JP3745457B2

JP3745457B2 - Manufacturing method of steel sheet for welding can excellent in weldability, corrosion resistance, appearance and adhesion

Info

Publication number: JP3745457B2
Application number: JP16257696A
Authority: JP
Inventors: 茂平野; 八七大八木
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1995-07-06
Filing date: 1996-06-24
Publication date: 2006-02-15
Anticipated expiration: 2016-06-24
Also published as: JPH0971878A

Description

【０００１】
【発明の属する技術分野】
本発明は、製缶素材として、特にシーム溶接性、耐食性、外観性、塗料及びフィルム密着性に優れた溶接缶用鋼板の製造方法に関するものである。
【０００２】
【従来の技術】
近年、ワイヤーシーム抵抗溶接法による溶接缶の製缶技術が急速に進展し、飲料缶分野での実用化が急速に進展してきた。この種の溶接缶に使用される缶用鋼板は、電気めっきによりＦｅ−Ｎｉ合金めっきを行った後、Ｓｎめっきを行い、更に溶錫処理し、クロメート処理を行うシーム溶接性に優れた製缶用表面処理鋼板の製造方法（特開昭６０−２０８４９４号公報）、あるいは、Ｆｅ−Ｎｉ合金を施した後、Ｓｎめっき、クロメート処理することにより塗料密着性、溶接性に優れたシーム溶接缶用表面処理鋼板の製造方法（特開昭６０−１３０９８号公報）により作製される。確かにこのような発明による製造方法は、溶接性、耐食性、塗料密着性を備えた溶接缶用表面処理鋼板を提供するものである。
更に、これらの容器用表面処理鋼板を用いて、缶内面には耐食性を確保するための塗装焼き付けが行われ、缶外面には多色刷り印刷が行われる。この後、ワイヤーシーム溶接法により製缶が行われて、実用に供されている。
【０００３】
【発明が解決しようとする課題】
近年では、より一層の製缶技術の進歩と製缶コストダウンが相俟って、製缶工程の大幅な生産性向上を狙って、塗装・印刷の代わりに、缶内面かつ／または外面に有機フィルムをラミネートした材料が使用されるようになった。
ところが、缶内面かつ／または外面に有機フィルムをラミネートする材料として、上記に述べた容器用表面処理鋼板を適用した場合、溶接部近傍で塗料やフィルム密着性不良が発生する。これは、上記の容器用表面処理鋼板は、めっき層に合金化していない金属Ｓｎを含有しているため、溶接余熱によりＳｎ融点以上に温度上昇される溶接部近傍は、めっき層が溶融する。この時、めっき層上の塗料やフィルムは溶融した液体金属Ｓｎ上にいわば浮かんでいる様な状態になるため、塗料やフィルム密着性が極めて低くなり、冷却風による塗料やフィルム剥離や塗料やフィルムの内部応力による塗料やフィルム収縮が起こり易くなり、塗料やフィルム密着不良が生じる。
【０００４】
【課題を解決するための手段】
塗料やフィルム密着不良を回避するためには、金属Ｓｎのめっき量を少なくし、金属Ｓｎの被覆率を低下させれば、確かに塗料及びフィルム密着性は向上する。しかし、Ｓｎめっき量が減少すれば、溶接缶用鋼板として具備すべき特性である溶接性や耐食性が劣化するため、フィルム密着性、溶接性、外観性、塗料密着性を全て満足する溶接缶用材料の製造は困難であった。
本発明者等は、これらの問題点に対して、外観性、塗料及びフィルム密着性、溶接性、塗料密着性を全て満足する溶接缶用材料として、Ｓｎが島状化し、金属Ｓｎの存在しないフィルム密着性の優れたＦｅ−Ｎｉ合金めっき層が露出するめっき構造を有する鋼板が、溶接熱影響部のようなＳｎの融点を超える箇所でも、優れた密着性を確保することが出来ることを見出し、その製造において経済的に優れた製造方法を発明した。
【０００５】
即ち本発明は、
（１）鋼板表面にＮｉを５〜５５％含有しためっき量５０〜８００ｍｇ／ｍ² のＦｅ−Ｎｉ合金めっき層を形成し、その表面に膜厚１〜５００ｎｍである部分の面積被覆率を５０％以上とする水酸化物層を形成し、次いでその表面にめっき量４００〜２５００ｍｇ／ｍ² のＳｎめっき層を形成した後、溶融溶錫処理を行った後、最表層にＣｒ換算量で２〜４０ｍｇ／ｍ² のクロメート被覆層を形成することを特徴とする溶接性、耐食性、外観性及び密着性に優れた溶接缶用鋼板の製造方法。
【０００６】
（２）鋼板表面にＮｉを５〜５５％含有しためっき量５０〜８００ｍｇ／ｍ² のＦｅ−Ｎｉ合金めっき層を形成し、その表面に膜厚１〜５００ｎｍである部分の面積被覆率を５０％以上とする水酸化物層を形成し、次いでその表面にめっき量４００〜２５００ｍｇ／ｍ² のＳｎめっき層を形成した後、溶融溶錫処理を行って、前記Ｓｎめっき層を面積被覆率４０〜９８％の島状Ｓｎとし、さらに最表層にＣｒ換算量で２〜４０ｍｇ／ｍ² のクロメート被覆層を形成することを特徴とする溶接性、耐食性、外観性及び密着性に優れた溶接缶用鋼板の製造方法。
【０００７】
（３）鋼板表面にＮｉを５〜５５％含有しためっき量５０〜８００ｍｇ／ｍ² のＦｅ−Ｎｉ合金めっき層を形成し、その表面に膜厚１〜５００ｎｍである部分の面積被覆率を５０％以上とする水酸化物層を形成し、次いでその表面にめっき量４００〜２５００ｍｇ／ｍ² のＳｎめっき層を形成した後、溶融溶錫処理を行って、前記Ｓｎめっき層を面積被覆率８０％を超えて９８％以下の島状Ｓｎとし、さらに最表層にＣｒ換算量で２〜４０ｍｇ／ｍ² のクロメート被覆層を形成することを特徴とする溶接性、耐食性、外観性及び密着性に優れた溶接缶用鋼板の製造方法。
