JPS61166992A - Electric galvanizing method - Google Patents

Abstract

PURPOSE:To form a plating layer having excellent specular surface gloss in appearance in the stage of subjecting a steel sheet to electroplating in an acidic Zn plating bath by adjusting the crystal grain size on the surface of the steel sheet to a specific range. CONSTITUTION:The acidic plating bath such as zinc sulfate-contg. plating bath having 1.0-2.5pH is used as the electrogalvanizing bath having the uniform electrodeposition characteristic and excellent gloss equivalent to said characteristic and gloss of a cyan bath is used in the stage of electrogalvanizing the surface of the steel sheet. The steel sheet of which the surface crystal grain size is No.7.0-10 the grain size specified by JIS G 0552 Method of Ferrite Grain Size Test for Steel, i.e., the fine crystal grain size of 35-10mu crystal grain size and 1.0-2.0 grain elongation is selected and used for the steel sheet to be plated in this case. The galvanized steel sheet having excellent appearance equiv. to the appearance obtd. when the cyan bath is used is thus obtd. by using the acidic bath having less problems of pollution than the cyan bath.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は、電気亜鉛メッキ方法に関し、さらに詳細には
、硫酸浴、塩化浴等の酸性浴を使用しながら、良好な外
観と光沢を有する電気亜鉛メッキ材を製造することので
きる方法に関する。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrolytic galvanizing method, and more particularly, to a galvanizing method that provides good appearance and gloss while using an acidic bath such as a sulfuric acid bath or a chloride bath. The present invention relates to a method capable of producing electrogalvanized materials.

（従来の技術） 一般に、電気亜鉛メッキ鋼材は、溶融メッキ鋼材と比べ
て、皮膜の均一性および外観において優ｔているため、
自動車、家電、建材用途等に広く用いらｎている。(Prior Art) In general, electrogalvanized steel is superior to hot-dip galvanized steel in terms of coating uniformity and appearance.
It is widely used in automobiles, home appliances, building materials, etc.

この電気亜鉛メッキに使用さｎるメッキ浴としては、シ
アン浴が特に均一電着性および光沢において優ｎている
０ところが、シアン浴は公害問題のため使用することが
できず、この念め、現在ではノンシアン浴として、ジン
ケート浴をはじめとして硫酸浴、塩化浴が一般に用いら
ｎている。そして、特に、生産性向上を目的とする高速
メツキラインでは、硫酸浴、塩化浴等の酸性浴が主流と
なっている。As a plating bath used for this electrogalvanizing, cyan bath is particularly superior in terms of uniform electrodeposition and gloss, but cyan bath cannot be used due to pollution problems. Currently, zincate baths, sulfuric acid baths, and chloride baths are generally used as non-cyanide baths. In particular, in high-speed plating lines aimed at improving productivity, acidic baths such as sulfuric acid baths and chloride baths are mainstream.

しかしながら、こｎらの浴では、やはり、均一電着性（
メッキのつきまわり性）および光沢において、シアン浴
には及ばず、こｎが酸性浴の欠点となっていた。However, these baths still have poor uniform electrodeposition (
This was a drawback of acidic baths, as they were not as good as cyan baths in terms of plating throwing power and gloss.

すなわち、亜鉛メッキの外観および光沢等の表面特性は
、つぎのような理由により、製造側にとっては無視でき
ない重要な項目となっている。従来、亜鉛メッキ鋼板は
塗装下地用として用いらｎていたが、最近では、ユーザ
ー側からの塗装省略要求によって、亜鉛メッキの上にク
ロメート、有機樹脂コーティングを施し、耐食性、耐指
紋性に優ｎた表面処理鋼板として裸のまま使用されるこ
とが多くなってきている。この場合、亜鉛メッキの外観
、光沢は製品の外観、光沢としてそのまま反映さｎる。That is, the surface characteristics such as the appearance and gloss of zinc plating are important items that cannot be ignored by manufacturers for the following reasons. Conventionally, galvanized steel sheets were used as a base for painting, but recently, in response to requests from users to omit painting, chromate and organic resin coatings have been applied on top of the galvanizing to provide superior corrosion resistance and anti-fingerprint properties. It is increasingly being used as a bare surface-treated steel sheet. In this case, the appearance and gloss of galvanizing are directly reflected as the appearance and gloss of the product.

