JP2004293755A - Raceway ring for rolling bearing, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raceway ring for a rolling bearing capable of improving a fatigue service life of a raceway surface and capable of restricting plastic deformation in a surface opposite to the raceway surface, and to provide a manufacturing method thereof. <P>SOLUTION: In this outer ring 1 for a rolling bearing made of steel and having a thickness of 25 mm or more, metal organization of a surface layer 3 of the inner peripheral surface 2 as a raceway surface is composed of martensite and residual austenite. Metallographical structure of a part P1 at 1/4 of the whole thickness from the inner peripheral surface 2 is composed of martensite and pearlite. Metallographical structure of a part P2 at 1/2 of the whole thickness from the inner peripheral surface 2 is composed of pearlite. Metallographical structure of a surface layer part 5 of the outer peripheral surface 4 is composed of martensite and the residual austenite, and metallographical structure of a part P3 at 1/4 of the whole thickness from the outer peripheral surface 4 is composed of martensite and pearlite. Quantity of the residual austenite in both the surface layer parts 3 and 5 is set at 5-30 vol.%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bearing ring for a rolling bearing and a method of manufacturing the same.
[0002]
[Prior art]
For example, an outer ring having a rolling bearing thickness of 25 mm or more is used for a backup roll of a multi-stage rolling mill. Such rolling bearings are often used with lubricating oil contaminated with foreign matter, and naturally it is required to extend the rolling fatigue life under lubricating conditions with lubricating oil contaminated with foreign matter. However, the outer ring is required to have a fracture resistance and a deformation resistance to plastic deformation due to heat and load of the outer ring. This is because if the outer ring is cracked, it causes a line stop of the rolling line, and if the outer ring is plastically deformed, the rolling quality deteriorates. Normally, periodic inspections are performed to prevent such line stoppage of the rolling line and deterioration of the rolling quality, and rolling bearings are replaced before they are damaged.
[0003]
However, if the outer ring of a rolling bearing used as a backup roll breaks or undergoes plastic deformation in a short period of time, the above-mentioned periodic inspection needs to be performed at a relatively short cycle, and the work is troublesome.
[0004]
Conventionally, such a backup roll is made of steel and has a hardness of at least Rockwell C hardness (HRC) 58 in a region from the outermost surface of the inner peripheral surface which is the raceway surface to a depth of 3 mm, and the outer peripheral surface has It is known that the hardness of a region from the outermost surface to a depth of 5 mm is HRC 40 to 50 (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2002-102927 (Claim 3, Paragraph 0002)
[0006]
[Problems to be solved by the invention]
However, in the case of the backup roll described in Patent Literature 1, the hardness of the outer peripheral surface that comes into contact with the rolling roll is HRC 40 to 50, so that depending on the use conditions, the hardness is insufficient and plastic deformation is likely to occur. is there.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem, improve the rolling fatigue life of the raceway surface, and effectively suppress the plastic deformation of the surface opposite to the raceway surface even under use conditions in which plastic deformation easily occurs. An object of the present invention is to provide a bearing ring for a rolling bearing and a method of manufacturing the same.
[0008]
Means for Solving the Problems and Effects of the Invention
The rolling bearing race according to the invention of claim 1 is a rolling race bearing ring made of steel and having a wall thickness of 25 mm or more, wherein the metal structure of the surface layer of the raceway surface is composed of martensite and residual austenite. The metal structure of a quarter of the total thickness from the surface is composed of martensite and pearlite, and the metal structure of a half of the total thickness from the raceway surface is composed of pearlite. The amount is 5 to 30 vol%.
[0009]
In the invention of claim 1, the reason why the amount of retained austenite in the surface layer is limited to 5 to 30 vol% is that if it is less than 5 vol%, toughness is reduced, and foreign matter is present, for example, as in a backup roll of a rolling mill. This is because when used in a poor environment, the service life is significantly reduced, and when it exceeds 30 vol%, dimensional stability is deteriorated.
