Nobuhito Ishikawa
Abstract
Butt curl which occurs in the semi-direct chill (DC) casting of aluminum slabs can cause metal bleeding and hot cracking accompanied by coincident bowing that leads to poor yields in slab preparation. To understand the mechanism of butt curl, the author has proprietarily developed a solidification stress model based on the elasto-plastic incremental strain theory involving solidification. The analysis using the model shows that butt curl grows immediately after secondary cooling water begins to impinge on the slab bottom, but its growth rate decreases as the bottom block descends and the slab bottom is cooled increasing in rigidity. It is also shown that the driving force for butt curl growth is the torque moment around the center of the slab bottom, which is caused by the tensile stress generated in the mushy zone along the sump profile.
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