Note: Descriptions are shown in the official language in which they were submitted.
~0~20~ig
SPECIFICATION
METHOD OF AUTOMATICALLY STARTING A CONTINUOUS CASTlNG
APPARATUS
''
FIELD OF THE INVENTION
: The present invention relates to a method of
automatically starting a continuous casting apparatus and,
more particularly, to an automatic starting method for a
continuos casting apparatus, such as twin or tripple
casting, for casting a plurality of 31abs by mean~ of a
common strand guide and for a continuous casting apparatu~
using a level gauge for mea~uring the ~urface level o~
molten metal within a narrow measuring range.
BACKGROUND OF THE INVENTION
A typical prior-art method of starting a continuous
casting apparatus comprises the following steps. A Command
. signal for starting the teeming of molten steel from a
tundi~h into a mold is first issued by a wPight control
device for controlling the weight of molten steel in the
tundish or a level control device for controlling the
surface level of molten steel in the tundish, and in
response to the command signal a stopper for opening and
closing a pouring opening is automatically opened which is
provided in the tundish, whereby teeming of molten steel
from the tundish into the mold is commenced. When the
surface of the molten steel in the mold, that i5, the level
of the molten steel, reaches a lower measurement limit of a
radioactive type or eddy-current type level gauge, pinch
rolls are started and simultaneously the speed of the rolls
is controlled to permit the molten steel level in the mold
to rise up to a steady control level.
However, according to such prior-art starting method, in
which a non-contacting level gauge, such as radioactive
type or eddy-current type, is employed for mol-ten steel
level measurement, the possible measurement range ls
limited, for prac-tical purposes, to about 100 mm and, on the
lower side relative to the s~eady control level, to about 60
mm. Primarily, when star-ting a continuous castlng
apparatus, it is effective to start up pinch rolls at a low
speed and gradually upward. Because of the above noted
measurement limits of the level gauge, however, gradual
start-up of the pinch rolls is likely to result in
overflowing from the mold of molten steel teemed from the
tundish into the mold. Therefore, there is no alternative
but staring up the pinch rolls at a fast spee~. Even in
this case, there is still some possibility of molten steel
overlowing from the mold or the like trouble. Especially
where the continuous casting apparatus employed is a twin or
tripple casting apparatus for casting a plurality of slabs
-- 2 --
~213~9
by means of a common strand guide, it is extremely difficult
to start the apparatus while controlling the speed oE the
pinch rolls.
SUMMARY OF THE INV~NTION
The primary ob~ect of the present invention is to
provide a method of starting a con-tinuous casting apparatus
which eliminates the above mentioned problem with the prior
art and thus enables steady starting of the casting
apparatus.
In order to accompllsh this object, according to the
invention there is provided a method of automatically
starting a continuous casting apparatus having a mold, a
tundish for temporarily storing therein molten steel for
subsequent transfer to the mold, means for transfe:rrlng the
molten steel from the tundish to the mald, a level meas-lring
device for measuring the surface level of the molten steel
in the mold and means for controlling the quantity of the
molten steel to be transferred from the tundish to the mold
on the basis of a level value measured by the level
measuring device, said method comprising, stopping the
transfer of molten steel from the tundish to the mold once
the surface of the molten steel in the mold reaches a
predetermined level after the transfer is commenced,
allowing the molten steel in the mold to stand as it is for
a predetermined period of time thereby to stabilize the
o~9
surface of the molten steel in the mold, subsequently
starting the drawing of a slab formed by means of the mold,
and simultaneously resuming the trans~er of molten steel
from the tundish to the mold to bring the surface of the
molten steel in the mold to a steady control level.
~ ccording to the method of -the invention as described
above, after the transfer of molten steel from the tundish
to the mold and when the surface of the molten steel in the
mold reaches the predetermined level, the transfer of molten
steel is stopped once, so that actual level mea~urement of
the molten steel surface during the automatic start-up of
the contiuous casting apparatus can be performed in a stable
stationary condition. At the same time, shifting fro~ the
mea~ured level to a ~teady control level can be made quickly
with no particular speed control being required of pinch
rolls only for the purpose of automatic starting. According
to the invention, therefore, it i~ possible to automatically
start the continuous casting apparatus with no possible
overflow or breakout. e~pecially where the continuous
castin~ apparatus is one for casting a plurality of slabs by
means of a common strand guide, such as a twin or tripple
casting apparatus, it is possible to stabilize the level of
molten steel in the mold at a predetermined value during the
start-up of the apparatus, and thus to automatically start
the ca~ting apparatus at ease.
