JP3810545B2

JP3810545B2 - Hot pot for floating metal plating

Info

Publication number: JP3810545B2
Application number: JP01016998A
Authority: JP
Inventors: 一郎山下; 保男深田; 千昭加藤; 敏明天笠; 敦司安藤; 拓弥橋田
Original assignee: JFE Steel Corp; Mitsubishi Heavy Industries Ltd
Current assignee: JFE Steel Corp; Mitsubishi Heavy Industries Ltd
Priority date: 1998-01-22
Filing date: 1998-01-22
Publication date: 2006-08-16
Anticipated expiration: 2018-01-22
Also published as: JPH11209858A

Description

【０００１】
【発明の属する技術分野】
本発明は、溶融めっき設備にあって、溶融めっき金属浮上用空中ポット及び溶融めっき鋼帯の生産方法に関する。
【０００２】
【従来の技術】
通常の連続溶融めっき設備では、還元焼鈍炉で表面活性化された鋼帯を溶融めっき浴に浸漬し、この溶融めっき浴に浸漬された状態で回転駆動されるシンクロールにより、この溶融めっき浴から垂直方向に鋼帯を引き上げることが行なわれる。
【０００３】
この場合、鋼帯表面と接触した状態ではシンクロールが回転するため、シンクロールとの接触不良に起因した擦り疵が鋼帯表面に発生するのを避けられず、鋼帯表面に形成されるめっき層に悪影響を及ぼす。
【０００４】
また、シンクロールによって鋼帯に曲げが付与されるため、シンクロールを通過した後の鋼帯に板幅方向の反りが発生し、この板幅方向の反りは、溶融めっき浴から引上げられた鋼帯をガスワイピングする際にワイピングノズルと鋼帯表面との距離を変動させることになって、結果として不均一ワイピングによって板幅方向に関するめっき付着量にバラツキが発生し易くなる。
【０００５】
更に、溶融めっき浴にシンクロールが浸漬されることから、大容量の溶融めっき槽が必要とされ、浴組成の切換えが困難になる。
【０００６】
シンクロールを用いた溶融めっき設備は、上述の如き問題が生じており、このため現在では、このようなシンクロールによる悪影響を排除して高品質の溶融めっき鋼帯を製造するため、シンクロールを使用しない溶融めっき設備を用い、鋼帯を下から上に一方向に走行させて空中ポットに収容した溶融めっき金属中を通過させる方式が検討されており、特開平８−３３３６６３号公報等で提案されている。
【０００７】
空中ポットを用いた溶融めっき設備では、図２に示すように、還元焼鈍炉で表面活性化された鋼帯１は、導入室２内に配置されているデフレクタロール３を経て上方へ引き上げられ、シールロール４を経て空中ポット５に導入される。
鋼帯１の酸化を防止するため導入室２内には、Ｈ₂−Ｎ₂ガスが満たされており、シールロール４と空中ポット５との間にはＮ₂ガスが満たされている。シールロール４は、導入室２と空中ポット５との間をガス遮断し、めっき開始時及びめっき停止時等に導入室２への大気侵入を防止する。
【０００８】
溶融めっき金属６は、ポンプ７によりサブポット８から供給配管９を経て空中ポット５へ送り込まれる。空中ポット５内の溶融めっき金属６は、鋼帯１と接する側で上へ流れるように循環し、両側部からオーバーフローして接続室へ落ち、排出管１２を経てサブポット８内へ流下する。
空中ポット５は、図３の如く、底部に鋼帯搬入開口部１３が形成されており、この開口部１３から溶融めっき金属６が漏出・流下しないように、上向きの電磁力を溶融めっき金属６に付与する電磁石１０が開口部１３の周囲に設けられている。
【０００９】
溶融めっき金属６を満たした空中ポット５に底部から鋼帯１を導入し、溶融めっき金属６と接触させた後、上方に引き上げることにより鋼帯１が溶融めっきされる。空中ポット５を出た後の鋼帯１にガスワイピングノズル１１からワイピングガスを吹き付けることにより過剰量の溶融めっき金属６が除去され、めっき付着量が調整された溶融めっき鋼帯が製造される。
めっき作業中は、空中ポット５の排出管１２につながる接続室側の壁をプラグ１４で塞ぎ、電磁石１０による電磁力で鋼帯搬入開口部１３から溶融めっき金属６が漏出・流下するのを阻止しながら、空中ポット５内に所定量の溶融めっき金属６を溜めて保持する。
めっき作業を停止させるときには、プラグ１４を開放し、排出管１２を経由して空中ポット５内の溶融めっき金属６をサブポット８に排出する。
【００１０】
電磁石１０は、図４（ａ）に示すように通常、開口部１３内を通過する鋼帯１の両面に対向する配置の一対の磁極面１７を対峙させた構成の鉄心コア１５とこの鉄心コア１５に設けた複数個の励磁コイル１６とで構成されている。この場合、一対の磁極面１７は板幅方向に平行に相互に一定間隔ｇを隔てて設けられている。そして、励磁コイル１６へ通電すると、図５に示すように磁極面１７間に鋼帯１の表裏を貫通する方向に磁束Ｂを発生し、磁束Ｂにより溶融めっき金属内に生じる板幅方向の誘導渦電流Ｉによって、上向きの電磁押上力Ｆが発生する。この上向きの電磁力Ｆで鋼帯搬入開口部１３内の溶融めっき金属６を押し上げ保持することによって溶融めっき金属６の漏出・流下が防止される。
【００１１】
上述のように電磁力にて溶融めっき金属の保持が行われるが、更に、従来では、例えば特開平７−４８６６０号公報に開示されるように、溶融金属より電気伝導度が大きいブスバ−を鋼帯搬入開口部１３の回りに、図６、７、８の如く配置することにより、渦電流をこのブスバ−１８に流して溶融金属中の電流の方向転換による押上力の低下を防止するという改良も行われている。
