JPH11267800A - Tundish for continuous casting and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent splashing and to regulate the pouring flow of open pouring by constituting inlet refractories which constitute an inlet and have a through-hole of a flow regulating cylindrical section and a pouring nozzle part which is enclosed by the same, exists in the lower part of at the flow regulating cylindrical section and encloses the through-hole of the inlet refractories. SOLUTION: The flow regulating cylindrical section 3 made of the refractories having the through-hole 4 is arranged in the upper part and outer periphery of the pouring nozzle section 2. The flow regulating cylindrical section 3 is integrally composed of the refractories and the pouring nozzle section 2 is formed to the form that this section is inserted into the flow regulating cylindrical section 3 and, therefore, the external shape of the inlet refractories is determined by the shape of the flow regulating cylindrical section 3. The height above the inlet nozzle section 2 is required to be >=50 mm in order to sufficiently exhibit a flow regulating effect. When the top end of the flow regulating cylindrical section 3 is lower than the surface of the refractories at the bottom of the tundish and a large difference in level occurs, a pouring basin part is formed in the upper part of the flow regulating cylindrical section 3 and harmful vortexes are generated to splash the pouring flow and, therefore, the flow regulating cylindrical section 3 is so arranged as to obviate the occurrence of the difference in level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting tundish having an inlet for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal. is there.

[0002]

2. Description of the Related Art Molten metal typified by molten steel is cast into a slab mainly after continuous refining in a converter or an electric furnace, etc., by a continuous casting method. The molten metal that has been refined is stored in a ladle, then poured into a continuous casting mold through an intermediate container called a tundish, and solidified from four rounds in the process of being drawn below the mold, and finally solidified. It becomes a completed slab. The reason for using tundish is
In order to distribute molten metal to a plurality of strands at the same time, and in continuous casting, casting is not interrupted even when casting for one ladle is completed, and casting is continuously performed over a plurality of ladle heats. This is because it functions as an intermediate container for preventing the supply of the molten metal to the mold from being interrupted when the ladle is replaced.

[0003] A tundish is a container for intermediately storing a molten metal, the inner surface of which is covered with a refractory, and has a refractory injection nozzle at the bottom for injecting the molten metal into a continuous casting mold. . In a multi-strand mill that performs casting with a large number of molds at the same time, there are as many tundish injection nozzles as there are molds. Each injection nozzle is usually provided with a refractory stopper or a sliding nozzle corresponding to a valve for controlling the opening and closing of the injection flow path and the flow rate of the injection flow.

In a continuous slab casting apparatus or a bloom continuous casting apparatus having a large slab cross section, the injection nozzle extends into the continuous casting mold and uses an immersion nozzle immersed in a molten metal bath in the mold. It prevents the molten metal from coming into contact with the surrounding atmosphere to promote oxidation.
However, in a small-section continuous billet continuous casting device, it is difficult to insert the immersion nozzle into the mold because the cross-sectional size of the mold is small. Open implantation, which is exposed to the surrounding atmosphere, is commonly used.

When performing an open injection, it is essential that the injection flow has a stable rectification. If the injection flow is not rectified,
When scattering occurs, the surface quality of the produced slab increases due to the progress of oxidation from the surface of the droplet and the instability of the molten metal surface in the mold. Further, when the droplets adhere to and grow on the wall surface of the mold, the solidified shell is broken immediately below the mold, which causes a breakout in which the molten metal inside leaks out. In addition, the adhesion of the droplets to the mold wall surface causes fluctuations in the molten metal surface level due to malfunction of the molten metal surface level detector in the mold and causes the liquid level at the upper end of the slab to fall out of the lower end of the mold. Becomes

When performing an open injection, it is generally difficult to use a stopper or a sliding nozzle for controlling the injection flow rate. This is because, if the injection flow rate is controlled by narrowing the injection flow path using a stopper or a sliding nozzle, the injection flow is not rectified and scattering occurs. Therefore, when performing open injection, the stopper is used only for opening and closing the injection port, and during injection, the stopper is fully opened and injection flow control by the stopper is not performed. Therefore, the injection flow rate into the mold is determined only by the static pressure of the molten metal in the tundish and the cross-sectional area of the injection port. In a multi-strand continuous caster, the static pressure of the molten metal in the tundish is usually kept constant since it affects the injection flow of all strands.
Therefore, the cross-sectional area of the through hole of the injection port needs to be kept constant, and the erosion of the inner wall of the through hole of the injection nozzle constituting the injection port during injection needs to be minimized.

