CN108026973B

CN108026973B - Sliding member, rolling bearing, and retainer

Info

Publication number: CN108026973B
Application number: CN201680051973.5A
Authority: CN
Inventors: 多田晶美; 佐藤洋司
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2015-08-03
Filing date: 2016-08-03
Publication date: 2020-06-16
Anticipated expiration: 2036-08-03
Also published as: JP6769775B2; CN108026973A; JP2017032141A; WO2017022803A1

Abstract

The invention provides a sliding member, a rolling bearing and a retainer having a sliding surface with excellent sliding performance even under the conditions of high sliding speed and high surface pressure in lubricating oil. A sliding member used in an oil-lubricated environment, comprising a sliding layer formed on an iron-based metal base, wherein the sliding layer has a base layer comprising a heat-resistant resin and a first fluororesin on the surface of the iron-based metal base, and has a second fluororesin layer on the surface of the base layer, the heat-resistant resin is a resin containing carbon atoms in the main chain of the polymer structure and further containing at least 1 atom of an oxygen atom, a nitrogen atom and a sulfur atom, and the second fluororesin layer is a crosslinked fluororesin layer obtained by crosslinking at least the vicinity of the surface layer.

Description

Sliding member, rolling bearing, and retainer

Technical Field

The present invention relates to a sliding member, a rolling bearing, and a cage, and more particularly to a sliding member, such as a rolling bearing cage, having excellent wear resistance on the surface of the sliding member and capable of maintaining the excellent wear resistance for a long period of time, and a rolling bearing using the cage.

Background

Lubricating oil, grease, or the like is supplied to the sliding surfaces of the rolling bearing, the cage, or the like to reduce rolling friction or sliding friction. In addition, the sliding surface is subjected to surface treatment for further improving the slidability. One of the surface treatments is a method for forming a fluororesin coating film. For example, the following methods are known: a polytetrafluoroethylene (hereinafter referred to as PTFE) film formed on a sliding portion of a sliding member is irradiated with radiation at a dose of 50 to 250kGy, thereby improving wear resistance and adhesion to a base material (patent document 1).

The following methods for producing a modified fluororesin coating material are known: a coating film of a fluororesin is formed on the surface of a substrate having excellent heat resistance selected from the group consisting of metal materials such as polyimide resins, copper, aluminum, and alloys thereof, ceramics, and glass, and the coating film is irradiated with ionizing radiation at a temperature equal to or higher than the melting point of the fluororesin (patent document 2).

As a sliding member made of a fluororesin used for a non-lubricated bearing, a dynamic seal, or the like, a fluororesin is known which is heated to a temperature equal to or higher than its crystal melting point and is irradiated with ionizing radiation in a range of an irradiation dose of 1kGy to 10MGy in the absence of oxygen (patent document 3).

The following film or sheet-like articles are known: the film or sheet-like product is formed by laminating a film or sheet-like inclined material made of PTFE and a base material selected from the group consisting of aluminum, iron, stainless steel, polyimide and ceramics, wherein the polymer present on one surface of the material not in contact with the base material and in a layer adjacent thereto has a three-dimensional structure, the polymer present on the other surface of the material in contact with the base material and in a layer adjacent thereto has a two-dimensional structure, the content of the three-dimensional structure of the polymer present between the one surface and the other surface continuously changes, and the thickness of the material is 5 to 500 [ mu ] m (patent document 4).

On the other hand, there are rolling bearings used in engines of automobiles, motorcycles, and the like, particularly needle roller bearings with retainers, and silver plating is performed on the retainer surface in order to prevent sintering of the retainer surface. The needle roller bearing with a retainer is composed of a pressed metal retainer that holds needle rollers at equal intervals, and the entire surface of the retainer is plated with silver (patent document 5).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-155443

Patent document 2: japanese laid-open patent publication No. 2002-225204

Patent document 3: japanese laid-open patent publication No. 9-278907

Patent document 4: japanese patent No. 5454903

Patent document 5: japanese patent No. 5189427

Disclosure of Invention

Problems to be solved by the invention

However, the production method disclosed in patent document 1 is a method for improving the adhesion to the base material because it is used under conditions of no lubrication and low surface pressure, and is difficult to apply to lubricating oil required for the sliding surfaces of various devices under conditions of high sliding speed and high surface pressure.

The fluororesin coating described in patent document 2 aims to achieve strong adhesion between a crosslinking reaction of the fluororesin and a chemical reaction between the fluororesin and the surface of the substrate by causing the crosslinking reaction and the chemical reaction to occur simultaneously; in the case of an iron base material such as a rolling bearing or a cage, it is difficult for a chemical reaction to occur with the surface of the base material, and there is a problem that a strong adhesion cannot be achieved.

The sliding member described in patent document 3 relates to a sliding member that is used for a non-lubricated bearing, a dynamic seal, or the like, is not in the shape of a film, and is made of a fluororesin. Therefore, the properties as a coating material are not clear, and it is difficult to apply the coating material to a rolling bearing application requiring a lubricating oil, a high sliding speed, and a high surface pressure.

The coating film described in patent document 4 is also, similarly to the coating film produced by the method described in patent document 1, unknown as to whether it can be used under a holder test piece, high surface pressure, high sliding speed, and oil lubrication, for evaluation of a flat plate test piece, low surface pressure, low sliding speed, and no lubrication.

In the silver-plated retainer described in patent document 5, a retainer with less change in wear amount of the sliding surface with time is required, and a sliding material instead of silver plating is required. In addition, silver plating has a problem of vulcanization due to sulfur components contained in engine oil. If silver plating and vulcanization are applied to the surface of the retainer, peeling and falling off occur from the retainer, and the base of the retainer is exposed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a sliding member, a rolling bearing, and a cage each having a sliding surface excellent in sliding properties even under conditions of high sliding speed and high surface pressure in a lubricating oil.

Means for solving the problems

The sliding member of the present invention is a sliding member used in an oil-lubricated environment and having a sliding layer formed on an iron-based metal base material. The sliding layer is characterized in that the surface of the iron-based metal base material is provided with a base layer containing a heat-resistant resin and a first fluororesin, the surface of the base layer is provided with a second fluororesin layer, the heat-resistant resin is a resin containing carbon atoms in at least a main chain of a polymer structure and further containing at least 1 atom of oxygen atoms, nitrogen atoms and sulfur atoms, and the second fluororesin layer is a crosslinked fluororesin layer crosslinking at least the vicinity of the surface of the sliding layer. The vicinity in the present invention means a layer having a distance of less than 2.5 μm from the target surface.

In the sliding member according to the present invention, the iron-based metal base material, the foundation layer, and the second fluorine resin layer are closely adhered to each other without providing an adhesive layer. Further, the sliding layer is characterized in that the crosslinking ratio of the first and second fluorine resins is reduced from the surface layer of the second fluorine resin layer to the surface of the iron-based metal base material.

Wherein the second fluorine resin is a polytetrafluoroethylene resin, and the second fluorine resin is a solid resin as compared with an uncrosslinked polytetrafluoroethylene resin¹⁹The chemical shift value (. delta.ppm) appearing in the Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) chart showed that at least 1 chemical shift value selected from-68 ppm, -70ppm, -77ppm, -80ppm, -109ppm, -112ppm, -152ppm and-186 ppm was observed in addition to-82 ppm, -122ppm and-126 ppm of the above-mentioned uncrosslinked polytetrafluoroethylene resin, or the signal intensity as a signal of the chemical shift value appearing at-82 ppm was increased as compared with that of the above-mentioned uncrosslinked polytetrafluoroethylene resin.

The heat-resistant resin is at least 1 aromatic resin selected from the group consisting of aromatic amide imide resins and aromatic imide resins, and the sliding layer has a layer thickness of 5 μm or more and less than 40 μm.

The iron-based metal cage of the present invention is a cage for holding rolling elements of a rolling bearing, and is characterized in that the iron-based metal cage is formed of the sliding member of the present invention.

The sliding layer forming the surface of the iron-based metal retainer is characterized in that the indentation hardness of the sliding layer after irradiation with radiation, as measured by ISO14577, is 58 to 82 MPa.

The other sliding layer forming the surface of the iron-based metal holder is characterized in that the melting point of the second fluorine resin after irradiation with radiation at least in the vicinity of the surface is 285 to 317 ℃.

The rolling bearing of the present invention is a rolling bearing using the iron-based metal retainer of the present invention, and is particularly a rolling bearing for a connecting rod large end portion, a rolling bearing for a connecting rod small end portion, or a rolling bearing for a crankshaft support shaft of an engine.

ADVANTAGEOUS EFFECTS OF INVENTION

The sliding member of the present invention has a sliding layer formed on an iron-based metal base material, the sliding layer being composed of a base layer and a fluororesin layer, at least the vicinity of the surface of the fluororesin layer being crosslinked, and is capable of suppressing wear even under conditions of high sliding speed and high surface pressure in a lubricating oil, and of maintaining the life of a sliding part and a bearing for a long period of time. The iron-based metal retainer formed of the sliding member exhibits sliding properties equal to or higher than those of a retainer having a silver plated layer. Further, the rolling bearing using the iron-based metal cage is excellent in sliding property in lubricating oil as a rolling bearing for a connecting rod used in lubricating oil.

Drawings

Fig. 1 is a sectional view of a slide member.

FIG. 2 is an enlarged view of an NMR chart of Experimental example 1.

FIG. 3 is an enlarged view of an NMR chart of Experimental example 2.

FIG. 4 is an enlarged view of an NMR chart of Experimental example 3.

FIG. 5 is a normalized signal intensity ratio of-82 ppm associated with crosslinking.

Fig. 6 is a graph showing a relationship between indentation hardness and irradiation dose.

FIG. 7 is a graph showing the relationship between the melting point and the dose of radiation.

Fig. 8 is a perspective view of a rolling bearing cage having needle rollers as rolling elements.

Fig. 9 is a perspective view showing the needle roller bearing.

Fig. 10 is a longitudinal sectional view of the 4-cycle engine.

Fig. 11 is a diagram showing an outline of the wear level testing apparatus.

Detailed Description

The sliding member of the present invention has a sliding layer formed on an iron-based metal base material. The sliding layer is composed of a base layer and a crosslinked fluororesin layer formed on the surface of the base layer and crosslinked in the vicinity of the surface layer.

Examples of the iron-based metal base material include bearing steel used for a rolling bearing and the like, carburized steel, carbon steel for machine structural use, cold rolled steel, hot rolled steel, and the like. The ferrous metal base material is adjusted to a predetermined surface hardness by quenching and tempering after being processed into the shape of the sliding member. For example, in the case of an iron-based metal cage using chromium molybdenum steel (SCM415), an iron-based metal base material having an Hv value adjusted to 484 to 595 is preferably used.

Fig. 1 shows a cross-sectional view of a sliding member according to the present invention. The sliding layer 2 constituting the sliding member 1 is composed of a base layer 4 formed on the surface of the iron-based metal base material 3 and a second fluorine resin layer 5 formed on the surface of the base layer 4. The underlayer 4 is formed on the surface of the ferrous metal substrate 3 and is a mixed resin layer of a heat-resistant resin indicated by a white circle in the drawing and a first fluororesin also indicated by a black circle in the drawing. The fluororesin contained in the second fluororesin layer 5 is a crosslinked fluororesin layer obtained by crosslinking at least the vicinity of the surface of the sliding layer. The second fluorine resin of the sliding layer 2 present in the surface layer and the layer in the vicinity thereof has a three-dimensional structure. The first fluororesin contained in the second fluororesin layer 5 and the underlayer 4 can be an inclined material in which the crosslinking ratio decreases from the surface to the surface of the ferrous metal substrate 3.

In the present invention, the fluororesin layer is not limited to the fluororesin layer in which the fluororesin layer is formed by a single layer or a plurality of layers, and the fluororesin layer may be formed by a single layer or a plurality of layers.

Cross-linking the layer thickness t of the fluororesin layer 5₁In terms of the layer thickness t relative to the base layer 4₂The total thickness of (a), i.e., the thickness t of the sliding layer, is 10 to 90%, preferably 25 to 75%.

The layer thickness t of the sliding layer 2 is 5 μm or more and less than 40 μm, preferably 15 μm or more and less than 30 μm. If the layer thickness is less than 5 μm, the metal base material may be exposed by peeling due to poor adhesion of the coating film and abrasion due to initial abrasion. If the thickness is 40 μm or more, cracks may be generated during film formation, and the film may be peeled off during operation, thereby deteriorating the lubrication state. By setting the layer thickness to a range of 5 μm or more and less than 40 μm, exposure of the metal base material due to initial abrasion can be prevented, and peeling during operation can be prevented for a long period of time.

The heat-resistant resin is a resin containing carbon atoms in at least the main chain of the polymer structure and further containing at least 1 atom of oxygen atoms, nitrogen atoms, and sulfur atoms. The resin is not thermally decomposed when the sliding layer is formed by firing. Here, the term "not thermally decomposed" means a resin that does not start to thermally decompose at the temperature and time of firing the underlying layer and the overlying layer. The resin containing carbon atoms in the main chain of the polymer structure and at least 1 atom of oxygen atoms, nitrogen atoms, and sulfur atoms can have a functional group that has excellent adhesion to the iron-based metal substrate and a functional group that also reacts with the first fluororesin in the main chain or at an end of the molecule.

Examples of the heat-resistant resin include epoxy resins, polyester resins, amide imide resins, ether imide resins, imidazole resins, polyether sulfone resins, polysulfone resins, polyether ether ketone resins, and silicone resins. In addition, urethane resin and acrylic resin which prevent shrinkage when a coating film is formed from the fluororesin can be used in combination.

Among the heat-resistant resins, a resin mainly containing an aromatic ring is preferable because of excellent heat resistance. Preferred examples of the heat-resistant resin include aromatic amide imide resins and aromatic imide resins.

The first fluororesin may be any resin that can be dispersed in the form of particles in the aqueous coating solution for forming the undercoat layer. As the first fluororesin, PTFE particles, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA) particles, tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP) particles, or 2 or more of them can be preferably used.

The aqueous coating liquid for forming the undercoat layer may contain, in addition to the heat-resistant resin and the first fluororesin, a nonionic surfactant such as polyoxyethylene alkyl ether, an inorganic pigment such as carbon black, an aprotic polar solvent such as N-methyl-2-pyrrolidone optionally mixed in water, and water as a main solvent. In addition, defoaming agent, drying agent, thickener, leveling agent, anti-shrinking agent (ハジキ prevented), etc. can be added. Examples of the aqueous coating liquid for forming the undercoat layer include EK series and ED series primer coating liquids manufactured by Dajin industries, Ltd.

In addition, instead of the aqueous coating solution, a solution-type coating solution in which a fluororesin is dissolved in a resin solution in which the heat-resistant resin is dissolved in an aprotic polar solvent, or a dispersion-type coating solution in which fine particles of the fluororesin are dispersed may be used.

The second fluorine resin layer is a layer of a fluorine resin that is formed on the surface of the underlayer and can be crosslinked by radiation. The first fluororesin and the second fluororesin may be the same or different, but the same fluororesin is preferably used. Examples of the second fluorine resin include PTFE, PFA, FEP, and ethylene-tetrafluoroethylene copolymer (ETFE). These resins can be used alone or as a mixture. Among these, PTFE excellent in heat resistance and sliding property is preferable.

The second fluororesin layer is obtained by coating and drying an aqueous dispersion in which PTFE resin particles are dispersed. Examples of the aqueous dispersion in which the PTFE resin particles are dispersed include teflon ═ PTFE enamel manufactured by dacian industries, ltd.

In the sliding member of the present invention, the iron-based metal base material, the foundation layer, and the second fluorine resin layer are in intimate contact with each other without providing an adhesive layer. A method for forming a sliding layer on the surface of an iron-based metal base material to be in close contact with each other will be described below.

(1) Surface treatment of ferrous metal material

For the iron-based metal substrate, it is preferable that: the surface roughness (Ra) of the metal base material is adjusted to 1.0 to 2.0 μm by sand blasting or the like before the sliding layer is formed, and then the metal base material is immersed in an organic solvent such as petroleum volatile oil and subjected to ultrasonic degreasing for about 5 minutes to 1 hour.

(2) Coating of aqueous coating liquid for forming underlayer

Before the aqueous coating liquid for forming the undercoat layer is applied, the aqueous dispersion is re-dispersed by rotating it for 1 hour at 40rpm, for example, using a ball mill in order to improve the dispersibility of the aqueous dispersion. The redispersed aqueous coating solution was filtered using a 100-mesh wire gauze and coated by a spray coating method.

(3) Drying of aqueous coating liquid for forming underlayer

The aqueous coating liquid is applied and then dried. The drying conditions are preferably drying in a thermostatic bath at 90 ℃ for about 30 minutes, for example. The layer thickness of the dried base layer is in the range of 2.5 to 20 μm, preferably 5 to 20 μm, and more preferably 10 to 15 μm. If the thickness is 2.5 μm or less, the metal base material may be exposed by peeling or initial abrasion due to poor adhesion of the coating film. If the thickness is 20 μm or more, cracks may be generated during film formation, and the film may be peeled off during operation, thereby deteriorating the lubrication state. By setting the layer thickness to be in the range of 2.5 to 20 μm, exposure of the metal base material due to initial abrasion can be prevented, and peeling during operation can be prevented for a long period of time.

(4) Application of aqueous coating solution for forming second fluorine resin layer

Before the aqueous coating liquid for forming the second fluorine resin layer is applied, the aqueous dispersion is re-dispersed by rotating the aqueous dispersion for 1 hour at 40rpm, for example, using a ball mill in order to improve the dispersibility of the aqueous dispersion. The redispersed aqueous coating solution was filtered using a 100-mesh wire gauze on the surface of the base layer dried without firing the base layer, and was coated by a spray coating method.

(5) Drying of aqueous coating liquid for forming second fluorine resin layer

The aqueous coating liquid is applied and then dried. The drying conditions are preferably drying in a thermostatic bath at 90 ℃ for about 30 minutes, for example. The thickness of the dried second fluorine resin layer is 2.5 to 20 μm, preferably 5 to 20 μm, and more preferably 10 to 15 μm. If the thickness is 2.5 μm or less, the metal base material may be exposed by peeling due to poor adhesion of the coating film and abrasion due to initial abrasion. If the thickness is 20 μm or more, cracks may be generated at the time of film formation, and the film may be peeled off during operation, thereby deteriorating the lubrication state. By setting the layer thickness to be in the range of 2.5 to 20 μm, exposure of the metal base material due to initial abrasion can be prevented, and peeling during operation can be prevented for a long period of time.

As the coating method of the underlayer and the second fluorine resin layer, in addition to the spray coating method, any coating method capable of forming a coating film, such as a dipping method and a brush coating method, can be used. The spray coating method is preferable in view of uniformity of the layer thickness by minimizing the surface roughness and coating shape of the coating film as much as possible.

