Speaker
Description
Development of Ultra High Strength Steel (UHSS) is a hot topic in recent years as demand for light weight automobile and machinery steels increases drastically. To understand the inclusion behaviors in a high Ti UHSS grade during casting and slab cooling, automated inclusion analysis tool was utilized to investigate the TiN precipitates distribution and their heterogeneous growth on oxide inclusions in conventional thick slab from surface to centerline. Precipitation size, number density and area fraction of TiN as well as complex heterogeneous TiN precipitates on oxide inclusions are studied at surface chill zone, chill to columnar transition zone, established columnar zone and centerline equiaxed zone. Thermodynamic modeling was made to understand the TiN precipitation under equilibrium condition in slabs at various temperatures during cooling. Kinetic modeling was made based on local solidification process from slab surface to centerline during casting and slab cooling. Attempt is made to utilize the TiN distribution from surface to slab center to back-calculate the segregation level inside a slab.