Hot-rolled strip re-reddening temperature changing law for late ultra fast-cooling in a CSP line

Higher cooling capacity is required after laminar cooling in order to develop dual-phase (DP) steel, and late ultra-fast cooling (UFC) equipment that was installed between the laminar cooling equipment and down coiler in a CSP line was developed. The strip temperature distribution along the thickness will affect the uniformity of the microstructure and properties, so in-depth research on the temperature distribution changing law during the ultra-fast cooling process should be conducted. The strip temperature was obtained by the numerical calculation method. By comparison some conclusions were obtained: the UFC re-reddening temperature decreases with an increase in the ultra-fast cooling rate and they present a quadratic relationship. The maximum temperature deviation between the center and surface, surface and boundary layer and center and boundary layer can be increased with an increase in the ultra-fast cooling rate, and they present a quadratic relationship. The finishing delivery temperature (FDT) and medium temperature (MT) do not affect the UFC re-reddening temperature obviously when the ultra-fast cooling rate is constant. There is a boundary layer along the thickness. The position of the boundary layer will remain in 1/4 strip thickness and the ultra-fast cooling rate, FDT, MT and strip thickness do not affect it. These results will provide a referenced role for the establishment of the ultra-fast cooling process.