As a refractory material of the injection nozzle, alumina graphite is usually used. However, alumina graphite cannot sufficiently prevent the progress of erosion due to the molten metal. Therefore, when performing open injection, it is necessary to use a zirconia (ZrO ₂ ) refractory whose erosion due to the molten metal is extremely small. . The injection nozzle made of zirconia refractory has a length of 22 mm due to the limitation of the method for producing zirconia refractory.
It is difficult to manufacture a refractory exceeding 0 mm, and if it is forcibly manufactured, it causes an increase in casting cost due to an increase in cost. On the other hand, the thickness of the refractory at the bottom of the tundish is
In order to prevent the deformation of the tundish steel shell due to thermal strain, 300 mm is usually required. Therefore, conventionally, as shown in FIG. 4A, the upper end of the injection nozzle 21 is located at a position lower than the surface of the refractory 8 at the bottom of the tundish, and the pool 22 of molten metal exists at the upper part of the injection nozzle. Was to be done.

On the other hand, conventionally, once one continuous casting is completed, the tundish is replaced until the start of the next continuous casting, and the tundish used so far is cooled to repair the refractory. I was Even if the life of the refractory has not expired in one continuous casting, the refractory on the surface in the tundish will spall during the cooling process, so the refractory on the surface will be completely repaired. I needed to.

If the refractory in the tundish can be used in a plurality of continuous castings, the cost of the refractory can be reduced. However, even in this case, it is necessary to replace the refractory and the stopper which form the injection port into the mold. At the end of the continuous casting, the remaining molten material (slag mixed from the molten metal container, heat insulating material on the molten metal surface in the tundish, etc.) left in the tundish is discharged from the tundish, and the tundish refractory is removed. The refractory at the injection port is exchanged while being heated red, and used as it is in the next continuous casting.

[0010]

When continuous casting of molten metal is performed by open injection using a short injection nozzle made of zirconia corresponding to open injection and a tundish having a puddle above the injection nozzle, the injection flow is reduced. Rectification did not occur, and the occurrence of scattering could not be completely prevented. The problem caused by the scattering is as described above. Conventionally, the refractory constituting the inlet is inserted into the bottom of the tundish from the top of the tundish. With this structure, it is impossible to replace the refractory at the inlet with the tundish refractory glowing red. Was.

According to the present invention, it is possible to prevent the occurrence of such scattering and to rectify the injection flow of the open injection, and to replace the refractory at the injection port while the refractory of the tundish remains red-hot. It is an object to provide a possible tundish and a method for producing it.

[0012]

The present inventors have conducted research on the relationship between the flow of molten metal in the tundish and the turbulence of the injection flow. As a result, FIG.
As shown in (b), there is a flow of molten metal, and the molten metal flow 23 from the ladle through the long nozzle 16 collides with the tundish wall to become a molten metal flow 24 along the bottom of the tundish, and this molten metal flows. As the stream 24 hits the sump 22 above the injection nozzle, the vortex 25 in the sump
Was found, and it was found that the vortex 25 was causing the turbulence of the injection flow.

In order to replace the refractory at the inlet while the refractory of the tundish remains red-hot, the refractory at the inlet is charged not from the top of the tundish but from the bottom of the tundish. It must be possible to install it. Further, if the refractory constituting the injection port is, for example, a plurality of refractories separated vertically, it is difficult to replace the refractory in a situation where the surrounding refractories are glowing red.

The present invention has been made based on the above research results, and the gist thereof is as follows. The first is a continuous casting tundish having an inlet for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal. The inlet refractory having a hole includes a rectifying tube portion, and an injection nozzle portion surrounded by the rectifying tube portion and located at least at a lower portion of the rectifying tube portion and surrounding the through-hole of the inlet refractory. The inlet refractory is a tundish for continuous casting, which is inserted into the tundish from below the bottom of the tundish. The injection nozzle can be made of zirconia refractory. The rectifying cylinder can be made of alumina graphite refractory, or can be formed of two members, an upper zirconia refractory and a lower alumina graphite refractory.

