JPS63140744A - Continuous casting method - Google Patents

Abstract

PURPOSE:To prevent the seizure of molten metal to a mold wall by fitting plural ultrasonic vibration at different positions to peripheral direction near the molten metal surface position in the mold and applying the ultrasonic waves having different natural frequencies to vibrators side by side. CONSTITUTION:The mold 1 is formed by facing two pieces of long side mold walls 1a, 1b fastening faced two pieces of short side mold walls 1c, 1d between them, and the molten metal 8 is poured into the mold 1 through a nozzle 10. At outside of these mold walls 1a, 1b, 1c, 1d, water cooling frames 2a, 2b, 2c, 2d are formed and the vibrating rods 7a, 7b, 7c, 7d are fixed on the mold walls 1a, 1b to peripheral direction near the molten metal surface position of long side mold walls 1a, 1b and the ultrasonic vibrators 6a, 6b, 6c, 6d are arranged at the other end parts of rods. In this constitution, in the vibrators 6a, 6b, the prescribed frequency signal is outputted and in the vibrators 6c, 6d, the different frequency signal is outputted. In this way, these vibrating compositions are mutually interfered, and by giving the other vibrating composition to the mold part having small amplitude, the amplitude is increased, and so the seizure of molten metal 8 is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for continuous casting by injecting molten metal into a continuous casting mold (hereinafter simply referred to as the mold) to which ultrasonic vibrations are applied. Then, ultrasonic vibrations of two or more different frequencies are applied to the mold wall from different positions to prevent the molten metal injected into the mold from sticking to the mold wall,
This provides a method for continuous casting.

[Prior art]

In continuous casting, the mold is vibrated at a constant amplitude to prevent molten metal from sticking to the mold walls.

Means for vibrating the mold include a vertical reciprocating mold method (ossocillation method) in which the mold itself moves up and down;
Alternatively, as shown in FIG. 5 (plan view), an ultrasonic vibrator 6 is attached to the outer surface of the mold wall 1 that cools the molten metal 8 via a vibration transmission rod 7 provided in a direction perpendicular to the outer surface of the mold wall 1. There is an ultrasonic vibration method that generates ultrasonic vibration in the thickness direction of 1.

This ultrasonic vibration method uses the function of applying the above-mentioned ultrasonic vibration to the mold wall, reducing the friction between the melting metal and the mold wall, and preventing the molten metal from sticking to the mold wall. This is what I did.

The function described above uses ultrasonic vibrations to vibrate the part of the mold wall that is in contact with the molten metal in the direction of its wall thickness, causing the molten metal to be unable to follow the movement of the mold wall and momentarily create a gap between the mold wall and the molten metal. It is thought that the creation of a space reduces friction between the two and prevents seizure. For this purpose, it is necessary that the vibration displacement in the thickness direction of the mold wall be large.

In Figure 6, the horizontal axis represents the position of the long side of a slab mold with a rectangular cross section, the vertical axis represents the vibration amplitude of the mold, and two ultrasonic vibrators are placed at the same height on each of the two long sides of the mold. This is a graph showing the relationship between the two in the horizontal direction of the ultrasonic transducer mounting position for one long side when the ultrasonic vibrations of the same frequency, for example, 16.2K Ilz are applied to the mold with the ultrasonic transducer mounted at the same position. . As can be understood from this figure, in the case of the conventional method, there is a problem in that there are parts of the mold where the vibration amplitude is small, and it is not possible to ensure a sufficiently large vibration over the entire surface.

In order to solve this problem, there is a method of uniformizing the vibration over the entire surface by periodically changing the oscillation frequency of the ultrasonic vibrator within a certain frequency range (Japanese Patent Application Laid-Open No. 55-45558), or using a mold near the steady state. Detect the vibration or mold temperature and follow the oscillation frequency of the ultrasonic transducer so that the maximum amplitude point is located near the above scene? 71 method (Unexamined Japanese Patent Publication No. 56-1115
No. 1, Japanese Unexamined Patent Publication No. 59-197366) has been proposed.

[Problem that the invention seeks to solve]

Both of these methods require a circuit for changing the frequency, and the configuration thereof is complicated. Also, the shape of the ultrasonic vibrator and vibration transmission rod.

