JPS62137562A - Flaw detector for continuous ingot - Google Patents

Abstract

PURPOSE:To detect a flaw on an ingot manufactured by a continuous casting apparatus by electromagnetically generating ultrasonic waves proceeding along the surface of the ingot from a transmitter provided in noncontact near the surface of the ingot and detecting the waves reflected from the flaw by a receiver. CONSTITUTION:A transmitter 42 is provided with a pulse generator 46 and HF oscillation coil 48. A high frequency current is outputted from the generator 46 and is made flow in the coil 48. When the coil 48 is supplied with the high frequency current, an alternating magnetic field is formed on the surface of a billet 30 whereby an eddy current is locally generated on a surface 32 and ultrasonic waves 50 with a wavelength equal to the pitch of the coil 48 and a frequency equal to that of the high frequency current are generated by a Lorentz's force accompanying the eddy current. On the other hand, in a receiver 44, reflected waves are detected based on the change in the eddy current produced when the reflected waves 58 that are the ultrasonic waves 50 reflected from a flaw 56 present near the surface 32 reach inside a magnetic from a flaw 56 present near the surface 32 reach inside a magnetic field formed near the surface 32 by an electromagnet 52.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a flaw detection device for detecting flaws present in a cast piece manufactured by a continuous casting apparatus.

BACKGROUND OF THE INVENTION There is a continuous casting apparatus that produces cast pieces such as billets by pouring molten metal into a predetermined mold and continuously drawing solidified metal from the mold. For example, FIG. 4 is a diagram illustrating an example.
The molten metal poured into the mold 12 from 0 is first solidified near the outer peripheral surface within the mold 12, and then,
A cast piece 20 having a predetermined cross-sectional shape is manufactured by being guided by the guide roller 14 and pulled out downward by the drawing roller 16 and cooled by cooling water jetted from the nozzle 18 . Such a continuous casting apparatus has been widely used in recent years because it can efficiently produce large quantities of cast pieces 20 of a constant quality.

By the way, in order to guarantee the quality of cast pieces manufactured by such a continuous casting apparatus, conventionally only an external appearance inspection to detect surface flaws has been performed. On the other hand, in the above-mentioned continuous casting method, the molten metal poured into the mold is generally coated with mold powder to prevent air from entering and oxidation. etc. near the surface of the cast piece, mainly from the surface to 1 (l
In some cases, the quality of the cast piece may be impaired due to contamination within a range of about n. For this reason, it is required to perform not only external inspection but also internal inspection.
It is also being considered to detect defects (defects).

Problems to be Solved by the Invention However, generally, on the surface of the above-mentioned continuously cast piece, there are a large number of irregularities called oscillation marks, which are approximately one dragon in size, and are spaced at approximately constant intervals. That is, in the continuous casting apparatus shown in FIG. As shown in FIG. 5, many oscillation marks 22 are formed on the surface of the cast piece 20 sent out from the casting device due to the reciprocating movement of the mold 12 in a direction perpendicular to the feeding direction. It's put away.

On the other hand, in the ultrasonic flaw detection method, the probe is placed in close contact with the surface of the cast piece to transmit and receive ultrasonic waves. Therefore, if there are any irregularities on the surface, the adhesion of the probe will be compromised and the ultrasonic waves will not be transmitted. Sending and receiving becomes difficult. Therefore, it has been difficult to detect flaws in continuous cast pieces having oscillation marks on the surface as described above using such ultrasonic flaw detection.

Means for Solving the Problems The present invention has been made to solve the above problems, and its gist is to provide flaw detection for detecting flaws present in cast pieces sent out from a continuous casting machine. An apparatus comprising: (a) a transmitter that is disposed near the surface of the cast piece in a non-contact manner with the surface and electromagnetically generates an ultrasonic wave that propagates along the surface; It is arranged in a pair with the transmitter in a non-contact state with respect to the surface on a straight line parallel to an oscillation mark formed on the cast piece, and is arranged in a pair with the transmitter in a non-contact state to the surface, and transmits the ultrasonic waves present in the cast piece. and (C) a flaw detection device that detects flaws based on the reflected waves received by the receiver. be.

