EP4635649A1

EP4635649A1 - Mold, mold manufacturing method, and slab

Info

Publication number: EP4635649A1
Application number: EP23903995.1A
Authority: EP
Inventors: Hyoung Jun Lee; Ji Joon Kim; Jong Chul Kim
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2022-12-15
Filing date: 2023-12-13
Publication date: 2025-10-22
Also published as: EP4635649A4; KR20240092944A; CN119730976A; WO2024128794A1; JP2025526850A

Abstract

An embodiment of the present invention is a mold provided with an inner space into which molten steel can be injected, the mold including a body having the inner space and a convex member which protrudes from the body toward the inner space and is formed to extend in the width direction of the body. In addition, the inner surface of each of the pair of side areas has a curved surface in the shape of 1/2 of a cosine curve having one period being 360°.

Therefore, according to embodiments of the present invention, in manufacturing a slab which is rolled to make a steel plate, it is possible to manufacture the slab which can suppress an edge defect of the steel plate caused by the spreading width of the slab.

Description

TECHNICAL FIELD

The present invention relates to a mold and a method for manufacturing the mold, and more particularly, to a mold, which is capable of effectively controlling a shape of a slab and preventing molten steel from leaking, and a method for manufacturing the mold.
The present invention relates to a slab, and more particularly, to a slab that is capable of suppressing an occurrence of edge defects occurring in a steel plate due to a spreading width of the slab during rolling in the steel plate manufactured by rolling the slab.

BACKGROUND ART

A slab manufactured by cooling molten steel in a mold is drawn to a lower side of the mold. The drawn slab moves along a cooling zone and undergoes secondary solidification by cooling water injected at this time. The solidified slab is cut to a specified length and then rolled in a rolling device, and the rolled slab is called a steel plate.
In the rolling device, the slab is disposed between an upper rolling roll and a lower rolling roll, and the slab is rolled by downward pressing force of the upper rolling roll and the upward pressing force of the lower rolling roll. Here, each of the upper rolling roll and the lower rolling roll extend in a width direction of the slab. In addition, a plurality of upper rolling rolls are arranged in a longitudinal direction at an upper side of the slab, and a plurality of lower rolling rolls are arranged in a longitudinal direction at a lower side of the slab.
When the upper and lower rolling rolls press the slab, a phenomenon of spreading width in which both edges of the slab in a width direction are distorted and spread outward occurs. This spreading of the slab causes wrinkle-shaped edge defects at both edges of the steel plate in the width direction. Thus, the steel plate with the edge defects is delivered to the customer after cutting both the edges in the width direction. However, there is a problem that actual yield is deteriorated as both the edges of the steel plate in the width direction are cut in this manner.
In order to solve the problem of the edge defects occurring due to the spreading width of the slab during the rolling, a convex member has been provided on an inner surface of the mold. That is, in long-side members and short-side members, which form the mold, the convex member protruding toward an internal space of the mold is provided on an inner surface of each of the short-side members. Here, the longer a length of the convex member protruding toward the internal space, the more the spreading width of the slab during the rolling is suppressed to reduce an occurrence of the edge defects in the steel plate.
As the protrusion length of the convex member increases, an angle between an edge of the inner surface of the convex member facing the internal space and an inner surface of each of the long-side members decreases. Thus, as the protrusion length of the convex member increases, a size of a gap between the inner edge of the convex member and the inner surface of the long-side member, that is, a size of a space between the inner edge of the convex member and the inner surface of the long-side member, becomes narrower, and a shape roughly similar to a triangle may be formed. In addition, the smaller the space between the inner edge of the convex member and the inner surface of the long-side member, the more easily the molten steel or solidified shell becomes caught in the space between the inner edge of the convex member and the inner surface of the long-side member. In addition, an operational accident in which the slab is torn within the mold due to the catching of the molten steel or solidification shell to cause the molten steel to flow out of the mold.
(Prior art document) (Patent Document 1) Japanese Patent Registration No. 2586769

DISCLOSURE OF THE INVENTION

TECHNICAL PROBLEM

The present invention provides a mold that is capable of capable of effectively controlling a shape of a slab and preventing molten steel from leaking, and a method for manufacturing the mold.
The present invention provides a slab that is capable of suppressing an occurrence of edge defects in a steel plate in a slab that becomes a steel plate through a rolling process.

TECHNICAL SOLUTION

An embodiment of the present invention provides a mold having an internal space into which molten steel is injected, the mold including: a body having the internal space; and a convex member protruding from the body toward the internal space and extending in a width direction of the body, wherein the convex member includes a pair of side areas disposed at one side and the other side of the convex member in the width direction, each of the pair of side areas has a shape in which a protrusion length decreases as away from the center, and an inner surface of each of the pair of side areas has a surface in a shape of half of a cosine curve with 360° as one cycle.
The convex member may include a central area disposed between the pair of side areas, wherein a protrusion length of the central area may have the same in the width direction, and
an inner surface that is a surface of the central area, which faces the internal space, may have a plane.
The pair of side areas may be symmetrical in shape with respect to the central area.
One of the pair of side areas may have an inner surface in a shape of a section of 0° to 180° of a cosine curve as one period, and the other may have an inner surface in a shape of a section of 180° to 360° of a cosine curve as one period.
The body may include: a pair of long-side members, each of which is formed to extend in one direction and which are installed to face each other in a direction intersecting an extension direction; and a pair of short-side members, each of which is formed to extend to intersect the long-side members and which are installed to face each other to be sealed between the pair of long-side members, wherein the convex member may be formed to protrude from the short-side member toward the internal space.
An angle between an inner surface of the lone-side member and an edge of an inner surface of the side area may be 90°.
The protrusion length of the central area of the convex member may exceed 5 mm.
A width of the convex member may be the same as a width of the short-side member, and a width of the central area of the convex member may be 10% to 15% of a width of the short-side member.
The width of each of the short-side member and the convex member may decrease as it goes downward, and the width of the central area of the convex member may be the same in a vertical direction.
The width of each of the short-side member and the convex member may decrease as it goes downward, and the width of the central area of the convex member may decrease as it goes downward.
A length of the convex member in a vertical direction may be the same as a length of the short-side member in the vertical direction.
An embodiment of the present invention provides a method for manufacturing a mold, which includes a body having an internal space and a convex member protruding from the body toward the internal space, the method including: preparing a design plan so that the convex member includes first and second side areas on which a protrusion length decreases toward both ends of a width direction center, and an inner surface of each of the first and second side areas has a surface in a shape of half of a cosine curve with one period of 360°; and processing a base material to have the shape of the convex member included in the design plan.
The preparing of the design plan may include: determining a width (W_m) and a vertical length (H_m) of the body to be manufactured; and preparing a design for the inner surface of the convex member having the shape of the inner surface of each of the first and second side areas.
The preparing of the design for the inner surface of the convex member may include: determining a protrusion length (T_c) and a width (W_c) of the central area in the width direction of the convex member to be manufactured; and preparing a design for the first side area so that a shape of the inner surface of the first side area becomes a shape of half of one-period cosine curve by using the determined width (W_m) of the body, the determined protrusion length (T_c) and width (W_c) of the central area of the convex member.
The preparing of the design for the first side area may include: determining a width (W_s) of the first side area to be manufactured using the determined width (W_m) of the body and the determined width (W_c) of the central area; providing a cosine curve equation including the determined width (W_s) of the first side area, the determined protrusion length (T_c) of the central area, a width direction position (X) of the convex member, and a thickness direction position (Y) of the convex member; and calculating the thickness direction position (Y) according to the width direction position (X) using the cosine curve equation, wherein a value of the width direction position (X) applied to the cosine curve equation may be a value of a section from one end of the determined width (W_m) of the body to a point spaced apart by the determined width (W_s) of the first side area, wherein a plurality of values may be applied in the section.
The preparing of the design for the first side area may include connecting a plurality of thickness direction positions (Y) calculated for each width direction position (X) to create a design line for the first side area, which is in the shape of half of the one-period cosine curve.
Preparing the design for the inner surface of the convex member may include preparing a design for the central area, which is a design for the inner surface of the central area disposed between the first and second side areas, and the preparing of the design for the central area may include creating a design line for the center area by extending a line from an end of the design line for the first side area to the determined width (W_c) of the center area.
The method may further include preparing a design for the second side area so that a shape of the inner surface of the second side area is in a shape of half of one-period cosine curve, wherein the preparing of the design for the second side area may include forming a design line for the second side area symmetrically with respect to the design line for the first side area using the central area as a center.
The method may further include preparing a base material of which a width direction length is the determined width (W_m) of the body, and a length in the thickness direction intersecting the width direction exceeds the determined protrusion length (T_c) of the central area of the convex member, wherein processing of the base material may include processing one surface of both surfaces of the base material in the thickness direction so that a shape from each of both ends in the width direction to a point spaced apart by a length of the determined width (W_s) of the side area is the design line for each of the first and second side areas.
An embodiment of the present invention provides a slab manufactured by solidifying molten steel, wherein each of both surfaces of the slab has a convex shape that is recessed inward, and a portion of each of both the surfaces has a curve surface in a shape of half of a cosine curve with 360° as one cycle.
Each of both the surfaces may include a central surface and a pair of side surfaces disposed at one side and the other side of the central surface, respectively, and each of the pair of side surfaces may have a curve surface in the shape of half of a cosine curve with one period of 360°, wherein the center surface has a plane.
The pair of side surfaces may have a shape symmetrical with respect to the center surface, and one of the pair of side surfaces may have a shape in a range of 0° to 180° in the one-period cosine curve, and the other may have a shape of a section of 180° to 360° of a cosine curve as one period.

ADVANTAGEOUS EFFECTS

The mold according to the embodiments of the present invention may manufacture the slab that is capable of suppressing the edge defects of the steel plate occurring by the spreading width of the slab in the manufacturing of the slab that becomes the steel plate by the rolling. In addition, when manufacturing the slab by solidifying the molten steel inside the mold or when varying in width of the mold, it is possible to suppress or prevent the steel or the solidified shell from being caught in the space between the inner surface of the edge of the convex member and the inner surface of the long-side member. Thus, it is possible to prevent the occurrence of the operational accident in which the molten steel flows out of the mold due to the tearing of the mold. That is, the mold according to the embodiments of the present invention may manufacture the slab capable of suppressing the occurrence of the edge defects in the steel plate, while preventing the occurrence of the operational accident due to the leakage of the molten steel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a casting device including a mold according to embodiments of the present invention.
FIG. 2 is a three-dimensional view of a mold according to an embodiment of the present invention.
FIG. 3 is a front view when viewed from a side 'A' in FIG. 2 to explain an installation state of first and second short-side members.
FIG. 4 is a front view when viewed form a side 'B' in FIG. 2 to explain a shape of the short-side member.
FIG. 5 is a conceptual view illustrating a state in which defects occur in an edge in a width direction in a steel plate manufactured by rolling a slab.
(a) of FIG. 6 is a three-dimensional view of a short-side part according to an embodiment of the present invention.
(b) of FIG. 6 is a plan view of the short-side part illustrated in (a) of FIG. 6 when viewed at different heights ⓐ, ⓑ, and ⓒ.
(c) of FIG. 6 is a front view of a convex member when (a) of FIG. 6 is viewed at a side 'C'.
FIG. 7 is a plan view of the short-side part when viewed from an upper side according to an embodiment of the present invention.
(a) of FIG. 8 is a three-dimensional view of a short-side part according to a modified example of an embodiment.
(b) of FIG. 8 is a plan view of the short-side part illustrated in (a) of FIG. 8 when viewed at different heights ⓐ, ⓑ, and ⓒ.
(c) of FIG. 8 is a front view of a convex member when (a) of FIG. 8 is viewed at a side 'C'.
(a) to (c) of FIG. 9 are flowcharts illustrating a method for preparing a design plan for an inner surface of a convex member to manufacture the short-side part provided with a convex member according to according to an embodiment of the present invention.
FIG. 10 is a view illustrating a slab manufactured using a mold according to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments will be described in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.
FIG. 1 is a view of a casting device including a mold according to embodiments of the present invention.
Referring to FIG. 1, a casting device includes a tundish 20 that supplies molten steel from a ladle 10 to store the molten steel, a mold 3000 that receives the molten steel from the tundish 20 to initially solidify the molten steel into a certain shape, and a nozzle 22 that supplies the molten steel from the tundish 20 to the mold 3000.
In addition, the casting device is installed at a lower side of the mold 3000 and includes a cooling part 40 that injects cooling water onto the slab 1 drawn from the mold 3000 to completely solidify the slab 1. Here, the cooling part 40 may be a means including a plurality of segments 41. In addition, each of the plurality of segments 41 may be a means having a plurality of rolls that are rotatable by force by which the slab 1 moves and a nozzle disposed between the plurality of rolls to inject the cooling water onto the slab 1.
The slab 1 manufactured in the casting device is transferred to a rolling device so as to be rolled, thereby manufacturing a steel plate.
Hereinafter, another mold according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4.
FIG. 2 is a three-dimensional view of a mold according to an embodiment of the present invention. FIG. 3 is a front view when viewed from a side 'A' in FIG. 2 to explain an installation state of first and second short-side members. FIG. 4 is a front view when viewed form a side 'B' in FIG. 2 to explain a shape of the short-side member.
Referring to FIG. 2, the mold 3000 may include a body 3100 and a convex member CV protruding from an inner surface of the body 3100 toward an inner space. In addition, the mold 3000 may include a cooling water passage (not shown) installed to be embedded within the body 3100 to circulate cooling water.
Referring to FIG. 2, the body 3100 includes first and second short-side members 3121, each of which extends in one direction (X-axis direction) and which are arranged to be spaced apart from each other in a direction (Y-axis direction) intersecting the extension direction, and first and second long-side members 3111, each of which extends in a direction intersecting or orthogonal to the extension direction (X-axis direction) of the first and second short-side members 3121 and which are arranged to be spaced apart from each other in the extension direction of the first and second short-side members 3121.
Each of the first and second short-side members 3121 may have a shorter extension length than each of the first and second long-side members 3111. That is, the length of each of the first and second long-side members 3111 extending in the Y-axis direction may be shorter than the length of each of the first and second short-side members 3121 extending in the X-axis direction.
The body 3100 is provided in the form of a tube having an internal space IS in which the first and second long-side members 3111 and the first and second short-side members 3121 are interconnected or coupled to each other. For example, one end of each of the first and second short-side members 3121 is connected to an inner surface of the first long-side member 3111 in the X-axis direction, and the other end is connected to an inner surface of the second long-side member 3111. In addition, the first short-side member 3121 and the second short-side member 3121 are disposed to be spaced apart from each other in the Y-axis direction. Here, a distance between the first short-side member 3121 and the second short-side member 3121 is disposed to be greater than a distance between the first long-side member 3111 and the second long-side member 3111. Thus, the body 3100 having the internal space IS with a rectangular shape is provided. More specifically, the body 3100 having the rectangular internal space IS of which a length in the Y-axis direction is longer than that in the X-axis direction is provided.
Hereinafter, the extension direction of each of the long-side member 3111 and the short-side member 3121 is defined as a width direction. Thus, the length in the extension direction of each of the long-side member 3111 and the short-side member 3121 may be defined as a 'width'. Thus, the width of the long-side member 3111 is a length in the Y-axis direction, and the width of the short-side member 3121 is a length in the X-axis direction. In addition, in each of the long-side member 3111 and the short-side member 3121, the direction intersecting the extension direction is defined as a thickness direction. Thus, the length in the direction intersecting the extension direction of each of the long-side member 3111 and the short-side member 3121 may be defined as a 'thickness'. Therefore, the thickness of the long-side member 3111 is a length in the X-axis direction, and the thickness of the short-side member 3121 is a length in the Y-axis direction.
The first short-side member 3121 and the second short-side member 3121 are installed to face each other, and as illustrated in FIG. 3, a spaced distance G between the first short-side member 3121 and the second short-side member 3121 decreases as they go downward. Thus, the first and second short-side members 3121 may be installed to be tilted or inclined.
Thus, a length in a longitudinal direction (length in the Y-axis direction) of the internal space IS of the mold 3000 decreases as it goes downward. As described above, the spaced distance G between the first and second short-side members 3121 decreases as it goes downward, and thus, shrinkage of a solidification shell in the long-side direction may be compensated. To explain more specifically, the solidification shell (long-side solidification shell) formed by solidifying the molten steel along the first and second long-side members 3111 may be compensated for the shrinkage in the extension direction of the first and second long-side members 3111. This may suppress an occurrence of a gap between the inner surface of the body 3100 and the solidification shell due to the shrinkage of the solidification shell in the long-side direction, thereby suppressing solidification delay and an occurrence of defects caused thereby.
In addition, each of the first and second short-side members 3121 is provided so that its extension length, i.e., width W_m decreases as it goes downward, as illustrated in FIG. 4. In other words, each of the first and second short-side members 3121 is provided so that the extension length W_m in the X-axis direction, which is the short-side direction of the mold 3000, decreases as it goes downward. Thus, one surface and the other surface of each of the first and second short-side members 3121 are inclined with respect to the X-axis direction. That is, a side surfaces of each of the first and second short-side members 3121 is inclined to get closer to a center in the width direction as its goes downward. In addition, the first and second long-side members 3111 are connected to side surfaces of the first and second short-side members 3121, respectively. Thus, the first and second side members 3111 are installed so that the spaced distance between the first and second side members 3111 decreases as they go downward.
As described above, the side surface of the short-side member 3121 is formed to be inclined, and the first and second long-side members 3111 installed to be in contact with the short-side member 3121 are installed to become closer to each other as they go downward, in order to compensate for the shrinkage in the short-side direction of the solidification shell. That is, this is to compensate for the shrinkage of the solidification shell (short-side solidification shell) formed by solidifying the molten steel formed along the first and second short-side members 3121 in the extension direction of the first and second short-side members 3121. This may suppress an occurrence of a gap between the inner surface of the body 3100 and the solidification shell due to the shrinkage of the solidification shell in the short-side direction, thereby suppressing solidification delay and an occurrence of defects caused thereby.
The convex member CV may be provided on the inner surface of each of the first and second short-side members 3121 of the body 3100. Hereinafter, a configuration including the short-side member 3121 and the convex member CV installed on the short-side member 3121 is defined as the short-side member 3120. Thus, the mold 3000 may be described as including first and second short-side parts 3120 each of which has a convex member CV, and first and second long-side parts 3111.
The body 3100 includes an inner surface IF, which is a surface facing the inner space IS and in direct contact with the molten steel or solidified shell, and an outer surface OF, which is an opposite surface of the inner surface IF and is exposed to the outside. Here, the outer surface OF of the body 3100 may mean the outer surface OF of each of the first and second long-side members 3111 and the outer surface OF of each of the first and second short-side members 3120. In addition, the outer surface OF of each of the first and second short-side members 3120 refers to a surface disposed at an opposite side to the convex member CV of both surfaces of the first and second short-side members 3121 in the Y-axis direction. Thus, the outer surface OF of the short-side part 3120 may mean a surface opposite to the convex member CV of the surfaces of each of the first and second short-side members 3121.
In addition, the inner surface IF of the body 3100 may mean an inner surface IF of each of the first and second long-side members 3111 and an inner surface IF of each of the first and second short-side members 3120. Here, the inner surface IF of each of the first and second short sides 3120 refers to a surface of the convex member CV facing the internal space IS. To explain more specifically, the convex member CV protrudes from the inner surface of the short-side member 3121 toward the inner space IS. Thus, it may be defined that the surface facing the short-side member 3121 of both surfaces of the convex member CV in the Y-axis direction is an outer surface, and the surface opposite to the short-side member 3121 is an inner surface IF. Thus, the inner surface IF of the short-side portion 3120 may mean a surface of the convex member CV opposite to the short-side portion 3121 or a surface facing the internal space IS.
FIG. 5 is a conceptual view illustrating a state in which edge defects occur in an edge in the width direction in the steel plate manufactured by rolling the slab.
The manufactured slab 1 is cut to a predetermined length and then loaded into the rolling device for the rolling. The slab 1 loaded into the rolling device is pressed and rolled in the thickness direction by an upper rolling roll and a lower rolling roll. Thus, the steel plate 2 is prepared by rolling the slab 1. However, when the slab 1 is rolled, an edge of the slab 1 in the width direction is distorted to cause a spreading width. The spreading width causes defects such as wrinkles on the edge of the steel plate 2 in the width direction as illustrated in FIG. 5.
In order to suppress or prevent the occurrence of the wrinkle defects, the convex member was conventionally provided on the inner surface of the short-side member. The convex member protrudes from the inner surface of the short-side member toward the internal space, and is provided in a shape in which a protrusion length decreases as it goes toward the edge in the width direction. The shape of the convex member is roughly a fan-shaped arc (circular arc shape). When the molten steel is solidified using the mold in which the convex member is formed on the short-side member, the short side of the slab becomes a concave shape.
In addition, when rolling the slab having the short side with the concave shape, an amount of spreading width may be reduced compared to when rolling the slab having the short side with a non-concave shape. Thus, the occurrence of the edge defects of the steel plate in the width direction may be suppressed.
As the protrusion length of the convex member increases, the spreading width during the rolling may be suppressed, and as a result, the occurrence of the edge defects such as the wrinkles on the edge of the steep plate in the width direction may be suppressed. However, as the protrusion length of the convex member increases, an angle between the edge of the inner surface of the convex member facing the internal space and the inner surface of the long-side member decreases, and the angle may be an acute angle. Thus, as the protrusion length of the convex member increases, a size of a gap between the inner edge of the convex member and the inner surface of the long-side member, i.e. a size of an interspace becomes narrower. In addition, the shape of the interspace may be sharpened in a roughly triangular shape. In addition, the smaller the space between the inner edge of the convex member and the inner surface of the long-side member, the more easily the molten steel or solidified shell becomes caught in the space between the inner edge of the convex member and the inner surface of the long-side member. In addition, the slab may be torn inside the mold due to catching of the molten steel or the solidification shell to cause an operational accident in which the molten steel flows out of the mold.
Thus, it is necessary to manufacture the slab 1 that is capable of suppressing the occurrence of the defects in the steel plate 2 while providing the mold that is capable of preventing the occurrence of the operational accident in which the molten steel flows out. For this, in an embodiment of the present invention, the convex member CV is provided on the inner surface of the short-side member 3121, and while manufacturing the slab 1 capable of suppressing the occurrence of the defects, the convex member CV is provided to prevent the occurrence of the operational accident in which the molten steel flows out. For this, the convex member CV is provided so that an angle between the inner surface IF of the edge of the convex member CV in the width direction (X-axis direction) and the inner surface IF of the edge of the long-side member 3111 in the width direction (Y-axis direction) is 90° or a right angle. In addition, in order that the angle between the inner surface IF of the long-side member 3111 and the long-side member 3112 is 90° or a right angle, the shape of the inner surface IF of the convex member CV is provided in the form of a cosine curve in the width direction.
Hereinafter, a short-side part according to an embodiment of the present invention will be described with reference to (a) to (c) of FIGS. 6 and FIG. 7. Here, first and second short-side parts, which are disposed to face each other, have the same configuration, shape, and size, and thus, one short-side part will be described as an example. In addition, for the convenience of explanation, the first and second short-side parts are not simply named as the first and second short-side parts and the first and second short-side members, but are instead named as a 'short-side part' and a 'short-side member.'
