JP2910136B2 - Temperature control system for tundish molten steel plasma heating system - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a temperature control device for a tundish molten steel plasma heating apparatus, and more particularly, to an object to be heated in a heating space, such as the heating of molten steel in a tundish. The present invention relates to a PID control device for controlling the temperature of an object to be heated on the exit side of a heating space under a condition in which the accumulation amount and the passing speed of the air fluctuate.

[Prior Art] In a tundish molten steel plasma heating apparatus, the steelmaking temperature is conventionally controlled by feedback control using a PID temperature controller. FIG. 4 is an explanatory diagram showing a configuration of a temperature control system in the dundish molten steel plasma heating apparatus.

In the figure, (1) is a plasma torch, (2) is plasma, (3) is an injection chamber (tundish), (4) is a heating chamber, (5) is a casting chamber, (6) is a plasma power source, and ( 7)
Is a furnace bottom electrode, (8) is a temperature controller, (9) is a molten steel temperature detector, (10) is a molten steel temperature setter, (14) is a ladle, (15)
Is a mold.

The molten steel received in the ladle (14) is injected into the injection chamber (3) and then flows into the heating chamber (4). Here, plasma (2) is generated by the plasma torch (1), and the molten steel is heated to a predetermined temperature. The molten steel is then cast into the casting room (5)
From the mold (15). Here heating room (4)
The temperature rise characteristic of the molten steel at is expressed by the following transfer function.

Here, K is a proportional gain [° C./Kw] of the heating chamber, T is a response time constant [min], L is a control dead time [min], and S is a Laplace operator.

The controlled variable of the controlled object represented by the equation [1] is the heating chamber (4)
The temperature T _a of the exit side of the temperature T _a is the molten steel temperature detector (9)
Is detected by Temperature controller (8) is compared with the target temperature T _r, given the value of this T _a temperature setter (10), the temperature
T _a feedback control is performed by operating the plasma source (6) of the heating device to be equal to the target temperature T _r.

FIG. 5 is a block diagram showing a signal flow of this feedback control system, wherein (4) is a heating chamber, (8) is a PID controller as a temperature controller, and (32) is a superheater. The superheater (32) is composed of a power source (6) including a plasma feed line in FIG. 4, a plasma torch (1), and a bottom electrode (7), and its transfer function H is defined by the following equation, It is expressed as

[Problems to be Solved by the Invention] In the conventional apparatus, the PID values of the gain K _p , the integration time constant T _i , and the differentiation time constant T _{d in} the temperature controller (8) are determined by heating under a specific condition. Room heating characteristics, that is, specific K ₁ ,
After the temperature is set so as to conform to the temperature rising characteristic in the combination of the values of T and L, the control is performed with a constant value as it is.

However, this temperature rise characteristic is not constant, and fluctuates depending on the flow rate of the molten steel in the heating chamber F [Kg / min] and the storage amount of the steel in the heating chamber W [Kg]. Keeping the values of F and W constant by replacing a ladle or the like is inconsistent with the actual operation, and changes in characteristics cannot be avoided. Therefore, the K _P ,
When the values of T _i and T _d are fixed, appropriate control is performed in some combination areas of K, T, and L, but if this changes and the control moves to another area, control is performed. Is not successful.

The present invention has been made in order to solve the above-mentioned problems, and the PID of the controller can respond to the change in overheating characteristics.
It is an object of the present invention to obtain a temperature control device capable of always obtaining stable control by automatically adjusting a constant.

[Means for Solving the Problems] A temperature control device for a tundish molten steel plasma heating apparatus according to the present invention includes a heating chamber exit side molten steel temperature detector, a molten steel temperature setter for setting a target molten steel temperature value, A PID operation function for operating a plasma power supply so that a detected temperature value input from the heating chamber exit side molten steel temperature detector is equal to a set temperature value input from the molten steel temperature setter is provided.
From the temperature controller, the heating chamber molten steel flow detector, the heating chamber steel storage weight detector, and the heating chamber molten steel flow detector, the gain, the differential time constant, and the integration time constant of the ID operation are variably set by an external signal. The gain, differential time constant, and integration time constant obtained by calculating the input molten steel flow value and the stored steel weight value input from the heating chamber stored steel weight detector by a predetermined arithmetic expression are used for the temperature control. And a PID constant calculator which outputs the gain, differential time constant, and integration time constant of the device as setting signals.

[Operation] The temperature rising characteristics of the molten steel in the tundish by the heating device greatly fluctuate due to changes in the flow rate of the molten steel in the heating chamber and the weight of the steel storage in the heating chamber. According to the present invention, the gain, differential time constant, and integration time constant of the PID controller, which are optimal for the heating characteristics of the heating chamber in that state, are calculated based on the molten steel flow rate and the detected value of the stored steel weight, and each constant of the PID controller is calculated. Is variably set to this value in accordance with the output of the arithmetic unit, whereby a stable and optimal control operation can always be maintained.

Embodiment FIG. 1 is a configuration diagram of a temperature control system of a tundish molten steel plasma heating apparatus showing an embodiment of the present invention. In the figure, each element of (1) to (10), (14) and (15) is equivalent to the conventional one shown in FIG. In addition, (11)
Is a PID constant calculator, (12) is a molten steel flow rate detector, and (13) is a steel storage weight detector.

Here delivery temperature T _a of the heating chamber (4) is detected by the molten steel temperature detector (9). Temperature controller (8) is the value of this T _a, temperature setter compares the target temperature T _r given in (10), T _a is equal as heating device T _r plasma power source (6) Operate. Gain in this PID control operation
Each constant of K _p , integration time constant T _i , and differentiation time constant T _d is given by a PID constant calculator (11).