(6) Firing into

After drying the second fluorine resin layer, the base layer and the second fluorine resin layer are simultaneously fired in a heating furnace in air at a temperature of the melting point of the second fluorine resin or higher, preferably in the range of (melting point (Tm) +30 ℃) to (melting point (Tm) +100 ℃) for 5 to 40 minutes. When the first and second fluorine resins are PTFE, they are preferably fired in a heating furnace at 380 ℃ for 30 minutes. The first and second fluorine resins are not coated and dried and then fired, but both are fired simultaneously, whereby the base layer and the second fluorine resin layer can be adhered to each other without providing an adhesive layer.

(7) Crosslinking of the second fluororesin layer

The fired film is irradiated with radiation at an irradiation temperature of from 30 ℃ lower than the melting point of the second fluororesin layer to 50 ℃ higher than the melting point thereof or lower, preferably from 20 ℃ lower than the melting point of the second fluororesin layer to 30 ℃ higher than the melting point thereof, and with an irradiation dose of 250kGy to 800kGy, preferably more than 250kGy and 750kGy, to crosslink the fluororesin layer, and as the radiation, there can be used particle rays such as α rays (particle rays of helium-4 nuclei emitted from radioactive seeds undergoing α decay), β rays (negative electrons and positive electrons emitted from nuclei), electron beams (electron beams having a substantially constant kinetic energy and accelerated in vacuum), gamma rays (electromagnetic waves of waves emitted and absorbed by nuclei, elementary particles, inter-stage transitions, pairs of elementary particles, annihilation of elementary particles, generation, and the like), and the like.

If the irradiation temperature is outside the temperature range of 30 ℃ lower than the melting point of the second fluororesin layer to 50 ℃ higher than the melting point, the crosslinking of the fluororesin layer does not proceed sufficiently. The increase in hardness of the fluororesin layer does not proceed sufficiently. In addition, in the irradiation atmosphere, in order to effectively perform crosslinking, it is necessary to reduce the oxygen concentration in the irradiation region by evacuation or injection of an inert gas. The oxygen concentration is preferably in the range of 0 to 300 ppm. In order to maintain the oxygen concentration in the above concentration range, an inert atmosphere injected with nitrogen gas is preferred from the viewpoints of operability and cost.

If the dose of the irradiation is less than 250kGy, the crosslinking becomes insufficient, the amount of abrasion becomes large, and the metal substrate may be exposed. Further, if the dose of irradiation exceeds 800kGy, crosslinking proceeds excessively, and the hardness of the film increases, so that the film may become brittle and may be easily damaged by peeling or the like.

The surface hardness of the sliding layer, which is indicated by indentation hardness, can be set to 58 to 82MPa by crosslinking the fluororesin layer by irradiating the fluororesin layer with radiation at an irradiation dose of 250 to 800kGy in a temperature range from a temperature lower by 30 ℃ than the melting point of the second fluororesin layer to a temperature higher by 50 ℃ than the melting point. In addition, the surface of the sliding layer can be made to have a low melting point of 285 to 317 ℃.

The acceleration voltage at the time of irradiation is 40kV or more and less than 500kV, preferably 40kV or more and 300kV or less, and more preferably 50kV or more and less than 100 kV. When the voltage is less than 40kV, the penetration of electron beams into the vicinity of the surface layer of the second fluorine resin layer becomes shallow, and when the voltage is 500kV or more, the first and second fluorine resin layers are entirely crosslinked. Since the radiation intensity is attenuated in the fluororesin if the fluororesin layer is irradiated with the radiation, the radiation sufficiently reaches the vicinity of the surface irradiated with the radiation without reaching the other surface, and the vicinity of the surface of the second fluororesin layer can be crosslinked.

Further, by setting the acceleration voltage at the time of irradiation to 40kV or more and less than 500kV and irradiating an electron beam in an inert atmosphere in which nitrogen gas is injected, it is possible to increase the irradiation dose of the surface of the sliding member to which the electron beam is irradiated in the vertical direction with respect to the irradiation surface and to irradiate the electron beam to a surface parallel to the irradiation direction of the electron beam adjacent to the surface of the sliding member by scattering of the electron beam. The irradiation of the electron beam to the parallel surface decreases as the irradiation distance becomes longer. For example, the irradiation dose of the portion of the plane parallel to the beam irradiation window close to the beam irradiation window may be changed to 500kGy or 300kGy as the irradiation dose is increased to 750 kGy.

In order to evaluate the wear resistance of the sliding layer obtained by the above-described method in the lubrication-free and oil lubrication, the specific wear amount and the friction coefficient were measured by the サバン type frictional wear test. Test conditions of the test piece and the mating material (counter material) are shown below.

(1) Production of test piece

Test piece: a sliding layer was formed on a flat metal plate made of SPCC and having a thickness of 30mm × 30mm and a thickness of 2 mm. A primer coating (type: EK-1909S21R) made by Daiku corporation was used for the base layer, and a topcoat coating (type: EK-3700C21R) made by Daiku corporation was used for the second fluorine resin layer. In terms of drying time, each was dried in a thermostatic bath at 90 ℃ for 30 minutes, and the base layer and the second fluorine resin layer were simultaneously fired in a heating furnace at 380 ℃ for 30 minutes.

Then, the test piece was irradiated with an electron beam from the sliding layer surface side under the following conditions.

The using device comprises the following steps: EB engine made by Kobuska Kobushiki ホトニクス K.K

Irradiation dose: 0kGy for Experimental example 1 (non-irradiated), 500kGy for Experimental example 2, and 1000kGy for Experimental example 3

Acceleration voltage: 70kV

Coating temperature at irradiation: 340 deg.C

Atmosphere in chamber at irradiation: heating nitrogen

(2) Test piece coating film of experimental example

Experimental example 1: PTFE coating (dose of irradiation: 0kGy, layer thickness: 20 μm)

Experimental example 2: PTFE coating (dose of radiation: 500kGy, layer thickness: 20 μm)

Experimental example 3: PTFE coating (dose of radiation: 1000kGy, layer thickness: 20 μm)

(3) Conditions for model サバン Friction wear test

Matching materials: SUJ2 quenched and tempered ring having a diameter of 40mm, a width of 10mm and a minor curvature R60mm

Lubricating oil: 2 levels of no lubrication and モービルベロシティオイル No.3(VG2) lubrication

Sliding speed: 0.05m/s

Loading: 50N

Sliding time: the lubrication of example 1 was 600 minutes, the non-lubrication of example 1 was 5 minutes, the lubrication of example 2 was 600 minutes, and the non-lubrication of example 2 was 60 minutes (4) as a result of the test

The test results are shown in table 1. The specific wear amount is a value obtained by dividing a wear volume by a sliding distance and a load, and the wear volume is calculated from a minor diameter of a formed wear mark and a shape size (φ 40mm and R60mm) of a mating material. Table 1 shows the specific wear amount and the friction coefficient of experimental example 2, where the specific wear amount and the friction coefficient of experimental example 1 were 1.000.

