METHOD OF USING SAME
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY
[0001] This application claims the benefit of priority of U.S. Provisional Application No.
62/037,949 filed August 15, 2014, the complete disclosure of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to impact pads used in steel-making, especially to tundish
impact pads adapted to reduce turbulence and bath surface disruption generated by a molten steel
ladle stream fed into a continuous caster tundish. The invention further relates to tundishes and
apparatus including the impact pads, and methods of using the impact pads, tundishes, and
apparatus.
BACKGROUND
[0003] A steel caster is an apparatus for carrying out continuous casting, also referred to
in the art as strand casting. Continuous casting involves transferring molten steel from a
steelmaking furnace into a ladle. From the ladle, the molten steel is fed through a shroud of the
ladle (also referred to as a ladle shroud) extending into a container or vessel referred to as a
tundish. The molten steel typically is fed at a continuous or semi-continuous liquid flow into a
molten steel bath contained in the tundish. The tundish typically acts as a reservoir from which
the molten steel may be fed, without interruption or unwanted downtime, into caster molds. In
order to protect the molten steel in the tundish from unwanted chemical reaction, e.g., excessive
oxidation, and air-borne particulates, a protective slag cover/layer or "flux" is allowed to form at
the surface of the molten steel bath.
[0004] Surface requirements and cleanliness standards of modern high quality steel
products allow for very low tolerances of impurities and chemical changes. Impurities and
chemical changes often are the result of turbulence created by the incoming ladle stream of
molten steel fed into the tundish. Certain tundish designs for receiving liquid steel from the ladle
shroud lead to unfavorable fluid flow conditions, such as turbulence, inside the tundish and
promote high free surface flow activities. For example, the fluid flow generated by an incoming
ladle stream may be reflected from the flat tundish floor and sidewalls toward the surface of the
liquid steel. This generated fluid flow causes a turbulent boiling action, extensive wave motion,
and splashing at the surface of the steel bath.
[0005] For example, Fig. 10 illustrates a longitudinal cross section of a single strand
tundish 1 having an asymmetrical fluid flow 9a. The ladle shroud 7 is shown adjacent end wall 3
opposite a well block (not shown in Figs. 10 and 11). Water flow-model studies have shown that
the fluid flow, generated by an incoming ladle stream 8 from the ladle shroud 7, is reflected from
the flat tundish floor 4 in an upward direction toward the surface of the liquid steel. If this fluid
flow is restricted by the tundish walls 2 and 3, the restricted fluid flow is forced upward along
the surface of such walls 2, 3. This upward flow follows a circular path 9c, and creates an
upward surge along the face of the end wall 3, and a downward flow around a ladle shroud 7.
The upward surge of the circular flow 9c causes excessive turbulence at the surface of the bath.
These high free surface activities in the tundish give rise to a phenomenon called "open-eye,"
whereby the protective slag cover 6 on top of the steel bath is broken. The broken slag cover 6
exposes the liquid steel to the surrounding atmosphere and sets up conditions conducive to
altering the chemistry of the steel bath and creating inclusions in the steel bath. The chemical
changes typically involve loss of aluminum from the bath and/or absorption of oxygen and
nitrogen into the steel bath and consequent surface re-oxidation. Re-oxidation and other
undesired reactions can introduce, for example, excess alumina, manganese sulfide, and calcium
sulfide into the steel bath. Additionally, the downward flow around the ladle shroud 7 generates
shear and vortices, and entraps and pulls broken particles 10 from the broken flux cover 6 down
into the liquid steel bath. These broken particles 10 eventually are discharged from the tundish
with the molten steel and create inclusions within the finished steel product.
[0006] The chemical changes and inclusions ultimately reduce steel quality and are a
primary cause of rejection of high value steel grades such as HIC and armor plate grades.
Further, splashing of the high temperature liquid steel against the tundish walls may present
safety hazards for operators. Using conventional equipment, problems can also arise with
respect to lack of steel bath temperature homogeneity and insufficient residence time to allow
inclusion particles to float to the protective slag cover, where the particles can be isolated and/or
separated from the liquid steel.
[0007] There have been various attempts to reduce or eliminate surface turbulence within
a continuous caster tundish to improve the quality of the finished steel product. These attempts
have included a wide assortment of dams and weirs which redirect the ladle stream fluid flow
away from the surface of the molten steel bath. Although some known fluid flow control devices
have been somewhat successful in controlling fluid flow and reducing surface turbulence, such
control devices tend to be insufficient for the demands of high quality steel and/or cause
operational problems such as those described above.
SUMMARY OF THE INVENTION
[0008] According to a first aspect of the invention, a tundish impact pad is provided that
features a base having a base surface with a conical impact surface area that establishes an apex,
a sidewall, and a top wall extending inwardly relative to the sidewall to terminate an inner edge
establishing a mouth opening spaced above and centered relative to the apex. The top wall
includes a lip sloping radially inwardly and downwardly towards the conical impact surface.
[0009] A second aspect of the invention provides an apparatus featuring a continuous
caster tundish for containing a reservoir of molten metal having fluid flow generated by an
incoming ladle stream, and a tundish impact pad in the continuous caster tundish. The tundish
impact pad includes a base having a base surface with a conical impact surface area establishing
an apex, a sidewall, and a top wall extending inwardly relative to the sidewall to terminate at an
inner edge establishing a mouth opening spaced above and centered relative to the apex. The top
wall includes a lip sloping radially inwardly and downwardly towards the conical impact surface.
[0010] A third aspect of the invention provides a strand casting method or molten steel
processing method in which an incoming ladle stream of molten liquid steel is fed into a
continuous caster tundish and impacted against a conical impact surface area of the tundish
impact pad before being allowed to flow through a mouth opening of the tundish impact pad and
into a tundish reservoir. The tundish impact pad includes a base having a base surface, a
sidewall, and a top wall extending inwardly relative to the sidewall to terminate at an inner edge
establishing the mouth opening spaced above and centered relative to an apex of the conical
impact surface area. The top wall includes a lip sloping radially inwardly and downwardly
towards the conical impact surface.
[0011] In accordance with an embodiment of each of the aspects described herein, the top
wall of the tundish impact pad features a lower surface that, collectively with the base surface
and a continuous inner surface of the sidewall, establish a continuous annular chamber
configured to reduce turbulence of an incoming ladle stream of molten liquid steel.
[0012] In accordance with another embodiment of the above aspects, the conical impact
surface area has an axis, passing through the apex, about which the conical impact surface area
has rotational symmetry.
[0013] In accordance with still another embodiment of the above aspects, the conical
impact surface area has a linear profile.
[0014] In accordance with a further embodiment of the above aspects, the conical impact
surface area has a cone angle, measured from a horizontal plane in which an outer perimeter of
the conical impact surface area lies to an oblique plane in which the conical impact surface area
lies, in a range of about 15 degrees to about 25 degrees.
[0015] In accordance with a still further embodiment of the above aspects, the lip has a
downward lip angle, measured from a horizontal plane to a lower surface of the lip, in a range of
about 20 degrees to about 25 degrees.
[0016] According to another embodiment of the above aspects, the continuous annular
chamber has a radius of curvature of about 30 mm.
[0017] According to still another embodiment of the above aspects, protuberances, for
example hemispherical protuberances, are distributed about a lower surface area of the lip.
[0018] The above embodiments may be practiced in any combination with one another.
