Planning and scheduling of steel plates production. Part II: Scheduling of continuous casting

Production planning and scheduling in the steel industry are challenging problems due to large number of products being produced. This work deals with scheduling of the continuous casting of steelmaking, i.e. determination of charge sequence in each casting machine. Since a full-space model Mixed-Integer Linear Programming (MILP) approach is computationally intractable for long term continuous casting scheduling due to a huge number of binary variables, we propose a two-level optimization method. At the top level, we solve the planning problem that determines the number of pots of each grade for every planning period by solving the relaxed mixed integer linear problem. At the lower level, the scheduling problem is solved by an algorithm which combines ideas from parallel simulated annealing and shuffled frog leaping. Real-world steel-plate production data are utilized to examine the effectiveness of the proposed two-level optimization algorithm.