JPH07118683A - Lubricant for ball and roller bearing - Google Patents

Abstract

PURPOSE:To obtain the ball and roller bearing lubricant prolonging a time from fluid lubrication to boundary lubrication, supporting direct contact on the surface of a metal, having improved seizing resistance and wear resistance, by mixing a lube oil with ultrafine particles having a specific average particle size in a prescribed ratio. CONSTITUTION:A mineral oil is used as a lube oil. 0.05-15wt.% based on the lube oil of ultrafine particles such as ultrafine particles of diamond having <=0.1mum average particle diameter or ultrafine particles of graphite is uniformly dispersed into the lubricating oil to give the lubricant for ball and roller bearing, capable of prolonging a time from fluid lubrication to boundary lubrication, suppressing the surface of a metal which should be brought into contact through a lubricant with a bearing from directly coming into contact with the bearing even during boundary lubrication, improving seizing resistance and wear resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing lubricant, and more particularly to a rolling bearing lubricant having improved seizure resistance and wear resistance of a rolling bearing.

[0002]

2. Description of the Related Art Conventionally, various lubricants have been used for the purpose of lubricating rolling bearings. In a rolling bearing using this lubricant, the lubrication state between the metal surfaces contacting via the lubricant depends on the absolute viscosity of the lubricant used, the load and the rotational speed of the rolling bearing, and the like. For this reason, when the bearing is used at high speed and under high load, the lubricating oil used has a low viscosity, water is mixed in the lubricating oil, or the lubricating oil supply is insufficient. Under severe conditions such as exhaustion, boundary lubrication is reached, and as a result, the thickness of the oil film formed on the surface fluctuates or decreases due to the lubricating oil, and the metal surface to be contacted through the lubricating oil However, there is a problem in that the rolling bearing comes into direct contact early and the seizure resistance of the rolling bearing deteriorates.

Therefore, for rolling bearings used under the severe conditions as described above, molybdenum disulfide (MoS ₂ ), graphite (C), boron nitride (B
N), particles of a solid lubricant such as tungsten disulfide (WS ₂ ), are added, and a lubricant having the function of a solid lubricant added to fluid lubrication is used. In other words, this lubricant allows solid lubricant particles to be introduced together with the lubricating oil between the metal surfaces to be contacted via the lubricant of the rolling bearing, so that the good fluid lubrication inherent to the lubricating oil can be achieved by the solid lubricant. By adding the function of a lubricant, it is intended to improve the lubrication characteristics during boundary lubrication.

[0004]

However, in the lubricant obtained by adding the solid lubricant to the lubricating oil, the thickness of the oil film (fluid film) formed between the metal surfaces to be contacted via the lubricant of the rolling bearing. A solid lubricant having a larger average particle size was used. Therefore, there is a drawback that the solid lubricant particles cannot completely enter the oil film formed between the metal surfaces. Therefore, there has been a problem that when the boundary lubrication is performed under the severe conditions as described above, the function originally possessed by the solid lubricant cannot be sufficiently exhibited.

Furthermore, even if the solid lubricant enters between the metal surfaces, since the average particle diameter of the solid lubricant is larger than the thickness of the oil film, it is difficult to form an oil film between the metal surfaces, and fluid lubrication is performed. There was a problem that the function of was impaired. The present invention has an object to solve such conventional problems, and it is possible to further extend the time until boundary lubrication without impairing the function of fluid lubrication, and at the same time, boundary lubrication. An object of the present invention is to provide a rolling bearing lubricant capable of suppressing direct contact of the metal surface even when the oil film becomes thin or broken and improving seizure resistance and wear resistance. .

[0006]

In order to achieve this object, the present invention comprises a lubricating oil and ultrafine particles having an average particle size of 0.1 μm or less, wherein the ultrafine particles are used as the lubricating oil. On the other hand, the present invention provides a lubricant for rolling bearings, characterized by being added in a proportion of 0.05% by weight or more and 15% by weight or less.

[0007]

The rolling bearing lubricant according to the present invention contains ultrafine particles having an average particle size of 0.1 μm or less in the lubricating oil in a proportion of 0.05% by weight or more and 15% by weight or less with respect to the lubricating oil. Since it has the composition added in, the time from fluid lubrication to boundary lubrication is extended. Further, even at the time of boundary lubrication, direct contact between metal surfaces to be contacted via a lubricant is suppressed, and seizure resistance and wear resistance are improved.

