JP2015231642A - Electrolytic processing method and electrolytic processing device for hard metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic processing method for hard metal, capable of preventing Co elution on a part where it contacts an electrolyte during electrolytic processing, and preventing Co elution on a processed surface, in Co ion addition to the electrolyte.SOLUTION: When the hard metal is subjected to electrolytic processing, as an electrolytic processing solution, a solution mainly formed of salt water or nitric acid soda solution, is used. Cobalt ion is added to the electrolytic processing solution, and during electrolytic processing, flushing is performed so that the electrolyte is circulated between an electrode and workpiece. A charge amount of current in which the electrode is a negative electrode is larger than a charge amount of current in which the electrode is a positive electrode.

Description

  The present invention relates to electrolytic machining of cemented carbide.

A cemented carbide is a material obtained by sintering tungsten carbide (WC) and cobalt (Co) as a binder, and titanium carbide (TiC), tantalum carbide (TaC) and the like are often added as components. Cemented carbide is a material having high hardness and high wear resistance, and conventionally, electric discharge machining has often been used for shape machining.
In the case of machining by electric discharge machining, in rough machining, the roughness when obtaining the maximum machining speed of 1 gr / min is about 50 μm Rz, and the consumption ratio of the copper-tungsten electrode is about 15%. There are also cracks. In order to reduce the generation of cracks, even if the processing speed is reduced to about 0.2 gr / min, the finished surface roughness is 10 μmRz to 20 μmRz and the electrode wear ratio is about 15%.
If the finished surface roughness is 4 μm Rz, the processing speed is 0.05 g / min at the maximum, and the electrode wear ratio is 15% or more. However, at that time, EDM was used for shape machining of cemented carbide, and even if cracks were generated in EDM, the machining speed was significantly reduced to reduce cracks, and cracks were further removed by polishing work. It was removed and used as a product.

  In recent years, shape processing by cutting has been attempted. There are also some research announcements that machining of cemented carbide is possible with cutting, but the tool edge is very worn, especially at the roughing stage where rough shapes are processed, and it is still difficult to be economically viable There is. In high-speed cutting and medium machining, there is a problem that machining conditions such as cutting and feeding cannot be increased due to tool wear, and the machining time is long. At the current machining speed, it takes many times longer than electric discharge machining. Grinding and grinding using an electrodeposition tool have been tried as well as cutting, but have similar problems.

  On the other hand, electrolytic processing has been studied several decades ago (see, for example, Non-Patent Document 1, Patent Document 1, and Patent Document 2). In electrolytic machining, the electrode consumption is almost zero, the machining speed of the region (3-4 μmRz) with a fine finished surface roughness is high, and there is no cracking of the machining surface as in electric discharge machining. Even when the machining speed of the electrolytic machining was carried out around 1967, the machining speed when obtaining a surface roughness of 3 to 4 μm Rz was as extremely high as 2 g / min. (Fig. 1 and Fig. 2)

Yuedo Maeda, Nagao Saito, Yuichiro Haishi, "Mitsubishi Electric Technical Review" Vol. 41, No. 10 (1967) 1272-1279 Japanese Patent Publication No.41-1086 Japanese Patent Publication No.41-1087

  In this way, it has extremely excellent processing characteristics, but has a large drawback and has not been put into practical use until now. The disadvantages are that the electrolytic processing fluid changes in quality as processing progresses, making it impossible to continue processing, there is a safety problem that generates chlorine gas, and a method for treating chemically changed sludge generated by processing is established. It was not recognized at the time, and quality degradation due to elution of cobalt (Co), which is a constituent component of cemented carbide, caused by immersing the cemented carbide in the electrolytic processing liquid.

  As described above, the electrolytic processing technology at that time was not yet mature as an industrial product, although research results were obtained. The problem will be described in detail below, but before that, a description will be given of the electrolytic processing technology of cemented carbide at that time.

