JPS6033809A - Method for controlling tandem rolling mill at time of changing sheet thickness in running - Google Patents

Abstract

PURPOSE:To realize a rolling flow which is smooth and free from material breakage by treating separately the changing portion of forward slip going with rolling reduction, which is disregarded in the past, and making correctingly the portions corresponding to the casual relations at respective interstands cooperated with each other. CONSTITUTION:When a sheet-thickness changing point arrives at the (i)th stand (expressed by Si hereafter); its draft position is changed at the Si to a value corresponding to a prescribed sheet-thickness change, and its roll speed is also corrected by its changing portion of forward slip in cooperation with the change of draft position. Simultaneously, at the Si-1 stand or at respective stands on the upstream upper than the Si-1; those roll speeds are corrected by the changing portion corresponding to the sheet-thickness change at the Si in cooperation with those draft positions. Further, the draft position of the Si-1 is corrected at the Si-1 to conform the downstream tension of Si-1 to the prescribed tension of upstream pass-schedule, and also its roll speed is corrected by its changing portion of forward slip in cooperation with the correction of its draft position. In this way, the changes of sheet thickness and tension from the pass schedule of downstream to that of upstream are performed extremely smoothly, and the changes of draft position and roll speed are made to cooperate with each other while keeping perfectly their casual relation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for 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 a control method when changing the running plate thickness of a tandem rolling mill.

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. It is necessary to stop the rolling mill, which reduces rolling efficiency: (B) Many people are required to thread the strip into the rolling mill; (C) Roll consumption rate decreases due to scratches on the roll that occur during threading. (D) The yield is reduced due to the presence of a defective plate thickness at the tip and rear end of the coil.

Therefore, in order to alleviate these problems, a completely continuous tandem rolling method has been developed in which each coil is welded and connected and rolled successively and continuously without stopping rolling. In this case, if the thickness of the strip metal material is changing, it is essential to change the thickness between runs.

This has conventionally been done using the methods shown in FIGS. 1 to 3. Figure 1 shows the change in running plate thickness by the conventional method at the stage where the plate thickness change point P has passed the first stand (the first stand counted from the upstream side, hereinafter referred to as the I stand). It shows the situation. In the figure, h is the material thickness (mn), T is the tension between the stands (ton), I is the downstream pass schedule, ■ is the upstream pass schedule, and the subscripts i -2 to i+1 on the lower right are the stand numbers, respectively. There is.

As is clear from Fig. 1, the outlet plate thickness h1 of the i-stand is changed from the downstream pass schedule ■ to the upstream pass schedule ■, and the upstream tension of one stand (the tension between the i-1 stands) T and 1 is changed downstream. Work is performed to sequentially change the roll speed and rolling position of each stand so that the pass schedule changes from pass schedule A to upstream bus schedule II. For i-stand, the entrance side plate thickness h i-1,
Since the exit side plate thickness hi and the upstream tension T i-+ change, both the rolling position and roll speed are changed, and in the 1-1 stand, the downstream tension T +-+ changes, so the rolling position 1, Change in roll speed is required. Furthermore, i −1
Regarding the stand upstream from the stand, as shown in Figure 2, in order to maintain the mass 70- while maintaining the plate speed pattern of the upstream pass schedule ■, the roll speed is changed based on the change in plate thickness at the i stand. correction is necessary. Generally, the responses of the rolling position control system and the roll speed eating control system are different, so if only a change is given and changed, the roll speed control system will reach the target value first, resulting in extremely transient problems. High tension may occur. In order to avoid this, a method (hereinafter referred to as cooperation) is used in which both change rates are made to match and changes are made within the same time. Put these together,
Fig. 3 shows the chronological correspondence between changes in rolling position and changes in roll speed in conventional stands.

However, in such a conventional control method for changing the running plate thickness of a tandem rolling mill, coordination is performed only for changes in the rolling position and roll speed in the same stand, as shown in Fig. 3. Because sufficient consideration was not necessarily given to the cause-and-effect relationship between the mutual movements of each stand, the actual situation was that tension fluctuations could become large when changing plate thickness, and there was a high risk of material breakage. Ta.

