JPS6261382B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a level control device for molten metal in a mold (hereinafter referred to as MD) or an intermediate sump (hereinafter referred to as TD) of continuous casting equipment. The following explanation will focus on controlling the molten metal level in the TD (see Figure 1). The operating end of these TD internal molten metal level controls is a sliding type.
Nozzles, slide gates, rotary nozzles, etc. are used (in the case of controlling the level of molten metal in the MD, a stopper may be used.Hereinafter collectively referred to as operation nozzles), they are constantly in contact with the high-temperature molten metal. Therefore, even if the nozzle is made of expensive refractory material, its lifespan is short, and its lifespan becomes even shorter in proportion to the number of sliding movements associated with control operations. While suppressing the number of sliding movements as much as possible to the extent that it does not affect the operation, we also take care of the looseness and bumpiness of the connection parts that are unavoidable due to the operating nozzle drive mechanism, as well as variations in the surface pressure, operating speed, and sliding resistance of the operating nozzle. Under such physical constraints, the TD head, that is, the molten metal level in the TD (or the weight in the TD determined from the shape of the TD) necessary for stabilizing the molten metal level in the MD can be obtained stably. It is desirable to control the Several methods have already been proposed for this type of control method, but the main ones are (1) simple PID feedback continuous control.
The operation nozzle is driven by calculation, and although the control accuracy to the target value is high, it has the disadvantage that the number of sliding movements is very large. (2) On/off control Determine whether the above deviation (weighing scale signal - target value) is positive or negative, and during that time, close signals are sent to the operating nozzles, respectively.
It outputs an open signal.As a modification of this method, instead of the target value, a suitable dead zone is provided above and below the target value, and the control output is not output when the target value is within the dead zone. This method causes cycling due to excessive control near the target value, which is a feature of on-off control, and the number of operations is also large, although not as many as in (1) above. (3) Trend determination method with sampling While the above (1) and (2) are continuous adjustment types, the TD weight value is sampled at appropriate intervals,
By comparing the target value (target value with dead band) with the sampled current value (distinguishing the size), relative comparison with past sampled values, etc., each determines the trend of the sampled value and operates based on its own logic. There is a method to control the output pulse of the nozzle. This method is generally more effective than (1) and (2) above because it can reduce the frequency of control output. As explained above, there are various methods that have been proposed, but no sufficiently effective method has yet been proposed. The present invention has been made in view of the conventional technical circumstances as described above, and therefore, an object of the present invention is to further reduce the number of operations of an operating nozzle to extend the life of the nozzle, and to improve control accuracy. The purpose of this invention is to provide a device for controlling the molten metal level in a TD. This invention belongs to method (3) above, but it further reduces the frequency of operation of the operation nozzle by devising the logic of determining the trend of sampling values. Since a pulse method is used in this case, the pulse width of the output pulse (hereinafter the operation signal will be referred to as the operation pulse) is also variable in accordance with the operating characteristics of the nozzle being operated. The main points of the structure of this invention are as follows. That is, in controlling the molten metal level in the TD or MD of continuous casting equipment, the molten metal level at the current time and the sampled value one sampling period ago are compared, and when the difference exceeds a certain threshold value, the first one generates an output. a second discriminator that generates a force when the current sampling value differs from the reference value by a certain threshold value or more based on a certain sampling value, and a large number of deviation detectors. When receiving the output from the first or second discriminator, the sequence circuit refers to the output status from the deviation detector to determine whether the sampled value at that time remains within a predetermined dead zone or not. It is determined whether the dead zone is exceeded and the dead zone is shifted to another dead zone, and when it is determined that the dead zone is shifted, an operating pulse is sent out to control the operating end and adjust the molten metal level. Moreover, the pulse width of the operating pulse outputted in this manner is variably adjusted by automatically determining the characteristics of the operating end, or by a preset constant determined by the characteristics of the operating end. In this way, the number of outputs of operation pulses and, by extension, the frequency of operation of the operation end are reduced, and its lifespan is extended. Next, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention. In FIG. 1, 1 is a molten metal stored in a ladle 2, 3 is a drive device such as a motor for operating an operating nozzle, and 4 is a tundish 6 from the ladle 2, such as a sliding gate valve.
