U.S. patent application number 13/496272 was filed with the patent office on 2012-08-30 for molten metal discharge nozzle.
This patent application is currently assigned to KROSAKIHARIMA CORPORATION. Invention is credited to Arito Mizobe.
Application Number | 20120217271 13/496272 |
Document ID | / |
Family ID | 43758442 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120217271 |
Kind Code |
A1 |
Mizobe; Arito |
August 30, 2012 |
MOLTEN METAL DISCHARGE NOZZLE
Abstract
Provided is a molten metal discharge nozzle which has a bore
configuration capable of creating a low-energy loss and smooth
(stabilized) molten metal flow to suppress the occurrence of an
adhesion matter. In the molten metal discharge nozzle, a radius
r(0) of an upper end (12) of a bore (11) thereof is 1.5 times or
more a radius r(L) of a lower end (13) of the bore, and a
cross-sectional shape of a bore wall surface 14 taken along an axis
of the bore has no bend point. Further, a radius r(z) of the bore
at a position downwardly away from the upper end of the bore by a
distance z (where L is an axial length of the bore) is in a range
between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+z]].sup.1/1.5.tim-
es.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+z]].sup.1/6.times.r-
(L).
Inventors: |
Mizobe; Arito; (Fukuoka,
JP) |
Assignee: |
KROSAKIHARIMA CORPORATION
Fukuoka
JP
|
Family ID: |
43758442 |
Appl. No.: |
13/496272 |
Filed: |
June 2, 2010 |
PCT Filed: |
June 2, 2010 |
PCT NO: |
PCT/JP2010/059308 |
371 Date: |
May 16, 2012 |
Current U.S.
Class: |
222/591 |
Current CPC
Class: |
B22D 41/50 20130101 |
Class at
Publication: |
222/591 |
International
Class: |
B22D 41/50 20060101
B22D041/50 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2009 |
JP |
2009-214718 |
Claims
1. A molten metal discharge nozzle having in an axial direction
thereof a bore for allowing passage of molten metal, wherein: a
radius r(0) of an upper end of the bore is 1.5 times or more a
radius r(L) of a lower end of the bore; a line indicative of a wall
surface of the bore in a cross-section taken along an axis of the
bore has no bend point; a radius r(1/4 L) of the bore at a position
downwardly away from the upper end of the bore by a distance of 1/4
L (where L is an axial length of the bore) is in a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+1/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+1/4
L]].sup.1/6.times.r(L); a radius r(1/2 L) of the bore at a position
downwardly away from the upper end of the bore by a distance of 1/2
L is in a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+1/2
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+1/2
L]].sup.1/6r(L); and a radius r(3/4 L) of the bore at a position
downwardly away from the upper end of the bore by a distance of 3/4
L is in a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+3/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+3/4
L]].sup.1/6r(L).
Description
TECHNICAL FIELD
[0001] The present invention relates to a molten metal discharge
nozzle designed to be installed in a bottom of a molten metal
vessel to discharge molten metal from the molten metal vessel, and
configured such that it has in an axial direction thereof a bore
for allowing passage of molten metal,.
BACKGROUND ART
[0002] To explain a molten metal discharge nozzle by taking as an
example an upper nozzle designed to be fitted into a discharge
opening of a tundish or a ladle, alumina and other inclusions are
apt to adhere to a wall surface of a bore of the upper nozzle for
allowing passage of molten metal to form an adhesion matter
thereon, which narrows a flow passage to hinder a casting
operation, or is likely to fully clog the flow passage to preclude
the casting operation. As means for preventing the occurrence of
such an adhesion matter, for example, a method has been proposed
which is intended to provide a gas injection port to inject an
inert gas (see, for example, the following Patent Document 1 or
2).
[0003] However, due to a mechanism for gas injection, an upper
nozzle disclosed in the Patent Document 1 or 2 has a complicated
structure which requires time-consuming fabrication, and it is
necessary to supply gas during a casting operation, which leads to
an increase in cost. Moreover, even if the gas injection-type
nozzle is employed, it is difficult to completely prevent the
occurrence of the adhesion matter.
[0004] Meanwhile, a widely used type of upper nozzle includes, for
example, a type consisting of a reverse taper region formed on an
upper(upstream) side thereof and a straight region formed on a
lower(downstream) side thereof (see FIG. 8(a)), and a type having
an arc-shaped region continuously extending from the reverse taper
region and the straight region (see FIG. 9(a)). In FIGS. 2 to 9,
each diagram suffixed by (a) illustrates an upper nozzle under the
condition that it is installed in a sliding nozzle device
(hereinafter referred to as "SN device"), wherein a region downward
(downstream) of the one-dot chain line is a bore of an upper plate,
and a region downward of a position where two bores are out of
alignment is a bore of an intermediate plate or a lower plate.
