JPS59148865A - Internal defect detecting method of ultrasonic flow detection - Google Patents

Abstract

PURPOSE:To perform high-speed flaw detection on on-line basis by performing the oblique flaw detection of the surface layer of a material to be detected by an ultrasonic probe and operating an estimated defect position from the position relation between the probe and material to be detection, the angle of incidence of an ultrasonic wave, etc. CONSTITUTION:The ultrasonic probe 7 is set in a specific state, and while the ultrasonic wave beam S is moved on a surface of incidence in parallel, oblique flaw detection is performed on the sides of surface layers on adjacent flanks to operates the estimated defect position when the beam is projected upon the surface of the material 2 to be detected from the position relation between the probe 7 and material 2 to be detected, the angle of incidence of the ultrasonic wave, and a defect echo time. This method allows the high-speed flaw detection over the entire surface layer of a billet without any undetected area although a conventional internal flaw detecting means can not perform flaw detection in an area which is several mm from the surface of the steel material.

Description

[Detailed Description of the Invention] The present invention relates to a subcutaneous defect detection method using ultrasonic flaw detection.
More specifically, the purpose is to distinguish and detect surface defects and subcutaneous defects of a test material using practical means.

In recent years, manufacturers of secondary processing of wire rods and steel bars have been focusing on labor-saving and
Processes are being omitted to reduce energy and costs, and processing conditions for wire rods and steel bars are becoming increasingly severe. For this reason, processing cracks during cold forging and wire breakage during wire drawing caused by minute inclusions existing inside wire rods and steel bars have become a problem, and efforts have been made to remove inclusions and prevent contamination during the iron and steel manufacturing stages. It has become essential to establish out-of-furnace refining technology and inspection technology to detect the presence or absence of fine inclusions from the perspective of quality assurance.

As for this inspection technology, for steel bar products, there is an ultrasonic flaw detection device that rotates the bar or rotates a probe around the bar while projecting a focused ultrasonic beam into the material.
Similar flaw detection methods cannot be applied to wire products due to their small diameters, and it is currently impossible to perform flaw detection on the entire circumference and length of wire products at the final stage of coiling.

Incidentally, problematic inclusions in wire rods and steel bars exist from the raw material stage. Therefore, if inclusions are detected at the stage of rectangular steel pieces, the internal quality of the product can be guaranteed, and especially in wire rods. In some cases, as a substitute for internal flaw detection of the product,
Ultrasonic flaw detection inside the square steel billet is utilized. And inside this intermediate process.

The introduction of partial flaw detection has great benefits because defective steel pieces can be removed in advance and the length of the tested material is shorter than flaw detection at the small product stage, which improves flaw detection processing efficiency. However, in order to ensure its reliability, it is required to exhibit high detection accuracy even for minute inclusions.

Conventionally, as an ultrasonic flaw detection method for rectangular steel pieces, a method of performing vertical flaw detection using a two-piece probe is known.

However, this method has a major problem in that, although defects existing inside can be detected, defects existing beneath the surface of the square steel slab cannot be detected. In other words, when actually processing square steel pieces into products, inclusions that cause problems such as processing cracks often exist under the surface skin, and it is desired to establish a flaw detection method that detects internal defects including under the surface skin. There is.

Therefore, the applicant of the present application proposed a surface layer flaw detection method applying angle angle flaw detection in Japanese Patent Application No. 57-233944.

In flaw detection that applies this angle flaw detection, defects in the surface layer and inside can be detected from the bare surface of a square steel piece without a dead zone. For these reasons, the accuracy of estimating the position of the detected defect is not very good. Therefore, it has been difficult to determine whether the detected defect is a superficial defect or a subcutaneous defect.

Defects on the surface (surface flaws) can be removed by chipping or grinding in the billet processing process.
This does not pose a problem during secondary processing of finished products. Therefore,
It is important to identify whether the detected defect is a surface defect or a subcutaneous defect in the square steel piece.

Therefore, the present invention was invented in view of the above-mentioned problems, and it is an object of the present invention to provide a method for distinguishing and detecting surface defects and subcutaneous defects of a test material by practical means. , its characteristics are that the surface layer of the material to be inspected is obliquely inspected using an ultrasonic probe, and the positional relationship between the probe and the material to be inspected, the incident angle of the ultrasonic waves, and the defect echo detection time are determined. Then, the estimated defect position when projected onto the surface of the material to be inspected is calculated, and the surface defect detection device detects only the surface defect, and the predetermined area of the defect position is determined. By subtracting information, only subcutaneous defects are detected.

The present invention will be explained in detail below.

First, the introduction of the angle angle flaw detection method in the present invention will be explained.