This action is considered to be obtained for the following reasons. 0.1 for small oil-lubricated rolling bearings
It is known that fluid lubrication is performed with a minimum oil film thickness of about μm. Therefore, in a rolling bearing of a commonly used size, the film thickness of the oil film formed between the metal surfaces contacting each other through the lubricant is 0.1 μm or more.

In the present invention, since the average particle diameter of the ultrafine particles, which is a constituent element of the rolling bearing lubricant, is set to 0.1 μm or less, the ultrafine particles have a particle diameter smaller than the oil film thickness. Therefore, since the ultrafine particles easily enter between the metal surfaces together with the lubricating oil, the ultrafine particles do not prevent fluid lubrication. Then, the ultra-fine particles that have entered between the metal surfaces are semi-permanently attached to both metal surfaces,
A convex portion is formed here. Therefore, the lubricating oil between the metal surfaces is less likely to be scraped out between the metal surfaces due to the presence of the protrusions. Therefore, it is considered that the lubricating oil is prevented from being completely removed (removed) from between the metal surfaces. Therefore, it is considered that the lubricating oil is retained between the metal surfaces for a long time and the life of the oil film is improved.

Further, even if the oil film becomes thin or breaks during use of the rolling bearing and sufficient fluid lubrication cannot be performed, since ultrafine particles exist between the metal surfaces, Direct contact between the metal surfaces is suppressed. And, in particular, the average particle diameter of the ultrafine particles is 0.0
When the thickness is 5 μm or less, the ultrafine particles are more likely to enter between the metal surfaces. Therefore, the original fluid lubrication action of the lubricating oil is more sufficiently exhibited, and the life of the oil film formed between the metal surfaces is further improved. Therefore, contact between the metal surfaces is further suppressed.

The "average particle diameter of ultrafine particles" described in the present invention means the average diameter of uncondensed primary particles (single particles). When the addition amount of the ultrafine particles is less than 0.05% by weight with respect to the lubricating oil, it becomes difficult to sufficiently exert the action of making the lubricating oil less likely to be scratched between the metal surfaces. Further, when the oil film becomes thin or breaks and sufficient fluid lubrication is not performed, it is considered difficult to sufficiently exert the effect of suppressing direct contact between the metal surfaces. .

On the other hand, if the amount of the ultrafine particles added exceeds 15% by weight with respect to the lubricating oil, the concentration of particles in the oil film becomes high, so that the function of fluid lubrication by the lubricating oil is hindered.
Moreover, during boundary lubrication, the surface roughness on the metal surface increases, and conversely, metal contact locally occurs, and the baking phenomenon is accelerated. Therefore, the amount of the ultrafine particles added is limited to 0.05% by weight or more and 15% by weight or less with respect to the lubricating oil.

The ultrafine particles are made of a substance harder than a metal surface which is in contact with the rolling bearing through a lubricant.
Particularly preferred. The reason for this is that if the ultrafine particles are harder than the metal surface, a part of the ultrafine particles are easily eroded (embedded) in the metal surface due to the stress applied when the rolling bearing is used. Ultrafine particles,
This is because it can be attached more firmly.

Examples of the ultrafine particles having such a property include ultrafine diamond particles and ultrafine diamond particles having a surface layer (surface layer portion) formed of graphite. And, ultrafine diamond particles whose surface layer is made of graphite are particularly preferable as the ultrafine particles used in the present invention.

The reason for this is that the surface of the ultrafine particles is formed of graphite, which is a solid lubricant, and the inside is made of hard diamond, so that good fluid lubrication by the oil film cannot be performed during use of the rolling bearing. It is considered that in this case, graphite plays a role of a lubricant and solid lubrication is performed. Then, due to the action of the hard diamond constituting the inside, due to the stress applied when using the rolling bearing, a part of the ultrafine particles are easily eroded into the metal surface in contact with the lubricant,
It is considered that this is because the ultrafine particles can be more strongly adhered to the metal surface.

