JPS6160209A - Control system of sheet passing speed in tandem mill - Google Patents

Abstract

PURPOSE:To reduce the off-gauge quantity of a passing sheet and the variations of its thickness respectively, by detecting the rolling condition of a stand located at the rear stage of a tandem mill and regulating the drooping characteristics of the motor of a prescribed stand to zero or a <= specific value, for the purpose of reducing the drooping due to the variation of tension or making it to be zero. CONSTITUTION:When a detector 8 detects that a stand 3 at the rear stage of a tandem mill comes into a rolling state, the drooping due to the variation of the tension, etc. of a rolled stock 1 to be rolled is reduced or made to be zero, by regulating the drooping characteristics of the driving motors of prescribed stands 2,3 to zero or <= specific values, with the aid of a control device 6. Thus, the off-gauge quantity of a passing steel sheet 1 is reduced and the variation of its thickness is also reduced. This control is performed in the same manner when the sheet passes through the stands.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a strip threading speed control method in a tandem rolling mill, and in particular, to a method for controlling the strip passing speed in a tandem rolling mill that can reduce the amount of off-gauge and reduce strip thickness fluctuations. This relates to a threading speed control method.

[Conventional technology]

Conventionally, in tandem rolling mills, each stand has been used to control the threading speed (i
ffi plate start), acceleration, steady rolling, deceleration.

Each tail removal operation is controlled step by step in accordance with a predetermined target threading speed value (metal strip feed target speed by motor), and such control is performed for each metal strip to be wound as a coil, for example. The current situation is that

In such tandem rolling operations, problems such as plate breakage or deterioration of rolled shape due to tension fluctuation or excessive tension arise due to the accuracy of plate passing speed control, so the work rolls of each stand (STD) are driven. It is common to add drooping characteristics to the feed control of the motor in order to absorb the load fluctuations of the motor.

Here, motor drooping means changing the motor feed speed according to the magnitude of the load, and is expressed by the following equation.

■ However, D: roll diameter, ■=load current.

Imax: Rated current, Ntop: Set rotation speed.

d needle looping value, 1ff with ΔV needle looping
l plate speed l plate weight. Note that the set rotation speed N top may be any rotation speed, for example, the maximum rotation speed or a preset rotation speed.

According to the above equation (1), as the load on the motor increases, the load current increases, the plate passing speed ΔV increases, and the motor feeding speed becomes slower.

[Problem that the invention seeks to solve]

However, when such drooping control as shown in equation (1) is used, the tip of the metal strip gets caught in the stand of the rolling mill, and as the load on the stand increases, the current reaches an upper limit, and the strip threading speed decreases as the load increases. There is a problem that the amount of off-gauge decreases further and the amount of off-gauge occurs increases.

In addition, tension fluctuations due to interaction between stands of a rolling mill, etc. also change the rolling reduction ratio of the metal strip, increasing plate thickness fluctuations or the amount of off-gauge.

[Purpose of the invention]

It is an object of the present invention to provide a strip threading speed control system in a tandem rolling mill that can solve the problems of the prior art, reduce the amount of off-gauge, and reduce variations in strip thickness.

[Means for solving problems]

Means in the strip-threading speed control system for a tandem rolling mill of the present invention that achieves the above object and eliminates the above-mentioned problems is to detect whether the material to be rolled has entered the rolling state in at least the subsequent stand of a predetermined stand. When the material to be rolled enters the rolling state in the subsequent stand,
The drooping characteristic given to the motor of the work roll of the predetermined stand is set to zero or reduced from its set value.

By the way, the ratio between the amount of sheet passing speed reduction due to drooping and the sheet passing speed command value πDn is as follows from equation (1).

πDn　　　　n becomes.

Now, the relationship between the amount of current, the actual threading speed, and the ratio of the actual threading speed to the threading speed command with respect to the threading speed command is as follows.
The graphs shown in Figure (a), Figure 7 (b), and Figure 7 (C,) are shown, and as seen from this and this equation (2),
When the threading speed command is low, that is, when threading or stripping, the ratio of the temporary speed drop of 1 ffl due to drooping becomes large. Therefore, it can be seen that the feed speed of the work roll motor decreases, making it impossible to obtain a predetermined rolling reduction ratio, and the amount of off-gauge also increases.

On the other hand, considering the tension relationship, if there is no drooping, the top part of the coil when forming the material to be rolled into a coil shape will be caught in the 1+1st stand (hereinafter referred to as i+1-5TD) (the metal to be rolled Before the strip is threaded (so-called metal-in) in the stand, there is no tension on the output side of the i-th stand (hereinafter referred to as 1-3TD), and there is no tension in order to obtain the specified rolling reduction. Then, the tension at the input end becomes excessive and a state where it is likely to break occurs occurs.

In addition, when drooping is applied, the load on 1-3TD increases as there is no tension on the output side, and along with this increase, the amount of decrease in the threading speed also increases, as shown in Figure 6 (
As seen in the graphs shown in a) and (b) (,1-3T
In D, the rolling reduction rate is small until metal-in to i+1-ST D, and even if metal-in to i+1-3TD, the original target rolling rate M (here, M=30%)
much lower. Further, in this case, even in the 1-1-3TD, even if metal is inserted into the subsequent 1-3TD and i+1-3TD, the value falls below the target value.

Therefore, the tension on the input side of the 1-3TD is also large (not large), making it difficult for breakage to occur, but the amount of off-gauge increases.

From the above, when drooping is used, the reduction ratio becomes smaller and the amount of off-gauge is increased, but on the other hand, it has the advantage of preventing problems such as plate breakage, and has the effect of stabilizing plate threading and bottom shedding. There is. On the other hand, if drooping is eliminated, the rolling reduction ratio reaches the target value and the amount of off-gauge is reduced, but a contradictory problem arises in that there is a risk of breakage.

[Effect]

Therefore, as shown in the above configuration, by changing the drooping value to an appropriate state depending on whether or not the metal strip is metal-in to the stand after a certain stand, the tension relationship is maintained appropriately and the rupture occurs. In addition, it is possible to reduce the off-gauge amount and perform control that achieves both of these.

As a result, it is possible to realize a tandem rolling mill that can appropriately control tension fluctuations in the material to be rolled, reduce the amount of off-gauge, and reduce plate thickness fluctuations.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of the main parts of a tandem rolling mill according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the bottom removal state, FIG. (b) is a graph showing the characteristics of the rolling reduction rate in the control, and FIG.
It is a graph of the characteristics of the i-th stand in accordance with the tension and controlling the drooping value in accordance with the metal-in of the second subsequent stage, and showing the change in the rolling reduction ratio. In addition, the same parts in these figures are indicated by the same reference numerals.

In FIG. 1, 10 is a tandem rolling mill for rolling the metal strip 1, 2 is the i-th stand 1-3TD for rolling the metal strip 1, and 3 is
The i+1st stand for rolling this metal strip 1 is i+L S T D.

Here, the work rolls 2a and 2b of 1-3TD2 are driven by a motor 4, and the load current thereof is detected by a detector 5 and inputted to a control device 6. Similarly, i+1
- Work roll 3a of 3TD3.

3b is driven by the motor 7, and the load current is detected by the detector 8 and input to the control device 6. In addition, i+2-3T, which is a stand after i+1-3TD3,
D (not shown), . . . have a similar configuration and are subject to similar control.

On the other hand, 9 shown in FIG. 2 is 1 which is the previous stage of 1-3TD2.
-1-STD, and has work rolls 9a and 9b. This also has the same configuration as the 1-3TD2 and is subject to similar control.

Here, in FIG. 2, the metal strip 1 is 1-1-3TD.
9 (a state where there is no metal strip 1 to be rolled, the so-called metal otsu state), and eventually 1-
This shows a case where 5TD2 is in a buttless state,
In FIG. 1, on the contrary, the metal strip 1 is
Already in rolling state at 3TD2, i+1-3TD3
This is the case when metal-in is to be performed from now on.

