Technical field
[0001]
The present invention relates to a cooling apparatus of hot-dip plated steel sheet.
Background technique
[0002]
Conventionally, molten plating is known as one method of forming a metal film (plating layer) on the surface of the steel sheet. In a typical hot-dip plating step, after dipping the steel sheet in a plating bath filled with molten metal, by pulling the steel plate from the plating bath to form a plating layer on the surface of the steel sheet. Hereinafter, it referred the steel sheet plated layer is formed on the surface by hot dipping molten plated steel sheet.
[0003]
After dip plated steel sheet was pulled up from the plating bath, in the process of plating layer solidifies, it reacts with the metal contained in the iron plating layer included in the steel sheet as the base material, between the steel sheet and the plated layer hard and brittle alloy layer is produced. This alloy layer, since cause the plating layer is peeled off from the hot-dip plated steel sheet, it is necessary to suppress the generation of alloy layers by forcibly cooling the molten plated steel sheet pulled up from the plating bath.
[0004]
As described above, cooling conditions of the molten plated steel sheet is a very important factor that determines the quality of the hot dip plated steel sheet. For example, the following Patent Document 1, in the cooling step of hot-dip plated steel sheet, by controlling the flow rate of the cooling gas in accordance with the temperature or the solidified state of the molten plated steel plate, discloses a technique to ensure the required quality of the hot dip plated steel sheet It is. However, such a cooling system of a conventional melt for plated steel sheets, has problems as follows.
[0005]
8A and 8B are views schematically showing a cooling apparatus for hot-dip plated steel sheet in the prior art. Figure 8A is a view of the cooling device 100 from the width direction of the hot dip plated steel sheet PS. 8B is a view of the cooling device 100 from the thickness direction of the hot dip plated steel sheet PS (direction perpendicular to the surface of the molten plated steel sheet PS). 8A and 8B, the arrows Z indicate the conveying direction of the hot dip plated steel sheet PS. Hot dip plated steel sheet PS, after being pulled up from the plating bath, and is conveyed along the conveying direction Z of the vertically upward.
[0006]
Cooling device 100, in the conveying path of the hot-dip plated steel sheet PS, which is disposed above the wiping nozzles (not shown). As is well known, and the wiping nozzles, by injecting wiping gas onto the surface of hot dip plated steel sheet PS, which is a nozzle for adjusting the thickness of the plating layer. Cooling device 100 is provided with a pair of cooling gas injectors 101 and 102 which are disposed to face each other across the molten plated steel sheet PS.
[0007]
Cooling gas injection device 101 injects vertically cooling gas Gc against one surface of the hot dip plated steel sheet PS. Cooling gas injector 102 injects vertically cooling gas Gc to the other surface of the molten plated steel sheet PS. Thus, when the cooling gas Gc to both surfaces of the hot dip plated steel sheet PS from a pair of the cooling gas injectors 101 and 102 is injected, descending gas flow descending from the inlet of the cooling device 100 along both sides of the hot dip plated steel sheet PS Gd is generated.
[0008]
At the inlet side of the cooling apparatus 100, the plating layer of the hot dip plated steel sheet PS is unsolidified state (state where a thin oxide film on the surface is formed). Further, the flow velocity of the downward gas flow Gd near the center in the width direction of the hot dip plated steel sheet PS is faster than the flow velocity of the downward gas flow Gd in the vicinity of the edge of the hot-dip plated steel sheet PS. As a result, as shown in FIG. 8B, at the inlet side of the cooling apparatus 100, semicircular wrinkles (wind ripple) W is generated in the oxide film formed on the surface of the plating layer.
[0009]
As described above, in a state where the semicircular wrinkles W occur in the oxide film of the plated layer, melt plated steel sheet PS is passes through the cooling apparatus 100, the plating layer in a state in which wrinkles W occur solidifies. Dip plated steel sheet PS having such wrinkles W, since being selected as appearance defective product in an inspection process, wrinkles W may lead to a decrease in yield of the hot-dip plated steel sheet PS. Such wrinkles W, especially as alloy plating layer of a multi-component system including Zn-Al-Mg-Si, notably occur when forming a plating layer having a wide solidification temperature range.
[0010]
As a method of avoiding the occurrence of wrinkles W, by reducing the flow rate of the cooling gas Gc, and a method of suppressing the generation of the downward gas flow Gd. However, reducing the flow rate of the cooling gas Gc, the cooling capacity of the cooling apparatus 100 is lowered. As a result, it no longer be sufficiently suppress the formation of the alloy layer which causes peeling of the plating layer, is another problem lowering the productivity of hot dip plated steel sheet PS occurs.
[0011]
For example, the following Patent Document 2, without reducing the cooling capacity of the cooling apparatus 100, poor appearance as a technique for suppressing occurrence of (wrinkles W), the hot-dip plated steel sheet PS from the lower side of the cooling apparatus 100 (the inlet side) by providing the gas knife for injecting gas, a technique for blocking the descending gas flow Gd blown from the inlet of the cooling device 100 is disclosed obliquely upward with respect to the surface.
CITATION
Patent Document
[0012]
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-106881
Patent Document 2: Japanese Laid-Open Patent Publication No. 2004-59944
Summary of the Invention
Problems that the Invention is to Solve
[0013]
When the thickness of the thickness and the plating layer of the steel sheet as the base material to produce a thin dip plated steel sheet PS, the disclosed in Patent Document 2 technology, appearance effective technique for suppressing the occurrence of defects (wrinkles W) it is.
[0014]
However, the greater the thickness of the steel sheet as the base material, the thickness of the plating layer is also increased (the amount of plating deposition is large), the oxide film of the plated layer surface, in the width direction of the hot dip plated steel sheet PS by its own weight there is a case in which hangs down from the vicinity of the center. In that case, even blocked descending gas flow Gd blown from the inlet of the cooling device 100 by using a gas knife, semicircular wrinkles W oxide film of the plating layer may occur.
[0015]
The present invention has been made in view of the above circumstances, in the manufacturing process of the thickness of the thick hot-dip plated steel sheet of thickness and the plating layer of the steel sheet as the base material, the surface of the surface (plated layer of molten plated steel sheet ) and to provide a cooling device capable dip plated steel sheet to prevent the wrinkle is generated in.
