Polishing equipment and method for manufacturing annealed steel sheet

Abstract

To provide polishing equipment capable of polishing a transport roll while inhibiting uneven wear due to uneven contact.SOLUTION: Polishing equipment polishes a transport roll that transports a steel sheet in continuous annealing equipment. The polishing equipment includes: a first polishing roll brought into contact with a peripheral surface of the transport roll; a rotation device that rotates the first polishing roll; a movement device that moves the first polishing roll in an axial direction of the transport roll; and a pressing mechanism that presses the first polishing roll against the transport roll. The first polishing roll has a barrel shape in which a diameter of a central part in the axial direction of the first polishing roll is larger than a diameter of each of both end parts.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a polishing facility for polishing a conveying roll for conveying a steel sheet in a continuous annealing facility and a method for manufacturing an annealed steel sheet.

Background Art

[0002] In recent years, the demand for high-tensile steel sheets has been increasing, and the production ratio of high-tensile steel sheets has been rising. It has been shown that high-tensile steel sheets can potentially be manufactured into steel sheets that are advantageous for strength and processing by adding Si and Mn. On the other hand, when manufacturing high-tensile steel sheets in a continuous annealing process, from the perspective of increasing strength, a process of cooling the heated steel sheet is required. Also, from the perspective of press formability, a tempering process of reheating the cooled steel sheet is necessary.

[0003] The steel sheet is, for example, annealed and tempered through an annealing process in which it is preheated to about 150°C in a preheating zone, heated to about 800°C in an oxidation-reduction zone, and rapidly cooled to 500°C in a rapid cooling zone. At that time, in a steel sheet containing easily oxidizable elements such as Si and Mn, the added elements such as Si and Mn are concentrated on the surface of the steel sheet in the reduction zone, and these oxides are generated. The roll deposits formed by these oxides adhering to the conveying roll cause push marks (surface defects) on the steel sheet.

[0004] As a technique for preventing push marks on the steel sheet caused by roll deposits adhering to the conveying roll, Patent Document 1 discloses an apparatus in which a doctor blade for removing foreign substances from the surface of the conveying roll and a dust collection and suction mechanism are integrated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Although the technique disclosed in Patent Document 1 can remove roll deposits, it is not easy to uniformly press a flat plate against the conveying roll in an annealing furnace in which a thermal crown is formed, and there is a problem that the flat plate contacts only one side and uneven wear occurs. The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a polishing facility capable of polishing a conveying roll while suppressing uneven wear due to one-sided contact, and a method for manufacturing an annealed steel sheet in which the conveying roll is polished by the polishing facility and the annealed steel sheet is manufactured by a continuous annealing facility.

Means for Solving the Problems

[0007] The means for solving the above problems are as follows. [1] A polishing facility for polishing a conveying roll that conveys a steel sheet in a continuous annealing facility, comprising a first polishing roll that contacts the peripheral surface of the conveying roll, a rotating device that rotates the first polishing roll, a moving device that moves the first polishing roll in the axial direction of the conveying roll, and a pressing mechanism that presses the first polishing roll against the conveying roll, wherein the first polishing roll has a barrel shape in which the diameter of the central portion in the axial direction of the first polishing roll is larger than the diameters of both ends. [2] The polishing facility according to [1], wherein the first polishing roll is a brush roll having a plurality of metal wires protruding radially from the peripheral surface. [3] The polishing facility according to [2], wherein the diameter of the wire is 20 μm or more and 500 μm or less. [4] The polishing facility according to [2] or [3], wherein the wire is made of tungsten, molybdenum, cobalt, nickel-chromium alloy or stainless steel. [5] The polishing facility according to any one of [1] to [4], having a polishing member that contacts the peripheral surface of the first polishing roll, wherein the polishing member is a flat plate, a grindstone or a second polishing roll. [6] The polishing facility according to any one of [1] to [5], having a recovery device for recovering dropped objects from the conveying roll and the first polishing roll. [7] A method for manufacturing an annealed steel sheet, comprising polishing the conveying roll with the polishing equipment according to any one of [1] to [3], and annealing the steel sheet with the continuous annealing equipment to manufacture an annealed steel sheet.

