TW202338120A - Molten Al-Zn-plated steel sheet and method for producing same - Google Patents
Molten Al-Zn-plated steel sheet and method for producing same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 133
- 239000010959 steel Substances 0.000 title claims abstract description 133
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 20
- 229910018137 Al-Zn Inorganic materials 0.000 claims abstract description 104
- 229910018573 Al—Zn Inorganic materials 0.000 claims abstract description 104
- 238000007747 plating Methods 0.000 claims abstract description 65
- 239000013078 crystal Substances 0.000 claims abstract description 35
- 239000002244 precipitate Substances 0.000 claims abstract description 35
- 230000005496 eutectics Effects 0.000 claims abstract description 32
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 31
- 239000000956 alloy Substances 0.000 claims abstract description 31
- 239000011159 matrix material Substances 0.000 claims abstract description 28
- 239000000203 mixture Substances 0.000 claims abstract description 24
- 210000001787 dendrite Anatomy 0.000 claims abstract description 21
- 239000012535 impurity Substances 0.000 claims abstract description 16
- 229910052742 iron Inorganic materials 0.000 claims abstract description 14
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 14
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 7
- 239000011248 coating agent Substances 0.000 claims description 51
- 238000000576 coating method Methods 0.000 claims description 51
- 238000000034 method Methods 0.000 claims description 23
- 238000001816 cooling Methods 0.000 claims description 18
- 238000005253 cladding Methods 0.000 claims 1
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- 230000007797 corrosion Effects 0.000 abstract description 43
- 238000005260 corrosion Methods 0.000 abstract description 43
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- 238000012360 testing method Methods 0.000 description 10
- 238000011282 treatment Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 230000001133 acceleration Effects 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 8
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- 238000011156 evaluation Methods 0.000 description 6
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- 230000008018 melting Effects 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 229910018125 Al-Si Inorganic materials 0.000 description 3
- 229910018520 Al—Si Inorganic materials 0.000 description 3
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- 239000010960 cold rolled steel Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
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- 239000004566 building material Substances 0.000 description 2
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
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- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
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- 229910052720 vanadium Inorganic materials 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
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- 238000001479 atomic absorption spectroscopy Methods 0.000 description 1
- LFYJSSARVMHQJB-QIXNEVBVSA-N bakuchiol Chemical compound CC(C)=CCC[C@@](C)(C=C)\C=C\C1=CC=C(O)C=C1 LFYJSSARVMHQJB-QIXNEVBVSA-N 0.000 description 1
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- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
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- 229910052739 hydrogen Inorganic materials 0.000 description 1
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- 229910052738 indium Inorganic materials 0.000 description 1
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- 229910000765 intermetallic Inorganic materials 0.000 description 1
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- 238000004020 luminiscence type Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
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- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- 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
- C23C2/04—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
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Thermal Sciences (AREA)
- Coating With Molten Metal (AREA)
Abstract
Description
本發明是有關於一種彎曲加工性及彎曲加工部的耐蝕性優異的熔融Al-Zn系鍍覆鋼板及其製造方法。The present invention relates to a molten Al-Zn-based plated steel sheet having excellent bending workability and corrosion resistance of a bent portion, and a method for producing the same.
已知熔融Al-Zn系鍍覆鋼板可兼顧Zn的犧牲防蝕性與Al的高耐蝕性，因此於熔融鍍鋅鋼板中亦顯示出高耐蝕性。因此，熔融Al-Zn系鍍覆鋼板多用於長期暴露於室外的屋頂或牆壁等建材領域、護欄（guardrail）、配線配管、隔音牆等土木建築領域。特別是，對於因大氣污染產生的酸雨、積雪地帶處的道路防凍結用融雪劑的噴灑、海岸地區開發等更嚴峻的使用環境下的、耐蝕性優異的材料、免維護材料的要求不斷提高，因此近年來，熔融Al-Zn系鍍覆鋼板的需求增加。It is known that molten Al-Zn-based plated steel sheets can achieve both the sacrificial corrosion resistance of Zn and the high corrosion resistance of Al, and therefore also exhibit high corrosion resistance in molten galvanized steel sheets. Therefore, molten Al-Zn-based plated steel sheets are often used in building materials such as roofs and walls that are exposed to the outdoors for a long time, and in civil construction fields such as guardrails, wiring piping, and soundproof walls. In particular, the requirements for materials with excellent corrosion resistance and maintenance-free materials are increasing in severe usage environments such as acid rain caused by air pollution, spraying of snow melting agents to prevent freezing of roads in snow-covered areas, and coastal area development. Therefore, in recent years, the demand for molten Al-Zn-based plated steel sheets has increased.
此處，熔融Al-Zn系鍍覆鋼板的鍍覆皮膜包含主層、及存在於基底鋼板與主層的界面處的界面合金層，主層主要包含：過飽和地含有Zn且Al進行枝晶（dendrite）凝固的部分（α-Al相的枝晶部分）、以及剩餘的枝晶間隙的部分（枝晶間），且具有將所述α-Al相於鍍覆皮膜的膜厚方向上積層多個而成的結構。藉由此種特徵性的皮膜結構，自表面的腐蝕行進路徑變得複雜，因此腐蝕不易容易地到達基底鋼板，熔融Al-Zn系鍍覆鋼板與鍍覆皮膜的厚度相同的熔融鍍鋅鋼板相比，可實現更優異的耐蝕性。Here, the coating film of the molten Al-Zn-based plated steel sheet includes a main layer and an interface alloy layer existing at the interface between the base steel sheet and the main layer. The main layer mainly contains Zn in a supersaturated manner and Al undergoes dendrites ( dendrite) solidified part (the dendrite part of the α-Al phase) and the remaining part of the dendrite gap (interdendrite), and the α-Al phase is laminated in the film thickness direction of the coating film. structure. With this characteristic film structure, the path of corrosion from the surface becomes complicated, so corrosion cannot easily reach the base steel plate. The molten Al-Zn-based plated steel sheet is different from the molten galvanized steel sheet with the same thickness of the coating film. ratio, achieving better corrosion resistance.
但是，熔融Al-Zn系鍍覆鋼板雖然具有優異的耐蝕性，但存在鍍覆皮膜較熔融鍍鋅鋼板硬、彎曲加工性差的問題。因此，於對鋼板實施彎曲加工時，彎曲加工部前端的鍍覆皮膜容易產生裂紋（開裂）。該裂紋當然會損毀外觀，裂紋會到達鍍覆皮膜的中途為止，藉此會引起該部的鍍覆保護層厚度變薄、或者裂紋貫通鍍覆皮膜使得基底鋼板露出等現象，從而成為熔融Al-Zn系鍍覆鋼板原本具有的優異的耐蝕性於彎曲加工部顯著降低的原因。However, although the molten Al-Zn-based plated steel sheet has excellent corrosion resistance, there are problems in that the coating film is harder than that of the molten galvanized steel sheet and the bending workability is poor. Therefore, when the steel plate is bent, cracks (cracking) are likely to occur in the coating film at the tip of the bent portion. Of course, the crack will damage the appearance, and the crack will reach the middle of the coating film, which will cause the thickness of the coating protective layer to become thinner, or the crack will penetrate the coating film and expose the base steel plate, thereby becoming molten Al- This is because the excellent corrosion resistance originally possessed by Zn-based plated steel sheets is significantly reduced in the bent portion.
因此，一直以來都在進行欲謀求熔融Al-Zn系鍍覆鋼板的彎曲加工性的改善的各種嘗試。 例如，可列舉藉由對鍍覆後的熔融Al-Zn系鍍覆鋼板施加規定的熱歷程來謀求彎曲加工性的改善的技術（例如，參照專利文獻1及專利文獻2）。 [現有技術文獻] [專利文獻] Therefore, various attempts have been made to improve the bending workability of molten Al—Zn-based plated steel sheets. For example, there is a technique for improving the bending workability by applying a predetermined thermal history to the molten Al-Zn-based plated steel sheet after plating (for example, see Patent Document 1 and Patent Document 2). [Prior art documents] [Patent Document]
專利文獻1：日本專利第3654521號公報 專利文獻2：日本專利特開2013-245355號公報 Patent Document 1: Japanese Patent No. 3654521 Patent Document 2: Japanese Patent Application Publication No. 2013-245355
[發明所欲解決之課題] 於專利文獻1及專利文獻2般的對熔融Al-Zn系鍍覆鋼板實施熱歷程的技術中，可使鍍覆皮膜軟質化，彎曲加工性能夠實現某種程度上的改善。 然而，關於藉由專利文獻1及專利文獻2的技術進行改善的彎曲加工性，於進行更嚴格的彎曲加工時不可謂充分，若考慮到適用於各種建築構件，則期望彎曲加工性及加工部的耐蝕性的進一步改善。進而，亦期望開發一種可更可靠地（穩定地）提高彎曲加工性及加工部的耐蝕性的技術。 [Problem to be solved by the invention] In the technology of subjecting a molten Al-Zn-based plated steel sheet to a thermal history like Patent Document 1 and Patent Document 2, the coating film can be softened and the bending workability can be improved to some extent. However, the bending workability improved by the technology of Patent Document 1 and Patent Document 2 is not sufficient when performing more severe bending processing. If the application to various building components is considered, the bending workability and processing parts are desired. further improvement of corrosion resistance. Furthermore, it is also desired to develop a technology that can more reliably (stablely) improve bending workability and corrosion resistance of processed parts.
