JP3915494B2 - Zinc-based plated steel sheet and manufacturing method thereof - Google Patents

Description

【０１６４】
【表２】

【０１６５】
【表３】

【０１６６】
【表４】

【０１６７】
【表５】

【０１６８】
【表６】

【０１６９】
【表７】

【０１７０】
【表８】

【０１７１】
【表９】

【０１７２】
【表１０】

【０１７３】
【表１１】

【０１７４】
【表１２】

【０１７５】
【表１３】

［実施例２］
この実施例では以下に示す亜鉛系めっき鋼板を用いた。
【０１７６】
(1) ＧＡ：合金化溶融亜鉛めっき鋼板（１０mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４５ｇ/ｍ²である。
【０１７７】
(2) ＧＩ：溶融亜鉛めっき鋼板であり、めっき付着量は両面ともに９０ｇ／ｍ²である。
【０１７８】
以上の亜鉛系めっき鋼板のめっき層表面に対し、以下に示すような処理を施した。なお、処理する亜鉛系めっき鋼板は、アルカリ脱脂によりプレス油を除去したものを使用した。
【０１７９】
皮膜形成用の水溶液のうち、金属イオンとしてＦｅイオンを含むものについては、硫酸第一鉄とオルトリン酸を各成分が所定の濃度となるように脱イオン水に溶解させた水溶液に、硫酸イオン含有リン酸第一鉄、クエン酸を添加し、表１４に示した組成となるように調整した。また、金属イオンとしてＦｅイオンとＡｌイオンを含むものについては、硫酸第一鉄とオルトリン酸から調整される水溶液と、水酸化アルミニウムとオルトリン酸から調整される水溶液を適宜所定の濃度比となるように混合し、表１４に示した組成となるように調整した。
【０１８０】
表１４に示した処理液（室温）を、室温にて上記亜鉛系めっき鋼板の表面にロールコーター又はバーコーターにより塗布し、加熱乾燥して皮膜を形成させた。形成される皮膜の付着量は、組成物の濃度及び塗布条件（ロールの圧下力、回転速度、バーコーターの番手等）により適宜調整した。
【０１８１】
また、皮膜の付着量の測定、皮膜中の金属元素量とリン系酸化物量のモル比の測定は、実施例１と同様にして行った。
【０１８２】
比較例として、従来の塗布タイプのプレフォス処理を亜鉛系めっき鋼板の表面に皮膜付着量を変えて施した。塗布タイプのプレフォスの皮膜付着量は、重クロム酸アンモニウム２０ｇ、２５％アンモニア水４９０ｇを１Ｌのイオン交換水に溶かした溶液中で皮膜を溶解し、溶解前後の重量変化により算出した。また、皮膜中のＰ付着量は後述する脱膜性評価に記載の方法と同様にＦＸにより測定した。
【０１８３】
以上のようにして得られた亜鉛系めっき鋼板の性能評価は、下記のようにして行った。
【０１８４】
(1) プレス成形性：実施例１と同じ
(2) 化成処理性：実施例１と同じ
(3) 脱脂時の脱膜性
本発明例及び比較例の亜鉛系めっき鋼板のサンプル（１５０ｍｍ×７０ｍｍ）にプレス油としてパーカー興産（株）製の“ノックスラスト５５０ＨＮ”を１．５〜２．０ｇ/ｍ²の付着量で塗布した後、以下の条件でアルカリ脱脂を行った。使用したサンプルの皮膜中のＰ付着量は、当該サンプルの採取位置を挟む位置から採取した４８ｍｍφのサンプルのＰ付着量をＦＸにより定量し、その平均値をＰ付着量とした。
【０１８５】
脱脂後のサンプルのほぼ中央位置の４８ｍｍφ部分をサンプリングし、ＦＸによりこの部分のＰ付着量を定量した。上記の初期Ｐ付着量と脱脂後のＰ付着量から以下の式により脱膜率を算出した。
【０１８６】
脱膜率＝１−（［脱脂後Ｐ付着量］／［初期Ｐ付着量］）
・アルカリ脱脂条件
脱脂液が劣化した条件を想定して、アルカリ脱脂液（日本パーカライジング（株）製の“ＦＣ４４８０”）に防錆油（日本パーカライジング（株）製の“ノックスラスト５５０ＨＮ”）を５ｇ／ｌ添加したものを用い、浸漬法により脱脂を行った。浸漬時間は１２０秒、脱脂液の温度は４３℃とした。脱脂はプロペラ型の攪拌器を回転（回転数：３００ｒｐｍ）させた３０Ｌの円筒の容器を用いて浸漬処理により行った。
(4) 接着接合性
２５ｍｍ×２００ｍｍのサンプルの防錆油を溶剤脱脂により除去した後、洗浄油（スギムラ化学（株）製の“プレトンＲ３５２Ｌ”）を塗布した。このサンプルを２枚一組とし、塩ビ系のヘミング用接着剤を２５ｍｍ×１４０ｍｍの範囲に塗布し（サンプルの端から５０ｍｍは接着剤を塗布せず）、０．１５ｍｍ厚のスペーサーを介して貼り合わせて試験片を作成した。これを１６０℃×１０分で乾燥させた後、２４〜７２時間の間、常温にて放置し、その後、引張り試験機を用いて試験片がＴ型の状態から２枚の試験片が剥離するまで引っ張り、この引っ張り時の試験片の平均強度を測定した。
【０１８７】
表１５に各供試材の処理条件と上記性能評価の結果を示すが、比較例に較べて本発明例は化成処理性及びプレス成形性だけでなく、脱膜性と接着接合性にも優れている。
【０１８８】
【表１４】

【０１８９】
【表１５】

［実施例３］
この実施例では以下に示す亜鉛系めっき鋼板を用いた。
【０１９０】
(1) ＧＡ：合金化溶融亜鉛めっき鋼板（１０mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４５ｇ/ｍ２である。
【０１９１】
処理原板の前処理は実施例２と同様とした。
【０１９２】
硫酸イオン含有皮膜形成用水溶液としては、硫酸第一鉄とオルトリン酸を各成分が所定の濃度となるように脱イオン水に溶解させた水溶液、硫酸イオンを含まない水溶液としては、特級試薬の電解鉄粉とオルトリン酸から調整される水溶液を、表１６に示した組成となるように調整した。
【０１９３】
表１６に示した処理液（室温）を、室温にて上記亜鉛系めっき鋼板の表面にバーコーターにより塗布し、加熱乾燥して皮膜を形成させた。形成される皮膜の付着量はバーコーターの番手、組成物の濃度により調整した。
【０１９４】
また、皮膜の付着量の測定、皮膜中の金属元素量とＰ成分量のモル比の測定は、実施例１と同様にして行った。
【０１９５】
さらに、皮膜に存在するＳとリン系酸化物成分（Ｐ成分量）の比率はＸＰＳ（Ｘ線光電子分光法）により以下のようにして定量した。
Ｘ線源としてモノクロメーターで単色化したＡｌ−Ｋα線を用い、Ａｒイオンにより試料表面の汚染物をＣ１ｓのピーク強度がスパッタ前の６〜８割になるように除去した後、１０ｍｍ²程度の領域を測定した。Ｓ２ｐとＰ２ｓのピークの積分強度に相対感度因子法を適用して、ＳとＰの原子個数比を求め、これを、皮膜中のＳ（ｆ）とＰ成分量（Ｐ₂Ｏ₅換算量）（ｂ）のモル比（ｆ）／（ｂ）に換算した。
【０１９６】
以上のようにして得られた亜鉛系めっき鋼板の性能評価は、下記のようにして行った。
【０１９７】
（１）プレス成形性：実施例１と同じ
（２）化成処理性：実施例２の評価２と同じとし、化成処理条件のみ通常規定の浸漬時間（１２０秒）に対し、浸漬時間を３０秒と短くして評価した。評価基準は、実施例２の評価２と同じとした。
【０１９８】
（３）接着接合性：実施例２と同じ
表１７に各供試材の処理条件と上記性能評価の結果を示すが、比較例に較べて本発明例は化成処理性及びプレス成形性だけでなく、脱膜性と接着接合性にも優れている。
【０１９９】
【表１６】

