JPS5861462A - Method and device for ultrasonic flaw detection for square material - Google Patents

Abstract

PURPOSE:To permit flaw detection with high accuracy by changing an ultrasonic flaw detecting area at each fluctuation in the sectional size or shape of square steel by following up to said fluctuations even when said size and shape fluctuate. CONSTITUTION:The transmission pulse output Ta from a signal transmission part 10 is converted to ultrasonic waves by a probe (a). Said ultrasonic waves are transmitted toward square steel 1. The ultrasonic waves reflected from the steel 1 are received by the probe (a), where the waves are converted again to an electric signal. The signal is amplified up to a prescribed value by a signal receiving amplifier 13, whereby R signals, that is, signals of a transmission echoes (T), surface echoes (S), bottom echoes (B1, B2...) are obtained. Wall thickness signals E1, E2 are obtained by a generating part 14 for wall thickness signals by the use of said receiving signals R and the S echo gate Gs1, B echo gate Gs2 of said generating part 11. The signals E1 and E2 obtained here indicate the sectional size of the square steel, and said size is measured by counting said signals with a counter 16 via a flip-flop circuit 15, etc. A control part 17 for flaw detection gates determines the beginning and end points of the flaw detection gate by subtracting the predetermined depth Wa of the dead zone in the surface layer part and the thickness Wb of the dead zone in the bottom layer part from the size value of the wall thickness of said square steel. Thus the flaw detection gate is controlled always to the specified depths of the dead zones in the surface and bottom layer parts in accordance with the wall thickness size of the square steel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method and apparatus for long square bars (hereinafter referred to as square steel) having a square cross section or a shape similar to a square.

Recently, continuous casting has become the main type of rolled steel products due to the spread of continuous casting, and internal defects such as non-metallic inclusions in steel products are relatively unevenly distributed in the center, whereas in continuous casting. The wood tends to be approximately evenly distributed. Therefore, in internal inspection using ultrasonic flaw detection, if it is an ingot material, most of the internal defects can be detected by testing only the center, but with continuous casting materials, the distribution of defects is even, so it is possible to detect most of the internal defects by testing only the center. There is a growing risk of overlooking internal defects.

More recently, P L (Product Liabli)
ty) Due to issues such as this, the quality requirements and assurance level for steel materials has become extremely sophisticated, and in some high-end dramas, the tolerance in terms of parts is 0.0.
01%, and in order to satisfy this guarantee level, it is insufficient to detect defects in only the central part of the steel, and it has become essential to detect defects in the entire surface of the steel material, including directly below the surface. @ For such situations, conventional ultrasonic flaw detection of square steel is the first
As shown in the figure, a device equipped with a saddle-shaped tracing mechanism and a two-split probe transmits ultrasonic waves 2 perpendicularly from two sides of the square steel 1 to detect flaws inside the square steel 1, or inside a tank filled with water. Internal flaw detection of square steel was carried out using a device that was equipped with one probing probe and used a vertical method to detect flaws from two directions on the top of the square steel.

In the figure, 3 indicates an internal defect, and 5A indicates a flaw detection echo.

However, flaw detection using these vertical methods generally has the drawback of dead zones Wa and Wb at the bottom surface of the test material. That is, the shallow dead zone Wa is due to the difficulty in separating the reflected echo from the surface of the test material, and the bottom dead zone Wb is
This is based on the change in the position of the echo reflected from the back surface due to the change in the shape of the square steel. In particular, square steel has larger shape fluctuations such as defective shapes called types, bends, and twists than thick plates, pipes, etc., and also has poor surface properties, so there is a dead zone Wa about 20 degrees deep in the surface layer and a dead zone Wa in the bottom layer. A dead zone wb with a depth of about 5 glue was created. In addition, as shown in Fig. 2 (a) K, the conventional flaw detection gate t is generally set using a gate fixed method in which the starting and ending points of the gate are fixed, or as shown in Fig. 2 (a) K, the gate starting point is set to A surface echo tracking method was used in which the length of the gate was kept constant while the gate moved rapidly as the gate's position changed. Therefore, the second flJ (a)
In the figure, when the starting point 6 and ending point 7 of the gate are set, even if the positions of the surface echo 4m and the bottom echo 5m change due to changes in the thickness of the water film, they remain fixed regardless of the changes in the thickness of the water film. In b), when the surface echo changes its position from 4m to 4B, the starting point of the gate moves from 6m to 6m and always keeps a constant distance Lm from the rising position 9 of the surface echo, so it is a water belly. However, the end point 7 remained fixed at a constant distance t from the starting point 6m of the gate, regardless of the positions of the bottom echoes 5A and 5B. Therefore, in both methods shown in Fig. 2 (, ) and (b), if the end point 7 of the flaw detection gate is set very close to the bottom echo, if there is a change in the wall thickness of the square steel, the bottom echo will enter the flaw detection gate. In order to avoid this risk, K must be set taking into account the margin of positional variation of the bottom echo due to wall thickness variation, and therefore the dead zone in the bottom layer should be made small. I couldn't do it. In addition, the beam width per probe is usually 20 to 30 mm, and in order to expand the flaw detection area of a square steel cross section, it is necessary to arrange multiple probes in the horizontal direction of the cross section. However, as mentioned above, the shape of the square steel Kld varies greatly depending on the type, etc., and the positional variation of the bottom echo in each probe due to the shape change is large, causing a further increase in the dead zone.

