This paper provides a detailed description of complex bainitic microstructures obtained during the recent development of low carbon linepipe steels with strengths in the range of X100 to X120. New experimental techniques based on a high resolution FEG-SEM and EBSD have been used to characterise and quantify the mixture of ultrafine bainitic ferrite and nanosize second phases in these steels. It was found that the occurrence of incomplete transformation generates new, previously unexplored bainitic microstructures with a wealth of microstructural features that is beyond classification based on conventional concepts. Clear differences in distributions of boundary misorientations and effective grain size were noted between upper, lower and granular bainites. Based on these results a new classification scheme and definition of bainite is proposed.

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In solidifying bodies, there is no stress-free reference state for the displacements as in normal bodies with fixed dimensions, which are stress free, in all their volume elements, in the isothermal state prior to cooling or prior to heating. This difficulty has been solved in the present work by using displacement rates, rather than displacements, and all the other relevant quantities also in time differentiated form. The equations obtained for the time differentiated quantities are integrated with respect to time to obtain the quantities themselves. Different assumptions on the material behavior have been used, viz. viscoplastic-elastic or purely elastic behavior. The concept was applied to bodies with cylindrical symmetry and, for the sake of simplicity and clarity, to the state of plane strain. The computational examples refer to the solidification of steel with 0.6 pct carbon in a round continuous casting mold. The calculated stress distributions show compressive circumferential stress at the surface of the strand and tensile stress in the interior of the solid shell. Shrinkage profiles depend mainly on the temperature profile and on the thermal strain data used, and can be approximated by the free shrinkage of the strand surface.

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A model for the calculation of flow patterns and inclusion separation in continuous casting tundishes is described. Velocity and turbulence fields for the liquid steel are calculated, assuming three-dimensional, turbulent steady-state flow. A transport equation for particles is solved, which takes into account buoyancy, convection und turbulent dispersion. Particle concentration fields and the percentage of removed particles are calculated as a function of particle rise velocity. The influence of increased tundish width and height and of dams and weirs on the rate of inclusion separation is investigated for a slab caster tundish. Non-dimensional representations and approximation expressions are discussed and used to compare the computed removal rates to measured values from literature. Stahlstromunq und EinschluBabscheidung in GieBverteilern von StranggieBanlagen. Ein Modell zur Berechnung von Stromungsprofilen und EinschluBabscheidung in Verteilerqefalsen von StranggieBanlagen wird beschrieben. Geschwindigkeitsund Turbulenzfelder fur flussiqen Stahl werden unter Annahme eines dreidimensionalen, turbulent stationaren Strornunqszustandes berechnet. Unter Berucksichtiqunq von Antrieb, Konvektion und turbulenter Dispersion wird eine Transportgleichung fur Teilchen erstellt. Konzentrationsfelder der Teilchen und der Prozentsatz der abgeschiedenen Teilchen werden als Funktion der Teilchen-Aufstiegsgeschwindigkeit berechnet. Der EinfluB einer Verqrolserunq des Verteilerqefafses in Breite und Hohe sowie von Dammen und Wehren auf die Abscheidungsrate von Einschliissen wird fur ein VerteilergefaB einer Brammenstrang-gieBanlage ermittelt. Dimensionslose Darstellungen und Naherunqsforrneln werden diskutiert und zum Vergleich von berechneten Abscheidungsraten mit MeBwerten aus der Literatur verwendet.