JP6804156B2 - Grease composition for rolling bearings - Google Patents

Description

The present invention relates to a grease composition for rolling bearings, and more specifically to a grease composition for machine bearings of steelmaking equipment, and more specifically, urea grease used for bearings of rolling mills of steelworks.

Traditionally, the lubrication environment for bearings used in steelmaking equipment has been harsh, and in particular, segment roll bearings for continuous casting equipment rotate at extremely low speeds in high temperature environments and have a large load. Bearings operate in extremely harsh environments due to insufficient formation of the lubricating film and the inclusion of water and scale. Therefore, in order to improve the lubrication environment and extend the bearing life, mechanical improvement measures such as changing the bearing structure and improving the oil seal to prevent foreign matter from entering are taken, and the lubrication performance of grease is improved. By doing so, a method for extending the bearing life has been proposed.

For example, in Patent Document 1, by adding metal salicylate to diurea-based grease, triurea-based grease, and tetraurea-based grease, the grease structure is kept in a state of being hard to break and homogeneous when water is mixed in the bearing. A method has been proposed in which the ability to form a lubricating film is improved and the bearing lubrication life can be extended by forming a proper grease.

Further, in Patent Document 2, a grease composition containing benzotriazole and additives such as calcium salicylate, magnesium salicylate, calcium phenate and calcium sulfonate in a grease composition containing sodium thiosulfate is described in steel equipment and food machinery. Bearings, gears, etc. have been proposed to solve lubrication problems such as rusting under conditions of contact with a large amount of water.

Further, in Patent Document 3, it is added to grease containing a calcium sulfonate complex thickener as a lubricating grease in order to adapt to an environment of high speed and high load of bearings of iron making machines and the like. As an agent, a grease composition containing molybdenum, dialkyl, dithiocalcium, organic bentonite, a thiadiasol-based metal deactivator, amorphous polypropylene, and polyethylene wax has been disclosed, but it is still satisfactory. is not.

Japanese Unexamined Patent Publication No. 2000-198994 JP-A-2002-53889 Japanese Unexamined Patent Publication No. 11-131086

Here, self-aligning roller bearings are widely used as segment roll bearings for continuous casting equipment, but it is difficult to sufficiently form a lubricating film with conventional grease, especially in low-speed, high-load usage environments. It has been confirmed that slippage occurs due to a slight difference in peripheral speed on the rolling surface of the inner and outer rings, causing stepped wear (double-ridge wear). The occurrence of stepped wear develops into troubles such as early damage and cracking of bearings, leading to an increase in running costs. Therefore, extending the life of segment roll bearings leads to reduction of maintenance cost, reduction of manufacturing cost, and improvement of operating rate, and it is required to solve these problems by using higher performance grease. ..

Therefore, the specific grease composition of the present invention retains the basic performance required for grease for machine bearings of steelmaking equipment such as heat resistance and water resistance, and even under severe lubrication conditions of low speed and high load. It is an object of the present invention to provide urea grease which can sufficiently form a grease lubricating film and has a function of suppressing fatal stepped wear generated on the starting surface of the inner and outer rings of the bearing.

As a result of intensive research to achieve the above object, it was found that a specific grease combining a specific urea thickener, a base oil and a specific additive can solve the above-mentioned problems, and the present invention was completed. I let you.

（式中Ｒは炭素数８〜２２のアルキル基である）
５）前記カルシウムサリシレートをグリース組成物全体に対して１〜５質量％配合してなり、
６）前記カルシウムスルホネートをグリース組成物全体に対して０．５〜５質量％配合してなる、軸受の転動体の回転速度が１００ｒｐｍ以下の低速回転軸受用であるころがり軸受用グリース組成物である。
本発明［２］は
前記ワックスが合成ポリエチレンワックスである前記発明［１］のころがり軸受用グリース組成物である。 More specifically, the present invention provides the following [1] to [2].
The present invention [1]
1) One or more thickeners selected from the diurea thickeners represented by the following general formulas (a) to (c) {However, R ₁ and R ₃ in the entire diurea thickener The molar ratio (R ₁ : R ₃ ) is 20:80 to 80:20} and (a) R ₁ NHCONHR ₂ NHCONHR ₁
(B) R ₃ NHCONHR ₂ NHCONHR ₃
(C) R ₁ NHCONHR ₂ NHCONHR ₃
(In the formula, R ₂ is a diphenylmethane residue, R ₁ is a saturated hydrocarbon group having 6 to 10 carbon atoms, and R ₃ is a saturated hydrocarbon group having 12 to 18 carbon atoms).
2) Group 1 classified by the American Petroleum Institute (API) where the kinematic viscosity of the base oil at 40 ° C is in the range of 150 mm ² / sec to 400 mm ² / sec and the viscosity index is less than 120. Or a grease based on a mineral oil belonging to 2
3) Consistency is in the range of NLGI classification No. 0 to 00 (Consistency: 355-430).
4) As an additive, calcium salicylate, calcium sulfonate and wax represented by the following formula (1) are blended.

(R in the formula is an alkyl group having 8 to 22 carbon atoms)
5) The calcium salicylate is blended in an amount of 1 to 5% by mass based on the entire grease composition.
6) A grease composition for rolling bearings, which comprises 0.5 to 5% by mass of the calcium sulfonate in the entire grease composition and is used for low-speed rotary bearings in which the rotation speed of the rolling element of the bearing is 100 rpm or less. ..
The present invention [2] is a grease composition for a rolling bearing according to the present invention [1], wherein the wax is a synthetic polyethylene wax.

According to the present invention, the lubricating film is maintained and excellent wear resistance is maintained even under the harsh usage conditions of high temperature, low speed, high load and mixed with water, scale, etc., which are the usage environments of segment roll bearings. It is possible to provide a urea-based grease having a property and capable of extending the bearing life.

FIG. 1 is a diagram showing an outline of a water resistance lubrication wear resistance test.

The grease composition according to this embodiment comprises a urea grease mixed with a specific additive. Hereinafter, the specific components, the blending amount of each component, the manufacturing method, the physical properties (performance), and the uses of the grease composition according to the present embodiment will be described in detail, but the present invention is not limited thereto.

≪Grease composition (ingredients) ≫
[Thickener]
The grease composition according to this embodiment contains any one or more thickeners selected from the diurea thickeners represented by the following general formulas (a) to (c).
(A) R ₁ NHCONHR ₂ NHCONHR ₁
(B) R ₃ NHCONHR ₂ NHCONHR ₃
(C) R ₁ NHCONHR ₂ NHCONHR ₃
(In the formula, R ₂ is a diphenylmethane residue, R ₁ is a saturated hydrocarbon group having 6 to 10 carbon atoms, and R ₃ is a saturated hydrocarbon group having 12 to 18 carbon atoms).

However, in the grease composition, the molar ratio of R ₁ to R ₃ (R ₁ : R ₃ ) in the entire diurea thickener needs to be 20:80 to 80:20. As the combination of the diurea thickener, only (c), (a) and (b), (a) and (c), (b) and (c), and (a) are used as long as the relevant conditions are satisfied. , (B) and (c) may be in any form.

The method for synthesizing the diurea thickener used in the present embodiment is not particularly limited, and a known method (for example, the method described in Japanese Patent No. 4976795) can be appropriately selected. The following is an example of a suitable synthesis method for the diurea thickener.

After reacting 2 mol of the primary monoamine consisting of the carbon number of R ₁ with 1 mol of the diisocyanate consisting of the carbon number of R _{2 in} the grease reaction kettle, 2 mol of the primary monoamine consisting of the carbon number of R _{3 and} the carbon number of R ₂ may be reacted with a diisocyanate 1mol consisting, after conversely by reacting a diisocyanate 1mol consisting carbon atoms of primary monoamines and R ₂ consisting of carbon atoms of R _2, primary monoamines consisting of carbon atoms of R ₁ 2 mol may be reacted with 1 mol of diisocyanate having R ₂ carbon atoms. Further, these diureas may be synthesized separately and the obtained diurea grease may be mixed at room temperature.

Examples of the isocyanate used as a raw material include 4,4'-diphenylmethane diisocyanate (MDI). Examples of the primary amine include octylamine (caprylamine), isooctylamine, laurylamine, myristylamine, palmitylamine, stearylamine, isostearylamine and the like.

