JPS6048699B2 - Internal defect detection method for continuous casting materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention overcomes hollow internal defects (such as blowholes and vibration defects) that occur near the center of continuous casting materials such as copper aluminum during the process of continuous casting and rolling. This invention relates to a detection method using sound waves.

Internal defects in this cast material are caused by hot cracking during subsequent rolling,
This causes the occurrence of flaws, and further results in wire breakage and the occurrence of flaws during cold working (wire drawing, rolling, etc.) after rolling.

Therefore, it is necessary to detect these internal defects in the continuous casting and rolling process and thereby adjust the continuous casting conditions and control the quality of the cast material itself.For this purpose, the present inventors have We previously proposed a method that enables continuous ultrasonic flaw detection (Patent Application No. 1972-159, dated December 28, 1975).
No. 718).

In this method, as shown in FIG. 1, internal defects are detected by a detection device 30 before the cast material 3 sent from the continuous casting machine 20 enters the rolling mill 40.

The detection device 30 has a pair of rollers 2 and 2' that clamp two opposing surfaces (upper and lower surfaces) of the casting material 3, and the pressure device 1 applies pressure to a predetermined pressure. The rollers 2 and 2' have hollow holes 4 and 4', respectively. Inside the hollow hole 4 is an ultrasonic transmitting transducer 5, inside the hollow hole 4' is a receiving receiver 7, and a shoe 6, respectively. It is attached so that it may contact the inner surface of the rollers 2, 2' via 6'. Ultrasonic waves transmitted from the vibrator 5 pass through the shoe 6, the roller 2, the cast material 3, the roller 2' and the shoe 6', and are received by the receiver 7, and the amount of ultrasound transmitted is measured. Of the cast materials 3. If there is a defect such as a blowhole in the part, the ultrasonic waves will be reflected or attenuated there, so the internal defect can be detected by measuring the amount of transmission. This method uses the clamping pressure of the rollers 2 and 2' to improve the transmission of ultrasonic waves, even when the sawing temperature of the cast material is, for example, 500 to 600°C for aluminum material or 800 to 900°C for copper material. , which enables ultrasonic detection, has the following practical drawbacks (as it turns out).

In other words, in the above method, ultrasonic waves are penetrated into the casting material.
(i uses a roller as a medium to
If the pressure applied to the rollers is small, the transmission of ultrasonic waves at the interface between the rollers and the casting material will be poor, and the ratio of flaw signal to noise signal (S/N) will decrease. In order to improve this, the best way was to increase the clamping pressure of the rollers on the casting.

However, although this improves ultrasound transmission,
As a secondary phenomenon, meandering of the casting material and obstruction of smooth flow occur, which has a fatal negative impact on continuous casting.
There were drawbacks that made it impossible to continue production. The method of the present invention solves the above-mentioned drawbacks by effectively transmitting ultrasonic waves through a cast material that is sandwiched and pressed between a pair of rollers containing ultrasonic transmitting and receiving elements, and press-welding the rollers and the cast material. The present invention aims to provide a method for detecting internal defects in cast materials that further improves the S/N ratio by suppressing the noise L-novel that acts on the boundary conditions.

The present invention provides a method for detecting internal defects in a continuous casting material using a pair of clamping pressure rollers with built-in ultrasonic transmitting and receiving elements as described above, in which a pair of rollers having hollow holes is provided with a crown-shaped convex surface as a transmitting roller. There are some types of rollers that have a flat outer circumferential surface as the receiving roller L, and others that have a flat outer circumferential surface.

The method of the present invention is particularly effective for casting materials such as copper or copper alloys (hereinafter referred to as copper), aluminum or aluminum alloys (hereinafter referred to as aluminum), and the predetermined pressure applied with rollers is 500k9/Cl in the case of copper. As mentioned above, it is desirable that the pitch of aluminum is 150 k9/d or more, and the required frequency of the ultrasonic wave is preferably 1.0 MHz for copper and 1.0 to 2.0 MHz for aluminum.

If the clamping pressure is within the above range, the range of variation in the amount of ultrasonic transmission can be suppressed to 2 dB or less, and if it is less than the above range, the boundary conditions between the roller and the cast material will be poor and the S/N will be reduced. Furthermore, when the ultrasonic frequency is outside the above range, the attenuation of the ultrasonic waves within the cast material increases, making it difficult to detect hollow defects. Hereinafter, the present invention will be explained in detail with reference to the drawings and examples.

