WO2023055028A1 - 내식성 및 굽힘성이 우수한 도금 강판 및 이의 제조방법 - Google Patents
내식성 및 굽힘성이 우수한 도금 강판 및 이의 제조방법 Download PDFInfo
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- WO2023055028A1 WO2023055028A1 PCT/KR2022/014438 KR2022014438W WO2023055028A1 WO 2023055028 A1 WO2023055028 A1 WO 2023055028A1 KR 2022014438 W KR2022014438 W KR 2022014438W WO 2023055028 A1 WO2023055028 A1 WO 2023055028A1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 120
- 239000010959 steel Substances 0.000 title claims abstract description 120
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 22
- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000007797 corrosion Effects 0.000 title abstract description 41
- 238000005260 corrosion Methods 0.000 title abstract description 41
- 229910003023 Mg-Al Inorganic materials 0.000 claims abstract description 22
- 238000007747 plating Methods 0.000 claims description 125
- 229910017706 MgZn Inorganic materials 0.000 claims description 99
- 238000001816 cooling Methods 0.000 claims description 75
- 230000001629 suppression Effects 0.000 claims description 15
- 229910052782 aluminium Inorganic materials 0.000 claims description 13
- 239000012535 impurity Substances 0.000 claims description 13
- 229910052749 magnesium Inorganic materials 0.000 claims description 10
- 229910001335 Galvanized steel Inorganic materials 0.000 claims description 7
- 239000008397 galvanized steel Substances 0.000 claims description 7
- 239000011261 inert gas Substances 0.000 claims description 7
- 238000007711 solidification Methods 0.000 claims description 7
- 230000008023 solidification Effects 0.000 claims description 7
- 238000005246 galvanizing Methods 0.000 claims description 6
- 239000011701 zinc Substances 0.000 description 155
- 239000010410 layer Substances 0.000 description 76
- 230000000052 comparative effect Effects 0.000 description 68
- 239000011777 magnesium Substances 0.000 description 65
- 239000006104 solid solution Substances 0.000 description 19
- 239000000203 mixture Substances 0.000 description 18
- 230000005496 eutectics Effects 0.000 description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 12
- 238000005452 bending Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 229910052725 zinc Inorganic materials 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 9
- 229910001297 Zn alloy Inorganic materials 0.000 description 8
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 229910000765 intermetallic Inorganic materials 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 229910018137 Al-Zn Inorganic materials 0.000 description 2
- 229910018573 Al—Zn Inorganic materials 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910015372 FeAl Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 229910000617 Mangalloy Inorganic materials 0.000 description 2
- 229910007570 Zn-Al Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 230000016507 interphase Effects 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 241000446313 Lamella Species 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910009369 Zn Mg Inorganic materials 0.000 description 1
- 229910007573 Zn-Mg Inorganic materials 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Images
Classifications
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- 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
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
- C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
- C23C2/18—Removing excess of molten coatings from elongated material
- C23C2/20—Strips; Plates
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
- C23C2/29—Cooling or quenching
-
- 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
- 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
- C23C2/40—Plates; Strips
Definitions
- the present invention relates to a highly corrosion resistant plated steel sheet having excellent corrosion resistance and bendability 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.
- the Zn-Mg-Al-based zinc alloy-coated steel sheet may deteriorate coating adhesion due to oxides such as dross being attached to the Zn-Mg-Al-based zinc alloy-coated steel sheet in the process of plating, or the reactivity with the steel sheet being weakened.
- oxides such as dross being attached to the Zn-Mg-Al-based zinc alloy-coated steel sheet in the process of plating, or the reactivity with the steel sheet being weakened.
- Patent Document 1 Korean Publication No. 2010-0073819
- the present invention is intended to provide a coated steel sheet excellent in corrosion resistance and bendability and a manufacturing method thereof.
- it is intended to provide a coated steel sheet excellent in corrosion resistance and bendability as well as plating adhesion and a manufacturing method thereof.
- the plating layer is MgZn 2 phase; and a Zn single phase formed along the outline of the MgZn 2 phase.
- Another aspect of the present invention is,
- the base steel sheet in weight%, Mg: 4.0 to 7.0%, Al: 11.0 to 19.5%, the balance Zn and immersing in a plating bath containing other unavoidable impurities to perform hot-dip galvanizing;
- the W air represents the interval of the air knife, and the unit is mm.
- the P air represents the pressure of the air knife, and the unit is kPa.
- the T represents the temperature of the supplied inert gas, , unit is °C.
- Example 1 shows a photograph taken with a Field Emission Scanning Electron Microscope (hereinafter referred to as 'FE-SEM') by magnifying the surface of the plated steel sheet obtained in Example 1 at a magnification of 1,500.
- 'FE-SEM' Field Emission Scanning Electron Microscope
- FIG. 2 shows a photograph taken with a field emission scanning electron microscope (FE-SEM) of the surface of the plated steel sheet obtained in Example 3 at a magnification of 5,000.
- FE-SEM field emission scanning electron microscope
- FIG. 3 shows a photograph taken with a field emission scanning electron microscope (FE-SEM) of the surface of the plated steel sheet obtained in Example 4 at a magnification of 5,000.
- FE-SEM field emission scanning electron microscope
- FIG. 4 is an enlarged view of the rectangular display portion shown in FIG. 3 .
- 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%.
- the Zn-Mg-Al-based zinc alloy-coated steel sheet also had a problem of deterioration in coating adhesion due to the adhesion of Mg-based dross.
- the inventors of the present invention conducted intensive studies to solve the above-mentioned problems and at the same time provide a coated steel sheet excellent in not only corrosion resistance, but also bendability and/or coating adhesion, and as a result, not only the composition of the coating layer, but also the MgZn formed in the coating layer It was discovered that the single phase of Zn formed along the outline of the two phases was an important element, and the present invention was completed.
- the coated steel sheet according to the present invention includes a base steel sheet; and a Zn-Mg-Al-based plating layer provided on at least one surface of the base steel sheet.
- the type of base steel sheet may not be particularly limited.
- the base steel sheet may be a Fe-based base steel sheet used as a base steel sheet of a general zinc-based coated steel sheet, that is, a hot-rolled steel sheet or a cold-rolled 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% (more preferably 0.001% or more) 0.18% or less, Si: more than 0% (more preferably 0.001% or more) 1.5%
- Mn 0.01 to 2.7%
- P more than 0% (more preferably 0.001% or more) 0.07% or less
- S more than 0% (more preferably 0.001% or more) 0.015% or less
- Al 0 More than % (more preferably 0.001% or more) 0.5% or less
- Nb more than 0% (more preferably 0.001% or more) 0.06% or less
- Cr more than 0% (more preferably 0.001% or more) 1.1% or less
- B more than 0% (more preferably 0.001% or more) 0.03% or less and the balance including Fe and other unavoidable impurities may have a composition that
- 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 10 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 further included between the base steel sheet and the Zn-Mg-Al-based plating layer.
- the Fe-Al-based suppression layer is a layer mainly containing (for example, 60% or more) an intermetallic compound of Fe and Al, and the intermetallic compound of Fe and Al includes FeAl, FeAl 3 , Fe 2 Al 5 , etc. can be heard
- 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 by alloying by Fe diffused from the base steel sheet in the initial stage of plating and components of the plating bath.
- 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 sheet.
- the Zn-Mg-Al-based plating layer in weight%, Mg: 4.0 ⁇ 7.0%, Al: 11.0 ⁇ 19.5%, the balance Zn and other inevitable May contain impurities.
- Mg 4.0 ⁇ 7.0%
- Al 11.0 ⁇ 19.5%
- Mg 4.0% or more and 7.0% 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 4.0% or more to secure the desired excellent corrosion resistance.
- Mg is added excessively, dross may be generated, and a large amount of hard MgZn 2 phase may be formed in the plating layer, resulting in deterioration of bendability such as cracking in the plating layer during bending. can be controlled to 7.0% 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% and commercialized.
- the Mg content in order to further improve corrosion resistance, it is necessary to increase the Mg content to 4% or more, but if Mg is included in the plating layer by 4% or more, there is a problem in that dross is generated due to oxidation of Mg in the plating bath.
- the upper limit of the Al content in the plating layer is preferably controlled to 19.5%.
- 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 plating layer includes a MgZn 2 phase as a microstructure.
- various top coats such as Zn single phase, Al-Zn-based binary eutectic phase, Zn-MgZn 2 -Al-based ternary eutectic phase, Al single phase, etc. may be included in the plating layer.
- the MgZn 2 phase refers to a phase mainly composed of MgZn 2
- the Zn single phase refers to a phase mainly composed of Zn and containing 85% or more of Zn in weight%.
- the Al single phase is a phase mainly composed of Al, and includes 85% or more by weight of Al, but refers to a phase in which components such as Zn and Mg are dissolved in addition to the Al component.
- 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 Zn phase included in the ternary process phase is not included in the Zn single phase formed along the outline of the MgZn 2 phase described later in this specification.
- the plating layer includes a Zn single phase formed along the outline of the MgZn 2 phase.
- the Mg component when included in a large amount of 4% or more, a large amount of hard MgZn 2 phase is formed in the plating layer, causing cracks in the plating layer during bending, resulting in poor bendability. There was a problem.
- the inventors of the present invention precisely controlled the plating composition and manufacturing conditions to form a soft phase Zn single phase along the outline of the hard phase MgZn 2 phase in the plating layer, thereby forming a MgZn 2 phase and a Zn-MgZn 2 -Al system. It was found that it was possible to secure even bendability while improving corrosion resistance by performing a buffering role between the three-way process phases.
- the Zn-MgZn 2 -Al-based ternary eutectic phase and the MgZn 2 phase are linked by the Zn single phase, thereby improving plating adhesion. found that it could be improved.
- the Zn single phase formed along the outline of the MgZn 2 phase in the plating layer can be confirmed through a photograph taken using FE-SEM of the surface of the plated steel sheet.
- FIG. 1 For example, in order to observe the surface structure of the plated steel sheet obtained from Example 1 of the present invention, a photograph taken at a magnification of 1,500 using FE-SEM is shown in FIG. 1 . As can be seen in FIG. 1, it can be confirmed that there is a Zn single phase formed along the outline of the MgZn 2 phase mainly composed of MgZn 2 .
- phase formed along the outline of the MgZn 2 phase corresponds to a single phase of Zn is determined by utilizing the cross-sectional photograph taken by the above-described FE-SEM and at the same time, based on Zn having a weight % content of 85% or more of Zn. Whether or not it is a phase can be distinguished based on EDS (Energy Dispersive Spectroscopy).
- EDS Electronic Datapersive Spectroscopy
- the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase may be 2 ⁇ m to 7 ⁇ m.
- the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase is less than 2 ⁇ m, the adhesion between the MgZn 2 phase and the Zn-MgZn 2 -Al-based ternary eutectic phase is weak due to the lack of Zn single phase that can act as a buffer. Problems may occur in bending workability and plating adhesion.
- the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase exceeds 7 ⁇ m, the Zn phase is excessively increased and Mg is lacking, which may cause a problem in local corrosion resistance.
- the lower limit of the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase may be 5.0 ⁇ m, or the average of the Zn single phase formed along the outline of the MgZn 2 phase.
- An upper limit of the thickness may be 6.9 ⁇ m.
- the method for measuring the average thickness of the Zn single phase formed along the outline of the above-described MgZn 2 phase is not particularly limited, but using a surface photograph of the plating layer taken by FE-SEM and EDS, the MgZn 2 phase of 5 ⁇ m or more Based on the length of the outline, the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase may be measured.
- a Zn single phase (hereinafter, referred to as 'first Zn single phase') having an Mg solid solution rate of less than 4wt% is formed to be adjacent to the outline of the MgZn 2 phase.
- a Zn single phase (hereinafter, referred to as 'second Zn single phase') is formed secondarily adjacent to the above-described first Zn single phase, but having a high Mg solid solution rate of 4 wt% or more.
- FIG. 2 shows a photograph of the surface of the coated steel sheet obtained from Example 3 of the present invention at 5,000 magnification.
- the region corresponding to A in FIG. 2 corresponds to the aforementioned first Zn single phase formed adjacent to the outline of the MgZn 2 phase, and the second Zn single phase formed adjacent to the first Zn single phase corresponding to B in FIG. 2 applicable
- the MgZn 2 phase The average distance from the outline to the Zn single phase having a high Mg employment rate of 4 wt% or more (for example, the average distance from the outline of the MgZn 2 phase in FIG. 2 to the region including the 'B' region) It is defined as 'average thickness'.
- the ratio of the length of the Zn single phase formed along the outline of the MgZn 2 phase occupying the outline of the MgZn 2 phase may be 30 to 98%.
- the ratio of the length of the Zn single phase formed along the outline of the MgZn 2 phase occupying the outline of the MgZn 2 phase is less than 30%, a problem in that the entire steel sheet is not uniform in terms of bendability and adhesion may occur.
- the ratio of the length of the Zn single phase formed along the outline of the MgZn 2 phase that occupies the outline of the MgZn 2 phase exceeds 98%, corrosion spreads rapidly in the Zn single phase first, resulting in insufficient corrosion resistance. there is.
- the lower limit of the ratio of the length of the Zn single phase formed along the outline of the MgZn 2 phase to occupy the outline of the MgZn 2 phase may be 60%.
- the upper limit of the ratio of the length of the Zn single phase formed along the outline of the MgZn 2 phase to occupy the outline of the MgZn 2 phase may be 90%.
- the method of measuring the ratio of the length of the MgZn 2 phase occupied by the single phase of Zn along the outline of the MgZn 2 phase is not particularly limited.
- the Zn single phase having a Zn content of 85 wt% or more has an outline of the MgZn 2 phase It can be obtained by measuring the ratio of occupied lengths.
- the Zn single phase includes both the first Zn single phase and the second Zn single phase.
- the present inventors conducted an intensive study to further improve the characteristics of improving adhesion between phases, and as a result, the Zn single phase formed along the outline of the MgZn 2 phase had a Mg solid solution rate of less than 4%. 1 Zn single phase) and a Zn single phase having an Mg solid solution ratio of 4% or more (second Zn single phase).
- the inventors of the present invention have repeatedly studied, and among the Zn single phases formed along the outline of the MgZn 2 phase, 1) the Zn single phase having a Mg solid solution rate of 4% or more contributes to improving adhesion with the Zn-MgZn 2 -Al-based ternary eutectic phase, , 2) It was found that the Zn single phase with the Mg solid solution ratio of less than 4% contributed to the improvement of adhesion with the MgZn 2 phase.
- the area ratio of the Zn single phase (or the first Zn single phase) having a Mg solid solution rate of less than 4wt% is formed along the outline of the MgZn 2 phase It may be 10 to 90% of the total area of the Zn single phase. If the ratio of the Zn single phase having the Mg solid solution ratio of less than 4wt% is less than 10%, the effect of improving connectivity with MgZn 2 may be insignificant. On the other hand, if the proportion of the Zn single phase in which the Mg employment rate is less than 4wt% is greater than 1%, uneven connection between the phases may occur locally.
- the lower limit of the ratio of the Zn single phase in which the Mg solid solution rate is less than 4 wt% may be 12%, or the Mg solid solution rate is less than 4 wt% Zn single phase
- the upper limit of the ratio of may be 75%.
- the ratio of the area of the Zn single phase (or the second Zn single phase) having a Mg employment rate of 4 wt% or more is formed along the outline of the MgZn 2 phase. It may be 10 to 90% of the total area of the Zn single phase.
- the area ratio of the Zn single phase having the Mg solid solution ratio of 4 wt% or more is less than 10%, the effect of improving connectivity with the Zn-MgZn 2 -Al-based ternary eutectic phase may be insignificant.
- the area ratio of the Zn single phase having the Mg employment rate of 4 wt% or more exceeds 90%, a problem of uneven connection between the phases may occur locally.
- the lower limit of the area ratio of the Zn single phase having the Mg solid solution ratio of 4 wt% or more may be 25%, or the above
- the upper limit of the area ratio of the Zn single phase in which the Mg employment rate is 4wt% or more may be 88%.
- the Zn single phase formed along the outline of the MgZn 2 phase has, in area%, a first Zn single phase in which the Mg employment rate is less than 4wt%: 10 to 90% and the Mg employment rate 4wt% or more of the second Zn single phase: 10 to 90% may be included.
- the first Zn single phase may be adjacent to the outline of the MgZn 2 phase, or the second Zn single phase may be adjacent to the first Zn single phase. Meanwhile, the above description is equally applicable to the first Zn single phase and the second Zn single phase.
- the method for distinguishing the above-described Zn single phase having a Mg employment rate of 4 wt% or more and the Zn single phase having a Mg employment rate of less than 4 wt% is the Mg weight of the Zn single phase at each point measured using FE-SEM and EDS It can be distinguished by measuring the % content.
- the method for measuring the area ratio of the Zn single phase having a Mg solid solution of 4wt% or more and the area ratio of the Zn single phase having a Mg solid solution of less than 4wt% is not separately limited, but, for example, the surface of the plating layer is measured by FE-SEM and EDS. It can be measured by obtaining the area % of each Zn single phase with respect to the entire phase of the plating layer based on the surface of the plating layer having an area of 10 ⁇ m 2 or more through the photograph taken.
- the Zn single phase having a Mg solid solution ratio of 4 wt% or more may exist in a single connected shape or may exist in an island shape separated from each other.
- FIG. 3 when the single phase of Zn having a Mg employment rate of 4wt% or more exists in an island shape separated from each other, the shortest distance between two adjacent island shapes as shown in the rectangular portion of FIG. 3 draw a line of An enlarged picture of the square marked portion is shown in FIG. 4, and FIG. 4 shows a line of the shortest distance drawn between two islands. Subsequently, a line connecting the outer outline of the Zn single phase having a Mg employment rate of 4 wt% or more and the line of the shortest distance between the aforementioned island shape is drawn as shown in FIG. 3 .
- each Zn Measure the area ratio of the single phase.
- a step of first preparing a base steel sheet may be further included, and the type of base steel plate 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 base steel sheet of a conventional hot-dip galvanized 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, but is not limited thereto. At this time, the above description can be equally applied to the base steel sheet.
- the prepared base steel sheet in weight%, Mg : 4.0 ⁇ 7.0%, Al: 11.0 ⁇ 19.5 Hot-dip galvanizing is performed by immersing in a plating bath containing %, balance Zn and other unavoidable impurities.
- 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 in 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 lead-in temperature of the base steel sheet is controlled to satisfy the range of T B +10°C to T B +50°C relative to the plating bath temperature (T B ).
- the plating bath temperature (T B ) may be maintained in the range of 440 to 500 °C.
- the lead-in temperature of the base steel sheet is less than T B +10 ° C, the interfacial adhesion is insignificant and a problem of dross adhesion may occur.
- the lead-in temperature of the base steel sheet exceeds T B +50° C., ash (Zn fumes) are generated and adsorbed to the steel sheet, which may cause problems with plating surface quality.
- the lower limit of the lead-in temperature of the base steel sheet may be T B +20 ° C
- the upper limit of the lead-in temperature of the base steel plate may be T B +45 ° C range
- the W air represents the interval of the air knife, and the unit is mm.
- the P air represents the pressure of the air knife, and the unit is kPa.
- the T represents the temperature of the supplied inert gas, , unit is °C.
- argon (Ar) gas, nitrogen (N 2 ) gas, or a mixed gas of argon and nitrogen may be used as the inert gas, and nitrogen gas It is more preferable to use
- the interval between the air knives may be in the range of 20 to 45 mm (more preferably, 30 to 40 mm).
- the pressure of the air knife may be in the range of 8 to 20 kPa (more preferably, 10 to 18 kPa).
- the temperature of the supplied gas may be in the range of 30 to 100 °C (more preferably, 65 to 85 °C).
