JPH1068419A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing which can surely have wear resistance under severe conditions and improve its life. SOLUTION: A race (outer ring, inner ring) and a rolling body (ball) have hardness of not less than 600HV at 300 deg.C at the surfaces thereof and are constituted by carbides and carbonitride deposited on the surface whose maximum particle size is not more than 5μm. Since the surface hardness is specified at a high temperature of 300 deg.C, the race and the rolling body has surely wear resistance of not less than a predetermined value to improve the life of a bearing. Since the maximum particle size of the carbides and carbonitrides deposited on the surface are not more than 5μm by hardening of the surface, roughness of the surface caused by wear is reduced to improve wear resistance and durability life of the bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing, and more particularly to a rolling bearing which is effective when used in an environment in which lubrication conditions are severe and a large slip occurs between a bearing ring and a rolling element. Things.

[0002]

2. Description of the Related Art Rolling bearings whose main components are raceways (inner and outer rings) and rolling elements are subjected to severe shearing under repeated high stresses under high surface pressure. Need to be secured. In addition to the rolling stress during operation, the bearing repeatedly slips between the bearing ring and the rolling element, thereby causing abrasion. Therefore, it is desired that the bearing has good wear resistance.

[0003] Therefore, usually, high chromium carbon bearing steel is used for the material of the bearing ring and the rolling elements, and quenching / tempering is performed on the bearing steel, or after carburizing the case hardened steel, quenching / tempering is required. Rolling fatigue characteristics and wear resistance have been secured.

However, recently, the use of rolling bearings has been increased in load and speed, and the operating conditions of the bearings have become much more severe than in the past, such as higher temperatures, insufficient oil film formation, and high PV values. Therefore, the wear resistance of the bearing has become unsatisfactory.

In order to cope with such a severe use environment, in the prior art, a raceway and a rolling element contain a large amount of carbide forming elements typified by stainless steel and high-speed materials (SKH material and M50 steel). Using alloy steel, a large amount of carbide is precipitated on the surface to increase the surface hardness and improve wear resistance.

[0006]

However, when high-carbon bearing steel (SUJ2) or carburized ordinary case hardened steel is used as the material for the bearing, the wear is extremely rapid under the severe conditions as described above. There is a problem that the life is short and the life is short.

Further, in order to improve wear resistance, the use of the above-mentioned high alloy steel (stainless steel or high-speed steel material) makes it possible to use a conventional high-carbon bearing steel (SUJ).
Abrasion resistance is improved as compared with the case of using normal case hardened steel subjected to 2) or carburizing.

However, in a more severe environment, even in a bearing using the above-mentioned conventional high alloy steel as a material, an enlarged photograph of the raceway surface of the raceway ring and the raceway surface of the rolling element is shown in FIG. As shown in a), band-like wear occurs (a part blackened up and down in the photograph is a band-like wear part), that is, a running trace on the raceway surface between the bearing ring and the rolling element. Is constant and wear occurs locally, deteriorating vibration and acoustic characteristics, and further, there is a problem that surface damage such as peeling may occur and the bearing may be damaged.

This is because, as described later, there is no correlation between the surface hardness at room temperature and the wear resistance. Therefore, even if the surface hardness at room temperature is increased, the wear resistance is not necessarily improved. This is one of the causes (see Fig. 3).

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a rolling bearing capable of reliably ensuring wear resistance under severe conditions and improving the life of the bearing. .

[0011]

In order to solve the above-mentioned problems, a rolling bearing according to the present invention is characterized in that at least one of a bearing ring and a rolling element is made of steel in which at least one of carbide and carbonitride is precipitated on a surface layer portion. In the rolling bearing, at least one finished surface of the bearing ring and the rolling element made of the steel has a hardness of HV600 or more and 700 or less at 300 ° C., and has a maximum particle size of the carbide and carbonitride. 5 μm
It is characterized as follows.

