JP6763261B2 - Continuous hot-dip galvanized steel sheet and manufacturing method of alloyed hot-dip galvanized steel sheet - Google Patents

Description

The present invention manufactures a continuous hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet, in which a steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating device to alloy the hot-dip galvanized layer. Regarding the method.

In a continuous hot-dip galvanizing apparatus that continuously zinc-plats a steel sheet, the steel sheet may be passed through a hot-dip zinc bath and then heated to form an alloyed layer of zinc and iron in the hot-dip galvanized layer. The heating of the steel sheet at the time of alloying is often performed by high frequency induction heating, and the LF (Longitudinal Flux: parallel magnetic flux) method is adopted as the induction heating method (see Patent Document 1). In the LF method, a high-frequency current is passed through an induction coil surrounding the steel sheet, the magnetic flux is passed through the cross section in the traveling direction of the steel sheet, and the induced current circulates in the width direction cross section of the steel sheet perpendicular to the magnetic flux. Generate and heat the steel sheet.

Japanese Unexamined Patent Publication No. 6-330276

However, as disclosed in Patent Document 1, when heating is performed by LF induction heating during alloying after hot dip galvanizing, the degree of alloying may be non-uniform in the width direction of the steel sheet. The possible causes are as follows.

FIG. 9 is a diagram showing the temperature distribution of the hot-dip galvanized steel sheet (hereinafter referred to as hot-dip galvanized steel sheet) when heated by the LF method induction heating. In the figure, the vertical axis indicates the temperature, the horizontal axis indicates the position from the center of the steel sheet in the plate width direction, and the portion ± 1 on the horizontal axis is the end of the steel plate in the plate width direction.

As shown in FIG. 9A, the hot-dip galvanized steel sheet immediately after induction heating by the LF method has an alloying temperature as a whole, and the temperature is constant in the plate width direction.
As the hot-dip galvanized steel sheet moves on the sheet passing line, the overall temperature of the hot-dip galvanized steel sheet decreases as shown in FIG. 9 (B), and in particular, the end portion thereof is a portion without a high temperature steel sheet next to it. In addition to the front and back surfaces, the area also dissipates heat from the end faces, so the temperature is significantly lower than in the central part.
Then, in the latter half of the alloyable section defined on the through plate line, the temperature of the end portion of the hot-dip galvanized steel sheet becomes lower than the alloying temperature as shown in FIG. 9 (C). In some cases. In that case, there is a problem that the degree of alloying becomes non-uniform in the width direction of the steel sheet.

Further, the hot-dip galvanized steel sheet is edge overcoated due to the surface tension of the hot-dip zinc, that is, the thickness of the hot-dip galvanized layer is thicker at the end portion than at the central portion. Therefore, it is difficult to heat the end portion of the hot-dip galvanized steel sheet as compared with the central portion, and the temperature may be lower than that of the central portion even immediately after heating. In that case, even if the central portion of the hot-dip galvanized steel sheet is at the alloying temperature, the end portion may be lower than the alloying temperature, and the degree of alloying may be non-uniform in the width direction of the steel sheet.

The present invention has been made in view of this point, and is a continuous hot-dip galvanized steel sheet in which a steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating device to alloy the hot-dip galvanized layer. An object of the present invention is to enable the entire steel sheet to be appropriately alloyed in a plating apparatus and a method for manufacturing an alloyed hot-dip galvanized steel sheet.

In order to achieve the above object, the present invention is a continuous hot-dip galvanizing device for a steel sheet in which a steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating device to alloy the hot-dip galvanized layer. Therefore , a plurality of the induction heating devices having a heating range of the entire width of the steel sheet are provided along the plate passing direction, and at least the most downstream of the plurality of induction heating devices is heated by the vertical magnetic flux method. A TF (Transverse Flux) heating device that performs heating , at least one is an LF heating device that heats by a parallel magnetic flux method, and a width direction thermometer that measures the temperature distribution in the width direction of a steel sheet is the TF. It is provided upstream or downstream of the heating device, and further includes a control device that controls the induction heating device, and the control device is (a) a plate of a steel plate based on the measurement result of the width direction thermometer. When temperature adjustment is required only at the end in the width direction, the heating amount of the TF heating device is increased or decreased. (B) When temperature adjustment is required only at the center of the steel plate in the width direction, the LF heating device is used. When it is necessary to increase or decrease the amount of heating and (c) adjust the temperature of the entire width of the steel sheet from the center to the end in the plate width direction, the amount of heating by the TF heating device and the amount of heating by the LF heating device Both are characterized by increasing or decreasing .

Downstream of the TF heating device of the plurality of induction heating apparatus is made different from a plurality of TF heating device having a plate width which can be applied, those used by switching to one in accordance with the plate width which can be the application Is preferable.

Of the induction heating devices, at least the most upstream one is preferably the LF heating device that heats by a parallel magnetic flux method.

Wherein the control device, if the temperature adjustment of the total width obtained by multiplying the ends of the plate width direction central portion of the steel sheet is required, controlling the ratio of the heating quantity of the heating quantity and the LF heating device in the TF heating device indicator It is preferable to use it for.

The TF heating device has a magnetic core that concentrates the magnetic flux generated by the induction coil, the magnetic core is provided so as to be movable in the width direction of the steel plate, and the control device is the magnetic core. The TF heating device may be controlled by adjusting the position of the steel plate in the width direction.

The TF heating device has a shielding plate that shields the magnetic flux concentrated by the magnetic core, and the control device controls the TF heating device by adjusting the position of the shielding plate. May be good.

The TF heating device has a magnetic core that concentrates the magnetic flux generated by the induction coil and a shielding plate that shields the magnetic flux concentrated by the magnetic core, and the control device has a position of the shielding plate. The TF heating device may be controlled by adjusting the above.

The control device may control the induction heating device based on the measurement result of the alloying distribution of the steel sheet that has passed through the induction heating device.

According to the present invention from another viewpoint , the above-mentioned continuous hot-dip galvanizing apparatus is used, in which a steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating apparatus to alloy the hot-dip galvanized layer . a method for manufacturing a galvannealed steel sheet, before SL on the basis of the measurement result of the width direction thermometer, the induction heating device temperature the plate widthwise end of the plate width direction end portion of the steel sheet after passing It is characterized in that the induction heating device is controlled so that the temperature becomes higher than the temperature other than the portion.

It is preferable to control the induction heating device so that the temperature shortage portion is heated to the alloying temperature or higher based on the measurement result by the width direction thermometer.

It is preferable to control the induction heating device based on the measurement result of the alloying distribution of the steel sheet that has passed through the induction heating device.

According to the continuous hot-dip galvanizing apparatus for steel sheets and the method for producing alloyed hot-dip galvanized steel sheets of the present invention, the entire steel sheet can be appropriately alloyed.

It is a figure which shows the outline of the continuous hot dip galvanizing apparatus of the steel sheet which concerns on 1st Embodiment of this invention. It is a figure which shows the outline of the LF heating apparatus of FIG. It is a figure which shows the outline of the TF heating apparatus of FIG. It is a figure which shows the temperature distribution of the hot-dip galvanized steel sheet heated by the alloying heating apparatus of FIG. It is a figure which shows the outline of the continuous hot dip galvanizing apparatus of the steel sheet which concerns on 2nd Embodiment of this invention. It is a figure which shows the outline of the TF heating apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the outline of the TF heating apparatus which concerns on 4th Embodiment of this invention. It is a figure which shows the outline of the continuous hot dip galvanizing apparatus of the steel sheet which concerns on 6th Embodiment of this invention. It is a figure which shows the temperature distribution of the hot-dip galvanized steel sheet at the time of heating by the conventional induction heating.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

(First Embodiment)
FIG. 1 is a diagram showing an outline of a continuous hot-dip galvanizing apparatus for a steel sheet according to the first embodiment of the present invention.
The continuous hot-dip galvanizing apparatus 1 in the figure improves the weldability, corrosion resistance, pressability, etc. of the steel sheet H by hot-dip galvanizing the steel sheet H and alloying the hot-dip galvanized layer.

In the continuous hot-dip galvanizing apparatus 1 of FIG. 1, the steel plate H is annealed in a continuous annealing furnace (not shown) and then melted through a duct-shaped snout 11 provided to prevent oxidation by the outside air. It is introduced into the galvanizing bath 2.
The steel plate H introduced into the hot-dip galvanizing bath 2 is turned upward by the sink roll 3 provided in the bath 2, and after the warp is corrected by the support roll 4, it is pulled out from the hot-dip galvanizing bath 2. Is done.
Then, the hot-dip galvanized steel sheet H is sprayed with wiping gas from the gas wiping nozzle 5 toward both sides thereof, and the amount of plating adhesion is adjusted.

