JPH06313434A - Corrosion resistant rolling bearing - Google Patents

Abstract

PURPOSE:To provide a corrosion resistant rolling bearing having the corrosion resistance and capable of obtaining the good running-in performance of rolling elements and the raceway surfaces of inner/outer races by forming nickel plated layer. CONSTITUTION:In a rolling bearing 1 formed by thermosetting after the cementation or the carbonitriding or assembling after the seizing thermosetting a member made of alloyed steel out of respective members of an outer race 2, an inner race 4, rolling elements 5 and a cage 8, a nickel plated layer is formed on the front surface of at least one member out of the outer race 2, the inner race 4, the rolling elements 5 and the cage 8. Thereby, its corrosion resistance is good under the hard corrosive environment such as salt spray, and also the running-in performance is good.

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 washing machines, fishing tackle, etc., which are easily rusted by water or seawater.

[0002]

2. Description of the Related Art Each member such as an outer ring, an inner ring (hereinafter referred to as a bearing ring) of rolling bearings, rolling elements, and cages is, for example, C
0.8 wt% or less of SCr420H, SCM420H, S
Carburized steel such as AE8620H, SAE4320H, or bearing steel such as SUJ-2, or SKH, S
It is made of alloy steel such as tool steel such as KD. It is carburized or carbonitrided and then heat treated or hardened by quenching to obtain a required surface hardness, and then assembled into a rolling bearing. In the case of a normal rolling bearing, the above-mentioned plural kinds of bearing materials and heat treatment are used in an appropriate combination.

However, such a bearing material has a drawback that it is easily rusted by water or seawater. For example, when this bearing material is used for a roller clutch bearing for a washing machine, rusting shortens the durable life of the roller clutch. Will end up. Proposals for improving the corrosion resistance of such conventional rolling bearings include those disclosed in, for example, Japanese Utility Model Laid-Open Nos. 3-6135 and 4-105223.

The former relates to a one-way clutch,
By forming a nitride layer on the surface of a carbon steel press-molded shell, corrosion resistance is improved and rusting can be prevented even when water or seawater is applied to the shell. The latter is also related to the one-way clutch, and it is not necessary to bend the outer ring opening side after inserting the retaining ring that holds the rolling member into the outer ring that has been subjected to anticorrosion treatment. The destruction of water is prevented and the corrosion of seawater, water and dust is prevented. As the anticorrosion treatment, nitriding treatment or another treatment for improving the corrosion resistance is given to the inner and outer peripheral surfaces of the outer ring.

[0005]

The prior art of the above publication discloses that the surface of a member made of carbon steel is subjected to a nitriding treatment to improve the corrosion resistance. However, since the nitrided layer is hard and has little ductility effect, when applied to rolling bearings, it is difficult to expect low vibration and low noise due to the "compatibility effect" between the rolling elements and the raceways in the initial stage of rotational use. There was a problem. By the way, in the roller clutch, this "familiar effect" is particularly important in order to smoothly perform the lock-unlock operation.

Therefore, the present invention has been made by paying attention to such a conventional problem, and by forming a nickel plating layer, corrosion resistance is provided and the raceway surface of the rolling elements and the inner and outer races is formed. It is an object of the present invention to provide a corrosion-resistant rolling bearing that can also obtain good "compatibility".

[0007]

According to the present invention for achieving the above-mentioned object, a method of carburizing or carbonitriding a member made of an alloy steel among members of an outer ring, an inner ring, a rolling element, and a cage and then heat treating and hardening it is described. Or a rolling bearing formed by hardening by quenching heat treatment and assembling, and having a nickel plating layer on the surface of at least one member of the outer ring, the inner ring, the rolling element and the cage.

Here, the rolling bearing may be a roller clutch. Further, the nickel plating layer may be an electroless nickel plating layer. Moreover, the thickness of the nickel plating layer can be 5 to 30 μm. Further, the outer ring, inner ring, rolling elements and a nickel plating layer formed before the surface hardness of the cage H _R C58~H _R C65, the hardness of the nickel plating layer may be a H _V 450 to 800.

