JP3766652B2

JP3766652B2 - Continuous hot-dip plating and continuous annealing method and apparatus for steel plate

Info

Publication number: JP3766652B2
Application number: JP2002261259A
Authority: JP
Inventors: 誠司杉山; 克彦小浦
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2002-09-06
Filing date: 2002-09-06
Publication date: 2006-04-12
Anticipated expiration: 2022-09-06
Also published as: JP2004099953A

Description

【０００１】
【発明の属する技術分野】
本発明は１つの設備ラインで鋼板の連続溶融メッキと連続焼鈍とを切替えて行うことができる連続溶融メッキ及び連続焼鈍兼用方法ならびにその装置に関するものである。
【０００２】
【従来の技術】
鋼板の連続溶融メッキと連続焼鈍とは別々の装置にて実施されるのが一般的である。ところが、連続溶融メッキでは溶融メッキ処理する前工程で鋼板の連続焼鈍を行うことから、連続溶融メッキ装置には連続焼鈍装置が付設されている。その連続焼鈍装置を利用して、連続メッキラインで連続溶融メッキと連続焼鈍とを兼用して行う技術が種々提案されている。
【０００３】
例えば、従来の連続亜鉛メッキラインを用いた冷延鋼板の製造方法では、連続溶融メッキを行う場合には図１（ａ）に示すように、連続焼鈍炉１で焼鈍した鋼板５を溶融メッキ浴に先端を浸漬したスナウト２を通じて溶融メッキ浴４に導入して連続的に溶融メッキを行い、そして、連続焼鈍を行う場合には、図１（ｂ）に示すように、着脱自在のスナウト先端部３を取外してスナウト出口を溶融メッキ浴の上方に臨ませ、焼鈍炉で焼鈍された鋼板５をスナウト２出口を経て、一対の案内ロール６に掛け回し、溶融メッキパスラインとは異なるパスラインで導出するようにした連続焼鈍方法が開示されている（例えば、特許文献１参照）。
【０００４】
この方法は、スナウトの先端部を取外す作業や鋼板を溶融メッキパスラインとは異なるパスラインに切替える作業が必要となり、切り替え時間を要するため生産性を悪化させるという問題がある。
【０００５】
また、従来の連続焼鈍及び溶融メッキ兼用設備では、連続焼鈍を行う場合には、図２に示すように、連続焼鈍炉１による焼鈍後の鋼板５が空気中の酸素と反応して鋼板表面に酸化膜を生成するのを防止するために、焼鈍炉最終冷却部に鋼板を１５０℃以下に冷却する複数ロールからなるロール冷却装置７を設置し、冷却装置により冷却された鋼板をスナウト２を通じて、溶融メッキパスライン８とは異なる溶融メッキ浴４上の連続焼鈍パスライン９で導出するようにした連続焼鈍が開示されている（例えば、特許文献２）。
【０００６】
この設備は、冷却ロール装置に費用がかかると共に、鋼板を溶融メッキパスラインと異なる焼鈍パスラインに切替える作業が必要となり、切り替え時間を要するため生産性を悪化させるという問題がある。
【０００７】
【特許文献１】
特開昭５５−６４６９号公報（第１頁左欄第６〜１６行、第１図、第２図）
【特許文献２】
特開２０００−２０４４１７号公報（第２欄第２７〜４９行、第１図）
【０００８】
【発明が解決しようとする課題】
そこで、本発明は上記問題点に鑑み、連続溶融メッキパスラインと連続焼鈍パスラインとを同じパスラインにし、パスラインの切替え作業を不要とすることにより生産性の悪化を防止すると共に、切替え毎に整備していたロールの整備費用を削減できる連続溶融メッキ及び連続焼鈍兼用方法ならびにその装置を提供することを課題とするものである。
【０００９】
【課題を解決するための手段】
本発明者は、連続溶融メッキと連続焼鈍とを同じパスラインで行うことについて鋭意研究した。その結果、表面に酸化膜を形成した鋼板は溶融メッキ浴中に浸漬しても、酸化膜が鋼板と溶融メタル（Ｚｎ、Ａｌ等）との合金化反応を阻害するので、表面に溶融メッキが施されないことに着目し、本発明を完成した。
【００１０】
本発明の要旨は次の通りである。
【００１１】
（１）鋼板の連続溶融メッキラインを用いて、鋼板の連続溶融メッキと連続焼鈍とを切替えて行う方法であって、連続溶融メッキを行う場合には、伸縮自在のスナウトのスナウト先端を溶融メッキ浴中に浸漬するように配置し、スナウトを通過した鋼板を溶融メッキ浴に浸漬して溶融メッキを行う。また、連続焼鈍を行う場合には、伸縮自在のスナウトのスナウト先端を溶融メッキ浴面上となるように配置し、スナウト内に酸化性ガスを吹き込んで、スナウトを通過する鋼板の表面に酸化膜を形成した後に、鋼板を溶融メッキ浴に浸漬することを特徴とする鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１２】
（２）連続焼鈍から連続溶融メッキに切替える際には、スナウト内に吹き込んでいた酸化性ガスを非酸化性ガスに切替えてスナウト内を非酸化性ガスでパージした後に、スナウト先端を溶融メッキ浴中に浸漬させ、スナウトを通過した鋼板を溶融メッキ浴に浸漬させることを特徴とする上記（１）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１３】
（３）連続溶融メッキから連続焼鈍に切替える際には、スナウト先端を溶融メッキ浴中からメッキ浴面上に移動させ、スナウト内に酸化性ガスを吹き込んで、スナウトを通過する鋼板の表面に酸化膜を形成した後に、スナウトを通過した鋼板を溶融メッキ浴に浸漬することを特徴とする上記（１）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１４】
（４）浴面上に設置したセンサーにより溶融メッキ浴面とスナウト先端との間隔を検出し、検出信号に基づいて伸縮自在のスナウトの伸縮、溶融メッキ槽の昇降又はメッキ浴中に地金を浸漬、取出しすることによってスナウト先端と浴面との位置関係を制御することを特徴とする上記（１）〜（３）の内のいずれかに記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１５】
（５）連続焼鈍を行う際には、スナウト内酸化性雰囲気が焼鈍炉内に逆流するのを防止できるように、焼鈍炉内雰囲気とスナウト内酸化性雰囲気との間をシールし、スナウト内雰囲気気圧を焼鈍炉内雰囲気圧より低くすることを特徴とする上記（１）、（３）または（４）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１６】
（６）連続焼鈍を行う際には、溶融メッキ浴から引き上げた鋼板の表面にワイピングを施し、冷却した後に、鋼板表面の酸化膜を酸化膜除去装置により除去することを特徴とする上記（１）、（３）、（４）又は（５）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１７】
（７）鋼板表面の酸化膜の除去を化学的、電気化学的又は機械的に行うことを特徴とする上記（５）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１８】
（８）スナウト内に吹き込む酸化性ガスが、空気であることを特徴とする請求項（１）〜（３）のいずれかに記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００１９】
（９）スナウト内に吹き込む非酸化性ガスが、窒素ガス、アルゴンガスであることを特徴とする上記（２）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００２０】
（１０）焼鈍炉内雰囲気とスナウト内雰囲気との間のシールが、ガスシール又はロールタッチシールであることを特徴とする上記（４）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用方法。
【００２１】
（１１）鋼板が必ず溶融メッキ浴に浸漬する同一のパスラインを通過する構造であって、鋼板の連続溶融メッキと連続焼鈍とを切替えることが可能な兼用装置において、鋼板の連続焼鈍炉、焼鈍後の鋼板を溶融メッキ槽に導くスナウト、溶融メッキ槽、溶融メッキ槽の上部に配設した鋼板のワイピング装置、ワイピング後の鋼板冷却装置及び鋼板表面の酸化膜を除去する酸化膜除去装置を備え、かつ、スナウト内に酸化性ガスと非酸化性ガスとを切替えて吹き込むことが可能なガス吹き込み装置を備え、かつ、前記ガス吹き込み装置の取付け位置に対してスナウト上流側のみにガス逆流防止用シール装置を備え、かつ、前記ガス吹き込み装置の取付け位置に対してスナウト下流側のみにスナウト内ガスの自然排出と密閉とを切替え可能とする装置を備えていることを特徴とする鋼板の連続溶融メッキ及び連続焼鈍兼用装置。
【００２２】
（１２）前記スナウト内ガスの自然排出と密閉とを切替え可能とする装置は、スナウト先端を溶融メッキ浴上又は溶融メッキ浴中とすることができる伸縮自在のスナウトであることを特徴とする上記（１１）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用装置。
【００２３】
（１３）浴面上にセンサーを配置し、該センサーにより浴面とスナウト先端との間隔を検出し、伸縮自在のスナウトの伸縮、溶融メッキ槽の昇降又はメッキ浴中に地金を浸漬、取出しすることによって、スナウト先端と浴面との位置関係を制御する制御装置を備えていることを特徴とする上記（１１）又は（１２）記載の鋼板の連続溶融メッキ及び連続焼鈍兼用装置。
【００２４】
（１４）スナウトが耐熱性材料からなっていることを特徴とする上記（１１）〜（１３）の内のいずれかに記載の鋼板の連続溶融メッキ及び連続焼鈍兼用装置。
【００２５】
【発明の実施の形態】
以下、本発明を詳細に説明する。
【００２６】
連続溶融メッキパスラインで連続焼鈍を実施しようとすると、鋼板を溶融メッキ浴に浸漬することが必須となり、鋼板にメッキを施すことなしに連続焼鈍のみを実施することはできない。
【００２７】
そこで、鋼板を溶融メッキ浴に浸漬してもメッキが施されないようにすれば、従来のように異なるパスラインを使用しなくても、連続溶融メッキと同じパスラインで連続焼鈍が実施できることに着想し鋭意研究を行った。その結果、本発明者は、鋼板表面に酸化膜が形成されていると、その鋼板を溶融メッキ浴に浸漬しても、酸化膜が鋼板と溶融メタル（Ｚｎ、Ａｌ等）との合金化反応を阻害するので、表面に溶融メッキが施されないことに着目し溶融メッキに浸漬する前工程のスナウト内で、焼鈍された鋼板表面に酸化膜を形成し、メッキ浴から取り出した後に、酸化膜を除去することにより連続焼鈍を行う本発明を完成した。
【００２８】
以下、本発明を図３及び図４を参酌して説明する。
【００２９】
図３は、本発明の鋼板の連続溶融メッキ及び連続焼鈍兼用装置の概要を示す図である。
【００３０】
図３に示すように、鋼板５は加熱帯、均熱帯、冷却帯等からなる連続焼鈍炉１で均質な機械的性質を与える常法どおりの焼鈍を施される。焼鈍後の鋼板を連続溶融メッキする場合には、溶融メッキ浴中に先端が浸漬（図中では点線で示してある）されているスナウト２を通じて鋼板を溶融Ｚｎや溶融Ａｌ等の溶融メッキ浴４中に浸漬し、メッキ浴４中に設置してあるシンクロール１０を介してメッキ浴上方に引き出す。メッキ浴面上に設置してあるガスワイピング等のワイピング装置１１でメッキ浴から出た鋼板のメッキ付着量を制御し、必要に応じて加熱装置で合金化処理を行った後に、冷却装置１２で冷却を行って溶融メッキ鋼板を得る。
【００３１】
連続溶融メッキ作業から連続焼鈍作業に切替える場合には、スナウト先端とメッキ浴面との間に間隙を形成させる。間隙の形成は、図４（ａ）に示すように中間に蛇腹１３等を設けた伸縮自在のスナウト２を配設してあるので、スナウトを収縮（図中の点線で示す先端部を収縮させる）させて行うことができる。また、スナウトを収縮することに代えて、図示していないが溶融メッキ槽に昇降装置を設けて昇降させることによってスナウト先端とメッキ浴面との間隙を制御することや、メッキ浴中に地金を浸漬或いは取り出すことによっても間隙を制御することができるが、スナウトの伸縮によって行うことが好ましい。また、図４（ｂ）に示すように、スナウトをスナウト内管１４及び外管１５からなる二重管で構成し、スライドさせて伸縮自在としても良い。なお、内管と外管との間をシール１６して内部雰囲気が外部に漏れないようにすることが好ましい。図４に伸縮自在のスナウトの例を示したが、本発明はこれらの例に限られるものでなく、伸縮自在の構造のスナウトであれば使用することができる。
【００３２】
スナウト２先端とメッキ浴４面との間隙の制御は、浴面上にセンサー１７を設置し、センサーによりメッキ浴面とスナウト先端との間隙を検出し、間隙距離が２０ｍｍ以内、好ましくは１０ｍｍ以内の範囲となるようにスナウトの伸縮を制御することが好ましい。
【００３３】
即ち、図５に示すように浴面上に設置したセンサー１７により、スナウト２先端とメッキ浴４面との間隙を検出し、その検出した検出信号をスナウト間隙制御装置２２に送り、所定の間隙となるようにスナウト間隙制御装置からの信号に基づき電動機又はクランク機構等のスナウト先端の駆動装置２３によりスナウトを伸縮させて間隙を調整する。なお、スナウト先端はメッキ浴面と非接触状態に間隙を設定してあるが、時々メッキ浴に浸入しても酸化性ガスが外部に排出される限り問題は生じない。連続溶融メッキを行う場合にはスナウト先端をメッキ浴中に浸漬させるように調整することができる。
【００３４】
次いで、溶融メッキ操業中にスナウト内に導入していた非酸化性ガス（例えばＮ₂）を酸化性ガス（例えば空気）に切替弁で切替える切替弁付ガス吹込装置１８によりスナウト内を酸化性雰囲気とする。スナウト内酸化性雰囲気が焼鈍炉内に逆流しないように焼鈍炉とスナウトの間にガス吹き込み装置１９によりガスを吹込むガスシール（例えばＮ₂）やロールタッチのシール等のシール装置２０によりシールを行うと共に、スナウト内雰囲気圧Ｐを焼鈍炉内雰囲気圧Ｐよりも低く、例えば、１００ｍｍＡｑ以下とするが、２０ｍｍＡｑ以下とすることが好ましい。これによりスナウト２内に吹き込まれた酸化性ガスは、スナウト先端と浴面の隙間から外部に排出させることができる。よって、スナウト内へ導入したガスが焼鈍炉１内へ混入し製造トラブルを発生することがない。スナウト内に吹き込まれた酸化性ガスによって、焼鈍炉１からスナウト２内を通過する鋼板５は、高温（例えば４００〜５００℃）となっているので、その表面を酸化され鋼板表面に酸化膜が形成される。酸化膜の厚さは３５０Å〜１０μｍの範囲にすることが好ましい。酸化膜の厚さが３５０Å以下であると、通板中にガイドロールやメッキ浴中のシンクロールと接触した際に、皮膜の一部に擦過傷ができたときに、その部分がメッキされることとなり、一方１０μｍを超えると後述する酸化膜の除去が困難となるから好ましくない。
【００３５】
また、スナウトを構成する材料としては、スナウト内面が酸化性ガスと接触するため、耐熱性に優れた材料、例えば、公知のステンレス鋼等を用いて構成させれば、スナウトが酸化されることなく長期間使用することが可能となる。
【００３６】
スナウト内で表面に酸化膜を形成された鋼板５は、スナウトからメッキ浴４中に導入され、シンクロール１０を介して上方に引き上げられる。
【００３７】
鋼板のラインスピードがあるため、鋼板表面にはメッキ浴４のメタルが付着して持ち上げられるので、付着したメタルをガスワイピング等のワイピング装置１１により除去する。付着したメタルはガスワイピングの吹き付けガスにより容易に剥離除去することができる。付着したメタルを除去しないと、メタルがロール（例えばガイドロールやトップロール等）に付着して鋼板表面に傷をつけ、製品欠陥を生ずることとなり好ましくない。
【００３８】
ガスワイピング装置には傾動機構を設け、下向きにガスワイピングをして付着したメタルを除去することが好ましい。
【００３９】
ワイピング後の鋼板は冷却装置１２（例えばガス冷却）で冷却し、トップロール２１を介して通板方向を変えて、不要な酸化膜を除去する酸化膜除去装置２２に導入される。必要に応じて、酸化膜除去装置に導入する前にブラシ２３等により表面を機械的に研磨しても良い。酸化膜除去は、酸洗槽による化学的酸洗や、ブラシにより機械的に除去することや、電解処理（例えば電解酸洗）により除去することができる。また、ワイピングにより除去されないで鋼板表面に残存したメタルは酸化膜除去工程で酸化膜と一緒に除去される。
【００４０】
なお、酸化膜除去後にさらに機械的な研削或いは研磨手段で鋼板表面の均一、平滑化を行ってよい。
【００４１】
また、連続焼鈍作業から連続溶融メッキ作業に切替える場合には、スナウト２に吹き込むガスを酸化性ガスから非酸化性ガスに切替え、スナウト内を非酸化性ガスでパージした後に、スナウト先端をメッキ浴４中に浸漬して、最初に説明した連続溶融メッキ操業を行うようにする。
【００４２】
上記に説明したように本発明では連続溶融メッキと連続焼鈍とを同じパスラインで操業することができるので、溶融メッキ作業から焼鈍作業への切替え時間或いは焼鈍作業から溶融メッキ作業への切替え時間が大幅に短縮できる。
【００４３】
【実施例】
以下、本発明の実施例を説明する。
【００４４】
図３に示す連続溶融メッキ及び連続焼鈍兼用装置を用いて、連続溶融メッキの試験を行った。板厚０．８ｍｍ、板幅１０００ｍｍのサイズの鋼板にラインスピード８０ｍｐｍで焼鈍炉で焼鈍を施し、焼鈍後に４８０℃に冷却した後、メッキ浴に先端が浸漬しているスナウトを通じて溶融亜鉛メッキ浴に浸漬した。メッキ浴から引き上げてワイピング圧力１．０ｋｇ／ｃｍ²でワイピング後所定の目付け量に目付けを施し、冷却して亜鉛メッキ鋼板を得た。
【００４５】
次いで、連続溶融メッキ作業から連続焼鈍作業に切替える試験を行った。
【００４６】
まず、伸縮自在のスナウトを収縮させてその先端をメッキ浴面上に引き上げ、センサーによりスナウト先端とメッキ浴面の間隔を検出し、スナウト先端と浴面ギャップを５ｍｍに調整した。焼鈍炉とスナウト間をシールするガスシール装置にＮ₂ガスを７８０Ｎｍ³／ｈｒ導入してシールを行うと共に、スナウト内に空気を３００Ｎｍ³／ｈｒ導入してスナウト内を酸化性雰囲気とした。この時の焼鈍炉内圧力は１５ｍｍＡｑ、スナウト内圧力は１４ｍｍＡｑとした。焼鈍後４８０℃に冷却した鋼板をスナウトを通じて溶融亜鉛メッキ浴に浸漬した。鋼板はスナウト内で酸化されその表面に厚さ約４９０Åの酸化膜が形成されていた。メッキ浴から引き出された鋼板に、ワイピングノズルの圧力を２ｋｇ／ｃｍ²、鋼板との間隔を５ｍｍに調整してワイピングガスを吹き付けた。その結果、鋼板と共に持ち上げられた亜鉛は全部排除され、鋼板表面には、酸化膜が鋼板とメタルとの合金化反応を阻害するためメッキが施されていなかった。ワイピング後鋼板をガス冷却装置により冷却し、トップロールを介して垂直方向から水平方向に通板方向を変えて、ブラシにより鋼板表面を研磨し、５０℃の１０％Ｈ₂ＳＯ₄浴中で１０Ａ／ｄｍ²の電流密度で５秒間の電解酸洗を施して酸化膜を除去した。その結果、酸化膜のない焼鈍された鋼板が得られた。
【００４７】
さらに、連続焼鈍作業から連続溶融メッキ作業に切替える試験を行った。
【００４８】
スナウト内に吹き込む空気をＮ₂ガスに切替え３００Ｎｍ³／ｈｒ吹き込んで、スナウト内をＮ₂ガスでパージした。その後スナウト先端をメッキ浴中に浸漬し、最初に述べたと同様に連続溶融メッキを施した。
【００４９】
以上述べたように、本発明では連続溶融メッキと連続焼鈍とを同じパスラインを使用して行うことができた。
【００５０】
【発明の効果】
本発明によれば、同じパスラインで連続溶融メッキと連続焼鈍とを行うので、連続溶融メッキ作業から連続焼鈍作業への切替え作業或いはその逆の切替え作業が容易となり、かつ切り替え時間が大幅に短縮でき、ラインの生産性を悪化させることも回避されると共に、従来、切替え毎に整備していたロールの整備費用も大幅に削減できる。
【００５１】
また、同じ装置に連続溶融メッキと連続焼鈍の異なる２つの処理能力を持たせた兼用装置で処理を行うため、生産コストが大幅に低下できる。
【図面の簡単な説明】
【図１】従来の連続焼鈍及び溶融メッキ兼用設備の概要を示す図で、（ａ）は連続溶融メッキ、（ｂ）は連続焼鈍を示す図である。
【図２】従来の連続焼鈍及び溶融メッキ兼用設備の概要を示す図である。
【図３】本発明の連続焼鈍及び溶融メッキ兼用装置の概要を示す図である。
【図４】伸縮自在のスナウトの例を示す図で、（ａ）は蛇腹を設けたスナウトの例、（ｂ）は二重管構造としたスナウトの例を示す図である。
【図５】スナウト先端と溶融メッキ浴面との間隙を制御する例を示す図である。
【符号の説明】
１連続焼鈍炉
２スナウト
３着脱自在のスナウト先端
４溶融メッキ浴
５鋼板
６案内ロール
７ロール冷却装置
８連続溶融メッキパスライン
９連続焼鈍パスライン
１０シンクロール
１１ワイピング装置
１２冷却装置
１３蛇腹
１４スナウト内管
１５スナウト外管
１６シール
１７センサー
１８切替弁付ガス吹込装置
１９ガス吹込装置
２０シール装置
２１トップロール
２２スナウト間隙制御装置
２３スナウト先端駆動装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous hot dipping and continuous annealing combined method and apparatus capable of switching between continuous hot dipping and continuous annealing of a steel sheet in one equipment line.
[0002]
[Prior art]
