摘要
为改善疲劳极限,使用260t转炉、2 250mm热连轧机组生产了一种添加镧的700MPa挂车大梁钢板.通过高频轴向疲劳实验研究了添加微量镧对700MPa汽车大梁钢板5×10^6周次下的疲劳极限强度的影响,并采用金相显微镜和扫描电镜分析了试样微观组织变化情况.结果表明:700MPa大梁钢板的疲劳极限为222MPa,添加0.002 5%稀土镧的700MPa汽车大梁实验钢板的疲劳极限为237MPa.加镧虽然未改变钢板的拉伸性能,但提高了7%的疲劳极限.700MPa大梁钢板疲劳极限的提高决定于加镧的材料微观组织的变化.其机理是添加稀土镧细化了700MPa大梁钢板中贝氏体尺寸,当量长度大于1μm的贝氏体占比由9%提高到15%;稀土镧的添加促进了带状或者长条状的夹杂物向球状含镧化合物转变,减缓了夹杂物引起的应力集中.不论是否添加稀土镧,700MPa大梁钢板裂纹萌生及疲劳断裂的起因是Ti和Nb碳氮化析出物的存在.
In order to improve the fatigue limit,a new lanthanum-bearing 700 MPa steel plate for trailer girder was produced by 260 tons converter and 2 250 mm hot rolling mill.Effects of trace lanthanum addition on the fatigue limit strength of 700 MPa steel plate for trailer girder were studied by high frequency axial fatigue test at 5×10^6 cycles,and the microstructural evolution of specimens was analyzed by OM and SEM.The results show that the fatigue limit of 700 MPa steel plate is 222 MPa,and that of the steel plate modified by 0.002 5%lanthanum is 237 MPa.The fatigue limit of the plate is increased by 7% by lanthanum addition,although the tensile properties is not improved significantly.The improvement of fatigue limit of 700 MPa steel plate for trailer girder depends on the changed microstructure.The mechanism is that the size of bainite in 700 MPa steel plate for trailer girder is refined by lanthanum addition,and the proportion of bainite larger than 1μm in equivalent length is increased from9%to 15%.Lanthanum addition promotes the transformation of banded or elongated inclusions to lanthanumbearing spherical compounds,and reduces the stress concentration caused by inclusions.Whether rare earth lanthanum is added or not,the cause of crack initiation and fatigue fracture of 700 MPa steel plate for trailer girder is attributed to the existence of Ti and Nb carbonitriding precipitates.
作者
高志国
张嘉华
金自力
GAO Zhiguo;ZHANG Jiahua;JIN Zili(College of Mechanical and Electrical Engineering,Wuyi University,Wuyishan Fujian 354300,China;Technology Center,Inner Mongolia Baogang Steel Union Co.,Ltd,Baotou Inner Mongolia 014010,China;School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou Inner Mongolia 014010,China)
出处
《复旦学报（自然科学版）》
CAS
CSCD
北大核心
2020年第4期443-448,共6页
Journal of Fudan University：Natural Science
基金
包头市重大科技发展项目(2013Z1001)。
关键词
疲劳极限
汽车大梁钢板
镧
微观组织
fatigue limit
steel plate for trailer girder
lanthanum
microstructure
