JP7138512B2 - Hydrogen resistance evaluation test method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrogen resistance evaluation test method.

When a rolling bearing is used under conditions that involve sliding, the hydrogen generated by decomposition of the lubricant or water mixed in the lubricant (hereinafter, such a reaction is referred to as a hydrogen generation reaction) Also, it may enter the inside of the rolling elements and bearing ring from the raceway surface. In particular, when the new metal surface is exposed due to the metallic contact between the rolling elements and the bearing rings, the penetration of the hydrogen evolution reaction and the hydrogen generated by the hydrogen evolution reaction into the rolling elements and the bearing rings is promoted. Such penetration of hydrogen may lead to premature flaking due to hydrogen embrittlement. Among the hydrogen that has penetrated into the rolling elements and bearing rings, diffusible hydrogen has a large effect on premature flaking caused by hydrogen embrittlement. This is because diffusible hydrogen can move relatively freely in the steel that makes up the rolling elements and bearing rings.

As a method for measuring the diffusible hydrogen that has penetrated into the material by actively exposing the nascent metal surface and evaluating the hydrogen resistance of the material, the method described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-234833) and Non-Patent Document 1 (Toshiya Kinami, Effect of penetrating hydrogen on rolling contact fatigue strength of hydrogen embrittlement type, Daido Steel Technical Report Vol.84, No.1, pp. 55-60, 2013) is known how.

In the method described in Patent Document 1, a sliding member is pressed against the surface of the test piece and the sliding member is slid on the surface of the test piece. As a result, hydrogen is generated on the surface of the test piece, and the hydrogen penetrates into the interior of the test piece. Then, the hydrogen resistance of the material is evaluated by detecting the hydrogen that permeates the test piece.

In the method described in Non-Patent Document 1, a roller chipping test (a two-cylinder rolling contact fatigue test with slip) is performed. In the method described in Non-Patent Document 1, the hydrogen resistance of the material is evaluated by reproducing early flaking caused by hydrogen embrittlement in the test and detecting diffusible hydrogen that has entered the test piece during the test. ing.

JP 2013-234833 A

Toshiya Kinami, Effect of Penetrating Hydrogen on Rolling Contact Fatigue Strength of Hydrogen Embrittlement Type, Daido Steel Technical Report Vol.84, No.1, pp.55-60, 2013

In the method described in Patent Literature 1, hydrogen generated by direct contact between the test piece and the sliding member, entering the test piece, and permeating the test piece is targeted for detection. Therefore, according to the method described in Patent Document 1, for example, the influence of the lubricant cannot be considered. Moreover, the method described in Patent Document 1 is an analysis method in a sliding mode, and is not necessarily realistic as a method for evaluating the hydrogen resistance of rolling bearings.

The outer diameter of the test piece used in the method described in Non-Patent Document 1 is large (more specifically, 26 mm). Normally, the size of a test piece that can be measured by a hydrogen analyzer is 20 mm or less in outer diameter. Therefore, according to the method described in Non-Patent Document 1, it is necessary to cut the test piece for measuring diffusible hydrogen.

In the method described in Non-Patent Document 1, the number of rotations of the test piece is high (more specifically, about 750 to 1500 rotations/min). The test temperature is high (more specifically 90°C). Therefore, in order to prevent the seizure of the test piece, ancillary equipment for supplying a large amount of temperature-controlled lubricating oil is required.

The present invention has been made in view of the problems of the prior art as described above. More specifically, the present invention provides a test method for evaluating diffusible hydrogen that does not require cutting a test piece.

A hydrogen resistance evaluation test method according to one aspect of the present invention includes a step of rotating a first test piece around a central axis, and a step of rotating a second test piece around the central axis relative to the first test piece. and a step of supplying lubricant to the outer peripheral surfaces of the first and second test pieces to form an oil film, and a step of performing a rolling and sliding test, and measuring the amount of diffusible hydrogen in the first test piece. and a step of performing. The first and second test pieces are cylindrical and made of steel. When the first test piece and the second test piece are rotating around the central axis, the outer peripheral surface of the first test piece and the outer peripheral surface of the second test piece come into contact with each other through the oil film. The outer diameter of the first test piece is 20 mm or less.

