JP2014074482A - Rolling device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling device which can suppress the formation of a smear ring and permits further elongation of a lubrication life.SOLUTION: In a rolling device, a solid lubrication coating film which contains MoS, Sn or Cu on at least a part of raceway surface of a member serving as at least a stationary ring, of an inner member and an outer member, has a thickness of 0.1 to 2.0 μm and has an average surface roughness Ra of 1 μm or less is formed. At the same time, on the surface of the rolling body, the average surface roughness Ra is 0.08 μm or less, and the average surface roughness Ra(x) in the direction parallel to the rolling direction and the average surface roughness Ra(y) in the direction vertical to the rolling direction has a relation of [0.5≤Ra(x)/Ra(y)≤2.0].

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 processing of a rolling element and a raceway surface.

  In a rolling mill roll neck bearing that supports a rolling roll of a rolling mill of a steel manufacturing facility, an oil film is formed on a race surface using grease in order to prevent metal contact due to rolling and sliding contact. However, the rolling mill roll neck bearing is used under high temperature, has a high load, and further enters the rolling water, which is an unfavorable operating condition for oil film formation. In some cases, the oil film breaks, smearing (micro-seizure) occurs, and progresses to surface peeling.

  In order to prevent such poor lubrication, surface modification is performed on the rolling surface or raceway surface by plating, sputtering, ion plating, or the like. However, these methods have complicated processes and require a long time, resulting in an increase in cost and a decrease in production efficiency. Therefore, the present applicant has previously proposed in Patent Document 1 that shot peening of zinc powder and tin powder to form a metal film containing zinc and tin.

Japanese Patent No. 4513775

  Since the shot peening method only needs to project metal powder, the process is simple and the cost increase can be suppressed. However, further improvement in lubrication performance is inevitable, and an object of the present invention is to provide a rolling device that further suppresses the occurrence of smearing and further extends the lubrication life.

  As a result of intensive studies to solve the above problems, the present inventors have formed a specific solid lubricating film on the raceway surface while suppressing the occurrence of smearing, while the roughness of the rolling element surface is a specified value. The inventors have found that it is effective to make the smooth surface smaller than the above, and have completed the present invention.

That is, the present invention provides the following.
(1) 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 disposed on the outer side of the inner member, and between both the raceway surfaces A rolling device comprising a plurality of rolling elements arranged so as to be freely rotatable,
Among the inner member and the outer member, at least a part of the raceway surface of the member that becomes the fixed ring contains molybdenum disulfide, tin, or copper, has a thickness of 0.1 to 2.0 μm, and an average surface roughness A solid lubricant film having a thickness Ra of 1 μm or less is formed,
On the surface of the rolling element, the average surface roughness Ra is 0.08 μm or less, and the average surface roughness Ra (x) in the direction parallel to the rolling direction and the average surface roughness Ra (y in the direction orthogonal to the rolling direction) ) Satisfies the following expression (1).
0.5 ≦ Ra (x) / Ra (y) ≦ 2.0 (1)
(2) The rolling device according to (1), wherein the solid lubricant film is a film formed by shot peening.
(3) The rolling device according to claim 1 or 2, wherein the surface of the rolling element is processed by shot polishing or a combination of chemical polishing and barrel polishing.
(4) The above-described (1), wherein a coating made of manganese phosphate or zinc phosphate is formed on at least a part of a raceway surface of a member that becomes a rotating wheel among the inner member and the outer member. The rolling device according to any one of (1) to (3).

  In the rolling device of the present invention, a specific solid lubricating film is formed on the raceway surface, and the rolling element surface is a smooth surface having an average surface roughness Ra of 0.08 μm or less and having no roughness directionality. As a result, the oil film is prevented from breaking between the raceway surface and the rolling element surface, and smearing does not occur.

It is a fragmentary longitudinal cross-section which shows the structure of the rolling device (taper roller bearing) for rolling mill roll necks which is an example of the rolling device which concerns on this invention. It is sectional drawing of the life test machine used in the Example.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  Although there is no restriction | limiting in the kind of rolling device in this invention, For example, the rolling device for rolling mill roll necks shown with a fragmentary sectional view in FIG. 1 can be illustrated. The rolling device for a rolling mill roll neck shown in the figure is a tapered roller bearing, and 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 plurality of rollers 3 (rolling elements) that are arranged to freely roll between the raceway surface 1a of the inner ring 1 and the raceway surface 2a of the outer ring 2, and a cage that holds the plurality of rollers 3 between the two wheels 1 and 2. 4 is provided. The inner ring 1, outer ring 2 and roller 3 can be made of SUJ2 material, SCM420 material, SCr420 material or the like, and may be further subjected to carbonitriding, submerged quenching, induction quenching or the like.

