Temperature measuring device, continuous annealing furnace, and plated steel sheet manufacturing equipment

Abstract

This prevents deterioration of the surface quality of steel materials caused by corrosion products adhering to the surface of water-cooled piping falling onto the steel strip surface, and by foreign matter generated by the temperature difference between the inside of the continuous annealing furnace and the vicinity of the plate thermometer falling onto the steel strip surface. [Solution] The temperature measuring device of the present invention is a temperature measuring device for measuring the temperature of a steel strip being conveyed horizontally, and is characterized by comprising: a cylindrical device body positioned above the steel strip and having openings at its upper and lower ends; a plate thermometer inserted into the device body from the upper end and measuring the temperature of the steel strip being conveyed horizontally from above in a non-contact manner; a cooling device provided inside the device body and cooling the inside of the device body; and a receiving member having an opening provided at the lower part of the device body for receiving foreign objects falling inside the device body and not obstructing the measurement of the steel strip temperature by the plate thermometer.

Description

Technical Field

[0001] The present invention relates to a temperature measuring device, a continuous annealing furnace, and a galvanized steel sheet manufacturing facility.

Background Art

[0002] In a continuous annealing furnace, heat treatment is performed for the purpose of adjusting the mechanical properties, crystal structure, etc. of a steel strip. The heat treatment in the continuous annealing furnace is executed by feedback control using the temperature inside the continuous annealing furnace with a sheet thermometer such as a radiation thermometer installed in the continuous annealing furnace (see, for example, Patent Document 1 and Patent Document 2). The use temperature range of the sheet thermometer is defined to be 100°C or lower, and it is common to measure in a non-contact manner while cooling using, for example, a cooling pipe. Further, by arranging the cooling pipe along the vertical direction instead of the horizontal direction, it is possible to contribute to an improvement in maintainability.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a pretreatment such as an electrolytic cleaning treatment or a pickling treatment, for example, the steel strip is conveyed to the heating zone of the continuous annealing furnace in a state where the oxide scale on the surface of the steel strip has been removed. The pickling solution remaining on the surface of the steel strip is vaporized in the process of the steel strip being conveyed through the heating zone of the continuous annealing furnace. The vaporized pickling solution penetrates near the radiation thermometer and corrodes the surface of the cooling pipe. As a result, corrosion products adhere to the surface of the cooling pipe. A part of the corrosion products adhering to the surface of the cooling pipe may peel off from the surface of the cooling pipe and fall onto the surface of the steel strip and adhere to the surface of the steel strip.

[0005] Furthermore, conveyor rollers are generally used as a means of transporting steel strips. Grease is applied as a lubricant to the bearing portion of these conveyor rollers. The temperature of the heating zone of the continuous annealing furnace reaches approximately 800°C or higher, while the vaporization temperature of grease is, for example, 250°C. Therefore, the grease applied to the bearing portion of the conveyor rollers vaporizes. The vaporized grease remains inside the heating zone of the continuous annealing furnace, and some of it condenses near the radiation thermometer. In addition, the grease that condenses near the radiation thermometer may fall onto the surface of the steel strip and adhere to its surface.

[0006] For example, in the manufacture of plated steel sheets, if some corrosion products or grease from the cooling pipes adhere to the surface of the steel strip, the molten plating material will not adhere well to the surface of the steel strip, leading to plating defects. Also, in the manufacture of rolled steel sheets, if some corrosion from the cooling pipes or grease adheres to the surface of the steel strip, the corroded parts can get caught in the steel strip at the subsequent rollers, degrading the surface quality of the rolled steel.

