工程机械用超高强钢的弯曲性能及弯曲过程中的微观组织演变  

Bendability and microstructure evolution during bending of ultra-high strength steel for construction machinery

作　　者：郑东升 范才河[1] 蹇海根[1] 孙雅馨 罗登[2] 刘丹[2] 张青学[2] ZHENG Dong-sheng;FAN Cai-he;JIAN Hai-gen;SUN Ya-xin;LUO Deng;LIU Dan;ZHANG Qing-xue(College of Materials and Advanced Manufacturing,Hunan University of Technology,Zhuzhou 412007,China;Technology and Quality Department,Xiangtan Iron and Steel Co Ltd of Hunan Valin,Xiangtan 411101,China)

机构地区：[1]湖南工业大学材料与先进制造学院,湖南株洲412007 [2]湖南华菱湘潭钢铁有限公司技术质量部,湖南湘潭411101

出　　处：《材料热处理学报》2022年第3期81-88,共8页Transactions of Materials and Heat Treatment

基　　金：湖南省教育厅科学研究项目(19C0574);湖南省教育厅科学研究项目(20A147);湖南省科技创新计划项目(2018XK2301);湖南工业大学2021年度大学生创新创业训练计划项目(99)。

摘　　要：采用熔-铸-轧-热处理一体化工艺制备了屈服强度超过1200 MPa的工程机械用超高强钢,通过180°自由弯曲试验研究了其弯曲性能,利用光学显微镜(OM)、扫描电镜(SEM)和电子背散射衍射(EBSD)等分析了试验钢弯曲过程中的微观组织演变,并探讨了其弯曲变形行为及失效机理。结果表明:内弯曲半径为板厚的1.5倍时,制备的工程机械用超高强钢的弯曲试样仍保持完好状态。随着内弯曲半径的减小,弯曲试样外表面层板条马氏体各种亚结构边界的密度增加,并出现变形织构的特征,其内表面层马氏体组织的压扁程度增大。试验钢的弯曲失效是应变局部化和微孔发展引起的,裂纹从自由表面产生后,沿着剪切带扩展一定长度,与马氏体块界等大角度晶界相遇时,其扩展方向不断变化,直至断裂。Ultra-high strength steel for construction machinery with yield strength greater than 1200 MPa was prepared by integrated process of melting,casting,rolling and heat treatment.The bendability of the steel was investigated by 180°air-bending test.Microstructure evolution of the experimental steel during bending was analyzed by mean of optical microscope(OM),scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD)technique,and bending deformation behavior and failure mechanism were discussed.The results show that when the inner bending radius is 1.5 times of the plate thickness,the bending specimen of ultra-high strength steel for construction machinery still remain in good condition.With the decrease of the inner bending radius,the density of various substructure boundaries of lath martensite at the outer surface layer of the bending specimens increases,and it exhibits the characteristics of deformation texture.Meanwhile,the flattening degree of martensite structure at the inner surface layer of the bending specimens increases.The bending failure of the experimental steel is caused by strain localization and micro-voids development.After the cracks are generated from the free surface,they propagate along the shear band for a certain length.When the cracks meet the large angle grain boundaries such as martensite block boundary,their propagation direction changes continuously until fracture.

关 键 词：工程机械用超高强钢 弯曲性能 微观组织 弯曲半径 

分 类 号：TG142.3[一般工业技术—材料科学与工程]