JP2001049277A - Corrosion resistant rolling bearing - Google Patents

Abstract

[PROBLEMS] To provide a long-life corrosion-resistant rolling bearing having excellent corrosion resistance even in a highly corrosive environment such as underwater. A rolling bearing including an inner ring, an outer ring, a rolling element, and a retainer, wherein at least one of the inner ring, the outer ring, the rolling element, and the retainer has C: 0.5% by weight or less; 12.0 to 16.0% by weight, Mn;
0.5% by weight, Si; 0.1 to 1.0% by weight, N;
A stainless steel containing from 0.8 to 0.20% by weight of a trace component, having a eutectic carbide size of 2 μm or less and an area ratio of the eutectic carbide of 5% or less; The space between the outer ring and the outer ring is provided with a lubricant-containing resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used for food machinery, agricultural machinery, semiconductor-related equipment (for example, a hard disk cleaning device), and more particularly to a metal bearing such as water. The present invention relates to a corrosion-resistant rolling bearing that can be suitably used in an environment where the rolling bearing comes into contact with a corrosive substance.

[0002]

2. Description of the Related Art Conventional corrosion-resistant rolling bearings include, for example, inner and outer rings made of corrosion-resistant stainless steel.
There is a rolling bearing filled with a lubricating oil-containing polymer in an inner space of a rolling bearing provided with a rolling element (described in Japanese Patent Application Laid-Open No. Hei 6-313435 by the present applicant). In this rolling bearing, the inner ring, the outer ring, and the rolling elements are excellent in corrosion resistance and have a hardness of at least HRC 58 required for the bearing.
Martensitic SUS440, a stainless steel
C, and a space between the inner ring and the outer ring is filled with a lubricating oil-containing polymer composed of a poly-α-olefin polymer and a lubricating oil. It is a rolling bearing having a long service life even underneath.

[0003]

However, the conventional corrosion-resistant rolling bearing as described above has the following problems. When the Cr-rich stainless steel contains a large amount of C and Cr, for example, when it contains C exceeding 0.6% by weight, coarse eutectic carbide exceeding 10 μm is combined with a large amount of Cr. Many are formed. Such a coarse eutectic carbide not only reduces the rolling fatigue life, toughness, corrosion resistance, etc. of stainless steel, but also has a bad effect of deteriorating workability such as forgeability and machinability.

[0004] When a rolling bearing is used in a highly corrosive environment such as underwater, a high degree of corrosion resistance and a life (abrasion resistance) in the environment are required. However, SUS44
0C corrodes from the Cr-deficient layer around the eutectic carbide and rusts because the corrosion resistance in such an environment is insufficient. As a result, the accuracy such as the roughness of the raceway surface is deteriorated, and the life is shortened.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a long-life corrosion-resistant rolling bearing having excellent corrosion resistance even in a highly corrosive environment such as underwater. .

[0006]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, the corrosion-resistant rolling bearing of the present invention is an inner ring, an outer ring, a rolling element, and a rolling bearing including a retainer, wherein the inner ring, the outer ring,
At least one of the rolling element and the retainer is C;
0.5% by weight or less, Cr; 12.0 to 16.0% by weight,
Mn: 0.1 to 0.5% by weight, Si: 0.1 to 1.0% by weight, N: 0.08 to 0.20% by weight and a small amount of eutectic carbide It is made of stainless steel having a thickness of 2 μm or less and an amount of the eutectic carbide of 5% or less in area ratio, and further includes a lubricant-containing resin in a space between the inner ring and the outer ring.

With such a configuration, the corrosion-resistant rolling bearing of the present invention has excellent corrosion resistance even in a highly corrosive environment such as underwater. Further, since the lubricant is supplied from the lubricant-containing resin to the lubricated portion of the rolling bearing for a long period of time, the rolling bearing has a long life. Further, since the lubricant-containing resin also acts as a seal for the rolling bearing, a corrosive substance such as water hardly enters the rolling bearing.
Therefore, the inside of the rolling bearing such as the raceway surface is protected from the corrosive environment and is less susceptible to corrosion.

Hereinafter, stainless steel having corrosion resistance and a lubricant-containing resin, which are components of the corrosion-resistant rolling bearing of the present invention, will be described in detail. First, the trace components contained in the corrosion-resistant stainless steel will be described. 1. Carbon (C) C is an element that improves the hardness after quenching and tempering by forming carbides and transforming the matrix into martensite, thereby increasing the strength of steel. However, from the viewpoint of corrosion resistance, a smaller amount is preferable.
Forms coarse eutectic carbides during steelmaking. As a result, not only the Cr concentration in the matrix is insufficient but sufficient corrosion resistance cannot be obtained, but also the rolling fatigue life and toughness are reduced. Therefore, the C content is 0.5% by weight or less, more preferably 0.1% by weight.
It is preferably at most 45% by weight.

[0009] 2. Chromium (Cr) Cr is the most necessary element for imparting corrosion resistance to steel, and it is necessary to contain 10% by weight or more in order to obtain good corrosion resistance. However, if the Cr content increases, the corrosion resistance improves, but if added more than necessary, δ ferrite is generated and the steel becomes brittle, deteriorating the toughness. Also,
If the Cr concentration in the matrix is too high, the martensite transformation start temperature (Ms) decreases, and in some cases, sufficient quench hardness may not be obtained. From these, C
The r content is preferably 12.0 to 16.0% by weight, more preferably 12.0 to 14.0% by weight. 14.0
If the content is more than 10% by weight, eutectic carbide is likely to be generated depending on the C content.

[0010] 3. Manganese (Mn) Mn is an element necessary as a deoxidizing agent in steel making, and is contained in an amount of 0.1% by weight or more. However, when added in a large amount, not only deteriorates forgeability and machinability, but also decreases corrosion resistance by coexisting with impurities such as S and P, and the amount of retained austenite increases significantly depending on the nitrogen content. , Sufficient quenching hardness may not be obtained. For these reasons, the Mn content is preferably 0.1 to 0.5% by weight.

4. Silicon (Si) Si is required to be 0.1% by weight or more as a deoxidizing agent at the time of steel making like Mn. Furthermore, the tempering softening resistance is increased,
It is an effective element for improving the rolling fatigue life. However, if contained in a large amount, the toughness of the steel is reduced.
1-1.0% by weight is preferred.

5. Nitrogen (N) N has the effect of strengthening martensite and improving corrosion resistance similarly to C, and has the effect of suppressing the formation of coarse primary eutectic carbides. Contained. In general, when elements such as V, Mo, Cr and Mn are mixed, the solubility of N increases, but the nitrogen solubility in molten steel is small in a normal steel making method under atmospheric pressure, and the solubility is as high as 0.20% by weight. %.

In order to add more N, steelmaking equipment in a high-pressure nitrogen atmosphere is required, but this is not preferable because it increases the cost. Also, if an attempt is made to add a large amount of N under atmospheric pressure, bubbles are generated during the coagulation process and a large amount of bubbles are introduced into the ingot, or depending on the N content (over 0.20% by weight), a large amount of Remaining austenite may be generated and the quenching hardness may be reduced, which may cause variations in the life of the rolling bearing.

From these facts, the upper limit of the N content is set to 0.20% by weight which can be contained by a normal steel making method. next,
The size and amount of the eutectic carbide present in the stainless steel will be described. If coarse eutectic carbides are present in the matrix, Cr will be deficient in the vicinity of the matrix, making it more susceptible to local corrosion. In particular, eutectic carbides generated during the solidification process during steelmaking are likely to be coarsened, and are not easily melted in the matrix by the subsequent heat treatment, so that the corrosion resistance is significantly adversely affected. If the size exceeds 5 μm in the major axis, the rolling fatigue life is adversely affected.
It is preferably at most 1.5 μm, more preferably at most 1.5 μm. Further, even if the eutectic carbide is fine, if the amount thereof exceeds 5% in area ratio, the passivation characteristics are significantly reduced. Therefore, the amount is preferably 5% or less in area ratio, more preferably 3% or less.

Next, the lubricant-containing resin will be described.
The lubricant-containing resin in the present invention is composed of a raw material resin and a lubricant. As the raw material resin, polyolefin resins such as polyethylene, polypropylene, polybutylene, and polymethylpentene are most preferable in consideration of resistance such as hydrolysis resistance to acids and alkalis.

However, a resin having an excellent ability to contain a lubricant (hereinafter referred to as an oil retaining property) can be used depending on the use environment, even if the resistance is slightly inferior. Examples of such a resin include a thermoplastic resin that can be injection-molded such as a polyester elastomer, and a thermosetting resin such as a polyurethane and a polyurea elastomer.

In the case of a thermoplastic resin such as a polyolefin-based resin, a lubricant is mixed with a raw material resin, heated and melted at a temperature not lower than the melting point of the raw material resin, and then solidified by cooling, whereby a lubricant-containing resin is obtained. can get. Preferably used lubricants include paraffinic hydrocarbon oils such as poly-α-olefin oils, naphthenic hydrocarbon oils, and paraffinic mineral oils in consideration of the resistance as in the case of the raw material resin. Most stable and most suitable. Depending on the use environment, ether oils such as dialkyldiphenyl ether and ester oils such as phthalic acid ester can be used. These can be used alone or in combination of two or more. Various additives such as an antioxidant, a rust inhibitor, an antiwear agent, a defoaming agent, and an extreme pressure agent may be added to the lubricant before use.

