【発明の詳細な説明】[Detailed description of the invention]
本発明は電縫鋼管製造ラインに備えられる電磁
誘導加熱器等の電磁誘導加熱方法に関する。
電縫鋼管は鋼帯を連続送給して両側端縁同志を
衝き合せるようにして曲成して筒状にし、衝き合
せられる端縁を高周波加熱すると共に側圧を加え
て溶着させることにより連続的に製造される。こ
の電縫鋼管の溶接部は内外のビード余盛が切削さ
れた後、電磁誘導加熱器に至り、ここで１〜10k
Hz程度の高周波で電磁誘導加熱されて焼きなまし
又は焼ならしを行い、残留応力の除去及び組織の
改善が図られる。
第３図は電磁誘導加熱器を示している。この電
磁誘導熱器１０は直方体状の鉄心１１と、その外
周に配された導電部１２とからなる。鉄心１１は
その長手方向を鋼管移送方向に一致させており、
珪素鋼板をその方向に多数枚積層してある。各鋼
板は倒立Ｕ字状をなし、鉄心１１の下面側に凹溝
が形成されている。導電部１２はこの凹溝内に‖
入配置された中央導体１２ａと、平面視でコ字状
をなし、鉄心１１の上流側、下流側夫々の半分を
抱持するように配された外側導体１２ｂ，１２ｃ
と外側導体１２ｂ，１２ｃ夫々の両側辺部の端末
に接続され、鉄心１１に跨るように配されたター
ミナル部１２ｄ，１２ｅとからなり、外側導体１
２ｂ，１２ｃは夫々のコの字の内奥部相当部分の
下部にて中央導体１２ａの各端末に接続されてい
る。高周波発電機又はサイリスタを用いた高周波
電源は出力変圧器（いずれも図示せず）を介して
上記ターミナル部１２ｄ，１２ｅに接続され、導
電部１２に高周波が通電される。導電部１２中の
矢符はあるサイクルにおける電流の方向を示して
いる。中央導体１２ａには外側導体１２ｂ，１２
ｃに示された方向とは逆方向の電流が流れるか
ら、この中央導体１２ａの電流による磁束はこの
とき図中に１点鎖線で示す如く鋼管SPに鎖交す
る。したがつて、鋼管にはこの鎖交磁束による渦
電流が流れ、そのジユール熱により溶接部WSが
加熱され、所期の目的が達成される。
ところで、最近は電縫鋼管に要求される品質が
高級化し、また厚肉管の需要も増加しており、更
に生産性向上のために鋼管移送速度を高速化する
目的で、上述の如き電磁誘導加熱器を２〜３基タ
ンデムに設置する趨勢にある。而して、これら複
数基の電磁誘導加熱器の夫々に対しては、略等し
い交流電圧が印加されているのが現状である。そ
れ故に、電磁誘導加熱器の基数の増加にともない
夫々の電磁誘導加熱器によつて電縫鋼管に誘起さ
れる電圧は直列的に加わつて電縫鋼管の対地電圧
が増加して、大地に流れる無効漏洩電流を増加さ
せて電力損失が増加し、また対地電圧の上昇にと
もない、電縫鋼管の送給ロール等への漏洩電流が
増加して送給ロール等の電触や焼付等の弊害が生
じ、感電する虞れがある等の不都合があり、電縫
鋼管の高品質化、鋼管移送速度の高速化を図る上
で問題がある。
そのため、複数の加熱コイルにおける、少なく
とも１つの加熱コイルに生じる磁束の方向が他の
加熱コイルに生ずる磁束の方向と互いに逆方向と
なるようにして、漏洩磁束による電圧を抑制する
誘導加熱装置の給電方式が特開昭47−40537号に
より提案されている。
しかし乍ら、この給電方式では加熱コイルの電
源が同一である場合、又は電圧位相が同期してい
る別々の電源を使用する場合には、所期の効果が
得られるが、加熱コイルの電源が非同期のもので
ある場合は有効ではない。また加熱コイル数が偶
数である場合は誘起電圧を相殺して０にすること
が可能であるが、加熱コイル数が奇数である場合
は誘起電圧を、単一の加熱コイルにて生じる誘起
電圧Ｅ以下に低下させ得ない。
本発明は上述の如き問題に対処すべく、被溶接
材である電縫鋼管に生じる誘起電圧を測定して、
測定した誘起電圧に基づいて電磁誘導加熱器に対
して印加する電圧の位相を制御することにより、
夫々の電磁誘導加熱器に電圧を印加する電源が別
電源又は位相が同期していない電源であり、しか
も電磁誘導加熱器の数が奇数であつても電縫鋼管
に生じる誘起電圧を単一の電磁誘導加熱器によつ
て生じる誘起電圧以下に抑制することにより、電
縫鋼管の対地電圧等を抑制させて電縫鋼管から大
地に流れる漏洩電流を減少せしめて電力ロスを低
減すると共に、送給ロール等での焼付を防止し、
また感電の虞れも解消して高効率で加熱処理でき
る電磁誘導加熱方法を提案したものである。
以下本発明をその実施例を示す図面に基づいて
詳述する。
本発明に係る電磁誘導加熱方法は電磁誘導加熱
器が複数基電縫管移送方向にタンデムに配設され
る場合に適用される。
第１図は本発明に係る電磁誘導加熱方法を実施
するための構成を電縫鋼管とともに概略的に示し
たものである。
第１図において、２０は被加熱材である電縫鋼
管、２１，２２，２３は電縫鋼管２０の溶接接合
部に近接して電縫鋼管２０の移送方向に縦列に適
宜間隔を離隔して配設されている第１，第２及び
第３の電磁誘導加熱器である。
電磁誘導加熱器２１，２２，２３の加熱コイル
２１ａ，２２ａ，２３ａは夫々第１，第２，第３
の高周波電源４７，４８，４９の出力端子に直接
接続されている。高周波電源４７，４８，４９は
サイリスタ，インバータを用いて高周波出力を得
るように構成したものである。誘起電圧検出電極
３４，３５は接続線４４，４４′により電圧検出
器４５に接続されており、電圧検出器４５により
電縫鋼管に発生した誘起電圧が連続的に検出され
る。この電圧検出器４５の出力信号は位相制御器
４６に入力されるべく接続されており、位相制御
器４６の出力信号は第２の高周波電源４８の位相
制御信号としている。即ち、高周波電源４８のイ
ンバータの転流を行わせるサイリスタの導通位相
制御信号を位相制御器４６にて作成しており、電
圧検出器４５による検出電圧を低減せしめるべく
導通位相を変更させる。
したがつて、このような電圧の導通位相制御を
した場合には以下の如くなる。
例えば電磁誘導加熱器２１，２２，２３夫々が
単体で電縫鋼管に生じる誘起電圧が最大Ｅである
とする。いま、位相制御対象としない電磁誘導加
熱器２１，２３，の夫々に与えられた電圧位相が
相異していて、これらによつて電縫鋼管に生じる
誘起電圧の和が1.8Eであるときには、高周波電源
４８により電磁誘導加熱器２２に与える電圧を位
相制御して逆位相のＥを生ぜしめれば３者の誘起
電圧の和は1.8E−Ｅとなし得る。つまり電縫鋼管
全体に生じる誘起電圧が、単一の電磁誘導加熱器
により生じる誘起電圧Ｅより低い例えば0.8Eに低
減する。また電磁誘導加熱器２１，２３による誘
起電圧がＥ程度に低い場合には、電磁誘導加熱器
２１に印加する電位の位相制御にて３者による誘
起電圧の和を０近くまで低減する。つまり、各高
周波電源が各別である場合、各高周波電源の電圧
位相が同期していない場合、又は電磁誘導加熱器
の数が奇数である場合であつても、電縫鋼管全体
の誘起電圧をきわめて低い値になし得るのであ
る。
また位相制御をしない高周波電源４７，４９の
出力状態の変化、または電縫鋼管の変化があつた
場合にも自動的に追随して位相制御が行われて、
電縫鋼管に生じる誘起電圧を常に安定したものと
なし得る。このように位相制御を行い位相差をも
つて電磁誘導加熱器２１，２２，２３に高周波電
圧をを印加した場合には、電縫鋼管２０に発生す
る誘起電圧も位相差をもことになり、位相の異な
る誘起電圧により互いに相殺されて電縫鋼管２０
に発生する全体の誘起電圧を単一の電磁誘導加熱
器により生じる誘起電圧以下に抑制することがで
き、所期の目的が達成できる。
なお、本実施例においては電磁誘導加熱器を３
基タンデムに配設したが、３基に限定されるもの