FIG. 2 is a cross-sectional view showing the structure of the roller and the contact state between the roller and the continuous casting material in an embodiment of the method of the present invention.

The method of the invention is carried out in a manner similar to that shown in FIG. 1 using specially designed rollers. In FIGS. 1 and 2, two opposing surfaces (upper and lower surfaces) of a cast material 3 sent out from a continuous casting machine are moved by a pair of opposing rollers 2 and 2' having hollow holes 4 and 4', respectively. , the pressurizing device 1 applies pressure at a predetermined pressure.

In the present invention, the structure of the rollers 2 and 2' is as shown in FIG. of! It has an outer peripheral surface 9. An ultrasonic transmitting transducer 5 is installed in the hollow hole 4 of the transmitting roller 2, and a receiving receiver 7 is installed in the hollow hole 4' of the receiving roller 2. The ultrasonic waves are transmitted through roller 2. It passes through the casting material 3, is received by the receiver 7 via the roller 2', and the amount of penetration is measured.

Conventionally, when a flat roller was used as the transmission roller 2, it was necessary to apply a large load to press the entire surface of the cast material 3, but in the present invention, since the outer peripheral surface 8 has a crown-like convex surface with a high center, The cast material 3 is pressed only near the center of the upper surface, and the surface pressure of the roller can be improved with the same load, so the total load can be reduced.

Moreover, since cast materials usually have internal defects such as blowholes near the center, ultrasonic waves only need to penetrate near the center of the top surface, and there is no problem in detecting the defects. Therefore, according to the method of the present invention, the total load of the clamping rollers to obtain good boundary conditions is reduced, so the braking effect on the casting material is reduced, and the meandering of the casting material and obstruction of smooth flow are reduced. This prevents the occurrence of flaws and allows effective penetration of ultrasonic waves for flaw detection, which has the effect of significantly lowering the noise level. The shape of the outer circumferential surface 8 of the transmission roller 2 may be a circular arc or an inert circular convex surface to achieve the above effect, or the curvature R may be appropriately selected depending on the cross-sectional dimensions of the cast material, and there are no particular restrictions. There is no.

For example, for a cast material with a top surface width of approximately 73Tnm, a height of approximately 627Tgn, and a cross section of 3600TrfiL, the curvature of the arc is R.
Approximately 10 μm is used. The width of the outer peripheral surface of the transmitting roller 2 is appropriately selected depending on the cross-sectional dimensions of the casting material, the transmitter, the dimensions of the receiver, etc., and is usually about 30 to 6077!77.
1 is appropriate. If it is less than about 3 hours, it is insufficient for the width of the ultrasonic beam, so the amount of transmission decreases, and if it exceeds about 6 hours, the clamping pressure will be increased needlessly. Also, receiving roller 2'
It is desirable that the width of the outer circumferential surface of the casting material is normally larger than the width of the lower surface of the cast material, but there is no particular restriction. There is no particular limit to the diameter of the transmitting and receiving elements, but in practice, the diameter of the transmitting element is approximately 15 to 20 mm.
=FWL) Approximately 20 to 25 TW1 is suitable for the receiver.

Next, in the method of the present invention, even better results can be obtained by adopting the following method regarding ultrasonic transmission.

That is, as shown in FIG. 3, the first method is characterized in that internal defects such as blowholes 12 in the continuous casting material 3 occur near the center thereof.
A lens-type coupled transducer is used as the transducer, and the focal point 11 of the sound wave beam 10 extending from the transducer 5 to the receiver 7 is concentrated on the receiver 7 side below the central position where the defect occurs in the casting material 3. Make it.

By transmitting the ultrasonic waves in this manner, the internal defects of the cast material are intensively irradiated with the sound waves, which has the effect of increasing the S/N ratio. In the second method, as shown in FIG. 4, the transmitting vibrator 5 is tilted by about 1 to 2 degrees in the direction opposite to the advancing direction 13 of the casting material 3 with respect to the direction of the receiving element 7. Place it in By arranging the vibrator in this way, S/
It was confirmed through practical tests that the N ratio was improved. Example: Using a continuous casting machine, electrical aluminum with the dimensions shown in Figure 5 was produced.
(hereinafter referred to as EC aluminum) Cast bar 21C77I/
Sec, and internal defects were continuously detected by a detection device before entering the rolling mill as shown in FIG.

The measurement conditions of the present invention and the conventional method are as shown in the following table. Transmission amount chart (chart speed 1m/s
ec) is as shown in Figure 6 A, and Figure A shows the method of the present invention;
The diagram shows the conventional method.

As can be seen from the figure, the noise is large and the flaws are unclear in the conventional method, while the noise is small and the flaws are clearly visible in the method of the present invention.According to the present invention, internal defects in the cast material can be accurately identified. It can be seen that it can be detected with good sensitivity.

As described above, the present invention uses a roller having a crown-shaped convex outer circumferential surface as a transmitting roller out of a pair of rollers with built-in transmitting and receiving elements that press the upper and lower surfaces of a cast material. Since the contact condition between the roller and the casting material is improved even with clamping pressure, the clamping pressure can be reduced, and the noise level acting on the pressure welding boundary conditions is suppressed without causing meandering of the casting material or obstruction of smooth flow. ,
．． It has the effect of improving the ratio of flaw signal to noise signal (S/N) and detecting internal defects in casting materials accurately and with high sensitivity.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an example of a method for detecting internal defects in a cast material. FIG. 2 is a cross-sectional view showing the structure of the roller and the contact state between the roller and the continuous casting material in an embodiment of the method of the present invention. FIGS. 3 and 4 are cross-sectional views illustrating other embodiments of the present invention. FIG. 5 is a diagram showing the cross-sectional dimensions of a continuously cast material in an example of the present invention. Figure 6 A. The mouth is
It is a figure which shows the chart of the amount of ultrasound transmission by the method of this invention and a conventional method. 1... Pressure device, 2,2
'・・・Roller, 3...Casting material, 4
, 4'... Hollow hole, 5... Vibrator,
6, 6'...Shoe, 7...Receiver, 8...Outer peripheral surface of crown-shaped convex surface, 9...
... Plane outer peripheral surface, 10 ... Sound wave beam, 1
1...Focus, 12...Blowhole,
13... Direction of travel.

Claims (1)

[Scope of Claims] 1. Two opposing surfaces of a cast material sent out from a continuous casting machine are cast in a predetermined manner by a pair of opposing rollers each having a hollow hole and having a crown-like convex surface and a flat outer circumferential surface, respectively. At the same time, at least a lens-coupled vibrator is placed in the hollow hole of the convex roller as the vibrator of the transmitting device, and a receiving device is placed in the hollow hole of the flat roller. Receivers are respectively provided, so that the focus of the sound wave beam from the vibrator of the transmitting device to the receiver of the receiving device is focused toward the receiver from a central portion of the casting material where internal defects are likely to occur. A device for detecting internal defects in continuous casting materials, characterized in that flaws existing inside the casting material are detected by measuring the amount of ultrasonic waves transmitted by the transmitting and receiving devices. 2 The width of the crown-shaped convex roller is approximately 30 to 60 mm.
A method for detecting internal defects in continuous casting material according to claim 1. 3. The method for detecting internal defects in a continuous cast material according to claim 1 or 2, wherein the transmitting transducer has a size of about 15 to 20 mmφ and the receiver has a size of about 20 to 25 mmφ. 4. Continuously cast material according to claim 1, 2 or 3, in which the transmitting vibrator is inclined by 1 to 2 degrees in a direction opposite to the advancing direction of the cast material with respect to the direction of the receiver. internal defect detection method. 5. A method for detecting internal defects in a continuous cast material according to claim 1 or 2, wherein the cast material is made of copper or aluminum. 6 The predetermined pressure for clamping is 500 if the casting material is copper.
kg/cm^2 or more, 150 kg for aluminum
6. The method for detecting internal defects in a continuous cast material according to claim 5, wherein the internal defect detection value is at least /cm^2. 7 The required frequency of ultrasonic waves is 1.0M if the cast material is copper.
Hz, and in the case of aluminum, 1.0 to 2.0 MHz, the method for detecting internal defects in a continuous cast material according to claim 5 or 6.