JPS5943980B2 - Furnace tension control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an in-furnace tension control method for arbitrarily controlling the tension distribution of a steel strip in a furnace.

In continuous heat treatment furnaces, helper rolls are used to transport the steel strip.

Conventionally, to drive these helper rolls, several to several dozen rolls were grouped together and power was supplied from a common power source.

Although this is mainly due to economic reasons, it has also caused drawbacks in recent years in the production of composite structure high-strength cold-rolled steel sheets.

In the heating zone in section A of FIG. 2, the copper strip is gradually heated and thermally expanded, so if the steel strip tension is low, the copper strip may become slack and meander.

In addition, on the exit side of the heating zone and in the soaking zone, the copper strip becomes hot and softens, lowering its yield point. Therefore, if the steel strip tension is too high, the amount of plastic deformation increases and the copper strip becomes soft. There is a possibility that it will expand in the longitudinal direction and shrink in the width direction.

This causes shape deformations if the tension is too high.

This results in meandering, cooling buckles, and slippage in the copper strip.

The cause of deformation of the copper strip is due to an imbalance in the tension of the copper strip, but in the past, the tension was not directly controlled, but only by controlling the power supply voltage applied to the drive motor. The tension imbalance was not corrected (there is no proportional relationship between tension and power supply voltage, and the causal relationship is not clear).

There is also a method of controlling the field current If of a DC motor, but since the properties of the materials and the temperature characteristics of the elements that make up the control system fluctuate, the control state fluctuates not only with the season but also with the weather, making it difficult to achieve high accuracy. In addition, it is economically disadvantageous because it is necessary to individually control the motor's f.

Therefore, control is performed using a speed command as shown in Fig. 1, a feedback signal that is the output of the pulse generator PLO, and an automatic tension setting device ATR (which outputs the deviation between the command value and the actual tension value) provided for each motor. A control device consisting of a speed regulator ASR controlled by the speed regulator ASR and a drive unit Du controlled thereby can be installed on each of the helper rolls HR, and the drive motor M can be controlled individually according to the tension state. However, this is difficult to implement due to economic and maintenance considerations.

An object of the present invention is to provide an in-furnace tension control system which can arbitrarily set the tension distribution without having a separate control circuit for each helper roll, and which eliminates the above-mentioned conventional drawbacks.

The present invention detects the actual tension of the reference helper roll, and based on this value, causes the other helper roll motors to operate in accordance with the temperature pattern associated with the tension cover turn.

FIG. 2 shows the temperature pattern characteristics of a continuous annealing furnace consisting of a heating zone A, a soaking zone B, a first cold soaking zone C1, and a second cold soaking zone.

Although this temperature pattern varies depending on the properties of the material, it can not only be recognized in advance but also correspond to the pattern of the upholstery.

Thus, the tension deviation between each helper roll is known from this temperature pattern, and the tension of the other helper rolls can be calculated based on the tension of the helper roll in the range.

Of course, it would be possible to install a tension meter for each helper roll, but this would be extremely uneconomical and impractical.

FIG. 3 is a block diagram showing an embodiment of the present invention.

A digital processing device, for example, a computer 1 outputs a tension reference value sT and a tension deviation set value TR based on each of the copper strip speed S1, tension Te, steel strip dimension Si, and temperature pattern TP.

The tension deviation set value TR is calculated by the following equation.

Here, various quantities are determined as follows.

Vo: Speed of the n-th roll L: Steel plate length determined by roll arrangement go: Young's modulus A of the steel plate on the n-th roll Cross-sectional area of the Ni strip βan: Coefficient of thermal expansion at the stop of the n-th roll θsn
: // Temperature βB of // // //
, : Coefficient of thermal expansion of the nth roll θB n :
The temperature of // // // is expressed by equation (1), which expresses the change in speed between the n-th roll and the next roll as a change in the length of the steel plate.

From this, the tension deviation is determined by the speed change.

If the reference roll speed is v8, the tension deviation setting value TR for each roll can be expressed as follows.

The dimensions Si and temperature pattern TP of the steel strip are given prior to operation and stored in the computer, and the speed SP and tension are similarly set from time to time as set values.

The tension reference value ST is set as a constant value using automatic tension regulators (A, T).
R)2, and the actual variation is given to the tension detector (TM)
3, it is given as the actual measured value AT.

A reference roll is provided in a section where temperature changes are small, such as the first cooling zone, and the tension detector 3 is attached to this reference roll to perform tension detection.

Further, the tension control range is from the heating zone where plastic deformation is likely to occur to the reference roll setting point.

Based on the tension reference value ST and the actual measurement value AT, the ATR 2 outputs the tension command at that time to the calculator 4.

The arithmetic unit 4 is composed of multiplication circuits 411 to 41n, and A
The output of TR2 is given to each of the circuit groups.

The number of multiplication circuits corresponds to the number of helper roles to be controlled.

The tension deviation setting value TR from the computer 1 is calculated by the multiplication circuit 4.
11 to 41n, but the multiplication circuit 411 corresponds to the helper roll provided immediately before the reference roll.
Setting values are given in stages from to the multiplication circuit 411 corresponding to the first helper roll of the heating zone.

Specifically, the temperature difference in the temperature pattern shown in FIG. 2 is given as the tension deviation.

Multiplication circuits 41□ to 41o provided for each helper role
Each output becomes a speed correction signal for the helper roll motors 51 to 5o.

If this signal is replaced with a speed command, the subsequent configuration is the same as that shown in FIG. 1 with the addition of a correction circuit.

That is, a motor control device is constituted by an automatic speed regulator (ASR6, ~6o) whose other input is the output of a speed detector (PLO7, ~zn), and drive units 11~To controlled by this output. ing.

With the above configuration, even if tension imbalance occurs due to thermal expansion, plastic deformation, etc. of the copper strip due to temperature difference in the atmosphere, it can be removed by the present invention, resulting in breakage due to meandering, occurrence of cooling buckles, and slippage. It is possible to prevent changes in the shape of the product due to the occurrence of scratches or the like.

In the embodiment shown in FIG. 3, a DC motor is used as the motor, but an AC motor may of course be used.

In this case, it is only necessary to provide an orthogonal to alternating current converter between the ASR and the motor.

(Although not shown in FIG. 3, it is necessary to provide an AC/DC converter to convert AC power to DC power).

In particular, when an AC motor is used, the structure is simpler, so it is much more advantageous than a DC motor in terms of maintenance and economy.

Further, in the embodiment shown in FIG. 3, a case has been described in which a helper roll at a stage before the reference roll is controlled, but it goes without saying that a helper roll at a stage after the reference roll may also be controlled.

As is clear from the above, according to the present invention, the tension balance within the furnace can be arbitrarily controlled.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional control circuit, FIG. 2 is a temperature pattern diagram according to the present invention, and FIG. 3 is a block diagram of an embodiment of the present invention. 1... Computer, 2... Automatic tension adjustment device, 3... Tension detector, 4...
Arithmetic unit, 5, ~5o...Motor, 61~6o・
...ASR, 7, ~7o... Drive section, P
LO... Speed detector.

Claims (1)

[Claims] 1. Detecting the tension in at least one copper strip in a predetermined area in a continuous heat treatment furnace in which a plurality of helper rolls are installed,
The furnace is characterized in that the detected value is used as a reference value and a speed command corresponding to the tension deviation to be sequentially given to each of the helper rolls is given to each of the helper roll control devices based on the temperature pattern in the predetermined area. Internal tension control method.