Metal strip cooling device and metal strip cooling method

Abstract

To provide a metal strip cooling device and a metal strip cooling method in which cooling performance is greatly improved by making the jetting speed of cooling gas jetted from a nozzle supersonic.SOLUTION: A metal strip cooling device includes a header through which cooling gas flows and a nozzle attached to the header. The nozzle is a supersonic nozzle capable of realizing a supersonic gas jetting speed. A metal strip is cooled by the supersonic cooling gas jetted from the nozzle.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a metal strip cooling apparatus and a metal strip cooling method, and more particularly to a metal strip cooling apparatus and a metal strip cooling method capable of rapidly cooling a metal strip in a continuous annealing facility for a steel strip, which is a type of metal strip, a continuous hot-dip galvanizing facility, and the like. [Background technology]

[0002] In recent years, the demand for high-strength metal sheets has been increasing. One example of high-strength metal sheets is a high-tensile steel sheet. In order to manufacture a high-tensile steel sheet that satisfies desired mechanical properties, it is necessary to cool the hot-rolled high-tensile steel sheet. When cooling a steel strip, which is a type of metal strip, the hot-rolled high-tensile steel sheet is passed through a continuous annealing facility in sequence. In this way, by passing the high-tensile steel sheet through the continuous annealing facility in sequence, a steel strip made of a high-tensile steel sheet that satisfies desired mechanical properties can be manufactured.

[0003] As a method for cooling hot-rolled high-tensile steel, a method of gas-jet cooling of high-tensile steel in a continuous annealing furnace has been proposed. Specifically, a gas-jet cooling device for steel sheets in a continuous annealing furnace has been proposed, which has wind boxes arranged on both sides of the steel sheet in a cooling chamber, which sandwich the steel sheet and cool the steel sheet by blowing cooling gas from nozzles onto the steel sheet, and a means for cooling the gas introduced from the cooling chamber and supplying it to the wind boxes (for example, Patent Document 1).

[0004] In the gas jet cooling device for steel plate described in Patent Document 1, the distance between the tip of the nozzle in the wind box and the steel plate is defined relative to the nozzle diameter, and the length of the wind box in the steel plate pass line direction is defined relative to the width of the steel plate. That is, a conventional gas jet cooling device for steel plate arranges 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 than the nozzle diameter, enabling efficient cooling.

[0005] In addition, a continuous annealing apparatus and a continuous annealing method for steel sheets for hot-dip galvanizing have been proposed that can save the furnace length space of the entire continuous annealing apparatus in a steel sheet line for hot-dip galvanizing as compared with the conventional method, and can obtain a higher reduction effect and a faster cooling rate (for example, Patent Document 2).

[0006] The continuous annealing apparatus and method for continuous annealing of steel sheet for hot-dip galvanizing described in Patent Document 2 are provided with a gas jet cooler that sprays high-concentration hydrogen onto the steel sheet surface at high speed, and the flow velocity of the cooling gas is set to 100 to 190 m / s and the hydrogen gas concentration is set to 20 to 80 vol.%. The continuous annealing apparatus and method for continuous annealing of steel sheet for hot-dip galvanizing described in Patent Document 2 can increase the cooling rate by improving the heat transfer coefficient during cooling. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-344128 A [Patent Document 2] JP 2006-144104 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional technology has the following problems to be solved. That is, the gas jet cooling device described in Patent Document 1 has a limit to the flow speed of the cooling gas ejected from the nozzle of the group of circular or polygonal holes. Therefore, the gas jet cooling device described in Patent Document 1 has a limit to the flow speed of the cooling gas ejected from the nozzle, and the cooling performance cannot be further improved.

[0009] The continuous annealing apparatus and method for continuous annealing of steel sheet for hot-dip galvanizing described in Patent Document 2 need to inject cooling gas containing high concentration of hydrogen gas in order to improve cooling performance. Therefore, the continuous annealing apparatus and method for continuous annealing of steel sheet for hot-dip galvanizing described in Patent Document 2 have a problem that the use of expensive hydrogen gas increases the cost for cooling the steel sheet for hot-dip galvanizing.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a metal strip cooling device and a metal strip cooling method in which cooling performance is significantly improved by making the ejection speed of cooling gas from the nozzle supersonic. [Means for solving the problem]

[0011] In order to solve the above problems, the inventors conducted various experiments and discovered that the cooling performance of the metal strip can be significantly improved by making the cooling gas ejected from the nozzle, which ejects the cooling gas supplied from the head through which the cooling gas flows, supersonic. The present invention was made based on the above findings, and the gist of the present invention is as follows.

