Title of Invention

METHOD OF PRODUCING ANTI-ALUMINA-BUILDUP IMMERSION NOZZLE FOR CONTINUOUS CASTING

Abstract Disclosed is a method of producing an immersion nozzle for continuous casting, which comprises integrally molding a first zirconia-graphite compound applied to a powder-line portion of the nozzle, and a second compound applied to at least an inner hole portion of the nozzle. The second compound includes 10 mass% or more of clinker particles each containing CaO as a mineral phase, and the surface of at least a part of the clinker particles is subjected to an anti-hydration treatment, such as a heat treatment to be performed under a CO2 atmosphere to convert CaO to CaCO3. The method of the present invention can suppress volume expansion caused by the reaction between CaO and water released from resin added as binder, so as to prevent the occurrence of cracks during a burning process of the molded piece.
Full Text METHOD OF PRODUCING ANTI-ALUMINA-BUILDUP IMMERSION
NOZZLE FOR CONTINUOUS CASTING
TECHNICAL FIELD
The present invention relates to a method of producing an immersion nozzle for
continuous casting, and more particularly to a method of producing an anti-alumina-buildup
immersion nozzle with an inner hole whose wall surface serving as a molten-steel flow passage
is formed of a CaO-containing material to prevent buildup of alumina thereon.
BACKGROUND ART
With increasingly strict quality control demanded of steel products, the buildup of
non-metallic inclusions, such as alumina, on the wall surface of an inner hole of a submerged or
immersion nozzle has a serious disadvantage for steel production. Therefore, a good deal of
effort has been made to reduce the buildup of non-metallic inclusions, such as alumina, on the
wall surface of an inner hole of an immersion nozzle for continuous casting (hereinafter referred
to as "immersion nozzle" or "nozzle").
As one of measures against the alumina buildup, there has been known a technique in
which argon gas is injected from the inner surface of a nozzle into molten steel to prevent the
alumina buildup in physical manner. In this technique, if the argon gas is injected excessively,
bubbles of the injected argon gas will be incorporated into molten steel to form pinholes in slabs.
Thus, due to the restriction in the allowable injection amount of argon gas, this method cannot
be fully employed as a sufficient measure to prevent alumina buildup.
There has also been known a technique intended to provide an anti-alumina-buildup
function to refractories themselves. For example, Japanese Patent Laid-Open Publication No.
57-71860 discloses a casting nozzle using refractories including a combination of graphite and
either one of sintered calcia, fused calcia and another ceramic material containing a CaO
component. This invention is intended to induce a reaction between CaO contained in the
refractories and alumina attached on the wall surface of a nozzle inner hole so as to form a

low-melting-point or fusible substance to prevent the alumina buildup.
Such CaO-containing refractories exhibit a certain level of anti-alumina-buildup effect.
In particular, refractories using a clinker containing CaO as a mineral phase, such as
calcia-magnesia clinkers including calcia clinker and dolomite clinker, have an excellent effect.
For this reason, immersion nozzles have been increasingly produced by integrally molding
a compound using a clinker containing CaO as a mineral phase, which is applied to only an
inner hole portion of an immersion nozzle or an nozzle body including the inner hole portion,
and a zirconia-graphite compound applied to a powder-line portion of the nozzle, and then
burning the molded piece in a reduction atmosphere.
This production method involves a problem concerning cracks to be generated at the
boundary between the different compositions during the burning process. This would be
because phenol resin, which is added to the CaO-containing refractories at about several % to
less than 20% as a binder or for forming a carbon bond in the refractory matrix, decomposes
during heating to release water therefrom, and the resulting hydration reaction between the
water and the CaO contained as a mineral phase in the clinker causes volume expansion
different from the expanding behaviors in other portions during heating.
Japanese Patent Laid-Open Publication No. 2000-514394 proposes one measure against
this problem, in which a CaO-containing powder is added into a zirconia-graphite compound for
use in a powder-line portion so as to equalize expanding behavior in each portion to prevent the
occurrence of cracks. However, the CaO-containing powder added to the zirconia-graphite
compound causes deterioration in corrosion resistance, resulting in undesirably deteriorated
durability of a powder-line portion to be formed of the compound.
DISCLOSURE OF INVENTION
In view of the problem in the conventional immersion-nozzle production method
comprising integrally molding a zirconia-graphite compound applied to a powder -line portion of
an immersion nozzle, and a compound using a clinker containing CaO as a mineral phase, which
is applied to at least an inner hole portion of the nozzle to prevent alumina buildup, and then
burning the molded piece in a reduction atmosphere, it is therefore an object of the present

