JP2003232777A - Method for detecting anomalous part in steel product surface through the use of eddy current and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection method and a detection apparatus capable of highly accurately detecting parts uncut by turning for removing surface decarburized layers caused by heat treatments on steel pipes and round bar steels at low costs in a short time. <P>SOLUTION: Two detecting coils 12 of an eddy current sensor comprised of an exciting coil 13 and the two detecting coils 12 are arranged at microintervals to the surface of a steel product ring to be inspected. The detecting coils 12 are moved relatively to a steel product surface, and a high-frequency current is made to flow through the exciting coil 13 to generate an overcurrent in the surface of the steel product ring. By detecting a signal difference caused by the overcurrent and based on the magnetic characteristics of two adjacent locations in a defect part such as a sound part and a decarburized layer of the steel product surface through the use of the two detecting coils 12, the anomalous part in the steel product surface is detected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of an unturned portion of a turning surface by turning of a steel material by utilizing an eddy current, and in particular, a black skin in surface turning due to uneven thickness of a steel pipe or defective mechanical core of a turning device. Regarding non-destructive inspection of unturned parts.

[0002]

2. Description of the Related Art A decarburized layer of about 0.1 to 0.3 mm is formed on the surface of a steel pipe or a round bar steel due to heat treatment or the like. Therefore, the decarburized layer on this surface is usually removed by turning. However, when there is uneven thickness in the steel pipe, there is a bend in the steel pipe or round bar steel, or the turning machine has a defective mechanical core, there is an uncut portion on the steel pipe or round bar steel when turning with a turning machine. , The black skin during heat treatment may remain on the surface of the uncut portion. A decarburized layer remains on the black skin of the uncut portion. That is, FIG.
(A) shows an uneven thickness ring 1 which is a cut piece of a steel pipe having uneven thickness, and the uneven thickness ring 1 has a thick portion 2 and a thin portion 3. When this uneven thickness ring 1 is heat-treated, a decarburized layer 7 is produced on the surface portion thereof, and a black skin 6 is produced on the surface thereof. Therefore, as shown in (b), in order to remove the decarburized layer 7 and the flaws on the surface or to improve the dimensional accuracy, turning is performed by a turning machine, but as in the area surrounded by a circle in (b), Since the ring has an uneven thickness, the decarburization layer 7 is formed on the inner surface of the uneven thickness ring 1.
And the unturned portion 5 consisting of the surface black skin 6 remains.

By the way, the black skin 6 of the unturned portion 5 can be detected by the dimension measurement when measuring the dimension of the steel material when the size thereof is relatively large. However, when the size of the black scale 6 of the unturned portion 5 was small and within the dimensional tolerance, the black scale 6 of the unturned portion 5 could not be detected during the dimension measurement. Generally, the black skin 6 formed by the unturned turning portion 5 is visually inspected after turning. However, this requires inspection personnel and inspection time. Further, the surface of the steel material after turning can be photographed by a CCD camera and detected by image processing of a computer. However, the equipment cost for that purpose, the inspection takes time, and the installation environment of the turning line is not suitable for installing the equipment by these image processing. Further, the tact time of the turning line is generally 1.0 to 2.0 sec / pc, and when inspecting on the turning line, the inspection time needs to be within that tact time. However, since it is not possible to perform image processing in such a short time, it is difficult to apply it to a turning line. For the above reasons, there is a problem that it is not suitable for inspection of mass-produced products.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a detection method and a detection apparatus which solve the above-mentioned problems in the detection of the uncut portion of turning for removing the surface decarburized layer by heat treatment of a steel pipe or a round bar steel. In addition, it is possible to detect the uncut part of the turning of the recess by transferring the flaw of the rolling roll such as flat bar, round bar steel or steel pipe or detect the uncut part of the black skin and detect the flaw such as crack. Is.

[0005]

[Means for Solving the Problems] When the decarburized layer having a depth of about 0.1 to 0.3 mm caused by the influence of heat treatment or the like on the surface of the steel pipe is removed by spinning, the surface of the defective portion, which is the uncut portion, is removed. There is a difference in the amount of C contained between the black skin part, the decarburized layer, and the sound part of the main body surface from which the decarburized layer has been removed, so that the magnetic properties thereof differ. For example, when a steel material is annealed or heat-treated, a difference in C concentration occurs in the steel surface layer due to decarburization, and there is a relationship between the C content and the magnetic permeability (that is, the relative magnetic permeability) as shown in FIG. Is about 1/4 of the decarburized layer with a C content of 1% in the hardened material and about 1% of the decarburized layer with a C content of 0% in the annealed material. / 2.

Therefore, a high-frequency current is passed through an exciting coil to be excited and a conductor made of a steel material such as a steel pipe to be inspected is disposed in the magnetic flux to generate an overcurrent in the conductor. In this case, the overcurrent flows concentratedly on the surface of the conductor due to the skin effect, magnetism is generated by the overcurrent, and the magnetic characteristics of the magnetism generated due to the difference in the C concentration due to the heat treatment of the steel material to be inspected are different. It occurs, and by detecting and comparing the difference in the magnetic characteristics as a signal by the detection coil of the eddy current sensor, the uncut portion of the steel material can be confirmed.

Further, the magnetic characteristics generated by generating the eddy current have a phase difference in the magnetic characteristics signal due to defects such as black skin (that is, decarburized layer) or cracks in the surface characteristics of the steel material, and these surface characteristics are caused. In contrast to the magnetic characteristic signal (which is a “backlash signal” in the present invention), which is a noise peculiar to the flaw detection device, the magnetic characteristic signal due to, for example, a signal from the sound part of the steel material, the black skin, and the decarburized layer below it. The black-skin signal based on the difference between the black-skin signal and the rattling signal has a phase difference of about 45 °. Have a phase difference. Therefore, the phase of these signals is 2
When displayed in dimensions, as shown in FIG. 4, when the phase angle is set so that the backlash signal, which is noise peculiar to the flaw detector, comes on the X axis and the value in the Y direction is set to 0, the Since the split signals are displayed in directions of different phases, each separated by about 45 °, the existence of both can be detected at the same time.

Therefore, the means for solving the above problems of the present invention is, in the invention of claim 1, an exciting coil and a coil.
The detection coil of the eddy current sensor consisting of individual detection coils is arranged with a slight gap from the steel surface of the steel material to be inspected, the detection coil is moved relative to the steel surface, and a high-frequency current is applied to the exciting coil. An overcurrent is generated in the steel material, and the two detection coils detect the difference in the signals based on the magnetic characteristics of two parts, that is, a sound portion of the adjacent steel material surface and a defective portion such as a decarburized layer caused by the overcurrent. This is a method for detecting an abnormal portion of a steel material surface using an eddy current by an eddy current sensor.

According to a second aspect of the present invention, the steel material to be inspected is a steel pipe or a round bar steel, and the method for detecting an abnormal portion on a steel material surface using an eddy current by the eddy current sensor according to the first aspect.

According to a third aspect of the present invention, the steel material to be inspected is a rectangular material, and the eddy current sensor is used to detect an abnormal portion on the surface of the steel material.

In the invention of claim 4, the abnormal portion of the steel material surface is
The eddy current by the eddy current sensor according to any one of claims 1 to 3, which is an uncut portion of the black skin when the decarburized layer is turned by heat treatment of the steel surface of the steel material having uneven thickness and bending. This is a method for detecting abnormal parts on the surface of a steel material using.

In the invention of claim 5, the abnormal portion of the steel material surface is
The eddy current sensor according to any one of claims 1 to 3, wherein the eddy current sensor is an uncut portion at the time of turning a recess or a crack caused by transfer of a rolling roll flaw on a steel surface of a steel material having uneven thickness or bending. This is a method for detecting abnormal parts on the steel surface using eddy currents.

According to the sixth aspect of the present invention, in the detection of the signal difference based on the magnetic characteristics, when the signal magnitude is indicated by the XY coordinates of the two-dimensional display, the backlash signal which is the noise peculiar to the eddy current flaw detector is X. By setting the phase angle so that it is located on the axis, there is a black skin signal based on the difference in the signals from the black skin and decarburization layer, which are the sound part and the defective part of the steel surface, and the sound part and the defective part of the steel surface. 6. The crack signals based on the difference in the signals from the crack portions are displayed simultaneously with their phases shifted, and the abnormal black skin portion and the abnormal crack portion are detected at the same time. This is a method for detecting an abnormal portion of a steel material surface using an eddy current by the eddy current sensor of the above means.

