GAS-WATER COOLING METHOD OF CONTINUOUS HEAT TREATMENT INSTALLATION

PURPOSE:To improve furnace pressure control and to perform gas-water cooling in an optimum pattern by determining the number of nozzle stages and cooling water flow according to a target cooling condition, supplying the water at a low flow rate at every stage in the stage of starting cooling and increasing the flow rate of the water over the entire part at the point of the time when the water is supplied to the prescribed number of the stages. CONSTITUTION:The inlet side and outlet side of a gas-water cooling chamber 2 are connected respectively through passages to an adjacent soaking chamber and overaging chamber. A steel strip 1 is guided by a hearth roll 15 to travel in said cooling chamber. A cooling medium mixture composed of cooling water and cooling gas is ejected from cooling nozzles 3 disposed in plural stages along the steel strip 1 toward the strip 1 so that gas-water cooling is accomplished. The nozzle headers in the respective stages are opened at a prescribed gradient at a primary opening degree (about