Heat transfer in the mold is the heart of the continuous casting process and its quantitative analysis was pioneered by Keith Brimacombe. With many different processes currently competing, it is appropriate to apply modeling to investigate the theoretical limits of continuous casting speed and productivity. The heat transfer rate during solidification processes drops with time so the shell thickness at mold exit drops with increasing casting speed. A computational heat flow model similar to those of Brimacombe is applied to investigate the consequences of very high casting speed on shell thickness at mold exit. Next, a finite-element stress model is applied to predict the minimum shell thickness at mold exit that should have sufficient strength to avoid rupture due to longitudinal tearing of the weak shell under the forces of ferrostatic pressure. The critical shel thickness is predicted to be on the order of 3 mm for most grades and casting conditions. The models are then applied to pedict maximum casting speeds for different steel grades, section sizes, and mold lengths. The theoretical limits to casting speed are predicted to be extremely high, exceeding 21 m/min for a conventional 800-mm long, 200-mm square bloom mold, which corresponds to 3.5 million tonnes per year. The infeasibility of these high limits in practice is due to other problems, such as achieving shell thickness uniformity and liquid flux lubrication. This work suggests that if shortening mold length can solve lubrication, taper, and other problems, then it should be explored as a potential means to increase productivity.
展开▼
