FORM 2

THE PATENTSACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. PLATINGDEVICEAND PLATING METHOD
2.
1. (A) POSCO
(B) Republic of Korea
(C) (Goedong-dong) 6261, Donghaean-ro, Nam-gu, Pohang-si, Gyeongsangbuk-do
37859 Republic of Korea
The following specification particularly describes the invention and the manner in which it is to be performed.
【Technical Field】
The present invention relates to an apparatus and a method for continuously plating a surface of a steel plate with molten metal.
【Background Art】
A technology for imparting corrosion resistance by plating a surface of a steel plate with zinc-based metal or a metal alloy is widely used. A plated steel plate has excellent corrosion resistance, and thus the use of the plated steel plate is being gradually increased in the fields of typical building materials as well as exterior plates of home appliances, vehicles, ships, and the like that require an aesthetically attractive surface management.
A molten zinc plating facility (continuous galvanizing line (CGL)) refers to a facility for producing plated steel plates by depositing molten zinc on the surface of the steel plate. In the molten zinc plating facility, the steel plate is plated by being immersed in the molten zinc accommodated in a plating pot while passing a sink roll disposed in the plating pot.
The direction of the steel plate on which the molten zinc is deposited is changed while passing the sink roll, such that the steel plate comes out of an upper side of the plating pot. Subsequently, the steel plate, which is extracted from the zinc plating pot, is subjected to a process of adjusting a plating coating weight on the surface of the steel plate and a process of cooling a plating layer, and then used to manufacture a plated steel plate.
Recently, the plated steel plates are mass-produced by various manufacturers, and thus there is a need for development on a discriminative technology capable of simplifying a plating process and improving plating quality in order to further increase product competitiveness.

【DISCLOSURE】
【Technical Problem】
The present invention has been made in an effort to provide a plating apparatus and a plating method capable of simplifying a process and improving productivity and quality of products.
The present invention has also been made in an effort to provide a plating apparatus and a plating method capable of more easily and precisely controlling a plating coating weight.
The present invention has also been made in an effort to provide a plating apparatus and a plating method capable of simplifying a process of controlling a plating coating weight and minimizing a plating defect that may occur during the process of controlling the plating coating weight.
The present invention has also been made in an effort to provide a plating apparatus and a plating method capable of simplifying a process of cooling a steel plate and more quickly performing a cooling process.
The present invention has also been made in an effort to provide a plating apparatus and a plating method capable of improving plating quality by minimizing a plating coating weight on a plated steel plate or a deviation between textures of plating layers.
The present invention has also been made in an effort to provide a plating apparatus and a plating method capable of manufacturing plated steel plates having various compositions.
【Technical Solution】
An exemplary embodiment of the present invention provides a plating apparatus including: a plating bath which plates a steel plate with molten metal; a wiping unit which

is disposed at one side or both sides of the steel plate at a rear end of the plating bath in a traveling direction of the steel plate and controls a plating coating weight on the steel plate; and a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate, in which the wiping unit includes a knife which is in contact with a plating layer on the surface of the steel plate and controls a plating coating weight, and a refrigerant supplying unit which supplies the knife with a cryogenic liquid including liquid nitrogen or liquid helium to cool the knife.
Another exemplary embodiment of the present invention provides a plating apparatus including: a plating bath which plates a steel plate with molten metal; a wiping unit which is disposed at one side or both sides of the steel plate at a rear end of the plating bath in a traveling direction of the steel plate and controls a plating coating weight on the steel plate; and a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate, in which the cooling unit includes one or more cooling bodies which are in close contact with a plating layer on a surface of the steel plate and cool the plating layer, and a refrigerant supplying unit which supplies the cooling bodies with a cryogenic liquid including liquid nitrogen or liquid helium to cool the cooling bodies.
Still another exemplary embodiment of the present invention provides a plating apparatus including: a plating bath which plates a steel plate with molten metal; a wiping unit which is disposed at one side or both sides of the steel plate at a rear end of the plating bath in a traveling direction of the steel plate and controls a plating coating weight on the steel plate; and a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate, in which the wiping unit includes a knife which is in

contact with a plating layer on the surface of the steel plate and controls a plating coating weight, and a refrigerant supplying unit which supplies the knife with a cryogenic liquid including liquid nitrogen or liquid helium to cool the knife, and the cooling unit includes one or more cooling bodies which are in close contact with the plating layer on the surface of the steel plate and cool the plating layer, and a refrigerant supplying unit which supplies the cooling bodies with a cryogenic liquid including liquid nitrogen or liquid helium to cool the cooling bodies.
The knife may include a body which extends in a width direction of the steel plate and has an interior in which the cryogenic liquid is circulated, and a tip portion which is installed at a tip of the body and comes into contact with the plating layer on the steel plate to control the plating coating weight.
The tip portion of the knife may be cooled to a temperature of -250°C to 5°C.
The knife may include a rotating body which is rotatably installed, extends in the width direction of the steel plate, and has an interior in which the cryogenic liquid is circulated, tip portions which are installed on an outer circumferential surface of the rotating body at intervals in a circumferential direction and come into contact with the plating layer on the surface of the steel plate to control the plating coating weight, and a rotational drive unit which is connected to the rotating body and rotates the rotating body to dispose one tip portion toward the surface of the steel plate.
The tip portion may be detachably installed on the body or the rotating body.
The wiping unit may further include a load sensor which is provided on the knife and detects a contact load of the tip portion applied to the steel plate, and a control unit which controls pressing force of the tip portion applied to the steel plate by moving the knife relative to the steel plate in accordance with a detection signal of the load sensor.
The tip portion may be structured to be disposed in parallel with the width direction of the steel plate.

The tip portion may be structured to be disposed to be inclined with respect to the width direction of the steel plate.
The tip portion may be structured to be bent and disposed in a V shape or an inverted V shape in a movement direction of the steel plate.
The wiping unit may further include a chill roll which extends in the width direction of the steel plate at a rear end of the knife in the traveling direction of the steel plate, has an interior in which the cryogenic liquid is circulated, comes into close contact with the plating layer on the surface of the steel plate to control the plating coating weight, and rapidly cools the steel plate.
The wiping unit may further include a load sensor which is provided on the chill roll and detects a contact load of the chill roll applied to the steel plate, and a control unit which controls pressing force of the chill roll applied to the steel plate by moving the chill roll relative to the steel plate in accordance with a detection signal of the load sensor.
The wiping unit may further include a scraper which is in contact with the chill roll and removes contaminants attached to the surface of the chill roll.
The cooling body may include multiple cooling rolls which extend in the width direction of the steel plate, have interiors in which the cryogenic liquid is circulated, and press the plating layer on the surface of the steel plate to apply cold air, and the multiple cooling rolls may be disposed at intervals in the traveling direction of the steel plate.
The cooling body may further include a cooling belt which is installed to be wound around two or more cooling rolls and comes into close contact with the plating layer on the surface of the steel plate to apply cold air.
A pattern, which is to be transferred to the plating layer, may be formed on a surface of the cooling belt.
The chill roll or the cooling roll may be cooled to a temperature of -250°C to 5°C.
Surface roughness of the chill roll or the cooling roll may be 0.1 to 3 um on

average.
The cooling unit may further include a load sensor which is provided on the cooling roll and detects a contact load of the cooling belt applied to the steel plate, and a control unit which controls pressing force of the cooling belt applied to the steel plate by moving the cooling roll relative to the steel plate in accordance with a detection signal of the load sensor.
