微合金元素Nb 对低碳铸钢强度和冲击韧性的影响

Microalloyed low-carbon cast steels with different Nb contents were prepared by medium-frequency furnace smelting. The effects of Nb microalloying on the microstructure, strength and impact toughness of low-carbon cast steels were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hydraulic universal strength testing machine, semi-automatic impact testing machine, etc. The results show that adding an appropriate microalloying element Nb can reduce the grain size of low-carbon cast steel by 20.8% - 34.6%, and at the same time promote the formation of fine NbC precipitated phases, which can effectively improve the strength and impact toughness of low-carbon cast steel. Grain refinement and precipitation strengthening are the main strengthening and toughening mechanisms. Among them, the yield strength of the microalloyed cast steel with 0.044% Nb content is 350 MPa, the tensile strength is 520 MPa, and the impact energy at room temperature is 119.7 J. Compared with ordinary low-carbon cast steel, its plasticity remains basically unchanged, but the yield strength, tensile strength and impact energy at room temperature are increased by 20.7%, 7.2% and 25.6% respectively.

采用中频炉冶炼制备不同 Ｎｂ含量的微合金低碳铸钢，用光学显微镜（ ＯＭ ）、扫描电子显微镜（ ＳＥＭ ）、透射电子显微镜（ ＴＥＭ ）、液压万能强度试验机、半自动冲击试验机等手段研究了 Ｎｂ 微合金化对低碳铸钢显微组织、强度和冲击韧性的影响。结果表明，添加合适的微合金元素 Ｎｂ可以使低碳铸钢的晶粒尺寸减小２０．８％～３４．６％ ，同时促进细小 ＮｂＣ析出相的形成，能有效提高低碳铸钢的强度和冲击韧性，晶粒细化和析出强化为其主要的强韧化机制。其中，含 Ｎｂ 量为 ０．０４４％ 的微合金铸钢屈服强度为３５０ＭＰａ ，抗拉强度为 ５２０ＭＰａ ，室温冲击功为 １１９．７Ｊ 。与普通低碳铸钢相比，其塑性基本保持不变，但屈服强度、抗拉强度和室温冲击功分别提高了２０．７％ 、 ７．２％和２５．６％ 。