Acta Metall Sin  2020, Vol. 56 Issue (4): 558-582    DOI: 10.11900/0412.1961.2020.00058
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High Performance Steels: the Scenario of Theoryand Technology
DONG Han1,2(),LIAN Xintong1,HU Chundong1,LU Hengchang1,PENG Wei1,ZHAO Hongshan1,XU Dexiang1
1.School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
2.Central Iron and Steel Research Institute, Beijing 100081, China
Abstract

Strengthening and toughening are the main topics of steels, and accompanied fatigue failure and delayed fracture requiring to be solved simultaneously. Not just more than that, better performances in fabrication and service are quite important for an intentional steel to be used eventually. It is worth to pay close attention to match up three main courses: steel processing, component fabrication and service evaluation. Over past two decades, ferrite grains can be refined to micron scale in both plain low carbon steel products and microalloyed steel products and lead to remarkable increase of strength. The reason to define the limitation of ferrite grain refinement to microns is ductility decrease, low processing efficiency and heat affected zone (HAZ) coarsening. Ten years ago, a novel microstructure M3 (multiphase, metastable and multiscale) was proposed to overcome the problems stated above, and led to ductility and/or toughness improvement. It based on the idea of crack initiation and propagation retardment. It led to prevalence of the 3rd generation advanced high strength steel (AHSS) and the 3rd generation high strength low alloy (HSLA) steel, presenting higher ductility and/or toughness at high strength level. In the near future, it is imaginable that polymorphic alloying will be taken into consideration instead of recent hot issue on microstructure control during whole processing. From the view point of classic alloying theory, solution and precipitation of alloying elements play an important role on processing and then final microstructure. The distribution and occurrence of small atom radius elements (e.g. C and N) and comparable atom radius elements (e.g. Cr, Mn, Ni, Co) in iron seem quite clear. The ambiguous situation still remains for B and P, and even larger atom radius elements such as rare earth (RE) elements. Segregation of small amount of them to defects and boundaries maybe lead to decrease of energy and result in remarkable change of microstructure characterization. Thanks to the advancement in processing and instrumentation technologies, the distribution and occurrence of alloying elements in steel and the advantages of different alloying elements in steel matrix and surface can be taken, so called the polymorphic alloying. The practices of polymorphic alloying in steel development are engaged to improve corrosion resistance, strengthening and toughening. The performance enhancements are discussed in cases of weathering steel microalloyed with RE, ultrahigh strength steel strengthening by carbide and intermetallic precipitates, bolt steel with C and microalloying elements, austenitic stainless steel alloyed with N, and martensitic stainless steel alloyed with C and Ag.

Key words:  steel      high performance      theory      technology
 ZTFLH: TG142
Fund: National Key Research and Development Program of China(2017YFB0304401);National Key Research and Development Program of China(2017YFB-0304701);China Postdoctoral Science Foundation(2019M651465);Shanghai Educational Development Foundation(2019-01-07-00-09-E00024)
Corresponding Authors:  Han DONG     E-mail:  13910077790@163.com
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