[0005] A distribution of pressures to be applied to a wall surface
of a bore in an upper nozzle (length: 230 mm) having the
configuration illustrated in FIG. 8(a) during passage of molten
steel through the bore was calculated (by computer simulation-based
fluid analysis). As a result, it was ascertained that the pressure
is rapidly changed in a region beyond a position (away from an
upper(upstream) end of the bore by 180 mm) where the bore wall
surface is changed from a reverse taper configuration to a straight
configuration, as indicated by the dotted line in FIG. 8(b).
[0006] The computer simulation-based fluid analysis was performed
using fluid analysis software (trade name "Fluent Ver. 6.3.26
produced by Fluent Inc.).
[0007] Input parameters in the fluid analysis software are as
follows: [0008] The number of calculational cells: about 120,000
(wherein the number can vary depending on a model) [0009] Fluid:
water(wherein it has been verified that the evaluation for molten
steel can also be performed in a comparative manner) [0010]
Density=998.2 kg/m.sup.3 [0011] Viscosity=0.001003 kg/m s [0012]
Hydrostatic Head (H'): 1000 mm [0013] Pressure: Inlet (Molten steel
surface)=((700+a length (mm) of a nozzle).times.9.8) Pa (gage
pressure) [0014] Outlet (Lower end of the nozzle)=0 Pa [0015]
Length of Nozzle: 230 mm [0016] Viscous Model: K-omega
calculation
[0017] Further, a distribution of pressures to be applied to a wall
surface of a bore in an upper nozzle (length: 230 mm) having the
configuration illustrated in FIG. 9(a) during passage of molten
steel through the bore was calculated. As a result, it was
ascertained that the pressure is changed in an arc curve, i.e., a
pressure change is not constant, as illustrated in FIG. 9(b),
although the rapid pressure change is suppressed as compared with
the upper nozzle in which the bore wall surface is changed from the
reverse taper configuration to the straight configuration, as
illustrated in FIG. 8(a). In FIGS. 2 to 9, a region rightward of
the one-dot chain line in each graph suffixed by (b) indicates
pressures to be applied to the bore wall surface of the upper
plate.
[0018] The rapid pressure change and the arc-curved pressure change
are caused by a phenomenon that a molten steel flow is changed
along with a change in configuration of the bore wall surface from
the reverse taper configuration to the straight configuration. In a
swirling nozzle adapted to intentionally change a molten steel
flow, an adhesion matter is observed around a position where the
molten steel flow is changed. Thus, it is considered that an
adhesion matter on the bore wall surface can be suppressed by
creating a smooth molten steel flow, i.e., a molten steel flow
having an approximately constant pressure change with respect to
the bore wall surface.
[0019] As a technique for stabilizing a molten steel flow, an
invention concerning a configuration of a bore of a tapping tube
for a converter has been proposed (see, for example, the following
Patent Document 3).
[0020] However, a technique disclosed in the Patent Document 3 is
intended to prevent a vacuum area from being formed in a central
region of a molten steel flow so as to suppress entrapment of slag
and incorporation of oxygen, nitrogen, etc., but it is not intended
to prevent the occurrence of the adhesion matter. Further, the
technique disclosed in the Patent Document 3 is designed for a
converter(refining vessel), wherein the effect of preventing
entrapment of slag, etc., becomes important in a last stage of
molten steel discharge (assuming that a tapping time is 5 minutes,
the last stage is about 1 minute). On the other hand, in order to
prevent the occurrence of the adhesion matter in a ladle or a
tundish (casting or pouring vessel), it is necessary to bring out
an intended effect particularly in a certain period other than the
last stage of molten steel discharge, i.e., a desired period for
bringing out the intended effect is different.
LIST OF PRIOR ART DOCUMENTS
Patent Documents
[0021] Patent Document 1: JP 2007-090423A
[0022] Patent Document 2: JP 2005-279729A
[0023] Patent Document 3: JP 2008-501854A
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0024] It is therefore an object of the present invention to
provide a molten metal discharge nozzle having a bore configuration
capable of facilitating stabilization of a pressure to be applied
from an outer peripheral region of a molten metal flow onto a bore
wall surface, so as to create a low-energy loss and smooth molten
metal flow to suppress the occurrence of an adhesion matter.