【０２００】
【表１７】

（実施の形態２）
本発明者らは、亜鉛系めっき鋼板のめっき層表面に、Ｎ成分とＰ成分とを適正な組成範囲で含有する複合皮膜を形成することによりプレス成形性と化成処理性がともに優れた亜鉛系めっき鋼板が得られること、また、このようなプレス成形性と化成処理性がともに優れた亜鉛めっき鋼板は、亜鉛系めっき鋼板のめっき層表面に適正な成分と組成範囲を有するリン酸系水溶液を塗布して皮膜を形成することにより安定して得られることを見い出した。
【０２０１】
本発明の実施の形態２（以下、実施の形態２において単に本発明と呼ぶ）はこのような知見に基づきなされたもので、その特徴は以下の通りである。
[1] 亜鉛系めっき鋼板のめっき層表面に、皮膜構成成分としてＮ成分とＰ成分とを、Ｐ成分をリン系化合物及び／又は窒素・リン系化合物の形態で、Ｎ成分を窒素化合物及び／又は窒素・リン系化合物の形態でそれぞれ含有し、Ｎ成分量（ａ′）とＰ成分量（ｂ）のモル比（ａ′）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）が０．２０超え６以下であり、且つ皮膜付着量がＰ付着量として５〜３００ｍｇ／ｍ²である複合皮膜を形成したことを特徴とする亜鉛系めっき鋼板。
[2]複合皮膜が、さらにＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属元素を含有し、Ｎ成分と前記金属元素の合計量（ａ）とＰ成分量（ｂ）のモル比（ａ）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）が０．２０超え６以下であることを特徴とする上記[1]に記載の亜鉛系めっき鋼板。
[3]複合皮膜が、金属元素として少なくともＦｅを含有することを特徴とする上記[1]又は[2]の亜鉛系めっき鋼板。
[4]複合皮膜が、さらにシリカを含有し、シリカ量（ｅ）とＰ成分量（ｂ）のモル比（ｅ）／（ｂ）（但し、シリカ量はＳｉＯ₂換算量、Ｐ成分量はＰ₂Ｏ₅換算量）が０．０１〜５０であることを特徴とする上記[1]〜[3]のいずれかに記載の亜鉛系めっき鋼板。
[5]複合皮膜が、さらに水溶性樹脂及び／又は水分散性樹脂を皮膜中での付着量として０．０１〜１０００ｍｇ／ｍ²含有することを特徴とする上記[1]〜[4]のいずれかに記載の亜鉛系めっき鋼板。
[6] 実質的にＮＨ₄ ⁺からなるカチオン成分（α）とリン酸成分（β）とを含有し、カチオン成分（α）とリン酸成分（β）のモル濃度比（α）／（β）（但し、リン酸はＰ₂Ｏ₅換算モル濃度）が０．２０超え６以下である水溶液を、亜鉛系めっき鋼板のめっき層表面に塗布し、引き続き水洗することなく乾燥して皮膜を形成することを特徴とする亜鉛系めっき鋼板の製造方法。
[7] 実質的にＮＨ₄ ⁺とＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属イオンとからなるカチオン成分（α）と、リン酸成分（β）とを含有し、カチオン成分（α）の合計とリン酸成分（β）のモル濃度比（α）／（β）（但し、リン酸はＰ₂Ｏ₅換算モル濃度）が０．２０超え６以下である水溶液を、亜鉛系めっき鋼板のめっき層表面に塗布し、引き続き水洗することなく乾燥して皮膜を形成することを特徴とする亜鉛系めっき鋼板の製造方法。
[8]めっき層表面に塗布される水溶液に含まれるカチオン成分（α）の合計とリン酸成分（β）のモル濃度比（α）／（β）（但し、リン酸はＰ₂Ｏ₅換算モル濃度）が０．４０〜６であることを特徴とする上記[6]又は[7] に記載の亜鉛系めっき鋼板の製造方法。
[9]めっき層表面に塗布される水溶液が、さらにシリカ（ε）を含有し、シリカ（ε）とリン酸成分（β）のモル濃度比（ε）／（β）（但し、シリカはＳｉＯ₂換算モル濃度、リン酸はＰ₂Ｏ₅換算モル濃度）が０．０１〜５０であることを特徴とする上記[6]〜[8] に記載の亜鉛系めっき鋼板の製造方法。
[10]めっき層表面に塗布される水溶液が、さらに水溶性樹脂及び／又は水分散性樹脂を含有することを特徴とする上記[6]〜[9] に記載の亜鉛系めっき鋼板の製造方法。
[11]めっき層表面に塗布される水溶液が、カチオン成分として少なくともＦｅを含有することを特徴とする上記[6]〜[10] に記載の亜鉛系めっき鋼板の製造方法。
[12]めっき層表面に塗布される水溶液が、さらにカルボン酸を含有することを特徴とする上記[6]〜[11] に記載の亜鉛系めっき鋼板の製造方法。
[13]めっき層表面に塗布される水溶液に含まれるカルボン酸がオキシカルボン酸であることを特徴とする上記[12] に記載の亜鉛系めっき鋼板の製造方法。
[14]オキシカルボン酸がクエン酸であることを特徴とする上記[13] に記載の亜鉛系めっき鋼板の製造方法。
【０２０２】
本発明が対象とする亜鉛系めっき鋼板（皮膜処理の母材となる亜鉛系めっき鋼板）とは、鋼板の表面に溶融めっき法、電気めっき法又は気相めっき法等により亜鉛系めっき層を形成させためっき鋼板である。亜鉛系めっき層の組成は、純亜鉛からなるめっき層のほかに、Ｆｅ、Ｎｉ、Ｃｏ、Ｃｒ、Ａｌ、Ｍｏ、Ｔｉ、Ｓｉ、Ｗ、Ｓｎ、Ｐｂ、Ｎｂ、Ｔａ等の金属若しくはその酸化物、有機物の中から選ばれる１種又は２種以上を含有する単層又は複層の亜鉛めっき層などである。また、これらの亜鉛系めっき層はＳｉＯ₂、Ａｌ₂Ｏ₃等の酸化物微粒子や、有機樹脂の１種又は２種以上を含有していてもよい。また、亜鉛系めっき鋼板としては、めっき組成が異なる複数のめっき層を有する複層めっき鋼板、めっき層の組成を層厚方向で傾斜状に変化させた機能傾斜めっき鋼板などを使用することもできる。
【０２０３】
亜鉛系めっき鋼板の具体例としては、溶融亜鉛めっき鋼板、蒸着亜鉛めっき鋼板、鉄−亜鉛合金化溶融亜鉛めっき鋼板、亜鉛−アルミニウム系合金溶融めっき鋼板（例えば、Ｚｎ−５％Ａｌ合金溶融めっき鋼板、Ｚｎ−５５％Ａｌ合金溶融めっき鋼板）、めっき層のうち鋼板に近い層のみが合金化されている合金化溶融亜鉛めっき鋼板（一般にハーフアロイと呼ばれる）、片面が鉄−亜鉛合金化溶融亜鉛めっき層からなり、他の片面が溶融亜鉛めっき層からなるめっき鋼板、或いは上記各めっき鋼板のめっき層の上層に、さらに電気めっき、蒸着めっき等により亜鉛又は亜鉛主体の合金めっき層を施しためっき鋼板、亜鉛をマトリックスとし、ＳｉＯ₂等の微粒子を分散させためっき層を有する分散めっき鋼板などが挙げられる。
【０２０４】
本発明の亜鉛系めっき鋼板は、上記のような素材めっき鋼板のめっき層表面に、Ｎ成分（例えば、窒素化合物の形態で）とＰ成分（例えば、リン系酸化物の形態で）とを適正な組成範囲で含有する複合皮膜を形成させることにより、優れた化成処理性とプレス成形性を付与したものである。
【０２０５】
以下、本発明の詳細をその限定理由とともに説明する。
【０２０６】
一般に従来の亜鉛系めっき鋼板は、プレス成形性が冷延鋼板に較べて劣っている。その原因は、高面圧下において低融点且つ軟質の亜鉛と金型とが凝着現象を起こすために、摺動抵抗が増大することにある。これを防ぐためには、亜鉛系めっき鋼板のめっき層の表面に亜鉛又は亜鉛合金めっき層よりも硬質で且つ高融点の皮膜を形成することが有効である。
【０２０７】
本発明はこれを実現するために、めっき層表面に、皮膜構成成分としてＮ成分とＰ成分とを、Ｐ成分をリン系化合物及び／又は窒素・リン系化合物の形態で、Ｎ成分を窒素化合物及び／又は窒素・リン系化合物の形態でそれぞれ含有し、且つこのＮ成分とＰ成分の組成比を特定の範囲に規制した硬質且つ高融点の複合皮膜を形成させる。この複合皮膜はＮ成分とＰ成分を特定の組成比で含むために、非常に均一に亜鉛系めっき鋼板表面を被覆し、薄膜でも亜鉛と金型の直接接触を抑制することができる。このような均一な皮膜形成が可能な理由は、この複合皮膜を構成するＮ成分の働きによるものである。
【０２０８】
この複合皮膜の形成方法に特に制限はないが、通常は皮膜成分を含む水溶液をめっき層表面に塗布・乾燥することにより形成される。ここで、皮膜成分がリン系酸化物のみでは、そのエッチング作用によってめっき層の亜鉛を溶解し、皮膜成分として取り込んでしまう。この場合、亜鉛とリン酸が反応して結晶質のリン酸塩が生成しやすく、このような結晶質のリン酸塩が形成されると皮膜の均一性が低下し、薄膜の状態でめっき層表面を完全に被覆することが困難となる。これに対して本発明のように皮膜中にＮ成分が存在する場合には、皮膜形成過程でのリン酸と亜鉛との反応が抑制される結果、リン酸成分が亜鉛との結晶質になりにくく、Ｎ成分とリン酸成分（Ｐ成分）がガラス質のネットワーク皮膜を形成する。そして、このような作用は、Ｎ成分量（ａ′）とＰ成分量（ｂ）のモル比（ａ′）／（ｂ）を特定の範囲とした場合に得られ、これにより均一な皮膜形成が可能となる。
【０２０９】
さらに皮膜構成成分として、Ｎ成分に加えてＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｎｉ、Ｃｏ、Ｃｕ、Ｍｏから選ばれる１種又は２種以上の金属元素を含む場合に、特に皮膜の均一性が良好になり、プレス成形性が良好となる。これは、Ｎ成分の存在による効果に加え、これら金属元素成分がリン酸成分とネットワーク皮膜を形成するためであると考えられる。特に、Ｎ成分の存在による亜鉛とリン酸との反応抑制効果と、上記金属元素成分とリン酸成分のネットワーク形成効果が相乗効果となり、より均一性の高い皮膜が形成されるものと考えられる。
【０２１０】
次に、上記複合皮膜と化成処理性との関係について説明する。
【０２１１】
通常、化成処理工程の前処理として、プレス加工で用いたプレス油を除去するための脱脂工程がある。本発明においてめっき層表面に形成される複合皮膜はアルカリ性の脱脂液により溶解しやすいため、脱脂工程ではその皮膜の大部分が除去される。この結果、化成処理工程では皮膜がほとんど溶解除去された状態で処理がなされるため、めっき面に健全なリン酸塩結晶が形成される。また、脱脂液の劣化や部位によって脱脂液の回り込みが十分でないこと等により、脱脂工程での複合皮膜の脱膜（皮膜の溶解除去）が十分に行われず、皮膜の一部が残存するような場合でも、本発明の亜鉛系めっき鋼板では良好な化成処理性を得ることができる。これは、皮膜成分としてＮ成分を用い且つその組成比を特定の範囲に限定しているため、この皮膜は脱脂液中だけでなく化成処理液中でも十分な溶解性が得られるためである。
【０２１２】
すなわち、上記のような皮膜の溶解性（脱膜性）は、皮膜を構成するＮ成分とＰ成分の比率により異なったものとなる。一般にＮ成分に対してのＰ成分量が多いと皮膜自体の溶解性は高まるが、Ｐ成分が多い皮膜を形成するためにはリン酸等のエッチング性の高い成分が多量に存在する水溶液を塗布・乾燥する必要があるため、皮膜中への亜鉛の取り込み量が増え、この結果、皮膜の溶解性が逆に低下してしまう。したがって、Ｎ成分に対するＰ成分の割合は、皮膜自体の溶解性の確保とエッチングによる亜鉛取り込みの抑制効果がうまくバランスするように調整する必要がある。また、Ｐ成分に対してＮ成分の量が極端に過剰になると皮膜のネットワーク形成能が低下し、この場合には皮膜の溶解性は高くなるものの均一な皮膜形成が困難となり、やはり優れたプレス成形性の確保が困難となる。
【０２１３】
なお、上記複合皮膜には、不可避的にめっき層から取り込まれる亜鉛が存在する。本発明のリン系酸化物皮膜はＮ成分、及び特定の金属元素成分とリン系酸化物とが特定の比率で存在することにより、亜鉛が含まれていても優れた化成処理性を示すため、亜鉛の存在量は特に規定されない。
【０２１４】
以下、本発明の亜鉛系めっき鋼板が有する複合皮膜の成分とその限定理由について詳細に説明する。
【０２１５】
複合皮膜には、Ｐ成分（例えば、リン系酸化物の形態で含まれるＰ成分）とともに、皮膜に溶解性を与えるための構成成分としてＮ成分（例えば、窒素系化合物の形態で含まれるＮ成分）が含有される。Ｎ成分とＰ成分の皮膜中での存在形態に特に制限はなく、Ｎ成分としては、窒素系化合物（例えば、アンモニア、窒素酸化物）、窒素・リン系化合物（例えば、リン酸アンモニウム、ＺｎＮＨ₄ＰＯ₄）などが挙げられ、Ｐ成分としては、オルトリン酸、縮合リン酸などのリン系酸化物や、窒素・リン系化合物などが挙げられ、ぞれぞれがいずれの形態で存在していてもよい。したがって、本発明の複合皮膜は、窒素系化合物、リン系酸化物、窒素・リン系化合物のうちのいずれかの形態として含まれるＮ成分及びＰ成分、さらに後述するような必要に応じて含有される特定の金属元素成分の１種以上、シリカ、有機樹脂を実質的な構成成分とし、残りは亜鉛などの不可避不純物からなるのが好ましい。
【０２１６】
複合皮膜中でのＮ成分量（ａ′）とＰ成分量（ｂ）のモル比（ａ′）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）は０.２０超え６以下とする。このモル比（ａ′）／（ｂ）が０．２０以下ではＰ成分の比率が過剰であるため皮膜が不均一となりやすく、プレス成形性が劣る。さらに、複合皮膜が化成処理時に脱離し難くなるため、化成処理性も低下する。一方、モル比（ａ′）／（ｂ）が６を超えるとＮ成分が過剰となるため、同様に皮膜の均一性が低下し、薄膜の部分と厚膜の部分が共存しやすくなる。このため自動車製造過程での塗装前処理である化成処理時に処理液との反応が膜厚の厚い部分で阻害され、この結果、健全なリン酸塩結晶が生じにくくなり、化成処理不良が生じる。また、皮膜の均一性が低下するためプレス成形性の改善効果も小さい。さらに、皮膜の安定性が低いために、湿潤環境において保管された場合や結露環境におかれた場合などに、皮膜の一部が溶解し電解質として作用し、亜鉛系めっき鋼板の腐食をもたらす。
【０２１７】
なお、さらに好ましいＮ成分量（ａ′）とＰ成分量（ｂ）のモル比（ａ′）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）の下限は０．４０、上限は２.００である。
【０２１８】
また、複合皮膜中に、さらにＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｎｉ、Ｃｏ、Ｃｕ、Ｍｏから選ばれる１種又は２種以上の金属元素を含有する場合に、特に均一被覆性とともに脱膜性（溶解性）が良好になる。これは、これら金属元素がＮ成分と共存することによる皮膜の溶解性の向上効果に加え、金属元素成分の共存による亜鉛とリン酸成分との反応抑制効果が相乗効果として作用し、より脱膜性の高い皮膜が形成されるためであると考えられる。
【０２１９】
また、上述した金属元素成分の中でもより好ましい成分としては、Ａｌ、Ｆｅ、Ｃｏが挙げられ、皮膜中にこれらの金属元素成分が含有された場合、化成処理液中で皮膜がより溶解し易くなるため、より優れた化成処理性を示す。
【０２２０】
また、複合皮膜が金属元素成分としてＦｅを含有する場合には、化成処理におけるリン酸塩結晶の成長が殆ど阻害されないため、特に優れた化成処理性が得られる。その理由は必ずしも明らかではないが、複合皮膜がＦｅを含有する場合には化成処理時に皮膜が残留している状態でも化成処理結晶が生成することが確認された。脱脂工程における複合皮膜の脱膜性はアルカリ脱脂液の状態や脱脂条件により大きく異なり、極端に劣化した脱脂液やスプレー処理のような強い脱脂が行われない条件下では、脱膜が十分に行われない可能性も高い。このような場合において、Ｆｅを含有する複合皮膜は化成処理性に対して有効に作用する。
【０２２１】
また、一般に自動車や家電用途では溶接部の補強、耐食性の強化などの目的で接着剤による鋼板同士の接合が行われる。この際、潤滑特性を高めるために付与された皮膜の存在が接着接合性を著しく低下させることがある。従来のリン酸含有潤滑性皮膜では特にこの傾向が強く、その改善が望まれていた。このような課題に対して、上記複合皮膜に金属元素成分としてＦｅを含有させることにより接着剤適合性が著しく改善されることが判った。
【０２２２】
したがって、以上のような効果を期待する場合には、複合皮膜中に金属元素として少なくともＦｅを含有させ、より好ましくは金属元素としてＦｅを単独で含有させることが望ましい。
【０２２３】
皮膜中におけるＦｅの存在形態には特に制限はなく、金属、酸化物、リン酸成分との化合物などのいずれの形態で存在していてもよい。
【０２２４】
複合皮膜が、Ｎ成分とともにＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属元素を含有する場合、Ｎ成分と前記金属元素の合計量（ａ）とＰ成分量（ｂ）のモル比（ａ）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）は０．２０超え６以下とする。このモル比（ａ）／（ｂ）が０．２０以下ではＰ成分の比率が過剰であるため皮膜が不均一となりやすく、プレス成形性が劣る。さらに、複合皮膜が化成処理時に脱離し難くなるため、化成処理性も低下する。一方、モル比（ａ）／（ｂ）が６を超えるとＮ成分や金属元素成分が過剰となるため、同様に皮膜の均一性が低下し、薄膜の部分と厚膜の部分が共存しやすくなる。このため自動車製造過程での塗装前処理である化成処理時に処理液との反応が膜厚の厚い部分で阻害され、この結果、健全なリン酸塩結晶が生じにくくなり、化成処理不良が生じる。また、皮膜の均一性が低下するためプレス成形性の改善効果も小さい。さらに、皮膜の安定性が低いために、湿潤環境において保管された場合や結露環境におかれた場合などに、皮膜の一部が溶解し電解質として作用し、亜鉛系めっき鋼板の腐食をもたらす。
【０２２５】
なお、さらに好ましいＮ成分と金属元素の合計量（ａ）とＰ成分量（ｂ）のモル比（ａ）／（ｂ）（但し、Ｎ成分量はアンモニウム換算量、Ｐ成分量はＰ₂Ｏ₅換算量）の下限は０．４０、上限は２.００である。
【０２２６】
本発明の複合皮膜には、さらにシリカを含有させることができ、これにより摺動性をより改善することができる。これは、シリカ成分に油の保持性を高める効果があることや、乾燥摩擦状態でシリカ成分が潤滑材として作用するためであると考えられる。さらに、水溶液を塗布し乾燥するような皮膜形成手法を採用する場合、皮膜中にシリカを添加すると水溶液の亜鉛系めっき皮膜への濡れ性が改善され、めっき層への均一な皮膜形成が可能になる。
【０２２７】
複合皮膜中にシリカを含有させる場合、皮膜中におけるシリカ量（ｅ）とＰ成分量とのモル比（ｅ）／（ｂ）（但し、シリカ量はＳｉＯ₂換算量、Ｐ成分量はＰ₂Ｏ₅換算量）が０．０１〜５０である場合にその効果が特に顕著になる。モル比（ｅ）／（ｂ）が０．０１未満ではシリカを含有させることによる効果が十分に得られない。一方、モル比（ｅ）／（ｂ）が５０を超えるとシリカ成分が過剰に存在することになり、プレス成形時にシリカ成分が削り取られ、表面欠陥やカジリの原因となる。
【０２２８】
シリカとしては、例えばシリカゾルやヒュームドシリカ等の乾式シリカを用いることができる。シリカゾルとしては、例えば日産化学工業（株）製の“スノーテックス”（商品記号：Ｏ、ＯＳ、ＯＵＰ、ＡＫ、Ｎ、２０、３０、４０）や、触媒化成工業（株）製の“カタロイド”（商品記号：Ｓ、ＳＩ、ＳＡ、ＳＮ）、旭電化工業（株）製の“アデライト”（商品記号：ＡＴ−２０、ＡＴ−５０、ＡＴ−２０Ｎ、ＡＴ−３００、ＡＴ−３００Ｓ、ＡＴ−２０Ｑ）等が挙げられる。この中でも、アンモニウムイオンにより表面電位を中和したタイプが特に好ましい。また、ヒュームドシリカとしては、例えば日本アエロジル（株）製の“ＡＥＲＯＳＩＬ２００”、“ＡＥＲＯＳＩＬ３００”等が挙げられる。
【０２２９】
本発明の複合皮膜中には、潤滑性を向上させる目的でさらに有機樹脂成分を含有させることができる。この有機樹脂としては、他の無機成分と水溶液中で共存できる水溶性樹脂及び／又は水分散性樹脂が好ましい。これら有機樹脂としては、エポキシ系樹脂、アクリル系樹脂、アクリル−エチレン共重合体、アクリル−スチレン共重合体、アルキド樹脂、ポリエステル樹脂、ウレタン系樹脂、ポリブタジエン系樹脂、ポリアミド系樹脂などが挙げられる。さらに、これら樹脂に加えて、水溶性エポキシ樹脂、水溶性フェノール樹脂、水溶性ブタジエンラバー（ＳＢＲ、ＮＢＲ、ＭＢＲ）、メラミン樹脂、ブロックイソシアネート、オキサゾリン化合物などを架橋剤として併用することが有効である。
【０２３０】
複合皮膜中に含有させる有機樹脂量としては、皮膜中での付着量として０．０１〜１０００ｍｇ／ｍ²が適当である。有機樹脂量が０．０１ｍｇ／ｍ²未満ではその効果が十分に得られず、一方、１０００ｍｇ／ｍ²を超えると皮膜が厚くなり、皮膜剥離を生じやすくなるため十分な効果が得られない。
【０２３１】
本発明の亜鉛系めっき鋼板において、めっき層表面に形成される複合皮膜の付着量は、Ｐ付着量として５〜３００ｍｇ／ｍ²、好ましくは１０〜１５０ｍｇ／ｍ²、特に好ましくは３０〜１２０ｍｇ／ｍ²とする。皮膜付着量が少ないとプレス成形性の向上効果が十分得られず、一方、皮膜付着量が多過ぎると化成処理性が低下する。
【０２３２】
また、本発明の複合皮膜は、皮膜の脱膜性及び均一被覆性が確保されていれば、結晶質、アモルファス状のいずれの皮膜形態であってもよい。また、皮膜中に結晶成分に付随する結晶水としてのＨ₂Ｏ成分、アモルファス状皮膜に混在するＨ₂Ｏ成分などが混在していてもよい。
【０２３３】
次に、上述した複合皮膜を有する亜鉛系めっき鋼板の製造方法について説明する。
【０２３４】
本発明の亜鉛系めっき鋼板が有する複合皮膜は、例えば、アンモニウムイオンとを含有する水溶液をめっき層表面に塗布した後、乾燥させることにより形成することができる。この場合、皮膜成分の比率に合わせて水溶液のカチオン成分とリン酸成分の比率を適宜変えることが可能である。
【０２３５】
したがって本発明の亜鉛系めっき鋼板の製造方法では、実質的にＮＨ₄ ⁺からなるカチオン成分（α）と、アニオン成分であるリン酸成分（β）とを含み、これらの成分を特定の比率（モル濃度比（α）／（β）で０．２０超え〜６以下）で存在させた水溶液を亜鉛系めっき鋼板のめっき層表面に塗布し、水洗することなく乾燥させて皮膜を形成する。この結果、亜鉛系めっき皮膜の表面にはＮ成分とＰ成分とを窒素系化合物、リン系酸化物、窒素・リン系化合物のいずれかの形態で含有する硬質且つ高融点の薄い皮膜が緻密且つ均一に形成される。
【０２３６】
通常、亜鉛系めっき鋼板の表面にリン酸塩皮膜等のようなリンを含有する皮膜を形成するには、めっき鋼板をリン酸イオンなどのリン酸成分を含有する水溶液に浸漬させるなどの処理が行われる。一般にアルカリ金属以外のカチオンを含有するリン酸塩は、中性又はアルカリ性領域で不溶性であるため水溶液は酸性となる。また、これらのカチオン成分とリン酸の混合水溶液は沈殿しやすく、通常は、カチオン成分に対し過剰にリン酸イオンが存在する場合に水溶液として安定に存在できる。このようなリン酸過剰の水溶液ではめっき層の亜鉛はエッチングされやすく、溶出した亜鉛はリン酸成分と反応し、結晶を形成するか或いは界面に亜鉛を含む反応層を形成しやすい。先に述べたように皮膜に結晶質の成分が多く存在すると、プレス成形の際にこれら結晶成分が剥離し、これが金型との間に堆積して摺動性を阻害する結果、型カジリなどを生じやすい。また、亜鉛と皮膜が反応層を形成するため化成処理過程での皮膜の脱離が生じ難く、化成処理性が十分でない。
【０２３７】
これに対して本発明で用いる皮膜形成用の水溶液では、カチオン成分（α）が実質的にアンモニウムイオンからなる点（ただし、後述するようにカチオン成分（α）としてさらに特定の金属イオンを添加してもよい。）、及びカチオン成分（α）に対するリン酸成分（β）の比率を規定している点に特徴がある。アンモニウムイオンを存在させることにより、カチオン成分に対するリン酸成分濃度を低く抑えても沈殿の生じない溶液とすることができ、めっき層中の亜鉛のエッチングを極力抑制した皮膜形成用水溶液とすることができる。この結果、本発明の処理を行うことにより、化成処理性を低下させることなく、優れたプレス成形性を示す亜鉛系めっき鋼板を得ることができる。
【０２３８】
通常、化成処理工程の前処理として、プレス油を除去するための脱脂工程がある。本発明で行われる処理により形成される皮膜の場合、亜鉛との反応層の形成が抑制され、亜鉛系めっき層との界面がアルカリ性の脱脂液により溶解しやすいため、脱脂工程で皮膜の大部分が除去される。この結果、化成処理工程において皮膜がほぼ完全に溶解することができ、健全なリン酸塩結晶が形成される。また、このような作用効果により、脱脂液の劣化や部位によって脱脂液が十分に回り込まないなどの原因で脱脂工程での脱膜性が十分でない場合でも、本発明により得られる亜鉛系めっき鋼板は良好な化成処理性が得られる。
【０２３９】
本発明により得られる亜鉛系めっき鋼板が良好な化成処理性を示すのは、主に以下のような理由によるものと考えられる。
【０２４０】
(1) 後述するようにめっき層表面に緻密且つ均一な皮膜が形成されるため、極く薄い皮膜であっても十分なプレス成形性が実現でき、このため皮膜が化成処理液との反応を阻害するような厚みとならない。
【０２４１】
(2) 亜鉛との反応層の形成が抑制されるため、化成処理液での皮膜の脱離が生じ易い。
【０２４２】
また、本発明では皮膜形成用の水溶液中のカチオン成分（α）（実質的にアンモニウムイオンからなるカチオン成分）とリン酸成分（β）のモル濃度比を特定の範囲とすることにより、均一且つ緻密な薄い皮膜を形成することができる。水溶液中のカチオン成分（α）とリン酸成分（β）の比率が皮膜形態に影響を及ぼす理由は必ずしも明らかでないが、処理液のエッチング性と処理液の溶解性がそれぞれの成分の比率により変化するため、これらが皮膜形態に変化をもたらすものと推定される。すなわち、リン酸成分（β）が過剰の場合には処理液のエッチング性が高くなり、亜鉛と反応した結晶質成分が形成されやすく、薄膜というよりは塊状の結晶質成分の集合体のような皮膜形態となる。一方、カチオン成分（α）が過剰の場合には、処理液の溶解性が高くなるため、乾燥過程で皮膜がゲル化しにくく、均一な皮膜となりにくい。
【０２４３】
このため、実質的にアンモニウムイオン（ＮＨ₄ ⁺）からなるカチオン成分（α）とリン酸成分（β）の比率は、モル濃度比（α）／（β）（但し、リン酸成分はＰ₂Ｏ₅換算のモル濃度）で０．２０超え６以下、好ましくは０．４０以上６以下、さらに好ましくは０．６０以上４.００以下、特に好ましくは１.００以上４.００以下とする。
【０２４４】
モル濃度比（α）／（β）が０．２０以下ではリン酸成分が過剰となり、亜鉛とリン酸との結晶成分が形成され易く、優れた摺動特性が得られにくい。さらに、皮膜が化成処理時に脱離し難くなるため、化成処理性が低下する。また、モル濃度比（α）／（β）が６を超えると皮膜が不均一に形成されるため、薄膜の部分と厚膜の部分が共存しやすくなる。このため自動車製造過程での塗装前処理である化成処理時に処理液との反応が膜厚の厚い部分で阻害され、この結果、健全なリン酸塩結晶が生じにくくなり、化成処理不良が生じる。また、皮膜の均一性が低下するためプレス成形性の改善効果も小さい。さらに、皮膜の溶解性が高くなるため、湿潤環境において保管された場合や結露環境におかれた場合などに、皮膜の一部が溶解して電解質として作用し、亜鉛系めっき鋼板の腐食をもたらす。
【０２４５】
皮膜形成用の水溶液に添加されるアンモニウムイオンは、アンモニア水を用いて添加するほかに、第一リン酸アンモニウム（リン酸二水素アンモニウム）、第二リン酸アンモニウム（リン酸水素二アンモニウム）、第三リン酸アンモニウム（リン酸三アンモニウム）等のリン酸塩、硝酸アンモニウム、硫酸アンモニウム、酢酸アンモニウム、クエン酸アンモニウム等のアンモニウム塩の形でも添加できる。これらのうち、リン酸アンモニウム塩はアンモニウムイオンとリン酸イオンを同時に添加できるが、リン酸イオンとアンモニウムイオンのモル濃度比をコントロールするため、第一リン酸アンモニウムと第二リン酸アンモニウム、或いは第二リン酸アンモニウムと第三リン酸アンモニウムを混合して使用することが特に好ましい。また、リン酸塩以外のアンモニウム塩を使用する場合、リン酸以外のアニオン成分が過剰に存在すると、乾燥後の皮膜中でこれらの成分が水溶性成分として作用するため、できるだけその添加量を少なくすることが好ましい。
【０２４６】
皮膜形成用の水溶液中のリン酸成分は、水溶液のｐＨや添加するリン酸の重合度、酸化状態等によりその存在形態を変化させるため、リン酸成分の存在形態については特に規定しない。したがって、オルトリン酸、或いはピロリン酸、トリポリリン酸、テトラポリリン酸、ヘキサメタリン酸等の縮合リン酸、亜リン酸、次亜リン酸等の任意の形態で含まれるリン酸イオンのすべてを本発明で言うリン酸成分と定義する。
【０２４７】
水溶液に添加されるリン酸成分は、リン酸アンモニウム塩や、リン酸、ピロリン酸、トリポリリン酸、テトラポリリン酸、ヘキサメタリン酸、亜リン酸、次亜リン酸或いはこれらのアンモニウム塩等の形で添加することができる。
【０２４８】
本発明で用いる皮膜形成用の水溶液には、カチオン成分（α）として、さらにＭｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属イオンを添加することができる。
【０２４９】
これらのカチオン成分を含む場合には、プレス成形性及び化成処理性がさらに良好となる。その理由は必ずしも明らかではないが、水溶液塗布後の乾燥の過程でこれら金属イオンがリン酸との間で難溶性化合物を生成し、これが亜鉛系めっき鋼板のめっき層を均一に被覆できる緻密な皮膜形成に寄与するものと推定される。このように皮膜がより均一且つ緻密化するため、化成処理時の処理液との反応に悪影響を及ぼさない薄い膜厚でプレス成形性をより向上させる効果が得られ、これにより化成処理性及びプレス成形性をより高度に両立させることができる。
【０２５０】
また、上記金属イオンの中でもより好ましい成分としては、Ａｌ、Ｆｅ、Ｃｏが挙げられる。これらの金属イオンを添加した場合、化成処理液中で皮膜がより溶解し易くなるため、より優れた化成処理性を示す。
【０２５１】
また、皮膜形成用の水溶液中に金属イオンとしてＦｅを添加した場合には、化成処理におけるリン酸塩結晶の成長が殆ど阻害されないため、特に優れた化成処理性が得られる。その理由は必ずしも明らかではないが、水溶液中にＦｅを添加した場合には化成処理時に皮膜が残留している状態でも化成処理結晶が生成する。脱脂工程における複合皮膜の脱膜性はアルカリ脱脂液の状態や脱脂条件により大きく異なり、極端に劣化した脱脂液やスプレー処理のような強い脱脂が行われない条件下では、脱膜が十分に行われない可能性も高い。このような場合において、Ｆｅを添加した水溶液で処理を行うことが化成処理性に対して有効に作用する。
【０２５２】
また、一般に自動車や家電用途では溶接部の補強、耐食性の強化などの目的で接着剤による鋼板同士の接合が行われる。この際、潤滑特性を高めるために付与された皮膜の存在が接着接合性を著しく低下させることがある。従来のリン酸含有潤滑性皮膜では特にこの傾向が強く、その改善が望まれていた。このような課題に対して、上記水溶液中に金属イオンとしてＦｅを添加することにより接着剤適合性が著しく改善されることが判った。
【０２５３】
したがって、以上のような効果を期待する場合には、水溶液中に金属イオンとして少なくともＦｅを添加し、より好ましくは金属イオンとしてＦｅを単独で、或いは先に述べたＡｌとともに添加することが望ましい。
【０２５４】
水溶液中のカチオン成分（α）が実質的にアンモニウムイオン（ＮＨ₄ ⁺）と上記金属イオン（Ｍｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属イオン）からなる場合、それらカチオン成分（α）の合計とリン酸成分（β）の比率は、モル濃度比（α）／（β）（但し、リン酸成分はＰ₂Ｏ₅換算のモル濃度）で０．２０超え６以下、好ましくは０．４０以上６以下、さらに好ましくは０．６０以上４.００以下、特に好ましくは１.００以上４.００以下とする。
【０２５５】
モル濃度比（α）／（β）が０．２０以下ではリン酸成分が過剰となり、亜鉛とリン酸との結晶成分が形成され易く、優れた摺動特性が得られにくい。さらに、皮膜が化成処理時に脱離し難くなるため、化成処理性が低下する。また、モル濃度比（α）／（β）が６を超えると皮膜が不均一に形成されるため、薄膜の部分と厚膜の部分が共存しやすくなる。このため自動車製造過程での塗装前処理である化成処理時に処理液との反応が膜厚の厚い部分で阻害され、この結果、健全なリン酸塩結晶が生じにくくなり、化成処理不良が生じる。また、皮膜の均一性が低下するためプレス成形性の改善効果も小さい。さらに、皮膜の溶解性が高くなるため、湿潤環境において保管された場合や結露環境におかれた場合などに、皮膜の一部が溶解して電解質として作用し、亜鉛系めっき鋼板の腐食をもたらす。
【０２５６】
皮膜形成用の水溶液中に金属イオンとしてＡｌを添加する場合、Ａｌ（δ）とリン酸成分（β）のモル濃度比（δ）／（β）（但し、リン酸はＰ₂Ｏ₅換算モル濃度）は１／１０以上、２／３未満とすることが好ましく、これによりプレス成形性と化成処理性がさらに良好となる。これは、このようなモル濃度比の範囲において皮膜の均一性と皮膜溶解性がさらに高くなるためであると考えられる。モル濃度比（δ）／（β）が２／３以上ではＡｌが過剰となるため結晶性の成分が現われやすくなり、皮膜も難溶化しやすくなるものと考えられる。
【０２５７】
Ｍｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属イオンは、リン酸塩のほかに、硝酸塩、硫酸塩、酢酸塩等の水溶性の金属塩の形で添加することができる。また、上記金属を含む酸化物又は水酸化物をオルトリン酸と反応させて得られた水溶液を用いてもよい。この場合には、カチオン成分（α）とリン酸成分（β）のモル濃度比が上述の範囲となるように調合するとよい。さらに、遊離リン酸量ができるだけ少なくなるように、金属カチオン成分とリン酸成分を所定の温度、時間で反応させた水溶液を利用すると、皮膜のネットワーク性が高まり特に好適である。
【０２５８】
本発明で用いる皮膜形成用の水溶液に含まれるカチオン成分（α）は、実質的にアンモニウムイオン（ＮＨ₄ ⁺）、さらに必要に応じて添加される上記金属イオン（Ｍｇ、Ａｌ、Ｃａ、Ｔｉ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏの中から選ばれる１種又は２種以上の金属イオン）からなり、したがって不純物として含まれるカチオン成分を除き、他のカチオン成分は添加しない。
【０２５９】
特に、アルカリ金属は皮膜に可溶性成分が残存しやすいため好ましくない。また、亜鉛イオンは結晶質の皮膜となりやすいため好ましくない。
【０２６０】
またアニオン成分については、カチオン成分を硝酸塩、硫酸塩、酢酸塩などの酸化物、水酸化物やリン酸塩以外の塩として水溶液に添加する場合、硝酸イオン、硫酸イオン、酢酸イオンなどのアニオン成分が存在しても良い。本発明で用いる皮膜形成用の水溶液中には、さらに適量のシリカ（ε）を添加してもよく、これによりさらに良好なプレス成形性及び化成処理性を示す皮膜が形成される。シリカを添加することにより、薄膜でのプレス成形性の向上効果がより顕著に発現する。これは、シリカの添加により皮膜形成用の水溶液の濡れ性が改善され、めっき層に対してミクロ的なはじきの無い均一な皮膜が形成されるためであると考えられる。そして、このように薄い皮膜であってもプレス成形性の向上効果がより顕著に発現するため、化成処理時の皮膜の脱離がより容易に生じ、化成処理性が良好となる。
【０２６１】
シリカ（ε）の添加量は、リン酸成分とのモル濃度比（ε）／（β）（但し、シリカはＳｉＯ₂換算のモル濃度、リン酸成分はＰ₂Ｏ₅換算のモル濃度）が０．０１〜５０となる量とする。
【０２６２】
モル濃度比（ε）／（β）が０．０１未満ではシリカ添加による効果が十分に得られない。一方、モル濃度比（ε）／（β）が５０を超えると、シリカ成分が過剰に存在することになるため、プレス成形時にシリカ成分が削りとられ、押し疵状の表面欠陥やカジリの要因となる。
【０２６３】
シリカ（ε）は、シリカゾルやヒュームドシリカ等の乾式シリカを水溶液中に直接添加すればよい。
【０２６４】
シリカゾルとしては、例えば日産化学工業（株）製の“スノーテックス”（商品記号：Ｏ、ＯＳ、ＯＵＰ、ＡＫ、Ｎ、２０、３０、４０）や、触媒化成工業（株）製の“カタロイド”（商品記号：Ｓ、ＳＩ、ＳＡ、ＳＮ）、旭電化工業（株）製の“アデライト”（商品記号：ＡＴ−２０、ＡＴ−５０、ＡＴ−２０Ｎ、ＡＴ−３００、ＡＴ−３００Ｓ、ＡＴ−２０Ｑ）等が挙げられる。この中でも、アンモニウムイオンにより表面電位を中和したタイプが特に好ましい。また、ヒュームドシリカとしては、例えば日本アエロジル（株）製の“ＡＥＲＯＳＩＬ２００”、“ＡＥＲＯＳＩＬ３００”等が挙げられる。
【０２６５】
本発明で用いる皮膜形成用の水溶液中には、さらに有機樹脂成分を適量添加してもよく、これにより形成される皮膜の潤滑性がさらに向上する。この有機樹脂としては、他の無機成分と水溶液中で共存できる水溶性樹脂及び／又は水分散性樹脂が好ましい。これら有機樹脂としては、エポキシ系樹脂、アクリル系樹脂、アクリル−エチレン共重合体、アクリル−スチレン共重合体、アルキド樹脂、ポリエステル樹脂、ウレタン系樹脂、ポリブタジエン系樹脂、ポリアミド系樹脂などが挙げられる。さらに、これら樹脂に加えて、水溶性エポキシ樹脂、水溶性フェノール樹脂、水溶性ブタジエンラバー（ＳＢＲ、ＮＢＲ、ＭＢＲ）、メラミン樹脂、ブロックイソシアネート、オキサゾリン化合物などを架橋剤として併用することが有効である。
【０２６６】
複合皮膜中の有機樹脂の付着量は、皮膜形成用の水溶液中の樹脂濃度を適宜変えることにより調整することができる。水溶液中の樹脂濃度は、複合皮膜中での樹脂付着量が０．０１〜１０００ｍｇ／ｍ²となるような濃度とすることが好ましい。複合皮膜中での樹脂付着量が０．０１ｍｇ／ｍ²未満ではその効果が十分に得られず、一方、１０００ｍｇ／ｍ²を超えると皮膜が厚くなり、皮膜剥離を生じやすくなるため十分な効果が得られない。
【０２６７】
また、本発明で使用する水溶液には、さらにカルボン酸を含有させることができ、これにより化成処理前のアルカリ脱脂における皮膜の溶解性が特に高くなる。これは、カルボン酸のような有機酸を含有した水溶液を塗布・乾燥することにより皮膜が可溶性となり、脱膜すなわち溶解し易くなるためであると推定される。カルボン酸としては、ぎ酸、酢酸、乳酸、シュウ酸、クエン酸などがあげられるが、特に、オキシカルボン酸（又はオキシ酸ともいう）の場合に皮膜の溶解性が高くなる。これは、リン酸成分と金属元素成分がオキシカルボン酸との組み合わせにより、ガラス質の溶解しやすい皮膜を形成するためであると推定される。皮膜が溶解しやすい理由としては、オキシカルボン酸が有する水酸基の存在が皮膜の親水性を高め、皮膜内部へのアルカリ脱脂液の浸透が高まるため脱膜性が向上するか、或いは皮膜そのものが溶解し易くなるためであると考えられる。オキシカルボン酸としては酒石酸、乳酸、グリセリン酸、リンゴ酸、サリチル酸、クエン酸などが挙げられるが、特にクエン酸が有効である。
【０２６８】
また、本発明では皮膜形成用の水溶液にカチオン成分として上述した特定の金属イオンを添加するが、水溶液中での金属イオン濃度が高く、水溶液のｐＨが３を超えるよう高ｐＨになると水溶液が安定に存在できなくなるおそれがある。例えば、Ｆｅイオンの場合にはリン酸成分と共存させると水溶液がゲル化しやすい傾向にある。このような場合、ぎ酸、酢酸、乳酸、シュウ酸、酒石酸、クエン酸などのような金属イオンと錯体を形成するカルボン酸を添加することにより、水溶液のゲル化が抑制できる。
【０２６９】
特に、水溶液にＦｅイオンを添加したものについては、これにクエン酸を添加することにより水溶液としての安定性が向上し、ゲル化しにくくなるため特に有効である。
【０２７０】
これらのカルボン酸成分を水溶液中に存在させる方法に特別な制限はないが、一般にはカルボン酸又は各種金属のカルボン酸塩を水溶液に溶解させるのがよい。具体的には、ギ酸、酢酸、乳酸、シュウ酸、クエン酸、酒石酸、或いはクエン酸鉄やクエン酸鉄アンモニウムなどの鉄塩を水溶液に溶解させる。
【０２７１】
皮膜形成用の水溶液中でのカルボン酸の濃度としては、水溶液中でのリン酸成分（Ｐ₂Ｏ₅換算量）：１モルに対して、カルボン酸が０．００１〜５モルの範囲となるようにするのが望ましい。カルボン酸の濃度が０．００１モル未満では効果が十分でなく、一方、５モルを超えると皮膜が吸湿しやすくなり、腐食などが生じやすくなる。カルボン酸濃度の特に好ましい範囲は、リン酸成分（Ｐ₂Ｏ₅換算量）：１モルに対して０．０１〜１モル、さらに好ましくは０．０５〜０．５モルである。
【０２７２】
皮膜形成用の水溶液中でのカチオン成分（α）、リン酸成分（β）、シリカ（ε）の好ましい濃度は、以下の通りである。カチオン成分（α）の濃度は０．０１〜３ｍｏｌ／Ｌ、さらに好ましくは０．０２〜２ｍｏｌ／Ｌの範囲が望ましい。カチオン成分（α）の濃度が過剰であると皮膜厚の不均一化を招くため好ましくない。また、リン酸成分（β）の濃度はＰ₂Ｏ₅換算で０．０５〜２ｍｏｌ／Ｌ、さらに好ましくは０．０５〜１ｍｏｌ／Ｌの範囲が望ましい。リン酸成分（β）の濃度が過剰であると水溶液の反応性が高まるため好ましくない。さらに、シリカ（ε）の濃度は０．０００１〜６ｍｏｌ／Ｌ、さらに好ましくは０．１〜１．０ｍｏｌ／Ｌの範囲が望ましい。シリカ（ε）の濃度が過剰であると皮膜厚の不均一化を招くため好ましくない。
【０２７３】
本発明によりめっき層表面に形成される皮膜の付着量（固形分）は、Ｐの付着量として５〜３００ｍｇ／ｍ²、好ましくは１０〜１５０ｍｇ／ｍ²、特に好ましくは３０〜１２０ｍｇ／ｍ²である。皮膜付着量が上記下限値を下回るとプレス成形性の向上効果が十分に得られず、一方、上記上限値を超えると化成処理性が低下する。
【０２７４】
本発明で使用する皮膜形成用の水溶液は、通常、上述した添加成分を脱イオン水に溶解して作製する。
【０２７５】
水溶液を塗布する亜鉛系めっき鋼板は、塗布処理の前に活性化処理等の処理を施してもよい。活性化処理としては、めっき鋼板をアルカリ性水溶液や酸性水溶液中に浸漬したり、これら水溶液をスプレー処理することなどにより行われる。
【０２７６】
本発明において亜鉛系めっき鋼板に皮膜形成用の水溶液を塗布する方法としては、塗布法、浸漬法、スプレー法などの任意の方法を採用できる。塗布法としては、ロールコーター（３ロール方式、２ロール方式等）、スクイズコーター、ダイコーター、バーコーターなどのいずれの手段を用いてもよい。また、スクイズコーター等による塗布処理、浸漬処理又はスプレー処理の後にエアナイフ法やロール絞り法により塗布量の調整、外観の均一化、膜厚の均一化を行うことも可能である。
【０２７７】
水溶液の塗布後、水洗することなく加熱乾燥を行う。加熱乾燥処理には、ドライヤー、熱風炉、高周波誘導加熱炉、赤外線炉等を用いることができる。加熱処理は到達板温で５０〜２００℃、好ましくは５０〜１４０℃の範囲で行うことが望ましい。加熱温度が５０℃未満では皮膜中の水分が多量に残存し、シミ状の欠陥を発生し易い。また、加熱温度が１４０℃を超えると非経済的であり、さらに２００℃を超えると皮膜が脆くなり剥離しやすくなる。
【０２７８】
皮膜形成用の水溶液の温度は特に規定されないが、２０〜７０℃が好適である。水溶液の温度が２０℃未満では液の安定性が低下する。一方、水溶液の温度が７０℃を超えると、水溶液を高温に保持するための設備や熱エネルギーを要し、製造コストの上昇を招き不経済である。
【０２７９】
［実施例１］
この実施例では以下に示す各種亜鉛系めっき鋼板を用いた。
【０２８０】
(1) ＧＡ：合金化溶融亜鉛めっき鋼板（１０mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４５ｇ/ｍ²である。
【０２８１】
(2) ＧＩ：溶融亜鉛めっき鋼板であり、めっき付着量は両面ともに９０ｇ／ｍ²である。
【０２８２】
(3) ＥＧ：電気亜鉛めっき鋼板であり、めっき付着量は両面ともに５０ｇ／ｍ²である。
【０２８３】
(4) Ｚｎ−Ｆｅ：電気Ｚｎ−Ｆｅ合金めっき鋼板（１５mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４０ｇ／ｍ²である。
【０２８４】
(5) Ｚｎ−Ｎｉ：電気Ｚｎ−Ｎｉ合金めっき鋼板（１２mass％Ｎｉ、残部Ｚｎ）であり、めっき付着量は両面ともに３０ｇ／ｍ²である。
【０２８５】
(6) Ｚｎ−Ａｌ：溶融Ｚｎ−Ａｌ合金めっき鋼板（５mass％Ａｌ、残部Ｚｎ）であり、めっき付着量は両面ともに６０ｇ／ｍ²である。
【０２８６】
以上の亜鉛系めっき鋼板のめっき層表面に対し、以下に示すような処理を施した。なお、処理する亜鉛系めっき鋼板は、トルエンを用いた溶剤脱脂またはアルカリ脱脂によりプレス油を除去したものを使用した。
【０２８７】
使用した処理液は、表１８〜表２０に示した組成となるように、▲１▼アンモニア水、▲２▼第一リン酸アンモニウム（リン酸二水素アンモニウム）、▲３▼第二リン酸アンモニウム（リン酸水素二アンモニウム）、▲４▼第三リン酸アンモニウム（リン酸三アンモニウム）の１種又は２種以上と、オルトリン酸と、さらに必要に応じて配合される各種カチオン成分を含む酸化物又は水酸化物とを所定の比率で脱イオン水に混合して調整したリン酸塩水溶液、又はこれに各種カチオン成分を含む金属塩と、さらに必要に応じてシリカ又は水溶性樹脂（水溶性エポキシ樹脂）を適宜混合して調整したリン酸塩水溶液である。
【０２８８】
また、シリカ成分としては、日産化学（株）製の“スノーテックスＮ”を所定のモル濃度となるように適宜添加した。
【０２８９】
表１８〜表２０に示した処理液（室温）を、室温にて上記亜鉛系めっき鋼板の表面にロールコーター又はバーコーターにより塗布し、加熱乾燥して皮膜を形成させた。形成される皮膜の付着量は、組成物の濃度及び塗布条件（ロールの圧下力、回転速度、バーコーターの番手等）により適宜調整した。
【０２９０】
また、皮膜の付着量の測定は以下のようにして行った。まず、皮膜付着量が異なる亜鉛系めっき鋼板について、めっき層を皮膜ごと希塩酸により溶解剥離し、この溶解液中のＰ濃度をＩＣＰ分析により定量した。上記溶解剥離を行うめっき鋼板箇所（２個所）の中央部におけるＰの蛍光Ｘ線強度を予め測定しておき、このＰの蛍光Ｘ線強度とＩＣＰで得られた上記Ｐ濃度との関係式を求めた。そして、各供試材のＰの蛍光Ｘ線強度を測定し、この測定値から上記関係式に基づき各供試材の皮膜のP付着量を求めた。
【０２９１】
また、複合皮膜に存在するＮ成分量（アンモニウム換算量）は以下のようにして求めた。まず、複合皮膜をめっき皮膜とともに塩酸水溶液に溶解した後、溶解液中のアンモニウムを蒸留により遊離してアルカリ性水溶液に吸収し、この液中のアンモニウム濃度をインドフェノール青吸光光度法により定量し、皮膜中のＮＨ₄量を特定した。得られた値は、Ｎのモル濃度に換算した。また、複合皮膜中の金属元素量とＰ成分量（Ｐ₂Ｏ₅換算量）は以下のようにして求めた。まず、亜鉛系めっき鋼板に形成した複合皮膜をめっき層ごと希塩酸に溶解し、この溶解した皮膜構成元素を定量した。一方、複合皮膜形成前の亜鉛系めっき鋼板のめっき層を希塩酸で溶解して同じく皮膜構成元素を定量し、この金属元素成分量を先に述べた複合皮膜をめっき層ごと溶解して得られた金属元素成分量から差し引き、これを皮膜構成元素量とした。この際、測定対象面積は０．０６ｍ²とした。また、複合皮膜中の有機樹脂成分量は、皮膜成分の酸による溶解液を比色法で定量することにより求めた。
【０２９２】
以上のようにして得られた亜鉛系めっき鋼板の性能評価は下記のようにして行った。
【０２９３】
(1) プレス成形性
プレス成形性を評価するために、各供試材の摩擦係数を図１に示す摩擦係数測定装置により測定した。
【０２９４】
なお、潤滑油としては、パーカー興産（株）製の“ノックスラスト５５０ＨＮ”を試料１の表面に塗布して試験を行った。供試材とビード６との間の摩擦係数μは、式：μ＝Ｆ／Ｎで算出した。なお、押付荷重Ｎ：４００ｋｇｆ、試料の引き抜き速度（スライドテーブル３の水平移動速度）：１００ｃｍ／ｍｉｎとした。
【０２９５】
図２は、使用したビード６の形状・寸法を示す斜視図である。
【０２９６】
(2)化成処理性
［評価１］
プレス成形後の試料の状態を想定して、各供試材に潤滑油（パーカー興産（株）製の“ノックスラスト５５０ＨＮ”）を塗布し、その後、「下記▲１▼の条件による脱脂→水洗→乾燥→下記▲２▼の条件による表面調整→下記▲３▼又は▲３▼′の条件による化成処理→水洗→乾燥」という工程で化成処理を施した。
【０２９７】
▲１▼ 脱脂：日本パーカライジング（株）製の“ＦＣ−４４６０”、スプレー時間：６０秒（スプレー圧：１ｋｇｆ／ｃｍ２）、脱脂液温度：４３℃
▲２▼ 表面調整：日本パーカライジング（株）製の“ＰＬ−Ｚ”、薬液濃度：１．５ｇ／ｌ、浸漬時間：２０秒、処理液温度：室温
▲３▼ 化成処理：日本パーカライジング（株）製の“ＰＢ−３０３０”、浸漬時間：１２０秒、処理液温度：５２℃
▲３▼′化成処理：日本パーカライジング（株）製の“ＰＢ−３０２０”（フッ素含有系）、浸漬時間：１２０秒、処理液温度：４３℃
それぞれ上記２種類の化成処理を行った後、化成処理後のリン酸塩結晶形態をＳＥＭにて観察し、下記により評価した。
【０２９８】
◎：平均のリン酸塩結晶サイズが８μｍ未満であり、スケが無く緻密に形成されている。
【０２９９】
○：平均のリン酸塩結晶サイズが８μｍ以上１２μｍ未満であり、スケが無く緻密に形成されている。
【０３００】
○−：平均のリン酸塩結晶サイズが１２μｍ以上であるが、スケが認められない。
【０３０１】
△：平均のリン酸塩結晶サイズが１２μｍ未満で、且つスケも無く緻密に形成されている部分と、リン酸塩結晶が全く形成されていない部分とが混在している。
【０３０２】
×：平均のリン酸塩結晶が粗大化し（結晶サイズが１２μｍ以上）、スケが多く認められる。或いはリン酸塩結晶が全く成長していない。
［評価２］
また、さらに厳しい化成処理性評価を行うため、脱脂スプレーの当たりが悪いために脱脂工程における脱膜作用が十分に得られないような状況を想定し、上記［評価１］の化成処理性試験における「脱脂工程」を省略した化成処理を実施した。すなわち、上記▲１▼の脱脂工程を行うことなく、「上記▲２▼の条件による表面調整→上記▲３▼′の条件による化成処理→水洗→乾燥」という工程で化成処理を施した。なお、この化成処理性試験では［評価１］の化成処理性試験のようなプレス油の塗布は実施しなかった。また、化成処理液としては日本パーカライジング（株）製のＰＢ−３０８０を用いた。
【０３０３】
上記化成処理を行った後、リン酸塩結晶形態をＳＥＭにて観察し、下記により評価した。
【０３０４】
◎ ：平均のリン酸塩結晶サイズが８μｍ以上、１２μｍ以下であり、スケが無く緻密に形成されている。
【０３０５】
○ ：平均のリン酸塩結晶サイズが１２μｍ以上であるが、スケが認められない。
【０３０６】
○−：リン酸塩結晶が形成されている部分と、リン酸塩結晶が形成されていない部分が混在している。
【０３０７】
△ ：ほとんどの領域でリン酸塩結晶が成長していないが、一部箇所で微細な結晶が認められる。
【０３０８】
× ：全くリン酸塩結晶が成長していない。
【０３０９】
表２１〜表２９に、各供試材の処理条件と上記性能評価の結果を示す。これら表において、Ｎｏ．１１、Ｎｏ．５３は処理液中のアンモニウムイオンとリン酸イオンの濃度比率が本発明範囲よりも低く、リン酸イオンが過剰であるため摩擦係数も高く、化成処理性も不良である。また、Ｎｏ．１２、Ｎｏ．５４は処理液中のカチオン濃度が高いため皮膜が不均一であり、このため外観不良を生じている。また、Ｎｏ．２９、Ｎｏ．７１は処理液中のカチオン成分としてＺｎを含むため、結晶質成分が多くなり、摩擦係数が高い。また、エッチング性の高いフッ素含有系の化成処理（ＰＢ−３０２０）での化成処理性は良好であるものの、他の化成処理液では化成処理性が不良である。
【０３１０】
Ｎｏ．３０、Ｎｏ．７２は処理液中のカチオン成分にアルカリ金属が含しているため皮膜が不均一となり、膜厚に分布を生じているため摩擦係数が高い。また、エッチング性の高いフッ素含有系の化成処理（ＰＢ−３０２０）での化成処理性は良好であるものの、他の化成処理液では化成処理性が不良である。
【０３１１】
Ｎｏ．３７、Ｎｏ．３８、Ｎｏ．３９、Ｎｏ．７９、Ｎｏ．８０、Ｎｏ．８１は処理液中にアンモニウムイオンを含まないため摩擦係数が高く、且つ化成処理性が不良である。
【０３１２】
Ｎｏ．９４、Ｎｏ．９５、Ｎｏ．９６はめっき層表面に皮膜が存在しないため、化成処理性は良好であるが摩擦係数が高い。
【０３１３】
以上の比較例に対して本発明例は化成処理性に優れるか、或いはプレス成形性が優れ且つ異なる化成処理条件で処理しても化成処理性の劣化が小さく、プレス成形性と化成処理性が両立している。
【０３１４】
【表１８】