Secondly, in the refractory for a continuous casting tundish for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal, a through hole is formed. The inlet refractory comprises a rectifying cylinder portion, and an injection nozzle portion surrounded by the rectifying cylinder portion and located at least at a lower portion of the rectifying cylinder portion and surrounding a through-hole of the inlet refractory. The outer diameter of the refractory is smaller at the upper end than at the lower end of the refractory.

Third, in a method for producing a continuous casting tundish having an injection port for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal. An inlet refractory having a through hole formed with an inlet, a flow straightening cylinder portion, and an injection nozzle portion surrounded by the flow straightening cylinder portion and located at least below the flow straightening cylinder portion and surrounding the through hole of the inlet refractory. Wherein the refractory at the inlet is inserted into the bottom of the tundish from the outside of the bottom of the tundish.

As a result of arranging the rectifying cylinder above the injection nozzle corresponding to the injection nozzle in the prior art, the injection flow into the continuous casting mold was very well rectified. It is considered that as a result of arranging the rectifying cylinder portion, the pool in the upper portion of the injection nozzle portion disappeared, and the generation of the vortex which caused the disturbance of the injection flow was eliminated. In addition, the outer diameter of the refractory at the inlet is made thinner at the upper end than at the lower end of the refractory at the inlet, and the refractory at the inlet is inserted into the bottom of the tundish from below the bottom of the tundish. Even when the dish refractory is red hot, it is possible to easily replace the filler refractory as a single unit, and in multiple continuous castings, replace only the filler refractory and continue to use other tundish refractories. It is now possible to use.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the bottom of a tundish is such that an outer shell is provided on the outside, a heat insulating board for heat insulation is disposed thereon, and a perm brick is disposed thereon. Wear bricks are placed on top and coated refractories are placed on top. The thickness of the refractory at the bottom of the tundish excluding the iron skin is about 300 mm.

The inlet refractory 1 of the present invention has a height approximately equal to the thickness of the refractory at the bottom of the tundish.
The injection nozzle portion 2 of the inlet refractory 1 may be any refractory that can minimize the change in inner diameter due to erosion of the injection nozzle portion even in open injection, and is most preferably made of zirconia refractory. It is suitable. In the case of open injection, since the slab cross-sectional area is small, the injection amount per unit time is small, and the inner diameter of the through hole of the injection nozzle portion 2 is 14 to 19 mmφ.
Before and after. In addition, the height of the injection nozzle portion 2 is around 100 to 150 mm based on the manufacturing restrictions of zirconia refractories.

FIG. 1 shows an upper part and an outer part of the injection nozzle portion 2.
As shown in (1), a rectifying cylinder portion 3 made of a refractory and having a through hole is arranged. Since the rectifying cylinder portion is integrally formed of a refractory material, and the injection nozzle portion is inserted into the rectifying cylinder portion, the outer shape of the injection port refractory 1 is determined by the shape of the rectifying cylinder portion 3. In order to sufficiently exhibit the rectifying effect, the height of the portion of the rectifying cylinder portion above the injection nozzle portion needs to be 50 mm or more. If the upper end of the rectifying cylinder is lower than the refractory surface at the bottom of the tundish, a large step is formed, and a basin is formed at the top of the rectifying cylinder, causing harmful vortices to occur and causing the injection flow to scatter. Therefore, it is necessary to arrange the rectifying cylinder so that a large step does not occur between the upper end of the rectifying cylinder and the surface of the refractory at the bottom of the tundish.

The inner diameter of the through-hole of the rectifying cylinder is preferably 1
5 mm or more and 50 mm or less. With a through-hole having an inner diameter of less than 15 mm, the injection flow rate into the mold cannot be substantially secured, and with a through-hole having an inner diameter of more than 50 mm, the through-hole becomes a pool and a harmful vortex is generated therein. Because. In the case where a stopper 14 made of a refractory material is disposed above the rectifying cylinder and the on / off control of the injection flow is performed by opening and closing between the stopper 14 and the rectifying cylinder 3, the through-hole of the rectifying cylinder is provided with an injection nozzle. The part slightly larger than the inner diameter of the through hole of the part has an advantage that the injection can be restarted stably when the stopper is opened again.

