JPS581176B2 - Method for controlling steel strip tension in a furnace in a continuous steel strip heating line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for preventing tension fluctuations in a heating furnace, particularly in a continuous heat treatment line for cold rolled steel strips and the like.

In a continuous heat treatment line where strip coils are welded together and fed seamlessly to the heating furnace, looping bits or loopers are installed at important points on the line so that the strip continues to be fed even while the coils are connected. has been established.

An example of such a continuous processing line can be explained using the continuous heating furnace of the continuous galvanizing line shown in Fig. 1.
is a loop car 2 that runs on rails powered by an electric motor.
and a plurality of support cars 3 pulled by a loop car 2. Normally, the strip 5 sent out from the return machine 4 is sent to the heating furnace 6 with the loop shown in the figure. While the supply is interrupted, the loop car 2 moves to the left in the diagram to reduce the loop and continue feeding the strip to the furnace.

The tension of the strip in the heating furnace 6 is detected by the detector 7, and the speed of the priddle roll 9 is automatically controlled so that the detected value matches a target value given to the controller 8 in advance. The structure is such that fluctuations in the tension within the furnace are prevented.

In addition, in the figure, 10 is a DC motor for driving roll 9, and 11 is a DC motor for driving roll 9.
1 is a variable DC power supply, and 12 is an in-furnace tension setting device.

However, when feeding the strip from the looper 1, the loop car 2 collides with the front support force 3, and this impact is transmitted through the strip into the heating furnace 6, causing fluctuations in the tension in the furnace. It turned out that there was.

It is well known that fluctuations in tension in a strip heated to high temperatures in a furnace can cause irregular elongation, leading to a deterioration in the quality of the strip product. Such a method of detecting the actual in-furnace tension and performing feedback control cannot appropriately deal with the problem.

The present inventor focused on the fact that there is a time delay between the tension fluctuation propagating from the looper and manifesting as the tension in the furnace, and detected the tension fluctuation in the looper in advance and made a correction signal based on the detected value. We succeeded in solving the above-mentioned problems in the conventional control system by feeding the in-furnace tension control system.

That is, the present invention provides the tension fluctuation amount at the looper as a correction signal for the furnace tension to the furnace tension control system after a predetermined time delay T, and adjusts the amount of tension fluctuation at the looper at the time when the tension fluctuation appears in the furnace tension fluctuation. The gist of the present invention is to provide a method for controlling tension in a furnace, which is characterized in that the priddle rolls are operated in unison to compensate for this.

The above delay time T is T = T1 - T2 where T1: Time required for tension fluctuation to propagate T2: Dead time of the in-furnace tension control system, and propagation time T1 mainly depends on the line configuration and is usually 0.3 It is about seconds to 0.8 seconds.

To specifically explain the case where the method of the present invention is carried out on the continuous galvanizing line, as shown in FIG. .

The amplifier 14 inputs the detected value (c) and the tension reference value (+), and outputs a signal corresponding to the amount of tension variation (-) to the delay circuit 15.

If attenuation becomes a problem when the tension fluctuation propagates, the amplifier 14 adjusts the gain according to the degree of attenuation to match the tension fluctuation amount appearing in the furnace tension with the output signal of the amplifier 14.

Note that if the looper is equipped with a tension control system, it is sufficient to input a tension correction signal to the amplifier 14 or the delay circuit 15.

The delay circuit 15 delays the input signal by the set time T and outputs it to the furnace tension controller 8, thereby reducing the dead time T2 of the control system.
A signal to correct the tension in the furnace is sent in advance.

As a result, the furnace tension control system allows the rotation of the priddle roll 9 to reach a desired value at the time when the tension fluctuation in the looper propagates to the furnace tension, and if the amount of fluctuation is larger than the standard value, the rotation of the roll increases and Fluctuations are prevented by simultaneously relaxing the internal tension.

On the other hand, if the amount of variation is smaller than the reference value, the rotation of the rolls is reduced and the tension necessary to prevent variation is applied to the strip, thereby preventing tension variation from appearing in the tension in the furnace.

Note that in a continuous heat treatment line, a looper is usually installed in front of the winder on the exit side of the line, but as in the galvanizing line mentioned above, each process such as cooling, washing, and drying is interposed between the looper and the heating furnace. In this case, the tension fluctuation in the looper is attenuated before propagating to the heating furnace, and therefore does not become a disturbance factor that is particularly controlled by the present invention.

Next, the effects of implementing the present invention are shown in Table 1 in comparison with the conventional example.

The test results are the results of actual operation conducted on the continuous galvanizing line, where the propagation time T1 = 0.3 sec and the control system dead time T2 = 0. 1 sec, heating temperature 1200℃,
The strip advancing speed is 90 m/min.

As shown in the above table, by implementing the present invention, the tension in the furnace is largely stabilized, and the deformation of the strip is suppressed to an unavoidable degree.

As is clear from the above description, the present invention combines feedback control of the tension in the furnace with feedforward control that predicts and controls tension fluctuations propagating from the louver to the heating furnace. Fluctuations in the tension in the furnace can be prevented from occurring due to disturbances caused by temporary stoppages, etc. This allows for stable heat treatment, which is highly effective in improving product quality.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing an example of implementing the present invention in a continuous galvanizing line. Symbols in the diagram: 1: looper, 2: loop car, 3: support car, 4: return machine, 5: strip, 6: heating furnace, 7
, 13: Tension detector, 8: In-furnace tension controller, 9: Prydle roll for controlling in-furnace tension, 14: Amplifier, 15: Delay circuit.

Claims (1)

[Claims] 1 In a continuous steel strip heat treatment line that automatically controls the speed of the priddle roll on the furnace entry side or exit side so that the tension in the furnace of the steel strip that advances continuously in the heating furnace matches the target value, it is installed in the line. The tension in the furnace is adjusted using the amount of variation in tension in the copper strip in the looper as a correction signal for the tension in the furnace, so that the tension variation in the looper appears as a variation in tension in the heating furnace with time correction so that the priddle roll operates. A method for controlling steel strip tension in a furnace in a continuous heating line for steel strips, characterized by canceling fluctuations in steel strip tension propagated from a looper into a heating furnace by applying it to a control system.