したがって、いかにして鏡面光沢を有し外観の美麗なメ
ッキを施すかが重要な課題となっている。Therefore, it has become an important issue how to provide plating with specular luster and beautiful appearance.

そこで、たとえば硫酸酸性浴による亜鉛メッキの外観を
改善する方°法として、 （１）デキストリン、グリセリン、グルコース、フルフ
ラール等の有機添加剤をメッキ浴に添加する方法（［電
気化学Ｊ　ｖｏｌ、　５２．１’ｈ　５　（１９８４）
ｐ２８’６）、（２）メッキ浴中にＳ　ｒ　Ｃ０３＋　
Ｂ　ａ　ＣＯｓ　ｋ添加してメッキ浴を浄化する方法（
特公昭５３−１８１７０号公報）、等が提案さｎている
。Therefore, as a method for improving the appearance of zinc plating using a sulfuric acid acid bath, for example, (1) a method of adding organic additives such as dextrin, glycerin, glucose, and furfural to the plating bath ([Electrochemistry J vol, 52. 1'h 5 (1984)
p28'6), (2) S r C03+ in the plating bath
Method for purifying a plating bath by adding B a COs k (
Japanese Patent Publication No. 53-18170), etc. have been proposed.

（発明が解決しようとする問題点） しかしながら、上記（１）の方法は、有機添加剤が実際
にカンード界面に吸着さｎルベリング作用（平滑化作用
）によシ光沢を改善する効果は有するものの、添加剤の
濃度管理範囲は狭く、しかも分析上、管理が困難であシ
、特に操業時メッキ浴組成の変動しやすい高速高電流密
度メッキでは・製品の均質性が保証されない問題がある
。また、添加剤自体カソード界面で還元さｎ１実際に亜
鉛皮膜中に取り込まｎるため、添加剤によってはメッキ
の耐食性、クロメート反応性を劣化させる問題がある。(Problems to be Solved by the Invention) However, in the method (1) above, although the organic additive is actually adsorbed to the cand interface and has the effect of improving gloss through the leveling effect (smoothing effect), The concentration control range for additives is narrow and analytically difficult to control.Especially in high speed, high current density plating where the composition of the plating bath tends to fluctuate during operation, there is a problem in that the homogeneity of the product cannot be guaranteed. Further, since the additive itself is reduced at the cathode interface and actually incorporated into the zinc film, there is a problem that some additives deteriorate the corrosion resistance and chromate reactivity of the plating.

また、上記（２）の方法についても、（１）の方法と同
様に、分析管理上の煩雑さと、亜鉛中に微量のＳ　ｒ　
＋Ｂａが共析することによる皮膜特性の劣化の問題があ
る。In addition, as with method (1), method (2) above also suffers from the complexity of analytical management and the presence of trace amounts of S r in zinc.
There is a problem of deterioration of film properties due to eutectoidation of +Ba.

Ｃ問題点を解決するための手段） 本発明の発明者らは、上記したように、メッキ浴中に有
機添加剤を添加する従来の方法が種々の問題点を有して
いることに鑑みて、メッキ外観に及ぼすメッキ母材側の
要因に着目して鋭意研究し友ところ、亜鉛の初期電析過
程において、結晶方　“　１位（集合組織）または結晶
粒度（すなわち結晶粒径）が優先因子であることを知見
して本発明を成すに到り友〇 さらに詳細に説明すると、硫酸酸性電気メッキとして、
第１表に示す浴組成を用い、各種冷延鋼材をメッキ母材
として、第１表に示す電析条件で電気亜鉛メッキを施し
たところ、第１図に示すような結果が得らｎた０すなわ
ち、メッキ母材の表面結晶粒度ｔ−ＪＩｓ　　Ｇ　　０
５５２に示さｎる粒度洩７．０以上伊なわち結晶粒径３
５μ以下）とすることにより、メッキ外観の良好なメッ
キ材を容易に得らｎることか判明した。C) Means for Solving Problems) The inventors of the present invention have taken into account that the conventional method of adding organic additives to a plating bath has various problems as described above. , focused on the factors of the plating base material that affect the appearance of the plating, and found that in the initial zinc deposition process, the crystal orientation (texture) or grain size (i.e., crystal grain size) is the priority factor. Friend who came to realize the present invention by finding out that
When electrogalvanizing was performed using the bath composition shown in Table 1 and various cold rolled steel materials as plating base materials under the electrodeposition conditions shown in Table 1, the results shown in Figure 1 were obtained. 0, that is, the surface grain size of the plating base material t-JIs G 0
Grain size leakage 7.0 or more as shown in 552, that is, crystal grain size 3
It has been found that a plating material with a good plating appearance can be easily obtained by setting the plating thickness to 5μ or less.

第　　１　　表 Ｚｎ５Ｏ４Ｈ７Ｈ２０３５０，！ｉ’／１ＮａｚＳＯ４
５０，９／１ ＣＨｓ　ＣＯＯＮａ　　　１０１１／１ｐＨ：　　１．
８　　　温度：６０℃ 電流密度：４ＯＡ／ｄ７Ｆ１″　目付量：３０．！ｉ’
／ｍそこで、本発明は、酸性亜鉛メッキを施すに際し、
メッキ母材として、表面粒度がＮｌＸ７．０〜１０（す
なわち結晶粒径３５μ〜１０μ）、好ましくはＮ１１８
〜１０、展伸率が１．０〜２．０の微細な結晶粒を持つ
鋼材を選択し、この鋼材’ｉ　ｐＨ１〜２．５のメッキ
浴で、たとえば第１表に示すような条件で亜鉛メッキを
施すことを特徴とするものである。Table 1 Zn5O4H7H20350,! i'/1NazSO4
50,9/1 CHs COONa 1011/1pH: 1.
8 Temperature: 60℃ Current density: 4OA/d7F1″ Fabric weight: 30.!i'
/m Therefore, in the present invention, when applying acidic zinc plating,
As a plating base material, the surface grain size is NlX7.0~10 (i.e. crystal grain size 35μ~10μ), preferably N118
~10, a steel material with fine grains with an elongation ratio of 1.0 to 2.0 is selected, and this steel material is coated in a plating bath with a pH of 1 to 2.5 under the conditions shown in Table 1, for example. It is characterized by being galvanized.

ここでいう、粒度隆、展伸率は鋼板圧延面に垂直な方向
から見た際の表面結晶粒度、展伸率のことであシ、その
算出値は、ＪＩＳ　Ｇ　　０５５２に従う値とさｎる。The grain size height and elongation rate referred to here refer to the surface crystal grain size and elongation rate when viewed from the direction perpendicular to the rolling surface of the steel plate, and the calculated values are values in accordance with JIS G 0552. .