Means for Solving the Problems
[0016]
The present invention, in order to achieve the object according to solve the above problems, adopts the following means.
(1) first cooling device of hot dip plated steel sheet according to aspect of the present invention, there is provided a cooling device provided above the plating thickness control device in the conveying path of the hot dip plated steel sheet to be conveyed vertically upward from the plating bath, the main cooling device and for injecting the main cooling gas perpendicularly to hot dip plated steel sheet; provided precooling zone between the plating thickness control device and the main cooling device in the transport path, the pre-cooling section It comprises; a precooling system for injecting a pre-cooling gas to a plurality of gas collision position set along.
[0017]
(2) In the cooling apparatus of hot-dip plated steel sheet according to (1), the pre-cooling apparatus, wherein injecting the pre-cooling gas obliquely upward with respect to each of the gas collision position; wherein the gas collision position said closer to the lower end of the pre-cooling section, or may be the not pre-made injection direction of the cooling gas and the angle is small the conveying direction of the hot dip plated steel sheet.
[0018]
(3) In the cooling device of the above (1) or dip plated steel sheet according to (2), a temperature sensor the preliminary cooling device, for detecting the surface temperature of the hot dip plated steel sheet in the gas collision position of at least the lowermost When, at least the first flow rate sensor and which detects the flow rate of the gas stream flowing downward along from the gas collision position of the lowermost to the surface of the hot dip plated steel sheet; temperature detection results obtained from the temperature sensor and the first based on the velocity detection result obtained from the flow rate sensor, a first control device for controlling the discharge flow rate of at least said pre-cooling gas injected into the gas collision position of the lowermost; may comprise.
In this case, the temperature detection results obtained from the temperature sensor is defined as T [° C.], wherein said flow rate detection results obtained from the first flow rate sensor is defined as Vd [m / s], the hot dip plated steel sheet when wrinkles are defined as the limit descent velocity wrinkles occurrence limit descent velocity VL1 generated [m / s] on the surface, the first control device, the following equation (3) and with respect to said gas impingement position of at least the lowermost ( 4) as equation is satisfied, it may control the discharge flow rate of the said pre-cooling gas injected into the gas collision position of the bottom.
VL1 = A · (T-C) 2 + B · (T-C) -D ...
(3) | Vd | ≦ | VL1 | ... (4)
(however, in equation (3), A, B, C and D is a constant)
[0019]
(4) In the cooling apparatus of hot-dip plated steel sheet according to (3), when the solidification starting temperature of the hot-dip plated steel sheet was defined as Ts [° C.], the first control device, said obtained from the temperature sensor detected temperature T [° C.] may perform a control of the discharge flow rate when satisfying the following conditional expression (5).
Ts-49 ≦ T ≦ Ts + 9 ... (5)
[0020]
(5) above (1) or in the cooling device of hot dip plated steel sheet according to (2), a gas in which the pre-cooling device, flows upward along the surface of the hot dip plated steel sheet from the gas collision position of at least the lowermost the second flow rate sensor and which detects the flow rate in the flow; on the basis of the second flow rate obtained from a flow rate sensor detection result, controls the discharge flow rate of at least said pre-cooling gas injected into the gas collision position of the lowermost the second control unit and; may comprise.
In this case, the second the flow rate detection results obtained from the flow rate sensor is defined as Vu [m / s], the molten plating limits increase a flow rate of wrinkle occurrence limit rise velocity wrinkles are generated on the surface of the steel sheet VL2 [m / s] from which it was defined, the preliminary second control device, which is injected at least in the so following condition (6) is satisfied with respect to the gas collision position of the bottom, the gas collision position of the lowermost the discharge flow rate of the cooling gas may be controlled.
| Vu | ≦ | VL2 | ... (6)
[0021]
(6) In the cooling device of hot dip plated steel sheet according to any one of the above (1) to (5), the pre-cooling device may be provided with a plurality of pre-cooling nozzle separate separately respectively.
[0022]
In the cooling apparatus of hot-dip plated steel sheet according to (7) above (6), the pre-cooling device, between the pre-cooling nozzle adjacent to each other, the preliminary cooling gas used for cooling of the hot dip plated steel sheet it may be provided with a gap for discharging.
[0023]
(8) In the cooling apparatus of hot-dip plated steel sheet according to any one of the above (1) to (5), and the main cooling device and the precooling system may be configured integrally.
Effect of the Invention
[0024]
According to the above aspect, in the manufacturing process of the thickness is thicker dip plated steel sheet of thickness and the plating layer of the steel sheet as the base material, it prevents the wrinkles are generated on the surface (the surface of the plated layer) of the hot-dip plated steel sheet it is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025]
It is a view (view of the cooling device 10 from the width direction of the hot dip plated steel sheet PS) of the cooling device 10 of the hot dip plated steel sheet PS according to an embodiment of FIG 1A] The present invention is illustrated schematically.
It is a view (view of the cooling device 10 from the thickness direction of the hot dip plated steel sheet PS) of the cooling device 10 of the hot dip plated steel sheet PS according to an embodiment of FIG. 1B] The present invention is illustrated schematically.
FIG. 2 is an enlarged view of the vicinity of the lowermost gas collision position P1 in the preliminary cooling section.
In the Figure 3A] When sheet temperature is high (when there is a high fluidity of the plating layer) is a schematic view showing a state in which the oxide film tends to sag of the plating layer.
In the Figure 3B] When the plate temperature is low (if less liquid of the plating layer) is a schematic view showing a hard state where oxide films sag of the plating layer.
[Figure 4] and sheet temperature before cooling is a diagram showing the relationship between the creasing critical velocity at the surface of hot dip plated steel sheet PS.
5 is a diagram showing a modification of the embodiment.
6 is a diagram showing a modification of the embodiment.
7 is a diagram showing a modification of the embodiment.
[FIG 8A] is a diagram viewed a conventional cooling device 100 from the width direction of the hot dip plated steel sheet PS.
[FIG 8B] is a diagram viewed a conventional cooling apparatus 100 from (the direction perpendicular to the surface of the hot dip plated steel sheet PS) thickness direction of the hot dip plated steel sheet PS.
DESCRIPTION OF THE INVENTION
[0026]
It will be described in detail with reference to the accompanying drawings, an embodiment of the present invention.