The present invention was made in view of the above situation, and is aimed at reducing the deep dead zone W on the surface that occurs during ultrasonic flaw detection of long square materials such as square steel.
The purpose of the present invention is to reduce a to the value of a shallow dead zone wb at the bottom, prevent the dead zones Wa and wb from varying depending on the shape of the test material, and perform ultrasonic flaw detection with high accuracy. (1) In a method of detecting internal defects in a square piece of steel by emitting and receiving ultrasonic waves perpendicular to the plane of incidence from the surface of the square piece of steel using the pulse reflection method, nine or more probes are placed so as to follow each side of the square piece of steel. Transmits and receives ultrasonic waves from the square steel, calculates the cross-sectional dimensions of the square steel from the surface reflected waves and bottom reflected waves, and calculates the gate by subtracting the predetermined surface dead zone depth and bottom dead zone depth from this dimension. and an ultrasonic flaw detection method for square steel, which is characterized by detecting internal defects within the gate (2).
) In an ultrasonic flaw detection device that detects flaws by emitting and receiving ultrasonic waves perpendicular to the incident surface of a square steel using the pulse reflection method, the system traces two adjacent surfaces of the square steel from two opposing directions and scans one screen of the square steel. A pair of saddle-shaped flaw detection heads consisting of a plurality of probes, a gate circuit that detects the position of the surface reflected wave and the bottom reflected wave for each probe based on the reflected signal from each probe, and An ultrasonic flaw detection device for square steel characterized by a gate setting circuit that determines the position of the flaw detection gate based on each reflected wave detected by the gate circuit, (3) the probe individually detects the surface of the square steel; The gist of this invention is a device based on the above item (2), which is arranged so that its surface can be changed according to the following.

The present invention will be explained below based on the drawings. Fig. 3 is a partially sectional front view showing an embodiment of the present invention, Fig. 4 is a block diagram showing an embodiment of the present invention, and Fig. 5 is an example of ultrasonic flaw detection according to the present invention. It is a diagram.

The present invention has a pair of saddle-shaped flaw detection heads that follow the surface of the square steel from two opposing directions when the square steel is viewed in cross section.

That is, as shown in FIG. 3, the saddle-type flaw detection head 30.40 according to the present invention straddles two adjacent surfaces of the square steel 1 and receives the square steel 1 in opposing directions, for example, in the vertical direction. Install it so that it follows the surface of the square steel. Saddle type flaw detection head 30
is for carrying out ultrasonic flaw detection perpendicularly to the A side and the 8th side of the square steel 1, and has an A side flaw detection head 31 and an 8 side flaw detection head 32, and the A side flaw detection head 31 is for the square steel. A plurality of probes a, b, e, and d are arranged in parallel in the width direction of the square steel 1 for transmitting and receiving ultrasonic waves into the square steel 1 following the surface of the square steel 1. Similarly, the eight-sided flaw detection head 32 has +h on a plurality of probes "*'*.

On the other hand, the saddle-type flaw detection head 40 is for flaw-detecting C and D surfaces of the square steel 1, and similarly to the saddle-type flaw detection head 30,
It consists of a zero-plane flaw detection head 41 and a zero-plane flaw detection head 42 that conduct ultrasonic flaw detection from the surface, and the head 41 is Lj-ksL.
The head 42 has m, +a, o, and p probes, and transmits and receives ultrasonic waves from each probe to perform ultrasonic flaw detection on the square steel 1. Probe a
-p are individually installed on each flaw detection head so as to follow the surface of the square steel 1, as will be described later, and the functions of the respective probes are the same.

