JPH0332746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method for detecting flaws existing in the surface layer of square metal pieces such as blooms and square billets that are bloomed or continuously cast from steel ingots. .

Today, there are strict demands on the quality of rolled products such as wire rods, and efforts are being made to improve quality in each process from steel making, rolling, and finishing, and significant progress has been made in quality. Nowadays, even higher quality is required. For this reason, when it comes to materials such as wire rods, it is strictly required to reduce defects that exist inside long rectangular materials (hereinafter referred to as square steel billets) with approximately square cross-sectional shapes such as billets and blooms. Of course, there are defects in
Strict checks are also required for defects existing on the surface and in the shallow area just below the surface, near the so-called subcutaneous layer (hereinafter collectively referred to as the surface layer).

Conventionally, the method of flaw detection for square steel pieces has been to send and receive ultrasonic waves vertically from the surface toward the inside, but with this method, it is difficult to detect flaws in the center of the inside. Although ultrasonic waves have the advantage of being able to perform a wide range of measurements and are easy to handle, they have the problem that defects existing in the surface layer of a square steel slab cannot be detected. It was almost impossible to detect surface defects, especially at corners.

The present invention has been made to solve such problems, and it is possible to distinguish the types of harmful flaws that exist near the corners and on the surface of the surface of a square metal piece such as a square steel piece, and to easily locate the position. The purpose of the present invention is to provide an ultrasonic flaw detection method that can be performed with high precision.

In the method of the present invention, an oblique probe is installed on the side surface of a square metal piece that is conveyed in the longitudinal direction, and the probe emits angular ultrasonic waves of longitudinal waves, transverse waves, and surface waves. The corner formed by the incident surface and the adjacent surface is
Transverse waves are used to detect flaws on the adjacent surfaces of the incident surface, and the surface waves are used to locate flaw positions.

The method of the present invention will be explained in detail below. First, in order to compare the detection ability of ultrasonic longitudinal waves and transverse waves of defects existing in the surface layer of the corner of a square steel piece 1, an artificial defect S was provided on the surface layer of the corner of a square steel piece 1 as shown in Fig. 1, and the ultrasound Oblique flaw detection was performed using longitudinal waves and transverse waves. Artificial defect S has a diameter of 1
A drill hole of mm is made at a depth of dmm, and the depth dmm of this artificial defect is varied in four ways, and the detection situation (echo height) when detected using ultrasonic longitudinal waves and transverse waves is determined as follows. Shown in Figures A to C. In this case, the refraction angle θ is varied by changing the incident angle of the ultrasonic wave, and in Figure 2 A, the refraction angle θ is 67
Similarly, in the case of degrees, B is for 73 degrees and C is for 83 degrees, and the results with longitudinal waves are shown by solid lines, and the results with transverse waves are shown by broken lines. As is clear from FIG. 2, in the range of refraction angles from 65 to 85 degrees, the detection ability using the longitudinal wave oblique angle was 10 dB or more (more than 3 times) better than when using the transverse wave oblique angle. Especially when the refraction angle is approximately
If the temperature exceeds 83 degrees, measurements using transverse waves are impossible.

Figures 3A and 3C show the detection results when the same defect was detected by longitudinal wave and transverse wave oblique angle flaw detection at frequencies of 4MHz and 5MHz, respectively, with a refraction angle of 73 degrees, as displayed on the cathode ray tube of the flaw detector. It can be seen that the noise is lower in the flaw detection results using longitudinal waves, and that the flaw detection results using longitudinal waves are better than those using transverse waves.

On the other hand, the results of adjustment for defects in the surface layer of the surface portion are shown below. Figure 4 A, B, and C are each one side.
An artificial defect S extending in the horizontal direction and an artificial defect S extending in the vertical direction (both 2 mm in length) were created by electric discharge machining at a depth of 1 mm from the surface at about 1/3 (≒ 37 mm) of a 110 mm square steel piece. Furthermore, a drill hole with a diameter of 2 mm (horizontal hole parallel to the surface in contact with the probe) S
(The machining depth is 5 mm from the machined surface in the case of electrical discharge machining, and 30 mm for the drill hole), and Fig. 4 d is the same as Fig. 4 a,
The relationship between the refraction angle and the detection ability (echo height) when the artificial defect S shown in B and C is detected using a transverse wave oblique angle (frequency 5KHz) is shown by a broken line, a dashed-dotted line, and a solid line, respectively. The flaw detection results were best in the angle range of 40 to 50 degrees. Therefore, when detecting flaws in the surface layer of corners using longitudinal waves, the refraction angle is 65 to 85.
Good flaw detection results can be obtained by setting the refraction angle to 40 to 50 degrees when detecting flaws in the surface layer of the surface using transverse waves.

Figure 5 (a) and (b) show artificial defects created by a drilled hole with a depth of 1 mm and a diameter of 2 mm at a frequency of 2 MHz, respectively, in order to measure the monitoring range when defects in the surface layer of the surface are detected using one bevel probe. , shows the relationship between the probe distance (distance between the probe and the position on the detection surface directly above the flaw position) and the echo height when flaws are detected at 5MHz, and each shows the relationship between -6dB (maximum echo The scanning range at the position where the height is 1/2) is approximately 30 mm when the frequency is 2MHz, and approximately 12mm when the frequency is 5MHz.
Therefore, the lower the flaw detection frequency, the better (the beam spread is wider and the number of probes required is smaller).
I understand. In this case, 2MHz was selected based on the size of the defect to be detected.

Figure 6 A, B, and C show an artificial defect on the surface layer of one side of a square billet with a side of 130 mm to adjust the refraction angle.
Figure 7 is a schematic cross-sectional view of the test material when transverse wave angle flaw detection is performed at a angle of 45 degrees and a square steel billet conveyance speed of 30 m/mm, and the results are shown in Figure 6 A. 68mm from the surface with a diameter of 3mm and a depth of 3mm
A drill hole of mm is provided, and B is 65 mm from the adjacent surface.
A slit with a depth of 2 mm was provided at the position C, and a drill hole with a diameter of 2 mm was provided at a position 62 mm from the adjacent surface and 2 mm deep, and good flaw detection results were obtained in both cases.

To summarize the above results, the frequency is 2MHz to 5MHz.
Detect the required number of flaws in the surface layer of the corner of a square steel piece using a longitudinal wave at a refraction angle of 65 to 80 degrees, and on the surface layer of the corner section using a transverse wave in the same frequency range at a refraction angle of 40 to 50 degrees. By placing probes on each surface and detecting defects on the surface adjacent to the ultrasonic incident surface, it becomes possible to detect harmful defects present in the surface layer of the square steel piece. Another feature of this method is that the flaw position is located using surface waves. Since surface waves propagate only on the surface of a rectangular metal piece, it is possible to detect flaws on and near the surface. On the other hand, oblique flaw detection using longitudinal waves and transverse waves allows detection of surface and internal defects. Therefore, oblique flaw detection is performed on the corner surface layer of the surface adjacent to the entrance surface and the opposite surface using a longitudinal wave at a refraction angle of 65 to 80 degrees, and on the surface adjacent to the entrance surface using a transverse wave at a refraction angle of 40 to 50 degrees. Angle angle flaw detection was performed on the surface layer of the square steel piece, and flaws were detected on the surface of the square steel piece and its vicinity using surface waves.Flaws that were detected using longitudinal waves or transverse waves and also detected using surface waves were found to be located near the surface. If there is,
Flaws that can only be detected by longitudinal waves or transverse waves are identified as being internal.

FIG. 8 is a schematic front view of the ultrasonic flaw detection device for square steel pieces used in carrying out the method of the present invention, viewed from the upstream side in the conveyance direction of the square steel piece 1. It is conveyed by rollers 8 (so-called diamond conveyance) so that it becomes . Attachment holders 2, 2 are provided on both the left and right sides of the square steel piece 1 in the conveyance direction (referred to as left and right when facing the downstream side in the conveyance direction of the square steel piece 1; the same applies hereinafter). Both mounting holders 2, 2 have the same shape and are provided to face each other. To explain the left mounting holder 2, an upper plate 21 and a lower plate 22 are parallel to the left upper and lower surfaces of the square steel piece 1. are connected to the left side of the left corner of the square steel piece by a U-shaped connecting member 23 that has a recess formed on the side of the square steel piece 1, and a mounting block 24 is fixed to the connecting member 23, and the mounting In block 24,
A trunnion is supported on the left side of the mounting block 24, and the tip of the rod 31 of the air cylinder 3 is attached with the direction in which the rod advances to the right. Then, the upper plate 21 of the mounting holder 2 and the mounting block 24
The lower ends of tension springs 5 and 6, whose upper ends are locked above the conveyance area of the square steel piece 1, are respectively locked, so that the entire mounting holder 2 follows the bending of the square steel piece 1, etc. It's hanging. Further, a guide roller 4 is pivotally supported on the upper plate 21 and lower plate 22 of the mounting holder 2 so as to fit into the recess of the connecting member 23. It is designed to guide you.