  It will be described below what kind of electrochemical reaction the cemented carbide is processed. Some cemented carbides are mainly composed of WC and Co and include TiC and TaC. It describes what kind of electrochemical reaction each component is eluted and removed. The electrolyte is assumed to use NaCl aqueous solution or NaCl + NaOH aqueous solution.

First, let us look at the reaction of tungsten carbide (WC), the main component of cemented carbide. When cemented carbide is used as the positive electrode, the surface is anodized to produce a blue-blue film. This is WO ₃ produced by oxidation of WC. Then, when the cemented carbide is used as the negative electrode, WO ₃ comes into contact with Na ions, so that gas is vigorously generated from the surface, that is, WO _3, and the background color of the cemented carbide is obtained. This reaction is represented by the following chemical formula.
(Anode) WC + 9/2 [O] → WO ₃ + 1 / 2CO + 1 / 2CO _2- (1)
(Cathode) WO ₃ + 2NaOH → Na ₂ WO ₄ + H ₂ O ― (2)
The electrolytic machining fluid can be processed by replacing NaNO ₃ instead of NaCl.

Next, elution of cobalt (Co) will be described. Since Co is a normal metal, it reacts and elutes as follows when the cemented carbide is a positive electrode.
^{Co + 2Cl - -2e - → CoCl} 2 - (3)
CoCl ₂ is soluble in water. CoCl ₂ reacts with water (H ₂ O) in the electrolyte after several hours, releases Co (OH) ₂ , releases Cl, reacts with Na ions, and NaCl. Is produced.

Next, elution of titanium carbide (TiC) will be described. TiC is thought to elute by the following chemical reaction.
(Anode) TiC + 7/2 [O] → TiO ₂ + 1 / 2Co + 1 / 2Co ₂ ― (4)
(Cathode) TiO ₂ + 2H ₂ O → Ti (OH) _2- (5)
This series of chemical reaction formulas are reaction formulas that are assumed by examining reaction products by analysis or the like based on experiments. There is a TiCl ₂ process for the chemical reaction of TiO ₂ with Ti (OH) ₂ .
In the case of tantalum carbide (TaC), it is considered that the reaction is similar to that in the case of TiC.
In addition, as the electrolytic processing liquid, it is assumed that a NaCl aqueous solution is basically added and NaOH is added thereto. However, when sodium nitrate (NaNO ₃ ) is used, NO ₃ may be replaced instead of Cl.

  The problem in the electrolytic processing of cemented carbide has not been discussed much, but cobalt (Co), which is a constituent of cemented carbide, is selectively eluted and the strength of the material is reduced. It means that it cannot withstand use as a mold. FIG. 3 is a photograph of the surface of the cemented carbide when the cemented carbide is left immersed in water (rather than electrolytic processing) for about 8 hours. This photo was conducted as a test to investigate the problems of wire electrical discharge machining. The immersion liquid was water, and although the elution of Co was less than that of the electrolyte, Co was removed and the material was removed. It turns out that it has deteriorated. (However, in the current wire discharge, technology to suppress the elution of cobalt has been developed, and cobalt does not elute in this way.) Many cemented carbide users use cemented carbide as a conductive liquid. Don't forget that you have an aversion to touching.

In general, an aqueous solution such as NaCl or NaNO ₃ is used as an electrolytic solution for electrolytic processing. Non-Patent Document 1 shows that WC (WO ₃ ) can be eluted by using an electrolytic solution containing NaOH. However, in order to avoid NaOH in handling, an electrolytic solution mainly composed of NaCl is used. It has also been proposed to process hard alloys.
When performing electrolytic machining, it is of course important that there is no quality degradation of the machined surface, but it is also important that there are parts that come into contact with the electrolyte even if it is not a direct machining surface, and there is no quality degradation of those parts. It is. First, an immersion test was conducted using NaCl and NaOH as an electrolyte solution as an investigation of the influence on the portion other than the processed surface that touches the electrolyte solution. NaOH was used because the reaction of Co eluting with NaCl solution
_{H 2 O + 1 / 2O 2} + 2e - → 2OH -
Co → Co ²⁺ + 2e ^{-
_{(Co + 2Cl - → CoCl 2}} + 2e -)
This is because it was thought that the increase of OH ⁻ could prevent the elution of Co. FIG. 4 is an SEM photograph of the surface of the cemented carbide when the cemented carbide is immersed in a solution of NaCl, NaOH, NaCl + NaOH for 18 hours. The solutions used are as shown in Table 1, and are (a) NaCl solution, (b) NaOH solution, (c) NaCl + NaOH solution (2: 1), and (d) NaCl + NaOH solution (1: 2). Cemented carbide (particle size: about 0.8 μm, WC: about 87 wt%, Co: about 13 wt%) (5 mm × 5 mm × 30 mm) was immersed in 100 ml of the solution for 18 hours. The test piece was finished with a diamond paste after dry polishing a 5 mm × 5 mm surface with abrasive paper. Since it is not a material that has been subjected to HIP processing, fine voids exist. For comparison, a photograph of the cemented carbide as-polished is shown in (o). The SEM observation is a polished 5 mm × 5 mm surface. A photograph when immersed in the same solution for 110 hours is shown in FIG.
FIG. 4 shows that when the cemented carbide is immersed in a NaCl solution, only Co is selectively eluted without applying a voltage. On the other hand, in the case of NaOH solution, it can be seen that the Co elution phenomenon is suppressed. Furthermore, even in the case of NaCl + NaOH solution, Co elution seems to be suppressed. However, in the immersion test for a long time, the black part increases in the SEM photograph of the surface, and it seems that Co elution occurs. FIG. 6 shows the result of elemental analysis on the polished surface, and FIG. 7 shows the result of elemental analysis on the surface shown in FIG. Co appears to elute.
The surface of the test piece immersed in the NaCl solution for a long time was discolored and SEM observation was not successful. Although it appears that the deposit is on the surface, it is not well understood.
The NaOH solution, which is an extreme case as an electrolytic solution, seems to suppress the elution phenomenon of Co, but there is a possibility that Co cannot be electrolytically processed, and there is a problem in terms of hygiene. It is desirable to use an electrolyte that is not a NaOH-based solution to prevent selective elution of Co.
Table 1 Solution for immersion test

  The object of the present invention is to solve these problems of electrolytic processing technology of cemented carbide and establish processing technology with high quality and high accuracy at high speed.

Although the description so far has been made with respect to the electrolytic processing liquid containing NaCl as a main component, the same discussion can be made with other electrolytic processing liquids such as NaNO ₃ . The same immersion test (18 hours) was performed with a NaNO ₃ aqueous solution, which is a common component of the electrolytic solution. The result is shown in FIG. As in the case of using the NaCl aqueous solution, it is observed that Co on the cemented carbide surface is eluted.

According to a first aspect of the present invention, there is provided a method of electrolytic machining a cemented carbide comprising: a cemented carbide that is a workpiece by applying a voltage between the electrode and the cemented carbide that is the workpiece and applying a voltage to the electrode as a negative electrode. Tungsten carbide (WC), which is a component, is anodized to form tungsten oxide (WO ₃ ), and at the same time, cobalt (Co) is electrolytically eluted. In the machining of cemented carbide, where tungsten oxide (WO ₃ ) is chemically dissolved, the main component is saline (NaCl aqueous solution) or sodium nitrate aqueous solution (NaNO ₃ ) as the electrolytic machining fluid By adding cobalt ions (Co ²⁺ ) to the electrolytic processing solution using an aqueous solution, cobalt (Co), which is a constituent component, from the cemented carbide contacted with the electrolytic processing solution during and after electrolytic processing is electrolytically processed. In liquid It is characterized in preventing the phenomenon of elution.