Further, when the rolling bearing is a roller clutch, the raceway surface roughness of the inner ring is reduced to H _max by processing after plating.
It can be 2.0 μm or less.

[0010]

By plating at least one of the outer ring, the inner ring, the rolling element and the cage with nickel, a rolling bearing (including a roller clutch) having both good corrosion resistance and "compatibility" can be obtained. Hereinafter, the characteristics and the like of the corrosion resistant coating of the corrosion resistant rolling bearing according to the present invention will be described in detail.

The outer ring, inner ring of the corrosion-resistant rolling bearing of the present invention,
The surface hardness of the rolling elements and the cage before forming the nickel plating layer is preferably H _R C58 to H _R C65. If it is less than H _R C58 is too soft their member surface, it can not be guaranteed rolling fatigue rating life of the bearing. on the other hand,
The upper limit of the surface hardness does not have to be limited to H _R C65, but in the case of ordinary carburized steel and bearing steel, in the relation of tempering treatment (temperature 160 to 180 ° C.) for removing strain after quenching, Hardness more than the value is hard to come out. That is, now
An example of the correlation between the tempering temperature of steel and the Rockwell hardness is as shown in the graph of FIG. The steel type is the case of YCS3 and YCS4 of the carbon tool steels for oil quenching having the heat treatment standard of Table 1 and the C content corresponding to the bearing material.

[0012]

[Table 1]

From FIG. 1, the hardness is almost constant at H _R C65 up to the tempering temperature of 100 ° C., but when it exceeds 100 ° C., the hardness starts to decrease as the temperature rises.
It becomes about _R C58. In the tempering temperature range higher than that, the hardness sharply decreases in inverse proportion to the temperature. From this, in the case of the present invention, the upper limit value of the surface hardness of the member before forming the nickel plating layer is H _R C65.

The thickness of the nickel plating layer of the present invention is 5 to
It is desirable to set it to 30 μm. Especially in the case of races and rolling elements, it forms a "familiar layer" when the inner and outer ring raceways and rolling elements roll relative to each other, while at the same time maintaining a coating that has long-term corrosion resistance to seawater, water, etc. Required to do so. To meet this requirement, a nickel plating layer having the above thickness is required. If the thickness is less than 5 μm, the “familiar effect”
In addition, the corrosion resistance is insufficient, and a thickness of 10 μm or more is preferable in order to reduce conformability and variations in life. On the other hand, when the thickness exceeds 30 μm, the nickel plating treatment time becomes long, but the cost becomes high, although the “compatibility effect” and the corrosion resistance can be obtained.

The hardness of the nickel plating layer of the present invention is H _V 4
It is desirable to set it to 50 to 800. Electroless nickel plating is used to form the nickel plating layer [for example, Kanigen (registered name) which is a catalytic nickel plating method).
"General American Transportation Cooperation (GATC)" is suitable, but in that case, it is amorphous immediately after plating and transforms and crystallizes when heated. A eutectic of trinickel trioxide (Ni ₃ P) precipitates, and a precipitation hardening phenomenon occurs, which makes it harder. In the present invention, the lower limit is set to H _V 450
Preferably, it is necessary to set H _{V to} 500 or more in order to reduce the variation.

On the other hand, the upper limit of the hardness of the nickel plating layer is closely related to the heat treatment temperature. FIG. 2 is a graph showing the correlation between the hardness of the electroless nickel plating layer and the heat treatment temperature. The Vickers hardness is H _V 500 at 100 ° C., but the hardness increases as the heat treatment temperature increases, and the temperature increases at 300 ° C. At H _V 800 and 400 ° C., it reaches a maximum of H _V 900, and thereafter hardness decreases with increasing temperature.

That is, in order to harden the nickel plated film, the hardness rises up to a certain point by raising the temperature. However, the outer ring, inner ring, and rolling elements are generally finally tempered from low alloy carbon steel and the hardening heat treatment is completed. Therefore, as described above, the lower limit of the surface hardness of the steel member is set to H _R C5 in order to guarantee the rolling fatigue rated life of the rolling bearing.
In order to maintain the temperature at 8, it is impossible to raise the tempering temperature to 300 ° C. or higher as is clear from FIG. From FIG.
The plating layer hardness that can be achieved at the heat treatment temperature of 300 ° C. is about H _V 800, and the value is the maximum hardness of the nickel plating layer in the present invention.

[0018]

EXAMPLES Next, examples of the present invention will be described. (First Example): (1) Corrosion resistance / durability test of nickel-plated bearings: bearing outer diameter 62 mm, bearing inner diameter 30 mm, width 1
A single row deep groove ball bearing (6206) having a diameter of 6 mm and a ball diameter of 9.525 mm (3/8 inch) was manufactured, and the basic rating life (L ₁₀ ) was measured using a ball bearing life tester manufactured by NSK Ltd.

The nickel plating layer was formed on the outer ring, inner ring and rolling elements of the rolling bearing under test by performing the following electroless nickel plating treatment. Triclen vapor degreasing. Alkaline boiling degreasing, 5-10 minutes. Wash with water.

Pickling (10% hydrochloric acid), 1 to 3 minutes. Wash with water. Electroless nickel plating by immersing in Kanigen plating solution.
The immersion time was selected in the range of 1 to 3 hours depending on the type of parts, and the plating film thickness was adjusted to 5 μm to 35 μm.

Washing with water. Warm air drying (in furnace). Heat treatment. The temperature is selected in the range of 100 to 400 ° C. by the continuous furnace, and the hardness of the nickel plating layer is H _V 500 to 90.
It was set to 0. This corrosion resistance. In the durability test, JIS Z2371 "salt spray test method"
With reference to, the bearing surface S to be tested was sprayed with a sodium chloride aqueous solution adjusted to a concentration of 5% on the transfer surface for 1 minute, and the corrosion resistance to salt water was tested. That is, the number of cycles until the vibration value of the bearing under test reaches a predetermined value (total rotation time) is defined as 1 cycle of "1 minute salt water spray and continuous rotation for 11 hours".
Is the lifetime. It was stopped after 40 cycles. The test conditions are as follows.

Bearing rotation speed: 2000 rpm, radial load P: 1400 kgf, test temperature: room temperature The results of the above life test are shown in FIGS. FIG. 3 shows the relationship between the thickness of the nickel plating layer and the rolling bearing life, and FIG. 4 shows the relationship between the hardness of the nickel plating layer with a predetermined thickness (20 μm) (which varies with the heat treatment temperature) and the rolling bearing life. ing.

From FIG. 3, regarding the thickness of the nickel plating layer, there is a marked difference in bearing life between the thickness of 0 μm (without plating) and the thickness of 5 μm. Further, as the thickness of the nickel plating increases, the variation in life decreases. It can be said that when it exceeds 20 μm, it becomes completely stable for 40 cycles or more. From this result, the lower limit of the thickness of the nickel plating layer is 5 μm, preferably 10 μm.
It is m or more. On the other hand, the upper limit of the thickness is preferably about 30 μm in consideration of cost.

Further, from FIG. 4, regarding the hardness of the nickel plating layer, the plating layer hardness H _V 400 is too soft and easily worn, and the bearing life is short. When the hardness of the nickel-plated layer reaches H _V 450, some exceed 40 cycles and the life is remarkably extended. The hardness of the plating layer itself increases as the heat treatment temperature after plating increases, and the bearing life becomes stable at all 40 cycles. Incidentally, the heat treatment temperature after plating is high, the bearing outer ring, inner ring, rolling surface hardness of the body is decreased, and the measured value, H _R in H _R C65,200 ℃ heat treatment temperature of 100 ° C. C60, 300
° C. becomes H _R C50 in H _R C58,400 ℃ with. When the hardness of the nickel plating layer exceeds H _V 800, the heat treatment temperature becomes 300 ° C. or higher, so that the surface hardness of the material of the bearing outer ring, inner ring, and rolling element decreases to H _R C58 or less. As a result, the strength of the nickel-plated layer is substantially reduced, resulting in a drastic shortening of the bearing life. Then, the life at hardness H _V 900 (bearing material surface hardness H _R C50) is reduced to several cycles.

