JPH0116383B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic angle flaw detection method for square steel pieces, and is capable of setting a desired flaw detection area with high accuracy and improving the accuracy of defect position estimation.

When it is necessary to detect the interior or surface layer of a square steel piece using angle angle flaw detection and estimate the position of the detected defect, the positional relationship between the probe and the square steel piece, the propagation direction of the ultrasonic beam (refraction angle) ) is determined by calculation from the path length determined from the detection time difference between the reflected echo from the incident surface of the square steel piece and the defect echo. However, since actual square steel pieces have irregularities such as surface irregularities and sagging, the accuracy of estimating the defect position deteriorates. For example, as shown in FIG. 1, if the surface of a square steel piece 1 on which the ultrasonic beam S is incident is uneven, the set incident angle and the actual incident angle β will differ depending on the incident position of the ultrasonic beam S. Furthermore, even when the incident light is from the same position as shown in Figure 2 a and b, the set angle of incidence and the actual angle of incidence β differ because the surface shape at that position differs depending on the square steel piece 1. . As a result, the refraction angle θ also changes and becomes different from the calculated propagation direction of the ultrasonic beam S in the square steel piece 1. Furthermore, as shown in Fig. 3, if the square steel piece 1 has sagging (the actual square steel piece 1b is different from the standard square steel piece 1a), for example, the lower half of the side surface of the square steel piece 1 adjacent to the ultrasonic incident surface may be bent. I intended to perform flaw detection in the flaw detection area a by sector scanning in the scanning range b, but as shown in the figure, the center part of the side surface of the square steel piece 1b or the square steel piece 1
In some cases, the bottom and side surfaces of part b are being inspected, and problems may occur before the defect position can be estimated. The same thing occurs when the refraction angle θ changes due to the irregular shape of the ultrasonic wave incident surface. Therefore, when performing oblique flaw detection on the square steel piece 1, it is difficult to guide the ultrasonic beam S to the desired flaw detection area, and furthermore, it is not possible to accurately estimate the position of the detected flaw.

Furthermore, the range in which a flaw detection gate is applied changes depending on the purpose of flaw detection, that is, surface layer flaw detection or internal flaw detection.In the conventional internal flaw detection method, the gate is applied to obtain flaw detection data only in the flaw detection area a. As shown in Fig. 4, the gate starting point c is set at a point where the reflected echo S1 from the incident surface of the square steel piece ₁ rises and the influence of the leakage of the reflected echo _S1 is reduced. The fixed gate method uses the width B of piece 1 as a reference and sets the gate range in advance to a point where the influence of the reflected echo B ₁ from the bottom surface is small, and the fixed gate method uses the probe 2 to detect the reflected echo from the bottom surface as shown in Figure 5. B ₁ is constantly detected (B ₁ echo tracking), and a certain dimension l is detected from the reflected echo B ₁ .
A variable gate method is used in which the gate end point d is controlled so that the gate end point d is positioned as close as possible. By using the method described below, the dead zone (depth from the surface) of the surface layer on the bottom side can be kept constant regardless of the irregular shape of the square steel piece 1. However,
In order to reduce the surface dead zone in internal flaw detection of the square steel piece 1 or to perform surface layer flaw detection, the square steel piece 1 is
When performing oblique inspection, the reflected echo from the bottom surface
Since there are almost no B ₁ or equivalent echoes reflected from the side, a variable gate method such as tracking the B ₁ reflected echo from the bottom surface during vertical flaw detection cannot be used. In this angle flaw detection, using the fixed gate method has more problems than in the case of vertical flaw detection because of the uncertainty in the ultrasonic propagation direction due to the aforementioned irregular shape of the square steel piece 1. For example, as shown in Fig. 6, if a square steel slab 1b with sagging is covered with a gate for internal flaw detection in the same way as a standard square steel slab 1a without sagging, the surface of the square steel slab 1b will be inspected as well as the inside. Then, the surface defect F is expressed as its defect echo.
There is a risk of false detection as an internal defect due to _F1 .

The present invention solves the above problems.

First, an overview of the present invention will be described. When inspecting the interior or surface layer of a square steel piece by the ultrasonic angle flaw detection method, first, the vicinity of the lower corner of the side surface adjacent to the ultrasonic incidence surface is subjected to the angle angle flaw detection. Then, the ultrasonic beam scanning position where the reflected echo from the corner becomes the maximum is detected, and the ultrasonic beam scanning range and flaw detection gate range are corrected based on that scanning position so that the desired flaw detection area can be detected. Then, the actual flaw detection is carried out.

Hereinafter, a method for detecting flaws in the surface layer of the lower half of the side surface adjacent to the ultrasonic incident surface of a square steel piece using electronic sector + linear scanning will be specifically described.

As shown in Fig. 7, the incident point O of the ultrasonic beam S
Assuming that the center of the incident surface of the square steel piece 1 is the center of the incident surface of the square steel piece 1, the reflected echo from the corner part becomes the maximum when the ultrasonic beam S
passes through the center of curvature A of the lower corner, and the refraction angle θc in the standard state (in the case of the square steel piece 1a) at that time is calculated by the following formula.

θc = arc tanB-2R/2 (B-R) B: Width of the square steel slab R: Radius of curvature of the corner If the square steel slab 1 has an irregular shape (in the case of the square steel slab 1b), the reflected echo from the corner part The refraction angle θp at which θp becomes maximum varies. For example, width B is 155mm,
If the square steel piece 1 has a radius of curvature R of 18 mm and the allowable folding angle α is ±3°, then in the standard state, θp = θc =
For 23.5°, the refraction angle θp takes a value in the range of 20.9° to 25.9°. Therefore, in this case, the refraction angle θp at which the corner echo peaks can be detected by first performing sector+linear scanning in the scanning range f in which the refraction angle θ is about 18° to 28°.

