WO2017111523A1

WO2017111523A1 - Plating device and plating method

Info

Publication number: WO2017111523A1
Application number: PCT/KR2016/015153
Authority: WO
Inventors: 김수영
Original assignee: 주식회사 포스코
Priority date: 2015-12-24
Filing date: 2016-12-23
Publication date: 2017-06-29
Also published as: CN108431284A; JP2018538448A; KR101711856B1; MX2018007843A; JP6667641B2

Abstract

A plating device is provided in order to enable a simplified process and increase productivity and product quality, the plating device comprising: a plating bath for hot-dipping a steel sheet; a wiping part disposed on the rear-end of the plating bath on one surface or both surfaces of the steel sheet along the progressing direction of the steel sheet so as to control the amount of plating attached to the steel sheet; and a cooling part disposed on the rear-end of the wiping part on one surface or both surfaces of the steel sheet along the progressing direction of the steel sheet in order to cool the steel sheet, wherein the wiping part comprises a knife and a refrigerant supply part, the knife making contact with the plating layer on the surface of the steel sheet so as to control the plating attachment amount, and the refrigerant supply part cooling the knife by supplying, to the knife, a cryogenic liquid including liquid nitrogen or liquid helium.

Description

Plating apparatus and plating method

The present invention relates to a plating apparatus and a plating method for continuously plating a molten metal on a steel sheet surface.

The technique of providing corrosion resistance is widely performed by plating a zinc type metal or a metal alloy on the surface of a steel plate. Based on the excellent corrosion resistance, the coated steel sheet is increasingly used for exterior construction materials such as home appliances, automobiles, shipbuilding, etc., which require beautiful surface management.

Continuous Galvanizing Line (CGL) is a facility for producing galvanized steel by attaching molten zinc to the surface of steel sheet. In the hot-dip galvanizing equipment, the steel sheet is plated in a plating port containing molten zinc while going through a sink roll disposed in the plating port.

Molten zinc is attached to the steel plate through the sink roll is turned to the top of the plating port. The steel sheet drawn out of the galvanizing port is then made into a plated steel sheet through a process of adjusting the coating amount on the surface of the steel sheet and then cooling the plating layer.

Recently, various companies have been mass-producing plated steel sheets. In order to enhance product competitiveness, it is required to develop differentiated technologies that can improve plating quality while simplifying the plating process.

It provides a plating apparatus and plating method that can increase productivity and product quality while simplifying the process.

The present invention provides a plating apparatus and a plating method that enable easier and precise control of the coating weight.

Provided are a plating apparatus and a plating method that simplify the plating deposition amount control process and minimize the occurrence of plating defects that may occur during the plating deposition amount control process.

Provided are a plating apparatus and a plating method that simplify the steel sheet cooling process and enable faster cooling.

The present invention provides a plating apparatus and a plating method which can improve plating quality by minimizing plating adhesion amount and plating layer structure deviation of plated steel sheet.

Provided are a plating apparatus and a plating method capable of manufacturing plated steel sheets of various compositions.

To this end, the plating apparatus of the present embodiment,

Plating bath for hot-dip steel plate, a wiping part disposed on one side or both sides of the steel plate at the rear end of the plating bath along the steel plate traveling direction to control the plating adhesion amount of the steel plate, and one side of the steel plate at the rear end of the wiping part along the steel plate traveling direction Or a cooling unit disposed on both sides to cool the steel sheet, wherein the wiping unit contacts the plating layer on the surface of the steel sheet to control the plating amount, and supplies the cryogenic liquid including liquid nitrogen or liquid helium to the knife. It may include a refrigerant supply for cooling the knife.

Plating apparatus of this embodiment,

Plating bath for hot-dip steel plate, a wiping part disposed on one side or both sides of the steel plate at the rear end of the plating bath along the steel plate traveling direction to control the plating adhesion amount of the steel plate, and one side of the steel plate at the rear end of the wiping part along the steel plate traveling direction Or a cooling unit disposed on both sides to cool the steel sheet, wherein the cooling unit is in contact with the plating layer on the surface of the steel sheet and at least one cooling body for cooling the plating layer, and the cryogenic liquid containing liquid nitrogen or liquid helium as the cooling body. It may include a refrigerant supply for supplying to cool the cooling body.

Plating apparatus of this embodiment,

Plating bath for hot-dip steel plate, a wiping part disposed on one side or both sides of the steel plate at the rear end of the plating bath along the steel plate traveling direction to control the plating adhesion amount of the steel plate, and one side of the steel plate at the rear end of the wiping part along the steel plate traveling direction Or a cooling unit disposed on both sides to cool the steel sheet, wherein the wiping unit contacts the plating layer on the surface of the steel sheet to control the plating amount, and supplies the cryogenic liquid including liquid nitrogen or liquid helium to the knife. Refrigerant supply unit for cooling the knife, The cooling unit is in contact with the plating layer on the surface of the steel plate at least one cooling body for cooling the plating layer, and supplying the cryogenic liquid containing liquid nitrogen or liquid helium to the cooling body to cool the cooling body It may include a refrigerant supply for cooling.

The knife may include a body extending in the width direction of the steel sheet and having a mild cryogenic liquid therein, and a tip portion installed at the tip of the body and in contact with the plating layer of the steel sheet to control the plating amount.

The knife may be cooled to a temperature of the tip portion -250 to 5 ℃.

The knife extends in the width direction of the steel plate and is rotatably installed therein, and a rotating body in which cryogenic liquid is circulated therein, and is disposed at intervals along the circumferential direction on the outer circumferential surface of the rotating body and in contact with the plating layer on the surface of the steel plate to control the plating amount. It may include a tip portion, and a rotary driving portion connected to the rotating body to rotate the rotating body to place one tip portion toward the steel plate surface.

The tip portion may be detachably installed on the body or the rotating body.

The wiping unit further includes a load sensor provided in the knife to detect a contact load of the tip portion with respect to the steel plate, and a control unit for controlling the pressing force against the steel sheet by moving the knife with respect to the steel plate according to the detection signal of the load sensor. It may include.

The tip portion may be a structure disposed parallel to the width direction on the steel sheet.

The tip portion may have a structure inclined with respect to the width direction of the steel sheet.

The tip portion may be bent to form a V-shape or an inverted V-shape along the moving direction of the steel sheet.

The wiping part may further include a chill roll extending from the rear end of the knife in the steel plate width direction along the moving direction of the steel plate to circulate the cryogenic liquid therein, to control the coating amount by closely contacting the plating layer on the surface of the steel plate, and to quench the steel plate. .

The wiping unit further includes a load sensor provided in the chill roll to detect a contact load of the chill roll with respect to the steel sheet, and a control unit for controlling the pressing force of the chill roll against the steel sheet by moving the chill roll with respect to the steel sheet according to the detection signal of the load sensor. It may include.

The wiping unit may further include a scraper in contact with the chill roll to remove contaminants attached to the chill roll surface.

The cooling body includes a cooling roll extending in the width direction of the steel sheet and having a cryogenic liquid circulated therein and pressurized by a plating layer on the surface of the steel sheet to apply cold air, and the plurality of cooling rolls are arranged at intervals along the advancing direction of the steel sheet. It may be a structure.

The cooling body may further include a cooling belt wound and installed between at least two cooling rolls to apply cold air in close contact with the plating layer on the surface of the steel sheet.

The cooling belt may be a pattern to be transferred to the plating layer on the surface.

The chill roll or cooling roll may be cooled to a temperature of -250 to 5 ℃.

The chill roll or cooling roll may have an average surface roughness of 0.1 to 3um.

The cooling unit is provided on the cooling roll to control the pressing force of the cooling belt against the steel sheet by moving the cooling roll with respect to the steel sheet in accordance with the load sensor for detecting the contact load of the cooling belt to the steel sheet, and the detection signal of the load sensor The control unit may further include.

In the moving direction of the steel sheet, the gap from the steel plate decreases as it goes from the knife to the cooling roll, thereby reducing the thickness of the plated layer of the steel plate.

The plating method of the present embodiment includes a plating step of plating the steel sheet, an adjusting step of adjusting the plating adhesion amount of the steel sheet, and a cooling step of cooling the steel sheet, wherein the adjusting step comprises adjusting the plating deposition amount with a knife contacting the plating layer on the surface of the steel sheet. The step of adjusting first, and cooling the knife by supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the knife.

The plating method of the present embodiment includes a plating step of plating the steel sheet, an adjusting step of adjusting the plating adhesion amount of the steel sheet, and a cooling step of cooling the steel sheet, wherein the cooling step is cold air to the steel sheet with a cooling body in contact with the plating layer on the surface of the steel sheet. Cooling the steel sheet by adding a, and supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the cooling body to cool the cooling body.

The plating method of the present embodiment includes a plating step of plating the steel sheet, an adjusting step of adjusting the plating adhesion amount of the steel sheet, and a cooling step of cooling the steel sheet, wherein the adjusting step comprises adjusting the plating deposition amount with a knife contacting the plating layer on the surface of the steel sheet. Firstly adjusting, and cooling the knife by supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the knife, wherein the cooling step comprises cooling air to the steel sheet by a cooling body in contact with a plating layer on the surface of the steel sheet. And cooling the steel sheet to supply the cryogenic liquid including liquid nitrogen or liquid helium to the cooling body to cool the cooling body.

The adjusting step includes the steps of: cooling the steel sheet while secondly adjusting the plating adhesion amount with the chill roll which is in close contact with the plating layer on the surface of the steel sheet, and supplying the cryogenic liquid containing liquid nitrogen or liquid helium to the chill roll to cool the chill roll. It may further include.

The adjusting step may further include detecting a contact load of the knife or chill roll on the steel sheet, and controlling the pressing force of the knife or chill roll on the steel sheet according to the detected contact load.

The cooling step may further include detecting a contact load of the cooling body against the steel sheet, and controlling a pressing force of the cooling body against the steel sheet according to the detected contact load.

The adjusting step and the cooling step may be a structure that gradually reduces the thickness of the plated layer of the steel sheet along the moving direction of the steel sheet.

In the adjusting step, the tip portion of the knife can be maintained at a temperature of -250 to 5 ℃.

In the adjusting step, the chillol may be maintained at a temperature of -250 to 5 ℃.

In the cooling step, the cooling body may be maintained at a temperature of -250 to 5 ℃.

The plated steel sheet may be quenched at a cooling rate of 20 ° C./sec or more.

The plated steel sheet may be quenched to a temperature of 250 ° C. or less at a cooling rate of 20 ° C./sec or more.

The method may further include using the exhaust gas by the liquid nitrogen used in the adjusting or cooling step as a reducing gas in the heat treatment furnace, an atmosphere maintaining gas of the cooling process.

In the cooling step, the method may further include transferring the pattern formed on the surface of the cooling body to the plating layer to form a pattern on the surface of the plating layer.

According to the present embodiment as described above, by simplifying the process to reduce the quality control elements, it is easy to manage and increase the productivity. As a result, it is possible to increase product competitiveness and improve profitability compared to competitors.

In addition, by quenching the steel sheet more effectively by increasing the cooling efficiency, it is possible to reduce the length of the equipment for cooling, to reduce the occurrence of steel sheet surface defects can be produced a plated steel sheet with excellent surface quality.

In addition, the cooling gas does not come into contact with the steel sheet, thereby eliminating problems of generation of galvanized scattering, dross and noise caused by conventional gas injection.

In addition, as the rapid cooling is performed by using the chill roll in direct contact with the steel sheet, it is possible to obtain an effect of improving the plating property even for non-plated steel grades.

In addition, it is easy to precisely control the plating deposition amount, it is possible to manufacture a high quality plated steel sheet by minimizing the plating deposition amount deviation or plating layer structure deviation in the width direction of the steel sheet.

1 is a schematic diagram showing a hot dip galvanizing apparatus according to the present embodiment.

2 is a schematic view showing a knife structure of the hot dip galvanizing apparatus according to the present embodiment.

3 is a schematic view showing another embodiment of a knife of the hot dip galvanizing apparatus according to the present embodiment.

4 is a schematic view showing a contact load control structure for the steel sheet of the knife according to the present embodiment.

5 is a schematic view showing various embodiments of the tip structure of the knife and the arrangement structure with respect to the steel sheet according to the present embodiment.

6 is a schematic diagram showing the structure of a chill roll of a hot dip galvanizing apparatus according to the present embodiment.

7 to 8 are schematic views showing the cooling unit structure of the hot dip galvanizing apparatus according to the present embodiment.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art can easily understand, the embodiments described below may be modified in various forms without departing from the concept and scope of the invention, and the embodiments described herein. It is not limited to the example.

It is noted that the figures are schematic and not drawn to scale. The relative dimensions and ratios of the parts in the figures have been exaggerated or reduced in size for clarity and convenience in the figures and any dimensions are merely exemplary and not limiting.

Hereinafter, the present embodiment will be described by way of example a hot dip galvanizing apparatus for plating a zinc-based metal or a metal alloy on a steel sheet surface with a plating apparatus. The present plating apparatus is not limited to the plating of zinc-based metals or metal alloys, and is applicable to both hot dip plating apparatuses for various metals.

1 schematically shows a hot dip galvanizing apparatus according to the present embodiment.

As shown in Figure 1, the plating apparatus of the present embodiment is a plating bath 10 for hot-dip steel plate (P), the steel plate is disposed on one side or both sides of the steel plate at the rear end of the plating bath 10 along the steel plate traveling direction Wiping part for controlling the plating deposition of the, and the cooling unit for cooling the steel sheet is disposed on one side or both sides of the steel plate at the rear end of the wiping portion along the steel plate traveling direction.

The steel sheet P guided to the plating bath 10 is immersed in the molten metal while passing through a sink roll 12 disposed in the plating bath 10 to perform a hot dip plating process. The steel sheet P is moved in the direction of movement by the sink roll 12 to move above the plating bath 10. The steel plate P whose surface is plated by the molten metal in the plating bath 10 is drawn out to the upper portion of the plating bath 10. The steel sheet is made of a plated steel sheet via a wiping portion and a cooling portion that are sequentially disposed along a traveling direction. The steel sheet quenched through the cooling section proceeds to the process via the tension roll (14).

The plating solution applicable in the present embodiment may be applied to both metal and alloy melts such as zinc and zinc alloys and aluminum and aluminum alloys, and may be applied without any limitation as long as the plating solution is metal and alloy.

In this embodiment, the wiping part is in direct contact with the plating layer attached to the surface of the steel sheet to have a structure for adjusting the plating adhesion amount.

To this end, the wiping unit 20 contacts the plating layer on the surface of the steel sheet P to control the coating amount, and supplies the cryogenic liquid including liquid nitrogen or liquid helium to the knife 20 to supply the knife 20. It may include a refrigerant supply unit 50 for cooling).

By directly contacting the knife 20 with the plating layer, it is possible to prevent the oxide mixing of the plating bath surface and to control the plating deposition amount of the steel sheet more easily. The coolant supply unit 50 cools the knife 20 to a cryogenic liquid, thereby lowering the temperature of the knife 20 so that the plating solution is fused to the knife 20 even when the knife 20 is in direct contact with the hot plating layer. Can be prevented.

In addition, in the present embodiment, the cooling unit is configured to cool the steel sheet by directly contacting the plating layer on the surface of the steel sheet.

To this end, the cooling unit is in contact with the plating layer on the surface of the steel sheet at least one cooling body 60 for cooling the plating layer, and supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the cooling body (60) 60 may include a refrigerant supply unit 50 for cooling.

By directly cooling the plate 60 to the plated layer to cool the plated layer of the steel sheet, it is possible to maximize the cooling capacity to quench the plated layer more quickly. The cooling unit cools the cooling body 60 to a cryogenic liquid, thereby lowering the temperature of the cooling body 60 so that the plating solution is fused to the cooling body 60 even when the cooling body 60 is in direct contact with the hot plating layer. Can be prevented.

The refrigerant supply unit 50 is for supplying cryogenic liquid to the knife 20 or the cooling body 60, for example, a tank containing cryogenic liquid, a supply line for transporting cryogenic liquid, a supply installed on a supply line It may include a pump. The refrigerant supply unit 50 is applicable to all of the structural surface to supply the cryogenic liquid can be variously modified.

As the cryogenic liquid used in the refrigerant supply unit 50, various liquids such as liquid argon may be used in addition to liquid nitrogen and liquid helium. The use of liquid nitrogen can be more economical.

As such, the knife 20 and the cooling body 60 cooled by using the cryogenic liquid directly contact the steel sheet P to control and rapidly cool the plating amount of the steel sheet, thereby precisely adjusting the plating adhesion amount of the plated steel sheet through this embodiment. It can control and can raise the cooling rate of a plated steel plate to 20 degree-C / sec or more. Therefore, it is possible to significantly shorten the equipment line length for cooling the steel sheet and increase the product production speed.

The cryogenic liquid supplied to the knife 20 or the cooling body 60 through the coolant supply unit 50 may be gasified by heat exchange with the plating layer while passing through the knife 20 or the cooling body 60. The gas discharged from the knife 20 or the cooling body 60 may be recycled by using a reducing gas in a heat treatment furnace of a steelmaking process or a gas for maintaining a non-oxidizing atmosphere in a cooling process through an appropriate filtration device. .

2 illustrates a specific structure of the knife according to the present embodiment.

In this embodiment, the knife 20 is disposed opposite to both sides of the steel sheet to adjust the deposition amount of the plating liquid on both sides of the steel sheet (P). Knife 20 disposed on both sides of the steel sheet (P) is made of the same structure, the following description will be described by way of example only a knife for one surface of the steel sheet.

As shown in FIG. 2, the knife 20 extends in the width direction of the steel plate P and has a body 22 in which a cryogenic liquid is gentle, and is installed at the tip of the body 22 and in contact with a plating layer of the steel plate. Including the tip portion 24, it may be a structure that primarily controls the amount of plating on the surface of the steel sheet.

The body 22 and the tip portion 24 are made of metal, ceramic, or ceramic coated metal such as stainless steel having excellent cryogenic durability, so that the body 22 and the tip portion 24 can be stably used in a cryogenic environment due to the use of liquid nitrogen. Can be prepared.

The body 22 has a flow path 26 formed therein so that cryogenic liquid passes therethrough. The refrigerant supply 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 where the tip 24 is positioned to sufficiently cool the tip 24 installed at the tip of the body 22, so that the cryogenic liquid can contact the tip 24.

In this embodiment, the tip part 24 may be detachably installed with respect to the body 22.

The tip portion 24 keeps in contact with the hot plating layer and wears out. Accordingly, the tip portion 24 that is consumable can be replaced to replace the tip portion 24 in the body 22 when worn, so that the knife 20 can be continuously used. The tip portion 24 may have a structure that is pointed toward the tip for more precise plating deposition control.

The cryogenic liquid supplied to the body 22 is circulated along the flow path 26 to cool the tip 24, thereby keeping the tip 24 at a low temperature. Accordingly, the tip part 24 may first control the plating adhesion layer more accurately while preventing the plating solution from being attached to the tip part 24 in the state in contact with the plating layer.

3 illustrates another embodiment of a knife. Knife according to the embodiment of Figure 3 has a structure having a plurality of tips to be used immediately to replace the tip portion.

To this end, the knife 21 of the present embodiment extends in the width direction of the steel sheet and is rotatably installed therein and a space along the circumferential direction on the outer circumferential surface of the rotating body 23 and the outer surface of the rotating body 23 circulating cryogenic liquid. The tip part 24 which is installed in contact with the plated layer on the surface of the steel sheet P and controls the plating amount, and is connected to the rotating body 23 to rotate the rotating body 23 so that the one side tip part 24 faces the steel plate surface. It may include a rotation driving unit to be disposed.

Accordingly, when an abnormality such as wear of the tip part 24 occurs, the tip part 24 is immediately moved by rotating the rotating body 23 to separate the tip part 24 in use from the steel plate and moving the other tip part 24 in the air toward the steel plate. It can be replaced. As illustrated in FIG. 3, four tip parts 24 may be disposed at an angle of 90 degrees along the outer circumferential surface of the rotating body 23. As a result, the rotating body 23 is rotated at an angle of 90 degrees to move each tip portion 24 toward the steel plate surface. The number of installation of the tip portion 24 can be variously modified.

In this embodiment, the rotating body 23 may have a cylindrical shape. The rotating body 23 is not limited to a cylindrical shape, for example, may have a structure in which the above-mentioned body 22 is continuously disposed at an angle along the outer circumferential surface of the rotating shaft. Both ends of the rotating body 23 may be rotatably supported by a separate support (not shown) on the installation.

The rotating body 23 may also be made of metal, ceramic, or ceramic coated metal material having excellent cryogenic durability such that it can be stably used for a long time in a cryogenic environment due to the use of liquid nitrogen.

The rotating body 23 is formed with a flow path (not shown) so that the cryogenic liquid passes therein. The flow path formed inside the rotating body 23 may be connected to the refrigerant supply unit 50 through both ends of the rotating shaft of the rotating body 23. The cryogenic liquid supplied from the coolant supply unit 50 is circulated and supplied to the flow path inside the rotor 23 through the tip of the rotor 23. The flow path is formed to extend to the surface on which the tip portion 24 is located to sufficiently cool the tip portion 24 installed on the outer circumferential surface of the rotating body 23 to allow the cryogenic liquid to contact the tip portion 24.

A tip portion 24 is installed along the axial direction on the surface of the rotating body 23. The tip part 24 may be detachably installed on the surface of the rotating body 23.

The rotation driving unit is applicable to all of the structural surface to rotate the rotating body 23 by a predetermined angle. For example, as shown in FIG. 3, the rotating shaft may include a step motor 27 connected to the rotating body 23 and the driving belt 25 to transmit power. Thus, when the step motor 27 is rotated by a predetermined amount, power is transmitted to the rotating body 23 through the driving belt 25 so that the rotating body 23 is rotated by the disposition interval of the tip portion 24. As the rotor 23 rotates, the new tip portion 24 provided on the rotor 23 surface in the air moves toward the steel sheet and contacts the plating layer on the steel sheet surface. And the tip portion 24 that is worn or abnormal according to the rotation of the rotor 23 is spaced outward from the steel plate surface is moved to the standby position. The worn tip 24 is processed through a replacement or surface polishing operation in the standby position.

As described above, in the present embodiment, by simply rotating the tip portion 24 by rotating the rotor 23 at a predetermined angle, the time required for replacing the tip portion 24 can be reduced and the work can be continuously performed.

In the present embodiment, the

knives

20 and 21 may circulate the cryogenic liquid therein to cool the tip portion 24 to -250 to 5 ° C. When the temperature of the tip part 24 is higher than 5 ° C., a problem arises in that the hot plating solution is attached to the tip part 24. When the temperature of the tip portion 24 is lower than −250 ° C., low temperature brittle fracture of the tip portion 24 occurs.

The

knives

20 and 21 are moved relative to the steel plate to precisely control the amount of plating deposition by the tip portion 24 by varying the distance from the steel plate.

As the knife 20 approaches the plated layer of the steel sheet further or is spaced outward from the plated layer, the gap between the tip portion 24 and the steel sheet P is changed to control the plating adhesion amount of the steel sheet.

As shown in FIG. 4, in order to precisely control the plating amount by the knife 20, the wiping part is provided in the knife 20 to detect a contact load of the tip part 24 against the steel plate P. The load sensor 30 and the control unit 32 for controlling the pressing force of the tip portion 24 with respect to the steel sheet by moving the knife 20 with respect to the steel sheet in accordance with the detection signal of the load sensor 30 have.

The interval between the tip portion 24 and the steel sheet P can be confirmed through the contact load of the tip portion detected through the load sensor 30. When the gap between the tip portion 24 and the steel sheet P is narrowed, the tip portion 24 deeply enters the plating layer of the steel sheet, and the contact load increases as the amount of contact with the plating solution increases, whereas the tip portion 24 becomes the steel sheet P. When spaced apart from) decreases the contact load with the plating solution.

The controller 32 controls the plating amount by calculating the detection value of the load sensor 30 by moving the knife 20 with respect to the steel plate P according to the plating amount set primarily.

Movement of the knife 20 relative to the steel sheet may be made through, for example, a driving unit 34 such as a driving cylinder coupled to the knife 20. The drive unit 34 may be used a variety of power sources such as a drive cylinder or a motor, it is possible to apply both of the structural surface to move the knife 20 in a straight line with respect to the steel sheet.

In addition, the control unit 32 may detect the change in the measured value of the load sensor 30, and determine whether there is a device abnormality. When determining the abnormality of the device, it is possible to immediately take the necessary measures, such as replacing the tip portion 24 in the knife 20.

5 illustrates the shape of the tip portion of the knife with respect to the steel plate and the arrangement of the tip portion with respect to the steel plate.

In the present embodiment, the tip portion 24 installed in the

knife

20, 21 may be formed in a variety of structures, such as a straight form, or a bent in the middle to form a V-shape. The body 22 or the rotating body 23 of the knife in which the tip part 24 is installed may also have the same structure as that of the tip part 24. For example, when the tip portion 24 has a V shape, the body 22 of the knife 20 on which the tip portion 24 is installed may also have a V shape having the same shape as the tip portion 24. .

As shown in FIG. 5, the tip portion 24 may be disposed parallel to the steel plate P with respect to the width direction. In addition, the tip portion 24 may be disposed to be inclined with respect to the width direction of the steel sheet.

In addition, in the case where the tip portion 24 is bent in a V shape, the bent portion may be disposed in an inverted V shape or in a V shape so that the bent portion faces the moving direction of the steel plate or faces the moving direction of the steel plate. Can be.

In this way, by varying the arrangement of the tip portion 24 in contact with the plated layer with respect to the steel plate (P), it is possible to reduce the load of the plating solution applied to the tip portion 24 when the plated layer contacts, thereby more smoothly adjusting the deposition amount of the plated layer. .

1 and 6, the wiping portion is disposed at the rear end of the knife 20 along the steel plate traveling direction to more precisely control the plating deposition amount of the steel sheet and to rapidly cool the plating layer of the steel sheet 40 It may further include.

The chill roll 40 is a roll structure that is disposed in the width direction of the steel sheet and is in close contact with the plating layer. Both ends of the chill roll 40 may be rotatably supported by a separate support (not shown) on the installation. The chill roll 40 may be freely rotatable and may be rotated according to the movement of the steel sheet or may be rotated at a set speed by being connected to a separate driving source.

In this embodiment, the chill roll 40 may have an average surface roughness of 0.1 to 3um.

If the surface roughness of the chill roll 40 is higher than 3um, a non-uniform after-treatment problem occurs due to poor surface quality. If the surface roughness of the chill roll 40 is lower than 0.1um, there is a problem that post-treatment characteristics such as chemical conversion are lowered.

The chill roll 40 has a structure in which the cryogenic liquid is circulated inside and cooled to a low temperature. The chill roll 40 may be made of metal, ceramic, or ceramic coated metal material having excellent cryogenic durability such that it can be stably used for a long time in a cryogenic environment due to the use of liquid nitrogen.

As shown in FIG. 6, a flow path is formed in the chill roll 40 to allow cryogenic liquid to pass. The flow path formed in the chill roll 40 may be connected to the refrigerant supply unit (see 50 of FIG. 1) through both ends of the rotation shaft of the chill roll 40. The cryogenic liquid supplied from the coolant supply unit 50 is circulated and supplied to the flow path inside the chill roll 40 through the tip of the chill roll 40. The surface of the chill roll 40 is maintained at a low temperature by the cryogenic liquid supplied into the chill roll 40. Thus, the chill roll 40 prevents the plating solution from adhering to the surface of the chill roll 40 in a state of being in contact with the plating layer of the steel sheet P, and rapidly cools the plating layer.

The chill roll 40 is pressed in close contact with the plating layer on the surface of the steel sheet (P) to control the plating deposition amount of the steel sheet in which the plating deposition amount is primarily controlled while passing through the knife 20. In addition, the chill roll 40 is capable of rapidly cooling the plating layer through direct heat exchange with the steel sheet in a state of being in close contact with the steel plate plating layer.

In the present embodiment, the chill roll 40 may circulate the cryogenic liquid therein to cool the temperature to -250 to 5 ° C. When the temperature of the chill roll 40 is higher than 5 ° C., the cooling performance and the surface quality improvement efficiency of the coated steel sheet are deteriorated. When the chill roll 40 has a temperature lower than −250 ° C., low temperature brittle fracture of the chill roll 40 occurs.

As described above, the plating apparatus of the present embodiment can more precisely control the plating adhesion amount and adjust the thickness of the plating layer through the low temperature knife 20 and the chill roll 40 in contact with the plating solution on the surface of the steel sheet. In addition, the chill roll (40) cooled to a low temperature pressurizes the plating layer and rapidly cools the microstructure of the plating layer, thereby making it possible to obtain a small and uniform surface solidification structure, and to effectively reduce the plating deposition amount variation and the plating layer structure variation in the width direction. do.

By the chill roll 40 contacting the plating layer to solidify the plating solution in a faster time, the plating apparatus can quench the steel sheet at a cooling rate of 20 ° C / sec. In addition, the chill roll 40 can improve the plating performance even for the non-plated steel type because the cooling proceeds while pressing the plating layer under a predetermined pressure.

In addition, in the present embodiment, the sink roll 12 and the chill roll 40 of the plating bath 10 are interlocked to support the steel sheet P so that the steel sheet passes through the contact knife 20 in the width direction. Bending does not occur at all. That is, the steel sheet passes through the sink roll 12 and the chill roll 40 at the front end and the rear end of the knife 20 in the steel plate moving direction, respectively. Thus, the steel sheet P passes through the knife 20 without the occurrence of the bending phenomenon in the flattened state by the sink roll 12 and the chill roll 40.

When the steel sheet is bent, the plating adhesion amount deviation in the width direction occurs, and plating surface defects such as comb defects due to side over plating occur. In the conventional structure, plating surface defects frequently occur due to the bending of the steel sheet, but in the present embodiment, by preventing bending of the steel sheet, it is possible to manufacture a coated steel sheet having almost no plating deposition amount and plating layer structure deviation in the width direction. .

The wiping part of the present embodiment is provided on the chill roll 40 like a knife for precise control of the plating adhesion amount by the chill roll 40 and detects a contact load of the chill roll 40 against the steel sheet. And a control unit 32 for controlling the pressing force of the chill roll 40 against the steel sheet by moving the chill roll 40 with respect to the steel sheet by operating the driving unit 34 according to the detection signal of the load sensor.

As the chill roll 40 approaches the plating layer of the steel sheet P or is spaced outward from the plating layer, the gap between the chill roll 40 and the steel sheet is changed to precisely control the plating adhesion amount of the steel sheet and the thickness of the plating layer.

The structure of the load sensor and the control unit for the chill roll 40 is the same as that of the load sensor 30 and the control unit 32 and the drive unit 34 for the knife 20 mentioned above, and the same reference numerals are used, and the structure thereof. And the action refers to the description of the load sensor 30 and the control unit 32 for the knife 20, the detailed description thereof will be omitted. Thus, the control unit 32 may calculate the detection value of the load sensor 30 to move the chill roll 40 against the steel sheet to press the plating layer, thereby more precisely controlling the amount of plating and the thickness of the plating layer accordingly. In addition, as the plating layer is pressed by the chill roll and quenched at a cooling rate of 20 ° C./sec or more, it is possible to obtain a plating layer having a finer structure while minimizing the variation in the width direction plating amount.

In addition, the wiping unit is configured to remove contaminants on the surface of the chill roll 40 in case the surface of the chill roll 40 is contaminated. To this end, as shown in FIG. 7, the wiping unit may further include a scraper 44 in contact with the chill roll 40 to remove contaminants attached to the surface of the chill roll 40. The scraper 44 may be installed to extend in the axial direction of the chill roll 40 to contact the surface of the chill roll 40. As a result, as the chill roll 40 is rotated, contaminants attached to the chill roll 40 surface are caught by the scraper 44 and removed from the chill roll 40 surface.

The coating amount is precisely adjusted and quenched through the wiping part. The steel sheet is rapidly cooled below the set 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.

7 and 8 illustrate the structure of the cooling unit according to the present embodiment.

The cooling unit adheres to the plating layer on the surface of the steel sheet to supply at least one cooling body 60 to cool the plating layer, and to supply the cryogenic liquid including liquid nitrogen or liquid helium to the cooling body 60 to supply the cooling body 60. It may include a refrigerant supply unit 50 for cooling.

In the present embodiment, the cooling body 60 may include a cooling roll 62 extending in the width direction of the steel sheet and having a cryogenic liquid circulated therein and pressurized to the plating layer on the surface of the steel sheet P to apply cold air. The cooling rolls 62 may have a structure in which a plurality of cooling rolls 62 are arranged in multiple stages at intervals along a traveling direction of the steel sheet.

The cooling roll 62 is a roll structure that is disposed in the width direction of the steel sheet similarly to the chill roll 40. Both ends of the cooling roll 62 may be rotatably supported by a separate support (not shown) on the installation. The cooling roll 62 may be freely rotatable and may be rotated according to the movement of the steel sheet or may be rotated at a set speed by being connected to a separate driving source.

The cooling roll 62 has a structure in which the cryogenic liquid is circulated and cooled to low temperature.

Like the chill roll 40, the cooling roll 62 has a flow path 64 formed therein to allow the cryogenic liquid to pass therethrough. The flow path 64 formed in the cooling roll 62 may be connected to the refrigerant supply unit (see 50 of FIG. 1) through both ends of the rotation shaft of the cooling roll 62. The cryogenic liquid supplied from the coolant supply unit 50 is circulated and supplied to the flow path 64 inside the cooling roll 62 through the tip of the cooling roll 62. The surface of the cooling roll 62 is maintained at a low temperature by the cryogenic liquid supplied into the cooling roll 62.

In addition, the cooling body 60 may further include a cooling belt 66 that is wound and installed between at least two cooling rolls 62 and presses and adheres to the plating layer on the surface of the steel sheet P to apply cold air. In this structure, the cooling belt 66, not the cooling roll 62, is in direct contact with the plated layer of the steel sheet.

The cooling roll 62 and the cooling belt 66 are metal, ceramic, or ceramic coated metal such as stainless steel having excellent cryogenic durability, so that the cooling roll 62 and the cooling belt 66 can be stably used in a cryogenic environment due to the use of liquid nitrogen. Or the like.

In this embodiment, the cooling roll 62 or the cooling belt 66 in contact with the surface of the steel sheet may have an average surface roughness of 0.1 to 3um. If the surface roughness of the cooling roll 62 or the cooling belt 66 is higher than 3um, non-uniform after-treatment problems may occur due to poor surface quality, and if the surface roughness is lower than 0.1um, post-treatment such as chemical conversion The problem that a characteristic falls is produced.

In this embodiment, the cooling belts 66 are wound around the two cooling rolls 62 to form one cooling body 60, and one or more of these cooling bodies 60 are disposed at intervals along the advancing direction of the steel sheet. Structure. Installation intervals and the number of the respective cooling bodies 60 can be variously modified depending on the facilities and process conditions.

Each of the cooling bodies 60 may have the same structure, and the structure of one cooling body will be described below as an example.

The cooling belt 66 is wound around the two cooling rolls 62 spaced apart from each other, and the cooling belt 66 is in surface contact with the plating layer on the surface of the steel sheet. The cooling belt 66 may be rotated according to the moving speed of the steel sheet by, for example, the rotational drive of the cooling roll 62 in contact with the steel sheet. By rotating the cooling belt 66 in accordance with the moving speed of the steel sheet, it is possible to minimize the friction between the steel sheet and the cooling belt 66 and to prevent the plating layer damage due to the friction.

The cooling roll 62 cools the provided cooling belt 66 to a low temperature. The cooling belt 66 is in surface contact with the plating layer in a state of being cooled to a low temperature by the cooling roll 62, so that the plating layer can be rapidly cooled. That is, the cooling belt 66 is in surface contact with the plated layer on the surface of the steel sheet between the two cooling rolls (62). Thus, the cooling area of the plated layer of the steel sheet is increased by the contact area by the cooling belt 66. Therefore, the cooling unit of the present embodiment can increase the cooling area for the steel plate plated layer through the cooling belt 66 to increase the cooling rate.

In this embodiment, the cooling roll 62 may circulate the cryogenic liquid therein to cool the temperature of the cooling belt 66 in contact with the plating layer to -250 to 5 ° C. When the temperature of the cooling belt 66 is higher than 5 ℃ causes a problem that the cooling performance and surface quality improvement efficiency of the coated steel sheet is lowered. When the temperature of the cooling belt 66 is lower than -250 ℃ problem of low temperature brittle fracture of the cooling belt 66 occurs.

As such, the cooling belt 66 provided on the cooling roll 62 contacts the plating layer and rapidly solidifies the plating solution within a faster time, so that the plating apparatus of the present embodiment cools the steel sheet through the cooling section at a cooling rate of 20 ° C / sec. It can be quenched to the temperature below 250 degreeC.

The cooling unit may tension the cooling belt 66 by adjusting a gap between two cooling rolls 62 constituting the unit. As the cooling belt 66 is tensioned and unfolded, the plating layer on the surface of the steel sheet and the cooling belt 66 are in contact with each other and the pressing force is uniform, and the plated layer can be pressure-cooled more evenly.

As shown in FIG. 8, for this purpose, a driving cylinder 68 may be installed between the cooling rolls 62 between the two cooling rolls 62 in which the cooling belt 66 is wound. The driving cylinder 68 is driven in accordance with the signal of the control unit 32 to be separated between the cooling roll 62. As the gap between the cooling rolls 62 opens, the cooling belt 66 is stretched taut.

In addition, the cooling roll 62 can precisely adjust the pressing force on the plated layer of the steel sheet. To this end, the cooling roll 62 is not shown, but may be provided with a load sensor, a control unit and a driving unit in the same manner as the chill roll 40. The pressing force adjusting structure of the cooling roll is the same as the structure of the load sensor 30 and the control unit 32 and the driving unit 34 for the chill roll 40 mentioned above, and a detailed description thereof will be omitted. Thus, the cooling roll is pressed tightly to the cooling belt at a set pressure to precisely control the thickness of the plated layer of the steel sheet.

That is, as the cooling roll 62 approaches the plating layer of the steel sheet or is spaced outward from the plating layer, the gap between the cooling belt 66 wound on the cooling roll 62 and the steel sheet is changed to adjust the pressing force on the plating layer of the steel sheet. do. As described above, the cooling unit calculates the detection value of the load sensor to move the cooling roll 62 with respect to the steel sheet to precisely adjust the plated layer pressing force by the cooling belt 66, thereby precisely controlling the thickness of the plated layer. .

Here, the pressing force of the cooling belt 66 according to the movement of the cooling roll 62 may be the same or different for each of the plurality of cooling bodies 60 arranged along the moving direction of the steel sheet. That is, each of the cooling bodies 60 arranged along the moving direction of the steel sheet may be in close contact with the steel sheet with the same pressing force. Alternatively, the cooling bodies 60 may be in close contact with the steel sheet by gradually increasing the pressing force along the moving direction of the steel sheet. In the case of such a structure, the steel sheet receives a progressively high pressing force while passing through each cooling body 60 to gradually reduce the thickness of the plating layer.

As a result, the thickness of the plating layer may be gradually reduced by going from the knife 20 to the cooling unit along the moving direction of the steel sheet, thereby more precisely controlling the plating layer thickness.

In addition, by cooling the plated layer while pressing the plated layer under a predetermined pressure, the cooling unit can improve the plating performance even for non-plated steel grades. In addition, the cooling unit may finally control the surface roughness of the steel plate plating layer through a cooling roll or a cooling belt disposed at the end of the rear end in the traveling direction of the steel sheet. Thus, higher quality products can be produced.

As described above, the plating apparatus of the present embodiment can rapidly cool the plating layer in comparison with the prior art by closely cooling the cooling belt cooled by the cryogenic liquid to the plating layer. Plated steel sheet cooling has a direct impact on the surface quality of the product. If the uncondensed plating layer comes in contact with contaminated gas or rolls in the rear of the installation, the plating layer must be completely solidified before entering the rear of the installation, as this causes direct surface defects. In the case of the conventional structure by using the gas or water cooling method, the heat capacity is low, the cooling capacity is lowered, and in order to cool the plated steel sheet below a certain temperature to completely solidify the plated layer required a very long multi-stage cooling line. Therefore, in the related art, the cooling line is considerably complicated and the size of the facility is so large that it is difficult to effectively manage the facility, so that surface defects are frequently generated. In particular, when the difference between the solidification start temperature and the solidification completion temperature of the plating layer is large, such as an alloy plated steel sheet in which a large amount of Al and Mg are added to the Zn plating solution, it is difficult to obtain a sufficient cooling effect using a conventional gas method. Accordingly, the cooling of the plating layer is not properly performed, and a coarse and fragile plating layer structure containing Al and Mg, which is a strong oxidizing metal, is generated. In this region, plating layer surface bonding such as black spots and black edges occurs, and problems of plating layer cracking and deterioration of corrosion resistance are generated. Will cause.

On the contrary, in the present embodiment, the cooling belt 66 directly contacts the plating layer of the steel sheet, thereby applying the cooling ability by the cryogenic liquid to the plating layer, thereby further increasing the cooling efficiency. As a result, the time required for cooling the plating layer can be greatly shortened. Therefore, according to the present embodiment, the cooling rate of the plated steel sheet is increased to 20 ° C./sec or more, thereby further reducing the facility line of the cooling unit. In addition, since gas is not directly in contact with the steel sheet, it is possible to minimize the occurrence of surface defects, and to obtain a smaller and more uniform surface structure, thereby manufacturing a high quality coated steel sheet. In addition, it is possible to prevent the generation of dust harmful to the environment by not using the cooling gas.

In addition, in the present embodiment, the cooling belt 66 may have a structure formed by stamping a pattern on the plating layer in the process of pressing and cooling the plating layer of the plated steel sheet. Here, the pattern may mean a repetitive pattern or pattern.

Since the plated layer of the plated steel sheet is influenced by the surface shape of the cooling belt in contact with the plated layer for cooling, the surface of the plated layer may be processed through a structure in which various patterns are formed on the cooling belt and transferred. To this end, the cooling belt 66 may be a pattern to be transferred to the plating layer on the surface. Thus, in the process of cooling the plating layer by pressing the cooling belt in close contact with the plating layer, the pattern formed on the surface of the cooling belt is pressed and transferred to the plating layer, thereby forming a pattern having the same shape as the pattern of the cooling belt on the plating layer.

As such, by rapidly cooling the contacting cooling belt to the plated layer of the plated steel sheet, a pattern can be easily formed on the plated layer without going through an apparatus for forming a separate pattern.

Hereinafter, the plating process which concerns on a present Example is demonstrated.

According to the present embodiment, the steel plate coated with molten zinc through the plating bath is moved to the upper portion of the plating bath to manufacture a plated steel sheet through a process of adjusting the plating adhesion amount of the steel plate and a process of cooling the steel plate.

In order to adjust the plating deposition amount of the steel sheet, the steel sheet coming out of the plating bath is primarily controlled by the low temperature knife contacting the plating layer on the surface of the steel sheet. Then, the plating deposition amount is secondarily controlled by the low temperature chill roll in contact with the steel plate surface plating layer at the rear end of the knife.

The coating amount adjustment by the knife and the chill roll can be precisely controlled by detecting the contact load between the knife and the chill roll with respect to the steel sheet, and controlling the pressing force by moving the knife and the chill roll with respect to the steel sheet in accordance with the detected contact load.

The knife and chill roll are cooled to a low temperature by supplying a cryogenic liquid such as liquid nitrogen. The tip portion provided to the knife is cooled to a temperature of 5 ° C or lower by the cryogenic liquid supplied to the knife. As a result, the plating solution is not fused to the tip portion cooled to a low temperature in a state in which the tip portion contacts the plating layer to adjust the plating deposition amount. Therefore, the knife can accurately control the plating adhesion amount of the plating layer in a state where the tip portion is in physical contact with the plating layer. In this way, the plated amount of the plated layer of the steel sheet from the plating bath is controlled by the knife.

The chill roll primarily contacts the plating layer of the steel sheet whose deposition amount is controlled by the knife and physically pressurizes the plating layer, thereby controlling the plating deposition amount more precisely.

The chill roll is also cooled to low temperature by the cryogenic liquid supplied therein, so that the surface of the chill roll in contact with the plating layer is cooled to 5 ° C or lower. Thus, the plating solution does not adhere to the chill roll surface in the state where the chill roll is pressed against the plating layer and pressed. Therefore, by pressing the chill roll on the plating layer, it is possible to precisely control the plating adhesion amount of the plating layer, and to adjust the thickness of the plating layer of the steel sheet.

The plated layer of the steel sheet is rapidly cooled by a chilled chill roll while the steel sheet is pressed by the chill roll to control the coating amount. The chill roll is rapidly cooled as the plating layer in contact with the chill roll heats up with the chill roll while being cooled by the cryogenic liquid as mentioned. In this way, the chill roll is in contact with the plating layer to cool the plating layer, the plated steel sheet can be quenched at a cooling rate of 20 ° C / sec or more.

The steel sheet rapidly cooled while passing through the chill roll is quenched below a set temperature while passing through a cooling section disposed at the rear end of the chill roll.

In the cooling section, a plurality of units including a cooling roll and a cooling belt are continuously arranged as the cooling body, and the cooling belt of each unit is pressed against the plated layer on the surface of the steel sheet.

The chill roll, like the chill roll, is supplied with a cryogenic liquid such as liquid nitrogen to the inside, and cooled to a low temperature. Cold air of the cooling roll is applied to the plating layer through the cooling belt to quench the plating layer.

The cooling belt is cooled to low temperature by the cryogenic liquid so that the plating layer is not attached to the cooling belt while the cooling belt is pressed against the plating layer.

The cooling belt cools the plating layer in a state in which the plating layer of the steel sheet is pressed at an appropriate pressure. Adjusting the pressing force of the cooling belt with respect to the steel sheet can detect the contact load of the cooling belt with respect to the steel sheet, and move the cooling belt with respect to the steel sheet according to the detected contact load to precisely control the pressing force.

Thus, the plated steel sheet subjected to the chill roll may be cooled by a cooling belt while passing through a cooling section, and may be quenched to a temperature of 250 ° C. or less at a cooling rate of 20 ° C./sec or more.

As the chill roll and the cooling belt directly contact and press the plating layer during the process of adjusting the coating weight and cooling the plating layer, the thickness of the steel sheet is gradually reduced along the moving direction of the steel sheet, so that the thickness of the steel sheet can be more precisely controlled. do.

In addition, since the cooling of the plating layer proceeds under pressure by the chill roll and the cooling belt, it is possible to improve the plating property of the non-galvanized steel as well as hot dip galvanizing.

Liquid nitrogen may be gasified in the process of adjusting the coating weight and cooling the plating layer, and the exhaust gas generated in this process may be reduced gas in the furnace or gas for maintaining the atmosphere of the plating steel plate cooling process after filtration. Can be recycled.

Here, in the cooling process of the plated layer of the steel sheet by the cooling belt, a pattern may be formed on the surface of the plated layer of the plated steel sheet.

While the cooling belt presses and cools the plated layer, the pattern formed on the surface of the cooling belt presses the plated layer. Thus, the pattern formed on the surface of the cooling belt is transferred to the plating layer as it is, the same pattern as the pattern formed on the surface of the cooling belt is formed on the surface of the plating layer.

As such, in the process of simply cooling the plating layer, a pattern having a desired shape may be formed on the surface of the plated steel sheet.

While the exemplary embodiments of the invention have been illustrated and described as described above, various modifications and other embodiments may be made by those skilled in the art. Such modifications and other embodiments are all considered and included in the appended claims, without departing from the true spirit and scope of the invention.

Claims

Plating bath for hot-dip steel plate;

A wiping part disposed on one side or both sides of the steel plate at the rear end of the plating bath along the advancing direction of the steel plate to control the plating adhesion amount of the steel plate; And

A cooling unit for cooling the steel sheet is disposed on one side or both sides of the steel sheet at the rear end of the wiping portion along the steel plate traveling direction,

The cooling unit plating apparatus comprising at least one cooling body in close contact with the plating layer on the surface of the steel sheet to cool the plating layer, and a refrigerant supply unit for supplying cryogenic liquid containing liquid nitrogen or liquid helium to the cooling body to cool the cooling body.
The method of claim 1,

The wiping unit includes a knife for contacting the plated layer on the surface of the steel sheet to control the plating amount, and a refrigerant supply unit for supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the knife to cool the knife.
The method of claim 2,

The wiping part further includes a chill roll extending from the rear end of the knife in the steel plate width direction along the steel plate traveling direction, and having a cryogenic liquid circulated therein, in close contact with the plating layer on the surface of the steel plate, to control the coating amount and to quench the steel plate. .
Plating bath for hot-dip steel plate;

A wiping part disposed on one side or both sides of the steel plate at the rear end of the plating bath along the advancing direction of the steel plate to control the plating adhesion amount of the steel plate; And

A cooling unit for cooling the steel sheet is disposed on one side or both sides of the steel sheet at the rear end of the wiping portion along the steel plate traveling direction,

The wiping unit includes a knife for contacting the plated layer on the surface of the steel sheet to control the plating amount, and a refrigerant supply unit for supplying a cryogenic liquid containing liquid nitrogen or liquid helium to the knife to cool the knife.
The method of claim 4, wherein

The wiping part further includes a chill roll extending from the rear end of the knife in the steel plate width direction along the steel plate traveling direction, and having a cryogenic liquid circulated therein, in close contact with the plating layer on the surface of the steel plate, to control the coating amount and to quench the steel plate. .
The method according to any one of claims 2 to 5,

The knife includes a body extending in the width direction of the steel sheet and the inside is a mild cryogenic liquid, and a tip portion provided at the tip of the body and in contact with the plating layer of the steel sheet to control the coating amount.
The method according to any one of claims 2 to 5,

The knife extends in the width direction of the steel plate and is rotatably installed therein, and a rotating body in which cryogenic liquid is circulated therein, and is disposed at intervals along the circumferential direction on the outer circumferential surface of the rotating body and in contact with the plating layer on the surface of the steel plate to control the plating amount A plating apparatus comprising a tip portion, and a rotary driving portion connected to the rotating body to rotate the rotating body to place one tip portion toward the steel plate surface.
The method of claim 6,

The wiping unit further includes a load sensor provided in the knife to detect a contact load of the tip portion with respect to the steel plate, and a control unit for controlling the pressing force against the steel sheet by moving the knife with respect to the steel plate according to the detection signal of the load sensor. Plating device comprising.
The method of claim 6,

The knife is a plating apparatus wherein the tip is cooled to a temperature of -250 to 5 ℃.
The method of claim 6,

And the tip portion is disposed on the steel sheet in parallel with the width direction.
The method of claim 6,

The tip portion plating apparatus having a structure arranged inclined with respect to the width direction of the steel sheet.
The method of claim 6,

The tip portion is formed by bending, the plating apparatus having a structure arranged in a V-shape or inverted V-shape along the moving direction of the steel sheet.
The method according to claim 3 or 5,

The wiping unit further includes a load sensor provided in the chill roll to detect a contact load of the chill roll with respect to the steel sheet, and a control unit for controlling the pressing force of the chill roll against the steel sheet by moving the chill roll with respect to the steel sheet according to the detection signal of the load sensor. Plating device comprising.
The method according to claim 3 or 5,

The chill roll is a plating apparatus that is cooled to a temperature of -250 to 5 ℃.
The method according to claim 3 or 5,

The chill roll or the cooling roll has a surface roughness of 0.1 to 3um average plating device.
The method according to any one of claims 1 to 3,

The cooling body includes a cooling roll extending in the width direction of the steel sheet and having a cryogenic liquid circulated therein and pressurized by a plating layer on the surface of the steel sheet to apply cold air, and the plurality of cooling rolls are arranged at intervals along the advancing direction of the steel sheet. Plating device of structure.
The method of claim 16,

The cooling apparatus further comprises a cooling belt wound and installed between at least two cooling rolls and in close contact with the plating layer on the surface of the steel sheet to apply cold air.
The method of claim 17,

The cooling belt is a plating apparatus that is cooled to a temperature of -250 to 5 ℃.
The method of claim 17,

The cooling unit is provided on the cooling roll to control the pressing force of the cooling belt against the steel sheet by moving the cooling roll with respect to the steel sheet in accordance with the load sensor for detecting the contact load of the cooling belt to the steel sheet, and the detection signal of the load sensor Plating apparatus further comprising a control unit.
The method of claim 16,

The cooling belt is a plating apparatus having a pattern to be transferred to the plating layer on the surface.