1A and 1B, the cooling apparatus 10 of the hot dip plated steel sheet PS according to the present embodiment is a view schematically showing. Figure 1A is a view of the cooling device 10 from the width direction of the hot dip plated steel sheet PS. Figure 1B is a view of the cooling device 10 from the thickness direction of the hot dip plated steel sheet PS (direction perpendicular to the surface of the molten plated steel sheet PS).
[0027]
As shown in FIG. 1A, the steel sheet S as the base material of the hot dip plated steel sheet PS is immersed in a molten plating bath 3 of molten coating pot 2 via the snout 1. Steel S, after being pulled up from the molten coating bath 3 through the bath folded roll 4 and the bath support rolls 5 are arranged in the molten coating pot 2, as a molten plated steel sheet PS plating layer is formed on the surface It is transported vertically upward.
[0028]
In the transport path of the hot dip plated steel sheet PS (transport path a vertically upward to the conveying direction Z), the position above the hot dipping pot 2, plating thickness control for controlling the thickness of the plating layer of the hot dip plated steel sheet PS device 6 is disposed. The plating thickness control device 6 is provided with a pair of wiping nozzle 7 and 8 are arranged so as to face each other across the molten plated steel sheet PS. From each of these wiping nozzle 7 and 8, by the wiping gas is injected along the thickness direction of the hot dip plated steel sheet PS, the thickness of the plating layer of the hot-dip plated steel sheet PS is adjusted.
[0029]
Cooling device 10, in the transport path of the hot-dip plated steel sheet PS, it is disposed above the plating thickness control device 6. Cooling apparatus 10 includes a main cooling system 20 and the pre-cooling device 30. The main cooling system 20 includes a pair of main cooling gas injectors 21 and 22 are arranged so as to face each other across the molten plated steel sheet PS.
[0030]
The main cooling device 20 corresponds to the conventional cooling device 100, primarily the hot dip plated steel sheet PS by forcibly and rapidly cooled, plays a role in suppressing the production of the alloy layer which causes peeling of the plating layer there. That is, the main cooling gas injection device 21 is vertically injects main cooling gas Gc against one surface of the hot dip plated steel sheet PS (front). Main cooling gas injection device 22 injects the main cooling gas Gc perpendicular to the other surface of the hot dip plated steel sheet PS (rear surface).
Incidentally, the main cooling gas Gc is injected from the main cooling gas injectors 21 and 22, similarly to the conventional cooling device 100, lowering the gas descending along from the inlet of the main cooling device 20 on both sides of the hot dip plated steel sheet PS flow Gd occurs.
[0031]
As shown in FIG. 1B, of the surface of the main cooling gas injection device 21, the surface opposite the front surface of the molten plated steel sheet PS, is provided with a plurality of slit nozzle 21a extending along the width direction of the hot dip plated steel sheet PS ing. By main cooling gas Gc from these slit nozzle 21a is ejected perpendicularly to the front surface of the molten plated steel sheet PS, the main cooling gas Gc is evenly sprayed over the entire front surface of the hot dip plated steel sheet PS.
Although not shown in FIG. 1B, of the surface of the main cooling gas injection device 22, also the surface facing the rear surface of the hot dip plated steel sheet PS, a plurality of slit nozzle extending along the width direction of the hot dip plated steel sheet PS It is provided.
The nozzle for the main cooling gas jet provided in the main cooling gas injectors 21 and 22 is not limited to the above-mentioned slit nozzle. For example, as a nozzle for the main cooling gas injection, it may also be used round nozzles or the like in place of the slit nozzle.
[0032]
Precooling system 30, hot dipping in the transport path of the steel sheet PS is provided in the section (pre-cooling section) between the main cooling system 20 and the plating thickness control device 6 mainly dip plated steel sheet in a preliminary cooling section PS It plays a role in suppressing the fact that wrinkles W occurs. Precooling system 30 injects precooled gas Gs obliquely upward with respect to the gas impingement position P1, P2 and P3 of the multiple set along the pre-cooling section (3 as an example in the present embodiment).
[0033]
In particular, pre-cooling device 30 is provided with a first pre-cooling nozzle 31 and 32 of the pair, a pair of second pre-cooling nozzle 33 and 34, and a pair of third pre-cooling nozzles 35 and 36. These pre-cooling nozzle, respectively, nozzle positions, preinjection direction of the cooling gas Gs, and the discharge flow rate (discharge air volume) of the pre-cooling gas Gs to be individually adjustable independent nozzles.
[0034]
The first pre-cooling nozzle 31 is arranged on the front side of the hot-dip plated steel sheet PS, injects precooled gas Gs obliquely upward with respect to the gas impingement position P1 from the front side of the hot-dip plated steel sheet PS. The first pre-cooling nozzle 32 is disposed on the rear surface side of the hot-dip plated steel sheet PS, injects precooled gas Gs obliquely upward with respect to the gas impingement position P1 from the rear surface side of the hot-dip plated steel sheet PS.
As shown in FIG. 1B, the first pre-cooling nozzle 31 and 32 is configured to extend along the width direction of the hot dip plated steel sheet PS. That is, pre-cooling the gas Gs ejected from the first pre-cooling nozzle 31 and 32 is injected uniformly along the width direction of the hot dip plated steel sheet PS.
[0035]
As shown in Figure 1A, the angle between the conveying direction Z of the injection direction and dip plated steel sheet PS precooling gas Gs ejected from the first pre-cooling nozzle 31 is defined as [alpha] 1. Further, the angle between the conveying direction Z of the injection direction and dip plated steel sheet PS precooling gas Gs ejected from the first pre-cooling nozzle 32 is defined as [alpha] 2. The angle α1 of the first pre-cooling nozzle 31 and the angle α2 of the first pre-cooling nozzle 32 is set to the same value.
Incidentally, in the conveying direction Z, the position of the first pre-cooling nozzle 31 and the position of the first pre-cooling nozzle 32 is the same. That is, the first pre-cooling nozzle 31 and 32 are installed in the same height position.
