JP2003028166A - Roll neck bearing for rolling mill - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent early damage and early peeling (hydrogen embrittlement peeling) even in a poor lubricating environment in which water or the like enters inside and mixes with a lubricant. Reduce the amount of water that enters the water to further extend the service life. In a roll neck bearing for a rolling mill, a roller (14) is provided between inner and outer rings (10, 11) so as to roll freely, and annular seal members (16) are attached to both ends of an outer ring. The outer ring, which is the raceway ring, has an N concentration of 100 pp
m, O concentration 15 ppm or less, S concentration 0.020
% Or less, the Ti concentration is 50 ppm or less, and the Ni concentration is 1 to 5
%, P concentration is 0.020% or less, Mo concentration is 0.1 to 5%.
% Of steel, and the C concentration of the raceway surface is 0.6-1.
2% and the residual compressive stress of the raceway surface is 100 to
500 MPa, and as the annular seal member 16,
A surface contact type annular seal member in which the seal lip portion makes surface contact with the inner ring is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll neck bearing for a rolling mill, which is used in an environment where water enters inside and mixes with a lubricant.

[0002]

2. Description of the Related Art Martensitic stainless steel is often used as a material for rolling bearings used in a corrosive environment. This is because it is effective to increase the corrosion resistance of the steel in order to increase the corrosion resistance of the steel.
On the other hand, in roller bearings, slippage due to skew is inherent, so it is necessary to increase the seizure resistance of the material, but martensitic stainless steel is not suitable for use in roller bearings because of its low thermal conductivity. In a poor lubricating environment in which water enters the bearing and mixes with the lubricant, an oil film of the lubricant is difficult to form and seizure easily occurs on the sliding surface.

Further, as a roll neck bearing for a rolling mill of a steel plant used in an environment where there is a risk of contact with water, the one described in JP-A-2000-104747 is known. This rolling mill rolling neck bearing has an inner ring having two double-row inner rings, an outer ring having one double-row outer ring, and two single-row outer rings arranged on both ends of the double-row outer ring via spacers. A row outer ring is provided, and four rows of rolling elements are arranged between the inner ring and the outer ring so as to be rollable in the circumferential direction. Also,
Annular seal members are attached to both ends of the outer ring with their seal lips in contact with the outer peripheral surface of the inner ring, and an intermediate seal member is provided on the inner peripheral side of the abutting ends of the two double-row inner rings. It is installed.

By forming a slit for the vent mechanism in the intermediate seal member, even if the air inside the bearing expands and contracts due to temperature change, the pressure difference between the inside and outside of the bearing is automatically balanced, and water etc. Is designed to prevent intrusion.

[0005]

By the way, since rolling water containing water as a main component is injected into the steel rolling mill and the temperature is high, the humidity around the rolling mill is extremely high. For this reason,
In the above-mentioned conventional roll neck bearing for a rolling mill, the invasion of water cannot be prevented but the invasion of gaseous water cannot be prevented, and the life extension effect is insufficient. Therefore, there still remains the problem that the gaseous life that has entered the inside of the bearing due to changes in the bearing internal pressure shortens the life of the bearing.

Therefore, in order to solve such a problem, the applicant of the present invention first proposed the rolling bearing described in Japanese Patent Application No. 2000-330575. This rolling bearing is a rolling bearing in which a plurality of rolling elements are rotatably arranged between inner and outer races as races, and at least non-rotating side races have an N concentration of 100 ppm or less and an O concentration of 15ppm
Below, S concentration is 0.020% or less, Ti concentration is 50 pp
m or less, Ni concentration of 1 to 5%, P concentration of 0.020% or less, and Mo concentration of 0.1 to 5%, and the C concentration of the raceway surface of the race is 0.6. .About.1.2%, and the residual compressive stress of the raceway surface is set to 100 to 500 MPa, whereby excellent seizure resistance and high corrosion fatigue strength are secured, and water or gaseous moisture is contained inside. Even under a bad lubricating environment in which is introduced and mixed into the lubricant, it is possible to prevent the early damage and the early delamination (hydrogen embrittlement delamination) and prolong the life of the bearing.

However, when the rolling bearing having such a structure is used for a roll neck bearing for a rolling mill, the seal lips of the annular seal members mounted on both ends of the outer ring in the axial direction are normally in line contact with the outer peripheral surface of the inner ring. Since it is a type that re-grinds frequently, the seal lip part is significantly damaged in the environment where the rolling roll is frequently attached and detached, and therefore,
Rolling water or cooling water penetrates into the bearing by 20% or more of the grease and mixes with the lubricant (usually a grease lubricant using a lithium thickener such as Adlex or Albania),
There is a problem that the lubricating oil film is lowered to cause early damage of the bearing due to poor lubrication.

