JPH10131970A - Rolling bearing and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing having a good lubricating bearing ring and rolling unit with good corrosion resistance further with generation difficult of oil film break by a uniform nitride layer and a manufacture method of the rolling bearing. SOLUTION: In a rolling bearing 1, a nitride layer N is formed in each surface of a rolling body 3 and a bearing ring 2. Before nitride treatment, an oxide in a surface, substituted for a metal fluoride film by fluoride treatment, is removed. The metal fluoride film prevents generation of the oxide. This surface is applied with nitride treatment. The nitride layer N is formed finely uniformly sufficiently formed in each surface, to hold its smoothness, an oil film break in each part is prevented. In this way, the fine uniform smooth nitride layer N can be stably formed, corrosion resistance is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rolling bearing and a method of manufacturing the same. In particular, it relates to a bearing ring and a rolling element.

[0002]

2. Description of the Related Art Conventionally, rolling bearings are sometimes used after being lubricated with grease. With such lubrication, it is assumed that the oil content of the grease does not spread to the entire bearing and rust occurs in the bearing. In particular, rolling bearings such as water pumps,
In the case where it is used as an accessory of an automobile engine, it preferably has corrosion resistance.

In addition, as a rolling bearing having corrosion resistance, it is known that a surface treatment including a nitriding treatment such as salt bath nitriding and gas nitriding, which is called a so-called tuftride treatment, is applied to a bearing ring or a rolling element (referred to as a so-called tuftride treatment). JP-A-6-341442
Reference). By performing the nitriding treatment, there is also an advantage that the lubricity can be improved. However, as described above, even in a race or a rolling element having improved lubricity by nitriding treatment,
When used in a condition where lubrication conditions are not very good, for example, when lubricated with grease as described above, the oil film may break, and in some cases, seizure may occur between the race and the rolling element. There was fear.

[0004] Further, in a nitride layer formed by a conventional nitridation process,
Since the surface roughness is large and the smoothness is poor, there is also a problem that the rotational vibration and noise of the bearing increase. The following can be considered as causes of the oil film shortage.
That is, the oxide on the surface is removed in the pretreatment before the nitriding treatment. However, not only is it difficult to completely remove the oxide, but also after the removal, oxygen adsorption and oxidization work again, so that the oxide on the surface cannot be completely removed. When a nitriding treatment is performed in this state, the nitrided layer becomes
The portion where the oxide was removed was formed sufficiently, and the portion where the oxide was left was formed insufficiently. As a result, the nitrided layer was uneven and many cracks were formed. On the surface of the insufficient nitrided layer, the smoothness was originally insufficient, cracks were present, and it was difficult for the lubricating oil to be retained on the outermost surface of the nitrided layer, so that the oil film was easily cut and the lubrication was insufficient. Can be

Therefore, the main object of the present invention is to solve the above-mentioned technical problems, to provide a uniform nitrided layer which has good corrosion resistance, hardly causes oil film breakage, and has good lubricity. An object of the present invention is to provide a rolling bearing having a rolling element. Another object of the present invention is to provide a manufacturing method capable of stably manufacturing the above-mentioned rolling bearing.

[0006]

In order to achieve the above object, a rolling bearing according to the first aspect of the present invention is characterized in that at least one surface of a bearing ring and a rolling element made of general bearing steel has an average particle size of nitride. A dense nitride layer having a diameter of 1 μm or less is formed. According to this configuration, the nitride layer can be formed densely, uniformly, and sufficiently on the surface. In the bearing ring or rolling element having such a nitrided layer formed thereon, the oil film does not break, and good lubricity as a rolling bearing can be maintained.

[0007] Examples of the general bearing steel include carburized steel, heat-resistant steel, stainless steel, tool steel, chromium steel, and chromium molybdenum steel in addition to high carbon chromium bearing steel. This rolling bearing can be manufactured, for example, by the following method for manufacturing a rolling bearing according to the second aspect of the present invention.

According to a second aspect of the present invention, there is provided a method for manufacturing a rolling bearing in which a nitrided layer is formed on at least one surface of a bearing ring and a rolling element made of steel for general bearings. The present invention is characterized in that the method further comprises a fluoride treatment for replacing an oxide on at least one surface of the bearing ring and the rolling element with a metal fluoride film. According to this configuration, the activated fluorine atoms used in the fluoridation process remove foreign substances such as processing aids attached to the surface of the base material steel by being destroyed or the like, and purifying the surface. at the same time,
Passive films, such as oxide films on steel surfaces, are replaced by metal fluoride films. By being replaced in this way, the surface of the steel is covered and protected by the metal fluoride film, and the generation of oxide is prevented until the subsequent nitriding treatment, so that the oxide can be surely removed. Therefore, a dense, uniform and sufficient nitride layer can be formed on the surface.