[0007] The present invention aims to provide a technology that can prevent deterioration of the surface quality of steel materials caused by corrosion products adhering to the surface of water-cooled piping falling onto the surface of the steel strip, and by foreign matter generated by the temperature difference between the inside of a continuous annealing furnace and the vicinity of a plate thermometer falling onto the surface of the steel strip. [Means for solving the problem]

[0008] One temperature measuring device, in which the temperature of a steel strip being transported horizontally is measured, is characterized by comprising: a cylindrical device body positioned above the steel strip and having openings at its upper and lower ends; a plate thermometer inserted into the device body from the upper end and measuring the temperature of the horizontally transported steel strip non-contact from above the steel strip; a cooling device provided inside the device body and cooling the inside of the device body; and a receiving member having an opening positioned at the lower part of the device body to receive foreign objects falling inside the device body and not obstructing the measurement of the steel strip temperature by the plate thermometer.

[0009] Furthermore, the cooling device preferably consists of cooling pipes wound in a coil shape, with a thermal spray coating formed on the surface of the cooling pipes by ceramic thermal spraying.

[0010] Furthermore, it is preferable that the device is equipped with a nozzle for ejecting air toward the surface of the steel strip, and that the tip of the nozzle is held in a state where it is inserted into the opening.

[0011] Furthermore, it is preferable that the device body has at least a lid member that holds a plate thermometer while the upper end of the device body is closed, and an adsorption member fixed to the bottom surface of the lid member that adsorbs and holds the lubricant liquefied inside the device body by a cooling device.

[0012] Furthermore, a continuous annealing furnace from another perspective includes a heating zone that heats the steel strip while it is being transported, a cooling zone that cools the steel strip heated by the heating zone while it is being transported, and the aforementioned temperature measuring device that measures the temperature of the steel strip being transported horizontally downstream of the heating zone.

[0013] Furthermore, a plated steel sheet manufacturing facility from another perspective is characterized by comprising the continuous annealing furnace described above, and an immersion tank into which the plating material is melted and the steel strip annealed in the continuous annealing furnace is immersed. [Effects of the Invention]

[0014] According to this disclosure, it is possible to prevent deterioration of the surface quality of steel materials caused by corrosion products adhering to the surface of water-cooled piping falling onto the surface of the steel strip, and by foreign matter generated by the temperature difference between the inside of the continuous annealing furnace and the vicinity of the plate thermometer falling onto the surface of the steel strip. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram showing a partial configuration of a continuous hot-dip galvanizing line. [Figure 2] Figure 2 is a partial cross-sectional view showing one configuration of a temperature measuring device. [Figure 3] Figure 3(a) is an explanatory diagram showing the removal of dust from the surface of a steel plate using a purge nozzle, and Figure 3(b) is an explanatory diagram showing the removal of vaporized grease using a purge nozzle. [Modes for carrying out the invention]

[0016] The embodiment will now be described with reference to the drawings. Figure 1 is a schematic diagram showing a part of the configuration of a continuous hot-dip galvanizing line, which is an example of a plated steel sheet manufacturing facility. As shown in Figure 1, the continuous hot-dip galvanizing line 10 is equipped with payoff reels 11, 11, a welding machine 12, an entry looper 13, a pretreatment device 14, a continuous annealing furnace 20, and a zinc pod (hot-dip galvanizing bath) 40, etc. Although not shown in the illustration, the continuous hot-dip galvanizing line 10 is also equipped with an alloying furnace, a cooling zone, a post-treatment zone, an exit looper, a tension reel, etc., downstream of the zinc pod 40.

[0017] For example, cold-rolled coils are loaded into each of the payoff reels 11, 11, and steel sheets S1 are alternately fed out from each of the payoff reels 11, 11 into which the coils are loaded. Then, in the welding machine 12, the rear end of the steel sheet S1 that was fed out first and the front end of the steel sheet S1 that was fed out later are connected. In this way, the steel sheets S1 are continuously transported along the line 10. Hereafter, the continuously transported steel sheets S1 will be referred to as steel strips S2.

[0018] The entry looper 13 has a storage function for the steel strip S2. As described above, the steel plates S1 are alternately drawn out from each of the payoff reels 11, 11 and connected in the welding machine 12, and then transported to the annealing furnace 20 as steel strip S2.

[0019] For example, the process of cutting the defective part of the steel sheet S1 generated at the coil end, and the process of connecting the rear end of the previously fed steel sheet S1 and the front end of the steel sheet S1 fed later are executed in a state where the steel sheet S1 is stopped. On the other hand, the steel strip S2 is conveyed through the continuous hot-dip galvanizing line 10 without being stopped. That is, the in-side looper 13 can store a steel strip S2 of a predetermined length so that the steel strip S2 is conveyed through the continuous hot-dip galvanizing line 10 without being stopped.

[0020] The pretreatment device 14 is equipment for performing electrolytic cleaning treatment and pickling treatment. The electrolytic cleaning treatment is a treatment for cleaning the conveyed steel strip S2 by electrolysis using the steel strip S2 as the counter electrode. The pickling treatment is a treatment for pickling the oxide scale on the surface of the steel strip S2 by immersing the steel strip in a hydrochloric acid layer or a sulfuric acid bath.

[0021] The continuous annealing furnace (hereinafter simply referred to as the annealing furnace) 20 is provided for adjusting the mechanical properties such as the tensile strength and elongation of the conveyed steel strip S2. The annealing furnace 20 has, for example, a preheating zone 21, a heating zone 22, and a cooling zone 23. The preheating zone 21 heats (preheats) the conveyed steel strip S2 by using the heat of the exhaust gas generated when heating the steel strip S2 in the heating zone 22.

[0022] The heating zone 22 heats the steel strip S2 to, for example, 940 °C (preferably 700 °C or higher). As the heating method of the steel strip S2 in the heating zone 22, for example, a direct heating method or an RT (Radiant Tube) heating method is used. The direct heating method is a heating method in which, for example, a combustion burner is installed on the furnace wall to directly heat the conveyed steel strip S2. Examples of the direct heating method include a direct-firing reduction method and a straight-section non-oxidation method. The RT heating method is a heating method in which a combustion burner is installed in a radiant tube, and the conveyed steel strip S2 is indirectly heated by the radiant heat of the radiant tube.

[0023] In addition to the direct heating method and RT heating method described above, other heating methods such as induction heating, roll heating, and electrical resistance heating can also be used to heat the steel strip S2 in the heating zone 22.

[0024] The cooling zone 23 cools the steel strip S2, which has been heated by the heating zone 22, to a predetermined temperature (e.g., 500°C). Cooling methods include, for example, gas jet cooling, roll cooling, and water cooling. Although Figure 1 shows a single cooling zone 23, it is also possible to use multiple cooling zones.

[0025] Molten zinc (hereinafter referred to as molten zinc) is held in the zinc pod 40. The steel strip S2, cooled by the cooling zone 23, is immersed in the zinc pod 40. During the immersion process, the steel strip S2 is turned upward by the sink roll 41 and pulled out of the zinc pod 40. Wiping devices 44, 44 are provided between the support rolls 42, 42 and the touch rolls 43, 43. The wiping devices 44, 44 are devices that blow gas onto both sides of the steel strip S2 to adjust the amount of molten zinc adhering to both sides of the steel strip S2. The steel strip S2, with the amount of molten zinc adhering to it adjusted, is then transported to the alloying furnace. The steel strip transported to the alloying furnace is heated and cooled inside the furnace to form an alloy.

[0026] A temperature measuring device 50 is provided at the exit side of the heating zone 22 of the annealing furnace 20 described above. The temperature measuring device 50 measures the temperature of the steel strip S2 being transported inside the heating zone 22 from above the steel strip S2. The temperature measuring device 50 is provided, for example, on a wall portion 22a located above the steel strip S2 being transported in the horizontal (V1) direction.

[0027] As shown in Figure 2, the temperature measuring device 50 includes a plate thermometer 51, cooling pipes 52, a purge nozzle 53, a blanket 54, a tray 55, an upper cover 56, and the device body 57.

[0028] The plate thermometer 51 measures the temperature of the steel strip S2 being transported on the heating zone 22 from above the steel strip S2 in a non-contact manner. The plate thermometer 51 is, for example, a radiation thermometer. The plate thermometer 51 is fixed to the upper cover 56 so that the temperature of the steel strip S2 can be measured through an opening 55a provided in the receiving tray 55.

[0029] The cooling pipe 52 is provided to cool the plate thermometer 51 and its peripheral edge. Although details are omitted from the illustration, the cooling pipe 52 is composed of, for example, one or more pipes wound in a coil shape. The cooling pipe 52 is manufactured, for example, from copper. The central axis (L1) of the coiled cooling pipe is horizontal in the vertical direction.

[0030] A ceramic spray coating (hereinafter simply referred to as the spray coating) is formed on the surface of the cooling pipe 52. The spray coating is formed on the surface of the cooling pipe 52 by ceramic spraying using, for example, MCrAlY (where M is an alloy of Ni, Co, and NiCr). By forming a spray coating on the surface of the cooling pipe 52, corrosion of the surface of the cooling pipe 52 caused by condensation is suppressed. The thickness of the spray coating is, for example, 100 μm.

[0031] The purge nozzle 53 sprays air toward the surface of the steel strip S2 being transported through the heated zone 22 when a compressor (not shown) is driven. The purge nozzle 53 is fixed to the upper cover 56 with its tip inserted into the internal space A1 of the cooling pipe 52 from the upper cover 56. When the purge nozzle 53 is inserted into the internal space A1 of the cooling pipe 52, the direction of the central axis (L2) at the tip of the purge nozzle 53 is parallel to the vertical, or inclined at 0 to 10 degrees with respect to the vertical. In Figure 2, the case in which the direction of the central axis (L2) at the tip of the purge nozzle 53 is parallel to the vertical is illustrated. Here, the purge nozzle 53 corresponds to the spray nozzle described in the claim.

[0032] When the purge nozzle 53 is inserted into the internal space A1 of the cooling pipe 52, the tip 53a of the purge nozzle 53 is inserted into, for example, the opening 55a of the receiving tray 55 of the temperature measuring device 50. In Figure 2, the tip 53a of the purge nozzle 53 is held in a state inserted into the opening 55a of the receiving tray 55, but the position of the purge nozzle 53 is not particularly limited as long as the air ejected from the tip 53a of the purge nozzle 53 is blown onto the surface of the steel strip S2 and the vaporized grease does not flow into the inside of the device body 57 from the opening 55a. The material of the purge nozzle 53 is, for example, SUS304. The pressure of the air ejected from the purge nozzle 53 is, for example, 0.1 to 0.49 MPa. The air pressure is preferably 0.3 MPa.

[0033] The blanket 54 is a component fixed to the bottom surface of the upper lid 56. The blanket 54 is provided to adsorb liquefied grease. The blanket 54 is made of, for example, mullite (a compound of alumina and silicon dioxide). The thickness of the blanket 54 is, for example, 100 mm. Here, the blanket 54 corresponds to the adsorption member described in the claim.

[0034] The receiving tray 55 is provided at the lower end of the main body 57 of the device and receives liquefied grease in the internal space A1 and corroded parts that have peeled off from the surface of the cooling pipe 52. The receiving tray 55 corresponds to the receiving member described in the claim.

[0035] The receiving tray 55 is provided with an opening 55a. The opening 55a is positioned so as not to obstruct the measurement area A2 of the plate thermometer 51 when measuring the temperature of the steel strip S2 with the plate thermometer 51. Figure 2 illustrates the case where the opening 55a is located in the center of the receiving tray 55. The shape of the opening 55a is, for example, circular. The diameter of the opening 55a is set to a size that does not interfere with the measurement area of ​​the plate thermometer 51. For example, the diameter of the opening 55a is, for example, 200 mm.

[0036] Furthermore, the shape and size of the opening 55a are not particularly limited, as long as it does not obstruct the measurement area A2 of the plate thermometer 51 when measuring the temperature of the steel strip S2 with the plate thermometer 51. Also, the position of the opening 55a in the receiving tray 55 does not need to be limited to the center of the receiving tray 55, as long as it does not obstruct the measurement area A2 of the plate thermometer 51 when measuring the temperature of the steel strip S2 with the plate thermometer 51.

[0037] The receiving tray 55 is provided with a fall prevention wall 55b that protrudes upward, connected to the opening 55a. The fall prevention wall 55b is provided around the entire periphery of the opening 55a. The fall prevention wall 55b prevents grease and corroded parts received in the receiving tray 55 from falling from the opening 55a towards the steel strip S2. The height of the fall prevention wall 55b is, for example, 20 mm. However, it is preferable that the height of the fall prevention wall 55b is at least 10 mm.

[0038] The receiving tray 55 may be a single component, or it may be made up of multiple fan-shaped components combined to form a donut shape.

[0039] The upper cover 56 closes the upper end of the device body 57 and is a member that holds the plate thermometer 51 and purge nozzle 53 inserted inside the device body 57. A blanket 54 is fixed to the bottom surface of the upper cover 56. The upper cover 56 corresponds to the cover member described in the claim. In the case of a temperature measuring device 50 in which the purge nozzle 53 is located outside the device body 57, the upper cover 56 holds only the plate thermometer 51.

[0040] The main body 57 is a component that houses the cooling pipes 52 inside. The main body 57 is a cylindrical component with open upper and lower ends. The main body 57 is made of a refractory material such as ceramic fiber. This main body 57 is installed on the wall portion 22a of the heating zone 22 of the annealing furnace 20.

[0041] Next, the operation of the temperature measuring device 50 shown in this embodiment will be described. As mentioned above, the temperature inside the heating zone 22 of the annealing furnace 20 is, for example, 800°C or higher. This temperature is outside the operating temperature range of the plate thermometer 51. Therefore, cooling water is circulated inside the cooling pipe 52 to cool the air in the internal space A1 formed by the cooling pipe 52. In this state, the temperature of the steel strip S2 is measured by the plate thermometer 51.

[0042] After undergoing electrolytic cleaning and pickling in the pretreatment device 14, the steel strip S2 is transported through the heating zone 22 of the continuous annealing furnace 20. At this time, pickling solution remains on the surface of the steel strip S2. The pickling solution vaporizes as the steel strip S2 is transported through the heating zone 22 of the continuous annealing furnace 20. The vaporized pickling solution enters the vicinity of the plate thermometer 51.

[0043] As described above, a thermal spray coating is formed on the surface of the cooling pipe 52. Therefore, when vaporized pickling solution enters the vicinity of the plate thermometer 51, corrosion of the surface of the cooling pipe 52 is prevented (suppressed). This prevents corrosion products from adhering to the surface of the cooling pipe 52. Furthermore, by preventing corrosion products from adhering to the surface of the cooling pipe 52, the occurrence of events in which corrosion products detach from the cooling pipe is suppressed. Even if corrosion products do adhere to the surface of the cooling pipe 52 and detach from the cooling pipe 52, the detached corrosion products are received in the receiving tray 55. As a result, the detached corrosion products are prevented from falling onto the surface of the steel strip S2.

[0044] Although details are omitted from the illustration, when a conveying roller is used as a conveying means for transporting the steel strip S2, grease (lubricating oil) is applied to the bearing portion of the conveying roller. The grease applied to the bearing portion of the conveying roller vaporizes because the temperature of the heating zone 22 of the continuous annealing furnace 20 is higher than the vaporization temperature of the grease itself, and remains inside the heating zone 22 of the continuous annealing furnace 20.

[0045] As shown in Figure 3(a), the purge nozzle 53 constituting the temperature measuring device 50 ejects air from its tip 53a toward the surface of the steel strip S2. The air ejected from the tip 53a of the purge nozzle 53 is blown onto the surface of the steel strip S2. Therefore, dust 60 adhering to the surface of the steel strip S2 is blown away from the surface of the steel strip S2 by the blown air.

[0046] Incidentally, the tip 53a of the purge nozzle 53 is located near the opening 55a created by the receiving tray 55. Therefore, the air ejected from the tip 53a of the purge nozzle 53 makes it difficult for grease remaining inside the heating zone 22 of the continuous annealing furnace 20 to flow into the internal space A1 through the opening 55a. If vaporized grease does flow into the internal space A1 through the opening 55a, condensation will occur in the internal space A1. A blanket 54 is provided on the bottom surface of the upper lid 56. Therefore, some of the condensed grease is absorbed by the blanket 54.

[0047] Furthermore, condensed grease (reference numeral 62 in Figure 3(b)) may adhere to the surface of the cooling pipe 52. The grease adhering to the surface of the cooling pipe 52 may fall off the surface of the cooling pipe 52, but it is received by the receiving tray 55 that constitutes the temperature measuring device 50. As a result, it is prevented that the condensed grease falls onto the surface of the steel strip S2.

[0048] In this way, corrosion products and grease after condensation are prevented from adhering to the surface of the steel strip S2. As a result, when the steel strip S2 is immersed in the subsequent zinc pod, the molten zinc adheres more easily to the surface of the steel strip S2, suppressing the occurrence of plating defects in the resulting galvanized steel sheet.

[0049] Finally, the incidence rate of plating defects will be explained using Table 1. [Table 1]

[0050] As shown in Table 1, the temperature measuring device 50 described in this embodiment, which includes a cooling pipe 52 with ceramic spraying, a receiving tray 55, a blanket 54, and a purge nozzle 53, is designated as Invention Example 1. Furthermore, a temperature measuring device equipped with a cooling pipe without ceramic spraying, as well as a receiving tray 55 and a purge nozzle 53, is designated as Invention Example 2. Note that the blanket 54 is omitted in the temperature measuring device in Invention Example 2.

[0051] Furthermore, in addition to cooling pipes that have not undergone ceramic spraying, a temperature measuring device equipped with a receiving tray 55 was presented as Invention Example 3. In the temperature measuring device of Invention Example 3, the configuration of the blanket 54 and the purge nozzle 53 is omitted.

[0052] Furthermore, a temperature measuring device using cooling pipes 52 that were not subjected to ceramic spraying was designated as Comparative Example 1. The temperature measuring device designated as Comparative Example 1 is a conventional temperature measuring device and does not include a receiving tray 55, a blanket 54, and a purge nozzle 53.

[0053] The defect rate was 1.03% in Comparative Example 1, compared to 0.05% in Invention Example 1, 0.27% in Invention Example 2, and 0.53% in Invention Example 3, indicating a reduction in the occurrence of plating defects. In other words, even if a cooling pipe 52 that has not undergone ceramic spraying is used, if corrosion or condensation occurs in the cooling pipe, foreign matter that falls as a result can be caught in the receiving tray 55. As a result, the occurrence of plating defects is reduced. Furthermore, the air ejected from the tip of the purge nozzle 53 is blown onto the steel strip S2. This blows away dust and other particles from the surface of the steel strip S2. As a result, the plating material adheres more easily to the surface of the steel strip S2, which contributes to a reduction in the occurrence of plating defects. Similarly, the blanket 54 provided on the upper cover 56 adsorbs and holds the liquefied grease in the internal space A1. As a result, the liquefied grease in the internal space A1 is prevented from adhering to the surface of the transported steel strip S2. In this case as well, as a result, the plating material adheres more easily to the surface of the steel strip S2, which contributes to a reduction in the occurrence of plating defects.

[0054] The temperature measuring device 50 of this embodiment is illustrated as being installed in an annealing furnace 20 of a continuous hot-dip galvanizing line 10 for manufacturing galvanized steel sheets, but it can also be installed in an annealing furnace of a manufacturing line for manufacturing cold-rolled steel sheets, etc.

[0055] The annealing furnace 20 shown in this embodiment has a pre-heating zone 21, a heating zone 22, and a cooling zone 23, but an annealing furnace may also be provided with a soaking zone between the heating zone and the cooling zone, for example.

[0056] The temperature measuring device 50 shown in this embodiment is an example of a temperature measuring device 50 that includes a cooling pipe 52 having a thermal spray coating on its surface, a purge nozzle 53 that sprays air toward the surface of the steel strip S2, a blanket 54 that adsorbs liquefied lubricant, and a receiving tray 55 that receives falling foreign matter. However, if a receiving tray 55 is provided, the configuration of the cooling pipe 52, purge nozzle 53, and blanket 54 is not necessarily required. Alternatively, a temperature measuring device may be provided with at least one of the cooling pipe 52 having a thermal spray coating, the purge nozzle 53, and the blanket 54 in addition to the receiving tray 55.

[0057] <Summary of effects> The temperature measuring device 50 of this embodiment is a temperature measuring device 50 for measuring the temperature of a steel strip S2 being conveyed in the horizontal direction, and is characterized by comprising: a cylindrical device body 57 positioned above the conveyed steel strip and having an open upper and lower end; a plate thermometer 51 inserted into the device body 57 from the upper end and measuring the temperature of the steel strip S2 being conveyed in the horizontal direction non-contact from above the steel strip S2; a cooling pipe 52 provided inside the device body 57 and cooling the inside of the device body 57; and a receiving tray 55 having an opening 55a provided at the lower part of the device body for receiving foreign objects falling inside the device body 57 and not obstructing the measurement of the temperature of the steel strip S2 by the plate thermometer 51.

[0058] According to this, when corrosion products adhering to the surface of the cooling pipe 52 are detached by the vaporized pickling solution, these corrosion products are received in the receiving tray 55. Also, when grease that vaporizes and accumulates inside the heating zone 22 of the continuous annealing furnace 20 enters the internal space A1 and condenses, the condensed grease is received in the receiving tray 55. In this way, it is prevented that the detached corrosion products and condensed grease fall onto and adhere to the surface of the steel strip S2.

[0059] Furthermore, it is preferable to use a cooling pipe 52 wound in a coil shape as a cooling device, and to have a thermal spray coating formed on the surface of the cooling pipe 52 by ceramic thermal spraying.

[0060] According to this, corrosion of the surface of the cooling pipe 52 by vaporized pickling solution is prevented, and the occurrence of corrosion products adhering to the surface of the cooling pipe 52 is reduced.

[0061] Furthermore, it is preferable that the device is equipped with a purge nozzle 53 that sprays air toward the surface of the steel strip S2, and that the tip of the purge nozzle 53 is held in a state where it is inserted through the opening 55a.

[0062] According to this, the air ejected from the purge nozzle 53 can remove dust adhering to the surface of the steel strip S2. In addition, the air ejected from the purge nozzle 53 prevents vaporized grease from entering the internal space A1, which is the inside of the device, through the opening 55a. As a result, vaporized grease is less likely to condense in the internal space A1.

[0063] Furthermore, it is preferable that the device has an upper cover 56 that closes the upper end of the main body 57 and holds at least the plate thermometer 51, and a blanket 54 that is fixed to the bottom surface of the upper cover 56 and adsorbs and holds the grease that has been liquefied by cooling from the cooling pipe 52.

[0064] According to this, a portion of the grease condensed in the internal space A1 is adsorbed and held by the blanket 54. As a result, it is possible to prevent the condensed grease from falling onto the surface of the steel strip S2.

[0065] Furthermore, the continuous annealing furnace 20 of this embodiment is characterized by comprising a heating zone 22 for heating the steel strip S2 while conveying it, a cooling zone 23 for cooling the steel strip S2 heated by the heating zone 22 while conveying it, and the temperature measuring device 50 described above for measuring the temperature of the steel strip S2 being conveyed horizontally at the exit side of the heating zone 22.

[0066] This prevents detached corrosion products and condensed grease from falling onto and adhering to the surface of the steel strip S2. As a result, the deterioration of the surface quality of the steel strip S2 can be suppressed.

[0067] Furthermore, the plated steel sheet manufacturing line 10 of this embodiment is characterized by comprising a continuous annealing furnace 20 and a zinc pod 40 into which the plating material is melted and the steel strip S2 annealed by the continuous annealing furnace 20 is immersed.

[0068] This prevents detached corrosion products and condensed grease from falling onto and adhering to the surface of the steel strip S2. As a result, molten metals such as molten zinc adhere more easily to the surface of the steel strip S2, suppressing the occurrence of plating defects. [Explanation of symbols]

[0069] 10 Continuous hot-dip galvanizing lines 20 Annealing Furnace 40. Zinc Pod (Hot-dip galvanizing bath) 50 Temperature measuring device 51 Plate thermometer 52 Cooling piping 53 Purge nozzle 54 Blankets 55 Drip tray 56 Upper lid S1 steel plate S2 steel strip

Claims

1. In a temperature measuring device for measuring the temperature of a steel strip being conveyed horizontally, A cylindrical device body is positioned above the steel strip and has open upper and lower ends, A plate thermometer is inserted into the interior of the apparatus body from the upper end of the apparatus body and measures the temperature of the steel strip, which is being conveyed in the horizontal direction, from above the steel strip without contact. A cooling device is provided inside the main body of the device and cools the inside of the main body of the device, A temperature measuring device characterized by comprising: a receiving member having an opening at the lower part of the device body that receives foreign objects falling inside the device body and that does not obstruct the measurement of the steel strip temperature by the plate thermometer.

2. The cooling device is a cooling pipe wound in a coil shape, The temperature measuring device according to claim 1, characterized in that a thermal spray film is formed on the surface of the cooling pipe by thermal spraying.

3. The steel strip is equipped with a nozzle that ejects air toward the surface of the steel strip, The temperature measuring device according to claim 1, characterized in that the tip of the ejection nozzle is held in a state inserted through the opening.

4. The steel strip is equipped with a nozzle that ejects air toward the surface of the steel strip, The temperature measuring device according to claim 2, characterized in that the tip of the ejection nozzle is held in a state inserted through the opening.

5. With the upper end of the device body closed, at least a lid member for holding the plate thermometer, The temperature measuring device according to any one of claims 1 to 4, further comprising an adsorption member fixed to the bottom surface of the lid member, which adsorbs and holds the lubricant liquefied inside the main body of the device by the cooling device.

6. A heating zone that heats the steel strip while it is being transported, A cooling zone that cools the steel strip heated by the heating zone while transporting it, A continuous annealing furnace comprising a temperature measuring device according to any one of claims 1 to 4, which measures the temperature of the steel strip being conveyed horizontally downstream of the heating zone.

7. A heating zone that heats the steel strip while it is being transported, A cooling zone that cools the steel strip heated by the heating zone while transporting it, A continuous annealing furnace comprising a temperature measuring device according to claim 5, which measures the temperature of the steel strip being conveyed horizontally downstream of the heating zone.

8. A continuous annealing furnace according to claim 6, An immersion tank into which the plating material is melted and the steel strip annealed in the continuous annealing furnace is immersed, A plated steel sheet manufacturing apparatus characterized by being equipped with the following features.

9. A continuous annealing furnace according to claim 7, An immersion tank into which the plating material is melted and the steel strip annealed in the continuous annealing furnace is immersed, A plated steel sheet manufacturing apparatus characterized by being equipped with the following features.

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