Note: Descriptions are shown in the official language in which they were submitted.
~,c6591Z
1 --
The presen-t invention is a modi~ication of the invention
described and claimed in Canadian patent application No.
489,950 filed on September 4, 1985 in the name of Metacon AG.
This invention relates, like that of the said Canadian
patent application No. 489,950, to a method of casting or
pouring a molten metal, in particular a steel melt, from an
intermediate vessel into a plurality of continuous casting
moulds, wherein the filling level of the melt in each mould is
maintained, within a measuring zone, at a desired level by
means of controllable discharge valves and the resultant
continuous castings are withdrawn at the same speed by means
of common withdrawing means.
The said Canadian patent application No. 489,950 proposes
that, in such a method, when the discharge valves have been
opened at the intermediate vessel for commencing the casting
on process, the actual filling level which rises in each mould
above a starting bar head effects, on its reachiny a first pre-
determined threshold value or a first signal plane, located in
the lower region of the measuring zone, throttling of its dis-
charge valve in order to equaIize all of the actual filling
levels and subsequently the actuation of the casting withdrawing
drive. This actuation, in the event of the equalization not
having taken place, is effected at the latest at a second pre-
determined threshold value or a second signal plane located
~5 below a desired filling level and above the first signal plane,
on the first actual filling level reaching the second signal
plane. The casting on process performed at the same withdrawing
speed is thereby improved, in particular concerning its opera-
tional reliability, with simple procedural steps.
The present invention is a modification of a cas-ting-on
process controlled within a filling level measuring zone in
~ continuous casting moulds by way of discharge valves, with
- constant withdrawing speed. An object of the invention is
the improvement of the casting-on process by reducing the
casting-on time by means of simplified procedural steps.
` ~. : ,.: .
. .
. ~,. ~ . ,
~5~
-- 2
According to the present inventlon -there i5 hence
provided a method of pouriny a molten metal from an in-ter-
mediate vessel into a plurality of continuous castiny moulds
through respective controllable discharge valves and with-
drawing all the resultant castings from the moulds with cornmonwithdrawing means at the same speed, which includes
opening all the valves to initiate the pouring process;
monitoring the filling level within each mould in a
measuring zone;
activating the withdrawing means on the actual filling
levels of all the moulds reaching a first predetermined thres-
hold value within the measuring zone or on a first actual
filling level reaching a second predetermined value, within
the measuring zone, above the first predetermined threshold
value; and
regulating each actual filling level to move, from the
first predetermined threshold value to a desired filling level,
at a predetermined rate.
In this manner the equalization of the actual filling
levels of all the continuous casting moulds (at which equaliza-
tion the invention of the said Canadian patent application No.
489,350 aims) is avoided and control of the actual filling
level of each continuous casting mould can be introduced
smoothly in a separate manner into the normal feed regulation
of the desired filling level, the casting withdrawing means
being suitably actuated at a filling level of at least one of
the continuous casting moulds between the lower and the upper
predetermined threshold values or signal planes of the measur-
ing zone, which ensures reliable withdrawal of the continuous
castings. The withdrawing means accoxdingly reacts upon that
which occurs first during the rise of the actual filling levels
in the continuous casting moulds. In other words, the withdraw-
ing means switches on when the lower signal plane is exceeded
by the last actual filling level or, if this does not occur, as
soon as the first actual filling level has reached the upper
signal plane. As in the invention of the said Canadian patent
; application No. 489,950, after the withdrawing means has been
:.
. .
:: "
: ~ : : : ,:
~65~
-- 3
actuated, the discharge valves of those continuou~ casting
moulds of which the actual filliny level is still located
below the lower signal plane, close automatically.
