JP2004042190A

JP2004042190A - Electrode for electric discharge machining

Info

Publication number: JP2004042190A
Application number: JP2002203224A
Authority: JP
Inventors: Tetsuya Okamoto; 岡本　哲也; Akira Mishima; 三島　彰
Original assignee: Nippon Tungsten Co Ltd
Current assignee: Nippon Tungsten Co Ltd
Priority date: 2002-07-11
Filing date: 2002-07-11
Publication date: 2004-02-12

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for electric discharge machining for performing accurate machining over a long time, having the long electrode service life, and having a high machining speed in the electrode for the electric discharge machining composed of a Cu-W composite material used for the electric discharge machining, particularly, die sinking electric discharge machining. <P>SOLUTION: This electrode for the electric discharge machining is composed of the Cu-W composite material including Cu by 5 to 40 wt.% and having the average particle size of W not more than 2 μm. The electric discharge machining is performed by using the electrode for the electric discharge machining of this Cu-W composite material. The service life longer than a conventionally used electrode is obtained. The accurate machining is performed over a long time. Machining accuracy is improved. Cost is reduced. The machining speed is increased. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、主に型彫放電加工に使用する放電加工用電極である。
【０００２】
【従来の技術】
現在まで特に型彫放電加工に使用する放電加工用電極は、各種高融点金属材料、Ｗ材料、Ｃｕ−Ｗ複合材、Ａｇ−Ｗ系複合材、Ｗ−Ｔｉ系複合材等から始まり、特開昭５６−７６３４１号公報のように表面処理を施したものや、特開昭６３−４７６２３号公報のように炭素の薄膜を付けたもの、特開平０３−６６５２０号公報のようにＣｒＣ材料、ＺｒＣ材料を用いたもの等などさまざまなものが考案されてきた。それらのなかでも現在特に超硬合金や導電性セラミックス等の加工を行う場合には、加工速度、寿命、価格、被加工性、汎用性などの面で優れるＣｕ−Ｗ系複合材電極およびそれに特開昭４９−１２１２９６号公報や、特開昭５２−２２１９７号公報のようにホウ素、ホウ化物、ホウ酸化物を添加して電極寿命と加工速度を改善したものが多くの場合用いられているが、これらの材料を使用しても電極の消耗や加工速度は十分な結果は得られない。特に、消耗は早期に進むと加工精度が悪くなり、求める寸法精度、面精度がいずれも得られずに、近年ますます高精度が要求される加工に対応できない。また、同時に、これらの材料はそもそも高価であることと、電極は被加工物に対して体積率で約１０〜２０％又はそれ以上の電極消耗があることから、放電加工のコスト高の一因となっている。
【本発明が解決しようとする課題】
放電加工、特に型彫放電加工に用いるＣｕ−Ｗ系複合材からなる放電加工用電極において、精度良い加工が長時間でき、電極寿命が長く、かつ、加工速度が速い放電加工用電極を得ることを課題とする。
【０００３】
【課題を解決するための手段】
請求項１に記載の本発明は、Ｃｕを５〜４０重量％含有し、Ｗの平均粒子径が２μｍ以下であるＣｕ−Ｗ系複合材料からなることを特徴とする放電加工用電極である。Ｃｕ−Ｗ系複合材よりなる電極は特に超硬合金や導電性セラミックスの型彫放電加工を行う場合に適しており、加工速度、寿命、価格、被加工性、汎用性などの面を総合的に判断した場合に他の電極材質よりも優れている。
【０００４】
電極の消耗は以下の機構によって行われる。すなわち、図１に示す通り、放電加工時に発生するアーク５は電極側の飛び出した部分４（以下「突起４」と記載する）より発生する。Ｃｕは耐アーク性が低く放電により融解が起こりやすく、また、熱伝導率が高いために連続したＣｕの部分を伝い熱が広がり、連続したＣｕの部分を融解させやすい。
【０００５】
一方、Ｗは比較的耐アーク性が高く、また、熱伝導率が低いためにアーク時の熱が他の粒子に移動しにくく、アークの発生した部分の粒子だけが融解しやすい。
【０００６】
この突起４がＣｕであるならば、Ｃｕはアークにより最寄りのＷ粒子に遮られるまでＣｕの部分を優先的に熱が伝わって、そのＣｕの部分が融解する。
【０００７】
また、突起４がＷであるならば、アーク放電による熱はＷ粒子を昇温、融解させるのにその多くの部分が使われ、隣接するＣｕや他のＷ粒子は融解しにくい。
