JP2016079421A - Continuous molten metal plating device and manufacturing method for molten metal plating steel band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an amount of metallurgical fume flowing into an annealing furnace by efficiently discharging the same from a turndown roll chamber and a snout of a continuous molten metal plating device.SOLUTION: A continuous molten metal plating device comprises: an annealing furnace; a turndown roll; a molten metal tank; a snout isolated from an ambient atmosphere; and a turndown roll chamber. The continuous molten metal plating device also has: a first shielding plate which is installed in the turndown roll chamber or the snout and shields a molten metal plating bath from the annealing furnace at one surface side of a steel band; a second shielding plate which shields the molten metal plating bath from the annealing furnace at the other surface side of the steel band. At least either the first shielding plate or the second shielding plate includes: an upstream side shielding plate arranged at the side of the annealing furnace and a downstream side shielding plate arranged at the side of the molten metal plating bath; and an exhaust port to exhaust atmosphere gas in a region between the upstream side shielding plate and the downstream side shielding plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a continuous molten metal plating apparatus and a method for manufacturing a molten metal plated steel strip, in which a steel strip that is continuously conveyed is annealed, and then a molten metal is attached to the surface of the steel strip to perform plating treatment.

  In a continuous molten metal plating line in which a molten metal-plated steel strip is manufactured, a steel strip carried from an entry-side coil unwinder is heated to a high temperature in an annealing furnace and then cooled and annealed. Moreover, the annealed steel strip passes through a turn-down roll and a snout, is introduced into a molten metal bath, and is immersed in a molten metal plating bath. Furthermore, after the steel strip to which the plating has adhered is pulled up from the molten metal plating bath, the amount of plating is adjusted by gas wiping.

  One end of the turn-down roll chamber and the snout housing the turn-down roll is connected to an annealing furnace and the other end is immersed in a molten metal plating bath in order to block the inside from the atmospheric air. The inside of the turn-down roll chamber and the snout is maintained in a reducing atmosphere in order to prevent deterioration of plating adhesion due to adhesion between the plating layer and the steel strip, oxidation of the steel strip surface, dirt, and the like. For example, the inside of the turn-down roll chamber and the snout is maintained at a low level with an oxygen concentration of about 50 ppm or less.

  However, in the continuous molten metal plating line, the molten metal evaporates from the surface of the molten metal plating bath in the snout, and metal fumes are generated. Such metal fume flows to the annealing furnace side in the snout and turndown roll chambers. When a portion having a temperature lower than the freezing point of the molten metal exists, the metal fume is cooled at the low temperature portion and is deposited in a metal state or an oxidized state. This deposit falls as the amount of deposition increases. When the deposit falls on the steel strip or the transport roll, a steel plate flaw is generated.

  Further, when metal fume is deposited on, for example, a heat exchanger of a jet cooler provided in a cooling zone of an annealing furnace, when the jet cooler is operated and blown, the deposit is sprayed on the steel strip, Steel plate wrinkles will occur. Therefore, it is necessary to prevent the metal fume generated from the surface of the molten metal plating bath in the snout from entering the annealing furnace side.

  On the other hand, in Patent Document 1, a reflux port and a suction port for removing zinc fume are provided on the front and back surfaces of the steel plate in the snout, respectively, and a pair of upper and lower sides are provided, and the suction port is formed to the full width of the snout. A technique is disclosed that is disposed across the front and back surfaces of a steel sheet. Further, in Patent Document 2, a sealing device is provided between the plating bath and the annealing furnace or the cooling furnace, and the gas in the facility is disposed between the plating bath and the sealing device from the exhaust ports near both ends in the width direction of the steel strip. A technique for exhausting is disclosed.

JP 08-176773 A Japanese Patent Application Laid-Open No. 07-157853

  The technique described in Patent Document 1 prevents a zinc fume from entering the upstream side by generating a circulating flow in the snout and sucking the zinc fume from the suction port. However, in the technique disclosed in Patent Document 1, the space between the steel strip and the inner surface of the snout is open, and there is a limit in discharging most of the zinc fume from the discharge port on the circulation flow.

  Moreover, the technique described in Patent Document 2 arranges a plate-like sealing device on the front and back surfaces of a steel strip, forms a downward flow on the plating bath side of the sealing device, and between the plating bath and the sealing device. The gas is discharged. However, in the technique disclosed in Patent Document 2, it is difficult to reduce the gap between the steel strip and the sealing device in consideration of the vibration of the steel strip in order to provide the sealing device in the snout. Therefore, it is difficult to ensure sealing performance with a single plate-like sealing device, and there is a limit to discharging most of the zinc fume from the outlet through the downward flow.

  The present invention has been made in view of the above problems, and an object of the present invention is to efficiently discharge metal fume from the turndown roll chamber and the snout of the continuous molten metal plating apparatus, It is an object of the present invention to provide a continuous molten metal plating apparatus capable of reducing the amount of metal fume flowing into the metal.

  In order to solve the above problems, according to an aspect of the present invention, an annealing furnace for heating a continuously conveyed steel strip, and a turn-down roll for changing a traveling direction of the steel strip annealed by the annealing furnace downward A molten metal bath containing a molten metal plating bath in which a steel strip whose traveling direction has been changed by the turn-down roll is immersed, and a steel strip which is partitioned from the surrounding atmosphere and whose traveling direction has been changed by the turn-down roll And a turndown roll chamber that is provided between the annealing furnace and the snout and that is partitioned from the ambient atmosphere and accommodates the turndown roll. In the apparatus, provided in the turn-down roll chamber or the snout, the molten metal plating bath side and the annealing furnace side on one surface side of the steel strip, A first shielding plate for shielding and a second shielding plate for shielding the molten metal plating bath side and the annealing furnace side on the other surface side of the steel strip; and the first shielding plate and the second shielding plate. At least one of the shielding plates includes an upstream shielding plate located on the annealing furnace side and a downstream shielding plate located on the molten metal plating bath side, and between the upstream shielding plate and the downstream shielding plate. A continuous molten metal plating apparatus including an exhaust port for discharging a predetermined amount of atmospheric gas from the region is provided.

  Further, the first and second shielding plates are provided in the turn-down roll chamber, and an end portion of the first shielding plate is disposed in proximity to a steel strip on the turn-down roll, The edge part of 2 shielding board may be arrange | positioned adjacent to the surface below the said turndown roll.

  The first shielding plate may be pivotally supported so as to be rotatable along the traveling direction of the steel strip.

  Moreover, the edge part of the said 1st and 2nd shielding board may have a shape corresponding to the external shape of the said turndown roll.

  The first shielding plate may be a single shielding plate, and the second shielding plate may include the upstream shielding plate and the downstream shielding plate.

  Further, the opening area of the exhaust port may be set based on the upper limit target value of the ratio of metal fume that enters the annealing furnace among the metal fume generated from the molten metal plating bath in the snout.

  Further, an exhaust device capable of adjusting the discharge amount of the atmospheric gas may be provided in an exhaust passage connected to the exhaust port.

  Further, the exhaust amount by the exhaust device may be set based on the upper limit target value of the ratio of metal fume entering the annealing furnace among the metal fume generated from the molten metal plating bath in the snout.

  Moreover, in order to solve the above-mentioned problem, according to another aspect of the present invention, a steel strip that is continuously conveyed is annealed in an annealing furnace, and then melted through a turn-down roll chamber and a snout partitioned from an ambient atmosphere. In the method of manufacturing a molten metal plated steel strip that is plated on the steel strip by being immersed in a metal plating bath, in the turn-down roll chamber or the snout, on one surface side and the other surface side of the steel strip, respectively. The molten metal plating bath side and the annealing furnace side are shielded, and at least one of the one surface side and the other surface side is an upstream shielding position located on the annealing furnace side and the molten metal plating bath. A downstream shielding position located on the side shields the molten metal plating bath side and the annealing furnace side, and applies a predetermined amount of atmospheric gas from a region between the upstream shielding position and the downstream shielding position. To output method for producing a molten metal plated steel strip is provided.

  Moreover, the pressure of the atmospheric gas in the region between the above may be set lower than the pressure of the atmospheric gas in the annealing furnace and the pressure of the atmospheric gas in the snout.

  According to the present invention, the flow of atmospheric gas to the annealing furnace can be blocked in two stages by the upstream shielding plate and the downstream shielding plate provided in the turn-down roll chamber or the snout. In addition, since convection occurs in the region between the upstream shielding plate and the downstream shielding plate, the atmospheric gas can be efficiently discharged from the exhaust port provided in the region between the upstream shielding plate and the downstream shielding plate. In particular, if the pressure of the atmospheric gas in the region in between is set lower than the pressure of the atmospheric gas in the annealing furnace or the snout, the atmospheric gas can be discharged more efficiently from the exhaust port. Therefore, the atmospheric gas containing metal fume is efficiently discharged through the exhaust port, and the amount of metal fume flowing to the annealing furnace side can be reduced.

FIG. 1 is a diagram showing a schematic configuration example of a continuous molten metal plating apparatus according to an embodiment of the present invention. FIG. 2 is a view for explaining the flow of the atmospheric gas in the turn-down roll chamber. FIG. 3 is a diagram illustrating a schematic configuration example of the continuous molten metal plating apparatus according to the first modification. FIG. 4 is a diagram illustrating a schematic configuration example of a continuous molten metal plating apparatus according to Modification 2. FIG. 5 is a perspective view showing a turn-down roll and a shielding plate according to the second modification. FIG. 6 is a diagram illustrating a turn-down roll and a shielding plate according to the second modification. FIG. 7 is a diagram illustrating a schematic configuration example of a continuous molten metal plating apparatus according to Modification 3. FIG. 8 is a diagram illustrating a schematic configuration example of a continuous molten metal plating apparatus according to Modification 4. FIG. 9 is a graph showing the relationship between the exhaust amount from the exhaust port and the metal fume entry rate into the annealing furnace.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Configuration example of continuous molten metal plating equipment>
First, an example of the entire configuration of a continuous molten metal plating apparatus according to an embodiment of the present invention will be described in detail. FIG. 1 is a schematic diagram schematically showing a configuration example of a continuous molten metal plating apparatus 10 according to the present embodiment. The continuous molten metal plating apparatus 10 includes an annealing furnace 20, a turndown roll chamber 30 in which a turndown roll 31 is accommodated, a snout 40, a molten metal tank 50, and a gas wiping apparatus 60.

  The inside of the annealing furnace 20 is maintained in a reducing atmosphere and heats the steel strip H that is continuously conveyed. The annealing furnace 20 activates the surface of the steel strip H and adjusts the mechanical properties of the steel strip H. Generally, the pressure of the atmospheric gas in the annealing furnace 20 is set higher than the atmospheric pressure. The turn-down roll chamber 30 has an upstream end connected to the annealing furnace 20 and a downstream end connected to the snout 40. The snout 40 has an upstream end connected to the turn-down roll chamber 30 and a downstream end immersed in the molten metal plating bath 51. Thereby, the insides of the turn-down roll chamber 30 and the snout 40 are shielded from the atmospheric atmosphere. The insides of the turn-down roll chamber 30 and the snout 40 are maintained in a reducing atmosphere. In general, the pressure of the atmospheric gas inside the snout 40 is set higher than the atmospheric pressure and lower than the pressure of the atmospheric gas inside the annealing furnace 20.

  A turndown roll 31 is accommodated in the turndown roll chamber 30. The turndown roll 31 has a rotation axis parallel to the width direction of the steel strip H. The width of the outer peripheral surface of the turn-down roll 31 is equal to or greater than the width of the steel strip H. The turn-down roll 31 changes the conveying direction of the steel strip H downward. The molten metal tank 50 accommodates a molten metal plating bath 51 such as hot dip galvanizing. The molten metal tank 50 is provided with a sink roll 53. The sink roll 53 has a rotation axis parallel to the width direction of the steel strip H. The width of the outer peripheral surface of the sink roll 53 is equal to or greater than the width of the steel strip H. The sink roll 53 changes the conveying direction of the steel strip H upward.

  The gas wiping device 60 scrapes off a part of the molten metal plating adhering to the surface of the steel strip H by spraying gas onto both surfaces of the steel strip H led out from the molten metal plating bath 51. Thereby, the adhesion amount of the molten metal plating on the surface of the steel strip H is adjusted.

  In the continuous molten metal plating apparatus 10, the steel strip H is conveyed in one direction from an unillustrated entrance coil unwinder to an exit coil winder. The steel strip H which is continuously conveyed is annealed by being heated in the annealing furnace 20 and then cooled, and immersed in the molten metal plating bath 51 through the turn-down roll chamber 30 and the snout 40. The steel strip H immersed in the molten metal plating bath 51 is then led out from the molten metal plating bath 51, and gas is blown by the gas wiping device 60, whereby the thickness of the molten metal plating layer is adjusted.

<2. Shield plate and exhaust port>
The continuous molten metal plating apparatus 10 according to this embodiment includes a first shielding plate 101 and a second shielding plate 111 in the turn-down roll chamber 30. The first shielding plate 101 is provided on the inner wall of the upper part of the turn-down roll chamber 30 on one surface (upper surface) side of the steel strip H. The upper end portion of the first shielding plate 101 is joined to the upper inner wall of the turn-down roll chamber 30, and the lower end portion is disposed close to the upper surface of the steel strip H on the turn-down roll 31. The first shielding plate 101 shields the annealing furnace 20 side and the molten metal plating bath 51 side in the space on the upper surface side of the steel strip H.

  In this embodiment, the 1st shielding board 101 has the upstream shielding board 101a located in the annealing furnace 20 side, and the downstream shielding board 101b located in the molten metal plating bath 51 side. The upstream shielding plate 101a and the downstream shielding plate 101b shield the annealing furnace 20 side and the molten metal plating bath 51 side at the respective positions. The upstream shielding plate 101a and the downstream shielding plate 101b are formed in the turndown roll chamber 30 on the upper surface side of the steel strip H over the entire width direction of the steel strip H and the annealing furnace 20 side and the molten metal plating bath 51. Shield to the side. In the region A1 between the upstream shielding plate 101a and the downstream shielding plate 101b, an exhaust port 103 for discharging atmospheric gas from the region A1 therebetween is provided.

  Here, for example, if the pressure of the atmospheric gas at the exhaust port 103 is approximately the same as the atmospheric pressure, the pressure of the atmospheric gas is the pressure of the atmospheric gas in the annealing furnace 20 and the atmospheric gas in the snout 40. Lower than the pressure of. Thereby, atmospheric gas containing a metal fume can be discharged | emitted efficiently.

  The second shielding plate 111 is provided on the inner wall at the bottom of the turn-down roll chamber 30 on the other surface (lower surface) side of the steel strip H. The lower end portion of the second shielding plate 111 is joined to the inner wall of the bottom portion of the turn-down roll chamber 30, and the upper end portion is disposed close to the outer peripheral surface of the turn-down roll 31. The second shielding plate 111 shields the annealing furnace 20 side and the molten metal plating bath 51 side in the space on the lower surface side of the steel strip H.

  In this embodiment, the 2nd shielding board 111 has the upstream shielding board 111a located in the annealing furnace 20 side, and the downstream shielding board 111b located in the molten metal plating bath 51 side. The upstream shielding plate 111a and the downstream shielding plate 111b shield the annealing furnace 20 side and the molten metal plating bath 51 side at the respective positions. The upstream side shielding plate 111a and the downstream side shielding plate 111b are formed in the space below the turn-down roll 31 on the lower surface side of the steel strip H over the entire width direction of the steel strip H and on the annealing furnace 20 side and the molten metal. Shield against the plating bath 51 side. In the region A2 between the upstream shielding plate 111a and the downstream shielding plate 111b, an exhaust port 113 for discharging the atmospheric gas from the region A2 between the upstream shielding plate 111a and the downstream shielding plate 111b is provided.