-- 4 --
i9
BRIEF DESCRIPTION OF T~E DRAWIMGS
FIG. 1 is a sectlonal view showing the arrangement of a
continuous casting apparatus representing a first embodiment
of the invention;
FIG. 2 is a block diagram showing a control system in
the first embodiment;
FIGs. 3a, 3b and 3c are flow charts showing the process
of automatic starting for the flrst embodiment;
FIGs. 4a, 4b, and 4c are graphs respectively showing the
;. relatlons between molten steel level and time, between
stopper opening and time, and between drawing ~peed and
time, with re~pect to the first embodiment;
FIG. 5 is a sectional view showing the arrangement of a
continuous ca~ting apparatus representing a second
embodiment of the invention;
FIG. 6 is a block diagram showing a control system in
the second embodiment;
FIG. 7 is a sectional view showing the arrangement of a
continuous casting apparatus representing a third embodiment
of the invention;
FIG .~ is a block diagram showing a control system in
the third embodiment;
FIGS. 9a, 9b, and 9c are flow charts showing the process
of automatic starting for the third embodiment; and
FIGS. lOa, lOb, and lOc are graphs respectively showing
. -- 5 --
., ' .
the relation~ between molten steel level and time, between
stopper opening and t.ime, between sllde nozz:le opening and
time, and between drawing speed and tlme.
DESCRIPTION OF EMRODIMENTS
Firstly, a flrst embodiment of the invention will be
described with reference to FIGS. 1 through 4.
; FIG. 1 shows the arrangement of a continuous casting
apparatus. Numeral 1 designates a ladle at the bo-ttom side
of which a ladle-side long nozzle 3 ~s provided through the
intermediary of a slide no2zle 2. Di~posed below the ladle
1 i~ a tundish 4 which i9 formed at the bottom thereo~ with
a pouring openlny 5, and directly below the pouring opening
5 there i~ provided a tundlsh-side long nozzle ~ for
conducting the molten metal in the tundish 4 into a
continuous ca~tlng mold 6. A bar-like stopper 8 for opening
and closing the pouring opening 5 is mounted in the tundish
4 through a support rod 9. At one end of the support rod 9
there are provided a manual lift device 10 for moving the
stopper 8 upward and downward and a hydraulic cylinder 11
for automatically moving the stopper 8 upward and downward.
The manual lift device 10 comprises a rack 12 mounted to the
support rod 9, a pinion 14 disposed ad~acent a guide member
13 of the rack 12 for mesh engagement with the rack 12, and
a control handle 15 for rotating the pinion 14.
Numeral 16 designates a load cell for measuring the
2~3~9
weiyht of the molten steel in the tundish 4, and numeral 1
designates a non-contacting level gauge (such as a
radioactive type or eddy-current type level gauge~ for
measuring the surface level of the molten steel in the mold
6. Numeral 21 designates pinch rolls for drawing a slab
through a dummy bar 22 which is driven by a motor 24 through
a reduction gear 23. The motor 24 is controlled by a draw
control unit 25. Shown by 26 is a guide roll.
Nextly, a control system for the continuous casting
apparatus will be described with reference to FI~
A level control unit 31 receives a signal from the load
cell 16 as an on / off signal through a weight measuring
unit 32 and a contaat 33 and also receives a ~igna:l from the
level gauge 17 through a level gauge amplifier 34. There i~
provided a servo valve 35 for controllin~ the hydraulic
cylinder 11 which actuates the stopper a. The servo valve
35 receives a control signal from the level control unit 31
through a servo amplifier 36. Designated by 37 i~ a
hydraulic unit. Hydraulic pipes 38 run from the ~ervo valve
35 to the hydraulic cylinder 11, and a bypass pipe 39 is
provided at an intermediate point on the hydraulic pipes
3a, with an electromagnetic on-off valve 40 disposed midway
on the bypass pipe 39, so that at position I hydraulic
fluid is bypassed to prevent the hydraulic cylinder 11 from
being actuated by a signal from the servo amplifier 36. At
- 7 -
~0~2(~
po~ition II, of course, the hydraulic cylinder 11 is
actuated. The elec-tromagnetic on-off valve 40 is controlled
through an electromagnetic valve con-trol unlt 41 b~ an on /
off signal which is inputted from the level control unit 31
to a contact 42 for the valve control unit 41~ A signal
from a position detector ~e. g., a potentiometer) 43 for the
stopper 8 connected to a rod portion lla of the hydraulic
cylinder 11 is entered into both the servo amplifier 36 and
the level control unlt 31. The draw control unit 25
controls the ~otor 24 for driving the pinch rolls 21 and, in
conjunctlon therewith, receives a signal from a rotation
speed detector 44 for pinch rolls 21. Thi~ draw control
unit 25 is controlled by an on / off signal from the level
control unit 31 which is inputted to a contact 4B of the
unit 25. De~ignated by 46 is a push-button switch for
initia-ting control operation of the level control unit 31.
Nextly, the manner of control operation will be
explained mainly with reference to FIGS. 3a, 3b, and 3c.
Prior to the start of operation of the continuous
casting apparatus, the operator manipulates the control
handle 15 for registering the stopper 8 with the pouring
opening 5 in preparation for the start of operation. Upon
completion of the step of registering, the stopper 8 is
first brought to its fully closed position and tbe push-
button switch 46 is turned on, whereupon the level control
2~3S9
unit 31 executes step 100 and then reads various set values
(step 101). Subsequently, a value for the position of -the
rod portion lla of the hydraulic cylinder 11 connected to
the support rod 9 is fetched by line 61 through the position
detector 43 (step 102). The weight of the molten metal
teemed into the tundish 4 i5 measured by the load cell 16,
and a signal for the measured weight is conducted to the
weight measuring unit 32. The weight measuring unit 32
outputs a signal to the level control unit 31 through the
contact 33 when the weight of molten metal reaches a pre-set
value. The level control unit 31 starts control ~or
automatic starting upon rece.lpt of an ON signal (step 103).
An initial stopper opening command value preset in the level
control unit 31 is glven via line 62 to a servo system
consisting of the servo amplifier 36, ~ervo valve 35,
hydraulic unit 37 for feeding hydraulic fluid to the servo
valve 35, hydraulic cylinder 11, position detector 43, and
electromagnetic on-off valve 40 for bypassing the hydraulic
pipe 3a from the servo valve 35, and simultaneously an ON
signal is outputted to the electromagnetic valve control
unit 41 through the contact 42 (step 104), whereupon the
electromagnetic valve 40 is switched over from its bypass
state to a control state in which it can control the
hydraulic cylinder 11. Therefore, the stopper a i5 SO
positioned by the hydraulic cylinder 11 as to meet the
: .
g
i9
initial stopper opening command value. Thus, molten steel
is teemed from the tundish 4 into the mold 6 -through the
pouring opening 5 and long nozzle 7 so that the level of the
molten steel in the mold 6 rises. When the molten steel
level reaches a lower limit of the mea~uring range of the
level yauge 17, the level gauge 1~ starts molten steel level
measurement (positlon B in FIG. 4a). A level signal from
the level gauge 17 i9 conducted to the level gauge amplifier
34 in which it is amplified for being fetched into the level
control unit 31. In FIG. 4a, LC designates a steady level
control target value, LCD designate~ a transition level
control target value set at a posit:ion lower than LC, I.CU
designates a transition level control target value set at a
position higher ~hat LC, and l,S5 designates a set value for
detecting an initial level for commenicing automatic
starting operation. The above noted set values may be
exemplified as follows: where point A in FIG. 4a is level 0
mm, LC = 100 mm, LCD = 110 mm, LCU = 90 mm, and LSS = 120
mm. When the molten steel level reaches the automatic
starting level (LSS) preset in the level control unit 31,
the level control unit 31 gives a position command value for
bringing -the stopper ~ to its fully closed position (STPC)
: to the servo amplifier 36 through the line 62 (steps 105,
106), and accordingly the stopper 8 is so posi-tioned by the
hydraulic cylinder 11 as to meet the full-close command
-- 10 --
value, whereupon teeming of molten steel into the mold 6 is
stopped so that the molten steel level in the mold 6 stops
rising and is stabilized. Thls process is illustrated in
FIG. 4a by way of a level rise pattern. In region } which
is outslde the measuring range of -the level gauye 17, the
level gauge 1~ issues no output. When the level of the
molten steel reaches point B, the level gauge 17 starts
measurement (region 2). When the molten steel level reaches
LSS, a full close command value i5 outputted to the stopper
8 a5 above stated. Until the ~topper 8 i9 brought to its
fully closed position, therefore, the molten steel level
continues to rise gradually; and then it stops rising
(region~ 3 and 4 ). The level control unit 31 ~tarts a
timer when it ha~ outputted a ~ull-close commarl~ value tstep
107~, and when a preset period of tlme ~TL) has Iapsed (~tep
108~, a current value for the molten steel level i5
determined (step 10~). It is noted here that the expression
"current value for the molten steel level is determined"