Since the dimensions are constant, even if the frequency is varied over a wide range, it is not possible to apply vibration in the thickness direction to the mold with the same efficiency over the entire range. In particular, when using the latter method, it is necessary to attach a detection element to the mold to detect the amount of vibration of the mold or the temperature of the mold, which poses problems such as difficulty in maintenance.

The present invention was made in view of the above circumstances, and eliminates the need for a circuit for changing the frequency, eliminates the need for a detection element that is difficult to maintain, and generates sufficient vibration throughout the entire inner circumferential surface of the mold. It is an object of the present invention to provide a method that allows continuous casting in a state where 6' is maintained and seizure is prevented.

[Means for solving problems]

In the present invention, ultrasonic vibrations of two or more different natural frequencies are applied to the mold from different positions thereof.

That is, in the continuous casting method according to the present invention, a plurality of ultrasonic transducers are installed at different positions in the circumferential direction near the molten metal level of a continuous casting mold into which molten metal is injected, and from each ultrasonic transducer, The method is characterized in that continuous casting is performed by applying ultrasonic vibration to the mold using at least two types of frequencies and by making the oscillation frequencies of adjacent vibrators different.

[Effect]

In the present invention, since ultrasonic vibrations with two or more different natural frequencies are applied to the mold, these vibration components interfere with each other, and other vibration components are generated in parts of the mold where the amplitude of the two vibration amounts is small. is applied to increase the amplitude of that part.

〔Example〕

The present invention will be explained below based on the drawings. FIG. 1 is a perspective view showing the implementation state of the present invention, and FIG. 2 is a cross-sectional view showing the vicinity of the attachment position of the ultrasonic transducer. Shows the mold to be used. The molten metal 8 injected into the mold 1 is primarily cooled here to become a slab with a peripheral wall formed thereon, and is drawn out downward.

The mold 1 has two opposing short side mold walls 1c, ld sandwiched between two long side mold walls 1a, lb. On the outside of each mold wall 1a, lb, lc, ld. is a water-cooling frame 2 that covers the outer surface part so as to have a space inside.
a.

2b, 2c, and 2d are formed, and cooling water is supplied between each water cooling frame and the mold wall.

The water cooling frame 2a is provided with circular holes 3a and 3b whose centers are approximately 50 g lower than the molten metal surface of the long side mold wall 1a, that is, the part facing the meniscus. Similarly, make two holes 3c +3 in frame 2b.
d has been established.

Column-shaped vibration transmission rods 7a, 7b, 7c, and 7d penetrate horizontally through the holes 3a, 3b, 3c, and 3d, and vibration transmission rods 7a, 7b, 7c, and 7d penetrate through the holes 3a, 3b, and 3c. , 3d, a sealing member with a vibration absorbing effect, such as a Q IJ ring 4a, 4b.
, 4c, and 4d, and the vibration transmission rod 7a+
7b, 7c+ 7d and holes 3a, 3b, 3c, 3
d is sealed by the O-ring. Vibration transmission rod 7a.

7b has male threaded parts 5a, 5b formed on the tip side thereof, which have a smaller diameter than the middle part in the axial direction, and which are fitted into female threaded parts 9a, 9b formed on the long side mold wall 1a. The sides are fixed, and the ultrasonic transducers 6a and 6b are connected to the proximal end. The vibration transmission rods 7c, 7d also have male threaded portions 5c, 5d formed on their distal ends and having a smaller diameter than the middle portion in the axial direction, and female threaded portions 9c, 9d formed on the long side mold wall 1b. The distal end side is fixed by fitting into the transducer, and ultrasonic transducers 6c and 6d are connected to the proximal end side.

An oscillator (not shown) that outputs a predetermined frequency signal is connected to one ultrasonic transducer 6a, 6b of each of the two long side mold walls 1a, lb, and the remaining ultrasonic transducer 6b , 6d are also connected to an oscillator (not shown) that outputs a predetermined frequency signal. These oscillators have at least two types of frequencies, and adjacent oscillators have different frequencies. The oscillation frequency is generally 50 KH due to the manufacturing limit of a vibrator that can obtain a strong output.
z or less is better, and 5KHz or more is better due to noise to the surrounding environment and restrictions on vibrator size, and as a result, 5 to 50KHz.
A range of is preferred.