The consistency of the grease of this embodiment is adjusted in the range of No. 0 to No. 00 (concentration: 355 to 430) of the NLGI classification. If the hardness of the grease is harder than this range (the value of the consistency is small), the fluidity will be poor and the supply of grease to the lubricating interface will be insufficient, and the effect of preventing wear cannot be expected. If the grease is soft (the consistency value is large), leakage from the bearing will increase and satisfactory lubrication will not be possible.

Here, since the hardness of the grease and the amount of the thickener are greatly related to each other, it is desirable to adjust the grease with an appropriate blending amount. Therefore, as the total amount of the thickener in the present embodiment, 100 parts by mass of the entire grease composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 7 parts by mass, and further preferably 2 to 2 parts by mass. 5 parts by mass can be blended. The thickener used in the grease composition of the present embodiment may be only the diurea thickener, or may contain other known thickeners (for example, the entire thickener). It may be blended in less than 50% by mass, preferably less than 25% by mass, and more preferably less than 10% by mass).

[Base oil]
As the base oil used in the grease composition of this embodiment, mineral oil belonging to Group 1 or 2 classified by the American Petroleum Institute (API) is used as the base oil. Here, the API base oil category is a broad classification of base oil materials defined by the American Petroleum Institute to create guidelines for lubricating base oils. The method for producing mineral oil is not particularly specified, but as a preferable example, solvent is removed, solvent extraction, and hydrocracking are performed on the lubricating oil distillate obtained by atmospheric distillation and vacuum distillation of crude oil. , Paraffin-based mineral oil obtained by appropriately combining one or more kinds of refining means such as solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and white clay treatment.

The kinematic viscosity of the base oil directly affects the oil film thickness at the lubricating interface and is an important factor leading to wear prevention. The viscosity of the base oil in this composition is 150 mm ² / at 40 ° C. in the range of 400 mm ² / sec from sec, preferably 350 mm ² / sec from ^{175mm 2 / sec, 200mm 2 /} sec from 300 mm ² / sec is more preferred. If the kinematic viscosity of the base oil is smaller than this range, the effect of preventing wear cannot be expected, and if it is larger than this range, the intervention of grease on the lubricating surface is lowered and the effect of preventing wear cannot be obtained. The base oil is a paraffinic mineral oil belonging to Group 1 or 2 classified by the American Petroleum Institute (API) having a viscosity index of less than 120. For example, Group 3 Highly refined mineral oils and base oils such as Group 4 polyα-olefin (PAO) have poor affinity for urea thickeners, and the greases obtained from these base oils are available at the lubricating interface. The thickener and the base oil tend to separate from each other, causing stabilization and making the lubricating film very unstable, resulting in increased wear.

The amount of the base oil to be blended is 100 parts by mass, preferably 50 to 95 parts by mass, more preferably 60 to 90 parts by mass, and further preferably 70 to 85 parts by mass.

[Additive]
The grease composition of the present embodiment is obtained by adding specific additives (calcium salicylate, calcium sulfonate and wax) to the grease containing the above-mentioned thickener (diurea). By adding these additives to the diurea grease composition, the basic performance required for grease for machine bearings of steelmaking equipment such as heat resistance and water resistance is maintained, and even under low-speed, high-load lubrication conditions. A grease lubricating film can be sufficiently formed, and excellent wear resistance can be realized.

（式中Ｒは炭素数８〜２２のアルキル基である） The calcium salicylate used in the grease composition of this embodiment is represented by the following formula (1).

(R in the formula is an alkyl group having 8 to 22 carbon atoms)

Next, examples of the calcium sulfonate include calcium sulfonate known as a rust preventive and a metal-based cleaning agent, and examples thereof include a calcium salt of petroleum sulfonic acid, a calcium salt of alkyl aromatic sulfonic acid, and petroleum sulfonic acid. The hyperbasic calcium salt of the above, the hyperbasic calcium salt of the alkyl aromatic sulfonic acid and the like can be mentioned.