Conventionally, when the nitriding treatment is performed at 480 ° C.
In the temperature range of 700 ° C., Cr, Mn, Si, A
Metal elements such as 1 are easily oxidized. However, in the above-mentioned temperature range, since it is difficult to create an atmosphere for maintaining these metal elements completely neutral or reducing, the metal elements are almost oxidized in the above-mentioned temperature range,
As a result, a grain boundary oxide is formed on the surface of the steel material during the nitriding treatment, and the grain boundary oxide hinders the nitriding treatment. As a result, a nitrided layer could not be stably formed on the surface of the steel material.

On the other hand, according to the present invention, since the oxide can be surely removed, a certain nitrided layer can be stably formed. That is, at the time of the nitriding treatment,
At a temperature of about 0 ° C., a gas having a nitrogen source (eg, NH ₃
By introducing a mixed gas of (gas) and H ₂ gas into the furnace, the metal fluoride film covering and protecting the steel material surface is broken and removed by the H ₂ gas. This allows
A purified and activated metal matrix appears, and N atoms in a nitriding gas (for example, NH ₃ gas) act on the activated metal matrix to quickly permeate and diffuse into the inside to form a deep nitride layer uniformly. . That is, from the surface of steel to the inside, Cr
An ultra-hard compound layer (nitride layer) containing nitrides such as N, Fe ₂ N, Fe ₃ N, and Fe ₄ N is formed uniformly and deeply, followed by a hard N atom diffusion layer. The above compound layer + diffusion layer constitutes a fully nitrided layer. The hardness of the nitrided layer is the same as that of the conventional tufftrided product, and the surface hardness is Vickers hardness 450 HV (test load 50 gf).
Has been maintained.

The fluorine-based gas used in the fluorination treatment of the present invention includes NF ₃ , BF ₃ , CF ₄ , HF, SF ₆ , F
The fluorine source component comprising ₂ alone or a mixture was contained in an inert gas such as N ₂ gas is preferably used.
Among them, NF ₃ is the most excellent in terms of safety, reactivity, controllability, handleability and the like, and is practical. In such a fluorine-based gas, a fluorine source component such as NF ₃ is contained in an amount of 0.05% to 20% (weight basis, the same applies hereinafter) from the viewpoint of the effect.
Is set to the density of Preferred is in the range of 3% to 5%.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a rolling bearing and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, the bearing of the present invention will be described. FIG. 1 is a sectional view of a ball bearing which is a bearing according to the present invention. Please refer to FIG.

The bearing 1 includes a plurality of rolling elements 3 formed in a spherical shape and a cylindrical inner ring 4 for rollingly guiding the rolling elements 3.
And a race 2 composed of an outer race 5. Rolling element 3
Is rotatably held between the inner ring 4 and the outer ring 5,
Rolling guide. A raceway groove for rolling and guiding the rolling element 3 is formed on the outer peripheral surface of the inner race 4 and the inner peripheral surface of the outer race 5. Along the orbital grooves, the rolling elements 3 are held at predetermined intervals by a retainer 6 and arranged in an annular shape. In addition, the rolling elements 3 and the bearing rings 2 are formed of predetermined bearing steel.

The rolling element 3 and the bearing ring 2 of the present invention are
A nitride layer N composed of Fe ₃ N as a main component and a nitride layer N in a state of being densely and uniformly laminated so that the average particle diameter thereof is 1 μm or less is formed by a manufacturing method described later. I have. The nitrided layer N may be formed on any one of the rolling element 3 and the race 2, and the nitrided layer N may be formed on at least a portion where the members contact each other. For example, in the bearing ring 2, the nitrided layer N may be formed only in the bearing groove of the bearing ring 2, may be formed in the above-described bearing groove and other portions, or may be formed in one of the inner ring 4 and the outer ring 5. May be formed on the rolling element 3 alone, or may be formed on both the bearing ring 2 and the rolling element 3.