5 is the molten metal stored in the tundish 6 as an intermediate sump, 7 is the amplifier for amplifying the output signal of the load cell 8, 9 is the mold, and 10 is the regulator. show. Now, in FIG. 1, a tundish 6 exists in the ladle 2 as an intermediate reservoir for distributing and injecting the molten metal 1 into molds 9 (a plurality of molds). In the tundish 6, it is necessary to keep the level of the molten metal constant in order to keep the amount of molten metal distributed and injected into the molds 9 (a plurality of molds) 9 constant. The level of the molten metal 5 in the tundish 6 can be determined by measuring the weight of the tundish 6 using the load cell 8, since the volume of the tundish 6 containing the molten metal 5 is constant. A signal representing the molten metal level in the tundish 6 obtained in terms of weight from the load cell 8 is amplified by the amplifier 7 and then applied to the regulator 10 as a process amount signal of 1 to 5 V DC. Regulator 1
0, a predetermined logical decision is made based on this incoming process quantity, and as a result, an operating output pulse is sent to the motor 3, causing the motor 3 to operate the operating nozzle 4. When you operate the nozzle, ladle 2
Since the opening area of the nozzle at the bottom of the tundish changes, thereby changing the amount of molten metal falling from the ladle 1 into the tundish 6, the weight of the molten metal in the tundish 6 and, as a result, the level of the molten metal can be controlled. The temperature of the molten metal is high, around 1600℃ for steel, so the material of the operating nozzle is naturally fire-resistant, but it still has a short lifespan, and the more frequently it is operated, the shorter it will be. There is a tendency. FIG. 2 is a detailed block diagram of regulator 10 in FIG. In FIG. 2, 101 is a variable setting device for setting the sampling period, and 102 is a setting device 10.
Load cell 8 receives the sampling command from 1.
103 is a sampling circuit that samples the weight signal from 1 cycle ago, L _o - ₁
and a memory circuit that stores the current sample value L _o ,
108 to 111 are deviation detectors, 104 to 10, respectively.
The upper limit H ₂ , the upper limit H ₁ , the lower limit L ₁ , and the lower lower limit L ₂ are set by the level setter No. 7 around the target value SV given by the target value setter 112, respectively. 113
determines whether |L _o - ₁ -L _o |>L _A with respect to the threshold L _A set by the threshold setter 114, and in that case, whether L _o - ₁ >L _o or L _o - This is an arithmetic discriminator that discriminates ₁ <L _o and sends a discriminating output to the sequence circuit 122. The hold circuit 115 includes a memory circuit that stores L _o at that point in time when control is started (the stored value is set as X _L ), and 1
16 is an arithmetic discriminator that determines |L _o −X _L |> _LA . The hold circuit 115 is the arithmetic discriminator 1
When it is determined in 16 that |L _o -X _L |> _LA , it receives a signal to that effect from the discriminator 116, closes the contact, and automatically rewrites _Lo at that time to X _L. Reference numerals 117 to 121 are time setting devices set as characteristic characteristic values of the operation nozzle SN (hereinafter sometimes simply referred to as SN), and the sequence circuit 12
2 to the motor 3. In this case, the operation signal is for adjusting the pulse (time) width of the pulse. Reference numerals 117 and 118 are constant setters for correcting the mechanical backlash of the operating nozzle, and when the polarity of the output sent to the motor 3 is reversed (i.e., from the open direction to the closed direction, from the closed direction to the open direction), 12
The set _{time width is given by the set time width of t BC for} the closing direction and t _BO for the open direction. In addition, 119 and 120 are setting devices for correction values for each direction that take into account the backlash of the SN mechanism and the variation in the amount of movement per unit time, and each correction value is given by the time width of the closing direction t _C and the opening direction t _O. . 121 specifies the basic operation pulse width for driving the SN, and is determined by taking into consideration the minimum response time and sampling period of the operation nozzle drive motor 3 side, the responsiveness after driving the operation nozzle, etc. (usually about 1 to 3 seconds). A sequence circuit 122 outputs operation pulses to the SN drive motor 3. In other words, the sequence circuit 122 has the operation discriminator 113,1
Based on the output data given from 16, and with reference to the output status from deviation detectors 108 to 111, it determines whether or not to output an operating pulse to the motor 3 according to its own logical judgment, and determines the time of the output pulse. The width is variably set by setting devices 117 to 121. 3A to 3D show the sequence circuit 122
FIG. 3 is an explanatory diagram for further supplementary explanation of the logic of logical judgment in FIG. FIG. 3A is an explanatory diagram showing the logic when the signal representing the level obtained by weight suddenly changes.