【０００８】
（４）膜厚１〜５００ｎｍである部分の面積被覆率を５０％以上とする水酸化物層を、Ｆｅ系水酸化物、Ｎｉ系水酸化物の１種または２種から構成することを特徴とする前記（１）〜（３）に記載の溶接性、耐食性、外観性及び密着性に優れた溶接缶用鋼板の製造方法。
（５）膜厚１〜５００ｎｍである部分の面積被覆率を５０％以上とする水酸化物層の形成を、Ｆｅ−Ｎｉ合金めっき液を使用し、Ｆｅ−Ｎｉ合金めっき層とその上層の水酸化物層を同時に形成することを特徴とする前記（１）〜（４）に記載の溶接性、耐食性、外観性及び密着性に優れた溶接缶用鋼板の製造方法にある。
【０００９】
【発明の実施の形態】
以下に本発明の作用である、溶接性、耐食性、外観性、塗料及びフィルム密着性に優れた溶接缶用鋼板の製造方法について詳細に説明する。
本発明においてめっき原板は特に規制されるものではなく、通常、容器材料として使用される鋼板を用いる。めっき原板の製造法、材質なども特に規制されるものではなく、通常の鋼片製造工程から熱間圧延、酸洗、冷間圧延、焼鈍、調質等の工程を経て製造される。更に、このめっき原板は必要とされる缶体強度および板厚に応じて冷間圧延後、焼鈍を行ってから再冷間圧延（即ち２ＣＲ法）する工程で製造してもよい。
【００１０】
上記のめっき原板に、めっきを行う場合、通常、めっき原板表面を清浄化するため前処理として脱脂、酸洗が行われるが、それらの方法は特に規制するものでは無く、例えば、１０％苛性ソーダ中で脱脂した後、５％硫酸溶液中で酸洗を行えばよい。脱脂、酸洗に引き続き、表面に水酸化物層を有するＦｅ−Ｎｉ合金めっき層を形成させる。Ｆｅ−Ｎｉ合金めっき層の役割は、耐食性と溶接性の両特性の確保である。Ｎｉは高耐食金属のため、Ｎｉを含む合金めっきをする事により、めっき層の耐食性を向上させることが出来る。
【００１１】
また、溶接性は、合金化していない金属Ｓｎが増加すると良好になることが知られている。一般に、溶接缶用鋼板は溶接前に塗装焼き付けやフィルムラミネートにより加熱処理が行われるため、当初めっきした金属Ｓｎは、これらの加熱処理により合金化され、溶接性が劣化する傾向にある。しかし、下地にＦｅ−Ｎｉ合金めっき層が存在すると、これらの加熱処理によっても、合金化の進行が抑制されるため、金属Ｓｎが残留し良好な溶接性が確保される。
【００１２】
これら耐食性と溶接性の両特性を確保するためには、Ｆｅ−Ｎｉ合金めっき量は以下の様に規定される。Ｆｅ−Ｎｉ合金めっき量が片面当たり５０ｍｇ／ｍ² 未満では、Ｆｅ−Ｎｉ合金めっきの層を有する合金化の抑制効果が十分発揮されず良好な溶接性が確保されない。めっき量が５０ｍｇ／ｍ² 以上になると、合金化の抑制効果が発揮され、良好な溶接性が確保される。溶接性の向上効果は、めっき量が増加する程、向上するが８００ｍｇ／ｍ² を越えると、その効果は飽和するため、Ｆｅ−Ｎｉ合金めっき量は経済的に８００ｍｇ／ｍ² 以下で良い。
【００１３】
更に、Ｆｅ−Ｎｉ合金めっき層中のＮｉ含有率が５％未満では、十分な耐食性が確保できないためＮｉ含有率は５％以上にする必要がある。また、Ｎｉ含有率が５５％を越えると、Ｆｅ−Ｎｉ合金めっきの合金化抑制効果が失われるため、Ｆｅ−Ｎｉ合金めっき層中のＮｉ含有率は５５％以下にする必要がある。
従って、実用上、耐食性と溶接性を確保するために必要なＦｅ−Ｎｉ合金めっき量は鋼板片面当たり５０〜８００ｍｇ／ｍ² 、Ｆｅ−Ｎｉめっき層中のＮｉ含有率は５〜５５％にする必要がある。
【００１４】
一方、Ｆｅ−Ｎｉ合金めっきの上層に付与される水酸化物めっき層は、引き続き行われるＳｎめっき後の溶融溶錫処理時に、溶融液化したＳｎに対して低い濡れ性を有している事から、Ｓｎを球状化する役割を果たす。この結果、金属Ｓｎの存在しない塗料及びフィルム密着性の優れたＦｅ−Ｎｉ合金めっき層が露出するため、溶接熱影響部のようなＳｎの融点を超える箇所でも、優れた密着性を確保することが出来る。
【００１５】
本発明者等は、上述の密着性向上効果をもたらすＳｎめっき用下地めっきを検討した結果、水酸化物層をＳｎの下地めっきとして使用すれば、実用上、優れた耐食性、溶接性を確保した上、優れた密着性を確保できる表面処理鋼板を製造出来ることを明らかにした。図１は、優れた、溶接性、密着性を発揮しためっき鋼板のＧＤＳ分析結果であり、Ｓｎめっき層下に水酸化物の酸素が検出されていることが判る。更に、電気合金めっきを用いれば、Ｆｅ−Ｎｉ合金めっき層上に水酸化物層を同時に形成することが出来、工業的には極めて有益である。
【００１６】
本発明におけるＦｅ−Ｎｉ合金めっきとは、Ｎｉ金属とＦｅ金属および残部が不可避的不純物からなるめっきを示す。Ｆｅ−Ｎｉ合金めっき層上に形成させる水酸化物は、Ｆｅ系水酸化物、Ｎｉ系水酸化物の１種または２種から構成されている。従って、Ｆｅ系水酸化物、Ｎｉ系水酸化物、Ｆｅ系水酸化物とＮｉ系水酸化物の混合物の何れの物質を形成させても、本発明の主旨であるＳｎめっき後の溶融溶錫処理時に、溶融液化したＳｎを島状化する役割を果たす。
【００１７】
また、Ｆｅ−Ｎｉ合金めっき上に形成される水酸化物は、１原子層でも効果があるが、本発明の効果を十分に発揮させるためには、厚さ１ｎｍ以上の水酸化物層を被覆率５０％以上に形成させることが望ましい。水酸化物層の厚みが厚くなる程、溶融Ｓｎの球状化効果は促進されるが、５００ｎｍを越えると、水酸化物は凝集力が低いため、凝集破壊による密着不良を起こしやすくなる。従って、水酸化物層の厚さは１〜５００ｎｍにすることが望ましい。
