Rolls for transporting steel plates

Abstract

To make it easier to prevent the adhesion of foreign matter to the surface of a steel sheet transportation roll.SOLUTION: A steel sheet transportation roll according to the present invention has a thermal spray coating on the surface of the transportation roll substrate, and an abradable coating on the surface of the thermal spray coating, the abradable coating containing polysiloxane as well as zirconia particles, boron nitride particles, and colloidal particles dispersed in the polysiloxane.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to rolls for conveying steel sheets.

Background Art

[0002] In a continuous annealing furnace or a continuous annealing facility, and in a plating bath of a continuous electroplating line, there are provided conveying rolls for continuously conveying a steel sheet to be processed. Among these conveying rolls, those provided in the furnace may be called hearth rolls, and those provided in the plating bath may be called sink rolls.

[0003] On the surface of these conveying rolls, various metal oxides (in the case of inside the furnace) or alloys (in the case of inside the plating bath) adhere according to the environment in which they are arranged. Such a phenomenon of foreign matter adhering to the surface of the conveying roll is called build-up. Build-up occurring on the surface of the conveying roll causes defects on the surface of the conveyed steel sheet. Therefore, conventionally, techniques for preventing build-up have been studied.

[0004] Hitherto, in order to prevent build-up on the surface of the conveying roll, development has been carried out mainly focusing on making the film applied to the surface of the conveying roll less reactive. For example, in Patent Document 1 below, a technique is proposed for forming a film containing aluminum phosphate and inorganic particles having a hexagonal crystal structure with a layered crystal structure on an oxide-based ceramic sprayed film provided on a roll base material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, even if measures are taken to make the coating less reactive, as proposed in Patent Document 1, buildup cannot be completely prevented, and the conveying rolls must be replaced after a certain period of time. It appears that the method of making the coating less reactive has reached its limits.

[0007] Therefore, there is a need for technology that can easily prevent foreign matter from adhering to the surface of conveying rolls, using a different approach than making the coating less reactive.

[0008] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to provide a steel plate conveying roll that can more easily prevent foreign matter from adhering to the surface of the steel plate conveying roll. [Means for solving the problem]

[0009] In order to solve the above problems, the inventors of this invention conducted intensive research and came up with the idea that, rather than aiming to make the surface of the conveying roll less reactive, if a condition could be achieved in which the coating on the surface of the conveying roll is thin and easily peeled off, it would be possible to more easily prevent foreign matter from adhering to the surface of the conveying roll. In other words, if the coating on the surface of the conveying roll is thin and easily peeled off (in other words, if the coating on the surface of the conveying roll has so-called "abraable properties"), even if foreign matter adheres to the coating on the surface of the conveying roll, if there is a very slight difference in peripheral speed between the conveying roll and the steel plate, the low strength of the coating on the surface of the conveying roll will cause the coating to peel off thinly along with the adhered matter due to the shear force, and it is expected that the proportion of steel plates with surface defects can be greatly reduced.

[0010] Based on the above-mentioned idea, the inventors conducted further studies and came up with the idea of ​​giving the coating applied to the surface of the conveying roll so-called abradability (easily eroded property), and thus completed the invention described below. The gist of the present invention, completed based on this idea, is as follows:

