JPH05123727A - Plate thickness control method for cold tandem rolling mill - Google Patents

Abstract

(57) [Summary] [Purpose] The sheet thickness variation at the intermediate stand caused by rolling a material with rapid hardness variation such as the front and rear ends of the hot rolled coil is corrected, Stable manufacturing of cold-rolled strip products with high plate thickness accuracy. [Structure] In a cold tandem rolling mill, a plate thickness gauge 20 is provided between a final stand and an upstream stand thereof, and based on the output of the plate thickness gauge 20, the plate thickness gauge 20 moves from the first stand to one before the final stand. The roll speed up to the stand and the roll-down position of the final stand, or the roll velocity of the final stand and the roll-down position of the final stand are simultaneously changed by the feedforward method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip thickness control method for a cold tandem rolling mill.

[0002]

2. Description of the Related Art Generally, a cold tandem rolling mill employs the following plate thickness control (AGC) method as shown in FIG. 2 (Steel Manual III (1) "Rolling Foundation / Steel Plate" P5).
74 ~ P579). In FIG. 2, 1 is a material to be rolled, 2
A, 2B and 2C are plate thickness gauges, and 3 is a rolling down device.

(1) AGC for controlling the plate thickness on the outlet side of the first stand to be constant (a) Feed-forward reduction AGC ... The pressing position of the first stand based on the deviation of the mother plate thickness measured by the first stand inlet side plate thickness gauge 2A To change. (b) Gauge meter rolling down AGC: The strip thickness is calculated from the rolling position of the first stand and the rolling load, and the rolling position is changed so that this becomes constant. (c) Feedback reduction AGC ... The first stand reduction position is changed based on the deviation of the first stand outlet thickness measured by the first stand outlet thickness gauge 2B.

(2) AGC feed-forward tension AGC for controlling the second stand outlet side plate thickness to a constant value ... Based on the first stand outlet side plate thickness deviation measured by the first stand outlet side plate thickness gauge 2B, the first stand roll speed To change.

(3) AGC feedback tension AGC for controlling the plate thickness on the delivery side of the final stand to be constant.
The final stand roll speed is changed based on the product thickness deviation measured in C.

That is, in the cold tandem rolling mill, the plate thickness control corrects the plate thickness fluctuation of the hot-rolled plate at the first stand, and thereafter passes through each stand as it is to obtain a high plate thickness accuracy. Therefore, in a normal cold tandem rolling mill, variations in the thickness and hardness of the hot-rolled sheet hardly affect the subsequent stands.

[0007]

However, in the completely continuous tandem rolling mill, since the hot rolling coil is welded and rolled at the entrance side of the tandem rolling mill, the front and rear ends of the hot rolling coil (hot tandem mill) are rolled. However, even if it has a rapid hardness change, it is necessary to roll with high accuracy as in the case of the steady part in the center of the coil. However, when rolling the front and rear ends of the hot-rolled coil with the above-described completely continuous tandem rolling mill, even if a relatively good strip thickness accuracy is obtained on the delivery side of the first stand, it is possible to heat it in the subsequent stand. The effect of a sudden change in hardness of the rolled coil appears, and at the final stand,
There is a problem that the plate thickness accuracy is significantly deteriorated.

The present invention corrects the plate thickness fluctuation at the intermediate stand caused by rolling a material having a rapid hardness change such as the front and rear ends of the hot rolled coil, and the plate thickness at the exit side of the final stand is corrected. The object is to stably manufacture cold-rolled strip products with high accuracy.

[0009]

According to the present invention as set forth in claim 1, in a cold tandem rolling mill, a plate thickness gauge is provided between a final stand and a stand upstream thereof, and an output of the plate thickness gauge is provided. The roll speed from the first stand to the stand one before the last stand and the rolling position of the final stand, or the roll speed of the final stand and the rolling position of the final stand are changed at the same time by the feedforward method. It is the one.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the amount of change in the roll speed is determined so that the final stand delivery side plate thickness is constant, and the rolling position The amount of change is determined so that the tension between the final stand and the preceding stand is kept constant.

