铌对高强度51CrV钢组织及性能的影响

Effect of niobium on microstructure and properties of high strength 51CrV steel

借助光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)与万能拉伸试验机等研究了铌元素的添加对51CrV钢奥氏体晶粒尺寸、淬火和回火组织以及力学性能的影响。结果表明:0Nb和0.02wt%Nb试验钢的奥氏体平均晶粒尺寸分别为10.0μm和3.1μm,添加0.02wt%Nb的51CrV钢奥氏体晶粒尺寸显著细化、板条马氏体尺寸减小,回火过程中析出碳化物的尺寸更细,两种试验钢850℃淬火+400℃回火后,屈服强度均大于1300 MPa,抗拉强度均大于1400 MPa。而加入0.02wt%Nb试验钢由于晶粒细化,断后伸长率达到9.50%,不含Nb试验钢伸长率为8.69%。51CrV钢添加微量的Nb元素在保证高强度的同时,塑性得到提高,综合性能比无Nb钢优异。

Effect of niobium addition on austenite grain size,quenching and tempering microstructure and mechanical properties of 51 CrV steel was observed by means of optical microscope,scanning electron microscope,transmission electron microscope and universal tensile testing machine.The results show that the austenite grain size of Nb free and 0.02 wt%Nb steels is 10.0μm and 3.1μm,respectively.The grain size of 51 CrV steel with Nb element is significantly refined,the size of lath martensite reduces,and the size of carbide precipitated during tempering is finer.After quenching at 850℃ and tempering at 400℃,both the yield strength and tensile strength of the two tested steels are greater than 1300 MPa and 1400 MPa,respectively.The elongation of 0.02 wt%Nb tested steel increases to 9.50% because of the grain refinement.And the elongation of Nb free steel is 8.69%.51 CrV steel microalloyed by Nb element has both high strength and high plasticity and its comprehensive properties are better than Nb-free steel.