押し上げ力Ｆの発生に係る詳細は、次のようになる。図４の電磁石１０の励磁コイル１６に交流を通電し、鉄心コア１５内に交番磁界を発生させると、磁極面１７間にも交番磁界が現われる。ここにおいて、図６、図７、図８にて示す渦電流用ブスバー１８と溶融めっき金属６、鋼帯１からなる系に着目するとき、ある瞬間の磁束密度は、磁極間空間にてＢ_g、溶融めっき金属内でＢ_zg、磁極間鋼帯挿入部でＢ_s、溶融めっき金属内の鋼帯挿入部でＢ_zsとなり、この交番磁束を打ち消すように誘導渦電流が流れる。すなわち、溶融めっき金属底面及び一部鋼帯表面〜渦電流ブスバー１８からなる閉ループを図８に示す如きＩ_z，Ｉ_zs〜Ｉ_bという具合に流れる。なお、鋼帯１の表面での渦電流はＩ_sが流れる。
この結果、電磁石１０による磁束密度と渦電流とによるベクトルの外積が電磁力となって渦電流に作用することになり、溶融めっき金属底面に流れる渦電流には絶えず上向きの力（図５Ｆ）が働くことになる。
【００１２】
【発明が解決しようとする課題】
しかし、上述にて説明した空中ポットにおいては、次のような問題が生じている。図４に示すように電磁石１０の磁極面１７は板幅方向に平行に形成され、換言すれば磁極面１７間の間隔ｇが一様に形成されている。この場合、めっき作業時鋼帯１が空中ポット５の鋼帯搬入開口部１３を通過していると、鋼帯１による磁束Ｂのしゃ断作用によって図４（ｂ）の如く「板あり部」ａと「板なし部」ｂとで磁束密度分布が変化する。つまり、交番磁束にて生ずる金属中の渦電流により交流磁束は侵入しにくくなり金属は、一種の磁気シールドとなるが、また、溶融めっき金属ではこの渦電流によって制限される磁束と渦電流とによって電磁押上力が発生するのであるが、交流磁束に対して直交するよう位置する鋼帯１ではこの表面の渦電流による磁場のため磁束密度が減少することになる。この結果、「板なし部」ｂでは略一定の磁束密度が保たれる反面、「板あり部」ａでは鋼帯１の中央部にて磁束密度が最も低下するという放物線状の磁束分布となる。なお、この磁束密度分布は実験にても確認された。
【００１３】
かかる鋼帯１の板幅方向での磁束密度分布の変化は、板幅方向での電磁押上力Ｆの分布に変化をもたらし、鋼帯搬入開口部１３付近の溶融めっき金属６に板幅方向の不規則な流れを生じさせ、この開口部１３内の溶融めっき金属６を不安定にする。この開口部１３内の溶融めっき金属６が不安定になると、この開口部１３からの溶融めっき金属６流出が生じ易くなる。同時に、空中ポット５内の溶融めっき金属６の循環が乱れて鋼帯１への均質な溶融めっきを阻害する原因となるのを避けられない。
また、この板幅方向での磁束密度分布の変化による鋼帯搬入開口部１３の溶融めっき金属６の保持力の低下を補うために、電磁石１０には運転中に高めの電磁力を生じさせることが必要になり、大きい投入電力が必要になる。
【００１４】
本発明は、上述の問題に鑑み、鋼帯の板幅方向に均一な磁束密度分布となるようにした溶融めっき金属浮上用空中ポット及び溶融めっき鋼帯の生産方法を提供する。
【００１５】
【課題を解決するための手段】
上述の目的を達成する本発明の溶融めっき金属浮上用空中ポットは、次の発明特定事項を有する。
（１）鋼帯の搬入開口部からの溶融めっき金属の流下を防止する電磁力を発生する電磁石を上記搬入開口部の両側から挟むように対峙させた溶融めっき金属浮上用空中ポットにおいて、
前記鋼帯の搬入開口部を挟んで対峙する前記電磁石の磁極面の形状は、この磁極面間の磁束密度が前記鋼帯の板幅方向の各点において一定となるよう凸面形状に形成したことを特徴とする。
（２）溶融めっき金属が満たされると共に、下方から上方に向かって鋼帯を通過させる鋼帯搬入開口部が底部に形成された空中ポットと、
前記鋼帯搬入開口部を通過する前記鋼帯の両面に一対の磁極面を対峙させるよう配置した鉄心コアと、この鉄心コアに設けた複数の励磁コイルとを有し、前記溶融めっき金属が前記鋼帯搬入開口部から漏出・流下しないように上向きの電磁力を当該溶融めっき金属に付与するよう前記鋼帯搬入開口部の周囲に設けられた電磁石とを有し、
前記電磁石の一対の磁極面は、前記鋼帯搬入開口部の中央部分で双方の磁極面の間隔が最小となり前記鋼帯搬入開口部の両端部で双方の磁極面の間隔が最大となるように、相互に凸面形状に形成されていることを特徴とする。
【００１６】
また本発明の溶融めっき鋼帯の生産方法は、次の発明特定事項を有する。
（３）鋼帯の搬入開口部からの溶融めっき金属の流下を防止する電磁力を発生する電磁石を上記搬入開口部の両側から挟むように対峙させた溶融めっき金属浮上用空中ポットを用いた溶融めっき鋼帯の生産方法において、
前記搬入開口部を挟んで対峙する前記電磁石の磁極面の形状は、この磁極面間の磁束密度が前記鋼帯の板幅方向の各点において一定となるよう凸面形状に形成し、
前記電磁石の磁極面の間に磁束を発生させた状態で、鋼帯を下方から上方に向けて前記搬入開口部を通過させて溶融めっき金属の中を通過させることを特徴とする。
（４）溶融めっき金属が満たされると共に、鋼帯搬入開口部が底部に形成された空中ポットと、
前記鋼帯搬入開口部を通過する前記鋼帯の両面に一対の磁極面を対峙させるよう配置した鉄心コアと、この鉄心コアに設けた複数の励磁コイルとを有し、前記溶融めっき金属が前記鋼帯搬入開口部から漏出・流下しないように上向きの電磁力を当該溶融めっき金属に付与するよう前記鋼帯搬入開口部の周囲に設けられた電磁石とを有し、
前記電磁石の一対の磁極面は、前記鋼帯搬入開口部の中央部分で双方の磁極面の間隔が最小となり前記鋼帯搬入開口部の両端部で双方の磁極面の間隔が最大となるように、相互に凸面形状に形成されている溶融めっき金属浮上用ポットを用いた溶融めっき鋼帯の生産方法であって、
前記励磁コイルに一定の電力を供給しつつ、鋼帯を下方から上方に向けて前記鋼帯搬入開口部を通過させて前記空中ポットに収容した前記溶融めっき金属の中を通過させることを特徴とする。
【００１７】
【発明の実施の形態】
ここで、図１を参照して本発明の実施の形態の一例を説明する。なお、図１において、図２〜図８と同一部分には同符号を付す。
まず、一般的には、図１、図５に示す構成にあって、電磁石１０の励磁コイル１６への通電によって磁極面１７間に得られる鋼帯１面と直角方向の磁束密度Ｂと、この磁束密度Ｂによって生じる誘導渦電流Ｉと、この誘導渦電流１により発生する上向きの電磁押上力Ｆとをベクトルとして捕らえると、前述の如く外積〔Ｆ＝Ｉ×Ｂ］として表わされる。
しかも、誘導渦電流Ｉは磁束密度Ｂに比例することになるので、磁極面１７間の磁束密度Ｂと電磁押上力ＦとはＦ∝Ｂ²に示す関係が生ずる。したがって、磁束密度Ｂの少しの変化であっても電磁押上力Ｆは大きく違ってくることになる。
【００１８】
一方、電磁石１０上の励磁コイル１６のコイル巻数をＮ、励磁コイル１６に流れる電流をＩ_c、励磁コイル１６の起磁力をｆ₁とすると、起磁力ｆ₁は次の式で表わされる。
ｆ₁＝２・Ｎ・Ｉ_c ・・・・・・・・・・・・・（１）
また、磁極面１７間における、「板あり部」ａと、「板なし部」ｂの透磁率をμ₀としてほぼ同一の定数と考え、磁路の断面積をＡ，磁束密度をＢとすれば、磁束密度Ｂは、次の式で表わされる。
Ｂ＝μ₀・ｆ₁／Ａ・ｇ＝μ₀・２・Ｎ・Ｉ_c／Ａ・ｇ・・（２）
【００１９】
この結果、（２）式において、起磁力ｆ₁＝２・Ｎ・Ｉ_cを一定にすれば、磁束密度Ｂの大きさは、磁極面１７間の間隔ｇの大きさに依存し、一定の割合で反比例することになる。
【００２０】
本例については、前記（２）式の関係に着目し、図１（ｂ）に示す如く、磁極面１７間の「板あり部」ａと、「板なし部」ｂとで、一定の平均した磁束密度Ｂを保つように、鋼帯搬入開口部１３を挾んで対峙する磁極面１７を、図４（ｂ）に示す鋼帯１の通過時の遮蔽作用による板幅方向の磁束密度変化を補償するように、板幅方向に異なる磁極面間隔ｇ分布を設定し、図１（ａ）に示す凸曲面状の磁極端面で構成したものである。
すなわち、板幅方向の複数点で、前記（２）式に基いて磁束密度変化を補償するに必要な磁極面間隔ｇ値を設定し、電磁石１０の磁極面１７間を、鋼帯搬入開口部１３の中央部で最少の磁極面間隔ｇ_min、鋼帯搬入開口部１３の両端部で最大の磁極面間隔ｇ_maxとする間隔ｇの分布にて、相互に凸曲面状の端面で向かい合う磁極面として構成したものである。
【００２１】
図１に示す構成の電磁石１０では、空中ポット５にサブポット８から溶融めっき金属６をポンプ７により供給し、電磁石１０の励磁コイル１６に設計された一定の電力（電流）を通電し、この状態で空中ポット５に鋼帯１が下から上へ通過開始されると、相互に凸曲面状の端面で向かい合う磁極面１７間には、前記（２）式にて磁極面間隔ｇが小さい位置ほど、すなわち、板幅中央部分ほど大きい磁束密度Ｂが発生し、この磁束密度Ｂに対応した電磁押上力Ｆが発生する。
【００２２】
このとき、鋼帯１の通過時の遮蔽作用による板幅方向の磁束密度Ｂの低下量を、板幅方向に適当なピッチで予め計測し、これを基に前記（２）式により磁束密度Ｂの計測位置毎の低下量を補償するに必要な磁極面間隔ｇの分布を設定しておくことによって、磁極面１７間で発生する上向き電磁押上力Ｆが、鋼帯１の遮蔽作用による磁束密度Ｂの低下分布を相殺し、図１（ｂ）に示すように鋼帯搬入開口部１３の「板あり部」ａ及び「板なし部」ｂを含む全幅域に、均等な所定の磁束密度Ｂを保つことができるようになる。
【００２３】
【発明の効果】
以上説明したように本発明によれば、鋼帯の搬入開口部を挾んで対峙する電磁石の磁極面を、前記搬入開口部を通過する前記鋼帯による板幅方向の磁束密度変化を補償するように形成したことにより、例えば凸曲面状に形成したことにより、実際の開口部内の溶融めっき金属には、板幅方向に設計値通りの均等な分布の電磁押上力が働くようになり、鋼帯搬入開口部内の溶融めっき金属の不安定な遊動がなくなり、めっき運転中におけるこの開口部からの溶融めっき金属流出の危険がなくなる。同時に空中ポット内の溶融めっき金属の循環が安定し、均質な溶融めっき鋼帯を生産できるようになる。
また、鋼帯が磁束を遮蔽することで生じる磁束密度分布の低下を、大きい投入電力で補う必要がなくなり、経済的に溶融めっき鋼帯を生産できる効果が得られる。
【図面の簡単な説明】
【図１】本発明の実施の形態の一例の平面及び特性線図。
【図２】従来例の断面（図３のII−II線断面）図。
【図３】従来例の平面（図２のIII−IIIからみた平面）図。
【図４】従来例の平面及び特性線図。
【図５】電磁押上力の説明図。
【図６】渦電流ブスバーの配置状態図。
【図７】渦電流ブスバーの簡略平面図。
【図８】磁束密度と渦電流との状態図。
【符号の説明】
１鋼帯
５空中ポット
６溶融めっき金属
１０電磁石
１３鋼帯搬入開口部
１７磁極面
１８渦電流用ブスバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot dipping metal floating aerial pot and a method for producing a hot dipped steel strip in a hot dipping facility.
[0002]
[Prior art]
In ordinary continuous hot dipping equipment, a steel strip surface-activated in a reduction annealing furnace is dipped in a hot dipping bath, and a sink roll that is rotated in the dipped hot dipping bath is used to remove the steel strip from the hot dipping bath. The steel strip is pulled up in the vertical direction.
[0003]
In this case, since the sink roll rotates in contact with the steel strip surface, it is inevitable that scratches due to poor contact with the sink roll will occur on the steel strip surface, and plating formed on the steel strip surface Adversely affects the layer.
[0004]
Also, since the steel strip is bent by the sink roll, warpage in the plate width direction occurs in the steel strip after passing through the sink roll, and this warpage in the plate width direction is caused by the steel pulled up from the hot dipping bath. When gas wiping the band, the distance between the wiping nozzle and the surface of the steel band is changed, and as a result, the plating adhesion amount in the plate width direction is likely to vary due to non-uniform wiping.
[0005]
Further, since the sink roll is immersed in the hot dipping bath, a large-capacity hot dipping bath is required, and switching of the bath composition becomes difficult.
[0006]
The hot-dip plating equipment using sink rolls has the above-mentioned problems. Therefore, in order to produce high-quality hot-dip steel strip by eliminating the adverse effects of such sink rolls, A method of allowing a steel strip to travel in one direction from the bottom to the top and passing it through a hot dipped metal housed in an air pot using a hot dipping equipment that is not used is proposed in Japanese Patent Application Laid-Open No. 8-333663. Has been.
[0007]
In the hot dipping equipment using an aerial pot, as shown in FIG. 2, the steel strip 1 surface-activated in the reduction annealing furnace is pulled upward through a deflector roll 3 disposed in the introduction chamber 2, It is introduced into the aerial pot 5 through the seal roll 4.
In order to prevent oxidation of the steel strip 1, the introduction chamber 2 is filled with H ₂ —N ₂ gas, and the space between the seal roll 4 and the air pot 5 is filled with N ₂ gas. The seal roll 4 gas-blocks between the introduction chamber 2 and the aerial pot 5 to prevent air from entering the introduction chamber 2 when starting plating or stopping plating.
[0008]
The galvanized metal 6 is sent from the subpot 8 to the aerial pot 5 through the supply pipe 9 by the pump 7. The hot-dipped metal 6 in the air pot 5 circulates so as to flow upward on the side in contact with the steel strip 1, overflows from both sides, falls into the connection chamber, and flows down into the subpot 8 through the discharge pipe 12.
