JPH0642980B2 - Pouring method and immersion nozzle in twin-drum type continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for pouring molten metal into a pool portion provided between a pair of cooling drums while preventing the temperature of the surface layer from decreasing. It relates to a dipping nozzle used in the method.

[Conventional technology]

Recently, attention has been focused on a method for directly producing a thin strip having a thickness of about several mm close to the final shape from a molten metal such as molten steel. This continuous casting method does not require a multi-step hot rolling process as in the prior art, and the rolling to the final shape may be mild, so that the process and equipment can be simplified.

The twin drum method is one of such continuous casting methods. In this method, a pair of cooling drums rotating in opposite directions are horizontally arranged, and a hot water pool is formed in a recess defined by the pair of cooling drums and side weirs in some cases. The molten metal contained in the molten metal pool is cooled and solidified at a portion in contact with the cooling drum to become a solidified shell. As the cooling drum rotates, the solidified shell moves to a so-called drum gap portion where the pair of cooling drums face each other at the position closest to each other. In this drum gap portion, the solidified shells formed on the surfaces of the respective cooling drums are pressed and integrated with each other to form the desired metal ribbon.

Injection of the molten metal into the molten metal pool provided between the cooling drums has hitherto been carried out by flowing the molten metal from a pouring nozzle arranged above the molten metal pool. The present inventors also developed this flow-down type pouring nozzle and applied for it as Japanese Patent Application No. 61-123581.

[Problems to be solved by the invention]

When the molten metal is supplied from the pouring nozzle arranged above the molten metal pool, the molten metal poured flows as shown in FIG. That is, the molten metal b flowing down from the pouring nozzle a mainly flows vertically in the molten metal pool portion d formed between the cooling drums c due to the falling energy.

For this reason, the molten metal surface of the molten metal pool d is less affected by the falling energy of the molten metal b. Since the surface of the molten metal is cooled by the outside air, the temperature of the surface of the molten metal decreases, and a thin skin in which the molten metal b is solidified is likely to be formed there. This thin skin rides on the molten metal flow in the molten metal pool d and is carried to the solidified shell e formed on the peripheral surface of the cooling drum c.
When a thin skin is wound or attached to the solidified shell e, internal defects such as voids, double skin, etc. are formed in the metal ribbon h obtained by integrating the solidified shell e with the drum gap f of the cooling drum c. Remain as surface defects.

Further, the molten metal b that has entered the molten metal pool d is cooled by the cooling drum c.
It may reach the solidified shell e on the peripheral surface. This position is directly above the drum gap f because the molten metal b is in the vertical downward flow. The solidified shell e at this position grows in the process in which the cooling drum c rotates in the arrow direction. When the molten metal b in an overheated state is supplied to this, re-melting of the solidified shell e occurs, and the thinned portion g
Occurs. Since the generation state of the thinned portion g changes irregularly due to the molten metal flow in the pool p,
The thickness of the manufactured metal ribbon h does not become constant, which causes an increase in surface irregularities.

Therefore, the present invention eliminates the adverse effect that a thin skin is generated on the surface of the molten metal pool and the flow of the supplied molten metal has on the growth of the solidified shell, by improving the molten metal pouring. The aim is to produce quality metal ribbons.

[Means for solving problems]

The pouring method in the twin drum type continuous casting of the present invention is
In order to achieve the object, a nozzle is immersed in a hot water pool provided between a pair of cooling drums, and a molten metal having a horizontal component is flown from an opening formed in a side wall of the nozzle. Is supplied to the hot water pool.

Further, the immersion nozzle for twin-drum type continuous casting apparatus used in this method is a nozzle that is immersed in a molten metal pool provided between a pair of cooling drums, and has long sides extending in the axial direction of the cooling drum. It has a rectangular cross section consisting of a side wall and a short side wall perpendicular to the axis of the cooling drum, and a plurality of openings are formed in the long side wall portion below the molten metal surface of the basin, and the bottom surface is formed. It is characterized by being formed of a non-perforated plate.

〔Example〕

Hereinafter, the features of the present invention will be specifically described by way of examples with reference to the drawings.

FIG. 1 shows a twin-drum type continuous casting apparatus equipped with the immersion nozzle of the present invention.

This continuous casting apparatus includes a pair of cooling drums 1a and 1b. The peripheral surfaces of these cooling drums 1a and 1b and the cooling drums 1a and 1b
By the side weirs 2a, 2b arranged on the side surface, the pool 3
Is partitioned. A pouring nozzle 4 is arranged along the longitudinal direction of the basin 3.

This pouring nozzle 4 has a double structure of an inner nozzle 5 and an outer nozzle 6, as shown in the partial sectional view of FIG. Further, on the lower side surface of the inner nozzle 5, an opening 7 oriented in the longitudinal direction of the molten metal pool 3 is provided symmetrically with respect to the tube axis of the inner nozzle 5. The outer nozzle 6 is formed in a divergent shape along the longitudinal direction of the basin 3, so that the lower end surface of the outer nozzle 6 corresponds to the shape of the basin 3. Therefore, the molten metal poured from a container such as a tundish spreads in the longitudinal direction of the outer nozzle 6 through the opening 7 of the inner nozzle 5.

A plurality of nozzle holes 8 are provided in the longitudinal side wall of the outer nozzle 6 along the longitudinal direction thereof, and the bottom wall 9 is non-perforated. Then, the outer nozzle 6 is immersed in the basin 3 so that the nozzle hole 8 of the outer nozzle 6 is below the surface of the basin 3. Therefore, the molten metal 10 that has spread inside the outer nozzle 6 via the inner nozzle 5 is supplied to the pool 3 as a flow having a horizontal component.

