JP2541380B2 - Method for producing iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers having excellent electrodeposition coatability - Google Patents
Method for producing iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers having excellent electrodeposition coatabilityInfo
- Publication number
- JP2541380B2 JP2541380B2 JP3014803A JP1480391A JP2541380B2 JP 2541380 B2 JP2541380 B2 JP 2541380B2 JP 3014803 A JP3014803 A JP 3014803A JP 1480391 A JP1480391 A JP 1480391A JP 2541380 B2 JP2541380 B2 JP 2541380B2
- Authority
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- Japan
- Prior art keywords
- zinc alloy
- iron
- layer
- steel sheet
- plating layer
- 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.)
- Expired - Lifetime
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Description
【０００１】[0001]
【産業上の利用分野】この発明は、電着塗装性に優れ
た、複数の鉄−亜鉛合金めっき層を有する鉄−亜鉛合金
めっき鋼板の製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an iron-zinc alloy plated steel sheet having a plurality of iron-zinc alloy plating layers, which is excellent in electrodeposition coatability.
【０００２】[0002]
【従来の技術】合金化溶融亜鉛めっき鋼板には、電気亜
鉛めっき鋼板に比べて、めっき層を厚くすることが容易
であり、優れた耐食性が得られる利点がある。従って、
耐食性の一段の向上が望まれている自動車用鋼板等とし
て好適であり、近年、その需要が高まっている。2. Description of the Related Art Alloyed hot-dip galvanized steel sheets have the advantage that a thicker plated layer can be obtained and superior corrosion resistance can be obtained than electrogalvanized steel sheets. Therefore,
It is suitable as a steel sheet for automobiles for which further improvement in corrosion resistance is desired, and in recent years, its demand is increasing.
【０００３】合金化溶融亜鉛めっき鋼板の表面上には、
その使用される部位によって、電着塗装による塗膜が形
成される。合金化溶融亜鉛めっき鋼板の表面上に対する
塗膜の形成は、一般に、合金化溶融亜鉛めっき層の表面
上に、化成処理によって燐酸塩被膜を形成し、次いで、
カチオンタイプの電着塗装法により、燐酸塩被膜の上に
所定の厚さの塗膜を形成することにより行われる。On the surface of the galvannealed steel sheet,
A coating film formed by electrodeposition coating is formed depending on the portion to be used. The formation of the coating film on the surface of the galvannealed steel sheet is generally performed by forming a phosphate coating on the surface of the galvannealed layer by chemical conversion treatment, and then forming
It is carried out by forming a coating film of a predetermined thickness on the phosphate coating film by a cationic type electrodeposition coating method.
【０００４】しかしながら、上記により形成された塗膜
面には、電着塗装時に発生し、塗膜内に閉じ込められた
水素ガスによってピンホールが生ずる。塗膜に生じたピ
ンホールは、局部的な発錆の起点となるとともに、塗装
面の外観上の欠陥になる。However, on the surface of the coating film formed as described above, pinholes are generated by hydrogen gas generated during electrodeposition coating and confined in the coating film. The pinhole generated in the coating film becomes a starting point of local rusting and also becomes a defect in the appearance of the coated surface.
【０００５】上述した問題を解決するめっき鋼板とし
て、特公昭58−15554 号公報には、下記からなる、カチ
オン電着塗装用めっき鋼板が開示されている。鋼板の少
なくとも１つの表面上に形成された、40wt.%超の亜鉛を
含有する下層としての鉄−亜鉛合金めっき層、および、
前記下層としての鉄−亜鉛合金めっき層の上に形成され
た、40wt.%以下の亜鉛を含有する上層としての鉄−亜鉛
合金めっき層（以下、先行技術という）。As a plated steel sheet for solving the above-mentioned problems, Japanese Patent Publication No. Sho 58-15554 discloses a plated steel sheet for cationic electrodeposition coating, which comprises: An iron-zinc alloy plating layer formed on at least one surface of a steel sheet as an underlayer containing more than 40 wt.% Zinc, and
An iron-zinc alloy plating layer (hereinafter referred to as a prior art) as an upper layer containing 40 wt.% Or less of zinc, which is formed on the iron-zinc alloy plating layer as the lower layer.
【０００６】[0006]
【発明が解決しようとする課題】上述した先行技術に
は、次に述べるような問題がある。即ち、先行技術によ
る、下層としての厚い合金化溶融鉄−亜鉛合金めっき層
と、上層としての鉄−亜鉛合金電気めっき層とからなる
めっき鋼板によれば、塗膜に生ずるピンホールは防止さ
れるが、一方、先行技術によるめっき鋼板に対して、プ
レスなどによって厳しい成形加工を施すと、下層として
の厚い合金化溶融鉄−亜鉛合金めっき層が破壊して、め
っき層の剥離や脱落が発生する。The above-mentioned prior art has the following problems. That is, according to the prior art, a plated steel sheet comprising a thick alloyed molten iron-zinc alloy plating layer as a lower layer and an iron-zinc alloy electroplating layer as an upper layer prevents pinholes from occurring in the coating film. On the other hand, however, when the plated steel sheet according to the prior art is subjected to severe forming processing such as pressing, the thick alloyed molten iron-zinc alloy plating layer as the lower layer is broken, and the plating layer is peeled or dropped. .