[ Table 1]

Next, the sliding member used in the present invention will be described as having a crosslinked structure in the vicinity of the surface layer of the second fluororesin layer. In general, fluorine-based resins, particularly polytetrafluoroethylene resins, are chemically very stable and are also very stable against organic solvents and the like, and thus it is difficult to identify molecular structures, molecular weights and the like. However, by using¹⁹Measurement and analysis by Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) method (high-speed magic angle nuclear magnetic resonance) can identify the crosslinked structure of the sliding member of the present invention.

For the measurement, an NMR apparatus JNM-ECX400 manufactured by Nippon electronic Co., Ltd was used, and an appropriate measurement seed was used (¹⁹F) Resonance frequency (376.2MHz), MAS (magic angle spinning) rotation speed (15 and 12kHz), sample size (at 4 m)m about 70 μ L in a solid NMR tube), a waiting time (10 seconds), and a measurement temperature (about 24 ℃). The results are shown in fig. 2 to 5. FIG. 2 shows NMR of the surface layer of Experimental example 1, and FIG. 3 shows an enlarged view of the NMR chart of Experimental example 2. In addition, NMR of the surface layer of experimental example 3 is shown in fig. 4. In fig. 2 to 4, the upper stage shows the MAS rotation speed of 15kHz, and the lower stage shows the MAS rotation speed of 12 kHz. FIG. 5 is a graph obtained by normalizing the signal intensity at-82 ppm, which increases in intensity with crosslinking, to the signal intensity at-122 ppm, which is the main signal. In fig. 5, the upper stage represents measurement values, and the lower stage represents a graph. It is considered that the higher the signal intensity ratio, the more crosslinking occurs.

When the second fluorine resin layer (Experimental example 1, 0kGy) which was not irradiated with radiation was measured under the above conditions, signals of-82 ppm, -122ppm, and-162 ppm were observed at a MAS rotation speed of 15kHz (upper part of FIG. 2). In addition, at a MAS rotation speed of 12kHz, signals of-58 ppm, -82ppm, -90ppm, -122ppm, -154ppm and-186 ppm were similarly observed (the lower part of FIG. 2). As is known, 122ppm is-CF₂-CF₂Signal of F atom in bond, -82ppm is-CF₂-CF₃In a bond of-CF₃The signal of F atom(s). Thus, it can be seen that: signals at MAS rotation rate of 15kHz of-82 ppm and-162 ppm, and at MAS rotation rate of 12kHz of-58 ppm, -90ppm, -154ppm and-186 ppm are Spin Side Bands (SSB). In the region of-122 ppm to-130 ppm, a signal which is hidden in-122 ppm and broadened was observed. The signal is-CF which should be observed at-126 ppm₂-CF₃In a bond of-CF₂-signal of the F atom of (a). Therefore, the uncrosslinked second fluorine resin layer which is not irradiated with radiation has a property of being classified as-CF₂-CF₂-122ppm of bonds, assigned to-CF₂-CF₃The NMR chart of the signals at-82 ppm and-126 ppm.

If the solid of the surface layer of the second fluorine resin irradiated with radiation of a radiation dose of 500kGy (Experimental example 2, 500kGy) was measured under the same conditions as those of the uncrosslinked second fluorine resin layer¹⁹F MAS NMR showed that-68 ppm, -70ppm, -80ppm, -82ppm, and,Signals of-109 ppm, -112ppm, -122ppm, -126ppm, -152ppm and-186 ppm (upper part of FIG. 3 and lower part of FIG. 3). The signals of-68 ppm, -70ppm, -80ppm, -109ppm, -112ppm, -152ppm and-186 ppm are newly appeared by irradiation of radiation, and the intensity of the signal of-82 ppm is increased compared with that without irradiation.

If the solid of the surface layer (Experimental example 3, 1000kGy) of the second fluorine resin irradiated with a radiation dose of 1000kGy of radiation was measured under the same conditions as those of the uncrosslinked second fluorine resin layer¹⁹The F MAS NMR showed signals of-68 ppm, -70ppm, -77ppm, -80ppm, -82ppm, -109ppm, -112ppm, -122ppm, -126ppm, -152ppm and-186 ppm except for the spin side band (upper part of FIG. 4 and lower part of FIG. 4). The signals of-68 ppm, -70ppm, -77ppm, -80ppm, -109ppm, -112ppm, -152ppm and-186 ppm are newly appeared by irradiation of radiation, and the signal intensity of the signal of-82 ppm is increased as compared with that upon irradiation of 500 kGy.

In the above signals, if the assigned F atom is underlined, for example, -70ppm is known to be assigned to ═ CF-CF ₃-109ppm belongs to-CF ₂-CF(CF₃)-CF ₂-, -152ppm is attributed to ═ CF-CF-186ppm is attributable to ≡ CF(salt fuels and Ulrich Schelr., branched and Cross-Linking in Radiation-Modified Poly (tetrafluoroethylene): A Solid-State NMRInvestivation. macromolecules, 33, 120-124.2000).

These signals indicate the presence of chemically non-equivalent fluorine atoms, while indicating that the surface layer of the second fluorine resin forms a three-dimensional structure resulting from crosslinking. Further, according to the above-mentioned document, it is known that the intensity of the observed signal is increased by 1000kGy of the irradiation dose as compared with 500kGy of the irradiation dose, and the signal is increased as the irradiation dose increases at least up to 3000kGy of the irradiation dose. It is considered that the structure of the second fluorine resin layer differs depending on the irradiation conditions of the radiation with respect to the signals not described in the above documents, but the signals are represented by ═ CF-CF ₃、-CF ₂-CF(CF₃)-CF ₂-、＝CF-CF＝、≡CFThe presence of these structures indicates that a crosslinked structure is formed.

As shown in fig. 5, the normalized signal intensity ratio increases as the irradiation dose increases. It was found that the crosslinked structure was clearly observed at an irradiation dose of 500 kGy.