The bearing 1 is manufactured, for example, as follows. That is, FIG. 2 is a schematic process diagram of the manufacturing method of the present invention. Hereinafter, the manufacturing method according to the present invention will be described with reference to FIG. This manufacturing method includes the rolling element 3 and the race 2
A forming process 11 for forming the shape of each component, a fluoride treatment 12 for replacing an oxide on the surface of each formed component with a metal fluoride film, and a nitriding treatment 13 for forming a nitride layer N. . Thereafter, an assembling step 14 of assembling each of the parts subjected to the nitriding treatment into the bearing 1 is performed.

In the forming step 11, the rolling elements 3 and the race 2
Is processed into a predetermined shape from a predetermined bearing steel. For example, a forging process, a cutting process, or the like is performed to form a molded product having the shape of the rolling elements 3 and the races 2. Fluorination treatment 1
In 2, the molded article to be treated is replaced with nitrogen trifluoride (NF
₃ ) In a mixture of nitrogen or the like, a predetermined fluoride temperature T1, for example, 300 ° C. to 400 ° C., for a predetermined time (10 minutes to 120 ° C.).
Min) hold. As a result, foreign substances and the like on the surface of the molded product are destroyed by activated fluorine atoms used in the fluoridation treatment and removed, and the surface is purified and, at the same time, a passive film such as an oxide film on the steel surface is removed. Is replaced by a metal fluoride film. At this time, since the metal fluoride film formed on the surface is a passive film, it prevents the adsorption and oxidation of oxygen to the surface and prevents the formation of oxide until the next nitriding treatment 13. As a result, the oxide can be reliably removed.

In the nitriding process 13, gas nitriding is performed.
The fluorinated molded article (the surface of which is covered with a metal fluoride film), which is the article to be treated here, has a predetermined reaction gas,
For example in the NH ₃ made from a single piece gas or NH ₃ and a mixed gas consisting of a carbon source (e.g. RX gas), to a predetermined nitriding temperature T2, the predetermined time (0.5 hour to 5 hours) it is maintained.

In the process of raising the temperature from the fluoride temperature T1 to the nitriding temperature T2, the metal fluoride film on the surface of the article to be processed becomes an activated film. As a result, in the nitriding treatment 13, nitrogen quickly penetrates deeply into the metal, and a nitrided layer N is formed. Thereafter, it is cooled for a predetermined time. The article to be processed is kept in the nitrogen gas until the cooling is completed, so that generation of oxide on the surface is prevented.

The nitriding temperature T2 and the holding time in the nitriding process 13 are preferably set to predetermined values according to the depth of the nitride layer N formed in the nitriding process 13. Nitriding temperature T2
If the temperature is 480 ° C. to 700 ° C., a hard nitrided layer can be formed on the surface. Therefore, lubricity can be improved. Further, since the surface of the article to be treated is activated by the fluoridation treatment 12, the nitriding temperature T2 can be made lower than the temperature at which the article to be treated is held when a conventional nitride layer is formed. As the nitriding temperature T2 decreases, the surface of the nitrided layer N tends to be formed more smoothly. In particular, when the nitriding temperature T2 is 480 ° C. to 700 ° C. as described above, the nitrided layer N is formed at this nitriding temperature T2. The surface of the nitrided layer N becomes smoother than the surface of the nitrided layer of a conventionally formed tufted product.
The surface roughness of the nitrided layer N is an untreated product, that is, the roughness of the polished surface (center line average roughness Ra = 0.7 μm to 1.0 μm).
μm, ten-point average roughness Rz = 4.0 μm to 7.0 μm, and maximum height Rmax = 4.5 μm to 7.5 μm). The surface roughness of the conventional tufftrided product is Ra = 1.5 μm to 2.0 μm, Rz = 10.0 μm
m-15.0 μm, Rmax = 14.0 μm-18.0
Since the thickness is μm, the nitrided layer N of the present invention has a smaller surface roughness than that of a conventional tuftride-treated product, and has considerably increased smoothness.

Further, since the nitrided layer N is smooth and dense as described above, and has almost no cracks, it has good lubricating oil retention properties on the outermost surface of the nitrided layer N. Is improved (see the column of Example). Further, in the nitrided layer N, there is no possibility that the friction is increased, so that the oil film is hardly broken and the seizure can be made more difficult. Incidentally, the coefficient of friction in the non-lubricated state is 0.24, which is 0.54 that of the conventional tuftride-treated product.
Is less than half. The test conditions were as follows: a test piece (SUJ2 material having a nitrided layer N formed on the surface) and a ball (SUJ2 material) were measured with an HRIDON abrasion tester.
Load 200gf, speed 100mm / sec, distance 20mm
, And the coefficient of kinetic friction at that time was measured, and the average of the maximum values of the measured values was determined.

