Patent Description:
When a surface of a steel sheet formed of aluminum or steel is plated with zinc or a zinc-alloy, a cooling process is performed to solidify a plated layer on the surface of the steel sheet.

Conventionally, such a cooling process may be performed during conveyance of a steel sheet to post-processing or during the post-processing. A period, in which such a cooling process is performed, may be significantly limited.

Therefore, water or air (hereinafter referred to as "cooling fluid") may be supplied to a steel sheet to perform strong cooling within an allowable cooling process period. In this case, a large amount of cooling fluid is used.

Such a cooling process and apparatus are for example described in <CIT>, <CIT>, <CIT> and <CIT>.

Since the cooling fluid colliding with the surface of the steel sheet is discharged along an edge of the steel sheet in a width direction, a flow rate of the cooling fluid tends to be increased in a direction toward the edge of the steel sheet. Due to the flow rate increased in the direction toward the edge of the steel sheet, surface defects such as a blowing mark may occur on the edge of the steel sheet.

An aspect of the present disclosure is to improve cooling efficiency of a steel sheet and to suppress occurrence of a defect on a surface of the steel sheet.

Another aspect of the present disclosure is to improve production efficiency of a steel sheet.

The present disclosure relates to an apparatus for cooling a steel sheet.

An apparatus for cooling a steel sheet according to an example embodiment includes: an apparatus body provided to be spaced apart from a steel sheet in a conveying path of the steel sheet; and a cooling unit provided in the apparatus body to supply a cooling fluid. The apparatus body includes: a first edge body facing a first edge portion extending from one side end of the steel sheet by a predetermined distance in a center direction of the steel sheet; and a second edge body facing a second edge portion extending from the other end of the steel sheet by a predetermined distance in the center direction of the steel sheet. Each of the first and second edge bodies is provided such that a cross-section in a direction, perpendicular to a conveying direction of the steel sheet, is stepped.

Each of the first and second edge bodies is provided such that a cross-section in a direction, perpendicular to the conveying direction of the steel sheet, is stepped in a width direction of the steel sheet, and a shortest distance to a surface of the steel sheet in a thickness direction of the steel sheet varies on a surface of each of the first and second edge bodies in the width direction of the steel sheet.

In the apparatus body, an absolute value of a plurality of first inclination angles, formed between an extension line of a symmetry point at which the first edge body and the second edge body intersect each other and the first and second edge bodies, is <NUM>° or more to <NUM>° or less.

Each of the first and second edge bodies includes a first inclined section forming the first inclination angle together with the symmetry point and being a region inclined in a direction away from the steel sheet; a non-inclined section, connected to the first inclined section, from which a shortest distance to the steel sheet in the thickness direction of the steel sheet is provided to be constant; and a second inclined section connected to the non-inclined section and being a region inclined in a direction toward the steel sheet.

The first and second edge bodies may be provided to form a second inclination angle in the second inclined section together with an extension line of the non-inclined section in the width direction of the steel sheet, and an absolute value of the second inclination angle may be at least <NUM>°.

A length of the first inclined section in the width direction of the steel sheet may be at least <NUM>, a length of the non-inclined section in the width direction of the steel sheet may be at least <NUM>, and a length of the second inclined section in the width direction of the steel sheet may be at least <NUM>.

The apparatus body may include at least one dimple region formed to be concave on a surface, facing the steel sheet, in a direction opposing the steel sheet.

The first edge body and the second edge body may extend outwardly of an external circumference of the steel sheet in the width direction of the steel sheet.

The first and second edge bodies may be symmetrical with each other in the width direction of the steel sheet with respect to the symmetry point at which the first edge body and the second edge body intersect each other.

A diameter of the dimple region may be a value greater than <NUM> to <NUM> or less, a depth of the dimple region may be a value greater than <NUM> to <NUM> or less, and a maximum pitch of the dimple region may be <NUM>.

The cooling unit may include a plurality of cooling means spaced apart from each other in the conveying direction of the steel sheet in the apparatus body. The cooling means may include: a plurality of cooling nozzles facing the steel sheet to supply a cooling fluid; a slot accommodating the cooling nozzles therein; and a supply means connected to the cooling nozzles to supply the cooling fluid at constant pressure.

In a second embodiment the apparatus body further includes a center body facing a center in a width direction of the steel sheet and present between the first edge body and the second edge body, and the center body is provided such that a shortest distance to the steel sheet in the thickness direction of the steel sheet is provided to be constant in the width direction the steel sheet.

Each of the first edge body and the second edge body includes: a first inclined section facing the edge portion of the steel sheet and formed by providing an external circumference of the first inclined section so as to be inclined in a direction away from a surface of the steel sheet; a non-inclined section connected to the first inclined section and formed by providing an external circumference of the non-inclined section so as not to be inclined; and a second inclined section connected to the non-inclined section and formed by providing an external circumference of the second inclined section so as to be inclined in a direction toward the surface of the steel sheet.

A length of the non-inclined section in the width direction of the steel sheet may be greater than <NUM> and may be a certain value less than or equal to <NUM>/<NUM> of a total length of the center body in the width direction of the steel sheet.

The first and second inclined sections may be provided to be linearly inclined.

The apparatus body may include a plurality of partition walls disposed to be spaced apart from each other in the width direction of the steel sheet inside the apparatus body, and a spacing distance between the plurality of partition walls may at least equal to a length of the center body in the width direction of the steel sheet.

An absolute value of a third inclination angle, formed between an extension line of the center body and the first inclined section, may be a certain value between <NUM>° or more to <NUM>° or less.

A length of the second inclined section in the width direction of the steel sheet may be greater than <NUM>, and may be a certain value within a range less than or equal to a length of the non-inclined section in the width direction of the steel sheet.

An absolute value of a second inclination angle, formed between an extension line of the non-inclined section in the width direction of the steel sheet and the second inclined section, may be greater than <NUM>° and may be a value less than or equal to an absolute value of an inclination angle of the first inclined section.

The apparatus body may include a plurality of dimple regions formed to be concave on a surface, facing the steel sheet, in a direction opposing the steel sheet, and the plurality of dimple regions may be disposed in the width direction of the steel sheet.

The cooling unit may include a plurality of cooling means spaced apart from each other in the conveying direction of the steel sheet in the apparatus body. The cooling means may include: a plurality of cooling nozzles facing the steel sheet to supply a cooling fluid; a slot accommodating the cooling nozzles therein; and a supply means connected to the cooling nozzles to supply the cooling fluid at constant pressure. The plurality of cooling nozzles may be provided with a plurality of cooling nozzles in the width direction of the steel sheet in the apparatus body, and may be provided in the apparatus body to supply the cooling fluid in a position closer to the steel sheet than an external circumference of the apparatus body.

The plurality of cooling nozzles may be spaced apart from the steel sheet at regular intervals in the thickness direction of the steel sheet.

As set forth above, cooling efficiency of a steel sheet may be improved, and surface quality of the steel sheet may be improved.

In addition, production efficiency of the steel sheet may be improved.

In order to facilitate an understanding of the description of example embodiments of the present disclosure, the same reference numerals are used for the same elements in the accompanying drawings, and related elements among elements performing the same function in each example embodiment are denoted by the same number or the number of extension.

Further, in order to clarify the gist of the present disclosure, a description of elements and techniques well known in the related art will be omitted, and the present disclosure will be described in detail with reference to the accompanying drawings.

It is to be understood, however, that the scope of the present disclosure are not limited to the example embodiments illustrated, but other forms may be suggested by those skilled in the art while specific components are added, changed, and deleted, which also included within the scope of the same idea as the present disclosure.

In accompanying drawings, an X-axis refers to a thickness direction of a steel sheet, a Y-axis refers to a width direction of the steel sheet, and a Z-axis refers to a length direction of the steel sheet.

A cooling fluid to be described below may be at least one of water, air, and nitrogen. Alternatively, water, air, and nitrogen may be appropriately mixed to be used as the cooling fluid. The type of the cooling fluid may be appropriately selected and applied depending on characteristics of a steel sheet, characteristics of a plating process, and the like.

A steel sheet to be described below may be a galvanized steel sheet or a zinc-alloy plated steel sheet in which magnesium is contained in an amount of <NUM>% or more.

The above-mentioned steel sheet may be a hot-rolled or cold-rolled steel sheet, and may have a width of <NUM> to <NUM>.

A shortest distance from an injection port of a cooling nozzle for supplying a cooling fluid to the surface of the steel sheet may be <NUM> to <NUM>, and the cooling nozzle may be provided with a plurality of cooling nozzles in a width direction and a length direction of the steel sheet. In this case, the cooling nozzle may be spaced apart from the steel sheet by at least <NUM> in the width direction of the steel sheet.

In addition, the cooling nozzle may adopt various types such as a straight slit type, a round type, and the like.

Hereinafter, a unit of an angle is degrees (°).

As illustrated in <FIG>, a heat-treated steel sheet <NUM> may be introduced into a plating bath <NUM> through a snout <NUM> of an annealing furnace, so that a direction of the steel sheet <NUM> may be changed by a sink roll <NUM>. Then, the steel sheet <NUM> may be vertically guided by a guiding roll to be conveyed to an air knife <NUM>.

The air knife <NUM> may supply a fluid at high speed to control a thickness of a plated layer. The steel sheet <NUM>, passing through the air knife <NUM>, may be provided to an apparatus <NUM> for cooling a steel sheet according to the present disclosure.

The steel sheet <NUM>, in which a plated layer is cooled, solidified, and hardened while passing through the apparatus <NUM> for cooling a steel sheet, is conveyed to post-processing.

The apparatus <NUM> for cooling a steel sheet according to the present disclosure, disposed in plating equipment of a steel sheet, includes an apparatus body <NUM> facing the steel sheet <NUM>. The apparatus body <NUM> may include a first apparatus body 110a, facing one side surface of the steel sheet <NUM>, and a second apparatus body 110b, facing the other side surface of the steel sheet <NUM> to be spaced apart from the first apparatus body 110a.

A cooling fluid supply line 101a may be connected to the first apparatus body 110a and the second apparatus body 110b, and a cooling fluid may be continuously supplied to the first apparatus body 110a and the second apparatus body 110b through the cooling fluid supply line 101a.

A suction means, not illustrated, providing constant suction pressure to suction the supplied cooling fluid, may be connected to the first apparatus body 110a and the second apparatus body 110b. However, the present disclosure is not limited thereto, and the suction means may be appropriately selected and applied by those skilled in the art.

As illustrated in <FIG>, a cooling means <NUM> for supplying the cooling fluid to the steel sheet <NUM> may be provided on a surface of the apparatus body <NUM> facing the steel sheet <NUM>.

The cooling means <NUM> may include a plurality of cooling nozzles <NUM>. The plurality of cooling nozzles <NUM> may be provided in the apparatus body <NUM> to be spaced apart from each other in the width direction of the steel sheet <NUM>.

The cooling nozzle <NUM> may adopt a slit type, a round type, or the like, but the type of the cooling nozzle <NUM> is not limited by the present disclosure.

A flow rate of the cooling fluid, passing in the vicinity of the steel sheet <NUM>, is increased in a direction toward the edge of the steel sheet <NUM>. This is because the amount of the cooling fluid, passing in the vicinity of the steel sheet <NUM>, is increased due to accumulation of the cooling fluid injected from the cooling nozzle <NUM>.

Such an increased flow rate is a main cause of surface defects such as a blowing mark on a first edge portion 1a, one side edge of the steel sheet <NUM>. The surface defects may also occur on the other side edge.

Accordingly, as illustrated in <FIG>, the apparatus for cooling a steel sheet according to the present disclosure includes a first edge body <NUM> and a second edge body <NUM>. The first edge body <NUM> faces a first edge portion 1a extending from one side end of the steel plate by a predetermined distance in the center direction of the steel plate. The second edge body <NUM> faces a second edge portion 1b extending from the other end side end of the steel sheet by a predetermined distance in the center direction of the steel sheet.

In addition, each of the first and second edge bodies <NUM> and <NUM> have a linearly inclined cross-section in a Z direction, a direction perpendicular to a conveying direction of the steel sheet <NUM>. In this case, an end portion of the first edge body <NUM> and an end portion 112a of the second edge body <NUM> are provided to be inclined in a direction away from the steel such that the end portions 111a and 112a are present farthest from the steel in an X direction, in a thickness direction of the steel sheet.

Accordingly, a spacing distance between the first edge body <NUM> and the second edge body <NUM>, and the steel sheet <NUM> is gradually increased to provide a wide space in which the cooling fluid is able to be discharged.

As a result, time for which the cooling fluid remains in the first edge portion 1a and the second edge portion 1b of the steel sheet may be reduced, and the amount of the cooling fluid remaining in the first edge portion 1a and the second edge portion 1b of the steel sheet may be reduced, so that surface detects of the steel sheet caused by the increased flow rate of the cooling fluid may be prevented.

In addition, even when the first edge body <NUM> and the second edge body <NUM> are not elongated in the width direction of the steel sheet <NUM>, a wide space in which the cooling fluid is able to be discharged may be provided. Therefore, surface quality of the steel sheet may be improved without enlargement of equipment. Such an effect may be equivalently applied to the apparatus bodies <NUM> in other embodiments of the present disclosure to be described later.

The first and second edge bodies <NUM> and <NUM> may be symmetrical in the width direction of the steel sheet, for example, in a Y-axis direction, with respect to a symmetry point C at which the first edge body <NUM> and the second edge body <NUM> intersect each other.

In addition, a cooling means <NUM> may be provided on the surfaces of the first and second edge bodies <NUM> and <NUM>. The cooling means <NUM> may include a plurality of cooling nozzles <NUM>, disposed along a surface of the apparatus body <NUM> in the Y-axis direction, and a slot <NUM> accommodating the cooling nozzles <NUM> therein and opened in the direction of the steel sheet <NUM>.

The cooling fluid, supplied from the cooling nozzle <NUM>, may flow along the slot <NUM> to reach the surface of the steel sheet. The slot <NUM> may serve to increase supply pressure of the cooling fluid, allowing supply of the cooling fluid supplied from the cooling nozzle <NUM> to the steel sheet to be useful and reducing the amount of loss of the cooling fluid.

The cooling means <NUM> may be provided with a plurality of cooling means in the apparatus body <NUM> in the conveying direction of the steel sheet, for example, in a Z-axis direction, to constitute a cooling unit 120a on the apparatus body <NUM>.

