JP7786428B2 - Metal strip cooling device and metal strip cooling method - Google Patents

Description

The present invention relates to a metal strip cooling device and a metal strip cooling method. In particular, the present invention relates to a metal strip cooling device and a metal strip cooling method that can rapidly cool a metal strip in continuous annealing equipment for steel strips, a type of metal strip, and continuous hot-dip galvanizing equipment.

In recent years, demand for high-strength metal sheets has been increasing. One example of such high-strength metal sheets is high-tensile steel sheet. To manufacture high-tensile steel sheets with the desired mechanical properties, hot-rolled high-tensile steel sheets must be cooled. When cooling steel strips, which are a type of metal strip, the hot-rolled high-tensile steel sheets are passed through a continuous annealing facility in sequence. By passing the high-tensile steel sheets through the continuous annealing facility in this way, steel strips made of high-tensile steel sheets with the desired mechanical properties can be manufactured.

A method of gas jet cooling of high-tensile steel in a continuous annealing furnace has been proposed as a method for cooling hot-rolled high-tensile steel. Specifically, a gas jet cooling device for steel plates in a continuous annealing furnace has been proposed, which includes wind boxes arranged on both sides of the steel plate in a cooling chamber, with the steel plate sandwiched between them, and which spray cooling gas onto the steel plate from nozzles to cool it, and a means for cooling the gas introduced from the cooling chamber and supplying it to the wind boxes (see, for example, Patent Document 1).

The gas jet cooling device for steel plates described in Patent Document 1 defines the distance between the tip of the nozzle in the wind box and the steel plate relative to the nozzle diameter, and defines the length of the wind box in the steel plate pass line direction relative to the width of the steel plate. In other words, conventional gas jet cooling devices for steel plates position nozzles with groups of circular or polygonal holes on both sides of the steel plate, with the distance between the nozzle tip and the steel plate being 10 times or less the nozzle diameter, enabling efficient cooling.

Furthermore, a continuous annealing apparatus and a continuous annealing method for steel sheets for hot-dip galvanizing have been proposed that can reduce the furnace length space of the entire continuous annealing apparatus in a hot-dip galvanizing steel sheet line compared to conventional methods, while also achieving a higher reduction effect and a faster cooling rate (for example, Patent Document 2).

The continuous annealing equipment and continuous annealing method for steel sheets for hot-dip galvanizing described in Patent Document 2 are equipped with a gas jet cooler that sprays highly concentrated hydrogen onto the steel sheet surface at high speed, with the cooling gas flow rate set to 100 to 190 m/s and the hydrogen gas concentration set to 20 to 80 vol.%. Furthermore, the continuous annealing equipment and continuous annealing method for steel sheets for hot-dip galvanizing described in Patent Document 2 improves the heat transfer coefficient during cooling, thereby enabling the cooling rate to be increased.

Japanese Patent Application Laid-Open No. 2005-344128 Japanese Patent Application Laid-Open No. 2006-144104

However, the above-mentioned conventional technology still has the following problems that need to be solved. Specifically, the gas jet cooling device described in Patent Document 1 has a limit to the flow rate of the cooling gas ejected from the nozzle, which is a group of circular or polygonal holes. As a result, the gas jet cooling device described in Patent Document 1 has a limit to the flow rate of the cooling gas ejected from the nozzle, and it is not possible to further improve cooling performance.

The continuous annealing apparatus and continuous annealing method for steel sheets for hot-dip galvanizing described in Patent Document 2 require the injection of cooling gas containing a high concentration of hydrogen gas to improve cooling performance. Therefore, the continuous annealing apparatus and continuous annealing method for steel sheets for hot-dip galvanizing described in Patent Document 2 have the problem that the use of expensive hydrogen gas increases the cost of cooling the steel sheets for hot-dip galvanizing.

The present invention was made in consideration of the above circumstances, and aims to provide a metal strip cooling device and metal strip cooling method that significantly improves cooling performance by making the cooling gas ejected from the nozzle eject at supersonic speeds.

The inventors conducted various experiments to solve the above problem and discovered that the cooling performance of the metal strip can be significantly improved by increasing the ejection speed of the cooling gas ejected from the nozzle, which ejects the cooling gas supplied from the head through which the cooling gas flows, to supersonic speed. The present invention was made based on the above findings and is summarized as follows.

