JPH10113751A - Continuous casting mold and continuous casting method - Google Patents

Abstract

(57) [Summary] [Problem] The vicinity of a meniscus on the long side of a mold swells, and high-speed casting is difficult. SOLUTION: This is a continuous casting mold 1 having an internal water-cooling structure for successively solidifying a molten metal 11 to perform continuous casting, and a cooling box 4 is provided with an actuator 7 for controlling the surface shape of a long side 1a of the mold in contact with the slab. doing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting mold having an internal water-cooled structure for continuous casting of molten metal, and more particularly to a continuous casting mold having an improved internal structure on the long side of the mold.

[0002]

2. Description of the Related Art Conventionally, a continuous casting mold having an internal water-cooled structure, in which a cooling box for reinforcing and cooling a copper or copper alloy mold is provided on the back surface of a copper or copper alloy mold, has been used.
In recent years, high-speed casting at 2 m / min or more has been promoted. In this high-speed continuous casting operation, powder is supplied onto the molten metal of the mold, and the powder becomes molten powder due to the heat of the molten metal, flows between the mold and the solidified shell, and functions as a lubricant for the slab. .

However, the surface of the mold in contact with the slab during casting swells to the slab side due to the thermal load in the vicinity of the meniscus. Gap generation (air gap generation,
The unevenness of heat flow due to powder flow irregularity) and the deterioration of the slab surface properties due to the load of deformation strain applied to the solidified shell hinder the high-speed casting.

[0004] As a technique relating to this kind of high-speed continuous casting, Japanese Patent Application Laid-Open No. 5-15949 proposes an invention relating to a "metal continuous casting apparatus and casting method". The present invention provides a immersion nozzle made of a refractory for supplying a liquid metal to a mold, a metal cooling mold having an internal water-cooling structure for solidifying the liquid metal, and a metal provided with an energizing coil which circulates around the mold to flow a high-frequency current. Wherein the mold has a segment portion having an internally coolable structure which is divided by a plurality of slits extending in a casting direction at an upper portion thereof and not reaching an upper end thereof. And a plurality of girders connecting the upper ends of the opposing molds preferably. "

[0005] Also, in this publication, "a mold is provided with a current-carrying coil which circulates a high-frequency current around the mold, and a plurality of slits are formed in the mold so as to be coolable. The induced magnetic field penetrates into the inner surface of the mold through the, and a pinch force acts on the molten metal, so that the meniscus portion can be largely curved. "
Is disclosed. That is, according to the present invention, the meniscus is curved to smoothly flow the lubricant (powder) into the mold surface, so that the contact pressure between the mold and the slab at the early stage of solidification is reduced. It is possible to stably produce a slab having good properties, and to produce an effect that the deformation of the mold due to the heat of the molten steel is small.

[0006]

In a conventional continuous casting apparatus, a plurality of slits are formed in a mold in order to efficiently apply a pinch force. In order to solve the concern of the above, the slit is filled with a refractory or the like. Further, in order to prevent the occurrence of a gap due to a difference in thermal expansion, the upper ends of the opposite molds are connected by a plurality of digits.

However, when the refractory is filled in the slit,
The refractory is easily damaged by washing with water during cleaning after casting. In addition, if a plurality of girders are provided at the upper end of the mold, the girders obstruct the working field of view at the time of casting and hinder the insertion of the dummy bar.

Further, even if the inflow of powder is controlled by the electromagnetic force of high frequency, it is difficult to control the inflow of powder if the mold swells, and it is necessary to eliminate the cause of irregularities immediately below the meniscus. .

In view of the above problems, the present invention controls the overhang of the mold to the slab side in the vicinity of the meniscus, and improves the stable supply of powder by forming the mold along the solidification shrinkage of the slab. An object of the present invention is to provide a continuous casting mold and a continuous casting method capable of stably producing a slab having good surface properties in high-speed casting.

[0010]

In order to achieve the above object,
The continuous casting mold of the present invention is a continuous casting mold having an internal water-cooled structure that solidifies molten metal sequentially to perform continuous casting, in which a cooling box is equipped with an actuator that controls a surface shape of a long side of the mold in contact with a slab. Things.

Preferably, the actuator is connected to a back surface of a copper or copper alloy plate on a long side of the mold via a buffer plate.

Preferably, the actuator is a hydraulic cylinder, and its stroke is set based on a detection signal of a thermocouple disposed on a long side of the mold.

On the other hand, according to the continuous casting method of the present invention, in a continuous casting method in which molten metal is solidified sequentially by a continuous casting mold having an internal water-cooled structure and continuous casting is performed, a detection signal of a thermocouple disposed on a long side of the mold is provided. The stroke of the actuator is adjusted on the basis of this, and the surface profile of the long side of the mold is controlled in accordance with the solidification shrinkage of the slab.

According to the present invention, defect-free slabs are manufactured without deteriorating slab quality even in high-speed casting, with the aim of improving productivity (higher speed) of continuous casting. The influence of casting speed, steel type, powder, etc. is avoided by controlling the surface profile of the long side of the mold in accordance with the solidification shrinkage of the slab by focusing on the behavior of the mold during casting.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing the structure of the long side of the continuous casting mold according to the present invention. In FIG. 1, the surface layer of the continuous casting mold 1 of the present embodiment is made of a copper plate or a copper alloy plate (hereinafter, simply referred to as a “copper plate” but includes a copper alloy plate) 2.
A buffer plate 3 made of stainless steel (SUS) is superimposed on the rear surface of the copper plate 2.

On the back surface of the buffer plate 3, a cooling box 4 for reinforcing and cooling the copper plate 2 is provided. Therefore, the cooling box 4 has a structure for supplying and discharging cooling water.

A projecting portion 6 having a through hole 5 through which a tie rod (not shown) is inserted is provided on both side surfaces of the cooling box 4, and the mold short side 1a is located between the mold long sides 1a.
By fastening the tie rods between the overhang portions 6 and 6 while holding the b and 1b, the rectangular cylindrical mold 1 is sectioned and formed.

As shown in FIGS. 1 and 2, the cooling box 4 is equipped with an actuator 7 for controlling the surface shape of the long sides 1a of the mold. Specifically, the actuator 7 is fixed to a mold frame 8 that defines the outer wall of the mold 1, and its stroke portion 7 a penetrates through the cooling box 4 and is fixed to the back surface of the buffer plate 3. In the present embodiment, the actuator 7 is constituted by two hydraulic cylinders, for example, ± 0.01 mm
One that can control the stroke with the precision described above is used. Further, a thermocouple for detecting the surface temperature is arranged on the copper plate 2 on the long side 1a of the mold, and the stroke of the hydraulic cylinder 7 is set based on the detection signal of the thermocouple. I have.

That is, when a swelling of the copper plate 2 on the long side of the mold 1a toward the slab is detected by the thermocouple, a signal is transmitted to the hydraulic cylinder 7 and the hydraulic cylinder 7 transfers the copper plate 2 through the buffer plate 3. By attracting, the swelling of the copper plate 2 is eliminated. In the present embodiment, a hydraulic cylinder is employed as the actuator 7, but the invention is not limited to this, and an electric actuator or a mechanical actuator may be employed as long as the stroke can be adjusted with high accuracy. Further, the number of actuators 7 is not limited to the present embodiment.

Next, the continuous casting method of the present invention, which is performed using the continuous casting mold 1, will be described. In inventing the continuous casting method of the present invention, the inventor paid attention to the behavior during casting of the mold, which is the greatest problem in quality. FIG.
FIG. 4 is an explanatory diagram showing a displacement of the long side of the mold in the casting direction, and FIG. 4 is an explanatory diagram showing a displacement of the long side of the mold in the width direction. According to FIGS. 3 and 4, it can be seen that the mold during casting has a bulge near the meniscus at the center in the width direction.

More specifically, as shown in FIG. 5, when the molten metal 11 is injected from the ladle through the tundish and the nozzle into the mold 1, the molten metal 11 injected into the mold 1 Is supplied with powder 12, and this powder 1
2 is melted by the heat of the molten metal 11 to form a powder layer 12a.
Is formed and flows between the copper plate 2 of the mold 1 and the solidified shell 13 formed by cooling, thereby functioning as a lubricant.

However, as shown in FIG. 6, the copper plate 2 on the long side 1a of the mold in contact with the slab during casting bulges toward the slab due to the thermal load near the meniscus at the center in the width direction (see FIG. 6). , F.), due to solidification shrinkage of the slab near the meniscus and the difference in the mold profile, the formation of an air gap G, uneven heat removal from the slab, uneven powder layer thickness, uneven friction coefficient, etc. Will occur, and it will develop into a slab crack.

Therefore, in the continuous casting method of the present invention, as shown in FIGS. 7 and 8, the stroke of the hydraulic cylinder 7 is adjusted based on the detection signal of the thermocouple 9 disposed on the back of the long side 1a of the mold. The bulge near the meniscus is eliminated by controlling the surface profile of the long side 1a of the mold in accordance with the solidification shrinkage of the slab. That is, the bulge portion F near the meniscus of the copper plate 2 on the long side 1a of the mold is pulled by the hydraulic cylinder 7 from the cooling box 4 side, and a profile is formed so as to become narrower in a substantially linear manner toward the lower part of the mold. I do. Since the surface profile of the long side 1a of the mold is formed substantially linearly so that the space between the molds is gradually narrowed, the side shape of the short side 1b of the mold is also straight, and the processing management is simplified.

Therefore, the hydraulic cylinder 7 is desirably provided so as to correspond to the bulging portion F near the meniscus of the copper plate 2 on the long side 1a of the mold. In the present embodiment, since the hydraulic cylinder 7 is connected to the copper plate 2 on the long side 1a of the mold via the buffer plate 3, the degree of overhang of the copper plate 2 can be adjusted substantially linearly. Rippling can be effectively prevented.

The specific control of the hydraulic cylinder 7 is performed, for example, as shown in FIG. That is, when the air gap G or the like occurs, the detection values of the thermocouples 9 arranged on the long side 1a of the mold vary. The temperature distribution of the copper plate 2 is determined from the detected value and the heat flow rate obtained from the operation information such as the casting speed, the steel type, the size, the copper plate cooling water amount, and the copper plate cooling inlet / outlet water temperature difference. It grasps and controls the stroke of the hydraulic cylinder 7.

[0026]

As described above, according to the continuous casting mold and the continuous casting method according to the present invention, the overhang of the mold to the slab side near the meniscus is controlled, and the slab is solidified and shrunk. By adopting a mold shape, a stable supply of powder is improved, and an excellent effect that a slab having good surface properties can be stably manufactured in high-speed casting is exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structure of a long side of a continuous casting mold according to the present invention.

FIG. 2 is a schematic side view showing a cross-sectional structure of a continuous casting mold of the present embodiment.

FIG. 3 is an explanatory diagram showing displacement of a long side of a mold with respect to a casting direction.

FIG. 4 is an explanatory view showing displacement of a long side of a mold in a width direction.

FIG. 5 is a schematic view showing a normal operation of the continuous casting mold of the present embodiment.

FIG. 6 is a schematic diagram illustrating a mold deformation state in the present embodiment.

FIG. 7 is a schematic diagram illustrating a control state of mold deformation in the present embodiment.

FIG. 8 is a schematic diagram illustrating a control state of mold deformation and an arrangement of thermocouples in the present embodiment.

FIG. 9 is an explanatory diagram showing a specific control state of a hydraulic cylinder in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous casting mold 1a Mold long side 1b Mold short side 2 Copper plate 3 Buffer plate 4 Cooling box 7 Actuator 9 Thermocouple 11 Molten metal

Claims (4)

[Claims] 1. A continuous casting mold having an internal water cooling structure for successively solidifying molten metal to perform continuous casting, wherein a cooling box is provided with an actuator for controlling a surface shape of a long side of the mold in contact with a slab. For continuous casting. 2. The continuous casting mold according to claim 1, wherein the actuator is connected to a back surface of a copper or copper alloy plate on a long side of the mold via a buffer plate. 3. The continuous casting mold according to claim 1, wherein the actuator is a hydraulic cylinder, and a stroke thereof is set based on a detection signal of a thermocouple arranged on a long side of the mold. 4. A continuous casting method for performing continuous casting by successively solidifying molten metal by a continuous casting mold having an internal water cooling structure, wherein the stroke of an actuator is adjusted based on a detection signal of a thermocouple arranged on a long side of the mold. A continuous casting method wherein the surface profile of the long side of the mold is controlled in accordance with the solidification shrinkage of the slab.