JPH0520174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control method for a reversing rolling mill that prevents the occurrence of warping of the biting tip of a rolled material when the rolled material is bited into the reversing rolling mill. It is.

When rolling a material such as a slab using a large twin-drive reversible rolling mill such as a plate rolling mill, there is a temperature difference between the upper and lower surfaces of the material during the heating process, conveyance process, roll coolant water injection, etc. , roll characteristics such as surface roughness difference, hardness difference, and diameter difference between the upper and lower work rolls; difference in moment of inertia between the upper and lower work rolls due to differences in spindle length between the upper and lower work rolls; As shown in Fig. 1, if there is a difference in the biting end torque of the upper and lower work rolls 1 and 1' when the rolled material S is biting due to various causes such as imbalance in load sharing, the upper and lower workpieces There is a difference in the amount of impact drop between the rolls 1 and 1', which may cause warping of the radius of curvature ρ at the tip of the material S to be rolled.

The impact drop of the upper and lower work rolls 1, 1' is a temporary decrease in the rotational speed of the upper and lower work rolls 1, 1' when the material to be rolled S is bitten, as shown in Fig. 2. The impact drop amount is defined as n/N ₀ .

Note that N ₀ is the rotational speed of the upper and lower work rolls 1, 1' before the rolled material is bitten, and n is the maximum amount of rotational speed drop of the upper and lower work rolls 1, 1' in the impact drop generation area. It is a value.

Conventionally, as a means to prevent warping of a rolled material caused by a difference in the impact drop amounts of the upper and lower work rolls, for example, a method was used to make the impact drop amounts of the upper and lower work rolls equal to each other.
Either the rolling speed command value in the drive control system for the upper and lower work rolls was controlled, or the absolute amount of impact drop was reduced.

However, as described above, various factors are involved in the occurrence of warpage at the biting tip of the rolled material, and therefore the conventional means described above have not been able to reliably prevent warping of the rolled material.

In view of such conventional problems, the present invention is designed to reliably prevent the occurrence of warpage at the biting tip of the rolled material, and an example of its implementation will be described below based on FIG. 3. explain.

In FIG. 3, 1 and 1' are upper and lower work rolls in the reversing rolling mill, and 2 and 2' are upper and lower back-up rolls in the reversing rolling mill.

3, 3' are driving motors for the upper and lower work rolls 1, 1'; 4, 4' are driving motors 3, 4' for driving the upper and lower work rolls 1, 1';
3' rotation speed detector.

The electric motors 3, 3' have rotational speed detectors 4,
4', speed controller 5, 5', current controller 6, 6',
Voltage controller 7, 7', gate pulse generator 8,
8' and thyristors 9, 9' (drive control system for the upper and lower work rolls 1, 1').

That is, for example, regarding the rotational speed control of the driving electric motor 3 of the upper work roll 1, the rolling speed command value and the rotational speed detection value by the rotational speed detector 4 are given as input signals to the speed controller 5. The comparison calculation value is outputted from the speed controller 5 and given as an input signal to the current controller 6.

Further, the detected value of the armature current (load current) of the motor 3 is given as an input signal to the current controller 6, which is compared with the output signal from the speed controller 5, and the comparison value is used as the current controller. 6 and is given as an input signal to the voltage controller 7.

The voltage controller 7 receives the armature voltage detection value of the motor 3 as an input signal, compares it with the output signal from the current controller 6, and uses the comparison value to generate a gate pulse from the voltage controller 7. The pulse generator 8 controls the phase of the firing angle of the thyristor 9 in the armature circuit of the motor 3 through the gate pulse generator 8, thereby controlling the terminal voltage of the motor 3.

Note that the rotational speed control of the driving electric motor 3' of the lower work roll 1' is performed in the same manner.

Therefore, the present invention provides a current controller in a rotational speed control device (drive control system for the upper and lower work rolls 1, 1') of the driving electric motors 3, 3' of the upper and lower work rolls 1, 1' as described above. 6 and 6', an impact drop correction amount signal is given as a comparison calculation element when the rolled material S is bitten, thereby appropriately controlling the impact drop amount of the upper and lower work rolls 1 and 1'. In addition, the occurrence of warpage at the biting tip of the rolled material S is reliably prevented.

That is, as shown in FIG. 3, when rolling the material S to be rolled by the upper and lower work rolls 1 and 1',
The rolling torque calculation unit 10 predicts and calculates the rolling torque required to roll the material S to be rolled, and also calculates the rolling torque required for rolling the material S to be rolled, and also calculates the required upper and lower work rolls 1 and 1' to prevent warping at the tip of the material S to be rolled. An impact drop amount difference calculation unit 11 predicts and calculates the difference in impact drop amounts.

Then, the impact drop amount difference that does not cause warping is compared with the predicted calculated value of the impact drop amount difference between the upper and lower work rolls 1 and 1' when rolling is performed without the control of the present invention, The impact drop correction amount so that both of them are equal is determined from the rolling torque, the work roll rotation speed before the rolled material is bitten, and the impact drop amount of the upper and lower work rolls 1 and 1'. The impact drop correction amount is calculated by the correction amount calculation unit 12, and the calculated value of the impact drop correction amount is transmitted to the current controllers 6, 6, 6' as a correction input signal.

Note that the impact drop correction amount signal is
When the rolled material S is bitten by the work rolls 1 and 1', the current controllers 6 and 6' are inputted via the function generators 13 and 13', respectively, when the rolled material S is bitten by the work rolls 1 and 1'. For example, the biting stress of the upper back-up roll 2 at this time is detected by the load cell 14, the biting detector 15 is operated by the signal from this load cell 14, and the signal from this biting detector 15 is transmitted to each function generator. 13, 13' as a trigger signal to operate each function generator 13, 13'.

Here, the impact drop amount difference calculator 1
1. The impact drop correction amount calculator 12 and the like will be explained.

The impact drop amount difference calculator 11 calculates the difference between the upper and lower work rolls 1 and 1' which is necessary to prevent warping of the curvature radius ρ as shown in FIG. Impact drop amount difference
This is to calculate Xn.

The curvature 1/ρ is expressed as a function of the difference x _o between the impact drop amount of the upper work roll 1 and the impact drop amount of the lower work roll 1', as shown below.
It is given by equation (1).

1/ρ=fρ(xn〓...) ...(1) And, for example, fρ becomes the following (1') as an experimental relational expression.

1/ρ = a ₀ + a ₁ xn ... (1') Note that a ₁ and a ₀ mainly depend on the roll characteristics such as the difference in roll diameter and hardness between the upper and lower work rolls, and the thickness of the material to be rolled S. It is a fixed coefficient.

From the above equation (1'), the impact drop amount difference Xn required to make the curvature 1/ρ zero is expressed by the following equation (2) (calculated in the calculator 11).

Xn=-a ₀ /a ₁ ...(2) Figure 4 shows the conditions under which the thickness of the material to be rolled S is 8 to 10 mm, the difference in diameter between the upper and lower work rolls 1 and 1' is 1.89 mm, and the difference in hardness is 2.0. This shows the experimental results of determining the impact drop amount difference Xn necessary to prevent warping at the biting tip of the rolled material S in this case.
Xn is -1.2%.

Incidentally, the rolling torque calculator 10
The method predicts and calculates the rolling torque T _L from the rolling conditions before the rolled material S is bitten.

Generally, rolling torque T _L is given from torque arm coefficient λ, contact projection length d, and rolling load P as shown in equation (3) below.

T _L =λ・d・P (3) The rolling torque calculator 10 receives the predicted values of the torque arm coefficient λ, contact projection length d, and rolling load P, and calculates the predicted values according to the above equation (3). An operation is performed.

The impact drop correction amount calculator 12 calculates the impact drop amount difference Xn, which is necessary to prevent warpage from occurring at the biting tip of the rolled material S, from the impact drop amount difference calculator 11. , an impact drop correction amount Z is calculated before the rolled material S is bitten so that the impact drop amount difference xn when rolling is performed without the control of the present invention is equal to the impact drop amount difference xn.

First, the impact drop amount difference xn during normal rolling is determined.

The impact drop amount n/N ₀ is expressed as a function of the predicted rolling torque T _L and the rotational speed N ₀ of the work roll before the biting of the rolled material, as shown in the following (4).
It is given by the formula.

n/N ₀ = _fo /N ₀ (T _L , N ₀ ...) ... (4) And, for example, _fo /N ₀ becomes the following equation.

n ₁ /N ₀₁ =b ₀ +b ₁ T _L1 +b ₂ /N ₀₁ ...(4′) n ₁ ′/N ₀₁ ′=b ₀ ′+b ₁ ′T _L1 ′+b ₂ ′/N ₀₁ ′
...(4″) Note that b ₀ , b ₁ , b ₂ and b ₀ ′, b ₁ ′, b ₂ ′ are coefficients, and equation (4′) is the impact drop amount of the upper work roll 1. The formula (4″) for calculating n ₁ /N ₀₁ is a formula for calculating the impact drop amount n ₁ ′/N ₀₁ ′ of the lower work roll 1′.

The impact drop amount difference Xn between the upper and lower work rolls 1 and 1' when rolling is performed without the control of the present invention is given by the following equation (5).

xn=n ₁ /N ₀₁ −n ₁ ′/N ₀₁ ′ ...(5) Next, the impact drop amount difference Xn and the above
The impact drop amount difference xn obtained by equation (5) is compared with the impact drop amount difference xn, and an impact drop correction amount Z is determined so that the two are equal.

For example, if xn>xn, the impact drop correction amount to the upper work roll 1 is set to zero, and the impact drop correction amount to the lower work roll 1' is calculated.

If xn<xn, the impact drop correction amount to the lower work roll 1' is set to zero, and the impact drop correction amount to the upper work roll 1 is calculated.

The impact drop correction amount Z is the rolling torque
The experimental relational expression is given by the following equation (6) from T _L , the rotational speed N ₀ of the work roll before biting of the rolled material, the impact drop amount n/N ₀ , etc.

Z=fz (T _L , N ₀ , n/N ₀ ,...) ...(6) The function fz in the above equation (6) is, for example, the following (6')
The formula becomes

fz=c ₀ +c ₁ T _L +c ₂ /N ₀ +c ₃ n/N ₀ ... (6') Note that c ₀ , c ₁ , c ₂ , and c ₃ are coefficients, and the upper and lower work rolls 1 and 1 ′ respectively.

The function generators 13, 13' are connected to the bite detector 15.
The impact drop correction amount signal Z is input to the current controllers 6, 6' as a waveform of a pre-specified pattern, and the waveform is shown in FIG. A single triangular waveform as shown was used, T was fixed and V was adjusted.

Fig. 6 shows the experimental results under the same load and the same biting speed. In this case, in order to make the impact drop amount difference xn -2%, for example,
The amount of correction to the lower work roll may be set to zero, and the amount of correction to the upper work roll may be set to 0.38.

Here, to explain a specific method of using the impact drop correction amount, the correction amount calculated by the above equation (6) is converted into a current correction value as the maximum value, and the current controller 6, 6' is input as a correction signal.

The commands from the current controllers 6 and 6' control the roll rotation speed and rolling torque of the work roll to be corrected (page 11, lines 10 to 17), which were determined when the correction value was calculated. The drop amount is corrected.

As shown in the time chart of FIG. 7, the timing of the correction is executed at the time when the load cell detects the biting of the rolled material into the roll.

The maximum value of the correction amount is given at the time of detection of jamming, and the correction amount is decreased to zero during time T along a predetermined triangular pattern as shown in FIG.

As mentioned above, the impact drop correction amount Z is
By inputting the current to the current controller simultaneously with the biting, the work roll rotation speed changes as shown by the broken line in FIG. 7, and as a result, it is possible to suppress the occurrence of warpage.

As described above, when rolling a material to be rolled using a reversible rolling mill, the present invention provides the necessary rolling torque to roll the material to be rolled and the necessary rolling torque to prevent the occurrence of warping at the biting tip of the material to be rolled. The difference in the amount of impact drop between the upper and lower work rolls and the difference in the amount of impact drop between the upper and lower work rolls when rolling is not performed under the control of the present invention are predicted and calculated to create an impact drop that does not cause the above-mentioned warpage. The impact drop correction amount is set such that the impact drop amount difference is equal to the impact drop amount difference when rolling without the control of the present invention is performed using the rolling torque and the work roll before the rolled material is bitten. Calculated from the rotational speed and the impact drop amount of the upper and lower work rolls, and this impact drop correction amount calculation value is input for correction to the current controller in the work roll drive control system when the rolled material is bitten. Since it is given as a signal, it is possible to appropriately control the impact drop amount of the upper and lower work rolls, and it is therefore possible to reliably prevent the occurrence of warpage at the biting tip of the rolled material.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a state in which warpage has occurred at the biting tip of the rolled material, Fig. 2 is an explanatory diagram of an impact drop, and Fig. 3 is a block diagram showing an example of the implementation of the present invention. FIG. 4 is a graph showing an example of the relationship between the impact drop amount difference and the curvature of warpage at the biting tip of the rolled material, FIG. 5 is an explanatory diagram showing an example of the impact drop correction amount signal, FIG. 6 is a graph showing an example of the relationship between the correction amount and the impact drop amount, and FIG. 7 is a time chart showing the timing of correction of the impact drop amount.

Claims (1)

[Claims] 1. When rolling a material to be rolled using a reversible rolling mill, the rolling torque necessary to roll the material to be rolled,
The difference in the amount of impact drop between the upper and lower work rolls necessary to prevent warping at the biting tip of the rolled material, and the impact drop between the upper and lower work rolls when rolling is performed without the control of the present invention. The impact drop amount difference is predicted and calculated, and the impact drop amount difference that does not cause warping is equal to the impact drop amount difference when rolled without the control of the present invention. The impact drop correction amount is calculated from the rolling torque, the work roll rotation speed before the rolled material is bitten, and the impact drop amount of the upper and lower work rolls. 1. A speed control method for a reversible rolling mill, characterized in that, at the time of biting, a signal is given as a correction input signal to a current controller in a work roll drive control system.