Also, good results have been obtained using the present invention.
The ultrafine particles to be used include the diamond fine particles and the surface layer.
Fine particles whose part is made of graphite
In addition to the above, for example, titanium oxide (TiO 2₂), Aluminum oxide
Ni (Al₂O₃), Magnesium oxide (MgO),
Silicon oxide (SiO₂), PTZ, silicon nitride (Si
₃N _Four), Titanium nitride (TiN), zirconium nitride
(ZrN), chromium nitride (CrN), silicon carbide (Si
C), titanium carbide (TiC), tungsten carbide (W
C), aluminum titanium nitride (TiAlN), etc.
Examples include ceramics.

Solid lubricants such as molybdenum disulfide (MoS ₂ ), graphite (C), boron nitride (BN), and tungsten disulfide (WS ₂ ) can also be used. As a method of supplying the ultrafine particles to the inner space of the rolling bearing, for example, a method of using oil plating,
There are various methods such as a method of adding it to grease, a forced lubrication method of oil air, oil mist, etc., a method of containing it in a cage, and the like.

Further, by interposing the ultrafine particles between the metal surfaces, even if the lubricant is additionally supplied after the fluid lubrication is not sufficiently performed, the lubricant is still formed by the ultrafine particles. It also has a function of passing through the formed space (gap) and being immediately and uniformly supplied between the metal surfaces to form a good oil film again.

[0019]

EXAMPLES Next, examples of the present invention will be described. (Example 1) Mineral oil was used as a lubricating oil, and in the mineral oil, diamond ultrafine particles having an average particle size shown in Table 1, diamond ultrafine particles having a graphite layer as a surface layer, and graphite ultrafine particles are shown in Table 1, respectively. Lubricants (Sample No. 1 to No. 2) added at the indicated concentration (% by weight to lubricating oil)
4) is produced.

Next, the service life of these lubricants used in rolling bearings was investigated under the following conditions. (Survey condition) As a rolling bearing for test, inner diameter = 30m
m, outer diameter = 62 mm, width = 16 mm, number of balls = 9, deep groove ball bearing (open type) was used, and each of the above lubricants was used in the internal space of the rolling bearing for test by using a microsyringe. (Sample No. 1 to No. 24) 3.2μ
l Insert.

The oil film thickness initially formed by the lubricant under these conditions is estimated to be 0.13 μm from the calculated value. Next, for these bearings, radial load = 440K
A rotation test was performed under the conditions of g and rotation speed = 3000 rpm while monitoring vibration and temperature, and the time until both vibration and temperature rise was defined as the life time of the lubricant.

The results are shown in Table 1.

[0023]

[Table 1]

(Comparative Example 1) Next, the following comparative sample was prepared. The same mineral oil as in Example 1 was used as the lubricating oil, and the lubricant consisted of only the lubricating oil (no addition of ultrafine particles) (Sample No. 25). Concentration of fine particles and graphite ultrafine particles shown in Table 2 (% by weight relative to lubricating oil)
The lubricant (Sample No. 26 to No. 33) added in step 3 is prepared.

Next, the lifespan of these lubricants when used in test rolling bearings was investigated in the same manner as in Example 1. The results are shown in Table 2.

[0026]

[Table 2]

From Tables 1 and 2, ultrafine particles having an average particle size in the range of 0.01 to 0.1 μm are contained in the lubricating oil in an amount of 0.05 to 15.00% by weight based on the lubricating oil. The lubricants added in the range (Sample No. 1 to No. 24) are the lubricants (Sample No. 2) in which ultrafine particles were not added to the lubricating oil.
From 5), it can be seen that the life time is improved. And among them, in particular, ultrafine particles having an average particle size of 0.05 μm or less are 0.30 to 5.00% by weight with respect to the lubricating oil.
Lubricant added in the range of (Sample No. 2, No. 3, N
o. 6, No. 7, No. 10, No. 11, No. 18, No.
It can be seen that the life time of No. 19, No. 22, No. 23) was improved.

This is because the particle size of the ultrafine particles added to the lubricating oil penetrates with the lubricating oil between the metal surfaces of the rolling bearing for test that are in contact with each other through the lubricant, and the stress applied to the rolling bearing causes It is considered that this is because the metal was pressed against both metal surfaces and semi-permanently adhered to form a convex portion. That is, since the convex portion prevents the lubricant from being scratched between the metal surfaces, the lubricant is retained between the metal surfaces for a long time. Therefore, it is considered that the life of the oil film formed between the metal surfaces is improved.