FIG. 3 is a diagram for explaining the flow of the molten metal in the molten metal pool 3. Since the molten metal 10 flows out from the nozzle hole 8 provided in the side wall of the outer nozzle 6, it flows in the circumferential direction of the cooling drums 1a and 1b while stirring the molten metal surface of the molten metal pool 3. Since the molten metal 10 immediately after flowing out is in an overheated state, it prevents a decrease in the temperature of the molten metal surface, which tends to be cooled by the outside air. Further, since there is a temperature difference with the molten metal already in the basin 3, the molten metal 10 immediately after being poured has a relatively small specific gravity. Therefore, convection in the basin 3 is promoted, and this also prevents the temperature of the basin from falling.
Therefore, a thin skin is prevented from being formed on the molten metal surface by solidification of the molten metal, and internal defects and external defects due to the thin skin being taken in or attached to the solidified shell 11 are not generated in the metal ribbon 12.

The molten metal 10 in the overheated state remelts the initial solidified shell 11 formed on the peripheral surfaces of the cooling drums 1a and 1b near the molten metal surface. This part is in an extremely unstable state according to the fluctuation of the molten metal level. Therefore, the solidified shell produced here 11
Has many defects such as wrinkles and irregular shapes. When the solidified shell 11 is used as the metal ribbon 12 as it is, its defects are introduced into the product. In this respect, in the present embodiment, by supplying the molten metal 10 in an overheated state, the solidification char 11 is prevented from being generated in the vicinity of the molten metal surface. Therefore, the shape characteristics of the product itself are also good.

Further, when the molten metal 10 is poured in this way, it does not reach the vicinity of the drum gap 13. Therefore, the growth of the solidification shell 11 performed in the process accompanying the rotation of the cooling drums 1a and 1b is also stable. In particular,
Since the solidified shell 11 does not redissolve in the vicinity of the drum gap 13, fluctuations in wall thickness, corrugation, etc. in the obtained metal ribbon 12 are reduced.

In the example of FIG. 2, the nozzle hole 8 is provided on the side wall of the outer nozzle 6 at an inclination angle θ with respect to the horizontal plane. This inclination angle θ is preferably 7 degrees or less. In this way, the molten metal 10 is slightly lowered and the molten metal 10 is poured into the pool 3
When it is made to flow into the pool 3, the stirring effect of the molten metal in the pool 3 is further improved. When the inclination angle θ exceeds 7 degrees, the molten metal 10 in the overheated state is solidified by the solidified shell 11
There is a tendency that the defect described with reference to FIG. From this point, the inclination angle θ is set to 7 degrees or less. Further, the inclination angle θ is zero, that is, the molten metal 10 can flow out from the nozzle hole 8 horizontally to the molten metal surface. In this case as well, the same stirring effect is obtained, and the temperature drop on the molten metal surface is prevented.

Next, specific operating conditions and properties of the produced metal ribbon will be shown.

An outer nozzle 6 having a long side length of 700 mm and a short piece side length of 50 mm was used, and ten nozzle holes 8 having a long diameter of 50 mm and a short diameter of 7 mm were bored at equal intervals on the long side wall. The pouring nozzle 4 equipped with the outer nozzle 6 was immersed in the basin 3 so that the nozzle hole 8 was located 5 mm below the surface of the basin 3. Then, molten steel having a composition of ordinary steel and a temperature of 1525 ° C. was injected into the pool 3 at a flow rate of 950 kg / min.

Neither internal defects nor external defects due to the uptake of the thin skin were detected in the metal ribbon 12 as the obtained product. In addition, the shape of the metal ribbon 12 was stable, and surface defects such as wrinkles and corrugations did not occur.

〔The invention's effect〕

As described above, in the present invention, the molten metal poured from the pouring nozzle into the puddle portion is made to flow with a horizontal component, thereby stirring the molten metal in the puddle portion. Is going. Therefore, the hot water surface of the hot water pool is not cooled by the outside air, and a thin skin is not formed there.
Therefore, it is possible to prevent surface defects such as double skin and internal defects such as cavities from occurring in the obtained metal ribbon. Also,
The molten metal poured into the molten metal re-melts the solidified shell near the surface of the molten metal to stabilize the initial cooling conditions and does not touch the solidified shell near the drum gap. Also improves. In this way, according to the invention, it is possible to produce metal ribbons of excellent quality.

[Brief description of drawings]

FIG. 1 shows the apparatus used in the embodiment of the present invention,
FIG. 2 shows the main part of the pouring nozzle, and FIG. 3 is a view for explaining the flow of the molten metal poured into the pool. On the other hand, FIG. 4 is a diagram for explaining a conventional pouring method.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor, Kunimasa Sasaki 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Factory (72) Inoue Shigeza, Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 4-62-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (56) Reference JP 61-195747 (JP, A) JP 63-183752 (JP, A)

Claims (2)

[Claims] 1. A nozzle is immersed in a hot water pool portion provided between a pair of cooling drums, and the molten metal is made into a flow having a horizontal component from an opening bored in a side wall of the nozzle. A pouring method for twin-drum type continuous casting, which is characterized by supplying to a pool. 2. A nozzle immersed in a hot water pool provided between a pair of cooling drums, wherein a long side wall extending in the axial direction of the cooling drum and a short side wall perpendicular to the axis of the cooling drum. A twin drum having a rectangular cross section consisting of a plurality of openings formed in the long side wall portion below the surface of the molten metal pool, and the bottom surface of which is a non-perforated plate. Nozzle for continuous casting equipment.