[0010]
In the first aspect of the present invention, the surface layer portion of the raceway surface refers to a portion on the surface and in the vicinity of the surface, which has an effect on rolling life and surface deformation. For example, in the case of a bearing ring made of steel having a thickness of 25 mm or more, the depth is 1 mm from the outermost surface of the bearing surface. In such a race, at least at the depth where the maximum shear stress acts on the raceway surface, the required hardness is not obtained unless a structure composed of martensite and retained austenite is obtained, and a good life cannot be obtained. By setting the portion from the outermost surface of the raceway surface to 1 mm as the above property, the depth at which the maximum shear stress acts can be sufficiently covered.
[0011]
According to the invention of claim 1, the hardness of the raceway in the thickness direction is highest at the surface layer portion of the raceway surface, and gradually decreases inward in the thickness direction, and is 1 / th of the thickness. It becomes lowest in the part of 2. Therefore, the rolling fatigue life of the raceway surface is improved, and the toughness is improved, thereby preventing breakage.
[0012]
The rolling bearing race according to the second aspect of the present invention is a rolling bearing race ring made of steel and having a thickness of 25 mm or more, wherein the metal structure of the surface layer on the opposite surface opposite to the raceway surface remains with martensite. Austenitic, the metal structure of a quarter of the total thickness from the opposite surface is composed of martensite and pearlite, and the metal structure of a half of the total thickness from the opposite surface is composed of pearlite. , Wherein the amount of retained austenite in the surface layer portion is 5 to 30 vol%.
[0013]
In the invention of claim 2, the reason why the amount of retained austenite in the surface layer portion is limited to 5 to 30 vol% is that if it is less than 5 vol%, toughness is reduced, and foreign matter is present, for example, as in a backup roll of a rolling mill. This is because when used in a poor environment, the service life is significantly reduced, and when it exceeds 30 vol%, dimensional stability is deteriorated.
[0014]
In the second aspect of the present invention, the surface layer opposite to the raceway surface means a portion having a depth of 2 mm from the outermost surface of the opposite surface. The surface opposite to the raceway surface is, for example, a roll surface in the case of a backup roll of a rolling mill and needs to be polished and reused.
[0015]
According to the invention of claim 2, the hardness of the bearing ring in the thickness direction is highest at the surface layer portion on the opposite surface, and gradually decreases inward in the thickness direction. / 2 is the lowest. Therefore, when this bearing ring is used as a backup roll of a multi-stage rolling mill, plastic deformation of the outer peripheral surface on the opposite side to the raceway surface in contact with the rolling roll is suppressed, and the life of the backup roll is improved and the toughness is improved. It is improved and breakage is prevented.
[0016]
According to a third aspect of the present invention, in the rolling bearing ring according to the first or second aspect, the surface hardness of the surface layer is 58 or more in Rockwell C hardness, and is 1/4 of the total thickness. The hardness of the portion is 50 or less in Rockwell C hardness, and the hardness of a half portion of the total thickness is 45 or less in Rockwell C hardness.
[0017]
In the invention of claim 3, the surface hardness of the surface layer portion of the raceway surface is set to HRC58 or more because if the surface hardness is less than HRC58, indentations are likely to occur due to foreign substances contained in the lubricating oil. Further, in the invention of claim 3, the surface hardness of the surface layer on the surface opposite to the raceway surface is set to be HRC58 or more. If the surface hardness is less than HRC58, the raceway ring is multistage type. This is because, when used as a backup roll of a rolling mill, the outer peripheral surface opposite to the raceway surface that comes into contact with the rolling roll is likely to be plastically deformed. The surface hardness of these surface layers is preferably HRC61 or less in order to suppress the occurrence of cracks.
[0018]
In the invention of claim 3, it is sufficient that the hardness of a portion of 1/4 of the total thickness from the raceway surface is HRC50 or less, and the hardness of a portion of a half of the total thickness is HRC45 or less. This is because it is necessary to obtain the breakage resistance. Further, in the invention of claim 3, the hardness of a quarter of the total thickness from the opposite surface opposite to the raceway surface is set to HRC50 or less, and the hardness of a half of the total thickness is similarly reduced. The reason for setting the HRC at 45 or less is that it is necessary to obtain sufficient breakage resistance.
[0019]
The method for manufacturing a bearing ring for a rolling bearing according to the invention of claim 4 is the method for manufacturing a bearing ring for a rolling bearing according to claim 1, wherein the track is formed by using steel to have a thickness of 25 mm or more. When the quenching process is performed on the wheel material, the cooling rate of the surface layer of the raceway surface is set to 11 ° C./sec or more, and the cooling rate of the quarter of the total thickness from the raceway surface is set to 4 ° C./sec or less. It is characterized by the following.
[0020]
In the invention according to claim 4, the cooling rate of the surface layer portion of the raceway surface is set to 11 ° C./sec or more. If the cooling speed is less than 11 ° C./sec, the surface layer portion has a structure other than martensite and residual austenite. That is, bainite and pearlite are generated, the hardness is reduced, and a predetermined performance for rolling life and deformation resistance cannot be obtained. Similarly, the cooling rate of 1/4 of the total thickness from the raceway surface was set to 4 ° C./sec or less. If this cooling rate exceeds 4 ° C./sec, the inner part of the surface layer is more polished than pearlite. This is because unnecessary bainite having a high hardness is generated and the breakage resistance is deteriorated.
[0021]
In the invention of claim 4, the heating temperature during the quenching treatment is preferably 840 to 870 ° C, and the heating time is preferably 1 to 3 hours. The reason is that the heating temperature is to make the amount of carbon dissolved in the matrix an appropriate amount, and the heating time is to make the temperature of the raceway material uniform.
[0022]
Further, in the invention of claim 4, the cooling rate of the surface layer portion of the raceway surface is set to 11 ° C./sec or more, and the cooling rate of a quarter of the total thickness from the raceway surface is set to 4 ° C./sec or less. Is quenched so that the injection pressure at the injection port becomes 0.6 to 2.1 kg / cm ² by the nozzle on the surface to be the raceway surface when quenching in quenching oil after heating in the quenching process. This is preferably performed by injecting oil. If the injection pressure is less than 0.6 kg / cm ² , the cooling rate of the surface layer on the raceway surface cannot be increased to 11 ° C./sec or more, and if it exceeds 2.1 kg / cm ² , the total thickness from the raceway surface increases. This is because the cooling rate of the 1/4 portion cannot be made 4 ° C./sec or less. This injection pressure is preferably from 1.4 to 2.1 kg / cm ² . Further, the distance between the nozzle outlet and the surface to be the raceway surface is preferably 150 to 300 mm, and more preferably 200 to 250 mm.
[0023]
According to the invention of claim 4, the bearing ring for a rolling bearing having the above-described effects can be relatively easily manufactured.
[0024]
The method for manufacturing a bearing ring for a rolling bearing according to the invention of claim 5 is the method for manufacturing a bearing ring for a rolling bearing according to claim 2, wherein the race is formed by using steel to have a thickness of 25 mm or more. When the quenching process is applied to the wheel material, the cooling rate of the surface layer on the opposite surface opposite to the raceway surface is set to 11 ° C./sec or more, and cooling of a quarter of the total thickness from the opposite surface is performed. The speed is set to 4 ° C./sec or less.
[0025]
In the invention of claim 5, the heating temperature during the quenching treatment is preferably 840 to 870 ° C, and the heating time is preferably 1 to 3 hours. The reason is that the heating temperature is to make the amount of carbon dissolved in the matrix an appropriate amount, and the heating time is to make the temperature of the raceway material uniform.
[0026]
Further, in the invention of claim 5, the cooling rate of the surface layer on the opposite surface opposite to the raceway surface is set to 11 ° C./sec or more, and the cooling rate of 1/4 of the total thickness from the opposite surface is similarly set to 4 ° C. In order to reduce the temperature to ℃ / sec or less, when quenching in quenching oil after heating in the quenching treatment, the injection pressure at the injection port is 1.4 to 2.1 kg / cm ² by the nozzle on the opposite surface. It is preferable to perform quenching oil injection. The injection pressure can not be the cooling rate of the surface layer portion of the opposite surface is less than 1.4 kg / cm ² to 11 ° C. / sec or more, the total thickness from the surface opposite to the exceeding 2.1 kg / cm ² This is because the cooling rate of the 1/4 portion cannot be made 4 ° C./sec or less. Further, the distance between the nozzle outlet and the surface to be the raceway surface is preferably 150 to 300 mm, and more preferably 200 to 250 mm.
[0027]
According to the fifth aspect of the present invention, it is possible to relatively easily manufacture a bearing ring for a rolling bearing having the above-described effects.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the present invention is applied to an outer ring for a rolling bearing used as a backup roll of a multi-stage rolling mill.
[0029]
In FIG. 1 showing an outer ring for a rolling bearing used as a backup roll of a multi-stage rolling mill, a thickness t of an outer ring (1) is 25 mm or more, and a depth t of 1 mm from an inner peripheral surface (2) serving as a raceway surface. The metal structure of the surface layer portion (3) is composed of martensite and retained austenite. The amount of retained austenite in the surface portion (3) is 5 to 30 vol%. The metal structure of a portion (P1) (1 / 4t portion) of a quarter of the total thickness t from the inner peripheral surface (2) of the outer ring (1) is composed of martensite and pearlite. ), The metal structure of a portion (P2) (１ ／ t portion) of a half of the total thickness t is made of pearlite.
[0030]
The metal structure of the surface layer portion (5) from the outer peripheral surface (4) in contact with the rolling roll in the outer ring (1) to a depth of 2 mm is composed of martensite and retained austenite. The amount of retained austenite in the surface portion (5) is 5 to 30 vol%. Further, the metal structure of a portion (P3) (ｔ t portion) of the entire thickness t from the outer peripheral surface (4) of the outer ring (1) is composed of martensite and pearlite.
[0031]
The hardness of the surface layers (3) and (5) of both the inner and outer peripheral surfaces (2) and (4) of the outer ring (1) is HRC58 or more, and the hardness of the 1 / 4t portions (P1) and (P3) is HRC50. And the hardness of the 1 / 2t portion (P2) is HRC45 or less. The hardness distribution of the outer ring (1) in the thickness direction changes smoothly from the inner and outer peripheral surfaces (2) and (4) to the 1 / 2t portion (P2).
[0032]
The outer ring (1) is manufactured by a method described below.
[0033]
First, a cylindrical outer race material (10) having a thickness of 25 mm or more is formed using steel. Next, after heating the outer ring material (10) at 840 to 870 ° C. for 1 to 3 hours, it is quenched in quenching oil. At the time of quenching, as shown in FIGS. 2 and 3, one first quenching oil injection device (11) extending in the axial direction on the central axis on the inner peripheral side of the outer race material (10) is arranged. At the same time, second quench oil injection devices (12) extending in the axial direction are arranged at a plurality of locations at equal intervals in the circumferential direction on the outer peripheral side of the outer race material (10). The same number of nozzles (11a) as the second quenching oil injection device (12) are provided at a plurality of places at equal intervals in the vertical direction in the first quenching oil injection device (11). Is formed. In addition, nozzles (12a) facing the central axis of the outer race material (10) are formed at a plurality of locations at equal intervals in the vertical direction in the second quenching oil injection device (12). The ejection ports (11b) and (12b) formed in the nozzles (11a) and (12a) of both devices (11) and (12) are vertically rectangular. In this embodiment, among the nozzles (11a) of the first quenching oil injection device (11), a plurality of upper nozzles (11a) are located above the oil level (L) of the quenching oil. All the nozzles (12a) of the quenching oil injection device (12) are located below the oil level of the quenching oil. The number of nozzles (11a) located below the oil level (L) of the quenching oil in the first quench oil injection device (11) is the number of nozzles (12a) in the second quench oil injection device (12). And the nozzle (11a) of the first quenched oil injection device (11) and the nozzle (12a) of the second quenched oil injection device (12) located below the oil level (L) have the same height. In position. Then, the injection pressure at the injection port (11b) is set to 0.6 to 2.1 kg / cm ² by the nozzle (11a) of the first quenching oil injection device (11) on the inner peripheral surface of the outer ring material (10). The quenching oil is injected into the outer ring material (10) and the injection pressure at the injection port (12b) is set to 1.4 to 2.1 kg by the nozzle (12a) of the second quenching oil injection device (12). Quenching oil is sprayed so as to be / cm ² . In this way, the cooling rate of the surface layer of the inner and outer peripheral surfaces of the outer ring material (10) is set to 11 ° C./sec or more, and the cooling rate of 1/4 of the total thickness from the inner and outer peripheral surfaces is set to 4 ° C./sec or less. And
[0034]
After the quenching, the outer ring material (10) is taken out of the quenched oil and tempered. Finally, the inner and outer peripheral surfaces and both end surfaces of the outer race material (10) are subjected to predetermined finishing such as cutting and polishing. Thus, the outer ring (1) is manufactured.
[0035]
Next, specific examples of the present invention will be described.
[0036]
C1.01 wt%, Si0.43 wt%, Mn0.49 wt%, P0.01 wt%, S0.007 wt%, Cu0.09 wt%, Ni0.06 wt%, Cr1.18 wt% and Mo0.03 wt%, the balance Fe and A cylindrical outer ring material (10) having an outer diameter of 300 mm, an inner diameter of 220 mm, a wall thickness of 40 mm, and a length of 170 mm was formed using steel made of unavoidable impurities.
[0037]
Then, after heating the outer ring material (10) at 860 ° C. for 100 minutes, the outer ring material (10) is immersed and quenched in a quenching oil composed of master quench A at an oil temperature of 80 ° C. The nozzle (11a) of the first quenching oil injection device (11) controls the injection pressure at the injection port (11b) of the nozzle (11a) to 0.6 kg / cm ^{2 on} the inner peripheral surface of the outer ring material (10). The quenching oil is injected, and the injection pressure of the nozzle (12a) of the second quenching oil injection device (12) at the injection port (12b) of the nozzle (12a) is 1.9 kg / cm ^2. Quenching oil was sprayed. Here, the ejection ports (11b) and (12b) of the nozzles (11a) and (12a) are 20 mm in length and 4 mm in width. The number of the second quenching oil injection devices (12) is eight. The quenching conditions are shown below. The oil temperature was 80 ° C., the distance between the nozzles (11a) and (12a), and the inner and outer peripheral surfaces of the material (10) was 200 mm, and the injection time was 6 minutes.
[0038]
After the quenching was completed, the outer ring material (10) was taken out of the quenched oil and subjected to a tempering treatment of heating at 200 ° C. for 5 hours. Thereafter, predetermined cutting and grinding were performed on both the inner and outer peripheral surfaces and both end surfaces of the outer race material (10).
