JP2010269436A - Manufacturing method for ceramic ball and rolling element consisting of the ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a ceramic ball for increasing an amount of peening processing for applying toughening processing on a surface of the ceramic ball and facilitating finish polishing after the processing. <P>SOLUTION: In this manufacturing method for the ceramic ball, at least an internal wall 2 of a polygonal drum 1 having an impeller 4 for stirring in its inside and a surface of the impeller 4 are formed into flexible resin-made faces, the ceramic ball is rotated in the drum 1 and is stirred, and the impeller 4 for stirring is rotated in the reverse direction to the drum 1 so as to toughen the surface of the ceramic ball through collision between the ceramic balls, collision of the ceramic ball with the resin-made face of the internal wall of the drum, and collision of the ceramic ball with the resin-made face of the surface of the impeller when performing the peening processing for toughening the surface of the ceramic ball by using the drum 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to silicon nitride (Si ₃ N ₄ ), zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), used as rolling element parts such as ball bearings, ball screws, linear guides, ball splines, and linear ball bearings. The present invention relates to a method for producing ceramic spheres such as silicon carbide (SiC) and a ceramic rolling element comprising spheres obtained by the method.

Conventionally, a rolling bearing using a silicon nitride as a rolling element and a bearing steel as an inner ring and an outer ring as a ceramic combined rolling bearing is generally known, and has excellent characteristics due to silicon nitride, and the density of silicon nitride. Is relatively small at about 3.3 g / cm ³ , so that it is used for spindle bearings for machine tools in order to reduce the contact stress of the outer ring due to the centrifugal force of the rolling elements.

In addition, since semiconductor devices, liquid crystal panels, etc. are cleaned with various chemicals in the manufacturing process, the rolling bearings incorporated in the manufacturing devices and transport devices are required to operate well even in corrosive environments. All-ceramic bearings using ceramics for rolling pairs exist. (For example, see Patent Document 1)
Further, in a hydraulic lash adjuster in a valve operating apparatus for an internal combustion engine, ceramic balls containing silicon nitride are used for the valve body between the low pressure chamber and the high pressure chamber in order to cope with wear of the seat surface of the valve opening. . (For example, see Patent Document 2)
On the other hand, a planetary ball mill is used as a technique for improving the physical properties of ceramic spheres or ceramic products that have expanded applications as described above, and the same ceramic spheres are collided with each other, and the spheres are collided with the inner wall. Applying residual stress to the surface to improve seizure resistance (see, for example, Patent Document 3) or using an injection material (shot) having an average size of 0.1 μm to 200 μm uniformly on the surface of the ceramic product A method for forming a distributed linear dislocation structure has been proposed. (For example, see Patent Document 4)

JP 2005-163893 A Japanese Patent Laid-Open No. 2004-211585 JP 2008-169996 A JP 2004-136372 A

However, the technology for improving the physical property value of the ceramic sphere or ceramic product according to the above proposal requires a small amount of processing at one time, and requires many devices for mass production, resulting in high cost. Also,
In these methods, metallic fine powder and foreign matter are generated during processing, and these adhere to or bite into the surface of the ceramic sphere, so cleaning is required after processing, and the efficiency for increasing the machining allowance in finishing polishing is also required. Will fall. Further, the method of forming a linear dislocation structure using a propellant is effective for plate-shaped ceramics, but is difficult to control with spherical ceramics and is not suitable for practical use.

  The present invention copes with the above-described actual situation, and in particular, at least the drum inner wall and impeller surface of the peening apparatus that performs toughening treatment on the surface of the ceramic sphere is coated with a resin to suppress the damage of the surface, thereby reducing the amount of peening treatment The purpose of this is to make the finish polishing after the treatment easier.

  That is, the present invention suitable for the above-described object is a method for producing ceramic spheres, which uses a polygonal drum having a stirring impeller inside to perform a surface toughening treatment on the ceramic spheres, and at least the inner wall of the drum and the impeller surface Is formed on a flexible resin surface, a large number of ceramic spheres are placed in the drum, the polygonal drum is rotated, the ceramic spheres are agitated, and the impeller for agitation is rotated in the opposite direction to the drums to A peening treatment is performed to strengthen the surface of the ceramic sphere by collision between the spheres, collision between the ceramic sphere and the resin surface of the drum inner wall, and collision between the ceramic sphere and the impeller surface resin surface.

  According to a second aspect of the present invention, a resin having a compressive elastic modulus exceeding 2 GPa, such as a phenol resin or a polyamide resin, is used as the resin covering the drum inner wall and the impeller surface. According to a third aspect of the present invention, a finish polishing process is performed following the peening process.

Claim 4 is a ceramic rolling element comprising ceramic spheres obtained by the above method. As a characteristic of the ceramic sphere constituting the ceramic rolling element, the surface compressive residual stress is 200 MPa or more and 1200 MPa or less, and the half width of the surface is At least one of 1.3 ° or more and 4.0 ° or less and a fracture toughness value of 9 MPa · m ^1/2 or more is uniformly distributed and satisfied.