The present invention has been made in order to eliminate such inconvenience, and assures excellent seizure resistance and high corrosion fatigue strength, and allows water or gaseous moisture to penetrate inside. Even under a poor lubricating environment such as when mixed with a lubricant, it is possible to prevent early damage and early delamination (hydrogen embrittlement delamination) as well as reduce the amount of water intrusion into the bearing. It is an object of the present invention to provide a roll neck bearing for a rolling mill, which can extend the life of the roll neck.

[0009]

In order to solve the above-mentioned object, the invention according to claim 1 is such that a plurality of rolling elements are rotatably arranged between inner and outer races as race rings, and In a roll-neck bearing for a rolling mill, in which annular seal members are attached to both axial end portions of the outer ring, at least the non-rotating side race ring has an N concentration of 100 ppm or less and an O concentration of 15 pp.
m or less, S concentration is 0.020% or less, Ti concentration is 50 p
pm or less, Ni concentration 1-5%, P concentration 0.020%
Hereinafter, the steel is made of steel having a Mo concentration of 0.1 to 5%, the C concentration of the raceway surface of the race is set to 0.6 to 1.2%, and the residual compressive stress of the raceway surface is set to 100. A surface contact type annular seal member whose surface is in contact with the inner ring of the seal lip portion is used as the annular seal member.

The invention according to claim 2 is characterized in that, in claim 1, grease using calcium sulfonate as a thickener is enclosed in the bearing space.
According to a third aspect of the present invention, in a rolling mill rolling neck bearing in which a plurality of rolling elements are rotatably arranged between inner and outer rings serving as bearing rings, at least the non-rotating side bearing ring has an N concentration of 100 ppm. Below, O concentration is 15ppm or less, S concentration is 0.020% or less, Ti concentration is 50ppm or less, Ni
It is made of steel having a concentration of 1 to 5%, a P concentration of 0.020% or less, and a Mo concentration of 0.1 to 5%, and the C concentration of the raceway surface of the race is 0.6 to 1.2. %, The residual compressive stress of the raceway surface is 100 to 500 MPa, and grease using calcium sulfonate as a thickener is enclosed in the bearing space.

According to the above-mentioned means, at least the non-rotating bearing ring has excellent seizure resistance and high corrosion fatigue resistance, so that water may enter inside and mix with the lubricant. It can be suitably used even in a poor lubricating environment. In a poor lubricating environment where water is mixed in the lubricant, rolling fatigue is likely to occur from the former austenite grain boundary of the rolling surface (raceway of raceway ring or rolling surface of rolling element), The fatigue life of rolling bearings is greatly reduced. This is because the presence of water between the rolling elements and the race makes it difficult for an oil film to be formed, which makes it easier for the rolling elements and the race to make metal contact, resulting in tangential force on the rolling surface. This is because peeling occurs on the rolling surface starting from carbides or non-metallic inclusions in the former austenite grain boundaries.

Then, the stress-loaded zone of the non-rotating side bearing ring where the product of the contact surface pressure and the stress repetition number becomes the maximum in the rolling bearing, is most susceptible to corrosion fatigue and the above-mentioned peeling is likely to occur. . Therefore, the stress-loaded zone of the non-rotating ring, that is, the raceway surface of the non-rotating ring, that is, the surface of the race and its vicinity (depth range up to 2% of rolling element diameter (2% Da)) ) Is effective in extending the life of rolling bearings.

In order to enhance the corrosion resistance and fatigue resistance of the rolling bearing without impairing the seizure resistance, it is not always necessary to enhance the corrosion resistance of the bearing material. Is called a grain boundary), and it is indispensable to give residual compressive stress to the raceway surface. In order to strengthen the grain boundaries, it is effective to reduce the grain size of the former austenite and to refine the carbides, nitrides, nonmetallic inclusions and phosphorus compounds in the grain boundaries.

First, the refining of carbide will be described.
When water enters the inside of the rolling bearing, hydrogen is generated from the water. Then, the grain boundaries on the raceway surface are caused by hydrogen to cause hydrogen embrittlement, and the grain boundaries are easily separated. In order to suppress such separation of grain boundaries, by refining carbides, a large number of interfaces of carbide crystals through which hydrogen atoms pass are formed, and hydrogen is dispersed in inclusions that are often present at the interfaces of carbide crystals. Is effective. If so, hydrogen is dispersed and embrittlement is less likely to occur, so that the effect of delaying hydrogen embrittlement flaking is imparted.