[0019] Other aspects and embodiments of the invention, including apparatus, assemblies,
devices, articles, methods of making and using, processes, and the like which constitute part of
the invention, will become more apparent upon reading the following detailed description of the
exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0020] The accompanying drawings are incorporated in and constitute a part of the
specification. The drawings, together with the general description given above and the detailed
description of the exemplary embodiments and methods given below, serve to explain the
principles of the invention. In such drawings:
[0021] Fig. 1 is a longitudinal cross-sectional front perspective view of a single strand
caster tundish including an impact pad according to an embodiment of the invention;
[0022] Fig. 2 is a longitudinal cross-sectional front view of the single strand caster
tundish of Fig. 1;
[0023] Fig. 3 is a front perspective view of the impact pad of the embodiment illustrated
in Fig. 1;
[0024] Fig 4 is a plan view of the impact pad of Fig. 3;
[0025] Fig. 5 is a cross-sectional view taken along the line V-V of Fig. 4;
[0026] Fig. 6 is a cut-away side perspective view of the impact pad of Figs. 3-5;
[0027] Fig. 7 is a cross-sectional end view taken from the view point of the arrow on the
right side of Figs. 1 and 2, showing the flow profile of incoming liquid steel introduced through a
shroud centered above the impact pad;
[0028] Fig. 8 is a cross-sectional view of an impact pad according to another embodiment
of the invention;
[0029] Fig. 9 is a bottom sectional view taken along line IX-IX of Fig. 8;
[0030] Figs. 10 and 11 are reproduced from U.S. Patent No. Re. 35,685, wherein Fig. 10
is a longitudinal cross-sectional view of a water flow-model study tundish and Fig. 11 is a
transverse cross-sectional view taken along line XI-XI of Fig. 10.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
AND EXEMPLARY METHODS
[0031] Reference will now be made in detail to the exemplary embodiments and methods
as illustrated in the accompanying drawings, in which like reference characters designate like or
corresponding parts throughout the drawings. It should be noted, however, that the invention in
its broader aspects is not necessarily limited to the specific details, representative materials and
methods, and illustrative examples shown and described in connection with the exemplary
embodiments and methods.
[0032] A tundish for a strand caster in accordance with an exemplary embodiment is
generally designated by reference numeral 10 in Figs. 1 and 2. Although a single-strand caster is
shown therein, it should be understood that embodiments of the present invention may be
practiced in connection with double-strand and other multiple-strand casters. An example of a
multi-strand caster setup, albeit with a different impact pad, is shown in Fig. 10 of U.S. Patent
No. RE 35,685. The tundish 10 includes tundish end walls 12 and 14, tundish front and rear
sidewalls (unnumbered), and a tundish floor 16 extending between and connected to (or integral
with) the end walls 12, 14 and sidewalls. The tundish end walls 12, 14 and floor 16 collectively
establish a chamber or reservoir 18 for receiving and holding a molten steel bath. A tundish
impact pad 20 is located in the reservoir 18, for example, closer to the end wall 12 than to the
end wall 14. Positioned above the tundish impact pad 20 is the lower part of a ladle shroud 22
for introducing an incoming ladle stream 24 (Fig. 7) of molten steel into the impact pad 20. The
ladle shroud 22 is shown penetrating through the top of the molten steel bath, with the end of the
ladle shroud 22 spaced above and centered coaxially with the tundish impact pad 20. The flow
of molten steel and the structure and function of impact pad 20 are discussed in further detail
below.
[0033] The tundish 10 further includes a weir 26 dividing the tundish 10 into right and
left (first and second) compartments 18a and 18b, respectively, with the impact pad 20 in the
right compartment 18a on the tundish floor 16 in Figs. 1 and 2. The bottom of the weir 26
includes a passage 26a for allowing fluid communication between the liquid steel in the left and
right compartments 18a, 18b. A diffuser 28 is positioned on the tundish floor 16 in the right
compartment 18a between the weir 26 and the tundish impact pad 20. A dam 30 having a
plurality of upwardly sloping (from right to left in the direction of flow) cylindrical passages 30a
rests on the tundish floor 16 in the left compartment 18b. On the opposite side of the dam 30
from the weir 26, a stopper rod 32 is aligned with an output port or tundish well block 34 through
which liquid steel is discharged from the tundish 10. Upward and downward movement of the
stopper rod 32 controls outflow of molten steel from the tundish 10 and into casts (not shown).
[0034] The tundish impact pad 20 may be made of a material or materials suitable for the
intended use in a caster tundish for molten steel processing. Typically, such material(s) have
high impact and abrasion resistance, high hot strength and refractoriness, and good castability.
Metals, ceramics, and sand with ceramic coatings are examples of suitable materials. As specific
but non-limiting examples, low-moisture, high-alumina castable compositions such as Narcon 70
Castable and coarse high alumina low cement castable compositions such as Versaflow® 70C
Plus are refractory materials suitable for use as the tundish impact pad 20. According to product
literature: Narcon 70 Castable contains (calcined basis) 26.9% silica (Si0 2), 69.8% alumina
(A120 3), 1.7% titania (Ti0 2), 0.8% iron oxide (Fe20 3), 0.7% lime (CaO), and 0.1% alkali (Na20);
and Versaflow® 70C Plus contains (calcined basis) 27.5% silica (Si0 2), 67.3% alumina (A120 3),
2.1% titania (Ti0 2), 1.2% iron oxide (Fe20 3), 1.6% lime (CaO), 0.1% magnesia (MgO), and
0.2% alkalis (Na20+K 20). The body parts of the tundish impact pad 20 can be coated with an
erosion resistant material to form erosion resistant coatings for receiving and coming into contact
with the incoming ladle stream 24. The erosion resistant coatings may be made with medium
emissivity materials (such as Zirconia, Yttria, Silicon Carbide), high reflectivity materials (such
as aluminum and alumina), or high temperature, non-oxide lubricants (such as boron nitride).
[0035] Referring to the embodiment shown in Figs. 3-6, the tundish impact pad 20
includes a circular base 40 (relative to a plan or bottom view). The base 40 includes a top base
surface having a conical impact surface area 42 and an adjoining, adjacent annular base surface
area 44 concentrically surrounding the conical impact surface area 42. In the illustrated
embodiment, the conical impact surface area 42 is not truncated. Optionally, the top of the
conical impact surface area 42 may be slightly rounded while still retaining the conical shape.
As best shown in Fig. 5, the conical impact surface area 42 extends upwardly to terminate at an
apex or vertex 46. The conical impact surface area 42 has rotational symmetry about an
imaginary axis Az (Fig. 5) passing through the apex 46. In the illustrated embodiments, the
conical impact surface area 42 has a linear profile or cross section, as best shown in Fig. 5. The
bottom of the linear profile of the conical impact surface area 42 terminates at an outer perimeter
48 adjacent to and contiguous with a radially inner edge of the annular base surface area 44. The
top of the linear profile of the conical impact surface area 42 terminates at a point corresponding
to the apex 46 that is coincident with the axis Az. The annular base surface area 44 may be at
least partially flat and lie in a horizontal plane that is parallel to the bottom surface 40a of the
base 40.
[0036] The tundish impact pad 20 further includes a sidewall 50 having a sidewall inner
surface 52 that continuously/endlessly circles on itself to appear as an annulus when viewed from
above, as in Fig. 4. The sidewall 50 is shown having uniform thickness over its entire 360
degrees. The sidewall inner surface 52 is positioned concentrically outside of and generally
perpendicular to the annular base surface area 44. As best shown in the cross-sectional view of
Fig. 5, the sidewall inner surface 52 includes curved transition areas 54, 56 at its bottom and top,
respectively. The curved transition areas 54, 56 may be symmetrical to one another. The ends of
the lower curved transition area 54 are flush and contiguous with the annular base surface area
44 and the sidewall inner surface 52. The lower curved transition area 54 curves continuously
between the base 40 and the sidewall inner surface 52.
[0037] The tundish impact pad 20 still further includes a top wall 60 extending inwardly
from the top transition area 56 and generally perpendicular to the sidewall 50 to terminate at an
inner edge 62. The top transition area 56 is configured as a curvilinear undercut that curves
continuously between and whose ends are flush and contiguous with the sidewall inner surface
52 and the top wall 60. A mouth opening 64 established by the inner edge 62 is spaced above
and centered relative to the apex 46. In use, the mouth opening 64 is under and coaxial with the
ladle shroud 22 to receive the incoming ladle stream 24. In the illustrated embodiments, the
diameter of the mouth opening 64 is approximately equal to or less than the diameter of the outer
perimeter 48 of the conical impact surface area 42.
