JP4160649B2 - Electric heating device for sheet metal material - Google Patents

Electric heating device for sheet metal material Download PDF

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Publication number
JP4160649B2
JP4160649B2 JP05734698A JP5734698A JP4160649B2 JP 4160649 B2 JP4160649 B2 JP 4160649B2 JP 05734698 A JP05734698 A JP 05734698A JP 5734698 A JP5734698 A JP 5734698A JP 4160649 B2 JP4160649 B2 JP 4160649B2
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metal material
plate
ring
alternating current
electrodes
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JPH11238570A (en
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芳明 広田
敬介 藤崎
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Nippon Steel Corp
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Nippon Steel Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、スラブや厚板、薄板などの板状の金属材料、たとえば鉄やアルミニウム、銅、ならびにそれらの合金を所要の温度分布で連続的に効率よく通電加熱できる通電加熱装置に関する。
【0002】
【従来の技術】
従来、金属材料を加熱する場合、加熱・保温はガス加熱による輻射や電気ヒーターによる間接加熱がほとんどであった。しかし、これらの加熱方法は間接的に金属材料を表面から加熱するため、表面のみ温度が上がって内部伝熱律速となり急速な加熱ができないという問題があり、板厚や板幅などが変わるときには生産性に大きく制約を与えていた。
【0003】
この問題を解決するため、通電加熱を採用することが提唱されている。たとえば、実開昭61−82954号公報には、鋼板に通電ロールを介して直接通電し、鋼板自体を発熱体として高温化することが、また、特開平1−142032号公報や特開平1−187789号公報には、環状トランスを貫通する金属帯板通路の前後に通電ロールを設け、金属帯板を加熱する方法が記載されている。このように金属帯板に直接電流を流し、ジュール熱で加熱する場合は、ガスや電気の間接加熱と比べ単位時間当たりの加熱能力が高く、板厚や板幅の変更に伴う生産性低下という問題をなくすことができるとともに、設備がコンパクトにできる点で優れている。
【0004】
上記の様に進行方向に通電ロールを設け、比較的板厚の薄い金属材料が続けて供給される場合には、連続的に通電加熱できるため生産性が良いが、スラブや厚板などの様に長さが決められた金属材料の場合、先端部分と後端部分とにはどうしても通電ロールからはずれて加熱できない部分が生じ、歩留まり落ちが生じてしまうという問題がある。
【0005】
また、たとえば厚板材などでは幅が大きく変化するとともに、幅自体が広いため通電ロールの胴長も長くなってしまい、ロールがたわみやすくなることに加え通電電流密度が大きくなるため、被加熱材と通電ロールとの間でスパークが発生しやすいという問題もある。
【0006】
このような有限長材の先端部と後端部の加熱不足やスパーク発生の問題に対し、たとえば特開昭61−315319号公報などにみられるように電極を被加熱材の先端と後端に密着させ、材料全体をバッチ的に加熱する方法や、特開平7−220864号公報のように被加熱材の先端と後端にダミー材をつけて加熱する方法などが提案されている。
【0007】
【発明が解決しようとする課題】
しかし、電極を被加熱材の先端と後端に密着させ、材料全体を材料毎に加熱する方法では、たとえば厚鋼板などの場合のように材料の長さが数m〜20数mまで大きく変わる材料などでは、電極も材料の長さに合わせて大きく変化させなければならず、設備・スペース上の問題があった。また、全長にわたって加熱を行うには設備容量を大きくする必要があるとともに、加熱時間が長大になることから熱放散の影響が大きくなり、加熱効率が低下してしまうという問題、さらに長時間電極を被加熱材に接触し続けるため電極と被加熱材の間で溶着が起こりやすいという問題が生じる。また、ダミー材をつけて加熱する方法では、ダミー材の着脱工程、時間の増加、ダミー材そのものの材料代等が余分に必要となり、無駄が多い。
【0008】
そこで、本発明は、上記の課題を有利に解決するために、被加熱材の幅方向に流れる電流路が制御でき、長さ、幅、厚みによらず板状の被加熱金属材料を効率よく連続的に所要の温度パターンで加熱できる板状金属材料の通電加熱装置を提供することを目的とする。
【0009】
【課題を解決するための手段】
本発明の要旨は下記(1)〜(6)の通りである。
【0010】
(1)板状金属材料がその中を通過できるリング状磁性コアを有し、該リング状磁性コアの板状金属材料の幅方向両端部近辺に交流電流を流すコイルをそれぞれ巻くとともに、該リング状磁性コアの片面側の近傍でかつ前記板状金属材料の幅方向両端部に電極を設ける構成とし、該電極より交流電流を通じた際に、前記板状金属材料の長手方向に放射線状に広がろうとしながら前記電極間に流れる交流電流を、前記それぞれのコイルに流す交流電流によって、前記リング状磁性コアに、その断面において幅方向の一方側に時計周り方向の磁束および幅方向のもう一方側に反時計周り方向の磁束を発生させると共に、該発生した磁束により、前記板状金属材料に、前記リング状磁性コアで囲われたところでは前記電極間に流れる交流電流と打ち消し合い、前記リング状磁性コアで囲われていないところでは前記電極間に流れる交流電流と強め合うように誘導電流を発生させることで、前記電極間に流れる交流電流の放射線状の広がりを抑え、ジュール熱により前記板状金属材料を加熱することを特徴とする板状金属材料の通電加熱装置。
【0011】
(2)板状金属材料がその中を通過できる一対のリング状磁性コアを有し、該一対のリング状磁性コア各々における板状金属材料の幅方向両端部近辺に交流電流を流すコイルをそれぞれ巻くとともに、二つのリング状磁性コアの間の近傍でかつ前記板状金属材料の幅方向両端部に電極を設ける構成とし、該電極より交流電流を通じた際に、前記板状金属材料の長手方向に放射線状に広がろうとしながら前記電極間に流れる交流電流を、前記一対のリング状磁性コア各々における板状金属材料の幅方向両端部近辺に巻いたそれぞれのコイルに流す交流電流によって、前記一対のリング状磁性コア各々に、その断面において幅方向の一方側に時計周り方向の磁束および幅方向のもう一方側に反時計周り方向の磁束を発生させると共に、該発生した磁束により、前記板状金属材料に、前記リング状磁性コアで囲われたところでは前記電極間に流れる交流電流と打ち消し合い、前記リング状磁性コアで囲われていないところでは前記電極間に流れる交流電流と強め合うように誘導電流を発生させることで、前記電極間に流れる交流電流の放射線状の広がりを抑え、ジュール熱により前記板状金属材料を加熱することを特徴とする板状金属材料の通電加熱装置。