Means for Solving the Problem
[0025] The present invention provides a molten metal discharge
nozzle having in an axial direction thereof a bore for allowing
passage of molten metal, wherein: a radius r(0) of an upper end of
the bore is 1.5 times or more a radius r(L) of a lower end of the
bore; a line indicative of a wall surface of the bore in a
cross-section taken along an axis of the bore has no bend point; a
radius r(1/4 L) of the bore at a position downwardly away from the
upper end of the bore by a distance of 1/4 L (where L is an axial
length of the bore) is in a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+1/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+1/4
L]].sup.1/6.times.r(L); a radius r(1/2 L) of the bore at a position
downwardly away from the upper end of the bore by a distance of 1/2
L is in a range between [[L/{(r(0)/r(L)).sup.1.5-1}+L]/
[L{r(0)/r(L)).sup.1.5-1}+1/2 L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+1/2
L]].sup.1/6.times.r(L); and a radius r(3/4 L) of the bore at a
position downwardly away from the upper end of the bore by a
distance of 3/4 L is in a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+3/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+3/4
L]].sup.1/6.times.r(L).
EFFECT OF THE INVENTION
[0026] The molten metal discharge nozzle of the present invention
can suppress the occurrence of an adhesion matter on the wall
surface of the bore during passage of molten metal
therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a vertical cross-sectional view illustrating one
example of an upper nozzle according to the present invention.
[0028] FIGS. 2(a) and 2(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein n=4.
[0029] FIGS. 3(a) and 3(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein n=6.
[0030] FIGS. 4(a) and 4(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein n=1.
[0031] FIGS. 5(a) and 5(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein n=7.
[0032] FIGS. 6(a) and 6(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein n=4, and a radius ratio=1.5.
[0033] FIGS. 7(a) and 7(b) are, respectively, a diagram
illustrating a configuration of an upper nozzle, and a graph
illustrating a pressure distribution during passage of molten steel
through the upper nozzle, wherein the radius ratio=1.
[0034] FIGS. 8(a) and 8(b) are, respectively, a diagram
illustrating a configuration of a conventional upper nozzle, and a
graph illustrating a pressure distribution during passage of molten
steel through the conventional upper nozzle.
[0035] FIGS. 9(a) and 9(b) are, respectively, a diagram
illustrating a configuration of a conventional upper nozzle, and a
graph illustrating a pressure distribution during passage of molten
steel through the conventional upper nozzle.
[0036] FIG. 10 is a schematic axial cross-sectional view
illustrating a tundish and an upper nozzle.
[0037] FIG. 11 shows Table 1.
[0038] FIG. 12 shows Table 2.
[0039] FIG. 13 shows Table 3.
DESCRIPTION OF EMBODIMENTS
[0040] The present invention will now be specifically described
based on an embodiment thereof by taking an upper nozzle as an
example.
[0041] FIG. 1 is a cross-sectional view illustrating one example of
an upper nozzle according to the present invention, taken along an
axial direction of a bore thereof for allowing passage of molten
steel. As illustrated in FIG. 1, an upper nozzle 10 according to
the present invention is formed with a bore 11 for allowing passage
of molten steel, wherein the bore has a large-diameter end 12
adapted to be fitted into a discharge opening of a tundish or a
ladle, a small-diameter end 13 adapted to discharge molten steel
therefrom, and a bore wall surface 14 continuously extending from
the large-diameter end 12 to the small-diameter end 13.
[0042] The upper nozzle 10 according to the present invention is
configured such that a radius r(0) of an upper end (large-diameter
end 12) of the bore is 1.5 times or more a radius r(L) of a lower
end (small-diameter end 13) of the bore, and a line indicative of
the bore wall surface 14 in a cross-section taken along an axis of
the bore 11 has no bend point. Further, a radius r(1/4 L) of the
bore 11 at a position downwardly away from the upper end of the
bore by a distance of 1/4 L, a radius r(1/2 L) of the bore at a
position downwardly away from the upper end of the bore by a
distance of 1/2 L, and a radius r(3/4) of the bore at a position
downwardly away from the upper end of the bore by a distance of 3/4
L (where L is an axial length of the bore 11) are, respectively, in
a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+1/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+1/4
L]].sup.1/6.times.r(L), a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+1/2
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+1/2
L]].sup.1/6.times.r(L)), and a range between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L{r(0)/r(L)).sup.1.5-1}+3/4
L]].sup.1/1.5.times.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+3/4
L]].sup.1/6.times.r(L).
