Thermal spray material, conveyance roller for metallic strip, and method of manufacturing conveyance roller for metallic strip

Abstract

To provide a thermal spray material which enables formation of thermal spray coating having less deterioration of surface roughness in usage, and a conveyance roller for a metallic strip having the thermal spray coating.SOLUTION: A thermal spray material includes cermet particles. The cermet particles include metal carbide and binder metal. The metal carbide includes first particles having a first particle size distribution, and second particles having a second particle size distribution larger in a volume standard median diameter D50 than the first particle size distribution. (mass of the first particle) / (mass of the second particle) is equal to or less than 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal spray material, a conveying roll for metal strip, and a method for manufacturing a conveying roll for metal strip. [Background technology]

[0002] Conventionally, many rolls are installed to transport metal strips in various process lines that perform rolling, heat treatment, surface treatment, etc. on metal strips such as steel bands. By appropriately controlling the transport speed of the metal strip, the tension of the steel sheet, etc., the metal strip can be transported stably through the interaction between the metal strip and the transport rolls.

[0003] The surface roughness of the transport roll is an important control factor for stable transport of the transport roll. Patent Document 1 states that by controlling the surface roughness of a CPC roll, which is formed with a thermal spray coating using a specified thermal spray material, within an appropriate range, it is possible to improve the stability of metal strip transport and achieve wear resistance that allows the performance to be maintained for a long period of time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-342552 Summary of the Invention [Problem to be solved by the invention]

[0005] However, excessively reducing the surface roughness of the transport roll makes the metal strip more susceptible to slippage. On the other hand, significantly increasing the surface roughness of the transport roll increases the frictional force between the metal strip and the transport roll, making it more likely that a shape defect known as "squeezing" will occur in the metal strip. Furthermore, even if the initial surface roughness of the transport roll is set within an appropriate range that can suppress the occurrence of slippage and squeezing, the surface roughness will change due to wear during use of the transport roll. Therefore, simply controlling the surface roughness has been difficult to suppress both slippage and squeezing of the metal strip for a long period of time. Therefore, it is necessary to form a thermal spray coating that not only has excellent wear resistance but also can maintain its surface roughness for a long period of time.

[0006] The present application aims to provide a thermal spray material capable of forming a thermal spray coating in which the decrease in surface roughness during use is further suppressed, and a transport roll for a metal strip having such a thermal spray coating. [Means for solving the problem]

[0007] The present application has been made to solve the above problems, and its gist is as follows.

[0008] (1) A thermal spray material containing cermet particles, the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, A thermal spray material, characterized in that (mass of the first particles) / (mass of the second particles) is 1 or less.

[0009] (2) The thermal spray material according to (1) above, characterized in that (the mass of the first particles) / (the mass of the second particles) is 1 / 2 or less.

[0010] (3) The thermal spray material according to (1) above, characterized in that the median diameter D50 of the first particles is 0.5 μm or more and 4 μm or less.

[0011] (4) The thermal spray material according to (1) above, wherein the median diameter D50 of the second particles is 5 μm or more and 14 μm or less.

[0012] (5) The thermal spray material according to (1) above, wherein the median diameter D50 of the second particles is 6 μm or more and 9 μm or less.

[0013] (6) The thermal spray material according to (1) above, wherein the metal carbide is one or more metal carbides selected from the group consisting of tungsten carbide, titanium carbide, vanadium carbide, chromium carbide, and niobium carbide.

[0014] (7) The thermal spray material according to (1), wherein the binder metal is one or more metals selected from Ni, Cr, Co, and Fe, or an alloy containing any of these metals.

[0015] (8) A conveying roll for a metal strip, having a thermal spray coating formed on a roll surface by thermal spraying a thermal spray material containing cermet particles, the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, A transport roll for metal strips, wherein (mass of the first particles) / (mass of the second particles) is 1 or less.

[0016] (9) The metal strip conveying roll according to (8) above, wherein (mass of the first particles) / (mass of the second particles) is 1 / 2 or less.

[0017] (10) The conveying roll for metal strips according to (8) above, wherein the median diameter D50 of the first particles is 0.5 μm or more and 4 μm or less.

[0018] (11) The conveying roll for metal strips according to (8) above, wherein the second particles have a median diameter D50 of 5 μm or more and 14 μm or less.