【0012】
(3)前記(2)の通電加熱装置を板状金属材料の進行方向に複数配置したことを特徴とする板状金属材料の通電加熱装置。
【0013】
(4)前記リング状磁性コアの板状金属材料の幅方向両端部近辺にそれぞれ巻いた交流電流を流すコイルは、同一回巻かれていることを特徴とする前記(1)〜(3)の板状金属材料の通電加熱装置。
【0014】
(5)コイルに流す交流電流と電極から板状金属材料に流す交流電流との位相差を制御可能としたこと、および/または、コイルに流す交流電流の電流密度を調整可能としたことを特徴とする前記(1)〜(4)の板状金属材料の通電加熱装置。
【0015】
(6)交流電流を流すコイルにタップを設けたことを特徴とする前記(1)〜()の板状金属材料の通電加熱装置。
【0016】
【発明の実施の形態】
以下、本発明の実施の形態を図面を用いて説明する。
【0017】
図1は、本発明の板状金属材料の通電加熱装置を示す図である。移動する板状金属材料1は、図2の正面図に示す様な磁気特性に優れた珪素鋼板等でできたリング状磁性コア5、6の開口部を通過する。リング状磁性コア5、6の間には、電源4に導電部材で接続された電極2、3を配置する。電極2、3は図1では一つずつになっているが、複数に分割しても良い。電極2、3の形状はローラーの様な回転体が良いが、電流が大きいときなどには摺り板形状などを用いればよく、特にその形状を規定するものではない。電極2、3の材質は鉄やステンレス鋼等の導電性に優れる金属、あるいはカーボンや導電性セラミックスなどのバルク材でも、また溶射等によるコーティング皮膜を形成したものでも良い。
【0018】
リング状磁性コア5、6が無い場合、電極2、3からでた電流は、図3に示す電流15のように放射状に広がって流れようとする。そのため、板状金属材料1の断面内の電流密度は電極2、3の近傍が最も高く、温度も高くなり、電極2、3から離れると電流密度は極端に小さくなり、温度上昇量も小さくなって温度分布の不均一が生じる。また、電流が板状金属材料1の長手方向に広がって流れるため、板状金属材料1が接触している搬送ロールにも迷走電流が流れ、ロールのベアリング等を焼損してしまう等の問題が生じる。そこで本発明の通電加熱装置では、電極2、3から放射状に広がろうとする電流を効果的に制御し、均一な温度分布を得る。
【0019】
電極2、3間に流す電流を交流とし、磁気特性に優れた珪素鋼板等からなるリング状磁性コア5、6を電極2、3の前後に置くと、リング状磁性コア5、6間の板状金属材料1を流れる交流電流により電磁誘導でリング状磁性コア5、6に磁束が発生し、リング状磁性コア5、6の中を通過しようとする電流と逆位相の電流を板状金属材料1に誘起させることにより、リング状磁性コア5、6の外に流れようとする電流を制限することができる。電流路を定めることができれば、電流密度の不均一から生じる温度の不均一が解消できるとともに、板状金属材料1を通じて迷走電流がラインに流れるという問題もなくなる。
【0020】
しかし、実際にはリング状磁性コア5、6を置いただけでは効果が小さく、リング状磁性コア5、6の外に流れ出る電流を完全には阻止できない。そこで、リング状磁性コア5、6にコイル11、12、13、14を巻き、電源7、8、9、10により電流を流して強制的にリング状磁性コア5、6に磁束を発生させれば、板状金属材料1内にリング状磁性コア5、6で発生した磁束による誘起電流が発生し、電極2、3からの電流との相互作用により電極幅方向の電流パターンを変化させることができる。
【0021】
図4〜9は、有限要素法により計算した結果を模式的に示す図である。
【0022】
図4、5はリング状磁性コアを設置しないで電極2、3間で通電を行った例であり、図中の矢印は電流のベクトルを示す。図4は、電極2、3から流れた電流の向きと大きさを模式化して示すものである。電極3から流れた電流は、直進するものもあるが放射状に広がって流れるものもあり、電流密度は電極近傍が極めて高くなる。これを温度分布に直して示すのが図5である。図5は、発熱量が電流の2乗に比例することから、電流の2乗に応じたコンター図を示すが、電極近傍のみ密集し、温度差が大きくつく様子が明らかである。
【0023】
以上に対し、電極2、3間で電流を通じ、リング状磁性コア6の両端側にコイル12、14を巻いて電流を流し、リング状磁性コア6内に磁束を発生させたときの様子を示すのが図6〜9である。図6は、リング状磁性コア6の中に発生した磁束のベクトルを示す断面図である。この例では、右側では時計回りの方向に磁束が発生し、左側では反時計回りの方向に磁束が発生している。このリング状磁性コア6に発生した磁束により、板状金属材料1には図7、8に示す誘導電流が発生する。図7は、電極2、3から出た電流とリング状磁性コア6に発生した磁束によって作られる誘導電流とで作られる電流分布の実部の様子を示す。電流は、リング状磁性コア6を境に電極3から電極2に向かう割合が増え、リング状磁性コア6の外に発生する電流は極めて小さくなる。また、図8は電流虚部の分布を示す。電流は、リング状磁性コア6を設けないで通電したときの電流分布と比べると、電極2、3間の電流の向きは一致するが、リング状磁性コア6部では全く逆向きの電流が発生する。そのため、電極3からでた電流はリング状磁性コア6部で打ち消されることになり、リング状磁性コア6の外には電流が流れにくくなり、電極2、3間方向に電流が流れるようになる。この時の発熱分布を計算した結果を示すのが図9であり、リング状磁性コア6の上側の部分はコンターも広く分布し、温度が均一化されているのがわかる。
【0024】
以上の様に、幅方向電極2、3間で板状金属材料1を均一に加熱するためには電極2、3から放射状にでる電流を打ち消す様に電流を制御すればよい。特に、均一性を狙う場合には、電極2、3間に流す電流が交流であることを考えると、リング状磁性コア6に巻くコイルは、リング状磁性コアの両サイドに対称的に巻くのが望ましい。
【0025】
また、逆に局部的に加熱する場合には、リング状磁性コア6にコイル12、14により発生させる磁場分布を変化させればよい。すなわち、リング状磁性コア6から板状金属材料1に発生させる誘導電流の大きさと向きを変えれば、電極電流と誘導電流との相互作用で生じるトータルの電流の大きさ、向きが変わるため、それによって生じる温度分布も変えることができる。磁場の変化は、コイル12、14に流す電流の電流密度の大きさと電極電流との位相差を電源8、10で変化させることにより実現できる。同様に、磁場の変化は、リング状磁性コア6に巻くコイル12、14の巻き数を変化させることによっても実現できる。現実的には、厚み、幅、温度など負荷の状況に応じコイルに複数のタップを設け、タップを切り替えることにより磁場の強さを変化させることができる。タップの切り替えは、加熱する板状金属材料1の厚み、幅、種類により電極2、3に流す電流量が大きく変化することから、それに応じ切り替えれば良いし、あるいは局部的に温度を高めたい場合には温度分布を測定し、所要の加熱パターンが得られるように、タップを切り替えても良い。
【0026】