【００１８】
一方、水酸化物層の被覆率が向上すればＳｎはより島状化するが、被覆率が多すぎると外観性の劣るＦｅ−Ｎｉ合金めっき層が露出するため、Ｆｅ−Ｎｉ合金めっき条件を適当に制御し、水酸化物層の被覆率を制御する必要がある。外観性と密着性を兼備した島状Ｓｎを製造するためには、好ましくは水酸化物層の被覆率を５０〜８５％にすれば良い。水酸化物の厚み、被覆率の測定は、例えば、ＥＳＣＡ、ＳＩＭＳ、ＥＰＭＡ等で測定することが出来る。
【００１９】
Ｆｅ−Ｎｉ合金めっき層と上述の効果を発揮するＦｅ−Ｎｉ合金めっき層上の水酸化物層を同時に形成させるには、異常共析型のめっき浴を使用すればよい。例えば、硫酸イオン溶液中に２価のＦｅイオンと２価のＮｉイオンを含んだ溶液、或いは、硫酸イオン、塩化物イオン溶液中に２価のＦｅイオンと２価のＮｉイオンを含んだ溶液、或いは、ほう酸イオン、硫酸イオン、塩化物イオン溶液中に２価のＦｅイオンと２価のＮｉイオンを含んだ溶液中で、カソード電解すれば良い。また、カソード電解する時の電流密度も特に規制しないが、余りに低い電流密度で電解すると、Ｆｅ−Ｎｉ合金めっきが異常共析せず、水酸化物も生成しないため、異常共析する電流密度領域で電解する。
【００２０】
Ｆｅ−Ｎｉ合金めっきの後、Ｓｎめっきが行われる。ここで言うＳｎめっきとは、金属Ｓｎと不可避的不純物からなる。Ｓｎめっきは、前述したように溶接性を確保するために行われるが、工業的に効率良く溶接を行うには、Ｓｎのめっき量を４００ｍｇ／ｍ² 以上にする必要がある。Ｓｎめっき量が増加すると、溶接性の向上効果は増加するが、めっき量が２５００ｍｇ／ｍ² を越えると、溶接性の向上効果が飽和するため、経済的には２５００ｍｇ／ｍ² 以下にする必要がある。このＳｎめっき方法については特に規制するものではなく、例えば、通常の電気めっきにより行うことが出来る。
【００２１】
Ｓｎめっきの後、溶融溶錫処理が行われる。溶融溶錫処理に於いては、Ｓｎの融点を超える加熱処理を行えれば良く、例えば、通電加熱、誘導加熱、炉内加熱などの方法を使用すればよい。この溶融溶錫処理により、異常析出により形成された上層に水酸化物を有するＦｅ−Ｎｉ合金めっきの前述の効果により、めっきされたＳｎが島状化し、密着性の優れためっき層構造が形成される。この時の、Ｓｎの面積占有率は、４０〜９８％にすることが望ましい。これは、面積占有率が４０％以上を下回ると外観に優れたＳｎの面積率が少なすぎるため、外観性が劣化する。従って、Ｓｎの面積占有率は４０％以上必要である。また、より優れた外観性を発揮するためには、より好ましくはＳｎの面積占有率が８０％を上回ればよい。一方、鋼板の外観性はＳｎの面積占有率が増加するほど向上するが、面積占有率が９８％を越えると、フィルムの密着性が劣化するため９８％以下が望ましい。
【００２２】
引き続き、溶融溶錫処理の後、塗料密着性、フィルム密着性、耐食性（アンダーカッティングコロージョンの防止）を目的としてクロメート皮膜が付与される。ここで言うクロメート皮膜とは、水和酸化クロム単一の皮膜、即ち本来のクロメート皮膜といま一つは下層に金属クロム層、上層に水和酸化クロム層の二層よりなる被膜の二つの場合を指している。水和酸化クロム層には、後述するめっき助剤である硫酸イオンやフッ素イオンなどを含む場合がある。塗料密着性、フィルム密着性や耐食性は、この水和酸化クロムの官能基とラミネートされるフィルムの官能基が強固な化学的な結合を行うことによって確保される。
【００２３】
しかし、水和酸化クロム被膜は電気的に絶縁体のため電気抵抗が非常に高く、金属クロムも融点が高くかつ電気抵抗も高いので、両者とも溶接性を劣化せしめるマイナス要因である。そのため、良好なフィルム密着性、耐食性と実用的に溶接性を劣化せしめない適正なクロメート皮膜付着量が非常に重要となる。従って、クロメート皮膜付着量は金属クロム換算で片面当たり２〜４０ｍｇ／ｍ² が選定される。
即ち、クロメート皮膜付着量が２ｍｇ／ｍ² 未満では、フィルム密着性の向上、アンダーカッティングコロージョンの防止に効果が得られないので、２ｍｇ／ｍ² 以上の付着量が望ましい。一方、クロメート皮膜付着量が４０ｍｇ／ｍ² を越えると接触抵抗が著しく増加し、局部的な発熱による散りが発生し易くなり溶接性が劣化する。そのためクロメート皮膜付着量は４０ｍｇ／ｍ² 以下に規制される。
【００２４】
クロメート処理方法は、各種のクロム酸のナトリウム塩、カリウム塩、アンモニウム塩の水溶液による浸漬処理、スプレー処理、電解処理などいずれの方法で行っても良いが、特に陰極電解処理が優れている。とりわけ、クロム酸にめっき助剤として硫酸イオン、フッ化物イオン（醋イオンを含む）あるいはそれらの混合物を添加した水溶液中での陰極電解処理が最も優れている。
【００２５】
【実施例】
以下に本発明の実施例及び比較例について述べ、その結果を表１に示す。
冷間圧延もしくは焼鈍後の２回圧延により、所定の板厚に調整しためっき原板を５％苛性ソーダ中で電解脱脂し、水洗後１０％硫酸中で電解酸洗し、表面活性後表面処理を行った。このめっき原板に、（１）−（Ａ）〜（Ｄ）に示す条件でＦｅ−Ｎｉ合金めっき及びその上に水酸化物を同時に形成させた後、（２）−（Ａ）〜（Ｂ）に示す条件でＳｎめっきを行い、引き続き（３）−（Ａ）〜（Ｂ）に示す条件で加熱処理を行い、引き続き（４）−（Ａ）〜（Ｃ）に示す処理浴でクロメート皮膜を生成させたものを作製した。
【００２６】
【表１】