Here, the total total base value (BN, specified by JIS K2501 perchloric acid method) when these calcium salicylate and calcium sulfonate are mixed is preferably 5 to 600 mgKOH / g, more preferably 50 to 500 mgKOH / g. More preferably, 100 to 400 mgKOH / g. When the BN is within this range, the thickener of the urea grease of the present invention and the calcium carbonate contained in the metal-based cleaning agent are uniformly dispersed, the intervention on the lubricating interface is improved, and a strong lubricating film is formed. It is formed and wear can be prevented. Furthermore, since stable micelles are formed even when water is mixed in, the grease structure is weakened and softened due to the influence of water, and rust is generated and lubrication performance deteriorates due to insufficient dispersion of water. It can be suppressed.

As described above, these calcium salicylate and calcium sulfonate have a function of interacting with each other, salicylate has a high ability to disperse thickeners and additives such as calcium carbonate, and sulfonate is adsorbed at the lubricating interface. On the other hand, if the TBN is high, the coefficient of friction is increased and the grease structure is liable to be fragile. Therefore, it is preferable to add an appropriate amount. Therefore, it is preferable that the ratio of calcium salicylate to calcium sulfonate is in the range of 80 to 20% by mass with respect to the total of calcium salicylate and calcium sulfonate.

The amount of calcium salicylate added is 1 to 5% by mass with respect to the entire grease composition. The amount of calcium sulfonate added is 0.5 to 5% by mass with respect to the entire grease composition. The total amount of salicylate and calcium sulfonate added to the system cleaning agent to be blended in the grease is preferably 7.0% by mass or less, more preferably 2.0 to 5.0% by mass.

Further, the wax blended as an additive is not particularly limited, but is, for example, a modified wax such as polyethylene wax, polypropylene wax, or a derivative imparting a carboxyl group to these, or a copolymerized wax of ethylene and propylene. , Oxidation wax of ethylene-based copolymer and the like.

Wax is an essential component for reinforcing the lubrication film thickness in this grease composition, but depending on the type of wax, the compatibility with the grease may not be excellent, or even if the grease is excellent in solubility, the grease Some of them tend to greatly increase the physical hardness of the wax. Waxes that are not compatible with grease tend to hinder intervention at the lubricating interface, and waxes that have good solubility but tend to significantly increase the physical hardness of grease are those that flow grease. It tends to reduce the property and reduce the supply capacity to the lubricating interface. Therefore, it is preferable to select the wax after fully considering these factors, and among these, as a wax that can easily supply the grease to the lubricating interface together with the thickener and the base oil that are the constituents. Is preferably polyethylene wax (synthetic polyethylene wax).

Polyethylene wax has an average molecular weight of about 1,000 to 10,000, a high density type with a density of 0.96 or more, a medium density type with a density of 0.94 to 0.95, and a low density of 0.93 or less. Density type can be mentioned. The high-density type has a high melting point, softening point, and crystallinity, and has a high hardness, while the low-density type has a low melting point, softening point, and is soft. High-density type polyethylene wax tends to have low consistency (hardness) when blended with grease, which tends to affect the fluidity of grease and makes it difficult to form a stable lubricating film. There is. Therefore, a low-density type polyethylene wax is preferable, and among them, a wax having a molecular weight of 2000 to 5000 and a softening point of 130 ° C. or less is more preferable. Here, since wax is a component that affects the hardness and fluidity of grease while reinforcing the lubricating film thickness, it is preferable to add wax in an appropriate amount. Therefore, the total amount added to the grease is preferably 0.5 to 10% by mass, more preferably 1.0 to 7.0% by mass, and even more preferably 2.0 to 5.0% by mass. ..

