加压内冷却砂轮磨削镍基高温合金时的温度场研究
发布时间：2018-11-12 13:54
【摘要】：在难加工材料(如高温合金)的磨削加工中,由于被加工材料的磨削比能高,且导热性能差,使其在磨削加工中更容易出现弧区的热量聚集,以致引起磨削烧伤、砂轮磨损等问题。传统的解决方案一般是:在加工过程中浇注大量的磨削液来实现磨削弧区的润滑和冷却,然而,在磨削液的浇注过程中,能够进入到磨削弧区并真正起到换热作用的液体量相对较少,并且,加工表面高温导致磨削液会瞬间发生沸腾、汽化而在磨削表面形成蒸汽膜,不仅会阻碍新的磨削液进入磨削区,也会阻碍磨削弧区的热量向外散发。因此,常规的浇注冷却方式难以满足磨削加工过程中高温表面换热的实际要求,高效的冷却方法对磨削加工就显得尤为重要。本文基于加压内冷却技术与断续磨削技术设计制作出加压内冷却砂轮,以镍基高温合金GH4169作为加工对象,采用理论分析、有限元模拟和实验研究相结合的方法,研究了应用加压内冷却砂轮实现内冷却方式进行磨削镍基高温合金时对磨削弧区温度的控制能力。主要研究内容如下:(1)设计并制备出了用于平面磨削的加压内冷却砂轮,基于移动热源理论建立了加压内冷却砂轮平面磨削高温合金的传热学模型,开展了温度场的理论计算,建立了仿真湍流模型。(2)基于热源法建立了加压内冷却砂轮平面磨削高温合金的温度场仿真模型,分析了热流密度、砂轮转速以及外部压力三个因素分别对磨削弧区温度的影响规律,并在相同热流密度条件下对比了砂轮内通加压冷却液与不加冷却液两种方式时的弧区温度。(3)设计了单因素实验方案,进行了利用加压内冷却砂轮磨削镍基高温合金的实验研究,测量与对比了不同实验方案下使用不同冷却方式时的磨削力和磨削温度,观察了已加工工件表面粗糙度和表面形貌,探讨了利用新设计的加压内冷却砂轮在进行内冷却磨削高温合金时对磨削弧区的冷却效果、对工件已加工表面质量的影响规律以及各参数的变化对磨削性能的影响规律。另外,将实验结果和模拟结果相结合的方式对比分析了不同热流密度下的弧区温度,对应用加压内冷却砂轮实现内冷却方式进行磨削高温合金时可以有效降低磨削弧区温度的构想的可行性进行了分析。
[Abstract]:In the grinding of refractory materials (such as superalloy), because of the high specific grinding energy and poor thermal conductivity of the machined materials, the heat accumulation in the arc zone is more likely to occur in the grinding process, resulting in grinding burns. Grinding wheel wear and other problems. The traditional solution is that a large amount of grinding fluid is poured in the process of machining to realize the lubrication and cooling of the grinding arc area. However, in the process of pouring the grinding fluid, The amount of liquid that can enter the grinding arc area and really heat transfer is relatively small, and the high temperature of the machined surface will cause the grinding fluid to boil, vaporize and form steam film on the grinding surface. It not only prevents the new grinding fluid from entering the grinding area, but also prevents the heat emission from the grinding arc region. Therefore, the conventional casting cooling method is difficult to meet the actual requirements of high temperature surface heat transfer in grinding process, and efficient cooling method is particularly important for grinding process. Based on pressurized internal cooling technology and intermittent grinding technology, a pressurized internal cooling grinding wheel is designed and fabricated in this paper. The method of combining theoretical analysis, finite element simulation and experimental study is used to process nickel-based superalloy GH4169. The control ability of grinding arc temperature in grinding Ni-base superalloy by using pressurized internal cooling grinding wheel is studied in this paper. The main research contents are as follows: (1) A pressurized inner cooling grinding wheel for plane grinding is designed and fabricated. Based on the theory of moving heat source, a heat transfer model for plane grinding of superalloy with pressurized inner cooling grinding wheel is established. The theoretical calculation of temperature field is carried out, and the simulation turbulence model is established. (2) based on the heat source method, the temperature field simulation model of plane grinding superalloy with pressurized inner cooling grinding wheel is established, and the heat flux is analyzed. The three factors of grinding wheel speed and external pressure respectively affect the temperature of grinding arc zone. Under the same heat flux density, the arc zone temperature of the grinding wheel is compared with that of the cooling fluid with or without coolant. (3) A single factor experimental scheme is designed. The grinding force and temperature of Ni-base superalloy with different cooling methods under different experimental schemes were measured and compared, and the surface roughness and surface morphology of the machined workpiece were observed. This paper discusses the cooling effect of the newly designed pressurized internal cooling grinding wheel on the grinding arc zone, the influence of the surface quality of the workpiece and the influence of the parameters on the grinding performance when grinding the superalloy with internal cooling. In addition, the arc-zone temperature at different heat flux density is compared and analyzed by combining the experimental results with the simulated results. The feasibility of using pressurized internal cooling grinding wheel to realize internal cooling grinding of superalloy can effectively reduce the temperature of grinding arc zone is analyzed.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG580.6
，
本文编号：2327304
[Abstract]:In the grinding of refractory materials (such as superalloy), because of the high specific grinding energy and poor thermal conductivity of the machined materials, the heat accumulation in the arc zone is more likely to occur in the grinding process, resulting in grinding burns. Grinding wheel wear and other problems. The traditional solution is that a large amount of grinding fluid is poured in the process of machining to realize the lubrication and cooling of the grinding arc area. However, in the process of pouring the grinding fluid, The amount of liquid that can enter the grinding arc area and really heat transfer is relatively small, and the high temperature of the machined surface will cause the grinding fluid to boil, vaporize and form steam film on the grinding surface. It not only prevents the new grinding fluid from entering the grinding area, but also prevents the heat emission from the grinding arc region. Therefore, the conventional casting cooling method is difficult to meet the actual requirements of high temperature surface heat transfer in grinding process, and efficient cooling method is particularly important for grinding process. Based on pressurized internal cooling technology and intermittent grinding technology, a pressurized internal cooling grinding wheel is designed and fabricated in this paper. The method of combining theoretical analysis, finite element simulation and experimental study is used to process nickel-based superalloy GH4169. The control ability of grinding arc temperature in grinding Ni-base superalloy by using pressurized internal cooling grinding wheel is studied in this paper. The main research contents are as follows: (1) A pressurized inner cooling grinding wheel for plane grinding is designed and fabricated. Based on the theory of moving heat source, a heat transfer model for plane grinding of superalloy with pressurized inner cooling grinding wheel is established. The theoretical calculation of temperature field is carried out, and the simulation turbulence model is established. (2) based on the heat source method, the temperature field simulation model of plane grinding superalloy with pressurized inner cooling grinding wheel is established, and the heat flux is analyzed. The three factors of grinding wheel speed and external pressure respectively affect the temperature of grinding arc zone. Under the same heat flux density, the arc zone temperature of the grinding wheel is compared with that of the cooling fluid with or without coolant. (3) A single factor experimental scheme is designed. The grinding force and temperature of Ni-base superalloy with different cooling methods under different experimental schemes were measured and compared, and the surface roughness and surface morphology of the machined workpiece were observed. This paper discusses the cooling effect of the newly designed pressurized internal cooling grinding wheel on the grinding arc zone, the influence of the surface quality of the workpiece and the influence of the parameters on the grinding performance when grinding the superalloy with internal cooling. In addition, the arc-zone temperature at different heat flux density is compared and analyzed by combining the experimental results with the simulated results. The feasibility of using pressurized internal cooling grinding wheel to realize internal cooling grinding of superalloy can effectively reduce the temperature of grinding arc zone is analyzed.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG580.6
，
本文编号：2327304
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