【０００８】
いずれの場合も、融解を止める働きがあるのはＷ粒子であり、Ｗ粒子がより頻繁にアーク発生箇所となり、かつ、一度の放電にて融解するＣｕが少ない場合に電極消耗は非常に小さく押さえることができる。これを実現するためにはＷの粒子をなるべく小さくし、その粒子間に溶浸されているＣｕを細かく分散させればよい。
【０００９】
本発明の電極はＣｕを５〜４０重量％含有し、Ｗの平均粒子径が２μｍ以下であるＣｕ−Ｗ系複合材料からなることを特徴とする。Ｗの平均粒径が２μｍ以下であることより、上記アーク放電による融解の進行（＝電極の消耗）速度を低く押さえることができる。平均粒径が２μｍを超えると、ＣｕのネットワークがＷに遮られることなく連続しやすくなり、その結果一度のアーク放電にて融解の進行が大きく進み、寿命が短くなる。また、Ｗの平均粒径が２μｍ以下であり、かつ前記組成を有すことにより、放電中に面粗れが少なくなりアークの発生が安定して被加工面の一部に偏らず、被加工物の被加工面全面に均等に発生しやすくなるために、加工が効率よく行われ、加工速度が速い。
また、本発明の電極はＣｕを５〜４０重量％含むことを特徴とする。Ｃｕが４０重量％より多く含まれる複合材は、一度のＣｕの融解範囲が大きく、電極表面が粗れやすくなり、結果として加工速度が遅くなり、また、電極寿命も著しく短くなる。また、逆にＣｕが５重量％より少ない場合はＣｕの融解範囲は小さくなるが、Ｃｕの層が極端に薄くなるために、その部分の熱が直接周辺のＷを欠落させ、電極表面に凹凸を生じさせやすくなる。そのために均一に加工が進まず、加工速度が遅くなるためにやはり望ましくない。
【００１０】
請求項２に記載の本発明はＣｕ−Ｗ系複合材料の重量に対する添加物の重量の１００分率が０．０５〜１０％となるようにホウ素、ホウ化物又はホウ酸化物のうち１種以上添加したことを特徴とする請求項１記載の放電加工用電極である。ホウ素、ホウ化物、ホウ酸化物のうち１種以上を０．０５〜１０％添加したＣｕ−Ｗ系複合材は特開昭５２−２２１９７公報に示されているように、Ｗの仕事関数を低減化し、パルスの放電を安定させることが分かっている。ホウ素、ホウ化物、ホウ酸化物のうち１種以上の添加物を０．０５〜１０％添加したＣｕ−Ｗ系複合材は、それらを添加していないＣｕ−Ｗ複合材料と比較して使用時の加工速度は速く、被加工物の面粗さを改善することもできる。本発明に示すようにＷの平均粒径が２μｍ以下であれば、それ以上の平均粒径のホウ素、ホウ化物、ホウ酸化物のいずれか１種以上を０．０５〜１０％添加したＣｕ−Ｗ複合材料と比較して、より加工速度を上げることができ、電極寿命も同等以上である。ホウ素、ホウ化物、ホウ酸化物の添加量が０．０５％より少ないと添加による十分な効果が得られず、その特性は単純なＣｕ−Ｗ材料と差が見られず、添加の効果が出ない。また、１０％以上添加すれば製造時に焼結が著しく難しくなり、緻密な複合材を得られなくなる。そのためにホウ素、ホウ化物、ホウ酸化物のうちいずれか１種以上を０．０５〜１０％添加することが適当である。
【００１１】
【発明の実施の形態】
本発明の放電加工用電極は以下の方法により得ることができる。
【００１２】
すなわち、純度９９％以上で平均粒径が２μｍ以下のＷ粉末を５０〜３０００Ｋｇｆ／ｃｍ^２にて金型プレスを行いプレス体を得る。プレス体を水素などの還元雰囲気又は真空雰囲気にて１１００〜１７００℃にて熱処理を行って粒子同士にネッキングが起こるいわゆる仮焼結体を得る。
【００１３】
上記ＷとＣｕの混合比率は請求項１に記載の通り、Ｃｕの含有量が５〜４０重量％であることが、その特性（電極寿命および加工速度）上適している。
【００１４】
次に、仮焼結体と粉末状又は固まりの十分な体積を持つ純度９９％以上のＣｕを接触させた又は近傍に載置した状態で、還元雰囲気又は真空雰囲気中で銅の融点より高温の１２５０℃程度まで加熱し、仮焼結体中にＣｕを溶浸させる。
冷却後に溶浸しきれなかった余分な銅を紙やすり、研削盤、電気加工機などで除去し、研削盤、電気加工機等で加工を行い、所望の電極形状に加工する。以上の方法にて本発明の放電加工用電極を得ることができる。
ホウ素、ホウ化物、ホウ酸化物を添加したＣｕ−Ｗ系複合材料を作製する場合は、前記Ｗ粉末と十分に混合を行うことにより、同様の工程にて得ることができる。
【００１５】
また、以上は溶浸法について述べたが、同様のＷ粉末と平均粒径が０．１〜１０μｍ程度のＣｕの粉末（ホウ素、ホウ化物、ホウ酸化物を加える場合はそれらも）とを混合し、それをプレス、焼結を行って所望のＣｕ−Ｗ系複合材料を得ることもできる。以下実施例により、より詳細に説明する。
【００１６】
【実施例】
実施例１
純度９９．９％で平均粒径が１．０μｍのＷ粉末を３００Ｋｇｆ／ｃｍ^２にて金型プレスを行いプレス体を得た。プレス体を水素中、還元雰囲気にて１４００℃まで加熱し、粒子同士にネッキングが起こるいわゆるＷの仮焼結体を得た。
【００１７】
仮焼結体の形状はφ３．５ｍｍ×３５ｍｍの円柱形状であった。
【００１８】
次に、仮焼結体と粉末状の純度９９．９％のＣｕ５０ｇ中に埋設した状態で水素ガス中、還元雰囲気で銅の融点より高い１２００℃まで加熱し、仮焼結体中にＣｕを溶浸させた。溶浸後のＣｕ−Ｗ系複合材の組成はＷが８０重量％であり、Ｃｕが２０重量％であった。
【００１９】
冷却後に溶浸しきれなかった余分な銅を紙やすりで除去し、円筒研削盤、および平面研削盤にて加工を行い、所望の円柱形の電極形状（φ３．０ｍｍ×３０ｍｍ）に加工した。以上の方法にて得られた本発明の放電加工用電極を試料Ｎｏ．１とした。
【００２０】
次に試料Ｎｏ．１の試料を三菱電気（株）製の型彫放電加工機「ＤＩＡＸ−Ｖ３５ＦＨ」に放電加工用電極として装着し、ＷＣ−３重量％Ｃｏの組成を有す超硬合金を加工した。加工条件は表１に示す前記加工機加工条件パックである「００５３番（超硬合金加工用）」で行った。また、加工は図２に示すようにφ３０ｍｍ×５０ｍｍの形状を有す上記超硬合金の端面中心より深さ２０ｍｍのザグリ穴をあけ、消耗した電極の体積を測定することにより評価した。
【００２１】
【表１】

【００２２】
試料Ｎｏ．１の試料についてこの実験を行ったところ、消耗した電極の体積は１８．１ｍｍ^３であった。
【００２３】
次にＷ原料粉末の平均粒径を０．２５μｍ、０．５μｍ、０．７５μｍ、１．５μｍ、２．０μｍ、２．５μｍ、５μｍとして同様の工程にて電極を作製し、それぞれを試料Ｎｏ．２〜試料Ｎｏ．８とした。また、Ｗ原料粉末の平均粒径が１μｍで０．５％のホウ素、ＳｒＢ_２Ｏ_４、ＴｉＢ_２をそれぞれＷの原料粉末と十分混合し、同様の工程で得られた試料を試料Ｎｏ．７〜試料Ｎｏ．９とした。さらに、試料Ｎｏ．８の試料のＳｒＢ_２Ｏ_４の添加量をそれぞれ０．０１％、０．０５％、１％、５％、１０％、１５％へと変更した試料をそれぞれ試料Ｎｏ．１６、試料Ｎｏ．１０〜試料Ｎｏ．１３および試料Ｎｏ．１７とし、これらを用いて試料Ｎｏ．１と同様の試験を行い、電極消耗体積を測定したところ、表２に示す結果が得られた。また、電極消耗体積を超硬合金の加工体積で割ったものを電極消耗比率として計算し、表２に併せて記載した。
【００２４】
【表２】