ではなく、複数基であれば同様の効果を奏するこ
とができる。
次に第１図に示す方法によつた場合において中
間に位置する高周波電源４８の位相を逆相とした
ときの実測値について説明する。まず位相制御器
４６の位相調整により夫々の高周波電源４７，４
８，４９の出力電圧を位相を整合させて３台を同
相とし、電縫鋼管全体での誘起電圧が３倍になる
ようにして、各電磁誘導加熱器２１，２２，２３
の入力電圧，電流，及び電力並びに対地漏洩電流
を測定し、次いで位相制御器４６の操作により誘
導加熱器２２の印加電圧の位相を逆位相にして管
全体での誘起電圧が１基の誘導加熱器によるもの
となるようにした。
第１表はその測定結果を対比して示したもので
あり、対地漏洩電流が大幅に減少することは勿
論、入力電力も数％減少することが判る。
The present invention relates to an electromagnetic induction heating method for an electromagnetic induction heater or the like installed in an electric resistance welded steel pipe manufacturing line. ERW steel pipes are made by continuously feeding a steel strip so that the edges on both sides abut against each other and bending into a cylindrical shape.The edges that are abutted are heated with high frequency and lateral pressure is applied to weld them. Manufactured in After the inner and outer bead excess of the welded part of the ERW steel pipe is cut, it reaches the electromagnetic induction heater, where it is heated for 1 to 10k.
Annealing or normalization is performed by electromagnetic induction heating at a high frequency of around Hz to remove residual stress and improve the structure. FIG. 3 shows an electromagnetic induction heater. This electromagnetic induction heater 10 consists of a rectangular parallelepiped iron core 11 and a conductive part 12 arranged around its outer periphery. The iron core 11 has its longitudinal direction aligned with the steel pipe transfer direction,
A large number of silicon steel plates are laminated in that direction. Each steel plate has an inverted U-shape, and a groove is formed on the lower surface of the iron core 11. The conductive part 12 is placed inside this groove.
The central conductor 12a is arranged in a central conductor 12a, and the outer conductors 12b and 12c are arranged so as to have a U-shape in plan view and to hold the upstream and downstream halves of the iron core 11, respectively.
and terminal portions 12d and 12e connected to terminals on both sides of the outer conductors 12b and 12c, respectively, and arranged so as to straddle the iron core 11.
2b and 12c are connected to each terminal of the central conductor 12a at the lower part of the innermost part of each U-shape. A high frequency power source using a high frequency generator or a thyristor is connected to the terminal portions 12d and 12e via an output transformer (none of which is shown), and high frequency power is applied to the conductive portion 12. The arrow in the conductive portion 12 indicates the direction of current in a certain cycle. The central conductor 12a has outer conductors 12b, 12
Since the current flows in the direction opposite to the direction shown in c, the magnetic flux due to the current in the central conductor 12a at this time interlinks with the steel pipe SP as shown by the one-dot chain line in the figure. Therefore, an eddy current flows in the steel pipe due to this linkage magnetic flux, and the welded portion WS is heated by the Joule heat, thereby achieving the intended purpose. By the way, recently, the quality required for ERW steel pipes has become higher quality, and the demand for thick-walled pipes has also increased.In order to further improve productivity, the electromagnetic induction The trend is to install two or three heaters in tandem. Currently, approximately the same alternating current voltage is applied to each of these plurality of electromagnetic induction heaters. Therefore, as the number of electromagnetic induction heaters increases, the voltage induced in the ERW steel pipe by each electromagnetic induction heater is applied in series, increasing the ground voltage of the ERW steel pipe, and causing the voltage to flow to the ground. Increasing reactive leakage current increases power loss, and as the voltage to ground increases, leakage current to feed rolls of ERW steel pipes increases, causing problems such as electrical contact and seizure of feed rolls. This causes problems such as the risk of electric shock, which poses a problem in improving the quality of ERW steel pipes and increasing the speed of steel pipe transfer. Therefore, in a plurality of heating coils, the direction of the magnetic flux generated in at least one heating coil is opposite to the direction of the magnetic flux generated in the other heating coils, thereby suppressing the voltage caused by the leakage magnetic flux. A method has been proposed in Japanese Patent Application Laid-Open No. 47-40537. However, with this power supply method, the desired effect can be obtained when the heating coil power sources are the same or when separate power sources with synchronized voltage phases are used. It is not valid if it is asynchronous. Furthermore, if the number of heating coils is an even number, it is possible to cancel the induced voltage to zero, but if the number of heating coils is an odd number, the induced voltage can be reduced to the induced voltage E generated by a single heating coil. It cannot be lowered below. In order to deal with the above-mentioned problems, the present invention measures the induced voltage generated in the electric resistance welded steel pipe that is the material to be welded, and
By controlling the phase of the voltage applied to the electromagnetic induction heater based on the measured induced voltage,
Even if the power supplies that apply voltage to each electromagnetic induction heater are separate power supplies or power supplies whose phases are not synchronized, and even if the number of electromagnetic induction heaters is an odd number, the induced voltage generated in the ERW steel pipe can be absorbed by a single source. By suppressing the induced voltage below the voltage generated by the electromagnetic induction heater, the ground voltage of the ERW steel pipe is suppressed, reducing the leakage current flowing from the ERW steel pipe to the ground, reducing power loss, and reducing power loss. Prevents seizure on rolls, etc.
Furthermore, we have proposed an electromagnetic induction heating method that eliminates the risk of electric shock and can perform heat treatment with high efficiency. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. The electromagnetic induction heating method according to the present invention is applied when a plurality of electromagnetic induction heaters are arranged in tandem in the electric resistance welded pipe transfer direction. FIG. 1 schematically shows a configuration for carrying out the electromagnetic induction heating method according to the present invention together with an electric resistance welded steel pipe. In FIG. 1, reference numeral 20 denotes an electric resistance welded steel pipe which is a material to be heated, and 21, 22, and 23 are arranged in a column in the direction of transport of the electric resistance welded steel pipe 20, close to the welded joint of the electric resistance welded steel pipe 20, and spaced apart appropriately. These are first, second and third electromagnetic induction heaters arranged. The heating coils 21a, 22a, 23a of the electromagnetic induction heaters 21, 22, 23 are first, second, and third heating coils, respectively.
are directly connected to the output terminals of high frequency power supplies 47, 48, and 49. The high frequency power sources 47, 48, and 49 are configured to obtain high frequency output using thyristors and inverters. The induced voltage detection electrodes 34 and 35 are connected to a voltage detector 45 through connection lines 44 and 44', and the voltage detector 45 continuously detects the induced voltage generated in the electric resistance welded steel pipe. The output signal of this voltage detector 45 is connected to be input to a phase controller 46, and the output signal of the phase controller 46 is used as a phase control signal for the second high frequency power source 48. That is, the phase controller 46 generates a conduction phase control signal for the thyristor that commutates the inverter of the high frequency power supply 48, and changes the conduction phase in order to reduce the voltage detected by the voltage detector 45. Therefore, if such voltage conduction phase control is performed, the following will occur. For example, it is assumed that the induced voltage generated in the electric resistance welded steel pipe by each of the electromagnetic induction heaters 21, 22, and 23 is maximum E. Now, when the voltage phases applied to the electromagnetic induction heaters 21 and 23, which are not subject to phase control, are different, and the sum of the induced voltages generated in the ERW steel pipe by these is 1.8E, If the phase of the voltage applied to the electromagnetic induction heater 22 is controlled by the high frequency power source 48 to generate E of opposite phase, the sum of the three induced voltages can be 1.8E-E. In other words, the induced voltage generated in the entire electric resistance welded steel pipe is reduced to, for example, 0.8 E, which is lower than the induced voltage E generated by a single electromagnetic induction heater. Further, when the induced voltages caused by the electromagnetic induction heaters 21 and 23 are as low as E, the sum of the induced voltages from the three sources is reduced to nearly 0 by controlling the phase of the potential applied to the electromagnetic induction heaters 21. In other words, even if each high-frequency power source is separate, the voltage phase of each high-frequency power source is not synchronized, or the number of electromagnetic induction heaters is odd, the induced voltage of the entire ERW steel pipe can be controlled. It is possible to achieve extremely low values. In addition, even if there is a change in the output state of the high frequency power supplies 47, 49 that do not perform phase control, or a change in the electric resistance welded steel pipe, phase control is automatically performed to follow the change.
