Modeling And Optimization For Production Scheduling Problem In Continuous Annealing Line And Slabs Loading Problem In Iron And Steel Industry

The development of technology and the quality of the products in iron and steel industry can directly affect the development of the national economy. Reasonable production and logistics scheduling is important to keep the quality of the products, meanwhile, it is helpful to shorten the production cycle, enhance the productivity, and reduce the production costs.Cold rolling is an important production stage in the iron and steel industry stage after steelmaking, casting, and hot rolling process. Considering the production variety in cold rolling, reasonable production organization will keep the production stable and further reduce the production costs; slab stock is the intermediate in the production, which means it is not only the final product of steelmaking process but also the materials of subsequent rolling process. Slab stocks coordinate steelmaking and rolling, and balance the whole production process. Optimizing slab stocks scheduling has very important significance for continuous production to improve production efficiency.This thesis studies the production order scheduling problem for continuous annealing line in cold rolling area and slab stack position decision problem for hot rolling storage. By modeling and developing the differential evolution algorithm, the thesis can achieve reasonable solution for the two problems.The main contents are as follows:(1) The production order scheduling problem for continuous annealing line in cold rolling area is to determine the order selection and scheduling with the objective of minimizing the total production cost. To solve the problem, a mathematical model is formulated which can be optimally solved by CPLEX in small-scale. Then a DE algorithm is developed based on the structure of the problem. The efficiency of the proposed model and solution method is verified through experiments. With consideration of the uncertainty in production scheduling, an optimization via simulation model is extended from the above model and an effective algorithm is developed to achieve the stable solution for the practical case, which can deal with the uncertain penalties in the model.(2) The slab stack position decision problem for hot rolling storage is to determine the better stacks for the slabs and minimize the irregular degree of the slabs in the same stack with the objective of minimizing the crane moving distance. Firstly, a mathematical model is formulated, which can be optimally solved by CPLEX, then a DE algorithm is developed to solve the problem. Finally, the efficiency of the proposed model and solution method is verified through experiments.(3) Based on the investigation in an iron and steel enterprise in China, the order management in the cold-rolling planning system for iron and steel supply chain and the slab stack decision module in the hot rolling material stacking optimization system are developed respectively.