JP2000265254A - Device for removing foreign matter in continuous hot- dipping metal coating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the development of oxidized dross in a device for removing foreign matter of the dross, or the like, in a snout by utilizing the action of a gas lift pump. SOLUTION: In a hot dipping bath vessel 1, a U-shape communicating tube 6 is disposed so that the one end part 6a thereof positions near both end parts in the width direction of a steel strip S in the snout 3 and the other end part 6b positions near both corner parts at the back side of the snout 3 in the hot- dipping bath vessel 1, to dispose this tube in the molten zinc of the hot-dipping bath vessel 1. In the other end part 6b, a gas supplying pipe 7 is inserted from the upper part and the lower end part (the front end part) of this gas supplying pipe 7 reaches near the bottom portion (horizontal portion) of the U-shape communicating tube 6. Inert gas is supplied into the bottom portion in the perpendicular part at the other end side 6b of the communicating tube 6 and this supplied gas can be made to exhaust from the other end part 6b. The other end part 6b of each communicating tube 6 is projected upward from the bath surface of the molten zinc. The projecting height is made to in the range of 20-100 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter removing apparatus for a continuous hot-dip metal plating facility, and more particularly to an apparatus for suppressing the occurrence of defects due to foreign matter such as dross.

[0002]

2. Description of the Related Art In continuous hot-dip galvanizing, for example, as continuous hot-dip galvanizing, a steel strip guided from an annealing furnace through a snout to a plating bath is turned upward by a sink roll in the bath, After the warp is corrected by the support roll, the roll is generally lifted out of the bath and adjusted to a predetermined plating adhesion amount by a gas wiping nozzle.

In such continuous galvanizing,
Foreign matter called dross or foreign matter called ash may adhere to the steel strip in the bathtub and cause a quality defect.
The dross is Fe ₂ Al ₅ formed by the reaction of Fe eluted from the steel strip into the zinc bath and Al added to the zinc bath by 0.1 to 0.2% to improve plating adhesion and the like. Pressing a steel plate to which a large dross adheres may cause a defect such as a pressing scratch or damage to a mold. Also,
Ash is a solid of zinc fume, and when it adheres to a steel strip in a snout, it is blown off at the time of gas wiping, causing a problem that plating of the portion becomes insufficient.

Foreign materials such as dross and ash often adhere to the steel strip on the inner surface of the snout where the steel strip first enters the zinc bath, and as the steel strip advances into the zinc bath. The dross and the like floating in the zinc bath are drawn into the snout by the generated flow, and the dross and the like easily accumulate in the snout. Regarding such problems, various techniques have been conventionally proposed. For example, a method for providing a pump for molten zinc, a method of sucking dross on the bath surface in the snout out of the snout together with the molten zinc (see Japanese Patent Application Laid-Open No. H3-140448, the first prior art), a method of supplying molten zinc in the snout and There is a method in which a suction nozzle is installed to face the suction nozzle to create a flow in the snout toward the suction nozzle to remove dross (see Japanese Patent Application Laid-Open No. Hei 8-269659, second prior art).

Other conventional techniques utilizing the function of a gas lift pump include a technique disclosed in Japanese Patent Application Laid-Open No. 3-31460 (third conventional technique) and a technique disclosed in Japanese Patent Application Laid-Open No. 4 prior art). That is, FeZn _7, which is a reaction between Zn and Fe, which is called bottom dross, settles and accumulates at the bottom of the plating bath. Such bottom dross is rolled up by the progress of the steel strip and the rotation of the sink roll, The bottom dross is sucked up and removed by the action of a gas lift pump to cause the same defects as described above.

[0006]

However, in the first prior art and the second prior art, the service life of the pump for molten zinc is short (3 to 4) due to corrosion and wear by zinc.
Months), the repair cost is high, and the pump for hot-dip zinc is generally large, and it is difficult to apply it to plating equipment with a small space allowance. In particular, in the second prior art, such a problem is remarkable because two pumps are required.

