奥氏体不锈钢包壳管环向拉伸方法与性能研究

发布时间：2018-11-22 11:42

【摘要】：包壳管是反应堆内第一道安全屏障,服役过程中将承受裂变气体内压和芯块与包壳间机械应力的综合作用考验,变形主要发生在包壳管的环向方向,利用管材传统轴向拉伸测试方法难以对包壳管真实受力进行准确评估。鉴于此,本文以铅基反应堆包壳候选材料316Ti奥氏体不锈钢为研究对象,首先采用数值计算与环向拉伸试验相结合的手段,优化了管型件环向拉伸试样尺寸与摩擦系数,然后开展了温度和拉伸速率对316Ti包壳管的环向力学性能影响的试验研究。主要研究内容和结论如下:采用Abaqus有限元软件数值计算手段,开展了试样标距段宽度与夹具间摩擦系数对试样应力应变分布的影响研究。结果表明:试样标距段宽度为2 mm时,应力分布更加均匀,有利于防止应力集中;试样标距段应力随着摩擦系数的增加有增大的趋势。基于数值模拟结果,开展了试样标距段宽度与润滑剂对环向拉伸的影响验证试验。研究表明:虽然标距段宽度对强度影响很小,但标距段宽度2mm的试样表现出更好的塑性;试样强度随摩擦力的增大而增大,因此选用摩擦较小的石墨作为环向拉伸试样与夹具间的润滑剂。根据优化的试样尺寸与润滑剂选择方案,开展了温度及拉伸速率对316Ti包壳管环向拉伸性能影响的试验研究。结果表明:不同拉伸速率下试样抗拉强度与屈服强度随着温度的升高而降低,变形量随着温度的升高呈现先降低后增加的趋势;不同拉伸速率条件下,均发生了动态应变时效(DSA)现象,且不同拉伸速率条件下均存在一个DSA敏感温度区间,随拉伸速率的增加,DSA敏感温度区间具有向高温移动的趋势。通过微观组织分析与溶质原子扩散激活能的计算,认为316Ti中C和N等间隙溶质原子与移动的位错反复发生的钉扎与脱钉扎作用是DSA现象产生的本质。本文研究结果可为铅基反应堆包壳管环向性能的研究提供指导意义,并为铅基反应堆设计及安全分析提供数据支持。
[Abstract]:The cladding tube is the first safety barrier in the reactor. It will withstand the combined action of the fission gas internal pressure and the mechanical stress between the pellet and the cladding during the service, and the deformation mainly occurs in the circumferential direction of the cladding tube. It is difficult to accurately evaluate the true force of cladding tube by using traditional axial tensile test method. In view of this, 316Ti austenitic stainless steel, a candidate material for lead-based reactor cladding, is studied in this paper. Firstly, the dimension and friction coefficient of the tubular annular tensile specimen are optimized by the combination of numerical calculation and toroidal tensile test. Then the effects of temperature and tensile rate on the circumferential mechanical properties of 316Ti cladding tube were investigated. The main research contents and conclusions are as follows: the influence of the width of the specimen distance and the friction coefficient between the clamps on the stress and strain distribution of the specimen is studied by using the Abaqus finite element software. The results show that the stress distribution is more uniform when the width of the specimen is 2 mm, which is helpful to prevent the stress concentration, and the stress of the distance section increases with the increase of friction coefficient. Based on the results of numerical simulation, the effect of the width of the distance section and the lubricant on the circumferential tension was tested. The results show that although the width of the spaced segment has little effect on the strength, the specimen with the width of the spaced segment 2mm exhibits better plasticity. The strength of the specimen increases with the increase of the friction force, so graphite with less friction is chosen as the lubricant between the circumferential tensile specimen and the fixture. Based on the optimized sample size and lubricant selection scheme, the effects of temperature and tensile rate on the circumferential tensile properties of 316Ti cladding tubes were investigated. The results show that the tensile strength and yield strength decrease with the increase of temperature, and the deformation decreases first and then increases with the increase of temperature. Dynamic strain aging (DSA) phenomenon occurred at different tensile rates, and there was a DSA sensitive temperature range at different tensile rates. With the increase of tensile rate, the DSA sensitive temperature range moved to high temperature. Based on the microstructure analysis and the calculation of the activation energy of solute diffusion, it is considered that the repeated pinning and de-pinning between C and N interstitial solute atoms and moving dislocations in 316Ti is the essence of the DSA phenomenon. The results of this paper can provide guidance for the study of the circumferential performance of the cladding tubes of lead-based reactors and provide data support for the design and safety analysis of lead-based reactors.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG356.5

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