(a) of FIG. 6 is a three-dimensional view of the short-side part according to an embodiment of the present invention. (b) of FIG. 6 is a plan view of the short-side part illustrated in (a) of FIG. 6 when viewed at different heights ⓐ, ⓑ, and ⓒ. (c) of FIG. 6 is a front view of a convex member when (a) of FIG. 6 is viewed at a side 'C'. FIG. 7 is a plan view of the short-side part when viewed from an upper side according to an embodiment of the present invention.
The convex member CV protrudes from the inner surface of the short-side member 3121 toward the inner space IS, as illustrated in (a) of FIG. 2 and FIG. 6. In other words, the convex member CV is configured to protrude in the Y-axis direction from the inner surface of the short-side member 3121. In addition, the convex member CV extends in the width direction of the short-side member 3121, that is, in the X-axis direction. Here, the convex member CV is formed so that an extension length in the X-axis direction, i.e., a width W_cv is the same as a width W_m of the short-side member 3121, as illustrated in (b) of FIG. 6.
In addition, when the convex member CV is formed on the inner surface of the short-side member 3121, it is formed to extend from an upper end to a lower end of the inner surface of the short-side member 3121 as illustrated in (a) of FIG. 6. That is, the convex member CV is provided so that its height H_cv is equal to a height H_m of the short-side member 3121. In other words, the convex member CV is provided with an extension length H_cv in a vertical direction (Z-axis direction) that is the same as that of the short-side member 3121. Thus, a height of the upper end of the convex member CV may be the same as a height of the upper end of the short-side member 3121, and a height of the lower end of the convex member CV may be the same as a height of the lower end of the short-side member 3121. In addition, the protrusion length of the convex member CV may be the same in the vertical direction.
Referring to (a) and (b) of FIG. 6, the convex member CV is provided in a shape in which the protrusion length decreases from a central area A_c in the width direction (X-axis direction) toward both edges. In addition, as the protrusion length of the convex member CV decreases toward both the edges in the width direction, a decreasing rate is not constant, but decreases unevenly. Thus, the inner surface IF of the convex member CV facing the inner space IS is provided in a shape that includes a curved surface. The shape of the inner surface IF of the convex member CV extending in the width direction may include a curve.
Hereinafter, the convex member CV will be described in more detail with reference to FIG. 7.
In the width direction (X-axis direction), the convex member CV includes the central area A_c, a first side area A_s1 disposed at one side of the central area A_c, and a second side area A_s2 disposed at the other side of the central area A_c.
The central area A_c may be an area including a center of the convex member CV in the width direction and a section from the center to a point spaced a predetermined distance in each of one direction and the other direction. In addition, the central area A_c is provided with an equal protrusion length T_c in its width direction. Here, the protrusion length T_c of the central area A_c is set to exceed 5 mm. In other words, a spaced distance between the inner surface IF of the central area A_c of the convex member CV and the inner surface of the short-side member 3121 exceeds 5 mm. More preferably, the protrusion length T_c of the central area A_c is set to be greater than 5 mm and less than 20 mm.
As described above, the central area A_c of the convex member CV has a constant protrusion length T_c in the width direction (X-axis direction). Thus, the inner surface IF of the central area A_c of the convex member CV may have a shape having a plane. The central area A_c of the convex member CV is provided to have a predetermined width W_c, which is provided to be 10% to 15% of the width W_m of the short-side member 3121. In other words, the length W_c of the central area A_c in the Y-direction of the convex member CV is set to be 10% to 15% of the length W_m of the short-side member 3121 in the Y-direction (W_c = 0.1W to 0.15W).
The central area A_c may be equally provided to have the same protrusion length T_c in the width direction. Here, that the inner surface IF of the central area A_c is provided as a plane is for measuring an inclination of the short-side part 3120. To explain more specifically, a spaced distance between the pair of short-side parts 3120 may be adjusted before start of the casting according to a steel grade or a size of the slab 1 to be manufactured.
In addition, in order to adjust the inclination of each of the pair of short-side parts 3120 so that the spaced distance between the pair of short-side parts becomes smaller as they go downward, the installation inclination of the short-side parts 3120 may be adjusted before the start of the casting according to the steel grade or the size of the slab to be manufactured. Here, in order to install the short-side part 3120 so as to achieve a target inclination, it is necessary to measure the inclination of the short-side part 3120.
For this, an inclination measuring device is in contact with the inner surface of the short-side part 3120 to measure the inclination. Thus, when preparing the convex member CV, the central area A_c is prepared so that the protrusion length T_c is the same in the width direction, so that the inner surface IF of the central area A_c becomes a plane. In addition, the inclination measuring device is in contact with the central area A_c which has the flat shape so that the installation inclination of the short-side part 3120 is measured. In addition, the measured installation inclination is used to adjust the inclination of the short-side part 3120 to the target inclination.
In the case in which the width W_c of the central area A_c of the convex member CV exceeds 15% of the width W_m of the short-side member 3121, an angle θ between an edge of the inner surface IF of the convex member CV and an edge of the inner surface IF of the long-side member 3111 may be reduced to an acute angle of less than 90°. As a result, the molten steel or solidification shell may be caught in a space between the edge of the inner surface IF of the convex member CV and the edge of the inner surface IF of the long-side member 3111 to cause burst of the slab 1, and this may result in an operational accident in which the molten steel flows out of the mold 3000.
Conversely, in the case in which the width of the central area A_c of the convex member CV is less than 10% of the width of the short-side member, there is a problem in that the area for measuring the installation angle of the short-side member 3121, i.e., the inclination is narrow, causing measurement difficult. This may cause errors in the measurement of the inclination of the short-side member 3121.
The first side area A_s1 is an area between one end of the convex member CV and one end of the central area A_c, and the second side area A_s2 is an area between the other end of the central area A_c and the other end of the convex member CV. In addition, each of the first and second side areas A_s1 and A_s2 is provided with a protrusion length T_s that is not constant and is uneven in the width direction. That is, the protrusion length T_s of each of the first and second side areas A_s1 and A_s2 decreases as it gets farther away from the central area A_c. To explain more specifically, the first side area A_s1 is configured so that the protrusion length T_s decreases from one end of the central area A_c to one end of the convex member CV. In addition, the second side area A_s2 is configured so that the protrusion length T_s decreases from the other end of the central area A_c to the other end of the convex member CV.
When the protrusion length T_s of each of the first and second side areas A_s1 and A_s2 decreases, a decreasing rate or amount is not constant and decreases unevenly. Thus, in the convex member CV, the inner surfaces of the first and second side areas A_s1 and A_s2 are formed as curved surfaces. Here, the inner surface of each of the first and second side areas A_s1 and A_s2 is provided to have a surface in the shape of a cosine curve in the width direction. More specifically, each of the inner surfaces of the first and second side areas A_s1 and A_s2 has a surface in the shape of half of a cosine curve with one period of 360°. Here, '1/2 of the cosine curve' may mean a 'half period of the cosine curve with 360° as one cycle.' Thus, it may be described that each of the inner surfaces of the first and second side areas A_s1 and A_s2 has a curved shape in the form of a half period of the cosine curve with 360° as one cycle. In addition, 1/2 of the cosine curve with 360° as one period (a half period of the cosine curve) may mean a curve in a section from 0° to 180° and a curve in a section from 180° to 360° in the cosine curve.
As described above, each of the inner surfaces of the first and second side areas A_s1 and A_s2 is formed as a surface in the shape of half the cosine curve, that is, a surface in the shape of a half period of the cosine curve. Here, the inner surface of the first side area A_s1 may be in the form of a section of 0° to 180° of the cosine curve as one cycle. In addition, the inner surface of the second side area A_s2 can be in the shape of a section of 180° to 360° of the cosine curve as one period.
In order to provide the inner surface IF of each of the first and second side areas A_s1 and A_s2 in the shape of half the cosine curve having 360° as one cycle, the width W_m of the short-side member 3121, the width W_s of the central area A_c of the convex member CV, and the protrusion length T_c of the central area A_c of the convex member CV are used. This will be described again later with reference to FIG. 9.
As described above, the protrusion length T_c of the central area A_c of the convex member CV is set to exceed 5 mm, and preferably to exceed 5 mm and not more than 20 mm. When the protrusion length T_c of the central area A_c is 5 mm or less, an effect of suppressing the spreading width during the rolling of the slab 1 is minimal, and thus, an effect of suppressing the occurrence of the edge defects in the steel plate may be minimal.
Again, returning to (a) to (c) of FIG. 6, the convex member CV will be described. As described above, the convex member CV is formed with the same height as the short-side member 3121. That is, the convex member CV is formed to extend from the upper end to the lower end of the short-side member 3121. In addition, the width W_m of the short-side member 3121 decreases as it goes downward, and the width W_cv of the convex member CV is provided to be the same as that of the short-side member 3121. Thus, the width W_cv of the convex member CV decreases as it goes downward. Here, the width W_c of the central area of the convex member CV may be provided equally in the vertical direction as illustrated in (b) and (c) of FIG. 6. In addition, in the convex member CV, the width W_s of the side area A_s may be provided to decrease as it goes downward. In addition, in the convex member CV, the protrusion length T_c of the central area A_c may be the same in the vertical direction, and the protrusion length T_s of the side area A_s may be the same in the vertical direction.
(a) of FIG. 8 is a three-dimensional view of the short-side part according to a modified example of an embodiment. (b) of FIG. 8 is a plan view of the short-side part illustrated in (a) of FIG. 8 when viewed at different heights ⓐ, ⓑ, and ⓒ. (c) of FIG. 8 is a front view of the convex member when (a) of FIG. 8 is viewed at a side 'C'.
In the above-described embodiment, a case in which the width W_c of the central area A_c of the convex member CV is the same in the vertical direction has been described. However, without being limited thereto, the width W_c of the central area A_c of the convex member CV may be provided to decrease toward a lower side as illustrated in (a) to (c) of FIG. 8. In addition, here, the width W_s of the side area A_s may be set to be the same in the vertical direction or to decrease as it goes downward. In the case in which the width W_c of the central area A_c is provided to decrease toward the lower side as in a modified example, the solidification shrinkage of the solidification shell may be controlled more effectively than in the embodiment.
(a) to (c) of FIG. 9 are flowcharts illustrating a method for preparing a design plan including a design for an inner surface of a convex member to manufacture the short-side part provided with a convex member according to according to an embodiment of the present invention.
Hereinafter, with reference to FIGS. 7 and (a) to (c) of FIG. 9, a method for preparing a design plan including a design for an inner surface of a convex member according to an embodiment of the present invention and a method for preparing a short-side part using the same will be described.
The first side area A_s1 and the second side area A_s2 are identical in shape and size, with only their positions being different. Thus, in the following description, the width of the first side area A_s1 and the width of the second side area A_s2 are described as the same as 'W_s'.
First, the width W_m of the short-side member 3121 to be manufactured is determined. In addition, the protrusion length T_c of the central area A_c and the width W_c of the central area A_c for the convex member CV to be manufactured are determined.
The protrusion length T_c of the central area A_c of the convex member CV is determined in a range exceeding 5 mm, preferably in a range exceeding 5 mm and less than or equal to 20 mm. More preferably, the protrusion length T_c of the central area A_c of the convex member CV is determined in a range of 10 mm to 20 mm.
In addition, the width W_c of the central area A_c of the convex member CV is determined to be 10% to 15% of the width W_m of the short-side member 3121. In other words, when the width W_m of the short-side member 3121 is determined, the width W_c of the central area A_c of the convex member CV is determined using the determined width W_m of the short-side member 3121. Here, the width W_m of the short-side member 3121 is determined to be 10% to 15% of the width W_m of the short-side member 3121.
In addition, when the width W_m of the short-side member 3121 and the width W_c of the central area A_c of the convex member CV are determined, the width W_s of the first side area A_s1 is determined using the determined widths. Here, the width W_s of the first side area A_s1 may be determined as a half of the length obtained by subtracting the width W_c of the central area A_c of the convex member CV from the width W_m of the short-side member 3121 (see Equation 1). In addition, the width W_s of the second side area A_s2 is the same as the width W_s of the first side area W_s1. Thus, when the width W_s of the first side area W_s1 is determined, the width W_s of the second side area A_s2 is automatically determined. $W_{s} = \frac{W_{m} - W_{c}}{2}$
As described above, when the width W_m of the short-side member 3121, the protrusion length T_c, the width W_c of the central area A_c of the convex member CV, and the width W_s of the first side area A_s1 of the convex member CV are determined, a design plan for the inner surface of the first side area A_s1 to be manufactured is prepared using the determined values. That is, a design plan is prepared so that the shape of the inner surface IF of the first side area A_s1 of the inner surfaces IF of the convex member CV facing the inner space IS becomes a shape within a section of 0° to 180° of the cosine curve as one period.
Here, the design plan for the inner surface IF of the convex member CV may be prepared using an X-Y coordinate plane as illustrated in (a) to (c) of FIG. 9. In addition, the X-Y coordinate plane may be a coordinate plane on a base material for manufacturing the short-side part. On the X-Y coordinate plane, the X-axis direction may be a direction corresponding to the width direction of the short-side member 3121 and the convex member CV in the mold 3000 to be manufactured, and the Y-axis direction may be a direction corresponding to the thickness direction of the short-side member 3121 and the convex member CV.
Hereinafter, a point on an X-axis line of the X-Y coordinate plane in which an X-axis value is '0' is called a 'reference point X₀'. In addition, the 'reference point X₀' of which the X-axis value is '0' may be a point at one end of the short-side part 3120, the short-side member 3121, or the convex member CV.
In addition, reference symbol 'X_ws' indicated on the X-axis line on the X-Y coordinate plane refers to a position in the X-axis line and means a point spaced apart from the reference point X₀ by the width W_s of the side area A_s. Hereinafter, for convenience of explanation, a point spaced apart from the reference point X₀ on the X-axis by the width W_s of the side area A_s is named a 'boundary point X_ws'.
To prepare the design for the inner side IF of the side area A_s on the X-Y coordinate plane, the value of the Y-axis is determined according to the value of the X-axis. Here, the Y-axis value is determined according to different X values from the reference point X₀ at which the value of the X-axis is 0 to the boundary point X_ws at which the value of the X-axis is a value of the width W_s of the first side area A_s1.
When determining the Y-axis value according to the X value, the cosine curve equation is used. That is, the value of the Y-axis according to the value of the X-axis is calculated using the cosine curve equation (see Equation 2) that applies the width W_m of the short-side member 3121 and the protrusion length T_c and width W_c of the central area A_s in the convex member CV. $Y = \frac{T_{c}}{2} \times \cos (\frac{π}{W_{s}} \times X)$

