JP2010249215A - Roll bearing for hydrogen atmosphere - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roll bearing which is hardly worn or damaged and whose service life is long in addition to a structure change to a white structure hardly occurs even when used in a hydrogen atmosphere. <P>SOLUTION: An inner ring 1 and an outer ring 2 of a deep groove ball bearing is made up of alloy steel containing carbon of 0.5 mass% to 0.9 mass%, silicon of 0.6 mass% to 1 mass%, manganese of 0.6 mass% to 1.2 mass%, chromium of 6.5 mass% to 9.5 mass%, and molybdenum of 1 mass% or lower and whose remaining part is iron and unavoidable impurity. A resistance value of the structure change is 10 or more. Furthermore, hardening and tempering are performed. The residual austenite amounts of track surfaces 1a and 2a are 10 vol.% to 20 vol.% and hardness is Hv674 to 772. The old austenite grain size is 7 to 10 in the grain size number. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rolling bearing preferably used in a hydrogen atmosphere.

  Usually, a rolling bearing incorporated in a gas compressor is used in an atmosphere such as air or nitrogen. Therefore, as a method for extending the life of the rolling bearing, mainly the dimensional stability under a high temperature environment and the improvement of the seizure resistance at the time of high speed rotation. For example, Patent Document 1 discloses a rolling bearing excellent in dimensional stability in which high-temperature tempering is performed and the amount of retained austenite of a steel material is 5% by mass or less.

Further, rolling bearings used in corrosive gas are required to have excellent corrosion resistance. For example, Patent Document 2 discloses a rolling bearing that is excellent in corrosion resistance and seizure resistance, in which a bearing ring is made of martensitic stainless steel and a rolling element is made of ceramics.
On the other hand, as a technique for extending the life of a rolling bearing against hydrogen, a method of increasing the chromium content of steel constituting the race is conventionally known (see, for example, Patent Documents 3 to 5). This method takes into consideration that hydrogen is generated by the decomposition of the lubricating oil.

JP 2006-275131 A JP 2004-11896 A JP 2003-343577 A JP 2005-264216 A JP 2001-221238 A

  In recent years, from the viewpoint of environmental problems, development of technology using hydrogen (for example, a fuel cell) has progressed, and a compressor (hereinafter referred to as a hydrogen gas compressor) for compressing hydrogen gas is required. A rolling bearing incorporated in a hydrogen gas compressor may be used in a hydrogen atmosphere, and hydrogen is likely to enter the steel constituting the rolling bearing. When hydrogen intrudes into steel, the shear stress acting on the inside of the steel due to rolling contact with hydrogen causes a change in the martensitic structure of the steel into a structure called a white structure, which significantly increases the life of the rolling bearing. May decrease.

  Spherical roller bearings and relatively large ball bearings are often used for hydrogen gas compressors, but these types of rolling bearings are free from slippage between the rolling elements and the race. The amount is large and wear damage is likely to occur. Normally, an oxide film is formed on the metal surface, and the oxide film makes it difficult for wear damage to occur.However, since there is no oxygen in a hydrogen atmosphere and it is difficult to form an oxide film on the metal surface, wear damage occurs. Cheap. In addition, once wear occurs, the wear surface is chemically active, so hydrogen tends to enter the steel, and the above structural change is accelerated.

For these reasons, a rolling bearing incorporated in a hydrogen gas compressor needs to have both a countermeasure against the structural change due to hydrogen entering the steel and a countermeasure against wear damage in a hydrogen atmosphere.
However, the rolling bearing disclosed in Patent Document 1 has neither a countermeasure against the structural change caused by hydrogen penetrating into steel nor a countermeasure against wear damage in a hydrogen atmosphere. In addition, since the rolling bearing disclosed in Patent Document 2 has a raceway made of stainless steel, measures against the structural change due to hydrogen entering the steel are taken, and the resistance to the structural change is high. Although the structure change is less likely to occur, no countermeasure has been taken against wear damage in a hydrogen atmosphere.