An interval between the knife and the steel plate may be decreased in a direction from the knife to the cooling roll in the movement direction of the steel plate, such that a thickness of the plating layer on the steel plate is gradually decreased.
Yet another exemplary embodiment of the present invention provides a plating method including: a plating step of plating a steel plate; an adjustment step of adjusting a plating coating weight on the steel plate; and a cooling step of cooling the steel plate, in which the adjustment step includes: primarily adjusting the plating coating weight by using a knife which is in contact with a plating layer on a surface of the steel plate; and cooling the knife by supplying the knife with a cryogenic liquid including liquid nitrogen or liquid helium.
Still yet another exemplary embodiment of the present invention provides a plating method including: a plating step of plating a steel plate; an adjustment step of adjusting a plating coating weight on the steel plate; and a cooling step of cooling the steel plate, in which the cooling step includes: cooling the steel plate by applying cold air to the steel plate by using a cooling body which is in contact with a plating layer on a surface of the steel plate; and cooling the cooling body by supplying a cryogenic liquid including liquid nitrogen or liquid helium to the cooling body.
A further exemplary embodiment of the present invention provides a plating method including: a plating step of plating a steel plate; an adjustment step of adjusting a plating coating weight on the steel plate; and a cooling step of cooling the steel plate, in which the adjustment step includes: primarily adjusting the plating coating weight by using a knife which is in contact with a plating layer on a surface of the steel plate; and cooling the knife by supplying the knife with a cryogenic liquid including liquid nitrogen or liquid helium, and the cooling step includes: cooling the steel plate by applying cold air to the steel plate by using a cooling body which is in contact with the plating layer on the surface of the steel plate; and cooling the cooling body by supplying the cooling body with the cryogenic liquid including liquid nitrogen or liquid helium.
The adjustment step may further include: cooling the steel plate by secondarily adjusting the plating coating weight by using a chill roll which is in close contact with the plating layer on the surface of the steel plate; and cooling the chill roll by supplying the chill roll with the cryogenic liquid including liquid nitrogen or liquid helium.
The adjustment step may further include: detecting a contact load of the knife or the chill roll applied to the steel plate; and controlling pressing force of the knife or the chill roll applied to the steel plate in accordance with the detected contact load.
The cooling step may further include: detecting a contact load of the cooling body applied to the steel plate; and controlling pressing force of the cooling body applied to the steel plate in accordance with the detected contact load.
The adjustment step and the cooling step may have a structure in which a thickness of the plating layer on the steel plate is gradually decreased in the movement direction of the steel plate.
In the adjustment step, a tip portion of the knife may be maintained at a temperature of -250°C to 5°C.
In the adjustment step, the chill roll may be maintained at a temperature of -250°C to 5°C.
In the cooling step, the cooling body may be maintained at a temperature of -250°C to 5°C.
The plated steel plate may be rapidly cooled at a cooling speed of 20°C/sec or higher.
The plated steel plate may be rapidly cooled to a temperature of -250°C or lower at a cooling speed of 20°C/sec or higher.
The plating method may further include using discharge gas produced by liquid nitrogen used in the adjustment step or the cooling step, as reducing gas used in a heat treatment furnace or as gas for maintaining an environment in a cooling process.
The plating method may further include, in the cooling step, forming a pattern on the surface of the plating layer by transferring a pattern formed on a surface of the cooling body to the plating layer.
【Advantageous Effects】
According to the present exemplary embodiment as described above, it is possible to ensure an easy management and improve productivity by reducing the number of quality management factors by simplifying a process. Therefore, it is possible to improve product competitiveness and profitability compared to competitors.
In addition, the steel plate is more effectively and rapidly cooled by improving cooling efficiency, and as a result, it is possible to reduce a length of a facility for cooling the steel plate, and it is possible to manufacture the plated steel plate with excellent surface quality by reducing a defect of a surface of the steel plate.
In addition, the cooling gas does not come into contact with the steel plate, and as a result, it is possible to solve a problem of scattering of zinc coatings caused by gas injection, dross, or noise in the related art.
In addition, the steel plate is rapidly cooled by using the chill roll that comes into direct contact with the steel plate, and as a result, it is possible to obtain an effect of improving plating properties even for types of steel materials that are hardly plated.
In addition, it is possible to easily and precisely control the plating coating weight,
and it is possible to manufacture the plated steel plate with high quality by minimizing a deviation between the plating coating weights or a deviation between the textures of the plating layers in the width direction of the steel plate.
【Description of the Drawings】
FIG. 1 is a schematic view illustrating a molten zinc plating apparatus according to the present exemplary embodiment.
FIG. 2 is a schematic view illustrating a structure of a knife of the molten zinc plating apparatus according to the present exemplary embodiment.
FIG. 3 is a schematic view illustrating another exemplary embodiment of the knife of the molten zinc plating apparatus according to the present exemplary embodiment.
FIG. 4 is a schematic view illustrating a structure for controlling a contact load of the knife applied to a steel plate according to the present exemplary embodiment.
FIG. 5 is a schematic view illustrating various exemplary embodiments regarding a structure of a tip portion of the knife and a structure in which the tip portion of the knife is disposed with respect to the steel plate according to the present exemplary embodiment.
FIG. 6 is a schematic view illustrating a structure of a chill roll of the molten zinc plating apparatus according to the present exemplary embodiment.
FIGS. 7 and 8 are schematic views illustrating a structure of a cooling unit of the molten zinc plating apparatus according to the present exemplary embodiment.
【Mode for Invention】
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains may easily carry out the exemplary embodiments. It can be easily understood by those skilled in the art to which the present invention
pertains that the following exemplary embodiments may be modified into various forms without departing from the concept and the scope of the present invention, and the present invention is not limited to the exemplary embodiments described herein.
It is noted that the drawings are schematic, and are not illustrated based on actual scales. Relative dimensions and proportions of parts illustrated in the drawings are exaggerated or reduced in size for the purpose of clarity and convenience in the drawings, and any dimension is just illustrative but not restrictive.
Hereinafter, in the present exemplary embodiment, a molten zinc plating apparatus for plating a surface of a steel plate with zinc-based metal or a metal alloy will be described as an example of a plating apparatus. The present plating apparatus is not limited to plating of the steel plate with the zinc-based metal or the metal alloy, and the present plating apparatus may be applied to all of the molten plating apparatuses for plating the steel plate with various types of metal materials.
FIG. 1 schematically illustrates the molten zinc plating apparatus according to the present exemplary embodiment.
As illustrated in FIG. 1, the plating apparatus of the present exemplary embodiment includes a plating bath 10 which plates a steel plate P with molten metal, a wiping unit which is disposed at one side or both sides of the steel plate at a rear end of the plating bath 10 in a traveling direction of the steel plate and controls a plating coating weight on the steel plate, and a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate.
A molten plating process is performed as the steel plate P guided to the plating bath 10 is immerged in the molten metal while passing a sink roll 12 disposed in the plating bath 10. The traveling direction of the steel plate P is changed by the sink roll 12, such that the steel plate P is moved toward a position above the plating bath 10.
The steel plate P, of which the surface is plated with the molten metal in the plating bath 10, is extracted to the position above the plating bath 10. The steel plate is used to manufacture the plated steel plate while passing through the wiping unit and the cooling unit that are sequentially disposed in the traveling direction of the steel plate. The steel plate, which is rapidly cooled by passing through the cooling unit, travels to the subsequent process via a tension roll 14.
