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研究了19Mn2Cr2NiMoAl低碳合金钢表面获得硬贝氏体组织的热处理工艺及其组织结构特征。利用自行设计的滴注式可控气氛全自动渗碳炉渗碳,然后将试样加热进行奥氏体化处理,并直接淬入盐浴中,保温不同时间进行等温淬火。利用光学显微镜、透射电镜以及显微硬度计对热处理后19Mn2Cr2NiMoAl钢渗碳层的组织和硬度进行分析研究。结果表明,该钢经过230℃保温48h等温淬火后获得最佳的组织结构,其组织特征是,表层是平均尺寸约为80nm的贝氏体铁素体层片,片间为平均厚度为十几纳米的残余奥氏体膜组织;过渡层是硬贝氏体和低碳马氏体的混合组织;心部是低碳马氏体组织。由此获得的试样的表层硬度达到620HV,而心部的硬度为460HV。
The heat treatment process and microstructure of hard bainite in 19Mn2Cr2NiMoAl low carbon alloy steel were studied. The carburizing furnace with drip controllable atmosphere automatic carburizing furnace was designed and carburized by itself. The sample was then heated for austenitizing treatment and directly quenched into salt bath for isothermal quenching at different time. The microstructure and hardness of carburized layer of 19Mn2Cr2NiMoAl steel after heat treatment were analyzed by optical microscope, transmission electron microscope and microhardness tester. The results show that the steel obtained after 230 ℃ 48h isothermal quenching obtained the best organizational structure, the organization is characterized by the surface is the average size of about 80nm bainitic ferrite sheet, the average thickness between the sheets is more than a dozen Nano-retained austenite membrane structure; transition layer is a mixture of hard bainite and low-carbon martensite; heart is low-carbon martensite. The sample thus obtained had a surface hardness of 620 HV and a core hardness of 460 HV.