JP5523738B2 - Vacuum arc melting method and vacuum arc melting furnace - Google Patents

Vacuum arc melting method and vacuum arc melting furnace Download PDF

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JP5523738B2
JP5523738B2 JP2009114927A JP2009114927A JP5523738B2 JP 5523738 B2 JP5523738 B2 JP 5523738B2 JP 2009114927 A JP2009114927 A JP 2009114927A JP 2009114927 A JP2009114927 A JP 2009114927A JP 5523738 B2 JP5523738 B2 JP 5523738B2
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宜大 武田
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Osaka Titanium Technologies Co Ltd
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本発明は、消耗電極式真空アーク溶解法および消耗電極式真空アーク溶解炉に関し、さらに詳しくは、消耗電極式真空アーク溶解法を用いた金属精製におけるホットトップ制御に関するものである。   The present invention relates to a consumable electrode type vacuum arc melting method and a consumable electrode type vacuum arc melting furnace, and more particularly to hot top control in metal refining using a consumable electrode type vacuum arc melting method.

従来、チタンやジルコニウム等は融点が高く、しかも、高温での活性が極めて高いことから、これらの金属の精製には、消耗電極式真空アーク溶解法(Vacuume Arc Remelting:以下、「VAR法」という)が用いられる。VAR法は、真空または不活性ガス雰囲気下で、精製対象となる金属を円柱状の消耗電極とし、一定の間隔をあけて銅製坩堝の上方に配置し、消耗電極と銅製坩堝とに電流を流し、アーク放電を発生させ、その熱により消耗電極を溶融滴下し、不純物を蒸発させ、坩堝の中に金属を凝固させてインゴットを形成する方法である。   Conventionally, titanium, zirconium, and the like have a high melting point and extremely high activity at high temperatures. Therefore, consumable electrode type vacuum arc melting method (hereinafter referred to as “VAR method”) is used to purify these metals. ) Is used. In the VAR method, a metal to be purified is used as a cylindrical consumable electrode in a vacuum or an inert gas atmosphere, and is placed above a copper crucible at a certain interval, and a current is passed between the consumable electrode and the copper crucible. In this method, arc discharge is generated, a consumable electrode is melted and dripped by the heat, impurities are evaporated, and a metal is solidified in a crucible to form an ingot.

VAR法を用いた金属精製では、精製対象の金属を溶解し、水冷により冷却した銅製坩堝上に滴下させる。坩堝に滴下された金属は、坩堝の底面および側面により冷却され、順次凝固し、形成されたインゴットの上面は凹状となり溶解した金属が存在する。   In metal refining using the VAR method, the metal to be purified is dissolved and dropped onto a copper crucible cooled by water cooling. The metal dropped into the crucible is cooled by the bottom and side surfaces of the crucible and solidifies sequentially, and the top surface of the formed ingot becomes concave and there is a molten metal.

ここで通電を停止すると、アークによる溶解が停止するので、溶解した金属は上面からも冷却され凝固することになり、不純物の蒸発が不十分となり、インゴットの純度を低下させることになる。また、上面から凝固するとインゴット内部に巣や割れ等の欠陥が生じる場合がある。   When the energization is stopped here, the melting by the arc stops, so the melted metal is cooled and solidified also from the upper surface, and the evaporation of impurities becomes insufficient and the purity of the ingot is lowered. Further, when solidified from the upper surface, defects such as nests and cracks may occur inside the ingot.

これらの欠陥を回避するために、VAR法では、通常、溶解終了操作として徐々に電流を低下させる、ホットトップと呼ばれる操作が採用される。   In order to avoid these defects, the VAR method usually employs an operation called a hot top, in which the current is gradually reduced as a melting end operation.

ホットトップにより溶解を終了させる場合は、ホットトップ操作の開始および終了時期の制御が重要になる。ホットトップ操作の開始時期が早いと、低い電流による溶解時間が長くなるので、精製に要する時間が長くなる。一方、ホットトップ操作の開始時期が遅くなると、溶解終了までの時間が短くなり、インゴットの純度低下や巣の発生といった問題が生じる。   When melting is terminated by hot top, it is important to control the start and end timing of the hot top operation. If the start time of the hot top operation is early, the time required for purification becomes longer because the dissolution time with a low current becomes longer. On the other hand, if the start time of the hot top operation is delayed, the time until the end of melting is shortened, causing problems such as a decrease in ingot purity and generation of nests.

また、ホットトップ操作の終了時期が早いと、消耗電極の残存が長い状態で溶解が終了するので、歩留りが悪化する。一方、ホットトップ操作の終了時期が遅いと、消耗電極が過剰に溶解し、スタブ溶損が発生するおそれがある。   Also, if the hot top operation ends early, the dissolution ends with the remaining of the consumable electrode being long, so the yield deteriorates. On the other hand, if the end time of the hot top operation is late, the consumable electrode may be excessively dissolved and stub melting may occur.

ここで、スタブ溶損とは、消耗電極を支持する部品であるスタブ、または、スタブと消耗電極の接合部が、溶解し損傷する現象である。スタブ溶損が発生すると、VAR法による金属の精製操業に重大な事故を発生させることになる。   Here, the stub melt damage is a phenomenon in which a stub that is a part that supports a consumable electrode or a joint between the stub and the consumable electrode is melted and damaged. When stub melting occurs, a serious accident occurs in the metal refining operation by the VAR method.

ホットトップ制御に関して、特許文献1により、溶解電極の重量計測を用いた監視装置により、その開始と終了時期の調整に使用できることが知られている。この重量計測による監視装置を用いれば、溶解中の消耗電極の重量を監視することにより、重量から消耗電極の残存長さを把握することができる。したがって、消耗電極の重量に応じてホットトップ操作の開始と終了タイミングを制御できる。   With respect to hot-top control, it is known from Patent Document 1 that it can be used to adjust the start and end time by a monitoring device using weight measurement of a dissolved electrode. If the monitoring device based on this weight measurement is used, the remaining length of the consumable electrode can be grasped from the weight by monitoring the weight of the consumable electrode during dissolution. Therefore, the start and end timing of the hot top operation can be controlled according to the weight of the consumable electrode.

特許文献2には、金属の精製を開始する前に、消耗電極の上面に切り欠き加工を行うことにより、消耗電極の残存長さを把握し、ホットトップ操作の開始および終了を行う真空アーク溶解方法が提案されている。具体的には、消耗電極の溶解を進行させ、消耗電極の切り欠き部分まで溶解滴下させると、消耗電極の上面の輪郭が切り欠きを含んだ形状に変化する。この輪郭の変化により、消耗電極の残存長さを把握し、ホットトップ操作の開始と終了を行うものである。   Patent Document 2 discloses a vacuum arc melting method in which the remaining length of the consumable electrode is grasped by performing notch processing on the upper surface of the consumable electrode before the metal refining is started, and the hot top operation is started and ended. A method has been proposed. Specifically, when the consumable electrode is melted and dissolved and dropped to the notch portion of the consumable electrode, the contour of the upper surface of the consumable electrode changes to a shape including the notch. Based on the change in the contour, the remaining length of the consumable electrode is grasped, and the hot top operation is started and ended.

特開平11−293354号公報JP 11-293354 A 特開2007−322057号公報JP 2007-322057 A

通常、VAR法により、円柱状の消耗電極に電流を流して精製を行うと、消耗電極の底面の溶解は均一でなく、消耗電極の外周部に比べ中心部が、溶解し易くなる。このため、溶解が進行しホットトップ操作を行う際には、消耗電極の底面は中心部が凹んだ形状となる。そして、消耗電極底面の中心部の凹み形状は、同一条件で精製を行った場合でも一定の形状にならず、精製の都度、異なった形状となる。   Normally, when purification is performed by applying a current to a cylindrical consumable electrode by the VAR method, the bottom surface of the consumable electrode is not uniformly dissolved, and the central portion is more easily dissolved than the outer peripheral portion of the consumable electrode. For this reason, when melting proceeds and a hot top operation is performed, the bottom surface of the consumable electrode has a shape with a recessed central portion. The concave shape at the center of the bottom surface of the consumable electrode does not become a constant shape even when purification is performed under the same conditions, and becomes a different shape every time purification is performed.

前記特許文献1で提案される監視装置を用いて、または、前記特許文献2で提案される真空アーク溶解方法により、金属精製のホットトップ操作を行う場合には、下記の問題がある。   When performing a hot top operation of metal refining using the monitoring device proposed in Patent Document 1 or by the vacuum arc melting method proposed in Patent Document 2, there are the following problems.

前記特許文献1で提案される監視装置を用いた場合、ホットトップの開始操作は、精度よく行うことができる。   When the monitoring device proposed in Patent Document 1 is used, the hot top start operation can be performed with high accuracy.

一方、ホットトップの終了操作時には、スタブ溶損を発生させる場合がある。これは、消耗電極の中心部の凹みが深い形状で溶解が進行することにより、消耗電極の中心部で所定量を溶解しても、残留する外周部の電極重量によりホットトップの終了操作が行われないからである。   On the other hand, stub melt damage may occur during the hot top end operation. This is because melting progresses with a deep recess in the center of the consumable electrode, so that even if a predetermined amount is melted in the center of the consumable electrode, the hot top is terminated due to the remaining electrode weight of the outer periphery. Because it is not broken.

