JP2004184378A - Inspection method of decarbonization or burn mark of steel component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method of decarbonization or burn mark of a steel component capable of inspecting the decarbonization or the burn mark of the steel component simply, inexpensively and safely, without performing a breaking test of the steel component and without restricting a place for inspecting the decarbonization or the burn mark of the steel component. <P>SOLUTION: An SH wave transmitter 1 and an SH wave receiver 2 are installed in a mutually separated state respectively on an orbital plane 10A of an inner ring 10. An SH wave is transmitted from the SH wave transmitter 1, and the SH wave propagated near the surface layer of the inner ring 10 made of SUJ2 is received by the SH wave receiver 2, to thereby measure a propagation velocity of the SH wave to the inner ring 10. The decarbonization or the burn mark of the inner ring 10 is determined based on the propagation velocity. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for inspecting a steel part for decarburization or burning.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a method for inspecting decarburization of steel parts, there is a method using an electron probe micro analyzer (EPMA). In the method using the electron beam microanalyzer, a sample was prepared by cutting a steel part, extracting a part of the steel part from the steel part, and polishing a surface of a part of the steel part. Thereafter, the sample is irradiated with an electron beam to generate characteristic X-rays of carbon from the sample, and the characteristic X-rays of the carbon are measured. Then, the carbon content of the steel part is detected based on the measurement of the characteristic X-rays of the carbon to determine the decarburization of the steel part.
[0003]
As another inspection method for decarburization or polishing and burning of steel parts, there is a method using an X-ray irradiator. In the method using this X-ray irradiator, a steel part is irradiated with X-rays to measure the residual stress, the half width of the diffraction angle with respect to the X-ray diffraction intensity, and the residual austenite amount of the steel part. I have. Then, decarburization or polishing and burning of the steel part is determined based on the measurement result (for example, see Patent Document 1).
[0004]
Further, as a further inspection method for decarburization or polishing and burning of a steel part, there is a method of etching a mirror-finished surface (the outermost surface of a track or a cut surface) and observing the structure.
[0005]
[Patent Document 1]
JP-A-2000-304710
[0006]
[Problems to be solved by the invention]
However, the inspection method using the electron beam microanalyzer and the etching requires destruction of a steel part, and thus has a problem that the inspected steel part cannot be used.
[0007]
Also, when inspecting steel parts for decarburization or polishing (only using the method of etching), it requires destruction of steel parts and grinding of parts of steel parts taken out of steel parts. And the cost and labor required for inspection of decarburization or polishing and burning of steel parts are increased.
[0008]
On the other hand, in the inspection method using the X-ray irradiator, a large-scale X-ray irradiator is used for inspection of decarburization or polishing and burning of steel parts, so that this X-ray irradiator can be freely carried to the inspection site. In addition, there is a problem that the place where the inspection for decarburization or polishing and burning of steel parts is limited.
[0009]
Further, since X-rays which are dangerous to the human body are used, the operation of the X-ray irradiator requires skill, and there is a problem that the inspection of decarburization or polishing and burning of steel parts cannot be performed safely and easily.
[0010]
Therefore, an object of the present invention is to limit the place where the inspection of decarburization or polishing and firing of steel parts is not limited, and to easily perform decarburization or polishing and firing of steel parts without performing destructive inspection of steel parts. It is an object of the present invention to provide a method for inspecting decarburization or polishing and burning of steel parts which can be inspected cheaply and safely.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the method for inspecting decarburization or polishing and burning of a steel part according to the first aspect of the present invention includes transmitting a surface wave or a SH (horizontally polarized shear wave) to a surface layer of the steel part. It is characterized in that the steel part is inspected for decarburization or burning by measuring the propagation speed of the surface wave or SH wave propagating in the surface layer.
