JPH05177443A - Manufacture of electrode wire for electric discharge machining - Google Patents

Abstract

PURPOSE:To efficiently manufacture an electrode wire of excellent quality by making a wire linear while being traveled to give a desired tension, heating it at a temperature lower than the recrystallizing temperature and higher than 200 deg.C, and then quenching it to a temperature less than 100 deg.C in the state holding the linearity and tension. CONSTITUTION:A wire 1 drawn to a required diameter is made linear while traveling, a tension of 20% or more of the tensile breaking load of the wire 1 is added thereto by a tension loading device 2, and the wire is heated to a temperature lower than the recrystallizing temperature and higher than 200 deg.C. Thereafter, the wire is quenched to a temperature less than 100 deg.C with the water 6 in a quenching tank 5 in the state holding the linearity and tension to provide an electric discharge machining electrode wire having both mechanical strength and linearity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode wire for electric discharge machining.

[0002]

2. Description of the Related Art In electric discharge machining, an electrode wire is passed through a thin through hole formed in a workpiece prior to the start of machining. This is called wiring work. The electrode wire may be broken during processing, but in this case, the connection work is required again. Further, it is common to process two or more locations on the same workpiece, and in this case, when the processing of one location is completed, the process moves to the next processing location and the wiring work is started. Recently, many electric discharge machines equipped with an automatic wiring function that automatically and unattended these wiring work have been used.However, in order to increase the success rate of automatic wiring, the electrode wire has a mechanical strength, especially It is important to have straightness as well as strength. This can be easily understood by considering the operation of passing the thread through the needle hole.

If the electrode wire is not required to have tensile strength or waist strength, an annealed material or a semi-hard material can be used. In this case, the wire is not elastic, or even if it is small, straightening is possible. Bending can be relatively easily corrected by a wire-rolling machine such as a roll, and a straight wire can be easily obtained during wire drawing. However, as described above, the electrode wire is required to have a hardness which is in a relationship contrary to the ease of obtaining straightness.

As a conventional method for obtaining the straightness of the electrode wire, when the wire is drawn through 10 to 20 dies to obtain an electrode wire having a required diameter, the final die or the final die may be used. For the three dies, a method of finely adjusting the wire entry angle to the dies so that the wire drawn from the final die is straight, or in addition to this method, a heat treatment called strain relief annealing is applied to bend A method of improving straightness by removing the distorted strain that is the cause, even if it is limited, is adopted.

However, the method of finely adjusting the wire entry angle into the die as described above requires time for adjustment even by a skilled person, and worse is that the die wears or metal to the die inlet is used. Even if the dice are set so as to be straight once, they will change over time due to the accumulation of powder and the like. Also, the electrode wire is often 5kg on the reel,
A length of electrode wire with a diameter of 0.2 mm is wound for about 19 km, but even if the straightness is good at the beginning of the winding, the end of the winding is not always good.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a method for manufacturing an electrode wire for electric discharge machining which has both mechanical strength and straightness. While running the drawn wire, make it linear and apply a tension of 20% or more of the tensile breaking load of the wire, and heat it to a temperature lower than the recrystallization temperature and higher than 200 ° C. It is to rapidly cool to a temperature of 100 ° C or less while maintaining the tension.

FIG. 1 is a schematic diagram of a straightening apparatus in the manufacturing method of the present invention. Reference numeral 1 is a wire drawn to a required diameter for an electrode wire, and 2 is a tension load device, for example, an electromagnetic brake is used. 3 is a heating furnace, 4 is a pipe inserted into the heating furnace 3, and 5 is a quenching tank, which is filled with water as a refrigerant. Reference numeral 7 denotes a take-up device, which takes up the wire 1 at a predetermined linear velocity and then winds it on a reel (not shown). The tension on the wire 1 is applied between the tension applying device 2 and the take-up device 7, and the tension can be changed by adjusting the braking force with the tension applying device 2. A non-oxidizing or reducing gas is fed into the pipe 4 to prevent the wire 1 from being oxidized.
The water vapor generated by immersing one end of the above in water is the above-mentioned gas.

Wire 1 used in the manufacturing method of the present invention
Is a copper alloy in all or part of its cross section. Since such a wire has high mechanical strength and relatively good conductivity, it is applied to an electrode wire. In particular,
For example, the entire cross section is made of an alloy of copper and zinc, the alloy wire of copper and zinc is galvanized on the outer circumference, or the center is copper alloy or steel, etc., and the copper alloy is clad on the outer circumference. Examples include copper alloy clad materials. In addition to the above-mentioned copper alloys, tungsten wires and molybdenum wires are used as electrode wires, and it is considered that the manufacturing method of the present invention is also effective in principle for these wires.

