Transport roll and method for manufacturing the transport roll

Abstract

To provide a steel plate transport roll having a cleaning effect against adhesion of foreign matter. [Solution] A transport roll for transporting a steel sheet has a cermet sprayed coating formed on a roll surface of the transport roll, and the cermet sprayed coating has projections and recesses formed thereon, and the peak count number of the projections and recesses is less than 130. The peak count numbers are all 50 or more. The transport roll is any one of a conductor roll of a continuous electric plating line, a roll disposed in a continuous annealing line, a roll disposed in a molten metal plating line, a looper roll, a tension roll, and a deflector roll.

Description

[Technical field]

[0001] The present invention relates to a transport roll for transporting a steel sheet. [Background technology]

[0002] Steelworks are equipped with various types of conveying equipment that conveys steel sheets by rotating conveying rolls at high speeds, and it is known that foreign matter adheres to the roll surfaces during the conveying of the steel sheets.

[0003] For example, in a continuous electric tin plating line, tin and tin oxide from tin-plated steel sheets adhere to the thermal spray coating on the roll surface, causing the surface roughness to decrease significantly in a short period of time, which can lead to slippage or poor contact causing electric sparks and resulting in scratches on the steel sheet. Furthermore, in the case of transport rolls arranged upstream of the plating section, iron and iron oxide adhering to the steel sheet may adhere to the surface of the transport rolls, causing slippage and resulting in scratches on the steel sheet.

[0004] Patent Document 1 discloses a conveying roll for a steel strip process line, in which the roll surface is coated with a wear-resistant metal made of metallic chromium or a nickel-phosphorus alloy metal, and the wear-resistant metal surface is formed with unevenness by electrolytic etching. However, when electrolytic etching is applied to a coating in which metal and ceramics are unevenly distributed, such as a cermet thermal spray coating, the metal portion is etched and there is a shortage of metal to bond with the ceramic particles, so the thermal spray coating falls apart and the coating strength decreases.

[0005] Patent documents 2 and 3 disclose a technique for scraping off foreign matter adhering to the surface of a rotating roll by contacting a steel blade (thin doctor blade) with the roll. Patent document 4 discloses a method for covering the surface of a transport roll with a fluororesin to make it difficult for foreign matter to adhere thereto, and for removing the foreign matter with an adhesive roll. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3434966 [Patent Document 2] Patent No. 6686790 [Patent Document 3] Japanese Patent Application Publication No. 7-171954 [Patent Document 4] JP 2005-010265 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a transport roll for steel sheets that can easily remove foreign matter adhering thereto. In this specification, the function of such a transport roll may be referred to as a "cleaning effect against adhesion of foreign matter." [Means for solving the problem]

[0008] The present inventors have thoroughly investigated the above problems and discovered that a desired cleaning effect against adhesion of foreign matter can be achieved by controlling the peak count number of the irregularities formed on the roll surface. Specifically, one aspect of the present invention is characterized in that (1) there is a transport roll for transporting a steel sheet, the transport roll having a roll surface on which a cermet sprayed coating is formed, the cermet sprayed coating having irregularities, and the peak count number of the irregularities is less than 130. The peak count number in the circumferential direction of the roll cannot be measured due to the curved surface of the roll, but the result is similar to that of the peak count in the axial direction.

[0009] (2) The transport roll according to (1) above, wherein the peak count number is 50 or more.

[0010] (3) The transport roll according to (1) or (2) above, characterized in that the transport roll is any one of a conductor roll of a continuous electroplating line, a roll disposed in a continuous annealing line, a roll disposed in a molten metal plating line, a looper roll, a tension roll, and a deflector roll.

[0011] In another aspect, the present invention provides (4) a method for manufacturing a transport roll that transports a steel plate by spraying blast material onto the transport roll to form irregularities, the method comprising the steps of: forming a cermet sprayed coating on a surface of a roll base material of the transport roll, where a virtual line extending in a direction perpendicular to the shaft of the transport roll is defined as a reference line, a direction perpendicular to the shaft and the reference line is defined as a separation direction, and a roll radius of the transport roll is defined as R; rotating the transport roll and spraying blast material against the cermet sprayed coating while moving the blast gun parallel to the shaft, with the blast gun installed at a position 0.4R or more and 0.6R or less away from the reference line in the separation direction.

[0012] (5) The method for producing a transport roll according to the above (4), characterized in that a surface of a roll base of the transport roll is roughened, and the cermet spray coating is formed on the surface of the roughened roll base. Effect of the Invention

[0013] According to the present invention, it is possible to provide a transport roll that is excellent in cleaning effect against adhesion of foreign matter. [Brief description of the drawings]

[0014] [Figure 1] This is a diagram showing the layout of the blast gun (first comparative example). [Diagram 2] FIG. 11 is an explanatory diagram for explaining a method of spraying a blasting material. [Diagram 3] This is a diagram showing the layout of the blast gun (second comparative example). [Figure 4] This is a diagram showing the layout of the blast gun (example). [Diagram 5] The figure shows a schematic diagram of irregularities on the surface of a cermet thermal spray coating with a peak count of 130 or more. [Figure 6] Schematic diagram of irregularities on the surface of a cermet thermal spray coating having a peak count of less than 130. [Figure 7] FIG. [Figure 8] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The transport roll of the present invention is a transport roll for transporting a steel sheet. The transport roll includes a wide range of rolls required to have wear resistance and used in steelworks. The transport roll includes, for example, a conductor roll in a continuous electroplating line, a roll disposed in a continuous annealing line, a roll disposed in a molten metal plating line, a looper roll, a tension roll, and a deflector roll. The roll disposed in a continuous annealing line includes a bridle roll and a hearth roll. The roll disposed in a molten metal plating line includes a support roll and a sink roll.

[0016] A cermet spray coating having excellent wear resistance is generally formed on the surface of such a transport roll. The main components of the cermet spray coating are ceramics and binder metal. The ceramics are one or more of metal carbide, metal boride, and metal nitride. The binder metal is typically one or more of Co, Ni, and Cr, or an alloy containing one or more of Co, Ni, and Cr (e.g., Ni-based alloy, Co-based alloy, etc.). The cermet spray coating may be any common one used in the field of the transport roll described above, and detailed description thereof will be omitted.

[0017] The cermet sprayed coating is provided with a special roughening treatment, which will be described later, to have roughness that is excellent in cleaning effect against adhesion of foreign matter. In other words, the cermet sprayed coating of this embodiment has a different function from conventional coatings that aim for resistance to foreign matter adhesion (effect of making foreign matter less likely to adhere). Before explaining the special roughening treatment, the conventional roughening treatment before spraying will be explained with reference to the layout diagram of the blast gun in FIG. 1. The X-axis, Y-axis, and Z-axis are three axes that are mutually orthogonal (the same applies to other drawings). A virtual line that passes through the center of the shaft portion 11A and extends in a horizontal direction perpendicular to the shaft portion 11A is defined as the reference line RL. In other words, the reference line RL extends in a direction parallel to the X-axis direction.

[0018] A blast gun 12 is positioned on the reference line RL, and a roughening process is performed in which blast material is sprayed from the blast gun 12 onto the base material surface of the transport roll 11 (not the coating surface of the cermet spray coating) according to specified basic conditions.

[0019] The predetermined basic conditions are as follows: (Basic conditions) Blasting method: Sand blasting Grit number: #16 or more, #180 or less Compressed air pressure: 0.3Mpa or more, 0.6Mpa or less

[0020] According to these basic conditions, the following surface roughening treatment is performed. In the initial state, the blast gun 12 is disposed at a position corresponding to the axial end of the transport roll 11. The transport roll 11 is rotated at a constant speed in the direction of the arrow RT, and the blast gun 12 is moved at a constant speed in the Z-axis direction (in other words, the axial direction of the transport roll 11), while spraying the blast material onto the base material surface of the transport roll 11.

