碳素焙烧炉内N型铠装热电偶的失效机理研究  

Study of Failure Mechanism of N-Type Armored Thermocouples in Carbon Roasters

作　　者：周洪琴 王勇[2] 尹怀鑫 ZHOU Hongqin;WANG Yong;YIN Huaixin(Chongqing Duchin Instrument Co.,Ltd.,Chongqing 400700,China;College of Materials Science&Engineering,Chongqing University,Chongqing 400045,China)

机构地区：[1]重庆市大正仪表股份有限公司,重庆400700 [2]重庆大学材料科学与工程学院,重庆400045

出　　处：《自动化仪表》2022年第12期118-122,共5页Process Automation Instrumentation

摘　　要：炉温的准确测量和控制是保证碳素阳极焙烧产品质量的关键。针对碳素焙烧炉使用的N型铠装热电偶的常见失效现象进行了分析,利用扫描电镜和能谱仪等设备观察了失效热电偶丝的形貌特征和成分分布。分析结果表明:热电偶信号消失和时断时续现象都是由负极偶丝断裂造成的,后者是在偶丝断裂后又重新焊接的情况下发生,断裂包括整体熔断和过烧两种机制;严重测温漂移的主要原因是偶丝受到Mn污染、正极偶丝表面氧化及其Cr和Si的选择性氧化。在此基础上,提出了改进套管材料、偶丝预氧化、调整热电偶安装位置等新型改进方案。该研究不仅对改善N型热电偶的可靠性和使用寿命、保证碳素阳极的质量具有重要意义,还为热电偶制造和使用企业提供借鉴。Accurate measurement and control of furnace temperature is the key to ensuring the quality of carbon anode roasting products.The common failure phenomena of N-type armored thermocouples used in carbon roasters are analyzed,and the morphological characteristics and composition distribution of the failed thermocouple wires are observed using equipment such as scanning electron microscopy and energy spectrometry.The results show that the loss of thermocouple signal and the intermittent phenomenon are both caused by the fracture of the negative coupling wire,the latter occurring when the wire is fractured and then re-welded,with the fracture including both integral fusion and overturning mechanisms;the main causes of serious temperature drift are Mn contamination of the coupling wire,oxidation of the positive coupling wire surface and selective oxidation of its Cr and Si.On this basis,new improvement solutions such as improved casing material,pre-oxidation of the coupling wire and adjustment of the thermocouple mounting position are proposed.The study is not only important for improving the reliability and service life of N-type thermocouples and ensuring the quality of carbon anodes,but also provides reference for thermocouple manufacturing and using enterprises.

关 键 词：碳素焙烧 碳素阳极 N型热电偶 失效 熔断 过烧 Mn污染 测温漂移 

分 类 号：TH811[机械工程—仪器科学与技术]