The length of each of the vibration transmission rods 7a, 7b, 7c, and 7d is determined to be an integral multiple of 2 of the wavelength λ of the ultrasonic waves emitted from the ultrasonic transducers 6a, 6b, 6c, and 6d, and an O-ring Vibration transmission rods 7a, 7b supported by 4a, 4b, 4c, 4d.

The positions 7c and 7d are the nodes of the ultrasonic waves passing through the vibration transmission rod (
(where the amplitude is zero).

The method of the present invention using the apparatus configured as described above will be explained below.

First, a predetermined frequency signal is output from an oscillator (not shown) to the ultrasonic transducers 6a, 6b, 6c, and 6d.

When such preparation is completed, injection of molten metal 8 into mold 1 via nozzle 10 is started. Molten metal 8 is mold 1
For example, when the dummy bar head (not shown) is charged from below into the mold, the dummy bar head is stored, and when the dummy bar head rises to a steady state position of about 100 mm from the upper end of the mold, the dummy bar head is pulled out downward and the scene height increases. The injection amount of the molten metal 8 is adjusted so that the molten metal 8 is kept constant at a steady state position. In addition, a lubricant is poured onto the surface of the molten metal to lubricate the mold 1 and the slab.

The molten metal 8 injected into the mold 1 is not separated from the mold 1 because the above-mentioned ultrasonic vibration is applied to the mold 1.
It is promoted over the entire inner surface.

To explain this in detail, ultrasonic vibrations of two different frequencies are applied to each of the mold walls 1a, lb, and two vibration components are transmitted to the mold walls 1a, lb by the vibration transmission rods 7a, . . . 7.
It propagates inside the mold wall radially centering on the position where d contacts. At this time, when the vibration is caused by only one vibration component, there are parts of the mold where the amplitude is small as shown in Fig. 6, as in the conventional case, but since the frequencies of the other vibration components are different, the resulting vibration causes the parts of the mold where the amplitude is small. A large vibration is applied, and as a result, the two ultrasonic vibrations interfere, and the amplitude becomes larger over the entire surface than before.

The magnitude of this amplitude is influenced by the length of the vibration transmission rod and its fixed position in the longitudinal direction. In other words, if the position of the node of the ultrasonic wave emitted from the ultrasonic transducer is on the outer surface of the mold wall, vibration cannot be imparted to mold 1, and conversely, the position of the antinode (where the amplitude is maximum) is on the mold wall. At the outer surface of the mold, the amplitude of mold vibration is maximum.

For this reason, the length of the vibration transmission rod! (See FIG. 2), as described above, the amplitude of the mold vibration is maximized as an integral multiple of A of the wavelength λ of the ultrasonic wave propagating therein.

Furthermore, when the position where the vibration transmission rods 7a, 7b, 7c, and 7d are supported by the O-rings 4a, 4b, 4c, and 4d is the vibration transmission rod portion corresponding to the antinode of the ultrasonic wave propagating through the vibration transmission rod, In this case, the amplitude of the vibration transmitted to the mold 1 is attenuated, and the amplitude of the mold vibration becomes smaller overall. Therefore, vibration transmission rods 7a, 7b, 7c, 7d
The positions where the O-rings 4a, 4b, 4c, and 4d support the vibration transmitting rod correspond to the nodes of the ultrasonic wave propagating within the vibration transmitting rod, and are intended to prevent vibration attenuation.

The mold position where seizure occurs is in the range from the steady scene position to about 100 mm below it, and since the ultrasonic vibration is attenuated as it propagates inside the mold, the positions of holes 3a etc. A vibration transmission rod 7a is opened in the water cooling frame 2a, etc., approximately 50 degrees below the normal scene position, and is inserted through the vibration transmission rod 7a.
The ultrasonic vibration from the ultrasonic vibrator 6a etc. is applied to the central position in the height direction of the range where seizure is likely to occur, with little attenuation within the mold wall. The vibration applied to the mold wall propagates radially throughout the entire area centering on the applied position, and the mold vibrates with a larger amplitude than before in the entire area.

Therefore, in the case of the present invention, seizure can be effectively prevented, the flow of lubricant into the mold and between the slabs is made uniform, and there is no need to apply vibration to the mold as in the conventional off-sillion method. Therefore, slabs with smooth surfaces without off-sill marks can be produced.

