CA2156988C - Gas injection nozzle for pouring liquid metal - Google Patents
Gas injection nozzle for pouring liquid metal Download PDFInfo
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- CA2156988C CA2156988C CA 2156988 CA2156988A CA2156988C CA 2156988 C CA2156988 C CA 2156988C CA 2156988 CA2156988 CA 2156988 CA 2156988 A CA2156988 A CA 2156988A CA 2156988 C CA2156988 C CA 2156988C
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Abstract
The object of the present invention is to provide a gas injecting nozzle which is used for pouring liquid metal and which is prevented from being blocked in the course of continuous casting.
According to the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein (a) the nozzle consists of a porous refractory, (b) the circumference of the nozzle is surrounded by a iron shell which has a gas injection pipe, a band-like space (referred to as a gas pool hereinafter) which extends along the circumference of the nozzle perpendicularly to an axis of the nozzle is provided between the porous refractory and the iron shell, and (c) the gas pool is formed as a corrugated-band-like space along at least one portion of the circumference of the nozzle.
According to the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein (a) the nozzle consists of a porous refractory, (b) the circumference of the nozzle is surrounded by a iron shell which has a gas injection pipe, a band-like space (referred to as a gas pool hereinafter) which extends along the circumference of the nozzle perpendicularly to an axis of the nozzle is provided between the porous refractory and the iron shell, and (c) the gas pool is formed as a corrugated-band-like space along at least one portion of the circumference of the nozzle.
Description
SPECIFICATION
A GAS INJECTING NOZZLE FOR POURING LIQUID METAL
Field of Invention The present invention relates to a gas injection nozzle connected to an immersion nozzle used for pouring liquid metal (e.g. liquid steel) from a tundish into a mold during continuous casting, an upper or lower nozzle connected to an air seal pipe or an open nozzle for continuous casting and the like.
Related Art As is well known, an immersion nozzle is conventionally used for pouring melt steel from a tundish into a mold in continuous casting of steel. In the course of the continuous casting, alumina (Al203) contained in the liquid steel or that produced by the oxidation of Al contained in the liquid steel can adhere to the inner surface of the nozzle and cause what is called as nozzle blockage in which the nozzle is blocked by alumina inclusions .
Thus, in order to prevent this nozzle blockage and thereby to perform smooth casting, inert gas such as Ar gas, N~ gas or the like is injected from an upper nozzle or a lower nozzle connected to the immersion nozzle so that the alumina inclusions on the inner wall of the nozzleFs hole can be removed. This method is presently applied to an upper or lower nozzle which is connected to an immersion nozzle, an air seal pipe or the like as shown in FIG. 4 to 6 FIG. 4 shows an example of the mounting construction in which an immersion nozzle is connected to a tundish. As shown in this figure, an upper nozzle 10 is inserted into the bottom of a tundish located over this construction. Slide plates 11, 12 are 2ls6988 placed on the underside of the upper nozzle. Generally the upper slide plate 11 is fixed and the lower slide plate 12 is slidably attached so as to open/close a lower nozzle 20 connected to this lower slide plate 12. An immersion nozzle 30 is connected to the lower nozzle 20.
FIG. 5 shows an example of the mounting construction of what is known as an air seal pipe 40 which is used for pouring liquid steel from a ladle into a tundish. The ladle is provided over this structure and the tundish is located below it.
An upper nozzle 10 is mounted on the bottom of the ladle.
Slide plates 11, 12 are placed on the downside of this upper nozzle 10 in order to regulate the flow rate of liquid steel being poured into the tundish. Generally the upper slide plate 11 is fixed and the lower slide plate 12 is slidably attached so as to regulate the flow rate of melt steel. A lower nozzle 20 is provided below the slide plate 12 and an air seal pipe 40 is mounted on the underside of the lower nozzle 40.
FIG. 6 shows an example of the mounting construction in which an open nozzle 50 is mounted on the bottom of a tundish.
Slide plates 11,12 are attached to the underside of an upper nozzle 10. The open nozzle 50 is placed on the underside of the lower slide plate 12.