In the assembling step 14, the bearing 1 is assembled by the respective components such as the race 2 and the rolling elements 3 on which the nitride layer N is formed. As described above, according to the bearing 1 of the present embodiment,
The following operational effects are obtained. In the bearing ring 2 and the rolling element 3 on which the nitrided layer N is formed, the corrosion resistance is improved.
Even if an oil film is not sufficiently formed on the surface by the lubricant, it is possible to prevent the bearing ring 2 and the rolling elements 3 from rusting. Therefore, it is possible to obtain a rolling bearing that can be suitably used in a situation where lubrication is not sufficient, such as grease lubrication.

Further, as described in detail below, the nitride layer N
In addition to improvement in strength and prevention of wear, there is an advantage that lubricity can be improved. In particular, since the nitrided layer N of the present embodiment is formed uniformly and densely, it has a harder surface and better wear resistance than a conventional nitrided layer having a porous portion.

Further, in the rolling element 3 and the race 2 in which the nitrided layer N is formed, not only the mechanical strength of the steel is improved by the hard nitrided layer N on the surface, but also the inner unnitrided portion of the steel is used. Since the flexibility and toughness are maintained, the impact resistance is provided, and the strength as a rolling element and a bearing ring is further improved. Therefore, in the bearing 1 provided with at least one of the rolling element 3 and the bearing ring 2, even if the rolling element 3 and the bearing ring 2 come into contact with each part and receive an impact during the rotation, the bearing can withstand the impact. Thus, there is no possibility of breakage, and a bearing suitable for practical use can be obtained. In particular, the nitrided layer N formed by the manufacturing method of the present invention has a lower hardness at the center portion of the material as compared with the conventional tufftrided product (see the section of Examples described later), and as a result, the internal flexibility In addition, the toughness can be further improved to withstand impact. The strength of the rolling element 3 and the bearing ring 2 is not the mechanical strength of the material itself obtained by measuring a test piece having a simple shape, but the actual strength of the rolling element 3 and the bearing ring 2. 1 is the strength when used, and is the strength in which flexibility, toughness, impact resistance and the like are added to the strength of the material itself.

In the present embodiment, the nitride layer N is formed on the surface from which the oxide has been reliably removed by the fluoridation treatment 12.
Since it is formed densely, uniformly and uniformly, the lubricating oil can be held on the surface, the oil film does not break, and good lubricity can be maintained. On the other hand, the nitride layer formed by the conventional tuftride treatment is formed on the surface on which the oxide remains, and is not sufficiently formed on the surface on which the oxide remains, so that the nitride layer is an insufficient nitride layer and has a crack. Was present, so that the oil film could break.

In the rolling element 3 and the bearing ring 2 of the present invention,
The effect of improving the lubricity of the nitrided layer itself on the surface can be further improved by forming a dense, uniform and sufficient nitrided layer N, so that the above-mentioned effect can be obtained even in a situation where lubrication is difficult. Can be kept high. Therefore, the nitride layer N may be used in applications where lubrication is difficult to occur, for example, in a two-cycle engine for motorcycles and related equipment.
When a bearing provided with at least one of the bearing ring 2 and the rolling element 3 formed with the above is applied, there is a remarkable effect. by the way,
Even in the case of improving lubricity, when a concave portion serving as an oil reservoir is formed on the surface and the lubricant held in the concave portion improves the lubricity, the effect can be maintained in a situation where lubrication is difficult to be performed. Have difficulty.

The rolling element 3 and the bearing ring 2 of the bearing 1 are formed by using a general bearing steel as a base material and forming a nitrided layer N on the surface of the rolling element 3 and the bearing ring 2 to form an inner base material of the rolling element 3 and the like. nature,
For example, properties excellent in shape workability, economy, strength and the like are obtained, and in addition, properties of the nitrided layer N on the surface of the rolling element 3 and the like, for example, excellent in corrosion resistance, hardness, and seizure resistance. Nature can be obtained. Therefore, it is preferable as a bearing ring or a rolling element for a bearing.

Further, by using a general bearing steel as a base material of the bearing, corrosion resistance can be further improved. Because, in general, bearing steel is a material having a high degree of cleanliness with few impurities such as slag contained in the steel, so that the nitride when a nitride layer is formed on the surface thereof is also uniform. be able to. Therefore, a uniform nitride layer can be formed more densely than a non-uniform nitride layer containing nitride due to impurities, and the corrosion resistance can be improved. In addition, since the bearing steel has a high degree of cleanliness, the surface shape of the rolling elements and the like can be processed with good precision, that is, the surface irregularities before the nitriding treatment can be reduced. As a result, when the nitride layer is formed on the surface, the surface can be formed densely with less unevenness, and therefore, the corrosion resistance can be improved as compared with a non-densified nitride layer having more unevenness.

