JP2007247757A - Rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling device hard to rust with water entering therein. <P>SOLUTION: A tapered roller bearing has an inner ring 1, an outer ring 2, and a plurality of rolling elements rollingly arranged between a raceway surface 1a of the inner ring 1 and a raceway surface 2a of the outer ring 2. On at least part of the surface of at least one of the inner ring 1, the outer ring 2 and the rolling element 3, a metal coat containing zinc and tin is formed by the projection of zinc powder followed by the projection of tin powder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling device such as a rolling bearing, a linear guide device, a ball screw, a linear motion bearing, and the like, and more particularly, to a rolling device that hardly causes rusting.

  For example, a rolling mill roll neck bearing that supports a rolling roll of a rolling mill of a steel manufacturing facility often has rolling water or cooling water intruding into the bearing even if a housing seal is mounted. In addition, the bearing may be stopped for several hours due to roll replacement, etc., or the bearing may be removed from the rolling mill for periodic roll polishing. ) Is likely to occur. In such a use environment, the bearing life may be dominated by rusting including damage such as peeling starting from rust, not the rolling fatigue life due to internal peeling.

Conventionally, as a means of suppressing the occurrence of this rusting, a means for attaching a seal to prevent water intrusion at the expense of the load capacity of the bearing, which is the main factor of rolling fatigue life, or a phosphate coating on the entire surface of the bearing There are means for performing chemical conversion processing such as processing.
JP 2002-106588 A JP 2003-239992 A JP 9-329147 A

However, in the case of rolling mill roll neck bearings operated under harsh conditions, even if a seal that prevents water intrusion is installed, it may not completely prevent water from entering, so rusting will occur even if water enters. It is requested not to.
Further, since the chemical conversion treatment film such as a manganese phosphate coating is a corrosion coating, it slightly erodes the metal material (base material) constituting the bearing. Therefore, when chemical conversion treatment is applied to the bearing raceway surface, depending on the degree of erosion, peeling may occur from that part, and the life may be reached in a shorter time than the rusting life without chemical conversion treatment. was there.

Furthermore, if the degree of erosion of the base material is to be reduced, the crystal size of the coating will be affected, and the chemical conversion film will easily fall off due to rolling. As a result, there is a problem that the oil holding power after rolling is lowered and the rusting life cannot be extended.
Then, this invention solves the problem which the above prior arts have, and makes it a subject to provide the rolling device which is hard to produce rusting even if water penetrate | invades.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling device according to claim 1 of the present invention includes an inner member having a raceway surface on the outer surface, and a raceway surface facing the raceway surface of the inner member, and is disposed outward of the inner member. In the rolling device comprising: an outer member that is formed, and a plurality of rolling elements that are arranged to freely roll between the raceway surfaces, at least of the inner member, the outer member, and the rolling element One is characterized in that a metal coating containing zinc and tin is provided on at least a part of its surface.

  Zinc is a base metal rather than iron, which is the main component of the metal material (hereinafter also referred to as the base material) that constitutes the inner member, the outer member, and the rolling element. If zinc is coated on the surface, zinc preferentially dissolves even in an environment where rust is likely to occur (self-sacrificial rust prevention action), and iron in the base material is prevented from leaching and becoming rust. . From the rust prevention principle of zinc, which is a self-sacrificial type, if a metal film is coated on a portion of the portion that can be electrically conductive, the above rust prevention effect by zinc can be obtained. Therefore, if a metal film is coated on a part of the inner member, the outer member, and the entire surface of the rolling element (that is, the entire surface of the rolling device), the rust prevention effect by zinc can be obtained.

Further, tin is a noble metal than iron and zinc and is not easily rusted. Therefore, if a metal coating containing tin is coated on the surface, the base material is protected by tin and rusting is suppressed. In addition to this, the elution of zinc at an early stage is suppressed by tin, and the antirust effect is maintained over a long period of time.
A rolling device according to a second aspect of the present invention is the rolling device according to the first aspect, wherein the metal coating is formed using mechanical energy.