Now to explain the probe d, the ultrasonic waves emitted from the probe d travel inside the square steel 1 as shown by Dl, and C
It is reflected by the surface and returns to the probe d, during which flaw detection is performed in the area indicated by Dl.

The same applies to the probe t, and by transmitting and receiving ultrasonic waves from the C surface of the square steel 1, flaw detection is performed in the area indicated by Ll. The same applies to other probes. In ultrasonic flaw detection using probe d in flaw detection from the surface of square steel 1, the surface dead zone shown by subcutaneous KWa(t&) of the surface,
A bottom dead zone indicated by wb (zb) occurs on the opposing C surface, but by performing ultrasonic flaw detection with probe tC from the C surface, the deep dead zone Wa (ta) can be detected by flaw detection with probe l. It can be reduced to the value of the bottom dead zone indicated by the symbol Wa (Lc). Therefore, the ultrasonic flaw detection inside the square steel 1 should be performed from the four sides of the square steel 1 using the probe a-p K.
Therefore, the deep surface dead zone Wa can be reduced to the value K of the shallow dead zone wb, and the area in which ultrasonic flaw detection is possible in the cross section of the square steel is expanded accordingly.

However, since square steel is usually produced by rolling, it has variations with respect to the standard dimensions of its cross section, and also varies in its length direction. Furthermore, as mentioned above, the shape of each surface is not necessarily flat, but has unevenness, surface defects, etc., and varies in the length and width directions, and in the length direction, there are shape defects such as bending and twisting that are characteristic of long objects. .

When ultrasonic flaw detection is carried out continuously on such square steel, the ultrasonic flaw detection area changes due to changes in cross-sectional dimensions and surface shape, so conventional ultrasonic flaw detection with a fixed flaw detection area has poor accuracy. Good flaw detection is not possible.

The present invention enables highly accurate flaw detection by changing the ultrasonic flaw detection area each time to follow the change in cross-sectional dimensions and shape of square steel. That is, in the present invention, as shown in FIG. First, the cross-sectional dimensions of the square steel within the flaw detection area of each probe are measured by transmitting and receiving ultrasonic waves from the
An ultrasonic flaw detection area, ie, a gate, is set based on the measured value, and then ultrasonic flaw detection is performed within the set gate. FIG. #
Figure I5 is a diagram showing the operation of Figure 4, but now the probe aK
The flaw detection will be explained with reference to FIGS. 4 and 5.

In FIG. 4, 8 is a main control unit which has the function of controlling various components described later in relation to each other, and the function of setting the position and width of the gate, and 9 is a main control unit that receives signals from the main control unit 8. 10 is a signal T of the synchronizer 9, which generates a synchronous output waveform Tu+ as shown in FIG.
This is a transmitter that generates a transmission pulse Ta in synchronization with mK.

11 is a gate starting point signal Gs set by the main controller 8
+g, Ggzg and gate width signals G1z, Gsz
It is a gate generation unit that outputs two types of gates Gll + Gll2 based on tK, and Gll is a surface echo gate set with an arbitrary width centered on the surface depth of the square steel 1, and Gll is a gate generator that outputs two types of gates Gll + Gll2 based on t G, , is a bottom echo gate set with an arbitrary width around the bottom of the square steel 1.

The probe a is connected to the transmitting section 10, and the transmitting section 1
The transmitted pulse output T from 0 is converted to an ultrasonic wave by the probe a and transmitted toward the square steel 1.The ultrasonic wave reflected from the square steel 1 is received by the probe a, where It is again converted into an electrical signal and amplified to a predetermined value by the reception amplifier 13, and the eight signals shown in FIG. 5, namely the transmission echo (T),
Surface echo (S), bottom echo (B1 v Bt m
”----) etc. is obtained. Using this reception signal R and the 8 echo gates G11 and B echo gates G12 of the gate generation section 11, the thickness signal generation section 14 generates the thickness signal E. , , E are obtained. The signal width and width obtained here indicate the cross-sectional dimensions of the square steel, which can be measured with high accuracy by the method described below.

That is, 15 is a 7-rip, 7-p tube circuit, which generates a rectangular wave G1 that is set by the R transmission wave T and reset by E, and a rectangle wave G1 that is set by the R transmission wave T and reset by the bird. The width of these waves is measured by counting the clocks (cb) generated at minute intervals by the main clock pulse generator 18 using the counter 16. From this K, the interval between El and Aya, that is, the interval between the surface echo and the bottom echo can be detected with high accuracy. The flaw detection gate control unit 17 determines the start and end points of the flaw detection gate by subtracting a predetermined surface dead zone depth Wa and bottom dead zone depth Wb from the wall thickness value of the square steel. In this way, the flaw detection gate is always controlled at a constant dead zone depth in the surface layer and bottom layer based on the wall thickness of the square steel.

