JPS59148864A - Ultrasonic flaw detecting method of square billet - Google Patents

Abstract

PURPOSE:To improve the performance of the detection of an extremely small defect by setting an electron array type probe 1 in a plane perpendicular to the axial direction of a square billet, at specific distance from the surface of the square billet, and at a specific angle to the surface of the square billet. CONSTITUTION:When internal flaw detection is performed, the electron array type probe 1 is set in the plane perpendicular to the axial direction of the square billet 2, at the specific distance from the surface of the square billet and at the specific angle to the surface of th square billet. Said probe 1 makes an electron linear scan to perform the vertical internal flaw detection of the square billet 2. Then, the number (n) of elements (a) of the probe 1 used for ultrasonic wave transmission and reception and the convergence of an ultrasonic wave beam S are controlled according to the size of an internal defect of the square billet 2 to be detected. This method improves the detection performance to an extremely small defect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method for square steel pieces, and is intended to simplify online flaw detection equipment for ensuring the quality of square steel pieces.

Conventionally, surface flaw detection using magnetic particle flaw detection and internal flaw detection using a vertical two-piece probe have been used to ensure the quality of square steel slabs, but this is because each flaw detection device is independent.

It is necessary to install the devices on separate flaw detection lines or in tandem, which requires a large amount of space. In addition, in the current internal flaw detection using a vertical two-piece probe, the subcutaneous area on the surface becomes a dead zone, and quality assurance over the entire cross section cannot be performed.
The application of angle angle flaw detection is being considered for flaw detection on the surface layer, but if a flaw detection device using this method is introduced, a larger installation space will be required. Furthermore, in this case, an interface between each flaw detection device is required to discriminate between internal defects, subcutaneous defects, and surface defects. Furthermore, if each device is independent, the relative differences in defect position detection by each device may cause deterioration in detection accuracy.

The great invention solves the above problems.

First, to explain the outline of the embodiment of the great invention, the electronic scanning type ultrasonic flaw detection device can arbitrarily form the ultrasonic beam (convergence, divergence, etc.).

Since the ultrasonic beam can be scanned at high speed, this electronic scanning type ultrasonic flaw detection device has been used to perform full cross-section flaw detection of square steel slabs. using children.

Internal flaw detection using the same flaw detector by electronic scanning.

Surface Layer Flaw Detection 1 Surface flaw detection is carried out sequentially under the following limiting conditions. .

(+) The material to be inspected is a square steel piece.

(11) Set the flaw detector at a predetermined distance from the surface of the square steel piece in a plane perpendicular to the axial direction of the square steel piece, and at a predetermined angle to the surface of the square steel piece.

(In order to inspect the 1111 square steel piece over the entire MK, the square steel piece is transported.

Next, a method for detecting flaws in the interior, surface layer, and surface of a square steel piece will be described.

In the case of internal flaw detection, as shown in FIG. 1, by electronic linear scanning of the electronic array type probe Tll.

Perform vertical internal flaw detection on the square steel piece (2). Square steel piece 1 to be detected
Depending on the size of the internal defect (2), convergence control of the element (IL) of the probe fil used for transmitting and receiving ultrasonic waves and the ultrasonic beam C is performed. In other words, as the number n of elements used for transmission and reception increases, the effective transducer diameter increases, the directivity of the ultrasonic beam (scent) improves, and the defect detection level also improves. Therefore, the detection ability for even finer defects can be improved, since they are larger than the size of internal defects.

When detecting flaws in the surface layer, use an ultrasonic beam (there is no need to use an ultrasonic beam, so the conditions can be determined in relation to the flaw detection speed).
The narrower the lever, the finer the scanning pitch, or the more time it takes to detect flaws in the entire interior.) In addition, in FIG. 1, the shaded area (21k) of the steel piece f1) indicates the flaw detection area.

In the case of surface layer flaw detection, the probe fi+ is used for electronic linear scanning,
The steel piece (2) is subjected to oblique angle flaw detection by electronic sector scanning (see FIG. 2(1)) or electronic sector+linear scanning (see FIG. 2(la) (lbXIc)). Since it is necessary to detect even minute defects in this surface layer, a focused ultrasonic beam is used. The surface layer of the side surface of the steel piece (2) adjacent to the ultrasonic beam incident surface is detected in the flaw detection area (ga).
When selecting the refraction angle α within the range of 15° to 60', and when the bottom surface layer is the flaw detection area (2&), the refraction angle α should be selected within the range of 25° to 45°. Flaw detection is possible without a dead zone.

Surface flaw detection is performed using a surface wave (8') as shown in FIG. The incident angle 1 of the ultrasonic beam (s) for generating the surface wave (S') is determined by the following equation.

