Research On Scheduling And Matching Optimization Problems For Cold Rolling Stage In Iron And Steel Enterprises

Iron and steel industry plays an important role in the development of Chinese economy and it is also a pillar industry to improve China’s comprehensive national strength. Compared with other advanced manufacturing industries, steel production has long production cycle and highly complex processing technologies. Therefore, scientific and effective production plans are essential to guarantee the product quality, shorten the production cycle, reduce the materials and energy consumption, the work-in-process inventory, and the production cost.Cold rolling, which contains acid pickling, rolling, annealing, plating and finishing processes, is an important production stage to produce various products in iron and steel enterprises,. This thesis studies the integrated problem of production scheduling and inventory for continuous annealing and coil-order matching problem for multiple operations. In order to get effective production plans, the mathematical models and optimization algorithms are proposed for the two problems. In addition, the corresponding decision support systems for the two problems are developed respectively. The main content are as follows:(1) The integrated problem of production scheduling and inventory for continuous annealing is to determine the production sequence of the orders on each production line with the objective of minimizing the production and inventory costs as well as minimizing the penalty caused by order tardiness. First, the problem is formulated as a mixed-integer linear programming model. Then, for the small sized instances, optimal solutions are obtained by using the popular MIP solver CPLEX to directly solve the mathematical model. For the large sized instances, an estimation of distribution algorithm is developed to get the near optimal solution of the problem. Finally, numerical experiments demonstrate the performance of the proposed solution methods.(2) The coil-order matching problem for multiple operations is studied. First, considering the practical processing technical constraints, a mathematical model is formulated with the objective of minimizing the inventory of open-order coils, and maximizing the resource utilization and the order completeness. CPLEX is adopted to solve the formulation directly for the small sized instances. Since CPLEX cannot solve the practical large sized instances in reasonable time, a differential evolution algorithm is developed. The experimental results on practical data demonstrate that the proposed algorithm is superior to CPLEX.(3) Based on the investigation in an iron and steel enterprise in China, this thesis analyzed the key production planning problems faced by the steel enterprise. According to above research, the decision support systems for coil-order matching and the cold-rolling planning system are developed respectively. The decision support system for coil-order matching is developed to realize the automotive generation of the coil-order matching plans for multiple operations in cold rolling stage, while cold rolling planning system is to generate the production plans for the cold-rolling stage so as to reduce the production cost, the abrasion of the equipments and the resources consumption.