JP2653956B2 - Cooling drum for continuous sheet casting machine and its processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling drum (rotary casting drum) used as a mold in a twin-drum or single-drum continuous sheet casting apparatus. The present invention relates to a cooling drum having a recess, and a method of processing the cooling drum.

[0002]

2. Description of the Related Art A single-drum type or twin-drum type continuous casting machine for continuously and efficiently producing a thin cast slab having a thickness equal to or close to a hot strip from a molten metal such as molten steel at a stroke is known. , Equipped with a cooling drum as a mold that is rotationally driven by power and circulates cooling water inside, but in order to improve the quality of slabs,
Many techniques for improving the surface of a cooling drum have been proposed.

For example, as shown in FIG. 4, a twin-drum continuous thin-plate continuous casting apparatus is supported by an upper tundish 1 so as to be horizontal and parallel with a predetermined gap therebetween. And a pair of cooling drums 2 and 2 that are driven to rotate in the direction of the arrow and are cooled by circulating cooling water therein. And a pair of side dams 3, 3 which are in sliding contact with both ends of the drums 2, 2 in order to seal the pool in which the molten metal is continuously supplied through the inside of the pool. Solidified shell 4 formed on each surface by being cooled by the molten metal supplied to
However, when passing through a narrow gap between the cooling drums 2 and 2, they are superimposed upon receiving a rolling force to form a thin cast slab 5 having a thickness of about 1 to 7 mm, which is guided by pinch rolls 6, 6 and the like. It is designed to be wound up.

In order to obtain a high quality cast piece 5 having no defects such as cracks on the surface, the cylindrical surfaces of the cooling drums 2 and 2 are subjected to shot blasting, photo etching, electric discharge machining, electron beam machining, laser machining, and the like. By using the processing method, the depth is 5 to 100 μm and the diameter is 0.1 to 1.2.
It is effective to form a large number of minute dimples (dents) such as a circle or an oval having a diameter of about mm in Japanese Patent Application Laid-Open Nos. 60-184449 and 62-25495.
No. 3, JP-A-64-83342 and the like.

[0005] One of the beneficial effects that the dimples formed on the cylindrical surfaces of the cooling drums 2 and 2 are considered to have when the continuous casting is performed is that the low-temperature cooling drum 2 is used. , A thin gas film can be formed and held between the surface of the solidification shell 4 and the solidified shell 4 cooled by the solidified shell 4. Cooling is moderately moderate, the amount of distortion generated in the shell is reduced as compared to the case where there is no gas film, and the state in which the degree of cooling partially observed on the surfaces of the cooling drums 2 and 2 is reduced. Thus, cooling is performed substantially uniformly over the entire area of the solidified shell 4.

Another useful effect of the dimples provided on the surfaces of the cooling drums 2 and 2 is that the surface of the cooling drums 2 and 2 is provided with fine irregularities by providing the dimples. Has a spike action or a grip action on the solidified shell 4, and the unevenness on the surfaces of the cooling drums 2, 2 engages with the unevenness transferred on the surface of the solidified shell 4 to hinder relative movement. As a result, the shrinkage of the minute portion at any position of the solidified shell 4 caused by the cooling is absorbed in each minute portion, and as in the case where the surfaces of the cooling drums 2 and 2 are smooth, The problem that the shrinkage of the portion concentrates at a specific position and causes a relatively large crack in the slab 5 can be avoided.

[0007]

As described above, by providing dimples on the surface of the cooling drum used in the twin-drum or single-drum continuous sheet casting apparatus, the occurrence of large cracks in the slab is prevented. However, it is not always beneficial to provide any kind of dimple.

For example, stainless steel (for example, SUS30
In the continuous casting of the thin plate of 4), when the distribution density of the dimples is lowered and the distance between the dimple edges, which is the distance between the peripheral edges of the two dimples arbitrarily selected, is set to 0.35 mm or more, the cooling drum is used. On the surface of the cast slab, the difference in cooling rate between the projecting portion corresponding to the dimple and the other flat portion caused a difference in crystal grain size, and the slab was cold-rolled. Occasionally, so-called uneven gloss is exhibited (see Japanese Patent Application No. 2-279097 and Japanese Patent Application Laid-Open No. 2-52151). In other words, if the distance between the dimple edges is too large, subtle differences in the metallographic structure of the surface of the slab corresponding to the irregularities on the surface of the cooling drum become visible to the naked eye even after cold rolling. Deteriorates the surface properties of

However, if the distribution density of the dimples is increased and the peripheral edges of the dimples are closely spaced and densely arranged, fine cracks are generated on the surface of the slab by transmitting the dimples which are close to each other. Another problem arises: As shown in Table 1, in the continuous casting of a thin plate of stainless steel (for example, SUS304), the distance between dimple edges was 0.1.
Fine cracks are likely to occur on the surface of the slab corresponding to the portion of 0 mm or less.

[0010]

[Table 1]

Further, the fine cracks that are generated by transmitting the dimples are arranged more regularly and regularly than when the dimples are randomly arranged when the distribution density of the dimples is substantially the same. It is also known that the case where dimples are more likely to occur. Therefore, when dimples are formed at positions predetermined by a computer as in the case of photoetching, the computer generates the positions (coordinates) of the individual dimples. It is necessary to control by random numbers so that all dimples are arranged randomly.

In this case, if it is possible to reduce the diameter of each dimple, for example, in the case of continuous casting of a thin plate of stainless steel (SUS304 or the like), the distance between the dimple edges of the cooling drum used for the continuous casting is set as described above. It is possible to keep the diameter in the range of 0.10 to 0.35 mm, which can avoid the problem described above, but the minimum limit of the diameter of the dimple that can be stably processed by photoetching is about 0.3 mm. Therefore, when dimples having a constant diameter of about 0.3 mm are randomly arranged, the distance between dimple edges is set to 0.10 to 0.35 mm.
It is almost impossible to stably process the dimples over the entire circumference of the cooling drum while maintaining the above range.

However, if dimples having different diameters are used in combination, and a dimple having a small diameter is appropriately fitted into a portion having a large distance between dimple edges formed when random dimples having a large diameter are arranged, It is possible to set the distance between the edges of the dimples closest to each other to 0.10 mm (Japanese Patent Laid-Open No. 3-11 / 1990).
0044).

However, this method also has a problem that the calculation time of the computer for determining the coordinates of the dimple becomes very long. For example, in the case of a cooling drum having a diameter of 1200 mm and a width of 800 mm, the cooling drum extends over the entire peripheral surface of the cooling drum. This method is not practical, as it has been estimated that it would take a typical computer 20 days to determine the dimple coordinates.

The present invention has been made in view of the above-mentioned problems of the prior art, and in the case where dimples are processed at random positions on the surface of a cooling drum by photoetching, the surface of a slab continuously cast by the cooling drum has uneven gloss. SUMMARY OF THE INVENTION It is an object of the present invention to provide a practical means that does not cause defects such as cracks and the like and that can significantly reduce the time required for a computer to determine the arrangement of dimples. It is assumed that.

[0016]

According to the present invention, a distance which is randomly arranged on a surface and which is larger than the sum of the minimum distance between dimple edges and the diameter of a predetermined dimple circle is determined between adjacent center points. The inner area of the dimple circle set on the center point, and the diameter of the dimple circle and the maximum distance between the dimple edges also set on the center point
And the sum of the diameter of the external area of all the dimples outer circumference, i.e., variations that are not included in any dimples outside inner circle
And regions, the cooling drum that thin plates continuous casting apparatus according to claim which has been given a depression by photo etching is provided together.

The dimple pattern on the cooling drum includes an inner region of all dimple circles having predetermined diameters whose center points are efficiently set using a computer, and all virtual concentric circles of the dimple circles. External area of dimple outer circle, that is, included in any dimple outer circle
The area of the deformation which is not changed is designated as a dimple area, and the area is easily processed by depressing those areas to a predetermined depth by photoetching.

[0018]

According to the present invention, first, a number of center points having a distance larger than the sum of the minimum inter-dimple edge distance and the diameter of a predetermined dimple circle are randomly set between adjacent center points. Is done. Then, a dimple circle having a predetermined diameter is set on the center point, and a dimple in the inner area secures a minimum distance between dimple edges between adjacent dimple circles. The slab does not crack.

Since the dimple outer circumference circle set on the same center point has a diameter equal to the sum of the maximum distance between dimple edges and the diameter of the dimple circle, the diameter of all dimple outer circumference circles is set. Outer area , that is, which dimple circumference circle
When the area of the deformation not included in the dimple is formed as a dimple, the distance between edges between adjacent dimples becomes the minimum distance D _min between dimple edges and the maximum distance D between dimple edges.
_This is a value between _max , which can prevent the occurrence of cracks in the slab, and solves the problem of causing uneven gloss when the slab is cold-rolled.

As described above, the center point of the next dimple is randomly set in an area where the distance between the center points of the existing adjacent dimple circles is equal to or greater than a predetermined value, and the dimple circle and its concentric circle are set there. After setting the dimple outer circles, the inner areas of all the dimple circles and the deformation areas not included in any of the dimple outer circles are designated as dimple areas, and those areas are designated. Since the processing is only performed by photoetching, when the center position of the dimple circle is set by the computer, the calculation time is significantly reduced as compared with the conventional method.

[0021]

FIG. 1 schematically shows an enlarged view of the surface of a cooling drum 2 for carrying out the present invention. Before carrying out the present invention, the surface of the drum 2 is randomized according to the type of metal to be continuously cast. , The values of the minimum dimple edge distance D _min as the lower limit value of the dimple edge distance D and the maximum dimple edge distance D _max as the upper limit value are determined. That is, the distance D between the dimple edges created according to the present invention is _Dmin ≦ D ≦ _Dmax .

More specifically, the diameter A of the dimple circle 10 is selected from a range of 0.3 to 1.0 mm that can be photoetched and is not too large as the dimple circle 10. Also, if when the molten steel is for example SUS30 4, the minimum dimple edge distance D _min can be prevented from cracking occurs billet 5 0.10 mm
With the above values, the maximum distance _Dmax between dimple edges is set to a value of 0.35 mm or less that can prevent the occurrence of uneven gloss. That is, the maximum dimple edge distance D
_{Both max} and the minimum distance D _min between dimple edges are 0.
It will be selected from the range of 10 to 0.35 mm.

According to the present invention, a large number of dimple circles 10 having a diameter A are randomly formed on a surface of the drum 2 by a computer so that the distance D between the dimple edges is larger than the minimum distance D _min between the dimple edges. 1, the surface of the cooling drum 2 corresponding to the area 11 in the dimple circle 10 is basically depressed by about 50 to 200 μm by photoetching as shown by hatching in FIG. Outside of all the dimple circles 10, a dimple outer circle 12 having a diameter B is set as a concentric circle, and the deformed areas 13 not included in any of the dimple outer circles 12 are extracted, and the deformed areas 13 are extracted. The surface of the cooling drum 2 that hits the surface is also a dimple area, and is subjected to photo etching together with the dimple circle 10, It is characterized by recessing about beam 50 to 200 [mu] m.

In this case, the diameter B of the outer circumference 12 of the dimple
Is a value obtained by adding the _maximum distance _Dmax between dimple edges to the diameter A of the dimple circle 10. Accordingly, the distance D between the dimple edges is obtained for all the dimples corresponding to the area 11 in the dimple circle 10 and the area 13 of the deformation.
Automatically falls within the range between the minimum distance D _min between dimple edges and the maximum distance D _max between dimple edges. As in the conventional method, the distance between the minimum dimple edge and the distance Since it is not necessary to repeatedly calculate the maximum distance between the dimple edges, the time required for the calculation is significantly reduced. In this case, the total dimple area ratio is about 30 to 60%. If the deformed area 13 includes an abnormally long one, the slab 5 may have small cracks along the abnormally long area.
May be limited to 1.0 mm or less.

Next, an example of implementing the method of the present invention will be described more specifically with reference to the flowchart of FIG . 2 and FIG . This program is executed by an ordinary computer. When the program is started, step 101
5, the entire dimple drawing area is divided so as to be finished with a predetermined accuracy as shown in FIG. The mesh-divided intersection is a point at which the dimple center coordinates can be set. Considering the accuracy of the photo-etching process, the interval between the mesh division lines at this time is approximately 5 μm.

Next, in order to arrange the dimple circles 10 randomly, in a step 102, a random number value is read from a random number generator in the computer into a central processing unit (CPU), and the point having the random number value as a coordinate is The dimple circle 10 having the diameter A and the numerical value representing the dimple outer circle 12 having the diameter B centered on the point are registered (set) in the memory.

Next, in step 103, an area in which the center coordinates of the next dimple circle cannot be set, that is, an area included in the diameter (2A + 2D _min ) with the center point of the currently registered (set) dimple circle 10 as the center. calculate. This area is an area where the distance between edges becomes smaller than D _min when the next dimple circle 10 is set.

Next, in step 104, the points excluding the area where the center coordinates of the dimple circle calculated in step 103 cannot be set from the mesh division points of the dimple drawing area are set as areas where the next dimple center coordinates can be set. .

Next, in step 105, it is determined whether or not there is an area in which the coordinates of the center of the next dimple can be set. If it is determined that “exists” in step 105, the dimple circle can be set.
Returning to step 02, the calculation is repeated again. When it is determined as "no" in step 105, further, the setting of the dimples circle is impossible, and terminates the setting of dimples.

In the example of the flowchart shown in FIG. 2, the process further proceeds to step 106, where the area 11 inside the dimple circle 10 registered in the memory and the dimple outer circle 12
After the area 13 (shaded area in FIG. 1) outside the area is filled as a dimple area, a command to punch out on a large sheet of paper is given by a plotter, and when the processing is completed, the program ends in step 107. ing. However, since this need not be performed immediately after step 105, it is needless to say that the stamping can be performed at any time after the necessary data is accumulated in the memory including the external storage device.

FIG. 1 shows a diagram of the surface of the cooling drum 2, but an image formed on a sheet of paper by a plotter from a computer has a similar shape. Of course,
The dashed line indicating the outline of the dimple outer circle 12 is a latent image in the computer and does not appear as an image. Therefore, only the hatched portion surrounded by the solid line appears as a graphic. Subsequent processing is the same as in the case of conventional photoetching. After taking a picture of a figure and developing it to produce a negative film, the surface of the cooling drum 2 is coated with a photosensitive agent in advance and exposed from the negative film. Is performed, and a developing process for masking portions other than the dimple region in the hatched portion, an etching process for the dimple region, and the like are performed to dissolve the dimple region in FIG. 1 to a predetermined depth, thereby forming a depression having the same shape. Finally, cleaning is performed to complete the cooling drum 2 having a dimple pattern as shown in FIG. Of course, a method of directly outputting (exposing) a negative film from the memory of the computer without projecting the image on the paper from the computer is also conceivable, but the present invention is not characterized in such a point.

FIG. 3 shows a more practical example of the dimple pattern of the cooling drum manufactured as described above. In this example, the diameter A of the dimple circle 10 is 0.40 mm, the diameter B of the outer dimple circle 12 is 0.70 mm, and the center distance C between the circular dimples is 0.55 mm.
０．７0.70 mm, and the distance D between the dimple edges is distributed in the range of 0.15 to 0.30 mm.

[0033]

By using the cooling drum obtained by carrying out the present invention in a continuous sheet casting apparatus, cracks do not occur in the slab to be produced, and the cold rolling is performed. Sometimes uneven gloss does not occur. In addition, since the calculation process for producing the dimple pattern of the cooling drum has been simplified, the calculation time of the computer is significantly reduced as compared with the conventional technology,
For example, in the case of a cooling drum having a diameter of 1200 mm and a width of 800 mm, it is extremely practical because the time required for calculation is about one day even with a normal computer.

[Brief description of the drawings]

FIG. 1 is a plan view schematically illustrating a dimple pattern on a surface of a cooling drum.

FIG. 2 is a flowchart illustrating a computer program.

FIG. 3 is a plan view illustrating a dimple pattern on the surface of a cooling drum.

FIG. 4 is a cross-sectional view showing a schematic configuration of a twin-drum type thin sheet continuous casting apparatus.

FIG. 5 is an explanatory diagram showing an example of mesh division at the time of dimple pattern calculation.

FIG. 6 is an explanatory diagram illustrating a procedure for determining dimple center coordinates when calculating a dimple pattern;

[Explanation of symbols]

10: Dimple circle 11: Area within dimple circle 10 12: Dimple outer circle 13: Area of deformation not included in any dimple outer circle 12

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-261487 (JP, A) JP-A-3-110044 (JP, A) JP-A-2-295647 (JP, A)

Claims (2)

(57) [Claims] 2. A method according to claim 1, further comprising a step of randomly arranging the dimples on the surface and having a distance greater than a sum of a minimum dimple edge distance (D _min ) and a predetermined dimple circle diameter (A) between adjacent center points. an inner region of the set dimples circle on the center point (11), also the diameter of the sum of the diameters of the set before Symbol dimples circle on the center point (a) and the maximum dimple edge distance (D _max) A cooling drum for a continuous sheet casting apparatus, characterized in that a deformation region (13) not included in any of the dimple outer circles (12) to be (B) is provided with a depression by photoetching. . 2. Processing a dimple on the surface of a cooling drum of a continuous sheet casting apparatus by photo-etching using a computer. (1) Dividing the entire dimple drawing area into a mesh so as to finish it with a predetermined accuracy; Setting the intersection as a point at which the center coordinates of the dimple circle can be determined; (2) generating random numbers to generate the center coordinates of the dimple circle (10); and a dimple circle (10) having a predetermined diameter A. Setting a dimple circumference circle (12) having a predetermined diameter B; and (3) setting a dimple circle (10) set in the step (2 ).
Included in a circle of diameter (2A + 2D _min ) centered on the center point
Murrell regions, and calculating an area where the center coordinate can not be set for the next dimple yen (10), (4) the center coordinates can not be set region of the (3) dimples yen calculated in step (10) a region except for the steps of the center coordinates settable area for the next dimple yen (10), is (5) the center coordinates settable region of the dimple yen stage (4) (10) If there is, the process returns to the step (2) again to repeatedly set the center coordinates of the dimple circle (10) at random, and (6) the center of the dimple circle (10) at the step (4). when the coordinates have Tsu no longer exist available space setting, the center coordinates of the dimple yen (10), dimples yen (10),
A step to end the setting of the dimple periphery yen (12), and (7) inside the area of the dimple yen (10) (11), etc.
(8) Designating a deformation area (13) that is not included in the dimple outer circumference circle (12) as a dimple area on the cooling drum surface; Forming a dimple on the surface of the cooling drum of the continuous sheet casting apparatus.