【発明の詳細な説明】[Detailed description of the invention]
本発明はワイヤーカツト放電加工用電極線の改
良に関するもので、特に製造が容易で放電加工特
性の優れた電極線を提供するものである。
ワイヤーカツト放電加工は、ワイヤー状電極と
被加工体との間で放電現象を起させ、該放電によ
り生ずる熱で被加工体を溶融切断するもので、複
雑な形状を有する金型のような工作物の連続加工
に適している。一般にワイヤーカツト放電加工に
おいては、工作物の仕上り表面状態及び寸法精度
が良好なこと、放電加工時間が短いことなどが要
求されている。これらを満足させるためには、ワ
イヤー状電極と被加工体の間で起る放電現象効率
を向上させる必要がある。従つて放電加工機の形
式と被加工体が指定されると、工作物の仕上り表
面状態、寸法精度及び放電加工時間は使用するワ
イヤー状電極によつて左右される。
即ち工作物の仕上り表面状態と寸法精度を向上
するためにはワイヤー状電極からの放電が均一
で、しかも安定していることが必要であり、かつ
ワイヤー状電極には放電中の消耗が少なく、しか
も均一に消耗することが要求される。また放電加
工速度を向上するためには、ワイヤー状電極の単
位体積あたりの放電量の向上、並びに放電加工中
にワイヤー電極が断線しないことが望まれてい
る。
従来このようなワイヤー状電極には、目的に応
じて硬銅線、7/3黄銅線、タングステン線などが
用いられている。しかしながら硬銅線及び7/3黄
銅線は工作物の表面状態、寸法精度及び電極とし
ての消耗の点で劣り、またタングステン線が製造
が困難なばかりか、コストが高い欠点があつた。
本発明はこれに鑑み種々検討の結果、Zn又は
ZnとAlを含有する銅合金製のワイヤー状電極表
面に酸化被膜を形成することにより放電加工特性
が一段と向上することを知見し、放電加工特性が
優れた製造が容易なワイヤーカツト放電加工用電
極線を開発したもので、Zn1〜40％又はZn1〜40
％とAl3％以下を含み、残部Cuからなる直径0.1
〜0.3mmの線状体表面に該線状体の酸化被膜を0.1
〜50μの厚さに形成したことを特徴とするもので
ある。
即ち本発明は、CuにZn又はZnとAlを添加した
合金を通常の方法により伸線加工して直径0.1〜
0.3mmの線状体となし、これを酸化性雰囲気中で
200〜600℃に１〜120分間加熱することにより、
該線状体の表面にCuとZn又はCuとZnとAlの酸化
被膜を0.1〜50μの厚さに形成したものである。Zn
又はZnとAlを含有するCu合金線状体を酸化雰囲
気中で加熱処理すると該線状体の表面にCuとZn
又はCuとZnとAlの酸化被膜が生成し、前記放電
特性を著しく向上するも、その厚さが0.1μ未満で
は効果がなく、50μを越えるとより以上の効果が
得られず実用的でない。
本発明において、Zn又はZnとAlを含有するCu
合金を用いた理由は、Znの添加により放電性が
向上し、工作物の仕上り表面状態の改善、更には
放電加工速度の向上に有効であり、またAlの添
加は、前記Znの添加による効果を低減すること
なく、線状体表面に形成した酸化被膜を均一化
し、付着性を向上し、更にはCuの酸化被膜中に
Zn又はZnとAlの酸化物が生成して放電加工特性、
特に放電加工速度を高めるためである。しかして
Zn含有量を１〜40％、Al含有量を３％以下とし
た理由はZn含有量が１％未満では、Znの添加に
よる前記効果が発揮されず、またZn含有量が40
％を超えても、Al含有量が３％を超えても加工
性が著しく低下し、電極線の製造が困難となるた
めである。
次に本発明の実施例について説明する。
黒鉛ルツボを用いて銅を溶解し、その湯面を木
炭粉末で被覆した状態でZnを添加した後、Alを
添加し、これを鋳造して第１表に示す組成の巾25
mm、厚25mm、長さ250mmの鋳塊を得た。
次にこの鋳塊の表面を一面あたり2.5mm面削し
てから熱間加工を加えて直径８mmの線となし、続
いて伸線加工と焼鈍を繰返して直径0.2mmに仕上
げ、これを大気中で400℃に60分間加熱して表面
に酸化被膜を形成したワイヤー状電極を製造し
た。
上記製造工程中の伸線加工の難易度を観察し、
得られた電極表面の酸化膜の厚さを測定すると共
に、電極を放電加工機に取付けて放電加工特性
（電極消耗及び加工速度）を調べた。これ等の結
果を第１表に併記した。
尚酸化膜の厚さは大気中400℃に60分間加熱し
たものを還元電位法により、Cu、Zn、Alの酸化
量を測定して求めた。また伸線加工の難易度は上
記製造工程において、直径８mmの線材約50Kgを直
径１mmまでの伸線加工と、直径１mmで中間焼鈍を
施してから直径0.2mmまでの伸線加工における断
線回数を計測し、かつ直径0.2mmの線材から長さ
５mmのサンプルを採取し、線表面の欠陥数を計測
し、断線回数が３回以下で表面欠陥が２個以下の
ものを良とし、それ以上のものを難とした。
また放電加工特性は上記ワイヤー状電極を放電
加工機（Fanuc−ModelE）に取付け、下記条件
で放電加工を行なつて調べた。
加工条件：コンデンサー容量 0.7μF
電 圧 150V
パルス巾（Ton／Off） 6/5μs
水 温 17℃
ワーク（SKD−11焼入、焼戻し材）厚さ 25mm
電 極 直径0.2mm、
張力700gr
電極消耗は放電加工後の電極の10ケ所からラン
ダムにサンプリングして顕微鏡観察を行ない、放
電加工前後における断面減少率と放電加工後の断
面減少の均一性を調べ、断面減少率が90％以上で
良好なものを〇印、断面減少率が90％未満のもの
を△印で示した。尚断面減少率Ｎは電極線の放電
加工前の断面積をA0、放電加工後の断面積をＡ
とすると
Ｎ＝A0−Ａ／A0×100
で表わした。
また加工速度は上記放電加工条件でテーブル送
り速度を0.5mm／分から0.1mm／分間隔にて増加さ
せ、電極線が断線又は短絡を生じて加工不能にな
る限界を求め、これを最大加工速度とし、これを
硬銅線の加工速度と比較して硬銅線の加工速度を
100としたときの値で示した。従つてこの値が大
きい程加工速度は大きいことになる。
The present invention relates to improvements in wire-cut electrode wires for electrical discharge machining, and in particular provides an electrode wire that is easy to manufacture and has excellent electrical discharge machining characteristics. Wire cut electrical discharge machining involves creating an electrical discharge phenomenon between a wire-shaped electrode and the workpiece, and melting and cutting the workpiece using the heat generated by the discharge. Suitable for continuous processing of objects. Generally, wire cut electric discharge machining requires that the finished surface condition and dimensional accuracy of the workpiece be good, and that the electric discharge machining time be short. In order to satisfy these requirements, it is necessary to