[0011] (1) A steel plate conveying roll having a thermal spray coating located on the surface of the conveying roll substrate and an abradable coating located on the surface of the thermal spray coating, wherein the abradable coating contains polysiloxane and zirconia particles, boron nitride particles and colloidal particles dispersed in the polysiloxane. (2) The steel plate conveying roll according to (1), wherein the average particle size of the zirconia particles is 1 to 20 μm, the colloidal particles are at least one of zirconia colloidal particles or silica colloidal particles, and the average particle size of the colloidal particles is 10 to 300 nm. (3) The steel plate conveying roll according to (1) or (2), wherein the content of the zirconia particles in the abradable coating is 15 to 60% by mass of the total mass of the abradable coating. (4) A steel plate conveying roll according to any one of (1) to (3), wherein the mass ratio of zirconia particles to boron nitride particles (zirconia particles / boron nitride particles) in the abradable coating is in the range of 0.3 to 3.0. (5) A steel plate conveying roll according to any one of (1) to (4), wherein the content of the boron nitride particles in the abradable coating is 10 to 50% by mass with respect to the total mass of the abradable coating. (6) A steel plate conveying roll according to any one of (1) to (5), wherein the polysiloxane content in the abradable coating is 15 to 30% by mass relative to the total mass of the abradable coating. (7) A steel plate conveying roll as described in any one of (1) to (6), wherein the surface roughness of the abradable coating is 1.0 to 3.0 μm in terms of arithmetic mean roughness Ra as defined in JIS B0601 (2001) and 20.0 to 30.0 μm in terms of maximum height Rz as defined in JIS B0601 (2001). (8) A steel plate conveying roll according to any one of (1) to (7), wherein the average thickness of the abradable coating is 5 to 100 μm. (9) A steel plate conveying roll according to any one of (1) to (8), wherein the surface of the abradable coating is subjected to a reciprocating abrasion testing machine specified in JIS H8682 (2013), and in a coordinate plane with the vertical axis being the absolute value Δd (unit: μm) of the difference between the average thickness of the abradable coating at the test site after 250 sliding cycles n and the average thickness of the abradable coating before the test, and the horizontal axis being the number of sliding cycles n, the slope Δd / n is in the range of 0.10 to 0.50. (10) A steel plate conveying roll as described in any one of (1) to (9), used as a hearth roll installed in a continuous annealing furnace or continuous annealing equipment, or as an in-bath roll installed in a plating bath of a continuous hot-dip galvanizing line. [Effects of the Invention]

[0012] As described above, the present invention makes it easier to prevent foreign matter from adhering to the surface of the steel plate conveying roll. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram illustrating the configuration of a steel plate conveying roll according to an embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating the configuration of a steel plate conveying roll according to the same embodiment. [Figure 3] This is an explanatory diagram illustrating the abradable coating on a steel plate conveying roll according to the same embodiment. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0015] (Regarding the rolls used for transporting steel plates) Hereinafter, referring to FIGS. 1 to 3, the roll for transporting a steel sheet according to an embodiment of the present invention will be described in detail. FIGS. 1 and 2 are schematic diagrams for explaining the configuration of the roll for transporting a steel sheet according to the present embodiment. FIG. 3 is an explanatory diagram for explaining the abradable coating film of the roll for transporting a steel sheet according to the present embodiment.

[0016] <Regarding the overall configuration of the roll for transporting a steel sheet> As schematically shown in FIG. 1, a roll 1 for transporting a steel sheet (hereinafter abbreviated as "transport roll") includes a roll shaft 3 and a roll body 5 attached to the roll shaft 3. Such a transport roll 1 is used, for example, as a hearth roll provided in a continuous annealing furnace or a continuous annealing facility, or as a submerged roll provided in a plating bath of a continuous electroplating line. Here, the transport roll 1 has a roll width wider than the width of the steel sheet transported in various facilities such as a continuous annealing furnace, a continuous annealing facility, and a continuous electroplating line. For example, the roll width of the roll body 5 is about 1000 to 2500 mm, and the roll diameter φ is about 600 to 1000 mm.

[0017] Such a transport roll 1 is, for example, a drive roll and functions as a transport roll for transporting a steel sheet in various facilities as described above. That is, the transport roll 1 rotates around the roll shaft 3 and contacts the peripheral surface of the roll body 5 (hereinafter sometimes referred to as the roll peripheral surface) with the steel sheet, thereby transporting the steel sheet wound around the roll body 5 at a predetermined winding angle while changing the traveling direction.

[0018] Furthermore, as shown in FIGS. 1 and 2, the roll body 5 of the transport roll 1 has a roll base material 10, a sprayed coating film 20 formed on the surface of the roll base material 10, and an abradable coating film 30, which is the outermost layer film formed on the surface of the sprayed coating film 20. In addition, in order to prevent peeling due to the difference in thermal expansion coefficient between the roll base material 10 and the sprayed coating film 20, a base spray made of a heat-resistant alloy may be performed as necessary to form a base layer (not shown).

