JP2003254946A - Ultrasonic flaw detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method for selecting a round bar material satisfying a required quality using compact equipment. <P>SOLUTION: In this ultrasonic flaw detection method, a probe 5 comprising a vibrator 1 and a concave lens 3 are used. An ultrasonic wave 7 is emitted from the probe 5, and the ultrasonic wave 7 progresses toward the round bar material 9. The ultrasonic wave 7 is converged on a focal point F by the concave lens 3. The focal point F is positioned a little to the surface from the section center of the round bar material 9. The probe 5 makes a circuit around the round bar material 9. Internal flaw inspection by the high-density ultrasonic wave 7 is performed in the whole region surrounded by a virtual circle C1 and a virtual circle C2. Detection ability in the region is high. The position of the focal point F is determined corresponding to the use of the round bar material 9. <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 an ultrasonic flaw detection method for a metal round bar material.

[0002]

2. Description of the Related Art A round bar made of special steel is often used for important safety parts (for example, a steering shaft of an automobile). This round bar is required to have high strength and toughness. Since this round bar material is obtained by plastic working such as rolling, there may be internal flaws caused by the state of the material before working or internal flaws generated in the working process. Depending on the degree of internal flaws, the internal flaws may deteriorate the quality of the round bar and hinder its use. Steel material manufacturers inspect the inside quality of round bars and remove round bars that have a large degree of flaw.
The ultrasonic flaw detection method is adopted for the inspection of internal defects.

FIG. 5 is an explanatory view showing a conventional ultrasonic flaw detection method. In this method, the ultrasonic wave 53 emitted from the probe 51 is incident on the round bar 55 as a parallel beam. The incident ultrasonic waves 53 spread inside the round bar 55. When there is an internal flaw, the ultrasonic wave 53 is reflected by this internal flaw. By detecting this reflected wave, an internal flaw is detected. The probe 51 relatively rotates around the round bar 55, so that the entire region of the round bar 55 is inspected.

In this method, since the ultrasonic waves 53 are spread and the density thereof is small, the energy of the reflected wave is small.
Therefore, it is impossible to detect minute internal flaws.

FIG. 6 is an explanatory view showing another conventional ultrasonic flaw detection method. A probe 59 having a concave lens 57 is used in this method. The concave lens 57 is
The ultrasonic wave 61 is focused on the focal point F. The position of the focal point F coincides with the center of the cross section of the round bar 55. In this method, since the ultrasonic waves 61 are focused and the density thereof is high, the energy of the reflected wave due to the internal flaw is large. This method is superior to the ultrasonic flaw detection method shown in FIG. 5 in its ability to detect internal flaws.

However, in this method, the density of the ultrasonic waves 61 at the position away from the focus F (in other words, the position close to the surface of the round bar 55) is close to the focus F (in other words, the round bar). The density is lower than the density of the ultrasonic wave 61 in the vicinity of the cross-sectional center of 55). Therefore, the detection capability at a position away from the focus F is not so high, and it is impossible to detect a minute internal flaw at this position. With this method, it is difficult to reliably remove the round bar material 55 which is inappropriate for applications where internal flaws near the surface are not allowed.

[0007]

If a plurality of probes 59 having different focal points F are prepared and inspected by these, the region to be inspected by the ultrasonic waves 61 of high density is widened, and The defect detection rate increases. For example, by setting the focus F of the first probe 59 near the cross-sectional center of the round bar 55 and the focus F of the second probe 59 near the surface of the round bar 55, the center and the surface Ultrasonic waves are incident on both the vicinity and at a high density, and minute internal defects can be detected. However, in an inspection line equipped with a plurality of probes 59, equipment such as a control panel becomes large and a large space is required.
The large-scale equipment contributes to the increase in the production cost of the round bar 55.

The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic flaw detection method capable of selecting a round bar material satisfying the required quality and capable of being carried out with compact equipment. It is a thing.

[0009]

DISCLOSURE OF THE INVENTION The invention made to achieve the above object is to detect an internal flaw by injecting ultrasonic waves into a metal round bar to focus the ultrasonic wave inside the metal round bar. The ultrasonic flaw detection method according to claim 1, wherein the ultrasonic flaw is focused at a location other than near the center of the cross section of the metal round bar.

The metal round bar material has an application in which internal flaws in the vicinity of the center of the cross section are allowed (typically, when it is used in a cylindrical shape by hollowing out the vicinity of the center). In the present invention, since the ultrasonic waves are focused at a place other than near the center of the cross section, the ability to detect internal flaws near this place is high. Since the vicinity of the center of the cross section, which is an unnecessary part of the inspection, can be excluded from the inspection target, the inspection equipment can be made compact. This ultrasonic flaw detection method can be implemented at low cost. In the present specification, “a portion other than the vicinity of the center of the cross section” means a portion whose distance from the center of the cross section is 20% or more of the radius of the metal round bar.