【００２７】

【００２８】

【００２９】
（３）加熱処理条件
（Ａ）加熱炉法
４００℃雰囲気の加熱炉に５〜３０ｓｅｃ入れ、取り出して直ちに水冷する。
（Ｂ）通電加熱法
交流を２２０℃まで４〜１５ｓｅｃで昇温する様に通電し、通電後、直ちに水冷する。
【００３０】

【００３１】
上記処理材について、以下に示す（Ａ）〜（Ｅ）の各項目について実施し、その性能を評価した。
（Ａ）シーム溶接性
試験片は高温短時間での塗装焼付け条件を想定して３２０℃まで２３ｓｅｃで昇温する条件で焼付けを行い、以下の溶接条件でシーム溶接性を評価した。ラップ代０．５ｍｍ、加圧力４５ｋｇｆ、溶接ワイヤースピード８０ｍ／ｍｉｎの条件で、電流を変更して溶接を実施し、十分な溶接強度が得られる最小電流値と散りなどの溶接欠陥が目立ち始める最大電流値からなる適正電流範囲の広さおよび溶接欠陥の発生状況から総合的に判断して評価した。
【００３２】
（Ｂ）塗料密着性
試験片の缶内面側に相当する面にエポキシフェノール系塗料を５５ｍｇ／ｄｍ²塗布し、更に缶外観に相当する面にクリヤーラッカーを４０ｍｇ／ｄｍ²塗布し、２９０℃まで１５ｓｅｃの焼き付け条件で乾燥硬化した。引続き、各々の面に１ｍｍ間隔でスクラッチを入れ、約１００個の碁盤目を作製し、速やかにテープ剥離し、その剥離状況を観察し塗料密着性を評価した。
（Ｃ）フィルム密着性評価試験
試験片に厚さ１５μｍのＰＥＴ（ポリエチレンテレフタレート）系フィルムをラミネートした後、地鉄に達するまでクロスカットを入れ、速やかに２４０℃に加熱し、クロスカット中央部に５ｋｇ／ｃｍ² の空気ガスを垂直に吹きつけ、フィルムの剥離状況を評価した。
【００３３】
（Ｄ）ＵＣＣ（アンダーカッティングコロージョン）評価テスト
試験片の缶内面に相当する面の耐食性を評価するため、缶内面側に相当する面に厚さ１５μｍのＰＥＴ（ポリエチレンテレフタレート）系フィルムをラミネートした。その後、地鉄に達するまでクロスカットを入れ、１．５％クエン酸−１．５％食塩混合液からなる試験液中に大気開放下５５℃×４日間浸漬した。試験終了後、速やかにスクラッチ部および平面部をテープで剥離して、スクラッチ部近傍の腐食状況、スクラッチ部のピッティング状況および平面部のフィルム剥離状況を判断して総合的に評価した。
（Ｅ）外観性評価テスト
缶外面側に相当する面にホワイト印刷を行った厚さ１５μｍのＰＥＴ（ポリエチレンテレフタレート）系フィルムをラミネートし、色調の明るさを評価した。
【００３４】
【発明の効果】
表１に示すように、本発明により製造された溶接缶用鋼板は優れた溶接性、外観性、塗料密着性及びフィルム密着性、耐食性を有することが明らかになった。
【図面の簡単な説明】
【図１】本発明のめっき鋼板のＧＤＳ（グロー放電分光分析）測定結果を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a steel sheet for a welding can that is particularly excellent in seam weldability, corrosion resistance, appearance, paint and film adhesion as a can-making material.
[0002]
[Prior art]
In recent years, welding can manufacturing technology using wire seam resistance welding has been rapidly advanced, and practical application in the beverage can field has been rapidly progressing. The steel plate for cans used in this type of welded can is a can-making machine with excellent seam weldability in which Fe-Ni alloy plating is performed by electroplating, followed by Sn plating, further tin treatment, and chromate treatment. For surface treated steel sheets (Japanese Patent Laid-Open No. 60-208494), or for seam welded cans with excellent paint adhesion and weldability by applying Sn-plating and chromate treatment after applying Fe-Ni alloy It is produced by a method for producing a surface-treated steel sheet (Japanese Patent Laid-Open No. 60-13098). Certainly, the manufacturing method according to the present invention provides a surface-treated steel sheet for a welding can having weldability, corrosion resistance, and paint adhesion.
Furthermore, using these surface-treated steel sheets for containers, paint baking is performed on the inner surface of the can to ensure corrosion resistance, and multicolor printing is performed on the outer surface of the can. Thereafter, the can is made by a wire seam welding method and put into practical use.
[0003]
[Problems to be solved by the invention]
In recent years, combined with further advancement in can manufacturing technology and reduction in can manufacturing costs, aiming at significant productivity improvement in the can manufacturing process, instead of painting and printing, organic can inner and / or outer surface Film laminated materials have been used.
However, when the above-described surface-treated steel sheet for containers is applied as a material for laminating an organic film on the inner surface and / or outer surface of the can, paint and film adhesion defects occur in the vicinity of the weld. This is because the above-mentioned surface-treated steel sheet for containers contains metal Sn that is not alloyed in the plating layer, so that the plating layer is melted in the vicinity of the weld where the temperature is raised to the Sn melting point or more by the residual heat of welding. At this time, since the paint or film on the plating layer is in a state of floating on the molten liquid metal Sn, the adhesion of the paint or film becomes extremely low, and the paint or film is peeled off by the cooling air or the paint or film. The paint and film shrinkage easily due to the internal stress of the paint, and poor paint and film adhesion occur.
[0004]
[Means for Solving the Problems]
In order to avoid poor paint and film adhesion, reducing the amount of metal Sn plating and lowering the metal Sn coverage will certainly improve the paint and film adhesion. However, if the Sn plating amount decreases, the weldability and corrosion resistance, which should be provided as a steel plate for welded cans, deteriorate, so that for welded cans that satisfy all film adhesion, weldability, appearance, and paint adhesion. The production of the material has been difficult.
With respect to these problems, the present inventors have formed islands of Sn as a welding can material that satisfies all of the appearance, paint and film adhesion, weldability, and paint adhesion, and no metal Sn is present. It has been found that a steel sheet having a plating structure in which an Fe—Ni alloy plating layer with excellent film adhesion is exposed can ensure excellent adhesion even at a location exceeding the melting point of Sn, such as a weld heat affected zone. Invented an economically superior manufacturing method in its manufacture.
[0005]
That is, the present invention