[0021] In this method, the blasting material is sprayed onto the rotating transport roll 11 by moving the blast gun 12 in the axial direction of the transport roll 11, so that the blasting material is sprayed in a spiral pattern onto the base material surface of the transport roll 11, as indicated by the dotted arrow (see Figure 2).

[0022] A cermet sprayed coating is formed by spraying a thermal spray material onto the roughened surface of the substrate. The blasting conditions are adjusted within the above basic conditions depending on the composition of the cermet sprayed coating. This surface roughening is performed to increase the bonding strength between the sprayed coating and the substrate before thermal spraying, and is not intended to clean the adhesion of foreign matter. The transport roll manufactured according to the surface roughening treatment in Figure 1 may be referred to as the first comparative example.

[0023] The inventor further carried out a roughening treatment on the cermet sprayed coating of the transport roll according to the first comparative example. Figure 3 is a diagram showing the arrangement of blast guns corresponding to such roughening treatment, and corresponds to Figure 1. The roughening treatment was carried out under the same conditions as the blast treatment in Figure 1. Specifically, a blast gun 12 was arranged on the reference line RL, and a blast material was sprayed according to the basic conditions described above to impart roughness to the cermet sprayed coating, thereby manufacturing a transport roll. Such a transport roll may be referred to as the second comparative example.

[0024] However, the desired cleaning effect against adhesion of foreign matter could not be obtained even with the transport roll of Comparative Example 2. When the peak count number of the cermet spray coating of the transport roll of Comparative Example 2 was investigated, it was found that the peak count number was about 170.

[0025] The peak count is the number of average lengths of profile curve elements contained in the profile length L defined in JIS B0601 (2013) (in other words, the evaluation length L, which is 12.5 mm in this specification), and can be measured by a stylus-type surface roughness tester in accordance with JIS B0601 (2013). In other words, the peak count is the number of peaks contained in the evaluation length L.

[0026] The inventors considered that the conveying roll of the second comparative example had a large peak count of the cermet spray coating (which can be expressed as "high density of peaks or small intervals (valleys) between peaks"), which made it easy for foreign matter adhering to be held in the valleys, and thus did not achieve the desired cleaning effect against adhering foreign matter. Therefore, the inventors conducted extensive research into a method for reducing the peak count, which led to the creation of the special unevenness treatment of the present invention.

[0027] Fig. 4 is a diagram showing the arrangement of blast guns when performing special roughening treatment. The arrangement of the blast gun 12 in the second comparative example is shown by a dotted line. The radius of the transport roll 11 is defined as R (R is an abbreviation of "radius"). The radius R is the radius of the base roll that is the base material of the transport roll 11 (in other words, the transport roll 11 before the cermet spraying). The special roughening process is performed by changing the position of the blast gun 12 with respect to the second comparative example. Therefore, the conditions other than the position of the blast gun 12 follow the basic conditions described above. The basic conditions are listed again. (Basic conditions) Blasting method: Sand blasting Grit number: #16 or more, #180 or less Compressed air pressure: 0.3Mpa or more, 0.6Mpa or less

[0028] The position of the blast gun 12 in the special roughening process will be described. When the direction perpendicular to the shaft portion 11A and the reference line RL is defined as the separation direction P, the blast gun 12 is installed at a position 0.4R to 0.6R away from the reference line RL in the separation direction P. In other words, the blast gun 12 is installed so that the center of the nozzle of the blast gun 12 (the center when viewed from the X-axis direction) is located at a position 0.4R to 0.6R away from the reference line RL in the separation direction P.

[0029] This allows the outer surface of the cermet thermal spray coating 11B to have an "uneven shape with a peak count of less than 130." By suppressing the peak count to less than 130, foreign matter such as tin, tin oxide, iron, and iron oxide adhering to the steel sheet can be easily removed by a foreign matter removal device.

