JPH0428780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal material that is inexpensive and suitable for use as a wire electrode material for a wire-cut electrical discharge machining device, which can be machined with high precision at a processing speed comparable to that of conventional materials.

Wire-cut electric discharge machining equipment generates an electrical discharge between a wire electrode and a workpiece, and cuts the workpiece using the heat and shock generated by the discharge. Particularly suitable for machining workpieces.

Generally, in wire cut electrical discharge machining, the surface finish and dimensional accuracy of the workpiece must be good;
There are demands for short processing time, etc.
In order to satisfy these requirements, it is necessary to improve the machining efficiency due to electric discharge occurring between the wire electrode and the workpiece. On the other hand, once the power supply type of the electrical discharge machining device, material of the workpiece, surface finish, dimensional accuracy, etc. are specified, the electrical discharge machining time etc. will depend on the material and wire diameter of the wire electrode used. It turns out.

Therefore, the wire electrode material should be easy to draw, have good conductivity, have a high processing speed when used as an electrode, preferably have a small consumption ratio, and have good heat resistance. It is good and does not deteriorate in tensile strength especially at high temperatures and is difficult to break during use.
In addition, it is resistant to work hardening and short circuits, and is capable of two-dimensional machining, three-dimensional machining, and machining at locations where wire electrodes are wound or bent. The wire electrodes are required to have such properties as having a small amount of deflection (so-called flexure μ), good hydrophilicity, and low cost.

For this reason, pure copper or copper alloys such as brass are generally used as electrode materials.
In addition, copper alloys to which cuprous oxide is added have also been proposed.

Although copper electrodes have good values in terms of conductivity,
The wear ratio is around 60%, and it is also insufficient in terms of mechanical strength such as tensile strength and heat resistance, and brass wire is superior to copper wire in terms of mechanical strength such as tensile strength and processing speed. However, it is somewhat inferior in terms of conductivity and consumption ratio. Since the yellow conductor wire has tensile strength and hardness that exceeds that of hard copper, that is, it has spring properties, it remains curly, and unless it is moved with a sufficiently large tension between the guides,
It was difficult to achieve sufficient linearity, and the problems of processing accuracy and wire breakage were contradictory.

On the other hand, alloy wire made of pure copper mixed with 1 to 5% cuprous oxide Cu ₂ O has a conductivity that is not much different from that of pure copper and a low wear rate.
The processing speed is around 20-30%, and the processing speed is also excellent.
There is still a problem with difficulty in cutting.

As such copper alloy wire electrodes, brass alloy wire electrodes have come to be used, but due to the tendency to use them in large quantities and the trend toward higher precision, they are mainly due to the price and cost. It was unsatisfactory in terms of tensile strength.

On the other hand, there are wire electrodes made of tungsten, molybdenum, or their alloys drawn to a diameter of about 0.1 mm or less, but they are expensive and have only been used for special purposes.

In addition, a wire cut electric discharge machining device generally moves a wire electrode from one reel to the other reel, and processes a desired shape by performing electric discharge machining by performing pulse discharge while supplying machining fluid. Therefore, the wire electrode is twisted and bent every time it passes between the brake roller and the pinch roller, between the capstan and the pinch roller, between the guide roller and the guide guide, etc., and as a result, the wire electrode undergoes work hardening. This may result in loss of linearity, or conversely, if processing is to be performed at a strongly bent portion of the wire electrode, it is possible to obtain a small bending radius, thus reducing the overhang of the workpiece. There was a problem in that it was not possible to process the contours of the hollow portion of the extrusion die, the cutting edge portion of the trim die, etc., for example.

The present invention has been made based on the above-mentioned viewpoints, and its purpose is to be cheaper than brass alloys, to be able to be supplied in large quantities, to have high heat resistance and tensile strength, to be hard to break, and to be durable. The object of the present invention is to provide a novel wire-cut electric discharge machining electrode material that is small in quantity, has moderate electrical conductivity, has low contact resistance and barrier resistance, and has a machining speed comparable to that of brass alloy-based materials.

Therefore, the gist is that in terms of weight percentage, 0.29 to 0.66% C, 0.15 to 0.35% Si,
0.3-0.6% Mn, 0.05-3% rare earth elements,
The balance is Fe and impurities (usually less than 0.04% P and 0.04%
% or less of S).

The rare earth elements to be blended are as follows:
It is recommended to use any one of Y, Sm, La, Ce, or Mitsushi metal, or a mixture thereof.

Thus, wire cut electrical discharge machining electrode materials containing rare earth elements are known.

For example, in Japanese Patent Application Laid-Open No. 53-49397, Cu or
There is an electrode material in which Cu + Cu ₂ O is alloyed with one or more rare earth elements in an amount of 0.1 to 5% by weight.
and one or two of Mn, Mg, and rare earth elements.
An alloy for a wire-cut electrical discharge machining electrode is described, which contains a total of 0.1 to 3% of Cu and the remainder is Cu.

However, the addition of rare earth elements in these known electrode materials made of Cu-based alloys such as various brasses such as Cu and Cu-Zn not only improves tensile strength and break resistance, but also improves electrical discharge machining performance, especially Although it is effective in increasing the machining speed, which is thought to be a result of the contribution of rare earth elements to the generation of electrical discharge, it causes a large amount of deflection of the wire electrode during electrical discharge machining (the so-called deflection amount μ), and it is not possible to prevent short circuits. In terms of price and tensile strength, it was far inferior to hard steel wire rods, which will be described later.

In addition, A is the main component, and 0.5 to 0.5 to
Add 10% Ni and 0.05 to 0.5% Pd, or add 0.5 to 10% by weight based on A.
Ni, 0.05~0.5% Pd, and even 0.01~0.5%
Mitsushimetal or alloys based mainly on A with addition of rare earth elements such as Y ₂ O ₃ are almost the same or higher in price than brass alloys, and are suitable for special purposes and uses. In the case of general wire cut electric discharge machining except for
-49397 or JP-A No. 56-90943, even if it has some advantages in terms of tensile strength, break resistance, and machining speed. In terms of performance, there were many points in which they were inferior to those made of brass alloys.

According to various test studies conducted by the present inventor, hard steel wire generally called piano wire, especially JIS-
3506-SWRH62A or JIS-3506-SWRH32
The main alloy composition is 0.05% by weight.
The above problem could be solved by using an alloy containing ~3% of at least one rare earth element selected from Y, Sm, La, Ce, and Mitsushi metal.

These hard steel wire rods are inexpensive and easily available, and are mainly composed of Fe containing 0.04% or less S and P as impurities, and the content of C, Si, and Mn is 0.29 to 0.66% by weight, respectively. C, 0.15-0.35% Si,
Within the range of 0.3-0.6% Mn.

The composition of hard steel wire is specified in JISG3506,
The composition range of C has a lower limit of about 0.29% and an upper limit of about 0.29%.
It is 0.8%. If C is less than 0.29%, it is considered a mild steel wire (JISG3505). In the present invention, the upper limit of C is set to 0.8%, which is the upper limit of the above-mentioned hard steel wire.
The present invention limits C to a lower 0.66%.
In the range of more than 0.66% up to 0.8%, a rare earth element that is difficult to form a solid solution is mixed as an additive element, and a hard steel wire rod with a carbon content of more than 0.66% is mixed with a rare earth element according to the present invention. and,
The obtained hard steel wire is brittle and has a tensile strength lower than a predetermined value.

Si and Mn increase the strength of hard steel wires depending on their blending, but the effects become noticeable at Si of 0.15% or more and Mn of 0.3% or more. However, if Si exceeds 0.35%, graphitization of the blended C will be promoted and decarburization during hot drawing will be promoted, which is not good. Also, Mn is 0.6%
If the amount is larger, the toughness will be improved, but the crystals will become coarser, which is not good.

In addition, P and S are impurities, but when they are contained at 0.04% or more, they form phosphides and sulfides with Fe, Mn, etc., which become scattered at grain boundaries and reduce the line strength. Therefore, it is necessary to keep both amounts to 0.04% or less.

The present invention comprises 0.05 to 0.3% of rare earth elements, 0.29 to 0.66% of C, and 0.15 to 0.35% of Si in weight percentage.
By using an alloy material consisting of 0.3 to 0.6% Mn and the balance Fe and impurities as an electrode material, it has the flexibility, flexibility, tensile strength, and
It is possible to provide a wire material for wire electrodes having mechanical and electrical properties such as easy discharge property.

Therefore, P as an impurity of Fe, C excluding S,
If the content of Si and Mn is outside the above range, it will not be possible to obtain the above mechanical properties necessary for a wire electrode, and if the amount of rare earth elements added is less than 0.05%, the easy discharge property will be poor and short circuit will occur. If it exceeds 3.0%, the cost increases and the processing ability as an electrode decreases.

Therefore, JIS3506-SWRH62A and JIS3506-SWRH62A where the composition of the basic hard steel wire is within the above range.
Wire electrodes made from SWRH32 with the addition of rare earth elements in the range of 0.05 to 3.0% as described above give the best results.

In other words, it is possible to significantly improve the advantages of wire-cut electrical discharge machining electrode materials containing so-called rare earth elements, which are the ability to improve tensile strength and break resistance without significantly reducing electrical discharge machining performance and machining speed. In addition, it becomes possible to solve the disadvantages of increasing the so-called typhoon amount and not being able to prevent short circuits.

When performing electric discharge machining using the above alloy, the machining speed did not decrease significantly compared to conventional brass alloy-based wire-cut electric discharge machining electrode materials, the amount of contact was reduced, and short circuits were prevented. was completed.

Using the electrode material for wire-cut electrical discharge machining according to the present invention, machining was carried out under the following machining conditions.

Examples thereof will be shown below in comparison with processing examples using conventionally known electrode materials.

Example 1 [Machining conditions] No-load voltage 130V τon 6 to 15μs τoff 7μs IM (average machining current) 2.5A Machining fluid Specific resistance 30×10 ³ Ωcm pure water machining fluid Upper nozzle discharge pressure 0.6Kg/cm ² Machining fluid Lower nozzle discharge pressure 1Kg/cm ^2- wire electrode feeding speed 1.5m/min Wire electrode diameter 0.1mφ Thickness and material of workpiece 20mm, tension applied to S55C wire electrode 1.8Kg Alloy composition of wire electrode
0.32%C, 0.18%Si, 0.4%Mn, Mitsushi Metal
0.12%, balance Fe and impurities (approximately 0.03% P, 0.02%
When electric discharge machining was performed using a wire electrode made of the wire-cut electric discharge machining electrode material according to the present invention, machining could be performed at a machining speed of approximately 1.6 mm/min, and the machining accuracy was high. is approximately ±
It was 5 μm.

Moreover, the machined surface roughness at that time was 13 μmRmax.

Example 2 [Machining conditions] No-load voltage 130V τon 6 to 15μs τoff 7μs IM (average machining current) 7.0A Machining fluid Specific resistance 30×10 ³ Ωcm pure water machining fluid Upper nozzle discharge pressure 0.6Kg/cm ² Machining fluid Lower nozzle discharge pressure 1Kg/cm ^2- wire electrode feeding speed 1.5m/min Wire electrode diameter 0.2mφ Thickness and material of workpiece 25mm, tension applied to S55C wire electrode 4Kg Alloy composition of wire electrode
0.64%C, 0.21%Si, 0.4%Mn, Mitsushi Metal
0.8%, balance Fe and impurities (approximately 0.03% P, 0.02%
When electric discharge machining was performed using a wire electrode made of the wire-cut electric discharge machining electrode material according to the present invention, the machining speed was approximately 2.5 mm/min, and the machining accuracy was high. is approximately ±
It was 3 μm.

Moreover, the machined surface roughness at that time was 13μRmax.

On the other hand, we used a conventionally known electrode material for wire-cut electrical discharge machining, with the alloy composition of the wire electrode (Zn-Cu alloy): Zn 33% Cu 67%, wire electrode diameter: 0.2 mmφ, and tension applied to the wire electrode: 1.5 kg. When electrical discharge machining was performed on a 25 mm S55C material under the machining conditions of an average machining current IM of approximately 7.0 A, the machining speed was 3.5 mm/min and the machined surface roughness was
Although the result was 11 μRmax, which was better than the result of Example 2 of the present invention, the processing accuracy was about ±7 μm.

As described above, the present invention has the remarkable effect of improving machining accuracy without significantly reducing machining speed or machined surface roughness, compared to the case where a wire electrode made of brass alloy is used. It is.

Further, electric discharge machining was performed under the same conditions as above using another conventionally known electrode material for wire cut electric discharge machining.

Alloy composition of wire electrode (Cu-Zn-Mg-Mn-Ti-Al alloy) Cu 4% Zn 20% Mg 1.5% Mn 0.5% Ti 0.5% Al 73.5% This result is the same as the result above (Zn-Cu alloy). It was almost the same below.

Since the present invention is constructed as described above, when using the electrode material for wire cut electrical discharge machining according to the present invention, since the material is an alloy whose main component is iron, the material cost is low and wire drawing can be easily performed. Although it is an iron-based alloy, it has good conductivity due to the inclusion of rare earth elements, and since it has the above-mentioned composition as an iron-based alloy, it has heat resistance and high tensile strength. It is highly durable and does not easily cause curls in the wire electrode, and even when used under high tension, there is almost no disconnection, preventing short circuits, and as a steel alloy wire electrode, it can be processed at a high current density. As a result, processing can be performed with high accuracy without significantly reducing processing speed.

Claims (1)

[Claims] 1. 0.29 to 0.66% C, 0.15 to 0.35% Si, and 0.3 to 0.6% Mn in weight percentage (the same applies hereinafter);
An electrode material for wire cut electrical discharge machining, characterized by comprising 0.05 to 3% of rare earth elements, and the balance consisting of Fe and impurities. 2. The electrode material for wire cut electric discharge machining according to claim 1, wherein the rare earth element is Y. 3 Claim 1 in which the rare earth element is Sm
Electrode material for wire cut electric discharge machining as described in . 4 Claim 1 in which the rare earth element is La
Electrode material for wire cut electric discharge machining as described in . 5 Claim 1 in which the rare earth element is Ce
Electrode material for wire cut electric discharge machining as described in . 6. The electrode material for wire cut electrical discharge machining according to claim 1, wherein the rare earth element is Mitsushi metal.