According to a second aspect of the present invention, there is provided a method of electrolytic machining a cemented carbide which is a workpiece by applying a voltage between the electrode and a cemented carbide which is a workpiece and applying a voltage to the electrode as a negative electrode. Tungsten carbide (WC), which is a component, is anodized to form tungsten oxide (WO ₃ ), and at the same time, cobalt (Co) is electrolytically eluted. In the machining of cemented carbide, where tungsten oxide (WO ₃ ) is chemically dissolved, the main component is saline (NaCl aqueous solution) or sodium nitrate aqueous solution (NaNO ₃ ) as the electrolytic machining fluid Using an aqueous solution, cobalt ions (Co ²⁺ ) are added to the electrolytic processing solution, and during the electrolytic processing, flushing is performed so that the electrolytic solution circulates between the electrode and the workpiece,
It is characterized in that the charge amount of the current flowing with the electrode as the negative electrode is made larger than the charge amount of the current flowing with the electrode as the positive electrode.

  According to the present invention, in the electrolytic processing of cemented carbide, by adding Co ions to the electrolytic solution, it prevents Co elution at the part that touches the electrolytic solution during electrolytic processing, and prevents Co elution from the processed surface. And both.

It is explanatory drawing which shows the example of a process of the conventional electrolytic process. It is explanatory drawing which shows the example of a process of the conventional electrolytic process. It is a figure explaining the problem of Co elution of a cemented carbide. It is the photograph of the cemented carbide immersed in electrolyte solution. It is the photograph of the cemented carbide immersed in electrolyte solution. Elemental analysis of polished cemented carbide. It is an elemental analysis of the cemented carbide immersed in electrolyte solution. Is a photograph of dipping the cemented carbide in the electrolyte solution (NaNO _3). It is the photograph of the cemented carbide immersed in the electrolyte solution which added Co ion. It is an elemental analysis of the cemented carbide immersed in the electrolyte solution which added Co ion. It is explanatory drawing of an electrolytic processing apparatus. It is explanatory drawing of the waveform of an electrolytic processing apparatus. It is a photograph of the bipolar processing result in NaCl solution. It is a photograph of the bipolar processing result in NaCl solution. It is the photograph of the bipolar processing result in NaCl + NaOH solution. It is a photograph of the bipolar processing result in NaCl solution. It is the elemental analysis of the bipolar processing result in NaCl solution. It is a photograph of the bipolar processing result in the NaCl solution which added Co ion. It is an elemental analysis of the bipolar processing result in the NaCl solution which added Co ion.

それぞれの溶液に110時間浸漬した試験片の表面SEM写真を図９に示す。また、図９（１）（２）の試験片表面の元素分析の結果を図１０に示す。SEM写真からも元素分析結果からもCo量が減少しておらず、Coの溶出が抑えられているように見える。図９（２）（３）の表面は荒れて見えるが、図１０（２）からCl元素が検出されており、CoCl₂が表面に付着したものと考えられる。（元素分析の際に同定する元素からClは除外している。）
SEMによる観察結果と表面の元素分析とからの結果ではあるが、電解液中のCo²⁺濃度を上げることで、電解液に触れた超硬合金からのCoの溶出を防止できることがわかった。Coの溶出を抑制するために必要なCo²⁺濃度は他の溶液を用いた浸漬試験から極微量でよいことがわかり、約0.1wt%程度から効果があり、できれば、約0.5wt%以上であるのが望ましいようである。 Embodiment 1 FIG.
Co elution
Co → Co ²⁺ + 2e ^{-
_{(Co + 2Cl - → CoCl 2}} + 2e -)
^{(2H + + 2e - → H} 2)
It is considered that the elution of Co can be suppressed by increasing the Co ²⁺ concentration in the electrolytic solution. Therefore, the immersion test was performed by adding CoCl ₂ to the NaCl solution. Table 2 shows photographs of the solutions used later. (The weight of CoCl _{2 is} the weight of hexahydrate)
Table 2 Solutions for immersion test

The surface SEM photograph of the test piece immersed in each solution for 110 hours is shown in FIG. Moreover, the result of the elemental analysis of the test piece surface of FIG. 9 (1) (2) is shown in FIG. From the SEM photograph and the elemental analysis results, the amount of Co does not decrease, and it seems that the elution of Co is suppressed. Although the surfaces of FIGS. 9 (2) and 9 (3) appear rough, it is considered that Cl element was detected from FIG. 10 (2) and CoCl ₂ was adhered to the surface. (Cl is excluded from the elements identified during elemental analysis.)
Although it is a result from the observation result by SEM and the elemental analysis of the surface, it was found that elution of Co from the cemented carbide contacted with the electrolytic solution can be prevented by increasing the Co ²⁺ concentration in the electrolytic solution. From the immersion test using other solutions, it is clear that the Co ²⁺ concentration required to suppress the elution of Co is very small and is effective from about 0.1 wt%. It seems to be desirable.

Embodiment 2. FIG.
FIG. 11 shows a schematic diagram of the machining apparatus, and FIG. 12 shows an example of voltage / current waveforms between the electrode and the workpiece (hereinafter referred to as “between the electrodes”). The machining apparatus is connected to power sources E1 and E2 so that a voltage can be applied between the electrode 1 and the workpiece 2 so that a current can flow. The machining tank 4 stores the electrolytic machining liquid 3 in the electrolytic machining liquid 3. The work piece 2 is fixed to. The power supply E1 applies a positive voltage to the workpiece 2 and the power supply E2 applies a negative voltage. The ON / OFF timing of the switching elements (FET) SW1 and SW2 is controlled by a control circuit (not shown). The time for applying a positive voltage to the electrode 1, the time for applying a negative voltage, and the time for not applying a voltage can be determined by turning ON / OFF the switching elements SW1 and SW2. Here, a time during which no voltage is applied is not provided, and a plus voltage and a minus voltage are alternately applied using a function generator. (In the DC machining test, a positive workpiece voltage was applied continuously.)

In the processing test, a beaker was used as a processing tank, a 200 ml water and solute mixed solution was put into the beaker, and a cemented carbide of 5 mm x 5 mm x 30 mm dimensions was fixed upright in a steel jig. Soaked. The electrode used was 30 mm × 30 mm Gr. Here, we focused on only the Co elution phenomenon during the machining of cemented carbide, so the distance between the electrodes was set to about 1 mm, and the electrode / workpiece was fixed and machining was performed without feeding the electrode. Liquid flushing is not performed. Each condition was processed for 10 minutes.
The method of electrolytic processing of cemented carbide is based on the method of Non-Patent Document 1. The processing principle uses the following reaction as described in Non-Patent Document 1, Non-Patent Document 2, and the like. That is, if the electrode has a negative polarity,
On the anode side
^{Co + 2Cl - -2e - → CoCl} 2
_{^{2OH - -2e - → H 2 O}} + [O]
WC + 9/2 [O] → WO ₃ + 1 / 2CO + 1 / 2CO ₂
On the cathode side
2H ^{+ +} 2e ^- → H ₂
When the polarity of the electrode is positive,
WO ₃ + 2NaOH → Na ₂ WO ₄ + H ₂ O
2Cl ^- -2e ^- → Cl ₂
It becomes. That is, Co, which is a component of cemented carbide, is a pure electrolytic phenomenon, and WC is oxidized to WO ₃ and then dissolved in alkali.
By Nao Kurato, "Electrochemical Processing, Journal of the Institute of Electrical Engineers of Japan" Vol.85-5, No.920, (1965) 743-747