improve the efficiency of the discharge phenomenon that occurs between the wire-shaped electrode and the workpiece. Therefore, once the type of electric discharge machine and the workpiece are specified, the finished surface condition, dimensional accuracy, and electric discharge machining time of the workpiece are influenced by the wire-shaped electrode used. In other words, in order to improve the finished surface condition and dimensional accuracy of the workpiece, it is necessary that the discharge from the wire-shaped electrode be uniform and stable, and the wire-shaped electrode has little wear during discharge. Moreover, it is required to wear out evenly. In order to improve the speed of electrical discharge machining, it is desired that the amount of electrical discharge per unit volume of the wire electrode be improved and that the wire electrode should not be disconnected during electrical discharge machining. Conventionally, hard copper wire, 7/3 brass wire, tungsten wire, etc. have been used for such wire-shaped electrodes, depending on the purpose. However, hard copper wire and 7/3 brass wire are inferior in terms of the surface condition of the workpiece, dimensional accuracy, and wear as an electrode, and tungsten wire is not only difficult to manufacture, but also has the disadvantage of being high in cost. In view of this, as a result of various studies, the present invention has been developed based on Zn or
It was discovered that the electric discharge machining characteristics were further improved by forming an oxide film on the surface of a wire-shaped electrode made of a copper alloy containing Zn and Al, and the wire-cut electric discharge machining electrode has excellent electric discharge machining characteristics and is easy to manufacture. Zn1~40% or Zn1~40
% and less than 3% Al, with the balance being Cu, with a diameter of 0.1
~0.3mm oxide film of the linear body on the surface of the linear body
It is characterized by being formed to a thickness of ~50μ. That is, in the present invention, an alloy containing Cu and Zn or Zn and Al is wire-drawn by a conventional method to form a wire with a diameter of 0.1 to
A 0.3mm linear body is made into an oxidizing atmosphere.
By heating to 200-600℃ for 1-120 minutes,
An oxide film of Cu and Zn or Cu and Zn and Al is formed on the surface of the linear body to a thickness of 0.1 to 50 μm. Zn
Alternatively, when a Cu alloy linear body containing Zn and Al is heat-treated in an oxidizing atmosphere, Cu and Zn are formed on the surface of the linear body.
Alternatively, an oxide film of Cu, Zn, and Al is formed, which significantly improves the discharge characteristics, but if the thickness is less than 0.1 μm, there is no effect, and if it exceeds 50 μm, no further effect can be obtained and it is not practical. In the present invention, Cu containing Zn or Zn and Al
The reason for using the alloy is that the addition of Zn improves the electrical discharge performance, which is effective in improving the finished surface condition of the workpiece and further increasing the electrical discharge machining speed, and the addition of Al improves the effect of the addition of Zn. It uniformizes the oxide film formed on the surface of the linear body, improves adhesion, and even improves the adhesion of the Cu oxide film without reducing the
Zn or oxides of Zn and Al are generated to improve electrical discharge machining properties.
This is especially to increase the electrical discharge machining speed. However
The reason for setting the Zn content to 1 to 40% and the Al content to 3% or less is that if the Zn content is less than 1%, the effect of adding Zn will not be exhibited, and if the Zn content is 40% or less,
This is because even if the Al content exceeds 3%, the workability is significantly reduced and it becomes difficult to manufacture electrode wires. Next, examples of the present invention will be described. Copper is melted using a graphite crucible, the surface of the melt is coated with charcoal powder, Zn is added, Al is added, and this is cast to form a product with the composition shown in Table 1.
An ingot with a thickness of 25 mm and a length of 250 mm was obtained. Next, the surface of this ingot is milled by 2.5 mm per side, then hot worked to create a wire with a diameter of 8 mm, followed by repeated wire drawing and annealing to a diameter of 0.2 mm, and this is placed in the air. A wire-shaped electrode with an oxide film formed on the surface was manufactured by heating it to 400°C for 60 minutes. Observing the difficulty of wire drawing during the above manufacturing process,
The thickness of the oxide film on the surface of the obtained electrode was measured, and the electrode was attached to an electrical discharge machine to examine electrical discharge machining characteristics (electrode wear and machining speed). These results are also listed in Table 1. The thickness of the oxide film was determined by heating the film at 400°C for 60 minutes in the air and measuring the amount of oxidation of Cu, Zn, and Al using the reduction potential method. In addition, the difficulty of wire drawing is determined by the number of wire breaks during the above manufacturing process: drawing approximately 50 kg of wire with a diameter of 8 mm to a diameter of 1 mm, and after performing intermediate annealing at a diameter of 1 mm, drawing the wire to a diameter of 0.2 mm. A sample of 5 mm in length was taken from a wire with a diameter of 0.2 mm, and the number of defects on the wire surface was measured. If the number of breaks was 3 or less and the surface defects were 2 or less, it was considered good. made things difficult. Further, the electric discharge machining characteristics were investigated by attaching the above wire-shaped electrode to an electric discharge machine (Fanuc-Model E) and performing electric discharge machining under the following conditions. Processing conditions: Capacitor capacity 0.7μF Voltage 150V Pulse width (Ton/Off) 6/5μs Water temperature 17℃ Workpiece (SKD-11 quenched and tempered material) Thickness 25mm Electrode diameter 0.2mm, tension 700gr Electrode wear is caused by discharge Random samples were taken from 10 locations on the electrode after machining and microscopic observation was conducted to examine the area reduction rate before and after electrical discharge machining and the uniformity of the area reduction after electrical discharge machining. Those with a cross-sectional reduction rate of less than 90% are marked with a △ mark. The cross-sectional area reduction rate N is the cross-sectional area of the electrode wire before electric discharge machining is A 0 , and the cross-sectional area after electric discharge machining is A 0
Then, it is expressed as N=A 0 −A/A 0 ×100. In addition, the machining speed is determined by increasing the table feed rate from 0.5 mm/min to 0.1 mm/min at intervals of 0.1 mm/min under the above electric discharge machining conditions to determine the limit at which the electrode wire becomes disconnected or short-circuited and machining becomes impossible, and this is set as the maximum machining speed. , compare this with the machining speed of hard copper wire to determine the machining speed of hard copper wire.
The value is shown when it is set to 100. Therefore, the larger this value is, the higher the machining speed is.
【表】
第１表からも判るように、本発明電極No.１〜10
はいずれも製造（伸線加工）が容易で、しかも放
電加工特性は従来電極に比較し、はるかに優れて
いる。
これに対しZn含有量が少ない比較電極No.11、
No.15は放電加工特性の改善が全く認められず、か
えつて劣化している。またZn又はZnとAlの含有
量が多い比較電極No.12〜14はいずれも伸線加工が
困難なため、放電加工特性を調べることができな
かつた。
また本発明の電極の合金組成範囲内の電極であ
つても、表面に酸化膜を形成しない比較電極No.
16、17では加工速度の向上が望めないことが判
る。
このように本発明電極線は、製造が容易で、か
つ放電加工特性が優れている等顕著な効果を奏す
るものである。[Table] As can be seen from Table 1, the present invention electrodes No. 1 to 10
Both of these electrodes are easy to manufacture (wire drawing), and their electrical discharge machining properties are far superior to those of conventional electrodes. In contrast, comparative electrode No. 11, which has a low Zn content,
No. 15 showed no improvement in electrical discharge machining characteristics, and on the contrary, it deteriorated. Furthermore, it was not possible to examine the electrical discharge machining characteristics of comparative electrodes Nos. 12 to 14, which had a high content of Zn or Zn and Al, because wire drawing was difficult for all of them. Moreover, even if the electrode is within the alloy composition range of the electrode of the present invention, comparative electrode No. 1 does not form an oxide film on the surface.
16 and 17, it can be seen that no improvement in machining speed can be expected. As described above, the electrode wire of the present invention has remarkable effects such as being easy to manufacture and having excellent electrical discharge machining characteristics.