Sliding member, disk for false twisting machines, and method for producing sliding member

Abstract

The present invention provides a sliding member which is formed of a ceramic that is mainly composed of aluminum oxide, while containing fluorine, and which comprises a surface layer part that has a sliding contact part and an inner part that is surrounded by the surface layer part. With respect to this sliding member, the fluorine concentration on a sliding contact surface of the sliding contact part is higher than the fluorine concentration in the inner part as determined by elemental mapping by means of an energy dispersive X-ray spectrometer. A disk for false twisting machines according to the present invention is formed of this sliding member.

Description

Sliding member, false twisting machine disk, and method for manufacturing sliding member

[0001] The present disclosure relates to a sliding member, a false twisting machine disk using the sliding member, and a method for manufacturing the sliding member.

[0002] Due to their high abrasion resistance, aluminum oxide sintered bodies have traditionally been used as sliding members for seals, slide rings, pumps, pistons, false twisting machine disks, and the like. When the sliding member is a false twisting machine disk, it is required to have excellent twisting ability for sliding contact with the yarn to apply twist, and to be less likely to produce white powder (abrasion powder of the yarn) even during long-term false twisting. To meet these requirements, Patent Document 1 proposes a false twisting machine disk in which at least the sliding contact surface with the yarn is formed of alumina ceramic, the average particle diameter d of the sliding contact surface is 0.5≦d≦2.5 μm, and the load length ratio tp, as specified in JIS B0601-1994, is tp≦80% at a break level c=40%.

[0003] Japanese Patent Application Publication No. 9-256232

[0004] The sliding member of the present disclosure is made of a ceramic containing aluminum oxide as a main component and containing fluorine, and includes a surface layer portion having a sliding surface and an interior portion surrounded by the surface layer portion, and the fluorine concentration on the sliding surface, as determined by elemental mapping using an energy dispersive X-ray spectrometer, is higher than the fluorine concentration in the interior portion.

[0005] The disk for false twisting machines of the present disclosure comprises a sliding member. A manufacturing method for the sliding member of the present disclosure includes the steps of: subjecting the surface of a ceramic sintered body primarily composed of aluminum oxide to at least one of grinding and polishing; immersing the processed ceramic sintered body in an alkaline aqueous solution; and immersing the ceramic sintered body immersed in the alkaline aqueous solution in a solution containing at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride, and ammonium bifluoride, thereby obtaining a sliding member made of a ceramic that contains fluorine and has aluminum oxide as its primary component.

[0006] Fig. 1 is a cross-sectional view showing a sliding member according to an embodiment of the present disclosure.Fig. 2 is a perspective view showing an overview of a false twisting machine provided with a false twisting machine disk.

[0007] A sliding member according to an embodiment of the present disclosure will be described below. Fig. 1 is a cross-sectional view showing a sliding member 1 according to this embodiment. This sliding member 1 is used as a disk for a false twisting machine.

[0008] The sliding member 1 of this embodiment is made of a ceramic containing aluminum oxide as a main component and fluorine, and as shown in FIG. 1 , includes a surface layer 2 and an interior 3 surrounded by the surface layer 2. The sliding member 1 is, for example, disk-shaped. A through-hole 4 is formed in the center of the sliding member 1, and a rotating shaft is attached to the through-hole 4 to rotate the sliding member 1. In this embodiment, the term "main component" refers to a component that accounts for 80% by mass or more of the total 100% by mass of the components constituting the ceramic. The components constituting the ceramic can be identified using an X-ray diffractometer (XRD) using CuKα radiation. The content of each component can be determined by converting metal elements obtained using an X-ray fluorescence analyzer (XRF) or an inductively coupled plasma (ICP) emission spectrometer into the identified component.

[0009] The surface layer 2 is made up of a sliding contact portion 21 and a non-sliding contact portion 22. The sliding contact portion 21 is located on the outer periphery of the sliding member 1 and has a sliding contact surface 211 with which the yarn 5 fed in a predetermined direction slides. The sliding contact surface 211 refers to the surface with which the yarn 5 slides, and may be the entire outer periphery of the sliding contact portion 21. The interior 3 of the sliding member 1 is the area excluding the surface layer 2. The thickness of the surface layer 2 varies depending on the components and content of the grain boundary phase of the ceramic that forms the sliding member 1, but is usually between 1 μm and 50 μm, and preferably between 5 μm and 20 μm.