In the present invention, the surface of the roller 3 has an average surface roughness Ra of 0.08 μm or less and an average surface roughness Ra (x) in a direction parallel to the rolling direction and a direction orthogonal to the rolling direction. Smoothing is performed so that the average surface roughness Ra (y) satisfies the following expression (1).
0.5 ≦ Ra (x) / Ra (y) ≦ 2.0 (1)

  The smaller the average surface roughness Ra of the roller 3 is, the smoother the rolling surface is. However, since there is a surface undulation, the average surface roughness Ra is not 0.02 μm or less. Further, the “Ra (x) / Ra (y)” ratio is closer to 1, indicating that there is no directionality of roughness and the roughness is uniform over the entire surface. That is, the above definition shows that minute irregularities are uniformly distributed over the entire surface of the roller 3. As a result, an oil film is uniformly formed between the roller surface and the raceway surface, the ratio of metal contact is reduced, and smearing is less likely to occur.

  In order to make the above effect more reliable, the average surface roughness Ra of the roller 3 is preferably 0.06 μm or less, and the “Ra (x) / Ra (y)” ratio is 0.7 to 1.5. It is preferable that

  As a polishing method for smoothing the roller 3 as described above, shot polishing, chemical polishing or barrel polishing is preferable. Further, these polishing treatments may be combined. Among these, shot polishing or a combination of chemical polishing and barrel polishing is preferable.

  Further, in the present invention, a solid lubricating film (not shown) made of molybdenum disulfide, tin, or copper is formed on the raceway surface (1a) of at least one of the inner ring 1 and the outer ring 2 (in this case, the inner ring 1) which is a fixed ring. Form. If the roller surface is smooth as described above, an oil film is likely to be formed, and the solid lubricating film formed on the raceway surface 1a of the inner ring 1 is transferred to the raceway surface 2a of the outer ring 2 via the rollers 3. The occurrence of smearing is further suppressed.

  When a solid lubricant film is formed on the outer ring 2 that is a rotating wheel, the solid lubricant film is difficult to transfer to the inner ring side due to the action of centrifugal force. Therefore, when a solid lubricant film is formed on one of the rotating wheel and the fixed wheel, it is effective to form a solid lubricant film on the fixed wheel side.

  Further, when a solid lubricating film is formed on the raceway surface 1 a of the inner ring 1, it is preferable to form a manganese phosphate coating or a zinc phosphate coating on the raceway surface 2 a of the outer ring 2.

  The thickness of the solid lubricant film is 0.1 to 2.0 μm, and the average surface roughness Ra is 1 μm or less. If the thickness of the coating is less than 0.1 μm, a sufficient and sustained effect may not be obtained. If the thickness of the coating exceeds 2.0 μm, the coating tends to fall off. A preferred thickness is 0.4 to 1.5 μm.

  On the other hand, if the average surface roughness Ra of the solid lubricant film exceeds 1 μm, galling may occur or the acoustic characteristics may be insufficient. However, in order to reduce the average surface roughness Ra, more precise surface processing is required. Therefore, it is practical to set the average surface roughness Ra to 0.2 μm or more.

  The solid lubricant film is preferably formed by a shot peening method. The shot peening method is a method in which powder of a material for forming a film is sprayed on a surface to be processed to deposit the powder in a film shape. In the present invention, molybdenum disulfide powder, tin powder, copper powder, or a mixture thereof Powder is sprayed onto the raceway surface 1 a of the inner ring 1. The thickness and surface roughness of the solid lubricating coating can be adjusted by the powder injection pressure and time. This shot peening method has a simpler process and higher productivity than the plating method by plating, sputtering, or ion plating. However, it is difficult to form a thin film having a thickness of less than 0.1 μm by the shot peening method. If a thick film exceeding 2.0 μm is to be formed, the surface becomes rough, and the average surface roughness Ra should be 1 μm or less. Becomes difficult.

  In addition, since the bearing is likely to rust in an environment where it comes into contact with water, and the occurrence of smearing is promoted by rust, it is preferable to add Zn having self-rust prevention performance to the solid lubricating film. However, since the lubrication effect is reduced due to the addition of Zn, when there is no risk of rusting due to water, it is better to add no Zn.