[0012]
The above-mentioned polishing and sintering is the final step of polishing the surface of a steel part, in which the surface temperature of the surface of the steel part rises, the steel part is quenched again, and the material of the steel part is re-fired. It refers to a phenomenon in which a steel part becomes inconsistent with a predetermined standard because the steel part becomes hard and brittle or the material of the steel part softens due to tempering of the steel part. In the case of the above-mentioned reheating, it is relatively easy to find the abnormality of the steel part because it occurs when an abnormality occurs in the production line of the steel part, while in the case of the above-mentioned tempering, the abnormality of the steel part is found. Is difficult. The inspection method for polishing and polishing of a steel part according to the present invention mainly performs the inspection for tempering of the steel part.
[0013]
The above-mentioned decarburization is a phenomenon that occurs when steel is heated in an oxidizing atmosphere by reacting with oxygen in the steel. In the case of high-carbon steel such as bearing steel, the decarburization occurs relatively easily. It is known.
[0014]
The SH wave is an ultrasonic wave that propagates along the surface of the material in a direction in which the main vibration direction is perpendicular to the propagation direction and is substantially parallel to the surface of the material. Ultrasonic waves whose vibration direction is normal to the surface of the material and propagates along the surface of the material.
[0015]
In addition, the method for inspecting decarburization or polishing and burning of steel parts of the present invention is mainly performed for quality assurance of steel parts before use, but inspects the deterioration state of steel parts in use. Needless to say, it may be carried out in order to do so.
[0016]
The inspection method of decarburization or polishing and burning of a steel part of the first invention is performed, for example, as follows. The surface wave transmitter or the SH wave transmitter and the surface wave receiver or the SH wave receiver are arranged at predetermined intervals on the surface of a steel part to be inspected, and the surface wave transmitter or The surface wave or the SH wave transmitted from the SH wave transmitter and propagated through the steel part is received by the surface wave receiver or the SH wave receiver, and the propagation speed of the received surface wave or SH wave is determined. This is done by measuring.
[0017]
According to the method for inspecting decarburization or polishing and burning of a steel part of the first invention, for example, a surface wave transmitter or an SH wave transmitter and a surface wave receiver or an SH wave receiver are used for the steel part. Since the inspection for decarburization or polishing and burning of steel parts can be performed only by arranging them at predetermined intervals on the surface and measuring the propagation speed of surface waves or SH waves, the above electron beam microanalyzer can be used. Unlike the inspection method using etching or etching, there is no need to break or mirror-finish the steel part to inspect the decarburization or polishing and burning of the steel part. In addition, the number of steps for inspecting steel parts for decarburization or polishing and burning can be greatly reduced, and the cost and labor required for inspection of steel parts for decarburizing or polishing and burning can be significantly reduced.
[0018]
Further, according to the method for inspecting decarburization or polishing and burning of a steel part according to the first aspect of the present invention, a light, small and portable surface wave transmitter or SH wave transmitter, and a surface wave receiver or SH wave reception are provided. And the inspection of steel parts for decarburization or polishing and burning based on the propagation speed of surface waves or SH waves that are safe for the human body. Unlike the inspection method using an X-ray irradiator, which uses an X-ray irradiator, the place where the inspection for decarburization or polishing and burning of steel parts is not limited, and the inspection for decarburization or polishing and burning of steel parts can be performed safely. It can be carried out.
[0019]
Further, the inspection method for decarburization or polishing and burning of a steel part according to the second invention is a method for inspecting decarburization or polishing and burning of a steel part according to the first invention, wherein the steel part is SUJ2 ( High-carbon chromium bearing steel), and when the propagation speed of the surface wave or SH wave propagating on the surface layer of the SUJ2 normally quenched product is 3180 m / s or more, the SUJ2 normally quenched. It is characterized by determining that decarburization has occurred in the goods.
[0020]
The present inventor has found that there is a correlation between the propagation speed of the SH wave and the residual stress in the normally quenched product of SUJ2, and when the propagation speed of the SH wave is 3180 m / s or more, the SUJ2 is normally quenched. It was discovered that the product had tensile stress indicating decarburization.
