JPH0445569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing buckling in a continuous steel strip annealing apparatus, and particularly to a method for quickly responding and automatically preventing buckling.

Continuous annealing equipment is a device whose purpose is to obtain the desired mechanical properties by applying appropriate heat treatment to cold-rolled steel sheets, and usually consists of three zones: a heating zone, a soaking zone, and a cooling zone. In addition, the pre-cooling zone, the rapid cooling zone,
It consists of six zones, including an over-aging zone.

In the operation of continuous annealing equipment, buckling in the width direction of the steel strip (heat buckling) is caused by the thickness, width, and thickness of the steel strip.
It mainly occurs in the heating zone and soaking zone due to factors such as unsuitability of steel strip tension, furnace roll profile, heat treatment temperature, etc. Normally, steel strips have a slight crown to prevent meandering, but buckling tends to occur in the portion of the steel strip that contacts the boundary (shoulder) between the straight section and the tapered section of the hearth roll.
Figures 1A and 1B show the buckling 6 that has occurred in the steel strip 4 on the hearth roll 2, with A showing mild buckling and B showing severe buckling. When buckling 6 occurs, the steel strip 4 breaks in the furnace, causing a great deal of trouble in operation, and also significantly reducing product value.

Conventionally, this type of buckling was detected visually or by a television camera for monitoring the inside of the furnace, but
Regardless of the severe case shown in Figure B, the mild case shown in Figure 1 A, which occurs before severe buckling occurs,
When the steel strip 4 remains in the furnace, it cannot be detected by visual inspection or other methods, and it is detected only after the steel strip 4 leaves the furnace, and measures are taken to change the operating conditions to prevent buckling. There was a delay of several minutes before the procedure was completed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above, and to provide a buckling prevention method that can detect minute buckling in a furnace as soon as it occurs and immediately take preventive measures.

The gist of the present invention is as follows. That is, a step of detecting buckling of the steel strip to be annealed by a buckling prevention device provided near a plurality of hearth rolls for guiding the steel strip to be annealed in a continuous steel strip annealing apparatus, and a step of detecting the buckling of the steel strip to be annealed. A steel strip characterized by comprising the steps of calculating a speed command in a computing unit in order to change the steel strip tension based on a signal from a device, and changing the threading speed based on the speed command. This is a method for preventing buckling in continuous annealing equipment.

The details of the invention will be explained by means of illustrated examples. First, the apparatus used in the present invention will be explained. Figure 2 shows the arrangement of the buckling detection device. That is, a light projector 10 is provided on the furnace wall 12 to project light in the longitudinal direction of the hearth roll 2 near the roll neck portion 8A, and a portion of the light is blocked by the hearth roll 2 body. The light source of the projector 10 can be adjusted within a range of 20 to 100 mm in the width direction and 1 to 50 mm in the length direction. Further, near the roll neck portion 8B at the other end, a light receiver 14 is provided facing the light emitter 10, and the light receiver 14 is as shown in detail in FIG.
A photodiode array 16 is built-in, and the output voltage is changed according to the brightness of the image of the object formed by the lens 18, and the output signal for measurement is transmitted. The buckling detection device is composed of a light projector 10 and a light receiver that are placed opposite each other, and the arrangement thereof is shown in FIG. Figure 4 shows, from the left, a heating zone 20, a soaking zone 22, a rapid cooling zone 24, an overaging zone 26,
Although the furnace has five zones including the final cooling zone 28, the buckling detection devices indicated by black arrows are often located at the exit of the heating zone 20 and the soaking zone 22, where buckling 6 is particularly likely to occur; Four sets of soaking zones 22 are installed on the exit side of each upper hearth roll 2 from the central part where the steel plate temperature is high to the exit, and all soaking zones 22 are installed on each upper hearth roll 2. Rapid cooling zone 24, overaging zone 26, final cooling zone 2
The number of rollers 8 is smaller than this, and is installed every other or every second upper hearth roll 2.

Next, regarding the drive control relationship, as shown in the block diagram of FIG.
and hearth roll drive motor 32 and drive motor 32
The drive motor 32 includes a speed controller 34 and a pulse transmitter 36 attached to the drive motor 32 to detect the speed.

Next, a buckling prevention method of the present invention in a device having the above-mentioned configuration will be explained.

Since the buckling detection device of the present invention has the above-described configuration, when buckling 6 occurs in the steel strip 4 as shown in FIG. 6A, FIG. 7A, and FIG. B shows the output voltage as shown in FIGS. 7B and 8B.