Function and Effect of the Invention In other words, the present invention detects flaws near the surface of a continuously cast piece by generating surface waves using an electromagnetic ultrasonic device, which has conventionally been mainly used for detecting defects in hot-rolled materials. In this way, ultrasonic waves can be transmitted and received without contacting the surface of the cast piece, so ultrasonic flaw detection is possible regardless of the presence of the oscillation marks. .

In addition, the transmitter that generates ultrasonic waves and the receiver that receives reflected waves are arranged in a straight line parallel to the oscillation mark, and the ultrasonic wave traveling in a direction parallel to the oscillation mark is caused by defects in the cast piece. Since flaws are detected by receiving reflected waves,
Highly accurate flaw detection can be performed with relatively little interference from the unevenness of the oscillation mark.

In addition, although this type of surface wave flaw detection is mainly aimed at detecting surface defects, by selecting the frequency appropriately, it is also possible to detect flaws that exist at a slight depth from the surface. In the flaw detection of continuously cast pieces, which often have internal defects between the surface and the depth of about 1011, it is possible to conduct flaw detection that is practically sufficient.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIGS. 1 and 2, reference numeral 30 is a billet having a rectangular cross section as a cast piece. This billet 30
is manufactured by a continuous casting apparatus as shown in FIG. There are many oscillation marks 40 in the longitudinal direction, which are formed along a direction perpendicular to the feeding direction from the casting device. In addition, the oscillation marks 30 are cut into predetermined lengths after casting, are sufficiently cooled, and are continuously cut in the direction shown by arrow B in FIG. It can be moved.

In order to detect flaws existing in the billet 30 having such oscillation marks 40, the surface 3 is
Near the surfaces 32.34, 36.38, a plurality of pairs (four pairs in this embodiment) of transmitters 42 and receivers 44 are positioned facing the surfaces 32.34, 36.38. Fixedly placed. The transmitter 42 and the receiver 44 that are paired with each other are connected to the oscillation mark 4.
It is arranged in a straight line parallel to 0 without contacting the surface 32, 34, 36° 38.

FIG. 3 is a diagram illustrating the configuration of a pair of transmitters 42 and receivers 44 arranged opposite to the surface 32, but the other transmitters 42 and receivers 44 are configured in exactly the same way. . As is clear from this figure, the transmitter 42 includes a pulse generator 46 and a transmitting coil 48. From the pulse generator 46, for example, 0.2 to IOM
A high frequency current of approximately I(z) is output, and such high frequency current is applied to the transmitting coil.

This transmitting coil 48 is constructed by disposing conductive wires at equal pitches in a direction intersecting the oscillation mark 40 in a plane parallel to the surface of the billet 30, and the pitch of the conductive wires is determined by the frequency of the high-frequency current and the billet 30.
It is said to have the same length as the wavelength of ultrasonic waves, which is determined by the speed of sound in 0. When a high-frequency current is supplied to the transmitting coil 48, an alternating magnetic field is formed on the surface of the billet 30, and eddy currents due to the alternating magnetic field are locally generated on the surface 32, resulting in a Lorentzian current. The force creates an ultrasonic wave 50 having the same wavelength as the spacing of the transmitting coils 48 and the same frequency as the high frequency current. Further, the transmitting coil 48 is arranged along the width direction of the surface 32 parallel to the oscillation mark 40, so that the ultrasonic wave 50 travels in the width direction of the surface 32.

The receiver 44 includes an electromagnet 52 for forming an external magnetic field, and a receiving coil 54 which is similar to the transmitting coil 48 but has conductor wires separated by two wavelengths. A reflected wave 58 reflected by gE56 existing in the vicinity of
The reflected wave 58 is detected by the receiving coil 54 based on the change in the eddy current caused by reaching the magnetic field formed in the vicinity of the receiving coil 54 . The signal representing the reflected wave 58 detected in this way is first supplied to a flaw detection device 60, and the position and size of the flaw 56 are detected based on the signal. The magnitude is displayed on a cathode ray tube by the display/recording device 62 and recorded on a chart.

On the other hand, the four pairs of transmitters 42 and receivers 44 disposed opposite to one surface 32 are disposed at different positions or directions in the width direction of the surface 32, as shown in FIG. By detecting flaws in each pair of flaw detection areas C, flaw detection is performed on substantially the entire surface 32. This flaw detection area C
is relatively narrow, and the dimension in the width direction of the surface 32 is set to, for example, about 40 mm. Note that the other surface 34
．． 36. Also in 38, transmitters 4 provided in four pairs each
2 and the receiver 44, almost the entire surface is inspected for flaws.

