U.S. patent application number 10/936307 was filed with the patent office on 2005-02-10 for high-strength erosion electrode.
This patent application is currently assigned to BERKENHOFF GMBH. Invention is credited to Barthel, Bernd, Groos, Heinrich, Hermanni, Hans, Tauber, Klaus.
Application Number | 20050029232 10/936307 |
Document ID | / |
Family ID | 26029007 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050029232 |
Kind Code |
A1 |
Barthel, Bernd ; et
al. |
February 10, 2005 |
High-strength erosion electrode
Abstract
The invention concerns a high-strength erosion electrode having
good electrical conductivity. The erosion electrode is made up of a
steel core, an intermediate layer of copper or a copper-containing
alloy, and an outer layer containing at least 40% zinc or,
alternatively, a steel core and a zinc alloy outer layer having a
zinc content of from 40-60%. The steel core has a patented
structure which contains between 0.6 and 1 wt. % carbon and
occupies an area 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. %. In the alternative embodiment,
the steel core occupies an area corresponding to between 50 and 75%
of the erosion electrode diameter and the outer layer occupies the
balance.
Inventors: |
Barthel, Bernd; (Herborn,
DE) ; Groos, Heinrich; (Herborn, DE) ;
Hermanni, Hans; (Sinn-Fleisbach, DE) ; Tauber,
Klaus; (Biebertal, DE) |
Correspondence
Address: |
FLYNN THIEL BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008-1699
US
|
Assignee: |
BERKENHOFF GMBH
|
Family ID: |
26029007 |
Appl. No.: |
10/936307 |
Filed: |
September 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10936307 |
Sep 8, 2004 |
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09919537 |
Jul 31, 2001 |
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6806433 |
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09919537 |
Jul 31, 2001 |
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09202221 |
Dec 9, 1998 |
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6448527 |
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09202221 |
Dec 9, 1998 |
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PCT/EP97/04595 |
Aug 22, 1997 |
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Current U.S.
Class: |
219/69.12 |
Current CPC
Class: |
B23H 7/08 20130101 |
Class at
Publication: |
219/069.12 |
International
Class: |
B23H 007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 1996 |
DE |
196 35 775.6 |
Claims
What is claimed is:
1. A method of manufacturing a high-strength erosion electrode
having a patented steel core and an outer layer of a zinc alloy,
said method comprising the steps of: providing a steel core having
a carbon content of from 0.6 to 1 wt. %; applying an intermediate
layer of copper or a high copper content-containing alloy onto the
steel core; applying an outer layer of zinc or a high zinc
content-containing alloy onto the intermediate layer to form a wire
electrode; performing diffusion annealing on the wire electrode for
a period of time sufficient to completely consolidate the
intermediate layer into the outer layer and form an outer layer of
a zinc alloy having a zinc content of from 40-60% and a melting
point higher than the austenitization temperature required for
patenting of the steel core; and performing intermediate annealing
on the wire electrode under conditions sufficient to subject the
wire electrode to a patenting treatment and form the high strength
erosion electrode.
2. A method of manufacturing a high-strength erosion electrode
having a patented steel core and an outer layer of a zinc alloy,
said method comprising the steps of: applying an intermediate layer
of copper or a high copper-content containing alloy onto a patented
steel wire having a carbon content of from 0.6 to 1 wt. %; applying
an outer layer of zinc or a high zinc content-containing alloy onto
the intermediate layer; performing diffusion annealing to
completely consolidate the intermediate layer into the outer layer
and form a brass outer layer having a zinc content of 40-60% and a
predetermined strength; deforming the wire to reduce the diameter
thereof; and performing a patenting step after each deformation
step until the wire reaches its final diameter.
Description
[0001] This application is a divisional application of U.S. Ser.
No. 09/919 537 which is a continuation-in-part of U.S. Ser. No.
09/202 211, filed Dec. 9, 1998.
FIELD OF THE INVENTION
[0002] The invention relates to a method for the manufacture of a
wire electrode for the spark-erosion process and a wire electrode
for this method, which consists of a core of steel, an intermediate
layer of copper or a high copper-containing alloy, and an outer
layer with at least 40% zinc or a core of steel and a zinc alloy
outer layer having a zinc content of from 40-60%.
BACKGROUND OF THE INVENTION
[0003] Wire electrodes, which are designed with multiple layers,
which have a core of steel, an intermediate layer of copper
arranged around the core, and an outer zinc-containing layer, are
known, for example, from the DE-PS 29 06 245. All known wire
electrodes, which are constructed with a steel core, do indeed have
an increased strength compared with copper or brass electrodes,
however, all of these erosion electrodes have the disadvantage that
if they have comparatively high strengths, their electrical
conductivity is very low and merely reaches 8
S.multidot.m/mm.sup.2. This comparatively high tensile strength is
particularly advantageous for the cutting of high or thick
workpieces or, however, also for the cutting of very small parts
since high wire tensions are here demanded. However, these known
wire electrodes have the disadvantage that their erosion
performance is relatively low. In particular, in the case of
cutting very small parts with erosion-wire diameters of up to 10
.mu.m, high wire strengths are demanded in order to reduce
deflection and vibration of the wire to a minimum. Tungsten or
molybdenum wires have been used up to now for the cutting of very
small parts with wire thicknesses of 100 .mu.m and less, however,
tungsten or molybdenum wires are extremely expensive to
manufacture. Erosion wires with a steel core and a brass outer
layer have been unable to be successful up to now for this purpose
since they always, in comparison to tungsten wires, showed a lesser
strength and a poorer erosion behavior.
SUMMARY OF THE INVENTION
[0004] The basic purpose of the invention is to provide
high-strength erosion electrodes with, a core of steel of the
abovementioned type and a method for their manufacture, which
electrodes have strengths which are 1800 N/mm.sup.2 and higher and,
in addition, have a comparatively high conductivity of 10
S.multidot.m/mm.sup.2 and more.
BRIEF DESCRIPTION OF THE DRAWING
[0005] The single drawing FIGURE illustrates cross-section of the
inventive wire.
DETAILED DESCRIPTION
[0006] This purpose is attained by providing an erosion electrode
with a core of steel, an intermediate layer of copper or a high
copper-containing alloy and an outer layer with at least 40% zinc,
wherein the steel core has a patented structure with a carbon
content of 0.6 to 1 wt. %, which occupies an area of the core of 50
to 75% of the cross-sectional surface of the erosion electrode,
wherein the intermediate layer has an area of 5 to 40% and the
outer layer has an area of 10 to 30%, and wherein the zinc content
of the outer layer lies between 40 and 60 wt. %. The purpose is
also attained by providing a method for the manufacture of a
high-strength erosion electrode comprising a core of steel, an
intermediate layer of copper or a high copper-containing alloy, and
an outer layer of an alloy containing at least 40% zinc, wherein a
steel with a carbon content of 0.6 to 1 wt. % is used as the core,
onto which is applied the intermediate layer of copper or a high
copper-containing alloy, wherein an outer layer of zinc or a high
zinc-containing alloy is applied onto the intermediate layer,
wherein the wire, prior to a first intermediate annealing, is
subjected to a diffusion annealing such that on the one hand the
outer layer forms an alloy with a zinc content, the melting point
of which is higher than the austenitization temperature required
for the patenting of the steel core, and on the other hand the
diffusion process is carried out so long that, taking into
consideration one or rather several following patentings of the
erosion wire, the outer layer maintains the desired composition and
strength, whereby the erosion electrode is patented during each
intermediate annealing.
[0007] Thus, an erosion wire of the invention has a steel core K
with a carbon content of 0.6 to 1%, whereby a high
copper-containing copper alloy is applied as an intermediate layer
ZS onto said steel core. This intermediate layer is covered by an
outer layer MS which, when the erosion wire is finished, consists
of a zinc alloy, the zinc content of which lies between 40 and 60%.
The condition for achieving the comparatively high conductivity of
the erosion electrode with an equally high strength is that the
core has a patented structure, consists advantageously of sorbite,
whereby a further layer is arranged between the outer layer and the
core, which further layer contains high amounts of copper, that is,
it is only slightly alloyed. Silver in the form of the alloy CuAgl
has here proven to be particularly advantageous as the alloy
element. Also a copper alloy with a small amount of zinc can be
advantageously utilized for the intended purpose. An outer layer
has been applied to this intermediate layer, which outer layer
consists of a zinc alloy, in which the zinc content reaches at
least 40% and may reach a maximum of 60%.
[0008] In a second embodiment of the present invention, the erosion
electrode is formed from a steel core and an outer layer covering
the steel core. The steel core has a patented structure, a carbon
content of from 0.6 wt. % and occupies an area of the core of 50 to
75% of the cross-sectional surface of the erosion electrode. The
outer layer is a zinc alloy having a zinc content of from 40-60%
and forms the balance of the cross-sectional surface of the erosion
electrode.
[0009] A wire electrode of the invention could be manufactured in
such a manner that a sleeve out of a brass pipe or brass band is
applied to a steel core enveloped with copper, and the composite is
thereafter reduced by means of wire drawing. This type of
manufacture becomes more problematic the higher the zinc content in
the outer layer is supposed to be. A further method could consist
of providing a copper-enveloped steel wire with a zinc-containing
outer layer via a dipping method. The zinc content could be
adjusted at random. The difficulty with this method is to apply the
outer layer with an even thickness over the circumference.
[0010] A very advantageous method for the manufacture of a wire
electrode is that a steel core is enveloped with a copper layer,
whereby the structure of the steel core should exist in a patented
form. A zinc alloy is thereafter then applied to this copper
intermediate layer, whereby in the simplest case the outer layer
consists of pure zinc. This is followed by a diffusion annealing,
the duration of which is chosen in dependency of the diffusion
temperature such that the entire outer layer forms a zinc alloy,
the zinc content of which amounts to 60% at a maximum. The duration
of the diffusion annealing is furthermore determined such that the
demanded areas for the core wire, the intermediate layer and the
outer layer adjust, whereby these areas of the three sections are
not only important for the strength achieved in the final wire but
also for its conductivity. A further decisive factor for the
strength, however, and also for the conductivity of the erosion
wire is that in the final wire the core consists of a patented
structure, whereby the electrical conductivity and strength are
equally optimized.
[0011] To prepare the erosion electrode of the present invention
according to the second embodiment, an erosion electrode of the
first embodiment of the present invention is formed and the
electrode subjected to repeated diffusion annealing processes to
completely consolidate the intermediate layer into the outer
layer.
[0012] The wire, the core of which should already exist in the
patented state, is, after the diffusion annealing has occurred,
reduced in its diameter by drawing.
[0013] The area of the core on the electrode should lie between 50
to 75% of the entire electrode. The area of the intermediate layer
should lie between 5 and 40% and the area of the outer layer
between 10 to 30%. If one furthermore meets the demand that the
zinc content of the outer layer lies between 40 and 60%,
advantageously at slightly above 50%, then one obtains an electrode
with a conductivity which lies between 10 and 18
S.multidot.m/mm.sup.2, whereby at the same time strengths are
obtained which lie between 1800 and 2500 N/mm.sup.2. It must hereby
be noted that the demand for high conductivity and high strength is
in contrast, namely an inventive wire with a very high strength has
a comparatively low electrical conductivity and vice versa. The
wires of the invention can be drawn to a diameter of below 10
.mu.m, namely, to diameters which are sufficiently small for the up
to now known uses. It has thereby been found to be particularly
advantageous that these wires with a thin diameter can easily
replace the up to now used tungsten and molybdenum wires and are by
comparison significantly less expensive to manufacture, show no
aging, have lower raw-material costs, and moreover offer a higher
safety in manufacture and have constant erosion characteristics.
The achieved quality in manufacture is so great that the wire of
the invention will practically not break down on the erosion
machine, whereas the breakdown of the up to now utilized molybdenum
or tungsten wire amounts to up to 50%.
[0014] The high strength is particularly advantageous in the case
of erosion wires with diameters of above 100 .mu.m when workpieces
with a greater height are to be cut since high wire tensions are
required here in order to keep bending and vibrations low.
[0015] An electrode of the invention is distinguished by a high
conductivity and a comparatively high strength. Moreover, the
cutting quality with a high exactness in contours is very good,
whereby this precision is favored by the high wire tension based on
the high strength of the wire.
* * * * *