KR101767741B1

KR101767741B1 - Casting roll

Info

Publication number: KR101767741B1
Application number: KR1020150135696A
Authority: KR
Inventors: 임지우; 박성진; 권오성
Original assignee: 주식회사 포스코
Priority date: 2015-09-24
Filing date: 2015-09-24
Publication date: 2017-08-14
Also published as: KR20170036950A

Abstract

One embodiment of the present invention is to provide a casting roll improved in preventing the occurrence of surface defects such as depression, dent, cracks and the like during casting of a thin plate and preventing the thin plate from being caught in the casting roll due to mixing of skulls , A casting roll according to an aspect of the present invention is a casting roll having a casting roll body and a surface treatment portion formed on a surface of the casting roll body, wherein the surface treatment portion includes a plurality of A first gas channel; And a plurality of second gas channels which are formed continuously at least in the circumferential direction of the casting roll adjacent to the edge portion of the casting roll and are formed into a sloped groove in cross section.

Description

Casting roll {CASTING ROLL}

The present invention relates to a casting roll utilized in a twin roll thin sheet casting process.

In general, the casting process is a process of coagulating molten metal to produce a cast steel having a constant thickness. In recent years, a thin casting technique has been developed in which a molten metal is directly coagulated by using two casting rolls, .

In general, the twin roll type thin plate casting process is a process in which molten metal is injected through a nozzle between two casting rolls disposed adjacent to each other and rotating in the opposite direction, and solidified in the process of passing molten metal through the casting rolls, After being formed into a shell, it is pressed in rolls and is produced as a thin plate.

Such a thin sheet casting process is very important because the surface quality of the cast thin sheet is very important because the molten steel is rapidly solidified in the manufacturing process to cast it into a thin sheet having a thickness close to the final product thickness.

On the other hand, in the case of playing a slab which is several tens to several hundred times thicker than the final product, it is possible to remove defects on the surface even if there is a casting defect on the slab surface,

However, since the thin plate made of a thin thickness has a very short contact time between the casting roll and the molten steel, surface cracking due to uneven solidification occurs, or if defects such as a minute concave portion on the surface are formed during solidification, If these defects can not be removed and unevenness of the solidification structure occurs in the process or the like, the surface gloss unevenness is generated in the final product, and the product becomes less valuable.

In addition, when the dissolved gas dissolved in the molten steel state is generated by saturation during solidification, a concave dent defect is generated in the plate, or a gap is generated between the cast thin plate and the casting roll due to the generated gas pressure, Lt; / RTI >

The gas generated at this time is difficult to discharge in the uneven surface texture of the casting roll, causing surface defects.

Accordingly, in the field of thin plate casting, a method of resolving surface defects by applying dimples or forming irregularities by various methods at the time of casting roll surface treatment has been studied and proposed.

In recent years, a technique has been proposed in which a gas channel continuous in the circumferential direction is machined on the surface of a casting roll, and thus molten steel is coagulated through the gas channel and discharged, thereby minimizing surface defects such as dents Production.

However, such a casting roll can prevent defects such as dents and overlapping flaws in the entire width of the cast thin plate, but when a skull which is a solidified metal grown in an edge dam, which is a structure installed to prevent molten steel from the side of the casting roll, Rolls can be pushed into the gas channel, resulting in mechanical sticking where the coagulating sheet adheres to the casting roll.

If mechanical sticking occurs, the cast steel sheet which is weak in strength immediately after solidification is torn to the casting roll, so that the residue attached to the surface of the casting roll is re-married to the bath surface to cause pressure damage on the roll surface And can be made of a defective coil when passing through such a casting roll, and if the amount of tearing due to sticking is large, casting interruption due to plate breakage can occur.

1 and 2 are a perspective view and a sectional view showing a gas channel formed on the surface of a casting roll by conventional etching. 3 is a cross-sectional view of a cast thin plate sandwiched between gas channels by skull inclusion.

Referring to FIG. 3, when the depth of the gas channel formed by etching is deep, it is not etched only to the depth but is etched laterally. Therefore, when the skull is mixed and undergoes overpressure, the solidified cast thin plate is sandwiched between the gas channels It does not fall out.

Japanese Patent Application Laid-Open No. 2-295647 U.S. Patent No. 8343367

An embodiment of the present invention is to provide an improved casting roll which prevents occurrence of surface defects such as depression, dent, crack and the like during casting of the thin plate and prevents the thin plate from being caught in the casting roll due to inclusion of skull The purpose.

A casting roll according to an aspect of the present invention is a casting roll having a casting roll body and a surface treatment portion formed on the surface of the casting roll body, wherein the surface treatment portion is formed continuously in the circumferential direction of the casting roll, A plurality of first gas channels formed in a central direction from a point spaced 15 mm from both ends of the casting roll; And at least adjacent to an edge of the casting roll, the casting roll being formed continuously in the circumferential direction of the casting roll in an area of 1 to 15 mm in a central direction at both ends of the casting roll, And the second gas channel may have a gas discharge capability index of 30 to 200, which is defined as a value obtained by dividing the cross-sectional area of the groove by the pitch.

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Further, the first gas channel is formed by etching, and the second gas channel can be formed by mechanical processing by a bite of a cutter.

In addition, the second gas channel may have an angle formed by an inclined groove of 45 to 100 degrees.

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According to an embodiment of the present invention, it is possible to prevent defects such as depression, dent, and cracks from occurring during casting of the thin plate through the shape deformation of the gas channel formed near the edge of the casting roll, Can be prevented, and the quality of the thin plate to be cast can be improved.

1 and 2 are a perspective view and a sectional view showing a gas channel formed on the surface of a casting roll by conventional etching.
Fig. 3 is a cross-sectional view of a cast thin plate sandwiched between gas channels by skull mixing. Fig.
4 is a perspective view of a twin roll type thin sheet casting apparatus according to an embodiment of the present invention in which a casting roll is installed.
5 is a front view of a casting roll according to an embodiment of the invention.
6 is an enlarged cross-sectional view of part A of Fig.
7 is a cross-sectional view of a bite for processing a second gas channel of a casting roll in accordance with an embodiment of the present invention.
8 is a graph showing the relationship between the radius and the cross-sectional area of the bite tip in an embodiment of the present invention.
9 is a graph showing the relationship between the angle and the cross-sectional area of the bite tip in an embodiment of the present invention.
FIG. 10 is a view for explaining a gas discharge capability index in an embodiment of the present invention. FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

5 is a front view of a casting roll according to an embodiment of the present invention. FIG. 6 is a cross-sectional view of a portion A of FIG. 5 Fig.

4 to 6, the casting roll 1 of the present embodiment is an apparatus for rapidly solidifying molten steel to form a solidifying shell S, and in the twin roll type thin-film casting apparatus, the casting rolls 1 are paired And may be provided to rotate in opposite directions to each other.

Further, both ends of the casting roll 1 can be clogged by the edge dam 2.

In the twin roll type thin sheet casting apparatus, molten metal (molten steel) Y is injected into a pair of casting rolls 1 and solidified in the process of passing the molten metal Y through the casting rolls 1 After forming with the solidifying shell (S), the process of pressing down in rolls can be continuously carried out to produce thin plates.

The molten metal Y is in contact with and coagulates with the casting roll 1. The soluble gas (nitrogen gas, etc.) dissolved in the molten metal Y is saturated when solidified and is discharged into the gas state. A gas gap is formed and thus localized solidification delay may be induced which promotes distortion of the solidification shell S and causes depression, dent, crack, And the like.

In this embodiment, the casting roll 1 may include a casting roll body made of a material having a high thermal conductivity, provided with cooling means therein. Further, the surface of the casting roll body may be provided with a surface treatment portion for improving the wear resistance and improving contact properties with the molten metal (Y).

The surface treatment section may include a plurality of first gas channels 10 formed in a circumferential direction of the casting roll 1 and formed.

The first gas channel 10 may be formed by etching. The first gas channel 10 may be formed over the surface of the casting roll 1. After the surface of the first gas channel 10 is coated with the photoresist, the photoresist of the portion other than the pattern is removed by film or laser processing, A pattern can be formed. At this time, the first gas channel 10 has a depth of the groove of the gas channel in the process of etching by the etchant. At this time, a portion of the first channel is also etched and the width of the final pattern can be increased.

Preferably, the first gas channel 10 is formed in a continuous groove shape having a width of 400 to 500 mu m in the circumferential direction of the casting roll body and a depth of 50 to 150 mu m.

Preferably, the first gas channel 10 may be formed in a central direction from a point spaced 15 mm from both ends of the casting roll 1.

On the other hand, in the process of manufacturing the thin plate of the casting roll 1, the edge portion of the casting roll 1 can be increased in its coagulating ability due to the cooling effect by the edge dam 2 blocking both ends of the casting roll 1 So that a skull which is a solidified metal grown in the edge dam 2 is mixed and pressed in the roll, and can be caught in the gas channel.

Accordingly, the casting roll 1 of the present embodiment has a structure capable of preventing the thin plate from being caught in the gas channel of the casting roll 1 at a portion adjacent to the edge portion. Specifically, A plurality of second gas channels 20 may be formed.

The second gas channel 20 may be formed in the shape of a sloped groove, that is, a V-shaped groove.

The casting roll 1 having such a structure can easily fall off even if a skull solidified at the edge portion is mixed into the casting rolls 1 and is pushed into the second gas channel 20 together with the casting thin plate, It is possible to prevent a phenomenon in which the thin plate is caught in the casting roll 1, that is, a sticking phenomenon.

Preferably, the second gas channel 20 may be formed in an area of 1 to 15 mm at both ends, over an area of at least 5 mm or more at a position of 1 to 10 mm in the center direction at both ends of the casting roll 1.

Here, since the second gas channel 20 is formed at least 1 mm apart from both ends of the casting roll 1, it is possible to prevent the second gas channel 20 from being formed in contact with the edge of the casting roll 1 .

