JPH1122739A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sufficiently increased life at a low cost for a bearing even under a using situation that a moisture content is mixed in a lubricant from an external part and an influence by moisture content concentration in the lubricant is exercised. SOLUTION: A bearing ring material and a rolling element material contain Ni, Cr, and Mo, an Ni content deviation ΔNi obtained by subtracting the Ni content of the bearing ring material from the Ni content of the rolling element material is ΔNi >=+0.2% in wt.%. Further, A Cr content deviation ΔCr and an Mo content deviation ΔMo obtained by subtracting the Cr content and the Mo content of the bearing ring from the Cr content and the Cr content, respectively, of the rolling element material are set to ΔCr<=-0.2% and ΔMo<=-0.2% in wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rolling bearing,
More specifically, the present invention relates to a rolling bearing that is used in a usage environment in which moisture is mixed in a lubricant.

[0002]

2. Description of the Related Art In rolling bearings, it is generally known that if moisture is mixed in a lubricant, its durability is greatly reduced. For example, when 6% of moisture is mixed in a lubricant, It has been reported that the rolling fatigue life of bearings is reduced from several times to about one twentieth compared to the case without water contamination (Kyosaburo Furumura, Shinichi Shirota, Kiyoshi Hirakawa:
"Rolling fatigue from surface and internal origins", NSK
Bearing Journal, No. 636, pp. 1-10, 1977;

[0003] The incorporation of water into a lubricant has a great effect on the life characteristics (durability) of a rolling bearing.
Various techniques for preventing the incorporation of moisture into a lubricant have been studied and developed in the past depending on the application of the rolling bearing.

As a rolling bearing used on the assumption that moisture enters the lubricant, there is, for example, a work roll bearing for a rolling mill made of a steel material.

[0005] Conventionally, the work roll bearing is sealed inside the bearing by mounting a contact rubber seal on a chock (bearing box) having a bearing therein to prevent a large amount of rolling water from entering the chock. Water was prevented from entering the lubricant, but if the contact rubber seal deteriorated or was damaged, water entered the chock, and as a result, water also entered the lubricant inside the bearing. obtain. For this reason, a technology has recently been proposed to avoid the entry of moisture into the lubricant by installing a contact rubber seal inside the bearing (K. YAMAMOTO, M. YAMAZAKI, M.A.
KIYAMA, K. FURUMURA: `` Introducing of Sealed Bear
ings for Work Roll Necks in RollingMills '', Procee
dings of the JSLE international Tribology Conferen
ce, pp.609-614, July 8-10, 1985, Tokyo, Japa
n; hereinafter, referred to as “first related art”).

According to the first prior art, a contact rubber seal mounted on a chock outside the bearing and a contact rubber seal mounted on the inside of the bearing are used together, so that only the rubber contact seal mounted on the chock is used. The moisture concentration in the lubricant is reduced from 40% to 1
It is reported that it can be reduced to less than 0%, the consumption of lubricant can be reduced to 1/200, and furthermore, there have been no bearing failures that occurred several times a year.

Further, in the above-mentioned work roll bearing, as another conventional technique for preventing water from being mixed into a lubricant, a technique of supplying a lubricant to a chock using compressed air as a carrier gas has been proposed (NSK Technical). Journa
l No. 654, pp. 54-56, 1992; hereinafter referred to as "second conventional technology").

In the second prior art, by setting the air pressure in the chock high by using compressed air, it is possible to suppress the entry of water into the lubricant.

Further, as another example of a rolling bearing in which moisture can enter the lubricant, there is a bearing for electric equipment and auxiliary equipment of an automobile engine. Bearings for electrical components and accessories of automobile engines include bearings for auxiliary machines driven by a belt outside the automobile engine, such as alternator bearings, car cooler electromagnetic clutch bearings, idler pulley bearings, and water pump bearings. Meaning, in these bearings for electrical equipment and auxiliary equipment, muddy water and rainwater that jump up from the road surface easily enter the inside of the bearing, and for water pump bearings, circulating water for cooling the engine easily enters the inside of the bearing. .

[0010] In view of the above, a technique for improving the sealing performance of a built-in seal has been proposed as a means for preventing water from being mixed into a lubricant inside a bearing in a bearing for an electric component or an auxiliary device of an automobile engine from such a viewpoint. (NSK Tech
nical Journal No. 660, pp.15-22, 1995, No.6
52, pp. 66-67, 1992; hereinafter, referred to as "third prior art").

[0011] In addition, it has been reported that, in a rolling bearing, generally, when vibration is applied or when the rigidity around the bearing is weak, the durability life of the bearing is significantly reduced (Yasuo Murakami, Hiromichi Takemura: " Study on Flaking Phenomena of Electrical Bearings ", Proceedings of the Japan Society of Tribology (Japan) (Nagoya November 1993, pp. 295-298; hereinafter referred to as" Reference 2 ").

That is, when vibration is applied during operation, the formation of an oil film between the raceway surface and the rolling surface becomes insufficient and a tensile stress is applied to the contact surface, and the rotating shaft and the inner ring are strongly tied. When the rigidity of the bearing housing is reduced by fitting, the tensile stress always acts on the raceway surface, and as a result,
Even if moisture is not mixed into the lubricant from the outside, the bearing may be separated early due to the influence of the moisture originally contained in the lubricant, and the bearing life L may be reduced.

However, the bearings for electrical components and accessories of the automobile engine are susceptible to vibrations and the like, and therefore have excellent vibration damping effects in order to avoid early occurrence of flaking due to the vibrations. It has been proposed to use a grease which acts like a buffering agent as a lubricant (NSK Technical Journal No. 657, pp. 49 -51,
1994; hereinafter referred to as "fourth prior art").

Examples of other rolling bearings in which moisture can enter the lubricant include bearings for automobile wheels, bearings for guide rolls of continuous casting equipment for steel materials, bearings for backup rolls of rolling mills, and further, bearings for rolling rolls. There are bearings for dryer rolls of paper machines.

In a vehicle wheel bearing, moisture easily penetrates into the lubricant under the influence of muddy water and rainwater on the road surface. In addition, cooling water and rolling water easily penetrate into the lubricant for bearings for guide rolls in continuous casting equipment for steel materials and bearings for backup rolls in rolling mills. Further, since the bearing for a paper roll dryer roll is used in a drying step of drying wet paper containing water, water vapor easily enters the bearing, and therefore, the moisture concentration in the lubricant increases and the bearing for the dryer roll increases. (MJCulter: "Paper mach
ine bearing failure '', Tappi Journal, Vol. 79, N
o. 2, pp. 157-167, 1996; hereinafter referred to as “Reference 3”).