  Here, for example, if the pressure of the atmospheric gas at the exhaust port 113 is approximately the same as the atmospheric pressure, the pressure of the atmospheric gas is the atmospheric gas pressure in the annealing furnace 20 and the atmospheric gas in the snout 40. Lower than the pressure of. Thereby, atmospheric gas containing a metal fume can be discharged | emitted efficiently.

  The first and second shielding plates 101 and 111 are made of a material having at least heat resistance. For example, the first and second shielding plates 101 and 111 are made of a metal plate having heat resistance. In particular, it is preferable that the first and second shielding plates 101 and 111 are made of stainless steel plates because they are not easily oxidized even when exposed to an air atmosphere during maintenance or the like and are inexpensive.

  Since the turn-down roll 31 is pivotally supported, it is difficult to cause a displacement due to vibration. Further, the steel strip H on the turn-down roll 31 is not easily displaced because it is pressed onto the turn-down roll 31 by tension. Therefore, if it is a position which opposes the turndown roll 31, the edge part of 1st and 2nd shielding board 101,111 is made of steel strip H so that the 1st shielding board 101 may not contact steel strip H. It can be arranged close to the surface or the outer peripheral surface of the turndown roll 31. Therefore, the continuous molten metal plating apparatus 10 according to the present embodiment can make the shielding performance by the first and second shielding plates 101 and 111 relatively high.

  The distance of the gap between the end of the first shielding plate 101 and the surface of the steel strip H and the distance of the gap between the end of the second shielding plate 111 and the outer peripheral surface of the turndown roll 31 are The thickness is desirably 10 mm to 20 mm. Alternatively, when the heat buckle generated in the steel strip H passes, even if the heat buckle comes into contact with the first shielding plate 101, the rubber is prevented so that the heat buckle is caught and the steel strip H is not broken. Alternatively, the first shielding plate 101 having flexibility made of resin may be used. In this case, the first shielding plate 101 may be partially flexible on the end side close to the steel strip H, or the first shielding plate 101 may be entirely flexible. Also good. The first shielding plate 101 can be made of, for example, a flexible carbon sheet.

  Further, as described above, the exhaust ports 103 and 113 are provided in the regions A1 and A2, respectively. The exhaust ports 103 and 113 are provided at both ends in the width direction of the steel strip H, respectively. Atmospheric gas containing metal fumes generated from the surface of the molten metal plating bath 51 in the snout 40 flows out through the exhaust ports 103 and 113 while flowing to the annealing furnace 20 side. In FIG. 1, the exhaust ports 103 and 113 are provided on the wall surface of the turn-down roll chamber 30, but the positions where the exhaust ports 103 and 113 are provided are not limited to this example. The exhaust ports 103 and 113 may be provided on the upper surface or the bottom surface.

  Moreover, the opening area of the exhaust ports 103 and 113 is set based on the upper limit target value of the ratio of the metal fume flowing into the annealing furnace 20 side among the metal fume generated from the surface of the molten metal plating bath 51 in the snout 40. be able to. Such an upper limit target value is an allowable limit of metal fume flowing into the annealing furnace 20 side. That is, since the exhaust amount varies depending on the opening area of the exhaust ports 103 and 113, the opening area of the exhaust ports 103 and 113 can be set according to the desired exhaust amount.

  In this case, the opening area of the exhaust port 103 provided in the region A1 therebetween may be different from the opening area of the exhaust port 113 provided in the region A2 therebetween. When the exhaust ports 103 and 113 communicate with exhaust pipes of the same system, the total exhaust amount from the exhaust ports 103 and 113 becomes a constant amount. Therefore, by making the opening areas different, The rate of displacement is adjusted.

  For example, on the upper surface side of the steel strip H, with the rotation of the turn-down roll 31 and the movement of the steel strip H, a snout is introduced into the gap between the first shielding plate 101 and the steel strip H from the annealing furnace 20 side. An accompanying flow that flows toward the 40 side is generated. Thereby, the shielding property with respect to the flow to the annealing furnace 20 side of the atmospheric gas containing metal fume becomes higher than the shielding property of the gap between the second shielding plate 111 and the turn-down roll 31. Therefore, by making the opening area of the exhaust port 113 provided in the area A2 therebetween larger than the opening area of the exhaust port 103 provided in the area A1, the second shielding plate 111 and the turn-down roll 31 are provided. It is possible to improve the shielding property of the gap.

  As for the opening areas of the exhaust ports 103 and 113, the actual machine data is used in advance so that the ratio of the metal fume flowing into the annealing furnace 20 out of the metal fume generated from the molten metal plating bath 51 in the snout 40 is equal to or less than the upper limit target value. It is preferable to obtain by simulation or the like.

<3. Atmospheric gas flow>
Next, the flow of atmospheric gas in the turndown roll chamber 30 will be described. FIG. 2 is a diagram showing the flow of atmospheric gas in the turn-down roll chamber 30. The atmospheric gas containing metal fumes generated from the surface of the molten metal plating bath 51 in the snout 40 flows toward the turn-down roll chamber 30 side. Generally, the pressure of the atmospheric gas in the annealing furnace 20 and the pressure of the atmospheric gas in the snout 40 are set higher than the atmospheric pressure. The pressure of the atmospheric gas in the annealing furnace 20 is set higher than the pressure of the atmospheric gas in the snout 40.

  On one surface (upper surface) side of the steel strip H, the atmospheric gas containing the metal fume is blocked by the downstream shield plate 101b and passes through the gap between the downstream shield plate 101b and the steel strip H. Then, it enters the area A1 while the exhaust port 103 is provided. On the other hand, the atmospheric gas on the annealing furnace 20 side also enters the area A1 between the upstream side shielding plate 101a and the steel strip H, where the exhaust port 103 is provided. At this time, the atmospheric gas on the annealing furnace 20 side mainly becomes an accompanying flow accompanying the rotation of the turn-down roll 31 and the movement of the steel strip H, and flows into the region A1 therebetween.

  Accordingly, in the region A1 in the middle, convection is formed by the flow of the atmospheric gas containing the metal fume flowing from the downstream side and the flow of the atmospheric gas flowing from the upstream side, and the atmospheric gas containing the metal fume is efficiently discharged from the exhaust port 103. Discharged. For example, if the pressure of the atmospheric gas at the exhaust port 103 is approximately the same as the atmospheric pressure, the pressure of the atmospheric gas is lower than the pressure of the atmospheric gas in the annealing furnace 20 and the snout 40. Therefore, atmospheric gas containing metal fume can be efficiently discharged. In particular, on the upper surface side of the steel strip H, it is possible to suppress the atmospheric gas containing the metal fume from flowing into the annealing furnace 20 side due to the action of the accompanying flow described above.

  In addition, on the other surface (lower surface) side of the steel strip H, the atmospheric gas containing metal fume is blocked by the downstream shielding plate 111b, and the gap between the downstream shielding plate 111b and the turndown roll 31. Through the area A2 while the exhaust port 103 is provided. On the other hand, the atmospheric gas on the annealing furnace 20 side also enters the region A2 between the exhaust port 103 provided through the gap between the upstream shielding plate 111a and the turndown roll 31. Therefore, in the area A2 between the two, the convection is formed by the flow of the atmospheric gas containing the metal fume flowing from the downstream side and the flow of the atmospheric gas flowing from the upstream side, and the atmospheric gas containing the metal fume is efficiently discharged from the exhaust port 113. Discharged. For example, if the pressure of the atmospheric gas at the exhaust port 113 is approximately the same as the atmospheric pressure, the pressure of the atmospheric gas is lower than the pressure of the atmospheric gas in the annealing furnace 20 and the snout 40. Therefore, atmospheric gas containing metal fume can be efficiently discharged.

  As described above, the atmospheric gas containing the metal fume generated from the molten metal plating bath 51 in the snout 40 is efficiently discharged through the exhaust ports 103 and 113 on each of the upper surface side and the lower surface side of the steel strip H. . Thereby, the quantity of the metal fume which flows into the annealing furnace 20 side reduces. Therefore, it is possible to reduce steel sheet defects caused by deposits formed by solidification of metal fume in the low temperature portion on the annealing furnace 20 side.

<4. Modification>
The configuration of the continuous molten metal plating apparatus 10 according to the present embodiment can be variously modified. Hereinafter, modifications of the continuous molten metal plating apparatus 10 will be described.

(4-1. Modification 1)
FIG. 3 is a view schematically showing a turndown roll chamber 30 of the continuous molten metal plating apparatus according to the first modification. In the continuous molten metal plating apparatus according to the modified example 1, the first shielding plate 101 provided on the upper surface side of the steel strip H is rotatable along the traveling direction of the steel strip H. Specifically, the upstream shielding plate 101a and the downstream shielding plate 101b provided on the upper surface side of the steel strip H are supported by the support shafts 105a and 105b so as to be rotatable along the conveying direction of the steel strip H, respectively. ing. Thereby, even if the heat buckle generated in the steel strip H comes into contact with the upstream shielding plate 101a or the downstream shielding plate 101b, the upstream shielding plate 101a or the downstream shielding plate 101b rotates, Breakage of the steel strip H is avoided.

  Therefore, the end portions of the upstream shielding plate 101a and the downstream shielding plate 101b can be disposed closer to the steel strip H. The distance of the gap between the upstream shielding plate 101a and the downstream shielding plate 101b and the steel strip H can be set to 10 mm to 20 mm, for example. Therefore, the shielding property by the upstream shielding plate 101a and the downstream shielding plate 101b is enhanced, and the suppression effect on the metal fume flowing into the annealing furnace 20 side can be enhanced.

(4-2. Modification 2)
4-6 is a figure shown in order to demonstrate the continuous molten metal plating apparatus concerning the modification 2. As shown in FIG. FIG. 4 is a view schematically showing a turndown roll chamber 30 of the continuous molten metal plating apparatus according to the second modification. FIG. 5 is a perspective view showing the turn-down roll 31 and the first and second shielding plates 121 and 131. FIG. 6 is a view of the first and second shielding plates 121 and 131 and the turn-down roll 31 taken along the alternate long and short dash line in FIG.

  In the continuous molten metal plating apparatus according to the modified example 2, both ends of the first and second shielding plates 121 and 131 in the direction along the width direction of the steel strip H have shapes corresponding to the outer shape of the turndown roll 31. Have. The turn-down roll 31 according to the present embodiment includes a roll body 31a having a columnar shape, and tapered roll ends 31ba and 31bb each having a diameter reduced from the both ends of the roll body 31a toward the outside in the axial direction. have. In order to correspond to the outer shape of the turn-down roll 31, both end portions of the first and second shielding plates 121 and 131 protrude so as to be close to the outer peripheral surfaces of the roll end portions 31ba and 31bb.