Conventionally, the ultrasonic vertical flaw detection method has been applied to detect internal defects in square steel pieces, as described above, but in this case, as shown in Figure 1, the probe (1) is The ultrasonic wave [Sl] emitted by the ultrasonic wave produces a reflected echo (Sl) at the incident surface and a reflected echo (Bl) at the bottom surface, which has the drawback that there is a dead zone near the surface. On the other hand, when using the angle angle flaw detection method, as shown in Fig. 2, the reflected echo (Sl) from the incident surface of the ultrasonic wave fsl remains considerably, but the square steel piece (2)
Since the reflected echo from the side surface (S2) travels downward, no dead zone is caused by the reflected echo on the side surface. Therefore, by using the angle angle flaw detection method and setting the side surface adjacent to the entrance surface as the flaw detection area, it becomes possible to detect flaws from the surface to the inside of the square steel piece (2) without a dead zone.

Furthermore, when testing the surface layer of the surface opposite to the entrance surface,
As shown in FIG. 3, as in the case of side surface flaw detection, no dead zone occurs due to the reflected echo (Sl) from the bottom surface. Therefore, in oblique flaw detection, the surface layer of the bottom surface, which is opposite to the entrance surface, can also be used as the flaw detection area.

The basic principle of the present invention is to detect the surface layer of a square steel piece (21), which is a test material, by such an angle flaw detection method.

Next, in oblique angle flaw detection, the range of refraction angles of ultrasonic waves that can be used to detect flaws in the surface layer will be explained.

As shown in FIGS. 4 and 5, when the refraction angle (θ) becomes 30° or more, the bottom echo (Bl) becomes extremely small.

That is, there is no dead zone in the surface layer of the bottom surface, and surface layer flaw detection becomes possible. Therefore, in order to detect flaws in the surface layer of the bottom surface, it is desirable that the refraction angle (θ) is 30° or more.

From the results of the bottom surface above, it is found that the crack in which the flaw detection area is the side surface layer as shown in Figure 6 is 3.
It can be seen that if the ultrasonic wave is applied at an angle of 0° or more, the reflected echo from the side surface will not be a problem and the surface layer can be detected.

That is, it is desirable that the refraction angle (θ) is 60' or less.

Next, we will explain whether flaw detection is performed using longitudinal waves or transverse waves.

Figure 7 shows the angle of incidence b when ultrasonic waves are incident on iron from water.
), a graph showing the relationship between the refraction angle (θ) and the round-trip passage rate. In the graph, Ts indicates a transverse wave and TD indicates a longitudinal wave17.

As is clear from FIG. 7, in the region where the refraction angle is 35° or more, a higher passing rate is obtained for the transverse wave (T8) than for the longitudinal wave (TD). Therefore, if a transverse wave σ8) with a refraction angle of 35° or more is used, no longitudinal wave (TD) is generated, so there is no confusion. In other words, if longitudinal wave angle flaw detection is performed in this range, transverse waves will be generated at the same time, and the shear waves may pick up defect echoes from different directions. is desirable.

When using the side surface layer as the flaw detection area, the refraction angle (6 is 60°
It is desirable that the refraction angle (r) be less than ) becomes wider. Therefore, it is preferable to use shear wave angle flaw detection for flaw detection of the side surface layer.

However, an appropriate refraction angle (θ) of the transverse wave or longitudinal wave may be selected depending on the purpose of flaw detection and the area to be flaw detected.

Incidentally, the relationship between the refraction angle (θ) and the incident angle (θ) is expressed by the following equation.

sinα C1 5inθ C2 α; Incident angle θ; Refraction angle C1; Sound speed of the material on the incident side CQ: Sound speed of the material on the refraction side The scanning technology for flaw detection will be explained.

In order to perform online flaw detection over the entire length of the square steel piece (2), the ultrasonic beam fsl must be scanned at high speed. This scanning method can be roughly divided into mechanical scanning and electronic scanning, and for each of them, linear scanning in which the ultrasonic beam is moved in parallel, and sector scanning in which the ultrasonic beam is waved can be considered.

In other words, this can be summarized as follows.

As mechanical linear scanning, there is a belt-type linear scanning shown in FIG. In this system, a large number of transducers (4) are arranged on a belt (3), and while the belt is rotated, an ultrasonic beam is scanned while moving relatively over a square steel piece (2).

Furthermore, as the mechanical linear scanning, it is also possible to employ a vibrating linear scanning as shown in FIG. This scanning means arranges a plurality of transducers (4) in a - row, vibrates them in the width direction of the rectangular steel piece (2) and moves them relative to each other to scan the ultrasonic beam.

What is shown in FIG. 10 is a mechanical linear scan.1.
This scanning means includes a large number of transducers (4
), and while rotating the disc (5), square steel pieces (21
The ultrasonic beam is scanned by relatively moving the top.

