WO2020179147A1 - Tôle d'acier plaquée al-zn-mg-si-sr par immersion à chaud et procédé de fabrication associé - Google Patents
Tôle d'acier plaquée al-zn-mg-si-sr par immersion à chaud et procédé de fabrication associé Download PDFInfo
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- WO2020179147A1 WO2020179147A1 PCT/JP2019/045520 JP2019045520W WO2020179147A1 WO 2020179147 A1 WO2020179147 A1 WO 2020179147A1 JP 2019045520 W JP2019045520 W JP 2019045520W WO 2020179147 A1 WO2020179147 A1 WO 2020179147A1
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Images
Classifications
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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
- 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
- C23C2/12—Aluminium 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
- C23C2/26—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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc 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
- C23C2/26—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 molten Al-Zn-Mg-Si-Sr plated steel sheet having good surface appearance and excellent corrosion resistance of a flat plate portion and a processed portion, and a method for producing the same.
- Patent Document 1 discloses a hot-dip Al—Zn-based plated steel sheet containing 25 to 75 mass% of Al in the plating layer. Due to its excellent corrosion resistance, hot-dip Al-Zn plated steel sheets have been in increasing demand in recent years, mainly in the field of building materials such as roofs and walls that are exposed to the outdoors for a long period of time, and in the field of civil engineering and construction such as guardrails, wiring pipes, and soundproof walls. ing.
- the plating layer of the molten Al-Zn-based plated steel sheet is composed of a main layer and an interfacial alloy layer existing at the interface between the base steel plate and the main layer, and the main layer is a portion ( ⁇ -) in which Al mainly containing Zn is dendrite-solidified. It is composed of an Al phase dendrite portion) and a remaining dendrite gap portion (interdendrite) containing Zn as a main component, and has a structure in which a plurality of ⁇ -Al phases are laminated in the film thickness direction of the plating layer.
- the corrosion progress path from the surface becomes complicated, so that it becomes difficult for corrosion to easily reach the base steel sheet, and the molten Al-Zn-based plated steel sheet has the same coating layer thickness as the molten zinc. Excellent corrosion resistance can be achieved compared to plated steel sheets.
- Patent Document 2 includes an Al-Zn-Si alloy containing Mg in a plating layer.
- the Al-Zn-Si alloy is an alloy containing 45 to 60% by weight of elemental aluminum, 37 to 46% by weight of elemental zinc, and 1.2 to 2.3% by weight of elemental silicon, and the concentration of Mg is high.
- An Al-Zn-Mg-Si plated steel sheet having a content of 1 to 5% by weight is disclosed.
- the molten Al-Zg-based plated steel sheet containing Mg disclosed in the cited document 2 has excellent corrosion resistance, but it is caused by the oxide layer formed on the surface of the plated layer, and is from several mm to several hundred.
- wrinkle-like defects having a length of about mm (hereinafter, referred to as “wrinkle-like defects”) are likely to occur and the appearance of the surface of the plating layer is impaired. Therefore, for example, Patent Document 3 discloses a technique for improving the surface appearance of a molten Al—Zn—Mg-based plated steel sheet by including Sr in the plating layer.
- Patent Document 4 discloses a technique for improving workability of a molten Al—Zn—Mg-based plated steel sheet by including Sr in the plating layer.
- the molten Al-Zn-Mg-based plated steel sheets of Patent Documents 3 and 4 described above contain Sr in the plating layer, the occurrence of wrinkle-like defects can be suppressed and the surface appearance can be improved. There is.
- the content of Sr reduces the content of Mg 2 Si near the surface of the plating layer, and as a result, the corrosion resistance may decrease. was there.
- Mg 2 Si generated in the plating layer exerts an effect of improving corrosion resistance, the plating layer is formed when bending is performed. There is a problem that the cracks are generated and the corrosion resistance of the processed portion (processed portion corrosion resistance) is poor.
- the present invention includes a molten Al-Zn-Mg-Si-Sr plated steel sheet having good surface appearance and excellent corrosion resistance of the flat plate portion and the processed portion, and corrosion resistance of the flat plate portion and the processed portion. It is an object of the present invention to provide a method for producing a hot-dip Al-Zn-Mg-Si-Sr plated steel sheet excellent in heat resistance.
- the present inventors preferentially dissolve Mg 2 Si existing in the plating layer when the plating layer is corroded, and the effect of improving the corrosion resistance due to the inclusion of Mg is obtained. It was noted that Mg 2 Si existing near the surface of the plating layer is more important because Mg dissolved in the corrosion product generated on the surface of the layer is expressed by being concentrated. As a result of further earnest studies, most of Mg 2 Si contained in the main layer (hereinafter, also referred to as “plating main layer” or “main layer”) forming the plating layer was plated.
- Mg 2 Si in the plating main layer has a corrosion resistance improving effect, but becomes a propagation path to the plating main layer surface of cracks generated in the interface alloy layer during bending, We paid attention to the fact that the desired corrosion resistance of the processed part cannot be obtained because the workability is reduced.
- the present invention has been made based on the above findings, and its gist is as follows.
- the plating layer contains Al: 40 to 70% by mass, Si: 0.6 to 5% by mass, Mg: 0.1 to 10% by mass and Sr: 0.001 to 1.0% by mass, and the balance is Zn.