I i = a r cgin (-sin 90°)C.

c, = sound speed of the incident side medium (water) c, - sound speed of the refracting side medium (W4 order) where, Underwater sound speed CI = 148 Bait/μsea% Surface wave sound speed in steel billet (4 = 298 tsm/μsec From
The incident angle of surface wave generation (=29.8°, the delay time of each element (i) is controlled so that the ultrasonic beam (8) is most focused at the incident point (o) and 1M electronic linear scanning is performed. .

Since the surface wave (S') has a large attenuation in water, the detection area (2a) in which surface flaw detection is possible is within the range of + several waves due to the dead band caused by the SL echo. Therefore, the pitch of electronic linear scanning is set to ten wave invasiveness.

Next, a control method for ultrasonic beamforming will be explained. General pulse type flaw detector (4) shown in Figure 4
Now, as shown in Fig. 5, the transmission pulses (electrodes (alt7) attached to the upper and lower surfaces of the vibrator (5) A voltage is applied between them to excite the vibrator (6), and a transmission wave (q) is transmitted.

In the case of electronic scanning flaw detection equipment, as shown in Figure 6, each element (&□) (a□)...
...... (al) (After the delay time ΔT D' (1) set for each °°°°° (an), each element (al) (a-)... ai)・・・・・・(
an) (C compatible transmission pulse (1 (pm)...
・(Pl)...(Pn) is sent and excited, and the beam deflection and convergence of the transmitted wave (Q) are performed by the probe flll as a whole. At the time of reception, give the same delay to the received wave of each (ai) as at the time of transmission, and observe the combined waveform.

Here each element for ultrasonic beamforming)
(a,) (a,)... (al)...
An example of calculating the delay time ΔTD of (an) is shown. As shown in Figure 7, the element width is W, and the inter-element space M
, the deflection angle θ, and the focusing distance, the element (al)
The distance L(1) from to the gathering point (no) is.

B = −(n −1) (W+M) If the maximum value of the culm L(1) is L(i)max, each elm)(
al) The delay time ΔTn(i) to set Ic is T,(i
) max -I, (i) Δ'I'D (1) = -C = speed of sound in the medium.

Next, a description will be given of the method for detecting flaws on the inner surface layer and the surface of a square steel piece using the same probe. As described above, in the electronic scanning flaw detection device, the ultrasonic beam (S) can be arbitrarily formed for each transmission pulse 0. In other words, three types of transmission pulses (PI: forming for internal flaw detection, the next transmission pulse D: forming for surface layer flaw detection, and the next transmission pulse opening: forming for surface flaw detection; the same probe F1) can be used for three types. Can perform flaw detection. Here, a 5 MHz probe T1) is placed parallel to the surface of the square steel piece (2) in a plane perpendicular to the axial direction of the square steel piece (2) with respect to the square steel piece (2) K with a width of 155 fl. ,
An example of control when performing internal, surface layer, and surface flaw detection is shown below. Acoustic coupling is by water immersion method, and 8
．． Select a water distance that will prevent echoes. As shown in Figure 8, for internal flaw detection, the delay time ΔTD of the transmitted wave (a) was controlled so that the spread of the ultrasonic beam (S) down 3 dB was about 50 mm on the bottom side. ,
Linear scanning is performed in 4 steps (Fig. 1). For surface layer flaw detection, an ultrasonic beam (S) is applied from the center of the steel strip (2), and the lower half of both sides adjacent to the incident surface is transmitted to the flaw detection area (2a) using an ultrasonic beam (S) with a 3 dB reduction in ω. ) has a spread of 1
0. In the delayed surface flaw detection (a), in order to detect the entire area of the entrance surface, the flaw detection pitch is 10 wavelengths, that is, approximately 6B, and linear scanning is performed at 155/6=26 steps (Fig. 3). The transmission pulse [F] is divided into an internal flaw detection pulse (Pa), a surface layer flaw detection pulse (Pa), and a surface layer flaw detection pulse (,
Pb) and surface flaw detection pulse (Pc). That is, the transmission pulse (46 (=4-1-8-) of B
-8-)-26') Make one sequence with pulses.

In this one sequence, the flaw detection area (2a) shown in FIG. 9(,)(b)(,) can be simultaneously detected.

In this case, the size of the flaw detector (11) required is limited by surface flaw detection, which has the widest I range and requires a large deflection angle θ.In other words, in order to perform surface flaw detection on the entire entrance surface, the size of the steel piece (2 ) is required, which contributes to the spread of the ultrasonic beam (s), taking into account the entire required effective transducer diameter.

