Research on a Method of Ladle Scheduling Based on Rule Learning*

Abstract

In steel-making and continuous casting production processes, the starting time delay happens frequently, which may lead to casting break or processing conflict so that the static scheduling plan becomes unrealizable. The ladle rescheduling of steel-making and continuous casting production aims at continuously casting many charges with the same cast and avoiding conflicts of adjacent charges on the same machine. It decides the selected processing machines, the starting time and the completion time for not started charges at the steel-making stage and the refining stage. The completion time also should be decided for being processed charges. Then, based on the production equipment scheduling plan of the heat, the requirements of the processing equipment (converter, refining furnace and continuous casting machine) of the heat are met. Under the conditions of the start and end time of the equipment, a ladle carrying molten steel is selected, and determine the route of transporting the ladle. Since ladle scheduling must meet multiple conflicting goals and conflicting constraints, it is difficult to adopt existing optimal scheduling methods. This paper proposes a method of ladle scheduling in the production process of steelmaking-refining-continuous casting. First, scheduling optimization model of the steel-making and continuous casting production is built, which aims at minimizing the waiting time of all charges. The scheduling strategy of steel-making and continuous casting production is proposed by interval processing time of charges and scheduling expert experience. Then, the first-order rule learning is used to select the optimization target to establish the ladle optimal scheduling model. the ladle matching rules are extracted by the rule reasoning of the minimum general generalization; the ladle optimization scheduling method consisting of the optimal selection of the ladle and the preparation of the optimal path of the ladle is proposed. Ladle selection is based on the production process and adopts rule-based reasoning to select decarburized ladle, or select decarburized ladle after selecting dephosphorized ladle. Ladle path preparation, a multi-priority heuristic method is designed to decide the path of the ladle from the converter to the refining furnace to the continuous casting machine. Finally, based on a large-scale steel company in Shanghai, China, the method was actually verified, and the results showed that the production efficiency of steelmaking-refining-continuous casting was improved.