JPH0246282B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to the control of a rolling mill equipped with a hydraulic lowering device, and particularly to a running plate of a rolling mill that changes the thickness of a material to be rolled during rolling. Regarding the thickness changing method.

[Technical background of the invention]

In general, plate thickness changes during running are carried out mainly for the purpose of improving yield and saving energy. For example, in the single rolling mill shown in FIG. The thickness of the material to be rolled 2 is changed by changing the amount of reduction of the rolls when the material reaches just below.

In this case, since a certain amount of time is required to change the reduction amount, the time required to reduce the plate thickness during rolling and the reduction amount have the relationship shown in FIG. 2.

In other words, the change in the reduction amount is started at time t ₁ when the plate thickness change point D is bitten by the rolling roll, and the change in the reduction amount is completed at time t ₂ after a time determined by the characteristics of the reduction device, etc. Become.

Since the material to be rolled 2 continues to run during this change in the amount of rolling reduction, the thickness of the material to be rolled 2 also gradually changes accordingly, but the starting point of the thickness change and the thickness as seen from the material to be rolled 2 are as follows. It is desirable to make the distance between change end points as small as possible.

Fig. 3 is a block diagram showing the configuration of a control system for changing plate thickness during running using a conventional method, together with a rolling system.
Hydraulic lowering device 3 for adjusting the rolling position of the rolling rolls
In a rolling system that includes a position control device 4 that drives the roll, a motor 5 that rotates the roll, and a motor drive device 6 that drives the roll, a signal from a load meter 7 that detects rolling load and a signal from the motor 5 are detected. A signal from a counter 9 that counts the number of pulses of a pulse transmitter 8 that detects the rotation of the rolling machine and calculates the distance through which the material to be rolled 2 passes through the rolling mill is input to a change control device 10, and this change control device 10 is a position control device. A configuration is adopted in which a rolling reduction amount reference Ps is added to 4 and a rolling speed reference Vs is added to the motor drive device 6.

Here, the change control device 10 captures the signal of the load cell 7 used for plate thickness control as a rolling signal,
While this rolling signal is being applied, the counter 9
In response to the signal, the rolling machine passing distance of the material 2 to be rolled is
When it matches the preset change start point distance, the reduction amount standard Ps is corrected to match the plate thickness of the next schedule.

In this case, there is a relationship shown in FIG. 4, for example, between the rolling load P of a rolling mill equipped with a hydraulic lowering device and the upper limit V of rolling speed.

That is, as shown in curve A, the upper limit V of rolling speed when widening the roll gap gradually increases as the rolling load P increases, but on the contrary,
As shown by curve B, the upper limit V of rolling speed when narrowing the roll gap gradually decreases as the rolling load P increases.

The total variation range of rolling load P in normal rolling is
Pw, the smallest value within this fluctuation range Pw
Vs was considered to be the upper limit of the rolling speed allowed for the rolling system.

The change control device 10 shown in FIG. 3 uses this reduction speed upper limit value Vs to output a reduction amount reference Ps when changing the plate thickness.

Therefore, the change time ts [sec] is determined by the following equation.

t _s = |S _A −S _B |/Vs …(1) However, Vs: Upper limit of rolling speed [mm/sec] S _A : Rolling amount before change [mm] S _B : Rolling amount after change [mm] ] It is.

Further, the distance from the plate thickness change start point to the plate thickness change end point, that is, the change distance l [mm] is determined by the following equation.

l=v・_ts ...(2) where, v: rolling speed [mm/sec] _ts : changing time [sec].

As mentioned above, when changing plate thickness during running, it is required to make this changing distance l as short as possible, but in the conventional method, the smallest value Vs in the load fluctuation range Pw is used as the upper limit of the rolling speed. Therefore, in order to shorten the change distance l, the rolling speed v had to be lowered.

[Problems with background technology]

As is well known, lowering the rolling speed not only lowers the productivity but also causes a decrease in the temperature of the rolled material, so there is a limit to the adjustment range.

However, the conventional method for changing the plate thickness during running has the disadvantage that the changing distance l becomes long, which lowers the product yield.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a method for changing plate thickness during running, which can significantly shorten the changing distance and thereby significantly improve the product yield.

[Summary of the invention]

In order to achieve this object, the present invention provides a method for changing plate thickness during running in a rolling mill equipped with a hydraulic lowering device, in which the rolling load before changing the plate thickness and the rolling load after changing the plate thickness are predicted and calculated, The upper limit of rolling speed corresponding to these rolling loads is calculated using an approximate formula showing the relationship between the rolling load and the upper limit of rolling speed determined by the rolling mill, and among these, the upper limit of rolling speed with the smaller value is calculated. The invention is characterized in that the hydraulic lowering device is controlled according to the following.

[Embodiments of the invention]

The present invention will be described below with reference to the accompanying drawings.

First, the rolling load P and the upper limit of rolling speed V in FIG.
Curve A and curve B showing the relationship between .

V _OP = a ₁ · P ² + a ₂ · P + a ₃ … (3) V _CL = b ₁ · P ² + b ₂ · P + b ₃ … (4) However, V _OP : Upper limit of rolling speed in the roll gap opening direction V _CL : Upper limits of rolling speed in the roll gap closing direction a ₁ to a ₃ , b ₁ to b ₃ : constants.

For example, when trying to change the rolling reduction in the roll gap closing direction, the rolling load P ₁ before changing the plate thickness and the rolling load P ₂ after changing the plate thickness are determined by a predetermined rolling schedule using a well-known method. This makes it easy to predict and calculate. Therefore, by substituting these rolling loads P ₁ and P ₂ into the above equations (3) and (4), respectively, the upper limit value of rolling speed V CL1 before changing the sheet thickness and the upper limit value V _CL1 of rolling speed after changing sheet thickness can be obtained. _CL2 is calculated by the following formula.

V _CL1 =b ₁・P ₁ ² +b ₂・P ₁ +b ₃ …(5) V _CL2 =b ₁・P ₁ ² +b ₂・P ₂ +b ₃ …(6) This method attempts to change the reduction amount using the smaller value, in this case V _CL2 , and this reduction speed upper limit value V _CL2
is much larger than the smallest value Vs within the load fluctuation range Pw mentioned above as long as the rolling condition is normal.

FIG. 5 shows an example of an apparatus for carrying out the method for changing the running plate thickness according to the present invention, and the same reference numerals as in FIG. 3 indicate the same elements.
The difference from FIG. 3 is that a computing unit 11 is newly added.

Here, the calculator 11 predicts and calculates the rolling load before changing the plate thickness and the rolling load after changing the plate thickness according to the rolling schedule, and then calculates the above (( The upper limit value of the rolling speed is predicted using either equation 3) or (4), and the smaller value among these is added to the change control device 10 as the allowable rolling speed.

The change control device 10 changes the
Using equation (1), the change time t _s is calculated, and the reduction standard Ps during the change time t _s is determined and the position control device 4
I try to add it to

In this example, the computing unit 11 determines the upper limit values of the rolling load and rolling speed, but in actual plate thickness control, the rolling load may be predicted and calculated using a device other than the one shown in FIG. In this case, the computing unit 11
Alternatively, only the upper limit value of the rolling speed may be determined.

In addition, although the above embodiment describes changing the running plate thickness in a single rolling mill, this method can be applied to a continuous rolling mill in exactly the same way.

〔Effect of the invention〕

As is clear from the above explanation, according to the method for changing plate thickness during running of the present invention, the rolling speed can be increased within a range that can originally increase the rolling speed in view of the characteristics of the rolling system. Since the plate thickness is changed using the upper limit of rolling speed, the changing time is shortened accordingly, which has the excellent effect of significantly shortening the changing distance and significantly improving product yield. can get.

[Brief explanation of the drawing]

Figure 1 is a side view of the rolling mill showing the rolling state to explain the outline of changing the running plate thickness, and Figure 2 is a diagram showing the relationship between time and rolling reduction when changing the running plate thickness. , Fig. 3 is a block diagram showing the configuration of the running plate thickness control system using the conventional method for changing the running plate thickness, together with the rolling system, and Fig. 4 shows the rolling load of a rolling mill equipped with a hydraulic lowering device. A diagram showing the relationship between and the upper limit of rolling speed,
FIG. 5 is a block diagram showing an example of the configuration of a running plate thickness changing control system for implementing the running plate thickness changing method of the present invention, together with a rolling system. DESCRIPTION OF SYMBOLS 1... Rolling machine, 2... Material to be rolled, 3... Hydraulic lowering device, 4... Position control device, 5... Electric motor, 6
...Motor drive device, 7...Load cell, 8...Pulse transmitter, 9...Counter, 10...Change control device, 11...Arithmetic unit.

Claims (1)

[Claims] 1. In the method of changing plate thickness during running of a rolling mill equipped with a hydraulic lowering device, the rolling load before changing the plate thickness and the rolling load after changing the plate thickness are predicted and calculated, and the upper limit value of the rolling speed corresponding to these rolling loads is calculated. are calculated using approximate expressions indicating the relationship between the rolling load and the upper limit of the rolling speed determined by the rolling mill, respectively, and controlling the hydraulic lowering device according to the lower upper limit of the rolling speed among them. A method for changing plate thickness in a rolling mill, characterized by: