FIELD OF THE INVENTION
The present invention generally relates to a single strand tundish that is used in
steelmaking operation. More particularly, the invention relates to a single strand
tundish with tundish furniture for maximizing metallurgical performance of the
tundish. The invention further relates to a method of operating a single strand
tundish under a maximum operating level of molten steel.
BACKGROUND OF THE INVENTION
In continuous casting of steel, the molten steel is poured from a ladle into an
intermediate vessel namely a tundish, and from the tundish into a continuous
casting mould. A tundish enables buffering a batch operation into a continuous
one, and reduces unwanted non-metallic inclusions when the molten steel passes
through the tundish. A plurality of baffles, dams, weirs and impact pads are
positioned in the tundish. In this context, a baffle constitutes an obstruction to
steel flow extending from the floor of the tundish to above the uppermost level
of the molten steel, wherein a dam constitutes an obstruction protruding
upwardly from the floor of the tundish and over which the molten steel flows,
and wherein a weir constitutes an obstruction protruding downwardly into the
molten steel and under which the steel must flow. An impact pad, made of an
erosion-resistant material, is placed on the floor of the tundish. The impact pad
has a base to receive an incoming ladle stream and a sidewall extending
upwardly along the periphery of the base. The base of the impact pad has a
surface shaped to receive and reverse the direction of fluid flow generated by

the incoming ladle stream. For this purpose of further description, the baffles,
dams, weirs and impact pads will herein be referred collectively as the tundish
furniture.
Depending on the shape and size of a tundish including the desired metallurgical
performance, several types of furniture sets can be designed. However, usages
of each type of furniture has its own advantages and disadvantages for
example, increased cost & maintenance, low metallurgical performance, more
turndown time etc. Therefore, once the peak metallurgical performance of a
tundish including the most preferred type of furniture is determined, the
designers have to produce such a tundish at lower cost, and considering
minimum maintenance.
According to prior art, the molten steel is poured into the tundish through the
shroud submerged in the molten steel in the tundish. The flow of molten steel
into the tundish creates enormous turbulence around the pouring point. To
minimize turbulence around pouring point a set of dam-weir has been put as
depicted in the Fig. 2. This dam-weir combination virtually splits the tundish into
two parts retaining most of the turbulence confined within the first part itself
whereas a dam has been provided near the outlet to avoid short-circuiting to
the outlet along bottom.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an improved single

strand tundish with tundish furniture for maximized metallurgical performance in
a continuous casting process.
Another object of the invention is to propose an improved single strand tundish
with furniture, which provides improved parameters in terms of zone turbulence,
flow patterns, residence time distribution data, and heat loss and inclusion
removal.
A further object of the invention is to propose a method of operating a single
strand a tundish under a maximum operating level of molten steel.
SUMMARY OF THE INVENTION
According to the invention, there is provided a single strand tundish comprising a
base with an outlet, the outlet being longitudinally spaced-apart from a pour
zone, the pour zone receiving a stream of molten steel from a ladle, a set of
furniture having an impact pad disposed on the floor of the tundish for pouring
steel stream from the ladle, and a dam positioned near the outlet of the tundish.
The impact pad comprises a base having an impact surface, an upwardly
extending sidewall along the periphery of the base, the sidewall having an inner
surface with an undercut portion shaped to receive and reverse the direction of
flow of the incoming stream. The impact pad is made of erosion resistant
material, and configured to minimize surface turbulence in the tundish in addition
to act as an erosion-resistance means. By reducing pour zone turbulence, the

risk of the surface covering the flux layer being broken is eliminated and
exposure time of the steel to air is reduced, thereby reducing the levels of steel
reoxidation and heat loss.
According to a particular characteristic of the invention, the distance between
dam and tundish outlet may vary from 15 to 30% of the longitudinal distance
between inlet (pouring point) and tundish outlet.
According to another characteristic of the invention, the dam height may vary
from 15 to 30% of the liquid steel height at steady state in the tundish. The dam
extends over the full width of the tundish.
Preferably, the tundish has one outlet longitudinally spaced on one side of the
pour zone and a dam is provided near the outlet.
Preferably, the shape of the dam outer walls is smoothly inclined towards inward
to have less turbulence flow near it.
The invention enables a reduction in the requirement of tundish furniture
material compared to that of prior art. To enable the invention to be fully
understood, the furniture set and its characteristic is described hereinafter by
way of non-limiting examples.
As per the present invention, an impact pad is provided beneath the shroud to

