JPH02254355A - Ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To detect a surface defect and an internal defect of a continuously cast round steel material efficiently by setting a gate to extract a signal attributed to the surface defect and a signal attributed to the internal defect from a detection signal of reflected wave. CONSTITUTION:Excitation signal is inputted into a probe 210 from a flaw detector 22 at a detection of flaw and an ultrasonic wave oscillated according to the excitation signal is made incident askew within an axial section with respect to a normal of a continuously cast round steel material 1. Here, when a gate is set within the flaw detector 22, a surface defect echo and an internal defect echo are extracted from reflected echoes detected with the probe 210 and inputted into a chart recorder 23 with the flaw detector 22 to be recorded on a recorder 23. Based on a record thus obtained, a defect is judged. In addition, position detection signals of an axial position detector 24 and a circumferential position detector 25 are inputted into a probe position detector 26 and converted into a two-dimensional position signal to be inputted into a computer 27. Then, in the computer 27, results of two-dimensional detection of flaws are inputted into a display device 28 in a form of a development chart as bright or dark spots.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic flaw detection method for detecting defects in a metal material having a circular cross section, such as a continuously cast round steel material.

[Conventional technology]

Continuously cast round steel materials are used as materials for seamless joints and various rotating shafts, but small spherical defects such as CC powder entrainment and blowholes may occur near the surface of continuous cast round steel materials. .

Traditionally, these defects have been detected by visual inspection or eddy current testing. Further, as a method of detecting surface defects by ultrasonic flaw detection, a method of detecting defects by detecting surface scattered waves scattered by surface defects has been disclosed (Japanese Patent Application Laid-Open No. 60198456).

[Problem to be solved by the invention]

However, in the continuous casting round steel material, oscillation marks, which are formed by circumferentially extending grooves regularly arranged in the axial direction, occur, and scales generated during the cooling process are unevenly present on the surface, resulting in poor surface texture. Therefore, the accuracy of defect detection by the visual inspection or eddy current flaw detection was poor. Further, the method of detecting defects using surface scattered waves as described above detects extremely minute defects in silicon substrates and the like, and is not suitable for detecting defects in continuously cast round steel materials.

The present invention has been made in view of the above circumstances, and it is possible to continuously cast a round by setting a gate on a flaw detector to extract detection signals of surface defects and internal defects, and detecting defects within the gate. An object of the present invention is to provide an ultrasonic flaw detection method that efficiently detects surface defects and internal defects in steel materials without being affected by oncillation marks and scale.

[Means to solve the problem]

In the ultrasonic flaw detection method according to the present invention, an ultrasonic probe is arranged to be inclined within the axial cross section of the metal material with respect to the normal line of the metal material having a circular axial cross section, and the ultrasonic probe is In an ultrasonic flaw detection method that detects surface defects and internal defects in a metal material by injecting ultrasonic waves into the metal material and detecting the reflected waves, signals caused by surface defects and internal defects are detected from the detection signal of the reflected waves. The feature is that a gate is set to extract a signal caused by .

[Effect]

When ultrasonic waves are incident obliquely onto the surface of a metal material from an ultrasonic probe placed opposite to the normal line of a metal material with a circular axial cross section, the ultrasonic wave is first caused by the roughness of the surface of the metal material. Surface scattered waves caused by surface defects appear as reflected waves, and then surface reflected waves caused by surface defects appear. After the surface reflected waves are attenuated, internally reflected waves due to internal defects appear.

These three waveforms appear in chronological order, so if a gate is applied from the time the surface reflected wave appears until the internally reflected wave attenuates, the surface scattered wave is removed from the detected waveform by the gate, and the surface reflected wave and Since internally reflected waves are extracted, the flaw detection results are not affected by the surface texture of the metal material.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a perspective view of an ultrasonic flaw detection apparatus used in carrying out the method of the present invention, and FIG. 2 is a block diagram showing the configuration of its signal processing system.

In FIG. 1, reference numeral 4 denotes a frame framed in a rectangular shape, and the frame 4 has long sides 41a, 41b and short sides 4 facing each other.
2a, 42b, and is supported by a groove 3.3 attached below the short sides 42a, 42b. On the inside of the long sides 41a and 44b are short sides 42a and 42.
A guide rod 6 and a threaded rod 7 (only one of which is shown) are provided parallel to the long sides 41a and 41b. The guide rod 6 and the threaded rod 7 penetrate and support the inspection table 5, and the inspection table 5 is driven by an examination table drive motor M that rotates the threaded rod 7 disposed at one end of the long side 41a around its axis. It is arranged to move along the inside of the long sides 41a and 41b while sliding against the guide rod 6 and spiraling against the threaded rod 7 as the shaft rotates.

