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A Comparison of Steels for Nuclear Bolting Applications

核螺栓连接应用钢材的比较

基本信息

批准号：
2386027
负责人：
金额：
--
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-2386027
关键词：
Comparison Steels Nuclear Bolting Applications

项目摘要

At present, the bolts are produced from SA540 steel, which is very similar in composition to the common AISI 4340 steel. Previous work on SA540 has suggested that its composition is not well optimised for use in very large bolts - results suggest that, when oil quenched, through-thickness transformation to 100% martensite is unlikely to be achieved on a consistent basis. If processing is performed perfectly then the grade is capable of an exceptional combination of strength and toughness; however, the grade is not robust to variability in processing. The component size is at the limit of the hardenabilty of the composition. Hence, properties are non-uniform through the section. Furthermore, it has been demonstrated that small differences in cooling rate around a critical value can lead to significant changes in microstructure evolution, which in turn result in significant scatter in hardness values. This project will seek to compare SA540 to another grade of steel, A723, which is likely to be more hardenable in thick sections. It will involve applying industrial heat treatment processes to both SA540 and A723 and monitoring the evolution of microstructure and properties. A number of techniques will be utilised, including dilatometry, electron microscopy (both scanning and transmission) and mechanical testing (which is likely to extend to Charpy and fracture toughness tests).

目前，螺栓是用SA540钢生产的，这种钢在成分上与普通的AISI 4340钢非常相似。以前对SA540的研究表明，其成分不能很好地优化以用于超大型螺栓--结果表明，当油淬火时，不太可能在一致的基础上实现向100%马氏体的穿透厚度转变。如果加工过程完美，则该等级能够提供出色的强度和韧性组合；然而，该等级对加工过程中的变化性不是很强。成分尺寸处于组合物硬化性的极限。因此，在整个横断面中，属性是不一致的。此外，研究还表明，冷却速度在临界值附近的微小差异可以导致组织演变的显著变化，从而导致硬度值的显著分散。该项目将寻求将SA540与另一种牌号的A723钢进行比较，A723钢在厚壁中可能更具淬透性。它将涉及对SA540和A723应用工业热处理工艺，并监测组织和性能的演变。将使用许多技术，包括膨胀法、电子显微镜(扫描和透射)和机械测试(很可能扩展到夏比和断裂韧性测试)。