JP6733336B2 - Continuous casting machine and continuous casting method - Google Patents

Description

The present invention relates to a continuous casting machine and a continuous casting method.

In continuous casting, molten metal once stored in the tundish (for example, molten steel) is injected from above into the mold through an immersion nozzle, where the outer peripheral surface is cooled and the solidified slab is withdrawn from the lower end of the mold. , Continuous casting is performed.

Here, during continuous casting, if lubrication between the solidified layer (solidified shell) on the surface of the slab and the inner wall of the mold is not good, the solidified shell adheres to the inner wall of the mold and the solidified shell breaks. By doing so, there is a possibility that defects called bleeding may occur on the surface of the slab, and molten metal outflow called breakout may occur. Therefore, in order to lubricate the solidified shell and the inner wall of the mold, powder called powder is generally supplied from the upper part of the mold during continuous casting. Liquid phase powder (molten powder) melted by the heat of the molten metal enters between the solidification shell and the inner wall of the mold, so that lubrication between the solidification shell and the inner wall of the mold is maintained. At this time, the molten powder does not enter between the solidified shell and the inner wall of the mold as it is. Therefore, vibration is applied to the mold in the casting direction called oscillation (that is, the direction in which the slab is pulled out), causing molten powder to flow between the solidified shell and the inner wall of the mold, contributing to lubrication. ing.

Here, in order to improve the lubrication between the solidified shell and the inner wall of the mold, it is necessary to sufficiently flow the molten powder between them. Further, it is necessary to smooth the flow of the molten powder between the two. Even if the molten powder flows sufficiently between the solidified shell and the inner wall of the mold, if the flow is not smooth, the coefficient of friction between the two will be large, and good lubrication between the two will not be realized. is there. Alternatively, even if the flow of the molten powder between the solidified shell and the inner wall of the mold is not smooth, if the friction between the two can be reduced, good lubrication between the two can be realized.

On the other hand, the frequency of oscillation is usually about several Hz. Considering such vibration characteristics, although the oscillation can play a role of causing the molten powder to flow between the solidified shell and the inner wall of the mold as described above, it facilitates the flow of the molten powder between the two. It cannot be said that the effect and the effect of reducing the friction between them are sufficiently exerted.

Therefore, in order to smooth the flow of the molten powder between the solidified shell and the inner wall of the mold, and to improve the lubrication between them, instead of or in addition to the oscillation, other Techniques have been developed for providing a mold with vibration having vibration characteristics. In the following description, a vibration having other vibration characteristics given to the mold instead of or in addition to the oscillation is also referred to as a second vibration in order to distinguish it from the oscillation. To do. Correspondingly, the oscillation may also be described as the first vibration.

For example, in Patent Document 1, an ultrasonic vibrator is attached to a mold, and the ultrasonic vibrator is used in place of or in addition to the oscillation to generate a second vibration having a relatively high frequency of 10 to 30 kHz. A method of performing continuous casting while applying vibration is disclosed. In Patent Document 1, at that time, the vibration frequency of the ultrasonic transducer is periodically changed within a certain range to uniformly reduce the frictional resistance between the solidification shell and the inner wall of the mold, and thereby, It is said that the flow of the molten powder can be made uniform.

Further, for example, in Patent Document 2, a vibration device that vibrates the mold in a horizontal direction (that is, a direction orthogonal to the casting direction) is provided, and in addition to the oscillation, the vibration device causes an amplitude of 10 to 1000 μm and a vibration frequency. A method of performing continuous casting while applying a second vibration of 10 to 5000 Hz to the mold is disclosed. In Patent Document 2, in addition to oscillation, by superimposing a second vibration having such a vibration characteristic on the mold, the filling property of the molten powder between the solidification shell and the inner wall of the mold is improved and solidification is achieved. It is said that the frictional resistance between the shell and the inner wall of the mold can be reduced.

JP-A-59-6735 JP, 2015-212455, A

However, in order to actually perform the method described in Patent Document 1, a large number of ultrasonic transducers are required to vibrate a heavy mold, which generally weighs several tens of tons. Therefore, considering the cost for installing and maintaining a large number of ultrasonic transducers, the durability of the ultrasonic transducers, and the like, practical application is difficult.

Further, in the technique described in Patent Document 2, the second vibration is applied to the mold in the horizontal direction. Therefore, on either one of the long side surface and the short side surface of the mold, the vibration direction of the second vibration is perpendicular to the mold surface and perpendicular to the casting direction. In the plane, the vibration direction of the second vibration is parallel to the mold surface (in-mold surface direction) and perpendicular to the casting direction. Here, on the surface of the mold to which the second vibration is applied perpendicularly to the surface of the mold, the powder filling property between the solidification shell and the inner wall of the mold is improved, and the frictional resistance between them is reduced. However, it is considered that the effect cannot be obtained on the other mold surface to which the second vibration is applied in the direction parallel to the mold surface and perpendicular to the casting direction. Conversely speaking, on one of the long side surface and the short side surface of the mold, it is necessary to improve the powder filling property between the solidified shell and the inner wall of the mold, and reduce the frictional resistance between them. It may not be possible to prevent bleeding and breakout from occurring sufficiently.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to improve lubrication by reducing friction between the solidified shell and the inner wall of the mold in continuous casting. The present invention provides a new and improved continuous casting machine and continuous casting method that enable more stable casting.

In order to solve the above problems, according to an aspect of the present invention, a mold, a first vibrating mechanism for oscillating the mold in a casting direction, and the same direction as the oscillation with respect to the mold. A second vibrating mechanism for applying a second vibration, and the second vibrating mechanism includes two mechanical vibration generators using an unbalanced weight and a motor . Provided is a continuous casting machine that imparts the second vibration such that the maximum value of the vibration speed of the vibration is higher than the casting speed and the frequency of the second vibration is 20 Hz or more.

Further, in order to solve the above problems, according to another aspect of the present invention, there is provided a continuous casting method performed while oscillating a mold in a casting direction, wherein two unbalanced weights provided in the mold are used. And a mechanical vibration generator that uses a motor, applies a second vibration in the same direction as the oscillation to the mold, and the maximum value of the vibration speed of the second vibration is greater than the casting speed. A continuous casting method is provided in which the frequency of the second vibration is 20 Hz or higher.

As described above, according to the present invention, in continuous casting, it is possible to perform more stable casting by reducing the friction between the solidified shell and the inner wall of the mold to improve the lubrication. become.

It is a side sectional view showing a schematic structure of a continuous casting machine concerning one embodiment of the present invention. It is a figure which shows one structural example of the 1st vibration mechanism and the 2nd vibration mechanism which are provided with respect to a casting_mold|template according to this embodiment. It is a figure showing composition of an experimental device used for examination about the 2nd vibration. It is a graph which shows the experimental result in the examination about the vibration characteristic of a 2nd vibration. It is a graph which shows the experimental result in the examination about the vibration characteristic of a 2nd vibration. It is a graph which shows the experimental result in the examination about the vibration characteristic of a 2nd vibration. It is a graph which shows the experimental result in the examination about the vibration characteristic of a 2nd vibration. It is a graph figure which shows the relationship between the frequency and the friction coefficient in the examination about the vibration characteristic of a 2nd vibration. It is a figure for demonstrating the mechanism in which a friction coefficient falls by vibrating speed passing sliding speed.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and a duplicate description will be omitted.