  Thereby, not only in the area | region corresponding to the roll trunk | drum 31a of the turndown roll 31, but also in the area | region corresponding to roll edge part 31ba, 31bb of the both ends of the axial direction of the turndown roll 31, 1st and 2nd The shielding property by the shielding plates 121 and 131 is enhanced. Therefore, the suppression effect with respect to the atmospheric gas containing metal fume flowing into the annealing furnace 20 side can be enhanced.

  In particular, in the example shown in FIGS. 4 and 5, the upstream shielding plate 121 a and the downstream shielding plate 121 b constituting the first shielding plate 121 are supported so as to be rotatable along the conveying direction of the steel strip H. It is supported by shafts 125a and 125b. Therefore, similarly to the continuous molten metal plating apparatus according to the first modification, the end portions of the upstream shielding plate 121a and the downstream shielding plate 121b can be arranged closer to the steel strip H. Therefore, the shielding performance by the upstream shielding plate 121a and the downstream shielding plate 121b is enhanced, and the effect of suppressing the metal fume from flowing into the annealing furnace 20 side can be further enhanced.

  In this case, as shown in FIG. 6, the distance d1 of the gap between the roll body 31a and the upstream shielding plate 121a and the downstream shielding plate 121b needs to consider the thickness of the steel strip H to be passed through. For example, it may be 10 mm to 20 mm. The distance d2 of the gap between the roll end portions 31ba, 31bb and the upstream shielding plate 121a and the downstream shielding plate 121b can be set to 25 mm to 35 mm, for example. By providing a larger distance d2, even when the turn-down roll 31 is replaced, the upstream shielding plate 121a and the downstream shielding plate 121b are turned even if the axial position of the turn-down roll 31 is shifted. Contacting the down roll 31 can be prevented.

(4-3. Modification 3)
FIG. 7 is a view schematically showing a turn-down roll chamber 30 of the continuous molten metal plating apparatus according to the third modification. In the continuous molten metal plating apparatus according to Modification 3, the first shielding plate 141 provided on the upper surface side of the steel strip H is formed of a single shielding plate, and the exhaust port is provided on the upper surface side of the steel strip H. This is different from the continuous molten metal plating apparatus according to Modification 2 in that there is no point.

  As already described, in the continuous molten metal plating apparatus according to this embodiment, the first shielding plate 141 and the second shielding plate 131 are provided at a position where the vibration of the steel strip H is small. Therefore, the first shielding plate 141 and the second shielding plate 131 are arranged close to the steel strip H or the turn-down roll 31. Among these, the gap between the first shielding plate 141 provided on the upper surface side of the steel strip H and the surface of the steel strip H is annealed as the turn-down roll 31 rotates and the steel strip H moves. The accompanying flow passes from the furnace 20 side to the molten metal plating bath 51 side.

  Therefore, on the upper surface side of the steel strip H, the atmosphere gas containing metal fume is annealed only by shielding the annealing furnace 20 side and the molten metal plating bath 51 side with a single shielding plate without providing an exhaust port. The suppression effect with respect to flowing into the furnace 20 side is acquired. Further, the exhaust port on the upper surface side of the steel strip H is omitted, and the exhaust port 113 is provided only on the lower surface side of the steel strip H, so that the exhaust amount from the exhaust port 113 increases. Therefore, on the lower surface side of the steel strip H, the atmospheric gas containing the metal fume is discharged through the exhaust port 113 more efficiently. Thereby, compared with the modification 2, the amount of metal fume flowing into the annealing furnace 20 side can be reduced with a simpler configuration.

(4-4. Modification 4)
FIG. 8 is a diagram schematically showing a configuration of a continuous molten metal plating apparatus 10A according to Modification 4. The continuous molten metal plating apparatus 10A according to the modification 4 is different from the continuous molten metal plating apparatus according to the modification 3 in that an exhaust device is provided. The continuous molten metal plating apparatus 10A according to Modification 4 includes an exhaust pipe 71 communicating with the exhaust port 113, an ejector 70 serving as an exhaust device, and a cyclone 80 serving as a metal fume recovery device in this order from the exhaust port 113 side. I have.

  The ejector 70 evacuates the inside of the cylinder by supplying an inert gas G as a working fluid into the cylinder, and from the area A2 between the upstream shielding plate 131a and the downstream shielding plate 131b via the exhaust port 113. Atmospheric gas containing metal fume is sucked. The cyclone 80 separates and collects metal fume contained in the exhausted atmospheric gas. The atmospheric gas from which the metal fume is removed is exhausted as it is.

  The continuous molten metal plating apparatus 10 </ b> A according to the modification 4 can adjust the amount of exhaust from the region A <b> 2 between them by adjusting the flow rate of the inert gas G introduced into the ejector 70. Thereby, the ratio of the metal fume which flows into the annealing furnace 20 among the metal fume generated from the molten metal plating bath 51 in the snout 40 can be adjusted quantitatively. Therefore, the ratio of the metal fume flowing into the annealing furnace 20 can be controlled below the upper limit target value without changing the opening area of the exhaust port 113.