また、溶解電極を重量計測する監視装置は高価であり、設置に多くの時間と費用を要する。さらに、監視装置は溶解電極を重量計測する精度を維持するために、校正およびメンテナンスを定期的に行う必要がある。   In addition, the monitoring device for measuring the weight of the melting electrode is expensive and requires a lot of time and cost for installation. Furthermore, the monitoring device needs to be periodically calibrated and maintained in order to maintain the accuracy with which the melting electrode is weighed.

前記特許文献2で提案される真空アーク溶解方法では、ホットトップの開始操作を精度よく行うことができる。   In the vacuum arc melting method proposed in Patent Document 2, the hot top start operation can be performed with high accuracy.

一方、ホットトップの終了操作時には、スタブ溶損を発生させる場合がある。消耗電極の中心部の凹みが深い形状で精製が進行すると、消耗電極の中心部で所定量を溶解しても、消耗電極の外周部が残留し、切り欠きの深さよりも長くなる場合には、消耗電極の上面の輪郭は変化しない。このため、ホットトップの終了操作が行われないので、スタブ溶損が発生する事態となる。   On the other hand, stub melt damage may occur during the hot top end operation. When purification proceeds with a deep concavity at the center of the consumable electrode, even if a predetermined amount is melted at the center of the consumable electrode, the outer periphery of the consumable electrode remains and becomes longer than the notch depth. The contour of the upper surface of the consumable electrode does not change. For this reason, since the hot top end operation is not performed, a stub melt damage occurs.

また、前記特許文献2で提案される真空アーク溶解方法では、精製を開始する前に消耗電極毎に切り欠きを施す必要がある。チタン合金等の消耗電極に切り欠きを加工するには、高硬度であることから専用加工設備を設置する必要があり、さらに、高硬度金属の加工のため、加工時間も長時間となる。この専用加工設備の導入コストおよび切り欠きを加工に要する運用コストが問題となる。   Further, in the vacuum arc melting method proposed in Patent Document 2, it is necessary to make a notch for each consumable electrode before refining is started. In order to process a notch in a consumable electrode such as a titanium alloy, it is necessary to install a dedicated processing equipment because of its high hardness, and further, the processing time becomes long due to processing of a hard metal. The introduction cost of this dedicated processing equipment and the operation cost required for processing the notch are problems.

本発明は、上述した問題に鑑みてなされたものであり、高精度かつ最適時期にホットトップの開始および終了操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用費用を削減することができる、真空アーク溶解方法およびその溶解方法を適用できる真空アーク溶解炉を提供することを目的としている。   The present invention has been made in view of the above-described problems, and can start and end the hot top with high accuracy and at the optimum time, and reduce the introduction and operation costs of the equipment used for the hot top operation. An object of the present invention is to provide a vacuum arc melting method and a vacuum arc melting furnace to which the melting method can be applied.

本発明者は、上記課題を解決するためには、精製中の消耗電極の中心部の残存長さを適切に把握する必要がある。そこで、消耗電極の溶解が進行し、ホットトップ操作の段階になると、消耗電極が短くなるので、アークの熱により消耗電極の上面温度が上昇することに着目した。   In order to solve the above-mentioned problems, the present inventor needs to appropriately grasp the remaining length of the central portion of the consumable electrode being purified. Therefore, the melting of the consumable electrode progresses, and when the hot top operation stage is reached, the consumable electrode is shortened, so that the upper surface temperature of the consumable electrode is increased by the heat of the arc.

このため、アーク熱による消耗電極の上面温度の上昇を感知し、その温度により残存電極長さを把握し、ホットトップ操作の開始と終了タイミングの制御を行えば、高精度かつ最適時期にホットトップ操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用費用を削減した、真空アーク溶解方法が実現可能である。   Therefore, if the rise of the upper surface temperature of the consumable electrode due to arc heat is detected, the remaining electrode length is grasped based on that temperature, and the start and end timing of the hot top operation is controlled, the hot top can be accurately and optimally timed. It is possible to realize a vacuum arc melting method capable of performing operations and reducing the installation and operation costs of equipment used for hot top operations.

本発明は、上記の知見に基づいて完成したものであり、下記(1)〜(3)の真空アーク溶解方法および(4)の真空アーク溶解炉を要旨としている。   The present invention has been completed on the basis of the above findings, and the gist of the present invention is the following vacuum arc melting method (1) to (3) and vacuum arc melting furnace (4).

(1)消耗電極をアークにより溶解し、滴下する金属を凝固させてインゴットを製造する真空アーク溶解方法であって、前記消耗電極が溶解、滴下し、消耗電極の残存が短くなるのにともない溶解を終了させるホットトップ操作の際に、消耗電極の上面温度を感知する赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて開始時期を決定することを特徴とする真空アーク溶解方法。 (1) A vacuum arc melting method in which a consumable electrode is melted by an arc and a dripping metal is solidified to produce an ingot, which melts as the consumable electrode melts and drops and the remaining of the consumable electrode becomes short An infrared heat sensing device is provided to detect the upper surface temperature of the consumable electrode during the hot top operation, and the remaining length of the consumable electrode up to the stub is determined by measuring the detected upper surface temperature of the consumable electrode. A vacuum arc melting method characterized by determining a start time according to the remaining length .

(2)消耗電極をアークにより溶解し、滴下する金属を凝固させてインゴットを製造する真空アーク溶解方法であって、前記消耗電極が溶解、滴下し、消耗電極の残存が短くなるのにともない溶解を終了させるホットトップ操作の際に、消耗電極の上面温度を感知する赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて終了時期を決定することを特徴とする真空アーク溶解方法。 (2) A vacuum arc melting method in which a consumable electrode is melted by an arc and a dripping metal is solidified to produce an ingot, wherein the consumable electrode melts and drops and melts as the consumable electrode remains short An infrared heat sensing device is provided to detect the upper surface temperature of the consumable electrode during the hot top operation, and the remaining length of the consumable electrode up to the stub is determined by measuring the detected upper surface temperature of the consumable electrode. The vacuum arc melting method is characterized in that the end time is determined according to the remaining length .

(3)前記ホットトップ操作の際に、前記赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて開始時期および終了時期を決定することを特徴とする請求項1または2に記載の真空アーク溶解方法。 (3) During the hot top operation, the infrared heat sensing device is provided, and the upper surface temperature of the sensed consumable electrode is measured to determine the remaining length of the consumable electrode up to the stub. The vacuum arc melting method according to claim 1 or 2, wherein a start time and an end time are determined accordingly.

(4)アークにより溶解滴下する消耗電極と、滴下する金属を凝固させてインゴットとする坩堝と、前記消耗電極と前記坩堝または前記インゴットの距離を一定に保持する昇降装置と、前記消耗電極と前記昇降装置を接合するスタブと、前記消耗電極の上面温度を感知し、この上面温度を測定することによりスタブまでの消耗電極の残存長さを把握する赤外線熱感知装置とを備えることを特徴とする真空アーク溶解炉。
(4) A consumable electrode that melts and drops by an arc, a crucible that solidifies the dropped metal to form an ingot, a lifting device that maintains a constant distance between the consumable electrode and the crucible or the ingot, the consumable electrode, A stub that joins an elevating device, and an infrared heat sensing device that senses the upper surface temperature of the consumable electrode and grasps the remaining length of the consumable electrode up to the stub by measuring the upper surface temperature. Vacuum arc melting furnace.

さらに、上記(1)〜(3)に記載の真空アーク溶解方法と、上記(4)に記載の真空アーク溶解炉を、チタンやチタン合金の精製に使用すれば、高精度かつ最適時期にホットトップの開始と終了操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用費用を削減することができる。   Furthermore, if the vacuum arc melting method described in the above (1) to (3) and the vacuum arc melting furnace described in (4) above are used for refining titanium or a titanium alloy, it is hot at high precision and at the optimal time. The top start and end operations can be performed, and the introduction and operation costs of equipment used for hot top operation can be reduced.

本発明において、「赤外線熱感知装置」とは、物体から放射される赤外線、または、赤外線および可視光線の強度を測定して、物体の温度を感知する装置を意味する。   In the present invention, “infrared heat sensing device” means a device that senses the temperature of an object by measuring the intensity of infrared light emitted from the object, or infrared light and visible light.

本発明の真空アーク溶解炉は、赤外線熱感知装置を備えており、赤外線熱感知装置により感知された消耗電極の上面温度に応じ、前記消耗電極の溶解を終了させるホットトップ操作の開始および/または終了タイミングが制御できる。   The vacuum arc melting furnace of the present invention includes an infrared heat sensing device, and starts a hot top operation for ending melting of the consumable electrode according to the upper surface temperature of the consumable electrode sensed by the infrared heat sensing device and / or. End timing can be controlled.

本発明の真空アーク溶解方法によれば、消耗電極の上面温度に応じて、ホットトップ操作の開始と終了タイミングを制御することから、高精度かつ最適時期にホットトップ操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用費用を削減することができる。   According to the vacuum arc melting method of the present invention, the start and end timing of the hot top operation is controlled according to the upper surface temperature of the consumable electrode. It is possible to reduce the cost of introducing and operating equipment used for hot top operation.

