辊压机堆焊层金属的抗疲劳性能研究

发布时间：2018-03-11 17:04

本文选题：辊压机　切入点：堆焊层　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：水泥产业是国民经济的基础，而辊压机是水泥生产矿石破碎系统和粉磨系统的关键设备。在实际工况中，辊压机处在高磨损和高循环压力下，辊面不仅存在磨粒磨损和摩擦磨损，同时伴随有疲劳现象，最终导致辊面疲劳磨损失效甚至出现大块剥落，故研究辊压机辊面耐磨堆焊层的抗疲劳性能具有实际意义。本文使用目前辊压机常用的三种耐磨堆焊层药芯焊丝和一种过渡层药芯焊丝，采用熔化极自保护焊接方法在45钢板上堆焊，分别分析这四种堆焊层的成分和微观组织；用堆焊试板制备六种疲劳试样，分别为三种不带过渡层和三种带有过渡层的疲劳试样，采用自行设计的疲劳试验机进行疲劳试验，对比三种不带过渡层时耐磨堆焊层的抗疲劳性能差异及都带有渡层时的抗疲劳性能差异，分析过渡层对抗疲劳性能的影响及其作用机制，最后分析疲劳试样断口形貌。采用三种不同耐磨堆焊层药芯焊丝获得的堆焊层金属分别为：含铌合金钢，其微观组织以马氏体和残余奥氏体为主，还有大量NbC弥散分布在堆焊层里，其硬度较高，塑韧性相对较好；含铌高铬合金铸铁，其堆焊层下部为亚共晶组织，中部以共晶组织为主，上部为过共晶组织，也有NbC弥散整个堆焊层，硬度高，塑韧性较差；过共晶高铬合金铸铁，，其堆焊层上部和中部为过共晶组织，下部以共晶组织为主，其硬度更高，塑韧性也更差。过渡层药芯焊丝Cr和Mn含量高，堆焊层为奥氏体钢，塑性和韧性较好。试验发现没有过渡层的三种耐磨堆焊层金属疲劳裂纹萌生阶段差别不大，而裂纹扩展阶段差别较大；而带有过渡层的三种耐磨堆焊层疲劳裂纹萌生阶段差别大，而裂纹扩展阶段差别不大。含铌合金钢耐磨堆焊层抗疲劳性能最佳，母材裂纹扩展到过渡层与耐磨层界面时停止扩展，随着循环应力的加载，界面出现新裂纹后快速扩展通过耐磨层；其次是含铌高铬合金铸铁耐磨堆焊层，最差的是过共晶高铬合金铸铁耐磨堆焊层，母材裂纹都直接扩展通过两者的过渡层和耐磨层，并且都在耐磨层产生新裂纹，在过共晶高铬合金铸铁的耐磨层和过渡层熔合区还有剥离裂纹产生。过渡层使母材与耐磨层结合良好，可以有效的延长疲劳裂纹萌生阶段，同时由于其塑性较好，当母材裂纹扩展到母材与过渡层界面时，裂纹扩展路径由纵向转变为横向，从而提高疲劳强度。疲劳试样断口SEM分析可知，在裂纹扩展区内，有河流状的疲劳花纹出现，略带弧形，有较为规则的间距，与疲劳裂纹扩展方向垂直。
[Abstract]:The cement industry is the foundation of the national economy, and the roller press is the key equipment for the crushing system and grinding system of cement production ore. There is not only abrasive wear and friction wear on the roll surface, but also fatigue phenomenon, which leads to the fatigue wear failure of the roll surface and even the appearance of the bulk spalling. Therefore, it is of practical significance to study the fatigue resistance of the wear-resistant surfacing layer on the roll surface of the roller press. In this paper, three kinds of wear-resistant surfacing flux-cored wire and one transition layer flux-cored wire are used to surfacing 45 steel plate. The composition and microstructure of the four surfacing layers are analyzed respectively. Six kinds of fatigue specimens were prepared by surfacing welding test plate. They were three kinds of fatigue samples without transition layer and three kinds with transition layer. Fatigue tests were carried out by self-designed fatigue testing machine. The difference of fatigue resistance of three kinds of wear-resistant surfacing layers without transition layer and the difference of fatigue resistance with crossing layer are compared. The influence of transition layer on fatigue resistance and its mechanism are analyzed. Finally, the fracture morphology of fatigue specimen is analyzed. The surfacing metals obtained by using three kinds of flux-cored wire with different wear-resistant surfacing layer are: niobium alloy steel, its microstructure is mainly martensite and retained austenite, and a large number of NbC dispersed in surfacing layer, its hardness is higher. The high chromium alloy cast iron containing niobium has hypoeutectic structure in the lower part, eutectic structure in the middle, hypereutectic structure in the upper part and NbC dispersion in the whole surfacing layer with high hardness and poor ductility. Hypereutectic high chromium alloy cast iron has hypereutectic structure in the upper and middle part of the surfacing layer and eutectic structure in the lower part of the cast iron. Its hardness is higher and its ductility is worse. The flux-cored wire of transition layer has high Cr and mn contents, and the surfacing layer is austenitic steel. Good ductility and toughness. The results show that the fatigue crack initiation stage of the three wear-resistant surfacing layers without transition layer is not different, but the crack propagation stage is quite different, while the fatigue crack initiation stage of the three wear-resistant surfacing layers with transition layer is different greatly. The fatigue resistance of the wear-resistant surfacing layer of niobium alloy steel is the best. When the base metal crack extends to the interface between the transition layer and the wear-resistant layer, it stops to propagate, and with the loading of cyclic stress, The wear resistant overlay of high chromium alloy cast iron containing niobium is the second, the worst is hypereutectic high chromium cast iron, and the base metal crack extends directly through the transition layer and wear resistant layer of both. New cracks were found in the wear resistant layer and exfoliated cracks in the fusion zone of the hypereutectic high chromium alloy cast iron and in the fusion zone of the transition layer. The transition layer makes the base metal and wear-resistant layer combine well, which can effectively prolong the fatigue crack initiation stage. At the same time, because of its good plasticity, when the base metal crack extends to the interface between the base metal and the transition layer, the crack growth path changes from longitudinal to transverse. In order to improve fatigue strength, SEM analysis of fracture surface of fatigue specimen shows that there are fluvial fatigue patterns, arc shape, regular spacing and perpendicular to the direction of fatigue crack propagation in the crack growth zone.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG455

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