Molten metal bath composition analysis system, molten metal bath composition analysis method, hot-dip galvanizing bath management method, and hot-dip galvanized steel sheet manufacturing method

1 . A molten metal bath composition analysis system comprising:

a laser oscillator that oscillates a laser beam;

a cylindrical probe that includes an opening end immersed in a molten metal bath, supplies an inert gas toward the opening end, and guides the laser beam to the opening end to irradiate a molten metal with the laser beam; and

a detector that detects and spectroscopically analyzes plasma emission of the molten metal caused by the irradiation with the laser beam, wherein

at least one of a position of the opening end of the cylindrical probe in the molten metal bath and an angle of the cylindrical probe with respect to a vertical direction can be controlled,

the molten metal bath composition analysis system comprises a pressure sensor that measures a pressure of the inert gas, and

at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled on a basis of the pressure of the inert gas obtained by the pressure sensor.

2 . The molten metal bath composition analysis system according to claim 1 , wherein at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled by any one or more of the following:

controlling a gauge pressure of the inert gas obtained by the pressure sensor to be within a predetermined range;

controlling a fluctuation of the pressure of the inert gas to be equal to or less than a predetermined value;

controlling the temperature of the molten metal to be equal to or higher than a predetermined temperature; and

controlling a temperature fluctuation of the molten metal to be equal to or less than a predetermined value.

3 . The molten metal bath composition analysis system according to claim 1 , wherein the molten metal contains molten zinc, and the molten metal bath is a hot-dip galvanizing bath.

4 . The molten metal bath composition analysis system according to claim 3 , comprising a pressure sensor that measures a pressure of the inert gas, wherein

at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled such that a gauge pressure of the inert gas obtained by the pressure sensor is within a range of 10 to 20 kPa.

5 . The molten metal bath composition analysis system according to claim 3 , comprising a pressure sensor that measures a pressure of the inert gas, wherein

at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled such that a fluctuation of the pressure of the inert gas obtained by the pressure sensor is 1.0 kPa or less.

6 . The molten metal bath composition analysis system according to claim 3 , comprising a temperature sensor that measures a temperature of the molten metal at the opening end, wherein

at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled such that the temperature of the molten metal measured by the temperature sensor is 440° C. or higher.

7 . The molten metal bath composition analysis system according to claim 1 , comprising a temperature sensor that measures a temperature of the molten metal at the opening end, wherein

at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled such that a fluctuation of the temperature of the molten metal measured by the temperature sensor is within 5° C.

8 . A molten metal bath composition analysis method comprising:

immersing a cylindrical probe in a molten metal bath;

supplying an inert gas to an opening end of the cylindrical probe;

guiding a laser beam to the opening end to irradiate a molten metal with the laser beam; and

detecting and spectroscopically analyzing plasma emission of the molten metal caused by the irradiation with the laser beam, wherein

a pressure of the inert gas is measured, and

at least one of a position of the opening end in the molten metal bath and an angle of the cylindrical probe with respect to a vertical direction is controlled on a basis of the pressure of the inert gas.

9 . The molten metal bath composition analysis method according to claim 8 , wherein at least one of the position of the opening end of the cylindrical probe and the angle of the cylindrical probe with respect to the vertical direction is controlled by any one or more of the following:

controlling a gauge pressure of the inert gas to be within a predetermined range;

controlling a fluctuation of the pressure of the inert gas to be equal to or less than a predetermined value;

controlling the temperature of the molten metal to be equal to or higher than a predetermined temperature; and

controlling a temperature fluctuation of the molten metal to be equal to or less than a predetermined value.

10 . The molten metal bath composition analysis method according to claim 8 , wherein the molten metal is molten zinc, and the molten metal bath is a hot-dip galvanizing bath.

11 . The molten metal bath composition analysis method according to claim 10 , wherein at least one of controlling the position of the opening end of the cylindrical probe and controlling the angle of the cylindrical probe with respect to the vertical direction is performed

such that a gauge pressure of the inert gas is within a range of 10 to 20 kPa.

12 . The molten metal bath composition analysis method according to claim 10 , wherein at least one of controlling the position of the opening end of the cylindrical probe and controlling the angle of the cylindrical probe with respect to the vertical direction is performed

such that a fluctuation of the pressure of the inert gas is within 1.0 kPa.

13 . The molten metal bath composition analysis method according to claim 10 , wherein at least one of controlling the position of the opening end of the cylindrical probe and controlling the angle of the cylindrical probe with respect to the vertical direction is performed

such that the temperature of the molten metal is 440° C. or higher.

14 . The molten metal bath composition analysis method according to claim 10 , wherein at least one of controlling the position of the opening end of the cylindrical probe and controlling the angle of the cylindrical probe with respect to the vertical direction is performed

such that a fluctuation of the temperature of the molten zinc at the opening end is within 5° C.

15 . A hot-dip galvanizing bath management method comprising:

measuring a concentration of at least one of Al and Fe in a hot-dip galvanizing bath by the molten metal bath composition analysis method according to claim 8 ; and

controlling a concentration of either of Fe and Al in the hot-dip galvanizing bath on a basis of the concentration.

16 . A hot-dip galvanized steel sheet manufacturing method comprising:

measuring a concentration of at least one of Fe and Al in a hot-dip galvanizing bath by the molten metal bath composition analysis method according to claim 8 ; and

controlling an amount of either of Fe and Al in the hot-dip galvanizing bath on a basis of the concentration.