JP2785672B2 - Zn-based alloy-plated steel sheet with excellent perforation resistance and plating adhesion - Google Patents
Zn-based alloy-plated steel sheet with excellent perforation resistance and plating adhesionInfo
- Publication number
- JP2785672B2 JP2785672B2 JP2466694A JP2466694A JP2785672B2 JP 2785672 B2 JP2785672 B2 JP 2785672B2 JP 2466694 A JP2466694 A JP 2466694A JP 2466694 A JP2466694 A JP 2466694A JP 2785672 B2 JP2785672 B2 JP 2785672B2
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- Japan
- Prior art keywords
- steel sheet
- plating
- film
- based alloy
- plated steel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Other Surface Treatments For Metallic Materials (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は、耐孔あき性とめっき密
着性に優れるZn系合金めっき鋼板に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Zn-based alloy-coated steel sheet having excellent puncture resistance and plating adhesion.
【0002】[0002]
【従来の技術】自動車用の表面処理鋼板は、多湿で空気
中の土中の様々な化学成分に暴露される厳しい腐食環境
中で使用されることが多くなった。特に、寒冷地では、
融雪剤として道路上へ多量の塩類を散布するため、この
融雪剤による自動車床面の孔あき腐食が問題になってい
る。2. Description of the Related Art Surface-treated steel sheets for automobiles are often used in harsh corrosive environments exposed to various chemical components in the soil at high humidity and in the air. Especially in cold regions,
Since a large amount of salt is sprayed on the road as a snow melting agent, perforated corrosion of the automobile floor surface due to the snow melting agent has become a problem.
【0003】そのため、このような厳しい腐食環境にも
耐え得る高耐食性を持つ表面処理鋼板が要求されるよう
になってきており、その対策としてZn電気めっき鋼板や
Zn系合金電気めっき鋼板のめっき付着量を増大すること
などが検討されているが、付着量をこれ以上増加させる
ことはコスト的な負担を増大させることになり好ましく
ない。また、めっき付着量を増加させることにより、溶
接性や耐パウダリング性 (めっき密着性が悪いためプレ
ス加工時にめっき皮膜が粉末状に剥離する現象) が劣化
するといった欠点がある。特にめっき皮膜硬度の高いZn
−Ni合金電気めっき鋼板は付着量の増加とともに急激に
耐パウダリング性が劣化するため付着量を増やすことに
より耐食性を上げることは限界にきている。[0003] For this reason, surface-treated steel sheets having high corrosion resistance that can withstand such severe corrosive environments have been required.
Increasing the coating weight of the Zn-based alloy electroplated steel sheet is being studied, but increasing the coating weight further increases the cost burden and is not preferable. In addition, there is a disadvantage that the increase in the amount of plating adhesion deteriorates the weldability and the powdering resistance (the phenomenon that the plating film peels into a powder during press working due to poor plating adhesion). Especially Zn with high plating film hardness
-The powdering resistance of Ni-plated electroplated steel sheet rapidly deteriorates with the increase in the amount of adhesion. Therefore, increasing the amount of adhesion to increase the corrosion resistance has reached its limit.
【0004】そのため、Zn系めっき鋼板の表面にクロメ
ート皮膜とシリケートを含む有機樹脂皮膜 (塗膜) とを
施した有機複合被覆鋼板が提案された (特開昭58−2241
74号、同60−174879号等の各公報参照) 。しかし、この
有機被覆鋼板も母材とめっき間の密着力が弱く、耐パウ
ダリング性が十分に改善できたとは言い難く、有機被覆
層やクロメート皮膜が疵付きやすい加工部においては十
分な耐食性の改善には到らなかった。[0004] Therefore, an organic composite coated steel sheet in which a chromate film and an organic resin film (coating film) containing silicate are applied to the surface of a Zn-based plated steel sheet has been proposed (JP-A-58-2241).
Nos. 74 and 60-174879, etc.). However, this organic coated steel sheet also has a weak adhesion between the base material and the plating, so it is difficult to say that the powdering resistance has been sufficiently improved, and it has sufficient corrosion resistance in the processed part where the organic coating layer and the chromate film are easily scratched. It did not improve.
【0005】その後、母材にCu、Ni、Cr、Mo等の重金属
成分あるいはこれにPを添加し、めっき皮膜の成分組成
を特定範囲内に規定することによりめっき密着性が改善
できることが示された( 特開昭61−284561号、同61−28
4594号の各公報参照) 。これらの公報には母材にCu、N
i、Cr、Moの1種または2種以上とPを添加した鋼板の
表面に50%以上のZnを含有するめっき層を最下層として
有することでめっき密着性が改善できることが示されて
いるが、Cu、Ni、Cr、Mo等の重金属成分の添加は、我々
の知見によれば、これらの元素が鋼中に局部的に濃化す
ると、皮膜中のZnやZn以外の合金元素と局部電池を形成
しやすくなり、耐孔あき性をかえって劣化させることに
なり好ましくない。[0005] Thereafter, it has been shown that plating adhesion can be improved by adding a heavy metal component such as Cu, Ni, Cr, Mo or the like to the base material or adding P to the base material and defining the composition of the plating film within a specific range. (JP-A-61-284561, 61-28)
No. 4594). These publications contain Cu, N
It has been shown that plating adhesion can be improved by having a plating layer containing at least 50% Zn as the lowermost layer on the surface of a steel sheet to which one or more of i, Cr, and Mo and P are added. According to our findings, the addition of heavy metal components such as Cu, Ni, Cr, and Mo, when these elements are locally concentrated in steel, cause Zn and alloy elements other than Zn in the film to Is easily formed, and the puncture resistance is deteriorated instead of being unfavorable.