[0019] (12) The conveying roll for metal strips according to (8) above, wherein the second particles have a median diameter D50 of 6 μm or more and 9 μm or less.

[0020] (13) The conveying roll for metal strip according to (8) above, characterized in that the thermal spray coating has a surface roughness, arithmetic mean roughness Ra, of 2.0 or more and 8.0 or less, and in the unevenness of the surface roughness, the first particles form recesses and the second particles form protrusions.

[0021] (14) The conveying roll for metal strip according to (8) above, wherein the metal carbide is one or more metal carbides selected from the group consisting of tungsten carbide, titanium carbide, vanadium carbide, chromium carbide, and niobium carbide.

[0022] (15) The conveying roll for metal strip according to (8) above, wherein the binder metal is one or more metals selected from Ni, Cr, Co, and Fe, or an alloy containing any of these metals.

[0023] (16) A method for manufacturing a conveying roll for a metal strip, comprising spraying a thermal spray material containing cermet particles to form a thermal spray coating on a roll surface, the method comprising: the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, 1. A method for manufacturing a transport roll for a metal strip, wherein (mass of the first particles) / (mass of the second particles) is 1 or less.

[0024] (17) The method for producing a conveying roll for a metal strip according to (16) above, characterized in that the cermet particles are granulated and sintered, and then thermally sprayed by a high velocity flame thermal spraying method or a plasma thermal spraying method to form a thermal sprayed coating. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a thermal spray material capable of forming a thermal spray coating in which the decrease in surface roughness during use is further suppressed, and a transport roll for a metal strip having such a thermal spray coating. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing the structure of a thermal spray coating according to an embodiment of the present invention. [Figure 2] 1 shows an SEM image of a cross section of an actual thermal spray coating of this embodiment. [Figure 3] FIG. 1 is a schematic diagram of an abrasion evaluation tester used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0027] (thermal spray material) The thermal spray material of this embodiment will be described. The thermal spray material of this embodiment can be used to form a thermal spray coating on the surface of a conveying roll for a metal strip (hereinafter simply referred to as a "conveying roll"). The metal strip is a plate-shaped metal such as a steel band or steel plate. Conveying rolls include various rolls used in the manufacturing process of metal strip. Conveying rolls on which a thermal spray coating can be formed include rolls that convey, support, guide, grip, process, and energize the metal strip. Conveying rolls include hearth rolls and run-out table rolls. Supporting rolls and guiding rolls include side guide rolls, support rolls, wrapper rolls, unit rolls, steering rolls, and sink rolls. Gripping rolls include looper rolls, tension rolls, deflector rolls, bridle rolls, pinch rolls, pressure rolls, and wringer rolls. Processing rolls include work rolls, intermediate rolls, backup rolls, skin-pass rolls, leveler rolls, bending rolls, mandrels, tension reels, and payoff reels. The current-carrying roll includes a conductor roll.

[0028] The thermal spray material is characterized by containing multiple types of metal carbides with different particle size distributions to prevent drawing and slippage of the steel sheet. Specifically, the thermal spray material of this embodiment contains, as metal carbides, first particles having a first particle size distribution and second particles having a second particle size distribution that is coarser than the first particle size distribution (larger D50). In this embodiment, the first particles are also referred to as "small particles" and the second particles as "large particles." The thermal spray material is cermet particles containing these two types of metal carbides and a binder metal. The small particles and large particles form irregularities of a predetermined roughness on the surface of the thermal spray coating. The binder metal constitutes the matrix of the thermal spray coating.

[0029] By including small and large particles with different particle size distributions in the thermal spray material, the small particles can support the large particles in the thermal spray coating, while the large particles can be held in the coating. Furthermore, by controlling the size relationship between the small and large particles within a predetermined particle size distribution range, the small particles can fill the gaps between the large particles in the thermal spray coating, more reliably holding the large particles in the coating. In contrast, if the thermal spray material is made up of only large particles, voids will form between the large particles, making them more likely to fall off. As a result, sufficient durability cannot be achieved.

