高铬铸铁复合轧辊辊套界面结构及耐磨性研究

发布时间：2018-06-22 12:58

本文选题：复合轧辊 + 结合质量　；参考：《燕山大学》2016年博士论文

【摘要】：复合轧辊辊套的结合质量和耐磨性是人们关注的焦点,使用中不仅复合界面能够满足工作条件的要求而且轧辊工作层的组织结构要适宜,耐磨性能高。本文在分析镶铸法生产轧辊辊套浇铸工艺的基础上,利用通用有限元商用软件ProCAST模拟了实际生产工艺条件下充型和凝固过程的流场和温度场;研究了各因素影响金属固-液结合的规律;分析了在热处理过程中辊套工作层组织性能变化,探讨了不同硬度对磨样和不同碳化物自由程对高铬铸铁耐磨性的影响,优化了高铬铸铁热处理工艺。利用ProCAST软件对重力底铸轧辊辊套过程的流场和温度场进行了模拟,得出与实际工艺吻合的温度场,验证了模型和参数设定的正确性。在此基础上,探索了单一因素变化时结合层处温度变化,采用正交方法研究了各参数对结合界面最高温度的影响,各因素影响的主次顺序为:套筒预热温度浇铸温度浇铸时间型砂温度。同时研究了各参数对高温停留时间的影响,影响的主次顺序与最高温度的相同,但最优参数组合不同。对比分析了原工艺条件下和改进工艺条件下生产的辊套结合层形貌和元素分布。原工艺条件下,高铬铸铁熔体和45号钢套筒的结合方式为机械附着,改进工艺后为熔融结合。界面处有熔融层和扩散层,在靠近高铬铸铁一侧有颗粒碳化物出现,结合强度明显提高。结合理论计算和样品金相及扫描电镜分析确定了高铬铸铁的组织结构,铸态组织以残余奥氏体和马氏体为基体,其上分布有杆状或者菊花状的共晶碳化物M_7C_3和少量的M_(23)C_6碳化物。经热处理后,淬火态和铸态比较提高了硬度,弱化了冲击韧性,回火态和淬火态比较,硬度降低,冲击韧性提高。磨粒磨损的失重量由淬火试样到一次回火试样和二次回火试样依次降低。磨损机理是由脆性断裂控制的疲劳磨损机制。在干滑动磨损中,随着对磨样硬度逐渐升高,由20HRC变化到47HRC及54HRC,样品的磨损量先增大后减小。和相同硬度的对磨样进行磨损实验,淬火试样,一次回火试样和二次回火试样的磨损失重量逐渐减小。淬火试样的磨损主要表现为碳化物的破碎和剥落,而回火试样主要是粘着磨损和轻微的层状撕裂。自轧辊辊套的外表面向内,共晶碳化物的体积分数逐渐变小,碳化物的平均自由程逐渐增大。随着碳化物平均自由程增大,二次回火态高铬铸铁试样的耐磨性提高。摩擦系数在0.35附近波动,摩擦磨损机理主要是疲劳磨损和氧化磨损。二次回火试样在磨粒磨损中失重量明显大于摩擦磨损。磨粒磨损表面主要表现为碳化物的碎裂和磨粒的切削犁沟,磨损机制为切削磨损和磨粒磨损。分析了高铬铸铁在不同温度和介质下淬火和回火的组织、硬度、冲击韧性和耐磨性,试样的力学性能并非随着淬火或回火温度的变化而单调的增大或减小。空冷和水淬均可满足马氏体转变的冷却速度。试样在1050℃淬火硬度高和耐磨性能好,但是冲击韧性低。和一次回火试样相比,试样经二次回火后其硬度降低。随着回火温度由低到高,一次回火试样和二次回火试样的冲击韧性和耐磨性的变化规律不同。
[Abstract]:The combination quality and wear resistance of the roll sleeve of the compound roll are the focus of attention. In use, not only the composite interface can meet the requirements of working conditions, but also the organization structure of the roll working layer is suitable and the wear resistance is high. On the basis of the analysis of the casting process of the roll sleeve of the roll casting process, the general finite element commercial software ProCAST is used in this paper. The flow field and temperature field in the process of filling and solidification under actual production conditions are simulated, and the laws of the influence of various factors on the bonding of solid to liquid are studied. The changes in the microstructure and properties of the roll sleeve in the process of heat treatment are analyzed, and the effect of different hardness on the wear resistance of high chromium cast iron with different grinding samples and different carbides is discussed, and the optimization is made. The heat treatment process of chromium cast iron is made by using ProCAST software to simulate the flow field and temperature field of the roll sleeve of the gravity bottom casting roll. The temperature field which is consistent with the actual process is obtained, and the correctness of the model and parameter setting is verified. On this basis, the temperature changes at the binding layer at the single factor change are explored and the orthogonal method is used to study each other. The influence of the parameters on the maximum temperature of the interface is that the main and secondary order of the factors influencing the temperature of the casting time molding sand temperature is cast in the preheating temperature of the sleeve. At the same time, the influence of the parameters on the high temperature residence time is studied. The order of the influence is the same as the highest temperature, but the optimum combination is different. Under the original conditions, the combination