[0043] In FIG. 1, a curve (line) indicated by the reference numeral
15 is a locus of a radius r(z) represented by the following
formula:
[[L/{(r(0)/r(L)).sup.1.5-1}+L]]/[L/{(r(0)/r(L)).sup.1.5-1}+z].sup.1/1.5.-
times.r(L) Formula A
, and a curve (line) indicated by the reference numeral 16 is a
locus of a radius r(z) represented by the following formula:
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{(r(0)/r(L)).sup.6-1}+z]].sup.1/6.times.-
r(L) Formula B
[0044] In other words, the present invention requires that: each of
three radii r(1/4 L), r(1/2 L), r(3/4) of the bore at respective
points by which the axial length L of the bore is divided into
quarters falls within a range between the curve 15 and the curve
16; and the line indicative of the bore wall surface 14 in a
cross-section taken along the axis of the bore 11 has no bend
point.
[0045] The above requirement for the bore configuration will be
more specifically described. On an assumption that a low-energy
loss and smooth (constant or stabilized) molten steel flow can be
created by stabilizing a pressure distribution on a bore wall
surface of an upper nozzle in its height direction, the inventors
of this application have found out a bore configuration of the
present invention capable of suppressing a rapid change in pressure
on the bore wall surface, as described below.
[0046] Although an amount of molten steel flowing through a bore of
an upper nozzle is controlled by an SN device disposed underneath
(just downstream of) the upper nozzle, energy for obtaining a flow
velocity of molten steel is fundamentally a hydrostatic head of
molten steel in a tundish. Thus, a flow velocity v (z) of molten
steel at a position away from an upper end of the bore by a
distance z is expressed as follows:
v(z)=k(2g(H'+z)).sup.1/2,
[0047] where: g is a gravitational acceleration; [0048] H' is a
hydrostatic head height of molten steel; and [0049] k is a flow
coefficient.
[0050] A flow volume Q of molten steel flowing through the bore of
the upper nozzle is a product of a flow velocity v of the molten
steel and a cross-sectional area A of the bore. Thus, the flow
volume Q is expressed as follows:
Q=v(L).times.A(L)=k(2g(H'+L)).sup.1/2.times.A(L),
[0051] where: L is a length of the bore (a length of the upper
nozzle); [0052] v (L) is a flow velocity of molten steel at a lower
end of the bore; [0053] A (L) is a cross-sectional area of the
lower end of the bore; and [0054] g is a gravitational
acceleration.
[0055] Further, the flow volume Q is constant, irrespective of a
position of a cross-section of the bore taken along a direction
perpendicular to an axis of the bore. Thus, a cross-sectional area
A(z) at a position away from the upper end of the bore by a
distance z is expressed as follows:
A(z)=Q/v(z)=k(2g(H'+L)).sup.1/2.times.A(L)/k(2g(H'+z)).sup.1/2
This formula can be expressed as follows by dividing each of the
left-hand and right-hand sides by A(L):
A(z)/A(L)=((H'+L)/(H'+z)).sup.1/2
[0056] In the above formula, A(z)=.pi.r(z).sup.2, and
A(L)=.pi.r(L).sup.2, where .pi. is a ratio of the circumference of
a circle to its diameter. Thus, the above equation is expressed as
follows:
A(z)/A(L)=.pi.r(z).sup.2/.pi.r(L).sup.2=((H'+L)/(H'+z)).sup.1/2
r(z)/r(L)=((H'+L)/(H'+z)).sup.1/4
[0057] Thus, a radius r(z) of the bore at an arbitrary position is
expressed as follows:
r(z)=((H'+L)/(H'+z)).sup.1/4.times.r(L) Formula 1
[0058] Then, the bore is configured such that the radius r(z)
thereof at an arbitrary position satisfies the Formula 1, so that a
pressure applied onto the bore wall surface is reduced gradually
and gently in a downward direction from the upper end of the nozzle
(upper end of the bore) to provide a low-energy less, smooth and
straightened molten steel flow.
[0059] The above formula for calculating the pressure distribution
using the H' is set up on an assumption that molten steel flows
into the upper end of the bore directly and uniformly in an
approximately vertical direction according to a hydrostatic head
pressure of a molten steel bath in the tundish. However, in actual
casting operations, multi-directional flows of molten steel are
formed from the vicinity of a bottom surface of the tundish
adjacent to the upper end of the nozzle serving as an inlet of a
molten steel discharge passage, toward the bore, as described
above. Thus, to accurately figure out an actual pressure
distribution in the bore, it is necessary to use a hydrostatic head
having a large influence on a flow of molten steel from the
vicinity of the bottom surface of the tundish adjacent to the upper
end of the nozzle, in place of the H'.
[0060] Therefore, the inventers carried out studies based on
various simulations. As a result, the inventers found out that it
is effective to use a value of the H' to be obtained when zero is
assigned to z in the Formula 1, as a hydrostatic head height H for
the calculation, i.e., calculational hydrostatic head height H
(hereinafter referred to simply as "H", on a case-by-case
basis).