In general, continuous hot-dip plating and continuous annealing of a steel sheet are carried out by separate apparatuses. However, in continuous hot dip plating, a continuous annealing apparatus is attached to the continuous hot dip plating apparatus because continuous annealing of the steel sheet is performed in the previous step of hot dip plating. Various techniques have been proposed in which the continuous annealing apparatus is used for both continuous hot dipping and continuous annealing in a continuous plating line.
[0003]
For example, in the conventional method for producing a cold-rolled steel sheet using a continuous galvanizing line, when performing continuous hot-dip plating, as shown in FIG. When the hot-dip plating bath 4 is introduced into the hot-dip plating bath 4 through the snout 2 with the tip immersed in the hot-dip bath, and continuous hot-dip plating is performed, as shown in FIG. 3 is removed, the outlet of the snout is exposed to the upper side of the hot dipping bath, and the steel plate 5 annealed in the annealing furnace is passed through the outlet of the snout 2 and is wound around the pair of guide rolls 6 with a different pass line from the hot dipping pass line. A continuous annealing method that is derived is disclosed (for example, see Patent Document 1).
[0004]
This method has the problem that the work of removing the tip of the snout and the work of switching the steel sheet to a pass line different from the hot dipping pass line are required, and the switching time is required, so that the productivity is deteriorated.
[0005]
Moreover, in the conventional continuous annealing and hot dipping plating equipment, when performing the continuous annealing, as shown in FIG. 2, the steel plate 5 after annealing by the continuous annealing furnace 1 reacts with oxygen in the air to the steel plate surface. In order to prevent the formation of an oxide film, a roll cooling device 7 composed of a plurality of rolls for cooling the steel plate to 150 ° C. or lower is installed in the final cooling section of the annealing furnace, and the steel plate cooled by the cooling device is passed through the snout 2. There is disclosed a continuous annealing that is derived from a continuous annealing pass line 9 on a hot dipping bath 4 different from the hot dipping pass line 8 (for example, Patent Document 2).
[0006]
This equipment is expensive in terms of the cooling roll device, and requires an operation for switching the steel plate to an annealing pass line different from the hot dipping pass line, and there is a problem that productivity is deteriorated because it takes a switching time.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 55-6469 (page 1, left column, lines 6 to 16, lines 1 and 2)
[Patent Document 2]
JP 2000-204417 A (column 2, lines 27 to 49, FIG. 1)
[0008]
[Problems to be solved by the invention]
Therefore, in view of the above problems, the present invention prevents the deterioration of productivity by making the continuous hot dip plating pass line and the continuous annealing pass line the same pass line, and eliminates the need to change the pass line. It is an object of the present invention to provide a continuous hot dipping and continuous annealing method and apparatus capable of reducing the maintenance cost of rolls that have been maintained in the present invention.
[0009]
[Means for Solving the Problems]
The inventor has conducted intensive research on performing continuous hot dipping and continuous annealing on the same pass line. As a result, even when a steel plate with an oxide film formed on the surface is immersed in a hot dipping bath, the oxide film inhibits the alloying reaction between the steel plate and the hot metal (Zn, Al, etc.). Focusing on the fact that it was not applied, the present invention was completed.
[0010]
The gist of the present invention is as follows.
[0011]
(1) A method of switching between continuous hot-dip plating and continuous annealing of a steel plate using a continuous hot-dip plating line of a steel plate. When continuous hot-dip plating is performed, the tip of the snout of a stretchable snout is hot-plated. It arrange | positions so that it may immerse in a bath, the steel plate which passed snout is immersed in a hot dipping bath, and hot dipping is performed. Also, when performing continuous annealing, the snout tip of a stretchable snout is placed on the surface of the hot dipped bath, an oxidizing gas is blown into the snout, and an oxide film is formed on the surface of the steel plate passing through the snout. After forming the steel sheet, the steel plate is immersed in a hot dipping bath.
[0012]