In each of the above mentioned examples, inert gas is introduced from a gas injection pipe 5 into the upper nozzle 10 in order to prevent the blockage of this nozzle. The blockage of the lower nozzle is also prevented in such a manner as the upper nozzle.
FIG. 7 is a detailed sectional view of an upper nozzle of the prior art. This gas injecting nozzle is composed of a permeable porous refractory 4 and has a nozzle hole 3 through which liquid metal passes. Usually the whole circumference of this nozzle is surrounded by an iron shell 2 and is formed so that the gas introduced through a gas injection pipe 5 can be blown into the nozzle hole 3.
A gas pool la is usually provided in the middle portion of this porous refractory 4. This gas pool la is formed as a space between a portion of the circumference of the porous refractory 4 and the corresponding portion of an iron shell 2. Thanks to the existence of this gas pool, the gas supplied through the gas supplying pipe can penetrate into the porous refractory 4 and leak into the nozzle hole 3, which makes it possible to prevent such inclusions as alumina from depositing on the inner surface of the nozzle hole 3.
As shown in FIG. 7, the nozzle hole 3 is formed as a cylindrical space between the porous refractory 4 and the iron shell. When liquid metal has passed through the nozzle hole 3, the temperature or the nozzle 3 is high at its upper portion and low at its lower portion. Thus thermal stress is produced in the axial direction of the porous refractory 4. This thermal stress can lead up to a crack 6 which occurs in a direction perpendicular to the axial direction of the porous refractory 4 in the upper side of the gas pool la as shown in FIG. 7.
FIG. 8 is a detailed sectional view of an lower nozzle of the prior art. Similarly as in the case of the upper nozzle mentioned above, the thermal stress produced in the axial direction of the porous refractory 4 can lead up to a crack 6 which occurs in a direction perpendicular to this axial direction.
Summery of Invention When the cracks described above are produced in the early stages of continuous casting, a large amount of gas locally enters into the nozzle hole through these cracks. This hinders the gas penetration through the whole body of the nozzle and consequently causes a frequent occurrence of the blockage of this 2l56988 nozzle.
Therefore the object of the present invention is to provide a gas injecting nozzle for continuous casting, for example, which can prevent the occurrence of the cracks which are likely to be produced during continuous casting and which occur in a direction perpendicular to the axial direction of a porous refractory so that the blockage of this nozzle can be avoided even during long-duration casting.
Studies for finding the causes of the above mentioned cracks has showed that these cracks in the porous refractory are produced mainly because the gas pool is formed as a straight-band-like space which extends circumferentially in a direction perpendicular to the axial direction of the nozzle.
Therefore those cracks produced in a direction perpendicular to the axial direction of the nozzle can be prevented by forming the gas pool into a corrugated-band-like space in order to avoid the occurrence of the cracks in a direction perpendicular to the axial direction of the nozzle. Based on this knowledge, we have finally came to the proposition of the invention as described hereinafter.
(1) According to the first aspect of the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein (a) the nozzle consists of a porous refractory, (b) the circumference of the nozzle is surrounded by a iron shell which has a gas injection pipe, a band-like space (referred to as a gas pool hereinafter) which extends along the circumference of the nozzle perpendicularly to the axis of the nozzle is provided between the porous refractory and the iron shell, and (c) the gas pool is formed as a corrugated-band-like space along at least one portion of the circumference of the nozzle.
2ls6988 (2) According to the second aspect of the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein the width (W) of the corrugated gas pool is smaller than the depth (H) of its groove-like portion (see FIG. 3).
A GAS INJECTING NOZZLE FOR POURING LIQUID METAL
Field of Invention The present invention relates to a gas injection nozzle connected to an immersion nozzle used for pouring liquid metal (e.g. liquid steel) from a tundish into a mold during continuous casting, an upper or lower nozzle connected to an air seal pipe or an open nozzle for continuous casting and the like.
