JPS5839002B2 - Strip width control rolling method for continuous hot rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strip width control rolling method in a continuous hot rolling mill.

It is well known that generally, hot-rolled steel sheets (hot strips) are trimmed at their edges after pickling in consideration of product defects due to edge cracks and control during cold rolling in the subsequent process.

By the way, various attempts have been made to improve the accuracy of sheet width control in hot rolling in order to reduce the loss due to the trimming.

If the variation in the width of the hot strip is kept within the acceptable standard by controlling the width of the strip, the need for trimming will be eliminated, and the yield of the hot strip will be significantly improved.

As a prior art method for controlling the width of a hot strip, there is a method for controlling tension between stands.

One of these methods is to calculate the necessary tension corresponding to the deviation in the width of the rolled material at the entry side of the stand according to a predetermined relationship law based on the width, thickness, steel type, temperature, etc. of the rolled material, and calculate the tension between the stands in a predictive manner. A method for controlling this is disclosed.

By the way, as a result of trying the above-mentioned control method, the present inventors learned that the target strip width accuracy could not be achieved.As a result of various studies, the present inventors discovered that the passage time between the stands for the rolled material has a great influence on the tension control between the stands. The authors discovered that it is impossible to improve the precision of the hot strip width without taking into account the transit time, and succeeded in developing the method of the present invention. In a continuous rolling mill, the rolled Senju steel grade, the target strip width, the strip width and temperature measured at the entrance side of the stand, the planned strip thickness between the strip width control stands, the distance between the strip width control stands and the passing speed of the material to be rolled. From the passing time between the stands, which is determined from The present invention provides a strip width control rolling method that performs strip width control rolling while correcting the strip width control reference tension based on the speed, and performs the learning correction of the set relational expression coefficient O based on the measured strip width at the exit side of the stand.

As mentioned above, the main point of the present invention is the new knowledge that the tension application time, that is, the time for the material to be rolled to pass between stands is an important control factor for strip width control in tandem rolling.

This will be explained in detail according to the drawings.

Now, when the width of an arbitrary rolled plate material before rolling is B and the amount of change in the width of the plate after rolling is ΔB, the medium strain ε is expressed by the following equation (1).

ΔB ε=−・・・・・・・・・・・・・・・・・・・
...(1) The medium strain ε% and unit tension Tσ (kg/1t7
1? ) is determined by steel type and temperature as shown in Figure 1~
FIG. 6 is a graph.

Figures 1 to 3 are low carbon steel plates, Figures 4 to 6 are medium carbon steel plates, and Figures 1 and 4 are 900°C, Figure 2,
Fig. 5 shows the case at 950°C, and Figs. 3 and 6 show the case at 1000°C.

In Figures 1 to 6, curves a, b, c, and d show the relationship between medium strain ε and unit tension Tσ for each tension application time, and the curves a = d, tension application time τi, and The relationship is shown in Table 1 below.

The above-mentioned tension application time τi means the time for the material to be rolled to pass between the strip width control stands in the strip width control method using tension. In width control, it is clear that it is impossible to obtain the desired accuracy without considering the steel type, temperature, and rolling material passing time.

Now, Table 2 shows the results of an example in which the rolling material passing time τi between the strip width control stands was changed in actual tension strip width control.

As is clear from Table 2, when the steel type is the same and there is not much difference in the entrance plate width and temperature, the uneven strain ε is larger when the rolled material passes longer than the other, even though the tension between the stands is smaller. In other words, it can be seen that the influence of the rolling material passing time τi on strip width control is very significant.

Next, control according to the present invention will be explained.

Now, in the present invention, rolling is started by first applying a reference tension Ts between the strip width control stands, and the reference tension Ts is determined by the following equation (2).

Ts=f(BS/Bi-C・θi・τi) B1Ho
-...(2) However, Bs: Difference between the target plate width BA and the actual plate side Bi Bi: Actual plate width on the input side C: Coefficient representing the steel type θi: Actual measurement temperature on the input side τi: Mini plate width control stand Elapsed time τi=L/■.

L: Distance between strip width control stands ■o: Rolled material passing speed between strip width control stands Vo =
VR (1 + ψ) ■R: Planned roll speed ψ: Advance rate Ho: Planned thickness between strip width control stands The means for giving the reference tension Ts is a well-known means such as a looper provided between strip width control stands, or Any means such as tension loading rollers or changing the roll speed of the front and rear stands may be used.

Next, after the start of rolling, the measured plate thickness Hd and the measured roll speed V
Using the passing speed Vdd of the rolled material obtained from d, the above (
2) Replace Ho in the formula with Hd and Vo with Vdd and perform rolling while correcting the tension, and further minimize the difference between the measured plate width Bf on the exit side of the final stand and the product plate width Be. The learning correction of the coefficient in equation (2) is performed for each predetermined rolling loft to improve control accuracy.

Now, in the present invention, the board width control stands (plurality) need not be limited to a specific stand.

However, in order to absorb the thickness deviation that occurs due to changes in strip width at the subsequent stands, the distance between the first stands of a continuous rolling mill consisting of multiple stands, for example between 1 and 2 stands, between 2 and 3 stands, is
Between stands, any one between 3 to 4 stands,
Alternatively, it is preferable to carry out a combination of two stands, such as between 1 and 2 stands and between 2 and 3 stands.