表２中の試料Ｎｏ．に＊のある番号は本発明の範囲外の比較試料である
【００２５】
表２の結果より試料Ｎｏ．１〜試料Ｎｏ．６に示す本発明の範囲であるＷの平均粒径が２．０μｍ以下である放電加工用電極は、試料Ｎｏ．１４、試料Ｎｏ．１５に示す平均粒径２．０μｍを超えるものと比較して電極消耗比率が小さく、長寿命を得られることが分かった。特に、Ｗ平均粒径が０．５μｍ以下のものは電極消耗比率が小さかった。
【００２６】
次に、試料Ｎｏ．７〜試料Ｎｏ．１３の結果から、Ｃｕ−Ｗ系複合材料にホウ素、ホウ化物、ホウ酸化物を０．０５〜１０％加えることにより、ホウ素、ホウ化物、ホウ酸化物を添加していないＣｕ−Ｗ複合材料よりも、寿命面を得ることができた。また、試料Ｎｏ．１６の結果より、ホウ素、ホウ化物、ホウ酸化物を０．０５％より少量しか含んでいないものはその添加の効果が見られずに、Ｃｕ−Ｗ複合材と効果は同様であった。さらに、試料Ｎｏ．１７の結果からホウ素、ホウ化物、ホウ酸化物を１０％より多く含むものは焼結で十分緻密な複合材料を得られずに寿命も加工速度も望むように得られず、また、被加工物の面粗度も粗かった。
【００２７】
本発明による、消耗速度が遅く長寿命な放電加工用電極を放電加工に使用することで、精度良く放電加工を行える寿命が長くなった。本発明の放電加工用電極は精密加工にも適していることが分かった。
また、長寿命であることから、電極にかかるコストが押さえられるだけにとどまらず、電極の交換に関する人件費も押さえられ、その経済効果は大きい。
【００２８】
実施例２
純度９９．９％で平均粒径が１．０μｍのＷ粉末を３００Ｋｇｆ／ｃｍ^２にて金型プレスを行いプレス体を得た。プレス体を水素中、還元雰囲気にて１４００℃まで加熱し、粒子同士にネッキングが起こるいわゆるＷの仮焼結体を得た。
仮焼結体の大きさはφ３．５ｍｍ×３５ｍｍの円柱形状であった。
次に、仮焼結体と粉末状の純度９９．９％の銅５０ｇ中に埋設した状態で水素ガス中、還元雰囲気で銅の融点より高い１２００℃まで加熱し、仮焼結体中にＣｕを溶浸させた。溶浸後のＣｕ−Ｗ系複合材の組成はＷが８０重量％であり、Ｃｕが２０重量％であった。
【００２９】
冷却後に溶浸しきれなかった余分な銅を紙やすりで除去し、円筒研削盤、および平面研削盤にて加工を行い、所望の円柱形の電極形状（φ３．０ｍｍ×３０ｍｍ）に加工した。以上の方法にて得られた本発明の放電加工用電極を試料Ｎｏ．１とした。
次に、試料Ｎｏ．１とＷおよびＣｕの組成比をＷの熱処理温度や金型プレス時の圧力を調整することにより変え、Ｗが９８重量％、９５重量％、９０重量％、７０重量％、６０重量％、５０重量％、４０重量％で残部がＣｕである試料を作製し、それぞれ試料Ｎｏ．２１〜試料Ｎｏ．２７とした。
さらに、Ｗの平均粒子径が１μｍで、ホウ素、ＳｒＢ_２Ｏ_４、ＴｉＢ_２のいずれかを５％添加した試料で、ＷとＣｕの組成比を表４に示す組成に変えたものを、試料Ｎｏ．３０〜試料Ｎｏ．４３とした。
またさらに、Ｗの平均粒子径が１μｍで、ホウ素、ＳｒＢ_２Ｏ_４、ＴｉＢ_２の２種以上を５％添加した試料で、ＷとＣｕの組成比を表５に示す組成に変えたものを、試料Ｎｏ．５１〜試料Ｎｏ．５４とした。
これらの試料Ｎｏ．１、試料Ｎｏ．２１〜試料Ｎｏ．２７、試料Ｎｏ．３０〜試料Ｎｏ．４３、試料Ｎｏ．５１〜試料Ｎｏ．５４の試料について実施例１と同じ加工機、同じ条件にて放電加工の実験を行い、その際の電極消耗率と加工速度を求めた。
この実験における試料の組成と電極消耗率、加工速度を表３、表４および表５に示した。
【００３０】
【表３】

