JPH06341442A - Anticorrosion rolling bearing - Google Patents

Abstract

PURPOSE:To provide an anticorrosion rolling bearing to which stable anticorrosion is given, and the rolling fatigue life for a long term is guaranteed. CONSTITUTION:At least any one of an outer ring 2, an inner ring 4, and rolling bodies 5 is treated by salt bath soft nitriding, a compound layer of hardness of Hv 654-Hv 830 (HRC 58-HRC 65) and thickness of 5-20mum is formed on the surface, hence a protection film due to a soft nitriding layer is formed so as to exhibit stable anticorrosion without dispersion even under severe corrosive environment such as salt water spray, and the rolling fatigue life for a long term is guaranteed.

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 nitrocarburized and then heat treated or hardened by quenching to obtain the 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 corrosion resistance treatment, nitriding treatment or other corrosion resistance treatment is given to the inner and outer peripheral surfaces of the outer ring.

[0005]

However, the conventional carbon steel nitriding treatments disclosed in the above publications have variations in corrosion resistance, and there is a problem that stable rustproofness against water, seawater, etc. is not guaranteed. there were. Therefore, the present invention is
The present invention has been made by paying attention to such conventional problems, and an object thereof is to provide a corrosion-resistant rolling bearing which is provided with stable corrosion resistance and has a long-term rolling fatigue life guaranteed.

[0006]

According to the present invention for achieving the above object, at least one of an outer ring, an inner ring and a rolling element made of steel is soft-nitrided in a salt bath and the surface thereof has a hardness of H _V 654 to. H
Thickness using a _{V 830 (H R C58~H R C65} ) 5 to 20
It is characterized in that a compound layer of μm is formed. here,
The rolling bearing may be a roller clutch.

Further, when the rolling bearing is a roller clutch, the surface roughness of the bearing ring can be made R _max 0.5 to 2.0 μm by processing after forming the compound layer.

[0008]

In the corrosion-resistant rolling bearing of the present invention, the salt bath soft
H by nitriding_V654 (H_RC58) ~ H_V830 (H_R
C65) surface hardness is obtained and sufficient corrosion resistance
A soft nitrided layer is formed with a thickness of 5 to 20 μm. Furthermore, for oxygen solid solution
Fe on the outermost surface₃O _FourA dense protective film containing
It is formed and the corrosion resistance is further improved.

If the surface hardness is less than H _V 654 (H _R C58), the surface of these members is too soft and the rolling fatigue rated life of the bearing cannot be guaranteed. On the other hand, the upper limit of the surface hardness is not necessarily limited to _{H V 830 (H R C65)} , ordinary carburized steel, tempering process performed for removal distortion after quenching the bearing steel (temperature 160-180 It is difficult to obtain hardness higher than this value due to (° C).

The thickness of the compound layer composed of the soft nitrided layer is 5 μm.
If it is less than, sufficient rolling fatigue life cannot be obtained, and
Corrosion resistance is not sufficiently maintained against surface scratches. On the other hand, even if the thickness exceeds 20 μm, the effect of corrosion resistance does not change so much, but the processing time becomes long and the cost becomes high. When the present invention is applied to a roller clutch, the surface roughness of the bearing ring is set to R _max 0.5 to 2.0 μm. If R _max is less than 0.5 μm, the surface roughness is too good and the slip angle becomes large. on the other hand,
When the slip angle α exceeds R _max 2.0, the value of the slip angle varies due to abrasion powder, especially the surface roughness of the inner ring raceway surface is 2μ.
This is because discontinuous sound tends to be produced when m is exceeded.

As the salt bath nitrocarburizing process of the present invention, for example, the SQP process (trade name of Parker Heat Treatment Industry Co., Ltd.) can be preferably used. This process is a process consisting of the following series of steps. Liquid soft nitriding treatment by Tufftride method (TF1):
Cyanide (KCNO and NaCNO) as a main component and the balance consisting of K ₂ CO ₃ and Na ₂ CO ₃ , and CNO ^- 2
6-39%, CN ^- 0-6% containing soft nitriding salt bath (T
F1 bath), and nitriding treatment is performed under the conditions of 580 ° C. × 60 to 90 minutes.

As a result, the cyanate is thermally decomposed to generate CO in addition to nitrogen N in the generator, which diffuses nitrogen N and carbon C into the steel to form nitrides and carbides. Therefore, unlike the simple nitriding treatment, C, N
Is subjected to soft nitriding treatment to form a solid solution. Immersion treatment in oxidizing salt bath: Using an oxidizing salt bath (AB1 bath) containing NaOH and KOH as main components and containing 2 to 20% of alkali metal nitrate, the above-mentioned soft nitriding treatment is immediately put into this salt bath. The structure is stabilized by immersing and cooling at 350 to 400 ° C. for 10 to 20 minutes, and a dense rust preventive film made of Fe ₃ O ₄ is formed on the outermost surface. Water cooling: It is then water cooled. Lapping: Finally, lapping is performed in the range of 1 to 3 hours using a vibrating barrel, and the surface roughness is R _max 0.5 to 2.0 μ.
Adjust to m.

Unlike the nitriding layer, the compound layer produced by the above-mentioned process contains a large amount of oxygen in addition to nitrogen and carbon as a solid solution, which significantly improves the corrosion resistance and wear resistance, Improves seizure resistance.

[0014]

EXAMPLES Next, examples of the present invention will be described. (1) Using the roller clutch shown in FIGS. 1 and 2 as the rolling bearing for the test product, the corrosion resistance durability of the product of the present invention and that subjected to another corrosion resistance treatment are compared. In the illustrated roller clutch 1, an outer ring (shell) 2 has 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 (hollow, shaft if there is no inner ring). 5 and the same number of pockets 6 as the rollers 5 and a cage 8 made of plastics having a spring 7 for urging the rollers 5 in a direction of separating the rollers 5 from the slope of the recess 3.

Outer ring: inner diameter 17 x outer diameter 32 x length 4.5 inner ring: inner diameter 15 x outer diameter 17 x length 6.3 (A) Corrosion resistance treatment of the product of the present invention Outer ring 2 of the roller clutch 1 , The inner ring 4 and the roller 5 are subjected to SQP salt bath nitrocarburizing under the processing conditions shown in FIG.

The conditions for lapping after cooling with water are as follows. Vibrating barrel: [Made by Kyoei Polishing Co., Ltd. Media: Cup, SGT 8x8 (made by PGM) Compound: Anticorrosive Treatment time: 1 to 3 hours (Adjust appropriately depending on the size of sample to be polished) The parts are also finished to a roughness of R _max 1.0 μm.

The surface hardness of the outer ring 2 and the inner ring 4 is as follows. Outer ring: Hv780-790 Inner ring: Hv785-790 (B) Corrosion resistance treatment of comparative product Comparative product 1: Electrolytic nickel plating is applied to each of the outer ring 2, inner ring 4 and roller 5 of the roller clutch 1 and the thickness is 10 μm.
To form a Ni film.

Comparative product 2: The outer ring 2, the inner ring 4, and the roller 5 of the roller clutch 1 are plated with chrome to have a thickness of 1
A Cr film of 0 μm is formed. Comparative product 3: Each part of the outer ring 2, the inner ring 4, and the roller 5 of the roller clutch 1 is carbonitrided by a gas carbonitriding method using Rx gas and ammonia gas. (C) Salt Water Spray Test For each of the test roller clutches of the present invention product and the comparative product that have been subjected to the above-mentioned corrosion resistance treatment, a 5% salt water spray test was performed with reference to JIS Z2371 “Salt water spray test method”. Measure the rust time and investigate the corrosion resistance.

The results are shown in the graph of FIG. From this graph, it can be seen that the rusting time of the salt bath nitrocarburized product of the present invention is significantly longer than that of the comparative product, and the corrosion resistance is remarkably improved. The photograph in FIG. 5 shows the structure of a bearing component made of S45C steel material and subjected to SQP salt bath nitrocarburizing treatment. That is, S45C treated with TF1 tuftride for 90 minutes at 580 ° C. was placed in an oxidizing salt bath AB1 at 380 ° C. for 2 minutes.
The structure is shown in which the outermost surface is wrapped by water cooling after immersion for 0 minutes. The white layer observed in the photograph is the εFe ₂ to ₃ N compound layer 10 formed by tuftride. Generally, this white layer is formed with a thickness of 5 to 20 μm and is lapped by several μm to adjust the surface roughness after the oxidation treatment in the AB1 bath, but Fe ₃ O ₄ by oxygen solid solution is the main component on the outermost surface. The corrosion-resistant layer 11 having a thickness of several μm and formed of a dense iron tetrachloride layer is formed. This Fe ₃ O ₄ layer is structurally difficult to observe. Further, as a lower layer of the compound layer 10, there is a diffusion layer 12 of N solid solution over a depth of several hundred μm. This diffusion layer 12 is difficult to observe because it has a solvite structure due to the quenching and tempering treatment of S45C.

As described above, in the case of the salt bath soft nitriding product of this embodiment, oxygen is dissolved as a solid solution in addition to nitrogen and carbon. Also,
Furthermore, the improvement in corrosion resistance is remarkable. (2) The relationship between the slip ratio and the surface roughness of the roller clutch of the present invention is variously examined.

Each part is subjected to SQP salt bath nitrocarburizing to form a compound layer 10 (and a corrosion resistant layer 11) on the surface to a thickness of 20 μm, and the surface hardness of each is as follows. The outer ring _{(Shell): H V 773~H V 786 (} H R C63
~H _R C63.5) inner ring _{(hollow): H V 698~H V 760 (} H R C60
~H _R C62.5) rolling elements _{(rollers): H V 773~H V 830 (} H R C6
3 to H _R C65) The finished surface roughness of the transfer surface of the bearing ring is adjusted to a range of R _max less than 0.5 to 5 by changing the final lap treatment time by the barrel.

The average slip angle of the test roller clutch assembled from the above parts is measured. In addition, the average slip angle test is performed by swinging the roller clutch by ± θ (for example, ± 30).
°), the total number of swings n (for example, 1000 times), and the total rotation angle of the shaft (total angle at which the shaft is locked and rotated) T _a °, the average slip angle = (θ × n−T _a ) / n Calculate with.

The results are shown in FIG. If R _max is less than 0.5, the surface roughness is too good and the slip angle becomes large. On the other hand, when the slip angle exceeds R _max 2.0, the value of the slip angle varies due to abrasion powder. In particular, when the surface roughness of the inner ring exceeds 2 μm, discontinuous noise is likely to occur. From the above results, the surface roughness of the raceway surface of the roller clutch of the present invention is R _max 0.5 to R _max 2.0.
Can be said to be preferable.

In the above embodiment, among the outer ring, inner ring, rolling elements and cage which are the constituent members of the bearing under test, the outer ring, inner ring and rolling element are each subjected to salt bath nitrocarburizing treatment. However, the present invention is not limited to this, and can be applied to the case where only some of the constituent members are subjected to the salt bath nitrocarburizing treatment.

The present invention can also be applied to a roller clutch of a type in which the inner ring is omitted and the shaft is directly incorporated in the shaft.
Although the rolling bearing has been described as a roller clutch, the present invention can be similarly applied to a normal rolling bearing in which rollers, balls, and needle rollers are incorporated as rolling elements.

[0026]

As described above, according to the present invention,
At least one of an outer ring, an inner ring, and a rolling element made of steel is soft-nitrided in a salt bath, and the surface thereof has a hardness of H _V 654 to H _V 830.
For (H _R C58~H _R C65) in thickness was obtained by forming a compound layer of 5 to 20 [mu] m, a variation even formed protective film by soft nitriding layer on the severe corrosive environment such as salt spray In addition to exhibiting stable corrosion resistance, long-term rolling fatigue life is guaranteed.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a rolling bearing of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a process step diagram illustrating an example of a salt bath soft nitriding process for the product of the present invention.

FIG. 4 is a graph showing the salt spray test results of the product of the present invention and the comparative product.

FIG. 5 is a photograph showing the metallographic structure of a bearing component that has been subjected to the salt bath nitrocarburizing treatment of the present invention.

FIG. 6 is a graph showing the relationship between the surface roughness and the average slip angle in the roller clutch of the present invention.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. At least one of an outer ring, an inner ring, and a rolling element made of steel is soft-nitrided in a salt bath, and the surface thereof has a hardness of H _V 65.
A corrosion-resistant rolling bearing, wherein a compound layer having a thickness of 4 to H _V 830 and a thickness of 5 to 20 μm is formed.