[0030] If the position of the blast gun 12 exceeds the above-mentioned range (0.4R or more and 0.6R or less), the peak count number becomes excessively large, and the desired cleaning effect against adhesion of foreign matter cannot be obtained.

[0031] Fig. 5 shows a schematic diagram of the unevenness of a cermet sprayed coating surface with a peak count of 130 or more, and Fig. 6 shows a schematic diagram of the unevenness of a cermet sprayed coating surface with a peak count of less than 130. In these figures, M indicates the peaks of the unevenness, and F indicates a foreign object that has entered between adjacent peaks. In the configuration of Fig. 5, the interval between adjacent peaks M is small, making it difficult for a foreign object removal device such as a polisher or doctor blade to enter, and therefore it is difficult to remove the foreign object F. In this case, it is considered that the adhesion between the foreign object and the roll surface is strong because the peak count is large, i.e., the peak density is high.

[0032] 6, the intervals between the ridges M are large, and the foreign matter removal device can easily fit between adjacent ridges M, making it easy to remove the foreign matter F. In this case, the peak count is small, i.e., the ridge density is low, and therefore it is considered that the adhesion between the foreign matter and the roll surface is low.

[0033] The lower limit of the peak count is preferably 50. It is believed that the desired cleaning effect against adhesion of foreign matter can be obtained even if the peak count is less than 50, but when the basic conditions described above were adjusted, an uneven shape with a peak count of less than 50 was not obtained. Therefore, from the viewpoint of manufacturing limitations, the preferable lower limit is set to 50.

[0034] A method for calculating the peak count number will be described. As described above, the special roughening process is performed while moving the transport roll 11 and the blast gun 12 at a constant speed. Therefore, the value of the peak count number is generally the same regardless of the position of the transport roll 11 where the measurement is performed. Therefore, the measurement position of the peak count number is not particularly limited. For example, the value measured at the center of the transport roll 11 may be the peak count number, or the value measured at the end may be the peak count number.

[0035] At the measurement position, the peak count number can be measured by moving the needle of a stylus surface roughness measuring instrument (SURFCOM TOUCH-50 manufactured by Tokyo Seimitsu Co., Ltd.) in the roll axial direction. The measurement conditions are in accordance with the above-mentioned JIS-compliant method, and can be set to evaluation length L: 12.5 mm, count level (upper limit): 0.000 μm, and count level (lower limit): 0.000 μm.

[0036] 7 is a graph for explaining the measurement method. A portion of evaluation length L (12.5 mm) is cut from the acquired roughness curve in the direction of the center line, and two count levels parallel to the center line are set. In this embodiment, both the count level (upper limit) and the count level (lower limit) are set to 0, that is, they are made the same as the center line. When the intersections between the center line and the roughness curve arranged in order along the center line direction are defined as intersection K, intersection K+1, and intersection K+2, the portion corresponding to the distance between intersection K and intersection K+2 can be counted as one peak.

[0037] Here, before forming the cermet sprayed coating 11B, the roll substrate may be subjected to a surface roughening treatment in advance, or the cermet sprayed coating 11B may be directly formed on the roll substrate without performing the surface roughening treatment. However, as described above, by performing the surface roughening treatment in advance, the bonding strength between the cermet sprayed coating 11B and the substrate can be increased.

[0038] (Example) The present invention will be specifically described with reference to examples. While changing the basic conditions, the composition of the cermet spray coating, and the position of the blast gun 12, roughening treatment by sandblasting was carried out on a number of samples (rolls).

[0039] (Basic condition A) Grit number: #100 Compressed air pressure: 0.4Mpa (Basic condition B) Grit number: #120 Compressed air pressure: 0.3Mpa (Basic condition C) Grit number: #180 Compressed air pressure: 0.5Mpa Basic conditions A to C are all included in the scope of the basic conditions described above.

