The present invention relates to a refractory member designed for the casting of molten metal in a substantially downward direction from an upper metallurgic vessel such as a ladle or a tundish to a lower metallurgic vessel such as a tundish, a mold or an ingot mold.

Existing requirements concerning metal, in particular steel, quality make it necessary to protect the molten metal jet against any contact with the air, in order to prevent its oxidation, during pouring from a metallurgic vessel to another. The conventional method consists of extending the upper metallurgic vessel pouring hole by a jet protection tube made from refractory material. The end of this tube is immersed in the metal bath contained in the lower metallurgic vessel, so as to ensure a tight channel between the upper metallurgic vessel and the lower metallurgic vessel.

It is also often necessary to regulate the flow of molten metal between the upper and the lower metallurgic vessel. This regulation is generally performed by a constriction of the flow channel. For example, the regulation may be performed with a stopper plunging into the metal bath contained in the upper metallurgic vessel and closing progressively the pouring hole. It may also be performed with a slide valve able to receive two or more refractory plates, each having an orifice therethrough defining a flow channel. When the orifice of the plates fully overlap, the metal flows freely through the plates. When the plates are displaced relatively to each other so that the plates orifices are not in full register, the flow channel is progressively reduced so that the flow of liquid metal may be regulated. Eventually, when there is no overlap at all of the orifices, the casting hole is completely closed.

Conventionally, the upper plate (top plate) is fixedly connected to an internal nozzle placed in the bottom wall of the upper metallurgic vessel and forms the casting hole.

When the slide valve contains two plates, the lower plate (bottom plate) is mobile and ensure the connection with the jet protection tube.

When the slide valve contains three plates, the middle plate is mobile, while the bottom plate is fixedly connected to a jet protection tube.

A generally recognised problem bound to the regulation of the flow of metal liquid is that since the constriction necessary for the regulation is always located in or just under the upper metallurgic vessel, the inner part of the jet protection tube will always cause a depressurisation from the constriction level downwards. This depressurisation is lower than the external (atmospheric) pressure, and it may then cause air entry in the flow channel especially through the joints between the plates. It is then obvious that air will be sucked toward the liquid metal.

As said above, existing requirements concerning metal quality do not allow such an air

entry.

From the US patent 5,772,908, the content thereof being incorporated herein by reference, a casting member is known which discloses a device for controlling a flow of liquid steel from an upper metallurgic vessel (for example a ladle) to a lower metallurgic vessel (for example a tundish). Said device comprises a tube formed in a rigid plate/jet protecting tube assembly tightly applied under the bottom wall of the upper vessel and means for bringing about a constriction of the passage section offered to the steel.

These means are preferably located at the lower end of the jet protection tube. In an illustrated embodiment, these means are constituted by a refractory brick facing an outlet orifice of the jet protection tube. The regulation function is obtained by varying the distance between the refractory brick and the tube outlet.

The position of the constriction means at the bottom of the tube is particularly advantageous since the depressurisation will only occur at the bottom of the tube and will therefore be relatively less important than if placed at the top of the tube. As this constriction is placed under the level of the liquid metal bath of the lower metallurgic vessel, then, all air entries between the upper metallurgic vessel and the lower metallurgic vessel are fully prevented.

Pursuing its work in this direction, applicant has now devised a casting member which facilitates the regulation function at the bottom of the jet protection tube.

It is an object of the present invention to provide a convenient solution to avoid completely the problems of air entry in a casting installation between an upper and a lower metallurgical vessel although keeping the regulation function.

More particularly, the invention relates to a casting member for the casting of a molten metal in a substantially downward direction from an upper metallurgic vessel to a lower metallurgic vessel, said casting member having a substantially axial flow channel extending from its upper end to its lower end and comprising three distinct portions: i) a connecting portion adapted to connect said casting member either directly to the bottom wall of the upper metallurgic vessel or to a slide gate located under the upper metallurgic vessel; ii) a substantially tubular portion extending from the connecting portion to a regulating portion; and iii) a regulating portion.

In particular, the present invention is particularly useful when the means for bringing about the constriction are located under or near the liquid metal level of the lower metallurgic vessel.

This refractory casting member is characterised in that said regulating portion comprises a rotor rotatable in a stator about an axis aligned substantially horizontally and a stator, formed in an extension of the tubular portion and having a recess complementary to said rotor. It is further characterised in that the flow channel section is modifiable by movement of the rotor.

It is to be understood that the rotor according to the invention may be substantially cylindrical, conical, spherical or of any shape having an outer peripheral surface arranged symmetrically about the rotation axis.

The movement of the rotor modifying the flow channel section may be a rotation about its rotation axis or a translation within the stator or a combination of both movements.

