Thermo-mechanically Coupled Isotropic Analysis of Temperatures and Stresses in Cooling of Coils

A 2D transient thermo-mechanically coupled axi-symmetric FE model has been implemented and used to predict the temperatures and stresses under cooling of coils. The temperature trajectory as a function of geometrical position in as-coiled steel strip products is affected by several parameters as the: initial temperature inherited from upstream cooling on the Run Out Table (ROT), coil dimensions, strip surface quality, contact conditions and the surrounding environmental conditions etc. The layered structure makes the thermal conductivity anisotropic where the interfacial contact condition depends on the transient stress state caused by thermal and initial effects. The coil cooling rates are for HSLA-steel grades of importance in achieving proper final mechanical properties where too fast temperature drops ceases the precipitation hardening solely diffusional driven. Furthermore is a parameter influence study made revealing process parameter significance. The model has been validated against two full-scale bell furnace trials. A main objective with this model development work was to keep the model fast and accurate applicable on real plant situation and for process controlling.