The aqueous coating solution for forming the second fluorine resin layer used in the above experimental examples was applied under drying conditions of about 30 minutes in a thermostatic bath at 90 ℃ and then dried, and then baked in a heating furnace at 380 ℃ for 30 minutes in the air to prepare an uncrosslinked fluororesin coating film having a thickness of 4 μm. 5 sheets of the film were laminated in close contact, and electron beam irradiation was performed from one side under the above-described experimental condition 2. After the irradiation, the fluororesin film was separated, and NMR measurement was performed on each film by using NMR apparatus JNM-ECX400 manufactured by japan electronics corporation in accordance with the above experimental example. As a result of the measurement, the film present on the surface opposite to the irradiated surface from the irradiated surface was found to have an inclined structure because the signal intensity was reduced by the cross-linking.

The fluororesin is crosslinked on the surface by irradiation with radiation, and the surface hardness is increased. The surface hardness in experimental examples 1 to 3 was measured. For the surface hardness, the following were used: indentation hardness of the flat test pieces was measured with a nanoindenter (G200) by a method according to ISO 14577. The measurement values represent the average values of the surface roughness and the depth (stable hardness portion) not affected by the base material (SPCC), and 10 portions of each test piece were measured. The measurement conditions were as follows: the indenter had a shape of バーコビッチ type, the depth of indentation was 5mN, the load application rate was 10 mN/min, and the measurement temperature was 25 ℃. The indentation hardness was calculated from the indentation load and the displacement (area). The measurement results are shown in table 2.

[ Table 2]

	Indentation hardness (MPa)
		Experimental example 1	45.4
Experimental example 2	74.8
		Experimental example 3	84.2

The results of table 2 are plotted as fig. 6. In fig. 6(a), the ordinate represents indentation hardness, and the abscissa represents irradiation dose. Since the indentation hardness and the irradiation dose showed a good correlation, indentation hardnesses at 250kGy and 800kGy irradiation doses were calculated from regression lines of both. The results are shown in fig. 6 (b).

As shown in table 2 and fig. 6, by crosslinking the surface of the fluororesin, the surface hardness represented by the indentation hardness increases as the degree of crosslinking increases. In the present invention, the fluororesin layer is made to have a high hardness by irradiating the fluororesin layer with radiation so that the indentation hardness of the coating film becomes 58 to 82MPa, preferably 58.5 to 79.8 MPa. The dose of the irradiation is preferably 250 to 800 kGy. The surface hardness of the sliding layer can be adjusted within the range of the irradiation dose.

As a result of the irradiation, if the indentation hardness is lower than 58MPa, the amount of wear is large, and the metal base material may be exposed. Further, if the indentation hardness is higher than 82MPa, the hardness of the film increases, and therefore the film becomes brittle and film damage such as peeling easily occurs in some cases.

Further, the fluororesin can be crosslinked by irradiation with radiation to lower the melting point. The melting point was measured by a differential scanning calorimeter (エスアイアイ & ナノテクノロジー company, product name "DSC 6220"). The measurement sample was obtained by sealing 10 to 15mg of a fluororesin coating film in a sealed aluminum sample container (hereinafter referred to as "aluminum dish") made by the same companyThe sample (2) was prepared by using a fluororesin coating and the same amount of alumina (Al)₂O₃) The sample was sealed in an aluminum dish. The measurement conditions were measured by raising the temperature from 30 ℃ to 370 ℃ at a rate of 2 ℃/min under a nitrogen flow (200 mL/min) atmosphere, holding the temperature for 20 minutes, and then lowering the temperature from 370 ℃ to 40 ℃ at a rate of 2 ℃/min. The melting point was defined as the melting peak temperature at the peak top of the endothermic peak at the time of temperature rise. The measurement results are shown in table 3.

[ Table 3]

	Melting Point (. degree.C.)
		Experimental example 1	322
Experimental example 2	299
		Experimental example 3	282

The results of table 3 are plotted as fig. 7. In fig. 7(a), the vertical axis represents the melting point and the horizontal axis represents the irradiation dose. Since the melting point and the dose showed a good correlation, the melting point was calculated from the regression line of the both at the doses of 250kGy and 800 kGy. The results are shown in fig. 7 (b).

As shown in table 3 and fig. 7, the surface was crosslinked, and the melting point of the surface decreased as the degree of crosslinking increased. In the present invention, the fired coating is irradiated with radiation so that the temperature of irradiation is 30 ℃ lower than the melting point of the second fluororesin layer before radiation irradiation and 50 ℃ higher than the melting point, and the melting point of the coating is 285 to 317 ℃, preferably 289 to 311 ℃, to lower the melting point of the fluororesin layer. The dose of the irradiation is preferably 250kGy to 800kGy or less. As a result of the irradiation, if the melting point is higher than 317 ℃, the amount of abrasion is large and the metal base material may be exposed. Further, if the melting point is lower than 285 ℃, the hardness of the film increases, and therefore the film becomes brittle and film damage such as peeling easily occurs in some cases.

The iron-based metal base material having the sliding layer is excellent in adhesion between the sliding layer and the iron-based metal base material, and also excellent in wear resistance of the sliding surface in oil, and therefore can be suitably used for a cage made of an iron-based metal material and a rolling bearing having the cage. In particular, it is preferable to use a rolling bearing using needle rollers as rolling elements in oil, that is, a connecting rod large end bearing, a connecting rod small end bearing, or a crankshaft support shaft of an engine.

Fig. 8 shows the structure of the rolling bearing cage having the sliding layer. Fig. 8 is a perspective view of an iron-based metal cage for a rolling bearing in which needle rollers are used as rolling elements.

The retainer 6 is provided with pockets 7 for retaining the needle rollers, and the space between the needle rollers is maintained by a pillar portion 8 located between the pockets and both side ring portions 9 and 10 to which the pillar portion 8 is fixed. Since the column part 8 holds the needle roller, it is bent into a convex fold and a concave fold (mountain fold and valley fold) in the central part of the column part, and is formed into a complicated shape having a flat raised circular in plan view at the joint part with the both side ring parts 9 and 10. The present retainer manufacturing method can employ a method of cutting a ring from a blank material and forming the pocket 7 by press working by punching; a method of pressing a flat plate, cutting the flat plate into an appropriate length, rounding the flat plate into a ring shape, and joining the flat plate by welding. A sliding layer of a fluororesin coating is formed on the surface of the holder 6. The surface portion of the retainer forming the sliding layer is a portion in contact with the lubricating oil or grease, and the sliding layer is preferably formed on the entire surface of the retainer 6 including the surface of the pocket 7 in contact with the needle roller.