In the above hydrogen resistance evaluation test method, when the first test piece and the second test piece are rotating around the central axis, the temperature of the first test piece and the second test piece is 40 ° C. or less. good.

In the above hydrogen resistance evaluation test method, when the peripheral speed due to the rotation of the first test piece around the central axis is u _D and the peripheral speed due to the rotation of the second test piece around the central axis is u _F , ( The absolute value of u _D −u _F )/{(u _D +u _F )/2}×100 may be 1 or more.

In the above hydrogen resistance evaluation test method, the oil film parameter of the oil film may be 0.15 or less.

In the above hydrogen resistance evaluation test method, the rotational speed of the first test piece around the central axis may be 100 revolutions/min or less.

In the above hydrogen resistance evaluation test method, the maximum contact stress between the first test piece and the second test piece may be 2.5 GPa or more.

In the above hydrogen resistance evaluation test method, the lubricating oil is supplied by bringing a cloth member impregnated with the lubricating oil into contact with at least one of the outer peripheral surface of the first test piece and the outer peripheral surface of the second test piece. good.

According to the hydrogen resistance evaluation test method according to one aspect of the present invention, diffusible hydrogen can be measured without cutting the test piece.

1 is a perspective view of a first test piece 1; FIG. 3 is a perspective view of a second test piece 2; FIG. 3 is a schematic diagram of a rolling and sliding test device 3. FIG. It is a graph which shows the test result of a 1st test. It is a graph which shows the test result of a 2nd test. It is a graph which shows the test result of a 3rd test. It is a graph which shows the test result of the 4th test.

Details of embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are given to the same or corresponding parts, and the description thereof will not be repeated.

(Test pieces)
The test piece used in the rolling and sliding test method according to the embodiment will be described below.

FIG. 1 is a perspective view of the first test piece 1. FIG. As shown in FIG. 1, the first test piece 1 is cylindrical. The first test piece 1 has an outer diameter D1. The outer diameter D1 is 20 mm or less. The first test piece 1 is a test piece that is subjected to the measurement of diffusible hydrogen after the rolling and sliding test method is carried out.

The first test piece 1 is made of steel. The steel that constitutes the first test piece 1 is, for example, high carbon chromium bearing steel defined in the JIS standard (JIS4805:2008). The steel forming the first test piece 1 may be SUJ2 or SUJ3 defined in the JIS standard (JIS4805:2008).

FIG. 2 is a perspective view of the second test piece 2. FIG. As shown in FIG. 2, the second test piece 2 is cylindrical. The second test piece 2 has an outer diameter D2. Outer diameter D2 is preferably larger than outer diameter D1. The outer diameter D2 is, for example, 80 mm.

The second test piece 2 is made of steel. The steel constituting the second test piece 2 is, for example, high carbon chromium bearing steel defined in JIS (JIS4805:2008). The steel constituting the second test piece 2 may be SUJ2 or SUJ3 defined in the JIS standard (JIS4805:2008).

(test equipment)
The rolling-slip testing apparatus 3 used for the rolling-slip testing method according to the embodiment will be described below.

FIG. 3 is a schematic diagram of the rolling and sliding test device 3. As shown in FIG. As shown in FIG. 3, the rolling and sliding test device 3 includes a first servomotor 31, a first belt 32, a first spindle 33, a second servomotor 34, a second belt 35, a second spindle 36 and

A rotating shaft of the first servomotor 31 is connected to the first belt 32 . One end of the first spindle 33 is connected to the first belt 32 . Thereby, the first servomotor 31 rotates the first spindle 33 around the central axis.

A first test piece 1 is attached to the other end of the first spindle 33 . Therefore, the first servomotor 31 rotates the first test piece 1 around the central axis.

A rotating shaft of the second servomotor 34 is connected to the second belt 35 . One end of the second spindle 36 is connected to the second belt 35 . Thereby, the second servomotor 34 rotates the second spindle 36 around the central axis.

A second test piece 2 is attached to the other end of the second spindle 36 . Therefore, the second servomotor 34 rotates the second test piece 2 around the central axis.

The first test piece 1 and the second test piece 2 are arranged so that their outer peripheral surfaces are in contact with each other via an oil film, which will be described later. That is, the first test piece 1 and the second test piece 2 rotate around the central axis while their outer peripheral surfaces are in contact with each other via the oil film. The circumferential speeds of the first test piece 1 and the second test piece 2 are set to be different from each other. That is, the second test piece 2 rotates relative to the first test piece 1 around the central axis. As a result, slip occurs between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 .

Although not shown in FIG. 3 , lubricating oil is supplied to the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 . Lubricating oil is supplied, for example, by bringing a cloth member impregnated with lubricating oil into contact with at least one of the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 . This cloth member is, for example, a felt pad. An oil film is formed on the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 by supplying the lubricating oil. Bearing oil, for example, is used as the lubricating oil.

(Test conditions)
Test conditions in the rolling and sliding test method according to the embodiment will be described below.

The slip ratio is ₍ u _{D −u F} )/{(u _D +u _F )/2}×100. The absolute value of the slip ratio is preferably 30% or more.

The circumferential speed _uD is calculated by multiplying the rotational speed of the first test piece 1 around the central axis by the outer diameter D1. The circumferential speed _uF is calculated by multiplying the rotational speed of the second test piece 2 around the central axis by the outer diameter D2. Therefore, the slip ratio can be adjusted by appropriately changing the rotation speed of the first servomotor 31, the rotation speed of the second servomotor 34, the outer diameter D1, and the outer diameter D2.

The oil film parameter Λ of the oil film formed on the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is calculated by h ₀ /(σ ₁ ² +σ ₂ ² ) ^1/2 . _h0 is the minimum oil film thickness. σ ₁ is the standard deviation of the surface arithmetic mean roughness on the outer peripheral surface of the first test piece 1 . σ ₂ is the standard deviation of the surface arithmetic mean roughness on the outer peripheral surface of the second test piece 2 . σ ₁ and σ ₂ are measured by a surface roughness tester.

h ₀ is calculated by the formula of Chittenden et al. More specifically, h ₀ is R _x ×0.368×U ^0.68 ×G ^0.49 ×W ^−0.073 ×[1−exp{−1.23×(R _y /R _x } ^{2 /3} }].

_Rx is the equivalent radius of curvature in the direction of flow and _Ry is the equivalent radius of curvature in the direction perpendicular to the flow. R _x is calculated by 1/R _x = (1/R _x1 ) + (1/R _x2 ), and R _y is calculated by 1/R _y = (1/R _y1 ) + (1/R _y2 ) be done. R _x1 is the radius of curvature of the first test piece 1 in the flow direction, R _x2 is the radius of curvature of the second test piece 2 in the flow direction, and R _y1 is perpendicular to the flow of the first test piece 1 R _y2 is the radius of curvature of the second test piece 2 in the direction orthogonal to the flow. U is a velocity parameter and is calculated by (η ₀ ×u)/(E′×R _x ). η ₀ is the atmospheric viscosity. η ₀ is calculated by ρ×ν. ρ is the density of the lubricating oil and ν is the kinematic viscosity of the lubricating oil. u is the average value of the circumferential speed _uD and the circumferential speed _uF . E' is the equivalent Young's modulus. E' is calculated by 2/E'={(1-ν ₁ ² )/E ₁ }+{(1-ν ₂ ² )/E ₂ }. E ₁ is the Young's modulus of the first specimen 1 and E ₂ is the Young's modulus of the second specimen 2 . ν ₁ is the Poisson's ratio of the first specimen 1 and ν ₂ is the Poisson's ratio of the second specimen 2 .

G is a material parameter and is calculated by α×E′. α is the viscosity pressure coefficient. α is calculated by the Wu-Klaus-Duda formula. More specifically, α is calculated by (0.1657+0.2332×log ₁₀ ν)×m×10 ⁻⁸ . ν is the kinematic viscosity of the lubricating oil. m is a constant determined by the lubricating oil and calculated by the Walther-ASTM formula. More specifically, m is calculated by log ₁₀ {log ₁₀ (ν+0.7)}=−m×log ₁₀ T+K. T is the temperature and K is a constant determined by the lubricant. By substituting the two temperatures and the kinematic viscosities at the two temperatures into the Walther-ASTM equation and solving the simultaneous equations, the values of m and K can be calculated. W is a load parameter and is calculated by w/(E'×R _x ² ). w is the load.

The oil film parameter Λ is preferably 0.34 or less. More preferably, the oil film parameter Λ is 0.15 or less.

The rotational speed of the first test piece 1 around its central axis is preferably 100 rpm or less. The rotational speed of the first test piece 1 around its central axis is preferably 50 revolutions/min or more. The rotation speed of the second test piece 2 around the central axis is preferably 6.5 revolutions/min or more and 25 revolutions/min or less.

The maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is preferably 2.5 GPa or more. The maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is calculated according to Hertz's formula.

The test time is, for example, 200 minutes or less. The test time may be 140 minutes or less. The test time is calculated from the time during which the outer peripheral surfaces of the first test piece 1 and the second test piece 2 rotating around the central axis are in contact with each other through the oil film. The test may be performed until the total number of rotations of the first test piece 1 around the central axis reaches a predetermined value. This predetermined value is, for example, 20000 times.

(Method for measuring diffusible hydrogen)
A method for measuring diffusible hydrogen will be described below.

The amount of diffusible hydrogen in the first test piece 1 is measured after performing the rolling and sliding test. The amount of diffusible hydrogen in the first test piece 1 is measured by thermal desorption analysis. In this thermal desorption analysis, the temperature of the first test piece 1 is raised from room temperature to 200°C. The heating rate in the temperature programmed desorption test is 100°C/h. The amount of diffusible hydrogen in the first test piece 1 is measured based on the integrated value of the amount of hydrogen released from the first test piece 1 during this temperature rising process.

(Experimental result)
Below, the measurement results of the amount of diffusible hydrogen in the first test piece 1 after performing the rolling and sliding test under various test conditions are shown.

<First test>
Table 1 shows the test conditions in the first test. As shown in Table 1, the steel used for the first test piece 1 and the second test piece 2 in the first test is SUJ2. The outer diameter D1 is 20 mm and the outer diameter D2 is 80 mm. The arithmetic average roughness of the outer peripheral surfaces of the first test piece 1 and the second test piece 2 is 0.02 μm. The outer peripheral surface of the first test piece 1 is linear in a cross-sectional view along the central axis. The outer peripheral surface of the second test piece 2 has a curved shape with a radius of curvature of 10 mm in a cross-sectional view along the central axis.

In the first test, the rotational speed of the first test piece 1 around its central axis was 100 rpm. The rotational speed around the central axis of the second test piece 2 is 13.5 revolutions/min. In the first test, the slip rate is 60 percent. In the first test, the maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is 3.0 GPa. The test time is 200 minutes. The oil film parameter Λ is 0.13, 0.15, 0.34, 0.64 or 0.76.

FIG. 4 is a graph showing test results of the first test. In FIG. 4, the horizontal axis is the oil film parameter Λ, and the vertical axis is the amount of diffusible hydrogen. As shown in FIG. 4, no diffusible hydrogen was detected in the range where the oil film parameter Λ was 0.34 or more. On the other hand, diffusible hydrogen was detected within the range where the oil film parameter Λ was less than 0.34. From this comparison, it was experimentally clarified that diffusible hydrogen can be introduced into the first test piece 1 by performing the rolling and sliding test according to the embodiment within the range where the oil film parameter Λ is less than 0.34. rice field.

<Second test>
Table 2 shows the test conditions in the second test. As shown in Table 2, the test conditions of the second test are the same as those of the first test with respect to the first test piece 1, the second test piece 2, the rotation speed, and the test time.

In the second test, the maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is 2.0 GPa, 2.3 GPa, 2.5 GPa, 3.0 GPa or 3.5 GPa. In the second test, the slip rate is 60 percent. In the second test, lubricating oil conforming to VG5 defined in JIS K 2001:1993 was used. The oil film parameter in the second test is 0.14 or less.

FIG. 5 is a graph showing test results of the second test. In FIG. 5, the horizontal axis represents the maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2, and the vertical axis represents the amount of diffusible hydrogen. As shown in FIG. 5, diffusible hydrogen was detected in the range where the maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 was 2.5 GPa or more. From this, in the range where the maximum contact stress between the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2 is at least 2.5 GPa or more, by performing the rolling and sliding test according to the embodiment, It was experimentally clarified that diffusible hydrogen can be introduced into the first test piece 1 .

<Third test>
Table 3 shows the test conditions in the third test. As shown in Table 3, the test conditions of the third test were the maximum rotation speed of the first test piece 1, the rotation speed of the first test piece 1, and the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2. Regarding the contact stress, the test conditions are the same as those of the first test.

In the third test, the surface arithmetic mean roughness of the outer peripheral surface of the second test piece 2 is 0.6 μm. In the third test, the rotational speeds of the second test piece 2 around the central axis were 13.5 rev/min, 18.5 rev/min, 22.6 rev/min, 23.8 rev/min, and 24.7. revolutions/min, 25 revolutions/min or 25.3 revolutions/min. In the third test, the slip rate is -1 percent, 0 percent, 1 percent, 5 percent, 10 percent, 30 percent or 60 percent. In the third test, lubricating oil conforming to VG5 defined in JIS K 2001:1993 was used. The oil film parameter in the third test is 0.007 or less. In the second test, test time is 60 minutes.

FIG. 6 is a graph showing test results of the third test. In FIG. 6, the horizontal axis is the slip ratio, and the vertical axis is the amount of diffusible hydrogen. As shown in FIG. 6, diffusible hydrogen was detected when the slip ratio was -1 percent and when the slip ratio was 1 percent or more. From this, it is experimentally clarified that diffusible hydrogen can be introduced into the first test piece 1 by performing the rolling and sliding test according to the embodiment in the range where the absolute value of the slip ratio is 1% or more. was done.

<Fourth test>
Table 4 shows the test conditions in the fourth test. As shown in Table 4, the test conditions of the fourth test are the maximum contact stress between the first test piece 1, the second test piece 2, and the outer peripheral surface of the first test piece 1 and the outer peripheral surface of the second test piece 2. are common to the test conditions of the first test.

In the fourth test, the rotation speed of the first test piece 1 around the central axis is 50 rotations/min or 100 rotations/min. In the fourth test, the rotation speed around the central axis of the second test piece 2 was 6.8 rotations/min when the rotation speed around the central axis of the first test piece 1 was 50 rotations/min. When the rotation speed around the central axis of one test piece 1 is 100 rotations/min, it is 13.5 rotations/min. That is, the rotation speed of the second test piece 2 is adjusted according to the rotation speed of the first test piece 1 around the central axis so that the slip ratio is constant.

In the fourth test, the slip rate is 60 percent. In the fourth test, lubricating oil conforming to VG5 defined in JIS K 2001:1993 was used. The oil film parameter in the fourth test is 0.12 or less. The fourth test was conducted until the total number of rotations of the first test piece 1 around the central axis reached 20000 rotations.

FIG. 7 is a graph showing test results of the fourth test. In FIG. 7, the horizontal axis is the rotation speed of the first test piece 1 around the central axis, and the vertical axis is the amount of diffusible hydrogen. As shown in FIG. 7, diffusible hydrogen was detected when the rotational speed of the first test piece 1 around the central axis was in the range of 50 rpm or more and 100 rpm or less. From this, at least in the range of the rotation speed of the first test piece 1 around the central axis of 50 rpm or more and 100 rpm or less, the rolling and sliding test according to the embodiment is performed. It was experimentally clarified that diffusible hydrogen can be introduced into 1.

(Effect of rolling and sliding test method)
Below, the effect of the rolling and sliding test according to the embodiment will be described.

As described above, the outer diameter D1 of the first test piece 1 is 20 mm or less. Generally, the size of a test piece that can be put into a hydrogen analyzer is 20 mm or less in outer diameter. Therefore, according to the rolling-sliding test according to the embodiment, the diffusible hydrogen introduced by the rolling-sliding test can be measured without cutting the first test piece 1 .

In the rolling-sliding test according to the embodiment, even when the rotational speed of the first test piece 1 around the central axis is slow (for example, 100 rpm or less), the rolling-sliding test is performed to remove diffusible hydrogen. It can be introduced into the first test strip 1 . As a result, in the rolling and sliding test according to the embodiment, the temperature of the first test piece 1 and the second test piece 2 can be set to 40° C. or lower during the test. Therefore, in the rolling and sliding test according to the embodiment, incidental equipment (for example, oil temperature control equipment and lubrication Oil circulation equipment) can be made unnecessary.

Although the embodiment of the present invention has been described as above, it is also possible to modify the above-described embodiment in various ways. Also, the scope of the present invention is not limited to the embodiments described above. The scope of the present invention is indicated by the scope of claims, and is intended to include all changes within the meaning and scope of equivalence to the scope of claims.

The above embodiments are particularly advantageously applied to rolling and sliding test methods.

1 first test piece, 2 second test piece, 3 rolling and sliding test device, 31 first servo motor, 32 first belt, 33 first spindle, 34 second servo motor, 35 second belt, 36 second spindle, Λ oil film parameter, D1, D2 outer diameter, u _D , u _F peripheral speed.

Claims (3)

Rotating a first cylindrical steel test piece about a central axis; and rotating a second cylindrical steel test piece about a central axis relative to the first test piece. and a step of supplying lubricating oil to the outer peripheral surfaces of the first test piece and the second test piece to form an oil film;
measuring the amount of diffusible hydrogen in the first test piece without cutting the first test piece;
When the first test piece and the second test piece are rotating around the central axis, the outer peripheral surface of the first test piece and the outer peripheral surface of the second test piece are in contact via the oil film,
The outer diameter of the first test piece is 20 mm or less ,
The oil film parameter of the oil film is 0.34 or less,
When the first test piece and the second test piece are rotating around the central axis, the temperature of the first test piece and the second test piece is 40 ° C. or less,
When u _D is the peripheral speed of the first test piece rotated around the central axis and u _F is the peripheral speed of the second test piece rotated around the central axis , (u _D −u _F )/{( u _D + u _F )/2}×100 has an absolute value of 1 or more,
The rotation speed around the central axis of the first test piece is 100 rpm or less,
A hydrogen resistance evaluation test method , wherein the maximum contact stress between the first test piece and the second test piece is 2.5 GPa or more . The hydrogen resistance evaluation test method according to claim 1 , wherein the oil film parameter of the oil film is 0.15 or less. The lubricating oil is supplied by bringing a cloth member impregnated with the lubricating oil into contact with at least one of the outer peripheral surface of the first test piece and the outer peripheral surface of the second test piece. 2. Hydrogen resistance evaluation test method described in 2.

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