means that the current value (Li) of the molten steel level
at the end of time TL clocked by the timer i~ stored as LS =
Li in the level control unit 31 into which i~ constantly
fetched such current value. Such manner of control as ~n
the present embodiment that the stopper 8, after brought to
an open position, is again brought to its fully closed
position has not been employed in any prior art starting
z~9
method; and therefore, it has hitherto been difficult to
accurately determine a level for initiating automatic start-
up. This is one factor which has hither-to made it difficult
to carry out automatic start-up with hi~h sense af
reliabllity. Timer is then actuated (step 110), and when a
preset period of time (TS) has Iapsed (step 111), the pinch
rolls 21 are driven to start (step 112) and simultaneously
the stopper ~ is controlled (step 113). That is, an
operating signal is issued from the level control unit 31 to
the draw control uni-t 25 through the contact 45 so that the
drive motor 24 for the pinch rolls 21 i9 driven, and an
opening command value (ST) for the stopper ~ at the start of
drawing operation is outputted to the servo ampliPier 36
(s-teps 112, 113). ~ a result of these steps, t~eminy of
molten steel from the tundish 4 into the mold 6 is a~ain
commenced, and simultaneously the pinch rolls 21 are driven
to start. Thus, automatic starting of the continuous
casting apparatus is commenced. More specifically,
comparison operation is performed of the determined level
(LS) in relation to the control target values (LC, LCD, LCU)
in same timing as step 110 thereby to determine level
control target values (steps 114, 115, 116, and 118). Then,
level control is commenced by using STPC + STPS determlned
by step 113 as an initial value for stopper opening (step
119). At step 119, output MV of PI operation, that is, a
- 12 -
~D20S~
stopper opening command value in terms of STPC + STPS is
outputted as an initial value to the servo amplifier 36.
As a consequence of the above compari~on operation, the
control line branches into (A), ~B) and (C) Lines. When (B)
is automatically selected, LCD is set as a control target
value and according -the difference between LCD and current
level value (Li), that i5, dL = LCD - Li ls calculated (step
120), the level difference dL being subjected to PI
operation, the result of which is outputted as MV to the
servo amplifier 36 (step 122). Therefore, the ~-topper a is
controlled through the hydraulic cylinder 11 in such a way
that its opening ls increased; accordingly the molten steel
level rises. The re~ult of step 122 is logically operated
at ~tep 123, and as long as Li is smaller than the target
value LCD, steps 120 and 122 are repeated. When Li becomes
larger than LCD, the control target value is changed over
from LCD to LC (steps 123 and 12~), and the difference
between LC and current level value ~Li), that is, dL = LC -
Li is calculated (step 126), the level difference dL being
sub~ected to PI operation, the result of which i5 outputted
as MV to the servo amplifier 36 (step 127~ for steady level
control. When line (C) is automatically selected, as is the
case with line (B), steady level control can be accomplished
by steps 119, 121, 122, and 124. When line (A) is
automatically selected, steps 126 and 127 are executed
- 13 -
s~
immediately, whereby steady level control can be
accomplished. The steps for steady level control are
repeatedly continued until, for example, the operator
terminates level control (Step 128).
At step 123 (or step 124), it is arranged that advance
to step 125 depends upon the result of comparison operation
of control target value LCD (LCU) with current level value
(Li), while the posslbility of overshoot occurrence should
be considered in the practical process of level control.
As a result of step 123 ~step 124), the control target value
changes stepwise from LCD (LCU) to LC, but it ls noted -that
a change of the order of ten-odd mm as exemplified ls merely
a matter o~ ~hort tlme variation and has no adver~e e~fect
on the proce~s of level control from the standpoint of
practical control. In this way, a series of control ranying
from the start of stopper 8 control to the startin~ of the
pinch rolls 21 and further to steady level control is
performed for automatic startiny of the continuous casting
apparatus.
Stopper opening conditions are graphically shown in FIG.
4b, and draw speed - tlme relations are graphically shown in
FIG. 4c.