Effect of the Invention

[0008] In the polishing equipment according to the present invention, since the barrel-shaped first polishing roll is moved in the axial direction of the conveying roll to polish the conveying roll, it is possible to suppress the first polishing roll from hitting one side of the conveying roll. As a result, it becomes possible to polish the conveying roll while suppressing uneven wear due to one-sided contact using the first polishing roll.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments show a preferred example of the present invention, and the present invention is not limited by these embodiments.

[0011] The polishing equipment according to the present embodiment is suitably used for polishing the conveying roll that conveys the steel sheet 10 in the continuous annealing equipment 100. First, the continuous annealing equipment 100 will be described. FIG. 1 is a schematic diagram showing a configuration example of the continuous annealing equipment 100. The continuous annealing equipment 100 includes a heating zone 12, a soaking zone 14, a cooling zone 16, and an overaging zone 18. Further, the continuous annealing equipment 100 may be provided with equipment for performing surface treatment such as zinc plating as necessary.

[0012] The heating zone 12 is provided with equipment for raising the temperature of the steel plate 10. In the heating zone 12, a direct-fired or radiant combustion burner is used. In the heating zone 12, the steel plate 10 is heated to a preset temperature of about 600 to 900 °C according to its component composition.

[0013] The soaking zone 14 is provided with equipment for maintaining the steel plate 10 at a predetermined temperature. The equipment for maintaining the steel plate 10 at a predetermined temperature is equipment with a heating capacity sufficient to supplement the heat dissipated from the furnace body and the like.

[0014] The cooling zone 16 is provided with equipment for cooling the steel plate 10 to a predetermined temperature. As the cooling means in the cooling zone 16, liquid cooling, gas jet cooling, roll cooling, mist cooling (gas-liquid mixed cooling), etc. are used. Liquid cooling is often performed by water cooling (water quench) using water. Water cooling is a cooling means in which the steel plate 10 is immersed in an immersion water tank installed on the downstream side of the soaking zone 14 for cooling. Gas jet cooling is a cooling means in which gas is blown from a nozzle onto the surface of the steel plate 10. Roll cooling is a cooling means in which the steel plate 10 is brought into contact with a water-cooled roll for cooling. Mist cooling is a cooling means in which water is sprayed in a fine mist and the steel plate 10 is cooled by absorbing the latent heat of vaporization. In mist cooling, the size of the water droplets to be sprayed is often about 0.1 to 1 mm.

[0015] The post-aging zone 18 is equipment for performing a post-aging treatment in which the steel plate 10 is reheated to a temperature of about 300 to 400 °C and held at that temperature for a predetermined time. In such a continuous annealing facility 100, the steel plate 10 is heated and reduced in the heating zone 12 and the soaking zone 14 in a reducing atmosphere composed of a mixed gas of hydrogen, nitrogen, etc., cooled in the cooling zone 16, and tempered in the post-aging zone 18.

[0016] When the Si and Mn contents of the steel sheet 10 processed by the continuous annealing equipment 100 are 0.3% by mass or more, the Si and Mn in the steel sheet 10 are easily oxidized and concentrated on the surface layer. Si and Mn are elements effective for improving the mechanical properties of the steel sheet 10, and among Si and Mn, Si is more easily oxidized. Therefore, in the case of Si-added steel, while SiO2 is generated on the surface layer of the steel sheet 10, the generation of MnO is likely to be suppressed. However, in a steel sheet with a low Si content, Mn is most likely to concentrate on the outermost surface layer, so MnO of the steel sheet 10 is generated and concentrated on the surface layer.