An example of mechanical upper scanning is shown in FIG. 11, in which the camera element (4) is fixed to the reflector (6), while
The reflector plate (6) is vibrated to cause the ultrasonic beam fs) to swing and scan the square steel piece (2).

Next, electronic scanning will be explained. For electronic scanning, an electronic scanning array type probe (7) as shown in FIG. 12 is used. This probe (7) is constructed by arranging a large number of transducer elements (8) in a line on the plane of a base (9) and applying a coating (10) to the surface thereof. The ultrasonic beam from the probe is controlled by adjusting the timing of wave transmission and reception of each element (8) using a delay time control circuit.

For example, if the delay time is not set as shown in FIG. ) can be set appropriately, the beam (Sl) can be tilted as shown in Fig. 13 (Ila), the beam (Sl) can be narrowed down as shown in Fig. 13 (■b), or the beam (Sl) can be adjusted as shown in Fig. 13 (IIQ).
It is possible to freely form a tilted wavefront by constricting sl.

The characteristics of electronic linear or sector scanning, in which such a probe is electronically scanned and the ultrasonic beam is translated or swung onto the incident surface, are summarized as follows.

(1) High-speed scanning performance High-speed scanning is easier than mechanical scanning.

(IIk") Sharp directivity Since an electronic scanning probe operates a large number of transducer elements simultaneously, the probe as a whole is the same as a large-diameter transducer, and has sharp directivity.

(lft) As mentioned above, a converging electronic scanning probe is designed to give a predetermined delay time to the transmitted and received signals, and, like concave transducers and lens-equipped transducers, narrows the beam and increases the resolution. Enables increased flaw detection. Since this focal length can be set arbitrarily, the accuracy of detecting minute defects can be improved by focusing the beam on the flaw detection area in the material, and at the same time, the accuracy of estimating the defect position can also be improved. For reference, the ultrasonic beam diameter during flaw detection of a square steel piece and S/ for the horizontal hole of I2 are shown below.
The relationship between N is shown in Figure 14.

OV) Since the ultrasonic beam can be scanned with the probe fixed, a wide flaw detection area can be obtained with one probe.

Next, a case of performing electronic linear scanning and a case of performing electronic sector scanning using the electronically scanned array type probe (7) having such characteristics will be compared and explained.

First, in the case of electronic near scanning, the probe (7) is set in a predetermined state, and the ultrasonic beam @) is directed onto the incident surface as shown in Fig. 15 (a), (b), and (0). While moving parallel to the surface layer, flaws are detected on the surface layer side of the adjacent side surface. An example of the scanning circuit required in this case is shown in FIG. That is, for example, a linear array probe with 64 total elements (8) (71 to 16i
element (8) as one set, the probe (71) and the transmitter/receiver (II) are connected via the previously mentioned delay circuit θ2) and reed relay circuit θ3), and the changeover switch allows sequential transmission and reception. The ultrasonic beam is scanned by shifting the element (8).

On the other hand, when scanning electronic sectors, the probe (
7) in the predetermined state, as shown in Fig. 17(,)(b).
As shown in (,), the ultrasonic beam +81 is swung at the incident surface and the surface layer side of the lower half of the adjacent side surface is detected for flaws. An example of the scanning circuit required in this case is shown in FIG.

That is, for example, a probe with a total number of divided elements of 32 (
7) and the transceiver (II) are connected in a one-to-one correspondence via the delay circuit (121), and the inclination angle of the ultrasound beam is changed by sequentially changing the delay time setting by the delay circuit (I21). The beam is then swung for scanning.

Comparing the above-mentioned electronic linear scanning and electronic sector scanning, the latter can be said to be advantageous in that the following disadvantages mentioned above are overcome.

(1) In the case of electronic linear scanning, since the transmitting and receiving elements are sequentially shifted, the total number of elements increases and the overall transducer diameter increases.

(11) A large number of relays are required for switching, and the lifespan of these relays is short.

(111) In order to shift the transmitting and receiving elements sequentially, the transmitting/receiving device (T/RUnit) and the element are one-to-one.
Therefore, it is difficult to adjust sensitivity variations.

OV) Because the amount of movement of the incident point of the ultrasonic beam is large, the first
As shown in FIG. 9, the refraction angle changes under the influence of the surface irregularities of the square steel piece (21), and the defect position estimation accuracy deteriorates.

On the other hand, in electronic sector scanning, there is no need to sequentially shift the transmitting and receiving elements, so the total number of elements is small and the relay Q31 is not required. This makes it easy to adjust sensitivity variations.

However, in electronic sector scanning, the amount of movement of the point of incidence of the ultrasonic beam is small, so as shown in FIG. 20, it is less affected by the unevenness of the incidence surface.

