微量Nb对热镀锌DH780钢显微组织和力学性能的影响

Effect of a Minute Amount of Niobium on Microstructure and Mechanical Properties of Hot Galvanized DH780 Steel

采用拉伸试验机、光学显微镜、扫描电子显微镜、透射电子显微镜等分析了0.01%Nb(质量分数)对DH780高强钢显微组织和力学性能的影响。结果表明:含微量铌和不含铌的DH780钢的显微组织均为铁素体、贝氏体、马氏体和残留奥氏体;微量Nb的添加细化了DH780钢的晶粒,改善了镀锌层的均匀性。此外,与不含铌的DH780钢相比,含Nb钢具有较高的铁素体含量和较低的马氏体/贝氏体含量,屈服强度从490 MPa降低至465 MPa,抗拉强度从860 MPa降低至815 MPa,断后伸长率从15%提高至17%。

Influence of 0.01%Nb by mass on microstructure and mechanical properties of DH780 high-strength steel was analyzed by tensile test,optical microscope,scanning electron microscope,and transmission electron microscope.The result indicated that(a)the microstructure of the steels with and without Nb consisted of ferrite,bainite,martensite and retained austenite;(b)the addition of a minute amount of niobium rendered grain of the steel finer and zinc coat more uniform.Furthermore,the DH780 steel with niobium was higher in ferrite content and lower in content of martensite/bainite,and exhibited the decrease in yield strength from 490 to 465 MPa and in tensile strength from 860 to 815 MPa,and the increase in elongation from 15%to 17%,as compared with those of the steel without niobium.