TITLE OF THE INVENTION
Sliding nozzle plate
TECHNICAL FIELD
[0001]
The present invention relates to a sliding nozzle plate (hereinafter referred to as "SN plate")
which is a plate-shaped brick for use in a sliding nozzle device (hereinafter referred to as "SN
device") designed to control a flow rate of molten steel.
BACKGROUND ART
[0002]
In production of steel, an SN device is used as a means to control a flow rate of molten steel
to be discharged from a molten metal vessel, such as a ladle or a tundish. The SN device
comprises two or three SN plates each made of a refractory material and formed with a nozzle
hole. The SN plates are assembled such that they are slidably moved with respect to each other
under a constrained condition while being superimposed on each other under a surface pressure,
so as to adjust an opening between the nozzle holes to control a flow rate of molten steel.
[0003]
Therefore, an SN plate is required to have spalling resistance against thermal stress during
casting, as well as corrosion resistance against slag, inclusions, etc., in molten steel.
[0004]
Heretofore, as means to improve corrosion resistance of an SN plate, it has been known to
add a metal, such as aluminum or silicon (see, for example, Patent Document 1).
LIST OF PRIOR ART DOCUMENTS
[PATENT DOCUMENTS]
[0005]
Patent Document 1: JP 57-027968A

SUMMARY OF THE INVENTION
[PROBLEM TO BE SOLVED BY THE INVENTION]
[0006]
However, if a metal for improving corrosion resistance is added in a large amount, an
obtained SN plate will have high thermal expansibility, which leads to deterioration in spalling
resistance. Particularly, in a large-sized SN plate in which a hole diameter of a nozzle hole for
allowing molten steel to pass therethrough is greater than 50 mm (e.g., dimension A (length) =
550 mm, dimension B (width) = 250 mm, dimension C (thickness) = 45 mm), the problem of
deterioration in spalling resistance becomes prominent. More specifically, if such a large-sized
SN plate has high thermal expansibility, a practical use thereof becomes difficult, because the
high thermal expansibility is highly likely to cause a burning crack (crack occurring during
burning), and, even if no burning crack occurs, an initial crack (crack caused by spalling due to
passing of molten steel) is highly likely to occur.
[0007]
It is therefore an object of the present invention to provide an SN plate capable of being
formed in a large size while using a highly corrosion resistant and highly thermally expansible
refractory product.
[MEANS FOR SOLVING THE PROBLEM]
[0008]
The present invention provides a sliding nozzle plate which comprises a specific refractory
member having a thermal expansion rate as measured at 1500°C of 1.15 to 2.50% due to addition
of metallic aluminum, wherein the specific refractory member is arranged as a part of the sliding
nozzle plate to cover at least a practically critical region of the sliding nozzle plate, and fitted in a
refractory base member making up a portion of the sliding nozzle plate other than the specific
refractory member, through mortar, and wherein a thickness of the specific refractory member is
in a range of 15 to 25 mm.
[0009]
As used here, the term "practically critical region" conceptually means a partial region of a
sliding surface (operating surface) of an SN plate which is particularly required to have corrosion

resistance. This definition will be more specifically described later.
[EFFECT OF THE INVENTION]
[0010]
In the present invention, a specific refractory member having a high thermal expansion rate
as measured at 1500°C of 1.15 to 2.50% due to addition of a metal such as aluminum for
improving corrosion resistance of an SN plate is arranged to cover the practically critical region.
However, if an SN plate is entirely made using the same composition as that of the specific
refractory member, an influence of the deterioration in spalling resistance will become
prominent. Thus, in the present invention, the specific refractory member is arranged as a
"part" of the SN plate to cover at least the practically critical region. More specifically, in the
present invention, the specific refractory member is arranged in, or in and around, the practically
critical region particularly required to have corrosion resistance, and a portion of the SN plate
other than the specific refractory member is made of a suitable composition different from that of
the specific refractory member, to minimize a portion made up of the specific refractory member
with high thermal expansibility. This makes it possible to form a large-sized SN plate while
using the specific refractory member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
FIG. 1 is a schematic diagram illustrating a practically critical region of an SN plate
according to one embodiment of the present invention.
FIGS. 2(a) to 2(c) are schematic diagram illustrating various examples of modification of a
specific refractory member-arranging region in the SN plate.
FIGS. 3(a) and 3(b) illustrate an SN plate used in Example, wherein FIG. 3(a) is a bottom
view illustrating a sliding surface, and FIG. 3(b) is a sectional view.
FIG. 4 illustrates various CAD models corresponding to respective FEM-calculated models.
FIG. 5 is a graph illustrating an FEM calculation result of a maximum stress occurring at an
edge of a nozzle hole of an SN plate.

