EP0702375B1 - 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 line wire. Such an overhead line wire and a corresponding manufacturing method can be found in EP 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.

A CuAg alloy with an Ag content of 0.1% by weight Ag content is currently used for the contact wire of the Re250 control overhead line from Deutsche Bahn AG with a grooved profile and 120 mm ² diameter. This alloy has a tensile strength R _m of about 350 MPa (N / mm ² ) 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 "Eisenbahntechnische 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 vol., 1988, No. 9, pages 268 to 289).

To design the overhead line for regular operation with High speed of over 300 km / h becomes a contact wire pretension of up to 200 MPa. This requires under On the basis of the aforementioned safety margin a contact wire alloy with a minimum tensile strength κ of approx 550 MPa. The tensile strength is determined by tensile tests DIN 50145/46 determines (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 e.g. with from the mentioned copper alloys can be achieved. According to a special embodiment, sits down one of these alloys from 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 (rest) including unavoidable impurities together. The selected composition of the alloy requires that one of the melted components obtained casting strand after hot rolling to an output wire either by immersion in a water or oil bath must be cooled very quickly or after a slower one Air cooling then an additional heat treatment (Solution annealing) with rapid cooling got to. The preform obtained in this way then undergoes several cold deformations subjected to being interrupted by excretion annealing are. Because of the generally necessary rapid cooling of the preliminary product from the solution temperature (860 - 1000 ° C) the known method is relatively expensive and therefore not very suitable for commercial wire production.

An electrical wire is also made from US Pat. No. 4,755,235 a precipitation hardened Cu alloy with Cr (0.05 to 1.5 wt%), Zr (0.05 to 0.5 wt%) and Mg (0.005 to 0.1% by weight). Here too an alloy melt is said 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 K and which on the other hand enables the wire to be produced in a simplified manner compared to the known methods.

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 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): 0.2 ≤ b ≤ 0.8, 0.02 ≤ c ≤ 0.4, 0.01 ≤ d ≤ 0.2, 0.01 ≤ e ≤ 0.4, With 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 proportions mentioned the other components advantageous to a special one Treatment of the wire intermediate in the form of rapid cooling waived from the melting or solution temperature can be. A melted from the alloy according to the invention, then normal in the usual way, e.g. from 1200 ° C to room temperature in 5 to 10 min, cooled and optionally still pre-deformed, for example, by hot rolling Starting product or wire intermediate product therefore only needs to be cold worked and outsourced to using a wire to get 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 when the production of the wire only a single cold forming to be provided.

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. Because by avoiding it of an Si portion can be an undesirable reduction exclude the electrical conductivity κ (cf. e.g. the book "Materials in Electrical Engineering", Page 172).

The manufacturing method according to the invention is characterized in that that a wire intermediate is first created, whereby the Cu alloy melted and then opposed a rapid cooling cooled comparatively more slowly is then the wire intermediate by means of at least one Cold working is converted into a wire intermediate, then the intermediate wire product of at least one age heat treatment is subjected and if necessary the Cold forming and / or aging steps can be repeated at least once, with the last cold deformation the final shape of the wire is generated. The intermediate wire product can be produced directly from the melt of the Cu alloy. But it is also possible an initial product formed from the slowly solidified melt by means of at least one pre-deformation in the To transfer wire intermediate. Because for rapid cooling characteristic cooling rates at about 100 ° C / s and higher should lie in the process of the invention, the melt with a comparatively lower cooling rate, especially with at most 20 ° C / s in the important temperature range from Melting temperature to about 700 ° C, are cooled. Below of 700 ° C the cooling rate can be significantly lower and for example at 5 ° C / s. Let such cooling rates realize themselves without much effort, so that the invention Advantageously, the method is correspondingly simple to carry out is. The aging heat treatment is in itself known manner at elevated temperature and above such Period carried out that the hardening of the Precipitation of the material required with the cold forming trained dislocation structures.

Advantageous further developments of the catenary wire and Processes for its manufacture go from the respective dependent ones Claims.

The invention is described below using exemplary embodiments explained further.

For the production of a catenary wire from a Cu alloy with the composition according to the invention the material from the individual components preferably in a protective gas atmosphere such as melted under Ar. Of the Oxygen content in the melt should be as possible be low and preferably below 100 ppm. To one To ensure good homogeneity of the melt, must over the Melting point of Cu (1084 ° C), especially at least 1200 ° C to be heated. If necessary, even higher temperatures come in question. This is why induction melting is advantageous intended. The melt is then with a Cooling rate or rate (in ° C / min) cooled, the in the for the formation of the precipitation hardened material important temperature range between the melting temperature and about 700 ° C well below that for a quick Cooling characteristic cooling rates of at least about 100 ° C / s. In particular, cooling rates of at most come 20 ° C / s in the temperature range mentioned in question. Such cooling rates can be achieved, for example, by a simple one Pour into a water-cooled mold under air or in a protective gas atmosphere. On a scare So in a water or oil bath can be beneficial to be dispensed with. The direct pouring of the melt into one Pre-wire with e.g. 20 to 30 mm diameter by pulling the melt through a water-cooled, horizontally stored Chill mold is particularly suitable here.

The one, if necessary, cast into blocks or bars Melting mass can then be remelted to get out of it a wire preliminary product more suitable with regard to the wire shape to accomplish. In addition, the cooled melt mass can by hot rolling to a wire intermediate as one Process pre-wire. Hot rolling can also be done in one continuous step, a so-called casting roll, immediately connect to the melting of the Cu alloy. Furthermore, there is also a remelting of the cooled melt mass into an ingot possible, e.g. by extrusion a pre-wire is processed. From a corresponding one Ingots can also be worked out in pencil-like bodies, which then e.g. deformed into a pre-wire by round hammering will. The pre-wire cross-section should be set this way be that in the subsequent at least a cold forming a cross-sectional reduction of 50 to 99%, preferably from 60 to 95%, is done so as to achieve the desired one Obtain the final cross-section of the catenary wire.

The pre-wire (or the pre-wire) is then undergo a first cold working. Such cold deformation can e.g. by pressing or rolling or hammering, especially 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 section reduction from 38% to 34% (1st step) or from 34% to 30% (2nd step) or from 26% to 24% (3rd step) selected. With this cold deformation in the wire intermediate product to be obtained in this way Generated dislocation structures in a known manner, the prerequisite for sufficient hardening of the material.

The first cold-forming step is then followed by a first one Age heat treatment of the wire intermediate which is advantageous at a temperature between 350 ° C and 600 ° C, preferably between 450 ° C and 500 ° C, performed becomes. This heat treatment will harden the material due to excretions on those with cold forming generated dislocation structures achieved. The duration this heat treatment is generally between 10 minutes and 10 hours. Large batches are significant Heating and cooling times must be taken into account.

The processing steps of cold forming and / or hardening by heat treatment are advantageously repeated, advantageously completed with a cold working the desired end product of the catenary wire in the to get hard drawn condition. If this last cold working should be done in just one step, then should not exceed the cross-sectional reduction to be chosen here 20% to 22%. Of course, everyone can Cold forming, in particular also the last cold forming, Assemble from several cold forming steps.

With regard to making the catenary wire as simple as possible if necessary, you can also use a one-step only Provide cold working. The degree of deformation is higher here, of course.

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: 0.2 ≤ b ≤ 0.8, 0.02 ≤ c ≤ 0.4, 0.01 ≤ d ≤ 0.2, 0.01 ≤ e ≤ 0.4 and 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 während 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 is said to contain at least one of the elements from the group Al, P, S, Fe, Ni, Zn, Ag, Cd, In, Sn, Sb and Bi in a proportion between 0.01 and 0, 4 wt .-% included. 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.

Ensure the stated proportions of the individual components 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 ≅ A ₁₀₀ at room temperature were determined as standard. This was done in tensile tests on 100 mm long pieces of wire with mostly 1 mm  at a stretching speed of 1 mm / min corresponding to 1.7 x 10 ^-4 s ^-1 . The microhardness HV _{50 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.

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 / l ₀ = 44, ie a degree of deformation ϕ = ln (l / l ₀ ) of 1.39, could be achieved in all alloys investigated due to their high cold-forming capacity without material defects be achieved. 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, of course, represents only a basic alloy for a catenary wire for high speed electric railways to which if necessary, at least one other element proportionate to one small proportion of less than 0.1 wt .-% added can be. Such additional elements are particularly selected from the elements provided for the X component.

Claims (24)

1. Overhead conductor wire for a high speed electric railway line having a tensile strength (R_m ) of 550 MPa and an electrical conductivity (K) relative to that of annealed pure Cu (International Annealed Copper Standard) of at least 65%, consisting of an at least 5-component age-hardenable Cu alloy of the composition Cu_aCr_bZr_cMg_dX_e, wherein X is an element selected from the group of elements Al, P, S, Fe, Ni, Zn, Ag, Cd, In, Sn, Sb, and Bi, with the proviso that for the components (in each case in weight percent) : 0.2 ≤ b ≤ 0.8, 0.02 ≤ c ≤ 0.4, 0.01 ≤ d ≤ 0.2, 0.01 ≤ e ≤ 0.4, with
   a + b + c + d + e ≅ 100, including unavoidable impurity elements.
2. Wire according to claim 1, characterised in that for the X_e component: 0.02 ≤ e ≤ 0.2.
3. Wire according to claim 1 or claim 2, characterised in that for the Mg_d component: d ≥ 0.05% by wt.
4. Wire according to any one of claims 1 to 3, characterised in that for the Zr_c component: c ≤ 0.2% by wt.
5. Wire according to any one of claims 1 to 4, characterised in that for the Cr_b component: 0.3% by wt. ≤ b ≤ 0.6% by wt.
6. Wire according to any one of claims 1 to 5, characterised in that at least one further element from the group of the X elements is included in the Cu alloy in an amount less than 0.1% by wt.
7. Wire according to any one of claims 1 to 6, characterised in that the Cu alloy is practically free from Si.
8. Wire according to any one of claims 1 to 6, characterised in that the Cu alloy contains as a further component Si in an amount of at most 0.1% by wt.
9. Method for manufacturing the overhead conductor wire according to any one of claims 1 to 8, characterised by the following steps:

   a) a wire bar is made by first melting the Cu alloy and then cooling relatively slowly compared with a rapid cooling,

   b) the wire bar is then converted into an intermediate wire product by means of at least one cold working,

   c) the intermediate wire product is then subjected to at least one ageing heat treatment,

   d) if desired the steps b) and/or c) are repeated at least once more,

   the final form of the wire being produced by the last cold working.
10. Method according to claim 9, characterised in that the wire bar is formed by first making 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 bar by at least one preforming.
11. Method according to claim 10, characterised in that the at least one preforming is undertaken at elevated temperature.
12. Method according to claim 10 or claim 11, characterised in that the at least one preforming is undertaken by means of pressing and/or rolling and/or swaging.
13. Method according to any one of claims 10 to 12, characterised in that by means of the at least one preforming of the starting product a wire bar is formed the section of which makes a reduction in area by at least one subsequent cold working of 50 to 99%, preferably of 60 to 95%, necessary in order to obtain the desired final section of the wire.
14. Method according to claim 9, characterised in that the wire bar is cast from the Cu alloy melt.
15. Method according to any one of claims 9 to 14, characterised in that a cooling of the melt in step a) takes place in the temperature range between the melting temperature and 700°C at a cooling rate of less than 100°C/s, preferably of at most 20°C/s.
16. Method according to any one of claims 9 to 15, characterised in that the melting in step a) is undertaken at a temperature of at least 1200°C.
17. Method according to any one of claims 9 to 16, characterised in that at least two cold workings are performed, with a relatively small reduction in area taking place in the last cold working.
18. Method according to claim 17, characterised in that by the first cold working a reduction in area between 60 and 80% and by the last cold working a reduction in area between 10 and 30% is brought about.
19. Method according to any one of claims 9 to 18, characterised in that by the last cold working the end product of the wire is obtained.
20. Method according to any one of claims 9 to 16, characterised in that by a single cold working of the wire bar the final form of the wire is produced.
21. Method according to any one of claims 9 to 20, characterised in that at least one cold working comprises several working steps.
22. Method according to claim 21, characterised in that the last cold working comprises several working steps.
23. Method according to any one of claims 9 to 22, characterised in that the at least one cold working is effected by means of pressing and/or rolling and/or swaging and/or drawing
24. Method according to any one of claims 9 to 23, characterised in that the at least one ageing heat treatment takes place at a temperature between 350°C and 600°C.