A lot grouping algorithm for a continuous slab caster in an integrated steel mill

This paper discusses a lot grouping problem for a continuous slab easter in an integrated steel mill. Molten steel called 'charge' is transported to the continuous easter to be cast as the elongated rectangular solid steel pieces called 'slabs' of various sizes and metallurgical compositions. In order to enhance the productivity of the continuous easter, it is preferable to group as many charges as possible to form the cast. However, at the same time, lot grouping must be performed in compliance with several operational constraints as well as technological limitations of the continuous easter. The problem is formulated as an integer programming model, and it is shown that the problem is NP-complete. Hence, an efficient heuristic algorithm is developed to solve the problem by employing the column generation approach combined with a simple round-off scheme. In order to evaluate the performance of the proposed heuristic, the computation experiment is performed.