表３中の試料のＷ平均粒径はすべて１．０μｍである。
表３の試料Ｎｏ．に＊のある番号は本発明の範囲外の比較試料である。
【００３１】
【表４】

表４中すべての試料のＷ平均粒径は１．０μｍである。
表４の試料Ｎｏ．に＊のある番号は本発明の範囲外の比較試料である。
【００３２】
【表５】

表５中のすべての試料のＷとＣｕの組成はＷ量８０％、Ｃｕ量２０％である。
【００３３】
表３の結果より、Ｗの平均粒径が２μｍ以下のＣｕ−Ｗ系複合材よりなる放電加工用電極については、加工速度を得るために適したＣｕ、Ｗの組成比があり、その組成はＣｕが５〜４０重量％、残部がＷであることが分かった。また、表４の結果より、０．０５〜１０％のホウ素、ホウ化物、ホウ酸化物のいずれか１種以上を添加したＣｕが５〜４０重量％、残部がＷの複合材料も同様に加工速度を速くすることができた。さらに、表５の結果より、ホウ素、ホウ化物、ホウ酸化物のうち２種以上を含むものも、同様の効果があることが分かった。
【００３４】
【発明の効果】
本発明のＣｕ−Ｗ系複合材の放電加工用電極を用いて放電加工を行うことにより、従来用いられていた電極よりも長寿命を得られ、精度良い加工を長時間行うことができ、加工の精度向上およびコストダウンを行うことができた。また、加工速度も速めることができた。
【図面の簡単な説明】
【図１】放電加工におけるアーク放電の模式図を示す
【図２】放電加工試験に用いた被加工物の形状と、被加工部の形状を示す斜視図である
【符号の説明】
１　放電加工用電極
２　被加工物
３　突起、アーク発生部（被加工物側）
４　突起、アーク発生部（電極側）
５　アーク
６　被加工物（超硬合金製）
７　被加工部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is an electrode for electric discharge machining mainly used for die-sinking electric discharge machining.
[0002]
[Prior art]
Until now, the electrodes for electric discharge machining particularly used for die-sinking electric discharge machining have started from various refractory metal materials, W materials, Cu-W composite materials, Ag-W composite materials, W-Ti composite materials, and the like. JP-A-56-76341, surface-treated ones, JP-A-63-47623, carbon thin films, CrC material, ZrC as described in JP-A-03-66520. Various things such as those using materials have been devised. Among them, especially when processing cemented carbides or conductive ceramics at present, the Cu-W based composite electrode and its special features are excellent in processing speed, life, price, workability, versatility, etc. As disclosed in JP-A-49-112296 and JP-A-52-22197, those in which boron, boride, and borate are added to improve the electrode life and processing speed are used in many cases. However, even if these materials are used, sufficient results cannot be obtained in terms of electrode consumption and processing speed. In particular, if the wear progresses early, the machining accuracy deteriorates, and the required dimensional accuracy and surface accuracy cannot be obtained, and it is not possible to cope with machining that requires increasingly higher accuracy in recent years. At the same time, these materials are expensive in the first place, and the electrodes consume about 10 to 20% or more by volume of the workpiece with respect to the workpiece. It has become.
[Problems to be solved by the present invention]
To obtain an electrode for electrical discharge machining, particularly an electrical discharge machining electrode made of a Cu-W based composite material used for die sinking electrical discharge machining, capable of performing accurate machining for a long time, having a long electrode life, and having a high machining speed. As an issue.
[0003]
[Means for Solving the Problems]
The present invention according to claim 1 is an electrode for electric discharge machining, comprising a Cu-W-based composite material containing 5 to 40% by weight of Cu and having an average particle diameter of W of 2 µm or less. Electrodes made of Cu-W based composite material are particularly suitable for die-sinking electrical discharge machining of cemented carbides and conductive ceramics, and are comprehensive in terms of processing speed, life, price, workability, versatility, etc. Is superior to other electrode materials.
[0004]
The electrode is consumed by the following mechanism. That is, as shown in FIG. 1, the arc 5 generated at the time of electric discharge machining is generated from a protruding portion 4 on the electrode side (hereinafter, referred to as “projection 4”). Cu has low arc resistance and is likely to be melted by electric discharge, and because of its high thermal conductivity, the heat spreads through the continuous Cu portion and the continuous Cu portion is easily melted.
[0005]
On the other hand, W has a relatively high arc resistance and a low thermal conductivity, so that heat at the time of arc hardly moves to other particles, and only particles in a portion where an arc is generated are easily melted.
[0006]
If the projection 4 is made of Cu, heat is transmitted preferentially to the Cu portion until the Cu is blocked by the nearest W particles, and the Cu portion is melted.
[0007]
Further, if the projections 4 are made of W, the heat generated by the arc discharge is used to raise and melt the W particles, and most of the heat is used to melt the adjacent Cu and other W particles.
[0008]
In any case, it is the W particles that have the function of stopping the melting, and the W particles become more frequent arc generating locations, and when the amount of Cu that is melted by one discharge is small, the electrode consumption is suppressed to a very small value. be able to. In order to achieve this, the W particles should be made as small as possible, and the Cu infiltrated between the particles should be finely dispersed.
[0009]
The electrode of the present invention is characterized by comprising a Cu-W-based composite material containing 5 to 40% by weight of Cu and having an average particle diameter of W of 2 µm or less. When the average particle diameter of W is 2 μm or less, the rate of progress of the melting by the arc discharge (= electrode consumption) can be suppressed low. If the average particle size exceeds 2 μm, the Cu network is likely to be continuous without being interrupted by W, and as a result, melting progresses greatly by one arc discharge, and the life is shortened. Further, since the average particle diameter of W is 2 μm or less and having the above-mentioned composition, surface roughness during discharge is reduced, arc generation is stabilized, and there is no bias toward a part of the surface to be processed. The processing is performed efficiently and the processing speed is high, because the processing easily occurs uniformly on the entire surface of the workpiece.