[0030] The small particles of metal carbide contained in the thermal spray material preferably have a D50 (median diameter) of 0.5 μm or more and 4 μm or less. A diameter of 0.5 μm or more allows for stable powder delivery to the thermal spray gun, while a diameter of 4 μm or less facilitates uniform distribution among the large metal carbide particles. A diameter of 1 μm or more and 3 μm or less is evenly distributed among the large metal carbide particles. This range allows for more stable powder delivery and allows for uniform distribution of the small metal carbide particles among the large metal carbide particles.

[0031] The large particles of metal carbide preferably have a D50 of 5 μm or more and 14 μm or less. When the D50 is 5 μm or more, they are less likely to disappear than small particles even when worn, and can remain on the surface of the thermal spray coating for a longer period of time. In other words, sufficiently high wear resistance can be obtained. As a result, the difference in wear performance between the large and small particles of metal carbide during the wear process of the thermal spray coating can maintain the surface roughness of the thermal spray coating. Regarding the upper limit, a D50 of 14 μm or less is because thermal spraying is easy. In addition, if the large particles are too large compared to the small particles, the small particles in the thermal spray coating cannot adequately support the large particles, resulting in reduced durability. Furthermore, it is more preferable that the D50 of the large particles be 6 μm or more and 9 μm or less. This is because this particle size can further ensure a difference in wear resistance performance compared to small particles of metal carbide, which has good thermal spray yield (deposition efficiency of thermal spray powder). In other words, within this range, the lower limit of D50 for the large particles is further away from the upper limit of D50 for the small particles, and the difference in particle size distribution between the small and large particles becomes greater. As a result, the difference in abrasion resistance (ease of abrasion) between the two particles can be controlled within a more appropriate range, resulting in durability that can further maintain the unevenness of the thermal spray coating surface.

[0032] In this embodiment, the D50 (median diameter) of particles is the cumulative 50% particle size (median diameter) in the volumetric particle size distribution measured using a laser diffraction particle size distribution analyzer (manufactured by HORIBA, model number LA-950).

[0033] The thermal spray material preferably contains 50% to 92% by mass of metal carbide, with the remainder being the binder metal. If the metal carbide content is 50% or more, excellent wear resistance can be obtained and a decrease in surface roughness can be suppressed. If the content is 92% or less, a sufficient amount of binder metal can be contained, ensuring that the metal carbide is securely held in place.

[0034] The blending ratio of large particles to small particles of metal carbide can be a ratio that contains the same amount of large particles as the small particles, on a mass basis. In other words, the blending ratio of small particles to large particles on a mass basis (mass of small particles / mass of large particles) can be 1 or less. If the amounts are the same, a thermal spray coating with excellent durability and reduced deterioration in surface roughness can be obtained. If the amount of large particles is greater than the amount of small particles, a thermal spray coating with even less reduction in surface roughness can be obtained.

[0035] Furthermore, the blending ratio of the two particles (mass of small particles / mass of large particles) is preferably 1 / 10 or more (0.1 or more) and 1 / 2 or less (0.5 or less). By keeping the ratio 1 / 2 or less, changes (deterioration) in the roughness (surface roughness) of a thermal spray coating formed with this thermal spray material over time can be more effectively suppressed, resulting in the formation of a thermal spray coating with excellent durability. Also, by keeping the mass ratio 0.1 or more, loss of metal carbide particles due to wear of the binder metal between the metal carbide particles can be sufficiently prevented.

[0036] The metal carbide can be one or more metal carbides selected from tungsten carbide, titanium carbide, vanadium carbide, chromium carbide, and niobium carbide. That is, the metal carbide can be a metal carbide containing any of W, Ti, V, Cr, and Nb as a metal, and may contain one type of metal carbide or two or more types of metal carbides.

[0037] The binder metal contained in the thermal spray material can be one or more metals selected from Ni, Cr, Co, and Fe, or an alloy containing any of these metals. The binder metal may be any granular material that can be used as a thermal spray material. In the case of an alloy, the binder metal may be a granular material produced by granulation sintering. Note that the binder metal may contain unavoidable impurities.

[0038] The thermal spray material can be any suitable combination of the above-mentioned metal carbide and binder metal, such as a WC-NiCr alloy, a TiC-NiCoCr alloy, or a WC-Cr3C2-NiCr alloy.