[0040] The cermet spray coating was one of the following: M1, a typical WC-NiCr cermet spray coating for conductor rolls; M2, a typical WC-Co cermet spray coating for bath rolls; and M3, a typical WC-NiCr cermet spray coating for bridle rolls. The roll size of each sample was the same as that of the actual product. The spray conditions were set to a spray particle velocity of 300 m / s or more and a spray particle temperature of 1400°C or more, and the cermet spray coating was formed by the high-velocity flame spraying method.

[0041] After roughening treatment was performed on the cermet spray coating of each sample, the peak count was measured using a stylus surface roughness tester in accordance with JIS B0601 (2013).

[0042] The cleaning effect against adhesion of foreign matter was evaluated by an abrasion test simulating the Suga abrasion test. Figure 8 is a schematic diagram of the test device used in the abrasion test of this embodiment. The weight of each sample (roll) was measured before the abrasion test. Then, an abrasion test was performed in which an Fe plate was pressed against each sample (roll) with a load of 3 kg and the Fe plate was moved back and forth 2000 times to both the left and right sides. After the abrasion test, a foreign matter removal process was performed with Scotch Brite.

[0043] Weight changes 1 to 3 defined below were measured. Weight change 1: Weight change of the sample (roll) before and after the abrasion test This weight change 1 corresponds to the amount of foreign matter that adhered to the sample (roll) during the abrasion test. Weight change 2: Difference in weight between the sample (roll) before the abrasion test and the sample (roll) after the foreign matter removal treatment This weight change 2 corresponds to the amount of foreign matter that could not be completely removed by the foreign matter removal process. Weight change 3: Weight difference obtained by subtracting weight change 2 from weight change 1 This weight change 3 corresponds to the amount of foreign matter removed by the foreign matter removal process. The percentage (foreign matter removal rate) was calculated by dividing weight change 3 by weight change 1 to evaluate the cleaning effect. In other words, the larger the percentage calculated by (weight change 1-weight change 2) / weight change 1), the better the cleaning effect can be evaluated.

[0044] The measured peak counts, weight change 1, weight change 2, etc. are shown in Table 1. [Table 1] [Explanation of symbols]

[0045] 11 Transport roll 11A Roll shaft 11B Cermet spray coating 12 Blast Gun

Claims

1. A conveying roll for conveying a steel plate, a cermet spray coating is formed on the roll surface of the transport roll, The cermet thermal spray coating has irregularities formed therein, the irregularities having a depth within the range of the thickness of the cermet thermal spray coating, and the peak count of the irregularities is less than 130. A transport roll characterized by the above.

2. The peak count is 50 or more.

2. The transport roll according to claim 1 .

3. The transport roll is any one of a conductor roll of a continuous electroplating line, a roll disposed in a continuous annealing line, a roll disposed in a molten metal plating line, a looper roll, a tension roll, and a deflector roll.

3. The transport roll according to claim 1 or 2.

4. A method for manufacturing a conveying roll for conveying a steel plate, comprising spraying a blast material onto the conveying roll to form irregularities, When a virtual line extending in a direction perpendicular to the shaft portion of the transport roll is defined as a reference line, a direction perpendicular to the shaft portion and the reference line is defined as a separation direction, and a roll radius of the transport roll is defined as R, forming a cermet spray coating on a surface of a roll base of the transport roll; a step of rotating the conveying roll and spraying a blast material onto the cermet thermal spray coating while moving the blast gun parallel to the shaft portion in a state in which the blast gun is disposed at a position 0.4R or more and 0.6R or less away from the reference line in the separation direction; and blasting conditions are a sandblasting method, a grit size of #16 or more and #180 or less, and a compressed air pressure of 0.3 MPa or more and 0.6 MPa or less.

5. a surface of a roll base material of the transport roll is roughened, and the cermet thermal spray coating is formed on the surface of the roughened roll base material; The method for producing a transport roll according to claim 4 .

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