A Hierarchical Approach for the Application of Slabs to Strip Products in the Steel Industry
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Jufy - September 2005
OR Insighi Vol. 18 Issue. 3
The OR Society
A Hierarchical Approach for the Application of Slabs to Strip Products in the Steel Industry by
Francis J. Vasko, Mathematics Department, Kutztown University, Kutztown, PA 19530, USA Arthur J Harnrn, Sparrows Point, 5111 North Point Blvd, Sparrows Point, MD 21219, USA Kenneth L Reitmeyer, EDS-Mid Atlantic Solution Center, 113 Research Drive, Bethlehem, PA 18015, USA L. Richard Woodyatt PE, Pikewood, Inc 123 East Broad Street, Bethlehem, PA 18018 USA
ABSTRACT In the mid-1990's, the Sparrows Point Steel Plant began an initiative to achieve 100% on time slab availability to the hot strip mill. At that time, order dressing, heat building, slab application, and mill scheduling of strip product orders were manually intensive activities. It was decided to implement an integrated system to automate these activities. In this paper we discuss the central activity of this system-the application of slabs to strip product orders (used for appliance panels, steel storage sheds, food cans, etc.). A binary integer linear programming formulation will be given for the slab application problem. However, because of the size of typical problem instances, a robust and efficient hierarchical heuristic solution approach was developed that has been in daily use since 1999. Keywords: slab application, steel industry, mathematical programming application, heuristic application INTRODUCTION In the mid-1990's, Sparrows Point began an initiative to achieve 100% on time slab (a rectangular semi-finished piece of steel) availability to the hot strip mill. Order dressing or the specification of customer chemical and
physical properties requirements, heat building or the grouping of customer orders into batch sizes based on metallurgical grade and slab size requirements, slab application or the assigning of specific slabs (either already produced or yet to be produced) to strip product orders (used to make appliance panels, steel storage sheds, food cans, etc.), and hot strip mill scheduling or the selection and sequencing of slabs to be processed into coils on the hot strip mill were manually intensive. The systems for each were stand alone, each with similar but independent slab application rules. Many efforts to fine-tune the process and systems fell short of the 100% ontime goal. New hot strip mill requirements that could not be satisfied by existing slab inventory were converted to steel orders. These steel orders formed the input to the heat building system, and were manually arranged into heat lot (batch size) requirements for caster production. These heat lot plans were rarely revisited to accommodate order or inventory changes. Because individual slabs were tied to specific orders, slabs with lower quality than required by the mill order were de-applied during a daily run, while slabs produced with better quality than required remained coupled with the
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original order. Manual application / reapplication caused a ripple effect throughout the systems.
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