In this way, in the case of electronic sector scanning, there is no particular problem in practical use, but in order to further reduce the influence of unevenness on the incident surface, it is desirable to use electronic sector + linear scanning, which will be explained next. As shown in FIG. 21(I), electronic sector + linear scanning is performed to correct the deviation of the incident point of the ultrasonic beam (sl) due to electronic sector scanning.

That is, as shown in FIG. 21 (IIaXIJbXIia), the transmitting and receiving elements are shifted (linearly scanned) according to each beam inclination angle, thereby minimizing the deviation of the incident point, and making the incident plane more accurate than electron sector scanning. This is intended to improve the accuracy of defect position estimation by making it less susceptible to the effects of

Next, a probe setting method for performing electronic scanning having such characteristics will be described.

In an electronically scanned array type probe, the transducer element spacing d required to prevent the generation of grating lobes is as follows: λ: ultrasonic wave It is expressed in terms of wavelength in the propagation medium. Therefore, in order to increase the inclination angle of the ultrasonic beam (however), the element spacing d must be reduced when λ is constant (Figure 22 (b) shows the relationship between the element width and the maximum beam inclination angle io). show). That is, the element width needs to be made small.

Here, the grating lobe refers to the above-mentioned figure 13 (
This refers to the generation of a high-intensity beam in a direction other than the desired tilting direction, such as in II). Particularly in the case of water immersion or local water immersion described in the acoustic coupling method described later, since the wavelength λ in water is small, it is important to suppress the generation of grating lobes by reducing the element spacing d.

Now, a method of setting the probe for electronic linear scanning will be specifically explained. In this case, there are two methods:

(1) - is a method in which the probe is positioned at a predetermined distance from the surface of the square steel piece in a plane perpendicular to the axial direction of the piece and set horizontally to the plane of incidence.

However, in this case, the width of each element of the probe is made smaller and the number of divisions is increased. A feature of this set method is that since the maximum beam inclination angle is large, it is possible to detect flaws on both sides adjacent to the entrance surface.

(11) The other method is to position the probe at a predetermined distance from the surface of the square steel piece in a plane perpendicular to the axial direction of the piece, and tilt the probe at a predetermined inclination angle jo0 with respect to the incident plane. This is how to set it. A feature of this set method is that by setting the above-mentioned inclination angle to be the same as the incident angle, there is no need for a delay operation of each element to incline the beam. Further, the divided element width of the probe may be large, and when comparing probes with the same element division, a larger angle of incidence can be obtained than when set horizontally.

Now, when the probe (7) is set in a predetermined state like a queen on the square steel piece (2) and linear scanning is performed, the situation is conceptually shown in Figs. 15(a) and (b). This is the passage shown in (o).

Figure 23 shows an example of how the probe (7) is arranged on a square steel piece (2). In this case, one probe (7) is arranged horizontally on each side of the square steel piece (21). In other words, one probe (7) is used to detect flaws on one side or both sides of a piece of square steel (21) adjacent to the entrance plane as shown in the figure, but four probes (7) ), the entire surface layer of the square steel slab (2) can be inspected for flaws.In addition, in the case of flaw detection on both sides, the entire surface layer will be inspected from two directions in duplicate; If flaw detection is not necessary, by placing one probe on each adjacent entrance surface of the square steel piece (2), it is possible to detect flaws on the entire surface layer with two probes.

Next, a method of setting the probe for electronic sector scanning or electronic sector + linear scanning will be described.

(1) One method is to position the probe at a predetermined distance from the surface of the square steel piece in a plane perpendicular to the axial direction of the piece, and set the probe horizontally to the plane of incidence.

However, in this case, the width of each element of the probe is made smaller and the number of divisions is increased. A feature of this set method is that since the maximum beam inclination angle is large, it is possible to detect flaws on both sides that are in contact with Vtf to the incident surface.

(11) The other method is to position the probe at a predetermined distance from the surface of the 9-sided steel piece in a plane perpendicular to the axial direction of the piece, and align the probe with the center of sector scanning relative to the incident plane. This is a method of setting it by tilting it by the angle of incidence. A feature of this set method is that since the absolute value of the beam inclination angle becomes small, the maximum delay time can be shortened.

Furthermore, since the absolute value of the beam inclination angle becomes small, the number of element divisions of the probe may be small.

Now, the situation when the probe (7) is set on the square steel piece (2) in the predetermined state as described above and the sector is scanned is conceptually shown in Fig. 17 (-) (b) ( , ) is shown.

The state of electronic sector linear scanning is conceptually shown in FIG. 21 (UaXIIbXIlo).

