JPH092108A - Trolley wire manufacturing method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a manufacturing method of a trolley wire having tensile breaking strength, elongation and conductivity necessary for supplying power to a high-speed overhead line train. [Structure] Sn: 0.30 obtained by hot working after continuous casting
When a trolley wire is manufactured by cold-drawing a wire rod containing 0.1 to 0.45% by weight and the balance of Cu and inevitable impurities, the cold-drawing working rate x (%).
And the wire temperature before processing y (° C) is y = 5.6x
-320, y = 5.6x-420, y = -10 and y =
Set it so that it is within the range surrounded by -210.

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 a trolley wire used for supplying electric power to a high speed overhead line train.

[0002]

2. Description of the Related Art A trolley wire used for supplying electric power to an overhead line train is usually a copper wire or a copper alloy wire. By the way, recently, there is a strong demand for high-speed operation of electric trains. Therefore, it is required to further increase the strength of the trolley wire or to reduce the weight of the trolley wire.

That is, in order to increase the operating speed of the train, it is necessary to increase the wave propagation speed of the trolley wire. The wave propagation velocity C is expressed by the following mathematical formula 1.

[0004]

## EQU1 ## C = √ (T / ρ) (m / sec) where T is the overhead wire tension (N), and ρ is the linear density of the trolley wire (weight per unit length, kg / m). . Also, √
() Is the square root of the number in ().

Conventionally, a trolley wire made of copper or a copper alloy containing tin and having a cross-sectional area of 170 mm ² has a wire tension of 1500 kgf at the maximum, so that the wave propagation velocity C is 355 km / h.
However, the maximum speed of the train is limited to about 70% of the wave propagation speed so that the current collection performance of the train does not decrease. Therefore, the maximum speed in this case is about 250 km / h. Therefore, in order to enable high-speed operation of 300 km / h or more, which is currently under rapid development, it is necessary to increase the wave propagation velocity C by improving the material of the trolley wire. For this reason, it is necessary from Equation 1 to reduce the weight of the trolley wire to reduce the line density ρ or increase the overhead wire tension T of the trolley wire.

[0006] Thus, as a technique for decreasing the linear density ρ and increasing the wave propagation velocity C, an aluminum composite trolley wire has conventionally been proposed in which aluminum, which is lighter than copper, is coated and crimped around a steel wire. Has been done.

On the other hand, as a technique for increasing the tension T of the trolley wire to increase the tension T of the trolley wire to increase the wave propagation velocity C, the Cu-Ni-Si alloy trolley wire disclosed in Japanese Patent Laid-Open No. 5-125469. Or Nagasawa et al., MITSUBISHI ELECTRIC INDUSTRIAL JOURNAL, No. 88, pp. 56-60 (10
There is a precipitation-strengthened copper alloy trolley wire such as the Cu-Cr-Zr alloy trolley wire reported in (Mon.).

The trolley wire is required to have a high electrical conductivity and an elongation value, which is an index of ductility, of a certain value or more, in addition to increasing the tensile breaking load.

[0009]

However, the above-mentioned conventional trolley wire has the following problems.

First, in the aluminum composite trolley wire, since the fitting for the trolley wire is made of copper alloy,
There is a problem that the copper alloy of the fitting and the aluminum coating layer of the trolley wire come into contact with each other to cause contact corrosion. In order to prevent this corrosion, it is necessary to change all of the mounting metal fittings currently in widespread use to materials that do not cause contact corrosion with aluminum, which is not practical in terms of cost.

On the other hand, in the Cu-Ni-Si alloy trolley wire and the Cu-Cr-Zr alloy trolley wire, the alloy elements are strengthened by precipitating the added alloy elements as intermetallic compounds. As described above, in the method of adding the alloy element as a precipitate, the conductivity does not decrease even if the alloy element is added. However, in this conventional technique, a precipitation treatment in which heat is applied to the wire is necessary after cold working or during cold working. In this case, unlike the case of copper or copper alloy trolley wire, a step of heat treatment is added to the manufacturing process. For this reason, the manufacturing process becomes complicated and the product cost increases. Further, in the heat treatment for strengthening the wire rod by these precipitations, in order to obtain desired characteristics, delicate temperature control is required, and thus a large capital investment is required. Furthermore, in these precipitation-strengthened wire rods, the precipitates that contribute to the strengthening of the material are inherently accompanied by a change over time, so the strength of the wire rod may deteriorate over time. In particular, in the trolley wire which generates heat due to friction with the pantograph and electric discharge between the trolley wire and the pantograph, such strength change of the wire is unavoidable.

Conventionally, the standard of the tensile breaking load of a copper alloy trolley wire containing tin having a cross-sectional area of 170 mm ² is set to 6000 kgf or more. This trolley wire was a Cu: 0.3 wt% Sn alloy, and was manufactured by cold-drawing a roughly drawn wire having a diameter of about 20 to 30 mm so as to have a cross-sectional area of 170 mm ² . It is generally known that the strength of a metal material such as copper or a copper alloy increases as the cold working rate increases. Therefore, by increasing the cross-sectional area of the rough drawing wire before cold working, the cross-sectional area of 170 m
The strength of the trolley wire can be increased by processing with a large processing rate until it reaches m ² .

However, in general, a large-diameter rough drawn wire having a diameter of 30 mm or more has a weight of 6 kg or more per 1 m and a high strength against bending, resulting in extremely poor workability. For this reason, generally, a rough drawn wire having a diameter of 20 mm to 30 mm is used for manufacturing the trolley wire, and the processing rate cannot be increased.

On the other hand, it is known that the strength can be increased by increasing the amount of additive elements such as Sn in the copper alloy. For example, a tensile breaking load of 6000 kgf or more can be obtained by adding Sn in an amount of 0.3% by weight or more. However, in general, the conductivity decreases with the amount of added alloy elements. Specifically, the tin-containing copper alloy trolley wire is required to have an electric conductivity of 70% IACS or more, but when the Sn concentration exceeds 0.45 wt%, the electric conductivity becomes 70% IACS or less. there is a possibility. Therefore, it is not preferable that the Sn concentration to be added exceeds 0.45% by weight. Therefore, it is difficult to obtain a trolley wire having a tensile breaking load of 7600 kgf or more, which is necessary for high-speed operation of a train, while ensuring a conductivity of 70% IACS or more, by only adding tin.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a trolley wire that enables high-speed operation of an overhead line train.

[0016]

According to the method of manufacturing a trolley wire of the present invention, Sn: 0.3 obtained by hot working after continuous casting.
A trolley wire manufacturing method for manufacturing a trolley wire by cold drawing a wire rod containing 0 to 0.45% by weight, the balance being Cu and unavoidable impurities, wherein the cold drawing is Processing rate x (%) and wire temperature before processing y
The relationship with (° C.) is y = 5.6x−320, y = 5.6.
It is characterized in that it is carried out under a condition within a range surrounded by x-420, y = -10 and y = -210.

[0017]

The inventors of the present invention set Sn to 0.30 to 0.45.
It has been found that the object of the present invention can be achieved by increasing the strength by improving the processing technique while obtaining a tensile breaking load of 6000 kgf or more by adding it by weight%. That is, the inventors of the present application, after cooling the wire rod from the hot working temperature to various temperatures, add cold wire drawing at a predetermined working rate, measure the strength and elongation of this wire rod, and further measure the strength of this trolley wire. The central portion of the cross section was observed with a transmission electron microscope. As a result, the wire rod temperature y before cold drawing to obtain a tensile breaking load of 7600 kgf or more and an elongation of 3.2% or more (gauge length 250 mm) required for a high-strength trolley wire having a cross-sectional area of 170 mm ^2. It was found that (° C.) and the processing rate x (%) were in the ranges shown by hatching in FIG.

The stress required for plastically flowing a material is inversely proportional to the diameter of the cell (Asao et al., Plasticity and Processing, Vol. 26, pp. 1181-1187 (1985).
Year)). Therefore, the smaller the cell diameter (the size of the cell surrounded by the cell walls formed by disentangled dislocations), the higher the strength of the wire rod, and the tensile breaking load of the material consequently increases. In order to give the trolley wire a desired tensile breaking load, the cell diameter must be 0.6 μm or less. However, the cell diameter is 0.25
If it is less than μm, the ductility of the material is reduced, and the desired elongation cannot be obtained. Further, the twin deformation structure in the material does not contribute to the strengthening of the material, and the ductility is remarkably reduced.

When processed at a low temperature as shown in the range shown in FIG. 1, the cell diameter measured by the transmission microscope observation of the cross section of the wire is in the range of 0.25 to 0.6 μm, which is extremely small. It's a small one. As described above, when the processing temperature is low and the cell diameter of the wire is small, the strength of the material is high (for example, Wada et al., Plasticity and Processing Vol. 31, 99).
6-1000 (1990)).

When processed at low temperature, no twinning deformation structure was present. This twinned deformation structure significantly reduces ductility (elongation in tensile test).

Next, the reasons for limiting the cold drawing conditions of the trolley wire manufacturing method according to the present invention will be described. In FIG. 1, the horizontal axis represents the cold working rate x (%), and the vertical axis represents the wire material temperature y (° C) before wire drawing, and the tensile breaking load is 7600 kg.
It is a figure which shows the range which can obtain f or more and elongation 3.2% or more by hatching. This range is surrounded by the following mathematical formulas 2 to 5.

[0022]

## EQU00002 ## y = 5.6x-320

[0023]

## EQU3 ## y = 5.6x-420

[0024]

## EQU00004 ## y = -10

[0025]

[Mathematical formula-see original document] y = -210 Formulas 2 to 4 are experimentally determined. In the area on the upper left of the straight line expressed by Equation 2, the cell diameter is 0.6.
Although the value is more than μm and the elongation is 3.2% or more,
The tensile breaking load was insufficient. Next, in the lower right region of the straight line shown by Formula 3, the cell diameter is less than 0.25 μm,
The tensile breaking load was 7600 kgf or more, but the elongation was insufficient. At a temperature above the straight line shown by Formula 4, the relationship between the temperature and the cold working rate deviated from the straight line, and even if the working rate was increased, the increase in strength was extremely small. Further, Equation 5 was obtained from the vaporization temperature of liquid nitrogen, which is a practically usable refrigerant, under 1 atm. As a refrigerant having a vaporization temperature of liquid nitrogen or lower, for example, liquid helium or the like is used, but it is difficult to apply it to a wire rod in terms of cost.

When cold drawing is carried out under the working conditions in the above-mentioned region, if the Sn concentration in the wire is 0.45% or less, the conductivity of all the prepared samples is 70%.
It is IACS or more.

[0027]

EXAMPLE A method for producing a high-strength trolley wire (Example 1) actually produced by the present inventors will be described below. First, a rough wire having a diameter of 18 mm and containing 0.35% by weight of tin was manufactured by a continuous casting facility. Next, this rough-drawn wire was immersed in liquid nitrogen and cooled. After that, by cold drawing wire drawing equipment, 170mm ^{2 in} 3 pass wire drawing
Manufactured trolley wire. The wire rod surface temperature before wire drawing of each pass was set to -150 ° C.

Regarding the processed wire (Example 1), the conductivity was measured, the tensile breaking load by a tensile test and the elongation at a gauge length of 250 mm, and a transmission electron microscope observation of a sample prepared from the center of the trolley wire. I went. As a result, the conductivity is 73% IACS and the tensile breaking load is 7740.
The kgf and the elongation were 3.8%. Further, as a result of the transmission electron microscope structure, the average diameter of the cell was 0.4 μm, and no twin deformation structure was present.

The Sn concentration, the wire cooling temperature and the working rate of this Example 1 and other Examples and Comparative Examples are shown in Table 1, and the tensile breaking load, elongation, conductivity, cell diameter, and twinning deformation. Table 2 shows the determination results. Tensile breaking load 76
00 kgf or more, elongation 3.2% or more, and conductivity 70%
The trolley wire that was IACS or more was judged as ◯, and the other trolley wires were judged as x. Among the examples and comparative examples, those having a wire cooling temperature of -50 ° C or higher used dry ice as the refrigerant. Further, the processing rates and the wire cooling temperatures of Examples 1 and 2 and Comparative Examples 1 to 8 are shown in FIG.

In Examples 1 and 2, the tensile breaking load, the elongation and the electric conductivity were larger than the standard values. on the other hand,
In Comparative Examples 1, 3, 4, 6 and 8, the tensile breaking loads were 7510 kgf, 7340 kgf and 6970 kgf, respectively.
7480 kgf, 7570 kgf and less than 7600 kgf, and in Comparative Examples 2 and 5, the elongations are 2.8 and 2.8, respectively.
%, 3.0% and less than 3.2%. Further, in Comparative Example 7, the electrical conductivity was 69% IACS and less than 70% IACS.

As described above, in each of the comparative examples, the relationship between the cold working rate x (%) and the wire rod temperature y (° C) before working is out of the range specified in the present invention. In addition, the required tensile breaking load, elongation or conductivity could not be obtained.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

The trolley wire manufacturing method according to the present invention controls the working rate during cold drawing and the temperature of the wire material before working, so that the tensile breaking load, elongation and elongation required for high-speed operation of the train can be reduced. A trolley wire having electrical conductivity can be manufactured.

[Brief description of drawings]

[Fig. 1] Cold working rate x (%) and wire temperature y before working
It is a figure which shows the relationship with (degreeC).

FIG. 2 is a diagram showing a cold working rate x (%) and a wire rod temperature y (° C.) before working in Examples and Comparative Examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Kono 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Stock Company

Claims (1)

[Claims] 1. Sn: 0. 0 obtained by hot working after continuous casting.
A trolley wire manufacturing method for manufacturing a trolley wire by cold-drawing a wire rod containing 30 to 0.45% by weight, the balance being Cu and unavoidable impurities, wherein the cold drawing is Processing rate x (%) and wire temperature before processing y
The relationship with (° C.) is y = 5.6x−320, y = 5.6.
A method of manufacturing a trolley wire, which is performed under a condition within a range surrounded by x-420, y = -10 and y = -210.