Development of the hot charging pretreatment process for micro-alloyed steel slab

Hot delivery and hot charging of casting slab play a key role in energy saving and emission reduction. The gas consumption in heating furnace is reduced by about 5–8% with the hot charging temperature increasing by 100°C. The hot charging crack is a key factor in limiting the rise of the hot charging temperature. In this paper, the formation mechanism of hot charging crack was analysed, and in order to increase the hot charging temperature and eliminate the cracks at the same time, the technology of hot charging pretreatment in the last segment of the caster for the micro-alloyed steel slab was studied. Strong water quenching on the slab surface was implemented in the last caster segment. The slab surface temperature was fast dropped from over than 900°C to below 600°C, then rose to more than 650°C before hot charging. A dense tissue layer was formed within at least the 20 mm zone from the slab surface. This technology has been successfully applied on the 5# and 6# slab continuous casters in China Shougang Jingtang. The highest hot charging temperature was 658°C and the hot charging crack of steel plate was effectively eliminated.