したがって、本発明の真空アーク溶解炉は、これらの溶解方法を適用することにより、消耗電極の歩留りを向上させるとともに、不純物の残留や巣の発生といった製品欠陥の発生を減らすことができる。   Therefore, by applying these melting methods, the vacuum arc melting furnace of the present invention can improve the yield of the consumable electrodes and reduce the occurrence of product defects such as residual impurities and nests.

これにより、本発明の真空アーク溶解方法や真空アーク溶解炉をチタンやチタン合金の精製に用いれば、チタンやチタン合金の精製効率を高めることができるとともに、製品歩留りを大幅に向上させることができる。   Thereby, if the vacuum arc melting method or vacuum arc melting furnace of the present invention is used for the purification of titanium or titanium alloy, the purification efficiency of titanium or titanium alloy can be increased, and the product yield can be greatly improved. .

本発明の真空アーク溶解炉の構成例とそれを用いた金属精製の状態を示す図である。It is a figure which shows the structural example of the vacuum arc melting furnace of this invention, and the state of the metal refinement | purification using the same. 本発明の真空アーク溶解炉が備える赤外線熱感知装置により得られる消耗電極上面の模式的温度分布図である。It is a typical temperature distribution figure of the upper surface of the consumable electrode obtained by the infrared heat sensing apparatus with which the vacuum arc melting furnace of this invention is equipped.

以下に、本発明の真空アーク溶解炉の構成例を示すとともに、それに用いられる真空アーク溶解方法を図面に基づいて説明する。   Below, while showing the structural example of the vacuum arc melting furnace of this invention, the vacuum arc melting method used for it is demonstrated based on drawing.

図1は、本発明の真空アーク溶解炉の構成例とそれを用いた金属精製の状態を示す図である。同図に示す真空アーク溶解炉では、精製対象の金属からなる消耗電極1と、銅製坩堝2と、消耗電極1を支持するスタブ7と、溶解の進行に合わせて消耗電極1を昇降させる昇降装置8と、真空吸引口9と、消耗電極上面から放射される赤外線の強度を測定する赤外線カメラ5および赤外線カメラ6から構成されている。   FIG. 1 is a diagram showing a configuration example of a vacuum arc melting furnace of the present invention and a state of metal purification using the same. In the vacuum arc melting furnace shown in the figure, a consumable electrode 1 made of a metal to be refined, a copper crucible 2, a stub 7 that supports the consumable electrode 1, and a lifting device that raises and lowers the consumable electrode 1 as the melting progresses. 8, a vacuum suction port 9, and an infrared camera 5 and an infrared camera 6 that measure the intensity of infrared rays emitted from the upper surface of the consumable electrode.

本発明の真空アーク溶解炉は、赤外線熱感知装置を備えている。赤外線熱感知装置は赤外線カメラ5と、赤外線カメラ6と、図示されていない画像処理装置から構成されている。画像処理装置は、赤外線カメラ5および赤外線カメラ6の測定結果を温度分布図に変換する。画像処理装置により表示される温度分布図から、消耗電極上面温度を感知できる。   The vacuum arc melting furnace of the present invention includes an infrared heat sensing device. The infrared heat sensing device includes an infrared camera 5, an infrared camera 6, and an image processing device (not shown). The image processing apparatus converts the measurement results of the infrared camera 5 and the infrared camera 6 into a temperature distribution diagram. The upper surface temperature of the consumable electrode can be sensed from the temperature distribution diagram displayed by the image processing apparatus.

次に、本発明の真空アーク溶解方法および真空アーク溶解炉を用いた金属の精製方法を説明する。   Next, the vacuum arc melting method and the metal purification method using the vacuum arc melting furnace of the present invention will be described.

水冷により銅製坩堝2を冷却し、スタブ7に消耗電極1を接合する。また、真空吸引口9から空気を排出し、炉内を真空にする。消耗電極1の底面と銅製坩堝2の内側底面が一定の距離になるように昇降装置8を操作し、消耗電極1と銅製坩堝2の間に電圧を印加する。   The copper crucible 2 is cooled by water cooling, and the consumable electrode 1 is joined to the stub 7. Further, air is discharged from the vacuum suction port 9 to make the inside of the furnace vacuum. The elevating device 8 is operated so that the bottom surface of the consumable electrode 1 and the inner bottom surface of the copper crucible 2 are at a certain distance, and a voltage is applied between the consumable electrode 1 and the copper crucible 2.