The metal round bar material has applications in which only internal flaws near the surface pose a problem, and applications in which only internal flaws slightly inward from the surface pose a problem. By determining the ultrasonic focusing position according to the application, it is possible to easily select a metal round bar material with a quality that meets the requirements.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, with reference to the drawings,
The present invention will be explained in detail based on the preferred embodiments.

FIG. 1 is an explanatory view showing an ultrasonic flaw detection method according to an embodiment of the present invention. In this method, a probe 5 including a vibrator 1 and a concave lens 3 is used. The radius of curvature of the concave lens 3 is smaller than the radius of curvature of the concave lens 57 shown in FIG. An ultrasonic wave 7 is emitted from the probe 5, and this ultrasonic wave 7 is a metal round bar material 9.
It is incident toward (hereinafter simply referred to as "round bar material"). The ultrasonic wave 7 is focused on the focal point F by the concave lens 3. Since the radius of curvature of the concave lens 3 is small, the focal length is short, so the focal point F is located closer to the surface than the center of the cross section of the round bar 9. In the example of FIG. 1, the distance between the focal point F and the center of the cross section is 50% of the radius of the round bar 9.

The density of the ultrasonic waves 7 is high in the vicinity of the focal point F. Therefore, the energy of the reflected wave from the internal flaw existing near the focus F is large. Therefore, even if the internal flaw existing near the focal point F is minute, it can be detected.

The probe 5 makes one round around the round bar 9.
As a result, the virtual circle C1 shown in FIG. 1 (the radius of which is 1/3 of the radius of the round bar 9) and the virtual circle C2 (the radius of which is 2/3 of the radius of the round bar 9). The inspection is performed with a high detection rate in the entire area surrounded by (circle). Since the rod 5 rotates 360 degrees without the probe 5 moving,
An inspection may be done.

In this method, the density of ultrasonic waves in the vicinity of the center (inside the virtual circle C1) and the surface (outside of the virtual circle C2) of the round bar 9 is low. In this method, the ability to detect internal flaws near the center and the surface of the round bar 9 is not sufficient. The round bar material 9 that has passed this inspection may include relatively large internal flaws near the center and near the surface of the round bar material 9. This method is suitable for inspecting the round bar material 9 used for applications in which internal flaws near the center and near the surface are allowed.

In the conventional ultrasonic flaw detection method, although the internal flaw near the center is acceptable, the round bar is judged to be defective due to the presence of the internal flaw near the center. There was so-called false information. Although the yield may decrease due to the false alarm and the shipped product may have an excessive quality, the false alarm rate is reduced by the ultrasonic flaw detection method shown in FIG.

In this ultrasonic flaw detection method, the focal length is controlled by the curvature of the concave lens 3, but the vibrator 1 itself may be a concave surface, and the focal length may be controlled by the curvature of this concave surface.

FIG. 2 is an explanatory view showing an ultrasonic flaw detection method according to another embodiment of the present invention. Also in this method, the probe 13 including the vibrator 1 and the concave lens 11 is used. The radius of curvature of the concave lens 11 is smaller than that of the concave lens 3 shown in FIG. 1, and therefore its focal length is shorter. The focal point F is located near the surface of the round bar 9. In the example of FIG. 2, the distance between the focal point F and the center of the cross section is 83% of the radius of the round bar 9.

The probe 13 moves relatively around the circumference of the round bar 9.
By the circumference, the inspection by the high-density ultrasonic wave 7 is performed in the region outside the virtual circle C2 (the circle whose radius is 2/3 of the radius of the round bar 9). Even if the internal flaw existing in this area is minute, it can be detected.

In this method, the density of the ultrasonic waves 7 inside the virtual circle C2 is low. In this method, the ability to detect internal flaws inside the virtual circle C2 is not sufficient. The round bar material 9 that has passed this inspection may include relatively large internal flaws inside the virtual circle C2. This method is suitable for inspecting a round bar material 9 (for example, a round bar material 9 which is hollowed out in the vicinity of the center and formed into a cylindrical shape) used for the purpose of allowing internal flaws existing inside the virtual circle C2. There is. This method also reduces the false alarm rate.

According to the knowledge obtained by the present inventor, this ultrasonic flaw detection method can detect an internal flaw existing near the surface of the round bar 9 and having a diameter of 0.15 mm. This is much smaller than the detection limit (diameter 0.5 mm) of the conventional ultrasonic flaw detection method shown in FIG.

FIG. 3 is an explanatory view showing an ultrasonic flaw detection method according to still another embodiment of the present invention. Also in this method, the probe 17 including the vibrator 1 and the concave lens 15 is used. The radius of curvature of the concave lens 15 is the same as the radius of curvature of the concave lens 57 shown in FIG. 6, and therefore its focal length is also the same as the focal length of the concave lens 57 shown in FIG. As is clear from the comparison between FIG. 3 and FIG. 6, the distance between the probe 17 and the round bar 9 is larger in the method of FIG. 3 than in the method of FIG. Therefore, the focus F is located near the surface of the round bar 9. In the example of FIG. 3, the distance between the focal point F and the center of the cross section is 83% of the radius of the round bar material 9.