In the figure, if a deviation of more than the threshold L _A occurs between L _o - ₁ and L _o , a close or open operation pulse is generated depending on the direction of increase or decrease. That is, if |L _o − L _o − ₁ |=ΔL>L _A and L _o >L _o − ₁ and L _o >L ₁ , it is a closed pulse, and if L _o <L _o − ₁ and L _o <H ₁ , it is a closed pulse. Outputs the open pulse and , respectively. This is to respond to instantaneous large changes such as sudden clogging, peeling, or loss of the SN, and the following cases are prioritized and handled. Figure 3B shows alarm setting levels L ₂ (lower limit) to _{H 2}
This is to explain the logic between (upper and lower limits),
That is, when |L _o −X _L |=ΔL>L _A , a closing pulse is applied when X _L <H ₁ <L _o or X _L <H ₂ <L _o , and when X _L >L ₁ >L _o or X _L >L ₂ > Outputs an open pulse at _Lo . Here, X _L is the value of L _o at the time when there was a difference of L _A or more, and is temporarily stored in the hold circuit 115 in _FIG . An operation pulse is output when _Lo is sandwiching one of the control lines L ₂ to _{H 2} and is moving away from the target value SV. As is clear from this, the area between L ₁ and _{H 1} is a dead zone, and the areas between L ₂ and _{L 1} and H ₁ and _{H 2} also constitute dead zones. Now, using Fig. _3C as an example, when the level signal represented by the weight changes at the level of H ₁ , normal on/off control with a dead band may be used, of course, and directional discrimination, such as simple Even if logic such as _Lo - ₁ < H ₁ < _Lo is added to the equation, it can be fully expected that the operation pulse output will continue to be output when the level signal H ₁ represented by the weight value fluctuates up and down. Now instead of L _o − ₁ , the threshold L _A
By adopting the value X _L when it changes beyond
It is possible to suppress the output of meaningless operation pulses as shown in FIG. 3C. That is, in FIG. 3C, the closing pulse is
Since X _L =L ₀ and L _o =L ₂ sandwich the control line of H ₁ , and L _o =L ₂ is moving away from the target value SV, it is output. At this time, X _L =L ₂ is set. Since L _o is approaching the target value SV, the pulse is not output, and the pulse is also |L _o −X _L
Since |=ΔL< _LA , it is not output. Like the pulse, the pulse is not output, and since L _o is approaching the target value, the pulse is not output, and at this time, X _L =
It is set as L ₈ . The pulse is _{X L (} =
L ₈ ) and L _o (=L ₁₀ ) exist, but since ΔL ₁₀ <L _A ,
Close pulse is not output. In this way, by employing the logic of the above-mentioned logical judgment, it is possible to suppress the meaningless output of operation pulses when the level signal fluctuates slowly within a predetermined limit. Figure 3D is for explaining the logic when L _o > H ₂ or L _o < L _2. When L _o > H ₂ and L _o > L _o - ₁ , a closed pulse is generated, and L _o < L ₂ and L _o < L _o - ₁ , an open pulse is output, respectively. Focusing on the target value SV,
If the level of H ₂ and L ₂ is exceeded and the level is moving away, the level control is starting to diverge, and if this continues, there is a risk of overflow or low level abnormality. In this case, an operation pulse is output according to the above logic every sampling period. The logic for outputting the operation pulse is as described above, and the effects of the four control levels L ₂ , L ₁ , H ₁ , and H ₂ can be explained as follows. In other words, by creating a dead zone between each level, the dead zone is doubled, or conversely, a control zone is created within the dead zone.