[0009]

In the process of studying a manufacturing method for obtaining a straight electrode wire, the present inventors, for example, tensions described in P257 to P258 of "Fundamentals and Industrial Technology of Copper and Copper Alloys" (Japan Copper and Brass Association). Focused on the annealing technology. In this method, a plate material is heated in a furnace and an appropriate tension is applied to remove or uniformize the strain, thereby eliminating bending. Then, the inventors of the present invention pursued appropriate conditions for obtaining straightness by using the apparatus schematically shown in FIG. 2 with the linear velocity, the heating temperature, and the wire tension as variables. In FIG. 2, 1
Is a wire, 2 is a tension load device, 3 is a heating furnace, 4 is a pipe, and 7 is a take-up device, which are the same as those in FIG. The difference from FIG. 1 is that in the quenching device of FIG. 1 there is a cooling zone 5 ′ in FIG. This cooling zone 5 '
Has a jacket attached to the outside of the pipe 4 for flowing water to cool the wire 1 from the outside of the pipe 4.

As a result of the above-mentioned examination, it was confirmed that depending on the conditions, a remarkable bending correction effect can be obtained without lowering the tensile strength and hardness of the wire. Especially, the bend with a large curvature was almost completely corrected. However, the bends with a curvature of around 100 mm and below remained and could not be removed.

As a result of detailed investigation of the bending of the same wire before and after applying the tension anneal, the present inventors have found that the bend having a small curvature remaining after the tension anneal exists before the tension anneal. Nothing,
Therefore, it was confirmed that the generation was caused by the tension anneal, and further that it was generated in the cooling zone in FIG. As shown in FIG. 1, the inventors of the present invention solve the non-uniform cooling by pulling a wire heated to a predetermined temperature into water under a predetermined tension to quench the wire.
No matter what kind of bending the wire has, it can be straightened and a method for manufacturing an electrode wire that is a straight wire without reducing mechanical properties, especially tensile strength and waist strength (stiffness) Established

A technique for applying heat and tensile tension to a plate to make it flat and straight is known as tension anneal. However, since the electrode wire is required to have sufficient tensile strength and waist strength, it cannot provide sufficient temperature required for strain removal or strain equalization, and the wire diameter Is 0.1 ~
It is as thin as 0.3 mm, and unevenness of minute strain also causes bending of the wire. Therefore, the bending cannot be removed by the conventional tension anneal method, and as described above, the wire is heated in a state where tension is applied, and then the wire is immersed in water for rapid cooling. As a result, the wire is cooled more uniformly than the gradual cooling, and the straightness at high temperature under tension can be maintained even after cooling to room temperature.

The condition for obtaining straightness by heat treatment under tension is considered to be a function of tension and temperature. The reason why the tension is set to 20% or more of the tensile breaking load of the wire is that even if the tension is lower than the recrystallization temperature of the wire, the temperature does not become straight, and the heating temperature is 200 ° C or more. The reason why the temperature is lower than the recrystallization temperature is that straightness cannot be obtained at a temperature of 200 ° C or lower even if the tension is close to the breaking load. Further, straightness can be easily obtained at the recrystallization temperature or higher, but the tensile strength and the waist strength after the straightening treatment are decreased, and the straightness is not suitable for the electrode wire. The temperature to quench
The reason why the temperature is 100 ° C or less is that water that is economical and easy to handle is used as a refrigerant.

The wire is heated by using an ordinary continuous heating furnace,
It may be performed in a non-oxidizing or reducing gas, or may be conducted by energizing the wire in a non-oxidizing or reducing gas. When the wire is heated by energization, an electrically insulating liquid may be used instead of the gas. Wire is often
When heated to a high temperature of around 400 ° C, not only does the surface oxidize in air and the appearance deteriorates, but it also affects the characteristics of the electrode wire. The mixed gas etc. of is used. As the liquid, water, alcohol, vegetable oil, mineral oil or the like is used.
The advantage of the electric heating is that the wire can be heated to a predetermined temperature in a short time, so that the straightening process can be performed at a high linear velocity and the wire temperature can be easily controlled by the electric current.
However, in the present invention, if the wire can be heated to a predetermined temperature, the effect can be obtained regardless of the heating method.

Water is used to quench the wire because it is the most economical and easy to handle. In addition to water, if it is a liquid such as oils and fats and alcohols at the operating temperature, cooling will be uniform, and the same effect as water can be obtained.
Water has the best practicality. The temperature of the cooling water will be close to 100 ° C if it is left to stand by the heat of the heated wire, but it has the effect of obtaining straightness up to 100 ° C. However, 60 ° C or less is desirable for practical use. Further, it is of course possible to carry out the process while keeping the water temperature at a predetermined temperature.

Further, if the straightening treatment by the heat treatment under tension of the present invention is performed by electric heating, it is possible at a linear velocity of several 100 to 1000 m / min. However, when straightening is separated from wire drawing and performed in a separate process, it is necessary to pay out the original wire (wire before processing) at the processing speed, but this is technically difficult and the processing speed is 200-300 m / Restricted to minutes. On the other hand, if wire drawing and continuous (tandem) processing are performed, this restriction on the speed is removed, and the steps due to tandemization can be omitted and the advantages of high speed processing can be obtained.

