不同钒、氮含量对低碳贝氏体钢组织及析出行为的影响

摘要

The precipitation behavior of vanadium carbonitrides and its effect on the microstructure and mechanical prop-erty during the thermomechanical control processes (TMCP)in low carbon bainitic steel with four different vanadium and nitrogen content are studied by means of field emission scanning electron microscopy(SEM),transmission electron micro-scope(TEM)and energy disperse spectroscopy (EDS).The results show that the microstructure of the four tested steels coiled at 450 ℃ are granular bainite.When the vanadium content increased from 0.05% to 0.15%,the yield strength and tensile strength of the tested steel increased 163 MPa,85 MPa,respectively.With the vanadium content increased,the bainite is apparently refined and volume fraction of very fine precipitated particles significantly increased.The average size of the precipitate is from 4 nm to 6 nm.The precipitated particles with 10 nm or less are in the form of fine pellets,and about 20 nm are generally elongated or ellipsoidal.The precipitated phase less than 10 nm is a complex precipitated phase V(C,N) or (V,Cr)(C,N)with face-centered cubic structure by TEM analysis.%借助场发射扫描电镜(SEM)、透射电子显微镜(TEM)和能谱仪(EDS)等方法研究了4种不同钒、氮含量的低碳贝氏体钢在控轧控冷过程中的微观组织、力学性能及碳氮化钒的析出行为.结果表明,在450℃卷取,4种试验用钢的组织都为粒状贝氏体,钒含量由0.05%增加到0.15%,试验用钢的屈服强度提高了163 MPa,抗拉强度提高了85 MPa.随着钢中钒、氮含量的增加,贝氏体组织明显细化;同时,在贝氏体铁素体基体中细小析出相的体积分数显著增加,析出相的平均尺寸为4~6 nm.尺寸<10 nm的析出颗粒呈细小碟片状,尺寸约为20 nm的析出相一般呈长条状或者椭球状.经TEM分析,尺寸<10 nm的析出相为具有面心立方结构的V(C,N)或(V,Cr)(C,N)复合析出相.