[0017] The concentration of oxides on the surface layer of the steel sheet 10 and the adhesion of the oxides to the conveying roll are highly correlated with the temperature of the steel sheet 10. The higher the temperature of the steel sheet 10, the more the concentration of oxides of Si and Mn on the surface layer of the steel sheet 10 is promoted. The oxides of Si and Mn concentrated on the surface layer of the steel sheet 10 adhere to the surface of the conveying roll. When the oxides of Si and Mn adhering to the surface of the conveying roll are heated, a sintered body of the oxides is formed and adheres firmly to the surface of the conveying roll. Since the temperature at which the sintered body is formed is about half of the melting point of the oxide, it becomes remarkable when the surface temperature of the conveying roll reaches 700 °C or higher.

[0018] In a vertical continuous annealing facility, since the steel sheet 10 is conveyed while being wound around the conveying roll, strain corresponding to the roll curvature of the conveying roll is introduced. In order to reduce the introduction of strain during conveyance, in a vertical continuous annealing facility, a conveying roll with a larger diameter is used compared to a horizontal continuous annealing facility. In a vertical continuous annealing facility, a conveying roll with a diameter of 400 mm or more is preferably used.

[0019] On the other hand, when the diameter of the conveying roll increases, due to thermal expansion, the diameter of the central part in the axial direction of the conveying roll becomes larger than the diameters of both ends, and the difference in roll circumference between the central part and both ends becomes larger. As a result, a speed difference occurs between the steel sheet 10 and the conveying roll depending on the axial position of the conveying roll, and the oxides concentrated on the surface layer of the steel sheet 10 are likely to adhere to the conveying roll due to rubbing between the steel sheet 10 and the surface of the conveying roll.

[0020] For the conveying rolls of the continuous annealing equipment 100, rolls sprayed with cermet or ceramics are used to reduce the reactivity and adhesion with deposits. However, even when such rolls are used, if the oxide concentrated on the surface layer of the steel sheet 10 firmly adheres to the conveying roll and does not easily fall off from the roll surface, deposits grow starting from that location, causing pressing flaw defects in the conveyed steel sheet 10.

[0021] To suppress the occurrence of such pressing flaw defects, the surface of the conveying roll with deposits adhered is polished with a doctor blade to remove the deposits adhered to the roll surface. However, when polishing a conveying roll whose diameter at the central part in the axial direction becomes larger than that at both ends due to thermal expansion with a flat doctor blade, the blade contacts only one side, causing uneven wear on the conveying roll. When uneven wear occurs on the conveying roll, the conveying roll needs to be replaced corresponding to the part with a large wear amount, shortening the life of the conveying roll and reducing the productivity of the continuous annealing equipment 100.

[0022] In contrast, the polishing equipment according to the present embodiment uses a crown roll, which is a barrel-shaped roll with a diameter at the central part in the axial direction of the first polishing roll for polishing the conveying roll larger than that at both ends, and the central part and both ends are smoothly connected by a tapered shape or an R shape, to polish the conveying roll while suppressing uneven wear due to one-sided contact.

[0023] Also, as described above, when the surface temperature of the conveying roll reaches 700 °C or higher, the conveying roll thermally expands and oxides adhere to the conveying roll and tend to solidify. Therefore, the polishing equipment according to the present embodiment is preferably used to polish the conveying rolls in the heating zone 12 or the soaking zone 14 where the steel sheet 10 is heated to 700 °C or higher in the continuous annealing equipment 100. However, even when the temperature is below 700 °C, the conveying roll thermally expands and deposits also adhere to the conveying roll. Therefore, the polishing equipment according to the present embodiment may also be applied to the conveying rolls used at temperatures below 700 °C.

[0024] FIG. 2 is a side schematic view showing a configuration example of the polishing equipment according to the present embodiment. Further, FIG. 3 is a front schematic view showing a configuration example of the polishing equipment according to the present embodiment.