Furthermore, the rolling bearings disclosed in Patent Documents 3 and 4 assume that a small amount of hydrogen generated by the decomposition of the lubricating oil enters the steel, so that the rolling bearing is used in a hydrogen atmosphere. Under such a harsh environment, the resistance to the tissue change was insufficient. In addition, measures against wear damage in a hydrogen atmosphere were not sufficient.
Accordingly, the present invention solves the above-described problems of the prior art, and in addition to being difficult to cause a change in structure to a white structure even when used in a hydrogen atmosphere, the rolling bearing has a long life and is less susceptible to wear damage. It is an issue to provide.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling bearing for a hydrogen atmosphere according to the present invention includes an inner ring having a raceway surface, an outer ring having a raceway surface facing the raceway surface of the inner ring, and a plurality of rolling rings arranged between the raceway surfaces. A rolling bearing comprising a rolling element and used in a hydrogen atmosphere, wherein at least one of the inner ring and the outer ring satisfies the following four conditions.

Condition 1: The carbon content is 0.5 mass% or more and 0.9 mass% or less, the silicon content is 0.6 mass% or more and 1 mass% or less, and the manganese content is 0.6 mass% or more. 2 mass% or less, chromium content is 6.5 mass% or more and 9.5 mass% or less, molybdenum content is 1 mass% or less, and the balance is iron and inevitable impurities. ing.
Condition 2: The content of silicon is Si%, the content of manganese is Mn%, the content of chromium is Cr%, the content of molybdenum is Mo%, 2.5 × Si% + 1.5 × The structure change resistance value calculated by the formula of Mn% + Cr% + 3 × Mo% is 10 or more.

Condition 3: Quenching and tempering are performed, the amount of retained austenite on the raceway surface is 10% by volume or more and 20% by volume or less, and the hardness is Hv674 or more and 772 or less.
Condition 4: The prior austenite grain size measured by the method defined in Japanese Industrial Standard JIS G0551 is 7 or more and 10 or less in grain size number.
In the rolling bearing for hydrogen atmosphere of the present invention, at least one of the inner ring and the outer ring is made of alloy steel containing silicon, manganese, chromium, and molybdenum, which are elements that suppress the diffusion of hydrogen in steel. Even if it is used in a hydrogen atmosphere, it does not easily change to a white structure. Therefore, the rolling bearing for hydrogen atmosphere of the present invention has a long life even when used in a hydrogen atmosphere.

In the rolling bearing for hydrogen atmosphere of the present invention, it is preferable that at least one of the inner ring and the outer ring further satisfies the following condition 5 together with the four conditions.
Condition 5: The maximum peak height Rp of the roughness curve in the axial direction of the raceway surface is 0.2 μm or less.
Since the maximum peak height Rp of the roughness curve along the axial direction of the raceway surface is 0.2 μm or less, wear due to metal contact hardly occurs, and a chemically active new surface is hardly generated. Therefore, in addition to being hard to cause wear damage, the penetration of hydrogen into the steel is also suppressed.

Moreover, it is preferable that the said rolling element is comprised with steel whose chromium content is 5 mass% or more and 18 mass% or less. Furthermore, it is preferable that the rolling element is made of ceramics.
Below, the critical significance of each numerical value (content of each alloy component contained in the alloy steel, etc.) relating to the inner ring, outer ring, rolling element, alloy steel, etc. in the present invention will be described.

[Carbon content]
Carbon (C) is an element for obtaining a hardness required as a rolling bearing by solid solution in the base by quenching. Moreover, it has the effect | action which combines with another alloy element and forms hard carbide | carbonized_material in alloy steel, and improves abrasion resistance. If the carbon content is less than 0.5% by mass, the rolling life and wear resistance may be insufficient. On the other hand, if the carbon content exceeds 0.9% by mass, eutectic carbides are likely to be generated in the alloy steel, which may reduce the rolling life. Also, cold workability and machinability may be reduced. Considering the stability of the quality of the alloy steel, the carbon content is preferably 0.6% by mass or more and 0.8% by mass or less.