[0012] 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.

[0013] In addition, it is considered that more preferable solutions for the metal strip cooling device of 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 a plurality of 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.

[0014] 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 apparatus, and is characterized in including: (I) a step of spraying the supersonic cooling gas from the supersonic nozzle onto the metal strip; and (II) a step of cooling the metal strip with the supersonic cooling gas. Effect of the Invention

[0015] According to the present invention, by making the ejection speed of the cooling gas ejected from the nozzle supersonic 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.

[0016] In other words, according to the metal strip cooling apparatus and cooling method using the supersonic nozzle of the present invention, the cooling gas ejected from the nozzle is made supersonic to make 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 checkerboard or staggered arrangement for cooling, thereby making it possible to significantly improve cooling performance compared to metal strip cooling apparatus and cooling methods which eject cooling gas at a subsonic ejection speed using conventional circular or slit-shaped nozzles, etc.

[0017] Furthermore, according to the metal strip cooling device and cooling method using the supersonic nozzle of the present invention, the heat transfer coefficient of the cooling gas can be improved, and the concentration of added hydrogen gas, which is very costly, can be significantly reduced. [Brief description of the drawings]

[0018] [Figure 1] 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; [Diagram 2] 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. 2(a) is a schematic diagram showing a case where a cylindrical header is used, and Fig. 2(b) is a schematic diagram showing a case where a rectangular header is used. [Diagram 3]1 is a schematic diagram showing a positional relationship (in a grid pattern) between a header provided in a metal strip cooling device according to the present embodiment and nozzles installed in a plurality of headers constituting the header. FIG. [Figure 4] 1 is a schematic diagram showing a 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 constituting the header. FIG. [Diagram 5] 1 is a cross-sectional view showing a cross-sectional structure of a nozzle (plug nozzle) provided in a metal strip cooling device according to the present embodiment. [Figure 6] FIG. 2 is a cross-sectional view showing a cross-sectional structure of a nozzle (aerospike nozzle) provided in the metal strip cooling device according to the present embodiment. [Figure 7] FIG. 2 is a schematic diagram illustrating conditions for cooling a metal strip using the metal strip cooling device according to the present embodiment. [Figure 8] 4 is a graph showing the relationship between the flow rate 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. [Figure 9] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [First embodiment] The metal strip cooling device according to the first embodiment will be described. The metal strip cooling device according to the present embodiment is characterized by comprising a header through which a cooling gas flows and a nozzle attached to the header, the nozzle being a supersonic nozzle capable of realizing a supersonic gas ejection speed, and cooling the metal strip with 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.

[0020] Fig. 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 Fig. 1, a metal strip cooling line 100 equipped with a 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 introduction pipe 103.

[0021] The metal strip cooling device 101 is a device that blows a cooling gas required for cooling the metal strip M onto the metal strip M at a supersonic gas jetting speed to cool the metal strip M. 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 for cooling the metal strip M. The blower 102 supplies the cooling gas in the cooling gas tank to the metal strip cooling device 101.

[0022] The cooling gas sucked by the blower 102 is supplied to the header 111 of the metal strip cooling apparatus 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 apparatus 101. Note that the inlet pipe 103 is not particularly limited as long as it can supply the cooling gas to the header 111 of the metal strip cooling apparatus 101.

[0023] Thus, the metal strip cooling line 100 includes the metal strip cooling device 101, the blower 102, and the introduction pipe 103, and cools the metal strip M with the cooling gas ejected from the metal strip cooling device 101 at a supersonic gas ejection velocity.

[0024] <About the header through which the 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-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-111D, the multiple headers 111A-111D are installed in multiple stages in the longitudinal direction of the metal strip, which is the conveying direction of the metal strip M.

[0025] FIG. 2 is a schematic diagram showing the positional relationship between the metal strip cooling device according to this embodiment and the metal strip. As shown in FIG. 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 may be installed on both sides. That is, in the metal strip cooling device 101 according to this embodiment shown in FIG. 2, an example is shown 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 be installed on only one side. When the metal strip cooling devices 101 are installed on both sides of the metal strip M, the metal strip M is cooled from both sides, which is preferable.

[0026] The shape of the header 111 is not particularly limited as long as the cooling gas sucked 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 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 appropriately set depending on the size of the metal strip cooling device 101 and the size of the metal strip M.

[0027] Furthermore, when 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.

