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

Abstract

This paper discusses a lot grouping problem for a continuous slab caster in an integrated steel mill. Molten steel called 'charge' is transported to the continuous caster 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 caster, 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 caster. 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, and it shows that the proposed heuristic is quite satisfactory in practice.