Abstract
A model-based process control of material production processes demands realistic material models describing the local evolution of the thermal and mechanical state variables, i.e., temperature, stress, strain, or plastic strain, for the relevant microstructure state. In the present work, a material model for the specific microstructure in a continuously cast strand shell, viable for reproducing cyclic viscoplastic effects, was developed for a 0.17 wt.% C steel. Experimental data was generated using directly-cast samples and a well-controllable testing facility to apply representative loading conditions. Displacement- and force-controlled experiments in the temperature range of 700–1100 °C were conducted, with a special focus on the relevant strain rates documented for the straightening operation. A temperature-dependent constitutive material model combining elastic, plastic, and viscoplastic effects was parameterized to fit the whole set of experimentally-determined material response curves. In order to account for the cyclic plastic material response, a combination of isotropic and kinematic hardening was considered. The material model sets a new standard for the material description of a continuously cast strand shell, and it can be applied in elaborate continuous casting simulations.
Highlights
The prediction of product quality in steel production is one of the main aims of the ongoing digitalization
The material model sets a new standard for the material description of a continuously cast strand shell, and it can be applied in elaborate continuous casting simulations
Thepunch resulting material model is capable of reproducing the loading types, but the agreements of the force-controlled experiments and the displacementthat the gradients strain rates rates change for the conditions ensures the strain material behavior for in thestrain wholeand range of strain present at different the straightening stage of the that continuous
Summary
The prediction of product quality in steel production is one of the main aims of the ongoing digitalization. “microscopic” means the order of magnitude of precipitations, dendrites, and grains (nm–μm) These microstructural characteristics depend on cooling conditions and local mechanical deformation and are most relevant for the defect sensitivity of steel at elevated temperatures. Kozlowski et al [6] introduced constitutive models that relate strain to strain rate, stress, temperature, and steel composition With respect to these dependencies, they proposed and compared four different elasto-viscoplastic constitutive equations, which are all unable to consider cyclic loading phenomena like kinematic hardening or the Bauschinger effect [7]. Grain morphology, inhomogeneities, and precipitations are of highest importance for the deformation behavior of steel at elevated temperatures, as will be shown in detail later on This is why in the early 2010s, Montanuniversitaet Leoben started the development of the experimental simulation of surface defect formation under the conditions for the continuous casting of steel.
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