Further, the electrode of the present invention is characterized by containing 5 to 40% by weight of Cu. A composite material containing more than 40% by weight of Cu has a large melting range of Cu at one time, and the electrode surface is easily roughened. As a result, the processing speed is reduced and the electrode life is significantly shortened. On the other hand, when Cu is less than 5% by weight, the melting range of Cu becomes small, but since the Cu layer becomes extremely thin, the heat at that portion directly drops W around the surface, and the surface of the electrode becomes uneven. Easily occur. Therefore, the processing does not proceed uniformly, and the processing speed is slow, which is also undesirable.
[0010]
The present invention according to claim 2, wherein at least one of boron, boride, and borate is selected so that the percentage of the weight of the additive to the weight of the Cu—W-based composite material is 0.05 to 10%. The electrode for electric discharge machining according to claim 1, wherein the electrode is added. As shown in JP-A-52-22197, a Cu-W-based composite material containing 0.05 to 10% of one or more of boron, boride and borate reduces the work function of W. To stabilize the discharge of the pulse. A Cu-W composite material containing 0.05 to 10% of one or more of boron, boride and borate is compared with a Cu-W composite material not containing them. Has a high processing speed and can improve the surface roughness of the workpiece. As shown in the present invention, if the average particle size of W is 2 μm or less, Cu— containing at least one of boron, boride, and borate having an average particle size of 0.05 to 10% is added. The processing speed can be further increased as compared with the W composite material, and the electrode life is equal to or longer than that. If the added amount of boron, boride or borate is less than 0.05%, sufficient effect by the addition cannot be obtained, and the characteristics are not different from those of a simple Cu-W material, and the effect of the addition is obtained. Absent. On the other hand, if 10% or more is added, sintering becomes extremely difficult at the time of production, and a dense composite material cannot be obtained. Therefore, it is appropriate to add at least one of boron, boride and borate in an amount of 0.05 to 10%.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The electrode for electric discharge machining of the present invention can be obtained by the following method.
[0012]
That is, a W powder having a purity of 99% or more and an average particle size of 2 μm or less is subjected to die pressing at 50 to 3000 kgf / cm ² to obtain a pressed body. The pressed body is subjected to a heat treatment at 1100 to 1700 ° C. in a reducing atmosphere such as hydrogen or a vacuum atmosphere to obtain a so-called temporary sintered body in which the particles are necked.
[0013]
As described in the first aspect, the mixing ratio of W and Cu is preferably such that the Cu content is 5 to 40% by weight in terms of its characteristics (electrode life and processing speed).
[0014]
Next, in a state where the temporary sintered body and Cu having a sufficient volume of powder or agglomerate and having a purity of 99% or more are in contact with or placed near, the temperature is higher than the melting point of copper in a reducing atmosphere or a vacuum atmosphere. Heat to about 1250 ° C. to infiltrate Cu into the temporarily sintered body.
After cooling, excess copper that could not be completely infiltrated is removed by sandpaper, a grinder, an electric machine, or the like, and processed by a grinder, an electric machine, or the like, and processed into a desired electrode shape. The electrode for electric discharge machining of the present invention can be obtained by the above method.
In the case of producing a Cu—W-based composite material to which boron, boride, and borate are added, it can be obtained in a similar process by sufficiently mixing with the W powder.
[0015]
Although the infiltration method has been described above, the same W powder is mixed with a Cu powder having an average particle diameter of about 0.1 to 10 μm (or boron, boride, or boride when they are added). Then, it can be pressed and sintered to obtain a desired Cu-W based composite material. Hereinafter, the present invention will be described in more detail with reference to examples.
[0016]
【Example】
Example 1
A W powder having a purity of 99.9% and an average particle diameter of 1.0 μm was subjected to a die press at 300 kgf / cm ² to obtain a pressed body. The pressed body was heated to 1400 ° C. in a reducing atmosphere in hydrogen to obtain a so-called temporary sintered body of W where necking between particles occurred.
[0017]
The shape of the temporary sintered body was a cylindrical shape of φ3.5 mm × 35 mm.
[0018]
Next, the pre-sintered body and the powdery state embedded in 50 g of Cu having a purity of 99.9% are heated to 1200 ° C. higher than the melting point of copper in a reducing atmosphere in a hydrogen gas in a state of being embedded in 50 g of Cu having a purity of 99.9%. Infiltrated. The composition of the Cu-W based composite material after infiltration was W at 80% by weight and Cu at 20% by weight.
[0019]
After cooling, excess copper that could not be completely infiltrated was removed with sandpaper, processed using a cylindrical grinder and a surface grinder, and processed into a desired cylindrical electrode shape (φ3.0 mm × 30 mm). The electrode for electrical discharge machining of the present invention obtained by the above method was used as a sample No. It was set to 1.
[0020]
Next, the sample no. The sample of No. 1 was mounted as an electrode for electric discharge machining on a die sinking electric discharge machine “DIAX-V35FH” manufactured by Mitsubishi Electric Corporation, and a cemented carbide having a composition of WC-3% by weight Co was processed. The processing conditions were the same as the processing machine processing condition pack “No. 0053 (for cemented carbide processing)” shown in Table 1. The processing was evaluated by drilling a counterbore hole 20 mm deep from the center of the end face of the cemented carbide having a shape of φ30 mm × 50 mm as shown in FIG. 2 and measuring the volume of the consumed electrode.
[0021]
[Table 1]