電圧の印加により、消耗電極1と銅製坩堝2の間にアーク放電が発生し、消耗電極1が溶解し、銅製坩堝2に滴下する。滴下した溶解金属は水冷された銅製坩堝2に冷却されて凝固し、インゴット4となる。昇降装置8により、インゴット4の上面と消耗電極1の底面の間隔を一定の距離に保ち、溶解を進行させる。   When voltage is applied, arc discharge occurs between the consumable electrode 1 and the copper crucible 2, and the consumable electrode 1 is melted and dropped onto the copper crucible 2. The dropped molten metal is cooled and solidified by a water-cooled copper crucible 2 to form an ingot 4. The elevating device 8 keeps the distance between the top surface of the ingot 4 and the bottom surface of the consumable electrode 1 at a constant distance, and the melting proceeds.

次に、本発明の真空アーク溶解方法および真空アーク溶解炉を用いたホットトップ操作を説明する。   Next, the hot top operation using the vacuum arc melting method and the vacuum arc melting furnace of the present invention will be described.

精製の開始段階および消耗電極1の長さが十分にあるときは、赤外線熱感知装置で感知される消耗電極1の上面温度は変化しない。この状態では、ホットトップ操作は行わず、一定の電流で溶解を進行する。溶解が進行し、消耗電極1の残存が短くなると、アークによる熱が消耗電極の上面に伝導し、消耗電極1の上面温度が上昇し、この温度上昇が赤外線熱感知装置により感知される。   When the purification start stage and the length of the consumable electrode 1 are sufficiently long, the upper surface temperature of the consumable electrode 1 detected by the infrared heat sensing device does not change. In this state, the hot top operation is not performed, and the dissolution proceeds at a constant current. When the melting progresses and the remaining of the consumable electrode 1 becomes short, the heat from the arc is conducted to the upper surface of the consumable electrode, the upper surface temperature of the consumable electrode 1 rises, and this temperature rise is detected by the infrared heat sensing device.

本発明の真空アーク溶解方法では、感知された消耗電極1の上面温度から、消耗電極1の残存長さを把握する。消耗電極1の上面温度が上昇し、一定の温度に到達すると、ホットトップの開始操作をし、消耗電極1と銅製坩堝2の間の電流を徐々に低くする。これにより、消耗電極1が溶解滴下する速度を徐々に低下させる。   In the vacuum arc melting method of the present invention, the remaining length of the consumable electrode 1 is grasped from the detected upper surface temperature of the consumable electrode 1. When the upper surface temperature of the consumable electrode 1 rises and reaches a certain temperature, a hot top start operation is performed, and the current between the consumable electrode 1 and the copper crucible 2 is gradually lowered. Thereby, the speed at which the consumable electrode 1 is dissolved and dropped is gradually reduced.

溶解が進行し、消耗電極1の残存が、さらに短くなると、消耗電極1の上面温度は、さらに上昇する。赤外線熱感知装置により消耗電極1の上面温度を感知し、消耗電極1の残存長さを把握する。消耗電極1の上面温度が一定の温度に到達すると、ホットトップの終了操作(溶解終了)をし、消耗電極1と銅製坩堝2の間の電流を徐々に低くし、最終的に溶解を停止させる。   When melting proceeds and the remaining of the consumable electrode 1 is further shortened, the upper surface temperature of the consumable electrode 1 further increases. The upper surface temperature of the consumable electrode 1 is sensed by an infrared heat sensing device, and the remaining length of the consumable electrode 1 is grasped. When the upper surface temperature of the consumable electrode 1 reaches a certain temperature, the hot top end operation (dissolution end) is performed, the current between the consumable electrode 1 and the copper crucible 2 is gradually lowered, and finally the dissolution is stopped. .

図2は、本発明の真空アーク溶解炉が備える赤外線熱感知装置により得られる消耗電極上面の模式的温度分布図である。同図中の濃淡が消耗電極1の上面温度の分布を示している。スタブ7が存在するため、消耗電極中心部の温度は感知することができない。   FIG. 2 is a schematic temperature distribution diagram of the upper surface of the consumable electrode obtained by the infrared heat sensing device provided in the vacuum arc melting furnace of the present invention. The shading in the figure shows the distribution of the upper surface temperature of the consumable electrode 1. Since the stub 7 exists, the temperature of the consumable electrode center cannot be sensed.

図2に示す温度分布からも確認できるように、消耗電極1の上面において、スタブ7の外周付近の温度が最も高温となる。スタブ7の外周付近の温度に応じて、ホットトップ操作の開始および終了を行うのが望ましい。なお、ホットトップ操作の開始および終了を行う温度については、諸条件により大きく変化するため、操業経験に基づき定めるのが望ましい。   As can be confirmed from the temperature distribution shown in FIG. 2, the temperature near the outer periphery of the stub 7 is the highest on the upper surface of the consumable electrode 1. It is desirable to start and end the hot top operation according to the temperature near the outer periphery of the stub 7. Note that the temperature at which the hot top operation starts and ends varies greatly depending on various conditions, so it is desirable to determine the temperature based on operational experience.