[0038] The top wall 60 includes a lip 66 angled inwardly and downwardly to terminate at
the inner edge 62. The top wall 60 has a first lower surface area 60a that extends substantially
horizontally and parallel to the bottom surface 40a and a second lower surface area (also referred
to herein as a lower lip surface) 66a corresponding to the bottom of the lip 66. The lower lip
surface 66a slopes radially inwardly and downwardly from the first lower surface area 60a
towards the conical impact surface 42. As best shown in Figures 4 and 5, the first lower surface
area 60a and the lower lip surface 66a interface at 60b.
[0039] The base 40, side wall 50, and top wall 60 may be integral, that is a unitary piece
or monolithic part. Alternatively, the base 40, the sidewall 50, the top wall 60 and/or other parts
of the tundish 10 may be formed of separate pieces temporarily or permanently joined to one
another. The conical impact surface area 42, the annular base surface area 44, the continuous
sidewall inner surface 52, the curved transition surface areas 54, 56, and the lower surface areas
60a, 66a collectively establish a continuous annular chamber about axis Az that may be in the
form of a torus.
[0040] Referring to Fig. 7, liquid steel is introduced into the tundish 10 through the
shroud or sprue 22 as the incoming ladle stream 24. It has been found that the ratio (Dj/Dm) of
the diameter Dj of the inner diameter of the shroud 22 to the diameter Dm of the mouth opening
64 in a range of about 0.3 to about 0.4 provides particularly good results. The ladle shroud 22
and the mouth opening 64 are coaxially aligned with one another in the exemplary embodiment.
The design of the exemplary embodiments described herein causes the incoming ladle stream 24
to impact against the conical impact surface area 42, which redirects the stream 24 radially
outward towards the lower transition portion 54 and the sidewall inner surface 52. The shape of
the continuous annular chamber forces the molten steel flow into a reversed direction back
towards the incoming ladle stream 24 to reduce the turbulence and dissipate the energy of the
molten steel before it flows from the impact pad 10. The reversed fluid flow is discharged
upward through the mouth opening 64, then generally radially outward in all directions towards
the walls of the tundish 10 as a substantially laminar flow. By providing a mouth opening 64
that is greater in diameter than the diameter of the shroud 22, an annular upward flow is created
between the incoming ladle stream 24 and the inner edge 62.
[0041] The molten steel exits the mouth opening 64 into the first compartment 18a. The
continuous inflow of the incoming ladle stream and removal of molten steel through the outlet 34
causes the molten steel in compartment 18a to flow towards the weir 26 and through the weir
passage 26a. After passing through the weir passage 28, the molten steel flows over the dam 30
and/or through the cylindrical passages 30a before being discharged through the output 34.
[0042] The reversing of molten steel flow onto itself creates a self-braking effect. As a
consequence, the outgoing flow of molten steel through the mouth opening 64 and into the first
compartment 18a is less turbulent and has less energy. The above-described "open-eye" and
splashing problems are thereby reduced significantly.
[0043] In a particularly exemplary embodiment designed to suppress "open-eye," the
conical impact surface area 42 has a cone angle (Fig. 5), measured from a horizontal plane in
which the outer perimeter 48 lies to an oblique plane in which the conical impact surface area 42
lies, in a range of about 15 degrees to about 25 degrees. In another particularly exemplary
embodiment designed to suppress "open-eye," the lip 66 has a downward lip angle theta (e),
measured from a horizontal plane to a plane in which the lower surface 66a of the lip 66 lies, in a
range of about 20 degrees to about 25 degrees. In another particularly exemplary embodiment
designed to suppress "open-eye," the continuous annular chamber has a radius of curvature of
about 30 mm. These exemplary embodiments may be practiced separately or together with one
another in any combination. The impact chamber may be provided with a height that is equal to
or greater than the inside diameter of the shroud to affect flow control.
