Method and device for controlling amount of hot dip galvanization adhesion

A method for controlling an amount of hot dip galvanization adhesion, the method comprises the steps of:

• spraying gas supplied from a gas supply device onto a steel plate to which molten metal adheres, by using a first nozzle and a second nozzle which communicate with the gas supply device via a duct;
• controlling an actual gas pressure P1a′ of the first nozzle by using a first a-valve and controlling an actual gas pressure P1b′ of the second nozzle by using a first b-valve;
• with the duct branching in two directions and having a first branched portion communicating with the first nozzle and the second nozzle and a second branched portion being open, controlling a gas flow rate Q2 of the gas diffused from the second branched portion of the duct to an outside of a system;
• setting a set gas pressure P1a of the first nozzle;
• setting a set gas pressure P1b of the second nozzle;
• setting a valve opening degree MV1a of the first a-valve such that the gas pressure P1a′ becomes equal to the set gas pressure P1a, setting a valve opening degree MV1b of the first b-valve such that the gas pressure P1b′ becomes equal to the set gas pressure P1b, and setting a valve opening degree MV2 of the second valve such that the total gas flow rate QT is constant;
• calculating a valve opening degree correction value C1a from a difference between the set gas pressure P1a and the gas pressure P1a′ and performing control to add the valve opening degree correction value C1a to the valve opening degree MV1a;
• and
• calculating a valve opening degree correction value C1b from a difference between a pressure difference ΔP and a pressure difference ΔP′ and performing control to add the valve opening degree correction value C1b to the valve opening degree MV1b, the pressure difference ΔP being a difference between the set gas pressure P1a and the set gas pressure P1b, the pressure difference ΔP′ being a difference between the gas pressure P1a′ and the gas pressure P1b′.