以上、リング状磁性コアが一つの場合で説明したが、図1の様にもう一つリング状磁性コア5を設けた場合でも同様の効果が得られる。特に、板状金属材料1の進行方向にも流れる電流を阻止するためには、リング状磁性コアを二つ設けると効果的である。
【0027】
【実施例】
以下、本発明の実施例について有限要素法により解析した結果に基づいて説明する。
【0028】
図1の様な構成で、断面積100cm2 の二つのリング状磁性コア5、6を100mm離し、板厚16mm、板幅500mm、長さ1000mmのSUS304材を内に通し、リング状磁性コア5、6間に電極長さ100mmの電極2、3を配置し、300Aの電流を流すとともに、コイル13、14をL側、コイル11、12をR側とし、このコイル11〜14に位相と電流密度を変えて電流を流した場合の磁場、電流密度、温度分布を計算した。表1に5分後の電極幅方向の温度差を示す。
【0029】
【表1】

Figure 0004160649
【0030】
本発明例では、リング状磁性コアの外に流れる電流はごくわずかあるが、ほとんど無視できる程度に小さく、かつコイルの位相を変えることにより幅方向の温度差を変えることができる。たとえば、L、R側コイル電流と電極電流の位相差が0の場合には、電極間の断面内温度分布を10℃程度にすることができ、位相差を変えることによりその差を大きくすることが可能である。表1の例は全てエッジ側の温度が高く中央がやや低くなる分布であるが、これを利用すれば板材のエッジ部の冷却が進みやすいのに対し、あらかじめエッジ部の温度を高く加熱することが可能となる。また、同様の効果はコイルの電流密度を変えることによっても得ることができる。表1では、コイル電流密度を6AT/mm2 と3AT/mm2 に変えることにより、位相差を90度変えたものと同等の加熱が可能であることがわかる。
【0031】
一方、比較例はリング状磁性コアが無く、単純に電極のみを配置した例であるが、加熱は電極近傍のみしか行われず、かつ電流は広く広がってしまう。したがって、電極から離れた所にロールなどがあり、アースされている場合には、そのロールから電流が流れ出す可能性が高く、設備、人心事故が起こる可能性もある。
【0032】
【発明の効果】
本発明によれば、有限長の板状金属材料を電気により連続的、安定的に効率よく内部加熱できるため、加熱の生産性を向上させることが可能となる。また、温度を任意に変化させることが可能となるほか、温度を均一にすることも可能であり、温度偏差による材質ばらつきを減らすことができるだけでなく、温度を均一にするための均熱工程を省略することができる。さらに、電極加熱であるため雰囲気を高温にする必要がなく、耐火物などの設備費が不要になるほか、ロール等の搬送設備やバーナー等の加熱設備に要する修繕を大幅に減らすことが可能となる。操業中も通電による迷走電流を抑えることができることから、安全面でも有利である。
【図面の簡単な説明】
【図1】本発明の板状金属材料の通電加熱装置の平面図である。
【図2】本発明の板状金属材料の通電加熱装置の正面図である。
【図3】リング状磁性コアを用いない場合の電流を示す図である。
【図4】リング状磁性コアを用いない場合の電流を示す図である。
【図5】リング状磁性コアを用いない場合の温度分布を示す図である。
【図6】リング状磁性コア内に発生させる磁場分布を示す図である。
【図7】リング状磁性コア内に発生させた磁場により板状金属材料内を流れる電流の実部を示す図である。
【図8】リング状磁性コア内に発生させた磁場により板状金属材料内を流れる電流の虚部を示す図である。
【図9】リング状磁性コア内に発生させた磁場による板状金属材料の温度分布を示す図である。
【符号の説明】
1 板状金属材料
2 電極
3 電極
4 電極
5 リング状磁性コア
6 リング状磁性コア
7 電源
8 電源
9 電源
10 電源
11 コイル
12 コイル
13 コイル
14 コイル
15 電流[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric heating apparatus capable of continuously and efficiently energizing and heating plate-like metal materials such as slabs, thick plates, and thin plates, for example, iron, aluminum, copper, and alloys thereof with a required temperature distribution.
[0002]
[Prior art]
Conventionally, in the case of heating a metal material, most of heating and heat retention are radiation by gas heating or indirect heating by an electric heater. However, because these heating methods indirectly heat the metal material from the surface, there is a problem that the temperature rises only on the surface and the internal heat transfer rate is limited, and rapid heating cannot be performed. There was a great restriction on sex.
[0003]
In order to solve this problem, it has been proposed to employ energization heating. For example, Japanese Utility Model Laid- Open No. 61-82594 discloses that a steel sheet is directly energized through an energizing roll to raise the temperature of the steel sheet itself as a heating element. Japanese Patent No. 187789 describes a method of heating the metal strip by providing energizing rolls before and after the metal strip passage passing through the annular transformer. In this way, when direct current is passed through the metal strip and heating is done with Joule heat, the heating capacity per unit time is higher than indirect heating of gas and electricity, and productivity decreases with changes in plate thickness and plate width. It is excellent in that the problem can be eliminated and the equipment can be made compact.