【0006】また、特開平5−65595 号、同5−65675
号、同5−65676 号の各公報には、C、N、Si、Mn、
P、S、Al、Nb、Ti、Cu、Ni、Bを所定範囲内に規定し
た母材を使用し、その上にZn系合金めっきを施し、さら
にクロメート皮膜、有機皮膜で覆うことにより耐食性と
成形性が良好な表面処理鋼板が製造できることが報告さ
れているが、これもめっき母材という面から従来の耐食
性鋼の成形性の改善を行っているにすぎず、耐パウダリ
ング性といった点からは通常の極低炭鋼母材を使用する
場合に比べ何等優れたところはない。[0006] Japanese Patent Application Laid-Open Nos. 5-65595 and 5-65675
Nos., 5-65676, C, N, Si, Mn,
Using a base material with P, S, Al, Nb, Ti, Cu, Ni, and B within a predetermined range, applying a Zn-based alloy plating thereon, and further covering with a chromate film and an organic film to improve corrosion resistance and It has been reported that a surface-treated steel sheet with good formability can be manufactured, but this is also merely improving the formability of conventional corrosion-resistant steel from the viewpoint of the base metal, and from the viewpoint of powdering resistance, etc. Has no advantage over the case of using a normal ultra-low carbon steel base material.
【0007】[0007]
【発明が解決しようとする課題】かくして、本発明の目
的は、このような状況の下で耐孔あき性に優れ、かつ、
めっき密着性の極めて良好な表面処理鋼板を提供するこ
とである。具体的には、めっき付着量を増加させずに、
融雪剤による厳しい腐食環境中での使用を満足する耐孔
あき性および厳しい加工条件での耐パウダリング性を満
足するめっき密着性を達成できる表面処理鋼板としての
Zn系合金めっき鋼板を提供することである。SUMMARY OF THE INVENTION Thus, an object of the present invention is to provide, under such circumstances, excellent puncture resistance and
An object of the present invention is to provide a surface-treated steel sheet having extremely good plating adhesion. Specifically, without increasing the plating weight
As a surface-treated steel sheet that can achieve plating resistance that satisfies perforation resistance that satisfies use in severe corrosive environments caused by snow melting agents and powdering resistance under severe processing conditions
An object of the present invention is to provide a Zn-based alloy plated steel sheet.
【0008】[0008]
【課題を解決するための手段】ここに、本発明者らは、
かかる目的を達成すべく、種々検討を重ねた結果、冷延
鋼板へのPの0.045 %以上という積極的添加と、特に不
純物としてのCr、Cu、Moの合計量を0.10%以下に抑える
とともに、好ましくは表面の結晶粒サイズを平均断面積
で0.0003mm2 以下とすることで、予想外にもめっき皮膜
の密着性と耐孔あき性が著しく改善されることを知り、
本発明を完成した。Means for Solving the Problems Here, the present inventors have
In order to achieve this purpose, as a result of various studies, the active addition of 0.045% or more of P to the cold-rolled steel sheet, and in particular, the total amount of Cr, Cu, and Mo as impurities were suppressed to 0.10% or less, Preferably, by setting the grain size of the surface to 0.0003 mm 2 or less in average cross-sectional area, it is unexpectedly found that the adhesion and perforation resistance of the plating film are significantly improved,
The present invention has been completed.
【0009】よって、本発明の要旨とするところは、重
量%で、P:0.045〜0.120 %を含有し、不純物としての
Cr、Cu、Moの合計が0.10%以下の冷延鋼板の少なくとも
片面にZnよりも電位的に貴な元素を合計含有率で 0.5〜
30重量%含み、めっき付着量がめっきの総重量で5〜50
g/m2のZn系合金電気めっき皮膜が施されていることを特
徴とする耐孔あき性とめっき密着性に優れたZn系合金め
っき鋼板である。Therefore, the gist of the present invention is that P contains 0.045 to 0.120% by weight and contains P as an impurity.
At least one side of a cold rolled steel sheet having a total of 0.10% or less of Cr, Cu, and Mo contains an element that is more noble in potential than Zn in a total content of 0.5 to
Includes 30% by weight, and coating weight is 5-50 in total plating weight
It is a Zn-based alloy-plated steel sheet having a g / m 2 Zn-based alloy electroplating film and excellent in puncture resistance and plating adhesion.
【0010】また、別の面からは、本発明は、重量%
で、P:0.045〜0.120 %を含有し、不純物としてのCr、
Cu、Moの合計が0.10%以下で、鋼板表面に対し垂直方向
から観察した時の表面の結晶粒サイズが結晶粒の平均断
面積で0.0003mm2 以下の冷延鋼板を少なくとも片面にZn
よりも電位的に貴な元素を合計含有率で 0.5〜30重量%
含み、めっき付着量がめっきの総重量で5〜50g/m2のZn
系合金電気めっき皮膜が施されていることを特徴とする
耐孔あき性とめっき密着性に優れたZn系合金めっき鋼板
である。In another aspect, the present invention provides
And contains P: 0.045 to 0.120%, Cr as an impurity,
A cold-rolled steel sheet having a total grain size of 0.0003 mm 2 or less in terms of the average cross-sectional area of the grains when the total of Cu and Mo is 0.10% or less and the grain size of the surface when observed from a direction perpendicular to the steel sheet surface is Zn
0.5 to 30% by weight in total content of noble elements more potential than
Includes Zn with a coating weight of 5 to 50 g / m 2 in total plating weight
The present invention is a Zn-based alloy-plated steel sheet characterized by being provided with a system-based electroplating film and having excellent puncture resistance and plating adhesion.
【0011】本発明の好適態様によれば、上述のように
して得られたZn系合金めっき鋼板の上に第2層としてク
ロメート皮膜およびそのクロメート皮膜の上に第3層と
して有機皮膜をさらに設けてもよい。According to a preferred embodiment of the present invention, a chromate film is further provided as a second layer on the Zn-based alloy-plated steel sheet obtained as described above, and an organic film is further provided as a third layer on the chromate film. You may.
【0012】[0012]
【作用】以下、本発明の作用について詳細に説明する。
本発明の表面処理鋼板、つまりZn系合金めっき鋼板は、
Pを比較的多量に含み、不純物としてCr、Cu、Moの含有
量が少ない冷延鋼板の上にZn系合金電気めっきを施して
得るのであり、また、Pを含み、Cr、Cu、Moの含有量が
少なく、表面の結晶粒サイズが小さい冷延鋼板の上にZn
系合金電気めっきを施して得るものである。The operation of the present invention will be described below in detail.
The surface-treated steel sheet of the present invention, that is, a Zn-based alloy-plated steel sheet,
It is obtained by subjecting a Zn-based alloy to electroplating on a cold-rolled steel sheet containing a relatively large amount of P and having a small content of Cr, Cu, and Mo as impurities, and containing P and containing Cr, Cu, and Mo. Zn on cold rolled steel sheet with low content and small surface grain size
It is obtained by subjecting a base alloy to electroplating.
【0013】次に、冷延鋼板中の各成分および冷延鋼板
表面の結晶サイズの限定理由およびめっきの限定理由に
ついて述べる。なお、冷延鋼板の各成分の「%」ならび
にめっき皮膜を構成する各成分の「%」はいずれも「重
量%」を意味する。Next, each component in the cold-rolled steel sheet, the reason for limiting the crystal size of the surface of the cold-rolled steel sheet, and the reason for limiting the plating will be described. In addition, "%" of each component of the cold-rolled steel sheet and "%" of each component constituting the plating film mean "% by weight".
【0014】P:Pは本発明の中で最も特徴的な元素で
ある。Pには腐食初期に錆を緻密化し、酸素透過性の少
ない安定錆層を形成し、耐孔あき性を改善させる作用が
あるが、この作用は鋼板表面をZn系合金電気めっき鋼板
で覆った場合特に著しい。これは、めっき鋼板の場合に
は、先ず、めっき皮膜の腐食が起こり、部分的にめっき
皮膜が薄くなったり、剥離したところから鋼の腐食が起
こるため、裸の冷延鋼板に比べ、Zn系合金電気めっき鋼
板では、鋼の初期腐食の進行する速度が遅く、安定錆層
を形成する十分な時間があることと、鋼板表面をZn系合
金電気めっき鋼板で覆った場合には、腐食初期にめっき
皮膜中で電位的に卑なZnの優先溶出が起こり、電位的に
貴な非Zn合金元素が濃化され、この非Zn合金元素に鋼中
に添加する重金属と同様の安定錆層の生成助長効果があ
るためと考えられる。P: P is the most characteristic element in the present invention. P has the effect of densifying rust in the early stage of corrosion, forming a stable rust layer with low oxygen permeability, and improving the puncture resistance. This action covered the steel sheet surface with a Zn-based alloy electroplated steel sheet. Especially notable in some cases. This is because, in the case of a plated steel sheet, the corrosion of the plating film occurs first, and the corrosion of the steel occurs when the plating film is partially thinned or peeled off. In the case of alloy electroplated steel sheets, the rate at which the initial corrosion of steel progresses is slow, and there is sufficient time to form a stable rust layer.If the steel sheet surface is covered with a Zn-based alloy electroplated steel sheet, The preferential elution of potential-potential Zn occurs in the plating film, enriching the potential noble non-Zn alloy element, and forming a stable rust layer similar to the heavy metal added to steel to this non-Zn alloy element This is probably because there is a promoting effect.
【0015】このようなZn系合金電気めっき鋼板に特有
の鋼中へのP添加効果は0.045 %から現れる。このため
Pの下限を0.045 %とする。一方、0.120 %を越えると
効果の程度が頭打ちとなり、また、溶接性や成形性の劣
化が起こる。従って上限は0.120 %とする。好ましく
は、0.045 〜0.080 %である。[0015] The effect of adding P to steel, which is unique to such a Zn-based alloy electroplated steel sheet, appears from 0.045%. Therefore, the lower limit of P is set to 0.045%. On the other hand, if it exceeds 0.120%, the degree of the effect reaches a plateau, and the weldability and the formability deteriorate. Therefore, the upper limit is 0.120%. Preferably, it is 0.045 to 0.080%.
【0016】Cu、Mo、Cr:Cu、Cr、Moの添加は、冷延鋼
板の場合には、鋼表面に安定な酸化物が形成され安定錆
層の生成を助長する効果があるが、Zn系合金電気めっき
鋼板の場合には、めっき皮膜の腐食が起こる過程で電位
的に卑なZnの優先溶出が起こり、Znが優先的に腐食さ
れ、非Zn合金元素が鋼板表面に濃化するため特にこれら
の元素を添加する必要がない。そればかりか鋼中に添加
されたCu、Cr、Moは鋼中に局部的に濃化していたり、あ
るいは腐食過程で鋼中に局部的に濃化したりすると、め
っき皮膜中のZnやZn以外の合金元素と局部電池を形成し
やすくなるため、めっき皮膜の腐食を早め、十分な安定
錆層が形成される前に鋼の局部腐食を起こし、耐孔あき
性をかえって劣化させる。なお、Cu、Cr、Moが鋼中に局
部的に濃化しているとめっき密着性をも低下させる。こ
のためCu、Cr、Moは鋼中にできるだけ添加しない方が好
ましく、Cu、Cr、Moは合計で不純物レベルの0.10%以
下、好ましくは0.06%以下とする。Cu, Mo, Cr: The addition of Cu, Cr and Mo has the effect of forming a stable oxide on the steel surface and promoting the formation of a stable rust layer in the case of a cold-rolled steel sheet. In the case of a system alloy electroplated steel sheet, preferential elution of potential-negative Zn occurs in the process of corrosion of the plating film, Zn is preferentially corroded, and non-Zn alloy elements concentrate on the steel sheet surface In particular, there is no need to add these elements. In addition, Cu, Cr, and Mo added to the steel are locally concentrated in the steel, or locally concentrated in the steel during the corrosion process. This facilitates the formation of a local battery with an alloy element, thereby accelerating the corrosion of the plating film, causing local corrosion of the steel before a sufficient stable rust layer is formed, and deteriorating the perforation resistance. When Cu, Cr, and Mo are locally concentrated in the steel, the adhesion of plating is also reduced. Therefore, it is preferable not to add Cu, Cr and Mo to the steel as much as possible, and the total of Cu, Cr and Mo should be 0.10% or less, preferably 0.06% or less of the impurity level in total.