[0036]
The second pre-cooling nozzle 33 is disposed above the first pre-cooling nozzle 31 on the front side of the hot-dip plated steel sheet PS, precooled obliquely upward with respect to the gas impingement position P2 from the front side of the hot-dip plated steel sheet PS to inject the gas Gs. The second pre-cooling nozzle 34, in the rear side of the hot-dip plated steel sheet PS is disposed above the first pre-cooling nozzle 32, precooled obliquely upward with respect to the gas impingement position P2 from the rear surface side of the hot-dip plated steel sheet PS to inject the gas Gs.
As shown in FIG. 1B, the second pre-cooling nozzle 33 and 34 are configured to extend along the width direction of the hot dip plated steel sheet PS. That is, pre-cooling the gas Gs injected from the second pre-cooling nozzle 33 and 34 is injected uniformly along the width direction of the hot dip plated steel sheet PS.
[0037]
As shown in Figure 1A, the angle between the conveying direction Z of the injection direction and dip plated steel sheet PS precooling gas Gs injected from the second pre-cooling nozzle 33 is defined as .alpha.3. Further, the angle between the conveying direction Z of the injection direction and dip plated steel sheet PS precooling gas Gs injected from the second pre-cooling nozzle 34 is defined as alpha 4. The angle α3 of the second pre-cooling nozzle 33 and the angle α4 of the second pre-cooling nozzle 34 is set to the same value.
Incidentally, in the conveying direction Z, the position of the second pre-cooling nozzle 33 and the position of the second pre-cooling nozzle 34 is the same. That is, the second pre-cooling nozzle 33 and 34 are installed in the same height position.
[0038]
The third pre-cooling nozzle 35, the front side of the hot-dip plated steel sheet PS is disposed above the second pre-cooling nozzle 33, precooled obliquely upward with respect to the gas impingement position P3 from the front side of the hot-dip plated steel sheet PS to inject the gas Gs. The third pre-cooling nozzle 36, the molten plating at the rear surface of the steel sheet PS is disposed above the second pre-cooling nozzle 34, precooled obliquely upward with respect to the gas impingement position P3 from the rear surface side of the hot-dip plated steel sheet PS to inject the gas Gs.
As shown in FIG. 1B, the third pre-cooling nozzles 35 and 36 are configured to extend along the width direction of the hot dip plated steel sheet PS. That is, pre-cooling the gas Gs ejected from the third pre-cooling nozzles 35 and 36 are injected uniformly along the width direction of the hot dip plated steel sheet PS.
[0039]
As shown in Figure 1A, the angle between the conveying direction Z of the pre-cooling gas Gs injection direction and dip plated steel sheet PS ejected from the third pre-cooling nozzle 35 is defined as .alpha.5. Further, the angle between the conveying direction Z of the pre-cooling gas Gs injection direction and dip plated steel sheet PS ejected from the third pre-cooling nozzle 36 is defined as alpha6. The angle α5 of the third pre-cooling nozzle 35 and the angle α6 third preliminary cooling nozzle 36 is set to the same value.
Incidentally, in the conveying direction Z, the position of the third pre-cooling nozzle 35 and the position of the third pre-cooling nozzle 36 is the same. That is, the third pre-cooling nozzles 35 and 36 are installed in the same height position.
[0040]
In pre-cooling device 30, the closer the gas collision position is at the lower end of the pre-cooling section, the angle between the injection direction of the pre-cooling gas Gs to the transport direction Z of the hot dip plated steel sheet PS becomes smaller. That is, the angle [alpha] 1, .alpha.3 and α5 are set so as to satisfy the following relational expression (1). Further, the angle [alpha] 2, alpha 4 and α6 are set so as to satisfy the following equation (2).
　　　　　　　　　.alpha.5> .alpha.3> [alpha] 1 ... (1)
　　　　　　　　　alpha6> alpha 4> [alpha] 2 ... (2)
　　　　　(however, α1 = α2, α3 = α4 , α5 = α6)
[0041]
As described above, pre-cooling device 30 is, during the pre-cooling nozzle adjacent to each other, it may be provided with a gap for discharging the pre-cooling gas Gs which is used for cooling the hot-dip plated steel sheet PS.
[0042]
Figure 2 is an enlarged view of the vicinity of the lowermost gas collision position P1 in the preliminary cooling section. As shown in this Figure 2, pre-cooling device 30 in the present embodiment, a temperature sensor 31a and 32a, a first flow rate sensor 31b and 32b, further comprising a first control unit 37.
[0043]
Temperature sensor 31a detects the surface temperature of the front surface side of the hot-dip plated steel sheet PS at the bottom of the gas collision position P1, and outputs a signal indicating the detected temperature to the first control unit 37. Temperature sensor 32a detects the surface temperature of the rear surface side of the hot-dip plated steel sheet PS at the bottom of the gas collision position P1, and outputs a signal indicating the detected temperature to the first control unit 37.
[0044]
The first flow rate sensor 31b detects the flow rate of the gas stream flowing downward along the surface (front surface) of the hot-dip plated steel sheet PS from the gas collision position P1 of the bottom, a signal indicating the flow rate detection result first controller and outputs it to the 37. The first flow rate sensor 32b detects the flow rate of the gas stream flowing downward along the gas collision position P1 lowermost on the surface (rear surface) of the hot-dip plated steel sheet PS, a signal indicating the flow rate detection result first controller and outputs it to the 37.
[0045]
The first control unit 37 based on the flow rate detection results obtained from the temperature sensor 31a and the detected temperature obtained from 32a and the first flow rate sensor 31b and 32b, the bottom of the respective first pre-cooling nozzle 31 and 32 It controls the discharge flow rate of the pre-cooling gas Gs to be injected into the gas collision position P1. The detailed operation of the first control unit 37 will be described later.
[0046]
The following describes effects of the cooling device 10 according to the present embodiment configured as described above.
As already mentioned, the greater the thickness of the steel sheet S which is a base material, hot dip plated steel sheet and the thickness of the plating layer is also increased (the amount of plating deposition is large), the oxide film of the plated layer surface, by its own weight in some cases depending from near the center in the width direction of the PS.