- the plating layer consists of an interface alloy layer present at the interface with the base steel sheet and a main layer present on the alloy layer, Of Mg 2 Si observed in the cross section in the thickness direction of the plating layer, the area ratio of Mg 2 Si existing within the thickness range of 50% from the surface of the main layer is 50% or more, and The area ratio of Mg 2 Si continuously present in the interdendrite portion from the interface alloy layer to the surface of the main layer (hereinafter, may be “extended”) is 50% or less. Hot-dip Al-Zn-Mg-Si-Sr plated steel sheet.
- the area ratio of Mg 2 Si existing in the thickness range of up to 50% from the surface of the main layer is 60% or more, and The molten Al-Zn-Mg-Si-Sr according to 1 above, wherein the area ratio of Mg 2 Si extending from the surface of the main layer to the interface alloy layer is 50% or less. Plated steel sheet.
- the area ratio of Mg 2 Si existing in the thickness range of up to 50% from the surface of the main layer is 60% or more, and 2.
- the molten Al-Zn-Mg-Si-Sr according to the above 2, wherein the area ratio of Mg 2 Si extending from the surface of the main layer to the interfacial alloy layer is 40% or less. Plated steel sheet.
- the Si phase observed in the cross section in the thickness direction of the plating layer has a ratio of the area ratio of the Si phase to the total area ratio of Mg 2 Si and Si phase observed in the cross section in the thickness direction of the plating layer. , 30% or less, the molten Al-Zn-Mg-Si-Sr plated steel sheet according to any one of 1 to 3 above.
- the main layer has an ⁇ -Al phase dendrite portion, and the average distance between dendrite arms of the dendrite portion and the thickness of the plating layer satisfy the following formula (1).
- the steel plate is heated at an average cooling rate of 10° C./s or more until the plate temperature reaches a temperature obtained by subtracting 150° C. from the bath temperature of the plating bath (plating bath temperature ⁇ 150° C.).
- a molten Al-Zn-Mg-Si-Sr plated steel sheet having a good surface appearance and excellent corrosion resistance of a flat plate portion and a processed portion, and a flat plate portion and a flat plate portion and a processed portion have a good surface appearance. It is possible to provide a method for producing a molten Al-Zn-Mg-Si-Sr-plated steel sheet having excellent corrosion resistance in the processed part.
- (A) is the figure which showed the state before and after corrosion about a hot-dip Al-Zn-Mg type plated steel plate
- (b) is the figure which showed the state before and after corrosion about a hot-dip Al-Zn type plated steel sheet.
- (A) shows the state of each element of the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention by energy dispersive X-ray spectroscopy (SEM-EDX) of a scanning electron microscope
- (b) is a diagram for part of the molten Al-Zn-Mg-Si- Sr -plated steel sheet, it has been described a method for observing the Mg 2 Si and Si phases shown in (a).
- FIG. 4 is a diagram for explaining a method of calculating the area ratio of Mg 2 Si extending from the surface of the main layer to the interface alloy layer among Mg 2 Si observed in the cross section in the thickness direction of the plating layer. .. It is a figure for demonstrating the measuring method of the distance between dendrite arms. It is a figure for demonstrating the flow of the combined cycle test (JASO-CCT) of a Japanese automobile standard.
- JSO-CCT combined cycle test
- the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention has a plated layer on the surface of the steel sheet, and the plated layer includes an interface alloy layer existing at the interface with the base steel sheet and the alloy layer. It consists of the main layer that exists above.
- the plating layer contains Al: 40 to 70% by mass, Si: 0.6 to 5% by mass, Mg: 0.1 to 10% by mass, and Sr: 0.001 to 1.0% by mass, The balance has a composition of Zn and unavoidable impurities.
- the Al content in the plating layer is 40 to 70% by mass, preferably 45 to 65% by mass, from the viewpoint of the balance between corrosion resistance and operation.
- the main layer mainly contains Zn in a hypersaturation, and is composed of a portion where Al is dendrite solidified (a dendrite portion of the ⁇ -Al phase) and a portion of the remaining dendrite gap (interdendrite portion), and the dendrite portion is a film of a plating layer. It is possible to realize a structure having excellent corrosion resistance laminated in the thick direction.
- the Al content in the plating layer is preferably 45% by mass or more.
- the Al content in the plating layer exceeds 70% by mass, the content of Zn having a sacrificial anticorrosion effect on Fe decreases, and the corrosion resistance deteriorates. Therefore, the Al content in the plating layer is set to 70% by mass or less.
- the Al content in the plating layer is 65% by mass or less, the adhesion amount of the plating is reduced, and even if the base steel sheet is easily exposed, it has a sacrificial anticorrosion action on Fe, Excellent corrosion resistance is obtained. Therefore, the Al content of the plating main layer is preferably 65% by mass or less.
- Si in the plating layer is added to the plating bath for the purpose of suppressing the growth of the interfacial alloy layer generated at the interface with the base steel sheet, for the purpose of improving corrosion resistance and workability, and necessarily in the main layer. Contained.