Related Art As is well known, an immersion nozzle is conventionally used for pouring melt steel from a tundish into a mold in continuous casting of steel. In the course of the continuous casting, alumina (Al203) contained in the liquid steel or that produced by the oxidation of Al contained in the liquid steel can adhere to the inner surface of the nozzle and cause what is called as nozzle blockage in which the nozzle is blocked by alumina inclusions .
Thus, in order to prevent this nozzle blockage and thereby to perform smooth casting, inert gas such as Ar gas, N~ gas or the like is injected from an upper nozzle or a lower nozzle connected to the immersion nozzle so that the alumina inclusions on the inner wall of the nozzleFs hole can be removed. This method is presently applied to an upper or lower nozzle which is connected to an immersion nozzle, an air seal pipe or the like as shown in FIG. 4 to 6 FIG. 4 shows an example of the mounting construction in which an immersion nozzle is connected to a tundish. As shown in this figure, an upper nozzle 10 is inserted into the bottom of a tundish located over this construction. Slide plates 11, 12 are 2ls6988 placed on the underside of the upper nozzle. Generally the upper slide plate 11 is fixed and the lower slide plate 12 is slidably attached so as to open/close a lower nozzle 20 connected to this lower slide plate 12. An immersion nozzle 30 is connected to the lower nozzle 20.
FIG. 5 shows an example of the mounting construction of what is known as an air seal pipe 40 which is used for pouring liquid steel from a ladle into a tundish. The ladle is provided over this structure and the tundish is located below it.
An upper nozzle 10 is mounted on the bottom of the ladle.
Slide plates 11, 12 are placed on the downside of this upper nozzle 10 in order to regulate the flow rate of liquid steel being poured into the tundish. Generally the upper slide plate 11 is fixed and the lower slide plate 12 is slidably attached so as to regulate the flow rate of melt steel. A lower nozzle 20 is provided below the slide plate 12 and an air seal pipe 40 is mounted on the underside of the lower nozzle 40.
FIG. 6 shows an example of the mounting construction in which an open nozzle 50 is mounted on the bottom of a tundish.
Slide plates 11,12 are attached to the underside of an upper nozzle 10. The open nozzle 50 is placed on the underside of the lower slide plate 12.
In each of the above mentioned examples, inert gas is introduced from a gas injection pipe 5 into the upper nozzle 10 in order to prevent the blockage of this nozzle. The blockage of the lower nozzle is also prevented in such a manner as the upper nozzle.
FIG. 7 is a detailed sectional view of an upper nozzle of the prior art. This gas injecting nozzle is composed of a permeable porous refractory 4 and has a nozzle hole 3 through which liquid metal passes. Usually the whole circumference of this nozzle is surrounded by an iron shell 2 and is formed so that the gas introduced through a gas injection pipe 5 can be blown into the nozzle hole 3.
A gas pool la is usually provided in the middle portion of this porous refractory 4. This gas pool la is formed as a space between a portion of the circumference of the porous refractory 4 and the corresponding portion of an iron shell 2. Thanks to the existence of this gas pool, the gas supplied through the gas supplying pipe can penetrate into the porous refractory 4 and leak into the nozzle hole 3, which makes it possible to prevent such inclusions as alumina from depositing on the inner surface of the nozzle hole 3.
As shown in FIG. 7, the nozzle hole 3 is formed as a cylindrical space between the porous refractory 4 and the iron shell. When liquid metal has passed through the nozzle hole 3, the temperature or the nozzle 3 is high at its upper portion and low at its lower portion. Thus thermal stress is produced in the axial direction of the porous refractory 4. This thermal stress can lead up to a crack 6 which occurs in a direction perpendicular to the axial direction of the porous refractory 4 in the upper side of the gas pool la as shown in FIG. 7.
FIG. 8 is a detailed sectional view of an lower nozzle of the prior art. Similarly as in the case of the upper nozzle mentioned above, the thermal stress produced in the axial direction of the porous refractory 4 can lead up to a crack 6 which occurs in a direction perpendicular to this axial direction.
Summery of Invention When the cracks described above are produced in the early stages of continuous casting, a large amount of gas locally enters into the nozzle hole through these cracks. This hinders the gas penetration through the whole body of the nozzle and consequently causes a frequent occurrence of the blockage of this 2l56988 nozzle.
Therefore the object of the present invention is to provide a gas injecting nozzle for continuous casting, for example, which can prevent the occurrence of the cracks which are likely to be produced during continuous casting and which occur in a direction perpendicular to the axial direction of a porous refractory so that the blockage of this nozzle can be avoided even during long-duration casting.
Studies for finding the causes of the above mentioned cracks has showed that these cracks in the porous refractory are produced mainly because the gas pool is formed as a straight-band-like space which extends circumferentially in a direction perpendicular to the axial direction of the nozzle.
Therefore those cracks produced in a direction perpendicular to the axial direction of the nozzle can be prevented by forming the gas pool into a corrugated-band-like space in order to avoid the occurrence of the cracks in a direction perpendicular to the axial direction of the nozzle. Based on this knowledge, we have finally came to the proposition of the invention as described hereinafter.
(1) According to the first aspect of the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein (a) the nozzle consists of a porous refractory, (b) the circumference of the nozzle is surrounded by a iron shell which has a gas injection pipe, a band-like space (referred to as a gas pool hereinafter) which extends along the circumference of the nozzle perpendicularly to the axis of the nozzle is provided between the porous refractory and the iron shell, and (c) the gas pool is formed as a corrugated-band-like space along at least one portion of the circumference of the nozzle.
2ls6988 (2) According to the second aspect of the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein the width (W) of the corrugated gas pool is smaller than the depth (H) of its groove-like portion (see FIG. 3).
(3) According to the third aspect of the present invention, a gas injecting nozzle for pouring liquid metal is provided, wherein the width (W) of the corrugated gas pool is smaller than the depth (H) of its groove-like portion, the corrugated-band-like shape of the gas pool is sinusoidal, and the circumference of the nozzle has a shape of a sinusoidal wave of 1 cycle or more.
BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a sectional view showing a structure of an upper nozzle according to the present invention.
FIG. 2 is a sectional view showing a structure of a lower nozzle according to the present invention.
FIG. 3 shows longitudinal sectional and expansion views of a gas pool according to the present invention.
FIG. 4 is a sectional view showing a interconnection of an upper nozzle, a lower nozzle and a tundish which is adopted for continuous casting.
FIG. 5 is a sectional view showing a mounting construction of an air seal pipe for pouring liquid metal from a ladle into a tundish.
FIG. 6 is a sectional view showing a structure of a known open nozzle used for continuous casting.
FIG. 7 is a schematic diagram showing a structure of a known -upper nozzle and the cracks which are produced in a gas pool formed as a straight-band-like space extending in a direction perpendicular to the axis of the upper nozzle.
FIG. 8 is a schematic diagram showing the structure of a known lower nozzle and the cracks which are produced perpendicularly to the axis of the lower nozzle.
DETAILED DESCRIPTION OF I~VENTION
As described hereinbefore, for a known gas injecting nozzle for continuous casting, a gas pool is formed as a straight-band-like space between a portion of the circumference of a porous refractory and the corresponding portion of an iron shell. This gas pool extends along the circumference of the nozzle perpendicularly to the axis of the nozzle.
For a gas injecting nozzle according to the present invention, a gas pool is formed as a corrugated-band-like space which extends along the circumference of the nozzle perpendicularly to its axis. Similarly as this, for an upper or lower nozzle, a gas pool is formed as a corrugated-band-like space. This gas pool of a corrugated-band-shape extends along at least one portion of the circumference of the nozzle, and preferably it extends along the entire circumference of the nozzle.
Since the gas pool is formed as a corrugated-band-like space, the cracks caused by thermal stress are apt to occur along the corrugated form of the gas pool and, as a result, cannot propagate in a direction perpendicular to the nozzle axis. Thus such cracks are produced only locally and the blockage of the nozzle can be prevented because a large amount of gas does not penetrate into the nozzle hole through the crack rapidly.