Further, even if the oil film becomes thin or breaks during the use of the rolling bearing and sufficient fluid lubrication cannot be performed, the presence of the ultrafine particles may cause the metal surfaces to come into direct contact with each other. It is thought that this is because it was suppressed. This effect is especially due to the average particle size of 0.05μ.
Ultra fine particles having a particle size of 0.3 m or less are added to the lubricating oil.
It was confirmed that the lubricant added in the range of 00 wt% remarkably appeared.

Further, in particular, a lubricant (sample for which ultrafine diamond particles whose surface layer is a graphite layer is added is added.
No. 17 to No. 20) had a longer service life than other lubricants. It is considered that this is because the surface of the ultrafine particles is formed of the ultrafine particles which is a solid lubricant, and the inside is made of hard diamond.

That is, when the fluid lubrication by the oil film is not performed while the rolling bearing is in use, it is considered that the graphite serves as a lubricant and the solid lubrication is further performed. To be Then, due to the action of the hard diamond forming the inside, the ultrafine particles are
It is considered that the ultrafine particles are more strongly adhered to the metal surface because the metal surface of the rolling bearing is easily bitten (embedded) in contact with the lubricant through the lubricant.

On the other hand, the lubricants (Samples No. 26 to No. 33) to which ultrafine particles having an average particle diameter of 0.5 μm are added are
Lubricants in which ultrafine particles were not added to the lubricating oil (Sample N
From 25., it can be seen that the life time is further reduced. And since this is because the average particle size of the ultrafine particles is larger than the thickness of the oil film formed inside the test rolling bearing, the ultrafine particles are contacted via the lubricant of the test rolling bearing. It is considered that, in addition to the fact that the particles could not sufficiently enter between the surfaces, the movement (movement) of the lubricating oil was blocked by the ultrafine particles and the fluid lubrication was blocked.

Further, the decrease in the life time became more remarkable as the concentration of the ultrafine particles in the lubricating oil increased. Furthermore, in Comparative Example 1, Sample No. 30 to No. 33
It can be seen that, although the ultrafine particles made of graphite, which is a solid lubricant, were used, the life time was not improved.

From this, it is possible to add ultrafine particles to the lubricating oil.
To improve the life of the lubricant obtained by
The average particle size of the particles and the amount added to the lubricating oil are large.
It is understood that the cause is. Next, conduct the same survey as above.
Boron nitride having a uniform particle size of 0.5 μm and 0.01 μm
(BN), molybdenum disulfide (MoS₂), Aluminum oxide
Ni (Al₂O ₃), Magnesium oxide (MgO),
To the lubricating oil used in Example 1, respectively.
0.05% by weight, 0.80% by weight, 5.00% by weight
%, 15.00% by weight, added lubricant
The same investigation as in Example 1 was conducted.

As a result, the lubricant to which the ultrafine particles having an average particle diameter of 0.01 μm were added was superior to the lubricant to which no ultrafine particles were added (Sample No. 25) at all concentrations.
Life time was improved. On the other hand, the average particle size is 0.5 μm
Lubricants with the addition of ultrafine particles of
Lubricant with no ultrafine particles added (Sample No. 25)
Therefore, the life time was reduced.

As a result, also for the other ultrafine particles, the ultrafine particles having an average particle size of 0.1 μm or less are added to the lubricating oil in a ratio of 0.05% by weight or more and 15% by weight or less with respect to the lubricating oil. It turns out that it is necessary to add. (Example 2) Mineral oil was used as a lubricating oil, and in the mineral oil, diamond ultrafine particles having an average particle size shown in Table 3, diamond ultrafine particles having a graphite layer as a surface layer, and graphite ultrafine particles are shown in Table 3, respectively. Lubricants (Sample No. 34 to No. 34) added at the indicated concentration (% by weight relative to lubricating oil)
57) is prepared.

Next, the life when these lubricants were used in rolling bearings was examined under the following conditions. (Survey conditions) As a rolling bearing for test, inner diameter = 25m
m, outer diameter = 52 mm, width = 16 mm, number of rollers = 19,
Using tapered roller bearings, the oil plating (diluting the lubricant to 20% with hexane, dipping the test bearing into this solution, and then evaporating the hexane to dryness) was performed. A lubricant film is formed on the surface), and each lubricant (Sample Nos. 34 to 57) is applied to the raceway surface and rolling surface of the bearing to form an oil film.

The initial oil film thickness of the lubricant under this condition is estimated to be 0.22 μm from the calculated value. Next, these bearings were subjected to a rotation test under the conditions of radial load = 440 Kg and rotation speed = 1000 rpm while monitoring vibration and temperature, and the time until the vibration and temperature both increased was the life of the lubricant. And

The results are shown in Table 3.

[0040]

[Table 3]

Comparative Example 2 Next, the following comparative sample was prepared. The same mineral oil as in Example 2 was used as the lubricating oil, and the lubricant consisted of only the lubricating oil (no addition of ultrafine particles) (Sample No. 58). Concentration of fine particles and graphite ultrafine particles shown in Table 4 (% by weight relative to lubricating oil)
The lubricant (samples No. 59 to No. 66) added in step 1 is prepared.

Next, the life when these lubricants were used in a rolling bearing for test was examined by the same method as in Example 2. The results are shown in Table 4.

[0043]

[Table 4]

From Tables 3 and 4, ultrafine particles having an average particle size in the range of 0.01 to 0.1 μm are added to the lubricating oil in an amount of 0.05 to 15.00% by weight based on the lubricating oil. The lubricant added in the range (Sample No. 34 to No. 57) was the lubricant (Sample No. 5) in which ultrafine particles were not added to the lubricating oil.
It can be seen that the life time is significantly improved as compared with 8).

Among them, in particular, the average particle size is
Ultra fine particles of 0.05 μm or less were added to the lubricating oil in an amount of 0.
Lubricant added in the range of 05 to 5.00% by weight (Sample No. 34, No. 36, No. 38 to No. 40, No. 4
2 to No. 44, No. 46 to No. 48, No. 50 to 52, N
It can be seen that the life time of o.54-56) was significantly improved.

Also in the same manner as in Example 1, the protrusions made of ultrafine particles formed between the metal surfaces of the rolling bearing for test contacting each other through the lubricant are scratched by the lubricant from between the metal surfaces. It is considered that this is because the lubricant is prevented from being discharged and the lubricant is retained between the metal surfaces for a long time, so that the life of the oil film formed between the metal surfaces is improved.

Further, even if the oil film becomes thin or breaks during use of the rolling bearing and sufficient fluid lubrication cannot be performed, the presence of the ultrafine particles may cause the metal surfaces to directly contact with each other. It is thought that this is because it was suppressed. This effect is especially due to the average particle size of 0.05μ.
Ultra fine particles of m or less are used in an amount of 0.05-5.
It was confirmed that the lubricant added in the range of 00 wt% remarkably appeared.

Further, as in the case of Example 1, in particular, the lubricants (sample Nos. 50 to 53) to which the ultrafine diamond particles having the graphite layer as the surface layer were added had a longer service life than other lubricants. Was improving. This is also the first embodiment
Similar to the above, it is considered that when the fluid lubrication due to the oil film is not performed during the use of the rolling bearing, the graphite plays a role of a lubricant and the solid lubrication is further performed. .

Then, due to the action of the hard diamond constituting the inside, the ultrafine particles are easily eroded (embedded) into the metal surface in contact via the lubricant of the rolling bearing, so that the ultrafine particles are deposited on the metal surface. It is considered that this is because the particles were more firmly attached. On the other hand, the average particle size is
Lubricant added with ultrafine particles of 0.5 μm (Sample No.
59 to No. 66), it is understood that the life time is further shortened as compared with the lubricant (Sample No. 58) in which ultrafine particles were not added to the lubricating oil.

Also in this case, as in the case of Example 1, in addition to the fact that the ultrafine particles could not sufficiently enter between the metal surfaces of the test rolling bearing contacting with each other through the lubricant, It is considered that this is because the movement (movement) of the lubricating oil was blocked by the ultrafine particles and the fluid lubrication was blocked. Further, the decrease in the life time became more remarkable as the concentration of the ultrafine particles in the lubricating oil increased.

Next, the same investigation as above was conducted to find that the average particle size was
0.5 μm and 0.01 μm boron nitride (BN),
Molybdenum sulfide (MoS₂), Aluminum oxide (Al
₂O ₃), Magnesium oxide (MgO), in Example 1
The lubricating oil used for
% By weight, 0.80% by weight, 5.00% by weight, 15.00
%, The lubricant added was prepared in the same manner as in Example 2.
I had a inspection.

As a result, the lubricant to which the ultrafine particles having an average particle diameter of 0.01 μm were added was superior to the lubricant to which no ultrafine particles were added (Sample No. 58) at all concentrations.
Life time was improved. On the other hand, the average particle size is 0.5 μm
Lubricants with the addition of ultrafine particles of
Lubricant with no ultrafine particles added (Sample No. 58)
Therefore, the life time was reduced.

As a result, also for the other ultrafine particles, the ultrafine particles having an average particle size of 0.1 μm or less are added to the lubricating oil in a ratio of 0.05% by weight or more and 15% by weight or less with respect to the lubricating oil. It turns out that it is necessary to add. The rolling bearing lubricant according to the present invention is used in Examples 1 and 2.
In addition to the rolling bearings described above, the present invention can be applied to all rolling bearings such as thrust ball bearings, angular ball bearings, cylindrical roller bearings, rod roller bearings and needle roller bearings.

The rolling bearing lubricant according to the present invention is
In addition to the ultrafine particles introduced in Examples 1 and 2, for example, titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ),
(PTZ), silicon nitride (Si ₃ N ₄ ), titanium nitride (T
iN), zirconium nitride (ZrN), chromium nitride (C
rN), silicon carbide (SiC), titanium carbide (TiC),
Various ceramics such as tungsten carbide (WC) and aluminum titanium nitride (TiAlN), and various solid lubricants such as tungsten disulfide (WS ₂ ) can be used.

Further, in the first and second embodiments,
Although the example in which mineral oil is used as the lubricating oil has been described, the lubricating oil is not limited to this, and any kind of lubricating oil such as ester oil, silicone oil, and fluorine oil can be used as long as it can be used as the lubricating oil. May be used. In Example 1, a microsyringe was used to insert a lubricant into the internal space of the test rolling bearing, and in Example 2, an oil plating was used to insert the lubricant into the internal space of the test rolling bearing. However, the method for supplying the ultrafine particles to the inner space of the rolling bearing is not limited to this, and examples thereof include a method of adding the ultrafine particles into grease, a forced lubrication method such as oil air and oil mist, and As long as an oil film is sufficiently formed in the inner space of the rolling bearing, various methods may be used, such as a method of containing it.

[0056]

As described above, the rolling bearing lubricant according to the present invention contains, in the lubricating oil, ultrafine particles having an average particle size of 0.1 μm or less in an amount of 0.05% by weight based on the lubricating oil. As described above, since it has a composition added in a proportion of 15% by weight or less, the ultrafine particles can completely penetrate into the oil film formed between the metal surfaces contacting each other through the lubricant of the rolling bearing. Therefore, it can easily enter between the metal surfaces together with the lubricating oil. Since the ultrafine particles have an average particle size smaller than the thickness of the oil film, they do not affect the fluidity of the lubricating oil. Therefore, the fluid lubrication characteristics of the lubricant can be maintained.

Further, the ultrafine particles adhere to the metal surface to form a convex portion here, but the presence of the convex portion prevents the lubricating oil between the metal surfaces from being scratched out from here. it can. Therefore, the lubricating oil is prevented from being completely removed (removed) from between the metal surfaces,
The life of the oil film can be improved. Further, during use of the rolling bearing, even if the oil film becomes thin or breaks and sufficient fluid lubrication is not performed, since ultrafine particles are present between the metal surfaces, the metal surface It is possible to suppress direct contact between the two.

For this reason, the time from fluid lubrication to boundary lubrication is extended, and further during boundary lubrication,
There is an effect that direct contact with a metal surface to be contacted via a lubricant is suppressed. As a result, it is possible to improve the seizure resistance and wear resistance of the rolling bearing and provide a rolling bearing lubricant having a long life.

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Claims (1)

[Claims] 1. A lubricating oil and ultrafine particles having an average particle size of 0.1 μm or less, wherein the ultrafine particles are contained in an amount of 0.05% by weight or more and 15% by weight or less with respect to the lubricating oil. A lubricant for rolling bearings characterized by being added.