In the case of a thermosetting resin, a lubricant-containing resin cannot be obtained by the above-described method using a thermoplastic resin. Therefore, a lubricant-containing resin is produced by the following method. In the case of the polyurethane, a lubricant-containing resin can be obtained by the following method using grease as a lubricant. That is, after uniformly mixing grease with each or either of the urethane prepolymer having an isocyanate group and the amine-based curing agent which are the raw materials of the polyurethane, the urethane prepolymer and the amine-based curing agent are mixed. The mixture is filled into rolling bearings. If necessary, the resin is heated and reacted, and cured in a state in which the grease is contained to obtain a lubricant-containing resin.

In the case of a polyurea elastomer,
An amine component comprising a mixture of an aromatic polyamine compound and an aromatic diamine containing a soft segment in a molecular chain is uniformly mixed with a lubricating oil compatible therewith or a grease using the lubricating oil as a base oil. Add ingredients and mix. Then, the mixture is filled in a mold having a desired shape, and heated and reacted as needed,
It is cured with the lubricant contained.

The composition ratio of the raw material resin to the lubricant in the lubricant-containing resin is preferably 10 to 50% by weight of the raw material resin and 90 to 50% by weight of the lubricant. Raw material resin is 1
If the content is less than 0% by weight, the resin containing the lubricant has sufficient hardness,
It cannot give strength or the like. Then, when a load is applied to the lubricant-containing resin due to rotation of the rolling bearing or the like, it is difficult to maintain the initial shape, and there is a possibility that a problem such as falling off from the rolling bearing may occur. Also,
When the amount of the raw material resin exceeds 50% by weight, the amount of the lubricant contained in the lubricant-containing resin decreases, so that the amount of the lubricant supplied to the rolling bearing decreases, and the life of the rolling bearing is shortened.

In general, resins have various average molecular weights (the same basic structure), and the physical properties may differ depending on the average molecular weight. Therefore, a raw material resin having desired physical properties can be adjusted by mixing resins having various average molecular weights as needed. For example, in the case of a polyolefin-based resin, a wax classified into a wax having an average molecular weight of 700 to 1 × 10 ⁴ (for example, polyethylene wax) and a wax having a relatively low molecular weight having an average molecular weight of 1 × 10 ⁴ to 1 × 10 ⁶ are used. And an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶
And ultra high molecular weight.

In the present invention, those having a relatively low molecular weight as a main component and those classified as wax or ultrahigh molecular weight can be mixed and used as necessary. A combination of a relatively low molecular weight lubricant and a lubricant can provide a lubricant-containing resin having a certain level of mechanical strength, lubricant supply capacity, and oil retaining properties. Replacing some of the relatively low-molecular-weight substances in this category with those classified as wax increases the affinity for lubricants due to the small difference in molecular weight between those classified as wax and lubricants. As a result, the oil retention of the lubricant-containing resin is improved, and the lubricant can be supplied for a longer period of time. However, on the other hand, the mechanical strength decreases. In addition, as wax,
In addition to a polyolefin resin such as a polyethylene wax, a hydrocarbon wax having a melting point in the range of 100 to 130 ° C. or more (for example, a paraffin synthetic wax) can be used.

On the other hand, when a part of a relatively low molecular weight compound is replaced with an ultra high molecular weight compound, the difference in molecular weight between the ultra high molecular weight compound and the lubricant is large, so that the affinity for the lubricant is low. It tends to lower the oil retention as a result. As a result, the lubricant quickly exudes from the lubricant-containing resin, and the period during which the lubricant can be supplied to the rolling bearing is shortened, so that the life of the bearing is shortened. However, the mechanical strength is improved.

Considering the balance of moldability, mechanical strength, oil retention, and lubricant supply, the composition ratio of the lubricant-containing resin is 0 to 5% by weight for waxes and relatively low molecular weight. It is preferred that the content is 8 to 48% by weight, the content of the ultrahigh molecular weight is 2 to 15% by weight, the total of the three types is 10 to 50% by weight, and the remainder is a lubricant. Various additives may be added to the lubricant-containing resin in the present invention as long as the object of the present invention is not impaired.