[0004]
When a current-carrying roll is provided in the traveling direction as described above and a relatively thin metal material is continuously supplied, productivity can be improved because continuous heating can be performed, but slabs, thick plates, etc. In the case of a metal material having a predetermined length, there is a problem in that the front end portion and the rear end portion are inevitably separated from the energizing roll and cannot be heated, resulting in a drop in yield.
[0005]
In addition, for example, in the case of a thick plate material, the width greatly changes and the width itself is wide, so that the length of the energizing roll becomes long, and in addition to the roll being easily bent, the energizing current density is increased, There is also a problem that sparks are easily generated between the current-carrying rolls.
[0006]
With respect to such problems of insufficient heating and spark generation at the front and rear ends of the finite length material, as shown in, for example, Japanese Patent Application Laid-Open No. 61-315319 , electrodes are attached to the front and rear ends of the material to be heated. There are proposed a method in which the entire material is heated in batches, a method in which dummy materials are attached to the front and rear ends of a material to be heated, as in JP-A-7-220864 , and the like.
[0007]
[Problems to be solved by the invention]
However, in the method in which the electrode is brought into close contact with the front end and the rear end of the material to be heated and the entire material is heated for each material, the length of the material greatly varies from several meters to several tens of meters as in the case of, for example, a thick steel plate. For materials, etc., the electrodes had to be changed greatly in accordance with the length of the material, and there was a problem in equipment and space. Moreover, in order to perform heating over the entire length, it is necessary to increase the capacity of the equipment, and since the heating time becomes long, the influence of heat dissipation becomes large and the heating efficiency is lowered. Since it continues to contact the heated material, there arises a problem that welding is likely to occur between the electrode and the heated material. In addition, in the method of heating with the dummy material attached, the dummy material attaching / detaching process, the time increase, the material cost of the dummy material itself, etc. are required, which is wasteful.
[0008]
Therefore, the present invention can control the current path flowing in the width direction of the material to be heated in order to advantageously solve the above-mentioned problems, and can efficiently use the plate-shaped metal material to be heated regardless of the length, width, and thickness. It is an object of the present invention to provide an energization heating device for a plate-like metal material that can be continuously heated in a required temperature pattern.
[0009]
[Means for Solving the Problems]
The gist of the present invention is as follows (1) to (6).
[0010]
(1) The ring-shaped metal material has a ring-shaped magnetic core through which the plate-shaped metal material can pass, and each coil is wound with a coil for passing an alternating current near both ends in the width direction of the plate-shaped metal material of the ring-shaped magnetic core. An electrode is provided in the vicinity of one side of the plate-like magnetic core and at both ends in the width direction of the plate-like metal material, and when an alternating current is passed through the electrode, the plate-like metal material spreads radially in the longitudinal direction of the plate-like metal material. The alternating current flowing between the electrodes while trying to stagnate is caused by the alternating current flowing in the respective coils to cause the ring-shaped magnetic core to have a magnetic flux in the clockwise direction on the one side in the width direction and the other in the width direction in the cross section. together to generate a magnetic flux in the counterclockwise direction to the side, the magnetic flux the occurrence, in the plate-like metal material, strikes an AC current flowing between the electrodes at surrounded by the ring-shaped magnetic core However, by generating an induced current so as to strengthen the alternating current flowing between the electrodes where it is not surrounded by the ring-shaped magnetic core, suppressing the radial spread of the alternating current flowing between the electrodes, A plate-like metal material energization heating apparatus, wherein the plate-like metal material is heated by Joule heat.
[0011]
(2) The plate-shaped metal material has a pair of ring-shaped magnetic cores through which the plate-shaped metal material can pass, and each of the pair of ring-shaped magnetic cores has a coil for passing an alternating current in the vicinity of both ends in the width direction of the plate-shaped metal material. In addition to winding, an electrode is provided in the vicinity between the two ring-shaped magnetic cores and at both ends in the width direction of the plate-shaped metal material. When an alternating current is passed through the electrode, the longitudinal direction of the plate-shaped metal material The alternating current that flows between the electrodes while trying to spread in a radial manner is caused by the alternating current that flows in the respective coils wound around the both ends in the width direction of the plate-shaped metal material in each of the pair of ring-shaped magnetic cores. a pair of ring-shaped magnetic cores, respectively, which both generates the magnetic flux of the counter-clockwise direction to one side in the width direction in its cross-section to the other side of the magnetic flux and the width direction of the clockwise direction and the generator The bundle, the plate-like metal material, said at surrounded by ring-shaped magnetic core cancel each other and the alternating current flowing between the electrodes, where that is not surrounded by the ring-shaped magnetic core flows between the electrodes AC By generating an induced current so as to strengthen the current, a radial spread of the alternating current flowing between the electrodes is suppressed, and the plate-like metal material is heated by Joule heat. Electric heating device.
[0012]
(3) An electric heating apparatus for a plate-like metal material, wherein a plurality of the electric heating devices of (2) are arranged in the traveling direction of the plate-like metal material.
[0013]
(4) a coil passing an alternating current wound widthwise ends respectively in the vicinity of the sheet metal material of the ring-shaped magnetic core, said, characterized in that it he same time winding (1) - (3) An electric heating device for sheet metal materials.
[0014]
(5) The phase difference between the alternating current flowing through the coil and the alternating current flowing from the electrode to the plate-like metal material can be controlled, and / or the current density of the alternating current flowing through the coil can be adjusted. The plate-like metal material energization heating device of (1) to (4).
[0015]
(6) The electric heating apparatus for plate-shaped metal material according to any one of (1) to ( 4 ), wherein a tap is provided on a coil for passing an alternating current.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a diagram showing a current-carrying heating apparatus for a sheet metal material according to the present invention. The moving plate-shaped metal material 1 passes through openings of ring-shaped magnetic cores 5 and 6 made of a silicon steel plate or the like having excellent magnetic properties as shown in the front view of FIG. Between the ring-shaped magnetic cores 5 and 6, electrodes 2 and 3 connected to the power supply 4 by conductive members are arranged. Although the electrodes 2 and 3 are one each in FIG. 1, they may be divided into a plurality. The shape of the electrodes 2 and 3 is preferably a rotating body such as a roller. However, when the current is large, the shape of the sliding plate may be used, and the shape is not particularly specified. The material of the electrodes 2 and 3 may be a metal having excellent conductivity such as iron or stainless steel, or a bulk material such as carbon or conductive ceramics, or a coating film formed by thermal spraying or the like.
[0018]
In the absence of the ring-shaped magnetic cores 5 and 6, the currents from the electrodes 2 and 3 tend to spread radially and flow like a current 15 shown in FIG. Therefore, the current density in the cross section of the plate-shaped metal material 1 is highest in the vicinity of the electrodes 2 and 3, and the temperature becomes high. When the metal material 1 is separated from the electrodes 2 and 3, the current density becomes extremely small, and the temperature increase is also small. This causes uneven temperature distribution. Moreover, since the current spreads and flows in the longitudinal direction of the plate-shaped metal material 1, the stray current flows also to the transport roll in contact with the plate-shaped metal material 1, causing problems such as burning the roller bearings and the like. Arise. Therefore, in the energization heating device of the present invention, the current that is going to spread radially from the electrodes 2 and 3 is effectively controlled to obtain a uniform temperature distribution.
[0019]
When the ring-shaped magnetic cores 5 and 6 made of a silicon steel plate or the like having excellent magnetic properties are placed between the electrodes 2 and 3 before and after the electrodes 2 and 3 are AC, the current between the electrodes 2 and 3 is a plate between the ring-shaped magnetic cores 5 and 6. A magnetic flux is generated in the ring-shaped magnetic cores 5 and 6 by electromagnetic induction due to an alternating current flowing in the ring-shaped metal material 1, and a current having a phase opposite to that of the current passing through the ring-shaped magnetic cores 5 and 6 is applied to the plate-shaped metal material. By inducing it to 1, the current that flows out of the ring-shaped magnetic cores 5 and 6 can be limited. If the current path can be determined, the temperature non-uniformity resulting from the non-uniform current density can be eliminated, and the problem of stray current flowing in the line through the plate-shaped metal material 1 can be eliminated.
