WO2022265307A1 - Highly corrosion-resistant plated steel sheet having excellent corrosion resistance and surface quality, and manufacturing method therefor - Google Patents
Highly corrosion-resistant plated steel sheet having excellent corrosion resistance and surface quality, and manufacturing method therefor Download PDFInfo
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- WO2022265307A1 WO2022265307A1 PCT/KR2022/008200 KR2022008200W WO2022265307A1 WO 2022265307 A1 WO2022265307 A1 WO 2022265307A1 KR 2022008200 W KR2022008200 W KR 2022008200W WO 2022265307 A1 WO2022265307 A1 WO 2022265307A1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 181
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 230000007797 corrosion Effects 0.000 title description 158
- 238000005260 corrosion Methods 0.000 title description 158
- 229910003023 Mg-Al Inorganic materials 0.000 claims abstract description 76
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- 239000011574 phosphorus Substances 0.000 claims 1
- 229910017708 MgZn2 Inorganic materials 0.000 abstract 2
- 230000005764 inhibitory process Effects 0.000 abstract 1
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- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 229910000617 Mangalloy Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- 241000446313 Lamella Species 0.000 description 1
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Images
Classifications
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- B21B1/32—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
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- C—CHEMISTRY; METALLURGY
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
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- C—CHEMISTRY; METALLURGY
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
- C23C28/025—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only with at least one zinc-based layer
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
- B21B2001/221—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by cold-rolling
Definitions
- the present invention relates to a highly corrosion resistant plated steel sheet having excellent corrosion resistance and surface quality and a manufacturing method thereof.
- the zinc-based coated steel sheet When exposed to a corrosive environment, the zinc-based coated steel sheet has a characteristic of a sacrificial method in which zinc, which has a lower oxidation-reduction potential than iron, is corroded first and corrosion of the steel is suppressed.
- zinc in the plating layer oxidizes, a dense corrosion product is formed on the surface of the steel material to block the steel material from the oxidizing atmosphere, thereby improving the corrosion resistance of the steel material. Thanks to these advantageous characteristics, the range of application of zinc-based coated steel sheets has recently been expanding to steel sheets for construction materials, home appliances, and automobiles.
- Zn-Mg-Al-based zinc alloy-coated steel sheets are often used after being processed in a zinc-based manner. Since they contain a large amount of intermetallic compounds with high hardness in the plating layer, bending workability such as causing cracks in the plating layer during bending is poor. The downside is that it gets worse.
- zinc-based coated steel sheets are often provided on the outer shell of a product, but the product with a higher Mg content in the plating layer has a darker appearance, and due to the addition of surface damage factors due to processing, the surface quality is poor, resulting in poor appearance quality. Improvement was needed.
- Patent Document 1 Korean Publication No. 2010-0073819
- it is intended to provide a coated steel sheet excellent in corrosion resistance and appearance quality in a bent portion as well as corrosion resistance in a flat plate portion and a method for manufacturing the same.
- the total area ratio of the Al single phase and the MgZn 2 phase is 45 to 60%, and the area ratio of the MgZn 2 phase to the Al single phase is 1.2 to 3.3.
- Another aspect of the present invention is,
- the cooling step satisfies the following relational expressions 1-1 and 1-2, and the ratio (De / Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion satisfies 60 to 99% It provides a manufacturing method of a plated steel sheet in which cooling is performed so as to
- t is the thickness of the steel sheet (mm)
- A is the average cooling rate (° C./s) from the solidification start temperature to 375° C.
- B is at 375° C. Average cooling rate (°C/s) up to 340°C is shown.
- FIG. 1(a) shows a surface specimen capable of observing the surface of the plated steel sheet of Example 13, and magnifying the surface specimen at a magnification of 700 to obtain a Field Emission Scanning Electron Microscope (FE-SEM). It is a photograph observed by), and FIG. 1 (b) shows the measured ratio of each phase with respect to the photograph.
- FE-SEM Field Emission Scanning Electron Microscope
- FIG. 2(a) shows the coated steel sheet of Example 13, the same as that of FIG. 1, after polishing to the 1/2t point, and then making a 1/2t surface specimen from which the polished surface can be observed. It is a photograph observed with a scanning electron microscope (FE-SEM) by magnifying 700 times, and FIG. 2 (b) shows the measured ratio of each phase with respect to the photograph.
- FE-SEM scanning electron microscope
- Figure 3 (a) shows that a surface specimen for observing the surface of the plated steel sheet of Comparative Example 1 was made, and the surface specimen was magnified at 700 magnification to obtain a Field Emission Scanning Electron Microscope (FE-SEM). It is a photograph observed by), and FIG. 3 (b) shows the measured ratio of each phase with respect to the photograph.
- FE-SEM Field Emission Scanning Electron Microscope
- FIG. 4(a) shows the coated steel sheet of Comparative Example 1, the same as that of FIG. 3, after polishing to the 1/2t point, and then making a 1/2t surface specimen from which the polished surface can be observed. It is a photograph observed with a scanning electron microscope (FE-SEM) by magnifying 700 times, and FIG. 4 (b) shows the measured ratio of each phase with respect to the photograph.
- FE-SEM scanning electron microscope
- FIGS. 1 to 4 Figure 5 is observed with EDS (Energy Dispersive Spectrometer) on the Al single phase, the second Al single phase, and the Al-Zn-based binary process referred to in FIGS. 1 to 4, and the fraction of the elements dissolved in the microstructure It is an urbanized graph.
- EDS Electronic Dispersive Spectrometer
- Mg was added to improve corrosion resistance, but when Mg is added excessively, floating dross in the plating bath increases, so the dross must be removed frequently. , the upper limit of the amount of Mg added was limited to 3%. Accordingly, studies have been conducted to further improve corrosion resistance by increasing the amount of Mg added to more than 3%, but as the amount of Mg added increases, a large amount of intermetallic compounds with high hardness are generated, causing cracks in the plating layer during bending. There is a problem.
- the inventors of the present invention as a result of intensive examination to solve the above-mentioned problems, as well as corrosion resistance of the flat plate part, corrosion resistance of the bending part and excellent appearance quality, as a result of intensive examination, under a corrosive environment (or in an atmospheric environment) When maintained for a long time), it is important to uniformly form LDH (Layered Double Hydroxide; (Zn,Mg) 6 Al 2 (OH) 16 (CO 3 ) 4H 2 O)) as an initial corrosion product on the surface of the processing part. discovered and completed the present invention.
- LDH Layered Double Hydroxide; (Zn,Mg) 6 Al 2 (OH) 16 (CO 3 ) 4H 2 O)
- LDH is formed as an initial corrosion product on the surface of the bending workpiece, and at the same time, LDH is uniformly distributed over the entire surface of the workpiece over time, so that the corrosion active area can be shielded.
- a coated steel sheet includes a holding steel sheet; a Zn-Mg-Al-based plating layer provided on at least one surface of the base steel sheet; and a Fe-Al-based suppression layer provided between the base steel sheet and the Zn-Mg-Al-based plating layer.
- the type of the base steel sheet may not be particularly limited.
- the holding steel sheet may be a Fe-based holding steel sheet, that is, a hot-rolled steel sheet or a cold-rolled steel sheet, which is used as a holding steel sheet of a general zinc-based coated steel sheet, but is not limited thereto.
- the base steel sheet may be, for example, carbon steel, ultra-low carbon steel, or high manganese steel used as a material for construction, home appliances, and automobiles.
- the holding steel sheet in weight%, C: more than 0% and 0.18% or less, Si: more than 0% and 1.5% or less, Mn: 0.01 to 2.7%, P: more than 0% and 0.07% or less, S: More than 0% and not more than 0.015%, Al: more than 0% and not more than 0.5%, Nb: more than 0% and not more than 0.06%, Cr: more than 0% and not more than 1.1%, Ti: more than 0% and not more than 0.06%, B: more than 0% and not more than 0.03% It may have a composition comprising the following and balance Fe and other unavoidable impurities.
- a Zn-Mg-Al-based plating layer made of a Zn-Mg-Al-based alloy may be provided on at least one surface of the base steel sheet.
- the plating layer may be formed on only one side of the base steel sheet, or may be formed on both sides of the base steel sheet.
- the Zn-Mg-Al-based plating layer refers to a plating layer containing Mg and Al and mainly containing Zn (ie, containing 50% or more of Zn).
- the thickness of the Zn-Mg-Al-based plating layer may be 5 to 100 ⁇ m, more preferably 5 to 90 ⁇ m. If the thickness of the plating layer is less than 5 ⁇ m, the plating layer may locally become too thin due to errors due to variations in the thickness of the plating layer, and thus corrosion resistance may be deteriorated. If the thickness of the plating layer exceeds 100 ⁇ m, cooling of the hot-dip plating layer may be delayed, for example, solidification defects such as flow patterns may occur on the surface of the plating layer, and productivity of the steel sheet may decrease in order to solidify the plating layer.
- a Fe-Al-based suppression layer may be provided between the base steel sheet and the Zn-Mg-Al-based plating layer.
- the Fe-Al-based suppression layer is a layer mainly containing an intermetallic compound of Fe and Al, and examples of the Fe and Al intermetallic compound include FeAl, FeAl 3 , Fe 2 Al 5 , and the like.
- some components derived from the plating layer, such as Zn and Mg may be further included, for example, 40% or less.
- the suppression layer is a layer formed due to alloying by Fe diffused from the base steel sheet in the initial stage of plating and plating bath components.
- the suppression layer may serve to improve adhesion between the base steel sheet and the plating layer, and at the same time prevent diffusion of Fe from the base steel sheet to the plating layer. At this time, the suppression layer may be formed continuously or discontinuously between the base steel sheet and the Zn-Mg-Al-based plating layer. With respect to the suppression layer, except for the above description, contents commonly known in the art may be equally applied.
- the thickness of the suppression layer may be 0.02 ⁇ 2.5 ⁇ m.
- the suppression layer serves to secure corrosion resistance by preventing alloying, but may affect workability due to brittle, so its thickness may be 2.5 ⁇ m or less.
- the upper limit of the thickness of the suppression layer may be preferably 1.8 ⁇ m.
- the lower limit of the thickness of the suppression layer may be 0.05 ⁇ m.
- the thickness of the suppression layer may mean a minimum thickness in a direction perpendicular to the interface of the base steel plate.
- the Zn-Mg-Al-based plating layer may include Mg: 4 to 6%, Al: 8.2 to 14.2%, the balance Zn and other unavoidable impurities in weight%.