As shown in FIG. 3, the aerial pot 5 has a steel strip carry-in opening 13 formed at the bottom, and an upward electromagnetic force is applied to the molten plated metal 6 so that the molten plated metal 6 does not leak out or flow down from the opening 13. An electromagnet 10 is provided around the opening 13.
[0009]
The steel strip 1 is introduced from the bottom into the aerial pot 5 filled with the hot dipped metal 6, brought into contact with the hot dipped metal 6, and then pulled upward to hot drip the steel strip 1. By spraying a wiping gas from the gas wiping nozzle 11 onto the steel strip 1 after leaving the aerial pot 5, an excessive amount of the hot-dip plated metal 6 is removed, and a hot-dip plated steel strip having an adjusted plating adhesion amount is manufactured.
During the plating operation, the wall on the side of the connection chamber connected to the discharge pipe 12 of the aerial pot 5 is closed with a plug 14 to prevent the molten plated metal 6 from leaking and flowing down from the steel strip carry-in opening 13 by the electromagnetic force of the electromagnet 10. Meanwhile, a predetermined amount of hot dipped metal 6 is accumulated and held in the air pot 5.
When stopping the plating operation, the plug 14 is opened, and the molten plating metal 6 in the air pot 5 is discharged to the subpot 8 via the discharge pipe 12.
[0010]
As shown in FIG. 4 (a), the electromagnet 10 is generally composed of an iron core 15 having a configuration in which a pair of magnetic pole faces 17 arranged to face both surfaces of the steel strip 1 passing through the opening 13 are opposed to each other, and the iron core. 15 and a plurality of exciting coils 16 provided in 15. In this case, the pair of magnetic pole surfaces 17 are provided in parallel to the plate width direction at a predetermined interval g. When the excitation coil 16 is energized, a magnetic flux B is generated between the magnetic pole faces 17 in the direction passing through the front and back of the steel strip 1 as shown in FIG. An upward electromagnetic lifting force F is generated by the eddy current I. By leaking and flowing down the molten plated metal 6 by pushing up and holding the molten plated metal 6 in the steel strip carry-in opening 13 by the upward electromagnetic force F.
[0011]
As described above, the hot-dip plated metal is held by electromagnetic force. However, conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 7-48660, a bus bar having a higher electrical conductivity than the molten metal is used as a steel. By arranging as shown in FIGS. 6, 7 and 8 around the band carrying-in opening 13, the eddy current is caused to flow through the bus bar 18 to prevent the push-up force from being lowered due to the direction change of the current in the molten metal. Has also been done.
Details relating to the generation of the push-up force F are as follows. When alternating current is applied to the exciting coil 16 of the electromagnet 10 of FIG. 4 to generate an alternating magnetic field in the iron core 15, an alternating magnetic field also appears between the magnetic pole faces 17. Here, when paying attention to the system composed of the eddy current bus bar 18, the hot dipped metal 6, and the steel strip 1 shown in FIGS. 6, 7, and 8, the magnetic flux density at a certain moment is B _{g in the} space between the magnetic poles. _Bzg in the hot dip metal, B _{s in} the steel strip insertion portion between the magnetic poles, and B _zs in the steel strip insertion portion in the hot dip metal, an induced eddy current flows so as to cancel this alternating magnetic flux. That is, a closed loop composed of the bottom surface of the galvanized metal and part of the steel strip to the eddy current bus bar 18 flows as I _z and I _{zs to} I _b as shown in FIG. Note that I _s flows through the eddy current on the surface of the steel strip 1.
As a result, the vector outer product of the magnetic flux density and the eddy current generated by the electromagnet 10 acts as an electromagnetic force on the eddy current, and the upward force (FIG. 5F) is constantly applied to the eddy current flowing on the bottom surface of the molten plated metal. Will work.
[0012]
[Problems to be solved by the invention]
However, the following problems occur in the air pot described above. As shown in FIG. 4, the magnetic pole surface 17 of the electromagnet 10 is formed in parallel with the plate width direction, in other words, the gap g between the magnetic pole surfaces 17 is formed uniformly. In this case, when the steel strip 1 passes through the steel strip carry-in opening 13 of the aerial pot 5 during the plating operation, the “plate portion” a as shown in FIG. And “plateless portion” b change the magnetic flux density distribution. In other words, eddy currents in the metal caused by alternating magnetic flux make it difficult for AC magnetic flux to penetrate, and the metal becomes a kind of magnetic shield. On the other hand, in galvanized metal, the eddy current limits the magnetic flux and eddy current. Although an electromagnetic lifting force is generated, in the steel strip 1 positioned so as to be orthogonal to the alternating magnetic flux, the magnetic flux density decreases due to the magnetic field due to the eddy current on the surface. As a result, a substantially constant magnetic flux density is maintained in the “plateless portion” b, while a parabolic magnetic flux distribution in which the magnetic flux density is the lowest in the central portion of the steel strip 1 in the “platened portion” a. . This magnetic flux density distribution was also confirmed in experiments.
[0013]
The change in the magnetic flux density distribution in the plate width direction of the steel strip 1 causes a change in the distribution of the electromagnetic lifting force F in the plate width direction, and the hot-dip plated metal 6 near the steel strip carry-in opening 13 in the plate width direction. An irregular flow is generated, and the hot-dip metal 6 in the opening 13 is made unstable. When the hot dip metal 6 in the opening 13 becomes unstable, the hot dip metal 6 flows out of the opening 13 easily. At the same time, it is inevitable that the circulation of the hot dip metal 6 in the aerial pot 5 is disturbed to hinder homogeneous hot dip plating on the steel strip 1.
Further, in order to compensate for the decrease in the holding force of the hot-dip plated metal 6 in the steel strip carry-in opening 13 due to the change in the magnetic flux density distribution in the plate width direction, a high electromagnetic force is generated in the electromagnet 10 during operation. And a large input power is required.
[0014]
In view of the above-mentioned problems, the present invention provides an aerial pot for galvanized metal levitation and a method for producing a galvanized steel strip so as to have a uniform magnetic flux density distribution in the plate width direction of the steel strip .
[0015]
[Means for Solving the Problems]
The aerial pot for flotation metal floating of the present invention which achieves the above-mentioned object has the following invention specific matters.
(1) In an aerial pot for galvanized metal levitation in which electromagnets that generate electromagnetic force to prevent the molten metal from flowing down from the steel strip carry-in opening are opposed to be sandwiched from both sides of the carry-in opening,
The shape of the magnetic pole surface of the electromagnet facing the steel strip loading opening is formed in a convex shape so that the magnetic flux density between the magnetic pole surfaces is constant at each point in the plate width direction of the steel strip. It is characterized by .
( 2 ) An aerial pot in which a hot-dip plated metal is filled and a steel strip carry-in opening that allows the steel strip to pass from below to above is formed at the bottom;
A steel core that is disposed so that a pair of magnetic pole faces face each other on both sides of the steel strip passing through the steel strip carry-in opening, and a plurality of exciting coils provided on the core; An electromagnet provided around the steel strip carry-in opening so as to impart an upward electromagnetic force to the hot-dip plated metal so as not to leak and flow down from the steel strip carry-in opening,
The pair of magnetic pole faces of the electromagnet is such that the distance between both magnetic pole faces is minimized at the central portion of the steel strip carrying-in opening and the distance between both magnetic pole faces is maximized at both ends of the steel strip carrying-in opening. They are characterized by being formed in a convex shape with respect to each other.
[0016]
Moreover, the production method of the hot dip galvanized steel strip of the present invention has the following invention specific matters.
( 3 ) Melting using an aerial pot for levitation of a galvanized metal that faces the electromagnet that generates electromagnetic force to prevent the galvanized metal from flowing down from the carry-in opening of the steel strip so as to be sandwiched from both sides of the carry-in opening In the production method of plated steel strip,
The shape of the magnetic pole face of the electromagnet facing the carry-in opening is formed in a convex shape so that the magnetic flux density between the magnetic pole faces is constant at each point in the plate width direction of the steel strip,
In a state where magnetic flux is generated between the magnetic pole surfaces of the electromagnet, the steel strip is passed from the lower side to the upper side to pass through the carry-in opening and is passed through the hot dipped metal.
( 4 ) An aerial pot filled with hot-dipped metal and having a steel strip carry-in opening formed at the bottom;
A steel core that is disposed so that a pair of magnetic pole faces face each other on both sides of the steel strip passing through the steel strip carry-in opening, and a plurality of exciting coils provided on the core; An electromagnet provided around the steel strip carry-in opening so as to impart an upward electromagnetic force to the hot-dip plated metal so as not to leak and flow down from the steel strip carry-in opening,
The pair of magnetic pole faces of the electromagnet is such that the distance between both magnetic pole faces is minimized at the central portion of the steel strip carrying-in opening and the distance between both magnetic pole faces is maximized at both ends of the steel strip carrying-in opening. , A method for producing a hot-dip galvanized steel strip using hot-dip galvanized metal levitation pots that are formed in a mutually convex shape,
While supplying a constant electric power to the exciting coil, the steel strip is passed from the bottom to the top to pass through the steel strip carry-in opening, and is passed through the hot-dip plated metal housed in the air pot. To do.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Here, an example of an embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIGS.
First, in general, in the configuration shown in FIGS. 1 and 5, the magnetic flux density B perpendicular to the surface of the steel strip 1 obtained between the magnetic pole faces 17 by energizing the exciting coil 16 of the electromagnet 10, When the induced eddy current I generated by the magnetic flux density B and the upward electromagnetic push-up force F generated by the induced eddy current 1 are captured as vectors, they are expressed as an outer product [F = I × B] as described above.
In addition, since the induced eddy current I is proportional to the magnetic flux density B, the relationship shown by F∝B ² occurs between the magnetic flux density B between the magnetic pole faces 17 and the electromagnetic lifting force F. Therefore, even if the magnetic flux density B slightly changes, the electromagnetic lifting force F varies greatly.
[0018]
On the other hand, assuming that the number of turns of the exciting coil 16 on the electromagnet 10 is N, the current flowing through the exciting coil 16 is I _c , and the magnetomotive force of the exciting coil 16 is f ₁ , the magnetomotive force f ₁ is expressed by the following equation.
f ₁ = 2 · N · I _c (1)
Further, assuming that the magnetic permeability of the “plate portion” a and the “plateless portion” b between the magnetic pole faces 17 is substantially the same constant with μ ₀ , let A be the cross-sectional area of the magnetic path and B be the magnetic flux density. For example, the magnetic flux density B is expressed by the following equation.
B = μ ₀ · f ₁ / A · g = μ ₀ · 2 · N · I _c / A · g (2)
[0019]
As a result, in equation (2), if the magnetomotive force f ₁ = 2 · N · I _c is made constant, the magnitude of the magnetic flux density B depends on the size of the gap g between the magnetic pole faces 17 and is constant. It will be inversely proportional.
[0020]
In this example, paying attention to the relationship of the above equation (2), as shown in FIG. 1 (b), a constant average is obtained between the “plate portion” a and the “no plate portion” b between the magnetic pole surfaces 17. In order to maintain the magnetic flux density B, the magnetic pole surface 17 facing the steel band carrying-in opening 13 is subjected to a change in magnetic flux density in the plate width direction due to the shielding action when the steel band 1 passes as shown in FIG. In order to compensate, different magnetic pole face spacing g distributions are set in the plate width direction, and the magnetic pole end faces are formed as convex curved surfaces as shown in FIG.
That is, at a plurality of points in the plate width direction, the magnetic pole face spacing g value necessary to compensate for the change in magnetic flux density is set based on the above formula (2), and the steel strip carry-in opening between the magnetic pole faces 17 of the electromagnet 10 is set. The magnetic pole faces facing each other at the end faces of the convex curved surface in the distribution of the gap g with the minimum magnetic pole face gap g _min at the center part 13 and the maximum magnetic pole face gap g _max at both ends of the steel strip carry-in opening 13 It is constituted as follows.
[0021]
In the electromagnet 10 having the configuration shown in FIG. 1, the hot-dip plated metal 6 is supplied to the aerial pot 5 from the subpot 8 by the pump 7, and a constant electric power (current) designed to the exciting coil 16 of the electromagnet 10 is supplied. When the steel strip 1 starts to pass through the aerial pot 5 from the bottom to the top, the position between the magnetic pole surfaces 17 facing each other at the end surfaces having a convex curved surface is closer to the position where the magnetic pole surface interval g is smaller in the equation (2). That is, a larger magnetic flux density B is generated at the central portion of the plate width, and an electromagnetic lifting force F corresponding to the magnetic flux density B is generated.
[0022]
At this time, the amount of decrease in the magnetic flux density B in the plate width direction due to the shielding action when passing through the steel strip 1 is measured in advance at an appropriate pitch in the plate width direction, and based on this, the magnetic flux density B is calculated by the above equation (2). By setting the distribution of the magnetic pole face spacing g necessary to compensate the amount of decrease at each measurement position, the upward electromagnetic push-up force F generated between the magnetic pole faces 17 causes the magnetic flux density due to the shielding action of the steel strip 1 to be increased. The offset distribution of B is offset, and as shown in FIG. 1 (b), a uniform predetermined magnetic flux density B is applied to the entire width region including the “plate portion” a and the “plateless portion” b of the steel strip carry-in opening portion 13. Will be able to keep.
[0023]
【The invention's effect】
As described above, according to the present invention, the magnetic pole surface of the electromagnet that faces the carry-in opening of the steel strip is compensated for the magnetic flux density change in the plate width direction due to the steel strip passing through the carry-in opening. For example, by forming it into a convex curved surface, an electromagnetic push-up force with an even distribution according to the design value in the plate width direction works on the hot-plated metal in the actual opening. The unstable movement of the hot dip metal in the carry-in opening is eliminated, and there is no danger of the hot dip metal flowing out from this opening during the plating operation. At the same time, the circulation of the hot-dip metal in the aerial pot is stabilized, and a homogeneous hot-dip steel strip can be produced.
Moreover, it is not necessary to compensate for the decrease in the magnetic flux density distribution caused by the steel strip shielding the magnetic flux with a large input power, and an effect of economically producing a hot-dip galvanized steel strip can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view and a characteristic diagram of an example of an embodiment of the present invention.
2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a plan view of a conventional example (a plan view as viewed from III-III in FIG. 2).
FIG. 4 is a plan view and characteristic diagram of a conventional example.
FIG. 5 is an explanatory diagram of an electromagnetic lifting force.
FIG. 6 is an arrangement state diagram of eddy current bus bars.
FIG. 7 is a simplified plan view of an eddy current bus bar.
FIG. 8 is a state diagram of magnetic flux density and eddy current.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel strip 5 Aerial pot 6 Hot-dip plated metal 10 Electromagnet 13 Steel strip carrying-in opening part 17 Magnetic pole surface 18 Bus bar for eddy current

Claims

鋼帯の搬入開口部からの溶融めっき金属の流下を防止する電磁力を発生する電磁石を上記搬入開口部の両側から挟むように対峙させた溶融めっき金属浮上用空中ポットにおいて、
前記鋼帯の搬入開口部を挟んで対峙する前記電磁石の磁極面の形状は、この磁極面間の磁束密度が前記鋼帯の板幅方向の各点において一定となるよう凸面形状に形成したことを特徴とする溶融めっき金属浮上用空中ポット。In an aerial pot for floating plating metal levitation in which electromagnets that generate electromagnetic force to prevent the molten plating metal from flowing down from the carry-in opening of the steel strip are opposed to be sandwiched from both sides of the carry-in opening,
The shape of the magnetic pole surface of the electromagnet facing the steel strip loading opening is formed in a convex shape so that the magnetic flux density between the magnetic pole surfaces is constant at each point in the plate width direction of the steel strip. hot-dip coating metal flying aerial pot characterized by.

溶融めっき金属が満たされると共に、下方から上方に向かって鋼帯を通過させる鋼帯搬入開口部が底部に形成された空中ポットと、
前記鋼帯搬入開口部を通過する前記鋼帯の両面に一対の磁極面を対峙させるよう配置した鉄心コアと、この鉄心コアに設けた複数の励磁コイルとを有し、前記溶融めっき金属が前記鋼帯搬入開口部から漏出・流下しないように上向きの電磁力を当該溶融めっき金属に付与するよう前記鋼帯搬入開口部の周囲に設けられた電磁石とを有し、
前記電磁石の一対の磁極面は、前記鋼帯搬入開口部の中央部分で双方の磁極面の間隔が最小となり前記鋼帯搬入開口部の両端部で双方の磁極面の間隔が最大となるように、相互に凸面形状に形成されていることを特徴とする溶融めっき金属浮上用ポット。An aerial pot in which a steel strip carrying opening that allows the steel strip to pass from below to above is formed at the bottom, while being filled with a hot dipped metal,
A steel core that is disposed so that a pair of magnetic pole faces face each other on both sides of the steel strip passing through the steel strip carry-in opening, and a plurality of exciting coils provided on the core; An electromagnet provided around the steel strip carry-in opening so as to impart an upward electromagnetic force to the hot-dip plated metal so as not to leak and flow down from the steel strip carry-in opening,
The pair of magnetic pole faces of the electromagnet is such that the distance between both magnetic pole faces is minimized at the central portion of the steel strip carrying-in opening and the distance between both magnetic pole faces is maximized at both ends of the steel strip carrying-in opening. A hot-dip galvanized metal levitation pot characterized by being formed in a convex shape.

鋼帯の搬入開口部からの溶融めっき金属の流下を防止する電磁力を発生する電磁石を上記搬入開口部の両側から挟むように対峙させた溶融めっき金属浮上用空中ポットを用いた溶融めっき鋼帯の生産方法において、
前記搬入開口部を挟んで対峙する前記電磁石の磁極面の形状は、この磁極面間の磁束密度が前記鋼帯の板幅方向の各点において一定となるよう凸面形状に形成し、
前記電磁石の磁極面の間に磁束を発生させた状態で、鋼帯を下方から上方に向けて前記搬入開口部を通過させて溶融めっき金属の中を通過させることを特徴とする溶融めっき鋼帯の生産方法。Hot-dip galvanized steel strip using an aerial pot for galvanized metal levitation in which electromagnets that generate electromagnetic force to prevent the galvanized metal from flowing down from the carry-in opening of the steel strip are sandwiched from both sides of the carry-in opening. In the production method of
The shape of the magnetic pole face of the electromagnet facing the carry-in opening is formed in a convex shape so that the magnetic flux density between the magnetic pole faces is constant at each point in the plate width direction of the steel strip,
A hot dip steel strip, characterized in that in a state where a magnetic flux is generated between the magnetic pole surfaces of the electromagnet, the steel strip is passed from the lower side to the upper side through the carry-in opening and through the hot dip metal. Production method.

溶融めっき金属が満たされると共に、鋼帯搬入開口部が底部に形成された空中ポットと、
前記鋼帯搬入開口部を通過する前記鋼帯の両面に一対の磁極面を対峙させるよう配置した鉄心コアと、この鉄心コアに設けた複数の励磁コイルとを有し、前記溶融めっき金属が前記鋼帯搬入開口部から漏出・流下しないように上向きの電磁力を当該溶融めっき金属に付与するよう前記鋼帯搬入開口部の周囲に設けられた電磁石とを有し、
前記電磁石の一対の磁極面は、前記鋼帯搬入開口部の中央部分で双方の磁極面の間隔が最小となり前記鋼帯搬入開口部の両端部で双方の磁極面の間隔が最大となるように、相互に凸面形状に形成されている溶融めっき金属浮上用ポットを用いた溶融めっき鋼帯の生産方法であって、
前記励磁コイルに一定の電力を供給しつつ、鋼帯を下方から上方に向けて前記鋼帯搬入開口部を通過させて前記空中ポットに収容した前記溶融めっき金属の中を通過させることを特徴とする溶融めっき鋼帯の生産方法。An aerial pot filled with hot-dipped metal and having a steel strip carry-in opening formed at the bottom;
A steel core that is disposed so that a pair of magnetic pole faces face each other on both sides of the steel strip passing through the steel strip carry-in opening, and a plurality of exciting coils provided on the core; An electromagnet provided around the steel strip carry-in opening so as to apply an upward electromagnetic force to the hot-dip plated metal so as not to leak and flow down from the steel strip carry-in opening,
The pair of magnetic pole faces of the electromagnet is such that the distance between both magnetic pole faces is minimized at the central portion of the steel strip carrying-in opening and the distance between both magnetic pole faces is maximized at both ends of the steel strip carrying-in opening. , A method of producing a hot-dip galvanized steel strip using hot-dip galvanized metal levitation pots that are formed in a mutually convex shape,
While supplying a constant electric power to the exciting coil, the steel strip is passed from the bottom to the top to pass through the steel strip carry-in opening, and is passed through the hot-dip plated metal housed in the air pot. To produce hot-dip galvanized steel strip.