Here, t _p = t _l + t _h + t _s + t _R , where t _p : Light emission length t _l : Light reception length t _h : Shading length due to the bulge of buckling 6 t _s : Shading due to the thickness of steel strip 4 Length t _R : Length of light shielded by the hearth roll 2 Therefore, t _h = t _p − (t _l + t _s + t _R ) In other words, the buckling detection device consisting of the emitter 10 and the receiver 14 detects a minute t _h . Buckling 6 can be detected along with its magnitude.

Next, speed control of the hearth roll 2 will be explained with reference to FIG. Normally, the speed of the hearth roll 2 is determined by two systems: a speed command 40 and a tension command 42. That is, basically, the hearth roll drive motor 32 is controlled based on the speed command 40 and the tension command 42, but among these, tension control is performed by controlling the hearth roll in contact with the steel strip 4 in the range where the tension is to be increased, for example. This is done by making the control current of the second drive motor 32 larger than the control current of the drive motors 32 of the hearth rolls 2 before and after it. The opposite is true when lowering the tension.

In the present invention, when the buckling 6 is detected by the buckling detection device installed near the hearth roll 2, the buckling 6 is detected according to the height t _h of the buckling 6 as shown in FIG. The tension acting on the steel strip 4 is corrected by the tension reduction command 44. That is, the tension command 42 corrected by the tension reduction command 44 from the buckling detection device is further corrected by the actual tension value 46 from a detector such as a tension meter, and then input to the calculator 30. Ru. The tension command is converted into a speed command in the arithmetic unit 30, and is input to the speed controller 34 together with the original speed command 40, where it is amplified and the drive motor 32 is controlled. Further, at this time, the pulse transmitter 36 corrects the speed command based on the feedback signal 48 of the actual measurement value of the drive motor 32, and also enters the arithmetic unit 30 to correct the tension command. That is, in this embodiment, even minute buckling is detected as soon as it occurs in the furnace, and speed control measures are automatically taken to instantly change the tension, thereby preventing the occurrence of buckling.

As is clear from the above embodiments, the present invention instantly detects the occurrence of minute buckling in the furnace using a buckling detection device installed near the hearth roll, and immediately and automatically takes speed control measures to change the tension. By doing so, we were able to prevent the occurrence of buckling and improve the quality and yield of steel strip.

[Brief explanation of drawings]

Figures 1A and 1B are both plan views showing the occurrence of buckling in steel strips; A is mild, B is severe, and the second
The figure is a plan view showing the arrangement of the buckling detecting device used in the present invention, FIG. 3 is a plan view showing the buckling detecting device used in the present invention, and FIG. 4 is a plan view showing the buckling detecting device used in the present invention. A schematic sectional view showing the arrangement inside the annealing device, FIG. 5 is a block diagram of the hearth roll speed (tension) control system of the present invention, and FIGS. 6A, 7A, and 8A are all buckling FIG. 6B, FIG. 7B, and FIG. 8B are schematic cross-sectional views showing the occurrence state of
9 is a diagram showing the corresponding output voltage of the light receiver of the present invention, and FIG. 9 is a diagram showing the relationship between the buckling height t _h and the tension reduction command value in the present invention. 2... Hearth roll, 4... Steel strip, 6... Buckling, 8A, 8B... Roll neck portion, 10... Emitter, 14... Light receiver, 16... Photodiode array, 18... Lens, 30 ...Arithmetic unit, 3
2... Hearth roll drive motor, 34... Speed controller, 36... Pulse transmitter, 40... Speed command, 42... Tension command, 44... Tension reduction command from buckling detection device, 46... Actual tension value, 48...
Feedback signal.

Claims (1)

[Claims] 1. Detecting buckling of the steel strip to be annealed by a buckling detection device installed near a plurality of hearth rolls that guide the steel strip to be annealed in a continuous steel strip annealing device. , comprising the steps of calculating a speed command in a calculator to change the steel strip tension based on the signal of the buckling detection device, and changing the threading speed based on the speed command. Features: Buckling prevention method in continuous steel strip annealing equipment. 2. The buckling detection device includes a light projector that is provided near one end of the roll neck portion of the hearth roll and projects light in the longitudinal direction of the roll, with a portion of the light being blocked by the roll body, and a light projector that is provided near the other end of the roll neck portion. 2. A method for preventing buckling in a continuous steel strip annealing apparatus according to claim 1, comprising: a light receiver provided in said light projector for receiving light from said light projector.