Further, since there are few surface irregularities, vibration and noise generated when the rolling element passes through the raceway surface can be reduced,
A rolling bearing excellent in silence can be obtained. Also,
By using general bearing steel as the base material of the bearing, the seizure resistance can be further improved for the same reason as described above in which the corrosion resistance can be improved.

In particular, as a general bearing steel capable of improving the corrosion resistance and seizure resistance as described above, a high carbon chromium bearing steel such as SUJ2 can be exemplified, and aluminum, titanium, vanadium and the like which form a stable nitride can be used. Contained steel is preferred.
Further, since the bearing of the present invention is excellent in corrosion resistance and seizure resistance, it is preferably used for an auxiliary device such as a water pump of an automobile engine, for example.

According to the bearing manufacturing method of the present embodiment, the following operation and effect can be obtained. Nitriding treatment 1
Since No. 3 is gas nitriding, there is no concern about environmental pollution such as salt bath nitriding. Further, in the conventional manufacturing method, in the temperature range of 480 ° C. to 700 ° C. during the nitriding treatment, Cr, M
Metal elements such as n, Si, and Al were almost oxidized, and grain boundary oxides were formed on the surface of the steel material. This grain boundary oxide hinders the nitriding treatment, and as a result, a nitrided layer cannot be stably formed on the surface of the steel material. On the other hand, in the present invention, since the oxide can be reliably removed by the fluoridation treatment 12, a constant nitrided layer N can be formed stably. The hardness of the nitrided layer is also the same as that of the conventional tufftrided product, and the surface hardness is maintained at Vickers hardness of 450 HV (see Examples described later).

In addition, since the nitriding treatment 13 is gas nitriding, the reactant gas actively moves around, and the nitrogen molecules are spread all over the surface of the article to be treated, and the nitride layer N
Can be formed uniformly. For example, the nitrided layer N is also formed on the raceway groove, the edge, and the like of the raceway ring 2. Therefore,
The wear resistance of the bearing ring 2 and the rolling elements 3 as a whole is good.

Conventionally, in the case of gas nitriding, heat transfer is slow, and it sometimes takes a long time for the surface of the article to be processed to be sufficiently activated. On the other hand, in the method of the present invention, the metal fluoride film formed on the surface of the article to be treated is sufficiently activated at the nitriding temperature T2, so that the nitrogen quickly penetrates into the metal, and it takes a long time. A sufficient nitride layer N is formed without being applied.

Further, as described above, since the nitriding temperature T2 can be lower than the temperature at which the article to be processed is held during the conventional formation of the nitride layer, the influence of heat such as thermal deformation can be reduced. . In addition, the bearing of the present invention and the method of manufacturing the same may be applied to at least one of the rolling element 3 and the race 2. Further, the rolling element 3 and the bearing ring 2 to which the present invention is applied are not particularly limited as to how the shape is formed. The material is not limited to bearing steel. For example, high carbon chrome bearing steel (SUJ1, S
In addition to UJ2, SUJ3, SUJ4, SUJ5, etc., carburized steel (SAE5120, etc.), heat-resistant steel (M 、 50, etc.), stainless steel (SUS440C, etc.), tool steel (SKH4, etc.)
Etc.), chromium steel, chromium molybdenum steel, etc.

The bearing and the method of manufacturing the same according to the present invention
In addition to the above-described ball bearings, the present invention can be applied to various shapes of rolling elements and bearing rings for various rolling bearings such as cylindrical roller bearings, tapered roller bearings, spherical roller bearings, and needle roller bearings. Further, the bearing of the present invention and the method of manufacturing the same can be applied to a bearing in which the bearing ring 2 is formed integrally with a rotating shaft, a housing, and the like.

In addition, various design changes can be made without changing the gist of the present invention.

[0036]

EXAMPLE A bearing manufactured by the above-described method for manufacturing a bearing of the present invention was analyzed and tested. The results will be described.
As a comparative example, analysis and test of a conventional bearing were similarly performed. The bearing of the comparative example is a bearing which has been subjected to salt bath nitriding by removing the oxide by a conventional method without performing a fluoridation treatment. Note that the bearing is a combination of a bearing ring having a nitrided layer formed thereon and a rolling element having a nitrided layer formed thereon.