Mounting members 2 for mounting four probes 2121 (only two shown) via probe mounting plates 20 and 20 are attached to the bottom surface of the test table 5 in parallel to the bottom surface of the test table 5. Probe mounting plates 20 and 20 are respectively mounted on the lower surface of the mounting member 2 at an angle with respect to the lower surface. As shown in FIG. 2, each of the probe mounting plates 20, 20 includes a probe 210 for transmitting and receiving ultrasonic waves, and a probe 210.
A probe holder 211 that immerses the probe surface of 210 in water and spouts water onto the surface of the continuous cast round steel material 1 that is the material to be tested.
．． 211, the probes 21 and 21 that perform ultrasonic flaw detection on a continuously cast round steel material l by the water immersion method are arranged such that the transmission and reception directions of the ultrasonic waves are inclined within the axial cross section of the steel material with respect to the normal to the steel material l. The long sides 41a and 41b are arranged in parallel in the longitudinal direction so that the long sides 41a and 41b are arranged in parallel. Directly below the mounting member 2 is a turning roller 10, 10, which rotates the continuous cast round steel material 1 around its axis.
... are arranged with their rotational axes directed in the longitudinal direction of the long sides 41a, 41b.

When performing flaw detection on the continuously cast round steel material 1 using an ultrasonic flaw detection device having such a configuration, the continuous cast round steel material 1 is placed on the turning rollers 10.
0... rotates the continuous cast round steel material 1 around its axis. Then, by moving the detection stand 5 with respect to the continuously cast round steel material 1, the probes 21 and 21 are moved in the axial direction of the continuously cast round steel material 1 with a predetermined pinch, and the probes 2L and 21 are used in each flaw detection direction. Flaw detection is performed over the entire length and circumference of the continuously cast round steel material 1 in a spiral pattern of two threads each, for a total of four threads.

The probes 210 and 210 of the probes 21 and 21 are respectively connected to the flaw detector 22, and during flaw detection, an excitation signal is input from the flaw detector 22 to the probes 210 and 210, and the probe 2
10°210 oscillates ultrasonic waves in response to this excitation signal,
Ultrasonic waves are made obliquely incident within the axial cross section with respect to the normal line of the continuously cast round steel material 1 through the water in the probe holder 211.211. The incident ultrasonic waves are reflected by surface scattering 1 and internal defects in the continuously cast round steel material 1, and are received by the probe 2 and the sail 210 as reflected echo signals. This reflected echo signal is input to the flaw detector 22 from the probes 210 and 210.

A chart recorder 23 is connected to the flaw detector 22, and the flaw detector 22 applies a gate to the reflected echo signal to extract only the defect signal, inputs the extracted signal to the chart recorder 23, and inputs the extracted signal to the chart recorder 23. The reflected echo signal is recorded on recording paper.

The operator identifies defects from this record. In addition to the chart recorder 23, a device described below is provided to output the flaw detection results in the form of a developed diagram. A probe 21 in the axial direction of the continuously cast round steel material 1 is mounted on the inspection table 5.
An axial position detector 24 for detecting the position of 0.210 is provided, and small-area reflectors (not shown) are attached at appropriate length intervals in the circumferential direction of the continuous cast round steel material l, and a position opposite to the reflector is provided. A circumferential position detector 25 is provided, which includes a photoelectric detector (not shown), and detects the position of the probes 210, 210 in the circumferential direction of the continuous cast round steel material 1 by detecting the reflective plate with the photoelectric detector. .

The position detection signals of the axial position detector 24 and the circumferential position detector 25 are input to the probe position detector 26 , where they are converted into two-dimensional position signals and input to the computer 27 . In addition, the flaw detection signal output from the flaw detector 22 is input to the computer 27, and the computer 27 correlates the input position signal and the flaw detection signal, and develops two-dimensional flaw detection results as bright spots or dark spots. The information is inputted to a display device 28 that outputs the data in a diagram format on a CRT or recording paper.

If the surface quality of the continuously cast round steel material 1 is extremely poor and the defect determination by the chart recorder 23 is difficult, the operator inspects the flaw detection result output on the display device 28 to determine the defect.

3 and 4 are schematic diagrams showing the principle of oblique ultrasonic flaw detection used in the method of the present invention.

FIG. 3 shows a method for detecting surface defects F in a continuously cast round steel material 1 by a water immersion method. In FIG. 3, the ultrasonic waves emitted from the probe 210 obliquely within the cross-section with respect to the normal to the continuous cast round steel material 1 are detected by , and this reflected echo is received by the probe 210.

Furthermore, Fig. 4 shows internal defects F! of continuously cast round steel material 1 by the water immersion method. It shows how to detect flaws.

In Fig. 4, from the probe 210, the series 'II cast round steel material 1
The ultrasonic wave oscillated obliquely to the normal to the continuous cast round steel material 1 is incident on the continuous cast round steel material 1, is refracted by a predetermined amount on its surface, propagates inside the continuous cast round steel material 1, and is reflected by the internal defect F2. ,
This reflected echo is received by the probe 210. As is clear from this figure, when detecting the surface defect F and the internal defect F2, the reflected echoes appear in the order of the surface defect F and the internal defect F2 in chronological order.

The inventor of the present application has developed an ultrasonic wave that is applied obliquely to the surface of the material to be inspected within the cross section, so it is hardly affected by the oscillation marks, and there are few surface scattered echoes in the reflected echoes, and the ultrasonic waves can be applied to shallow areas near the surface. Round fins are easier to identify from the surface scattered echoes of existing surface defects than conventional ones. In order to accurately detect surface defects and internal defects in continuous cast round steel material 1 with poor surface quality using the angle angle flaw detection method used for flaw detection in steel sheets 1, the flaw detection conditions were experimentally determined and the results obtained. Based on the results obtained, we discovered a method for detecting both surface defects and internal defects using a single probe.

