机械密封环表面泵送槽的凸模压制成形技术研究

发布时间：2018-03-15 09:21

本文选题：新型零泄漏高性能机械密封环　切入点：保压抽芯法　出处：《江苏大学》2016年硕士论文　论文类型：学位论文

【摘要】：新型零泄漏高性能机械密封在减小端面间的摩擦磨损的同时可以实现密封介质的零(或少)泄露,其产业化可以解决传统机械密封频繁失效造成的泄露和环境污染等问题。但目前仍然没有理想的方法快速高效地加工新型零泄漏密封环表面泵送槽,泵送槽的成型成为制约其产业化应用的最大瓶颈。其中激光加工技术成型泵送槽,存在耗时长、成本高的特点;凸模压制成型端面槽,虽然高效、低成本,但仍存在槽边缘粘膜的缺陷。为此,本文采用保压抽芯凸模压制法实现宏观泵送槽的成型,在此基础上,并对其成型实验及素坯的烧结实验开展研究,主要研究内容及成果如下:首先,对粉末压制成型过程的基本理论及力进行分析和研究,介绍了粉末颗粒压制成型过程中出现的拱桥效应和压坯回弹效应;对素坯在烧结过程中进行分析,并且阐述了表面张力作为烧结驱动力在宏观和微观上的表现形式,为后续粉料成型及烧结实验研究提供理论基础。其次,分析了保压抽芯凸模压制密封环泵送槽的基本原理,并根据其原理及密封环几何形状设计了浮动式粉末压制模具结构,结果发现:该成型模具结构稳定性较好、泵送槽压制成功率高,且泵送槽轮廓清晰、边缘无脱落开裂现象;对比无槽压坯和端面带有泵送槽的压坯发现,端面结构复杂的压坯压制后整体的回弹率较低;同时随着压制力的增大,压坯所受侧压力增大,由于密封环受到外摩擦力的影响,压坯外径回弹率大于内径回弹率,凹槽的回弹率大于密封环本身的回弹率。然后,针对不同结构泵送槽型的素坯进行烧结实验,从表面张力的角度分析了素坯泵送槽型结构对密封环烧结体收缩性能的影响机制,实验结果表明:密封环在烧结过程中的收缩率与凹槽的弯曲弧度有很大关系,随着凹槽弯曲弧度的增大,所受表面张力越大,凹槽向内收缩所受驱动力也越大,所以三种槽型中椭圆型槽在径向和周向上的收缩率最大,圆弧型槽次之,螺旋型槽的收缩率最小;泵送槽的收缩率大于密封环的内外径的收缩率,并且槽型的面积越大,密封环的内外径收缩相对越小;凹槽径向方向的收缩率大于周向方向的收缩率;由于重力作用的影响,密封环在轴向方向的收缩率大于在径向方向的收缩率。最后,将压制后的素坯进行无压固相烧结,研究了烧结工艺中添加剂(石墨、酚醛树脂、碳化硼)对试样致密性、烧结尺寸的影响规律,实验结果表明:添加剂的含量对烧结后密封环的密度、失重率和内外径收缩率都有较大的影响,适量的添加剂能够提高密封环的体积密度、降低密封环烧结收缩变形;利用扫面电子显微镜(SEM)观察了不同颗粒级配比下的密封环断面形貌,研究了及碳化硅颗粒级配比对烧结体致密性的影响,结果发现:纯微米级碳化硅颗粒之间容易形成封闭的孔洞,即使在压力作用下,封闭的孔洞也不易被完全填充;当素坯由多种尺寸的颗粒组成时,颗粒之间容易形成连通的开孔,中、细小颗粒会填充到间隙中,所以形成的试样相对致密。
[Abstract]:A new type of zero leakage and high performance in reducing the mechanical seal between the end faces of the friction and wear of sealing medium and can achieve zero (or less) leakage problem of the industrialization can solve the traditional mechanical seal failure caused by frequent leakage and environmental pollution. But there is still no ideal method for efficiently processing new zero leakage sealing surface of pump send the ring groove, forming pumping grooves become the biggest bottleneck of its industrial application. The laser processing technique forming pumping grooves, are time-consuming, high cost characteristics; punch pressing end groove, while the high efficiency, low cost, but there are still defects in the groove edge mucosa. Therefore, this paper uses Paul compression core pulling punch pressing method to realize the macro pumping grooves, on this basis, and the sintering experiment on the molding experiment and blank research, the main research contents and results are as follows: first, the powder pressing Analysis and Research on the basic theory of the forming process and force, introduces the effect and effect of powder pressing arch compacts rebound in the process of forming; analysis of the blank in the sintering process, and expounds the surface tension as the sintering driving force in macro and micro forms, provides the theoretical basis for the follow-up powder molding and sintering experiments. Secondly, analyzes the basic principle of pressure core pulling punch pressing sealing ring pumping grooves, and according to the principle and design of the floating seal ring geometry powder pressing die structure, the results show: the mold structure has good stability and high success rate of pumping groove pressing, and pumping groove outline clear, non shedding edge cracking phenomenon; comparison of blank blank and groove with end pumping grooves that face complex pressing pressure after the overall rebound rate is low; at the same time as Increase the pressing force, pressed by lateral pressure, because the sealing ring is affected by external friction, pressure rebound rate is greater than the outer diameter inner diameter groove of the rebound rate, rebound rate is greater than that of the sealing ring itself. Then the rebound rate, according to the different structure of pumping groove blank, sintering experiment, the surface tension of the analysis of the blank pumping groove structure on the influence mechanism of shrinkage of the sintered body sealing ring, the experimental results show that: there is a lot of relationship between curvature shrinkage and seal ring groove in the sintering process, with the increase of curvature of the groove, the surface tension of the groove, inward contraction by driving force the greater, so three kinds of grooves in the elliptic groove in radial and circumferential direction of the maximum shrinkage rate, arc groove of the spiral groove of the smallest shrinkage; pumping groove contraction rate is greater than the diameter of the inner and outer sealing ring shrinkage, and groove The area is large, and the sealing ring diameter shrinkage is smaller; the radial direction of the groove contraction rate is greater than the circumferential direction of the shrinkage; due to the effect of gravity, the sealing ring in the axial direction of the contraction rate is greater than in the radial direction of the contraction rate. Finally, after pressing blank without solid pressure the sintering additives on the sintering process (graphite, phenolic resin and boron carbide) of sample density, influence of sintering dimension, the experimental results show that the sintered ring density additive content, weight loss rate and diameter shrinkage has a greater impact, the amount of additive can increase the volume density of the seal ring, seal ring to reduce the sintering shrinkage deformation; by using scanning electron microscopy (SEM) were observed in the section of the seal ring with different particle morphology level ratio, and the research of silicon carbide particle size ratio on the influence of density of sintered body, Results: the closed hole is easily formed between pure micron SiC particles, even under pressure, closed pores are not easy to be completely filled; when the blank by various sizes of particles, particles easy to form holes communicated, fine particles will fill into the gap, so the formation of the sample is relatively dense.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH136;TF125

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