[Arbitrary ingredient]
The grease composition of the present embodiment further includes any antioxidant, rust preventive, oily agent, extreme pressure agent, abrasion resistant agent, solid lubricant, metal deactivator, polymer, non-metallic detergent, colorant. Additives may be blended, for example, about 0.1 to 20 parts by mass of any component as a whole, with 100 parts by mass of the entire grease composition being added. For example, as antioxidants, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylparacresol, p, p'-dioctyldiphenylamine, N-phenyl-α-naphthylamine , Phenothiazine, etc. For example, examples of the rust preventive include oxide paraffin, carboxylic acid metal salt, carboxylic acid ester, succinic acid ester, sorbitan ester, and various amine salts. For example, examples of oil-based agents, extreme pressure agents and abrasion resistant agents include zinc dialkyl dithiophosphate sulfide, zinc diallyl dithiophosphate sulfide, zinc dialkyl dithiocarbamate sulfide, zinc diallyl dithiocarbamate sulfide, molybdenum dialkyl dithiophosphate sulfide, and molybdenum diallyl dithiophosphate sulfide. , Molybten sulfide dialkyldithiocarbamate, molybdenum diallyldithiocarbamate sulfide, organic molybdenum complex, olefin sulfide, triphenyl phosphate, triphenyl phosphorothionate, tricresin phosphate, other phosphate esters, sulfide oils and fats and the like. For example, solid lubricants include molybdenum disulfide, graphite, boron nitride, melamine cyanurate, PTFE (polytetrafluoroethylene), tungsten disulfide, graphite fluoride and the like. For example, examples of the metal deactivator include N, N'disalicylidene-1,2-diaminopropane, benzotriazole, benzimidazole, benzothiazole, thiadiazole and the like. For example, examples of the polymer include polybutene, polyisoprene, polyisobutylene, polyisoprene, polymethacrylate and the like. For example, as a non-metallic cleaning agent, imide succinate and the like can be mentioned.

≪Grease composition (blending amount of each component) ≫
The blending amount of each component such as the base oil, the thickener and the additive in the grease composition according to the present embodiment is not particularly limited, but may be within the above range. Further, as for the blending amount of any component, if necessary, the blending amount may be appropriately blended.

≪Manufacturing method≫
The method for producing the grease composition according to this embodiment is not particularly limited, and for example, it can be produced by adding and mixing each of the above-mentioned components by an arbitrary procedure.

<< Performance of grease composition >>
[Mixing consistency]
In the mixing consistency test, the grease composition of the present embodiment preferably has a consistency of 0 to 00 (consistency: 355 to 430), and more preferably 385 to 400 between 0 and 00. Grease. The consistency represents the external hardness of the grease. Here, as the consistency, the value of the mixing consistency measured according to JIS K 22207 is used.

[Drip point]
Although the grease composition of this embodiment has no performance relevance at the drip point, it is preferable that the thickener structure of urea grease reaches 180 ° C. or higher or higher as an index of reaching the original bond. The drip point refers to the temperature at which the viscous grease loses its thickener structure as the temperature is raised. Here, the measurement of the drip point can be performed according to JIS K 22208.

[EHD oil film thickness / lubrication film thickness]
Generally, the oil film thickness of the lubricating oil is proportional to the viscosity of the base oil, and the base oil having a high viscosity has a thick oil film thickness, and the base oil having a low viscosity has a thin oil film thickness. However, in the case of grease, since the thickener affects the lubrication behavior, even if the grease uses a highly viscous base oil, the film thickness may be thinned or a stable lubricating film may not be formed. For example, in the case of grease having a weak affinity between the thickener and the base oil, the base oil and the thickener are separated from each other at the lubrication interface, and the separated thickener causes the flow behavior of the grease at the lubrication interface. The oil film becomes thin when it accumulates, and when it intervenes, the oil film becomes extremely thick. Therefore, a grease having a good affinity between the thickener and the base oil and exhibiting a lubrication behavior similar to that of the base oil is less likely to cause fluctuations in the lubricating film at the interface, and can form and maintain a stable lubricating film. The effect of suppressing wear is enhanced.

In order to evaluate these lubrication characteristics, the film thickness of the grease composition and the film thickness of the base oil are measured using an oil film thickness measuring device (EHD2 oil film thickness measuring device manufactured by PCS) of the optical interferometry method. , The lubrication performance can be judged by the size of the difference between the film thicknesses of the two. Here, the calculation formula used for determining the lubrication performance is as follows.
Rate of change in grease film thickness with respect to base oil film thickness =
(Average film thickness of grease-Average film thickness of base oil) / Average film thickness of grease x 100 ... (*)

The rate of change of the grease film thickness with respect to the film thickness of the base oil is preferably within ± 15%, more preferably within ± 10%, and further preferably within ± 8%. Within this range, since the film thickness of the base oil and the film thickness of the grease are close to each other, the thickener and the base oil, which are constituents of the grease, intervene at the lubricating interface as one. Therefore, since a stable lubricating film can be formed and maintained, high wear resistance can be exhibited in the usage environment of the segment roll bearing of this embodiment, particularly under harsh usage conditions of low speed and high load. The specific test conditions for measuring the film thickness are as follows.
(Test condition)
Equipment: PCS EHD2 oil film thickness measuring instrument Ball: 3/4 inch steel ball Material: SUJ2
Disc: Chromium silica vapor deposition glass Load: 46N
Rotation speed: 3 mm / sec
Measurement time: Measure one point on the disc every minute, average value of 10 times Temperature and record: Measure at each temperature of 25 ° C, 40 ° C, 60 ° C, 80 ° C, 100 ° C, oil film in the entire temperature range Enter the average value.

[SRV friction and wear test]
The grease composition of this embodiment has a friction coefficient of preferably 0.135 μ or less, more preferably 0.132 μ or less, still more preferably 0.129 μ or less in the SRV friction and wear test. The SRV friction and wear test is a widely used test for evaluating the lubrication performance of lubricating oil and grease, and is important for determining the lubrication performance of grease in a lubrication environment accompanied by sliding friction. Here, the measurement of the SRV friction and wear test can be performed using an apparatus compliant with ASTMD5707, but the test piece of the SRV friction and wear test in this embodiment is similar to the component shape of the roller bearing used in the actual machine. The test is carried out in the form of friction of line contact between discs using the cylinder. The specific test conditions are as follows.
(Test condition)
Equipment: Optimole SRV4 friction and wear test equipment Cylinder: Diameter 15 mm x Length 22 mm, SUJ2 equivalent Disc: Diameter 24 mm x Thickness 7.9 mm, SUJ2 equivalent Surface pressure: 500 MP (load: 1,120 N)
Temperature: 100 ° C
Vibration x Amplitude: 10Hz x 1mm
Time: 30min

[High-speed walk wear resistance test]
In the grease composition of this embodiment, the wear mark diameter of the steel ball after the test in the high-speed walk wear resistance test is preferably 0.65 mm or less, more preferably 0.63 mm or less, and further preferably 0. It is 0.6 mm or less. The high-speed four-ball wear resistance test is a more widely used test for evaluating the wear resistance of lubricating oil and grease, and is an index of the wear resistance of grease in a sliding friction lubrication environment. Here, the measurement of the high-speed walk wear resistance test can be performed according to ASTMD2266. The specific test conditions are as follows.
(Test condition)
Temperature: 75 ° C
Rotation speed: 1,200 rpm
Load: 40kgf
Time: 60min

[Water resistance, lubrication, wear resistance test]
In the grease composition of this embodiment, the bearing wear amount after the test in the water resistance lubrication wear resistance test is preferably 18 mg or less, more preferably 15 mg or less, and further preferably 12 mg or less. Here, the method of the water resistance lubrication wear resistance test is as follows. FIG. 1 is a diagram showing an outline of a water resistance lubrication wear resistance tester. As shown in the figure, this testing machine is a testing machine that evaluates the lubricity of grease while injecting water into the housing. This method is an improvement of the water-washing water resistance tester specified in JIS K 2220 5.12. Specifically, as in the JIS specifications, circulating water is not sprayed (300 ml / min) onto the outer ring retainer (seal plate) of the test ball bearing, but distilled water is directly injected into the housing to make it clean. Since it is possible to inject an accurate amount of water, there is little variation and it has been improved so that highly accurate lubricity can be evaluated. As a specific method, the test bearing is filled with 5.0 g of test grease, the bearing is assembled to the housing, and then distilled water heated to 40 ° C. is injected into the housing at 100 ml per minute at 3,000 rpm. Drive for 120 minutes. The injected water is discharged to the outside through the inside of the test bearing filled with the test grease. To evaluate the lubricity of grease, the difference between the bearing weight before the test and the bearing weight after the test (after cleaning) weighed in advance is calculated as the amount of wear and used as an index of the lubricity of the grease when it contains water. The specific test conditions are as follows.
(Test condition)
Test bearing: No.22208EAE4 (self-aligning roller bearing)
Grease filling amount: 5.0 g
Rotation speed: 3,000 rpm
Radial load: 15kgf
Water temperature: 40 ° C
Amount of water: 100 ml / min
Time: 120 minutes

[Simulation test of segment roll bearing actual machine]
In the test simulating an actual segment roll bearing, the grease composition of this embodiment has a volume wear amount of the outer ring race surface of the bearing after the test, preferably 10 mm ³ or less, more preferably 7 mm ³ or less, and further. The amount of wear is preferably 5 mm ³ or less, and particularly preferably 3 mm ³ or less. If the amount of wear is 10 mm ³ or less, the frequency of replacement of the segment roll bearing in the actual machine can be reliably extended, which can greatly contribute to the reduction of running cost. The specific test conditions are as follows.
(Test condition)
Bearing: 22222RHR Self-aligning roller bearing Load: Fr: 100kN, Fa: 10kN
Temperature: 110 ° C
Rotation speed: 11.5 rpm
Grease amount: 3.24 g / h
Test time: 30 days

≪Use of grease composition≫
In the grease composition of this embodiment, the rotation speed of the rolling element (for example, a ball or roller) of the bearing is 100 rpm or less (for example, the rotation speed assumed during equipment operation is in the range of 1 to 100 rpm). It can be used for rolling bearings in low-speed rotary bearings. In particular, it is possible to exhibit excellent lubricity in segment roll bearings of continuous casting equipment operating in a harsh environment where water, scale, etc. are mixed at low speed and high load.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

≪Raw materials≫
The raw materials used in Examples 1 to 3 and Comparative Examples 1 to 4 are as follows.

(Base oil)
-Base oil A: Paraffinic mineral oil obtained by dewaxing solvent refining belonging to Group 1 classified by the American Petroleum Institute (API) with a kinematic viscosity of 99.05 mm ² / s at 40 ° C. and viscosity. The index is 97.
-Base oil B: Paraffinic mineral oil obtained by dewaxing solvent refining belonging to Group 1 classified by the American Petroleum Institute (API) with a kinematic viscosity of 480.2 mm ² / s at 40 ° C. and viscosity. The index is 96.
-Base oil C: A base oil synthesized by the Fischertrop method belonging to Group III classified by the American Petroleum Institute (API), with a kinematic viscosity of 43.40 mm ² / s at 40 ° C. and a viscosity index. Is 143.
(Thickener)
-Urea: Weigh the raw materials so that the ratio of octylamine is 1.3 mol and laurylamine is 0.7 mol to 1.0 mol of 4,4'-diphenylmethane diisocyanate, and completely in the base oil in an autoclave dedicated to grease. It is a reaction to synthesize a urea thickener.
(Additive)
-Additive A: Calcium salicylate (manufactured by INFINEUM, M7125) (BN71 mgKOH / g)
-Additive B: Calcium salicylate (manufactured by INFINEUM, M7121) (BN225 mgKOH / g)
-Additive C: Calcium sulfonate (manufactured by LUBRIZOL, Lz5342) (BN307 mgKOH / g)
-Additive D: Calcium sulfonate (OLOA246A) (BN3.0 mgKOH / g)
-Additive E: Low-density polyethylene wax (CASNo: 9002-88-4) having a molecular weight of 4000 and a softening point of 122 ° C.

≪Manufacturing method≫
According to the composition shown in Table 1, the grease compositions according to Examples 1 to 3 and Comparative Examples 1 to 4 were obtained by a known method.

≪Exam≫
For Examples and Comparative Examples, the mixing consistency test, drip point, EHD oil film thickness, SRV friction wear test, high-speed walk wear resistance test, and water resistance lubrication life test were carried out by the above-mentioned test methods. The properties of the obtained greases of Examples and Comparative Examples are also shown in Table 1.

The consistency of the greases of Examples is in the range of 0 to 00, the greases of Comparative Examples 1 to 3 are in the same range as those of Examples, and the grease of Comparative Example 4 is slightly hard at No. 1 consistency. Grease. The drip point is a value comparable to that of urea grease at 220 ° C. or higher for all greases.

Although it can be judged from the results of the EHD oil film thickness, SRV friction and wear test, and high-speed four-ball wear resistance test, which are indicators of grease lubricity, the greases of the examples are all superior to the greases of the comparative examples. (Stable lubrication film formation state, low friction coefficient, wear resistance) was shown.

The index of water resistance can be determined by the amount of wear of the bearing after the test in the water resistance lubrication wear resistance test, but all of the greases of the examples have stricter conditions in which a larger amount of water is mixed into the bearing than the grease of the comparative example. It also showed excellent wear resistance underneath.

Further, with respect to the greases of Example 1 and Comparative Example 4, a segment roll bearing actual machine simulation test was conducted according to the above-mentioned test method. The test results are shown in Table 2.

As shown in Table 2, in the segment roll bearing actual machine simulation test operated in an environment very close to the actual machine, the grease of the example is in a very good state of the bearing after the test and becomes a starting point of damage. There was almost no stepped wear (double mountain wear) that occurred on the rolling surfaces of the rollers and the inner and outer rings, and the actual measurement result of the wear amount was 1.5 mm ³ , which was an extremely small volume wear amount. The grease of Comparative Example 4 stopped due to abnormal vibration of the bearing (caused by wear) after only 13 days of operation without waiting for the test time of 30 days, and the bearing rolling surface after the test became clear. Stepped wear is progressing, and the actual measurement result of the amount of wear shows an excessive amount of volume wear of more than 10 mm ³ . It was clarified that the grease of the example had much better lubricity than the grease of the comparative example.

The actual lubrication performance of the bearing correlates with the EHD oil film thickness and the results of the SRV friction wear test and the high-speed four-ball wear resistance test. In particular, the oil film formation is extremely high in the bearing that rolls at low speed in this embodiment. Since it becomes unstable, grease that shows stable oil film formation in the evaluation of EHD oil film thickness has a stable oil film formation even in actual bearings such as actual machine simulation tests, and has a large tendency to suppress bearing wear, resulting in high correlation. It is presumed that there is. Therefore, the grease according to the present invention, which exhibits these performances in a well-balanced manner, exhibits extremely excellent performance when used in a rolling bearing for a low-speed rotary bearing. Further, in the usage environment of the segment roll bearing of the present embodiment, cooling water for cooling the steel ingot is often mixed in the bearing, but in the present invention showing excellent wear resistance in the water resistance lubrication wear resistance test. Such grease can be expected to exhibit high wear resistance even when cooling water is mixed in the bearing in an actual use environment.

Claims (2)

1) One or more thickeners selected from the diurea thickeners represented by the following general formulas (a) to (c) {However, R ₁ and R ₃ in the entire diurea thickener The molar ratio (R ₁ : R ₃ ) is 20:80 to 80:20} and (a) R ₁ NHCONHR ₂ NHCONHR ₁
(B) R ₃ NHCONHR ₂ NHCONHR ₃
(C) R ₁ NHCONHR ₂ NHCONHR ₃
(In the formula, R ₂ is a diphenylmethane residue, R ₁ is a saturated hydrocarbon group having 6 to 10 carbon atoms, and R ₃ is a saturated hydrocarbon group having 12 to 18 carbon atoms).
2) Group 1 classified by the American Petroleum Institute (API) where the kinematic viscosity of the base oil at 40 ° C is in the range of 150 mm ² / sec to 400 mm ² / sec and the viscosity index is less than 120. Or a grease based on a mineral oil belonging to 2
3) Consistency is in the range of NLGI classification No. 0 to 00 (Consistency: 355-430).
4) As an additive, calcium salicylate, calcium sulfonate and wax represented by the following formula (1) are blended.

(R in the formula is an alkyl group having 8 to 22 carbon atoms)
5) The calcium salicylate is blended in an amount of 1 to 5% by mass based on the entire grease composition.
6) A grease composition for rolling bearings, which comprises 0.5 to 5% by mass of the calcium sulfonate in the entire grease composition and is used for low-speed rotary bearings in which the rotation speed of the rolling element of the bearing is 100 rpm or less. The grease composition for rolling bearings according to claim 1, wherein the wax is a synthetic polyethylene wax.

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