JPH09225596A - Twin roll continuous casting method and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twin roll continuous casting method, by which a cast slab having smooth crown shape can be cast, and a continuous casting apparatus thereof. SOLUTION: An immersion nozzle 1 providing plural molten metal spouting holes 2 opened in the roll axial direction toward the peripheral surface of the rolls 6a, 6b and porous bodies 3a-3c in the inner part, is arranged in a mold demarcated with one pair of cooling rolls 6a, 6b rotated to mutually reverse directions while holding a prescribed interval and one pair of side weirs 5 slidingly contacting with the side surface of the rolls. The porous body is divided into the porous body 3a at the center part, the porous body 3c at the endmost part and the porous body 3b between them and the diameters of holes 7a, 7b, 7c in the porous bodies 3a, 3b, 3c are reduced in this order. By this constitution, the flowing rate of the molten metal per unit area from the spouting hole 2, i.e., the flowing speed, is made to large at the center part and small at the end part, and smooth temp. distribution is developed in the axial direction in the cooling rolls 6a, 6b and the curve of this heat deformation is smoothened, and the crown shape of the poured cast slab is formed in good.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-drum type continuous casting method and apparatus, and more particularly to a twin-drum type continuous casting method and apparatus for pouring molten metal so that a slab having a good cross-sectional shape can be obtained.

[0002]

2. Description of the Related Art In a twin-drum type continuous casting machine, a casting mold is defined by a pair of cooling drums which rotate in opposite directions with a predetermined distance and a pair of side dams slidingly contacting the side surfaces of the cooling drums. The molten metal is supplied into the mold by pouring a dipping nozzle for pouring, and a thin plate is cast as the cooling drum rotates.

As the molten metal pouring nozzle, one having a molten metal discharge port opened in the drum axial direction toward the peripheral surface of the cooling drum and a porous body inside is used. As the pouring nozzle for pouring, various structures have been proposed.

For example, as disclosed in Japanese Patent Laid-Open No. 06-126395, as shown in FIGS. 5 and 6, a nozzle body having a slit-shaped discharge port, and an intermediate nozzle for supplying molten metal incorporated in the nozzle body. It is composed of. FIG.
In FIG. 6, 1 is a dipping nozzle for pouring, 2 is its discharge port, 3 is an internal porous body, and 10 is a degassing hole. Reference numeral 20 denotes an intermediate nozzle.

In this nozzle, as described above, the porous body 3 is used.
Is provided inside the pouring dipping nozzle 1 so that the molten metal can escape to the nozzle discharge port 2 through the porous body 3. However, in this nozzle, the void portions of the porous body 3 have almost the same distribution in the nozzle 1, and the nozzle discharge ports 2 are also at substantially equal intervals.

Also, in the flat nozzle for continuous casting disclosed in Japanese Patent Laid-Open No. 07-60415, on both side walls of the cooling drum near the lower closed end, which is immersed in the molten metal pool in the moving mold during steady operation. The slit-shaped nozzle holes to be provided are formed to have substantially the same size.

Further, in the flat nozzle for twin-drum type continuous casting disclosed in Japanese Patent Laid-Open No. 07-68357, FIG.
As shown in FIG. 3, a rectifying refractory material 30 having a large number of through holes 30a is arranged at the bottom thereof, and the hole area ratio of the rectifying refractory material 30 is small in the center and large in both side portions. An example of the shape of the cast slab 25 obtained by casting using the nozzle is shown in FIG. 8. However, there is a problem such that a thicker part than the center is formed between the center and the end of the slab cross section. It was

[0008]

As described above, in twin-drum type continuous casting, casting is performed by arranging a pouring immersion nozzle in a mold defined by a pair of cooling drums and a pair of side dams. At times, the molten metal flows through the nozzle discharge port in the drum body surface direction, but the velocity of the molten metal flow colliding with the drum outer peripheral surface rapidly decreases at the nozzle end, causing thermal deformation of the drum, resulting in casting. The crown shape (cross-sectional shape) of the piece became uneven as shown in FIG. 8, and it was impossible to obtain a cast piece having a good shape.

