JP7161292B2 - Continuous hot dip metal plating apparatus and continuous hot dip metal plating method - Google Patents

Description

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

In a continuous hot-dip metal plating apparatus, a steel strip is heated in a heat treatment furnace to activate its surface, and then the steel strip is introduced into a hot-dip metal plating bath through a snout for plating. One end of the snout is connected to a heat treatment furnace via a connecting part and the other end is immersed in a molten metal plating bath in order to shield 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 (coating defects) caused by oxidation and dirt on the surface of the steel strip. Metal fumes enter the snout. The metal fume in the snout flows in the direction opposite to the advancing direction of the steel strip, and when cooled, adheres to the inner wall surface of the apparatus as foreign matter. When this foreign matter falls off from the inner wall surface or the like and adheres to the steel strip, it causes surface defects in the hot-dip metal-plated steel strip.

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

JP-A-2000-290761 JP-A-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 fumes, and foreign matter may adhere to the steel strip due to the inflow of metal fumes. In the method of Patent Document 3, although adhesion of foreign matter in the snout can be suppressed, metal fumes flow into the upstream of the snout. adhere to.

The present invention has been made to solve the above-mentioned problems, and is capable of suppressing the occurrence of surface defects in a hot-dip metal plated steel strip caused by metal fumes and a continuous hot-dip metal plating method. intended to provide

As a result of intensive research aimed at solving the above problem, the inventors of the present invention have found that foreign matter caused by metal fumes tends to adhere to the steel strip in the region upstream of the snout, and based on this knowledge, the steel strip is By providing a gas blowing means for blowing an inert gas onto the surface of the steel strip between the turndown roll advancing the snout and the heat treatment furnace, it was found that adhesion of foreign matter caused by metal fumes could be suppressed, The present invention has been completed.

That is, the present invention is a continuous hot-dip metal plating apparatus for performing plating by introducing a steel strip heat-treated in a heat treatment furnace into a hot-dip metal plating bath through a snout, wherein the steel strip is advanced through the snout. Between the down roll and the heat treatment furnace, gas blowing means for blowing an inert gas onto the surface of the steel strip is provided, and the gas blowing means is a slit-shaped blower parallel to the width direction of the steel strip. The slit-shaped spraying port has a length equal to or greater than the width of the steel strip, and the inert gas is sprayed in a direction opposite to the direction in which the steel strip advances. is 3 to 60° with respect to the steel strip .
The present invention also provides a continuous hot-dip metal plating method in which a steel strip heat-treated in a heat treatment furnace is introduced into a hot-dip metal plating bath through a snout for plating, wherein the steel strip is advanced through the snout. An inert gas is blown onto the surface of the steel strip from a gas blowing means provided between the down roll and the heat treatment furnace, and the gas blowing means blows a slit-shaped blow parallel to the width direction of the steel strip. a spout, the length of the slit-shaped spray spout being equal to or greater than the width of the steel strip, the inert gas being sprayed in a direction opposite to the advancing direction of the steel strip, It relates to a continuous hot dip metal plating method in which the gas blowing angle is 3 to 60° with respect to the steel strip .

According to the present invention, it is possible to provide a continuous hot-dip metal plating apparatus and a continuous hot-dip metal plating method that can suppress the occurrence of surface defects in a hot-dip metal plated steel strip caused by metal fumes.

1 is a schematic configuration diagram of a continuous hot dip metal plating apparatus according to an embodiment of the present invention; FIG.

The continuous hot-dip metal plating apparatus of the present invention performs plating by introducing a steel strip heat-treated in a heat treatment furnace into a hot-dip metal plating bath through a snout. A gas blowing means for blowing an inert gas onto the surface of the steel strip is provided between the steel strip and the heat treatment furnace.
In the continuous hot dip metal plating method of the present invention, the steel strip heat-treated in the heat treatment furnace is introduced into the hot dip metal plating bath through the snout for plating. An inert gas is blown onto the surface of the steel strip from a gas blowing means provided between the rolls and the heat treatment furnace.
BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the continuous hot-dip metal plating apparatus and the continuous hot-dip metal plating method of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of a continuous hot dip metal plating apparatus according to an embodiment of the present invention.
The continuous hot dip metal plating apparatus of the present embodiment includes a heat treatment furnace 1 (for example, an annealing furnace) including a heating zone 1a and a soaking zone and/or 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 containing a molten metal plating bath 4 in which the other end of the snout 2 is immersed. A turndown roll 6 for advancing the steel strip 10 heat-treated in the heat treatment furnace 1 toward the snout 2 is provided inside the connecting portion 3 . Between the turndown roll 6 and the heat treatment furnace 1 (in particular, the soaking zone and/or the cooling zone 1b of the heat treatment furnace 1), a gas spraying means 7 for spraying an inert gas onto the surface of the steel strip 10 is provided. It is Furthermore, a sink roll 8 is provided in the hot dip metal plating bath 4 to guide the steel strip 10 upward in the hot dip metal plating bath 5 .
Among the members of the continuous hot-dip metal plating apparatus described above, members other than the gas blowing means 7 are known in the art. Therefore, members other than the gas blowing means 7 can adopt 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. is.

In the continuous hot-dip metal plating apparatus, metal fumes evaporated from the surface of the hot-dip metal plating bath 4 in the snout 2 enter the snout 2 and flow 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 substance. At this time, since the steel strip 10 advances at an angle within the snout 2 , even if a foreign object falls off from the inner wall surface or the like, it is unlikely to adhere to the surface of the steel strip 10 . On the other hand, since the steel strip 10 advances upstream of the snout 2 while keeping it horizontal, any foreign matter falling off the inner wall surface or the like is likely to adhere to the surface of the steel strip 10 . Therefore, in the continuous hot dip metal plating apparatus according to the present embodiment, the gas spraying means 7 is provided between the turndown roll 6 and the heat treatment furnace 1, and the inert gas is applied to the surface of the steel strip 10 from the gas spraying means 7. 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-sectional connecting portion 3a) having a smaller vertical cross-sectional area (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. preferably included. This narrow cross-section connecting portion 3a is provided on the heat treatment furnace 1 side. By providing the narrow cross-section connecting portion 3a, the flow velocity of the inert gas at the narrow cross-section connecting portion 3a becomes faster than the flow velocity of the inert gas at the portion where the gas spraying means 7 is provided, so that the surface of the steel strip 10 The effect of removing foreign matter adhering to is enhanced. From the viewpoint of sufficiently obtaining such effects, it is preferable to adjust the cross-sectional area of the narrow cross-section connecting portion 3a so that the flow velocity of the inert gas in the narrow cross-section connecting portion 3a is 0.1 m/sec or more.

The gas blowing means 7 is not particularly limited as long as it can blow an inert gas onto the surface of the steel strip 10, and known means 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 equal to or greater than the width of the steel strip 10 . With the gas blowing means 7 having such a blowing port, the inert gas can be blown over the entire width direction of the steel strip 10, so that foreign matter adhering to the surface of the steel strip 10 can be stably removed. can be done. In addition, since the gas spraying means 7 can function as a gas shield, it is possible to make it difficult for metal fumes to flow in before the region to which the inert gas is sprayed.

It is preferable that the gas spraying means 7 be provided on the upper surface side of the steel strip 10 because foreign matter resulting from metal fumes tends to adhere to the upper surface of the steel strip 10 .
Moreover, the gas blowing means 7 may be provided not only on the upper surface side of the steel strip 10 but also on the lower surface side. Various foreign substances brought in from the upstream side may adhere to the lower surface side of the steel strip 10 due to various factors. can be removed.