A second embodiment of the invention will now be
described with reference to FIGS. 5 and 6.
FIG. 5 illustrates the arrangement of a continuous
- 14 -
32~
casting apparatus repre~enting the second embodiment. The
apparatus i~ differen~ from the one shown in FIG. 1 in that
a contacting type level detec~or 17A (e. g., a thermocouple
type or resistance wire type level detector) for positlve
detection of the ~urface level of the mo:Lten steel in the
mold 6 is provided separately from the non-contacting le~el
gauge 17 (e. g., a radioactive type or eddy-current type
level gauge) for measuring -the level of the molten steel.
FIG. 6 shows a control sy~tem for the continuous casting
apparatus of the second embodiment. Thi~ control system is
different from the one show in FIG. 2 in that not only
~ ~ignals from the level gauge 1~ but al~o signal~ from the
level detector 17A can be received into the level control
unit 31 through an ampli~ier 34A.
Nextly, the manner of control operation will be
expla1ned. The flow of control operations i5 quite same as
that shown in FIG. 3a to 3c, except that a rise in the
surface level of molten steel teemed from the tundish 4 into
the mold 6 is, in this second embodiment, detected by the
level detector l~A and, when the surface of the molten steel
reaches the predetermined level (LSS), a detection signal
from the level detector l~A is fetched into the level
control unit 31 through the amplifier 34A, the stopper 8
being then closed via same steps as in the case of the first
embodiment. The level of the molten steel after the stopper
- 15 -
8 belng closed is re~uired to be within the measurable range
of the level yauge 17, but the dtecting position of the
level detector 17a i9 not necessarily required to be within
such measurable range, because the molten steel level will
slightly rise after it is detected by the level detector
17A. Simultaneously with operation of the level detector
17A, changeover from the level detector 17A to the level
gauge 17 is effected by the level control unit 31, and
thereafter control of the molten steel level is carried out
on the basis of a level signal from the level gauge 17.
According to this ~econd embodiment, the con-tact-type
level detector l~A and the non-contac~in~ type level gauge
1~ are used in combination for the purpo~e of measurin~ the
level of the molten steel in the mold. Therefore,
improvement can be obtained over the first embodlment in
respect of response performance in molten steel level
measurement, and in addition more accurate detection of
moltem steel level is possible. Thus, stable measurem~ents
of molten steel level can be obtained.
Nextly, a third embodiment of the invention will be
described with reference to FIGS. 7 to 10.
FIG. 7 illustrates the arrangement of a continuous
casting apparatus representing the third embodiment. The
apparatus is different from the one shown in FIG. 1 in that
a tundish-side slide nozzle ~hereinafter referred to as
,J~3,3,~t~9
slide nozzle) 2~ is separately disposed below the pourlng
opening 5, and in that a second hydraulic cylinder 28 for
controlling the opening of the pouring opening 5 is
connected to the slide nozzle ~.
FIG. 8 shows a control system for the continuous casting
apparatus of the third embodiment. This control system is
different from the one shown in FIG. 2 in that a servo valve
4~ for controlling the second hydraulic cylinder 28 for
actuating the slide nozzle 27 is separately provided and in
that the servo valve 47 receives a control signal from the
level control unit 31 through a servo amplifier 48. Shown
at 49 is a hydraulic unit. Further, signals from a posit:lon
detector (e. g., a potentiometer) 50 for the slide nozzle 2
connected to a rod por~ion 28a of the second hydraulic
cylinder 28 are inputted to the servo amplifier 48 and level
control unit 31.
Nextly, the manner of control operation will be
described with reference to flow charts shown in FIGS. 9a,
9b, and, 9c.
As is the case with the first embodiment, registration
of the stopper ~ with pouring opening 5 is first carried out
and then the stopper ~ is brought to its fully closed
position, and the push-button switch 46 is turned on.
Accordingly the level control unit 31 carries out step 100
and reads various set values (step 101). Subsequently, as
~2~$9
in the case of the first embodiment, a current level of the
stopper ~ is read (step 102) and, when the weight of molten
steel poured into the tundish ~ reaches a pre set value,
control for automomatic starting i9 commenced (step 103).