鑒於該情況，本發明的目的在於提供一種穩定且彎曲加工性及彎曲加工部的耐蝕性優異的熔融Al-Zn系鍍覆鋼板及其製造方法。 [解決課題之手段] In view of this situation, an object of the present invention is to provide a molten Al—Zn-based plated steel sheet that is stable and has excellent bending workability and corrosion resistance of the bent portion, and a method for producing the same. [Means to solve the problem]
本發明者等人為了解決所述課題，對包括鍍覆皮膜的熔融Al-Zn系鍍覆鋼板進行了研究，所述鍍覆皮膜具有含有Al：45質量%～65質量%及Si：1.0質量%～3.0質量%、剩餘部分包含Zn、Fe及不可避免的雜質的組成，結果發現，鍍覆皮膜具有：主要包含Al初晶的枝晶、以及包含Al-Zn共晶的枝晶間隙，其中，於Al初晶中，於散佈在α-Al相的基質內的Zn析出物為100 nm以下的微細的情況下，著眼於對枝晶的硬質化造成影響，藉由將基質中的Zn含量抑制得低，可於抑制上文所述的Zn析出物的微細化及增加的同時，謀求枝晶的軟質化，實現穩定且優異的彎曲加工性及加工部的耐蝕性。 另外，發現，對於上文所述的Al初晶中的Zn析出物，著眼於與形成鍍覆皮膜後的熱歷程的條件密切相關，對於形成鍍覆皮膜後的熱歷程，藉由謀求最高達到溫度、以及升溫時間及冷卻時間的恰當化，而將所述基質中的Zn含量抑制得低，從而可獲得一種具有優異的彎曲加工性及加工部的耐蝕性的熔融Al-Zn系鍍覆鋼板。 進而，亦發現，於Al-Zn共晶中，具有Al部與Zn部交替配置成條狀的組織（以下稱為「條紋狀組織」），於其週期為2 μm以下的情況下，著眼於降低熔融Al-Zn系鍍覆鋼板的彎曲加工性，藉由使條紋狀組織消失，可實現優異的彎曲加工性及加工部的耐蝕性。 此外，還發現，藉由將硬度大的界面合金層的厚度抑制為1 μm以下，可進一步提高彎曲加工性。 In order to solve the above problems, the present inventors studied a molten Al-Zn-based plated steel sheet including a plating film containing Al: 45 mass % to 65 mass % and Si: 1.0 mass %. % to 3.0% by mass, with the remainder including Zn, Fe and inevitable impurities. It was found that the plated film had: dendrites mainly containing Al primary crystals, and dendritic gaps containing Al-Zn eutectic, where , in the Al primary crystal, when the Zn precipitates dispersed in the matrix of the α-Al phase are as fine as 100 nm or less, focusing on the impact on the hardening of the dendrites, by changing the Zn content in the matrix By suppressing it to a low level, it is possible to soften the dendrites while suppressing the miniaturization and increase of the Zn precipitates described above, thereby achieving stable and excellent bending workability and corrosion resistance of the processed portion. In addition, it was found that the Zn precipitate in the Al primary crystal mentioned above is closely related to the conditions of the thermal history after the formation of the plating film. The thermal history after the formation of the plating film can be achieved by seeking the highest By appropriately optimizing the temperature, heating time, and cooling time, and suppressing the Zn content in the matrix to a low level, a molten Al-Zn-based plated steel sheet with excellent bending workability and corrosion resistance of the processed portion can be obtained. . Furthermore, it was also found that the Al-Zn eutectic has a structure in which Al portions and Zn portions are alternately arranged in a stripe shape (hereinafter referred to as a "striated structure"). When the period is 2 μm or less, attention is paid to By reducing the bending workability of the molten Al-Zn-based plated steel sheet and eliminating the stripe structure, excellent bending workability and corrosion resistance of the processed part can be achieved. In addition, it was found that bending workability can be further improved by suppressing the thickness of the interface alloy layer with high hardness to 1 μm or less.
再者，所謂本發明中所述的優異的彎曲加工性，是實用上充分的彎曲加工性，於以「T彎曲」進行評價時，最低需要「6T無裂紋」，較佳為「4T無裂紋」程度。再者，所謂「T彎曲」，是於夾著鋼板的板厚的狀態下實施的180°彎曲試驗，例如若為「6T彎曲」，則於對象材料的內側夾著6塊同一板厚的板來進行180°彎曲。此時，所謂「無裂紋」，表示例如利用放大鏡以10倍觀察彎曲加工部的外側前端時，未觀察到裂紋的狀態。再者，關於彎曲試驗，是依照日本工業標準（Japanese Industrial Standard，JIS）G 3321（2019年）中記載的鍍覆的密接性試驗的彎曲試驗。 順帶提及，通常的熔融Al-Zn系鍍覆鋼板的彎曲加工性亦取決於鍍覆皮膜的條件，但大多為「12T無裂紋」以上，即便為「10T彎曲」亦不會成為「無裂紋」。 Furthermore, the excellent bending workability described in the present invention means bending workability that is sufficient for practical purposes. When evaluated by "T bending", a minimum of "6T without cracks" is required, and "4T without cracks" is preferred. "degree. In addition, the so-called "T bend" is a 180° bend test performed with the thickness of the steel plate sandwiched. For example, in the case of "6T bend", six plates of the same thickness are sandwiched inside the target material. to perform a 180° bend. At this time, "no cracks" means a state in which no cracks are observed when the outer front end of the bent portion is observed with a magnifying glass at 10 times magnification, for example. In addition, the bending test is a bending test based on the plating adhesion test described in Japanese Industrial Standard (JIS) G 3321 (2019). By the way, the bending workability of ordinary molten Al-Zn-based plated steel sheets also depends on the conditions of the coating film, but most of them are "12T crack-free" or above, and even "10T bending" will not become "crack-free" ”.
本發明是基於以上見解而成者，其主旨如下所述。 1.一種熔融Al-Zn系鍍覆鋼板，包括：鍍覆皮膜，具有含有Al：45質量%～65質量%及Si：1.0質量%～3.0質量%、剩餘部分包含Zn、Fe及不可避免的雜質的組成；以及界面合金層，形成於所述鍍覆皮膜的與基底鋼板的界面側，且包含Fe、Al、Si、Zn及不可避免的雜質，所述熔融Al-Zn系鍍覆鋼板的特徵在於， 所述鍍覆皮膜具有：主要包含Al初晶的枝晶、以及包含Al-Zn共晶的枝晶間隙， 所述Al初晶包含α-Al相的基質及Zn析出物，所述基質中的Zn含量為30質量%以下， 所述界面合金層的厚度為1 μm以下。 The present invention is based on the above findings, and its gist is as follows. 1. A molten Al-Zn based plated steel sheet, comprising: a coating film containing Al: 45% by mass to 65% by mass and Si: 1.0% by mass to 3.0% by mass, with the remainder containing Zn, Fe and unavoidable The composition of impurities; and an interface alloy layer formed on the interface side of the coating film and the base steel plate, and containing Fe, Al, Si, Zn and unavoidable impurities, the molten Al-Zn based plated steel plate Characteristically, The plated film has: dendrites mainly containing Al primary crystals, and dendritic gaps containing Al-Zn eutectic, The Al primary crystal includes a matrix of α-Al phase and Zn precipitates, and the Zn content in the matrix is 30 mass% or less, The thickness of the interface alloy layer is less than 1 μm.
2.如所述1中記載的熔融Al-Zn系鍍覆鋼板，其特徵在於，所述Al初晶中的所述Zn析出物的最大直徑的平均為100 nm以上。2. The molten Al-Zn-based plated steel sheet according to 1 above, wherein the average maximum diameter of the Zn precipitates in the Al primary crystal is 100 nm or more.
3.如所述1或所述2中記載的熔融Al-Zn系鍍覆鋼板，其特徵在於，所述枝晶間隙的Al-Zn共晶不具有週期為2 μm以下的條紋狀組織。3. The molten Al-Zn-based plated steel sheet according to 1 or 2 above, wherein the Al-Zn eutectic in the dendrite gaps does not have a stripe-like structure with a period of 2 μm or less.
4.一種熔融Al-Zn系鍍覆鋼板的製造方法，為如所述1至所述3中任一項中記載的熔融Al-Zn系鍍覆鋼板的製造方法，其特徵在於，包括： 於基底鋼板形成具有含有Al：45質量%～65質量%及Si：1.0質量%～3.0質量%、剩餘部分包含Zn、Fe及不可避免的雜質的組成的鍍覆皮膜的步驟；以及 於形成所述鍍覆皮膜後，對鋼板賦予最高達到溫度為150℃以上且277℃以下的熱歷程的步驟， 於所述賦予熱歷程的步驟中，將自所述最高達到溫度至150℃為止的冷卻時間設為未滿2小時，將自150℃至常溫為止的冷卻時間設為3小時以上。 [發明的效果] 4. A method for manufacturing a molten Al-Zn-based plated steel sheet, which is a method for manufacturing a molten Al-Zn-based plated steel sheet as described in any one of the above 1 to the above 3, characterized in that it includes: The step of forming a plating film having a composition containing Al: 45% to 65% by mass, Si: 1.0% to 3.0% by mass, and the remainder including Zn, Fe, and unavoidable impurities on the base steel plate; and After forming the plating film, the step of giving the steel plate a thermal history with a maximum reaching temperature of 150°C or more and 277°C or less, In the step of providing a heat history, the cooling time from the maximum temperature to 150°C is less than 2 hours, and the cooling time from 150°C to normal temperature is 3 hours or more. [Effects of the invention]
根據本發明，可提供一種穩定且彎曲加工性及彎曲加工部的耐蝕性優異的熔融Al-Zn系鍍覆鋼板及其製造方法。According to the present invention, it is possible to provide a molten Al-Zn-based plated steel sheet that is stable and has excellent bending workability and corrosion resistance of the bent portion, and a manufacturing method thereof.
（熔融Al-Zn系鍍覆鋼板） 本發明的熔融Al-Zn系鍍覆鋼板於鋼板表面具有鍍覆皮膜。 並且，所述鍍覆皮膜具有含有Al：45質量%～65質量%及Si：1.0質量%～3.0質量%，剩餘部分實質上包含Zn、Fe及不可避免的雜質的組成。藉由所述熔融鍍覆鋼板的鍍覆皮膜具有上文所述的組成，可實現良好的耐蝕性。 再者，該鍍覆皮膜包含存在於與基底鋼板界面側的界面合金層及存在於該界面合金層之上的主層。 (Molten Al-Zn based plated steel sheet) The molten Al-Zn-based plated steel sheet of the present invention has a coating film on the surface of the steel sheet. Furthermore, the plated film has a composition containing Al: 45% by mass to 65% by mass, Si: 1.0% by mass to 3.0% by mass, and the remainder substantially includes Zn, Fe, and inevitable impurities. When the coating film of the hot-dip steel plate has the composition described above, good corrosion resistance can be achieved. Furthermore, the plating film includes an interface alloy layer existing on the interface side with the base steel plate and a main layer existing on the interface alloy layer.
就耐蝕性與操作面的平衡而言，所述鍍覆皮膜中的Al含量設為45質量%～65質量%，較佳為50質量%～60質量%。 若所述鍍覆皮膜中的Al含量至少為45質量%，則產生Al初晶的枝晶凝固，可獲得枝晶凝固組織於鍍覆皮膜的膜厚方向上積層的結構。藉由採用所述枝晶凝固組織於鍍覆皮膜的膜厚方向上積層的結構，鍍覆皮膜的腐蝕行進路徑變得複雜，從而可提高耐蝕性。另外，該枝晶積層得越多，腐蝕行進路徑越複雜，腐蝕越不易容易地到達基底鋼板，耐蝕性提高。 另一方面，若所述鍍覆皮膜中的Al含量超過65質量%，則枝晶中存在的Zn幾乎全部被取入至固溶於Al初晶的組織，從而無法抑制腐蝕進行時的Al初晶的溶解反應，耐蝕性劣化。 In terms of the balance between corrosion resistance and operating surface, the Al content in the plated film is set to 45% to 65% by mass, preferably 50% to 60% by mass. If the Al content in the plated film is at least 45% by mass, dendritic solidification of Al primary crystals occurs, and a structure in which dendritic solidification structures are laminated in the film thickness direction of the plated film can be obtained. By adopting a structure in which the dendritic solidification structure is laminated in the film thickness direction of the plated film, the corrosion progression path of the plated film becomes complicated, thereby improving the corrosion resistance. In addition, the more dendrites are laminated, the more complicated the corrosion path will be, and the less likely it will be for corrosion to reach the base steel plate, thereby improving the corrosion resistance. On the other hand, if the Al content in the plated film exceeds 65% by mass, almost all of the Zn present in the dendrites will be incorporated into a structure in which the Al primary crystals are solidly dissolved, making it impossible to suppress the formation of Al primary crystals when corrosion proceeds. dissolution reaction, deterioration of corrosion resistance.
所述鍍覆皮膜中的Si是出於抑制在與基底鋼板的界面處生成的界面合金層的成長，並且不使所述鍍覆皮膜與基底鋼板的密接性劣化的目的而添加。 於本發明的熔融Al-Zn系鍍覆鋼板的情況下，當將鋼板浸漬於含有Si的Al-Zn系鍍覆浴中時，鋼板表面的Fe與鍍覆浴中的Al或Si發生合金化反應，Fe-Al系及/或Fe-Al-Si系的金屬間化合物於基底鋼板/鍍覆膜界面處生成為層狀（形成界面合金層），此時，Fe-Al-Si系合金的成長速度較Fe-Al系合金慢，因此Fe-Al-Si系合金的比率越高，越可抑制合金相整體的成長。因此，所述鍍覆皮膜中的Si含量需要為1.0質量%以上。 另一方面，於所述界面合金層的形成中未被消耗而殘餘的Si於鍍覆皮膜中作為Si相而析出，但Si相較Al初晶或Al-Zn共晶於電氣化學方面更貴，且作為陰極發揮作用，因此具有促進鍍覆皮膜的腐蝕而降低耐蝕性的作用。具體而言，若所述鍍覆皮膜中的Si含量超過3.0質量%，則不僅所述合金相的成長抑制效果飽和，而且Si相的量增加而促進腐蝕，因此Si含量設為3.0質量%以下。 就同樣的觀點而言，所述鍍覆皮膜中的Si含量更佳為2.5質量%以下。 Si in the plating film is added for the purpose of suppressing the growth of an interface alloy layer generated at the interface with the base steel plate and not deteriorating the adhesion between the plating film and the base steel plate. In the case of the molten Al-Zn-based plated steel sheet of the present invention, when the steel sheet is immersed in an Al-Zn-based plating bath containing Si, Fe on the surface of the steel sheet is alloyed with Al or Si in the plating bath. During the reaction, Fe-Al-based and/or Fe-Al-Si-based intermetallic compounds are formed into layers (forming an interface alloy layer) at the base steel plate/plated film interface. At this time, the Fe-Al-Si based alloy The growth rate is slower than that of Fe-Al-based alloys, so the higher the ratio of Fe-Al-Si-based alloys, the more the growth of the overall alloy phase can be suppressed. Therefore, the Si content in the plated film needs to be 1.0% by mass or more. On the other hand, Si that is not consumed in the formation of the interface alloy layer and remains is precipitated as a Si phase in the plating film, but the Si phase is electrochemically more expensive than Al primary crystals or Al-Zn eutectics. , and functions as a cathode, so it has the effect of promoting corrosion of the plated film and reducing corrosion resistance. Specifically, if the Si content in the plated film exceeds 3.0% by mass, not only the growth inhibitory effect of the alloy phase is saturated, but also the amount of the Si phase increases, thereby promoting corrosion. Therefore, the Si content is set to 3.0% by mass or less. . From the same viewpoint, the Si content in the plated film is more preferably 2.5% by mass or less.
再者，所述鍍覆皮膜含有Zn、Fe及不可避免的雜質。 該些成分中，Fe有因鋼板或浴中設備於鍍覆浴中溶出而不可避免地含有的成分，或在形成所述界面合金層時藉由來自基底鋼板的擴散而供給的成分，為於所述鍍覆皮膜中不可避免地含有的成分。關於所述鍍覆皮膜中的Fe，無法將自基底鋼板取入的Fe與自所述鍍覆浴中溶出的Fe加以區分來進行定量。所述鍍覆皮膜中的Fe含量通常為0.3質量%～2.0質量%左右。 另外，作為所述Fe以外的不可避免的雜質，可列舉Cr、Ni、Cu等。 關於所述Fe及所述不可避免的雜質的總含量，並無特別限定，但於過剩地含有的情況下，有可能對鍍覆鋼板的各種特性造成影響，因此較佳為合計為5.0質量%以下，更佳為3.0質量%以下。 Furthermore, the plated film contains Zn, Fe and inevitable impurities. Among these components, Fe is a component that is inevitably contained due to the elution of the steel plate or the equipment in the bath in the plating bath, or a component that is supplied by diffusion from the base steel plate when forming the interface alloy layer. Ingredients inevitably contained in the plated film. Regarding Fe in the plating film, Fe taken in from the base steel plate and Fe eluted from the plating bath cannot be distinguished and quantified. The Fe content in the plated film is usually about 0.3% by mass to 2.0% by mass. In addition, examples of unavoidable impurities other than Fe include Cr, Ni, Cu, and the like. The total content of the Fe and the unavoidable impurities is not particularly limited, but when contained excessively, various characteristics of the plated steel sheet may be affected, so the total content is preferably 5.0% by mass. or less, more preferably 3.0% by mass or less.
另外，於本發明的熔融Al-Zn系鍍覆鋼板中，就可發揮提高腐蝕生成物的穩定性、延遲腐蝕進行的效果的方面而言，所述鍍覆皮膜亦可更含有合計為0.01質量%～10質量%的、選自Mg、Cr、Mn、V、Mo、Ti、Ca、Ni、Co、Sb及B中的一種或兩種以上。將上文所述的成分的合計含量設為0.01質量%～10質量%的原因在於，可獲得充分的腐蝕延遲效果，並且效果亦不會飽和。In addition, in the molten Al-Zn-based plated steel sheet of the present invention, in order to exhibit the effect of improving the stability of corrosion products and delaying the progression of corrosion, the coating film may further contain a total of 0.01 mass % to 10% by mass of one or more types selected from Mg, Cr, Mn, V, Mo, Ti, Ca, Ni, Co, Sb and B. The reason why the total content of the above-mentioned components is set to 0.01% by mass to 10% by mass is that a sufficient corrosion delay effect can be obtained and the effect will not be saturated.
再者，就滿足各種特性的觀點而言，所述鍍覆皮膜的附著量較佳為每一面45 g/m 2～120 g/m 2。其原因在於，於所述鍍覆皮膜的附著量為45 g/m 2以上的情況下，對於建材等需要長期耐蝕性的用途亦可獲得充分的耐蝕性，而且，於所述鍍覆皮膜的附著量為120 g/m 2以下的情況下，可於抑制加工時的鍍覆開裂等的發生的同時實現優異的耐蝕性。 就同樣的觀點而言，所述鍍覆皮膜的附著量更佳為45 g/m 2～100 g/m 2。 Furthermore, from the viewpoint of satisfying various characteristics, the adhesion amount of the plating film is preferably 45 g/m 2 to 120 g/m 2 per side. The reason for this is that when the adhesion amount of the plated film is 45 g/m 2 or more, sufficient corrosion resistance can be obtained for applications requiring long-term corrosion resistance such as building materials, and furthermore, in the case of the plated film, When the adhesion amount is 120 g/m 2 or less, excellent corrosion resistance can be achieved while suppressing the occurrence of plating cracks during processing. From the same viewpoint, the adhesion amount of the plated film is more preferably 45 g/m 2 to 100 g/m 2 .
此處，關於所述鍍覆皮膜的附著量，例如，可藉由如下方法來導出：利用JIS H 0401：2013年所示的鹽酸與六亞甲基四胺的混合液溶解剝離特定面積的鍍覆皮膜，並根據剝離前後的鋼板重量差而算出。為了藉由該方法獲得每一面的鍍覆附著量，可利用膠帶密封以免非對象面的鍍覆表面露出，然後實施所述溶解。Here, the adhesion amount of the plating film can be derived, for example, by using a mixture of hydrochloric acid and hexamethylenetetramine as shown in JIS H 0401: 2013 to dissolve and peel off the plating of a specific area. coating film and calculated based on the weight difference of the steel plate before and after peeling off. In order to obtain the plating adhesion amount on each side by this method, it is possible to seal with tape to prevent the non-target surface from being exposed, and then perform the dissolution.
另外，關於所述鍍覆皮膜的成分組成，例如可將鍍覆皮膜浸漬於鹽酸等中使其溶解，並藉由感應耦合電漿（Inductively Coupled Plasma，ICP）發光分光分析或原子吸收光譜分析等確認該溶液。該方法僅為一例，只要是可正確地對鍍覆皮膜的成分組成進行定量的方法，可為任意方法，並無特別限定。In addition, regarding the composition of the plated film, for example, the plated film can be immersed in hydrochloric acid or the like to dissolve it, and analyzed by inductively coupled plasma (ICP) luminescence spectrometry or atomic absorption spectrometry. Confirm the solution. This method is only an example, and any method can be used as long as it can accurately quantify the component composition of the plated film, and is not particularly limited.
再者，藉由本發明獲得的熔融Al-Zn系鍍覆鋼板的鍍覆皮膜整體上與鍍覆浴的組成大致相同。因此，所述鍍覆皮膜的組成的控制可藉由控制鍍覆浴組成來高精度地進行。Furthermore, the entire coating film of the molten Al-Zn-based plated steel sheet obtained by the present invention has substantially the same composition as that of the plating bath. Therefore, the composition of the plating film can be controlled with high precision by controlling the composition of the plating bath.
另外，關於所述鍍覆皮膜中的界面合金層，為所述鍍覆皮膜中的存在於與基底鋼板的界面處的層，且為包含Fe、Al、Si、Zn及不可避免的雜質的層狀的界面合金層。如上所述，所述界面合金層是基底鋼板表面的Fe與鍍覆浴中的Al或Si發生合金化反應而必然形成的。 由於該界面合金層硬且脆，增厚成長時會成為加工時的裂紋產生的起點，因此需要儘量減薄。因此，於本發明的熔融Al-Zn系鍍覆鋼板中，要求所述界面合金層的厚度為1 μm以下，較佳為0.8 μm以下。若所述界面合金層的厚度超過1 μm，則彎曲加工性降低。 In addition, the interface alloy layer in the plated film is a layer in the plated film that exists at the interface with the base steel plate, and is a layer containing Fe, Al, Si, Zn and inevitable impurities. shaped interface alloy layer. As mentioned above, the interface alloy layer is inevitably formed by the alloying reaction between Fe on the surface of the base steel plate and Al or Si in the plating bath. Since this interface alloy layer is hard and brittle, when it thickens and grows, it will become the starting point for cracks during processing, so it needs to be as thin as possible. Therefore, in the molten Al-Zn based plated steel sheet of the present invention, the thickness of the interface alloy layer is required to be 1 μm or less, preferably 0.8 μm or less. If the thickness of the interface alloy layer exceeds 1 μm, bending workability decreases.
再者，關於所述界面合金層，於使用掃描電子顯微鏡（SEM）等以三個視場以上觀察所述鍍覆皮膜的截面時，取存在於各視場內的界面合金層的平均厚度的測定值的平均而獲得的值。 另外，關於抑制所述界面合金層的厚度的方法，並無特別限定。例如，可列舉：如上所述般調整鍍覆皮膜中的Si的含量的方法、如後所述般調整於形成鍍覆皮膜後賦予熱歷程時的冷卻時間的方法等。 Furthermore, regarding the interface alloy layer, when the cross section of the plated film is observed in three or more fields of view using a scanning electron microscope (SEM) or the like, the average thickness of the interface alloy layer present in each field of view is taken as The value obtained by averaging the measured values. In addition, there is no particular limitation on the method of suppressing the thickness of the interface alloy layer. For example, a method of adjusting the Si content in the plated film as described above, a method of adjusting the cooling time when providing a thermal history after forming the plated film as described below, etc. can be cited.
此處，於本發明的熔融Al-Zn系鍍覆鋼板中，所述鍍覆皮膜具有：主要包含Al初晶的枝晶、以及包含Al-Zn共晶的枝晶間隙。 並且，於本發明的熔融Al-Zn系鍍覆鋼板中，其特徵在於，所述Al初晶於α-Al相的基質中具有Zn析出物，所述基質中的Zn含量為30質量%以下。 Here, in the molten Al-Zn-based plated steel sheet of the present invention, the plated film has dendrites mainly containing Al primary crystals and dendritic gaps containing Al-Zn eutectic. Furthermore, in the molten Al-Zn-based plated steel sheet of the present invention, the Al primary crystal has Zn precipitates in the matrix of the α-Al phase, and the Zn content in the matrix is 30 mass % or less. .
於所述α-Al相的基質中，若Zn過飽和地（於Zn含量超過30質量%的狀態下）以保持固溶的狀態凝固，則由於Zn的固溶強化，硬度變大，因此伸長減少，彎曲加工性降低。因此，於本發明中，藉由將所述基質中的Zn含量限定為30質量%以下，抑制所述Al初晶的固溶強化，提高熔融Al-Zn系鍍覆鋼板的彎曲加工性，進而提高加工部的耐蝕性。另外，有Zn析出物越微細，析出強化引起的彎曲加工性的降低越顯著的傾向，因此藉由使所述α-Al相的基質中的Zn含量為30質量%以下，亦可促進Zn析出物的成長。再者，所謂所述基質中的Zn含量，為基質中所含的Zn的含量，不包含析出分離的Zn（Zn析出物）的含量。 就同樣的觀點而言，所述基質中的Zn含量較佳為25質量%以下，更佳為20質量%以下。 In the matrix of the α-Al phase, if Zn solidifies in a solid solution state while being supersaturated (in a state where the Zn content exceeds 30% by mass), the hardness increases due to the solid solution strengthening of Zn, and therefore the elongation decreases. , the bending workability is reduced. Therefore, in the present invention, by limiting the Zn content in the matrix to 30% by mass or less, solid solution strengthening of the Al primary crystal is suppressed, and the bending workability of the molten Al-Zn based plated steel sheet is improved, thereby further improving the bending workability of the molten Al-Zn based plated steel sheet. Improve the corrosion resistance of processed parts. In addition, the finer the Zn precipitates, the more significant the reduction in bending workability caused by precipitation strengthening. Therefore, by setting the Zn content in the matrix of the α-Al phase to 30 mass % or less, Zn precipitation can also be promoted. growth of things. Furthermore, the Zn content in the matrix refers to the Zn content contained in the matrix, and does not include the content of Zn separated by precipitation (Zn precipitate). From the same viewpoint, the Zn content in the matrix is preferably 25 mass% or less, more preferably 20 mass% or less.
所謂所述Zn析出物，為以Zn為主成分的粒狀的析出物，於本發明中，觀察中使用的極低加速電壓掃描電子顯微鏡（Ultra Low Accelerating Voltage Scanning Electron Microscope，以下稱為「極低加速SEM」）的空間解析度約為30 nm，無法觀察到較其更小的Zn析出物，因此將具有所述30 nm以上的直徑的析出物視為Zn析出物。The Zn precipitates are granular precipitates containing Zn as the main component. In the present invention, an Ultra Low Accelerating Voltage Scanning Electron Microscope (Ultra Low Accelerating Voltage Scanning Electron Microscope, hereafter referred to as "Ultra Low Accelerating Voltage Scanning Electron Microscope") is used for observation. The spatial resolution of "Low Acceleration SEM") is about 30 nm, and Zn precipitates smaller than this cannot be observed, so precipitates with a diameter of 30 nm or more are regarded as Zn precipitates.
關於所述Al初晶，於Zn析出物散佈於α-Al相的基質內的情況下，如上所述，由於析出強化而存在彎曲加工性降低的傾向，析出物越微細該傾向越顯著。因此，使所述Zn析出物大幅成長更有利於彎曲加工性。具體而言，所述Al初晶中的所述Zn析出物的最大直徑的平均較佳為100 nm以上。 再者，所謂所述Zn析出物的最大直徑的平均，為例如於藉由極低加速SEM（加速電壓 3 kV、20000倍以上的倍率）以三個視場以上觀察Al初晶時，按照自大到小的順序以10點測定各視場內存在的以Zn為主的析出物的長徑，並取該些測定值的平均而得的值。 Regarding the Al primary crystal, when Zn precipitates are dispersed in the matrix of the α-Al phase, as mentioned above, there is a tendency to reduce bending workability due to precipitation strengthening, and this tendency becomes more significant as the precipitates become finer. Therefore, making the Zn precipitates grow significantly is more beneficial to the bending workability. Specifically, the average maximum diameter of the Zn precipitates in the Al primary crystal is preferably 100 nm or more. Furthermore, the average maximum diameter of the Zn precipitates is, for example, when an Al primary crystal is observed with three or more fields of view using an extremely low acceleration SEM (acceleration voltage: 3 kV, magnification of 20,000 times or more). The major diameter of the Zn-based precipitates present in each field of view was measured at 10 points in descending order, and the average of these measured values was obtained.
