JP2004283898A - Ceramic roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic roll which can suppress a warp in the middle part of a conveyed steel sheet by enhancing resistance to thermal shock of a silicon nitride base sintered compact itself which forms ceramic sleeves. <P>SOLUTION: This ceramic roll is used for conveying the steel sheet in a hot-rolling line and is constituted by fitting one or a plurality of ceramic sleeves on the outer circumference of a metallic shaft member. One of the ceramic sleeves is fit so as to cover the middle part in the axial length direction of the metallic shaft material and consists of the sintered compact consisting essentially of silicon nitride which has a relative density of ≥ 98%, a four-point bending strength of ≥ 600 MPa at room temperature and a thermal conductivity of ≥ 50 W/(mK) at room temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a roll used for transporting a steel sheet in a hot rolling line, and more particularly to a ceramic roll in which a ceramic sleeve is fitted around a metal shaft.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, metal rolls are often used as transport rolls used in steel hot rolling lines. However, there has been a problem that the metal roll is easily worn and is inferior in corrosion resistance, oxidation resistance and heat resistance. In addition, there is a problem that the work of replacing the roll is not easy due to the heavy weight of the metal itself. Therefore, in order to solve these disadvantages, various ceramic rolls have been proposed in place of metal rolls.
[0003]
For example, Patent Document 1 discloses a transfer roll used in a hot rolling line in which ceramics such as alumina and zirconia are sprayed on a roll surface made of metal to a thickness of 50 to 100 μm in order to improve the insulating property of the roll. Is described.
[0004]
Further, in Patent Document 2, in a hot rolling line, induction heating coils opposed to each other from above and below a rolled steel sheet are arranged, and disposed directly under or before and after an induction heating device that heats both ends in the width direction of the rolled steel sheet, A roller for a hot rolling line in which a ceramic sleeve is fitted to a metal core, and the ceramic sleeve is made of a silicon nitride sintered body, and is externally fitted to both sides of the metal core in the body length direction. It is described that the sleeve outer fitting portion has a larger diameter than the central portion of the roller in the body length direction.
[0005]
[Patent Document 1]
Japanese Utility Model Registration No. 2551611 [Patent Document 2]
JP 2002-178020 A
[Problems to be solved by the invention]
However, in the roll disclosed in Patent Literature 1, ceramics such as alumina and zirconia having a thermal expansion coefficient of about 7 to 11 × 10 ⁻⁶ / ° C. are sprayed on the roll surface with a thickness of 50 to 100 μm. The thermal expansion coefficient of the metal roll is about 15 to 40 × 10 ⁻⁶ / ° C., which is so large that a very thin sprayed film such as alumina or zirconia peels off when the entire roll is heated and cooled. There is a problem that it is easy.
[0007]
Patent Document 2 solves this problem, and a roller for a hot rolling line, in which a ceramic sleeve is fitted to a metal core, has a small diameter at the center in the body length direction and an air gap is formed, and the rolled steel sheet to be heated. However, the influence of thermal shock on the roller surface can be suppressed, but the both ends of the steel sheet are heated without supporting the central part of the steel sheet.
[0008]
Therefore, the present invention improves the thermal shock resistance of the silicon nitride-based sintered body itself forming the ceramic sleeve, and can suppress the warping of the central portion of the conveyed steel sheet, and furthermore, the uniformity of the conveyed steel sheet. An object of the present invention is to provide a ceramic roll capable of achieving thermalization and suppressing warping of a central portion of a steel sheet.
[0009]
[Means for Solving the Problems]
That is, the ceramic roll of the first invention is a ceramic roll used for transporting a steel sheet in a hot rolling line, and one or a plurality of ceramic sleeves are fitted on the outer periphery of a metal shaft. One of the ceramic sleeves is fitted so as to cover the central portion in the axial direction of the metal shaft material. The ceramic sleeve has a relative density of 98% or more and has four points at room temperature. It is characterized by comprising a sintered body mainly composed of silicon nitride having a bending strength of at least 600 MPa and a thermal conductivity at room temperature of at least 50 W / (m · K).
