EP0702375A2 - Overhead contact wire of high speed electrical railways and process for manufacturing the same - Google Patents

Abstract

The conductor wire is made of a Cu alloy of formula CuaCrbZrcMgdXe (I), where X is one from Al, P, S, Fe, Ni, Zn, Ag, Cd, In, Sn, Sb and Bi. b is 0.2-0.8, c is 0.02-0.04, d is 0.01-0.2 and e is 0.01-0.4. a + b + c + d + e = 100.

Description

The invention relates to a catenary wire of a high-speed electrical railway line with a tensile strength (R _m ) of the wire of at least 550 MPa and an electrical conductivity (κ) of at least 65%, based on that of annealed pure copper according to the International Annealed Copper Standard (IACS) . The invention further relates to a method for producing such an overhead contact wire. Such an overhead contact wire and a corresponding manufacturing method are described in ER 0 569 036 A.

On high-speed rail lines, high mechanical pretensioning of the contact wire is an indispensable prerequisite for the safe supply of energy via an overhead line system. The contact wire material is therefore subject to the highest demands with regard to its mechanical tensile strength R _m with high electrical conductivity κ at the same time.

At present, a CuAg alloy with an Ag content of 0.1% by weight Ag content is used for the contact wire of the Re250 control overhead line from Deutsche Bahn AG with a grooved profile and 120 mm² diameter. This alloy has a tensile strength R _m of about 350 MPa (N / mm²) with a conductivity κ of about 95%, based on that of annealed pure Cu according to IACS (International Annealed Copper Standard). The contact wire is designed for regular operation at speeds of up to 250 km / h. Taking into account an unavoidable wear, it is prestressed at 125 MPa, ie with about 36% of its tensile strength κ or a safety margin against breakage of about 2.8 (cf. "Electrical Railways", 80th year, 1982, p. 4, Pages 119 to 125 or "Railway engineering Rundschau ", vol. 35, H. 9, Sept. 1986, pages 593 to 599). This pretension was briefly increased to 175 MPa for a high-speed drive at over 400 km / h (" electric railways ", 86th year, 1988 , H. 9, pages 268 to 289).

A contact wire pretension of up to 200 MPa is required to design the overhead contact line for regular operation at high speeds of over 300 km / h. Based on the aforementioned safety margin, this requires a contact wire alloy with a minimum tensile strength κ of approximately 550 MPa. The tensile strength is determined by tensile tests according to DIN 50145/46 (cf. the book "Materials in Electrical Engineering" by H. Fischer, 3rd edition, G. Hanser Verlag Munich Vienna, 1987, pages 113 to 121).

Such a high minimum tensile strength can be achieved, for example, with Cu alloys to be taken from the EP-A mentioned. According to a special embodiment, one of these alloys consists of the components Cr (0.1 to 1%), Zr (0.01 to 0.3%), Mg (0.001 to 0.05%), O (maximum 10 ppm) and Cu (balance) together including unavoidable impurities. The selected composition of the alloy means that a casting strand obtained from the melted components must be cooled very quickly after hot rolling to an initial wire, either by immersing it in a water or oil bath, or after a slower air cooling, then an additional heat treatment (solution annealing) with rapid cooling must be subjected. The preform obtained in this way is then subjected to a number of cold deformations which are interrupted by precipitation annealing. Because of the generally necessary rapid cooling of the preliminary product from the solution temperature (860-1000 ° C.), the known method is relatively complex and therefore not very suitable for commercial wire production.

From US Pat. No. 4,755,235 an electrical wire made of a precipitation hardened Cu alloy with Cr (0.05 to 1.5% by weight), Zr (0.05 to 0.5% by weight) and Mg ( 0.005 to 0.1% by weight). Here too, an alloy melt should be cooled rapidly (within 1 to 2 minutes from about 1200 ° C to room temperature).

The object of the present invention is to provide a catenary wire made of a material which, on the one hand, meets the minimum requirements mentioned with regard to the mechanical tensile strength R _m and the electrical conductivity κ and, on the other hand, enables the wire to be produced in a simplified manner compared to the known methods.

mit $$\text{a + b + c + d + e ≅ 100}$$

unter Einschluß unvermeidbarer Verunreinigungselemente.This object is achieved in that the catenary wire consists of an at least 5-component, hardenable Cu _a Cr _b Zr _c Mg _d X _e alloy, where X is an element from the group of the elements Al, P, S, Fe, Ni , Zn, Ag, Cd, In, Sn, Sb and Bi and should apply to the components (each in percent by weight): $$\begin{array}{c}\begin{array}{c}\text{0.2 ≦ b ≦ 0.8,}\\ \text{0.02 ≦ c ≦ 0.4,}\\ \text{0.01 ≦ d ≦ 0.2,}\\ \text{0.01 ≦ e ≦ 0.4,}\end{array}\end{array}$$

With $$\text{a + b + c + d + e ≅ 100}$$

including unavoidable pollution elements.

The invention is based on the knowledge that, with the choice of the Mg component in combination with the stated proportions of the other components, a special treatment of the wire precursor in the form of rapid cooling from the melting or solution temperature can advantageously be dispensed with . A melted from the alloy according to the invention, then normal in the usual way, for example from 1200 ° C. to room temperature in 5 to 10 minutes, cooled and optionally still, for example, pre-deformed starting product or wire preliminary product by hot rolling only needs to be cold-formed and stored in order to obtain a wire with the desired properties. It was recognized that the materials to be selected for the X component (5th component) advantageously increase the yield strength of the Cu alloy and improve the formability of the wire intermediate. These properties are particularly important if only one single cold forming is to be provided in the manufacture of the wire.

Al or In is particularly advantageously selected as the X component. The corresponding Cu alloy is characterized by relatively high tensile strength values R _m and relatively high values of the 0.01% elongation limit (= technical elastic limit).

It is also advantageous if the wire according to the invention has a Si-free Cu alloy. By avoiding an Si component, an undesirable reduction in the electrical conductivity κ can be ruled out (cf. e.g. the book "Materials in Electrical Engineering", page 172).

The manufacturing method according to the invention is characterized in that first a wire intermediate is created, the Cu alloy is melted and then cooled comparatively more slowly compared to rapid cooling, then the wire intermediate is converted into an intermediate wire by means of at least one cold deformation, then the intermediate wire is subjected to at least one aging heat treatment and, if necessary, the steps of cold working and / or the aging treatment are repeated at least once more, the final shape of the wire being produced with the last cold working. The intermediate wire product can be produced directly from the melt of the Cu alloy. However, it is also possible to convert an initial product formed from the slowly solidified melt into the intermediate wire product by means of at least one preliminary deformation. Since the cooling rates which are characteristic of rapid cooling are around 100 ° C./s and higher, in the process according to the invention the melt should have a comparatively lower cooling rate, in particular at a maximum of 20 ° C./s in the important temperature range from the melting temperature to around 700 ° C. , are cooled. Below 700 ° C the cooling rate can be significantly lower, for example 5 ° C / s. Such cooling rates can be achieved without great effort, so that the method according to the invention is advantageously easy to carry out. The aging heat treatment is carried out in a manner known per se at an elevated temperature and over such a period of time that the precipitates required for hardening the material form on the dislocation structures produced by the cold deformation.

Advantageous further developments of the catenary wire and the method for its production emerge from the respective dependent claims.

The invention is explained in more detail below on the basis of exemplary embodiments.

To produce a catenary wire from a Cu alloy with the composition according to the invention, the material from the individual components is first melted, preferably in a protective gas atmosphere, such as under Ar. The oxygen content in the melt should namely be as low as possible and preferably below 100 ppm. In order to ensure good homogeneity of the melt, the melting point of Cu (1084 ° C.), in particular to at least 1200 ° C., must be used for heating. If necessary, even higher temperatures are possible. This is why induction melting is advantageous intended. The melt is then cooled at a cooling rate or rate (in ° C / min) which, in the temperature range important for the formation of the precipitation-hardened material, between the melting temperature and about 700 ° C is clearly below the cooling rates characteristic of rapid cooling of at least is about 100 ° C / s. Cooling rates of at most 20 ° C./s in the temperature range mentioned are particularly suitable. Such cooling rates can be achieved, for example, by simply pouring them into a water-cooled mold under air or in a protective gas atmosphere. Quenching in a water or oil bath can therefore advantageously be dispensed with. The direct pouring of the melt into a pre-wire with a diameter of 20 to 30 mm, for example, by pulling off the melt through a water-cooled, horizontally stored mold is particularly suitable here.

The melt mass, which may be cast into blocks or bars, can then be remelted in order to create a wire preliminary product which is more suitable with regard to the wire shape. In addition, the cooled melt mass can be processed into a wire intermediate as a pre-wire by hot rolling. Hot rolling can also directly follow the melting of the Cu alloy in a continuous step, a so-called casting roll. Remelting of the cooled melt mass to form an ingot is also possible, which is processed, for example by extrusion, to form a pre-wire. Pin-like bodies can also be worked out from a corresponding ingot, which are then deformed, for example by round hammers, to form a pre-wire. The pre-wire cross-section should be set so that a cross-section reduction of 50 to 99%, preferably 60 to 95%, takes place in the subsequent at least one cold deformation in order to obtain the desired final cross-section of the overhead wire.

The wire pre-product (or the pre-wire) is then subjected to a first cold forming. Such cold working can e.g. by pressing or rolling or hammering, in particular by pulling. The degree of deformation is generally between 20 and 80%, preferably between 40 and 70%. For example, three drawing steps with a cross-sectional reduction of 38% to 34% (1st step) or from 34% to 30% (2nd step) or from 26% to 24% (3rd step) are selected. With this cold deformation, dislocation structures are produced in the wire intermediate product to be obtained in a known manner, which are prerequisites for sufficient hardening of the material.

The first cold-forming step is then followed by a first aging heat treatment of the wire intermediate, which is advantageously carried out at a temperature between 350 ° C. and 600 ° C., preferably between 450 ° C. and 500 ° C. With this heat treatment, hardening of the material is achieved due to precipitations on the dislocation structures produced with the cold forming. The duration of this heat treatment is generally between 10 minutes and 10 hours. Considerable heating up and cooling down times have to be considered for large batches.

The processing steps of cold working and / or hardening by heat treatment are expediently repeated, it advantageously being concluded with cold working in order to obtain the desired end product of the overhead contact wire in the hard-drawn state. If this last cold deformation is to be carried out in just one step, the cross-sectional reduction to be selected here should not exceed 20% to 22%. Of course, each cold deformation, in particular the last cold deformation, can be composed of several cold deformation steps.

With regard to making the overhead contact wire as simple as possible, it is also possible, if appropriate, to provide only one-step cold forming. The degree of deformation is of course higher here.

und $$\text{a + b + c + d + e = 100 - δ,}$$

wobei δ durch den Einschluß unvermeidbarer Verunreinigungselemente in der Legierung bestimmt ist. Dieser Anteil δ an Verunreinigungselementen liegt im allgemeinen unter 100 ppm pro Verunreinigungselement.An at least 5-component Cu alloy of the composition Cu _a Cr _b Zr _c Mg _d X _{e is} provided for the catenary wire to be produced in this way. In order to be able to guarantee a minimum strength R _m of 550 MPa and an electrical conductivity κ of at least 65% IACS, the following proportions (each in% by weight) are selected for the individual components: $$\begin{array}{c}\begin{array}{c}\text{0.2 ≦ b ≦ 0.8,}\\ \text{0.02 ≦ c ≦ 0.4,}\\ \text{0.01 ≦ d ≦ 0.2,}\\ \text{0.01 ≦ e ≦ 0.4}\end{array}\end{array}$$

and $$\text{a + b + c + d + e = 100 - δ,}$$

where δ is determined by the inclusion of inevitable impurity elements in the alloy. This proportion δ of impurity elements is generally less than 100 ppm per impurity element.

• 1) Das Material besitzt gegenüber der nur 4-komponentigen CuCrZrMg-Legierung eine verbesserte Kaltumformbarkeit.
• 2) Der Kaltverfestigungsgrad wahrend der abschließenden Kaltumformung ist vergleichsweise höher, so daß eine gegenüber der 4-komponentigen Legierung erhöhte Elastizitätsgrenze erreicht wird. Diese Vorteile kommen insbesondere bei einer nur einstufigen Kaltverformung zum Tragen.

In view of the required material properties and the relatively simple processing possibility to form an overhead line wire, it is to be regarded as particularly advantageous if the proportion d of the Mg component is at least 0.05% by weight. The Mg addition then apparently also keeps the two other components Cr and Zr in solution during the relatively slow cooling phase of the melt. At the same time, a proportion b of the Cr component is advantageously selected which is at least 0.3% by weight and is advantageously less than 0.6% by weight. Furthermore, the proportion c of the Zr component should be at least 0.15% by weight. In addition, the Cu alloy of the catenary wire according to the invention should have at least one of the elements from the group Al, P, S, Fe, Ni, Zn, Ag, Cd, In, Sn, Sb and Bi contained in a proportion between 0.01 and 0.4 wt .-%. These elements, which remain essentially dissolved in the Cu even after the heat treatment, are particularly advantageous from the following two points of view:

• 1) The material has improved cold formability compared to the only 4-component CuCrZrMg alloy.
• 2) The degree of work hardening during the final cold forming is comparatively higher, so that a higher elastic limit than the 4-component alloy is reached. These advantages come into play particularly in the case of only one-step cold forming.

The stated proportions of the individual components ensure good hardenability and thus tensile strength of the alloy with sufficient conductivity and sufficient elongation at break of the material.

The following table shows the tensile strength R _m , the microhardness HV, the conductivity κ and the elongation at break ε _B for some wires made of Cu alloys according to the invention in comparison to the known CuAg0.1 alloy for different processing states. For mechanical characterization, the tensile strength R _m , the so-called 0.01% proof stress (= technical elastic limit) R _p0.01 and the elongation at break ε _B ≅ A₁₀₀ at room temperature were determined as standard. This was done in tensile tests on 100 mm long pieces of wire with mostly 1 mm φ at a stretching speed of 1 mm / min corresponding to 1.7 x 10⁻⁴ s⁻¹. The microhardness HV₅₀ was determined on cross sections perpendicular to the longitudinal direction of the wire. The electrical conductivity κ was measured with 0.2 to 1 A alternating current in lock-in technology at 370 Hz using a four-point method. The conductivity values determined apply to a temperature of 20 ° C. The specified properties are the same for corresponding catenary wires.

von 1,39, konnte bei allen untersuchten Legierungen aufgrund eines hohen Kaltverformungsvermögens ohne Materialfehler erzielt werden. Die Wärmebehandlungen wurden in einem Quarzrohr unter Ar-Atmosphäre durchgeführt. Nach Auslagerungsglühungen (450 bis 500°C) wurde das Material im Quarzrohr außerhalb des Ofens relativ langsam abgekühlt.High-purity elements (99.99%) of the components were used to manufacture the alloys listed in the table. Cylindrical reguli (approx. 60 g) were inductively melted with the elements in an Ar protective gas atmosphere in a MgO crucible and then remelted into bars (length approx. 10 to 15 cm) in an arc furnace. Pins with a circular cross-section (typically 3 mm in diameter ⌀) were cut out of the ingots by spark erosion and by turning, the slag bag formed during the melting being removed. The pins were first hammered to about 2 mm ⌀ and then pulled to about 1.5 mm ⌀. The cold forming was carried out with small passes from 0.1 to 0.05 mm. A relative reduction in cross section during cold drawing of approx. 75%, corresponding to an elongation of l / l₀ = 44, ie a degree of deformation ${\text{φ = ln (l / l}}_{\text{0}}\text{)}$

of 1.39, could be achieved with all examined alloys due to a high cold forming capacity without material defects. The heat treatments were carried out in a quartz tube under an Ar atmosphere. After aging annealing (450 to 500 ° C) the material in the quartz tube was cooled relatively slowly outside the furnace.

Deviating from the Cu alloys listed in the table, the specified tensile strength and conductivity conditions must also be met with the following alloys according to the invention (details in% by weight): CuCr 0.3 Zr 0.2 Mg 0.1 In 0.1 CuCr 0.3 Zr 0.1 Mg 0.1 Al 0.05 CuCr 0.3 Zr 0.05 Mg 0.05 In 0.15 CuCr 0.3 Zr 0.2 Mg 0.05 Al 0.085 CuCr 0.55 Zr 0.2 Mg 0.2 Sn 0.05 CuCr 0.55 Zr 0.1 Mg 0.1 Zn 0.15 CuCr 0.55 Zr 0.05 Mg 0.05 Ni 0.2 CuCr 0.55 Zr 0.05 Mg 0.2 CD 0.05 CuCr 0.5 Zr 0.18 Mg 0.06 Ag 0.15 CuCr 0.6 Zr 0.15 Mg 0.05 Bi 0.15 CuCr 0.3 Zr 0.1 Mg 0.05 Fe 0.03 CuCr 0.4 Zr 0.1 Mg 0.08 P 0.04 CuCr 0.3 Zr 0.05 Mg 0.1 S 0.05 CuCr 0.5 Zr 0.18 Mg 0.05 Sb 0.1

The 5-component alloy according to the invention is of course only a base alloy for a catenary wire for high-speed electrical railways, to which at least one further element may optionally be added in a relatively small proportion of less than 0.1% by weight. Such additional elements are selected in particular from the elements provided for the X component.

Claims (24)

Catenary wire of a high-speed electrical railway line with a tensile strength (R _m ) of the wire of at least 550 MPa and an electrical conductivity (κ), based on that of annealed pure Cu (International Annealed Copper Standard), of at least 65%, consisting of at least 5- component, hardenable Cu _a Cr _b Zr _c Mg _d X _e alloy,
where X is an element from the group of the elements Al, P, S, Fe, Ni, Zn, Ag, Cd, In, Sn, Sb and Bi and applies to the components (each in% by weight): $$\begin{array}{c}\begin{array}{c}\text{0.2 ≦ b ≦ 0.8}\\ \text{0.02 ≦ c ≦ 0.4,}\\ \text{0.01 ≦ d ≦ 0.2,}\\ \text{0.01 ≦ e ≦ 0.4,}\end{array}\end{array}$$

With $\text{a + b + c + d + e ≅ 100}$

including unavoidable pollution elements. Wire according to Claim 1, characterized in that the following applies to the X _e component: $$\text{0.02 ≦ e ≦ 0.2.}$$

Wire according to claim 1 or 2, characterized in that the following applies to the Mg _d component: $$\text{d ≧ 0.05\% by weight.}$$

Wire according to one of Claims 1 to 3, characterized in that the following applies to the Zr _c component: $$\text{c ≦ 0.2\% by weight.}$$

Wire according to one of Claims 1 to 4, characterized in that the following applies to the Cr _b component: $$\text{0.3\% by weight ≦ b ≦ 0.6\% by weight.}$$

Wire according to one of claims 1 to 5, characterized in that at least one further element from the group of X elements is added to the Cu alloy in a proportion below 0.1% by weight. Wire according to one of claims 1 to 6, characterized in that the Cu alloy is practically free of Si. Wire according to one of Claims 1 to 6, characterized in that the Cu alloy contains Si as a further component in a proportion of at most 0.1% by weight. Method for producing the overhead contact wire according to one of claims 1 to 8, characterized by the following steps: a) A preliminary wire product is first created, the Cu alloy being melted and then cooled comparatively more slowly compared to rapid cooling, b) the intermediate wire product is then converted into an intermediate wire product by means of at least one cold forming, c) the intermediate wire product is then subjected to at least one aging heat treatment, d) steps b) and / or c) are optionally repeated at least once, the final shape of the wire is generated with the last cold deformation. A method according to claim 9, characterized in that the wire pre-product is formed by first creating a starting product from the elements of the Cu alloy by means of melting and subsequent cooling and then converting the starting product into the wire pre-product by means of at least one pre-deformation. A method according to claim 10, characterized in that the at least one pre-deformation is carried out at elevated temperature. A method according to claim 10 or 11, characterized in that the at least one pre-deformation is carried out by pressing and / or rolling and / or hammering. Method according to one of claims 10 to 12, characterized in that a wire preliminary product is formed by means of the at least one pre-deformation of the starting product, the cross-section of which necessitates a cross-sectional reduction of 50 to 99%, preferably 60 to 95%, by the at least one subsequent cold deformation to obtain the desired final cross section of the wire. A method according to claim 9, characterized in that the wire intermediate is cast from the melt of the Cu alloy. Method according to one of claims 9 to 14, characterized in that the melt is cooled in step a) in the temperature range between the melting temperature and 700 ° C with a cooling rate of less than 100 ° C / s, preferably of at most 20 ° C / s . Method according to one of claims 9 to 15, characterized in that the melting in step a) is carried out at a temperature of at least 1200 ° C. Method according to one of claims 9 to 16, characterized in that at least two cold deformations are provided, with the last cold deformation there is a comparatively smaller reduction in cross-section. A method according to claim 17, characterized in that a cross-sectional reduction of between 60 and 80% takes place with the first cold deformation and a cross-sectional reduction between 10 and 30% with the last cold deformation. Method according to one of claims 9 to 18, characterized in that the final product of the wire is obtained with the last cold working. Method according to one of claims 9 to 16, characterized in that the final shape of the wire is produced with a single cold deformation of the wire intermediate. Method according to one of claims 9 to 20, characterized in that at least one cold deformation comprises several deformation steps. A method according to claim 21, characterized in that the last cold deformation comprises several deformation steps. Method according to one of claims 9 to 22, characterized in that the at least one cold forming is carried out by pressing and / or rolling and / or hammering and / or drawing. Method according to one of claims 9 to 23, characterized in that the at least one aging heat treatment is carried out at a temperature between 350 ° C and 600 ° C.