On the other hand, the third prior art and the fourth prior art have an advantage that the dross can be easily sucked out as compared with the first prior art and the second prior art. There is a problem that zinc oxide is easily generated. In other words, since zinc is a metal that is easily oxidized, a zinc oxide film is always formed on the bath surface of the molten zinc. This can prevent the bond between zinc and oxygen. However, the gas discharged from the end of the tube for the gas lift pump undulates the bath surface, the oxide film is broken, and the zinc bath comes into contact with air, so that zinc oxide (dross) further increases.

The present invention has been made in view of such unresolved problems of the prior art, and can remove foreign substances such as dross by utilizing the action of a gas lift pump.
Moreover, it is an object of the present invention to provide a foreign matter removing apparatus for a continuous molten metal plating facility which can suppress a vicious cycle in which dross is further generated due to stirring by a gas discharged from an end of a pipe.

[0009]

In order to achieve the above object, the invention according to claim 1 is to provide a steel strip continuously through a snout having a tip portion inserted into a molten metal of a plating bath. In the foreign-matter removing apparatus of the continuous molten metal plating equipment carried in, one end is located on the bath surface of the molten metal in the snout and the other end is located on the bath surface of the molten metal outside the snout. Disposing a U-shaped communication pipe in the molten metal, providing gas supply means for supplying gas into the communication pipe so as to be discharged from the other end side,
Then, the other end of the communication pipe protruded above the bath surface of the molten metal.

According to a second aspect of the present invention, in the foreign matter removing apparatus of the continuous molten metal plating equipment according to the first aspect of the present invention, the other end of the communication pipe is set to be 20 mm or more above the molten metal bath surface. It protruded in the range of 100 mm. Further, the invention according to claim 3 is the foreign matter removing device for a continuous molten metal plating facility according to the invention according to claim 1 or 2, wherein a float is attached to the one end and the other end of the communication pipe so that the melting is performed. It is possible to follow the fluctuation of metal bath surface.

According to a fourth aspect of the present invention, in the foreign matter removing apparatus of the continuous molten metal plating equipment according to the first to third aspects, the molten metal is provided around the other end of the communication pipe. An enclosure was provided so that the lower part could be immersed.
In order to achieve the above object, an invention according to claim 5 is a continuous molten metal plating equipment for continuously carrying a steel strip into the molten metal through a snout having a tip portion inserted into the molten metal in a plating bath. In a foreign matter removing device that is used for sucking out foreign matter by using the function of a gas lift pump, the foreign matter discharge side end of a pipe for sucking out the foreign matter is placed above the molten metal bath surface. Protruded.

According to a sixth aspect of the present invention, in the foreign matter removing apparatus of the continuous molten metal plating equipment according to the fifth aspect of the present invention, the foreign matter discharge side end of the pipe is connected to the molten metal bath surface. It protruded upward in the range of 20 mm to 100 mm. Further, the invention according to claim 7 is the above-described claim 1 to claim 1.
In the foreign matter removing apparatus for a continuous molten metal plating facility according to the fourth aspect, the gas supply means includes a gas supply pipe inserted into the other end side pipe of the communication pipe, and an inert gas supplied to the gas supply pipe. A gas supply source, and a diameter (A2) of the gas supply pipe with respect to a diameter (A1) of the other end side pipe.
(A2 / A1) was set to 0.12 or more.

The invention according to claim 8 is the invention according to claim 4, wherein in the foreign matter removing apparatus of the continuous molten metal plating facility, an inert gas is introduced above the bath surface in the enclosure. Oxygen was prevented from touching the bath surface in the enclosure.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show a first embodiment of the present invention, in which the present invention is applied to a continuous hot-dip galvanizing apparatus. FIG. 1 is a side view showing the configuration of the plating bath 1, and FIG.
FIG. 3 is an enlarged view of a main part of FIG.

First, the construction will be described. In the plating bath 1, molten zinc is accommodated, and a sink roll 2 is
Is disposed, and the steel strip S to be plated is carried into the plating bath 1 from an obliquely upper side through the snout 3, and its traveling direction is changed by the sink roll 2 to move right above. After the warp is corrected by the support roll 4, it is carried out of the bathtub, the amount of adhesion is adjusted by the gas wiping nozzle 5, and further conveyed upward.