[0019] <Regarding the roll base material 10> The roll base material 10 is formed of a metal such as steel, etc., and forms the basic shape of the conveying roll 1. As this roll base material 10, for example, stainless steel-based heat-resistant cast steel is used, and particularly SCH22 is optimal. A coating treatment such as a thermal spraying treatment is performed on such a roll base material 10.

[0020] In the present embodiment, a thermal spray coating 20 is formed on the surface of the roll base material 10, and further, an abradable coating 30 is formed on the surface of such a thermal spray coating 20.

[0021] <Regarding the thermal spray coating 20> As the thermal spray coating 20, for example, various known thermal spray coatings such as a cermet thermal spray coating obtained by thermally spraying a cermet material in which ceramics and a heat-resistant alloy are combined onto a base material, an oxide-based ceramic thermal spray coating obtained by thermally spraying oxide-based ceramics onto a base material, etc. are used.

[0022] Examples of the cermet thermal spray coating include a WC-WB-Co-based cermet coating obtained by thermally spraying WC, WB, Co, W, CoB, W2CoB onto a base material, a CrC-based cermet coating obtained by thermally spraying Cr3C2-CoNiCrAlY onto a base material, a WC-Co-based cermet coating obtained by thermally spraying WC, W2C, and Co onto a base material, etc. Examples of the oxide-based ceramic thermal spray coating include a thermal spray coating obtained by thermally spraying oxides such as stabilized ZrO2, ZrSiO4, etc. Examples of the thermal spray coating in which ceramics and a heat-resistant alloy are combined include the thermal spray coating described in International Publication No. 2016 / 052741, etc.

[0023] The average thickness of the thermal spray coating 20 (thickness d1 in Figure 2) is not particularly limited, but is, for example, 50 to 200 μm. Here, the average thickness of the thermal spray coating 20 can be measured by observing the cross-section of the roll 1 with an optical microscope. More specifically, the length from the interface between the roll substrate 10 and the thermal spray coating 20 to the interface between the thermal spray coating 20 and the abradable coating 30 (described later) is measured at any position on the cross-section of the roll 1. This measurement is performed at 10 arbitrary locations, and the average of the 10 obtained measurements is taken as the average thickness of the thermal spray coating 20.

[0024] Furthermore, the hardness of the thermal spray coating 20 is preferably 600 to 1000 in Vickers hardness HV as defined in ISO 6507-1. If the Vickers hardness HV of the thermal spray coating 20 is less than 600, metal oxides, which are buildup sources, are more likely to adhere to the thermal spray coating 20 on the hearth roll surface, and alloy foreign matter is more likely to adhere to the bath roll surface. If the Vickers hardness HV of the thermal spray coating 20 is between 600 and 1000, the adhesion of foreign matter to the hard thermal spray coating 20 can be suppressed. Also, if the Vickers hardness HV of the thermal spray coating 20 exceeds 1000, the thermal spray coating 20 may crack and peel off easily. The Vickers hardness HV can be measured in accordance with the test method specified in ISO 6507-1.

[0025] <About Abradable Coating> The abradable coating 30 according to this embodiment is a coating located on the surface of the thermal spray coating 20 and is a coating that has so-called abradable properties. This abradable coating 30 contains polysiloxane and zirconia particles, boron nitride particles, and colloidal particles dispersed in the polysiloxane. In addition to these components, the abradable coating 30 may also contain impurities.

[0026] As the abradable coating 30 according to this embodiment is composed of the above-described components, when the conveying roll 1 is exposed to the operating environment, the carbon component in the polysiloxane decreases, resulting in the development of appropriate abradability. This reduces the film strength of the abradable coating 30, and even if foreign matter adheres to the surface, the film peels off relatively easily in thin layers, thereby suppressing the adhesion of foreign matter such as metal oxides and alloys to the surface of the abradable coating 30. As a result, it becomes possible to extend the replacement cycle of the conveying roll.

