JP2010031307A - Roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rolling fatigue life by inhibiting production of incompletely quenched structures in a member composing a roller bearing. <P>SOLUTION: An inner ring, an outer ring or a roller is obtained by processing a material into a prescribed shape and subsequently quenching and tempering the same, wherein the material is made of an alloy steel which comprises, by mass, 0.90-1.2% C, 0.20-0.70% Si, 0.30-1.20% Mn, 0.90-1.6% Cr, ≤0.30% Mo and the balance being Fe and unavoidable impurities and has a DI value of 5.0-9.0, which is defined by the equation (1): (1) DI=(0.18[C]+0.16)(0.7[Si]+1.0)(3.4[Mn]+1.0)(2.2[Cr]+1.0)(3.0[Mo]+1.0). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a roller bearing.

Examples of rolling bearings that support a rotating shaft (an input shaft and an output shaft of a transmission disposed between a blade and a generator) of a wind turbine for wind power generation (hereinafter simply referred to as a “wind turbine”) include an outer Large roller bearings having a diameter of 200 mm or more (particularly 280 mm or more) are used.
Since the bearing ring and the rolling element of the rolling bearing generate a high surface pressure at the contact portion between them, and a high shear stress is generated inside, it is necessary to have a hardness that can withstand this. In particular, large bearings are required to be hardened to a deep position because shear stress acts deep inside. Moreover, since the roller bearing has a large contact area between the race and the rolling element, a region where shear stress acts is large.

  As a manufacturing method of the bearing ring and rolling element of the rolling bearing, there are a method of quenching and tempering after processing a material made of alloy steel into a predetermined shape, or a method of carburizing or carbonitriding and quenching and tempering. And since the method of performing a carburizing or carbonitriding process requires cost, it is preferable to employ | adopt the method of quenching and tempering from the point of cost. However, when the races and rolling elements of a large roller bearing are manufactured by quenching and tempering, even if the surface hardness is sufficient, an incompletely quenched structure may be generated inside, and sufficient hardness may not be obtained.

  A windmill bearing is used under conditions where slippage is likely to occur between the race and the rolling elements. When slippage occurs between the race and the rolling elements, hydrogen is likely to be generated from the lubricating oil. Further, the rotational speed of the wind turbine bearing is likely to change. In applications where the rotational speed is variable, synthetic oil such as polyalkylene glycol is sometimes used instead of mineral oil in order to stably form an oil film between the race and the rolling elements. Some synthetic oils are more prone to generate hydrogen than mineral oil. If there is an incompletely quenched structure inside the raceway and rolling elements, this hydrogen is easily trapped and the metal structure is likely to change, causing delamination starting from this and causing a decrease in the rolling fatigue life.

From the above, when a large roller bearing using a bearing ring place manufactured by quenching and tempering after processing a material made of alloy steel into a predetermined shape is used as a windmill bearing, the inside of the bearing ring place Incompletely hardened structures tend to occur, and the rolling fatigue life may be shortened.
Patent Document 1 listed below reduces surface damage by reducing friction between the inner ring and outer ring of a rolling bearing used for a rotation support portion of a windmill and rolling elements to suppress slippage due to metal contact, thereby extending life. In order to lengthen the rolling element, the rolling element is formed of an alloy steel having a silicon content of 0.5% by weight or more, and carbonitriding, quenching, and tempering are performed to reduce the amount of retained austenite on the surface of the rolling element to 20 volumes. It is described to be less than%.

  In Patent Document 2 below, an inexpensive alloy steel having a hardenability equivalent to or higher than that of carburized steel SNCM815 or SNCM420 as alloy steel for large-sized bearing parts, and having reduced Ni and Mo contents. Is used to extend the life of a large-sized bearing by carburizing and quenching and tempering to cause a martensitic transformation to the center to obtain sufficient hardness.

Patent Document 3 below describes that steel having a specific composition is used in order to obtain a bearing component having a hardness distribution similar to that of a carburized product by quenching and tempering. Moreover, the surface hardness after manufacturing a large-sized bearing part with an outer diameter of 150 mm or more using the material made of this steel and quenching and tempering is set to HRC58 to 65, and the hardness of the center is set to HRC25 to 45. Is described. In this case, an incompletely hardened structure is generated in an intermediate region between the surface and the center of the obtained bearing part.
JP 2006-118575 A JP-A-7-278740 JP 2001-123244 A

  An object of the present invention is to provide a bearing component member (inner ring, outer ring, and roller) of a roller bearing manufactured by performing quenching and tempering after processing a material made of alloy steel into a predetermined shape. It is to increase the rolling fatigue life even when it is used under severe conditions such as an application for supporting the rotating shaft of a wind turbine by preventing a completely quenched structure.