[0025] The polishing equipment 30 according to the present embodiment includes a first polishing roll 32, a flat plate 34, a recovery container 36, drive motors 40 and 44, a bearing 42, and a pressing mechanism 48. As the first polishing roll 32, for example, a roll obtained by applying cermet spraying or ceramic spraying to the peripheral surface of a roll made of heat-resistant cast steel is used. The first polishing roll 32 is provided in contact with the peripheral surface of the conveying roll 20 on the furnace top side, and polishes the conveying roll 20 to remove the deposits adhering to the conveying roll 20. The first polishing roll 32 is a barrel-shaped polishing roll.

[0026] The roll diameter of the first polishing roll 32 is smaller than the roll diameter of the conveying roll 20, and is preferably 100 mm or more. Thereby, a decrease in the roll life of the first polishing roll 32 and deformation due to deflection can be suppressed. Further, the roll diameter difference between the central portion and both end portions in the axial direction of the polishing roll 32 may be 0.1 mm or more, and is preferably 0.2 mm or more. The roll diameter difference between the central portion and both end portions in the axial direction may be appropriately adjusted in consideration of the temperature of the contacting conveying roll 20, the ambient temperature, and the balance between the initial crown and the thermal crown of the conveying roll 20. In that case, it is preferable to also consider the thermal crown due to the contact of the first polishing roll 32 with the high-temperature conveying roll 20.

[0027] The flat plate 34 is a steel or ceramic plate that contacts the first polishing roll 32 and polishes the first polishing roll 32. By polishing the first polishing roll 32 with the flat plate 34, the deposits removed from the conveying roll 20 can be removed when they adhere to the first polishing roll. The mounting angle of the flat plate 34 is preferably an acute angle smaller than 90° with respect to the roll surface of the first polishing roll 32. Thereby, an increase and fluctuation in the torque load of the first polishing roll 32 can be suppressed without hindering the rotation of the first polishing roll 32.

[0028] The flat plate 34 is an example of a polishing member that contacts the circumferential surface of the first polishing roll 32. Instead of the flat plate 34, a second polishing roll that polishes the circumferential surface of the first polishing roll, or a contact body such as a grinding stone or a metal brush may be used. For the second polishing roll as well, similar to the first polishing roll, for example, a roll obtained by performing cermet spraying or ceramic spraying on the circumferential surface of a roll made of heat-resistant cast steel is used. Note that the roll diameter of the second polishing roll is smaller than the roll diameter of the first polishing roll 32 and is preferably 100 mm or more. Thereby, a decrease in the roll life of the second polishing roll and deformation due to deflection can be suppressed.

[0029] The recovery container 36 is a steel box that recovers deposits (hereinafter referred to as "dropped materials") that fall off from the conveying roll 20 and the first polishing roll 32. By providing the recovery container 36, dropped materials from the conveying roll 20 and the first polishing roll 32 can be recovered, and it is possible to prevent the dropped materials from adhering to the steel plate 10 again or adhering to the continuous annealing facility 100. Note that the recovery container 36 is an example of a recovery device that recovers dropped materials from the conveying roll 20 and the first polishing roll 32.

[0030] The drive motor 40 rotates the first polishing roll 32 while supporting the rotation shaft of the first polishing roll 32 with the bearing 42. The drive motor 40 rotates the first polishing roll 32 in a direction opposite to the contact position with the conveying roll 20. Thereby, the conveying roll 20 can be polished to remove deposits adhering to the surface of the conveying roll 20.

[0031] Also, if there is a peripheral speed difference between the first polishing roll 32 and the conveying roll 20, the first polishing roll 32 can polish the conveying roll to remove deposits. Therefore, when there is a peripheral speed difference between the first polishing roll 32 and the conveying roll 20, the drive motor 40 may rotate the first polishing roll 32 in a rotational direction that is the same in the contact position. The peripheral speed difference between the first polishing roll 32 and the conveying roll 20 may be 1 m / min or more and 1000 m / min or less. Thereby, deposits adhering to the surface of the conveying roll 20 can be removed. Note that the drive motor 40 and the bearing 42 are an example of a rotating device that rotates the first polishing roll 32.

[0032] The drive motor 44 moves the first polishing roll 32 in the axial direction of the conveying roll 20. As described above, since the first polishing roll 32 is a barrel-shaped roll, by moving it in the axial direction of the conveying roll 20 and polishing the surface of the conveying roll 20, the conveying roll 20 can be polished while suppressing uneven wear due to single-sided contact. Note that the drive motor 44 is an example of a moving device that moves the first polishing roll 32 in the axial direction of the conveying roll 20.

[0033] Thus, since the first polishing roll 32 moves in the axial direction of the conveying roll 20, it is preferable that the length of the first polishing roll 32 in the axial direction is shorter than the length of the conveying roll 20 in the axial direction. By shortening the length of the first polishing roll 32 in the axial direction, the moving distance of the first polishing roll 32 can be ensured, and it becomes easier to move the first polishing roll 32 relative to the conveying roll 20.

[0034] The length of the first polishing roll 32 in the axial direction is preferably half or less of the length of the conveying roll 20 in the axial direction, and more preferably 1 / 4 or less. If the length of the first polishing roll 32 in the axial direction is half or less of that of the conveying roll 20, the first polishing roll 32 can move within a range of half or more of the length of the conveying roll 20 in the axial direction, and the conveying roll 20 can be polished. Further, if the length of the first polishing roll 32 in the axial direction is 1 / 4 or less of that of the conveying roll 20, the first polishing roll 32 can move within a range of 3 / 4 or more of the length of the conveying roll 20 in the axial direction, and the conveying roll 20 can be polished.

[0035] The pressing mechanism 48 presses the first polishing roll 32 against the conveying roll 20. The pressing mechanism 48 preferably measures the torque of the drive motor 40 and controls the pressing load of the first polishing roll 32 against the conveying roll 20 so that the torque is within a predetermined range. Thereby, wear due to excessive contact between the conveying roll 20 and the first polishing roll 32 can be avoided, and an appropriate external force can be applied to the first polishing roll 32 for removing deposits.

[0036] As the first polishing roll 32, it is preferable to use a barrel-shaped brush roll having a plurality of metal wires protruding radially from the roll circumferential surface. By using a brush roll as the first polishing roll 32, the contact area with the adherend is reduced and the adhesion force is decreased, so that the adherend can be detached from the first polishing roll 32 with a slight force.

[0037] The diameter of the plurality of metal wires protruding radially from the roll circumferential surface is preferably 20 μm or more and 500 μm or less. Thereby, it is possible to enhance the detachability of the adherend while suppressing an increase in the manufacturing cost of the brush roll and a shortening of the life of the brush roll. On the other hand, if the diameter of the wire is less than 20 μm, mass production of the brush roll becomes difficult and the manufacturing cost of the brush roll increases, which is not preferable. Further, if the diameter of the wire is less than 20 μm, the wear of the wire becomes fast and the life of the brush roll becomes short, which is not preferable. Also, if the diameter of the wire is larger than 500 μm, the contact area between the adherend and the wire becomes large and the detachability of the adherend decreases, which is not preferable.

[0038] The wire is preferably made of tungsten, molybdenum, cobalt, nickel-chromium alloy or stainless steel having heat resistance and wear resistance. Thereby, even in a high-temperature environment of 700° C. or higher, the conveying roll 20 can be polished to remove the adherend.

[0039] For the roll portion of the brush roll, it is preferable to use a metal having excellent heat resistance such as heat-resistant cast steel, chromium alloy or nickel alloy. The roll diameter of the brush roll is smaller than the roll diameter of the conveying roll 20 and is preferably 100 mm or more. Thereby, a decrease in the roll life of the brush roll and deformation due to deflection can be suppressed. Also, the wire density in the brush roll is preferably 3 / 5 or more with respect to the roll surface area in which the wires are embedded. By using a high-density brush roll with a high wire density, damage to the wires due to wear is reduced and the durability of the brush roll is improved.

[0040] FIG. 4 is a side schematic view showing another configuration example of the polishing equipment according to the present embodiment. In the polishing equipment 31 shown in FIG. 4, the same components as those in the polishing equipment 30 shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The polishing equipment 31 shown in FIG. 4 is different from the polishing equipment 30 shown in FIG. 2 in that it has a dust collecting device 38 and does not have a recovery container 36.

[0041] Since the self-weight of the steel sheet 10 does not act on the conveying roll 20 on the hearth side, the surface pressure due to the steel sheet 10 becomes small. For this reason, the growth of deposits adhering to the conveying roll 20 is less than that in the configuration shown in FIG. 2. However, even in the configuration shown in FIG. 4, deposits adhere to the conveying roll 20 and grow starting from the deposits. Therefore, by using the polishing equipment 31 according to the present embodiment, the conveying roll 20 can be polished while suppressing uneven wear due to single-sided contact.

[0042] In the configuration shown in FIG. 4, unlike the configuration shown in FIG. 2, there is no space for collecting the dropped objects that have fallen by gravity. Therefore, it is preferable to provide a dust collecting device 38 instead of the recovery container 36. By providing the dust collecting device 38 in this way, it is possible to prevent the dropped objects from the conveying roll 20 and the first polishing roll 32 from adhering to the steel sheet 10 and the conveying roll 20 again. Note that the dust collecting device 38 is another example of a recovery device that recovers the dropped objects from the conveying roll 20 and the first polishing roll 32.

[0043] As described above, by using the polishing equipment according to the present embodiment, the conveying roll 20 can be polished while suppressing uneven wear due to single-sided contact. As a result, the uneven wear of the conveying roll 20 is suppressed, and it becomes possible to suppress a decrease in the productivity of the continuous annealing equipment 100 due to the shortening of the life of the conveying roll 20 caused by the uneven wear. That is, by polishing the conveying roll 20 with the polishing equipment according to the present embodiment and annealing the steel sheet 10 with the continuous annealing equipment 100 having the conveying roll 20, it becomes possible to manufacture annealed steel sheets with higher productivity than before.

[0044] In addition, in this embodiment, although an example in which the polishing facilities 30 and 31 have a polishing member and a recovery device has been described, the present invention is not limited thereto. As a configuration for obtaining the effect of suppressing uneven wear of the conveying roll 20, the polishing facilities 30 and 31 may not have a polishing member and a recovery device. However, as described above, by having a polishing member, it becomes possible to remove the deposits adhering to the first polishing roll 32. Therefore, it is preferable that the polishing facilities 30 and 31 have a polishing member. Furthermore, by having a recovery device, it is possible to prevent the dropped matter from the conveying roll 20 and the first polishing roll 32 from adhering to the steel sheet 10 and the conveying roll 20. Therefore, it is preferable that the polishing facilities 30 and 31 have a recovery device.

Example

[0045] [Example 1] Next, Example 1 will be described in which, in the continuous annealing facility 100 shown in FIG. 1, after continuously annealing a steel sheet containing 0.3 mass% or more of Si or Mn at 2000 tons or more, the number of deposits of 100 μm or more adhering to the conveying roll was confirmed. The thickness of the steel sheet continuously annealed in Example 1 was in the range of 0.6 to 1.8 mm, and the sheet width was in the range of 800 to 1500 mm. The continuous annealing conditions are as follows.

[0046] Atmospheric temperature: 700 °C or higher Atmospheric gas: 5% by volume of hydrogen, 95% by volume of nitrogen Dew point: -35 °C

[0047] After continuous annealing, the conveying roll installed on the furnace top side at the rear stage of the soaking zone where the temperature of the steel sheet is the highest in the continuous annealing facility 100 was taken out, and the number of deposits adhering to the conveying roll was confirmed.

[0048] The conveying roll used is a roll with a diameter of 800 mm, obtained by spraying cermet or ceramics on the circumferential surface of a heat-resistant cast steel roll. Also, as the first polishing roll for polishing the conveying roll, a barrel-shaped polishing roll or a barrel-shaped brush roll with a roll diameter of 300 mm, obtained by spraying cermet or ceramics on the circumferential surface of heat-resistant cast steel, was used. While rotating the roll, it was moved in the axial direction of the conveying roll to remove the deposits adhering to the conveying roll. The crown shape of the barrel roll is a tapered crown, the roll surface length is 1 m, and the flat part width is 500 mm. The difference between the central diameter and the diameters at both ends is 0.2 mm. The wire of the brush roll is made of Ni-Cr alloy, the wire diameter is 300 μm, the length to the wire tip is 15 mm, and the wire density is 3 / 5 of the ratio of the wire embedding area to the roll surface area. The pressing force of the first polishing roll against the conveying roll was adjusted to 0.02 kgf / mm. The wire of the brush roll is made of Ni-Cr alloy, the wire diameter is 300 μm, the length to the wire tip is 15 mm, and the wire density is 3 / 5 of the ratio of the wire embedding area to the roll surface area. Also, as a polishing device, a plate-shaped steel plate was used to remove the deposits adhering to the barrel-shaped polishing roll and the barrel-shaped brush roll, and the deposits (detached materials) were collected in a collection container.

[0049]

Table 1

[0050] In Table 1, the peripheral speed difference “>160 - 500” means that the peripheral speed difference fluctuated within the range of 160 to 500 m / min. This fluctuation of the peripheral speed difference is due to the fluctuation of the peripheral speed of the conveying roll caused by the fluctuation of the line speed. As shown in Table 1, in Reference Examples 1 and 2 where no polishing member for polishing the conveying roll was provided, a large number of deposits of 100 μm or more adhered to the conveying roll. Therefore, it can be seen that when using the conveying rolls of Reference Examples 1 and 2, a large number of pressing defects will occur on the steel plate.

[0051] In Comparative Examples 1 and 2 using a doctor blade as the polishing member, since the transfer roll was polished with the doctor blade to remove the deposits, the number of deposits of 100 μm or more adhering to the transfer roll decreased. However, since the transfer roll with thermal crown formed by thermal deformation was polished with a flat doctor blade, the doctor blade hit only one side of the transfer roll and uneven wear occurred.

[0052] On the other hand, in Invention Examples 1 and 2 using a barrel-shaped polishing roll as the polishing member and Invention Examples 3 and 4 using a barrel-shaped brush roll, the transfer roll could be polished without causing uneven wear due to one-sided contact, and the number of deposits of 100 μm or more adhering to the transfer roll could be greatly reduced. From these results, it was confirmed that by using the polishing equipment according to the present embodiment, the transfer roll can be polished while suppressing uneven wear due to one-sided contact, and the deposits adhering to the transfer roll can be removed.

[0053] Also, when comparing the polishing roll and the brush roll, the number of deposits of 100 μm or more adhering to the transfer roll was smaller in Invention Examples 3 and 4 using the brush roll than in Invention Examples 1 and 2 using the polishing roll. From these results, it was confirmed that it is preferable to use a brush roll as the polishing member for polishing the transfer roll.

[0054] [Example 2] Next, Example 2 in which the influence of the diameter of the wire in the brush roll was confirmed will be described. In Example 2, in a furnace with the furnace temperature controlled at 800°C, a steel sheet having a Si content of 1.6% by mass and a Mn content of 0.3% by mass was regarded as a transfer roll, and a sliding test was performed in which the steel sheet and a small sample of the brush roll were slid. The test conditions of Example 2 are as follows.