The steel sheet H whose plating adhesion amount has been adjusted passes through the vibration damping device 6 that suppresses the vibration of the steel sheet H. In addition to the function of suppressing the vibration of the steel plate H, the vibration damping device 6 may have a function of defining the angle of the steel plate H with respect to the alloying heating device 7.
As a method for suppressing vibration and defining an angle by the vibration damping device 6, a method of spraying a high temperature gas (for example, 450 ° C. or higher) on the end portion of the steel sheet H can be considered. Further, the method may be based on a pinch force of electromagnetic force.
Further, for example, a method may be used in which a roller heated to 450 ° C. or higher comes into contact with the end portion of the steel sheet H to suppress the vibration of the steel sheet H and define the angle of the steel sheet H. The hot-dip galvanized layer of the steel sheet H is deformed by the contact with the rollers or the like, but the hot-dip galvanized layer is molten while the steel sheet H is passed through the alloying heating device 7. The deformed portion of the zinc plating layer returns to the state before deformation.

The torsional vibration of the steel plate H may be suppressed by the wiping gas from the gas wiping nozzle 5 without providing the vibration damping device 6 described above.
Further, the torsional vibration of the steel plate H may be suppressed by adjusting the intermesh amount (roll pushing amount) of the support roll 4 without providing the vibration damping device 6.

After passing through the vibration damping device 6, the steel sheet H is heated by the alloying heating device 7 and heated to, for example, 550 ± 10 ° C., and the hot-dip galvanized layer of the steel sheet H is reached before the steel sheet H reaches the upper roll 8. Is alloyed. The alloying heating device 7 has a plurality of induction heating devices, and in the present embodiment, the LF heating device 7a is on the upstream side and the TF heating device 7b is on the downstream side.
The alloyed steel plate H is cooled by a cooling device (not shown), and then the plate passing direction is changed by the upper roll 8.

Further, the continuous hot-dip galvanizing device 1 includes a control device (not shown). The control device is, for example, a computer, and has a program storage unit and a data storage unit. The program storage unit stores a program for controlling various processes in the continuous hot-dip galvanizing apparatus 1, a program for controlling the operation of the drive system, and the like. Various data necessary for various processes in the continuous hot-dip galvanizing apparatus 1 are stored in the data storage unit. This control device also controls the alloying heating device 7, and controls the alloying heating device 7 by using the ratio of the heating amount in the LF heating device 7a and the heating amount in the TF heating device 7b as a control index. ..

The data and the program can be stored in a computer-readable storage medium such as a computer-readable hard disk (HD), flexible disk (FD), compact disk (CD), magnet optical desk (MO), or memory card. It may have been recorded and installed in the control device from the storage medium.

FIG. 2 is a diagram showing an outline of the LF heating device 7a. FIG. 3 is a diagram showing an outline of the TF heating device 7b, FIG. 3A is a schematic front view of the TF heating device 7b viewed from a direction perpendicular to the steel plate surface, and FIG. 3B is FIG. 3A. It is a schematic cross-sectional view which shows the AA cross section of).

As shown in FIG. 2, the LF heating device 7a has an induction coil 7c that surrounds the steel plate H through which the plate is passed.
The induction coil 7c is made of a conductor such as copper and is connected to the high frequency power supply 7d. In the LF heating device 7a, the magnetic flux M1 generated by the induction coil 7c intensively penetrates the surface layer of the steel plate H in the cross section in the plate-passing direction (cross section orthogonal to the plate-passing direction of the steel plate) close to the induction coil. An induced current is generated in the cross section of the steel plate H perpendicular to the magnetic flux M1 in the plate-passing direction, and the induced current heats the steel plate H. That is, the LF heating device 7a heats the steel sheet H by induction heating of the LF (parallel magnetic flux) method.
In the heating by the LF heating device 7a, the temperature distribution of the steel sheet tends to be relatively uniform in the plate width direction because it is heated by the annular current that goes around the cross section of the steel sheet.

As shown in FIG. 3A, for example, the TF heating device 7b includes a track-shaped induction coil 7e for half a circumference of athletics composed of a semicircular portion and a straight portion on the front surface side and the back surface side of the steel plate, respectively. It has four magnetic cores 7f arranged and fixed in the plate width direction on the induction coil 7e. As shown in FIG. 3B, there are two sets of the induction coil 7e and the magnetic core 7f on the front side and the back side of the steel plate, and two sets on the front and back sides, and each set sandwiches the steel plate H with each other. It is provided so as to face each other. Further, the induction coil 7e is provided so that the semicircular portion thereof is outside the width of the steel plate, and the front side and the back surface side of the steel plate are on the width side of the steel plate opposite to each other. A high-frequency power supply (not shown) is connected to the ends of the two straight portions on the opposite sides of the steel plate H from the semicircular portion of 7e.
The magnetic core 7f is composed of a core made of a ferromagnetic material such as ferrite, a laminated electromagnetic steel plate, and an amorphous alloy.

The induction coil 7e is made of a conductor such as copper and is connected to a high frequency power supply (not shown). The magnetic flux M2 generated by the induction coil 7e passes through the magnetic core 7f, penetrates the steel plate H in the thickness direction, and heads toward the opposing magnetic core 7f. In the TF heating device 7b, an induced current perpendicular to the magnetic flux M2 is generated in the plate surface of the steel plate H, and the induced current heats the steel plate H. That is, the TF heating device 7b heats the steel sheet H by TF (Transverse Flux: vertical magnetic flux) induction heating.
In the heating by the TF heating device 7b, it is possible to heat regardless of the magnetism, the plate thickness, etc. of the material to be heated, and it is possible to heat both the central portion and the end portion in the plate width direction of the steel plate, but the edges The temperature of the part is higher than that of the central part.

FIG. 4 is a diagram showing the temperature distribution of the hot-dip galvanized steel sheet H (hereinafter, hot-dip galvanized steel sheet H) heated by the alloying heating device 7 having the LF heating device 7a and the TF heating device 7b. In the figure, the vertical axis indicates the temperature, the horizontal axis indicates the position from the center of the hot-dip galvanized steel sheet H in the plate width direction, and the portion ± 1 on the horizontal axis is the end of the steel plate H on the plate width direction. The part surrounded by indicates the alloying temperature range.

As shown in FIG. 4A, the hot-dip galvanized steel sheet immediately after induction heating by the alloying heating device 7 has an alloying temperature as a whole. Further, since the alloying heating device 7 is heated not only by the LF heating device 7a but also by the TF heating device 7b, the temperature of the end portion of the hot-dip galvanized steel sheet H in the plate width direction is induced and heated by the alloying heating device 7. Immediately after this, the temperature can be higher than that of the central portion.

The temperature of the hot-dip galvanized steel sheet H decreases as it moves on the plate passing line, and the temperature decrease rate at that time is larger at the end portion in the plate width direction than at the central portion. However, as described above, the temperature of the end portion of the hot-dip galvanized steel sheet H in the plate width direction is set to a high temperature. Therefore, whether it is near the middle between the alloying heating device 7 and the upper roll 8 or near the upstream side of the upper roll 8, that is, the intermediate portion of the alloyable section defined on the through plate line. Regardless of whether it is in the vicinity or in the final part, for example, as shown in FIGS. 4 (B) and 4 (C), the temperature at the end thereof does not fall below the alloying temperature. Therefore, in the continuous hot-dip galvanizing apparatus 1 provided with the alloying heating apparatus 7, the entire hot-dip galvanized steel sheet H can be appropriately alloyed.

Further, the continuous hot-dip galvanizing apparatus 1 of the present embodiment is configured to include not only the TF heating apparatus 7b but also the LF heating apparatus 7a. Therefore, the continuous hot-dip galvanizing apparatus 1 according to the present embodiment can be configured by incorporating the TF heating apparatus 7b into the existing continuous hot-dip galvanizing apparatus having only the LF heating apparatus 7a.

In this example, the LF heating device 7a and the TF heating device 7b are provided one by one, but a configuration in which both or a plurality of these heating devices 7a and 7b are provided may be provided. Since the TF type induction heating device generally has a limited plate width, it is difficult for one unit to cope with a change of about 600 mm width to about 1800 mm, which is a general size of a steel plate. Therefore, by installing two or three TF induction heating devices having different applicable plate widths, it is possible to freely heat a narrow steel plate to a wide steel plate with a desired temperature distribution, which is difficult with the LF method. Alternatively, since it is possible to heat while limiting the heating rate and the heating output / heating temperature distribution, it is also possible to heat while controlling the surface texture of the plating.
Further, in this example, the TF heating device 7b is provided on the downstream side in the plate-passing direction from the LF heating device 7a, but may be provided on the upstream side in the plate-passing direction from the LF heating device 7a.

(Second Embodiment)
FIG. 5 is a diagram showing an outline of a continuous hot-dip galvanizing apparatus for a steel sheet according to a second embodiment of the present invention.
The continuous hot-dip galvanizing apparatus 1 of FIG. 5 includes a width direction thermometer 9 in addition to the configuration of the apparatus of the first embodiment.

The width direction thermometer 9 measures the temperature distribution of the steel plate H in the plate width direction, and is provided on the downstream side of the TF heating device 7b.
In the continuous hot-dip galvanizing device 1 of the present embodiment, the control device controls the alloying heating device 7 based on the measurement result of the width direction thermometer 9.

Specifically, for example, in the control device, if the temperature of the hot-dip galvanized steel sheet H is lower than the desired temperature as a result of measurement with the width direction thermometer 9, both the LF heating device 7a and the TF heating device 7b The output is controlled to increase, and if the temperature is higher than the desired temperature as a whole, both outputs are controlled to decrease.

If only the end portion of the hot-dip galvanized steel sheet H in the plate width direction is lower than the desired temperature, the control device may control so that the output is increased only by the TF heating device 7b.
Further, if the temperature of the portion of the hot-dip galvanized steel sheet H other than the end portion in the plate width direction is lower than the desired temperature, the control device may control so that the output is increased only by the LF heating device 7a.
In this example, the width direction thermometer 9 is provided on the downstream side of the TF heating device 7b, but may be provided on the upstream side of the heating device 7b in order to measure the temperature before heating. When the width direction thermometer 9 is provided on the upstream side of the TF heating device 7b, it may be provided between the TF heating device 7b and the LF heating device 7a.

(Third Embodiment)
The continuous hot-dip galvanizing apparatus for steel sheets according to the third embodiment of the present invention has a different configuration of the TF heating apparatus from the apparatus according to the first and second embodiments.
FIG. 6 is a schematic front view of the TF heating device according to the third embodiment of the present invention as viewed from a direction perpendicular to the schematic steel plate, and FIG. 6 (A) is a magnetic core during wide material processing. 6 (B) is a schematic front view showing the arrangement of magnetic cores during narrow material processing.
The position of the magnetic core 7f of the TF heating device 7b in FIG. 3 with respect to the steel plate H in the plate width direction was fixed. In this case, in general, TF heating may cause the temperature of the end portion of the steel sheet to become too high.

On the other hand, in the continuous hot-dip galvanizing apparatus according to the third embodiment, the magnetic core 7f of the TF heating apparatus 7b is provided so as to be movable in the plate width direction of the steel plate H as shown in FIG. 6 (A). ing.
Then, in the continuous hot-dip galvanizing apparatus according to the third embodiment, the control apparatus adjusts the position of the magnetic core 7f in the plate width direction and adjusts the magnetic flux density of the magnetic flux passing through the steel plate F. Thereby, the heating distribution in the plate width direction in the TF heating device 7b can be adjusted, and the end portion of the steel plate H can be prevented from becoming too high.

Further, since the magnetic core 7f is movable in the plate width direction, not only the wide material as shown in FIG. 6 (A) but also the magnetic core 7f in the plate width direction as shown in FIG. 6 (B). By narrowing the interval, narrow-width materials can also be processed.
The magnetic core 7f is provided on both the front side and the back side of the steel plate H, but one of the front side and the back side may be configured to be movable in the plate width direction. However, it may be both.

(Fourth Embodiment)
The continuous hot-dip galvanizing apparatus for steel sheets according to the fourth embodiment of the present invention has a different configuration of the TF heating apparatus from the apparatus according to the first and second embodiments.
FIG. 7 is a diagram showing an outline of a TF heating device according to a fourth embodiment of the present invention, and FIG. 7A is a schematic front view of the TF heating device viewed from a direction perpendicular to a steel plate, FIG. 7 (A). B) is a side view seen from the through plate direction.
As shown in FIG. 7, the TF heating device 7b has a magnetic shielding plate 7g that can freely appear and disappear in the plate width direction of the steel plate H. The magnetic shielding plate 7g is made of, for example, copper, which is a non-magnetic metal or the like, and can shield the magnetic flux generated by the magnetic core 7f. The magnetic shielding plate 7g may appear and disappear not only in the plate width direction but also in the plate passing direction, and may appear and disappear only in the plate passing direction.

Then, in the continuous hot-dip galvanizing apparatus for steel sheets according to the fourth embodiment, the control apparatus controls the TF heating apparatus 7b by adjusting the position of the magnetic shielding plate 7g. More specifically, in the continuous hot-dip galvanizing apparatus according to the fourth embodiment, the control device moves the magnetic shielding plate 7g in the plate width direction and / or the plate passing direction, and the magnetic core 7f and the hot-dip galvanizing. The area of the shielding plate 7g interposed between the steel plate H is adjusted, and the magnetic flux passing through the steel plate H is adjusted. Thereby, the heating distribution in the plate width direction in the TF heating device 7b can be effectively adjusted. In particular, in the TF type induction heating, the end portion of the steel plate is overheated, so that the magnetic flux control by the magnetic shielding plate is effective in controlling the temperature of the plate end portion.

(Fifth Embodiment)
The continuous hot-dip galvanizing apparatus according to the fifth embodiment of the present invention is different from the apparatus according to the first embodiment, based on the information of the steel sheet before the control apparatus is heated by the alloying heating apparatus. The ratio of the heating amount in the TF heating device to the heating amount in the LF heating device is determined. Specifically, for example, a width direction thermometer is provided on the upstream side of the alloying heating device, information on the measurement result of the width direction thermometer is acquired as the information of the steel sheet, and the center of the molten zinc plated steel sheet H in the width direction. When the temperature difference between the portion and the end portion in the plate width direction is equal to or greater than a predetermined value, the above ratio is determined so that the amount of heating by the TF heating device becomes large.

As described above, in the continuous hot-dip galvanizing apparatus according to the present embodiment, the hot-dip galvanized steel sheet can be appropriately heated and alloyed based on the information of the steel sheet before being heated by the alloying heating apparatus.

(Sixth Embodiment)
FIG. 8 is a diagram showing an outline of a continuous hot-dip galvanizing apparatus for a steel sheet according to a fifth embodiment of the present invention.
The continuous hot-dip galvanizing apparatus 1 of FIG. 8 includes an alloying degree meter 10 in addition to the configuration of the apparatus of the first embodiment.

The alloying degree meter 10 measures the alloying degree of the hot-dip galvanized steel sheet H, and more specifically, measures the distribution of the alloying degree of the steel sheet H in the plate width direction using monochromatic X-rays. To do. It is preferable that the alloying degree meter 10 is provided on the downstream side of the TF heating device 7b and near the final portion of the alloyable section, that is, near the upstream side of the upper roll 8.
In the continuous hot-dip galvanizing device 1 of the present embodiment, the control device controls the alloying heating device 7 based on the measurement result of the alloying degree meter 10.

Specifically, for example, as a result of measurement with the alloying degree meter 10, the control device controls the alloying heating device 7 so that if there is an alloying insufficient portion, the portion is heated more. If there is an overalloy portion, the control device controls the alloying heating device 7 so that the degree of heating of the portion becomes small. If the insufficiently alloyed portion or the overalloyed portion is the end portion of the steel plate H in the plate width direction, the degree of heating of the portion can be changed by increasing or decreasing the output of the TF heating device 7b, for example. Further, if the under-alloyed portion or the over-alloyed portion is a portion other than the end portion in the plate width direction of the steel plate H, for example, if the TF heating device 7b is configured in the same manner as in the third embodiment, the degree of heating of the portion is increased. Can be changed.

The method of acquiring the degree of alloying is not limited to the method of acquiring with the degree of alloying meter 10, for example, a method of irradiating visible light to measure the reflectance and acquiring the degree of alloying based on the measurement result. May be good. Alternatively, a method may be used in which the surface of the hot-dip galvanized steel sheet H is imaged with an imaging device and the imaging result is image-analyzed to obtain the degree of alloying.

The embodiments disclosed in this application can be combined as appropriate.

The present invention is useful in a technique for alloying a hot-dip galvanized layer of a steel sheet by induction heating.

1 ... Continuous hot-dip galvanizing device 2 ... Continuous hot-dip galvanizing bath 3 ... Sink roll 4 ... Support roll 5 ... Gas wiping nozzle 6 ... Vibration damping device 7 ... Alloy heating device 7a ... LF heating device 7b ... TF heating device 7c ... Induction coil 7d ... High frequency power supply 7e ... Induction coil 7f ... Magnetic core 7g ... Magnetic shielding plate 8 ... Upper roll 9 ... Width thermometer 10 ... Alloying degree meter 11 ... Snout

Claims (11)

A continuous hot-dip galvanizing device for a steel sheet in which a steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating device to alloy the hot-dip galvanized layer.
A plurality of the induction heating devices having a heating range of the entire width of the steel sheet are provided along the plate passing direction.
Of the plurality of induction heating devices , at least the most downstream one is a TF heating device that heats by a vertical magnetic flux method , and at least one is an LF heating device that heats by a parallel magnetic flux method.
A width direction thermometer for measuring the temperature distribution in the width direction of the steel sheet is provided upstream or downstream of the TF heating device.
Further, a control device for controlling the induction heating device is provided.
The control device is based on the measurement result of the width direction thermometer.
(A) When it is necessary to adjust the temperature only at the end portion of the steel plate in the plate width direction, increase or decrease the heating amount of the TF heating device.
(B) When it is necessary to adjust the temperature only in the central portion of the steel plate in the plate width direction, increase or decrease the heating amount of the LF heating device.
(C) When it is necessary to adjust the temperature of the entire width of the steel sheet from the center to the end in the plate width direction, increase or decrease both the heating amount of the TF heating device and the heating amount of the LF heating device. A continuous hot-dip galvanizing device for steel sheets. Downstream of the TF heating device of the plurality of induction heating apparatus is made different from a plurality of TF heating device having a plate width which can be applied, those used by switching to one in accordance with the plate width which can be the application The continuous hot-dip galvanizing apparatus for a steel sheet according to claim 1, wherein the steel sheet is continuously hot-dip galvanized. The continuous hot-dip galvanizing apparatus for a steel sheet according to claim 1 or 2, wherein at least the most upstream of the induction heating apparatus is the LF heating apparatus. Wherein the control device, if the temperature adjustment of the total width obtained by multiplying the ends of the plate width direction central portion of the steel sheet is required, controlling the ratio of the heating quantity of the heating quantity and the LF heating device in the TF heating device indicator The continuous hot-dip galvanizing apparatus for a steel sheet according to any one of claims 1 to 3 , wherein the device is used in the above-mentioned. The TF heating device has a magnetic core that concentrates the magnetic flux generated by the induction coil, and the magnetic core is provided so as to be movable in the width direction of the steel sheet.
The continuous melting of the steel sheet according to any one of claims 1 to 4 , wherein the control device controls the TF heating device by adjusting the position of the magnetic core in the width direction of the steel sheet. Zinc plating equipment. The TF heating device has a shielding plate that shields the magnetic flux concentrated by the magnetic core.
The continuous hot-dip galvanizing device for a steel sheet according to claim 5, wherein the control device controls the TF heating device by adjusting the position of the shielding plate. The TF heating device has a magnetic core that concentrates the magnetic flux generated by the induction coil, and a shielding plate that shields the magnetic flux concentrated by the magnetic core.
The continuous hot-dip galvanizing device for a steel sheet according to any one of claims 1 to 4 , wherein the control device controls the TF heating device by adjusting the position of the shielding plate. The invention according to any one of claims 1 to 7 , wherein the control device controls the induction heating device based on the measurement result of the alloying distribution of the steel sheet that has passed through the induction heating device. Continuous hot dip galvanizing equipment for steel sheets. The continuous hot-dip galvanizing of a steel sheet according to any one of claims 1 to 8 , wherein the steel sheet is hot-dip galvanized and the hot-dip galvanized steel sheet is heated by an induction heating device to alloy the hot-dip galvanized layer. A method for manufacturing an alloyed hot-dip galvanized steel sheet using an apparatus .
Based on the measurement result of the previous SL widthwise thermometer, as the temperature of the plate width direction end portion of the steel sheet after the induction heating apparatus through which a high temperature than the temperature outside the plate width direction end portion, the induction heating A method for manufacturing an alloyed hot-dip zinc-plated steel sheet, which comprises controlling an apparatus. The method for producing an alloyed hot-dip galvanized steel sheet according to claim 9 , wherein the induction heating device is controlled so that the insufficient temperature portion is heated to the alloying temperature or higher based on the measurement result by the width direction thermometer. The method for producing an alloyed hot-dip galvanized steel sheet according to claim 9 or 10 , wherein the induction heating device is controlled based on the measurement result of the alloying distribution of the steel sheet that has passed through the induction heating device. ..

Images