The gas pool can take any smooth corrugated shape.
Preferably the width (W) of the corrugated gas pool should be 2l56988 smaller than the depth (H) of its groove-like portion (see FIG.
3), because, in this condition, a crack produced in a direction perpendicular to the nozzle axis encounters the nearest ridge or groove in the course of its propagation and stops at this ridge or groove.
Furthermore the designing and production of a porous refractory can be made easier by employing a sinusoidal shape for the corrugated-band-like gas pool. When this sinusoidal shape is used, the gas pool preferably extends along at least one portion of the circumference of the nozzle, and more preferably it extends along the entire circumference of it. Moreover it is desirable that the gas pool has a sinusoidal shape of 1 cycle or more along the circumference of the nozzle.
Example 1 FIG. 1 shows a gas injecting nozzle according to the first embodiment of the present invention, in which a corrugated-band-like gas pool located in the middle portion of the upper nozzle 10 extends in a direction perpendicular to the nozzle axis and has a corrugated-band-like shape in the direction of the nozzle axis.
Example 2 FIG. 2 shows the lower nozzle 20 which is provide with a corrugated-band-like gas pool 1 similar as that of the upper nozzle 10 shown in FIG. 1.
FIG. 3 shows the details of the corrugated-band-like gas pool 1 of the lower nozzle 20 shown in FIG. 2.
FIG. 3(a) shows the shape of the gas pool 1 in its vertical section.
FIG. 3(b) shows an illustration of the gas pool 1 which is developed in one plane. For preventing the concentration of thermal stress, it is desirable that this corrugated-band-like gas pool extends in a direction perpendicular to the nozzle axis and its shape draws a curve as smoothly as possible.
Thus, in order to prevent the occurrence of cracks induced by the concentration of thermal stress, it is desirable that each of the curves of the ridges and grooves of the corrugated-band-like shape has the same radius (R). Preferably this corrugated shape has at least one cycle along the circumference of the porous refractory.
In addition to this, it is desirable that the width (W) of the corrugated-band-like gas pool is smaller than the depth (H) of its groove-like portion as shown in FIG. 3(b). Because, when W is larger than H, a crack produced in the gas pool propagates around the circumference in a direction perpendicular to the nozzle axis, while, when W is smaller than H, such a crack must encounter the nearest groove or ridge of the corrugated-band-like shape in the course of its propagation and stop at it, which makes it possible to prevent the propagation of the crack around the circumference.
It is preferable that the corrugated-band-like shape of the gas pool draws a smooth curve as described hereinbefore. It is more preferable that the curve of this corrugated-band-like shape is sinusoidal. Because such a sinusoidal shape has a regularity and facilitates the designing and manufacture of the nozzle. The gas pool of the upper nozzle can also take a corrugated-band-like shape similar as the upper nozzle.
Thus it is possible that the tensile stress which can be produced in the axial direction of the nozzle during the early stages or the succeeding stages of pouring is prevented from causing a crack to occur in a direction perpendicular to the nozzle axis.
21$6988 As one embodiment of the present invention, a performance comparison test was conducted between an immersion nozzle connected to an upper nozzle and a lower nozzle each of which has a gas pool of a 6-cycle sinusoidal shape along its circumference and an immersion nozzle connected to an upper nozzle and a lower nozzle each of which has a conventional gas pool of a simple-band-like shape.
In this comparison test, in order to simulate the behavior of each of these immersion nozzles in the course of pouring, the variations of their back pressures (mmAq) were measured while heating each of their nozzle holes by a burner and introducing Ar gas into it at a flow rate of 5 l/min.
Furthermore the porous refractory material used in this test was of a high alumina material (Al20~) content of not less than 80~) which had a porosity of 18 to 22 %, a bulk specific gravity of 2.9 to 3.0 g/cm3, compression strength of 15 to 60 MPa/cm2, and an average pore diameter of S to 60 ~m.