W_s: Width of side area of convex member
T_c: Protrusion length of central area of convex member
x: x-axis value
y: y-axis value

In Equation 2, the protrusion length T_c of the central area A_c of the convex member CV is a value that has already been determined. In addition, in Equation 2, the width W_s of the first side area A_s1 of the convex member CV is a value determined by the width W_m of the short-side member 3121 that has already been determined and the width W_c of the central area A_c of the convex member CV (see Equation 1). In addition, in Equation 2, 'X' is a value of the X-axis from the reference point X₀ to the boundary point X_ws. That is, the value applied to X in Equation 2 is greater than or equal to 0 (zero) and less than or equal to the width of the side area W_s (see Equation 1). $0 \leq x \leq W_{s}$
In determining the Y-axis value according to the X value using Equation 2, as described above, when a value greater than or equal to 0 (zero) and less than or equal to the width W_s of the first side area A_s1 is applied to Equation 2 to perform an operation, the Y value according to each X value is calculated. That is, in the section from the reference point X₀ to the boundary point X_ws, the Y-axis value is calculated according to the X-axis value.
To explain with a specific example, if applying '0(zero)' to X in Equation 2 to perform the operation, the value of Y, i.e., $\frac{T_{c}}{2}$ is calculated. In addition, if representing the value as an X-Y coordinate value, it may be expressed as 0, $\frac{T_{c}}{2}$ . Here, the point with the 0, $\frac{T_{c}}{2}$ coordinate value is a point at which the side area starts, and thus, a point having the 0, $\frac{T_{c}}{2}$ coordinate value is named a starting point P_s in the following.
As another example, if applying 'W_s' to X to perform an operation, the value of Y, i.e., $- \frac{T_{c}}{2}$ is produced. In addition, if representing the value as an X-Y coordinate value, it may be expressed as 0, $- \frac{T_{c}}{2}$ . Here, the point having the coordinate value 0, $- \frac{T_{c}}{2}$ is a boundary between the side area and the central area and is a point at which the side area is ended. Hereinafter, the point having the coordinate value 0, $- \frac{T_{c}}{2}$ is named an end point P_e.
In the same way, when a value between 0(zero) and W_s is applied to X in Equation 2 to perform an operation, the Y value for each X is calculated. To explain more specifically, an example in which the calculation of Y-axis values for 10 different X values among the values greater than 0 (zero) and less than W_s will be described. In this case, 10 points P₁, P₂, ..., P₉, and P₁₀ having different X-Y coordinate values are created. That is, 10 different points P₁, P₂, ..., P9, and P₁₀ are created between the start point P_s and the end point P_e.
Thus, as illustrated in (a) of FIG. 9, the start point P_s and the end point P_e and a plurality of points P₁, P₂, ..., P₉, and P₁₀ between the start point P_s and the end point P_e are created on the X-Y coordinates.
Next, one line connecting the starting point P_s, the plurality of points P₁, P₂, ..., P₉, and P₁₀, and the ending point P_e is created. Thus, a curve connecting the start point P_s and the end point P_e as in (b) of FIG. 9 is created, and the curve takes the form of half of the cosine curve with 360° as one cycle. That is, the curve is in the form of a section of 0° to 180° of the cosine curve as one period. In other words, the curve is in the form of a half period of the cosine curve with 360° as one cycle, and is in the form of a section of 0° to 180°.
The cosine curve-shaped line connecting the start point P_s, the end point P_e, and the plurality of points P₁, P₂, ..., P₉, and P₁₀ therebetween is a design line for manufacturing the first side area A_s1 (hereinafter, referred to as a design line DL_S1 for the first side area). In other words, it is a design line DL_S1 for the first side area A_s1 of the inner surface IF of the convex member CV.
Next, a design line (hereinafter, referred to as a design line for the central area DL_c) is created for the inner surface IF of the central area A_c of the convex member CV on the X-Y coordinate plane. Here, it is created to start from the end point P_e and have a length of the width W_c of the predetermined central area A_c. Thus, the design line DL_c for the central area for manufacturing the central area A_c is created, and the design line DL_c for the central area may be a straight line in which the value of the Y axis is not changed according to the value of the X axis, as illustrated in (c) of FIG. 9.
Next, the design line for manufacturing the second side area A_s2 disposed on the other side of the central area A_c is created (hereinafter, referred to as a design line for the second side area DL_s2). When preparing the design line DL_s2 for the second side area, it is prepared symmetrically with respect to the design line DL_c for the central area. Thus, a design line DL_s2 for the second side area in the shape of the cosine curve is created as illustrated in (d) of FIG. 9.
As described above, the line connecting the design line for the first side area DL_S1, the design line for the central area DL_c, and the design line for the second side area DL_s2 is a design for the inner surface IF of the convex member CV (hereinafter, referred to as an "inner surface design"). Thus, the inner design may be described as including the design line DL_S1 for the first side area, the design line DL_c for the central area, and the design line DL_s2 for the second design area.
In addition, the central area A_c of the short-side member 3121 and the convex member CV is designed so that each of the widths W_m and W_cv decreases as its go downward. In addition, the protrusion length T_c of the central area A_c may be the same in the vertical direction. Thus, when preparing the inner design of the convex member CV, it is desirable to be prepared for each height. For this, the width of the short-side member 3121 and the widths W_m and W_cv of the central area A_c of the convex member CV are determined for each height. In addition, an inner design is prepared for each height using the width W_m of the short-side member 3121 for each determined height, the width W_cv of the central area A_c of the convex member CV for each height, and the protrusion length T_c of the determined central area A_c.
When the design line DL of the inner surface IF of the convex member CV is prepared, the short-side member 3121 and the short-side member 3120 including the convex member CV are prepared using the design line DL. Here, the short-side member 3121 and the convex member CV are prepared to have the width W_m of the short-side member 3121 that is determined in advance, the width W_c of the central area A_c of the convex member CV, the protrusion length T_c of the central area A_c of the convex member CV, and the width W_s of the side area A_s of the convex member CV. In addition, in the surfaces on both sides of the convex member CV in the thickness direction (Y-axis direction), the inner surface IF that is opposite to the short-side member 3121 is designed to have the same shape as the pre-prepared inner surface design.
A more specific example thereof is given below.
First, a base material for preparing the short-side part 3120 is prepared. Here, the base material may be a square plate made of copper (Cu). In addition, in preparing the base material, a length in one direction is the predetermined width W_m of the short-side member 3121, and a length in the other direction intersecting the one direction is prepared to exceed the predetermined protrusion length T_c of the central area A_c of the convex member CV.
Here, one direction of the base material is a direction corresponding to the width direction of the short-side member 3121, and the other direction of the base material is a direction corresponding to the thickness direction of the short-side member 3121. Thus, one direction of the base material is named the width direction, and the other direction of the base material is named the thickness direction.
Next, the base material is processed. Here, the means for processing the base material is not particularly limited, but for example, processing may be performed using a ball-type cutter.
When processing the base material, one of both surfaces in the thickness direction of the base material is processed. Here, a shape from both ends in the width direction on the one surface to a point spaced apart by the length of the width W_s of the side area A_s determined in advance is processed to become the design lines DL_S1 and DL_s2 for the side area. That is, a surface in the shape of a section of 0° to 180° of the cosine curve as one cycle is created on one side of the central area in the width direction of the base material, and a surface in the shape of a section of 180° to 360° of the cosine curve as one cycle is created on the other side. As described above, the curved surfaces provided at both sides of the central area on one surface of the base material correspond to the inner surface of the side area A_s of the convex member CV to be manufactured. In addition, in one surface of the base material, the central area corresponds to the inner surface of the central area A_c of the convex member CV to be manufactured.
Thus, the short-side member 3121 having the predetermined width W_m, the short-side member 3120 that is formed to protrude from the short-side member 3121 and has the central area A_c having a predetermined protrusion length T_c and width W_c, and the convex member CV of which inner surfaces of first and second side areas A_s1 and A_s2 are formed as cosine curves are provided. Here, the inner surface of the first side area A_s1 is provided in the form of a section of 0° to 180° of the cosine curve as one cycle, and the inner surface of the second side area A_s2 is provided in the form of a section of 180° to 360° of the cosine curve as one cycle.
In addition, as described above, the width W_m of the short-side member 3121 and the width W_c of the central area A_c of the convex member CV have to be designed to decrease toward the lower side. Thus, it is manufactured to match the width W_m of the short-side member 3121 determined in advance for each height and the width W_s of the central area A_c of the convex member CV. In addition, since the width W_s of the central area A_c of the short-side member 3121 and the convex member CV are different for each height, an inner design was prepared for each height. Thus, when preparing the inner surface IF of the convex member CV, it is prepared so that it has the same shape as the inner surface design prepared for each height.
As described above, when the pair of short-side members 3120 having the convex member CV and the short-side member 3121 are prepared, the mold is manufactured by coupling the pair of short-side parts 3120 to the long-side member 3111. That is, as illustrated in FIG. 2, one end of each of the first and second short-side members 3121 is connected to the inner surface of the first long-side member 3111, and the other end of each of the first and second short-side members 3121 is connected to the inner surface of the second long-side member 3111. Thus, the mold having the inner space IS surrounded by the inner surface IF of the convex member CV provided on the first and second short-side members and the inner surface IF of the first and second long-side members 3111 is prepared.
Here, the inner surface IF of the short-side part 3120, that is, the inner surface IF of the convex member CV, of both the side areas As is in the shape of the cosine curve. That is, the inner surface of the first side area A_s1 is provided in the form of a section of 0° to 180° of the cosine curve as one cycle, and the inner surface of the second side area A_s2 is provided in the form of a section of 180° to 360° of the cosine curve as one cycle. Thus, as illustrated in FIG. 7, an angle θ between the edge and the inner surface IF of the long-side member 3111 in the inner surface of the side area A_s becomes 90° or a right angle. In other words, the angle θ between the inner surface IF of the edge of the convex member CV in the width direction and the inner surface IF of the edge of the long-side member 3111 in the width direction is 90° or a right angle. As described above, the angle θ between the inner surface of the edge of the convex member CV in the width direction and the inner surface of the edge in the width direction is 90°, and this means that a space between the inner surface IF of the edge of the convex member CV in the width direction and the inner surface of the edge of the long-side member 3111 in the width direction is wider than when the angle θ is an acute angle (less than 90°).
Thus, when casting the slab 1 by solidifying the molten steel inside the mold 3000, it is possible to suppress or prevent the molten steel or the solidification shell from being caught in the space between the inner surface IF of the edge of the convex member CV in the width direction and the inner surface IF of the edge of the long-side member 3111 in the width direction. Thus, it is possible to prevent the operational accident in which the molten steel flows out of the mold 3000 due to the tearing of the slab 1. In addition, the convex member CV may be provided on the inner surface IF of the short-side member 3121, when manufacturing the steel plate 2 by rolling the slab 1, it is possible to suppress the occurrence of the wrinkle defects or the edge defects on the edge of the steel plate 2 in the width direction. In other words, the mold 3000 provided with the convex member CV prepared according to the method according to an embodiment may be used to manufacture the slab that is capable of suppressing the occurrence of the edge defects in the steel plate 2, while preventing the occurrence of the operational accident due to the leakage of the molten steel.
FIG. 10 is a view illustrating the slab manufactured using the mold according to an embodiment of the present invention.
Referring to FIG. 10, the surfaces at both sides in the width direction of the slab 1 are provided in a concave shape that is recessed inward. Here, each surface at both sides has a curve in the shape of half of the cosine curve with one period of 360°. In other words, each of both the surfaces has a curve in the shape of a half period of the cosine curve with one period of 360°. More specifically, each of both the surfaces includes a central surface F_c and a pair of side surfaces F_s1 and F_S2 disposed at one side and the other side, respectively, of the central surface F_c. In addition, each of the pair of side surfaces F_s1 and F_S2 has a curve in the shape of half of the cosine curve with one period of 360°. Here, the central surface F_c may be in the shape of a plane, and the pair of side surfaces F_s are symmetrical with respect to the central surface F_c. That is, one of the pair of side surfaces F_s has a shape of a section of 0° to 180° of the cosine curve as one period, and the other has a shape of a section of 180° to 360° of the cosine curve as one period.
When the slab 1 having a concave shape on each of both surfaces as described above is rolled, an amount of spreading width due to the rolling may be reduced compared to the conventional method. As a result, it is possible to suppress the occurrence of the edge defects in the steel plate 2 due to the spreading width of the slab 1.
Table 1 shows results illustrating the width of the area on which the defects occur on the edge of the steel plate in the width direction when manufacturing the slab using the mold having the convex member according to an embodiment and Comparative Example, and when the manufactured slab is rolled to manufacture the steel plate.
Here, the convex member according to an embodiment is the convex member manufactured by the method described in FIG. 9 and manufactured as illustrated in FIGS. 2, 6, and 7. That is, it is the convex member having the central area of which the protrusion length is the same in the width direction and the side area of which the shape extending in the width direction is the cosine curve. In addition, in the convex member, the protrusion length of the central area has a specific length within a range of 10 mm to 20 mm, and the width of the central area is 10% to 15% of the width of the short-side member. In addition, in the mold having the convex member according to an embodiment, the angle θ between the inner surface of the edge of the convex member in the width direction and the inner surface of the edge of the long-side member in the width direction is 90°.
The convex member according to Comparative Example has a fan-shaped arc shape (circular arc shape), and the protrusion length of the center of the convex member in the width direction is 5 mm. In addition, the inner shape of the convex member is not the cosine curve. In addition, in the mold having the convex member according to Comparative Example, the angle between the inner surface of the edge of the convex member in the width direction and the inner surface of the edge of the long-side member in the width direction is an acute angle of less than 90°.
In Table 1, first to eleventh steel grades represent different steel grades having different components. In addition, all the first to eleventh steel grades are steel grades for manufacturing stainless steel plates, but the first to eleventh grades are steel grades with some different components.
For the experiment, the molten steel of each of the first to eleventh steel grades was injected into each mold according to Comparative Example and an embodiment, to manufacture the slab. In addition, the slab manufactured in this manner was rolled under the same conditions to manufacture the steel plate.

Next, the width of the area on which the wrinkle defects occur along the edge of the steep plate in the width direction was measured. Here, when starting from the outermost edge of the steel plate in the width direction, the wrinkles toward the center were searched, and a distance from the wrinkle disposed closest to the outermost edge to the wrinkle disposed farthest was measured, and this was defined as a 'defect occurrence width'.

[Table 1]

		First steel grade	Secon d steel grade	Third steel grade	Fourt h steel grade	Fifth steel grade	Sixth steel grade	Seven th steel grade	Eight h steel grade	Ninth steel grade	Tenth steel grade	Eleve nth steel grade
Width (mm) of defec	Comp arat ive Exam ple	15	18	15	10	16	15	12	9	13	22	19
t occur rence area	Embo dime nt	9	14	11	7	8	10	11	7	9	20	13

Referring to Table 1, it is confirmed that the defect occurrence width is reduced in an embodiment when compared to Comparative Example.
In addition, while injecting the molten steel into the mold according to Comparative Example to cast the slab, an accident in which the molten steel flows out of the mold occurs. However, during the casting of the slab by injecting the molten steel into the mold according to an embodiment, only a single incident of the molten steel leaking out of the mold did not occur.
As described above, in the mold 3000 provided with the convex member CV according to an embodiments, when casting the slab 1 by solidifying the molten steel inside the mold 3000, it is possible to suppress or prevent the molten steel or the solidification shell from being caught in the space between the inner surface IF of the edge of the convex member CV in the width direction and the inner surface IF of the edge of the long-side member 3111 in the width direction. Thus, it is possible to prevent the operational accident in which the molten steel flows out of the mold 3000 due to the tearing of the slab 1. In addition, it is possible to manufacture the slab 1 that is capable of suppressing the occurrence of the wrinkle defects or the edge defects on the edge of the steel plate 2 in the width direction. That is, it is possible to manufacture the slab that is capable of suppressing the occurrence of the edge defects in the steel plate 2, and also prevent the occurrence of the operational accident due to the leakage of the molten steel.

INDUSTRIAL APPLICABILITY

The mold according to the embodiments of the present invention may manufacture the slab that is capable of suppressing the edge defects of the steel plate occurring by the spreading width of the slab in the manufacturing of the slab that becomes the steel plate by the rolling. In addition, when manufacturing the slab by solidifying the molten steel inside the mold or when varying in width of the mold, it is possible to suppress or prevent the steel or the solidified shell from being caught in the space between the inner surface of the edge of the convex member and the inner surface of the long-side member. Thus, it is possible to prevent the occurrence of the operational accident in which the molten steel flows out of the mold due to the tearing of the mold.

Claims

A mold having an internal space into which molten steel is injected, the mold comprising:
a body having the internal space; and

a convex member protruding from the body toward the internal space and extending in a width direction of the body,

wherein the convex member comprises a pair of side areas disposed at one side and the other side of the convex member in the width direction,

each of the pair of side areas has a shape in which a protrusion length decreases as away from the center, and

an inner surface of each of the pair of side areas has a surface in a shape of half of a cosine curve with 360° as one cycle.
The mold of claim 1, wherein the convex member comprises a central area disposed between the pair of side areas,
wherein a protrusion length of the central area has the same in the width direction, and

an inner surface that is a surface of the central area, which faces the internal space, has a plane.
The mold of claim 2, wherein the pair of side areas are symmetrical in shape with respect to the central area.
The mold of claim 3, wherein one of the pair of side areas has an inner surface in a shape of a section of 0° to 180° of a cosine curve as one period, and the other has an inner surface in a shape of a section of 180° to 360° of a cosine curve as one period.
The mold of claim 4, wherein the body comprises:
a pair of long-side members, each of which is formed to extend in one direction and which are installed to face each other in a direction intersecting an extension direction; and

a pair of short-side members, each of which is formed to extend to intersect the long-side members and which are installed to face each other to be sealed between the pair of long-side members,

wherein the convex member is formed to protrude from the short-side member toward the internal space.
The mold of claim 5, wherein an angle between an inner surface of the lone-side member and an edge of an inner surface of the side area is 90°.
The mold of claim 2, wherein the protrusion length of the central area of the convex member exceeds 5 mm.
The mold of claim 5, wherein a width of the convex member is the same as a width of the short-side member, and
a width of the central area of the convex member is 10% to 15% of a width of the short-side member.
The mold of claim 8, wherein the width of each of the short-side member and the convex member decreases as it goes downward, and
the width of the central area of the convex member is the same in a vertical direction.
The mold of claim 8, wherein the width of each of the short-side member and the convex member decreases as it goes downward, and
the width of the central area of the convex member decreases as it goes downward.
The mold of claim 5, wherein a length of the convex member in a vertical direction is the same as a length of the short-side member in the vertical direction.
A method for manufacturing a mold, which comprises a body having an internal space and a convex member protruding from the body toward the internal space, the method comprising:
preparing a design plan so that the convex member comprises first and second side areas on which a protrusion length decreases toward both ends of a width direction center, and an inner surface of each of the first and second side areas has a surface in a shape of half of a cosine curve with one period of 360°; and

processing a base material to have the shape of the convex member included in the design plan.
The method of claim 12, wherein the preparing of the design plan comprises:
determining a width (W_m) and a vertical length (H_m) of the body to be manufactured; and

preparing a design for the inner surface of the convex member having the shape of the inner surface of each of the first and second side areas.
The method of claim 13, wherein the preparing of the design for the inner surface of the convex member comprises:
determining a protrusion length (T_c) and a width (W_c) of the central area in the width direction of the convex member to be manufactured; and

preparing a design for the first side area so that a shape of the inner surface of the first side area becomes a shape of half of one-period cosine curve by using the determined width (W_m) of the body, the determined protrusion length (T_c) and width (W_c) of the central area of the convex member.
The method of claim 14, wherein the preparing of the design for the first side area comprises:
determining a width (W_s) of the first side area to be manufactured using the determined width (W_m) of the body and the determined width (W_c) of the central area;

providing a cosine curve equation comprising the determined width (W_s) of the first side area, the determined protrusion length (T_c) of the central area, a width direction position (X) of the convex member, and a thickness direction position (Y) of the convex member; and

calculating the thickness direction position (Y) according to the width direction position (X) using the cosine curve equation,

wherein a value of the width direction position (X) applied to the cosine curve equation is a value of a section from one end of the determined width (W_m) of the body to a point spaced apart by the determined width (W_s) of the first side area, wherein a plurality of values are applied in the section.
The method of claim 15, wherein the preparing of the design for the first side area comprises connecting a plurality of thickness direction positions (Y) calculated for each width direction position (X) to create a design line for the first side area, which is in the shape of half of the one-period cosine curve.
The method of claim 16, wherein preparing the design for the inner surface of the convex member comprises preparing a design for the central area, which is a design for the inner surface of the central area disposed between the first and second side areas, and
the preparing of the design for the central area comprises creating a design line for the center area by extending a line from an end of the design line for the first side area to the determined width (W_c) of the center area.
The method of claim 17, further comprising preparing a design for the second side area so that a shape of the inner surface of the second side area is in a shape of half of one-period cosine curve,
wherein the preparing of the design for the second side area comprises forming a design line for the second side area symmetrically with respect to the design line for the first side area using the central area as a center.
The method of claim 18, further comprising preparing a base material of which a width direction length is the determined width (W_m) of the body, and a length in the thickness direction intersecting the width direction exceeds the determined protrusion length (T_c) of the central area of the convex member,
wherein processing of the base material comprises processing one surface of both surfaces of the base material in the thickness direction so that a shape from each of both ends in the width direction to a point spaced apart by a length of the determined width (W_s) of the side area is the design line for each of the first and second side areas.
A slab manufactured by solidifying molten steel, wherein each of both surfaces of the slab has a convex shape that is recessed inward, and a portion of each of both the surfaces has a curve surface in a shape of half of a cosine curve with 360° as one cycle.
The slab of claim 20, wherein each of both the surfaces comprises a central surface and a pair of side surfaces disposed at one side and the other side of the central surface, respectively, and
each of the pair of side surfaces has a curve surface in the shape of half of a cosine curve with one period of 360°, wherein the center surface has a plane.
The slab of claim 21, wherein the pair of side surfaces have a shape symmetrical with respect to the center surface, and
one of the pair of side surfaces has a shape in a range of 0° to 180° in the one-period cosine curve, and the other has a shape of a section of 180° to 360° of a cosine curve as one period.