In order to refine the carbides at the grain boundaries, in the (finished) bearing ring after carburizing (carbonitriding) treatment and quenching / tempering, the carbon concentration on the raceway surface is set to 0.6 to
It should be 1.2%. If less than 0.6%, the hardness is H
It becomes difficult to set it to RC58 or more, and the corrosion fatigue strength may decrease. If it exceeds 1.2%, the carbides at the grain boundaries are likely to become coarse.

Further, since Ni is an element having an effect of refining old austenite crystal grains, it is necessary to set the Ni concentration in steel to 1.0% or more. However, if it exceeds 5.0%, the austenite is stabilized and the hardness is lowered, or if annealing is performed after carburizing, annealing becomes difficult. Further, since Mo is an element having an effect of refining carbides at grain boundaries, it is necessary to set the Mo concentration in steel to 0.1% or more. However, if it exceeds 5.0%, Mo is solid-solved in the matrix during quenching, so that the quenching temperature must be remarkably increased, which is uneconomical.

Next, the nitride will be described. Since the compound of iron and nitrogen (N) is hard and brittle and remarkably reduces the strength of the grain boundary, it is necessary to reduce the N concentration in steel to 100 ppm or less. The lower the N concentration, the better, but the cost of steelmaking tends to increase. This condition (N
VAR steel (remelted steel) is mentioned as a steel satisfying the (concentration), and it is preferable to use VAR steel as a steel constituting the roll neck bearing for a rolling mill of the present invention.

Next, the non-metallic inclusion will be described. Oxygen (O), sulfur (S), and titanium (Ti) are elements that form non-metallic inclusions at grain boundaries and reduce rolling fatigue life. Therefore, in order to improve the corrosion fatigue resistance, it is preferable that the amount is smaller, and the O concentration in the steel is 15 pp.
m or less, S concentration 0.020% or less, Ti concentration 50p
It must be pm or less. However, in order to improve the corrosion fatigue resistance, it is preferable that the amount is smaller, but the steelmaking cost tends to increase.

The same applies to phosphorus compounds,
In order to improve the corrosion fatigue strength, the smaller the amount, the more preferable, and the P concentration in the steel needs to be 0.020% or less. Next, the residual compressive stress on the raceway surface will be described. Applying a residual compressive stress of 100 MPa or more to the raceway surface is effective in improving the corrosion fatigue strength. However, if it exceeds 500 MPa, tensile stress (such as tangential force acting on the raceway surface when metal contact occurs) that acts on the raceway surface due to slippage is promoted, and conversely the corrosion fatigue strength is reduced. The method of applying residual compressive stress to the raceway surface is not particularly limited, but a method by carburizing and quenching is economical and preferable.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) First, referring to FIG. 1 and FIG. 2, this rolling neck rolling mill bearing is a four-row tapered roller bearing, and the inner ring is provided with two double-row inner rings 10 and the outer ring is Single row outer rings 1 that are adjacent to each other and are provided with four single row outer rings 11
Spacers 12, 13 are interposed between the two. Four rows of tapered rollers (rolling elements) 14 are provided between the inner ring and the outer ring of the cage 1.
It is arranged so as to be able to roll in the circumferential direction via 5. Also,
Annular seal members 16 are attached via seal holders 17 to both axial ends of the outer ring. Annular seal member 1
6 is a metal cored bar 18 with hydrogenated nitrile rubber (H-
An elastic material 19 such as NBR) is integrally fixed by vulcanization adhesion or the like, and a seal lip portion 20 on the inner peripheral side thereof is in contact with the outer peripheral surfaces of both axial ends of the inner ring to form a sealed bearing.

Here, in this embodiment, as the annular seal member 16, a surface contact type annular seal member in which the seal lip portion 20 makes surface contact with the outer peripheral surfaces of both ends in the axial direction of the inner ring is used, and the annular seal member 16 is installed in the bearing space. Grease (WR-500) using calcium sulfonate as a thickener is enclosed, and the single row outer ring 11 which is a non-rotating side race ring has an N concentration of 100 ppm or less, an O concentration of 15 ppm or less, and an S concentration of 0.020% or less, Ti concentration of 50 ppm or less, N
i concentration is 1 to 5%, P concentration is 0.020% or less, and Mo concentration is 0.1 to 5%, and the C concentration on the raceway surface of the race is 0.6 to 1. In addition to 2%, the residual compressive stress of the raceway surface is set to 100 to 500 MPa.

FIG. 2 shows an example of the surface contact type annular seal member 16. FIG. 3A shows a state in which the seal lip portion 20 of the surface contact type annular seal member 16 is in contact with the outer peripheral surface of the inner ring, and FIG. 3B shows an example of surface pressure distribution. It can be seen that the seal lip portion 20 is in contact with the outer peripheral surface of the inner ring over a wide area. On the other hand, FIG. 4 shows an example of the line contact type annular seal member 30 which has been conventionally used. This wire-contacting annular seal member 30 has an elastic member 32 such as hydrogenated nitrile rubber (H-NBR) integrally fixed to a metal core 31 by vulcanization adhesion or the like, and a seal on the inner peripheral side thereof. The lip portion 33 is adapted to come into line contact with the outer peripheral surfaces of both ends of the inner ring in the axial direction. FIG. 5A shows a state in which the seal lip portion 33 of the line contact type annular seal member 30 is in contact with the outer peripheral surface of the inner ring, and FIG. 5B shows an example of surface pressure distribution. It can be seen that the seal lip portion 33 is in contact with the outer peripheral surface of the inner ring in a small area.

FIG. 6 shows the relationship between heat generation temperature and time in the surface contact type annular seal member 16 and the line contact type annular seal member 30. Regarding the heat generation temperature, the respective lip portions 20 when the seal lip portions 20 and 33 of the respective annular seal members 16 and 30 are brought into contact with the rotary shaft and the rotary shaft is rotated at a peripheral speed of 18 m / sec without using cooling water. , 33, the increase in the surface temperature of the rotating shaft was measured. As is apparent from FIG. 6, the surface contact type annular seal member 16 has a significantly lower heat generation temperature than the line contact type annular seal member 30.

Further, FIG. 7 shows a comparison of the water content in the bearing between the bearing equipped with the surface contact type annular seal member 16 and the bearing equipped with the line contact type annular seal member 30 when cooling water is used. 8 shows a comparison of the wear powder ratios in the bearings. In addition, in each figure, both the water mixing ratio in the bearing and the wear powder ratio in the bearing are shown with the line contact type annular seal member 30 as 1. As is clear from the respective drawings, the surface contact type annular seal member 16 has a ratio of water content in the bearing of about 1/3 and a wear powder ratio in the bearing of about 1/2 as compared with the line contact type annular seal member 30. It can be seen that the effect of preventing water from entering the bearing and the effect of preventing abrasion powder from entering the bearing are excellent.

Next, the grease filled in the bearing will be described. Table 1 shows a grease using calcium sulfonate as a thickening agent (WR-500) and a grease using a lithium thickening agent (Palmax RG).
B, Palmax RS, Adlex) shows general properties.

[0026]

[Table 1]

A bearing lubricity test was conducted on each grease in Table 1 by using a tester shown in FIG. A steep tapered roller bearing 40 was used as the test bearing, and the bearing space was filled with grease at about 100% of the bearing space volume, and a predetermined amount of grease was also filled around the bearing.
The amount of water mixed in the bearing was set to 15%. The test is
There are two types of conditions: high speed condition and low speed and high load condition. The high speed condition is rotation speed 4200 rpm (constant), axial load 18.6.
The test time was 5 h at 2 kN (constant), and the low speed and high load conditions were a rotation speed of 1200 rpm (constant) and an axial load of 18
The test time was set to 5 h at 6.2 kN (constant). Then, the temperature of the flange portion of the inner ring of the bearing was measured, and the difference from the room temperature was calculated as ΔT (degree of increase in flange temperature). The results are shown in Table 2.

[0028]

[Table 2]

As is clear from Table 2, grease (WR-) containing calcium sulfonate as a thickener.
500), greases using lithium-based thickeners (Palmax RGB, Palmax RS) have higher heat resistance than greases using lithium-based thickeners (Adlex) under both high speed and low speed and high load conditions. It turns out that it is excellent.

In this case, PULMAX RGB and PULMAX RS are very expensive, so it is understood that WR-500, which is inexpensive and has excellent water resistance and heat resistance, is the most suitable grease. Next, the life test of the roll neck bearing for a rolling mill of the present invention was conducted by substituting a tapered roller bearing. Regarding the grease filled in the bearing space,
A grease containing a lithium thickener was used.

In this tapered roller bearing 1, referring to FIG. 12, a plurality of rollers 4 are arranged between an inner ring 2 and an outer ring 3 via a cage 5, and an inner diameter of 85 mm and an outer diameter of 130 m.
m, assembly width 29 mm, basic dynamic load rating C = 143 kN,
The basic static load rating C ₀ = 231 kN, and the diameter (average diameter) of the rollers 4 is 10.6 mm. The outer ring 3 was made of steel having the compositions shown in Tables 3, 5, and 7, and the surface was adjusted to various carbon concentrations by carburizing, and then ground to complete.

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

[Table 8]

The outer ring 3 (non-rotating ring) of such a tapered roller bearing 1 is incorporated into the housing 7 of the life tester shown in FIG. 13, and the inner ring 2 (rotating ring) is set to the rotary shaft 6.
And a life test was performed while rotating the rotary shaft 6. At that time, the radial load Fr and the axial load Fa were applied to the tapered roller bearing 1 and water was intermittently injected into the tapered roller bearing 1. The inner ring 2 and the rollers 4 were made of case hardening steel SAE5120. The surface roughness of the rolling surfaces (the raceways of the inner ring 2 and the outer ring 3 and the rolling surfaces of the rollers 4) is about 0.1 μmRa.

The test condition is a radial load Fr = 71.5.
kN, axial load Fa = 15.6 kN, the number of rotations of the inner ring 2 was 2500 rpm, and the lubricant used was 60 g of grease composed of Li soap (thickener) and base oil of viscosity VG64. For water injection, add 20 ml of water to 3
Inject once a time, in order to prevent water leakage at that time,
A rubber seal (O-ring) was attached between the rotary shaft 6 and the housing 7 of the life tester. The test temperature was about 60 ° C., and the rated fatigue life (calculated value of 10% failure life) was 67 hours.

The inner ring 2, the outer ring 3, and the roller 4 of the tapered roller bearing 1 have an effective hardening depth (surface layer thickness of Vickers hardness Hv550 or more) of 1.5 mm by quenching and tempering treatment after carburization. . The carbon concentration on the surface is adjusted by the dew point at the time of carburization and is set to various levels within the range of 0.40 to 1.50%. However, the carbon concentration on the surface of the inner ring 2 and the roller 4 was 0.9%, and the surface hardness of the raceway surface of the inner ring 2 and the rolling surface of the roller 4 was HRC62. The surface hardness of the raceway surface of the outer ring 3 was set to HRC55 to 62 as shown in Table 4, Table 6 and Table 8.

Until half of the tested bearings peel
Time (L₅₀Life) was used to evaluate the life. Life test
The test results are shown in the rightmost columns of Tables 4, 6 and 8. Peeling site
Were all in the stress-loaded zone of the outer ring 3. In addition, the remaining of the raceway surface
Residual stress σ_RWas electropolished to remove the surface layer by 50 μm.
Then, the surface stress was measured by the X-ray method. Table 4, Table 6,
Residual stress σ in Table 8_RThe negative value of the
And indicates. Residual stress σ _RIs -500 and -600 MPa
The outer ring 3 is shot peened.

13 to 21 are graphs showing the results of Examples and Comparative Examples in Tables 3 to 8. 13 to 21 show L ₅₀ life and N concentration, O concentration, S concentration of the outer ring 3,
The relationships between Ti concentration, Ni concentration, P concentration, Mo concentration, C concentration on the raceway surface, and residual stress σ _R on the raceway surface are shown respectively. It should be noted that, in the portions surrounded by ellipses in each drawing, the variables on the horizontal axis satisfy the conditions of the present invention, but other variables do not satisfy the conditions of the present invention.

From the respective drawings, in a lubricating environment in which water is mixed in the lubricant, the steel constituting the outer ring 3 (the non-rotating bearing ring) has a N concentration of 100 ppm or less and an O concentration of 15 pp.
m or less, S concentration is 0.020% or less, Ti concentration is 50 pp
The tapered roller bearing 1 has a m content of 1 to 5%, a Ni content of 1 to 5%, a P content of 0.020% or less, and a Mo content of 0.1 to 5%.
It can be seen that has a long life.

