Modeling And Solutions For Finished Products Logistics In Steel Industry

Finished products logistics in steel industry is the process that products yielded from the production line go through a series of operations including transport, storage and handling, and finally reach the customers. The efficiency of logistics operations directly affects the logistics cost and customer satisfaction. With the development of logistics technology in recent years, it becomes an effective means by improving the logistics operation management level to reduce the logistics cost and increase the enterprise competitiveness. Reasonable products logistics control strategy can equipoise the inventory between production terminals and finished products warehouse to avoid production processes from obstructing by excess inventory, reduce the delivery time and increase the efficiency of transport operations, thus reduce the logistics cost and improve the customer satisfaction.After treatment process from the production line, steel products are stored in the production terminals, and then they need to be transported to the finished products warehouse or storage yard to wait for the delivery according to re-deposit planning and export requests. Delivery planning consists of consolidation planning and stowage planning. Consolidation planning is to select a set of products to be loaded on a given conveyance (ship, wagons or trucks) according to the information within products" destination, storage position, variety, weight and so on. Stowage planning is to arrange the set of products with exact positions on the premise of ensuring compliance with the loading criterion.In this paper, we focus on re-deposit direction problem and delivery planning problem for finished products logistics in steel industry, and conduct a study on the entire products logistics processes. Main work shows as follows:1) The re-deposit direction problem for finished products from production terminals to finished products warehouse in the steel enterprises is researched. The problem is to decide where and when the products should be re-deposited considering both storage and handling capacity. It is formulated as a0-1integer programming model to maximize revenue of re-deposit, and to consider the constraints of storage capacity and handling capacity. 2) For the NP-hardness of re-deposit direction problem, ordinary methods such as dynamic programming and branch and bound can only obtain optimal solutions for small-scale instances. This problem is a practical problem with the characteristics of large-scale, complex-constraints which derives from the logistics of steel enterprises; therefore, discussing approximation algorithm for the problem becomes the main research means. This paper proposes a mathematical programming method based on Lagrangian relaxation with two different relaxation modes. For the second mode, we import an invalid inequality to improve the upper bound. Computational results carried out on randomly generated data of different sizes show that:(1) Both of the two mode of Lagrangian relaxation method can get small dual gap within a short time.(2) For small scale instances, the solutions obtained from the two modes are the same as or close to that from standard optimization software CPLEX; For middle and large scale instances, the upper bound of the two modes are close to the optimal solution or the best feasible solution.(3) The upper bound of the first mode is appreciably better than the second, but the computational time is longer; the second mode can often get better feasible solution than the first.3) Based on the analysis of finished products delivery logistics operations of a domestic steel enterprise, the finished products delivery process is divided into two sets with consolidation planning and stowage planning. The finished product logistics consolidation and stowage decision support system of the three transportation modes is designed and developed. Aiming at the dynamic factors which are actual existence in the logistics operations of steel enterprises, the function and algorithms of the system have been improved to better adapt to environmental changes and take on stronger robustness.4) Make a study on every aspect of logistics operations in the process of products from production terminals to customers, and compare them with logistics operations in container terminals of the logistics system. The similarities and differences in the operation between the two logistics operations are indicated.