- a coated steel sheet having excellent corrosion resistance, bendability, and plating adhesion may be manufactured by adjusting air wiping conditions to satisfy the above range.
- the air-wiped steel sheet is cooled at an average cooling rate of 2 to 5° C./s based on the surface temperature until the solidification end temperature.
- the average cooling rate is less than 2 ° C / s, there may be a problem with the productivity of the plated steel sheet, and if it exceeds 5 ° C / s, formed along the outline of the MgZn 2 phase defined in the present invention Zn single-phase structure may not occur.
- the air-wiped steel sheet is subjected to a temperature range of 450 ° C or less to 420 ° C or more at an average cooling rate of 1.0 to 2.0 ° C / s.
- primary cooling to cool Secondary cooling to cool the primary cooled steel sheet at an average cooling rate of 2.1 to 4.0 ° C / s in a temperature range of less than 420 ° C and greater than 340 ° C; and tertiary cooling to cool the secondary cooled steel sheet in a temperature range of less than 340°C to 150°C or more at an average cooling rate of 5.0 to 7.0°C/s.
- the inventors of the present invention found that there is an effect of further improving the bendability by gradually increasing the cooling rate in each section by dividing the slow cooling into sections of primary, secondary and tertiary cooling. Specifically, when the average cooling rate is less than 1.0 °C/s during the primary cooling, a problem in productivity of the steel sheet may occur. On the other hand, if it exceeds 2.0 °C/s during the primary cooling, a problem may arise in securing uniform interfacial adhesion between the base steel sheet and the plating layer. In addition, in the case of the secondary cooling, if the average cooling rate is less than 2.1 °C / s, a problem of productivity of the steel sheet may occur.
- the average cooling rate exceeds 4.0 °C/s during the secondary cooling, a problem may arise in securing adhesion between the single phase of MgZn 2 and Zn in the plating layer.
- the average cooling rate is less than 5.0 °C/s during the tertiary cooling, there may be a problem in that the plating layer sticks to the top roll of the cooling tower due to the delay in completion of solidification of the steel sheet.
- the average cooling rate exceeds 7.0 °C/s during the tertiary cooling, a problem may arise in adhesion between the Zn single phase and the Zn-MgZn 2 -Al-based ternary eutectic phase in the plating layer.
- the following relational expression 2 may be further satisfied.
- the adhesion between the MgZn 2 phase and the Zn single phase and the Zn-MgZn 2 -Al Improvement of the adhesion between the ternary eutectic phase and the Zn single phase can be promoted, and the bendability of the plating layer can be further improved.
- C 1 represents the average cooling rate [°C/s] during primary cooling
- C 2 represents the average cooling rate [°C/s] during secondary cooling
- C 3 represents the average cooling rate during secondary cooling [°C/s]. It represents the average cooling rate [°C/s] during cooling.
- a base steel sheet having a composition of balance Fe and impurities and having a thickness of 2 mm and a width of 1300 mm is prepared.
- Hot-dip galvanizing was performed by immersing the prepared base steel sheet in a plating bath under the conditions shown in Table 1 below. Then, the hot-dip galvanized steel sheet was subjected to air wiping treatment using nitrogen (N 2 ) gas under the conditions shown in Table 1 below, and then cooled under the conditions shown in Table 2 below.
- N 2 nitrogen
- Specimens of the plated steel sheet obtained by the methods of Tables 1 and 2 were prepared, the plated layer was dissolved in a hydrochloric acid solution, and then the dissolved liquid was analyzed by a wet analysis (ICP) method to measure the composition of the plated layer.
- ICP wet analysis
- the average thickness of the Zn single phase formed along the outline of the MgZn 2 phase was measured using FE-SEM, based on the outline length of the MgZn 2 phase of 5 ⁇ m, and is shown in Table 3 below.
- 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
- 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 material was cut into 30 mm ⁇ 100 mm, and the number of cracks occurring within a length of 10 mm after 3t bending was observed with FE-SEM, and the bendability was evaluated according to the following criteria. .
- ⁇ 10 or more and less than 20
- the material is cut into 30 mm ⁇ 100 mm, each plated steel is bent at 180° (0T bending), and each of the bent test pieces is taped, and then the area of the test piece peeled off was measured, and plating adhesion was evaluated according to the following criteria.
- the evaluation criteria of plating adhesion are as follows.
- composition of the plating layer the presence or absence of the single phase of Zn formed along the outline of the MgZn 2 phase, and the average thickness were measured in the same manner as in Experimental Example 1 and are shown in Table 7 below.
- the ratio of the Zn single phase formed along the outline of the MgZn 2 phase occupying the outline length of 10 ⁇ m of the MgZn 2 phase was measured in the same manner as described above in the specification, which is shown in Table 7 below. showed up
- the area ratio of the Zn single phase having a Mg solid solution rate of 4 wt% or more and the Mg solid solution rate of less than 4 wt% as in the method described above in this specification was measured, and these values are shown in Table 7 below.
- Example 6 Air wiping conditions plating bath composition (balance Zn and impurities) [wt%] plating bath temperature Base steel plate inlet temperature air knife side spacing air knife pressure Temperature of supplied nitrogen No. Mg Al [°C] [°C] [mm] [kPa] [°C] Example 6 4.0 11.0 440 450 20 10 30 Example 7 5.8 17.6 475 485 40 14 50 Example 8 4.5 11.5 450 470 30 16 65 Example 9 5.0 12.3 455 485 35 17 75 Example 10 6.0 19.1 490 535 40 18 85 Comparative Example 15 6.4 10.3 450 450 35 13 45 Comparative Example 16 5.6 7.9 470 480 40 5 30
- 1st cooling* Cooling in the temperature range of 450°C or less and 420°C or more
- 3rd cooling* Cooling in the temperature range below 340°C and above 150°C
- Plating layer composition [wt%] Zn single phase formed along the outline of the MgZn 2 phase Contrast of the total area of the Zn single phase formed along the outline of the MgZn 2 phase No. Mg Al existence and nonexistence [ ⁇ / ⁇ ] Occupying MgZn two -phase outline [%] average thickness [ ⁇ m] Area ratio of Zn single phase with Mg employment rate of 4wt% or more [area%] Area ratio of Zn single phase with Mg employment rate less than 4wt% [area%]
- Example 6 4.0 11.1 ⁇ 29 2.1 9 91
- Example 7 5.8 17.7 ⁇ 57 3.6 51 49
- Example 8 4.5 11.6 ⁇ 75 5.2 64 36
- Example 9 5.0 12.4 ⁇ 65 5.7 25 75
- Example 10 6.0 19.2 ⁇ 89 6.9 88 12
- Comparative Example 15 6.4 10.4 ⁇ 15 1.0 63 37 Comparative Example 16 5.6 8.0 ⁇ 26 1.1 85 15
- the Zn single phase with a Mg solid solution of 4% or more contributes to improving the interphase adhesion with the Zn-MgZn 2 -Al-based ternary eutectic phase
- the Zn single phase with the Mg solid solution of less than 4% contributes to the improved interphase adhesion with the MgZn 2 phase. , it is estimated that it ultimately contributes to the improvement of plating adhesion.
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Abstract
Description
도금 조건 | 에어 와이핑 조건 | ||||||
No. | 도금욕 조성 (잔부 Zn 및 불순물) [wt%] |
도금욕 온도 |
소지 강판 인입 온도 | 에어 나이프 편측 간격 | 에어 나이프의 압력 | 공급된 질소의 온도 | |
Mg | Al | [℃] | [℃] | [mm] | [kPa] | [℃] | |
실시예 1 | 4.0 | 11.0 | 440 | 450 | 20 | 10 | 30 |
실시예 2 | 4.5 | 11.5 | 450 | 460 | 25 | 11 | 35 |
실시예 3 | 5.0 | 12.3 | 455 | 475 | 30 | 12 | 40 |
실시예 4 | 5.5 | 14.5 | 460 | 470 | 35 | 13 | 45 |
실시예 5 | 6.0 | 19.1 | 490 | 500 | 45 | 15 | 55 |
비교예 1 | 3.8 | 9.0 | 440 | 450 | 30 | 12 | 40 |
비교예 2 | 6.4 | 10.3 | 450 | 460 | 35 | 13 | 45 |
비교예 3 | 5.6 | 7.9 | 470 | 480 | 40 | 14 | 50 |
비교예 4 | 7.0 | 20.1 | 490 | 500 | 45 | 15 | 55 |
비교예 5 | 3.8 | 9.0 | 440 | 440 | 30 | 12 | 40 |
비교예 6 | 7.3 | 20.5 | 500 | 480 | 35 | 9 | 55 |
비교예 7 | 7.6 | 19.2 | 490 | 490 | 50 | 13 | 60 |
비교예 8 | 4.3 | 8.0 | 470 | 460 | 45 | 14 | 70 |
비교예 9 | 4.8 | 6.2 | 460 | 450 | 30 | 11 | 80 |
비교예 10 | 6.7 | 10.9 | 470 | 470 | 25 | 10 | 90 |
비교예 11 | 7.8 | 21.0 | 510 | 490 | 25 | 10 | 90 |
비교예 12 | 6.0 | 10.7 | 460 | 450 | 30 | 11 | 80 |
비교예 13 | 6.8 | 7.8 | 490 | 480 | 40 | 5 | 30 |
비교예 14 | 5.3 | 12.2 | 460 | 480 | 40 | 7 | 50 |
No. | C* |
실시예 1 | 2.9 |
실시예 2 | 3.1 |
실시예 3 | 3.3 |
실시예 4 | 3.9 |
실시예 5 | 4.4 |
비교예 1 | 4.6 |
비교예 2 | 4.5 |
비교예 3 | 3.7 |
비교예 4 | 2.8 |
비교예 5 | 3.6 |
비교예 6 | 4.7 |
비교예 7 | 3.9 |
비교예 8 | 3.8 |
비교예 9 | 1.6 |
비교예 10 | 7.2 |
비교예 11 | 7.8 |
비교예 12 | 5.5 |
비교예 13 | 6.5 |
비교예 14 | 6.1 |
도금층 조성 [wt%] | MgZn2상의 외곽선을 따라 형성된 Zn 단상 | |||
No. | Mg | Al | 유무 [○/×]* | 평균 두께 [㎛] |
실시예 1 | 4.0 | 11.1 | ○ | 2.1 |
실시예 2 | 4.5 | 11.6 | ○ | 2.3 |
실시예 3 | 5.0 | 12.4 | ○ | 2.5 |
실시예 4 | 5.5 | 14.6 | ○ | 3.3 |
실시예 5 | 6.0 | 19.2 | ○ | 3.8 |
비교예 1 | 3.8 | 9.1 | ○ | 1.9 |
비교예 2 | 6.4 | 10.4 | ○ | 1.7 |
비교예 3 | 5.6 | 8.0 | ○ | 1.4 |
비교예 4 | 7.0 | 20.2 | ○ | 1.2 |
비교예 5 | 3.8 | 9.1 | ○ | 0.7 |
비교예 6 | 7.3 | 20.6 | ○ | 0.5 |
비교예 7 | 7.6 | 19.3 | ○ | 0.6 |
비교예 8 | 4.3 | 8.1 | ○ | 0.7 |
비교예 9 | 4.8 | 6.3 | ○ | 1.5 |
비교예 10 | 6.7 | 10.9 | ○ | 1.3 |
비교예 11 | 7.8 | 21.1 | Х | - |
비교예 12 | 6.0 | 10.8 | Х | - |
비교예 13 | 6.8 | 7.9 | Х | - |
비교예 14 | 5.3 | 12.2 | Х | - |
No. | 내식성 | 굽힘성 | 도금 밀착성 |
실시예 1 | ○ | ○ | ○ |
실시예 2 | ○ | ○ | ○ |
실시예 3 | ○ | ○ | ○ |
실시예 4 | ○ | ○ | ○ |
실시예 5 | ○ | ○ | ○ |
비교예 1 | × | △ | ○ |
비교예 2 | ○ | △ | × |
비교예 3 | × | ○ | × |
비교예 4 | ○ | Х | △ |
비교예 5 | × | △ | △ |
비교예 6 | ○ | △ | △ |
비교예 7 | ○ | △ | △ |
비교예 8 | × | △ | △ |
비교예 9 | × | △ | △ |
비교예 10 | ○ | × | × |
비교예 11 | ○ | × | × |
비교예 12 | ○ | × | × |
비교예 13 | ○ | × | × |
비교예 14 | ○ | × | × |
도금 조건 | 에어 와이핑 조건 | ||||||
도금욕 조성 (잔부 Zn 및 불순물) [wt%] |
도금욕 온도 |
소지 강판 인입 온도 | 에어 나이프 편측 간격 | 에어 나이프의 압력 | 공급된 질소의 온도 | ||
No. | Mg | Al | [℃] | [℃] | [mm] | [kPa] | [℃] |
실시예 6 | 4.0 | 11.0 | 440 | 450 | 20 | 10 | 30 |
실시예 7 | 5.8 | 17.6 | 475 | 485 | 40 | 14 | 50 |
실시예 8 | 4.5 | 11.5 | 450 | 470 | 30 | 16 | 65 |
실시예 9 | 5.0 | 12.3 | 455 | 485 | 35 | 17 | 75 |
실시예 10 | 6.0 | 19.1 | 490 | 535 | 40 | 18 | 85 |
비교예 15 | 6.4 | 10.3 | 450 | 450 | 35 | 13 | 45 |
비교예 16 | 5.6 | 7.9 | 470 | 480 | 40 | 5 | 30 |
1차 냉각* | 2차 냉각* | 3차 냉각* | 응고 종료 온도까지 | |
No. | 평균 냉각 속도 [℃/s] | 평균 냉각 속도 [℃/s] | 평균 냉각 속도 [℃/s] | 평균 냉각 속도 [℃/s] |
실시예 6 | 0.9 | 2.1 | 5.1 | 2.9 |
실시예 7 | 1.4 | 3.7 | 7.8 | 4.0 |
실시예 8 | 1.1 | 3.6 | 7.0 | 3.3 |
실시예 9 | 1.3 | 2.3 | 5.2 | 3.2 |
실시예 10 | 1.9 | 3.3 | 6.8 | 4.4 |
비교예 15 | 4.5 | 5.6 | 2.1 | 2.7 |
비교예 16 | 4.3 | 5.9 | 1.9 | 2.5 |
도금층 조성 [wt%] | MgZn2상의 외곽선을 따라 형성된 Zn 단상 | MgZn2상의 외곽선에 따라 형성된 Zn 단상의 전체 면적 대비 | |||||
No. | Mg | Al | 유무 [○/×] |
MgZn2상 외곽선을 점유하는 비율 [%] | 평균 두께 [㎛] |
Mg 고용률이 4wt% 이상인 Zn 단상의 면적 비율 [면적%] |
Mg 고용률이 4wt% 미만인 Zn 단상의 면적 비율 [면적%] |
실시예 6 | 4.0 | 11.1 | ○ | 29 | 2.1 | 9 | 91 |
실시예 7 | 5.8 | 17.7 | ○ | 57 | 3.6 | 51 | 49 |
실시예 8 | 4.5 | 11.6 | ○ | 75 | 5.2 | 64 | 36 |
실시예 9 | 5.0 | 12.4 | ○ | 65 | 5.7 | 25 | 75 |
실시예 10 | 6.0 | 19.2 | ○ | 89 | 6.9 | 88 | 12 |
비교예 15 | 6.4 | 10.4 | ○ | 15 | 1.0 | 63 | 37 |
비교예 16 | 5.6 | 8.0 | ○ | 26 | 1.1 | 85 | 15 |
No. | 내식성 | 굽힘성 | 도금 밀착성 |
실시예 6 | ○ | ○ | ○ |
실시예 7 | ○ | ○ | ○ |
실시예 8 | ○ | ◎ | ◎ |
실시예 9 | ○ | ◎ | ◎ |
실시예 10 | ○ | ◎ | ◎ |
비교예 15 | ○ | △ | △ |
비교예 16 | ○ | △ | △ |
Claims (10)
- 소지 강판; 및상기 소지 강판의 적어도 일면에 구비된 Zn-Mg-Al계 도금층;을 포함하고,상기 도금층은 MgZn2상; 및 상기 MgZn2상의 외곽선을 따라 형성된 Zn 단상;을 포함하는, 도금 강판.
- 제 1 항에 있어서,상기 도금층은 중량%로, Mg: 4.0~7.0%, Al: 11.0~19.5%, 잔부 Zn 및 기타 불가피한 불순물을 포함하는, 도금 강판.
- 제 1 항에 있어서,상기 소지 강판과 상기 Zn-Mg-Al계 도금층 사이에 구비된 Fe-Al계 억제층을 더 포함하는, 도금 강판.
- 제 1 항에 있어서,상기 MgZn2상의 외곽선을 따라 형성된 Zn 단상이 상기 MgZn2상의 외곽선을 점유하는 길이의 비율은 30~98%인, 도금 강판.
- 제 1 항에 있어서,상기 MgZn2상의 외곽선을 따라 형성된 Zn 단상의 평균 두께는 2~7㎛인, 도금 강판.
- 제 5 항에 있어서,상기 MgZn2상의 외곽선에 따라 형성된 Zn 단상은, 면적%로, Mg 고용률이 4wt% 미만인 제1 Zn 단상: 10~90% 및 Mg 고용률이 4wt% 이상인 제2 Zn 단상: 10~90%을 포함하는, 도금 강판.
- 제 6 항에 있어서,상기 제 1 Zn 단상은, 상기 MgZn2상의 외곽선에 인접하는, 도금 강판.
- 도금욕 온도(TB) 대비 TB+10℃~TB+50℃의 인입 온도를 충족하도록, 소지 강판을 중량%로, Mg: 4.0~7.0%, Al: 11.0~19.5%, 잔부 Zn 및 기타 불가피한 불순물을 포함하는 도금욕에 침지하여 용융 아연 도금하는 단계;상기 용융 아연 도금된 강판에 하기 관계식 1을 충족하도록 불활성 가스를 이용하여 에어 와이핑을 실시하는 단계; 및상기 에어 와이핑된 강판을 응고 종료 온도까지 2~5℃/s의 평균 냉각 속도로 냉각하는 단계;를 포함하는, 도금 강판의 제조방법.[관계식 1]0.005 ≤ Pair/(Wair × T)(상기 관계식 1에 있어서, 상기 Wair는 에어 나이프의 간격을 나타내고, 단위는 ㎜이다. 상기 Pair은 에어 나이프의 압력을 나타내고, 단위는 kPa이다. 상기 T는 공급된 불활성 가스의 온도를 나타내고, 단위는 ℃이다.)
- 제 8 항에 있어서,상기 냉각하는 단계는,상기 에어 와이핑된 강판에 450℃ 이하 420℃ 이상의 온도 범위를 평균 냉각 속도 1.0~2.0℃/s로 냉각하는 1차 냉각;상기 1차 냉각된 강판에 420℃ 미만 340℃ 이상의 온도 범위를 평균 냉각 속도 2.1~4.0℃/s로 냉각하는 2차 냉각; 및상기 2차 냉각된 강판에 340℃ 미만 150℃ 이상의 온도 범위를 평균 냉각 속도 5.0~7.0℃/s로 냉각하는 3차 냉각;을 실시하는, 도금 강판의 제조방법.
- 제 9 항에 있어서,상기 냉각하는 단계는 하기 관계식 2를 충족하는, 도금 강판의 제조방법.[관계식 2]C1 + C2 ≤ C3 ≤ 1.5×(C1 + C2)(상기 관계식 2에 있어서, C1은 1차 냉각 시의 평균 냉각 속도[℃/s]를 나타내고, C2는 2차 냉각 시의 평균 냉각 속도[℃/s]를 나타내고, C3는 3차 냉각 시의 평균 냉각 속도[℃/s]를 나타낸다.)
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