Similarly, the C concentration on the raceway surface of the outer ring 3 is 0.6 to 1.2%, and the residual compressive stress on the raceway surface of the outer ring 3 is 1%.
It can be seen that the tapered roller bearing 1 has a long life when it is from 00 to 500 MPa. Thus, in this embodiment, the seal lip portion 20 is used as the annular seal member 16.
Improves the effect of preventing water intrusion into the bearing by using the surface-contact type annular seal member that makes surface contact with the outer peripheral surfaces of both ends of the inner ring in the axial direction, and uses calcium sulfonate as a thickener in the bearing space. By enclosing a grease (WR-500), deterioration of water resistance and heat resistance when water is mixed is suppressed, and the single row outer ring 11 which is a non-rotating side race ring has an N concentration of 100 ppm or less and an O concentration. Is 15p
pm or less, S concentration is 0.020% or less, Ti concentration is 50
ppm or less, Ni concentration 1 to 5%, P concentration 0.020
% Or less, and a Mo content of 0.1 to 5%,
The C concentration of the raceway surface of the race is set to 0.6 to 1.2%, and the residual compressive stress of the raceway surface is set to 100 to 500 MPa.
As a result, a bearing having excellent seizure resistance and high corrosion fatigue strength, which can be suitably used even in a poor lubricating environment in which water enters the inside and mixes in the lubricant, Therefore, by combining and and / or, it is possible to further extend the life of the roll neck bearing for a rolling mill.

(Second Embodiment) The roll neck bearing for a rolling mill of this embodiment is different from that of the first embodiment only in the steel composition of the outer ring which is the non-rotating side bearing ring. Therefore, only the differences will be described. That is, this roll neck bearing for a rolling mill has a single row outer ring 11 which is a non-rotating side race ring in FIG.
O concentration is 15 ppm or less, S concentration is 0.020% or less,
Ti concentration is 50 ppm or less, Ni concentration is 1 to 5%, P concentration is 0.020% or less, Mn concentration is 1.0% or less, Mo
It is made of steel having a concentration of 0.05 to 5% and a Cr concentration of 1.5% or less, and the C concentration of the raceway surface of the bearing ring is 0.6 to 1.
2% and the residual compressive stress of the raceway surface is 100 to 500
It is set to MPa.

Then, the roll neck bearing for a rolling mill was subjected to a life test under the condition that gaseous water penetrated. In this life test, the tapered roller bearing 1 shown in FIG. 12 was used as a substitute, as in the first embodiment. That is, the tapered roller bearing 1 is mounted on the life tester shown in FIG. 12, and 120 ° C. saturated water is supplied (wet air: drawn out from the inside of the bearing by a tube not shown) to the inside of the bearing. I tested while.

The structure and test conditions of the tapered roller bearing used in the life test are the same as those in the first embodiment, and the description thereof will be omitted. However, the composition of the steel forming the outer ring 3 and the properties of the raceway surface of the outer ring 3 are as shown in Tables 9 to 16, and the test temperature is 120 ° C.

[0048]

[Table 9]

[0049]

[Table 10]

[0050]

[Table 11]

[0051]

[Table 12]

[0052]

[Table 13]

[0053]

[Table 14]

[0054]

[Table 15]

[0055]

[Table 16]

The life was evaluated by the time until half of the tested bearings peeled off (L ₅₀ life). The results of the life test are shown in the rightmost columns of Table 10, Table 12, Table 14, and Table 16. All the peeled parts were in the stress-loaded zone of the outer ring 3. The residual stress σ _R of the raceway surface was 5 after electropolishing.
After removing 0 μm, the surface stress was measured by the X-ray method. Residual stress σ _{R in} Table 10, Table 12, Table 14 and Table 16
A negative value indicates compressive stress. Residual stress σ
The outer ring 3 having _R of -500 and -600 MPa is shot peened.

22 to 32 are graphs showing the results of Examples and Comparative Examples in Tables 9 to 16. 22 to 32
Is the L ₅₀ life and N concentration, O concentration, S concentration, Ti concentration, Ni concentration, Ni concentration, P concentration, raceway surface C concentration, raceway surface residual stress σ _R , Mo concentration, Mn concentration, Cr The relationship with the concentration is shown respectively. From these figures, under the environment where moist air penetrates inside the bearing,
The steel forming the outer ring 3 (non-rotating side race ring) has N concentration of 100 ppm or less, O concentration of 15 ppm or less, S concentration of 0.020% or less, Ti concentration of 50 ppm or less, Ni concentration of 1 to 5%, When the P concentration is 0.020% or less, the Mo concentration is 0.05 to 5%, the Mn concentration is 1.0% or less, and the Cr concentration is 1.5% or less, the tapered roller bearing 1 may have a long life. I understand.