For a particularly smooth and operationally reliable
casting on, the present invention proposes that -the regulation
of the discharge valves, which is initiated at the lower signal
plane, is such that the predetermined rate is in a region above
the congealing limit of the melt in the valves, on the one
hand, and below the splashing limit of the melt over the mould
edge on the transition to the regulation of the desired filling
level, on the other hand, ie. it takes place along an ascending
curve when the filling level (y-axis) is plotted against time
(x-axis). With this process, the transition from rapid regula-
tion alony the ascending curve, which is defined by rapid
changes of the flow cross-section at the discharge valves, to
relatively slow regulation of the desired filling level with
relatively undisturbed residual casting mould bath level, can
take place. Furthermore congealing which can occur in the
discharge valves and impede the pouring stream of molten metal
is substantially reduced. This counteraction is further
assisted by pouring being effected with the discharge valves
being throttled up to 50%. Those discharge valves which are
the most remote from the feed point of the intermediate vessel,
ie. the discharge valves associated with the outer casting
moulds, are advantageously less throttled than those of the
inner casting moulds. In this manner the lower temperatures
of the melt which prevail in the outer regions of a continuous
casting plant or of an intermediate vessel are effectively
taken into acdount. There is furthermore the possibility of
opening~the discharge valves fully ,in the event o~ the actual
fiIling levels lagging during pouring below the lower signal
plane, before regulating the levels along the ascending curve,
in order to flush away congealing crusts.
The invention will now be described by way of example with
reference to the accompanying drawings in which
:: :
.
: ,: :~ ,
: ~ :
: - : ~,
,
~:` ~ : ' ~'', , ,
5~
-- a~
FIGURE 1 is a diagrammatic view of a multiple con-tinuous-
casting installation in a pouriny-on pos:ition; and
FIGURES 2 and 3 diagrammatically illustrate different
possible operational pouring sequences at pouriny on, ie. at
commencement of pouring.
Reference numeral 1 in Figure 1 indicates a casting ladle
from which steel melt is supplied via a controllable discharge
valve 2 to an intermediate vessel 3 which, for its part, has
three discharge valves in the form of sliding gate valves 4
which regulate the supply of melt through respective pouring
channels or tubes 5 into three continuous casting moulds A, s,
C. Each sliding gate valve 4 is mechanically coupled to an
actuator or positioning member 6 whose operational position
at any time is detected by a position indicator or sensor 7.
The free ends of the pouring channels 5 project into the
continuous casting moulds A, B, C. For each casting mould, a
desired filling level 8 set for normal operation, is located
within a measuring zone 9 of a filling level measuring device
associated with each continuous casting mould A, ~, C and
comprising a transmitter 10 and a receiver 11.
Downstream of the continuous casting moulds A, B, C is
a secondary cooling device which is not shown for the sake of
simplicity, and withdrawing means, common to all continuous
castings 18 formed in the moulds A, B, C, and comprising
drive rolls 12, a drive motor 13, a drive regulator or
controller 14, and a withdrawing velocity or speed sensor 15.
The latter supplies signals firstI~ to the drive regulator 14
and secondly to a processor 16 which also receives and processes,
in addition, signals from the position indicators 7 indicative
of the degree of opening cf the sliding gate valves 4 and
signals from the xeceivers 11 indicative of the açtual filling
levels in the moulds. The dat~ obtained are supplied to a
~` control computer 17 integrated in the processor 16, the computer
giving appropriate control commands to the actuators 6 of the
`~:
~ ''-^" :
`; :
,' :~ ~ ,. ... . .
' ' : : :, . ;,
~65~
-- 5
sliding gate valves 4 and to the reyulator 14 of the withdraw-
ing means. The withdrawing speed is set as a constant, ie. the
continuous castings 18 formed in the moulds A, B, C are with-
drawn by the common withdrawing means at a constant speed,
which means that the filliny levels 8 are regula-ted solely
from the feed or supply side by means of the slidiny yate
valves. For this purpose, the slidiny yate valves 4 are main-
tained in normal pouring operation in throttled positions in
order to enable the flow through them to be increased as well
as decreased.