Figure 5+al~ (C1 is a typical waveform diagram of the results of flaw detection by the method of the present invention. In the figure, the horizontal axis all represents time, and the vertical axis all represents voltage.

In FIG. 5, (al) is a waveform diagram when a continuous cast round steel material 1 having no defects is tested, and surface scattered echoes S due to surface roughness are detected.

fb) is a waveform diagram when flaw detection is performed on the continuously cast round steel material 1 having surface defects as shown in FIG. 3, and a surface defect echo Fs appears following the surface scattered echo S. (C
1 is a waveform diagram when a continuously cast round steel material 1 having an internal defect as shown in FIG.
1 appears.

It is clear from these waveform diagrams that the surface defect echo F and the internal defect echo F1 appear in a specific time range. By setting a gate at As a result of experiments conducted by the present inventor, it was found that when detecting both surface defects F and internal defects F2, the incident angle of ultrasonic waves that is good for both defects is around 18°. Figure 6 shows the S vs. frequency when an internal defect with a diameter of 3 mm at a depth of 61 m is detected using ultrasonic waves with an incident angle of 18° and by changing the frequency of the ultrasonic waves. /N
A graph showing the relationship between the ratios, Figure 7 is a graph showing the relationship between the S/N ratio and the frequency when a surface defect with a diameter of 3 dragons is detected using ultrasonic waves with an incident angle of 18°. The horizontal axis in Figure 7 shows the frequency, and the vertical axis shows the S/
The N ratio is taken.

Further, the results shown by the solid line in FIG. 7 show the case where the surface quality of the continuous cast round steel material 10 is good, while the results shown by the broken line show the case where the surface quality is poor.

As is clear from these figures, the frequency of the ultrasonic wave is 5 MH
It can be seen that the z neighborhood is optimal. In addition, experimental results show that the optimum beam diameter for ultrasonic waves is 2 to 5 fins, and that when the beam diameter is smaller than this optimum value, the influence of the surface texture appears, while when the beam diameter is increased, the S/N ratio decreases. This was obtained through an experiment conducted by the applicant.

When a gate is set on the flaw detector 22 based on the above-described principle, a surface defect echo F and an internal defect echo F are detected from the reflected echoes detected by the probe 210.

is extracted, inputted from the flaw detector 22 to the chart recorder 23, and recorded in the chart recorder 23. A worker determines defects based on this record. If the surface quality is extremely poor and it is difficult to determine the defect using the chart recorder 23, the defect is determined based on the display result on the display device 28 in the form of a developed diagram.

FIG. 8 shows the flaw detection results output from the display device 28. The layer indicated by A in FIG. 8 is a rough surface area,
The black dots indicated by circle B are internal defects, and the other black dots are surface defects. When the display device 28 is used in this manner, two-dimensional flaw detection results are obtained, and parts with poor surface texture are displayed continuously in the axial direction, making it easy to distinguish between poor surface texture and defects. .

Although four probes 210 are used in this embodiment, flaw detection can be performed at a faster speed by adding more probes 210 and increasing the moving speed of the inspection table 5. is possible.

〔Effect of the invention〕

The ultrasonic flaw detection method according to the present invention includes presetting a gate on a flaw detector to extract only detection signals of surface defects and internal defects;
The present invention has excellent effects such as being able to efficiently detect surface defects and internal defects in continuously cast round steel materials without being affected by oscillation marks and scales in order to detect defects within the gate.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an ultrasonic flaw detection device used when carrying out the method of the present invention, and FIG. 2 is a block diagram showing its configuration.
Figures 3 and 4 are schematic diagrams showing the principle of ultrasonic flaw detection using the method of the present invention, Figure 5 is a waveform diagram showing typical waveforms of the results of surface scattering flaw detection and oblique angle flaw detection, and Figure 6 The figure is a graph showing the relationship between frequency and S/N ratio when an internal defect is detected, and Figure 7 is a graph showing the relationship between frequency and S/N ratio when a surface defect is detected.
A graph showing the relationship with the N ratio, and FIG. 8 is a flaw detection diagram showing the output results of the expandable display device. ■... Continuously cast round steel material 5... Inspection table 21...
Probe 210...Probe patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Diagram time-solid time diagram frequency (MHz) diagram frequency vi (MHz) diagram

Claims (1)

[Claims] 1. An ultrasonic probe is arranged to be inclined within the axial cross section of the metal material with respect to the normal line of the metal material having a circular axial cross section, and the ultrasonic probe is used to detect the metal material with a circular axial cross section. In an ultrasonic flaw detection method that detects surface defects and internal defects in metal materials by injecting ultrasonic waves into the surface and detecting the reflected waves, the detection signal of the reflected waves detects signals caused by surface defects and signals caused by internal defects. An ultrasonic flaw detection method characterized by setting a gate to extract a signal.