Now, the control device 6 has a control circuit 1) including a microprocessor, etc., and a motor drive circuit group 12 that drives the work flow of each stand forming the tandem.
The control circuit 1) is connected to the detector (...detector 5) of each stand.
．． Detector 8. ...), and compares it with a predetermined value to determine whether or not the material to be rolled has entered the rolling state on that stand as a sheet passing state, and whether or not the rolling state has ended as a bottom removal state. Judgment means 13 receives these judgment signals from this judgment means 13, and when the strip passes through the stand one stage before, or when the strip passes through the stand one stage after, It has sheet threading speed control means 14 that generates a sheet threading speed control signal corresponding to each stand by changing the drooping value of the stand.

Next, the operation of this tandem rolling mill 10 will be explained according to FIGS. 1 to 4.

First, regarding the rolling line for the metal strip 1 formed into a coil shape, considering the drooping of 1-3 TD2, the signal from the detector 5 for 1-3 TD2 and the detection for i+1-ST D 3 one stage after it In response to the signal from the device 6, the determining means 13 determines the rolled down state, and the coil top portion of the metal strip 1 is 1.
-3 TD2 metal-in), i+1-3
Until I metal-in TD 3, I focused on workability,
A predetermined control signal generated from the speed control means 14 is
The amount of drooping in TD2 is set to a large value (about 3%), for example, 0.5% or more. Then, as the rolling progresses, the speed control means 14 receives a signal from the determination means 13 that the coil top portion has metal-ined into l+1-3TD3 (a signal indicating that it has been caught), and as shown in FIG. , 1-3
A control signal that reduces the drooping amount of TD2 to "0" or a value close to "0" is generated, and this is sent to the circuit corresponding to 1-3 TD2 of the motor drive circuit group 12, so that the motor 4 operates at a predetermined level. It is driven so that the feed speed corresponds to the sheet threading speed. As a result, the rolling reduction ratio of 1-3TD2 is as shown in Figure 3 (
As shown in a), at that point it becomes close to the original target value (target rolling reduction rate M=30%). Similarly i-S
It is detected that the metal is in TD2, and at this point, the drooping amount of 1-1-3TD9 is set to 10" or "
If a control signal is generated to reduce it to a value close to 0, the rolling reduction rate of the 1-1-3 TD9 in the previous stage will be close to the original target value M at this point, as shown in Figure 3(b). .

Here, in addition to the detector that detects the load current, each stand is provided with a detector that detects the tension on its output side or input side, and the tension is detected and the motor 4 of 1-3TD2 is controlled. In this case, 1-1-3TD9
~ When the tension between 1-3TD2 becomes high and the drooping value cannot be lowered to "O", regarding the control of 1-3TD2 in Fig. 4,
As you can see in the actual 4JID, the coil top part is one more.
When metal-in is performed on the l+2-ST D of the next stage, the drooping value is set to θ'' or approximately "0".

When the metal is inserted into l+1-3TD3 of the next stage of 1-3TD2, in order to suppress this tension, set it to a predetermined value on the 0'' side of about 0.7 to 1% as an intermediate value. It is intended to do so.

In this case, as shown by the dotted line U, the rolling reduction rate increases so as to become closer to the target value, corresponding to the change in the decreasing direction of the doping amount.

Next, as shown in FIG. 2, the metal strip 1 is
1-3TD2, which is the case where -3TD9 is missed, will be explained.

Considering the drooping of the 1-3TD2, as shown by the solid line in Figure 4, when the 1-1-3TD9 goes off the edge, the j-3TD2 reduces its drooping amount to 0'' or almost 0. This is to increase the drooping amount to a predetermined value 1 of 0.5% or more, for example, the above-mentioned 3%.By changing the amount of drooping in this way, the decrease in tension due to tail drop can be prevented with respect to the next 5TD2. Able to maintain proper tension.

Note that the above explanation is based on the stand of 1-3TD2, but the same applies to l+1-3TD3, and i
is 1 to the number of tandemly connected stands 1, e.g. 4
Similar control is performed for tandem, 5-tandem, 6-tandem, etc. In this case, there is no STD before or after the first STD and the last STD. Therefore, the amount of drooping of the first STD is controlled by the metal-in at the subsequent stage, and the amount of drooping of the last STD is controlled by the metal-in at the previous stage.