[0010]
The ceramic roll according to the second aspect of the present invention is a ceramic roll used for transporting a steel sheet in a hot rolling line, and a plurality of ceramic sleeves are fitted on the outer periphery of a metal shaft. One of the ceramic sleeves (sleeve 1b) is fitted so as to cover the central portion in the axial direction of the metal shaft material. The sleeve 1b has a relative density of 98% or more and has a relative density of 4% at room temperature. Other ceramic sleeves (sleeve 1a and sleeve 1c) made of a sintered body mainly composed of silicon nitride having a point bending strength of at least 600 MPa and a thermal conductivity at room temperature of at least 50 W / (m · K). Are fitted on both sides of the sleeve 1b, and the sleeve 1a and the sleeve 1c are made of ceramics whose thermal conductivity at room temperature is smaller than that of the sleeve 1b. And wherein the Rukoto.
[0011]
In the ceramic roll according to the first aspect of the present invention, one ceramic sleeve is fitted and arranged so as to cover the central portion of the metal shaft in the axial direction, so that the central portion of the conveyed steel plate is formed. Can be properly supported, so that the central portion of the steel plate can be prevented from warping. In addition, the ceramic sleeve is formed of a sintered body containing silicon nitride as a main component, which is excellent in wear resistance, corrosion resistance, oxidation resistance, and heat resistance, and has a relative density of 98% or more and a four-point bending strength at room temperature of 600 MPa or more. By increasing the thermal conductivity at room temperature to 50 W / (m · K) or more, destruction due to thermal shock can be sufficiently prevented. More preferably, the four-point bending strength at room temperature of the sintered body is 700 MPa or more, and the thermal conductivity at room temperature is 60 W / (m · K) or more.
[0012]
In the ceramic roll according to the second aspect of the present invention, in order to properly support the central portion of the conveyed steel sheet as in the first aspect of the present invention, one ceramic sleeve is formed of a metal shaft. It is fitted and arranged so as to cover the central part in the axial direction. Further, in the rolling step, the temperature of the central portion of the steel sheet is raised higher than that of both ends of the steel sheet. A sleeve made of a sintered body containing silicon nitride having high thermal conductivity as a main component is arranged at a portion in contact with the central portion of the steel plate to enhance heat dissipation, and a heat contact portion is provided at a portion in contact with both ends of the steel plate. By arranging another sleeve made of ceramics sintered body such as silicon nitride or sialon with low conductivity, the temperature difference between the center and both ends of the steel sheet is reduced, the steel sheet is soaked, and the warpage of the steel sheet is reduced. It can be further suppressed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic view of a ceramic roll according to an embodiment of the present invention. In FIG. 1, one hollow cylindrical ceramic sleeve 1 was fitted to the outer periphery of a solid metal shaft member 5 so as to have a gap of about 1 mm. The ceramic sleeve 1 was disposed and fitted at a position covering the central portion of the metal shaft member 5 in the axial length direction. At both ends of the ceramic sleeve 1, a metal sleeve 2a and a metal sleeve 2b were arranged. The outer diameter of the metal sleeves 2a and 2b is smaller than that of the ceramic sleeve 1.
[0014]
The elastic member 3a is fitted to the outer periphery of the shaft member 5 so as to be adjacent to the end of the metal sleeve 2a (the end not on the side of the ceramic sleeve 1), and further adjacent to the elastic member 3a. Thus, the metal fastening member 4a was screwed into the shaft member 5. A screw groove is formed on the inner peripheral surface of the metal fastening member 4a, and is screwed to a screw portion provided on the outer peripheral surface of the end of the body of the shaft member 5. Similarly, the elastic member 3b is fitted to the outer periphery of the shaft member 5 so as to be adjacent to the end of the metal sleeve 2b (the end not on the side of the ceramic sleeve 1), and further adjacent to the elastic member 3b. The metal fastening member 4b was screwed to the shaft member 5 so as to perform the operation.