The results of the test are listed in Table. 1. As shown in this table, the back pressure of the conventional immersion nozzle began to decrease in the vicinity of 900 ~C. In contrast to this, the immersion nozzle connected to a gas injecting nozzle according to the present invention did not exhibit such a phenomenon and no crack was developed in its porous refractory.
Moreover an immersion nozzle connected to a gas injecting nozzle according to the present invention was actually applied to continuous casting of steel and its nozzle blockage condition during this casting was investigated. The result of this investigation showed that almost no blockage of the nozzle caused by alumina inclusions was observed.
In this embodiment, as described hereinbefore, the present invention has been described mainly in connection with upper and lower nozzles of an immersion nozzle used for continuous casting.
21$6988 However the application of the concept of the present invention is not limited to these nozzles. The present invention can be applied to an air seal pipe as shown in FIG. 5 and to an open nozzle as shown in FIG. 6.
As described above, in a gas injecting nozzle according to the present invention, a gas pool located between an iron shell and an inner porous refractory extends along the circumference of the nozzle in a direction perpendicular to the nozzle axis in a form that a band-like gas pool corrugates in the direction of the nozzle axis. Therefore it is possible to easily prevent the thermal stress produced in the axial direction of the nozzle from causing the occurrence of cracks in a direction perpendicular to the nozzle axis.
Thus it is possible to prevent the accumulation of alumina inclusions or the like on the inner surface of the nozzle hole and, thereby, to perform gas injection OI long-duration in the course of liquid metal casting. Therefore smooth and long-duration casting can be achieved. The present invention makes it possible to produce high-quality, continuous castings and other ingots and will provide great industrial benefits.
21$6988 Temperature(C)1Present Invention2 Prior Art2 Room Temp. 400 400 Notes l:The temperature of the nozzle hole heated by a burner.
2:The back pressure (mmAq) measured when Ar gas was injected into the nozzle at the flow rate of 5 l/min.
BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a sectional view showing a structure of an upper nozzle according to the present invention.
FIG. 2 is a sectional view showing a structure of a lower nozzle according to the present invention.
FIG. 3 shows longitudinal sectional and expansion views of a gas pool according to the present invention.
FIG. 4 is a sectional view showing a interconnection of an upper nozzle, a lower nozzle and a tundish which is adopted for continuous casting.
FIG. 5 is a sectional view showing a mounting construction of an air seal pipe for pouring liquid metal from a ladle into a tundish.
FIG. 6 is a sectional view showing a structure of a known open nozzle used for continuous casting.
FIG. 7 is a schematic diagram showing a structure of a known -upper nozzle and the cracks which are produced in a gas pool formed as a straight-band-like space extending in a direction perpendicular to the axis of the upper nozzle.
FIG. 8 is a schematic diagram showing the structure of a known lower nozzle and the cracks which are produced perpendicularly to the axis of the lower nozzle.
DETAILED DESCRIPTION OF I~VENTION
As described hereinbefore, for a known gas injecting nozzle for continuous casting, a gas pool is formed as a straight-band-like space between a portion of the circumference of a porous refractory and the corresponding portion of an iron shell. This gas pool extends along the circumference of the nozzle perpendicularly to the axis of the nozzle.
For a gas injecting nozzle according to the present invention, a gas pool is formed as a corrugated-band-like space which extends along the circumference of the nozzle perpendicularly to its axis. Similarly as this, for an upper or lower nozzle, a gas pool is formed as a corrugated-band-like space. This gas pool of a corrugated-band-shape extends along at least one portion of the circumference of the nozzle, and preferably it extends along the entire circumference of the nozzle.
Since the gas pool is formed as a corrugated-band-like space, the cracks caused by thermal stress are apt to occur along the corrugated form of the gas pool and, as a result, cannot propagate in a direction perpendicular to the nozzle axis. Thus such cracks are produced only locally and the blockage of the nozzle can be prevented because a large amount of gas does not penetrate into the nozzle hole through the crack rapidly.
The gas pool can take any smooth corrugated shape.
Preferably the width (W) of the corrugated gas pool should be 2l56988 smaller than the depth (H) of its groove-like portion (see FIG.
3), because, in this condition, a crack produced in a direction perpendicular to the nozzle axis encounters the nearest ridge or groove in the course of its propagation and stops at this ridge or groove.
Furthermore the designing and production of a porous refractory can be made easier by employing a sinusoidal shape for the corrugated-band-like gas pool. When this sinusoidal shape is used, the gas pool preferably extends along at least one portion of the circumference of the nozzle, and more preferably it extends along the entire circumference of it. Moreover it is desirable that the gas pool has a sinusoidal shape of 1 cycle or more along the circumference of the nozzle.
Example 1 FIG. 1 shows a gas injecting nozzle according to the first embodiment of the present invention, in which a corrugated-band-like gas pool located in the middle portion of the upper nozzle 10 extends in a direction perpendicular to the nozzle axis and has a corrugated-band-like shape in the direction of the nozzle axis.
Example 2 FIG. 2 shows the lower nozzle 20 which is provide with a corrugated-band-like gas pool 1 similar as that of the upper nozzle 10 shown in FIG. 1.
FIG. 3 shows the details of the corrugated-band-like gas pool 1 of the lower nozzle 20 shown in FIG. 2.
FIG. 3(a) shows the shape of the gas pool 1 in its vertical section.
FIG. 3(b) shows an illustration of the gas pool 1 which is developed in one plane. For preventing the concentration of thermal stress, it is desirable that this corrugated-band-like gas pool extends in a direction perpendicular to the nozzle axis and its shape draws a curve as smoothly as possible.
Thus, in order to prevent the occurrence of cracks induced by the concentration of thermal stress, it is desirable that each of the curves of the ridges and grooves of the corrugated-band-like shape has the same radius (R). Preferably this corrugated shape has at least one cycle along the circumference of the porous refractory.
In addition to this, it is desirable that the width (W) of the corrugated-band-like gas pool is smaller than the depth (H) of its groove-like portion as shown in FIG. 3(b). Because, when W is larger than H, a crack produced in the gas pool propagates around the circumference in a direction perpendicular to the nozzle axis, while, when W is smaller than H, such a crack must encounter the nearest groove or ridge of the corrugated-band-like shape in the course of its propagation and stop at it, which makes it possible to prevent the propagation of the crack around the circumference.
It is preferable that the corrugated-band-like shape of the gas pool draws a smooth curve as described hereinbefore. It is more preferable that the curve of this corrugated-band-like shape is sinusoidal. Because such a sinusoidal shape has a regularity and facilitates the designing and manufacture of the nozzle. The gas pool of the upper nozzle can also take a corrugated-band-like shape similar as the upper nozzle.
Thus it is possible that the tensile stress which can be produced in the axial direction of the nozzle during the early stages or the succeeding stages of pouring is prevented from causing a crack to occur in a direction perpendicular to the nozzle axis.
21$6988 As one embodiment of the present invention, a performance comparison test was conducted between an immersion nozzle connected to an upper nozzle and a lower nozzle each of which has a gas pool of a 6-cycle sinusoidal shape along its circumference and an immersion nozzle connected to an upper nozzle and a lower nozzle each of which has a conventional gas pool of a simple-band-like shape.
In this comparison test, in order to simulate the behavior of each of these immersion nozzles in the course of pouring, the variations of their back pressures (mmAq) were measured while heating each of their nozzle holes by a burner and introducing Ar gas into it at a flow rate of 5 l/min.
Furthermore the porous refractory material used in this test was of a high alumina material (Al20~) content of not less than 80~) which had a porosity of 18 to 22 %, a bulk specific gravity of 2.9 to 3.0 g/cm3, compression strength of 15 to 60 MPa/cm2, and an average pore diameter of S to 60 ~m.