Molten steel flow detector (12) and steel storage weight detector (13)
The flow rate F [Kg / min] and the stored steel weight W [Kg] in the heating chamber (4) are detected, and the detection signals are supplied to the PID constant calculator (11). The PID constant arithmetic unit (11)
According to the values of F and W, the PID constant K _p , which is optimal for the temperature rising characteristic of the heating chamber (4), which varies depending on the process variables of F and W,
Calculate the T _d and T _i values to set the constants of the PID controller.

FIG. 2 is a block diagram showing a signal flow of this temperature control system. In addition to the flow diagram of FIG. 5, a PID constant calculator (1
The flow of the setting signal of K _p , T _d , and T _i according to 1) is shown, but the operation of the PID constant number arithmetic unit (11) is performed based on the following description.

Coefficients [K ₁ , T, L] included in the transfer function of the heating chamber (4)
Is the flow rate of the molten steel in the heating chamber F [Kg / min] and the amount of steel stored in the heating chamber W [K
for variations in g], K ₁ is inversely proportional to F, T is proportional to W / F, L is is ascertained which is proportional to W / F, therefore is T = αL ... [3] . Here, α is a unique constant that differs for each tundish facility, and takes a value of 1.5 to 2.5.

In the well-known Ziegler-Nichols limit sensitivity method, the adjustment values of K _p , T _d , and T _i for realizing the optimal control operation of the PID controller in the process control are represented by K ₂ = 0.6 K _c . _{] T d = 0.125P c ... [} 5] T i = 0.5P c ... is the [6], where K ₂ = K _p H a (first reference 5 Figure) K _c is hunting gain, P _c is hunting It is a cycle.

K ₂ erases the terms involving T _d term and T _i of FIG. 5 of the PID regulator (8), the case of controlling only K _2, hunting increasingly greater to the control system of K ₂ from a small value the value of K ₂ when starting the K _c, (see [4] type) which is multiplied by 0.6 to obtain. Hunting period of Kotoki is P _c.

Between the hunting angular frequency ω _c and K _c , P _c P _c = 2π / ω _c [8] The relationship between ω _c , L, and T is Tan ⁻¹ ω _c T + ω _c L = π (9). Assuming that θ = ω _c T, Tan ⁻¹ θ = π−1 / α · θ (10) is obtained from the expressions [3] and [9]. The solution of θ in the equation [10] is obtained as the θ coordinate of the intersection of the curve representing the left side and the straight line representing the right side shown in the illustration of FIG. 3, and within the normal range of α (α: 1.5 to 2.5) Approximately:

θ = 1.6α + 0.4 (11) where 1.5 <α <2.5 [4] to [8] and the relationship of ω _c T = θ And K ₂ , T _d and T _i can be calculated.

K ₂ , K ₁ and T are as follows: K ₂ = K _pH , K ₁ = k ₁ / F, T = t W / F
( _Kp , k, t are constants), [12] to [14] indicate that three variable constants to be given to the PID controller can be set as follows.

Here, K _p , t _d and t _i are constants.

Equations [15], [16], and [17] show that the PID feedback control has the optimal controllability when the transfer function of the heating chamber (4) to be controlled in FIG. 1 varies with the values of F and W. It is shown that K _p , T _d , and T _i can be variably controlled in accordance with this equation in order to maintain. As shown in FIG. 2, the PID constant calculator (11) always updates and maintains the three constants optimally with respect to the control target characteristic by the calculation of the formulas [15], [16], and [17]. This can be achieved by:

[Effects of the Invention] According to the present invention, PID feedback control at a stable temperature can always be performed with respect to large fluctuations in the flow rate of molten steel to be heated and the accumulated amount of molten steel. There is an effect that can be expanded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a temperature control system of a tundish molten steel plasma heating apparatus showing one embodiment of the present invention, FIG. 2 is a block diagram showing a signal flow of the temperature control system of one embodiment of the present invention, and FIG. Fig. 4 is a diagram for obtaining a solution of the equation, Fig. 4 is a block diagram showing an example of a temperature control system of a conventional tundish molten steel plasma heating apparatus, and Fig. 5 is a block diagram showing a signal flow of the conventional temperature control system. FIG. (4) ... heating room, (6) ... plasma power supply, (8) ...
... temperature controller, (9) ... molten steel temperature detector, (10) ...
Molten steel temperature setting device, (11)… PID constant value calculator, (12)…
… Molten steel flow detector, (13)… Steel storage weight detector.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-178353 (JP, A) JP-A-3-124351 (JP, A) JP-A-3-174957 (JP, A) JP-A-3-17851 285746 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B22D 11/10 B22D 41/01

Claims (1)

(57) [Claims] In a tundish molten steel plasma heating apparatus, a molten steel temperature detector on the exit side of a heating chamber, a molten steel temperature setter for setting a target molten steel temperature value, and an input from the molten steel temperature detector on the exit side of the heating chamber are provided. PID operation function to operate the plasma power supply so that the detected temperature value becomes equal to the set temperature value input from the molten steel temperature setting device.The gain, differential time constant, and integration time constant of each PID operation can be changed by an external signal. A temperature controller to be set, a heating chamber molten steel flow detector, a heating chamber storage steel weight detector, a molten steel flow value input from the heating chamber molten steel flow detector, and an input from the heating chamber storage steel weight detector. The gain, differential time constant, and integral time constant obtained by calculating the stored steel weight value by a predetermined arithmetic expression are output as gain, differential time constant, and integral time constant setting signals of the temperature setting device. PID constant calculator and Temperature controller tundish molten steel plasma heating apparatus characterized by comprising.