[0061] Specifically, the H can be expressed as follows:
H=((r(L)/r(0)).sup.4.times.L)/(1-(r(L)/r(0)).sup.4)
[0062] As above, the H is defined by a ratio between the radius
r(0) of the bore at the upper end of the nozzle and the radius r(L)
of the bore at the lower end of the nozzle, and the axial length L
of the bore. This calculational hydrostatic head height H has an
influence on a pressure of molten steel within the bore of the
nozzle of the present invention. In other words, a cross-sectional
shape of the bore wall surface calculated using the H in place of
the H' in the Formula 1 makes it possible to suppress a rapid
pressure change which would otherwise occur adjacent to the upper
end of the bore.
[0063] When the H in the above formula is converted to a ratio of
the r(0) to the r(L), the formula can be transformed into the
following formula:
r(0)/r(L)=((H+L)/(H+0)).sup.1/4 Formula 2
[0064] The Formula 2 can be transformed as follows:
r(0)/r(L)=(1+L/H).sup.1/4
L/H=(r(0)/r(L)).sup.4-1
H=L/((r(0)/r(L)).sup.4-1) Formula 3
[0065] The H is indicated in FIG. 10 which is a schematic axial
cross-sectional view illustrating a tundish and an upper nozzle,
wherein the upper end of the bore is an origin (zero point) of the
distance z.
[0066] Through further researches, the inventors have found out
that the rapid pressure change which would otherwise occur adjacent
to the upper end of the bore can be suppressed by setting the
radius r(0) of the upper end of the bore to be 1.5 times or more
the radius r(L) of the lower end of the bore. This is because, if
the radius r(0) of the upper end of the bore is less than 1.5 times
the radius r(L) of the lower end of the bore, it becomes difficult
to sufficiently ensure a distance for smoothing a configuration
from the tundish or ladle to the upper nozzle, so that the
configuration is rapidly changed. Preferably, the radius r(0) of
the upper end of the bore is equal to or less than 2.5 times the
radius r(L) of the lower end of the bore, because a discharge
opening of the tundish or ladle will be unrealistically increased
along with an increase in the radius r(0) of the upper end of the
bore.
[0067] Further, on an assumption that a molten steel flow smoother
than ever before can be formed by using the calculational
hydrostatic head height H, in the Formula 1 (i.e.,
r(z)=((H'+L)/(H'+z)).sup.1/4).times.r(L)), in place of the
hydrostatic head height H' of a molten steel bath, and setting a
cross-sectional configuration of the bore wall surface of the upper
nozzle according to Formula 4:
r(z)=((H+L)/(H+z)).sup.1/n.times.r(L)) (wherein n may be any
integer other than 4), the inventors verified a pressure on a bore
wall surface in each of various upper nozzles with bore
configurations set by changing a value of the n.
[0068] The variable n is applied to the Formula 3 to express the
calculational head height H as follows:
H=L/((r(0)/r(L)).sup.n-1) Formula 5
[0069] Then, the Formula 4 can be expressed as follows by assigning
the Formula 5 thereto:
r(z)=[[L/{(r(0)/r(L)).sup.n-1}+L]/[L/{(r(0)/r(L)).sup.n-1}+z]].sup.1/n.t-
imes.r(L)] Formula 6
In other words, the radius r(z) of the bore at a position
downwardly away from the upper end of the bore by an arbitrary
distance z is expressed by the Formula 6.
[0070] In the Formula 6, r(z) for n=1.5 corresponds to the curve
(line) 15 in FIG. 1 represented by the aforementioned Formula A,
and r(z) for n=6 corresponds to the curve (line) 16 in FIG. 1
represented by the aforementioned Formula B.
[0071] The present invention will be more specifically described
based on examples. It is to be understood that that the following
examples will be shown simply by way of illustrative embodiments of
the present invention, and the present invention is not limited to
the examples.
