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Lecture

Microstructural characterization procedure using EBSD technique for intercritically deformed low carbon steels

Thursday (27.09.2018)
12:00 - 12:15 S1/01 - A4
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Intercritical rolling, also known as warm rolling, is a widely used rolling strategy consisting of giving the last deformation passes within the austenite/ferrite two-phase region. Under given conditions, intercritical rolling can lead to important industrial benefits in terms of lower rolling forces, energy saving, as well as improved strength. However, the control of the final mechanical properties is more complex compared to a standard austenitic rolling strategy, because of the combination of several microstructural phenomena, such as restoration and recrystallization taking place in both austenitic and ferritic regions. In order to obtain a deeper knowledge of the evolution of the microstructure during intercritical deformation, laboratory thermomechanical simulations reproducing intercritical rolling conditions were performed in a Bähr DIL805D deformation dilatometer, for two low carbon steels with three different intercritical ferrite volume fractions. Different ferrite populations are identified in the resulting microstructures, composed of intercritically deformed ferrite and non-deformed ferrite transformed during final air cooling. In the deformed ferrite grains well defined substructure is clearly noticed, whereas the non-deformed grains formed during air cooling step don´t show any evidence of substructure. The present analysis develops a methodology to quantify microstructural features in an intercritically deformed microstructure. Based on the Grain Orientation Spread (GOS) parameter, a threshold value of 2º was defined to distinguish deformed and non-deformed ferrite grains. The proposed procedure allows distinguishing both ferrite populations and quantifying microstructural parameters of each family. Considering the described methodology, the effect of the addition of carbon and austenite/ferrite balance on the microstructural evolution is analyzed.

Speaker:
Additional Authors:
  • Dr. Nerea Isasti Gordobil
    Ceit and Universidad de Navarra (Tecnun)
  • Dr. Pello Uranga Zuaznabar
    Ceit and Universidad de Navarra (Tecnun)
  • Prof. Dr. Jose María Rodriguez Ibabe
    Ceit and Universidad de Navarra (Tecnun)