JP7238620B2 - Fatigue progress evaluation method - Google Patents

Description

The present invention relates to a fatigue progress evaluation method.

When hydrogen penetrates into the steel that forms the rolling member of the rolling device, the metallographic structure of the steel may change due to the interaction between the hydrogen and the shear stress acting inside the steel due to rolling contact. This change in metal structure is a phenomenon in which martensite, which is the base structure of steel, changes into fine ferrite grains. When etching is performed and the changed structure is observed, it looks white, so the metal structure changed by the penetration of hydrogen is called "white structure". If a white structure occurs in steel, fatigue cracks will occur from the interface between the structure-changed portion and the normal portion (structure-unchanged portion), and the steel will peel off. Hereinafter, detachment accompanied by tissue change to white tissue as described above may be referred to as “white tissue detachment”. Also, damage caused by white tissue (including white tissue detachment) is sometimes referred to as "white tissue damage".
By quantifying the amount of room-temperature diffusible hydrogen among the hydrogen that penetrated into the rolling members during operation of the rolling device, the progress of fatigue due to white tissue flaking of the rolling device (hereinafter referred to as "fatigue progress") was measured. It is possible to evaluate and predict the life due to white tissue exfoliation (see Patent Document 1, for example).

However, in the case of a rolling device used in an actual machine (for example, an alternator for automobiles), even if an attempt is made to quantify the amount of room temperature diffusible hydrogen contained in the rolling member, the room temperature diffusible hydrogen is transferred before measurement. Accurate quantification of room-temperature diffusible hydrogen was difficult because it may be released from moving parts. Therefore, it was difficult to evaluate the degree of progress of fatigue due to flaking of the white tissue of the rolling device used in the actual machine and to predict the life due to the flaking of the white tissue.

Japanese Patent No. 6072504

An object of the present invention is to provide a method for evaluating the degree of progress of fatigue due to white tissue flaking of a rolling device.

A fatigue progress evaluation method according to an aspect of the present invention is provided with two rolling contact members that are in rolling contact with each other, and at least one of the two rolling contact members is a steel rolling contact member. In this method, the degree of fatigue progress is the degree of progress of fatigue of the rolling device due to white texture exfoliation occurring in the steel rolling contact member, and the rolling contact fatigue of the steel rolling member is caused by rolling contact. A rolling contact fatigue site, which is a part, has a white structure and a black structure. Based on the amount of room temperature non-diffusible hydrogen contained in the white structure of the rolling contact fatigue site, the degree of fatigue progress of the rolling device is evaluated. The gist is to

According to the present invention, it is possible to evaluate the degree of progress of fatigue caused by white tissue flaking of a rolling device.

It is an example of the graph explaining the fatigue progress evaluation method which concerns on one Embodiment of this invention. FIG. 10 is a chart showing small peaks separated from hydrogen desorption curves by statistical treatment using Gaussian distribution; FIG. It is a microphotograph of the cross section of the groove bottom of the bearing ring after the end of the operation. FIG. 4 is a schematic explanatory diagram for explaining FIG. 3;

First, definitions of terms used in this specification will be collectively described.
As described above, "white texture flaking" means flaking that occurs in steel rolling members of a rolling device accompanied by structural change to white texture.
As described above, "white tissue failure" means damage caused to a steel rolling member of a rolling device due to white tissue, and includes white tissue spallation.

"Hydrogen environment" refers to various environments in which the rolling device is placed during operation (e.g., magnitude of stress acting on steel rolling members (surface pressure), number of repetitions of stress acting on steel rolling members ( operating time of the rolling device), the atmosphere of the rolling device, and the temperature), which means the environment related to hydrogen. For example, the "hydrogen environment" includes the atmosphere in which the rolling device is operated and lubricants such as lubricating oil used in the rolling device. Lubricants such as lubricating oil are included in the “hydrogen environment” because they decompose to generate hydrogen during operation of the rolling device.

The “fatigue progress” means the progress of fatigue of the rolling device due to flaking of the white tissue generated in the steel rolling member. Define the ratio of time T as T/L10.
By "cold diffusible hydrogen" is meant hydrogen that is relatively weakly trapped in steel and relatively free to move in steel rolling members. This room temperature diffusible hydrogen can be released outside from the steel rolling member with time at room temperature.

By "cold non-diffusible hydrogen" is meant hydrogen that is relatively strongly trapped in steel and cannot move freely in steel rolling members. This room temperature non-diffusible hydrogen is not released outside from the steel rolling member at room temperature.
“Normal temperature” is a temperature specified in JIS Z8703, specifically a temperature within the range of 5° C. or higher and 35° C. or lower.

"Rolling device" means a device comprising two rolling members that are in rolling contact with each other, and includes, for example, a rolling bearing, a ball screw, a linear motion guide device (linear guide device), a linear motion bearing, and the like. be.
A "rolling member" is a part that constitutes a rolling device, and means members that are in rolling contact with each other. Specifically, if the rolling device is a rolling bearing, the inner ring, outer ring, and rolling elements are used. If the rolling device is a ball screw, the screw shaft, nut, and rolling elements. , rolling elements, and in the case of linear motion bearings, the shaft, the outer cylinder, and the rolling elements, respectively.

Next, one embodiment of the present invention will be described. As a result of intensive studies by the present inventors, new findings were found regarding steel, hydrogen, and rolling contact fatigue, which will be described in detail below.
Comparing an unoperated rolling device in which white tissue flaking does not occur and a rolling device in which white tissue exfoliation occurs after operation, the latter contains a larger amount of non-diffusible hydrogen at room temperature. The reason for this is thought to be that the weakly trapped room temperature diffusible hydrogen is strongly trapped in the trap sites generated by rolling contact fatigue, thereby changing to room temperature non-diffusible hydrogen.

From this, it was found that the amount of increase in room-temperature non-diffusible hydrogen due to the operation of the rolling device indicates the degree of structural change due to rolling contact fatigue. Therefore, for each operating condition such as the type of rolling device, the temperature during operation, and the hydrogen environment of the rolling device during operation, the amount of increase in room-temperature non-diffusible hydrogen due to the operation of the rolling device and the fatigue of the rolling device By storing the correlation between progress and service life as a database and comparing the data stored in this database with the actual measurement data of the amount of non-diffusible hydrogen at normal temperature in the rolling device after operation It is also possible to evaluate the progress of fatigue and predict the life of the rolling device after operation.

Furthermore, as a result of the study by the present inventors, the following new knowledge was found, which is listed below. Both the black tissue, which is a general fatigue texture generated without the participation of hydrogen, and the white texture, which is the fatigue texture generated with the participation of hydrogen, trap non-diffusible hydrogen at room temperature. In addition, the larger the load during rolling (the magnitude of the stress acting on the rolling contact fatigue portion of the steel rolling member due to rolling contact), the larger the amount of structural change, so the amount of black structure generated increased. Conversely, the smaller the load during rolling, the smaller the amount of black texture generated. Therefore, the larger the load during rolling, the larger the amount of room-temperature non-diffusible hydrogen trapped in the black tissue. There is a correlation with On the other hand, the amount of room-temperature non-diffusible hydrogen trapped in the white structure has no correlation with the magnitude of the load during rolling.

No white tissue is formed in the black tissue, and both are completely independent hydrogen trap sites. The black tissue strongly traps non-diffusible hydrogen at room temperature. The room temperature non-diffusible hydrogen trapped in the tissue is the room temperature non-diffusible hydrogen that exists in the cracks that are the starting point of the white tissue exfoliation. be.

When the amount of room temperature non-diffusible hydrogen possessed by the rolling device is measured, the total amount of the amount of room temperature non-diffusible hydrogen trapped in the white tissue and the amount of room temperature non-diffusible hydrogen trapped in the black tissue (hereinafter referred to as It is sometimes written as "the total amount of non-diffusible hydrogen at room temperature"), so it is not possible to evaluate the progress of fatigue due to flaking of the white tissue of the rolling device or predict the life from this measurement alone. In order to evaluate the progress of fatigue due to flaking of the white tissue of the rolling device and to predict the life, the room temperature non-diffusible hydrogen trapped in the white tissue and the room temperature non-diffusible hydrogen trapped in the black tissue are separated. It is necessary to obtain the amount of room-temperature non-diffusible hydrogen trapped in the white tissue.

However, it is difficult to directly measure the amount of room temperature non-diffusible hydrogen trapped in the white tissue and the amount of room temperature non-diffusible hydrogen trapped in the black tissue. Therefore, the present inventors have found a method of measuring the amount of black tissue and evaluating the amount of normal temperature non-diffusible hydrogen trapped in the black tissue from the measured value. The amount of black tissue can be measured, for example, by X-ray analysis, backscattered electron diffraction, image analysis of tissue. In the case of X-ray analysis, the amount of black tissue can be calculated from the half width of the detected peak of black tissue by X-ray analysis. When the amount of change in the half-value width before and after the operation of the rolling device is large, it means that the black texture has increased, and when the amount of change in the half-value width before and after the operation of the rolling device is small, the white texture increases. (because white tissue is localized fatigue).

However, since it is not possible to directly subtract the amount of black tissue from the amount of non-diffusible hydrogen at room temperature, the total amount of non-diffusible hydrogen at room temperature, the amount of black tissue, and the progress of fatigue of the rolling device are weighted. Formulate using regression analysis to derive a multiple regression equation. Using the derived multiple regression equation, it is possible to calculate the progress of fatigue of the rolling device from the amount of room-temperature non-diffusible hydrogen and the amount of black tissue.

In this way, we evaluate the fatigue progression of a rolling device comprising two rolling members in rolling contact with each other, at least one of the two rolling members being a steel rolling member. found a way. That is, in the fatigue progress evaluation method of the present embodiment, out of the white structure and black structure of the rolling contact fatigue portion, which is the portion of the steel rolling contact member that has undergone rolling contact fatigue due to rolling contact, the white structure contains It has an evaluation step of evaluating the progress of fatigue of the rolling device based on the amount of normal temperature non-diffusible hydrogen. The degree of progress of fatigue is the degree of progress of fatigue of the rolling device due to flaking of the white tissue generated in the steel rolling members.

However, as described above, it is difficult to directly determine the amount of room temperature non-diffusible hydrogen contained in the white structure of the rolling contact fatigue site. Estimate the amount of room temperature non-diffusible hydrogen contained in the white tissue of the rolling contact fatigue site from the total amount of hydrogen and the amount of black tissue of the rolling contact fatigue site, and use the estimated room temperature non-diffusible hydrogen amount to A method was found to evaluate the degree of fatigue progression of the device. The method is described in detail below.

First, a rolling device of the same type (the type, shape, dimensions, material (type of steel forming the steel rolling member), etc. is all the same) as the rolling device whose fatigue progression is to be evaluated is Prepare as a device. Then, the total amount of non-diffusible hydrogen at room temperature and the black Measure the amount of tissue. Instead of measuring the total amount of normal temperature non-diffusible hydrogen and the amount of black structure contained in the steel rolling members of the database creation rolling device that has not been operated, the database creation rolling device after operation The total amount of normal temperature non-diffusible hydrogen and the amount of black structure contained in the non-rolling contact fatigue portion of the steel rolling member may be measured.

Next, at least one of the magnitude of stress acting on the rolling contact fatigue portion of the steel rolling member due to rolling contact, the operating time, the temperature during operation, and the hydrogen environment of the rolling device for database creation during operation The database creation rolling device is operated under each of a plurality of different operating conditions, and the total amount of normal temperature non-diffusible hydrogen contained in the rolling contact fatigue portion of the steel rolling contact member of the database creation rolling device after operation Measure the amount of black tissue.

As a result, the measurement results for the database-creating rolling device that has not yet been operated and the measurement results for the database-creating rolling device that has been in operation can be obtained. The amount of change ΔNDH in the total amount of non-diffusible hydrogen contained at room temperature and the amount of change ΔDEC in the amount of black tissue in the rolling contact fatigue portion are calculated.

Here, the temperature during operation and the hydrogen environment of the rolling device for creating the database during operation are the same, and the plurality of rollers are operated under different operating conditions in terms of at least one of the magnitude of the stress acting on the rolling contact fatigue portion and the operating time. Let the rolling devices for creating the database of 1 be the rolling device group for multiple regression analysis. The amount of change ΔNDH in the total amount of room-temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue are obtained for a plurality of rolling device groups for multiple regression analysis. Extract the amount of change ΔNDH in the total amount of normal temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black texture for the database creation rolling device included in .

Then, the amount of change ΔNDH in the total amount of the extracted normal temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue, and the fatigue progress T defined by the ratio of the operating time T to the L10 life of the rolling device for database creation /L10 are formulated using multiple regression analysis to derive the following multiple regression equation with A, B, and C as constants. At this time, the constant B becomes a negative number. By subtracting ΔDEC, which corresponds to the amount of room-temperature non-diffusible hydrogen trapped in the black tissue, from the amount of change in the total amount of room-temperature non-diffusible hydrogen ΔNDH, the amount of hydrogen trapped in the white tissue is obtained. means that
T/L10=A×ΔNDH+B×ΔDEC+C

A multiple regression equation is derived for each of a plurality of rolling device groups for multiple regression analysis, and a database in which the multiple regression equations are classified for each operating condition (that is, for each rolling device group for multiple regression analysis) and stored is prepared in advance. create it. This database preferably stores as many multiple regression equations as possible. It is preferable to obtain multiple regression equations for as many types of rolling devices as possible and create a database. That is, various types of rolling devices with different at least one of the types, shapes, dimensions, and materials (types of steel forming the steel rolling members) are operated under many operating conditions, and many multiple regression equations are calculated. It is preferable to create a database in which the multiple regression equations are classified according to these conditions and stored.

Using the database created in this manner, the fatigue progression T/L10 of the rolling device whose fatigue progression is to be evaluated is calculated. The method is described below.
As for the rolling devices whose fatigue progression should be evaluated, the total amount of room temperature non-diffusible hydrogen contained in the steel rolling members of the rolling devices that have not been operated and the black structure measure the quantity and Furthermore, the rolling device whose fatigue progress is to be evaluated is operated under predetermined operating conditions, and the normal temperature contained in the rolling contact fatigue portion of the steel rolling contact member of the rolling device whose fatigue progress is to be evaluated after operation The total amount of non-diffusible hydrogen and the amount of black tissue are measured. In addition, instead of measuring the total amount of normal temperature non-diffusible hydrogen and the amount of black structure contained in the steel rolling member of the rolling device whose fatigue progress before operation is to be evaluated, the fatigue progress after operation may be measured for the total amount of room-temperature non-diffusible hydrogen and the amount of black structure contained in the non-rolling contact fatigue portion of the steel rolling member of the rolling device to be evaluated.

As a result, it is possible to obtain the measurement results of the rolling device whose fatigue progress should be evaluated before operation and the measurement results of the rolling device whose fatigue progress should be evaluated after operation. The amount of change ΔNDH in the total amount of normal-temperature non-diffusible hydrogen contained in the rolling contact fatigue site and the amount of change ΔDEC in the amount of black tissue in the rolling contact fatigue site before and after operation are calculated.

Here, a database prepared in advance is searched, and the multiple regression equation when the temperature during operation and the hydrogen environment during operation are all the same as the operating conditions of the rolling device whose fatigue progress is to be evaluated. is retrieved from the database. As a result of searching the database, if there is no "multiple regression equation when all the operating conditions are the same", extract any multiple regression equations from the database and use the extracted multiple regression equations. The "multiple regression equation when all operating conditions are the same" is estimated from the equation by a method such as linear interpolation. That is, each constant of the "multiple regression equation when all the operating conditions are the same" is estimated from each constant of the extracted multiple regression equations by a technique such as linear interpolation.

A plurality of multiple regression equations extracted from the database, for example, when the temperature during operation and the hydrogen environment during operation are partly the same as the operating conditions of the rolling device for which the degree of progress of fatigue is to be evaluated, but are different in the other part. A multiple regression equation or a multiple regression equation in the case where the operating conditions of the rolling device whose degree of progress of fatigue should be evaluated are all close to each other can be used.
Then, by substituting the amount of change ΔNDH in the total amount of room-temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue for the rolling device whose fatigue progression is to be evaluated into the multiple regression equation obtained or estimated from the database, fatigue A fatigue progress T/L10 of the rolling device whose progress is to be evaluated is calculated.

As described above, before and after the operation of the rolling device, the total amount of room temperature non-diffusible hydrogen and the amount of black structure contained in the rolling contact fatigue portion of the steel rolling contact member were measured. The amount of change ΔNDH in the total amount of normal temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue are obtained. By substituting these variations into the multiple regression equation, the degree of progress of fatigue of the rolling device can be evaluated. In addition, it is possible to evaluate the progress of fatigue even for rolling devices used in actual equipment, which is usually difficult to evaluate. Furthermore, even at a stage where white structure damage such as white structure exfoliation has not occurred in the steel rolling contact member, the progress of fatigue can be evaluated.

In the fatigue progress evaluation method of the present embodiment, the amount of black tissue may be calculated from the half width of the detection peak of black tissue by X-ray analysis, as described above.
Further, in the fatigue progress evaluation method of the present embodiment, in at least one of the rolling device for database creation and the rolling device whose fatigue progress is to be evaluated, the amount of change ΔNDH in the total amount of normal temperature non-diffusible hydrogen is as follows. It can be calculated as follows. First, each of the steel rolling contact members when not in operation and the rolling fatigue site after operation is heated while increasing the temperature to release hydrogen, and by detecting the released hydrogen with a detector, a plurality of Obtain a hydrogen desorption curve consisting of overlapping small peaks of . Statistical processing then separates the hydrogen release curve into a plurality of small peaks.

Next, the corresponding small peaks of the steel rolling contact member before operation and the rolling contact fatigue portion after operation were compared, and the small peak where the amount of detected hydrogen increased the most was regarded as the room temperature non-diffusible A change amount ΔNDH of the total amount of room-temperature non-diffusible hydrogen is calculated from the small peak obtained by detecting the total amount of hydrogen.
By separating the hydrogen release curve into multiple small peaks by statistical processing and extracting only room temperature non-diffusible hydrogen that is harmful to the life due to white tissue exfoliation, it is possible to evaluate the progress of fatigue and predict the life with high accuracy. be able to. Although the type of statistical processing is not particularly limited, for example, statistical processing using Gaussian distribution can be mentioned.

Before obtaining a hydrogen release curve by heating while increasing the temperature to release hydrogen, the steel rolling member may be kept at a temperature of 100° C. or less to release room temperature diffusible hydrogen from the steel rolling member. By doing so, the room temperature diffusible hydrogen is reliably released from the steel rolling member, so that the amount of the room temperature non-diffusible hydrogen can be measured more accurately.
The temperature at which the steel rolling member is held is not particularly limited as long as it is 100° C. or less, but in order to suppress the release of room temperature non-diffusible hydrogen and more accurately measure the amount of room temperature non-diffusible hydrogen. is more preferably 80° C. or lower. In addition, the temperature at which the steel rolling member is held is not particularly limited as long as it is higher than room temperature, but the room temperature diffusible hydrogen is reliably released to more accurately measure the amount of room temperature non-diffusible hydrogen. In order to do so, it is more preferably 35° C. or higher.

The embodiment described above is an example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications or improvements can be added to the present embodiment, and forms to which such modifications or improvements are added can also be included in the present invention. Furthermore, the present invention is a method for evaluating the progress of fatigue of a rolling device, but is applicable not only to rolling devices but also to two rolling members that are in rolling contact with each other.

EXAMPLES The present invention will be described more specifically below by way of examples. First, create a database according to the following procedures (1) to (12).
[I] Creating a database (1) A rolling bearing for creating a database of the same type (same type, shape, dimensions, material (type of steel forming the bearing ring), etc.) as the rolling bearing whose fatigue progress should be evaluated. prepare. Then, the portion immediately below the groove bottom of the raceway groove of the bearing ring of the rolling bearing for database creation which has not yet been operated is cut out, and the amount of normal temperature non-diffusible hydrogen is measured by the method described later (see [II] Normal temperature non-diffusible hydrogen measurement method). Measure.

(2) After separating the hydrogen release curve obtained in (1) into a plurality of small peaks by statistical processing using a Gaussian distribution (see [III] Separation method for small peaks by statistical processing described later) , an evaluation peak, which is a small peak obtained by detecting the total amount of room-temperature non-diffusible hydrogen, is extracted from among the separated small peaks. This evaluation peak is a peak in which both normal-temperature non-diffusible hydrogen trapped in the black tissue and normal-temperature non-diffusible hydrogen trapped in the white tissue are detected.

(3) X-ray analysis is performed on the portion immediately below the groove bottom of the raceway groove of the bearing ring of the database-creating rolling bearing that has not yet been operated, and the half-value width of the detection peak of the black tissue is measured by the X-ray analysis.
(4) The rolling bearing for creating a database that has not yet been operated is operated under predetermined operating conditions, and a rolling test is conducted. The operating time shall be less than the L10 life of the rolling bearing for database creation.

(5) Cut out the portion immediately below the groove bottom of the raceway groove of the bearing ring of the database-creating rolling bearing whose operation has been completed, and measure room-temperature non-diffusible hydrogen by the method described later (see [II] Normal-temperature non-diffusible hydrogen measurement method). Measure quantity. The area immediately below the groove bottom is the load zone of the bearing ring, and is a mixed portion of black texture and white texture. FIG. 3 shows a microphotograph of a cross section of the groove bottom of the bearing ring immediately below the bearing ring after the end of operation, and FIG. 4 shows a schematic explanatory view for explaining FIG. When cutting out the portion directly below the groove bottom, it is preferable to cut only the area where the rolling elements travel.

(6) In the same manner as in (2) above, after separating the hydrogen desorption curve obtained in (5) into a plurality of small peaks, the total amount of normal temperature non-diffusible hydrogen is calculated from among the separated small peaks. An evaluation peak, which is a detected small peak, is extracted.
(7) X-ray analysis is performed on the portion directly below the groove bottom of the raceway groove of the raceway ring of the database-creating rolling bearing whose operation has been completed, and the half-value width of the detection peak of the black texture is measured by the X-ray analysis.

(8) Compare the measurement results of the database creation rolling bearing that has not been operated with the measurement results of the database creation rolling bearing that has been operated. Then, from the difference in the size of the evaluation peak, the amount of change ΔNDH in the total amount of normal temperature non-diffusible hydrogen contained in the groove bottom (rolling contact fatigue site) before and after operation is calculated, and the half width is calculated. From the difference, the amount of change ΔDEC in the amount of black tissue that is present immediately below the groove bottom before and after operation is calculated.

(9) The temperature during operation and the hydrogen environment of the rolling bearing for database creation during operation were not changed from the above operating conditions, and the load (magnitude of stress acting on the rolling fatigue portion of the bearing ring due to rolling contact) and A number of rolling tests are performed with various running times. Then, according to the above procedures (4) to (8), the amount of change ΔNDH in the total amount of room temperature non-diffusible hydrogen contained in the groove bottom immediately below the groove bottom before and after the operation, and the amount of black texture that the groove bottom has A plurality of data on the amount of change ΔDEC are accumulated.

(10) The degree of fatigue progress T defined by the obtained amount of change ΔNDH in the total amount of normal temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue, and the ratio of operating time T to L10 life of the rolling bearing for database creation /L10 is formulated using multiple regression analysis to derive a multiple regression equation T/L10=A×ΔNDH+B×ΔDEC+C where A, B, and C are constants. Here, A×ΔNDH+B×ΔDEC+C is defined as the degree of hydrogen damage.

(11) Create a graph with the degree of hydrogen damage on the X-axis and the progress of fatigue on the Y-axis.
(12) The degree of hydrogen damage was calculated from the obtained amount of change ΔNDH in the total amount of room temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of black tissue, and the X axis was the degree of hydrogen damage and the Y axis was the degree of fatigue progression ( While plotting on the graph of (11), the straight line which shows the multiple regression equation derived|led-out by (10) is drawn on the graph of (11). An example of the graph is shown in FIG.
The graph shown in FIG. 1 is an example in the case of using a deep groove ball bearing with bearing number 6206 as a rolling bearing for creating a database. The inner and outer rings of this deep groove ball bearing are made of SUJ2, and the rolling elements are made of carbonitrided SUJ2. Further, the operating conditions of the deep groove ball bearing are that the dynamic equivalent load P/basic dynamic load rating C is 0.21 to 0.60, the rotational speed is 3000 min ^-1 , the temperature is 110 ° C, and the lubrication used The oil is equivalent to ISO-VG32.

[II] Method for measuring non-diffusible hydrogen at room temperature (1) Cut the bearing ring of the rolling bearing, and cut out the portion immediately below the groove bottom of the raceway groove. When cutting out the portion immediately below the groove bottom of the raceway groove of the bearing ring of the rolling bearing that has undergone rolling contact fatigue, it is preferable to cut only the area where the rolling elements travel.

(2) Heating the immediately lower portion of the cut groove bottom while increasing the temperature in a vacuum or an inert gas such as argon to release the room-temperature non-diffusible hydrogen trapped in the steel. The released hydrogen is detected by a detector to obtain a hydrogen release curve consisting of overlapping small peaks. The heating rate is preferably 50° C./h to 600° C./h in order to facilitate peak separation by statistical processing. The temperature may be raised using a thermal desorption spectrometer. As a detector, a quadrupole mass spectrometer or gas chromatography can be used.

[III] Method of Separating Small Peaks by Statistical Processing (1) Steel contains hydrogen trap sites such as dislocations, grain boundaries, vacancies, vacancy clusters, and precipitates, each of which has a different trap energy. Therefore, when the temperature immediately below the cut groove bottom is heated while increasing the temperature to release hydrogen, the temperature at which hydrogen is released differs depending on the trap site, so a hydrogen release curve in which a plurality of small peaks overlap is obtained. .

(2) The hydrogen desorption curve can be separated into a plurality of small peaks by statistical analysis using a Gaussian distribution.
An example is shown in FIG. The chart in FIG. 2 depicts a hydrogen desorption curve obtained by measurement using a thermal desorption spectrometer and five small peaks separated by statistical processing using a Gaussian distribution.
(3) Compare the corresponding small peaks of the rolling bearing that has not been operated and the rolling bearing that has been operated, and detect the small peak where the amount of detected hydrogen has increased the most, and the total amount of normal temperature non-diffusible hydrogen. The evaluation peak is a small peak obtained by From this evaluation peak, the amount of change ΔNDH in the total amount of room-temperature non-diffusible hydrogen is calculated and used for evaluating the progress of fatigue and predicting the life.

Next, the prepared database is used to evaluate the progress of fatigue of the rolling bearing to be evaluated.
[IV] Evaluation of fatigue progress of rolling bearings used in actual machines (1) Rolling bearings used in actual machines in the market (hereinafter referred to as "actual bearings") are used as rolling bearings whose fatigue progress should be evaluated. . The operating conditions of the actual bearing, that is, the temperature during operation and the hydrogen environment of the actual bearing during operation, may or may not be the same as the operating conditions of the rolling bearing for creating the database from which the multiple regression equation was derived in [I]. It doesn't have to be.
Of the bearing ring of this actual bearing, cut out the shoulder portion, which is the part that is not subjected to rolling fatigue, and measure the amount of non-diffusible hydrogen at room temperature by the method described above (see [II] Measurement method for non-diffusible hydrogen at room temperature). do. It should be noted that instead of the shoulder portion of the bearing ring, the portion immediately below the groove bottom of the non-load zone portion of the raceway groove of the bearing ring may be cut out.

(2) After separating the hydrogen desorption curve obtained in (1) into a plurality of small peaks by statistical processing using a Gaussian distribution (see [III] Separation method of small peaks by statistical processing), An evaluation peak, which is a small peak obtained by detecting the total amount of room-temperature non-diffusible hydrogen, is extracted from among the plurality of small peaks obtained.

(3) X-ray analysis is performed on the shoulder portion of the bearing ring of the actual bearing (the portion at a depth of 100 μm from the surface), and the half-value width of the detection peak of the black texture is measured by the X-ray analysis.
(4) From the raceway groove of the bearing ring of the actual bearing, cut out the portion immediately below the groove bottom in the load zone, and measure the amount of non-diffusible hydrogen at room temperature by the method described above (see [II] Measuring method for non-diffusible hydrogen at room temperature). to measure. When cutting out the portion directly below the groove bottom, it is preferable to cut only the area where the rolling elements travel.

(5) In the same manner as in (2) above, after separating the hydrogen desorption curve obtained in (4) into a plurality of small peaks, the total amount of normal temperature non-diffusible hydrogen is calculated from among the separated small peaks. An evaluation peak, which is a detected small peak, is extracted.
(6) X-ray analysis is performed on the groove bottom of the raceway groove of the bearing ring of the actual bearing, and the half width of the detection peak of the black texture is measured by the X-ray analysis.

(7) Compare the measurement result of the shoulder portion of the actual bearing with the measurement result of the groove bottom directly below. Then, from the difference in the magnitude of the evaluation peak, the amount of change ΔNDH in the total amount of room-temperature non-diffusible hydrogen contained in the bearing ring with and without fatigue is calculated. A change amount ΔDEC of the amount of black tissue of the bearing ring is calculated.
(8) Substituting the amount of change in the total amount of room-temperature non-diffusible hydrogen ΔNDH and the amount of change in the amount of black tissue ΔDEC calculated in (7) into the multiple regression equation derived in [I], the degree of hydrogen damage and fatigue A degree of progress T/L10 is calculated.

From the numerical value of the calculated degree of progress of fatigue T/L10, the degree of progress of fatigue of the actual bearing can be evaluated in the form of a ratio to the life of L10. For example, when the numerical value of the calculated fatigue progress T/L10 is 0.3, it can be evaluated as "fatigue progress corresponding to 30% of L10 life". For example, if the numerical value of the fatigue progress T/L10 is 0.1 to 0.3, there is no white tissue, if it is 0.4 to 0.6, the amount of white tissue is small, and 0.7 to 1.0. If it is 0, it can be evaluated that the amount of white tissue is large.

Further, the remaining life of the actual bearing can be predicted from the calculated value of the degree of progress of fatigue T/L10. For example, when the numerical value of the calculated degree of progress of fatigue T/L10 is 0.3, it can be predicted that "the remaining life of the actual bearing is 70% of the L10 life." Furthermore, by multiplying (multiplying) the calculated value of the degree of progress of fatigue T/L10 by the L10 life of the actual bearing, it is possible to estimate the actual operating time of the actual bearing.

Claims (4)

A method for evaluating fatigue progression in a rolling device comprising two rolling members in rolling contact with each other, at least one of said two rolling members being a steel rolling member, comprising:
The degree of progress of fatigue is the degree of progress of fatigue of the rolling device due to white tissue flaking occurring in the steel rolling contact member,
A rolling contact fatigue portion, which is a portion of the steel rolling member subjected to rolling contact fatigue due to rolling contact, has a white structure and a black structure. A fatigue progress evaluation method for evaluating the fatigue progress of the rolling device based on the amount of hydrogen. A rolling device of the same kind as the rolling device whose fatigue progress should be evaluated is prepared as a rolling device for creating a database,
While measuring the total amount of normal temperature non-diffusible hydrogen and the amount of black structure contained in the steel rolling members of the database creation rolling device that has not been operated,
At least one of the magnitude of the stress acting on the rolling contact fatigue portion of the steel rolling member due to rolling contact, the operating time, the temperature during operation, and the hydrogen environment of the rolling device for creating the database during operation is different. The database-creating rolling device is operated under each of a plurality of operating conditions, and the total amount of room-temperature non-diffusible hydrogen contained in the rolling fatigue sites of the steel rolling contact members of the database-creating rolling device after operation; measuring the amount of black tissue and
From the measurement results of the database-creating rolling device that has not been operated and the measurement results of the database-creating rolling device that has been operated, the room-temperature non-diffusible hydrogen contained in the rolling contact fatigue portion before and after operation Calculate the amount of change ΔNDH in the total amount of and the amount of change ΔDEC in the amount of black structure possessed by the rolling contact fatigue site,
A plurality of rolling bearings operated under operating conditions in which the temperature during operation and the hydrogen environment of the database-creating rolling device during operation are the same, and at least one of the magnitude of stress acting on the rolling contact fatigue portion and the operating time are different. The database-creating rolling devices are a multiple regression analysis rolling device group, and the total amount of the room temperature non-diffusible hydrogen for the database-creating rolling devices included in one multiple regression analysis rolling device group Extracting the amount of change ΔNDH and the amount of change ΔDEC in the amount of the black tissue,
The degree of fatigue progress defined by the amount of change ΔNDH in the total amount of the extracted normal-temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of the black tissue extracted, and the ratio of the operating time T to the L10 life of the rolling device for database creation. T / L10 is formulated using multiple regression analysis to derive the following multiple regression equation with A, B, and C as constants,
T/L10=A×ΔNDH+B×ΔDEC+C
Deriving the multiple regression equations for each of the plurality of rolling device groups for multiple regression analysis, and creating in advance a database in which the multiple regression equations are classified and stored for each operating condition,
For the rolling device to be evaluated for the progress of fatigue, the total amount of normal temperature non-diffusible hydrogen and the amount of black structure contained in the steel rolling member of the rolling device that is not in operation are measured, and the progress of fatigue The rolling device whose fatigue degree should be evaluated is operated, and the total amount of normal temperature non-diffusible hydrogen contained in the rolling contact fatigue site of the steel rolling contact member of the rolling device whose fatigue progress degree after operation is to be evaluated measure the amount of tissue and
From the measurement results of the non-operated rolling device whose fatigue progress should be evaluated and the measurement results of the rolling device whose fatigue progress after operation should be evaluated, the rolling contact fatigue parts before and after operation Calculate the amount of change ΔNDH in the total amount of non-diffusible hydrogen contained at room temperature and the amount of change ΔDEC in the amount of black tissue in the rolling contact fatigue site,
Obtaining from the database the multiple regression equation when the temperature during operation and the hydrogen environment during operation are all the same as the operating conditions of the rolling device for which the progress of fatigue is to be evaluated,
Substituting the amount of change ΔNDH in the total amount of room-temperature non-diffusible hydrogen and the amount of change ΔDEC in the amount of the black tissue for the rolling device for which the degree of progress of fatigue is to be evaluated into the multiple regression equation obtained from the database 2. The fatigue progress evaluation method according to claim 1, wherein the fatigue progress T/L10 of the rolling device whose fatigue progress is to be evaluated is calculated. 3. The fatigue progress evaluation method according to claim 2, wherein the amount of said black tissue is calculated from the half-value width of a detection peak of black tissue by X-ray analysis. In at least one of the database-creating rolling device and the rolling device for which the degree of progress of fatigue should be evaluated, the steel rolling member before operation and the rolling contact fatigue portion after operation are heated. By heating while heating, hydrogen is released, the released hydrogen is detected with a detector to obtain a hydrogen release curve in which a plurality of small peaks overlap, and the hydrogen release curve is statistically processed to the above-mentioned plurality of separated into small peaks,
Corresponding small peaks in the steel rolling contact member before operation and the rolling contact fatigue portion after operation are compared, and the small peak at which the amount of detected hydrogen increases the most is regarded as the normal temperature non-diffusion 4. The fatigue progress evaluation method according to claim 2 or 3, wherein the detected small peak is the total amount of non-diffusible hydrogen at room temperature, and the amount of change ΔNDH in the total amount of normal-temperature non-diffusible hydrogen is calculated from the small peak.

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