[0027] As will be explained again below, the abradable coating 30 is formed by applying a solution consisting of zirconia particles as the main aggregate, boron nitride particles, colloidal raw material, water, and isopropyl alcohol to the surface of the thermal spray coating 20, and then heating it at 450-500°C. The colloidal raw material is prepared by hydrolyzing and modifying the OH groups and dimethylsilane on the particle surface in a colloidal aqueous solution adjusted to pH 3-4, thereby supporting ceramic particles of about 20 nm. During this process, the organosilane compound polymerizes to form a polysiloxane, and the zirconia particles, boron nitride particles, and colloidal particles become dispersed in this polysiloxane.

[0028] In this embodiment, the average thickness of the abradable coating 30 (thickness d2 in Figure 2) is preferably 5 to 100 μm. An average thickness of 5 to 100 μm allows for the uniform formation of a smooth abradable coating 30 over the entire circumferential surface of the roll 1, while achieving appropriate abradability. More preferably, the average thickness of the abradable coating 30 is 10 to 50 μm. Here, the average thickness of the abradable coating 30 can be measured by observing the cross-section of the roll 1 with an optical microscope, similar to the thermal spray coating 20. More specifically, the length from the interface between the thermal spray coating 20 and the abradable coating 30 to the surface of the abradable coating 30 is measured at any position on the cross-section of the roll 1. This measurement is performed at 10 arbitrary locations, and the average of the 10 measured values ​​is taken as the average thickness of the abradable coating 30.

[0029] Here, the organosilane compound used as the colloidal raw material for forming the abradable film 30 is not particularly limited. Examples of such organosilane compounds include various known compounds such as dimethylsilane.

[0030] Furthermore, in the abradable coating 30 according to this embodiment, the polysiloxane content is preferably 15 to 30% by mass of the total mass of the abradable coating. By keeping the polysiloxane content within this range, it is possible to maintain the strength of the coating while exhibiting appropriate abradability. In other words, it becomes possible to more reliably achieve both coating strength and abradability.

[0031] The polysiloxane content in the abradable coating 30 can be measured by taking a sample of the coating and using an energy-dispersive X-ray spectrometer (EDS) and a Fourier transform infrared spectrometer (FT-IR), or by gas chromatography-mass spectrometry (GC / MS).

[0032] The zirconia particles used as the main aggregate and the boron nitride particles used as aggregate are, respectively, particles of zirconia and boron nitride that are not in a colloidal state. Here, the zirconia particles used as the main aggregate have a high melting point and heat resistance, and a coefficient of linear expansion of approximately 10 × 10⁻¹⁰ -6 Its coefficient of thermal expansion (K) is relatively high even among ceramics. As a result, the difference in coefficient of thermal expansion between it and the metal-based conveyor rolls is small, which helps prevent the abradable coating from peeling off thickly in high-temperature environments. Note that zirconia undergoes transformation at high temperatures. Therefore, stabilizers such as Y2O3, CaO, MgO, and CeO2 are added to zirconia, and it may be used as fully stabilized or partially stabilized zirconia. Accordingly, when zirconia is referred to in this specification, it includes these fully stabilized and partially stabilized zirconia.

[0033] Here, it is particularly preferable to include hexagonal boron nitride (h-BN) particles having a hexagonal crystal structure with a layered structure as the boron nitride particles. By including such boron nitride particles in the abradable coating 30, the coating strength is reduced, and the wettability with metal components present in the roll usage environment and the nonreactivity with such metal components can be further improved, thereby further suppressing the adhesion of foreign matter to the conveying roll.

[0034] Furthermore, colloidal particles are particles of compounds in a colloidal state, and can be obtained by modifying the compound of interest with substituents such as hydroxyl groups.

[0035] In this embodiment, it is preferable to use at least one of zirconia colloidal particles, silica colloidal particles, alumina colloidal particles, or titania-zirconia particles as the colloidal particles. Among these colloidal particles, it is particularly preferable to use at least one of zirconia colloidal particles or silica colloidal particles. By using zirconia colloidal particles or silica colloidal particles, the affinity with the zirconia particles, which are the main aggregate, and the polysiloxane, which is the binder resin, is increased, and it becomes possible to disperse the colloidal particles more uniformly in the polysiloxane.