In other words, the metal strip cooling device of the present invention, which advantageously solves the above-mentioned problems, is a metal strip cooling device comprising a header through which cooling gas flows and a nozzle attached to the header, wherein the nozzle is a supersonic nozzle capable of achieving a supersonic gas ejection velocity, and the metal strip is cooled by the supersonic cooling gas ejected from the nozzle.

In addition, it is believed that more preferable solutions for the metal strip cooling device according to the present invention are that (a) the header is installed on one or both sides of the metal strip in the transport direction of the metal strip, and multiple supersonic nozzles are attached to the header, (b) the nozzles are attached to the header in a checkerboard or staggered arrangement, and (c) the nozzles are plug nozzles or aerospike nozzles.

The metal strip cooling method of the present invention, which advantageously solves the above-mentioned problems, is a metal strip cooling method using the above-mentioned metal strip cooling device, and is characterized by including: (I) the step of ejecting the supersonic cooling gas from the supersonic nozzle onto the metal strip; and (II) the step of cooling the metal strip with the supersonic cooling gas.

According to the present invention, by setting the ejection speed of the cooling gas from the nozzle to supersonic speed and ejecting the supersonic cooling gas from the nozzle onto the metal strip to cool it, it is possible to provide a metal strip cooling device and a metal strip cooling method with significantly improved cooling performance.

In other words, with the metal strip cooling device and cooling method using the supersonic nozzle of the present invention, the cooling gas ejected from the nozzle is made supersonic, making the ejection speed of the cooling gas as fast as possible, while using multiple headers and arranging the nozzles in a regular pattern such as a grid or staggered arrangement for cooling. This allows for significantly improved cooling performance compared to metal strip cooling devices and cooling methods that eject cooling gas at subsonic ejection speeds using conventional circular or slit-shaped nozzles, etc.

Furthermore, the metal strip cooling device and cooling method using the supersonic nozzle of the present invention can improve the heat transfer coefficient of the cooling gas and significantly reduce the concentration of hydrogen gas added, which is very costly.

1 is a schematic diagram showing a metal strip cooling line equipped with a metal strip cooling device according to an embodiment of the present invention; 2A and 2B are schematic diagrams showing the positional relationship between the metal strip cooling device and the metal strip according to the present embodiment, in which Fig. 2A is a schematic diagram showing a case where a cylindrical header is used as the header shape, and Fig. 2B is a schematic diagram showing a case where a rectangular pillar header is used. 1 is a schematic diagram showing the positional relationship (in a grid pattern) between a header provided in the metal strip cooling device according to the present embodiment and nozzles installed in a plurality of headers that make up the header. FIG. 1 is a schematic diagram showing the positional relationship (staggered arrangement) between a header provided in the metal strip cooling device according to the present embodiment and nozzles installed in a plurality of headers that make up the header. FIG. 1 is a cross-sectional view showing the cross-sectional structure of a nozzle (plug nozzle) provided in a metal strip cooling device according to the present embodiment. FIG. FIG. 2 is a cross-sectional view showing the cross-sectional structure of a nozzle (aerospike nozzle) provided in the metal strip cooling device according to the present embodiment. FIG. 2 is a schematic diagram illustrating the conditions for cooling a metal strip using the metal strip cooling device according to the present embodiment. 10 is a graph showing the relationship between the flow rate of the cooling gas and the cooling capacity when the metal strip is cooled using the metal strip cooling device according to the present embodiment. 1 is a graph showing the relationship between the flow velocity (Mach [−]) of the cooling gas and the cooling capacity when a metal strip is cooled using the metal strip cooling device according to the present embodiment.

[First embodiment]
The metal strip cooling apparatus according to the first embodiment will be described. The metal strip cooling apparatus according to the present embodiment includes a header through which a cooling gas flows and a nozzle attached to the header. The nozzle is a supersonic nozzle capable of achieving a supersonic gas ejection velocity, and the metal strip is cooled by the supersonic cooling gas ejected from the nozzle.
Hereinafter, each member of the metal strip cooling device according to this embodiment will be described with reference to the drawings.

Figure 1 is a schematic diagram showing a metal strip cooling line equipped with a metal strip cooling device according to this embodiment. As shown in Figure 1, the metal strip cooling line 100 equipped with the metal strip cooling device according to this embodiment is a cooling line for cooling a metal strip M. The metal strip cooling line 100 includes a metal strip cooling device 101, a blower 102, and an inlet pipe 103.

The metal strip cooling device 101 is a device that cools the metal strip M by spraying the cooling gas required to cool the metal strip M onto the metal strip M at a supersonic gas jet velocity. In other words, the metal strip cooling device 101 cools the metal strip M that is continuously passing through. The cooling gas contains hydrogen and nitrogen. The blower 102 is connected to a cooling gas tank that stores the cooling gas required to cool the metal strip M. The blower 102 supplies the cooling gas from the cooling gas tank to the metal strip cooling device 101.

The cooling gas sucked in by the blower 102 is supplied to the header 111 of the metal strip cooling device 101 via the inlet pipe 103. The cooling gas supplied to the header 111 via the inlet pipe 103 flows inside the header 111. The inlet pipe 103 is a pipe for supplying the cooling gas supplied from the blower 102 to the header 111 of the metal strip cooling device 101. There are no particular restrictions on the inlet pipe 103, as long as it is capable of supplying the cooling gas to the header 111 of the metal strip cooling device 101.

As such, the metal strip cooling line 100 comprises a metal strip cooling device 101, a blower 102, and an inlet pipe 103, and cools the metal strip M with cooling gas ejected from the metal strip cooling device 101 at a supersonic gas ejection velocity.

<About the header through which cooling gas flows>
The metal strip cooling device according to this embodiment includes a header through which a cooling gas flows and a nozzle attached to the header. The header 111 may be a single header or may be composed of multiple headers (e.g., headers 111A to 111D), and may be installed on one or both sides of the metal strip M in the conveying direction of the metal strip. When the header 111 is composed of multiple headers 111A to 111D, the multiple headers 111A to 111D are installed in multiple stages in the longitudinal direction of the metal strip M, which is the conveying direction of the metal strip M.

Figure 2 is a schematic diagram showing the positional relationship between the metal strip cooling device and the metal strip according to this embodiment. As shown in Figure 2, the headers 111 (headers 111A, 111B) constituting the metal strip cooling device 101 according to this embodiment may be installed on only one side of the metal strip M, or on both sides. That is, the metal strip cooling device 101 according to this embodiment shown in Figure 2 shows an example in which the headers 111 (headers 111A, 111B) are installed on both sides of the metal strip M, but the headers 111 (headers 111A, 111B) may also be installed on only one side. When the metal strip cooling device 101 is installed on both sides of the metal strip M, the metal strip M is cooled from both sides, which is preferable.

The shape of the header 111 is not particularly limited as long as the cooling gas sucked in by the blower 102 and supplied to the header 111 via the inlet pipe 103 can flow through the header 111 at a constant flow rate. The shape of the header 111 (headers 111A, 111B) may be a cylinder with a circular cross section, as shown in FIG. 2(a). The shape of the header 111 (headers 111A, 111B) may also be a prism with a rectangular cross section, as shown in FIG. 2(b). The size of the header 111 (headers 111A, 111B) can be set appropriately depending on the size of the metal strip cooling device 101 and the size of the metal strip M.

Furthermore, if the header 111 constituting the metal strip cooling device 101 is composed of multiple headers, multiple headers may be installed in the vertical direction in which the metal strip M to be cooled is transported. In other words, the headers constituting the header 111 provided in the metal strip cooling device 101 can be installed in multiple stages in the width direction of the metal strip M. The entire metal strip M can be cooled by the headers 111 constituting the metal strip cooling device 101 installed at each stage in the width direction of the metal strip M.

For example, the headers 111 constituting the metal strip cooling device 101 may be configured as two tiers consisting of headers 111A and 111B, with the first tier header 111A installed in the width direction of the metal strip M and a second tier header 111B installed above the header 111A. Furthermore, the headers 111 constituting the metal strip cooling device 101 may be configured as three tiers consisting of headers 111A, 111B, and 111C, with the first tier header 111A installed in the width direction of the metal strip M and a second tier header 111B installed above the header 111A and a third tier header 111C installed above the header 111B.