In this way, the drooping amount of 1-3TD is increased until the material to be rolled gets caught in l+1-S, TD.
−3TD metal-in is detected and the value is set to 0.
By lowering the rolling reduction ratio to a value close to "or 10", the rolling reduction ratio can be brought close to a predetermined value, and if necessary, l + 2- S T
By completely setting it to "0" at the same time as metal-in D, the rolling reduction ratio can be controlled to approximately the target value or a value close to the target value.

And then, on the other hand, 1-1- S T
By increasing the drooping from "0" to a predetermined value at the same time as D metals off, the influence of tail drop can also be eliminated.

By the way, as a method for increasing or decreasing drooping, in order to prevent sudden changes in threading speed and tension, it is preferable to use a method such as first-order delay or ramp function control, and to gradually increase or decrease the amount of drooping. It's good to change it.

-Also, as a method for detecting metal-in or metal-off, in addition to the method of detecting changes in the drive current of 1-3TD, it is also possible to detect the rolling blade of 1-3TD via a signal from a load cell, etc. Alternatively, the tension on the input side of the 1-3TD may be monitored to determine whether or not this has been established. Furthermore, these conditions can be detected in combination.

Now, comparing an example of the off-gauge length when controlled as described above with the conventional control method, when the drooping amount is changed and controlled, the off-gauge length is 20 m in cold rolling of a certain metal strip. Therefore, the amount of drooping can be reduced to about 1/2 of the conventional case where the amount of drooping is constant.

As explained above, this invention does not necessarily require controlling drooping for both metal-in and metal-off, and does not require control on the metal-off side. It is sufficient to control looping.

In addition, metal-in detection at the subsequent stage is not limited to the metal-in at the 1st and 2nd stage as in the embodiment, but also the metal-in at the 3rd and 4th stage, depending on the tension relationship of each STD. The drooping may be controlled to be "θ" depending on the angle.

By the way, this invention can be applied to rolling in general, including cold rolling and hot rolling, and any rolling mill can be used as long as it is connected in tandem with two or more stages. .

〔Effect of the invention〕

As can be understood from the above explanation, in the present invention, it is detected whether or not the material to be rolled has entered the rolling state in at least the subsequent stand of a predetermined stand, and the material to be rolled has entered the rolling state in the subsequent stand. Since the drooping characteristic imparted to the motor of the work roll of the predetermined stand is set to zero or is reduced from its set value when the motor of the work roll of the predetermined stand is inserted, the metal When the strip metals in, its drooping will decrease or change to "θ". As a result, it is possible to perform control that does not cause breakage and reduces the off-gauge amount.

Therefore, appropriate control can be performed in accordance with tension fluctuations in the rolled material, the amount of off-gauge can be reduced, and plate thickness fluctuations can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a tongue and dem rolling mill according to an embodiment of the present invention, FIG. Figure (b) is a graph showing the characteristics of the rolling reduction rate in each control, and Figure 4 is a graph showing the characteristics of the rolling reduction rate in each control.
The drooping value of the first stand is controlled according to the tension, and the drooping value is controlled according to the metal-in of the second stage, and the characteristic graph showing the change in the rolling reduction ratio is shown in Figure 5. Characteristic graph, Figure 6 (a), No. 6
FIG. 7(b) is a graph showing the characteristics of rolling reduction in conventional control, FIG. 7(a), and FIG. 7(b). FIG. 7(C) is a graph of each control characteristic regarding the relationship between the threading speed command and current, the actual threading speed, and the ratio of the actual threading speed and the threading speed command. It is. 1- Strip, 2-i-th Nostan F (i-3TD2), 2a, 2b
, 3a, 3b, 9a, 9b -'')-crawl, 3...-i +4th 0) Stuff V (i+1-
3TD3) 4.7--Motor, 6 ・-Control device, 1
0-・-tandem rolling mill, 1)- control circuit, 12-
Motor drive circuit group, 13-determination means, l4-speed control means. D-・Control characteristics of drooping value, U-・Characteristics of rolling reduction ratio.

Claims (1)

[Claims] (1) Detect whether the material to be rolled has entered the rolling state in at least a stand subsequent to a predetermined stand, and when the material to be rolled has entered the rolling state in the subsequent stand, the work roll of the predetermined stand A strip threading speed control method in a tandem rolling mill, characterized in that the drooping characteristic imparted to the motor is made zero or reduced from its set value.