The results of the test are listed in Table. 1. As shown in this table, the back pressure of the conventional immersion nozzle began to decrease in the vicinity of 900 ~C. In contrast to this, the immersion nozzle connected to a gas injecting nozzle according to the present invention did not exhibit such a phenomenon and no crack was developed in its porous refractory.
Moreover an immersion nozzle connected to a gas injecting nozzle according to the present invention was actually applied to continuous casting of steel and its nozzle blockage condition during this casting was investigated. The result of this investigation showed that almost no blockage of the nozzle caused by alumina inclusions was observed.
In this embodiment, as described hereinbefore, the present invention has been described mainly in connection with upper and lower nozzles of an immersion nozzle used for continuous casting.
21$6988 However the application of the concept of the present invention is not limited to these nozzles. The present invention can be applied to an air seal pipe as shown in FIG. 5 and to an open nozzle as shown in FIG. 6.
As described above, in a gas injecting nozzle according to the present invention, a gas pool located between an iron shell and an inner porous refractory extends along the circumference of the nozzle in a direction perpendicular to the nozzle axis in a form that a band-like gas pool corrugates in the direction of the nozzle axis. Therefore it is possible to easily prevent the thermal stress produced in the axial direction of the nozzle from causing the occurrence of cracks in a direction perpendicular to the nozzle axis.
Thus it is possible to prevent the accumulation of alumina inclusions or the like on the inner surface of the nozzle hole and, thereby, to perform gas injection OI long-duration in the course of liquid metal casting. Therefore smooth and long-duration casting can be achieved. The present invention makes it possible to produce high-quality, continuous castings and other ingots and will provide great industrial benefits.
21$6988 Temperature(C)1Present Invention2 Prior Art2 Room Temp. 400 400 Notes l:The temperature of the nozzle hole heated by a burner.
2:The back pressure (mmAq) measured when Ar gas was injected into the nozzle at the flow rate of 5 l/min.
Claims (3)
1. A gas injecting nozzle for continuous casting, wherein (a) the nozzle comprises of a porous refractory, (b) a circumference of the nozzle is surrounded by a iron shell which has a gas injection pipe, a band-like space (referred to as a gas pool hereinafter) which extends along the circumference of the nozzle perpendicularly to an axis of the nozzle is provided between the porous refractory and the iron shell, and (c) the gas pool is formed as a corrugated-band-like space along at least one portion of the circumference of the nozzle.
2. A gas injecting nozzle according to claim 1, wherein a width (W) of the gas pool is smaller than a depth (H) of its groove-like portion.
3. A gas injecting nozzle according to claim 1, wherein a width (W) of the gas pool is smaller than a depth (H) of its groove-like portion, a corrugated-band-like shape of the gas pool is sinusoidal, and the circumference of the nozzle has a shape of a sinusoidal wave of 1 cycle or more.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7-152765/1995 | 1995-05-29 | ||
| JP15276595A JP2797068B2 (en) | 1995-05-29 | 1995-05-29 | Gas injection nozzle |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2156988A1 CA2156988A1 (en) | 1996-11-30 |
| CA2156988C true CA2156988C (en) | 2001-10-30 |
Family
ID=15547666
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2156988 Expired - Fee Related CA2156988C (en) | 1995-05-29 | 1995-08-25 | Gas injection nozzle for pouring liquid metal |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP2797068B2 (en) |
| CA (1) | CA2156988C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4815821B2 (en) * | 2005-02-28 | 2011-11-16 | Ｊｆｅスチール株式会社 | Continuous casting method of aluminum killed steel |
| JP5849982B2 (en) * | 2013-03-26 | 2016-02-03 | Ｊｆｅスチール株式会社 | Continuous casting method of steel with excellent hydrogen-induced cracking resistance |
-
1995
- 1995-05-29 JP JP15276595A patent/JP2797068B2/en not_active Expired - Lifetime
- 1995-08-25 CA CA 2156988 patent/CA2156988C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2156988A1 (en) | 1996-11-30 |
| JP2797068B2 (en) | 1998-09-17 |
| JPH08318354A (en) | 1996-12-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |