Microstructural Characteristics of Copper–Steel Composite Cooling Staves After Long-Term and High-Temperature Service

Copper–steel composite cooling stave is an important technology to solve the safety problem of the high heat load area of the blast furnace. The effect of high-temperature service on the performance of copper–steel composites is in relatively few studies. In this paper, the copper–steel composite cooling stave in service for 4 years was investigated. The results show that the thickness of the copper–steel diffusion layer increases significantly in long-term service and Kirkendall voids are formed near the interface. Cracking occurred inside the vortex zone under the influence of thermal stress. Significant secondary recrystallization occurs on the copper side and the grains grow significantly. The steel side remains equiaxed crystalline, and the Abs band formed by the explosion welding is at an angle of 45° to the interface, and the grain size grows. Microhardness test shows that the vortex area and copper side due to the growth of grain size and the elimination of work hardening, microhardness significantly reduced. The nanoindentation results show that the nanoindentation of the substrate and the vortex zone is also significantly reduced after service. Graphical Abstract