[About silicon content]
Silicon (Si) is an element that dissolves in the matrix to improve hardenability and improve temper softening resistance. It also has the effect of strengthening the base structure and improving the rolling life and wear resistance. If the silicon content is less than 0.6% by mass, these effects cannot be obtained sufficiently. On the other hand, if the silicon content exceeds 1% by mass, cold workability and machinability may be insufficient.

[About manganese content]
Manganese (Mn) is an element that dissolves in the matrix and improves hardenability. It also has an effect of assisting formation of retained austenite on the surface, which is important in the present invention. There exists a possibility that said effect | action may become inadequate that content of manganese is less than 0.6 mass%. On the other hand, if the manganese content exceeds 1.2% by mass, the amount of retained austenite after quenching increases so that the dimensional stability may be insufficient.

[Chromium content]
Chromium (Cr) is an element that dissolves in the base and improves hardenability, corrosion resistance, etc., and combines with carbon to form hard carbides in the alloy steel, thereby improving wear resistance. Moreover, it also has the effect | action which improves the resistance with respect to the tissue change to the white structure | tissue important in this invention. That is, chromium has a function of reducing the rate at which hydrogen enters the alloy steel. Furthermore, even if hydrogen invades, it stabilizes the base tissue, thereby suppressing the rolling life due to hydrogen. There exists a possibility that said effect | action may become inadequate that content of chromium is less than 6.5 mass%. On the other hand, if the chromium content exceeds 9.5% by mass, cold workability and machinability become insufficient, and eutectic carbides are likely to be generated in the alloy steel, which may reduce the rolling life. There is.

[Molybdenum content]
Molybdenum (Mo) has the effect | action which dissolves in a base | substrate and improves hardenability and temper softening resistance. Moreover, it has the effect | action which forms a hard carbide | carbonized_material in alloy steel and improves abrasion resistance and a rolling life. Furthermore, like chromium, it has the effect of reducing the rate at which hydrogen enters the alloy steel. Furthermore, even if hydrogen invades, it stabilizes the base tissue, thereby suppressing the rolling life due to hydrogen. If the molybdenum content exceeds 1% by mass, cold workability and machinability may be insufficient. In consideration of the stability of the quality of the alloy steel, the molybdenum content is preferably 0.5% by mass or more and 1% by mass or less.

[About tissue change resistance]
Silicon, manganese, chromium, and molybdenum have a function of suppressing the change in structure caused by hydrogen by strengthening the metal structure by forming a solid solution in the base of the metal structure as a substitutional element. In addition, some of the above four elements form carbon and carbides in the alloy steel, but these carbides strongly trap hydrogen, which prevents the hydrogen in the alloy steel from accumulating in the stress concentration part. The tissue change to the white tissue due to the penetration of hydrogen is suppressed.

  The strength of these actions varies depending on each alloy element, and the resistance of the alloy steel to the structural change is a structural change calculated by the formula 2.5 × Si% + 1.5 × Mn% + Cr% + 3 × Mo%. It can be defined by a resistance value. If this structure change resistance value is 10 or more, even if a rolling bearing is used in a hydrogen atmosphere, the structure change is suppressed, so that a reduction in the rolling life of the rolling bearing is suppressed.

  If the structure change resistance value is 10 or more, the rolling life of the rolling bearing is long in a hydrogen atmosphere. However, if the structure change resistance value is 13 or more, the rolling bearing is used even in a severe hydrogen atmosphere where the hydrogen pressure is normal pressure or higher. Since the structural change is suppressed, a decrease in the rolling life of the rolling bearing is suppressed. In addition, it is preferable that a structure change resistance value is 16.8 or less for the above-mentioned reason regarding the critical value of each alloy element.

[Amount of retained austenite on raceway surface]
Residual austenite is formed by being dispersed in the metal structure of the alloy steel, and has a function of strongly trapping hydrogen that has penetrated into the alloy steel and significantly reducing the hydrogen diffusion rate. Accordingly, accumulation of hydrogen in the stress concentration portion is suppressed, and the change in structure is suppressed. The amount of retained austenite can be controlled by the alloy components and heat treatment conditions. If the amount of retained austenite on the raceway surface is less than 10% by volume, the above action may be insufficient. On the other hand, if it exceeds 20% by volume, the dimensional stability may be insufficient.

[Vickers hardness Hv of raceway]
The surface hardness of the raceway surface is a factor that affects the rolling life of the rolling bearing, and if it is less than Hv674 (HRC59), the rolling life of the rolling bearing may be insufficient. On the other hand, if the surface hardness of the raceway surface exceeds Hv772 (HRC63), the toughness may be insufficient.

[Old austenite grain size]
The grain size of prior austenite grains in the alloy steel is a factor that affects the degree of reduction in rolling fatigue strength and fracture toughness due to hydrogen penetration. The grain size of the prior austenite crystal grains can be measured as the prior austenite grain size by the method specified in Japanese Industrial Standard JIS G0551.

  If the prior austenite grain size is less than 7 in grain size number, the penetration of hydrogen may lower the toughness of the alloy steel, resulting in insufficient toughness. On the other hand, if the prior austenite grain size is more than 10 in the grain size number, the structure change is likely to occur due to the penetration of hydrogen, and the rolling fatigue strength may be insufficient. In order to make such inconvenience less likely to occur, the prior austenite grain size is preferably 8 to 9 in terms of grain size number.

[About the maximum peak height Rp of the axial roughness curve of the raceway surface]
When there are protrusions on the raceway surface, metal contact is likely to occur between the raceway surface and the rolling surface of the rolling element. When metal contact occurs in a hydrogen atmosphere, an oxide film is difficult to be formed. Therefore, the portion where the metal contact occurs becomes a chemically active new surface, and adhesion wear tends to occur. Further, since hydrogen easily enters the alloy steel from the new surface, the occurrence of the structural change is accelerated. In general, the arithmetic average roughness Ra is used for the management of the surface roughness, but high correlation between the likelihood of wear damage in the hydrogen atmosphere and the arithmetic average roughness Ra cannot be obtained.

  As a result of intensive studies, the present inventors have found that controlling the maximum peak height Rp of the roughness curve representing the height of the protrusion on the raceway surface is effective in suppressing wear damage in a hydrogen atmosphere. I found. If the maximum peak height Rp of the roughness curve along the axial direction of the raceway surface is more than 0.2 μm, metal contact occurs at the protrusions, adhesion wear of the raceway surface, and hydrogen penetration into the alloy steel. We found that is easy to occur.

  Since the alloy steel used in the present invention has a high structure change resistance value, silicon, manganese, chromium, and molybdenum form hard carbides. Since these hard carbides impair grindability, the maximum peak height Rp of the roughness curve tends to be larger than that of ordinary bearing steel. Therefore, in order to set the maximum peak height Rp of the roughness curve to 0.2 μm or less, it is necessary to suitably select the type of grindstone, the cutting speed, and the peripheral speed used in the grinding process. In consideration of the productivity and cost of the bearing rings, the maximum peak height Rp of the roughness curve is more preferably 0.1 μm or more and 0.2 μm or less.

[Materials that make up rolling elements]
Since the rolling elements are less susceptible to damage than the races, bearing steel, which is a material constituting the rolling elements of general rolling bearings, and case-hardened steel that has been subjected to carburizing or carbonitriding are used in the present invention. It can be adopted without any problem as a material constituting the moving body.
However, when used in a harsh hydrogen atmosphere where the hydrogen pressure is higher than normal pressure, when the slip between the bearing ring and the rolling element is large, when the rotational speed of the rolling bearing is high, or when the rolling bearing receives When the usage environment of a rolling bearing is severe, such as when the load is high, it is preferable to use steel having a chromium content of 5 mass% or more and 18 mass% or less as a material constituting the rolling element. Chromium has the effect of reducing the rate at which hydrogen enters the steel. Moreover, even if hydrogen invades, it stabilizes the base structure, thereby suppressing the rolling life from being reduced due to hydrogen intrusion.