The induced voltage generated in the electric resistance welded steel pipe can be kept stable at all times. When high frequency voltage is applied to the electromagnetic induction heaters 21, 22, 23 with a phase difference through phase control in this way, the induced voltage generated in the ERW steel pipe 20 also has a phase difference. The induced voltages with different phases cancel each other out and the electric resistance welded steel pipe 20
The overall induced voltage generated in the electromagnetic induction heater can be suppressed to less than the induced voltage generated by a single electromagnetic induction heater, and the intended purpose can be achieved. In addition, in this example, three electromagnetic induction heaters are used.
Although the bases are arranged in tandem, the number is not limited to three, and the same effect can be achieved if a plurality of bases are used. Next, actual measured values when the phase of the high frequency power source 48 located in the middle is set to be in reverse phase in the case of the method shown in FIG. 1 will be explained. First, by adjusting the phase of the phase controller 46, the respective high frequency power sources 47, 4
The output voltages of 8 and 49 are matched in phase so that the three units are in phase, so that the induced voltage across the entire ERW steel pipe is tripled, and each electromagnetic induction heater 21, 22, 23
Measure the input voltage, current, power, and ground leakage current of It was made to depend on the container. Table 1 shows a comparison of the measurement results, and it can be seen that not only the ground leakage current is significantly reduced, but also the input power is reduced by several percent.
【表】
以上詳述した如く、本発明に係る電磁誘導加熱
方法は、電縫鋼管２０を電磁誘導加熱するに際し
て電磁誘導加熱器２２に印加する電圧の位相を、
電縫鋼管２０に発生した誘起電圧に基づいてこれ
を抑制すべく制御するようにしたので、電源の同
期／非同期又は電磁誘導加熱器の数に関係なく電
縫鋼管全体の誘起電圧を１つの電磁誘導加熱器に
より生じる誘起電圧以下に低減させることができ
る。そのため、従来に比して電縫鋼管２０の製造
速度を高め得て、電縫鋼管２０の生産効率を大幅
に高めることができる等、優れた効果を奏する。
なお、本発明は電縫鋼管の製造ラインに限らず他
の連続的加熱処理ラインにも適用できる。[Table] As detailed above, the electromagnetic induction heating method according to the present invention changes the phase of the voltage applied to the electromagnetic induction heater 22 when heating the ERW steel pipe 20 by electromagnetic induction.
Since the control is performed to suppress the induced voltage generated in the ERW steel pipe 20, the induced voltage of the entire ERW steel pipe is suppressed by one electromagnetic induction heater, regardless of the synchronous/asynchronous power supply or the number of electromagnetic induction heaters. It is possible to reduce the induced voltage below that generated by an induction heater. Therefore, the production speed of the electric resistance welded steel pipe 20 can be increased compared to the conventional method, and the production efficiency of the electric resistance welded steel pipe 20 can be greatly improved, and other excellent effects can be achieved.
Note that the present invention is applicable not only to a production line for electric resistance welded steel pipes but also to other continuous heat treatment lines.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は本発明に係る電磁誘導加熱方法を実施
するたの電縫鋼管を加熱する手段を示す電気回路
図、第２図は第１図における高周波電源の出力電
圧波形を示した波形図、第３図は電磁誘導加熱器
の外観図である。
２０……電縫鋼管、２１，２２，２３……電磁
誘導加熱器、３４，３５……誘起電圧検出電極、
４５……電圧検出器、４６……位相制御器、４
７，４８，４９……高周波電源。
FIG. 1 is an electric circuit diagram showing means for heating an ERW steel pipe for carrying out the electromagnetic induction heating method according to the present invention, FIG. 2 is a waveform diagram showing the output voltage waveform of the high frequency power source in FIG. 1, FIG. 3 is an external view of the electromagnetic induction heater. 20... ERW steel pipe, 21, 22, 23... Electromagnetic induction heater, 34, 35... Induced voltage detection electrode,
45... Voltage detector, 46... Phase controller, 4
7, 48, 49...High frequency power supply.