[0036] Here, the average particle size of the zirconia particles is preferably 1 to 20 μm, and the average particle size of the colloidal particles is preferably 10 to 300 nm. By setting the average particle sizes of the zirconia particles and colloidal particles within the above ranges, it is possible to densify the resulting abradable film 30. When particles with such two particle size distributions are present, the polysiloxane preferentially binds to the colloidal particles with a smaller average particle size. As a result, strong bonding by the polysiloxane does not occur between zirconia particles with an average particle size of 1 to 20 μm, making it possible to achieve more appropriate abradability.

[0037] Furthermore, the average particle size of the boron nitride particles is preferably 1 to 10 μm. By including boron nitride particles having such an average particle size, it becomes possible to more reliably achieve the effects of reduced film strength, improved wettability and nonreactivity as described above.

[0038] Here, the average particle size of the zirconia particles is more preferably 1 to 5 μm, and the average particle size of the boron nitride particles is more preferably 1 to 5 μm. Furthermore, the average particle size of the colloidal particles is more preferably 10 to 50 nm.

[0039] Furthermore, the average particle sizes of zirconia particles, boron nitride particles, and colloidal particles can be measured by laser diffraction.

[0040] Here, the zirconia particle content in the abradable coating 30 is preferably 15 to 60% by mass of the total mass of the abradable coating 30. By having a zirconia particle content within the above range, it becomes possible to more reliably achieve the desired strength of the coating. The zirconia particle content in the abradable coating 30 is more preferably 50 to 60% by mass.

[0041] Furthermore, the content of such boron nitride particles is preferably 10 to 50% by mass relative to the total mass of the abradable film. By having a boron nitride particle content within the above range, it becomes possible to more reliably achieve the effects of reduced film strength, improved wettability and nonreactivity as described above. The boron nitride particle content is more preferably 15 to 20% by mass.

[0042] Here, the content of such zirconia particles and boron nitride particles can be measured by SEM-EPMA observation of the cross-sectional structure of the coating.

[0043] In the abradable coating 30, the mass ratio of zirconia particles to boron nitride particles (more specifically, the mass ratio of zirconia particles to boron nitride particles, zirconia particles / boron nitride particles) is preferably in the range of 0.30 to 3.00. By having the mass ratio of zirconia particles to boron nitride particles within the above range, it becomes possible to achieve a more favorable balance between coating strength and abradability in the abradable coating 30. The mass ratio of zirconia particles to boron nitride particles is more preferably in the range of 2.50 to 3.00.

[0044] For the abradable film 30 composed of the above-described components, the surface roughness after firing is preferably 1.0 to 3.0 μm in terms of arithmetic mean roughness Ra as defined in JIS B0601 (2001), and 20.0 to 30.0 μm in terms of maximum height Rz as defined in JIS B0601 (2001). The fact that both types of surface roughness of the abradable film 30 are within the above ranges means that the surface of the formed abradable film 30 is extremely flat. Having the above-described surface roughness of the abradable film 30 makes it possible to more reliably suppress the adhesion of foreign matter. The arithmetic mean roughness Ra is more preferably 1.5 to 2.5 μm. The arithmetic mean roughness Ra and maximum height Rz can be measured using a surface roughness measuring instrument compliant with JIS B0601 (2001).

[0045] [Regarding the abradability of the abradable coating 30] In order to specifically quantify the abradability of the abradable coating 30 according to this embodiment, the following methods can be used. Specifically, the surface of the abradable coating after firing is subjected to a wear test using a reciprocating abrasion testing machine specified in JIS H8682 (2013). At this time, attention is paid to the absolute value Δd (unit: μm) of the difference between the average thickness of the abradable coating 30 at the test site after n=250 sliding cycles and the average thickness of the abradable coating 30 before the test. This absolute value Δd of the difference can be considered to correspond to the magnitude of the step in the abradable coating 30 caused by the reciprocating abrasion test.

