JPS61219449A - Continuous casting method for thin sheet - Google Patents

Abstract

PURPOSE:To prevent the hindrance of the formation of a solidified shell by pouring flow and to stabilize casting by starting pouring while the tip of a pouring nozzle is held in proximity to the neutral point of a drum as far as possible and rising the nozzle up to a prescribed level position while maintaining the specified immersion depth. CONSTITUTION:The freely extensible and contractable pouring nozzle 6 is extended to the position in proximity to the neutral point of the drum (the position nearest both peripheral surfaces of water cooling drums 1, 1' for casting) as far as possible and the pouring is started in this state. The tip of the pouring nozzle 6 is raised with an increase in the molten metal level up to the prescribed molten metal level while the specified immersion depth of the tip of the nozzle 6 is maintained in the stage when the tip of the nozzle 6 is immersed down to the prescribed depth.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a continuous thin plate casting method.

(Prior art) In the twin-drum continuous thin plate casting method in which molten metal is poured between two drums and thin plates are continuously cast, it is not possible to strictly control the thickness of the solidified shell μ generated on the drum surface. This is an essential requirement for a reservoir to maintain good properties of slabs. In particular, in an unsteady state from the start of pouring to a steady state (a state in which the drum rotation speed and surface height increase to a predetermined value),
Since the drum rotation speed and the hot water level change over time, leakage due to unsolidified water or cracks due to oversolidification are likely to occur17, so it is necessary to control the thickness of the solidified shell even more strictly. . However, in the conventional method, the pouring nozzle μ is located at a high position (relative to the neutral point of the drum).
□' The distance from the tip of the pouring nozzle μ is long and the position is higher than the molten metal level in a steady state), and there are the following disadvantages: the thickness of the solidified shell cannot be sufficiently controlled; □ Also, the slab properties was also not satisfactory.

(1) The molten metal hits the drum surface at the start of pouring, which has the disadvantage of inhibiting the formation of a solidified shell. This phenomenon is called the washing phenomenon of the shell due to the flow of pouring metal.

(2) Because the molten metal flows between the drums in an unsteady state,
It has the disadvantage that the occurrence of hot water wrinkles etc. is significant, which impairs the surface quality of the slab.

(Problems to be Solved by the Invention) The present invention aims to provide a thin plate continuous casting method that eliminates the above-mentioned drawbacks of the conventional means, prevents the formation of a solidified shell from being inhibited, and minimizes the flow of molten metal. purpose.

(Another Means to Solve the Problems) The present invention, as a means to achieve the above object, pours molten metal with the tip of the molten metal pouring nozzle as close to the neutral point of the drum as possible so that the molten metal flow does not hit the drum surface. As the molten metal level rises, the molten metal is kept at a constant immersion depth and then allowed to rise. The pouring nozzle μ is raised at the same speed). That is, the present invention consists of two water-cooled casting drums that are arranged horizontally in parallel with a gap corresponding to the thickness of the metal strip to be manufactured and that rotate in different directions, and two fixed weirs that are pressed against the end surfaces of these drums. In the continuous casting method to obtain thin plate slabs by pouring molten metal into the space formed by
This is a thin plate continuous casting method characterized by starting pouring with the tip of the pouring nozzle as close to the neutral point of the drum as possible, and raising the nozzle to a predetermined level while maintaining a constant immersion depth.

Hereinafter, the present invention will be explained in detail based on FIG. 1st
The figure is a longitudinal sectional view of a continuous thin plate casting apparatus suitable for carrying out the present invention. The apparatus shown in FIG. 1 includes a water-cooled casting drum 1.1' for casting thin plate slabs 6, side fixed weirs 2 and 2' for preventing leakage of molten metal 4 between the water-cooled casting drums 1 and 1', and molten metal such as molten steel. The main components include a kundish 5 for storing 4 and a pouring nozzle 6. To explain this device in detail, the water-cooled casting drums 1, 1 are arranged horizontally in parallel and are driven to rotate (in the direction of the arrow) by a drive device (not shown). The water-cooled casting drums i and f are hollow drums made of copper, copper alloy, or steel, and have a built-in water cooling mechanism, and are designed to provide a large contact area with the molten metal 4. It is a drum of the same diameter. Furthermore, fixed weirs 2, 2' made of refractory material are provided at both ends of the water-cooled casting drums 1, 1' to seal the sides.
is being pressed. Furthermore, below the tundish 5 that stores the molten metal 4, there is installed a pouring nozzle μ6 made of a refractory material and consisting of a telescopic double pipe that is vertically extended or shortened by hydraulic pressure or an electric motor.
Molten metal 4 is poured into a space formed by two water-cooled casting drums 1, 1' and two fixed weirs 2, 2' by this telescopic pouring nozzle /L/6. The molten metal 4 is cooled by contacting the surfaces of the water-cooled casting drums 1 and 1', respectively, and the resulting solidified shells are integrated into a slab 3 as the drums rotate. This slab is pulled out by a vinyl roll 7. Note 8
is a guide role.

In the above device, the present invention provides a telescopic pouring nozzle/L.
/6 to extend the drum neutral point (water-cooled casting drum 1) as much as possible.
, 1' (closest position of both circumferential surfaces), start pouring, and when the tip of pouring nozzle/I/6 is immersed in the molten metal to a predetermined depth, Keep the immersion depth of the tip constant (
While maintaining the temperature at 10 to 20 tran), the tip of the pouring nozzle 1/B is raised as the molten metal level rises at a predetermined molten metal level L/-4.

As described above, as an embodiment of the present invention, a retractable pouring nozzle μ is used to adjust the immersion depth into the molten metal.
In some cases, the nozzle may be of a fixed type, or the tundish itself may be configured to be movable up and down to adjust the depth of immersion of the attached pouring nozzle into the molten metal. It is included.

Although the present invention has been described in detail above, the present invention will be explained in more detail by giving specific examples of the present invention.

〔Concrete example〕

The dimensions and various conditions of the structural members in the case of casting steel are as follows.

(1) Water-cooled cast drum Made of steel with internal water cooling system, this drum has a diameter of 2
000m+φ, drum width 1200mm. The dimensions of the slab are 3mm x 1200+nm width, and the drum rotation speed (casting speed) in steady state is about 28 m/min.

(2) Molten metal In the case of ordinary steel, the temperature of the molten metal in the tundish is 152
The temperature is 0 to 1560°C. The head of the molten metal on the water-cooled casting drum is about 500 m.

(3) Pouring nozzle μ The material was Si3N4, and vertical movement was performed using hydraulic pressure.

Casting was carried out under the above conditions, and a good slab could be stably obtained without any operational troubles such as leakage.

[Effects of the present invention]

As detailed above, the present invention starts pouring with the tip of the pouring nozzle as close to the neutral point of the drum as possible, and raises the nozzle to a predetermined level while maintaining a constant immersion depth. Therefore, it is possible to prevent the formation of a solidified shell due to the pouring flow immediately after the start of pouring, to suppress the flow of molten metal between the drums as much as possible, to stabilize casting in an unsteady state, and to obtain good slabs. The effect that can be achieved is produced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a continuous thin plate casting apparatus suitable for carrying out the present invention. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] A space formed by two water-cooled casting drums that rotate in different directions, arranged horizontally with a gap corresponding to the thickness of the metal strip to be manufactured, and two fixed weirs pressed against the end surfaces of these drums. In the continuous casting method to obtain thin plate slabs by pouring molten metal into the drum, pouring is started with the tip of the pouring nozzle as close to the neutral point of the drum as possible, and the nozzle is moved to a predetermined level while maintaining a constant immersion depth. A thin plate continuous casting method characterized by ascending.