稀磁铜铁低温热电偶丝材不均匀性研究

发布时间：2018-09-19 16:54

【摘要】：热电偶丝材的不均匀性,可能会导致严重的测量误差,是反映热电偶复现性、稳定性质量的最主要的参数,也是评价热电偶性能的最主要指标。而稀磁铜铁低温热电偶作为低温温区(4K~273K)内,唯一可替代贵金属稀磁金铁材料的热电偶,提高其性能和质量,推广其应用具有重要的实际应用价值和经济效益。课题来源于“国家自然科学基金”(No:51276070),稀磁铜铁合金低温热电动势应用基础研究。本文针对稀磁铜铁低温热电偶丝材,采用双介质法设计了一套实验台架,并测量了漆包铜铁合金丝(Cu+0.13%at Fe)、铜铁合金裸丝(Cu+0.13%at Fe)和对比用的镍铬丝材的不均匀性。实验时首先评估了实验台架本身对实验结果的影响,随后对测量得到的热电势序列进行了统计分析,并对不同状态的铜铁合金铸锭进行了微观结构分析。分析发现,各种丝材的不均匀性都可分为平缓变化的微弱不均匀性和突变的较强不均匀性。对于不同的丝材,镍铬丝材的均匀性最好,这与其工艺成熟有关。铜铁合金裸丝具有微弱的周期性,这与其拉拔成丝缠绕成卷后的退火不均匀有关。铜铁漆包线均匀性好于铜铁裸线,漆包工艺及之后的低温退火工艺削弱了周期性而提高了材料的均匀性。而突起的较强不均匀性可以看作是晶粒中的点缺陷导致的,而缓慢变化的不均匀性则是晶粒之间形态差别导致,同时晶粒差别可能导致合金成丝后应力分布不均,进一步影响热电势不均匀性。通过低温退火可以降低这些不均匀性,但无法消除点缺陷的影响。本研究和分析方法揭示了稀磁铜铁热电极不均匀性的特征与影响因素,可以为热电极制造工艺的提升提供参考,有利于稀磁铜铁低温热电偶的推广使用,并可用来建立热电偶的质量控制系统,且能推广应用于其他类型热电偶,改善和提高热电偶的性能。
[Abstract]:The nonuniformity of thermocouple wire may lead to serious measurement error, which is the most important parameter to reflect the reproducibility and stability of thermocouple, and also the main index to evaluate the performance of thermocouple. As a low-temperature thermocouple (4K~273K), dilute magnetic copper-iron low temperature thermocouple can only replace the precious metal dilute magnetic gold and iron material, improve its performance and quality, and promote its application has important practical application value and economic benefit. The subject comes from National Natural Science Foundation (No:51276070), basic research on low temperature thermoelectromotive force of dilute magnetic copper ferroalloy. In this paper, a set of experimental bench is designed for thin magnetic copper iron low temperature thermocouple material by double medium method. The inhomogeneity of enamelled copper iron alloy wire (Cu 0.13%at Fe) and contrast nickel chrome wire is measured. In the experiment, the influence of the test bench itself on the experimental results was first evaluated, then the thermoelectric potential series was statistically analyzed, and the microstructure of copper ferroalloy ingot in different states was analyzed. It is found that the inhomogeneity of all kinds of wires can be divided into weak inhomogeneity of gentle variation and strong heterogeneity of abrupt change. The uniformity of nickel-chromium wire is the best for different wire materials, which is related to the maturity of the process. Copper ferroalloy bare wire has weak periodicity, which is related to the annealing inhomogeneity after winding. The uniformity of copper and iron enamelled wire is better than that of copper iron bare wire. The coating process and the subsequent low temperature annealing process weaken the periodicity and improve the homogeneity of the material. The strong inhomogeneity of the protuberance can be regarded as the result of the point defect in the grain, while the inhomogeneity of the slow change is caused by the difference of the morphology among the grains, and the difference of the grain size may lead to the uneven distribution of the stress after the formation of the wire. It further affects the unevenness of thermoelectric potential. These inhomogeneity can be reduced by low temperature annealing, but the effect of point defects can not be eliminated. This research and analysis method reveals the characteristics and influencing factors of the inhomogeneity of dilute magnetic copper-iron thermoelectric poles, which can provide a reference for the promotion of the manufacturing process of the hot electrodes, and is conducive to the popularization and use of low-temperature thermocouples of dilute magnetic copper-iron thermocouples. It can be used to establish the quality control system of thermocouple and can be applied to other types of thermocouple to improve and improve the performance of thermocouple.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH811

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