[0022]
Sample No. When this experiment was performed on one sample, the volume of the consumed electrode was 18.1 mm ³ .
[0023]
Next, the average particle diameter of the W raw material powder was set to 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 2.0 μm, 2.5 μm, and 5 μm, and electrodes were prepared in the same process. . No. 2 to sample no. And 8. Further, boron, SrB ₂ O ₄ , and TiB ₂ each having an average particle diameter of 1 μm and 0.5% of W were sufficiently mixed with the W raw powder, and a sample obtained in the same process as Sample No. 7 to sample no. It was set to 9. Further, the sample No. Sample No. 8 was prepared by changing the amount of SrB ₂ O ₄ added to 0.01%, 0.05%, 1%, 5%, 10%, and 15%, respectively. 16, sample no. 10 to sample no. 13 and sample no. Sample No. 17 using these. The same test as in Example 1 was performed, and the electrode consumption volume was measured. The results shown in Table 2 were obtained. The electrode consumption ratio was calculated by dividing the electrode consumption volume by the machining volume of the cemented carbide, and is also shown in Table 2.
[0024]
[Table 2]

Sample No. in Table 2 The numbers marked with * are comparative samples outside the scope of the present invention.
From the results in Table 2, Sample No. No. 1 to No. 1 The electric discharge machining electrode having an average particle diameter of W of 2.0 μm or less in the range of the present invention shown in FIG. 14, sample no. As compared with those having an average particle diameter of more than 2.0 μm shown in FIG. 15, the electrode consumption ratio was small, and it was found that a long life was obtained. In particular, those having a W average particle size of 0.5 μm or less had a small electrode consumption ratio.
[0026]
Next, the sample no. 7 to sample no. From the result of No. 13, by adding 0.05% to 10% of boron, boride and boride to the Cu-W based composite material, Cu-W composite material containing no boron, boride and borate was obtained. Also, a lifespan could be obtained. Further, the sample No. From the results of No. 16, those containing less than 0.05% of boron, boride, and borate showed no effect of the addition, and the effect was similar to that of the Cu-W composite material. Further, the sample No. According to the results of No. 17, those containing more than 10% of boron, boride and boride cannot obtain a sufficiently dense composite material by sintering, and cannot obtain a desired life and a desired processing speed. Was also rough.
[0027]
By using the electrode for electric discharge machining having a low consumption rate and a long life according to the present invention for electric discharge machining, the life of the electric discharge machining which can be performed with high accuracy is extended. It has been found that the electrode for electric discharge machining of the present invention is also suitable for precision machining.
Further, since the electrode has a long life, not only the cost for the electrode is reduced, but also the labor cost for replacing the electrode is reduced, and the economic effect is large.
[0028]
Example 2
A W powder having a purity of 99.9% and an average particle diameter of 1.0 μm was subjected to a die press at 300 kgf / cm ² to obtain a pressed body. The pressed body was heated to 1400 ° C. in a reducing atmosphere in hydrogen to obtain a so-called temporary sintered body of W where necking between particles occurred.
The size of the temporary sintered body was a cylindrical shape of φ3.5 mm × 35 mm.
Next, the pre-sintered body and the powder embedded in 50 g of copper having a purity of 99.9% are heated to 1200 ° C. higher than the melting point of copper in a reducing atmosphere in a hydrogen gas in a state of being buried in 50 g of copper having a purity of 99.9%. Was infiltrated. The composition of the Cu-W based composite material after infiltration was W at 80% by weight and Cu at 20% by weight.
[0029]
