含工艺缺陷PE管道热熔焊接接头失效机理分析

发布时间：2018-05-19 02:13

  本文选题：PE管道 + 热熔焊接接头　； 参考：《哈尔滨理工大学》2015年硕士论文

【摘要】：随着社会和科技的进步，聚乙烯（PE）管道由于其优越的性能，逐步取代了传统金属管道，，在给水和燃气输送等领域的应用越来越广，已成为维持城镇居民正常生活必不可少的管道系统。聚乙烯管道的连接方式主要有热熔焊接和电熔焊接，其中热熔焊接的应用最为广泛。在聚乙烯管道热熔焊接过程中，由焊接参数选择不当引起的工艺缺陷极容易被忽视，给聚乙烯管道系统留下了重大隐患。因此，对含工艺缺陷的热熔焊接接头的力学性能进行研究，分析焊接接头的失效机理，可有效的避免聚乙烯管道热熔焊接过程中工艺缺陷的产生，保证管道系统的安全稳定。 本文通过对聚乙烯管材力学性能试验方法的总结与对比，并结合本试验目标与条件，决定采用拉伸试验来判定聚乙烯管道热熔焊接接头的性能优劣。在拉伸试验之前，根据标准GB/T8804和GB/T19810，对拉伸试样形式进行改进，获得了制备简便，能直接获得热熔焊焊缝拉伸性能的试样形式，并重新确定了拉伸速率。对热熔焊接接头的拉伸屈服强度进行方差分析，分析得出加热温度和焊接压力两个焊接参数对热熔焊接接头拉伸性能的影响十分显著，而其他三个焊接参数（加热时间、切换时间和压焊冷却时间）相比于加热温度和焊接压力来说，其影响可以说是微乎其微，在加热温度为210℃和焊接压力为0.2MPa时热熔焊接接头的拉伸性能最佳。 本文从PE管道热熔焊接接头的焊缝失效断口入手，采用扫描电镜对含工艺缺陷热熔焊接接头的焊缝失效断口进行显微观察，并利用X射线衍射法测量了焊缝的结晶度。对大量的断口形貌进行对比，总结得出失效断口的微观形貌组成，分为银纹区域和黑色片层区域，两区域之间有明显分界，并分析得出了断口形貌的成因。最后结合热熔焊接接头的拉伸屈服强度，分析焊缝失效断口的显微形貌和焊缝的结晶度与拉伸性能的关系，获得了由加热温度和焊接压力引起的工艺缺陷的失效机理，其最主要影响因素就是，受到应力作用时热熔焊接接头处聚乙烯无定形区内系带分子链的数量与取向。
[Abstract]:With the development of society and science and technology, the PE pipe has gradually replaced the traditional metal pipeline because of its superior performance, and has been used more and more widely in the fields of water supply and gas transportation. It has become an indispensable pipeline system to maintain the normal life of urban residents. The connection modes of PE pipeline are mainly hot-melt welding and electric fusion welding, among which the hot-melt welding is the most widely used. In the process of hot-melt welding of polyethylene pipeline, the technological defects caused by improper selection of welding parameters are easily ignored, leaving a great hidden danger to the polyethylene pipeline system. Therefore, the mechanical properties of hot-melt welded joints with process defects are studied, and the failure mechanism of welded joints is analyzed, which can effectively avoid the production of technological defects in the process of hot-melt welding of polyethylene pipelines and ensure the safety and stability of pipeline systems. Based on the summary and comparison of the test methods of mechanical properties of polyethylene pipes and combined with the objectives and conditions of this test, this paper decides to use tensile test to judge the properties of hot-melt welded joints of polyethylene pipes. Before the tensile test, according to the standard GB/T8804 and GBR / T19810, the form of the tensile specimen was improved, and the form of the sample which was easy to be prepared and the tensile properties of the weld could be obtained directly was obtained, and the tensile rate was redetermined. The variance analysis of tensile yield strength of hot-melt welded joint shows that the two welding parameters, heating temperature and welding pressure, have a significant effect on the tensile properties of hot-melt welded joint, while the other three welding parameters (heating time, etc.) Compared with heating temperature and welding pressure, the effect of switching time and welding cooling time is minimal, and the tensile properties of hot-melt welded joints are the best when heating temperature is 210 鈩

本文编号：1908250