In the present invention, a twin-drum type continuous casting method and a twin-drum type continuous casting method capable of casting a slab having a smooth cross section by uniformly changing the collision velocity of the pouring flow on the drum surface are provided. An object is to provide a continuous casting device.

[0010]

In order to solve the above problems, the present invention provides a mold defined by a cooling drum and a side weir, in which a plurality of molten metal spouts opened in the drum axial direction toward the peripheral surface of the cooling drum. A twin-drum continuous casting in which a pouring dipping nozzle equipped with a porous body inside the outlet and inside is placed, and the pouring is performed by making the molten metal speed from the molten metal discharge port of the pouring dipping nozzle smaller at the end than at the center Adopt the method.

According to the twin-drum type continuous casting method of the present invention, the flow rate per unit area from the discharge port of the pouring dipping nozzle, that is, the flow velocity, is made large at the central portion and small at the end portion, so that the heat of the molten metal is generated. The amount of heat transfer that flows into the water-cooled drum is affected by the flow of the molten metal, and gradually decreases toward the end in the central part, causing a gradual change in heat load. Although a temperature distribution is generated in a certain direction and thermal deformation occurs, the thermal deformation curve becomes gentle.

In the twin-drum type continuous casting method according to the present invention described above, the flow rate per unit area at the nozzle discharge port, that is, the flow velocity, is 0.4 in terms of the speed ratio of the endmost discharge port to the central discharge port. It is preferably within the range of 0.8. That is, when the flow velocity on the extreme end side exceeds 0.8 times that of the central portion, the difference in the pouring flow velocity at the nozzle end portion becomes large, and a thicker part than the central portion is formed between the central portion and the end of the slab. Because. Also, when the flow velocity on the extreme end side becomes 0.4 times or less that of the central part, the difference in flow velocity of the pouring flow also increases in this case, and the shape similar to that when the cast piece shape exceeds 0.8 times the above Is not suitable.

In order to solve the above problems, the present invention provides
In the mold defined by the cooling drum and the side weir, a plurality of molten metal discharge ports opened in the drum axial direction toward the peripheral surface of the cooling drum and a molten metal pouring nozzle equipped with a porous body inside are arranged. Provided is a twin-drum type continuous casting device in which the porosity of the central portion of a porous body of a pouring nozzle for pouring molten metal is larger than the porosity of the end portions.

As an embodiment of the twin-drum type continuous casting apparatus according to the present invention, the discharge port of the pouring immersion nozzle is divided into a plurality of parts in the axial direction of the drum, and the divided nozzle discharge port openings are used. The flow rate per unit area, that is, the flow velocity, is made larger in the central part and smaller in the end part, so that the porosity of the porous body that becomes the resistance of the fluid inside the nozzle is changed so that the resistance of the porous body becomes smaller in the central part. To do.

In order to change the porosity of the porous body in the dipping nozzle for pouring molten metal used in the twin drum type continuous casting apparatus according to the present invention as described above, the pore diameter of the central portion of the porous body is made larger than the pore diameter of the end portion. It is also possible to adopt an appropriate structure, such as

According to the twin-drum type continuous casting apparatus of the present invention thus constructed, the above-described twin-drum type continuous casting method of the present invention is effectively realized, and a slab having a gentle sectional shape is cast. be able to.

On the other hand, in the twin-drum type continuous casting apparatus, when the length of the nozzle in the drum axial direction is shorter than the length of the drum in the axial direction, the heat flow velocity distribution in the drum axial direction is also obtained by the casting method of the present invention. There may be some unevenness in the shape, and the heat-deformed shape may be distorted, that is, thin in the central portion. Therefore, the twin-drum type continuous casting apparatus according to the present invention described above preferably has a structure in which the molten metal discharge port at the end of the pouring immersion nozzle is opened toward the intersection of the cooling drum and the side dam.