[0039] The method for producing the thermal spray material (cermet) containing metal carbide and binder metal (type of powder) is not particularly limited, but a thermal spray material produced by a sintering-pulverization method or a granulation-sintering method can be used.

[0040] (Metal strip transport roll) Next, the metal strip transport roll of this embodiment will be described. The metal strip transport roll has a thermal spray coating formed by thermally spraying the above-mentioned thermal spray material onto the surface of a roll substrate. FIG. 1 is a schematic diagram showing the structure of the thermal spray coating of this embodiment. FIG. 2 shows SEM images of a cross section of an actual thermal spray coating of this embodiment (spray material: 65% WC-25% Cr3C2-10% NiCr alloy). The two SEM images were taken at different locations on the thermal spray coating. In the thermal spray coating, small particles fill the gaps between large particles, thereby more reliably retaining the large particles in the coating.

[0041] Furthermore, the small and large particles of the thermal spray material form a predetermined level of unevenness on the surface of the thermal spray coating. More specifically, the small particles form the concave portions of the roughness curve, while the large particles form the convex portions of the roughness curve, forming the unevenness. In this way, the roughness (surface roughness) formed by the small and large particles improves the maintenance of the roll surface roughness and suppresses changes in roughness during use. This is presumably because, even when the roll surface wears during use, the large particles maintain the convex portions due to their excellent wear resistance, while the small particles (and binder metal) maintain the concave portions. Specifically, the particle size of the metal carbide particles significantly affects their wear resistance, resulting in differences in wear performance between large and small particles with different particle sizes (particle size distributions). In other words, large particles are less susceptible to wear than small particles. Therefore, large particles can remain in the convex portions longer than smaller particles, thereby maintaining the convex portions for a longer period of time. Although small particles are more susceptible to wear than large particles, they are protected by the convex portions, which are less susceptible to wear, and can remain in the concave portions. Therefore, the unevenness of the thermal spray coating surface can be maintained for a longer period of time during use. In addition, even if large particles wear away and disappear, new protrusions are formed by the next large particles below them. On the other hand, small particles and binder metal are more easily worn away than large particles. Therefore, the small particles and binder metal surrounding the new protrusions are more likely to wear away and become recessed, and as a result, recesses are reformed just as they were initially. Therefore, the thermal spray coating according to this embodiment can suppress a decrease in surface roughness for a longer period of time, and can maintain the initial roughness for a longer period of time.

[0042] By forming a thermal spray coating by thermal spraying the two types of thermal spray materials described above, it is possible to form a thermal spray coating that has a predetermined roughness or more that can suppress the occurrence of slippage and a predetermined roughness or less that can suppress the occurrence of squeezing in the metal strip. Therefore, according to this embodiment, a transport roll can be obtained that has a thermal spray coating that suppresses the occurrence of slippage and squeezing, and that also suppresses a change in roughness to one that is more likely to cause slippage (a decrease in roughness). In other words, it is possible to provide a transport roll that can maintain both the suppression of squeezing and the suppression of slippage for a longer period of time.

[0043] The thickness of the thermal spray coating formed on the transport roll is preferably 30 μm or more and 500 μm or less. This is because a thickness of 30 μm or more ensures a sufficient thickness for the thermal spray coating. If the thickness exceeds 500 μm, the thermal spray coating is prone to peeling.

[0044] The arithmetic mean roughness Ra, which is the surface roughness of the thermal spray coating, is specified according to the type of roll, but it is preferable to set it to between Ra 2.0 and 8.0. This is because a Ra of 2.0 or higher makes it difficult for the roll and the transported material to slip. A Ra of 8.0 or lower makes it difficult for shape defects such as drawing of the metal strip to occur. The arithmetic mean roughness Ra can be determined using a surface roughness measuring instrument conforming to JIS B 0601 (2001). As mentioned above, in the unevenness of the surface roughness, small particles (first particles) (and binder metal) are located in the recesses, and large particles (second particles) are located in the protrusions.

[0045] Although the present embodiment describes an example in which two types of metal carbide particles are used, a thermal spray coating may be formed using a thermal spray material containing three or more types of particles with different particle size distributions. In this case, it is possible to combine various types of metal carbide particles with a difference in D50 of 2 μm or more. This similarly allows the thermal spray coating to maintain a predetermined surface roughness, thereby providing a transport roll that can simultaneously suppress both the occurrence of squeezing and slippage in the metal strip.

[0046] (Method for forming thermal spray coating, method for manufacturing conveyor roll) A method for forming a thermal spray coating and a method for manufacturing a conveying roll using the method will be described. The thermal spray coating can be formed by thermal spraying the thermal spray material of this embodiment. The thermal spraying method is not particularly limited, and any method that can spray a powdered thermal spray material can be used. For example, flame spraying, high-velocity flame spraying, plasma spraying, cold spraying, detonation spraying, etc. can be used.

[0047] For example, a thermal spray coating can be formed by granulating and sintering cermet particles and then thermally spraying them by a high-velocity flame spraying method or a plasma spraying method. As an example, when forming by a high-velocity flame spraying method, a transport roll can be manufactured by forming a thermal spray coating under conditions of a flame temperature of 3000°C or less and a spray particle velocity of 300 m / sec or more. When using other thermal spraying methods, a thermal spray coating can also be formed under appropriate spraying conditions.

[0048] According to the present embodiment, since the thermal spray coating contains small and large particles of metal carbide, it is possible to form a thermal spray coating that can maintain the surface roughness at the time of manufacture for a longer period of time. By maintaining the initial surface roughness of the coating, it is possible to manufacture a transport roll with excellent durability that can suppress both slippage and squeezing for a longer period of time. [Example]

[0049] The thermal spray materials of the embodiments will be further explained using examples. Thermal spray materials were prepared with the compositions shown in Tables 1 to 3. The test example shown in Table 1 is a thermal spray material containing WC as the metal carbide. The test example shown in Table 2 is a thermal spray material containing TiC as the metal carbide. The test example shown in Table 3 is a thermal spray material containing WC and Cr3C2 as the metal carbides. In each thermal spray material, the metal combined with the metal carbide is the binder metal. The contents (mass fraction) of the metal carbide and binder metal in each thermal spray material, the ratio of small particles to large particles in each thermal spray material, and the median diameter D50 of the small particles and large particles are as shown in Table 1.

[0050] Each thermal spray material was sprayed onto the test piece using the high-velocity flame spraying method to form a thermal spray coating. The thermal spraying was carried out under the conditions shown in Table 4. The thermal spray coating was formed to a thickness of 150 μm. The test piece used was made of SUS304 material and measured 30 × 50 × 5 mm.

[0051] (Wear evaluation test) Abrasion tests were conducted to evaluate the wear resistance of each test piece with a thermal spray coating. Figure 3 shows a schematic diagram of the wear evaluation tester 1. The wear evaluation tester 1 is a Suga-type wear tester. The wear evaluation tester 1 has a rotating roller 21. Emery paper 22 is wrapped around the surface of the rotating roller 21. The rotating roller 21 generates friction by rotating a predetermined angle with each reciprocation of the test piece 31. Using this wear evaluation tester 1, the surface of the test piece 31 on which the thermal spray coating 31A was formed was brought into contact with the emery paper 22 of the rotating roller 21, and the test piece 31 was reciprocated 2,400 times to evaluate the wear resistance. #400 emery paper was used, and the load pressing the test piece 31 against the rotating roller 21 was 3 kg. The reciprocating speed of the test piece 31 was 40 times / min, and the stroke length of the reciprocating motion was 30 mm.

[0052] The surface roughness of the thermal spray coating 31A of the test piece 31 was measured before and after the above wear evaluation test, and the rate of reduction in roughness was determined. The surface roughness (arithmetic mean roughness Ra) was measured in accordance with the method specified in JIS B0601. Specifically, Ra was measured at any five points on the surface of the thermal spray coating 31A using a surface roughness meter "SV-3000S CNC" manufactured by Mitutoyo Corporation. The average value of Ra measured at the five points was taken as the arithmetic mean roughness Ra of the thermal spray coating 31A of that test piece 31. The reference line length and cutoff value were both 0.8 mm.

[0053] The roughness of the thermal spray coating 31A of the test piece 31 was measured before and after the wear evaluation test using the above method. (Surface roughness before test - Surface roughness after test) / Surface roughness before test The reduction rate (%) of roughness was calculated by the above formula. A reduction rate of 30% or less was marked "◎", a reduction rate of more than 30% and less than 40% was marked "○", and a reduction rate of more than 40% was marked "×". The test results are shown in Tables 1 to 3.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4]

[0058] In the test examples (Test Examples 1 to 3, 7 to 9, 13 to 15) using thermal spray materials containing more large metal carbide particles than small particles, the reduction in surface roughness was 30% or less, confirming that the reduction in roughness could be suppressed. Test Examples 4, 10, and 16, which contained equal amounts of small and large particles, were able to suppress the reduction in roughness to a certain extent, although not as effectively as the test examples with more large particles. On the other hand, Test Examples 6, 12, and 18, which contained only small particles, and Test Examples 5, 11, and 17, which contained more small particles, showed a greater reduction in roughness. [Explanation of symbols]

[0059] 1. Wear evaluation test machine 21 Rotating roller 22 Emery Paper 31 Test specimens 31A Thermal spray coating

Claims

1. A thermal spray material comprising cermet particles, the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, A thermal spray material characterized in that (mass of the first particles) / (mass of the second particles) is 1 or less.

2. 2. The thermal spray material according to claim 1, wherein (mass of the first particles) / (mass of the second particles) is 1 / 2 or less.

3. 2. The thermal spray material according to claim 1, wherein the median diameter D50 of the first particles is 0.5 μm or more and 4 μm or less.

4. 2. The thermal spray material according to claim 1, wherein the median diameter D50 of the second particles is 5 μm or more and 14 μm or less.

5. 2. The thermal spray material according to claim 1, wherein the median diameter D50 of the second particles is 6 μm or more and 9 μm or less.

6. 2. The thermal spray material according to claim 1, wherein the metal carbide is one or more metal carbides selected from the group consisting of tungsten carbide, titanium carbide, vanadium carbide, chromium carbide, and niobium carbide.

7. 2. The thermal spray material according to claim 1, wherein the binder metal is one or more metals selected from the group consisting of Ni, Cr, Co, and Fe, or an alloy containing any of these metals.

8. A conveying roll for a metal strip, the conveying roll having a thermal spray coating formed on a roll surface by thermal spraying a thermal spray material containing cermet particles, the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, A metal strip conveying roll, characterized in that (mass of the first particles) / (mass of the second particles) is 1 or less.

9. 9. The metal strip transport roll according to claim 8, wherein (mass of the first particles) / (mass of the second particles) is 1 / 2 or less.

10. 9. The metal strip transport roll according to claim 8, wherein the first particles have a median diameter D50 of 0.5 μm or more and 4 μm or less.

11. 9. The metal strip transport roll according to claim 8, wherein the second particles have a median diameter D50 of 5 μm or more and 14 μm or less.

12. 9. The metal strip transport roll according to claim 8, wherein the second particles have a median diameter D50 of 6 μm or more and 9 μm or less.

13. 9. The metal strip conveying roll according to claim 8, wherein the thermal spray coating has a surface roughness, arithmetic mean roughness Ra, of 2.0 or more and 8.0 or less, and the first particles constitute recesses and the second particles constitute protrusions in the surface roughness.

14. 9. The metal strip conveying roll according to claim 8, wherein the metal carbide is one or more metal carbides selected from the group consisting of tungsten carbide, titanium carbide, vanadium carbide, chromium carbide, and niobium carbide.

15. 9. The metal strip transport roll according to claim 8, wherein the binder metal is one or more metals selected from the group consisting of Ni, Cr, Co and Fe, or an alloy containing any of these metals.

16. A method for manufacturing a conveying roll for a metal strip, comprising: thermally spraying a thermal spray material containing cermet particles to form a thermal spray coating on a roll surface, the cermet particles include a metal carbide and a binder metal; the metal carbide includes first particles having a first particle size distribution and second particles having a second particle size distribution having a volume-based median diameter D50 larger than that of the first particle size distribution, A method for manufacturing a transport roll for a metal strip, characterized in that (mass of the first particles) / (mass of the second particles) is 1 or less.

17. The method for manufacturing a conveying roll for a metal strip according to claim 16, wherein the cermet particles are granulated and sintered, and then thermally sprayed by a high velocity flame thermal spraying method or a plasma thermal spraying method to form a thermal sprayed coating.

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