  As described above, in the present embodiment, the tapered roller bearing has been described, but in addition, a deep groove ball bearing, an angular ball bearing, a self-aligning ball bearing, a needle roller bearing, a cylindrical roller bearing, a self-aligning roller bearing, a thrust Examples include ball bearings and thrust roller bearings. It can also be applied to ball screws, linear guide devices, linear motion bearings, and the like.

  The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

(Examples 1-30, Comparative Examples 1-12)
Tapered roller bearings for rolling mill roll necks were prepared and their smearing occurrence 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

The inner ring, outer ring and tapered roller are made of SUJ2 steel and carbonitrided, and the properties 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

  Further, the solid lubricant film indicated on the outer ring is formed by shot peening or chemical conversion treatment (Comparative Example 5), and the film thickness, average surface roughness Ra, and “Ra (x) / Ra (y)” ratio are measured. did. Further, the surface of the tapered roller was subjected to the indicated polishing process, and the average surface roughness Ra was measured. In Example 4 and Comparative Example 7, a manganese phosphate chemical conversion treatment film was formed on the inner ring.

  In the test, each tapered roller bearing was mounted on a life tester shown in FIG. 2 and rotated to measure the life. Lubrication with a base oil viscosity of 150 cSt was used for lubrication, and the amount of grease replenished was 5 g / h to generate smearing. The initial amount of grease was 30 g per bearing. Then, when the temperature increased by 10 ° C. or when the vibration value increased three times the initial value, it was assumed that smearing occurred, and the time until that time was measured. Each test was performed 10 times, and the average life was obtained. The results are shown in Table 1, but are shown as relative values with respect to Comparative Example 1 in which no treatment was applied to the inner ring, the outer ring and the rollers.

  In the test apparatus, 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 tester, and the outer ring 12 is fitted and fixed to the outer ring fitting member 18 of the housing 17 of the tester. A radial load Fr (60000 N) 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 (15000 N) is applied to the outer ring fitting member 18 by a hydraulic cylinder (not shown), whereby the workpiece W is loaded with an axial load.

  As shown in Table 1, according to the present invention, a solid lubricating film made of molybdenum disulfide, tin, or copper, having a thickness of 0.1 to 2.0 μm, and Ra of 1 μm or less is formed on the outer ring that is a fixed ring. In an example in which the roller Ra is 0.08 μm or less and the “Ra (x) / Ra (y)” ratio satisfies 0.5 to 2.0, the smearing life is excellent. .

  In particular, the comparison between Examples 3 and 4 shows that the smearing life is greatly extended by forming the manganese phosphate coating on the rotating wheel (inner ring). From the comparison between Examples 9, 10, and 11, it can be seen that a molybdenum disulfide film is preferable as the solid lubricating film. From the comparison of Examples 12 to 15, it is found that shot polishing is preferable as a method for polishing the roller, and that even when chemical polishing and barrel polishing are combined, good smoothness can be obtained. From the comparison of Examples 1 to 3, Examples 5 to 8 and Comparative Examples 2 and 3, the ratio of “Ra (x) / Ra (y)” is 0.5 to 2.0, preferably 0.7 to It turns out that it is 1.5. From comparison of Examples 16-20, it turns out that the average surface roughness Ra of a rolling element is 0.08 micrometer or less. From the comparative examples of Examples 21 to 30 and Comparative Examples 9 and 10, it can be seen that the thickness of the solid lubricating coating is 0.1 to 2.0 μm, preferably 0.4 to 1.5 μm.

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

Claims (4)

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,
Among the inner member and the outer member, at least a part of the raceway surface of the member that becomes the fixed ring contains molybdenum disulfide, tin, or copper, has a thickness of 0.1 to 2.0 μm, and an average surface roughness A solid lubricant film having a thickness Ra of 1 μm or less is formed,
On the surface of the rolling element, the average surface roughness Ra is 0.08 μm or less, and the average surface roughness Ra (x) in the direction x parallel to the rolling direction and the average surface roughness Ra in the direction y orthogonal to the rolling direction. (Y) satisfies the following expression (1).
0.5 ≦ Ra (x) / Ra (y) ≦ 2.0 (1)   The rolling device according to claim 1, wherein the solid lubricant film is a film formed by shot peening.   The rolling device according to claim 1 or 2, wherein the surface of the rolling element is processed by shot polishing or a combination of chemical polishing and barrel polishing. The film which consists of manganese phosphate or a zinc phosphate is formed in at least one part of the track surface of the member used as a rotating ring among an inner member and an outer member, The Claims 1-3 characterized by the above-mentioned. A rolling device given in any 1 paragraph.

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