JPS58223527A - Electrode copper material for electrospark machining with high cutting property - Google Patents

Abstract

PURPOSE:To hold high conductivity while improving cutting property of an electrode by providing a structure having copper containing oxygen and fine dispersed copper oxide while tempering it for removing residual stress. CONSTITUTION:An electrode copper material has a structure containing 0.02- 0.05% by weight of oxygen and fine copper oxide uniformly dispersed so that it is not made brittle and the cutting property is improved. Also, since residual stress is removed, transformation does not occur. Further, it has at least 70 of Vicker's hardness and wear amount in electrospark machining is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel material with excellent machinability suitable for use as an electrode for electrical discharge machining.

Generally, pure steel is used for the electrode phase for electric discharge machining because high conductivity is required. However, this type of pure steel has a purity of 99.90% by weight (by the way, oxygen content is 0005-0015% by weight), a Vickers hardness of 65 or less (usually 50-60), and is soft. However, it is virtually impossible to perform cutting without light cutting, and therefore, it takes a considerable amount of time and skill to finish the desired electrode shape with good dimensional accuracy.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to obtain an electrode steel material for electrical discharge machining that has good machinability while having the high conductivity required for an electrode for electrical discharge machining. , copper is made to contain oxygen so that it has a structure in which fine copper oxide (mainly consisting of cuprous oxide) is uniformly dispersed, and is subjected to cold working and annealing to remove residual stress at a temperature just below the softening point. When the copper phase is applied to the surface and has a Vickers hardness of 70 or more, the resulting copper phase has excellent machinability while retaining technical strength, and is therefore suitable for electrical discharge machining electrodes. When used in the manufacturing of
It has been found that machining can be performed with good machinability and dimensional accuracy, and there is virtually no residual stress, so no deformation occurs.

Therefore, this invention has been made based on the findings described in 1. The present invention has a composition containing 0.02 to 0.05% oxygen by weight, the remainder being Cu and unavoidable impurities, and a composition in which fine copper oxide is uniformly distributed. The present invention is characterized by an electrode steel material for electric discharge machining that has a dispersed structure, has a Pinkers hardness of near 0 or more, and has excellent machinability in a state where there is substantially no residual stress.

In addition, in the electrode steel material for electric discharge machining of this invention, the oxygen content is limited to 0.02 to 0.05% by weight because if the content is less than 0.02%, precipitation of fine copper oxide is insufficient. On the other hand, if the content exceeds 0.05%, the machinability will further improve, but embrittlement will become significant and it will be difficult to obtain the desired excellent machinability during hot working of the ingot. This is because cracks are more likely to occur, and the reason why the Vickers hardness is set to near 0 or higher is to improve machinability due to the effect of the fine copper oxide mentioned above, and also to improve machinability during electrical discharge machining. Therefore, if the Vickers hardness is less than 70, satisfactory machinability cannot be obtained even if the precipitation of fine oxidized steel is sufficient.

Next, the electrode steel material for electrical discharge machining of the present invention will be specifically explained using Examples.

Example Using a low-frequency groove electric furnace, molten steel with the purity and oxygen content shown in Table 1 was prepared, and then cast by a continuous casting method at a temperature of about 1200 to ℃ to a thickness of 160 mm.
An ingot with the dimensions of x width: 370 g x length: 1400 mm is hot rolled at a temperature of approximately 900°C to form a hot rolled plate with a thickness of near 5 mm, in which case hot processing is applied. For the purpose of evaluating the properties, the presence or absence of cracks was observed, and then a portion of the hot-rolled sheet with no cracks was cold-rolled to obtain a plate thickness of 5.
A cold-rolled sheet having a thickness of 0 mm was prepared, and a portion of this cold-rolled sheet was held at a temperature of 250°C for 2 hours and then subjected to residual stress removal annealing by cooling in the atmosphere. Preparations 1 to 8 were each prepared.

Next, the electrical conductivity and Vickers hardness of the resulting steel materials 1 to 3 of the present invention and comparison steel materials 1 to 8 were measured, and a cutting test, a residual stress measurement test, and an electric discharge machining test were conducted.

In addition, the cutting test was performed using an outer diameter of 25. , using a φ drill,
Komei machined a test piece with a thickness of 50 mm without cutting oil, and allowed the chips generated at this time to fall naturally into a female cylinder with an inner diameter of 50 mm and a height of 200 mm. The volume (V) of the chips in the female cylinder is measured, and the weight (W) of the chips is also measured. Based on the measurement results, the following formula is calculated.

This is done by calculating η according to
The machinability was evaluated based on the value of (the smaller the value of η, the better the machinability).

In addition, in the residual stress measurement test, a circular saw with a blade width of 2 mm and a brazed high-speed steel tip was used to cut the specimen along the same direction as the rolling direction. As a result, an overload current flows to the motor. This was done by reading this phenomenon, and the current value when there was no tightening by the test piece was taken as a factor of 100, and the overload rate was evaluated based on this value. .

Furthermore, the electrical discharge machining test was performed using a thickness of 30mm x width.

A test piece of 30 mm x length: 50 mm was cut out, and this test piece was used as an electrode. Work material: commercially available tool steel plate with a plate thickness of 25 mm. Setting: Ip2. Setting °Fine adjustment, △Ip 5. Pulse: ON3. Pause: 0FF4. Servo voltage: 0. Current: 2A, Suction: 20-25CTLH/
The test was carried out under the following conditions, and the amount of wear of the electrode test piece was measured. These measurement results are also shown in Table 1.

As is clear from the results shown in Table 1, steel materials 1 to 3 of the present invention having an oxygen content of 0.02 to 0.05% by weight, a Vickers hardness of near 0 or more, and no residual stress, All of them have high electrical conductivity and excellent machinability, and have low wear amount even during electrical discharge machining. On the other hand, as seen in Comparative Steel Materials 1 to '8, even if any of the oxygen content, Vickers hardness, and residual stress are outside the scope of the present invention, it is still difficult to manufacture electrodes for electrical discharge machining. However, it does not show satisfactory results in terms of the above and characteristics.

In addition, Fig. 1 shows a photo of the microscopic structure of the copper material 3 of the present invention, and as shown in the figure, it has a structure in which fine copper oxide is uniformly dispersed and precipitated in a substrate, and this structure has an excellent structure. It is clear that good machinability is ensured.

As mentioned above, the steel of the present invention has excellent machinability, so when it is used to manufacture electrodes for electrical discharge machining, it can be processed into final products with high dimensional accuracy in a short machining time. and there is no residual stress, so
There is no dimensional change, therefore accurate dimensional accuracy is maintained, and it also has a high hardness of 70 or more Vickers hardness, so when used as an electrode, there is less wear and the service life is extended, making it an industrial choice. ”It has dual characteristics.

[Brief explanation of the drawing]

Figure 1 is a microscopic micrograph of the copper phase of the present invention (100x magnification). Applicant: Tamagawa Machinery & Metals Co., Ltd. Agent Tomi 1) Kazuo

Claims (1)

[Scope of Claims] It has a composition containing 0.02 to 0.05% oxygen by weight, the remainder consisting of CU and non-avoidable impurities, and a structure in which fine copper oxide is uniformly dispersed, and substantially Vickers hardness in the absence of residual stress. An electrode steel material for electric discharge machining with excellent machinability, characterized by having a hardness of 70 or more.