JPH07316760A - Device for preventing generation of dross in snout for continuous hot dip coating - Google Patents

Abstract

PURPOSE:To prevent generation of dross on a plating bath surface in a snout installed between a steel strip annealing furnace and plating metal bath of a continuous hot dip coating line. CONSTITUTION:A heater 11 and an atmosphere gas treating circuit 12 (having a suction device 13, separator 14, heater 15) are installed in the snout 10. The plating metal vapor in the snout 10 is heated by a heater 11 to prevent temp. fall and coagulation. The atmosphere gas in the snout is introduced into the circuit 12 and, after the plating metal vapor in the gas is coagulated and separated by the separator 14 (having a cooler), the atmosphere gas is heated up to the atmosphere temp. of the snout and is returned into the snout 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for suppressing and preventing the generation of dross on a plating metal bath surface in a snout in a continuous hot dip galvanizing line.

[0002]

2. Description of the Related Art A steel strip S supplied to a continuous hot dip coating line is subjected to a predetermined annealing treatment in a reduction annealing furnace F as shown in FIG. It is introduced into the plating bath M through the inside of the snout 10 which is a cylindrical body installed between the and, and is pulled up above the bath through the sink roll R in the bath. Snout 10 is an annealing furnace F
The steel strip S derived from (1) is cut off from the atmosphere and sent into the plating bath M in a clean surface state. The inside of the snout 10 is maintained in the same reducing atmosphere as the atmosphere in the annealing furnace F.

From the bath surface of the hot-dip galvanizing bath M, vapor V of the metal to be plated (in hot dip galvanizing, a vapor pressure of approximately 0.3 mmHg at a temperature of approximately 470 ° C.) is generated, and the metal vapor is Snout 1
It comes into contact with the inner wall surface of No. 0, becomes ash A, and adheres to the inner wall surface of the snout. Since the bath surface level of the hot dip plating bath slightly fluctuates (for example, ± 20 mm) during the plating operation process, the ash A of the plated metal adhered to the inner wall surface of the snout melts due to contact when the plating bath surface rises. It becomes dross D and floats on the bath surface. The ash A adhered to a height position where it does not come into contact with the plating bath also peels off from the wall surface and falls onto the hot dip bath when the deposited thickness increases, causing dross D.
Becomes The dross D generated / floating on the surface of the hot-dip plating bath in the snout 10 adheres to the surface of the steel plate S entering the plating bath, which hinders the formation of a uniform plating film on the surface of the steel strip, resulting in a quality defect of the steel plate. Will cause.

As measures against this, (a) the drainage work inside the snout 10 is carried out regularly, and (b) the snout 1
A gas injection nozzle is installed at 0, and the dross D is pushed toward the inner wall surface of the snout with an injection flow of an inert gas (nitrogen gas, etc.) to prevent the dross D from contacting the steel strip surface. Forced cooling is externally applied to the plating metal vapor generated from the hot dip plating bath to condense it immediately above the bath surface and drop it into the plating bath (JP-A-63-277746).
(D) As shown in FIG. 5, the dross suction duct 6 opening to the wall surface of the snout 10 is installed at the bath surface height position of the hot dip plating bath M, and the generated dross D is sucked and discharged at appropriate times. Various methods such as JP-A-5-140709 have been proposed, and some of them have been put to practical use.

[0005]

As described above, various methods are known as a countermeasure for dross on the plating metal bath surface in the snout 10, but the method (a) is performed every time the dross removing work is performed. , The line operation must be interrupted and the productivity reduced due to it, and the dross removal work
After the snout 10 is pulled up onto the bath and the inside of the snout is changed to the atmosphere, dross is removed, and after the removal work is completed,
The complicated work process of replacing the inside of the snout with a reducing atmosphere is required again. The method (b) is relatively effective as a measure when the amount of dross produced is relatively small, but not only requires a large amount of inert gas consumption,
As the amount of dross produced increases, the anti-adhesion effect decreases rapidly. In the method of (C), the effect of the forced cooling action of condensing the plating metal vapor is added to the steel strip S passing through the inside of the snout 10, which causes a problem such as deterioration of the plating property on the surface of the steel strip. The method (d) requires a complicated device and a complicated processing operation for sucking and discharging the dross and processing the discharged dross (the molten plated metal also flows out together with the dross), and a great burden is imposed on the device maintenance. Will be forced to. The present invention provides a novel dross generation preventing device for solving the above-mentioned problems relating to dross generation on the plating metal bath surface in a snout.