By having H ₁ and L ₁ , even if there is a large fluctuation in the flow rate to the mold and the deviation from the operating nozzle becomes large (that is, even if there is a large disturbance)
By crossing the control levels of the first and second stages, in the case of a general one-stage dead zone (this is L ₂ , H ₂
Corresponds to only cases. ) has a remarkable effect in reducing the amount of overshoot and the number of operation outputs (SN sliding number). Next, when outputting these open or close pulses, it is very important to determine the pulse width by taking into account the operating characteristics of the SN. In other words, for the sampling control system, since there is a blank time after outputting the operation output until the next sampling, the output operation pulse is controlled by the operation nozzle and its operation mechanism so that it causes a predetermined movement at the operation end. The pulse width must be suitable for the operating characteristics of each operating nozzle, including the part, and for this purpose, the mechanical backlash and variations in operating nozzle movement should be measured in advance for each operating nozzle in each direction during opening and closing. Or, it is necessary to find the following quantities by measuring during control.

[Table] As for the variation in
You can also do this. Furthermore, since pulse driving is used here, the unit is converted by the operating speed of the operating nozzle, and each physical quantity is expressed as time (msec). Now, when outputting the operation pulse in the above cases ~, the pulse output width is as follows: Closed pulse = T _S +t _BC +t _C Open pulse = T _S +t _BO +t _O. Here, T _S is the basic pulse width set by _the time setter 121 in _FIG . Time setting device 1 shown in the figure
17,118. This results in
The mechanical play of the SN and its characteristics can be corrected by varying the operation pulse width. Furthermore, although the present invention is designed so that SV and L ₂ to H ₂ can be set individually, it is of course possible to relatively change L ₂ to _{H 2} in conjunction with SV. Also, without subdividing the pulse output width as described above,
It is also possible to use the open pulse width = T _SO and the closed pulse width = T _SC as eigenvalues obtained empirically in actual operation. According to this invention, when controlling the ladle SN as the operating end in tundish level control, compared to the conventional method, the number of sliding operations of the operating nozzle is increased by trend discrimination type sampling control with two stages of dead zones. By reducing the noise and extending the service life, it is possible to reduce operating costs.Furthermore, by varying the operation pulse width using the control nozzle play correction logic, the play in the control nozzle can be mechanically repaired frequently. Control accuracy can be maintained constant without any problems, and stable automatic control can be obtained. This invention is not limited to the TD level control described above, but can also be applied to level control within a mold by shortening the sampling period. It goes without saying that the present invention can also be applied to cases where the operating end is of a type other than pulse control.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a detailed block diagram of the regulator 10 in FIG. It is an explanatory diagram for explaining. Explanation of symbols, 1... Molten metal, 2... Ladle, 3...
...Motor, 4...Operation nozzle, 5...Molten metal, 6...
...Tandite, 7...Amplifier, 8...Load cell, 9...Mold, 10...Adjuster, 101...
Sampling timer, 102... Sampling circuit, 103... Memory, 104-107... Level setter, 108-111... Deviation detector, 1
12...Target setter, 113, 116...Calculation discriminator, 114...Threshold value setter, 115...Hold circuit, 117-121...Time setter, 1
22...Sequence circuit.

Claims (1)

[Scope of Claims] 1. Sampling detection means for detecting the level of molten metal in an intermediate pool or mold containing molten metal at regular intervals; and an operation nozzle for controlling the amount of molten metal poured into the intermediate pool or mold; A molten metal level control device comprising: a regulator that receives a level sampling value from the detection means and outputs an operation signal for driving the operation nozzle to open or close, the regulator comprising: (a) the detection means; a plurality of deviation detectors each generating an output when the sampling value of the level from is compared with the self-set level and the former exceeds the latter; and (b) each sampling value of the molten metal level at the current time and one sampling period before. a first arithmetic discriminator that generates an output when the difference between (d) a second arithmetic discriminator that re-sets the current sampling value as the reference value and generates an output when the reference value has gone above or below by a certain threshold value; When receiving the output from the first or second calculation discriminator, determine whether the sampled value of the molten metal level at that time remains within a predetermined dead zone or exceeds the dead zone in light of the output status from the deviation detector. a sequence circuit that determines whether or not the dead zone has shifted to another dead zone, and outputs an operation signal for driving the operation nozzle when the transition has occurred, the operation signal for driving the operation nozzle output from the sequence circuit the sequence circuit comprising a correction means that can artificially correct the pulse width of the operation signal according to the operating characteristics of the operation nozzle to be driven; Control device.