructural evolution, specifically examining the effects of time, temperature and alloy chemistry on carbide dissolution kinetics and their final distribution in heat treated steels. A comprehensive assessment of important mechanical properties will be correlated to the final microstructural state. These pursuits will result in an analytical model that can accurately describe carbide dissolution and precipitation behavior at temperature ranges employed for heat treatments of ultra-high carbon steels.

钢是以铁和碳为主要成分的金属材料。 钢的性能可以根据碳含量和加工过程而有很大差异。 超高含碳量的钢表现得更像陶瓷而不是金属;它们非常硬，非常脆。 这些钢主要用于工具部件中，以形成较软的钢和其他金属，但如果可以降低其脆性，则可以看到更大的用途。 到目前为止，脆性已经通过加热和成型的循环来降低，这些方法在大规模生产中具有挑战性。 可以通过简单的加热来降低这些材料的脆性;然而，现有的热处理是能源密集型的，并且远未优化。 该奖项支持对超高碳钢在加热过程中的结构转变行为进行基础研究。 该研究利用新的实验方法来观察加热过程中真实的钢结构的变化，并开发可用于优化加工和性能的新指标。 这些基础研究将导致改进的热处理策略，从而能够生产具有改进的性能组合的超高碳钢，同时还可以减少能源使用。 这项研究的结果还将向材料科学专业的本科生介绍现代炼钢的基本主题，并将向初中和高中学生介绍用于表征材料的数字图像分析和方法。超高碳钢与其它较低碳含量的钢相比，可表现出上级硬度和强度。 然而，这些钢中的高比例碳化物使它们对于许多结构应用来说太脆。 该项目旨在研究含有超高碳含量（1.7- 2.3wt%）的钢在高温下的显微组织转变以及这些转变对机械性能（韧性、硬度、强度和延展性）的影响。 本研究将应用原位共聚焦扫描激光显微镜和非原位电子显微镜来研究和量化微观结构的演变，特别是研究时间，温度和合金化学对碳化物溶解动力学及其在热处理钢中的最终分布的影响。 重要机械性能的综合评估将与最终的微观结构状态相关联。 这些追求将导致一个分析模型，可以准确地描述碳化物的溶解和析出行为的温度范围内采用超高碳钢的热处理。