[0011]

FIG. 1 is a control system diagram of a plate thickness control device 10 used in an embodiment of the plate thickness control method according to the present invention.

The material 1 to be rolled is rolled by the first to n-th (one stand before the last stand) rolls,
A rapid change in hardness of the front and rear ends of the hot-rolled coil causes a change in plate thickness. This plate thickness variation is measured by the plate thickness gauge 20, and the measured value Δh _n-1 of the _n- 1th stand outlet side plate thickness variation is output to the speed change amount calculation device 21. In the speed change amount calculation device 21, using the formula (1), the final (n-th) stand outlet side plate thickness h
_In order to keep _n constant, the speed change amount ΔV _Rn of the nth stand is calculated.

[0013]

[Equation 1]

The speed change amount ΔV _Rn is sent to the speed control device 22 to change the roll speed. In addition, the measured value Δh _n−1 of the outlet side plate thickness variation of the _n− 1th stand is sent to the reduction position change amount calculation device 23, and the tension T _n−1 between the _n− 1th stand and the nth stand is kept constant. (2) to keep n
The amount of change ΔS _n of the rolling position of the stand is calculated.

[0015]

[Equation 2]

The reduction position change amount ΔS _n is sent to the reduction position control device 24, and the reduction position by the reduction device 25 is changed.

The roll speed and the rolling position are changed at the same time when the plate thickness variation portion measured by the plate thickness gauge 20 reaches the n-th stand, as in the normal feedforward system. Further, when the responsiveness of the roll speed control and the responsiveness of the rolling position control are significantly different, it is natural that a delay circuit needs to be provided in the control system with fast responsiveness in order to match the responsiveness. In some cases, it may be possible to compensate for the apparent responsiveness shift by first changing the control system having the slow responsiveness.

According to this method, the variation of the plate thickness on the delivery side of the (n-1) th stand (the plate thickness variation caused by the rolling of the 1st to the (n-1) th stand) between the n-1st stand and the nth stand. It is possible to improve the tension at the n-th stand without disturbing the tension, and as a result, compared with the case of simply controlling the plate thickness by changing the speed, the occurrence of slippage at the n-th stand due to the disturbance of the tension, the first to the n-th It is possible to suppress the occurrence of new plate thickness variation in the -1 stand. Incidentally, in order to improve the plate thickness fluctuation in the n-stand due to the hardness fluctuation of the material to be rolled, it is naturally conceivable to correct the speed change amount ΔV _Rn and the rolling position change amount ΔS _{n accordingly} .

Further, instead of changing the speed changing stand to the nth stand, the speeds of the 1st to n-1st stands can be changed while maintaining the current speed ratio of the 1st to n-1st stands. It is possible to obtain the effect of.

Further, the method of the present invention can of course be carried out in combination with the conventional method shown in FIG.

Further, the method of the present invention is intended to correct the plate thickness fluctuation newly generated at the intermediate stand up to the final stand. Therefore, not only the final stand but one stand before the final stand, and further It is naturally within the scope of the present invention to apply it to the preceding stand and a plurality of stands.

[0022]

EXAMPLE A mother plate having a plate width of 800 mm and a plate thickness of 2.0 mm was cold-rolled to 0.24 mm in a 5-stand cold tandem rolling mill train.

As the plate thickness control system, both the plate thickness control system of the present invention method of FIG. 1 and the conventional plate thickness control system of FIG. 2 were installed.

In the conventional method, the feed-forward reduction AGC of the first stand shown in FIG. 2, the gauge meter AGC, the feedback reduction AGC, and the feed-forward tension AG
C and the feedback tension AGC of the fifth stand (conventional method I), the feed forward tension AGC of the fifth stand shown in FIG. 3 is added to the conventional method I of FIG. 2 (conventional method I). II), and rolling of the welded portion of the hot rolled coil for each of the conventional method I of FIG. 2 and the fifth stand shown in FIG. 1 to which control for simultaneously changing the rolling position and the roll speed is added (invention method). Was done. The feedforward tension AGC shown in FIG.
The speed change amount by is calculated in the same way as in Eq. (1).

FIG. 4 shows the fourth stand outlet side plate thickness deviation amount, the fifth
The stand-out side plate thickness deviation amount and the tension between the fourth and fifth stands are shown. On the delivery side of the fourth stand, due to a sudden change in hardness of the front and rear ends of the hot-rolled coil, a change in plate thickness occurs again in the intermediate stand, and a change of ± 10 μm or more occurs.

In the conventional method I, since the plate thickness control at the fifth stand is performed only by the feedback tension AGC, the steady deviation on the exit side of the fifth stand is completely corrected.
It is not possible to deal with sudden changes in plate thickness due to changes in hardness of the front and rear ends of the hot-rolled coil near the welding point. Further, due to this change in hardness, the tension between the fourth and fifth stands also changes.

In the conventional method II, since the plate thickness control is performed by the feed-forward method only by changing the tension, the tension between the 4th and 5th stands is largely changed as compared with the conventional method I, and the tension on the high tension side is the same. There is a risk of slippage and breakage on the 5 stand, and a risk of squeezing on the low tension side, and it is difficult to continue the actual operation even if it can be experimentally performed. Further, regarding the deviation of the plate thickness on the delivery side of the fifth stand, the tension between the fourth and fifth stands greatly changes. Therefore, if control is performed so as to keep the plate thickness on the delivery side of the fifth stand constant, the plate thickness due to the tension variation in the fourth stand will occur. It has not been completely corrected because it creates a new deviation.

On the other hand, in the method of the present invention, the roll speed is controlled so as to correct the plate thickness deviation, and at the same time, the rolling position is changed so as not to cause tension fluctuation. Therefore, the tension between the fourth and fifth stands is made substantially constant. it can. As a result, since the plate thickness deviation due to the tension fluctuation in the fourth stand does not occur, the fifth stand exit side plate thickness deviation can be controlled to be much smaller than in the conventional methods I and II.

That is, according to the method of the present invention, it is possible to correct the plate thickness fluctuation newly generated in the intermediate stand due to the hardness fluctuation or the like without causing the tension fluctuation, and as a result, the plate thickness deviation is corrected. It is possible to stably manufacture a cold-rolled strip product having a small amount of trouble without troubles such as slip of the plate, breakage of the plate, and squeezing.

[0030]

As described above, according to the present invention, the plate thickness variation in the intermediate stand caused by rolling a material having a rapid hardness variation such as the front and rear ends of the hot rolled coil is corrected, On the delivery side of the final stand, it is possible to stably manufacture a cold-rolled strip product with high plate thickness accuracy.

[Brief description of drawings]

FIG. 1 is a control system diagram showing an example of a plate thickness control device for carrying out the present invention.

FIG. 2 is a control system diagram showing an example of a plate thickness control device used conventionally.

FIG. 3 is a control system diagram when a feedforward tension AGC is applied to a final stand.

FIG. 4 is a diagram showing a result of improving the plate thickness accuracy according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 10 Plate thickness control device 20 Plate thickness gauge 21 Speed change amount calculation device 22 Speed control device 23 Reduction position change amount calculation device 24 Reduction position control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruhiro Saito 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Kawasaki Steel Co., Ltd. (72) Inventor Sadayuki Miyoshi 1 Kawasaki-cho, Chiba-shi, Chiba Steel Co. In-house

Claims (2)

[Claims] 1. In a cold tandem rolling mill, a plate thickness gauge is provided between a final stand and a stand upstream thereof, and based on the output of the plate thickness gauge, the first stand to the one before the final stand. A plate thickness control method for a cold tandem rolling mill, characterized in that the roll speed to the stand and the rolling position of the final stand, or the roll speed of the final stand and the rolling position of the final stand are simultaneously changed by a feedforward method. .. 2. The amount of change in the roll speed is determined so that the final stand exit side plate thickness is constant, and the amount of change in the rolling position is maintained constant in tension between the final stand and the preceding stand. The method for controlling the plate thickness of a cold tandem rolling mill according to claim 1, wherein the method is determined.