There exists a possibility that said effect | action may become inadequate that content of chromium is less than 5 mass%. On the other hand, if it exceeds 18% by mass, coarse eutectic carbides are formed, and the rolling life may be insufficient. Considering the stability of the quality of the steel, the chromium content is more preferably 12% by mass or more and 18% by mass or less.
Further, ceramics can be used as a material constituting the rolling elements. Ceramics are preferred because they do not deteriorate in physical properties due to hydrogen and are excellent in wear resistance.

  The rolling bearing for a hydrogen atmosphere of the present invention has a long life, in addition to being less susceptible to wear damage, in addition to being less likely to change to a white structure even when used in a hydrogen atmosphere.

It is a fragmentary longitudinal cross-section which shows the structure of the deep groove ball bearing which is one Embodiment of the rolling bearing for hydrogen atmosphere which concerns on this invention.

An embodiment of a rolling bearing for a hydrogen atmosphere according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial longitudinal sectional view showing a structure of a deep groove ball bearing which is an embodiment of a rolling bearing for a hydrogen atmosphere according to the present invention.
The deep groove ball bearing of FIG. 1 includes an inner ring 1 having a raceway surface 1a on an outer peripheral surface, an outer ring 2 having a raceway surface 2a facing the raceway surface 1a of the inner ring 1 on an inner peripheral surface, and both raceway surfaces 1a and 2a. There are provided a plurality of rolling elements 3 arranged so as to be capable of rolling, a cage 4 for holding the rolling elements 3 between both raceway surfaces 1a, 2a, and sealing devices 5, 5 such as rubber seals. The cage 4 and the sealing device 5 may not be provided.

  The inner ring 1 and the outer ring 2 have a carbon content of 0.5% by mass to 0.9% by mass, a silicon content of 0.6% by mass to 1% by mass, and a manganese content of 0.8%. 6 mass% or more and 1.2 mass% or less, chromium content is 6.5 mass% or more and 9.5 mass% or less, molybdenum content is 1 mass% or less, and the balance is iron and inevitable impurities It is made of a certain alloy steel (Condition 1).

In this alloy steel, assuming that the silicon content is Si%, the manganese content is Mn%, the chromium content is Cr%, and the molybdenum content is Mo%, 2.5 × Si% + 1. The tissue change resistance value calculated by the formula 5 × Mn% + Cr% + 3 × Mo% is 10 or more (Condition 2).
Furthermore, the inner ring 1 and the outer ring 2 are manufactured by quenching and tempering, and the amount of retained austenite of the raceway surfaces 1a and 2a is 10% by volume or more and 20% by volume or less. Furthermore, the surface hardness of the raceway surfaces 1a and 2a is Hv674 to 772 (HRC 59 to 63) (Condition 3).

Furthermore, the prior austenite crystal grains possessed by the inner ring 1 and the outer ring 2 have a grain size number of 7 or more and 10 or less in terms of grain size number (condition 4) as measured by the method defined in Japanese Industrial Standard JIS G0551.
Furthermore, it is preferable that the maximum peak height Rp of the roughness curve in the axial direction of the raceway surfaces 1a and 2a is 0.2 μm or less (Condition 5).

  Since such a deep groove ball bearing satisfies the above conditions 1 to 5, in addition to being hard to cause a change in structure to a white structure even when used in a hydrogen atmosphere, it has a long life and hardly suffers from wear damage. Therefore, it is suitable as a rolling bearing used in a hydrogen atmosphere like a rolling bearing incorporated in a compressor that compresses hydrogen gas. Although these conditions 1-5 should just satisfy | fill only one among the inner ring | wheel 1 and the outer ring | wheel 2, it is preferable that both the inner ring | wheel 1 and the outer ring | wheel 2 are satisfy | filling.

Furthermore, it is preferable that the rolling element 3 is comprised with the steel or ceramics whose chromium content is 5 mass% or more and 18 mass% or less.
In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, in the present embodiment, a deep groove ball bearing has been described as an example of a hydrogen atmosphere rolling bearing, but the present invention can be applied to various types of rolling bearings other than deep groove ball bearings. . For example, radial rolling bearings such as angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing.

