JP2001270777A - Ceramic guide roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the durability, lighten the weight and lower the cost of guide rollers for conveying metallic material. SOLUTION: The objective guide rollers comprises tetragonal zirconia ceramic or a composite ceramic including tetragonal zirconia ceramic. The guide roller has characteristically an average surface roughness of <=0.2 μm and/or the maximum surface roughness of >=0.8 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic guide roller for conveyance, and more particularly to a guide roller for conveying a metal material.

[0002]

2. Description of the Related Art Metal rollers such as stainless steel and resin rollers such as nylon have been used as guide roller materials for transporting metal materials. However, if these materials are used, high speed transport and strong transport are required. The roller surface was severely worn due to insufficient strength due to impact or the like, and had a single life, and the roller had to be replaced frequently.

For the purpose of improving the durability, a roller made of alumina having a high hardness was examined. However, since the strength and the toughness were low, the roller could not withstand a strong impact force and was broken.

[0004]

[0007] Metal rollers and resin rollers have been used as guide rollers for transporting metal materials. However, in view of the increase in transport speed accompanying the recent increase in production, particularly durable materials have been used. Is desired.

[0005] With the ceramic guide roller for conveyance of the present invention, the metal material conveyed is hardly scratched on the surface, and the roller is less worn and less damaged, so that it can be used for a long time, and the roller can be replaced. As a result, the production time is improved.

[0006]

Means for Solving the Problems As a result of diligent studies by the inventors for technical improvement, the present invention relates to a ceramic guide roller comprising a tetragonal zirconia ceramic or a composite ceramic containing tetragonal zirconia. A ceramic guide roller characterized in that an outer peripheral member made of tetragonal zirconia ceramics or a composite ceramic containing tetragonal zirconia is fitted on a surface of a core roller made of metal or a metal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Tetragonal zirconia ceramics have high strength and toughness and have particularly excellent mechanical properties among structural ceramics. Further, the composite ceramics containing tetragonal zirconia has improved mechanical properties as compared with a matrix alone containing no zirconia. In particular, a composite ceramic in which alumina, mullite, silicon carbide, silicon nitride, or the like having a smaller coefficient of thermal expansion than tetragonal zirconia is used as a matrix and to which tetragonal zirconia is added in an amount of 20% by weight or more, The effect is remarkable.

[0008] A guide roller for transporting a metal material is required to have heat resistance in addition to strength and impact resistance. For these reasons, a ceramic material containing tetragonal zirconia is most suitable as the material of the guide roller.

The tetragonal zirconia contains 2 to 6 mol% of magnesia and / or yttria as a stabilizer, and preferably contains 5 to 25% by weight of a monoclinic to a depth of 50 μm from the surface. Is less than 2 mol%, the monoclinic crystal is easily transformed and sufficient strength cannot be exhibited. On the other hand, if the amount of the stabilizer exceeds 6 mol%, the stabilization proceeds excessively, the strengthening mechanism by phase transformation does not work, and sufficient strength cannot be exhibited. Further, 2.2 to 3.5
A mole% range is more preferred.

Further, if there is a specific range of monoclinic crystals from the surface of tetragonal zirconia to a certain depth from the surface, a compressive stress is applied to the surface due to volume expansion generated during transformation from tetragonal to monoclinic. Works. Thereby, the hardness of the surface is increased, and the wear resistance is improved and strengthened. In the present invention, when the monoclinic ratio from the surface to a depth of 50 μm is in the range of 5 to 25% by weight, the durability of the roller is improved by the surface compression effect. If it is less than 5% by weight, the compression effect is small, and if it exceeds 25% by weight, monoclinic crystals become too large and microcracks are generated, which is not preferable.

In the composite ceramic containing tetragonal zirconia, the amount of tetragonal zirconia is 20 to 80% by weight, and the balance is at least one of alumina, mullite, silicon carbide, silicon nitride, tungsten carbide, and titanium carbide. It is preferable to include the above compounds. When the amount of tetragonal zirconia is less than 20% by weight, the contribution of the transformation strengthening mechanism of tetragonal zirconia is not sufficient. On the other hand, if it exceeds 80% by weight, the matrix becomes too small and the contribution of the zirconia dispersion strengthening mechanism is not sufficient, and the strength cannot be exhibited. Further, the amount of tetragonal zirconia is more preferably 30 to 60% by weight.

On the surface of the ceramic guide roller, it is preferable that the average surface roughness measured by a stylus type surface roughness meter is 0.2 μm or less and / or the maximum surface roughness is 0.8 μm or less. Within this range of the surface roughness, the metal material is not damaged, and smooth conveyance is possible.

When an outer peripheral member made of tetragonal zirconia ceramics or a composite ceramic containing tetragonal zirconia ceramics is fitted on the surface of a core roller made of metal, the thickness of the outer peripheral member is set to 10 times the entire diameter.
By fitting up to 50%, the production cost can be reduced as compared with the case where the whole is made of ceramics, so that the economic effect is large.