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

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

Although the temperature (T) of the inert gas is not particularly limited, it 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 temperature of the inert gas within the above range, it is possible to obtain a hot-dip metal plated steel strip with fewer surface defects. If the temperature (T) of the inert gas is less than (the temperature [° C.] of the hot dip metal plating bath 4 −150° C.), when the steel strip 10 is introduced into the hot dip metal plating bath 4, The surface of is likely 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, the molten metal plating is difficult to form on the surface of the steel strip 10.
The temperature of the molten metal plating bath 4 cannot be uniquely defined because it depends on the type of metal. For example, if the hot dip metal plating bath 4 is a hot dip galvanizing bath, its temperature is typically 440-480°C. Further, when the hot dip metal plating bath 4 is a hot dip aluminum-zinc plating bath, its temperature is generally 580-700.degree.

The inert gas is sprayed in a direction opposite to the advancing direction of the steel strip 10, and the spray angle of the inert gas is preferably more than 0° and 65° or less, more preferably 3 to 60°, with respect to the steel strip 10. °, more preferably 5 to 55°. By blowing the inert gas under such conditions, the effect of removing foreign matter can be enhanced.

The distance between the blowing port of the gas blowing means 7 and the steel strip 10 may be appropriately adjusted according to the type of the gas blowing means 7 used, and is not particularly limited, but is preferably more than 0 mm and 70 mm or less. More preferably 5 to 65 mm, still more preferably 10 to 60 mm, particularly preferably 15 to 55 mm. If the distance between the blowing port of the gas blowing means 7 and the steel strip 10 is within the above range, the effect of removing foreign matter can be enhanced.

In a continuous hot-dip metal plating apparatus provided with a gas spraying means 7 between a turndown roll 6 and a heat treatment furnace 1, a steel strip 10 whose surface has been activated by heating in the heat treatment furnace 1 is heated by the turndown roll 6. After being introduced into the snout 2 , it is introduced into the molten metal plating bath 4 through the snout 2 . At this time, foreign matter caused by vapor deposition fumes tends to adhere to the surface of the steel strip 10 in the region (connecting portion 3) between the snout 2 and the heat treatment furnace 1, but between the turndown roll 6 and the heat treatment furnace 1 Foreign matter adhering to the surface of the steel strip 10 can be removed by the gas blowing means 7 provided in the steel strip 10, so the steel strip 10 free of foreign matter can be introduced into the molten metal plating bath 4. . After that, the steel strip 10 entering the molten metal plating bath 4 is moved upward by the sink roll 8 and pulled up from the molten metal plating bath 4 . A gas wiping device (not shown) adjusts the coating amount of the plating metal on the pulled steel strip 10, and the steel strip 10 is led to the next step. The hot-dip metal plated steel strip obtained in this way has few surface defects because the steel strip 10 is plated to which no foreign matter caused by metal fumes adheres.

The contents will be described in more detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited thereto.

(Example 1)
Using the continuous hot-dip metal plating apparatus shown in FIG. 1, continuous hot-dip 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 . Further, 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 . The narrow cross-section connecting portion 3a has a cross-sectional area at which the flow velocity of the inert gas is 0.1 m/sec.
(Comparative example 1)
Continuous hot-dip 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) occurring in the hot-dip metal plated steel strips obtained in Example 1 and Comparative Example 1 was visually evaluated. Specifically, a hot-dip metal plated steel strip coil with one or more surface defects confirmed is regarded as a defectively plated coil, and the ratio of defectively plated coils to all coils that have been plated (number of defectively plated coils/plated It was evaluated by calculating the total number of coils). In addition, the rate of occurrence of surface defects in Example 1 was a relative evaluation when the rate of defectively plated coils in Comparative Example 1 was taken as 100%. Table 1 shows the results.

As shown in Table 1, in Example 1, the incidence of surface defects in the hot-dip metal plated steel strip was lower than in Comparative Example 1.
As can be seen from the above results, according to the present invention, it is possible to provide a continuous hot dip metal plating apparatus and a continuous hot dip metal plating method that can suppress the occurrence of surface defects in hot dip metal plated steel strips caused by metal fumes. can be done.

