JP2002266869A - Steel retainer for rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, at low cost, a steel retainer for rolling bearing which is excellent in corrosion resistance and abrasion resistance even in an environment in which a lubricating condition is made worse than a conventional lubricating condition, and is capable of being applicable to a non-magnetic application. SOLUTION: This steel retainer 1 for rolling bearing holds a plurality of rolling elements 3 arranged to be capable of rolling between an inner peripheral side rolling contact surface of an outer ring 2 and an outer peripheral side rolling contact surface of an inner ring 1. The steel retainer 1 for rolling bearing is constituted of a press molded item of an austenitic stainless steel, and provided, at its surface, with a carbonizing hardening layer having hardness of HV 500 to HV 1100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel press retainer for a rolling bearing.

[0002]

2. Description of the Related Art As a conventional steel press retainer of this type, there is known a press retainer manufactured by press-forming a steel plate such as SPCC or SPCE. Steel press cages have low material costs and good press formability, so they have the advantage of high mass productivity and low cost. On the other hand, their hardness is as low as about HV100 to HV190, and they are low in strength. If vibration or impact load acts on
Breakage of the retainer becomes a problem, and when the supply of lubricating oil is small, there is a problem that the pocket portion is worn.

In order to solve such a problem, for example,
It has been proposed to apply a surface hardening treatment including nitriding treatment such as salt bath nitriding and gas nitriding to the surface of the corrugated press cage or the crown press cage made of SPCC to improve the strength and wear resistance. ing. By performing the nitriding treatment, a nitrogen compound layer is formed on the surface, and it is possible to exhibit extremely excellent performance with respect to seizure, abrasion, etc., at higher temperatures, at higher speeds, or under dilute lubrication. Can be used.

However, the rolling bearings are used in a wide variety of environments, for example, in rolling bearings used in liquid crystal / semiconductor manufacturing facilities, food machines, medical inspection devices, linear motor cars, and other electronic equipment. Since it may be used in a corrosive environment or may be used in a magnetic field environment, corrosion resistance and / or non-magnetic properties may be required. Cannot satisfy the required quality.

Therefore, austenitic stainless steel press retainers have conventionally been used as steel press retainers which require corrosion resistance and / or non-magnetic properties.

[0006]

However, in the above-mentioned conventional austenitic stainless steel press retainer, the rolling bearing is used in a vacuum or in a corrosive environment, so that the lubrication is increased more than before. Conditions tend to be worse, and there is a demand for improved cage durability.

SUMMARY OF THE INVENTION The present invention has been made to solve such inconveniences, and the use conditions of a rolling bearing are in a vacuum or in a corrosive environment, and the lubrication conditions are worse than ever before. Also, an object of the present invention is to provide a steel cage for a rolling bearing which has excellent corrosion resistance and wear resistance and is applicable to non-magnetic applications.

[0008]

In order to achieve the above-mentioned object, a steel cage for a rolling bearing according to the present invention comprises an inner member-side rolling surface of an outer member and an outer member-side rolling surface of an inner member. A steel cage for a rolling bearing for holding a plurality of rolling elements disposed so as to be freely rotatable between a press-formed product of austenitic stainless steel and having a surface of HV500
Ｈ1100 is provided with a carburized hardened layer having a hardness of HV1100.

In general, there is a nitriding treatment or the like as a method of hardening the surface of an austenitic stainless steel retainer. The nitridated retainer has a very high surface hardness exceeding HV1000. In terms of corrosion resistance, magnetic permeability, etc., crystalline Cr nitride precipitates and significantly deteriorates the properties of the base material, but in the present invention, it is necessary to provide excellent corrosion resistance and wear resistance. Therefore, it can be applied not only to a vacuum environment, a corrosive environment, and the like, but also to a non-magnetic application because there is no decrease in magnetic permeability.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steel cage for a rolling bearing as an example of an embodiment of the present invention will be described below. Generally, austenitic stainless steel has a high corrosion resistance C on the surface.
Although it has an r oxide film (passive coating), its surface modification is extremely difficult. Therefore, in the steel cage for a rolling bearing of this embodiment, austenitic stainless steel was press-formed. Later, first, an oxide film removal process is performed.

Further, the conventional carburizing method is performed at a relatively high processing temperature, generally at a high temperature of about 800 to 100 ° C., in which case, the permeated carbon bonds with Cr and the like in the steel. Then, it is precipitated as carbide on the surface, and as a result,
The treated product has a remarkable dimensional change due to the swelling of the carbide,
In addition, Cr is consumed by the carbides, and properties such as corrosion resistance are significantly reduced.