DESCRIPTION OF EMBODIMENTS
[0012]
In the present invention, a specific refractory member having a thermal expansion rate as
measured at 1500°C of 1.15 to 2.50% as a result of addition of a metal excellent in a corrosion
resistance-imparting effect, such as aluminum, is arranged as a part of an SN plate to cover at
least a practically critical region of the SN plate. A portion (base member) of the SN plate
other than the specific refractory member may be made up, for example, of an unburned or
burned refractory product consisting primarily of an alumina-carbon composite, which are
commonly used for SN plates.
[0013]
As used here, the term "practically critical region" means a partial region of a sliding
surface of an SN plate particularly required to have corrosion resistance. More specifically, as
illustrated in FIG. 1, in a sliding surface of an SN plate 1 according to one embodiment of the
present invention, the practically critical region corresponds to a total D of a stroke region S (a
region to be subjected to direct contact with molten steel during actual casting operation) and a
nozzle hole-surrounding region H. In FIG. 1, S1 indicates a distance between respective center
positions of a nozzle hole at fully opened and fully closed positions, and a indicates a width of
the nozzle hole-surrounding region H. The distance S1 is determined by specifications of an
SN device. The width a is a so-called safe or margin dimension, and preferably set in the range
of 10 to 30 mm. If the width a is less than 10 mm, the base member is likely to exposed to
molten steel due to chipping of a edge of the nozzle hole. Moreover, such a structure can be
hardly produced. Even if it can be successfully produced, process yield will be significantly
deteriorated. On the other hand, if the width a is greater than 30 mm, an influence of the
deterioration in spalling resistance will become prominent.
[0014]
In the present invention, the specific refractory member is arranged as a part of the SN plate
to cover at least the practically critical region D illustrated in FIG. 1. For example, the specific
refractory member may be arranged only in the practically critical region D illustrated in FIG. 1.
Alternatively, as illustrated in FIGS. 2(a), 2(b) and 2(c), the specific refractory member may be

arranged in one of a region D1, a region D2 and a region D3 each covering the practically critical
region D illustrated in FIG. 1.
[0015]
The specific refractory member for use in the SN plate of the present invention is made of a
composition containing a raw material excellent in a corrosion resistance-imparting effect. For
example, the raw material excellent in a corrosion resistance-imparting effect includes metallic
aluminum, magnesium oxide and chromium oxide. Such a raw material leads to an increase in
thermal expansibility of the SN plate, which has an adverse impact on spalling resistance. For
example, when metallic aluminum is added to an alumina-carbon based SN plate material in an
amount of 5 mass%, corrosion resistance is improved, whereas a thermal expansion rate is
increased to 1.15%, which is liable to crack during use of an obtained refractory product due to
its high thermal expansibility. The raw material excellent in a corrosion resistance-imparting
effect brings out the corrosion resistance-imparting effect when it is added in an amount
corresponding to a thermal expansion rate of up to 2.50%. However, even if it is added in an
amount corresponding to a thermal expansion rate of greater than 2.50%, further corrosion
resistance-imparting effect cannot be expected. In either case, although the SN plate having a
thermal expansion rate of 1.15 to 2.50% becomes highly corrosion resistant, it cannot be uses as
an SN plate, particularly a large-sized SN plate, due to a problem of burning crack during
production, or crack (initial crack) caused by spalling during use. The present invention is
intended to improve the above problem by limiting the use of the refractory product having a
thermal expansion rate as measured at 1500°C of 1.15 to 2.50%, i.e., the specific refractory
member, to a part of an SN plate covering at least the practically critical region
[0016]
A thickness of the specific refractory member is set in the range of 15 to 25 mm. If the
thickness of the specific refractory member is less than 15 mm or greater than 25 mm, a
maximum stress occurring in an edge of a nozzle hole will be increased (see an aftermentioned
FEM calculation result), which raises concerns about a problem of chipping of the edge or crack.
[0017]
Preferably, an outer peripheral edge of a bottom portion of the specific refractory member is