前記図1に示す、本発明の真空アーク溶解方法および真空アーク溶解炉を用いて金属精製を行い、本発明の有効性を検証した。   Metal purification was performed using the vacuum arc melting method and vacuum arc melting furnace of the present invention shown in FIG. 1 to verify the effectiveness of the present invention.

本発明例では、本発明で規定する赤外線熱感知装置を用い、ホットトップ操作の開始および終了を実施した。比較例1では、溶解電極の重量計測による監視装置を用い、電極重量に応じてホットトップ操作の開始および終了を実施した。さらに、比較例2では、消耗電極に切り込み加工を施し、消耗電極上面の輪郭変化に応じてホットトップ操作の開始および終了を実施した。   In the example of the present invention, the hot top operation was started and ended using the infrared heat sensing device defined in the present invention. In Comparative Example 1, the hot-top operation was started and ended in accordance with the electrode weight using a monitoring device based on the weight measurement of the dissolved electrode. Furthermore, in Comparative Example 2, the consumable electrode was cut and the hot top operation was started and ended according to the contour change of the upper surface of the consumable electrode.

表1に、本発明例、比較例1および比較例2における、スタブの溶損頻度、および導入コスト、保守・校正・加工コストについて、それぞれの場合の比較評価を記す。   Table 1 shows the comparative evaluation in each case for the stub melting frequency, introduction cost, maintenance / calibration / processing cost in the present invention example, comparative example 1 and comparative example 2.

Figure 0005523738
Figure 0005523738

表1に記す通り、スタブ溶損が発生した頻度を表すスタブ溶損頻度は、本発明例を30とすると、比較例1が100、比較例2が95となった。このことから、本発明の真空アーク溶解方法および真空アーク溶解炉を用いると、従来技術よりスタブ溶損の発生を3分の1以下にできることが確認できた。   As shown in Table 1, the stub erosion frequency representing the frequency of occurrence of stub erosion was 100 in Comparative Example 1 and 95 in Comparative Example 2, assuming that the invention example was 30. From this, it has been confirmed that when the vacuum arc melting method and the vacuum arc melting furnace of the present invention are used, the occurrence of stub melt damage can be reduced to one third or less than in the prior art.

赤外線熱感知装置、溶解電極の重量計測による監視装置および切り欠き加工に用いる加工設備の設置に必要なコストを表す導入コストは、本発明例を5とすると、比較例1が100、比較例2が40となった。このことから、本発明の真空アーク溶解方法および真空アーク溶解炉を用いると、従来技術より導入コストを8分の1以下にすることが確認できた。   The introduction cost representing the cost required for installing the infrared heat sensing device, the monitoring device for measuring the weight of the melting electrode, and the processing equipment used for the notch processing is 100 for Comparative Example 1 and 5 for Comparative Example 2 Became 40. From this, when the vacuum arc melting method and the vacuum arc melting furnace of the present invention were used, it was confirmed that the introduction cost was reduced to 1/8 or less than the prior art.

溶解電極の重量計測による監視装置や赤外線熱感知装置の保守や校正、消耗電極への切り欠き加工に必要なコストを表す運用コストは、本発明例を1とすると、比較例1が20、比較例2が100となった。このことから、本発明の真空アーク溶解方法および真空アーク溶解炉を用いると、従来技術より運用コストを20分の1以下にすることが確認できた。   The operational cost that represents the cost required for maintenance and calibration of the monitoring device by measuring the weight of the melting electrode and the infrared heat sensing device, and the notch processing to the consumable electrode is 20 for Comparative Example 1 and 1 for Comparative Example 1. Example 2 was 100. From this, when the vacuum arc melting method and the vacuum arc melting furnace of the present invention were used, it was confirmed that the operation cost was reduced to 1/20 or less than that of the prior art.

このように、本発明の真空アーク溶解炉および真空アーク溶解方法を用いると、高精度かつ最適時期にホットトップ操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用コストを削減することができることが確認された。   As described above, when the vacuum arc melting furnace and the vacuum arc melting method of the present invention are used, the hot top operation can be performed with high accuracy and at the optimum time, and the introduction and operation costs of the equipment used for the hot top operation are reduced. It was confirmed that it was possible.

本発明の真空アーク溶解方法によれば、消耗電極の上面温度に応じて、ホットトップ操作の開始と終了タイミングを制御することから、高精度かつ最適時期にホットトップ操作を行うことができるとともに、ホットトップ操作に用いる設備の導入および運用費用を削減することができる。したがって、本発明の真空アーク溶解炉は、これらの溶解方法を適用することにより、消耗電極の歩留りを向上させるとともに、不純物の残留や巣の発生といった製品欠陥の発生を減らすことができる。   According to the vacuum arc melting method of the present invention, the start and end timing of the hot top operation is controlled according to the upper surface temperature of the consumable electrode. It is possible to reduce the cost of introducing and operating equipment used for hot top operation. Therefore, by applying these melting methods, the vacuum arc melting furnace of the present invention can improve the yield of the consumable electrodes and reduce the occurrence of product defects such as residual impurities and nests.

このため、本発明の真空アーク溶解方法および真空アーク溶解炉を、チタンやチタン合金等の金属精製に適用することにより、安価な導入および運用コストで、製品欠陥の発生を減らし、歩留りを向上させることができ、チタンやチタン合金等の金属精製の効率を高めることができる。   For this reason, by applying the vacuum arc melting method and the vacuum arc melting furnace of the present invention to refining metals such as titanium and titanium alloys, the occurrence of product defects is reduced and the yield is improved at a low introduction and operation cost. And the efficiency of refining metals such as titanium and titanium alloys can be increased.

1.消耗電極 2.銅製坩堝
3.アーク 4.インゴット
5.赤外線カメラ 6.赤外線カメラ
7.スタブ 8.昇降装置
9.真空吸引口
1. Consumable electrode 2. Copper crucible Arc 4. 4. Ingot Infrared camera Infrared camera Stub 8. Elevating device 9. Vacuum suction port

Claims (4)

消耗電極をアークにより溶解し、滴下する金属を凝固させてインゴットを製造する真空アーク溶解方法であって、
前記消耗電極が溶解、滴下し、消耗電極の残存が短くなるのにともない溶解を終了させるホットトップ操作の際に、消耗電極の上面温度を感知する赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて開始時期を決定することを特徴とする真空アーク溶解方法。
A vacuum arc melting method in which a consumable electrode is melted by an arc and a dripping metal is solidified to produce an ingot,
An infrared heat sensing device is provided to sense the upper surface temperature of the consumable electrode during hot top operation in which the consumable electrode is dissolved and dripped and the remaining of the consumable electrode is shortened to terminate melting, and the consumable electrode sensed A vacuum arc melting method characterized by grasping the remaining length of the consumable electrode up to the stub by measuring the upper surface temperature of the tube and determining the start time according to the remaining length .
消耗電極をアークにより溶解し、滴下する金属を凝固させてインゴットを製造する真空アーク溶解方法であって、
前記消耗電極が溶解、滴下し、消耗電極の残存が短くなるのにともない溶解を終了させるホットトップ操作の際に、消耗電極の上面温度を感知する赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて終了時期を決定することを特徴とする真空アーク溶解方法。
A vacuum arc melting method in which a consumable electrode is melted by an arc and a dripping metal is solidified to produce an ingot,
An infrared heat sensing device is provided to sense the upper surface temperature of the consumable electrode during hot top operation in which the consumable electrode is dissolved and dripped and the remaining of the consumable electrode is shortened to terminate melting, and the consumable electrode sensed A vacuum arc melting method characterized by grasping the remaining length of the consumable electrode up to the stub by measuring the upper surface temperature of the tube and determining the end time according to the remaining length .
前記ホットトップ操作の際に、前記赤外線熱感知装置を設け、感知された消耗電極の上面温度を測定することによりスタブまでの消耗電極の残存長さを把握し、当該残存長さに応じて開始時期および終了時期を決定することを特徴とする請求項1または2に記載の真空アーク溶解方法。 When the hot top operation is performed, the infrared heat sensing device is provided, and the remaining temperature of the consumable electrode up to the stub is grasped by measuring the upper surface temperature of the sensed consumable electrode, and starts according to the remaining length. The vacuum arc melting method according to claim 1 or 2, wherein a time and an end time are determined. アークにより溶解滴下する消耗電極と、
滴下する金属を凝固させてインゴットとする坩堝と、
前記消耗電極と前記坩堝または前記インゴットの距離を一定に保持する昇降装置と、
前記消耗電極と前記昇降装置を接合するスタブと、
前記消耗電極の上面温度を感知し、この上面温度を測定することによりスタブまでの消耗電極の残存長さを把握する赤外線熱感知装置とを備えることを特徴とする真空アーク溶解炉。
A consumable electrode that melts and drops by an arc;
A crucible that solidifies the dripping metal into an ingot;
A lifting device for maintaining a constant distance between the consumable electrode and the crucible or the ingot;
A stub for joining the consumable electrode and the lifting device;
A vacuum arc melting furnace comprising an infrared heat sensing device that senses the upper surface temperature of the consumable electrode and measures the upper surface temperature to determine the remaining length of the consumable electrode to the stub .
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