| 摘要 |
PURPOSE:To control the strength of a steel sheet with high accuracy without decreasing the productivity thereof by controlling the accelerated cooling by the target flow rate of cooling liquid and cooling time determined by using the difference between the quantity of increasing strength to be determined from final strength and the target value thereof, the differential coefft. of the quantity of increasing strength with respect to the flow rate of cooling water and cooling time, etc. CONSTITUTION:The quantity Tu of increasing strength is determined by the equation I (To is air cooled strength) from the final strength T* obtd. by accelerated cooling in the titled method which cools acceleratively a hot-rolled steel sheet by injecting the cooling liquid thereto and increasing the strength of the steel sheet. The target quantity Tu* for increasing strength necessary for making the strength T* coincident with the target final strength Ta* is therefore expressed by the equation II. The quantity Tu is indicated as the function of the flow rate W of cooling liquid and accelerated cooling time t. The target flow rate of the cooling liquid and target accelerated cooling time at and for which the respective weighted sums or weighted square sums of the differential coeffts. with respect to each of the difference between the quantity Tu and Tu*, the flow rate W of the quantity Tu and the time as well as the time are min. are determined. The accelerated cooling is controlled at and for such flow rate. |