【０００７】めっき層に剥離や脱落が発生すると、燐酸
塩被膜の形成のための化成処理時に、露出した鋼板によ
ってめっき層の溶解が促進される結果、燐酸塩結晶が異
常に成長する。このように異常に成長した燐酸塩結晶
は、結晶水を多量に含有しており、この結晶水が、電着
塗装の塗膜焼き付け時に、燐酸塩結晶から離脱しそして
蒸発する。この結果、塗膜に気泡状欠陥が発生する。こ
のような塗膜に発生した気泡状欠陥は、塗装面の外観上
の欠陥になる。When the plating layer is peeled or dropped, during the chemical conversion treatment for forming the phosphate coating, the exposed steel sheet promotes the dissolution of the plating layer, resulting in abnormal growth of phosphate crystals. Such abnormally grown phosphate crystals contain a large amount of water of crystallization, and the water of crystallization separates from the phosphate crystals and evaporates during baking of the coating film for electrodeposition coating. As a result, bubble defects occur in the coating film. The bubble-like defects generated in such a coating film become defects in the appearance of the coated surface.
【０００８】従って、この発明の目的は、プレス等によ
って厳しい成形加工が施されても、塗膜に、下層として
の合金化溶融鉄−亜鉛合金めっき層に発生した剥離や脱
落に基づく気泡状欠陥が生ぜず、且つ、ピンホールも殆
ど生じない、電着塗装性に優れた、複数の鉄−亜鉛合金
めっき層を有する鉄−亜鉛合金めっき鋼板を製造するた
めの方法を提供することにある。Accordingly, an object of the present invention is to provide a bubble-like defect due to peeling or dropping generated in the alloyed hot-dip iron-zinc alloy plating layer as the lower layer in the coating film even if severe forming processing is performed by pressing or the like. It is an object of the present invention to provide a method for producing an iron-zinc alloy plated steel sheet having a plurality of iron-zinc alloy plating layers, which is excellent in electrodeposition coatability and which does not cause pinholes and which hardly causes pinholes.
【０００９】[0009]
【課題を解決するための手段】本発明者等は、上述した
問題を解決すべく、下層としての合金化溶融鉄−亜鉛合
金めっき層と、上層としての鉄−亜鉛合金電気めっき層
とからなる、複数の鉄−亜鉛合金めっき層を有する鉄−
亜鉛合金めっき鋼板の成形加工時に、下層としての合金
化溶融鉄−亜鉛合金めっき層に剥離や脱落が発生する原
因について、調査および研究を行った結果、次のことが
分かった。In order to solve the above-mentioned problems, the inventors of the present invention comprise an alloyed molten iron-zinc alloy plating layer as a lower layer and an iron-zinc alloy electroplating layer as an upper layer. , An iron having a plurality of iron-zinc alloy plating layers-
As a result of investigations and studies on the cause of peeling or dropping of the alloyed hot-dip iron-zinc alloy plated layer as the lower layer during the forming process of the zinc alloy plated steel sheet, the following was found.
【００１０】下層としての合金化溶融鉄−亜鉛合金めっ
き層は、熱的に形成されているので、めっき層中に内部
応力は存在しない。これに対し、上層としての鉄−亜鉛
合金電気めっき層は、金属の析出により形成されている
ので、めっき層中に大きな内部応力が存在している。こ
の結果、上層としての、内部応力が大きい鉄−亜鉛合金
電気めっき層は、下層としての合金化溶融鉄−亜鉛合金
めっき層を強く拘束し、このような拘束は、局部的に集
中する。このために、合金化溶融鉄−亜鉛合金めっき層
は、極めて脆くなり、成形加工時にめっき層が破壊し
て、鋼板から剥離しやすくなる。この結果、塗膜に前述
した気泡状欠陥が発生する。Since the alloyed molten iron-zinc alloy plating layer as the lower layer is formed thermally, there is no internal stress in the plating layer. On the other hand, since the iron-zinc alloy electroplating layer as the upper layer is formed by depositing a metal, a large internal stress exists in the plating layer. As a result, the iron-zinc alloy electroplating layer having a large internal stress as the upper layer strongly restrains the alloyed molten iron-zinc alloy plating layer as the lower layer, and such restraints are locally concentrated. For this reason, the alloyed hot-dip iron-zinc alloy plating layer becomes extremely brittle, and the plating layer is destroyed during the forming process, and is easily separated from the steel sheet. As a result, the above-mentioned bubble defects occur in the coating film.
【００１１】このような、気泡状欠陥の発生と、めっき
層の破壊の程度との関連について調べた結果、気泡状欠
陥が発生していない場合の、下層としての合金化溶融鉄
−亜鉛合金めっき層には、剥離や脱落は生ぜず、微細な
クラックが全面にわたって均一に発生していることが分
かった。上述したことから、プレス成形時に、下層とし
ての合金化溶融鉄−亜鉛合金めっき層に多数の微細なク
ラックを形成させれば、前述した、上層からの局部的な
応力の集中を緩和して、下層としての合金化溶融鉄−亜
鉛合金めっき層の剥離や脱落が防止され、従って、塗膜
に気泡状欠陥が発生しなくなる。As a result of investigating the relationship between the occurrence of such bubble-like defects and the degree of destruction of the plating layer, the alloyed molten iron-zinc alloy plating as the lower layer when no bubble-like defects have occurred It was found that the layers did not peel or fall off, and fine cracks were uniformly generated over the entire surface. From the above, during press forming, if a large number of fine cracks are formed in the alloyed molten iron-zinc alloy plating layer as the lower layer, the aforementioned concentration of local stress from the upper layer is relaxed, The alloyed hot-dip iron-zinc alloy plating layer as the lower layer is prevented from peeling or falling off, and therefore, the coating film is free from bubble defects.
