JP4044888B2 - Method for producing alloyed hot-dip galvanized steel sheet or cold-rolled steel sheet - Google Patents

Description

The present invention relates to an apparatus for manufacturing an alloyed hot-dip galvanized steel sheet and an operation method thereof.
Specifically, the present invention relates to a method for producing an alloyed hot-dip galvanized steel sheet or a cold-rolled steel sheet, in which a steel sheet annealed after cold rolling is immersed in a hot dip galvanizing bath for plating and then alloyed .

When producing alloyed hot-dip galvanized steel sheets, it is known that the steel sheet temperature that penetrates the plating bath has a significant effect on the plating characteristics, especially when the steel sheet annealed after cold rolling is subjected to cooling treatment. Both ends are easy to remove heat, and the temperature tends to be lower than the central part of the steel sheet, alloying plating becomes uneven in the width direction of the sheet, and the shape of the steel sheet and the control of sheet passing deteriorate, leading to a walk. There was a problem that cooling buckle occurred.
Thus, various proposals have been made in the past regarding methods for uniformizing the temperature distribution in the width direction of the steel sheet.
For example, in Japanese Patent Laid-Open No. 10-25558, in the latter stage of heat treatment of a steel strip, using a hearth roll having an induction heating device, both ends of the steel strip in the width direction are heated and heated from the central portion to a hot dip galvanizing bath. A method is disclosed in which a uniform zinc-iron alloyed hot-dip galvanized steel strip is produced by conducting a heat alloying treatment after conducting plating and controlling to a predetermined adhesion amount.

Japanese Patent Application Laid-Open No. 2000-297331 discloses gas jet cooling that can change the air volume distribution in the width direction of a steel sheet by dividing a wind box that blows cooling gas onto the steel sheet into three chambers by two partition plates. The device is being hourly.
Furthermore, in Japanese Patent Application Laid-Open No. 2001-294940, when the width size of the steel plate is changed to a wide width, the heating range of the steel plate is adjusted according to the width size of the steel plate, and the temperature distribution in the steel strip width direction on the cooling zone exit side. A heat treatment method and apparatus that can make the temperature uniform are disclosed.
However, each of the above-mentioned prior arts discloses a single device for heating and cooling uniformly in the width direction of the steel plate, and a device for producing an alloyed hot-dip galvanized steel plate by combining these devices. No specific study has been made on the configuration and the arrangement of the apparatus when the plated steel sheet and the cold-rolled steel sheet are separately produced.
Japanese Patent Laid-Open No. 10-25558 JP 2000-297331 A JP 2001-294940 A

The present invention solves the problems of the prior art as described above, and has excellent plating uniformity when alloying is performed after the steel sheet annealed after cold rolling is immersed in a hot dip galvanizing bath and plated. Another object of the present invention is to provide a method for producing an alloyed hot-dip galvanized steel sheet or a cold-rolled steel sheet that can produce cold-rolled steel sheets that do not generate walks or cooling buckles.

As a result of intensive studies to solve the above-mentioned problems, the present invention can provide a uniform alloy plating by making the temperature distribution in the width direction of the steel sheet uniform, and a cold-rolled steel sheet that does not generate walks or cooling buckles. A method for producing a galvannealed steel sheet or a cold-rolled steel sheet that can be produced separately has been found, and the gist thereof is as follows.
(1) An alloyed hot dip galvanized steel using a galvannealed steel plate manufacturing apparatus having cooling dampers divided in the width direction of the plate to adjust the spraying position of the cooling gas to the cooling zone of the steel plate annealed after cold rolling. A method for producing a plated steel sheet or a cold-rolled steel sheet,
When producing an alloyed hot-dip galvanized steel sheet, only the central part of the cooling damper in the first half of the cooling zone is opened, the other cooling dampers are fully closed, and the end of the steel sheet cooled to 500 ° C. to 460 ° C. in the cooling zone And steel plate with a temperature difference in the range of ± 5 ° C within the range of ± 5 ° C is immersed in a hot dip galvanizing bath and plated, and then alloyed.
When manufacturing a cold-rolled steel sheet, only the end of the cooling damper in the first half of the cooling zone is closed, the other cooling dampers are opened, and the opening is changed in the range of 0 to 100 according to the plate width of the steel sheet. Thus, the temperature difference between the end portion and the central portion of the steel plate cooled to about 500 ° C. to 100 ° C. within the cooling zone is within a range of ± 15 ° C. Production method.
(2) An alloyed hot-dip galvanized steel sheet or cold-rolled steel sheet according to (1), characterized in that an apparatus for producing an alloyed hot-dip galvanized steel sheet having a roll chamber for heating a transport roll above and below the cooling zone is used. Manufacturing method.

According to the present invention, the temperature distribution in the width direction of the steel sheet can be made uniform and uniform alloy plating can be performed, and the alloyed hot dip galvanizing that can separately produce cold-rolled steel sheets that do not generate walks or cooling buckles. The manufacturing method of a steel plate or a cold-rolled steel plate can be provided, and there exists a remarkable effect useful industrially.

An embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing an equipment configuration of an apparatus for producing an galvannealed steel sheet according to the present invention.
In FIG. 1, 1 is a steel plate, 2 is a bottom roll, 3 is a bottom roll chamber,
4 is a cooling damper, 5 is a top roll, 6 is a top roll chamber, 7 is an edge heating roll, 8 is a path switching roll, 9 is a width direction thermometer, 10 is a plating pot, 11 is a sink roll, and 12 is attached to the plating A quantity control device, 13 is a movable burner, and 14 is an alloying device.
In this embodiment, a steel sheet annealed after cold rolling is immersed in a hot dip galvanizing bath and plated, and then an alloyed hot dip galvanized steel sheet that is alloyed and a cold rolled steel sheet that is not plated are separately produced. An alloyed hot-dip galvanized steel sheet manufacturing apparatus capable of manufacturing each steel sheet will be described below.

In the plated steel sheet, in this step, it is cooled to about 500 ° C. to 460 ° C. The problem in this case is that the temperature difference in the width direction of the steel sheet becomes ± 5 ° C or more, and the Fe concentration in the zinc changes in the alloying process after galvanization, causing problems such as powdering partially. Is to prevent. This problem is particularly likely to occur at the end of the steel plate.
<Alloyed hot-dip galvanized steel sheet>
First, the steel sheet 1 annealed after cold rolling is transported from a soaking zone (not shown) to a cooling zone and cooled by blowing cooling gas from a cooling damper 4 while moving up and down between the bottom roll 2 and the top roll 5. Is done.
As shown in FIG. 2, the cooling damper 4 has a structure in which, for example, a wind box provided with a large number of air jets is divided into three in the width direction of the steel plate, and is sprayed on the steel plate at the center and end portions of the steel plate. The amount of cooling gas can be changed in the plate width direction.
In order to cool the steel plate 1 out of the soaking zone (not shown) uniformly in the plate width direction from about 500 ° C. to an intrusion target value ± 5 ° C. of the hot dip galvanizing bath, the cooling zone 4 is used. Only the central part of the cooling damper 4 in the first half is opened, and the other cooling dampers 4 are fully closed.
As a result, the cooling temperature can be properly controlled and overcooling of the steel plate end can be prevented, so that a delay in alloying due to overcooling of the steel plate end as in the conventional case is suppressed, and the alloy in the plate width direction is controlled. Can be made uniform.

Further, when the steel plate 1 comes into contact with the top roll 5 and the bottom roll 2 for conveying the steel plate and heat is removed from the roll surface, the temperature distribution in the width direction of the steel plate 1 becomes non-uniform. The top roll chamber 6 and the bottom roll chamber 3 that store the roll 2 are respectively installed above and below the cooling zone, and a roll heater is installed around the top roll 5 and the bottom roll 2 to heat the roll.
By this bar-shaped heater, the roll is uniformly heated in the width direction, and particularly, the end of the steel plate is in contact with the heated roll, whereby a non-uniform temperature drop in the width direction of the steel plate 1 can be prevented. At this time, it is preferable to control the set temperature of the roll chamber within the range of the furnace temperature + 50 ° C., and when the temperature steel plate thickness is thin, the end portion of the steel plate 1 is likely to be overcooled, so that the temperature is increased. preferable.
Next, an edge heating roll 7 is installed on the exit side of the cooling zone, that is, on the entrance side of the plating bath, and by heating the end portion of the steel plate 1 thereby, the temperature distribution in the plate width direction is made uniform. Can be
The edge heating roll 7 can control the roll surface temperature so that the steel sheet temperature when entering the plating bath is ± 5 ° C. of the target value. For example, as shown in FIG. By having a plurality of induction heating coils 15 and selecting the coil to be used, the end portion of the steel plate 1 can be selectively heated, so that overcooling of the end portion can be prevented. It is preferable to apply to a steel plate such as a steel plate that tends to cause end supercooling.

Here, after checking the plate | board temperature of the width direction of the steel plate 1 with the width direction thermometer 9, after being immersed in a plating bath with the plating pot 10 through a snout, and changing direction with the sink roll 11, it adheres to plating. An appropriate plating thickness can be obtained by the quantity control device 12.
The plated steel plate is subjected to alloying treatment by the alloying device 14 after the end portion is heated by the movable burner 13.
This movable burner 13 is a burner capable of causing the position of the burner nozzle to follow the position of the end of the steel plate even when the width of the steel plate 1 is changed as shown in FIG. 4, for example, before performing the alloying process. By selectively heating the end of the steel plate, overcooling of the end of the steel plate can be prevented and uniform alloy plating can be performed.
As described above, according to the present invention, it is possible to perform uniform alloy plating in the width direction by preventing overcooling of the steel plate end portion, and to improve sheet feeding controllability by improving the steel plate shape. Can do.

In the production of the cold-rolled steel sheet, in this step, it is cooled to about 500 ° C to 100 ° C. The problem at this time is to prevent the occurrence of walk and cooling buckle caused by 1) non-uniform material in the width direction and 2) non-uniform cooling in the width direction caused by a sudden temperature change from 500 ° C to 100 ° C. It is to improve plate properties.
<Cold rolled steel sheet>
When manufacturing a cold-rolled steel sheet using the steel sheet manufacturing facility in the embodiment of FIG.
By passing the steel plate 1 through the dotted cold-rolled steel plate line by the path switching roll 8 of FIG. 1, cold-rolled steel plates that are not subjected to plating treatment can be made separately using an alloyed hot-dip galvanized steel plate manufacturing apparatus.
In the present embodiment, when the cold-rolled steel sheet is manufactured by installing the path switching roll 8 in the middle of the edge heating roll 7 and the plating pot 10 as in the case of the alloyed hot-dip galvanized steel sheet. By using the cooling damper 4 divided in the plate width direction and the upper and lower roll chambers 3 and 6, uniform cooling in the plate width direction can be performed.
However, in the case of a cold-rolled steel sheet, the target temperature of the steel sheet after cooling to make the material in the width direction uniform is remarkably lower than that in the case of a plated steel sheet, which is about 100 ° C. to 200 ° C., and the variation is ± 15 ° C. Therefore, only the end of the cooling damper 4 in the first half of the cooling zone is closed, the other cooling dampers are opened, and the opening of the cooling gas spraying position is in the range of 0 to 100% depending on the plate width of the steel plate. To change drastically.
For example, for wide materials with a plate width of 1200 mm or more, by adjusting the opening degree of the cooling damper in the range of 10 to 85%, conventionally, a steel sheet walk or a cooling buckle occurs during operation. Even wide materials with problems can be produced without problems.

Furthermore, in order to separate the alloyed hot-dip galvanized steel sheet and the cold-rolled steel sheet, it is preferable that the heating temperature of the bottom roll chamber 3 and the top roll chamber 6 can be adjusted widely from 500 ° C. to 100 ° C. The plate-through property of the wide material can be improved.
In addition, when the roll temperature is lowered, a heat crown occurs due to contact with the steel sheet, and a centering effect occurs in which the steel sheet tends to move to the center in the sheet width direction, but in the case of a thin wide steel sheet, a cooling buckle occurs. Therefore, it is preferable to set the temperature of the subsequent roll chamber to a higher value (for example, + 150 ° C.) from the normal 200 to 250 ° C.
In the case of a cold-rolled steel sheet, the temperature deviation in the width direction can be allowed to be about ± 15 ° C. as compared with a plated steel sheet, and therefore, a heating roll and a movable burner used in the case of a plated steel sheet are not used.
As described above, according to the present invention, it is possible to improve the sheet passing controllability by improving the shape of the steel sheet by preventing overcooling of the end of the steel sheet.

The roll chamber shown in FIG. 1 has a rod-shaped heater so that it can be heated in the plate width direction, and it is preferable that the heater can be controlled to 100 ° C. to 500 ° C.
FIG. 2 is a diagram illustrating a cooling damper used in the present invention.
In FIG. 2, 1 is a steel plate, 4 is a cooling damper, 4-1 is a central portion of the cooling damper, and 4-2 is an end portion of the cooling damper.
As shown in FIG. 2, the cooling damper used in the present invention is divided into, for example, three in the width direction of the steel plate 1, and the opening and closing control of the cooling gas is performed in the range of 0 to 100% for each of the divided sections. can do.
In addition, a cooling gas jetting port is provided on the surface of the cooling damper facing the steel plate 1, and the cooling temperature in the width direction of the steel plate is controlled by adjusting the flow rate of the cooling gas blown from the jetting port. Can do.
In addition, when manufacturing a cold-rolled steel sheet, since the steel sheet temperature after cooling is lower than that of an alloyed hot-dip galvanized steel sheet, the cooling damper satisfies the manufacturing conditions of both the plated steel sheet and the cold-rolled steel sheet. It is preferable that the cooling gas spray position and spray amount can be adjusted widely.

FIG. 3 is a diagram illustrating a heating roll used in the present invention.
In FIG. 3, 1 is a steel plate, 7 is a heating roll, and 15 is an induction heating device.
As shown in FIG. 3, since the induction heating device 15 is disposed at a portion where the heating roll contacts the end portion of the steel plate 1, by selectively heating this portion, the steel plate end portion is prevented from being overcooled. can do.
FIG. 4 is a diagram illustrating a movable burner used in the present invention.
In FIG. 4, 1 is a steel plate, 13 is a movable burner, and 16 is a burner nozzle.
As shown in FIG. 4, when the plate width of the steel plate 1 is changed, the burner nozzle moves in the direction of the arrow and can follow the end of the steel plate 1, so that the end of the steel plate 1 is selectively used. It is possible to prevent overcooling of the end portion of the steel sheet by heating the steel plate.

It is a figure which illustrates embodiment of this invention. It is a figure which illustrates the cooling damper used for the present invention. It is a figure which illustrates the edge heating roll used for this invention. It is a figure which illustrates the movable burner used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Bottom roll 3 Bottom roll chamber 4 Cooling damper 4-1 Center part (cooling damper)
4-2 End (cooling damper)
5 Top roll 6 Top roll chamber 7 Edge heating roll 8 Path switching roll 9 Width direction plate thermometer 10 Plating pot 11 Sink roll 12 Plating adhesion amount control device 13 Movable burner 14 Alloying device 15 Induction heating device 16 Burner nozzle

Claims (2)

In order to adjust the spraying position of the cooling gas to the cooling zone of the steel sheet annealed after cold rolling, an alloyed hot dip galvanized steel sheet or a galvanized steel sheet having a cooling damper divided in the width direction of the steel sheet is used. A method of manufacturing a cold rolled steel sheet,
When producing an alloyed hot-dip galvanized steel sheet, only the central part of the cooling damper in the first half of the cooling zone is opened, the other cooling dampers are fully closed, and the end of the steel sheet cooled to 500 ° C. to 460 ° C. in the cooling zone And steel plate with a temperature difference in the range of ± 5 ° C within the range of ± 5 ° C is immersed in a hot dip galvanizing bath and plated, and then alloyed.
When manufacturing a cold-rolled steel sheet, only the end of the cooling damper in the first half of the cooling zone is closed, the other cooling dampers are opened, and the opening is changed in the range of 0 to 100 according to the plate width of the steel sheet. Thus, the temperature difference between the end portion and the central portion of the steel plate cooled to about 500 ° C. to 100 ° C. within the cooling zone is within a range of ± 15 ° C. Production method. The method for producing an alloyed hot-dip galvanized steel sheet or cold-rolled steel sheet according to claim 1, wherein an apparatus for producing an alloyed hot-dip galvanized steel sheet having a roll chamber for heating a transport roll above and below the cooling zone is used. .

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