With such a structure, the relative velocity between the pouring flow and the peripheral surface of the drum gradually changes from the central portion to the end portion. As a result, the heat-deformed shape of the drum becomes smooth, and a good shape, that is, a slab with a uniform plate thickness in the width direction or a slightly thick central portion can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A twin-drum type continuous casting method and apparatus according to the present invention will be specifically described below with reference to the embodiments shown in FIGS. In the following embodiments, the same components as those of the conventional device shown in FIGS. 5 and 6 are designated by the same reference numerals for simplification of description.

(First Embodiment) First, a twin-drum type continuous casting apparatus according to the first embodiment of the present invention shown in FIG. 1 will be described. In FIG. 1, 6a and 6b are a pair of cooling drums, and the cooling drums 6a and 6b and the side dam 5 having a pair of heat-resistant ceramic side dam refractories 5a and 5b slidably contacting the side surfaces of the cooling drums 6a and 6b Is defined. 5c is a side weir heater provided on the side weir. An immersion nozzle 1 for pouring molten metal is arranged in the mold.

The immersion nozzle 1 for pouring molten metal is provided with a molten metal discharge port 2 for supplying the molten metal into the mold. The molten metal discharge port 2 is divided into a plurality in the axial direction of the drum, and the flow rate of the molten metal per unit area from the divided opening of each discharge port 2, that is, the flow velocity, is large in the central part and small in the end part. In order to do so, the porous body 3 which is a resistance of the fluid is provided inside the nozzle.

That is, the porous body 3 is constituted by the porous body 3a at the center of the pouring nozzle 1 for pouring the molten metal, the porous bodies 3b on both sides thereof, and the porous body 3c at the end, and these porous bodies 3
The diameters of the holes 7a, 7b and 7c of a, 3b and 3c are made smaller in this order. As a result, the resistance to the molten metal passing through the porous body 3 is low at the central portion and high at the end portions. The overall structure of the pouring nozzle 1 is shown in FIG.

As described above, in the twin-drum type continuous casting apparatus shown in FIG. 1, the discharge port 2 of the dipping nozzle 1 for pouring the molten metal.
Is divided into a plurality of parts in the axial direction of the drum, and the flow rate per unit area, that is, the flow velocity from the opening of each of the divided discharge ports 2 is increased in the central part and is reduced in the end part. Since the porosity of is large in the central part and small in the end part, the heat transfer amount of the heat of the molten metal flowing into the cooling drums 6a, 6b is affected by the flow of the molten metal, and the amount of heat transfer increases in the central part toward the end. It gradually becomes smaller, causing a gentle change in heat load.

Due to this heat load, the cooling drums 6a, 6a
Although a gentle temperature distribution is generated in the inside of b in the axial direction to cause thermal deformation, the thermal deformation curve becomes smooth. The nozzle 1
Even if the porosity 3 provided in the inside is the same as the porosity, a large opening in the central portion facilitates the flow, and a small opening in the end causes the flow to be gentler than the central portion. Similar results can be derived.

The flow rate per unit area at the discharge port 2, that is, the flow velocity, is preferably small within the range of 0.4 to 0.8 in the speed ratio between the central discharge port and the end discharge port. there were. That is, when the flow velocity on the extreme end side exceeds 0.8 times that of the central part, the difference in the pouring flow velocity at the nozzle end becomes large, and a thicker part is formed between the central part and the end on the slab than the central part. It was Also,
If the flow velocity on the extreme end side becomes 0.4 times or less that of the central part, the difference in the flow velocity of the pouring flow also becomes large in this case, and the shape is the same as when the slab shape exceeds 0.8 times the above-mentioned, which is not suitable. Became.

(Second Embodiment) Next, a twin-drum type continuous casting apparatus according to a second embodiment of the present invention shown in FIG. 3 will be described. In the pouring immersion nozzle 1 used in the apparatus shown in FIG. 3, the opening direction of the discharge port 2 at the end of the nozzle is perpendicular to the cooling drum axis, or the molten metal surface, the cooling drum body surface, and the side dam 5 are connected. It is between the intersection of. In addition, the direction of the discharge port 2 at the intermediate position is the direction (angle) of the central discharge port 2.
It may be set so as to be in the middle of the direction (angle) of the discharge port 2 on the end side. The entire structure of this pouring immersion nozzle 1 is the same as that shown in FIG.

In the twin-drum type continuous casting apparatus, when the length of the immersion nozzle for pouring the molten metal in the axial direction of the drum is shorter than the axial length of the drum, the distribution of the heat flow velocity in the axial direction of the drum tends to be slightly uneven. The heat-deformed shape of the cast slab may be distorted, that is, thin in the central portion.

Therefore, as shown in FIG. 3, the opening direction of the nozzle discharge port at the end of the nozzle 1 is set to the direction perpendicular to the cooling drum axis or the direction of the intersection of the drum peripheral surface and the side weir, and the pouring flow and the drum peripheral surface. The relative speed of and is gradually changed from the central part to the end part. As a result, the heat-deformed shape of the drum becomes smooth, and a good shape, that is, a slab having a uniform plate thickness in the width direction or a slightly thick central portion can be obtained.

[0029]

EXAMPLES Next, examples of the twin-drum type continuous casting method according to the present invention will be described.

(First Embodiment) A twin drum having a diameter of 120
Two cooling drums with a diameter of 0 mm and a width of 800 mm were used. The nozzle shape used was that shown in FIGS. 1 and 4, but the axial length of the nozzle immersion part was 680 mm and the opening width of the discharge port 2 was 2 at the center.
00mm, 50mm for the outer edge, 140 for those in between
mm, porous body (porous ceramics filter) 3
Holes 7a, 7b, 7c of a, 3b, 3c, the diameter of the central porous body 3a is 6 mmφ, and the diameter of the outer end porous body 3c is 3.9 mm.
φ, the porous body 3b between them is 5 mmφ, and the porosity is 20
They were arranged in a zigzag pattern so that the ratio becomes%.

During casting, the width of the molten metal surface (distance between the drums in contact with the molten metal surface) was kept at 280 mm, continuous casting was carried out at a casting speed of 60 m / min with the tip of the nozzle immersed (inserted) in the molten metal surface. .

As a result, the outer peripheral portions of the cooling drums 6a and 6b are deformed so that the slab crown shape has a uniform curvature change, and the slab shape as shown in FIG. 2 is obtained. Tc was thicker than the slab end wall thicknesses te and te ', and the intermediate wall thicknesses tm and tm' were intermediate values between tc and te, te ', indicating a good shape.

Further, the holes 7a of the porous bodies 3a, 3b, 3c,
Even when the diameters of 7b and 7c were 6 mmφ at the central portion, 1 mmφ at the outermost portion and the porosity was 20%, a good cast shape was obtained.

(Second Embodiment) A cooling drum having a diameter of 12
The one having a diameter of 00 mm and a width of 1330 mm was used. The same dipping nozzle 1 for pouring was used as that of the first embodiment, except that the discharge port 2 at the outer end having a width of 50 mm was set at the drum circumference from the intersection of the molten metal surface with the cooling drum body surface and the side dam. Casting was performed by setting the discharge direction so that the center side was 100 mm on the surface. As a result of this casting, the thermal deformation of the drum shows a uniform change in curvature, and the slab also shows in FIG.
A good shape was obtained as shown in.

(Third Embodiment) In the first embodiment, the diameter of the porous body 3 is 6 mmφ for the central porous body 3a, 4 mmφ for the outer end porous body 3c, and 5 mmφ for the porous body 3b therebetween. The porosity is set to 30% in the central porous body 3a, the number of holes is the same in the outer end porous body 3c and the intermediate porous body 3b, and the porosity is set to 13.3% and 20.8%, respectively. I served.

