供货态T91钢管内壁渗碳现象浅析  

Analysis of carburizing phenomenon in inner wall of as-supplied T91 steel tube

作　　者：陈莉君 张娟 谢逍原 曾辉 白青花 陶祎 Chen Lijun;Zhang Juan;Xie Xiaoyuan;Zeng Hui;Bai Qinghua;Tao Yi(Material Research Institute,Dongfang Boiler Group Co.,Ltd.,Zigong Sichuan 643001,China;Laboratory for High Temperature-High Pressure Material and Welding Engineering of China Machinery Industry Federation,Zigong Sichuan 643001,China)

机构地区：[1]东方电气集团东方锅炉股份有限公司材料研究所,四川自贡643001 [2]中国机械工业高温高压材料与焊接工程实验室,四川自贡643001

出　　处：《金属热处理》2019年第10期201-205,共5页Heat Treatment of Metals

摘　　要：针对供货态T91小口径钢管内壁存在渗碳现象,采用化学法、金相法和显微硬度法对渗碳层进行了定性和定量分析,利用SEM、EDS和XRD分别对渗碳层组织进行观察,对元素组成及相组成进行分析,并提出相应预防措施。结果表明:采用金相法、化学法及显微硬度法可定性定量分析渗碳层碳含量及渗碳层深度。内壁渗碳层的主要组成为Fe2.5C、Cr7C3及Cr2C,这是由于T91钢冷成形制管过程内壁所用的润滑剂未去除干净,继而在气氛保护炉中正火热处理时,润滑剂燃烧不充分,残碳原子扩散到管子内壁,与其他元素结合形成了碳化物。对渗碳样品进行正火+回火处理可减轻或消除渗碳层,使用气氛保护炉热处理时,内壁渗碳有所减轻,但未能完全消除;而使用无气氛保护炉热处理时,可以消除渗碳层,但同时会产生较厚且易脱落的氧化皮。生产实践表明,在正火处理之前将润滑剂去除干净是防止钢内壁渗碳的关键所在。Unexpected carburizing phenomenon was found in the inner wall of the as-supplied T91 steel tube.The carburizing layer was qualitatively and quantitatively analyzed by means of chemical method,metallographic method and microhardness method.The element composition and phase composition of the carburizing layer are respectively observed by means of SEM,EDS and XRD.The corresponding preventive measures were proposed.The results show that the carbon content and the depth of the carburized layer can be qualitatively and quantitatively analyzed by metallographic method,chemical method and microhardness method.The main components of the carburized layer are Fe2.5C,Cr7C3 and Cr2C.This is because the lubricant attached to inner wall during the cold forming process of T91 steel tube is not clearly cleaned and then the lubricant is not fully burned during the normal heat treatment in the atmosphere protection furnace.The residual carbon atoms diffuse into the inner wall of the tube and combine with other elements to form carbides.The normalized and tempered treatment of the carburized sample can reduce or eliminate the carburized layer.When the inert atmosphere furnace is used during normalizing heat treatment,the inner wall carburization is alleviated.When the normalizing is conducted without the atmosphere protection furnace,the inner wall carburization can be eliminated,but it will also produce a thick oxide coating which is easy to fall off.Production practices have shown that removing the lubricant before normalizing is the key to prevent carburization of the inner wall.

关 键 词：T91钢管 内壁渗碳层 定量分析 渗碳层组成 热处理 预防措施 

分 类 号：TG115[金属学及工艺—物理冶金]