Thermo-mechanical modeling of snouts deformation

摘要

The snout is the last element which connects the annealing furnace with the zinc bath on Hot Dip Galvanizing line. The main role of the snout is to prevent oxygen atoms to access and damage the steel surface before entering into the zinc pot. Snout-end deformation is today the main reason of snout end-of-life. It generates air leaks, leading to defects generations as non-coated spots. ArcelorMittal R&D developed 3D thermo-mechanical models of industrial snout-ends. Models take into account the industrial snout lifetime, i.e. the successive heating and cooling phases during the snout emersions and immersions in the zinc pot. Boundary conditions were determined thanks to specific measurements at laboratory and on industrial plant. The model shows that the main origin of the snout deformation are the temperature gradients between immersed and non-immersed parts, and the dilatation generated during the snout immersion. The creeping effect appears to be negligible. During heating phase like during the cooling, strong compressive stresses appears in the snout walls leading to cracks occurrence and buckling of the snout walls. In all cases, the level and mode of deformation depend strongly on the snout design and fixation system of the snout lower part. This model has been used to define and to test the actions (snout design and/or operating procedure modifications) which limit and control the snout deformation and to evaluate their impact.