[0010] In the present disclosure, the fluorine concentration on the sliding contact surface 211 of the sliding contact portion 21 is higher than the fluorine concentration in the interior 3. Fluorine needs to be contained at least in the sliding contact portion 21, and the non-sliding contact portion 22 may contain no fluorine or may contain less fluorine than the sliding contact portion 21. Specifically, the fluorine concentration on the sliding contact surface 211 is preferably 0.1 mass % or more and 1 mass % or less, and preferably 0.2 mass % or more and 0.8 mass % or less. On the other hand, the fluorine concentration in the interior 3 is preferably 0.4 mass % or less, and preferably 0.1 mass % or less, of the fluorine concentration on the sliding contact surface 211. The fluorine concentration can be determined by elemental mapping using an energy dispersive X-ray spectrometer. Specifically, a semi-quantitative analysis is performed using an EDS-equipped scanning electron microscope (SEM / EDS) to determine the ratio of the specified element to the main element, using a ZAF correction method to approximate the total concentration of the peak intensities of elements detected within a specified analysis range (for example, a range of 60 μm horizontally and 45 μm vertically at a magnification of 2000 times). The accelerating voltage used for element mapping is 15 kV.

[0011] The value A-B obtained by subtracting the average circle-equivalent diameter B of the fluorine detection areas from the average distance A between the centers of gravity of adjacent fluorine detection areas on the sliding surface 211 of the sliding portion 21, as determined by elemental mapping, is preferably 6 μm or less. In other words, when the value A-B is 6 μm or less, the distance between adjacent fluorine particles becomes narrow, thereby further suppressing the generation of wear powder. The value A-B is preferably 2 μm or more.

[0012] The circular equivalent diameter of the fluorine detection region can be determined using image analysis software. Examples of image analysis software that can be used include Image-Pro from Hakuto Co., Ltd., WinROOF2021 from Mitani Corporation, and A-Zō-kun (ver. 2.52) (registered trademark) from Asahi Kasei Engineering Co., Ltd. When A-Zō-kun (ver. 2.52) is used as the image analysis software, the circular equivalent diameter of the fluorine detection region can be measured as follows. The circular equivalent diameter of the fluorine detection region can be determined by a method called particle analysis using an element mapping image (a range of 60 μm in horizontal length and 45 μm in vertical length) obtained with an energy dispersive X-ray spectrometer. The setting conditions for this method are, for example, a threshold value, which is an index indicating the brightness of the image, of 20, brightness of bright, and a small figure removal area of ​​0 μm. ２ In this way, it is possible to distinguish between a fluorine detection area and an area where fluorine is not detected by binarization, and the circle-equivalent diameter of the fluorine detection area can be obtained by a technique called particle analysis.

[0013] Here, the binarized fluorine detection area roughly matches the area colored in blue, light blue, yellow-green, yellow, red, pink, white, etc. in the elemental mapping image of fluorine when elemental mapping is performed. In the above measurement, the threshold value was set to 20, but the threshold value may be adjusted according to the brightness of the elemental mapping. This threshold value adjustment was performed by setting the brightness to bright, the binarization method to manual, and the small figure removal area to 0 μm ２ With the noise reduction filter in place, the threshold value may be adjusted so that the fluorine detection area in the element mapping image roughly coincides with the binarized fluorine detection area.

[0014] The equivalent circle diameter of the fluorine detection region determined by the above-described method is, for example, 0.2 μm or more and 3 μm or less. Hereinafter, the image analysis software "A-zo-kun" refers to the image analysis software manufactured by Asahi Kasei Engineering Corporation.

[0015] The distance between the centers of gravity of the fluorine detection areas can be determined by the following method. Using the element mapping described above, the distance between the centers of gravity of the fluorine detection areas can be determined by a method called the distance between centers of gravity method for dispersity measurement using image analysis software. The setting conditions for this method can be the same as those used to determine the circle-equivalent diameter of the fluorine detection areas.

[0016] In this embodiment, it is preferable that a compound containing fluorine and calcium is present on the sliding contact surface 211. That is, in addition to free carbon, a compound containing fluorine and calcium is present on the sliding contact surface 211. An example of a compound containing fluorine and calcium is a compound having a composition formula of CaF ２ or CaF ３ Compounds containing fluorine and calcium act as solid lubricants and can reduce the frictional force generated by sliding contact with a sliding contact material (for example, the yarn 5).