[0020]
However, in practice, the effect is small if only the ring-shaped magnetic cores 5 and 6 are placed, and the current flowing out of the ring-shaped magnetic cores 5 and 6 cannot be completely prevented. Therefore, the coils 11, 12, 13, and 14 are wound around the ring-shaped magnetic cores 5 and 6, and current is supplied from the power sources 7, 8, 9, and 10 to forcibly generate magnetic flux in the ring-shaped magnetic cores 5 and 6. For example, an induced current is generated in the plate-shaped metal material 1 due to the magnetic flux generated in the ring-shaped magnetic cores 5 and 6, and the current pattern in the electrode width direction can be changed by interaction with the currents from the electrodes 2 and 3. it can.
[0021]
4-9 is a figure which shows typically the result calculated by the finite element method.
[0022]
4 and 5 are examples in which energization is performed between the electrodes 2 and 3 without installing a ring-shaped magnetic core, and arrows in the drawings indicate current vectors. FIG. 4 schematically shows the direction and magnitude of the current flowing from the electrodes 2 and 3. Some of the current flowing from the electrode 3 travels straight, but some flows radially and flows, and the current density is extremely high near the electrode. FIG. 5 shows this as a temperature distribution. FIG. 5 shows a contour diagram corresponding to the square of the current because the amount of heat generation is proportional to the square of the current, but it is clear that only the vicinity of the electrodes is dense and the temperature difference becomes large.
[0023]
On the other hand, when a current is passed between electrodes 2 and 3, coils 12 and 14 are wound around both ends of ring-shaped magnetic core 6, a current is passed, and a magnetic flux is generated in ring-shaped magnetic core 6. This is shown in FIGS. FIG. 6 is a cross-sectional view showing a vector of magnetic flux generated in the ring-shaped magnetic core 6. In this example, magnetic flux is generated in the clockwise direction on the right side, and magnetic flux is generated in the counterclockwise direction on the left side. Due to the magnetic flux generated in the ring-shaped magnetic core 6, an induced current shown in FIGS. 7 and 8 is generated in the plate-shaped metal material 1. FIG. 7 shows the real part of the current distribution created by the currents from the electrodes 2 and 3 and the induced current created by the magnetic flux generated in the ring-shaped magnetic core 6. The ratio of current flowing from the electrode 3 to the electrode 2 with the ring-shaped magnetic core 6 as a boundary increases, and the current generated outside the ring-shaped magnetic core 6 becomes extremely small. FIG. 8 shows the distribution of the imaginary part of the current. Compared with the current distribution when the current is applied without the ring-shaped magnetic core 6, the current direction between the electrodes 2 and 3 is the same, but a current in the opposite direction is generated in the ring-shaped magnetic core 6 part. To do. Therefore, the current from the electrode 3 is canceled out by the ring-shaped magnetic core 6, and it becomes difficult for the current to flow outside the ring-shaped magnetic core 6, and the current flows in the direction between the electrodes 2 and 3. . FIG. 9 shows the result of calculating the heat generation distribution at this time, and it can be seen that the upper part of the ring-shaped magnetic core 6 has a wide distribution of contours and the temperature is made uniform.
[0024]
As described above, in order to uniformly heat the plate-shaped metal material 1 between the width direction electrodes 2 and 3, the current may be controlled so as to cancel out the current that radiates from the electrodes 2 and 3. In particular, when aiming at uniformity, considering that the current flowing between the electrodes 2 and 3 is alternating current, the coil wound around the ring-shaped magnetic core 6 is symmetrically wound on both sides of the ring-shaped magnetic core. Is desirable.
[0025]
Conversely, when heating locally, the magnetic field distribution generated by the coils 12 and 14 in the ring-shaped magnetic core 6 may be changed. That is, if the magnitude and direction of the induced current generated from the ring-shaped magnetic core 6 to the plate-like metal material 1 is changed, the magnitude and direction of the total current generated by the interaction between the electrode current and the induced current will change. The temperature distribution produced by can also be changed. The change of the magnetic field can be realized by changing the phase difference between the current density of the current flowing through the coils 12 and 14 and the electrode current by the power supplies 8 and 10. Similarly, the magnetic field can be changed by changing the number of turns of the coils 12 and 14 wound around the ring-shaped magnetic core 6. In reality, the coil can be provided with a plurality of taps according to the load conditions such as thickness, width, temperature, and the magnetic field strength can be changed by switching the taps. When switching the tap, the amount of current flowing through the electrodes 2 and 3 varies greatly depending on the thickness, width, and type of the plate-shaped metal material 1 to be heated. Therefore, the tap may be switched accordingly, or the temperature may be increased locally. Alternatively, the temperature distribution may be measured and the taps may be switched so that the required heating pattern is obtained.
[0026]
As described above, the case where there is one ring-shaped magnetic core has been described, but the same effect can be obtained even when another ring-shaped magnetic core 5 is provided as shown in FIG. In particular, it is effective to provide two ring-shaped magnetic cores in order to prevent a current flowing in the traveling direction of the plate-shaped metal material 1.
[0027]
【Example】
Hereinafter, examples of the present invention will be described based on results of analysis by a finite element method.
[0028]
1, two ring-shaped magnetic cores 5 and 6 having a cross-sectional area of 100 cm 2 are separated by 100 mm, and a SUS304 material having a plate thickness of 16 mm, a plate width of 500 mm, and a length of 1000 mm is passed through the ring-shaped magnetic core 5. The electrodes 2 and 3 having an electrode length of 100 mm are arranged between the electrodes 6 and 6, and a current of 300 A is allowed to flow. The coils 13 and 14 are set to the L side, and the coils 11 and 12 are set to the R side. The magnetic field, current density, and temperature distribution when current was passed at different densities were calculated. Table 1 shows the temperature difference in the electrode width direction after 5 minutes.
[0029]
[Table 1]
Figure 0004160649
[0030]
In the example of the present invention, the current flowing outside the ring-shaped magnetic core is very small, but it is almost negligible and the temperature difference in the width direction can be changed by changing the phase of the coil. For example, when the phase difference between the L and R side coil currents and the electrode current is 0, the temperature distribution in the cross section between the electrodes can be about 10 ° C., and the difference can be increased by changing the phase difference. Is possible. All the examples in Table 1 have a distribution in which the temperature on the edge side is high and the center is slightly low, but if this is used, the edge portion of the plate material can be easily cooled, but the temperature of the edge portion is heated high in advance. Is possible. Similar effects can also be obtained by changing the current density of the coil. Table 1 shows that by changing the coil current density to 6 AT / mm 2 and 3 AT / mm 2 , heating equivalent to that obtained by changing the phase difference by 90 degrees is possible.
[0031]
On the other hand, the comparative example is an example in which there is no ring-shaped magnetic core and only electrodes are arranged, but heating is performed only in the vicinity of the electrodes, and the current spreads widely. Therefore, when there is a roll or the like away from the electrode and it is grounded, there is a high possibility that an electric current flows out from the roll, and there is a possibility that a facility or human accident occurs.
[0032]
【The invention's effect】
According to the present invention, a plate-shaped metal material having a finite length can be internally heated continuously and stably with electricity efficiently, so that it is possible to improve heating productivity. In addition to being able to change the temperature arbitrarily, it is also possible to make the temperature uniform, not only reducing the material variation due to temperature deviation, but also a soaking step to make the temperature uniform. Can be omitted. Furthermore, because the electrode is heated, the atmosphere does not need to be high, and equipment costs such as refractories are not required. In addition, repairs required for transport equipment such as rolls and heating equipment such as burners can be greatly reduced. Become. Since the stray current due to energization can be suppressed even during operation, it is advantageous in terms of safety.
[Brief description of the drawings]
FIG. 1 is a plan view of a plate-like metal material energization heating apparatus of the present invention.
FIG. 2 is a front view of a plate-like metal material energization heating apparatus of the present invention.
FIG. 3 is a diagram showing a current when a ring-shaped magnetic core is not used.
FIG. 4 is a diagram showing a current when a ring-shaped magnetic core is not used.
FIG. 5 is a diagram showing a temperature distribution when a ring-shaped magnetic core is not used.
FIG. 6 is a diagram showing a magnetic field distribution generated in a ring-shaped magnetic core.
FIG. 7 is a diagram showing a real part of a current flowing in a plate-shaped metal material by a magnetic field generated in a ring-shaped magnetic core.
FIG. 8 is a diagram showing an imaginary part of a current flowing in a plate-shaped metal material by a magnetic field generated in a ring-shaped magnetic core.
FIG. 9 is a diagram showing a temperature distribution of a plate-shaped metal material due to a magnetic field generated in a ring-shaped magnetic core.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plate-shaped metal material 2 Electrode 3 Electrode 4 Electrode 5 Ring-shaped magnetic core 6 Ring-shaped magnetic core 7 Power supply 8 Power supply 9 Power supply 10 Power supply 11 Coil 12 Coil 13 Coil 14 Coil 15 Current

Claims (6)

板状金属材料がその中を通過できるリング状磁性コアを有し、該リング状磁性コアの板状金属材料の幅方向両端部近辺に交流電流を流すコイルをそれぞれ巻くとともに、該リング状磁性コア片面側の近傍でかつ前記板状金属材料の幅方向両端部に電極を設ける構成とし、
該電極より交流電流を通じた際に、前記板状金属材料の長手方向に放射線状に広がろうとしながら前記電極間に流れる交流電流を、前記それぞれのコイルに流す交流電流によって、前記リング状磁性コアに、その断面において幅方向の一方側に時計周り方向の磁束および幅方向のもう一方側に反時計周り方向の磁束を発生させると共に、該発生した磁束により、前記板状金属材料に、前記リング状磁性コアで囲われたところでは前記電極間に流れる交流電流と打ち消し合い、前記リング状磁性コアで囲われていないところでは前記電極間に流れる交流電流と強め合うように誘導電流を発生させることで、前記電極間に流れる交流電流の放射線状の広がりを抑え、ジュール熱により前記板状金属材料を加熱することを特徴とする板状金属材料の通電加熱装置。
Each of the ring-shaped magnetic cores has a ring-shaped magnetic core through which the plate-shaped metal material can pass, and each of the ring-shaped magnetic cores is wound with a coil for passing an alternating current near both ends in the width direction of the plate-shaped metal material. A configuration in which electrodes are provided in the vicinity of one side and at both ends in the width direction of the plate-shaped metal material,
When an alternating current is passed through the electrodes, the ring-shaped magnetic material is converted into an alternating current flowing between the electrodes while trying to spread radially in the longitudinal direction of the plate-like metal material by an alternating current flowing through the coils. the core, the one side in the width direction together to generate a magnetic flux in the counterclockwise direction to the other side of the clockwise direction the magnetic flux and the width direction in its cross-section, the magnetic flux the occurrence, in the plate-like metal material, the In the area surrounded by the ring-shaped magnetic core, the alternating current flowing between the electrodes cancels out, and in the area not surrounded by the ring-shaped magnetic core, an induced current is generated so as to strengthen the alternating current flowing between the electrodes. By suppressing the radial spread of the alternating current flowing between the electrodes, the plate-like metal material is heated by Joule heat. Electric heating device.
