Examination of factors and mechanisms contributing to surface wear on copper cooling staves within large blast furnaces

•Copper cooling staves are worn by solid charge instead of gas erosion.•Differences exist in the wear of staves, with a maximum wear rate of 5.64 mm/a.•Cooling staves wear more at bends and junctions.•Abrasive wear is the predominant type and oxidative wear contributes less.•The loose structure of the surface abrasion promotes the loss of copper. Copper cooling stave is an important cooling equipment to ensure the safe production of blast furnaces. However, the breakage mechanism of copper cooling staves in large blast furnaces is still controversial. The field measurements and samples of the replacement copper cooling stave were performed to elucidate the breakage cause and mechanism. Additionally, the wear parameters of the copper cooling stave were analyzed using SEM, EDS, microhardness, and optical microscopy. According to measurement data, the most problematic areas of copper cooling stave, are situated at the junction of shaft and belly, the junction of belly and bosh, and the joints of the two cooling staves. The annual wear rate in these areas can be as high as 5.64 mm per year. The microanalysis results reveal numerous furrows on the surface of the copper cooling stave and the furrows through the pure copper and the surface of the slag are continuous. It has been observed that abrasive wear is the predominant type of wear, with a minor contribution from oxidative wear. After wear, the subsurface of the copper cooling staves develops wavy undulations, accompanied by the formation of microcracks. In certain specific areas, a multi-layer loose structure was formed which weakened the surface strength of the cooling stave and speeded up the wear of the cooling stave. It was eventually determined that slag peeling was directly responsible for the wear of the copper cooling stave, and the surface heating caused by the high-temperature gas contributed to the wear of the copper cooling stave.