Effects of Nickel Content, Inclusion Type and Heat Treatment on the Microstructures and Strength and Toughness of New, Cobalt Free, Ultra-high Strength Steels of High Toughness

镍含量、夹杂物类型和热处理对新型无钴超高强高韧性钢显微组织和强韧性的影响

• 批准号: 1362459
• 负责人: Warren Garrison
• 金额: $ 35万
• 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: 2014-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1362459&HistoricalAwards=false
• 关键词: Effects; Nickel; Content; Inclusion; Type

Currently available ultra-high strength steels of high fracture toughness contain large amounts of cobalt and nickel. Because of these large amounts of cobalt and nickel these steels are relatively expensive. The ultimate objective of this research is the further development of new ultra-high strength steels of high fracture toughness, which contain no cobalt and much less nickel than currently available ultra-high strength steels of high fracture toughness. Explicitly the work will provide a basic understanding as to the effects of composition and heat treatment on the strength and toughness of the new steels. This basic understanding will facilitate the eventual commercial development of a new class of ultra-high strength steels of high fracture toughness, which are much less expensive than currently available ultra-high strength steels of high fracture toughness. Based on the initial results obtained in this work there has been interest in the new steels from steel producers and users of such steels and thus it is felt that the new steels have the potential to be of lasting technological and engineering significance. As the new steel contains no cobalt, which must be imported, the new steels also have benefits in terms of sustainability and national security. This work will contribute to the scientific/engineering training of a woman graduate student who will be supported by the project, and several undergraduates during the school year and summers through the NSF Research Experience for Undergraduates supplemental grants. The new steels are medium carbon secondary hardening steels in which nickel additions, rather than cobalt, are used to enhance strengthening by secondary hardening, which is the strengthening by the precipitation of fine alloy carbides. Nickel is used instead of cobalt because nickel is less expensive than cobalt and because nickel lowers the ductile-to-brittle transition temperature while cobalt raises the ductile-to-brittle transition temperature. Both the strength and toughness of the new steels are strongly influenced by the amount of nickel added to the steel. Thus a major objective of the proposed work is to understand how nickel additions influence the microstructure and hence the strength and toughness of the new steels. The second objective of the proposed work is to examine the effects of inclusion type on the toughness of the new steels. Inclusions in steels are second phase particles used to remove from solid solution certain impurities such as sulfur. The inclusion type can influence the toughness when the fracture mode is ductile and can also influence the ductile-to-brittle transition temperature. Our specific interest in this work is to assess the effects of inclusion type on the ductile-to-brittle transition temperature of the new steels.

目前可用的具有高断裂韧性的超高强度钢含有大量的钴和镍。由于这些大量的钴和镍，这些钢相对昂贵。本研究的最终目的是进一步开发具有高断裂韧性的新型超高强度钢，与现有的具有高断裂韧性的超高强度钢相比，这种钢不含钴，镍含量也少得多。显然，这项工作将为成分和热处理对新钢的强度和韧性的影响提供一个基本的认识。这一基本认识将促进新型高断裂韧性超高强度钢的最终商业化开发，这种钢比目前可用的高断裂韧性超高强度钢便宜得多。根据这项工作取得的初步结果，钢铁生产商和这种钢材的使用者对这种新钢材产生了兴趣，因此认为这种新钢材具有持久的技术和工程意义的潜力。由于这种新型钢材不含必须进口的钴，因此在可持续性和国家安全方面也有好处。这项工作将有助于在学年和夏季期间通过NSF本科生研究经验补充资助对一名女研究生和几名本科生进行科学/工程培训，该研究生将由该项目资助。新钢是中碳二次硬化钢，其中添加镍而不是钴来增强二次硬化的强化，这是通过细合金碳化物的析出来增强的。镍被用来代替钴，因为镍比钴便宜，而且镍降低了韧脆转变温度，而钴提高了韧脆转变温度。新钢的强度和韧性都受到钢中添加镍的量的强烈影响。因此，提出的工作的一个主要目标是了解镍的添加如何影响新钢的微观结构，从而影响强度和韧性。提出的工作的第二个目标是检查夹杂物类型对新钢韧性的影响。钢中的夹杂物是用于从固溶体中去除某些杂质（如硫）的第二相颗粒。当断裂方式为延性时，夹杂物类型会影响其韧性，也会影响韧脆转变温度。我们在这项工作中特别感兴趣的是评估夹杂物类型对新钢的韧脆转变温度的影响。