【０３１５】
【表１９】

【０３１６】
【表２０】

【０３１７】
【表２１】

【０３１８】
【表２２】

【０３１９】
【表２３】

【０３２０】
【表２４】

【０３２１】
【表２５】

【０３２２】
【表２６】

【０３２３】
【表２７】

【０３２４】
【表２８】

【０３２５】
【表２９】

［実施例２］
この実施例では以下に示す亜鉛系めっき鋼板を用いた。
【０３２６】
(1) ＧＡ：合金化溶融亜鉛めっき鋼板（１０mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４５ｇ/ｍ²である。
【０３２７】
(2) ＧＩ：溶融亜鉛めっき鋼板であり、めっき付着量は両面ともに９０ｇ／ｍ²である。
【０３２８】
以上の亜鉛系めっき鋼板のめっき層表面に対し、以下に示すような処理を施した。なお、処理する亜鉛系めっき鋼板は、アルカリ脱脂によりプレス油を除去したものを使用した。
【０３２９】
皮膜形成用の水溶液のうち、金属イオンとしてＦｅイオンを含むものについては、クエン酸鉄と第一リン酸アンモニウムを各成分が所定の濃度となるように脱イオン水に溶解させた。また、硫酸第一鉄とオルトリン酸を各成分が表３０に記載の濃度となるように脱イオン水に溶解させた水溶液に、硫酸イオン含有リン酸第一鉄、クエン酸を適宜添加した水溶液も使用した。
【０３３０】
表３０に示した処理液（室温）を、室温にて上記亜鉛系めっき鋼板の表面にロールコーター又はバーコーターにより塗布し、加熱乾燥して皮膜を形成させた。形成される皮膜の付着量は、組成物の濃度及び塗布条件（ロールの圧下力、回転速度、バーコーターの番手等）により適宜調整した。
【０３３１】
また、皮膜の付着量の測定、皮膜中のＮ成分量、金属元素量とＰ成分量の測定は、実施例１と同様にして行った。
【０３３２】
比較例として、従来の塗布タイプのプレフォス処理を亜鉛系めっき鋼板の表面に皮膜付着量を変えて施した。塗布タイプのプレフォスの皮膜付着量は、重クロム酸アンモニウム２０ｇ、２５％アンモニア水４９０ｇを１Ｌのイオン交換水に溶かした溶液中で皮膜を溶解し、溶解前後の重量変化により算出した。また、皮膜中のＰ量は後述する脱膜性評価に記載の方法と同様にＦＸにより測定した。
【０３３３】
以上のようにして得られた亜鉛系めっき鋼板の性能評価は、下記のようにして行った。
【０３３４】
(1) プレス成形性：実施例１と同じ
(2) 化成処理性：実施例１と同じ
(3) 脱脂時の脱膜性
本発明例及び比較例の亜鉛系めっき鋼板のサンプル（１５０ｍｍ×７０ｍｍ）にプレス量としてパーカー興産（株）製の“ノックスラスト５５０ＨＮ”を１．５〜２．０ｇ/ｍ²の付着量で塗布した後、以下の条件でアルカリ脱脂を行った。使用したサンプルの皮膜中のＰ付着量は、当該サンプルの採取位置を挟む位置から採取した４８ｍｍφのサンプルのＰ付着量をＦＸにより定量し、その平均値をＰ付着量とした。
【０３３５】
脱脂後のサンプルのほぼ中央位置の４８ｍｍφ部分をサンプリングし、ＦＸによりこの部分のＰ付着量を定量した。初期Ｐ付着量と脱脂後のＰ付着量から以下の式により脱膜率を算出した。
【０３３６】
脱膜率＝１−（［脱脂後Ｐ付着量］／［初期Ｐ付着量］）
・アルカリ脱脂条件
脱脂液が劣化した条件を想定して、アルカリ脱脂液（日本パーカライジング（株）製の“ＦＣ４４８０”）に防錆油（日本パーカライジング（株）製の“ノックスラスト５５０ＨＮ”）を５ｇ／ｌ添加したものを用い、浸漬法により脱脂を行った。浸漬時間は１２０秒、脱脂液の温度は４３℃とした。脱脂はプロペラ型の攪拌器を回転（回転数：３００ｒｐｍ）させた３０Ｌの円筒の容器を用いて浸漬処理により行った。
(4) 接着接合性
２５ｍｍ×２００ｍｍのサンプルの防錆油を溶剤脱脂により除去した後、洗浄油（スギムラ化学（株）製の“プレトンＲ３５２Ｌ”）を塗布した。このサンプルを２枚一組とし、塩ビ系のヘミング用接着剤を２５ｍｍ×１４０ｍｍの範囲に塗布し（サンプルの端から５０ｍｍは接着剤を塗布せず）、０．１５ｍｍ厚のスペーサーを介して貼り合わせて試験片を作成した。これを１６０℃×１０分で乾燥させた後、２４〜７２時間の間、常温にて放置し、その後、引張り試験機を用いて試験片がＴ型の状態から２枚の試験片が剥離するまで引っ張り、この引っ張り時の試験片の平均強度を測定した。
【０３３７】
表３１及び表３２に各供試材の処理条件と上記性能評価の結果を示すが、比較例に較べて本発明例は化成処理性及びプレス成形性だけでなく、脱膜性と接着接合性にも優れている。
【０３３８】
【表３０】

【０３３９】
【表３１】

【０３４０】
【表３２】

（実施の形態3）
本願発明者らは、実施の形態１および２で示した本願発明複合皮膜のリン系酸化物構造を従来技術の結晶性リン酸塩皮膜と比較し、プレス成形性、化成処理性、接着接合性との関係について評価し、前記特性に優れる皮膜構造を見出した。更に、化成処理液の劣化をより抑制する皮膜構造を見出した。その特徴は以下のとおりである。
[1] 亜鉛系めっき鋼板のめっき層表面に形成した複合皮膜のＸＡＮＥＳ法により測定されたP―K edgeのスペクトルが、Ｚｎ₃（ＰＯ₄）₂・4Ｈ₂ＯのＸＡＮＥＳスペクトルを基準としたＲ−factorで０．０２以上の値を示すことを特徴とする亜鉛系めっき鋼板。
[2] 前記複合皮膜のＸＡＮＥＳ法により測定されたP―K edgeのスペクトルの半価幅が、Ｚｎ₃（ＰＯ₄）₂・4Ｈ₂Ｏのそれを1とした場合、１．０３以上の値を有することを特徴とする亜鉛系めっき鋼板。
【０３４１】
上記の皮膜構造を見出したのは、本願発明複合皮膜のリン系酸化物と従来技術の結晶質もしくは非晶質リン酸塩皮膜との特性の相違はリンを含む構造に起因すると推察し、両者を形成させた亜鉛系めっき鋼板の表面をＸＡＮＥＳ法（X-ray Absorption Near Edge Structure）で調査した成果である。ＸＡＮＥＳは注目する元素のＸ線吸収端エネルギー前後でのＸ線の吸収スペクトル（入射Ｘ線のエネルギーを変化させながら、試料によるＸ線吸収率を測定して得られるスペクトル）に現れるスペクトル形状のことである。ＸＡＮＥＳは測定対象が結晶質、非晶質いずれであっても、着目する元素の電子状態やその周囲の短距離の原子配列を反映した構造を示すので、結晶質、非晶質いずれであっても、その電子状態や短距離原子配列を調査する有効な手段である。
【０３４２】
ここで、前記両者のＸＡＮＥＳ測定結果の違いを明確にする為に、Ｒ−factorを用いた。Ｒ−factorはスペクトルの差分を評価するファクターであり、
Ｒ-factor＝Σ(χobs(E)−χcal(E))²／Σχobs(E)²
と定義される。両者のスペクトルが同一であれば、Ｒ−factorは０となり、両者のスペクトルの差が大きいほどＲ−factorは大きな値となる。χobs(E)はＸ線のエネルギーＥでの試料のスペクトル強度、χcal(E)が標準試料のスペクトル強度である。
【０３４３】
図３には、従来技術の結晶性リン酸亜鉛皮膜を表面に形成させた亜鉛めっき鋼板のＸＡＮＥＳスペクトルを示した。
【０３４４】
複合皮膜のP―K edgeＸＡＮＥＳスペクトル（PのK吸収端で測定したＸＡＮＥＳスペクトル）が、Ｚｎ₃（ＰＯ₄）₂・4Ｈ₂Ｏ（結晶質ホパイト）のＸＡＮＥＳスペクトルを基準としたＲ−factorで０．０２以上の値を示す場合により良好な化成処理性を示す。前述のようにＲ−factorはスペクトルの差分を評価するファクターであり、その値が０．０２以上であるということは、本願発明の複合皮膜構造にはホパイトの短距離原子配列との違いが存在することを意味する。一方、従来技術皮膜のＲ−factorは０．０２より小さい値をとるが、これは、従来技術皮膜の短距離原子配列がホパイトに近いことを意味する。
【０３４５】
化成処理としては一般にリン酸亜鉛処理が行われ、結晶質のホパイト皮膜が生成する。従来技術ではリン酸亜鉛処理に先立って、事前に非晶質もしくは結晶質のホパイト皮膜を生成させた状態になっているために、既に表面に生成しているリン酸亜鉛皮膜は後段のリン酸亜鉛処理で溶解しづらく、リン酸亜鉛結晶の正常成長が阻害されるものと考えられる。これに対して、本願発明では複合皮膜がホパイトとは異なる短距離原子配列を有するためにリン酸亜鉛処理液中で皮膜が溶解し、その後のリン酸亜鉛結晶の生成が均一に起こるものと考えられる。
【０３４６】
また、複合皮膜のＸＡＮＥＳ（X-ray Absorption Near Edge Structure）法により測定されたP―K edgeのスペクトルの半価幅が、Ｚｎ₃（ＰＯ₄）₂・4Ｈ₂Ｏのそれを１とした場合、１．０３以上の値を有する場合に化成処理液の劣化が抑制される。これは、リン酸イオン同士の結合強度が上がると、半価幅が大きくなるが、その場合には、リン系酸化物皮膜（複合皮膜）中に脱脂液や油成分の進入が抑制され、化成処理液への混入量が低下して、化成処理液の劣化が抑制されるからであると考えられる。
［実施例１］
この実施例では以下に示す各種亜鉛系めっき鋼板を用いた。
【０３４７】
(1) ＧＡ：合金化溶融亜鉛めっき鋼板（１０mass％Ｆｅ、残部Ｚｎ）であり、めっき付着量は両面ともに４５ｇ/ｍ²である。
【０３４８】
本鋼板に対し、以下に示すような処理を施した。なお、処理する合金化溶融亜鉛めっき鋼板は、アルカリ脱脂によりプレス油を除去したものを使用した。
重量比でＦｅＳＯ₄：Ｈ₃ＰＯ₄＝４：５となる水溶液、もしくはリン酸アンモニウム：クエン酸第二鉄＝３．２：２．０となる水溶液を、室温にて上記亜鉛系めっき鋼板の表面にロールコーター又はバーコーターにより塗布し、加熱乾燥して皮膜を形成させた。形成される皮膜の付着量は、組成物の濃度及び塗布条件（ロールの圧下力、回転速度、バーコーターの番手等）により適宜調整した。比較試料としては従来の塗布型プレフォス処理を施した上記亜鉛系めっき鋼板を用いた。
【０３４９】
また、皮膜の付着量の測定は以下のようにして行った。まず、皮膜付着量が異なる亜鉛系めっき鋼板について、めっき層を皮膜ごと希塩酸により溶解剥離し、この溶解液中のＰ濃度をＩＣＰ分析により定量した。上記溶解剥離を行うめっき鋼板箇所（２個所）の中央部におけるＰの蛍光Ｘ線強度を予め測定しておき、このＰの蛍光Ｘ線強度とＩＣＰで得られた上記Ｐ濃度との関係式を求めた。そして、各供試材のＰの蛍光Ｘ線強度を測定し、この測定値から上記関係式に基づき各供試材の皮膜のP付着量を求めた。
【０３５０】
ＸＡＮＥＳ測定は試料吸収電流測定による全電子収量ＸＡＮＥＳ（ＴＥＹ−ＸＡＮＥＳ）法で行った（N Okude, H Noro, M Nagoshi, H Yamamoto, Y Baba and T A Sasaki, J. Electron Spectrosc. Relat. Phenom., 88-91 (1998) 467）。試料にＸ線を照射した場合Ｘ線吸収率に相当する量の電子が試料から放出される。ＴＥＹ−ＸＡＮＥＳ法は、その際に流れる試料電流を測定することでＸＡＮＥＳスペクトルを測定する手法である。各試料について、Ｚｎ₃（ＰＯ₄）₂・４Ｈ₂ＯのP-K edge ＸＡＮＥＳスペクトル（図３）を基準としたＲ−factorの算出、半価幅の比較を行った。Ｒ−factorは次式で定義される。
【０３５１】
Ｒ＝Σ(χobs(E)−χcal(E))²／Σχobs(E)²
χobs(E)はＸ線のエネルギーＥでの試料のスペクトル強度、χcal(E)が標準試料のスペクトル強度である。
【０３５２】
Ｒ−factorの算出にはリガク電機のＸＡＦＳ解析用ソフト「ＲＥＸ２０００」を用い次のようにして行った。
▲１▼以下のVictoreenの式を用いて、バックグラウンドを除去する。
【０３５３】
Dλ⁴+Cλ³ λ：波長
この時にスペクトルの高エネルギー端（〜２１９０ｅＶ）付近における強度が ０．１５±０．０１程度（ピークトップが１）になるように揃える。
▲２▼ピークトップが１になるようにNormalizeする
▲３▼ＺｎＰＯ₄のスペクトルとフィッティングしてＲ−factorを導出する
（ＺｎＰＯ₄のスペクトルも▲２▼と同様にNormalizeしている）
（フィッティングのエネルギー範囲：２１３６〜２１９０ｅＶ)
▲４▼フィッティングの際にＲ−factorを最小にするようにスペクトルに重みがかけられるので、得られたＲ−factorをその係数で除算して最終的なＲ−factorとする
亜鉛系めっき鋼板の性能評価は下記のようにして行った。
(1) プレス成形性
プレス成形性の評価は実施の形態1、２と同様な方法で行った。
(2)化成処理性
プレス成形後の試料の状態を想定して、各供試材に潤滑油（パーカー興産（株）製の“ノックスラスト５５０ＨＮ”）を塗布し、その後、「下記▲１▼の条件による脱脂→水洗→乾燥→下記▲２▼の条件による表面調整→下記▲３▼の条件による化成処理→水洗→乾燥」という工程で化成処理を施した。
【０３５４】
▲１▼脱脂：脱脂液が劣化した条件を想定して、アルカリ脱脂液（日本パーカライジング（株）製の“ＦＣ４４８０”）に防錆油（日本パーカライジング（株）製の“ノックスラスト５５０ＨＮ”）を５ｇ／ｌ添加したものを用い、浸漬法により脱脂を行った。浸漬時間は１２０秒、脱脂液の温度は４３℃とした。脱脂はプロペラ型の攪拌器を回転（回転数：３００ｒｐｍ）させた３０Ｌの円筒の容器を用いて浸漬処理により行った。
【０３５５】
▲２▼表面調整：日本パーカライジング（株）製の“ＰＬ−Ｚ”、薬液濃度：１．５ｇ／ｌ、浸漬時間：２０秒、処理液温度：室温
▲３▼化成処理：日本パーカライジング（株）製の“ＰＢ−L３０３０M”、浸漬時間：１２０秒、処理液温度：５２℃
それぞれ上記の化成処理を行った後、化成処理後のリン酸塩結晶形態をＳＥＭにて観察し、下記により評価した。
【０３５６】
○：ＧＡ、ＧＩ上と同等のリン酸塩結晶が生成している。
【０３５７】
×：リン酸塩が非晶質化、もしくは形状が不定。
【０３５８】
(3) 接着接合性
２５ｍｍ×２００ｍｍのサンプルの防錆油を溶剤脱脂により除去した後、洗浄油（スギムラ化学（株）製の“プレトンＲ３５２Ｌ”）を塗布した。このサンプルを２枚一組とし、塩ビ系のヘミング用接着剤を２５ｍｍ×１４０ｍｍの範囲に塗布し（サンプルの端から５０ｍｍは接着剤を塗布せず）、０．１５ｍｍ厚のスペーサーを介して貼り合わせて試験片を作成した。これを１６０℃×１０分で乾燥させた後、２４〜７２時間の間、常温にて放置し、その後、引張り試験機を用いて試験片がＴ型の状態から２枚の試験片が剥離するまで引っ張り、この引っ張り時の試験片の平均強度を測定した。
(4)耐脱脂液、塗油浸透性
脱脂後試料のをＸＰＳで測定し定量分析を行った。脱脂液成分もしくは塗油成分が皮膜に侵入しているとＳｉが検出される。Ａｒビームスパッタで最表面の汚染を除去した後測定した定量値で、Ｓｉのモル濃度／金属元素の合計モル濃度を求め、下記により評価した。
【０３５９】
○：０．１２未満
×：０．１２以上
表３３に各供試材の処理条件とＲ-factor、半価幅、上記性能評価の結果を示す。本発明例はプレス成形性が良いだけでなく、比較例に較べて化成処理性及び、接着接合性、脱脂液、塗油浸透性が優れている。
【０３６０】
【表３３】