[0047]
As shown in FIG. 3A, the sag of the oxide film, in particular the initial stages of the solidification process of the plating layer, that is, immediately after the hot dip plated steel sheet PS is pulled from the plating bath, the plate temperature (i.e. steel S of the molten plated steel sheet PS it plate temperature) is higher is considered likely to occur at stage high fluidity of the plating layer due. In step high fluidity of the plating layer is believed to likely be amplified sag of the oxide film by downward gas flow Gd discharged from the inlet of the main cooling device 20. On the other hand, as shown in FIG. 3B, the plate temperature of the hot-dip plated steel sheet PS is low, the solidification of the plating layer progresses fluidity of the plating layer decreases, the oxide film is considered to be difficult to sag.
[0048]
Therefore, preliminary in the conveying path between the plating thickness control device 6 and the main cooling device 20 (i.e. pre-cooling section), while suppressing the lowering gas flow Gd discharged from the inlet of the main cooling device 20, the hot dip plated steel sheet PS to cool (to promote solidification of plating layer) is believed to be effective as a countermeasure for suppressing the occurrence of wrinkles W due to sagging of the oxide film.
[0049]
The present inventors, in order to verify the validity of the measures, by using the conventional cooling device 100, the sheet temperature before cooling, the wrinkling critical velocity wrinkles W are generated on the surface of the hot dip plated steel sheet PS It was to investigate the relationship. Here, the sheet temperature before cooling is the temperature of the measured dip plated steel sheet PS immediately below the cooling device 100 (the inlet side of the cooling apparatus 100). In addition, the creasing critical velocity, was measured immediately below the cooling device 100, a flow rate of gas flowing along the surface of the molten plated steel sheet PS (maximum flow rate wrinkles W occur). At the time of investigation of the relationship, in order to increase the plating layer of the molten plated steel sheet PS, coating weight per surface 150 g / m 2 was set to.
[0050]
As shown in FIG. 4, immediately below the cooling device 100, melted if the upward gas flow to the surface of the plated steel sheet PS is generated, the flow velocity is predetermined speed (limit increased flow rate: In Figure 4 about 60 m / s) if less, wrinkles W does not occur regardless of the sheet temperature. Hereinafter, defines the limit increased flow rate wrinkles W are generated on the surface of the hot dip plated steel sheet PS (shown in Figure 4 60 m / s) and wrinkle occurrence limit rise velocity VL2 [m / s]. On the other hand, immediately below the cooling device 100, if occurred (corresponding to downward gas flow Gd) dip plated steel sheet downward gas flow to the surface of the PS, the higher the sheet temperature, lower than the upward gas flow velocity ( wrinkles W is likely to occur at the limit descent velocity). Hereinafter, a definition of the limits downward flow velocity wrinkles W are generated on the surface of the hot dip plated steel sheet PS and wrinkle occurrence limit downward velocity VL1 [m / s].
Incidentally, when the wrinkle occurrence limit descent velocity VL1 shown in FIG. 4 is approximated by the regression equation, wrinkle occurrence limit descent velocity VL1 can be expressed by the following equation (3) is a quadratic function of the plate temperature T. In the following equation (3), A, B, C and D are constants.
= A · VL1 (T-C) 2 + B · (T-C) -D ... (3)
[0051]
From the above findings, the higher the sheet temperature, i.e., the higher the fluidity of the plating layer, even at low flow rates of a gas flow directed downwardly, sagging of the oxide film was found to be likely to occur. This is because, as described above, the higher the fluidity of the plating layer, that sagging of the oxide film tends to occur considered why by the weight of the oxide film. Therefore, in order to suppress the sag of the oxide film, the higher the sheet temperature, it is more necessary to suppress the downward gas stream.
[0052]
The survey results, such as the above, the effectiveness of the above-mentioned measures has been confirmed. The present inventors, based on the above findings, as a countermeasure for suppressing the occurrence of wrinkles W due to sagging of the oxide film were found two measures below.
(Measure 1) for injecting a pre-cooling gas obliquely upward with respect to the plating thickness control device 6 and a plurality of gas collision position set along the transport path (pre-cooling section) between the main cooling system 20.
(Countermeasure 2) closer gas collision position to the lower end of the pre-cooling section (i.e., the higher the sheet temperature), to reduce the angle between the conveying direction Z of the hot dip plated steel sheet PS and the injection direction of the pre-cooling gas Gs.
[0053]
　By adopting the measures 1, while suppressing the lowering gas flow Gd discharged from the inlet of the main cooling device 20, it is possible to hot dip plated steel sheet PS preliminarily cooled (to facilitate the solidification of the plating layer) . Further, by adopting the measures 2, the higher the sheet temperature (i.e., the higher the fluidity of the plating layer), it is possible to further suppress lowering gas flow Gd. The smaller the angle between the injection direction of the precooled gas Gs to the transport direction Z of the hot-dip plated steel sheet PS, the effect is also obtained to support the oxide film obliquely from below by pre-cooling gas Gs, more effective sag oxide film it can be suppressed to.
[0054]
Cooling device 10 according to the present embodiment includes a pre-cooling device 30 to realize the above-mentioned measures 1 and 2. That is, pre-cooling device 30, to the pre-cooling three gas impingement position set along the section P1, P2 and P3, to inject pre-cooling gas Gs from the front obliquely upward dip plated steel sheet PS 3 One of the pre-cooling nozzle (first pre-cooling nozzle 31, the second pre-cooling nozzle 33 and the third pre-cooling nozzle 35) and, with respect to the gas impingement position P1, P2 and P3, obliquely upward from the rear surface side of the hot-dip plated steel sheet PS and a three preliminary cooling nozzle for injecting the pre-cooling gas Gs (first pre-cooling nozzle 32, the second pre-cooling nozzle 34 and the third pre-cooling nozzle 36) to.
[0055]
Furthermore, the pre-cooling device 30, the closer the gas collision position is at the lower end of the pre-cooling section, the angle between the injection direction of the pre-cooling gas Gs to the transport direction Z of the hot dip plated steel sheet PS becomes smaller. That is, the angle α1 of the first pre-cooling nozzle 31, the angle α5 of the angle α3 and third preliminary cooling nozzle 35 of the second pre-cooling nozzle 33 is set so as to satisfy the following relational expression (1) . Also, the angle α2 of the first pre-cooling nozzle 32, an angle α4 and the angle α6 third preliminary cooling nozzle 36 of the second pre-cooling nozzle 34 is set so as to satisfy the following relation (2) .
