【摘要】 采用宏观形貌观察、光学显微镜(OM)、扫描电镜(SEM)及拉伸试验等方法，对用于大型跨海桥梁等工程项目的两种??75 mm大直径预应力钢筋42CrMo和42CrMnNiMo的显微组织与力学性能进行对比分析。结果表明，相较于42CrMo钢，42CrMnNiMo钢退火态原材料含有更多细小、均匀且弥散分布的粒状珠光体，有利于调质处理后形成细小均匀的回火索氏体组织。调质处理后，42CrMnNiMo钢获得了更加细小均匀的回火索氏体组织，其屈服强度、抗拉强度及断后伸长率分别较42CrMo钢提升了17.6%、14.1%和27.8%,同时其螺纹根部缺陷更少。相比之下，42CrMo钢淬透性较差，心部在淬火过程中易生成铁素体和上贝氏体，导致其强度和硬度均低于42CrMnNiMo钢。此外，由于组织不均匀引发的变形不协调，加之螺纹根部为应力集中区域，42CrMo钢在冷滚压过程中更易产生根部缺陷。综合分析表明，42CrMnNiMo钢具备更优异的冷变形能力，更适用于制造高强度大直径冷滚压预应力螺纹钢筋。更多还原

【Abstract】 Microstructure and mechanical properties of two types of ??75 mm large-diameter pre-stressed steel rebars 42CrMo and 42CrMnNiMo for large-scale projects such as cross-sea bridges were compared and analyzed by means of macrostructure observation, optical microscope(OM), scanning electron microscope(SEM) and tensile test. The results demonstrate that compared to 42CrMo steel, the raw materials of 42CrMnNiMo steel in the annealed state contains a higher proportion of fine, uniform and dispersed granular pearlite, which facilitates the formation of a finer and more homogeneous tempered martensite after quenching and tempering. After quenching and tempering, the 42CrMnNiMo steel exhibits a more refined and uniform tempered martensite, with yield strength, tensile strength and elongation after fracture increasing by 17.6%, 14.1% and 27.8%, respectively, compared to the 42CrMo steel. Additionally, the 42CrMnNiMo steel shows fewer defects at the thread roots. In contrast, 42CrMo steel exhibits inferior hardenability, leading to the formation of ferrite and upper bainite at core during quenching, resulting in lower strength and hardness than that of the 42CrMnNiMo steel. Furthermore, due to microstructural inhomogeneity-induced deformation incompatibility and stress concentration at the thread roots, 42CrMo steel is more prone to root defects during cold rolling. Comprehensive analysis indicates that 42CrMnNiMo steel possesses superior cold deformation capability, making it more suitable for manufacturing high-strength, large-diameter cold-rolled prestressed threaded steel bars.更多还原