Next, an example of implementing the method of the present invention will be described using the block diagram shown in FIG.

In Fig. 7, F1 to Fn indicate the last stand of the first stand in the continuous rolling mill.
is an entry side plate width gauge, 2 is an entry side thermometer, 3 is a finished plate width gauge, 4 is an input device for input data, that is, steel type and target plate width, 5
6 is a sheet width calculation and control device, 6 is a tension applying device such as the looper or tension loading roller, 7 is the planned sheet thickness Ho and Fl of the sheet width control stand, and the planned roll speed V of the stand.
R input device, 8 is rolling load meter, 9 is roll speed meter, 1
0 is a roll gap measuring device (screw position transmitter).

Now, strip width control rolling using the above-mentioned apparatus is performed as follows.

First, the target plate width BA of the steel type C1 is input from the input device 4 to the plate width calculation control device 5 .

Next, before the material to be rolled is bitten into the Fl stand, the entrance side sheet width Bi1 and the actual measured temperature θi on the person's side are similarly input to the sheet width calculation control device 5 by the entrance sheet width meter 1 and the entrance side thermometer 2, and Planned plate thickness between the device 7 and the plate width control stand, that is, Fl in this embodiment; Stand exit side plate thickness Ho and Fl
Similarly, the roll speed vH of the stand is determined by the board width calculation control device 5.
is input.

The board width calculation control device 5 calculates the distance L between the board width control stands given in advance (Fl, F2 in this example).
As described above, the inter-stand transit time τi is calculated based on the following equations (3) and (4) from the stand-to-stand distance) and the roll speed vR input from the input device 7.

Next, as explained in FIGS. 1 to 6 above, from the relationship between the unit tension Tσ and medium strain ε given for each steel type, temperature, and passing time τi, the target plate width BA and the measured plate width Bi are determined.
and the input devices 4 and 7 described above.
Based on the input signal from the reference tension Ts according to equation (2) above,
is calculated, rolling is started, the looper 6 is operated, and the reference tension Ts is applied to the material to be rolled between the strip width control stands Fl and F2.

Next, the materials to be rolled are Fl and F. After passing through the stand, the reference tension Ts is corrected by correcting the stand opening passage time τi and the planned plate thickness Ho in equation (2) from the plate thickness Hd on the exit side of the stand, the measured roll speed, and Vd.

Therefore, the plate thickness Hd on the exit side is determined by the following equation (5).

The corrected tension Tsd is calculated from the above-mentioned actual plate thickness Hd1 and actual measured stan continuous passage time d as Tsd = f (Bs/Bi-c-θi・τ1d)B
i ((d...(7)).

Thus, while rolling continues, the above-mentioned actually measured plate thickness Hd.

The actually measured inter-stand transit time τid is constantly fed back.

Next, the actual plate width Bf is measured by the finished plate width gauge 3, and the coefficient in the formula (7), ie, B s
Coefficients such as 7 b = C are learned and corrected, and then the above-described procedure is repeated to improve the accuracy of board width control.

Therefore, the product board width Be and the target board width BA between the board width control stands are Be- to -BA...
・・・・・・・・・There is the relationship shown in (8), but the coefficient is determined by the load distribution and rolling reduction rate of each rolling stand after the strip width control stand, and is determined by a statistical method from the rolling results.
Although these coefficients are determined in advance according to the entrance plate thickness, steel type, and temperature of the rolled material, according to the experience of the present inventor, the coefficient can be considered to be approximately 1.0.

Therefore, in the above-mentioned embodiment, an example of control was shown where Be=BA.

As a result of applying the method of the present invention to various steel plates, we succeeded in improving the accuracy of plate width control.

Table 3 below shows a comparison of accuracy between the conventional method and the method of the present invention in terms of the difference between the target board width and the measured average board width.

The conventional method shown in Table 3 is a strip width control method using tension that does not take into account the transit time τi between strip width control stands.

As described in detail above, the present invention provides a highly accurate strip width control method in a continuous hot rolling mill.

[Brief explanation of drawings]

Figures 1 to 6 are graphs showing the relationship between tension and medium strain;
The figure is a schematic block diagram of an apparatus for carrying out the method of the invention. 1: Entrance side board width meter, 2: Entrance side thermometer 1.3: Finished plate width meter,
4: input device, 5: plate width calculation control device, 6: tension applying device, 7: input device, 8: rolling load meter, 9: roll speed meter, 10: roll gap measuring device.

Claims (1)

[Claims] 1. In a continuous hot rolling mill consisting of multiple stands,
Steel type to be rolled, target strip width, strip width and temperature measured at the entrance side of the stand, planned strip thickness between strip width control stands,
The strip width control reference tension between the strip width control stands is determined from the distance between the strip width control stands and the passing time between the stands determined from the rolling material passing speed according to a set relational expression, and rolling is started. After biting of the rolled material in , width control rolling is performed while correcting the strip width control reference tension from the measured strip thickness and the measured roll speed, and learning correction of the set relational expression coefficient is performed based on the actually measured strip width on the exit side of the stand. A strip width control rolling method for a continuous hot rolling mill, characterized in that: