Design and Development of Fire-Resistant Ferritic Steels for Structural Applications

这项研究旨在将两个新的科学概念整合到耐火钢的设计和制造中。首先，将使用纳米级的共格铜沉淀物代替碳进行初次强化。低碳含量使钢易于焊接，无需预热或后热处理。随着温度的升高，共格析出物的粗化速度变慢，导致较高温度下的强度退化较小。第二，Nb或Ti将作为合金化元素，延缓向可能发生快速晶粒长大、析出粗化和位错回复的高温区的转变，并通过形成金属碳化物析出物来促进二次强化。这项研究为设计满足更严格标准的更强大的耐火钢提供了智力基础，其结果很容易移植到其他高温应用中，如锅炉、涡轮机和动力总成，以提高效率。此外，这项研究解决了铁合金的纳米级结构-性能关系，这种关系通常被认为是成熟和过时的，这是一个弥漫在整个社区的错误印象。主要研究人员开展的外联活动将是解决这一谬误的第一步，使学生能够从更广泛的角度思考纳米技术，使工业科学家和工程师更好地了解冶金学的现代进步，并使政府机构愿意在技术开发方面发挥带头作用。随着每年数以百万计的钢材被用于建筑、公路和桥梁，许多机会等待着廉价、易于生产的高性能钢材的开发。

The research is to integrate two novel scientific concepts in the design and fabrication of fire-resistant steels. First, instead of carbon, nanosized coherent copper precipitates will be used for primary strengthening. The low carbon content makes the steel readily weldable without pre- or post-heat treatment. Coherent precipitates tend to coarsen slower with increasing temperature, resulting in less strength degradation at higher temperatures. Second, either Nb or Ti will be used as an alloying element to delay the transition to the high-temperature regime in which rapid grain growth, precipitate coarsening, and dislocation recovery may occur, and to promote secondary strengthening by the formation of metal carbide precipitates. The research provides the intellectual basis for designing stronger fire-resistant steels that meet tougher standards, with results that are readily portable to other high-temperature applications such as boilers, turbines and powertrains for enhanced efficiency. Further, this research addresses nanoscale structure-property relationships in ferrous alloys that are often considered to be mature and old-fashioned, an erroneous impression that permeates throughout the community. Outreach activities conducted by the principal investigators will represent the first step to addressing this fallacy, resulting in students who can think about nanotechnology in broader terms, in industrial scientists and engineers who are better informed about modern advances in metallurgy, and in government agencies willing to take a lead in technology developments. With millions of tons of steels being used in buildings, highways, and bridges every year, many opportunities await the development of inexpensive, easily produced, high-performance steels.