<About supersonic nozzles>
The nozzles 112 provided in the metal strip cooling device 101 are attached to the header 111 so as to face the metal strip M to be cooled. When the metal strip cooling devices 101 are installed on both sides of the metal strip M, the metal strip cooling devices 101 may be installed so that the tips of the nozzles 112 located on both sides of the metal strip M face each other across the metal strip M. The nozzles 112 are supersonic nozzles capable of achieving a supersonic gas ejection velocity. In other words, the nozzles 112 are nozzles that can eject the cooling gas supplied from the header 111 as supersonic cooling gas having a supersonic gas ejection velocity.

Supersonic speed means that the relative speed between an object moving through a medium and the medium exceeds the speed of sound in that medium. In other words, nozzle 112 is a supersonic nozzle that can achieve a cooling gas ejection speed where the relative speed between the air moving through the air and the cooling gas exceeds 1,225 km/h (340.31 m/s, 15°C, 1 atmosphere). Nozzle 112 is not particularly limited as long as it can achieve a supersonic gas ejection speed. Examples of nozzle 112 include plug nozzles, aerospike nozzles, and Laval nozzles. Note that Laval nozzles generally cause cooling gas separation due to shock waves, so by eliminating these shock waves, they can be used as nozzle 112.

A plurality of nozzles 112 may be attached to the header 111. The number of nozzles 112 constituting the plurality of nozzles 112 can be determined appropriately depending on the longitudinal length, which is the transport direction of the metal strip M to be cooled. The plurality of nozzles 112 may be installed in a regular arrangement on the header 111. Note that the nozzles constituting the plurality of nozzles 112 may be one type of plug nozzle, aerospike nozzle, Laval nozzle, etc., or two or more types of supersonic nozzles may be used depending on the location of the metal strip M to be cooled.

In this way, the metal strip cooling device of this embodiment employs a header through which the cooling gas flows and a supersonic nozzle attached to the header that can achieve a supersonic gas ejection speed, thereby enabling the supersonic cooling gas to be ejected from the nozzle. In other words, the metal strip cooling device of this embodiment is able to eject the supersonic cooling gas ejected from the supersonic nozzle onto the metal strip, thereby significantly improving the cooling capacity of the metal strip. Furthermore, the metal strip cooling device of this embodiment can dramatically improve the cooling capacity of the metal strip by installing headers on one or both sides of the metal strip.

As explained above, the invention of the first embodiment provides a metal strip cooling device with significantly improved cooling performance by employing a header through which cooling gas flows and a supersonic nozzle attached to the header that can achieve supersonic gas ejection velocities.

Second Embodiment
A metal strip cooling apparatus according to a second embodiment will now be described. The metal strip cooling apparatus according to this embodiment is characterized in that, in the above-described metal strip cooling apparatus, the nozzles are attached to the header in a grid or staggered arrangement.

Figure 3 is a schematic diagram showing the positional relationship (in a grid pattern) between the header provided in the metal strip cooling device according to this embodiment and the nozzles installed in the multiple headers that make up the header. As shown in Figure 3, the header 111 provided in the metal strip cooling device 101 according to this embodiment is made up of multiple headers that make up the header, which are composed of header 111A, header 111B, header 111C, and header 111D, in that order from below to above the metal strip M. Header 111A, header 111B, header 111C, and header 111D that make up the header 111 each have multiple nozzles 112.

The multiple nozzles 112 are installed at equal intervals on each of the headers 111A to 111D. The multiple nozzles 112 are supersonic nozzles that can eject the cooling gas supplied from the headers 111A to 111D at a supersonic gas ejection velocity. Because the header 111 is composed of headers 111A to 111D, the metal strip cooling device 101 according to this embodiment has four stages of nozzles.

For this reason, in the metal strip cooling apparatus 101 according to this embodiment, the supersonic cooling gas is ejected in a grid pattern on one or both sides of the metal strip M. As a result, multiple center points of the cooling regions formed by the supersonic cooling gas ejected from the nozzles 112 are formed in a grid pattern on one or both sides of the metal strip M to be cooled by the metal strip cooling apparatus 101 according to this embodiment.
Then, the cooling areas of the metal strip M that spread radially from the center point of the cooling area formed by the supersonic cooling gas ejected from the nozzles 112 overlap with one or both sides of the metal strip M, thereby cooling the entire one or both sides of the metal strip M. Furthermore, even if the cooling areas of the metal strip M that spread radially from the center point of the cooling area formed by the supersonic cooling gas ejected from the nozzles 112 do not overlap with one or both sides of the metal strip M and the distance between the headers is large, the entire one or both sides of the metal strip M can be cooled by transporting the metal strip M to the metal strip cooling device 101 in which the nozzles 112 are attached to the headers in a grid or staggered arrangement.