Probe holders 71 and 72 are provided with two push springs 11 and 11 on the upper corner of the upstream side and the left corner of the downstream side of the upper plate 21 of the mounting holder 2, respectively, on the surface facing the square steel piece 1. , 11, 11. FIG. 9 is a schematic front view of the probe holders 71 and 72 on the left upper surface of the square steel piece 1 as seen from the upstream side, and FIG. 10 is a plan view taken from the direction of the arrow in FIG. At each of the four corners of the surface of each probe holder 71, 72 facing the square steel piece 1, there are rolling wheels 9, 9,..., 9,
9,... are respectively pivotally supported, and the probe holder 7
A gap is formed between 1 and 72 and the left upper surface of the square steel piece 1, and water as a contact medium is fed into the gap from water conduit pipes 12, 12, 12, 12.

Two bevel probes are provided in each of the upstream and downstream parts of the upstream contact holder 71, for a total of four angle probes. An oblique probe a that emits longitudinal waves as ultrasonic waves is provided, and an oblique probe b that emits surface waves as ultrasonic waves is provided at a position closer to the left corner of the probe a. There is also a square steel piece on the downstream side.
Two oblique probes c and d are provided that emit transverse waves as ultrasonic waves from the upper corner to the left corner. Then, probe a emits a longitudinal wave toward the surface layer near the upper corner of the lower right surface with a refraction angle of 65 to 80 degrees, and probe b emits a surface wave toward the upper right surface. , the surface wave is made to propagate along the right upper surface layer portion. Further, the probes c and d allow ultrasonic transverse waves to be incident thereon at a refraction angle of 40 to 50 degrees, and propagate the transverse waves to the surface layer of the upper right surface.

In the probe holder 72 on the downstream side, a total of four probes are provided, two on each of the upstream and downstream sides, and the upstream side includes oblique probes c and d that emit transverse waves.
is provided from the left corner to the upper corner of the square steel piece 1, and on the downstream side, from the left corner to the upper corner of the square steel piece 1, there is an oblique angle probe a that emits longitudinal waves, and an oblique angle probe a that emits a surface wave. A corner probe b is provided. The probes a to d in the probe holder 72 emit ultrasonic waves toward the surface layer of the lower left surface, and the probe a propagates longitudinal waves to the surface layer near the left corner of the square steel piece 1. death,
Probe b propagates surface waves along the entire surface layer of the left lower surface, and probes c and d propagate transverse waves along the entire surface layer of the left lower surface.
Therefore, the ultrasonic longitudinal waves detect flaws in the vicinity of the corners of the square steel piece 1, the transverse waves detect flaws in the surface layer of the surface adjacent to the ultrasonic incident surface, and the surface waves similarly detect the adjacent surfaces.

The lower plate 22 of the mounting holder 2 is also supported by push springs 11, 11, . Probe holders 71 and 72
are provided, and as mentioned above, the rolling wheels 9, 9
..., water conduit pipes 12, 12... are provided, and an ultrasonic angle probe a that emits longitudinal waves is located at a position close to the right corner of the square steel piece 1 on the upstream side in the upstream probe holder 71. A probe b that emits a surface wave is provided at a position closer to a lower corner than the probe a, and further downstream, beveled probes c and d that emit a transverse wave are provided. , Also, in the probe holder 72 on the downstream side, there are two oblique probes c, which emit transverse waves on the upstream side.
d, and on the downstream side of each probe c, d, an oblique probe a that emits longitudinal waves from a position close to the lower corner of the square steel piece 1, and a probe b that emits a surface wave are installed, respectively. It is provided.

On the other hand, on the right side of the left mounting holder 2, a right mounting holder 2 is provided facing the mounting holder 2. The mounting holder 2 on the right side has almost the same structure as the mounting holder 2 on the left side, with the right and left sides reversed, but the probe holders 71, 72, 71, 72 attached to the upper plate 21 and the lower plate 22 are are in different positions. That is, the upstream probe holder 71 attached to the upper plate 21 is located near the right corner of the square steel piece 1;
The probe holder 72 on the downstream side is located near the upper corner. Further, the upstream probe holder 71 attached to the lower plate 22 is located near the lower corner of the square steel piece 1, and the downstream probe holder 72 is located near the right corner of the square steel piece 1. As described above, in each probe holder, a probe a that emits longitudinal waves is installed near each corner of the square steel piece, and a probe b that emits a surface wave is installed at a position close to each corner of the square steel piece.
is provided inside the probe a, and the probes c and d that emit transverse waves are arranged so as to move away from a position near the corner of the square steel piece 1.

FIGS. 11 and 12 show the probe holder 71,
71..., 72, 72... is a schematic diagram showing the propagation state of ultrasonic waves emitted from the probes in the four probe holders 71, 71... located on the upstream side in the direction of conveyance of the square steel piece 1. The probes a, b and the probes c, d, which are located on the same orthogonal plane and are located in each probe holder 71, emit ultrasonic waves in opposite directions, respectively.
Ultrasonic waves are propagated along the surface layer of the side surface adjacent to the side surface on which the probe holder 71 is located or obliquely to the surface. Also, 4 located on the downstream side
The three probe holders 72, 72, . The probe holder 7 emits ultrasonic waves in the opposite direction.
The ultrasonic waves are propagated along the surface layer of the side surface adjacent to the side surface where 2 is located or obliquely to the surface.

When performing flaw detection with a device configured as described above, air cylinders 3, 3 are used to bring the guide rollers 4, 4 into rolling contact with the left and right corners of the square steel piece 1 being conveyed.
The rod 31 is advanced, and each probe holder 71,
The rolling wheels 9, 9... in 71...72, 72,... are brought into contact with the side surface of each steel piece 1. and water pipe 12,1
2,..., the couplant water is poured into the gap between the side surface of the square steel piece 1 and the probes a, b, c, d in each probe holder 71, 71,..., 72, 72,... Fill each contactor a, b, c, in this state.
Flaw detection is performed by emitting ultrasonic waves from d.

In this case, each probe holder 71, 71..., 7
2, 72... are square steel pieces 1 with push springs 11, 11,...
Since the probe is pressed against each side of the probe, the gap between each side and each probe is always constant, minimizing changes in the sensitivity of each probe. In addition to the push springs 11, 11, ..., the tension springs 5, 5, 6, 6 that suspend the entire mounting holder 2, 2 allow each probe to follow the bending, twisting, etc. of the square steel piece. The gap between each side of 1 is constant.

In the above embodiment, a probe that emits only longitudinal waves, transverse waves, and surface waves was used, but instead of this, a probe that incorporates multiple transducers and emits longitudinal waves, transverse waves, and surface waves is used. A composite type probe may also be used. In addition, two probes that emit transverse waves were placed side by side on each side of the square steel piece in a direction perpendicular to the conveyance direction.
The number may be increased according to the size of the square steel piece,
Furthermore, attach each probe holder 71, 72 to the mounting holder 2.
It may also be made to be able to slide freely against the container, so that it can be adapted to the case where square steel pieces of different sizes are transported.

As described in detail above, the present invention is an ultrasonic flaw detection method for detecting flaws in a rectangular metal piece transported in the longitudinal direction. Each of these three types of ultrasonic waves is propagated into the rectangular metal piece using a probe in order to detect flaws in the surface layer of the adjacent surface of the incident surface and to locate the flaw position using surface waves. , the surface layer of square metal pieces can be detected with high precision and reliability.
In particular, the present invention has many features that contribute to improving the precision of non-destructive testing of square metal pieces, such as being able to perform flaw detection at corners with high precision and ensuring the location of flaws.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the angle angle flaw detection method, Fig. 2 (a) to (c) are graphs showing the flaw detection results in Fig. 1, Fig. 3 (a) and (b) are photographs of signal waveforms from the cathode ray tube flaw detector, and Fig. 4 (a) and (b). , C are schematic diagrams showing the state of artificial defects, D is a graph showing the relationship between the refraction angle and echo height when each artificial defect is detected using a transverse wave oblique angle, and Figure 5 A and B are graphs showing the relationship between the probe distance and Graph showing echo height,
Figure 6 A, B, and C are schematic diagrams of the transverse wave angle flaw detection method, Figure 7 is a graph showing the flaw detection results of Figure 6, and Figure 8 is a schematic front view of the equipment used to carry out the method of the present invention. ,
FIG. 9 is a schematic diagram of one probe holder, FIG. 10 is a view in the direction of the arrow in FIG. 9, and FIGS. 11 and 12 are schematic diagrams showing the ultrasonic propagation state, respectively. 1... Square steel piece, 2... Mounting holder, 3... Air cylinder, 4... Guide roller, 5, 6... Tension spring, 71, 72... Probe holder, 8... Roller, a, b , c, d... probe.

Claims (1)

[Claims] 1 In an ultrasonic flaw detection method for detecting flaws in a rectangular metal piece transported in the longitudinal direction, longitudinal waves are used to detect the vicinity of the corner surface formed by the incident surface and the adjacent surface, and transverse waves are used to detect the surface area of the surface adjacent to the incident surface. An ultrasonic flaw detection method characterized by propagating each of these three types of ultrasonic waves into a rectangular metal piece in order to detect each flaw and to locate the flaw position using surface waves.