According to such a flaw detection device, the transmitter 42 and the receiver 44 can transmit and receive the ultrasonic 50° reflected waves 58 to and from the surfaces 32, 34° 36.38 of the billet 30 in a non-contact state. Regardless of the presence of the mark 40, ultrasonic flaw detection can be performed successfully. Moreover, the transmitters 42 and the receivers 44, which form 52 pairs of each other, are arranged along the oscillation mark 40,
Since the ultrasonic waves 509 and the reflected waves 58 traveling in the same direction as the oscillation mark 40 are transmitted and received, there is relatively little interference from the unevenness of the oscillation mark 40, and highly accurate flaw detection can be performed. I can do it.

In addition, in flaw detection using such surface waves, it is possible to detect not only surface defects but also defects that exist at a slight depth from the surface. In the flaw detection of billet 30, which is often performed, it is possible to perform flaw detection that is practically sufficient. Note that the smaller the frequency of the ultrasonic wave 50, that is, the frequency of the high-frequency current supplied from the pulse generator 46 to the transmitting coil 48, the more defects existing in a deeper part from the surface can be detected.

) - On the other hand, since the crystal grains of the billet 30 manufactured by such a continuous casting apparatus are relatively large, the attenuation of the ultrasonic waves 50 is also large. Four pairs of transmitters 42 and receivers 44 are provided for each surface 32° 34, 36, 38, and a flaw detection area C to be detected by the pair of transmitters 42 and receivers 44 is set to a relatively narrow range. Therefore, the attenuation of the ultrasonic waves 50 is small, and even small flaws can be detected with high accuracy.

In addition, in this embodiment, since the sufficiently cooled billet 30 is tested for flaws, the magnetic permeability is large, and the magnetic flux density is accordingly large, making it possible to generate strong ultrasonic waves 50. , hot billet 30
Since the attenuation of the ultrasonic wave 50 is smaller than that of the ultrasonic wave 50, more accurate flaw detection can be performed than in the case of flaw detection of the hot billet 30, which has a large attenuation.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, the flaw detection is performed on the billet 30 that has been cut and sufficiently cooled, but it is also possible to perform the flaw detection on the billet 30 that is in a high temperature state such as before cutting. do not have.

Further, in the embodiment described above, the flaw detection device is installed in a fixed position and the flaw detection is performed by moving the billet 30 in the direction indicated by the arrow and mark B. However, conversely, the flaw detection device is moved relative to the billet 30. It is also possible to do so.

Furthermore, in the embodiment, four surfaces 32 of the billet 30
, 34, 36, and 38 each have four pairs of transmitters 42. Although flaws are detected by the receiver 44, if necessary, it may be possible to detect flaws only on one of the surfaces.
It is also possible to use a pair of transmitter 42° receiver 44 to detect flaws on the entire surface.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state in which a transmitter/receiver of a flaw detection apparatus according to an embodiment of the present invention is placed facing the surface of a billet as a continuously cast piece. FIG. 2 is a plan view showing the arrangement of four pairs of transmitters/receivers provided facing each other on one side of the billet of FIG. 1. FIG. FIG. 3 is a diagram illustrating the configuration of a pair of transmitters and receivers provided facing each other on one surface of the billet of FIG. 1. FIG. FIG. 4 is a schematic diagram illustrating an example of a continuous casting apparatus. Fifth
The figure is a perspective view showing a cast piece manufactured by the continuous casting apparatus of FIG. 4. 30: Billet (cast piece) 32.34, 36.38: Surface 40 niosilsion mark

Claims (1)

[Scope of Claims] A flaw detection device for detecting flaws existing in a cast piece sent out from a continuous casting device, the flaw detection device being arranged near the surface of the cast piece without contacting the surface, a transmitter that electromagnetically generates an ultrasonic wave traveling along the cast piece; and a pair of the transmitter and the transmitter in a straight line parallel to the oscillation mark formed on the cast piece in a non-contact state with the surface. a receiver configured to electromagnetically receive a reflected wave of the ultrasonic wave reflected by a flaw existing in the cast piece; and a flaw is detected based on the reflected wave received by the receiver. 1. A flaw detection device for continuously cast pieces, comprising a flaw detection device.