[0028] For example, the headers 111 constituting the metal strip cooling device 101 may be configured in two stages consisting of headers 111A and 111B, with the first stage header 111A being installed in the width direction of the metal strip M, and a second stage header 111B being installed above the header 111A. Furthermore, the headers 111 constituting the metal strip cooling device 101 may be configured in three stages consisting of headers 111A, 111B, and 111C, with the first stage header 111A being installed in the width direction of the metal strip M, and a second stage header 111B being installed above the header 111A, and a third stage header 111C being installed above the header 111B.

[0029] <About supersonic nozzles> The nozzles 112 provided in the metal strip cooling device 101 are attached to the header 111 facing 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. The nozzles 112 are supersonic nozzles capable of achieving a supersonic gas ejection speed. In other words, the nozzles 112 are nozzles capable of ejecting the cooling gas supplied from the header 111 as supersonic cooling gas having a supersonic gas ejection speed.

[0030] Supersonic speed means that the relative speed between an object moving in a medium and the medium exceeds the speed of sound in the medium. In other words, the nozzle 112 is a supersonic nozzle that can realize a cooling gas ejection speed in which the relative speed between the air moving in the air and the cooling gas exceeds 1225 km / h (340.31 m / s, 15°C, 1 atm). The nozzle 112 is not particularly limited as long as it is a nozzle that can realize a supersonic gas ejection speed. Examples of the nozzle 112 include a plug nozzle, an aerospike nozzle, and a Laval nozzle. In general, a Laval nozzle causes separation of the cooling gas due to shock waves, so that the nozzle 112 can be adopted by removing such shock waves.

[0031] 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 appropriately determined 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, or the like, or two or more types of supersonic nozzles may be used depending on the location of the metal strip M to be cooled.

[0032] In this way, the metal strip cooling apparatus according to this embodiment employs a header through which the cooling gas flows and a supersonic nozzle that can achieve a supersonic gas ejection speed as a nozzle attached to the header, thereby making it possible to eject supersonic cooling gas from the nozzle. In other words, the metal strip cooling apparatus according to this embodiment can eject supersonic cooling gas ejected from the supersonic nozzle onto the metal strip, thereby making it possible to significantly improve the cooling capacity of the metal strip. Moreover, the metal strip cooling apparatus according to this embodiment can remarkably improve the cooling capacity of the metal strip by installing headers on one or both sides of the metal strip.

[0033] As described above, according to the invention relating to the first embodiment, by adopting a header through which cooling gas flows and a supersonic nozzle attached to the header that can achieve a supersonic gas ejection velocity, it is possible to provide a metal strip cooling device with significantly improved cooling performance.

[0034] [Second embodiment] A metal strip cooling apparatus according to a second embodiment will be described. The metal strip cooling apparatus according to this embodiment is characterized in that, in the above-mentioned metal strip cooling apparatus, the nozzles are attached to the header in a grid or staggered arrangement.

[0035] Fig. 3 is a schematic diagram showing the positional relationship (in a grid pattern) between a header provided in the metal strip cooling device according to this embodiment and nozzles provided in the multiple headers that constitute the header. As shown in Fig. 3, the header 111 provided in the metal strip cooling device 101 according to this embodiment is composed of multiple headers that constitute the header, and is composed of header 111A, header 111B, header 111C, and header 111D in this order from below to above the metal strip M. The header 111A, header 111B, header 111C, and header 111D that constitute the header 111 each have multiple nozzles 112.

[0036] The multiple nozzles 112 are installed at equal intervals in 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 speed. Since the header 111 is composed of the headers 111A to 111D, the metal strip cooling apparatus 101 according to this embodiment has four nozzle stages.

[0037] For this reason, in the metal strip cooling apparatus 101 according to this embodiment, the supersonic cooling gas is ejected in a checkerboard pattern on one or both sides of the metal strip M. As a result, a plurality of center points of cooling regions formed by the supersonic cooling gas ejected from the nozzle 112 are formed in a checkerboard 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 entire one or both sides of the metal strip M are cooled by overlapping one or both sides of the metal strip M with the cooling areas of the metal strip that spread radially from the center point of the cooling area formed by the supersonic cooling gas ejected from the nozzle 112. Even if the cooling areas of the metal strip that spread radially from the center point of the cooling area formed by the supersonic cooling gas ejected from the nozzle 112 do not overlap one or both sides of the metal strip M and the header distance is large, the entire one or both sides of the metal strip M are 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 checkerboard or staggered arrangement.

