JPS6030510A - Method for controlling tension at time of changing sheet thickness during rolling in tandem mill - Google Patents

Abstract

PURPOSE:To prevent the breakage of material caused by the variation of tension by regulating all the tensions between the stand of a specified order and the stand located at its downstream side to the tension lower than the breaking strength of a band-shaped material to be rolled at the stage when a sheet-thickness changing point, where a thick material is changed into a thin one, among sheet thickness changing points passes the stand of specified order. CONSTITUTION:This method is to control a tension at the time of changing sheet thickness while rolling a band-shaped material to be rolled containing a sheet-thickness changing point continuously without stopping its rolling by a tandem mill. That is, all of the tension Ti[II] between the (i)th stand where a sheet thickness changing point P exists and the (i+1)th stand located at its downstream side are regulated to the tensions not much exceeding the breaking strength of the band-shaped material to be rolled, at the stage when the point P where a thick material is changed to a thin one among sheet thickness changing points, passes the (i)th stand.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling tension when changing plate thickness during running in a tandem rolling mill, and in particular, to continuously control a strip-shaped rolled material including a plate thickness change point without stopping rolling. This invention relates to an improvement in the method of controlling tension when changing the running plate thickness in a tandem rolling mill that performs continuous rolling.

Conventionally, in the rolling process of strip-shaped metal materials, rolling was carried out by setting (set-up) the roll gap of the tandem rolling machine stand for each coil, but with this method, (A) It is necessary to stop rolling, which reduces rolling efficiency; (B) It requires a large number of personnel to thread the strip into the rolling mill; (C) It is necessary to prevent IC from scratches on the rolls that occur during threading. Problems such as the roll consumption rate deteriorates; and (D) the yield decreases due to the presence of defective plate thickness at the leading and trailing ends of the roll.

In order to alleviate these problems, a fully continuous tandem rolling system has been developed in which the coils are welded together and rolled one after another without stopping the rolling. In this case, for poems in which the plate thickness of the strip metal material changes, it is essential to change the plate thickness between runs, but this has conventionally been done using the following method. That is, when the plate thickness change point comes to the i-th stand, the rolling position of the i-th stand and the roll rotation speed upstream from this are changed. FIG. 1 shows the state of change in plate thickness during running according to the conventional method at the stage where the plate thickness change point P has passed the first stand. In the figure, h is the thickness of the material plate (11), ■ is the total tension between the stands (tons),
I and ■ represent the bus schedule, and subscripts 1-2 to ++i on the lower right represent stand numbers, respectively. Here, total tension Tk:
If you pay attention to it, the bus schedule is set between the 1st and 1st stands, and the bus schedule between the i+1th and subsequent stands downstream from the 1st is set by bus schedule e. The total tension was the value T+[IJ specified in Bus Schedule I.

That is, the total tension T was changed from that of bus schedule E to that of (2) after the first stand. Since the first stand does not belong to either path schedule I or H, it is called a transient stand. Such a conventional control method is effective in reducing the defective plate thickness portion (71 gauge) at the rear end of the front coil. Further, when changing the plate thickness from a thin material to a thick material as shown in FIG. 1 (A>), since the total tension of the thin material is set to be low, the problem of excessive unit tension does not occur.

However, as shown in Fig. 1(B), when the running plate thickness is changed from a thick material to a thin material, the total tension Ti [IJ (ton) of the bus schedule ■ for the thick material is directly applied to the thin material, A disadvantage arises in that the unit tension (kuf/d) of the thin material becomes high. In other words, in general, in tandem rolling, the unit tension is approximately constant, regardless of whether the material is thick or thin.
The rolling operation is controlled by kuf/il(), but in this case, in the thinner part of the plate near the plate thickness change point P, an amount that is inversely proportional to the plate thickness ratio than the normal set unit tension is applied. However, since a high unit tension was applied, there was a problem in that there was a risk of material breakage due to slight fluctuations in tension.

The present invention has been made in view of the above-mentioned conventional problems, and when the thickness change point where the plate thickness changes from thick to thin passes between each stand as described above, The object of the present invention is to provide a method for controlling the tension when changing the running plate thickness in a tandem rolling mill without increasing the unit tension and causing no risk of breakage or the like.

The present invention provides a method for controlling tension when changing the running plate thickness in tandem rolling in which a strip-shaped rolled material including a plate thickness change point is continuously rolled without stopping rolling. Among the points, when the plate thickness change point where the plate thickness is changed from thick to thin passes through the first stand, the connection between the first stand where the plate thickness change point exists and the 1+1th stand downstream from this is determined. The above objective is achieved by suppressing the total tension between the strips to a level that does not cause the strip-shaped rolled material to break.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a schedule pattern corresponding to one embodiment of the present invention. In this embodiment, between the stands including the provisional +V change point P, rolling is performed at the total tension T; Lml set in the bus schedule (2) for the next coil with a thin plate thickness. In this case, since the rear tension of the (i+1)th stand is changing, the settings of the rolling position and roll rotation speed are also changed for this stand. That is, in this case, the i+1th stand becomes the transient stand. Tables 1 and 2 show how to change the settings of the specific pass schedule (2) at each stand.

Table 1 shows the conventional method, and Table 2 shows the method of this embodiment. In these tables, S is the rolling position, ■ is the roll speed, 1) Two coils of low-carbon hot-rolled steel strip having the thickness and width shown in (2) are connected and rolled in a 5-stand cold tandem rolling mill, and the running plate thickness at the welding point is changed from the conventional method. The comparison results of the tension change state when the method of the present example is carried out are shown.

Table 3 (1) Bus schedule (2) Pass schedule■ The figure shows the total tension and cornit tension between the stands when the plate thickness change point P passes between the fourth and fifth stands. It shows change. In the conventional method, the plate thickness change point P
Since the total tension between the stands is a high value corresponding to pass schedule 1 of the thick front coil,
During this period, the tension of the unit for the thin material was 30 kgr/m, which is approximately twice that of the method of this embodiment, and it can be seen that the risk of material breakage is extremely high. On the other hand, in the method of this embodiment, the plate thickness change is started at the fourth stand, and the total tension between the stands is changed to a low value corresponding to the pass schedule (2) of the next coil of the thin material. That l
C, while the plate thickness change point P exists during this period, the unit tension of the front coil of the thick material is half. That is, it can be seen that according to the method of this embodiment, even when sheets having widely different thicknesses are continuously rolled, a tension t exceeding the normal set unit tension is not generated. As a result, constraints on the process are significantly relaxed, such as almost no need to implement welding restrictions based on plate thickness.

Note that the method of the present invention starts from the i1th stand where the plate thickness change point P exists, by setting the total tension between the +1st stands to an arbitrary value 1b
One example of this is to make the total tension match the total tension setting value T+ [II] in the next bus schedule (2) as shown in the above embodiment. That is, for example, when rolling a material where the plate thickness change point P and the welding point are related, the welding force is weak, and there is a high risk of breakage, the total tension between the stands where the plate thickness change point P exists is The pass schedule set corresponding to the plate thickness before and after the thickness change point P may be set to a lower value that is different from the value specified by The method of the present invention also includes setting the bus schedule to an intermediate value between the values specified by the bus schedule LIE in order to increase the bus schedule.

As explained above, according to the present invention, the unit tension can be kept low at all times even when the plate thickness change point from thick to thin passes through each stand. This has the effect of preventing material breakage due to tension fluctuations during rolling.

[Brief explanation of the drawing]

Figure 1 (A>(B) shows an example of a schedule diagram using the tension control method when changing the running plate thickness, which is popular in conventional tandem rolling profiling. (B) shows the case where the plate thickness is changed from thick to thin, and (B) shows the case where the plate thickness is changed from thick to thin. Figure 2 shows the running plate thickness in the tandem rolling mill according to the present invention. An example of a method of controlling one tension at the time of change is shown in Fig. 1 (
B) Corresponding Schedule Diagram FIG. 3 is a graph showing a comparison of the measurement results of tension changes when changing the running plate thickness between the conventional example and the above-mentioned example. P... Plate thickness change, +-1, +, t +1... Stand number, ■, ■・
...Bus schedule, 11...Plate thickness, T...Total tension. Agent Takaya Ron (and 1 other person) Figure 1 (A) I-L Stand L Stand Country Su7nd (B)! -1st 7nd l stand ++Is7nd 2nd figure 1-1st 1st i s7n y + 1st stand〉do Figure 3 Atsushi Hayashi

Claims (1)

[Claims] (1) In a method of controlling tension when changing the running plate thickness in a tandem rolling mill that continuously rolls a strip-shaped rolled material including a plate thickness change point without stopping rolling, the method includes the above-mentioned plate thickness change. Among the points, when the plate thickness change point where the plate thickness is changed from thick to thin passes the first stand, the first stand where the plate thickness change point exists and the i11th stand downstream from this stand 1. A method for controlling tension when changing plate thickness during running in a tandem rolling mill, characterized in that the total tension between the strip and the material to be rolled is suppressed to an extent that does not destroy the strip-shaped material to be rolled.