JPH08176774A - Production of galvanized stel sheet and production dvice threfor - Google Patents

Abstract

PURPOSE: To rapidly and easily adjust the size of spangles by spraying spangle adjusting agents in a molten state to the surfaces of a galvanized steel sheet adjusted in adhesion. CONSTITUTION: The strip 1 is galvanized while passing a galvanizing bath 4. The strip 1 is adjusted in the coating weight of zinc of the surfaces by gas throttling devices 7. Any of the spangle adjusting agents of Pb, Sn, Bi, K, Cd, Sb, etc., are sprayed by a thermal spraying method into galvanizing layers of an unmolten state adjusted in the coating weight of the zinc after pulling up from the galvanizing bath 4 by thermal spraying machines 8. The sprayed spangle adjusting agents melt and diffuse in the galvanizing layers. The amt. of the spangle adjusting agents to be sprayed by the thermal spraying machines 8 is changed, by which the size of the spangles is changed. As a result, the adhesion of the splashed spangle agents on the equipment is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a galvanized steel sheet, and more particularly, a method and an apparatus for producing a galvanized steel sheet suitable for producing a galvanized steel sheet produced by a continuous hot dip galvanizing line. Regarding

[0002]

2. Description of the Related Art Galvanized steel sheets whose surfaces are coated with zinc are widely used. As one of the methods for producing this galvanized steel sheet, a continuous hot dip galvanizing method is known in which the steel sheet is immersed in a hot dip galvanizing bath and pulled up to coat the surface of the steel sheet with zinc. An acicular zinc crystal pattern called spangle appears on the surface of the galvanized steel sheet produced by this hot dip galvanizing method. It is known that the size of this spangle changes depending on the components in the hot-dip galvanizing bath, and in particular Pb, Sn, Bi, K, C
Various metals of d and Sb (spangle adjusters) have a great influence on the size of spangle. For example, as shown in FIG. 3, the spangle becomes smaller as the Pb content decreases. Therefore, as one of the methods for obtaining the plating spun surface layer of the minimum spangle (the spangle having the smallest size), a method of reducing the content of each of the above elements in the hot-dip galvanizing bath is used. .

According to this method, in order to manufacture a steel sheet having a plating film surface layer with different spangle sizes, for example, the Pb content in the hot dip galvanizing bath must be adjusted each time, and this is extremely practiced. difficult. That is, in the continuous hot dip galvanizing line, the capacity of the hot dip galvanizing bath is
Usually, there are about several hundred tons, so to change the Pb content from a high level to a low level, and vice versa, use a large amount of zinc metal with different Pb content. However, there is a problem in that it is necessary to replace the entire zinc bath, which requires a great deal of time.

Therefore, a strip of Pb base metal is continuously supplied to the molten plating coating layer while being in contact with the molten coating layer, and Pb is melted and diffused in the plating layer to diffuse the zinc coating layer. A spangle adjusting method and apparatus for continuous hot-dip galvanizing, which can change and adjust the Pb content, that is, the size of the spangle, has been proposed (see Japanese Patent Laid-Open No. 59-118869).

[0005]

However, in the above-mentioned conventional method of bringing the strip-shaped Pb metal into contact with the above-mentioned molten plating coating layer, the temperature of the plating coating layer is constant and its thickness is about 10 μm. Since it is thin, P in a short time
b It is difficult to dissolve the metal. Further, if the line speed is increased, the metal is not sufficiently dissolved in the plating coating layer, so that there is a problem that the line speed cannot be increased. Furthermore, before wiping to adjust the amount of molten zinc deposited on the surface of the steel sheet, the molten zinc deposited on the surface of the steel sheet is scraped off by the Pb metal, which causes a large variation in the amount of molten zinc deposited after wiping. There is. Therefore, in manufacturing a galvanized steel sheet on which a plated coating layer having a uniform thickness is formed, it is difficult in practice to change the size of the spangle easily in a short time.

In view of the above circumstances, it is an object of the present invention to provide a galvanized steel sheet manufacturing method and manufacturing apparatus capable of easily changing the size of spangles in a short time.

[0007]

Means for Solving the Problems A method for manufacturing a galvanized steel sheet according to the present invention to achieve the above object is the method for manufacturing a galvanized steel sheet, comprising: (1) an attaching step of attaching molten zinc to the steel sheet surface; ) Adjusting process for adjusting the amount of molten zinc adhering to the steel plate surface (3) The size of the spangle is adjusted by spraying a spangle adjusting agent in a molten state onto the surface of the steel plate to which the molten zinc whose adhering amount has been adjusted adheres. It is characterized by including a spraying step for adjusting the height.

Further, the apparatus for producing a galvanized steel sheet according to the present invention for achieving the above-mentioned object makes molten zinc adhere to the surface of the steel sheet and adjusts the amount of the molten zinc adhering to the surface of the steel sheet with a wiping machine. In a galvanized steel sheet manufacturing apparatus for manufacturing a galvanized steel sheet by cooling a steel sheet with the amount of molten zinc adhered adjusted, (4) a molten state on the surface of the steel sheet to which the amount of molten zinc adhered is adhered A spraying machine disposed above the wiping machine for spraying the spangle adjusting agent of (5) Around the spraying machine for collecting the scattered spangle adjusting agent of the spangle adjusting agent sprayed on the steel plate surface. It is characterized by having a collection hood arranged at.

[0009]

According to the method for producing a galvanized steel sheet of the present invention,
Since the spangle adjusting agent in a molten state is sprayed onto the surface of the steel sheet to which the molten zinc whose amount has been adjusted has adhered, the amount of molten zinc applied after adjusting the amount does not vary, and the spangle adjusting agent is easy to use. It is dissolved in molten zinc and diffused. Since the spangle adjusting agent becomes a crystal nucleus of spangle generation, the size of the spangle can be easily adjusted in a short time by changing the amount of the spangle adjusting agent to be sprayed.

Further, according to the galvanized steel sheet manufacturing apparatus of the present invention, the size of the spangle can be easily adjusted in a short time by changing the amount of the spangle adjusting agent sprayed by the spraying machine. Also, since the spangled agent that has been scattered is collected by the collection hood, the spangled agent that has scattered is
For example, it is possible to prevent the molten zinc bath from being contaminated or attached to other equipment.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method and apparatus for manufacturing a galvanized steel sheet according to the present invention will be described below with reference to the drawings. FIG.
FIG. 4 is a schematic diagram showing a galvanizing step in a continuous hot-dip galvanizing line to which the present invention is applied.

The strip 1 is continuously guided to the molten zinc bath 4 through the snout 3 guided by the turndown 2. A sink roll 5 is installed in the molten zinc bath 4, and the strip 1 is conveyed upward through this sink roll 5 and is subjected to a subsequent process by a deflector roll 6 installed above the molten zinc bath 4. It is transported continuously. The strip 1 galvanized while passing through the hot dip zinc bath 4 is coated with zinc by the gas squeezing device (wiping device) 7 installed above the hot dip zinc bath 4 and below the deflector roll 6. Is adjusted and then sent to the deflector roll 6. Gas expansion device 7
Directly above and below the deflector roll 6, a thermal spray machine (an example of a spraying machine according to the present invention) 8 is installed. In the galvanized layer which is still in a molten state, which is pulled up from the molten zinc bath 4 by the thermal spraying machine 8 and whose amount of zinc deposited on the surface is adjusted by the gas expansion device 7, Pb, Sn,
Any of the spangle modifiers such as Bi, K, Cd and Sb is sprayed by the thermal spraying method. The sprayed spangle modifier dissolves and diffuses in the galvanized layer. The size of the spangle can be changed by changing the amount of the spangle adjusting agent sprayed by the thermal spraying machine 8.

FIG. 2 is a schematic view illustrating the structure of the thermal spraying machine 8. Spangle adjuster 9 stored in hopper 10
After being cut out by the quantitative cut-out device 11 and supplied to the thermal spraying machine 8 by the powder carrier gas 14, the molten spangle adjusting agent 9 is sprayed onto the galvanized layer adhering to the surface of the strip 1 in the molten state. Is sprayed by. The sprayed spangle adjusting agent 9 is dissolved and diffused in the galvanized layer. A dust collection hood 13 is disposed above and below the thermal spraying machine 8 to collect the spangle adjusting agent 9 that has not been sprayed onto the galvanized layer and is scattered. It prevents the bath 4 from being contaminated and adhering to other equipment.
In the illustrated example, a plurality of thermal sprayers 8 are installed on both sides of the strip 1 in the width direction, and the size of the spangles of the galvanized layers on both sides of the strip 1 can be adjusted. The thermal spraying machine 8 is generally used, and the melting fuel 15 (propane gas, acetylene gas) and oxygen 16 are supplied to the thermal spraying machine 8 and mixed and burned with Pb powder for thermal spraying.

As the quantitative cut-out device 11, the number of revolutions is adjusted by a disc feeder, and the spangle adjusting agent is passed through a fluidized bed (not shown) in which the spangle adjusting agent is in a fluid state inside the hopper 10. By adjusting the flow rate of the carrier gas containing the agent with the flow rate control valve,
What controls the spray amount of the spangle adjuster can be used. Further, since the spangle adjusting agent is melted by the thermal spraying machine 8 and then blown out into the galvanized layer, the upper limit of the line speed is not regulated for dissolving the spangle adjusting agent. In addition, it is possible to solve the problem of causing variations in the zinc areal weight after wiping.

In this way, by controlling the spraying amount using the thermal spraying machine 8 and spraying the spangle adjusting agent into the molten zinc plating layer to dissolve and diffuse it, the minimum spangle can be adjusted to any size. It is possible to manufacture galvanized steel sheets with a plated coating layer showing spangles of various sizes up to regular spangles without adjusting the bath components of the molten zinc bath, and to instantly change the size of spangles. can do.

Next, a test example of the method for producing a galvanized steel sheet of the present invention will be described together with a comparative test example. In the continuous hot-dip galvanizing line shown in FIG. 1, the average particle size is 40
Pb powder having a size of less than or equal to μm is charged into the hopper 10 shown in FIG.
A steel strip having a plate thickness of 0.5 mm and a plate width of 914 mm was hot dip galvanized at a line speed of 150 mpm. Here, the Pb content in the hot dip galvanizing is 0.01 wt%
Below, the Pb powder used was an electrolytic powder of Pb 100%. Further, the sprayed amount of Pb powder in the test example of the present invention was 0.129 g / min, and the bath temperature of the molten zinc bath 4 was 460 ° C. Further, the melting temperature of zinc in this molten zinc bath 4 was about 420 ° C., and the temperature of the unsolidified coating layer of molten zinc at the position where the Pb powder was sprayed was 440 ° C.

Table 1 shows the difference in the spangle generation pattern between the case where the production method of the present invention is carried out and the case where the production method of the present invention is not carried out, and the difference in the Pb content in the plating film. As shown in Table 1, in the present invention, a galvanized steel sheet having regular spangles could be manufactured, but conventionally, a galvanized steel sheet having minimum spangles was produced. Further, since the thermal spraying machine 8 (see FIG. 1) was used in the above test example, the minimum spangle can be switched to the regular spangle instantaneously, and the manufactured galvanized steel sheet has a uniform spangle pattern. there were.

[0018]

[Table 1]

When the molten Pb powder is sprayed onto the galvanized layer which is still in a molten state as in the present invention, the Pb element is instantly dissolved in zinc because the dissolution rate and diffusion rate of Pb are sufficiently high. Can be diffused. After that, spangles grow during the cooling process of zinc, and a galvanized steel sheet on which spangles of a desired size are formed can be manufactured.

[0020]

According to the method for producing a galvanized steel sheet of the present invention, since a spangle adjusting agent in a molten state is sprayed onto the surface of the steel sheet to which the molten zinc having the adjusted amount of adhesion is attached,
The amount of molten zinc adhered after adjusting the amount of adhering hardly fluctuates, and the spangle adjuster is easily dissolved and diffused in molten zinc, and the amount of spangle adjuster sprayed is changed to reduce the spangle size in a short time. Can be adjusted easily.

Also, according to the galvanized steel sheet manufacturing apparatus of the present invention, the size of the spangle can be easily adjusted in a short time by changing the amount of the spangle adjusting agent sprayed by the spraying machine, and the scattered spangle agent Is collected by the collection hood, it is possible to prevent the spangle agent scattered from contaminating the molten zinc bath or adhering to other equipment.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a galvanizing process in a continuous hot-dip galvanizing line to which the present invention is applied.

FIG. 2 is a schematic view illustrating the structure of a thermal spraying machine.

FIG. 3 is a graph showing the relationship between Pb content and spangle size.

[Explanation of symbols]

 1 strip 2 deflector roll 3 snout 4 molten zinc bath 5 sink roll 6 deflector roll 7 gas squeezing device (wiping device) 8 spraying machine for spangle adjustment 9 Pb, Sn, Bi, K, Cd, Sb metal powder 10 hopper 11 quantitative Cutting device 12 Thermal sprayer body 13 Dust collecting hood 14 Powder conveying gas 15 Melting fuel 16 Oxygen

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsumi Kimura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Inside the Chiba Works, Kawasaki Steel Co., Ltd. (72) Hiroyuki Nakajima 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Chiba Steel Works, Ltd.

Claims (2)

[Claims] 1. A method of manufacturing a galvanized steel sheet, wherein an adhesion step of adhering molten zinc to the surface of the steel sheet, an adjusting step of adjusting an adhesion amount of the molten zinc adhering to the surface of the steel sheet, and an adhesion amount are adjusted. A method for producing a galvanized steel sheet, comprising: a spraying step of adjusting the size of the spangle by spraying a spangle adjusting agent in a molten state onto the surface of the steel sheet to which the molten zinc is attached. 2. A galvanized steel sheet in which molten zinc is adhered to the surface of a steel sheet, the amount of molten zinc adhering to the surface of the steel sheet is adjusted by a wiping machine, and the steel sheet with the amount of adhering molten zinc is cooled. In the manufacturing apparatus of the galvanized steel sheet for producing, spraying a spangle adjusting agent in a molten state on the steel sheet surface to which the molten zinc of which the adhesion amount is adjusted is attached, a spraying machine disposed above the wiping machine, An apparatus for manufacturing a galvanized steel sheet, comprising: a recovery hood arranged around the spraying machine to recover the scattered spangle adjusting agent among the spangle adjusting agents sprayed on the surface of the steel sheet.