奥氏体不锈钢膨胀节失效原因分析及组织表征

张志伟1，刘素芬1，李兆杰2，张　杨1，王　凡1，孙远东1

（1.中国兵器工业第五二研究所，内蒙古　包头　014034；2.包头稀土研究院，内蒙古　包头　014034）

摘　要：研究了S30408 亚稳态奥氏体不锈钢膨胀节由于在冷变形过程中诱发马氏体转变及其对合金性能的影响。结果表明，该膨胀节波峰处的失效特征为脆性开裂。该处冷变形量较大，形变诱发的铁磁相马氏体数量较多，导致该处材料硬度高，塑性、韧性低，是其脆性开裂的主要原因。分析认为，该膨胀节波峰处未在合理的温度范围内进行冷变形，造成该处冷变形量较端部大，主要以马氏体转变及其变形为主，形变诱发的数量较多，马氏体为铁磁相，从而使膨胀节应对环境结构变形的能力不足，安装使用后，因不能满足环境结构的应力变化而导致其发生开裂现象。

关键词：奥氏体不锈钢；冷变形；马氏体转变；微观组织

中图分类号：TG172.7　文献标识码：A

作者简介：张志伟（1983—），男，硕士，助理研究员，主要从事金属材料及失效分析方面的研究工作，E-mail：zhzhwhero＠126.com。(www.xing528.com)

Failure analysis and microstructure characterization of expansion joint of S30408 austenitic stainless steel

ZHANG Zhiwei1，LIU Sufen1，LI Zhaojie2，ZHANG Yang1，WANG Fan1，SUN Yuandong1

（1.No.52 Institute of China Ordnance Industry，Baotou 014034，China；2.Baotou Research Institute of Rare Earths，Baotou 014034，China）

Abstract：It was studied that the effect of martensite transformation induced by cold deformation on the properties of S30408 metastable austenitic stainless steel expansion joint.It shows that the failure characteristic is brittle cracking at the wave crest of the expansion joint.And the main reason for brittle cracking is the large a⁃mount of cold deformation and the large amount of ferromagnetic martensite induced by cold deformation，which results in the high hardness，low plasticity and toughness of the material.The analysis shows that the cold deforma⁃tion at the peak of the expansion joint is not carried out in a reasonable temperature range，resulting in a larger cold deformation than the end of the joint，mainly martensite transformation and deformation，and a larger number of martensite induced by deformation is ferromagnetic phase，so that the expansion joint has insufficient ability to cope with the deformation of the environmental structure.After installation and use，the expansion joint can not meet the stress changes of the environmental structure.It causes cracking.

Keywords：austenitic stainless steel；cold deformation；martensite transformation；microstructure