In the following description, the case where the molten metal supplied to the mold in continuous casting is molten steel, that is, the case where continuous casting of steel is performed will be described. However, the present invention is not limited to such an example, and the technique according to the present invention may be applied to continuous casting of any metal other than steel (for example, aluminum, aluminum alloy, titanium, etc.).

(1. Background of the invention)
Before describing the preferred embodiments of the present invention, in order to make the effects of the present invention clearer, the background of the present inventors' idea of the present invention will be described.

As described above, in continuous casting, powder is supplied from the upper part of the mold. The powder is an oxide-based flux whose properties such as melting point and viscosity when melted are adjusted by its composition. The molten powder melted by the heat of the molten steel enters between the solidification shell and the inner wall of the mold, so that the lubrication between the solidification shell and the inner wall of the mold is maintained. Further, the powder has a function of keeping the temperature of the molten steel and preventing oxidation by covering the surface of the molten steel in the mold, and a function of removing non-metallic inclusions floating on the surface of the molten steel in the mold to improve the purity of the molten steel. Also has.

Here, if the solidification shell and the inner wall of the mold are not well lubricated, the solidification shell may adhere to the inner wall of the mold during casting, and the solidification shell may be broken. When the fracture is large, so-called breakout occurs in which molten steel inside the slab flows out from the fractured portion, which causes great damage to the equipment. When the breakage of the solidified shell is slight, a large amount of molten steel can be avoided, but the leaked molten steel solidifies and causes defects called bleeding on the surface of the slab. Therefore, in order to suppress the occurrence of these bleeds and breakouts and realize more stable operation, it is important to keep the lubrication between the solidified shell and the inner wall of the mold by the molten powder better.

As a method for improving the lubrication between the solidified shell and the inner wall of the mold, it is conceivable to adjust the composition of the powder and control the viscosity of the molten powder. For example, if the viscosity of the molten powder is relatively high, it is difficult for the molten powder to flow between the solidified shell and the inner wall of the mold, which may result in unstable lubrication. On the other hand, if the viscosity of the molten powder is relatively low, the molten powder easily flows between the solidified shell and the inner wall of the mold, and the lubrication becomes stable. Therefore, from the viewpoint of improving the lubrication between the solidified shell and the inner wall of the mold, the viscosity of the molten powder is preferably lower.

On the other hand, focusing on the surface of the molten steel in the mold, the surface of the molten steel (metal surface) changes during casting due to the influence of the molten steel discharged from the immersion nozzle and the like. When the molten powder is caught in the molten steel due to the fluctuation of the molten metal surface, it causes a powdery quality defect in the cast slab. At this time, if the viscosity of the molten powder is relatively high, it is difficult for the molten powder to be caught in the molten steel due to fluctuations in the molten metal surface. Entrapment easily occurs. That is, in order to suppress the generation of powdery defects, the viscosity of the molten powder is preferably higher.

As described above, the viscosity of the molten powder is preferably low from the viewpoint of operation stability, but the viscosity of the molten powder is preferably high from the viewpoint of ensuring the quality of the slab. Therefore, it is considered difficult to achieve both stability of operation and securing of slab quality by adjusting the viscosity of the molten powder.

On the other hand, in continuous casting, for example, vibration in the casting direction called oscillation, which has a frequency of about several Hz (100 to 300 cpm) and an amplitude of about 3 to 10 mm, is applied to the mold. It is believed that the oscillation promotes the inflow of molten powder between the solidified shell and the inner wall of the mold.Oscillation, even when the viscosity of the molten powder is high, allows the solidified shell to flow. It may be possible to keep good lubrication between the mold and the inner wall of the mold.

However, in order to achieve good lubrication between the solidified shell and the inner wall of the mold, it is necessary to allow the molten powder to flow sufficiently between them, but if the inflow of the molten powder is insufficient. Even in the case of becoming, it is necessary to reduce the friction between them. The oscillation characteristics of the oscillation as described above can promote the inflow of the molten powder between the solidified shell and the inner wall of the mold, but are not necessarily appropriate for reducing the friction between the two. I can't say.

Therefore, as shown in Patent Documents 1 and 2 described above, in order to improve the lubrication between the solidified shell and the inner wall of the mold, other vibration characteristics may be used instead of or in addition to the oscillation. A technique has been developed for promoting the inflow of the molten powder between the two by applying the vibration to the mold and smoothing the flow of the molten powder between the two. However, as described above, the technique described in Patent Document 1 is not practical, and in the technique described in Patent Document 2, the powder filling property is improved on all mold surfaces, and the solidification shell and the inner wall of the mold are improved. It is difficult to reduce the frictional resistance with.

In view of the above circumstances, the inventors of the present invention are keenly aware of a technique capable of maintaining good lubrication between the solidified shell and the inner wall of the mold even when using a molten powder having a relatively high viscosity. As a result of the examination, the present invention has been conceived. As described above, by using the molten powder having a high viscosity, it is possible to suppress the deterioration of the slab quality due to the entrainment of the molten powder. Therefore, according to the present invention, the occurrence of bleeding and breakout can be suppressed and the operation can be suppressed. It becomes possible to secure the quality of the slab while securing the stability. Hereinafter, a preferred embodiment of the present invention conceived by the present inventors will be described.

(2. Overall structure of continuous casting machine)
A schematic configuration of a continuous casting machine according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a side sectional view showing a schematic configuration of a continuous casting machine according to an embodiment of the present invention. It should be noted that in the drawings shown below including FIG. 1, the sizes of some of the constituent members may be exaggerated for the sake of explanation, and the relative sizes of the respective constituent members shown in the drawings may be exaggerated. Does not always accurately represent the magnitude relationship between the actual constituent members.

As shown in FIG. 1, a continuous casting machine 10 according to the present embodiment is an apparatus for continuously casting molten steel 2 using a casting mold 1 for continuous casting to produce a slab 3 of a slab or the like. The continuous casting machine 10 includes a mold 1, a ladle 4, a tundish 5, an immersion nozzle 6, a secondary cooling device 7, and a cast piece cutting machine 8.

The ladle 4 is a movable container for transporting the molten steel 2 from the outside to the tundish 5. The ladle 4 is arranged above the tundish 5, and the molten steel 2 in the ladle 4 is supplied to the tundish 5. The tundish 5 is arranged above the mold 1, stores the molten steel 2 and removes inclusions in the molten steel 2. The immersion nozzle 6 extends downward from the lower end of the tundish 5 toward the mold 1, and its tip is immersed in the molten steel 2 in the mold 1. The immersion nozzle 6 continuously supplies the molten steel 2 from which inclusions have been removed by the tundish 5 into the mold 1.