(1) An Fe—Ni alloy plating layer containing 50 to 800 mg / m ² of Ni containing 5 to 55% of Ni is formed on the surface of the steel sheet, and the area coverage of the portion having a film thickness of 1 to 500 nm is 50 on the surface. %, And after forming a Sn plating layer having a plating amount of 400 to 2500 mg / m ^{2 on} the surface and then carrying out molten tin treatment, the outermost layer is 2 in terms of Cr. A method for producing a steel sheet for a welding can excellent in weldability, corrosion resistance, appearance and adhesion, characterized by forming a chromate coating layer of ˜40 mg / m ² .
[0006]
(2) An Fe—Ni alloy plating layer having a plating amount of 50 to 800 mg / m ² containing 5 to 55% of Ni is formed on the surface of the steel sheet, and the area coverage of the portion having a film thickness of 1 to 500 nm is 50 on the surface. %, And after forming a Sn plating layer having a plating amount of 400 to 2500 mg / m ^{2 on} the surface thereof, a molten tin treatment is carried out so that the Sn plating layer has an area coverage of 40 A welding can excellent in weldability, corrosion resistance, appearance and adhesion, characterized in that it has an island-shaped Sn content of ˜98% and further a chromate coating layer of ² to 40 mg / m ^{2 in} terms of Cr is formed on the outermost layer. Steel plate manufacturing method.
[0007]
(3) An Fe—Ni alloy plating layer having a plating amount of 50 to 800 mg / m ² containing 5 to 55% of Ni is formed on the steel sheet surface, and the area coverage of the portion having a film thickness of 1 to 500 nm is 50 on the surface. % Of a hydroxide layer is formed, and then an Sn plating layer having a plating amount of 400 to 2500 mg / m ² is formed on the surface thereof. Then, molten tin treatment is performed, and the Sn plating layer has an area coverage of 80%. % To 98% or less of island-like Sn, and further, a chromate coating layer of ² to 40 mg / m ^{2 in} terms of Cr is formed on the outermost layer, and the weldability, corrosion resistance, appearance and adhesion are characterized by An excellent method for manufacturing steel sheets for welding cans.
[0008]
(4) The hydroxide layer having an area coverage of 50% or more in the portion having a thickness of 1 to 500 nm is composed of one or two of Fe-based hydroxide and Ni-based hydroxide. The manufacturing method of the steel plate for welding cans which was excellent in the weldability, corrosion resistance, external appearance property, and adhesiveness as described in said (1)-(3).
(5) The formation of a hydroxide layer having an area coverage of 50% or more in a portion having a thickness of 1 to 500 nm is made by using an Fe—Ni alloy plating solution, and an Fe—Ni alloy plating layer and water on the upper layer thereof. An oxide layer is formed at the same time. The method for producing a steel sheet for a welding can having excellent weldability, corrosion resistance, appearance and adhesion as described in (1) to (4) above.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Below, the manufacturing method of the steel plate for welding cans which was the effect | action of this invention and was excellent in weldability, corrosion resistance, external appearance property, a coating material, and film adhesiveness is demonstrated in detail.
In the present invention, the plating original plate is not particularly limited, and a steel plate used as a container material is usually used. There are no particular restrictions on the manufacturing method, material, and the like of the plating original plate, and the plate is manufactured through normal steel slab manufacturing processes such as hot rolling, pickling, cold rolling, annealing, and tempering. Further, the plating original plate may be manufactured in a step of performing cold rolling (ie, 2CR method) after performing cold rolling and annealing after depending on the required strength of the can body and the plate thickness.
[0010]
When plating is performed on the above-described plating base plate, usually, degreasing and pickling are performed as pretreatment to clean the plating base plate surface, but these methods are not particularly restricted, for example, in 10% caustic soda After degreasing, the pickling may be performed in a 5% sulfuric acid solution. Following degreasing and pickling, an Fe—Ni alloy plating layer having a hydroxide layer on the surface is formed. The role of the Fe—Ni alloy plating layer is to ensure both characteristics of corrosion resistance and weldability. Since Ni is a highly corrosion resistant metal, the corrosion resistance of the plating layer can be improved by plating with an alloy containing Ni.
[0011]
Further, it is known that the weldability becomes better when the amount of non-alloyed metal Sn increases. In general, since steel plates for welding cans are subjected to heat treatment by paint baking or film lamination before welding, the initially plated metal Sn is alloyed by these heat treatments, and the weldability tends to deteriorate. However, if an Fe—Ni alloy plating layer is present in the base, the progress of alloying is suppressed by these heat treatments, so that metal Sn remains and good weldability is ensured.
[0012]
In order to ensure both the corrosion resistance and the weldability, the amount of Fe—Ni alloy plating is specified as follows. When the amount of Fe—Ni alloy plating is less than 50 mg / m ² per side, the effect of suppressing alloying having a layer of Fe—Ni alloy plating is not sufficiently exhibited, and good weldability is not ensured. When the plating amount is 50 mg / m ² or more, the effect of suppressing alloying is exhibited and good weldability is ensured. The effect of improving the weldability is improved as the plating amount is increased. However, since the effect is saturated when the amount exceeds 800 mg / m ² , the Fe—Ni alloy plating amount may be economically 800 mg / m ² or less.
[0013]
Furthermore, if the Ni content in the Fe—Ni alloy plating layer is less than 5%, sufficient corrosion resistance cannot be ensured, so the Ni content needs to be 5% or more. Further, if the Ni content exceeds 55%, the effect of suppressing the alloying of the Fe—Ni alloy plating is lost, so the Ni content in the Fe—Ni alloy plating layer needs to be 55% or less.
Therefore, practically, the Fe—Ni alloy plating amount necessary to ensure corrosion resistance and weldability is 50 to 800 mg / m ² per one surface of the steel sheet, and the Ni content in the Fe—Ni plating layer is 5 to 55%. There is a need.
[0014]
On the other hand, the hydroxide plating layer applied to the upper layer of the Fe—Ni alloy plating has low wettability with respect to the molten liquefied Sn during the subsequent molten tin treatment after Sn plating. , Plays a role of spheroidizing Sn. As a result, the paint and the Fe—Ni alloy plating layer having excellent film adhesion without the presence of metal Sn are exposed, so that excellent adhesion can be ensured even at locations exceeding the melting point of Sn, such as the weld heat affected zone. I can do it.
[0015]
As a result of studying the base plating for Sn plating that brings about the above-described adhesion improving effect, the present inventors have practically ensured excellent corrosion resistance and weldability when the hydroxide layer is used as the base plating of Sn. In addition, it was clarified that a surface-treated steel sheet capable of ensuring excellent adhesion can be produced. FIG. 1 is a GDS analysis result of a plated steel sheet exhibiting excellent weldability and adhesion, and it can be seen that hydroxide oxygen is detected under the Sn plating layer. Furthermore, if electroalloy plating is used, a hydroxide layer can be simultaneously formed on the Fe—Ni alloy plating layer, which is extremely useful industrially.
[0016]
The Fe—Ni alloy plating in the present invention refers to plating in which Ni metal, Fe metal, and the balance are inevitable impurities. The hydroxide formed on the Fe—Ni alloy plating layer is composed of one or two of Fe-based hydroxide and Ni-based hydroxide. Therefore, even if any substance of Fe-based hydroxide, Ni-based hydroxide, and a mixture of Fe-based hydroxide and Ni-based hydroxide is formed, molten tin after Sn plating, which is the gist of the present invention, is formed. At the time of processing, it plays a role of islanding melted Sn.
[0017]
In addition, the hydroxide formed on the Fe—Ni alloy plating is effective even in a single atomic layer, but in order to fully exhibit the effects of the present invention, a hydroxide layer having a thickness of 1 nm or more is coated. It is desirable to form at a rate of 50% or more. As the thickness of the hydroxide layer increases, the spheroidizing effect of molten Sn is promoted. However, when the thickness exceeds 500 nm, the hydroxide has a low cohesive force, and therefore, adhesion failure due to cohesive failure tends to occur. Therefore, the thickness of the hydroxide layer is desirably 1 to 500 nm.
[0018]
On the other hand, if the coverage of the hydroxide layer is improved, Sn becomes more island-like, but if the coverage is too high, the Fe—Ni alloy plating layer with poor appearance is exposed. It is necessary to control appropriately and to control the coverage of the hydroxide layer. In order to produce island-shaped Sn having both appearance and adhesion, the coverage of the hydroxide layer is preferably 50 to 85%. The thickness and coverage of the hydroxide can be measured by, for example, ESCA, SIMS, EPMA or the like.
[0019]
In order to simultaneously form the Fe—Ni alloy plating layer and the hydroxide layer on the Fe—Ni alloy plating layer exhibiting the above-described effects, an abnormal eutectoid plating bath may be used. For example, a solution containing divalent Fe ions and divalent Ni ions in a sulfate ion solution, or a solution containing divalent Fe ions and divalent Ni ions in a sulfate ion or chloride ion solution, Alternatively, cathodic electrolysis may be performed in a solution containing divalent Fe ions and divalent Ni ions in a borate ion, sulfate ion, or chloride ion solution. Also, the current density during cathode electrolysis is not particularly restricted, but if electrolysis is performed at a too low current density, the Fe-Ni alloy plating does not abnormally eutect and does not generate hydroxide, so the current density region where abnormal eutectoid occurs. Electrolyze with.
[0020]
After the Fe—Ni alloy plating, Sn plating is performed. Sn plating mentioned here consists of metal Sn and inevitable impurities. As described above, Sn plating is performed to ensure weldability. However, in order to perform welding industrially efficiently, it is necessary to set the Sn plating amount to 400 mg / m ² or more. As the amount of Sn plating increases, the effect of improving weldability increases. However, when the amount of plating exceeds 2500 mg / m ² , the effect of improving weldability is saturated, so it is necessary to economically make it 2500 mg / m ² or less. There is. The Sn plating method is not particularly limited, and can be performed by, for example, ordinary electroplating.
[0021]
After Sn plating, molten tin treatment is performed. In the molten tin treatment, it is only necessary to perform a heat treatment exceeding the melting point of Sn. For example, methods such as energization heating, induction heating, and furnace heating may be used. By this molten tin treatment, the plated Sn is formed into islands by the above-described effect of Fe—Ni alloy plating having hydroxide on the upper layer formed by abnormal precipitation, and a plating layer structure with excellent adhesion is formed. Is done. At this time, the Sn area occupation ratio is desirably 40 to 98%. This is because when the area occupancy is less than 40% or more, the area ratio of Sn excellent in appearance is too small, and the appearance is deteriorated. Accordingly, the area occupation ratio of Sn needs to be 40% or more. Moreover, in order to exhibit the outstanding external appearance property, More preferably, the area occupation rate of Sn should just exceed 80%. On the other hand, the appearance of the steel sheet is improved as the Sn area occupancy increases. However, if the area occupancy exceeds 98%, the adhesion of the film is deteriorated.
[0022]
Subsequently, after the molten tin treatment, a chromate film is applied for the purpose of paint adhesion, film adhesion, and corrosion resistance (prevention of undercutting corrosion). The chromate film referred to here is a single film of hydrated chromium oxide, that is, the original chromate film and another one of two films: a metal chromium layer on the lower layer and a hydrated chromium oxide layer on the upper layer. Pointing. The hydrated chromium oxide layer may contain sulfate ions or fluorine ions which are plating aids described later. Paint adhesion, film adhesion, and corrosion resistance are ensured by a strong chemical bond between the functional group of the hydrated chromium oxide and the functional group of the laminated film.
[0023]
However, since the hydrated chromium oxide film is an electrical insulator, the electrical resistance is very high, and the metallic chromium has a high melting point and high electrical resistance, both of which are negative factors that degrade the weldability. Therefore, it is very important to have good film adhesion, corrosion resistance, and an appropriate amount of chromate film that does not practically degrade weldability. Therefore, 2-40 mg / m ² per side is selected as the amount of chromate film adhesion in terms of metallic chromium.
That is, if the chromate film adhesion amount is less than 2 mg / m ² , the effect of improving film adhesion and preventing undercutting corrosion cannot be obtained. Therefore, an adhesion amount of ² mg / m ² or more is desirable. On the other hand, if the amount of chromate film deposited exceeds 40 mg / m ² , the contact resistance is remarkably increased, and scattering due to local heat generation is likely to occur, resulting in poor weldability. Therefore, the amount of chromate film adhesion is regulated to 40 mg / m ² or less.
[0024]
The chromate treatment method may be performed by any method such as immersion treatment with various sodium salts, potassium salts, and ammonium salts of chromic acid, spray treatment, electrolytic treatment, etc., but cathodic electrolytic treatment is particularly excellent. In particular, cathodic electrolysis in an aqueous solution in which sulfate ions, fluoride ions (including soot ions) or a mixture thereof is added to chromic acid as a plating aid is most excellent.
[0025]
【Example】
Examples of the present invention and comparative examples are described below, and the results are shown in Table 1.
Cold-rolled or twice-rolled after annealing, the plating plate adjusted to the specified plate thickness is electrolytically degreased in 5% caustic soda, then washed with water, electrolytically pickled in 10% sulfuric acid, and surface treatment is performed after surface activation. It was. (2)-(A)-(B) after forming a Fe-Ni alloy plating and a hydroxide on it on this plating original plate on the conditions shown to (1)-(A)-(D) simultaneously. Sn plating is performed under the conditions shown in the following, followed by heat treatment under the conditions shown in (3)-(A) to (B), and subsequently, the chromate film is formed in the treatment bath shown in (4)-(A) to (C). What was produced was produced.
[0026]
[Table 1]

[0027]

[0028]

[0029]
(3) Heat treatment conditions (A) Heating furnace method Place in a heating furnace at 400 ° C. for 5 to 30 seconds, take out and immediately cool with water.
(B) Energization heating method Energization is performed so that the alternating current is heated to 220 ° C. in 4 to 15 seconds, and immediately after the energization, water cooling is performed.
[0030]

[0031]
About the said processing material, it implemented about each item of (A)-(E) shown below, and evaluated the performance.
(A) The seam weldability test piece was baked under the condition that the temperature was raised to 320 ° C. in 23 seconds assuming the coating baking condition in a short time at high temperature, and the seam weldability was evaluated under the following welding conditions. Welding is performed by changing the current under the conditions of a lapping margin of 0.5 mm, a pressing force of 45 kgf, and a welding wire speed of 80 m / min, and the maximum current value at which sufficient welding strength can be obtained and welding defects such as scattering start to stand out. Evaluation was made comprehensively based on the range of the appropriate current range consisting of current values and the occurrence of welding defects.
[0032]
(B) An epoxy phenol-based paint 55 mg / dm ^{2 is} applied to the surface corresponding to the inner surface of the paint adhesion test piece, and a clear lacquer is applied 40 mg / dm ² to the surface corresponding to the can appearance. It was dried and cured under baking conditions of 15 sec. Subsequently, scratches were placed on each surface at intervals of 1 mm to produce about 100 grids, and the tape was peeled off quickly. The peeled state was observed to evaluate the paint adhesion.
(C) Film adhesion evaluation test After laminating a 15 μm thick PET (polyethylene terephthalate) film on a test piece, a crosscut is made until it reaches the ground iron, and it is quickly heated to 240 ° C. in the center of the crosscut. 5 kg / cm ² of air gas was blown vertically to evaluate the peeling state of the film.
[0033]
(D) UCC (Under Cutting Corrosion) Evaluation In order to evaluate the corrosion resistance of the surface corresponding to the inner surface of the can of the test specimen, a PET (polyethylene terephthalate) film having a thickness of 15 μm was laminated on the surface corresponding to the inner surface of the can. Then, the crosscut was put in until it reached the ground iron, and it was immersed in the test liquid which consists of a 1.5% citric acid-1.5% sodium chloride mixed solution at 55 degreeC x 4 days in open air. Immediately after the test, the scratch part and the flat part were peeled off with tape, and the corrosion situation near the scratch part, the pitting situation of the scratch part and the film peeling situation of the flat part were judged and evaluated comprehensively.
(E) Appearance evaluation test A 15 μm thick PET (polyethylene terephthalate) film with white printing was laminated on the surface corresponding to the outer surface side of the can, and the brightness of the color tone was evaluated.
[0034]
【The invention's effect】
As shown in Table 1, it was revealed that the steel sheet for welding cans produced according to the present invention has excellent weldability, appearance, paint adhesion, film adhesion, and corrosion resistance.
[Brief description of the drawings]
FIG. 1 is a diagram showing a GDS (glow discharge spectroscopic analysis) measurement result of a plated steel sheet according to the present invention.

Claims

An Fe—Ni alloy plating layer having a plating amount of 50 to 800 mg / m ² containing 5 to 55% Ni is formed on the surface of the steel sheet, and the area coverage of the portion having a thickness of 1 to 500 nm is 50% or more on the surface. after the hydroxide layer was formed, followed by forming a Sn plating layer of the plated amount 400~2500mg / m ² on the surface of, after the molten溶錫treatment, to 40 mg of Cr equivalent amount in the outermost layer / A method for producing a steel sheet for a welding can excellent in weldability, corrosion resistance, appearance and adhesion, characterized by forming a chromate coating layer of m ² .

An Fe—Ni alloy plating layer having a plating amount of 50 to 800 mg / m ² containing 5 to 55% Ni is formed on the surface of the steel sheet, and the area coverage of the portion having a thickness of 1 to 500 nm is 50% or more on the surface. After forming a hydroxide layer to be formed, and subsequently forming a Sn plating layer having a plating amount of 400 to 2500 mg / m ^{2 on} the surface thereof, a molten tin treatment is performed to cover the Sn plating layer with an area coverage of 40 to 98%. A steel plate for a welding can excellent in weldability, corrosion resistance, appearance and adhesion, characterized in that a chromate coating layer of ² to 40 mg / m ^{2 in} terms of Cr is formed on the outermost layer of the island-shaped Sn. Production method.

An Fe—Ni alloy plating layer having a plating amount of 50 to 800 mg / m ² containing 5 to 55% Ni is formed on the surface of the steel sheet, and the area coverage of the portion having a thickness of 1 to 500 nm is 50% or more on the surface. After forming a hydroxide layer to be formed, and subsequently forming a Sn plating layer with a plating amount of 400 to 2500 mg / m ^{2 on} the surface, the molten tin treatment is performed, and the Sn plating layer exceeds the area coverage of 80%. Welding excellent in weldability, corrosion resistance, appearance and adhesion, characterized by forming an island-shaped Sn of 98% or less and further forming a chromate coating layer of ² to 40 mg / m ^{2 in} terms of Cr on the outermost layer. Manufacturing method of steel plate for cans.

The hydroxide layer having an area coverage of a portion having a thickness of 1 to 500 nm of 50% or more is composed of one or two of Fe-based hydroxide and Ni-based hydroxide. The manufacturing method of the steel plate for welding cans excellent in weldability, corrosion resistance, external appearance property, and adhesiveness of Claims 1-3.

The formation of a hydroxide layer having an area coverage of 50% or more in a portion having a thickness of 1 to 500 nm is made by using an Fe—Ni alloy plating solution, and an Fe—Ni alloy plating layer and an upper hydroxide layer thereof. The method for producing a steel sheet for a welding can excellent in weldability, corrosion resistance, appearance and adhesion as claimed in claim 1, wherein: