JP2007270176A - Hot-dip galvannealed steel sheet excellent in surface appearance and adhesion to plated layer - Google Patents
Hot-dip galvannealed steel sheet excellent in surface appearance and adhesion to plated layer Download PDFInfo
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本発明は、自動車の外板や構造部材等に適する、表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板に関する。 The present invention relates to an alloyed hot-dip galvanized steel sheet that is suitable for an automobile outer plate, a structural member, and the like and excellent in surface appearance and plating adhesion.
合金化溶融亜鉛めっきは、鋼板の防食を目的として施され、自動車の外板や構造部材等、広範囲に使用されている。その製造方法としては、連続式溶融亜鉛めっきライン(以下、CGLと称する)において、脱脂洗浄後、H2及びN2を含む還元雰囲気にて、ラジアントチューブによる間接加熱により焼鈍し、めっき浴温度近傍まで冷却した後に、溶融亜鉛めっき浴に浸漬し、めっき浴を出た後に再加熱して合金化すると言う全還元炉方式がある。 Alloying hot dip galvanizing is applied for the purpose of corrosion protection of steel sheets, and is widely used for automobile outer plates and structural members. As its manufacturing method, in a continuous hot dip galvanizing line (hereinafter referred to as CGL), after degreasing and cleaning, it is annealed by indirect heating with a radiant tube in a reducing atmosphere containing H 2 and N 2 , near the plating bath temperature There is an all-reduction furnace method in which the alloy is soaked in a hot dip galvanizing bath, cooled and then reheated and alloyed.
めっき前の焼鈍については、無酸化炉を有したCGLにおいて、脱脂洗浄後、無酸化炉中で非酸化性雰囲気にて加熱し、その後、H2及びN2を含む還元雰囲気にて焼鈍すると言う無酸化炉方式も行われる場合がある。 About annealing before plating, in CGL with a non-oxidizing furnace, after degreasing and cleaning, heat in a non-oxidizing atmosphere in a non-oxidizing furnace, and then anneal in a reducing atmosphere containing H 2 and N 2 A non-oxidizing furnace method may also be performed.
近年、自動車業界においては、車体の軽量化及び衝突安全性の向上を目的として、使用される鋼材の高強度化が求められている。しかし、一般に、鋼材の強度が上昇すると延性が低下するため、鋼中にSi、Mn、Al等の元素を多量に添加し、延性を落とさずに強度を上昇させた鋼材が採用されている。 In recent years, in the automobile industry, the strength of steel materials to be used has been demanded for the purpose of reducing the weight of a vehicle body and improving the collision safety. However, generally, since the ductility is lowered when the strength of the steel material is increased, a steel material in which a large amount of elements such as Si, Mn, Al and the like are added to the steel and the strength is increased without decreasing the ductility is employed.
車体の防錆能力向上のために、これらの高強度鋼板に対しても合金化溶融亜鉛めっきすることが求められるが、高強度鋼板では、溶融亜鉛めっき浴に浸漬時、不めっきが発生すると言う問題がある。不めっきは、合金化しても残存するため、表面外観に劣る。また、不めっきが発生しなくても、めっき密着性が低下すると言う問題がある。 In order to improve the anti-corrosion ability of the car body, it is required to galvanize these high-strength steel sheets, but in high-strength steel sheets, non-plating occurs when immersed in a hot-dip galvanizing bath. There's a problem. Since non-plating remains even after alloying, the surface appearance is inferior. Further, there is a problem that the plating adhesion is lowered even if non-plating does not occur.
不めっきやめっき密着性の低下の原因としては、高強度化するために添加している鋼中のSi、Mn、Al等の易酸化性の元素が、Feに対する還元雰囲気においても容易に酸化するため、CGLの焼鈍工程において選択酸化し、鋼板表面に外部酸化膜を形成することにあると考えられてきた。 As the cause of non-plating and deterioration of plating adhesion, oxidizable elements such as Si, Mn, Al, etc. in steel added to increase the strength easily oxidize even in a reducing atmosphere for Fe. Therefore, it has been considered that selective oxidation is performed in the CGL annealing process to form an external oxide film on the steel sheet surface.
外部酸化膜とは、鋼中の易酸化性元素が鋼板表面まで外方拡散して酸化し、形成した酸化膜のことを指す。外部酸化現象は、易酸化性元素の外方拡散速度が、焼鈍雰囲気中の酸素が鋼中へ内方拡散する速度よりも早い場合に起こる。 The external oxide film refers to an oxide film formed by oxidization of an easily oxidizable element in steel by outward diffusion to the steel sheet surface and oxidation. The external oxidation phenomenon occurs when the outward diffusion rate of the easily oxidizable element is faster than the rate at which oxygen in the annealing atmosphere diffuses inwardly into the steel.
鋼板がめっき浴から出る際に、鋼板表面に易酸化性元素の外部酸化膜が存在していると、溶融亜鉛との濡れ性が悪いために、不めっきが発生する。不めっきが発生しない場合でも、めっき後に鋼板とめっき層の界面に残存する外部酸化膜が多ければ、プレス成型等の加工時に、外部酸化膜を起点としてめっき層が剥離するために、めっき密着性が低下する。 When the steel sheet comes out of the plating bath, if an external oxide film of an easily oxidizable element exists on the surface of the steel sheet, non-plating occurs due to poor wettability with molten zinc. Even when non-plating does not occur, if there is a lot of external oxide film remaining at the interface between the steel plate and the plating layer after plating, the plating layer peels off from the external oxide film during processing such as press molding. Decreases.
これらの問題を解決する手段として、CGLの焼鈍工程において、易酸化性元素の選択酸化を抑制し、鋼板表面への外部酸化膜の形成を防止する手段が採用されてきた。 As means for solving these problems, means for suppressing the selective oxidation of easily oxidizable elements and preventing the formation of an external oxide film on the steel sheet surface has been adopted in the annealing process of CGL.
例えば、特許文献1には、焼鈍前に特定の電気めっきを付与することで、易酸化性元素が外方拡散して鋼板表面まで到達する時間を稼ぎ、鋼板表面への外部酸化膜の形成を防止する方法が開示されている。 For example, in Patent Document 1, by giving specific electroplating before annealing, it takes time for the oxidizable elements to diffuse outward and reach the steel sheet surface, and to form an external oxide film on the steel sheet surface. A method of preventing is disclosed.
特許文献2には、熱延鋼板を黒皮スケールの付いた状態のまま加熱して、地鉄に内部酸化層を形成させ、連続式溶融めっきラインの焼鈍工程において、易酸化性元素の外方拡散を抑制し、外部酸化膜の形成を防止する方法が開示されている。 In Patent Document 2, the hot-rolled steel sheet is heated with the black skin scale attached, and an internal oxide layer is formed on the base iron. A method for suppressing diffusion and preventing formation of an external oxide film is disclosed.
特許文献3には、CGLの焼鈍工程において、雰囲気中に水蒸気を導入することによって酸素の内方拡散速度を増加させ、易酸化性元素を鋼板内部で酸化させることによって、外部酸化を抑制し、鋼板表面への外部酸化膜の形成を防止する方法が開示されている。 In Patent Document 3, in the annealing process of CGL, oxygen in-diffusion rate is increased by introducing water vapor into the atmosphere, and oxidizable elements are oxidized inside the steel sheet to suppress external oxidation, A method for preventing the formation of an external oxide film on the surface of a steel sheet is disclosed.
特許文献4には、めっき層中に、Si酸化物、Mn酸化物、SiとMnの複合酸化物のいずれか一種以上の酸化物粒子を含有させることにより、FeとZnの反応を促進させた合金化溶融亜鉛めっき鋼板が開示されている。 Patent Document 4 promotes the reaction between Fe and Zn by including one or more oxide particles of any one of Si oxide, Mn oxide, and Si and Mn composite oxide in the plating layer. An alloyed hot dip galvanized steel sheet is disclosed.
しかし、前記特許文献1に開示される技術では、CGLの焼鈍炉前段に新たにめっき設備を設けるか、もしくは、予め電気めっきラインにおいてめっき処理を行わなければならず、大幅なコストアップとなる。特許文献2では、熱延後に再び加熱する工程を経ねばならず、製造コストが増加する。特許文献3では、雰囲気中の水蒸気濃度を規定値内に制御しなければならず、製造可能範囲が狭くなる。特許文献4では、めっき層中の酸化物粒子にはめっき密着性を悪化させる効果はないものの、酸化物粒子がない場合に比べて加工時のめっき密着性を改善する効果はなかった。 However, in the technique disclosed in Patent Document 1, a new plating facility must be provided in front of the CGL annealing furnace, or a plating process must be performed in advance in the electroplating line, resulting in a significant cost increase. In Patent Document 2, a process of heating again after hot rolling must be performed, which increases the manufacturing cost. In Patent Document 3, the water vapor concentration in the atmosphere must be controlled within a specified value, and the manufacturable range becomes narrow. In Patent Document 4, although the oxide particles in the plating layer do not have an effect of deteriorating the plating adhesion, there is no effect of improving the plating adhesion during processing as compared with the case where no oxide particles are present.
本発明は、前述のような従来技術の問題点を解決し、表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板を提供することを目的とする。 An object of the present invention is to solve the problems of the prior art as described above, and to provide an alloyed hot-dip galvanized steel sheet excellent in surface appearance and plating adhesion.
上記問題を解決するため、本発明者らは鋭意検討を重ねた結果、めっき層中に、Si、Mn又はAlの1種又は2種以上の元素を含む層状酸化物を含有させることによって、不めっきが抑制されることを見出した。また、めっき密着性に関しては、めっき層中に上記の層状酸化物を含有しない場合と比較して、著しく向上することを見出し、表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板の提供を可能とした。 In order to solve the above problems, the present inventors have conducted intensive studies, and as a result, the plating layer contains a layered oxide containing one or more elements of Si, Mn, or Al. It has been found that plating is suppressed. In addition, regarding plating adhesion, it has been found that it is significantly improved compared to the case where the above-mentioned layered oxide is not contained in the plating layer, and provision of an alloyed hot-dip galvanized steel sheet excellent in surface appearance and plating adhesion Made possible.
不めっきが抑制されたり、めっき密着性が向上する理由の詳細については不明であるが、めっき層を上記の構造とすることで、不めっきが抑制され、めっき密着性に優れることを見出したのである。 The details of the reason why non-plating is suppressed or the plating adhesion is improved are unclear, but by finding that the plating layer has the above structure, non-plating is suppressed and the plating adhesion is excellent. is there.
本発明は、上記知見に基づいて完成されたもので、その要旨とするところは以下の通りである。
(1) 質量%で、
C:0.001〜0.3%、
Si:0.001〜3.0%、
Mn:0.1〜3.0%、
Al:0.001〜2.0%、
P:0.0001〜0.3％、
S:0.0001〜0.1％、
N:0.0001〜0.007％を含有し、
残部がFe及び不可避的不純物からなる鋼板の表面に、質量%で、
Fe:3.0〜20.0%、
Al:0.001〜0.5%を含有し、
残部がZn及び不可避的不純物からなるめっき層を有する合金化溶融亜鉛めっき鋼板であって、該めっき層が、Si、Mn又はAlの1種又は2種以上を含む層状酸化物を含有することを特徴とする表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
(2) めっき層が、さらに、質量%で、
Si:0.001〜0.5%、
Mn:0.001〜0.5%の1種又は2種を含有している上記(1)に記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
(3) めっき層中に存在する層状酸化物と、めっき層と鋼板の界面との距離dが、式(A)の条件を満たす上記(1)又は(2)に記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
0.01μm≦d≦5μm ・・・ (A)
(4) めっき層中に存在する層状酸化物の厚さTが、式(B)の条件を満たす上記(1)〜(3)のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
1nm≦T≦100nm ・・・ (B)
(5) めっき層中に存在する層状酸化物の厚さTと長さLの比L/Tが、式(C)の条件を満たす上記(1)〜(4)のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
1.5≦L/T≦30000 ・・・ (C)
(6) 鋼板母材が、さらに質量％で、Nb、Ti、V、Zr、Hf、Taの1種又は2種以上を合計で0.001〜0.5%含有する上記(1)〜(5)のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
(7) 鋼板母材が、さらに質量%で、Cr、Ni、Cuの1種又は2種以上を、合計で0.001〜5.0％含有する上記(1)〜(6)のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
(8) 鋼板母材が、さらに質量%で、
B:0.0001〜0.005％を含有する上記(1)〜(7)のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。
The present invention has been completed based on the above findings, and the gist thereof is as follows.
(1)% by mass
C: 0.001-0.3%
Si: 0.001 to 3.0%,
Mn: 0.1-3.0%
Al: 0.001 to 2.0%,
P: 0.0001-0.3%
S: 0.0001-0.1%,
N: contains 0.0001-0.007%,
On the surface of the steel sheet, the balance of which is Fe and inevitable impurities,
Fe: 3.0-20.0%,
Al: contains 0.001-0.5%,
The balance is an alloyed hot-dip galvanized steel sheet having a plating layer made of Zn and inevitable impurities, and the plating layer contains a layered oxide containing one or more of Si, Mn, or Al. Alloyed hot-dip galvanized steel sheet with excellent surface appearance and plating adhesion.
(2) The plating layer is further mass%,
Si: 0.001-0.5%
The alloyed hot-dip galvanized steel sheet having excellent surface appearance and plating adhesion as described in (1) above, containing one or two of Mn: 0.001 to 0.5%.
(3) The surface appearance and plating adhesion according to (1) or (2) above, wherein the distance d between the layered oxide present in the plating layer and the interface between the plating layer and the steel sheet satisfies the condition of the formula (A) Alloyed hot-dip galvanized steel sheet with excellent properties.
0.01μm ≦ d ≦ 5μm (A)
(4) The alloy having excellent surface appearance and plating adhesion according to any one of the above (1) to (3), wherein the thickness T of the layered oxide present in the plating layer satisfies the condition of the formula (B) Hot-dip galvanized steel sheet.
1nm ≦ T ≦ 100nm (B)
(5) The surface according to any one of the above (1) to (4), wherein the ratio L / T of the thickness T and the length L of the layered oxide present in the plating layer satisfies the condition of the formula (C) Alloyed hot-dip galvanized steel sheet with excellent appearance and plating adhesion.
1.5 ≦ L / T ≦ 30000 (C)
(6) Any of the above (1) to (5), wherein the steel plate base material further contains 0.001 to 0.5% in total of one or more of Nb, Ti, V, Zr, Hf, and Ta in mass%. An alloyed hot-dip galvanized steel sheet excellent in surface appearance and plating adhesion according to crab.
(7) The surface according to any one of (1) to (6) above, wherein the steel plate base material further contains 0.001 to 5.0% in total of one or more of Cr, Ni, and Cu in mass%. Alloyed hot-dip galvanized steel sheet with excellent appearance and plating adhesion.
(8) Steel plate base material is further mass%,
B: The galvannealed steel sheet excellent in surface appearance and plating adhesion according to any one of the above (1) to (7), containing 0.0001 to 0.005%.
本発明の合金化溶融亜鉛めっき鋼板は、めっき層がSi、Mn又はAlの1種又は2種以上を含む層状酸化物を含有することにより、不めっきが抑制され、めっき密着性に優れるので、自動車の外板や構造部材等の用途に極めて有効である。 The alloyed hot-dip galvanized steel sheet of the present invention contains a layered oxide containing one or more of Si, Mn, or Al, thereby preventing non-plating and excellent plating adhesion. It is extremely effective for applications such as automobile outer panels and structural members.
本発明(1)において、鋼板母材中の各元素を限定している理由について、以下に述べる。 The reason why each element in the steel plate base material is limited in the present invention (1) will be described below.
鋼板母材中のC含有量を0.001〜0.3質量%の範囲に規定しているのは、強度を確保するために必要な下限を0.001質量%とし、溶接性を保持可能な上限として0.3質量%としたからである。 The C content in the steel plate base metal is defined in the range of 0.001 to 0.3% by mass, the lower limit necessary for securing the strength is 0.001% by mass, and 0.3% by mass as the upper limit capable of maintaining weldability Because.
鋼板母材中のSi含有量を0.001〜3.0質量%の範囲に限定しているのは、0.001質量%未満とするのは、コスト的に不利となるからであり、上限を3.0質量%としたのは、これを超える添加は溶接性に悪影響を及ぼすためである。 The reason why the Si content in the steel sheet base metal is limited to the range of 0.001 to 3.0% by mass is to be less than 0.001% by mass because it is disadvantageous in terms of cost, and the upper limit is set to 3.0% by mass. This is because addition exceeding the above has an adverse effect on weldability.
鋼板母材中のMn含有量を0.1〜3.0質量%の範囲に限定しているのは、0.1質量%未満とするのは、コスト的に不利となるからであり、上限を3.0質量%としたのは、これを上回る添加は伸びに悪影響を及ぼすためである。 The reason why the Mn content in the steel plate base metal is limited to the range of 0.1 to 3.0% by mass is to be less than 0.1% by mass because it is disadvantageous in terms of cost, and the upper limit is set to 3.0% by mass. This is because the addition exceeding this adversely affects the elongation.
鋼板母材中のAl含有量を0.001〜2.0質量%の範囲に限定しているのは、0.001質量%未満とするのはコスト的に不利となるからであり、2.0質量%を超えると溶接性を悪化させるためである。 The reason why the Al content in the steel plate base metal is limited to the range of 0.001 to 2.0% by mass is that it is disadvantageous in terms of cost if it is less than 0.001% by mass. It is for worsening.
鋼板母材中のP含有量を0.0001〜0.3質量%の範囲に限定しているのは、0.0001質量%未満とするのはコスト的に不利となるからであり、0.3質量%を超えると溶接性を悪化させるためである。 The reason why the P content in the steel plate base metal is limited to the range of 0.0001 to 0.3% by mass is that it is disadvantageous in terms of cost if it is less than 0.0001% by mass. It is for worsening.
鋼板母材中のS含有量を0.0001〜0.1質量%の範囲に限定しているのは、0.0001質量%未満とするのはコスト的に不利となるからであり、0.1質量%を超えると溶接性を悪化させるためである。 The reason why the S content in the steel plate base metal is limited to the range of 0.0001 to 0.1% by mass is that it is disadvantageous in terms of cost if it is less than 0.0001% by mass. It is for worsening.
鋼板母在中のN含有量を0.0001〜0.007質量%の範囲に限定しているのは、0.0001質量%未満とするのはコスト的に不利となるからであり、0.007質量%を超えると加工性が低下するからである。 The reason why the N content in the base of the steel sheet is limited to the range of 0.0001 to 0.007% by mass is that it is disadvantageous in terms of cost if it is less than 0.0001% by mass. This is because of a decrease.
次に、本発明(1)において、めっき層の構造について限定した理由を説明する。 Next, the reason why the structure of the plating layer is limited in the present invention (1) will be described.
めっき層中のFe含有量を3.0〜20.0質量%の範囲に限定しているのは、3.0質量%以下ではスポット溶接性が劣るからであり、20.0質量%を超えると、めっき層自体の密着性を損ない、加工の際めっき層が破壊・脱落し、金型に付着することで、成形時の疵の原因となるからである。 The reason why the Fe content in the plating layer is limited to the range of 3.0 to 20.0 mass% is that spot weldability is inferior at 3.0 mass% or less, and when it exceeds 20.0 mass%, the adhesion of the plating layer itself This is because the plating layer breaks or falls off during processing and adheres to the mold, which causes defects during molding.
めっき層中のAl含有量を0.001〜0.5質量%の範囲に限定しているのは、0.001質量%未満では、ドロス発生が顕著で良好な外観が得られないこと、0.5質量%を超えてAlを添加すると、合金化反応を著しく抑制してしまい、合金化溶融亜鉛めっき層を形成することが困難となるためである。 The Al content in the plating layer is limited to the range of 0.001 to 0.5% by mass.If it is less than 0.001% by mass, dross generation is remarkable and a good appearance cannot be obtained, and Al exceeds 0.5% by mass. This is because the alloying reaction is remarkably suppressed and it becomes difficult to form an alloyed hot-dip galvanized layer.
めっき層中のFe及びAlの含有量を測定するには、めっき層を酸で溶解し、溶解液を化学分析する方法を用いればよい。例えば、30mm×40mmに切断した合金化溶融亜鉛めっき鋼板について、インヒビタを添加した5%HCl水溶液で、鋼板母材の溶出を抑制しながらめっき層のみを溶解し、溶解液をICP発光分析して得られた信号強度と、濃度既知溶液から作成した検量線からFe及びAlの含有量を定量する方法を用いればよい。また、各試料間の測定ばらつきを考慮して、同じ合金化溶融亜鉛めっき鋼板から切出した、少なくとも3つの試料を測定した平均値を採用すればよい。 In order to measure the content of Fe and Al in the plating layer, a method of dissolving the plating layer with an acid and chemically analyzing the solution may be used. For example, for an alloyed hot-dip galvanized steel sheet cut to 30 mm x 40 mm, with a 5% HCl aqueous solution with inhibitor added, only the plating layer was dissolved while suppressing elution of the steel sheet base material, and the solution was analyzed by ICP emission spectrometry. What is necessary is just to use the method of quantifying the content of Fe and Al from the obtained signal intensity and a calibration curve prepared from a solution having a known concentration. In addition, in consideration of measurement variations among the samples, an average value obtained by measuring at least three samples cut out from the same alloyed hot-dip galvanized steel sheet may be employed.
めっき付着量については、特に制約は設けないが、耐食性の観点から片面付着量で5g/m2以上であることが望ましい。また、めっき密着性を確保すると言う観点からは、片面付着量で100g/m2を超えないことが望ましい。本発明の溶融亜鉛めっき鋼板上に、塗装性、溶接性を改善する目的で、上層めっきを施すことや、各種の処理、例えば、クロメート処理、りん酸塩処理、潤滑性向上処理、溶接性向上処理等を施しても、本発明を逸脱するものではない。 The plating adhesion amount is not particularly limited, but is preferably 5 g / m 2 or more in terms of single-sided adhesion from the viewpoint of corrosion resistance. Further, from the viewpoint of ensuring plating adhesion, it is desirable that the amount of adhesion on one side does not exceed 100 g / m 2 . On the hot dip galvanized steel sheet of the present invention, for the purpose of improving paintability and weldability, it is possible to apply upper layer plating, various treatments such as chromate treatment, phosphate treatment, lubricity improvement treatment, weldability improvement. Even if processing is performed, it does not depart from the present invention.
本発明の合金化溶融亜鉛めっき鋼板は、めっき層中にSi、Mn、Alの内の1種以上の元素を含む層状酸化物を含有することで、不めっきが抑制され、めっき密着性に優れる。本発明の合金化溶融亜鉛めっき鋼板の断面構造の模式図の一例を、図1に示す。層状酸化物とは、図1中の2に示すような、厚さよりも長さの方が大きい酸化物のことを指し、これはCGLの焼鈍工程で鋼板表面に形成した易酸化性元素の外部酸化膜が、めっき層中に取り込まれたものである。層状酸化物の分布形態は、特に限定されるものではなく、細かく分散していても、めっき層の厚さ方向に重なっていても本発明の要件を満たす。めっき層が図1のような構造であることにより、不めっきを抑制することができるのは、鋼板がめっき浴から出る際に、鋼板表面と溶融亜鉛との物理的濡れ性が向上するからであると推定される。 The alloyed hot-dip galvanized steel sheet of the present invention contains a layered oxide containing one or more elements of Si, Mn, and Al in the plating layer, thereby preventing non-plating and excellent plating adhesion. . An example of a schematic view of the cross-sectional structure of the galvannealed steel sheet of the present invention is shown in FIG. The layered oxide refers to an oxide that is longer than the thickness, as indicated by 2 in FIG. 1. This is the outside of the oxidizable elements formed on the steel sheet surface during the CGL annealing process. An oxide film is taken into the plating layer. The distribution form of the layered oxide is not particularly limited, and satisfies the requirements of the present invention even if it is finely dispersed or overlapped in the thickness direction of the plating layer. Because the plating layer has the structure shown in Fig. 1, non-plating can be suppressed because the physical wettability between the steel sheet surface and molten zinc improves when the steel sheet comes out of the plating bath. Presumed to be.
めっき層が前記のような層状酸化物を含有しない場合と比較して、本発明の合金化溶融亜鉛めっき鋼板がめっき密着性に著しく優れるのは、めっき層と鋼板の界面に層状酸化物が残存しないことによって、めっき層が剥離する起点がなくなり、めっき密着性の悪化因子が消滅する効果に加え、加工時にめっき層と鋼板の界面から発生する亀裂の進展を、層状酸化物が停止する効果が存在するからであると推定される。 Compared to the case where the plating layer does not contain the layered oxide as described above, the alloyed hot-dip galvanized steel sheet of the present invention is remarkably excellent in plating adhesion because the layered oxide remains at the interface between the plating layer and the steel sheet. In addition to the effect of eliminating the starting point at which the plating layer peels off, the deterioration factor of the plating adhesion disappears, and the effect of the layered oxide stopping the growth of cracks occurring at the interface between the plating layer and the steel plate during processing. Presumably because it exists.
めっき層が層状酸化物を含有していることを確認するには、めっき鋼板の断面より組織観察を行い、層状物を組成分析し、層状物がSi、Mn又はAlの1種又は2種以上を含む酸化物であることを確認すればよい。例えば、集束イオンビーム加工装置(FIB)により、めっき層を含むように鋼板断面を薄片に加工した後、電解放出型透過型電子顕微鏡(FE-TEM)による観察と、エネルギー分散型X線検出器(EDX)による組成分析を行う方法が挙げられる。FIBにより観察用試料を作製した後、FE-TEMにより5万倍で層状酸化物を観察した例を、図2に示す。図2中には、4、5で示すような層状酸化物が存在する。また、図2中の4で示す層状酸化物をEDXで分析して得たスペクトルを、図3に示す。図3より、図2中に4で示す層状酸化物は、Si、Mnを含む層状酸化物であることが分かる。ここで検出されたMoは、観察用試料を載せているMo製のメッシュに由来する。 To confirm that the plating layer contains a layered oxide, the structure is observed from the cross section of the plated steel sheet, the composition of the layered material is analyzed, and the layered material is one or more of Si, Mn or Al. What is necessary is just to confirm that it is an oxide containing. For example, after processing the cross section of a steel sheet into thin pieces so as to include a plating layer using a focused ion beam processing device (FIB), observation with a field emission transmission electron microscope (FE-TEM) and an energy dispersive X-ray detector The method of performing composition analysis by (EDX) is mentioned. FIG. 2 shows an example in which a layered oxide was observed by FE-TEM at a magnification of 50,000 times after an observation sample was prepared by FIB. In FIG. 2, layered oxides as indicated by 4 and 5 exist. Further, FIG. 3 shows a spectrum obtained by analyzing the layered oxide indicated by 4 in FIG. 2 by EDX. From FIG. 3, it can be seen that the layered oxide indicated by 4 in FIG. 2 is a layered oxide containing Si and Mn. Mo detected here is derived from a mesh made of Mo on which an observation sample is placed.
Si、Mn、Alの1種以上を含む層状酸化物をめっき層に含有させるには、CGLの焼鈍工程において、鋼板表面に易酸化性元素の外部酸化膜を形成させた後、めっき浴に浸漬し、めっき浴中で外部酸化膜を剥離して、めっき層に含有させる必要がある。 To include a layered oxide containing one or more of Si, Mn, and Al in the plating layer, an external oxide film of an easily oxidizable element is formed on the surface of the steel sheet in the CGL annealing process, and then immersed in the plating bath. Then, the external oxide film must be peeled off in the plating bath and contained in the plating layer.
鋼板表面に易酸化性元素の外部酸化膜を形成するには、鋼中の易酸化性元素が外部酸化するように、CGLの焼鈍工程における雰囲気を適切な範囲に制御することが必要である。即ち、焼鈍雰囲気中のH2濃度と露点を管理することが特に重要であり、通常使用されるH2濃度が20体積%以下のN2雰囲気では、露点を-20℃以下とすることによって、易酸化性元素の外部酸化膜を形成することができる。また、外部酸化膜が形成することが重要であるので、易酸化性元素が一部内部酸化しても構わない。 In order to form an external oxide film of an easily oxidizable element on the surface of the steel sheet, it is necessary to control the atmosphere in the annealing process of CGL within an appropriate range so that the easily oxidizable element in the steel is externally oxidized. That is, it is particularly important to manage the concentration of H 2 and dew point of the annealing atmosphere, the concentration of H 2 is 20% by volume or less of N 2 atmosphere normally used by lower than -20 ℃ dew point, An external oxide film of an easily oxidizable element can be formed. Further, since it is important to form an external oxide film, a part of the easily oxidizable element may be internally oxidized.
焼鈍工程で鋼板表面に形成した外部酸化膜を、めっき浴中で剥離し、めっき層中に含有させる方法について、以下に説明する。本発明者らが鋭意検討した結果、めっき浴中に鋼板が進入した直後に、鋼板に高周波振動を加えることによって、めっき浴中で外部酸化膜が剥離し、めっき層中に含有させることが可能であることを見出した。めっき浴中で鋼板に高周波振動を加えるには、めっき浴の外側に発振器を設置し、めっき浴中に振動子を設置すればよい。本発明者らによれば、鋼板から10cm以内の距離に振動子を設置し、15kHz〜30kHzの周波数の振動を加えることによって、外部酸化膜の剥離が可能であることが分かった。また、振動子は、それ自体の温度が高温になり過ぎると作動しないため、振動子を常に冷却して、温度が200℃以下になるように制御した。 A method for peeling the external oxide film formed on the steel sheet surface in the annealing process in the plating bath and including it in the plating layer will be described below. As a result of intensive studies by the present inventors, it is possible to cause the external oxide film to peel off in the plating bath and to be contained in the plating layer by applying high-frequency vibration to the steel plate immediately after the steel plate enters the plating bath. I found out. In order to apply high-frequency vibration to the steel plate in the plating bath, an oscillator may be installed outside the plating bath and a vibrator may be installed in the plating bath. According to the present inventors, it has been found that the external oxide film can be peeled off by installing a vibrator at a distance within 10 cm from the steel plate and applying vibration with a frequency of 15 kHz to 30 kHz. In addition, since the vibrator does not operate when the temperature of the vibrator itself becomes too high, the vibrator is always cooled so that the temperature is controlled to 200 ° C. or lower.
めっき浴中で鋼板に高周波振動を加えることによって、外部酸化膜の剥離が可能となるのは、鋼板周辺に微小なキャビテーションが発生し、この気泡が潰れる際の衝撃によって、外部酸化膜に外力が加えられるためではないかと推定される。 By applying high-frequency vibrations to the steel sheet in the plating bath, the external oxide film can be peeled off because minute cavitation occurs around the steel sheet, and external force is applied to the external oxide film due to the impact when these bubbles collapse. It is presumed to be added.
また、層状酸化物をめっき層中に含有させるためには、めっき浴への鋼板の進入速度を管理することも重要であることが分かった。即ち、進入速度が大き過ぎれば、めっき浴中で剥離した外部酸化膜がめっき層中に留まることなく、めっき浴中に流出してしまい、めっき層中に層状酸化物を含有させることができない。即ち、めっき密着性の著しい向上が望めないため、進入速度を150m/min以下とすることが重要であることを見出した。また、進入速度が小さ過ぎれば、高周波振動による外部酸化膜の剥離が促進されて、外部酸化膜がめっき浴中に流出してしまう。このため、進入速度を50m/min以上とすることが重要であることを見出した。 Moreover, in order to contain a layered oxide in a plating layer, it turned out that it is also important to manage the approach rate of the steel plate to a plating bath. That is, if the penetration speed is too high, the external oxide film peeled off in the plating bath does not stay in the plating layer but flows out into the plating bath, and the layered oxide cannot be contained in the plating layer. That is, it was found that it is important to set the approach speed to 150 m / min or less because significant improvement in plating adhesion cannot be expected. On the other hand, if the approach speed is too low, peeling of the external oxide film due to high-frequency vibration is promoted, and the external oxide film flows out into the plating bath. For this reason, it was found that it is important to set the approach speed to 50 m / min or more.
本発明(2)で、めっき層中のSi含有量を0.001〜0.5質量%の範囲に限定しているのは、0.001質量%以上で、不めっきの抑制及びめっき密着性の向上の効果が顕著に現れるようになるためであり、0.5質量%を超えると、前記効果が飽和すると共に、溶接性が悪化する可能性が高まるからである。より好ましくは0.001〜0.3質量%の範囲であり、さらに好ましくは0.001〜0.25質量%の範囲である。 In the present invention (2), the Si content in the plating layer is limited to the range of 0.001 to 0.5% by mass, 0.001% by mass or more, and the effect of suppressing non-plating and improving plating adhesion is remarkable. This is because if the amount exceeds 0.5% by mass, the above-described effect is saturated and the possibility of deterioration of weldability increases. More preferably, it is the range of 0.001-0.3 mass%, More preferably, it is the range of 0.001-0.25 mass%.
めっき層中のMn含有量を0.001〜0.5質量%の範囲に限定しているのは、0.001質量%以上で、不めっきの抑制及びめっき密着性の向上の効果が顕著に現れるようになるためであり、0.5質量%を超えると、前記効果が飽和すると共に、溶接性が悪化する可能性が高まるからである。より好ましくは0.001〜0.3質量%の範囲であり、さらに好ましくは0.001〜0.25質量%の範囲である。 The reason why the Mn content in the plating layer is limited to the range of 0.001 to 0.5% by mass is that 0.001% by mass or more, and the effect of suppressing non-plating and improving the plating adhesion will appear remarkably. If the content exceeds 0.5% by mass, the above effects are saturated, and the possibility that the weldability deteriorates increases. More preferably, it is the range of 0.001-0.3 mass%, More preferably, it is the range of 0.001-0.25 mass%.
めっき層がSiやMnを含有するのは、めっき層中に存在する層状酸化物が含むSiやMnに由来する。層状酸化物中の成分として存在する、めっき層中のSiやMnの含有量を測定するには、例えば、30mm×40mmのサイズに切断した合金化溶融亜鉛めっき鋼板について、めっき層のみをインヒビタ入りの5%HCl水溶液で溶解した後、酸不溶性であるため溶け残る層状酸化物をろ過し、抽出残渣に炭酸ナトリウムを加えて加熱溶解し、溶融体に10%HCl水溶液を加えて、ICP発光分析で定量する方法を用いればよい。また、各試料間の測定ばらつきを考慮して、同じ合金化溶融亜鉛めっき鋼板から切出した、少なくとも3つの試料を測定した平均値を採用すればよい。 The plating layer contains Si and Mn because Si and Mn are contained in the layered oxide present in the plating layer. To measure the content of Si and Mn in the plating layer, which is present as a component in the layered oxide, for example, for an alloyed hot-dip galvanized steel sheet cut to a size of 30 mm x 40 mm, only the plating layer is included in the inhibitor After dissolving in 5% HCl aqueous solution, the layered oxide that remains undissolved because of acid insolubility is filtered, sodium carbonate is added to the extraction residue and heated to dissolve, and 10% HCl aqueous solution is added to the melt, ICP emission analysis The method of quantifying with may be used. In addition, in consideration of measurement variations among the samples, an average value obtained by measuring at least three samples cut out from the same alloyed hot-dip galvanized steel sheet may be employed.
本発明(3)で、めっき層中に存在する層状酸化物と、めっき層と鋼板の界面との距離dを0.01μm≦d≦5μmの範囲に限定しているのは、0.01μm未満ではめっき密着性が劣る可能性があるためであり、5μmを超えると層状酸化物がめっき層中に存在している効果が弱くなってしまうからである。この効果は、dが小さいほど大きいので、好ましくは0.01μm≦d≦3μmの範囲であり、より好ましくは0.01μm≦d≦2μmの範囲とすることである。 In the present invention (3), the distance d between the layered oxide present in the plating layer and the interface between the plating layer and the steel sheet is limited to the range of 0.01 μm ≦ d ≦ 5 μm. This is because the adhesion may be inferior, and if it exceeds 5 μm, the effect of the layered oxide present in the plating layer is weakened. Since this effect is larger as d is smaller, it is preferably in the range of 0.01 μm ≦ d ≦ 3 μm, and more preferably in the range of 0.01 μm ≦ d ≦ 2 μm.
本発明(4)で、めっき層中に存在する層状酸化物の厚さTを1nm≦T≦100nmの範囲に限定しているのは、1nm未満であれば、加工時にめっき層と鋼板の界面から発生した亀裂の進展を停止する効果が現れ難く、著しいめっき密着性の向上が認められ難いからであり、100nmを超えると、めっき層中に含有することによって生じる歪が大きく、歪を緩和させるために亀裂が生じて、めっき密着性を悪化させてしまう虞があるからである。めっき密着性の観点から、好ましくは1nm≦T≦50nmの範囲であり、より好ましくは1nm≦T≦20nmの範囲とすることである。 In the present invention (4), the thickness T of the layered oxide present in the plating layer is limited to the range of 1 nm ≦ T ≦ 100 nm, if less than 1 nm, the interface between the plating layer and the steel sheet during processing This is because the effect of stopping the growth of cracks generated from the metal is difficult to appear, and it is difficult to notice a significant improvement in plating adhesion. When the thickness exceeds 100 nm, the strain caused by inclusion in the plating layer is large, and the strain is alleviated. For this reason, there is a possibility that cracks may occur and the plating adhesion may be deteriorated. From the viewpoint of plating adhesion, the range is preferably 1 nm ≦ T ≦ 50 nm, more preferably 1 nm ≦ T ≦ 20 nm.
本発明(5)で、めっき層中に存在する層状酸化物の厚さTと長さLの比L/Tを、1.5≦L/T≦30000の範囲に限定しているのは、1.5以上で酸化物が層状であることによるめっき密着性を向上させる効果が発現し易くなり、30000を超えると溶接性が悪化する虞が高まるからである。めっき密着性の観点から、好ましくは1.5≦L/T≦1000の範囲であり、より好ましくは1.5≦L/T≦100の範囲である。 In the present invention (5), the ratio L / T of the thickness T and the length L of the layered oxide present in the plating layer is limited to a range of 1.5 ≦ L / T ≦ 30000, 1.5 or more This is because the effect of improving the plating adhesion due to the oxide being layered tends to be exhibited, and when it exceeds 30000, the weldability is likely to deteriorate. From the viewpoint of plating adhesion, the range is preferably 1.5 ≦ L / T ≦ 1000, and more preferably 1.5 ≦ L / T ≦ 100.
層状酸化物と、めっき層と鋼板の界面との距離d、層状酸化物の厚さT、層状酸化物の厚さTと長さLの比L/Tを測定する方法としては、例えば、前述したような、FIBで観察用試料を作製した後、FE-TEMで観察し、得られた画像データから測定する方法を用いればよい。例えば、図2中4で示した層状酸化物について、d、T、L/Tを測定すると、dは層状酸化物の下端からめっき層と鋼板の界面までの距離を測定すればよく、0.54μmとなる。Tは層状酸化物の下端から上端までの厚さを測定すればよく、57nmとなる。L/Tは、Lを層状酸化物の左端から右端までの距離として測定して850nmとなり、L/Tの比を計算して、14.9となる。
本発明においては、一つの合金化溶融亜鉛めっき鋼板について、5万倍で10視野観察し、それぞれの視野で観察された層状酸化物について、上記のようにd、T、L/Tの測定を行い、測定した値の内、それぞれの最大値と最小値を除いた後の平均値が前述した範囲に入っていれば、本発明の要件を満たしていることとする。例えば、観察した視野において、前述の範囲に入っていない層状酸化物が含まれていても、最大値と最小値を除いた後の平均値が本発明の範囲内であれば、本発明の要件を満たしていることとする。
Examples of the method for measuring the distance d between the layered oxide and the interface between the plating layer and the steel sheet, the layered oxide thickness T, and the layered oxide thickness T to length L ratio L / T include, for example, A method for observing with FE-TEM after preparing a sample for observation with FIB and measuring from the obtained image data may be used. For example, for the layered oxide indicated by 4 in FIG. 2, when d, T, and L / T are measured, d may be measured by measuring the distance from the lower end of the layered oxide to the interface between the plating layer and the steel sheet, 0.54 μm. It becomes. T may be determined by measuring the thickness from the lower end to the upper end of the layered oxide, and becomes 57 nm. L / T is 850 nm when L is measured as the distance from the left end to the right end of the layered oxide, and the L / T ratio is calculated to be 14.9.
In the present invention, for one alloyed hot-dip galvanized steel sheet, 10 fields of view were observed at 50,000 times, and the layered oxides observed in each field of view were measured for d, T, and L / T as described above. Of the measured values, if the average value after removing the maximum value and the minimum value is within the aforementioned range, the requirement of the present invention is satisfied. For example, even if the observed visual field contains a layered oxide that does not fall within the above range, the average value after removing the maximum value and the minimum value is within the range of the present invention. It shall be satisfied.
本発明(6)で、鋼板母材中のNb、Ti、V、Zr、Hf、Taの1種又は2種以上の合計の含有量を0.001〜0.5質量%の範囲に限定しているのは、0.001質量%以上の添加で、これらの元素が微細な炭化物、窒化物または炭窒化物を形成して鋼板の強度が上昇するからであり、0.5質量%を超えると加工性が低下するからである。 In the present invention (6), the total content of one or more of Nb, Ti, V, Zr, Hf, Ta in the steel plate base material is limited to a range of 0.001 to 0.5 mass%. The addition of 0.001% by mass or more increases the strength of the steel sheet by forming fine carbides, nitrides, or carbonitrides of these elements, and the workability decreases when the content exceeds 0.5% by mass. is there.
本発明(7)で、鋼板母材中のCr、Ni、Cuの1種又は2種以上の合計の含有量を0.001〜5.0質量%の範囲に限定しているのは、0.001質量%以上の添加で強度が上昇するからであり、5.0質量%を超えると加工性が低下するからである。 In the present invention (7), the total content of one or more of Cr, Ni, Cu in the steel plate base material is limited to a range of 0.001 to 5.0 mass%, 0.001 mass% or more This is because the strength is increased by the addition, and if it exceeds 5.0% by mass, the workability is lowered.
本発明(8)で、鋼板母材中のBの含有量を0.0001〜0.005質量%の範囲に限定しているのは、0.0001質量%以上の添加で粒界の強化や鋼板の高強度化の効果が現れるからであり、0.005質量%を超えると加工性が低下するからである。 In the present invention (8), the content of B in the steel plate base metal is limited to the range of 0.0001 to 0.005 mass% because of the addition of 0.0001 mass% or more to strengthen grain boundaries and increase the strength of the steel plate. This is because the effect appears, and if it exceeds 0.005% by mass, the workability deteriorates.
以下、実施例により本発明を具体的に説明するが、本発明は本実施例に限定されるものではない。 EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.
表1に示す組成からなるスラブを1150〜1200℃に加熱し、仕上げ温度900〜930℃で熱間圧延をして、厚さ4mmの熱間圧延鋼帯とし、580〜680℃で巻き取った。酸洗後、冷間圧延を施して、厚さ1.0mmの冷間圧延鋼帯とした後、ライン内焼鈍方式のCGLを用いて、合金化溶融亜鉛めっきを行った。焼鈍は、N2-5体積%H2、露点が-40℃の雰囲気中において、800℃で60秒間行い、冷却した後、460℃であるZn-0.13mass%Al-0.03mass%Feの組成のめっき浴に3秒間浸漬して引き上げた後、460〜580℃で5秒〜2分間合金化した。 A slab having the composition shown in Table 1 was heated to 1150 to 1200 ° C, hot-rolled at a finishing temperature of 900 to 930 ° C to form a hot-rolled steel strip having a thickness of 4 mm, and wound at 580 to 680 ° C. . After pickling, cold rolling was performed to obtain a cold rolled steel strip having a thickness of 1.0 mm, and then alloyed hot dip galvanizing was performed using an in-line annealing CGL. Annealing, N 2 -5 vol% H 2, in an atmosphere at a dew point of -40 ° C., carried out for 60 seconds at 800 ° C., after cooling, the composition of the Zn-0.13mass% Al-0.03mass% Fe is 460 ° C. After being dipped in the plating bath for 3 seconds and pulled up, it was alloyed at 460-580 ° C. for 5 seconds-2 minutes.
合金化溶融亜鉛めっき過程において、めっき層中にSi、Mn、Alの1種又は2種以上の元素を含む層状酸化物を含有させるため、めっき浴内での高周波振動の印加の有無、鋼板がめっき浴に侵入する速度を、表2に示すような条件に管理した。 In the alloying hot dip galvanizing process, in order to contain a layered oxide containing one or more elements of Si, Mn, Al in the plating layer, whether or not high frequency vibration is applied in the plating bath, The speed of entering the plating bath was controlled under the conditions shown in Table 2.
めっき層中のFe含有量、Al含有量は、前述のように、インヒビタを添加した5%HCl水溶液でめっき層のみを溶解し、溶解液をICP発光分析することにより測定した。 As described above, the Fe content and Al content in the plating layer were measured by dissolving only the plating layer with a 5% HCl aqueous solution to which an inhibitor was added, and performing ICP emission analysis on the solution.
めっき層中のSi含有量、Mn含有量は、前述のように、インヒビタを添加した5%HCl水溶液でめっき層のみを溶解した後、溶解液をろ過して残った抽出残渣に炭酸ナトリウムを加えて加熱溶解し、溶融体に10%HCl水溶液を加えて、ICP発光分析で定量した。 As described above, the Si content and Mn content in the plating layer were obtained by dissolving only the plating layer with 5% HCl aqueous solution to which inhibitor was added, and then filtering the solution and adding sodium carbonate to the remaining extraction residue. Then, 10% HCl aqueous solution was added to the melt and quantitatively determined by ICP emission analysis.
めっき層中の、Si、Mn、Alの1種又は2種以上の元素を含む層状酸化物の有無は、FIBによりめっき層を含むように鋼板断面を薄片に加工した後、FE-TEMによって観察し、EDXによる組成分析を行うことにより確認した。 The presence or absence of layered oxide containing one or more elements of Si, Mn, Al in the plating layer is observed by FE-TEM after processing the steel sheet cross-section into thin pieces so as to include the plating layer by FIB It was confirmed by performing a composition analysis by EDX.
めっき層中の層状酸化物と、めっき層と鋼板の界面との距離d、めっき層中の層状酸化物の厚さT、めっき層中の層状酸化物の厚さTと長さLの比L/Tは、FIBで観察用試料を作製した後、FE-TEMで観察し、得られた画像データから、前述したような方法を用いて測定した。 Distance d between the layered oxide in the plated layer and the interface between the plated layer and the steel sheet, the thickness T of the layered oxide in the plated layer, the ratio L between the thickness T and the length L of the layered oxide in the plated layer / T was measured using the method described above from the image data obtained by observing with FE-TEM after preparing an observation sample with FIB.
表面外観の評価は、不めっきの発生状況を目視判断し、評点付けすることにより、行った。不めっきなしを◎、直径0.5mm以下の微小不めっきが発生したが、外観上の許容範囲であるものを○、直径2mm以下の不めっきが発生したものを△、直径2mmを超える不めっきが発生したものを×とし、◎、○を合格レベルとした。 The appearance of the surface was evaluated by visually judging the occurrence of non-plating and scoring. No unplating, fine unplating with a diameter of 0.5 mm or less occurred, ○ with acceptable appearance, △ with unplating with a diameter of 2 mm or less, unplating with a diameter exceeding 2 mm What occurred was set as x, and ◎ and ○ were set as acceptable levels.
圧縮応力が加わる加工時の、めっき密着性を評価するため、60°V曲げ試験後、曲げ部内側にテープを貼り、テープを引き剥がした。テープと共に剥離しためっき層の剥離状況から、めっき密着性を評価した。◎はめっき剥離が殆どないもの(剥離幅3mm未満)、○は実用上差し支えない程度の軽微な剥離(剥離幅3mm以上7mm未満)、△は相当量の剥離が見られるもの(剥離幅7mm以上10mm未満)、×は剥離が激しいもの(剥離幅10mm以上)とし、◎、○を合格とした。 In order to evaluate the plating adhesion at the time of processing to which compressive stress was applied, a tape was applied to the inside of the bent portion after the 60 ° V bending test, and the tape was peeled off. The plating adhesion was evaluated from the peeled state of the plating layer peeled off with the tape. ◎ indicates that there is almost no plating peeling (less than 3 mm peeling width), ○ indicates slight peeling that does not interfere with practical use (peeling width of 3 mm or more and less than 7 mm), and △ indicates a considerable amount of peeling (peeling width of 7 mm or more) (Less than 10 mm) and x were those with severe peeling (peeling width 10 mm or more), and ◎ and ○ were acceptable.
さらに厳しい加工が加わった際のめっき密着性を評価するために、ビード引抜き試験を行い、試験後ビード通過面にテープを貼り、テープと共に剥離しためっき層の剥離量からめっき密着性を評価した。ビード引抜き試験は、ビード先端部の曲率半径を2mm、押し付け荷重を2.94kNとして行った。単位面積当たりのめっき層の剥離量が5g/m2未満のものを◎、5g/m2以上10g/m2未満のものを○、10g/m2以上15g/m2未満を△、15g/m2以上を×とし、◎、○を合格とした。 In order to evaluate the plating adhesion when further severe processing was applied, a bead pull-out test was performed, and after the test, a tape was applied to the bead passage surface, and the plating adhesion was evaluated from the amount of peeling of the plating layer peeled off with the tape. In the bead pull-out test, the radius of curvature of the bead tip was 2 mm and the pressing load was 2.94 kN. Peeling amount of plating layer per unit area is less than 5g / m 2 ◎, 5g / m 2 or more and less than 10g / m 2 ○, 10g / m 2 or more and less than 15g / m 2 △, 15g / m m 2 or more was evaluated as x, and ◎ and ○ were regarded as acceptable.
評価結果を表2に示す。表2より、本発明例は全て、表面外観、めっき密着性の評価が合格レベルを満たしている。本発明の範囲を満たさない比較例は、いずれも表面外観、めっき密着性の評価が低い。 The evaluation results are shown in Table 2. From Table 2, in all of the examples of the present invention, the evaluation of the surface appearance and plating adhesion satisfies the pass level. The comparative examples that do not satisfy the scope of the present invention have low evaluations of surface appearance and plating adhesion.
1 合金化溶融亜鉛めっき層
2 Si、Mn、Alのいずれか1種以上を含む層状酸化物
3 鋼板母材
4 めっき層中に存在する層状物
5 めっき層中に存在する層状物
6 合金化溶融亜鉛めっき層
7 鋼板母材
1 Alloyed hot-dip galvanized layer
2 Layered oxide containing at least one of Si, Mn, and Al
3 Steel plate base material
4 Layered material present in the plating layer
5 Layered material present in the plating layer
6 Alloyed hot-dip galvanized layer
7 Steel plate base material
Claims (8)
C:0.001〜0.3%、
Si:0.001〜3.0%、
Mn:0.1〜3.0%、
Al:0.001〜2.0%、
P:0.0001〜0.3％、
S:0.0001〜0.1％、
N:0.0001〜0.007％を含有し、
残部がFe及び不可避的不純物からなる鋼板の表面に、質量%で、
Fe:3.0〜20.0%、
Al:0.001〜0.5%を含有し、
残部がZn及び不可避的不純物からなるめっき層を有する合金化溶融亜鉛めっき鋼板であって、該めっき層が、Si、Mn又はAlの1種又は2種以上を含む層状酸化物を含有することを特徴とする表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。 % By mass
C: 0.001-0.3%
Si: 0.001 to 3.0%,
Mn: 0.1-3.0%
Al: 0.001 to 2.0%,
P: 0.0001-0.3%
S: 0.0001-0.1%,
N: contains 0.0001-0.007%,
On the surface of the steel sheet, the balance of which is Fe and inevitable impurities,
Fe: 3.0-20.0%,
Al: contains 0.001-0.5%,
The balance is an alloyed hot-dip galvanized steel sheet having a plating layer composed of Zn and inevitable impurities, and the plating layer contains a layered oxide containing one or more of Si, Mn, or Al. Alloyed hot-dip galvanized steel sheet with excellent surface appearance and plating adhesion.
Si:0.001〜0.5%、
Mn:0.001〜0.5%の1種又は2種を含有している請求項1に記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。 The plating layer is further mass%,
Si: 0.001-0.5%
2. The galvannealed steel sheet excellent in surface appearance and plating adhesion according to claim 1, containing one or two of Mn: 0.001 to 0.5%.
0.01μm≦d≦5μm ・・・ (A) The alloying excellent in surface appearance and plating adhesion according to claim 1 or 2, wherein the distance d between the layered oxide present in the plating layer and the interface between the plating layer and the steel sheet satisfies the formula (A). Hot dip galvanized steel sheet.
0.01μm ≦ d ≦ 5μm (A)
1nm≦T≦100nm ・・・ (B) 4. The galvannealed steel sheet excellent in surface appearance and plating adhesion according to any one of claims 1 to 3, wherein the thickness T of the layered oxide present in the plating layer satisfies the condition of the formula (B).
1nm ≦ T ≦ 100nm (B)
1.5≦L/T≦30000 ・・・ (C) The ratio L / T of the thickness T and the length L of the layered oxide present in the plating layer is the surface appearance and plating adhesion according to any one of claims 1 to 4 satisfying the formula (C). Excellent galvannealed steel sheet.
1.5 ≦ L / T ≦ 30000 (C)
B:0.0001〜0.005％を含有する請求項1〜7のいずれかに記載の表面外観及びめっき密着性に優れた合金化溶融亜鉛めっき鋼板。 The steel plate base material is further mass%,
The alloyed hot-dip galvanized steel sheet excellent in surface appearance and plating adhesion according to any one of claims 1 to 7, containing B: 0.0001 to 0.005%.
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