【００１２】 この発明は、上記知見に基づいてなされ
たものであって、鋼板を、０．２０ｗｔ．％以下のアル
ミニウムを含有し、残部が亜鉛および不可避不純物から
なる溶融亜鉛めっき浴に通し、前記鋼板の表面上に亜鉛
めっき層を形成し、次いで、前記鋼板を加熱して、前記
亜鉛めっき層と前記鋼板とを合金化させ、このような合
金化の過程において、前記鋼板が前記溶融亜鉛めっき浴
中に浸入してから、少なくとも、亜鉛めっき層の表面に
鉄−亜鉛合金相が形成されるまでの間、前記鋼板を５０
０℃以下の温度に保つことによって、めっき層の表層
に、微細な凹凸を有する柱状鉄−亜鉛合金結晶（ζ結
晶）を生成せしめ、かくして、前記鋼板の少なくとも１
つの表面上に、微細な凹凸を有する柱状鉄−亜鉛合金結
晶（ζ結晶）が生成された、８〜１２ｗｔ．％の鉄を含
有する下層としての合金化溶融鉄−亜鉛合金めっき層を
形成し、次いで、前記下層としての合金化溶融鉄−亜鉛
合金めっき層が形成された鋼板に対し、酸化処理を施す
ことによって、前記合金化溶融鉄−亜鉛合金めっき層の
表面上に酸化被膜を形成し、次いで、前記酸化被膜を有
する下層としての合金化溶融鉄−亜鉛合金めっき層が形
成された鋼板を、鉄−亜鉛合金電気めっき浴に通し、前
記鋼板に陰極電解処理を施すことにより、前記下層とし
ての合金化溶融鉄−亜鉛合金めっき層の上に、５０ｗ
ｔ．％以上の鉄を含有する、１〜１０ｇ／ｍ２の量の上
層としての鉄−亜鉛合金電気めっき層を形成することに
より、成形加工時に、前記酸化被膜を起点として、多数
の微細なクラックを生成せしめ、生成した微細なクラッ
クにより、上層からの局部応力が下層に集中することを
抑制して、塗膜に生ずる気泡状欠陥を防止することに特
徴を有するものである。The present invention has been made on the basis of the above-mentioned findings, and a steel sheet of 0.20 wt. % Aluminum and the rest is passed through a hot dip galvanizing bath consisting of zinc and unavoidable impurities to form a galvanized layer on the surface of the steel sheet, and then the steel sheet is heated to form the galvanized layer. After alloying with the steel sheet, in the process of such alloying, after the steel sheet penetrates into the hot dip galvanizing bath, at least until the iron-zinc alloy phase is formed on the surface of the galvanized layer While the steel plate is
By maintaining the temperature at 0 ° C. or lower, columnar iron-zinc alloy crystals (ζ-bonding) having fine irregularities on the surface of the plating layer
Crystals) and thus at least one of the steel sheets
Columnar iron-zinc alloy crystals (ζ crystals) having fine irregularities were formed on one surface, 8 to 12 wt. Forming an alloyed molten iron-zinc alloy plating layer as a lower layer containing 1% of iron, and then subjecting the steel sheet on which the alloyed molten iron-zinc alloy plating layer as the lower layer is formed to an oxidation treatment By forming an oxide film on the surface of the alloyed molten iron-zinc alloy plating layer, and then forming a steel sheet on which the alloyed molten iron-zinc alloy plating layer as the lower layer having the oxide film is formed, iron- By passing through a zinc alloy electroplating bath and subjecting the steel sheet to cathodic electrolysis, 50 w is formed on the alloyed molten iron-zinc alloy plating layer as the lower layer.
t. % Containing more iron, iron as the upper layer in an amount of 1 to 10 g / m 2 - to form a zinc alloy electroplating layer
Therefore, during the molding process, a large number of
Generated fine cracks in the
The local stress from the upper layer is concentrated in the lower layer
It is characterized by suppressing and preventing bubble-like defects generated in the coating film .
【００１３】[0013]
【作用】この発明においては、上述したように、下層と
しての、微細な凹凸を有する合金化溶融鉄−亜鉛合金め
っき層の表面上に酸化被膜が形成されている。この結
果、成形加工時に、酸化被膜を起点として、多数の微細
なクラックが生成するため、この多数の微細なクラック
によって、上層からの局部応力が下層に集中することが
抑制される。従って、下層としての合金化溶融鉄−亜鉛
合金めっき層に剥離や脱落が生じないので、塗膜に生ず
る気泡状欠陥が防止される。In the present invention, as described above, the oxide film is formed on the surface of the alloyed molten iron-zinc alloy plating layer having fine irregularities as the lower layer. As a result, a large number of minute cracks are generated from the oxide film as a starting point during the molding process, and thus it is possible to suppress the concentration of local stress from the upper layer on the lower layer due to the large number of minute cracks. Therefore, the alloyed hot-dip iron-zinc alloy plating layer as the lower layer does not peel or fall off, so that bubble-like defects occurring in the coating film are prevented.
【００１４】 以下に、この発明の方法を説明する。鋼
板を、０．２０ｗｔ．％以下のアルミニウムを含有し、
残部が亜鉛および不可避不純物からなる溶融亜鉛めっき
浴に通し、鋼板の表面上に亜鉛めっき層を形成する。こ
のようにして、その表面上に亜鉛めっき層が形成された
鋼板を加熱して、亜鉛めっき層と鋼板とを合金化させ
る。この合金化の過程において、鋼板が溶融亜鉛めっき
浴中に浸入してから、少なくとも、亜鉛めっき層の表面
に鉄−亜鉛合金相が形成されるまでの間、即ち、合金化
の初期段階において、鋼板を５００℃以下の温度に保
つ。この結果、めっき層の表層に、微細な凹凸を有する
柱状の鉄−亜鉛合金結晶（ζ結晶）が生成する。このよ
うな柱状の鉄−亜鉛合金結晶（ζ結晶）がめっき層中に
存在することにより、耐パウダリング性が向上する。The method of the present invention will be described below. A steel plate was used as 0.20 wt. % Aluminum or less,
The balance is passed through a hot dip galvanizing bath consisting of zinc and unavoidable impurities to form a galvanized layer on the surface of the steel sheet. In this way, the steel sheet having the galvanized layer formed on the surface thereof is heated to alloy the galvanized layer with the steel sheet. In the course of this alloying, the steel plate intrudes into the galvanizing bath, at least, on the surface of the galvanized layer of iron - until the zinc alloy phase is formed, i.e., in the early stages of the alloying , Keep the steel plate at a temperature below 500 ° C. As a result, columnar iron-zinc alloy crystals (? Crystals) having fine irregularities are formed on the surface layer of the plating layer. The presence of such columnar iron-zinc alloy crystals (? Crystals) in the plating layer improves the powdering resistance.
【００１５】鋼板を500 ℃以下の温度に保つ手段として
は、例えば、合金化のための加熱の少なくとも初期段階
において、加熱炉の温度を、鋼板が500 ℃以下の温度に
保たれるように制御することによって行うことができ
る。このような加熱炉として、高周波誘導加熱炉を使用
すれば、加熱温度の制御を容易に行うことができる。As means for keeping the steel sheet at a temperature of 500 ° C. or lower, for example, at least in the initial stage of heating for alloying, the temperature of the heating furnace is controlled so that the steel sheet is kept at a temperature of 500 ° C. or lower. Can be done by doing. If a high-frequency induction heating furnace is used as such a heating furnace, the heating temperature can be easily controlled.
【００１６】 上述のようにして、下層としての合金化
溶融鉄−亜鉛合金めっき層の表層に、微細な凹凸を有す
る柱状の鉄−亜鉛合金結晶（ζ結晶）が生成した鋼板に
対し、酸化処理を施す。この結果、柱状の鉄−亜鉛合金
結晶（ζ結晶）の凸部の表面に、硬い酸化被膜が生成す
る。鋼板に対し酸化処理を施す手段としては、合金化処
理後の鋼板を大気中において加熱するか、または、合金
化処理後の鋼板を、薬液、例えば、硝酸および過酸化水
素を含有する水溶液中に浸漬することによって行うこと
ができる。なお、上記合金化処理後の鋼板の加熱を、加
湿した大気中で行えば、より効率的に酸化処理を施すこ
とができる。 As described above, the steel sheet on which the columnar iron-zinc alloy crystal (ζ crystal) having fine irregularities is formed on the surface layer of the alloyed hot-dip iron-zinc alloy plating layer as the lower layer is oxidized. Give. As a result, a hard oxide film is formed on the surface of the protrusion of the columnar iron-zinc alloy crystal (ζ crystal) . As a means for subjecting a steel sheet to an oxidation treatment, an alloying treatment is used.
After heating the steel sheet in the atmosphere or alloy
It can be performed by immersing the steel sheet after the chemical treatment in a chemical solution, for example, an aqueous solution containing nitric acid and hydrogen peroxide. The heating of the steel sheet after the alloying treatment was
If it is performed in a moist atmosphere, the oxidation treatment will be performed more efficiently.
Can be.
【００１７】 大気中または加湿した大気中における、
鋼板の加熱温度は、２５０〜３５０℃の範囲内とすべき
である。加熱温度が２５０℃未満では、酸化被膜を十分
に生成させることができない。一方、加熱温度が３５０
℃を超えると、亜鉛めっき層の合金化が必要以上に進行
し、合金化溶融鉄−亜鉛合金めっき層中の鉄含有量が多
くなり過ぎる問題が生ずる。In the air or in a humid atmosphere ,
The heating temperature of the steel plate should be in the range of 250-350 ° C. If the heating temperature is less than 250 ° C, the oxide film cannot be sufficiently formed. On the other hand, the heating temperature is 350
If the temperature exceeds ℃, alloying of the galvanized layer will proceed unnecessarily, and there will be a problem that the iron content in the alloyed molten iron-zinc alloy plated layer becomes too large.
【００１８】鋼板の表面上に亜鉛めっき層を形成するた
めの溶融亜鉛めっき浴としては、0.20wt.%以下のアルミ
ニウムを含有し、残部が亜鉛および不可避不純物からな
るめっき浴を使用すべきである。めっき浴中のアルミニ
ウム含有量が0.20wt.%を超えると、合金化処理段階にお
ける、鉄−亜鉛合金相の生成が著しく抑制される結果、
鋼板の少なくとも１つの表面上に形成される合金化溶融
鉄−亜鉛合金めっき層が不均一になる問題が生ずる。As the hot dip galvanizing bath for forming the galvanizing layer on the surface of the steel sheet, a galvanizing bath containing 0.20 wt.% Or less of aluminum and the balance being zinc and inevitable impurities should be used. . If the aluminum content in the plating bath exceeds 0.20 wt.%, The production of the iron-zinc alloy phase is significantly suppressed in the alloying treatment stage,
The problem arises that the alloyed hot-dip iron-zinc alloy plating layer formed on at least one surface of the steel sheet becomes non-uniform.
【００１９】鋼板の少なくとも１つの表面上に形成され
る合金化溶融鉄−亜鉛合金めっき層中の鉄含有量は、８
〜12wt.%の範囲内に限定すべきである。鉄含有量が８w
t.%未満では、成形加工時に、めっき層の鋼板からの剥
離即ちフレーキングが発生する。一方、鉄含有量が12w
t.%を超えると、加工性が劣化し、成形加工時にめっき
層の粉状の剥離即ちパウダリングが発生する。The iron content in the alloyed molten iron-zinc alloy plating layer formed on at least one surface of the steel sheet is 8
It should be limited to the range of ~ 12 wt.%. Iron content is 8w
If it is less than t.%, peeling of the plating layer from the steel sheet, that is, flaking occurs during the forming process. On the other hand, the iron content is 12w
If it exceeds t.%, the workability deteriorates, and powdery peeling of the plating layer, that is, powdering occurs during the molding process.
【００２０】上層としての鉄−亜鉛合金電気めっき層中
の鉄含有量は、50wt.%以上とすべきである。鉄含有量が
50wt.%未満では、塗膜に気泡状欠陥およびピンホールが
発生する。The iron content in the iron-zinc alloy electroplating layer as the upper layer should be 50 wt.% Or more. Iron content
If it is less than 50% by weight, bubble-like defects and pinholes occur in the coating film.
【００２１】上層としての鉄−亜鉛合金電気めっき層の
めっき量は、鋼板の片面当たり１〜10g/m2の範囲内とす
べきである。めっき量が鋼板の片面当たり１g/m2未満で
は、下層としての合金化溶融鉄−亜鉛合金めっき層を均
一に被覆することができず、塗膜にピンホールが発生す
る。一方、めっき量が鋼板の片面当たり10g/m2を超える
と、めっき層が厚くなり過ぎ、加工性が劣化し、成形加
工時にめっき層の粉状の剥離即ちパウダリングが発生す
る。The amount of the iron-zinc alloy electroplating layer as the upper layer should be in the range of 1 to 10 g / m 2 per one side of the steel sheet. When the amount of plating is less than 1 g / m 2 per side of the steel sheet, the alloyed molten iron-zinc alloy plating layer as the lower layer cannot be uniformly coated, and pinholes are generated in the coating film. On the other hand, when the plating amount exceeds 10 g / m 2 per one side of the steel sheet, the plating layer becomes too thick and the workability deteriorates, and powdery separation of the plating layer, that is, powdering occurs during the forming process.
【００２２】下層としての合金化溶融鉄−亜鉛合金めっ
き層のめっき量は、鋼板の片面当たり30〜70g/m2の範囲
内であることが好ましい。めっき量が鋼板の片面当たり
30g/m2未満では、耐食性が劣化する。一方、めっき量が
鋼板の片面当たり、70g/m2を超えると、加工性が劣化す
る。The amount of the alloyed molten iron-zinc alloy plating layer as the lower layer is preferably in the range of 30 to 70 g / m 2 per one side of the steel sheet. Plating amount per side of steel plate
If it is less than 30 g / m 2 , the corrosion resistance deteriorates. On the other hand, if the plating amount per one side of the steel sheet exceeds 70 g / m 2 , the workability deteriorates.
【００２３】次に、この発明の方法を、実施例により、
比較例と対比しながら説明する。Next, the method of the present invention will be described with reference to an embodiment.
This will be described in comparison with a comparative example.
【実施例】板厚0.8mm の冷延鋼板に対し、下記に示す条
件で合金化溶融亜鉛めっき処理を施し、鋼板の表面上
に、微細な凹凸を有する柱状鉄−亜鉛合金結晶が生成さ
れた下層としての合金化溶融鉄−亜鉛合金めっき層を形
成した。 めっき浴化学成分組成： Al： 0.12wt.% 、 Zn： 残り めっき浴温度： 460℃ めっき浴浸入供試体温度： 470℃ 合金化温度 ： 490℃ 合金化時間 ：所定の鉄含有量が得られるように調
整。[Example] A cold-rolled steel sheet having a thickness of 0.8 mm was subjected to an alloying hot dip galvanizing treatment under the conditions shown below, and columnar iron-zinc alloy crystals having fine irregularities were formed on the surface of the steel sheet. An alloyed hot-dip iron-zinc alloy plating layer was formed as a lower layer. Chemical composition of plating bath: Al: 0.12wt.%, Zn: Remaining plating bath temperature: 460 ° C Temperature of plating bath immersion sample: 470 ° C Alloying temperature: 490 ° C Alloying time: To obtain the specified iron content Adjusted to.
【００２４】 次いで、下層としての合金化溶融鉄−亜
鉛合金めっき層が形成された鋼板に対し、加熱または薬
液中への浸漬からなる酸化処理を施して、めっき層の表
面上に酸化被膜を形成した。Next, the steel sheet on which the alloyed hot-dip iron-zinc alloy plating layer as the lower layer is formed is subjected to an oxidation treatment of heating or immersion in a chemical solution to form an oxide film on the surface of the plating layer. did.
【００２５】次いで、酸化被膜を有する下層としての合
金化溶融鉄−亜鉛合金めっき層が形成された鋼板に対
し、下記に示す条件で電気めっき処理を施し、下層とし
ての合金化溶融鉄−亜鉛合金めっき層の表面上に、所定
量の鉄−亜鉛合金電気めっき層を形成した。 めっき浴の化学成分組成： FeSO4 ・7H2O：380g/l、 ZnSO4 ・7H2O ：20g/l
、 Na2SO4 ： 30g/l、 CH3COONa・3H2O：20g/l めっき浴のpH値：2.0 めっき浴の温度：50℃ めっき電気量 ：50A/dm2 Next, the steel sheet on which the alloyed molten iron-zinc alloy plating layer as the lower layer having the oxide film is formed is subjected to electroplating treatment under the following conditions to form the alloyed molten iron-zinc alloy as the lower layer. A predetermined amount of iron-zinc alloy electroplating layer was formed on the surface of the plating layer. Chemical composition of the plating bath: FeSO 4 · 7H 2 O: 380g / l, ZnSO 4 · 7H 2 O: 20g / l
, Na 2 SO 4 : 30g / l, CH 3 COONa ・ 3H 2 O: 20g / l pH value of plating bath: 2.0 Temperature of plating bath: 50 ℃ Plating electricity: 50A / dm 2
【００２６】このようにして、鋼板の表面上に、酸化被
膜が生成された下層としての合金化溶融鉄−亜鉛合金め
っき層と、上層としての鉄−亜鉛合金電気めっき層とを
有する、この発明の鉄−亜鉛合金めっき鋼板の供試体
（以下、本発明供試体という）No. １〜６を調製した。
第１表に、本発明供試体No. １〜６の弱酸化処理手段を
示す。Thus, the present invention has the alloyed molten iron-zinc alloy plating layer as the lower layer and the iron-zinc alloy electroplating layer as the upper layer on the surface of the steel sheet, where the oxide film is formed. Samples of iron-zinc alloy-plated steel sheets (hereinafter referred to as “samples of the present invention”) Nos. 1 to 6 were prepared.
Table 1 shows the weak oxidation treatment means of Sample Nos. 1 to 6 of the present invention.
【００２７】 [0027]
【００２８】[0028]
【比較例】比較のために、下層としての合金化溶融鉄−
亜鉛合金めっき層の表層に酸化被膜が形成されていない
ほかは、上述した実施例と同じ条件でめっき層を形成し
た比較用の鉄−亜鉛合金めっき鋼板の供試体（以下、比
較用供試体という）No. １を調製した。[Comparative Example] For comparison, alloyed molten iron as a lower layer-
Specimen of a comparative iron-zinc alloy-plated steel sheet (hereinafter, referred to as a comparative specimen) in which the oxide layer was not formed on the surface layer of the zinc alloy plating layer, and the plating layer was formed under the same conditions as in the above-described examples. ) No. 1 was prepared.
【００２９】このようにして調製された本発明供試体お
よび比較用供試体の各々について、電着塗装性を、以下
に述べる性能試験によって調査した。電着塗装性試験本
発明供試体および比較用供試体の各々の表面上に、浸漬
処理によって燐酸塩被膜を形成した後、下記条件によっ
てカチオンタイプの電着塗装を施した。 電圧 ： ２８０Ｖ 浴温 ： ２７℃ 塗膜の厚さ ： ２０μｍ 焼き付け温度： １７５℃ 焼き付け時間： ２０分 塗料 ： エレクロンNo. 2000 (関西ペイント株
式会社製）The electrodeposition coatability of each of the specimens of the present invention and the specimens for comparison thus prepared was investigated by the performance test described below. Electrodeposition coatability test A phosphate coating was formed on each surface of the sample of the present invention and the sample for comparison by dipping treatment, and then cation type electrodeposition coating was applied under the following conditions. Voltage: 280V Bath temperature: 27 ° C Coating thickness: 20 μm Baking temperature: 175 ° C Baking time: 20 minutes Paint: Elektron No. 2000 (manufactured by Kansai Paint Co., Ltd.)
【００３０】上記のようにして電着塗装を施した供試体
に対し、直径30mmの頭部を有する平頭ポンチを使用して
高さ10mmの張り出し成形加工を施し、供試体の塗膜に生
じた気泡状欠陥の個数を目視によって調べ、下記によっ
て評価した。 ◎：０〜５個、 ○：６〜10個、 △：11〜100 個、
×：101 個The specimen coated with electrodeposition as described above was subjected to an overhanging process with a height of 10 mm by using a flat-head punch having a head with a diameter of 30 mm, and a coating film of the specimen was formed. The number of bubble-like defects was visually examined and evaluated by the following. ◎: 0 to 5, ○: 6 to 10, △: 11 to 100,
×: 101
【００３１】第２表に、本発明供試体および比較用供試
体の各々に対する、上述した電着塗装性試験結果を、め
っき層の成分組成およびめっき量と共に示す。Table 2 shows the results of the above-mentioned electrodeposition coatability test for each of the present invention specimen and the comparative specimen, together with the component composition of the plating layer and the plating amount.
【００３２】 [0032]
【００３３】第１表および第２表から明らかなように、
下層としての合金化溶融鉄−亜鉛合金めっき層に酸化被
膜が形成されていない比較用供試体No. １は、塗膜中に
気泡状欠陥が極めて多量に発生し、電着塗装性が悪かっ
た。これに対して、本発明供試体No. １〜６は、何れ
も、塗膜に殆ど気泡状欠陥が発生せず、電着塗装性に優
れていた。As is clear from Tables 1 and 2,
The comparative sample No. 1 in which an oxide film was not formed on the alloyed hot-dip iron-zinc alloy plating layer as the lower layer had an extremely large amount of bubble-like defects in the coating film, and the electrodeposition coatability was poor. . On the other hand, in all of Sample Nos. 1 to 6 of the present invention, almost no bubble-like defects were generated in the coating film, and the electrodeposition coatability was excellent.
【００３４】[0034]
【発明の効果】以上述べたように、この発明によれば、
プレス等によって厳しい成形加工が施されても、塗膜
に、下層としての合金化溶融鉄−亜鉛合金めっき層に発
生した剥離や脱落に基づく気泡状欠陥が生ぜず、且つ、
ピンホールも殆ど生じない、電着塗装性に優れた、複数
の鉄−亜鉛合金めっき層を有する鉄−亜鉛合金めっき鋼
板が得られる、工業上有用な効果がもたらされる。As described above, according to the present invention,
Even if subjected to severe molding by pressing, etc., the coating film does not cause bubble-like defects due to peeling or dropping that has occurred in the alloyed molten iron-zinc alloy plating layer as the lower layer, and,
An industrially useful effect is obtained in which an iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers, which has almost no pinholes and which is excellent in electrodeposition coatability, is obtained.
フロントページの続き (72)発明者 阿部 雅樹 東京都千代田区丸の内一丁目１番２号日 本鋼管株式会社内 (72)発明者 平谷 晃 東京都千代田区丸の内一丁目１番２号日 本鋼管株式会社内 (56)参考文献 特開 平２−243780（ＪＰ，Ａ) 特開 平１−108396（ＪＰ，Ａ) 特開 昭63−157847（ＪＰ，Ａ) 特開 平２−57670（ＪＰ，Ａ) 特開 昭63−230861（ＪＰ，Ａ)Front page continuation (72) Inventor Masaki Abe 1-2, Marunouchi, Chiyoda-ku, Tokyo Main steel pipe Co., Ltd. (72) Inventor Akira Hiratani 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Main steel pipe stock In-house (56) Reference JP-A-2-243780 (JP, A) JP-A-1-108396 (JP, A) JP-A-63-157847 (JP, A) JP-A-2-57670 (JP, A) ) JP-A-63-230861 (JP, A)
Claims (3)
ニウムを含有し、残部が亜鉛および不可避不純物からな
る溶融亜鉛めっき浴に通し、前記鋼板の表面上に亜鉛め
っき層を形成し、次いで、前記鋼板を加熱して、前記亜
鉛めっき層と前記鋼板とを合金化させ、 このような合金化の過程において、前記鋼板が前記溶融
亜鉛めっき浴中に浸入してから、少なくとも、亜鉛めっ
き層の表面に鉄−亜鉛合金相が形成されるまでの間、前
記鋼板を５００℃以下の温度に保つことによって、めっ
き層の表層に、微細な凹凸を有する柱状鉄−亜鉛合金結
晶（ζ結晶）を生成せしめ、かくして、前記鋼板の少な
くとも１つの表面上に、微細な凹凸を有する柱状鉄−亜
鉛合金結晶（ζ結晶）が生成された、８〜１２ｗｔ．％
の鉄を含有する下層としての合金化溶融鉄−亜鉛合金め
っき層を形成し、次いで、前記下層としての合金化溶融
鉄−亜鉛合金めっき層が形成された鋼板に対し、酸化処
理を施すことによって、前記合金化溶融鉄−亜鉛合金め
っき層の表面上に酸化被膜を形成し、 次いで、前記酸化被膜を有する下層としての合金化溶融
鉄−亜鉛合金めっき層が形成された鋼板を、鉄−亜鉛合
金電気めっき浴に通し、前記鋼板に陰極電解処理を施す
ことにより、前記下層としての合金化溶融鉄−亜鉛合金
めっき層の上に、５０ｗｔ．％以上の鉄を含有する、１
〜１０ｇ／ｍ２の量の上層としての鉄−亜鉛合金電気め
っき層を形成することにより、成形加工時に、前記酸化
被膜を起点として、多数の微細なクラックを生成せし
め、生成した微細なクラックにより、上層からの局部応
力が下層に集中することを抑制して、塗膜に生ずる気泡
状欠陥を防止することを特徴とする、電着塗装性に優れ
た、複数の鉄−亜鉛合金めっき層を有する鉄−亜鉛合金
めっき鋼板の製造方法。1. A steel plate is coated with 0.20 wt. % Aluminum and the rest is passed through a hot dip galvanizing bath consisting of zinc and unavoidable impurities to form a galvanized layer on the surface of the steel sheet, and then the steel sheet is heated to form the galvanized layer. Alloying with the steel sheet, in the process of such alloying, after the steel sheet has penetrated into the hot dip galvanizing bath, at least until the iron-zinc alloy phase is formed on the surface of the galvanized layer While maintaining the steel sheet at a temperature of 500 ° C. or lower during this period, columnar iron-zinc alloy crystals (ζ crystals) having fine irregularities are generated on the surface layer of the plating layer, and thus at least one surface of the steel sheet. The columnar iron-zinc alloy crystal (ζ crystal) having fine irregularities was formed on the upper surface of 8 to 12 wt. %
An alloyed molten iron-zinc alloy plating layer as a lower layer containing iron, and then performing an oxidation treatment on the steel sheet on which the alloyed molten iron-zinc alloy plating layer as the lower layer is formed. By applying a heat treatment to form an oxide film on the surface of the alloyed molten iron-zinc alloy plating layer, and then a steel sheet on which the alloyed molten iron-zinc alloy plated layer as a lower layer having the oxide film is formed. Is passed through an iron-zinc alloy electroplating bath, and the steel sheet is subjected to cathodic electrolysis to form 50 wt.% On the alloyed molten iron-zinc alloy plating layer as the lower layer. Containing% or more of iron, 1
By forming an iron-zinc alloy electroplating layer as an upper layer in an amount of 10 to 10 g / m 2 , the above-mentioned oxidation during molding is performed.
Many fine cracks are generated starting from the film.
Therefore, the generated minute cracks may cause local reaction from the upper layer.
Air bubbles generated in the coating film by suppressing the concentration of force on the lower layer
A method for producing an iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers, which is excellent in electrodeposition coatability, and which is characterized by preventing a state defect .
金めっき層が形成された鋼板に対する前記酸化処理を、
大気中または加湿した大気中において、２５０〜３５０
℃の範囲内の温度で３０秒以上加熱することによって行
う、請求項１記載の方法。2. The oxidation treatment of the steel sheet having the alloyed hot-dip iron-zinc alloy plating layer as the lower layer,
In the atmosphere of dampening in or pressurized atmosphere, 250 to 350
The method according to claim 1, which is carried out by heating at a temperature in the range of ° C for 30 seconds or more.
金めっき層が形成された鋼板に対する前記酸化処理を、
薬液中に浸漬することによって行う、請求項１記載の方
法。3. The oxidation treatment for a steel sheet having an alloyed hot-dip iron-zinc alloy plating layer as the lower layer,
The method according to claim 1, which is performed by immersing in a chemical solution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3014803A JP2541380B2 (en) | 1991-01-14 | 1991-01-14 | Method for producing iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers having excellent electrodeposition coatability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3014803A JP2541380B2 (en) | 1991-01-14 | 1991-01-14 | Method for producing iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers having excellent electrodeposition coatability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04236752A JPH04236752A (en) | 1992-08-25 |
| JP2541380B2 true JP2541380B2 (en) | 1996-10-09 |
Family
ID=11871202
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3014803A Expired - Lifetime JP2541380B2 (en) | 1991-01-14 | 1991-01-14 | Method for producing iron-zinc alloy-plated steel sheet having a plurality of iron-zinc alloy plating layers having excellent electrodeposition coatability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2541380B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT412403B (en) * | 2003-07-29 | 2005-02-25 | Voestalpine Stahl Gmbh | Corrosion-protection layer for hardened metallic profiled structural part of motor vehicle, has roller-formed profiled elements having affinity to oxygen, and oxide skin comprising oxides of elements |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63157847A (en) * | 1986-12-19 | 1988-06-30 | Nippon Steel Corp | Manufacture of alloying-galvanized steel sheet |
| JPH0631475B2 (en) * | 1987-10-21 | 1994-04-27 | 住友金属工業株式会社 | Manufacturing method of galvannealed steel sheet for cationic electrodeposition coating |
| JPH0257670A (en) * | 1988-08-22 | 1990-02-27 | Nippon Steel Corp | Alloying hot dip galvanized steel sheet excellent in powdering resistance and flaking resistance and its production |
| JP2702217B2 (en) * | 1989-03-16 | 1998-01-21 | 川崎製鉄株式会社 | Method for producing galvannealed steel sheet having powdering resistance |
-
1991
- 1991-01-14 JP JP3014803A patent/JP2541380B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04236752A (en) | 1992-08-25 |
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