The mold 1 has a rectangular tubular shape corresponding to the width and thickness of the slab 3, and is assembled, for example, such that a pair of long side mold plates sandwiches a pair of short side mold plates from both sides in the width direction. These mold plates are made of, for example, water-cooled copper plates. The mold 1 cools the molten steel 2 in contact with such a mold plate to manufacture a cast slab 3 including an unsolidified portion 3b inside the solidified shell 3a of the outer shell. As the slab 3 moves downward in the mold 1, the solidification of the unsolidified portion 3b inside proceeds, and the thickness of the solidified shell 3a of the outer shell gradually increases. The cast piece 3 including the solidified shell 3a and the unsolidified portion 3b is pulled out from the lower end of the mold 1. In the following description, the pulling-out direction (casting direction) of the cast slab 3 is also referred to as a vertical direction. The direction orthogonal to the vertical direction is also called the horizontal direction.

Although not shown in FIG. 1, the mold 1 is supplied with the molten steel 2 and powder from above. The supplied powder is melted by the heat of the molten steel 2, and the powder that has become liquid is present between the solidified shell 3 a and the inner wall of the mold 1.

Here, the mold 1 is provided with a vibration generator 121 that applies a second vibration to the mold 1 in the vertical direction. The vibration generator 121 is provided on the outer wall of each of the pair of long side template plates. Although not shown in FIG. 1, the continuous casting machine 10 is also provided with a first vibrating mechanism for vertically oscillating the mold 1. That is, in the present embodiment, the mold 1 is provided with the first vibrating mechanism for oscillation and the second vibrating mechanism including the vibration generating device 121 for giving the second vibration. .. Details of the first vibrating mechanism and the second vibrating mechanism will be described later with reference to FIG.

The secondary cooling device 7 is provided in the secondary cooling zone 9 below the mold 1, and cools the cast slab 3 pulled from the lower end of the mold 1 while supporting and transporting the slab 3. The secondary cooling device 7 includes a plurality of pairs of support rolls (for example, support rolls 11, pinch rolls 12, and segment rolls 13) arranged on both sides of the slab 3 in the thickness direction, and cooling water for the slab 3. And a plurality of spray nozzles (not shown) for ejecting.

The support rolls provided in the secondary cooling device 7 are arranged in pairs on both sides of the slab 3 in the thickness direction, and function as a supporting and transporting unit that transports the slab 3 while supporting it. By supporting the slab 3 from both sides in the thickness direction by the support roll, breakout and bulging of the slab 3 during solidification in the secondary cooling zone 9 can be prevented.

The support roll 11, the pinch roll 12, and the segment roll 13, which are support rolls, form a transport path (pass line) for the cast slab 3 in the secondary cooling zone 9. As shown in FIG. 1, the pass line extends vertically under the mold 1, then curves in a curved shape, and finally extends horizontally. In the secondary cooling zone 9, a portion where the pass line extends in the vertical direction is referred to as a vertical portion 9A, a curved portion is referred to as a curved portion 9B, and a portion which extends in the horizontal direction is referred to as a horizontal portion 9C. The continuous casting machine 10 having such a pass line is called a vertical bending type continuous casting machine 10. The present invention is not limited to the vertical bending type continuous casting machine 10 as shown in FIG. 1, but can be applied to various other continuous casting machines such as a curved type or a vertical type.

The support roll 11 is a non-drive type roll provided in the vertical portion 9A immediately below the mold 1, and supports the cast slab 3 immediately after being pulled out from the mold 1. Since the solidified shell 3a of the cast slab 3 immediately after being pulled out from the mold 1 is in a thin state, it is necessary to support it at a relatively short interval (roll pitch) in order to prevent breakout and bulging. Therefore, as the support roll 11, it is desirable to use a roll having a small diameter that can reduce the roll pitch. In the example shown in FIG. 1, three pairs of support rolls 11 each having a small diameter are provided on both sides of the slab 3 in the vertical portion 9A with a relatively narrow roll pitch.

The pinch roll 12 is a drive type roll that is rotated by a drive unit such as a motor, and has a function of pulling out the slab 3 from the mold 1. The pinch rolls 12 are arranged at appropriate positions in the vertical portion 9A, the curved portion 9B, and the horizontal portion 9C, respectively. The slab 3 is pulled out of the mold 1 by the force transmitted from the pinch roll 12, and is conveyed along the pass line. The arrangement of the pinch rolls 12 is not limited to the example shown in FIG. 1, and the arrangement position may be set arbitrarily.

The segment roll 13 (also referred to as a guide roll) is a non-drive type roll provided on the curved portion 9B and the horizontal portion 9C, and supports and guides the slab 3 along the pass line. The segment roll 13 is, depending on the position on the pass line, and with the F surface (Fixed surface, the lower left surface in FIG. 1) and the L surface (Loose surface, the upper right surface in FIG. 1) of the slab 3, They may be arranged with different roll diameters and roll pitches.

The slab cutting machine 8 is arranged at the end of the horizontal portion 9C of the pass line and cuts the slab 3 conveyed along the pass line into a predetermined length. The cut plate-shaped slab 14 is conveyed to the equipment of the next step by the table roll 15.

The overall configuration of the continuous casting machine 10 according to the present embodiment has been described above with reference to FIG. The type and size of the cast piece 3 produced by the continuous casting machine 10 are not particularly limited. For example, the slab 3 may be a slab having a thickness of about 250 to 300 (mm), a bloom or a billet exceeding 500 (mm), or a thin slab having a thickness of about 100 (mm), A thin strip continuous casting slab of 50 (mm) or less may be used.

(3. Configuration of vibration mechanism)
As described above, the continuous casting machine 10 is provided with the first vibration mechanism and the second vibration mechanism for the mold 1. The configurations of the first vibrating mechanism and the second vibrating mechanism provided for the mold 1 will be described with reference to FIG. FIG. 2 is a diagram showing a configuration example of the first vibrating mechanism and the second vibrating mechanism according to the present embodiment, which are provided for the mold 1.

The first vibrating mechanism 110 is one that oscillates the mold 1 in the vertical direction (provides the first vibration in the vertical direction to the mold 1). The first vibrating mechanism 110 is composed of a vibrating table 111 on which the mold 1 is placed, a support 112, a main arm 113, a sub arm 114, and a cylinder 115.

The main arm 113 is installed on the vibration table 111, the support body 112, and the cylinder 115. At this time, one end of the main arm 113 is pin-connected to the vibration table 111, and the other end is pin-connected to the cylinder 115. Further, an intermediate portion of the main arm 113 is pin-coupled to the support 112. In these pin couplings, the main arm 113 and the respective members are coupled so that the main arm 113 can rotate about the coupling portion.

The sub-arm 114 is installed on the vibration table 111 and the support 112. At this time, one end of the sub arm 114 is pin-coupled to the vibration table 111, and the other end is pin-coupled to the support 112. In these pin couplings, the sub-arm 114 and the respective members are coupled so that the sub-arm 114 can rotate about the coupling portion.