【0017】本発明にかかるZn系合金電気めっき鋼板に
おいては、これだけでも十分な耐食性改善硬化が得られ
るが、さらに耐孔あき性およびめっき密着性を向上させ
るためには次のようにするのが望ましい。In the Zn-based alloy electroplated steel sheet according to the present invention, sufficient corrosion resistance improvement hardening can be obtained by itself, but in order to further improve the puncture resistance and plating adhesion, the following is required. desirable.
【0018】本発明にかかるめっき鋼板に使用する冷延
鋼板においては、0.045 〜0.120 %のPを添加して腐食
初期に安定錆層を形成させ、その錆の環境遮断効果によ
り母材の腐食を抑制するため、この安定錆層をいかに厚
く、緻密に形成させるかが重要となる。In the cold-rolled steel sheet used for the plated steel sheet according to the present invention, a stable rust layer is formed at the initial stage of corrosion by adding P in an amount of 0.045 to 0.120%. To suppress this, it is important how thick and dense this stable rust layer is formed.
【0019】本発明の好適態様ではこれらの点を、冷延
鋼板表面結晶サイズを規定することで実現しており、か
くして本発明によれば、めっき密着性を改善することに
より、耐孔あき性に十分な安定錆層を形成することに成
功している。以下にこの本発明の好適実施態様について
詳細に示す。In a preferred embodiment of the present invention, these points are realized by defining the surface crystal size of the cold-rolled steel sheet. Thus, according to the present invention, by improving the plating adhesion, the puncture resistance is improved. Successfully formed a sufficient stable rust layer. Hereinafter, preferred embodiments of the present invention will be described in detail.
【0020】冷延鋼板中でPは結晶粒界に濃化する。こ
のPの濃化部分はめっき前処理の酸洗時にエッチングさ
れやすい。また、Pの濃化していない部分は比較的エッ
チングされにくいため微小な凹凸が形成され、この上に
めっきを施すとめっきとのアンカー効果によりめっき密
着性が改善される。特にZn系合金電気めっき鋼板の場合
にはめっきが硬質なためめっき密着性が悪いと加工時に
めっきが粉末状に剥離(パウダリング) する現象が生じ
るが、本発明の好適態様によればこの現象が改善され
る。In a cold-rolled steel sheet, P is concentrated at the grain boundaries. This P-enriched portion is easily etched at the time of pickling in plating pretreatment. In addition, since the portion where P is not concentrated is relatively difficult to be etched, minute irregularities are formed, and when plating is performed thereon, plating adhesion is improved by an anchor effect with plating. In particular, in the case of a Zn-based alloy electroplated steel sheet, if the plating is hard and the plating adhesion is poor, a phenomenon occurs in which the plating peels off (powder) during processing, but according to a preferred embodiment of the present invention, this phenomenon occurs. Is improved.
【0021】また、さらに加工部でめっきの剥離が起き
にくいため腐食初期の錆の保持効果を増大し、緻密な安
定錆層が形成されやすくなるため耐食性が著しく改善さ
れる。Further, since the plating is less likely to be peeled off in the processed portion, the effect of retaining rust at the initial stage of corrosion is increased, and a dense stable rust layer is easily formed, so that the corrosion resistance is significantly improved.
【0022】このような効果が生じるのは冷延鋼板の表
面の結晶粒サイズが鋼板表面に対し垂直方面から観察し
たときの結晶粒の平均断面積で0.0003mm2 以下のときで
ある。なお、通常は、断面で結晶粒の大きさを観察して
おり、表面部および中心部の平均粒径を求めていること
になる。Such an effect occurs when the crystal grain size on the surface of the cold-rolled steel sheet is 0.0003 mm 2 or less in the average sectional area of the crystal grains when observed from a direction perpendicular to the steel sheet surface. Normally, the size of the crystal grains is observed in the cross section, and the average particle size of the surface portion and the central portion is determined.
【0023】すなわち、結晶粒が微細になり、結晶粒界
部分が多くなる程エッチングの差により、前記微少な凹
凸部分が多く形成され、この上にめっきを施すと、めっ
きとのアンカー効果によりめっき密着性が向上するので
ある。That is, as the crystal grains become finer and the number of crystal grain boundaries increases, the above-mentioned minute irregularities are formed more due to the difference in etching. When plating is performed thereon, the plating effect occurs due to the anchor effect with the plating. The adhesion is improved.
【0024】このため本発明の好適態様にあっては、冷
延鋼板の表面の結晶粒サイズを鋼板表面に対し垂直方面
から観察したときの結晶粒の平均断面積で0.0003mm2 以
下とする。また、結晶粒サイズの小さい方は特に規定し
ないが製造上0.00003mm2程度が限界となる。For this reason, in a preferred embodiment of the present invention, the crystal grain size on the surface of the cold-rolled steel sheet is 0.0003 mm 2 or less as the average cross-sectional area of the crystal grains when observed from a direction perpendicular to the steel sheet surface. The smaller crystal grain size is not particularly specified, but the production limit is about 0.00003 mm 2 .
【0025】このように結晶粒サイズを下げる方法とし
ては、熱間圧延の仕上げ温度をAr3点直上まで下げるの
が最も望ましい。この方法により、通常は、鋼板表面に
対し垂直方面から観察したときの結晶粒の平均断面積で
0.002 〜0.0005mm2 程度である冷延鋼板の結晶粒サイズ
を0.0003mm2 以下に下げることが可能になる。その他の
手段としては焼鈍温度を再結晶温度+20℃以内にする方
法を挙げることができる。As a method of reducing the crystal grain size in this way, it is most desirable to lower the finishing temperature of hot rolling to just above the Ar 3 point. By this method, usually, the average cross-sectional area of the crystal grains when observed from the perpendicular direction to the steel sheet surface
It is possible to reduce the crystal grain size of the cold-rolled steel sheet is 0.002 ~0.0005mm 2 about the 0.0003 mm 2 or less. As another means, there can be mentioned a method in which the annealing temperature is set within the recrystallization temperature + 20 ° C.
【0026】このような冷延鋼板の表面に施すめっき
は、めっき皮膜硬度が高く、パウダリングを起こしやす
いZn系合金電気めっき皮膜のときにその耐食性およびめ
っき密着性改善効果が著しい。The plating applied to the surface of such a cold-rolled steel sheet has a high plating film hardness, and has a remarkable effect of improving the corrosion resistance and plating adhesion when the Zn-based alloy electroplated film is apt to cause powdering.
【0027】また、Zn系合金めっき皮膜のZnよりも電位
的に貴な元素は合計含有率で 0.5〜30重量%とする。Zn
よりも電位的に貴な元素が合計含有率で0.5 %未満では
腐食初期のZnの溶出に伴いZnよりも電位的に貴な元素の
濃化が起こらないため、Znが完全になくなるまで溶出が
続き、耐孔あき性が劣化する。一方、Znよりも電位的に
貴な元素の合計含有量が30重量%を超える場合ではめっ
きが硬質化しすぎ、冷延鋼板中へのP添加によるめっき
密着性の改善効果を上回るためめっきが剥離しやすくな
る。好ましくは、例えば、Zn−Ni系では4〜20%、Zn−
Co系では 0.5〜20%、Zn−Cr系およびZnより電位的に貴
な他の元素では1〜20%であり、より好ましくはZn−Ni
系では4〜15%、Zn−Co系では 0.5〜10%、Zn−Cr系お
よびZnより電位的に貴な他の元素では1〜15%である。Further, the total content of the elements which are more noble in potential than Zn in the Zn-based alloy plating film is 0.5 to 30% by weight. Zn
If the total potential content of noble elements no more than 0.5% is less than 0.5%, the elution of Zn in the early stage of corrosion does not cause concentration of noble elements nobleer than Zn, so elution will occur until Zn is completely eliminated. Subsequently, the perforation resistance deteriorates. On the other hand, when the total content of elements that are more noble in potential than Zn exceeds 30% by weight, the plating becomes too hard, and the plating peels because the addition of P to the cold-rolled steel sheet exceeds the effect of improving the adhesion of the plating. Easier to do. Preferably, for example, 4-20% for Zn-Ni system, Zn-Ni
0.5 to 20% for Co-based, 1 to 20% for Zn-Cr-based and other elements which are more noble than Zn, more preferably Zn-Ni
The content is 4 to 15% in the system, 0.5 to 10% in the Zn-Co system, and 1 to 15% in the Zn-Cr system and other elements which are more noble than Zn.
【0028】ここに、Znよりも電位的に貴な元素として
は、例えば、Ni、Co、Fe、Cr、Sn、Pb、Cu等多くを挙げ
ることができるが、好ましくはNi、Co、Cr、Feであり、
特に好ましくはNi、Co、Crである。また、めっき皮膜構
造は多層構造であってもよい。このとき、Znよりも電位
的に貴な元素はめっきの平均組成として 0.5〜30重量%
であればよい。Here, as the element which is more noble in potential than Zn, for example, Ni, Co, Fe, Cr, Sn, Pb, Cu and the like can be mentioned, but preferably Ni, Co, Cr, Fe
Particularly preferred are Ni, Co and Cr. Further, the plating film structure may be a multilayer structure. At this time, the element which is more noble in potential than Zn is 0.5 to 30% by weight as the average composition of plating.
Should be fine.
【0029】また、めっき付着量はめっきの総重量で5
g/m2未満では十分な対孔あき性が得られず、50g/m2超で
はコストが増大し、またパウダリング性の劣化も起こる
のでめっき付着量はめっきの総重量で5〜50g/m2とす
る。好ましくは10〜40g/m2である。The coating weight is 5% by the total weight of the plating.
g / m, sufficient Taiana Aki property is obtained is less than 2, the cost is increased in the 50 g / m 2, greater than The coating weight since deterioration also occurs in the powdering property is the total weight of the plating 5 to 50 g / and m 2. Preferably from 10 to 40 g / m 2.
【0030】さらに耐食性を増すにはZn系合金めっき層
の上に、第2層としてクロメート皮膜を、第3層として
有機皮膜を施すことが望ましい。その場合、クロメート
皮膜はめっき皮膜の耐食性を増大させると共に、第1層
のZn系合金めっき層と第3層の有機皮膜を密着させる作
用がある。Zn系合金めっき層と有機皮膜を密着させるこ
とによりパウダリングがさらに生じ難くなるため、冷延
鋼板の初期腐食速度が抑えられ安定錆層の形成が一層促
進される。In order to further increase the corrosion resistance, it is desirable to apply a chromate film as the second layer and an organic film as the third layer on the Zn-based alloy plating layer. In that case, the chromate film has the effect of increasing the corrosion resistance of the plating film and the function of adhering the first Zn-based alloy plating layer and the third organic film. By making the Zn-based alloy plating layer and the organic film adhere to each other, powdering is more difficult to occur, so that the initial corrosion rate of the cold-rolled steel sheet is suppressed, and the formation of a stable rust layer is further promoted.
【0031】クロメート皮膜の形成方法は塗布型、反応
型、電解型のいずれでも可能である。クロメート皮膜の
付着量はCr付着量として10〜200 mg/m2 が好ましい。10
mg/m2 未満では耐食性改善効果が期待できず、200 mg/m
2 超では加工性、溶接性が劣化する。より好ましくは30
〜100mg/m2である。また、クロメート皮膜には6価のCr
が存在した方が好ましい。Cr6+は鋼板が傷ついた場合、
そこからの腐食を抑制する作用を有する。The method of forming the chromate film can be any of a coating type, a reaction type and an electrolytic type. The attached amount of the chromate film is preferably 10 to 200 mg / m 2 as the attached amount of Cr. Ten
can not be expected corrosion resistance improvement is less than mg / m 2, 200 mg / m
If it exceeds 2 , workability and weldability deteriorate. More preferably 30
100100 mg / m 2 . Hexavalent Cr is used for the chromate film.
Is preferably present. Cr 6+ , if the steel plate is damaged,
It has the effect of suppressing corrosion from there.
【0032】塗布型、反応型クロメート処理液は、部分
的に還元されたクロム酸溶液を主成分とし、必要に応じ
これに水分散性または水溶性のアクリル樹脂等の有機樹
脂および/またはコロイダルシリカを含有させたもので
ある。この場合Cr3+: Cr6+の割合は50:1〜1:3が好
ましい。Cr3+: Cr6+の割合は一般の還元剤を使用して所
定の割合に調節する。このとき塗布型クロメートはこの
溶液をロールコータ、スプレー等で塗布し、水洗するこ
となく乾燥して皮膜を得る。反応型クロメートはこの溶
液にめっき鋼板を浸漬することにより表面に不溶性のCr
2O3 を生成させて皮膜を得る。The coating-type and reaction-type chromate treatment solutions mainly contain a partially reduced chromic acid solution, and if necessary, an aqueous resin or a water-soluble organic resin such as an acrylic resin and / or colloidal silica. Is contained. In this case, the ratio of Cr 3+ : Cr 6+ is preferably 50: 1 to 1: 3. The ratio of Cr 3+ : Cr 6+ is adjusted to a predetermined ratio using a general reducing agent. At this time, the coating type chromate is applied with this solution using a roll coater, a spray or the like, and dried without washing with water to obtain a film. Reactive chromate is made of insoluble Cr on the surface by immersing a plated steel sheet in this solution.
2 O 3 is generated to obtain a film.
【0033】電解型クロメートは無水クロム酸と硫酸、
リン酸フッ化物またはハロゲン酸素酸等のアニオンの1
種または2種以上を含有する浴で陰極電解処理を施し、
水洗乾燥して皮膜を形成させる。The electrolytic chromate is chromic anhydride and sulfuric acid,
1 of anions such as phosphoric acid fluoride or halogen oxyacid
Cathodic electrolytic treatment in a bath containing one or more species,
Rinse and dry to form a film.
【0034】塗布型、反応型クロメートは耐食性に優れ
るという利点があるため耐食性を重視する自動車用表面
処理鋼板では特に好ましく、その中でも塗布型は片面処
理が可能なので特に好ましい。The coating type and the reaction type chromate have the advantage of excellent corrosion resistance, and therefore are particularly preferable for a surface-treated steel sheet for automobiles in which corrosion resistance is important. Among them, the coating type is particularly preferable because one-side processing is possible.
【0035】有機皮膜は水、塩素などの腐食性物質から
めっき皮膜や鋼板を遮断する働きがある。さらにそれに
加え腐食初期の安定錆層生成期にこの環境遮断効果によ
り錆層の急激な腐食を抑制し、安定錆層の生成に寄与す
る。The organic film has a function of shielding the plating film and the steel sheet from corrosive substances such as water and chlorine. In addition to this, in the stage of forming a stable rust layer in the early stage of corrosion, this environmental shielding effect suppresses rapid corrosion of the rust layer and contributes to the formation of a stable rust layer.
【0036】有機皮膜の厚みは0.1 〜2μm の厚さが好
ましい。0.1 μm 未満だと耐食性の改善効果がみられ
ず、2μm を超えると溶接性、電着塗装性が著しく低下
する。The thickness of the organic film is preferably from 0.1 to 2 μm. If it is less than 0.1 μm, the effect of improving corrosion resistance is not seen, and if it exceeds 2 μm, the weldability and electrodeposition coating properties are significantly reduced.
【0037】この有機皮膜は、従来より塗装鋼板の製造
に使用されてきた各種の樹脂系被覆組成物を使用して形
成することができる。有機樹脂皮膜は、装置が簡便で造
膜も速い熱硬化型皮膜が工業的には好ましいが、紫外線
または電子線硬化型皮膜や常温乾燥型皮膜とすることも
できる。この中で特に好ましい樹脂種は熱硬化型皮膜で
あるエポキシ系樹脂であり、エポキシ系樹脂とシリカを
主成分とするものが最適である。This organic film can be formed using various resin-based coating compositions conventionally used in the production of painted steel sheets. As the organic resin film, a thermosetting film which is simple in equipment and has a fast film formation is industrially preferable, but an ultraviolet or electron beam curable film or a room temperature drying film can also be used. Among them, a particularly preferred resin type is an epoxy resin which is a thermosetting film, and an epoxy resin and silica as main components are most suitable.
【0038】この樹脂液をロールコータなどの適当な塗
布手段でクロメート皮膜上に塗布し、加熱して塗膜を硬
化させ、有機樹脂皮膜を形成させる。加熱温度はエポキ
シ系の場合80〜250 ℃である。This resin liquid is applied on the chromate film by a suitable application means such as a roll coater, and the coating is cured by heating to form an organic resin film. The heating temperature is 80 to 250 ° C in the case of the epoxy type.
【0039】これらの皮膜の作用により特に加工部で著
しい耐食性の改善効果が得られるため、本発明にかかる
表面処理鋼板であるZn系合金めっき鋼板は、加工と腐食
の厳しい自動車用表面処理鋼板として特に優れた性能を
有するものである。次に、本発明の作用効果について実
施例を参照しながらさらに具体的に説明する。Since the effect of these coatings can significantly improve the corrosion resistance especially in the processed part, the Zn-alloy-coated steel sheet, which is the surface-treated steel sheet according to the present invention, is used as a surface-treated steel sheet for automobiles which is severely processed and corroded. It has particularly excellent performance. Next, the operation and effect of the present invention will be described more specifically with reference to examples.
【0040】[0040]
(実施例1)本例では、表1および表2に示す化学組成を
有する板厚0.8 mmの冷延鋼板に対して、アルカリ電解脱
脂および酸洗を行った後、以下に示した方法でZn系合金
電気めっきを施した。(Example 1) In this example, a 0.8 mm-thick cold-rolled steel sheet having the chemical composition shown in Tables 1 and 2 was subjected to alkaline electrolytic degreasing and pickling, and then Zn was subjected to the following method. A system alloy was electroplated.
【0041】めっき方法:めっき浴は硫酸亜鉛浴 (pH=
2) を使用し、皮膜中の合金成分はその金属の硫酸塩を
添加し、合金金属イオン濃度/Znイオン濃度を変化させ
ることで、皮膜中の合金成分割合を変化させた。Znおよ
び合金成分イオンの浴中添加濃度は合計で100 g/l とし
た。また、めっき浴中にはこの他に導電性電解質として
100 g/l のNa2SO4を添加した。Plating method: The plating bath was a zinc sulfate bath (pH =
By using 2), the alloy component in the film was changed by adding a sulfate of the metal and changing the alloy metal ion concentration / Zn ion concentration to change the alloy component ratio in the film. The total concentration of Zn and alloy component ions in the bath was 100 g / l. In addition, as a conductive electrolyte,
100 g / l Na 2 SO 4 was added.
【0042】上記のめっき浴を使い、電流密度40〜60A/
dm2 の直流電流を用い、浴温40〜60℃の範囲でめっきを
行った。めっき皮膜の付着量は電気量をコントロールし
て変化させた。Using the above plating bath, a current density of 40 to 60 A /
Plating was performed using a direct current of dm 2 at a bath temperature of 40 to 60 ° C. The adhesion amount of the plating film was changed by controlling the amount of electricity.
【0043】また、表3および4に示したサンプルにつ
いてはめっきの上に塗布型クロメート処理によるクロメ
ート層およびロールコーター塗布による有機樹脂 (エポ
キシ系樹脂) 層を形成させた。このようにして得られた
各めっき鋼板について次の要領でそれぞれの特性評価を
行った。For the samples shown in Tables 3 and 4, a chromate layer was formed on the plating by a coating type chromate treatment and an organic resin (epoxy resin) layer was formed by a roll coater coating. Each of the plated steel sheets thus obtained was evaluated for its properties in the following manner.
【0044】耐食性評価:上記のようにして作製した表
面処理鋼板を直径50mm、高さ25mmの形状に円筒絞りし、
円筒の内側とエッジ部を防水加工して試験サンプルとし
て、孔あき腐食試験を行って耐孔あき性を評価した。な
お、孔あき腐食試験機ではSST(6hr)→乾燥(50℃×2hr)
→湿潤 (相対湿度95%、50℃×16hr) を1サイクルと
してめっきの上に何も施さない場合には40サイクルの繰
り返し試験を行った後の最大侵食深さをポイントマイク
ロメーターで測定し、0.2 mm以下であれば良 (○) 、0.
1 mm以下であれば (◎) とした。めっきの上にクロメー
トおよび有機樹脂からなる皮膜を施す場合には200 サイ
クル後の最大侵食深さを測定し、0.2 mm超であれば不良
(×) 、0.2 mm以下であれば良 (○) 、0.1 mm以下であ
れば優 (◎) とした。Evaluation of corrosion resistance: The surface-treated steel sheet prepared as described above was cylindrically drawn into a shape having a diameter of 50 mm and a height of 25 mm.
The inside and the edge of the cylinder were subjected to waterproof processing, and as a test sample, a perforated corrosion test was performed to evaluate the perforation resistance. SST (6hr) → Dry (50 ℃ × 2hr)
→ If nothing is applied on the plating with one cycle of wet (relative humidity 95%, 50 ° C x 16hr), the maximum erosion depth after performing 40 cycles of repetitive tests is measured with a point micrometer, Good if less than 0.2 mm (○), 0.
If it was 1 mm or less, it was marked as (◎). When applying a coating consisting of chromate and organic resin on the plating, measure the maximum pit depth after 200 cycles.
(×), good (○) if less than 0.2 mm, excellent (優) if less than 0.1 mm.
【0045】なお、この試験で「◎」に相当する耐食性
は、めっき付着量を増加させずに融雪剤等による厳しい
腐食環境中での使用を満足する耐食性に対応するもので
あって、これまでは実用上実現できなかったすぐれた特
性である。The corrosion resistance equivalent to “◎” in this test corresponds to the corrosion resistance that satisfies the use in a severe corrosive environment caused by a snow melting agent or the like without increasing the amount of plating. Are excellent characteristics that could not be realized in practice.
【0046】めっき密着性 (耐パウダリング性) 試験:
上記のようにして作製した表面処理鋼板を直径50mm、高
さ25mmの形状に円筒絞り加工を行い、円筒側面のテープ
剥離試験により剥離しためっき皮膜剥離量でめっき密着
性を調べ、テープ剥離量が10 mg/テープ1個未満のもの
は優 (◎) 、10〜30 mg/テープ1個のものは良 (○) 、
30 mg/テープ1個以上のものは不良 (×) とした。Plating adhesion (powdering resistance) test:
The surface-treated steel sheet prepared as described above was subjected to cylindrical drawing to a shape of 50 mm in diameter and 25 mm in height, and the plating adhesion was examined by the peeling amount of the plating film peeled off by the tape peeling test on the cylindrical side surface. Those with less than 10 mg / tape are excellent (◎), those with 10-30 mg / tape are good (○),
Samples with 30 mg / tape or more were evaluated as defective (x).
【0047】試験結果を表1〜4に併せて示す。この結
果から明らかなように、本発明例では耐食性、めっき密
着性ともに良好である。The test results are shown in Tables 1 to 4. As is evident from the results, both the corrosion resistance and the plating adhesion are excellent in the examples of the present invention.
【0048】これに対して母材の化学組成、またはめっ
き付着量あるいはめっき皮膜組成が本発明例で定める範
囲から外れる場合はいずれも耐食性もしくはめっき密着
性のどちらかあるいは両方が不良である。また、この傾
向はめっき皮膜の上にクロメート層と有機樹脂層があっ
ても変わらない。On the other hand, when the chemical composition of the base material, the plating amount or the plating film composition is out of the range specified in the present invention, either or both of the corrosion resistance and the plating adhesion are poor. This tendency does not change even if there is a chromate layer and an organic resin layer on the plating film.
【0049】[0049]
【表1】 [Table 1]
【0050】[0050]
【表2】 [Table 2]
【0051】[0051]
【表3】 [Table 3]
【0052】[0052]
【表4】 [Table 4]
【0053】(実施例2)本例では冷延鋼板の表面の平均
結晶サイズを変えた同様の供試鋼を使用して実施例1を
繰り返した。供試鋼の鋼組成、結晶粒サイズ等および試
験の結果は表5〜表8にまとめて示す。なお、テープ剥
離試験で「◎」に相当するめっき密着性はこれまで上述
の耐食性試験で「◎」以上の評価とは同時に達成できな
かった特性である。Example 2 In this example, Example 1 was repeated using a similar test steel in which the average crystal size on the surface of the cold-rolled steel sheet was changed. Tables 5 to 8 collectively show the steel composition, crystal grain size, and the like of the test steels and the results of the tests. The plating adhesion equivalent to “に” in the tape peeling test is a characteristic that could not be achieved at the same time as the evaluation of “◎” or more in the above-mentioned corrosion resistance test.
【0054】[0054]
【表5】 [Table 5]
【0055】[0055]
【表6】 [Table 6]
【0056】[0056]
【表7】 [Table 7]
【0057】[0057]
【表8】 [Table 8]
【0058】[0058]
【発明の効果】本発明によれば、上記のように、腐食抑
制作用をもつ特定の合金元素を冷延鋼板中に添加するこ
とによりめっき鋼板全体の腐食性を増加させるのみなら
ず、意図的に冷延鋼板表面の結晶粒子サイズを細かくす
ることにより、めっき皮膜と鋼板の密着性の改善および
耐食性のより一層の増加を図ることができる。このこと
から、本発明にかかるZn系合金めっき鋼板は、加工部の
高耐食性を重要視する自動車用防錆鋼板として利用で
き、工業的価値が非常に高い。According to the present invention, as described above, by adding a specific alloying element having a corrosion inhibiting action to a cold-rolled steel sheet, it is possible not only to increase the corrosiveness of the entire plated steel sheet but also to intentionally increase the corrosion resistance. By reducing the crystal grain size on the surface of the cold-rolled steel sheet, the adhesion between the plating film and the steel sheet can be improved and the corrosion resistance can be further increased. For this reason, the Zn-based alloy-plated steel sheet according to the present invention can be used as a rust-preventive steel sheet for automobiles that emphasizes high corrosion resistance of a processed portion, and has extremely high industrial value.
フロントページの続き (56)参考文献 特開 平1−108392(JP,A) 特開 平6−228772(JP,A) 特開 平5−65676(JP,A) 特開 平5−65675(JP,A) 特開 平5−65595(JP,A) 特開 昭61−284594(JP,A) (58)調査した分野(Int.Cl.6,DB名) C25D 5/00 - 5/52 C23C 30/00Continuation of front page (56) References JP-A-1-108392 (JP, A) JP-A-6-228772 (JP, A) JP-A-5-65676 (JP, A) JP-A-5-65675 (JP) JP-A-5-65595 (JP, A) JP-A-61-284594 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C25D 5/00-5/52 C23C 30/00
Claims (3)
し、不純物としてのCr、Cu、Moの合計が0.10%以下の冷
延鋼板の少なくとも片面にZnよりも電位的に貴な元素を
合計含有率で 0.5〜30重量%含み、めっき付着量がめっ
きの総重量で5〜50g/m2のZn系合金電気めっき皮膜が施
されていることを特徴とする耐孔あき性とめっき密着性
に優れたZn系合金めっき鋼板。1. A cold-rolled steel sheet containing, by weight%, P: 0.045 to 0.120% and having a total of Cr, Cu, and Mo as impurities of 0.10% or less, and at least one surface of which is more noble than Zn. And a plating resistance of 0.5 to 30 g / m 2 in terms of the total weight of the plating. Zn alloy plated steel sheet with excellent adhesion.
し、不純物としてのCr、Cu、Moの合計が0.10%以下で、
鋼板表面に対し垂直方向から観察した時の表面の結晶粒
サイズが結晶粒の平均断面積で0.0003mm2 以下の冷延鋼
板を少なくとも片面にZnよりも電位的に貴な元素を合計
含有率で 0.5〜30重量%含み、めっき付着量がめっきの
総重量で5〜50g/m2のZn系合金電気めっき皮膜が施され
ていることを特徴とする耐孔あき性とめっき密着性に優
れたZn系合金めっき鋼板。2. The composition contains P: 0.045 to 0.120% by weight, and the total of Cr, Cu and Mo as impurities is 0.10% or less,
The crystal grain size of the surface when observed from the direction perpendicular to the steel sheet surface is a cold-rolled steel sheet with an average cross-sectional area of the crystal grains of 0.0003 mm 2 or less. comprises 0.5 to 30 wt%, the amount of plating deposition is excellent in coating adhesion and pitting corrosion resistance properties, characterized in that the Zn-based alloy electroplated film of 5 to 50 g / m 2 by total weight of the plating is applied Zn-based alloy plated steel sheet.
鋼板の上に第2層としてクロメート皮膜および該クロメ
ート皮膜の上に第3層として有機皮膜を設けたことを特
徴とするZn系合金めっき鋼板。3. A Zn-based alloy comprising a Zn-based alloy plated steel sheet according to claim 1 and a chromate film as a second layer and an organic film as a third layer on the chromate film. Plated steel sheet.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2466694A JP2785672B2 (en) | 1994-02-23 | 1994-02-23 | Zn-based alloy-plated steel sheet with excellent perforation resistance and plating adhesion |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2466694A JP2785672B2 (en) | 1994-02-23 | 1994-02-23 | Zn-based alloy-plated steel sheet with excellent perforation resistance and plating adhesion |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH07233498A JPH07233498A (en) | 1995-09-05 |
JP2785672B2 true JP2785672B2 (en) | 1998-08-13 |
Family
ID=12144472
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2466694A Expired - Lifetime JP2785672B2 (en) | 1994-02-23 | 1994-02-23 | Zn-based alloy-plated steel sheet with excellent perforation resistance and plating adhesion |
Country Status (1)
Country | Link |
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JP (1) | JP2785672B2 (en) |
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1994
- 1994-02-23 JP JP2466694A patent/JP2785672B2/en not_active Expired - Lifetime
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JPH07233498A (en) | 1995-09-05 |
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