[0038] Fig. 4 is a schematic diagram showing the positional relationship (staggered arrangement) between a header provided in the metal strip cooling device according to this embodiment and nozzles installed in the multiple headers constituting the header. As shown in Fig. 4, the header 111 provided in the metal strip cooling device 101 according to this embodiment is composed of multiple headers, and is composed of a first stage header 111A, a second stage header 111B, a third stage header 111C, and a fourth stage header 111D, in that order from the bottom to the top of the metal strip M. The headers 111A, 111B, 111C, and 111D constituting the header 111 each have multiple nozzles 112.

[0039] The installation pattern of the multiple nozzles 112 installed in the first header 111A is the same as the installation pattern of the multiple nozzles 112 installed in the third header 111C. The installation pattern of the multiple nozzles 112 installed in the second header 111B is the same as the installation pattern of the multiple nozzles 112 installed in the fourth header 111D.

[0040] For this reason, in the metal strip cooling apparatus 101 according to this embodiment, supersonic cooling gas is sprayed in a staggered arrangement onto one or both sides of the metal strip M. As a result, a plurality of cooling center points formed by the supersonic cooling gas sprayed from the nozzle 112 are formed in a staggered arrangement 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 entire one or both sides of the metal strip M are cooled by the cooling regions of the metal strip radially spreading from the cooling center points formed by the supersonic cooling gas sprayed from the nozzle 112 onto one or both sides of the metal strip M.

[0041] In this way, the metal strip cooling device according to this embodiment employs a header consisting of multiple headers, and by attaching the supersonic nozzles in a checkerboard or staggered arrangement, it is possible to form the cooling centers formed by the supersonic cooling gas ejected from the supersonic nozzles in a checkerboard or staggered arrangement on one or both sides of the metal strip M. As a result, the metal strip cooling device according to this embodiment can cool the entirety of one side or the entirety of both sides of the metal strip M.

[0042] As described above, according to the invention of the second embodiment, by attaching supersonic nozzles capable of achieving a supersonic gas ejection velocity to the header in a checkerboard or staggered arrangement, it is possible to provide a metal strip cooling device with significantly improved cooling performance.

[0043] [Third embodiment] A metal strip cooling apparatus according to a third embodiment will be described below. 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.

[0044] Fig. 5 is a cross-sectional view showing the cross-sectional structure of a nozzle (plug nozzle) provided in the metal strip cooling apparatus according to this embodiment. As shown in Fig. 5, the nozzle 112 provided in the metal strip cooling apparatus 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. An end of the plug case 113 located on the header 111 side is connected to and attached to the side surface of the header 111. The plug case 113 is attached so as to protrude from the side surface of the header 111 in the direction of the metal strip M.

[0045] The tip portion of the plug case 113 located on the metal strip M side is open as a nozzle outlet 118 so that the cooling gas supplied from the header 111 can pass through, and faces the metal strip M. The plug case 113 has a cylindrical shape and a plug 114A is formed in the center of the plug case 113. The tip end 116 located on the metal strip M side 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 side further than the tip end 116 of the plug case 113.

[0046] The cooling gas supplied from the header 111 passes through a cooling gas flow passage 117 formed by the inner wall of the plug case 113 and the surface of the plug tip 115 of the plug 114A in the direction of the arrow. The cooling gas that has passed through the cooling gas flow passage 117 formed by the inner wall of the plug case 113 and the surface of the plug tip 115 of the plug 114A is ejected 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 toward the metal strip M as a cooling gas having a supersonic gas ejection speed. The cooling gas flow passage that has passed through the cooling gas flow passage 117 narrows suddenly near the nozzle outlet 118 and then expands, so that the ejection speed of the cooling gas that has passed through the cooling gas flow passage 117 becomes supersonic.

[0047] Fig. 6 is a cross-sectional view showing the cross-sectional structure of a nozzle (aerospike nozzle) provided in the metal strip cooling apparatus according to this embodiment. As shown in Fig. 6, the nozzle 112 provided in the metal strip cooling apparatus 101 according to this embodiment is an aerospike nozzle 112B. The structure of the aerospike nozzle 112B is the same as that of the plug nozzle 112A, except for the structure of its plug 114B.

[0048] The plug 114B of the aerospike nozzle 112B has a shape obtained by cutting off the plug tip 115 of the plug 114A of the plug nozzle 112A. The tip 119 of the plug 114B protrudes toward the metal strip M further than the pointed tip 116 located on the metal strip M side of the plug case 113.

[0049] The cooling gas that has passed through cooling gas flow passage 117 formed by the inner wall of plug case 113 and the surface of tip 119 of plug 114B is ejected from nozzle outlet 118 formed by tip pointed end 116 and the surface of tip 119 of plug 114B as cooling gas having a supersonic gas ejection velocity toward metal strip M. The gas flow passage of the cooling gas that has passed through cooling gas flow passage 117 is abruptly narrowed near nozzle outlet 118, so that the ejection velocity of the cooling gas that has passed through cooling gas flow passage 117 becomes supersonic.

[0050] In this way, the metal strip cooling apparatus 101 according to this embodiment employs a plug nozzle or an aerospike nozzle as the nozzle 112, which is a supersonic nozzle, and can make the ejection speed of the cooling gas ejected from the supersonic nozzle as high as possible, thereby ejecting the cooling gas at a supersonic ejection speed onto the metal strip. This allows the metal strip cooling apparatus 101 according to this embodiment to increase the heat transfer coefficient of the metal strip M being cooled.

[0051] On the other hand, conventional metal strip cooling devices use nozzles having a circular or slit shape 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 means a speed of so-called Mach number 0.8 or less. In this way, the metal strip cooling device 101 according to this embodiment can significantly improve the cooling performance compared to conventional metal strip cooling devices that use nozzles having a slit shape as cooling gas ejection nozzles.

[0052] As described above, according to the invention relating to the third embodiment, by adopting a plug nozzle or an aerospike nozzle as a supersonic nozzle, making the ejection speed of the cooling gas ejected from the supersonic speed 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.

[0053] [Fourth embodiment] A metal strip cooling method according to a fourth embodiment will 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 embodiment, 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.

[0054] That is, in the metal strip cooling method according to the present embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which a header is installed on one or both sides of the metal strip in the transport direction of the metal strip, and a plurality of supersonic nozzles are attached to the header. Furthermore, in the metal strip cooling method according to the present embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which supersonic nozzles are attached to the header in a checkerboard or staggered arrangement. In the metal strip cooling method according to the present embodiment, the metal strip may be cooled using a metal strip cooling device 101 in which the supersonic nozzle is a plug nozzle or an aerospike nozzle. Each step included in the metal strip cooling method according to the present embodiment will be described below.

[0055] <Step (I): Step of ejecting supersonic cooling gas from a supersonic nozzle> The metal strip cooling method according to this embodiment includes step (I): ejecting the supersonic cooling gas from a supersonic nozzle. Step (I) is a step of generating 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.

[0056] The cooling gas flowing through the header 111 is a mixed gas containing mainly nitrogen and hydrogen. Here, the metal strip cooling device 101 according to the above embodiment used in the metal strip cooling method according to the present embodiment is a cooling device with significantly improved cooling performance, so that the ratio of hydrogen contained in the cooling gas flowing through the header 111 can 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. Next, the cooling gas that has passed through the cooling gas flow path 117 becomes a cooling gas having a supersonic gas ejection velocity from a nozzle outlet 118 formed by the tip tip 116 and the surface of the plug tip 115 of the plug 114, and ejects toward the metal strip M. Then, it becomes a supersonic cooling gas having a supersonic gas ejection velocity from the nozzle outlet 118 formed by the tip tip 116 and the plug tip 115 of the plug 114.

[0057] The metal strip cooling method according to the present embodiment includes step (II); a step of cooling the metal strip M by the supersonic cooling gas. Step (II) is a step of cooling the metal strip M by the ejected supersonic cooling gas. The cooling of the metal strip M is performed until the temperature of the metal strip M after cooling falls 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. Then, taking into consideration the time required for cooling and the set temperature of the metal strip M after cooling, the cooling rate is set to a range of 20 to 50°C / sec. In step (II), the number of stages of the metal strip cooling device 101 according to the above embodiment (for example, the 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 central point from which the supersonic cooling gas is ejected is set so that the temperature of the cooled metal strip M becomes uniform throughout the entire strip, and the metal strip M is cooled.

[0058] Thus, the metal strip cooling method of this embodiment includes step (I); a step of generating supersonic cooling gas for cooling the metal strip M and spraying the supersonic cooling gas onto the metal strip M, and step (II); a step of cooling the metal strip M with the sprayed supersonic cooling gas, thereby making it possible to significantly improve cooling performance and cool the metal strip by using the supersonic cooling gas having a supersonic gas spray velocity.

[0059] 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 realizing cooling of the metal strip with significantly improved cooling performance.

[0060] [Other embodiments] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the technical scope of the present invention. In addition, systems or devices that combine the separate features included in each embodiment in any way are also included in the technical scope of the present invention. EXAMPLES

[0061] The effects of the present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0062] Example 1 A metal strip was cooled using the metal strip cooling device 101 according to the present invention. That is, as an embodiment (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 a supersonic nozzle provided in the metal strip cooling device 101. A plug nozzle was used as the supersonic nozzle.

[0063] FIG. 7 is a schematic diagram illustrating the conditions for cooling a metal strip using a metal strip cooling device 101. As shown in FIG. 7, in this embodiment, a steel plate was used as the metal strip, and cooling of the metal strip made of the steel plate was carried out under conditions in which the pressure before the header, i.e., the cooling gas ejection speed at the nozzle outlet, was changed. A steel plate having a size of 1000 mm square and a thickness of 1 mm was used as the metal strip. After the surface temperature of the steel plate was heated to 350° C. or higher, the surface temperature of the steel plate was cooled to 50° C. or lower at a predetermined cooling rate by the supersonic cooling gas ejected from the plug nozzle. In this embodiment, the plug nozzle-to-steel plate distance h was 100 mm, the pitch between the plug nozzles was 100 mm, and the header distance S was 140 mm. Compressed air was used as the cooling gas.

[0064] 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.

[0065] FIG. 8 shows the flow rate (Nm m) of the cooling gas when the metal strip is cooled using the metal strip cooling device 101 according to this embodiment. 37 is a graph showing the relationship between the cooling gas flow rate (Nm / h) and the cooling capacity (-) based on the measurement results measured in Example 1 and the comparative example. 3 8 shows the relationship between the cooling time (h) and the cooling capacity (-) of the metal strip cooling device. In the graph shown in Fig. 8, the data measured in Example (invention example) 1 are indicated by ●, and the data measured in Comparative Example 1 are indicated by ▲.

[0066] As is clear from Figure 8, when the metal strip was cooled using the metal strip cooling apparatus 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 apparatus in Comparative Example 1, the same or greater metal strip cooling capacity can be ensured even if the amount of cooling gas used is 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 apparatus 101 of the present invention in Example 1, a cooling capacity more than 2.0 times higher 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 apparatus in Comparative Example 1.

[0067] Fig. 9 is a graph showing the relationship between the flow velocity (Mach [-]) of the cooling gas and the cooling capacity when the metal strip is cooled using the metal strip cooling device. As is clear from Fig. 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 can be secured by using a supersonic cooling gas that can realize a supersonic gas ejection velocity of Mach 2.5 [-] or more from the nozzle outlet, compared to when the metal strip is cooled using the conventional metal strip cooling device in Comparative Example 1.

[0068] In this way, it has become clear that the metal strip cooling apparatus and metal strip cooling method of the present invention, by using a supersonic cooling nozzle that can achieve a supersonic gas ejection speed, enables rapid cooling of the metal strip with significantly improved cooling capacity compared to conventional metal strip cooling apparatuses and metal strip cooling methods, and can also significantly reduce the hydrogen concentration added to the cooling gas. [Industrial Applicability]

[0069] According to the metal strip cooling device of the present invention, the supersonic cooling gas ejected from the supersonic nozzle is ejected onto the metal strip to cool it, thereby making it possible to greatly improve the cooling performance of the metal strip, thereby contributing to the related development of the steelmaking industry and the like and being extremely useful industrially. [Explanation of symbols]

[0070] 100 Metal Strip Cooling Line 101 Metal strip cooling device 102 Blois 103 Introductory tube M Metal strip 111 Header 111A Header (1st 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 tip 117 Cooling gas flow path 118 Nozzle outlet 119 Plug tip (aerospike nozzle)

Claims

1. 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 apparatus, characterized in that the metal strip is cooled by the supersonic cooling gas ejected from the nozzle.

2. The header is provided on one or both sides of the metal strip in a transport direction of the metal strip, 2. The metal strip cooling system of claim 1, wherein a plurality of said nozzles are attached to said header.

3. 3. The metal strip cooling device according to claim 1, wherein the nozzles are attached to the header in a checkerboard or staggered arrangement.

4. 3. The metal strip cooling apparatus according to claim 1, wherein the nozzle is a plug nozzle or an aerospike nozzle.

5. A metal strip cooling method using the metal strip cooling apparatus according to claim 1, comprising the steps of: ejecting the supersonic cooling gas from the supersonic nozzle onto the metal strip; and cooling the metal strip with the supersonic cooling gas.

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