Next, when zirconia is used for the guide roller of the present invention, the zirconia is obtained according to the following manufacturing steps. The molar ratio of [the powder type and synthetic methods] and 99.9% pure oxychloride and yttrium chloride solution as zirconia (ZrO ₂₎ and yttria (Y ₂ O ₃₎ is 95: 5 to 98: 2 and so as Adjust to mix.
A hydrolysis method for obtaining crystalline hydrated zirconia in an autoclave set at a temperature of about 100 ° C. from the adjusted mixed solution, or neutralization by adding ammonia water or the like to lower the solubility to reduce the solubility, A zirconia precursor is obtained by a method such as a neutralization coprecipitation method in which zirconium hydroxide and yttrium hydroxide are precipitated, and then fired to obtain a high-strength zirconia powder raw material. [Powder Properties and Physical Properties] The primary particle size of the powder is affected by the sintering temperature.
It is distributed in the range of 01 to 0.2 μm, and the average primary particle size is about 0.1 μm. When measured by a laser diffraction method, the secondary particle size is distributed in the range of 0.01 to 30 μm, and the average secondary particle size is about 1 μm. [Molding method] The method of forming into the shape of the guide roller is
There are a rubber press type and an extrusion type. In particular, extrusion molding facilitates mass production and cost reduction.

To prepare a slurry for extrusion molding, 10 g of water and 5 g of a water-soluble binder are added to 100 g of zirconia powder, and the mixture is dispersed and mixed well by a kneader.

The green formed in a cylindrical shape is cut into an appropriate length by extrusion, a metal rod or a glass rod is inserted into the green so as to fit the inner diameter, and the green is dried in a drying furnace. [Sintering and processing method] The molded green is
By baking for 30 minutes to 3 hours in the range of 00 to 1500 ° C., a dense sintered body can be obtained. The finish is polished by a honing machine or a cylindrical grinder, and is finally finished to a mirror surface having a maximum roughness of 50 nm or less. [Structure and Physical Properties of Sintered Body] It is desirable that the average surface roughness of the roller surface is 0.2 μm or less and the maximum surface roughness is 0.8 μm or less. When the average surface roughness is 0.2 μm or less, and the maximum surface roughness is 0.8 μm or less,
The surface is very smooth and does not damage the transported metal material. The average surface roughness of the roller surface is 0.2 μm
When the maximum surface roughness exceeds 0.8 μm, the surface is too rough, and the metal material to be conveyed is undesirably worn or scratched.

The ceramic material suitable for the guide roller needs to have appropriate hardness and strength. The hardness is preferably 1100 to 2000 in Vickers hardness. If it is less than this range, it is too soft and the rollers are worn out. On the other hand, if it is too hard, the metal to be conveyed is worn out.

Further, the sintered body is desirably made of tetragonal high-strength zirconia containing monoclinic crystals by analyzing the crystal structure by X-ray diffraction. The tetragonal zirconia surface is carefully polished with abrasive grains and measured by X-ray diffraction at a depth of 10 μm. In this way,
The monoclinic content from the surface up to a depth of 50 μm is 5-25.
It is desirable to contain the weight%. Within this range of monoclinic content, a zirconia guide roller having high surface hardness and excellent strength can be obtained.

The guide roller made of tetragonal zirconia has been described above. In the composite ceramics containing tetragonal zirconia, the amount of tetragonal zirconia is 20 to 8%.
The same effect can be expected by using a material containing 0% by weight and a balance of at least one compound selected from alumina, mullite, silicon carbide, silicon nitride, tungsten carbide, and titanium carbide.

[0020]

The present invention will be described below with reference to examples.

A powder obtained by adding 0.5% or less of Al ₂ O ₃ powder and 3% by mole or less of Y ₂ O ₃ powder to zirconia powder was stamped by a molding machine, and then fired at 1400 ° C., and the result of X-ray analysis was 95 The weight% was tetragonal.

It is polished. Polishing method is as follows. Diamond paste abrasive grains are polished at 0.6 μm so that no load is applied to produce ceramic guide rollers, and when used for transportation, conventional resin rollers have an average of 3.8 months. It was found that the surface condition was good without any change even after 8 months, and the life was twice or more.

[0023]

The guide roller for transporting the metal material is
Since it is always exposed to shock and frictional heat generated, using a ceramic material containing tetragonal zirconia, which has both high toughness and heat resistance, not only can prolong the service life, but also reduce the weight of the roller itself to rotate. It will be very smooth.

Further, by fitting the ceramic containing tetragonal zirconia to the surface of the metal core, it is possible to maintain the performance and at the same time expect the effect of cost reduction.

Claims (6)

[Claims] 1. A ceramic guide roller comprising a tetragonal zirconia ceramic or a composite ceramic containing tetragonal zirconia. 2. A ceramic guide roller, wherein an outer peripheral member made of tetragonal zirconia ceramics or a composite ceramic containing tetragonal zirconia is fitted on a surface of a core roller made of metal. 3. A composite ceramic comprising at least 20% by weight of tetragonal zirconia.
Or the ceramics guide roller according to 2. 4. The method according to claim 1, wherein the tetragonal zirconia contains 2 to 6 mol% of magnesia and / or yttria as a stabilizer, and contains 5 to 25% by weight of a monoclinic crystal to a depth of 50 μm from the surface. 4. The ceramic guide roller according to any one of 1 to 3, above. 5. The composite ceramic containing tetragonal zirconia, wherein the amount of tetragonal zirconia is 20 to 80% by weight, and the balance is at least one of alumina, mullite, silicon carbide, silicon nitride, tungsten carbide, and titanium carbide. 2. The composition of claim 1, wherein the composition comprises one or more compounds.
5. The ceramic guide roller according to any one of items 1 to 4. 6. The ceramic guide roller according to claim 1, wherein the surface of the ceramic guide roller has an average surface roughness of 0.2 μm or less and / or a maximum surface roughness of 0.8 μm or less. Ceramic guide roller.