[0017] Such a compound containing fluorine and calcium may be mixed with aluminum oxide, which is the main component, during the production of the slide member 1, but calcium carbonate, which is used as a sintering aid, forms a grain boundary phase as an oxide of calcium. When immersed in a solution containing a fluorine-containing compound, part of the calcium migrates and aggregates, and can form the above-mentioned compound by bonding with fluorine. The presence of a compound containing fluorine and calcium on the slide surface 211 can be confirmed, for example, by elemental mapping of fluorine and calcium using an X-ray diffraction method or an energy dispersive X-ray spectrometer (EDS). When EDS mapping reveals an area on the slide surface 211 where the mapping image of fluorine and the mapping image of calcium overlap, it may be assumed that a compound containing fluorine and calcium is present in this area.

[0018] The average value of the skewness (Rsk) in the roughness curve of the sliding surface 211 is preferably 0 or less. The skewness (Rsk) is a type of index that represents surface properties and indicates the degree of bias of the uneven shape formed on the surface. When the skewness (Rsk) is positive (i.e., Rsk > 0), the larger the Rsk, the more steep convex portions and gentle concave portions there are in the roughness curve. On the other hand, when the skewness (Rsk) is negative (i.e., Rsk < 0), the smaller the Rsk, the more steep concave portions and gentle convex portions there are in the roughness curve. In this embodiment, since the average value of the skewness (Rsk) is 0 or less, the convex portions on the sliding surface 211 are rounded, thereby reducing the risk of damaging the sliding contact material (e.g., the yarn 5). The average value of the skewness (Rsk) is preferably -0.8 or more and 0 or less.

[0019] The skewness (Rsk) can be measured as follows. Specifically, in accordance with JIS B0601:2001, it can be measured from the roughness curve of the sliding surface 211 obtained using an ultra-deep color 3D shape measuring microscope (for example, the VK-X1000 manufactured by Keyence Corporation or its successor model). The measurement conditions include a coaxial illumination method, a measurement magnification of 480x, no cutoff value λs, a cutoff value λc of 0.08 mm, end effect correction, and a measurement range per measurement target of 710 μm × 533 μm. Two measurement ranges are set from the sliding surface 211. When the shape of the sliding member 1 is a circular plate, such as a false twisting disc, the sliding surfaces 211 are set to face each other in the radial direction. Then, four lines to be measured are drawn in each measurement range at approximately equal intervals in the longitudinal direction, and the line roughness is measured to calculate the average skewness (Rsk). The length of each line to be measured is, for example, 560 μm.

[0020] The average value of the root mean square slope (RΔq) of the roughness curve of the sliding contact surface 211 is preferably 0.5 or more and 1.4 or less. The root mean square slope (RΔq) of the roughness curve is the root mean square of the local slope dZ / dx at the reference length l of the roughness curve measured in accordance with JIS B 0601:2001, and is defined by the following formula: The roughness curve is obtained in the same manner as above.

[0021] When the root-mean-square slope (RΔq) value is large, the surface unevenness becomes steep, while when the root-mean-square slope (RΔq) value is small, the surface unevenness becomes gentle. When the contact material is, for example, a yarn 5, if the average value of the root-mean-square slope (RΔq) is 0.5 or more, the sliding surface 211 can apply an appropriate friction force to the yarn 5, thereby obtaining a suitable twist. On the other hand, if the average value of the root-mean-square slope (RΔq) is 1.4 or less, the slope of the sliding surface 211 becomes gentle, reducing the risk of damaging the yarn 5. The root-mean-square slope (RΔq) can be measured under the same measurement conditions as those used to measure skewness (Rsk).

[0022] The ceramics constituting the sliding member 1 preferably have an aluminum oxide content of 87% by mass or more and 91% by mass or less. The ceramics may contain, in addition to aluminum oxide, fluorine, calcium, chromium, magnesium, silicon, etc. When the aluminum oxide content is 87% by mass or more, the area occupied by the grain boundary phase on the sliding surface 211 is reduced, and the amount of unavoidable impurities contained in the grain boundary phase is also reduced, thereby improving wear resistance. Furthermore, when the aluminum oxide content is 87% by mass or more, the analytical accuracy of the fluorine concentration on the sliding surface 211 obtained by elemental mapping using an energy dispersive X-ray spectrometer is improved. On the other hand, when the aluminum oxide content is 91% by mass or less, the area occupied by the grain boundary phase on the sliding surface 211 is increased, thereby reducing the contact angle with pure water and suppressing the adhesion of dirt, particularly dirt such as snow that contains almost no moisture.

