JP2009221493A - Rolling bearing, method for manufacturing race ring - Google Patents

Abstract

A bearing ring having high rolling fatigue characteristics of a raceway surface and small dimensional change as a whole is obtained.
An inner ring is formed using a steel material having a carbon content of 0.2% by mass or more and 1.2% by mass or less. The carbon content of the surface layer portion is set to 0.6 mass% or more and 1.2 mass% or less by carburizing treatment or carbonitriding treatment, and after performing quenching treatment, induction tempering treatment is performed from the opposite side of the raceway surface 11. As a result, the amount of retained austenite in the surface layer portion is set to 25% by volume or more and 45% by volume or less on the raceway surface side, and 15% by volume or less on the opposite side of the track surface, and the hardness of the surface layer portion is Hv ( (Vickers hardness) 650 or more, and Hv450 or more on the opposite side of the raceway surface.
[Selection] Figure 1

Description

  The present invention relates to a rolling bearing and a method for manufacturing a bearing ring constituting the rolling bearing.

Foreign matter such as metal chips, shavings, burrs, and wear powder mixed in the bearing lubricating oil may damage the bearing rings and rolling elements of the rolling bearing, resulting in a significant decrease in the life of the rolling bearing. Is well known.
In order to extend the life of rolling bearings when foreign matter is mixed in the lubricating oil (under foreign matter mixed lubrication), the periphery of the indentation (depressed part) generated on the raceway surface due to the inclusion of foreign matter It is necessary to alleviate the concentration of stress on the part. Therefore, conventionally, carburizing treatment and carbonitriding treatment have been performed for the purpose of increasing the amount of retained austenite on the raceway surface. However, since the retained austenite is thermally decomposed with time, if the amount of retained austenite is too large, the dimensional change accompanying aging deformation becomes large.

In Patent Document 1 below, as a heat treatment for a bearing component (inner ring, outer ring, or rolling element of a rolling bearing), after carbonitriding, it is cooled to below the A ₁ transformation point and subjected to normal quenching (secondary quenching). Therefore, it is described that the amount of retained austenite in the surface layer portion is in the range of 11% to 25%. Moreover, it is described that the balance between the surface damage resistance and the aging change characteristics can be achieved by specifying the amount of retained austenite in the surface layer within this range.
However, in the case of the raceway surface, when the amount of retained austenite in the surface layer portion is 11% or more and 25% or less, the surface damage resistance property (rolling fatigue property) is insufficient.
Japanese Patent Laid-Open No. 2006-316821

  An object of the present invention is to provide a bearing ring having high rolling fatigue characteristics of the raceway surface and small dimensional change as a whole.

  In order to solve the above problems, the present invention has a carbon content of the core part of 0.2% by mass or more and 1.2% by mass or less, and a carbon content of the surface layer part of 0.6% by mass or more and 1.2% or less. The amount of retained austenite in the surface layer portion is 25% by volume or more and 45% by volume or less on the raceway surface side, and 15% by volume or less on the opposite side of the raceway surface. The hardness of the surface layer portion is Hv on the raceway surface side. (Vickers hardness) Provided is a rolling bearing having a bearing ring of 650 or more and Hv450 or more on the opposite side of the raceway surface.

  The present invention is also formed of a steel material having a carbon content of 0.2 mass% or more and 1.2 mass% or less, and the carbon content of the surface layer portion is 0.6 mass% or more by carburizing treatment or carbonitriding treatment. The amount of retained austenite in the surface layer is 25% by volume or more and 45% by volume on the raceway surface side after being subjected to quenching treatment and induction tempering treatment from the opposite side of the raceway surface. In the following, the bearing ring is 15% by volume or less on the opposite side of the raceway surface, the hardness of the surface layer portion is Hv (Vickers hardness) 650 or more on the raceway side, and Hv450 or more on the opposite side of the raceway surface. A rolling bearing provided with

  The present invention is also a method for manufacturing a bearing ring constituting a rolling bearing, which is formed using a steel material having a carbon content of 0.2% by mass or more and 1.2% by mass or less, and is carburized or carbonitrided. The amount of residual austenite in the surface layer portion is obtained by performing the induction tempering treatment from the opposite side of the raceway surface after the carbon content of the surface layer portion is set to 0.6% by mass or more and 1.2% by mass or less by the treatment and the quenching treatment is performed. Of 25% by volume or more and 45% by volume or less on the raceway surface side, and 15% by volume or less on the opposite side of the raceway surface, and the hardness of the surface layer portion is Hv (Vickers hardness) 650 or more on the raceway surface side. The manufacturing method of the bearing ring which makes Hv450 or more on the opposite side is provided.

According to the method of the present invention, by performing the induction tempering process from the opposite side of the raceway surface, a temperature gradient can be obtained in which the surface opposite to the raceway surface is hotter during tempering. The amount of retained austenite can be kept low.
In the method of the present invention, it is preferable to perform induction tempering while cooling the raceway surface. As a result, the aforementioned temperature gradient is increased, and the difference in the amount of retained austenite between the raceway surface side and the opposite side can be increased, so that the amount of retained austenite on the opposite side of the track surface can be further reduced.

  According to the rolling bearing of the present invention, the amount of retained austenite in the surface layer portion of the raceway is set to 25% by volume or more and 45% by volume or less on the raceway surface side, and 15% by volume or less on the opposite side of the raceway surface. By setting the hardness to Hv (Vickers hardness) 650 or higher on the raceway surface side and Hv450 or higher on the opposite side of the raceway surface, the rolling fatigue characteristics of the raceway surface can be improved and the dimensional change as a whole can be reduced.

When the amount of retained austenite in the surface layer portion of the raceway surface of the raceway is less than 25% by volume, a stress concentration relaxation effect on the peripheral portion of the indentation (depression) generated on the raceway surface under the contamination with foreign matter can be substantially obtained. Therefore, rolling fatigue characteristics are poor. Further, when the amount of retained austenite in the surface layer portion of the raceway surface of the raceway exceeds 45% by volume, the raceway surface hardness becomes less than Hv650, and the hardness necessary for improving rolling fatigue characteristics is obtained. Absent.
When the amount of retained austenite in the surface layer portion on the opposite side of the raceway surface of the raceway exceeds 15% by volume, the dimensional stability of the raceway as a whole becomes poor. When the hardness of the surface layer portion on the opposite side of the raceway surface of the raceway is less than Hv450, the wear resistance is poor.

  ADVANTAGE OF THE INVENTION According to this invention, when it is set as a rolling bearing, the bearing ring has the high rolling fatigue characteristic of a raceway surface, and a small ring change as a whole is provided.

Hereinafter, embodiments of the present invention will be described.
The alloy ring content was the ratio shown in Table 1 below, and the inner ring was formed by processing a material made of a steel material in which the balance is inevitable impurities and iron. As shown in FIG. 1A, the inner ring 1 has an inner diameter (A) of 95 mm, an outer diameter (A + 2B) of 100.6 mm, a width (C) of 17 mm, and the radius of curvature of the raceway groove (track surface) 11 is 3. The groove width (D) is 6.0 mm at 8 mm. Next, heat treatment was performed by each heat treatment method shown in FIGS. As shown in FIG. 1A, the induction tempering was performed under the conditions of a frequency of 3 kW and an output of 50 kW with the heating coil 2 disposed inside the inner ring 1.
In addition, when performing induction tempering with respect to the outer ring | wheel 3, the heating coil 2 is arrange | positioned on the outer side (opposite side of the track surface 31) of the outer ring | wheel 3, as shown in FIG.1 (b).

About the obtained inner ring of each No., the amount of retained austenite (γ _R ) at a depth of 50 μm from the raceway surface was measured.
Further, the amount of retained austenite (γ _R ) on the opposite side of the raceway surface was measured at each position indicated by “x” in FIG. The position of “x” is (½) t from the opposite surface 12 of the raceway surface 11 and the opposite surface 12 of the raceway surface 11 when the thickness at the raceway surface 11 position of the inner ring 1 is “t”. 5 points of the position and each point (3 points from the opposite surface 12 to (1/8) t, (1/4) t, (3/8) t) divided into 4 parts. The average value of the measured amount of retained austenite at the point was calculated. The results are also shown in Table 2 below.

  The results are summarized in a graph showing the relationship between the “average amount of retained austenite on the opposite side of the raceway surface” and “the amount of retained austenite on the raceway surface”. This graph is shown in FIG. In this graph, “●” is a plot when both of the retained austenite amounts are within the range of the present invention, and “▲” indicates that one of the retained austenite amounts is within the range of the present invention and the other retained austenite amount is within the range of the present invention. It is a plot when the amount is outside the scope of the present invention, and “x”, a plot when both residual austenite amounts are outside the scope of the present invention.

Further, the surface hardness (Hv) of the obtained inner ring raceway surface 11 and the opposite surface 12 of each No. was measured. The results are also shown in Table 2 below.
Further, a deep groove ball bearing having an outer diameter of 120 mm, an inner diameter of 95 mm, and a width of 17 mm is assembled using the inner ring 1, an outer ring and a ball manufactured by the following method, and a steel cage, and rolling fatigue is performed under the following conditions. A test was conducted to check the lifetime.
The outer ring was manufactured by forging a material made of high carbon chromium bearing steel, turning it to the shape of the outer ring, then carbonitriding, and performing a grinding process for finishing.
The ball was produced by roughly forming a material made of high carbon chromium bearing steel into a ball shape, then performing heat treatment including quenching and tempering, and then performing a grinding process for finishing.

The rolling fatigue life test is a foreign material in which 100 ppm of iron powder (HRC52) with an average particle size of 100 μm is mixed with lubricating oil (turbine oil for high temperature, “Jet Oil II” (compatible with MIL-L23699C) manufactured by Mobil Oil Co., Ltd.). Under mixed lubrication, the rotation was performed under the conditions of a load P _MAX = 4900 MPa, a temperature of 130 ° C., and a rotation speed of 1000 min ⁻¹ , and the total number of rotations until flaking occurred was defined as the lifetime. This life test was carried out by making 10 inner rings 1 of each No., assembling 10 bearings for each No., and performing a Weibull plot to determine the L ₁₀ life. When the L ₁₀ life was 2.0 × 10 ⁶ cycles or more, the rolling fatigue life was judged to be good (◯), and when it was less than 2.0 × 10 ⁶ cycles, it was judged to be defective (×). The results are also shown in Table 2 below.

  In addition, each of the obtained inner rings is subjected to a test that is maintained at 150 ° C. for 2500 hours, and the inner diameter of the inner ring is measured before and after the test to calculate the difference in inner diameter before and after the test. The dimensional change rate was obtained by dividing by the value. If this dimensional change rate is within 0.010%, it can be judged that the thermal stability code 27 of the ISO standard is satisfied and the dimensional stability is good. Therefore, those having a dimensional change rate of 0.010% or less were designated as “◯”, and those exceeding 0.010% were designated as defective “x”. The results are also shown in Table 2 below.

  As can be seen from this result, the rolling bearings of Nos. 1, 3, 10 and 12 corresponding to the examples of the present invention have a carbon content of the core part of 0.2% by mass or more and 1.2% by mass or less. The carbon content of the surface layer part is 0.6% by mass or more and 1.2% by mass or less, the amount of retained austenite in the surface layer part is 25% by volume or more and 45% by volume or less on the raceway surface, and 15% on the opposite side of the raceway surface. The inner ring has a volume% or less, and the hardness of the surface layer portion is Hv (Vickers hardness) 650 or more on the raceway surface side and Hv450 or more on the opposite side of the raceway surface. Also improved.

Further, by performing induction tempering instead of tempering by furnace heating, the amount of retained austenite on the opposite side of the raceway surface can be reduced to 15% by volume or less, and the amount of retained austenite on the raceway surface can be decreased to 25 to 45% by volume. .
In addition, No. 4 to 7 are performed under the same conditions except for “cooling of the raceway surface during tempering”, but in No. 4, the raceway surface is not cooled during tempering, and in No. 5, metal contact is made. In No. 6, cooling was performed by gas injection, and in No. 7, cooling was performed by water injection. By performing such cooling, the temperature gradient at which the surface on the side opposite to the raceway surface becomes higher at the time of tempering becomes larger than the case where cooling is not performed. Therefore, the difference in the amount of retained austenite between the raceway side and the opposite side is larger in Nos. 5 to 7 than in No. 4.

It is sectional drawing which shows arrangement | positioning (a) of a heating coil in the case of performing induction tempering with respect to an inner ring | wheel, and arrangement | positioning (b) of a heating coil in the case of performing induction tempering with respect to an outer ring | wheel. It is a figure which shows the heat processing method performed in embodiment. It is a figure which shows the measurement point of the amount of retained austenite of the surface on the opposite side to the track surface of the inner ring | wheel performed in embodiment. It is a graph which shows the result obtained in the embodiment in relation to the “average amount of retained austenite on the opposite side of the raceway surface” and “the amount of retained austenite on the raceway surface”.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 11 Inner ring raceway surface 12 Opposite surface of inner ring raceway surface 2 Heating coil 3 Outer ring 31 Outer ring raceway surface

Claims (4)

  The carbon content of the core part is 0.2% by mass or more and 1.2% by mass or less, the carbon content of the surface layer part is 0.6% by mass or more and 1.2% by mass or less, and the amount of retained austenite in the surface layer part Is 25% by volume or more and 45% by volume or less on the raceway surface side, and 15% by volume or less on the opposite side of the raceway surface, and the hardness of the surface layer portion is Hv (Vickers hardness) 650 or more on the raceway surface side, opposite the raceway surface Rolling bearings with raceways that are Hv450 or higher.   It is formed of a steel material having a carbon content of 0.2% by mass or more and 1.2% by mass or less, and the carbon content of the surface layer portion is 0.6% by mass or more and 1.2% by mass or less by carburizing or carbonitriding. It is obtained by performing induction tempering treatment from the opposite side of the raceway surface after quenching treatment, and the amount of retained austenite of the surface layer portion is 25% by volume or more and 45% by volume or less on the raceway surface. A rolling bearing provided with a bearing ring that is 15% by volume or less on the opposite side, the hardness of the surface layer portion is Hv (Vickers hardness) 650 or more on the raceway surface side, and Hv450 or more on the opposite side of the raceway surface. A method of manufacturing a bearing ring constituting a rolling bearing,
It is formed using a steel material having a carbon content of 0.2 mass% or more and 1.2 mass% or less, and the carbon content of the surface layer portion is 0.6 mass% or more and 1.2 mass% by carburizing treatment or carbonitriding treatment. %, And after performing quenching treatment, induction tempering treatment is performed from the opposite side of the raceway surface, so that the amount of retained austenite in the surface layer portion is 25% by volume or more and 45% by volume or less on the raceway surface. And 15% by volume or less on the side, and the hardness of the surface layer is set to Hv (Vickers hardness) 650 or more on the raceway side and Hv450 or more on the opposite side of the raceway.   The method for manufacturing a bearing ring according to claim 4, wherein the induction tempering process is performed while cooling the raceway surface.

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