1 heat treatment furnace 1a heating zone
1b Soaking zone and/or cooling zone 2 Snout 3 Connection 3a Narrow section connection 4 Hot dip metal plating bath 5 Hot dip metal plating bath 6 Turndown roll 7 Gas blowing means 8 Sink roll 10 Steel strip

Claims (14)

A continuous hot dip metal plating apparatus for plating by introducing a steel strip heat-treated in a heat treatment furnace into a hot dip metal plating bath through a snout,
gas spraying means for spraying an inert gas onto the surface of the steel strip between the heat treatment furnace and the turndown roll that advances the steel strip to the snout;
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 ,
A continuous hot-dip metal plating apparatus , wherein the inert gas is blown in a direction opposite to the advancing direction of the steel strip, and the spraying angle of the inert gas is 3 to 60° with respect to the steel strip . 2. The continuous hot dip metal plating apparatus according to claim 1, wherein said gas blowing means is provided between said turndown roll and a soaking zone and/or a cooling zone of said heat treatment furnace. The gas blowing means is provided inside a connecting portion that connects the heat treatment furnace and the snout, and the connecting portion is vertically cut away from the portion where the gas blowing means is provided. 3. The continuous hot dip metal plating apparatus according to claim 1, having a portion with a small area on the heat treatment furnace side. The continuous hot dip metal plating apparatus according to any one of claims 1 to 3, wherein said gas spraying means is provided on the upper surface side of said steel strip. The continuous hot dip metal plating apparatus according to any one of claims 1 to 4, wherein the inert gas spray speed is 3.0 m/sec or more. The continuous hot dip metal plating apparatus according to any one of claims 1 to 5, wherein the temperature (T) of said inert gas satisfies the following conditions.
(Temperature of molten metal plating bath [°C] -150°C) ≤ T ≤ Temperature of molten metal plating bath [°C] The continuous hot dip metal plating apparatus according to any one of claims 1 to 6 , wherein the distance between the blowing port of said gas blowing means and said steel strip is more than 0 mm and not more than 70 mm. A continuous hot dip metal plating method in which a steel strip heat treated in a heat treatment furnace is introduced into a hot dip metal plating bath through a snout for plating,
blowing an inert gas onto the surface of the steel strip from a gas spraying means provided between the heat treatment furnace and a turndown roll that advances the steel strip to the snout;
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 ,
A continuous hot-dip metal plating method , wherein the inert gas is sprayed in a direction opposite to the advancing direction of the steel strip, and the spraying angle of the inert gas is 3 to 60° with respect to the steel strip . 9. The continuous hot dip metal plating method according to claim 8 , wherein said gas blowing means is provided between said turndown roll and a soaking zone and/or cooling zone of said heat treatment furnace. The gas blowing means is provided inside a connecting portion that connects the heat treatment furnace and the snout, and the connecting portion is vertically cut away from the portion where the gas blowing means is provided. 10. The continuous hot dip metal plating method according to claim 8 or 9 , wherein a portion having a small area is provided on the heat treatment furnace side. The continuous hot dip metal plating method according to any one of claims 8 to 10 , wherein the inert gas is blown onto the upper surface of the steel strip. The continuous hot dip metal plating method according to any one of claims 8 to 11 , wherein the inert gas is sprayed at a speed of 3.0 m/sec or more. The continuous hot dip metal plating method according to any one of claims 8 to 12 , wherein the temperature (T) of said inert gas satisfies the following conditions.
(Temperature of molten metal plating bath [°C] -150°C) ≤ T ≤ Temperature of molten metal plating bath [°C] The continuous hot-dip metal plating method according to any one of claims 8 to 13 , wherein the distance between the blowing port of said gas blowing means and said steel strip is more than 0 mm and not more than 70 mm.

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