[0017]

【Example】Type of wire tested A: Copper 65% -Zinc 35% alloy wire B: Copper 80% -Zinc 20% alloy wire with a thickness of 15 μm Zinc plating C: Copper 98% -Tin 2% alloy wire with a thickness of 15 μm Zinc plating D: Iron core Cross-sectional area ratio of 40% copper 99.4% -tin 0.6% alloy
Each of the 15 μm-thick zinc-plated composite wires clad with was made into a 0.2 mm diameter by drawing and was tested. A
The lead plating thickness is the thickness at a diameter of 0.2 mm.Straight processing method The method of the present invention shown in FIG. 1 and the tension coil shown in FIG.
Conducted by Neil method, heating furnace length is 4 m, processing linear velocity is 150 m /
MinutesStraightness evaluation  (1) Cut 1m wire exactly and fix one end
It hangs vertically along the flat plate under its own weight. Wire
Draw a horizontal line at the bottom of the
Measure the length of the dropped perpendicular and use it as L to evaluate straightness
Using. (2) Accurately cut 1m wire and fix one end
On the wire when it hangs along the flat plate by its own weight.
How far the wire is from the perpendicular drawn from the end,
Measure the deviation from the vertical line at the furthest point, and set it as W
Used for evaluation of straightness. (3) Accurately cut 1m wire and fix one end
On the wire when it hangs along the flat plate by its own weight.
Measure the number of peaks that swing to the left and right with respect to the perpendicular drawn from the edge
However, S was used for evaluation of straightness.

A number of trial manufactures and studies were carried out by changing the type of wire, the straightening method, the straightening condition, etc., and the contents of four examples will be described below. Table 1 shows the outline of the implementation contents and the results. In addition, although the furnace temperature is shown in Table 1, the temperature of the wire is not described. This is because it is technically difficult to measure the wire temperature in the trial experiment and the temperature cannot be measured. However, in Example 1, it was confirmed that the wire was not softened at the furnace temperature of 510 ° C., but when the wire was heated to 530 ° C., the wire was softened. In the furnace temperature range shown in Table 1, the wire is not softened and remains hard even after straightening.

[0019]

EXAMPLE The above-mentioned four kinds of test wires were drawn by a usual method to a wire diameter of 0.2 mm, and the wire was drawn by the tension annealing method shown in FIG. 2 and the method of quenching after the tension annealing of the present invention. The straightening treatment was performed while changing the load applied to and the heating temperature, and the straightness was evaluated for each of them as described above. The results are shown in Table 1, and in any of the wire types, the wire which has been drawn and which has not been straightened has a large curvature and a large deflection. By processing this with the tension anneal method of FIG. 2, the straightness is greatly improved. However, many bends S with a small curvature are generated, and the straightness is unsatisfactory in practical use and in terms of commercial value. On the other hand, by performing straightening by the method of the present invention in which the material is rapidly cooled after tension annealing, the small bend S is also eliminated and satisfactory straightness is obtained.

[0020]

[Table 1]

[0021]

As described above, according to the method for manufacturing an electrode wire for electric discharge machining of the present invention, straightness, which is one of the most important characteristics as an electrode wire, does not require skill.
Since it can be automatically obtained over the entire length of the wire, it is possible to efficiently manufacture an electrode wire with excellent quality.

[Brief description of drawings]

FIG. 1 is a schematic view of a straight processing apparatus in a manufacturing method of the present invention.

FIG. 2 is a schematic view of a tension anneal device used for straightening and straightening a conventional plate material.

[Explanation of symbols]

 1 Wire 2 Tension Loading Device 3 Heating Furnace 4 Pipe 5 Quenching Tank 6 Water 7 Collection Device

Claims (7)

[Claims] 1. A wire drawn to a required diameter is made linear while running, and a tension of 20% or more of the tensile breaking load of the wire is applied, and the wire is lower than the recrystallization temperature.
A method for producing an electrode wire for electric discharge machining, which comprises heating to a temperature higher than ℃, and then rapidly cooling to a temperature of 100 ℃ or less while maintaining linearity and tension. 2. The method of manufacturing an electrode wire for electric discharge machining according to claim 1, wherein the wire is made of a copper alloy in all or part of its cross section. 3. The method for producing an electrode wire for electric discharge machining according to claim 1, wherein the wire is heated in a non-oxidizing or reducing gas using a continuous heating furnace. 4. The method of manufacturing an electrode wire for electric discharge machining according to claim 1, wherein the heating of the wire is performed by energizing the wire in a non-oxidizing or reducing gas. 5. The method of manufacturing an electrode wire for electric discharge machining according to claim 1, wherein the heating of the wire is performed by energizing the wire in an electrically insulating liquid. 6. The method of manufacturing an electrode wire for electric discharge machining according to claim 1, wherein the quenching is performed by immersing the wire in water. 7. The method of manufacturing an electrode wire for electric discharge machining according to claim 1, wherein the wire drawing to a required diameter and the heat treatment under tension are continuously performed.