  According to the method of the present invention, a plurality of ceramic balls are placed in a polygonal drum having a stirring impeller inside to be toughened, so that the size of the polygonal drum and the size of the stirring impeller are changed. Thus, the number of pieces that can be processed can be easily changed, and the surface can be toughened without injection of a spray material (shot) at the time of processing. In particular, since a drum inner wall having a flexible resin surface and an impeller surface are used, finish polishing can be performed without interposing metal fine powder and foreign matter, and surface damage can be minimized.

  In addition, by changing the rotation speed of the impeller and the processing time, it is possible to control the compressive residual stress, half-value width and fracture toughness value of ceramic spheres, and toughen even inexpensive ceramic spheres with low fracture toughness values. There is also an effect that it is possible to extend the life and further cost reduction by processing.

  The present invention can be applied to ceramic spheres made of silicon nitride, alumina, zirconia, β sialon, etc., and includes various additives such as those containing addition of sintering aids and those produced through a HIP treatment process. It can be applied to ceramic spheres.

It is the schematic which shows the example of the surface toughening processing apparatus used for this invention, (a) is sectional drawing which shows an internal structure, (b) is a side view. It is the schematic which shows another aspect of the surface toughening processing apparatus used for this invention, (a) is sectional drawing which shows an internal structure, (b) is a side view. It is a graph which shows the result of the seizure test of the ceramic sphere processed in the Example of this invention. It is a graph which shows the relationship between the compressive residual stress of the ceramic sphere processed in the Example of this invention, and seizure property. It is a graph which shows the half value width of the ceramic sphere processed in the Example of this invention, and the relationship between seizure property. It is a graph which shows the relationship between the fracture toughness value and seizure property of the ceramic sphere processed in the Example of this invention.

  Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. 1 (a) and 1 (b) show an example of a surface toughening treatment apparatus used in the present invention. In the figure, 1 is a polygonal, and in the figure is an octagonal drum, and the inner wall thereof is a resin plate. 2 and a plurality of ribs 3 for efficiently stirring the ceramic spheres that are thrown in, and a resin impeller 4 for stirring is provided inside the drum.

  The polygonal drum 1 and the resin impeller 4 can rotate around the axis of the resin impeller, and the rotation speed is appropriately restricted by an inverter. However, the rotation of the polygonal drum 1 and the resin impeller is not limited. It is effective that the directions are opposite to each other. In FIG. 1, the rib 3 is provided on the inner wall of the drum. However, the rib 3 is not essential as shown in FIGS. 2A and 2B, and may be omitted.

  The method for producing ceramic spheres of the present invention is carried out by using the surface toughening treatment apparatus described above. A large number of ceramic spheres are placed in the drum 1 and the polygonal drum 1 and the impeller 4 for stirring are rotated in opposite directions. The ceramic balls are subjected to a peening treatment for surface toughening of the ceramic balls by collision between the ceramic balls in the drum 1, collision between the ceramic balls and the inner wall of the drum, and collision between the ceramic balls and the impeller 4 surface for stirring. Strengthen the surface.

  When treated with a peening treatment device, which is a metal surface toughening treatment device, metallic fine powder or foreign matter usually adheres or bites into the surface of the ceramic. It is very important to coat the impeller surface with a resin, and the method of the present invention uses a flexible resin inner wall of the drum and the impeller surface. Thus, finish polishing can be easily performed, and surface damage can be minimized. The resin used for coating the drum inner wall and impeller surface is preferably a relatively flexible resin having a compressive elastic modulus exceeding 2 GPa, as typified by, for example, a phenol resin or a polyamide resin.

  In addition, the fracture toughness value, compressive residual stress, and half width of toughened ceramic spheres can be controlled by appropriately changing and selecting polygon rotation speed, impeller rotation speed, and processing time during processing. The obtained ceramic sphere can be provided with characteristics suitable as a rolling element.

  The rolling element according to the present invention is composed of ceramic spheres obtained by the above method and controlled to have the required characteristics, and the fracture toughness value, compressive residual stress, and half width have the following characteristics, respectively. It is characterized by that.

  Here, among the above fracture toughness value, compressive residual stress, and half-value width, the fracture toughness value is the most preferable characteristic as a rolling element. As an effect is improved.

The compressive residual stress existing on the surface of the ceramic sphere used for the rolling element after toughening treatment is preferably 200 MPa or more in absolute value, 400 MPa or more, 600 MPa or more, and further 800 MPa or more. Is most preferred. Further, the half width is preferably 1.3 ° or more. These compressive residual stress and half width can both be measured by X-ray diffraction. On the other hand, fracture toughness value is preferably in the 9 MPa · m ^1/2 or more, and more preferably 10 MPa · m ^1/2 or more. However, since excessive peening treatment causes harmful defects such as cracks in the ceramic sphere, the compressive residual stress is preferably 1200 MPa or less and the half-value width is 4.0 ° or less.