Therefore, in a vehicle wheel bearing, a contact rubber seal external to the bearing and a contact rubber seal built in the bearing are used together, as in the first prior art.
Alternatively, a technique using only a high-performance seal has been proposed (NSK Technical Journal No. 647, pp. 55-57, 19).
87) In addition, bearings for guide rolls and bearings for backup rolls of rolling mills are also using contact rubber seals to prevent moisture from penetrating into the lubricant.
Also, as for the bearing for the paper roll dryer roll, it is necessary to take measures to prevent the infiltration of water because the water vapor easily penetrates into the bearing as is clear from the above-mentioned Reference 3. Since it is generally used under high temperature conditions, it is difficult to apply a contact rubber seal used for work roll bearings and automotive wheel bearings in consideration of heat resistance. It has been considered to use rubber to prevent moisture from entering.

That is, the other rolling bearings such as a vehicle wheel bearing are also disclosed in the first prior art and the third rolling bearing.
In principle, similar to the prior art described above, a contact rubber seal is used in principle to try to avoid the intrusion of moisture into the lubricant inside the bearing. ").

On the other hand, when the temperature of the inside of the housing of the bearing decreases and reaches the dew point when the machinery or the vehicle or the like on which the rolling bearing is mounted is stopped, moisture around the bearing condenses, As a result, it has been reported that water droplets adhere to the bearings or mix into the lubricant, which causes a reduction in the bearing life L (Gonichi Uchida: NSK Tech)
nical Journal No. 632, pp. 40-45, 1973; hereinafter referred to as “Reference 4”), and when the lubricant is oxidized and deteriorated, water is generated, and the generated water adheres to the bearing to reduce the life L of the bearing. It has been reported that they will be invited (Masao Seki: Proceedings of the Rolling Fatigue Symposium, pp. 125-130, 1993; hereinafter referred to as “Reference 5”).

According to these documents 4 and 5, even if water is not directly mixed into the lubricant from the outside, the lubricant may contain water due to an environmental change or the like. To avoid a decrease in L,
As a countermeasure against moisture infiltration into the lubricant, it is necessary to consider means other than the contact rubber seal described above.

In view of this, from this viewpoint, martensitic stainless steel (S
US440C) prevents the occurrence of rust due to the adhesion of moisture to the bearings and avoids a decrease in durability (Rolling Bearing Engineering Editorial Board: Rolling Bearing Engineering, pp. 71-72) , Yokendo (1976); hereinafter, referred to as "sixth prior art").

[0021]

According to the first prior art, as described above, the water concentration in the lubricant can be reduced from 40% to less than 10%, and the consumption of the lubricant can be reduced. As a result of investigating the results of the use of work roll bearings afterwards, it was found that the seizure accident had been drastically reduced. However, the use time until the occurrence of peeling, that is, the bearing life L was significantly improved. It turned out not to be. This is because the decrease in the seizure accident is due to a decrease in the outflow of the lubricant due to the contact rubber seal built in the bearing, and the reason that the bearing life L has not been improved is due to the incorporation of moisture into the lubricant. It is considered that the rolling fatigue strength of the bearing is significantly reduced.

That is, it has been reported that the rolling fatigue strength of a bearing material is reduced by 32 to 48% even when a small amount of water of about 100 ppm is mixed in a lubricant (P. Schatzberg, IMFelsen). : "Effects of water a
nd oxygen during rolling contact lubrication '', wea
r, 12, pp. 331-342, 1968; hereinafter referred to as “Reference 6”)
When the contact rubber seal mounted on the chock outside the bearing and the contact rubber seal built in the bearing are used in combination, the water concentration in the lubricant can be suppressed until it becomes less than about 10%. However, as described in Reference 6, it is impossible to avoid a decrease in the rolling fatigue strength of the bearing material. In other words, in the first prior art, it is not possible to completely prevent water from being mixed into the lubricant, so that the rolling fatigue strength of the bearing material is reduced and a desired bearing life L excellent in durability is obtained. There is a problem that can not be.

In the second prior art, since the infiltration of water is prevented by increasing the air pressure in the chock, it does not depend on the waterproofing ability of the contact rubber seal as in the first prior art. 100p moisture concentration in lubricant
pm or less, it is difficult to prevent nearly perfect moisture penetration.

Further, the third prior art is based on the first principle.
In the same manner as in the prior art, the infiltration of moisture is prevented by a contact rubber seal. As described above, it is difficult to suppress the moisture concentration in the lubricant to 100 ppm or less, and it is not possible to obtain a desired durability. There is a problem.

Also, in the fourth prior art, the use temperature of electric and auxiliary bearings is increased due to the recent improvement in the performance of automobiles, and as a result, the grease is softened and the vibration damping capacity of the grease is reduced. As a result, it is not possible to prevent early peeling of the bearing, and together with the above-described infiltration of water into the lubricant, the life of the bearing is reduced, and a desired durability cannot be obtained. .

Also, in the fifth prior art, a contact rubber seal is used in principle similarly to the first prior art, and it is difficult to completely prevent the ingress of moisture. There is a point.

Further, in the sixth prior art, since the thermal conductivity of stainless steel is lower than that of low alloy steel, seizure damage is apt to occur, and moisture is mixed in the lubricant as described above. There is a problem that it is difficult to apply to a rolling bearing having poor lubrication conditions. Further, the corrosion resistance of the stainless steel is maintained by a passivation film formed on the surface.However, in a rolling bearing, when the raceway surface of a bearing ring contacts a rolling surface of a rolling element, the passivation degree film is formed. The pit is broken, resulting in selective corrosion
Is generated, so that there is also a problem that peeling damage originating from the hole is likely to occur. Further, even in the case of manufacturing a bearing, the quenching temperature is 1010 for stainless steel.
Since the temperature is as high as 〜１０1070 ° C. and a salt bath furnace must be used as a heating furnace, there is also a problem that the production equipment may rise in price (the Iron and Steel Institute of Japan: heat treatment of steel revised 5)
Editions pp. 563-568 (1989)).

In addition, since the stainless steel has a low thermal conductivity as described above, the grinding speed is reduced and the grinding cost is high. Further, since the stainless steel is a high alloy steel, the material cost is low. There is also a problem that it may cause a soaring price.

The present invention has been made in view of such a problem, and even when water is mixed into the lubricant from the outside or under a use condition affected by the water concentration in the lubricant, An object of the present invention is to provide a rolling bearing capable of obtaining a sufficient bearing life at a low cost.

[0030]

SUMMARY OF THE INVENTION The applicant of the present invention has developed a rolling bearing capable of preventing the progress of corrosion of a bearing portion even when used under lubricating conditions containing moisture in a lubricant.
As a result of intensive research, the metal (matrix) side mainly composed of Fe at the interface between the raceway surface of the bearing ring and the non-metallic inclusion is used as the anode, and the carbide on the rolling surface of the rolling element is cathode. It was found that it is effective to change the corrosion mode to contact corrosion as the (cathode).

That is, when water is mixed in the lubricant, even if the amount of water is very small, unavoidable nonmetallic inclusions (oxides, sulfides, etc.) formed on the raceway surface of the raceway ring. ) And the metal base cause local corrosion, and the progress of the local corrosion causes peeling at the bearing portion. And
In this case, in particular, it was found that a large amount of hydrogen was absorbed in the race and corrosion proceeded, leading to a reduction in bearing life.

Therefore, in order to avoid a reduction in bearing life, it is important to suppress the amount of hydrogen absorbed into the bearing ring, and it is considered that this can prevent corrosion.

Therefore, the applicant of the present application has paid attention to the fact that the rolling surface and the raceway surface come into metallic contact in the rolling bearing, and changed the corrosion form from the local corrosion described above to the contact corrosion between the rolling element and the raceway. Has been found to be effective in suppressing the amount of hydrogen absorbed into the bearing ring. That is, it is effective to make the corrosion form contact corrosion by using the metal base material at the interface as the anode and the carbide on the rolling surface of the rolling element as the cathode to suppress the hydrogen absorption amount of the raceway. The carbide existing on the raceway (hereinafter referred to as “rolling plane carbide”) is made more electrochemically noble than the carbide existing on the raceway (hereinafter referred to as “raceway carbide”). In order to increase the efficiency of supplying electrons to the bearing, the corrosion form can be changed to contact corrosion by making the metal body on the rolling surface electrochemically more noble than the metal body on the raceway surface.

As described above, in order to use the metal base material at the interface of the bearing ring as an anode and the carbide on the rolling surface of the rolling element as a cathode, the composition of the material is adjusted to adjust the raceway material and the rolling element. It is necessary to clarify the electrochemical nobleness between each metal base of the material and between the raceway material and each carbide of the rolling element material.

However, Ni, Cr, M
When a low alloy steel containing o is used, the carbide contained in the bearing material is represented by the general formula (Fe, M) ₃ C (M = Cr, M
As shown in o), the Cr component and the Mo component are contained in the carbide. Needless to say, the metal component contains a Ni component. Therefore, by reducing the content of Cr and Mo, which are chemically unstable compared to Fe, the carbide can be made electrochemically noble as compared with the normal case, and the main component of the metal base is By increasing the content of Ni, which is chemically stable as compared with a certain Fe, the metal base can be made electrochemically noble as compared with a normal case. That is, Cr, Mo, Ni are used so that the nobleness becomes electrochemically clear between the rolling element material and the bearing ring material.
By providing a difference in the content of, the rolling surface carbide can be made more electrochemically more noble than the raceway surface carbide, and the metal body of the rolling surface can be made more electrochemically than the metal body of the raceway surface. You can be noble. From the experimental results of the applicant of the present invention, specifically, these content deviations were 0.2 wt.
It turned out that it was necessary to set it to more than%.

The present invention has been made based on such knowledge, and a rolling bearing according to the present invention has a raceway composed of an outer ring and an inner ring, and a rotatable arrangement between the outer ring and the inner ring. In the rolling bearing provided with the provided rolling elements, the Ni content deviation ΔNi obtained by subtracting the Ni content of the bearing ring material from the Ni content of the rolling element material is ΔN in weight%.
i ≧ + 0.2%, and from the Cr content and Mo content of the rolling element material, the Cr content and Mo of the bearing ring material
The Cr content deviation ΔCr and the Mo content deviation ΔMo, whose contents were respectively reduced, were expressed as% by weight, ΔCr ≦ −0.2%, ΔM
It is characterized in that o ≦ −0.2%.

[0037]

Embodiments of the present invention will be described below.

As described above, it is known that the lubricating condition in which the lubricant contains water causes a decrease in the rolling fatigue strength of the bearing material. It is not clear why the contamination reduces the rolling fatigue strength (E. Ioannides, B. Jacobso)
n: "Dirty lubricants-reduced bearing life", Ba
ll Bearing Journal Special '89, pp. 22-27, 198
9).

Therefore, the present applicant has started to theoretically elucidate the above mechanism.

When water is mixed into the lubricant, it is difficult to form an oil film even when the amount of water is very small, and the rolling element and the race ring form a metal between the rolling surface and the raceway surface. Although the rolling elements and the raceway contact, the surface condition of the rolling element and the raceway is non-uniform and non-uniform and inevitable non-metallic inclusions such as oxides and sulfides are formed on the rolling surface and raceway surface. When moisture is mixed in the lubricant, these nonmetallic inclusions and Fe
When water infiltrates the interface with the metal base containing as a main component, a local battery is formed and local corrosion occurs. That is, since there is always a contact portion between the rolling element and the bearing ring near the interface, a tensile stress is always applied to the interface between the non-metallic inclusions and the metal base present on the raceway surface and the rolling surface, Under such tensile stress, a minute gap is formed at the interface between the nonmetallic inclusion and the metal substrate. When water is mixed in the lubricant, even if the amount of the water is very small, the viscosity of the water is lower than the viscosity of the lubricant. As a result, a corrosion reaction occurs inside the minute gap. Further, when the inner ring and the rotating shaft are fitted with a close fit, a tensile stress always acts on the raceway surface, so that a larger tensile stress is applied to the interface between the nonmetallic inclusion and the metal base. Thus, a gap is formed under the large tensile stress.

In this corrosion reaction, since the corrosion product closes the entrance of the minute gap, it becomes difficult to supply oxygen from the surface to the minute gap, and as a result, the metal base, which is electrochemically lower than carbide, is removed from the anode. And a chemical reaction formula (1) using a carbide that is electrochemically more noble than a metal base as a cathode
-A hydrogen-generating type corrosion reaction as shown in (4).

[0042]

Embedded image Here, H (ads) indicates a hydrogen atom adsorbed on the surface of the bearing material, and H (abs) indicates a hydrogen atom absorbed inside the bearing material.

That is, as shown in the chemical reaction formula (1), on the anode side, Fe reacts with water to cause an oxidation reaction in which electrons are released, while on the cathode side, the inside of the minute gap is formed. It becomes difficult to supply oxygen to the surface, and hydrogen is adsorbed on the surface of the bearing material as shown in chemical reaction formula (2). Then, as shown in chemical reaction formula (3), a part of the adsorbed hydrogen is As shown in the chemical reaction formula (4), the hydrogen atoms adsorbed on the surface of the bearing material combine to form hydrogen molecules (gas). And the hydrogen molecules are released to the outside. Since the progress of the chemical reaction formula (3) is substantially negligible on the carbide, the chemical reaction of the chemical reaction formula (4) mainly proceeds. Therefore, when hydrogen gas can be easily released from the minute gap to the outside, it is considered that even if corrosion occurs, absorption of hydrogen gas into the bearing material does not occur.

