The NEU Research Team Solved the Problem of Ultra-high Strength Steel Processing and Preparing
Recently, the NEU research team developed an ultra-high strength steel material featured a new microscopic structure with a simple and efficient preparation process. This material is less liable to fracture in the course of processing and forming, and can improve the hardness with the change of shape. It has broken through the upper limit of the performance of the existing materials of the same category in many aspects such as strength and plasticity. The research findings were published online in full recently in the journal Science.
The strength and plasticity of steel are often incompatible. Generally speaking, for a same kind of steel with different processing, the higher the strength is, the plasticity will be lower.Dr. Li Yunjie in the research team said: Steel is easily fractured, so this problem with ultra-high strength steel is a general difficulty for steel materials.”
Especially in the fields of aerospace, auto and deep diving, the strength of ultra-high strength steel used for load-bearing is often required to be several times higher than that of ordinary steel, and at this time the plasticity of steel will drop dramatically, Prof. Yuan Guo said. The fundamental reason for this phenomenon is that with the continuous extension and deformation of steel, the microstructure inside the material changes, which is easy to produce insufficient work hardening or local stress concentration, thus leading to the fracture of steel, he added.
Therefore, addressing the contradiction between strength and plasticity of ultra-high strength steel materials has become a hot topic for scholars at home and abroad. Most of the existing production processes usually adopt the traditional micro-structure control mode, that is, it needs to add nickel, molybdenum and other precious metals as an auxiliary or increase process flows to improve the performance. Such a mode is expensive and not convenient for large-scale industrial applications, and the improvement of plasticity is very limited. For that reason, the NEU research team has innovatively put forward a new mechanism to improve both strength and plasticity, and successfully prepared a series of low-cost new ultra-high strength steel featured a “carbon-manganese alloy system. It has broken the dependence of ultra-high strength steel on complex preparation process and expensive alloy composition, thus having great practical significance to promoting the preparation and application of low-cost, large-size ultra-high strength steel materials with plasticity.
This new idea of organization structure design is applicable to not only forging, but also rolling and other processing methods. It can be used for the production and manufacture of shafts, bars and plates, and is expected to be applied to large engineering machinery equipment, deep sea, national defense security and other fields. Next, the research team will conduct further study on the industrial application of this type of ultra-high strength steel, said Wang Guodong, academician of Chinese Academy of Engineering (CAE).