The advantages of a casting member according to the invention are already visible when the regulating portion is located near the metal bath level and especially when the regulating portion is under the level of the liquid metal bath, therefore, in a particular embodiment of the invention, the regulating portion is located at the lower third, preferably, the lower quarter of the casting member and in a preferred embodiment, the regulating portion is adapted to be located under the molten steel level.

In order to avoid excessive wear of the rotor and/or of the stator when regulating the molten metal flow, preferably, the parts of the rotor and/or of the stator which are supposed to contact each other are made of a mechanically resistant material. In another embodiment, wherein excessive erosion by the flowing liquid metal of the parts of the rotor and/or the stator constituting the flow channel is to be avoided, the parts of the rotor and/or the stator which are intended to contact the flowing liquid metal are made of a refractory mechanically resistant material. For example, a zirconia (or any other mechanically resistant material) sleeve may be inserted in the stator and/or the rotor.

When the rotor is located under the liquid metal bath, it is not essential that the rotor and the stator forms a tight joint since the liquid metal above the rotor level will prevent air entry even if there is an important depressurisation caused by a construction of the flow channel at this level. Moreover, potential leaks of molten metal at this level would not affect negatively the casting operations since it is located near or under the molten metal and slag bath level.

On the contrary, it may be advantageous to have a mechanical play between the rotor and the stator. In case the casting member is used for the casting of liquid metal between a ladle and a tundish, at the beginning of the casting operations, there is some air contained within the tube which must be evacuated and said play helps evacuating the air. It is therefore advantageous that the play be large enough for air to escape at the opening of the upper mechanical vessel.

For example, a suitable play between the rotor and the stator is comprised between 0.05 and 0.5 mm.

According to a particular embodiment of the invention, especially useful when the rotor is located under the molten metal level, the rotor is connected to at least a refractory arm or handle for actuation of said rotor. It is to be understood that the term refractory arm or handle should not be construed strictly and that it may be a simple boss at an end of the rotor.

Said refractory arm extends upwardly and forms an angle a of between 90 and 135°, preferably between 90 and 120° with the rotation axis of the rotor. Preferably however, said arm has a length sufficient so that at least a part of the arm is above the liquid metal and slag bath. Preferably, the rotor and the stator will be placed just under the metal bath so that a short arm may be used.

In a particularly preferred embodiment, said rotor and said at least a refractory arm form a monolithic refractory body.

In another preferred embodiment, the refractory arm forms in full opening position, an angle ß of between 30 and 60°, preferably of 45°, with a plane defined by the flow channel axis and the rotation axis of the rotor.

Preferably, the refractory arm forms in full closing position, an angle t of between-60 and-30°, preferably of-45°, with a plane defined by the flow channel axis and the rotation axis of the rotor. Such an arrangement allows to keep the refractory arm or at least the extremity thereof above the liquid metal bath.

In a preferred embodiment, the casting member according to the invention comprises also a tubular segment downstream the rotor and the stator and preferably, the tubular segment downstream the rotor and the stator has a section larger than the section of the tubular portion. Even more preferably, the tubular segment downstream the rotor and the stator has a section diverging downstreamly.

In case of casting between a ladle and a tundish, such an arrangement would facilitate the sand evacuation at opening of the ladle.

As to the upper part of the casting member, it is to be understood that all kind of connections between the casting member and the upper metallurgic vessel are possible. However, it may be preferred that the connecting portion consists in a conical segment adapted to be connected to a collector nozzle located at the bottom of the upper metallurgic vessel or at the bottom of a gate valve. Even more preferably, the connecting portion consists in a plate formed at the upper end of the casting member, said plate being positionable against the lower face of a slide gate plate or of the metallurgic vessel. The last arrangement allows pressing the plate against the lower face of a slide gate plate or of the metallurgic vessel and provide a safe, relatively tight and strong connection.

In a particular variant, the stator opens laterally at only one side thereto and the rotor extends from this opening, the refractory arm being connected to the external portion of the rotor.

In another variant, the stator opens laterally at both sides thereto and the rotor extends from at least one of these openings, at least a refractory arm being connected to an external portion of the rotor. This last arrangement avoids lateral pressure tending to push the rotor outside the stator and prevents the metal to freeze between the closed side of the stator and the rotor end.

In a particular embodiment, at the level of the regulating portion, the flow channel is

defined by a bore in the rotor extending from an inlet port to an outlet port therethrough, wherein said bore is aligned on an axis substantially coaxial with the casting direction when the rotor is in full opening position.

Said bore has preferably a diameter at least equal to the diameter of the upstream flow channel.

In another embodiment, at the level of the regulating portion, the flow channel is defined by a region comprised between the end of the rotor and the internal wall of the stator.

In yet another embodiment, the rotor is designed as a bolt and the stator as a nut complementary thereto. In that case, for example, the regulating movement of the rotor is a combination of a rotation and a translation.

In a variant the casting member of the invention comprises a lock system in order to avoid horizontal movement of the rotor during casting operations and to limit the movement to rotation only. In that case, it is particularly of interest that the lock system indicates the full opening position. In a variant, the lock system prevents the rotation of the rotor in one direction beyond the full opening position.

For example, the lock may be an annular recess arranged perpendicularly to the rotation axis of the rotor in the stator fitting a pin located on the outer peripheral surface of the rotor. Preferably, the annular recess is only present in the upper part of the stator so that the rotor may be placed in the stator with the arm extending downwardly and the pin enters the recess upon rotation of the rotor.

Of course, it is to be understood that the full opening position may be indicated by any other means.

In another of its aspect, the present invention relates to a refractory rotor for a rotary regulating valve comprising i) a first portion arranged symmetrically about the rotation axis of said rotor; and ii) a second portion forming an arm and having an angle a of between 90 and 135°, preferably between 90 and 120° with the rotation axis of the rotor.

Preferably, said first and second portions form a monolithic refractory body.

In a particularly preferred embodiment, the rotor comprises a bore defining a flow channel for a molten metal said bore extending from an inlet port to an outlet port therethrough, wherein said bore is aligned on an axis substantially perpendicular to the rotation axis of the rotor.

Preferably, the refractory arm forms an angle S of between 30 and 60°, preferably of 45°, with a plane defined by the bore axis and the rotation axis of the rotor.

In a specific embodiment of the rotor according to the invention, the rotor is designed as a bolt.

The invention also relates to a regulating device for controlling the discharge of molten metal in a substantially downward direction from an upper metallurgic vessel to a lower metallurgic vessel, comprising the refractory casting element according to the

invention and a rotor actuator.

To achieve regulation of the molten metal flow, the refractory arm of the rotor is actuated by the rotor actuator, optionally through a connecting rod.

Preferably, the rotor is oriented on the jet protecting tube so that its rotation axis is substantially perpendicular to the device used to put the tube in place. Henceforth, the refractory arm may be actuated with an actuator located on the said device. It is to be noted that according to the invention, the rotation axis of the rotor must not compulsorily have an intersection with the axis of the flow channel. In other words, the casting member according to the invention is not compulsorily axisymmetric.

The invention will now be described with reference to the accompanying drawings wherein: Fig. 1 depicts a vertical section through a casting member according to the invention used to cast molten metal from a ladle to a tundish ; Fig. 2 depicts a vertical section through the same casting member shown at Fig. 1, but turned 90° with respect to the position illustrated at Fig. 1; Fig. 3 depicts a casting member according to the invention; Fig. 2 depicts the same casting member shown at Fig. 3, but turned 90° with respect to the position illustrated at Fig. 3.

These figures show a casting member according to the invention for the continuous casting of molten metal from an upper metallurgical vessel 1 (a ladle in the figures) to a lower metallurgical vessel 2 (a tundish in the figures). The casting member designated by the general reference 3 comprises a connecting section 4, a tubular portion 5 and a regulating portion 6. In the illustrated embodiment, the regulating portion 6 is located under the molten metal and slag bath level 7.

At figures 1 and 2, the connecting portion 4 comprises a plate 8 formed at the upper end of the casting member 3. At figures 3 and 4, the connecting portion 4 comprises a conical segment adapted to be connected to a connector nozzle.

The tubular section 5 extends from the connecting portion 4 to the regulating portion 6.

The regulating portion comprises a stator 8 (not visible on figure 1) and a rotor 9.

The rotor is connected to a refractory arm 10 which itself may be actuated by an actuator 11 through an articulated transmission rod 12. The regulating portion comprises also a tubular segment 13 downstream the rotor and the stator, the internal section of the tubular segment 13 diverges downstreamly. The rotor has a bore 14 substantially perpendicular to its rotation axis defining a flow channel.

Here follows a description of a possible method of use of the casting member according to the invention.

The rotor 9 is placed into the stator 8 in the casting member 3 before installation of the casting member under the upper metallurgic vessel 1. The casting member 3 is then introduced into a device used to place the tube into casting position (e. g. a tube

changer or a tube manipulator). The transmission rod 12 is then attached to the refractory arm 10 and the casting member 3 is connected to the upper refractory vessel 1 (ladle). The ladle 1 is lowered until the bottom end 15 of the casting member reaches the metal bath level 7 (but with the rotor 9 and the stator 8 above the metal bath level).

The ladle 1 is then opened and, under the ferrostatic pressure, the air contained in the casting member is then flushed through the play between the rotor 9 and the stator 8.

This way of starting the casting operations aims at limiting the pressure shock at the beginning of the casting operation.

The ladle 1 is then lowered until the rotor 9 and the stator 8 are submersed.

At figures 3 and 4, the casting member is provided with a lock 16 to avoid horizontal movements of the rotor 9 in the stator 8. Visible at figure 4 is a positive stop 17 referencing the full opening position.