  In the peening process in the method of the present invention, compressive residual stress is introduced near the surface of the ceramic sphere by utilizing the energy generated by the collision between the ceramic spheres and the collision between the ceramic sphere and the drum inner wall and between the ceramic sphere and the impeller. If the ceramic sphere is too small, it is difficult to introduce compressive residual stress. Therefore, the diameter of a suitable ceramic sphere is 0.3 mm or more, more preferably 0.8 mm or more, and further preferably 2 mm or more. Further, in the method of the present invention, it is preferable to perform finish polishing after the peening step, and thereby the surface roughness of the ceramic sphere subjected to the peening step becomes rough or the roundness decreases. However, ceramic spheres with excellent dimensional accuracy, seizure resistance and toughness can be obtained.

Using the manufacturing method described above, ceramic balls were treated under the following conditions using a drum having a capacity of 18 liters and containing 20% (3.6 liters) of the drum capacity, and the seizure properties were evaluated. The capacity of the planetary ball mill in Patent Document 3 is 45 milliliters, and the processing of the present invention is much larger processing than this. Tables 1A-K show the compressive residual stress, half-value width, and fracture toughness values of the treated examples together with untreated products. The compressive residual stress value and the half width were measured with an X-ray diffraction apparatus (PSPC micro-part stress produced by Rigaku Corporation), and the fracture toughness value was measured with a Vickers hardness tester using the Niihara equation. The compression residual stress, fracture toughness value and surface hardness of the treated ceramic spheres were measured without polishing.
Surface toughening treatment conditions Polygon drum rotation speed: 42 rpm
Impeller rotation speed: 700-1200rpm
Ball size: 11/32 inch
Processing time: 1-2H

As apparent from Table 1, it can be seen that the fracture toughness value increases as the compressive residual stress and the half width increase. Particularly in Example F, the compressive residual stress value increased to 1000 MPa, the half-value width increased to 3.0 °, and the fracture toughness value increased to 14.4 MPa · m ^1/2 . However, when the compressive residual stress exceeds 1200 MPa and the half-value width exceeds 4.0 °, the ceramic spheres are damaged as shown in G and K of Table 1.

Next, in order to evaluate the seizure resistance of the ceramic spheres for the inventive product excluding G and K treated by the above-mentioned method, a four-ball type test was carried out. The test conditions are as follows. Using a high-speed 4-ball type testing machine manufactured by Takachiho Seiki Co., Ltd., placing the ceramic balls on top of 3 steel balls, rotating the ceramic balls in a poorly lubricated state, and the torque is 2.5 times the initial torque The test was terminated at the point of time, and the seizure property was evaluated by the test time from the start of the test to the end of the test.
<Seizure test conditions>
Test load: 73.5N
Rotation speed: 3500rpm
Model of measuring machine: CH-HSF-10K
FIG. 3 shows the baking time of each example as a ratio, where the baking time of the untreated product is 1. As is apparent from the figure, the seizure property of the ceramic sphere produced by the method of the present invention is improved by 88% at the maximum.

Further, FIG. 4 shows that the compressive residual stress is preferably 200 MPa or more in order to improve the seizure property of the ceramic sphere by at least 10% or more. Further, as is clear from FIG. 5, it is found that the half width is preferably 1.3 ° or more in order to improve the seizure property of the ceramic sphere by at least 10%. It is understood that the fracture toughness value is preferably 9 MPa · m ^1/2 or more in order to improve the property by at least 10% or more.

1: Polygonal drum 2: Drum inner wall 3: Rib 4: Impeller

Claims (4)

  When performing the surface toughening treatment of the ceramic sphere using a polygonal drum having an impeller for stirring inside, at least the inner wall and the impeller surface of the drum are formed on a flexible resin surface, and a large number of drums are formed in the drum. Putting the ceramic sphere, rotating the polygonal drum, stirring the ceramic sphere, rotating the impeller for stirring in the opposite direction to the drum, the collision of the ceramic spheres, the ceramic sphere and the drum inner wall resin surface And a peening process for strengthening the surface of the ceramic sphere by the collision between the ceramic sphere and the impeller surface resin surface.   2. The method for producing ceramics according to claim 1, wherein the resin covering the inner wall of the drum and the impeller surface is a resin having a compression elastic modulus exceeding 2 GPa, as typified by a phenol resin or a polyamide resin.   The method for producing ceramic spheres according to claim 1 or 2, wherein finish polishing is performed after the peening treatment. A ceramic sphere obtained by the method according to claim 1, 2, or 3, wherein the sphere has a compressive residual stress of 200 MPa or more and 1200 MPa or less in absolute value, and a half width of the surface of 1.3 ° or more and 4 A ceramic rolling element characterized by being a sphere satisfying at least one of 0 ° or less and a fracture toughness value of 9 MPa · m ^1/2 or more.

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