JPH1194704A - Method for evaluating lubricant for rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a lubricant for rolling bearing can be evaluated by checking the service life of the lubricant in a short time without conducting life tests on a rolling bearing for a long time until the bearing is broken. SOLUTION: A method for evaluating lubricant for rolling bearing includes a step of hardening the constituent members of a rolling bearing in a hardening furnace substantially maintained in a hydrogen-free atmosphere, a step of obtaining a first hydrogen concentration by measuring the hydrogen concentration in a member which becomes the bearing ring or rolling member of the hardened constituent members, and a step of performing rotation tests on the bearing by using a lubricant to be evaluated after the bearing is assembled by using the hardened constituent members. The method also includes a step of obtaining a second hydrogen concentration by measuring the hydrogen concentration in the member of the bearing after rotation tests. Then the increment of the hydrogen concentration is found from the difference between the first and second hydrogen concentrations in the member of the bearing and the harmfulness of the lubricant on the rolling life of the bearing is discriminated from the increment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating the effect of a lubricant used for a rolling bearing on the rolling fatigue life.

[0002]

2. Description of the Related Art The effect of a lubricant on the rolling fatigue life is complicated and has not been elucidated in detail at present. For example, the relationship between the additive in the lubricant and the rolling fatigue life is unknown, and after all, the relationship between the lubricant and the rolling fatigue life can only be obtained by conducting a long-term life test until it actually breaks. Can not.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and has been developed for lubricating a rolling bearing without subjecting the rolling bearing to a long-term life test until the rolling bearing is damaged. It is an object of the present invention to provide a method for examining the effect of a lubricant on the rolling life in a short time and thereby evaluating a lubricant.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a step of quenching components of a rolling bearing in a quenching furnace in an atmosphere substantially containing no hydrogen gas, after quenching. Among the constituent members of the rolling bearing, by measuring the hydrogen concentration in the member that will be the race and the rolling element,
A step of obtaining a first hydrogen concentration, a step of subjecting a rolling bearing obtained by combining the components of the rolling bearing after the quenching treatment to a rotation test using a lubricant as an object to be evaluated, and a step of rolling after the rotation test. Measuring the hydrogen concentration in the member of the bearing to obtain a second hydrogen concentration,
Provided is a method for determining an increase in hydrogen concentration based on a difference between a second hydrogen concentration and a first hydrogen concentration in the member of the rolling bearing, and determining a degree of harmfulness to the rolling life of the lubricant based on the increase in hydrogen concentration. I do.

Hereinafter, the present invention will be described in detail. In the method for evaluating a lubricant for a rolling bearing according to the present invention, the quenching treatment of the components of the rolling bearing, the atmosphere substantially free of hydrogen gas includes, for example, vacuum, N ₂ gas, and air. No. The conditions for the quenching process are as follows:
After holding at 840 ° C. for 30 minutes, it can be determined as appropriate such as immediately immersing in oil at 60 ° C. After the quenching treatment, low-temperature tempering at 160 to 200 ° C. for 1 to 2 hours is selectively performed.

[0006] The components of the quenched rolling bearing are subjected to a hydrogen concentration analysis. The first hydrogen concentration is obtained by performing the hydrogen concentration analysis. In the hydrogen analysis, a test piece collected from the member is gradually heated at a constant heating rate, and the released hydrogen is analyzed at each temperature (thermal desorption method, Th method).
Thermal Desorption Spectrometry (TDS)) can be used.

In the calibration of the hydrogen concentration, first, hydrogen gas from a standard cylinder whose hydrogen gas leakage rate is known is introduced into the analysis unit, and hydrogen gas ions (H ₂
⁺ ) Measure strength. One unit of the obtained ionic strength is
Calculate how many g / sec of the hydrogen gas leak rate corresponds (conversion coefficient K) and calculate the hydrogen gas ion (H
₂ ⁺ ) Measure intensity I.

The hydrogen release rate and the hydrogen concentration in steel at each temperature are given by the following equations (1) and (2), respectively, using the aforementioned hydrogen gas ion (H ₂ ⁺ ) intensity I and conversion coefficient K.