Figures 24 and 25 show the probe (7) for the square steel piece (2).
) is shown below. First, in the case of the example shown in FIG. 24, one probe (7) is arranged parallel to each surface of the square steel piece (2). That is, one probe (7)
As shown in the figure, the lower halves of both sides of the square steel piece (2) adjacent to the entrance plane are tested for flaws, and the entire surface layer of the square steel piece (2) is detected using four probes (7). - In the case of the example shown in FIG. 25, two probes (7) are arranged at a predetermined angle to each surface of the square steel piece (2).

In this case, one probe (7) is used to detect the lower half of one side of the square steel piece (2) adjacent to the entrance plane as shown in the figure, and a total of eight probes (7) are used to detect flaws. ) is used to detect flaws on the entire surface layer of the square steel piece (2). In either arrangement, high-speed flaw detection can be performed online over the entire surface layer of a square steel piece.

Next, the probe (7) of the test material (2) used in the present invention
The acoustic coupling method will be explained.

Acoustic coupling methods include a direct contact method and a water immersion method.

In the direct contact method, the probe and the ultrasound entrance surface of the specimen are in contact through a thin film of water or other liquid couplant. The present invention can be applied to the case where the array type probe (7) is arranged parallel to the material surface as shown in FIGS. 23 and 24. However, in the case of direct contact, the efficiency of transmitting and receiving ultrasonic waves tends to fluctuate due to the thickness of the couplant and the roughness and irregular shape of the ultrasonic incident surface of the test material (2).

The water immersion method is a method in which ultrasonic waves emitted from a probe are propagated through water (or liquid) over a fairly long distance and then made to enter the specimen.As shown in Figure 26, A water tank penetration method (Fig. 26 (a)) in which a square steel piece (2), which is the test material, is immersed in water (I4) for a certain length, and a probe (7).
A local water immersion method (FIG. 26(b)(O)) that locally fills only the space between the ultrasonic wave incident surface of the test material (2) and the ultrasonic wave incident surface of the test material (2) can be considered.

In the case of this water immersion method, the ultrasound waves are first transmitted to the probe (7
) into the water 04), the transmission and reception of sound is more stable than with the direct contact method. In the present invention, either may be used.

Now, the above explanation is a detailed explanation of the specific means for angle-angle flaw detection of the surface layer of the test material (210) using the ultrasonic probe (7). Although subcutaneous flaw detection can be performed on the surface of the material to be inspected (2) without a dead zone, there is a risk that surface defects (flaws on the surface) may also be detected at the same time.

These surface defects can be removed by chipping in the billet processing process or processing using a grinder, and do not pose a problem during secondary processing of wire rod and steel bar products. Therefore, as already mentioned at the beginning, it is necessary to distinguish and extract each detected node into surface defects and subcutaneous defects.

Therefore, next, the surface defect discrimination process, which is the most important point of the present invention, will be explained.

Surface echo (Sx echo) and defect echo F
), the setting of the refraction angle ρ) is known, and the incident point of the ultrasonic beam () is
Regardless of the scanning method described above, the probe (
It can be determined by calculation from the positional relationship between 7) and the test material (2).

Now, if we calculate the incident point position (χ0) using the upper right corner of the square steel piece (2) shown in Fig. 27 as a reference, then
The defect position (χ, A) is expressed by the following equation.

. = Engineering. -ΔT2-Csin 19 A=Δ2 aos (9 Δ'I': Time difference C between Sl echo and defect echo stimulation);
Consular sound speed In reality, there is an error in the estimated defect position due to the spread of the ultrasonic beam, the irregular shape of the material to be inspected (2) (surface irregularities, sagging, etc.), the tracking error of the probe (7), etc. It is difficult to distinguish between surface defects and subcutaneous defects using only the reed and angle flaw detection information.

Therefore, in order to distinguish between these, it is necessary to use a flaw detection method that detects surface defects and cavities.Only the surface flaws are detected separately, and the surface By subtracting defect information, only surface subcutaneous defects are extracted.

As an information processing method for surface defect discrimination, basically all you have to do is subtract information 2 from information 1, as shown in Figure 28. However, as mentioned above, angle flaw detection is difficult to estimate defect position accuracy. Information 1 contains many factors that reduce
cannot be simply subtracted because it is less reliable than the defect position information (information 2) from surface defect detection and has a large defect position estimation error range.

That is, as shown in Fig. 29, for an actual surface defect θ5), information 1 is obtained assuming that the defect position detected by the above-mentioned ultrasonic angle flaw detection is the position marked ◎ in the figure, and other When information 2 is obtained assuming that the surface defect position detected by the surface defect detection device is the position marked with ■ in the figure, these pieces of information are
When processed with t, each defect is determined to be a separate defect, and information 1 is left as subcutaneous defect information. In other words, it is classified as a subcutaneously defective material even though it actually has only surface defects (16).

In order to prevent this, information 2 has a certain area, and information 1 that falls within that area is canceled, thereby preventing erroneous detection of a surface defect as a subcutaneous defect.

Here, the area provided for information 2 is the area shown by the dashed line in FIG. 29, and needs to be larger than the defect position estimation error range of information 1 (the area indicated by the dotted line in the figure). Therefore, with respect to the estimated surface defect position (■ mark) of information 2, the width of ±ΔH in the width direction of the square steel piece, and the entire flaw detection area (region of δ) in the depth direction
Information 1 within the area (dot-dash line area) is canceled.

In this way, information 2 can be given a certain area and information 1 can be determined to be a surface defect.

Here, canceling the angle detection information for a width of ±ΔH in the width direction of the square steel slab (2) means that a subcutaneous defect is actually detected in that area, but it is not a subcutaneous defect. There are cases where this happens. In order to reduce the probability that this contradiction will occur, the width of ±ΔH must be made small. In other words, in oblique angle detection, it is better to introduce a scanning method with good defect position estimation accuracy.

In the above-mentioned linear scanning type, the influence of irregularities in the shape of the inspected material is large, and the accuracy of defect position estimation is worse than in the case of sector scanning. Therefore, sector scanning is dominant.

In addition, the sector +
It goes without saying that linear scanning is the most advantageous.

In sector scanning and sector+linear scanning, the following two methods can be used in combination to further improve defect position estimation accuracy.

One method is to make the ultrasonic waves incident from the center of the surface, where the influence of irregularities on the incident surface is considered to be the least.

By doing this, even if the surface of the square steel piece (21) is uneven, the central part of the surface can be approximated as being substantially flat, as shown in FIGS. 30(a) and 30(b).

Another method is to detect the echo from a part of the corner and calculate its maximum value in order to correct the apparent change in the angle of refraction (So-+S) due to the inclination of the incident surface as shown in Figure 31. The purpose is to find the angle of incidence shown. Then, the slope of the incident surface is calculated from that value, and the incident angle is corrected so that the beam enters the desired flaw detection area.

Now, next, a description will be given of a surface defect detection device for detecting the surface defect a-candy.

Surface flaw detection methods include magnetic particle flaw detection, eddy current flaw detection, surface wave flaw detection, and optical flaw detection, and apparatuses suitable for each method are well known. However, the detectability of each of the above-mentioned surface defect detection methods differs depending on the type of surface defect.

For example, for various surface defects as shown in FIG.
The detection performance of each flaw detection method is shown in the table below. (1 in Figure 32)
5g) shows cracking, (15b) shows sagging, and (150) shows oyster scratches.

That is, according to the above table, surface wave flaw detection detects all of the surface defects detected by oblique flaw detection, but magnetic particle flaw detection hardly detects anything other than a crack (15 g).

However, in surface wave flaw detection, if there is one surface defect, the propagation of sound waves to other areas is extremely reduced, so if there are many surface defects, it may be overlooked.

As described above, each surface defect detection method has its advantages and disadvantages, and the discrimination characteristics between surface defects Qυ and subcutaneous defects differ depending on which method is combined with angle inspection.

-Next, as a specific example of the present invention, we will explain surface layer defects when an electronic scanning type flaw detector is used for angle angle flaw detection, and a surface wave flaw detector and a magnetic particle flaw detector are used for surface flaw detection. Information processing for discrimination from surface defects will be explained.

First, a method of processing oblique flaw detection data will be explained.

As shown in Fig. 53, the electronic scanning flaw detection device scans the flaw detection area in sectors + linear scans in 8 steps with the lower corner position as a reference, and at each step, a preset echo level ( If there are echoes greater than or equal to (open chain),
As shown in Figure 34, the step horse where the maximum echo was obtained, the echo height, the detection time, and the axial position of the square steel piece (2) are taken in as flaw detection data, and the flaws are transferred onto the surface of the square steel piece based on the refraction angle and detection time. The projected estimated position of the defect is calculated, converted into position information obtained by dividing the width direction of the square steel piece (2) at a constant pitch, and the data is aggregated by looking at the continuity of the defect in the axial direction of the square steel piece (2). defect plane, defect origin (axial direction),
Information on the defect length (in the axial direction) and the position in the width direction.

In addition, in Fig. 35, the flaw detection gate (I6) in the flaw detection area is
), the path length change due to the deformation of the test material (2) is measured,
This is done over a long period of time so that flaws can be detected completely from the surface.

However, in some corners, it is limited to a range where corner echoes are not picked up.