〔Example〕
Rolling bearings were manufactured by the method described below. An alloy steel having a predetermined composition is formed into a shape of a raceway by forging and cutting or only by cutting. Next, after quenching and tempering so as to contain residual austenite, polishing was performed to complete the race. Quenching was performed by oil cooling or gas cooling after holding at 950-1050 ° C. In addition, tempering was performed by holding the furnace at 160 to 240 ° C. and then cooling the furnace or air. And this rolling ring was combined with a rolling element, a cage, and a seal to form a rolling bearing.

  Below, the example which manufactured the deep groove ball bearing is shown. An inner ring and an outer ring for a deep groove ball bearing having a nominal number 6316 were manufactured by the same method as described above using alloy steel of steel type B in Table 1 as a raw material. As a rolling element, a ball composed of steel type O shown in Table 1 was used. These inner rings, outer rings, and rolling elements were assembled to obtain a deep groove ball bearing having a nominal number 6316.

  The amount of retained austenite of the inner ring and the outer ring of this deep groove ball bearing was measured with an X-ray diffractometer and found to be 10% by volume and 15% by volume, respectively. Moreover, the surface hardness of the raceway surface was Hv722 and Hv717, respectively. Further, the prior austenite grain size was 8 in grain size number. Furthermore, the maximum peak heights Rp of the roughness curve in the axial direction of the raceway surface were 0.19 μm and 0.20 μm, respectively.

Next, the example which manufactured the self-aligning roller bearing is shown. An inner ring and an outer ring for a self-aligning roller bearing having a nominal number 22218 were manufactured by using the alloy steel of steel type B shown in Table 1 as a raw material in the same manner as described above. As the rolling elements, rollers composed of steel type N shown in Table 1 were used. These inner rings, outer rings, and rolling elements were assembled to obtain a self-aligning roller bearing having a nominal number 22218.
When the amount of retained austenite of the inner ring and outer ring of this self-aligning roller bearing was measured with an X-ray diffractometer, it was 13% by volume and 20% by volume, respectively. Moreover, the surface hardness of the raceway surface was Hv712 and Hv720, respectively. Further, the prior austenite grain size was 8 in grain size number. Furthermore, the maximum peak heights Rp of the axial roughness curve of the raceway surface were 0.18 μm and 0.19 μm, respectively.

  Next, the example which manufactured the thrust ball bearing is shown. Using the alloy steels of steel types A to K shown in Table 1 as raw materials, an inner ring and an outer ring for a thrust ball bearing having a nominal number 51305 were manufactured by the same method as described above. As the rolling elements, balls composed of steel types G, M, N, O or ceramics P, Q shown in Table 1 were used. These inner rings, outer rings, and rolling elements were assembled to obtain a thrust ball bearing having a nominal number 51305. However, the number of balls was set to three in order to adjust the surface pressure under the test conditions.

These thrust ball bearings were subjected to a rolling fatigue test under the following three test conditions in a hydrogen atmosphere to determine the life (L ₅₀ ) at which the cumulative failure probability was 50%.
・ Test condition A
Hydrogen pressure: 0.12 MPa
Surface pressure: 3.1 GPa
Rotational speed: 1000min ^-1
Lubricating oil: Lubricating oil whose ISO viscosity grade is ISO VG68 ・ Test condition B
Hydrogen pressure: 0.12 MPa
Surface pressure: 3.8 GPa
Rotational speed: 1000min ^-1
Lubricating oil: Lubricating oil whose ISO viscosity grade is ISO VG32-Test condition C
Hydrogen pressure: 0.4 MPa
Surface pressure: 3.1 GPa
Rotational speed: 1000min ^-1
Lubricating oil: Lubricating oil whose ISO viscosity grade is ISO VG68 Table 2 shows the test results under test condition A. Table 2 also shows the structure change resistance value and prior austenite grain size of the alloy steel, the retained austenite amount of the raceway surface, the surface hardness, the arithmetic mean roughness Ra, and the maximum peak height Rp of the roughness curve. . The life in Table 2 is shown as a relative value when the life of Comparative Example 1 is 1. The alloy steel G used in Comparative Example 1 is a steel corresponding to SUJ2 that is generally used as a material for rolling bearings.