次に表３の電解液を使用して、両極性電流により電解加工を行った（T1=10ms、T2=10ms）。図１３にNaCl溶液で電解加工を行った超硬合金の表面写真を示す。Coが優先的に除去されると予想したが、実際には、加工面には、Coが多く存在していた。この表面のCoは超硬合金のCoが溶出せずに残ったものではなく、電極がプラスの極性になった時に、
Co²⁺＋2e^- → Co
と、析出してきたものと考えられる。電解液にNaCl＋NaOHを使用した場合もほぼ同じような状況だった。これは、加工中にフラッシングをしていないことが原因と考えられ、本来の電解加工を行った場合の状況とは異なると考えられるが、一方で、超硬合金近傍の電解液中のCo²⁺イオン濃度が増したときには同様の現象が起きるということでもある。Co²⁺イオン濃度を高い状態にし、極性を制御することで、加工面のCoの溶出量を調整できる可能性があると考えることができる。図１４にNaCl溶液を用いて、T1=16ms、T2=4ms（Duty 80%）で加工を行った超硬合金の表面写真、図１５にNaCl＋NaOHで加工を行った超硬合金の表面写真を示す。工作物がプラスの極性の時間が長くなることで、Coの付着が抑えられている（Coの溶出が進んだ）ことがわかる。尚、図１３、１４、１５は加工した超硬合金（5mm×5mm）の中央付近の写真である。 Table 3 Types of electrolyte

Next, electrolytic processing was performed with a bipolar current using the electrolytic solution of Table 3 (T1 = 10 ms, T2 = 10 ms). FIG. 13 shows a surface photograph of a cemented carbide that has been electrolytically processed with a NaCl solution. Although Co was expected to be removed preferentially, in practice, there was a lot of Co on the machined surface. The Co on this surface is not a cemented carbide that remains without eluting, and when the electrode has a positive polarity,
Co ²⁺ + 2e ^- → Co
It is thought that it has precipitated. The situation was almost the same when NaCl + NaOH was used as the electrolyte. This is thought to be caused by the fact that no flashing was performed during processing, and is considered to be different from the situation when the original electrolytic processing was performed, but on the other hand, Co ^{2 in} the electrolyte near the cemented carbide ^{+ This} also means that the same phenomenon occurs when the ion concentration increases. It can be considered that the amount of Co elution on the processed surface may be adjusted by setting the Co ²⁺ ion concentration to a high level and controlling the polarity. FIG. 14 shows a surface photograph of a cemented carbide processed with a NaCl solution at T1 = 16 ms and T2 = 4 ms (Duty 80%), and FIG. 15 shows a surface photograph of a cemented carbide processed with NaCl + NaOH. . It can be seen that the adhesion of Co is suppressed (the elution of Co has progressed) as the time of the positive polarity of the workpiece becomes longer. FIGS. 13, 14 and 15 are photographs of the vicinity of the center of the processed cemented carbide (5 mm × 5 mm).

When actually performing electrolytic processing, since the electrolytic solution flows between the electrodes, it is considered that the Co ²⁺ ion concentration between the electrodes does not increase as in the case of these tests. FIG. 16 shows a photograph observing the vicinity of the edge of the processed surface of a workpiece that is considered to have a relatively low Co ²⁺ ion concentration during processing, and FIG. 17 shows the result of elemental analysis. It can be seen that the state is different between the central part and the edge part. Furthermore, it can be seen that the amount of Co is reduced (Co is selectively eluted) at the edge portion. Similar trends were seen for workpieces using other electrolytes. This state is considered to be close to the original electrolytic processing state, that is, the state in which the electrolyte solution is sufficiently flushed. That is, when a cemented carbide is electrolytically processed using an electrolytic solution mainly composed of NaCl, Co is likely to be selectively eluted. Next, it was confirmed whether or not the elution of Co in this portion could be suppressed by increasing the Co ²⁺ ion concentration in the electrolyte.

Electrolytic processing was performed using an aqueous solution obtained by adding 10 g of CoCl ₂ to an aqueous NaCl solution (water 200 ml, NaCl 30 g) as an electrolytic solution. FIG. 18 shows a photograph of a work edge portion similar to FIG. 16, and FIG. 19 shows the result of elemental analysis. FIG. 18 shows that the edge portion is different from the central portion as in FIG. 16, but FIG. 19 shows that the elution of Co is also suppressed in the edge portion. From this result, it was confirmed that the addition of Co ²⁺ ions can prevent the elution of Co, which was a concern in the processing of cemented carbide. Although the processing conditions used this time are Duty 80% (T1 = 16ms, T2 = 4ms) and Co is likely to elute, Co elution can be suppressed when aiming to increase the processing speed. This means that the choice of processing conditions is widened. In this experiment, NaOH was not added to the electrolytic solution. The fact that Co elution was prevented even in an alkaline environment could be said to have increased options in terms of safety. As in the first embodiment, the Co ²⁺ ion concentration is effective even in a small amount, but when processing is performed, the ratio of the electric charge flowing in each polarity and the Co ²⁺ ion concentration are affected. In other words, if the Co ²⁺ ion concentration is high, the selective elution of Co is not angry even if there is a large amount of charge flowing through the workpiece plus, but as the Co ²⁺ ion concentration decreases, the charge flowing through the workpiece plus increases. It is necessary to reduce gradually. In CoCl ₂ terms, in the case of more than about 0.5 wt%, the workpiece can be a positive flow in the charge larger than the charge flow in negative, i.e., if the current flowing in both polarities equal, the Duty 50 % Or more. This is because the electrolytic processing of cemented carbide has a positive polarity of the electrode, and Co elution (removal processing) and reaction to WO ₃ by anodic oxidation of WC lead to an increase in processing speed.

  The method of electrolytic machining of cemented carbide according to the present invention achieves both the prevention of Co elution at the part that touches the electrolytic solution during electrolytic machining and the prevention of Co elution on the machined surface by adding Co ions to the electrolytic solution. can do.

DESCRIPTION OF SYMBOLS 1 Electrode 2 Workpiece 3 Electrolytic machining fluid 4 Processing tank E1, E2 Power supply SW1, SW2 Switching element

Claims (3)

Tungsten carbide (WC), which is a component of cemented carbide, which is a workpiece, is anodized by applying a voltage between the electrode and the cemented carbide, which is the workpiece, and applying a current to the electrode as a negative electrode to produce tungsten oxide. (WO ₃ ) and electrolytically eluting cobalt (Co), applying a voltage with an electrode as a negative electrode and applying a current to chemically dissolve tungsten oxide (WO ₃ ) produced by anodization. In electrolytic machining of cemented carbide to be processed,
As an electrolytic processing solution, an aqueous solution mainly composed of saline (NaCl aqueous solution) or sodium nitrate aqueous solution (NaNO ₃ aqueous solution) is used.
By adding cobalt ions (Co ²⁺ ) to the electrolytic processing liquid,
A method of electrolytic processing of a cemented carbide comprising preventing a phenomenon that cobalt (Co) as a constituent component is eluted from the cemented carbide in contact with the electrolytic processing fluid during and after the electrolytic processing. . Tungsten carbide (WC), which is a component of cemented carbide, which is a workpiece, is anodized by applying a voltage between the electrode and the cemented carbide, which is the workpiece, and applying a current to the electrode as a negative electrode to produce tungsten oxide. (WO ₃ ) and electrolytically eluting cobalt (Co), applying a voltage with an electrode as a negative electrode and applying a current to chemically dissolve tungsten oxide (WO ₃ ) produced by anodization. In electrolytic machining of cemented carbide to be processed,
As an electrolytic processing solution, an aqueous solution mainly composed of saline (NaCl aqueous solution) or sodium nitrate aqueous solution (NaNO ₃ aqueous solution) is used.
Cobalt ions (Co ²⁺ ) are added to the electrolytic processing liquid,
During electrolytic machining, flushing is performed so that the electrolyte circulates between the electrode and the workpiece,
A method of electrolytic processing of a cemented carbide characterized in that the amount of electric charge flowing through an electrode as a negative electrode is larger than the amount of electric charge flowing through an electrode as a positive electrode. A power source for applying an alternating voltage between the electrode and a workpiece made of cemented carbide;
An electrolytic processing apparatus provided with a processing tank for storing an electrolytic processing solution obtained by adding cobalt ions (Co ²⁺ ) to a saline solution (NaCl aqueous solution) or a sodium nitrate aqueous solution (NaNO ₃ aqueous solution).

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