　　　　　　　　　.alpha.5> .alpha.3> [alpha] 1 ... (1)
　　　　　　　　　alpha6> alpha 4> [alpha] 2 ... (2)
　　　　　(however, α1 = α2, α3 = α4 , α5 = α6)
[0056]
The structure of the pre-cooling device 30 for realizing such measures 1 and 2, even when the steel sheet S and the plating layer is a base material is thick, pre-cooling section from the plating thickness control device 6 to the main cooling device 20 throughout the, it is possible to suppress the drooping of the oxide film of the plated layer surface. Therefore, according to the cooling apparatus 10 according to the present embodiment, in the process of manufacturing the thickness and the thickness is thicker dip plated steel sheet PS of the plated layer of the steel sheet S as the base material, the hot-dip plated steel sheet PS surface (of the plating layer it is possible to prevent the wrinkles W are generated on the surface).
[0057]
In the present embodiment, the temperature sensor 31a detected temperature obtained from the (front side of the surface temperature of the hot dip plated steel sheet PS at the bottom of the gas collision position P1) is defined as T [° C.]. The first flow rate sensor 31b is a flow rate detection results obtained from the (surface of the molten plated steel sheet PS from the bottom of the gas collision position P1 (flow rate of the gas stream flowing downward along the front surface)) Vd [m / s] and Define. Further, as described above, a definition of the limits downward flow velocity wrinkles W are generated on the surface of the hot dip plated steel sheet PS and wrinkle occurrence limit downward velocity VL1 [m / s].
[0058]
The first control unit 37 of the pre-cooling device 30 in the present embodiment, on the basis of the flow rate detection result Vd obtained from the detected temperature T and the first flow rate sensor 31b obtained from the temperature sensor 31a, a gas collision position of the lowermost P1 with respect to the following expressions (3) and (4) is satisfied, controls the discharge flow rate of the pre-cooling gas Gs ejected from the first pre-cooling nozzle 31 to the gas impingement position P1. = A ·
VL1 (T-C) 2 + B · (T-C) -D ... (3) | Vd | ≦ | VL1 | ... (4)
[0059]
Further, the solidification starting temperature of the molten plated steel sheet PS when defined as Ts [° C.], the first controller 37, the temperature detection result T obtained from the temperature sensor 31a is, in the case of satisfying the following conditional expression (5) controls the discharge flow rate as described above. This is because only in a temperature range expressed by the following conditional expression (5), equation (3) representing the wrinkle occurrence limit descent velocity VL1 is established.
Ts-49 ≦ T ≦ Ts + 9 ... (5)
[0060]
The preliminary discharge flow rate control of the cooling gas Gs as described above, the flow velocity Vd of the gas stream flowing downward along the surface (front surface) of the hot-dip plated steel sheet PS from gas collision position P1, regardless of sheet temperature T, wrinkles smaller than the limit downward flow velocity VL1. As a result, it is possible to prevent the wrinkles W are generated on the surface (front surface) of the hot-dip plated steel sheet PS (refer to FIG. 4).
[0061]
Similarly, the first control unit 37 based on the flow rate detection result Vd obtained from the detected temperature T and the first flow rate sensor 32b obtained from the temperature sensor 32a, the temperature detection result T obtained from the temperature sensor 32a is, the when satisfying the expression (5), as described above (3) and (4) is satisfied with respect to gas collision position P1 of the lowermost, it is injected from the first pre-cooling nozzle 32 to the gas collision position P1 It controls the discharge flow rate of the pre-cooling gas Gs.
Thus, the flow velocity Vd of the gas stream flowing downward along the surface (rear surface) of the hot-dip plated steel sheet PS from gas collision position P1, regardless of sheet temperature T, smaller than the wrinkle occurrence limit descent velocity VL1. As a result, it is possible to prevent the wrinkles W are generated on the surface (rear surface) of the hot-dip plated steel sheet PS.
[0062]
The present invention is not limited to the above embodiments include the following modifications.
(1) In the above embodiment, the flow rate of the lowermost and the surface temperature of the hot dip plated steel sheet PS Gas collision position P1, the gas stream flowing downward along the surface of the molten plated steel sheet PS from the gas collision position P1 of the lowermost detecting the door, on the basis of their detection results, and illustrates the case of controlling the discharge flow rate of the pre-cooling gas Gs to be injected into the gas collision position P1 of the bottom.
[0063]
　Not limited thereto, as described above with respect to the two gas collision positions P1 and P2 (3) and equation (4) below is satisfied, or all of the gas collision position P1, the terms P2 and P3 (3) and equation ( 4) as equation is satisfied, it may control the discharge flow rate of the pre-cooling gas Gs. That is, at least, as described above (3) and (4) is satisfied with respect to gas collision position P1 lowermost, may be controlled discharge flow rate of the pre-cooling gas Gs.
[0064]
(2) In the above embodiment, the flow rate of the lowermost and the surface temperature of the hot dip plated steel sheet PS Gas collision position P1, the gas stream flowing downward along the surface of the molten plated steel sheet PS from the gas collision position P1 of the lowermost detecting the door, on the basis of their detection results, as described above (3) and (4) is satisfied, controls the discharge flow rate of the pre-cooling gas Gs to be injected into the gas collision position P1 of the lowermost If illustrate.
[0065]
　Not limited thereto, may be adopted precooling system 30A having the configuration as shown in FIG. As shown in FIG. 5, precooling system 30A of the present modification, the first pre-cooling nozzle 31 and 32 and (not shown), a second pre-cooling nozzle 33 and 34 (not shown), a third pre-cooling in addition to the nozzle 35 and 36, further comprising a second flow sensor 31c and 32c, and a second control unit 38.
[0066]
The second flow rate sensor 31c detects the flow rate of the gas stream flowing upward along the gas collision position P1 lowermost on the surface (front surface) of the hot-dip plated steel sheet PS, a signal indicating the flow rate detection results second control device and outputs it to the 38. The second flow rate sensor 32c detects the flow rate of the gas stream flowing upward along the gas collision position P1 lowermost on the surface (rear surface) of the hot-dip plated steel sheet PS, a signal indicating the flow rate detection results second control device and outputs it to the 38.
[0067]
The second control unit 38, based on the second flow rate sensor 31c and a flow rate detection results obtained from 32c, controls the discharge flow rate of the pre-cooling gas Gs to be injected into the gas collision position P1 of the bottom.
Here, the flow rate detection result obtained from the second flow rate sensor 31c is defined as Vu [m / s], the hot-dip plated steel sheet marginal rise velocity wrinkles occurrence limit rise velocity VL2 wrinkles W on the surface of the PS occurs [m / s] to be defined. As shown in FIG. 4, wrinkle occurrence limit rise velocity VL2 is, for example, 60 [m / s] constant.
The second control unit 38, based on the flow rate detection result Vu obtained from the second flow rate sensor 31c, as the following conditional expression (6) is satisfied with respect to gas collision position P1 lowermost, the first pre-cooling nozzle 31 It controls the discharge flow rate of the pre-cooling gas Gs to be injected into the gas collision position P1 of the bottom.
| Vu | ≦ | VL2 | ... (6)
[0068]
　The discharge flow rate control of pre-cooling the gas Gs in this variation described above, the flow velocity Vu of the gas stream flowing upward along the gas collision position P1 on the surface (front surface) of the hot-dip plated steel sheet PS is involved in the sheet temperature T no smaller than wrinkle occurrence limit rise velocity VL2. As a result, it is possible to prevent the wrinkles W are generated on the surface (front surface) of the hot-dip plated steel sheet PS (refer to FIG. 4).
[0069]
　Similarly, the second control unit 38, based on the flow rate detection result Vu obtained from the second flow rate sensor 32c, as the conditional expression (6) is satisfied with respect to gas collision position P1 of the bottom, the first precooling It controls the discharge flow rate of the pre-cooling gas Gs ejected from the nozzle 32 to the gas collision position P1 of the bottom.
Thus, the flow velocity Vu of the gas stream flowing upwardly along the surface (rear surface) of the hot-dip plated steel sheet PS from gas collision position P1, regardless of sheet temperature T, smaller than the wrinkle occurrence limit rise velocity VL2. As a result, it is possible to prevent the wrinkles W are generated on the surface (rear surface) of the hot-dip plated steel sheet PS.
[0070]
Also in this modification, as the conditional expression (6) is satisfied with respect to two gas collision positions P1 and P2, or the conditional expression (6) is satisfied for all gas collision positions P1, P2 and P3 as it may control the discharge flow rate of the pre-cooling gas Gs. That is, at least, as the conditional expression (6) is satisfied with respect to gas collision position P1 lowermost, may be controlled discharge flow rate of the pre-cooling gas Gs.
[0071]
(3) In the above embodiment, the preliminary three gas impingement position in the cooling section P1 ~ P3 are set, pre-cooling device 30 is, spare three sets corresponding to each of the gas collision position P1 ~ P3 (total of six) a case having a cooling nozzle illustrated. However, the number of gas collision positions set to pre-cooling section is not limited to the above embodiment, it may be two or more. Also, depending on the number of gas collision position, the number of sets (total number) of the pre-cooling nozzle may also be changed as appropriate.
[0072]
(4) In the above embodiments, pre-cooling device 30 is a plurality of pre-cooling nozzle (first pre-cooling nozzle 31 and 32 respectively separately and independently, the second pre-cooling nozzle 33 and 34, the third pre-cooling nozzle 35 and 36) was exemplified when equipped with. Instead of such a pre-cooling device 30 may be provided with a pre-cooling device 40 shown in FIG. 6, for example.
[0073]
　As shown in FIG. 6, precooling system 40 includes a pre-cooling gas injector 41 with the first pre-cooling nozzle 31, the function of the second pre-cooling nozzle 33 and the third pre-cooling nozzle 35, the first pre-cooling nozzle 32, and a pre-cooling gas injection device 42 having the function of the second pre-cooling nozzle 34 and the third pre-cooling nozzle 36. That is, if the feasible constituting the measures 1 and 2, as in the pre-cooling device 30, it is not necessary to use a separate independent multiple precooled nozzle.
[0074]
(5) In the above embodiment, the main cooling device 20 and the pre-cooling device 30, and illustrates the case are each separately independent device. In contrast, as shown in FIG. 7, the main cooling system 20 and the pre-cooling device 30 may be configured integrally. 7, a first cooling gas injection device 51, the main cooling gas injector 21, the first pre-cooling nozzle 31, the function of the second pre-cooling nozzle 33 and the third pre-cooling nozzle 35. Further, a second cooling gas injection device 52, the main cooling gas injection device 22, the first pre-cooling nozzle 32, the function of the second pre-cooling nozzle 34 and the third pre-cooling nozzle 36.
Example
[0075]
　After pre-cooling and main cooling of hot dip plated steel sheet using a cooling device according to the present invention was verified the occurrence of wrinkles in the surface of the hot dip plated steel sheet. It shows the verification results in Table 1 and Table 2. In Table 1 and Table 2, the "nozzle number" corresponds to the set number of gas collision position in pre-cooling section. Further, the "nozzle No", indicating a number assigned from the bottom of the pre-cooling nozzle in order. In other words, the "nozzle No", indicating a number assigned by the gas collision position of the lowermost order.
[0076]
　In Table 1 and Table 2, "the angle alpha (°)" is the angle between the injection direction of the pre-cooling gas injected from the pre-cooling nozzle to the gas collision position, the transport direction of the hot dip plated steel sheet (e.g., Fig. 1A indicating the reference α1 etc.) shown in. "Rise velocity Vu (m / s)" is the detection result of the flow velocity of the gas stream flowing upward along the surface of the hot dip plated steel sheet PS from gas collision position (flow rate detection result obtained from the second flow velocity sensor). "Descent velocity Vd (m / s)" is a detection result of the flow velocity Vd of the gas stream flowing downward along the surface of the molten plated steel sheet PS from gas collision position (flow rate detection result obtained from the first flow velocity sensor) . In Table 1 and Table 2 represent the upward positive, defines a downwardly negative, therefore, represents the increase in flow velocity Vu a positive value, the descending velocity Vd by a negative value. "Nozzle position of the sheet temperature T (° C.)" is the detection result of the surface temperature of the hot dip plated steel sheet PS at gas collision position (temperature detection result obtained from the temperature sensor).