(2) When switching from continuous annealing to continuous hot dipping, the oxidizing gas blown into the snout is switched to a non-oxidizing gas, the inside of the snout is purged with a non-oxidizing gas, and then the tip of the snout is melt-plated. A method for continuous hot-dip plating and continuous annealing of a steel plate as described in (1) above, wherein the steel plate immersed in the snout is immersed in a hot dipping bath.
[0013]
(3) When switching from continuous hot-dip plating to continuous annealing, the tip of the snout is moved from the hot-dip plating bath onto the plating bath surface, and an oxidizing gas is blown into the snout to oxidize the surface of the steel sheet passing through the snout. After the film is formed, the steel plate that has passed through the snout is dipped in a hot dipping bath, and the method for continuous hot dipping and continuous annealing of the steel plate as described in (1) above.
[0014]
(4) The distance between the hot dipped bath surface and the tip of the snout is detected by a sensor installed on the bath surface. Based on the detection signal, the expandable / contracted snout, the raising / lowering of the hot dipping bath, or the metal in the plating bath The continuous hot dipping and continuous annealing method for a steel sheet according to any one of the above (1) to (3), wherein the positional relationship between the tip of the snout and the bath surface is controlled by dipping and taking out.
[0015]
(5) When performing continuous annealing, seal between the atmosphere in the annealing furnace and the oxidizing atmosphere in the snout so that the oxidizing atmosphere in the snout can be prevented from flowing back into the annealing furnace, and the atmosphere in the snout The method for continuous hot-dip plating and continuous annealing of steel sheets according to (1), (3) or (4) above, wherein the atmospheric pressure is lower than the atmospheric pressure in the annealing furnace.
[0016]
(6) When performing the continuous annealing, the surface of the steel sheet pulled up from the hot dipping bath is wiped and cooled, and then the oxide film on the surface of the steel sheet is removed by an oxide film removing device (1) ), (3), (4) or (5) The continuous hot dipping and continuous annealing method for steel sheets.
[0017]
(7) The continuous hot dipping and continuous annealing method for steel sheet according to (5) above, wherein the oxide film on the steel sheet surface is removed chemically, electrochemically or mechanically.
[0018]
(8) The continuous hot dipping and continuous annealing method for steel sheets according to any one of claims (1) to (3), wherein the oxidizing gas blown into the snout is air.
[0019]
(9) The continuous hot dipping and continuous annealing method for steel sheets according to (2) above, wherein the non-oxidizing gas blown into the snout is nitrogen gas or argon gas.
[0020]
(10) The continuous hot dipping and continuous annealing method for steel sheets according to (4) above, wherein the seal between the atmosphere in the annealing furnace and the atmosphere in the snout is a gas seal or a roll touch seal.
[0021]
(11) A steel plate is a structure that always passes through the same pass line that is immersed in a hot dipping bath, and can be used to switch between continuous hot dipping and continuous annealing of a steel plate. Snout for guiding the steel plate to the hot dipping bath, hot dipping bath, a steel plate wiping device disposed above the hot dipping bath, a steel plate cooling device after wiping, and an oxide film removing device for removing the oxide film on the steel plate surface And a gas blowing device capable of switching between an oxidizing gas and a non-oxidizing gas into the snout, and for preventing gas backflow only on the upstream side of the snout with respect to the mounting position of the gas blowing device. A sealing device is provided, and the natural discharge and sealing of the gas inside the snout can be switched only on the downstream side of the snout with respect to the mounting position of the gas blowing device. Continuous hot dip and continuous annealing compatible apparatus of a steel sheet which is characterized in that it comprises location.
[0022]
(12) The device capable of switching between natural discharge and sealing of the gas in the snout is a telescopic snout whose tip can be on a hot dipping bath or in a hot dipping bath. (11) A continuous hot-dip plating and continuous annealing apparatus for steel sheets according to (11).
[0023]
(13) A sensor is placed on the bath surface, the distance between the bath surface and the tip of the snout is detected by the sensor, and the expansion and contraction of the extendable snout, the elevating and lowering of the hot dipping bath, or the metal in the plating bath is taken out The apparatus for continuous hot-dip plating and continuous annealing of steel sheet according to (11) or (12) above, comprising a control device for controlling the positional relationship between the tip of the snout and the bath surface.
[0024]
(14) The continuous hot dipping and continuous annealing apparatus for steel sheets according to any one of (11) to (13) above, wherein the snout is made of a heat resistant material.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0026]
If continuous annealing is to be carried out in a continuous hot dipping pass line, it is essential to immerse the steel sheet in a hot dipping bath, and it is not possible to carry out only continuous annealing without plating the steel sheet.
[0027]
Therefore, the idea is that continuous annealing can be performed with the same pass line as continuous hot dipping without using different pass lines as in the past, if plating is not performed even if the steel sheet is immersed in the hot dipping bath. I conducted intensive research. As a result, when the present inventors have formed an oxide film on the surface of the steel sheet, even if the steel sheet is immersed in a hot dipping bath, the oxide film reacts with the steel sheet and molten metal (Zn, Al, etc.). Focusing on the fact that the surface is not subjected to hot-dip plating, an oxide film is formed on the surface of the annealed steel sheet in the snout of the previous step immersed in hot-dip plating. The present invention which performs continuous annealing by removing was completed.
[0028]
Hereinafter, the present invention will be described with reference to FIGS.
[0029]
FIG. 3 is a view showing an outline of a continuous hot dipping and continuous annealing apparatus for steel sheets according to the present invention.
[0030]
As shown in FIG. 3, the steel plate 5 is subjected to normal annealing in a continuous annealing furnace 1 composed of a heating zone, a soaking zone, a cooling zone, and the like that gives uniform mechanical properties. In the case of continuously hot-plating the annealed steel plate, the hot-dip plating bath 4 such as molten Zn or molten Al is used for the steel plate through a snout 2 whose tip is immersed in the hot-dip plating bath (shown by a dotted line in the figure). It is dipped in and pulled out above the plating bath through a sink roll 10 installed in the plating bath 4. The wiping device 11 such as gas wiping installed on the plating bath surface controls the plating adhesion amount of the steel plate coming out of the plating bath, and after alloying with a heating device as necessary, the cooling device 12 Cooling is performed to obtain a hot dip plated steel sheet.
[0031]
When switching from the continuous hot dipping operation to the continuous annealing operation, a gap is formed between the snout tip and the plating bath surface. As shown in FIG. 4 (a), the gap is formed by retracting the retractable snout 2 provided with a bellows 13 or the like in the middle, so that the snout is contracted (the tip shown by the dotted line in the figure is contracted). ). Further, instead of contracting the snout, although not shown, a lifting device is provided in the hot dipping bath to control the gap between the snout tip and the plating bath surface, The gap can also be controlled by dipping or taking out, but it is preferable to perform the expansion / contraction of the snout. Moreover, as shown in FIG.4 (b), a snout is comprised with the double tube | pipe which consists of the snout inner pipe | tube 14 and the outer pipe | tube 15, and it is good also as it can slide and extend. It is preferable to seal 16 between the inner tube and the outer tube so that the internal atmosphere does not leak outside. FIG. 4 shows examples of telescopic snouts, but the present invention is not limited to these examples, and any snout having a telescopic structure can be used.
[0032]
Control of the gap between the tip of the snout 2 and the surface of the plating bath 4 is performed by installing a sensor 17 on the bath surface and detecting the gap between the plating bath surface and the tip of the snout by the sensor, and the gap distance is within 20 mm, preferably within 10 mm. It is preferable to control the expansion and contraction of the snout so as to be in the range.
[0033]
That is, the gap between the tip of the snout 2 and the surface of the plating bath 4 is detected by a sensor 17 installed on the bath surface as shown in FIG. 5, and the detected signal is sent to the snout gap control device 22 to obtain a predetermined gap. Based on the signal from the snout gap control device, the gap is adjusted by expanding and contracting the snout by the drive device 23 at the tip of the snout such as an electric motor or a crank mechanism. In addition, although the gap | interval is set in the snout front-end | tip in a non-contact state with the plating bath surface, even if it penetrates into a plating bath occasionally, as long as oxidizing gas is discharged | emitted outside, a problem will not arise. When performing continuous hot dipping, the tip of the snout can be adjusted to be immersed in the plating bath.
[0034]
Next, a non-oxidizing gas (for example, N ₂ ) introduced into the snout during the hot dipping operation is changed into an oxidizing gas (for example, air) by a switching valve, and the inside of the snout is oxidized in the snout by the gas blowing device 18 with a switching valve. And In order to prevent the oxidizing atmosphere in the snout from flowing back into the annealing furnace, the seal is sealed by a sealing device 20 such as a gas seal (for example, N ₂ ) or a roll touch seal that blows gas between the annealing furnace and the snout by a gas blowing device 19. At the same time, the atmospheric pressure P in the snout is lower than the atmospheric pressure P in the annealing furnace, for example, 100 mmAq or less, preferably 20 mmAq or less. As a result, the oxidizing gas blown into the snout 2 can be discharged to the outside through the gap between the snout tip and the bath surface. Therefore, the gas introduced into the snout is not mixed into the annealing furnace 1 and production trouble does not occur. Since the steel plate 5 passing through the inside of the snout 2 from the annealing furnace 1 is at a high temperature (for example, 400 to 500 ° C.) by the oxidizing gas blown into the snout, its surface is oxidized and an oxide film is formed on the surface of the steel plate. It is formed. The thickness of the oxide film is preferably in the range of 350 to 10 μm. When the thickness of the oxide film is 350 mm or less, when the guide roll or the sink roll in the plating bath comes into contact with the plate during passing, the part is plated when scratched. On the other hand, if it exceeds 10 μm, it will be difficult to remove the oxide film described later, which is not preferable.
[0035]
Moreover, as a material constituting the snout, since the inner surface of the snout comes into contact with the oxidizing gas, if the material is made of a material having excellent heat resistance, for example, a known stainless steel, the snout is not oxidized. It can be used for a long time.
[0036]
The steel plate 5 having an oxide film formed on the surface in the snout is introduced from the snout into the plating bath 4 and pulled up through the sink roll 10.
[0037]
Since there is a line speed of the steel plate, the metal of the plating bath 4 adheres to the steel plate surface and is lifted, so that the attached metal is removed by a wiping device 11 such as gas wiping. The adhered metal can be easily peeled and removed by a gas wiping gas. If the adhered metal is not removed, the metal adheres to a roll (for example, a guide roll or a top roll) and damages the surface of the steel sheet, resulting in a product defect.
[0038]
The gas wiping apparatus is preferably provided with a tilting mechanism, and the attached metal is removed by gas wiping downward.
[0039]
The steel plate after wiping is cooled by a cooling device 12 (for example, gas cooling), and is introduced into an oxide film removing device 22 that removes an unnecessary oxide film by changing a plate passing direction through a top roll 21. If necessary, the surface may be mechanically polished with a brush 23 or the like before being introduced into the oxide film removing apparatus. The oxide film can be removed by chemical pickling using a pickling tank, mechanical removal using a brush, or electrolytic treatment (for example, electrolytic pickling). Further, the metal remaining on the surface of the steel sheet without being removed by wiping is removed together with the oxide film in the oxide film removal step.
[0040]
In addition, after the oxide film is removed, the steel plate surface may be made uniform and smooth by mechanical grinding or polishing means.
[0041]
When switching from continuous annealing to continuous hot dipping, the gas blown into the snout 2 is switched from oxidizing gas to non-oxidizing gas, the inside of the snout is purged with non-oxidizing gas, and then the tip of the snout is plated. 4 so that the continuous hot dipping operation described first is performed.
[0042]
As described above, in the present invention, continuous hot-dip plating and continuous annealing can be operated in the same pass line, so the time required for switching from hot-dip work to heat treatment or the time required for changing from hot work to hot-dip plating work. Can be greatly shortened.
[0043]
【Example】
Examples of the present invention will be described below.
[0044]
Using the continuous hot dipping and continuous annealing apparatus shown in FIG. A steel plate having a thickness of 0.8 mm and a width of 1000 mm is annealed in an annealing furnace at a line speed of 80 mpm, cooled to 480 ° C. after annealing, and then passed through a snout whose tip is immersed in a hot dip galvanizing bath. Soaked. After lifting from the plating bath and wiping with a wiping pressure of 1.0 kg / cm ² , a predetermined basis weight was applied and cooled to obtain a galvanized steel sheet.
[0045]
Next, a test for switching from continuous hot dipping to continuous annealing was performed.
[0046]
First, the telescopic snout was contracted and its tip was lifted onto the plating bath surface, the distance between the snout tip and the plating bath surface was detected by a sensor, and the snout tip and the bath surface gap were adjusted to 5 mm. Sealing was performed by introducing N ₂ gas at 780 Nm ³ / hr into a gas seal device for sealing between the annealing furnace and the snout, and 300 Nm ³ / hr of air was introduced into the snout to create an oxidizing atmosphere inside the snout. At this time, the internal pressure of the annealing furnace was 15 mmAq, and the internal pressure of the snout was 14 mmAq. The steel plate cooled to 480 ° C. after annealing was immersed in a hot dip galvanizing bath through a snout. The steel plate was oxidized in the snout and an oxide film having a thickness of about 490 mm was formed on the surface. A wiping gas was sprayed onto the steel sheet drawn out of the plating bath while adjusting the pressure of the wiping nozzle to 2 kg / cm ² and the distance from the steel sheet to 5 mm. As a result, all the zinc lifted together with the steel plate was eliminated, and the steel plate surface was not plated because the oxide film hindered the alloying reaction between the steel plate and the metal. After wiping, the steel plate is cooled by a gas cooling device, the plate passing direction is changed from the vertical direction to the horizontal direction via a top roll, the steel plate surface is polished with a brush, and 10A in a 10% H ₂ SO ₄ bath at 50 ° C. The oxide film was removed by electrolytic pickling for 5 seconds at a current density of / dm ² . As a result, an annealed steel sheet without an oxide film was obtained.
[0047]
In addition, a test was conducted to switch from continuous annealing to continuous hot dipping.
[0048]
The air blown into the snout was switched to N ₂ gas and blown at 300 Nm ³ / hr, and the inside of the snout was purged with N ₂ gas. Thereafter, the tip of the snout was immersed in a plating bath and subjected to continuous hot dipping as described above.
[0049]
As described above, in the present invention, continuous hot dipping and continuous annealing can be performed using the same pass line.
[0050]
【The invention's effect】
According to the present invention, since continuous hot dipping and continuous annealing are performed on the same pass line, switching from continuous hot dipping to continuous annealing or vice versa becomes easy, and the switching time is greatly reduced. In addition, it is possible to avoid deteriorating the productivity of the line and to greatly reduce the maintenance cost of the roll that has been provided for each switching.
[0051]
In addition, since the processing is performed by a dual-purpose apparatus in which the same apparatus has two processing capabilities different from continuous hot dipping and continuous annealing, the production cost can be greatly reduced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing an outline of a conventional continuous annealing and hot-dip plating facility, where (a) shows continuous hot-dip plating and (b) shows continuous annealing.
FIG. 2 is a view showing an outline of a conventional continuous annealing and hot dipping facility.
FIG. 3 is a view showing an outline of a continuous annealing and hot dipping apparatus according to the present invention.
FIGS. 4A and 4B are diagrams showing examples of telescopic snouts. FIG. 4A is a diagram showing an example of a snout provided with a bellows, and FIG. 4B is a diagram showing an example of a snout having a double tube structure.
FIG. 5 is a diagram showing an example of controlling a gap between a snout tip and a hot dipping bath surface.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Continuous annealing furnace 2 Snout 3 Removable snout tip 4 Hot dipping bath 5 Steel plate 6 Guide roll 7 Roll cooling device 8 Continuous hot dipping pass line 9 Continuous annealing pass line 10 Sink roll 11 Wiping device 12 Cooling device 13 Bellows 14 In the snout Pipe 15 Snout outer pipe 16 Seal 17 Sensor 18 Gas blowing device 19 with switching valve Gas blowing device 20 Sealing device 21 Top roll 22 Snout gap control device 23 Snout tip drive device

Claims

This is a method of switching between continuous hot-dip plating and continuous annealing of steel sheets using a continuous hot-dip plating line of steel sheets. When performing continuous hot-dip plating, the snout tip of a stretchable snout is placed in the hot-dip plating bath. Place the steel plate that has passed through the snout in the hot dipping bath for hot dipping, and when performing continuous annealing, the snout tip of the extendable snout will be on the hot dipping bath surface The steel sheet is immersed in a hot dipping bath after the oxidizing gas is blown into the snout and an oxide film is formed on the surface of the steel sheet passing through the snout. An annealing method.

When switching from continuous annealing to continuous hot dipping, switch the oxidizing gas blown into the snout to a non-oxidizing gas, purge the inside of the snout with a non-oxidizing gas, and then immerse the tip of the snout in the hot dipping bath The method of combining continuous hot-dip plating and continuous annealing of a steel plate according to claim 1, wherein the steel plate that has passed through the snout is immersed in a hot dipping bath.

When switching from continuous hot-dip plating to continuous annealing, the tip of the snout is moved from the hot-dip plating bath onto the plating bath surface, and an oxidizing gas is blown into the snout to form an oxide film on the surface of the steel plate passing through the snout. The method of combining continuous hot-dip plating and continuous annealing of a steel sheet according to claim 1, wherein the steel sheet that has passed through the snout is immersed in a hot dipping bath.

The distance between the hot dipping bath surface and the tip of the snout is detected by a sensor installed on the bath surface. The continuous hot dipping and continuous annealing method for a steel sheet according to any one of claims 1 to 3, wherein the positional relationship between the tip of the snout and the bath surface is controlled.

When performing continuous annealing, seal between the atmosphere in the annealing furnace and the oxidizing atmosphere in the snout to prevent the oxidizing atmosphere in the snout from flowing back into the annealing furnace, and the atmospheric pressure in the snout is annealed. 5. The method for continuous hot-dip plating and continuous annealing of steel sheets according to claim 1, 3 or 4, wherein the pressure is lower than the atmospheric pressure in the furnace.

When performing continuous annealing, the surface of the steel sheet pulled up from the hot dipping bath is wiped, and after cooling, the oxide film on the steel sheet surface is removed by an oxide film removing device. A method for continuous hot dipping and continuous annealing of steel sheets according to 4 or 5.

6. The continuous hot dipping and continuous annealing method for steel sheets according to claim 5, wherein the oxide film on the steel sheet surface is removed chemically, electrochemically or mechanically.

The continuous hot-dip plating and continuous annealing method for a steel sheet according to any one of claims 1 to 3, wherein the oxidizing gas blown into the snout is air.

3. The continuous hot dipping and continuous annealing method for steel sheets according to claim 2, wherein the non-oxidizing gas blown into the snout is nitrogen gas or argon gas.

The continuous hot-dip plating and continuous annealing method for steel sheets according to claim 4, wherein the seal between the atmosphere in the annealing furnace and the atmosphere in the snout is a gas seal or a roll touch seal.

In a dual-purpose equipment that is capable of switching between continuous hot-dip plating and continuous annealing of steel sheets, where the steel sheets always pass through the same pass line that is immersed in the hot dipping bath. And a steel plate wiping device disposed at the top of the hot dip bath, a steel plate cooling device after wiping, and an oxide film removing device for removing the oxide film on the steel plate surface, and A gas blowing device capable of switching between oxidizing gas and non-oxidizing gas in the snout is provided, and a gas backflow prevention sealing device is provided only on the upstream side of the snout with respect to the mounting position of the gas blowing device. And a device capable of switching between natural discharge and sealing of the gas inside the snout only on the downstream side of the snout with respect to the mounting position of the gas blowing device. Continuously hot dip and continuous annealing compatible apparatus of a steel sheet, characterized in that are.

The device capable of switching between natural discharge and sealing of the gas in the snout is a telescopic snout whose tip can be on a hot dipped bath or in a hot dipped bath. For continuous hot dipping and continuous annealing of steel sheets.

By placing a sensor on the bath surface, detecting the distance between the bath surface and the tip of the snout by the sensor, expanding and contracting the extendable snout, elevating and lowering the hot dipping bath, or dipping and removing the metal in the plating bath 13. A combined use apparatus for continuous hot-dip plating and continuous annealing of steel sheets according to claim 11 or 12, further comprising a control device for controlling the positional relationship between the tip of the snout and the bath surface.

The apparatus for continuous hot-dip plating and continuous annealing of steel sheets according to any one of claims 11 to 13, wherein the snout is made of a heat resistant material.