[0044] Computational fluid dynamics (CFD) simulations were performed on impact pads
designed in accordance with the above parameters. The area average velocity, which is a
measure of flow activity on the pouring side of the top surface of the steel bath, is calculated to
be about 50% lower practicing an embodiment of the invention compared to a flat petal-shaped
impact pad. The probability of "open-eye" formation is also calculated to be reduced by the
same proportion. Using CFD analysis, in which velocities and areas are calculated for cells of a
mesh and area average velocity, area average velocity is determined as follows:
[0046] Generally, it is found that higher area average velocities correspond to greater
tundish flux entrainment and poorer quality steel, whereas lower area average velocities
correspond to lesser tundish flux entrainment and higher quality steel. Thus, a decrease of about
50% area average velocity constitutes a significant decrease in tundish flux entrainment and
leads to higher quality steel products. Without wishing to be bound by theory, it is believed that
the improved quality obtained using exemplary embodiments described herein is attributable to
one or more of the following: reduction of high velocity incoming flows and turbulence due to
the "self-braking" effect; less splash during start-up and continuous operation; longer residence
time of the molten steel in the reservoir; promotion of impurity and particle flotation; and more
uniform reservoir temperature.
[0047] Figs. 8 and 9 illustrate an impact pad according to another exemplary
embodiment. In the interest of brevity, the following description focuses on differences between
the exemplary embodiment of Figs. 8 and 9 and other exemplary embodiments described above.
Like reference characters designate like or corresponding parts in the different exemplary
embodiments.
[0048] In the exemplary embodiment of Figs. 8 and 9, protuberances 80 are distributed
360 degrees about the lower lip surface 66a. The protuberances 80 may be uniformly
distributed, such as in a matrix pattern, or distributed randomly or otherwise. In the illustrated
embodiment, the outer surfaces of the protuberances 80 have a hemispherical shape. However,
the protuberances 80 may undertake alternative shapes. Moreover, the protuberances 80 may
have identical or varying shapes relative to one another. It has been found that the protuberances
80, especially hemispherical protuberances, further decelerate the outgoing flow of liquid steel as
it exits the impact pad 20 through the mouth opening 64. Additionally or alternatively, the
protuberances 80 may be located elsewhere on the inner surface of the impact pad.
[0049] The foregoing detailed description of the certain exemplary embodiments has
been provided for the purpose of explaining the principles of the invention and its practical
application, thereby enabling others skilled in the art to understand the invention for various
embodiments and with various modifications as are suited to the particular use contemplated.
This description is not necessarily intended to be exhaustive or to limit the invention to the
precise embodiments disclosed. The specification describes specific examples to accomplish a
more general goal that may be accomplished in another way.
[0050] Only those claims which use the words "means for" are to be interpreted under 35
USC 112, sixth paragraph. Moreover, no limitations from the specification are to be read into
any claims, unless those limitations are expressly included in the claims.

WHAT IS CLAIMED IS:
1. A tundish impact pad, comprising:
a base having a base surface, the base surface comprising a conical impact surface area
establishing an apex;
a sidewall; and
a top wall extending inwardly relative to the sidewall to terminate at an inner edge
establishing a mouth opening spaced above and centered relative to the apex, the top wall
comprising a lip sloping radially inwardly and downwardly towards the conical impact surface.
2. The tundish impact pad of claim 1, wherein the sidewall includes a continuous
sidewall inner surface radially outward of the base surface, and wherein the top wall comprises a
lower surface that, collectively with the base surface and the continuous sidewall inner surface,
establish a continuous annular chamber configured to reduce turbulence of an incoming ladle
stream of molten liquid steel.
3. The tundish impact pad of claim 2, wherein:
the base surface further comprises a first flat annular area between the conical impact
surface area and the continuous sidewall inner surface;
the top wall comprises a second flat annular area extending between the continuous
sidewall inner surface and the lip; and
the first and second flat annular areas are spaced apart from and extend in planes parallel
to one another.
