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Cause Analysis Of Mould Wear During Continuous Casting
Mar 20, 2018

    In the meniscus of the mold, often copper cracks appear, the main reason is the copper surface temperature increase caused by the extremely high heat flux, at this high temperature, compared to the steel support facilities, copper tends to expand. Especially for thin slab continuous casting crystallizer, because the billet speed is fast, the copper surface temperature rises rapidly, the copper plate temperature exceeds its recrystallization temperature, thus causes its strength and the hardness to reduce greatly, causes the funnel shape transition area to undergo an obvious 3 dimensional expansion movement.

    This combination of thermal strain and mechanical strain combined with a decrease in hardness (up to 50%) leads to the appearance of surface cracks in the copper plate, and the crack tends to propagate further in the crystal mode. The high heat level in the casting process and the macroscopic plastic strain/deformation of the crystalline copper surface and the sub surface area are the main causes of the cracks in the meniscus of the mould. This damage mechanism is also enhanced by extremely high temperature regions. For example, the transition region from the mold funnel area to the Crystallizer parallel zone.

    At this time, the mold hot surface and cold between the local temperature gradient can reach hundreds of degrees Celsius. The working side surface (hot surface) of the mould copper plate is more or less subject to the influence of diffusion, and the F of Zn, S, CD and slag in molten steel is spread to the surface and sub surface of the copper plate. These diffusion elements lead to the thermal brittleness of the crystalline copper plate, which leads to the formation and diffusion of the crack.

    The key factor of crack damage is the maximum temperature and the service time of Crystallizer. When the high speed continuous casting, the crystallization equipment quality withstand ultra-high temperature another effect is the mold copper plastic strain, resulting in meniscus deformation, as well as the zinc in the molten steel into the copper plate formation of brass, that is, the so-called "brass" phenomenon. The latter issue is particularly acute for EAF mills or short process rolling mills, which are usually used for steelmaking by steel mills or short process rolling mills. The formation of brass makes the mold copper produces the hot brittleness, coupled with the high working temperature causes the stress, causes the mold copper plate to produce the crack.

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