Fig. 9 is a perspective view showing a needle roller bearing as an example of the rolling bearing. As shown in fig. 9, the needle roller bearing 11 is composed of a plurality of needle rollers 12, and a retainer 6 that holds the needle rollers 12 at regular intervals or at irregular intervals. In the case of a connecting rod portion bearing of an engine, a shaft such as a crankshaft or a piston pin is directly inserted into the inner diameter side of the retainer 6 without providing a bearing inner ring or a bearing outer ring, and the outer diameter side of the retainer 6 is fitted into a fitting hole of a connecting rod as a housing. Since the needle roller bearing 11 does not have the inner and outer races and uses the needle rollers 12 having a smaller diameter than the long diameter as the rolling elements, it is a small-sized roller bearing as compared with a general rolling bearing having the inner and outer races.

Fig. 10 is a longitudinal sectional view of a 4-cycle engine using the needle roller bearing.

Fig. 10 is a longitudinal sectional view of a 4-cycle engine using a needle roller bearing as an example of the rolling bearing of the present invention. The 4-cycle engine has: an intake stroke in which an intake valve 13a is opened and an exhaust valve 14a is closed to thereby draw an air-fuel mixture in which gasoline and air are mixed into a combustion chamber 15 through an intake pipe 13; a compression stroke for compressing the mixture by closing the suction valve 13a and pushing up the piston 16; an explosion stroke for exploding the compressed air-fuel mixture; and an exhaust stroke in which the exhaust valve 14a is opened to exhaust the exploded combustion gas through the exhaust pipe 14. Further, the method comprises: a piston 16 that performs linear reciprocating motion by combustion in these strokes, a crankshaft 17 that outputs rotational motion, and a connecting rod 18 that connects the piston 16 and the crankshaft 17 and converts the linear reciprocating motion into rotational motion. The crankshaft 17 rotates about a rotation center axis 19, and a balance of rotation is obtained by a balance weight 20.

The link 18 is formed of a link having a large end portion 21 provided below and a small end portion 22 provided above the linear rod. The crankshaft 17 is rotatably supported via a needle roller bearing 11a attached to an engagement hole of the large end portion 21 of the connecting rod 18. The piston pin 23 connecting the piston 16 and the connecting rod 18 is rotatably supported via a needle roller bearing 11b attached to an engagement hole of the small end portion 22 of the connecting rod 18.

By using the needle roller bearing having excellent sliding properties, the durability is excellent even in a 2-cycle engine or a 4-cycle engine which is reduced in size or has high output.

In fig. 9, a needle roller bearing is exemplified as the bearing, but the rolling bearing of the present invention can be used as other cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust self-aligning roller bearings, and the like. In particular, the present invention can be suitably used for a rolling bearing using an iron-based metal cage used in an oil-lubricated environment.

Further, the iron-based metal base material having the sliding layer is excellent in wear resistance even under lubrication with grease composed of a base oil and a thickener, and therefore can be suitably used for an iron-based metal cage and a rolling bearing having the cage. The grease is degraded by temperature rise of the bearing due to heat generation during high-speed rotation and metal wear powder entering due to friction between the rolling elements made of steel and the cage. On the other hand, by providing the sliding layer of the present invention on at least one of the iron-based metal substrates that slide against each other, the amount of increase over time (the amount of incorporation into the grease) of the metal wear debris can be suppressed as compared with the case where iron slides against each other. As a result, deterioration of the grease can be suppressed, and the lubricating life of the grease can be extended.

As an example of the bearing lubricated with grease, a bearing for a main motor of a railway vehicle uses a ball bearing as a bearing on a fixed side in accordance with expansion and contraction in an axial direction of a main shaft due to temperature change, and uses a cylindrical roller bearing capable of responding to expansion and contraction of the main shaft as a bearing on a free side. The ball bearing on the stationary side is, for example, a deep groove ball bearing, and includes a steel ball and iron plate wave-shaped cage. The free-side cylindrical roller bearing includes steel cylindrical rollers and a brass kneading and pulling holder. When these main motor bearings are used under high-temperature and high-speed rotation, grease containing lithium soap and mineral oil, for example, is used as a lubricant.

Since the lubrication life of grease in such a main motor bearing for a railway vehicle is short relative to the rolling fatigue life of the bearing, the grease is currently reloaded (maintained) in a vehicle decomposition inspection performed for each predetermined running distance. In addition, in the current maintenance cycle, deterioration of grease often progresses for the reasons described above. By applying the rolling bearing of the present invention to this bearing, the lubrication life of the grease can be extended, and the maintenance cycle can be extended.

Examples

Examples 1 to 7

A needle roller bearing retainer (substrate surface hardness Hv: 484-595) having a diameter of 44mm and a width of 22mm, which was made of chromium molybdenum steel (SCM415) subjected to quenching and tempering treatment, was prepared, and a PTFE surface sliding layer was coated, dried and fired under the same conditions as in Experimental example 1 using the same coating liquid as used for forming the underlayer and the second fluororesin layer used in the above Experimental example 1. The electron beam irradiation was performed in accordance with experimental example 2 using the electron beam irradiation apparatus used in experimental example 2. The acceleration voltage of the electron beam was 70 kV. The irradiation dose is shown in table 4. Table 4 shows the indentation hardness and the melting point of the surface obtained from the results of fig. 6 and 7.

The surface-treated needle roller bearing cage was evaluated by the following method. Fig. 11 shows an outline of the wear level testing apparatus.

In a state where a concave mating material 24 made of SUJ2, having a quenching and tempering treatment HRC62 and a concave surface roughness of 0.1 to 0.2 μm ra was pressed against a holder 6 attached to a rotating shaft from a vertical direction by a predetermined load 25, the holder 6 was rotated together with the rotating shaft, and the frictional properties of a coating film applied to the surface of the holder 6 were evaluated, and the amount of wear was measured. The measurement conditions were load: 440N, lubricating oil: mineral oil (10W-30), sliding speed: 930.6 m/min, measurement time: for 100 hours. In addition, by visual observationThe adhesion of the PTFE film was evaluated by observing the amount of separation at this time. In terms of the amount of peeling, "large" is a peeling area of the maximum peeled portion of 1mm²In the above case, "small" means that the maximum peeled portion has a peeled area of less than 1mm²The situation (2). The radius of the R-shaped recess is set to be 20 to 55 μm larger than the radius of the retainer. The lubricating oil is used in an amount impregnated to half the height of the retainer. The results are shown in Table 4.

