【作者】 武彬；

【导师】 孙宏飞；

【作者基本信息】 山东科技大学 ， 材料学， 2007， 硕士

【摘要】 随着循环流化床锅炉在我国的广泛应用，其高温工况条件下工件的腐蚀磨损问题表现越来越突出，成为亟待解决的问题。本文通过调研循环流化床锅炉的特点和工况条件；以热电偶保护套管为主要研究对象，分析循环流化床热电偶保护套管的失效机理；调研国内外耐热钢和循环流化床用热电偶保护套管材料的发展和研究现状；分析合金元素在高温耐磨钢中的作用及其对钢组织和性能的影响；在此基础上，自行设计出几组抗高温冲蚀合金材料。采用中频感应熔炼技术制得了均匀、致密的耐高温冲蚀合金材料，并对其进行相应的热处理。运用扫描电子显微镜、X射线衍射仪、透射电子显微镜等现代分析手段研究材料的微观结构，并进行抗高温氧化性、硬度、高温磨损等性能测试。试验结果表明，所设计的抗高温冲蚀材料的的铸态组织为奥氏体+少量铁素体+一次碳化物，一次碳化物相对非常粗大，呈网状分布在奥氏体晶界上；固溶态组织中，枝晶组织明显减轻，晶界原析出相呈断续链状，一次碳化物发生部分溶解；固溶+时效后的组织为奥氏体+少量铁素体+一次碳化物+二次碳化物。二次碳化物均匀弥散分布在奥氏体中，它是在固溶和高温时效处理过程中，从奥氏体中析出的细小碳化物。材料850℃和950℃下完全抗氧化。材料中添加适量的稀土元素可提高其抗氧化性能、硬度、改善其抗磨性能、细化晶粒、提高材料力学性能。高温冲蚀磨损试验表明，材料的冲蚀磨损行为表现为塑性冲蚀磨损。几种材料均具有比较高的抗高温冲蚀性能，其中9号材料抗高温冲蚀性能最理想。6号材料的时效态和9号材料铸态具有优异的综合力学性能和抗高温热冲蚀性能，能够长期使用在的环境下，可解决循环流化床热电偶保护套管因高温冲蚀磨损而过早失效问题。采用该合金材料试生产的循环流化床热电偶保护套管在山东华聚能源公司南屯电厂获得良好的应用效果。更多还原

【Abstract】 With the extensive use of Circulating Fluidized Bed Boiler(CFB) in our country, the phenomenon of heavy corrosion and wear of thermocouple-protection tube is more and more obvious and become a urgent problem that need to be solved. In this paper, the characteristic and working condition of CFB were studied, failure mechanism of thermocouple-protection tube used for CFB were analyzed, development and research present state of heat-resistant steel and CFB thermocouple-protection tube material were investigated. The effectiveness of alloying agents in high-temperature abrasion-resistant steel and impact of alloying agents to texture and performance were studied. On the base of these researches, several kinds of high-temperature abrasion-resistant alloy were designed. By medium-frequency induction smelting methods, uniform and compact high temperature abrasion-resistant steels were acquired. In addition, proper heat-treatments were proceeded. Alloy microstructures were assessed using modern analysis and testing technologies, such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). At last, High temperature resistance, hardness and high temperature erosion resistance were tested.The experimental results are below. The microstructure of designed materials at as-cast is austenite + a small amount of ferrite + primary carbide. The primary carbide is very coarse. It exists along grain boundary appearing reticular distribution. The microstructure at as-solution is similar to at as-cast, but tree-like texture become obscure. Precipitated phase along grain boundary is break chain. Partial primary carbide dissolve. The microstructure at as-aging is austenite + a small amount of ferrite + primary carbide + secondary carbide. Secondary carbide uniformly distributes and disperses in the grain. Close secondary carbide precipitates from austenite during aging process. The materials are totally oxidation resistant at 850℃and 950℃. By adding rear-earth elements in high temperature erosion resistant alloy, the performances of high temperature resistance, hardness and high temperature abrasion can be improved. At the same time, it can refine crystal grain, so to intensify mechanical property of materials. The erosion tests at elevated temperature show that test materials’ erosion behavior is plastic. 9# material has the best erosion resistance in all test materials. 6# aging sample and 9# cast sample have better erosion resistance at high temperature. They can be used at high temperature for long-term. These materials can be used to solve the problem of CFB thermocouple-protection tube premature failure that caused by heavy high temperature erosion. The prototype castings of CFB thermocouple-protection tube with the high temperature erosion resistant alloy acquire good application in NanTun electric power plant Shandong HuaJu energy limited company.更多还原