In this way, according to this control method, the cross-sectional dimensions of the square steel are calculated from the echo depth of the surface echo S1 and the bottom echo B1 for each repetition frequency, and the flaw detection gate can be set and controlled with extremely high precision based on this. For example, the clock (CL) generated by the main clock pulse generator 18 can be set to 32MH.
When z, the ff degree is a1■. By controlling the above-mentioned flaw detection gate not only for the probe son but also for all the remaining probes b-p, it is possible to detect flaws in the entire cross section with a good n degree regardless of changes in the shape of the square steel. Become. In addition to the method of controlling the flaw detection gate for each repetition frequency, if necessary, a method of obtaining an average value every few times and controlling based on that value may be used.

Next, we will explain the mechanism of the saddle-type flaw detection head that allows multiple probes to be placed on one side of square steel. Figure 6 shows one side of square steel.
A front view of a saddle-shaped flaw detection head that can accommodate four probes per surface, FIG. 7(A) is a plan view of the flaw detection head 31 according to the present invention, and FIG. 7(B) is a partial cross-section. The front view shown in is shown. 6 and 7 (A), (as shown in the figure, the probes d are each housed in a gimbal mechanism 19, and this gimbal is
Since it has a structure that can be rotated about the axis and is installed via a spring Y, it is possible to imitate the shape change (such as a tycoon) in the width direction of the square steel 1. In addition, four probes are housed in a holder 20, and this holder is
It is installed so that it can rotate around the z' axis. This allows it to imitate the shape change in the longitudinal direction of the square steel. Further, since the holder 20 is installed so as to be rotatable about the v-v' axis, it is possible to follow large changes in the surface of the square steel.

If each probe is made movable in the width direction of the square steel, even if the size of the square steel changes, it can be handled by sliding the probe.

According to the method and apparatus of the present invention as illustrated and explained above,
The flaw detection area can be expanded dramatically compared to conventional methods, and it has an extremely large effect on quality assurance of square steel.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing conventional flaw detection, Figures 3 and 4.
Figures 5, 6 and 7 are explanatory diagrams showing the method and apparatus of the present invention. 1: Square steel 15 near rip-flop 2:
Ultrasonic beam 16: Counter 3: Defect
17: Flaw detection gate control section 4: Surface echo
18: Main clock pulse generator 5: Bottom echo
19 Nishinpal mechanism 6: Flaw detection gate starting point
20: Holder Applicant: Nippon Steel Corporation (and 1 other person) Representative Patent Attorney: Minoru Aoyagi] Figure 2, Figure 2, CI' of yα L ε c3 ), 〜 −〜」
Baboon α 00 Tada OΦ0 Continued from page 1 0 Author: Yoji Tanaka, 325 Kamimachiya, Kamakura City, Mitsubishi Electric Corporation, Kamakura Works ■Applicant: Mitsubishi Electric Corporation, 2-2-3 Marunouchi, Chiyoda-ku, Tokyo

Claims (1)

[Scope of Claims] (1) In a method for detecting internal defects in a square timber by transmitting and receiving ultrasonic waves perpendicular to the incident plane from the surface of the square timber using a pulse reflection method, a plurality of ultrasonic waves arranged to follow each surface of the square timber are used. Ultrasonic waves are emitted and received from the probe, and the cross-sectional dimensions of the square timber are calculated from the waves reflected from the surface and the bottom of the square timber. From these dimensions, the predetermined values of the dead zone depth of the surface layer and the dead zone depth of the bottom layer are calculated. An ultrasonic flaw detection method for square timber, characterized by calculating the gate by subtracting the gate, and detecting internal defects within the gate. In an ultrasonic flaw detection device that performs flaw detection,
a pair of saddle-shaped flaw detection heads that follow two adjacent sides of the square timber from the direction and arrange a plurality of probes per side of the square timber;
A gate circuit detects the position of the surface reflected wave and bottom reflected wave for each probe using the reflected signal from each probe, and the position of the flaw detection gate is determined based on the reflected waves detected by each gate circuit. An ultrasonic flaw detection device for square timber, characterized by being equipped with a gate setting circuit. (3) The ultrasonic flaw detection device according to claim 2, wherein the probes are installed so that they can individually follow the surface of the square timber and change their directions.