CA2002059A1 - Method of automatically starting a continuous casting apparatus - Google Patents
Method of automatically starting a continuous casting apparatusInfo
- Publication number
- CA2002059A1 CA2002059A1 CA002002059A CA2002059A CA2002059A1 CA 2002059 A1 CA2002059 A1 CA 2002059A1 CA 002002059 A CA002002059 A CA 002002059A CA 2002059 A CA2002059 A CA 2002059A CA 2002059 A1 CA2002059 A1 CA 2002059A1
- Authority
- CA
- Canada
- Prior art keywords
- molten steel
- level
- mold
- tundish
- transfer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
- B22D11/201—Controlling or regulating processes or operations for removing cast stock responsive to molten metal level or slag level
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/161—Controlling or regulating processes or operations for automatic starting the casting process
Abstract
ABSTRACT OF THE DISCLOSURE
A method of automatically starting a continuous casting apparatus having a mold, a tundish for temporarily storing therein molten steel for subsequent transfer of the molten steel to the mold, a device for transferring the molten steel from the tundish to the mold, a level measuring device for measuring the surface level of the molten steel in the mold and a device 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, which comprises 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 surface of the molten steel in the mold, subsequently starting the drawing of a slab formed by means of the mold, and simulataneously resuming the transfer 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. According to this method, it is possible to easily carry out automatic starting of the continuous casting apparatus.
A method of automatically starting a continuous casting apparatus having a mold, a tundish for temporarily storing therein molten steel for subsequent transfer of the molten steel to the mold, a device for transferring the molten steel from the tundish to the mold, a level measuring device for measuring the surface level of the molten steel in the mold and a device 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, which comprises 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 surface of the molten steel in the mold, subsequently starting the drawing of a slab formed by means of the mold, and simulataneously resuming the transfer 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. According to this method, it is possible to easily carry out automatic starting of the continuous casting apparatus.
Description
~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 ~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.
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 ~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 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 ~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 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 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 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 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.
.~:
~. .
., 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.
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 ~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.
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 ~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 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 ~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 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 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 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 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.
.~:
~. .
., 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.
Claims (3)
1. 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 transferring the molten steel from the tundish to the mold, a level measuring 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 predetermind period of time thereby to stabilize the 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 transfer 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.
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 predetermind period of time thereby to stabilize the 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 transfer 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.
2. A method of automatically starting a continuous casting apparatus as set forth in claim 1, wherein said level measuring device for measuring the surface level of the molten steel in the mold comprises, in combination, a contacting type level detector and a non-contacting type level gauge, and wherein after the transfer of molten steel from the tundish to the mold is commenced and when the surface level of the molten steel in the mold reaches the predetermined level, the contacting type level detector detects that the predetermind level has been reached, and once the transfer of molten steel is stopped, subsequent measuring of the surface level of the molten steel is carried out by means of the non-contacting type level gauge.
3. A method of automatically starting a continuous casting apparatus as set forth in claim 1, wherein said transfer means comprise a bar-like stopper for opening and closing a pouring opening formed at the bottom of the tundish and a slide nozzle disposed below the pouring opening, and wherein the quantity of molten steel transferred from the tundish to the mold is controlled by operating said stopper and said slide nozzle through said controlling means.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63294956A JPH02142650A (en) | 1988-11-22 | 1988-11-22 | Method for automatically starting continuous casting machine |
| JP63-294956 | 1988-11-22 | ||
| JP63-294955 | 1988-11-22 | ||
| JP63294955A JPH02142649A (en) | 1988-11-22 | 1988-11-22 | Method for automatically starting continuous casting machine |
| JP01-78781 | 1989-03-29 | ||
| JP7878189A JPH0761528B2 (en) | 1989-03-29 | 1989-03-29 | Automatic starting method of continuous casting machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2002059A1 true CA2002059A1 (en) | 1990-05-22 |
Family
ID=27302806
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002002059A Abandoned CA2002059A1 (en) | 1988-11-22 | 1989-11-02 | Method of automatically starting a continuous casting apparatus |
Country Status (5)
| Country | Link |
|---|---|
| KR (1) | KR960005878B1 (en) |
| BR (1) | BR8905871A (en) |
| CA (1) | CA2002059A1 (en) |
| DE (1) | DE3937752A1 (en) |
| MX (1) | MX170682B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2766113B1 (en) * | 1997-07-16 | 1999-09-17 | Usinor | METHOD FOR STARTING A CONTINUOUS CASTING OF METALS |
| KR100458943B1 (en) * | 1999-06-30 | 2004-12-03 | 주식회사 포스코 | Method of foundry ending and withdrawalling thin salb in case of emergency |
| JP2003528730A (en) * | 2000-03-29 | 2003-09-30 | エス・エム・エス・デマーク・アクチエンゲゼルシャフト | Method and apparatus for automatically starting a continuous casting plant |
| FR2843056B1 (en) * | 2002-07-31 | 2004-09-03 | Realisations Tech Sert Soc Et | METHOD FOR THE AUTOMATIC START-UP OF A CONTINUOUS CASTING PLANT AND ASSEMBLY FOR THE IMPLEMENTATION OF THIS PROCESS |
| EP3437757A1 (en) * | 2017-08-04 | 2019-02-06 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
| EP3437759B1 (en) * | 2017-08-04 | 2022-10-12 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
| EP3437756B1 (en) * | 2017-08-04 | 2021-12-22 | Primetals Technologies Austria GmbH | Continuous casting of a metallic strand |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3221708C1 (en) * | 1982-06-09 | 1991-06-13 | Brown, Boveri & Cie Ag, 6800 Mannheim | Process and apparatus for filling a continuous casting mould while casting a strand |
| DE3538222A1 (en) * | 1985-10-26 | 1987-05-27 | Metacon Ag | METHOD FOR STARTING UP A CONTINUOUS CASTING SYSTEM WITH MULTIPLE STRINGS |
-
1989
- 1989-09-21 MX MX1842389A patent/MX170682B/en unknown
- 1989-11-02 CA CA002002059A patent/CA2002059A1/en not_active Abandoned
- 1989-11-14 DE DE3937752A patent/DE3937752A1/en not_active Withdrawn
- 1989-11-22 KR KR1019890016983A patent/KR960005878B1/en not_active IP Right Cessation
- 1989-11-22 BR BR898905871A patent/BR8905871A/en not_active Application Discontinuation
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| Publication number | Publication date |
|---|---|
| BR8905871A (en) | 1990-06-12 |
| KR900007507A (en) | 1990-06-01 |
| MX170682B (en) | 1993-09-07 |
| KR960005878B1 (en) | 1996-05-03 |
| DE3937752A1 (en) | 1991-05-16 |
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