According to a seventh aspect of the present invention, there is provided a plurality of rotating rolls for rotatably supporting the outer periphery of the work made of a circular cut piece of steel pipe or round bar steel and at least one drive roll, and an inner peripheral surface of the work to be detected or It is characterized by comprising an eddy current sensor composed of two detection coils arranged side by side with a slight separation facing the outer peripheral surface, a sensor head composed of an exciting coil arranged behind the eddy current sensor, and a support arm supporting the sensor head. This is a device for detecting abnormal parts on the steel surface using eddy currents.

According to an eighth aspect of the present invention, there is provided a plurality of rotating rolls for rotatably supporting the lower surface of the work made of a rectangular steel cut piece and at least one drive roll, and it is very small when facing the upper or lower surface of the work to be detected. Steel material using eddy current, characterized in that it comprises an eddy current sensor consisting of two detection coils arranged side by side, a sensor head consisting of an exciting coil arranged behind the eddy current sensor, and a support arm supporting the sensor head. It is a device for detecting an abnormal portion of a surface.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for schematically explaining a turning-remaining portion before and after turning of a steel pipe in which a steel material has uneven thickness.
FIG. 2 is a view schematically showing a detection method and a detection device for an abnormal portion of a ring-shaped work made of a circular cut piece of a steel pipe,
(A) is a figure which shows the arrangement relationship of a ring-shaped work, its rotation mechanism, and an eddy current sensor, (b) is a figure which shows the support mechanism of a ring-shaped work and a sensor head typically. FIG. 3 is a diagram illustrating a method of applying the sensor head to a steel material of a subject. FIG. 4 is a diagram showing the relationship of the phases of the abnormal signals detected by the eddy current sensor. FIG. 5 is a diagram showing the relationship between the C content and the relative magnetic permeability (immersion rate) of annealed and hardened steel materials. FIG. 6 is a diagram schematically showing an apparatus for detecting an abnormal portion of a rectangular work made of a cut piece of rectangular steel.

A steel pipe obtained by rolling a bearing steel such as high carbon chromium steel has an uneven thickness during hot rolling as shown in FIG. 1 (a), and a ring material obtained by cutting the steel pipe having the uneven thickness into a ring shape. Is the uneven thickness ring 1 of the thick portion 2 and the thin portion 3. When the uneven thickness ring 1 is subjected to heat treatment or the like, a decarburized layer 7 having a thickness of 0.1 to 0.3 mm is formed on the surface of the uneven thickness ring 1, and the black skin 6 is formed on the surface of the decarburized layer 7 of the uneven thickness ring 1. Are formed. Therefore, the decarburized layer 7 of the ring surface layer is removed by turning with a turning machine. At this time, since the ring material has an uneven thickness or the machine core of the turning machine is displaced, the turning ring 4 is turned on the inner surface of the area surrounded by a circle, for example, as shown in FIG. A portion 5 remains, and the decarburized layer 7 and the black leather 6 on the decarburization layer 7 remain on the turning residue 5.

In order to detect the remaining decarburized layer 7 efficiently, as shown in FIG. 2 (a), one piece that is brought into contact with the outer periphery of the turning ring 4 which is the subject to be driven and supported in the circumferential direction. The drive roll 8 and two rotary rolls 9, which are rotatably supported, are mounted on a rotating device. The drive roll 8 rotates the turning ring 4 in a rotation direction 10 indicated by an arrow by a motor (not shown). The rotation speed is 120 to 180 rotations / minute. In FIG. 2 (a), the sensor head 11 is arranged on the inner surface of the turning ring 4 because it detects flaws on the inner surface of the turning ring 4. Of course, in order to detect flaws on the outer surface of the turning ring 4, the sensor head 11 is arranged on the outer surface of the turning ring 4. It goes without saying that, in addition to the ring material, cut pieces of round bar steel can also be flaw-detected by the above device.

As shown in FIG. 3, the sensor head 11 includes an exciting coil 13 and a detecting coil 1 which is an eddy current sensor.
It consists of 2. The detection coil is two detection coils 12
and a detection coil 12b, which is composed of a sound portion 17 having a C content of 1%, for example, a sound portion 17 on the surface of the turning ring 4 as an object, a black skin 6 adjacent thereto, and a decarburized layer 7 having a C content of 0% as a lower layer. The detection coil 12a and the detection coil 12b are arranged so as to correspond to the defective portion. These detection coils 12
Is held by the sensor head 11 shown in FIG. 2B so as to be arranged with a gap of 0.3 to 0.5 mm from the surface of the turning ring 4. The sensor head 11 of this flaw detector comprises a mechanism for moving the arm 14 with a spring 15 interposed between them by a cylinder 16 and moving the arm 14 left and right on the surface of the turning ring 4 for positioning. This flaw detection device used in the present invention is composed of conventional devices such as a power supply unit, a magnetic generation unit, a control unit and a display unit, which are included in the conventional device, as in the conventional device.

The detection method of the present invention will be further described below.
The heat-treated turning ring 4 of the workpiece is rotated as shown in FIG. 2 by the drive roll 8 and the two free rotating rolls 9, 9. Cylinder 16 with sensor head 11
Is moved left and right on the turning ring 4 and stopped at a fixed position. At this time, the gap between the detection coil 12 of the eddy current sensor and the turning ring 4 is adjusted to 0.3 to 0.5 mm. Two detection coils 12a and 12 which are eddy current sensors
For b, those each having a diameter of about 3 to 5 mm are selected.

By the way, as shown in Table 1, the overcurrent generated in the conductor by the excitation of the exciting coil 13 flows concentratedly on the surface due to the skin effect. That is, as shown in Table 1, the conductor depth at which the overcurrent decreases to 37% of the conductor surface depends on the frequency applied to the exciting coil 13, and the higher the frequency, the shallower the magnetic penetration depth becomes. Will also be more concentrated in the epidermis. Since the decarburized layer 7 by heat treatment has a thickness of about 0.1 to 0.3 mm, the frequency of the exciting coil 13 is set to 256 KHz or more from Table 1.

[0022]

[Table 1]

When the steel to be flaw-detected is a rectangular steel cutting piece, as shown in FIG. 6, instead of the device shown in FIG. 2, a plurality of rectangular steel cutting pieces 18 for rotatably supporting the lower surface of the work piece are supported. A work moving device having a rotating roll 9 and one driving roll 8 is provided, and a vortex flow composed of two detection coils is provided above the rectangular steel cutting piece 18 with a gap of 0.3 to 0.5 mm from the surface. A sensor head 11 including a sensor and an exciting coil is arranged. Sensor head 11
Is the support arm 17 and the sensor head 11 in the cylinder 1.
Position with 6.

As described above, when the detection coil 12 of the eddy current sensor is positioned and stopped by the cylinder 16 at a predetermined position detected by the turning ring 4 of the work or the rectangular steel material cutting piece 18, the time is about 0.3 seconds after the stop. Place and start flaw detection. For example, in the case of the turning ring 4, the turning ring 4 is rotated twice or more. Rotation speed is 120
~ 180 rotations / minute. The magnetic signal detected by the detection coil 12 is displayed on the display unit of the flaw detection device as shown in FIG. 4, and the phase switch of the control unit of the flaw detection device is operated to move the rattling signal, which is a noise signal of the device, on the X-axis. Set the phase angle so that it is horizontal. With the above settings, the black skin signal based on the signal difference from the sound part of the work and the black skin and the decarburization layer below it, or the crack signal based on the signal difference from the sound part and the crack part, can be clearly understood at different positions. It is possible to verify a work having an abnormal portion.

[0025]

As described above, according to the present invention, defects or cracks such as black skin and decarburized layer underneath which are left after turning when the surface decarburized layer is removed by heat treatment of a work such as a steel ring. It is an unprecedented excellent method and apparatus capable of detecting the presence of the defect portion of 1. with extremely high efficiency and high accuracy and at low cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram for schematically explaining a non-turning portion before and after turning of a steel pipe in which a steel material has an uneven thickness.

FIG. 2 is a diagram schematically showing a detection method and a detection device for an abnormal portion of a ring-shaped work made of a circular cut piece of a steel pipe,
(A) is a figure which shows the arrangement relationship of a ring-shaped work, its rotation mechanism, and an eddy current sensor, (b) is a figure which shows the support mechanism of a ring-shaped work and a sensor head typically.

FIG. 3 is a diagram illustrating a method of applying an eddy current sensor to a steel material of a subject.

FIG. 4 is a diagram showing a relationship between phases of abnormal signals detected by an eddy current sensor.

FIG. 5 is a diagram showing the relationship between the C content and the relative permeability (immersion rate) of annealed and quenched steel materials.

FIG. 6 is a diagram schematically showing an apparatus for detecting an abnormal portion of a rectangular work made of a cut piece of a rectangular steel material.

[Explanation of symbols]

1 Uneven thickness ring 2 thick parts 3 Thin part 4 turning ring 5 Turning left 6 black skin 7 Decarburized layer 8 drive rolls 9 rotating rolls 10 rotation direction 11 sensor head 12 detection coil 13 Excitation coil 14 arms 15 spring 16 cylinders 17 sound department 18 Flat steel cutting pieces

Claims (8)

[Claims] 1. A detection coil of an eddy current sensor comprising an excitation coil and two detection coils is arranged with a minute gap from the steel surface of a steel material to be inspected, and the detection coil is moved relative to the steel surface. , A high-frequency current is passed through the exciting coil to generate an overcurrent in the steel material, and the two detection coils cause magnetism at two locations, namely, a sound portion of the adjacent steel material surface and a defective portion such as a decarburized layer caused by the overcurrent. A method of detecting an abnormal portion of a steel material surface using an eddy current by an eddy current sensor, which is characterized by detecting a signal difference based on characteristics. 2. The method for detecting an abnormal portion of a steel material surface using an eddy current according to claim 1, wherein the steel material to be inspected is a steel pipe or a round bar steel. 3. The method for detecting an abnormal portion of a steel material surface using an eddy current by the eddy current sensor according to claim 1, wherein the steel material to be inspected is a rectangular material. 4. The abnormal portion of the steel surface is an uncut portion of the black skin when the decarburized layer is turned by heat treatment of the steel surface of a steel material having uneven thickness and bending. A method for detecting an abnormal portion of a steel material surface using an eddy current by the eddy current sensor according to any one of claims. 5. The abnormal portion on the surface of the steel material is a residual portion at the time of turning a concave portion or a cracked flaw due to transfer of a rolling roll flaw on a steel material surface of a steel material having uneven thickness and bending. 4. A method of detecting an abnormal portion of a steel material surface using an eddy current by the eddy current sensor according to any one of 1 to 3. 6. In the detection of a signal difference based on magnetic characteristics, when the magnitude of the signal is indicated by XY coordinates in a two-dimensional display, the backlash signal which is a noise peculiar to the eddy current flaw detector is X.
By setting the phase angle so that it is located on the axis, there is a black skin signal based on the difference in the signals from the black skin and decarburization layer, which are the sound part and the defective part of the steel surface, and the sound part and the defective part of the steel surface. 2. A crack signal based on a difference between signals from the crack portion is displayed simultaneously with their phases being shifted, and the abnormal black skin portion and the abnormal crack portion are detected at the same time.
6. A method for detecting an abnormal portion of a steel material surface using an eddy current by the eddy current sensor according to claim 5. 7. A plurality of rotating rolls for rotatably supporting the outer periphery of a work made of a circular cut piece of a steel pipe or a round bar steel and at least one drive roll, and facing the inner or outer peripheral surface of the work to be detected. An eddy current is used, which is characterized in that it comprises an eddy current sensor consisting of two detection coils arranged side by side with a slight separation, a sensor head consisting of an exciting coil arranged behind the eddy current sensor, and a support arm supporting the sensor head. A device for detecting abnormal parts on the steel surface. 8. A plurality of rotating rolls for rotatably supporting a lower surface of a work made of a rectangular steel cut piece and at least one drive roll, and two of them are juxtaposed with each other with a slight separation facing the upper or lower surface of the work to be detected. Of the abnormal portion of the steel material surface using the eddy current, characterized by comprising a eddy current sensor composed of a detection coil, a sensor head composed of an exciting coil arranged behind the eddy current sensor, and a support arm supporting the sensor head. Detection device.