なお、上記（発明の実施の形態）では、説明の便宜上、（実施の形態１）〜（実施の形態３）に分けて説明したが、本願発明は、上記各実施形態に限定されるものでなく、実施段階ではその要旨を逸脱しない範囲で種々に変形することが可能である。また、各実施形態は可能な限り適宜組み合わせて実施してもよく、その場合組み合わされた効果が得られる。さらに、上記各実施形態には種々の段階の発明が含まれており、開示される複数の構成要件における適宜な組み合わせにより種々の発明が抽出され得る。
【０３６１】
【発明の効果】
以上述べたように本発明の亜鉛系めっき鋼板は優れたプレス成形性と化成処理性が得られる。
【０３６２】
また、本発明の亜鉛系めっき鋼板の製造方法によれば、プレス成形性及び化成処理性がともに優れた亜鉛系めっき鋼板を安定して製造することができる。
【図面の簡単な説明】
【図１】実施例で使用した摩擦係数測定装置を示す正面図である。
【図２】図１の装置を構成するビードの形状・寸法を示す斜視図である。
【図３】Ｚｎ₃（ＰＯ₄）₂・４Ｈ₂ＯのP-K edge ＸＡＮＥＳスペクトルを示す図であり、バックグラウンドを差し引き、ピークトップが１になるようにノーマライズしてある。
【符号の説明】
１ 摩擦係数測定用試料
２ 試料台
３ スライドテーブル
４ ローラ
５ スライドテーブル支持台
６ ビード
７ 第１ロードセル
８ 第２ロードセル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zinc-based plated steel sheet and a method for producing the same, and particularly to a zinc-based plated steel sheet excellent in press formability and chemical conversion treatment and a method for producing the same.
[0002]
[Prior art]
Zinc-based plated steel sheets are widely used as various rust-proof steel sheets because they have various excellent characteristics. In order to use this galvanized steel sheet as an anti-corrosion steel sheet for automobiles, in addition to corrosion resistance and paint compatibility, the performance required in the car body manufacturing process includes press formability, spot weldability, adhesion and chemical conversion. It is important that the process is excellent.
[0003]
However, galvanized steel sheets generally have the disadvantage of being inferior in press formability compared to cold rolled steel sheets. This is because the sliding resistance between the galvanized steel sheet and the press die is higher than that of the cold-rolled steel sheet. It becomes difficult to flow into the press die, and the steel sheet tends to break.
[0004]
As a method for improving the press formability of a galvanized steel sheet, a method of applying a high-viscosity lubricating oil is widely used. However, in this method, since the lubricating oil has a high viscosity, there are problems such as occurrence of a coating defect due to poor degreasing in the next coating process, and unstable press performance due to oil shortage. Therefore, there is a high demand for improving the press formability of galvanized steel sheets. Conventionally, the following techniques have been proposed to improve the press formability of galvanized steel sheets.
[0005]
(1) Japanese Patent Laid-Open No. 4-176878 discloses oxides and / or hydroxides of one or more metals of Mn, Mo, Co, Ni, Ca, Cr, V, W, Ti, Al and Zn. A zinc-based plated steel sheet having a layer mainly composed of an object and a film mainly composed of P, B oxygen acid and / or one or more oxide colloids of Si, Al, Ti is shown.
[0006]
(2) In JP-A-8-296058, after activating the surface of a galvanized steel sheet, one or more of Mn, Mo, Co, Ni, Ca, V, W, P, B are used. A method for producing a zinc-based plated steel sheet on which an inorganic oxide film is formed is shown.
[0007]
(3) Japanese Patent Application Laid-Open No. 9-170084 discloses a plated steel sheet having an amorphous reaction product of phosphorus and zinc on the surface of a plated layer of a zinc-based plated steel sheet and a method for producing the same.
[0008]
(4) Japanese Patent Laid-Open No. 4-88196 discloses a zinc-based plated steel sheet excellent in press formability and chemical conversion treatment, in which an amorphous P oxide is coated on the surface of a zinc-based plated steel sheet.
[0009]
[Problems to be solved by the invention]
However, these technologies have the following problems.
[0010]
In the technique (1), the zinc-based plating layer is treated with an aqueous solution containing an etching aid such as sulfuric acid and an oxidizing agent such as nitrate ion or potassium permanganate. When contacted with the system plating layer, zinc as a plating component dissolves in the aqueous solution, so that zinc is easily taken into the formed film. As a result, the formed film is ensured in adhesion at the interface with the plating layer, and can maintain the function of covering the plating layer following the deformation of the plating layer. However, this technique has the following problems. That is, since the coating as described above covers the zinc-based plating layer, it is usually a chemical conversion treatment (ie, phosphate treatment, which is performed as a pre-painting treatment for automobiles. In order to distinguish from the treatment to be performed, the reaction between the chemical conversion treatment solution and zinc does not occur sufficiently in the “chemical conversion treatment”), which causes problems such as coarsening of crystals or formation of no crystals. In general, the chemical conversion solution is added with fluorine ions or the like in order to improve the etching property of the film. However, when such an additive component is not contained or the presence of impurities, the etching property is deteriorated. In such a case, the above phenomenon becomes particularly remarkable because the film is not sufficiently dissolved or detached during the chemical conversion treatment.
[0011]
Further, the techniques (2) to (4) have the same problem. That is, the technique (2) increases the reactivity of the plating layer and increases the bonding force between the plating layer and the inorganic oxide film formed on the surface thereof. The point is that an amorphous reaction product of acid and zinc is formed, and the technique (4) is characterized by coating amorphous P oxide that does not dissolve even in the degreasing step. For this reason, in any chemical conversion treatment conditions where etching properties are inferior, it is difficult for the film to be detached during the chemical conversion treatment process, and a chemical conversion treatment failure tends to occur.
[0012]
Further, all of the techniques (1) to (4) are based on the premise that zinc is etched and zinc is taken into the film. Usually, when phosphate ions and zinc ions coexist, insoluble phosphate crystals tend to be formed. Therefore, when zinc-plated steel sheet is brought into contact with an aqueous solution that contains phosphoric acid and dissolves zinc, zinc, which is a crystal component, is always supplied from the plating layer. Once nuclei are formed, crystals tend to grow. In a film in which such crystals are present, these crystal components are peeled off and deposited between the molds during press molding, and as a result of hindering slidability, mold galling or the like is caused, leading to material breakage. There is a possibility.
[0013]
Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and to provide a zinc-based plated steel sheet excellent in both press formability and chemical conversion property.
[0014]
Another object of the present invention is to provide a production method capable of stably producing a galvanized steel sheet having such excellent characteristics.
[0015]
[Means for Solving the Problems]
By forming a composite film (hereinafter referred to as a composite film) containing a P component, an N component, and a specific metal element in an appropriate composition range on the surface of a plated layer of a zinc-based plated steel sheet. A galvanized steel sheet with both excellent press formability and chemical conversion treatment can be obtained, and such galvanized steel sheet with both excellent press formability and chemical conversion treatment can be applied to the surface of the galvanized steel sheet. It has been found that a phosphoric acid-based aqueous solution having an appropriate component and composition range is applied to form a film stably.
[0016]
The present invention has been made based on such findings, and the features thereof are as follows.
[0029]
[1] VirtuallyAl and / or FeA cation component (α) and a phosphoric acid component (β), and a molar ratio (α) / (β) (provided that phosphoric acid is added to the total of the cation component (α) and the phosphoric acid component (β). Ingredient is P₂O_Five(Converted molar concentration) is 0.20 to 6 and further, an aqueous solution containing carboxylic acid is applied to the surface of the plated layer of the galvanized steel sheet and then dried without washing with water to form a film. A method for producing a galvanized steel sheet.
[0030]
[2] The aqueous solution applied to the plating layer surface is used as a cation component.furtherNH_Four ⁺The method for producing a galvanized steel sheet according to the above [1], comprising:
[0031]
[3] The aqueous solution applied to the plating layer surface contains at least Fe as a cation componentThe molar concentration ratio (γ) / (β) of Fe (γ) and phosphoric acid component (β) (wherein the phosphoric acid component is P ₂ O _Five (Converted molar concentration) is more than 0.20 and less than 0.95The method for producing a galvanized steel sheet according to [1] or [2] above, wherein
[0033]
[ 4 ]The aqueous solution applied to the plating layer surface contains at least Al as a cation component.The molar concentration ratio (δ) / (β) of Al (δ) and phosphoric acid component (β) (wherein the phosphoric acid component is P ₂ O _Five (Converted molar concentration) is 1/10 or more and less than 2/3[1] to [1] characterized in that[ 3 ]The manufacturing method of the zinc-based plated steel plate in any one of.
[0035]
[ 5 ]The aqueous solution applied to the surface of the plating layer further contains silica (ε), and the molar concentration ratio (ε) / (β) of silica (ε) and phosphoric acid component (β) (wherein silica is SiO₂Equivalent molar concentration, phosphoric acid component is P₂O_Five[1] to [1] above, wherein the converted molar concentration is 0.01 to 50[ 4 ]The manufacturing method of the zinc-based plated steel plate in any one of.
[0036]
[ 6 ][1] to [1], wherein the aqueous solution applied to the surface of the plating layer further contains a water-soluble resin and / or a water-dispersible resin.[ 5 ]The manufacturing method of the zinc-based plated steel plate in any one of.
[0038]
[ 7 ][1] to [1], wherein the carboxylic acid contained in the aqueous solution applied to the surface of the plating layer is an oxycarboxylic acid[ 6 ]The manufacturing method of the zinc-based plated steel plate in any one of.
[0039]
[ 8 ]The oxycarboxylic acid is citric acid[ 7 ]The manufacturing method of the zinc-plated steel plate as described in 1 ..
[0040]
[ 9 ]The aqueous solution applied to the surface of the plating layer further contains sulfate ions (SO_Four ^2-) (Ζ) and sulfate ions (SO_Four ^2-) (Ζ) and the molar concentration ratio (ζ) / (β) of the phosphoric acid component (β) (wherein the phosphoric acid component is P₂O_Five[1] to [1] above, wherein the converted molar concentration is 0.05 to 1.00[ 8 ]The manufacturing method of the zinc-based plated steel plate in any one of.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The present inventors press-molded by forming a composite film (hereinafter referred to as a composite film) composed of a metal element having a proper component and composition range and a phosphorus-based oxide on the surface of a plated layer of a zinc-based plated steel sheet. Galvanized steel sheet with excellent properties and chemical conversion treatment properties is obtained, and such galvanized steel sheets with excellent press formability and chemical conversion property are suitable for the surface of the galvanized steel sheet. It has been found that a phosphoric acid aqueous solution having a component and a composition range is applied to form a film to stably obtain the film.
[0042]
The first embodiment of the present invention (hereinafter simply referred to as the present invention in the first embodiment) is based on such knowledge, and the features thereof are as follows.
[1] At least one metal element selected from the group consisting of Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo and a P component on the surface of the plated layer of the galvanized steel sheet The molar ratio (a) / (b) of the total amount (a) of the metal elements and the P component amount (b) (where the P component amount is P₂O_FiveConversion amount) is more than 0.20 and less than or equal to 6 and the film adhesion amount is 5 to 300 mg / m as the P adhesion amount.²A galvanized steel sheet characterized by forming a composite film.
[2] The galvanized steel sheet, wherein the composite film of [1] contains at least Fe as a metal element.
[3] Mole ratio (c) / (b) of Fe amount (c) and P component amount (b) contained in the composite film (where the P component amount is P₂O_FiveThe galvanized steel sheet according to [2] above, wherein the conversion amount is greater than 0.20 and less than 0.95.
[4] The galvanized steel sheet according to any one of [1] to [3], wherein the composite film contains at least Al as a metal element.
[5] Molar ratio (d) / (b) of the amount of Al (d) and the amount of P component (b) contained in the composite film (where the amount of P component is P₂O_FiveThe galvanized steel sheet according to [4] above, wherein the conversion amount is 1/10 or more and less than 2/3.
[6] The composite film further contains silica, and the molar ratio (e) / (b) of the amount of silica (e) and the amount of P component (b) (where the amount of silica is SiO₂Conversion amount, P component amount is P₂O_FiveThe galvanized steel sheet according to the above [1] to [5], wherein the conversion amount is 0.01 to 50.
[7] The composite film further has a water-soluble resin and / or a water-dispersible resin as an adhesion amount in the film of 0.01 to 1000 mg / m.²The galvanized steel sheet according to any one of [1] to [6], wherein the galvanized steel sheet is contained.
[8] The composite film further contains S, and the molar ratio (f) / (b) of the S amount (f) and the P component amount (b) (provided that the P component amount is P₂O_FiveThe galvanized steel sheet according to any one of [1] to [7], wherein the conversion amount is 0.05 or more and less than 1.00.
[9] A cation component (α) consisting essentially of at least one metal ion selected from the group consisting of Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo, and a phosphate component (β) The molar concentration ratio (α) / (β) of the total of the cation component (α) and the phosphoric acid component (β) (wherein the phosphoric acid component is P₂O_FiveAn aqueous solution having a converted molar concentration of more than 0.20 and not more than 6 is applied to the surface of a plated layer of a zinc-based plated steel sheet, and subsequently dried without being washed with water to form a film. Production method.
[10] The method for producing a galvanized steel sheet according to [9], wherein the aqueous solution contains at least Fe as a cation component.
[11] The aqueous solution has a molar concentration ratio (γ) / (β) of Fe (γ) and phosphoric acid component (β) (wherein the phosphoric acid component is P₂O_Five(Conversion molar concentration) is more than 0.20 and less than 0.95, The method for producing a galvanized steel sheet according to [10] above
[12] The method for producing a galvanized steel sheet according to [9] to [11], wherein the aqueous solution contains at least Al as a cation component.
[13] The aqueous solution contains a molar concentration ratio (δ) / (β) of Al (δ) and phosphoric acid component (β) (wherein the phosphoric acid component is P₂O_Five(Conversion molar concentration) is 1/10 or more and less than 2/3, The method for producing a galvanized steel sheet according to [12] above.
[14] The aqueous solution further contains silica (ε), and the molar concentration ratio (ε) / (β) of silica (ε) and phosphoric acid component (β) (wherein silica is SiO₂Equivalent molar concentration, phosphoric acid component is P₂O_Five(Conversion molar concentration) is 0.01-50, The manufacturing method of the galvanized steel sheet in any one of said [9]-[13] characterized by the above-mentioned.
[15] The method for producing a zinc-based plated steel sheet according to any one of [9] to [14], wherein the aqueous solution further contains a water-soluble resin and / or a water-dispersible resin.
[16] The method for producing a zinc-based plated steel sheet according to any one of [9] to [15], wherein the aqueous solution further contains a carboxylic acid.
[17] The method for producing a zinc-based plated steel sheet according to [16], wherein the carboxylic acid is an oxycarboxylic acid.
[18] The aqueous solution further contains sulfate ions (SO_Four ^2-) (Ζ) and sulfate ions (SO_Four ^2-) (Ζ) and the molar concentration ratio (ζ) / (β) of the phosphoric acid component (β) (wherein the phosphoric acid component is P₂O_Five(Conversion molar concentration) is less than 0.05 to less than 1.00. The method for producing a galvanized steel sheet according to [9] to [17] above.
[0043]
In the above (means for solving the problems), the total amount of at least one selected from the group consisting of N component, Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo is (a However, since the first embodiment is an embodiment that does not include an N component, the total amount of the metal elements is represented as (a) in (Embodiment 1).
[0044]
The zinc-based plated steel sheet (zinc-plated steel sheet used as the base material for film treatment), which is the subject of the present invention, is the formation of a zinc-based plating layer on the surface of the steel sheet by hot-dip plating, electroplating or vapor phase plating. A plated steel sheet. The composition of the zinc-based plating layer is not only a plating layer made of pure zinc, but also a metal such as Fe, Ni, Co, Cr, Al, Mo, Ti, Si, W, Sn, Pb, Nb, Ta or an oxide thereof. And a single-layer or multiple-layer galvanized layer containing one or more selected from organic materials. These zinc-based plating layers are made of SiO.₂, Al₂O_ThreeOxide fine particles such as, or one or more organic resins may be contained. In addition, as the zinc-based plated steel sheet, a multilayer plated steel sheet having a plurality of plating layers having different plating compositions, a functionally gradient plated steel sheet in which the composition of the plating layer is changed in an inclined shape in the layer thickness direction, or the like can also be used. .
[0045]
Specific examples of galvanized steel sheets include hot dip galvanized steel sheets, vapor-deposited galvanized steel sheets, iron-zinc alloyed hot dip galvanized steel sheets, zinc-aluminum alloy hot dip plated steel sheets (for example, Zn-5% Al alloy hot dip plated steel sheets). , Zn-55% Al alloy hot dip galvanized steel sheet), alloyed hot dip galvanized steel sheet (generally called half alloy) in which only the layer close to the steel sheet is alloyed among the plated layers, one side is iron-zinc alloyed hot dip zinc A plated steel plate consisting of a plated layer, the other side of which is a hot dip galvanized layer, or a plating layer of the above plated steel plate, further plated with zinc or a zinc-based alloy plated layer by electroplating, vapor deposition plating, etc. Steel sheet, zinc as matrix, SiO₂Examples thereof include a dispersion-plated steel sheet having a plating layer in which fine particles such as these are dispersed.
[0046]
The zinc-based plated steel sheet of the present invention imparts excellent chemical conversion property and press formability by forming a composite film having appropriate components and composition ranges on the surface of the plated layer of the material-plated steel sheet as described above. Is.
[0047]
Hereinafter, the details of the present invention will be described together with the reasons for limitation.
[0048]
In general, conventional galvanized steel sheets are inferior in press formability to cold-rolled steel sheets. The cause is that the sliding resistance increases because the low melting point and soft zinc and the mold cause adhesion under high surface pressure. In order to prevent this, it is effective to form a harder and higher melting point film than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet.
[0049]
In order to realize this, the present invention contains a specific metal element component and a phosphorus-based oxide (P component) as constituent components of the coating on the surface of the plating layer, and the metal element component and the phosphorus-based oxide ( A hard and high-melting composite film in which the composition ratio of the P component is regulated within a specific range is formed. Because this composite film contains a specific metal element component and phosphorus oxide (P component) at a specific composition ratio, it uniformly covers the surface of the galvanized steel sheet and suppresses direct contact between zinc and the mold even in a thin film. can do. The reason why such a uniform film can be formed is due to the action of the metal element components constituting the composite film.
[0050]
Although there is no restriction | limiting in particular in the formation method of this composite film, Usually, it forms by apply | coating and drying the aqueous solution containing a film | membrane component on the plating layer surface. Here, if the coating component is phosphoric acid alone, the zinc of the plating layer is dissolved by the etching action and taken up as a coating component. In this case, zinc and phosphoric acid react with each other to easily form crystalline phosphate, and when such crystalline phosphate is formed, the uniformity of the film is lowered, and the plating layer is in a thin film state. It becomes difficult to completely cover the surface. On the other hand, the composite film defined in the present invention is a phosphorus-based oxide film in which a specific metal element component is present. In this case, the reaction between phosphoric acid and zinc in the film formation process is suppressed, and the metal element component And a phosphorus-based oxide (P component) form a network film. And such an effect | action makes a metal element component 1 type, or 2 or more types chosen from Mg, Al, Ca, Ti, Fe, Co, Cu, Mo, Ni, and the total amount of these metal elements ( a) and phosphorus oxide amount (P component amount) (b) molar ratio (a) / (b) (provided that the phosphorus oxide amount is P₂O_FiveThis is obtained when the conversion amount is within a specific range, and this enables uniform film formation.
[0051]
Although the mechanism by which the presence of the metal element component contributes to the formation of a uniform network film is not clear, the crystalline component described above is suppressed by the reaction between the phosphoric acid component and zinc in the plating layer during film formation. The mechanism is considered to be that the formation of the above is suppressed, and that the metal element component and the phosphorus-based oxide (P component) form an inorganic polymer.
[0052]
Next, the relationship between the composite film and chemical conversion treatment will be described.
[0053]
Usually, there exists a degreasing process for removing the press oil used by press work as pre-processing of a chemical conversion treatment process. In the present invention, the composite film formed on the surface of the plating layer is easily dissolved by an alkaline degreasing solution, so that most of the film is removed in the degreasing step. As a result, in the chemical conversion treatment step, the treatment is performed in a state in which the film is almost dissolved and removed, so that healthy phosphate crystals are formed on the plated surface. In addition, due to the deterioration of the degreasing liquid and the fact that the degreasing liquid does not wrap around sufficiently, the film removal of the composite film in the degreasing process (dissolution removal of the film) is not performed sufficiently, and a part of the film remains. Even in the case, the chemical conversion processability can be obtained with the zinc-based plated steel sheet of the present invention. This is because a specific metal element component is used as a film component and the composition ratio is limited to a specific range, so that this film can be sufficiently dissolved not only in a degreasing liquid but also in a chemical conversion liquid. is there.
[0054]
That is, the solubility (film removal property) of the film as described above varies depending on the ratio of the metal element component and the phosphorus oxide (P component) constituting the film. In general, the solubility of the coating itself increases when the amount of phosphorus oxide (P component) with respect to the metal element component is large. However, in order to form a coating with a large amount of phosphorus oxide (P component), phosphoric acid or the like is used. Since it is necessary to apply and dry an aqueous solution containing a large amount of highly etchable components, the amount of zinc incorporated into the film increases, and as a result, the solubility of the film decreases. Therefore, it is necessary to adjust the ratio of the phosphorus-based oxide to the metal element component so that the solubility of the coating itself is well balanced with the effect of suppressing the zinc uptake by etching. In addition, when the amount of the metal element component is excessively excessive with respect to the phosphorus-based oxide, the network forming ability of the film is lowered, and in this case, although the solubility of the film is increased, it is difficult to form a uniform film. It is difficult to ensure excellent press formability.
[0055]
In the composite film, there is inevitably zinc taken from the plating layer. The composite film of the present invention exhibits excellent chemical conversion properties even when zinc is contained due to the presence of a specific metal element component and a phosphorus-based oxide in a specific ratio. Not.
[0056]
Hereinafter, the components of the composite film in the present invention and the reasons for limitation will be described in detail.
[0057]
The composite film in the present invention is selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo as constituent components for imparting solubility to the film together with the phosphorus-based oxide (P component). 1 type or 2 types or more of metallic elements contained are contained. There is no restriction | limiting in particular in the presence form of these metal element components, You may exist with any forms, such as a compound (phosphorus compound) with a metal, an oxide, and a phosphoric acid component. It is preferable that metal element components other than these are not present in the film as much as possible except for zinc inevitably mixed in the film. Therefore, the phosphorus-based oxide film of the present invention substantially contains one or more of the above-mentioned specific metal element components, a phosphorus-based oxide, and silica, an organic resin, and an S component that are contained as necessary as described later. It is preferable that the remaining components are inevitable impurities such as zinc.
[0058]
The molar ratio (a) / (b) of the total amount (a) of the above metal elements in the composite film and the amount of phosphorus oxide (P component amount) (b) (however, the amount of phosphorus oxide (P component amount) is P₂O_FiveThe conversion amount is more than 0.20 and 6 or less. When the molar ratio (a) / (b) is 0.20 or less, the amount of phosphorus oxide (P component amount) is excessive, so that the film tends to be non-uniform and press formability is poor.
[0059]
In particular, when the molar ratio (a) / (b) is low, the composite film becomes non-uniform, so that sliding is performed under conditions such as a punching surface where the surface pressure is low and the sliding distance is long. The properties are particularly lowered, and the press formability is inferior.
[0060]
Furthermore, when the molar ratio (a) / (b) is low, sufficient solubility of the composite film in the alkaline degreasing liquid and the chemical conversion liquid cannot be obtained. For this reason, the film is not removed at all by degreasing, and the growth of the chemical conversion treatment crystal is particularly hindered under the condition that the chemical conversion treatment is performed directly, and the chemical conversion treatment performance is lowered.
[0061]
On the other hand, when the molar ratio (a) / (b) exceeds 6, the metal element component becomes excessive, so that the uniformity of the film is similarly lowered, and the thin film portion and the thick film portion are likely to coexist. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the stability of the film is low, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dew-condensed environment, resulting in corrosion of the galvanized steel sheet.
[0062]
Further, the molar ratio (a) / (b) of the total amount (a) of the metal elements and the phosphorus oxide amount (P component amount) (b) (where the phosphorus oxide amount (P component amount) is P₂O_FiveConversion amount) is more than 0.20 and less than 1.00. When the molar ratio (a) / (b) is 1.00 or more, the metal element component and the phosphoric acid component react with each other and become crystalline easily, which is disadvantageous for forming a uniform film, and the press formability is slightly inferior. Moreover, a more preferable lower limit of the molar ratio (a) / (b) is 0.40.
[0063]
Among the above-described metal element components, more preferable components include Al, Fe, and Co. When these metal element components are contained in the film, the film is more easily dissolved in the chemical conversion solution. Therefore, more excellent chemical conversion processability is shown.
[0064]
Of these, when Al is contained, the uniform coverage and film removal (solubility) of the film are particularly good. The reason is not necessarily clear, but it is considered that Al has a high network forming ability in combination with a phosphoric acid component. In the case of Al, the film removal property in the pretreatment of the chemical conversion treatment is particularly good as compared with other metal elements. Furthermore, even in the chemical conversion solution, the film has high solubility, and excellent chemical conversion property can be obtained even when the film removal is insufficient due to degreasing. Since Al has a high ability to form a network with a phosphoric acid component, a gel-like compound can be easily obtained by heating an aqueous solution containing Al ions and a phosphoric acid component to about 80 to 120 ° C. and drying. It is considered that a film having uniformity can be obtained. Furthermore, since the phosphoric acid component and the Al component easily form a gel-like compound in the drying process, the etching amount of zinc by the phosphoric acid component is reduced. For this reason, it is considered that the amount of zinc taken into the film is small, and the film is easily dissolved. In addition, since the water retention of Al is high, it is considered that the compound easily condenses when it comes into contact with an alkaline degreasing solution and easily dissolves.
[0065]
Therefore, when the effects as described above are expected, it is desirable to include at least Al as the metal element in the composite film, and more preferably to include Al alone or together with Fe described later.
[0066]
The form of Al in the film is not particularly limited, and may be present in any form such as a metal, an oxide, and a compound with a phosphoric acid component.
[0067]
When the composite film contains Al as a metal element component, the molar ratio (d) / (b) of the amount of Al (d) and the amount of phosphorus-based oxide (P component amount) (b) in the film (however, phosphorus-based oxidation) Physical quantity (P component quantity) is P₂O_Five(Converted amount) is preferably 1/10 or more and less than 2/3, and thereby press formability and chemical conversion property are further improved. This is presumably because the film uniformity and film solubility are further enhanced within such a molar ratio range. The molar ratio (d) / (b) = 2/3 is the primary aluminum phosphate (Al (H₂PO_Four)_Three). When the molar ratio (d) / (b) is 2/3 or more, Al is excessive, so that a crystalline component is likely to appear and the film is likely to be hardly soluble.
[0068]
In addition, when the composite film contains Fe as a metal element component, the growth of phosphate crystals in the chemical conversion treatment is hardly inhibited, so that particularly excellent chemical conversion treatment properties can be obtained. Although the reason is not necessarily clear, it was confirmed that when the composite film contains Fe, chemical conversion-treated crystals are formed even when the film remains during the chemical conversion treatment. The film removal performance of the composite film in the degreasing process varies greatly depending on the condition of the alkaline degreasing solution and the degreasing conditions, and under conditions where strong degreasing is not performed, such as extremely deteriorated degreasing solution or spray treatment, the film is sufficiently removed. There is a high possibility of not being broken. In such a case, the composite film containing Fe effectively acts on chemical conversion treatment.
[0069]
In general, in automobiles and home appliances, steel plates are bonded to each other with an adhesive for the purpose of reinforcing welds and reinforcing corrosion resistance. At this time, the presence of a coating applied to enhance the lubrication characteristics may significantly reduce the adhesive bondability. This tendency is particularly strong in the conventional phosphoric acid-containing lubricating coating, and improvement thereof has been desired. It has been found that the adhesive compatibility is remarkably improved by including Fe as a metal element component in the composite film in response to such a problem.
[0070]
Therefore, when the effects as described above are expected, it is desirable to include at least Fe as a metal element in the composite film, and more preferably to include Fe alone or together with Al as described above. .
[0071]
The form of Fe in the film is not particularly limited, and may be present in any form such as a metal, an oxide, and a compound with a phosphoric acid component.
[0072]
When the composite film contains Fe (c) as a metal element component, the more preferable molar ratio (c) / (b) of Fe to phosphorus-based oxide (P component amount) (b) is more than 0.2, It is less than 0.95. When this ratio is 0.2 or less, the composite film becomes non-uniform as described above, so that the slidability under conditions where the surface pressure is low and the sliding distance is long, such as a punch surface. In particular, press formability is not good. Further, the solubility of the composite film in the alkaline degreasing solution and the chemical conversion solution cannot be sufficiently obtained. For this reason, the film is not removed at all by degreasing, and the growth of the chemical conversion-treated crystal is particularly hindered under the condition that the chemical conversion treatment is performed directly, and the chemical conversion treatment property is inferior.
[0073]
When the ratio of the amount of Fe to the amount of phosphorus-based oxide (P component amount) is 0.95 or more, the composite film is also likely to be non-uniform, resulting in poor slidability. Furthermore, adverse effects such as selective oxidation of the film during storage and deterioration of the appearance occur.
[0074]
The composite film of the present invention can further contain silica, whereby the slidability can be further improved. This is presumably because the silica component has an effect of enhancing oil retention, and the silica component acts as a lubricant in a dry friction state. Furthermore, when adopting a film formation method such as applying an aqueous solution and drying, adding wet silica to the film improves the wettability of the aqueous solution to the zinc-based plating film and enables uniform film formation on the plating layer. Become.
[0075]
When silica is contained in the composite film, the molar ratio (e) / (b) between the amount of silica (e) and the amount of phosphorus-based oxide (P component amount) in the film (however, the amount of silica is SiO₂Conversion amount, phosphorus oxide amount (P component amount) is P₂O_FiveThe effect is particularly remarkable when the conversion amount is 0.01 to 50. When the molar ratio (e) / (b) is less than 0.01, the effect of containing silica cannot be sufficiently obtained. On the other hand, when the molar ratio (e) / (b) exceeds 50, the silica component is excessively present, and the silica component is scraped off during press molding, causing surface defects and galling.
[0076]
As silica, for example, dry silica such as silica sol and fumed silica can be used. Examples of the silica sol include “Snowtex” (product symbol: O, OS, OUP, AK, N, 20, 30, 40) manufactured by Nissan Chemical Industries, Ltd., and “Cataloid” manufactured by Catalyst Chemical Industry Co., Ltd. (Product symbols: S, SI, SA, SN), “Adelite” manufactured by Asahi Denka Kogyo Co., Ltd. (product symbols: AT-20, AT-50, AT-20N, AT-300, AT-300S, AT- 20Q). Among these, the type in which the surface potential is neutralized with ammonium ions is particularly preferable. Examples of fumed silica include “AEROSIL200” and “AEROSIL300” manufactured by Nippon Aerosil Co., Ltd.
[0077]
The composite film of the present invention may further contain an organic resin component for the purpose of improving lubricity. The organic resin is preferably a water-soluble resin and / or a water-dispersible resin that can coexist with other inorganic components in an aqueous solution. Examples of these organic resins include epoxy resins, acrylic resins, acrylic-ethylene copolymers, acrylic-styrene copolymers, alkyd resins, polyester resins, urethane resins, polybutadiene resins, and polyamide resins. In addition to these resins, it is effective to use a water-soluble epoxy resin, a water-soluble phenol resin, a water-soluble butadiene rubber (SBR, NBR, MBR), a melamine resin, a blocked isocyanate, an oxazoline compound, or the like as a crosslinking agent. .
[0078]
The amount of organic resin contained in the composite film is 0.01 to 1000 mg / m as the amount of adhesion in the film.²Is appropriate. Organic resin amount 0.01mg / m²If it is less than 1, the effect is not sufficiently obtained, while 1000 mg / m²If it exceeds 1, the film becomes thick and the film is liable to peel off, so that a sufficient effect cannot be obtained.
[0079]
The composite film further contains S due to sulfate ions contained in the aqueous solution for film formation, and the molar ratio (f) / (S content (f) to phosphorus oxide content (P component content) (b). b) (However, the amount of phosphorus oxide (P component amount) is P₂O_FiveWhen the conversion amount) is 0.05 to less than 1.00, the film solubility in the alkaline degreasing liquid and the chemical conversion liquid is increased, and the film is particularly excellent in chemical conversion performance.
[0080]
When the molar ratio is low, the effect is not sufficient, and when the molar ratio exceeds 1.00, the stability of the film is lowered, the surface of the film is corroded during storage, and the appearance tends to be poor. By adding sulfate ions to the aqueous solution for film formation and treating with this aqueous solution, S can be mixed in the film.
[0081]
In the galvanized steel sheet of the present invention, the amount of the composite film formed on the surface of the plating layer is 5 to 300 mg / m as the P adhesion amount (P amount contained in the film).², Preferably 10 to 150 mg / m², Particularly preferably 30 to 120 mg / m²And If the coating amount is small, the effect of improving the press formability cannot be obtained sufficiently. On the other hand, if the coating amount is too large, the chemical conversion processability is lowered.
[0082]
Further, the composite film of the present invention may be in any form of crystalline or amorphous film as long as film removal property and uniform coating property of the film are ensured. In addition, H as crystallization water accompanying crystal components in the film₂O component, H mixed in amorphous film₂O component etc. may be mixed.
[0083]
Next, the manufacturing method of the galvanized steel plate which has the composite film mentioned above is demonstrated.
[0084]
The composite film possessed by the zinc-based plated steel sheet of the present invention can be formed, for example, by applying an aqueous solution containing a cation component and a phosphoric acid component of the metal element to the surface of the plating layer and then drying. In this case, it is possible to appropriately change the ratio of the cation component and the phosphoric acid component in the aqueous solution in accordance with the ratio of the film component.
[0085]
Therefore, in the method for producing a galvanized steel sheet according to the present invention, a cation substantially composed of one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo. Including a component (α) and a phosphoric acid component (β) which is an anionic component, these components were present in a specific ratio (molar concentration ratio (α) / (β) exceeding 0.20 and not more than 6). An aqueous solution is applied to the surface of the plated layer of the zinc-based plated steel sheet, and dried without washing with water to form a film. As a result, a hard and high-melting thin film containing a specific metal element and a phosphorus oxide is uniformly formed on the surface of the zinc-based plating film.
[0086]
Usually, in order to form a film containing phosphorus such as a phosphate film on the surface of a zinc-based plated steel sheet, a treatment such as immersing the plated steel sheet in an aqueous solution containing a phosphoric acid component is performed. In general, a phosphate containing a cation other than an alkali metal is insoluble in the neutral or alkaline region, so that the aqueous solution becomes acidic. Moreover, the mixed aqueous solution of these cation components and a phosphoric acid component tends to precipitate, and normally, when phosphoric acid components, such as a phosphate ion, exist excessively with respect to a cation component, it can exist stably as aqueous solution. In such an aqueous solution containing an excessive amount of phosphoric acid component, the zinc in the plating layer is easily etched, and the eluted zinc reacts with the phosphoric acid component such as phosphate ions to form crystals or form a reaction layer containing zinc at the interface. It's easy to do. As mentioned above, if there are many crystalline components in the film, these crystalline components will be peeled off during press molding, and this will accumulate between the mold and impede slidability. It is easy to produce. Further, since zinc and the film form a reaction layer, the film is hardly detached during the chemical conversion treatment process, and the chemical conversion property is not sufficient.
[0087]
On the other hand, in the aqueous solution for film formation used in the present invention, the ratio of the cation component and the phosphoric acid component is defined, and the reactivity of the treatment liquid is suppressed by keeping the concentration of the phosphoric acid component with respect to the cation component low. This is characterized in that the etching of zinc is suppressed as much as possible. As a result, by performing the treatment of the present invention, it is possible to obtain a zinc-based plated steel sheet that exhibits excellent press formability without reducing chemical conversion treatment properties.
[0088]
Hereinafter, the details of the present invention will be described.
[0089]
Usually, there exists a degreasing process for removing press oil as pre-processing of a chemical conversion treatment process. In the case of a film formed by the treatment performed in the present invention, formation of a reaction layer with zinc is suppressed, and the interface with the zinc-based plating layer is easily dissolved by an alkaline degreasing solution. Is removed. As a result, the film can be dissolved almost completely in the chemical conversion treatment step, and healthy phosphate crystals are formed. Moreover, even if the film removal property in the degreasing process is not sufficient due to such effects such as the deterioration of the degreasing liquid and the degreasing liquid not being sufficiently circulated by the site, the zinc-based plated steel sheet obtained by the present invention is Good chemical conversion processability is obtained.
[0090]
The reason why the galvanized steel sheet obtained by the present invention exhibits a good chemical conversion property is considered to be mainly due to the following reasons.
[0091]
(1) Since a dense and uniform film is formed on the surface of the plating layer as will be described later, sufficient press formability can be realized even with a very thin film, so that the film reacts with the chemical conversion treatment liquid. Thickness that does not hinder.
[0092]
(2) Since formation of a reaction layer with zinc is suppressed, the film is easily detached from the chemical conversion solution.
[0093]
In the present invention, the cation component (α) in the aqueous solution for film formation (a cation composed of one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo) Component) and phosphoric acid component (β) molar concentration ratio within a specific range can form a uniform and dense thin film and suppresses the etching of zinc in the plating layer as much as possible. Thus, formation of a reaction layer with zinc can be suppressed. A uniform and dense film is formed as described above because a slightly soluble compound is formed between the cation component and the phosphoric acid component during the drying process after application of the aqueous solution, and this can be applied uniformly to the plating layer. This is presumably because it contributes to the formation of a stable film. The reason why the ratio of the cationic component (α) and phosphoric acid component (β) in the aqueous solution affects the film morphology is not always clear, but the etchability of the treatment liquid and the solubility of the treatment liquid change depending on the ratio of each component. Therefore, it is presumed that these cause changes in the film form. That is, when the phosphoric acid component (β) is excessive, the etching property of the treatment liquid becomes high, and a crystalline component that reacts with zinc is likely to be formed, which is like an aggregate of bulky crystalline components rather than a thin film. It becomes a film form. On the other hand, when the cation component (α) is excessive, the solubility of the treatment liquid increases, so that the film is difficult to gel during the drying process, and it is difficult to form a uniform film.
[0094]
The ratio of the cation component (α) and the phosphate component (β) composed of one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo is the molar ratio. Concentration ratio (α) / (β) (however, the phosphoric acid component is P₂O_FiveThe converted molar concentration is 0.20 and 6 or less. When the molar ratio (α) / (β) is 0.20 or less, the phosphoric acid component becomes excessive, and crystals of zinc and the phosphoric acid component are easily formed, and excellent sliding characteristics are difficult to obtain. Furthermore, since it becomes difficult to detach | desorb at the time of a chemical conversion treatment, chemical conversion treatment property will fall. Further, when the molar concentration ratio (α) / (β) exceeds 6, the film is formed non-uniformly, so that the thin film portion and the thick film portion easily coexist. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the solubility of the film increases, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dewed environment, causing corrosion of the galvanized steel sheet. . Further, the more preferable molar concentration ratio (α) / (β) is more than 0.20 and less than 1.00. When the molar concentration ratio (α) / (β) is 1 or more, the metal ion and the phosphoric acid component react with each other and become crystalline, which is disadvantageous for forming a uniform film, and the press formability is slightly inferior. Further, a more preferable lower limit of the molar concentration ratio (α) / (β) is 0.4.
[0095]
Further, among the above metal ions, more preferable components include Al, Fe, and Co. When these metal ions are added, the formed film is more easily dissolved in the chemical conversion treatment solution, which is more excellent. It shows chemical conversion processability.
[0096]
Further, when Al is added among the metal ions described above, the uniform coating property and film removal property (solubility) of the film are particularly good. The reason is not necessarily clear, but it is considered that Al has a high network forming ability in combination with a phosphoric acid component. In the case of Al, the film removal property in the pretreatment of the chemical conversion treatment is particularly good as compared with other metal elements. Furthermore, even in the chemical conversion solution, the film has high solubility, and excellent chemical conversion property can be obtained even when the film removal is insufficient due to degreasing. Since Al has a high ability to form a network with a phosphoric acid component, a gel-like compound can be easily obtained by heating an aqueous solution containing Al ions and a phosphoric acid component to about 80 to 120 ° C. and drying. It is considered that a film having uniformity can be obtained. Furthermore, since the phosphoric acid component and the Al component easily form a gel-like compound in the drying process, the etching amount of zinc by the phosphoric acid component is reduced. For this reason, it is considered that the amount of zinc taken into the film is small, and the film is easily dissolved. In addition, since the water retention of Al is high, it is considered that the compound easily condenses when it comes into contact with an alkaline degreasing solution and easily dissolves.
[0097]
Therefore, when the effects as described above are expected, it is desirable to add at least Al as the metal ion in the aqueous solution, and more preferably to add Al alone or together with Fe described later as the metal ion.
[0098]
When Al is added as a metal ion to an aqueous solution for forming a film, the molar concentration ratio (δ) / (β) of Al (δ) and phosphoric acid component (β) (however, the phosphoric acid component is P₂O_Five(Converted molar concentration) is preferably 1/10 or more and less than 2/3, whereby the press moldability and the chemical conversion treatment property are further improved. This is considered to be because the uniformity of the film and the film solubility become higher in such a molar concentration ratio range. If the molar concentration ratio (δ) / (β) is 2/3 or more, Al is excessive, so that a crystalline component is likely to appear and the film is likely to be hardly soluble.
[0099]
In addition, when Fe is added as a metal ion to an aqueous solution for forming a film, the growth of phosphate crystals in the chemical conversion treatment is hardly inhibited, so that particularly excellent chemical conversion treatment properties can be obtained. The reason for this is not necessarily clear, but when Fe is added to the aqueous solution, a chemical conversion-treated crystal is formed even when the film remains during the chemical conversion treatment. The film removal property of the phosphorus-based oxide film in the degreasing process varies greatly depending on the state of the alkaline degreasing liquid and the degreasing conditions, and under conditions where strong degreasing such as an extremely deteriorated degreasing liquid or spray treatment is not performed, There is also a high possibility that this will not be done sufficiently. In such a case, the treatment with an aqueous solution to which Fe is added effectively acts on the chemical conversion treatment.
[0100]
In general, in automobiles and home appliances, steel plates are bonded to each other with an adhesive for the purpose of reinforcing welds and reinforcing corrosion resistance. At this time, the presence of a coating applied to enhance the lubrication characteristics may significantly reduce the adhesive bondability. This tendency is particularly strong in the conventional phosphoric acid-containing lubricating coating, and improvement thereof has been desired. It has been found that the adhesive compatibility is remarkably improved by adding Fe as metal ions to the aqueous solution.
[0101]
Therefore, when the above effects are expected, it is desirable to add at least Fe as a metal ion in the aqueous solution, and more preferably to add Fe alone or together with Al as described above.
[0102]
When the composite film contains Fe as a metal element component, the more preferable molar concentration ratio (γ) / (β) of Fe ions (γ) to phosphoric acid component (β) exceeds 0.2, Less than 95. When this ratio is 0.2 or less, the phosphoric acid component becomes excessive, crystals of zinc and the phosphoric acid component are formed, and the phosphorous oxide film becomes non-uniform. For this reason, the slidability under conditions where the surface pressure is low and the sliding distance is long, such as a punch surface, is particularly deteriorated, and the press formability is not good. Further, the solubility of the phosphorus-based oxide film in the alkaline degreasing liquid and the chemical conversion liquid cannot be sufficiently obtained. For this reason, the film is not removed at all by degreasing, and the growth of the chemical conversion-treated crystal is particularly hindered under the condition that the chemical conversion treatment is performed directly, and the chemical conversion treatment property is inferior.
[0103]
Furthermore, in order to ensure adhesive compatibility, an appropriate amount of Fe must be present in the film. For this reason, when the ratio of Fe ions to the phosphoric acid component is low, the adhesion amount is P amount and at least 150 mg / m²It is necessary to do more. With such a coating amount, a reduction in chemical conversion treatment is inevitable. On the other hand, increasing the Fe ion ratio is also effective from the viewpoint of obtaining good adhesive bondability even with a small amount of film.
[0104]
In addition, when the ratio of Fe ion to phosphoric acid component is 0.95 or more, the uniformity of the phosphorus-based oxide film is deteriorated, and the adverse effect such as the stability of the treatment liquid is reduced.
[0105]
As an aqueous solution for film formation used in the present invention, the cation component (one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo) is used. If an oxide or hydroxide mixed with phosphoric acid so that the cation component is in a predetermined ratio is used, no other anion component is contained in the aqueous solution, and no soluble component remains in the film. It is. However, sulfate may be used in order to allow the later-described sulfate ions to coexist. Furthermore, it is particularly preferable to use an aqueous solution obtained by reacting a metal cation component and a phosphoric acid component at a predetermined temperature and time so as to reduce the amount of free phosphoric acid as much as possible.
[0106]
One or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo are water-soluble such as nitrates, sulfates, and acetates in addition to phosphates. Can be added in the form of a functional metal salt.
[0107]
In addition, when using metal salts other than phosphate, if there are excessive anionic components other than phosphoric acid, these components will act as water-soluble components in the dried film, so the amount added should be as low as possible. It is preferable to do.
[0108]
The presence of the phosphoric acid component in the aqueous solution for film formation is not particularly defined because the presence of the phosphoric acid component is changed depending on the pH of the aqueous solution, the polymerization degree of phosphoric acid to be added, the oxidation state, and the like. Therefore, all phosphate ions contained in any form such as orthophosphoric acid, condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid and hexametaphosphoric acid, phosphorous acid and hypophosphorous acid are referred to in the present invention. Defined as phosphate component.
[0109]
The phosphoric acid component added to the aqueous solution is added in the form of ammonium phosphate, phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, phosphorous acid, hypophosphorous acid or their ammonium salts. can do.
[0110]
The cationic component (α) contained in the aqueous solution for forming a film used in the present invention is substantially one or more metals selected from Mg, Al, Ca, Ti, Fe, Co, Cu, and Mo. Other cation components are not added except for the cation component which is made of ions and thus contained as impurities.
[0111]
In particular, alkali metals are not preferred because soluble components are likely to remain in the film. Zinc ions are not preferred because they tend to form a crystalline film.
[0112]
As for anion components, when an cation component is added to an aqueous solution as an oxide such as nitrate, sulfate or acetate, or a salt other than hydroxide or phosphate, anion components such as nitrate, sulfate or acetate May exist. An appropriate amount of silica (ε) may be added to the aqueous solution for forming a film used in the present invention, whereby a film exhibiting better press moldability and chemical conversion property is formed. By adding silica, the effect of improving the press formability in a thin film is more remarkably exhibited. This is presumably because the addition of silica improves the wettability of the aqueous solution for film formation and forms a uniform film without microscopic repelling on the plating layer. And even if it is such a thin film | membrane, since the improvement effect of press moldability expresses more notably, detachment | desorption of the film | membrane at the time of chemical conversion treatment arises more easily, and chemical conversion treatment property becomes favorable.
[0113]
The amount of silica (ε) added is the molar concentration ratio (ε) / (β) with respect to the phosphoric acid component (where silica is SiO₂Converted molar concentration, phosphoric acid component is P₂O_Five(Molar concentration in terms of conversion) is set to an amount that makes 0.01 to 50.
[0114]
When the molar concentration ratio (ε) / (β) is less than 0.01, the effect of adding silica cannot be sufficiently obtained. On the other hand, when the molar concentration ratio (ε) / (β) exceeds 50, the silica component is excessively present, so that the silica component is scraped off during press molding, and the cause of the surface defects and galling of the ridge It becomes.
[0115]
For silica (ε), dry silica such as silica sol or fumed silica may be added directly to the aqueous solution.
[0116]
Examples of the silica sol include “Snowtex” (product symbol: O, OS, OUP, AK, N, 20, 30, 40) manufactured by Nissan Chemical Industries, Ltd., and “Cataloid” manufactured by Catalyst Chemical Industry Co., Ltd. (Product symbols: S, SI, SA, SN), “Adelite” manufactured by Asahi Denka Kogyo Co., Ltd. (product symbols: AT-20, AT-50, AT-20N, AT-300, AT-300S, AT- 20Q). Among these, the type in which the surface potential is neutralized with ammonium ions is particularly preferable. Examples of fumed silica include “AEROSIL200” and “AEROSIL300” manufactured by Nippon Aerosil Co., Ltd.
[0117]
An appropriate amount of an organic resin component may be added to the aqueous solution for forming a film used in the present invention, thereby further improving the lubricity of the formed film. The organic resin is preferably a water-soluble resin and / or a water-dispersible resin that can coexist with other inorganic components in an aqueous solution. Examples of these organic resins include epoxy resins, acrylic resins, acrylic-ethylene copolymers, acrylic-styrene copolymers, alkyd resins, polyester resins, urethane resins, polybutadiene resins, and polyamide resins. In addition to these resins, it is effective to use a water-soluble epoxy resin, a water-soluble phenol resin, a water-soluble butadiene rubber (SBR, NBR, MBR), a melamine resin, a blocked isocyanate, an oxazoline compound, or the like as a crosslinking agent. .
[0118]
The adhesion amount of the organic resin in the composite film can be adjusted by appropriately changing the resin concentration in the aqueous solution for film formation. The resin concentration in the aqueous solution is such that the resin adhesion amount in the composite film is 0.01 to 1000 mg / m.²The concentration is preferably such that The resin adhesion amount in the composite film is 0.01 mg / m²If it is less than 1, the effect is not sufficiently obtained, while 1000 mg / m²If it exceeds 1, the film becomes thick and the film is liable to peel off, so that a sufficient effect cannot be obtained.
[0119]
In addition, the aqueous solution used in the present invention can further contain a carboxylic acid, whereby the solubility of the film in alkali degreasing before chemical conversion treatment is particularly increased. This is presumably because the film becomes soluble by applying and drying an aqueous solution containing an organic acid such as carboxylic acid, and the film is removed, that is, easily dissolved. Examples of the carboxylic acid include formic acid, acetic acid, lactic acid, oxalic acid, and citric acid. In particular, in the case of oxycarboxylic acid (or oxyacid), the solubility of the film is increased. This is presumed to be because the phosphoric acid component and the metal element component are combined with oxycarboxylic acid to form a glassy and easily soluble film. The reason why the film is easy to dissolve is that the presence of the hydroxyl group of the oxycarboxylic acid increases the hydrophilicity of the film and the penetration of the alkaline degreasing liquid into the film increases, so that the film removal property is improved or the film itself dissolves. This is considered to be easy to do. Examples of the oxycarboxylic acid include tartaric acid, lactic acid, glyceric acid, malic acid, salicylic acid, citric acid and the like, and citric acid is particularly effective.
[0120]
In the present invention, the above-mentioned specific metal ions are added to the aqueous solution for film formation as a cation component. However, when the concentration of the metal ions in the aqueous solution is high and the pH of the aqueous solution exceeds 3, the aqueous solution becomes stable. May be unable to exist. For example, in the case of Fe ions, the aqueous solution tends to be easily gelled when coexisting with a phosphate component such as phosphate ion. In such a case, the gelation of the aqueous solution can be suppressed by adding a carboxylic acid that forms a complex with a metal ion such as formic acid, acetic acid, lactic acid, oxalic acid, tartaric acid, and citric acid.
[0121]
Particularly, an aqueous solution to which Fe ions are added is particularly effective because the stability as an aqueous solution is improved by adding citric acid to the solution, and it is difficult to gel.
[0122]
Although there is no special restriction | limiting in the method of making these carboxylic acid components exist in aqueous solution, Generally it is good to dissolve carboxylic acid or carboxylate of various metals in aqueous solution. Specifically, formic acid, acetic acid, lactic acid, oxalic acid, citric acid, tartaric acid, or an iron salt such as iron citrate or iron iron citrate is dissolved in the aqueous solution.
[0123]
The concentration of the carboxylic acid in the aqueous solution for film formation is the phosphoric acid component (P₂O_Five(Conversion amount) It is desirable that the carboxylic acid is in the range of 0.001 to 5 moles per mole. If the concentration of the carboxylic acid is less than 0.001 mol, the effect is not sufficient. On the other hand, if the concentration exceeds 5 mol, the film tends to absorb moisture and corrosion or the like tends to occur. A particularly preferred range of the carboxylic acid concentration is the phosphoric acid component (P₂O_Five(Conversion amount): 0.01 to 1 mol, more preferably 0.05 to 0.5 mol, relative to 1 mol.
[0124]
In addition, the aqueous solution used in the present invention contains sulfate ions (SO_Four ^2-) (Ζ) is the phosphoric acid component (however, the phosphoric acid component is P₂O_FiveWhen the molar ratio ([eta]) / ([beta]) with respect to (equivalent amount) ([beta]) is less than 0.05 to 1.00, the film solubility particularly in the alkaline degreasing liquid and the chemical conversion liquid becomes high, and the chemical conversion treatment Property is improved.
[0125]
In addition, when sulfate ions are present, the treatment liquid does not gel even when the ratio of metal cations to phosphate ions is increased, so that more metal cations can be present in the aqueous solution. It is estimated that the reason why the solubility of the film increases when it is treated with an aqueous solution containing a sulfuric acid component is that the amount of metal cation can be increased and that sulfate ions remain in the film. The Sulfate ion (SO_Four ^2-) (Ζ) and the phosphoric acid component (β) have a preferred molar ratio (ζ) / (β) of 0.05 to 1.00. If it is lower than 0.05, the effect is not sufficient, and if it exceeds 1.00, the residual amount of sulfate ions in the film increases, the stability of the film decreases, the surface of the film corrodes during storage, and the appearance It tends to be defective.
[0126]
Moreover, the preferable density | concentrations of the cation component ((alpha)), phosphoric acid component ((beta)), and silica ((epsilon)) in the aqueous solution for film formation are as follows. The concentration of the cationic component (α) is desirably in the range of 0.01 to 3 mol / L, more preferably 0.02 to 2 mol / L. If the concentration of the cation component (α) is excessive, it is not preferable because the film thickness becomes non-uniform. The concentration of the phosphoric acid component (β) is P₂O_FiveIt is 0.05-2 mol / L in terms of conversion, more preferably 0.05-1 mol / L. An excessive concentration of the phosphoric acid component (β) is not preferable because the reactivity of the aqueous solution increases. Further, the concentration of silica (ε) is desirably 0.0001 to 6 mol / L, more preferably 0.1 to 1.0 mol / L. An excessive concentration of silica (ε) is not preferable because it causes non-uniform film thickness.
[0127]
The adhesion amount (solid content) of the film formed on the plating layer surface according to the present invention is 5 to 300 mg / m as the adhesion amount of P.², Preferably 10 to 150 mg / m², Particularly preferably 30 to 120 mg / m²It is. If the coating amount is less than the lower limit, the effect of improving the press formability cannot be obtained sufficiently. On the other hand, if the amount exceeds the upper limit, the chemical conversion property is lowered.
[0128]
The aqueous solution for film formation used in the present invention is usually prepared by dissolving the above-described additive components in deionized water.
[0129]
The zinc-based plated steel sheet to which the aqueous solution is applied may be subjected to a treatment such as an activation treatment before the coating treatment. The activation treatment is performed by immersing the plated steel sheet in an alkaline aqueous solution or an acidic aqueous solution, or spraying the aqueous solution.
[0130]
In the present invention, any method such as a coating method, a dipping method, or a spraying method can be adopted as a method for applying the aqueous solution for film formation to the galvanized steel sheet. As a coating method, any means such as a roll coater (3-roll system, 2-roll system, etc.), a squeeze coater, a die coater, a bar coater, or the like may be used. In addition, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method after the coating process, dipping process or spraying process using a squeeze coater or the like.
[0131]
After application of the aqueous solution, heat drying is performed without washing with water. For the heat drying treatment, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace, or the like can be used. It is desirable that the heat treatment be performed in the range of 50 to 200 ° C., preferably 50 to 140 ° C. at the ultimate plate temperature. If the heating temperature is less than 50 ° C., a large amount of moisture remains in the film, and stain-like defects are likely to occur. Further, when the heating temperature exceeds 140 ° C., it is uneconomical, and when it exceeds 200 ° C., the film becomes brittle and easily peels off.
[0132]
The temperature of the aqueous solution for film formation is not particularly specified, but 20 to 70 ° C is preferable. When the temperature of the aqueous solution is less than 20 ° C., the stability of the solution is lowered. On the other hand, when the temperature of the aqueous solution exceeds 70 ° C., equipment and heat energy for maintaining the aqueous solution at a high temperature are required, resulting in an increase in production cost and uneconomical.
[0133]
[Example 1]
In this example, the following various zinc-based plated steel sheets were used.
[0134]
(1) GA: alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), with a coating weight of 45 g / m on both sides²It is.
[0135]
(2) GI: Hot dip galvanized steel sheet, with a coating weight of 90 g / m on both sides²It is.
[0136]
(3) EG: Electrogalvanized steel sheet, with a coating weight of 50 g / m on both sides²It is.
[0137]
(4) Zn-Fe: Electric Zn-Fe alloy-plated steel sheet (15 mass% Fe, balance Zn), with a coating weight of 40 g / m on both sides²It is.
[0138]
(5) Zn—Ni: an electric Zn—Ni alloy plated steel sheet (12 mass% Ni, balance Zn), and the coating weight is 30 g / m on both sides.²It is.
[0139]
(6) Zn-Al: Hot-dip Zn-Al alloy-plated steel sheet (5 mass% Al, balance Zn), with a coating weight of 60 g / m on both sides²It is.
[0140]
The following treatment was performed on the surface of the plated layer of the above zinc-based plated steel sheet. In addition, as the zinc-based plated steel sheet to be treated, one obtained by removing the press oil by solvent degreasing using toluene was used.
[0141]
The treatment liquid was prepared by mixing oxides or hydroxides containing various cation components and orthophosphoric acid at a predetermined ratio with deionized water so as to have the compositions shown in Tables 1 to 3. Salt aqueous solution, (2) a phosphate salt aqueous solution prepared by mixing a metal salt containing various cation components and orthophosphoric acid in deionized water at a predetermined ratio, and (3) silica or water-soluble resin ( What added the water-soluble epoxy resin suitably was used.
[0142]
As the silica component, “Snowtex O” manufactured by Nissan Chemical Co., Ltd. was appropriately added so as to have a predetermined molar concentration.
[0143]
The treatment liquid (room temperature) shown in Tables 1 to 3 was applied to the surface of the galvanized steel sheet at room temperature with a roll coater or a bar coater, and dried by heating to form a film. The amount of film formed was appropriately adjusted depending on the concentration of the composition and coating conditions (roll rolling force, rotational speed, bar coater count, etc.).
[0144]
Moreover, the measurement of the adhesion amount of the film was performed as follows. First, with respect to zinc-based plated steel sheets having different film adhesion amounts, the coating layer was dissolved and peeled with diluted hydrochloric acid together with the film, and the P concentration in the solution was quantified by ICP analysis. The fluorescent X-ray intensity of P in the central part of the plated steel plate part (two places) to be dissolved and peeled is measured in advance, and the relational expression between the fluorescent X-ray intensity of P and the P concentration obtained by ICP is Asked. Then, the fluorescent X-ray intensity of P of each test material was measured, and the P adhesion amount of the film of each test material was determined from this measured value based on the above relational expression.
[0145]
In addition, the amount of metal element and P component in the film (P₂O_FiveThe molar ratio of (converted amount) was determined as follows. First, the composite film formed on the galvanized steel sheet was dissolved in dilute hydrochloric acid together with the plating layer, and the dissolved film constituent elements were quantified. On the other hand, the coating layer of the galvanized steel sheet before the formation of the composite film was dissolved in dilute hydrochloric acid to determine the constituent elements of the film, and the amount of this metal element component was obtained by dissolving the composite film described above together with the plating layer. Subtracted from the amount of the metal element component, this was taken as the amount of film constituent elements. At this time, the area to be measured is 0.06 m.²It was. Then, the metal element amount and the P component amount (P₂O_FiveThe molar ratio was calculated. The amount of the organic resin component in the composite film was determined by quantifying the solution of the film component with an acid by a colorimetric method.
[0146]
The performance evaluation of the galvanized steel sheet obtained as described above was performed as follows.
[0147]
(1) Press formability
In order to evaluate the press formability, the friction coefficient of each test material was measured by a friction coefficient measuring apparatus shown in FIG. In the friction coefficient measuring device (front view) of FIG. 1, a sample stage 2 is fixed to the upper surface of a slide table 3 that can move horizontally, and a sample 1 for measuring a friction coefficient collected from a test material is placed on the sample stage 2. Fixed. On the lower surface of the slide table 3, there is provided a slide table support base 5 having a roller 4 in contact therewith and capable of moving up and down, and a pressing load applied to the friction coefficient measuring sample 1 by the bead 6 when the slide table is pushed up. A first load cell 7 for measuring N is attached to the slide table support 5. Further, a second load cell 8 for measuring a sliding resistance force F for moving the slide table 3 in the horizontal direction in a state where the pressing force is applied is attached to one end of the slide table 3. Yes.
[0148]
As the lubricating oil, “Knox Last 550HN” manufactured by Parker Kosan Co., Ltd. was applied to the surface of the sample 1 and tested. The friction coefficient μ between the test material and the bead 6 was calculated by the formula: μ = F / N. The pressing load N was 400 kgf, and the sample drawing speed (horizontal moving speed of the slide table 3) was 100 cm / min.
[0149]
FIG. 2 is a perspective view showing the shape and dimensions of the bead 6 used. The bead 6 slides with its lower surface pressed against the surface of the sample 1. The bead 6 has a width of 10 mm and a length of 69 mm in the sample sliding direction, the lower portions at both ends of the sample sliding direction are formed by curved surfaces with a curvature of 4.5 mmR, and the bottom surface of the bead to which the sample is pressed is 10 mm wide. It has a planar shape with a length of 60 mm in the sliding direction.
(2) Chemical conversion processability
[Evaluation 1]
Assuming the state of the sample after press molding, apply lubricating oil (“Knox Last 550HN” manufactured by Parker Kosan Co., Ltd.) to each test material, and then “degrease under the conditions of 1) → wash with water The chemical conversion treatment was performed in the steps of “drying → surface adjustment under the condition (2) → chemical conversion treatment according to the condition (3) or (3) ′ → water washing → drying”.
[0150]
(1) Degreasing: “FC-4460” manufactured by Nihon Parkerizing Co., Ltd., spray time: 60 seconds (spray pressure: 1 kgf / cm²), Degreasing temperature: 43 ° C
(2) Surface adjustment: “PL-Z” manufactured by Nihon Parkerizing Co., Ltd., chemical concentration: 1.5 g / l, immersion time: 20 seconds, treatment liquid temperature: room temperature
(3) Chemical conversion treatment: “PB-3030” manufactured by Nihon Parkerizing Co., Ltd., immersion time: 120 seconds, treatment liquid temperature: 52 ° C.
(3) Chemical conversion treatment: “PB-3020” (fluorine-containing system) manufactured by Nihon Parkerizing Co., Ltd., immersion time: 120 seconds, treatment liquid temperature: 43 ° C.
After each of the above two types of chemical conversion treatment, the phosphate crystal form after chemical conversion treatment was observed with an SEM and evaluated as follows.
[0151]
A: The average phosphate crystal size is less than 8 μm, and there is no scaling and it is densely formed.
[0152]
A: The average phosphate crystal size is 8 μm or more and less than 12 μm, and there is no scaling and it is densely formed.
[0153]
◯-: The average phosphate crystal size is 12 μm or more, but no scale is observed.
[0154]
Δ: A portion where the average phosphate crystal size is less than 12 μm and there is no scale and a portion where no phosphate crystal is formed is mixed.
[0155]
X: The average phosphate crystal is coarsened (crystal size is 12 μm or more), and a lot of scale is observed. Or the phosphate crystal is not growing at all.
[Evaluation 2]
Further, in order to perform a more rigorous chemical conversion treatment evaluation, it is assumed that the film removal action in the degreasing process cannot be sufficiently obtained due to poor hitting of the degreasing spray, and in the chemical conversion treatment test of [Evaluation 1] above. A chemical conversion treatment that omits the “degreasing step” was performed. That is, without performing the degreasing step (1), the chemical conversion treatment was performed in the steps of “surface adjustment under the condition (2) → chemical conversion treatment according to the condition (3) → washing → drying”. In this chemical conversion test, the application of press oil as in the chemical conversion test of [Evaluation 1] was not performed. Further, PB-3080 manufactured by Nippon Parkerizing Co., Ltd. was used as the chemical conversion treatment liquid.
[0156]
After the chemical conversion treatment, the phosphate crystal form was observed with SEM and evaluated as follows.
[0157]
A: The average phosphate crystal size is 8 μm or more and 12 μm or less, and there is no scaling and it is densely formed.
[0158]
◯: The average phosphate crystal size is 12 μm or more, but no scale is observed.
[0159]
○-: A portion where phosphate crystals are formed and a portion where phosphate crystals are not formed are mixed.
[0160]
Δ: Phosphate crystals are not grown in most regions, but fine crystals are observed in some places.
[0161]
X: No phosphate crystal has grown.
[0162]
Tables 4 to 13 show the processing conditions of the test materials and the results of the performance evaluation. The inventive examples are superior in chemical conversion treatment compared to the comparative examples, or are excellent in press formability and different chemical conversion treatments. Even if it processes on conditions, deterioration of chemical conversion property is small, and press moldability and chemical conversion property are compatible.
[0163]
[Table 1]

[0164]
[Table 2]

[0165]
[Table 3]

[0166]
[Table 4]

[0167]
[Table 5]

[0168]
[Table 6]

[0169]
[Table 7]

[0170]
[Table 8]

[0171]
[Table 9]

[0172]
[Table 10]

[0173]
[Table 11]

[0174]
[Table 12]

[0175]
[Table 13]

[Example 2]
In this example, the following zinc-based plated steel sheet was used.
[0176]
(1) GA: alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), with a coating weight of 45 g / m on both sides²It is.
[0177]
(2) GI: Hot dip galvanized steel sheet, with a coating weight of 90 g / m on both sides²It is.
[0178]
The following treatment was performed on the surface of the plated layer of the above zinc-based plated steel sheet. In addition, the zinc-plated steel plate to be processed was one from which press oil was removed by alkaline degreasing.
[0179]
Among aqueous solutions for film formation, those containing Fe ions as metal ions contain sulfate ions in an aqueous solution in which ferrous sulfate and orthophosphoric acid are dissolved in deionized water so that each component has a predetermined concentration. Ferrous phosphate and citric acid were added to adjust the composition as shown in Table 14. For metal ions containing Fe ions and Al ions, an aqueous solution prepared from ferrous sulfate and orthophosphoric acid and an aqueous solution prepared from aluminum hydroxide and orthophosphoric acid have a predetermined concentration ratio as appropriate. And adjusted to the composition shown in Table 14.
[0180]
The treatment liquid (room temperature) shown in Table 14 was applied to the surface of the galvanized steel sheet at room temperature with a roll coater or a bar coater, and dried by heating to form a film. The adhesion amount of the formed film was appropriately adjusted according to the concentration of the composition and coating conditions (roll rolling force, rotational speed, bar coater count, etc.).
[0181]
Moreover, the measurement of the adhesion amount of a film | membrane and the measurement of the molar ratio of the metal element amount in a film | membrane and the amount of phosphorus oxides were performed like Example 1. FIG.
[0182]
As a comparative example, a conventional coating type pre-phos treatment was applied to the surface of a galvanized steel sheet while changing the coating amount. The coating amount of the coating type prephos was calculated by dissolving the film in a solution of 20 g of ammonium dichromate and 490 g of 25% ammonia water in 1 L of ion exchange water, and calculating the weight change before and after dissolution. Moreover, the amount of P adhesion in the film was measured by FX in the same manner as described in the film removal property evaluation described later.
[0183]
The performance evaluation of the galvanized steel sheet obtained as described above was performed as follows.
[0184]
(1) Press formability: same as Example 1
(2) Chemical conversion processability: same as Example 1
(3) Film removal during degreasing
“Nox Last 550HN” manufactured by Parker Kosan Co., Ltd. as a press oil is applied to a sample (150 mm × 70 mm) of a zinc-based plated steel sheet of the present invention and a comparative example in a range of 1.5 to 2.0 g / m.²After coating with the amount of adhesion, alkaline degreasing was performed under the following conditions. The amount of P adhesion in the film of the used sample was determined by quantifying the amount of P adhesion of a 48 mmφ sample taken from a position sandwiching the sampling position of the sample by FX, and the average value was defined as the amount of P adhesion.
[0185]
A 48 mmφ portion at approximately the center position of the sample after degreasing was sampled, and the amount of P deposited on this portion was quantified by FX. The film removal rate was calculated from the above initial P adhesion amount and the P adhesion amount after degreasing by the following formula.
[0186]
Defilming rate = 1-([P adhering amount after degreasing] / [Initial P adhering amount])
・ Alkaline degreasing conditions
Assuming the condition that the degreasing liquid is deteriorated, 5 g / l of an anti-rust oil (“NOXLAST 550HN” manufactured by Nihon Parkerizing Co., Ltd.) is added to the alkaline degreasing liquid (“FC4480” manufactured by Nihon Parkerizing Co., Ltd.). The product was degreased by a dipping method. The immersion time was 120 seconds, and the temperature of the degreasing solution was 43 ° C. Degreasing was performed by dipping using a 30 L cylindrical container in which a propeller-type stirrer was rotated (rotation speed: 300 rpm).
(4) Adhesive bondability
After removing the antirust oil of the 25 mm × 200 mm sample by solvent degreasing, a cleaning oil (“Preton R352L” manufactured by Sugimura Chemical Co., Ltd.) was applied. Apply this sample as a set, apply a PVC-based hemming adhesive in the range of 25 mm x 140 mm (50 mm from the end of the sample without applying adhesive), and paste it through a 0.15 mm thick spacer A test piece was made together. After drying this at 160 ° C. for 10 minutes, it is left at room temperature for 24 to 72 hours, and then the two test pieces are peeled from the T-shaped state using a tensile tester. The average strength of the test piece at the time of pulling was measured.
[0187]
Table 15 shows the processing conditions of each test material and the results of the above performance evaluation. Compared with the comparative example, the present invention example is excellent not only in chemical conversion treatment and press formability, but also in film removal and adhesive bondability. ing.
[0188]
[Table 14]

[0189]
[Table 15]

[Example 3]
In this example, the following zinc-based plated steel sheet was used.
[0190]
(1) GA: Alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), and the amount of plating adhesion is 45 g / m2 on both sides.
[0191]
The pretreatment of the processing original plate was the same as in Example 2.
[0192]
As an aqueous solution for forming a sulfate ion-containing film, ferrous sulfate and orthophosphoric acid are dissolved in deionized water so that each component has a predetermined concentration, and an aqueous solution not containing sulfate ions includes electrolysis of a special grade reagent. An aqueous solution prepared from iron powder and orthophosphoric acid was adjusted to have the composition shown in Table 16.
[0193]
The treatment liquid (room temperature) shown in Table 16 was applied to the surface of the galvanized steel sheet at room temperature with a bar coater and dried by heating to form a film. The amount of film formed was adjusted by the count of the bar coater and the concentration of the composition.
[0194]
Moreover, the measurement of the adhesion amount of a film | membrane and the measurement of the molar ratio of the amount of metal elements in a film | membrane and the amount of P components were performed like Example 1. FIG.
[0195]
Furthermore, the ratio of S and phosphorus oxide component (P component amount) present in the film was quantified by XPS (X-ray photoelectron spectroscopy) as follows.
Using an Al—Kα ray monochromated with a monochromator as an X-ray source, contaminants on the sample surface were removed by Ar ions so that the peak intensity of C1s was 60 to 80% before sputtering, and 10 mm²A degree of area was measured. The relative sensitivity factor method is applied to the integrated intensities of the peaks of S2p and P2s to determine the atomic number ratio of S and P, and this is calculated as S (f) and P component amount (P₂O_FiveConverted to a molar ratio (f) / (b) of (converted amount) (b).
[0196]
The performance evaluation of the galvanized steel sheet obtained as described above was performed as follows.
[0197]
(1) Press formability: same as in Example 1
(2) Chemical conversion treatment property: The same as evaluation 2 in Example 2, and only chemical conversion treatment conditions were evaluated with the immersion time shortened to 30 seconds with respect to the normal prescribed immersion time (120 seconds). The evaluation criteria were the same as those in Evaluation 2 of Example 2.
[0198]
(3) Adhesive bondability: same as Example 2
Table 17 shows the processing conditions of each test material and the results of the performance evaluation. Compared with the comparative example, the present invention example is excellent not only in chemical conversion treatment and press formability but also in film removal and adhesive bonding. ing.
[0199]
[Table 16]

[0200]
[Table 17]

(Embodiment 2)
The inventors of the present invention have formed a composite coating containing an N component and a P component in an appropriate composition range on the surface of a plated layer of a zinc-based plated steel sheet, and both have excellent press formability and chemical conversion property. A galvanized steel sheet that is excellent in both press formability and chemical conversion treatment is obtained by using a phosphoric acid aqueous solution having an appropriate component and composition range on the surface of the plated layer of the galvanized steel sheet. It has been found that it can be stably obtained by coating to form a film.
[0201]
The second embodiment of the present invention (hereinafter simply referred to as the present invention in the second embodiment) is based on such knowledge, and the features thereof are as follows.
[1] On the surface of the plated layer of the galvanized steel sheet, the N component and the P component as coating components, the P component in the form of a phosphorus compound and / or nitrogen / phosphorus compound, the N component as a nitrogen compound and / or Or a nitrogen / phosphorus compound, and the molar ratio (a ′) / (b) of the N component amount (a ′) and the P component amount (b) (where the N component amount is an ammonium equivalent amount, P Ingredient amount is P₂O_FiveConversion amount) is more than 0.20 and less than or equal to 6 and the film adhesion amount is 5 to 300 mg / m as the P adhesion amount.²A galvanized steel sheet characterized by forming a composite film.
[2] The composite film further contains one or more metal elements selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo. Molar ratio (a) / (b) of the total amount (a) and the P component amount (b) (where the N component amount is an ammonium equivalent amount, the P component amount is P₂O_FiveThe galvanized steel sheet according to [1] above, wherein the conversion amount is 0.20 to 6 or less.
[3] The galvanized steel sheet according to the above [1] or [2], wherein the composite film contains at least Fe as a metal element.
[4] The composite film further contains silica, and the molar ratio (e) / (b) between the amount of silica (e) and the amount of P component (b) (however, the amount of silica is SiO₂Conversion amount, P component amount is P₂O_FiveThe galvanized steel sheet according to any one of [1] to [3] above, wherein the conversion amount is 0.01 to 50.
[5] The composite coating further has a water-soluble resin and / or a water-dispersible resin as an adhesion amount in the coating of 0.01 to 1000 mg / m.²The galvanized steel sheet according to any one of [1] to [4] above, which is contained.
[6] Substantially NH_Four ⁺A cation component (α) and a phosphoric acid component (β), and a molar concentration ratio (α) / (β) of the cation component (α) and the phosphoric acid component (β) (wherein phosphoric acid is P₂O_FiveAn aqueous solution having a converted molar concentration of more than 0.20 and not more than 6 is applied to the surface of a plated layer of a zinc-based plated steel sheet, and subsequently dried without being washed with water to form a film. Production method.
[7] Substantially NH_Four ⁺A cation component (α) composed of one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo, and a phosphoric acid component (β) The molar concentration ratio (α) / (β) of the total of the cation component (α) and the phosphoric acid component (β) (wherein phosphoric acid is P₂O_FiveAn aqueous solution having a converted molar concentration of more than 0.20 and not more than 6 is applied to the surface of a plated layer of a zinc-based plated steel sheet, and subsequently dried without being washed with water to form a film. Production method.
[8] Molar concentration ratio (α) / (β) of phosphoric acid component (β) to total cation component (α) contained in the aqueous solution applied to the plating layer surface (wherein phosphoric acid is P₂O_Five(Conversion molar concentration) is 0.40-6, The manufacturing method of the galvanized steel sheet as described in said [6] or [7] characterized by the above-mentioned.
[9] The aqueous solution applied to the plating layer surface further contains silica (ε), and the molar concentration ratio (ε) / (β) of silica (ε) and phosphoric acid component (β) (wherein silica is SiO₂Equivalent molar concentration, phosphoric acid is P₂O_Five(Conversion molar concentration) is 0.01-50, The manufacturing method of the zinc-plated steel plate as described in said [6]-[8] characterized by the above-mentioned.
[10] The method for producing a zinc-plated steel sheet according to the above [6] to [9], wherein the aqueous solution applied to the surface of the plating layer further contains a water-soluble resin and / or a water-dispersible resin. .
[11] The method for producing a galvanized steel sheet according to the above [6] to [10], wherein the aqueous solution applied to the surface of the plating layer contains at least Fe as a cation component.
[12] The method for producing a galvanized steel sheet according to the above [6] to [11], wherein the aqueous solution applied to the surface of the plating layer further contains a carboxylic acid.
[13] The method for producing a galvanized steel sheet according to the above [12], wherein the carboxylic acid contained in the aqueous solution applied to the surface of the plating layer is oxycarboxylic acid.
[14] The method for producing a zinc-based plated steel sheet according to the above [13], wherein the oxycarboxylic acid is citric acid.
[0202]
The zinc-based plated steel sheet (zinc-plated steel sheet used as the base material for film treatment), which is the subject of the present invention, is the formation of a zinc-based plating layer on the surface of the steel sheet by hot-dip plating, electroplating or vapor phase plating. A plated steel sheet. The composition of the zinc-based plating layer is not only a plating layer made of pure zinc, but also a metal such as Fe, Ni, Co, Cr, Al, Mo, Ti, Si, W, Sn, Pb, Nb, Ta or an oxide thereof. And a single-layer or multiple-layer galvanized layer containing one or more selected from organic materials. These zinc-based plating layers are made of SiO.₂, Al₂O_ThreeOxide fine particles such as, or one or more organic resins may be contained. In addition, as the zinc-based plated steel sheet, a multilayer plated steel sheet having a plurality of plating layers having different plating compositions, a functionally gradient plated steel sheet in which the composition of the plating layer is changed in an inclined shape in the layer thickness direction, or the like can also be used. .
[0203]
Specific examples of galvanized steel sheets include hot dip galvanized steel sheets, vapor-deposited galvanized steel sheets, iron-zinc alloyed hot dip galvanized steel sheets, zinc-aluminum alloy hot dip plated steel sheets (for example, Zn-5% Al alloy hot dip plated steel sheets). , Zn-55% Al alloy hot dip galvanized steel sheet), alloyed hot dip galvanized steel sheet (generally called half alloy) in which only the layer close to the steel sheet is alloyed among the plated layers, one side is iron-zinc alloyed hot dip zinc A plated steel plate consisting of a plated layer, the other side of which is a hot dip galvanized layer, or a plating layer of the above plated steel plate, further plated with zinc or a zinc-based alloy plated layer by electroplating, vapor deposition plating, etc. Steel sheet, zinc as matrix, SiO₂Examples thereof include a dispersion-plated steel sheet having a plating layer in which fine particles such as these are dispersed.
[0204]
The zinc-based plated steel sheet of the present invention has an appropriate N component (for example, in the form of a nitrogen compound) and P component (for example, in the form of a phosphorus-based oxide) on the plating layer surface of the material-plated steel sheet as described above. By forming a composite film containing in a wide composition range, excellent chemical conversion treatment properties and press formability are imparted.
[0205]
Hereinafter, the details of the present invention will be described together with the reasons for limitation.
[0206]
In general, conventional galvanized steel sheets are inferior in press formability to cold-rolled steel sheets. The cause is that the sliding resistance increases because the low melting point and soft zinc and the mold cause adhesion under high surface pressure. In order to prevent this, it is effective to form a harder and higher melting point film than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet.
[0207]
In order to realize this, the present invention provides the plating layer surface with N component and P component as film constituent components, P component in the form of phosphorus compound and / or nitrogen / phosphorus compound, and N component as nitrogen compound. And / or a composite film having a hard and high melting point, which is contained in the form of a nitrogen / phosphorus compound and the composition ratio of the N component and the P component is regulated within a specific range. Since this composite film contains the N component and the P component in a specific composition ratio, the surface of the zinc-based plated steel sheet can be coated very uniformly, and direct contact between zinc and the mold can be suppressed even with a thin film. The reason why such a uniform film can be formed is due to the action of the N component constituting this composite film.
[0208]
Although there is no restriction | limiting in particular in the formation method of this composite film, Usually, it forms by apply | coating and drying the aqueous solution containing a film | membrane component on the plating layer surface. Here, if the coating component is only a phosphorus oxide, zinc of the plating layer is dissolved by the etching action and taken in as a coating component. In this case, zinc and phosphoric acid react with each other to easily form crystalline phosphate, and when such crystalline phosphate is formed, the uniformity of the film is lowered, and the plating layer is in a thin film state. It becomes difficult to completely cover the surface. On the other hand, when the N component is present in the film as in the present invention, the reaction between phosphoric acid and zinc during the film formation process is suppressed, so that the phosphoric acid component becomes crystalline with zinc. Difficult, N component and phosphoric acid component (P component) form a vitreous network film. Such an effect can be obtained when the molar ratio (a ′) / (b) of the N component amount (a ′) and the P component amount (b) is in a specific range, thereby forming a uniform film. Is possible.
[0209]
In addition, as a film constituent component, in addition to the N component, when one or more metal elements selected from Mg, Al, Ca, Ti, Fe, Ni, Co, Cu, and Mo are included, the film uniformity is particularly good And the press formability becomes good. This is considered to be because these metal element components form a network film with the phosphoric acid component in addition to the effect due to the presence of the N component. In particular, it is considered that the effect of suppressing the reaction between zinc and phosphoric acid due to the presence of the N component and the network forming effect of the metal element component and the phosphoric acid component are synergistic effects, and a more uniform film is formed.
[0210]
Next, the relationship between the composite film and chemical conversion treatment will be described.
[0211]
Usually, there exists a degreasing process for removing the press oil used by press work as pre-processing of a chemical conversion treatment process. In the present invention, the composite film formed on the surface of the plating layer is easily dissolved by an alkaline degreasing solution, so that most of the film is removed in the degreasing step. As a result, in the chemical conversion treatment step, the treatment is performed in a state in which the film is almost dissolved and removed, so that healthy phosphate crystals are formed on the plated surface. In addition, due to the deterioration of the degreasing liquid and the fact that the degreasing liquid does not wrap around sufficiently, the film removal of the composite film in the degreasing process (dissolution removal of the film) is not performed sufficiently, and a part of the film remains. Even in the case, the chemical conversion processability can be obtained with the zinc-based plated steel sheet of the present invention. This is because the N component is used as the film component and the composition ratio is limited to a specific range, so that the film can be sufficiently dissolved not only in the degreasing liquid but also in the chemical conversion treatment liquid.
[0212]
That is, the solubility (film removal property) of the film as described above varies depending on the ratio of the N component and the P component constituting the film. In general, if the amount of P component relative to N component is large, the solubility of the film itself increases, but in order to form a film with a lot of P component, an aqueous solution containing a large amount of highly etchable components such as phosphoric acid is applied -Since it is necessary to dry, the amount of zinc incorporated into the film increases, and as a result, the solubility of the film decreases. Therefore, it is necessary to adjust the ratio of the P component to the N component so that the solubility of the film itself and the effect of suppressing the zinc uptake by etching are well balanced. In addition, when the amount of N component is excessively large with respect to P component, the network forming ability of the film is lowered. In this case, although the solubility of the film is increased, it is difficult to form a uniform film, which is also an excellent press. It becomes difficult to ensure moldability.
[0213]
In the composite film, there is inevitably zinc taken from the plating layer. Since the phosphorus-based oxide film of the present invention has an N component and a specific metal element component and a phosphorus-based oxide in a specific ratio, it exhibits excellent chemical conversion treatment properties even if zinc is contained. The amount of zinc present is not particularly specified.
[0214]
Hereinafter, the component of the composite membrane | film | coat which the galvanized steel plate of this invention has, and its limitation reason are demonstrated in detail.
[0215]
The composite film includes a P component (for example, a P component included in the form of a phosphorus oxide) and an N component (for example, an N component included in the form of a nitrogen compound) as a constituent component for imparting solubility to the film. ) Is contained. There are no particular restrictions on the form of the N component and P component in the film. Examples of the N component include nitrogen compounds (for example, ammonia and nitrogen oxides), nitrogen and phosphorus compounds (for example, ammonium phosphate, ZnNH)._FourPO_FourThe P component includes phosphorus-based oxides such as orthophosphoric acid and condensed phosphoric acid, and nitrogen / phosphorus-based compounds, each of which may exist in any form. . Therefore, the composite film of the present invention contains an N component and a P component included in any form of a nitrogen-based compound, a phosphorus-based oxide, and a nitrogen / phosphorus-based compound, and further included as necessary as described later. It is preferable that one or more of the specific metal element components, silica, and organic resin are substantial constituent components, and the remainder is inevitable impurities such as zinc.
[0216]
Molar ratio (a ′) / (b) of N component amount (a ′) and P component amount (b) in the composite film (where N component amount is ammonium equivalent amount, P component amount is P₂O_Five(Conversion amount) is more than 0.20 and not more than 6. If this molar ratio (a ′) / (b) is 0.20 or less, the ratio of the P component is excessive, so that the film tends to be non-uniform and press formability is poor. Furthermore, since it becomes difficult to detach | desorb at the time of a chemical conversion treatment, a chemical conversion treatment property also falls. On the other hand, when the molar ratio (a ′) / (b) exceeds 6, the N component becomes excessive, so that the uniformity of the film is similarly reduced, and the thin film portion and the thick film portion are likely to coexist. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the stability of the film is low, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dew-condensed environment, resulting in corrosion of the galvanized steel sheet.
[0217]
More preferably, the molar ratio (a ′) / (b) of the N component amount (a ′) and the P component amount (b) (where the N component amount is an ammonium equivalent amount, the P component amount is P₂O_FiveThe lower limit of (conversion amount) is 0.40, and the upper limit is 2.00.
[0218]
In addition, when the composite film further contains one or more metal elements selected from Mg, Al, Ca, Ti, Fe, Ni, Co, Cu, and Mo, the film removal is performed particularly with uniform coverage. Good (solubility). This is because, in addition to the effect of improving the solubility of the film due to the coexistence of these metal elements with the N component, the reaction suppressing effect of zinc and the phosphate component due to the coexistence of the metal element components acts as a synergistic effect, and more film removal This is considered to be because a highly resistant film is formed.
[0219]
Among the above-described metal element components, more preferable components include Al, Fe, and Co. When these metal element components are contained in the film, the film is more easily dissolved in the chemical conversion solution. Therefore, more excellent chemical conversion processability is shown.
[0220]
In addition, when the composite film contains Fe as a metal element component, the growth of phosphate crystals in the chemical conversion treatment is hardly inhibited, so that particularly excellent chemical conversion treatment properties can be obtained. Although the reason is not necessarily clear, it was confirmed that when the composite film contains Fe, chemical conversion-treated crystals are formed even when the film remains during the chemical conversion treatment. The film removal performance of the composite film in the degreasing process varies greatly depending on the condition of the alkaline degreasing solution and the degreasing conditions, and under conditions where strong degreasing is not performed, such as extremely deteriorated degreasing solution or spray treatment, the film is sufficiently removed. There is a high possibility of not being broken. In such a case, the composite film containing Fe effectively acts on chemical conversion treatment.
[0221]
In general, in automobiles and home appliances, steel plates are bonded to each other with an adhesive for the purpose of reinforcing welds and reinforcing corrosion resistance. At this time, the presence of a coating applied to enhance the lubrication characteristics may significantly reduce the adhesive bondability. This tendency is particularly strong in the conventional phosphoric acid-containing lubricating coating, and improvement thereof has been desired. It has been found that the adhesive compatibility is remarkably improved by including Fe as a metal element component in the composite film in response to such a problem.
[0222]
Therefore, when the effects as described above are expected, it is desirable to include at least Fe as a metal element in the composite film, and more preferably to include Fe alone as a metal element.
[0223]
The form of Fe in the film is not particularly limited, and may be present in any form such as a metal, an oxide, and a compound with a phosphoric acid component.
[0224]
When the composite coating contains one or more metal elements selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo together with the N component, the N component and the metal element Molar ratio (a) / (b) of the total amount (a) and the P component amount (b) (where the N component amount is an ammonium equivalent amount, the P component amount is P₂O_FiveThe conversion amount is more than 0.20 and 6 or less. When the molar ratio (a) / (b) is 0.20 or less, the ratio of the P component is excessive, so that the film tends to be nonuniform and the press formability is poor. Furthermore, since it becomes difficult to detach | desorb at the time of a chemical conversion treatment, a chemical conversion treatment property also falls. On the other hand, when the molar ratio (a) / (b) exceeds 6, the N component and the metal element component become excessive, so that the uniformity of the film is similarly reduced, and the thin film portion and the thick film portion are likely to coexist. Become. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the stability of the film is low, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dew-condensed environment, resulting in corrosion of the galvanized steel sheet.
[0225]
More preferably, the molar ratio (a) / (b) of the total amount (a) of the N component and the metal element (a) to the P component amount (b) (where the N component amount is an ammonium equivalent amount, the P component amount is P₂O_FiveThe lower limit of (conversion amount) is 0.40, and the upper limit is 2.00.
[0226]
The composite film of the present invention can further contain silica, whereby the slidability can be further improved. This is presumably because the silica component has an effect of enhancing oil retention, and the silica component acts as a lubricant in a dry friction state. Furthermore, when adopting a film formation method such as applying an aqueous solution and drying, adding wet silica to the film improves the wettability of the aqueous solution to the zinc-based plating film and enables uniform film formation on the plating layer. Become.
[0227]
When silica is contained in the composite film, the molar ratio (e) / (b) between the amount of silica (e) and the amount of P component in the film (however, the amount of silica is SiO₂Conversion amount, P component amount is P₂O_FiveThe effect is particularly remarkable when the conversion amount is 0.01 to 50. When the molar ratio (e) / (b) is less than 0.01, the effect of containing silica cannot be sufficiently obtained. On the other hand, when the molar ratio (e) / (b) exceeds 50, the silica component is excessively present, and the silica component is scraped off during press molding, causing surface defects and galling.
[0228]
As silica, for example, dry silica such as silica sol and fumed silica can be used. Examples of the silica sol include “Snowtex” (product symbol: O, OS, OUP, AK, N, 20, 30, 40) manufactured by Nissan Chemical Industries, Ltd., and “Cataloid” manufactured by Catalyst Chemical Industry Co., Ltd. (Product symbols: S, SI, SA, SN), “Adelite” manufactured by Asahi Denka Kogyo Co., Ltd. (product symbols: AT-20, AT-50, AT-20N, AT-300, AT-300S, AT- 20Q). Among these, the type in which the surface potential is neutralized with ammonium ions is particularly preferable. Examples of fumed silica include “AEROSIL200” and “AEROSIL300” manufactured by Nippon Aerosil Co., Ltd.
[0229]
The composite film of the present invention may further contain an organic resin component for the purpose of improving lubricity. The organic resin is preferably a water-soluble resin and / or a water-dispersible resin that can coexist with other inorganic components in an aqueous solution. Examples of these organic resins include epoxy resins, acrylic resins, acrylic-ethylene copolymers, acrylic-styrene copolymers, alkyd resins, polyester resins, urethane resins, polybutadiene resins, and polyamide resins. In addition to these resins, it is effective to use a water-soluble epoxy resin, a water-soluble phenol resin, a water-soluble butadiene rubber (SBR, NBR, MBR), a melamine resin, a blocked isocyanate, an oxazoline compound, or the like as a crosslinking agent. .
[0230]
The amount of organic resin contained in the composite film is 0.01 to 1000 mg / m as the amount of adhesion in the film.²Is appropriate. Organic resin amount 0.01mg / m²If it is less than 1, the effect is not sufficiently obtained, while 1000 mg / m²If it exceeds 1, the film becomes thick and the film is liable to peel off, so that a sufficient effect cannot be obtained.
[0231]
In the galvanized steel sheet of the present invention, the amount of the composite film formed on the surface of the plating layer is 5 to 300 mg / m as the amount of P adhesion.², Preferably 10 to 150 mg / m², Particularly preferably 30 to 120 mg / m²And If the coating amount is small, the effect of improving the press formability cannot be obtained sufficiently. On the other hand, if the coating amount is too large, the chemical conversion processability is lowered.
[0232]
Further, the composite film of the present invention may be in any form of crystalline or amorphous film as long as film removal property and uniform coating property of the film are ensured. In addition, H as crystallization water accompanying crystal components in the film₂O component, H mixed in amorphous film₂O component etc. may be mixed.
[0233]
Next, the manufacturing method of the galvanized steel plate which has the composite film mentioned above is demonstrated.
[0234]
The composite film which the galvanized steel sheet of the present invention has can be formed, for example, by applying an aqueous solution containing ammonium ions to the surface of the plating layer and then drying it. In this case, it is possible to appropriately change the ratio of the cation component and the phosphoric acid component in the aqueous solution in accordance with the ratio of the film component.
[0235]
Therefore, in the method for producing a galvanized steel sheet according to the present invention, substantially NH._Four ⁺And a phosphoric acid component (β) which is an anionic component, and these components are included in a specific ratio (molar concentration ratio (α) / (β) exceeding 0.20 to 6 or less). The aqueous solution present in step 1 is applied to the surface of the plated layer of the zinc-based plated steel sheet and dried without washing with water to form a film. As a result, on the surface of the zinc-based plating film, a hard and high-melting thin film containing the N component and the P component in any form of a nitrogen compound, a phosphorus oxide, and a nitrogen / phosphorus compound is dense and Uniformly formed.
[0236]
Usually, in order to form a film containing phosphorus such as a phosphate film on the surface of a zinc-based plated steel sheet, a treatment such as immersing the plated steel sheet in an aqueous solution containing a phosphoric acid component such as phosphate ion is performed. Done. In general, a phosphate containing a cation other than an alkali metal is insoluble in the neutral or alkaline region, so that the aqueous solution becomes acidic. Moreover, the mixed aqueous solution of these cation components and phosphoric acid is easy to precipitate, and normally, when an excessive amount of phosphate ions is present relative to the cation component, it can exist stably as an aqueous solution. In such an aqueous solution containing excess phosphoric acid, the zinc in the plating layer is easily etched, and the eluted zinc reacts with the phosphoric acid component to form crystals or a reaction layer containing zinc at the interface. As mentioned above, if there are many crystalline components in the film, these crystalline components will be peeled off during press molding, and this will accumulate between the mold and impede slidability. It is easy to produce. Further, since zinc and the film form a reaction layer, the film is hardly detached during the chemical conversion treatment process, and the chemical conversion property is not sufficient.
[0237]
In contrast, in the aqueous solution for film formation used in the present invention, the cation component (α) is substantially composed of ammonium ions (however, as described later, a specific metal ion is added as the cation component (α)). And the ratio of the phosphoric acid component (β) to the cationic component (α) is characteristic. By making ammonium ions present, it is possible to obtain a solution that does not cause precipitation even when the concentration of the phosphoric acid component relative to the cation component is kept low, and an aqueous solution for film formation that suppresses the etching of zinc in the plating layer as much as possible. it can. As a result, by performing the treatment of the present invention, it is possible to obtain a zinc-based plated steel sheet that exhibits excellent press formability without reducing chemical conversion treatment properties.
[0238]
Usually, there exists a degreasing process for removing press oil as pre-processing of a chemical conversion treatment process. In the case of a film formed by the treatment performed in the present invention, formation of a reaction layer with zinc is suppressed, and the interface with the zinc-based plating layer is easily dissolved by an alkaline degreasing solution. Is removed. As a result, the film can be dissolved almost completely in the chemical conversion treatment step, and healthy phosphate crystals are formed. Moreover, even if the film removal property in the degreasing process is not sufficient due to such effects such as the deterioration of the degreasing liquid and the degreasing liquid not being sufficiently circulated by the site, the zinc-based plated steel sheet obtained by the present invention is Good chemical conversion processability is obtained.
[0239]
The reason why the galvanized steel sheet obtained by the present invention exhibits a good chemical conversion property is considered to be mainly due to the following reasons.
[0240]
(1) Since a dense and uniform film is formed on the surface of the plating layer as will be described later, sufficient press formability can be realized even with a very thin film, so that the film reacts with the chemical conversion treatment liquid. Thickness that does not hinder.
[0241]
(2) Since formation of a reaction layer with zinc is suppressed, the film is easily detached from the chemical conversion solution.
[0242]
In the present invention, the molar concentration ratio of the cation component (α) (a cation component substantially consisting of ammonium ions) and the phosphoric acid component (β) in the aqueous solution for film formation is set to a specific range. A dense thin film can be formed. The reason why the ratio of the cationic component (α) and phosphoric acid component (β) in the aqueous solution affects the film morphology is not always clear, but the etchability of the treatment liquid and the solubility of the treatment liquid change depending on the ratio of each component. Therefore, it is presumed that these cause changes in the film form. That is, when the phosphoric acid component (β) is excessive, the etching property of the treatment liquid becomes high, and a crystalline component that reacts with zinc is likely to be formed, which is like an aggregate of bulky crystalline components rather than a thin film. It becomes a film form. On the other hand, when the cation component (α) is excessive, the solubility of the treatment liquid increases, so that the film is difficult to gel during the drying process, and it is difficult to form a uniform film.
[0243]
For this reason, ammonium ions (NH_Four ⁺The ratio of the cation component (α) to the phosphoric acid component (β) is a molar concentration ratio (α) / (β) (however, the phosphoric acid component is P₂O_FiveThe converted molar concentration is more than 0.20 and 6 or less, preferably 0.40 or more and 6 or less, more preferably 0.60 or more and 4.00 or less, and particularly preferably 1.00 or more and 4.00 or less.
[0244]
When the molar concentration ratio (α) / (β) is 0.20 or less, the phosphoric acid component becomes excessive, a crystal component of zinc and phosphoric acid is easily formed, and excellent sliding characteristics are difficult to obtain. Furthermore, since it becomes difficult to detach | desorb at the time of a chemical conversion treatment, chemical conversion treatment property will fall. Further, when the molar concentration ratio (α) / (β) exceeds 6, the film is formed non-uniformly, so that the thin film portion and the thick film portion easily coexist. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the solubility of the film increases, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dewed environment, causing corrosion of the galvanized steel sheet. .
[0245]
Ammonium ions added to the aqueous solution for film formation are added using ammonia water, primary ammonium phosphate (ammonium dihydrogen phosphate), secondary ammonium phosphate (diammonium hydrogen phosphate), It can also be added in the form of a phosphate such as ammonium triphosphate (triammonium phosphate), or an ammonium salt such as ammonium nitrate, ammonium sulfate, ammonium acetate, or ammonium citrate. Among these, ammonium phosphate salt can be added with ammonium ions and phosphate ions at the same time, but in order to control the molar concentration ratio of phosphate ions and ammonium ions, primary ammonium phosphate and secondary ammonium phosphate, It is particularly preferable to use a mixture of ammonium diphosphate and ammonium tertiary phosphate. In addition, when using an ammonium salt other than phosphate, if there is an excess of anionic components other than phosphoric acid, these components will act as water-soluble components in the dried film, so the amount added should be as small as possible. It is preferable to do.
[0246]
The presence of the phosphoric acid component in the aqueous solution for film formation is not particularly defined because the presence of the phosphoric acid component is changed depending on the pH of the aqueous solution, the polymerization degree of phosphoric acid to be added, the oxidation state, and the like. Therefore, all phosphate ions contained in any form such as orthophosphoric acid, condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid and hexametaphosphoric acid, phosphorous acid and hypophosphorous acid are referred to in the present invention. Defined as phosphate component.
[0247]
The phosphoric acid component added to the aqueous solution is added in the form of ammonium phosphate, phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, phosphorous acid, hypophosphorous acid or their ammonium salts. can do.
[0248]
In the aqueous solution for film formation used in the present invention, one or more metals selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo are further used as the cation component (α). Ions can be added.
[0249]
When these cationic components are included, press moldability and chemical conversion treatment properties are further improved. The reason for this is not always clear, but in the process of drying after application of an aqueous solution, these metal ions form a sparingly soluble compound with phosphoric acid, and this is a dense film that can uniformly coat the plated layer of galvanized steel sheet. Presumed to contribute to formation. Since the film becomes more uniform and dense in this way, the effect of further improving the press formability can be obtained with a thin film thickness that does not adversely affect the reaction with the treatment liquid at the time of the chemical conversion treatment. The moldability can be made more highly compatible.
[0250]
Among the metal ions, more preferred components include Al, Fe, and Co. When these metal ions are added, the film is more easily dissolved in the chemical conversion treatment solution, and thus more excellent chemical conversion property is exhibited.
[0251]
In addition, when Fe is added as a metal ion to an aqueous solution for forming a film, the growth of phosphate crystals in the chemical conversion treatment is hardly inhibited, so that particularly excellent chemical conversion treatment properties can be obtained. The reason for this is not necessarily clear, but when Fe is added to the aqueous solution, a chemical conversion-treated crystal is formed even when the film remains during the chemical conversion treatment. The film removal performance of the composite film in the degreasing process varies greatly depending on the condition of the alkaline degreasing solution and the degreasing conditions, and under conditions where strong degreasing is not performed, such as extremely deteriorated degreasing solution or spray treatment, the film is sufficiently removed. There is a high possibility of not being broken. In such a case, the treatment with an aqueous solution to which Fe is added effectively acts on the chemical conversion treatment.
[0252]
In general, in automobiles and home appliances, steel plates are bonded to each other with an adhesive for the purpose of reinforcing welds and reinforcing corrosion resistance. At this time, the presence of a coating applied to enhance the lubrication characteristics may significantly reduce the adhesive bondability. This tendency is particularly strong in the conventional phosphoric acid-containing lubricating coating, and improvement thereof has been desired. It has been found that the adhesive compatibility is remarkably improved by adding Fe as metal ions to the aqueous solution.
[0253]
Therefore, when the above effects are expected, it is desirable to add at least Fe as a metal ion in the aqueous solution, and more preferably to add Fe alone or together with Al as described above.
[0254]
The cationic component (α) in the aqueous solution is substantially ammonium ion (NH_Four ⁺) And the above metal ions (one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo), the total of these cation components (α). The ratio of the phosphoric acid component (β) is the molar ratio (α) / (β) (however, the phosphoric acid component is P₂O_FiveThe converted molar concentration is more than 0.20 and 6 or less, preferably 0.40 or more and 6 or less, more preferably 0.60 or more and 4.00 or less, and particularly preferably 1.00 or more and 4.00 or less.
[0255]
When the molar concentration ratio (α) / (β) is 0.20 or less, the phosphoric acid component becomes excessive, a crystal component of zinc and phosphoric acid is easily formed, and excellent sliding characteristics are difficult to obtain. Furthermore, since it becomes difficult to detach | desorb at the time of a chemical conversion treatment, chemical conversion treatment property will fall. Further, when the molar concentration ratio (α) / (β) exceeds 6, the film is formed non-uniformly, so that the thin film portion and the thick film portion easily coexist. For this reason, the reaction with the treatment liquid is inhibited at the thick part during the chemical conversion treatment, which is a pre-painting treatment in the automobile manufacturing process, and as a result, it is difficult to form a healthy phosphate crystal and a chemical conversion treatment failure occurs. Further, since the uniformity of the film is lowered, the effect of improving the press formability is small. Furthermore, since the solubility of the film increases, a part of the film dissolves and acts as an electrolyte when stored in a humid environment or in a dewed environment, causing corrosion of the galvanized steel sheet. .
[0256]
When Al is added as a metal ion in an aqueous solution for film formation, the molar concentration ratio (δ) / (β) of Al (δ) and phosphoric acid component (β) (however, phosphoric acid is P₂O_Five(Converted molar concentration) is preferably 1/10 or more and less than 2/3, whereby the press moldability and the chemical conversion treatment property are further improved. This is considered to be because the uniformity of the film and the film solubility become higher in such a molar concentration ratio range. If the molar concentration ratio (δ) / (β) is 2/3 or more, Al is excessive, so that a crystalline component is likely to appear and the film is likely to be hardly soluble.
[0257]
One or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo are water-soluble such as nitrates, sulfates, and acetates in addition to phosphates. Can be added in the form of a functional metal salt. Alternatively, an aqueous solution obtained by reacting an oxide or hydroxide containing the metal with orthophosphoric acid may be used. In this case, it is preferable to prepare such that the molar concentration ratio of the cation component (α) and the phosphoric acid component (β) is in the above range. Furthermore, it is particularly preferable to use an aqueous solution obtained by reacting a metal cation component and a phosphoric acid component at a predetermined temperature and time so as to reduce the amount of free phosphoric acid as much as possible.
[0258]
The cation component (α) contained in the aqueous solution for film formation used in the present invention is substantially ammonium ion (NH_Four ⁺), And the metal ions (one or more metal ions selected from Mg, Al, Ca, Ti, Fe, Co, Ni, Cu, and Mo) added as necessary. Except for the cation component contained as an impurity, no other cation component is added.
[0259]
In particular, alkali metals are not preferred because soluble components are likely to remain in the film. Zinc ions are not preferred because they tend to form a crystalline film.
[0260]
As for anion components, when an cation component is added to an aqueous solution as an oxide such as nitrate, sulfate or acetate, or a salt other than hydroxide or phosphate, anion components such as nitrate, sulfate or acetate May exist. An appropriate amount of silica (ε) may be added to the aqueous solution for forming a film used in the present invention, whereby a film exhibiting better press moldability and chemical conversion property is formed. By adding silica, the effect of improving the press formability in a thin film is more remarkably exhibited. This is presumably because the addition of silica improves the wettability of the aqueous solution for film formation and forms a uniform film without microscopic repelling on the plating layer. And even if it is such a thin film | membrane, since the improvement effect of press moldability expresses more notably, detachment | desorption of the film | membrane at the time of chemical conversion treatment arises more easily, and chemical conversion treatment property becomes favorable.
[0261]
The amount of silica (ε) added is the molar concentration ratio (ε) / (β) with respect to the phosphoric acid component (where silica is SiO₂Converted molar concentration, phosphoric acid component is P₂O_Five(Molar concentration in terms of conversion) is set to an amount that makes 0.01 to 50.
[0262]
When the molar concentration ratio (ε) / (β) is less than 0.01, the effect of adding silica cannot be sufficiently obtained. On the other hand, when the molar concentration ratio (ε) / (β) exceeds 50, the silica component is excessively present, so that the silica component is scraped off during press molding, and the cause of the surface defects and galling of the ridge It becomes.
[0263]
For silica (ε), dry silica such as silica sol or fumed silica may be added directly to the aqueous solution.
[0264]
Examples of the silica sol include “Snowtex” (product symbol: O, OS, OUP, AK, N, 20, 30, 40) manufactured by Nissan Chemical Industries, Ltd., and “Cataloid” manufactured by Catalyst Chemical Industry Co., Ltd. (Product symbols: S, SI, SA, SN), “Adelite” manufactured by Asahi Denka Kogyo Co., Ltd. (product symbols: AT-20, AT-50, AT-20N, AT-300, AT-300S, AT- 20Q). Among these, the type in which the surface potential is neutralized with ammonium ions is particularly preferable. Examples of fumed silica include “AEROSIL200” and “AEROSIL300” manufactured by Nippon Aerosil Co., Ltd.
[0265]
An appropriate amount of an organic resin component may be added to the aqueous solution for forming a film used in the present invention, thereby further improving the lubricity of the formed film. The organic resin is preferably a water-soluble resin and / or a water-dispersible resin that can coexist with other inorganic components in an aqueous solution. Examples of these organic resins include epoxy resins, acrylic resins, acrylic-ethylene copolymers, acrylic-styrene copolymers, alkyd resins, polyester resins, urethane resins, polybutadiene resins, and polyamide resins. In addition to these resins, it is effective to use a water-soluble epoxy resin, a water-soluble phenol resin, a water-soluble butadiene rubber (SBR, NBR, MBR), a melamine resin, a blocked isocyanate, an oxazoline compound, or the like as a crosslinking agent. .
[0266]
The adhesion amount of the organic resin in the composite film can be adjusted by appropriately changing the resin concentration in the aqueous solution for film formation. The resin concentration in the aqueous solution is such that the resin adhesion amount in the composite film is 0.01 to 1000 mg / m.²The concentration is preferably such that The resin adhesion amount in the composite film is 0.01 mg / m²If it is less than 1, the effect is not sufficiently obtained, while 1000 mg / m²If it exceeds 1, the film becomes thick and the film is liable to peel off, so that a sufficient effect cannot be obtained.
[0267]
In addition, the aqueous solution used in the present invention can further contain a carboxylic acid, whereby the solubility of the film in alkali degreasing before chemical conversion treatment is particularly increased. This is presumably because the film becomes soluble by applying and drying an aqueous solution containing an organic acid such as carboxylic acid, and the film is removed, that is, easily dissolved. Examples of the carboxylic acid include formic acid, acetic acid, lactic acid, oxalic acid, and citric acid. In particular, in the case of oxycarboxylic acid (or oxyacid), the solubility of the film is increased. This is presumed to be because the phosphoric acid component and the metal element component are combined with oxycarboxylic acid to form a glassy and easily soluble film. The reason why the film is easy to dissolve is that the presence of the hydroxyl group of the oxycarboxylic acid increases the hydrophilicity of the film and the penetration of the alkaline degreasing liquid into the film increases, so that the film removal property is improved or the film itself dissolves. This is considered to be easy to do. Examples of the oxycarboxylic acid include tartaric acid, lactic acid, glyceric acid, malic acid, salicylic acid, citric acid and the like, and citric acid is particularly effective.
[0268]
In the present invention, the above-mentioned specific metal ions are added to the aqueous solution for film formation as a cation component. However, when the concentration of the metal ions in the aqueous solution is high and the pH of the aqueous solution exceeds 3, the aqueous solution becomes stable. May be unable to exist. For example, in the case of Fe ions, the aqueous solution tends to gel when coexisting with a phosphoric acid component. In such a case, the gelation of the aqueous solution can be suppressed by adding a carboxylic acid that forms a complex with a metal ion such as formic acid, acetic acid, lactic acid, oxalic acid, tartaric acid, and citric acid.
[0269]
Particularly, an aqueous solution to which Fe ions are added is particularly effective because the stability as an aqueous solution is improved by adding citric acid to the solution, and it is difficult to gel.
[0270]
Although there is no special restriction | limiting in the method of making these carboxylic acid components exist in aqueous solution, Generally it is good to dissolve carboxylic acid or carboxylate of various metals in aqueous solution. Specifically, formic acid, acetic acid, lactic acid, oxalic acid, citric acid, tartaric acid, or an iron salt such as iron citrate or iron iron citrate is dissolved in the aqueous solution.
[0271]
The concentration of the carboxylic acid in the aqueous solution for film formation is the phosphoric acid component (P₂O_Five(Conversion amount) It is desirable that the carboxylic acid is in the range of 0.001 to 5 moles per mole. If the concentration of the carboxylic acid is less than 0.001 mol, the effect is not sufficient. On the other hand, if the concentration exceeds 5 mol, the film tends to absorb moisture and corrosion or the like tends to occur. A particularly preferred range of the carboxylic acid concentration is the phosphoric acid component (P₂O_Five(Conversion amount): 0.01 to 1 mol, more preferably 0.05 to 0.5 mol, relative to 1 mol.
[0272]
Preferred concentrations of the cationic component (α), phosphoric acid component (β), and silica (ε) in the aqueous solution for film formation are as follows. The concentration of the cation component (α) is preferably 0.01 to 3 mol / L, more preferably 0.02 to 2 mol / L. If the concentration of the cation component (α) is excessive, it is not preferable because the film thickness becomes non-uniform. The concentration of the phosphoric acid component (β) is P₂O_FiveIt is 0.05-2 mol / L in terms of conversion, more preferably 0.05-1 mol / L. An excessive concentration of the phosphoric acid component (β) is not preferable because the reactivity of the aqueous solution increases. Further, the concentration of silica (ε) is desirably 0.0001 to 6 mol / L, more preferably 0.1 to 1.0 mol / L. An excessive concentration of silica (ε) is not preferable because it causes non-uniform film thickness.
[0273]
The adhesion amount (solid content) of the film formed on the plating layer surface according to the present invention is 5 to 300 mg / m as the adhesion amount of P.², Preferably 10 to 150 mg / m², Particularly preferably 30 to 120 mg / m²It is. If the coating amount is less than the lower limit, the effect of improving the press formability cannot be obtained sufficiently. On the other hand, if the amount exceeds the upper limit, the chemical conversion property is lowered.
[0274]
The aqueous solution for film formation used in the present invention is usually prepared by dissolving the above-described additive components in deionized water.
[0275]
The zinc-based plated steel sheet to which the aqueous solution is applied may be subjected to a treatment such as an activation treatment before the coating treatment. The activation treatment is performed by immersing the plated steel sheet in an alkaline aqueous solution or an acidic aqueous solution, or spraying the aqueous solution.
[0276]
In the present invention, any method such as a coating method, a dipping method, or a spraying method can be adopted as a method for applying the aqueous solution for film formation to the galvanized steel sheet. As a coating method, any means such as a roll coater (3-roll system, 2-roll system, etc.), a squeeze coater, a die coater, a bar coater, or the like may be used. In addition, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method after the coating process, dipping process or spraying process using a squeeze coater or the like.
[0277]
After application of the aqueous solution, heat drying is performed without washing with water. For the heat drying treatment, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace, or the like can be used. It is desirable that the heat treatment be performed in the range of 50 to 200 ° C., preferably 50 to 140 ° C. at the ultimate plate temperature. If the heating temperature is less than 50 ° C., a large amount of moisture remains in the film, and stain-like defects are likely to occur. Further, when the heating temperature exceeds 140 ° C., it is uneconomical, and when it exceeds 200 ° C., the film becomes brittle and easily peels off.
[0278]
The temperature of the aqueous solution for film formation is not particularly specified, but 20 to 70 ° C is preferable. When the temperature of the aqueous solution is less than 20 ° C., the stability of the solution is lowered. On the other hand, when the temperature of the aqueous solution exceeds 70 ° C., equipment and heat energy for maintaining the aqueous solution at a high temperature are required, resulting in an increase in production cost and uneconomical.
[0279]
[Example 1]
In this example, the following various zinc-based plated steel sheets were used.
[0280]
(1) GA: alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), with a coating weight of 45 g / m on both sides²It is.
[0281]
(2) GI: Hot dip galvanized steel sheet, with a coating weight of 90 g / m on both sides²It is.
[0282]
(3) EG: Electrogalvanized steel sheet, with a coating weight of 50 g / m on both sides²It is.
[0283]
(4) Zn-Fe: Electric Zn-Fe alloy-plated steel sheet (15 mass% Fe, balance Zn), with a coating weight of 40 g / m on both sides²It is.
[0284]
(5) Zn—Ni: an electric Zn—Ni alloy plated steel sheet (12 mass% Ni, balance Zn), and the coating weight is 30 g / m on both sides.²It is.
[0285]
(6) Zn-Al: Hot-dip Zn-Al alloy-plated steel sheet (5 mass% Al, balance Zn), with a coating weight of 60 g / m on both sides²It is.
[0286]
The following treatment was performed on the surface of the plated layer of the above zinc-based plated steel sheet. In addition, as the zinc-based plated steel sheet to be treated, one obtained by removing the press oil by solvent degreasing using toluene or alkali degreasing was used.
[0287]
The treatment liquid used had the composition shown in Table 18 to Table 20. (1) Ammonia water, (2) Primary ammonium phosphate (ammonium dihydrogen phosphate), (3) Dibasic ammonium phosphate (4) diammonium hydrogen phosphate, (4) one or more of tertiary ammonium phosphate (triammonium phosphate), orthophosphoric acid, and an oxide containing various cationic components blended as necessary Alternatively, an aqueous phosphate solution prepared by mixing hydroxide with deionized water at a predetermined ratio, or a metal salt containing various cation components, and silica or a water-soluble resin (water-soluble epoxy as necessary) It is a phosphate aqueous solution prepared by appropriately mixing (resin).
[0288]
As a silica component, “Snowtex N” manufactured by Nissan Chemical Co., Ltd. was appropriately added so as to have a predetermined molar concentration.
[0289]
The treatment liquid (room temperature) shown in Table 18 to Table 20 was applied to the surface of the galvanized steel sheet at room temperature using a roll coater or a bar coater, and dried by heating to form a film. The adhesion amount of the formed film was appropriately adjusted according to the concentration of the composition and coating conditions (roll rolling force, rotational speed, bar coater count, etc.).
[0290]
Moreover, the measurement of the adhesion amount of the film was performed as follows. First, with respect to zinc-based plated steel sheets having different film adhesion amounts, the coating layer was dissolved and peeled with diluted hydrochloric acid together with the film, and the P concentration in the solution was quantified by ICP analysis. The fluorescent X-ray intensity of P in the central part of the plated steel plate part (two places) to be dissolved and peeled is measured in advance, and the relational expression between the fluorescent X-ray intensity of P and the P concentration obtained by ICP is Asked. And the fluorescent X ray intensity of P of each test material was measured, and P adhesion amount of the film | membrane of each test material was calculated | required from this measured value based on the said relational expression.
[0291]
Moreover, the amount of N component (ammonium conversion amount) present in the composite film was determined as follows. First, after dissolving the composite film together with the plating film in aqueous hydrochloric acid, the ammonium in the solution is liberated by distillation and absorbed into the alkaline aqueous solution. NH in_FourThe amount was specified. The obtained value was converted to the molar concentration of N. In addition, the amount of metal element and the amount of P component (P₂O_Five(Conversion amount) was determined as follows. First, the composite film formed on the galvanized steel sheet was dissolved in dilute hydrochloric acid together with the plating layer, and the dissolved film constituent elements were quantified. On the other hand, the coating layer of the galvanized steel sheet before the formation of the composite film was dissolved in dilute hydrochloric acid to determine the constituent elements of the film, and the amount of this metal element component was obtained by dissolving the composite film described above together with the plating layer. Subtracted from the amount of the metal element component, this was taken as the amount of film constituent elements. At this time, the area to be measured is 0.06 m.²It was. The amount of the organic resin component in the composite film was determined by quantifying the solution of the film component with an acid by a colorimetric method.
[0292]
The performance evaluation of the galvanized steel sheet obtained as described above was performed as follows.
[0293]
(1) Press formability
In order to evaluate the press formability, the friction coefficient of each test material was measured by a friction coefficient measuring apparatus shown in FIG.
[0294]
As the lubricating oil, “Knox Last 550HN” manufactured by Parker Kosan Co., Ltd. was applied to the surface of the sample 1 and tested. The friction coefficient μ between the test material and the bead 6 was calculated by the formula: μ = F / N. The pressing load N was 400 kgf, and the sample drawing speed (horizontal moving speed of the slide table 3) was 100 cm / min.
[0295]
FIG. 2 is a perspective view showing the shape and dimensions of the bead 6 used.
[0296]
(2) Chemical conversion processability
[Evaluation 1]
Assuming the state of the sample after press molding, apply lubricating oil (“Knox Last 550HN” manufactured by Parker Kosan Co., Ltd.) to each test material, and then “degrease under the conditions of 1) → wash with water The chemical conversion treatment was performed in the steps of “drying → surface adjustment under the condition (2) → chemical conversion treatment according to the condition (3) or (3) ′ → water washing → drying”.
[0297]
(1) Degreasing: “FC-4460” manufactured by Nihon Parkerizing Co., Ltd., spray time: 60 seconds (spray pressure: 1 kgf / cm 2), degreasing liquid temperature: 43 ° C.
(2) Surface adjustment: “PL-Z” manufactured by Nihon Parkerizing Co., Ltd., chemical concentration: 1.5 g / l, immersion time: 20 seconds, treatment liquid temperature: room temperature
(3) Chemical conversion treatment: “PB-3030” manufactured by Nihon Parkerizing Co., Ltd., immersion time: 120 seconds, treatment liquid temperature: 52 ° C.
(3) Chemical conversion treatment: “PB-3020” (fluorine-containing system) manufactured by Nihon Parkerizing Co., Ltd., immersion time: 120 seconds, treatment liquid temperature: 43 ° C.
After each of the above two types of chemical conversion treatment, the phosphate crystal form after chemical conversion treatment was observed with an SEM and evaluated as follows.
[0298]
A: The average phosphate crystal size is less than 8 μm, and there is no scaling and it is densely formed.
[0299]
A: The average phosphate crystal size is 8 μm or more and less than 12 μm, and there is no scaling and it is densely formed.
[0300]
◯-: The average phosphate crystal size is 12 μm or more, but no scale is observed.
[0301]
Δ: A portion where the average phosphate crystal size is less than 12 μm and there is no scale and a portion where no phosphate crystal is formed is mixed.
[0302]
X: The average phosphate crystal is coarsened (crystal size is 12 μm or more), and a lot of scale is observed. Or the phosphate crystal is not growing at all.
[Evaluation 2]
Further, in order to perform a more rigorous chemical conversion treatment evaluation, it is assumed that the film removal action in the degreasing process cannot be sufficiently obtained due to poor hitting of the degreasing spray, and in the chemical conversion treatment test of [Evaluation 1] above. A chemical conversion treatment that omits the “degreasing step” was performed. That is, without performing the degreasing step (1), the chemical conversion treatment was performed in the steps of “surface adjustment under the condition (2) → chemical conversion treatment according to the condition (3) → washing → drying”. In this chemical conversion test, the application of press oil as in the chemical conversion test of [Evaluation 1] was not performed. Further, PB-3080 manufactured by Nippon Parkerizing Co., Ltd. was used as the chemical conversion treatment liquid.
[0303]
After the chemical conversion treatment, the phosphate crystal form was observed with SEM and evaluated as follows.
[0304]
A: The average phosphate crystal size is 8 μm or more and 12 μm or less, and there is no scaling and it is densely formed.
[0305]
◯: The average phosphate crystal size is 12 μm or more, but no scale is observed.
[0306]
○-: A portion where phosphate crystals are formed and a portion where phosphate crystals are not formed are mixed.
[0307]
Δ: Phosphate crystals are not grown in most regions, but fine crystals are observed in some places.
[0308]
X: No phosphate crystal has grown.
[0309]
Tables 21 to 29 show the processing conditions of the test materials and the results of the performance evaluation. In these tables, no. 11, no. No. 53 has a concentration ratio of ammonium ions and phosphate ions in the treatment liquid lower than the range of the present invention. Since phosphate ions are excessive, the friction coefficient is high and the chemical conversion treatment property is also poor. No. 12, no. No. 54 has a high cation concentration in the treatment liquid, so the film is non-uniform, resulting in poor appearance. No. 29, no. Since 71 contains Zn as a cation component in the treatment liquid, the crystalline component increases and the friction coefficient is high. Moreover, although the chemical conversion treatment property in the fluorine-containing chemical conversion treatment (PB-3020) having high etching property is good, the chemical conversion treatment property is poor in other chemical treatment solutions.
[0310]
No. 30, no. No. 72 has a high coefficient of friction because the cation component in the treatment liquid contains an alkali metal and the coating becomes non-uniform and the film thickness is distributed. Moreover, although the chemical conversion treatment property in the fluorine-containing chemical conversion treatment (PB-3020) having high etching property is good, the chemical conversion treatment property is poor in other chemical treatment solutions.
[0311]
No. 37, no. 38, no. 39, no. 79, no. 80, no. No. 81 does not contain ammonium ions in the treatment liquid, so the friction coefficient is high and the chemical conversion treatment property is poor.
[0312]
No. 94, no. 95, no. Since no coating exists on the surface of the plating layer 96, the chemical conversion treatment property is good but the friction coefficient is high.
[0313]
In contrast to the above comparative examples, the present invention example is excellent in chemical conversion processability, or has excellent press moldability, and even when processed under different chemical conversion process conditions, the deterioration of chemical conversion processability is small, and the press moldability and chemical conversion processability are low. Both are compatible.
[0314]
[Table 18]

[0315]
[Table 19]

[0316]
[Table 20]

[0317]
[Table 21]

[0318]
[Table 22]

[0319]
[Table 23]

[0320]
[Table 24]

[0321]
[Table 25]

[0322]
[Table 26]

[0323]
[Table 27]

[0324]
[Table 28]

[0325]
[Table 29]

[Example 2]
In this example, the following zinc-based plated steel sheet was used.
[0326]
(1) GA: alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), with a coating weight of 45 g / m on both sides²It is.
[0327]
(2) GI: Hot dip galvanized steel sheet, with a coating weight of 90 g / m on both sides²It is.
[0328]
The following treatment was performed on the surface of the plated layer of the above zinc-based plated steel sheet. In addition, the zinc-plated steel plate to be processed was one from which press oil was removed by alkaline degreasing.
[0329]
Among the aqueous solutions for film formation, those containing Fe ions as metal ions were prepared by dissolving iron citrate and primary ammonium phosphate in deionized water so that each component had a predetermined concentration. Also, an aqueous solution in which ferrous sulfate-containing ferrous phosphate and citric acid are appropriately added to an aqueous solution in which ferrous sulfate and orthophosphoric acid are dissolved in deionized water so that each component has a concentration shown in Table 30 is also available. used.
[0330]
The treatment liquid (room temperature) shown in Table 30 was applied to the surface of the galvanized steel sheet at room temperature with a roll coater or a bar coater, and dried by heating to form a film. The adhesion amount of the formed film was appropriately adjusted according to the concentration of the composition and coating conditions (roll rolling force, rotational speed, bar coater count, etc.).
[0331]
Moreover, the measurement of the adhesion amount of a film | membrane, the measurement of the amount of N component in a film | membrane, the amount of metal elements, and the amount of P components were performed like Example 1. FIG.
[0332]
As a comparative example, a conventional coating type pre-phos treatment was applied to the surface of a galvanized steel sheet while changing the coating amount. The coating amount of the coating type prephos was calculated by dissolving the film in a solution of 20 g of ammonium dichromate and 490 g of 25% ammonia water in 1 L of ion exchange water, and calculating the weight change before and after dissolution. Further, the amount of P in the film was measured by FX in the same manner as described in the film removal property evaluation described later.
[0333]
The performance evaluation of the galvanized steel sheet obtained as described above was performed as follows.
[0334]
(1) Press formability: same as Example 1
(2) Chemical conversion processability: same as Example 1
(3) Film removal during degreasing
“Knox Last 550HN” manufactured by Parker Kosan Co., Ltd. as a press amount is applied to a sample (150 mm × 70 mm) of a zinc-based plated steel sheet of the present invention and a comparative example in a range of 1.5 to 2.0 g / m.²After coating with the amount of adhesion, alkaline degreasing was performed under the following conditions. The amount of P adhesion in the film of the used sample was determined by quantifying the amount of P adhesion of a 48 mmφ sample taken from a position sandwiching the sampling position of the sample by FX, and the average value was defined as the amount of P adhesion.
[0335]
A 48 mmφ portion at approximately the center position of the sample after degreasing was sampled, and the amount of P deposited on this portion was quantified by FX. The film removal rate was calculated from the initial P adhesion amount and the P adhesion amount after degreasing by the following formula.
[0336]
Defilming rate = 1-([P adhering amount after degreasing] / [Initial P adhering amount])
・ Alkaline degreasing conditions
Assuming the condition that the degreasing liquid is deteriorated, 5 g / l of an anti-rust oil (“NOXLAST 550HN” manufactured by Nihon Parkerizing Co., Ltd.) is added to the alkaline degreasing liquid (“FC4480” manufactured by Nihon Parkerizing Co., Ltd.). The product was degreased by a dipping method. The immersion time was 120 seconds, and the temperature of the degreasing solution was 43 ° C. Degreasing was performed by dipping using a 30 L cylindrical container in which a propeller-type stirrer was rotated (rotation speed: 300 rpm).
(4) Adhesive bondability
After removing the antirust oil of the 25 mm × 200 mm sample by solvent degreasing, a cleaning oil (“Preton R352L” manufactured by Sugimura Chemical Co., Ltd.) was applied. Apply this sample as a set, apply a PVC-based hemming adhesive in the range of 25 mm x 140 mm (50 mm from the end of the sample without applying adhesive), and paste it through a 0.15 mm thick spacer A test piece was made together. After drying this at 160 ° C. for 10 minutes, it is left at room temperature for 24 to 72 hours, and then the two test pieces are peeled from the T-shaped state using a tensile tester. The average strength of the test piece at the time of pulling was measured.
[0337]
Tables 31 and 32 show the processing conditions of each test material and the results of the performance evaluation. Compared with the comparative example, the present invention example has not only chemical conversion property and press formability but also film removal property and adhesive bondability. Also excellent.
[0338]
[Table 30]

[0339]
[Table 31]

[0340]
[Table 32]

(Embodiment 3)
The inventors of the present application compared the phosphorus-based oxide structure of the composite film of the present invention shown in Embodiments 1 and 2 with the crystalline phosphate film of the prior art, and demonstrated press moldability, chemical conversion treatment, adhesive bondability. The film structure with excellent properties was found. Furthermore, the membrane | film | coat structure which suppresses deterioration of a chemical conversion liquid more was discovered. Its characteristics are as follows.
[1] The P-K edge spectrum measured by the XANES method of the composite coating formed on the surface of the galvanized steel sheet is Zn_Three(PO_Four)₂・ 4H₂A galvanized steel sheet having an R-factor of 0.02 or more based on the XANES spectrum of O.
[2] The half width of the spectrum of the P-K edge measured by the XANES method of the composite film is Zn_Three(PO_Four)₂・ 4H₂A zinc-based galvanized steel sheet having a value of 1.03 or more when that of O is 1.
[0341]
The above-mentioned film structure was found because the difference in characteristics between the phosphorus-based oxide of the composite film of the present invention and the crystalline or amorphous phosphate film of the prior art is attributed to the structure containing phosphorus. This is a result of investigating the surface of the galvanized steel sheet formed with XANES method (X-ray Absorption Near Edge Structure). XANES is the spectrum shape that appears in the X-ray absorption spectrum (the spectrum obtained by measuring the X-ray absorption rate of the sample while changing the energy of the incident X-ray) before and after the X-ray absorption edge energy of the element of interest. It is. XANES shows the structure reflecting the electronic state of the element of interest and the short-range atomic arrangement around the element, regardless of whether the object to be measured is crystalline or amorphous. Is an effective means of investigating its electronic state and short-range atomic arrangement.
[0342]
Here, R-factor was used to clarify the difference between the XANES measurement results of the two. R-factor is a factor that evaluates the difference in spectrum.
R-factor = Σ (χobs (E) −χcal (E))²/ Σχobs (E)²
It is defined as If the two spectra are the same, the R-factor is 0, and the larger the difference between the two spectra, the larger the R-factor. χobs (E) is the spectral intensity of the sample at X-ray energy E, and χcal (E) is the spectral intensity of the standard sample.
[0343]
FIG. 3 shows an XANES spectrum of a galvanized steel sheet on which a crystalline zinc phosphate film of the prior art is formed.
[0344]
The P-K edgeXANES spectrum of the composite film (XANES spectrum measured at the K absorption edge of P) is Zn_Three(PO_Four)₂・ 4H₂When the R-factor based on the XANES spectrum of O (crystalline hopite) shows a value of 0.02 or more, better chemical conversion treatment property is exhibited. As described above, the R-factor is a factor for evaluating the difference in spectrum, and the value of 0.02 or more means that the composite film structure of the present invention has a difference from the short-range atomic arrangement of the hopeite. It means to do. On the other hand, the R-factor of the prior art film takes a value smaller than 0.02, which means that the short-range atomic arrangement of the prior art film is close to the hopeite.
[0345]
As the chemical conversion treatment, zinc phosphate treatment is generally performed, and a crystalline hopite film is formed. In the prior art, since the amorphous or crystalline hopite film is formed in advance prior to the zinc phosphate treatment, the zinc phosphate film that has already been formed on the surface is the latter phosphoric acid film. It is thought that it is difficult to dissolve by zinc treatment, and normal growth of zinc phosphate crystals is inhibited. In contrast, in the present invention, since the composite film has a short-range atomic arrangement different from that of hopite, it is considered that the film dissolves in the zinc phosphate treatment solution and the subsequent formation of zinc phosphate crystals occurs uniformly. It is done.
[0346]
In addition, the half width of the P-K edge spectrum measured by the XANES (X-ray Absorption Near Edge Structure) method of the composite film is Zn_Three(PO_Four)₂・ 4H₂When the value of O is 1, the deterioration of the chemical conversion solution is suppressed when it has a value of 1.03 or more. This is because when the bond strength between phosphate ions increases, the half-value width increases, but in that case, the entry of degreasing liquid and oil components into the phosphorus-based oxide film (composite film) is suppressed, and chemical conversion is achieved. This is presumably because the amount of mixing into the treatment liquid is reduced and deterioration of the chemical conversion treatment liquid is suppressed.
[Example 1]
In this example, the following various zinc-based plated steel sheets were used.
[0347]
(1) GA: alloyed hot-dip galvanized steel sheet (10 mass% Fe, balance Zn), with a coating weight of 45 g / m on both sides²It is.
[0348]
The steel plate was subjected to the following treatment. In addition, the alloyed hot-dip galvanized steel sheet to be treated was one from which press oil was removed by alkaline degreasing.
FeSO by weight_Four: H_ThreePO_Four= 4: 5 or an aqueous solution of ammonium phosphate: ferric citrate = 3.2: 2.0 was applied to the surface of the galvanized steel sheet at room temperature with a roll coater or bar coater. The film was formed by heating and drying. The adhesion amount of the formed film was appropriately adjusted according to the concentration of the composition and coating conditions (roll rolling force, rotational speed, bar coater count, etc.). As the comparative sample, the above-described galvanized steel sheet subjected to the conventional coating type pre-phos treatment was used.
[0349]
Moreover, the measurement of the adhesion amount of the film was performed as follows. First, with respect to zinc-based plated steel sheets having different film adhesion amounts, the coating layer was dissolved and peeled with diluted hydrochloric acid together with the film, and the P concentration in the solution was quantified by ICP analysis. The fluorescent X-ray intensity of P in the central part of the plated steel plate part (two places) to be dissolved and peeled is measured in advance, and the relational expression between the fluorescent X-ray intensity of P and the P concentration obtained by ICP is Asked. And the fluorescent X ray intensity of P of each test material was measured, and P adhesion amount of the film | membrane of each test material was calculated | required from this measured value based on the said relational expression.
[0350]
The XANES measurement was performed by the total electron yield XANES (TEY-XANES) method by measuring the sample absorption current (N Okude, H Noro, M Nagoshi, H Yamamoto, Y Baba and TA Sasaki, J. Electron Spectrosc. Relat. Phenom., 88-91 (1998) 467). When the sample is irradiated with X-rays, an amount of electrons corresponding to the X-ray absorption rate is emitted from the sample. The TEY-XANES method is a method of measuring a XANES spectrum by measuring a sample current flowing at that time. For each sample, Zn_Three(PO_Four)₂・ 4H₂The R-factor was calculated based on the P-K edge XANES spectrum of O (FIG. 3), and the half-value widths were compared. R-factor is defined by the following equation.
[0351]
R = Σ (χobs (E) −χcal (E))²/ Σχobs (E)²
χobs (E) is the spectral intensity of the sample at X-ray energy E, and χcal (E) is the spectral intensity of the standard sample.
[0352]
R-factor was calculated using Rigaku Electric's XAFS analysis software “REX2000” as follows.
(1) The background is removed using the following Victoreen equation.
[0353]
Dλ^Four+ Cλ^Three   λ: wavelength
At this time, the intensities in the vicinity of the high energy end (˜2190 eV) of the spectrum are aligned so as to be about 0.15 ± 0.01 (peak top is 1).
(2) Normalize so that the peak top is 1
(3) ZnPO_FourR-factor is derived by fitting with the spectrum of
(ZnPO_FourThe spectrum of is also normalized like (2))
(Fitting energy range: 2136-2190 eV)
(4) Since the spectrum is weighted so as to minimize the R-factor at the time of fitting, the obtained R-factor is divided by the coefficient to obtain the final R-factor.
The performance evaluation of the galvanized steel sheet was performed as follows.
(1) Press formability
Evaluation of press formability was performed in the same manner as in the first and second embodiments.
(2) Chemical conversion processability
Assuming the state of the sample after press molding, apply lubricating oil (“Knox Last 550HN” manufactured by Parker Kosan Co., Ltd.) to each test material, The chemical conversion treatment was performed in the steps of “drying → surface adjustment under the condition (2) → chemical conversion treatment according to the condition (3) → water washing → drying”.
[0354]
(1) Degreasing: Assuming the condition that the degreasing liquid is deteriorated, rust preventive oil ("Nox Last 550HN" manufactured by Nihon Parkerizing Co., Ltd.) is added to the alkaline degreasing liquid ("FC4480" manufactured by Nihon Parkerizing Co., Ltd.). Degreasing was performed by a dipping method using 5 g / l added. The immersion time was 120 seconds, and the temperature of the degreasing solution was 43 ° C. Degreasing was performed by dipping using a 30 L cylindrical container in which a propeller-type stirrer was rotated (rotation speed: 300 rpm).
[0355]
(2) Surface adjustment: “PL-Z” manufactured by Nihon Parkerizing Co., Ltd., chemical concentration: 1.5 g / l, immersion time: 20 seconds, treatment liquid temperature: room temperature
(3) Chemical conversion treatment: “PB-L3030M” manufactured by Nihon Parkerizing Co., Ltd., immersion time: 120 seconds, treatment liquid temperature: 52 ° C.
After each chemical conversion treatment, the phosphate crystal form after chemical conversion treatment was observed with an SEM and evaluated as follows.
[0356]
○: Phosphate crystals equivalent to those on GA and GI are formed.
[0357]
X: The phosphate is amorphous or the shape is indefinite.
[0358]
(3) Adhesive bondability
After removing the antirust oil of the 25 mm × 200 mm sample by solvent degreasing, a cleaning oil (“Preton R352L” manufactured by Sugimura Chemical Co., Ltd.) was applied. Apply this sample as a set, apply a PVC-based hemming adhesive in the range of 25 mm x 140 mm (50 mm from the end of the sample without applying adhesive), and paste it through a 0.15 mm thick spacer A test piece was made together. After drying this at 160 ° C. for 10 minutes, it is left at room temperature for 24 to 72 hours, and then the two test pieces are peeled from the T-shaped state using a tensile tester. The average strength of the test piece at the time of pulling was measured.
(4) Anti-degreasing solution, oil penetration
After degreasing, the sample was measured by XPS for quantitative analysis. Si is detected when the degreasing liquid component or oil coating component penetrates into the film. The molar concentration of Si / total molar concentration of metal elements was determined by quantitative values measured after removing contamination on the outermost surface by Ar beam sputtering, and evaluated as follows.
[0359]
○: Less than 0.12
X: 0.12 or more
Table 33 shows the processing conditions, R-factor, half-value width, and results of the performance evaluation for each specimen. The examples of the present invention not only have good press moldability, but also have excellent chemical conversion properties, adhesive bondability, degreasing liquid, and oil penetration properties as compared with the comparative examples.
[0360]
[Table 33]

In the above (Embodiment of the Invention), for the sake of convenience of explanation, the description has been divided into (Embodiment 1) to (Embodiment 3), but the present invention is limited to each of the above embodiments. In the implementation stage, various modifications can be made without departing from the scope of the invention. In addition, the embodiments may be appropriately combined as much as possible, and in that case, a combined effect is obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.
[0361]
【The invention's effect】
As described above, the zinc-based plated steel sheet of the present invention can provide excellent press formability and chemical conversion treatment.
[0362]
Moreover, according to the manufacturing method of the galvanized steel plate of this invention, the galvanized steel plate excellent in both press-formability and chemical conversion treatment property can be manufactured stably.
[Brief description of the drawings]
FIG. 1 is a front view showing a friction coefficient measuring apparatus used in Examples.
2 is a perspective view showing the shape and dimensions of beads constituting the apparatus of FIG. 1. FIG.
FIG. 3 Zn_Three(PO_Four)₂・ 4H₂It is a figure which shows the P-K edge XANES spectrum of O, the background was subtracted and it normalized so that the peak top might be set to 1.
[Explanation of symbols]
1 Friction coefficient measurement sample
2 Sample stage
3 Slide table
4 Laura
5 Slide table support
6 beads
7 First load cell
8 Second load cell

Claims (9)

It contains a cation component (α) substantially consisting of Al and / or Fe and a phosphoric acid component (β), and a molar concentration ratio (α) / of the sum of the cation component (α) and the phosphoric acid component (β) / (Β) (wherein the phosphoric acid component is a molar concentration of P ₂ O _{5 in} terms of P ₂ O ₅ ) is more than 0.20 and 6 or less, and further, an aqueous solution containing carboxylic acid is applied to the surface of the plated layer of the galvanized steel sheet. A method for producing a galvanized steel sheet, wherein the film is formed by drying without washing with water. The method for producing a galvanized steel sheet according to claim 1, wherein the aqueous solution applied to the surface of the plating layer further contains NH ₄ ⁺ as a cation component. The aqueous solution applied to the plating layer surface contains at least Fe as a cation component, and the molar concentration ratio (γ) / (β) of Fe (γ) and phosphoric acid component (β) (however, the phosphoric acid component is P ₂ The method for producing a galvanized steel sheet according to claim 1 or 2, wherein the molar concentration of O ₅ is greater than 0.20 and less than 0.95. The aqueous solution applied to the surface of the plating layer contains at least Al as a cation component, and the molar concentration ratio (δ) / (β) of Al (δ) and phosphoric acid component (β) (wherein the phosphoric acid component is P ₂ The method for producing a galvanized steel sheet according to any one of claims 1 to 3, wherein the molar concentration of O ₅ is 1/10 or more and less than 2/3. Aqueous solution applied to the plated layer surface, further contain silica (epsilon), silica (epsilon) and the molar concentration ratio of the phosphoric acid component (β) (ε) / ( β) ( where silica in terms of SiO ₂ moles _{5. The} method for producing a zinc-based plated steel sheet according to claim 1, wherein the concentration and the phosphoric acid component are 0.01 to 50 in terms of P ₂ O ₅ equivalent molar concentration. The method for producing a zinc-based plated steel sheet according to any one of claims 1 to 5, wherein the aqueous solution applied to the surface of the plating layer further contains a water-soluble resin and / or a water-dispersible resin. The method for producing a galvanized steel sheet according to any one of claims 1 to 6, wherein the carboxylic acid contained in the aqueous solution applied to the surface of the plating layer is oxycarboxylic acid. The method for producing a galvanized steel sheet according to claim 7, wherein the oxycarboxylic acid is citric acid. Aqueous solution applied to the plated layer surface, additionally contain sulfate ions (SO ₄ ^2-) (ζ), the molar concentration ratio of sulfate ion (SO ₄ ^2-) (ζ) and phosphoric acid component (beta) (zeta ) / (Β) (wherein the phosphoric acid component is a molar concentration in terms of P ₂ O ₅ ) is 0.05 to 1.00, Zinc-based plated steel sheet according to any one of claims 1 to 8 Manufacturing method.

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