板状金属材料がその中を通過できる一対のリング状磁性コアを有し、該一対のリング状磁性コア各々における板状金属材料の幅方向両端部近辺に交流電流を流すコイルをそれぞれ巻くとともに、二つのリング状磁性コアの間の近傍でかつ前記板状金属材料の幅方向両端部に電極を設ける構成とし、
該電極より交流電流を通じた際に、前記板状金属材料の長手方向に放射線状に広がろうとしながら前記電極間に流れる交流電流を、前記一対のリング状磁性コア各々における板状金属材料の幅方向両端部近辺に巻いたそれぞれのコイルに流す交流電流によって、前記一対のリング状磁性コア各々に、その断面において幅方向の一方側に時計周り方向の磁束および幅方向のもう一方側に反時計周り方向の磁束を発生させると共に、該発生した磁束により、前記板状金属材料に、前記リング状磁性コアで囲われたところでは前記電極間に流れる交流電流と打ち消し合い、前記リング状磁性コアで囲われていないところでは前記電極間に流れる交流電流と強め合うように誘導電流を発生させることで、前記電極間に流れる交流電流の放射線状の広がりを抑え、ジュール熱により前記板状金属材料を加熱することを特徴とする板状金属材料の通電加熱装置。
Each of the pair of ring-shaped magnetic cores has a pair of ring-shaped magnetic cores through which the plate-shaped metal material can pass, and each of the pair of ring-shaped magnetic cores is wound with a coil for passing an alternating current around both ends in the width direction, An electrode is provided in the vicinity between two ring-shaped magnetic cores and at both ends in the width direction of the plate-shaped metal material,
When an alternating current is passed through the electrodes, the alternating current that flows between the electrodes while trying to spread radially in the longitudinal direction of the plate-like metal material is changed to the plate-like metal material in each of the pair of ring-shaped magnetic cores. Due to the alternating current flowing through the coils wound in the vicinity of both ends in the width direction, each of the pair of ring-shaped magnetic cores has a magnetic flux in the clockwise direction on the one side in the width direction and a magnetic flux in the clockwise direction on the other side in the cross section. A magnetic flux in the clockwise direction is generated, and the generated magnetic flux cancels an alternating current flowing between the electrodes where the plate-shaped metal material is surrounded by the ring-shaped magnetic core. By generating an induced current so as to strengthen the alternating current flowing between the electrodes, the radial spread of the alternating current flowing between the electrodes is increased. The suppressed, resistance heating apparatus of a sheet metal material, characterized by heating the plate-shaped metal material by Joule heat.
請求項2記載の通電加熱装置を板状金属材料の進行方向に複数配置したことを特徴とする板状金属材料の通電加熱装置。  A plurality of the electric heating devices according to claim 2 arranged in the traveling direction of the plate metal material. 前記リング状磁性コアの板状金属材料の幅方向両端部近辺にそれぞれ巻いた交流電流を流すコイルは、同一回巻かれていることを特徴とする請求項1〜3のいずれか記載の板状金属材料の通電加熱装置。  The plate shape according to any one of claims 1 to 3, wherein the coils for passing an alternating current wound around both ends in the width direction of the plate-shaped metal material of the ring-shaped magnetic core are wound the same time. Electric heating device for metal materials. コイルに流す交流電流と電極から板状金属材料に流す交流電流との位相差を制御可能としたこと、および/または、コイルに流す交流電流の電流密度を調整可能としたことを特徴とする請求項1〜4のいずれか記載の板状金属材料の通電加熱装置。  It is possible to control a phase difference between an alternating current flowing through the coil and an alternating current flowing from the electrode to the plate-like metal material, and / or to adjust a current density of the alternating current flowing through the coil. Item 5. The energization heating device for a plate-shaped metal material according to any one of Items 1 to 4. 交流電流を流すコイルにタップを設けたことを特徴とする請求項1〜4のいずれか記載の板状金属材料の通電加熱装置。  The plate-like metal material energization heating device according to any one of claims 1 to 4, wherein a tap is provided on a coil through which an alternating current flows.
JP05734698A 1998-02-24 1998-02-24 Electric heating device for sheet metal material Expired - Fee Related JP4160649B2 (en)

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JP05734698A JP4160649B2 (en) 1998-02-24 1998-02-24 Electric heating device for sheet metal material

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JP05734698A JP4160649B2 (en) 1998-02-24 1998-02-24 Electric heating device for sheet metal material

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JP4160649B2 true JP4160649B2 (en) 2008-10-01

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