JPH0129855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a billet temperature control device for a billet heating furnace.

BACKGROUND ART In a billet heating furnace, a method of calculating the temperature of the billet at the outlet of the furnace using a device that calculates the billet temperature from the furnace temperature, time in the furnace, etc. is conventionally known.

However, with this method, if the calculation model contains errors, it is not possible to obtain the target billet temperature at the furnace outlet. In other words, setting up a calculation model is extremely important and requires a lot of effort and time.

The present invention has been made in view of the above-mentioned points.In addition to the device that calculates the temperature of the steel billet from the furnace temperature, time in the furnace, etc., a device that measures the surface temperature of the steel billet is provided, and Obtain the difference between the obtained surface temperature and the measured surface temperature, identify the parameters of the calculation model based on this difference, and calculate the furnace temperature so that the billet temperature at the furnace outlet matches the target value. This device is configured to control the temperature of the steel billet at the furnace outlet to a target value by making corrections.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the configuration of an embodiment of the present invention, in which numeral 1 denotes a steel billet heating furnace, into which steel billets 2 are charged and extracted from the left to the right in the figure. Ru. Then, the furnace temperature is detected by a thermocouple 3 provided in the furnace 1 and provided to a billet temperature calculation device 4. This calculation device 4 is given a target value θ ^DES (t _E , x) and φ, which will be described later, and a time signal is obtained from this and a time element built into the device. Further, the surface temperature of the steel piece is detected by a radiation thermometer 5 provided on the wall of the furnace 1, and the detected value θ(t, o) is provided to the φ correction device 6. The φ correction device 6 receives a calculated steel billet temperature signal θ(t, x) from the steel billet temperature calculation device 4.
is given, and the coefficient φ is corrected. This is the overall configuration shown in FIG.

In this configuration, the calculation device 4 performs calculations using the following equations (1) to (4).

Cρ∂θ(t, x)/∂ _t =k∂ ² θ(t, x)/∂ _x ²
…(1) ∂θ(t, x)/x/x=0=σ _s φ/k [T ⁴ (t)
−θ ⁴ (t, θ)] …(2) ∂θ(t, x)/∂ _x /x=h/2=0 …(3) θ(o, x)=θ〓(x) …(4 ) Here, C: Specific heat of steel billet ρ: Billet density k: Billet thermal conductivity θ(t, x): Billet temperature t: Time x: Distance in the thickness direction from the top surface of the steel billet h
is slab thickness T(t): Furnace temperature φ: Overall heat transfer coefficient σ _s : Stefan-Boltzmann constant In these four equations, equation (1) is a diffusion equation,
Equation (2) is the surface boundary condition, Equation (3) is the center boundary condition, and Equation (4) is the initial condition. In the above calculation formula, the overall heat transfer coefficient φ is a coefficient that varies depending on the type of steel billet, surface condition, furnace condition, etc. In order to correct this coefficient φ online, the steel piece surface temperature θ(t,
Calculation is repeatedly performed using the above configuration so that the calculation surface temperature θ(t, x) becomes equal to the calculation surface temperature θ(t, This coefficient φ is used to control the temperature rise of the billet heating furnace. In addition, another output T ^s 〓 of the steel billet temperature calculation device 4
(t) represents the furnace temperature at which the billet temperature at the furnace outlet at time t _E becomes the target value θ ^DES (t _E , x).

Figure 2 shows the temperature increase control characteristics using the above coefficient φ, and shows the target temperature increase curve to set the billet temperature at the furnace outlet at time t _E to the target value θ ^DES (t _E , x). The actual temperature rise curve when control is performed according to A until time t ₁ is B, and as a result of correction at time t ₁ , the control shifts to the actual measurement temperature rise curve C, and the target value θ ^DES
This means that the furnace exit billet temperature is controlled at (t _E , x).
Time t ₁ may be set appropriately. As a result, even if there is an error in the calculation model, it is corrected by actual measurement, and the temperature increase control of the steel billet temperature is not affected by the error in the calculation model.

In the above embodiment, only a one-dimensional model was considered for the temperature of the steel billet, but the model can be similarly applied to two-dimensional and three-dimensional models.

As described above, the present invention provides a device that measures the surface temperature of a steel billet in addition to a device that calculates the billet temperature from the furnace temperature, time of the billet in the furnace, etc. The parameters of the calculation model were identified based on the difference between the two values, and the furnace temperature at which the billet temperature at the furnace outlet matched the target value was recalculated and corrective action was performed. However, the temperature of the steel billet can be increased without being affected by this error.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing an example of control operation in the apparatus of the present invention. 1... Steel billet heating furnace, 2... Steel billet, 3... Thermocouple, 5... Radiation thermometer.

Claims (1)

[Claims] 1. A device that calculates the temperature of the steel billet from the furnace temperature of the billet heating furnace, time in the furnace of the billet, etc., a device that measures the temperature of the billet in the furnace, and each output of the calculation device and the measurement device given. and a correction device that corrects the heat transfer coefficient based on the difference between the calculated surface temperature and the measured surface temperature, and supplies the corrected heat transfer coefficient to the calculation device, and controls the billet temperature at the furnace outlet to match the target value. A billet temperature control device for a billet heating furnace.