MXPA99002095A - High-strength erosion electrode - Google Patents

Abstract

The invention concerns a high-strength erosion electrode having good electrical conductivity. Said erosion electrode comprises a steel core, an intermediate layer of copper or a copper-containing alloy, and an outer layer containing at least 40%zinc. The steel core comprises a patented structure which contains between 0.6 and 1 wt.%carbon and occupies an area of the core corresponding to between 50 and 75%of the erosion electrode diameter, the intermediate layer occupying an area of between 5 and 40%of the total diameter, the outer layer occupying an area of between 10 and 30%, and the zinc content of the outer layer being between 40 and 60 wt.%.

Description

HIGH RESISTANCE EROSIVE ELECTRODE Field of the invention "= - The invention relates to a method for • 5 the fabrication of a wire electrode for the process "of erosion by sparks, as well as a wire electrode > L =: __ for this procedure, which consists of a core of "? ^ steel, an intermediate layer of copper or a high alloy] ~ J content of copper and a jacket with at least 40 per 0 percent zinc.

BACKGROUND OF THE INVENTION Multilayer wire electrodes, having a steel core, an intermediate layer of copper 5 disposed around the core and an outer jacket containing zinc, are known, for example, from the Patent German DE-PS 29 06 245. All wire electrodes ..n known conformed with a steel core, although ------ have a greater resistance compared to the 0 copper or brass electrodes, all these erosive electrodes have the disadvantage to have a comparatively higher resistance, that their electrical conductivity is --- very low and reaches just 8 S.m / mm2. The comparatively high tensile strength is advantageous in particular for the cutting of high pieces or also of very small pieces, since high tensions of wire are present. These known wire electrodes, however, have the disadvantage that their erosion efficiency is relatively low. Particularly when cutting very small pieces with erosive wire diameters of up to 10 micrometers, high wire resistances are required, .Ilj- to reduce to a minimum the deviations and the vibration i of the wire. To cut very small pieces with wire thicknesses of 100 micrometers and less, tungsten or molybdenum wires have been used up to now, which are extremely expensive in their manufacture. Erosive wires with a steel core as well as a brass jacket have not been able to impose themselves in this field of application, since they always have a lower resistance and a less good erosion behavior in comparison with wolfram wires.

OBJECTIVES AND ADVANTAGES OF THE INVENTION The invention is based on the objective of providing high resistance erosive electrodes with a steel core, of the type mentioned at the beginning, as well as a process for their manufacture, so that they have resistances of 1800 N / mm2 and more and also have a comparatively high conductivity of 10 Sm / mirr. Said objective is achieved with the properties of claim 1, or of claim 6. An erosive wire according to the invention thus has a steel core K with a content carbon dioxide from 0.6 to 1 percent, being arranged over "said steel core as intermediate layer ZS, a copper alloy with high content thereof. --- is covered by an MS shirt, which in the erosive wire - finished consists of a zinc alloy, whose content is between 40 and 60 percent. To achieve the 0 comparatively high conductivity of the erosive electrode while maintaining the same resistance, it is required that the _ ~ _ ^ core present a patented structure, advantageously of - sorbitol, being arranged between the shirt and the core another The layer having a high copper content, ie only slightly alloyed, silver in the form of the CuAgl alloy has been particularly advantageous as an alloying element, and a copper alloy with an advantage for the purpose intended is also used. A small portion of zinc is disposed on this intermediate layer or a sleeve consisting of a zinc alloy in which the zinc portion reaches at least 40 percent and must not exceed 60 percent. The wire electrode according to the invention could be achieved by applying to a core 5 of copper-coated steel, a coating of a brass tube or band and then reducing the compound by wire drawing., the larger the portion of zinc in the shirt must be. Another method may be to provide a copper-clad steel wire, in the immersion process, of a jacket containing zinc. The zinc content can be adjusted in this case at discretion. The problem in this procedure is to apply the jacket with the same thickness throughout the periphery. A very advantageous method for manufacturing a wire electrode according to the invention is to coat a steel core with a copper jacket, the structure of the steel core having to be in patented form. Then, on this intermediate layer of copper, a zinc alloy is applied, the jacket being in the simplest case of pure zinc. Subsequently, a diffusion annealing is carried out, the duration of which is chosen in such a way according to the diffusion temperature, that the whole jacket forms a zinc alloy, whose content thereof is maximum 60 percent. The duration of the diffusion annealing is further determined in such a way that the surface portions required for the core wire, the intermediate layer and the jacket are also adjusted, these surface portions of the three zones being determinant not only for the resistance achieved in the finished wire, but also for its conductivity. It is also decisive for the "resistance and for the conductivity of the erosive wire that in the finished wire the core consists of a patented structure, optimizing in this case in equal measures the electrical conductivity and the resistance." After the diffusion annealing, the wire, whose core must already be in a patented state, is reduced to its diameter by wire drawing.The surface portion of the nucleus in the electrode must be between 50 and 75 percent of the total electrode.The surface portion of the intermediate layer must be between 5 and 40 percent and the surface portion of the jacket between 10 and 30 percent.If also meets the requirement that the zinc content of the shirt be between 40 and 60, advantageously at just over 50 percent, obtains an electrode with a conductivity between 10 and 18 S.m / mm2, with resistances between 1800 and 2500 N / mm. It should be borne in mind that the requirement of high conductivity and high resistance are opposite, that is, a wire in accordance with the invention with very high strength has a comparatively low electrical conductivity and vice versa. The wires according to the invention can be drawn to diameters of less than 10 micrometers, that is, to diameters that are small enough for known applications. It has been found to be particularly advantageous that these wires with thin diameters can easily replace the tungsten and molybdenum wires hitherto used and, in comparison with them, are more economical in their manufacture, do not present aging, cause low raw material costs and also offer high manufacturing safety and the same properties 'I. - erosive. The quality of production achieved is so high, or that there are almost no failures of the wire according to the invention in the erosive machine, whereas the faults of the molybdenum or wolfram wires used up to now is up to 50 percent. In the case of erosive wires with diameters of 5 more than 100 micrometers, the high strength is advantageous, particularly when high-height pieces have to be cut, since high wire tensions are required to keep the bending and vibrations small. An electrode according to the invention is characterized by a high conductivity with a comparatively high resistance. In addition, the quality of cut is very good and with a high precision of contours, favoring the previous thing by means of the high tension of wire thanks to the high resistance of the same.

Claims (9)

1. - NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered a novelty, and therefore the content of the following is claimed as property: CLAIMS - "" -------_- i. A process for the fabrication of a 0 high strength erosive electrode, with a core of "^ steel, an intermediate layer of copper or an alloy of __ high 'copper content and an alloy shirt that ^ _ contains at least 40 percent zinc, characterized ., -----_ because a steel with a carbon content of 0.6 to 1 weight percent is used as the core, on which the intermediate layer of copper or a high copper alloy is applied; because on the intermediate layer it ---- applies a zinc shirt or a high-content alloy '.- = - zinc; because the wire is subjected in such a way to diffusion annealing before a first intermediate annealing, that on the one hand the jacket forms an alloy with a zinc content, whose melting point is higher than the austenitization temperature necessary for he - patented steel core, and on the other hand, the diffusion process is carried out until, considering one or several subsequent patented erosive wire, '. the jacket obtains the desired composition and strength, and the erosive electrode is patented at each intermediate annealing.
2. 2. A method according to claim 1, characterized in that as - • = ~ Starting wire is a patented steel wire, provided with an intermediate layer of copper; because a high-0-zinc-containing jacket is applied on the intermediate layer; because then the wire is It is subjected to diffusion annealing in such a way that a brass jacket of predetermined composition and strength is obtained, and because the erosive electrode is patented • - "" after each section of deformation before reaching its final 5 diameter.
3. 3. A method according to claim 1 or 2, characterized in that after the first diffusion annealing, the sleeve presents , * ~ a zinc content that does not exceed 60 percent. 0 _
4. 4. A method according to claim 2 or 3, characterized in that the starting wire has a core diameter of 0.8 millimeters and a layer thickness of the intermediate layer of 0.1 millimeters; because the sleeve 5 applied on the intermediate layer is 30 micrometers; because the wire is then subjected to diffusion annealing at 400 degrees centigrade for 4 hours and then drawn to a diameter of approximately 0.4 millimeters; because then the erosive wire is patented and then drawn to its final diameter, eventually with additional patented.
5. 5. An erosive electrode with a steel core, an intermediate layer of copper or a high copper alloy and a jacket with at least 40 per cent zinc, characterized in that the steel core has a patented structure with a carbon content of 0.6 to 1 weight percent, which takes a portion of the core surface from 50 to 75 percent of the diameter of the erosive electrode; because the intermediate layer 5 has a surface portion of 5 to 40 percent and the jacket a surface portion of 10 to 30 percent and because the zinc content of the jacket is between 40 and -60 percent by weight.
6. 6. An erosive electrode according to claim 0, characterized in that the conductivity of the erosive electrode is at least 10, preferably greater than 12 S.m / mm2. -IS =
7. 7. An erosive electrode according to claim 5 or 6, characterized in that the intermediate layer is made of copper with a small portion of -tur "silver
8. 8. An erosive electrode according to claim 7, characterized in that the _ intermediate layer is CuAgl.
9. 9. An erosive electrode according to claim 1 of claim 5, characterized in that the resistance of the erosive electrode is at least 1800 N / mm2, advantageously at least 2000 N / mm2. i --- ^