【作者】 赵艳辉；

【导师】 王来； 马海涛；

【作者基本信息】 大连理工大学 ， 材料学， 2011， 硕士

【摘要】 为了缓解资源浪费和短缺的矛盾,减小失效、报废产品对环境的危害,最大限度地利用废旧产品,再制造工程作为一种新的发展模式应运而生。在高温服役过程中,奥氏体不锈钢因其化学成分的特点,σ相析出是必然的,大多数针对σ相析出的热处理工艺和合金元素的添加仅仅延缓了其析出的时间,而。相的存在严重地影响不锈钢的高温力学性能和耐腐蚀性能,进而影响其服役寿命。为了提高奥氏体不锈钢高温服役寿命和使用效率,需要尽快发展相应的再制造工程。本文主要针对在高温下长时间服役导致组织劣化的奥氏体不锈钢,探索研究其再制造的可能性,以在700℃下服役8万小时的AISI 321不锈钢为研究对象,将固溶处理技术作为其再制造工艺方法。本文首先对服役后AISI 321不锈钢的组织、性能进行了研究,对比研究了固溶处理对服役后的AISI 321不锈钢的微观组织、室温和高温力学性能的影响。通过研究,得到以下主要结论：1.在700℃服役8万小时后, AISI 321不锈钢的母材、热影响区和熔合区已经析出了大量的σ相,组织劣化严重。6相的析出使烟机管线材料严重脆化,承受应力能力大大降低。2.服役后的AISI 321不锈钢固溶处理后,由于超过了σ相存在的温度区间,熔合区、热影响区和母材中的σ相逐渐溶解；在σ相溶解的同时,奥氏体晶粒不断长大；部分奥氏体晶界在扩展的时候绕过σ相,使部分。相的位置从晶界处移到了晶内。3.在1050℃下进行固溶处理后,显微硬度明显降低；室温冲击韧性明显增大,大约为服役后不锈钢的10倍,固溶处理时间为2h至10h间的室温冲击韧性变化不明显；室温抗拉强度明显下降,断后伸长率有明显的升高,固溶后断口组织从固溶前的脆性断裂到固溶后的韧性断裂。4.在1050℃下固溶处理后,AISI 321不锈钢母材的高温抗拉强度有着明显升高的趋势,在固溶处理初期,断后伸长率明显的升高,当固溶处理达到2h后,断后伸长率显著降低。综上所述,固溶处理工艺可以使高温服役的奥氏体不锈钢中有害的σ相消除,恢复组织和力学性能,由此证明在高温下服役后组织劣化的奥氏体不锈钢有再制造的可能,固溶处理可作为经济、实用的一种工艺手段。更多还原

【Abstract】 In order to alleviate the contradiction of wastes and shortages of resources, reduce the harm of failure products to environment and make use of failure products at the maximum limit, remanufacturing engineering as a new kind of development mode arises at the historic moment. As aging at high temperature the precipitation of a phase from austenitic stainless steel due to its chemical composition is inevitable, while different processing technology and adding the elements only delay the precipitation time of a phase. The precipitation of a phase reduces seriously the properties and corrosion resistance of stainless steel, and then influences its service life. In order to improve its service life and its efficiency at high temperature, re-manufacturing engineering of austenitic stainless steel with the micro structure degradation needs to be developed as soon as possible.In this paper the possibility of the remanufacturing mainly for austenitic stainless steel service at high temperature for a long time with the degradation of the micro-structures was researched, AISI 321 stainless steel service for 80000 hours at 700℃as the research object, and solution treatment as the method of remanufacturing technol-ogy. In this paper, the tests of microstructure and properties of AISI 321 stainless steel service for 80000 hours at 700℃was carried out, and the influence of solution treat-ment with AISI 321 stainless steel service for 80000 hours at 700℃on the microstruc-ture, properties at room temperature and high temperature was discussed.The main conclusions are summarized as follows:1. After service for 80000 hours at 700℃, the parent, HAZ and weld precipitated a large number of a phase, and the degradation of micro structures was seriously. The precipita-tion of a phase made austenite stainless steel brittle, and the capacity to stand strain was reduced to a great extent.2. After solution treatment, a phase in all areas gradually dissolved. The higher temperature of solution treatment is, the fasterσphase dissolved. Austenitic grains obviously grew up and the growth of grains was the reason for the relative size ofσphase from intergranular to intragranular.3. After solution treatment, the micro hardness was obviously reduced; the impact tough-ness was drastically increased compared to AISI 321 service for 80000 hours at 700℃, about 10 times. The difference in impact toughness between 2-10 hours was small; the tensile strength at room temperature was obviously reduced after solution treatment, the fracture was changed from the obvious brittle after service to ductile after solution treat-ment and percentage elongation was raised after solution treatment.4. The tensile strength at the temperature of 700℃was increased with solution treatment time. Percentage elongation was raised with of solution time before two hours, after that it was reduced with the solution time.In all, solution treatment was capable to mend the microstructure and improve the me-chanical properties of AISI 321 service for 80000 hours at 700℃.So austenitic stainless steel with the microstructure degradation due to serve at high temperature for a long time is able to be reproduced, and solution treatment is able to be as the process of remanufacturing tech-nology of AISI 321 stainless steel service.更多还原