FIG. 34 (-) shows the cross section of the square steel piece (2), 071 shows the detected defect position, and 08) shows the projected estimated position information of the defect. FIG. 34(b) Fi shows the projected surface matrix of the square steel piece (2), (Pl) is the pitch of the scanning step, and (PR) is the flaw detection pitch in the axial direction of the square steel piece. Estimated defect projection position information (181) is collected on this matrix. If this information is not consecutive two or more times in the axial direction of the square steel piece, it is determined that there is no noise and it is not treated as defect information. Therefore, the information Qgl that occurs two or more times consecutively is processed as defect information (transfer).In other words, the detected defect Q71 is
As shown by the large frame in FIG. 4(b), information 1 has a long starting point (211).

Here, an example has been given in which sector + linear scanning is performed using an electronic scanning type flaw detection device, but the same processing can be performed by linear scanning, sector scanning, etc. In addition, although the flaw detection area is detected in eight steps, for example, increasing the number of steps allows for more dense flaw detection, which allows for finer division of a fixed pitch in the width direction of the square steel piece when projected onto the surface, allowing for discrimination. It is clear that performance is also improved.

Next, a method of processing surface defect detection data will be explained.

As shown in FIG. 35, a tire probe is used for surface wave flaw detection. In this case, the flaw detection area is the surface facing the ground surface of the probe (to), and each surface and a part of the corner are divided into three parts and gated. And 1st gate (goods), 2nd game) [24! For up to 3 echoes that exceed the darkness value, the echo height, detection time, and axial position of the square steel piece are imported as flaw detection data for the maximum echo that exceeds the darkness value from the corner gate □□□. , Similar to the collection of oblique flaw detection data, the estimated position of the defect in the axial direction of the square steel piece is calculated from the detection time, converted to position information in the width direction of the square steel piece when divided at a fixed pitch, and continuous in the axial direction of the square steel piece. Defect size, defect origin (axial direction), defect length (axial direction)
, information on the width direction position.

The information format for magnetic particle flaw detection data from magnetic particle flaw detection equipment will be the same as the aggregated information for side angle flaw detection and surface wave flaw detection.

In order to discriminate and process only the subcutaneous defect information from the information obtained by the above-mentioned oblique flaw detection and the information obtained by surface defect flaw detection, as described above, surface defect area information is obtained by adding a certain area to the surface defect information. , this information is subtracted from the angle angle flaw detection aggregate information. A processing block diagram thereof is shown in FIG.

The above surface defect area information includes width direction position information of surface defect aggregation information of surface wave flaw detection, magnetic particle flaw detection, or both.
The width of several blocks of the square steel strip in the width direction and the defect origin and length information are extended several tens of times.

FIG. 37 shows the concept of the discrimination process of the present invention, and shows that the combination of surface wave flaw detection and magnetic particle flaw detection prevents erroneous detection in which surface defects are treated as subcutaneous defects.

Regarding the probe placement for full-surface flaw detection during oblique flaw detection, see Section 2.
It has already been described in Figures 3 and 24. Therefore, to explain the arrangement of tire probes for full surface flaw detection, as shown in Fig. 38, we have adopted a model in which two probes are built into the tire I28), and these tire probes hz are placed opposite to each other. It is sufficient to install it on two sides. Of course, the test material is moved in the axial direction.

In the embodiment of the present invention described above, by combining an electronic scanning flaw detection device, a surface wave flaw detection device, and a magnetic particle flaw detection device,
It is possible to distinguish between surface defects and subcutaneous defects, and there are fewer oversights of surface defects than when a single surface defect is detected. In particular, in magnetic particle flaw detection, the detection noise of defects in a part of the corner is low, so the flaw detection information from the second gate of tire flaw detection can be used.

Note that the present invention is not limited to the above-mentioned embodiments, and the material to be tested may be in the shape of a round bar.
Using the annular play type probe described in Japanese Patent No. 8-3198, it is possible to simultaneously perform flaw detection on the surface layer and the surface, and to perform defect discrimination.

As described in detail above, the present invention performs oblique angle flaw detection on the surface layer of a test material using an ultrasonic probe, and detects the positional relationship between the probe and the test material, the incident angle of the ultrasonic waves, and the defect echo. From the detection time, calculate the estimated defect position when projected onto the surface of the material to be inspected, detect only the surface defect with a surface flaw detector, find the predetermined area of the defect position, and estimate the former defect. By subtracting the latter defect area information from the position information,
Since the present invention is characterized by detecting only subcutaneous defects, it is possible to detect defects in the entire surface layer of a rectangular steel billet, whereas conventional internal flaw detection methods cannot detect flaws in a numerical range from the surface of a steel billet. It is possible to perform high-speed online flaw detection without leaving undetected areas, and it is possible to distinguish between surface defects and subcutaneous defects over the entire length of the surface layer of a square steel piece. Further, by this discrimination detection, quality assurance can be quickly and accurately provided to the surface, subcutaneous, and internal parts of steel bars and wire rods as products.

