Auswirkungen intergranularer Oxidation auf die Oberflächenrissbildung beim Stranggießen von Stahl

Translated title of the contribution: Impact of intergranular oxidation on surface crack formation in continuous casting of steel

Research output: ThesisMaster's Thesis

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Abstract

Within the scope of the present work, high temperature oxidation and its effect on surface crack formation is investigated, simulating continuous casting for a 0.17 % C steel with different contents of silicon. Oxidation processes of silicon alloyed steel can lead to the formation of a liquid fayalite-wustite phase in the area of the steel surface at sufficiently high temperatures. There is a possibility that the liquid phase infiltrates the matrix along the austenite grain boundaries, leading to intergranular defects. In case of a subsequent tensile load, as it occurs e.g. during straightening in continuous casting, it results in stress concentration and thus to easier defect nucleation. The surface crack formation and oxidation was studied using the In-situ Material Characterization – Bending (IMC-B) test, which was developed at the chair of ferrous metallurgy, and simultaneous thermal analysis (STA). To analyse the influence of temperature, investigations were done for two different cooling strategies. The samples were evaluated by determining numbers, critical elongation for the formation of 2 cracks, depth and frequency of intergranular defects and mass gain due to scaling. A high number and depth of intergranular defects are formed exclusively in alloys with silicon for a cooling cycle with a sufficient high oxidation temperature. For this cooling strategy, silicon-free alloys do not show any increase of defect density due to the lack of intergranular defects, whereas the silicon-alloyed steels develop a distinctive crack network. The development of these crack networks in the bending test is due to the presence of intergranular defects. For all of the alloys examined, the critical temperature range for bending starts at 850 °C and extends to at least 900 °C. An increase of silicon causes a widening of the critical temperature range towards higher temperatures.
Translated title of the contributionImpact of intergranular oxidation on surface crack formation in continuous casting of steel
Original languageGerman
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Bernhard, Christian, Supervisor (internal)
  • Krobath, Roman, Co-Supervisor (internal)
  • Presoly, Peter, Co-Supervisor (internal)
Award date26 Mar 2021
Publication statusPublished - 2021

Bibliographical note

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Keywords

  • surface cracks
  • silicon
  • oxidation
  • intergranular oxidation
  • continuous casting
  • IMC-B test

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