Metallurgical insight of premature failure of a Blast Furnace copper stave

Abstract

Present study investigates the premature failure (leakage) of copper (Cu) cooling staves placed at the lower stack region of a Blast Furnace (BF). This failure resulted in an increased frequency of make-up/ reserve water compensation every 10 h instead of average 24hrs. Detailed macro and microstructural analysis were carried out to understand the mechanism of failure in the Cu stave using phenomena observations, dial gauge measurements, metallographic investigation, and chemical analysis. Directional accretion of burden fines and puncture (leakage) profile were observed macroscopically. Puncture occurred from outer surface to inner surface of the channels of the stave. Micrographs of puncture location revealed non-uniform microstructure and grain deformation. Analysis suggested surface wear of the Cu stave due to a combined effect of continuous accretion of burden along with hot gas flow. Wear led to reduction in thickness and subsequent puncture/ leakage took place at the channel locations having a minimum cross-sectional thickness. With the help of this study, a failure mechanism of BF Cu Stave, a process critical component, has been explored. Recommendations such as insert modification, using more wear-resistant material or protective layer and conducting intermittent ultrasonic thickness measurements have been proposed to get an early warning of any untoward damages and process delays.