新型Mn系超低碳贝氏体高强高韧钢的开发

Development of a new Mn system ultra-low carbon bainite steel with high strength and toughness

在Nb、Ti微合金化超低碳含Mn钢的成分设计基础上,通过控制轧制获得扁平奥氏体,随后控制冷却获得贝氏体组织,开发出新型的高韧性超低碳贝氏体钢。实验结果表明,在0.03C～3.4Mn微合金钢中使扁平奥氏体的厚度细化至4μm左右,超低碳贝氏体组织的屈服强度达到600 MPa,抗拉强度达到780 MPa,上平台冲击功约230 J,实现了强度与韧性的良好配合。利用电子背散射衍射(EBSD)技术对试验钢相变产物的组织形貌进行了表征,并对强韧化机理、成分和工艺的优越性进行了初步的分析。

A new type uhra-low carbon bainitic steel with high toughness was developed based on a novel chemical composition design, which consists of the alloying of Mn, ultra-low carbon content and micro-alloying with Nb and Ti. Through the thermo-mechanical processing, refined bainitic micrstructure was formed from pancaked austenite in the steel. The results show that the average thickness of pancaked prior-austenite is reduced to about 4μm in a 0. 03% C-3.4% Mn micro-alloyed steel, which results in a good combination of yield strength of 600 MPa and tensile strength of 780 MPa, and impact energy of the upper shelf is 230 J. The microstructure of transformed product in the steel studied is characterized using electron backscattered diffraction （EBSD） technique. The strengthening and toughening mechanisms and the advantages of the composition and processing design for the steel were also discussed.