Sliding gate for liquid metal flow control

Dispensing – Processes of dispensing – Molten metal

Reexamination Certificate

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Details

C222S600000

Reexamination Certificate

active

06783038

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to metal founding. More specifically, the invention relates to a method and apparatus for metering liquid metal during metal founding.
2. Description of the Related Art
Metering gates with three plates are used to control the rate of liquid metal flow exiting a teeming vessel, such as a tundish. For example, a metering gate may be used to control the rate of liquid steel flowing from the tundish of a continuous casting machine into a mold.
A metering gate consists of an assembly of refractory components, each of which has a flow channel. The flow channels (i.e. the holes or bores) within the refractory components are assembled together so as to provide a complete flow channel through the gate, which is in fluid communication with the teeming vessel and through which the liquid metal may be allowed to flow.
The refractory components of the metering gate are assembled and clamped together by mechanical means such that one component, a throttle plate, can slide laterally in the metering gate assembly to control the rate of liquid metal flow through the gate. By sliding the throttle plate to various positions, the gate may be either closed, partially open, or fully open to control the rate of flow exiting the teeming vessel.
Several problems are typically associated with controlling the flow of liquid steel exiting a tundish with metering gates. These problems include: (1) bending of metal flow in the flow channels of the gate, which can cause excessive turbulence and asymmetrical discharge of liquid metal; (2) severe non-uniform plugging of the flow channels from the accumulation of metallic and non-metallic materials which adhere to the channel walls with a subsequent loss of ability to obtain the desired rate and smoothness of liquid metal discharge; and (3) localized and accelerated eroding of a refractory component of the metering gate with subsequent contaminating of the liquid metal and potential loss of control or metal leakage.
Referring to
FIGS. 1 and 2
, a three-plate metering gate assembly
10
(hereinafter “gate
10
”) typically consists of five basic components: a well nozzle
20
, a top plate
30
, a throttle plate
40
, a bottom plate
50
and an outlet tube
60
. Liquid metal (not shown) flows into gate
10
at the top and flows out of gate
10
at the bottom.
The well nozzle
20
is a pipe, which allows the entry of liquid metal flowing from the teeming vessel (not shown) into a flow channel bore
22
at the top of the well nozzle
20
. The top plate
30
is in contact with the bottom of well nozzle
20
, and includes a flow channel bore
32
. The central axis
35
of the flow channel bore
32
in top plate
30
, as shown in
FIG. 2
, is collinear with central axis
25
of flow channel bore
22
in well nozzle
20
.
Throttle plate
40
is in contact with the bottom of top plate
30
. Gate
10
is designed so that throttle plate
40
may slide laterally relative to the other components of gate
10
. Bottom plate
50
is in contact with the bottom of throttle plate
40
, and includes a flow channel bore
52
. Central axis
55
of flow channel bore
52
in bottom plate
50
is collinear with central axis
25
of flow channel bore
22
in well nozzle
20
.
Outlet tube
60
is in contact with the bottom of bottom plate
50
, and includes a flow channel bore
62
. Central axis
65
of flow channel bore
62
in outlet tube
60
is collinear with central axis
25
of flow channel bore
22
in well nozzle
20
.
Central axes
25
,
35
,
55
and
65
of flow channels
22
,
32
,
52
and
62
in well nozzle
20
, top plate
30
, bottom plate
50
and outlet tube
60
, respectively, are collinear and all together define the “main central axis”
15
of gate
10
.
As shown in
FIGS. 3-5
, throttle plate
40
slides between fully open (FIG.
3
), partially open (
FIG. 4
) and gate closed (
FIG. 5
) positions. As shown in
FIG. 4
, during normal operations, throttle plate
40
typically is placed in a partially open position so that the flow rate of liquid metal through gate
10
may be metered, i.e., set and controlled, at a desired rate. As shown in
FIG. 3
, throttle plate
40
assumes a fully open position to maximize the flow of liquid metal through gate
10
. As shown in
FIG. 5
, throttle plate
40
may assume a closed position, which would stop the flow of liquid metal through gate
10
.
Metering gate components may be combined or subdivided. For example, to reduce the number of components, a gate
710
may be composed of only three parts, as shown in
FIG. 6
, in which the well nozzle may be combined with the top plate, defining a first component
712
, and/or the bottom plate may be combined with the outlet tube, defining a second component
714
, selectively placed in fluid communication with a throttle plate
740
. As shown in
FIG. 7
, to more easily replace the outlet tube of a gate
810
having a well nozzle
812
, a throttle plate
813
and a bottom plate
814
, the bottom plate
814
may be divided into two plates
816
and
818
.
Several variations of the fundamental three-plate gate components are used. For example, unlike the gate shown in
FIGS. 1-5
, in which well nozzle
20
has a tapered conical section bore
22
and bores
32
and
52
in plates
30
and
50
and bore
62
of outlet tube
60
define simple cylinders, as shown in
FIG. 8
, a gate
110
may have a well nozzle
120
with a cylindrical bore
122
and a top plate
130
with a conical bore section
132
with the bores in the throttle plate
140
, the bottom plate
150
and the outlet tube
160
being the same as in the gate
110
of
FIGS. 1-5
. Also, as shown in
FIG. 9
, a gate
210
may have conical bore sections
222
and
232
in both well nozzle
220
and top plate
230
with the bores in the throttle plate
240
, the bottom plate
250
and the outlet tube
260
being the same as in the gate
110
of
FIGS. 1-5
, and, as shown in
FIG. 10
, a gate
310
may have a well nozzle
320
having parabolically-shaped bore
322
and a top plate
330
having a conically-shaped bore
332
with the bores in the throttle plate
340
, the bottom plate
350
and the outlet tube
360
being the same as in the gate
110
of
FIGS. 1-5
.
FIG. 11
illustrates another variation of a gate
410
where cylindrical bore
442
in throttle plate
440
is canted at an angle to plate surface
443
in an attempt to direct the flow through throttle plate
440
back toward main central axis
415
of gate
410
.
FIGS. 12 and 13
illustrate partially open and gate closed positions, respectively, of gate
410
.
In gate
410
, bores
422
,
432
,
442
,
452
and
462
in well nozzle
420
, top plate
430
, throttle plate
440
, bottom plate
450
, and outlet tube
460
, respectively, generally are axisymmetrical. For example, the bores have either cylindrical or conical section geometry. The central axis
425
,
435
,
455
and
465
of well nozzle
420
, top plate
430
, bottom plate
450
, and outlet tube
460
generally are collinear.
Other variations of metering gates have been developed to provide for better draining of the throttle plate when it is closed. For example,
FIGS. 14-16
show a gate
510
, including a well nozzle
520
, a top plate
530
, throttle plate
540
, bottom plate
550
, and outlet tube
560
, in open, partially open and closed gate positions, respectively. Gate
510
is similar to that of
FIGS. 1-5
except that throttle plate flow channel bore
542
is extended by a special drain cut
544
near bottom edge
546
on one side to allow draining of bore
542
when the gate is in the closed position, as shown in FIG.
16
. This prevents trapping of liquid metal in throttle plate bore
542
which otherwise would solidify when the gate
510
is temporarily closed.
FIGS. 17-19
show another gate
610
, including a well nozzle
620
, a top plate
630
, throttle plate
640
, bottom plate
650
, and outlet tube
660
, in open, partially open and closed gate positions, respectively, which provides another drainage feature. A

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