[Brief explanation of the drawing]

Figure 1 shows the dead zone in the conventional vertical flaw detection method, Figure 2
The figure shows a side reflection echo obtained by the oblique flaw detection method according to the present invention, FIG. 3 shows a bottom reflection echo, FIG. 4 is a graph showing the relationship between reflection echo height and refraction angle, and FIG. Figure 6 is a graph showing the refraction angle for bottom echo, Figure 6 is a graph showing the refraction angle for side echo, Figure 7 is a graph showing the relationship between the incident angle, refraction angle, and round trip pass rate, and Figure 8 is the belt. Figure 9 is a diagram of the principle of linear scanning, Figure 9 is the principle of vibration type IJ near scanning, Figure 10 is a diagram of the principle of mechanical fishing IJ near scanning, Figure 1
Fig. 1 is a diagram showing the principle of mechanical sector scanning, Fig. 12 is a perspective view of an electronically scanned play type probe, Fig. 13 is a diagram showing how an ultrasonic beam is controlled by an electronically scanned array type probe, and Fig. 1
Figure 4 is a graph showing the relationship between ultrasonic beam diameter and S/N, Figure 15 is a diagram showing the principle of electronic linear scanning, Figure 16 is a control circuit diagram of electronic linear scanning, and Figure 17 is a diagram of electronic sector scanning. The principle diagram, Fig. 18 is a control circuit diagram of electronic sector scanning, Fig. 19 is a diagram showing variations in electronic linear scanning, and Fig. 2
Figure 0 is a diagram showing variations in electronic sector scanning, Figure 21 is a diagram of the principle of electronic sector + linear scanning, Figure 22 is a diagram showing the relationship between element width and beam inclination angle, and Figure 23 is a diagram showing linear scanning exploration. Figures 24 and 25 are probe layout diagrams, Figures 24 and 25 are sector scanning probe layout diagrams, Figure 26 is a diagram showing the acoustic coupling method, Figure 27 is a diagram showing defect positions, and Figure 28 is a diagram showing discrimination. Flowchart of processing, Figure 29 is a diagram of the principle of discrimination processing, Figure 30 is a diagram showing the incident point of the ultrasonic beam, Figure 3
Figure 1 is a diagram for determining the incident point from a part of the corner of the material to be inspected, Figure 32
Figure 35 shows the types of surface defects, Figure 35 shows electronic sector scanning, Figure 34 explains how to aggregate detected defects, Figure 35 shows the arrangement of tire contacts, Figure 36 shows FIG. 37 is a flowchart of the discrimination process, FIG. 37 is a diagram showing the concept of the discrimination process, and FIG. 58 is a layout diagram of tire contacts. (2)... Square steel piece (test material), 17+... Probe, Q51... Surface defect, aη... Detected defect position,
08)...Projection position, (2o)...Defect aggregation information,
(Foundation)...Tire probe (surface defect detection device), however)
...Ultrasonic wave, (φ... angle of incidence. Patent applicant Kobe Steel, Ltd. -339- Figure 28 Figure 29 i-Figure 30, Figure 32 Figure 35 ov; 12. 4 ), l myself, huh? (・sq!y
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Paraphrase No. 36 tA Procedural Supplementary Draft (spontaneous) 1 Recitation March 31, 1958 1 To the Commissioner of the Patent Office 1. 11 large and small 1988 patent application No. 23527 2 Name of the invention Subcutaneous defect detection by ultrasonic flaw detection Method ゛ (Relationship with the supplementary IF case Patent applicant (119) Co., Ltd. Kobe 11!laA office, 1 agent's approval I; 5. Notice of reasons for refusal dated 11, 1939, month, day, voluntary)
Character deletion 6 Subject of amendment/application-1-4μ 7. Contents of amendment (1) “Steel making” tr cracked pig iron on page 2, line 6 of the specification
I am corrected. (2) Same, No. 8 ¥1. %Correct "transverse wave" in the 5th line to "longitudinal wave". 0 (4) Same, page 17', line 8, and 19th line, line 6, correct all "horizontal" and "parallel" ◇ (5) Same, page 35 1Q to 20th rows and 3rd F
1W% Correct the second line to "Contact Jkr probe". (6) Amend the entire drawing “Figure 33” as shown in the attached sheet.

Claims (1)

[Claims] 1. An ultrasonic probe is used to perform oblique angle flaw detection on the surface layer of the test material, and the positional relationship between the probe and the test material, the incident angle of the ultrasonic waves, and
From the defect echo detection time, calculate the estimated defect position when projected onto the surface of the material to be inspected, detect only the surface defect with a surface defect detection device, and find the predetermined area of the defect position. A subcutaneous defect detection method using ultrasonic flaw detection, characterized in that only subcutaneous defects are detected by subtracting defect area information from estimated defect position information.