[0023] In this embodiment, in particular, the ceramic contains chromium and has an oxide (Cr ２ O ３) is preferably 3% by mass or more and 5% by mass or less. When the chromium content is within this range, the sliding surface 211 exhibits a reddish color tone such as a medium dark shade of pink-red, so that even if wear powder (snow) from the yarn 5 adheres to and accumulates on the sliding surface 211, it can be easily identified and quickly removed. ２ O ３ The chromium content in terms of Cr can be measured as follows: The Cr content of the sliding member 1 is measured using an ICP emission spectrophotometer, and the Cr content is calculated as follows: ２ O ３ Convert to the content as a whole.

[0024] The sliding surface 211 preferably has a lightness index L* of 60 to 65 in the CIE 1976 L*a*b* color space, a chromaticness index a* of 16 to 19 in the CIE 1976 L*a*b* color space, and a chromaticness index b* of 0.1 to 2 in the CIE 1976 L*a*b* color space. In other words, the sliding surface 211 exhibits a color tone described as a beautiful pink-red (a medium light shade of pink-red), thereby providing consumers with a sense of luxury, aesthetic satisfaction, and mental comfort for a long period of time. The CIE 1976 L*a*b* color space is defined by JIS Z 8781-4:2013. The lightness index L* and the chromaticness indices a* and b* can be measured using a spectrophotometer (e.g., the NF777 or a successor model manufactured by Nippon Denshoku Industries Co., Ltd.). The measurement conditions are set to a CIE standard illuminant D65 and a viewing angle of 2°.

[0025] The relative density of the ceramic constituting the sliding member 1 described above is preferably 95% or more. If the relative density is within the above range, the number of open pores is reduced, so that even when a sliding contact material slides in contact with the ceramic, grains are less likely to fall out from around the open pores located on the sliding contact surface 211. In particular, the relative density is preferably 98% or more. The relative density is expressed as a percentage (ratio) of the apparent density of the ceramic to the theoretical density of the ceramic. The apparent density of the ceramic may be determined in accordance with JIS R 1634:1998.

[0026] A method for manufacturing the sliding member 1 of this embodiment will be described below. First, the surface of a ceramic sintered body mainly composed of aluminum oxide is ground and / or polished to form a predetermined disk shape (for example, a disc shape). Next, the ceramic sintered body processed into a disk shape is immersed in an alkaline aqueous solution as needed. This is to facilitate the corrosive action of fluorine, which will be described later. Examples of alkaline aqueous solutions include aqueous solutions containing NaOH, KOH, NH ３ The alkaline substance concentration is preferably 20% by mass or more and 50% by mass or less. The immersion may be carried out, for example, in an aqueous solution at a temperature of 20° C. or more and 80° C. or less for a period of 30 minutes to 72 hours.

[0027] Next, the ceramic sintered body is removed from the alkaline aqueous solution, washed with water, dried, and then immersed in a solution containing a fluorine-containing compound. This produces a sliding member made of a ceramic containing fluorine and having aluminum oxide as its main component. The fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride, and ammonium bifluoride. By immersing the ceramic sintered body in a solution containing a specific fluorine-containing compound, the surface of the ceramic sintered body is corroded by fluorine, resulting in a rough surface with appropriate surface roughness, allowing for appropriate frictional force (e.g., appropriate twisting force) to be applied to the sliding contact material. Furthermore, the generation of friction powder from the sliding contact material can be reduced, thereby suppressing damage to the sliding contact material.

[0028] The concentration of the fluorine-containing compound in the solution containing the fluorine-containing compound is preferably 0.5% by mass or more and 5% by mass or less. The concentration of the fluorine-containing compound is particularly preferably 0.7% by mass or more and 1.5% by mass or less. Furthermore, immersion is preferably carried out in an aqueous solution at a temperature of 15°C or more and 80°C or less for a time period of 30 minutes to 72 hours, for example, in order to enhance the corrosive effect of fluorine. The immersion time is particularly preferably 30 minutes to 24 hours.

[0029] As described above, the slide member 1 of this embodiment has high wear resistance and can be used for a long period of time due to the high concentration of fluorine on the sliding surface 211. Furthermore, the aggressiveness (frictional force) of the sliding surface against the sliding material is reduced, thereby suppressing the generation of wear powder from the sliding material. Furthermore, the interior 3 of the slide member 1 has a low concentration of fluorine, which increases thermal expansion, and therefore, even if the interior 3 is repeatedly exposed to high temperatures and a large temperature difference is generated between the surface layer 2 and the interior 3, stress generated by repeated thermal expansion and contraction inside the slide member is reduced, making it less likely to develop cracks.

[0030] Next, a false twisting disc comprising the sliding member 1 will be described with reference to FIG. 2. The false twisting disc is used in the false twisting device of a draw false twisting machine. To twist the yarn 5, the yarn 5 is brought into contact with a plurality of rotating false twisting discs 11. As shown in FIG. 2, a plurality of units are prepared, each having a plurality of false twisting discs 11 attached to a rotating shaft 12 (three units are used in FIG. 2). When viewed in a plan view in the axial direction of the rotating shaft 12, the false twisting disc 11 of each unit partially overlaps the false twisting disc 11 of an adjacent unit. The rotating shafts 12 of the units are arranged parallel to each other, and the false twisting discs 11 do not contact each other or the rotating shafts 12 of adjacent units. In this state, the rotating shaft 12 is rotated at high speed, and the yarn 5 is made to travel at high speed between the units, whereby the yarn 5 comes into contact with the outer peripheral surface of the false twisting disk 11 of each unit (i.e., the sliding surface 211 of the sliding member 1), is rotated, and is false twisted and drawn.

[0031] The outer peripheral surface (sliding surface 211) of the rotating false twisting disk 11 is in direct contact with the yarn 5 and is therefore prone to wear, but the sliding member 1 according to this embodiment has excellent wear resistance and can be used for a long period of time. Furthermore, the sliding member 1 according to this embodiment has an appropriate frictional force, so it is excellent in twisting properties and can suppress the wear of the yarn 5 and the generation of wear powder (the above-mentioned snow).

[0032] The sliding member of the present disclosure is not limited to use as the disk 11 for a false twisting machine, but can also be used as a sliding member for a seal, a slide ring, a pump, a piston, or the like.

[0033] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the present disclosure.

[0034] REFERENCE SIGNS LIST 1 Sliding member 2 Surface layer 21 Sliding contact portion 211 Sliding contact surface 3 Inside 4 Through hole 5 Yarn 11 False twisting machine disk 12 Rotating shaft

Claims

1. A sliding member made of a ceramic containing fluorine and containing aluminum oxide as a main component, the sliding member having a surface layer portion having a sliding surface and an interior portion surrounded by the surface layer portion, the fluorine concentration on the sliding surface being determined by elemental mapping using an energy dispersive X-ray spectrometer being higher than the fluorine concentration in the interior portion.

2. 2. The sliding member according to claim 1, wherein a value obtained by subtracting an average value of a circle equivalent diameter of the fluorine detection areas from an average value of a distance between centers of gravity of adjacent fluorine detection areas on the sliding contact surface, which is obtained from the element mapping, is 6 μm or less.

3. 2. The sliding member according to claim 1, wherein a compound containing fluorine and calcium is present on said sliding contact surface.

4. 2. The sliding member according to claim 1, wherein an average value of skewness (Rsk) in a roughness curve of the sliding contact surface is 0 or less.

5. 2. The sliding member according to claim 1, wherein an average value of a root-mean-square slope (RΔq) of a roughness curve of the sliding contact surface is 0.5 or more and 1.4 or less.

6. 2. The slide member according to claim 1, wherein the ceramic has an aluminum oxide content of 87% by mass or more and 91% by mass or less.

7. The ceramic contains chromium, and Cr ２ O ３ 2. The sliding member according to claim 1, wherein the content in terms of Cr is 3 mass % or more and 5 mass % or less.

8. 2. The sliding member according to claim 1, wherein the lightness index L* of the sliding contact surface in a CIE 1976 L*a*b* color space is 60 or more and 65 or less, the chromaticness index a* is 16 or more and 19 or less, and the chromaticness index b* is 0.1 or more and 2 or less.

9. A disk for a false twisting machine, comprising the sliding member according to any one of claims 1 to 8.

10. A method for producing a slide member according to any one of claims 1 to 8, comprising the steps of: a step of subjecting a surface of the ceramic sintered body mainly composed of aluminum oxide to at least one of grinding and polishing; immersing the processed ceramic sintered body in a solution containing at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride, and ammonium hydrogen fluoride; The manufacturing method of a slide member comprising the steps of:

11. 11. The method for producing a slide member according to claim 10, further comprising the step of immersing the processed ceramic sintered body in an alkaline aqueous solution before immersing the ceramic sintered body in the solution containing the fluorine-containing compound.