Untersuchung des Einflusses von Walzparametern eines Duo Walzgerüsts auf die mechanischen Eigenschaften ausgewählter Stahlqualitäten

Translated title of the contribution: Investigation of the influence of rolling parameters on a duo rolling mill on the mechanical properties of selected steel grades

Stefan Ebenbauer

Research output: ThesisDiploma Thesis

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Abstract

In the interest of a constant improvement of their products and a concurrent rise of the throughput the Böhler Bleche GmbH and Co. KG has modified their existing rolling mill in 2013. Due to the new rolling technology stable rolling parameters shall be found to guarantee a constant process security. Hence, internal trials on the rolling mill and additional tests on a servohydraulic forming simulator were carried out for two chosen materials to find stable deformation parameters to integrate these then into the standard manufacturing route. The materials are a heat treatable steel and a Super-Duplex-Steel. Because of the different chemical composition and structure education, both materials show an absolutely different formability. After the analysis and evaluation of some sheets and additional literature review and so-called "Processing Maps", it was tried to find stable deformation parameters at the forming simulator. Stable areas are characterized by the appearance of softening processes, like recovery and recrystallization. It has turned out that higher temperatures and lower strain rates provide stable deformation conditions for both materials. Furthermore, the austenitising temperature should be raised to more than 880 °C for the heat treatable steel to allow a deformation in the single phase area. Besides, good knowledge was reached concerning the constantly appearing decarburization in the edge area because of the high dislocation density. Higher deformation temperatures of above 900 °C would be preferred basically for the Super-Duplex-Steel. Thereby, on the one hand, dynamic recovery (DRV) appears at preferentially lower strain rate because of time dependent processes, and, on the other hand, dynamic recrystallization (DRX) which is to be found because of the higher dislocation density preferentially at higher strain rate. However some of the parameters at the rolling mill cannot be changed. Hence, in practice it is only possible to converge to the optimal parameters. Subsequently, such parameters were tested in additional rolling trials in the real manufacturing process. For both materials proper rolling parameters could be found, which lead to a positive influence on the microstructure.
Translated title of the contributionInvestigation of the influence of rolling parameters on a duo rolling mill on the mechanical properties of selected steel grades
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Lehofer, Harald, Supervisor (external)
  • Buchmayr, Bruno, Supervisor (internal)
Award date30 Oct 2015
Publication statusPublished - 2015

Bibliographical note

embargoed until 07-09-2020

Keywords

  • warm rolling
  • heat treatable steel
  • Super-Duplex-Steel
  • dynamic recovery (DRV)
  • dynamic recrystallization (DRX)
  • Processing Maps

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