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Assessment of Best Scheduling Practice in Continuous Casting and Hot Rolling of Stainless Steel Strip by System Dynamics Simulation
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
2007 (English)In: Sheet Metal 2007, Trans Tech Publications Inc., 2007, Vol. 344, 897-904 p.Conference paper (Refereed)
Abstract [en]

A rapid flow of materials with little intermediate buffering between steel mill and hot strip mill has many benefits. One is energy savings due to raised charging temperature in the reheat furnaces of the hot strip mill. Another is that tied capital is freed up, thereby improving mill economy. Still, it is not unusual that average lead-time is in the order of days, or even weeks.

The aim of the present work was to show how lead-times from casting to rolling could be improved by changes in the scheduling function. A System Dynamics model of a stainless steel strip production facility with continuous caster and hot rolling mill was created. The model was used to study the dynamics of the system in response to changes in parameters that defined the scheduling configuration.

More frequent schedule updating generally resulted in less work in process (WIP) and shorter lead times from casting to rolling, with resulting higher charging temperatures. The amount of oscillation in the system was also reduced. More frequent work roll changes were required when scheduling frequency increased, resulting in an increased fraction of setup time in relation to total processing time. Therefore, a development towards increased scheduling frequency may have to be complemented by efforts to reduce changeover times.

The conclusion was that dynamic scheduling routines with frequent schedule updating result in better overall performance of the system due to lower WIP and better heat utilization. Dynamic scheduling routines with frequent updates make the system respond better to changes in the system and give better overall performance. The result is lower WIP, increased energy efficiency and less oscillation in the system.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2007. Vol. 344, 897-904 p.
, Key Engineering Materials, ISSN 1013-9826 ; 344
Keyword [en]
hot rolling, continuous casting, hot charging, stainless steel, production scheduling, simulation, system dynamics
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-11699DOI: 10.4028/ 000247343400110ScopusID: 2-s2.0-34248553843ISBN: 978-0-87849-437-8OAI: diva2:279606
12th International Conference on Sheet Metal (SheMet 2007), Univ Palermo, Palermo, Italy. Apr 01-04, 2007

QC 20100810

Available from: 2009-12-04 Created: 2009-12-04 Last updated: 2013-10-14Bibliographically approved
In thesis
1. Strategic and operational capabilities in steel production: Product variety and performance
Open this publication in new window or tab >>Strategic and operational capabilities in steel production: Product variety and performance
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Steel producers that employ niche market strategies are continuously seeking to reduce production cost while maintaining adiverse product mix. The business model is typically based onmarketing of high–strength special or stainless steels. However,the desire to avoid direct cost competition is over time gradually leading towards increased product variety and smaller ordervolumes (tonnes per order) for each product.

This thesis analyses how production cost is linked to productvariety in steel strip production. Results are based on new modelsfor assessment of opportunities for performance improvement inhigh product–variety steel production.

The need for flexible production processes increases with increasing product variety. Operational capabilities linked to processflexibility determine the extent to which steel producers caneliminate in–process inventory and accomplish close coupling between process steps. Niche market producers that invest inprocess flexibility improvements can lower production costs bothdue to reduced work–in–process and lower energy consumption.An additional benefit is reduced environmental impact.

The following problems are addressed:

• Development of a method to assess the influence of productvariety on performance in steel production.

• Development of models of continuous casting and hotrolling that account for product variety and cost effectswith consideration of varying degrees of process flexibility.

• Development of a strategy process model that focus on thestrategic value of operational capabilities related to processflexibility.

Investments in operational capabilities regarding process flexibility have a strategic impact. An appreciation for the effectsof process flexibility should permeate the organisation’s daily work since the accumulated contribution of many, seemingly unimportant, incremental changes significantly influences thestrategic opportunities of the company.

Abstract [en]

Stålproducenter med nischmarknadsstrategier försöker ständigt sänka sina produktionskostnader samtidigt som en varierad produktflora bibehålls. Affärsmodellen bygger i typfallet på försäljning av höghållfasta specialstål eller rostfria stål. Strävan att undvika direkt priskonkurrens leder dock med tiden gradvis till ökad produktvariation och mindre ordervolymer (ton per order)för varje produkt.

Denna avhandling analyserar hur produktionskostnaden är kopplad till graden av produktvariation vid tillverkning av band.Resultaten bygger på nya modeller för utvärdering av förutsättningarnaför prestandaförbättring i stålindustri med stor produktvariation.

Behovet av flexibla produktionsprocesser ökar med ökande produktvariation. Praktiska förmågor kopplade till processflexibilitet avgör till vilken grad ståltillverkare förmår att eliminera mellanlager och åstadkomma en tät koppling mellan processteg.Nischmarknadsproducenter som investerar i förbättrad flexibilitet kan sänka sina produktionskostnader både genom minskad mängd produkter i arbete och reducerad energiförbrukning. Detta medför också minskad miljöbelastning.Följande problemställningar adresseras:

• Utveckling av en metod för att utvärdera inverkan av produktvariationpå prestanda vid ståltillverkning.

• Utveckling av en modell för stränggjutning och varmvalsningsom tar hänsyn till produktvariation och kostnadseffekterför olika grad av processflexibilitet.

• Utveckling av en strategimodell som fokuserar på det strategiskavärdet av operativa förmågor kopplade till processflexibilitet.

Investeringar i operativa förmågor vad avser processflexibilitet är av strategisk betydelse. Förståelse för betydelsen av processflexibilitetbör genomsyra det dagliga arbetet eftersom det samladebidraget av många, till synes obetydliga, små förändringar haren avgörande inverkan på företagets strategiska förutsättningar

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xiv, 126 p.
Trita-IIP, ISSN 1650-1888 ; 09-08
Steel production, system dynamics, product variety, production strategy, cost models
National Category
Production Engineering, Human Work Science and Ergonomics
urn:nbn:se:kth:diva-11642 (URN)978-91-7415-507-5 (ISBN)
Public defence
2009-12-18, M311, Brinellvägen 68, KTH, Stockholm, 13:00 (Swedish)
QC 20100810Available from: 2009-12-04 Created: 2009-11-27 Last updated: 2010-08-10Bibliographically approved

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