JPS6313765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling tension between stands of a continuous rolling mill, and particularly to a method for correcting the influence of material temperature when tension is detected indirectly.

Tension control between stands in a continuous rolling mill plays an important role in improving product dimensional accuracy and stabilizing rolling operations. If abnormal tension or sag occurs between the stands, not only will it not be possible to obtain uniform product dimensions, but it will also have an adverse effect on rolling operations, sometimes making rolling operations impossible.

Conventional tension control methods between stands in continuous rolling mills include: (1) a method in which tension detectors are installed between stands, etc. to directly detect and control the tension, and (2) a method in which tension is directly detected and controlled using rolling variables (e.g. rolling torque, rolling load). There is a method for automatically detecting and controlling tension, and the present invention relates to method (2).

A typical example of method (2) above is to detect the difference between the rolling torque under no tension or at a target tension and the rolling torque under varying tension, and control the speed of the rolling mill drive motor according to the difference. There is a way to keep the tension between stands constant.

First, this method will be explained with reference to the drawings. FIG. 1 is a layout diagram in which a continuous rolling mill is represented by one stand and (i+1) stands. Further, FIG. 2 shows the temporal change in the rolling torque _G1 of the i-stand. The material 13 is caught in the i-stand at time ti and is in a tension-free state until it reaches the (i+1) stand at time ti+1. In this tension-free state, i
The rolling torque G _i of the stand is detected, the value is stored as the reference rolling torque G _iM , and the variation (G _iM − _{G i} ), the variation in rolling torque (G _iM −G _i ) becomes the torque corresponding to the inter-stand tension.

In order to make the space between the stands tension-free, the speed correction amount of the rolling mill drive motor of the i stand should be △N _i △N _i = g _i (G _iM −G _i ) ......(1) [However, g _i is a constant determined for each stand] is calculated and the speed of the motor is corrected by △N _i .

However, in general, rolling torque also changes due to temperature changes in the material, so in the above method, if a temperature change occurs in the material due to skidding, etc., even if there is no tension, the variation in torque due to temperature change will be compensated for by the change in tension. This has the disadvantage that the tension may be incorrectly detected, resulting in incorrect tension control.

As a method for improving this, there is a method of controlling using information on the rolling load in addition to the rolling torque, but there are cases where it is not possible to attach a rolling load meter due to the structure, and there is also a problem in terms of cost.

The present invention has been made in consideration of the above points, and
The present invention provides a rational inter-stand tension control method for a continuous rolling mill that enables highly accurate inter-stand tension control by eliminating the influence of material temperature even in a continuous rolling mill without a rolling load meter.

Hereinafter, the principle of the present invention will first be explained with reference to the case of two stands, i and (i+1) stands, shown in FIG.

The required rolling torque for the i-stand is expressed by the following equation (2).

G _i = 2b _i・R ² _i・Q _gi・k _ni ………(2) However, b _i : plate width, R _i : roll radius, Q _gi : torque function, and this torque function is based on theory. For example, it can be expressed as Q _gi = F (H _i , h _i , R _i , t _bi , t _fi . In other words, the torque function Q _gi of stand i is the input thickness H _i , the output thickness h _i , the roll radius R It is a function of _i , rear tension _tbi , and front tension _tfi , and is a value independent of temperature.

The rolling torque formula (2) is derived based on rolling theory, and the rolling torque is proportional to the sheet width, the square of the roll radius, the torque function, and the average deformation resistance.

_kni : Average deformation resistance.

Here, the average deformation resistance k _ni is a function of the material temperature θ _i in the i-stand, and is given by the following equation (3).

k _ni =F (ε, ε〓, θ _i ) ......(3) where ε: strain, ε〓: strain rate, θ _i : material temperature.

During rolling, changes in the strain ε and strain rate ε〓 in the material are small and are considered constant, and therefore the average deformation resistance k _ni can be expressed by the following equation (4).

However, A, B, m, n, and K are constants determined by the material and deformation conditions.

Furthermore, when formula (2) is transformed, G _i /k _ni =2b _i R ² _i Q _gi (5), and the right side of formula (5) becomes a value that is independent of temperature.
The present invention utilizes the fact that the ratio of rolling torque to average deformation resistance is not affected by temperature, as shown in equation (4).

Therefore, before the material bites into the (i+1) stand, calculate and store the ratio G _iM /k _niM between the rolling torque G _iM of the i stand under no tension and the average deformation resistance k _niM , and (i+1) Calculate the ratio of the actual rolling torque G _i of the i stand generated after it bites into the stand and the average deformation resistance k _ni and compare the two.
As shown in the following equation (6), G _iM /k _niM −G _i /k _ni =0 (6) If the speed of the motor is controlled so that the difference becomes zero, i ~ (i + 1 ) The tension between the stands becomes zero tension.

Also, equation (6) can be transformed as follows.

G _iM /k _niM・k _ni −G _i = 0 ......(7) The first term on the left side of equation (7) represents the rolling torque considering the influence of temperature, so in order to achieve tension-free control, As the speed correction amount △N _i of the rolling mill drive motor, △N _i = g _i (G _iM /k _niM・k _ni −G _i ) ......(8) is calculated, and the speed of the rolling mill drive motor is △N _i By modifying only this, the tension between the stands can be controlled to zero tension.

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

In Figure 3, 1 stands for i stand and (i+
1) The rolling roll of the stand; 2 is a thermometer that detects the temperature of the material to be rolled; 3 is a delay device that delays the material temperature signal detected by thermometer 2 by the travel time from the thermometer to the stand; 4 is a delay device Using the temperature signal delayed in step 3 as input, calculate the material temperature of the i-stand due to the temperature drop during the above running time,
An average deformation resistance calculation device that calculates the average deformation resistance of the i-stand from the material temperature, 5 an electric motor that drives the rolling roll of the i-stand, 6 a rolling torque calculation device that calculates the driving rolling torque of the i-stand,
7 is a divider that calculates the ratio between rolling torque and average deformation resistance of the i-stand, 8 is a storage device that stores the ratio of rolling torque and average deformation resistance when no tension is applied, and 9 is used to perform the above-mentioned storage operation. 10 is a multiplier that calculates the product of the rolling torque/average deformation resistance ratio at the time of no tension memorized in 8 and the average deformation resistance calculated by the average deformation resistance calculation device 4; 11 is a speed reference for the electric motor; 12 is a speed control device for the electric _motor .

In the present invention, tension control is performed as follows. After the material passes through thermometer 2, it is placed on the i-stand,
Rolling is performed in the order of (i+1) stands. First, the temperature of the material is detected from the time when the tip of the material reaches just below the thermometer 2. The material temperature detected by the thermometer 2 is delayed by the delay device 3 by the material transfer time from the thermometer 2 to each stand. The average deformation resistance calculating device 4 calculates the material temperature θ _i at the i-stand from the material temperature signal θ delayed by the delay device 3, and calculates the average deformation resistance k _ni from the material temperature θ _i . The material temperature θ _i of the i-stand is obtained using a well-known relational expression. For example, if there is no cooling device from the thermometer 2 to the i-stand and the temperature drops only by radiation, θ _i is calculated using the following equation (9) for a temperature model based on radiation.

However, c ₁ : constant determined by the material, t ₁ : material transfer time from thermometer 2 to i-stand.

In addition, if a cooling device is provided, θ _i is calculated using the following equation (10) regarding a temperature model using water cooling.

θ _i = θ _A + (θ−θ _A ) e ^c2 〓 ^t1 ………(10) However, θ _A ; t ambient temperature, C ₂ : constant determined by material, α : heat transfer coefficient, t ₁ ; Material transfer time from thermometer 2 to i-stand.

From the material temperature of each stand determined as described above, the average deformation resistance k _ni of each stand is calculated according to equation (4).

On the other hand, the rolling torque G _i is calculated by the arithmetic unit 6 from the drive motor 5 using the following well-known formula (11).

G _i =a ₁ V _i −r _i I _i /N _i I _i −a ₂ dN _i /dt− (a ₃ N _i +a ₄ )
...(11) However, V _i , I _i , N _i , r _i are the voltage, current, rotation speed, armature resistance of the stand drive motor, and a ₁ ~
a ₄ is a constant.

Here, before the material bites into the (i+1) stand, the rolling torque/average deformation resistance G _iM /k _niM is calculated by the calculation device 7 from the rolling torque G _iM of the i stand under no tension and the average deformation resistance k _niM . , are stored in the storage device 8. Next, the average deformation resistance of the i-stand after the material bites into the (i+1) stand
The product of k _ni and the rolling torque/average deformation resistance ratio G _iM /k _niM of the i-stand under no tension stored in the storage device 8, that is, G _iM /k _niM (12) is calculated by the multiplier 10. . Next, multiplier 10
The rolling torque G _i of stand i is subtracted from the output of , that is, the amount shown by equation (12), and the rolling torque corresponding to the true inter-stand tension without the influence of material temperature fluctuation (G _iM /k _niM・k _ni − G _i ) ...(13) is obtained.

Next, the speed standard correction device 11 calculates the speed standard correction amount △N _i according to equation (8), corrects the rotational speed of the electric motor of the i-stand by △N _i through the speed control device 12, and thereby i stand and (i+1)
Tension control between the stands is performed.

In the present invention, if the tension between the i stand and the (i+1) stand is not set to zero but is controlled to a certain target value, equation (8) can be changed to the following equation, that is, △N _i = g _i (G _iM /k _niM k _ni −G _i −△G _TREF ) ………(14) It can be controlled by transforming it as shown below. Here, △G _TREF in equation (14) is the torque corresponding to the target tension between the stands.

As explained above, according to the present invention, the material temperature at each rolling stand is predicted from the material temperature at the entrance of the continuous rolling mill, and thereby the influence of changes in the deformation resistance of the material due to temperature changes on the rolling torque is calculated. A highly accurate inter-stand tension control method of a continuous rolling mill can be obtained that compensates and prevents the influence of material temperature on inter-stand tension control.

[Brief explanation of the drawing]

Figure 1 shows the continuous rolling mill with i-stand and (i+
1) Layout diagram when represented by a stand, Figure 2 is a diagram showing an example of temporal changes in rolling torque G _i , Figure 3
The figure is a block diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Rolling roll, 2... Thermometer, 3... Delay device, 4... Average deformation resistance calculating device, 5... Rolling mill drive motor, 6... Rolling torque calculating device, 7...
... Divider, 8... Memory device, 9... Memory operation contact, 10... Multiplier, 11... Speed reference correction device, 12... Speed control device, 13... Rolling material.

Claims (1)

[Claims] 1. In a continuous rolling mill consisting of a plurality of rolling stands to which a rolling load meter is not attached, the material temperature θ at the entrance of the rolling mill is measured, and this temperature is determined based on the material temperature at the time of this measurement. Predict the material temperature θi when the material bites into the i-stand at the time of measurement, and calculate the deformation resistance of the material using this predicted temperature θi and the predicted strain ε and strain rate ε〓 based on the rolling schedule. , this calculated deformation resistance
Before the material bites into the downstream (i + 1) stand, the ratio (GiM/KmiM) of the rolling torque GiM of the i stand under no tension is memorized, and the material bites into the (i + 1) stand based on this memorized value. The difference between the product (GiM/KmiM・Kmi) multiplied by the predicted deformation resistance Kmi of the i-stand and the rolling torque Gi of the i-stand after the material bites into the (i+1) stand is the 1. A method for controlling inter-stand tension in a continuous rolling mill, comprising controlling the speed of a drive motor of an i-stand so that the amount corresponds to an inter-stand tension value.