  In addition, although the continuous molten metal plating apparatus 10A shown in FIG. 8 is provided with an exhaust device with respect to the continuous molten metal plating apparatus according to Modification 3, the continuous molten metal plating apparatus shown in FIG. 1, FIG. 3, and FIG. An exhaust device may be provided for the molten metal plating apparatus. Further, the exhaust device is not limited to an ejector, and may be an air supply device such as a blower.

  As described above, the continuous molten metal plating apparatus 10 according to the present embodiment includes the first shielding including the upstream shielding plates 101a and 111a and the downstream shielding plates 101b and 111b in the turn-down roll chamber 30, respectively. A plate 101 and a second shielding plate 111 are provided. The first shielding plate 101 and the second shielding plate 111 have an annealing furnace 20 side and a molten metal plating bath 51 side on one surface (upper surface) side and the other surface (lower surface) side of the steel strip H, respectively. Shield. Therefore, the metal fume generated from the surface of the molten metal plating bath 51 in the snout 40 does not flow directly into the annealing furnace 20 side.

  Further, exhaust regions 103 and 113 are provided in regions A1 and A2 between the upstream shielding plates 101a and 111a and the downstream shielding plates 101b and 111b, and metal fume is formed from the regions A1 and A2 therebetween. Is efficiently discharged. Therefore, the amount of metal fume flowing into the annealing furnace 20 can be reduced, and the occurrence of steel sheet flaws due to metal fume deposits can be suppressed.

  Next, examples of the present embodiment will be described.

  In the present embodiment, the plate width of the steel strip H, the furnace pressure of the annealing furnace 20 and the gas temperature in the furnace are set to the same conditions, while the configuration of the shielding plate is changed to reduce the displacement and the metal fume in the furnace, respectively. The relationship with the approach rate was obtained by simulation. Examples 1-3 were taken as the example at the time of using the continuous molten metal plating apparatus 10 concerning this embodiment shown in FIG. Examples 4-6 were taken as the example at the time of using the continuous molten metal plating apparatus concerning the modification 2 shown in FIG. Examples 7 to 9 are examples in which the continuous molten metal plating apparatus according to Modification 3 shown in FIG. 7 is used. Moreover, the turndown roll 31 used the turndown roll of the structure shown in FIG.5 and FIG.6.

  In any of Examples 1 to 9, the simulation is performed assuming that the plate width of the steel strip H is 1,850 mm, the pressure inside the annealing furnace 20 is 0.2939 kPa, and the gas temperature inside the annealing furnace 20 is 340 ° C. went. Also, the configuration of the first and second shielding plates 101, 111, 121, 131, 141, 151, the roll body 31a and the first and second shielding plates 101, 111, 121, 131, 141, 151 The distance d1 between the roll end portions 31ba and 31bb and the distance d2 between the first and second shielding plates 101, 111, 121, 131, 141, and 151 were set as shown in Table 1, respectively.

FIG. 9 shows the displacements (Nm ³ / N) shown in Table 1 for Examples 1 to 3 (broken line), Examples 4 to 6 (dashed line), and Examples 7 to 9 (solid line) using the same device. The graph showing the relationship between Hr) and the penetration rate (%) of metal fume into the furnace is shown. As shown in the graph of FIG. 9, when the same apparatus is used, as the flow rate of the atmospheric gas discharged through the exhaust ports 103 and 113 increases, the metal fume generated from the surface of the molten metal plating bath 51 in the snout 40 is increased. Of these, it can be seen that the rate of penetration into the annealing furnace 20 decreases.

In particular, as the displacement increases, the pressure of the atmospheric gas in the regions A1 and A2 decreases to about atmospheric pressure, and is sufficiently reduced with respect to the pressure of the atmospheric gas in the annealing furnace 20 and the snout 40. Therefore, the atmospheric gas containing metal fume is efficiently discharged, and the penetration rate of metal fume into the furnace is further reduced. For example, when the continuous molten metal plating apparatus according to the present embodiment shown in FIG. 1 is used (broken line), if the displacement is 205 Nm ³ / Hr or more, the penetration rate of metal fume into the furnace decreases to 10% or less. To do. Further, when the continuous molten metal plating apparatus according to Modification 2 shown in FIG. 4 is used (dashed line), if the displacement is 150 Nm ³ / Hr or more, the penetration rate of metal fume into the furnace is 10% or less. descend. Furthermore, when the continuous molten metal plating apparatus according to Modification 3 shown in FIG. 7 is used (solid line), the penetration rate of metal fume into the furnace decreases to 10% or less if the displacement is 110 Nm ³ / Hr or more. To do.

  When the first shielding plates 101 and 121 are the same apparatus including the upstream shielding plates 101a, 101b, 121a, and 121b, Examples 4 to 6 that shield the periphery of the roll end portions 31ba and 31bb are the roll ends. It can be seen that the penetration rate of metal fume into the furnace can be reduced with a small displacement compared to the first to third embodiments in which the surroundings of the portions 31ba and 31bb are not shielded. Further, when the periphery of the roll end portions 31ba and 31bb is shielded, the seventh to ninth embodiments having one first shielding plate 141 are the first shielding including the upstream shielding plate 121a and the downstream shielding plate 121b. Compared with Examples 4-6 which have the board 121, the penetration | invasion rate of a metal fume in a furnace can be made small with much smaller displacement.

For example, in the case of the shielding plate shown in FIG. 1, the amount of exhaust is set to 5% or less of the metal fume generated from the molten metal plating bath 51 in the snout 40 and flowing into the annealing furnace 20 side. What is necessary is just to be about 240 Nm < ³ > / Hr or less. Similarly, in order to make the ratio of the metal fume flowing into the annealing furnace 20 side 5% or less, in the case of the shielding plate shown in FIG. 4, the exhaust amount may be about 180 Nm ³ / Hr or less. Similarly, in order to make the ratio of the metal fume flowing into the annealing furnace 20 side 5% or less, in the case of the shielding plate shown in FIG. 7, the exhaust amount should be about 140 Nm ³ / Hr or less.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, in the turn-down roll chamber, the first and second shielding plates are provided on the one surface (upper surface) side and the other surface (lower surface) side of the steel strip H, respectively. The present invention is not limited to such an example. For example, the first and second shielding plates may be provided in the snout. In this case, in the snout, the vibration width of the steel strip H accompanying the conveyance of the steel strip H tends to be larger than the vibration width of the steel strip H on the turn-down roll, so the first and second shielding plates and The distance between the steel strip H and the steel strip H may be set slightly wider.

DESCRIPTION OF SYMBOLS 10,10A Continuous molten metal plating apparatus 20 Annealing furnace 30 Turndown roll chamber 31 Turndown roll 31a Roll body part 31ba, 31bb Roll end part 40 Snout 50 Molten metal tank 51 Molten metal plating bath 53 Sink roll 60 Gas wiping apparatus 70 Ejector 80 Cyclone 101, 121, 141 First shielding plate 101a, 121a Upstream shielding plate 101b, 121b Downstream shielding plate 103, 113 Exhaust port 105a, 105b Support shaft 111, 131, 151 Second shielding plate 111a, 131a, 151a Upstream shielding plate 111b, 131b, 151b Downstream shielding plate 125a, 125b Support shaft

Claims (10)

An annealing furnace for heating the continuously conveyed steel strip;
A turn-down roll that changes the traveling direction of the steel strip annealed by the annealing furnace downward;
A molten metal tank containing a molten metal plating bath in which a steel strip whose traveling direction has been changed by the turndown roll is immersed;
A snout that guides a steel strip that is partitioned from the surrounding atmosphere and whose traveling direction is changed by the turn-down roll to the molten metal plating bath;
A turn-down roll chamber provided between the annealing furnace and the snout, partitioned from an ambient atmosphere and containing the turn-down roll;
In a continuous molten metal plating apparatus equipped with
A first shielding plate provided in the turn-down roll chamber or the snout, and shields the molten metal plating bath side and the annealing furnace side on one surface side of the steel strip, and the other surface of the steel strip. A second shielding plate that shields the molten metal plating bath side and the annealing furnace side on the side,
At least one of the first shielding plate and the second shielding plate includes an upstream shielding plate located on the annealing furnace side and a downstream shielding plate located on the molten metal plating bath side,
A continuous molten metal plating apparatus comprising an exhaust port for discharging a predetermined amount of atmospheric gas from a region between the upstream shielding plate and the downstream shielding plate. The first and second shielding plates are provided in the turndown roll chamber,
The end of the first shielding plate is disposed close to the steel strip on the turndown roll,
2. The continuous molten metal plating apparatus according to claim 1, wherein an end of the second shielding plate is disposed close to a lower surface of the turn-down roll.   The continuous molten metal plating apparatus according to claim 2, wherein the first shielding plate is pivotally supported so as to be rotatable along a traveling direction of the steel strip.   The continuous molten metal plating apparatus according to claim 2 or 3, wherein ends of the first and second shielding plates have a shape corresponding to an outer shape of the turn-down roll.   The said 1st shielding board consists of one shielding board, and the said 2nd shielding board contains the said upstream shielding board and the said downstream shielding board, The continuation of any one of Claims 2-4. Molten metal plating equipment.   The opening area of the exhaust port is set based on an upper limit target value of a ratio of metal fume entering the annealing furnace among metal fume generated from the molten metal plating bath in the snout. The continuous molten metal plating apparatus of any one of these.   The continuous molten metal plating apparatus of any one of Claims 1-5 provided with the exhaust apparatus which can adjust the discharge | emission amount of the said atmospheric gas in the exhaust passage connected to the said exhaust port.   The exhaust amount by the exhaust device is set based on an upper limit target value of a ratio of metal fume entering the annealing furnace among metal fume generated from the molten metal plating bath in the snout. Continuous molten metal plating equipment. After the steel strip that is continuously conveyed is annealed in an annealing furnace, it is immersed in a molten metal plating bath through a turn-down roll chamber and a snout partitioned from the ambient atmosphere. In the manufacturing method,
While shielding the molten metal plating bath side and the annealing furnace side on one surface side and the other surface side of the steel strip in the turn-down roll chamber or the snout,
At least one of the one surface side and the other surface side is an upstream shielding position located on the annealing furnace side and a downstream shielding position located on the molten metal plating bath side, and the molten metal plating bath side and Shielding the annealing furnace side;
A method for producing a molten metal-plated steel strip, wherein a predetermined amount of atmospheric gas is discharged from a region between the upstream shielding position and the downstream shielding position. The method for producing a molten metal-plated steel strip according to claim 9, wherein the pressure of the atmospheric gas in the region between the two is set lower than the pressure of the atmospheric gas in the annealing furnace and the pressure of the atmospheric gas in the snout.

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