Surface Hardness The surface hardness of the bearing ring of the bearing of the example was measured by Vickers hardness. The measurement position is the surface of the portion that forms the raceway groove of the raceway. Average Hardness of Result Example 619 HV (test load 25 gf) Average Hardness 451 HV (test load 50 gf) Average Hardness 370 HV (test load 100 gf) Sectional Hardness The hardness of the bearing ring of the bearing of the example was measured from the surface. The measurement was performed at a plurality of cross-sectional positions at different distances. Similarly, the measurement was performed for the comparative example. The test load of Vickers hardness is
It is 100 gf.

Results FIG. 3 is a graph showing the relationship between the hardness of the bearing race and the distance from the surface. In FIG. 3, an example is shown by a line Ha (─ ○ 比較), a comparative example is shown by a line Hb (、), the hardness is shown by Vickers hardness (HV) on the vertical axis, and the surface is shown by the horizontal axis from the surface. Is shown as the distance (μm).

The nitride layer N of the embodiment has a hardness of about 4 near the surface.
50 HV, which is almost the same as the nitride layer of the comparative example. Further, the nitrided layer N of the embodiment is a portion closer to the inside from the surface,
Hardness is lower than the nitrided layer of the comparative example. This indicates that the nitrided layer N of the example has a two-layer hardness distribution with a hard surface and a soft inside, and that the example has a larger difference in hardness between the surface and the inside than the comparative example.

Therefore, it is considered that the examples have better impact resistance than the comparative examples. Seizure Resistance (A) Next, the results of the seizure resistance test will be described. The life of the above bearing was measured under the following conditions. Here, the life is a time required for the seizure to occur when lubrication is stopped.

As a comparative example, the life of a conventional bearing was measured in the same manner. Test condition applied bearing Deep groove ball bearing (call number 6305) Radial load 200Kgf Revolution 11000rpm Lubrication condition Before rotation, 0.01cc of lubricating oil for two-cycle engine was dropped Test result Product of the present invention Average life 38.5 minutes Comparison Example Average life 18.6 minutes As described above, the bearing of the present invention has a service life approximately twice that of the conventional product even under severe conditions that are almost lubricated.

The life of the bearing with anti-seizure (B) was measured under more severe conditions. Test conditions Radial load 400 kgf Rotation speed 11400 rpm Lubrication conditions Before starting rotation, 0.005 cc of lubricating oil for a two-cycle engine was dropped. Test result Product of the present invention Average life 6.1 minutes Comparative example Average life 3.9 minutes Thus, the present invention The bearing has a service life that is approximately 1.6 times that of the conventional product even under severer conditions.

Note that these tests are acceleration tests in which severe conditions that are not assumed in a normal use state are imposed. Therefore, the bearing of the present invention does not seize in normal use.

[0044]

According to the first aspect of the present invention, there is provided a rolling bearing in which a dense, uniform, and sufficiently formed nitrided layer is formed on at least one surface of a bearing ring and a rolling element. It has good corrosion resistance and can maintain good lubricity without breaking the oil film.

According to the second aspect of the present invention, the oxide on the surface can be surely removed by the fluoridation treatment.
In addition, a uniform and sufficient nitride layer can be formed.
In addition, since the oxide can be reliably removed, a certain nitrided layer can be stably formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bearing according to the present invention.

FIG. 2 is a schematic process diagram of a method for manufacturing a bearing according to the present invention.

FIG. 3 is a graph showing the relationship between the hardness of the bearing of the example and the comparative example and the distance from the surface, wherein the ordinate represents the hardness in Vickers hardness (HV), and the abscissa represents the distance from the surface. (Μm)
, The line Ha shows the case of the embodiment, and the line Hb shows the case of the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bearing 2 Track ring 3 Rolling element 12 Fluorination treatment 13 Nitriding treatment N nitrided layer

Claims (2)

[Claims] An average particle size of nitride is 1 μm on at least one surface of a race and a rolling element made of general bearing steel.
A rolling bearing, wherein the following dense nitride layer is formed. 2. A method for manufacturing a rolling bearing in which a nitrided layer is formed on at least one surface of a raceway ring and a rolling element made of general bearing steel, wherein at least one of the raceway ring and the rolling element is formed before nitriding treatment. A method for manufacturing a rolling bearing, comprising a fluorine treatment for replacing an oxide on the surface with a metal fluoride film.