However, the hydrogen gas is easily adsorbed on the metal substrate inside the minute gap while being released to the outside, and the adsorbed hydrogen gas is dissociated and adsorbed as an atom in the metal substrate, and the adsorbed hydrogen atom Is absorbed inside the bearing material. When a corrosion reaction occurs inside the minute gap, hydrogen is absorbed into the bearing material, causing hydrogen embrittlement of the bearing material, and as a result, the rolling fatigue life of the bearing material is reduced. It is considered.

Next, the applicant of the present application examined the peeling characteristics of the bearing material when water was mixed in the lubricant.

As described in the section [Problems to be Solved by the Invention], when water is mixed in the lubricant, the time required for the rolling bearing to separate, that is, the bearing life L decreases, but the separation occurs. Generally, the fixed ring is the most prominent as a component part of the bearing to be separated, and then the frequency of peeling decreases in the order of the rotating wheel and the rolling element. It is understood that the separation frequency of the rolling elements is lower than the separation frequency of the races because the hydrogen absorption of the races is smaller than the hydrogen absorption of the races. It is possible.

(1) In general, the rolling speed of a rolling bearing is much higher in a rolling element than in a bearing ring. Therefore, even if a small gap is formed on the rolling surface of the rolling element, moisture that has entered the minute gap is not increased. The material is flipped off by centrifugal force, and as a result, the progress of the corrosion reaction is suppressed, and the amount of hydrogen that infiltrates into the material is reduced.

(2) Since the working ratio of the rolling element from the casting material (ingot, bloom, billet, etc.) is greater than that of the raceway casting material, non-metallic intervening on the rolling surface of the rolling element. The object is smaller than non-metallic inclusions present on the raceway surface of the bearing ring. Therefore, in the rolling element, the interface between the non-metallic inclusion and the metal base is small and shallow, so that the progress of the hydrogen generating type corrosion reaction is suppressed, and the amount of hydrogen absorbed into the material is small.

The following reasons can be considered.

Further, with respect to the bearing ring, the frequency of occurrence of peeling of the rotating wheel is smaller than that of the fixed wheel for the following reason.
That is, in the rotating wheel, even if moisture enters the minute gap formed in the raceway surface, it is likely to be flipped off, so that the hydrogen absorption amount is smaller than that of the fixed wheel, and therefore, the frequency of occurrence of peeling is considered to be reduced. . However, when the inner ring and the rotating shaft are fitted with a close fit, tensile stress always acts on the raceway surface of the rotating ring, so stress corrosion is promoted even when the inner ring is a rotating ring. In addition, the above-described cathode reaction (chemical reaction formulas (2) to (4)) proceeds actively, and the amount of hydrogen absorbed by the rotating wheel increases, so that the frequency of peeling increases. In particular, the interference is 7/100 of the shaft diameter of the rotating shaft.
When the diameter exceeds 00 or when the tapered bore bearing is used with a close fit, the frequency of occurrence of peeling of the rotating wheel is equal to or higher than the frequency of occurrence of peeling of the fixed wheel. Note that when the inner ring is a fixed wheel and the inner ring and the rotating shaft are fitted together by interference fit, the hydrogen absorption amount is larger than when fitted by clearance fit. Not even.

In any case, it has been found that the raceway ring has a larger amount of hydrogen absorption than the rolling elements, and it has been found that the frequency of peeling is higher. Therefore, it is possible to suppress the progress of corrosion by suppressing the hydrogen absorption amount of the raceway. Prevention is considered to contribute to the improvement of the bearing life L.

Therefore, the applicant of the present application has conducted further studies, and as a result, in the rolling bearing, paying attention to the fact that the rolling surface of the rolling element and the raceway surface of the bearing ring are in metal contact with each other. It is effective to improve the bearing life L by changing the corrosion form from local corrosion to contact corrosion using the metal base side of the minute gap formed at the interface with the inclusion as the anode and the carbide on the rolling surface of the rolling element as the cathode. Turned out to be.

Thus, while the anodic reaction takes place on the metal base side of the interface, the cathode reaction takes place on the carbide on the rolling surface by using carbide on the rolling surface of the rolling element as a cathode, and oxygen is removed from the surroundings. Since it can be easily supplied, as shown in the following chemical reaction formulas (5) and (6), the corrosion reaction becomes an oxygen-consuming type corrosion reaction, and the absorption of hydrogen into the raceway is suppressed, resulting in hydrogen embrittlement. The accompanying reduction in bearing life can be prevented.

[0054]

Embedded image Thus, as described above, in order to use the metal base side in the minute gap as the anode and use the carbide on the rolling surface of the rolling element as the cathode, the rolling surface carbide is more electrochemically noble than the raceway surface carbide, Further, in order to increase the efficiency of supplying electrons to the carbide on the rolling surface, it is necessary to make the metal substrate on the rolling surface electrochemically more noble than the metal substrate on the raceway surface.

In order to use the metal base at the interface of the bearing ring as the anode and the carbide on the rolling surface of the rolling element as the cathode, the composition of the materials is adjusted to adjust the respective metal bases of the bearing ring material and the rolling element material. It is necessary to clarify the electrochemical nobleness between the bearing ring material and the carbide of the rolling element material.

As described in the section of [Problems to be Solved by the Invention], it is technically difficult to use a high alloy steel such as stainless steel (SUS440C) as a bearing material to suppress a corrosion reaction. Therefore, it is preferable to use a low alloy steel as the material steel for the bearing, because it is difficult and economically disadvantageous. For example, as the material steel of each bearing portion, the chemical component is, for example, C: 0.10
1.10 wt%, Si: 0.75 wt% or less, Mn: 1.7
0 wt% or less, Cr: 2.0 wt% or less, Mo: 1.50 wt
%, Ni: 4.50 wt% or less, Cu: 0.30 wt%
In the following, Al is used in an amount of 0.050 wt% or less, and the balance is made of a low alloy steel including Fe and inevitable impurities (O, S, Ti, etc.), and a desired surface hardness is obtained by subjecting the material steel to a desired heat treatment. It is effective to obtain a bearing portion having the same.

As the bearing material, N as described above is used.
When a low-alloy steel containing i, Cr, and Mo is used, the carbide contained in the bearing material is represented by the general formula (Fe, M) ₃ C (M
= Cr, Mo), the Cr component and the Mo component are contained in the carbide. Needless to say, the metal component contains a Ni component. Therefore, by reducing the contents of Cr and Mo, which are chemically unstable as compared with Fe, it is possible to make carbides electrochemically noble as compared with the normal case, and the main component of the metal base is By increasing the content of Ni, which is chemically more stable than a certain Fe, it becomes possible to make the metal substrate electrochemically noble as compared with a normal case. That is, C is set so that nobleness is clarified electrochemically between the rolling element material and the raceway material.
By providing a difference in the content of r, Mo, and Ni, the rolling surface carbide can be made more electrochemically more noble than the raceway surface carbide, and the metal body of the rolling surface can be replaced with the metal body of the raceway surface. Can be more electrochemically precious.

In order to make the electrochemical nobleness clear, these content deviations should be 0.1% by weight.
It is necessary to set it to 2 wt% or more. That is, the Ni content deviation ΔNi obtained by subtracting the Ni content of the bearing ring material from the Ni content of the rolling element material is ΔNi ≧% by weight.
+ 0.2%, and the Cr content and M of the rolling element material
The Cr content deviation ΔCr and the Mo content deviation ΔMo obtained by subtracting the Cr content and the Mo content of the bearing ring material from the o content, respectively, are expressed as% by weight: ΔCr ≦ −0.2%, ΔMo ≦
It needs to be -0.2%. When these content deviations ΔNi, ΔCr and ΔMo are excessively large, the melting of the raceway surface becomes remarkable due to an increase in electrochemical nobleness, and the reaction product may deteriorate the lubricant. In the present embodiment, since the low alloy steel having the above-described component composition range is used, ΔNi, ΔCr, and ΔMo do not become excessive.

In order to suppress the hydrogen absorption of the raceway material, it is also an effective means to suppress the anodic reaction (chemical reaction formula (1)) occurring inside the minute gap.

The above-mentioned anode reaction can be suppressed by making the metal substrate more noble electrochemically and making the carbide more noble so as to approximate the electrochemical characteristics between the metal substrate and the carbide. . That is, since the anode reaction occurs on the metal base side at the interface between the carbide and the metal base, the electrochemically noble metal base is shifted in the noble direction, and the electrochemically noble carbide is shifted in the base direction. In addition, the electrochemical characteristics of the metal base and the carbide can be made close to each other, whereby the progress of the anode reaction can be suppressed.

In order to make the metal base more precious, as described above, Ni is chemically stable compared to Fe.
It is effective to increase the addition amount of Cr, and in order to make the carbide more base, it is effective to increase the addition amount of Cr and Mo, which are chemically unstable compared to Fe contained in the carbide. It is. Specifically, the Ni content is 0.25 wt% or more, the Cr content is 0.7 wt% or more, and the Mo content is 0.2
By setting the content to 5% by weight or more, the electrochemical properties of the metal base and the carbide can be made close to each other, and as a result, the progress of the anodic reaction of the chemical reaction formula (1) can be suppressed.

Further, in order to suppress the absorption of hydrogen into the inside of the race and avoid the occurrence of hydrogen embrittlement, the progress of the chemical reaction represented by the above-mentioned chemical reaction formula (2) is suppressed. Is also effective.

Specifically, the reaction rate of the chemical reaction formula (2) can be reduced by lowering the hydrogen ion concentration of the lubricant, in other words, by increasing the hydrogen ion exponent pH of the lubricant. Thereby, hydrogen embrittlement can be avoided and durability can be improved. The optimum range of the hydrogen ion exponent pH in this case is 7 to 13.

That is, water dissolves a very small amount of carbon dioxide contained in the atmosphere, and as a result, the hydrogen ion exponent often becomes acidic with a hydrogen ion index of 7 or less. Although the ionic index pH can be increased, the reaction rate of the chemical reaction formula (2) is reduced to achieve sufficient suppression of hydrogen absorption into the race material,
Thus, in order to improve the bearing life L, it is necessary to set the hydrogen ion exponent pH to at least 7 or more. On the other hand, when the hydrogen ion exponent pH exceeds 13, the raceway surface 3 and the rolling surface 5 wear due to alkali corrosion, and the vibration during driving of the rolling bearing becomes gradually remarkable. Therefore, in the present embodiment, the hydrogen ion exponent pH of the lubricant is set to 7
~ 13.

The surface hardness of the rolling surface of the rolling element (hereinafter referred to as “rolling surface hardness”) and the raceway surface hardness of the bearing ring (hereinafter referred to as “track surface hardness”) are referred to as the rolling surface. It is desirable to set the hardness lower than the raceway surface hardness.

In a rolling bearing, slips such as revolving slip and differential slip always occur on the raceway surface of the bearing ring and the rolling surface of the rolling element. If a good oil film cannot be formed due to the influence of the moisture concentration (during low-speed rotation operation, including immediately after the start of operation or immediately before operation stop), if the operating temperature is high and the surface roughness is poor, In the case where the amount of the lubricant is small, for example), when the rolling surface and the raceway surface come into contact with each other, the lower rolling surface of the rolling surface and the raceway surface is worn. This can be easily confirmed by observing the polished surface of the raceway surface and rolling surface after use, measuring the iron powder concentration in the lubricant, etc., except for the use of a rolling bearing in a laboratory. In many cases, contact between the raceway and the race cannot be avoided.

Therefore, when the rolling surface hardness is higher than the raceway surface hardness, the raceway surface is worn, and the adhesion between the nonmetallic inclusion and the metal base on the raceway surface is reduced, and the nonmetallic inclusion and Water having a lower viscosity than the lubricant preferentially penetrates into the metal base to cause corrosion, and as a result, hydrogen embrittlement occurs.

However, as described above, since suppressing the hydrogen absorption of the bearing ring contributes to the improvement of the bearing life, it is also important to suppress the wear of the raceway surface. It is desirable to set the rolling surface hardness to be lower than the raceway surface hardness after securing the deviation of each content of Ni, Cr and Mo of the raceway material.

In this case, abrasion of the rolling elements is inevitable. However, it is necessary to avoid intense abrasion of the rolling elements. To this end, the metal structure of the rolling surface is changed to martensite and, if necessary, to martensite. It is necessary to constitute a structure to which residual austenite and carbides are added (hereinafter, this structure is referred to as “martensite structure”, and a steel having this structure is referred to as “martensite steel”). It is desirable that the HRC (hereinafter referred to as “surface hardness”) be 55 or more. Also, as described above, the raceway hardness is preferably set higher than the rolling surface hardness, but if the raceway hardness is set too high, the wear of the rolling elements becomes remarkable, and as a bearing material, When low alloy steel is used, it is desirable to set the surface hardness HRC to 66 or less.

Further, since the corrosion reaction in the bearing ring is caused by a minute gap formed between the non-metallic inclusion and the metal base, the formation of the non-metallic inclusion is required to prevent the corrosion. It is also preferable to suppress, for that purpose, it is desirable to make the total content of oxygen, sulfur, and titanium that cause the formation of oxides, sulfides, and titanium compounds constituting the nonmetallic inclusions 100 ppm or less. . Furthermore, in order to obtain good adhesion between the non-metallic inclusions and the metal substrate and avoid generation of minute gaps at the interface, the final refining method of the bearing material is performed by the ESR method or the VAR method. Is desirable.

Further, when carburizing treatment or carbonitriding treatment is performed, hydrogen enters the steel during the treatment step, so that after the carburizing treatment or carbonitriding treatment, the A ₁ transformation is performed in an inert gas, vacuum, or air. It is desirable to carry out an annealing treatment for dehydrogenation in a temperature range of 30 to 150 ° C. lower than the temperature.

Further, among the rolling bearings, in particular, the roll neck bearing of a steel rolling mill is generally used in an environment subjected to an impact load, so that the bearing ring is carburized or treated with low carbon steel (case-hardened steel). By performing carbonitriding treatment to harden the surface near the raceway surface and softening the inside near the core, it is manufactured to withstand both rolling contact stress and impact stress. However, in order to improve the hydrogen embrittlement resistance, it is important to improve the adhesion between the metal base and the non-metallic inclusions on the raceway surface to prevent water from entering the minute gaps. It is necessary to use low carbon steel having a carbon content of 0.10 to 0.45 wt% as a material. This is because it is necessary to set the carbon content to 0.45 wt% or less in order to reliably apply compressive residual stress to the raceway surface even when the interference between the inner ring and the rotating shaft is 7 / 10,000 of the shaft diameter. And the carbon content is 0.10
When the content is set to be not less than wt%, the treatment time required for carburizing or carbonitriding becomes long, and in consideration of the treatment efficiency, it is necessary to limit the upper limit of the carbon content to 0.10 wt%. In addition, when the rolling element has a solid shape, the tensile stress hardly acts on the surface,
Substitute steel may be used.

[0073]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

The applicant of the present application has prepared races and rolling elements having various chemical components subjected to a predetermined heat treatment, assembled tapered roller bearings, and determined the relationship between the concentration deviations ΔN, ΔCr, ΔMo and the bearing life L. It was measured.

Table 1 shows the chemical components of the bearing materials (bearings and rolling elements) of the embodiment of the present invention, and Table 2 shows the chemical components of the bearing materials (bearings and rolling elements) of the comparative example. .

[0076]

[Table 1]

[0077]

[Table 2] In the race, in the comparative example 54, the outer race and the inner race are composed of different chemical components, and in the other races, the outer race and the inner race are composed of the same chemical composition.

In Tables 1 and 2, ΔNi, ΔCr,
ΔMo indicates a content deviation obtained by subtracting each content of Ni, Cr and Mo of the raceway from each content of Ni, Cr and Mo of the rolling elements. In Comparative Example 54 in which the inner ring and the outer ring have different composition ranges, the Ni content deviation was calculated using the higher Ni content, and the Cr and Mo were calculated using the lower Ni contents. ΔCr content deviation and ΔMo
The content rate deviation is calculated.

S + Ti + O is a value indicating the total content of sulfur, titanium and oxygen contained in the raceway material. When the content is different between the inner ring and the outer ring as in Comparative Example 54, Using the higher content (S + Ti +
O) was calculated.

Next, the bearing material having the above composition range is subjected to heat treatment, and then the surface hardness HRC (track surface hardness and rolling surface hardness) of the heat-treated bearing ring and rolling element is calculated, and the inner ring is processed. Was mounted on a rotating body with a rotating wheel and an outer ring as a fixed wheel, and a durability life test was performed to evaluate life characteristics (durability). In addition, as a retainer, a cold-rolled steel material (SPC
Using the press cage formed in C), ten bearings were produced for each bearing (Examples 1 to 13 and Comparative Examples 51 to 54), and a durability life test was performed.

The bearing specifications are as follows. [Bearing specifications] Nominal number: HR32017XJ Outer ring outer diameter D: φ130 mm Inner ring inner diameter d: φ85 mm Assembly width t: 29 mm Basic dynamic load rating C: 143000N Tables 3 and 4 show the above-mentioned Examples 1 to 13 and 9 shows the heat treatment method, surface carbon concentration, surface hardness HRC, hardness deviation ΔHRC, hydrogen ion exponent pH of grease, and bearing life L of Comparative Examples 51 to 54.

[0082]

[Table 3]

[0083]

[Table 4] The heat treatment of the bearing ring is performed at a predetermined temperature until the total carburized depth reaches 1.2 mm for the bearing ring material having a predetermined component range.
After the carburizing treatment, except for Example 12, to perform dehydrogenation, immediately perform isothermal annealing treatment under a nitrogen atmosphere under the conditions of a heating temperature of 650 ° C and a heating time of 5 hours, and then a heating temperature of 800 to 860 ° C. The quenching treatment was performed under the conditions of a heating time of 30 minutes, and then the tempering treatment was performed under the conditions of a heating temperature of 160 to 180 ° C. and a heating time of 2 hours. The quenching oil used was oil at 80 ° C. The above-mentioned isothermal annealing treatment is performed in order to improve the treatment efficiency, and the intermediate annealing method of cooling after carburizing treatment, then raising the temperature to 650 ° C. and holding the same may be used at all.

In Example 12, in order to examine the annealing effect, the bearing ring material having the same composition as in Example 1 was subjected to quenching and tempering after carburizing without annealing. We have obtained bearing ring materials.

On the other hand, in the heat treatment of the rolling element, the rolling element material having a predetermined component range is subjected to a carburizing treatment at a predetermined temperature until the total carburizing depth becomes 1.2 mm, and then released until the temperature reaches room temperature. Cool, then heating temperature 800-850 ° C,
The quenching treatment was performed under the condition of a heating time of 30 minutes, and then the tempering treatment was performed under the condition of a heating temperature of 160 to 260 ° C. and a heating time of 2 hours. That is, as described in the section of [Embodiment of the Invention], even when moisture is mixed in the lubricant, the rolling element hardly absorbs hydrogen into the steel during use. Therefore, it was not necessary to perform annealing for dehydrogenation, and annealing was not performed.

Table 3 shows the surface carbon concentrations of the races and the rolling elements.
And as apparent from Table 4, 0.80 to 1.10 wt%
Was in the range.

The surface hardness HRC of the rolling elements and races
Was measured five times on a C scale of a Rockwell hardness tester, an average value of the average surface hardness Hav was calculated, and the average value was calculated using Expression (1).

HRC = Hav + ΔH (1) Here, ΔH is a hardness correction value for converting the hardness of the cylindrical surface into a plane, and is represented by the following equation (2).

ΔH = (14.8 / rx) × (1-Hav / 160) ² (2) (where x = a, b, c) where rx is the radius of curvature (mm) of the cylindrical surface. So, Figure 1
When the rolling element 11 is disposed between the outer ring 12 and the inner ring 13 so as to be able to roll freely, the average radius of the outer ring raceway surface is r1, the average radius of the inner ring raceway surface is r2, and the rolling element 11 is r3, the angle between the shaft core and the outer raceway surface is α1, and the angle between the shaft center and the inner raceway surface is α2, the radius of curvature ra of the outer raceway surface and the radius of curvature rb of the inner raceway surface , The radius of curvature rc of the rolling element 11 is given by Equations (3) to (5).
It is represented by

Ra = −r1 / cos α1 (3) rb = r2 / cos α2 (4) rc = r3 / cos {(α1-α2) / 2} (5) That is, the surface hardness of the outer ring is When calculating, the curvature radius ra calculated by the equation (3) is substituted into the equation (2) to calculate the hardness correction value ΔH, and the hardness correction value ΔH thus calculated is substituted into the equation (1). Then, the surface hardness HRC of the outer race was calculated. Similarly, when calculating the surface hardness of the inner ring, Equation (1) is calculated based on the radius of curvature rb calculated by Equation (4).
Using (2), the surface hardness HRC of the inner ring was calculated. Further, when calculating the surface hardness of the rolling element, the surface hardness HRC of the rolling element was calculated using the equations (1) and (2) based on the radius of curvature rc calculated by the equation (5).

Further, the hardness deviation ΔHRC was calculated by subtracting the surface hardness of the bearing ring from the surface hardness of the rolling element. When the surface hardness differs between the inner ring and the outer ring, ΔHRC is calculated using the lower value.

The surface hardness HRC is obtained by measuring the Vickers hardness Hv at a 0.1 mm depth position of a mirror-finished vertical section instead of the raceway surface hardness and the rolling surface hardness at a measurement load of 1 kgf.
May be measured five times to calculate the average value and convert from the average value. However, it is important that the numerical value of the surface hardness is not the absolute value of the rolling surface hardness and the raceway surface hardness, but the rolling surface. Since there is a relative value between the hardness and the raceway surface hardness, it is necessary to measure the hardness of each component in the same bearing by the same method.

Next, the durability life test will be described.

FIG. 2 is a sectional view of a main part of the durability test apparatus used in the present embodiment. The outer ring 12 is fixed to the housing 14 and the inner ring 13 is fitted on the rotating shaft 15 so that 10 cc / hour can be obtained. Water was injected into the bearing as shown in FIG. 2, while an axial load Fs and a radial load Fr were applied to the bearing, and a durability life test was performed while rotating the rotating shaft 15. The outer ring 12 and the housing 14 are assembled by loose fit, and the inner diameter of the housing 14 is formed to be larger than the outer diameter D of the outer ring 12 by 10 to 15 μm. The inner ring 13 and the rotating shaft 15 are fitted together by fitting, and the inner diameter d of the inner ring 13 is formed to be smaller by 8 to 15 μm than the shaft diameter of the rotating shaft 15.

The test conditions for the durability life test are as follows.

[Durability Life Test] Radial load Fr: 71500 N Axial load Fa: 15680 N Number of rotations of rotating shaft n: 2500 rpm Lubrication type: characteristic grease (see Tables 5 and 6) Grease amount: 60 g Water amount injected into bearing : 10 cc / hr Table 5 shows the specifications of the characteristic grease as a lubricant used in the endurance life test (excluding Example 6). That is, a mineral oil having a kinematic viscosity at 40 ° C. of 197 mm ² / sec was used as a base oil, and a grease to which 12% of lithium soap was added as a thickener was prepared. The pH value of the grease was measured by the following method. That is, a solvent was prepared in which toluene, 2-propanol and water were adjusted at a volume ratio of toluene: 2-propanol: water = 500: 495: 5, and 0.1 g of the grease was added at 25 ° C. to the solvent 5
The solution was dissolved in 0 mg, and the hydrogen ion exponent pH was measured with a pH meter to obtain a characteristic grease having the hydrogen ion exponent pH 7.0.

[0097]

[Table 5] Table 6 shows the specifications of the characteristic grease used in the durability life test of Example 6. A grease was prepared using the same solvent as in Table 5, and the hydrogen ion exponent pH was measured with a pH meter. As a result, the hydrogen ion exponent pH was 5.4.
Characteristic grease was obtained.

[0098]

[Table 6] The durability life test was performed in Examples 1 to 13 and Comparative Examples 51 to 55.
Performed each 10 destined to each bearing of the first operating time of exfoliated bearings and bearing life L, to evaluate the durability life of the bearing as compared to the nominal life L ₁₀ of the bearing.

[0099] The nominal life L ₁₀ of the bearing, when the bearing of the same lot of the same size rotating at the same conditions, to rotate without causing peeling due 90% of the bearing rolling fatigue number of its total number Calculation time corresponding to the total number of rotations that can be performed. In the case of a tapered roller bearing, the formula (6) is obtained from the basic dynamic load rating C (N), the radial load Fr (N), and the number of rotations n (rpm) of the rotating shaft 15. ) Is known.

L ₁₀ = (C / Fr) ^10/3 × 10 ⁶ / (60n) (6) A bearing made by using a modern technology related to material steel and machining has a rolling surface of a rolling element and a bearing ring. it is believed that it was none of peeling at the rated life L ₁₀ the following run time when a sufficient oil film between the raceway surface is formed.

[0102] Therefore, it is necessary to satisfy at least the rated life L ₁₀ as a rolling bearing durability evaluation of when water in the lubricant is mixed. That is, when moisture is mixed into the inside of the bearing from the outside, or when used in a situation where a large amount of moisture in the lubricant is received without mixing of moisture into the inside of the bearing from the outside (for example, at low speed rotation, the viscosity of the lubricant When the oil film is insufficiently formed between the rolling surface of the rolling element and the raceway surface of the raceway when receiving vibration, when the rotation shaft and the inner raceway are fitted with a strong bur fit, when acting constantly tensile stress on the raceway surface because low rigidity of the housing), it often occurs in peeling rated life L ₁₀ less operating time. Therefore, it is necessary time of occurrence of peeling at least rated life L ₁₀ or more as a durability evaluation. In the case of the present embodiment, the basic dynamic load rating C = 143000N, the radial load Fr = 715.
00N, since the rotational speed n = 2500 rpm of the rotary shaft 15, a 67-hour rated life L ₁₀ of the bearing from Equation (6), whether the life time until delamination exceeds the rated life L ₁₀ reference Becomes

Next, the experimental results will be described with reference to Tables 4 and 5.

In Comparative Example 51, since the rolling elements and the races were formed of a material having the same chemical composition, the metal base was formed in the minute gap formed at the interface between the nonmetallic inclusion and the metal base on the raceway surface. , The bearing life L is 23 hours, which is significantly lower than the rated life L ₁₀ (= 67 hours), and bearing breakage due to early peeling cannot be avoided. You can see that. In Comparative Example 52, the content of Ni, Cr, and Mo was slightly varied between the rolling element and the bearing ring, but between the metallic body and the carbide in the rolling element and the bearing ring. in no difference as electrical noble noble becomes clear, although bearing life L than in Comparative example 51 is improved, bearing life L stays in 52 hours, the desired order is less than the rated life L ₁₀ Durability cannot be obtained.

Further, in Comparative Example 53, the Cr content deviation Δ
The Cr and Mo content deviation ΔMo has a difference that makes the nobleness clear, and the cathode reaction progresses on the carbide on the rolling surface and the corrosion form becomes contact corrosion, but the Ni content ΔNi value it is smaller because less electron supply efficiency to the carbide of the rolling surface, thus although significant improvements were observed with respect to bearing life L, still can not exceed the rated life L _10, obtain a desired durability Can not.

In Comparative Example 54, Cr and Mo were added to the material in the direction in which the carbide on the bearing ring side became noble, and the corrosion form was localized corrosion, so that the bearing life L was extremely shortened. , The durability cannot be satisfied at all. Further, also in Comparative Example 55, the Ni content and C
The r content is not so different between the rolling element and the race, and the Mo content is not so different between the race and the rolling element that the electrochemical nobleness becomes clear. The experimental result was extremely short.

On the other hand, in Examples 1 to 13, each of the content deviations ΔNi, ΔCr, and ΔMo
Ni ≧ + 0.2 wt%, ΔCr ≦ −0.2 wt%, ΔMo ≦
-0.2 wt%, all have rated life L
₁₀ (= 67 hours), which indicates that a rolling bearing having sufficient durability can be obtained.

Further, among Examples 1 to 13, particularly Ni
Examples 4, 5, and 7 in which the content was 0.25 wt% or more, the Cr content was 0.7 wt% or more, the Mo content was 0.25 wt% or more, and the pH of the lubricant was 7.0. ~ 11 and 1
3 has a life time L exceeding 200 hours and a rated life L ₁₀
It was found that the bearing life L was twice or more.

Further, the first embodiment in which the hardness deviation ΔHRC obtained by subtracting the raceway surface hardness from the rolling surface hardness is ΔHRC <0,
In Examples 8 to 11 and Example 13, the bearing life L was 30
It can be seen that the bearing life L can be further improved as compared with the case where the hardness deviation ΔHRC exceeds Δ0RC and ΔHRC ≧ 0.

The composition ranges of the material components of Example 1 and Example 3 were the same, and the hardness deviation ΔHRC was varied by varying the tempering temperature of the rolling elements.
From the comparison between Example 1 and Example 3, the hardness deviation ΔHR was also obtained.
It can be seen that by setting C to ΔHRC <0 and making the rolling element hardness lower than the raceway hardness, the bearing life L can be improved.

As described above, ΔNi ≧ + 0.2 wt%, ΔCr
By satisfying ≦ −0.2 wt% and ΔMo ≦ −0.2 wt% and satisfying ΔHRC <0, sufficient durability can be obtained. More preferably, Ni ≧ 0.25 wt% or more, and By setting ≧ 0.7 wt% or more and Mo ≧ 0.25 wt% or more, it is possible to obtain a rolling bearing with a longer bearing life L.

As shown in Examples 5 and 6, the hydrogen ion exponent pH of the grease used as the lubricant was 7.0 with respect to the bearing material having the same composition. As a result of a comparative experiment between the case of pH value of 5.4 and the case of pH value of 5.4, it was found that the bearing life L was shorter when the hydrogen ion index pH was 5.4 than when the hydrogen ion index pH was 7.0. Further, the effect of the presence or absence of the annealing treatment of the bearing ring can also be compared between Example 1 and Example 12. In other words, the hydrogen content in the race can be reduced by the dehydrogenation effect of the annealing treatment, and the bearing life L
Can be improved.

Also, as in Embodiment 13, O, S and Ti
When the total amount exceeds 0.01 wt% (100 ppm), the bearing life L is shorter than when the total amount of O, S and Ti is 0.01 wt% or less.

[0113] As is apparent from this example, and at least the rated life L ₁₀ or more, in order to improve further bearing life L is first ΔNi ≧ + 0.2wt% to a 1, [Delta] CR ≦
It is important that −0.2 wt% and ΔMo ≦ −0.2 wt%, and if necessary, Ni ≧ 0.25 wt% or more.
Cr ≧ 0.7 wt% or more, Mo ≧ 0.25 wt% or more, ΔH
It is desirable that RC <0, the total amount of O, S, and Ti be 0.01 wt% or less.

Further, it has been found that when carburizing or carbonitriding is performed on the bearing ring, it is desirable to perform an annealing treatment after these treatments to dehydrogenate the bearing ring.

[0115]

As described in detail above, the rolling bearing according to the present invention comprises a raceway ring composed of an outer ring and an inner ring, and a rolling element rotatably disposed between the outer ring and the inner ring. In the rolling bearing provided, the bearing ring material and the rolling element material forming the bearing ring and the rolling element are at least Ni, Cr
And Mo, and a Ni content deviation ΔNi obtained by subtracting the Ni content of the bearing ring material from the Ni content of the rolling element material is ΔNi ≧ + 0.2% by weight, and
Cr obtained by subtracting the Cr content and the Mo content of the bearing ring material from the Cr content and the Mo content of the rolling element material, respectively.
The content deviation ΔCr and the Mo content deviation ΔMo are expressed in weight%.
Since ΔCr ≦ −0.2% and ΔMo ≦ −0.2%, the metal base side at the interface between the nonmetallic inclusions and the metal base on the raceway surface is defined as the anode, and the carbide on the rolling surface is defined as the cathode. Even when water is mixed into the lubricant, corrosion caused by hydrogen absorption into the race is suppressed, and therefore, it is possible to avoid early peeling of the bearing and improve the durability of the rolling bearing. it can.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the relationship between a bearing ring and rolling elements and a radius of curvature.

FIG. 2 is a sectional view of a main part of the durability test apparatus.

[Explanation of symbols]

 11 rolling element 12 outer ring 13 inner ring

Claims (1)

[Claims] 1. A rolling bearing comprising a raceway ring composed of an outer ring and an inner ring, and a rolling element rotatably disposed between the outer ring and the inner ring, wherein the Ni content of the rolling element material is From the raceway material Ni
The Ni content deviation ΔNi obtained by subtracting the content is ΔNi ≧ + 0.2% in weight%, and the Cr content and the Mo content of the bearing ring material from the Cr content and the Mo content of the rolling element material. Respectively, the Cr content deviation ΔCr and the Mo content deviation ΔMo,
A rolling bearing, characterized in that, in terms of% by weight, ΔCr ≦ −0.2% and ΔMo ≦ −0.2%.