- the plating bath contains Si and the hot dip plating treatment is performed, the base steel sheet is dipped in the plating bath and at the same time the steel sheet surface Fe and Al or Si in the bath undergo an alloying reaction to produce an alloy composed of a Fe-Al-based and/or Fe-Al-Si-based compound.
- this Fe-Al-Si-based interfacial alloy layer can suppress the growth of the interfacial alloy layer. And when Si content in the said plating layer is 0.6 mass% or more, the growth of the said interface alloy layer can be suppressed sufficiently. On the other hand, when the Si content of the plating layer exceeds 5%, the workability of the plating layer is deteriorated and the Si phase serving as the cathode site is easily deposited. The precipitation of the Si phase can be suppressed by increasing the Mg content and making a certain relationship between the Si content and the Mg content, as will be described later, but in that case, the manufacturing cost is increased and the Mg content is reduced.
- the Si content in the plating layer is 5% or less. Furthermore, considering that the growth of the interfacial alloy layer and the precipitation of the Si phase can be more reliably suppressed, and that it is possible to deal with the case where Si is consumed as Mg 2 Si, the Si content in the plating layer is It is preferably more than 2.3 and 3.5%.
- the plated layer contains 0.1 to 10 mass% of Mg.
- Mg is contained in the corrosion product, the stability of the corrosion product is improved, the progress of corrosion is delayed, and as a result, the corrosion resistance is improved. .. More specifically, Mg present in the main layer of the plating layer combines with the above-mentioned Si to form Mg 2 Si. As shown in FIG. 1A, this Mg 2 Si dissolves in the initial stage when the plated steel sheet is corroded, so that Mg is contained in the corrosion product. Mg contained in this corrosion product has the effect of densifying the corrosion product, and can improve the stability of the corrosion product and the barrier property against external corrosion factors.
- the corrosion product does not contain Mg, and desired corrosion resistance cannot be obtained.
- the Mg content of the plating layer is set to 0.1 mass% or more, when the plating layer contains Si in the concentration range described above, the Mg concentration is 0.1 mass% or more. Then, it becomes possible to generate Mg 2 Si, and a corrosion retarding effect can be obtained. From the same viewpoint, the Mg content of the plating layer is preferably 1% by mass or more, and more preferably 3% by mass or more.
- the content of Mg in the plating layer is set to 10% by mass or less, because when the content of Mg in the plating layer exceeds 10%, in addition to saturation of the effect of improving corrosion resistance, increase in manufacturing cost and plating This is because it is difficult to control the composition of the bath.
- the Mg content of the plating layer is preferably 6% by mass or less.
- the Mg content in the plating layer is set to 1% by mass or more, it is possible to improve the corrosion resistance after coating.
- the plating layer of a conventional molten Al-Zn-based galvanized steel sheet containing no Mg comes into contact with the atmosphere, a dense and stable oxide film of Al 2 O 3 is immediately formed around the ⁇ -Al phase, and protection by this oxide film is formed. Due to the action, the solubility of the ⁇ -Al phase becomes much lower than the solubility of the Zn rich phase in the interdendrite.
- the Mg content in the plating layer is preferably 1% by mass or more, and more preferably 3% by mass or more.
- the Mg 2 Si phase and the Mg—Zn compound (Mg Zn 2 , Mg 32 (Al,) precipitated in the interdent light Zn) 49, etc. melts out in the initial stage of corrosion, and Mg is incorporated in the corrosion product. Since the corrosion product containing Mg is very stable, and the corrosion is suppressed in the initial stage, the Zn-rich phase, which is a problem in the case of the coated steel sheet using the conventional Al-Zn system plated steel sheet as the base, The large swelling of the coating film due to the selective corrosion can be suppressed.
- the hot-dip Al—Zn-based plated steel sheet containing Mg in the plating layer exhibits excellent post-coating corrosion resistance.
- the Mg content in the plating layer is less than 1% by mass, the amount of Mg dissolved out during corrosion is small, and the corrosion resistance after coating may not be improved.
- the Mg content in the plating layer exceeds 10% by mass, not only the effect is saturated, but also the Mg compound is severely corroded and the solubility of the entire plating layer is excessively increased. Even if the product is stabilized, its dissolution rate becomes large, so that a large swollen width may occur and the corrosion resistance after coating may deteriorate. Therefore, in order to stably obtain excellent corrosion resistance after coating, it is preferable that the Mg content in the plating layer be 10% by mass or less.
- the plating layer contains 0.001 to 1.0 mass% of Sr.
- Sr in the plating layer, it is possible to suppress the occurrence of wrinkle defects and improve the surface appearance of the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention.
- the wrinkle-like defects are wrinkle-like irregularities formed on the surface of the plating layer, and are observed as whitish lines on the surface of the plating layer. Such streak defects are likely to occur when a large amount of Mg is added to the plating layer.
- the Sr content in the plating layer must be 0.001 mass% or more. This is to obtain the effect of suppressing the occurrence of the above-mentioned streak-like defects.
- the Sr content in the plating layer is preferably 0.005 mass% or more, more preferably 0.01 mass% or more, and 0.05 mass% or more. Especially preferable.
- the Sr content in the plating layer needs to be 1.0 mass% or less. This is because if the Sr content is too large, the effect of suppressing the generation of streak-like defects is saturated, which is disadvantageous in terms of cost.
