Visco-Plastic Multi-Physics Modeling of Steel Solidification

Thermo-mechanical steel solidification models, based on highly nonlinear elastic visco-plastic constitutive laws in solid and featuring efficient and robust local implicit integration scheme, are coupled with cfd turbulent calculations in the liquid pool via enhanced latent heat method. The new multi-physics model of metal solidification is applied to calculate temperature, stress, and deformation of solidifying shell in a commercial caster with real geometry. INTRODUCTION: Many manufacturing and fabrication processes such as foundry shape casting, continuous casting and welding have common solidification phenomena. One of the most important and complex of these is continuous casting, which produces 90% of steel today. Even though the process is constantly improving, there is still a significant need to minimize defects and to maximize quality and efficiency. The difficulty of plant experiments under harsh operating conditions makes computational modeling an important tool in the design and optimization of these processes. Increased computing power and better numerical methods have enabled researchers to develop better models of many different aspects of these processes. Coupling together the different models of heat transfer, solidification distortion, stress generation and turbulent fluid flow to make accurate predictions of the entire real processes remains a challenge. PROCEDURES, RESULTS AND DISCUSSION: Inertial effects are negligible in solidification problems, so using the static mechanical equilibrium as the governing equation is appropriate. ( ) 0 x b ∇ ⋅ σ + = (1) The rate decomposition of total strain in this elastic-viscoplastic model is given by: th ie el ε ε ε ε     + + = (2) where el ie th , ,    ε ε ε are the elastic, inelastic, and thermal strain rate tensors respectively. Viscoplastic strain includes both strain-rate independent plasticity and time dependant creep. Creep is significant at the high temperatures of the solidification processes and is indistinguishable from plastic strain [Kozlowski 1992] proposed a unified formulation with the following functional form to define inelastic strain.