receive incoming liquid steel stream from the ladle shroud and a dam near the
outlet. It would be shown with example that the furniture set-up as per the
invention improves the performance.
The desired fluid flow characteristics like bulk circulation through the top surface,
or the surface directed flow etc remain unaltered (Fig. 1 & 2). This phenomenon
is reflected in Residence Time Distribution (RTD) analysis (Fig. 6 & 7) as well.
The switch over from the double peak of the prior art to a single peak of the
present invention, allows elimination of the short circuiting flow within the
tundish. As detailed in Table 1, Plug Volume fraction (PV) goes up to 36% from
22% while Dead Volume fraction (DV) is reduced to 8% from 9%. Minimum
Residence Time (MRT) and Average Residence Time (ART) are kept as par.
Through the maximum surface velocity is higher than that of the prior art, but
the same subsequently stabilizes at a safe limit near the outlet (Fig. 8 & 10).
The furniture set-up as per the present invention is comparably economic.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Embodiments of the invention are now described by way of example only with
reference to the accompanying drawings in which:
FIG. 1 is a diagrammatic illustration in longitudinal cross-section of a tundish
showing the effect on steel flow with the furniture used in the present invention;

FIG. 2 shows a tundish according to prior art exhibiting the effect on steel flow;
FIG. 3 is a plan view of an impact pad in a tundish of the invention;
FIG. 4 is a section on mid point width of FIG.3;
Fig. 5 is a mid point length-wise section of FIG.3;
FIG. 6 is a residence time distribution graph of prior art;
FIG. 7 is a residence time distribution graph of the tundish as per present
invention;
FIG. 8 is a velocity magnitude profile of the tundish meniscus as per the present
invention;
FIG. 9 is a scale for FIG 8 & 10 velocity magnitude profile;
FIG. 10 is a velocity magnitude profile of the tundish meniscus of prior art;
TABLE 1 parametric comparison between tundish furniture of prior art and
present invention.
DETAIL DESCRIPTION OF THE INVENTION
In FIG. 1, a tundish 1 as per the invention has a floor 2 and end walls 3. An

impact pad 4 is located on floor 2 centrally of the tundish. The impact pad is
described in more detail below with reference to FIGS. 3, 4 and 5.
In FIG. 2, a tundish 9 as per prior art has a floor 10 and end walls 11. A dam-
weir combination 12 is located after a shroud 13.
As shown in FIG. 1, the shroud 5 from a ladle (not shown) is positioned directly
above the impact pad 4 so that steel poured into the tundish (1) will strike the
i
impact pad (4). The tundish (1) has an outlet region (6) spaced towards
longitudinal end of the tundish (1), the actual outlet in a base of the tundish (1)
is not shown.
The arrows show the directions of steel flow, as derived by modeling of the
tundish. The surface directed flow zones 8,16 have been revealed.
In FIG. 1, where like reference numerals indicate the tundish parts, the tundish
furniture has been completed by the addition of a dam 7 located approximately
15 to 30% of the longitudinal distance from the shroud (5) to outlet region 6.
The dam height may extend upwardly to about 15-30% of the normal maximum
operating steel level in the tundish (1).
Again in FIG. 2, the steel flow patterns are indicated by arrows as derived by
modelling of the tundish.
Overall, the steel flow pattern improves according to the present invention from
that of the prior art, leading to improved prospects of inclusion removal.

The impact pad 4 shown in FIGS. 3, 4 and 5 has a base 22 with an impact
surface 18 to receive an incoming stream of molten steel. It is of generally
rectangular configuration and has an upstanding sidewall 17 encompassing
continuously around its periphery. The sidewall encloses an interior space 20
having an upper opening 19 to receive the incoming stream. The opening 19 is
non-uniform, being rectangular, and its longer sides are positioned to extend in
the longitudinal direction of the tundish (1) when the impact pad (4) is
positioned on the floor (2) of the tundish (1). The sidewall 17 is provided is
provided with an inner face 20 shaped firstly to extend outwardly and upwardly
from the impact surface 18 and then inwardly and upwardly to the opening 19.
The sidewall (17) ends in a top surface 21 surrounding the opening 19 and
effectively provides an undercut portion at its inner surface to receive and
reverse the direction of steel flow generated by an incoming stream impacting on
the surface 18.
Velocity magnitude at meniscus 23 of the tundish (1) provided with furniture as
per the invention as shown in FIG. 8. Shroud position 25 is as depicted in the
FIG. 8. Velocity magnitude at the meniscus 24 of tundish (9) of the prior art
furniture is shown in FIG. 10. Weir position 26 is as depicted in the FIG. 10.
ADVANTAGES OF THE INVENTION
It will be understood that the type of tundish furniture set arrangement in
accordance with present invention has many advantages, some of which are
common to those of prior art, and the others are special to the present
invention:

1. The set of furniture in accordance with present invention ensures
the best in class residence time distribution which in turn provide better
plug volume fraction in the tundish and low level of dead volume
fraction. These characteristics all facilitates improved inclusion removal.
Clearly, increased residence time increases chances of inclusion removal
from the steel. A low level of dead volume fraction reduces static flow
regions of the tundish thereby helps in temperature homogenization and
inclusion removal.
2. The fluid flow in the tundish equipped with the set of furniture as in the
invention ensure surface directed flow hence maximum contact with
overlying slag / flux layer to maximize inclusion capture. The fluid flow
also avoids short circuiting of incoming liquid steel to outlet of the tundish.
3. The metallurgical performance of the furniture set matches / surpasses
the best found case where dam-weir combination has been used.
4. Another advantage of the invention is comparable lower cost. The
comparable cost of such furniture is expected to be much lower than that
of the best known set.
5. Yet another advantage of the invention is reduced steel re-oxidation by
reduced turbulence, particularly on pouring steel from a ladle into an
empty tundish. Thus, the use of the particular type of impact pad
dampens the energy of the steel poured into the tundish and the reduced

turbulence so achieved reduces the exposure of steel to air thereby
reducing the formation of oxide inclusions, e.g. alumina and iron oxides,
commonly produced during teeming of molten steel.
6. Yet another advantage of the invention is low level of ladle slag exiting
from the tundish outlet.
7. Preferably, use of an active surface layer of slag/ flux increases inclusion
trap.

WE CLAIM:
1. A method of operating a single strand tundish having a maximum
operating level of molten steel therein, the tundish comprising a floor
having an outlet, a pour zone, and side walls extending upwardly from
the floor, the side walls extending above the maximum operating level
of molten steel in the tundish; a dam disposed on the floor at a
location from outlet being 15 to 30% of the longitudinal distance
between a shroud and an outlet region of the tundish; an impact pad
positioned on the tundish floor in the pour zone, the impact pad
comprising a base, an impact surface, an upwardly extending sidewall
along the periphery of the base, the impact pad is enabled to receive
and reverse the direction of flow of the incoming steel stream; the
method comprising the steps of:
(a) positioning the dam in the tundish to extend upwardly from the
floor a distance in range 15-30% of the maximum operating level
of the molten steel in the tundish;
(b) pouring the molten steel in a stream into the tundish pour zone so
that the steel impacts the impact surface of the impact pad and
reverses the direction of flow of the incoming steel stream; and ;
(c) causing the molten steel to flow over the dam and exiting through
the outlet.

2. A method of operating a single strand tundish under a maximum
operating level of molten steel as substantially described herein with
reference to the accompanying drawings.

This invention relates to a method of operating a single strand tundish under a
maximum operating level of molten steel therein, the tundish comprising a floor
having an outlet, a pour zone, and side walls extending upwardly from the floor,
the side walls extending above the maximum operating level of molten steel in
the tundish; a dam disposed on the floor near the outlet at a distance of 15 to
30% of the longitudinal distance between a shroud and an outlet region of the
tundish; an impact pad positioned on the tundish floor in the pour zone, the
impact pad comprising a base, an impact surface, an upwardly extending
sidewall along the periphery of the base, the impact pad is enabled to receive
and reverse the direction of flow of the incoming steel stream; the method
comprising the steps of: (a) positioning the dam in the tundish to extend
upwardly from the floor a distance between about 15-30% of the maximum
operating level of the molten steel in the tundish; (b) pouring the molten steel in
a stream into the tundish pour zone so that the steel impacts the impact surface
of the impact pad and reverses the direction of flow of the incoming steel
stream; and (c) causing the molten steel to flow over the dam and exiting
through the outlet.
{FIGURE 1}