JPS58216950A - Ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To locate positions of harmful flaws existing at corners of an angular metal piece discriminating the type thereof by detecting flaws on corners with a vertical wave of an ultrasonic waves generated from an angle beam probe and the surface layer of an adjacent surface to the incident surface with a transverse wave thereof while the position of the flaws is located with a surface wave thereof. CONSTITUTION:A holder is equipped with four angle beam probes in groups of two as follows: An angle beam probe (a) is provided at the position close to the upper corner of an angular steel piece 1 to emit a vertical wave as ultrasonic wave and adjacent thereto, an angle beam probe (b) is provided to emit a surface wave as ultrasonic wave. Two angle beam probes (c) and (d) are provided from the upper to the left corners of the angular steel piece 1 to emit a transverse wave as ultrasonic wave. The probe (a) emits the vertical wave to the surface layer near the upper corner on the right undersurface at 65-80 deg.C in the angle of refraction while the probe (b) the surface wave to the right top surface at the same angle. The probes (c) and (d) receive the transverse waves at 40- 50 deg.C in the angle of refraction.

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 square steel pieces such as bloom blooms and square billets that are bloomed from steel ingots or continuously cast. .

Today, where the quality of rolled products such as wire rods is strictly required, efforts are being made to improve quality in each process from steelmaking, rolling, and finishing, and the progress in quality has been remarkable. Accordingly, even higher quality is being required. When it comes to materials such as wire rods, billets and blooms, the cross-sectional shape is approximately square (hereinafter referred to as square steel billets).
There is a strict requirement to reduce defects existing inside the skin, and not only defects existing in the center of the interior, but also defects existing on the surface and in the shallow area just below the surface, so-called subcutaneous area (hereinafter collectively referred to as table ms). Strict checks are also required for defects.

Traditionally, the method of flaw detection for square steel pieces involves transmitting and receiving ultrasonic waves vertically from the surface to 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, there is a problem in 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 this problem, and it is possible to distinguish the types of harmful flaws that exist near the corners and on the surface layer of square metal pieces such as reeds and square steel pieces, and to easily locate the flaws. The purpose of this invention is to provide an ultrasonic flaw detection method that can be carried out quickly and with high precision.

In the method of the present invention, an oblique probe is provided on the side surface of a rectangular metal piece that is conveyed in the longitudinal direction, and each ultrasonic wave of longitudinal waves, transverse waves, and surface waves is emitted by the probe. The corner formed by the entrance surface and the adjacent surface of a p-angle steel piece is subjected to flaw detection on the surface layer of the adjacent surface of the entrance surface using transverse waves, and the flaw position is located using the surface waves.

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 8 is created at a depth drMi with a diameter of 1 threshold, and the depth dffII+ of this artificial defect is changed four times to detect the detection situation using ultrasonic longitudinal waves and transverse waves ( echo height) are shown in Figures 2 (a) to (c). In this case, the incident angle of the ultrasonic wave is also varied to change the refraction angle θ.
If is 67 degrees, then (b) is 73 degrees and (c) is 83 degrees.
In the case of degrees, the results for longitudinal waves are shown by solid lines, and the results for transverse waves are shown by broken lines. As is clear from FIG. 2, when the refraction angle was in the range of 65 to 85 degrees, the detection ability using the longitudinal wave oblique angle was 10 dB or more (more than 3 times) better than that using the transverse wave oblique angle. In particular, when the refraction angle is about 83 degrees or more, measurement using transverse waves is impossible.

Figure 3 (a) and (b) are the same for longitudinal wave and shear wave angle flaw detection.
The detection results are shown when defects are detected at frequencies of 4 MHz and 5 MHz, respectively, and at a refraction angle of 73 degrees, as displayed on a cathode ray tube. It can be seen that the noise is low and the flaw detection results using longitudinal waves are better than those using transverse waves.

On the other hand, the results of investigating defects in the surface layer of the surface portion are shown below. Figure 4 (a), (b), and (c) are respectively - side 11
There is a surface depth at about 1/3 (middle 37r surface) of a 0 mm square steel piece! During the electric discharge machining process, the steps include an artificial defect 8 extending in the horizontal direction, an artificial defect 8 extending vertically (both 2M in length), and a drill hole with a diameter of errs (parallel to the surface in contact with the probe). In case of electric discharge machining, the machining depth is 5 mm, and the drilled hole is 30 mm.
b) When the artificial defect 8 shown in ←→ is detected using a transverse wave oblique angle, the relationship between the refraction angle and the detection ability (echo height) at frequency 5 [11z] is shown by the broken line, dashed-dotted line, and solid line, respectively. As shown, the flaw detection results were the best in the range of refraction angle of 40 to 50 degrees. Therefore, when detecting flaws in the surface layer of corners using longitudinal waves, the refraction angle should be 65 to 86 degrees, and when detecting flaws in the surface layer of surface areas using transverse waves, the refraction angle should be 40 to 50 degrees to obtain good results. can get.

Figures 5 (a) and (b) show an artificial hole drilled with a depth of 1 mm and a diameter of 2 mm to measure the monitoring range when detecting defects on the surface of the surface am using one angle probe. This graph shows the relationship between the probe distance (the distance between the probe and the position on the detection surface directly above the bottom position) and the echo height when defects are detected at frequencies of 2 MHz and 5 MHz, respectively. The scanning range of -(idB (position where I & large echo height is t7g)) is approximately 30 mm for a frequency of 2 MHz and approximately 12 mm for a frequency of 5 Mllz.
It is clear from Peng that the lower the flaw detection frequency, the better (the beam spread is wider and the number of probes required is smaller).

In this case, the size of the defect to be detected was selected as 2Ml]z.

Figures 6 (A1. A schematic cross-sectional view of the test material when angle flaw detection was performed. No. 7FgJ shows the flaw detection results. diameter 3
A drill hole of mm is provided, and (b) is 65 mm from the adjacent surface.
[A slit with a depth of 2 ann is made at a position of 1 m,
In addition, a drill hole with a diameter of 2 mm was provided at a position of 62 M5 and a depth of 211 m from the adjacent surface, and good flaw detection results were obtained in both cases.

To summarize the above results, when longitudinal waves with a frequency of 2 MHz to 5 MHz are applied, the refraction angle is set to 65 and -80 degrees, and the refraction angle is set to 40 to -80 degrees for transverse waves in the same frequency range on the surface of the corner of a square steel piece. If the necessary number of probes are placed on each surface so as to detect flaws in the surface layer of the surface at a 50 degree angle, and the IiJ contact surface of the ultrasonic incident surface is detected, harmful defects existing in the surface layer of the square steel piece can be detected. . Furthermore, a feature of this method is that it uses surface waves)
This is for locating the bottom position. 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 surface layer of the corners of the adjacent surface and the opposite surface of the incident surface using a longitudinal wave with a refraction angle of 65 to 80 degrees, and with a shear wave at a refraction angle of 40 to 50 degrees. Oblique flaw detection is performed on the surface layer of the adjacent surface, and flaw detection is performed on the surface of the square steel piece and its vicinity using surface waves.Flaws detected by longitudinal waves or transverse waves and also detected by surface waves exist near the surface. 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 an 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 direction of conveyance of the square steel piece 1. Conveyed by roller 8 so that it is horizontal (so-called diamond feeding)
has been done. Attachment holders 2, 2 are provided on both the left and right sides of the square steel piece 1 in the conveyance direction (left and right when facing the downstream side of the square steel piece 1 in the conveyance direction; the same applies hereinafter). Both mounting holders 2.2 have the same shape and are provided to face each other.The left mounting holder 2.2 has an upper plate 21 and a lower plate parallel to the left upper and lower surfaces of the square steel piece l. 22
are connected to the left side of the left corner of the square steel piece by a U-shaped connecting member 23 with 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 block 2
4 is supported by a trunnion 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 rod extending direction to the right. The upper plate 21 and the mounting block 24 of the mounting holder 2 are respectively fixed with the lower ends of tension springs 5.6 whose upper ends are fixed above the conveying area of the square steel piece 1. The whole is suspended so as to follow the curve of the square steel piece 1. 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 230, and the left corner of the square steel piece 1 is guided by the guide roller 4. It is supposed to be done.