That is, as the hardness range of the nickel plating layer, the surface hardness of the material of the bearing outer ring, inner ring, and rolling element is H.
_It can be said that H _V 450 to H _V 800 is appropriate in view of the heat treatment temperature that can be maintained in _R C58 to H _R C65. (2) Initial running-in effect test of rolling bearing: In this test, the vibration level (db) of the bearing S under test is determined, and the fluctuation of the vibration level at the initial stage of bearing operation (10 minutes) is measured based on this. Carried out.

FIG. 5 shows an outline of the vibration measuring and testing apparatus. P when the rolling bearing under test S is set on the rotating shaft 10 and the radial load Pkgf and dynamic load rating Ckgf are set.
Rotate the rotating shaft 10 under the load condition of /C=0.32,
While operating the bearing S under test, the vibration pickup 11 measures the vibration value every predetermined time. 12 is a housing.

The material surface hardness of the outer ring, inner ring and rolling element balls of the bearing S to be tested was H _R C60 to 61, and the hardness of the nickel plating layer formed on the surface was H _V 600. The result of the test is shown in FIG. From FIG. 6, the one without nickel plating (plating thickness 0 μm) has the same vibration level from the start to 10 minutes, and the initial running-in effect of the rolling bearing is not recognized. In the case where the nickel plating layer is formed, there is a "familiar effect" in all of the plating thickness from 5 μm to 35 μm, and the vibration level is significantly reduced by 2 minutes after the rotation, and thereafter becomes almost constant. There is no difference between the plating thicknesses of 30 μm and 35 μm, and there is an equivalent “familiar effect”. However, the film immersion treatment time required to form a nickel plating layer having a plating thickness of 35 μm is
The cost is 1.3 times higher than that of 0 μm.

After all, regarding the initial running-in effect of the rolling bearing, it can be said that it is appropriate to set the thickness of the nickel plating layer in the range of 5 to 30 μm. (Second Example): A roller clutch as a rolling bearing was formed with a nickel plating layer to obtain a bearing under test.

In the roller clutch 1 shown in FIG. 7, reference numeral 2 denotes an outer ring having a plurality of recesses 3 on its inner peripheral surface, and a plurality of rolling elements are provided between the outer ring 2 and the inner ring 4 (the shaft if there is no inner ring). The roller 5 and the same number of pockets 6 as that of the roller 5 and a cage 8 made of plastics, which is provided with a spring 7 for urging the roller 5 in a direction of separating the roller 5 from the slope of the recess 3, are interposed.

The dimensions (unit: mm) are as follows: outer ring: inner diameter 27 x outer diameter 32 x length 4.5 inner ring: inner diameter 15 x outer diameter 17 x length 6.3 The material surface hardness of each component is as follows. . Outer ... H _R C63~63.5 inner ... H _R C60~62.5 roller ... H _R C63~64 nickel plating layer, the surface of the steel material made of the outer ring 2 of the roller clutch 1, each of the rolling surface and the roller 5 of the inner ring 4 On the other hand, it was formed by performing electroless nickel plating under the same conditions as described in Example 1 above. (1) Relationship test between surface roughness and slip ratio in roller clutch: Table 2 shows the thickness and hardness of the nickel plating layer.

[0031]

[Table 2]

After the above nickel plating layer was formed, the raceway surface and the ball surface were polished and adjusted to various surface roughness, and the bearings under test S were used to measure the average slip angle. The average slip angle α is the swing angle θ of the roller clutch 1.
(Eg ± 30 °), total number of swings n (eg 1000
Times) and the total rotation angle of the shaft (the total angle at which the shaft is locked and rotated) T _a ° is calculated by α = (θ × n−T _a ) / n.

The results are shown in FIG. If it is less than H _max 0.5, the surface roughness is too good and the slip angle α becomes large. On the other hand, when the slip angle α exceeds H _max 2.0, the value of the slip angle α varies due to abrasion powder. In particular, when the surface roughness of the raceway surface 4a of the inner ring 4 exceeds 2 μm, discontinuous noise is likely to occur. From the above results, it can be said that the roughness of the nickel plating layer on the inner ring raceway surface of the roller clutch is preferably H _max 0.5 to H _max 2.0. (2) Relationship test between slip angle in roller clutch and hardness of nickel-plated film: The same bearing S to be tested as in the test of (1) was heat-treated at various temperatures to form a nickel-plated layer having a predetermined hardness. The average slip angle was measured by using the thing.

The results are shown in FIG. If the Vickers hardness of the nickel plating layer is less than H _V 450, it is too soft and the average slip angle α varies greatly depending on the mode of clutch operation (whether the lock is shocking or static). on the other hand,
When the Vickers hardness exceeds H _V 800, as described above, the steel material becomes too soft due to the high heat treatment temperature and the nickel plating layer begins to peel off, resulting in a large variation in the average slip angle α.

Therefore, it can be said that the hardness of the nickel plating layer of the steel member of the roller clutch is preferably H _V 450 to H _V 800. It should be noted that, in each of the above-mentioned embodiments, the outer ring, the inner ring, the rolling elements and the cage, which are the constituent members of the bearing to be tested, in which the outer ring, the inner ring and the rolling element are each formed with the nickel plating layer are described. The present invention is not limited to this, and is also applicable to the case where the nickel plating layer is formed only on a part of the constituent members.

[0036]

As described above, according to the present invention,
Outer ring, inner ring, rolling elements, and cage members made of alloy steel are carburized or carbonitrided, and then heat-treated or hardened by heat treatment to harden and assemble. Since a nickel plating layer is formed on the surface of at least one of the rolling elements and cage, it shows good corrosion resistance even under severe corrosive environments such as salt spray, and at the beginning of operation, "Familiarity" is also good, and the effect is that a rolling bearing with good usability can be provided.

[Brief description of drawings]

FIG. 1 is a graph illustrating the correlation between the tempering temperature and the Rockwell hardness of steel that can be used in the rolling bearing of the present invention.

FIG. 2 is a graph showing the correlation between the hardness of the electroless nickel plating layer applied to the present invention and the heat treatment temperature.

FIG. 3 is a graph showing the relationship between the thickness of the nickel plating layer of the present invention and the life of the rolling bearing.

FIG. 4 is a graph showing the relationship between the hardness of the nickel plating layer of the present invention and the life of the rolling bearing.

FIG. 5 is a diagram illustrating an outline of a rolling bearing vibration measurement test apparatus.

FIG. 6 is a graph showing the influence of the film thickness of the nickel plating layer on the “compatibility” at the initial stage of operation of the rolling bearing, as a variation in vibration level.

FIG. 7 is a sectional view of an embodiment of the present invention.

8 is a sectional view taken along line VIII-VIII of FIG.

9 is a graph showing the relationship between the surface roughness and the average slip angle of the nickel plating layer of the example of FIG.

10 is a graph showing the relationship between the hardness and the average slip angle of the nickel plating layer of the example of FIG.

[Explanation of symbols]

 1 rolling bearing 2 outer ring 4 inner ring 5 rolling element 8 cage

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location // C23C 18/34

Claims (1)

[Claims] 1. A rolling bearing formed by carburizing or carbonitriding a member made of an alloy steel among the members of the outer ring, the inner ring, the rolling elements and the cage, and then heat treating and hardening or assembling by hardening by heat treatment. A corrosion-resistant rolling bearing having a nickel plating layer on a surface of at least one member of the outer ring, the inner ring, the rolling element and the cage.