The probe 17 relatively surrounds the circumference of the round bar 9.
By going around, in the area outside the imaginary circle C2,
An inspection with high-density ultrasonic waves 7 is performed. Even if the internal flaw existing in this area is minute, it can be detected.

According to this method, the density of the ultrasonic waves 7 inside the virtual circle C2 is low. In this method, the ability to detect internal flaws inside the virtual circle C2 is not sufficient. The round bar material 9 that has passed this inspection may include relatively large internal flaws inside the virtual circle C2. This method is suitable for inspecting a round bar material 9 (for example, a round bar material 9 which is hollowed out in the vicinity of the center and formed into a cylindrical shape) used for the purpose of allowing internal flaws existing inside the virtual circle C2. There is. This method also reduces the false alarm rate.

FIG. 4 is an explanatory view showing an ultrasonic flaw detection method according to still another embodiment of the present invention. In this method, a large number of exciting elements 21 are used as the probe 19. These excitation elements 21 are linearly arranged in the left-right direction in FIG. An excitation pulse delay circuit 23 is connected to the excitation element 21. From the excitation pulse delay circuit 23, an excitation pulse 25 is emitted toward each excitation element 21. Upon receiving the excitation pulse 25, the excitation element 21 emits an ultrasonic wave 27. Since the excitation pulse delay circuit 23 emits the excitation pulse 25 with the timing shifted so that the reception of the inner excitation element 21 is delayed, the emission of the ultrasonic wave 27 is also delayed by the inner excitation element 21. As a result, as shown in FIG. 4, the group of ultrasonic waves 27 is focused at the focal point F. In the example of FIG. 4, the focal point F is located near the surface of the round bar material 9, and the distance between the focal point F and the center of the cross section is 83% of the radius of the round bar material 9.

Since the probe makes one round of the circumference of the round bar member 9, an inspection by the high-density ultrasonic wave 27 is performed in the area outside the virtual circle C2. Even if the internal flaw existing in this area is minute, it can be detected.

In this method, the density of the ultrasonic waves 27 inside the virtual circle C2 is low. In this method, the ability to detect internal flaws inside the virtual circle C2 is not sufficient. The round bar material 9 that has passed this inspection may include relatively large internal flaws inside the virtual circle C2. This method is suitable for inspecting a round bar material 9 (for example, a round bar material 9 which is hollowed out in the vicinity of the center and formed into a cylindrical shape) used for the purpose of allowing internal flaws existing inside the virtual circle C2. There is. This method also reduces the false alarm rate.

If the delay time of the excitation pulse 25 is changed by the control of the excitation pulse delay circuit 23, the focal length changes. That is, the single probe 19 and the probe 1
While keeping the distance between 9 and round bar 9 constant, focus F
The position of can be changed. The probe 19 includes a plurality of types of round bar members 9 which are different from each other in areas where high detection capability is required.
It is suitable for inspection lines that are washed away. A computer is preferably connected to the excitation pulse delay circuit 23. An appropriate focus position is determined for each type of the round bar 9, and the focus position data group is stored in the computer in advance as a table. The size of the inspection line can be extremely easily changed by controlling the excitation pulse delay circuit 23 by the computer based on this table.

The ultrasonic flaw detection method of the present invention (shown in FIGS. 1 to 4) is suitable for inspecting a round bar 9 made of special steel. Of course, the present invention can also be applied to the inspection of round bars made of other metal materials.

[0031]

As described above, according to the ultrasonic flaw detection method of the present invention, it is possible to easily select a round bar material that sufficiently satisfies the required quality. In this ultrasonic flaw detection method, excess quality due to false information is suppressed, and the yield is improved. This ultrasonic flaw detection method can be carried out in a short time with compact equipment.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an ultrasonic flaw detection method according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing an ultrasonic flaw detection method according to another embodiment of the present invention.

FIG. 3 is an explanatory view showing an ultrasonic flaw detection method according to still another embodiment of the present invention.

FIG. 4 is an explanatory view showing an ultrasonic flaw detection method according to still another embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a conventional ultrasonic flaw detection method.

FIG. 6 is an explanatory view showing another conventional ultrasonic flaw detection method.

[Explanation of symbols]

1 ... Transducer 3, 11, 15 ... Concave lens 5, 13, 17, 19 ... Transducer 7, 27 ... Ultrasound 9 ... Round bar 21 ... Excitation element 23 ... Excitation pulse delay circuit 25 ... Excitation pulse F ... focus

Claims (2)

[Claims] 1. An ultrasonic flaw detection method for detecting an internal flaw by injecting ultrasonic waves into a metal round bar material and converging it inside the metal round bar material. An ultrasonic flaw detection method, characterized in that ultrasonic waves are focused at a place other than the vicinity. 2. The ultrasonic flaw detection method according to claim 1, wherein the focus position of the ultrasonic waves is determined according to the application of the metal round bar.