A molten liquid made of metal and an alloy such as zinc, a zinc alloy, aluminum, and an aluminum alloy may be applied as a plating solution which may be applied to the present exemplary embodiment, and any plating solution may be applied without separate limitation as long as the plating solution is made of metal and an alloy.
In the present exemplary embodiment, the wiping unit is structured to be in direct contact with a plating layer attached to the surface of the steel plate to adjust the plating coating weight.
To this end, the wiping unit may include a knife 20 which is in contact with the plating layer on the surface of the steel plate P to control the plating coating weight, and a refrigerant supplying unit 50 which supplies the knife 20 with a cryogenic liquid including liquid nitrogen or liquid helium to cool the knife 20.
Since the knife 20 is in direct contact with the plating layer, it is possible to prevent mixing of oxides on a plating surface, and it is possible to more easily control the plating coating weight on the steel plate. Since the refrigerant supplying unit 50 cools the knife 20 with the cryogenic liquid, a temperature of the knife 20 is decreased, such that it is possible to prevent the plating solution from being fused with the knife 20 even in a state in which the knife 20 is in direct contact with the high-temperature plating layer.
In addition, in the present exemplary embodiment, the cooling unit is structured to be in direct contact with the plating layer on the surface of the steel plate to cool the steel plate.
To this end, the cooling unit may include one or more cooling bodies 60 which come into close contact with the plating layer on the surface of the steel plate to cool the plating layer, and the refrigerant supplying unit 50 which supplies the cooling bodies 60 with the cryogenic liquid including liquid nitrogen or liquid helium to cool the cooling bodies 60.
Since the cooling bodies 60 are in direct contact with the plating layer to cool the plating layer on the steel plate, it is possible to more quickly and rapidly cool the plating layer on the steel plate by maximizing a cooling ability. Since the cooling unit cools the cooling bodies 60 with the cryogenic liquid, temperatures of the cooling bodies 60 are decreased, such that it is possible to prevent the plating solution from being fused with the cooling bodies 60 even in a state in which the cooling bodies 60 are in direct contact with the high-temperature plating layer.
The refrigerant supplying unit 50 serves to supply the cryogenic liquid to the knife 20 or the cooling bodies 60, and for example, the refrigerant supplying unit 50 may include a tank which accommodates the cryogenic liquid, a supply line through which the cryogenic liquid is conveyed, and a supply pump which is installed on the supply line. Any structure of the refrigerant supplying unit 50 may be applied and the structure of the refrigerant supplying unit 50 may be variously modified as long as the refrigerant supplying unit 50 is structured to supply the cryogenic liquid.
In addition to the liquid nitrogen or the liquid helium, various liquids such as liquid argon may be used as the cryogenic liquid used for the refrigerant supplying unit 50. It is possible to further improve economic feasibility when the liquid nitrogen is used.
As described above, the knife 20 and the cooling bodies 60, which are cooled by using the cryogenic liquid, are in direct contact with the steel plate P to control the plating coating weight on the steel plate and rapidly cool the steel plate, and as a result, according to the present exemplary embodiment, it is possible to precisely control the plating coating weight on the plated steel plate, and it is possible to increase a cooling speed of the plated steel plate to 20°C/sec or higher. Therefore, it is possible to innovatively shorten a length of a facility line for cooling the steel plate and increase a production speed of products.
The cryogenic liquid, which is supplied to the knife 20 or the cooling bodies 60 by the refrigerant supplying unit 50, may be vaporized by exchanging heat with the plating layer while passing the knife 20 or the cooling bodies 60. The gas, which is discharged from the knife 20 or the cooling bodies 60, may pass through an appropriate filtration device and then be reused as reducing gas used in a heat treatment furnace in an iron manufacturing process or as gas for maintaining a non-oxidation environment in a cooling process.
FIG. 2 illustrates a specific structure of the knife according to the present exemplary embodiment.
In the present exemplary embodiment, the knives 20 are disposed to face each other at both sides of the steel plate to adjust a coating weight of a plating liquid on the both surfaces of the steel plate P. The knives 20, which are disposed at both sides of the steel plate P, have the same structure, and in the following description, only the knife disposed at one side of the steel plate will be described as an example.
As illustrated in FIG. 2, the knife 20 may include a body 22 which extends in a width direction of the steel plate P and has an interior in which the cryogenic liquid is circulated, and a tip portion 24 which is installed at a tip of the body 22 and is in contact with the plating layer on the steel plate, and the knife 20 may be structured to primarily control the plating coating weight on the surface of the steel plate.
The body 22 and the tip portion 24 may be made of metal such as stainless steel, ceramic, or a metal material coated with ceramic, which has excellent cryogenic durability, so that the body 22 and the tip portion 24 may be stably used over a long period of time in a cryogenic environment in which the liquid nitrogen is used.
The body 22 has therein a flow path 26 through which the cryogenic liquid passes. The refrigerant supplying unit 50 connected to the body 22 circulates and supplies the cryogenic liquid through the flow path 26. The flow path 26 extends to the tip of the body 22 where the tip portion 24 is positioned, in order to sufficiently cool the tip portion 24 installed at the tip of the body 22, such that the cryogenic liquid may come into contact with the tip portion 24.
In the present exemplary embodiment, the tip portion 24 may be detachably installed on the body 22.
The tip portion 24 is abraded since the tip portion 24 is continuously in contact with the high-temperature plating layer. Therefore, the tip portion 24 is configured as a consumable and replaceable component, and as a result, only the tip portion 24 may be replaced on the body 22 when the tip portion 24 is abraded, such that the knife 20 may be continuously used. The tip portion 24 may be structured to become pointy toward the tip thereof to more precisely control the plating coating weight.
The cryogenic liquid supplied into the body 22 cools the tip portion 24 while being circulated along the flow path 26, thereby maintaining the tip portion 24 in a low-temperature state. Therefore, the tip portion 24 prevents the plating solution from being attached to the tip portion 24 in the state in which the tip portion 24 is in contact with the plating layer, thereby more accurately controlling the plating coating weight primarily.
FIG. 3 illustrates another exemplary embodiment of the knife The knife
according to the exemplary embodiment in FIG. 3 is structured to have multiple tip portions so that the tip portion may be replaced and used immediately when the tip portion has a defect.
To this end, a knife 21 in the present exemplary embodiment may include a rotating body 23 which is rotatably installed, extends in the width direction of the steel plate, and has an interior in which the cryogenic liquid is circulated, tip portions 24 which are circumferentially installed at intervals on an outer circumferential surface of the rotating body 23 and are in contact with the plating layer on the surface of the steel plate P to control the plating coating weight, and a rotational drive unit which is connected to the rotating body 23 and rotates the rotating body 23 to dispose one tip portion 24 toward the surface of the steel plate.
Therefore, when the tip portion 24 has a defect such as abrasion, the rotating body 23 is rotated so that the used tip portion 24 is moved away from the steel plate and another tip portion 24 on standby is moved toward the steel plate, such that the tip portion 24 may be immediately replaced and used. As illustrated in FIG. 3, the four tip portion 24 may be disposed at an angle of 90 degrees along the outer circumferential surface of the rotating body 23. Therefore, the rotating body 23 is rotated at an angle of 90 degrees such that each of the tip portions 24 may be moved toward the surface of the steel plate. The number of tip portions 24 to be installed may be variously modified.
In the present exemplary embodiment, the rotating body 23 may be formed in a cylindrical shape. The shape of the rotating body 23 is not limited to the cylindrical shape, and for example, the aforementioned bodies 22 may be continuously disposed at an angle along an outer circumferential surface of a rotating shaft. Both tips of the rotating body 23 may be rotatably supported by a separate support (not illustrated) in the facility.
The rotating body 23 may also be made of metal such as stainless steel, ceramic, or a metal material coated with ceramic, which has excellent cryogenic durability, so that the rotating body 23 may be stably used over a long period of time in a cryogenic environment in which the liquid nitrogen is used.
The rotating body 23 has therein a flow path (not illustrated) through which the
cryogenic liquid passes. The flow path formed in the rotating body 23 may be connected to the refrigerant supplying unit 50 through both tips of the rotating shaft of the rotating body 23. The cryogenic liquid supplied from the refrigerant supplying unit 50 is circulated and supplied into the flow path in the rotating body 23 through the tips of the rotating body 23. The flow path extends to the sides where the tip portions 24 are positioned, in order to sufficiently cool the tip portions 24 installed on the outer circumferential surface of the rotating body 23, such that the cryogenic liquid may come into contact with the tip portions 24.
The tip portions 24 are installed on the surface of the rotating body 23 in an axial direction of the rotating body 23. The tip portions 24 may be detachably installed on the surface of the rotating body 23.
Any rotational drive unit may be applied as long as the rotational drive unit is structured to rotate the rotating body 23 by a preset angle. For example, as illustrated in FIG. 3, the rotational drive unit may include a step motor 27 which is connected to the rotating body 23 through a driving belt 25 and transmits power. Therefore, when the step motor 27 rotates by a predetermined degree, power is transmitted to the rotating body 23 through the driving belt 25, such that the rotating body 23 is rotated by a degree corresponding to the interval at which the tip portions 24 are disposed. As the rotating body 23 rotates, the new tip portion 24, which is installed on the surface of the rotating body 23 and on standby, is moved toward the steel plate and comes into contact with the plating layer on the surface of the steel plate. Further, as the rotating body 23 rotates, the tip portion 24, which is abraded or has a defect, is moved outward away from the surface of the steel plate, and is moved to a standby position. At the standby position, the abraded tip portion 24 is replaced or subjected to a surface polishing process.
As described above, in the present exemplary embodiment, the tip portion 24 is
simply replaced by rotating the rotating body 23 by a predetermined angle, such that it is possible to reduce the time required to replace the tip portion 24 and continuously perform the operation.
In the present exemplary embodiment, the knives 20 and 21 may cool the tip
portions 24 to -250°C to 5°C by circulating the cryogenic liquid in the knives 20 and 21.
If the temperature of the tip portion 24 is higher than 5°C, there occurs a problem in that
the high-temperature plating solution is attached to the tip portion 24. If the
temperature of the tip portion 24 is lower than -250°C, there occurs a problem in that the tip portion 24 is broken due to low-temperature brittleness.
The knives 20 and 21 are moved relative to the steel plate so that intervals from the steel plate vary, such that the plating coating weight is precisely adjusted by the tip portions 24.
The interval between the tip portion 24 and the steel plate P varies as the knife 20 further approaches the plating layer on the steel plate or moves outward away from the plating layer, and as a result, the plating coating weight on the steel plate is adjusted.
As illustrated in FIG. 4, to precisely control the plating coating weight by using the knife 20, the wiping unit may further include a load sensor 30 which is provided on the knife 20 and detects a contact load of the tip portion 24 applied to the steel plate P, and a control unit 32 which controls pressing force of the tip portion 24 applied to the steel plate by moving the knife 20 relative to the steel plate in accordance with a detection signal of the load sensor 30.
The interval between the tip portion 24 and the steel plate P may be ascertained based on the contact load of the tip portion detected by the load sensor 30. If the interval between the tip portion 24 and the steel plate P is decreased, the tip portion 24 is inserted deep into the plating layer on the steel plate such that a contact amount with the plating solution is increased and the contact load is increased, but in contrast, if the tip portion 24 is moved away from the steel plate P, the contact amount with the plating solution is decreased and the contact load is decreased.
The control unit 32 moves the knife 20 relative to the steel plate P in accordance with the plating coating weight primarily set by calculating a detection value of the load sensor 30, thereby controlling the plating coating weight.
The movement of the knife 20 relative to the steel plate may be performed by, for example, a drive unit 34 such as a driving cylinder coupled to the knife 20. Various power sources such as a driving cylinder or a motor may be used as the drive unit 34, and any drive unit may be applied as long as the drive unit may be structured to move the knife 20 rectilinearly relative to the steel plate.
In addition, the control unit 32 may check whether the apparatus has a defect by detecting a change in measured value of the load sensor 30. When the control unit 32 determines that the apparatus has a defect, a necessary operation such as an operation of replacing the tip portion 24 on the knife 20 may be immediately performed.
FIG. 5 illustrates shapes of the tip portions of the knife relative to the steel plate and a structure in which the tip portions are disposed relative to the steel plate.
In the present exemplary embodiment, the tip portion 24 installed on the knife 20 or 21 may be formed in various shapes such as a straight shape or a V shape having a bent intermediate portion. The body 22 or the rotating body 23 of the knife on which the tip portion 24 is installed may also have the same shape as the tip portion 24. For example, in a case in which the tip portion 24 is formed in a V shape, the tip of the body 22 of the knife 20 on which the tip portion 24 is installed may also be formed in the V shape identical to the shape of the tip portion 24.
As illustrated in FIG. 5, the tip portion 24 may be disposed in parallel with the width direction of the steel plate P. In addition, the tip portion 24 may be disposed to be inclined with respect to the width direction of the steel plate.
In addition, in the case in which the tip portion 24 is bent in a V shape, the tip portion 24 may be disposed in an inverted V shape or a V shape so that the bent portion is directed in the movement direction of the steel plate or a direction opposite to the movement direction of the steel plate.
Since the tip portion 24, which is in contact with the plating layer, is variously disposed with respect to the steel plate P as described above, it is possible to more smoothly adjust the coating weight of the plating layer by reducing the load of the plating solution applied to the tip portion 24 when the tip portion 24 comes into contact with the plating layer.
As illustrated in FIGS. 1 and 6, the wiping unit may further include chill rolls 40 which are disposed at the rear end of the knife 20 in the traveling direction of the steel plate to more precisely control the plating coating weight on the steel plate and rapidly cool the plating layer on the steel plate.
The chill rolls 40 are roll structures which are disposed in the width direction of the steel plate and pressed against and in close contact with the plating layer. Both tips of each of the chill rolls 40 may be rotatably supported by a separate support (not illustrated) in the facility. The chill roll 40 is structured to be freely rotatable, and may be structured to be rotated in conjunction with the movement of the steel plate or connected to a separate driving source and rotated at a preset speed.
In the present exemplary embodiment, surface roughness of the chill roll 40 may be 0.1 to 3 um on average.
If the surface roughness of the chill roll 40 is higher than 3 um, there occurs a problem of non-uniform post-processing due to degraded surface quality. If the surface roughness of the chill roll 40 is lower than 0.1 um, there occurs a problem in that post-processing properties such as a chemical conversion treatment deteriorate.
The chill roll 40 is structured to be cooled to a low temperature as the cryogenic
liquid is circulated in the chill roll 40. The chill roll 40 may be made of metal such as stainless steel, ceramic, or a metal material coated with ceramic, which has excellent cryogenic durability, so that the chill roll 40 may be stably used over a long period of time in a cryogenic environment in which the liquid nitrogen is used.