invention to provide an improved immersion-nozzle production method capable of preventing
the occurrence of cracks to be generatodduring the burning process.
work Through researchwork to wards solving the above conventional problem, the inventor
found that one factor of the occurrence of cracks as the problem in the conventional production
method, or the volume expansion arising during the burning process, can be prevented by
subjecting the clinker containing CaO as a mineral phase to an anti-hydration treatment so as to
suppress the hydration reaction between the CaO and the water released from the resin. The
present invention has been accomplished based on this knowledge.
Specifically, the present invention provides a method of producing an immersion nozzle
for continuous casting, which has zirconia-graphite refractories applied to a powder-line portion
thereof. The method comprises integrally molding the zirconia-graphite refractories, and a
compound applied to at least an inner hole portion of the immersion nozzle. The compound
includes 10 weight % or more of clinker particles each containing CaO as a mineral phase,
wherein the surface of at least a part of the particles is subjected to an anti-hydration treatment.
The anti-hydration treatment for the clinker containing CaO as a mineral phase may
specifically performed by converting the CaO exposed outside from the surface of the clinker
particle, to a compound nonreactive with water, or by coating the entire clinker particle with a
film impermeable to water.
In the former treatment, the CaO may be converted to a water-stable compound, such as
CaCO3, CaSO4 or Ca3 (PO4)2 For example, the CaO may be converted to CaCO3 by
subjecting untreated clinker to a heat treatment under a CO2 atmosphere at a temperature of 300
to 850°C.
In the latter treatment for coating the entire clinker particle with a film impermeable to
water, the water-impermeable film may be formed using heat-resistant resin, such as silicone
resin; pitch; or magnesium sulfate.
Among the above anti-hydration treatment, the treatment of converting the CaO exposed
outside from the surface of the clinker particle, to CaCO3, is most preferable in view of
treatment cost, anti-hydration performance, and influence on the quality of the refractories after
the burning process.

While it would be preferable to subject all of the clinker particles to the anti-hydration
treatment, only a part of the clinker particles may be subjected to the treatment as long as an
intended effect can be achieved.
The refractory compound comprising calcia-magnesia clinker including a dolomite clinker
and a calcia clinker containing CaO as a mineral phase may be a mixture of such clinkers and
binder. The refractory compound may selectively include any other suitable aggregate, such as
CaZrO3 clinker containing CaO without CaO as a mineral phase, material primarily consisting
of a CaO-SiO2 clinker and another CaO-based compound, oxide, carbide or carbon, etc.
In view of the anti-alumina-buildup function, the amount of the clinker particles each
containing CaO as a mineral phase is 10 mass% or more, preferably 20 mass% or more, even
more preferably 30 mass% or more, on the basis of 100 mass% of the entire compound. The
body of the immersion nozzle may be made of any suitable conventional material.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic sectional view of a dolomite clinker subjected to an anti-hydration
treatment in one embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the present invention will now be described in connection of
the Examples.
Table 1 shows the composition of compound including clinker particles each containing
CaO as a mineral phase, the application of a heat treatment performed under a CO2 atmosphere
to convert the CaO exposed outside from the surface of the clinker particle, to CaCO3, and the
inspection result of the presence of cracks after the burning process.
Each specimen for the testing was prepared by applying a zirconia-graphite on the
powder-line portion and a compound shown in Table 1 onto the main body or the inner hole
portion other than the powder-line portion, and carrying the whole body to CEP molding under a
pressure of 1000 Kg/cm2, or 98 Mpa, and burning under a reduction atmosphere at a
temperature of 1000°C.


In Table 1, all of the dolomite clinker particles in Inventive Examples 1 to 3 were subjected
to a heat treatment under a CO2 atmosphere, or an anti-hydration treatment. The dolomite
clinker particles in Comparative Examples 1 to 3 were conventional clinkers without application
of the anti-hydration treatment. The compound to be applied to the portion of the nozzle other
than the powder-line portion comprises either one of clinkers as shown in Table 1, which
contains CaO as a mineral phase. This compound was prepared by homogenously kneading
the clinker particles and an appropriate amount of phenol resin added thereto. The
zirconia-graphite compound comprises 90 mass% of zirconia and 10 mass% of graphite. The
zirconia-graphite compound was prepared by homogenously kneading the zirconia, the graphite
and an appropriate amount of phenol resin added thereto, and commonly applied to all of the
immersion nozzles in Table 1.
FIG. 1 is a schematic sectional view of the dolomite clinker particle as shown in Table 1,
which is subjected to an anti-hydration treatment for converting CaO contained in the clinker
particle and exposed outside from the surface of the clinker particle, to CaCO3.
Each of Inventive Examples 1 to 3 using the clinker particles subjected to the
anti-hydration treatment could avoid the occurrence of cracks during the burning process. In

