JPH02192810A - Sheet thickness control method for rolling mill - Google Patents

Abstract

PURPOSE:To obtain the exact target value of a sheet thickness and to allow the control up to the front end part as well by storing rolling load and starting the control to regulate the rolling reduction immediately when the detected sheet thickness on the outlet side of a rolling mill is within the required tolerance of the target value. CONSTITUTION:The load is measured by a rolling load detector 2 of the rolling mill 1 and the load is adjusted by a sheet thickness controller 6. The thickness of a material S to be rolled by a thickness gage 3 is then controlled to the target value. The rolling load is stored upon lapse of the prescribed time after the start of rolling and this stored load or the sheet thickness calculated therefrom is set as the target value at this time. The above-mentioned rolling load is stored by a control start commander 5 and the control to adjust the rolling reduction is started before the lapse of the above-mentioned prescribed time when the sheet thickness detected by the thickness gage 3 on the outlet side of the rolling mill 1 is within the required tolerance (+ or -alpha) determined for each of the materials with respect to the target value in the above- mentioned thickness control method for the rolling mill 1. The exact target value is obtd. in this way and the timing for starting the control is expedited. The thickness accuracy up to the front end part is improved and the product yield is improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for controlling plate thickness in a rolling mill.

[Conventional technology]

In rolling a steel strip, the thickness is controlled to a predetermined thickness.

The conventional plate thickness control method for rolling mills is to record the rolling load after a predetermined time after the material is bitten by the rolling rolls of the rolling mill, and use that load or the plate thickness calculated from that load as the target value. He was operating the rolling mill.

However, since the initial gap setting of the rolling mill is determined by predicting the rolling load based on the rolling operator's side temperature and plate thickness, in the conventional method, the actual rolling load may actually be different from the predicted load due to model calculation errors and detection errors. different. Therefore, the plate thickness accuracy at the leading edge of the material will depend on the initial gap setting accuracy, and the outlet side plate thickness tip will also deviate from the target plate thickness.

Therefore, if the load storage timing is accelerated in an attempt to control the plate thickness from the tip, not only will the target value be inaccurate, but the reduction will move rapidly in an attempt to follow changes in the plate thickness at the tip, causing trouble. Ta.

In plate thickness control in which the previous memorized rolling load is used as the target value, or the plate thickness is recorded from the rolling load and used as the target value, the rolling load is memorized after a predetermined time, so even if the actual rolling load is equal to the predicted rolling load, it will not be the same. The control start timing is the same even if there is no one. For this reason, if the rolling load predictions were different, even if the rolled material was rolled under the same conditions, the rolling load error in Section 70 would become large, making accurate control impossible. Therefore, a method was adopted in which the rolling load was recorded several seconds after the material was bitten, and the rolling load was controlled to be recorded several seconds after the material was bitten, avoiding recording the rolling load tα at the tip of the material to be rolled, where the temperature variation was large. However, with this method, the tip cannot be controlled, and control is not performed even when the thickness of the tip is close to the target value, so the controllability of the tip of the material is poor.

As a method of obtaining a predetermined thickness from the tip of the plate,
There is one described in Publication No. 5-64915.

This is a thickness gauge on the exit side, and the lowering device is operated in the opening direction or the closing direction until the exit side plate rL deviation becomes zero, and when the deviation signal of the exit side plate thickness becomes zero at a certain point, the zero detector is activated. The present invention proposes a method in which the lock-on mechanism is instructed to output its roll-down control output value by a lock-on command, starts plate thickness control, and forcibly approaches the plate thickness target value.

[Problem to be solved by the invention]

However, the method described in JP-A No. 55-64915 has the problem that it is very difficult to ensure the stability of sheet threading at the tip because the reduction is moved between the time when the material is bitten and the tension is stabilized. was there.

The present invention monitors the plate thickness with a plate thickness gauge on the outlet side of the stand so that the target value can be accurately controlled up to the tip, and when the conditions are met, the rolling load is recorded tα, control is started, and the target value is accurately controlled. This is a variable timing lock-on system that aims to speed up control start timing.

[Means to solve the problem]

In order to achieve this object, the method for controlling plate thickness of a rolling mill according to the present invention is equipped with a device for measuring the load and thickness of the material to be rolled, and a reduction control device for controlling the plate thickness to a target value. In a rolling mill plate thickness control method in which a rolling load is memorized after a period of time has elapsed, and the plate thickness calculated from the load or the plate thickness is set as a target value, when the rolling charge is memorized, a thickness gauge on the exit side of the rolling machine is used. Monitor the plate thickness, and if the plate thickness is within the required tolerance (±α) determined for each material with respect to the target value, record the rolling load at that time even before the predetermined time elapses. The method is characterized in that control is started to adjust the rolling reduction of the rolling mill so that the target load or target plate thickness is achieved.

In this plate thickness control method, the rolling load record tα starting conditions are such that the plate thickness is within a certain tolerance ±β that is larger than the target value, the slope of the plate thickness change is within ±T, and the plate thickness change is within ±T. By setting the direction of inclination to be in the target plate thickness direction, the accuracy of the target plate thickness becomes accurate and sudden rolling movements are eliminated.

[Effect]

In the present invention, after the material to be rolled is bitten by the rolling mill, the thickness of the material is successively monitored using a thickness gauge on the outlet side of the rolling mill.

As shown in Figure 2, the plate thickness deviation Δh on the plate thickness meter is equal to α′
If it is within h x α (the diagonally shaded range of ■ in FIG. 2), the rolling load is immediately memorized and the lubrication control is started. Note that here α (α') is the required tolerance determined for each material.

Even if the plate thickness deviation Δh is out of the shaded range in FIG. That is, α≦Δh and β or −β′ and Δh≦=α′, and Δ
The direction of variation of h is in the target plate thickness direction, and the slope of Δh is within ±γ (■ in Figure !02).

In the case of ■), control is started.

Even if Δh is Δh≧β, Δh≦−β′, α≦Δh, β or −β′, Δh≦−α′, if the direction of fluctuation of Δh is not the target plate thickness direction, or the slope of Δh is ±T In any of the above cases, as with the conventional method,
The rolling load is already recorded for a predetermined period of time, and control is started.

In this way, the timing of starting plate thickness control can be made earlier depending on the situation of plate thickness deviation, and compared to the conventional method of starting plate thickness control after a predetermined period of time, the yield of steel plates can be improved. can do.

〔Example〕

Hereinafter, the present invention will be specifically explained using a tandem rolling mill as an example.

FIG. 1 is a schematic diagram showing the final stand portion of a tandem rolling mill. In the figure, 1 is a rolling mill, 2 is a rolling load detection device for detecting the rolling load of the rolling mill 1, 3 is an X-ray plate thickness meter,
4 is a condition determination device, 5 is a board thickness control start command device, 6 is a board thickness control device, and S is a material.

In this embodiment, when the material is caught in the rolling mill 1, a signal appears in the pre-rolling m detection device 2 in a stepwise manner. After the signal is generated, the thickness of the material is measured using the plate thickness gauge 3. The condition judgment device 4 determines the plate FI- based on the plate thickness detected by the three plate plates in total.
The magnitude of the deviation Δh and the variation in plate thickness are calculated to determine the control start timing. At the same time, the plate thickness control device 6 starts counting the set time of the timer in order to start control based on conventional AGC control after the material has been bitten.

The timing conditions for starting the control based on the plate thickness deviation Δh in the plate thickness control device 6 are as explained above with reference to FIG. 2, and therefore their explanation will be omitted.

Figure 3 (a) shows that the plate thickness deviation Δh is within ±α, and Figure 3 (1)) shows that the plate thickness deviation Δh is within ±β and the rate of change of plate 17 is within ±γ. The improvement effect achieved by the present invention and the change in plate thickness achieved by the conventional method are shown below.

The dashed-dotted line in Fig. 3(a) indicates the AGCυj according to the conventional method.
In the conventional system, control is not started even if Δh is within ±α, so it takes time to bring Δh to zero. On the other hand, according to the present invention, Δh
When the value falls within ±α, since the 〇C control is started unconditionally, an improvement in Δh in the shaded area can be expected.

In addition, in Figure 3, etc.), if Δh exceeds ±α,
There is a possibility of trouble occurring due to sudden movement of pressure reduction.

Therefore, by starting the AG CjtI control under the conditions shown in FIG. 2, it is possible to expect an improvement in Δh shown in the shaded area in FIGS.

Although it varies depending on the constants of the rolling mill equipment and the gain of AGC, etc., the above α is 5% to 1% of the target plate thickness, β is 10% to 15%, and T is 1 to 2mff1/sec can be used as a guideline for setting.

Generally, the probability that the thickness of the tip of the material falls within the range ■ in Figure 2 is approximately 50%, and the probability that the thickness falls within the ranges ■ and ■ is approximately 90%.
Therefore, the yield of the leading edge of the material according to the present invention is expected to be about 0.0% compared to the conventional thickness control using a timer.
An improvement of about 1% can be achieved.

Although the above explanation has been given by taking a tandem rolling mill as an example, it goes without saying that the present invention can be similarly applied to other rolling equipment.

〔Effect of the invention〕

As described above, according to the present invention, board ¥:1. The timing to start thickness control is advanced according to the deviation situation, so if the thickness variation at the tip is small, the control timing can be made earlier. Compared to the above method, the plate thickness accuracy is extremely improved and the product yield can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a structure for implementing the plate thickness control method according to the present invention, FIG. 2 is an explanatory diagram showing conditions for advancing the timing of starting plate thickness control according to the present invention, and FIG. It is an explanatory diagram showing the improvement effect of the invention and the conventional method. 1: Rolling mill 2: Rolling load detection device 3: Plate thickness meter 4: Condition judgment device 5: Plate thickness control start command device 6: Plate thickness control device S: Material patent applicant Nippon Steel Corporation Representative Director
Masu Kobori (and 2 others) flute diagram

Claims (1)

[Claims] 1. Equipped with a device for measuring the load and thickness of the material to be rolled and a rolling control device for controlling the thickness to a target value, storing the rolling load after a predetermined period of time has elapsed after the start of rolling, and measuring the rolling load. Alternatively, in a rolling mill plate thickness control method in which the plate thickness calculated from the load is the target value, the plate thickness is monitored by a thickness meter on the outlet side of the rolling machine when the rolling load is memorized, and the plate thickness is set to the target value. If the value is within the required tolerance (±α) determined for each material, the rolling load at that time will be memorized and the target load or target plate thickness will be achieved even before the predetermined time has elapsed. A method for controlling plate thickness in a rolling mill, comprising starting control for adjusting rolling reduction in the rolling mill. 2. The rolling load storage start conditions are such that the plate thickness is within a certain tolerance ±β that is larger than the above α with respect to the target value, the slope of the plate thickness change is within ±γ, and the direction of the slope of the plate thickness change is within the target plate. 2. The method of controlling plate thickness of a rolling mill according to claim 1, wherein the control method is in the thickness direction.