The cylinder 115 is, for example, a hydraulic cylinder, and moves up and down in the vertical direction under the control of the control device 130 described later. Both ends of the main arm 113 vibrate vertically due to the vertical movement of the cylinder 115, and the vibration table 111 also vibrates vertically accordingly. Thereby, the mold 1 is oscillated in the vertical direction. As described above, by oscillating the mold 1, the inflow of the molten powder between the solidification shell 3a and the inner wall of the mold 1 can be promoted.

In the first vibrating mechanism 110, the control device 130 appropriately controls the driving of the cylinder 115, whereby the amplitude and frequency of oscillation can be controlled within a predetermined range. In this embodiment, the amplitude and frequency of oscillation can be controlled within the range of the amplitude and frequency of oscillation performed in a general continuous casting machine. For example, the oscillation of the mold 1 in the present embodiment has an amplitude of about 3 to 10 mm and a frequency of about several Hz (100 to 300 cpm).

The configuration of the first vibrating mechanism 110 is not limited to the above example, and the first vibrating mechanism 110 is used as a vibrating mechanism for oscillating a mold provided in a general continuous casting machine. Various configurations that have been described can be applied. For example, in the first vibration mechanism 110, instead of the cylinder 115, a mechanism including an eccentric cam, a connecting rod connected to the eccentric cam, and a rotary drive device that rotates the eccentric cam may be provided.

The second vibrating mechanism 120 applies a second vertical vibration to the mold 1. The second vibrating mechanism 120 includes a pair of vibration generators 121 provided on the outer walls of the long sides of the mold 1, and a damper 122 provided between the upper surface of the vibration table 111 and the bottom surface of the mold 1. To be done.

The vibration generator 121 is a device that imparts at least vertical vibration to the mold 1. The vibration generator 121 applies vibration to the mold 1 under the control of the controller 130 described later. Since the damper 122 is interposed between the vibration table 111 and the mold 1, the mold 1 vibrates on the vibration table 111 in the vertical direction when the vibration generator 121 is operated.

The vibration generator 121 can be various types of vibration generators represented by a mechanical type, an electromagnetic type, an electrostrictive type, a hydraulic type, a pneumatic type and the like. In this embodiment, as the vibration generator 121, a mechanical vibration generator capable of generating vibration by rotating a motor having an unbalanced weight attached to a rotary shaft is used. The vibration generator 121 can easily apply vibration to a heavy object by using a high-output motor. Therefore, the mechanical vibration generator 121 is suitable for applying vibration to the mold 1, which generally weighs several tens of tons.

Here, the second vibrating mechanism 120 is configured to be able to control at least the amplitude and frequency of the second vibration applied to the mold 1. In the present embodiment, in order to reduce the friction between the solidified shell 3a and the inner wall of the mold 1, the amplitude and frequency of this second vibration are controlled within an appropriate range. The amplitude of the second vibration can be controlled by adjusting the strength (elastic coefficient) of the damper 122. Further, in the mechanical vibration generator 121, the vibration frequency of the vibration applied to the mold 1 is determined by the rotation speed of the motor. Therefore, for example, by controlling the rotation speed of the motor of the vibration generation device 121 using an inverter or the like. , The frequency of the second vibration can be controlled.

In the present embodiment, as described above, the vibration generator 121 applies vertical vibration to the mold 1. However, in the mechanical vibration generator 121 using the unbalanced weight and the motor, vibration is generated by the rotation of the motor, but the vibration is generated in the entire circumferential direction of the rotation shaft of the motor. Therefore, if only one vibration generator 121 is provided for the mold 1, the vibration given to the mold 1 includes not only the vertical vibration component but also the horizontal vibration component. Become. In order to prevent this and preferably give only vertical vibrations to the mold 1, in the present embodiment, two vibration generators 121 are provided, one on each of the long side surfaces of the mold 1 in total. There is.

Specifically, these two vibration generators 121 are vibration generators 121 having the same ability to generate the same vibration force, and are installed such that the rotation axes of the motors are parallel to each other. It can be rotated in the opposite direction. At this time, the unbalance weights of these two vibration generators 121 are both rotated so as to be positioned at the top dead center and the bottom dead center at the same time. As a result, the horizontal vibration components generated by the two vibration generators 121 cancel each other out. As a result, only the vertical vibration can be applied to the mold 1 by the two vibration generators 121. In the above description, one vibration generating device 121 is provided on each of the long side surfaces of the mold 1, but if the vibration generating devices 121 are provided on the surfaces of the mold 1 that face each other, the same method is used. It is possible to cancel the directional vibration. Therefore, one vibration generator 121 may be provided on each of the short side surfaces of the mold 1.

The configuration of the second vibrating mechanism 120 is not limited to this example. For example, the vibration generator 121 only needs to be able to apply a desired frequency of vibration to the mold 1 in the vertical direction, and the configuration, the number of arrangements, the arrangement position, etc. may be arbitrary. For example, if a vibration generator 121 capable of generating only vertical vibration is used instead of the mechanical vibration generator 121 as described above, one of the surfaces of the mold 1 Only one vibration generator 121 may be provided. Further, the damper 122 is an example of a mechanism that supports the mold 1 so as to be movable in the vertical direction, and another member may be used instead of the damper 122 as long as the member has such a function. For example, instead of the damper 122, an elastic body such as a leaf spring may be used.

The continuous casting machine 10 is provided with a control device 130 that controls driving of the first vibrating mechanism 110 and the second vibrating mechanism 120. The controller 130 controls the drive of the cylinder 115 of the first vibrating mechanism 110 to control the amplitude and frequency of oscillation of the mold 1. The control device 130 also controls the driving of the vibration generator 121 of the second vibrating mechanism 120, thereby controlling the frequency of the second vibration applied to the mold 1.

Note that the specific device configuration of the control device 130 is not limited, and the control device 130 includes, for example, a control board on which various processors such as a CPU (Central Processing Unit) or a processor and a storage element such as a memory are mounted. Etc. Alternatively, when the continuous casting machine 10 is provided with a control device that controls the operation of the continuous casting machine 10 in order to adjust the casting conditions such as the casting speed, the control device 130 is integrated with the control device. May be configured as. Alternatively, the control device 130 does not have to be one device, and may be configured by a plurality of devices. The functions of the above-described control device 130 can be realized by the processor constituting the control device 130 operating in accordance with a predetermined program.