Further, in this embodiment, the second gas channel 20 may be formed by mechanical processing.

7, which is a cross-sectional view of a bite for machining a second gas channel 20 of a casting roll 1 according to an embodiment of the present invention, And may be formed by cutting with the cutting tool 30 provided in the cutting machine.

The second gas channel 20 can be machined by turning a sloped groove, i. E., A V-shaped groove, using a cutting tool, for example a bobbin 30, by means of a lathe.

The second gas channel 20 is spaced apart from the first gas channel 10 formed by etching while spirally rotating the rollers in order to feed the feed gas at a constant speed to the second gas channel 20, It can be different. Therefore, the lathe machining is not to feed at a constant speed but to move the cutting tool 30 by a predetermined pitch after machining the inclined grooves, that is, the V-shaped grooves, It is preferable that the second gas channel 20 is formed by repeating the process of rotating one revolution again.

Further, although the end of the bite 30 has a large curvature so that the shape of the groove is an arc, sticking by the skull can be prevented, but the gas discharging ability can be lowered.

8 shows the relationship between the radius r and the cross-sectional area of the tip of the bite 30 when the width of the groove on the surface is fixed at 400 占 퐉 and the angle? Of the bite 30 is 60 degrees.

9 shows the relationship between the angle of the bite 30 and the cross sectional area when the radius r of the tip of the bite 30 is fixed at 100 占 퐉 and the width of the groove is 400 占 퐉.

In the present embodiment, the shape of the bite 30 is better as the cross-sectional area of the groove is larger in order to discharge the gas. However, if the width of the bore is increased, It is preferable to limit the end angle of the light emitting diode to be not too large. For example, it is preferable that the light emitting diode is formed at about 100 degrees or less. If the radius of the bite 30 and the end angle of the bite 30 are too small, the tip of the bite 30 may break and the shape of the groove may become poor, which may cause poor gas discharge performance. It is desirable to keep the angle of 45 degrees or more.

Thus, in the course of processing the second gas channel by the bite, the angle formed by the V-shaped inclined grooves may be 45 to 100 degrees.

Further, since the channel is processed by the bite of the second gas channel, unlike the etching, the second gas channel is not machined in the width direction, so that even if the thin plate or the skull is caught in the second gas channel, Can be prevented.

In addition, the spacing P of the second gas channels 20 is an important variable to prevent dent or depression defects, together with the cross-sectional area of the second gas channel 20. [ That is, if the interval P between the second gas channels 20 is too large, a dent or a depression may be generated, and if it is too small, solidification may be difficult.

As described above, the gas discharge capability index (G index) can be typically used in relation to the cross-sectional area of the channel and the interval (P). 10, which is a view for explaining the gas discharging ability index in one embodiment of the present invention, the gas discharging capacity index is calculated by dividing the cross-sectional area (A) of the gas channel, that is, The gas channel is defined by the cross-sectional area obtained by multiplying the depth (d) and the channel width (w) by 1/2 divided by the channel spacing (p).

In the present embodiment, the casting roll 1 preferably has a gas index (G index) of 30 or more so as to prevent the occurrence of depression or dent. On the other hand, if the gas discharging ability index is too large, it is preferable that the gas discharging ability index does not exceed 200, since the gas discharging is smooth but the surface area is reduced and coagulation may be delayed.

In the casting roll 1 of this embodiment, the bite 30 having an angle of 60 degrees and a tip radius of 100 占 퐉 is used so that the gas exhausting ability is 85 in the range of 3mm to 15mm at the edge without processing to 3mm from both edges. And a second gas channel 20 having a pitch of 850 mu m and a depth of 270 mu m. In addition, the first gas channel 10 was formed by etching at an inner side of 15 mm at the edge.

As a result of thin plate casting of a high nitrogen steel using the casting roll 1 manufactured as described above, it was confirmed that a thin plate excellent in quality without depression and no occurrence of sticking when scull was mixed was cast.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. It will be clear to those who have knowledge.

1: casting roll 2: edge dam
10: first gas channel 20: second gas channel

Claims

A casting roll having a casting roll body and a surface treatment portion formed on the surface of the casting roll body,
The surface treatment unit may include:
A plurality of first gas channels formed continuously in the circumferential direction of the casting roll and formed in a central direction from a point spaced 15 mm from both ends of the casting roll; And
At least in the region of 1 to 15 mm in the center direction at both ends of the casting roll adjacent to the edge portion of the casting roll, the shape of the cross section being different from the first gas channel A plurality of second gas channels formed into sloped grooves;
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Wherein the second gas channel is defined as a value obtained by dividing a cross-sectional area of a groove by a pitch, and a gas ventilatability index is 30 to 200.

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The method according to claim 1,
Wherein the first gas channel is formed by etching,
Wherein the second gas channel is formed by mechanical working with a cutting tool bite.

The method of claim 3,
Wherein the second gas channel has an angle formed by an inclined groove of 45 to 100 degrees.

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