JP2019131880A - Continuous molten metal plating apparatus, and continuous molten metal plating method - Google Patents

Abstract

To provide a continuous molten metal plating apparatus capable of suppressing generation of a surface defect on a molten metal plating steel strip resulting from metallurgical fume.SOLUTION: In a continuous molten metal plating apparatus, a steel strip 10 heat-treated in a heat treatment furnace 1 is introduced into a molten metal plating bath 4 through a snout 2, to thereby perform plating. The continuous molten metal plating apparatus has gas spray means 7 for spraying inert gas to the surface of the steel strip 10, between a turndown roll 6 for progressing the steel strip 10 to the snout 2, and the heat treatment furnace 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a continuous molten metal plating apparatus and a continuous molten metal plating method.

  In a continuous molten metal plating apparatus, a steel strip is heated in a heat treatment furnace to activate the surface, and then the steel strip is introduced into a molten metal plating bath via a snout to perform a plating process. The snout has one end connected to a heat treatment furnace through a connecting portion and the other end immersed in a molten metal plating bath in order to block the inside from the atmosphere. The inside of the snout is maintained in a reducing atmosphere in order to prevent the occurrence of surface defects (plating defects) caused by oxidation, dirt, etc. on the surface of the steel strip, but it has evaporated from the surface of the molten metal plating bath in the snout. Metal fume enters the snout. And the metal fume in a snout flows in the direction opposite to the advancing direction of a steel strip, and will adhere as a foreign material to the inner wall surface etc. of an apparatus, if it cools. When the foreign matter falls off the inner wall surface and adheres to the steel strip, it causes surface defects in the molten metal-plated steel strip.

  Therefore, as a means for suppressing the occurrence of surface defects due to metal fume, a method of providing a gas seal part in the middle of the snout (Patent Document 1), an inert gas having a large specific gravity from a gas blowing pipe provided in the snout A method of blowing (Patent Document 2), a method of controlling the atmospheric gas temperature in the snout and the inner wall temperature of the snout (Patent Document 3), and the like have been proposed.

JP 2000-290761 A Japanese Patent Laid-Open No. 11-279730 Japanese Patent No. 2897668

  However, in the methods of Patent Documents 1 and 2, it is not possible to completely suppress the inflow of metal fume, and therefore foreign matter may adhere to the steel strip due to the inflowing metal fume. Further, in the method of Patent Document 3, although the adhesion of foreign matter in the snout can be suppressed, the metal fume flows upstream of the snout, so that the foreign matter due to the metal fume in the region upstream of the snout is a steel strip. It will stick to.

  The present invention has been made to solve the above-described problem, and is a continuous molten metal plating apparatus and a continuous molten metal plating method that can suppress the occurrence of surface defects in a molten metal plated steel strip caused by metal fume. The purpose is to provide.

  As a result of earnest research to solve the above problems, the present inventor has found that the steel strip is likely to adhere to the steel strip in the region upstream from the snout. It is found that by providing a gas blowing means for blowing an inert gas on the surface of the steel strip between the turndown roll and the heat treatment furnace to be advanced to the snout, it is possible to suppress the adhesion of foreign matters due to metal fume, The present invention has been completed.

That is, the present invention is a continuous molten metal plating apparatus for performing plating by introducing a steel strip heat-treated in a heat treatment furnace into a molten metal plating bath through a snout, wherein the steel strip is advanced to the snout. The present invention relates to a continuous molten metal plating apparatus having a gas spraying means for spraying an inert gas onto the surface of the steel strip between a down roll and the heat treatment furnace.
The present invention also relates to a continuous molten metal plating method for performing plating by introducing a steel strip heat-treated in a heat treatment furnace into a molten metal plating bath through a snout, wherein the steel strip is advanced to the snout. The present invention relates to a continuous molten metal plating method in which an inert gas is sprayed onto the surface of the steel strip from a gas spraying means provided between a down roll and the heat treatment furnace.

  ADVANTAGE OF THE INVENTION According to this invention, the continuous molten metal plating apparatus and continuous molten metal plating method which can suppress generation | occurrence | production of the surface defect of the molten metal plating steel strip resulting from a metal fume can be provided.

1 is a schematic configuration diagram of a continuous molten metal plating apparatus according to an embodiment of the present invention.

The continuous molten metal plating apparatus of the present invention is for introducing a steel strip heat-treated in a heat treatment furnace into a molten metal plating bath through a snout to perform plating, and a turn-down roll that advances the steel strip into a snout; Gas spraying means for spraying an inert gas on the surface of the steel strip is provided between the heat treatment furnace.
In addition, the continuous molten metal plating method of the present invention is a method in which a steel strip heat treated in a heat treatment furnace is introduced into a molten metal plating bath through a snout to perform plating, and the steel strip is advanced to a snout. An inert gas is sprayed on the surface of the steel strip from a gas spraying means provided between the roll and the heat treatment furnace.
Hereinafter, preferred embodiments of a continuous molten metal plating apparatus and a continuous molten metal plating method of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of a continuous molten metal plating apparatus according to an embodiment of the present invention.
The continuous molten metal plating apparatus of this embodiment includes a heat treatment furnace 1 (for example, an annealing furnace) including a heating zone 1a and a soaking zone and / or a cooling zone 1b, a snout 2, and one end of the heat treatment furnace 1 and the snout 2. And a molten metal plating bath 5 that accommodates a molten metal plating bath 4 in which the other end of the snout 2 is immersed. Inside the connecting portion 3, a turn-down roll 6 is provided for causing the steel strip 10 heat-treated in the heat treatment furnace 1 to advance to the snout 2. Further, a gas spraying means 7 for spraying an inert gas on the surface of the steel strip 10 is provided between the turn-down roll 6 and the heat treatment furnace 1 (particularly the soaking zone and / or the cooling zone 1b of the heat treatment furnace 1). It has been. Further, in the molten metal plating bath 4, a sink roll 8 for guiding the steel strip 10 to the upper side of the molten metal plating bath 5 is provided.
Of the members of the continuous molten metal plating apparatus, members other than the gas spraying means 7 are known in the art. Therefore, members other than the gas blowing means 7 can employ members known in the technical field, and members other than the illustrated members can be added as long as the effects of the present invention are not impaired. It is.

  In the continuous molten metal plating apparatus, the metal fume evaporated from the surface of the molten metal plating bath 4 in the snout 2 enters the snout 2 and flows in the direction opposite to the traveling direction of the steel strip 10. Specifically, the metal fume flows through the snout 2 to the connecting portion 3 and the heat treatment furnace 1. When the metal fume is cooled, it adheres to the inner wall surface of the apparatus as a foreign material, and therefore adheres to the surface of the steel strip 10 when the foreign material falls off the inner wall surface. At this time, in the snout 2, the steel strip 10 advances while being inclined, so that even if foreign matter falls off from the inner wall surface or the like, it is difficult to adhere to the surface of the steel strip 10. On the other hand, since the steel strip 10 advances while maintaining the level in the upstream of the snout 2, it is easy to adhere to the surface of the steel strip 10 when foreign matter falls off the inner wall surface or the like. Therefore, in the continuous molten metal plating apparatus according to the present embodiment, the gas spraying means 7 is provided between the turn-down roll 6 and the heat treatment furnace 1, and inert gas is supplied from the gas spraying means 7 to the surface of the steel strip 10. By spraying, it is possible to remove foreign matter adhering to the surface of the steel strip 10.

  The connecting portion 3 has a portion (narrow cross-section connecting portion 3a) having a smaller cross-sectional area in the vertical direction (cross-sectional area in the direction perpendicular to the traveling direction of the steel strip 10) than the portion where the gas blowing means 7 is provided. It is preferable to include. The narrow cross-section connecting portion 3a is provided on the heat treatment furnace 1 side. By providing the narrow cross-section connection portion 3a, the flow rate of the inert gas in the narrow cross-section connection portion 3a is faster than the flow rate of the inert gas in the portion where the gas blowing means 7 is provided. The effect of removing foreign matter adhering to the surface becomes high. From the viewpoint of sufficiently obtaining such an effect, it is preferable to adjust the cross-sectional area of the narrow cross-section connection portion 3a so that the flow rate of the inert gas in the narrow cross-section connection portion 3a is 0.1 m / second or more.

The gas spraying means 7 is not particularly limited as long as an inert gas can be sprayed on the surface of the steel strip 10, and a known one can be used.
Among them, the gas spraying means 7 preferably has a slit-shaped spray port parallel to the width direction of the steel strip 10, and the length of the slit-shaped spray port is preferably equal to or greater than the width of the steel strip 10. With the gas spraying means 7 having such a spraying port, an inert gas can be sprayed over the entire width of the steel strip 10, so that foreign matters adhering to the surface of the steel strip 10 can be stably removed. Can do. In addition, since such a gas blowing means 7 can provide a function as a gas shield, it is possible to make it difficult for metal fume to flow before the region where the inert gas is blown.

Since the foreign matters resulting from the metal fume are likely to adhere to the upper surface of the steel strip 10, the gas blowing means 7 is preferably provided on the upper surface side of the steel strip 10.
Further, the gas spraying means 7 may be provided not only on the upper surface side of the steel strip 10 but also on the lower surface side. Since various foreign substances brought in from the upstream side due to various factors may adhere to the lower surface side of the steel strip 10, by providing the gas blowing means 7 on the lower surface side of the steel strip 10, the foreign matter Can be removed.