[0006]

According to the present invention, a steel strip derived from a continuous annealing furnace is installed between an exit side of the annealing furnace F and a hot dip metal bath (hereinafter "plating bath") M. A device for preventing dross from being generated on the plating bath surface in the snout 10 in a continuous hot dip plating line which is introduced into the plating bath M by passing through the snout 10, and is generated from the plating bath in the snout 10. The heater 11 provided on the wall surface of the snout immediately above the plating bath for heating the plating metal vapor to be used, and the atmosphere gas in the snout containing the plating metal vapor are derived from the snout to remove the plating metal vapor, and then the snout 10, a suction device 13 for returning the gas to the inside of the separator 10, a separator 14 for condensing and separating the plating metal vapor in the atmosphere gas, and a snout for the atmosphere gas passing through the separator 14. Heater 1 for heating warm to ambient temperature
It is characterized by having an atmospheric gas processing circuit 12 including 5.

[0007]

The plating metal vapor evaporated from the hot dip bath M in the snout 10 is the heater 1 provided on the wall surface of the snout.
The heating effect of No. 1 prevents the temperature drop and condensation from being suppressed, and the atmosphere gas containing the plating metal vapor is stripped of the plating metal vapor in the atmosphere gas processing circuit 12. Due to the heating effect of the plating metal vapor in the snout and the atmosphere gas cleaning effect outside the snout, the inside of the snout is kept in an atmosphere in which the amount of the plating metal vapor mixed is small. Therefore, the generation and deposition of ash on the inner wall of the snout,
The generation of dross due to the peeling is reduced, and the plating metal bath in the snout 10 is kept in a bath surface state with less floating dross.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing embodiments. FIG. 1 is a front view schematically showing the device of the present invention, and FIG. 2 is an explanatory view showing flows of a snout atmosphere gas and a plating metal vapor in the device of the present invention. The snout 10 is provided with a heater 11 for heating the plating metal vapor in the snout, and an atmospheric gas treatment circuit 12 for purifying the atmospheric gas in the snout (separating and removing the plating metal vapor).

The heater 11 in the snout 10 has a function of heating the plating metal vapor generated from the plating metal bath M and preventing the vapor from being cooled and condensed. The heating temperature is
Above the boiling point of the plating metal (for example, in the case of zinc plating,
It is set to about 450 to 500 ° C.). As the heater 11, for example, a resistance heating element called a ribbon heater formed in a sheet shape or the like can be applied. Heater 11
Are installed on the outer surface of the snout 10, if desired.
For example, as shown in FIG. 3, by forming a jacket 11 ₁ surrounding the outer surface of the snout 10 and feeding a heating medium, for example, a combustion frame or the like through the supply / discharge port 11 ₂ to the jacket 11. Alternatively, the plating metal vapor inside may be heated through the wall surface of the snout 10 to prevent the temperature from falling and the condensation.

In the plating metal bath M, the consumption of the plating metal due to the passage of the steel plate S in the bath and the replenishment to cope with the consumption are carried out continuously or intermittently. With variations (eg ± 20 mm). When a ribbon heater or the like is applied, it may be installed at a height position that allows for vertical movement of the bath surface so as not to cause damage due to contact with the bath. In addition, the snout 10 is the upper main body 10
₁ and a snorkel 10 ₂ at the lower end which is detachably attached to this and is immersed in the plating bath (see FIG. 4).
Since the heater 11 is installed in the snorkel 10 ₂ , the maintenance of the heater 11 can be performed by removing the snorkel 10 ₂ from the main body 10 ₁ .

The atmosphere gas processing circuit 12 includes a suction device 13
(For example, a blower such as a turbo blower), the separator 14,
And the heater 15 and the starting end 12 of the pipeline.₁And the end
End 12₂Is located above the heater 11 and is a snout 1
It is open at 0. The separator 14 is a cooling device (for example,
Water cooling piping system), and the cooling action of the
Gas is generated by condensing the plating metal vapor in the atmosphere gas
Separated from the inside, the heater 15 (resistance heating element etc.)
The ambient gas cooled by passing through the motor 14 is
It has the role of heating up to the ambient temperature in 10. Suction
The device 13 allows the start 12 of the conduit₁Out of snout 10
The atmosphere gas discharged to the
The metal vapor is separated and then heated by heater 15 to a predetermined temperature.
Re-heated to the end of the pipe 12₂From snout 1
Returned within 0. Plating accumulated in the separator 14
The aggregated particles of the metal are discharged from the discharge port 14 at appropriate times. ₁Discharged from and collected
It Separating the plating metal vapor by the separator 14
Needless to say, the required cooling temperature depends on the grade of the hot-dip galvanized metal.
However, in the case of Zn plating, the temperature should be about 300 ° C or less and
In the case of soaking, the temperature may be about 500 ° C. or lower. Also, Suna
Reheat the atmospheric gas returned to the heater 10 with the heater 15.
The purpose is to maintain the atmosphere inside the snout 10 at a predetermined temperature.
(The temperature of the steel plate surface is lowered and the plating
This is to prevent problems such as deterioration of
The heating temperature is about 400 to 500 ° C.