Similarly, the C concentration on the raceway surface of the outer ring 3 is 0.6 to 1.2%, and the residual compressive stress on the raceway surface of the outer ring 3 is 1.
It can be seen that the tapered roller bearing 1 has a long life when it is from 00 to 500 MPa. Other configurations and operational effects are the same as those of the first embodiment, so description thereof will be omitted.

In each of the above embodiments, the outer ring is provided with four single-row outer rings 11, and four rows of tapered roller bearings in which spacers 12 and 13 are interposed between the single-row outer rings 11 adjacent to each other. However, instead of this, as shown in FIG. 10, a four-row tapered roller bearing having a double-row outer ring having one outer ring and two single-row outer rings is used as the outer ring. It may be adopted as a roll neck bearing for a rolling mill.

This rolling mill rolling neck bearing includes a double row inner ring 50 having two inner rings, a single row outer ring 51 having one outer ring, and spacers 52 at both ends of the double row outer ring 51. It is provided with two single-row outer rings 53 arranged, and four rows of tapered rollers 54 (rolling elements) are arranged between the inner ring and the outer ring so as to be rollable in the circumferential direction via a cage 55. ing. Further, surface contact type annular seal members 60 are attached via seal holders 61 to both axial end portions of the outer ring. As shown in FIG. 11, the annular seal member 60 has an elastic material 63 such as hydrogenated nitrile rubber (H-NBR) integrally fixed to a metal cored bar 62 by vulcanization adhesion or the like, and has an inner periphery thereof. The side seal lip portion 64 is in surface contact with the outer peripheral surfaces of both ends of the inner ring in the axial direction to form a sealed bearing.

Further, in each of the above embodiments, the tapered roller bearing is taken as an example, but the present invention is not limited to this, and the present invention may be applied to a cylindrical roller bearing as a rolling mill roll neck bearing. Further, in each of the above-mentioned embodiments, the four rows of tapered roller bearings are adopted as the roll neck bearings for the rolling mill, but the present invention may be applied to the double rows of tapered roller bearings as the roll neck bearings for the rolling mill.

[0062]

As is apparent from the above description, according to the invention of claim 1, excellent seizure resistance and high corrosion fatigue strength are ensured, and water or gaseous water penetrates inside. Even under a poor lubricating environment such as when mixed with a lubricant, it is possible to prevent early damage and early delamination (hydrogen embrittlement delamination) as well as reduce the amount of water intrusion into the bearing. The effect that the life can be extended can be obtained.

According to the invention of claim 2, in addition to the invention of claim 1, deterioration of water resistance and heat resistance of the grease when water is mixed can be suppressed, so that the life extension effect is further improved. The effect of being able to do is obtained. According to the invention of claim 3, excellent seizure resistance and high corrosion fatigue strength are ensured, and even under a poor lubricating environment in which water or gaseous water enters the lubricant and mixes with the lubricant. In addition to being able to prevent premature damage and premature peeling (hydrogen embrittlement peeling), it is possible to suppress the deterioration of the water resistance and heat resistance of the grease when water is mixed, and to further extend the service life. The effect is obtained.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view for explaining a roll neck bearing for a rolling mill according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a surface contact type annular seal member mounted on the roll neck bearing for a rolling mill of FIG.

FIG. 3A is an explanatory sectional view for explaining a state in which a seal lip portion of a surface-contact type annular seal member is in contact with an outer peripheral surface of an inner ring, and FIG. 3B is a surface-contact type annular seal member. It is a graph which shows an example of surface pressure distribution.

FIG. 4 is an enlarged cross-sectional view of a line contact type annular seal member.

5A is an explanatory cross-sectional view for explaining a state in which a seal lip portion of the line contact type annular seal member is in contact with an outer peripheral surface of an inner ring, and FIG. 5B is a line contact type annular seal member. It is a graph which shows an example of surface pressure distribution.

FIG. 6 is a graph showing a relationship between time and heat generation temperature in the surface contact type annular seal member and the line contact type annular seal member.

FIG. 7 is a graph showing a comparison of a water mixing ratio in a bearing between a surface contact type annular seal member and a line contact type annular seal member.

FIG. 8 is a graph showing a comparison of wear powder ratios in bearings of the surface contact type annular seal member and the line contact type annular seal member.

FIG. 9 is an explanatory sectional view for explaining a bearing lubricity tester.

FIG. 10 is an explanatory cross-sectional view for explaining a modification of the roll neck bearing for a rolling mill and the surface contact type annular seal member.

11 is an enlarged cross-sectional view of a surface contact type annular seal member mounted on the roll neck bearing for a rolling mill of FIG.

FIG. 12 is an explanatory sectional view for explaining a life tester using a tapered roller bearing.

FIG. 13 is a graph showing the relationship between N concentration and L ₅₀ life.

FIG. 14 is a graph showing the relationship between O concentration and L ₅₀ life.

FIG. 15 is a graph showing the relationship between S concentration and L ₅₀ life.

FIG. 16 is a graph showing the relationship between Ti concentration and L ₅₀ life.

FIG. 17 is a graph showing the relationship between Ni concentration and L ₅₀ life.

FIG. 18 is a graph showing the relationship between P concentration and L ₅₀ life.

FIG. 19 is a graph showing the relationship between Mo concentration and L ₅₀ life.

FIG. 20 is a graph showing the relationship between the C concentration on the raceway surface and the L ₅₀ life.

FIG. 21 is a graph showing the relationship between residual stress σ _{R on the} raceway surface and L ₅₀ life.

FIG. 22 is a graph showing the relationship between N concentration and L ₅₀ life in the roll neck bearing for rolling mills according to the second embodiment of the present invention.

FIG. 23 is a graph showing the relationship between O concentration and L ₅₀ life.

FIG. 24 is a graph showing the relationship between S concentration and L ₅₀ life.

FIG. 25 is a graph showing the relationship between Ti concentration and L ₅₀ life.

FIG. 26 is a graph showing the relationship between Ni concentration and L ₅₀ life.

FIG. 27 is a graph showing the relationship between P concentration and L ₅₀ life.

FIG. 28 is a graph showing the relationship between the C concentration on the raceway surface and the L ₅₀ life.

FIG. 29 is a graph showing the relationship between residual stress σ _{R on the} raceway surface and L ₅₀ life.

FIG. 30 is a graph showing the relationship between Mo concentration and L ₅₀ life.

FIG. 31 is a graph showing the relationship between Mn concentration and L ₅₀ life.

FIG. 32 is a graph showing the relationship between Cr concentration and L ₅₀ life.

[Explanation of symbols]

1 ... Tapered roller bearing 2 ... Inner ring 3 ... Outer ring 4 ... 10,50 ... Double row inner ring 11, 53 ... Single row outer ring 51 ... Double row outer ring 12, 13, 52 ... Zama 14, 54 ... 15,55 ... Cage 16, 60 ... Surface contact type annular seal member 18, 62 ... 19, 63 ... Elastic material 20, 64 ... Seal lip

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16C 19/38 F16C 19/38 33/66 33/66 Z 33/78 33/78 DF Term (reference) 3J016 AA04 BB03 CA02 3J101 AA16 AA43 AA54 AA62 BA54 EA02 EA63 FA02 FA08 FA32 FA33 GA36 3J103 CA62 DA05 FA11 FA12 FA25 FA26 GA17

Claims (3)

[Claims] 1. A roll neck for a rolling mill, wherein a plurality of rolling elements are rotatably arranged between inner and outer races serving as raceways and annular seal members are attached to both axial ends of the outer race. In the bearing, at least the non-rotating bearing ring has N concentration of 100 ppm or less, O concentration of 15 ppm or less, S concentration of 0.020% or less, Ti concentration of 50 ppm or less, Ni concentration of 1 to 5%,
It is made of steel having a P concentration of 0.020% or less and a Mo concentration of 0.1 to 5%, and the C concentration of the raceway surface of the race is 0.6.
~ 1.2% and the residual compressive stress of the raceway surface is set to 1
A roll-neck bearing for a rolling mill having a pressure of 0 to 500 MPa and using a surface contact type annular seal member whose seal lip portion is in surface contact with the inner ring as the annular seal member. 2. The roll neck bearing for a rolling mill according to claim 1, wherein grease containing calcium sulfonate as a thickener is enclosed in the bearing space. 3. A roll neck bearing for a rolling mill, wherein a plurality of rolling elements are rotatably arranged between inner and outer races as a race ring, wherein at least the non-rotating side race ring has an N concentration of 100 ppm or less, O Concentration is 15 ppm or less, S concentration is 0.020% or less, Ti concentration is 50 ppm or less, Ni concentration is 1 to 5%,
It is made of steel having a P concentration of 0.020% or less and a Mo concentration of 0.1 to 5%, and the C concentration of the raceway surface of the race is 0.6.
~ 1.2% and the residual compressive stress of the raceway surface is set to 1
A roll neck bearing for a rolling mill, wherein the rolling neck rolling mill has a grease of 0 to 500 MPa and calcium sulfonate as a thickening agent enclosed in the bearing space.