KR102045682B1 - Twin roll type thin plate manufacturing apparatus and method - Google Patents

Abstract

Provided in an embodiment of the present invention is a twin roll type thin plate manufacturing apparatus, which includes a pair of casting rolls that manufacture a cast piece from molten steel. Here, the twin roll type thin plate manufacturing apparatus comprises: a hydraulic cylinder controlling the position of casting rolls; a position sensor detecting the position of the hydraulic cylinder; a chattering determination unit which determines a gap between the pair of casting rolls by the detected location of the hydraulic cylinder, before performing a frequency analysis on the gap, to determine that chattering has occurred at a cast piece in the case that a peak value is higher than a critical value in a predetermined frequency band; a correction gap output unit which, in the case that it is determined that the chattering has occurred at the cast piece, outputs a correction gap by reducing a frequency response, which is in the frequency band where the peak value is higher than the critical value, at the gap; and a controller which, in the case that it is determined that the chattering has not occurred at the cast piece, controls the location of the casting rolls such that the gap may match a target gap, and, in the case that it is determined that the chattering has occurred at the cast piece, controls the position of the casting rolls such that the correction gap may match the target gap.

Description

Twin roll type sheet manufacturing apparatus and method {TWIN ROLL TYPE THIN PLATE MANUFACTURING APPARATUS AND METHOD}

The present invention relates to an apparatus and method for removing chattering marks on strip surfaces occurring in certain steel grades in controlling the forces and speeds of casting rolls used in twin roll sheet metal manufacturing processes.

In general, a twin roll thin plate manufacturing process is a process of continuously supplying molten steel to two rotating casting rolls to continuously prepare thin sheets from the molten steel. In the twin-roll type sheet manufacturing process, high-carbon-containing steels, which are difficult to produce in conventional casting processes, are produced through rapid solidification. These steels have a small change in force due to the small equiaxed section of the strip center during solidification. It appears in the form of uneven solidification on the surface, making it appear as a chattering mark. In the chattering mark part, even a severe crack may occur in the horizontal direction to cause a defect, and when a skull or the like is mixed in the crack part, the fracture may occur.

In the twin roll thin plate manufacturing process, when casting a steel grade having a small equiaxed crystal section at the center of the strip during solidification, the solidification state of the surface of the plate varies greatly even when there is a slight solidification change. If the control responsiveness of the casting machine is not fast enough, such plate solidification change may not be sufficiently removed for the periodic appearance, and in severe cases, it may be further expanded.

More specifically, in the twin roll sheet metal casting process, the most necessary physical components for manufacturing liquid molten steel into a solid strip product are two casting rolls. The molten steel is confined in a pool made between two casting rolls and the casting rolls are rotated in opposite directions to solidify the slabs, and then solidify at the surface of each casting roll at the closest point (rollnip) of the two casting rolls. The cast slabs are combined and discharged to the discharge port, and the thickness of the cast slab is minutely changed by the change of the casting roll surface or the change of the equiaxed portion.

Due to the overall control and mechanical performance of the casting machine, this non-uniformity occurs periodically for certain steel grades.In the case of high-carbon steels with less equiaxed parts, the non-uniformity of the casting is due to the roll separation force (RSF) of the casting machine. The difference is severe and results in unwanted casting roll gap changes. In the process of periodically changing the gap of the casting roll, repetition of the non-solidification and over-solidification section of the site occurs, and when the cast is contracted immediately after casting, cracks in the non-solidification section and the horizontal direction are caused by the contracting force of the over-solidification section. This occurs, which leads to the failure of the whole product. This phenomenon usually occurs easily at the beginning of casting before all casting conditions are stabilized, and disappears within 10 minutes of casting. However, casting occurs due to the difference in temperature of molten steel, temperature, stability of casting roll cleaning device, and contamination of volatile components throughout the casting machine. It can last up to the whole.

The controller used in the casting machine is basically a PI feedback controller, which applies well to the saturation problem of a certain value, but when the disturbance occurs periodically, the response is fast enough to eliminate the disturbance of the period. Requires properties. Theoretically, in order to sufficiently remove the periodic signal, it should have more than twice the control speed by Shannon's sampling theorem, and in the field, it needs 10 times the response speed considering the noise of the signal.

However, since the casting rolls and peripheral equipment used in the twin roll sheet manufacturing process are very large and have large inertia, it is very difficult for the actuators to keep up with the speed of the controller and to remove fine disturbances of small size. Therefore, a new control concept for the controller and equipment is needed.

Publication No. 10-2016-0024086 (2016.03.04) Patent Publication No. 10-2011-0069597 (2011.06.23) Patent Publication No. 10-1999-0053877 (1999.07.15)

An embodiment of the present invention is to provide a twin roll type thin plate manufacturing apparatus and method capable of removing chattering marks on the surface of cast steel.

One aspect of the present invention provides a twin roll thin plate manufacturing apparatus including a pair of cast rolls for producing cast steel from molten steel. The twin roll type thin sheet manufacturing apparatus determines the gap between a pair of casting rolls by the hydraulic cylinder which adjusts the position of a casting roll, the position sensor which detects the position of a hydraulic cylinder, and the position of the detected hydraulic cylinder, Frequency analysis, the chattering judging unit judges that chattering has occurred in the cast steel when the peak value in the predetermined frequency band is higher than the threshold value, and the peak value is higher than the threshold value when judged that chattering has occurred in the cast steel. Adjust the position of the casting roll so that the gap coincides with the target gap when it is determined that chattering has not occurred in the cast steel, and that it is determined that there is no chattering in the cast steel by reducing the frequency response of the frequency band in the gap. And if it is determined that chattering has occurred, a controller for adjusting the position of the casting roll so that the correction gap coincides with the target gap.

In one embodiment, the twin-roll thin plate manufacturing apparatus may further include an image acquisition unit for photographing the cast to obtain a cast image, and an image processor for processing the cast image to determine whether chattering occurs from the cast image, The chatter determination unit may determine whether chattering has occurred in the cast only when the image processor determines that chattering has occurred.

In one embodiment, the controller is a PI controller.

In one embodiment, the ratio of the frequency response of the frequency band reduced in the gap may be adjustable.

Another aspect of the present invention provides a method for producing a twin roll thin plate using a pair of cast rolls for producing cast steel from molten steel.

The twin roll type sheet manufacturing method includes detecting a position of a hydraulic cylinder for adjusting the position of a casting roll, determining a gap between a pair of casting rolls based on the detected position of the hydraulic cylinder, Analyzing and comparing the peak value with a threshold value in a predetermined frequency band to determine whether chattering occurs in the slab, and in the step of determining whether chattering occurs in the slab, when the peak value is higher than the threshold value, If it is determined that chattering has occurred and chattering has occurred in the slab, the frequency response of a frequency band whose peak value is higher than the threshold is reduced in the gap to output a correction gap, so that the correction gap coincides with the target gap. Adjust the position of the casting roll, and if it is judged that no chattering has occurred in the cast, adjust the position of the casting roll so that the gap coincides with the target gap. The.

In one embodiment, the bi-roll thin plate manufacturing method may further comprise the steps of obtaining the cast image by photographing the cast, and processing the cast image to determine whether chattering occurs from the cast image, the chatter in the cast The step of determining whether a ring occurs may be performed only when it is determined that chattering has occurred in the step of determining whether chattering has occurred.

In one embodiment, the ratio of the frequency response of the frequency band reduced in the gap may be adjustable.

According to the present invention, in controlling the force and speed of the casting roll used in the twin roll sheet metal manufacturing process, it is possible to remove the chattering marks on the strip surface.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of a general twin roll type thin plate manufacturing apparatus.
Figure 2 shows a schematic block diagram of a twin roll thin plate manufacturing apparatus according to an embodiment of the present invention.
3 shows an image of a cast steel in which chattering has occurred.
Figure 4 shows an image of the cast strip is removed chattering by a twin roll manufacturing apparatus according to an embodiment of the present invention.
Figure 5 shows a flow chart of a twin roll thin plate manufacturing method according to an embodiment of the present invention.

As described above, in the process of periodically changing the gap of the casting roll, repetition of the unsolidified and over solidified sections of the corresponding site occurs, thereby causing chattering marks on the cast steel. Adjusting the gap of the casting roll to keep it constant at the target gap is ideal for removing chattering marks, but because the control responsiveness of the casting roll is not fast enough due to the large inertia of the casting roll, the target gap is always kept constant. In the case of controlling the casting roll so that the large response speed may rather worsen the chattering phenomenon. As a result of continuing research, the inventors have found that adjusting the position of the casting roll to reduce the chattering phenomenon is such that the gap which reduces the frequency response at a specific frequency of the casting roll gap which changes with time becomes the target gap. Found.

Hereinafter, with reference to the accompanying drawings will be described a bi-roll thin plate manufacturing apparatus and method according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of a general twin roll type thin plate manufacturing apparatus. As shown in FIG. 1, a general twin roll thin plate manufacturing apparatus 100 includes a pair of casting rolls 130, an edge dam 140, and a rolling line 150.

The pair of cast rolls 130 may have a pair of rolls that rotate in opposite directions to form a cast, eg, strip S, from the injected molten steel. The edge dam 140 seals the side surfaces of the pair of casting rolls 130 to store molten steel. Molten steel flows from the ladle 110 to the molten steel pool surrounded by the edge dam 140 and the pair of casting rolls 130 through the nozzle of the tundish 120.

The strip S formed by the pair of casting rolls 130 is rolled up and rolled up by the rolling line 150. The rolling line 150 includes a hot rolling mill 151, a water cooler 152, a pinch roll 153, a winding coil 154, and the strip S includes a hot rolling mill 151 of the rolling line 150, After passing through the water cooler 152 and the pinch roll 153, the hot rolling may be cooled and then wound by the winding coil 154.

Figure 2 shows a schematic block diagram of a twin roll thin plate manufacturing apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the twin-roll thin plate manufacturing apparatus 200 according to an embodiment of the present invention includes a pair of casting rolls 210, a hydraulic cylinder 220, a position sensor 230, and a chatter. And a ring determination unit 240, a correction gap output unit 250, and a controller 260.

The pair of cast rolls 210, like the pair of cast rolls 130 shown in FIG. 1, produce casts, eg, strips, from molten steel. The pair of casting rolls 130 is driven by the hydraulic cylinder 220, the position is adjusted by the hydraulic cylinder 220. The position of the pair of casting rolls 130 can be adjusted, for example, by adjusting the position of the hydraulic cylinder 220.

The position sensor 230 detects the position of the hydraulic cylinder 220. Thus, the detected position of the hydraulic cylinder 220 corresponds to the position of the casting roll 210 adjusted by the hydraulic cylinder 220. Instead of this, the position sensor may directly detect the position of the pair of casting rolls 210. The position of the hydraulic cylinder 220 or the pair of casting rolls 210 detected by the position sensor 230 is provided to the chattering determination unit 240.

The chattering determination unit 240 determines the gap between the pair of casting rolls 210 in real time by the position of the provided hydraulic cylinder or the pair of casting rolls. The gap is constantly changing in value over time. The chattering determination unit 240 analyzes the frequency of the fluctuating gap, and determines that chattering has occurred in the slab when the gap value is higher than the threshold in the predetermined frequency band. This threshold can be adjusted according to the characteristics of the twin roll sheet metal manufacturing apparatus used.

When the chattering determination unit 240 determines that chattering has occurred in the slab, the correction gap output unit 250 outputs a correction gap by reducing the frequency response of the frequency band in which the peak value is higher than the threshold in the gap. For example, the correction gap output unit 250 may include a band cut filter, and output a correction gap by band cut filtering a frequency response of a frequency band whose peak value is higher than a threshold.

The band cut filter may be a notch filter, for example. In one embodiment, the ratio of the frequency response of the frequency band to be reduced in the gap is adjustable according to the characteristics of the twin roll sheet metal fabrication apparatus used.

If the chattering determination unit 240 determines that chattering has occurred in the cast steel, the controller 260 adjusts the position of the pair of casting rolls 210 so that the correction gap coincides with the target gap. On the other hand, if the chattering determination unit 240 determines that chattering has not occurred in the cast steel, the correction gap output unit 250 does not operate, and in this case, the controller 260 causes the gap to coincide with the target gap. Adjust the position of the cast rolls in the pair. Controller 260 may be, for example, a PI controller.

On the other hand, in one embodiment, the twin-roll thin plate manufacturing apparatus 200 may further include an image acquisition unit 270 and the image processing unit 280. The image acquisition unit 270 photographs the cast to obtain a cast image, and process the cast image to determine whether chattering occurs from the cast image. For example, the image acquirer 270 may acquire an image of the cast before the cast manufactured in the casting roll 210 enters the rolling line 150 as shown in FIG. 1. 3 and 4 show examples of the image of the cast steel that can be obtained by the image acquisition unit 270. FIG. 3 shows an image of a caster in which chattering has occurred, and FIG. 4 shows an image of a caster in which chattering has been removed by the twin-roll manufacturing apparatus 200 of the present invention. 1 in FIG. 3 represents an uncondensed portion at the time of chattering, and cracks may occur at the corresponding portion. In addition, (2) of FIG. 3 indicates a part that is over-solidified when chattering occurs.

In the case where the twin-roll thin plate manufacturing apparatus 200 includes the image acquisition unit 270 and the image processing unit 280, the chattering determination unit 240 only when the image processing unit 280 determines that chattering has occurred. It is possible to determine whether chattering has occurred in the cast steel. In general, the image processor 280 determines whether the chattering determination is made more precisely than the chattering determination unit 240 determines whether chattering occurs. Therefore, by first determining whether chattering has occurred using the image processor 280, and only when it is determined that chattering has been issued, the chattering determination unit 240 determines whether chattering has occurred, thereby continuing the chatter in real time. Reduce the burden of detecting ring occurrences. Therefore, the processing capacity of the chattering determination unit 240 can be reduced.

As such, when it is determined that no chattering has occurred, the position of the pair of casting rolls 210 is adjusted so that the gap becomes a predetermined gap (target gap), and when it is determined that chattering has occurred, a correction gap is determined. The position of the pair of casting rolls 210 is adjusted to match the target gap. Through this process, as shown in FIG. 4, it is possible to reduce the occurrence of chattering marks in the cast steel produced by the twin roll type sheet manufacturing apparatus.

Next, a twin roll type thin plate manufacturing method 500 according to an embodiment of the present invention will be described with reference to FIG. 5.

Figure 5 shows a flow chart of a twin roll type plate manufacturing method 500 according to an embodiment of the present invention. The twin roll type thin plate manufacturing method 500 first detects the position of the hydraulic cylinder which adjusts the position of a casting roll (S510). Instead of this, the position of the pair of casting rolls can be detected. Next, the gap between the pair of casting rolls is determined based on the detected position of the hydraulic cylinder or the position of the pair of casting rolls (S520). Next, the gap is frequency analyzed, and it is determined whether chattering occurs in the slab by comparing the peak value and the threshold value in a predetermined frequency band (S530). For example, it can be determined that chattering has occurred in the cast steel when the peak value is higher than the threshold value.

If it is determined that chattering has occurred in the cast steel (S530-Y), the frequency response of the frequency band whose peak value is higher than the threshold is reduced in the gap to output a correction gap, and the correction roll of the casting roll is aligned with the target gap. Adjust the position (S540). On the contrary, when it is determined that chattering has not occurred in the cast steel (S530-N), the position of the casting roll is adjusted so that the gap coincides with the target gap (S550).

Meanwhile, before determining whether chattering occurs in the cast steel (S530), photographing the cast steel to obtain a cast steel image (S522), and processing the cast steel image to determine whether chattering occurs from the cast steel image (S524). It may further include.

In this case, only when it is determined in step S524 that chattering has occurred (S524-Y), it can be determined whether chattering occurs in the cast steel (S530). If it is determined in step S524 that chattering has not occurred (S524-N), the position of the casting roll is adjusted so that the correction gap coincides with the target gap (S560).

According to the present invention, in controlling the force and speed of the casting roll used in the twin roll sheet metal manufacturing process, it is possible to remove the chattering marks on the strip surface.

As mentioned above, although this invention was demonstrated using an Example, the technical scope of this invention is not limited to the range as described in the said Example. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiments. It is evident from the description of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

100: twin roll lamination casting device
110: ladle
120: tundish
130: a pair of casting rolls
140: edge dam
150: rolling line
151: hot rolling mill
152: water cooler
153: pinch roll
154: winding coil
200: twin roll lamination casting device
210: a pair of casting rolls
220: hydraulic cylinder
230: position sensor
240: chatter determination unit
250: correction gap output
260: controller
270: image acquisition unit
280: image processing unit

Claims (7)

In the twin roll type thin plate manufacturing apparatus containing a pair of casting rolls which manufacture a cast steel from molten steel,
Hydraulic cylinder for adjusting the position of the casting roll;
A position sensor for detecting a position of the hydraulic cylinder;
The gap between the pair of casting rolls is determined by the detected position of the hydraulic cylinder, and the gap is frequency analyzed to determine that chattering has occurred in the cast when the peak value in a predetermined frequency band is higher than a threshold. A chattering determination unit;
A correction gap output unit for outputting a correction gap by reducing a frequency response of a frequency band in which the peak value is higher than a threshold value in the gap when it is determined that chattering has occurred in the slab; And
When it is determined that chattering has not occurred in the cast steel, the position of the casting roll is adjusted so that the gap coincides with a target gap, and when it is determined that chattering has occurred in the cast steel, the correction gap is the target. Controller to adjust the position of the casting roll to match the gap
Including,
Twin roll type sheet manufacturing apparatus. The method of claim 1,
An image acquisition unit for photographing the cast steel to obtain a cast steel image; And
An image processor which processes the cast image to determine whether chattering occurs from the cast image
More,
The chattering judging unit determines whether chattering has occurred in the cast steel only when the image processor determines that chattering has occurred.
Twin roll type sheet manufacturing apparatus. The method of claim 1,
The controller is a PI controller,
Twin roll type sheet manufacturing apparatus. The method of claim 1,
The ratio of the frequency response of the frequency band reduced in the gap is adjustable,
Twin roll type sheet manufacturing apparatus. In the twin roll type thin plate manufacturing method using a pair of casting rolls which manufacture a cast steel from molten steel,
Detecting a position of a hydraulic cylinder for adjusting a position of the casting roll;
Determining a gap between the pair of casting rolls based on the detected position of the hydraulic cylinder; And
Frequency analysis of the gap and comparing peaks and thresholds in a predetermined frequency band to determine whether chattering occurs in the slab.
Including,
In the step of determining whether chattering occurs in the slab, it is determined that chattering occurs in the slab when the peak value is higher than the threshold value,
When it is determined that chattering has occurred in the cast, the frequency response of a frequency band whose peak value is higher than a threshold is reduced in the gap to output a correction gap, and the position of the casting roll so that the correction gap coincides with a target gap. Adjust the
When it is determined that chattering has not occurred in the cast steel, the position of the casting roll is adjusted so that the gap coincides with the target gap.
Twin roll type sheet manufacturing method. The method of claim 5,
Photographing the cast to obtain a cast image; And
Processing the cast image to determine whether chattering occurs from the cast image
More,
Determining whether chattering occurs in the cast is performed only when it is determined that chattering has occurred in the step of determining whether chattering has occurred.
Twin roll type sheet manufacturing method. The method of claim 6,
The ratio of the frequency response of the frequency band reduced in the gap is adjustable,
Twin roll type sheet manufacturing method.

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