For example, a filler may be added to improve the mechanical strength of the lubricant-containing resin. For example, calcium carbonate, magnesium carbonate, inorganic whiskers such as potassium titanate whiskers and aluminum borate whiskers, inorganic fibers such as glass fibers and metal fibers, and those woven into a cloth, carbon black, graphite powder, carbon Fiber, aramid fiber, polyester fiber and the like. Among these fillers, potassium titanate whisker, aluminum borate whisker, glass fiber, and carbon fiber are most preferable in consideration of resistance to acid and alkali such as hydrolysis resistance.

The hardness (HD) which is one of the mechanical strengths
_A ) is preferably in the range of 65 to 85, more preferably in the range of 70 to 80. When the hardness (HD _A ) of the lubricant-containing resin is less than 65, the resin is weak in strength and may be damaged by rotation of the rolling bearing. Also,
When the hardness (HD _A ) exceeds 85, the force for restraining the rolling elements increases, so that the torque of the rolling bearings increases, and the heat generated by the rotation of the rolling bearings increases, and the temperature of the rolling bearings increases. May increase.

Further, in order to prevent deterioration of the starting resin such as polyolefin resin due to heat, N, N'-diphenyl-p-phenylenediamine, 2,2'-methylenebis (4-ethyl-6-t-butylphenol) are used. ), And for the purpose of preventing deterioration due to light, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone,
An ultraviolet absorber such as (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole may be added.

The addition amount of all the above additives (other than the raw material resin and the lubricant) is preferably 20% by weight or less of the whole in order to maintain the ability to supply the lubricant to the rolling bearing.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a corrosion-resistant rolling bearing according to the present invention will be described with reference to tables and drawings. FIG.
Are the inner ring 2, the outer ring 3, and the ball 4 held by the holder 5.
A deep groove ball bearing 1 comprising: a lubricant-containing resin 10 filled in a space between the inner ring 2 and the outer ring 3; and a contact seal 6 including a lip 6a and a core 6b.

The composition of the stainless steel constituting the inner ring 2, the outer ring 3, the balls 4, and the retainer 5 is C: 0.45% by weight, C
r: 13% by weight, Mn: 0.3% by weight, Si: 0.3% by weight, N: 0.14% by weight, the balance being Fe. Also,
The size of the eutectic carbide present in the stainless steel is at most 2 μm, and its amount is 5% in area ratio. The composition of the lubricant-containing resin 10 is as follows: 12.5% by weight of ultra high molecular weight polyethylene (ultra high molecular weight), 10% by weight of high density polyethylene (of relatively low molecular weight), and polyethylene wax (classified into wax). 2.5% by weight) and 75% by weight of a paraffinic mineral oil (lubricant).

Before the lubricant-containing resin 10 and the contact seal 6 are mounted, the deep groove ball bearing 1 is degreased and washed, and then coated with a fluorine-based release agent described in Japanese Patent Application Laid-Open No. Hei 7-139551 by the present applicant. To form a coating film. Next, with the bearing 1 held in a mold, the lubricant-containing resin
Injection molding (insert molding) was performed to fill the space between the inner ring 2 and the outer ring 3 as shown in FIG. The lubricant-containing resin 10 was injected from one side of the deep groove ball bearing 1, and the gate was provided at an intermediate position between the inner ring 2 and the outer ring 3 (pin gate). As the injection molding machine, the one described in JP-A-8-309793 by the present applicant (with improved hopper) was used. And the contact seal 6 was attached, and the deep groove ball bearing 1 of FIG. 1 was obtained.

Next, the performance of the corrosion-resistant rolling bearing of the present embodiment was evaluated by a salt spray test. Example 1 is the same rolling bearing as the above-mentioned deep groove ball bearing 1, and Comparative Example 1
Is a rolling bearing of Example 1 without a lubricant-containing resin, and Comparative Example 2 is a SUS440C stainless steel formed in the rolling bearing of Example 1,
Further, the rolling bearing is not provided with a lubricant-containing resin and is filled with grease. Table 1 shows the composition of the stainless steel constituting each rolling bearing.

The rolling bearings were sprayed with a 5% aqueous sodium chloride solution at room temperature, and the life of the rolling bearings was evaluated under the following conditions, and the appearance after 50 hours was observed. Bearing type: Nippon Seiko Co., Ltd. Identification number 6000 (with contact rubber seal) Test load: Fr 8 kgf, Fa 3 kgf Rotation speed: 1000 rpm Spray liquid: 5 wt% concentration sodium chloride aqueous solution Spray amount: 0.6 cc / min (1 second) Spraying / intermittent spraying for 9 seconds) Spray pressure: 0.2 MPa The test results are shown in Table 2. In addition, the life was indicated by a relative value where the life of the rolling bearing of Example 1 was set to 1.

[0034]

[Table 1]

[0035]

[Table 2]

The rolling bearing of Example 1 had no change in appearance and no rust was observed. In addition, there was no change in the quality of the lubricant-containing resin. On the other hand, in the rolling bearing of Comparative Example 1, although no rust was observed,
The life was about 50% of that of the rolling bearing of Example 1. Further, in the rolling bearing of Comparative Example 2, rust was remarkably generated on the whole rolling bearing, and water was mixed in the rolling bearing to emulsify the grease. Also, the life was short.

As described above, the corrosion-resistant rolling bearing of the present embodiment is not subject to corrosion even in a strongly corrosive environment due to the excellent corrosion resistance of the stainless steel constituting the rolling bearing. In addition, since the lubricant is supplied from the lubricant-containing resin to the raceway surface or the like for a long period of time and a lubricating effect can be imparted, the rolling bearing has a long life. Further, since the lubricant-containing resin filled in the inside of the rolling bearing also acts as a seal, it prevents salt water from entering the rolling bearing and adversely affecting the inside of the rolling bearing such as corrosion.

Next, the change in the life of the rolling bearing depending on the type of stainless steel constituting the rolling bearing was evaluated by a bearing rotation test (acid solution spray test). The test conditions are as follows. Bearing type: NSK Seiko Co., Ltd., model number 6000 (ET
(With FE contact seal) Test load: Fr 8 kgf, Fa 3 kgf Rotation speed: 1000 rpm Spray liquid: 1N-HCl (spray on the entire surface of the seal) Spray amount: 0.6 cc / min (1 second spray / intermittent spray of 9 seconds stop) Pressure: 0.2 MPa As for the stainless steel constituting each rolling bearing, Examples 2 and 3 in Table 3 are the same as Example 1, and Comparative Examples 3 to 8 are the same as Comparative Example 2. However, regarding the size (size of the largest one) and amount (area ratio) of the eutectic carbide,
As shown in Table 3. Further, all the rolling bearings are provided with the same lubricant-containing resin as the rolling bearing of the first embodiment.

In the evaluation, the life until the corrosion and wear progressed and the vibration became eight times or more the initial vibration of the rolling bearing was defined as the life. In addition, the life in Table 3 is shown as a relative value with the life of the rolling bearing of Example 2 as 1. As can be seen from the results shown in Table 3, the rolling bearing of the present embodiment had an excellent life even in a strongly corrosive environment. The lubricant-containing resin in each rolling bearing was composed of a polyolefin-based resin and a paraffin-based mineral oil, and was stable to acids and alkalis.

[0040]

[Table 3]

Thus, the corrosion-resistant rolling bearing of this embodiment is made of stainless steel having excellent corrosion resistance for the inner ring, the outer ring, the balls, and the like, and further has a lubricant-containing resin inside the bearing. An excellent rolling bearing having excellent corrosion resistance and long life even under a special environment such as contact with salt water or acid. In the present embodiment, a deep groove ball bearing has been described as an example, but the present invention is intended for various types of rolling bearings such as other types of ball bearings such as angular ball bearings and roller bearings. Of course.

The present invention can be applied to a rolling bearing provided with a seal or a shield or a rolling bearing not provided.

[0043]

As described above, the corrosion-resistant rolling bearing of the present invention has excellent corrosion resistance even in a highly corrosive environment such as underwater and has a long life.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing one embodiment of a corrosion-resistant rolling bearing of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Ball 5 Cage 6 Contact seal 6a Lip 6b Core 10 Lubricant-containing resin

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (reference) F16C 33/66 F16C 33/66 Z // C10N 40:02 F term (reference) 3J101 AA02 AA32 AA42 AA54 AA62 BA10 BA50 BA70 DA14 EA06 EA31 EA32 EA53 FA08 GA51 GA53 GA60 4H104 BA02A BA07A BB08A BB33A CA01C CA04A CA05A CB13C CE13C CE14C DA02A JA01 LA06 PA01 QA18 QA21

Claims (1)

[Claims] 1. A rolling bearing comprising an inner ring, an outer ring, a rolling element, and a retainer, wherein at least one of the inner ring, the outer ring, the rolling element, and the retainer has C: 0.5% by weight or less; Cr; 12.0 to 16.0% by weight, Mn;
0.1-0.5% by weight, Si; 0.1-1.0% by weight,
N: a stainless steel containing 0.08 to 0.20% by weight of a trace component, having a size of the eutectic carbide of 2 μm or less and an amount of the eutectic carbide of 5% or less in area ratio, Furthermore, a corrosion-resistant rolling bearing comprising a lubricant-containing resin in a space between the inner ring and the outer ring.