[0015]
With such a configuration, the metal tightening members 4a and 4b are screw-moved in the roll axis direction, the elastic members 3a and 3b are expanded and contracted to apply a side pressure to the metal sleeves 2a and 2b, The sleeve 1 was positioned and fixed at a predetermined position. After the positioning, the metal fastening members 4a and 4b were fixed to the shaft member 5 so that the screws of the metal fastening members 4a and 4b were not loosened.
[0016]
Next, a method for manufacturing the ceramic sleeve of the present invention will be described. As a sintering aid, 3.0% by weight of magnesium oxide powder having an average particle size of 0.2 μm and 3.0% by weight of yttrium oxide powder having an average particle size of 2.0 μm were added to silicon nitride powder having an average particle size of 0.5 μm. %, An appropriate amount of a dispersant was added, and the mixture was ground and mixed in ethanol. Next, after spray drying, the mixture was granulated through a sieve, filled in a rubber mold, and subjected to cold isostatic pressing (CIP) by hydrostatic pressure, to produce a molded body to be a hollow sleeve roll having a predetermined shape. The molded body was fired in a nitrogen gas atmosphere at 1950 ° C. and 60 atm for 5 hours to obtain a sleeve made of a silicon nitride ceramic sintered body. Further, the obtained sintered body was processed into a predetermined shape using a diamond grindstone to produce a silicon nitride-based ceramic sleeve of the present invention.
[0017]
Further, from the obtained silicon nitride-based ceramics sintered body, a test piece for measuring thermal conductivity and density of 10 mm in diameter × 3 mm in thickness and a 4-point bending test piece of 3 mm in length × 4 mm in width × 40 mm in length were sampled. . The density was determined from the Archimedes method based on JIS R2205. The relative density was a value obtained by calculating the measured density by the Archimedes method based on JIS R2205 and dividing the measured density by the theoretical density calculated by calculation. The thermal conductivity was calculated by measuring the specific heat and the thermal diffusivity at room temperature according to the laser flash method JIS R1611. The four-point bending strength was measured at room temperature in accordance with JIS R1601.
[0018]
As a result, the ceramic sleeve made of the silicon nitride-based sintered body of the present invention has a relative density of 99.2%, a thermal conductivity at room temperature of 70 W / (m · K), and a four-point bending strength at room temperature of 860 MPa. Yes, sufficient characteristics as a roll were obtained. And, as a result of applying the ceramic roll of the present invention to an actual machine line, the wear resistance, corrosion resistance, oxidation resistance and heat resistance are good, no destruction due to thermal shock is observed, and the warpage of the steel sheet can be suppressed. Stable operation was realized.
[0019]
FIG. 2 is a schematic view of a ceramic roll according to another embodiment of the present invention. In FIG. 2, one ceramic sleeve (sleeve 1b) is fitted and arranged so as to cover the central part of the metal shaft member 5 in the axial length direction. Further, other ceramic sleeves 1a and 1c were fitted and arranged on both sides of the sleeve 1b and at the portions in contact with both ends of the steel plate.
[0020]
As the ceramic sleeve 1, three silicon nitride ceramic sleeves (ceramic sleeves 1a, 1b, and 1c) having an outer diameter of 355 mm, an inner diameter of 305 mm, and a length of 100 mm were manufactured. The ceramic sleeves (sleeve 1a, 1b and 1c) made of these silicon nitride based sintered bodies have a relative density of 99.5%, a thermal conductivity of 55 W / (m · K) at room temperature, and a four-point bending at room temperature. The strength is 940 MPa.
[0021]
Using SUS304, which is austenitic stainless steel, as the shaft member 5, a solid shaft member having an outer diameter of 300 mm at the center of the body was manufactured. In addition, hollow cylinders having an outer diameter of 326 mm and a thickness of 13 mm were manufactured using SUS304 as the metal sleeves 2a, 2b, 2c and 2d. Ring-shaped disc springs were manufactured using SUS304 as the elastic members 3a and 3b, and five such disc springs were combined in series. As the metal fastening members 4a and 4b, hollow cylindrical bodies having thread grooves formed on the inner peripheral surface thereof were manufactured using SUS304.