After cooling, excess copper that could not be completely infiltrated was removed with sandpaper, processed using a cylindrical grinder and a surface grinder, and processed into a desired cylindrical electrode shape (φ3.0 mm × 30 mm). The electrode for electrical discharge machining of the present invention obtained by the above method was used as a sample No. It was set to 1.
Next, the sample no. The composition ratio of 1 to W and Cu is changed by adjusting the heat treatment temperature of W and the pressure at the time of pressing the mold, and W is 98% by weight, 95% by weight, 90% by weight, 70% by weight, 60% by weight, 50% by weight. % And 40% by weight, the balance being Cu. 21 to Sample No. 27.
Further, a sample having an average particle diameter of W of 1 μm and containing 5% of any of boron, SrB ₂ O ₄ , and TiB ₂ and changing the composition ratio of W and Cu to the composition shown in Table 4 was used as a sample. No. 30 to sample no. 43.
Further, a sample having an average particle diameter of W of 1 μm and adding 5% of two or more of boron, SrB ₂ O ₄ , and TiB ₂ and changing the composition ratio of W and Cu to the composition shown in Table 5 was used. , Sample No. 51 to sample no. 54.
These sample Nos. 1, sample no. 21 to sample no. 27, sample no. 30 to sample no. 43, sample no. 51 to sample no. An electrical discharge machining experiment was performed on 54 samples under the same processing machine and the same conditions as in Example 1, and the electrode consumption rate and the processing speed at that time were obtained.
Tables 3, 4, and 5 show the composition of the sample, the electrode wear rate, and the processing speed in this experiment.
[0030]
[Table 3]

All of the samples in Table 3 have a W average particle size of 1.0 μm.
In Table 3, sample No. The numbers marked with * are comparative samples outside the scope of the present invention.
[0031]
[Table 4]

In Table 4, the W average particle size of all the samples is 1.0 μm.
In Table 4, sample No. The numbers marked with * are comparative samples outside the scope of the present invention.
[0032]
[Table 5]

The composition of W and Cu of all the samples in Table 5 is 80% of W content and 20% of Cu content.
[0033]
From the results shown in Table 3, with respect to the electrode for electric discharge machining composed of a Cu—W-based composite material having an average particle diameter of W of 2 μm or less, there is a composition ratio of Cu and W suitable for obtaining a machining speed, and the composition is It turned out that Cu is 5 to 40 weight% and the balance is W. Further, from the results in Table 4, the composite material containing 5 to 40% by weight of Cu to which 0.05 or more of boron, boride, or boride of 0.05 to 10% is added, and the balance being W is similarly processed. Speed could be increased. Furthermore, from the results in Table 5, it was found that those containing two or more of boron, boride, and borate also had the same effect.
[0034]
【The invention's effect】
By performing the electric discharge machining using the electrode for electric discharge machining of the Cu-W based composite material of the present invention, a longer life can be obtained than the conventionally used electrode, and a more accurate machining can be performed for a longer time. Accuracy and cost reduction. In addition, the processing speed could be increased.
[Brief description of the drawings]
FIG. 1 is a schematic view of an arc discharge in electric discharge machining. FIG. 2 is a perspective view showing a shape of a workpiece used in an electric discharge machining test and a shape of a processed portion.
DESCRIPTION OF SYMBOLS 1 Electric discharge machining electrode 2 Workpiece 3 Projection, arc generating part (workpiece side)
4 Projection, arc generating part (electrode side)
5 Arc 6 Workpiece (made of cemented carbide)
7 Workpiece

Claims

An electric discharge machining electrode comprising a Cu-W composite material containing 5 to 40% by weight of Cu and having an average particle diameter of W of 2 μm or less.

At least one of boron, boride and boride is added so that the percentage by weight of the additive to the weight of the Cu-W-based composite material is 0.05 to 10%. An electrode for electrical discharge machining according to claim 1.