The cause of the dross D floating on the plating bath surface in the snout 10 is due to the reaction between the steel strip S and the plating metal in addition to the one caused by the ash of the plating metal vapor adhering to the wall surface of the snout. There is formation of intermetallic compounds. For example, in hot dip galvanizing (the plating metal bath usually contains about 0.1 to 0.3% Al), Fe-Zn
A compound and an Fe-Al compound are generated, and an Fe-Al compound having a small specific gravity among them is floated to become a dross. However, the generated amount is small, most of the dross inside the snout is derived from the ash of the plating metal vapor, and the dross generated amount is about the same as the conventional ash generation preventing effect of the snout wall surface according to the present invention. It can be drastically reduced to about 20 to 30%. Therefore, it is possible to almost avoid the adverse effect of dross on the plating quality in the continuous plating operation, and to more reliably prevent the dross adhesion on the surface of the steel strip, as an auxiliary means thereof.
For example, since the amount of floating dross on the bath surface is extremely small even when a conventionally known operation of blowing an inert gas is added,
The burden of the spraying work is remarkably lighter than in the conventional case, and the consumption of the inert gas can be reduced to about 1/10 or less of that in the conventional case.

[0013]

EFFECT OF THE INVENTION The device of the present invention is to prevent the dross generation from being suppressed in advance, unlike the conventional device for excluding the generated dross after the fact, and by reducing the floating dross in the snout, The adhesion of dross on the strip surface is suppressed and prevented, and the plating quality is improved and stabilized. The operation of the apparatus of the present invention can be carried out continuously or intermittently while the continuous hot dip galvanizing line is operating, and does not hinder the line operation. Also, when the amount of dross on the bath surface increases to some extent, it is necessary to perform dross discharge work, but the rate of increase in dross generation is significantly slowed, so the frequency of discharge work is greatly reduced. . Further, there is no waste of the molten plating metal bath like the conventional method in which floating dross is discharged outside the snout together with the molten plating metal, and a complicated process for separately collecting the discharged plating metal and dross. It does not require operation or complicated equipment, has less burden on equipment maintenance and is highly practical.

[Brief description of drawings]

FIG. 1 is a front view schematically showing an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view showing the flows of an atmosphere gas in a snout and a plating metal vapor in the device of the present invention.

FIG. 3 is a diagram showing another example of the installation mode of the plating metal vapor heating heater in the snout of the device of the present invention.

FIG. 4 is a diagram showing a line arrangement of a continuous hot-dip metal plating apparatus.

FIG. 5 is a diagram schematically showing a conventional dross eliminating device.

[Explanation of symbols]

10: Snout, 10 ₁ : Snout body part, 10 ₂ : Snout snorkel, 11: Heater for plating metal vapor, 12: Snout atmosphere gas treatment circuit, 13: Suction device, 14: Separator, 15: Gas reheating heater , A: Ash, D: Dross, F: Steel strip continuous annealing furnace, M: Plating metal bath, R: Sink roll, S: Steel strip to be plated, V: Plating metal vapor.

Claims (1)

[Claims] 1. A steel strip derived from a continuous annealing furnace is provided with a hot-dip metal bath (hereinafter “plating bath”) on the outlet side of the annealing furnace F.
A device for preventing dross from being generated on the plating bath surface in the snout 10 in a continuous hot dip plating line that is introduced into the plating bath M by passing through the snout 10 installed between the snout and the snout. A heater 11 provided on the wall surface of the snout directly above the plating bath for heating the plating metal vapor generated from the plating bath in 10 and an atmosphere gas in the snout containing the plating metal vapor are derived from the snout. After removing the steam, to return it to the snout 10,
An atmosphere gas treatment circuit 12 having a suction device 13, a separator 14 for condensing and separating the plating metal vapor in the atmosphere gas, and a heater 15 for heating and raising the atmosphere gas passing through the separator 14 to the atmosphere temperature in the snout. A device for preventing dross generation in snouts in continuous hot dip plating.