In the present invention, since the surface hardness at 300 ° C. is HV600 or more based on the high correlation between the surface hardness at high temperature and the wear resistance as described later, the wear resistance is surely improved. It becomes an excellent bearing part. Further, the hardness of the surface is increased by precipitating carbides and carbonitrides, and the maximum grain size is set to 5 μm or less, thereby suppressing the deterioration of the surface roughness.

Here, HV 600 or more at 300 ° C. and 7
The reason for limiting the surface hardness to 00 or less will be described.
It is generally thought that increasing the surface hardness (hardness at room temperature) improves wear resistance. However, experiments have shown that there is little correlation between surface hardness at room temperature and wear resistance. No relationship was seen. For example, if the surface hardness at room temperature is H
In the range of high hardness steel materials of V700 to 850, the wear resistance does not necessarily depend on the surface hardness at room temperature (see FIG. 3).

On the other hand, those which show high values of surface hardness at high temperature by experiments show a tendency to be excellent in abrasion resistance. Confirms that there is a high correlation, and 300
Since those having a surface hardness of HV600 or more at ° C exhibited good wear resistance, the surface hardness was limited to HV600 or more at 300 ° C (see FIGS. 4 to 6).

Incidentally, for example, 400 ° C. higher than 300 ° C.
Although it is possible to limit the surface hardness by the above, the content of the present invention is included if the surface hardness converted into 300 ° C. is within the range of the present invention.

The hardness at 300 ° C. may be any value as long as it is HV600 or more, but it is necessary to add a large amount of carbide-forming elements to increase the hardness. Based on this, 30
The upper limit of the surface hardness at 0 ° C. is HV700.

The reason that there was a high correlation between the wear characteristics in a room temperature atmosphere and the surface hardness at a high temperature is that the actual contact portions of the actual friction surfaces (the raceway surface and the rolling surface) are considerably hot. Mechanical strength, such as hardness at high temperatures,
It is presumed that this greatly affects the amount of wear.

Next, the maximum particle size of carbide and carbonitride is set to 5
The reason why the thickness is not more than μm will be described. When examining the relationship between the particle size and the surface roughness of carbides and carbonitrides, the larger the particle size, the more the surface roughness deteriorates, causing surface roughness,
Conversely, when the particle size was 5 μm or less, the deterioration of the surface roughness was very small and the state of the surface roughness was mild, so the maximum particle size was set to 5 μm or less (see FIG. 7).

Here, the maximum particle size of the carbide and carbonitride in the surface layer may be adjusted by the surface carbon concentration and surface nitrogen concentration after carburizing and carbonitriding.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings. Outer ring and inner ring (track ring), ball (rolling element) which are bearing parts of the rolling bearing of the present invention.
Each has a surface hardness of 300 属 C or more and an HV of 600 or more, and is composed of the surfaces of the finished products in which the maximum particle size of carbide and carbonitride deposited on the surface layer is 5 m or less. It is not always necessary to deposit both carbide and carbonitride on the surface layer. For example, only carbide may be deposited.

By specifying the surface hardness at a high temperature of 300 ° C., the bearing ring and the rolling elements are surely provided with a predetermined or higher wear resistance, and the life of the bearing is improved. Also,
Since the maximum particle size of carbides and carbonitrides precipitated due to surface hardening is 5 μm or less, surface roughness due to wear is reduced, and in this respect wear resistance is improved, and the durability life of the bearing is improved. Is further improved.

In the above description, all the finished products of the outer ring, the inner ring, and the rolling element are formed based on the present invention. However, the present invention is applied to only one or more of the outer ring, the inner ring, and the rolling element. May be applied.

The finished product having the above characteristics is manufactured by, for example, the following two manufacturing methods. The first manufacturing method uses Si, M, an alloy element having a tempering softening resistance.
The hypothesis of removing steel δ from the surface immediately after carbonitriding a steel containing 0.5% by weight or more of Si, 0.5% by weight or more of Mo, and 1.0% by weight or more of Cr, respectively. Carbonitriding is performed so that the carbon concentration on the surface is 0.8 to 1.0% by weight and the surface nitriding concentration is 0.2 to 1.0% by weight. Thereafter, it is manufactured by quenching and tempering.

That is, in a so-called black scale state immediately after the carbonitriding and before the quenching / tempering treatment, as shown in FIG. 15, a cutting allowance δ for a finished product is left, and The carbon concentration and the nitridation concentration refer to the surface carbon concentration and the surface nitrogen concentration at a place where the depth of the cut-off is entered from the surface of the above-mentioned black scale product. In FIG. 15, 1 indicates black scale, and 2 indicates the finished product surface.

Here, the reason why the content of Si is 0.5% by weight or more is that if it is less than 0.5%, the high-temperature hardness decreases, and
This is because HV 600 or more is not satisfied at 00 ° C. The upper limit of Si is 1.5% by weight. The reason is 1.5
If it exceeds 10% by weight, the surface will not have the specified (0.8% by weight or more) carbon concentration to inhibit carburization,
This is because carburization depth may be insufficient, and so on.

The reason why the content of Mo is set to 0.5% by weight or more is that if it is less than 0.5%, the high-temperature hardness decreases, and
This is because HV 600 or more at 0 ° C. is not satisfied. The upper limit of Mo is 3.0% by weight. The reason is that Mo is an expensive alloy element, and the hardness at a high temperature is not improved even if added in an amount of 3.0% by weight or more.

The reason why the content of Cr is set to 1.0% by weight or more is that if it is less than 1.0%, the high-temperature hardness decreases, and
This is because HV 600 or more is not satisfied at 00 ° C. The upper limit of Cr is set to 8.0% by weight. If added more than this, giant carbides will precipitate.

Further, the carbon concentration on the imaginary surface when removing the allowance δ from the surface immediately after carbonitriding was set to 0.8 to 1.0% by weight. This is because HV 600 or more at 300 ° C. is not satisfied. On the other hand, if it exceeds 1.0% by weight, giant carbides (greater than 5 μm) will precipitate.

Further, the nitrogen concentration on the imaginary surface obtained by removing the allowance δ from the surface immediately after carbonitriding is 0.2 to 1.0% by weight. This is because HV 600 or more at 300 ° C. is not satisfied. On the other hand, if the content exceeds 1.0% by weight, the machinability is significantly impaired.

In a second production method, Cr, Mo, and V, which are carbide-forming elements, are added to a steel material containing 0.7% by weight or less of carbon in an amount of 3.0 to 8.0% by weight, respectively. 3.0
% By weight, V is added in an amount of 0.5% by weight or more, and carburizing is performed so that the surface carbon concentration after carburization is 0.8 to 1.0% by weight, and then quenching is performed. It is manufactured by depositing fine carbides on the surface layer by performing high-temperature tempering.

Here, the definition of the surface carbon concentration is the same as in the first manufacturing method. In addition, when Cr is 3.0 to
If it is less than 3.0% by weight, the hardness at 300 ° C. is HV600 due to insufficient carbide precipitation hardening.
This is because the above is not satisfied. On the other hand, if it exceeds 8.0% by weight, carbides larger than 5 μm are formed at the stage of the raw material.

The reason why Mo is set to 3.0% by weight or more is that if it is less than 3.0% by weight, the hardness at 300 ° C. does not satisfy HV 600 or more due to insufficient carbide precipitation hardening. The upper limit of Mo is 6.0% by weight. Mo is an expensive alloy element, and the hardness at a high temperature is not significantly improved even if it is added in an amount of 6.0% by weight or more.

The reason why V is set to 0.5% by weight or more is as follows.
If the content is less than 0.5% by weight, the hardness at 300 ° C. will not be HV600 or more even if the amounts of Cr and Mo are specified. The upper limit of V is set to 2.0% by weight. The reason for this is that if it is added more than this, the workability is significantly deteriorated in the pre-processing (forging, cutting) step.

The reason why the carbon content of the raw material is set to 0.7% by weight or less is that if the content is more than 0.7% by weight, in the case of a material containing a large amount of Cr, Mo and V, carbides exceeding 5 μm will be generated during melting. It is because it is formed.

The reason for specifying the surface carbon concentration after carburizing and carbonitriding in the second manufacturing method without using the surface carbon concentration after quenching and tempering, which is a finished product, is that the second manufacturing method is used. This method requires high-temperature quenching of, for example, 1000 ° C. or more, so that carbon is diffused during the quenching, and the surface carbon concentration is significantly changed between after carburizing and carbonitriding and after quenching. on the other hand,
The carbides and large carbides of carbonitrides (expressed by the maximum particle size) generated during carburizing or carbonitriding are dominated by the surface carbon concentration during carburizing, and the carbon Less affected by diffusion (not too small). Therefore, in the second production method, the surface carbon concentration after carburizing and carbonitriding is specified.

When comparing the above two manufacturing methods, the first manufacturing method is more preferable. The reason is as follows. In terms of material cost, in the second manufacturing method, tempering resistance is imparted by an expensive alloy element. That is, it is necessary to use a large amount of Mo or V having softening resistance. Also,
This is because, in terms of production, the second production method requires high-temperature quenching at 1000 ° C. or higher, which requires special heat treatment equipment.

Next, the reason why the alloy elements, the surface carbon concentration, and the surface nitrogen concentration in the above two manufacturing methods are defined as described above will be described. When various materials and various heat treatments were performed, the surface hardness at room temperature and the surface hardness at high temperature, and the maximum particle size of carbides and carbonitrides were examined. The results shown in Table 1 below were obtained.

[0038]

[Table 1] Here, the materials A to L relate to the first manufacturing method, and the materials M to X relate to the second manufacturing method. The materials K, L, and X are based on the present invention manufactured according to the above manufacturing method.

The heat treatment methods a to f in Table 1 are shown in FIG.
14 to FIG. That is, heat treatment a: tempering is performed after normal quenching is performed (see FIG. 9).

Heat treatment b: normal quenching (sub-zero treatment)
, Tempering is performed (see FIG. 10). Heat treatment c: normal quenching and tempering are performed after carburizing (see FIG. 11).

Heat treatment d: After carbonitriding, normal quenching and tempering are performed (see FIG. 12). Heat treatment e: After high-temperature quenching (sub-zero treatment), tempering is performed a plurality of times (see FIG. 13).

Heat treatment f: After carburizing, high-temperature quenching (sub-zero treatment) is performed, and tempering is performed a plurality of times (see FIG. 14). The target surface carbon concentration and nitrogen concentration after carburizing / carbonitriding are set to respective values in Table 1.

First, the reasons for limiting the specified values in the first manufacturing method will be described. From the comparative materials A to E in Table 1 above, S
If i is less than the specified value of 0.5% by weight, even if Cr is 1.0% by weight or more of the specified amount and Mo is 0.5% by weight or more of the specified amount, as in Comparative material E, 300% It can be seen that the hardness at ℃ is not higher than HV600. Further, from the comparative material F, the content of Si was 0.5% by weight or more of the specified value and M
It can be seen that even if o is 0.5% by weight or more of the specified amount, if Cr is less than 1.0% by weight of the specified value, the hardness at 300 ° C. does not become HV600 or more. Further, from the comparative material G, the content of Si was 0.5% by weight or more of the specified value and
Is less than 0.5% by weight of the specified value, the hardness at 300 ° C. is HV.
It turns out that it does not become 600 or more.

For these reasons, the amounts of Si, Cr, and Mo added are, as described above, 0.5% by weight or more of Si, 0.5% by weight or more of Mo, and 1.0% by weight or more of Cr. Set to.

