JPH05329588A - Device and method for machining dimples on cooling drum for casting cast strip - Google Patents

Abstract

PURPOSE:To improve the reliability of machining size by executing feedback control to the size of formed dimple in a machining device and a machining method for forming the dimples on the surface of cooling drum for casting cast strip by irradiation of laser beam. CONSTITUTION:In the dimple machining device for forming the dimples on the peripheral surface of the cooling drum by the irradiation with the laser beam on the cooling drum 3 for casting the cast strip, a video means 1 for taking picture of the formed dimple on the peripheral surface of the cooling drum and compensating means 2 applying the feedback to a means for controlling the irradiating condition of the laser beam at the time of differing from the prescribed dimensional value by calculating at least either one between the diameter size and the depth size of the formed dimple with the video signal from the video means and comparing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling drum processing apparatus and method for casting a slab, and particularly to a single drum system,
The present invention relates to a processing device and a processing method for forming a dimple by irradiating a laser beam on the surface of a cooling drum such as a twin-drum system or a drum-belt system.

[0002]

2. Description of the Related Art In the field of continuous casting, it has been strongly desired to develop a technique for directly producing a thin slab having a wall thickness close to the final shape of a product (hereinafter referred to as a thin slab) from molten steel. In the case of casting a thin cast piece, the molten steel is cooled considerably more rapidly in the cooling drum than in the case of casting a thick cast piece, which causes fluctuations in wall thickness or surface cracks in the cast piece. Therefore, it is necessary to consider a cooling drum that does not cause these defects.

For example, in Japanese Patent Laid-Open No. 60-184449, it is proposed to form uniform "concavities and convexities" on the entire peripheral surface of the cooling drum to form "air pockets" and to form an "air layer" on the peripheral surface of the cooling drum. Has been done. This is because the heat removal capacity of the cooling drum is reduced by "air trapping" and the molten steel is cooled slowly, so that the thickness of the "solidified shell" that is formed is made uniform in the plate width direction, fluctuations in wall thickness and surface cracking. It enables the casting of thin-walled slabs that do not have.

[0004]

However, when casting is performed using a cooling drum provided with unevenness, uneven marks (transferring marks) are transferred to the surface of the slab. The unevenness of the transfer trace is smoothed by the subsequent rolling, which does not cause any trouble, but if coarse grains are present in a part of the transfer trace, it remains as "bruises",
It impairs the commercial value of the cast product.

Further, when molten steel is cast using a cooling drum provided with irregularities, "surface waves" are generated in the "pool of molten steel" to form wrinkles on the surface of the cast slab and to produce luster. It may cause defects such as unevenness and coarse crystal structure. Therefore, it is necessary to pay close attention not to generate "surface waves" during casting.

For example, the cause of the "bruise" is caused by a portion (coarse grain forming portion) that is "slowly cooled" by the above "air pool" and a portion (minute cooling) that is in direct contact with the cooling drum (a minute cooling). This is because there is a difference in the crystal grain size of the solidified molten steel between the grain forming portion) and the difference in grain size causes "bruise" due to the difference in light reflectance. This is because the unevenness formed on the peripheral surface of the cooling drum is large with respect to the cooling rate distribution of the molten steel.

On the other hand, the cause of the "surface wave" is that when the "solidified shell" is formed, there are a "quickly cooled" portion and a "slowly cooled" portion in the traveling direction of the molten steel at the cooling drum interface. This is because the boundary is formed almost continuously in a local area. The boundary is, for example, irregularities are regularly provided at intervals on the peripheral surface of the cooling drum, or the surface tension to be formed by the irregularities cannot be obtained, resulting in a "quick cooling" portion. Thereby, the "quenching" part is formed in a chain.

As described above, it is understood that the problems of "bruises" and "surface waves" are caused by the unevenness formed on the cooling drum. Then, in order to solve such a problem, it is necessary to consider the size, shape, and arrangement of the irregularities (or dimples) to be formed.

Conventionally, the method used for dimple processing of the cooling drum is mainly wet etching. Etching has achieved considerably fine processing in the field of microelectronics and the like, but in processing this cooling drum, the dimple diameter to be processed is made small and its depth is required, so there is a limit to the processing size. Actually, the dimple depth required to guarantee the surface tension to be formed by the above-mentioned uneven portion is about 70 μm, and in order to obtain this depth dimension, the dimple diameter dimension is about 300 μm minimum.
It will be m. In other words, if the dimple diameter dimension is 300 μm or less, the dimple depth cannot be obtained and the surface tension cannot be guaranteed.

In addition, it is difficult for etching to flexibly change the dimensions, shapes and arrangement of the dimples. In addition, there is a concern that etching has recently become a problem for the environment, including peripheral equipment related to chemical treatment used for its processing.

Besides, shot plast, electric discharge machining, machining, etc. are also used for dimple machining. But,
Similar to etching, shotplast has problems such as processing size limitations, size control, and processing accuracy. Although fine machining is possible in electrical discharge machining and machining, since the number of dimples to be machined on the cooling drum is extremely large,
It is industrially inappropriate or impossible in terms of time including replacement of electrodes.

Therefore, an object of the present invention is to provide a processing apparatus and a processing method for forming dimples by irradiating a "laser beam" on the peripheral surface of a cooling drum.
In particular, during processing, feedback control regarding the size of the dimples to be formed is performed to improve the reliability of the processed size.

[0013]

FIG. 1 shows one mode of the construction of a processing apparatus for achieving the above object. The dimple processing apparatus according to the present invention is a dimple processing apparatus that irradiates a laser beam on a slab casting cooling drum 3 to form dimples on the peripheral surface of the cooling drum, and is an image showing the dimples formed on the peripheral surface of the cooling drum. At least one of the diameter dimension and the depth dimension of the dimples formed from the means 1 and the image signal from the image means 1 is calculated and compared with each predetermined dimension value, and when different from each predetermined dimension value, Compensation means 2 for feeding back the means 4 and 5 for controlling the irradiation state of the laser beam.

[0014]

By using the laser beam, the diameter of the laser beam can be reduced to about 3 times the wavelength, so that it is possible to process the peripheral surface of the cooling drum with a fine dimension that cannot be achieved by the conventional processing apparatus. Become. In addition, because of the laser processing, its electrical control is possible, and it becomes possible to set dimensions with flexibility for the dimples to be formed. Also, it does not cause any problems related to the use of chemicals.

In the feedback control of the dimple size, it is possible to measure the dimple size in a non-contact manner by obtaining the image by the image means 1. Further, by comparing the calculated value with a predetermined value and feeding it back, the processing size can be guaranteed from the influence of the reflection of the laser beam on the processing surface or the like, disturbance, etc., and the accuracy of the dimple processing size can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dimple processing apparatus using a laser beam according to the present invention will be described in detail below with reference to the drawings.

An embodiment of the dimple processing apparatus according to the present invention is shown in FIG. The dimple processing apparatus includes a laser oscillator 20, a laser controller 21 that controls a laser output, and a condenser lens 2 that focuses a laser beam on the surface of a cooling drum.
2, a lens control unit 23 that changes the focal length of the condenser lens 22, a camera 24 with an automatic focus adjustment function that reflects the surface of the cooling drum, and image processing that performs image processing on the projected image and feedback-controls the dimple size. And a device 25.

The cooling drum 26 rotates at a constant speed ω about its rotation shaft 27, and the rotation ω is the rotation controller 2
Maintained by 8. Processing unit 29 of this processing device
Is suspended on a sweep device 30 that moves at a constant speed v in the direction of the rotation axis while maintaining a constant distance s ₁ with respect to the surface of the cooling drum. Since the speed v is maintained by the sweep controller 31, as a result, the laser beam 32 is emitted from the cooling drum 2.
The peripheral surface of 6 is scanned spirally. Of course, the positional relationship between the present processing apparatus and the cooling drum 26 may be such that the cooling drum 26 itself rotates and moves in the rotation axis direction.

The laser oscillator 20 of the present processing apparatus uses one YAG laser, but other laser devices, for example, a continuous oscillation type gas laser such as a carbon dioxide gas laser or a pulse oscillation type solid state laser such as a ruby laser may be used. It is possible. The laser output of the laser beam 32 and its oscillation frequency are controlled by the laser controller 21.

The condenser lens 25 is provided with a mechanical or electrical driving unit 33, and its focal length is changed by a control signal 34 from the lens control unit 23, and the divergence angle α of the laser beam focused on the surface of the cooling drum is changed. change. As a result, the focusing area of the laser beam on the irradiation surface 35 of the cooling drum changes, so that the dimple diameter size can be changed.

The laser controller 21 controls the output value of the laser by applying a control signal 36 to the laser oscillator 20 to change the laser excitation power. As a result, the energy of the laser beam 32 focused on the surface of the cooling drum changes, so that the dimple depth size can be changed. Further, the laser controller 21 can change the irradiation time interval of the laser beam with which the surface of the cooling drum 35 is irradiated by modulating the laser excitation timing of a constant cycle by the control signal 37. As a result, the position interval of the dimples can be changed in the rotation direction of the drum.

As described above, the positional intervals, diameters, and depths of the dimples are controlled by being replaced by the control signals 34, 36, and 37. Each control signal is also considered from the rotation speed ω of the cooling drum 26, the sweep speed v of the sweep device 31, and the like.

The camera 24 with the automatic focus adjustment function and the image processing device 25 are provided for controlling the dimensions of the dimple shape to be formed. That is, the dimple diameter dimension φc set for the dimple to be formed
And the depth dimension D is monitored.

The camera 24 having a close-up lens is provided near the condenser lens 22 with a constant distance s ₂ from the surface of the cooling drum, and the processing device 29 is used for dimple processing.
At the same time, it is swept in the direction of the rotation axis of the cooling drum. When the processing operation is started, the dimples are formed in a series of spiral shapes on the peripheral surface of the cooling drum, so that the loci of the processed dimples are formed in a row at regular intervals in the rotation axis direction of the cooling drum. For example, the camera 24 is aligned so as to project an image of an already formed dimple row several rows away from the dimple row to be formed. And camera 2
4 is aligned so that the dimple is projected at the center of the screen because the camera is automatically focused at the center of the screen.

Since the camera 24 is provided in the vicinity of the processing point 35, a wavelength selection filter is attached to avoid noise such as laser light and radiant light scattered from the processing point. The wavelength selection of the wavelength selection filter is the wavelength 600
It is preferable to cut the thickness to nm or less.

When the dimple processing is started and, for example, the locus of the processed dimple is formed for several turns, the camera 24 starts to display the processed dimple. The autofocus lens of the camera follows the dimples that are projected one after another while adjusting the distance between the surface and the cooling drum. An electric signal from the camera 24, which is used to control the autofocus lens to follow, is input to the image processing device 25 for use as a dimple number counter. The dimple image projected by the camera 24 is input to the image processing device 25 as image data at a predetermined time interval, and this interval is guided by the counter.

FIG. 3 shows the positional relationship between the camera 24 and the dimples 41. First, when the dimple is at the point A, the surface a of the cooling drum 26 is projected on the camera 24, and the distance s ₂ between the camera 24 and the cooling drum is defined as a reference. Then, when the dimple 41 reaches the point B, the inner side surface b of the dimple 41 starts to be reflected, and the bottom portion c of the dimple 41 is reflected at the point C. At this time, the electric signal v _c used for focusing the lens 42 of the camera from a'to c'becomes a counter signal indicating the passage of the dimple. Further, as described above, this electric signal v _c is transmitted to the image processing device 2 through the dimple 41 at a predetermined time interval.
5, used as a timing signal when inputting images,
The image processing device 25 outputs the dimple video signal 38 at point C.
To enter. In this case, the image processing device 25 obtains the dimple depth dimension d from the signal value of the electric signal v _c .

In the image processing device 25, the dimple diameter dimension φ is obtained by image analysis from the video signal 38,
Along with the dimple diameter dimension φ, each predetermined value φ _c , D is compared. When the values φ and d are different from the predetermined values, the size compensation signals 39 and 40 are given to the laser controller 21 and the lens controller 23.

This feedback control is repeatedly performed until the completion of the dimple processing work, and the effects due to the reflection of the laser light, the disturbance, the fluctuation of the laser and the like during the processing work are compensated in real time.

FIG. 4 shows an example of a flow chart for executing the feedback control by obtaining the dimple diameter dimension φ from the video signal 38 in the image processing device 25.

First, at step 60, a video signal is input and, at the same time, the signal is filtered and binarized, and then at step 62, an image is formed. This image shows one dimple formed on the cooling drum. Two
Dimples represented by "black" substantially circular lumps by the binarization are indicated by a large number of "black" pixels, and the other ones are indicated by "white" pixels. In the next step 64, the number of pixels of the cluster is sequentially counted to obtain the area of the dimple. In step 66, the dimple diameter dimension φ is derived from the area.

In step 68, the depth dimension d of the dimple obtained from the electric signal v _c of the camera lens is read. In step 70, it is compared whether or not the dimple depth dimension d satisfies the set value D. If different from the set value, step 72 provides a laser power compensation signal to the laser controller to compensate for the dimple depth dimension. In step 74, it is compared whether or not the dimple diameter dimension φ satisfies the set value φ _c . If it is different from the set value, in step 76, a lens position compensation signal is given to the lens controller in order to compensate the dimple diameter dimension.

The above flow chart is repeatedly executed to perform feedback control of each dimension. This flowchart is an example in which feedback control is executed for one dimple shown in the figure, but some dimple data obtained by sampling are aggregated, statistically calculated as an average value, and the control is executed. It doesn't matter. Further, each set value may be set within a predetermined range.

By performing the feedback control in this way, it was possible to form dimples adapted to the set value as follows.

Using a YAG laser having a wavelength of 1.06 μm, the laser output is oscillated at a frequency of 500 Hz and a pulse width of 0.1.
msec, 100mJ / pulse, focal length 50mm
The condensing lens of No. 1 and a camera with an automatic focusing function equipped with a wavelength selection filter that cuts light having a wavelength of 600 nm or less were used to perform dimple processing with a dimple diameter size of 250 μm and a dimple depth size of 100 μm.
As a result, when the feedback control was not performed, the dimple diameter dimension was 250 ± 10 μm and the dimple depth dimension was 100 ± 30 μm, whereas when the feedback control was performed, the dimple diameter dimension was 250 ± 10 μm.
3 μm, and the dimple depth dimension was improved to 100 ± 10 μm.

Then, as a result of casting stainless steel (SUS304) using a cooling drum provided with such dimples, a cast piece having a thickness of 5 mm and having no surface defects was obtained.

In the present embodiment, the dimple diameter dimension and the dimple depth dimension were measured by using the camera with the automatic focus adjustment function. However, the dimple diameter dimension is measured by the camera and the optical measuring means such as the laser type measuring device is used. It is also possible to measure the dimple depth and apply similar feedback control.

[0038]

As described above, according to the present invention, a processing apparatus and a processing method for forming dimples on a slab casting cooling drum by a "laser beam" are provided. Then, during processing, by performing feedback control on the dimple size to be formed, the reliability of the processing size is increased,
It was possible to guarantee an appropriate dimple size for the dimples to be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing one aspect of a processing apparatus configuration of the present invention.

FIG. 2 is a diagram showing an embodiment of a processing apparatus according to the present invention.

FIG. 3 is a diagram showing a positional relationship between a camera and dimples in the embodiment of FIG.

4 is a dimensional control flowchart in the image processing apparatus of FIG.

[Explanation of symbols]

 20 ... Laser oscillator 21 ... Laser controller 22 ... Condensing lens 23 ... Lens controller 24 ... Camera with automatic focus adjustment function 25 ... Image processing device 26 ... Cooling drum 28 ... Cooling drum rotation controller 31 ... Sweep controller 30 ... Cooling drum rotation controller 32 ... Sweep controller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H04N 7/18 C

Claims (4)

[Claims] 1. A dimple processing apparatus for irradiating a laser beam on a slab casting cooling drum (3) to form dimples on the peripheral surface of the cooling drum, and an image showing the dimples formed on the peripheral surface of the cooling drum. Means (1), and at least one of the diameter dimension and the depth dimension of the formed dimples is calculated from the video signal from the video means and compared with each predetermined dimension value to obtain each predetermined dimension value. A dimple processing apparatus comprising: a compensating means (2) for feeding back a means for controlling the irradiation state of a laser beam when different. 2. The dimple processing apparatus according to claim 1, wherein the imaging means (1) projects the dimples through a wavelength selection filter. 3. A dimple processing method for irradiating a laser beam onto a slab casting cooling drum (3) to form dimples on the peripheral surface of the cooling drum, wherein dimples formed on the surface of the cooling drum are image-inputted. Copying with a device, calculating at least one of the diameter dimension and the depth dimension of the dimple from the image of the dimple, comparing the obtained dimension with a predetermined value, When the dimension deviates from the predetermined value, feedback is given to a device that controls the irradiation of the laser beam, and a dimple processing method. 4. The dimple processing method according to claim 3, wherein the dimple shape is copied through a wavelength selection filter.