To improve cooling precision and to reduce variance in a mechanical property of a steel strip by supplying compressed air, in accordance with the stop of injection of a cooling water, to a nozzle communicating pipe part of a hair pin type upper part laminar header at the time of cooling a steel strip so as to instantly stop injection of a cooling water.
A cooling water 31 injected toward a table roller 9 side is introduced from a main header 15 into a chevron press body 18 of a cylinder 13 upper part through a water supply pipe 16, branch pipe 17 and supplied to an injection nozzle 19. A compressed air supply pipe 4 arranged with a compressed air injection valve 10 is arranged to the top part of the chevron press body 18, at the same time a cooling injection valve not shown in figure is stopped, the compressed air injection valve 10 is opened. By this method, the cooling water 31 filled inside the chevron press body 18 shuts off function as a continuous body, without causing siphon phenomenon, the cooling water in the nozzle 14 is fallen/stopped. Further, compressed air is not required to be high pressure, its value is roughly 0.0005Nm2/header.
UCHIMAKI SHINZO
NAKADA NAOKI
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