论文部分内容阅读
用45、40CrNiMo、40CrNiMoNb探讨了高温形变淬火的强韧化机理。用光学显微镜观察了奥氏体化温度、形变温度以及形变量对形变后所发生的再结晶过程的影响。得出高温形变后所发生的再结晶将使奥氏体晶粒显著细化。对于板条马氏体束,则不问高温形变后是否已发生再结晶,均可使之显著细化。用透射电镜观察了40CrNiMo的组织形貌。结果得出形变可以保留高温淬火的组织上的优点,即全部获得由薄壳状残余奥氏体包围的板条马氏体,不出现孪晶片状马氏体。而与此同时形变还可以克服高温淬火的缺点,其中包括使粗化了的奥氏体晶粒及板条马氏体束重新细化、促进ε-碳化物的析出以及改变奥氏体晶界析出物的分布。由此可以得出结论,高温形变淬火所得的组织对提高强韧性是十分有利的。对回火组织的观察表明,形变使回火析出的碳化物分布均匀、颗粒变细。形变温度愈低,回火时析出的碳化物愈细、分布愈均匀。测定了常规力学性能及断裂韧性。结果表明,高温形变淬火可使强韧性较高温淬火又有进一步提高,在淬火及淬火並低温回火状态下,奥氏体化温度愈高,强韧化效果愈好。这是因为,高温奥氏体化有利于获得能提高强韧性的组织,即获得由薄壳状残余奥氏体包围的板条马氏体组织。对于高温回火状态而言,得出奥氏体化温度愈低,形变温度愈低,强韧化效果愈好。这是因为形变温度愈低,碳化物颗粒愈细,分布愈均匀,故强韧性愈好。
With 40, 40CrNiMo, 40CrNiMoNb toughening hardening mechanism of high temperature deformation quenching. The effect of austenitizing temperature, deformation temperature and deformation on the recrystallization occurred after deformation was observed by optical microscope. It is concluded that the recrystallization occurred after deformation at high temperature will significantly refine the austenite grains. For the lath martensite beam, it can be remarkably refined regardless of whether recrystallization has taken place after deformation at a high temperature. The morphology of 40CrNiMo was observed by transmission electron microscopy. The results show that the deformation can retain the advantages of high temperature quenched microstructure, that is, all obtained by the thin shell retained austenite martensite lath, does not appear twins lamellar martensite. While at the same time deformation can also overcome the shortcomings of high temperature quenching, including the austenite grain coarsening and slab martensitic beam refinish to promote the precipitation of ε-carbides and change the austenite grain boundaries The distribution of precipitates. It can be concluded that the structure obtained by high temperature deformation quenching is very beneficial to improve the toughness. Tempering of the organization showed that the deformation of the carbide precipitation tempering uniform, thinner particles. The lower the deformation temperature, the more carbide precipitated during tempering, the more uniform the distribution. The conventional mechanical properties and fracture toughness were measured. The results show that high temperature deformation quenching can further improve the strength and toughness of high temperature quenching. In the condition of quenching and quenching and low temperature tempering, the higher the austenitizing temperature, the better the toughening effect. This is because high-temperature austenitization favors obtaining a structure that enhances toughness, ie, obtaining lath martensite surrounded by shell-like retained austenite. For the high temperature tempering state, the lower the austenitizing temperature, the lower the deformation temperature, the better the toughening effect. This is because the lower the deformation temperature, the finer the carbide particles, the more uniform the distribution, so the better the toughness.