[0021]
According to the inspection method for decarburization or polishing and sintering of steel parts according to the second aspect of the invention, an ordinary hardened product of SUJ2 is used as a steel part, and an SH wave or a surface wave (a surface propagating through a steel part) is used. (The propagation speed of the wave is almost the same as the propagation speed of the SH wave propagating through the steel part.) When the propagation speed is 3180 m / s or more, it is determined that decarburization has occurred in the normally quenched product of SUJ2. Therefore, the normally quenched SUJ2 product in which decarburization has occurred can be reliably found and eliminated, and the high-quality, normally quenched SUJ2 product can be distinguished.
[0022]
The inspection method for decarburization or polishing and burning of a steel part according to the third invention is a method for inspecting decarburization or polishing and burning of a steel part according to the first invention, wherein the steel part is an SUJ2. When the propagation speed of the surface wave or SH wave propagating on the surface layer of the SUJ2 normally quenched product is 3150 m / s or more, polishing and burning occur in the SUJ2 normally quenched product. It is characterized by judging that there is.
[0023]
The present inventor has found that there is a correspondence between the propagation speed of the SH wave and the occurrence of polishing burn. Specifically, it has been found that when the propagation speed of the SH wave is 3150 m / s or more, the above-mentioned SUJ2 ordinary hardened product is polished and burned.
[0024]
According to the method for inspecting decarburization or polishing and sintering of steel parts according to the third aspect of the invention, a normally quenched product of SUJ2 is used as a steel part, and the propagation speed of SH waves or surface waves is 3150 m / s or more. In this case, it is determined that polishing hardening has occurred in the normally hardened SUJ2 product, so that the normally hardened SUJ2 product in which the polishing hardening has occurred can be reliably detected and eliminated, and the high-quality SUJ2 normal hardened product can be removed. Quenched products can be distinguished.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for inspecting decarburization or polishing of the inner race 10 of a cylindrical roller bearing as an embodiment of the method for inspecting decarburization or polishing and burning of a steel part of the present invention will be described in detail with reference to the illustrated embodiment. . The inner ring 10 is made of SUJ2 which is a normally hardened product.
[0026]
FIG. 1A is a plan view showing a raceway surface 10 </ b> A of the inner ring 10, and FIG. 1B is a front view of the inner ring 10. In this embodiment, as shown in FIGS. 1A and 1B, the SH wave transmitter 1 is fixed to the inner ring so that the SH wave transmitter 1 and the raceway surface 10A of the inner ring 10 make line contact with the contact line 3. The SH wave receiver 2 is installed at substantially the center of the raceway surface 10A of the inner ring 10 in the axial direction, and the SH wave receiver 2 is so arranged that the SH wave receiver 2 and the raceway surface 10A of the inner race 10 make line contact with the contact line 5. The inner race 10 is installed at a substantially axial center of the raceway surface 10A of the inner race 10 in a state of being spaced apart from the inner race 1 in the circumferential direction. The axial dimension D1 of the SH wave transmitter 1 and the SH wave receiver 2 is one third of the axial dimension D2 of the inner race 10.
[0027]
Further, in this embodiment, as shown in FIG. 1B, a straight line Lr connecting the contact line 3 of the SH wave transmitter 1 and the center P0 of the inner ring 10, the contact line 5 of the SH wave receiver 2, The angle 2α formed by the straight line Lq connecting the center P0 was set to 40 °. The contact line 3 of the SH wave transmitter 1 is included in an effective portion 7 of the surface 1A facing the orbital surface 10A of the SH wave transmitter 1 that generates the SH wave. The contact line 5 is included in the effective portion 8 of the facing surface 2A of the SH wave receiver 2 facing the track surface 10A, which can detect the SH wave.
[0028]
In the above configuration, by driving an SH wave oscillating section (not shown) composed of a piezoelectric element incorporated in the SH transmitter 1, the effective portion 7 of the facing surface 1A is vibrated, and the SH transmitter 1 Emit waves. Then, the SH wave transmitted from the SH transmitter 1 and propagated in the vicinity of the surface of the inner ring 10 is received by the SH wave receiver 2, and the propagation speed of the SH wave is measured. Specifically, the propagation time of the SH wave from the contact line 3 of the SH wave transmitter 1 to the line contact 5 of the SH wave receiver 2 is set with reference to the zero-cross point of the SH wave at which the amplitude of the SH wave becomes 0. t is obtained, and the propagation velocity V of the SH wave is measured from the following equation (1).
[0029]
V = 2πr · (2α / 360 °) ÷ t
= 2πr / (9t) [m / s] (1)
(Here, r is the radius [m] of the raceway surface 10A, and π is the pi.)
[0030]
In the table of FIG. 2, in each of the ten SUJ2 inner rings with sample numbers, the propagation speed of the SH wave propagating through the inner ring and the cut surface of the inner ring by cutting a part of the inner ring with an optical microscope are shown. The results of pass / fail of polishing and burning of the inner ring structure by observing the structure of the surface layer portion of the raceway surface of the inner ring when observed are shown. As shown in this table, the inner rings of Sample Nos. 1 to 5, which were determined to be unacceptable in the above-described tissue observation, had SH wave propagation speeds of 3160 m / s or more, while the samples which were determined to be unacceptable in the tissue observation. The inner rings Nos. 6 to 10 all have SH wave propagation speeds of 3140 m / s or less. From this, it is possible to set the threshold value of the SH wave propagation velocity for determining whether or not polishing and burning has occurred in the inner ring made of SUJ2 to 3150 m / s. This means that the tempering state is a state in which the crystal grains in the inner ring 10 made of SUJ2 are aligned, but as the crystal grains in the inner ring are aligned, the propagation speed of the SH wave propagating through the inner ring increases. Because it becomes.
[0031]
FIG. 3 is a graph of the table of FIG. In FIG. 3, the inner rings of Sample Nos. 1 to 5 existing above the line drawn above the SH wave propagation velocity of 3150 m / s are rejected, while the Sample No. 6 existing below this line is rejected. 10 to 10 show that the inner ring passes.
[0032]
FIG. 4 is a diagram showing the relationship between the propagation speed of the SH wave propagating through the inner ring made of SUJ2 and the residual stress of the inner ring measured using an X-ray irradiator.
[0033]
As shown in FIG. 4, it can be seen that the residual stress of 0 MPa in the inner race in the inspection method using the X-ray irradiation device corresponds to the SH wave propagation velocity of 3180 m / s in the inspection method of the above embodiment.
[0034]
From this, the region where the residual stress of SUJ2 is a tensile stress with 0 as a boundary is a state where SUJ2 is decarburized, and the region where the SH wave propagation speed is 3180 m / s or more is the SUJ2. Is a state in which decarburization has occurred in the inner ring 10 made of steel. This is because, in a state where decarburization is occurring, a tensile stress is generated in the inner ring made of SUJ2, and when this tensile stress is generated, the propagation speed of the SH wave propagating through the inner ring is increased.
[0035]
In the table of FIG. 5, in each of the ten inner rings with sample numbers, the propagation speed of the SH wave propagating in the surface layer of the raceway surface of the inner ring and the raceway surface layer of the inner ring by cutting a part of the inner ring are shown. The result of pass / fail of decarburization of the inner ring structure by observing the structure of the inner ring when the cut surface of the portion is observed with an optical microscope is shown. As shown in this table, the inner rings of Sample Nos. 1 to 5, which were determined to be unacceptable in the above-described tissue observation, had SH wave propagation velocities of 3190 m / s or more, while the samples which were determined to be unacceptable in the tissue observation. The inner rings Nos. 6 to 10 all have SH wave propagation speeds of 3156 m / s or less. From this, it is possible to set the threshold value of the SH wave propagation speed for determining whether or not decarbonization has occurred in the inner ring made of SUJ2 to 3180 m / s.
[0036]
FIG. 6 is a graph of the table of FIG. FIG. 6 shows that the inner rings of Sample Nos. 1 to 5 existing above the line drawn on the SH wave propagation velocity of 3180 m / s are rejected, while the Sample No. 6 existing below this line is rejected. 10 to 10 show that the inner ring passes.
[0037]
According to the inspection method of decarburization or polishing and burning of a steel part of the above embodiment, the SH wave transmitter 1 and the SH wave receiver 2 are arranged on the surface of the inner race 10 at a predetermined interval, Decarburization or polishing of the inner ring 10 can be inspected only by measuring the propagation speed of the SH wave. Therefore, unlike the inspection method using the electron beam microanalyzer or etching, decarburization or polishing of the inner ring 10 is performed. There is no need to destroy the inner ring 10 or perform mirror finishing to perform the burn inspection. In addition, the number of steps required for inspecting the inner ring 10 for decarburization or polishing / burning can be significantly reduced, and the cost and labor required for inspection of the inner ring 10 for decarburization or polishing / burning can be significantly reduced.
[0038]
Further, according to the inspection method for decarburization or polishing and burning of a steel part of the above-described embodiment, the light, small, and portable SH wave transmitter 1 and SH wave receiver 2 can be used, and Since the inspection of decarburization or polishing and burning of the inner ring 10 is performed based on the propagation speed of the SH wave that is safe for the human body, unlike the inspection method using an X-ray irradiator that uses X-rays that are dangerous to the human body on a large scale, The place where the decarburization or polishing and baking of the inner ring 10 is inspected is not limited, and the inspection of the decarburization and polishing and baking of the inner ring 10 can be performed safely.
[0039]
In the inspection method for decarburization or polishing and burning of a steel part of the above embodiment, the inner ring 10 made of SUJ2 is used as the steel part, and the propagation speed when the SH wave propagates through the inner ring 10 is 3180 m / s. When the above propagation speed is reached, it can be determined that decarburization has occurred in the inner ring 10 made of SUJ2. Therefore, the inner ring 10 made of SUJ2 in which decarburization has occurred can be reliably detected and eliminated, and High quality SUJ2 inner races 10 can be distinguished.
[0040]
Further, in the inspection method for decarburizing or polishing and burning of steel parts of the above embodiment, the inner speed 10 made of SUJ2 is used as the steel part, and the propagation speed when the SH wave propagates through the inner ring 10 is 3150 m / s. When the above propagation speed is reached, it can be determined that the SUJ2 inner ring 10 has been polished and burned. Therefore, the SUJ2 inner ring 10 having polished and burned can be reliably found and eliminated. High quality SUJ2 inner races 10 can be distinguished.
[0041]
In the inspection method for decarburization or polishing and burning of a steel part in the above embodiment, the SH wave is propagated into the inner ring 10 as an example of the steel part using the SH wave transmitter 1 and the SH wave receiver 2. The inner ring 10 was inspected for decarburization or polishing and burnt. However, a surface wave having a propagation speed substantially equal to that of the SH wave was propagated through the inner ring 10 using a surface wave transmitter and a surface wave receiver. Ten decarburization or polishing burns may be inspected.
[0042]
In the inspection method for decarburization or polishing and burning of steel parts in the above embodiment, this inspection method is applied to the inner ring 10 of the cylindrical roller bearing made of SUJ2. However, this inspection method is applied to the cylindrical roller bearing made of SUJ2. May be applied to the outer ring. Further, this inspection method is not limited to the inner ring and the outer ring of the cylindrical roller bearing made of SUJ2, but may be applied to other bearings and steel parts made of SUJ2, and may be applied to steel parts other than SUJ2. good.
[0043]
In the inspection method for decarburizing or polishing and burning steel parts of the above embodiment, the propagation speed of the SH wave was measured based on the zero cross point of the displacement of the SH wave. In the polishing burn inspection method, the propagation speed of the SH wave may be measured based on a portion of the SH wave waveform where the displacement exceeds a predetermined threshold.
[0044]
【The invention's effect】
As is clear from the above, according to the inspection method for decarburization or polishing and burning of steel parts of the first invention, for example, a surface wave transmitter or SH wave transmitter, and a surface wave receiver or SH wave receiver Can be inspected for decarburization or polishing and sintering of a steel part simply by arranging them on the surface of the steel part at predetermined intervals and measuring the propagation speed of the surface wave or SH wave. In addition, there is no need to destroy the steel part to perform the inspection for decarburization or polishing and burning of the steel part. In addition, the number of steps for inspecting steel parts for decarburization or polishing and burning can be greatly reduced, and the cost and labor required for inspection of steel parts for decarburizing or polishing and burning can be significantly reduced.
[0045]
According to the inspection method for decarburizing or polishing and burning steel parts of the first invention, the use of a light, small and portable surface wave or SH wave transmitter, and a surface wave or SH wave receiver. In order to inspect steel parts for decarburization or polishing and burning based on the propagation speed of SH waves or surface waves that are safe for the human body, a place to inspect steel parts for decarburizing or polishing and burning However, it is not limited, and the inspection of decarburization or polishing and burning of steel parts can be performed safely.
[0046]
Further, the inspection method for decarburization or polishing and burning of steel parts according to the first invention has a small, lightweight, inexpensive and highly stable inspection equipment. It is easy to apply to the configured inspection device.
[0047]
According to the inspection method for decarburization or polishing and sintering of a steel part of the second invention, a normally quenched SUJ2 product is used as the steel part, and the propagation speed of the SH wave or surface wave is 3180 m / s. In the above case, since it is determined that decarburization has occurred in the normally quenched SUJ2 product, the normally quenched SUJ2 product in which decarburization has occurred can be reliably found and eliminated, and high-quality SUJ2 can be obtained. Can be distinguished.
[0048]
Further, according to the inspection method for decarburization or polishing and sintering of a steel part of the third invention, a normal quenched product of SUJ2 is used as the steel part, and the propagation speed of the SH wave or surface wave is 3150 m / s. In the above case, it is determined that polishing hardening has occurred in the normally hardened SUJ2 product, so that the normally hardened SUJ2 hardened product can be reliably found and eliminated, and a high quality SUJ2 can be obtained. Can be distinguished.
[Brief description of the drawings]
FIG. 1 (A) is an SH-wave transmitter and an SH-wave receiver on a raceway surface of an inner ring when an inspection method for decarburization or polishing and burning of an inner ring of a bearing according to an embodiment of the present invention is performed. FIG. 1B is a plan view showing the arrangement, and FIG. 1B is a front view of the inner ring in the axial direction.
FIG. 2 is a diagram showing a relationship between SH wave propagation velocities of ten samples and pass / fail of polishing and burning inspection in the structure observation of the ten samples.
FIG. 3 is a graph of FIG. 2;
FIG. 4 is a diagram showing a relationship between residual stress of an inner ring and SH wave propagation velocity.
FIG. 5 is a diagram showing a relationship between SH wave propagation velocities of ten samples and pass / fail of a decarburization inspection in the structure observation of the ten samples.
FIG. 6 is a graph of FIG.
[Explanation of symbols]
1 SH wave transmitter 2 SH wave receiver 10 Inner ring

Claims (3)

A steel part for propagating a surface wave or SH wave to the surface layer of a steel part and measuring the speed of propagation of the surface wave or SH wave propagating on the surface layer to inspect the steel part for decarburization or polishing. Inspection method for decarburization or polishing and firing. The inspection method for decarburization or polishing and sintering of a steel part according to claim 1, wherein the steel part is a normal quenched product of SUJ2, and the surface wave propagating on a surface layer of the normal quenched product of SUJ2. Alternatively, a method for inspecting decarburization or polishing and sintering of a steel part which determines that decarburization has occurred in the normally quenched SUJ2 product when the propagation speed of the SH wave is 3180 m / s or more. The inspection method for decarburization or polishing and sintering of a steel part according to claim 1, wherein the steel part is a normal quenched product of SUJ2, and the surface wave propagating on a surface layer of the normal quenched product of SUJ2. Alternatively, a method for inspecting decarburization or polishing and burning of a steel part which determines that polishing and burning has occurred in the normally quenched SUJ2 product when the propagation speed of the SH wave is 3150 m / s or more.

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