JPS59189041A - Continuous casting mold for ultrasonic oscillation - Google Patents

Abstract

PURPOSE:To decrease the attenuation in oscillation in a groove part by providing a thin walled part in the part corresponding to meniscus, forming the thin walled part into the groove shape extending in the horizontal direction of a casting mold, and controlling the width and length of the groove to the specific multiple value of the wavelength of the oscillation in the groove part. CONSTITUTION:A groove part 2 of a thickness (t), width (b) and length L is formed in the part corresponding to meniscus and an ultrasonic oscillator 3 is adhered therein, in long and short side molds 1-1, -, 1-2' which solidify a billet from a molten steel. The frequency is controlled in such a way that the two- times integrated value of the acceleration outputted from a displacement meter 4 is maximized within the frequency range of an oscillating circuit 5 for an exciter. Decision is made in a decision circuit 7 so that the drawing resistance value of the billet by a load cell 6 attains the satd. min. amplitude value. The output from the exciter is controlled in the circuit 5. The exciting frequency here is set at 15+ or -1kHz, and the width (b) or length L of the groove at the integer times value of 1/2 the wavelength of the oscillation. Then the groove part is oscillated near the resonance frequency in the length and width directions and the attenuation in the oscillation is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Continuous casting, particularly continuous casting of steel, has already been established and has achieved some success. The process in which molten steel is placed on top of the slab is mainly carried out in a cylinder made of a good thermal conductor called a mold, and at this time, the slab, which is still mostly unsolidified inside, and the mold In order to improve the abrasion of the mold, it is common practice to apply a rocking motion, commonly called oscillation, to the entire mold in parallel to the casting direction.

The problem in this case is that wavy surface textures called oscillation marks occur on the slab, and surface defects are likely to occur starting from the wavy surfaces. To prevent this, lQKHz
The mold surface is slightly vibrated at an order of magnitude higher frequency.
It is effective to replace the above-mentioned oscillation, and methods such as Japanese Patent Application Laid-open No. 11165/1983 employ this means. According to this method, compared to mechanical oscillation, the surface quality is smoother, powder consumption and slab pulling resistance are reduced.

In this heel mold, one or several vibrators are installed outside the mold, and a vibration propagation mechanism called a pawn is used to guide them to the thin wall i:9i that is to be vibrated.
Vibration components leaked to areas other than the thin-walled portions and were absorbed, and the vibration I11 became smaller as the vibration point was further away.

To solve this problem, conventional methods have been used in which the part to be vibrated is forcibly vibrated using a water immersion type vibrator, which is placed in close contact with the thin wall part of the mold to be vibrated and arranged to form a cooling water groove. It was taken. However, even with this method, it is difficult to obtain the amplitude of the thin-walled part of the mold necessary to suppress the slab pull-out resistance value below a certain value due to the absorption and leakage of vibration components to the cooling water in the cooling tank and the bank plate, etc. I couldn't do it.

In the present invention, the thickness of the meniscus part of the mold is reduced by 813 minutes to confine vibrations only to the groove part, and the grooves rJ-rb, groove length L, and ocean t of the mold groove part are selected. This is an attempt to solve the above problem (7).

That is, the gist of the present invention is that, in a mold in which a thin wall portion is provided in a portion corresponding to the meniscus and subjected to ultrasonic vibration, the thin wall portion is formed into a groove shape extending in the horizontal direction of the mold, and the groove portion 4 has a groove width or a groove length as necessary. It is in the mold that is an integral multiple of the % of the wavelength of the kinetic motion.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a continuous casting mold of the present invention. In the figure,]-]1. I-1 is a molded copper plate for long sides, 1-2
indicates a molded copper plate for the short side. Reference numeral 2 denotes a groove part where the thickness of the meniscus part is partially reduced, and has the dimensions of thickness t, groove width b, and groove length L, and the vibrator 3 is placed at the part of one end surface where vibration is desired. The other surfaces are covered with cushioning to prevent vibrations from leaking. The frequency is controlled so that the twice-integrated value of the output accelerometer of the displacement meter 4 provided in the groove becomes the maximum within the frequency variable range of the exciter oscillation circuit 50.

The slab drawing resistance value is detected by a load cell 6 provided in the mold, and as shown in FIG.
The oscillation circuit 5 controls the output of the oscillator.

In the present invention, the groove width or groove length is controlled to a value that is an integral multiple of % of the wavelength of the groove vibration, and this will be understood from the following explanation.

First, we will discuss the vibration of a rectangular plate using Figure 2 (al to fdl). Then, this figure represents the m+1-order vibration mode when the rectangular plate resonates.

In other words, the vibration at the 0 point (this is called the antinode of vibration) of Figure 2 (7 taking the 2nd-3rd order resonance moat of al as an example) and Figure 2 (bl) is the maximum, and the 0 point (this is the node of vibration) This shows that the vibrations of ℃ and ℃ are at a minimum.

The following two points should be noted here. In other words, the length between the nodes of the generated resonance mode, the so-called half wavelength of the standing wave, differs in the vertical direction (b direction) and the horizontal direction (L direction). It also differs depending on the resonance mode.Therefore, the above wavelength will change, and after determining the groove shape (b, t, L), it will be determined as 70' result. be.

The groove shape (b) determines in which resonance mode the amplitude at the point corresponding to the point ■ in Figure 2 (bl) becomes extremely thick while satisfying the conditions of 16 KHz > f > 14 KHz.

L, t), the aspect ratio L'/b, and the thickness ratio T/l of the thick inner part and the thinner part.

Next, the resonance mode frequency f at which these resonance modes occur is as follows for a peripherally fixed rectangular plate.

Here, b - groove width - Kaibara E - Young's modulus (groove member) Seapoanon ratio (groove member, 0.28 to 03 for steel) r - specific weight (groove member) JO5Cm/S) αm'n - temporary mounting Lateral ratio L/b, dimensionless number determined for each moat Here, αm, n are dimensionless numbers that vary depending on L/b and resonance moat, and are determined as shown in Figure 2 (Cl) depending on peripheral support conditions, for example. In the 1-1st order moat of a peripherally fixed rectangular plate, each L/b is as follows.

α l-] Knee 7.8] 3 (L/b
=], 5) α+, +=7.100 (L/b=
2.0) α+, +”6.703 (L/b=3.0
)α+,+””6.467 (L/b: bacteria). In the figure, a: 4 sides fixed, b: L side supported, L side fixed,
c: L-side fixed, L-side supported, d: 4-side supported.

Next, this mode frequency f decreases due to the temperature rise in the mold thin groove part, as shown in the actual example of Fig. 2 (dl).
In the example shown in the figure, a rise of 100°C causes a drop of about 100Hz. The figure shows an input of 500 W, a temperature drop of 1 samurai and water cooling, b: 807 f.
1m, L: An example of 2Q34ZIX is shown.

Also, regarding the thickness ratio T/l of the thin groove part and the thick plate part, if the vibration amplitude attenuation in the 0 part of FIG. At around 3.3, the attenuation is thick.

Next, we will discuss how to determine the shape of the thin mold groove. First, when using an ultrasonic vibration as an excitation source, the usable range of the excitation frequency is naturally limited. In other words, regarding the lower limit, 14. KHz
If it goes below 16 kHz, the noise becomes so intense that it becomes impossible to use it, and if the upper limit goes above 16 kHz, the abdominal amplitude value corresponding to the part ■ in BL becomes small, making it unusable. (. Therefore, the excitation frequency f of the plate is preferably set to 15 KHz±1.KHz, which is normally set to 7.

Next, regarding the groove shape (b, t+L),
The groove length is set to be larger than the length of the long side of the mold, and where T is the thickness of the thick part, T/l)z+. Also, in a whirlpool?
1; η For the combination (b, t) of thickness t, then obtained, and 16 KHz > f > ], 4 KHz
The amplitude value of the groove resonance that satisfies
1, 6 KHz) f obtained for the combination of t
> ] larger than the resonance amplitude value of the 71KHz range, and the upper limit in terms of strength) b) 4 s mm (on the ultrasonic 1゛ wave horn installed) and the upper limit of the thickness north -) t) i5 mm
(Strength) The groove width and sea t are selected so as to satisfy (in terms of strength).

According to the present invention, the thin groove vibrates near the resonant frequency in both the length direction and the width direction, so the attenuation is small in both directions as shown in FIG. In addition to suppressing the above-mentioned slab withdrawal resistance value below a certain value, it is also possible to respond by changing the optimum frequency depending on the properties of molten steel, casting speed, and cooling water pressure (as shown in Figure 4). Since it can be controlled to the minimum amplitude value at which the pull-out resistance value is saturated, there is also an energy saving effect in that energy proportional to the square of the amplitude is not consumed excessively.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the present invention, Fig. 2 (al, (1))
is a schematic diagram of the resonance mode, FIG. 2 fc] is a diagram of the resonance mode, and FIG. d) is a chart of temperature and frequency, FIG. 3 is a chart of amplitude ratio, and FIG. 4 is a chart of drawing resistance ratio. ]-1, 1-1'... Molded copper plate for long side 2... Thin groove 1-2 Molded copper plate for short side 3. Vibrator Figure 1 Figure 2 (α) 1-1 +-27-31 −δ m=1. n=2 m=2. n=2 m=3
．． n=2 (b) Fan 2 figure (C) L/b (J) -208- Flood 3 figure 4

Claims (1)

[Scope of Claims] 1. In a mold that applies ultrasonic motion (a) by providing a thin wall portion in a portion corresponding to the meniscus, the thin wall gB is formed into a groove shape extending in the horizontal direction of the mold, and the groove width is set to the wavelength of the groove vibration. A continuous casting mold for ultrasonic vibration characterized by an integral multiple of %. 2. In a mold that applies ultrasonic vibration by providing a thin wall portion in the area corresponding to the meniscus, the thin wall portion is formed into a groove shape extending in the horizontal direction of the mold, and the groove length is set to an integral multiple of % of the wavelength of the groove vibration. Continuous casting mold for ultrasonic vibration. 6 Patent r'j:'j range of search for ultrasonic vibration fc described in item 2 where the groove rl+ is an integral multiple of % of the wavelength of the vortex vibration
i-casting mold.