[0039]
Thus, the hardness distribution from the inner peripheral surface (2) to the outer peripheral surface (3) at the center in the length direction of the manufactured outer ring (1) was measured. As a result, as shown in FIG. 4, the hardness of the inner and outer peripheral surfaces (2) and (4) is 61.5 HRC, and the inner and outer peripheral surfaces (2) and (4) have a 1 / 4t portion (P1) (P3) from the inner and outer peripheral surfaces (2) and (4). The hardness was 45 HRC, and the hardness of a 1 / 2t portion (P2) from the inner and outer peripheral surfaces (2) and (4) was 36.5 HRC. The metal structure of the surface layers (3) and (5) from the inner and outer peripheral surfaces (2) and (4) to a depth of 2 mm was composed of martensite and retained austenite, and the amount of retained austenite was 15 vol%. The metal structure of the inner and outer circumferential surfaces (2) and (4) from the 1 / 4t portion (P1) and (P3) is composed of martensite and pearlite, and the 1 / 2t portion from the inner and outer circumferential surfaces (2) and (4). The metal structure of (P2) was pearlite.
[0040]
Further, when a rolling bearing is assembled using the outer ring (1) manufactured as described above, and the outer ring (1) is incorporated in a multi-stage rolling mill so that the outer ring (1) becomes a backup roll, a conventional outer ring is used. Even after 6 months of use, which required inspection and replacement, no damage or plastic deformation was found on the outer ring (1).
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a half of an outer ring of a rolling bearing according to the present invention.
FIG. 2 is a plan view showing an arrangement state of a quenching oil injection device that injects quenching oil to an outer race material during quenching oil.
FIG. 3 is a partially cutaway front view showing an arrangement state of a quenching oil injection device that injects quenching oil to an outer race material during quenching oil.
FIG. 4 is a graph showing a hardness distribution of an outer ring manufactured in a specific example.
[Explanation of symbols]
(1): Outer ring (2): Inner surface (3): Surface layer (4): Outer surface (5): Surface layer (10): Outer ring material (P1) (P3): 1/4 portion (P3) : 1/2 part t: wall thickness

Claims (5)

In a bearing ring made of steel and having a wall thickness of 25 mm or more, the metallographic structure of the surface layer of the raceway surface is composed of martensite and retained austenite, and the metal of a portion of 1/4 of the total thickness from the raceway surface is formed. The structure is composed of martensite and pearlite, the metal structure of a half of the total thickness from the raceway surface is composed of pearlite, and the amount of retained austenite in the surface layer is 5 to 30 vol%. And bearing rings for rolling bearings. In a bearing ring made of steel and having a wall thickness of 25 mm or more, the metallographic structure of the surface layer on the opposite surface opposite to the raceway surface is composed of martensite and retained austenite, and the total thickness from the opposite surface is reduced. The metal structure of 1/4 part is composed of martensite and pearlite, the metal structure of 1/2 part of the total thickness from the opposite surface is composed of pearlite, and the residual austenite amount of the surface layer is 5 to 30 vol% A bearing ring for a rolling bearing, characterized in that: The surface hardness of the surface layer is 58 or more in Rockwell C hardness, the hardness of a quarter of the total thickness is 50 or less in Rockwell C hardness, and 1/4 of the total thickness. 3. The bearing ring for a rolling bearing according to claim 1, wherein the hardness of the / 2 portion is 45 or less in Rockwell C hardness. The method of manufacturing a bearing ring for a rolling bearing according to claim 1, wherein when a quenching process is performed on a bearing ring material formed to have a thickness of 25 mm or more using steel, a surface layer portion of the raceway surface. A cooling rate of 11 ° C./sec or more, and a cooling rate of 1/4 of the total wall thickness from the raceway surface to 4 ° C./sec or less. The method for manufacturing a bearing ring for a rolling bearing according to claim 2, wherein when a quenching process is performed on a bearing ring material formed to have a thickness of 25 mm or more using steel, the bearing ring is opposite to the raceway surface. A cooling rate of the surface layer on the side opposite to the side is set to 11 ° C./second or more, and a cooling rate of a quarter of the total thickness from the opposite side is set to 4 ° C./second or less. Method of manufacturing bearing rings.

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