Also in this casting result, the thermal deformation of the drum showed a uniform curvature change, and a slab having a good shape as shown in FIG. 2 was obtained. In addition, the porous body 3a of the discharge port at the center of the nozzle
With a hole of 5 mmφ and a porosity of 20.8%, and the porous body 3c of the nozzle discharge port at the end has a diameter of 5 mmφ and a porosity of 16.6%, a good cast shape can be obtained. It was

[0037]

As described above, in the twin-drum type continuous casting method and apparatus according to the present invention, the molten metal velocity from the molten metal discharge port of the immersion nozzle for pouring is made smaller at the end portion than at the central portion. Therefore, the flow rate per unit area, that is, the flow velocity, is large in the central portion and small in the end portion.

Therefore, the heat transfer amount of the heat of the molten metal flowing into the water cooling drum is affected by the flow of the molten metal, and gradually decreases toward the end in the central portion, causing a gradual change in the heat load, As a result, a uniform heat-deformed shape of the water cooling drum can be obtained, and a slab having a good shape can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing a structure of a pouring immersion nozzle in a twin-drum type continuous casting apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a slab cast using the immersion nozzle for pouring shown in FIG.

FIG. 3 is a plan view showing the structure of a pouring immersion nozzle in a twin-drum type continuous casting apparatus according to a second embodiment of the present invention.

FIG. 4 is a side view showing a partially broken molten metal pouring nozzle in the twin-drum type continuous casting apparatus according to the embodiment of the present invention.

FIG. 5 is a side view similar to FIG. 4, showing a molten metal pouring immersion nozzle in a conventional twin-drum type continuous casting apparatus.

6 is a cross-sectional view of the nozzle shown in FIG. 5 in a direction perpendicular to the paper surface.

FIG. 7 is a view showing another example of the immersion nozzle for pouring molten metal in the conventional twin-drum type continuous casting apparatus, in which (a) is a sectional view,
(B) is a plan view.

FIG. 8 is a sectional view showing a sectional shape of a cast piece cast by a conventional twin-drum type continuous casting apparatus.

[Explanation of symbols]

 1 Immersion nozzle for pouring 2 Discharge port 3, 3a, 3b, 3c Porous body 4 Molten metal 5 Side dam 5a, 5b Side dam refractory 5c Side dam heater 6a, 6b Cooling drum 10 Degassing hole 20 Intermediate nozzle

Claims (5)

[Claims] 1. A mold, which is defined by a pair of cooling drums that rotate in opposite directions at a predetermined interval and that rotate in mutually opposite directions, and a pair of side dams that slidably contact the side surfaces of the drum, facing the peripheral surface of the drum. A continuous casting method in which a plurality of molten metal discharge ports opened in the drum axial direction and a molten metal pouring immersion nozzle having a porous body inside are arranged, and a thin plate is cast as the cooling drum rotates. A twin-drum type continuous casting method characterized in that the molten metal is discharged from the molten metal discharge port of the dipping nozzle at a smaller speed in the end portion than in the central portion. 2. The flow velocity ratio of the end portion to the central portion is set to 0.
The twin-drum type continuous casting method according to claim 1, wherein the twin-drum type continuous casting method is 4 to 0.8. 3. A mold defined by a pair of cooling drums which rotate in opposite directions at a predetermined interval and which rotate in mutually opposite directions, and a pair of side dams slidably contacting the side surfaces of the drum, facing the peripheral surface of the drum. A continuous casting device for arranging a plurality of molten metal discharge ports opened in the drum axial direction and a pouring immersion nozzle having a porous body inside, and a thin plate is cast as the cooling drum rotates, wherein the porous body is A twin-drum type continuous casting apparatus characterized in that the porosity of the central portion is made larger than the porosity of the end portions. 4. The twin-drum type continuous casting apparatus according to claim 3, wherein the hole diameter of the central portion of the porous body is larger than the hole diameter of the end portions. 5. The twin-drum type continuous casting apparatus according to claim 3, wherein the molten metal discharge port at the end of the pouring immersion nozzle is opened toward the intersection of the cooling drum and the side dam.