K × I × 10 ⁶ / W (ppm / sec) (1) t × ΣK × I × 10 ⁶ / W (ppm) (2) where W is a sample weight (g) and t is This is a measurement interval (sec) of the hydrogen gas ion (H ₂ ⁺ ) intensity I. Since the measured hydrogen gas ion intensity I includes a slight noise intensity B, the minimum value of I during the measurement is regarded as B,
Replacing (IB) with I again, the above-mentioned equation (1),
The calculation of (2) is performed.

The rolling bearing after measuring the hydrogen concentration in this way is subjected to a rotation test using a lubricant to be evaluated. The conditions of the rotation test are as follows: rotation speed n = 3900 rpm, ratio of load P to basic dynamic load rating C (P / C) = 0.7, etc.
For example, while a load of 13650 N is applied to the test bearing 6206 (deep groove ball bearing),
The inner ring is rotated at a rotation speed of 3900 rpm.

The test time can be determined as appropriate, such as 0.1 to 10 times the rated fatigue life (L10 cal), but is preferably about 240 hours or less. A second hydrogen concentration is obtained by measuring the hydrogen concentration of the member of the rolling bearing after the rotation test in the same manner as described above. For the stationary wheel, it is necessary to measure the hydrogen concentration near the maximum stress load position.

From the difference between the second hydrogen concentration and the first hydrogen concentration measured as described above, an increase in the hydrogen concentration in the member is determined, and the life increase effect of the lubricant is determined by the obtained hydrogen concentration increase. evaluate. Although it depends on the test temperature and test time, the rated fatigue life (L
If the increment of the hydrogen concentration in the above-mentioned member of the bearing is 0.02 ppm or less when the rotation test is performed up to 10 cal), it can be said that the hydrogen atoms in the lubricant are stable and the bearing material does not cause hydrogen embrittlement. .

The present inventors have made the present invention based on the following findings. When a rolling bearing absorbs hydrogen atoms from a lubricant during use, the bearing is embrittled with hydrogen and damaged. The hydrogen source here is a large amount of hydrogen atoms contained in the lubricant or hydrogen atoms in the lubricant water. The stability of hydrogen atoms in the lubricant, that is, the difficulty in transferring hydrogen atoms into the bearing steel material, seems to depend on the composition and temperature of the lubricant, but there are many unknowns and measurement methods are also available. Quantification is difficult because it is not performed. The damage mode of the bearing due to hydrogen embrittlement is mainly peeling.

On the other hand, the quenching of the components of the rolling bearing is performed in an endothermic furnace such as RX gas for the purpose of preventing the bearing surface from being oxidized. Hydrogen atoms are absorbed in the bearing by reaction with hydrogen gas. The hydrogen atoms absorbed here do not contribute to the hydrogen embrittlement of rolling bearings, but in the current hydrogen analysis method including the thermal desorption method, the hydrogen concentration caused by the lubricant and the absorption during quenching as described above And the concentration of hydrogen
It cannot be separated and measured.

Accordingly, the present inventors have determined the amount of hydrogen absorption due to the lubricant during use of the rolling bearing by:
It has been found that it is necessary to use a rolling bearing composed of a steel material substantially containing no hydrogen atoms. In the present invention, since the components of the rolling bearing are subjected to quenching in a quenching furnace in an atmosphere substantially containing no hydrogen gas, for example, a vacuum quenching furnace, hydrogen absorption to the bearing in this step is minimized. Could be reduced. That is, since the amount of hydrogen absorbed in the quenching step is almost negligible, a bearing in which the noise of the hydrogen concentration can be regarded as zero can be obtained.

After such a bearing is subjected to a rotation test using a lubricant to be evaluated for a certain period of time, hydrogen atoms present in the bearing may be determined to be substantially caused by the lubricant. it can. Therefore, if the hydrogen concentration at a predetermined position of the bearing after the rotation test is measured, the stability of the hydrogen atoms in the lubricant, that is, the bearing material of the lubricant (steel)
Can be quantified for the rolling fatigue life effect of the lubricant, which indicates the strength of the property that does not cause hydrogen embrittlement.

As described above, in the present invention, since the concentration of hydrogen absorbed by the bearing in the quenching process is significantly reduced, the concentration of hydrogen absorbed from the lubricant during the rotation test is measured with high accuracy. I was able to. Therefore, without conducting a long life test until the bearing breaks,
It has become possible to evaluate the life of the lubricant in a short time.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples. First, an outer ring, an inner ring, and a steel ball made of two types of bearing steel (SUJ2) are prepared, and the inner and outer rings are maintained at about 840 ° C. in a vacuum for 0.5 hour, and then subjected to a quenching treatment. The sphere was kept at about 820 ° C. for 0.3 hours in a nitrogen atmosphere and then subjected to a quenching treatment. Furthermore, in each case, low-temperature tempering (160 ° C., 2 hours) was performed in an air atmosphere after the quenching treatment.

The hydrogen concentration at an arbitrary position on the outer ring after the quenching process is analyzed by the above-described method, and the obtained hydrogen concentration release curve is shown in the graph of FIG. The released hydrogen was analyzed using a quadrupole mass spectrometer (MSQ-150A, manufactured by Nippon Vacuum Engineering Co., Ltd.), the temperature rising rate of the test piece was 3 ° C./min, and hydrogen gas ions (H ₂ ⁺ ) The measurement interval of intensity I was 20 seconds.

Next, a deep groove ball bearing (with a plastic retainer) having a contact rubber seal having a diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm, comprising the outer ring, the inner ring, and the rolling element, which has been subjected to the quenching treatment as described above, is provided. 2.3 g of a lubricant as a material, NSK Technical Journal, No.656,
A rotation test was performed for 100 hours as a pulley-side bearing of an alternator of an engine installed on a table described in pp. 1 to 14, 1993. In this rotation test, the inner ring was used as a rotating raceway, and the outer race was used as a non-rotating raceway.

In the rotation test, the load applied to the test bearing is 1890 N (the basic dynamic load rating of the test bearing is 13500 N), and the rotation speed of the inner ring is 2000 rpm.
It varied repeatedly between m and 14000 rpm. 20
The time required for acceleration from 00 rpm to 14000 rpm and the time required for deceleration from 14000 rpm to 2000 rpm were all 30 seconds. The rated fatigue life (L10cal) of this test bearing is L10cal = (13500/1890) ³ × 10 ⁶ / (8000 × 60) = 759 hours. Here, as the lubricant, two types of greases α and β as shown in Table 1 below were used.

[0022]

[Table 1]

The test bearing did not break in the 100-hour rotation test, but if a long-term life test was performed before the break, the raceway was damaged (peeled) on the raceway surface near the maximum stress load position of the outer ring. Occurs. Therefore, in this embodiment,
Although only the change in the hydrogen concentration of the outer ring will be described, it has been confirmed that the inner ring and the rolling elements do not substantially increase the hydrogen concentration.

After the rotation test, the vicinity of the maximum stress load position of the outer ring was cut out, and a hydrogen concentration analysis was performed under the same conditions as described above. FIG. 2 shows a hydrogen concentration release curve at the time of analyzing the hydrogen concentration in the outer ring load zone after performing the rotation test using grease α, and FIG. 3 shows the hydrogen concentration release curve after performing the rotation test using grease β. 4 shows a hydrogen concentration release curve at the time of analyzing the hydrogen concentration in the outer ring load zone.

The hydrogen release curves of the outer race after the rotation test shown in FIGS. 2 and 3 will be described in comparison with the hydrogen release curves of the outer race before the rotation test shown in FIG. FIG.
As shown in the figure, after the quenching process, there was no peak in the hydrogen release curve when analyzing the hydrogen concentration of the outer ring of the bearing before the rotation test, and the bearing was hardly absorbed by the quenching process in vacuum. You can see that it is not. In contrast, after a 100-hour rotation test using grease α, as shown in FIG. 2, there is a clear peak in the hydrogen release curve when analyzing the hydrogen concentration in the outer ring load zone. This indicates that hydrogen atoms were absorbed from the grease α into the outer ring load zone during the rotation test.

On the other hand, as shown in FIG. 3, there is no peak in the hydrogen release curve at the time of analyzing the hydrogen concentration in the outer ring load zone of the bearing after performing the rotation test for 100 hours using grease β. This indicates that no hydrogen atoms were absorbed from the grease β into the outer ring load zone during the rotation test.

The hydrogen concentration was calculated by integrating the hydrogen release curves shown in FIGS. 1 to 3 from 150 ° C. to 350 ° C. and found to be 0.01 ppm and 0.06 p, respectively.
pm, and 0.01 ppm. This result also indicates that when grease α was used, hydrogen was absorbed in the outer ring load zone.

Next, a life test was performed on the above-described bearing in which the grease α or β was sealed until the bearing was broken under the same rotation test conditions as described above. However, if the sample was not damaged by the time of the rated fatigue life, the test was terminated. The number of tests was five for each bearing. The life test results are as follows.

Bearing of grease α: 389, 254, 20
8,184,135 hours All outer ring exfoliated Grease β bearing: All interrupted after 759 hours (no exfoliation) Thus, grease β was confirmed to be more effective than grease α in extending the rolling fatigue life. The test took a lot of time. As described above, if the bearings that have been quenched in a given atmosphere are subjected to hydrogen analysis before and after the rotation test, grease β can provide a longer rolling fatigue life than α without performing a life test until breakage. It turns out that it is effective.

For comparison, hydrogen concentration was analyzed in the same manner as described above for the outer ring that had been quenched in an RX gas atmosphere furnace, and the results obtained are shown in the graph of FIG. Furthermore, except for using the outer ring thus hardened,
A bearing was formed using the same inner ring and steel ball as described above, and a rotation test as described above was performed using grease α. The hydrogen concentration near the maximum stress load zone of the outer ring after the rotation test was analyzed in the same manner as described above, and the hydrogen release curve is shown in the graph of FIG.

As shown in the graphs of FIGS. 4 and 5, a peak is present not only in the bearing after the test but also in the hydrogen release curve of the outer ring of the previous bearing. In the quenching treatment in the RX gas atmosphere furnace, It is clearly shown that hydrogen was absorbed in the outer ring. Further, when the hydrogen concentration was calculated by integrating the hydrogen release curves shown in FIGS. 4 and 5 from 150 ° C. to 350 ° C., they were 0.56 ppm and 0.52 ppm, respectively.
The value was as high as. From this result, it is understood that it is difficult to determine that hydrogen has been absorbed into the outer ring load zone when at least grease α is used.

Incidentally, the reason why the hydrogen concentration in the outer ring load zone slightly decreases after the rotation test is that the hydrogen atoms absorbed during the quenching treatment are released from the bearing during the rotation test, and this amount is absorbed by the lubricant. Due to the larger amount of hydrogen.

[0033]

As described above, according to the present invention,
A method is provided in which the life of a lubricant for a rolling bearing is examined in a short time and the lubricant is evaluated without being subjected to a long life test until the rolling bearing is damaged.

[Brief description of the drawings]

FIG. 1 is a hydrogen release curve at the time of hydrogen concentration analysis of an outer ring that has been quenched in vacuum before a rotation test.

FIG. 2 is a hydrogen release curve at the time of analyzing the hydrogen concentration in the outer ring load zone after performing a quenching treatment in a vacuum and performing a rotation test for 100 hours using grease α.

FIG. 3 is a hydrogen release curve at the time of analyzing hydrogen concentration in the outer ring load zone after a quenching treatment in vacuum and a 100-hour rotation test using grease β.

FIG. 4 is a hydrogen release curve during hydrogen concentration analysis before a rotation test of an outer ring that has been quenched in RX gas.

FIG. 5 is a hydrogen release curve at the time of analyzing hydrogen concentration in the outer ring load zone after a quenching treatment in RX gas and a 100-hour rotation test using grease α.

Claims (1)

[Claims] 1. A step of quenching components of a rolling bearing in a quenching furnace in an atmosphere substantially containing no hydrogen gas. Of the components of the rolling bearing after the quenching, the rolling elements serve as races and rolling elements. Measuring the hydrogen concentration in the member to obtain a first hydrogen concentration; and subjecting the rolling bearing formed by combining the components of the rolling bearing after the quenching treatment to a rotation test using a lubricant as an evaluation object. And a step of measuring a hydrogen concentration in the member of the rolling bearing after the rotation test to obtain a second hydrogen concentration, wherein a second hydrogen concentration and a first hydrogen in the member of the rolling bearing are obtained. A method of determining an increase in hydrogen concentration based on a difference from the concentration and determining the degree of harm to the rolling life of the lubricant based on the increase in hydrogen concentration.