4. The tundish impact pad of any one of claims 1 to 3, wherein the conical impact
surface area has an axis, passing through the apex, about which the conical impact surface area
has rotational symmetry.
5. The tundish impact pad of claim 4, wherein the conical impact surface area has a
linear profile.
6. The tundish impact pad of claim 5, wherein the conical impact surface area has a
cone angle, measured from a horizontal plane in which an outer perimeter of the conical impact
surface area lies to an oblique plane in which the linear profile of the conical impact surface area
lies, in a range of about 15 degrees to about 25 degrees.
7. The tundish impact pad of any one of claims 1 to 6, wherein the lip has a
downward lip angle, measured from a horizontal plane to a lower surface of the lip, in a range of
about 20 degrees to about 25 degrees.
8. The tundish impact pad of any one of claims 1 to 7, wherein the top wall
comprises a lower surface that, collectively with the base surface and the continuous sidewall
inner surface, establish a continuous annular chamber having a radius of curvature of about 30
mm.
9. The tundish impact pad of any one of claims 1 to 8, further comprising:
protuberances distributed about a lower surface area of the lip.
10. The tundish impact pad of claim 9, wherein the protuberances are hemispherical
in shape.
11. An apparatus comprising:
a continuous caster tundish for containing a reservoir of molten metal having fluid flow
generated by an incoming ladle stream; and
a tundish impact pad according to any one of claims 1 to 10.
12. A strand casting method, comprising:
feeding an incoming ladle stream of molten liquid steel into a continuous caster tundish,
the continuous caster tundish containing a tundish impact pad comprising
a base having a base surface, the base surface comprising a conical impact surface
area establishing an apex;
a sidewall; and
a top wall extending inwardly relative to the sidewall to terminate at an inner edge
establishing a mouth opening spaced above and centered relative to the apex and positioned to
receive the incoming ladle stream, the top wall comprising a lip sloping radially inwardly and
downwardly towards the conical impact surface;
impacting the incoming ladle stream of molten liquid steel against the conical impact
surface area; and
allowing the impacted molten liquid steel to discharge from the tundish impact pad
through the mouth opening.
13. The strand casting method of claim 12, wherein the sidewall includes a
continuous sidewall inner surface radially outward of the base surface, and wherein the top wall
comprises a lower surface that, collectively with the base surface and the continuous sidewall
inner surface, establish a continuous annular chamber configured to reduce turbulence of an
incoming ladle stream of molten liquid steel.
14. The strand casting method of claim 13, wherein:
the base surface further comprises a first flat annular area between the conical impact
surface area and the continuous sidewall inner surface;
the top wall comprises a second flat annular area extending between the continuous
sidewall inner surface and the lip; and
the first and second flat annular areas are spaced apart from and extend in planes parallel
to one another.
15. The strand casting method of any one of claims 12 to 14, wherein the conical
impact surface area has an axis, passing through the apex, about which the conical impact
surface area has rotational symmetry.
16. The strand casting method of claim 15, wherein the conical impact surface area
has a linear profile.
17. The strand casting method of claim 16, wherein the conical impact surface area
has a cone angle, measured from a horizontal plane in which an outer perimeter of the conical
impact surface area lies to an oblique plane in which the linear profile of the conical impact
surface area lies, in a range of about 15 degrees to about 25 degrees.
18. The strand casting method of any one of claims 12 to 17, wherein the lip has a
downward lip angle, measured from a horizontal plane to a lower surface of the lip, in a range of
about 20 degrees to about 25 degrees.
19. The strand casting method of any one of claims 12 to 18, wherein the top wall
comprises a lower surface that, collectively with the base surface and the continuous sidewall
inner surface, establish a continuous annular chamber having a radius of curvature of about 30
mm.
20. The strand casting method of any one of claims 12 to 19, further comprising:
protuberances distributed about a lower surface area of the lip.
21. The strand casting method of claim 20, wherein the protuberances are
hemispherical in shape.