EXAMPLE 1
[0072] In an inventive example 1, a distribution of pressures to be
applied onto a bore wall surface of an upper nozzle when a
hydraulic head height in a tundish or a ladle is 1000 mm was
calculated, wherein: a length of the upper nozzle is 230 mm; a
diameter of a large-diameter end of a bore of the upper nozzle is
140 mm; a diameter of a small-diameter end of the bore is 70 mm;
and a radius r(z) of the bore, i.e., a line indicative of the bore
wall surface in a vertical cross-section taken along an axis of the
bore, is expressed by
[[L/{(r(0)/r(L)).sup.n-1}+L]/[L/{r((0)/r(L)).sup.n-1}+z]].sup.1/n.times.r-
(L) ], where n=4 (inventive example 1), i.e.,
[[L/{(r(0)/r(L)).sup.4-1}+L]/[L/{r((0)/r(L)).sup.4-1}+z]].sup.1/4.times.r-
(L) ], as indicated by the solid line in FIG. 2(a). FIG. 2(b)
illustrates a result of the calculation on an assumption that a
pressure to be applied onto a wall surface at an upper end of a
bore of an upper nozzle illustrated in FIG. 7 as a conventional
upper nozzle is zero.
[0073] Further, a distribution of pressures to be applied onto a
bore wall surface in each of five other types of upper nozzles was
calculated and evaluated in the same manner as that in the
inventive example 1, wherein: a radius r(z) of a bore in a
respective one of the upper nozzles, i.e., a line indicative of the
bore wall surface in a vertical cross-section taken along an axis
of the bore, is derived from the Formula 6, where n=1.5 (inventive
example 2), n=2 (inventive example 3), n=6 (inventive example 4),
n=1 (comparative example 1) or n=7 (comparative example 2), i.e.,
expressed by:
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+z]].sup.1/1.5.t-
imes.r(L) ] (inventive example 2);
[[L/{(r(0)/r(L)).sup.2-1}+L]/[L/{r((0)/r(L)).sup.2-1}+z]].sup.1/2.times.r-
(L) ] (inventive example 3);
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+z]].sup.1/6.times.r-
(L)] (inventive example 4) (see FIG. 3(a));
[[L/{(r(0)/r(L)).sup.1-1}+L]/[L/{r((0)/r(L)).sup.1-1}+z]].sup.1/1.times.r-
(L)] (comparative example 1) (see FIG. 4(a)); or
[[L/{(r(0)/r(L)).sup.7-1}+L]/[L/{(r(0)/r(L)).sup.7-1}+z]].sup.1/7.times.r-
(L) ] (comparative example 2) (see FIG. 5(a)). A result of the
evaluation is illustrated in Table 1, FIG. 11.
TABLE 1
[0074] In the inventive example 1, it was verified that the
pressure is gradually changed from the upper end to the lower end
of the bore (see FIG. 2(b)). It is proven that no rapid pressure
change occurs, and a molten steel flow is approximately constant or
stabilized. In each of the inventive examples 2 (n=1.5) and 3
(n=2), it was also verified that the pressure is gradually changed
from the upper end to the lower end of the bore, as with the
inventive example 1.
[0075] In the inventive example 4 (n=6), it was verified that,
although a large pressure change is observed in an upper end region
of the bore, the pressure is subsequently gradually changed (see
FIG. 3(b)). It is proven that a molten steel flow is approximately
stabilized, except in the upper end region of the bore where the
bore is wide and therefore an adhesion matter is less likely to
cause a problem.
[0076] In the comparative example 1 (n=1), it was verified that the
pressure change from the upper end to the lower end of the inner
bore is small (see FIG. 4(b)). However, as is clear, for example,
when comparing between FIG. 2(b) and FIG. 4(b), it was verified
that a rapid pressure change occurs just after molten steel flows
from the upper nozzle into the upper plate, i.e., the molten steel
flow is rapidly changed in an area where the bore is narrow and
therefore a n is more likely to cause a problem.
[0077] It is considered that this is because the bore wall surface
of the upper nozzle has a reverse taper shape, so that a corner is
formed in a contact region with the upper plate, and a pressure
distribution curve has a very little slope, i.e., a high pressure
is maintained even at the lower end of the bore (see FIG.
4(b)).
[0078] In the comparative example 2 (n=7), the pressure is largely
changed from about 100 Pa in the upper end region of the bore, as
illustrated in FIG. 5. Specifically, it was verified that a
pressure greater than that in the conventional upper nozzle (FIG.
7) occurs in the upper end region of the bore, and subsequently the
pressure is extremely largely changed. In the comparative example
2, it is proven that the radius of the bore is sharply reduced in
the upper end region of the bore, and the molten steel flow is
rapidly changed in an area where the bore is narrow and therefore
an adhesion matter is more likely to cause a problem.
[0079] As above, in the present invention, it is proven that a
change in pressure to be applied to the bore wall surface is
approximately constant during passage of molten steel through the
bore of the upper nozzle, i.e., the molten steel flow is a
low-energy loss and stabilized flow. A molten-steel level in a
ladle will be gradually lowered from about 4000 mm, and a
molten-steel level in some tundishes is about 500 mm. However, as
mentioned above, molten metal flowing into the discharge opening is
molten metal located adjacent to the bottom surface of the tundish
or ladle. Thus, although a value of the pressure is changed due to
a change in molten-steel level height, the pressure distribution
has the same characteristic as those in the inventive and
comparative examples.
[0080] Secondly, the inventors carried out a study on a smooth
nozzle in which no corner(bend point) is formed in a bore wall
surface thereof, i.e., a nozzle in which a curve in a vertical
cross-section of a bore thereof is formed as a curve of continuous
differential values of r(z) with respect to z, i.e.,
(d(r(z))/dz).
[0081] Specifically, the inventors carried out a study on an upper
nozzle in which a curve in a vertical cross-section of a bore
thereof is smooth but it does not conform to that according to the
Formula 6, using, as criteria, three points by which the axial
length L of the bore is divided into quarters. A smooth bore
configuration having no bend point is substantially determined by
specifying total five points consisting of the upper and lower ends
of the bore and the above three points. Thus, it is considered
that, even if two upper nozzles are somewhat different from each
other in terms of bore configuration, such a difference is minor as
long as they satisfy the criteria, and they exhibit the same
tendency regarding the pressure change.
[0082] In the inventive example 5, a distribution of pressures to
be applied onto a bore wall surface of an upper nozzle was
calculated and evaluated in the same manner as that in the
inventive example 1, wherein: a length of the upper nozzle is 230
mm; a diameter of a large-diameter end of a bore of the upper
nozzle is 140 mm; a diameter of a small-diameter end of the bore is
70 mm; bore wall surfaces at the three points by which the axial
length L of the bore is divided into quarters, approximate
respective values derived from the Formula 6 where n=6, 4 and 1.5;
and the bore has no bend point. A result of the evaluation is
illustrated in Table 2, FIG. 12.
[0083] Further, a distribution of pressures to be applied onto a
bore wall surface in each of three types of upper nozzles was
calculated and evaluated in the same manner as that in the
inventive example 1, wherein radii at the three points approximate:
respective values derived from the Formula 6, where n=4, 6 and 4
(inventive example 6); respective values derived from the Formula
6, where n=2, 4 and 6 (inventive example 7); or respective values
derived from the Formula 6, where n=7, 6 and 4 (comparative example
3). A result of the evaluation is illustrated in Table 2.
TABLE 2
[0084] In the inventive example 5, it was verified that, although a
large pressure change is observed in the upper end region of the
bore, the pressure is subsequently gradually changed, as with the
inventive example 4. It is proven that a molten steel flow is
approximately stabilized, except in the upper end region of the
bore where the bore is wide and therefore an adhesion matter is
less likely to cause a problem.
[0085] In the inventive examples 6 and 7, it was verified that the
pressure is gradually changed from the upper end to the lower end
of the bore. It is proven that no rapid pressure change occurs, and
a molten steel flow is approximately stabilized.
[0086] In the comparative example 3, it was verified that a large
pressure occurs in the upper end region of the bore, and
subsequently the pressure is rapidly reduced, as with the
comparative example 2. In the comparative example 3, it is proven
that the radius of the bore is sharply reduced in the upper end
region of the bore, and the molten steel flow is rapidly changed in
an area where the bore is narrow and therefore an adhesion matter
is more likely to cause a problem.
[0087] As above, it is proven that, even if a bore configuration of
an upper nozzle is somewhat deviated from the Formula 6, an
excellent flow as compared to the conventional upper nozzle can be
created as long as bore wall surfaces at three points by which an
axial length L of a bore of the upper nozzle is divided into
quarters, approximate respective values derived from the Formula 6
where n=1.5 to 6, and the bore has no bend point.
[0088] Thirdly, the inventors carried out a study on a relationship
between a distribution of pressures to be applied onto a bore wall
surface of an upper nozzle, and an inner diameter ratio of an upper
end to a lower end of a bore of the upper nozzle.
[0089] In the inventive example 8, a distribution of pressures to
be applied onto a bore wall surface in each of three types of upper
nozzles was calculated and evaluated in the same manner as that in
the inventive example 1, wherein: a length of each of the upper
nozzles is 230 mm; a diameter of a small-diameter end of a bore in
each of the upper nozzles is 70 mm; a diameter of a large-diameter
end of the bore is 108 mm which is about 1.5 times the diameter D
of the small-diameter end (lower end) of the bore (1.54D), and a
radius r(z) of the bore is derived from the Formula 6, where n=1.5,
4 or 6, i.e., expressed by:
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+z]].sup.1/1.5.t-
imes.r(L) ];
[[L/{(r(0)/r(L)).sup.4-1}+L]/[L/{r((0)/r(L)).sup.4-1}+z]].sup.1/4.times.r-
(L) ];
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+z]].sup.1/6.t-
imes.r(L)]. A result of the evaluation is illustrated in Table 3,
FIG. 13. A result of the evaluation is illustrated in Table 3.
Further, as one example, the bore configuration and the calculation
result for n=4 are illustrated in FIG. 6.
[0090] Further, in three other cases where the diameter of the
large-diameter end of the bore is: 140 mm which is 2 times the
diameter D of the small-diameter end (lower end) of the bore (2D)
(inventive example 9); 280 mm which is 4 times (4D) (inventive
example 10); and 73 mm which is about 1 time (1.06D) (comparative
example 4), a distribution of pressures to be applied onto a bore
wall surface in the upper nozzle was calculated and evaluated,
wherein a radius r(z) of the bore is derived from the Formula 6,
where n=1.5, 4 or 6, as with the inventive example 8. A result of
the evaluation is illustrated in Table 3. Further, the bore
configuration and the calculation result in the comparative example
4 (n=4) are illustrated in FIG. 6.
TABLE 3
[0091] It was verified that, in the comparative example 4 where the
bore diameter ratio is about 1 time (1.06D), the pressure change is
large in the upper end region of the bore, whereas, in the
inventive example 8 where the bore diameter ratio is about 1.5
times (1.54D), the inventive example 9 where the bore diameter
ratio is 2 times (2D), and the inventive example 10 where the bore
diameter ratio is 4 times (4D), the pressure change is kept
approximately constant even in the upper end region of the bore.
When the configuration of the bore wall surface is represented by
the r(z), the wall surface continuously extending from the tundish
or ladle to the upper nozzle becomes smooth. Thus, a rapid pressure
change in the upper end region of the bore can be suppressed by
setting the diameter of the upper end of the bore to be 1.5 times
or more the diameter of the lower end of the bore.
[0092] Further, in view of the pressure changes in the conventional
upper nozzle and the comparative examples 1 to 4, the occurrence of
a large pressure change is observed due to the present of a corner
or a configuration similar to a corner. Thus, a molten steel flow
can be stabilized to suppress the occurrence of an adhesion matter
by providing a smooth cross-sectional configuration of a bore wall
surface having no corner(bend point), i.e., a cross-sectional
configuration based on continuous differential values of r(z) with
respect to z, i.e., (d(r(z))/dz), wherein the radius r(z) of the
bore it is in a rage between
[[L/{(r(0)/r(L)).sup.1.5-1}+L]/[L/{r((0)/r(L)).sup.1.5-1}+z]].sup.1/1.5.t-
imes.r(L) and
[[L/{(r(0)/r(L)).sup.6-1}+L]/[L/{r((0)/r(L)).sup.6-1}+z]].sup.1/6.times.r-
(L).
[0093] A configuration of an upper end region of the bore is likely
to be determined by a factor such as a configuration of a stopper.
Further, the upper end region of the bore has a relatively large
inner diameter, so that it is less likely to be affected by an
adhesion matter. On the other hand, a configuration of a lower end
region of the bore is likely to be determined in connection with
production conditions. For example, in some cases, it has to be
formed in a straight bore to allow a core or the like to be
inserted thereinto during production. In the present invention, the
lower end region of the bore is formed in a configuration close to
a straight bore, so that an influence on an anti-adhesion matter
effect is small. Therefore, the cross-section of the bore wall
surface may be formed in a configuration having no bend point,
except the upper end and lower end regions of the bore.
[0094] For example, the configuration having no bend point may
include a cross-sectional configuration based on continuous
differential values of r(z) with respect to z, such as
r(z)=[[L/{(r(0)/r(L)).sup.n-1}+L]/[L/{(r(0)/r(L)).sup.n-1}+z]].sup.1/n.ti-
mes.r(L)]. Further, a bubbling mechanism for injecting an inert
gas, such as Ar gas, may be used in combination.
[0095] Although the above embodiment has been described by taking
an upper nozzle as an example, the molten metal discharge nozzle of
the present invention is not limited to an upper nozzle, but the
present invention may be applied to any other nozzle, such as an
open nozzle, to be installed to a vessel, such as a tundish having
an approximately constant hydrostatic head height of molten
metal.
EXPLANATION OF CODES
[0096] 10: upper nozzle [0097] 11: bore [0098] 12: large-diameter
end [0099] 13: small-diameter end [0100] 14: bore wall surface
[0101] 15: bore wall surface for n=1.5 [0102] 16: bore wall surface
for n=6
* * * * *