- the Sr content in the plating layer is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, and 0.3% by mass or less. Especially preferable.
- the plating layer, the components of the base steel sheet taken into the plating during the reaction of the plating bath and the base steel sheet during the plating treatment, and unavoidable impurities contained in the ingot used when constructing the plating bath are included.
- Fe may be contained in about several percent.
- examples of the types of unavoidable impurities in the plating bath include Fe, Mn, P, S, C, Nb, Ti, and B as the base steel plate components.
- examples of impurities in the ingot include Fe, Pb, Sb, Cd, As, Ga, and V.
- the amount of Fe in the plating layer cannot be quantified by distinguishing between those taken from the base steel sheet and those in the plating bath.
- the total content of the unavoidable impurities is not particularly limited, but the total amount of the unavoidable impurities excluding Fe is 1% by mass or less from the viewpoint of maintaining the corrosion resistance and uniform solubility of the plating. preferable.
- the plating layer is known as a stable element of a corrosion product in Zn-Al system plating, Cr, Ni, Co, Mn, At least one or more selected from Ca, V, Ti, B, Mo, Sn, Zr, Li, Ag and the like can be further contained in a content of less than 1% of each element.
- the content of each of these elements is less than 1%, the effect disclosed in the present invention is not impaired, and the corrosion product stabilization effect further improves the corrosion resistance.
- the interfacial alloy layer is a layer existing at the interface with the underlying steel sheet among the plating layers, and as described above, Fe on the surface of the steel sheet and Al or Si in the bath inevitably undergo an alloying reaction. Fe-Al-based compounds and/or Fe-Al-Si-based compounds that are generated as a result. Since this interface alloy layer is hard and brittle, it grows thick and becomes a starting point of crack generation during processing. Therefore, it is preferable to thin the interface alloy layer.
- the molten Al-Zn-Mg-Si- Sr -plated steel sheet of the present invention among the Mg 2 Si which is observed in the thickness direction of the cross section of the plating layer, to 50% from the surface of the main layer thickness
- the area ratio of Mg 2 Si existing in the range is 50% or more, and the area ratio of Mg 2 Si extending from the surface of the main layer to the interfacial alloy layer is 50% or less.
- the molten Al-Zn-Mg-Si- Sr -plated steel sheet of the present invention among the Mg 2 Si which is observed in the thickness direction of the cross section of the plating layer, within the thickness range of up to 50% from the surface of the main layer
- the area ratio of Mg 2 Si present in the is 50% or more.
- the area ratio of Mg 2 Si existing in the thickness range of up to 50% from the surface of the main layer is large (50% or more). ) Therefore, most of Mg 2 Si on the surface of the main layer is dissolved during corrosion, and the Mg concentration of corrosion products formed on the plated surface after corrosion increases. Therefore, in the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention, excellent corrosion resistance can be realized while suppressing the occurrence of wrinkle-like defects.
- the conventional molten Al-Zn-Mg-Si-Sr plated steel sheet has a small amount of Mg 2 Si (less than 50%) existing in the thickness range of up to 50% from the surface of the main layer.
- the amount of Mg 2 Si dissolved during corrosion is not sufficient, and the concentration of Mg in the corrosion product on the plated surface after corrosion is relatively low. Therefore, in the conventional hot-dip Al-Zn-Mg-Si-Sr plated steel sheet, wrinkle-shaped defects can be suppressed from occurring, but the corrosion resistance is reduced.
- the above-mentioned area ratio of Mg 2 Si (area ratio of Mg 2 Si existing within a thickness range of up to 50% from the surface of the main layer) is derived by, for example, energy dispersion using a scanning electron microscope. Type X-ray spectroscopy (SEM-EDX).
- SEM-EDX Type X-ray spectroscopy
- FIG. 2A after obtaining the cross-sectional state of the plating layer in the thickness direction, mapping is performed for each of Mg and Si as shown in FIG. , Si is shown in blue). After that, of the mapped Mg and Si, the portion where they overlap at the same position (the portion shown in purple in FIG. 2B) can be set as Mg 2 Si.
- the obtained Mg 2 Si as shown in FIG.
- the area ratio (A%) of Mg 2 Si to the area of the entire main layer of the plating layer is measured. Then, the main layer is divided in half in the thickness direction, and the area ratio (B%) of Mg 2 Si existing in the thickness range from the surface to 50% of the area of the main layer is measured. Then, the ratio of the area ratio (B%) of Mg 2 Si existing in the thickness range from the surface of the main layer to 50% to the area ratio (A%) of Mg 2 Si in the entire main layer of the plating layer ( (B%) / (a% ) by calculating ⁇ 100%), of the Mg 2 Si present in the observation field, there from the surface of the main layer in the thickness range of up to 50% Mg 2 Si The area ratio (X%) occupied by can be obtained.
- the area ratio of Mg 2 Si extending from the surface of the main layer to the interfacial alloy layer is set to 50% or less.
- the corrosion resistance of the processed part can also be greatly improved.