contrast, all of Comparative Examples 1 to 3 had transverse cracks at the boundary between the
CaO-containing refractories and the zirconia-graphite refractories.
Table 1 also shows Inventive Examples 4 to 6 each of which includes calcia clinker
particles and dolomite clinker particles which are subjected to the heat treatment under a CO2
atmosphere, or the anti-hydration treatment. The dolomite clinker particles in Comparative
Examples 4 to 6 were conventional clinkers without application of the anti-hydration treatment.
In Inventive Examples 4 to 6 and Comparative Examples 4 to 6, the nozzle body was formed of
a magnesia-graphite compound prepared by adding an appropriate amount of phenol resin to 70
mass% of magnesia and 30 mass% of graphite, and homogenously kneading them. A
compound including clinker particles each containing CaO as a mineral phase was applied only
to the inner hole portion.
As seen in the results of Inventive Examples 4 to 6 and Comparative Examples 4 to 6, each
of Inventive Examples using the clinker particles subjected to the anti-hydration treatment could
avoid the occurrence of cracks during the burning process. In contrast, all of Comparative
Examples had transverse cracks at the boundary between the zirconia-graphite refractories and
the magnesia-graphite refractories, a part of which extended toward the outer periphery of the
nozzle.
As mentioned above, the method of the present invention can provide an immersion nozzle
for continuous casting, with an excellent anti-alumina-buildup function, while preventing the
occurrence of cracks during the burning process to provide enhanced process yield. The
obtained immersion nozzle can contribute to the improvement in operational efficiency of
continuous casting and in steel quality.
INDUSTRIAL APPLICABILITY
The present invention is applicable to the production of an immersion nozzle for
continuous casting, which uses a material containing CaO in the wall surface of an inner hole of
the nozzle serving as a molten-steel flow passage to prevent alumina buildup.

We Claim:
1. A method of producing an immersion nozzle for continuous
casting, which has zirconia-graphite refractories applied to a
powder-line portion hereof, said method comprising:
integrally molding said zirconia-graphite refractories, and a
compound applied to at least an inner hole portion of said
immersion nozzle, said compound including 10 mass% or more of
clinker particles each containing CaO as a mineral phase, wherein
the surface of at least a part of said clinker particles is subjected to
an anti-hydration treatment.
2. The method as claimed in claim 1, wherein said anti-hydration
treatment comprises converting the CaO exposed outside from the
surface of said clinker particle, to CaCO3.

Disclosed is a method of producing an immersion nozzle for continuous
casting, which comprises integrally molding a first zirconia-graphite
compound applied to a powder-line portion of the nozzle, and a second
compound applied to at least an inner hole portion of the nozzle. The second
compound includes 10 mass% or more of clinker particles each containing
CaO as a mineral phase, and the surface of at least a part of the clinker
particles is subjected to an anti-hydration treatment, such as a heat treatment
to be performed under a CO2 atmosphere to convert CaO to CaCO3. The
method of the present invention can suppress volume expansion caused by
the reaction between CaO and water released from resin added as binder, so
as to prevent the occurrence of cracks during a burning process of the
molded piece.

Documents:

00444-kolnp-2005-abstract.pdf

00444-kolnp-2005-claims.pdf

00444-kolnp-2005-correspondence-1.1.pdf

00444-kolnp-2005-correspondence-1.2.pdf

00444-kolnp-2005-correspondence-1.3.pdf

00444-kolnp-2005-correspondence.pdf

00444-kolnp-2005-description(complete).pdf

00444-kolnp-2005-drawings.pdf

00444-kolnp-2005-form-1.pdf

00444-kolnp-2005-form-18.pdf

00444-kolnp-2005-form-2.pdf

00444-kolnp-2005-form-26.pdf

00444-kolnp-2005-form-3.pdf

00444-kolnp-2005-international publication.pdf

00444-kolnp-2005-international search authority report.pdf

00444-kolnp-2005-pct other.pdf

00444-kolnp-2005-priority document.pdf

444-kolnp-2005-granted-abstract.pdf

444-kolnp-2005-granted-claims.pdf

444-kolnp-2005-granted-correspondence.pdf

444-kolnp-2005-granted-description (complete).pdf

444-kolnp-2005-granted-drawings.pdf

444-kolnp-2005-granted-examination report.pdf

444-kolnp-2005-granted-form 1.pdf

444-kolnp-2005-granted-form 18.pdf

444-kolnp-2005-granted-form 2.pdf

444-kolnp-2005-granted-form 26.pdf

444-kolnp-2005-granted-form 3.pdf

444-kolnp-2005-granted-form 5.pdf

444-kolnp-2005-granted-reply to examination report.pdf

444-kolnp-2005-granted-specification.pdf


Patent Number 230218
Indian Patent Application Number 444/KOLNP/2005
PG Journal Number 09/2009
Publication Date 27-Feb-2009
Grant Date 25-Feb-2009
Date of Filing 17-Mar-2005
Name of Patentee KROSAKIHARIMA CORPORATION
Applicant Address 1-1, Higashihama-machi, Yahatanishi-ku, Kitakyushu-shi, Fukuoka, 806-8586
Inventors:
# Inventor's Name Inventor's Address
1 HOOVER, DONALD BRUCE HILLOCK LANE 1710, YORK, PA 17403
2 OGATA, KOJI C/O KROSAKIHARIMA CORPORATION, 1-1, HIGHSHIHAMA-MACHI, YAHATANISHI-KU, KITAKYUSHU-SHI, FUKUOKA, 806-8586
PCT International Classification Number B22D 11/10
PCT International Application Number PCT/JP03/010473
PCT International Filing date 2003-08-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2002-239941 2002-08-20 Japan