It is preferable that the refractory constituting the rectifying cylinder is an alumina graphite refractory. The use of the alumina graphite refractory has an effect that the cost of the refractory can be reduced. Alumina graphite has a feature that the erosion rate by molten metal is faster than zirconia.However, by making the injection nozzle part made of zirconia, the inner diameter of the through hole of the rectifying cylinder part increases due to erosion during casting. Also, the injection rate does not fluctuate. According to the usual manufacturing method for alumina graphite refractories, after making the outer shape roughly have the shape of a rectifying cylinder, the part where the injection nozzle part is to be inserted is made into a shape with the correct dimensions by machining, and then the injection nozzle is inserted. Thus, the refractory at the inlet can be completed.

The inner diameter of the through-hole of the injection nozzle 2 and the inner diameter of the through-hole of the rectifying cylinder 3 above it do not necessarily have to match. However, it is preferable that the inner diameters of the two through-holes at the contact portion between the two are close to each other, because the step of the molten metal inflow passage is reduced and the injection flow is rectified. Specifically, it is desirable that the difference between the inner diameter of the through hole at the lower end where the straightening cylinder portion through hole is in contact with the injection nozzle portion and the inner diameter of the through hole at the upper end of the injection nozzle portion is 10 mm or less. If the inner diameter difference exceeds 10 mm, the flow is disturbed by the step between the rectifying cylinder portion and the injection nozzle portion, so that there is a disadvantage that the injection flow becomes unstable.

Above the refractory 1 at the inlet, a stopper 14 for on / off control of the injected flow may be arranged. In the case where the rectifying cylinder of the present invention is disposed, the counterpart that contacts the tip of the stopper and blocks the injection flow is the rectifying cylinder. Therefore, the upper end of the through-hole of the rectifying cylinder has a curved surface with a curvature,
It is necessary to ensure smooth contact with the tip of the stopper and prevent damage to the contact surface.

As shown in FIG. 1 (b), the upper portion 5 of the rectifying cylinder can be made of zirconia refractory, and the lower portion 6 can be made of alumina graphite refractory. When the upper portion is made of zirconia refractory, the contact state with the tip of the stopper can be improved. If the refractory material of the fitting portion is soft, it is easily melted, and if the refractory material is hard, trouble of leakage due to poor fitting is caused. Therefore, when a soft alumina graphite refractory is used for the stopper, it is effective to use a hard zirconia refractory as the partner refractory. The length of the zirconia refractory is limited based on manufacturing restrictions. However, by making the lower part of the rectifying cylinder part made of alumina graphite refractory, the rectifying cylinder part can secure a required length. The zirconia refractory in the upper part 5 of the rectifying cylinder and the alumina graphite refractory in the lower part 6 can be bonded and integrated. The surface where the zirconia refractory and the alumina graphite refractory are in contact with each other is not a flat surface, and a step can be provided as shown in FIG. 1 (b). Thereby, it becomes easy to accurately align the centers of the two and adhere them.

The injection nozzle 2 made of zirconia refractory is
It is effective to dispose it below the inlet refractory as shown in FIG. 1 (a). However, as shown in FIG. 1 (c), it should be made of zirconia refractory over the entire length of the through hole of the inlet refractory. Is also possible. In this case, by inserting a plurality of nozzles 7 made of zirconia refractory, the entire length of the through hole is covered.

When mounting the refractory 1 on the bottom of the tundish, the refractory 1 is inserted from below the bottom of the tundish. Tuyere refractories 10 and 11 having a shape to be fitted with the inlet refractory are arranged at the bottom of the tundish where the inlet refractory is to be inserted. By providing the inlet refractory 1 with a conical taper such that the tip on the upper side of the tundish becomes thinner, insertion into the tuyere refractories 10 and 11 becomes easier. An extrapolation method in which the inlet refractory 1 is inserted from below the bottom of the tundish is adopted.
Are configured as an integral refractory, so that the inlet refractory can be easily replaced even when the tundish refractory is heated to a high temperature. Therefore, continuous casting is performed using a tundish, and after a series of castings is completed,
When the refractory constituting the inlet and the refractory constituting the wall and the bottom of the tundish are to be exchanged, but the refractory constituting the tundish is to be continuously cast again, the refractory for the inlet 1 is cooled without cooling the refractory of the tundish. It can be exchanged.

[0028]

EXAMPLE The present invention was applied to a steel billet continuous casting apparatus. The continuous casting apparatus is an 8 strand mill, the slab size is 130 mm × 130 mm, and the casting speed is 2.6.
Casting was performed under the conditions of ~ 3.2 m / min. The tundish 12 is as shown in FIG. 3. The tundish capacity is 33 tons. The molten steel refined by the converter refining method is received in a ladle having a capacity of 240 tons. , Molten steel is injected through a long nozzle 16. A stopper 14 made of a refractory is disposed above a part of an injection hole serving as a discharge hole of the injection flow 18 into the mold 19, and ON / OFF control of the injection flow is performed.

FIG. 1 shows an inlet refractory 1 of the present invention.
(A) Three types shown in (b) and (c) (Example No. 1 of the present invention).
1, No. 2, No. 3) was used. Further, an injection nozzle 21 shown in FIG. 4A was used as a comparative example. The inlet refractory 1 of the example of the present invention has a height of 360 mm and the outer diameter of the thickest part is 165 mm. Each of the injection nozzle portions has a height of 135 mm and an inner diameter of a through hole through which the injection flow passes is 1.
7.5 mmφ, made of zirconia refractory. The outer shape of the rectifying cylinder portion is the same as that of the inlet refractory 1, and the inner diameter of the through-hole of the rectifying cylinder portion is no. 1 and No. 1 No. 2 is 25 mmφ, No. 3
Is 17.5 mmφ, and a taper is provided in the through-hole of the injection nozzle portion so that a step does not occur at the junction between the rectifying cylinder portion and the through-hole of the injection nozzle portion. The shape of the through-hole at the upper end of the rectifying cylinder is rounded at 30 mmR in order to make good contact with the stopper. The rectifying cylinder is
No. No. 1 was entirely made of alumina graphite.
In FIGS. 2 and 3, the lower part 6 which is a part thereof is made of alumina graphite, and the upper part 5 and the part 7 surrounding the through hole in FIGS. 1B and 1C are made of zirconia. The injection nozzle 21 of the comparative example has a height of 135 mm and an inner diameter of the through hole of 17.5 mm.
The shape of the through hole at the upper end of the injection nozzle 21 has a roundness of 30 mmR as in the case of the rectifying cylinder.

The injection nozzle 21 of the comparative example was inserted into the installation site from above the tundish 12. On the other hand, the inlet refractory 1 of the example of the present invention was inserted into the installation site by an extrapolation method of inserting from below the bottom of the tundish. In the example of the present invention, tuyere 10, 11
Is installed, and the inlet refractory 1 is inserted so as to fit into the tuyere. In the comparative example, the upper end of the injection nozzle 21 is 150 mm from the surface of the refractory at the bottom of the tundish.
As the refractory at the bottom of the tundish is in a low position, a refractory that is poured near the injection nozzle is used as the refractory at the bottom of the tundish.
A tapered pool 22 having a shape as shown in FIG.

In continuous casting, on average, 5 ladle heats are applied to 1
Casting is performed, and at the completion of each cast, molten steel in the tundish is completely injected, and the supply of molten steel to the mold is interrupted.
In the comparative example, refractory maintenance of the tundish was performed for each cast, and the injection nozzle was replaced at the timing of refractory maintenance. In the example of the present invention, the three casts are grouped into one group, and in each group, only the inlet refractory 1 and the stopper 14 are replaced for each cast, but the other refractories on the tundish wall surface and the bottom are not rebuilt. And When the casting is completed, the residual material such as residual molten steel and slag in the tundish is discharged, and then the tundish is tilted about 90 ° to erect the tundish bottom,
The used inlet refractory was removed from the eight inlets, and then a new inlet refractory was inserted from the outside so as to fit into the tuyere and attached. Similarly, the stopper was replaced with a new one. The time required to replace the refractory and the stopper at the inlet was 30 minutes on average, the temperature of the inner wall of the tundish and the bottom refractory was noticed, spalling of the refractory was not observed, and the next casting was performed. Could be done.

Table 1 shows the results of continuous casting. The present invention No. 1 to No. In No. 3, all the injection flows achieved rectification, and no scattering of the injection flow into the mold occurred. On the other hand, in the comparative example, the injection flow into the mold is disturbed and scattering occurs, and as a result, the incidence of surface defects of the slab is higher than that of the present invention, and the incidence of breakout is also higher. The result was. In addition, in the example of the present invention, since the tundish refractory except the injection port refractory and the stopper could be used as it was over an average of three casts, the refractory cost could be reduced.

[0033]

[Table 1]

[0034]

According to the present invention, by arranging an injection refractory having an injection nozzle portion and a rectifying cylinder portion at an injection port of a continuous casting for performing an open injection, rectification of an injection flow is realized and surface quality of a slab is improved. As a result, the frequency of breakouts was reduced, and fluctuations in the surface level of the molten metal in the mold were reduced. Furthermore, by extrapolating the refractory at the inlet from below the bottom of the tundish, the tundish refractory can be used over a plurality of casts, and the cost of the refractory can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a refractory at an inlet of a tundish of the present invention, in which (a) is an example in which a rectifying cylinder is formed of a single refractory, and (b) is a rectifying cylinder having an upper portion. An example composed of the lower two types of refractories, (c) is an example in which the zirconia refractories are arranged over the entire length of the through hole of the inlet refractory.

FIG. 2 is a partial cross-sectional view of a tundish incorporating an inlet refractory of the present invention.

FIG. 3 is a cross-sectional view showing the overall arrangement of a tundish, a ladle, and a mold according to the present invention.

4A and 4B are cross-sectional views illustrating a tundish injection nozzle according to a conventional example, in which FIG. 4A is a cross-sectional view illustrating a state of an injection nozzle incorporated in a tundish, and FIG. It is sectional drawing which shows an occurrence situation.

[Description of Signs] 1 Injection refractory 2 Injection nozzle part 3 Rectifying cylinder part 4 Through hole 5 Upper part of rectification cylinder part 6 Lower part of rectification cylinder part 7 Nozzle made of zirconia refractory 8 Tundish bottom refractory 9 Iron shell 10, 11 Tuyere 12 Tundish 13 Inlet 14 Stopper 15 Ladle 16 Long nozzle 17 Molten metal 18 Injection flow 19 Mold 20 Slab 21 Injection nozzle 22 Pool basin 23 Molten metal flow 24 Molten metal flow 25 Vortex

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Nao Iwata 1 Kimitsu, Kimitsu City Inside Nippon Steel Corporation Kimitsu Works (72) Inventor Koichi Kudo 1 Kimitsu, Kimitsu City Nippon Steel Corporation Kimitsu Inside the steelworks

Claims (6)

[Claims] 1. A continuous casting tundish having an inlet for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuous casting of a molten metal. The inlet refractory having a hole includes a rectifying tube portion, and an injection nozzle portion surrounded by the rectifying tube portion and located at least at a lower portion of the rectifying tube portion and surrounding the through-hole of the inlet refractory. A tundish for continuous casting, wherein the refractory at the inlet is inserted into the tundish from below the bottom of the tundish. 2. The tundish for continuous casting according to claim 1, wherein the injection nozzle portion is made of zirconia refractory. 3. The tundish for continuous casting according to claim 1, wherein the straightening cylinder portion is made of alumina graphite refractory. 4. The tundish for continuous casting according to claim 1, wherein the straightening cylinder portion has an upper portion made of zirconia refractory and a lower portion made of alumina graphite refractory. 5. An injection refractory for a continuous casting tundish for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal. The refractory at the inlet,
An injection nozzle portion surrounded by the rectifying cylinder portion and positioned at least below the rectifying cylinder portion and surrounding the through hole of the inlet refractory, wherein the outer diameter of the inlet refractory is smaller than that of the lower end of the inlet refractory. Injectable refractory, characterized in that the upper end is thinner. 6. A method for producing a continuous casting tundish having an injection port for performing an open injection in which a molten metal stream is exposed to a surrounding atmosphere when the molten metal is injected into a mold for continuously casting a molten metal. The inlet refractory formed and having a through-hole is formed of a rectifying cylinder portion and an injection nozzle portion surrounded by the rectifying cylinder portion and positioned at least at a lower portion of the rectifying cylinder portion and surrounding the through-hole of the inlet refractory, A method for producing a tundish for continuous casting, characterized in that the refractory at the inlet is inserted into the bottom of the tundish from outside the bottom of the tundish.