COOLING DEVICE, COOLING METHOD, MANUFACTURING DEVICE, AND MANUFACTURING METHOD FOR HOT-ROLLED STEEL SHEET

摘要

Provided are a cooling device for a hot-rolled steel sheet, a cooling method for a hot-rolled steel sheet, a manufacturing device for a hot-rolled steel sheet, and a manufacturing method for a hot-rolled steel sheet, which are capable of manufacturing a hot-rolled steel sheet having ultra-fine crystal grains and of increasing the usage efficiency of cooling water. The cooling device for a hot-rolled steel sheet, when an average cooling speed of the steel sheet surface present within a position equivalent of the radius of a work roll at the final stand is denoted by V1, an average cooling speed of the steel sheet surface present between the position equivalent of the radius of the work roll and the exit side of a housing post at the final stand is denoted by V2, and an average cooling speed of the steel sheet surface present between a cooling start point and the exit side of the housing post is denoted by Vm, satisfies the relationships V1 > V2 and Vm > 400 °C/s. The cooling method for a hot-rolled steel sheet uses the cooling device. The manufacturing device for a hot-rolled steel sheet includes the final stand in a hot finish rolling machine line and the cooling device. The manufacturing method for a hot-rolled steel sheet includes a step of processing, using the manufacturing device, a steel sheet rolled at the final stand in the hot finish rolling machine line.