- Mg 4 to 6%
- Al 8.2 to 14.2%
- the balance Zn and other unavoidable impurities in weight% may be described in detail.
- Mg 4% or more and 6% or less
- Mg is an element that serves to improve the corrosion resistance of coated steel materials, and in the present invention, the Mg content in the plating layer is controlled to 4% or more to secure the desired excellent corrosion resistance.
- the upper limit of the Mg content may not be particularly limited. However, as an example, when Mg is excessively added, dross may be generated, so the Mg content may be controlled to 6% or less.
- Mg was added at 1.0% or more in Zn-Mg-Al-based zinc alloy plating to secure corrosion resistance, but the upper limit of the Mg content was set at 3.0% to commercialize it.
- the upper limit of the Al content in the plating layer is preferably controlled to 14.2%, more preferably 14.0%.
- the remainder may be Zn and other unavoidable impurities. Any unavoidable impurities may be included as long as they can be unintentionally mixed in the manufacturing process of a typical hot-dip galvanized steel sheet, and those skilled in the art can easily understand their meaning.
- the Zn-Mg-Al-based plating layer may include MgZn 2 -phase and Al single-phase as a microstructure, and in addition, Al-Zn-based binary eutectic phase, Zn-MgZn 2 -Al-based ternary eutectic phase, Zn single-phase It may be included in various top coat plating layers, such as the like.
- the MgZn 2 phase refers to a phase mainly composed of MgZn 2
- the Al single phase refers to a phase mainly composed of Al, and specifically, Zn is dissolved in an atomic % of less than 27%. , the balance of which is composed of Al and other impurities. That is, in the Al single phase, in addition to the Al component, components such as Zn and Mg that can be included as components of the plating layer may be solidified.
- the Zn-MgZn 2 -Al-based ternary eutectic phase refers to a ternary eutectic phase in which all of the Zn phase, the MgZn 2 -phase and the Al phase are mixed
- the Al-Zn-based binary eutectic phase refers to an Al phase and Zn phases are alternately arranged in lamella or irregular mixed form.
- the Al phase in the Al-Zn-based binary eutectic phase and the Zn-MgZn 2 -Al-based ternary eutectic phase is not regarded as the above-mentioned Al single phase or the second Al single phase described later.
- MgZn 2 in the Zn-MgZn 2 -Al-based ternary eutectic phase is not regarded as the above-mentioned MgZn 2 phase mainly composed of MgZn 2 .
- the Zn-Mg-Al-based plating layer may further include a 'second Al single phase', which is distinguished from the Al single phase by a Zn solid solution rate.
- the second Al single phase refers to a single phase in which 27% or more and 60% or less (27 to 60%) of Zn is dissolved in atomic percent, and the balance is composed of Al and other impurities.
- the microstructure of the above-described Zn-Mg-Al-based plating layer may have a different distribution on the surface and cross-section, and the microstructure on the surface and cross-section is scanned by expanding the magnification of the plating layer for each surface specimen or cross-section specimen. It can be confirmed using an electron microscope (SEM) or a transmission electron microscope (TEM).
- SEM electron microscope
- TEM transmission electron microscope
- the Zn-Mg-Al-based plating layer includes various phases depending on the composition and manufacturing conditions of the plating layer, but the inventors of the present invention, in addition to the conventional corrosion resistance of the flat plate part, the corrosion resistance and appearance quality of the bending part are excellent in both the coated steel sheet As a result of careful examination to provide LDH (Layered Double Hydroxide; (Zn,Mg) 6 Al 2 (OH) 16 (CO It was found that the uniform formation of 3 ) ⁇ 4H 2 O) was an important factor.
- LDH Layered Double Hydroxide; (Zn,Mg) 6 Al 2 (OH) 16 (CO
- the initial formation of LDH as a corrosion product on the surface of the plated steel sheet is related to the microstructural features on the surface of the Zn-Mg-Al-based plating layer (ie, the surface of the exterior rather than the surface of the base iron). confirmed and came to complete the present invention.
- the total area ratio of the Al single phase and the MgZn 2 phase is 45 to 60%, and the area ratio of the MgZn 2 phase to the Al single phase is It is characterized by being 1.2 to 3.3.
- the total area ratio of the Al single phase and the MgZn 2 phase and the area ratio of the MgZn 2 phase to the Al single phase are measured based on a surface specimen having an area of 24,000 ⁇ m 2 or more. .
- the MgZn 2 phase and the Al single phase include an adjacent microstructure.
- the form in which the MgZn 2 phase and the Al single phase are adjacent includes the case where the Al single phase is completely included in the MgZn 2 phase or the Al single phase is partially included in the MgZn 2 phase, and additionally, the Al single phase is in contact with the MgZn 2 phase. Including the case where this exists.
- the Zn-Mg-Al-based plating layer may include a Zn single phase and a Zn-MgZn 2 -Al-based ternary eutectic phase, which are common in high corrosion-resistant plated steel sheets.
- the amount of the Zn single phase and Zn-MgZn 2 -Al-based ternary eutectic phase generated in the entire plating layer increases, and as the Al and Mg content in the plating layer increases, the MgZn 2 phase and The amount of Al single phase produced tends to increase.
- the MgZn 2 phase appears coarse as shown in FIG. Accordingly, a coarse Al single phase also coexists. Accordingly, the inventors of the present invention, in order to secure the corrosion resistance of the above-mentioned bending process, the total area ratio and area ratio of the MgZn 2 phase and the Al single phase adjacent to the MgZn 2 phase on the surface of the plating layer under a corrosive environment (or under an atmospheric environment for a long time) It was found that it contributes to the formation of LDH as a corrosion product initially during maintenance.
- the MgZn 2 phase and the Al single phase are adjacent to each other on the surface of the plating layer by a specific amount or more.
- the total area ratio of the MgZn 2 phase and the Al single phase satisfies 45 to 60%
- the MgZn 2 to the Al single phase By satisfying the area ratio of 1.2 to 3.3, it is possible to secure excellent corrosion resistance by performing a role of forming a sacrificial cell between the MgZn 2 phase and the Al single phase.
- the corrosion resistance includes not only the corrosion resistance of the flat plate part but also the corrosion resistance of the bent part, and this corrosion resistance is improved as the amount of MgZn 2 phase and Al single phase present on the surface of the plating layer is higher than that of the inside of the plating layer.
- the respective phases forming the anode (MgZn 2 ) and the cathode (Al) of the sacrificial cell are insufficient for bending processing. Secondary corrosion resistance may be insufficient, and light scattering due to phases present on the surface may also be insufficient, resulting in deterioration in appearance quality.
- the total area ratio of the MgZn 2 phase and the Al single phase exceeds 60%, a brittle MgZn 2 phase is excessively formed, resulting in excessive cracking of the plating layer during processing.
- the area ratio of the MgZn 2 phase to the Al single phase is less than 1.2, the amount of the MgZn 2 anode forming the sacrificial cell can be dissolved is small, resulting in corrosion resistance. Disadvantageous problems may occur, and if MgZn 2 is dissolved and transferred, there may be a limit to the rate of cathode reaction (oxygen reduction reaction) occurring in Al on the surface by accepting electrons that are dissolved and transferred.
- the corrosion resistance of the bending part is shaped by two mechanisms.
- the MgZn 2 phase and Al single phase present in the bending part form a complete sacrificial cell, and the corrosion product covers and hides the exposed portion of the steel sheet during bending.
- the potential of MgZn 2 is -1.2V on the hydrogen reduction potential and the potential of Al is -0.7V on the hydrogen reduction potential, securing a large potential difference, thereby acting as an anode and a cathode, respectively.
- it means to form a galvanic cell between the adjacent MgZn 2 -phase and Al single-phase microstructures.
- the inventors of the present invention have secured a high potential difference between the MgZn 2 phase and the Al single phase adjacent to the MgZn 2 phase on the surface of the plating layer, thereby ensuring corrosion resistance at the bending part by forming a galvanic cell. was confirmed, and it was found that the phase enabling a high potential difference to be secured adjacent to the MgZn 2 phase was an Al single phase having a Zn solid solution ratio of less than 27 atomic%.
- the phase capable of maintaining a high potential difference by existing adjacent to the MgZn 2 phase is an Al single phase (corresponding to 1) having a low Zn solid solution.
- the second Al in the Zn-Mg-Al-based plating layer, when a large number of second Al single phases having a high Zn solid solution rate of 27 atomic% or more are formed, the second Al existing around the MgZn 2 phase The number of single phases increases, and as a result, the potential difference between the anode and the cathode of the galvanic cell is reduced, which may impair excellent corrosion resistance and sacrificial corrosion resistance of the galvanic cell.
- the area ratio of the second Al single phase on the surface of the Zn-Mg-Al-based plating layer may be 2 to 9%. If the area ratio of the second Al single phase exceeds 9%, the second Al single phase is excessively formed around the MgZn 2 phase, reducing the potential difference of the galvanic cell and deteriorating corrosion resistance at the bending part. Therefore, in the present invention, on the surface of the Zn-Mg-Al-based plating layer, the area ratio of the second Al single phase is controlled to 9% or less, and the smaller the amount of the second Al single phase present on the surface, the better the corrosion resistance of the bending part. Since the effect is improved, the lower limit may not be separately limited. However, considering that the second Al single phase is necessarily formed in the temperature range in which the second Al single phase is formed during the cooling process after hot-dip plating, the lower limit may be set to 2%.
- the area ratio of the MgZn 2 phase may be 30 to 40%.
- the portion of the plating layer that is primarily in contact with the air and chloride environment is the surface, and the higher the ratio of the MgZn 2 phase acting as an anode in the sacrificial method, the higher the reactivity in the galvanic cell. Therefore, by promoting the formation of the aforementioned galvanic cell, the area ratio of the MgZn 2 phase on the surface of the plating layer may be set to 30% or more in order to secure corrosion resistance of the bending portion.
- the corrosion resistance of the bent portion may be insufficient.
- the MgZn 2 phase ratio exceeds 40% and is excessively high, the plating layer may become brittle and cause cracks on the surface.
- the Al single phase (ie, in atomic %, Zn is dissolved at less than 27%, , the balance of which includes Al and other impurities) may have an area ratio of 15 to 20%.
- the area ratio of the Al single phase is 15% or more, as described above, MgZn 2 acting as an anode in the galvanic cell can act as a cathode to help improve the corrosion resistance of the bending part, and the framework for the MgZn 2 phase By performing a holding function, the plating layer can contribute to a role as a physical protective barrier.
- the ratio of the Al single phase exceeds 20%, there is room for deterioration in stability due to Al corrosion.
- the total area ratio of the Zn single phase and the Zn-MgZn 2 -Al-based ternary phase on the surface of the Zn-Mg-Al-based plating layer may be 20 to 30%.
- the Zn single phase and the Zn-MgZn 2 -Al-based ternary eutectic phase present on the surface of the Zn-Mg-Al-based plating layer contribute to the formation of Simoncolite or hydrozincite rather than LDH at the initial stage of corrosion.
- the total area ratio of the Zn single phase and the Zn-MgZn 2 -Al-based ternary eutectic phase on the surface of the Zn-Mg-Al-based plating layer may be 20 to 30%.
- the total area ratio of the Zn single phase and the Zn-MgZn 2 -Al-based ternary phase on the surface of the Zn-Mg-Al-based plating layer is less than 20%, it is generated secondarily after LDH formation to help improve corrosion resistance.
- Simoncol There is a concern that the formation of light or hytrozinsite becomes insufficient and a problem arises in corrosion resistance.
- the area ratio of the MgZn 2 phase is 20 to 40%, , the area ratio of the Al single phase may be 8 to 26%.
- the properties of the plated steel sheet are related to the type and size of the crystal phase, and when the area ratio of the MgZn 2 phase is less than 20% or the area ratio of the Al single phase is less than 8%, the corrosion resistance of the plating layer may be weakened. On the other hand, when the ratio of the MgZn 2 phase present in the plating layer exceeds 40%, it may be too brittle, resulting in excessive cracking in the plating layer during processing.
- the area ratio of the MgZn 2 phase and the Al single phase based on the cross-section of the Zn-Mg-Al-based plating layer can be measured by observing a photograph of a cross-sectional specimen in the thickness direction of the coated steel sheet with FE-SEM.
- the corrosion resistance of the cut-edge of the steel sheet can be secured by satisfying the area ratio of the MgZn 2 phase and the Al single phase based on the cross section of the Zn-Mg-Al-based plating layer, the surface of the plating layer Area ratios of the MgZn 2 phase and the Al single phase secured may be different. Therefore, according to the area ratio distribution of each phase on the surface of the plating layer, the degree of corrosion resistance of the processed portion may be affected during bending.
- the inventors of the present invention have found that even if the above-mentioned MgZn 2 phase and Al single phase area ratio is secured on a cross-sectional basis in the thickness direction of the plating layer, securing a specific amount or more of the MgZn 2 phase and Al single phase on the surface of the plating layer is the surface of the plating layer in the early stage of corrosion. found that it is an important means to secure corrosion resistance of the processed part by promoting the uniform formation of LDH.
- the present invention it is important to maintain the ratio of the total area ratio of the MgZn 2 phase and the Al single phase at the center of the plating layer to the total area ratio of the MgZn 2 phase and the Al single phase on the surface of the plating layer at an appropriate level. additionally found.
- the total area ratio of the MgZn 2 phase and the Al single phase (C1 ), the ratio (S1/C1) of the total area ratio (S1) of the MgZn 2 phase and the Al single phase on the surface of the Zn-Mg-Al-based plating layer may be in the range of 0.8 to 1.2. If S1/C1 is less than 0.8, problems may arise in the corrosion resistance of the flat plate and processed parts due to the lack of microstructure forming LDH in the initial stage of corrosion on the surface layer of the plating layer. Excessive coarsening of the resulting brittle tissue may cause problems in workability and corrosion resistance of the processed part.
- the area ratio of the second Al single phase is 2 to 10% on the surface of any point in the region from 1/4t to 3/4t in the thickness direction of the Zn-Mg-Al-based plating layer. can If the value exceeds 10%, it may affect the structure of the surface layer portion and adversely affect the corrosion resistance of the bent portion. In addition, the lower limit may be controlled to 2% considering that the second Al single phase passes through the temperature range.
- the point where the plating layer thickness is the maximum in the plated specimen is regarded as the total thickness t, and based on the t, from 1/4t It may mean a region polished with respect to the surface of the specimen to include an arbitrary point in the region of 3/4t.
- the inventors of the present invention conducted additional studies to determine the Zn phase and the Zn-MgZn 2 -Al-based ternary process phase that penetrates into the inside and promotes the formation of Simoncolite and hydrozincite after the uniform formation of LDH on the surface of the plating layer. It was found that the ratio of the center to the surface is also an important factor to further improve the corrosion resistance.
- the Zn phase and the Zn-MgZn 2 - The ratio of the total area ratio (S2) of the Zn phase and the Zn-MgZn 2 -Al-based ternary phase on the surface of the Zn-Mg-Al-based plating layer to the total area ratio (C2) of the Al-based ternary eutectic phase (S2/C2) may be in the range of 0.6 to 1.2.
- S2/C2 is less than 0.6, a problem may arise in corrosion resistance due to lack of formation of simonicolite or hydrozincite, which is secondarily generated after the formation of LDH on the surface layer of the plating layer and helps to improve corrosion resistance.
- the above-mentioned MgZn 2 phase, Al single phase, 2nd Al single phase, Zn single phase and Zn-MgZn 2 -Al system 3 that can be derived from the surface of the Zn-Mg-Al-based plating layer satisfying the Mg and Al compositions according to the present invention
- the definition of each phase and the atomic percent employed for the original phase are shown in FIGS. 1 to 5.
- the plane of the plated steel sheet as shown in FIGS. 1 to 4 is enlarged to 700 times in BEI (backscattered electron image) observation mode, 1280x960 pixel / 254 DPI resolution, and 8-bit properties, and observed with a field emission scanning electron microscope (FE-SEM). From one photograph, an Al single phase in which Zn was dissolved at less than 27 at% and a second Al single phase in which Zn was dissolved at 27 at% or more and 60% or less were distinguished by tissue labeling of SEM images.
- BEI backscattered electron image
- FE-SEM field emission scanning electron microscope
- the fraction of elements dissolved in different phases for each light and shade of the SEM image can be obtained using an energy dispersive spectrometer (EDS) commonly known in the art.
- EDS energy dispersive spectrometer
- the Al-based phase except for the MgZn 2 phase, Zn single phase, and Zn-MgZn 2 -Al-based ternary phase, which are clearly distinguished by color, contrast, and shape for each microstructure, is averaged in the region of 1.
- Al is 73%
- Zn is 26%
- the balance is less than 1%.
- the Al single phase referred to in the present invention means the region 1 in which Zn is dissolved at less than 27% in atomic %
- the second Al single phase means the region in 2 in which Zn is dissolved at 27% or more and 60% or less in atomic %
- the Al-Zn-based binary eutectic phase refers to the region of 3, and Fe and other components may be included as impurities in each phase.
- the tissue labeling uses the image derived from the above-mentioned SEM measurement conditions, based on the Super-pixel algorithm of the Pohang Institute of Industrial Science and Technology (RIST)'s RISA (microtissue phase fraction analysis software), image automatic generation software.
- the superpixel algorithm divides the entire image into thousands or tens of thousands of regions (superpixels), compares superpixels with similar patterns or features to measure similarity, calculates a histogram of brightness values of pixels, and then calculates the similarity. It is a mechanism that automatically selects a superpixel when is greater than a predefined threshold.
- the boundaries of the Al single phase and the 2nd Al single phase of the image derived from the above-mentioned SEM measurement conditions are each based on the Zn employment rate of 27 atomic% employed in Al tissue using EDS.
- histogram of the brightness value of the soft phase and tissue discrimination are possible.
- the technical idea of the above-mentioned RISA microstructure phase fraction analysis software
- LDH may be formed on the surface of the plating layer before Simoncolite and hydrozincite are formed on the surface of the plating layer in an air environment and a chloride environment. Rapid nucleation-crystallization of LDH, a dense corrosion product, proceeds on the initial surface of the corrosive environment by the single phase. Thereafter, as time elapses, it is uniformly distributed over the entire surface to shield the corrosion active area, and induces uniform formation of secondarily formed corrosion products, simonicolite and hydrozincite.
- the LDH corrosion product formed on the surface layer portion of the plating layer can be formed within 6 hours in an air environment and within 5 minutes in a chloride environment (ie, as measured by ISO14993).
- the above-mentioned excellent corrosion resistance is that the time required for red rust to occur in a chloride environment including salt spray and immersion environments (i.e., as measured by ISO14993) is 40 to 40 to 40 in the flat plate compared to pure Zn plating of the same thickness. 50 times; And it may be 20 to 30 times in the 90 ° bending part.
- the evaluation of the red rust generation time performed can be comparatively evaluated by a test method conforming to ISO14993 using a salt spray tester (SST).
- a step of preparing a steel sheet may be further included, and the type of the steel sheet is not particularly limited. It may be a Fe-based steel sheet, that is, a hot-rolled steel sheet or a cold-rolled steel sheet, which is used as a holding steel sheet of a conventional hot-dip galvanized steel sheet, but is not limited thereto.
- the holding steel sheet may be, for example, carbon steel, ultra-low carbon steel, or high manganese steel used as a material for construction, home appliances, and automobiles, but is not limited thereto. At this time, the above description can be equally applied to the holding steel plate.
- the step of immersing the base steel sheet in a plating bath containing, by weight, Mg: 4-6%, Al: 8.2-14.2%, the balance Zn and other unavoidable impurities, to perform hot-dip galvanizing can include
- the description of the components of the plating layer described above can be equally applied to the reason for adding the components and the reason for limiting the content in the plating bath, except for the content of a small amount of Fe that may flow from the base steel sheet. .
- a composite ingot containing predetermined Zn, Al, and Mg or a Zn-Mg or Zn-Al ingot containing individual components may be used.
- the ingot is additionally melted and supplied.
- a method of directly immersing and dissolving the ingot in a plating bath may be selected, or a method of dissolving the ingot in a separate pot and then replenishing the molten metal in the plating bath may be adopted.
- the temperature of the plating bath may be maintained at a temperature 20 to 80° C. higher than the solidification start temperature (Ts) in the equilibrium state.
- Ts solidification start temperature
- the solidification initiation temperature on the equilibrium phase may be in the range of 390 to 460 ° C, or the temperature of the plating bath may be maintained in the range of 440 to 520 ° C.
- the temperature of the plating bath increases, it is possible to secure fluidity in the plating bath and form a uniform composition, and to reduce the amount of floating dross generated. If the temperature of the plating bath is less than 20° C.
- the dissolution of the ingot is very slow and the viscosity of the plating bath is high, making it difficult to secure excellent plating layer surface quality.
- the temperature of the plating bath exceeds 80° C. compared to the solidification initiation temperature on the equilibrium diagram, a problem of ash defects caused by Zn evaporation may occur on the plating surface.
- the step of cooling the hot-dip galvanized steel sheet using an inert gas at an average cooling rate of 2 to 12 ° C / s from the solidification start temperature to the solidification end temperature on the equilibrium diagram. can do. If the average cooling rate described above is less than 2°C/s, the MgZn 2 structure develops too coarsely on the surface, and the surface of the plating layer becomes brittle, resulting in severe cracking, and it may be disadvantageous in securing uniform corrosion resistance and workability. On the other hand, if the above-mentioned average cooling rate exceeds 12 ° C.
- the liquid phase starts to solidify during the hot dip plating process, and rapid solidification occurs in the temperature range while the liquid phase is all changed to the solid phase. Therefore, excessive coarsening and atomization of the MgZn 2 phase and the single phase of Al may occur on the surface of the plating layer, and as a result, non-uniform phases may be locally formed on the surface of the plating layer, resulting in deterioration in corrosion resistance.
- the cooling may control the cooling rate to satisfy the following relational expressions 1-1 and 1-2.
- t is the thickness (mm) of the steel sheet
- A is the average cooling rate (° C./s) from the solidification start temperature to 375° C.
- B is at 375° C. Average cooling rate (°C/s) up to 340°C is shown.
- the present invention divides the first temperature range from the solidification start temperature to 375°C and the second temperature range from 375°C to 340°C when cooling after hot-dip galvanizing, and averages the average in each interval according to the thickness of the steel sheet. It is characterized in that the cooling rate is controlled to satisfy the above relational expressions 1-1 and 1-2.
- the Al single phase adjacent to the MgZn 2 phase in the plating layer formed in the range of Mg and Al according to the present invention is cooled to form a binary process, and Zn is reduced by atomic %.
- the 'Al single phase' is distinguished from the 'second Al single phase' to be described later.
- Zn is 27% or more and 60% or less (ie, 27 to 60%). %) represents the formation temperature range of the second Al single phase.
- pre-temperature rolling (SPM) processing may be further included.
- the surface shape of the base steel sheet is uniformly controlled so that the thickness of the hot-dip plating layer formed by the subsequent plating process is uniform, and at the same time, By making the base steel sheet smooth, it is possible to minimize the generation sites of solidification nuclei.
- the roll rolling of the preliminary temper rolling treatment before the hot-dip galvanizing may be set to 250 to 300 tons.
- the base steel plate is placed in a heating furnace having a dew point temperature of -60 ° C or higher and -15 ° C or lower, and the temperature of the base steel plate in the last section of the heating furnace is compared to the plating bath temperature (Tb) to secure wettability of plating. It may include heating to a high temperature of 20 ° C to 80 ° C.
- the dew point temperature of the heating furnace is for preventing oxidation of the surface of the base steel sheet, and the temperature of the heating furnace may be -60°C or more -15°C in order to secure plating adhesion.
- the ratio of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion in the width direction of the hot-dip galvanized steel sheet during cooling can be cooled to meet 60 to 99%.
- the 'width direction' of the steel sheet refers to a direction perpendicular to the conveying direction of the steel sheet, based on the surface excluding the thickness-side surface of the hot-dip galvanized steel sheet (ie, the surface where the thickness of the steel sheet is visible).
- the damper opening rate is a numerical value referring to the opening degree of the control plate that controls the flow rate of the cooling gas to be sent from the cooling device to the steel plate.
- a damper is installed so that the total cooling gas input or controlled to the cooling device can be divided into the center part and the edge part according to the width direction of the steel plate and injected.
- the boundary between the dampers can be divided into three sections according to the width of the holding steel plate, and the position can be variably controlled so that the center portion is occupied by the center portion and the edge portion is occupied by two portions existing on the outer side.
- the edge portion and the center portion are cooled without using a method or device for adjusting the ratio of the ratio (De/Dc).
- the ratio (De/Dc) was set to 60 to 60 Uniform cooling performance in the width direction of the steel sheet can be realized by controlling the opening rate of the edge portion to be lower than that of the center portion within the range of 99%.
- the present inventors found that the edge portion in the width direction of the steel sheet has a larger area exposed to the external atmosphere than the center portion, so that the temperature of the steel sheet in the region corresponding to the edge portion is inevitably lowered at a faster rate than the center portion. and it was found that uniform characteristics of the surface of the plating layer can be secured by artificially reducing the cooling rate at the edge portion. That is, the cooling gas incident on the center portion in the above cooling process It passes through the edge and exits to the outer shell. However, since the edge part receives the cooling gas incident on the edge part and the cooling gas after entering the center part in an overlapping manner, the cooling gas may be overcooled compared to the center part, thereby adversely affecting the cooling gas.
- the damper opening rate of the edge portion It needs to be controlled in a direction lower than the center portion.
- the ratio (De / Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion according to the temperature range Cooling can be performed by giving a change.
- the ratio (De / Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion is from the solidification start temperature to 375 ° C. (in the 'first temperature section' Correspondence) may be performed to satisfy 60 to 70%, and to satisfy 90 to 99% from 375 ° C to 340 ° C (corresponding to the 'second temperature range').
- the aforementioned MgZn 2 -Al-based binary eutectic phase is formed uniformly in the width direction of the steel sheet from the solidification initiation temperature to 375 ° C.
- corrosion resistance can be improved uniformly over the whole width. In addition, from 375 ° C.
- the cooling step in order to improve the surface quality of the final product, it may further include the step of improving the surface and shape of the steel sheet by performing temper rolling (SPM) treatment.
- SPM temper rolling
- the temper rolling treatment may be performed by applying a roll reduction of 50 to 300 tons to the surface of the steel sheet using a bright roll having a surface roughness (Ra) of 0.2 to 1.0 ⁇ m. .
- the surface roughness Ra of the bright roll is less than 0.2 ⁇ m, the roughness of the roll is too low, and the frictional force between the steel sheet and the SPM roll is reduced, resulting in a problem of slipping of the steel sheet, and exceeding 1.0 ⁇ m.
- the microstructure of the surface of the backside plating layer may not be completely preserved, and excessive cracking may occur.
- the surface roughness Ra of the bright roll is in the range of 0.4 to 0.8 ⁇ m in terms of further improving the light scattering effect due to the textural characteristics of the plating layer.
- the roll reduction is less than 50 tons, a problem may arise in uniformizing the shape of the steel sheet in the width direction, and if it exceeds 300 tons, the microstructure of the surface of the plating layer cannot be completely preserved due to excessive reduction force, and the above-described bright roll Even in the surface roughness range of , excessive cracking may occur.
- the cooled steel sheet is subjected to temper rolling (SPM) treatment, and by optimizing conditions for temper rolling, it is possible to provide a coated steel sheet having a light scattering effect. Through this, it is possible to effectively provide even a plated steel sheet having excellent surface quality as well as excellent corrosion resistance of the flat plate part and corrosion resistance of the processed part.
- SPM temper rolling
- a pre-SPM treatment was performed on the steel sheet under the condition of 100 ton using a bright roll having a surface roughness (Ra) of 0.2 ⁇ m. Subsequently, the base steel sheet was heated at a temperature 20° C. higher than the plating bath temperature (Tb) in a heating furnace having a dew point temperature of -15° C., and then immersed in a plating bath having the composition shown in Table 1 below to obtain a hot-dip plated steel sheet. The hot-dipped steel sheet was cooled using at least one inert gas of N, Ar, and He in a part of the cooling section so as to satisfy the average cooling rate (Vc) shown in Table 1 from the solidification start temperature to the solidification end temperature.
- Vc average cooling rate
- the average cooling rate for each temperature section is controlled as shown in Table 1 below, and the average damper opening rate of the edge portion and the center portion in the width direction of the steel sheet based on the surface of the hot-dipped steel sheet is
- a temper rolling (SPM) treatment is performed at a roll reduction of 50 to 150 tons using a dumb roll having a surface roughness of 2 ⁇ m to improve the characteristics and shape of the steel sheet surface. treatment was performed.
- Ts* solidification initiation temperature on equilibrium diagram [°C]
- Tb* plating bath temperature [°C]
- A* average cooling rate from solidification onset temperature to 375°C [°C/s]
- B* average cooling rate from 375°C to 340°C [°C/s]
- Vc* Average cooling rate from solidification start temperature to solidification end temperature [°C/s]
- Specimens of the above-described plated steel sheet were prepared, the plated layer was dissolved in a hydrochloric acid solution, and the dissolved liquid was analyzed by wet analysis (ICP) to measure the composition of the plated layer, and the results are shown in Table 3 below.
- ICP wet analysis
- specimens of the hot-dipped steel sheet were prepared so that the surface of the specimen having an area of 24,000 ⁇ m 2 could be observed using an SEM device.
- the area ratio of the MgZn 2 phase and the Al single phase in which Zn was dissolved at less than 27 at% in the MgZn 2 -Al-based binary process phase was determined by using an image taken using an SEM device. After obtaining each, the total area ratio and area ratio were calculated and shown in Table 3 below.
- tissue labeling is performed by the Pohang Institute of Industrial Science and Technology (RIST)'s RISA (Using the super-pixel algorithm-based image generation software of microstructure phase fraction analysis software), each microstructure was distinguished by color and contrast difference, and area% was quantified.
- RIST Pohang Institute of Industrial Science and Technology
- Example 4 For each Example and Comparative Example, the properties were evaluated based on the following criteria, and the evaluation results of the properties are shown in Table 4 below.
- the salt spray tester (Salt Spray Tester, SST) was used to evaluate according to the following criteria in accordance with ISO14993 test method.
- Time required for occurrence of red rust is 30 times or more and less than 40 times compared to Zn plating of the same thickness
- ⁇ The time required for occurrence of red rust is 20 times or more and less than 30 times compared to Zn plating of the same thickness
- ⁇ The time required for occurrence of red rust is less than 20 times that of Zn plating of the same thickness
- ⁇ The time required for occurrence of red rust is 20 times or more and less than 30 times compared to Zn plating of the same thickness
- Time required for occurrence of red rust is 10 times or more and less than 20 times compared to Zn plating of the same thickness
- the visible ray wavelength band was placed in the integrating sphere. (400 ⁇ 800nm) light was incident and evaluated according to the test method according to ISO9001 according to the type of reflected light.
- ⁇ ratio of scattering reflectivity to average total reflectance in the width direction exceeding 80% and deviation of scattering reflectivity in the width direction less than 10%
- ⁇ Ratio of scattering reflectivity to average total reflectance in the width direction of 70% or more and less than 80% and deviation of scattering reflectivity in the width direction of 10% or more
- ⁇ Ratio of scattering reflectivity to average total reflectance in the width direction of 60% or more and less than 70% and deviation of scattering reflectivity in the width direction of 10% or more
- ⁇ ratio of scattering reflectivity to average total reflectance in the width direction less than 60% and scattering reflectivity deviation in the width direction greater than 10%
- Comparative Example 9 having an insufficient Al content, a small amount of Al single phase was formed due to the insufficient amount of Al added, so that LDH was not formed as an initial corrosion product on the surface of the plated steel sheet during the corrosion resistance evaluation experiment. Due to this, not only the corrosion resistance of the flat plate part and the corrosion resistance of the bent part were inferior, but also the scattering reflectance was inferior.
- a coated steel sheet was manufactured in the same manner as in Experimental Example 1 described above, except that the open rate ratio of the damper was changed as follows according to the temperature range divided based on the surface temperature of the steel sheet. At this time, it was confirmed that the base steel sheet, the Fe-Al-based suppression layer, and the Zn-Al-Mg-based plating layer were sequentially formed using the same analysis method as in Experimental Example 1.
- Example 7 A1 99 100 99% 98 100 98%
- Example 8 A1 60 92 65% 91 94 97%
- Example 9 A1 66 94 70% 95 97 98%
- Example 10 B1 99 100 99% 91 92 99%
- Example 11 B1 65 99 66% 90 100 90%
- 1st temperature range* range from solidification onset temperature to 375°C
- Second temperature range* range from 375°C to 340°C
- a surface specimen having a size of 5,400 ⁇ m 2 was taken in the same manner as in Experimental Example 1 described above, and the area ratios of the MgZn 2 phase and the Al phase in which Zn was dissolved at less than 27 at% in the MgZn 2 -Al-based binary process were measured, respectively. It is shown in Table 6 below. In addition, with respect to the surface specimens described above, the area ratios of the Zn phase and the Zn-MgZn 2 -Al-based ternary phase were measured.
- the plating composition of the present invention and the ratio (De / Dc) of the damper open rate (De) of the edge portion to the damper open rate (Dc) of the center portion are 60 to 70% from the solidification start temperature to 375 ° C, and 375 ° C
- Comparative Example 12 which does not satisfy the condition of 90 to 99% from 340 ° C.
- Simonkolleite was first formed on the surface of the coated steel sheet during the corrosion resistance evaluation experiment, and LDH did not appear on the surface until after 12 hours. was formed For this reason, it was confirmed that the corrosion resistance of the plate of Comparative Example 12, the corrosion resistance of the bending part, and the scattering reflectance were all inferior.
- the ratio (De / Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion of the present invention is 60 to 70% from the solidification initiation temperature to 375 ° C., solidification at 375 ° C.
- LDH Layerered Double Hydroxide
- the hot-dip galvanized and cooled steel sheet was plated under the same conditions as in Experimental Examples 1 and 2 described above, except that the photo temper rolling treatment, cooling, and temper rolling (SPM) treatment after cooling were performed under the conditions shown in Tables 8 and 9 below.
- SPM temper rolling
- Example 12 66 97 68% 90 98 92% Dull 2 138.0
- Example 13 60 93 65% 98 100 98% Bright 0.4 246.0
- Example 14 63 97 65% 95 98 97% Bright 0.8 299.0
- Example 15 62 95 65% 94 96 98% Bright 0.4 266.0
- Example 16 60 93 65% 91 96 95% Bright 0.8 248.0 Comparative Example 13 90 91 99% 96 96 100% Dull 2 107.0 Comparative Example 14 92 98 94% 98 100 98% Bright 0.4 218.0 Comparative Example 15 60 95 63% 97 100 97% Bright 0.8 255.0
- 1st temperature range* range from solidification onset temperature to 375°C
- Second temperature range* range from 375°C to 340°C
- surface polishing was performed on the plated steel sheets obtained in each Example and Comparative Example on the same basis to obtain a surface area of 24,000 ⁇ m 2 at any point in the region from 1/4t to 3/4t in the thickness direction of the plated layer. Observable specimens were prepared. The surface polishing was performed on a cold-mounted specimen with the surface facing upward so as to observe the surface along the depth direction. Surface polishing was performed at a speed of about 2 ⁇ m/min using an automatic polishing machine and a silica suspension under conditions of a load of 30 N, 105 RPM, and forward rotation.
- Example 12 45.5 30.0 46.9 33.9 9.9 0.97 0.88
- Example 13 50 22.3 42.1 28.6 9.8 1.18 0.78
- Example 14 48.0 30.0 44.0 31.0 8.2 1.09 0.97
- Example 15 47.7 25.8 47 22.4 6.8 1.01 1.15
- Example 16 49.0 23.0 47.0 24.0 9.6 1.04 0.96
- Comparative Example 13 71.5 23.6 67.2 14 9.8 1.06 1.69
- Comparative Example 15 65.2 19.5 53.2 20.1 7.8 1.23 0.97
- C1* Total area ratio of MgZn 2 phase and Al phase on the surface in the area from 1/4t to 3/4t in the thickness direction of the plating layer [%]
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Abstract
Description
No.No. |
도금욕 조성 [wt%] (잔부 Zn)Plating bath composition [wt%] (balance Zn) |
Ts*Ts* | Tb*Tb* | t*t* | A*A* | B*B* | Vc*Vc* | |
MgMg | AlAl | |||||||
A1A1 | 5.05.0 | 11.911.9 | 417417 | 470470 | 1.21.2 | 7.77.7 | 12.012.0 | 9.79.7 |
A2A2 | 5.35.3 | 12.312.3 | 425425 | 480480 | 2.02.0 | 6.26.2 | 11.011.0 | 8.28.2 |
A3A3 | 5.45.4 | 12.612.6 | 428428 | 460460 | 2.42.4 | 5.55.5 | 9.09.0 | 6.96.9 |
B1B1 | 5.05.0 | 11.011.0 | 419419 | 450450 | 3.03.0 | 4.74.7 | 7.37.3 | 5.95.9 |
B2B2 | 6.06.0 | 14.014.0 | 446446 | 500500 | 3.53.5 | 3.13.1 | 77 | 3.73.7 |
B3B3 | 4.84.8 | 12.212.2 | 418418 | 480480 | 4.24.2 | 2.82.8 | 6.36.3 | 3.63.6 |
CC | 5.15.1 | 12.912.9 | 423423 | 490490 | 0.70.7 | 13.813.8 | 14.014.0 | 13.913.9 |
DD | 4.24.2 | 11.511.5 | 417417 | 470470 | 1.01.0 | 14.014.0 | 6.56.5 | 10.610.6 |
EE | 5.75.7 | 14.014.0 | 433433 | 500500 | 2.02.0 | 12.012.0 | 2.12.1 | 8.38.3 |
FF | 4.54.5 | 11.711.7 | 416416 | 490490 | 3.03.0 | 16.016.0 | 15.015.0 | 15.515.5 |
GG | 5.05.0 | 13.513.5 | 425425 | 490490 | 3.53.5 | 9.09.0 | 5.95.9 | 7.77.7 |
HH | 5.95.9 | 13.013.0 | 440440 | 500500 | 4.04.0 | 10.010.0 | 2.92.9 | 7.57.5 |
II | 3.53.5 | 10.010.0 | 408408 | 450450 | 1.21.2 | 8.08.0 | 13.013.0 | 10.610.6 |
JJ | 6.56.5 | 12.012.0 | 457457 | 500500 | 1.41.4 | 7.57.5 | 12.512.5 | 9.09.0 |
KK | 5.55.5 | 8.08.0 | 442442 | 480480 | 3.03.0 | 5.05.0 | 8.08.0 | 6.06.0 |
LL | 6.06.0 | 14.514.5 | 440440 | 480480 | 2.02.0 | 6.06.0 | 12.512.5 | 8.38.3 |
MM | 6.06.0 | 12.012.0 | 445445 | 470470 | 2.02.0 | 6.06.0 | 6.06.0 | 6.06.0 |
비고note | No.No. | De*De* | Dc*Dc* | De/DcDe/Dc |
실시예 1Example 1 | A1A1 | 9797 | 100100 | 97%97% |
실시예 2Example 2 | A2A2 | 9090 | 9494 | 96%96% |
실시예 3Example 3 | A3A3 | 9393 | 9797 | 96%96% |
실시예 4Example 4 | B1B1 | 9292 | 9393 | 99%99% |
실시예 5Example 5 | B2B2 | 9191 | 9797 | 94%94% |
