A Two-Phase Heuristic for the Production Scheduling of Heavy Plates in Steel Industry

In this paper, the production scheduling of heavy plates is considered. Different from general hot rolling mill, the reheating furnace scheduling shares the same importance with the hot rolling scheduling due to the special characters of heavy plates such as the large differences in weight and dimension. One major characteristic of the reheating furnace is that it can simultaneously process multiple slabs. When the furnace is full, a slab can be drawn in only if the head slab in the furnace has been drawn out. Therefore, the practical heating time of a slab is variable and besides the weight and dimension, is also dependent on not only the slab heating sequence but also the furnace capacity. Since there is no buffer between the reheating furnace and the hot rolling line, a finished slab will reside in the furnace until the hot rolling line is available. To solve this problem, a two-phase heuristic is proposed. In the first phase, only the hot rolling scheduling problem is considered and a scatter search is developed for it. In the second phase, a decision tree-based heuristic is constructed to obtain the corresponding reheating furnace schedule. The experimental results on real production data show that the two-phase heuristic outperforms the current manual scheduling system.