In this case, the plurality of cooling means <NUM> may be spaced apart from each other by a predetermined distance in the conveying direction of the steel sheet, for example, in the Z-axis direction.

The cooling nozzle <NUM> may be a slot (an open hole) formed in a surface of the apparatus body <NUM>. The type and shape of the cooling nozzle <NUM> are not limited by the present disclosure.

As illustrated in <FIG>, an apparatus for cooling a steel sheet may include a first edge body <NUM> and a second edge body <NUM>. The first edge body <NUM> may face a first edge portion 1a extending from one side of the steel sheet <NUM> by a predetermined distance in a center direction of the steel sheet <NUM>. The second edge body <NUM> facing a second edge portion 1b extending from the other side end of the steel sheet <NUM> by a predetermined distance in the center direction of the steel sheet <NUM>.

In addition, a cross-section of the first edge body <NUM> and the second edge body <NUM>, for example, a cross-section in an X-Y plane perpendicular to a Z-axis direction may be provided with a stepped edge.

The sentence "a cross-section in an X-Y plane perpendicular to a Z-axis direction may be provided with a stepped edge" means that a facing surface of the first and second edge bodies <NUM> and <NUM> and the steel sheet <NUM> may be nonlinear in a Y-axis direction.

As described above, the first edge body <NUM> and the second edge body <NUM> are provided with a nonlinear surface in the Y-axis direction, so that the nonlinear surface in the Y-axis direction of the apparatus body may face the steel sheet <NUM>.

A cooling means <NUM> may be provided on the nonlinear surface of the apparatus body <NUM>. The cooling means <NUM> may include a plurality of cooling nozzles <NUM>, disposed along the nonlinear surface of the apparatus body in the Y-axis direction, a slot <NUM> accommodating the nozzles <NUM> therein opened in the direction of the steel sheet <NUM>.

The cooling, fluid supplied from the cooling nozzle <NUM>, may flows along the slot <NUM> to reach the surface of the steel sheet, and this slot <NUM> may serve to increase supply pressure of the cooling fluid, allowing supply of the cooling fluid supplied from the cooling nozzle <NUM> to the steel sheet to be useful and reducing the amount of loss of the cooling fluid.

The cooling means <NUM> may be provided with a plurality of cooling means in the apparatus body <NUM> in the conveying direction of the steel plate, for example, in a Z-axis direction, to constitute a cooling unit 120a on the apparatus body <NUM>.

In this case, the plurality of cooling means <NUM> may be spaced apart from each other by a predetermined distance in the conveying direction of the steel plate, for example, in the Z-axis direction.

As illustrated in <FIG>, the first edge body <NUM> may have a shape symmetrical to the second edge body (<NUM> in <FIG>) with respect to a symmetry point C.

The first edge body <NUM> may have a cross-section in an X-Y plane perpendicular to a conveying direction of the steel sheet, for example, in the Y-axis direction, provided to be stepped in the Y-axis direction, and thus, a thickness of the first edge body <NUM> is not regular in the Y-axis direction.

For example, the first edge body <NUM> is provided such that a shortest distance from the surface of the first edge body <NUM> to the surface of the steel sheet in the X-axis direction is changed in the Y-axis.

Accordingly, the thickness of the first edge body <NUM> may be not constant in the Y-axis direction, and may be changed in the Y-axis direction.

An angle, formed between a surface facing the steel sheet <NUM> in the first edge body <NUM> and an extension line of the symmetry point C, is defined as a first inclination angle Θ1. An absolute value of the first inclination angle Θ1 is a certain value within the range of <NUM>° or more to <NUM>° or less.

The first edge body <NUM> may include a first inclined section <NUM> provided by forming the first inclination angle between an external circumference of the first edge body <NUM> and the symmetry point C, a non-inclined section <NUM> present farther than the first inclined section <NUM> in the width direction of the steel sheet <NUM> from the symmetry point C by connecting the external circumference of the first edge body <NUM> to the first inclined section <NUM>, and a second inclined section <NUM> present farther than the non-inclined section <NUM> in the width direction of the steel sheet <NUM> from the symmetry point C by connecting the external circumference of the first edge body <NUM> to the non-inclined section <NUM>.

For example, the first inclined section <NUM>, the non-inclined section <NUM>, and the second inclined section <NUM> may be referred to as regions formed by bending the external circumference of the first edge body <NUM>, which is equivalently applies to the second edge body (<NUM> in <FIG>).

The first inclined section <NUM> may be a surface facing the first edge portion 1a of the steel sheet, and may continue to the outside of an end portion of the steel sheet.

The non-inclined section <NUM> may be a surface parallel to the surface of the steel sheet <NUM>, and may be present outside the first edge portion 1a in the Y-axis direction. A thickness of the non-inclined section <NUM> in the X-axis direction may be constant without being changed in the Y-axis direction.

The second inclined section <NUM>, connected to the non-inclined section <NUM> and having an end portion of the first edge body <NUM>, may be provided to be inclined in a direction toward the surface of the steel sheet <NUM>.

The second inclined section <NUM> may be a section inclined in a direction toward the surface of the steel sheet <NUM>, and a thickness of the second inclined section <NUM> in the X-axis direction may be greater than or equal to a thickness of the non-inclined section <NUM> in the X-axis direction.

In this case, the thickness of the second inclined section <NUM> in the X-axis direction may be linearly changed in the Y-axis direction. An angle, formed between an extension line of the non-inclined section <NUM> in the Y-axis direction and the second inclined section <NUM>, is defined as a second inclination angle Θ2, and an absolute value of the second inclination angle Θ2 may be at least <NUM>°.

The second inclination angle Θ2 may be present in the edge region of the first edge body <NUM>. When the second inclined section <NUM> is provided to be inclined by the second inclination angle Θ2, a flow rate of a cooling fluid may be increased and a pressure may be decreased immediately before the cooling fluid is discharged to the outside of the first edge body <NUM>. Therefore, the cooling fluid may be rapidly discharged right before a cooling fluid discharge outlet of the first edge body <NUM>.

This is equivalently applied to the second inclination angle Θ2 formed on a second edge body (<NUM> in <FIG>).

In an embodiment of the present disclosure, a width direction of the steel sheet <NUM> of the first inclined section <NUM>, for example, a length of a straight line of the first inclined section <NUM> in the Y-axis direction may be at least <NUM>, a length of a straight line of the non-inclined section <NUM> in the Y-axis direction may be at least <NUM>, and a length of a straight length of the steel sheet of the second inclined section <NUM> in the Y-axis direction may be at least <NUM>.

However, the thickness of the first edge body <NUM> in the X-axis direction may be appropriately adjusted such that each of the absolute values of the first inclination angle Θ1 and the second inclination angle θ2 is within the above range. This will be equivalently applied to the case of the third inclination angle (θ3 in <FIG>) to be described later.

The cooling nozzle <NUM> may be provided in a region corresponding to the first inclined section <NUM> of the first edge body <NUM>, and may be provided in a region of the first inclined section <NUM>, which does not face the first edge portion of the steel sheet <NUM>, to supply the cooling fluid to the steel sheet <NUM>.

In this case, when the slot <NUM> is provided in the first edge body <NUM> to accommodate the cooling nozzle <NUM>, a supply pressure of the cooling fluid may be increased to prevent the cooling fluid from being excessively used.

As illustrated in <FIG>, the second edge body <NUM> may be symmetrical to the first edge body (<NUM> of <FIG>) with respect to the symmetry point C in the width direction of the steel sheet <NUM>.

Accordingly, the absolute value of the first inclination angle Θ1 may be a certain value within the range of <NUM>° or more to <NUM>° or less, and the absolute value of the second inclination angle Θ2 may be at least <NUM>°.

The cooling nozzle <NUM> may be provided in a region of the first inclined section <NUM>, which does not face the second edge portion of the steel sheet <NUM>, to supply a cooling fluid to the steel sheet <NUM>.

According to the first edge body (<NUM> of <FIG>) and the second edge body <NUM> described above, a spacing distance between the first edge body (<NUM> of <FIG>) and the second edge body <NUM>, and the steel sheet <NUM> may be increased in a direction toward the first edge portion (1a of <FIG>) extending from one end portion of the steel sheet by a predetermined distance in a center direction of the steel sheet, and a region corresponding to the second edge portion extending from the other end portion of the steel sheet by a predetermined distance in the center direction of the steel sheet. Therefore, a space in which the cooling fluid is able to be discharged may be widened to that extent.

As a result, time for which the cooling fluid remains in the first edge portion (1a of <FIG>) and the second edge portion of the steel sheet may be reduced, and the amount of the cooling fluid remaining in the first edge portion (1a of <FIG>) and the second edge portion of the steel sheet may be reduced, so that surface detects of the steel sheet caused by the increased flow rate of the cooling fluid may be prevented.

As illustrated in <FIG>, in an embodiment of the present disclosure, the second edge body <NUM> may include a dimple region <NUM> having a shape of a groove formed to be concave in a direction opposing the steel sheet.

The dimple region <NUM> may also be formed in the first edge body (<NUM> in <FIG>), and may be provided with a plurality of dimple regions <NUM> formed in the first edge body (<NUM> in <FIG>) and the second edge body <NUM> in a Y-axis direction.

In addition, since end potions of the first edge body (<NUM> in <FIG>) and the second edge body <NUM> extend outside an external circumference of the steel sheet <NUM>, the dimple region <NUM> may be formed in the first edge body (<NUM> in <FIG>) and the second edge body <NUM> to be present to the outside of an end portion of the steel sheet.

The dimple region <NUM> may serve to reduce maximum shear stress generated on the surface of the steel sheet to reduce the amount of cooling fluid in the first edge portion (1a of <FIG>) and the second edge portion of the steel sheet and to prevent surface defects in the first edge portion (1a of <FIG>) and the second edge portion of the steel sheet.

In addition, the dimple region <NUM> may serve to promote formation of a turbulent boundary layer on the surfaces of the first edge body (<NUM> in <FIG>) and the second edge body <NUM>.

The dimple region <NUM>, disposed on the surfaces of the first edge body (<NUM> in <FIG>) and the second edge body <NUM> in a width direction of the steel sheet, may serve to reduce shear stress generated between the surfaces of the first edge body (<NUM> in <FIG>) and the second edge body <NUM>, and the cooling fluid, and thus, may increase a flow rate of the cooling fluid to smoothly discharge the cooling fluid.

Accordingly, the cooling fluid may be smoothly and rapidly discharged in the direction of the first edge portion (1a of <FIG>) and the second edge portion of the steel sheet.

Such a phenomenon may serve to suppress formation of a blowing mark, a type of defect, on the surface of the steel sheet.

As illustrated in <FIG> and <FIG>, the dimple region <NUM> formed in the second edge body (<NUM> in <FIG>) may have a diameter D which is a certain value within the range of more than <NUM> and <NUM> or less and a depth (E in <FIG>) which is a certain value within the range of more than <NUM> to <NUM> or less, and a maximum value of a pitch P may be <NUM>. Such a standard may be equivalently applied to not only the second edge body (<NUM> in <FIG>) but also the first edge body (<NUM> in <FIG>).

As illustrated in <FIG>, a cooling means <NUM> according to an embodiment of the present disclosure may include a plurality of cooling nozzles <NUM> facing a steel sheet and supplying a cooling fluid to a surface of the steel sheet, a slot <NUM> accommodating the cooling nozzles <NUM> therein, and a supply means <NUM> connected to the cooling nozzle <NUM> to supply the cooling fluid at a constant pressure. The supply means <NUM> may adopt a supply pump, connected to each of the cooling nozzles <NUM> to provide a constant supply pressure, or the like. However, the type of the supply means <NUM> is not limited by the present disclosure.

An apparatus for cooling a steel sheet according to another embodiment of the present disclosure is illustrated in <FIG>.

According to another embodiment of the present disclosure, an apparatus body further includes a center body <NUM> facing a center of a steel sheet in a width direction and present between the first edge body <NUM> and the second edge body <NUM>.

A shortest distance from the center body <NUM> to the steel sheet in the X-axis direction, in a thickness direction of the steel sheet, is constantly provided in the width direction of the steel sheet. A surface of the center body <NUM>, facing the steel sheet, may be disposed to be parallel to the surface of the steel sheet.

The center body <NUM> may not face a first edge portion 1a and a second edge portion 1b of the steel sheet, the first edge portion 1a of the steel sheet may face the first edge body <NUM>, and the second edge portion 1b of the steel sheet may face the second edge body <NUM>.

In addition, a plurality of cooling means <NUM> spaced apart from each other in the conveying direction of the steel sheet, in a Z-axis direction, may be provided to constitute a cooling unit 120a on the apparatus body.

The cooling means <NUM> may include a plurality of cooling nozzles <NUM>, formed in the apparatus body in a Y-axis direction, and a slot <NUM> accommodating the cooling nozzle <NUM> therein.

<FIG> illustrates half of the apparatus body <NUM>, and the apparatus body <NUM> may have a bilaterally symmetrical structure with respect to a centerline in the X-axis direction of <FIG>.

Therefore, it can be seen that a cross-section of the second edge body <NUM> in an X-Y plane, connected to half of the center body <NUM> and one side of the second edge body <NUM>, is illustrated in <FIG>. Matters concerning the edge body <NUM> to be described later may be equivalently applied to the first edge body (<NUM> in <FIG>).

The center body <NUM> may face a certain distance from the center of the steel sheet in the direction of the second edge portion 1b of the steel sheet. In addition, the second edge body may be provided to face the second edge portion of the steel sheet.

In this case, the cooling nozzle <NUM> may be provided only in the center body <NUM> to supply the cooling fluid to the steel sheet.

As illustrated in <FIG> and <FIG>, the second edge body <NUM> includes a first inclined section <NUM> facing the second edge portion 1b and formed to have an external circumference provided to be inclined in a direction away from a surface of a steel sheet, a non-inclined section <NUM> connected to the first inclined section <NUM> and formed parallel to the second edge portion 1b to have an external circumference provided so as not to be inclined in a Y-axis direction, and a second inclined section <NUM> connected to the non-inclined section <NUM> and formed to have an external circumference provided to be inclined in a direction toward the surface of the steel sheet.

In this case, a length of the non-inclined section <NUM> in the Y-axis direction may be a certain value greater than zero (<NUM>), and is less than or equal to <NUM>/<NUM> of a total length of the center body (<NUM> in <FIG>) in the width direction of the steel sheet.

In an embodiment of the present disclosure, a length of the center body (<NUM> of <FIG>) in a width direction of the steel sheet may be at least <NUM>, a length of the inclined section <NUM> in the width direction of the steel sheet may be at least <NUM>, a length of the non-inclined section <NUM> in the width direction of the steel sheet may be at least <NUM>, and a length of the second inclined section <NUM> in the width direction of the steel sheet may be at least <NUM>.

In addition, the first inclined section <NUM> and the second inclined section <NUM> may be provided to be linearly inclined.

The first inclined section <NUM> may be formed by being inclined in a direction away from the second edge portion such that the external circumference of the second edge member <NUM> and an extension line of the center body (<NUM> of <FIG>) forms a third inclination angle θ3.

The non-inclined section <NUM> may be connected from an end portion of the first inclined section <NUM>, and the second inclined section <NUM> may be formed by providing the external circumference of the second edge body <NUM> to be inclined again in a direction toward the second edge portion from the non-inclined section <NUM>.

The above description may be applied as the same principle to the first edge body (<NUM> of <FIG>) by reflecting that the first edge body (<NUM> of <FIG>) is symmetrical with the second edge body <NUM>.

In this case, an absolute value of the third inclination angle θ3 may be a certain value between <NUM>° or more and <NUM>° or less.

For example, in another embodiment of the present disclosure, a first inclination angle (θ1 in <FIG>) may not be present in the apparatus body <NUM>.

One partition wall <NUM>, separating the center body <NUM> and the second edge body <NUM> from each other, and another partition wall <NUM>, separating the center body <NUM> and the first edge body <NUM> from each other, may be provided inside the apparatus body <NUM>.

Accordingly, a pair of partition walls <NUM> may be present in the Y-axis direction inside the apparatus body (<NUM> in <FIG>), and a distance between the partition walls <NUM> may be equal to an overall length of the center body <NUM> in the Y-axis direction.

This may serve to prevent injection pressure of a cooling fluid from being unnecessarily dispersed in the apparatus body (<NUM> in <FIG>) when the injection pressure is provided to the cooling nozzle <NUM>.

In addition, a length of the second inclined section <NUM> in the Y-axis direction may be greater than zero (<NUM>) and may be a certain value within the range less than or equal to the length of the non-inclined section <NUM> in the Y-axis direction.

Accordingly, the length of the second inclined section <NUM> in the Y-axis direction may be less than or equal to the length of the non-inclined section <NUM> in the Y-axis direction.

In addition, as illustrated in <FIG>, the dimple region <NUM> may also be formed in the center body <NUM> and the second edge body <NUM>.

The dimple region <NUM> may be provided with a plurality of dimple regions <NUM> provided on the apparatus body (<NUM> in <FIG>) in the Y-axis direction, and details thereof may be applied in the same manner as those of the above-described dimple region <NUM>.

In addition, as illustrated in <FIG>, the supply means <NUM> may also be connected to the cooling nozzle <NUM> provided in the center body <NUM>.

The supply means may be provided as a supply pump, providing supply pressure of the cooling fluid, or the like, but is not limited by the present disclosure.

In addition, the cooling nozzle <NUM> may supply a cooling fluid to the steel sheet while being disposed to be closer to the surface of the steel sheet <NUM> than the external circumference of the center body <NUM> in the X-axis direction.

In this case, an opened supply hole of the slot <NUM> accommodating the cooling nozzle <NUM> therein may be disposed to be closer to the surface of the steel sheet in the X-axis direction than the cooling nozzle <NUM>.

Accordingly, loss of the supply pressure of the cooling fluid and the amount of loss of the cooling fluid may be reduced.

In addition, the plurality of cooling nozzles <NUM> may be spaced apart from the surface of the steel sheet at regular intervals in the X-axis direction to uniformly supply the cooling fluid.

The apparatus body <NUM> illustrated in <FIG> may have a bilaterally symmetrical structure with respect to a center line C1. In <FIG>, only a right region of the apparatus body <NUM> is illustrated for convenience of drawing.

Hereinafter, a description will be provided by dividing the apparatus body <NUM> in half in the Y-axis direction according to a first section Lc, a second section Li, a third section Le, and a fourth section Lei.

In this case, a boundary between the first section Lc and the second section Li may be a partition wall (<NUM> in <FIG>), and the first section Lc may be a region corresponding to the center body (<NUM> in <FIG>).

<FIG> illustrates a total of eight cases to which values the first section Lc, the second section Li, the third section Le, and the fourth section Lei and first, second, and third inclination angles θ1, θ2, and θ3 was applied.

<FIG> illustrates a region B of a cooling fluid discharge space of the apparatus body (<NUM> in <FIG>) for each case by applying seven cases, among eight cases, as Embodiment A.

In addition, <FIG> illustrates a volume C2 of a space formed between a surface of the apparatus body (<NUM> in <FIG>) and a surface of the steel sheet (<NUM> in <FIG>) for each case by applying the seven cases of <FIG> as Embodiment A. <FIG> illustrates a cooling flow rate F for each case by applying the seven cases of <FIG> as Embodiment A, <FIG> illustrates maximum shear stress G on a surface of a steel sheet in a discharge direction of a cooling fluid for each case by applying the seven cases of <FIG> as Embodiment A, and <FIG> illustrates maximum shear stress G on a surface of a steel sheet in a discharge direction of a cooling fluid depending on supply pressure of supplying an output H, for example, a cooling fluid, of the supply means (<NUM> of <FIG> and <NUM> of <FIG>) for supplying the cooling fluid from the apparatus body (<NUM> of <FIG>) at regular pressure when Case <NUM> and Case <NUM> of <FIG> are applied.

As can be seen from results of <FIG>, an area B of a cooling fluid discharge space in each of Cases <NUM> to <NUM> and Case <NUM> was about <NUM>% wider than that of Case <NUM>.

As can be seen from results of <FIG>, a volume C2 of a space formed between the surface of the apparatus body (<NUM> in <FIG>) and the surface of the steel sheet (<NUM> in <FIG>) was about <NUM>% larger than that of each of Case <NUM> and Cases <NUM> to <NUM>.

As can be seen from results of <FIG>, a cooling flow rate F of each of Cases <NUM> to <NUM> and Case <NUM> was increased by about <NUM>% as compared with Case <NUM>, and thus, cooling efficiency was improved.

As can be seen from results of <FIG>, maximum shear stress G on the surface of the steel sheet was decreased by about <NUM>% in the discharge direction of the cooling fluid in Cases <NUM> to <NUM> and Case <NUM>, as compared with Case <NUM>.

Referring to <FIG>, even in Case <NUM> in which the output H of the supply means (<NUM> in <FIG> and <NUM> in <FIG>) for supplying the cooling fluid was increased as compared with case <NUM>, maximum shear stress G on the surface of the steel sheet was not increased as compared with Case <NUM>, and thus, in Case <NUM>, even when a flow rate of the cooling fluid was increased, the maximum shear stress G on the surface of the steel sheet was not increased. As a result, occurrence of defects on the surface was suppressed while improving steel sheet cooling efficiency.

In addition, as can seen in <FIG>, maximum shear stress G on the surface of the steel sheet in the discharge direction of the cooling fluid was also decreased by <NUM>% in Embodiment A of Case <NUM>, as compared with Embodiment A of Case <NUM>. In the case of an embodiment (Case <NUM> + α) in which a dimple region α (<NUM> in <FIG>) was added to an embodiment of Case <NUM>, maximum shear stress G on the surface of the steel sheet in the discharge direction of the cooling fluid was reduced by about <NUM>% as compared with Embodiment A of Case <NUM>.

Therefore, using such values, the standard of an apparatus body (<NUM> in <FIG>) of an apparatus for cooling a steel sheet may be selected according to characteristics of each steel sheet and characteristics of processes.

The above-described apparatus for cooling a steel sheet according to the present disclosure may significantly reduce surface defects of the steel sheet during manufacturing of a hot-dip magnesium-aluminum alloy-plated steel sheet and a hot-dip aluminum-plated steel sheet having excellent corrosion resistance.

Claim 1:
An apparatus for cooling a steel sheet, the apparatus comprising:
an apparatus body provided to be spaced apart from a steel sheet in a conveying path of the steel sheet; and
a cooling unit provided in the apparatus body to supply a cooling fluid,
wherein the apparatus body comprises:
a first edge body facing a first edge portion extending from one side end of the steel sheet by a predetermined distance in a center direction of the steel sheet; and
a second edge body facing a second edge portion extending from the other end of the steel sheet by a predetermined distance in the center direction of the steel sheet, and
wherein each of the first and second edge bodies is provided such that a cross-section in a direction, perpendicular to a conveying direction of the steel sheet, is stepped,
wherein each of the first and second edge bodies is provided such that a cross-section in a direction, perpendicular to the conveying direction of the steel sheet, is stepped in a width direction of the steel sheet, and a shortest distance to a surface of the steel sheet in a thickness direction of the steel sheet varies on a surface of each of the first and second edge bodies in the width direction of the steel sheet,
wherein in the apparatus body, an absolute value of a plurality of first inclination angles, formed between an extension line of a symmetry point at which the first edge body and the second edge body intersect each other and the first and second edge bodies, is <NUM>° or more to <NUM>° or less,
wherein each of the first and second edge bodies comprises:
a first inclined section forming the first inclination angle together with the symmetry point and being a region inclined in a direction away from the steel sheet;
a non-inclined section, connected to the first inclined section, from which a shortest distance to the steel sheet in the thickness direction of the steel sheet is provided to be constant; and
a second inclined section connected to the non-inclined section and being a region inclined in a direction toward the steel sheet.