As illustrated in FIG. 6, the chill roll 40 has therein a flow path through which the
cryogenic liquid passes. The flow path formed in the chill roll 40 may be connected to
the refrigerant supplying unit (see reference numeral 50 in FIG. 1) through both tips of a
rotating shaft of the chill roll 40. The cryogenic liquid supplied from the refrigerant
supplying unit 50 is circulated and supplied into the flow path in the chill roll 40 through
the tips of the chill roll 40. A surface of the chill roll 40 is maintained in a
low-temperature cooled state by the cryogenic liquid supplied into the chill roll 40. Therefore, the chill roll 40 may prevent the plating solution from being attached to the surface of the chill roll 40 in the state in which the chill roll 40 is in contact with the plating layer on the steel plate P, and may rapidly cool the plating layer.
The chill roll 40 is pressed against and in close contact with the plating layer on the surface of the steel plate P, thereby secondarily and precisely controlling the plating coating weight on the steel plate on which the plating coating weight is primarily controlled by the knife 20. Furthermore, the chill roll 40 may rapidly cool the plating layer by directly exchanging heat with the steel plate in the state in which the chill roll 40 is pressed against and in close contact with the plating layer on the steel plate.
In the present exemplary embodiment, the chill roll 40 may lower the temperature to -250°C to 5°C by circulating the cryogenic liquid in the chill roll 40. If the temperature of the chill roll 40 is higher than 5°C, there occurs a problem in that an effect of improving a cooling performance and surface quality of the plated steel plate deteriorates. If the temperature of the chill roll 40 is lower than -250°C, there occurs a problem in that the chill roll 40 is broken due to low-temperature brittleness.
As described above, the plating apparatus of the present exemplary embodiment may more precisely control the plating coating weight and adjust a thickness of the plating layer by using the low-temperature knife 20 and the low-temperature chill roll 40 which are in contact with the plating solution on the surface of the steel plate. In addition, since the chill roll 40, which is cooled to a low temperature, presses and rapidly cools the plating layer, the texture of the plating layer may become fine, a small and uniform surface solidified texture may be obtained, and a deviation between the plating coating weights or a deviation between the plating layer textures in the width direction may be effectively reduced.
The chill roll 40 comes into contact with the plating layer to solidify the plating solution in a shorter time, and as a result, the plating apparatus may rapidly cool the steel plate at a cooling speed of 20°C/sec. In addition, the chill roll 40 cools the plating layer while pressing the plating layer under a predetermined pressure, such that it is possible to improve a plating performance even for types of steel materials that are hardly plated.
In addition, in the present exemplary embodiment, the sink roll 12 in the plating bath 10 and the chill rolls 40 cooperate with each other to support the steel plate P, and as a result, a bending phenomenon in which the steel plate is curved in the width direction does not occur while the steel plate passes the contact knife 20. That is, the steel plate passes the sink roll 12 and the chill rolls 40 at the front end and the rear end of the knife 20 in the movement direction of the steel plate. Therefore, the steel plate P passes the knife 20 without the bending phenomenon in a state in which the steel plate P is unfolded in a flatwise manner by the sink roll 12 and the chill rolls 40.
If the steel plate is bent, a deviation between the plating coating weights in the width direction occurs, and a plated surface defect such as a comb-pattern defect caused by excessive side plating occurs.The plating surface defect often occurs in the
related art due to the bending phenomenon of the steel plate, but according to the present exemplary embodiment, the bending phenomenon of the steel plate is prevented, and as a result, it is possible to manufacture the plated steel plate having almost neither deviation between the plating coating weights nor deviation between the plating layer textures in the width direction.
Similar to the knife, to precisely control the plating coating weight by using the chill roll 40, the wiping unit of the present exemplary embodiment may further include a load sensor 30 which is provided on the chill roll 40 and detects a contact load of the chill roll 40 applied to the steel plate, and a control unit 32 which controls pressing force of the chill roll 40 applied to the steel plate by moving the chill roll 40 relative to the steel plate by operating the drive unit 34 in accordance with a detection signal of the load sensor.
As the chill roll 40 approaches the plating layer on the steel plate P or moves outward away from the plating layer, the interval between the chill roll 40 and the steel plate varies, such that the plating coating weight on the steel plate and the thickness of the plating layer are precisely adjusted.
Because the structures of the load sensor and the control unit with respect to the chill roll 40 are the same as the aforementioned structures of the load sensor 30, the control unit 32, and the drive unit 34 with respect to the knife 20, like reference numerals are used, and the structures and the operations of the load sensor and the control unit with respect to the chill roll 40 will be described with reference to the descriptions of the load sensor 30 and the control unit 32 with respect to the knife 20, and hereinafter, detailed descriptions thereof will be described. Therefore, the control unit 32 calculates a detection value of the load sensor 30 and presses the plating layer by moving the chill roll 40 relative to the steel plate, and as a result, it is possible to precisely control the plating coating weight and the thickness of the plating layer according to the plating
coating weight. In addition, the plating layer is pressed and rapidly cooled by the chill roll at a cooling speed of 20°C/sec or higher, and as a result, it is possible to minimize a deviation between the plating coating weights in the width direction and obtain the plating layer having finer textures.
In addition, the wiping unit is structured to remove contaminants on the surface of the chill roll 40 to prepare for a case in which the surface of the chill roll 40 is contaminated. To this end, as illustrated in FIG. 7, the wiping unit may further include a scraper 44 which comes into contact with the chill roll 40 to remove contaminants attached to the surface of the chill roll 40. The scraper 44 extends in the axial direction of the chill roll 40 and may be installed to be in contact with the surface of the chill roll 40. Therefore, as the chill roll 40 rotates, the contaminants attached to the surface of the chill roll 40 are removed from the surface of the chill roll 40 by being caught by the scraper 44.
The plating coating weight is precisely adjusted by the wiping unit, and the rapid cooling is performed by the wiping unit. The steel plate is rapidly cooled to a preset or lower temperature while passing through the cooling unit disposed at the rear end of the wiping unit, and the thickness of the plating layer is precisely controlled.
FIGS. 7 and 8 illustrate the structure of the cooling unit according to the present exemplary embodiment.
The cooling unit may include the one or more cooling bodies 60 which are in close contact with the plating layer on the surface of the steel plate to cool the plating layer, and the refrigerant supplying unit 50 which supplies the cooling bodies 60 with the cryogenic liquid including liquid nitrogen or liquid helium to cool the cooling bodies 60.
In the present exemplary embodiment, the cooling body 60 may include cooling rolls 62 which extend in the width direction of the steel plate, has interiors in which the cryogenic liquid is circulated, and applies cold air to the plating layer on the surface of the steel plate P while pressing the plating layer on the surface of the steel plate P. The multiple cooling rolls 62 may be structured to be disposed at multiple stages at intervals in the traveling direction of the steel plate.
Similar to the chill roll 40, the cooling roll 62 is a roll structure disposed in the width direction of the steel plate. Both tips of each of the cooling rolls 62 may be rotatably supported by a separate support (not illustrated) in the facility. The cooling roll 62 is structured to be freely rotatable, and may be structured to be rotated in conjunction with the movement of the steel plate or connected to a separate driving source and rotated at a preset speed.
The cooling roll 62 is structured to be cooled to a low temperature as the cryogenic liquid is circulated in the cooling roll 62.
Similar to the chill roll 40, the cooling roll 62 has therein a flow path 64 through which the cryogenic liquid passes. The flow path 64 formed in the cooling roll 62 may be connected to the refrigerant supplying unit (see reference numeral 50 in FIG. 1) through both tips of a rotating shaft of the cooling roll 62. The cryogenic liquid supplied from the refrigerant supplying unit 50 is circulated and supplied into the flow path 64 in the cooling roll 62 through the tips of the cooling roll 62. A surface of the cooling roll 62 is maintained in a low-temperature cooled state by the cryogenic liquid supplied into the cooling roll 62.
In addition, the cooling body 60 may further include a cooling belt 66 which is installed to be wound between the two or more cooling rolls 62 and is pressed against and in close contact with the plating layer on the surface of the steel plate P to apply cold air to the plating layer on the surface of the steel plate P. In this structure, instead of the cooling roll 62, the cooling belt 66 is in direct contact with the plating layer on the steel plate.
The cooling roll 62 and the cooling belt 66 may be made of metal such as stainless steel, ceramic, or a metal material coated with ceramic, which has excellent cryogenic durability, so that the cooling roll 62 and the cooling belt 66 may be stably used over a long period of time in an cryogenic environment in which the liquid nitrogen is used.
In the present exemplary embodiment, surface roughness of the cooling roll 62 or the cooling belt 66 which is in contact with the surface of the steel plate may be 0.1 to 3 um on average. If the surface roughness of the cooling roll 62 or the cooling belt 66 is higher than 3 um, there occurs a problem of non-uniform post-processing due to degraded surface quality, and if the surface roughness is lower than 0.1 um, there occurs a problem in that post-processing properties such as a chemical conversion treatment deteriorate.
In the present exemplary embodiment, the cooling belt 66 is wound around the two cooling rolls 62 to constitute one cooling body 60, and the one or multiple cooling bodies 60 are disposed at intervals in the traveling direction of the steel plate. The number of cooling bodies 60, the interval at which the cooling bodies 60 are installed, or the like may be variously modified in accordance with facilities or process conditions.
The respective cooling bodies 60 may have the same structure, and hereinafter, the structure of the cooling body disposed at one side will be described as an example.
The cooling belt 66 is installed to be wound between the two cooling rolls 62 spaced apart from each other, and the cooling belt 66 is in surface-to-surface contact with the plating layer on the surface of the steel plate. For example, the cooling belt 66 may be rotated while being synchronized with a movement speed of the steel plate by the rotations of the cooling rolls 62 in the state in which the cooling belt 66 is in contact with the steel plate. Since the cooling belt 66 is rotated while being synchronized with the movement speed of the steel plate, it is possible to minimize friction between the steel plate and the cooling belt 66 and prevent damage to the plating layer caused by friction.
The cooling roll 62 cools the cooling belt 66, which is provided outside the cooling roll 62, to a low temperature. Since the cooling belt 66 is in surface-to-surface contact with the plating layer in the state in which the cooling belt 66 is cooled to a low temperature by the cooling roll 62, it is possible to rapidly cool the plating layer. That is, the cooling belt 66 is in surface-to-surface contact with the plating layer on the surface of the steel plate between the two cooling rolls 62. Therefore, a cooling area with respect to the plating layer on the steel plate is increased corresponding to a contact area by the cooling belt 66. Therefore, the cooling unit of the present exemplary embodiment may increase a cooling speed by increasing the cooling area with respect to the plating layer on the steel plate by using the cooling belt 66.
In the present exemplary embodiment, the cooling roll 62 may lower a temperature of the cooling belt 66, which is in contact with the plating layer, to -250°C to 5°C by circulating the cryogenic liquid into the cooling roll 62. If the temperature of the cooling belt 66 is higher than 5°C, there occurs a problem in that an effect of improving a cooling performance and surface quality of the plated steel plate deteriorates. If the temperature of the cooling belt 66 is lower than -250°C, there occurs a problem in that the cooling belt 66 is broken due to low-temperature brittleness.
As described above, the plating solution is rapidly solidified in a shorter time since the cooling belt 66 installed on the cooling rolls 62 is in contact with the plating layer, and as a result, the plating apparatus of the present exemplary embodiment may rapidly cool the steel plate at a cooling speed of 20°C/sec to a temperature of -250°C or lower by using the cooling unit.
The cooling unit may tense the cooling belt 66 tautly by adjusting the interval between the two cooling rolls 62 that constitutes the cooling unit. As the cooling belt 66 is tensed and unfolded tautly, the contact and the pressing force between the cooling
belt 66 and the plating layer on the surface of the steel plate are uniformly maintained, such that the plating layer may be more uniformly pressed and cooled.
To this end, as illustrated in FIG. 8, the cooling unit may be provided with a driving cylinder 68 which is disposed between the two cooling rolls 62 around which the cooling belt 66 is wound and increases or decreases the interval between the cooling rolls 62. The driving cylinder 68 is operated in accordance with a signal of the control unit 32 and widens a space between the cooling rolls 62. As the space between the cooling rolls 62 is widened, the cooling belt 66 is unfolded tautly.
In addition, the cooling roll 62 may precisely adjust pressing force applied to the plating layer on the steel plate. To this end, although not illustrated, similar to the chill roll 40, the cooling roll 62 may be provided with a load sensor, a control unit, and a drive unit. Because the structures for adjusting the pressing force of the cooling roll are the same as the aforementioned structures of the load sensor 30, the control unit 32, and the drive unit 34 with respect to the chill roll 40, detailed descriptions of the structures and the operations will be omitted. Therefore, the cooling rolls press and attach the cooling belt closely to the steel plate with preset pressure, thereby precisely controlling the thickness of the plating layer on the steel plate.
That is, the interval between the steel plate and the cooling belt 66 wound around the cooling rolls 62 varies as the cooling roll 62 approaches the plating layer on the steel plate or moves outward away from the plating layer, such that the pressing force applied to the plating layer on the steel plate is adjusted. As described above, the cooling unit calculates a detection value of the load sensor and precisely adjusts the pressing force, which is applied to the plating layer by the cooling belt 66, by moving the cooling rolls 62 relative to the steel plate, thereby precisely controlling the thickness of the plating layer.
Here, the cooling belts 66 of the multiple cooling bodies 60, which are disposed
in the movement direction of the steel plate, may apply the same or different pressing force generated by the movements of the cooling rolls 62. That is, the respective cooling bodies 60, which are disposed in the movement direction of the steel plate, may come into close contact with the steel plate with the same pressing force. Alternatively, the respective cooling bodies 60 may be in close contact with the steel plate while the pressing force is gradually increased in the movement direction of the steel plate. In this structure, the steel plate receives pressing force that gradually increases while passing the cooling bodies 60, such that the thickness of the plating layer may be gradually decreased.
Therefore, the thickness of the plating layer is gradually decreased in the direction from the knife 20 to the cooling unit in the movement direction of the steel plate, such that the thickness of the plating layer may be more precisely controlled.
In addition, the cooling unit rapidly cools the plating layer while pressing the plating layer under predetermined pressure, such that it is possible to improve a plating performance even for types of steel materials that are hardly plated. In addition, the cooling unit may finally control the surface roughness of the plating layer on the steel plate by using the cooling roll or the cooling belt disposed at the last position at the rear end in the traveling direction of the steel plate. Therefore, it is possible to produce a product with higher quality.
