安全阀关闭件研磨修复技术研究

发布时间：2018-04-01 07:03

本文选题：安全阀　切入点：研磨机构　出处：《江南大学》2017年硕士论文

【摘要】：安全阀是安装在承压类设备上的一种超压自动泄放装置,其阀座和阀瓣是确保安全阀良好密封性能的关键零部件,通常采用金属对金属平面密封的结构形式。在长期工作运行中,安全阀关闭件由于受到腐蚀、裂纹、磨损等影响造成密封失效,从而严重导致安全阀泄漏量超标。因此,安全阀的校验和维修工作就显得尤为重要。针对安全阀关闭件的研磨修复问题,本文设计开发了新型的安全阀研磨设备,应用Matlab仿真模拟阀瓣运动轨迹来合理选定研磨机构加工参数;着重研究了表面粗糙度与密封性能的影响关系,为实验选用粗糙度评定表面质量提供理论基础;以开发的新型研磨机构为设备基础进行研磨实验,制定了阀瓣研磨加工标准工艺路线,有效提高研磨效率和表面质量。本文的主要研究内容及成果如下:首先,采用Solidworks三维软件,建立安全阀阀座研磨机构和阀瓣研磨机构的三维模型,对机构的各关键部件包括支架、研磨头、机械臂等进行了结构优化,并对关键部件的运动特征进行了描述。其次,假设阀瓣全部分布在磨具的前提下,应用力学与运动学基本理论,对研磨过程阀瓣与磨具接触区域的压强分布及磨具受到的摩擦力矩进行了研究,得出偏心距、磨具转速是影响阀瓣转速的主要工艺参数。通过推导的单颗磨粒研磨方程,应用Matlab对阀瓣运动轨迹进行了仿真,发现转速比、偏心距、磨具转速、工件的初始位置是影响磨粒轨迹形态的主要因素。然后,对安全阀关闭件的磨削过程进行了理论研究,应用高斯分布函数建立了微观表面粗糙度的数学模型,得出随着表面粗糙度的增大,金属表面起伏程度越来越显著。研究了研磨介质与关闭件之间的相对运动特征对粗糙度的形成关系,并通过密封试验研究表面粗糙度、工作压力对安全阀关闭件泄漏量的影响,这为后续实验对研磨介质、研磨压力的选择以及用粗糙度评定表面质量提供一定的理论基础。最后,优化阀瓣粗磨和精磨工艺参数,制定研磨维修新工艺路线。以不同细度的砂纸作为研磨介质,采用SAS正交实验研究研磨压力、研磨时间、研磨转速在阀瓣粗磨和精磨工艺阶段对材料去除率、表面粗糙度及表面微观形貌的影响,并综合优化获得高效率和优质量的工艺参数。结果表明:在粗磨过程中,研磨压力为15 N,研磨转速为30 rpm,研磨时间为10 min是最佳工艺参数组合,材料去除率MRR为27.5μm/min,表面粗糙度Ra为0.213μm。在精磨过程中,研磨压力为15 N,研磨转速为20 rpm,研磨时间为4 min是最佳工艺参数组合,可获得材料去除率MRR为2.15μm/min,表面粗糙度Ra为0.102μm。本文关于安全阀阀座与阀瓣密封面维修设备的开发对实现连续自动化具有重要的工程应用价值,研磨工艺的研究为提高工件表面质量提供了坚实的理论基础。
[Abstract]:The safety valve is a kind of overpressure automatic relief device installed on the pressure equipment. Its seat and disc are the key parts to ensure the good sealing performance of the safety valve. The structure of metal to metal plane seal is usually adopted. In the long-term operation, the sealing failure of the safety valve closure is caused by corrosion, cracks, wear and so on, which seriously causes the leakage of the safety valve to exceed the standard. It is very important to check and maintain the safety valve. Aiming at the problem of grinding and repairing the safety valve closure, a new type of safety valve grinding equipment is designed and developed in this paper. The machining parameters of grinding mechanism are reasonably selected by using Matlab simulation to simulate disc motion trajectory, and the relationship between surface roughness and sealing performance is studied, which provides a theoretical basis for the experiment to select roughness to evaluate the surface quality. Based on the new lapping mechanism developed, the grinding experiment was carried out, and the standard technological route of disc grinding was worked out, which effectively improved the grinding efficiency and surface quality. The main contents and achievements of this paper are as follows: first of all, The 3D model of safety valve seat grinding mechanism and disc grinding mechanism is established by using Solidworks software. The key components of the mechanism, including the support, the grinding head, the mechanical arm and so on, are optimized. The motion characteristics of the key components are described. Secondly, assuming that the disc is all distributed in the grinding tool, the basic theory of mechanics and kinematics is applied. The pressure distribution in the contact area between disc and abrasive tool and the friction moment of grinding tool are studied. It is concluded that eccentricity and grinding tool speed are the main technological parameters affecting disc speed. The grinding equation of single abrasive particle is derived. The movement trajectory of disc is simulated by Matlab. It is found that rotational speed ratio, eccentricity, grinding tool speed and the initial position of workpiece are the main factors that affect the shape of abrasive particle trajectory. Then, the grinding process of safety valve closure is studied theoretically. The mathematical model of micro surface roughness is established by using Gao Si distribution function, and it is concluded that with the increase of surface roughness, The effect of surface roughness and working pressure on the leakage of safety valve closure is studied by sealing test. This provides a theoretical basis for further experiments on the selection of grinding medium, grinding pressure and surface quality evaluation with roughness. Finally, the process parameters of disc roughing and finishing grinding are optimized. The new grinding maintenance technology route was established. The grinding pressure, grinding time and grinding speed were studied by SAS orthogonal experiment with different fineness sandpaper as grinding medium. The material removal rate was studied in the stage of disc roughing and finishing grinding. The effects of surface roughness and surface micromorphology on the process parameters of high efficiency and high quality were comprehensively optimized. The results showed that: in the process of rough grinding, The optimum process parameters are lapping pressure of 15 N, grinding speed of 30 rpm and grinding time of 10 min. The material removal rate (MRR) is 27.5 渭 m / min, and the surface roughness Ra is 0.213 渭 m. The optimum process parameters are 15 N grinding pressure, 20 rpm grinding speed and 4 min grinding time. The available material removal rate (MRR) is 2.15 渭 m / min and the surface roughness (Ra) is 0.102 渭 m. In this paper, the development of maintenance equipment for relief valve seat and disc sealing surface has important engineering application value for realizing continuous automation. The study of grinding technology provides a solid theoretical basis for improving the surface quality of workpiece.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH134

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