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通过对20CrMnMo钢渗碳硬化层的组织结构、层内残余应力和硬度的分布以及渗碳硬化试棒的扭转性能进行系统的分析研究,经综合分析总结出20CrMnMo钢的渗碳硬化层具有下列几个特点,即:(1)渗碳层中基体组织的主体是枣核马氏体.枣核马氏体基体由表及里一直可延伸到含碳量为0.5%的层深部位(即有效层深,HV550处).(2)表面碳势为1.1%C的渗碳硬化层内,临近外表面部位的枣核马氏体中会出现显微裂纹.(3)残余奥氏体呈小块状(角状),它们被细小的枣核马氏体晶体分割.位于不同地点的残余奥氏体发生马氏体转变时,将对渗碳硬化层的性能起着不同的影响.(4)在心部组织相同的条件下,表面碳势及渗层深度与渗碳件的扭转塑变抗力无关,但马氏体内的显微裂纹和残余压应力的分布方式将直接影响渗碳硬化层的扭转断裂塑性.
Through the analysis of the microstructure, the distribution of residual stress and hardness in the layer of 20CrMnMo steel and the torsional behavior of the carburized hardened bar, the carburized hardened layer of the 20CrMnMo steel is summarized as follows A characteristic, namely: (1) carburizing layer matrix body is the body of the jujube martensite.The jujube martensite matrix from the table and has been extended to the depth of 0.5% of the carbon layer depth (ie effective Layer depth, HV550.) (2) Microscopic cracks appear in the martensite near the outer surface in the carburized hardened layer with a surface carbon potential of 1.1% C. (3) The retained austenite is small They are divided into fine jujube martensite crystals, and martensite transformation of the retained austenite in different locations will have different effects on the properties of the carburized hardened layer. ) Under the same condition of the heart tissue, the surface carbon potential and the depth of the infiltrated layer have nothing to do with the torsional plastic deformation resistance of the carburized part, but the distribution of the micro-cracks and residual compressive stress in the martensite will directly affect the hardenability of the carburized hardened layer Reversible plasticity.