又ここでいう、結晶粒径とは単位面積（１−）当りの結
晶粒の数から、すべての結晶粒を球として換算した平均
直径のことであるＯ本発明で母材の表面結晶粒度をＮ１
１７．０以上（すなわち結晶粒径３５μ以下）と規定し
友のは、第１図から明らかなように、ｌ’４７．０以上
の細かな結晶の場合に、メッキ外観をきめ細かな、平滑
観、光沢に優ルたものとする効果が顕著だからであり、
ま７’ＣＮ１８以上とすることにより一層美麗で光沢の
あるメッキを安定して製造することができる０ところが
、一方、粒度１’！ｌｌｏを超える（すなわち結晶粒径
１０μ１未満となると）と、新ら几に成形性の問題が生
じることとなるＯ 母材の展伸率を１．０〜２．０としたのは、母材の粒形
をなるべく球状形に近づけることによシメツキの外観・
光沢を向上させることができるからである。このような
母材は、鋼板の連続焼鈍や浸炭処理により製造供給する
ことができる。Also, the crystal grain size here refers to the average diameter obtained by converting all crystal grains into spheres from the number of crystal grains per unit area (1-).In the present invention, the surface crystal grain size of the base material is N1
17.0 or more (i.e., crystal grain size of 35 μ or less), as is clear from Figure 1, in the case of fine crystals of l'47.0 or more, the plating appearance is finely grained and smooth. This is because the effect of improving gloss is remarkable.
By setting the particle size to 7'CN18 or higher, it is possible to stably produce more beautiful and shiny plating.However, on the other hand, if the particle size is 1'! If it exceeds llo (i.e., if the crystal grain size is less than 10μ1), a new formability problem will occur. By making the particle shape as close to a spherical shape as possible, the appearance of stains and
This is because gloss can be improved. Such a base material can be manufactured and supplied by continuous annealing or carburizing treatment of a steel plate.

一方、酸性浴での亜鉛メッキの光沢は、一般にメッキ条
件（ｐＨ，温度、電流密度等）の影響をも受けることが
知らｎているが、上記のような母材を用いるメッキ材の
外観は、第２図に示すようにｐＨの影響を強く受け、ｐ
Ｈ１〜２．５の間で良好な光沢が得らｎる。ｐＨが１未
満の場合には、強酸による設備上の問題があり、好まし
くない０（作用） 一般に、多結晶上に電析する亜鉛の結晶形態は、硫酸浴
（添加剤を加えないもの）の場合、断層（六角状）を呈
する０ある一定の方向性を持つ断層結晶がそｎぞｎ犬き
く成長すると、キラキラし、外観は劣る（第３図（ａ）
）。こｎに対して、断層結晶が全体に微細なものは、外
観もきめ細かく、平滑観、光沢に優ｎでいる（第３図（
ｂ）　）　Ｑなお、第３図はＳＥＭ観察によるスケッチ
である〇一方、亜鉛の電析時、結晶の成長方位：は下地
（母材）の結晶方位の影響を受け、金属の酸化現象等で
よく観察さｎるエピタキシャル効果と類似の現象が生じ
る。このエピタキシャル効果に係る母材の結晶類は最表
面のものである０ メッキ母材がたとえば冷延鋼板のように多結晶体である
場合、亜鉛結晶はフェライト結晶粒１つづつに対応して
相互に競合しながら成長する（第４図〕。このとき、フ
ェライト結晶粒が小さけｎば小さいほど、この競合が高
まり、結果的に第３図（ｂ）に示すような結晶形態とな
る。そして、きめ細かな、良好な外観を呈す。さらに特
定的に言えば、第１図からも明らかなように、ＪＩＳ　
Ｇ　０５５２の表面粒度Ｎ１１７．　０〜１０の場合、
十分良好な外観・光沢が得ら【る。さらに、メッキ浴の
ｐＨ″ｆ、２．５以下とすることによシ、メッキに及ぼ
すメッキ浴ＰＨの影響を最も好ましいものとすることが
できる。On the other hand, it is known that the gloss of zinc plating in an acidic bath is generally affected by the plating conditions (pH, temperature, current density, etc.), but the appearance of plated materials using the above base material is , as shown in Figure 2, is strongly influenced by pH, and p
Good gloss can be obtained between H1 and 2.5. If the pH is less than 1, there is a problem with equipment due to strong acid, which is undesirable. In general, the crystal form of zinc deposited on polycrystals is the same as that of a sulfuric acid bath (without additives). In this case, if a fault crystal with a certain direction that exhibits a fault (hexagonal shape) grows too rapidly, it will sparkle and its appearance will be inferior (Figure 3 (a)).
). On the other hand, those with fine fault crystals as a whole have a fine-grained appearance, a smooth appearance, and excellent luster (see Figure 3).
b) ) Q: Figure 3 is a sketch based on SEM observation. On the other hand, during zinc electrodeposition, the crystal growth direction is influenced by the crystal orientation of the base (base material), and metal oxidation phenomena, etc. A phenomenon similar to the epitaxial effect often observed occurs. The crystals of the base material related to this epitaxial effect are those on the outermost surface.0 If the plated base material is polycrystalline, such as a cold-rolled steel sheet, zinc crystals interact with each other in correspondence to each ferrite crystal grain. (Fig. 4). At this time, the smaller the ferrite crystal grains, the more this competition increases, resulting in a crystal form as shown in Fig. 3 (b). , exhibits a fine and good appearance.More specifically, as is clear from Figure 1, JIS
Surface grain size of G 0552 N117. In the case of 0 to 10,
A sufficiently good appearance and gloss can be obtained. Furthermore, by setting the pH of the plating bath to 2.5 or less, the influence of the plating bath PH on plating can be made most preferable.

（実施例） 種々の表面結晶粒度および展伸率を有する鋼板に、第２
表に示す酸性浴を基本浴として亜鉛メッキを施し、メッ
キ外観および光沢を評価し友０その結果を、第５図およ
び第６図に示す。(Example) Steel plates with various surface grain sizes and elongation ratios were
Zinc plating was performed using the acidic bath shown in the table as a basic bath, and the plating appearance and gloss were evaluated. The results are shown in FIGS. 5 and 6.

第　　２　　表 硫酸浴　　　　　　　　　塩化浴 ＺｎＳＯ４・７Ｈ２０ＺｎＣｌ２２５０．９／Ａ３５０
　ｇ／Ｉ Ｎａｚ　５Ｏ４５０ｇ／１ＮＨ４ＣＩ２　　２００　ｇ
／／ｌＡ１２（ＳＯ４）３３０ｆｉ／ｌ ｐＨ：２．０　　　温度：６０°ＣｐＨ：２．ｏ　　　
温度：６０’Ｃ電流密度：４０Ａ／ｄｉ　　　　　電流
密度：４０Ａ／ｄｍ目付量”３０ｃ９／ｍ”　　　　　
　　　　　目付量　：３０ｇ／ｍ”第４〜６図から明ら
かなように、被メッキ材（メッキ母材）の表面結晶粒度
をＩＶ！１７．０〜１０、展伸率を１．０〜２．０とし
、ｐＨ１〜２．５のメッキ浴でメッキを施すことによフ
、外観に優ｎた鏡面光沢のある亜鉛メッキが製造される
。Table 2 Sulfuric acid bath Chloride bath ZnSO4・7H20ZnCl2250.9/A350
g/I Naz 5O450g/1NH4CI2 200g
//lA12 (SO4) 330fi/l pH: 2.0 Temperature: 60°C pH: 2. o
Temperature: 60'C Current density: 40A/di Current density: 40A/dm Fabric weight "30c9/m"
Fabric weight: 30 g/m" As is clear from Figures 4 to 6, the surface grain size of the material to be plated (plated base material) is IV! 17.0 to 10, and the elongation rate is 1.0 to 2.0. By plating with a plating bath having a pH of 1 to 2.5, a zinc plating with an excellent appearance and a mirror-like luster can be produced.

（発明の効果） 上記したように、本発明によりば、硫酸浴、塩化浴等の
酸性浴を使用しながら、きわめて外観の優【たメッキ鋼
材を製造することができるＯまた、優１−−□１１−−
響−―□−―−畠−ムーノーＩ−１□□、□Ｎ−−ｌ−
−１１−１機添加剤添加方法のかわりに、母材側からの
アプローチを採用したもので、メッキ母材の表面結晶粒
度を細かくするとともに、メッキ浴ｐＨを管理すること
によシ、メッキ外観を改善するものであるから、添加剤
の濃度管理上の困難性がなく、きわめて容易に安定した
効果を得ることができる。(Effects of the Invention) As described above, according to the present invention, plated steel materials with extremely excellent appearance can be manufactured while using an acidic bath such as a sulfuric acid bath or a chloride bath. □11--
Hibiki--□---Hatake-Moono I-1□□, □N--l-
-11-1 Instead of adding additives, this method adopts an approach from the base material side, which improves the appearance of the plating by reducing the surface grain size of the plating base material and controlling the pH of the plating bath. Therefore, there is no difficulty in controlling the concentration of additives, and stable effects can be obtained very easily.

また、皮膜自体の特性をほとんど変えずに外観（光沢）
を良好にするものであるので、耐食性、クロメート処理
性等のメッキ特性の劣化の問題がなく、さらに、高速（
高電流密度）メツキラインにも適用できる利点がある。In addition, the appearance (gloss) can be improved without changing the properties of the film itself.
Because it improves plating properties, there is no problem of deterioration of plating properties such as corrosion resistance and chromate treatment properties.
It has the advantage that it can also be applied to Metsuki lines (high current density).

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は被メッキ材の表面結晶粒変電とメッキ外観との
関係を示すグラフ、第２図はメッキ浴１）Ｈとメッキ光
沢との関係を示すグラフ、第３図（ａ）。 （ｂ）はＳＥＭ観察によるメッキ表面の結晶形態を示す
模式図、第４図は多結晶上の亜鉛電析成長の模式図、第
５図は硫酸亜鉛浴メッキの場合の被メッキ材表面結晶粒
変電とメッキ外観および光沢との関係を示すグラフ、第
６図は塩化亜鉛浴メッキの場片の被メッキ材表面結晶粒
度隔とメッキ外観および光沢との関係を示すグラフであ
る。 特許出願人　　　住友金属工業株式会社第３図 （（１）り４ｒＪｗＬ不東ワ憂観φツキ　　　（ｂ）基
筒１ＬｔＬ６壇１１西メッキ第４図 一自、方伐で戒七−シｒ、’ｉｉｉ！）季台１ｂ／　　
　　　　　　　　　　　　　　　　　　　　　　’１噛
亀　下電（÷末す 袴 ／・、７牛クト篭（８ ｘ（＞Ｑ　　◎FIG. 1 is a graph showing the relationship between surface crystal grain transformation of the material to be plated and plating appearance, FIG. 2 is a graph showing the relationship between plating bath 1) H and plating gloss, and FIG. 3 (a). (b) is a schematic diagram showing the crystal morphology of the plated surface as observed by SEM, Figure 4 is a schematic diagram of zinc electrodeposition growth on polycrystals, and Figure 5 is the crystal grains on the surface of the plated material in the case of zinc sulfate bath plating. FIG. 6 is a graph showing the relationship between electric power transformation, plating appearance and gloss, and FIG. 6 is a graph showing the relationship between the surface grain size interval of the plated material and the plating appearance and gloss of a piece subjected to zinc chloride bath plating. Patent Applicant: Sumitomo Metal Industries, Ltd. Figure 3 ((1) Ri4rJwL Futowa Gloomy φtsuki (b) Base tube 1LtL6 platform 11 West plating iii!) Kidai 1b/
'1 Kamikame Shimoden (÷Susu Hakama/・, 7 Ushikuto Kagome (8 x (＞Q ◎

Claims (1)

【特許請求の範囲】[Claims] （１）酸性浴電気亜鉛メッキにおいて、被メッキ材とし
て、ＪＩＳ　Ｇ　０５５２の鋼のフェライト結晶粒度試
験方法による表面結晶粒度がＮｏ．７．０〜Ｎｏ．１０
、展伸率が１．０〜２．０の鋼材を使用するとともに、
メッキ浴のｐＨを１．０〜２．５の範囲でメッキするこ
とを特徴とする電気亜鉛メッキ方法。(1) In acid bath electrogalvanizing, the material to be plated has a surface grain size of No. 1 according to the ferrite grain size test method of steel according to JIS G 0552. 7.0~No. 10
, using steel material with an elongation ratio of 1.0 to 2.0,
An electrogalvanizing method characterized by plating at a pH of a plating bath in the range of 1.0 to 2.5.