〔effect〕

In Figure 3, the horizontal axis represents the circumferential mold position on the long side and the short side, and the vertical axis represents the vibration amplitude (μm) of the mold. It is a graph showing the vibration amplitude change with respect to the mold position when ultrasonic vibration is applied. As for the amplitude measurement conditions, the vertical and horizontal dimensions of the horizontal cross section of the mold are 100 mm x 4QQ.
Ill, use a copper one with a thickness of 25 mm, and position it 50 mm below the steady scene position (15 mm from the top of the mold).
0 (position below the fin), vibration transmission rods 7a and 7c with a length of 330 mm are attached in the circumferential direction, and a 16.2 KHz vibration transmission rod is attached to this.
an ultrasonic transducer 6a that oscillates ultrasonic waves of (400W);
6c and a vibration transmission rod 7b having a length of 274 fins.
, 7d is attached, and an ultrasonic transducer 6b that oscillates an 18 KHz (400 W) ultrasonic wave.

6d was connected.

As understood from this figure, in the case of the present invention, 2
Since vibration components of two different frequencies interfere on the same mold wall on the long side, both the minimum amplitude and the overall amplitude level on the long side can be made larger than before, and the overall amplitude level on the long side can be increased to 10 μm or more. , and the overall amplitude level on the short side is set to 5.
μm or more, and the vibration amplitude is large at the mold position where the ultrasonic vibration is applied, as indicated by the arrow in the figure, i.e., where the vibration transmission rod is attached, and this position is a part where seizure is likely to occur. Therefore, burn-in can be effectively prevented.

However, in the case of a slab mold having a rectangular cross section, it is preferable to apply ultrasonic vibrations of different frequencies to one mold wall to make interference more likely to occur.

In addition, in the above description, two ultrasonic transducers are attached to one long-side mold wall, but the present invention is not limited to this, and a plurality of ultrasonic transducers are attached to the mold including the short-side mold wall. may be attached, and ultrasonic vibrations of at least two or more predetermined frequencies, each of which has a predetermined frequency, and in which adjacent vibrators have different oscillation frequencies, may be applied to the mold.

Further, in the above description, continuous casting is performed using a mold configured with long and short side mold walls, but the present invention is not limited to this, and as shown in FIG. 11
Even when using ultrasonic vibrators 16a, 16b and vibration transmitting rods 17a, 17b in two places, or attaching ultrasonic vibrators and vibration transmitting rods in three or more places, two or more types of A similar effect can be obtained by applying ultrasonic vibrations of different frequencies.

As described in detail above, the present invention installs a plurality of ultrasonic transducers at different positions in the circumferential direction near the molten metal level of the mold, and uses at least two or more types of frequencies from each ultrasonic transducer. Since ultrasonic vibrations are applied to the mold by making the oscillation frequencies of matching vibrators different, both the minimum amplitude and the overall amplitude of the mold vibration can be increased, thereby effectively preventing seizure. In addition, the present invention eliminates the need for a circuit that changes the frequency, which was required in the past, and also eliminates the need to detect the amount of mold vibration and mold temperature, so the installation of these detectors can be omitted and maintenance is simple. has excellent effects.

[Brief Description of the Drawings] Fig. 1 is a schematic diagram showing the implementation state of the present invention, Fig. 2 is an explanatory diagram of the installation details of the ultrasonic transducer when implementing the present invention, and Fig. 3 is a detailed diagram of the present invention. FIG. 4 is a schematic diagram showing another embodiment of the present invention, FIG. 5 is an explanatory diagram of the contents of the prior art, and FIG. 6 is an explanatory diagram of the problems of the prior art. ■...Mold 6a, 6b, 6c, 6d...Ultrasonic vibrator holder Applicant Agent Sumitomo Metal Industries Co., Ltd.
Patent Attorney Noboru Kono No. 4 Zushima S Zucho Yo%6

Claims (1)

[Claims] 1. A plurality of ultrasonic transducers are installed at different positions in the circumferential direction near the molten metal level of a continuous casting mold into which molten metal is injected, and each ultrasonic transducer emits at least two types of frequencies. A continuous casting method characterized by performing continuous casting by applying ultrasonic vibration to a mold so that adjacent vibrators have different oscillation frequencies.