Furthermore, even if the above-mentioned amounts of Si, Cr and Mo are respectively specified, the surface carbon concentration on the surface of the finished product is not more than 0.1.
If it is less than 8% by weight, the hardness at 300 ° C. does not satisfy HV600 or more as in Comparative Material I. Further, when the surface carbon concentration on the surface of the finished product is more than 1.0% by weight, the maximum particle diameters of carbides and carbonitrides are larger than 5 μm like the comparative materials D, F and H (see FIG. 8). ). further,
When the surface nitrogen concentration is less than 0.2% by weight, the comparative material J
The hardness at 300 ° C. does not satisfy HV600 or more.

For these reasons, the surface carbon concentration on the finished product surface is 0.8 to 1.0% by weight, and the surface nitriding concentration is 0.1% by weight.
It was set to 2% by weight or more. In Example K and Example L manufactured according to the above-mentioned specified values, the hardness at 300 ° C. satisfies HV600 or more, and the maximum particle size of carbide and carbonitride is 5 μm or less. It can be seen that the first manufacturing method can manufacture a bearing component having a finished product surface according to the present invention.

Next, the reasons for limiting the specified value in the second manufacturing method will be described based on Table 1 above. The reason for specifying the surface carbon concentration of the material before carburizing is that in this production method, a large amount of carbide forming elements is added, so if the carbon concentration of the material is high, carbide with a large particle size can be precipitated at the stage of the material This is because it is very difficult to reduce large carbides precipitated at a stage before carburizing in a later step (such as heat treatment).

From the investigation results in Table 1, when the carbon concentration of the material exceeds 0.7% by weight, the comparative materials M, N,
Like Q and U, it was confirmed that the particle size of the carbide on the surface of the finished product was significantly larger than 5 μm regardless of the amount of Cr affecting the size of the carbide and the surface carbon concentration after carburization. Therefore, the carbon concentration before carburizing was set to 0.7% by weight or less.

Further, from the comparative material Q in Table 1, it can be seen that when Cr is less than the prescribed value of 3.0% by weight, the hardness at 300 ° C. does not become HV600 or more. Further, even if Mo and V are specified amounts as in the comparative materials O and R, particularly the comparative material R, if the Cr is more than 8.0% by weight of the specified amount, the carbon concentration before carburizing and the carbon after carburizing are increased. Even if the concentration is the specified amount,
Carbides having a particle size larger than 5 μm were confirmed on the surface of the finished product. From the comparative material S, Mo was 3.0% by weight of the specified value.
If less, even if Cr and V are the specified amounts respectively,
It can be seen that the hardness at 300 ° C. does not become HV600 or more. From the comparative material T, if V is less than 0.5% by weight of the specified value, even if Cr and Mo are in the specified amounts, 3%
It can be seen that the hardness at 00 ° C. does not become HV600 or more.

For these reasons, as described above, Cr,
The specified amounts of Mo and V were set to Cr: 3.0 to 8.0% by weight, Mo: 3.0% by weight or more, and V: 0.5% by weight or more, respectively.

Even when Cr, Mo, and V are in specified amounts, when the surface carbon concentration after carburizing is less than 0.8% by weight, the hardness at 300 ° C. is HV6 as in Comparative material W.
It does not exceed 00. When the surface carbon concentration after carburization is higher than 1.0% by weight, the maximum diameter of carbides and carbonitrides on the surface of the finished product is much larger than 5 μm as in Comparative material V. (See FIG. 8).

For these reasons, the surface carbon concentration after carburization and before quenching and tempering was set to 0.8 to 1.0% by weight. In Example X manufactured according to the specified values of the above-described second manufacturing method, the hardness at 300 ° C. was HV6.
And the maximum particle size of carbides and carbonitrides is 5 μm or less. According to the first production method,
It can be seen that a bearing component having a finished product surface according to the present invention can be manufactured.

Next, when a wear test was performed on each of the materials A to X shown in Table 1 above, the results shown in Table 2 below were obtained. The abrasion test is a two-cylindrical abrasion test and a high-temperature high-speed thrust type test. The two-cylindrical wear test is a wear test in which the formation of an oil film is severe and the slip is large in an ultra-low speed range. The high-temperature high-speed thrust type test is a wear test in which the formation of an oil film is severe under high temperature and high pressure, and the spin slip is extremely increased by using the high-speed thrust type test.

[0054]

[Table 2] Here, in the two-cylindrical abrasion test, as shown in FIG. 1, a pair of cylindrical test pieces 3 are rotated and driven in a state of being brought into contact with a predetermined load. The specifications of the test conditions are as follows.

Test piece shape: Cylindrical shape having an outer diameter of 30 mmφ and a thickness of 7 mm Test piece roughness: Ra 0.008 to 0.01 μm Driving side rotation speed: 10 rpm Driving side rotation speed: 7 rpm Slip ratio: 30% Lubrication method: Dropping type lubricating oil: spindle oil No. 10 Test temperature: room temperature (20 ° C.) Surface pressure: 120 kgf / mm ² Sliding distance: 3000 m Abrasion investigation: Investigation of the amount of wear after the test (weight) As shown in FIG.
The ball-shaped test piece 5 is brought into contact with the plate-shaped test piece 4 and is rotated at a high speed with a thrust load applied. The specifications of the test conditions are as follows.

Test piece shape Plate: Disk with outer diameter of 60 mmφ and thickness of 6 mm Ball: (3/8) inch Specimen roughness before test Plate: Ra 0.008 to 0.01 μm Ball: Ra 0.006 μm P . C. D: 38.5 mm Rotation speed: 8000 rpm Lubrication system: forced lubrication Lubrication oil: MIL-L-23699D standard compliant oil Test temperature: 150 ° C. Surface pressure: 300 kgf / mm ² Test time: 20 hours Abrasion test: Plate after test Ball shape / roughness measurement, surface observation And as can be seen from the results of the two-cylindrical wear test in Table 2 above, the surface hardness at 300 ° C is HV600.
H, K, L, M, N, P, R, U,
V and X show good wear resistance.

Here, when the relationship between the wear amount as a result of the above-mentioned two-cylinder wear test and the hardness at each temperature is arranged, the results as shown in FIGS. 3 to 6 are obtained. As can be seen from these figures, no clear correlation was obtained between the surface hardness at normal temperature (20 ° C.) and the wear resistance (see FIG. 3). There is a correlation between
See FIG. 6).

That is, the surface hardness at room temperature is HV700-8.
It can be said that in the range of 50 high hardness steel materials, the wear resistance does not always depend on the value of the surface hardness at room temperature. On the other hand, those showing a high value of surface hardness at high temperature show a tendency to have excellent wear resistance,
There is a high correlation between the surface hardness at 0 ° C. or higher and the wear resistance.

Therefore, by evaluating the surface hardness at 300 ° C., the desired wear resistance of the bearing ring and the rolling element can be ensured. FIG. 7 shows the results of the high-temperature and high-speed thrust test shown in Table 2 in relation to the maximum particle size of carbide and carbonitride and the surface roughness after the test. In this test, the surface roughness before the test was set to be substantially constant as described above, the surface roughness was measured after the test, and the one having a large surface roughness after the test was inferior in wear resistance. I judge.

As can be seen from FIG. 7, as the particle size of carbide and carbonitride increases, the surface roughness after the test deteriorates, and material A having a particle size of 5 μm or less of carbide and carbonitride is used. , B, C, E, G, I, J, K, L, T, W, and X, the deterioration of the surface roughness after the test was smaller than that of other materials, and the particle size was set to 5 μm or less. It turns out to be valid.