If the trench beam (s) is thin, the axial flaw detection pitch will be fine.
If you don't scrape it off, you won't be able to detect flaws along the entire length, so
The culm degree is 0 fl. Next, assume that the element width is W.

−sinθ=15 W = element width λ = wavelength = 2T, /λ When the directivity angle θ' is 30-the wavelength λ is 14875.

W=15λ/πsinθ″=15X (14875
)/πsin 30cL-Q28 Therefore, element width W
is % Q25 mackerel.

Next, the arrangement of the probe for flaw detection of the entire cross section of the square steel piece will be explained. FIG. 10 (1) (Ia) (Ib) shows an example of the arrangement of the probe (1) for performing full cross-sectional flaw detection of a square steel piece (2) with a width of 155 m. The probes (1) of the size described above may be placed on each surface under the same conditions as described above.

Regarding the arrangement in the axial direction, there are two methods: a method in which all four are arranged in the same cross section (FIG. 10(la)), and a method in which they are arranged offset from each other in the axial direction (FIG. 10(lb)). 10th
In the case of the arrangement shown in Figure (Ia), if the probes (1) are excited at the same timing, they will interfere with each other. However, the axial conveyance speed of the square steel piece (2) is reduced to 1/4.
Otherwise, the flaw detection will be rough.・However, the flaw detection line requires less space. In the case of the arrangement shown in FIG. 10 (Ib), by shifting each probe (1), each probe m
Even if they are excited at the same timing, they will not interfere with each other. Furthermore, it is easier to increase the flaw detection speed than in the case of the arrangement shown in FIG. 10 (■&).

Regarding internal flaw detection, full cross-section flaw detection is performed either in one direction or in two directions using two adjacent probes fil.

As described above, according to the great invention, internal flaw detection, surface layer flaw detection, and surface flaw detection of a square steel piece are sequentially repeated by electronic scanning with an electronic array type probe, so that flaw detection of the entire cross section of the square steel piece is carried out in one step. It is possible to perform the test using only one flaw detection device, so the space required for the flaw detection line is extremely small, and the equipment cost is also low. Furthermore, the accuracy when discriminating flaw detection information into internal and subcutaneous surface defects is significantly improved.

[Brief explanation of the drawing]

Figure 1 shows the internal flaw detection method of the great invention, Figures 2 and 2 show the surface layer flaw detection method, Figure 3 shows the surface flaw detection method, and Figure 4 shows the configuration of the pulse type flaw detector. Figure 5 is a waveform diagram showing the transmission pulse and transmission wave of the same flaw detector, Figure 6 is a waveform diagram showing the excitation timing of the array type probe, and Figure 7 is a waveform diagram showing the excitation timing of the array type probe. A diagram showing an example of calculating the delay time, Figure 8 is a diagram showing the internal first surface layer and the flaw detection area by surface flaw detection using the same probe, and Figure 10 is a diagram showing the arrangement of the probe for testing the entire cross section of a rectangular steel piece. FIG. (1)'...Electronic array type probe + l5 (2)...Square steel piece. Patent applicant: Kobe Steel, Ltd. Procedural amendment (voluntary) March 1980 240 1 ・Indication of lff11 1988 Patent application No. 23526 2 Title of invention Ultrasonic flaw detection method for square steel billet 3 Person making the amendment ii Relationship with f'l Patent applicant (119) Company 2 Company Kobe Steel, Ltd. 4th generation T! 11 people 红577 6 Supplement 11:, Target 7, Correction content il+ rL(t)=! on page 6, line 19 of the specification. θ1B −(t−1)(W”M ))”
” to be corrected. (2) Page 7, line 1: “, L(1)=D2+(D−θ10%(W−M)(n
-21+1))” is corrected. (3) [L'(1) max J f on page 7, line 4]
Correct it to "L(1)max". (4) Delete "as shown in Figure 8" from the second to third lines of page 8. (6) On page 9, line 8, after “taking into consideration” “length 1
Approximately 70 mm is required. For the width of the probe (length in the axial direction of the steel piece), insert the width of the probe in the axial direction of the steel piece. (6) In the same page, page 10, line 14, ``1 naruga'' is corrected to ``suruka.''

Claims (1)

[Claims] 1. An electronic array type probe at a predetermined distance from the surface of a square steel piece in a plane perpendicular to the axial direction of the square steel piece. and set at a specified angle to the surface of the square steel piece. An ultrasonic flaw detection method for a square steel piece, characterized by sequentially repeating internal flaw detection, surface layer flaw detection, and surface flaw detection of the square steel piece by electronically scanning the probe.