Therefore, in this embodiment, the carburizing treatment is performed.
Perform oxide film removal treatment as a pretreatment, then compare
Austenitic stainless steel by carburizing at low temperature
Carburizing of HV500 to HV1100 on stainless steel surface
Form a layer. Order of oxide film removal treatment and low-temperature carburizing treatment
Will be described. (Oxide film removal process)
This is achieved by a fluorination treatment in an elemental gas atmosphere.
As a fluorine-based gas, NF_Three, BF_Three, CF_Four, H
F, SF₆, C _TwoF₆, WF₆, CHF_ThreeSiF_Four, C
IF_ThreeIt is possible to exemplify a fluorine compound gas comprising
Can be used alone or in combination of two or more
You.

Furthermore, can be used as these fluorine-based gas and F ₂ gas was generated by pyrolysis in the pyrolysis device, F ₂ gas is also the fluorine-based gas premade. Such a fluorine-based gas can be used alone, but it is preferable to use it after diluting it with an inert gas such as N ₂ gas to about 1 to 10% in order to obtain a mild reaction.

The most practical fluorine-based gas is NF ₃ . NF ₃ is gaseous at room temperature,
High chemical stability and easy to handle. In addition, the fluorination treatment is performed by inserting an untreated product into a furnace and keeping it in a heated state under the fluorine-based gas atmosphere. For example, a heating temperature of 250 to 450 ° C. and a holding time of 10 minutes to
When fluorination is performed under the condition of 1 hour, NF ₃ is decomposed /
When activated, the oxide film is replaced with a fluoride film on the surface of the austenitic stainless steel part, thereby enabling low-temperature carburizing.

It should be noted that the method is not limited to the above exemplified ones other than the fluorine-based gas as long as the method can remove the oxide film. (Low-temperature carburizing treatment) Carburizing treatment is performed subsequently to the above-described oxide film removing treatment. Here, the carburizing treatment is performed at a temperature of 600 ° C. or less, preferably 400 to 540 °.
C is heated to a temperature of C, and using a carburizing gas made of a mixed gas of CO + H ₂ or a carburizing gas made of a mixed gas of RX + CO _2, etc., and the inside of the furnace is made a carburizing atmosphere.

At this time, while the fluoride film formed by the oxide film removal treatment is removed by hydrogen in the atmosphere,
The carbon in the carburizing gas diffuses and penetrates from the surface to form a carburized hardened layer described later. In this embodiment, since a fluoride film is formed on the surface by the above-described fluoridation treatment to prevent oxidation, and this is removed by hydrogen during carburization, each batch treatment can be performed. become.

The carburized hardened layer has a form in which about 1.2 to 2.6 wt% of carbon is dissolved in the austenite phase as a base phase to cause lattice strain, and is significantly harder than the base material. (Room temperature) and abrasion resistance can be improved.
Therefore, unlike a process such as quenching or nitriding, since it does not involve lattice transformation unlike martensite transformation, there is no volume expansion and there is almost no dimensional change.

Therefore, the present invention can be applied to a steel press retainer manufactured by using an existing press die as it is, and there is an advantage that the production cost of a new die and the like can be reduced. Also, austenitic stainless steel, by cold working or pressing, etc., may affect the magnetic permeability, even when the induced transformation of austenite transformed to martensite by press working, etc., In addition to the solid solution in austenite, the permeated carbon disappears due to the formation of fine carbides due to the reaction with the ferrite component, which is a ferromagnet generated by the induced transformation, and the deterioration of corrosion resistance and permeability is somewhat recovered. There is action. Of course, in high-temperature carburizing at a carburizing temperature of 600 ° C. or higher, carbides are also precipitated from the austenite phase, so that deterioration in corrosion resistance, magnetic permeability, dimensional change, etc. is inevitable.

In general, S is higher than SUS304.
US316 or SUS316L has less ferrite component due to the induced transformation and tends to have higher hardness of the carburized layer. In this case, an increase in cost cannot be avoided, but it is within the scope of the present invention. Here, the hardness of the carburized hardened layer is HV500 or more and HV1100 or less. The hardness of the carburized hardened layer varies somewhat depending on the carbon concentration, alloy components, and the like permeated within this range, but specifically,
In the case of SUS304, HV500 to HV900, S
In case of US316 or SUS316L, HV70
0 to about HV1100. After the low-temperature carburizing treatment, the outermost surface layer is oxidized by CO ₂ gas to form a black oxide layer made of Fe ₃ O ₄ ,
In order to reduce the corrosion resistance to some extent, it is preferable to perform pickling treatment or barrel processing after the carburizing treatment to remove it.

The treatment liquid used for the pickling treatment is not particularly limited, and hydrofluoric acid, nitric acid, hydrochloric acid, sulfuric acid or a mixture thereof can be used. In addition,
The carburizing treatment may be a method described below. Carburizing gas, using an unsaturated hydrocarbon gas such as acetylene or ethylene, and performing the same vacuum carburizing treatment under a vacuum or reduced pressure of 1 Torr or less, the formation of a black oxide layer harmful to the corrosion resistance can be suppressed, In addition, uneven carburization due to sooting, which is particularly problematic during carburization, can be prevented. Further, as compared with the case of the same carburizing treatment time, the thickness of the carburized hardened layer becomes larger because it is less affected by oxygen in the atmosphere.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view in which a part of various rolling bearings using the cage for rolling bearing according to the present invention is partially broken, (a) is a ball bearing, (b) is a roller bearing, and (c) is a tapered roller. Bearings.

In each of these rolling bearings, a plurality of rolling elements 3 are provided between an inner peripheral rolling surface of an outer ring (outer member) 2 and an outer peripheral rolling surface of an inner ring (inner member) 1. It is held evenly so as to be able to roll in the circumferential direction via a steel cage 4 for a rolling bearing according to the invention. Here, the steel cage 4 for rolling bearings
Has a carburized hardened layer having a hardness of HV500 to HV1100 formed on the surface of an austenitic stainless steel press-formed product through the above-described oxide film removing treatment and low-temperature carburizing treatment.

As a result, even when the rolling bearing is used in a vacuum or in a corrosive environment, the lubricating conditions are worse than before, and the rolling bearing is excellent in corrosion resistance and wear resistance, and is non-magnetic. It can be made applicable in use. When corrosion resistance is required, the inner ring 1, the outer ring 2 and the rolling elements 3 are made of martensitic stainless steel (SUS440C, 13Cr stainless steel, etc.), ceramics (Si ₃ N ₄ etc.) or Ti alloy (α + β type or β Type Ti-6Al-4V, Ti-
15V-3Cr-3Sn-3Al, Ti-22V-4A
1, Ti-15Mo-5Zr-3Al) or the like. When other non-magnetic properties are required, at least the rotating wheel and the rolling elements 3 of the inner and outer rings 1 and 2 are made of austenite. It is preferable to be made of nonmagnetic steel, ceramics, Ti alloy or the like. When both corrosion resistance and non-magnetic properties are required, the inner ring 1, the outer ring 2, and the rolling elements 3 are preferably made of ceramics or a Ti alloy.

The details will be described below. First, the critical significance of the surface hardness HV500 to HV1100 of the carburized hardened layer will be described based on test results. Test conditions Austenitic stainless steel SUS304 and SUS
After using a 316 φ30 mm flat test piece, the flat test piece was brought into contact with a ring test piece (SUJ2) having an inner diameter of φ20 mm and an outer diameter of φ25 mm under a load of 200 g, and was rotated without lubrication at 1,000 rpm for 1 minute. The wear volume of the flat test piece was measured.

A plurality of flat test pieces are prepared, and after each fluorination treatment, 0.2 to 0.4 torr, 4
At 80 to 520 ° C., the carburizing time is appropriately changed for each test piece, the surface hardness is adjusted by performing vacuum carburizing treatment with acetylene gas, and acid cleaning and post-cleaning are performed to achieve a surface hardness of HV200. Test pieces up to about HV1100 were prepared, and the relationship between the surface hardness and the wear volume ratio of each test piece was examined. Evaluation is SUS304 of HV200 1.0
Was evaluated based on the wear volume ratio. The results are shown in FIG.

As can be seen from the figure, when the surface hardness is HV 500 or more, the wear characteristics are remarkably improved. Further, since HV1100 is the upper limit of the surface hardness (upper limit of lattice distortion type hardening) obtained in the present invention, and the wear resistance effect is saturated, the surface hardness of the carburized hardened layer is set to HV500 to HV1100. did. Next, the deep groove ball bearing 6
A corrugated press retainer used in 08 was prepared and the following tests were performed. As for the material of the cage, Example 1 and Comparative Example 1 were austenitic stainless steel SUS304, and Example 2 was used.
And Comparative Example 2 was austenitic stainless steel SUS
316, and in Examples 1 and 2, after the fluorination treatment, 0.2 to 0.4 torr and 480 ° C. to 5
Vacuum carburizing treatment with acetylene gas was performed at 20 ° C. for about 30 hours, and acid cleaning and post-cleaning were performed, and the surface hardness was set to HV690 and HV930, respectively. Comparative Example 1,
For No. 2, carburizing treatment was not performed, and the respective surface hardnesses were HV210 and HV190. The test was conducted for corrosion resistance, wear resistance and non-magnetism, and the test conditions were as follows. FIG. 3 shows a photograph of a cross-sectional structure of the cage of Example 1. (Corrosion resistance) (1) A salt spray test in accordance with JIS Z 2371 was performed for 24 hours to confirm the presence or absence of rust. (2) was dipped for 20 hours into 5N-H ₂ SO ₄ in and weighed decrease. (Abrasion resistance) An open-type deep groove ball bearing 608 in which the inner and outer rings and rolling elements are made of martensitic stainless steel SUS440 has a degree of vacuum of 1.3 × 10 ⁻⁵ Pa, a non-lubricated rotational speed of 500 rpm, and a temperature of 25. 1 × 10 ⁷ at ° C
Each time, a rotation test was performed to measure the amount of weight loss due to wear of the cage. (Non-magnetic) Non-magnetic steel (Hitachi Metal: YHD5)
0) An open-type deep groove ball bearing 608 having a rolling element made of ceramics was rotated in a static magnetic field, and a change in magnetic flux density accompanying rotation of the cage was measured with a Gauss meter.

Table 1 shows a summary of the evaluation results of the above test.

[0028]

[Table 1]

In the evaluation of corrosion resistance, no rusting was observed in all of Comparative Examples 1 and 2 and Examples 1 and 2 in the salt spray test. 5N-
The results of the evaluation of the corrosion resistance when immersed in H ₂ SO ₄ for 20 hours were obtained by measuring the corrosion weight loss, and expressed as a ratio when the corrosion weight loss of Comparative Example 1 in which the carburizing treatment was not performed was set to 1. In this evaluation, the cages of Examples 1 and 2 of the present invention have less corrosion loss and have better corrosion resistance than the cages of Conventional Examples 1 and 2 without carburizing treatment. It was confirmed that.

The evaluation of the abrasion resistance is shown by the ratio when the abrasion loss of Comparative Example 1 in which the carburizing treatment was not performed was set to 1. The retainers of the first and second embodiments are the same as those of the first and second prior arts.
The wear amount is 1/10 or less as compared with the retainer of No. 6, and it is understood that the wear amount is extremely excellent. Furthermore, as a result of measuring the effect on the magnetic field when the bearing rotates by a Gauss meter, when the amplitude of the magnetic flux density of Comparative Example 1 in which the carburizing treatment was not performed is set to 1, the cages of Examples 1 and 2 are:
The magnetic flux density decreased to １ ／ or less. This is considered to be due to the fact that a small amount of ferrite component contained in the steel is reduced by the carburizing treatment.

Although only the steel press retainer has been described above, in the case where all the components of the rolling bearing are made of austenitic stainless steel, the carburizing gas molecules sufficiently enter gaps and the like, and the uniformity is obtained. Since it is possible to form a hardened carburized layer, it is possible to apply the oxide film removing treatment and the low-temperature carburizing treatment to the completed bearing after assembly.

[0032]

As is apparent from the above description, according to the present invention, an inexpensive steel press retainer is used, and HV5 is applied to the surface of an austenitic stainless steel press-formed product.
Since the carburized hardened layer having a hardness of 00 to HV1100 is provided, even when the rolling bearing is used in a vacuum or in a corrosive environment, the lubricating condition becomes worse than before, and the corrosion resistance and A steel cage for a rolling bearing which has excellent wear resistance and is applicable to non-magnetic applications can be provided at low cost.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view in which a part of various rolling bearings using a steel cage for a rolling bearing according to the present invention is partially broken, and FIG.
Is a ball bearing, (b) is a roller bearing, and (c) is a tapered roller bearing.

FIG. 2 is a graph showing the relationship between surface hardness and wear volume ratio.

FIG. 3 is a photograph substituted for a drawing showing a cross-sectional structure of the configuration retainer for a rolling bearing of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inner ring (inner member) 2 ... Outer ring (outer member) 3 ... Rolling element 4 ... Cage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI theme coat ゛ (Reference) C23C 8/22 C23C 8/22 F term (Reference) 3J101 AA02 AA13 AA16 AA25 AA32 AA42 AA52 AA54 AA62 BA34 BA44 BA45 BA47 BA50 CA33 CA34 DA02 DA05 DA09 EA06 FA08 FA31 FA44 FA60 4K028 AA01 AB01 AB06

Claims (1)

[Claims] 1. A rolling bearing steel for holding a plurality of rolling elements rotatably disposed between an inner rolling surface of an outer member and an outer rolling surface of an inner member. A retainer made of austenitic stainless steel press-formed product and having a carburized hardened layer having a hardness of HV500 to HV1100 provided on a surface thereof.