cut. The cutting the outer peripheral edge of the bottom portion of the specific refractory
member makes it possible to improve efficiency of an operation for setting the specific refractory
member to a region covering the practically critical region. Preferably, the outer peripheral
edge of the bottom portion of the specific refractory member is cut with R5 or more, or cut with
C5 or more, to significantly bring out the above advantageous effect.
[EXAMPLE 1]
[0018]
An SN plate as an inventive sample was produced by arranging the specific refractory
member as a part of the SN plate to cover a practically critical region of the SN plate. Further,
an SN plate as a comparative sample was produced by forming the entire SN plate using the
same composition as that of the specific refractory member in the inventive sample.
[0019]
(Example 1-1)
The produced SN plate had a shape as illustrated in FIGS. 3(a) and 3(b). In Example 1-1,
the dimension A (length), the dimension B (width) and the dimension C (thickness) were set to
500 mm, 250 mm and 40 mm, respectively. In an inventive sample, under the condition that a
distance S1 between respective center positions of a nozzle hole at fully opened and fully closed
positions, a hole diameter φ of the nozzle hole, a margin dimension al in a sliding direction of
the SN plate and a margin dimension α2 in a direction perpendicular to the sliding direction of
the SN plate were set, respectively, to 250 mm, 100 mm, 10 mm and 25 mm, a specific
refractory member 1 a was arranged in a region D4 defined by a length in the sliding direction of
the SN plate (S1+ φ + 2 x α1) of 370 mm and a length in the direction perpendicular to the
sliding direction (φ + 2 x α2) of 150 mm, with a thickness of 20 mm. The region D4 covers the
practically critical region D described in connection with FIG. 1.
[0020]
The specific refractory member was prepared by subjecting a composition consisting of 92
mass% of alumina powder, 3 mass% of carbon powder and 5 mass% of metallic aluminum
powder to mixing, drying and burning. The specific refractory member had a thermal
expansion rate as measured at 1500°C of 1.15%, and an acoustic velocity-based elastic modulus

of 80 GPa (Composition A in Tables 3 and 4).
[0021]
In the inventive sample, the specific refractory member was limitedly used in the region D4,
and an alumina-carbon based refractory product prepared by subjecting a composition consisting
of 95 mass% of alumina powder, 3 mass% of carbon powder and 3 mass% of metallic silicon
powder to mixing, drying and burning was used in a region other than the region D4 (i.e., used as
a refractory base member). Specifically, the SN plate as the inventive sample was produced by
preparing a specific refractory member having a shape corresponding to the region D4, and
fitting the specific refractory member into the refractory base member through mortar. On the
other hand, in a comparative sample, the above composition of the specific refractory member
was used to form the entirety of the SN plate illustrated in FIGS. 3(a) and 3(b). Specifically, in
the comparative sample, the above composition of the specific refractory member was formed
into a shaped body corresponding to the entire SN plate, and the shaped body was subjected to
drying and burning.
[0022]
As a result of the production, the inventive sample was obtained as a satisfactory SN plate
without occurrence of crack. On the other hand, the comparative sample had visually
observable cracks, and it was evaluated that the comparative sample cannot be practically used.
[0023]
(Example 1-2)
The specific refractory member was prepared by subjecting a composition consisting of 87
mass% of alumina powder, 3 mass% of carbon powder and 10 mass% of metallic aluminum
powder to mixing, drying and burning, and an SN plate as an inventive sample was produced in
the same manner as that in Example 1-1. The specific refractory member in the inventive
sample had a thermal expansion rate as measured at 1500°C of 1.33%, and an acoustic
velocity-based elastic modulus of 120 GPa (Composition C in Tables 3 and 4). On the other
hand, in a comparative sample, the above composition of the specific refractory member was
used to form the entirety of the SN plate illustrated in FIGS. 3(a) and 3(b).
[0024]

As a result of the production, in the inventive sample formed by limitedly using the specific
refractory member in the region D4, although fine cracks were observed in the specific refractory
member, any crack connecting to a refractory base member surrounding the specific refractory
member was not observed, and it was therefore evaluated that the fine cracks are not particularly
problematic in terms of practical use. On the other hand, the comparative sample formed by
using the composition of the specific refractory member in the entirety of the SN plate had a
large number of cracks, and it was therefore evaluated that the comparative sample cannot be
practically used.
[0025]
(Example 1-3)
The specific refractory member was prepared by subjecting a composition consisting of 92
mass% of magnesia powder, 3 mass% of carbon powder and 5 mass% of metallic aluminum
powder to mixing, drying and burning, and an SN plate as an inventive sample was produced in
the same manner as that in Example 1-1. The specific refractory member in the inventive
sample had a thermal expansion rate as measured at 1500°C of 2.50%, and an acoustic
velocity-based elastic modulus of 80 GPa (Composition Din Tables 3 and 4). On the other
hand, in a comparative sample, the above composition of the specific refractory member was
used to form the entirety of the SN plate illustrated in FIGS. 3(a) and 3(b).
[0026]
As a result of the production, in the inventive sample formed by limitedly using the specific
refractory member in the region D4, although fine cracks were observed in the specific refractory
member, any crack connecting to a refractory base member surrounding the specific refractory
member was not observed, and it was therefore evaluated that the fine cracks are not particularly
problematic in terms of practical use. On the other hand, the comparative sample formed by
using the composition of the specific refractory member in the entirety of the SN plate had a
large number of cracks, and it was therefore evaluated that the comparative sample cannot be
practically used.
[0027]
As above, it was ascertained that, when the specific refractory member is limitedly used to

cover at least the practically critical region according to the present invention, a large-sized SN
plate can be produced without crack causing practical use problems.
[0028]
In the above inventive samples, a burned refractory product is used as the refractory base
member to be used in a region other than the region D4. Alternatively, an unburned refractory
product may be used as the refractory base member.
[EXAMPLE 2]
[0029]
A relationship between a thickness of the specific refractory member arranged in the
practically critical region and a maximum stress occurring in an edge of the nozzle hole was
calculated by FEM.
[0030]
The FEM calculation was performed under the following conditions.

CosmosWorks 2007 MSC. Marc 2008

A 1/2-size CAD model was formed. Based on the CAD model, an FEM model was
formed using 4-node quadrangle elements. A reference length for mesh division was set to 5
mm.

Initial temperature:
Nozzle hole (opening: 50%): 1550°C, 1.16 × 10-3 W/mm2 • K
Outer peripheral side: 25°C, 1.16 × 10-5 W/mm2 • K
Time step: 1 second/step, for 20 seconds

Initial temperature: 25°C
Giving displacement constraint in consideration of symmetry
Giving constraint in Y-direction for suppressing rotation
Giving displacement constraint in X-direction

Calculating thermal stress from thermal analysis result
[0031]
Table 1 illustrates a model number and a condition, and FIG. 4 illustrates CAD models
corresponding to models 1 to 5 illustrated in Table 1. As illustrated in Table 1 and FIG. 4, in
the models 1 to 5, the thickness of the specific refractory member la to be arranged in a region
covering the practically critical region of the SN plate (the region D4 in FIGS. 3(a) and 3(b)) was
changed in the range of 5 to 25 mm. The model 6 is an example in which no specific refractory
member is arranged.
[0032]

[0033]
The FEM calculation was performed under the condition that a heating region is set to the
nozzle hole, and an outer periphery of the nozzle plate is cooled. Further, physical property
values used in the FEM calculation was as illustrated in Table 2.
[0034]



[0035]
Under the above conditions, a maximum stress occurring in an edge of the nozzle hole
(edge on a side of the SN plate where the specific refractory member is arranged) was calculated
by FEM. FIG. 5 illustrates the FEM calculation result. As seen in FIG. 5, when the thickness
of the specific refractory member is in the range of 15 to 25 mm, a decrease in stress is observed.
[EXAMPLE 3]
[0036]
A relationship between a composition of the specific refractory member and corrosion
resistance was checked. Table 3 illustrates compositions used.
[0037]

[0038]
As for each of the compositions A to C, components thereof were subjected to mixing,
drying and burning in non-oxidizing atmosphere, to form a burned body. As for the
composition D, components thereof were subjected to mixing and drying, to form an unburned
body. Then, a sample made of each of the compositions was lined on a crucible in a
high-frequency induction furnace, and molten steel was put in the crucible. After adding mill
scale, the molten steel was stirred for 2 hours. After the test, corrosion resistance was evaluated
based on a wear speed of each sample. For each of the samples made of the compositions, an
acoustic velocity-based elastic modulus and a thermal expansion rate as measured at 1500°C
were evaluated. The acoustic velocity-based elastic modulus was evaluated by the elastic
modulus testing method defined in JIS R 1602, and the thermal expansion rate was evaluated by

the thermal expansion testing method defined in JIS R 2207-1. Table 4 illustrates the
evaluation result.
[0039]

[0040]
In Table 4, corrosion resistance of each of four samples made of the respective
compositions was represented by an index determined on the assumption that a wear speed of the
sample made of the composition A is 100, wherein a smaller value indicates better corrosion
resistance. As seen in Table 4, corrosion resistance tends to be improved as the acoustic
velocity-based elastic module becomes higher, which shows that the corrosion resistance is
improved by densification of a refractory microstructure along with an increased in elastic
modulus.
EXPLANATION OF CODES
[0041]
1: SN plate
1 a: specific refractory member
D: practically critical region
D1 to D4: region covering practically critical region
S: stroke region
H: nozzle hole-surrounding region

WE CLAIM
1. A sliding nozzle plate comprising a specific refractory member having a thermal expansion
rate as measured at 1500°C of 1.15 to 2.50% due to addition of metallic aluminum, wherein the
specific refractory member is arranged as a part of the sliding nozzle plate to cover at least a
practically critical region of the sliding nozzle plate, and fitted in a refractory base member
making up a portion of the sliding nozzle plate other than the specific refractory member,
through mortar, and wherein a thickness of the specific refractory member is in a range of 15 to
25 mm.
2. The sliding nozzle plate as defined in claim 1, wherein an outer peripheral edge of a bottom
portion of the specific refractory member is cut.
3. The sliding nozzle plate as defined in claim 2, wherein the outer peripheral edge of the
bottom portion of the specific refractory member is cut with R5 or more, or C5 or more.
4. The sliding nozzle plate as defined in any one of claims 1 to 3, wherein the refractory base
member is made up of an unburned or burned refractory product consisting primarily of an
alumina-carbon composite.