另外，所述鍍覆皮膜具有包含Al-Zn共晶的枝晶間隙。所述枝晶間隙除了包含Al-Zn共晶以外，有時亦包含單質Si相。 構成所述枝晶間隙的Al-Zn共晶包含Al部與Zn部。當該Al-Zn共晶被加熱至277℃以上時，Al部的Zn固溶度增加，Zn部幾乎固溶，從而成為更過飽和地含有Zn的Al部。然後，當Al-Zn共晶被冷卻時，於277℃以下再次變化為Al-Zn共晶，此時，所述Al-Zn共晶具有Al部與Zn部交替配置成條狀的條紋狀組織。 In addition, the plated film has dendrite gaps containing Al-Zn eutectic. In addition to Al-Zn eutectic, the dendrite gap sometimes also contains a simple Si phase. The Al-Zn eutectic constituting the dendrite gap includes an Al part and a Zn part. When the Al-Zn eutectic is heated to 277° C. or higher, the Zn solid solubility of the Al portion increases, and the Zn portion becomes almost in solid solution, thereby becoming an Al portion containing Zn in a more supersaturated manner. Then, when the Al-Zn eutectic is cooled, it changes into the Al-Zn eutectic again below 277°C. At this time, the Al-Zn eutectic has a stripe-like structure in which Al parts and Zn parts are alternately arranged in strips. .
並且，本發明者等人進行了研究，結果發現，雖然機理尚不明確，但該Al-Zn共晶的條紋狀組織使熔融Al-Zn系鍍覆鋼板的彎曲加工性降低，特別是於所述條紋狀組織的條紋的週期小至2 μm以下時，彎曲加工性的降低變得顯著。 因此，就進一步提高本發明的熔融Al-Zn系鍍覆鋼板的彎曲加工性及加工部的耐蝕性的觀點而言，較佳為於所述枝晶間隙的Al-Zn共晶中不存在週期為2 μm以下的條紋狀組織。再者，對於所述條紋狀組織的條紋週期的下限值，並無特別限定。但是，根據後述的測定裝置的性能，於條紋狀組織的週期未滿30 nm的情況下，難以確認其存在，因此於本發明中，將所述條紋週期為30 nm以上者視為條紋狀組織。 Furthermore, the present inventors conducted research and found that although the mechanism is not yet clear, the stripe-like structure of the Al-Zn eutectic reduces the bending workability of the molten Al-Zn-based plated steel sheet, especially in the When the period of the stripes of the stripe-like structure is as small as 2 μm or less, the bending workability is significantly reduced. Therefore, from the viewpoint of further improving the bending workability and the corrosion resistance of the processed portion of the molten Al-Zn-based plated steel sheet of the present invention, it is preferable that there is no periodicity in the Al-Zn eutectic in the dendrite gap. It is a striped structure below 2 μm. Furthermore, the lower limit of the stripe period of the stripe-like structure is not particularly limited. However, due to the performance of the measurement device described below, it is difficult to confirm the existence of the stripe-like structure when the period of the stripe-like structure is less than 30 nm. Therefore, in the present invention, the stripe-like structure is regarded as the stripe-like structure having a period of 30 nm or more. .
對於上文所述的Al-Zn共晶的條紋狀組織，可與Al初晶中的Zn析出物相同地藉由極低加速SEM（加速電壓3 kV）進行測定。於加速電壓高，例如加速電壓為15 kV以上的SEM中，無法檢測出條紋的週期小至2 μm以下的所述Al-Zn共晶的條紋狀組織，但於本發明中，藉由使用極低加速SEM進行觀察，能夠確認存在的有無。再者，所述Zn析出物及所述Al-Zn共晶的條紋狀組織均較施加熱歷程時生成的該些更微細，因此例如於利用加速電壓為15 kV的觀察中，並未考慮到該些的存在的有無。The striped structure of the Al-Zn eutectic described above can be measured by an extremely low acceleration SEM (acceleration voltage 3 kV) in the same way as the Zn precipitates in the Al primary crystal. In an SEM with a high accelerating voltage, for example, an accelerating voltage of 15 kV or more, the stripe-like structure of the Al-Zn eutectic with a stripe period as small as 2 μm or less cannot be detected. However, in the present invention, by using extremely Observation with low-acceleration SEM can confirm the presence or absence. Furthermore, the Zn precipitates and the striped structures of the Al-Zn eutectic are finer than those generated when a thermal history is applied. Therefore, for example, in the observation using an accelerating voltage of 15 kV, they were not taken into consideration. The existence or absence of such things.
再者，對於控制上文所述的基質中的Zn含量、Zn析出物的最大直徑及週期為2 μm以下的條紋狀組織的有無的方法，並無特別限定，可藉由製造條件的恰當化等進行適宜控制。 例如，如後所述，藉由在決定鍍覆浴的組成的基礎上，使形成鍍覆皮膜後的熱歷程的條件恰當化，可控制基質中的Zn含量、Zn析出物的最大直徑及週期為2 μm以下的條紋狀組織的有無。 Furthermore, there are no particular limitations on the method of controlling the Zn content in the matrix, the maximum diameter of the Zn precipitates, and the presence or absence of striped structures with a period of 2 μm or less, as described above, and they can be achieved by optimizing the manufacturing conditions. etc. for appropriate control. For example, as described later, by determining the composition of the plating bath and optimizing the conditions of the thermal history after the formation of the plating film, the Zn content in the matrix, the maximum diameter and the period of the Zn precipitates can be controlled. It refers to the presence or absence of striped tissue below 2 μm.
另外，本發明的熔融Al-Zn系鍍覆鋼板可於所述鍍覆皮膜上直接形成塗膜或隔著中間層形成塗膜。 再者，關於所述塗膜的種類、形成塗膜的方法，並無特別限定，可根據所要求的性能適宜選擇。例如可列舉：輥塗機塗裝、淋幕式塗裝、噴霧塗裝等形成方法。於塗裝含有有機樹脂的塗料後，能夠藉由熱風乾燥、紅外線加熱、感應加熱等方法進行加熱乾燥而形成塗膜。 In addition, the molten Al-Zn-based plated steel sheet of the present invention can form a coating film directly on the coating film or form a coating film via an intermediate layer. In addition, the type of the coating film and the method of forming the coating film are not particularly limited, and can be appropriately selected according to the required performance. Examples include: roller coater coating, curtain coating, spray coating and other forming methods. After the coating containing organic resin is applied, the coating film can be formed by heating and drying by methods such as hot air drying, infrared heating, and induction heating.
另外，關於所述中間層，只要是於熔融鍍覆鋼板的鍍覆皮膜與所述塗膜之間形成的層，則並無特別限定。例如可列舉化學轉化處理皮膜、黏接層等底漆。關於所述化學轉化處理皮膜，例如，能夠藉由塗佈鉻酸鹽處理液或無鉻化學轉化處理液，不水洗而進行鋼板溫度為80℃～300℃的乾燥處理的鉻酸鹽處理或無鉻化學轉化處理來形成。該些化學轉化處理皮膜可為單層亦可為多層，於多層的情況下依次進行多個化學轉化處理即可。In addition, the intermediate layer is not particularly limited as long as it is a layer formed between the coating film of the hot-dip steel plate and the coating film. Examples include primers such as chemical conversion treatment films and adhesive layers. The chemical conversion treatment film can be, for example, coated with a chromate treatment liquid or a chromium-free chemical conversion treatment liquid, and then dried without washing at a steel plate temperature of 80° C. to 300° C. or chromate treatment without water. Chromium is formed by chemical conversion treatment. The chemical conversion treatment films may be single-layer or multi-layer. In the case of multiple layers, multiple chemical conversion treatments may be performed in sequence.
（熔融Al-Zn系鍍覆鋼板的製造方法） 本發明的熔融Al-Zn系鍍覆鋼板的製造方法具有：於基底鋼板形成鍍覆皮膜的步驟、以及於形成所述鍍覆皮膜後，對鋼板賦予熱歷程的步驟。 (Method for manufacturing molten Al-Zn-based plated steel sheet) The manufacturing method of the molten Al-Zn-based plated steel sheet of the present invention includes the steps of forming a coating film on a base steel plate, and after forming the coating film, providing a thermal history to the steel plate.
再者，對於在所述基底鋼板形成所述鍍覆皮膜的形成方法，並無特別限定。例如，可藉由利用連續式熔融鍍覆設備，對所述基底鋼板進行清洗、加熱、鍍覆浴浸漬來製造。 於所述基底鋼板的加熱步驟中，為了控制基底鋼板自身的組織而實施再結晶退火等，並且防止鋼板的氧化且還原存在於表面的微量的氧化膜，因此於氮-氫氣氛等還原氣氛下的加熱是有效的。 Furthermore, there is no particular limitation on the method of forming the plating film on the base steel plate. For example, it can be produced by using continuous hot-dip plating equipment to clean, heat, and immerse the base steel plate in a plating bath. In the heating step of the base steel plate, recrystallization annealing and the like are performed in order to control the structure of the base steel plate itself, and to prevent oxidation of the steel plate and reduce a trace amount of oxide film existing on the surface, so in a reducing atmosphere such as a nitrogen-hydrogen atmosphere The heating is effective.
進而，對於所述基底鋼板的種類或鋼中成分亦並無特別限定，可根據所要求的性能或規格適宜使用冷軋鋼板或熱軋鋼板等，作為鋼中成分，例如可使用C：0.01質量%～0.10質量%的鋼中成分等。但是，C：未滿0.01%的鋼板於本發明中亦不除外。另外，除了含有C、Al、Si、Mn、P作為成分元素以外，亦含有N、S、O、B、V、Nb、Ti、Cu、Mo、Cr、Co、Ni、Ca、Sr、In、Sn、Sb等作為微量添加元素的鋼板亦處於本發明的範疇中。 此外，對於獲得所述基底鋼板的方法亦並無特別限定。例如，於所述熱軋鋼板的情況下，可使用經過了熱軋步驟、酸洗步驟者，於所述冷軋鋼板的情況下，可進而增加冷軋步驟來製造。進而，為了獲得鋼板的特性，於熔融鍍覆步驟之前，亦能夠經過再結晶退火步驟等。 Furthermore, the type of the base steel plate or the components in the steel are not particularly limited. A cold-rolled steel plate or a hot-rolled steel plate can be appropriately used according to the required performance or specifications. As the component in the steel, for example, C: 0.01 mass can be used %~0.10% by mass of steel components, etc. However, steel plates with C: less than 0.01% are not excluded from the present invention. In addition, in addition to C, Al, Si, Mn, and P as component elements, it also contains N, S, O, B, V, Nb, Ti, Cu, Mo, Cr, Co, Ni, Ca, Sr, In, Steel plates with trace additive elements such as Sn and Sb also fall within the scope of the present invention. In addition, there is no particular limitation on the method of obtaining the base steel plate. For example, in the case of the hot-rolled steel plate, one that has undergone a hot-rolling step and a pickling step can be used, and in the case of the cold-rolled steel plate, a cold-rolling step can be further added to produce the steel plate. Furthermore, in order to obtain the characteristics of the steel plate, a recrystallization annealing step or the like may be performed before the hot-dip plating step.
關於形成所述鍍覆皮膜時使用的鍍覆浴，如上所述，由於所述鍍覆皮膜的組成整體上與鍍覆浴的組成大致相同，因此使用具有含有Al：45質量%～65質量%及Si：1.0質量%～3.0質量%，剩餘部分實質上包含Zn、Fe及不可避免的雜質的組成者。As for the plating bath used when forming the plated film, as mentioned above, since the composition of the plated film as a whole is substantially the same as that of the plating bath, a bath containing Al: 45% by mass to 65% by mass is used. and Si: 1.0% by mass to 3.0% by mass, and the remainder essentially consists of Zn, Fe and inevitable impurities.
另外，所述鍍覆浴的浴溫並無特別限定，但較佳為設為（熔點+20℃）～650℃的溫度範圍。 將所述鍍覆浴的浴溫的下限設為熔點+20℃的原因在於，為了進行熔融鍍覆處理，需要使所述浴溫為凝固點以上，藉由設為熔點+20℃，防止所述鍍覆浴的局部的浴溫降低導致的凝固。另一方面，將所述浴溫的上限設為650℃的原因在於，若超過650℃，則所述鍍覆皮膜的急速冷卻變得困難，於所述鍍覆皮膜與所述基底鋼板的界面處形成的界面合金層有可能變厚。 In addition, the bath temperature of the plating bath is not particularly limited, but is preferably in the temperature range of (melting point + 20°C) to 650°C. The reason why the lower limit of the bath temperature of the plating bath is set to the melting point + 20°C is that in order to perform the melt plating process, the bath temperature needs to be equal to or higher than the freezing point. By setting the lower limit to the melting point + 20°C, it is possible to prevent the above Solidification caused by a local drop in bath temperature of the plating bath. On the other hand, the reason why the upper limit of the bath temperature is set to 650°C is that if it exceeds 650°C, rapid cooling of the plated film becomes difficult, and the interface between the plated film and the base steel plate The interface alloy layer formed at the interface may become thicker.
進而，對於浸入至所述鍍覆浴的所述基底鋼板的溫度（進入板溫）亦並無特別限定。例如，就確保所述連續式熔融鍍覆操作中的鍍覆特性或防止浴溫度的變化的觀點而言，較佳為控制為相對於所述鍍覆浴的溫度的±20℃以內。Furthermore, the temperature (incoming plate temperature) of the base steel plate immersed in the plating bath is not particularly limited. For example, from the viewpoint of ensuring the plating characteristics in the continuous molten plating operation or preventing changes in the bath temperature, it is preferable to control the temperature within ±20° C. with respect to the temperature of the plating bath.
進而，對於將所述基底鋼板浸漬於所述鍍覆浴中的時間，較佳為0.5秒以上。其原因在於，與所述浸漬時間未滿0.5秒的情況下，有可能無法於所述基底鋼板的表面形成充分的鍍覆皮膜。再者，對於所述浸漬時間的上限並無特別限定，但若延長浸漬時間，則形成於鍍覆皮膜與鋼板之間的界面合金層亦有可能變厚，因此較佳為設為8秒以內。Furthermore, the time for immersing the base steel plate in the plating bath is preferably 0.5 seconds or more. The reason for this is that if the immersion time is less than 0.5 seconds, a sufficient plating film may not be formed on the surface of the base steel plate. Furthermore, the upper limit of the immersion time is not particularly limited, but if the immersion time is extended, the interface alloy layer formed between the coating film and the steel plate may also become thicker, so it is preferably within 8 seconds. .
並且，於本發明的熔融Al-Zn系鍍覆鋼板的製造方法中，其特徵在於，於所述賦予熱歷程的步驟中，最高達到溫度為150℃以上且277℃以下，將自所述最高達到溫度至150℃為止的冷卻時間設為未滿2小時，將自150℃至常溫為止的冷卻時間設為3小時以上。 藉由賦予此種熱歷程，可獲得穩定且彎曲加工性及彎曲加工部的耐蝕性優異的熔融Al-Zn系鍍覆鋼板。 Furthermore, in the manufacturing method of the molten Al-Zn-based plated steel sheet of the present invention, in the step of providing a heat history, the maximum temperature is 150°C or more and 277°C or less, and the maximum temperature is 150°C or more and 277°C or less. The cooling time until the temperature reaches 150°C is less than 2 hours, and the cooling time from 150°C to normal temperature is 3 hours or more. By providing such a thermal history, a molten Al-Zn-based plated steel sheet can be obtained that is stable and has excellent bending workability and corrosion resistance of the bent portion.
將所述賦予熱歷程時的最高達到溫度設為150℃以上且277℃以下的原因在於，於所述最高達到溫度未滿150℃時Zn的擴散變慢，從而無法充分實現所述Al初晶中的固溶強化及析出強化的消除，而且，所述Al-Zn共晶中的條紋狀組織亦成為殘存的狀態，因此無法充分地獲得熔融Al-Zn系鍍覆鋼板的彎曲加工性。另一方面，若所述最高達到溫度超過277℃，則所述Al初晶中的固溶強化及析出強化被消除，而且Al-Zn共晶中的條紋狀組織亦分解，但之後進行冷卻並經過277℃時，於Al-Zn共晶中再次生成條紋狀組織，而導致熔融Al-Zn系鍍覆鋼板的彎曲加工性的變差。 就同樣的觀點而言，賦予所述熱歷程時的最高達到溫度較佳為設為170℃以上且250℃以下，更佳為設為190℃以上且230℃以下。 The reason why the maximum reaching temperature when imparting the heat history is 150°C or more and 277°C or less is that when the maximum reaching temperature is less than 150°C, the diffusion of Zn slows down and the Al primary crystal cannot be fully realized. The solid solution strengthening and precipitation strengthening in the Al-Zn eutectic are eliminated, and the stripe-like structure in the Al-Zn eutectic remains. Therefore, the bending workability of the molten Al-Zn-based plated steel sheet cannot be fully obtained. On the other hand, if the maximum reaching temperature exceeds 277°C, the solid solution strengthening and precipitation strengthening in the Al primary crystal are eliminated, and the stripe structure in the Al-Zn eutectic is also decomposed, but it is then cooled and After 277° C., a stripe-like structure is formed again in the Al-Zn eutectic, resulting in deterioration of the bending workability of the molten Al-Zn-based plated steel sheet. From the same viewpoint, the maximum temperature reached when imparting the thermal history is preferably from 170°C to 250°C, more preferably from 190°C to 230°C.
另外，於所述賦予熱歷程的步驟中，將自所述最高達到溫度至150℃為止的冷卻時間設為未滿2小時的原因在於，藉由抑制所述界面合金層的成長，實現彎曲加工性的提高，並且極力抑制於所述升溫加熱階段達成的所述鍍覆皮膜的組織於冷卻階段發生變化，從而維持上文所述的固溶強化及析出強化的消除，且抑制條紋狀組織的產生。 就同樣的觀點而言，自所述最高達到溫度至150℃為止的冷卻時間較佳為1小時以下。 In addition, in the step of providing a heat history, the reason why the cooling time from the maximum temperature to 150° C. is set to less than 2 hours is to achieve bending processing by suppressing the growth of the interface alloy layer. The improvement of the properties, and the structural changes of the plated film achieved in the heating stage are suppressed during the cooling stage, thereby maintaining the elimination of solid solution strengthening and precipitation strengthening mentioned above, and suppressing the formation of striped structures. produce. From the same viewpoint, the cooling time from the maximum temperature to 150° C. is preferably 1 hour or less.
進而，於所述賦予熱歷程的步驟中，將自所述150℃至常溫為止的冷卻時間設為3小時以上的原因在於，確保Zn於所述Al初晶中擴散的溫度及時間，將所述基質內的Zn含量設為30質量%以下，將所述Zn析出物的最大直徑平均設為100 nm以上，使Al初晶中的固溶強化及析出強化的消除充分。再者，所謂所述「常溫」，意指室溫，且假定25℃左右。 再者，就製造效率的觀點而言，自所述150℃至常溫為止的冷卻時間較佳為設為10小時以內。 Furthermore, in the step of imparting a thermal history, the reason why the cooling time from the 150° C. to normal temperature is set to 3 hours or more is to ensure the temperature and time for Zn to diffuse in the Al primary crystal, so that the The Zn content in the matrix is set to 30 mass % or less, and the maximum diameter of the Zn precipitates is set to 100 nm or more on average, so that solid solution strengthening and precipitation strengthening in the Al primary crystal can be fully eliminated. In addition, the "normal temperature" means room temperature, and is assumed to be about 25°C. Furthermore, from the viewpoint of manufacturing efficiency, the cooling time from 150° C. to normal temperature is preferably within 10 hours.
此處，圖1示出Al-Zn二元系平衡狀態圖。 於通常的熔融鍍覆製程中，鍍覆後的冷卻為驟冷，因此凝固時來不及自枝晶排出Zn，所述基質中，將Zn以過飽和（超過30質量%）地固溶的狀態凝固。因此，於Al初晶的α-Al相（基質）中過飽和地固溶的Zn引起固溶強化，硬度變高，結果伸長減少，彎曲加工性降低。 並且，當於形成所述鍍覆皮膜後實施加熱時，α-Al相的過飽和Zn析出，Zn固溶度下降，於之後的冷卻中，於分離為α-Al相的基質與Zn析出物的狀態下凝固。此時，可知，藉由將所述基質中的Zn含量控制為30質量%以下，Al初晶的固溶強化得以消除。 另外，Al-Zn共晶包含Al部與Zn部，當將其加熱至277℃以上時，Al部的Zn固溶度增加，Zn部幾乎固溶，從而成為更過飽和地含有Zn的Al部。並且，可知，藉由加熱後的冷卻，於277℃以下再次變化為Al-Zn共晶，該Al-Zn共晶成為Al部與Zn部交替配置成條狀的條紋狀組織。 Here, FIG. 1 shows an equilibrium state diagram of the Al-Zn binary system. In a normal melt plating process, the cooling after plating is quenching, so there is no time to discharge Zn from the dendrites during solidification. In the matrix, Zn is solidified in a supersaturated (more than 30% by mass) solid solution state. Therefore, Zn that is supersaturated in solid solution in the α-Al phase (matrix) of the Al primary crystal causes solid solution strengthening and increases the hardness. As a result, the elongation decreases and the bending workability decreases. Furthermore, when heating is performed after the formation of the plating film, supersaturated Zn in the α-Al phase precipitates, and the Zn solid solubility decreases. During subsequent cooling, the α-Al phase is separated into a matrix and a Zn precipitate. solidified state. At this time, it was found that solid solution strengthening of the Al primary crystal was eliminated by controlling the Zn content in the matrix to 30% by mass or less. In addition, the Al-Zn eutectic contains an Al part and a Zn part. When it is heated to 277° C. or higher, the Zn solid solubility of the Al part increases, and the Zn part becomes almost solid solution, thereby becoming an Al part containing more supersaturated Zn. Furthermore, it was found that by cooling after heating, the Al-Zn eutectic changes again to the Al-Zn eutectic at 277° C. or lower, and the Al-Zn eutectic becomes a stripe-like structure in which Al portions and Zn portions are alternately arranged in strips.
再者，於本發明的熔融Al-Zn系鍍覆鋼板的製造方法中，除了上文所述的形成鍍覆皮膜的步驟及賦予熱歷程的步驟以外的步驟，並無特別限定，可根據對熔融Al-Zn系鍍覆鋼板所要求的性能適宜實施任意的步驟。Furthermore, in the manufacturing method of the molten Al-Zn-based plated steel sheet of the present invention, the steps other than the steps of forming the coating film and the step of imparting a thermal history described above are not particularly limited, and can be performed according to the It is appropriate to carry out any step according to the required performance of the molten Al-Zn-based plated steel sheet.
另外，亦可更包括：於藉由所述本發明的熔融Al-Zn系鍍覆鋼板的製造方法獲得的熔融Al-Zn系鍍覆鋼板之上直接形成塗膜或隔著中間層形成塗膜的步驟。In addition, it may further include forming a coating film directly on the molten Al-Zn-based plated steel plate obtained by the manufacturing method of the molten Al-Zn-based plated steel plate of the present invention or forming a coating film through an intermediate layer. steps.
再者，關於形成所述塗膜的方法，並無特別限定，可根據所要求的性能適宜選擇。例如可列舉：輥塗機塗裝、淋幕式塗裝、噴霧塗裝等形成方法。於塗裝含有有機樹脂的塗料後，能夠藉由熱風乾燥、紅外線加熱、感應加熱等方法進行加熱乾燥而形成塗膜。In addition, the method of forming the coating film is not particularly limited, and can be appropriately selected depending on the required performance. Examples include: roller coater coating, curtain coating, spray coating and other forming methods. After the coating containing organic resin is applied, the coating film can be formed by heating and drying by methods such as hot air drying, infrared heating, and induction heating.
另外，關於所述中間層，只要是於熔融鍍覆鋼板的鍍覆皮膜與所述塗膜之間形成的層，則並無特別限定。關於所述中間層的種類或形成方法，與本發明的熔融Al-Zn系鍍覆鋼板中說明的內容相同。 [實施例] In addition, the intermediate layer is not particularly limited as long as it is a layer formed between the coating film of the hot-dip steel plate and the coating film. The type and formation method of the intermediate layer are the same as those described for the molten Al-Zn-based plated steel sheet of the present invention. [Example]
＜樣品1～樣品30＞ （1）熔融Al-Zn系鍍覆鋼板的製造 將藉由常用方法製造的板厚0.35 mm的冷軋鋼板用作基底鋼板，並藉由連續式熔融鍍覆設備進行退火處理、鍍覆處理，藉此製作了表1所示的鍍覆皮膜組成及附著量的熔融Al-Zn系鍍覆鋼板A～熔融Al-Zn系鍍覆鋼板C。 再者，關於在熔融鍍覆鋼板製造中使用的鍍覆浴的組成，使用以Al：55質量%、Si：1.6質量%、Fe：0.4質量%、剩餘部分實質上為Zn及不可避免的雜質的組成（鍍覆A）為基礎，變更了各成分的含量的組成（鍍覆B、鍍覆C）。 另外，鍍覆浴的浴溫均設為590℃，基底鋼板的鍍覆進入板溫控制為與鍍覆浴溫相同的溫度。進而，鍍覆皮膜的附著量控制為每一面均為85±10 g/m 2。 <Sample 1 to Sample 30> (1) Manufacturing of molten Al-Zn-based plated steel sheets. A cold-rolled steel sheet with a thickness of 0.35 mm manufactured by a common method is used as the base steel sheet, and is performed with a continuous molten plating equipment. Annealing treatment and plating treatment were performed to produce molten Al-Zn-based plated steel sheets A to molten Al-Zn-based plated steel sheets C having the coating film compositions and adhesion amounts shown in Table 1. Furthermore, regarding the composition of the plating bath used in manufacturing the hot-dip steel plate, Al: 55% by mass, Si: 1.6% by mass, Fe: 0.4% by mass, and the balance is substantially Zn and unavoidable impurities. Compositions (Plating B, Plating C) based on the composition (Plating A) but with the content of each component changed. In addition, the bath temperature of the plating bath was all set to 590°C, and the plating entry plate temperature of the base steel plate was controlled to be the same temperature as the plating bath temperature. Furthermore, the adhesion amount of the plating film was controlled to be 85±10 g/m 2 on each side.
（2）熱歷程的賦予 對所獲得的熔融Al-Zn系鍍覆鋼板於表2所示的條件下賦予熱歷程，從而獲得各樣品的熔融Al-Zn系鍍覆鋼板。 (2) Endowment of thermal history The obtained molten Al-Zn-based plated steel sheet was given a thermal history under the conditions shown in Table 2, thereby obtaining molten Al-Zn-based plated steel sheets of each sample.
（3）鍍覆皮膜的附著量、組成的確認 自各樣品的熔融Al-Zn系鍍覆鋼板沖裁100 mmϕ，利用膠帶將非測定面密封後，如JIS H 0401（2013年）所示般，藉由鹽酸與六亞甲基四胺的混合液將鍍覆加以溶解剝離，並根據剝離前後的樣品的質量差算出鍍覆皮膜的附著量。 然後，過濾剝離液，分別分析濾液與固體成分。具體而言，藉由對濾液進行ICP發光分光分析，對不溶Si以外的成分進行了定量化。 再者，固體成分於650℃的加熱爐內經乾燥、灰化後，藉由添加碳酸鈉及四硼酸鈉而使其熔解。另外，利用鹽酸將熔解物加以溶解，藉由對溶解液進行ICP發光分光分析，對不溶Si進行了定量化。鍍覆皮膜中的Si濃度是對藉由濾液分析而獲得的可溶Si濃度加上藉由固體成分分析而獲得的不溶Si濃度而得。 關於所獲得的鍍覆皮膜A～鍍覆皮膜C的組成及附著量，示於表1中。 (3) Confirmation of the adhesion amount and composition of the plating film The molten Al-Zn-based plated steel plate of each sample was punched out to 100 mmϕ, and the non-measurement surface was sealed with tape. Then, as shown in JIS H 0401 (2013), a mixture of hydrochloric acid and hexamethylenetetramine was used. The plating was dissolved and peeled off, and the amount of coating film attached was calculated based on the mass difference between the samples before and after peeling off. Then, the stripping liquid was filtered, and the filtrate and solid components were analyzed separately. Specifically, by subjecting the filtrate to ICP emission spectrometry, components other than insoluble Si were quantified. Furthermore, the solid component was dried and ashed in a heating furnace at 650° C., and then sodium carbonate and sodium tetraborate were added to melt it. In addition, the melt was dissolved with hydrochloric acid, and the insoluble Si was quantified by subjecting the solution to ICP emission spectrometry. The Si concentration in the plated film is obtained by adding the soluble Si concentration obtained by filtrate analysis and the insoluble Si concentration obtained by solid content analysis. Table 1 shows the composition and adhesion amount of the obtained plated films A to C.
[表1]
＜評價＞ 對於以上述方式獲得的熔融Al-Zn系鍍覆鋼板的各樣品，進行以下評價。將評價結果示於表1中。 ＜Evaluation＞ The following evaluations were performed on each sample of the molten Al-Zn-based plated steel sheet obtained as described above. The evaluation results are shown in Table 1.
（1）鍍覆皮膜的條件 對於各樣品的熔融Al-Zn系鍍覆鋼板，藉由極低加速SEM觀察鍍覆皮膜的截面，並藉由能量分散型X射線分光法（以下稱為「EDX（Energy Dispersive X-Ray analysis）」）進行分析。 所述鍍覆皮膜的觀察及分析的條件設為，使用蔡司（Zeiss）公司製造的ULTRA55（極低加速SEM）與牛津儀器（Oxford Instruments）公司製造的終極極限（Ultim Extreme）（EDX），以加速電壓3 kV、觀察倍率3000倍及20000倍、對規定部位進行點分析。 再者，Al初晶中存在的以Zn為主的析出物的最大直徑平均是藉由以20000倍進行三個視場觀察，自各視場的Al初晶中按照自大到小的順序提取10點以Zn為主的析出物，並測定其長徑，算出平均而獲得。另外，關於條紋狀組織的最小週期，以20000倍進行三個視場觀察，測定所存在的條紋狀組織的條紋週期，將該些中最小者作為最小週期。 將所獲得的鍍覆皮膜的條件（基質中的Zn濃度及Zn析出物的最大直徑的平均、Al-Zn共晶的條紋狀組織的有無及最小週期、以及界面合金層的厚度）示於表2中。 另外，對於樣品1及樣品14的熔融Al-Zn系鍍覆鋼板，將觀察Al初晶中存在的以Zn為主的析出物而得的照片示於圖2中。 進而，對於樣品1、樣品14及樣品22的熔融Al-Zn系鍍覆鋼板，將觀察Al-Zn共晶的條紋狀組織而得的照片示於圖3中。 (1) Conditions for coating film For each sample of the molten Al-Zn-based plated steel plate, the cross-section of the coating film was observed by ultra-low acceleration SEM, and energy dispersive X-ray spectroscopy (hereinafter referred to as "EDX (Energy Dispersive X-Ray analysis)" ”) for analysis. The conditions for observation and analysis of the coating film were to use ULTRA55 (ultra-low acceleration SEM) manufactured by Zeiss and Ultim Extreme (EDX) manufactured by Oxford Instruments. The acceleration voltage is 3 kV, the observation magnification is 3000 times and 20000 times, and point analysis is performed on the specified parts. Furthermore, the average maximum diameter of the Zn-based precipitates present in the Al primary crystal was determined by observing three fields of view at 20,000 times, and extracting 10 values from the Al primary crystals in each field of view in descending order. The precipitates mainly composed of Zn were spotted, their major diameters were measured, and the average value was calculated. In addition, regarding the minimum period of the stripe-like tissue, three fields of view were observed at a magnification of 20,000, the stripe period of the existing stripe-like tissue was measured, and the smallest one among them was regarded as the minimum period. The conditions of the obtained plated film (the Zn concentration in the matrix and the average maximum diameter of Zn precipitates, the presence or absence and minimum period of the striped structure of the Al-Zn eutectic, and the thickness of the interface alloy layer) are shown in the table. 2 in. In addition, for the molten Al-Zn-based plated steel sheets of Sample 1 and Sample 14, photographs showing Zn-based precipitates present in the Al primary crystals are shown in FIG. 2 . Furthermore, for the molten Al—Zn-based plated steel sheets of Sample 1, Sample 14, and Sample 22, photographs showing the striped structure of the Al—Zn eutectic are shown in FIG. 3 .
（2）彎曲加工性 對於各樣品的熔融Al-Zn系鍍覆鋼板，於10T～0T的範圍內，一邊各減少2T，一邊實施「T彎曲」的彎曲試驗（依照JIS G 3321（2019年）中記載的鍍覆的密接性試驗的彎曲試驗），於利用放大鏡以10倍進行觀察時，確認到成為「無裂紋」的彎曲T的極限。將結果示於表2中。 再者，所謂「T彎曲」，為於夾著鋼板的板厚的狀態下實施的180°彎曲試驗。另外，所謂進行觀察時的「無裂紋」，表示利用放大鏡以10倍觀察彎曲加工部的外側前端時，完全未觀察到裂紋的狀態。進而，所謂「彎曲T的極限」，為無裂紋的T彎曲中的最小的T。例如，於在6T彎曲中觀察到無裂紋，在4T彎曲中觀察到裂紋的情況下，彎曲T的極限成為「6T」。 (2) Bending workability For the molten Al-Zn-based plated steel sheets of each sample, a "T-bend" bending test was performed while reducing each sample by 2T in the range of 10T to 0T (in accordance with the coating described in JIS G 3321 (2019) The bending test of the adhesiveness test), when observing with a magnifying glass at 10 times, the bending T limit of "no cracks" was confirmed. The results are shown in Table 2. In addition, the so-called "T bend" is a 180° bending test performed with the thickness of the steel plate sandwiched between them. In addition, "no cracks" when observed means that when the outer front end of the bent portion is observed with a magnifying glass at 10 times, no cracks are observed at all. Furthermore, the so-called "limit of bending T" is the smallest T among T-bends without cracks. For example, if no cracks are observed in 6T bending and cracks are observed in 4T bending, the limit of bending T becomes "6T".
（3）彎曲加工部的耐蝕性 對於樣品1及樣品14的熔融Al-Zn系鍍覆鋼板，於在0T～9T的範圍內進行T彎曲的狀態下，於千葉市中央區進行了室外暴露試驗。目視觀察進行4年8個月暴露試驗後的彎曲加工部，按照以下的基準進行評價。將評價結果示於圖4中。 （評價基準） 1分：明確有紅鏽 2分：略微有紅鏽 3分：無紅鏽 (3) Corrosion resistance of bent parts An outdoor exposure test was conducted in Chuo-ku, Chiba City with the molten Al-Zn-based plated steel sheets of Sample 1 and Sample 14 being T-bent in the range of 0T to 9T. The bent portion after the exposure test for 4 years and 8 months was visually observed and evaluated based on the following standards. The evaluation results are shown in Figure 4 . (Evaluation criteria) 1 point: There is definitely red rust 2 points: slightly red rusty 3 points: No red rust
[表2]
根據表2及圖4的結果可知，本發明例的各樣品與比較例的各樣品相比，彎曲加工性及加工部的耐蝕性均平衡良好且優異。 [產業上的可利用性] From the results in Table 2 and FIG. 4 , it can be seen that the bending workability and the corrosion resistance of the processed portion of each sample of the present invention example are well-balanced and excellent compared with each sample of the comparative example. [Industrial availability]
根據本發明，可提供一種穩定且彎曲加工性及彎曲加工部的耐蝕性優異的熔融Al-Zn系鍍覆鋼板及其製造方法。According to the present invention, it is possible to provide a molten Al-Zn-based plated steel sheet that is stable and has excellent bending workability and corrosion resistance of the bent portion, and a manufacturing method thereof.
無without
圖1是Al-Zn二元系平衡狀態圖。 圖2是針對比較例1及本發明例14的熔融Al-Zn系鍍覆鋼板的樣品，分別示出了α-Al相的基質中的Zn含量、Al初晶中的Zn析出物的最大直徑的平均值、及觀察Al初晶的截面而得的照片的圖。 圖3是針對比較例1、本發明例14及比較例22的熔融Al-Zn系鍍覆鋼板的樣品，分別觀察鍍覆皮膜的截面而得的照片。 圖4是針對比較例1及本發明例14的熔融Al-Zn系鍍覆鋼板的樣品，分別表示彎曲加工部的耐蝕性的評價結果的圖表、觀察1T彎曲加工部而得的照片。 Figure 1 is an equilibrium state diagram of the Al-Zn binary system. Figure 2 is a sample of the molten Al-Zn-based plated steel sheet of Comparative Example 1 and Inventive Example 14, showing the Zn content in the matrix of the α-Al phase and the maximum diameter of Zn precipitates in the Al primary crystal. The average value and the photograph obtained by observing the cross section of the Al primary crystal. FIG. 3 is a photograph of a cross-section of a coating film of a sample of a molten Al-Zn-based plated steel sheet of Comparative Example 1, Inventive Example 14, and Comparative Example 22, respectively. 4 is a graph showing the evaluation results of the corrosion resistance of the bent portion of the samples of the molten Al-Zn-based plated steel sheets of Comparative Example 1 and Example 14 of the present invention, and a photograph of the 1T bent portion.
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