Sector + linear scanning for detecting corner peaks can accurately determine the refraction angle θp at which the corner echo is maximized by continuously changing the small angle, but there are restrictions on the division width of the array type probe. ,
Taking into account issues such as control for ultrasonic beam deflection, it is economically viable to perform flaw detection at a pitch of about 0.5°, and within that range, the refraction angle θ at which the maximum echo height is reached is approximately determined to maximize the reflected echo. It is regarded as the refraction angle θp.
Alternatively, in order to improve accuracy, the relationship between each refraction angle θ and the echo height may be approximated to a parabola, and the refraction angle θ at the peak of the parabola may be set as the maximum refraction angle θp.

Once the position where the corner echo is maximum is detected in this way, the next step is to use the refraction angle θp as a reference to detect flaws in the surface layer of the lower half of the side surface adjacent to the ultrasonic incident surface, which is the flaw detection area a. Correct the angle θi. In other words, the difference Δθ = θp - θc between the refraction angle θc calculated from a standard square steel piece 1a with no irregular shape and the actually measured refraction angle θp is determined as the refraction angle θi predetermined for testing the flaw detection area a. Add to. For example, calculated from θc = 23.5°, 8 sectors + linear scan at 4° pitch (θ ₁ = 23.5°, θ ₂ = 27.5°, θ ₃ = 31.5°,...
θ ₈ =
51.5°), and if we obtain a value of θp = ₂₅ °, then _Δθ =
15°, the scanning refraction angle θi′ is θ ₁ ′=25°, θ
₂ ′＝
29.0°, θ ₃ ′=33°, ... θ ₈ ′=53°. In other words, in the case of electronic scanning, it is necessary to control the delay time of each element of the array type probe according to the refraction angle θi'.
First, the scanning range f where the refraction angle θ is 18° to 28° is sector + linear scanned at a pitch of 0.5°, and the corner position is determined by approximating the relationship between the refraction angle θ and the echo height to a parabola using a computer. After calculating the refraction angle θp, add the difference Δθ to the predetermined refraction angle θi,
The delay time of each element may be controlled so that flaw detection can be performed using the corrected refraction angle θi'.

Next, as a method for correcting the flaw detection gate range, after calculating the refraction angle θp at which the corner echo is maximum, sector+linear scanning is performed from θ ₁ ′=θp. This θ ₁ ′ = θp is the time when the corner echo is at its maximum as described above, and by tracking the echo B ₁ reflected from the bottom surface during vertical flaw detection (see Figure 5), the same method can be used to track the echo B 1 in front of the corner echo. Gate end point d
Make it so that The method for determining the gate range of the flaw detection area a on the side surface other than the corner portion is shown below.

As shown in FIG. 8, once the refraction angle θp is calculated, the folding angle α of the square steel piece 1b can be approximately expressed by the following equation.

tanα=tanθp−tanθc When the refraction angle θi′=θi+Δθ, the distance Xi′= from the point of incidence O to the side surface is X′i=B/2sinθi′+ω/sinθi′ ω≒B/2tanθi(tanθp−tanθc) Xi ′≒B/2sinθi′(tanθp−tanθc/tanθi+1
) ω = Dimension from point D to square steel piece 1a (see Figure 8) Here, the distance Xi = from the incident point O to the side surface when the refraction angle θi, which is calculated in advance, is Xi = B/2sinθi Therefore, The path change ΔXi is expressed as ΔXi=Xi′−Xi. Therefore, this path change ΔXi is calculated by a computer, and the gate end point d at each refraction angle θi is determined. The gate starting point c is found by subtracting the flaw detection area a from the gate ending point d.

In the above embodiment, the case where the surface layer of the square steel slab 1 is used as the flaw detection area was explained, but even in the case of internal flaw detection or when the bottom surface side is used as the flaw detection area, the scanning range and gate are similarly determined based on the corner position. The range can be corrected. The scanning method is not limited to electronic sector + linear scanning, and general sector scanning and linear scanning are also applicable.

As described above, according to the present invention, the corner position is detected by performing oblique flaw detection near the corner, and the scanning range of the ultrasonic beam and the flaw detection gate range are corrected based on the corner position, and the flaw detection is performed at an oblique angle. Therefore, the desired flaw detection area can be detected accurately and reliably.
Moreover, when the defect position needs to be estimated, the position detection accuracy can be significantly improved.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams for explaining conventional problems;
Figures 4 and 5 are diagrams showing the conventional flaw detection method, Figure 6 is a diagram for explaining problems with the same flaw detection method, and Figure 7 is the corner position detection method and scanning range correction method of the present invention. FIG. 8 is a diagram showing a method of correcting the flaw detection gate range. 1...Square steel piece, S...Ultrasonic wave.

Claims (1)

[Claims] 1 Using ultrasonic waves, the corner position is detected by performing oblique angle flaw detection near the corner of the lower side of the square steel piece adjacent to the ultrasonic incidence surface, and the scanning range of the ultrasonic beam is determined based on the corner position. An ultrasonic angle angle flaw detection method for square steel pieces, which is characterized by correcting the flaw detection gate range and performing oblique angle flaw detection.