A test piece for lubricant oil immersion was prepared and subjected to a lubricant oil immersion test by the following method. The test conditions, test pieces, measurement methods, and the like are shown in detail below.

The coated 3 square rods were put into a 150 ℃ lubricating oil (poly- α -olefin ルーカント HL-10, Mitsui chemical Co., Ltd.) containing 1 wt% of ZnDTP (LUBRIZOL677A, manufactured by LUBRIZOL Co., Ltd.)]After immersing 2.2g in the lubricating oil for 200 hours, the concentration of the film component eluted from the lubricating oil was measured (eluted amount in ppm). Concentration measurement was performed by fluorescent X-ray measurement [ fluorescent X-ray measurement device: rigaku ZSX100e (リガク company)]And (4) quantifying. For the test piece, 3 mm. times.3 mm. times.20 mm square bars (total surface area 774 mm) made of 3 SCM415 were used²) An electron beam irradiated film was formed in the same manner as in examples 1 to 4. The results are shown in table 4.

Comparative example 1 and comparative example 2

A needle roller bearing holder similar to that of example 1 was obtained, except that the dose of electron beam irradiation was changed to the dose shown in table 4. Evaluation was performed in the same manner as in example 1. The results are shown in table 4.

Comparative example 3

A needle roller bearing holder was obtained in the same manner as in example 1, except that the PTFE film whose surface was not crosslinked was formed without being irradiated with an electron beam. Evaluation was performed in the same manner as in example 1. The results are shown in table 4.

Comparative example 4

A needle roller bearing holder was produced in the same manner as in example 1, except that the thickness of the sliding layer was changed to 40 μm. Since cracks were generated in the firing stage of the sliding film, the electron beam irradiation and the evaluation test were stopped thereafter.

Comparative example 5

No underlayer was formed, and a second fluorine resin layer was directly formed using the same coating liquid and the same conditions as in example 1, and subjected to electron beam irradiation at the irradiation dose shown in table 4. Evaluation was performed in the same manner as in example 1. The results are shown in table 4.

Comparative example 6

The surface of a needle roller bearing holder made of quenched and tempered chromium molybdenum steel (SCM415) having a diameter of 44mm and a width of 22mm was coated with a silver plating. Evaluation was performed in the same manner as in example 1. The results are shown in table 4.

[ Table 4]

1) Peeling occurred in 20 hours, and the test was interrupted

2) A PTFE film having a second fluorine resin directly formed on a substrate without forming an underlayer

3) Since peeling occurred from the vicinity of the substrate, the test was interrupted

Industrial applicability

The present invention can suppress wear even under conditions of high sliding speed and high surface pressure in lubricating oil, and can be used in the field of a cage used in lubricating oil using a cage made of an iron-based metal and a rolling bearing using the cage.

Description of reference numerals

1 sliding member

2 sliding layer

3 iron-based metal base material

4 base layer

5 crosslinked fluororesin layer

6 holder

7 pocket

8 column part

9 ring part

10 ring part

11 needle roller bearing

12 needle-like roller

13 air suction pipe

14 exhaust pipe

15 combustion chamber

16 piston

17 crankshaft

18 connecting rod

19 center axis of rotation

20 balance weight

21 large end

22 small end

23 piston pin

24 concave mating material

25 load

Claims

1. A sliding member used in an oil-lubricated environment and having a sliding layer on the surface of an iron-based metal base material,

the sliding layer has a base layer comprising a heat-resistant resin and a first fluororesin on the surface of the iron-based metal base material, and a second fluororesin layer on the surface of the base layer,

the heat-resistant resin is a resin containing carbon atoms in at least the main chain of the polymer structure and further containing at least 1 atom of oxygen atoms, nitrogen atoms and sulfur atoms,

the second fluororesin layer is a crosslinked fluororesin layer obtained by crosslinking at least the vicinity of the surface of the sliding layer.

2. The sliding member according to claim 1, wherein the iron-based metal base material, the foundation layer, and the second fluorine resin layer are adhered to each other without an adhesive layer.

3. The sliding member according to claim 1 or 2, wherein the sliding layer has a reduced crosslinking ratio of the first fluororesin and the second fluororesin from the surface layer of the second fluororesin layer to the surface of the iron-based metal base material.

4. The sliding member according to claim 1 or 2, wherein said second fluorine resin is a polytetrafluoroethylene resin.

5. The sliding member according to claim 3, wherein said second fluorine resin is a polytetrafluoroethylene resin.

6. The sliding member according to claim 4, wherein a solid is present in the vicinity of the surface layer of said second fluorine resin, as compared with an uncrosslinked polytetrafluoroethylene resin¹⁹The chemical shift value (. delta.ppm) shown in the magic angle spin Nuclear Magnetic Resonance (NMR) chart of F shows, in addition to-82 ppm, -122ppm and-126 ppm of the above-mentioned uncrosslinked polytetrafluoroethylene resin, at least 1 chemical shift value selected from-68 ppm, -70ppm, -77ppm, -80ppm, -109ppm, -112ppm, -152ppm and-186 ppm, or the signal intensity of the chemical shift value shown at-82 ppm is increased as compared with that of the above-mentioned uncrosslinked polytetrafluoroethylene resin.

7. The sliding member according to claim 1, wherein the heat-resistant resin is at least 1 aromatic resin selected from the group consisting of aromatic amide imide resins and aromatic imide resins.

8. The sliding member according to claim 1, wherein a layer thickness of the sliding layer is 5 μm or more and less than 40 μm.

9. An iron-based metal cage for holding rolling elements of a rolling bearing, characterized in that,

the ferrous metal-made retainer is formed of the sliding member according to claim 1, and the sliding layer after irradiation has an indentation hardness of 58 to 82MPa as measured by ISO 14577.

10. An iron-based metal cage for holding rolling elements of a rolling bearing, characterized in that,

the ferrous metal-made retainer is formed of the sliding member according to claim 1, and the melting point of the vicinity of the second fluorine resin surface layer after irradiation is 285 to 317 ℃.

11. A rolling bearing using the iron-based metal-made cage according to claim 9 or 10.

12. The rolling bearing according to claim 11, wherein the rolling bearing is a rolling bearing for a connecting rod large end portion, a rolling bearing for a connecting rod small end portion, or a rolling bearing for a crankshaft support shaft of an engine.