[0046] Here, as schematically shown in Figure 3, we consider a coordinate plane with the absolute value of the above difference (which can also be called the step difference) Δd (unit: μm) as the vertical axis and the number of sliding cycles n (unit: cycles) in the abrasion test as the horizontal axis. In this case, the slope Δd / n (unit: μm / cycle) of the line segment A defined by the origin (0,0) and point a (250 cycles, measured value obtained in the abrasion test) in the coordinate plane shown in Figure 3 is preferably within the range of 0.10 to 0.50. If the slope Δd / n is within the above range, it can be determined that the abradable coating 30 according to this embodiment maintains the desired abradability. More preferably, the slope Δd / n is 0.20 to 0.30.

[0047] Here, the wear test using the reciprocating wear testing machine described above is carried out as follows. First, a 50mm x 50mm x 5mm test specimen is coated with an abradable coating after thermal spraying. Then, with a load of 1kg, the obtained test specimen is placed in a reciprocating abrasion testing machine using SiC#1000 emery paper, and an abrasion test is performed with n=250 sliding cycles. After that, the size of the step created by the abrasion test is measured at the test site. This abrasion test is performed on 10 test specimens, and the average of the measured step values ​​is calculated. The average value obtained in this way is taken as the absolute value Δd of the difference created by the reciprocating abrasion test.

[0048] The conveying roll according to this embodiment has been described in detail above with reference to Figures 1 to 3.

[0049] (Regarding the manufacturing method of rolls for conveying steel plates) Next, we will explain the manufacturing method for the conveying rolls described above. The method for manufacturing a conveying roll according to this embodiment includes a thermal spray coating formation step of forming a thermal spray coating on a predetermined conveying roll substrate, and an abradable coating formation step of forming an abradable coating on the surface of the formed thermal spray coating. Furthermore, various pretreatments may be performed prior to the thermal spray coating formation step, such as pre-blast treatment of the roll substrate or treatment to form a base layer consisting only of a heat-resistant alloy.

[0050] Here, the pretreatment process is not particularly limited and can be carried out by various known methods. Similarly, the thermal spray coating formation process for forming the thermal spray coating is not particularly limited and can be carried out by various known methods, such as high-velocity oxygen-fuel thermal spraying process (HVOF). Therefore, detailed explanations of the pretreatment process and thermal spray coating formation process will be omitted below.

[0051] Next, we will explain the abradable coating formation process in detail. First, an aqueous solution of colloidal particles (hereinafter referred to as the colloidal aqueous solution) is prepared with a pH adjusted to the range of 3 to 4. In this colloidal aqueous solution, the -OH groups on the particle surface and the organosilane compound are hydrolyzed to create a silicone solution on which the colloidal particles are supported (hereinafter, this silicone solution will be abbreviated as the colloidal raw material).

[0052] Subsequently, zirconia particles, boron nitride particles, water, and isopropyl alcohol, which are the main aggregates, are added to the colloidal raw material to create a coating for forming an abrasive film.

[0053] The obtained coating is applied to the surface of the formed thermal spray coating to the desired thickness using a known application method, such as brush application or spraying, and then the coated roll is baked.

[0054] In this firing process, the heating temperature is set to, for example, 450-500°C, and the holding time is set to, for example, 0.5-2.0 hours. During this firing process, the organosilane compound polymerizes to form a polysiloxane, and the zirconia particles, which are the main aggregate, as well as the boron nitride particles and colloidal particles, which are also aggregates, become dispersed within the polysiloxane.

[0055] By following the steps described above, the conveying roll according to this embodiment can be manufactured. The method for manufacturing a conveying roll according to this embodiment has been described above. [Examples]

[0056] The following will provide a detailed explanation of the conveying roll according to the present invention, with reference to examples and comparative examples. It should be noted that the following examples are merely examples of the conveying roll according to the present invention, and the conveying roll according to the present invention is not limited to these examples.

[0057] The following examples and comparative examples focused on hearth rolls installed in an annealing furnace. In the following examples and comparative examples, SCH22 was used as the roll substrate, and a CrC cermet material was sprayed onto this roll substrate by high-velocity gas spraying (HVOF) to form a sprayed coating. The average thickness of the sprayed coating was 100 μm, and its Vickers hardness HV was 800.

[0058] Subsequently, an abradable coating was formed on the thermal spray coating according to the manufacturing method described earlier. The zirconia particles, boron nitride particles, and colloidal particles used (all commercially available general reagents) are shown in Table 1 below. Dimethylsilane (a general reagent) was used as the organosilane compound (binder resin) to create the coating for abradable film formation.

[0059] The prepared coating was applied by spraying to a roll substrate with a thermal spray coating to achieve the post-drying film thickness shown in Table 1 below, and then held at 450°C for 1 hour to create an abradable coating.

[0060] The conveying rolls manufactured as described above were used as hearth rolls in an actual production line (continuous annealing furnace line), and the time from build-up to the occurrence of steel sheet defects was measured.

[0061] Furthermore, the prepared paint was applied to the surface of a test piece measuring 50 mm × 50 mm × 5 mm, which had been prepared separately after thermal spray coating had been formed. An abrasion test was then conducted using a reciprocating abrasion tester with 250 sliding cycles, in accordance with the method described earlier. The slope Δd / n was calculated from the obtained measurement results (absolute value of the difference Δd).

[0062] The results obtained are summarized in Table 1 below.

[0063] [Table 1]

[0064] As is clear from Table 1 above, the abradable coatings corresponding to the examples of the present invention exhibit excellent abradability, while the abradable coatings corresponding to the comparative examples of the present invention do not possess adequate abradability.

[0065] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Explanation of symbols]

[0066] 1. Conveyor roll 3 Roll axis 5 Roll cylinder 10 rolls of base material 20 Thermal spray coating 30 Abrasive coating

Claims

1. A thermal spray coating located on the surface of the conveying roll substrate, Abradable coating located on the surface of the thermal spray coating, It has, The abradable coating is a steel plate conveying roll containing an organic polysiloxane and colloidal particles, which are non-colloidal zirconia particles and boron nitride particles, as well as colloidal compound particles, dispersed in the organic polysiloxane.

2. The average particle size of the zirconia particles is 1 to 20 μm. The steel plate conveying roll according to claim 1, wherein the colloidal particles are at least one of zirconia colloidal particles or silica colloidal particles, and the average particle size of the colloidal particles is 10 to 300 nm.

3. The steel plate conveying roll according to claim 1 or 2, wherein the content of the zirconia particles in the abradable coating is 15 to 60% by mass relative to the total mass of the abradable coating.

4. A steel plate conveying roll according to any one of claims 1 to 3, wherein the abradable coating has a mass ratio of zirconia particles to boron nitride particles (zirconia particles / boron nitride particles) in the range of 0.3 to 3.

0.

5. The steel plate conveying roll according to any one of claims 1 to 4, wherein the content of the boron nitride particles in the abradable coating is 10 to 50% by mass with respect to the total mass of the abradable coating.

6. The steel plate conveying roll according to any one of claims 1 to 5, wherein the content of the organic polysiloxane in the abradable coating is 15 to 30% by mass with respect to the total mass of the abradable coating.

7. The surface roughness of the abradable coating is, The arithmetic mean roughness Ra, as defined in JIS B0601 (2001), is 1.0 to 3.0 μm. A steel plate conveying roll according to any one of claims 1 to 6, wherein the maximum height Rz specified in JIS B0601 (2001) is 20.0 to 30.0 μm.

8. The steel plate conveying roll according to any one of claims 1 to 7, wherein the average thickness of the abradable coating is 5 to 100 μm.

9. A steel plate conveying roll according to any one of claims 1 to 8, wherein the surface of the abradable coating is subjected to a reciprocating abrasion testing machine specified in JIS H8682 (2013), and in a coordinate plane with the vertical axis being the absolute value Δd (unit: μm) of the difference between the average thickness of the abradable coating at the test site after 250 sliding cycles and the average thickness of the abradable coating before the test, and the horizontal axis being the number of sliding cycles n, the inclination Δd / n is in the range of 0.10 to 0.

50.

10. A steel plate conveying roll according to any one of claims 1 to 9, used as a hearth roll installed in a continuous annealing furnace or continuous annealing equipment, or as an in-bath roll installed in a plating bath of a continuous hot-dip galvanizing line.

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