Figure 4 is a schematic diagram showing the positional relationship (staggered arrangement) between the header provided in the metal strip cooling device according to this embodiment and the nozzles installed on the multiple headers that make up the header. As shown in Figure 4, the header 111 provided in the metal strip cooling device 101 according to this embodiment is made up of multiple headers, which are, in order from below to above the metal strip M, a first-tier header 111A, a second-tier header 111B, a third-tier header 111C, and a fourth-tier header 111D. Each of the headers 111A, 111B, 111C, and 111D that make up the header 111 has multiple nozzles 112.

The installation pattern of the multiple nozzles 112 installed in the first-stage header 111A is the same as the installation pattern of the multiple nozzles 112 installed in the third-stage header 111C. The installation pattern of the multiple nozzles 112 installed in the second-stage header 111B is the same as the installation pattern of the multiple nozzles 112 installed in the fourth-stage header 111D.

For this reason, the metal strip cooling device 101 of this embodiment sprays supersonic cooling gas in a staggered pattern onto one or both sides of the metal strip M. As a result, multiple cooling centers formed by the supersonic cooling gas sprayed from the nozzle 112 are formed in a staggered pattern on one or both sides of the metal strip M that is the target of cooling by the metal strip cooling device 101 of this embodiment. Then, the entire one or both sides of the metal strip M are cooled by the cooling areas of the metal strip that spread radially from the cooling centers formed by the supersonic cooling gas sprayed from the nozzle 112 onto one or both sides of the metal strip M.

In this way, the metal strip cooling device of this embodiment uses a header consisting of multiple headers and attaches supersonic nozzles in a checkerboard or staggered pattern, allowing the cooling centers formed by the supersonic cooling gas ejected from the supersonic nozzles on one or both sides of the metal strip M to be formed in a checkerboard or staggered pattern. As a result, the metal strip cooling device of this embodiment can cool the entirety of one or both sides of the metal strip M.

As explained above, according to the second embodiment of the invention, by attaching supersonic nozzles capable of achieving supersonic gas ejection velocities to the header in a checkerboard or staggered pattern, it is possible to provide a metal strip cooling device with significantly improved cooling performance.

[Third embodiment]
A metal strip cooling apparatus according to a third embodiment will be described. The metal strip cooling apparatus according to this embodiment is characterized in that the above-mentioned metal strip cooling apparatus is a plug nozzle or an aerospike nozzle.

Figure 5 is a cross-sectional view showing the cross-sectional structure of a nozzle (plug nozzle) provided in the metal strip cooling device according to this embodiment. As shown in Figure 5, the nozzle 112 provided in the metal strip cooling device according to this embodiment is a plug nozzle 112A. The plug nozzle 112A is composed of a plug case 113 and a plug 114A. The plug case 113 has a cylindrical shape. The end of the plug case 113 located on the header 111 side is connected to and attached to the side of the header 111. The plug case 113 is attached so as to protrude from the side of the header 111 in the direction of the metal strip M.

The tip of the plug case 113 facing the metal strip M is open as a nozzle outlet 118 to allow the cooling gas supplied from the header 111 to pass through, and faces the metal strip M. The plug 114A is formed in the center of the cylindrical plug case 113. The tip 116 facing the metal strip M of the plug case 113 is bent downward toward the plug 114A, and its thickness becomes thinner as it approaches the plug 114A, resulting in a sharp shape. The plug tip 115 of the plug 114A has a pointed shape. The plug tip 115 of the plug 114A protrudes toward the metal strip M more than the tip 116 of the plug case 113.

