Research On The Optimization Of Slab Retrieving Problem With Batch Moves In Hot Rolling

With the rapid development of iron and steel enterprises in recent years,the problem of integrated production planning and scheduling has been received more and more attention both at home and abroad.The slab storehouse is an important link in the steelmaking-continuous casting and hot rolling integrated production system.As the middle cushion of the continuous casting and hot rolling production,it plays a critical role in the balance of the steel rolling capacity and the steelmaking capacity and the balance of the whole production process.For the iron and steel enterprises,the optimization of the management of slabs has a significant impact on the continuous production and the production efficiency,which is effective and useful to improve the competitiveness of enterprises.The management of slab retrieving is one of the most important works in the optimization management of slab yard,which is directly related to the production efficiency of slab storehouse.With the development of machinery industry,cranes that can lift several slabs at a time begin to appear.Slabs which can be disregarded of their mutual order when retrieved are often marked as the same number in its stacking,to facilitate the subsequent processing needs of the continuous slab retrieving.In this thesis,we consider a slab retrieving problem with batch moves in hot rolling without considering rolling planning and moving costs.The main contributions in this thesis can be summarized as follow:(1)In this thesis,a thorough review of slab retrieving is given by consulting many domestic and foreign periodicals,monographs and conference proceedings.The main areas of the review include:hot-rolled slab retrieving problem in iron and steel production,slab loading problem and other management issues in the management of slabs,and container relocation problem,container pre-marshalling problem which are similar to the management of slab yard in container yard management.In addition,the algorithms for solving these types of problems are summarized.(2)In this thesis,a greedy algorithm is developed to solve the problem of slab retrieving with repetition numbers(i.e.,where different slabs have the same number).With respect to the algorithm,several corresponding rules are proposed according to the selection of retrieval slabs,the selection of shuffling slabs,and the selection of target stacking position for slabs to be shuffled.The effectiveness of the algorithm is demonstrated by randomly generated instances of different sizes,and some analysis is given.(3)Still considering the slab retrieving problem with repetition numbers,a lower bound of the problem is proposed,which mainly includes the lower bound of the number of relocations and the lower bound of the number of retrievals.In order to address the problem,a tree search algorithm is developed,which is based on the rule of depth-first search.Finally,the effectiveness of the algorithm is tested by a large number of randomly generated instances.And the influence of the key parameter of "the maximum number of slabs that can be moved at a time" to the problem is experimentally analyzed.Some empirical conclusions and managerial implications are obtained...