The present invention has been made in view of these conventional problems, and provides a control method when changing plate thickness during running of a tandem rolling mill that has a higher degree of coordination than the conventional method and has less tension fluctuation. The purpose is to achieve smooth rolling flow without material breakage.

The present invention provides a control method for changing the running plate thickness of a tandem rolling mill that continuously rolls a strip-shaped rolled material including a plate thickness change point without stopping, in which the plate thickness change point is one stand. When the i
In order to keep the roll speed of the 1+1 stand located further downstream at the predetermined speed of the downstream schedule and to maintain the tension between stands 1 to ++i stands constant, the rolling position of the stand is changed accordingly. The roll speed is corrected by the advance rate change in coordination with the change in the rolling position, and the mass flow is maintained at each stand upstream of the i-1 stand, including the i-1 stand, while maintaining the plate speed pattern of the upstream schedule. In order to maintain constant the roll speed of each stand, the roll speed of each stand is corrected by the change based on the change in plate thickness at the i-stand, and in addition, at the i-1 stand, the tension between the 1-1 stand and one stand is adjusted upstream. In order to maintain the predetermined tension of the bus schedule, the rolling position of the 1 to 1 stands is corrected, and the roll speed is corrected by the advance rate change in coordination with the correction of the rolling position. has been achieved.

In other words, the present invention handles the advance rate change due to rolling reduction, which was previously ignored, separately in the control method when changing the running plate thickness, and also deals with the causal relationship between each stand. This improves the accuracy of coordination by making the parts work together correctly, and prevents excessive tension from occurring.

The present invention will be described in detail below based on the drawings.

The roll speed during rolling is defined by the exit side plate thickness speed and the advance rate, as shown in equation (1).

VRi=V11/(1+ri)...(1) VRI;
Roll speed of i-stand V+; Plate speed on exit side of i-stand 1st Advance rate at stand, that is, change in plate thickness and tension from downstream bus schedule E to upstream pass schedule ■ will also affect exit side plate speed and advance rate Therefore, in order to improve the coordination of rolling control at each stand, it is necessary to separate the roll speed into plate speed and advance rate and consider them separately.

That is, as shown in FIG. 4, when the plate thickness change point P reaches the i stand, the plate thickness h r [I] of the downstream schedule
In order to change the plate thickness from upstream schedule (2) to 1 [II], it is first necessary to change the rolling position of the 1 stand accordingly. Next, the roll speed of the 1+1 stand located further downstream is set to the predetermined speed VRb+ of the downstream schedule ■.
In order to maintain the tension TI between the i stand and the ++1 stand at [TiLI], which is the set tension of the downstream schedule ■, while keeping the tension at [I], it is necessary to keep the outlet plate speed V1 of the 1 stand constant. be. For this purpose, the roll speed VR+ of one stand needs to be corrected by the amount of change in the advance rate due to the change in the rolling position. It is optimal that this correction is coordinated with the change in the rolled down position.

On the other hand, in order to maintain the mass flow constant while maintaining the upstream bus schedule ■, the inlet plate speed Vi-2 of the t-1 stand is determined by the outlet plate thickness h1 of the i stand being lz[I]
→h l It changes in response to becoming [I[], and it also affects the upstream stand (.

That is, the roll speed of each stand upstream from the 1-1 stand, including the 1-1 stand, needs to be corrected in response to the thickness change in one stand.

It is optimal for this correction to be coordinated among the upstream stands.

Furthermore, at the i-1 stand, the upstream bus schedule ■
Since the downstream tension, Tt-+, is changing in the state of I need to make some corrections. It is best to coordinate the correction of this reduction position and the correction of the change in advance rate.

If the above is summarized using the same display method as in FIG. 3, it will be as shown in FIG. 5. As is clear from the figure, in the control according to the present invention, when the plate thickness change point reaches the i-stand, first, in that one stand, the rolling position of the i-stand is changed in accordance with the predetermined plate thickness change, and The roll speed is corrected by the advance rate change in coordination with the change in the rolling position, and at the same time, the roll speed of each stand is adjusted to i at each stand upstream from the 1-1 stand including the +-1 stand. Cooperatively compensates for changes based on plate thickness changes at stand and stand.
Furthermore, in order to make the downstream tension of the +-1 stand the predetermined tension of the upstream bus schedule, the rolling position of the 1-1 stand is corrected, and the roll speed is coordinated with the correction of the rolling position. It was decided that the amount of change in the advanced rate would be corrected. By doing this, changes in plate thickness and tension from the downstream pass schedule to the upstream bus schedule can be made extremely smoothly, and changes in the rolling position and roll speed can be coordinated in a completely causal relationship. Become.

Next, Fig. 6 shows a 5-stand cold tandem test using a low-carbon hot-rolled copper strip having the thickness and width shown in Table 1 (1) and (2) without two coils, according to the pass schedule shown in the same table. When rolling with a rolling mill and changing the running plate thickness at the welding point,
The results of a comparison between the conventional method and the method of an embodiment of the present invention will be shown.

Table 1 (1) Pass schedule ■ (2) Pass schedule ■ The figure shows the results of measuring the tension T4 between the fourth stand and the fifth stand at this time.

As is clear from the figure, it can be confirmed that, compared to the conventional method, in the example method according to the present invention, fluctuations in tension when changing the pass schedule are extremely small, and the risk of material breakage is significantly reduced.

As explained above, according to the present invention, when changing the plate thickness while running in a tandem rolling mill, the rolling position at the stand near the plate thickness change point and each stand upstream and downstream thereof, All of the roll speeds are changed and corrected in coordination with each other, resulting in an effect that fluctuations in tension in the rolling flow are extremely reduced and the risk of material breakage is significantly reduced. Therefore, even when rolling is performed by connecting coils with significantly different thicknesses and changing the pass schedule between runs, there is no need to worry about breakage troubles, and the efficiency of the continuous rolling mill is significantly improved. This has the effect of being able to.

[Brief explanation of the drawing]

Fig. 1 is a schedule diagram showing an example of how the plate thickness h and tension T are changed in each stand according to the control method when changing the running plate thickness of a conventional tandem rolling mill. A diagram showing how the plate speed changes at each stand.
FIG. 4 is a diagram showing the change and coordination state of the rolling position and roll speed for each stand after i1'1, and FIG. , a schedule diagram similar to FIG. 1 showing an example of changes in plate thickness 11, tension T, etc. in each stand; FIG. 5 is a schedule diagram similar to FIG. FIG. 6 is a diagram similar to FIG. 3 showing the results of measurement of changes in tension when changing the running plate thickness between the conventional example and the above embodiment. i-1, i, t+1...Stand number, T...
Tension, h...Plate thickness ■...Downstream pass schedule, ■...Upstream pass schedule, V R...Roll speed, ■...Plate speed, T+-+L
IIJ: Tension between the i-1st to i-th stands in the upstream pass schedule. Agent Takayaron (1 idiot) Figure 1 i publication sft ';X7>)'' i+I stand Figure 3

Claims (1)

[Scope of Claims] <1) In a control method when changing the running plate thickness of a tandem rolling mill that continuously rolls a strip-shaped rolled material including a plate thickness change point without stopping, the said plate thickness When the change point reaches the first stand, at the i-th stand, change the rolling position of the i-th stand accordingly to change the plate thickness from the downstream schedule to the upstream schedule, and While keeping the roll speed of the i+1th stand located further downstream at the predetermined speed of the downstream schedule, the first stand~i
In order to maintain the tension between the +1st stands constant, the roll speed of the first stand is corrected by the change in advance rate in coordination with the change in the rolling position, and - At each stand upstream from the first stand, change the roll speed of each stand based on the change in plate thickness at the i-th stand in order to maintain a constant mass flow while maintaining the plate speed pattern of the upstream schedule. Furthermore, in order to maintain the tension between the i-1st stand and the i-th stand at the predetermined tension of the upstream pass schedule, the i-1st stand is reduced. 1. A method of controlling a tandem rolling mill when changing strip thickness in running, comprising: correcting the position, and correcting the roll speed by the change in advance rate in coordination with the correction of the rolling position.