The cooling gas supplied from the header 111 passes in the direction of the arrow through a cooling gas flow path 117 formed by the inner wall of the plug case 113 and the surface of the plug tip 115 of the plug 114A. After passing through the cooling gas flow path 117 formed by the inner wall of the plug case 113 and the surface of the plug tip 115 of the plug 114A, the cooling gas is ejected toward the metal strip M from a nozzle outlet 118 formed by the tip end 116 of the plug case 113 and the plug tip 115 of the plug 114A as cooling gas with a supersonic gas ejection velocity. As the cooling gas flow path that passes through the cooling gas flow path 117 suddenly narrows near the nozzle outlet 118 and then expands, the ejection velocity of the cooling gas that passes through the cooling gas flow path 117 becomes supersonic.

Figure 6 is a cross-sectional view showing the cross-sectional structure of the nozzle (aerospike nozzle) provided in the metal strip cooling device according to this embodiment. As shown in Figure 6, the nozzle 112 provided in the metal strip cooling device 101 according to this embodiment is an aerospike nozzle 112B. The structure of the aerospike nozzle 112B is identical to the structure of the plug nozzle 112A, except for the structure of its plug 114B.

The plug 114B of the aerospike nozzle 112B has a shape in which the plug tip 115 of the plug 114A of the plug nozzle 112A has been cut off. The tip 119 of the plug 114B protrudes further toward the metal band M than the tip pointed end 116, which is located on the metal band M side of the plug case 113.

The cooling gas that passes through the cooling gas flow path 117, formed by the inner wall of the plug case 113 and the surface of the tip 119 of the plug 114B, is ejected from the nozzle outlet 118, formed by the tip pointed end 116 and the surface of the tip 119 of the plug 114B, as cooling gas with a supersonic gas ejection velocity toward the metal strip M. Because the gas flow path of the cooling gas that has passed through the cooling gas flow path 117 narrows suddenly near the nozzle outlet 118, the ejection velocity of the cooling gas that has passed through the cooling gas flow path 117 becomes supersonic.

In this way, the metal strip cooling device 101 of this embodiment uses a plug nozzle or an aerospike nozzle as the nozzle 112, which is a supersonic nozzle, and can maximize the ejection speed of the cooling gas ejected from the supersonic nozzle, thereby spraying the cooling gas at a supersonic ejection speed onto the metal strip. As a result, the metal strip cooling device 101 of this embodiment can increase the heat transfer coefficient of the metal strip M being cooled.

On the other hand, conventional metal strip cooling devices use circular or slit-shaped nozzles as cooling gas ejection nozzles. Therefore, the ejection speed of the cooling gas ejected from the cooling gas ejection nozzles of conventional metal strip cooling devices is subsonic, which is less than supersonic. Here, subsonic speed refers to a speed of Mach number 0.8 or less. In this way, the metal strip cooling device 101 of this embodiment can significantly improve cooling performance compared to conventional metal strip cooling devices that use slit-shaped nozzles as cooling gas ejection nozzles.

As explained above, according to the invention of the third embodiment, by adopting a plug nozzle or an aerospike nozzle as the supersonic nozzle, making the ejection speed of the cooling gas ejected from the supersonic nozzle as high as possible, and spraying the supersonic cooling gas onto the metal strip, it is possible to provide a metal strip cooling device with significantly improved cooling performance.

[Fourth embodiment]
A metal strip cooling method according to a fourth embodiment will now be described. The metal strip cooling method according to this embodiment is a metal strip cooling method using the metal strip cooling apparatus described in the above embodiments, and is characterized by including: (I) a step of ejecting the supersonic cooling gas from the supersonic nozzle; and (II) a step of cooling the metal strip with the supersonic cooling gas.

That is, in the metal strip cooling method according to this embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which headers are installed on one or both sides of the metal strip in the transport direction of the metal strip, and multiple supersonic nozzles are attached to the headers. Furthermore, in the metal strip cooling method according to this embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which supersonic nozzles are attached to the headers in a checkerboard or staggered arrangement. In the metal strip cooling method according to this embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which the supersonic nozzles are plug nozzles or aerospike nozzles. Each step included in the metal strip cooling method according to this embodiment will be described below.

<Step (I): Step of ejecting supersonic cooled gas from a supersonic nozzle>
The metal strip cooling method according to this embodiment includes step (I): a step of ejecting the supersonic cooling gas from a supersonic nozzle. Step (I) is a step of generating a supersonic cooling gas for cooling the metal strip M and ejecting the supersonic cooling gas onto the metal strip M. In step (I), the supersonic cooling gas is formed by ejecting the cooling gas supplied from a header 111 through which the cooling gas flows from a nozzle 112 provided in the metal strip cooling apparatus 101 according to the above embodiment.

The cooling gas flowing through the header 111 is a mixed gas containing primarily nitrogen and hydrogen. The metal strip cooling device 101 according to the above embodiment, used in the metal strip cooling method according to this embodiment, is a cooling device with significantly improved cooling performance, allowing the proportion of hydrogen contained in the cooling gas flowing through the header 111 to be reduced. In step (I), the cooling gas passes through a cooling gas flow path 117 formed by the inner wall of the plug case 113 constituting the nozzle 112 and the surface of the tip of the plug 114. The cooling gas passing through the cooling gas flow path 117 then emerges from a nozzle outlet 118 formed by the tip end 116 and the surface of the plug tip 115 of the plug 114 as a cooling gas with a supersonic gas ejection velocity toward the metal strip M. The cooling gas then emerges from the nozzle outlet 118 formed by the tip end 116 and the surface of the plug tip 115 of the plug 114 as a supersonic cooling gas with a supersonic gas ejection velocity.

The metal strip cooling method according to this embodiment includes step (II): cooling the metal strip with the supersonic cooling gas. Step (II) is a step in which the metal strip M is cooled with the ejected supersonic cooling gas. The cooling of the metal strip M is carried out until the temperature of the metal strip M after cooling drops to a set temperature. The temperature of the metal strip M before cooling is in the range of 800 to 1000°C. The temperature of the metal strip M after cooling is set to a range of 200 to 50°C. The cooling rate is set to a range of 20 to 50°C/sec, taking into account the cooling time and the set temperature of the metal strip M after cooling. In step (II), the number of stages of the metal strip cooling device 101 according to the above embodiment (e.g., metal strip cooling devices 101A to 101D), the shape of the header 111, and the arrangement and shape of the nozzle 112, which is a supersonic nozzle, are determined according to the dimensions of the metal strip M. The center point from which the supersonic cooling gas is ejected is set so that the temperature of the cooled metal strip M is uniform throughout, and the metal strip M is cooled.

As such, the metal strip cooling method according to this embodiment includes step (I): generating supersonic cooling gas for cooling the metal strip M and injecting the supersonic cooling gas onto the metal strip M, and step (II): cooling the metal strip M with the injected supersonic cooling gas. This allows the metal strip to be cooled with significantly improved cooling performance using supersonic cooling gas with a supersonic gas injection velocity.

As described above, according to the invention of the fourth embodiment, by using the metal strip cooling device of the above embodiment, supersonic cooling gas can be generated, thereby achieving metal strip cooling with significantly improved cooling performance.

Other Embodiments
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the configuration and details of the present invention that are understandable to those skilled in the art within the technical scope of the present invention. Furthermore, systems or devices that combine the separate features included in each embodiment in any manner are also included in the technical scope of the present invention.

The effects of the present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

Example 1
A metal strip was cooled using a metal strip cooling device 101 according to the present invention. That is, as an example (invention example) of the present invention, the metal strip cooling devices 101 were installed on both sides of a heated metal strip, and the metal strip was cooled by supersonic cooling gas ejected from supersonic nozzles provided in the metal strip cooling devices 101. A plug nozzle was used as the supersonic nozzle.

FIG. 7 is a schematic diagram illustrating the conditions for cooling a metal strip using the metal strip cooling device 101. As shown in FIG. 7 , in this example, a steel plate was used as the metal strip, and cooling of the metal strip made of steel plate was carried out under conditions in which the header pre-pressure, i.e., the cooling gas ejection speed at the nozzle outlet, was varied. The metal strip used was a 1000 mm square steel plate with a thickness of 1 mm. After heating the surface temperature of the steel plate to 350°C or higher, the surface temperature of the steel plate was cooled to 50°C or lower at a predetermined cooling rate using supersonic cooling gas ejected from a plug nozzle.
In this example, the distance h between the plug nozzle and the steel plate was 100 mm, the pitch between the plug nozzles was 100 mm, and the distance S between the headers was 140 mm. Compressed air was used as the cooling gas.

(Comparative Example 1)
The metal strip was cooled using a conventional metal strip cooling device. That is, as a comparative example of the present invention, the metal strip was cooled in the same manner as in Example 1, except that metal strip cooling devices were installed on both sides of the heated metal strip and the metal strip was cooled by subsonic cooling gas ejected from round-hole nozzles equipped in the metal strip cooling devices.

Fig. 8 is a graph showing the relationship between the cooling gas flow rate (Nm ³ /h) and the cooling capacity (-) when a metal strip is cooled using the metal strip cooling apparatus 101 according to this embodiment. That is, Fig. 7 shows the relationship between the cooling gas flow rate (Nm ³ /h) and the cooling capacity (-) of the metal strip cooling apparatus based on the measurement results obtained in Example 1 and the comparative example. In the graph shown in Fig. 8, the data measured in Example (invention example) 1 is indicated by a black circle, and the data measured in Comparative example 1 is indicated by a triangle.

As is clear from Figure 8, when the metal strip was cooled using the metal strip cooling device 101 of the present invention in Example 1, it was found that, compared to when the metal strip was cooled using a conventional metal strip cooling device in Comparative Example 1, the same or greater metal strip cooling capacity could be ensured even if the amount of cooling gas used was reduced by more than 75% compared to the conventional case.
At the same time, it was found that when the metal strip was cooled using the metal strip cooling device 101 of the present invention in Example 1, a cooling capacity more than 2.0 times greater could be secured with the same flow rate of cooling gas compared to when the metal strip was cooled using a conventional metal strip cooling device in Comparative Example 1.

Figure 9 is a graph showing the relationship between the cooling gas flow velocity (Mach [-]) and cooling capacity when a metal strip is cooled using a metal strip cooling device. As is clear from Figure 9, when the metal strip is cooled using the metal strip cooling device 101 of the present invention in Example 1, it was found that a cooling capacity of more than 2.0 times greater can be ensured compared to when the metal strip is cooled using a conventional metal strip cooling device in Comparative Example 1, using supersonic cooling gas that can achieve a supersonic gas ejection velocity of Mach 2.5 [-] or more from the nozzle outlet.

As such, it has been revealed that the metal strip cooling device and metal strip cooling method of the present invention, by using a supersonic cooling nozzle that can achieve supersonic gas ejection velocities, enables rapid cooling of the metal strip with significantly improved cooling capacity compared to conventional metal strip cooling devices and metal strip cooling methods, and also significantly reduces the hydrogen concentration added to the cooling gas.

The metal strip cooling device of the present invention can significantly improve the cooling performance of a metal strip by injecting supersonic cooling gas from a supersonic nozzle onto the metal strip to cool it, thereby contributing to the development of related industries such as the steelmaking industry and being extremely useful industrially.

100 Metal strip cooling line 101 Metal strip cooling device 102 Blower 103 Inlet pipe M Metal strip 111 Header 111A Header (first stage)
111B Header (2nd row)
111C Header (3rd row)
111D Header (4th row)
112 Nozzle 112A Plug nozzle 112B Aerospike nozzle 113 Plug case 114 Plug 114A Plug (plug nozzle)
114B Plug (Aerospike Nozzle)
115 Plug tip (plug nozzle)
116 Tip sharp end 117 Cooling gas flow path 118 Nozzle outlet 119 Plug tip (aerospike nozzle)

Claims (5)

A metal strip cooling device comprising: a header through which a cooling gas flows; and a nozzle attached to the header,
the nozzle is a supersonic nozzle capable of realizing a supersonic gas ejection velocity,
A metal strip cooling device characterized in that the metal strip is cooled by the supersonic cooling gas ejected from the nozzle. the header is installed on one or both sides of the metal strip in the transport direction of the metal strip,
2. The metal strip cooling apparatus according to claim 1, wherein a plurality of said nozzles are attached to said header. A metal strip cooling device as described in claim 1 or 2, characterized in that the nozzles are attached to the header in a checkerboard or staggered arrangement. A metal strip cooling device as described in claim 1 or 2, characterized in that the nozzle is a plug nozzle or an aerospike nozzle. A metal strip cooling method using the metal strip cooling apparatus according to claim 1,
ejecting the supersonic cooling gas from the supersonic nozzle onto the metal strip;
and cooling the metal strip with the supersonic cooling gas.