TY - THES

T1 - Optimization of processing parameters on an ESP line

AU - Dierer, Florian

N1 - embargoed until 22-05-2020

PY - 2015

Y1 - 2015

N2 - The present work is the result of cooperation between Chair for Iron and Steel Metallurgy of MU Leoben, plant manufacturer Primetals Technologies Austria and Italian steel producer Acciaeria Arvedi. Headline of this project is “Optimization of processing parameters on an ESP line”, which means certain parameters for coupled processes of ESP line (restriction to hot rolling, cooling section and coiling) had to be identified. Further their individual influence on coil microstructure and final mechanical properties had to be investigated. This work contains assessment and development of strategies in order to improve strip properties by using simulations and large scale trials. Validation of trial results was realized by metallographic analysis and mechanical tests. Aim was to modify process parameters in order to obtain improved mechanical properties (in particular impact toughness values) of selected steel grades, such as Nb-V alloyed HSLA (S420MC) and medium-carbon C-Mn (S355J2) steels. In a literature study, several aspects of hot rolling, austenite to ferrite transformation and the relationship microstructure-properties are discussed closely. Particularly, grain refinement is found to be a very effective way to improve both, strength and impact toughness, which was tried to apply in large scale trials. For this aim, several strips of medium-carbon steel (0.18C-1.25Mn-0.02Si) with 9.5 and 11.9 mm thickness were produced. With focus on grain refinement, different combinations of temperatures along ESP line were tested to improve impact toughness values. In order to identify processing parameters that influence the properties of 2.0 mm HSLA steel (0.04C-0.55Mn-0.02Nb-0.03V), strips were produced under different cooling and coiling conditions. An increase in strength, which was observed at higher coiling temperatures, is related to the formation of NbV(C,N) precipitations.

AB - The present work is the result of cooperation between Chair for Iron and Steel Metallurgy of MU Leoben, plant manufacturer Primetals Technologies Austria and Italian steel producer Acciaeria Arvedi. Headline of this project is “Optimization of processing parameters on an ESP line”, which means certain parameters for coupled processes of ESP line (restriction to hot rolling, cooling section and coiling) had to be identified. Further their individual influence on coil microstructure and final mechanical properties had to be investigated. This work contains assessment and development of strategies in order to improve strip properties by using simulations and large scale trials. Validation of trial results was realized by metallographic analysis and mechanical tests. Aim was to modify process parameters in order to obtain improved mechanical properties (in particular impact toughness values) of selected steel grades, such as Nb-V alloyed HSLA (S420MC) and medium-carbon C-Mn (S355J2) steels. In a literature study, several aspects of hot rolling, austenite to ferrite transformation and the relationship microstructure-properties are discussed closely. Particularly, grain refinement is found to be a very effective way to improve both, strength and impact toughness, which was tried to apply in large scale trials. For this aim, several strips of medium-carbon steel (0.18C-1.25Mn-0.02Si) with 9.5 and 11.9 mm thickness were produced. With focus on grain refinement, different combinations of temperatures along ESP line were tested to improve impact toughness values. In order to identify processing parameters that influence the properties of 2.0 mm HSLA steel (0.04C-0.55Mn-0.02Nb-0.03V), strips were produced under different cooling and coiling conditions. An increase in strength, which was observed at higher coiling temperatures, is related to the formation of NbV(C,N) precipitations.

KW - steel

KW - hot rolling

KW - microstructure

KW - properties

KW - Stahl

KW - Warmwalzen

KW - Mikrostruktur

KW - Eigenschaften

M3 - Master's Thesis

ER -