  As can be seen from Table 2, in Examples 1 to 6, the alloy composition, the structure change resistance value, the prior austenite grain size, the amount of retained austenite on the raceway surface, and the surface hardness of the alloy steel constituting the raceway are of the present invention. Since it is within the range, even if it is used in a hydrogen atmosphere, the service life is hardly reduced and wear damage is hardly caused. Therefore, the rolling life was long. In particular, Examples 1 to 3 had a longer life because the alloy composition and the prior austenite grain size were in a more preferable range.

  On the other hand, Comparative Examples 1 to 4 had a short life because the alloy composition of the alloy steel constituting the race was outside the scope of the present invention. In Comparative Example 5, the alloy composition was within the range of the present invention, but the structure change resistance value was less than 10, so the life was short. Further, in Comparative Examples 6 and 7, the alloy composition is within the range of the present invention, but the amount of retained austenite on the raceway surface is out of the range of the present invention because the heat treatment conditions are not suitable. there were.

  Further, Comparative Examples 8 and 9 had a short life because the alloy composition was within the range of the present invention, but the prior austenite grain size was out of the range of the present invention because the heat treatment conditions were not suitable. . Furthermore, in Comparative Examples 10 and 11, the alloy composition is within the range of the present invention, but the surface hardness of the raceway surface is out of the range of the present invention because the heat treatment conditions are not suitable. there were.

  Next, Table 3 shows the test results under test condition B. Table 3 also shows the structure change resistance value and the prior austenite grain size of the alloy steel, the amount of retained austenite on the raceway surface, the surface hardness, the arithmetic mean roughness Ra, and the maximum peak height Rp of the roughness curve. . In the case of test condition B, since the oil film thickness becomes thin, metal contact between the race and the rolling element is likely to occur. Therefore, in order to suppress metal contact, it is necessary to control the surface roughness of the raceway surface. Therefore, in the case of the test condition B, as can be seen from Table 3, a track ring having a surface roughness different from that of the test condition A is used. The life in Table 3 is shown as a relative value when the life of Comparative Example 21 is 1.

  As can be seen from Table 3, in Examples 21 to 26, the alloy composition, the structure change resistance value, the prior austenite grain size, the amount of retained austenite on the raceway surface, the surface hardness, and the roughness curve of the alloy steel constituting the raceway ring. Since the maximum peak height Rp is within the range of the present invention, even when used in a hydrogen atmosphere, the life is hardly reduced and wear damage is hardly caused. Therefore, the rolling life was long. In particular, Examples 21 to 23 had a longer life because the alloy composition and the prior austenite grain size were in a more preferable range.

In Examples 27 to 29, the alloy composition is within the range of the present invention, and the arithmetic average roughness Ra of the raceway surface is smaller than those of Examples 24 to 26, but the maximum peak height of the raceway surface roughness curve. Since Rp deviated from the preferred range of the present invention, the lifetime was slightly shorter than that of Examples 24-26, although the lifetime was longer than that of the comparative example.
On the other hand, Comparative Examples 21 to 24 had a short life because the alloy composition of the alloy steel constituting the race was outside the scope of the present invention. In Comparative Example 25, the alloy composition was within the range of the present invention, but the structure change resistance value was less than 10, so the life was short. Further, Comparative Examples 26 and 27 have a short life because the alloy composition is within the range of the present invention, but the amount of retained austenite on the raceway surface is out of the range of the present invention because the heat treatment conditions are not suitable. there were.

  Furthermore, Comparative Examples 28 and 29 had a short life because the alloy composition was within the scope of the present invention, but the prior austenite grain size was outside the scope of the present invention because the heat treatment conditions were not suitable. . Furthermore, Comparative Examples 30 and 31 have a short life because the surface hardness of the raceway surface is outside the range of the present invention because the alloy composition is within the range of the present invention but the heat treatment conditions are not suitable. there were.