A ~topper lnitial opening command value preset in the
level control unit 31 is outputted to the servo amplifier
36, and simultaneously an ON signal is outputted to the
electromagnetic valve control unit 41 through the contact 42
(step 104). Thus, the stopper 8 is so positioned by the
hydraulic cylinder 11 as to meet the stopper initial opening
command value. Simultaneously, a slide no2zle opening
command value (SNP) is outputted to the servo ampllfier 48
through line 63 (step 104); accordingly a servo ~y~tem
consistiny of the servo amplifier 48, servo valve 47,
hydraulic pipe 51, second hydraulic cylinder 2a and position
detector 50 for the slide nozzle 27 is actuated so that the
opening of the slide nozzle 2~ is positloned to the opening
command value (SNP). In this way, molten steel is teemed
from the tundish 4 into the mold 6 through the pouring
opening 5 and slide nozzle 10, and aocordingly the level of
the molten steel in the mold 6 rises. When the molten steel
level reaches a lower limit of the measuring range of the
level gauge 1~, the level gauge 17 starts molten steel level
measurement (position B in FIG. lOa). A level signal from
the level gauge 17 is conducted to the level gauge amplifier
.
,; ~
t~ 2~
34 in which i~ is amplified, and i5 then fetched into the
level control device 31.
When the molten steel level reaches an automatic
starting level (LSS~ preset ln the level control unit 31,
the level control unlt 31 supplies to the servo amplifier
36 via line 62 a posltion command value ~STPC) for full
closing of the stopper 8 ~steps 105, 106), and accordingly
the stopper 8 is so positioned by the hydraulic cylinder 12
as to meet the full close command value, whereupon molten
steel teeming into the mold ~ is stopped 50 that the molten
steel level ln the mold 6 stops rising and becomes
stabilized. FIG. lOa shows a pattern of molten steel level
rising in the mold 6 which i~ same a~ that shown in FIG. 4a,
description being therefore omitted herein witl~ respect to
the level rislng pattern.
Upon outputting of a full close command value, the level
control unit 31 starts timer (step 107) and, when a preset
period of time ~TL) has passed (step 108), a current value
of the molten steel level ~Li) is determined as LS = Li and
stored in the level control unit 31 (step 109).
Subsequently, timer is ayain actuated ~step 110) and,
when a preset period of time ~TS) has passed ~step 111),
starting of the pinch rolls 21 ~step 112) and control of the
stopper 8 and slide noz~le 27 ~step 113) are simultaneously
carried out. That is, an operating signal is outputted from
-- 19 --
t"~
the level control unit 31 to the draw control unit 25
through contact 45 to thereby drive ~he drive motor 2~ for
the pinch rolls 21, and an opening command value for the
stopper a (ST) at start o~ drawing i5 outputted to the servo
amplifier 36 and an opening command value for the slide
nozzle 27 (SNPS) at start of drawing i9 outputted to the
servo amplifier 48. As a result of these steps 112, 113,
molten steel teeming from the tundish 4 into the mold 6 is
again commenc~d and simultaneously the pinch rolls are
actuated. Thus, automatic starting of the continuous
casting apparatus is commenced.
Then, comparison operation is carried out of the
determined level (LS) relative to the above noted control
target values (LC, LCD, LCU) wlth same timing ag that in
step 110 so that level control target values are determind
(steps 114, 115, 116, 11~, and 118). Accordingly, level
control is commenced using the SNPS value determined by step
113 as initial value for slide nozzle opening (step 119).
At step 119, output MV of PI operation, that is, slide
,
nozzle opening command value is outputted as an initial
value in SNPS value terms to the servo amplifier 4a.
As a result of the above comparison operation, the
control line is branched into lines (A), (B) and (C) and
thereafter steps 120 through 128 are carried out according
: to same procedure as in the case of the first embodiment.
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.~:
~. .
.,
2~9
Steady level control i5 thus accompli~hed.
In this manner, a series oP control from -the start of
control of the sllde rozzed 27 to start-up of pinch rolls 21
and ~urther to steady .level contro:l is carried out for
automatic starting of the continuous casting apparatus.
Stopper opening conditions are graph.ically shown in FIG.
lOb, slide no~zle opening conditions are graphically shown
in FIG. lOc, and draw speed - time relations are graphically
shown in FIG. lOd.
According to the arrangement of this third embodiment,
slide nozzle 27 i~ employed whereby the quantity of molten
steel transferred from the tundish 4 to the mold 6 can be
accurately controlled.
In the preqent ivention, it is needless to say that a
method of automatically starting a continuous casting
apparatus comprising a combination of respective features of
the second and third embodiments can be emplyed.
- 21 -