In the plating bath 1, two U-shaped communication tubes 6 are provided. As shown in FIG. 2, one end 6a of each of the communication pipes 6 is located in the snout 3 at a position close to each of both ends in the width direction of the steel strip S, and the other end 6b is outside the snout 3. And a position that does not hinder the movement of the steel strip S (in this case, the plating bath 1
(In the vicinity of both corners on the back side of the snout 3) in the molten zinc of the plating bath 1.

As shown in an enlarged view in FIG. 3, one end 6a of each communication pipe 6 is cut off obliquely, so that even if the molten zinc bath surface slightly fluctuates, it floats on the bath surface. Foreign matter such as dross can be sucked. Further, in order to make it easy to suck in foreign matter near the steel strip S, the opening part of the one end 6a which is cut off obliquely faces the steel strip S side in the snout 3.

On the other hand, a gas supply pipe 7 is inserted into the other end 6b of each communication pipe 6 from above, and the lower end (tip) of the gas supply pipe 7 is connected to the U-shaped communication pipe 6. It has reached the vicinity of the bottom (horizontal part). The other end (not shown) of the gas supply pipe 7 is connected to a supply source of N ₂ gas as an inert gas. With such a configuration, the bottom of the vertical portion on the other end 6b side of the communication pipe 6 has: The N ₂ gas is supplied, and the supplied N ₂ gas can be discharged from the other end 6b. Gas supply means is constituted by the gas supply pipe 7 and the supply source.

The other end 6b of each communication pipe 6 protrudes above the molten zinc bath surface. Its protruding height H
₁ is in the range of 20 mm to 100 mm. Further, an enclosure 8 is provided so as to surround the other end 6 b of each communication pipe 6. The enclosure 8 is a cylindrical member having a diameter of about 500 mm with upper and lower ends opened. The upper part is located above the bath surface, and the lower part is immersed in the molten zinc. Height H ₂ of the part is immersed into the molten zinc enclosure 8 is equal to or greater than 300 mm, protrusion height protruding above the bath surface of the enclosure 8 H ₃
Is about 100 mm.

Next, the operation of this embodiment will be described. That is, when the steel strip S is carried into the molten zinc of the plating bath 1 through the snout 3, the steel strip S passes through the tip of the snout 3, rotates around the sink roll 2, and changes the traveling direction. It moves right above and is carried out of the plating bath 1. On the other hand, by operating a gas supply source (not shown),
N ₂ gas is fed into the gas supply pipe 7. Then, N ₂ gas from the tip of the gas supply pipe 7 is supplied to the communicating tube 6, the N ₂ gas is discharged to the atmosphere from the other end 6b side up the vertical part of the communicating tubes 6. At this time, the other end 6b of the communication pipe 6
In the vertical portion on the side, molten zinc and N ₂ gas are mixed and the apparent specific gravity becomes smaller than the specific gravity of the molten zinc, and the specific gravity difference causes the one end 6a side to the other end 6b.
There is a flow of molten zinc toward the side. That is, the function of the gas lift pump is obtained.

Then, foreign matters such as dross and ash floating in the snout 3 flow together with the molten zinc flowing in the communication pipe 6 by the gas lift pump, and the other end 6b
Discharged from the side. At this time, the mixture of the N ₂ gas and the molten zinc overflows from the other end 6b, but in this embodiment, the other end 6b is projected upward from the bath surface of the molten zinc by a height H _1. Therefore, disturbance of the bath surface due to the overflowing mixture can be minimized, and generation of oxidized dross can be suppressed. That is, according to the experiment conducted by the present inventors, when the other end 6b is located below the bath surface, the disturbance near the bath surface due to the discharged N ₂ gas is the most intense, and the amount of oxidized dross is large. It turned out to happen. Moreover, too high a protrusion height H _1, turn, intensifies zinc flow to fall into the bath surface along the communicating pipe 6 overflows from the other end 6b, when the zinc flow enters the bath It was also confirmed that a large amount of air was entrained and rather large amounts of oxidized dross were generated. Furthermore, if the communicating pipe 6 protruding above the bath surface is too long, zinc tends to solidify and adhere to the discharged portion, and there is a problem that the work for removing the zinc is troublesome. From the above, the protruding height H ₁ is obtained by determining that it is appropriate in the range of 20Mm～100mm.

Foreign matter such as dross discharged from the other end 6b floats on the bath surface around the other end 6b. In the present embodiment, since the enclosure 8 is provided, This prevents foreign substances from spreading into the plating bath 1 and imposing an extra burden on the collection. Further, since the enclosure 8 covers both the upper side and the lower side of the bath surface, it also helps to prevent the bath surface from waving due to the molten zinc flow overflowing from the other end 6b and to reduce the plating quality. According to an experiment performed by the present inventors, the height H ₂ is set to be 300 mm or more, and the height H ₃ is set to 100 mm or more.
It has been confirmed that a value of about mm is appropriate in terms of workability and effects.

According to the present embodiment, since the foreign matter such as dross is recovered by using the function of the gas lift pump, the space cost is reduced as compared with the case where the molten zinc pump is used. In addition, since the other end 6b of the communication pipe 6 protrudes above the bath surface to suppress the generation of oxidized dross, the yield of molten zinc deteriorates. There is also an advantage that can be suppressed.

FIG. 4 is a diagram showing a second embodiment of the present invention. Since the overall configuration is the same as that of the first embodiment, its illustration and description are omitted, and only different points will be described. That is, in the present embodiment, the float 10 is attached to each of the one end portion 6a and the other end portion 6b of the communication pipe 6, and thereby, both the one end portion 6a and the other end portion 6b are connected to the molten zinc bath surface. We can follow the fluctuation. More specifically, a horizontal position between a bracket or the like for supporting the communication tube 6 in the plating bath 1 and the communication tube 6 is restricted, but a relative movement is possible in the up-down direction. Moves up and down according to the vertical movement of the bath surface,
Accordingly, both the one end 6a and the other end 6b can be moved up and down.

The float 10 may be, for example, a box-shaped member made of a metal having corrosion resistance to molten zinc and having an open top, a metal mass having a specific gravity lower than that of molten zinc and having corrosion resistance to molten zinc, or a ceramic. And so on. In other words, since the width of the bath surface fluctuation of the molten zinc is usually about 40 mm, depending on the size of the oblique opening of the one end 6a, there may be situations where dross floating on the bath surface cannot be sucked. When the end 6b is projected 20 mm above the bath surface, the end 6b may sink below the bath surface. However, if it is possible to follow the bath surface fluctuation as in the present embodiment, the one end 6a In addition, the relationship between the other end 6b and the bath surface can always be maintained in an appropriate state, and foreign substances in the snout 3 can be more efficiently removed.

FIG. 5 is a diagram showing a third embodiment of the present invention. This embodiment is the same as the first embodiment, except that the upper side of the cylindrical enclosure 8 is closed by the lid member 9. The lid 9 is a cylindrical body slightly larger in diameter than the enclosure 8, and its upper end is closed and its lower end is opened. The peripheral surface of the lid 9, inlet pipe 9a of the N ₂ gas is an inert gas is provided. This pipe 9a is made of N ₂
Connected to a gas supply. A through hole is provided in the upper end face of the lid 9 that is closed, through which the gas supply pipe 7 inserted into the other end 6 b of the communication pipe 6 passes. The upper end surface of the lid 9 is disposed above the upper end of the enclosure 8, and the lower part of the lid 9 is immersed in the molten zinc outside the enclosure 8.

[0027] Thus, if the N ₂ gas is supplied to the pipe 9a from N ₂ gas supply source, is introduced N ₂ gas in the lid member 9, above the bath surface of the enclosure 8 are of N ₂ gas atmosphere . This prevents air (oxygen) from coming into contact with the bath surface in the enclosure 8, so that the effect of suppressing the generation of oxidized dross is higher than in the first embodiment. The communication pipe 6
If the diameter of the gas supply pipe 7 inserted into the other end 6b is too small, the lower end of the gas supply pipe 7 may be blocked by dross sucked and transferred from the bath surface in the snout. For example, 1-2
It is conceivable that the lower end of the gas supply pipe 7 is closed in a week and the flow of the molten zinc in the communication pipe 6 stops. According to experiments conducted by the present inventors in this regard, the communication pipe 6
The ratio (A2 / A1) of the diameter (A2) of the gas supply pipe 7 to the diameter (A1) of the pipe 60 on the other end 6b side is 0.12 or more, preferably 0.13 or more, more preferably 0.19 or more.
It was confirmed that dross in the snout could be stably sucked by the above.

FIG. 6 shows that the diameter (A1) of the pipe 60 is 80 mm.
6 is a graph showing the relationship between the pipe diameter ratio (A2 / A1) and the flow rate of molten zinc in the communication pipe 6 when the diameter (A2) of the gas supply pipe 7 is changed while keeping the pressure constant. Here, an experiment was started by introducing N ₂ gas into the gas supply pipe 7 so that the flow rate of the molten zinc was 70 liters / minute, and the flow rate after 8 days was examined. As can be seen from this graph, the larger the pipe diameter ratio (A2 / A1), the smaller the decrease in the flow rate of the molten zinc, and especially when it is 0.19 or more, the flow rate of the molten zinc does not decrease even after 8 days. .

However, if this pipe diameter ratio (A2 / A1) exceeds 0.5, the gap between the two pipes becomes too narrow, and violent discharge occurs at the other end 6b of the communication pipe 6, Since the disturbance of the bath surface may be promoted, it is preferable to set the upper limit of the pipe diameter ratio (A2 / A1) to 0.5. FIG. 7 is a diagram showing a fourth embodiment of the present invention.
The present embodiment is the same as the first embodiment except that instead of the cylindrical enclosure 8 whose upper and lower ends are opened, an enclosure 80 whose upper end is closed is used. .

The enclosure 80 has an upper end closed and a lower end open.
The lower part of the cylindrical body which is opened is the enclosure of FIG.
It is immersed in the molten zinc to the same depth as 8. Also,
The upper end face of the enclosure 80 is closed at the other end of the communication pipe 6.
6b is disposed above the upper end. Of this enclosure 80
On the peripheral surface, a position above the upper end of the communication pipe 6 is inactive.
N which is a neutral gas_TwoA gas introduction pipe 80a is provided.
This pipe 80a is N _TwoConnected to a gas supply.
The other end of the communication pipe 6 is provided on the closed upper end face of the enclosure 80.
6b is provided with a through hole through which the gas supply pipe 7 inserted
is there.

[0031] Thus, if the N ₂ gas is supplied from the N ₂ gas supply source to the pipe 80a, is introduced N ₂ gas within the enclosure 80, above the bath surface in the enclosure 80 is N ₂ gas atmosphere. As a result, air (oxygen) is added to the bath surface in the enclosure 80.
Is not touched, so that compared to the first embodiment,
The effect of suppressing the generation of oxidized dross increases.

[0032]

[Example] The maximum sheet width is 1800 at the temperature of molten zinc of 465 ° C.
The above-mentioned equipment for galvanizing steel strip S
The same configuration as that of the embodiment is applied. The other conditions are as follows: the communication pipe 6 constituting the gas lift pump is a pipe having an inner diameter of 80 mm; the gas supply pipe 7 is an inner diameter of 10 mm;
The flow rate of the N ₂ gas was 5 to 30 liter / min. The enclosure 8 has a diameter of about 500 mm and H ₂ of 5
00mm, H ₃ was 100mm.

After operating continuously for about 10 days under the above conditions, there was no quality defect due to dross or ash in the snout 3. When the deterioration of zinc yield due to the increase in oxidized dross was also evaluated, the effect was at a negligible level.

[0034]

As described above, according to the present invention,
Since the end of the pipe that discharges foreign matter such as dross is made to protrude above the bath surface by the action of the gas lift pump, it is possible to suppress the generation of oxidized dross and to suppress the deterioration of the yield of the molten metal. In particular, according to the third aspect of the invention, the effect of the present invention is more remarkable because the relation between the end of the pipe for discharging foreign substances such as dross and the bath surface can be maintained in an optimal state by the action of the gas lift pump. become.

Further, according to the invention of claim 4, there is also an effect that it is possible to prevent the bath surface from waving and the plating quality from being lowered. In the invention according to claim 7, the effect of suppressing the generation of oxidized dross is further enhanced. Further, according to the invention of claim 8, there is an effect that dross in the snout can be stably sucked.

[Brief description of the drawings]

FIG. 1 is a side view showing an overall configuration of a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is an enlarged view of a main part of the first embodiment.

FIG. 4 is a diagram showing a main part of a second embodiment of the present invention.

FIG. 5 is a diagram showing a main part of a third embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a pipe diameter ratio (A2 / A1) and a flow rate of molten zinc in a communication pipe.

FIG. 7 is a diagram showing a main part of a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating bath 2 Sink roll 3 Snout 6 Communication pipe 6a One end 6b The other end (end on the foreign matter discharge side) 7 Gas supply pipe 8 Enclosure 80 Enclosure 80a Inert gas introduction pipe 9 Lid 9a Inert gas introduction Piping for float 10

Continued on the front page (72) Inventor Hiroshi Kuramoto 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. None) Inside of Mizushima Works, Kawasaki Steel Corporation (72) Inventor Kazuhiro Abotani 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. AD10 AD23 AE04 AE08 AE33 AE36 AE37

Claims (8)

[Claims] 1. A foreign matter removing apparatus for a continuous hot-dip metal plating facility for continuously carrying a steel strip into a molten metal through a snout having a tip portion inserted into the molten metal of a plating bath, one end of which is provided with the snout. A U-shaped communication pipe is disposed in the molten metal so that the other end is located on the molten metal bath surface outside the snout and the other end is located on the molten metal bath surface outside the snout. Gas supply means for supplying gas into the communication pipe so as to be discharged from the pipe, and the other end of the communication pipe is projected upward from a bath surface of the molten metal. Foreign matter removal equipment for metal plating equipment. 2. The apparatus for removing foreign matter in a continuous molten metal plating facility according to claim 1, wherein the other end of said communication pipe projects from a bath surface of said molten metal in a range of 20 mm to 100 mm. 3. The apparatus for removing foreign matter in a continuous molten metal plating facility according to claim 1, wherein floats are attached to the one end and the other end of the communication pipe so as to be able to follow a variation in bath surface of the molten metal. . 4. The foreign material of the continuous molten metal plating equipment according to claim 1, wherein an enclosure is provided around the other end of the communication pipe so that a lower portion is immersed in the molten metal. Removal device. 5. A continuous molten metal plating facility for continuously carrying a steel strip into said molten metal through a snout having a tip portion inserted into the molten metal of a plating bath, utilizing the function of a gas lift pump. A foreign matter removing device adapted to suck out foreign matter, wherein the end of the pipe for sucking out the foreign matter on the foreign matter discharge side is protruded above a bath surface of the molten metal; Foreign matter removal equipment for plating equipment. 6. The foreign matter removing apparatus for a continuous molten metal plating facility according to claim 5, wherein an end of the pipe on the foreign matter discharge side protrudes above a bath surface of the molten metal in a range of 20 mm to 100 mm. 7. The gas supply means includes a gas supply pipe inserted into the other end side pipe of the communication pipe, and a gas supply source for supplying an inert gas to the gas supply pipe. Diameter (A2) of gas supply pipe with respect to diameter (A1) of piping on the part side
The foreign matter removing device for a continuous molten metal plating facility according to any one of claims 1 to 4, wherein the ratio (A2 / A1) is set to 0.12 or more. 8. The apparatus according to claim 4, wherein an inert gas is introduced above the bath surface in the enclosure to prevent oxygen from touching the bath surface in the enclosure.