- Mg 2 Si contained in the plating main layer has an effect of improving corrosion resistance, it serves as a propagation path for cracks generated in the interfacial alloy layer as described above and reduces workability. Therefore, conventional molten Al-Zn is used. With the Mg-based plated steel sheet, sufficient workability, and thus corrosion resistance of the processed portion, could not be obtained.
- the amount of Mg 2 Si that reaches from the interfacial alloy layer to the surface of the plating main layer is reduced (the area ratio of Mg 2 Si is 50%).
- the derivation of the area ratio of Mg 2 Si as described above also, for example, energy dispersive using a scanning electron microscope X-ray spectroscopy (SEM-EDX) can be used.
- SEM-EDX scanning electron microscope X-ray spectroscopy
- the area ratio (A%) of Mg 2 Si to the area of the entire main layer of the plating layer is measured. After that, among the Mg 2 Si particles existing in the observation field, the Mg 2 Si particles (particles indicated by arrows in FIG. 4) extending from the surface of the main layer to the interfacial alloy layer of the plating layer The area ratio (C%) to the entire main layer is measured.
- the area ratio of Mg 2 Si in the entire main layer of the plated layer to the (A%) the area ratio of the extension to Mg 2 Si to reach the interface alloy layer from the surface of the main layer in the entire main layer of the plated layer.
- the Mg 2 Si in the present invention “extends from the surface of the main layer to the interface alloy layer”, the Mg 2 Si reaches (contacts) the interface alloy layer from the surface of the main layer. ), the distance between the lower end of the Mg 2 Si and the upper end of the interface alloy layer is very small and substantially reaches the interface layer (for example, in the thickness direction of the plating layer).
- the case where the distance between the lower end of the Mg 2 Si and the upper end of the interface alloy layer when observed in the cross section is 1.0 ⁇ m or less). Also in this case, when cracks originate from the interface alloy layer, most of them reach the surface of the plating main layer.
- Mg 2 Si observed in the cross section in the thickness direction of the plating layer from the viewpoint of being able to realize more excellent corrosion resistance, Mg 2 Si existing in the thickness range of 50% from the surface of the main layer is used.
- the area ratio is preferably 60% or more.
- the Mg 2 Si observed in the cross section in the thickness direction of the plating layer extends from the surface of the main layer to the interfacial alloy layer from the viewpoint of realizing better corrosion resistance of the processed portion.
- the area ratio of Mg 2 Si is preferably 40% or less.
- the Mg 2 Si observed in the cross section of the plating layer in the thickness direction is within the thickness range of up to 50% from the surface of the main layer from the viewpoint of realizing better corrosion resistance and corrosion resistance of the processed portion.
- the area ratio of Mg 2 Si existing in the surface layer is 60% or more, and the area ratio of Mg 2 Si extending from the surface of the main layer to the interface alloy layer is from the surface of the main layer to the interface alloy. More preferably, the area ratio of Mg 2 Si extending to reach the layer is 40% or less.
- the plating layer contains Si as a composition component
- a Si phase may be formed in the plating layer depending on the composition of Si and Mg in the plating layer as described above.
- the content ratio of Mg 2 Si that improves corrosion resistance and the Si phase that becomes a cathode site during corrosion of the plating layer and deteriorates corrosion resistance is important.
- the essence of the present invention is that even if the absolute amount of Mg2Si that improves corrosion resistance is large, good corrosion resistance cannot be ensured if the amount of Si phase that deteriorates corrosion resistance is large, so the ratio is controlled to a certain value or less. Especially.
- the area ratio of Mg 2 Si and Si phase observed in the cross section in the thickness direction of the plated layer measured by the method shown below The area ratio of Si phase (area ratio of Si phase/total area ratio of Mg 2 Si and Si phase) observed in the cross section in the thickness direction of the plating layer is preferably 30% or less with respect to the total of More preferably, it is 10% or less.
- the method of deriving the area ratio of the Si phase may be performed by energy dispersive X-ray spectroscopy (SEM-EDX) using a scanning electron microscope, as in the case of Mg 2 Si described above.
- mapping is performed for each of Mg and Si (FIG. 2B).
- the portion shown in blue in FIG. 2B in which Mg does not exist at the position where Si exists can be regarded as the Si phase.
- the area ratio (D%) of the Si phase can be calculated from the ratio of the total area of the blue portion and the area of the plating layer in the observed visual field.
- the area ratio of the Si phase observed in the cross section in the thickness direction of the plating layer with respect to the total area ratio of the Mg 2 Si and Si phases area ratio of Si phase/total area ratio of Mg 2 Si and Si phase).
- the area ratio of the Si phase to the total area of the Mg 2 Si and Si phases observed in the cross section of the plating layer in the thickness direction is observed in 10 randomly selected cross sections of the plating layer. It is an average of the area ratios of the Si phases to be formed.
- the area ratio of the Si phase observed in the cross section in the thickness direction of the plating layer (area ratio of the Si phase in the observation visual field: D%) is preferably 10% or less, and preferably 3% or less. Is more preferable.
- the area ratio of the Si phase observed in the cross section of the plating layer in the thickness direction the area ratio of the Si phase observed in 10 randomly selected cross sections of the plating layer is averaged. Is.
- the area ratio of the Si phase observed on the surface of the plated layer is preferably 1% or less, and 0 More preferably, it is 5.5% or less.