  Next, Table 4 shows the test results under test condition C. Table 4 also shows the structure change resistance value and the prior austenite grain size of the alloy steel, the amount of retained austenite on the raceway surface, the surface hardness, the arithmetic mean roughness Ra, and the maximum peak height Rp of the roughness curve. . In the case of the test condition C, since the hydrogen pressure is high, measures against hydrogen are also required for the rolling elements. Therefore, steel types G, M, N, O or ceramics P, Q were used as materials constituting the rolling elements. The life in Table 4 is shown as a relative value when the life of Comparative Example 41 is 1.

  As can be seen from Table 4, in Examples 41 to 47, the alloy composition, the structure change resistance value, the prior austenite crystal grain size, the retained austenite amount on the raceway surface, and the surface hardness of the alloy steel constituting the raceway are of the present invention. Since it is within the range, even if it is used in a hydrogen atmosphere, the service life is hardly reduced and wear damage is hardly caused. Therefore, the rolling life was long. In particular, Examples 41 to 44 had a longer life because the alloy composition and the prior austenite grain size were in a more preferable range. Moreover, since the rolling element is also made of a preferable material, the rolling element has a long life without being damaged.

  On the other hand, Comparative Examples 41 to 44 had a short life because the alloy composition of the alloy steel constituting the race was outside the scope of the present invention. In Comparative Example 45, the alloy composition was within the range of the present invention, but the structure change resistance value was less than 10, so the life was short. Further, in Comparative Examples 46 and 47, although the alloy composition is within the range of the present invention, the amount of retained austenite on the raceway surface is out of the range of the present invention because the heat treatment conditions are not suitable. there were.

  Furthermore, Comparative Examples 48 and 49 had a short life because the alloy composition was within the scope of the present invention, but the prior austenite grain size was outside the scope of the present invention because the heat treatment conditions were not suitable. . Further, in Comparative Examples 50 and 51, although the alloy composition is within the range of the present invention, the surface hardness of the raceway surface is out of the range of the present invention because the heat treatment conditions are not suitable. there were.

1 inner ring 1a raceway surface 2 outer ring 2a raceway surface 3 rolling element

Claims (4)

An inner ring having a raceway surface, an outer ring having a raceway surface opposite to the raceway surface of the inner ring, and a plurality of rolling elements arranged to roll between the raceway surfaces, and used in a hydrogen atmosphere. A rolling bearing for a hydrogen atmosphere in which at least one of the inner ring and the outer ring satisfies the following four conditions.
Condition 1: The carbon content is 0.5 mass% or more and 0.9 mass% or less, the silicon content is 0.6 mass% or more and 1 mass% or less, and the manganese content is 0.6 mass% or more. 2 mass% or less, chromium content is 6.5 mass% or more and 9.5 mass% or less, molybdenum content is 1 mass% or less, and the balance is iron and inevitable impurities. ing.
Condition 2: The content of silicon is Si%, the content of manganese is Mn%, the content of chromium is Cr%, the content of molybdenum is Mo%, 2.5 × Si% + 1.5 × The structure change resistance value calculated by the formula of Mn% + Cr% + 3 × Mo% is 10 or more.
Condition 3: Quenching and tempering are performed, the amount of retained austenite on the raceway surface is 10% by volume or more and 20% by volume or less, and the hardness is Hv674 or more and 772 or less.
Condition 4: The prior austenite grain size measured by the method defined in Japanese Industrial Standard JIS G0551 is 7 or more and 10 or less in grain size number. The rolling bearing for a hydrogen atmosphere according to claim 1, wherein at least one of the inner ring and the outer ring further satisfies the following condition 5 together with the four conditions.
Condition 5: The maximum peak height Rp of the roughness curve in the axial direction of the raceway surface is 0.2 μm or less.   The rolling element for a hydrogen atmosphere according to claim 1 or 2, wherein the rolling element is made of steel having a chromium content of 5 mass% or more and 18 mass% or less.   The rolling bearing for a hydrogen atmosphere according to claim 1 or 2, wherein the rolling element is made of ceramics.

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