JP2005290418A - HOT-DIP Al-Zn ALLOY PLATED STEEL SHEET SUPERIOR IN PRESS FORMABILITY, AND MANUFACTURING METHOD THEREFOR - Google Patents
HOT-DIP Al-Zn ALLOY PLATED STEEL SHEET SUPERIOR IN PRESS FORMABILITY, AND MANUFACTURING METHOD THEREFOR Download PDFInfo
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Abstract
Description
本発明は、めっき皮膜中のAl含有量が20〜80mass%の溶融Al−Zn系めっき鋼板及びその製造方法に関する。 The present invention relates to a molten Al—Zn-based plated steel sheet having an Al content in a plating film of 20 to 80 mass% and a method for producing the same.
めっき皮膜中にAlを20〜80mass%含有する溶融Al−Zn系めっき鋼板は、溶融亜鉛めっき鋼板に比べて優れた耐食性を示すことから、近年、建材分野を中心に需要が伸びている(例えば、特許文献1参照)。
この溶融Al−Zn系めっき鋼板は、酸洗脱スケールした熱延鋼板又はこれをさらに冷間圧延して得られた冷延鋼板を下地鋼板とし、連続式溶融めっき設備において以下のようにして製造される。
Since the hot-dip Al-Zn-based plated steel sheet containing 20 to 80 mass% of Al in the plating film exhibits excellent corrosion resistance as compared with the hot-dip galvanized steel sheet, demand has recently increased mainly in the building material field (for example, , See Patent Document 1).
This hot-dip Al-Zn-based plated steel sheet is manufactured as follows using a hot-rolled steel sheet pickled and descaled or a cold-rolled steel sheet obtained by further cold rolling the base steel sheet in a continuous hot-dip plating facility. Is done.
連続式溶融めっき設備では、下地鋼板は還元性雰囲気に保持された焼鈍炉内で所定温度に加熱され、焼鈍と同時に鋼板表面に付着する圧延油等の除去、酸化膜の還元除去が行われた後、下端がめっき浴に浸漬されたスナウト内を通って所定の濃度のAlを含有した溶融亜鉛めっき浴中に浸漬される。めっき浴に浸漬された鋼板はシンクロールを経由してめっき浴の上方に引き上げられた後、めっき浴上に配置されたガスワイピングノズルから鋼板表面に向けて加圧した気体を噴射することによりめっき付着量が調整され、次いで冷却装置により冷却され、所定のめっき皮膜が形成された溶融Al−Zn系めっき鋼板が得られる。 In the continuous hot dip plating facility, the base steel sheet was heated to a predetermined temperature in an annealing furnace maintained in a reducing atmosphere, and simultaneously with the annealing, the rolling oil adhered to the steel sheet surface was removed, and the oxide film was reduced and removed. Thereafter, the lower end passes through the inside of the snout immersed in the plating bath and is immersed in a hot dip galvanizing bath containing a predetermined concentration of Al. The steel plate immersed in the plating bath is pulled up above the plating bath via a sink roll, and then plated by injecting pressurized gas toward the steel plate surface from a gas wiping nozzle disposed on the plating bath. The adhesion amount is adjusted and then cooled by a cooling device to obtain a molten Al—Zn-based plated steel sheet on which a predetermined plating film is formed.
連続式溶融めっき設備における焼鈍炉の熱処理条件及び雰囲気条件、めっき浴組成やめっき後の冷却速度などの操業条件は、所望のめっき品質や材質を確保するために所定の管理範囲で精度よく管理される。
上記のようにして製造されためっき鋼板のめっき皮膜は、主としてZnを過飽和に含有したAlがデンドライト凝固した部分と、残りのデンドライト間隙の部分からなっており、デンドライトはめっき皮膜の膜厚方向に積層している。このような特徴的な皮膜構造により、溶融Al−Zn系めっき鋼板は優れた耐食性を示す。
Operating conditions such as annealing furnace heat treatment conditions and atmosphere conditions, plating bath composition and cooling rate after plating in a continuous hot-dip plating facility are accurately controlled within a predetermined control range to ensure the desired plating quality and material. The
The plating film of the plated steel sheet produced as described above is mainly composed of a part where Al containing Zn is supersaturated and dendrite solidified and a part of the remaining dendrite gap, and the dendrite is in the film thickness direction of the plating film. Laminated. Due to such a characteristic film structure, the molten Al—Zn-based plated steel sheet exhibits excellent corrosion resistance.
また、めっき浴には通常Alに対して3mass%程度のSiが添加されているが、このSiの働きにより、溶融Al−Zn系めっき鋼板はめっき皮膜/下地鋼板界面の合金相成長が抑えられ、合金相厚さは約1〜2μm程度である。この合金相が薄ければ薄いほど、優れた耐食性を示す特徴的な皮膜構造の部分が多くなるので、合金相の成長抑制は耐食性の向上に寄与する。また、合金相はめっき皮膜よりも固く加工時にクラックの起点として作用するので、合金相の成長抑制はクラックの発生を減少させ、加工性の向上効果をもたらす。また、クラック部は下地鋼板が露出していて耐食性に劣るので、クラックの発生を減じることは加工部耐食性をも向上させる。 In addition, about 3 mass% Si is usually added to the plating bath with respect to Al, but the action of Si suppresses the growth of the alloy phase at the plating film / underlying steel plate interface in the molten Al—Zn-based steel plate. The alloy phase thickness is about 1-2 μm. The thinner the alloy phase, the more part of the characteristic film structure that exhibits excellent corrosion resistance. Therefore, the suppression of the growth of the alloy phase contributes to the improvement of the corrosion resistance. In addition, since the alloy phase is harder than the plating film and acts as a starting point of cracks during processing, suppressing the growth of the alloy phase reduces the occurrence of cracks and brings about an effect of improving workability. Moreover, since the base steel plate is exposed in the crack portion and the corrosion resistance is poor, reducing the occurrence of cracks also improves the corrosion resistance of the processed portion.
通常、めっき浴には不可避的不純物、鋼板やめっき浴中の機器等から溶出するFe、合金相抑制のためのSiが含まれるが、それら以外にも何らかの元素が添加される場合もあり、合金相やめっき皮膜中にはそれら元素が合金或いは単体の形で存在している。
また、溶融Al−Zn系めっき鋼板は、実用に供されるに当たって溶融めっきのままで使用されることは極く稀で有り、通常はめっき鋼板表面に化成処理や塗装を施した表面処理鋼板、塗装鋼板として使用される。
In addition, the hot-dip Al-Zn-based plated steel sheet is rarely used as it is in hot-dip plating when it is put to practical use, and is usually a surface-treated steel sheet that has been subjected to chemical conversion treatment or coating on the surface of the plated steel sheet, Used as a painted steel plate.
溶融Al−Zn系めっき鋼板は、折り曲げなどの加工を施すと加工の程度によって被加工部のめっき皮膜にクラックが生じる。このめっき鋼板では、めっき皮膜/下地鋼板界面に存在する約1〜2μm厚の合金相がクラックの起点となり、まためっき皮膜のデンドライト間隙部がクラックの伝播経路になる。このため、同程度の加工を行った場合でも、同一めっき皮膜厚の溶融亜鉛めっき鋼板に比べてクラックの伝播経路が限られており、クラックの発生数が少ない一方で各クラックが比較的大きく開口する傾向がある。このため加工の程度によってはクラックが肉眼で視認され、外観を損ねるという問題がある。またクラック部は下地鋼板が露出しているため、クラックのない部分と比較して耐食性が著しく低下するという問題もある。 When the molten Al—Zn-based plated steel sheet is subjected to processing such as bending, cracks occur in the plating film of the processed part depending on the degree of processing. In this plated steel sheet, an alloy phase having a thickness of about 1 to 2 μm existing at the plating film / underlying steel sheet interface serves as a crack starting point, and a dendrite gap portion of the plating film serves as a crack propagation path. For this reason, even when the same degree of processing is performed, the propagation path of cracks is limited compared to hot-dip galvanized steel sheets with the same plating film thickness, and the number of cracks generated is small, but each crack is relatively large in size. Tend to. For this reason, the crack is visually recognized with the naked eye depending on the degree of processing, and there is a problem that the appearance is impaired. Moreover, since the base steel plate is exposed at the crack portion, there is also a problem that the corrosion resistance is remarkably lowered as compared with the portion without the crack.
さらに、上述のように溶融Al−Zn系めっき鋼板は、同一めっき皮膜厚の溶融亜鉛めっき鋼板に比べて優れた耐食性を発揮するが、プレス加工のように、変形のみではなく摺動も加わる加工様式においては、クラックの開口が大きくなって隣接するクラックの間隔が長くなるほど、めっき皮膜が剥離しやすくなる傾向がある。 Furthermore, as described above, the hot-dip Al-Zn-based plated steel sheet exhibits excellent corrosion resistance compared to the hot-dip galvanized steel sheet with the same plating film thickness, but it is not only deformed but also subjected to sliding as well as deformation. In the mode, the plating film tends to peel more easily as the opening of the crack becomes larger and the interval between adjacent cracks becomes longer.
したがって、本発明の目的は、めっき皮膜中のAl含有量が20〜80mass%の溶融Al−Zn系めっき鋼板において、従来にない優れたプレス加工性を有するめっき鋼板を提供することである。 Accordingly, an object of the present invention is to provide a plated steel sheet having an unprecedented excellent press workability in a molten Al-Zn-based plated steel sheet having an Al content in a plated film of 20 to 80 mass%.
上記課題の解決のために本発明者らは、溶融Al−Zn系めっき鋼板のプレス加工性を向上させる手法について鋭意検討を行った。その結果、デンドライト間隙部に晶出する単体Si量を制御しためっき皮膜構造とすることにより、従来にない優れたプレス加工性が得られること、また、めっき浴中に含まれるSi量とめっき浴温を最適化することにより、そのようなめっき皮膜構造を得ることができることを見出した。 In order to solve the above-mentioned problems, the present inventors diligently studied a method for improving the press workability of the molten Al—Zn-based plated steel sheet. As a result, it is possible to obtain an unprecedented excellent press workability by adopting a plating film structure in which the amount of elemental Si crystallized in the dendrite gap is controlled, and the amount of Si contained in the plating bath and the plating bath It has been found that such a plated film structure can be obtained by optimizing the temperature.
本発明は、このような知見に基づいてなされたもので、その特徴は以下のとおりである。
[1] めっき皮膜中のAl含有量が20〜80mass%の溶融Al−Zn系めっき鋼板であって、下地鋼板とめっき皮膜界面の合金相部分を除くめっき皮膜中に、Siを単体で2〜9mass%含有することを特徴とする、プレス加工性に優れた溶融Al−Zn系めっき鋼板。
[2] めっき皮膜中のAl含有量が20〜80mass%の溶融Al−Zn系めっき鋼板であって、下地鋼板とめっき皮膜界面の合金相部分を含むめっき皮膜中に、Siを下記(1)式及び(2)式を満足する条件で含有することを特徴とする、プレス加工性に優れた溶融Al−Zn系めっき鋼板。
0.02×T−14.5≦S1≦0.02×T−7.5 … (1)
770≦T≦1000 … (2)
但し T :溶融Al−Znめっき時のめっき浴温(K)
S1:めっき皮膜中のSi含有量(mass%)
The present invention has been made based on such findings, and the features thereof are as follows.
[1] A molten Al—Zn-based plated steel sheet having an Al content of 20 to 80 mass% in the plated film, and Si alone is 2 to 2 in the plated film excluding the alloy phase portion of the base steel sheet and the plated film interface. A molten Al-Zn-based plated steel sheet excellent in press workability, characterized by containing 9 mass%.
[2] A molten Al-Zn-based plated steel sheet having an Al content of 20 to 80 mass% in the plated film, and Si is contained in the plated film including the alloy phase portion at the interface between the base steel sheet and the plated film (1) A hot-dip Al—Zn-based plated steel sheet excellent in press workability, characterized by containing the formula and the formula (2).
0.02 × T-14.5 ≦ S1 ≦ 0.02 × T-7.5… (1)
770 ≦ T ≦ 1000 (2)
T: Plating bath temperature (K) during molten Al-Zn plating
S1: Si content in the plating film (mass%)
[3] 上記[1]又は[2]の溶融Al−Zn系めっき鋼板の表面に化成処理皮膜を有することを特徴とする、プレス加工性に優れた表面処理鋼板。
[4] 上記[1]又は[2]の溶融Al−Zn系めっき鋼板の表面に化成処理皮膜を有し、さらにその上層に、単層または複層の塗膜を有することを特徴とする、プレス加工性に優れた塗装鋼板。
[5] 連続式溶融めっき設備において、上記[1]又は[2]の溶融Al−Zn系めっき鋼板を製造するに当たり、
1000K以下でかつ下記(3)式を満足するめっき浴温の溶融Al−Znめっき浴にて鋼板をめっきすることを特徴とする、プレス加工性に優れた溶融Al−Zn系めっき鋼板の製造方法。
2.5×A+720≦T≦50×S2+725 … (3)
但し T :めっき浴温(K)
A :めっき浴中のAl含有量(mass%)
S2:めっき浴中のSi含有量(mass%)
[3] A surface-treated steel sheet excellent in press workability, comprising a chemical conversion coating on the surface of the molten Al—Zn-plated steel sheet of [1] or [2].
[4] The above-mentioned [1] or [2] has a chemical conversion treatment film on the surface of the molten Al-Zn-based plated steel sheet, and further has a single-layer or multiple-layer coating on the upper layer, Painted steel sheet with excellent press workability.
[5] In producing the hot-dip Al-Zn-based plated steel sheet according to [1] or [2] above in a continuous hot-dip plating facility,
A method for producing a molten Al-Zn-based plated steel sheet excellent in press workability, comprising plating a steel sheet in a molten Al-Zn plating bath having a plating bath temperature satisfying the following formula (3) below 1000K .
2.5 × A + 720 ≦ T ≦ 50 × S2 + 725 (3)
T: Plating bath temperature (K)
A: Al content in the plating bath (mass%)
S2: Si content in the plating bath (mass%)
[6] 上記[5]の製造方法で得られた溶融Al−Zn系めっき鋼板の表面に化成処理皮膜を形成することを特徴とする、プレス加工性に優れた表面処理鋼板の製造方法。
[7] 上記[5]の製造方法で得られた溶融Al−Zn系めっき鋼板の表面に化成処理皮膜を形成し、さらにその上層に、単層または複層の塗膜を形成することを特徴とする、プレス加工性に優れた塗装鋼板の製造方法。
[6] A method for producing a surface-treated steel sheet having excellent press workability, wherein a chemical conversion treatment film is formed on the surface of the molten Al—Zn-based plated steel sheet obtained by the production method of [5].
[7] A chemical conversion film is formed on the surface of the molten Al—Zn-plated steel sheet obtained by the production method of [5] above, and a single-layer film or a multi-layer film is formed thereon. The manufacturing method of the coated steel plate excellent in press workability.
本発明によれば、プレス加工性に優れた溶融Al−Zn系めっき鋼板を得ることができる。 According to the present invention, a molten Al—Zn-based plated steel sheet having excellent press workability can be obtained.
本発明のめっき鋼板は、めっき皮膜中にAlを20〜80mass%含有する溶融Al−Zn系めっき鋼板であるが、性能面(耐食性、加工性等)と操業面のバランスから、めっき皮膜中のAl量のより好ましい範囲は45〜65mass%である。
先に述べたように溶融Al−Zn系めっき鋼板は、曲げ加工時のクラック伝播経路がめっき皮膜のデンドライト間隙部に限られているため、クラックの数が少ない一方で各クラックが比較的大きく開口する傾向がある。本発明では、このようなめっき皮膜構造とクラックの関係を利用して、めっき皮膜にクラックの伝播経路を積極的に導入することにより、微細なクラックを多量に発生させること、すなわちクラックの数を増加させることで各クラックの開口巾を小さくすることを狙いとするものであり、以下に述べるように、このようなクラックの生成形態は、デンドライト間隙部に晶出する単体Si量を制御しためっき皮膜構造とすることにより実現することができる。また、この皮膜構造は、めっき浴中に含まれるSi量とめっき浴温を適切な範囲に制御することにより得ることができる。
The plated steel sheet of the present invention is a molten Al-Zn-based plated steel sheet containing 20 to 80 mass% of Al in the plated film, but from the balance of performance (corrosion resistance, workability, etc.) and operational surface, A more preferable range of the amount of Al is 45 to 65 mass%.
As described above, the molten Al-Zn-based plated steel sheet has a crack propagation path limited to the dendrite gap of the plating film, so the number of cracks is small and each crack is relatively large. Tend to. In the present invention, by utilizing such a relationship between the plating film structure and cracks, a crack propagation path is actively introduced into the plating film, thereby generating a large amount of fine cracks, that is, the number of cracks. The aim is to reduce the opening width of each crack by increasing it, and as described below, the generation form of such cracks is plating in which the amount of simple Si crystallized in the dendrite gap is controlled. This can be realized by adopting a film structure. Moreover, this film structure can be obtained by controlling the amount of Si contained in the plating bath and the temperature of the plating bath within an appropriate range.
前述のように溶融Al−Zn系めっき鋼板を製造するためのめっき浴には、通常Alに対して3mass%程度のSiが添加されているが、このSiの働きにより、溶融Al−Zn系めっき鋼板はめっき皮膜/下地鋼板界面の合金相成長が抑えられ、合金相厚さは約1〜2μm程度になる。合金相の生成抑制に寄与しなかった余剰Siは、めっき皮膜へのSi固溶量を超えるとめっき皮膜内にSi単体として晶出し、めっき皮膜のAlデンドライトの成長を妨げる物理的な障壁になる。また、晶出SiはAlデンドライトと混ざり合わないので、デンドライト間隙部に分散する。晶出Siを含んだデンドライト間隙部は、晶出Siの境界部が剥離しやすくなるので、晶出Siのないデンドライト間隙部よりも容易にクラックが伝播する。このため、晶出Siが多くなるほど、変形時に微細なクラックが多数発生しやすくなる。従来の溶融Al−Zn系めっき鋼板においても、合金相の生成抑制に寄与しなかった余剰Siがめっき皮膜内にSi単体として極くわずかに晶出している場合もあったが、その量は1mass%未満の極く少量であった。 As described above, in a plating bath for producing a molten Al—Zn-based plated steel sheet, Si of about 3 mass% is usually added to Al. Due to the function of Si, molten Al—Zn-based plating is performed. In the steel plate, alloy phase growth at the plating film / underlying steel plate interface is suppressed, and the alloy phase thickness is about 1 to 2 μm. Excess Si, which did not contribute to the suppression of alloy phase formation, crystallizes as a simple substance in the plating film when it exceeds the amount of Si solid solution in the plating film, and becomes a physical barrier that hinders the growth of Al dendrite in the plating film. . Further, since crystallized Si does not mix with Al dendrite, it is dispersed in the dendrite gap. In the dendrite gap including crystallized Si, the boundary between the crystallized Si becomes easy to peel off, so that the crack propagates more easily than the dendrite gap without crystallized Si. For this reason, the more crystallized Si, the more likely to generate many fine cracks during deformation. Even in the conventional molten Al-Zn-based plated steel sheet, there was a case where the surplus Si that did not contribute to the suppression of the formation of the alloy phase was crystallized very slightly as a simple substance in the plating film, but the amount is 1 mass. It was a very small amount of less than%.
晶出Siが少なすぎるとクラック伝播経路が十分に増加せず、逆に多すぎるとクラック伝播経路が増加しすぎてクラックが無数に入り、めっき皮膜が粉末状に破壊したり、晶出Siが偏在して局部的にめっき皮膜が脆くなる懸念がある。そのため、下地鋼板とめっき皮膜界面の合金相部分を除くめっき皮膜中の晶出Si(Si単体)量は2〜9mass%とする。 If the amount of crystallized Si is too small, the number of crack propagation paths will not increase sufficiently. Conversely, if the number of crystallized Si is too large, the number of crack propagation paths will increase and countless cracks will occur. There is a concern that the plating film becomes unevenly distributed and becomes locally brittle. Therefore, the amount of crystallized Si (Si simple substance) in the plating film excluding the alloy phase portion at the interface between the base steel plate and the plating film is 2 to 9 mass%.
また、上記のように下地鋼板とめっき皮膜界面の合金相部分を除くめっき皮膜中のSi単体の含有量を2〜9mass%とするには、下地鋼板とめっき皮膜界面の合金相部分を含むめっき皮膜中のSi含有量を、下記(1)式及び(2)式を満足する条件とすることが好ましい。
0.02×T−14.5≦S1≦0.02×T−7.5 … (1)
770≦T≦1000 … (2)
但し T :溶融Al−Znめっき時のめっき浴温(K)
S1:めっき皮膜中のSi含有量(mass%)
浴温上昇に伴って合金相に消費されるSiは増加するが、上記のような条件で、下地鋼板とめっき皮膜界面の合金相部分を含むめっき皮膜中にSiを含有させることにより、合金相の生成抑制に寄与しなかった余剰Siが十分に晶出するため、めっき皮膜のデンドライト間隙部の単体Siが増加してクラック伝播経路が十分に増加する。
Moreover, in order to make the content of Si simple substance in the plating film excluding the alloy phase part of the base steel plate and the plating film interface as described above to be 2 to 9 mass%, the plating including the alloy phase part of the base steel plate and the plating film interface is performed. The Si content in the film is preferably set to satisfy the following formulas (1) and (2).
0.02 × T-14.5 ≦ S1 ≦ 0.02 × T-7.5… (1)
770 ≦ T ≦ 1000 (2)
T: Plating bath temperature (K) during molten Al-Zn plating
S1: Si content in the plating film (mass%)
Si consumed in the alloy phase increases as the bath temperature rises, but by adding Si in the plating film including the alloy phase part of the base steel sheet and the plating film interface under the above conditions, the alloy phase Since surplus Si that has not contributed to the suppression of the formation of crystallization is sufficiently crystallized, the amount of single Si in the dendrite gap portion of the plating film is increased, and the crack propagation path is sufficiently increased.
なお、溶融Al−Znめっき浴中には、上述したAl、Zn、Si以外にも、例えば、Mg、Sr、V、Mn、Ni、Co、Cr、Ti、Sb、Ca、Mo、B等の元素が1種以上添加される場合もあるが、本発明のめっき鋼板に特有の作用効果であるクラック伝播経路の導入を妨げるものでなければ、どのような元素を添加しても差し支えない。 In addition to Al, Zn, and Si described above, for example, Mg, Sr, V, Mn, Ni, Co, Cr, Ti, Sb, Ca, Mo, and B are used in the molten Al—Zn plating bath. One or more elements may be added, but any element may be added as long as it does not prevent the introduction of a crack propagation path, which is a function and effect peculiar to the plated steel sheet of the present invention.
以上のようなめっき皮膜構造を有する本発明の溶融Al−Zn系めっき鋼板は、1000K以下でかつ下記(3)式を満足するめっき浴温の溶融Al−Znめっき浴にて鋼板をめっきすることにより得ることができる。
2.5×A+720≦T≦50×S2+725 … (3)
但し T :めっき浴温(K)
A :めっき浴中のAl含有量(mass%)
S2:めっき浴中のSi含有量(mass%)
めっき浴中のAl含有量が増加すると浴の融点が高くなるため、めっき浴温を高くする必要がある。一方、浴温に応じて合金相に消費されるSi量は変化する。よって、単体Siを十分に確保するためには、上記のような条件で製造することが望ましい。
The molten Al—Zn plated steel sheet of the present invention having the plating film structure as described above is plated with a molten Al—Zn plating bath having a plating bath temperature of 1000 K or less and satisfying the following expression (3). Can be obtained.
2.5 × A + 720 ≦ T ≦ 50 × S2 + 725 (3)
T: Plating bath temperature (K)
A: Al content in the plating bath (mass%)
S2: Si content in the plating bath (mass%)
As the Al content in the plating bath increases, the melting point of the bath increases, so the plating bath temperature must be increased. On the other hand, the amount of Si consumed in the alloy phase varies depending on the bath temperature. Therefore, in order to ensure sufficient single Si, it is desirable to manufacture under the above conditions.
本発明の溶融Al−Znめっき鋼板は、その表面に化成処理皮膜を形成することにより表面処理鋼板とすることができる。この化成処理皮膜の種類に特に制限はないが、例えば、めっき皮膜面にクロメート処理液を塗布し、水洗することなく80〜300℃で乾燥処理するクロメート処理を含む1又は2以上の処理を行い、化成処理皮膜を形成することができる。この化成処理皮膜は複層皮膜により構成されていてもよく、この場合には複数の処理が順次行われる。 The molten Al—Zn plated steel sheet of the present invention can be made a surface-treated steel sheet by forming a chemical conversion coating on the surface thereof. Although there is no restriction | limiting in particular in the kind of this chemical conversion treatment film, For example, the chromate process liquid is apply | coated to the plating film surface, and 1 or 2 or more processes including the chromate process of drying at 80-300 degreeC are performed without washing with water. A chemical conversion treatment film can be formed. The chemical conversion treatment film may be formed of a multilayer film, and in this case, a plurality of treatments are sequentially performed.
さらに、上記表面処理鋼板の表面に単層又は複層の塗膜を形成し、塗装鋼板とすることができる。この塗膜としては、例えば、ポリエステル樹脂系塗膜、エポキシ樹脂系塗膜、アクリル樹脂系塗膜、ウレタン樹脂系塗膜、フッ素樹脂系塗膜等が挙げられる。また、上記樹脂の一部を他の樹脂で変性した、例えばエポキシ樹脂変性ポリエステル樹脂系塗膜等も適用できる。さらに、上記樹脂には必要に応じて硬化剤、硬化触媒、顔料、添加剤等を添加することができる。 Furthermore, a single-layer or multi-layer coating film can be formed on the surface of the surface-treated steel sheet to obtain a coated steel sheet. Examples of the coating film include a polyester resin coating film, an epoxy resin coating film, an acrylic resin coating film, a urethane resin coating film, and a fluororesin coating film. Moreover, for example, an epoxy resin-modified polyester resin-based coating film in which a part of the resin is modified with another resin can be applied. Furthermore, a curing agent, a curing catalyst, a pigment, an additive, and the like can be added to the resin as necessary.
表面処理鋼板の表面に塗膜を形成するための塗装方法は特に規定しないが、塗装方法としてはロールコーター塗装、カーテンフロー塗装、スプレー塗装などが挙げられる。塗料を塗装後、一般に熱風乾燥、赤外線加熱、誘導加熱等の手段により加熱乾燥して塗膜を形成させる。
但し、上記表面処理鋼板及び塗装鋼板の製造方法は一例であり、これに限定されるものではない。
A coating method for forming a coating film on the surface of the surface-treated steel sheet is not particularly defined, but examples of the coating method include roll coater coating, curtain flow coating, and spray coating. After coating the paint, it is generally heated and dried by hot air drying, infrared heating, induction heating or the like to form a coating film.
However, the manufacturing method of the said surface-treated steel plate and a coated steel plate is an example, and is not limited to this.
常法で製造した冷延鋼板(板厚1.0mm)を連続式溶融めっき設備に通板し、表1〜表4に示す組成の溶融Al−Znめっき浴を用いて溶融めっきを行った。ラインスピードは120m/分とした。次いで、上記により得られた溶融Al−Zn系めっき鋼板に対して、連続式溶融めっき設備内でインラインの化成処理を行った。化成処理条件は、アクリルエマルジョン樹脂とクロム酸を樹脂固形分:Cr=100:1(質量比)で混合した液を溶融めっき鋼板面にCr付着量40mg/m2となるように塗布し、120℃で乾燥した。 A cold-rolled steel plate (plate thickness: 1.0 mm) manufactured by a conventional method was passed through a continuous hot-dip plating facility, and hot-dip plating was performed using a hot-dip Al-Zn plating bath having the composition shown in Tables 1 to 4. The line speed was 120 m / min. Next, in-line chemical conversion treatment was performed on the hot-dip Al—Zn-based plated steel sheet obtained as described above in a continuous hot-dip plating facility. The chemical conversion treatment was carried out by applying a liquid obtained by mixing acrylic emulsion resin and chromic acid at a resin solid content: Cr = 100: 1 (mass ratio) to the surface of the hot-dip plated steel sheet so that the Cr adhesion amount was 40 mg / m 2, and 120 Dried at ℃.
このようにして得られた表面処理鋼板について、ドロービード試験でプレス加工性を評価した。ドロービード試験条件は、ビード先端径を0.5Rとし、押え荷重200kgで4mm押し込んだまま引抜きを行なった。ドロービード試験後のサンプルは、テープ剥離をテープに新たな付着物が着かなくなるまで繰り返し、その後、外観観察して以下の基準で評価した。この評価基準で4点以上であれば、プレス加工性が良好であると判断される。
5:目視で観察してクラックが認められず。
4:目視で観察してクラックが認められる。
3:部分的に剥離(剥離面積<未剥離面積)。
2:部分的に剥離(剥離面積≧未剥離面積)。
1:全面剥離
The surface-treated steel sheet thus obtained was evaluated for press workability by a draw bead test. The draw bead test conditions were as follows: the bead tip diameter was 0.5 R, and the drawing was performed with the press load being 200 kg, while being pushed in by 4 mm. For the sample after the draw bead test, tape peeling was repeated until no new deposits adhered to the tape, and then the appearance was observed and evaluated according to the following criteria. If this evaluation criterion is 4 points or more, it is judged that the press workability is good.
5: No cracks are observed by visual observation.
4: Cracks are observed by visual observation.
3: Partially peeled (peeled area <unpeeled area).
2: Partially peeled (peeled area ≧ unpeeled area).
1: Full surface peeling
図1は、本実施例における下地鋼板とめっき皮膜界面の合金相部分を除くめっき皮膜中に含まれる単体Si含有量とプレス加工性との関係を整理して示したものである。これらの結果から、本発明条件を満足することによりプレス加工性の向上が図られ、プレス加工性に優れた表面処理鋼板が得られることが判る。 FIG. 1 shows the relationship between the Si content contained in the plating film excluding the alloy phase portion at the interface between the base steel plate and the plating film and the press workability in this example. From these results, it can be seen that by satisfying the conditions of the present invention, the press workability is improved, and a surface-treated steel sheet having excellent press workability is obtained.
Claims (7)
0.02×T−14.5≦S1≦0.02×T−7.5 … (1)
770≦T≦1000 … (2)
但し T :溶融Al−Znめっき時のめっき浴温(K)
S1:めっき皮膜中のSi含有量(mass%) A molten Al-Zn-based plated steel sheet having an Al content of 20 to 80 mass% in the plating film, wherein Si is contained in the plating film including the alloy phase portion of the base steel sheet and the plating film interface in the following formula (1) and ( 2) A molten Al-Zn-based plated steel sheet excellent in press workability, characterized by containing the compound under conditions satisfying the formula.
0.02 × T-14.5 ≦ S1 ≦ 0.02 × T-7.5… (1)
770 ≦ T ≦ 1000 (2)
T: Plating bath temperature (K) during molten Al-Zn plating
S1: Si content in the plating film (mass%)
1000K以下でかつ下記(3)式を満足するめっき浴温の溶融Al−Znめっき浴にて鋼板をめっきすることを特徴とする、プレス加工性に優れた溶融Al−Zn系めっき鋼板の製造方法。
2.5×A+720≦T≦50×S2+725 … (3)
但し T :めっき浴温(K)
A :めっき浴中のAl含有量(mass%)
S2:めっき浴中のSi含有量(mass%) In producing the hot-dip Al-Zn-based plated steel sheet according to claim 1 or 2, in a continuous hot-dip plating facility,
A method for producing a molten Al-Zn-based plated steel sheet excellent in press workability, comprising plating a steel sheet in a molten Al-Zn plating bath having a plating bath temperature satisfying the following formula (3) below 1000K .
2.5 × A + 720 ≦ T ≦ 50 × S2 + 725 (3)
T: Plating bath temperature (K)
A: Al content in the plating bath (mass%)
S2: Si content in the plating bath (mass%)
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