mode of high chromium cast iron melt and No. 45 steel sleeve is mechanically attached, and the process is fused after the improvement. There are melting and diffusion layers at the interface, and there are granular carbides on the side of high chromium cast iron, and the bonding strength is obviously improved. The microstructure of high chromium cast iron was determined by rational calculation and sample metallography and scanning electron microscopy. The cast microstructure was based on the retained austenite and martensite. The eutectic carbides M_7C_3 and a small amount of M_ (23) C_6 carbides were distributed in the form of the retained austenite and martensite. After heat treatment, the hardness was improved by the quenching state and the casting state, and the impact was weakened. The toughness, the tempering state and the quenching state are compared, the hardness is reduced, the impact toughness is increased. The loss weight of the abrasive wear is reduced from the quenched sample to the first tempered sample and the two tempered sample. The wear mechanism is the fatigue wear mechanism controlled by brittle fracture. In dry sliding wear, the hardness of the grinding sample is gradually increased from 20HRC to 47HR C and 54HRC, the wear amount of the sample increases first and then decreases. The wear test of the grinding sample with the same hardness is carried out, and the wear loss of the quenched sample, the first tempering sample and the two tempering sample decreases gradually. The wear of the quenched specimen is mainly characterized by the fragmentation and exfoliation of the carbides, while the specimens of the back fire are mainly adhesive wear and slight laminar tear. The volume fraction of eutectic carbide gradually becomes smaller and the average free path of carbides gradually increases. With the increase of the average free course of carbides, the wear resistance of high chromium cast iron specimens of two tempered tempered States is improved. The friction coefficient fluctuates near 0.35, and the mechanism of friction and wear is mainly fatigue wear and oxidation wear. The weight loss of the two tempering specimens is obviously greater than that of the friction and wear. The surface of the abrasive wear is mainly characterized by the fragmentation of carbides and the cutting furrows of the abrasive particles. The wear mechanism is the cutting wear and abrasive wear. The microstructure, hardness, impact toughness and wear resistance of high chromium cast iron at different temperatures and medium, hardness, impact toughness and wear resistance are analyzed. The mechanical properties of the sample are not monotonically increasing or decreasing with the change of quenching or tempering temperature. Both air cooling and water quenching can meet the cooling rate of martensitic transformation. The hardness and wear resistance of the sample are high at 1050 C, but the impact toughness is low. Compared with the one tempered sample, the hardness of the sample is reduced after two tempering. With the tempering, the sample is tempered with tempering. The impact toughness and wear resistance of the tempering sample and the two tempering sample are different from low to high.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG333.17;TG250;TG164

【相似文献】