For casting on, ie. at commencement of pouring or casting,
startiny bars or cold castings l9 are introduced into the con-
tinous casting moulds A, s, C and the withdrawing drive 13 is
switched off. The measuring zone 9 has a lower signal plane 21
and an upper signal plane 22 which serve for controlling the
sliding gate valves 4 and the drive motor 13. However, this
is effected in a different fashion than in the invention of the
said Canadian patent application No. 489,950, in which the
actual filliny levels 20 of all three continuous casting moulds
A, B, C between the signal planes 21 and 22 are brought to one
level during pouring.
For pouring-on according to the present invention, the
slide valves 4 a~e opened partially, preferably only 35~, ie.
they are by no means fully open~d. ~here are hence created
controlled reserves for the valves 4 both in the closing as
well as in the opening directions, which allow each actual
rising filling level 20 in each continuous casting mould A, B,
C (see Figure 2) to rise from the lower signal plane 21 to the
desired filling level 8 at a predetermined ra-te, ie. along a
predetermined ascending curve 40, which is matched to the
operational conditions of the respective plant by suitable
programming of the processor 16.
The criterium of curve 40 which determine the filling
speed of the continuous casting moulds A, B, C during pouring,
'-, ,' ` .
.,
.. . ~ . .
,,
,
-- 6
is that it must no-t be so flat -that it falls below the con-
gealing limit of the melt in the slidiny valves, nor must i-t
be so steep that the upper splashing limit at the edge of the
continuous casting mould is exceeded. The regulating of each
slide valve 4 according to curve 40 starts, as mentioned, a-t
the lower signal plane 21 and is triygered by the rising filling
level 20 in the continuous casting moulds A, B, C. When, on
rising, the last of all the actual filliny levels A20 or B20
or C20 passes the lower signal plane 21, the control computer
17 of the processor 16 switches on the withdrawiny drive motor
13 of the common withdrawing means for the castings 18. The
rising of the actual filling levels A20, B20, C20 then take
place independently from one another, continuing on the basis
of the same criteria and, consequently, according to graphically
parallel ascending curves 40 until the desired filling level
set for normal casting operation is reached. If, during this
transition stage the sliding gate valves would have received
excessive signals due to a too rapidly rising filling level 20,
splashing of the melt over the edge of the continuous casting
mould would occur. If, during pouring, an actual filling level
20 of a continuous casting mould A or B or C has already reached
the upper signal plane 22, whilst the others are still below
the lower signal plane 21, closing signals would issue to the
sliding gate valves 4 associated with the moulds whose actual
filling levels 20 are iagging in the said manner.
The graphic illustrations according to Figure 2 appl~ to
the actual filling levels 20 indicated in Figure 1. According
to these, the actual filling level 20 of the continuous casting
mould C has reached the lower signal plane 21 first within a
time Ct, after the simultaneous throttled opening of all the
sliding gate valves 40 at the commencement of pouring. The
sliding gate valve 4 associated with the continuous casting
mould C then~regulates of the melt suppl~v according to the
predetermined ascending curve 40. As a result, the actual filling
levels 20 of the continuous casting moulds B and A pass
successively in the times Bt and At through the signal plane 21,
'
-:
: , . - :
, .
: -
i55~
-- 7 --
and their rising is then also regulated to follow ascending
curves 40~ None of the actual filling levels 20 lays sub-
stantiall~v behind the others. A20 reaches the lower signal
plane or level 21 before C20 has reached to the upper siynal
plane 22, so that the start command for the casting withdraw-
ing drive motor 13 oriyinates from the actual filliny level
A20 reaching the lower signal plane 21.
This is, however, not the case in the example according
to Figure 3, in which the actual filling level A20 has reached
the upper signal plane 22, and the actual filliny level B20
has exceeded the lower signal plane 21, but the actual filling
level C20 lags behind, below the lower signal plane or level
21. ~ith this arrangement of actual filling levels the casting
withdrawing drive motor 13 is triggered at the upper signal
plane 22 through the actual filling level A20 and at the same
time the slide valve 4 for the actual filliny level C20, which
has not risen above the lower signal plane 21, is closed.
. . , , . , ~ ;, .. ~ - , .
: ~ . .