Probe holders 71 and 72 are mounted on the upper corner of the upstream side of the surface facing the square steel piece l of the upper plate 21 of the mounting holder 2, and the probe holders 71 and 72 are mounted on the upper corner of the downstream side of the room, respectively, and two push springs 11 are mounted on the upper plate 21 of the mounting holder 2, respectively. ,11
, 11.11. FIG. 9 is a schematic front view of the probe holder 71, 72 on the upper left surface of the square steel piece 1, seen from the upstream side, and FIG. 10 is a plan view taken from the direction of the arrow in FIG. Each probe holder 71. Rolling wheels 9, 9. ..., 9, 9,
... are respectively pivotally supported, and the probe holder 71.72
A gap is formed between the upper left surface of the square steel piece 1, and water as a contact medium flows into the gap.
2.12) has been sent.

Two bevel probes are provided in each of the upstream and downstream parts of the upstream probe holder 71, for a total of four probes.
An oblique probe a that emits longitudinal waves as ultrasonic waves is provided at a position close to the upper corner of the square steel piece l on the upstream side, and the probe a
An oblique probe that emits surface waves as ultrasonic waves is installed at the left side corner approach. Two angle probes c and d are provided that emit transverse waves as sound waves.

Then, the probe a emits a longitudinal wave toward the surface layer near the upper corner of the lower right side so that the refraction angle is 65 to 80 degrees,
The probe emits a surface wave toward the upper right surface and propagates the surface wave along the surface layer of the upper right surface. Further, the probes c and d allow ultrasonic transverse waves to be incident thereon at a refraction angle of 40 to 60 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 has beveled probes c and d that emit transverse waves. The square steel piece 1 is provided from the left corner to the upper corner of the square steel piece 1, and the square steel piece 1 is provided on the downstream side.
An oblique angle probe a that emits longitudinal waves and an oblique angle probe S that emits surface waves are provided from the left corner to the upper corner. Then, 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 is
A longitudinal wave is propagated to the surface layer near the left corner of the probe, and the surface wave is propagated along the entire surface layer of the lower left surface of the probe. This allows transverse waves to propagate along the entire area. Therefore, the ultrasonic longitudinal wave detects flaws in the vicinity of the corners of the four-sided steel billet l, the transverse wave detects flaws in the surface layer of the surface adjacent to the ultrasonic incident surface, and the surface wave detects flaws in the adjacent surface.

Similarly, push springs 11.11. Supported by...
Probe holders 71 and 72 are provided, respectively, located near the left corner on the upstream side and near the corner on the downstream side, and as described above, the rolling wheels 9, 9..., water pipes 12, 12...・
An ultrasonic angle probe a that emits longitudinal waves is provided at a position close to the right corner of the square steel piece l on the upstream side of the upstream probe holder 71, and the probe a A probe that emits surface waves is provided near the lower corner, and beveled probes c and d that emit transverse waves are provided on the downstream side. Inside the child holder 72, two beveled probes c and d that emit transverse waves on the upstream side are provided, and on the downstream side of each probe c and d, a position close to the lower corner of the square steel piece 1 is provided. An oblique probe a1 that emits a longitudinal wave from a surface wave and a probe a1 that emits a surface wave are provided, respectively.

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 upper plate 21. The positions of the probe holders 71.72, 71.72 attached to the lower plate 22 are different.

That is, the upstream probe holder 7 attached to the upper plate 21
1 is located near the right corner of the square steel piece 1, and the downstream probe holder 72 is located near the upper corner. Further, the probe holder 71 on the upstream side attached to the lower plate 22 is located near the lower corner of the square steel piece l, and the downstream probe holder 72 is located near the right corner of the square steel piece l. In each probe holder, as mentioned above, a probe a that emits longitudinal waves is installed at a position close to each corner of the square steel piece, and the probe a that emits a surface wave A probe C1d, which is provided on the inner side and emits transverse waves, is arranged so as to move away from a position near the corner of the square steel piece l.

Figures 11 and 12 show probe holders 71, 71, respectively.
This is a schematic diagram showing the propagation state of ultrasonic waves emitted from the probes in... Probes a, b and probes c, d, which are located on the same plane orthogonal to the transport direction of the probe holder 71 and located in each probe holder 71, emit ultrasonic waves in opposite directions to detect the probes. The ultrasonic waves are propagated along the surface layer of the side surface adjacent to the side surface on which the feeler holder 71 is located or obliquely to the surface. Also, 4 located on the downstream side
Two probe holders '12. '12. ... are located on the same plane perpendicular to the conveyance direction of the square steel piece 1, and the probes a, b and probes C and d in each probe holder 72 emit ultrasonic waves in opposite directions. Then, the ultrasonic waves are propagated along the surface layer of the side surface adjacent to the side surface on which the probe holder 72 is located, or obliquely to the surface.

When performing flaw detection using the device with the above-mentioned escape structure, the rods 31 of the air cylinders 3, 3 are advanced to bring the guide rollers 4.4 into rolling contact with the left and right corners of the square billet l being conveyed. , each probe holder 7L, 71...72, 72,...
The rolling wheels 9, 9... inside are brought into contact with the side surface of the square steel piece l. and water pipes tg, t2. ...Sprinkle couplant water onto the 1llII surface of the square steel piece and each probe holder 71.71
,...,'12,72. ...probes t, b,
It is filled in the gap between the probes o and d, and in this state, flaw detection is performed by emitting ultrasonic waves from the respective probe heads b, c, and d.

In this case, each probe holder 71, 71..., 72°7
2... are push springs 11, 11. A square piece of steel! Since the probe is pressed against each side of the probe, the gap between each side and each probe is always constant, minimizing the change in sensitivity of each probe. In addition to the push springs 11゜11,..., tension springs 6.5, 6 that suspend the entire mounting holder 2.2.
．． At step 6, each probe follows the bending, twisting, etc. of the square steel piece,
The gap between each side of the square steel piece 1 is constant.

In the above-mentioned embodiment, a probe that only emits longitudinal waves, transverse waves, and surface waves was used, but instead of this, a plurality of built-in transducers are used to emit longitudinal waves, transverse waves, and surface waves.

A composite probe that emits surface waves may also be used.

In addition, although the probes that emit transverse waves are arranged in parallel on each side of the square steel piece in the direction perpendicular to the conveying direction, the number may be increased according to the size of the square steel piece, and each probe holder 71 and 72 may be made slidable with respect to the mounting holder 2, 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. Because there is
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 position of the round bottom.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the angle angle flaw detection method, Figure 2 (a) -? + This is a graph showing the flaw detection results in Fig. 1, Fig. 3 (a) and (b) are photographs of signal waveforms from the cathode ray tube of the flaw detector, and Fig. 4 (a), (b), and P→ are the states of artificial defects. Schematic diagram showing
is a graph showing the relationship between the refraction angle and the echo height when each artificial defect is detected using a shear wave oblique angle; Figures 6 (a), (b), and (c) are schematic diagrams of the transverse wave angle flaw detection method, Figure 7 is a graph showing the gs diagram flaw detection results, and Figure 8 is the equipment used to implement the method of the present invention. FIG. 9 is a schematic diagram of one probe holder, FIG. 10 is a diagram in the direction of the arrow in FIG. 9,
@Figures 11 and 12 are schematic diagrams showing the state of ultrasonic propagation, respectively. l... Square steel piece, 2... Mounting holder, 3... Air cylinder 4... Guide ruler 6, 6... Tension spring 71.72... Probe holder 8... Roller
a, b, c, d...Probe characteristics Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Figure 0 Loincloth Figure 10 Figure 11 Figure T2

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 of the adjacent surface of the incident surface. Ultrasonic flaw detection method 0 characterized by propagating each of these three types of ultrasonic waves into a rectangular metal piece in order to detect flaws in each part and to locate flaw positions using surface waves.