Untersuchung von Erstarrungsphänomenen im Blockguss

Translated title of the contribution: Investigation of solidification phenomena in ingot casting

Florian Penz

Research output: ThesisMaster's Thesis

Abstract

High quality steel grades require a high steel cleanness as well as a chemical and physical homogeneous microstructure. Based on different solidification conditions in ingot casting, solidification phenomena will appear, which have their sources in various physical and thermodynamical conditions. The aim of this master thesis is to analyse the solidification phenomena using different analytical methods. By means of numerical simulation an influence in terms of the time to solidus as well as porosity is desired. Two Cr-Mo-alloyed ingots, with different isolating covering were investigated to explain their solidification phenomena. In both ingots samples along the ingot width in two heights were analyzed, to receive a predication about the influence on the solidification phenomena on their position in the ingot as well as the covering- The basics of solidification, primary structure and non-metallic inclusions are explained on a comprehensive literature review. Special attention is paid to segregation and porosity criterias. In predefined heights the primary structure and the spacing of secondary dendrites were measured by optical microscopy. Segregation was visualized by optical emission spectroscopy along the width of the sample areas. With a scanning electron microscope with integrated EDS selected positions were investigated concerning inclusion content, number, size and chemical modification. A sensitivity study describes the influence of simulation parameters on the numerical simulation and solidification. The final parameter analysis has the aim to show objective possibilities to minimize porosity and to influence solidification. Small differences in primary structure and the secondary dendrite arm spacing were found in the upper parts between the two ingots. The concentration profiles show no impact of the covering in the lower ingot part. In the upper part significant miscellaneous results appear between the two ingots. The SEM/EDS-analysis showed between the two ingots an unequal inclusion content and number which are caused by differing natural and thermal convection. No significant distinctions in chemical composition were found along the ingot width. As a result of the sensitivity study the grid size and various initial and boundary conditions were found, which have an impact on the simulation and the solidification. In the parameter analysis a variable heat transfer coefficient between steel and mold was detected as the most powerful parameter to change the solidification structure.
Translated title of the contributionInvestigation of solidification phenomena in ingot casting
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Schramhauser, Sebastian, Supervisor (external)
  • Bernhard, Christian, Supervisor (internal)
  • Loder, Denise, Co-Supervisor (internal)
  • Riedler, Michael, Co-Supervisor (internal)
Award date26 Jun 2015
Publication statusPublished - 2015

Bibliographical note

embargoed until 22-05-2020

Keywords

  • Ingot casting
  • Segregation
  • Simulation
  • Modelling
  • Niyama
  • Secondary dendrite arm spacing
  • Porosity
  • Non-metallic inclusions
  • SEM/EDS
  • OES-PDA

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