Furthermore, the rolling device according to claim 3 according to the present invention is the rolling device according to claim 1, wherein the metal coating is formed by shot peening of zinc powder and tin powder. .
Since the metal film is formed using mechanical energy, there is no possibility that hydrogen is generated during the treatment process and embrittles the base material as in the conventional film formation method such as electroplating and chemical plating. Therefore, delayed fracture and white peeling are unlikely to occur in the rolling device. Moreover, since it is not exposed to a high temperature in the treatment process unlike hot dip plating, a metal film can be formed without causing a decrease in the hardness of the base material and a change in the surface structure. Therefore, the performance of the rolling device is not impaired.
As a method for forming a metal film using mechanical energy, shot peening in which zinc powder or tin powder is sprayed on the surface to be treated is preferable because the metal film can be easily formed in a short time.

Furthermore, the rolling device of Claim 4 which concerns on this invention is a rolling device as described in any one of Claims 1-3, The said metal film is provided with the zinc layer and the tin layer, The said zinc layer It is obtained by forming the tin layer on the substrate.
Since the tin layer is formed on the zinc layer, the base material and the zinc layer are protected by the tin layer, and rusting is further suppressed.
Furthermore, the rolling device according to claim 5 according to the present invention is the rolling device according to any one of claims 1 to 4, wherein the metal coating contains an alloy of zinc and tin. And

Furthermore, the rolling device of Claim 6 which concerns on this invention is a rolling device as described in any one of Claims 1-5. WHEREIN: The thickness of the said metal film is 0.5 micrometer or more and 8 micrometers or less. Features.
If the thickness of the metal coating is less than 0.5 μm, there is a possibility that a sufficient and continuous rust preventive effect cannot be obtained. On the other hand, if the thickness of the metal coating is more than 8 μm, the metal coating is liable to fall off and may become a foreign substance for the rolling device.

Furthermore, the rolling device according to a seventh aspect of the present invention is the rolling device according to any one of the first to sixth aspects, wherein the surface of the inner member, the surface of the outer member, and the rolling device. A dimple having a depth of not less than 0.1 μm and not more than 5 μm is provided on at least a portion of the surface of the moving body provided with the metal coating.
The dimple improves the adhesion between the metal coating and the base material. Further, since the metal film that has fallen off when the rolling device is driven is trapped in the dimples, the antirust effect is maintained for a long time. In order to obtain such an effect, the depth of the dimple is preferably set to 0.1 μm or more. However, even if the dimple depth exceeds 5 μm, no further effect can be expected. Therefore, the dimple depth is preferably 5 μm or less.

Furthermore, the rolling device according to claim 8 according to the present invention is the rolling device according to any one of claims 1 to 7, wherein the center line average roughness Ra of the surface of the metal coating is 0.1 μm or more. It is 1 μm or less.
With such a configuration, an antirust effect is obtained, galling is unlikely to occur in the rolling device, and acoustic characteristics are good. In particular, when the metal coating is formed on the raceway surface of the inner member, the raceway surface of the outer member, and the rolling surface of the rolling element, the center line average roughness Ra of the surface of the metal coating is within the above range. It is preferable. If the center line average roughness Ra of the surface of the metal coating is more than 1 μm, galling may occur or the acoustic characteristics may be insufficient. On the other hand, if the center line average roughness Ra is less than 0.1 μm, the rolling device may be expensive.

  The present invention can be applied to various rolling devices. For example, a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like. Further, the inner member in the present invention means an inner ring when the rolling device is a rolling bearing, a screw shaft when the ball screw is also used, a guide rail when the linear guide device is used, and a linear motion bearing. Means each axis. The outer member is the outer ring when the rolling device is a rolling bearing, the nut when it is a ball screw, the slider when it is a linear guide device, and the outer cylinder when it is also a linear bearing. Each means.

  In the rolling device of the present invention, rusting hardly occurs.

An embodiment of a rolling device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial longitudinal sectional view showing the structure of a tapered roller bearing which is an embodiment of a rolling device according to the present invention.
The tapered roller bearing shown in FIG. 1 includes an inner ring 1 (inner member) fixed to a shaft (not shown), an outer ring 2 (outer member) fixed to a housing (not shown), a raceway surface 1 a of the inner ring 1, and an outer ring 2. There are provided a plurality of rolling elements 3 arranged so as to be able to roll between the raceway surface 2a, and a retainer 4 for holding the plurality of rolling elements 3 between both wheels 1 and 2. At least one of the inner ring 1, the outer ring 2, and the rolling element 3 includes a metal coating (not shown) containing zinc and tin on at least a part of its surface.

  Zinc, which is a base metal rather than iron, is contained in the metal coating, so that zinc preferentially melts even in an environment where rust is likely to occur, and iron in the base material is eluted and becomes rust. Is suppressed. In addition, since the metal coating contains tin that is a noble metal than iron or zinc and is less likely to rust, the base material is protected by tin and rusting is suppressed. In addition to this, since elution of zinc at an early stage is suppressed by tin, the antirust effect is maintained over a long period of time. Therefore, in this tapered roller bearing, rusting of the inner ring 1, the outer ring 2, and the rolling element 3 is suppressed even in an environment where rust is likely to occur.

  The location where the metal coating is formed is not particularly limited as long as it is the surface of the inner ring 1, the outer race 2, and the rolling element 3, and rusting at the location where the metal coating is formed can be suppressed. If a metal film is formed on at least one of the raceway surface 1a, the raceway surface 2a of the outer ring 2, and the rolling surface 3a of the rolling element 3, rusting of these surfaces can be suppressed, so that the tapered roller The bearing can have a long life.

  Since this metal film is preferably formed by a method using mechanical energy such as shot peening, it may be formed by projecting zinc powder or tin powder onto the surface to be treated. If a metal film is formed by utilizing mechanical energy, no erosion that causes a problem in chemical conversion treatment, which is a conventional film formation method, occurs. And it is preferable that the formed metal film is equipped with the zinc layer and the tin layer, and the tin layer is formed on the zinc layer. If the tin layer is formed on the zinc layer, the base material and the zinc layer are protected by the tin layer, and rusting is further suppressed.

  When forming a tin layer on a zinc layer by shot peening, it is good to project tin powder further after projecting zinc powder. Then, since the tin powder is projected onto the zinc layer, an alloy layer of zinc and tin is first formed on the zinc layer, and further, a tin layer is formed thereon (that is, a three-layer structure). Become). However, although the metal coating in this embodiment contains zinc and tin, zinc and tin may be an alloy, or may be a simple mixture instead of an alloy. Moreover, both an alloy and a mixture may be mixed. Furthermore, it may have a two-layer structure of a zinc layer and a tin layer. In addition, if a mixed powder of zinc powder and tin powder is projected, it is possible to form a metal coating made of zinc-tin alloy.

  The thickness of the metal coating is preferably 0.5 μm or more and 8 μm or less. Moreover, it is preferable to provide dimples having a depth of 0.1 μm or more and 5 μm or less on at least a portion of the surface of the inner ring 1, the surface of the outer ring 2, and the surface of the rolling element 3 that is covered with the metal film. Furthermore, the center line average roughness Ra of the surface of the metal film is preferably 0.1 μm or more and 1 μm or less.

  In the present embodiment, the tapered roller bearing is described as an example of the rolling device, but the type of the rolling bearing is not limited to the tapered roller bearing, and the present invention is applicable to various types of rolling bearings. It can be applied to. For example, radial rolling bearings such as deep groove ball bearings, angular contact ball bearings, self-aligning ball bearings, needle roller bearings, cylindrical roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing. Furthermore, the present invention can be applied not only to rolling bearings but also to various types of various rolling devices. For example, a ball screw, a linear guide device, a linear motion bearing, or the like.

〔Example〕
The present invention will be described more specifically with reference to the following examples. Tapered roller bearings for rolling mill roll necks were prepared and their life was evaluated. The specifications of this tapered roller bearing are as follows.
Identification number: HR32017XJ
Bearing inner diameter: 85mm
Bearing outer diameter: 130mm
Assembly width: 29mm
Basic dynamic load rating: 143000N

Moreover, the inner ring, the outer ring, and the rolling element are made of SUJ2 steel, and the properties thereof are as follows.
Surface hardness: HRC58-64
Surface retained austenite amount: 20 to 45% by volume
Surface carbon concentration: 0.8-1.1% by mass
Surface nitrogen concentration: 0.05 to 0.3% by mass
In the present embodiment, the inner ring, the outer ring, and the rolling element are subjected to carbonitriding, but may be subjected to submerged quenching and induction quenching without performing carbonitriding. Further, instead of SUJ2 steel, SCM420 and SCr420 subjected to carburizing treatment or carbonitriding treatment may be used.

  Furthermore, the metal film having the three-layer structure as described above is formed on the outer peripheral surface of the outer ring by projecting tin powder following the projection of zinc powder, and the metal film is formed on the surfaces of the inner ring and the rolling element. Not formed. As comparative examples, a zinc coating was formed by projecting only zinc powder on the outer peripheral surface of the outer ring, a conventional chemical conversion treatment film (manganese phosphate coating) was formed on the outer peripheral surface of the outer ring, and a coating such as a metal coating We prepared each one that was not prepared at all.

  In this embodiment, a metal film is formed on the outer peripheral surface of the outer ring, but a metal film may not be formed on the outer peripheral surface of the outer ring, and a metal film may be formed on the surface of the inner ring or the surface of the rolling element, Similar effects can be obtained. Alternatively, a metal film may be formed on any two or more of the inner ring surface, the outer ring surface, and the rolling element surface. Moreover, you may form a metal film in a part of these surfaces. Further, a metal film may be formed on the surface of the cage.

A shot peening apparatus was used for forming the metal coating, and zinc powder having an average particle size of 45 μm (as defined in JIS R6001) and tin powder having an average particle size of 45 μm (as defined in JIS R6001) were used as the projection material. The injection pressure is 0.196 to 0.882 MPa, and the injection time is 10 to 20 minutes. The mass of the outer ring used for one treatment was 1 to 20 kg.
Table 1 shows the thickness and centerline average roughness Ra of the metal coating coated on the outer peripheral surface of the outer ring and the depth of the dimple formed on the outer peripheral surface of the outer ring. In addition, although the comparative example 2 is not provided with the film, centerline average roughness Ra shown in Table 1 is the roughness of the outer peripheral surface of the outer ring.

Dimples are formed on the outer peripheral surface of the outer ring of some of the examples and comparative examples by performing pretreatment before forming the metal coating. Although this pretreatment (dimple formation method) is not particularly limited, shot peening treatment is employed in this embodiment. The shot peening process was performed using a shot peening apparatus. For the projecting material, steel balls, SiC, SiO ₂ , Al ₂ O ₃ , glass beads, etc. with an average particle size of 45 μm specified in JIS R6001 are used. Sprayed on the surface.

The dimples may be formed by barrel processing, or the dimples may be formed by using both shot peening processing and barrel processing. The barrel processing is performed by roughing to form large irregularities on the outer peripheral surface of the outer ring using a blend of various media and additives, and finishing to adjust the roughness of the plateau part.
The method for measuring the dimple depth is as follows. A three-dimensional non-contact surface shape measuring instrument was used to observe the outer peripheral surface of the outer ring at 30 fields of view at a magnification of 100 times, and the obtained image was converted into a cross-sectional profile. Then, the dimple depth was measured at five cross sections in the X direction and the Y direction, and the results were averaged.

  Moreover, the method of measuring the thickness of a metal film is as follows. First, a pyrrolidone solution of polyamide-imide, which is a thermosetting resin, was applied to the outer peripheral surface of the outer ring provided with a metal coating, and was cured by heating at 175 ° C. for 2 hours to form a protective film for the metal coating. The outer ring was cut and embedded in an epoxy resin, and the outer ring was mirror-finished by buffing. Furthermore, in order to give unevenness, after corroding with a 3% picral solution for 5 seconds, a nano-order chromium layer was coated on the surface by sputtering to impart electrical conductivity.

Using an electron microscope (SEM), 30 fields of view were observed at a magnification of 5000 times. In each field of view, the thickness of the metal film was measured at five points, the average value of these five points was determined, and this average value was taken as the thickness of the metal film in the field of view. And the average value of the thickness of the metal film of 30 visual fields was calculated | required.
Such a tapered roller bearing was mounted on a life tester as shown in FIG. 2 and rotated to measure the life. However, before mounting on the life tester, 10 ml of 0.5 mass% NaCl aqueous solution was dropped inside the bearing and left in an environment of temperature 60 ° C. and humidity 90% or more for 20 hours.

In FIG. 2, reference numeral W denotes a tapered roller bearing (workpiece) of the device under test, reference numeral 11 denotes an inner ring, reference numeral 12 denotes an outer ring, reference numeral 13 denotes a tapered roller, and reference numeral 14 denotes a cage. The work W is mounted by fitting the inner ring 11 to the bearing seat 16a at one end of the rotating shaft 16 of the life test machine, and the outer ring 12 is fitted and fixed to the outer ring fitting member 18 of the housing 17 of the test machine. A radial load Fr is applied to the rotary shaft 16 by a radial load loading means (not shown), thereby loading the workpiece W with a radial load. Further, an axial load Fs is applied to the outer ring fitting member 18 by a hydraulic cylinder (not shown), thereby applying an axial load to the workpiece W.
The conditions of the life test are as follows.
Radial load: 35750N
Axial load: 15680N
Inner ring rotation speed: 1500rpm
Lubricant: Pure grease lubrication (grease amount 60g)

The rotation test was performed under the above conditions, and the rotation was stopped when the vibration value became five times the initial value or the outer ring 12 reached 160 ° C. When the vibration value increased 5 times, the presence or absence of damage was confirmed using a stereomicroscope. If there was damage, the life was reached. If there was no damage, the rotation test was resumed. When the outer ring 12 reached 160 ° C., it was determined that seizure had occurred, and the life was determined.
Table 1 shows the results of the life test. In addition, the numerical value of the lifetime in Table 1 is shown by the relative value when the lifetime of the bearing of the comparative example 1 provided with the conventional chemical conversion treatment film is set to 1. In Examples 1 to 3, since a metal coating containing zinc and tin was formed on the outer peripheral surface of the outer ring, rust was hardly generated and the life was long.

It is a fragmentary longitudinal cross-section which shows the structure of the tapered roller bearing which is one Embodiment of the rolling device which concerns on this invention. It is sectional drawing of a life test machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Rolling element 3a Rolling surface

Claims (8)

An inner member having a raceway surface on the outer surface, an outer member having a raceway surface opposite to the raceway surface of the inner member, and arranged on the outer side of the inner member, and rolling between the both raceway surfaces In a rolling device comprising a plurality of freely arranged rolling elements,
At least one of the inner member, the outer member, and the rolling element is provided with a metal coating containing zinc and tin on at least a part of its surface.   The rolling device according to claim 1, wherein the metal coating is formed using mechanical energy.   The rolling device according to claim 1, wherein the metal coating is formed by shot peening of zinc powder and tin powder.   4. The metal coating according to claim 1, wherein the metal coating includes a zinc layer and a tin layer, and is obtained by forming the tin layer on the zinc layer. The rolling device described.   The rolling device according to claim 1, wherein the metal coating contains an alloy of zinc and tin.   The rolling device according to claim 1, wherein a thickness of the metal coating is 0.5 μm or more and 8 μm or less.   Of the surface of the inner member, the surface of the outer member, and the surface of the rolling element, dimples having a depth of 0.1 μm or more and 5 μm or less are provided on at least a portion provided with the metal coating. The rolling device according to any one of claims 1 to 6.   The rolling device according to claim 1, wherein a center line average roughness Ra of the surface of the metal coating is 0.1 μm or more and 1 μm or less.

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