실시예 6Example 6 | B3B3 | 9898 | 9999 | 99%99% |
비교예 1Comparative Example 1 |
C |
100100 | 9393 | 108%108% |
비교예 2Comparative Example 2 | DD | 9696 | 9797 | 99%99% |
비교예 3Comparative Example 3 |
E |
100100 | 9292 | 109%109% |
비교예 4Comparative Example 4 | FF | 9595 | 9393 | 102%102% |
비교예 5Comparative Example 5 | GG | 9898 | 9393 | 105%105% |
비교예 6Comparative Example 6 | HH | 9797 | 9797 | 100%100% |
비교예 7Comparative Example 7 | II | 9999 | 100100 | 99%99% |
비교예 8Comparative Example 8 | JJ | 9191 | 9898 | 93%93% |
비교예 9Comparative Example 9 | KK | 9898 | 9696 | 102%102% |
비교예 10Comparative Example 10 | LL | 9191 | 9494 | 97%97% |
비교예 11Comparative Example 11 | MM | 9797 | 100100 | 97%97% |
No.No. |
도금층 조성 (잔부 Zn) [wt%]plating layer composition (balance Zn) [wt%] |
Zn-Mg-Al계 도금층의 표면Surface of Zn-Mg-Al-based plating layer | |||||
MgMg | AlAl | Al 단상과 MgZn2상의 합계 면적율[%]Total area ratio of Al single phase and MgZn 2 phase [%] | MgZn2상 면적율 [%]MgZn 2 phase area ratio [%] | Al단상 면적율 [%]Al single phase area ratio [%] | 제2 Al 단상 면적율 [%]2nd Al single phase area ratio [%] | Al단상에 대한 MgZn2 상의 면적비Area ratio of MgZn 2 phase to Al single phase | |
실시예 1Example 1 | 5.05.0 | 11.911.9 | 45.545.5 | 3535 | 10.510.5 | 5.55.5 | 3.33.3 |
실시예 2Example 2 | 5.35.3 | 12.312.3 | 49.849.8 | 3535 | 14.814.8 | 88 | 2.42.4 |
실시예 3Example 3 | 5.45.4 | 12.612.6 | 45.845.8 | 30.130.1 | 15.715.7 | 99 | 1.91.9 |
실시예 4Example 4 | 5.05.0 | 11.011.0 | 52.252.2 | 3535 | 17.217.2 | 6.86.8 | 2.02.0 |
실시예 5Example 5 | 6.06.0 | 14.014.0 | 5353 | 35.235.2 | 17.817.8 | 55 | 2.02.0 |
실시예 6Example 6 | 4.84.8 | 12.212.2 | 50.650.6 | 31.431.4 | 19.219.2 | 88 | 1.61.6 |
비교예 1Comparative Example 1 | 5.15.1 | 12.912.9 | 38.338.3 | 20.720.7 | 17.617.6 | 2.92.9 | 1.21.2 |
비교예 2Comparative Example 2 | 4.24.2 | 11.511.5 | 41.541.5 | 23.123.1 | 18.418.4 | 12.312.3 | 1.31.3 |
비교예 3Comparative Example 3 | 5.75.7 | 14.014.0 | 27.527.5 | 14.714.7 | 12.812.8 | 1010 | 1.11.1 |
비교예 4Comparative Example 4 | 4.54.5 | 11.711.7 | 44.544.5 | 29.729.7 | 14.814.8 | 7.27.2 | 2.02.0 |
비교예 5Comparative Example 5 | 5.05.0 | 13.513.5 | 42.742.7 | 22.622.6 | 20.120.1 | 1010 | 1.11.1 |
비교예 6Comparative Example 6 | 5.95.9 | 13.013.0 | 43.543.5 | 26.526.5 | 1717 | 1515 | 1.61.6 |
비교예 7Comparative Example 7 | 3.53.5 | 10.010.0 | 29.529.5 | 12.512.5 | 1717 | 33 | 0.70.7 |
비교예 8Comparative Example 8 | 6.56.5 | 12.012.0 | 71.571.5 | 46.546.5 | 2525 | 99 | 1.91.9 |
비교예 9Comparative Example 9 | 5.55.5 | 8.08.0 | 41.741.7 | 31.531.5 | 10.210.2 | 99 | 3.13.1 |
비교예 10Comparative Example 10 | 6.06.0 | 14.514.5 | 6262 | 3838 | 2424 | 88 | 1.61.6 |
비교예 11Comparative Example 11 | 6.06.0 | 12.012.0 | 65.265.2 | 43.243.2 | 2222 | 1414 | 2.02.0 |
No.No. | 표면에 최초로 형성되는 부식 생성물의 종류Types of corrosion products that first form on the surface | 특성 평가Characteristic evaluation | ||
평판부 내식성reputation department corrosion resistance |
굽힘 가공부 내식성bending part corrosion resistance |
산란 반사도spawning reflectivity |
||
실시예 1Example 1 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
실시예 2Example 2 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
실시예 3Example 3 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
실시예 4Example 4 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
실시예 5Example 5 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
실시예 6Example 6 | Layered Double HydroxideLayered Double Hydroxide | ○○ | ○○ | △△ |
비교예 1Comparative Example 1 | SimonkolleiteSimonkolleite | △△ | ХХ | ХХ |
비교예 2Comparative Example 2 | SimonkolleiteSimonkolleite | △△ | △△ | ХХ |
비교예 3Comparative Example 3 | SimonkolleiteSimonkolleite | △△ | △△ | ХХ |
비교예 4Comparative Example 4 | SimonkolleiteSimonkolleite | △△ | ХХ | ХХ |
비교예 5Comparative Example 5 | SimonkolleiteSimonkolleite | △△ | △△ | ХХ |
비교예 6Comparative Example 6 | SimonkolleiteSimonkolleite | △△ | △△ | ХХ |
비교예 7Comparative Example 7 | SimonkolleiteSimonkolleite | ХХ | ХХ | ХХ |
비교예 8Comparative Example 8 | LDHLDH | ○○ | ХХ | △△ |
비교예 9Comparative Example 9 | SimonkolleiteSimonkolleite | △△ | ХХ | ХХ |
비교예 10Comparative Example 10 | LDHLDH | ○○ | ХХ | △△ |
비교예 11Comparative Example 11 | LDHLDH | ○○ | ХХ | △△ |
비고note | No.No. | 제1 온도 구간*1st temperature zone* | 제2 온도 구간*Second temperature zone* | ||||
De*De* | Dc*Dc* | De/DcDe/Dc | De*De* | Dc*Dc* | De/DcDe/Dc | ||
실시예 7Example 7 | A1A1 | 9999 | 100100 | 99%99% | 9898 | 100100 | 98%98% |
실시예 8Example 8 |
A1 |
6060 | 9292 | 65%65% | 9191 | 9494 | 97%97% |
실시예 9Example 9 | A1A1 | 6666 | 9494 | 70%70% | 9595 | 9797 | 98%98% |
실시예 10Example 10 | B1B1 | 9999 | 100100 | 99%99% | 9191 | 9292 | 99%99% |
실시예 11Example 11 | B1B1 | 6565 | 9999 | 66%66% | 9090 | 100100 | 90%90% |
실시예 12Example 12 | B1B1 | 6868 | 9797 | 70%70% | 9090 | 9292 | 98%98% |
비교예 12Comparative Example 12 | II | 9595 | 9292 | 103%103% | 9696 | 100100 | 96%96% |
비고note | Zn-Mg-Al계 도금층 단면Cross section of Zn-Mg-Al-based plating layer | Zn-Mg-Al계 도금층의 표면Surface of Zn-Mg-Al-based plating layer | |||||
MgZn2상 면적율 [%]MgZn 2 phase area ratio [%] | Al단상 면적율 [%]Al single phase area ratio [%] | MgZn2상 면적율 [%]MgZn 2 phase area ratio [%] | Al단상 면적율 [%]Al single phase area ratio [%] | Al단상과 MgZn2상의 합계 면적율 [%]Total area ratio of Al single phase and MgZn 2 phase [%] | Al단상에 대한 MgZn2 상의 면적비Area ratio of MgZn 2 phase to Al single phase | Zn상 및 Zn-MgZn2-Al계 3원 공정상의 합계 면적율 [%]Total area ratio of Zn phase and Zn-MgZn 2 -Al-based ternary eutectic phase [%] | |
실시예 7Example 7 | 2727 | 1515 | 3535 | 10.510.5 | 45.545.5 | 3.33.3 | 30.730.7 |
실시예 8Example 8 | 4040 | 1818 | 37.837.8 | 15.115.1 | 52.952.9 | 2.52.5 | 25.425.4 |
실시예 9Example 9 | 3939 | 1515 | 36.936.9 | 16.816.8 | 53.753.7 | 2.22.2 | 26.926.9 |
실시예 10Example 10 | 3535 | 1111 | 3030 | 25.625.6 | 55.655.6 | 1.21.2 | 23.723.7 |
실시예 11Example 11 | 2929 | 2323 | 35.135.1 | 19.119.1 | 54.254.2 | 1.81.8 | 24.124.1 |
비교예 12Comparative Example 12 | 22.422.4 | 2525 | 22.522.5 | 1010 | 32.532.5 | 2.32.3 | 40.240.2 |
No.No. | LDH 부식 생성물이 형성되는 시간Time for LDH corrosion products to form | 특성 평가Characteristic evaluation | ||
평판부내식성Plate corrosion resistance | 굽힘 가공부내식성Corrosion resistance of bending parts | 산란반사도scattering reflectance | ||
실시예 7Example 7 | 10min10min | ○○ | ○○ | △△ |
실시예 8Example 8 | 5min5min | ◎◎ | ◎◎ | △△ |
실시예 9Example 9 | 5min5min | ◎◎ | ◎◎ | △△ |
실시예 10Example 10 | 5min5min | ◎◎ | ◎◎ | △△ |
실시예 11Example 11 | 5min5min | ◎◎ | ◎◎ | △△ |
비교예 12Comparative Example 12 | -- | △△ | ХХ | ХХ |
비고note | No.No. |
용융 아연 도금 전, 사전 SPM 처리 조건Before hot dip galvanizing, Pre-SPM processing conditions |
||
롤 종류roll type | 롤 표면 조도 Ra [㎛]Roll surface roughness Ra [㎛] | 강판 표면에 가하는 롤 압하 [ton]Roll pressure applied to the steel plate surface [ton] | ||
실시예 12Example 12 | A1A1 | BrightBright | 0.40.4 | 100.0100.0 |
실시예 13Example 13 | A1A1 | BrightBright | 0.40.4 | 200.0200.0 |
실시예 14Example 14 | A1A1 | BrightBright | 0.80.8 | 300.0300.0 |
실시예 15Example 15 | B1B1 | BrightBright | 0.40.4 | 250.0250.0 |
실시예 16Example 16 | B1B1 | BrightBright | 0.80.8 | 288.0288.0 |
비교예 13Comparative Example 13 | JJ | BrightBright | 0.40.4 | 50.050.0 |
비교예 14Comparative Example 14 | KK | BrightBright | 0.40.4 | 102.0102.0 |
비교예 15Comparative Example 15 | MM | BrightBright | 0.80.8 | 250.0250.0 |
비고note | 제1 온도 구간*1st temperature zone* | 제2 온도 구간*Second temperature zone* | SPM 처리 조건SPM processing conditions | ||||||
De*De* | Dc*Dc* | De/DcDe/Dc | De*De* | Dc*Dc* | De/DcDe/Dc | 롤 종류roll type | 롤 표면 조도 Ra [㎛]Roll surface roughness Ra [㎛] | 강판 표면에 가하는 롤 압하 [ton]Roll pressure applied to the steel plate surface [ton] | |
실시예 12Example 12 | 6666 | 9797 | 68%68% | 9090 | 9898 | 92%92% | DullDull | 22 | 138.0138.0 |
실시예 13Example 13 | 6060 | 9393 | 65%65% | 9898 | 100100 | 98%98% | BrightBright | 0.40.4 | 246.0246.0 |
실시예 14Example 14 | 6363 | 9797 | 65%65% | 9595 | 9898 | 97%97% | BrightBright | 0.80.8 | 299.0299.0 |
실시예 15Example 15 | 6262 | 9595 | 65%65% | 9494 | 9696 | 98%98% | BrightBright | 0.40.4 | 266.0266.0 |
실시예 16Example 16 | 6060 | 9393 | 65%65% | 9191 | 9696 | 95%95% | BrightBright | 0.80.8 | 248.0248.0 |
비교예 13Comparative Example 13 | 9090 | 9191 | 99%99% | 9696 | 9696 | 100%100% | DullDull | 22 | 107.0107.0 |
비교예 14Comparative Example 14 | 9292 | 9898 | 94%94% | 9898 | 100100 | 98%98% | BrightBright | 0.40.4 | 218.0218.0 |
비교예 15Comparative Example 15 | 6060 | 9595 | 63%63% | 9797 | 100100 | 97%97% | BrightBright | 0.80.8 | 255.0255.0 |
비고note | Zn-Mg-Al계 도금층의 표면Surface of Zn-Mg-Al-based plating layer | |||||
MgZn2상 면적율 [%]MgZn 2 phase area ratio [%] | Al단상 면적율 [%]Al single phase area ratio [%] | Al단상과 MgZn2상의 합계 면적율 [%]Total area ratio of Al single phase and MgZn 2 phase [%] | Al단상에 대한 MgZn2 상의 면적비Area ratio of MgZn 2 phase to Al single phase | Zn단상 및 Zn-MgZn2-Al계 3원 공정상의 합계 면적율 [%]Total area ratio of Zn single phase and Zn-MgZn 2 -Al ternary eutectic phase [%] |
제2 Al 단상 면적율 [%]2nd Al single phase area ratio [%] |
|
실시예 12Example 12 | 3535 | 10.510.5 | 45.545.5 | 3.33.3 | 3030 | 7.37.3 |
실시예 13Example 13 | 30.630.6 | 21.821.8 | 5050 | 1.41.4 | 22.322.3 | 7.57.5 |
실시예 14Example 14 | 32.232.2 | 15.815.8 | 4848 | 2.02.0 | 3030 | 5.45.4 |
실시예 15Example 15 | 30.630.6 | 20.120.1 | 47.747.7 | 1.51.5 | 25.825.8 | 9.59.5 |
실시예 16Example 16 | 3232 | 1717 | 4949 | 1.91.9 | 2323 | 6.56.5 |
비교예 13Comparative Example 13 | 46.546.5 | 2525 | 71.571.5 | 1.91.9 | 23.623.6 | 2.92.9 |
비교예 14Comparative Example 14 | 31.531.5 | 10.210.2 | 41.741.7 | 3.13.1 | 42.142.1 | 7.27.2 |
비교예 15Comparative Example 15 | 43.243.2 | 2222 | 65.265.2 | 2.02.0 | 19.519.5 | 8.68.6 |
비고note | Zn-Mg-Al계 도금층의 표면Surface of Zn-Mg-Al-based plating layer | 도금층의 두께방향으로 1/4t로부터 3/4t까지의 영역 중의 표면Surface in the region from 1/4t to 3/4t in the thickness direction of the plating layer | S1/C1S1/C1 | S2/C2S2/C2 | |||
S1*S1* | S2*S2* | C1*C1* | C2*C2* | 제2 Al 단상 면적율 [%]2nd Al single phase area ratio [%] | |||
실시예 12Example 12 | 45.545.5 | 30.030.0 | 46.946.9 | 33.933.9 | 9.99.9 | 0.970.97 | 0.880.88 |
실시예 13Example 13 | 5050 | 22.322.3 | 42.142.1 | 28.628.6 | 9.89.8 | 1.181.18 | 0.780.78 |
실시예 14Example 14 | 48.048.0 | 30.030.0 | 44.044.0 | 31.031.0 | 8.28.2 | 1.091.09 | 0.970.97 |
실시예 15Example 15 | 47.747.7 | 25.825.8 | 4747 | 22.422.4 | 6.86.8 | 1.011.01 | 1.151.15 |
실시예 16Example 16 | 49.049.0 | 23.023.0 | 47.047.0 | 24.024.0 | 9.69.6 | 1.041.04 | 0.960.96 |
비교예 13Comparative Example 13 | 71.571.5 | 23.623.6 | 67.267.2 | 1414 | 9.89.8 | 1.061.06 | 1.691.69 |
비교예 14Comparative Example 14 | 41.741.7 | 42.142.1 | 56.956.9 | 12.712.7 | 6.56.5 | 0.730.73 | 3.313.31 |
비교예 15Comparative Example 15 | 65.265.2 | 19.519.5 | 53.253.2 | 20.120.1 | 7.87.8 | 1.231.23 | 0.970.97 |
No.No. | 특성 평가Characteristic evaluation | ||
평판부 내식성Corrosion resistance of plate part | 굽힘 가공부 내식성Corrosion resistance of bending parts | 산란 반사도scattering reflectivity | |
실시예 12Example 12 | ○○ | ○○ | △△ |
실시예 13Example 13 | ◎◎ | ◎◎ | ◎◎ |
실시예 14Example 14 | ◎◎ | ◎◎ | ◎◎ |
실시예 15Example 15 | ◎◎ | ◎◎ | ◎◎ |
실시예 16Example 16 | ◎◎ | ◎◎ | ◎◎ |
비교예 13Comparative Example 13 | ○○ | ХХ | ХХ |
비교예 14Comparative Example 14 | △△ | △△ | ХХ |
비교예 15Comparative Example 15 | ○○ | ХХ | ХХ |
Claims (17)
- 소지강판;base steel plate;상기 소지강판의 적어도 일면에 구비된 Zn-Mg-Al계 도금층; 및a Zn-Mg-Al-based plating layer provided on at least one surface of the base steel sheet; and상기 소지강판과 상기 Zn-Mg-Al계 도금층 사이에 구비된 Fe-Al계 억제층;을 포함하고,Including; Fe-Al-based suppression layer provided between the base steel sheet and the Zn-Mg-Al-based plating layer,Zn-Mg-Al계 도금층의 표면에서,Al 단상과 MgZn2상의 합계 면적율은 45~60%이고, 상기 Al 단상에 대한 상기 MgZn2상의 면적비는 1.2~3.3인, 도금 강판.On the surface of the Zn-Mg-Al-based plating layer, the total area ratio of the Al single phase and the MgZn 2 phase is 45 to 60%, and the area ratio of the MgZn 2 phase to the Al single phase is 1.2 to 3.3.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층은, 중량%로, Mg: 4~6%, Al: 8.2~14.2%, 잔부 Zn 및 기타 불가피한 불순물을 포함하는, 도금 강판.The plated steel sheet, wherein the Zn-Mg-Al-based plating layer contains, in weight percent, Mg: 4 to 6%, Al: 8.2 to 14.2%, the balance Zn and other unavoidable impurities.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 단면을 기준으로, MgZn2상의 면적율은 20~40%이고, Al 단상의 면적율은 8~26%인, 도금 강판.Based on the cross section of the Zn-Mg-Al-based plating layer, the area ratio of the MgZn 2 phase is 20 to 40%, and the area ratio of the Al single phase is 8 to 26%.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 표면에서, 상기 MgZn2상의 면적율은 30~40%인, 도금 강판.On the surface of the Zn-Mg-Al-based plating layer, the area ratio of the MgZn 2 phase is 30 to 40%, the plated steel sheet.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 표면에서, 상기 Al 단상의 면적율은 15~20%이고,On the surface of the Zn-Mg-Al-based plating layer, the area ratio of the Al single phase is 15 to 20%,상기 Al 단상은 원자%로, Zn가 27% 미만으로 고용되고, 잔부가 Al 및 기타 불순물을 포함하는 상인, 도금 강판.The Al single phase is a phase in which Zn is dissolved by less than 27% in atomic percent, and the balance includes Al and other impurities, the coated steel sheet.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 두께방향으로 1/4t로부터 3/4t까지의 영역 중 어느 하나에 해당하는 지점의 표면에서 MgZn2상과 Al 단상의 합계 면적율(C1)에 대한 상기 Zn-Mg-Al계 도금층의 표면에서 MgZn2상과 Al 단상의 합계 면적율(S1)의 비(S1/C1)는 0.8~1.2 범위인, 도금 강판.The Zn-Mg with respect to the total area ratio (C1) of the MgZn 2 phase and the Al single phase on the surface of a point corresponding to any one of the regions from 1/4t to 3/4t in the thickness direction of the Zn-Mg-Al-based plating layer. -A plated steel sheet in which the ratio (S1/C1) of the total area ratio (S1) of the MgZn 2 phase and the Al single phase on the surface of the Al-based plating layer is in the range of 0.8 to 1.2.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 표면에서 Zn상 및 Zn-MgZn2-Al계 3원 공정상의 합계 면적율은 20~30%인, 도금 강판.The total area ratio of the Zn phase and the Zn-MgZn 2 -Al-based ternary process phase on the surface of the Zn-Mg-Al-based plating layer is 20 to 30%, the plated steel sheet.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층의 두께방향으로 1/4t로부터 3/4t까지의 영역 중 임의 지점의 표면에서 Zn상과 Zn-MgZn2-Al계 3원 공정상의 합계 면적율(C2)에 대한 상기 Zn-Mg-Al계 도금층의 표면에서 Zn상과 Zn-MgZn2-Al계 3원 공정상의 합계 면적율(S2)의 비(S2/C2)는 0.6~1.2 범위인, 도금 강판.The total area ratio (C2) of the Zn phase and the Zn-MgZn 2 -Al-based ternary process phase on the surface of any point in the region from 1/4t to 3/4t in the thickness direction of the Zn-Mg-Al-based plating layer The ratio (S2/C2) of the total area ratio (S2) of the Zn phase and the Zn-MgZn 2 -Al-based ternary eutectic phase on the surface of the Zn-Mg-Al-based plating layer is in the range of 0.6 to 1.2, the plated steel sheet.
- 제 1 항에 있어서,According to claim 1,상기 Zn-Mg-Al계 도금층 표면에서, 원자%로, Zn를 27~60% 고용하는 제2 Al 단상의 면적율은 2~9%인, 도금 강판.On the surface of the Zn-Mg-Al-based plating layer, the area ratio of the second Al single phase in which 27 to 60% of Zn is dissolved in atomic percent is 2 to 9%.
- 제 1 항에 있어서,According to claim 1,대기 환경 및 ISO14993의 염화물 환경 하에서, 상기 Zn-Mg-Al계 도금층의 표면에LDH((Zn,Mg)6Al2(OH)16(CO3)·4H2O)가 시몬콜라이트(Zn5(OH)8Cl2) 및 하이드로진사이트(Zn5(OH)6(CO3)2)보다 먼저 형성되는, 도금 강판. Under the atmospheric environment and the chloride environment of ISO14993, LDH ((Zn,Mg) 6 Al 2 (OH) 16 (CO 3 ) 4H 2 O) on the surface of the Zn - Mg-Al-based plating layer is (OH) 8 Cl 2 ) and hydrozincite (Zn 5 (OH) 6 (CO 3 ) 2 ), which is formed before the plated steel sheet.
- 제 1 항에 있어서,According to claim 1,대기 환경 및 ISO14993의 염화물 환경 하에서, 상기 Zn-Mg-Al계 도금층의 표면에LDH((Zn,Mg)6Al2(OH)16(CO3)·4H2O)가 대기환경에서 6시간, 염화물 환경에서 5분 이내에 형성되는, 도금 강판. LDH ((Zn,Mg) 6 Al 2 (OH) 16 (CO 3 )·4H 2 O) is applied to the surface of the Zn-Mg-Al-based plating layer in an atmospheric environment and a chloride environment of ISO14993 for 6 hours in an atmospheric environment, Plated steel, formed in less than 5 minutes in a chloride environment.
- 제 1 항에 있어서,According to claim 1,염수분무 및 침지 환경을 포함한 ISO14993의 염화물 환경에서 적청 발생에 걸리는 시간이 동일 두께의 Zn도금 대비, 평판부에서 40~50배; 및 90도 굽힘 가공부에서 20~30배인, 도금 강판.In the chloride environment of ISO14993, including salt spray and immersion environments, the time required for red rust to occur is 40 to 50 times higher than that of Zn plating of the same thickness in flat parts; and coated steel sheet, which is 20 to 30 times in the 90 degree bending processing part.
- 소지강판을 중량%로, Mg: 4~6%, Al: 8.2~14.2%, 잔부 Zn 및 기타 불가피한 불순물을 포함하고, 평형상태도상 응고 개시 온도 대비 20~80℃ 높은 온도로 유지되는 도금욕에 침지하여 용융 아연 도금하는 단계; 및In a plating bath containing the base steel sheet in weight percent, Mg: 4-6%, Al: 8.2-14.2%, the balance Zn and other unavoidable impurities, maintained at a temperature 20-80°C higher than the solidification initiation temperature in equilibrium. immersion and hot-dip galvanizing; and상기 용융 아연 도금된 강판을 응고 개시 온도로부터 응고 종료 온도까지 2~12℃/s의 평균 냉각 속도로 불활성 가스를 이용하여 냉각하는 단계;를 포함하고,cooling the hot-dip galvanized steel sheet from a solidification start temperature to a solidification end temperature using an inert gas at an average cooling rate of 2 to 12° C./s;상기 냉각하는 단계는 하기 관계식 1-1 및 1-2를 충족하고, 센터부의 댐퍼 개도율(Dc)에 대한 에지부의 댐퍼 개도율(De)의 비율(De/Dc)이 60~99%를 충족하도록 냉각을 실시하는, 도금 강판의 제조방법.The cooling step satisfies the following relational expressions 1-1 and 1-2, and the ratio (De / Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion satisfies 60 to 99% A method for manufacturing a plated steel sheet, wherein cooling is performed so as to do so.[관계식 1-1][Relationship 1-1]A <{(5-2lnt)/(7-3lnt)}×BA < {(5-2lnt)/(7-3lnt)}×B[관계식 1-2] [Relationship 1-2]15t(-0.8) ≤ B ≤ 20t(-0.8) 15t (-0.8) ≤ B ≤ 20t (-0.8)(상기 관계식 1-1 및 1-2에 있어서, 상기 t는 강판의 두께(㎜)이고, 상기 A는 응고 개시온도에서 375℃까지 평균 냉각 속도(℃/s)이고, 상기 B는 375℃에서 340℃까지의 평균 냉각 속도(℃/s)를 나타낸다.)(In the relational expressions 1-1 and 1-2, t is the thickness of the steel sheet (mm), A is the average cooling rate (° C./s) from the solidification start temperature to 375° C., and B is at 375° C. Average cooling rate (°C/s) up to 340°C is shown.)
- 제 13 항에 있어서,According to claim 13,상기 냉각하는 단계는, 온도 구간에 따라, 상기 센터부의 댐퍼 개도율(Dc)에 대한 에지부의 댐퍼 개도율(De)의 비율(De/Dc)에 변화를 주어 냉각을 실시하고,In the cooling step, cooling is performed by changing the ratio (De/Dc) of the damper opening rate (De) of the edge portion to the damper opening rate (Dc) of the center portion according to the temperature range,상기 센터부의 댐퍼 개도율(Dc)에 대한 에지부의 댐퍼 개도율(De)의 비율(De/Dc)은 응고 개시 온도에서 375℃까지 60~70%이고, 375℃에서 340℃까지 90~99%인, 도금 강판의 제조방법.The ratio (De / Dc) of the damper open rate (De) of the edge portion to the damper open rate (Dc) of the center portion is 60 to 70% from the solidification start temperature to 375 ° C, and 90 to 99% from 375 ° C to 340 ° C A method for manufacturing phosphorus and plated steel sheets.
- 제 14 항에 있어서,15. The method of claim 14,상기 냉각하는 단계 이후, 조질압연 처리를 행하여 소지강판의 표면 및 형상을 개선하는 단계를 더 포함하고, After the cooling step, further comprising the step of improving the surface and shape of the steel sheet by performing a temper rolling treatment,상기 조질압연 처리는 표면 조도(Ra)가 0.2~1.0㎛인 브라이트 롤을 이용하여, 50~300ton의 롤 압하를 강판 표면에 가하도록 수행되는, 도금강판의 제조방법.The temper rolling treatment is performed by using a bright roll having a surface roughness (Ra) of 0.2 to 1.0 μm to apply a roll reduction of 50 to 300 tons to the surface of the steel sheet.
- 제 13 항에 있어서,According to claim 13,상기 용융 아연 도금 전, 표면 조도(Ra)가 0.2~0.4㎛인 브라이트 롤을 이용하여, 200~300ton의 롤 압하를 강판 표면에 가하는 사전 조질 압연 처리를 행하는 단계를 더 포함하는, 도금 강판의 제조방법.Before the hot-dip galvanizing, using a bright roll having a surface roughness (Ra) of 0.2 to 0.4 μm, a pre-temperature rolling treatment of applying a roll reduction of 200 to 300 tons to the surface of the steel sheet Further comprising the step of manufacturing a plated steel sheet method.
- 청구항 16에 있어서,The method of claim 16상기 사전 조질 압연 처리 시, 롤 압하는 250~300ton인, 도금 강판의 제조방법.During the pre-temperature rolling treatment, the roll rolling is 250 to 300 ton, a method of manufacturing a coated steel sheet.
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Citations (7)
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KR20100073819A (en) | 2008-12-23 | 2010-07-01 | 주식회사 포스코 | Method for manufacturing high manganese hot dip galvanizing steel sheet with superior surface property |
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KR20190078331A (en) | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | Method and apparatus for producing labeling image of microstructure using super-pixels |
KR20190078435A (en) * | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | Zinc alloy coated steel having excellent surface property and corrosion resistance, and method for manufacturing the same |
KR20210035722A (en) * | 2019-09-24 | 2021-04-01 | 주식회사 포스코 | Plated steel sheet having excellent corrosion resistance, galling resistance, workability and surface property and method for manufacturing the same |
KR20210071631A (en) * | 2019-12-06 | 2021-06-16 | 주식회사 포스코 | Galvanizing steel sheet having excelent bendability and corrosion resistance, and manufacturing method thereof |
WO2021256906A1 (en) * | 2020-06-19 | 2021-12-23 | 주식회사 포스코 | Plated steel sheet having excellent corrosion resistance, workability and surface quality and method for manufacturing same |
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2021
- 2021-06-18 KR KR1020210079649A patent/KR102529740B1/en active IP Right Grant
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2022
- 2022-06-10 WO PCT/KR2022/008200 patent/WO2022265307A1/en active Application Filing
- 2022-06-10 CN CN202280043481.7A patent/CN117561347A/en active Pending
- 2022-06-10 EP EP22825232.6A patent/EP4357478A1/en active Pending
- 2022-11-18 KR KR1020220155578A patent/KR20220169450A/en active Application Filing
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KR20100073819A (en) | 2008-12-23 | 2010-07-01 | 주식회사 포스코 | Method for manufacturing high manganese hot dip galvanizing steel sheet with superior surface property |
KR20160078912A (en) * | 2014-12-24 | 2016-07-05 | 주식회사 포스코 | Zn ALLOY PLATED STEEL SHEET HAVING EXCELLENT PHOSPHATABILITY AND SPOT WELDABILITY AND METHOD FOR MANUFACTURING SAME |
KR20190078331A (en) | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | Method and apparatus for producing labeling image of microstructure using super-pixels |
KR20190078435A (en) * | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | Zinc alloy coated steel having excellent surface property and corrosion resistance, and method for manufacturing the same |
KR20210035722A (en) * | 2019-09-24 | 2021-04-01 | 주식회사 포스코 | Plated steel sheet having excellent corrosion resistance, galling resistance, workability and surface property and method for manufacturing the same |
KR20210071631A (en) * | 2019-12-06 | 2021-06-16 | 주식회사 포스코 | Galvanizing steel sheet having excelent bendability and corrosion resistance, and manufacturing method thereof |
WO2021256906A1 (en) * | 2020-06-19 | 2021-12-23 | 주식회사 포스코 | Plated steel sheet having excellent corrosion resistance, workability and surface quality and method for manufacturing same |
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EP4357478A1 (en) | 2024-04-24 |
KR20220169450A (en) | 2022-12-27 |
CN117561347A (en) | 2024-02-13 |
KR102529740B1 (en) | 2023-05-08 |
KR20220169338A (en) | 2022-12-27 |
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