[0055] Wire material: Ni-Cr alloy Wire length: 12 mm Sliding time: 30 h Sliding speed: 300 mm / min Surface pressure between the steel sheet and the brush roll: 0.001 kg / mm 2 Wire density of the brush roll: 3 / 5 of the ratio of the wire embedding area to the roll surface area

[0056] After sliding the steel sheet on the brush roll for 30 hours under the above test conditions, the number of deposits of 30 μm or more adhering to the brush roll and the wear amount of the wire after sliding were measured. The number of deposits of 30 μm or more adhering to the surface of the brush roll was measured by observing the surface of the brush roll with a laser microscope. The wear amount of the wire was measured by measuring the wire length before and after the sliding test, and the difference between these was taken as the wear amount. The results of Example 2 are shown in Table 2 below.

[0057]

Table 2

[0058] As shown in Table 2, when the diameter of the wire of the brush roll was decreased, the wear amount of the wire became longer. In particular, when the diameter of the wire was less than 20 μm, it was confirmed that the wear amount of the wire became significantly longer. From this result, it was confirmed that the diameter of the wire is preferably 20 μm or more, and thereby the wear of the wire can be suppressed.

[0059] On the other hand, when the diameter of the wire increases, the contact area with the deposits increases, and the adhesion force of the deposits to the brush roll surface increases. In particular, when the diameter of the wire is more than 500 μm, the adhesion force of the deposits adhering to the brush roll increases, and the number of deposits of 30 μm or more adhering to the brush roll surface becomes significantly larger. Even when the brush roll is used as a polishing roll for polishing the conveying roll, reducing the adhesion force of the deposits adhering to the brush roll is preferable because the deposits can be easily removed and can be removed without adhering the deposits to the conveying roll again. Therefore, it was confirmed that the diameter of the wire of the brush roll is preferably 500 μm or less.

Explanation of reference numerals

[0060] 10 Steel sheet 12 Heating zone 14 Soaking zone 16 Cooling zone 18 Overaging zone 20 Conveyor roll 32 First grinding roll 30 Grinding equipment 34 Flat plate 36 Recovery container 38 Dust collection device 40 Driving motor 42 Bearing 44 Driving motor 48 Pressing mechanism 100 Continuous annealing equipment

Claims

1. A polishing facility for polishing a conveying roll that conveys a steel sheet in a continuous annealing facility, a first polishing roll that contacts the circumferential surface of the conveying roll, a rotating device that rotates the first polishing roll, a moving device that moves the first polishing roll in the axial direction of the conveying roll, a pressing mechanism that presses the first polishing roll against the conveying roll, and having, The first polishing roll has a barrel shape in which the diameter of the central portion in the axial direction of the first polishing roll is larger than the diameters of both ends, a polishing facility.

2. The first polishing roll is a brush roll having a plurality of metal wires protruding radially from the circumferential surface, the polishing facility according to claim 1.

3. The diameter of the wire is 20 μm or more and 500 μm or less, the polishing facility according to claim 2.

4. The wire is made of tungsten, molybdenum, cobalt, nickel-chromium alloy or stainless steel, the polishing facility according to claim 2 or claim 3.

5. It has a polishing member that contacts the circumferential surface of the first polishing roll, The polishing member is a flat plate, a grindstone or a second polishing roll, the polishing facility according to any one of claims 1 to 3.

6. It has a polishing member that contacts the circumferential surface of the first polishing roll, The polishing member is a flat plate, a grindstone or a second polishing roll, the polishing facility according to claim 4.

7. It has a recovery device for recovering debris from the conveying roll and the first polishing roll, the polishing facility according to any one of claims 1 to 3.

8. It has a recovery device for recovering debris from the conveying roll and the first polishing roll, the polishing facility according to claim 4.

9. It has a recovery device for recovering debris from the conveying roll and the first polishing roll, the polishing facility according to claim 5.

10. It has a recovery device for recovering debris from the conveying roll and the first polishing roll, the polishing facility according to claim 6.

11. A method for manufacturing an annealed steel sheet, which polishes the conveying roll with the polishing facility according to any one of claims 1 to 3 and anneals the steel sheet with the continuous annealing facility to manufacture an annealed steel sheet.

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