The configurations of the first vibrating mechanism 110 and the second vibrating mechanism 120 provided for the mold 1 have been described above. In the present embodiment, during continuous casting, the first vibrating mechanism 110 oscillates the mold 1, and the second vibrating mechanism 120 applies second vibration to the mold 1. As a result, the mold 1 is given a vibration in which the second vibration is superimposed on the oscillation. The oscillation can promote the inflow of the molten powder between the solidified shell 3a and the inner wall of the mold 1. Further, by applying the second vibration to the mold 1, it is possible to reduce the friction between the solidification shell 3a and the inner wall of the mold 1. Therefore, by applying the second vibration to the mold 1 in addition to the oscillation, the solidified shell 3a and the inner wall of the mold 1 are separated from each other even when a molten powder having a relatively high viscosity is used, for example. Good lubrication between is achieved. Therefore, it is possible to realize a more stable operation in which the occurrence of bleeding and breakout is suppressed while suppressing the deterioration of the quality of the slab due to the inclusion of the molten powder.

Here, in the technique described in Patent Document 2 as well, the second vibration is applied to the mold in addition to the oscillation. However, in the technique, the oscillation is the vibration in the vertical direction, and the second vibration is applied. Was horizontal vibration. Therefore, in the technique described in Patent Document 2, the effect of improving the powder filling property between the solidified shell and the inner wall of the mold by the second vibration and reducing the frictional resistance between the two is the long length of the mold. It occurs only on one of the side surface and the short side surface. Therefore, it is considered that the occurrence of bleeding and breakout cannot be sufficiently suppressed. On the other hand, according to the present embodiment, as described above, as the second vibration, the same vibration in the vertical direction as the oscillation is applied to the mold 1. Therefore, the friction between the solidified shell 3a and the inner wall of the mold 1 can be reduced on both the long side surface and the short side surface of the mold 1, and more stable operation can be realized.

(4. Vibration characteristics of the second vibration)
As described above, in the present embodiment, the solidified shell is promoted by the oscillation to flow the molten powder between the solidified shell 3a and the inner wall of the mold 1, and the second vibration is applied to the mold 1. The friction between 3a and the inner wall of the mold 1 is reduced. At this time, it is considered that the oscillation and the second vibration have appropriate vibration characteristics for achieving the purpose. Of these, as described in, for example, Patent Documents 1 and 2, among them, the oscillation has the same vibration characteristics (for example, amplitude: about 3 to 10 mm, frequency: several Hz (100). It is considered that the inflow of the molten powder between the solidification shell 3a and the inner wall of the mold 1 can be sufficiently realized at about 300 to about 300 cpm). On the other hand, the second vibration is newly introduced by the present inventors in the present embodiment, and it is necessary to define the appropriate vibration characteristic. Therefore, the present inventors have conducted the following studies in order to define an appropriate vibration characteristic of the second vibration.

In the mold 1, the solidified shell 3a is moving vertically downward at a predetermined speed corresponding to the casting speed. In order to reduce the friction between the solidification shell 3a and the inner wall of the mold 1, when the second vertical vibration is applied to the mold 1 in this state, the solidification shell 3a and the inner wall of the mold 1 are It suffices if the friction coefficient between the two becomes small. Therefore, the present inventors slid the substrate on a linear reciprocating friction wear tester capable of measuring the coefficient of friction between the test piece and the substrate while sliding the substrate on the test piece. We created an experimental device that incorporates an exciter that vibrates in a vibration direction parallel to the direction.

FIG. 3 shows the configuration of the experimental apparatus. FIG. 3 is a diagram showing a configuration of an experimental device used for studying the second vibration. Referring to FIG. 3, the experimental device 140 includes a stage 141 that can reciprocate in one direction in a horizontal plane, a stage drive mechanism 142 that reciprocates the stage, a vibrator 143 that is mounted on the stage 141, and a vibrator. A substrate 144 supported by a shaker 143 so that its upper surface is substantially horizontal, a pressing member 145 that presses the test piece 148 in the vertical direction on the upper surface of the substrate 144, and a pressing member 145 provided on the pressing member 145 to reciprocate the stage 141. Accordingly, the load cell 146 that measures the frictional force between the test piece 148 and the substrate 144 when the substrate 144 moves while sliding on the test piece 148, and the displacement of the substrate 144 that is provided in the vicinity of the substrate 144 are measured. And an eddy current sensor 147. The substrate 144 was made of stainless steel, and the test piece 148 was made of block-shaped steel.

The pressing member 145 is configured to press the test piece 148 against the substrate 144 with a predetermined static load. When the test piece 148 is pressed against the substrate 144, the stage driving mechanism 142 moves the stage 141 in one direction in the horizontal plane, so that the substrate 144 also slides on the test piece 148 and moves in that direction. .. Further, the substrate 144 is vibrated in the same direction as the sliding direction by the vibrator 143 while sliding the substrate 144 with respect to the test piece 148. The frictional force between the test piece 148 and the substrate 144 at this time is measured by the load cell 146. The displacement (vibration displacement) of the substrate 144 in the vibration direction at this time is measured by the eddy current sensor 147.

The sliding corresponds to the movement of the solidified shell 3a associated with casting, and the vibration caused by the vibrator 143 corresponds to the second vibration. Using the experimental apparatus 140, the vibration displacement of the substrate 144, the vibration velocity of the substrate 144, and the coefficient of friction between the test piece 148 and the substrate 144 were measured while applying vibration by the vibrator 143 during sliding. went. At that time, the vibration characteristics of the vibration given by the vibrator 143 were variously changed, and the influence of the change of the vibration characteristics on the friction coefficient was examined.

Specifically, the sliding speed is kept constant at 10 mm/s for a predetermined period (that is, the stage 141 and the substrate 144 are moving in one direction at a substantially constant velocity (10 mm/s)). Vibration was given by the shaker 143, and the vibration displacement of the substrate 144, the vibration speed of the substrate 144, and the friction coefficient between the test piece 148 and the substrate 144 during that period were measured. The vibration displacement of the substrate 144 was obtained from the measurement value by the eddy current sensor 147. The vibration velocity of the substrate 144 was obtained by differentiating the vibration displacement of the substrate 144 with respect to time. Further, the friction coefficient between the test piece 148 and the substrate 144 was obtained by dividing the frictional force measured by the load cell 146 by the static load applied to the test piece 148. Regarding the vibration given by the shaker 143, its frequency is set to be substantially constant at 50 Hz, and only its amplitude is changed.

The results are shown in FIGS. FIG. 4 to FIG. 7 are graphs showing the experimental results in the examination of the vibration characteristics of the second vibration. In FIG. 4 to FIG. 7, the horizontal axis represents time, and the vertical axis represents the vibration displacement of the substrate 144, the vibration velocity of the substrate 144, and the friction coefficient between the test piece 148 and the substrate 144. The time change is plotted.

In the above-described experimental device 140, of the frictional forces acting between the test piece 148 and the substrate 144, the frictional force acting in the direction opposite to the sliding direction (that is, the frictional force acting as a resistance against sliding). Can only measure). Therefore, the friction coefficient can be calculated only in the value corresponding to this direction. That is, the friction coefficient shown in FIGS. 4 to 7 is a plot of the friction coefficient corresponding to the frictional force acting as resistance against sliding. On the other hand, in the graphs shown in FIGS. 4 to 7, the region where the friction coefficient is zero is actually the region where the friction force is zero, or the friction force in the same direction as the sliding direction is generated. Area. However, as described with reference to FIG. 9, such a frictional force in the same direction as the sliding direction is a frictional force in the direction of accelerating the sliding and does not hinder the sliding. Therefore, it means that the closer the value of the friction coefficient shown in FIGS. 4 to 7 is to zero, the smaller the frictional force acting as resistance against sliding becomes, and thus the sliding can be performed smoothly. It is shown that.

FIG. 4 to FIG. 7 each show the result when vibration is applied by the vibrator 143 under different vibration conditions. Specifically, FIG. 4 shows the result when no vibration is applied by the vibrator 143. 5 to 7 show the results when vibrations of different amplitudes are applied by the shaker 143, respectively. In addition, in FIG. 4, since the result is shown when no vibration is applied, only the vibration displacement of the substrate 144 and the friction coefficient between the test piece 148 and the substrate 144 are plotted. 5 to 7, the sliding speed is also plotted. As the sliding speed, the moving speed of the stage 141 by the stage drive mechanism 142 is plotted. 5 to 7, the sliding speed is shown as a negative speed. Therefore, when the absolute value of the vibration velocity in the minus direction in the figure becomes larger than the absolute value of the sliding velocity, the vibration velocity exceeds the sliding velocity (that is, the vibration velocity is in the same direction as the sliding velocity). , It became larger than the sliding speed).

Referring to FIG. 4, when no vibration is applied, the vibration displacement is substantially constant, and it can be confirmed that the substrate 144 certainly does not vibrate with respect to the test piece 148. Further, since the substrate 144 slides on the test piece 148 at a substantially constant speed, the coefficient of friction is also substantially constant.

FIG. 5 shows the result in the case where the vibration having a relatively small amplitude is applied so that the vibration speed does not exceed the sliding speed. Referring to FIG. 5, specifically, vibration having an amplitude of 0.052 mm and a maximum vibration velocity of 8.2 mm/s is applied. In this case, it can be seen that the coefficient of friction between the test piece 148 and the substrate 144 also periodically changes in response to the periodic change of the vibration velocity.

FIG. 6 shows the results in the case of applying a vibration of a medium scale such that there is a period in which the vibration speed exceeds the sliding speed. Referring to FIG. 6, specifically, vibration having an amplitude of 0.174 mm and a maximum vibration velocity of 27.3 mm/s is applied. As shown in the figure, it can be seen that the friction coefficient between the test piece 148 and the substrate 144 is significantly reduced during the period in which the vibration speed exceeds the sliding speed. Further, it can be seen that the average value of the friction coefficient is greatly reduced as compared with the case shown in FIG.

FIG. 7 shows the result in the case where a vibration having a relatively large amplitude is given such that there is a more prominent period in which the vibration speed exceeds the sliding speed. Referring to FIG. 7, specifically, vibration having an amplitude of 0.340 mm and a maximum vibration velocity value of 53.4 mm/s is applied. Comparing the results shown in FIG. 6 and the results shown in FIG. 7, as the degree of the vibration speed overtaking the sliding speed increases, the decrease in the friction coefficient between the test piece 148 and the substrate 144 becomes more remarkable, and the friction coefficient It can be seen that the average value of is further decreased.

From the above results, it was found that it is possible to reduce the coefficient of friction between the test piece 148 and the substrate 144 by applying vibration such that the vibration speed exceeds the sliding speed. It was also found that the friction coefficient can be further reduced by increasing the vibration speed and increasing the degree of the vibration speed overtaking the sliding speed.

In the graphs shown in FIGS. 4 to 7, the vibration velocity obtained by differentiating the vibration displacement with time is plotted, but the vibration velocity is the amplitude of the vibration and the cycle of the vibration obtained from the measured value of the vibration displacement. It can also be calculated theoretically. Specifically, assuming that 1/2 of the vibration amplitude is A, the vibration cycle is T, and ω=(2π/T), the vibration displacement x(t) can be expressed by the following mathematical expression (1). ..

If both sides of the above formula (1) are time-differentiated, the vibration velocity V(t) becomes the following formula (2).

In addition, from the above mathematical expression (2), the maximum value maxV of the vibration speed becomes the following mathematical expression (3).

In the above experiment, similar results were obtained even when the vibration velocity was calculated using the above equation (2).

Here, the results shown in FIGS. 4 to 7 are results in the case where vibration with a frequency of 50 Hz is applied. Therefore, the present inventors further conducted an experiment for confirming whether similar results could be obtained at other frequencies. Specifically, using the above-described experimental apparatus 140, similar experiments were performed for the case where vibrations with frequencies of 5 Hz, 10 Hz, 20 Hz, 100 Hz and 500 Hz were applied in addition to 50 Hz, and the vibration frequency and the friction coefficient were compared. I investigated the relationship. In addition, also in the said experiment, the sliding speed was made substantially constant at 10 mm/s.

The results are shown in Fig. 8. FIG. 8 is a graph showing the relationship between the vibration frequency and the friction coefficient in the examination of the vibration characteristics of the second vibration. In FIG. 8, the horizontal axis represents the maximum value of the vibration velocity and the vertical axis represents the measured value of the friction coefficient, and the relationship between the two is plotted. In addition, the maximum value of the vibration velocity was calculated from the measured values of the amplitude and the period using the above mathematical expression (3). In addition, FIG. 8 shows the results obtained by changing the amplitude to 5 levels and performing the measurement for each of the cases where the vibrations having the frequencies of 5 Hz, 10 Hz, 20 Hz, 50 Hz, 100 Hz and 500 Hz are applied. In addition, the results (the leftmost plot group in the graph) when no vibration is applied are also shown.

With reference to FIG. 8, it can be confirmed that the friction coefficient decreases as the maximum value of the vibration speed increases, regardless of the frequency. The case where the maximum value of the vibration velocity is large indicates that the vibration velocity can exceed the sliding velocity. That is, it was found from the results shown in FIG. 8 that the friction coefficient can be reduced by giving vibration such that the vibration speed exceeds the sliding speed regardless of the frequency.

The reason why the friction coefficient decreases as the vibration speed exceeds the sliding speed can be understood as follows. FIG. 9 is a diagram for explaining a mechanism in which the friction coefficient is lowered by vibrating speed exceeding the sliding speed. In FIG. 9, the case where the substrate 144 is vibrated in the sliding direction while the test piece 148 slides in one direction at a constant speed with respect to the substrate 144, and the direction of the sliding speed is shown in the upper stage. , The direction of the vibration velocity, the direction of the relative velocity of the test piece 148 with respect to the substrate 144, and the direction of the frictional force between the test piece 148 and the substrate 144 are schematically shown. In the lower part, the sliding speed, the vibration speed, the vibration displacement, and the frictional force between the test piece 148 and the substrate 144 are schematically shown as a graph. In this graph, unlike in FIGS. 5 to 7, the sliding speed is shown as a positive value. Therefore, the absolute value of the vibration speed in the plus direction in the figure is larger than the absolute value of the sliding speed. It should be noted that the vibration speed has exceeded the sliding speed when it becomes. Also in this graph, as in the case where the friction coefficient is plotted in FIGS. 5 to 7, the direction in which the frictional force acts as resistance to sliding is defined as the positive direction, and the frictional force in this positive direction is set. Only the negative friction force is considered to be zero.

When the test piece 148 slides in one direction with respect to the substrate 144, the frictional force between the test piece 148 and the substrate 144 acts in the opposite direction to the sliding direction as resistance against sliding. ((A) in the figure). This frictional force is a dynamic frictional force, and as long as the pressing load of the test piece 148 with respect to the substrate 144 is constant, as long as the relative speed of the test piece 148 with respect to the substrate 144 has a predetermined value that is not zero, it is approximately Considered to be constant. When the vibration is applied to the substrate 144, the vibration speed in the same direction as the sliding speed is periodically applied. During this period, the relative speed becomes small, but when the vibration speed is smaller than the sliding speed, , The relative speed becomes a predetermined value that is not zero. Therefore, the frictional force does not decrease ((b) in the figure).

On the other hand, when the vibration speed increases and the vibration speed becomes equal to the sliding speed, the relative speed of the test piece 148 with respect to the substrate 144 becomes zero. At this time, no frictional force is generated between the test piece 148 and the substrate 144 ((c) in the figure). When the vibration speed further increases and the vibration speed exceeds the sliding speed, a frictional force in the opposite direction, that is, a frictional force that accelerates sliding is generated between the test piece 148 and the substrate 144. This frictional force does not act as a resistance against sliding ((d) in the figure). That is, as shown in (c) and (d) in the figure, when the vibration speed is equal to or higher than the sliding speed, the frictional force in the direction of acting as a resistance against sliding is not generated.

In the above experiment, if the substrate 144 and the test piece 148 are regarded as the inner wall of the mold 1 and the cast piece 3 (solidified shell 3a), the same phenomenon is considered to occur in the continuous casting machine 10. That is, from the above experimental results, the present inventors solidify the second vibration by giving the second vibration so that the vibration speed thereof is higher than the casting speed (corresponding to the sliding speed in the above experiment). It was found that the coefficient of friction between the shell 3a and the inner wall of the mold 1 can be reduced, and good lubrication between them can be maintained.

More specifically, the vibration speed of the second vibration may periodically change as shown in FIGS. 5 to 7, but from the above experimental results, even if the period in which the vibration speed is higher than the sliding speed is small, If present, the effect of lowering the coefficient of friction can be obtained. Therefore, in the present embodiment, the vibration characteristic of the second vibration applied to the mold 1 is controlled so that the maximum value of the vibration speed becomes higher than the casting speed. Specifically, as shown in the above mathematical expression (3), the maximum value of the vibration velocity of the second vibration is determined by A and the period T, which is 1/2 of the amplitude. The number may be controlled so that the maximum value of the vibration speed obtained from the above formula (3) is higher than the casting speed.

Here, as will be described later in detail in the following [Examples], as a result of studies by the present inventors, in order to maintain good lubrication between the solidification shell 3a and the inner wall of the mold 1, the second vibration It has been found that it is preferable to set the frequency to 20 Hz or higher. In summary, in the present embodiment, the vibration characteristic of the second vibration (specifically, the maximum value of the vibration speed of the second vibration is higher than the casting speed and the frequency is 20 Hz or more). Control the amplitude and frequency). This makes it possible to maintain good lubrication between the solidified shell 3a and the inner wall of the mold 1 even when a molten powder having a relatively high viscosity is used. It is possible to realize more stable operation in which the occurrence of bleeding and breakout is suppressed while suppressing the deterioration of the quality.

Here, the technique described in Patent Document 2 will be considered. As described above, the present inventors apply the second vibration in parallel to the drawing direction of the cast piece 3 and when the vibration speed becomes higher than the casting speed, the solidification shell 3a and the inner wall of the mold 1 It was found that the friction between them was reduced. On the other hand, in the technique described in Patent Document 2, the second vibration is applied to the mold in the horizontal direction. Therefore, according to the technique described in Patent Document 2, on either one of the long side surface and the short side surface of the mold, the second surface is parallel to the mold surface and perpendicular to the casting direction. Since the vibration is applied, the vibration speed does not exceed the casting speed and the friction cannot be reduced. Therefore, in the technique described in Patent Document 2, even if the second vibration is applied, the effect of improving the powder filling property between the solidification shell and the inner wall of the mold and reducing the frictional resistance between them Is generated only on one of the long side surface and the short side surface of the mold, and it is considered that the occurrence of bleeding and breakout cannot be sufficiently suppressed.

In the above description, the amplitude and frequency of the second vibration such that the maximum value of the vibration speed is larger than the casting speed can be obtained from the above mathematical expression (3), but the present embodiment is applicable. It is not limited to the example. The amplitude and frequency of the second vibration such that the maximum value of the vibration speed becomes larger than the casting speed may be obtained by any other method. For example, as in the following [Example], continuous casting is actually performed using a continuous casting machine while changing the vibration characteristics of the second vibration, and the maximum value of the vibration velocity at that time is determined using an eddy current sensor or the like. By measuring, the amplitude and frequency of the second vibration satisfying such a condition may be experimentally obtained. Alternatively, the amplitude and frequency of the second vibration that satisfies such conditions may be obtained by simulation, theoretical calculation, or the like.

Here, with respect to the second vibration, there may be a preferable range for the vibration characteristic due to restrictions on equipment. For example, regarding the frequency, considering the weight of the mold 1, it is considered difficult to vibrate the mold 1 at a frequency higher than 500 Hz, for example. Therefore, considering the lower limit value described above, the frequency of the second vibration is preferably between 20 Hz and 500 Hz.

Further, regarding the amplitude, for example, if the amplitude of the second vibration is to be increased, the output of the vibration generator 121 needs to be increased, and the damper 122 is also heavily loaded. Considering the loads on the vibration generator 121 and the damper 122, the amplitude of the second vibration is preferably, for example, 1 mm or less. As described above, in the present embodiment, the lower limit value of the amplitude of the second vibration can be defined as a value such that the maximum value of the above-described vibration speed is higher than the casting speed. The upper limit value may be defined to be, for example, 1 mm or less in consideration of facility restrictions.

An example in which the continuous casting method according to the present embodiment described above is applied to a test continuous casting machine having the same function as an actual continuous casting machine in a steel plant will be described. In this embodiment, the second vibrating mechanism is provided for the continuous casting machine including the first vibrating mechanism for oscillation (having the same configuration as the first vibrating mechanism 110 shown in FIG. 2). .. The second vibrating mechanism has the same structure as the second vibrating mechanism 120 shown in FIG. 2, that is, a damper and an unbalance weight provided between the vibrating table and the mold are attached to the rotary shaft of the motor. A mechanical vibration generator was used.

Continuous casting was performed using the continuous casting machine having the above structure while oscillating the mold and applying the second vibration to the mold by the second vibrating mechanism. At that time, the vibration characteristics (amplitude and frequency) of the second vibration were changed, and continuous casting was performed multiple times. The amplitude of the second vibration was controlled by adjusting the elastic force of the damper of the second vibration mechanism. The frequency of the second vibration was controlled by adjusting the rotation speed of the motor of the vibration generator of the second vibration mechanism.

Other conditions in continuous casting are as follows. In addition, in order to confirm that the lubrication between the solidified shell and the inner wall of the mold can be preferably maintained by applying the second vibration, even the molten powder having high viscosity can be used as the powder. The one having a relatively high viscosity was used.

(conditions)
Molten steel amount: 8 ton
Mold width: 700 mm
Mold thickness: 150 mm
Mold height: 900mm
Length of slab: 9m
Casting speed: 1 mpm (16.7 mm/s)
Oscillation condition (first vibration condition): frequency 2.5 Hz (150 cpm), amplitude 3 mm
Viscosity of molten powder: 100 poise

An eddy current sensor was installed on the upper part of the mold, and while performing continuous casting under the above conditions, the vibrational displacement of the mold in the vertical direction was measured by the eddy current sensor to determine the amplitude of the second vibration during continuous casting. .. Further, the maximum value of the vibration velocity was obtained from the measured value of the vibration displacement by using the above mathematical expression (3). Furthermore, the occurrence of bleeding was investigated for the cast pieces after casting.

The results are shown in Table 1. In the table, "Example" corresponds to the conditions included in the continuous casting method according to the present embodiment described above, "Comparative Example", the conditions not included in the continuous casting method according to the present embodiment. It corresponds to.

The condition 1 is a case where only the oscillation is performed without applying the second vibration. In this case, bleeding occurred as shown in Table 1. This is because the oscillation promotes the inflow of the molten powder between the solidification shell and the inner wall of the mold, but the oscillation has a poor effect of reducing the friction between the solidification shell and the mold. It is considered that this is because the adherence to the inner wall of was not effectively suppressed.

All the other conditions 2 to 14 apply the second vibration. Focusing on the vibration velocity of the second vibration, the conditions 2, 4, 6, 8, and 10 are that although the second vibration is applied in addition to the oscillation, the maximum value of the vibration velocity of the second vibration is the casting value. This is the case when the speed is smaller than the speed. In this case, bleeding occurred as shown in Table 1. This is because the second vibration is superposed on the oscillation, but the vibration characteristic of the second vibration is not appropriate, and the maximum value of the vibration speed of the second vibration was smaller than the casting speed. This is probably because the effect of reducing the friction between the solidified shell and the inner wall of the mold was not obtained.

On the other hand, the conditions 7, 9, 11, and 13 are cases in which, in addition to the oscillation, the second vibration is applied so that the maximum value of the vibration speed is higher than the casting speed. In this case, as shown in Table 1, bleeding did not occur. This is because, while superimposing the second vibration on the oscillation, the vibration characteristic of the second vibration is appropriately controlled so that the maximum value of the vibration speed of the second vibration is larger than the casting speed. It is considered that this is because the friction between the solidified shell and the inner wall of the mold could be reduced.

Condition 14 is a case where only the second vibration is applied without oscillation. In addition, under the condition 14, as shown in Table 1, the vibration characteristic of the second vibration is controlled to be close to that of the condition 11, that is, an appropriate one such that the maximum value of the vibration speed is higher than the casting speed. There is. However, under condition 14, a breakout occurred. This is because even if the vibration characteristic of the second vibration is properly controlled, if the oscillation is not performed, the molten powder is not sufficiently flown between the solidification shell and the inner wall of the mold, so that the solidification shell and the inner wall of the mold are not melted. It is considered that this is because it is not possible to suppress the sticking with. From the results shown in Conditions 1 and 14, in order to maintain good lubrication between the solidified shell and the inner wall of the mold, the mold 1 is oscillated and the second vibration is applied to the mold 1. It was confirmed that it was necessary to do

Here, paying attention to the conditions 3, 5, 7, 9, 11, and 13, under these conditions, in addition to the oscillation, the second vibration in which the maximum value of the vibration speed is larger than the casting speed is obtained. Is given. However, although the bleeding could be suppressed as described above under the conditions 7, 9, 11, and 13, the bleeding occurred under the conditions 3 and 5. The difference between the conditions 3, 5, 7, 9, 11, and 13 is the frequency of the second vibration. Specifically, the conditions 3 and 5 are more frequent than the conditions 7, 9, 11, and 13. small. That is, this result shows that even if the second vibration is applied in addition to the oscillation so that the maximum value of the vibration speed is higher than the casting speed, when the frequency of the second vibration is small, the solidification It indicates that the effect of suppressing the adhesion between the shell and the inner wall of the mold cannot be sufficiently obtained. Specifically, from the results shown in Table 1, when the frequency of the second vibration is smaller than 20 Hz, it becomes difficult to suppress the sticking between the solidification shell and the inner wall of the mold. Therefore, in order to further suppress the adhesion between the solidified shell and the inner wall of the mold, the frequency of the second vibration is preferably 20 Hz or higher. The frequencies of the second vibration under the conditions 3 and 5 of 5 Hz and 10 Hz can be included in the range of frequencies that can be applied by oscillation. In other words, the result that bleeding occurs under Conditions 3 and 5 can be said to support that it is difficult to suppress the occurrence of bleeding only by oscillation.

From the above results, by applying the present invention, it becomes possible to maintain good lubrication between the solidified shell and the inner wall of the mold even when using a relatively high-viscosity molten powder. Therefore, it becomes possible to realize more stable operation while suppressing the deterioration of the quality of the slab due to the entrainment of the molten powder.

(5. Supplement)
The preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, but the present invention is not limited to these examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

1 mold 2 molten steel 3 slab 3a solidified shell 3b unsolidified part 4 ladle 5 tundish 6 immersion nozzle 10 continuous casting machine 110 first vibration mechanism 111 vibration table 112 support body 113 main arm 114 sub-arm 115 cylinder 120 second Vibration mechanism 121 Vibration generator 122 Damper 130 Controller

Claims (2)

A mold,
A first vibrating mechanism for oscillating the mold in the casting direction;
A second vibrating mechanism that applies a second vibration in the same direction as the oscillation to the mold;
Equipped with
The second vibrating mechanism is
Equipped with two mechanical vibration generators using unbalanced weights and motors,
The second vibration is applied such that the maximum value of the vibration speed of the second vibration is larger than the casting speed and the frequency of the second vibration is 20 Hz or more.
Continuous casting machine. A continuous casting method performed while oscillating the mold in the casting direction,
Two vibrations in the same direction as the oscillation are applied to the mold by a mechanical vibration generator using an unbalanced weight and a motor provided in the mold,
The maximum value of the vibration speed of the second vibration is larger than the casting speed, and the frequency of the second vibration is 20 Hz or more.
Continuous casting method.

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