  The blowing speed of the inert gas in the gas blowing means 7 may be appropriately adjusted according to the gas blowing means 7 to be used, and is not particularly limited, but is preferably 3.0 m / second or more, more preferably 4. It is 0 m / second or more, more preferably 5.0 m / second or more, and particularly preferably 6.0 m / second or more. With such a spraying speed, the effect of removing foreign matters can be enhanced.

  The inert gas is not particularly limited, and those known in the technical field can be used. Examples of the inert gas include nitrogen gas, argon gas, and AX gas. These can be used alone or in combination of two or more.

The temperature (T) of the inert gas is not particularly limited, but preferably satisfies the following conditions.
(Temperature of molten metal plating bath 4 [° C.] − 150 ° C.) ≦ T ≦ Temperature of molten metal plating bath 4 [° C.]
By setting the inert gas to the temperature range as described above, a molten metal plated steel strip with fewer surface defects can be obtained. When the temperature (T) of the inert gas is less than (temperature of molten metal plating bath 4 [° C.] − 150 ° C.), when the steel strip 10 is introduced into the molten metal plating bath 4, the molten metal plating bath 4 The surface of the material tends to solidify, and surface defects may occur. On the other hand, when the temperature (T) of the inert gas is higher than the temperature of the molten metal plating bath 4, it is difficult for the molten metal plating to be formed on the surface of the steel strip 10.
Note that the temperature of the molten metal plating bath 4 cannot be uniquely defined because it depends on the type of metal. For example, when the molten metal plating bath 4 is a hot dip galvanizing bath, the temperature is generally 440 to 480 ° C. When the molten metal plating bath 4 is a molten aluminum-zinc plating bath, the temperature is generally 580 to 700 ° C.

  The inert gas is sprayed in the direction opposite to the traveling method of the steel strip 10, and the spray angle of the inert gas is preferably more than 0 ° and not more than 65 °, more preferably 3 to 60, with respect to the steel strip 10. °, more preferably 5 to 55 °. By spraying inert gas under such conditions, the effect of removing foreign substances can be enhanced.

  The distance between the spray port of the gas spraying means 7 and the steel strip 10 may be adjusted as appropriate according to the type of the gas spraying means 7 to be used, and is not particularly limited. More preferably, it is 5-65 mm, More preferably, it is 10-60 mm, Most preferably, it is 15-55 mm. If the distance between the spray port of the gas spray means 7 and the steel strip 10 is in the above range, the effect of removing foreign substances can be enhanced.

  In the continuous molten metal plating apparatus in which the gas spraying means 7 is provided between the turn-down roll 6 and the heat treatment furnace 1, the steel strip 10 heated in the heat treatment furnace 1 to activate the surface is After being introduced into the snout 2, it is introduced into the molten metal plating bath 4 through the inside of the snout 2. At this time, the foreign matter caused by the vapor deposition fume is likely to adhere to the surface of the steel strip 10 in the region between the snout 2 and the heat treatment furnace 1 (connecting portion 3), but between the turndown roll 6 and the heat treatment furnace 1. Since the foreign matter adhering to the surface of the steel strip 10 can be removed by the gas spraying means 7 provided in the steel strip 10, the steel strip 10 to which no foreign matter is attached can be introduced into the molten metal plating bath 4. . After that, the steel strip 10 that has entered the molten metal plating bath 4 is pulled up from the molten metal plating bath 4 by the sink roll 8 changing the traveling method upward. The steel strip 10 that has been pulled up is adjusted in the amount of plating metal deposited by a gas wiping device (not shown) and guided to the next step. Since the molten metal-plated steel strip obtained in this way is plated with the steel strip 10 to which no foreign matter due to metal fume adheres, the occurrence of surface defects is small.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not construed as being limited thereto.

Example 1
Using the continuous molten metal plating apparatus shown in FIG. 1, continuous molten metal plating was performed on the steel strip 10 of 3000 coils under the conditions shown in Table 1. AX gas was used as the inert gas, and a molten aluminum-zinc plating bath (temperature: 600 ° C.) was used as the molten metal plating bath 4. Moreover, the gas spraying means 7 has a slit-shaped spray port parallel to the width direction of the steel strip 10, and the length of the slit-shaped spray port is equal to or greater than the width of the steel strip 10. In addition, the narrow cross-section connection part 3a has a cross-sectional area where the flow rate of the inert gas is 0.1 m / sec.
(Comparative Example 1)
Continuous molten metal plating was performed in the same manner as in Example 1 except that the inert gas was not sprayed from the gas spraying means 7.

  The presence or absence of surface defects (plating defects) that occurred in the molten metal plated steel strip obtained in Example 1 and Comparative Example 1 was visually evaluated. Specifically, a coil of a molten metal-plated steel strip in which one or more surface defects have been confirmed is regarded as a poorly plated coil, and the ratio of defectively plated coils to the number of all plated coils (number of defectively plated coils / plated) The number of all coils was evaluated. Moreover, the incidence rate of the surface defect of Example 1 was made into relative evaluation when the ratio of the poorly-plated coil of Comparative Example 1 was set to 100%. The results are shown in Table 1.

As shown in Table 1, Example 1 had a lower incidence of surface defects in the hot metal plated steel strip than Comparative Example 1.
As can be seen from the above results, according to the present invention, there is provided a continuous molten metal plating apparatus and a continuous molten metal plating method capable of suppressing the occurrence of surface defects in a molten metal plated steel strip caused by metal fume. Can do.

1 Heat treatment furnace 1a Heating zone
DESCRIPTION OF SYMBOLS 1b Soaking zone and / or cooling zone 2 Snout 3 Connection part 3a Narrow-section connection part 4 Molten metal plating bath 5 Molten metal plating bath 6 Turn-down roll 7 Gas spraying means 8 Sink roll 10 Steel strip

Claims (17)

A continuous molten metal plating apparatus for performing plating by introducing a steel strip heat treated in a heat treatment furnace into a molten metal plating bath via a snout,
The continuous molten metal plating apparatus which has a gas spraying means which sprays an inert gas on the surface of the said steel strip between the turndown roll which advances the said steel strip to the said snout, and the said heat processing furnace.   The continuous molten metal plating apparatus according to claim 1, wherein the gas spraying means is provided between the turn-down roll and a soaking zone and / or a cooling zone of the heat treatment furnace.   The gas spraying means is provided inside a connecting part for connecting the heat treatment furnace and the snout, and the connecting part has a cross-sectional area in a vertical direction with respect to a portion provided with the gas spraying means. The continuous molten metal plating apparatus of Claim 1 or 2 which has a part with small in the said heat processing furnace side.   The continuous molten metal plating apparatus as described in any one of Claims 1-3 with which the said gas spraying means is provided in the upper surface side of the said steel strip.   The gas spraying means has a slit-shaped spray port parallel to the width direction of the steel strip, and the length of the slit-shaped spray port is equal to or greater than the width of the steel strip. 5. The continuous molten metal plating apparatus according to claim 4.   The continuous molten metal plating apparatus as described in any one of Claims 1-5 whose spraying speed of the said inert gas is 3.0 m / sec or more. The continuous molten metal plating apparatus as described in any one of Claims 1-6 with which the temperature (T) of the said inert gas satisfy | fills the following conditions.
(Temperature of molten metal plating bath [° C.] − 150 ° C.) ≦ T ≦ Temperature of molten metal plating bath [° C.]   The said inert gas is sprayed in the direction opposite to the advancing method of the said steel strip, The spray angle of the said inert gas is 0 degree over 65 degrees or less with respect to the said steel strip. A continuous molten metal plating apparatus according to claim 1.   The continuous molten metal plating apparatus as described in any one of Claims 1-8 whose distance between the spraying port of the said gas spraying means and the said steel strip is 0 mm excess and 70 mm or less. A continuous molten metal plating method in which a steel strip heat-treated in a heat treatment furnace is introduced into a molten metal plating bath through a snout to perform plating,
A continuous molten metal plating method in which an inert gas is sprayed onto the surface of the steel strip from a gas spraying means provided between a turn-down roll for causing the steel strip to advance into the snout and the heat treatment furnace.   The continuous molten metal plating method according to claim 10, wherein the gas spraying means is provided between the turn-down roll and a soaking zone and / or a cooling zone of the heat treatment furnace.   The gas spraying means is provided inside a connecting part for connecting the heat treatment furnace and the snout, and the connecting part has a cross-sectional area in a vertical direction with respect to a portion provided with the gas spraying means. The continuous molten metal plating method according to claim 10 or 11, wherein a portion having a small diameter is provided on the heat treatment furnace side.   The continuous molten metal plating method according to any one of claims 10 to 12, wherein the inert gas is sprayed on an upper surface of the steel strip.   The continuous molten metal plating method according to any one of claims 10 to 13, wherein the inert gas spraying speed is 3.0 m / sec or more. The continuous molten metal plating method according to claim 10, wherein the temperature (T) of the inert gas satisfies the following condition.
(Temperature of molten metal plating bath [° C.] − 150 ° C.) ≦ T ≦ Temperature of molten metal plating bath [° C.]   The inert gas is sprayed in a direction opposite to a traveling method of the steel strip, and a spray angle of the inert gas is greater than 0 ° and not more than 65 ° with respect to the steel strip. The continuous molten metal plating method as described in any one of Claims.   The continuous molten metal plating method according to any one of claims 10 to 16, wherein a distance between a spray port of the gas spraying means and the steel strip is greater than 0 mm and equal to or less than 70 mm.

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