[0077]
[Table 1]

[0078]
[Table 2]

[0079]
The 5-stage evaluation was performed on wrinkles occurrence of. In other words, "×" indicates that it does not reach the pass line as a product. "△" indicates that it is barely reached the pass line as a product. "○" indicates that you have reached with a margin pass line as a product. "◎", along with has reached with a margin pass line as a product, show that it has a wrinkle less excellent appearance. "◎◎", as well has reached with ease pass line of the product, indicating that it has the appearance of wrinkles is very good almost no.
[0080]
　As shown in Table 1 and Table 2, for Examples 5-14 of the present invention, any, wrinkles occurrence has reached the pass line of the product. In particular, a configuration for injecting the pre-cooling gas obliquely upward with respect to three or more gas collision position set along the pre-cooling section, gas collision position is closer to the lower end of the pre-cooling section, the precooled gas the injection direction and the angle α becomes smaller configuration of the conveying direction of the hot dip plated steel sheet, it is highly evaluated wrinkles condition is confirmed.
[0081]
　In contrast, pre-cooling nozzle has only one stage (set number of gas collision position in pre-cooling section is "1") with respect to Comparative Examples 1-4 are each, pass wrinkles status as a product line that is not reached has been confirmed.
DESCRIPTION OF SYMBOLS
[0082]
1 snout
2 hot dipping pot
3 dip plating bath
4 bath folded roll
5 bath support rolls
6 plating thickness control device
7,8 wiping nozzle
10 cooling device
20 main cooling device
21 main cooling gas injector
21a slit nozzle
30, 30A, 40 precooling system
31 first preliminary cooling nozzle
33 and the second pre-cooling nozzle
35, 36 the third pre-cooling nozzles
31a, 32a temperature sensor
31b, 32 b first flow rate sensor
31c, 32c second flow sensor
37 the first controller
38 second control unit
41 pre-cooling the gas injection device
51 first cooling gas injection device
52 second cooling gas injection system
PS dip plated steel sheet
S steel sheet
Z conveyance direction
W wrinkles
Gc cooling gas
Gd descending gas flow
Gs precooled gas
P1 gas collision position

The scope of the claims
[Claim 1]
A cooling device provided above the plating thickness control device in the conveying path of the hot dip plated steel sheet to be conveyed vertically upward from the plating bath,
main cooling device for injecting a main cooling gas perpendicularly to the hot dip plated steel sheet When;
inject pre-cooling gas to pre-provided in the cooling section, a plurality of gas collision position set along the pre-cooling section between the main cooling device and the plating thickness control device in the transport path ; and precooling system for
cooling apparatus for molten plated steel sheet, characterized in that it comprises a.
[Claim 2]
The precooling system injects the precooled gas obliquely upward with respect to each of the gas collision position;
as the gas collision position is close to the lower end of the pre-cooling section, the the injection direction of said precooled gas the angle between the conveying direction of the hot dip plated steel sheet is decreased;
that the cooling apparatus for molten plated steel sheet according to claim 1, wherein the.
[Claim 3]
The precooling system can
; a temperature sensor for detecting the surface temperature of the hot dip plated steel sheet in the gas collision position of at least the lowermost
downward along at least the from the gas collision position of the lowermost to the surface of the hot dip plated steel sheet the first flow rate sensor and which detects the flow rate of gas flowing in;
based on said obtained from the temperature sensor detected temperature and the first flow rate obtained from a flow rate sensor detection result, the gas collision position of at least the lowermost the first control device and which controls the discharge flow rate of the pre-cooling gas injected;
equipped with,
the detected temperature obtained from the temperature sensor is defined as T [° C.],
obtained from the first flow rate sensor wherein the flow rate detection result is defined as Vd [m / s],
defined as wrinkling limit downward velocity VL1 [m / s] of the limit descent velocity that wrinkles are generated on the surface of the hot dip plated steel sheet When in,
the first control apparatus, as the following equation (3) and with respect to said gas impingement position of at least the lowermost (4) is satisfied, the preliminary to be injected into the gas collision position of the lowermost cooling apparatus for molten plated steel sheet according to claim 1 or 2, wherein the controller controls the discharge flow rate of the cooling gas.
VL1 = A · (T-C) 2 + B · (T-C) -D ...
(3) | Vd | ≦ | VL1 | ... (4)
(however, in equation (3), A, B, C and D is a constant)
[Claim 4]
　When the solidification starting temperature of the hot-dip plated steel sheet was defined as Ts [° C.],
the first control device, said obtained from the temperature sensor detected temperature T [° C.] is, satisfies the following conditional expression (5) cooling apparatus for molten plated steel sheet according to claim 3, characterized in that for controlling the discharge flow rate when.
Ts-49 ≦ T ≦ Ts + 9 ... (5)
[Claim 5]
The precooling system includes
a second flow rate sensor for detecting the flow rate of the gas stream flowing upwardly along from the gas collision position of at least the bottom to the surface of the hot dip plated steel sheet;
the second is obtained from a flow rate sensor flow rate detection based on the results, a second and a control device for controlling the discharge flow rate of at least said pre-cooling gas injected into the gas collision position of the lowermost;
equipped with,
the velocity detection result obtained from the second flow rate sensor defined as vu [m / s],
when said wrinkles on the surface of the hot dip plated steel sheet was defined as wrinkling limit rise velocity VL2 [m / s] of the limit increase flow velocity occurs,
the second control device, at least the as described below (6) is satisfied with respect to the gas collision position of the bottom, especially to control the discharge flow rate of the pre-cooling gas injected into the gas collision position of the lowermost Cooling apparatus for molten plated steel sheet according to claim 1 or 2, symptoms.
| Vu | ≦ | VL2 | ... (6)
[Claim 6]
The precooling system are individually independent plural of hot dip plated steel sheet according to any one of claims 1 to 5, characterized in that it comprises a pre-cooling nozzle cooling device.
[Claim 7]
The precooling system, during the pre-cooling nozzle adjacent to each other, according to claim 6, characterized in that it comprises a gap for discharging the pre-cooling gas used for cooling of the hot dip plated steel sheet cooling apparatus for molten plated steel sheet.
[8.]
The main cooling device and the pre-cooling device and the cooling device of hot dip plated steel sheet according to any one of claims 1 to 5, characterized in that it is integrally formed.