热风炉出风管失效分析-中国材料进展

文章信息/Info

Author(s):: CAI Xiaowen; CHEN Xingyuan; （State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization, Pangang Group Research Institute Co., Ltd., Chengdu 610300, China）

Keywords:: intergranular crack; expansion joint; creep strain; brittle fracture; high temperature oxidation

摘要:: 某不锈钢制成的热风炉出风管膨胀接头过早失效。主要现象表现为热风炉出风管膨胀接头于失效处壁厚减薄，并伴随破裂、穿孔等现象。经取样观察，膨胀接头在减薄处存在裂纹，局部坍塌凹陷。通过扫描电子显微镜（SEM）对裂纹处断口形貌进行观察，发现断口处穿晶和沿晶裂纹并存。利用传统金相检验及化学分析等方法多角度分析了缺陷样品的形貌及成分。结果显示，工件的环境温度和蠕变增加了晶粒粗化和形成楔形空穴的趋势。腐蚀、蠕变、晶界析出物析出之后基体的贫铬引起了出风管管壁变薄、开裂并最终导致热风管过载失效。

Abstract:: Stainless steel drain tube from a hot-blast stove for the preheating air was premature failure. The main phenomenon was that the wall thickness of the expansion joint of the hotair stove-s air outlet tube was reduced at the failure point，with cracking and punching. It was observed that certain areas occurred through-way cracking in the thinned tube while others showed significant collapsing. A fracture taken from cracking areas was analyzed by SEM and was found to have a mixture of intergranular and transgranular cracking. Metallographic examination and chemical analysis of two specimens, also from the failed region, revealed the presence of large grain with widened grain boundary and wedge-type cavities at grain-boundary triple points, which were caused by operating temperature exceed those intended for this steel and may be promoted by grain-boundary precipitates. Failure of the tube was attributed to creep-type rupture at high-temperature conditions resulting from prolonged overheating and to thinning of the way by high-temperature corrosion and oxidation to the point at which the hot-air pressure in the tube and eventually lead to overload failure of the hot air pipe.