In order to solve the above-described problems, the roller bearing of the present invention includes any one of an inner ring, an outer ring, and a roller made of alloy steel satisfying the following configuration (a), or both the configuration (a) and the configuration (b). It is obtained by processing a raw material made of alloy steel to be filled into a predetermined shape, followed by quenching and tempering.
[Configuration (a)]
Carbon content [C] is 0.90 to 1.2% by mass, silicon content [Si] is 0.20 to 0.70% by mass, and manganese content [Mn] is 0.30. % By mass or more and 1.20% by mass or less, chromium content [Cr] of 0.90% by mass or more and 1.6% by mass or less, molybdenum content [Mo] of 0.30% by mass or less, and the balance being iron (Fe) In addition, it is an inevitable impurity, and the DI value represented by the following formula (1) satisfies 5.0 or more and 9.0 or less.
DI = (0.18 [C] +0.16) (0.7 [Si] +1.0) (3.4 [Mn] +1.0) (2.2 [Cr] +1.0) (3.0 [Mo] +1.0) (1)

[Configuration (b)]
When the maximum thickness of the rolling part (the raceway surface part of the inner ring and the outer ring, the rolling surface part of the roller) is t (mm), the following expression (2) is satisfied.
DI / t ≧ 0.20 (2)
[Configuration (a)]
The reason why [C] is 0.90 mass% or more and 1.2 mass% or less is as follows.
Carbon (C) is an element that strengthens steel by solid solution in matrix (matrix) by quenching and martensifying the structure. Moreover, it has the effect | action which combines with another alloy element and forms hard carbide | carbonized_material in steel, and improves abrasion resistance. In order to obtain a necessary strength as a bearing without generating an incompletely quenched structure after quenching, the carbon content is set to 0.90% by mass or more. Preferably it is 0.95 mass% or more.
However, if the carbon content exceeds 1.2% by mass, coarse carbides are easily generated in the steel, and the toughness and workability become insufficient. Preferably it is 1.1 mass% or less.

The reason why [Si] is 0.20 mass% or more and 0.70 mass% or less is as follows.
Silicon (Si) dissolves in the base to improve the hardenability and has the effect of suppressing the generation of incompletely hardened structures. It also has the effect of improving temper softening resistance. If the silicon content is less than 0.20% by mass, the action cannot be substantially obtained. Preferably it is 0.50 mass% or more.
However, when the silicon content exceeds 0.70% by mass, cold workability and machinability become insufficient.

The reason why [Mn] is 0.30 mass% or more and 1.20 mass% or less is as follows.
Manganese (Mn) is dissolved in the matrix to improve the hardenability and has the effect of suppressing the occurrence of incompletely hardened structure. It also has the effect of increasing the amount of retained austenite and improving the fatigue life against surface damage. If the manganese content is less than 0.30% by mass, the action cannot be substantially obtained. Preferably it is 0.80 mass% or more, More preferably, it is 0.90 mass% or more.
However, if the manganese content exceeds 1.20% by mass, the amount of retained austenite increases too much and the dimensional stability decreases. Preferably it is 1.15 mass% or less.

The reason why [Cr] is 0.90 mass% or more and 1.6 mass% or less is as follows.
Chromium (Cr) has the effect | action which dissolves in a base | substrate and improves hardenability and suppresses generation | occurrence | production of an incompletely hardened structure | tissue. Moreover, it combines with carbon to form hard carbides in the steel, improving wear resistance. When the chromium content is less than 0.90% by mass, these effects are not substantially obtained. Preferably it is 1.3 mass% or more.
However, if the chromium content exceeds 1.6% by mass, cold workability and machinability become insufficient.

The reason for making [Mo] 0.30 mass% or less is as follows.
Molybdenum (Mo) has the effect | action which dissolves in a base | substrate and improves hardenability and suppresses generation | occurrence | production of an incompletely hardened structure | tissue. It also has the effect of improving temper softening resistance. Moreover, it combines with carbon to form hard carbides in the steel, improving wear resistance.
Molybdenum is not an essential component, but if the content is less than 0.10% by mass, these effects cannot be substantially obtained. Therefore, when molybdenum is contained, the content is 0.10% by mass. % Or more.
However, if the molybdenum content exceeds 0.30% by mass, cold workability and machinability become insufficient. Preferably it is 0.25 mass% or less.

The reason why the DI value represented by the above formula (1) satisfies 5.0 or more and 9.0 or less is as follows.
Hardness (Vickers hardness measurement) of bearing components (inner rings, outer rings, rollers) obtained by processing a material made of alloy steel satisfying the above ranges of each component into a predetermined shape and then quenching and tempering However, if the DI value is less than 5.0, an incompletely quenched structure is likely to be formed after quenching even if the hardness measured with a vessel or the like is a value sufficient as the hardness of the rolling bearing. The incompletely quenched structure is weaker than the surrounding structure and easily traps hydrogen. Therefore, peeling from the incompletely quenched structure and a change in the metal structure due to hydrogen are likely to occur. Along with this, the rolling fatigue life is reduced. Preferably, the DI value is 7.0 or more.
However, if the DI value exceeds 9.0, the workability becomes insufficient.

[Configuration (b)]
Since the cooling rate by quenching decreases from the surface of the bearing component (inner ring, outer ring, roller) toward the inside, the thicker the bearing component, the easier it is to form an incompletely quenched structure. Therefore, it is necessary to increase the DI value as the thickness is increased to suppress the incompletely quenched structure. Therefore, “DI / t” is an index indicating the generation of an incompletely quenched structure.
When the maximum thickness of the rolling part (the raceway surface part of the inner ring and the outer ring, the rolling surface part of the roller) is t (mm), if “DI / t” is 0.20 or more, the incompletely quenched structure Generation is suppressed. “DI / t” is preferably 0.25 or more, and more preferably 0.30 or more.

  In the case of a cylindrical roller bearing, the maximum thickness t of the rolling part (inner ring and outer ring raceway surface part, roller rolling surface part) is the raceway of the inner ring 1 and outer ring 2 as shown in FIGS. The thickness of the surface and the diameter of the cylindrical roller 3. In the case of the tapered roller bearing, as shown in FIG. 3, the diameter of the large diameter portion of the tapered roller 3, the thickness of the thickest portion of the outer ring 2 where the tapered roller contacts, and the thickest portion of the raceway groove of the inner ring 1 Is the thickness. In the case of a self-aligning roller bearing, as shown in FIG. 4, the maximum diameter of the barrel roller 3, the maximum thickness of the raceway surface of the outer ring 2, and the maximum thickness of the raceway surface of the inner ring 1.

  According to the roller bearing of the present invention, by specifying the composition of the alloy steel constituting the bearing component (inner ring, outer ring, roller) using the DI value as an index, an incompletely hardened structure is less likely to occur in the bearing component. Even when used under severe conditions such as for supporting the rotating shaft of a windmill, the rolling fatigue life can be extended.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a sectional view showing a tapered roller bearing corresponding to an embodiment of the present invention. The tapered roller bearing includes an inner ring 1, an outer ring 2, a tapered roller 3, and a cage 4.
As the tapered roller bearing of the shape shown in FIG. 1, the tapered roller bearing with the identification number “HR30326” (inner diameter: 130 mm, outer diameter: 280 mm, width: 63.75 mm) and the tapered roller bearing with “HR31326” (inner diameter: 130 mm, outer diameter) : 280 mm, width: 72 mm).
First, materials made of steel types A to E and G to J in Table 1 were prepared as the material for the inner ring 1 and the material for the outer ring 2, respectively. Moreover, as a material for the tapered roller 3, a material made of steel types F and K shown in Table 1 was prepared.

Each material was processed into the shapes of the inner ring 1, the outer ring 2, and the tapered roller 3 by a normal method, and then heat-treated by the following procedure.
First, as a quenching treatment, after holding at a temperature of 1093 to 1133K for 1 to 3 hours, cooling with oil (oil quenching) was performed. Next, as a tempering treatment, the mixture was kept at 443 to 483 K for 1.5 to 2.5 hours and then allowed to cool.

Using the obtained inner ring 1, outer ring 2, tapered roller 3, and general steel-made cage cage 4, three tapered roller bearings are assembled in the combinations shown in Table 2, and the load: P / Time until a rotation test is performed under the conditions of C = 0.45, rotation speed: 700 min ⁻¹ , lubricant: polyalkylene glycol, and destruction such as peeling occurs in any of the inner ring 1, the outer ring 2, and the cylindrical roller 3. Was defined as the bearing life.

The average value (average life) of the bearing life of the three bodies of each sample was calculated, and the relative value (life ratio) where the average life of sample No. 9 was set to “1” was calculated from the average life of each sample. The results are also shown in Table 2. “Life ratio of 5.0 or more” in Table 2 indicates that the test was terminated because peeling did not occur even after 5.0 times or more of the life of sample No. 9 had elapsed. In addition, as a result of this test, all peeling occurred on the inner ring. Table 2 shows the DI value, the maximum thickness t, and DI / t of the inner ring.
FIG. 5 shows a graph summarizing the relationship between the life ratio and the DI value of the inner ring, and FIG. 6 shows a graph summarizing the relationship between the life ratio and the DI / t of the inner ring.

  As can be seen from this result, in the tapered roller bearing with the nominal number “HR30326”, the No. 1-8 in which the DI value of the inner ring 1 is 5.0 or more and “DI / t” is 0.20 or more, A life of 3.1 times or more of No. 9 having a DI value of 4.2 and “DI / t” of 0.18 was obtained. In particular, Nos. 5 to 8 in which the DI value of the inner ring 1 is 7.0 or more and “DI / t” is 0.30 or more, the DI value is 4.2 and “DI / t” is 0. A life of 5.0 times or more that of No. 9 which is 18 was obtained.

  All samples (No. 12 to 14) of tapered roller bearings with the identification number “HR31326” have a DI value of 5.0 or more and “DI / t” of 0.20 or more, so the cone with the identification number “HR30326” A roller bearing sample having a DI value of 4.2 and "DI / t" of 0.18 was 3.3 times longer than No. 9. In particular, No. 14 in which the DI value of the inner ring 1 is 7.0 or more and “DI / t” is 0.30 or more has a life of 5.0 times or more that of No. 9.

As in this example, in the case of the test conditions in which the inner ring peels, the life can be extended by setting the DI value of the inner ring to 5.0 or more and DI / t to 0.20 or more. The life can be extended by setting the DI value to 5.0 or more and DI / t to 0.20 or more of the outer ring in the use condition in which peeling occurs and the roller in the use condition in which peeling occurs in the roller.
In this example, the test is performed using a tapered roller, but the present invention is also effective in the case of other cylindrical roller bearings and self-aligning roller bearings.

It is sectional drawing which shows the tapered roller bearing corresponded to one Embodiment of this invention. It is a figure which shows the maximum thickness t of the rolling part (The race surface part of an inner ring and an outer ring, the rolling surface part of a roller) in the case of a cylindrical roller bearing. It is a figure which shows the maximum thickness t of the rolling part in the case of a tapered roller bearing (the raceway surface part of an inner ring and an outer ring, the rolling surface part of a roller). It is a figure which shows the maximum thickness t of the rolling part (The race surface part of an inner ring and an outer ring, the rolling surface part of a roller) in the case of a self-aligning roller bearing. It is the graph which put together the result of the test done in the embodiment in the relation between the DI value of the inner ring and the life ratio. It is the graph which put together the result of the test done in the embodiment in the relation between “DI / t” of the inner ring and the life ratio.

Explanation of symbols

1 Inner ring 2 Outer ring 3 Cylindrical roller 4 Cage

Claims (3)

Any of the inner ring, outer ring, and roller
Carbon content [C] is 0.90 to 1.2% by mass, silicon content [Si] is 0.20 to 0.70% by mass, and manganese content [Mn] is 0.30. % By mass or more and 1.20% by mass or less, chromium content [Cr] of 0.90% by mass or more and 1.6% by mass or less, molybdenum content [Mo] of 0.30% by mass or less, and the balance being iron (Fe) And an inevitable impurity obtained by processing a material made of an alloy steel satisfying a DI value of 5.0 or more and 9.0 or less represented by the following formula (1) into a predetermined shape, followed by quenching and tempering. A roller bearing characterized by being a thing.
DI = (0.18 [C] +0.16) (0.7 [Si] +1.0) (3.4 [Mn] +1.0) (2.2 [Cr] +1.0) (3.0 [Mo] +1.0) (1) Any of the inner ring, outer ring, and roller
Carbon content [C] is 0.90 to 1.2% by mass, silicon content [Si] is 0.20 to 0.70% by mass, and manganese content [Mn] is 0.30. % By mass or more and 1.20% by mass or less, chromium content [Cr] of 0.90% by mass or more and 1.6% by mass or less, molybdenum content [Mo] of 0.30% by mass or less, and the balance being iron (Fe) And the inevitable impurity, the DI value represented by the following formula (1) satisfies 5.0 or more and 9.0 or less, and the maximum thickness of the rolling part is t (mm). A roller bearing obtained by processing a material made of alloy steel satisfying the formula into a predetermined shape, followed by quenching and tempering.
DI = (0.18 [C] +0.16) (0.7 [Si] +1.0) (3.4 [Mn] +1.0) (2.2 [Cr] +1.0) (3.0 [Mo] +1.0) (1)
DI / t ≧ 0.20 (2)   The roller bearing according to claim 1, wherein the roller bearing is used for supporting a rotating shaft of a wind turbine for wind power generation.

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