[0022]
Using these members, three ceramic sleeves 1a, 1b and 1c made of the same material and metal sleeves 2a, 2b, 2c and 2d are fitted to the shaft member 5, and then the elastic members 3a and 3b are attached. After fitting, the metal fastening members 4a and 4b were rotated to perform positioning. After the positioning, the metal fastening members 4 a and 4 b were fixed to the shaft 5. In the present invention, the number of ceramic sleeves is not limited to three, and may be more than three.
[0023]
The ceramic roll according to the second aspect of the present invention will be described with reference to FIG. The roll assembling method is the same as described above, except that the ceramic sleeve 1b and the ceramic sleeves 1a and 1c are made of different materials. In FIG. 2, one ceramic sleeve (sleeve 1b) is fitted and arranged so as to cover the central part of the metal shaft member 5 in the axial length direction. Further, other ceramic sleeves 1a and 1c were fitted and arranged on both sides of the sleeve 1b.
[0024]
The sleeve 1b arranged at the portion in contact with the central portion of the steel plate has a relative density of 99.5%, a thermal conductivity at room temperature of 70 W / (m · K), and a four-point bending strength at room temperature of 920 MPa. Consists of union. Further, the sleeve 1a and the sleeve 1c arranged at the portions in contact with both ends of the steel plate are both made of a sialon ceramic sintered body having a thermal conductivity of 17 W / (m · K) at room temperature, which is smaller than that of the sleeve 1b.
[0025]
And, as a result of applying the ceramic roll of the second invention to the actual machine line, the abrasion resistance, corrosion resistance, oxidation resistance and heat resistance are good, no destruction due to thermal shock is observed, The temperature difference between both ends became small, the steel sheet was soaked, the warpage of the steel sheet was further suppressed, and stable operation was realized. In the second aspect of the present invention, the number of ceramic sleeves is not limited to three, and may be more than three.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the ceramics roll of this invention, it is excellent in abrasion resistance, corrosion resistance, oxidation resistance, and heat resistance, and can suppress the destruction by a thermal shock, and the center part of the steel plate conveyed can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic view of a ceramic roll according to an embodiment of the present invention.
FIG. 2 is a schematic view of a ceramic roll according to another embodiment of the present invention.
[Explanation of symbols]
1 ceramic sleeve, 1a (1b, 1c) ceramic sleeve,
2a (2b, 2c, 2d) metal sleeve,
3a (3b) elastic member,
4a (4b) metal fastening member, 5 shaft material

Claims (2)

A ceramic roll used for transporting a steel sheet in a hot rolling line, wherein one or more ceramic sleeves are fitted around the outer periphery of a metal shaft, and one of the ceramic sleeves is provided. Is fitted so as to cover the central part of the metal shaft material in the axial length direction. The ceramic sleeve has a relative density of 98% or more, a four-point bending strength at room temperature of 600 MPa or more, and a thermal conductivity at room temperature. Characterized by comprising a sintered body containing silicon nitride as a main component and having a wattage of 50 W / (m · K) or more. A ceramic roll used for transporting a steel sheet in a hot rolling line, comprising a plurality of ceramic sleeves fitted on the outer periphery of a metal shaft, and one of the ceramic sleeves (sleeve 1b) ) Is fitted so as to cover the central part in the axial direction of the metal shaft material, the sleeve 1b has a relative density of 98% or more, a four-point bending strength at room temperature of 600 MPa or more, and heat conduction at room temperature. And a ceramics sleeve (sleeve 1a and sleeve 1c) fitted on both sides of the sleeve 1b. A ceramic roll wherein the thermal conductivity at room temperature of the sleeve 1a and the sleeve 1c is smaller than that of the sleeve 1b.

Images