Here, from the surface observation results after the test, as shown in FIG. 16 (a), those having a large grain size of carbide and carbonitride are roughened, and FIG. As shown, those having a particle size of 5 μm or less were slightly rough. Further, when the surface roughness is enlarged and observed, as shown in FIG. 16 (b) and FIG. 17 (b), fine indentations are continuously generated. It almost coincided with the maximum particle size of carbonitride. Considering from these results, the wear in this test is due to the difference in hardness and Young's modulus of the carbide and carbonitride from the base material (martensite) under severe lubrication conditions and metal contact. Damage to the ball in the case of a plate, the plate in the case of a ball), and the carbides and carbonitrides fall off due to the strong tangential force. This is considered to be due to the formation of biting indentations and damage. When actually observing the surface of the ball 5 after the test,
As shown in the photographs of FIG. 16 and FIG. 17, traces of the carbide falling off are seen.

From the above results, in a use environment in which lubrication is severe and slippage is large, carbides having a large particle size or the like may cause deterioration of surface roughness. Therefore, as described above, the maximum particle size is 5 μm or less. Is desirable.

As described above, when comparing the results of two types of wear tests under different conditions, it can be seen that different material factors affect the wear resistance. The wear resistance when the bearing is actually used is not limited to the use conditions, and it is desired that the wear resistance under both of the above two conditions be good. It can be seen that only the materials K, L and M according to the present invention have excellent wear resistance under both of these two conditions.

[0064]

As described above, the rolling bearing of the present invention has an effect that the wear resistance under severe conditions can be reliably ensured. As a result, the durable life is improved even when used in a severe environment such as oil film formation, such as operation at an extremely low speed or operation in a high temperature environment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a two-cylinder wear test.

FIG. 2 is a schematic diagram for explaining a high-temperature high-speed thrust type test.

FIG. 3 is a diagram showing the relationship between the surface hardness at normal temperature (20 ° C.) and the amount of wear.

FIG. 4 is a diagram showing the relationship between the surface hardness at 200 ° C. and the amount of wear.

FIG. 5 is a diagram showing the relationship between the surface hardness at 300 ° C. and the amount of wear.

FIG. 6 is a diagram showing the relationship between the surface hardness at 400 ° C. and the amount of wear.

FIG. 7 is a graph showing the relationship between the maximum particle size of carbide and carbonitride and the surface roughness after the test.

FIG. 8 is a graph showing the relationship between the surface carbon concentration after carburizing / carbonitriding and the maximum particle size of carbide / carbonitride.

FIG. 9 is a conceptual diagram showing a heat treatment a.

FIG. 10 is a conceptual diagram showing a heat treatment b.

FIG. 11 is a conceptual diagram showing a heat treatment c.

FIG. 12 is a conceptual diagram showing a heat treatment d.

FIG. 13 is a conceptual diagram showing a heat treatment e.

FIG. 14 is a conceptual diagram showing a heat treatment f.

FIG. 15 is a conceptual diagram showing a relationship between a surface of a finished product and a cutting allowance.

FIG. 16 is a photograph showing the metal structure of the ball surface after the wear test when the maximum particle size of the carbide is 12 μm,
(A) is a photograph magnified 100 times, and (b) is a photograph magnified 400 times.

FIG. 17 is a photograph showing the metal structure of the ball surface after the wear test when the maximum particle size of the carbide is 0.9 μm,
(A) is a photograph magnified 100 times, and (b) is a photograph magnified 400 times.

[Explanation of symbols]

 2 Finished product surface 3 ~ 5 Test piece

Claims (1)

[Claims] 1. A rolling bearing in which at least one of a bearing ring and a rolling element is made of steel in which at least one of carbide and carbonitride is precipitated on a surface layer, wherein at least one of the bearing ring and the rolling element made of the steel is completed. A rolling bearing, wherein a surface of the product has a hardness of 300 to HV of HV600 to 700, and a maximum particle size of the carbide and carbonitride is 5 μm or less.