As described above, the plating apparatus of the present exemplary embodiment cools the plating layer by bringing the cooling belt, which is cooled by the cryogenic liquid, into close contact with the plating layer, and as a result, it is possible to rapidly cool the plating layer in comparison with the related art. The cooling of the plated steel plate directly affects surface quality of a product. If a plating layer, which is not solidified, comes into contact with contaminated gas or a roll at a rear end of a facility, this contact directly causes a surface defect, and therefore, the plating layer needs to be
completely solidified before the plating layer enters the rear end of the facility. In the case of the structure in the related art, because gas or a water-cooled method is used, a cooling ability is degraded because of a low heat capacity, and a very long multi-stage cooling line is required to completely solidify the plating layer by cooling the plated steel plate to a predetermined or lower temperature. Therefore, in the related art, because a cooling line is significantly complicated and a facility has a very large size, it is difficult to effectively manage the facility, and as a result, a surface defect often occurs. In particular, it is difficult to obtain a sufficient cooling effect through a method of using gas in the related art in a case in which there is a great difference between a temperature when the plating layer begins to be solidified and a temperature when the plating layer is completely solidified, like the steel plate plated with an alloy including a large amount of Al and a large amount of Mg in a Zn plating solution. For this reason, the plating layer cannot be appropriately cooled, and as a result, plating layer textures, which contain Al and Mg, metal having high oxidizability, and are coarse and weak, are created, surface defects of the plating layer such as black stops or black defects are generated in this area, and there occur problems of occurrence of plating layer cracks and deterioration in corrosion resistance.
In contrast, in the case of the present exemplary embodiment, the cooling belt 66 comes into direct contact with the plating layer on the steel plate and applies a cooling ability of the cryogenic liquid to the plating layer, and as a result, it is possible to further improve the cooling efficiency. Therefore, it is possible to greatly shorten the time required to cool the plating layer. Therefore, according to the present exemplary embodiment, since a cooling speed of the plated steel plate is increased to 20°C/sec or higher, it is possible to further reduce a facility line of the cooling unit. In addition, since no gas comes into direct contact with the steel plate, it is possible to minimize the occurrence of surface defects, obtain smaller and uniform surface textures, and thus
manufacture the plated steel plate with high quality. In addition, since no cooling gas is used, it is possible to prevent the occurrence of dust harmful to the environment.
In addition, in the present exemplary embodiment, the cooling belt 66 may be structured to imprint and form patterns on the plating layer during the process of pressing and cooling the plating layer on the plated steel plate. Here, the patterns may mean repetitive patterns or design.
Since the plating layer on the plated steel plate is affected by a shape of a surface of the cooling belt which is in contact with the plating layer for cooling the plating layer, it is possible to process the surface of the plating layer by the structure in which various patterns are formed on the cooling belt and transferred to the plating layer. To this end, patterns to be transferred to the plating layer may be formed on the surface of the cooling belt 66. Therefore, while the cooling belt is pressed against and in close contact with the plating layer and cools the plating layer, the patterns formed on the surface of the cooling belt are pressed against and transferred to the plating layer, such that patterns identical to the patterns on the cooling belt are formed on the plating layer.
As described above, the cooling belt comes into contact with the plating layer on the plated steel plate, and the plating layer is rapidly cooled, such that the patterns may be easily formed on the plating layer without using a separate device for forming patterns.
Hereinafter, a plating process according to the present exemplary embodiment will be described.
According to the present exemplary embodiment, the steel plate, which is plated with molten zinc through the plating bath, is manufactured as the plated steel plate through a process of moving the steel plate to the position above the plating bath and adjusting the plating coating weight on the steel plate, and a process of cooling the steel plate.
To adjust the plating coating weight on the steel plate, the plating coating weight on the steel plate, which comes out of the plating bath, is primarily controlled by the low-temperature knife which primarily comes into contact with the plating layer on the surface of the steel plate. Further, the plating coating weight is secondarily controlled 5 by the low-temperature chill roll which comes into contact with the plating layer on the surface of the steel plate at the rear end of the knife.
The plating coating weights may be precisely adjusted by the knife and the chill roll by detecting the contact loads of the knife and the chill roll applied to the steel plate, and controlling the pressing force by moving the knife and the chill roll relative to the
10 steel plate in accordance with the detected contact loads.
The knife and the chill roll are cooled to a low temperature as the cryogenic liquid such as liquid nitrogen is supplied into the knife and the chill roll. The tip portion installed on the knife is cooled to a temperature of 5°C or lower by the cryogenic liquid supplied into the knife. Therefore, the plating solution is not fused with the tip portion
15 cooled to a low temperature in the state in which the tip portion is in contact with the plating layer to adjust the plating coating weight. Therefore, it is possible to accurately control the plating coating weight of the plating layer in the state in which the tip portion of the knife is physically in contact with the plating layer. As described above, the plating coating weight of the plating layer on the steel plate, which comes out of the
20 plating bath, is primarily controlled by the knife.
The chill roll comes into contact with the plating layer on the steel plate and physically presses the plating layer of which the coating weight has been primarily controlled by the knife, thereby secondarily and more precisely controlling the plating coating weight.
25 The chill roll is also cooled to a low temperature by the cryogenic liquid supplied
into the chill roll, such that the surface of the chill roll, which is in contact with the plating
32 layer, is cooled to 5°C or lower. Therefore, the plating solution is not attached to the surface of the chill roll in the state in which the chill roll is in contact with and pressed against the plating layer. Therefore, it is possible to precisely control the plating coating weight of the plating layer and adjust the thickness of the plating layer on the steel plate by pressing the chill roll against the plating layer.
The plating layer on the steel plate is rapidly cooled by the low-temperature chill roll during the process of pressing the chill roll against the steel plate and controlling the plating coating weight. As described above, in the state in which the chill roll is cooled by the cryogenic liquid, the plating layer, which is in contact with the chill roll, is rapidly cooled while exchanging heat with the chill roll. As described above, the chill roll comes into contact with the plating layer and cools the plating layer, such that the plated steel plate may be rapidly cooled at a cooling speed of 20°C/sec or higher.
The steel plate, which is rapidly cooled while passing the chill roll, is rapidly cooled to a preset or lower temperature while passing through a cooling section disposed at the rear end of the chill roll.
The multiple units, which include the cooling rolls and the cooling belts as the cooling bodies, are continuously disposed in the cooling section, and the cooling belt of each of the units is pressed against and in close contact with the plating layer on the surface of the steel plate.
Similar to the chill roll, the cooling roll is cooled to a low temperature as the cryogenic liquid such as liquid nitrogen is supplied into the cooling roll. The cold air of the cooling roll is applied to the plating layer through the cooling belt, thereby rapidly cooling the plating layer.
Since the cooling belt is cooled to a low temperature by the cryogenic liquid, the plating layer is not attached to the cooling belt in the state in which the cooling belt is pressed against the plating layer.
The cooling belt cools the plating layer in the state in which the cooling belt presses the plating layer on the steel plate with appropriate pressure. The pressing force of the cooling belt applied to the steel plate may be precisely controlled by detecting the contact load of the cooling belt applied to the steel plate, and moving the cooling belt relative to the steel plate in accordance with the detected contact load.
Therefore, the plated steel plate, which has passed the chill roll, is cooled by the cooling belt while passing through the cooling section, such that the plated steel plate may be rapidly cooled to a temperature of -250°C or lower at a cooling speed of 20°C/sec or higher.
The chill roll and the cooling belt come into direct contact with and press the plating layer during the process of adjusting the plating coating weight and the process of cooling the plating layer, such that the thickness of the plating layer on the steel plate is gradually decreased in the movement direction of the steel plate, and as a result, it is possible to more precisely control the thickness of the plating layer on the steel plate.
In addition, since the plating layer is cooled under pressure by the chill roll and the cooling belt, it is possible to improve plating properties molten zinc as well as types of steel materials that are hardly plated.
The liquid nitrogen may be vaporized during the process of adjusting the plating coating weight and the process of cooling the plating layer, and the gas discharged during these processes may be subjected to a filtration process and then reused as reducing gas used in a heat treatment furnace or as gas for maintaining an environment for the process of cooling the plated steel plate.
Here, patterns may be formed on the surface of the plating layer on the plated steel plate during the process of cooling the plating layer on the steel plate by using the cooling belt.
While the cooling belt presses and cools the plating layer, the patterns formed on
the surface of the cooling belt push and press the plating layer. Therefore, the patterns formed on the surface of the cooling belt are transferred, as they are, to the plating layer, such that the patterns identical to the patterns formed on the surface of the cooling belt are formed on the surface of the plating layer.
As described above, the desired patterns may be simply formed on the surface of the plated steel plate during the process of cooling the plating layer.
While the exemplary embodiment of the present invention has been illustrated and described above, various modifications and other exemplary embodiments may be implemented by those skilled in the art. It is noted that all of the modifications and other exemplary embodiments are contemplated and included in the appended claims, and do not depart from the true purpose and the scope of the present invention.

10 : Plating bath 12 : Sink roll
20, 21 : Knife 22 : Body
23 : Rotating body 24 : Tip portion
25 : Driving belt 26, 42, 64 : Flow path
27 : Step motor 30 : Load sensor
32 : Control unit 34 : Drive unit
40 : Chill roll 50 : Refrigerant supplying unit
60 : Cooling body 64 : Cooling roll
66 : Cooling belt 68 : Driving cylinder
WE CLAIM: 【Claim 1】
A plating apparatus comprising:
a plating bath which plates a steel plate with molten metal;
a wiping unit which is disposed at one side or both sides of the steel plate at a rear end of the plating bath in a traveling direction of the steel plate and controls a plating coating weight on the steel plate; and
a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate,
wherein the cooling unit includes one or more cooling bodies which are in close contact with a plating layer on a surface of the steel plate and cool the plating layer, and a refrigerant supplying unit which supplies the cooling bodies with a cryogenic liquid including liquid nitrogen or liquid helium to cool the cooling bodies.
【Claim 2】
The plating apparatus of claim 1, wherein:
the wiping unit includes a knife which is in contact with the plating layer on the surface of the steel plate and controls a plating coating weight, and a refrigerant supplying unit which supplies the knife with a cryogenic liquid including liquid nitrogen or liquid helium to cool the knife.
【Claim 3】
The plating apparatus of claim 2, wherein:
the wiping unit further includes a chill roll which extends in a width direction of
the steel plate at a rear end of the knife in the traveling direction of the steel plate, has an interior in which the cryogenic liquid is circulated, comes into close contact with the plating layer on the surface of the steel plate to control the plating coating weight, and rapidly cools the steel plate.
【Claim 4】
A plating apparatus comprising:
a plating bath which plates a steel plate with molten metal;
a wiping unit which is disposed at one side or both sides of the steel plate at a rear end of the plating bath in a traveling direction of the steel plate and controls a plating coating weight on the steel plate; and
a cooling unit which is disposed at one side or both sides of the steel plate at a rear end of the wiping unit in the traveling direction of the steel plate and cools the steel plate,
wherein the wiping unit includes a knife which is in contact with the plating layer on the surface of the steel plate and controls a plating coating weight, and a refrigerant supplying unit which supplies the knife with a cryogenic liquid including liquid nitrogen or liquid helium to cool the knife.
【Claim 5】
The plating apparatus of claim 4, wherein:
the wiping unit further includes a chill roll which extends in a width direction of the steel plate at a rear end of the knife in the traveling direction of the steel plate, has an interior in which the cryogenic liquid is circulated, comes into close contact with the plating layer on the surface of the steel plate to control the plating coating weight, and rapidly cools the steel plate.
【Claim 6】
The plating apparatus of any one of claim 2 to claim 5, wherein:
the knife includes a body which extends in the width direction of the steel plate and has an interior in which the cryogenic liquid is circulated, and a tip portion which is installed at a tip of the body and comes into contact with the plating layer on the steel plate to control the plating coating weight.
【Claim 7】
The plating apparatus of any one of claim 2 to claim 5, wherein:
the knife includes a rotating body which is rotatably installed, extends in the width direction of the steel plate, and has an interior in which the cryogenic liquid is circulated, tip portions which are installed on an outer circumferential surface of the rotating body at intervals in a circumferential direction and come into contact with the plating layer on the surface of the steel plate to control the plating coating weight, and a rotational drive unit which is connected to the rotating body and rotates the rotating body to dispose one tip portion toward the surface of the steel plate.
【Claim 8】
The plating apparatus of claim 6, wherein:
the wiping unit further includes a load sensor which is provided on the knife and detects a contact load of the tip portion applied to the steel plate, and a control unit which controls pressing force of the tip portion applied to the steel plate by moving the knife relative to the steel plate in accordance with a detection signal of the load sensor.
【Claim 9】
The plating apparatus of claim 6, wherein:
the tip portion of the knife is cooled to a temperature of -250°C to 5°C.
【Claim 10】
The plating apparatus of claim 6, wherein:
the tip portion is structured to be disposed in parallel with the width direction of the steel plate.
【Claim 11】
The plating apparatus of claim 6, wherein:
the tip portion is structured to be disposed to be inclined with respect to the width direction of the steel plate.
【Claim 12】
The plating apparatus of claim 6, wherein:
the tip portion is structured to be bent and disposed in a V shape or an inverted V shape in a movement direction of the steel plate.
【Claim 13】
The plating apparatus of claim 3 or claim 5, wherein:
the wiping unit further includes a load sensor which is provided on the chill roll and detects a contact load of the chill roll applied to the steel plate, and a control unit which controls pressing force of the chill roll applied to the steel plate by moving the chill roll relative to the steel plate in accordance with a detection signal of the load sensor.
【Claim 14】
The plating apparatus of claim 3 or claim 5, wherein: the chill roll is cooled to a temperature of -250°C to 5°C.
【Claim 15】
The plating apparatus of claim 3 or claim 5, wherein:
surface roughness of the chill roll or the cooling roll is 0.1 to 3 um on average.
【Claim 16】
The plating apparatus of any one of claim 1 to claim 3, wherein:
the cooling body includes multiple cooling rolls which extend in the width direction of the steel plate, have interiors in which the cryogenic liquid is circulated, and press the plating layer on the surface of the steel plate to apply cold air, and the multiple cooling rolls are disposed at intervals in the traveling direction of the steel plate.
【Claim 17】
The plating apparatus of claim 16, wherein:
the cooling body further includes a cooling belt which is installed to be wound around two or more cooling rolls and comes into close contact with the plating layer on the surface of the steel plate to apply cold air.
【Claim 18】
The plating apparatus of claim 17, wherein:
the cooling belt is cooled to a temperature of -250°C to 5°C.
【Claim 19】
The plating apparatus of claim 17, wherein:
the cooling unit further includes a load sensor which is provided on the cooling roll and detects a contact load of the cooling belt applied to the steel plate, and a control unit which controls pressing force of the cooling belt applied to the steel plate by moving the cooling roll relative to the steel plate in accordance with a detection signal of the load sensor.
【Claim 20】
The plating apparatus of claim 16, wherein:
a pattern, which is to be transferred to the plating layer, is formed on a surface of the cooling belt.