- the method of deriving the area ratio of the Si phase on the surface of the plating layer energy dispersive X-ray spectroscopy (SEM-EDX) is performed using a scanning electron microscope as in the case of observing the cross section. Can be done using.
- the area ratio can be determined according to the cross-sectional observation method, and the area ratio of the Si phase observed on the randomly selected 10 surfaces of the plating layer can be averaged.
- the area of the Si phase observed in the cross section in the thickness direction of the plating layer with respect to the total area of Mg 2 Si and the Si phase observed on the surface of the plating layer is preferably 20% or less, and more preferably 10% or less.
- the actual observation method and the method of obtaining the area ratio are in accordance with the cross-section observation method described above.
- the cross section or the surface of the plating layer is polished and/or etched and then observed.
- There are several kinds of methods for polishing or etching the cross section or the surface but there is no particular limitation as long as they are generally used when observing the cross section or the surface of the plating layer.
- the observation conditions with a scanning electron microscope are, for example, an acceleration voltage of 5 to 20 kV, and a cross-section of the plating layer is clearly defined if the magnification is about 500 to 5000 times in a secondary electron beam image or a backscattered electron image. It is possible to observe.
- mapping with EDX the above area ratio can be obtained by analyzing with the same magnification.
- the main layer of the plating layer has an ⁇ -Al phase dendrite portion, and the average distance between the dendrite arms of the dendrite portion and the thickness of the plating layer satisfy the following formula (1).
- t thickness of plating layer ( ⁇ m)
- d average distance between dendrite arms ( ⁇ m)
- the distance between the dendrite arms of the dendrite part means the center distance between adjacent dendrite arms (dendritic arm spacing).
- the surface of the plating layer main layer is magnified and observed (for example, observed at 200 times) using a scanning electron microscope (SEM) or the like, and a randomly selected field of view is observed.
- the interval of the second widest dendrite arm (secondary dendrite arm) is measured as follows. A portion where three or more secondary dendrite arms are aligned is selected (in FIG. 5, three between A and B are selected), and a distance is set along the direction in which the arms are aligned (see FIG. 5). Now, the distance L) is measured.
- the measured distance is divided by the number of dendrite arms (L / 3 in FIG. 5) to calculate the distance between the dendrite arms.
- the distance between dendrite arms is measured at three or more points in one visual field, and the average of the obtained distances between dendrite arms is calculated as the average distance between dendrite arms.
- the thickness of the plating layer is preferably 10 to 30 ⁇ m, and more preferably 20 to 25 ⁇ m from the viewpoint of achieving both a high level of workability and corrosion resistance. This is because when the plating layer is 10 ⁇ m or more, sufficient corrosion resistance can be ensured, and when the plating layer is 30 ⁇ m or less, workability can be sufficiently ensured.
- the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention may be a surface-treated steel sheet further provided with a chemical conversion treatment film and/or a coating film on its surface.
- the manufacturing method of the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention is Al: 40 to 70% by mass, Si: 0.6 to 5% by mass, Mg: 0.1 to 10% by mass and Sr: When hot-dip galvanizing a steel sheet using a plating bath containing 0.001 to 1.0% by mass, the balance of which is Zn and unavoidable impurities, and a bath temperature of 585 ° C. or lower, the plating is performed.
- the steel plate temperature at the time of bath entry is set to a temperature (plating bath temperature + 20 ° C.) or less obtained by adding 20 ° C. from the bath temperature of the plating bath.
- the hot-dip Al-Zn-Mg-Si-Sr plated steel sheet obtained by the above-described manufacturing method has a favorable surface appearance and also has excellent corrosion resistance in the flat plate portion and the processed portion.
- the method for producing a hot-dip Al-Zn-Mg-Si-Sr plated steel sheet of the present invention is not particularly limited, but a continuous hot-dip galvanizing facility is usually adopted from the viewpoint of production efficiency and quality stability.
- the type of base steel sheet used for the molten Al-Zn-Mg-Si-Sr plated steel sheet of the present invention is not particularly limited.
- a hot rolled steel sheet or steel strip that has been pickled and descaled, or a cold rolled steel sheet or steel strip obtained by cold rolling them can be used.
- the conditions of the pretreatment step and the annealing step are not particularly limited, and any method can be adopted.
- the plating bath contains Al: 40 to 70% by mass, Si: 0.6 to 5% by mass, and Mg: 0.1 to 10% by mass. %, and Sr: 0.001 to 1.0% by mass, with the balance being Zn and inevitable impurities.
- a molten Al-Zn-Mg-Si-Sr plated steel sheet having a desired composition can be obtained.
- the type, content, and action of each element contained in the plating bath are described in the above-mentioned molten Al—Zn—Mg—Si—Sr plated steel sheet of the present invention.
- the molten Al-Zn-Mg-Si-Sr plated steel sheet obtained by the production method of the present invention has almost the same composition as the plating bath as a whole. Therefore, the composition of the main layer can be accurately controlled by controlling the composition of the plating bath.
- the contents of Mg and Si in the plating bath satisfy the following formula (2).
- M Si Si content (mass %)
- the formed plating layer suppresses the generation of Si phase (for example, is observed in the cross section in the thickness direction of the plating layer).
- the area ratio of the Si phase is 10% or less, the area ratio of the Si phase observed on the surface of the plating layer is 1% or less), and the workability and corrosion resistance can be further improved.
- M Mg /(M Si ⁇ 0.6) is more preferably 2.0 or more, and further preferably 3.0 or more.
- the bath temperature of the plating bath is 585°C or lower, and preferably 580°C or lower.
- the bath temperature By setting the bath temperature, a large amount of Mg 2 Si that reaches the interface alloy layer from the surface of the main layer of the plating layer can be reduced. It also has the effect of suppressing the growth of the interface alloy layer.
- the reason why the low bath temperature effectively works is that the time period during which the steel sheet stays in the high temperature region where the Mg 2 Si and the interface alloy layer grow can be shortened.
- the bath temperature of the plating bath exceeds 585° C., even if the steel plate temperature at the time of entering the plating bath is optimized, a large amount of Mg 2 Si that reaches the interface alloy layer from the surface of the main layer is obtained. However, since the interface alloy layer grows thicker, the desired workability and corrosion resistance of the processed portion cannot be obtained.
- the temperature of the steel sheet at the time of entering the plating bath is added by 20 ° C. from the bath temperature of the plating bath ( Plating bath temperature +20°C) or less.
- This can reduce a large amount of Mg 2 Si that reaches the interface alloy layer from the surface of the main layer of the plating layer.
- the reason why the amount of large Mg 2 Si can be reduced by reducing the approach plate temperature is that the Mg 2 Si and the interfacial alloy layer grow in the high temperature region, similar to the effect of lowering the bath temperature. This is because it is possible to shorten the time that the steel sheet stays.
- the entry plate temperature of the steel sheet is preferably equal to or lower than the temperature obtained by adding 10° C. to the bath temperature of the plating bath (plating bath temperature+10° C.) and is equal to or lower than the bath temperature of the plating bath. preferable.
- the plate temperature of the plating bath is 10°C/s or more at an average cooling rate. It is preferable to cool the steel sheet until a temperature obtained by subtracting 150°C from the bath temperature (plating bath temperature-150°C) is reached. It is known that Mg 2 Si formed in the above-mentioned plating layer is easily generated in a temperature range up to a temperature obtained by subtracting 150° C. from the bath temperature of the plating bath (plating bath temperature ⁇ 150° C.).
- the average cooling rate is determined by determining the time required for the steel sheet to reach a temperature obtained by subtracting 150°C from the plating bath temperature, and dividing 150°C by that time.
- the amount of Mg 2 Si existing near the surface of the plating main layer can be increased to 50% or more of the whole. ..
- the reason for this is as follows.
- the interface alloy layer is generated by a solid-liquid reaction (reaction between Al in the bath and the steel sheet) in the plating bath, and Si is also incorporated in the interface alloy layer during this reaction. Therefore, the Si concentration near the interface alloy layer when the interdendrite is solidified is lower than the average Si concentration of the plating main layer, and the distribution of Mg 2 Si is closer to the surface of the plating main layer than to the interface alloy layer side. Is more.
- cooling of the steel sheet after the hot dip coating is more preferably performed at an average cooling rate of 20° C./sec or more, further preferably at an average cooling rate of 30° C./sec or more, and 40° C./sec. It is particularly preferable to perform the cooling at an average cooling rate of sec or more.
- the production method of the present invention is not particularly limited except for the bath temperature and the temperature of the approach plate at the time of hot-dip galvanizing and the cooling conditions after hot-dip galvanizing, and the hot-dip Al-Zn-Mg-Si is according to a conventional method.
- -Sr plated steel sheet can be manufactured.
- a chemical conversion treatment film is further formed on the surface thereof (chemical conversion treatment step), or a coating film is further formed in a separate coating facility. It can also be formed (coating film forming step).
- the chemical conversion coating is subjected to, for example, a chromate treatment or a chromate-free chemical conversion treatment in which a chromate treatment liquid or a chromate-free chemical conversion treatment liquid is applied and a drying treatment is performed to bring the steel sheet temperature to 80 to 300 ° C. without washing with water. It is possible to form.
- These chemical conversion treatment films may be a single layer or multiple layers, and in the case of multiple layers, a plurality of chemical conversion treatments may be sequentially performed.
- the coating film may be formed by roll coater coating, curtain flow coating, spray coating or the like. After coating a coating material containing an organic resin, it is possible to form a coating film by heating and drying by means of hot air drying, infrared heating, induction heating or the like.
- Samples 1 to 25 A cold-rolled steel sheet having a plate thickness of 0.5 mm produced by a conventional method was used as a base steel sheet, and hot-dip Al—Zn system plated steel sheets of Samples 1 to 25 were produced in a continuous hot-dip plating facility.
- the composition of the plating bath used for production is almost the same as the composition of the plating layer of each sample shown in Table 1, and the bath temperature of the plating bath, the entry plate temperature of the steel plate, and the bath temperature of the plating bath are 150°C.
- the cooling rate up to the subtracted temperature is shown in Table 1.
- Corrosion resistance evaluation corrosion resistance of flat plate part
- the combined cycle test (JASO-CCT) of the Japanese automobile standard was conducted for each sample of the molten Al-Zn-based plated steel sheet.
- JASO-CCT as shown in FIG. 6, it is a test in which salt spray, drying and wetting are one cycle under specific conditions. The number of cycles until red rust was generated in each sample was measured and evaluated according to the following criteria.
- each sample of the present invention example is superior in balance with respect to surface appearance, corrosion resistance, and processed portion corrosion resistance as compared with each comparative example sample.
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Abstract
Priority Applications (7)
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KR1020237034407A KR20230145257A (ko) | 2019-03-01 | 2019-11-14 | 용융 Al-Zn-Mg-Si-Sr 도금 강판 및 그 제조 방법 |
CN201980093481.6A CN113631748A (zh) | 2019-03-01 | 2019-11-14 | 熔融Al-Zn-Mg-Si-Sr镀覆钢板及其制造方法 |
CN202410170601.0A CN117987688A (zh) | 2019-03-01 | 2019-11-14 | 熔融Al-Zn-Mg-Si-Sr镀覆钢板及其制造方法 |
SG11202109471QA SG11202109471QA (en) | 2019-03-01 | 2019-11-14 | HOT-DIP Al-Zn-Mg-Si-Sr COATED STEEL SHEET AND METHOD OF PRODUCING SAME |
JP2020511539A JP6715399B1 (ja) | 2019-03-01 | 2019-11-14 | 溶融Al−Zn−Mg−Si−Srめっき鋼板及びその製造方法 |
KR1020217027753A KR20210123340A (ko) | 2019-03-01 | 2019-11-14 | 용융 Al-Zn-Mg-Si-Sr 도금 강판 및 그 제조 방법 |
MYPI2021004943A MY193467A (en) | 2019-03-01 | 2019-11-14 | Hot-dip al-zn-mg-si-sr coated steel sheet and method of producing same |
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CN (1) | CN113631748A (fr) |
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Cited By (3)
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KR20230082044A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg계 도금 강판, 표면 처리 강판 및 도장 강판 |
KR20230082045A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg-Sr계 도금 강판, 표면 처리 강판 및 도장 강판 |
KR20230082043A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg계 도금 강판, 표면 처리 강판 및 도장 강판 |
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KR102589282B1 (ko) * | 2021-12-14 | 2023-10-13 | 현대제철 주식회사 | 열간 프레스용 강판 및 이를 이용하여 제조된 핫 스탬핑 부품 |
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JP2007284718A (ja) * | 2006-04-13 | 2007-11-01 | Jfe Galvanizing & Coating Co Ltd | 耐食性および加工性に優れた溶融Zn−Al合金めっき鋼板及びその製造方法 |
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JP4136286B2 (ja) * | 1999-08-09 | 2008-08-20 | 新日本製鐵株式会社 | 耐食性に優れたZn−Al−Mg−Si合金めっき鋼材およびその製造方法 |
JP4102035B2 (ja) * | 2000-04-18 | 2008-06-18 | 新日本製鐵株式会社 | 耐食性に優れためっき製品およびその製造方法 |
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KR20160055962A (ko) * | 2011-07-14 | 2016-05-18 | 신닛테츠스미킨 카부시키카이샤 | 알코올 또는 그 혼합 가솔린에 대한 내식성 및 외관이 우수한 알루미늄 도금 강판 및 그 제조 방법 |
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2019
- 2019-11-14 KR KR1020217027753A patent/KR20210123340A/ko not_active IP Right Cessation
- 2019-11-14 WO PCT/JP2019/045520 patent/WO2020179147A1/fr active Application Filing
- 2019-11-14 CN CN201980093481.6A patent/CN113631748A/zh active Pending
- 2019-11-14 SG SG11202109471QA patent/SG11202109471QA/en unknown
- 2019-12-06 TW TW108144608A patent/TWI724674B/zh active
Patent Citations (3)
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JP2007284718A (ja) * | 2006-04-13 | 2007-11-01 | Jfe Galvanizing & Coating Co Ltd | 耐食性および加工性に優れた溶融Zn−Al合金めっき鋼板及びその製造方法 |
JP2011514934A (ja) * | 2008-03-13 | 2011-05-12 | ブルースコープ・スティール・リミテッド | 金属被覆スチールストリップ |
JP2018172783A (ja) * | 2017-03-31 | 2018-11-08 | Jfeスチール株式会社 | 溶融Al系めっき鋼板とその製造方法 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20230082044A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg계 도금 강판, 표면 처리 강판 및 도장 강판 |
KR20230082045A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg-Sr계 도금 강판, 표면 처리 강판 및 도장 강판 |
KR20230082043A (ko) | 2020-10-30 | 2023-06-08 | 제이에프이 스틸 가부시키가이샤 | 용융 Al-Zn-Si-Mg계 도금 강판, 표면 처리 강판 및 도장 강판 |
Also Published As
Publication number | Publication date |
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CN113631748A (zh) | 2021-11-09 |
KR20210123340A (ko) | 2021-10-13 |
TW202033791A (zh) | 2020-09-16 |
TWI724674B (zh) | 2021-04-11 |
SG11202109471QA (en) | 2021-09-29 |
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