Some
researchers put graphite electrode into molten metal (such as Cu or Al) in
order to improve the properties of graphite electrode in EDM. At the same time,
pressing the liquid metal and make Cu or Al fill in the pore of graphite
electrode for improving the strength and thermal conductivity of the electrode.
Except
graphite, Cu, Cu-based and Cu composite material is also widely used as
electrode in EDM, ECM or other machining.
2.
Cu, Cu-based and Cu Composite Material
Copper
(commonly known as red copper), which is a kind of electrode material, especially
in machining non-ferrous metal. Cu has low melting point so that its wastage is
high, the lifespan is short and the cost too much, which requires that other
material with high melt point to improve its properties.
Tungsten
copper (Cu-W) not only has high melt point, low coefficient of expansion and
spark resistance, but also has good conductivity so that it is a new kind of
high-performance electrode material. Tungsten copper electrode is widely used
in die steel and WC work-pieces, the common ratio of Cu/W is 25:75. However,
the higher price than graphite or copper, tungsten copper spreading has been
blocked to some extent.
Some
researchers use copper, tungsten copper, brass and aluminum as electrode for
hardened steel machining. The result shows that Cu and Al have higher speed and
better precision, Cu and tungsten copper (W-Cu) has the lowest electrode
wastage and brass electrode wastage is the largest. Therefore, Cu is a kind of
ideal electrode for hardened steel machining, which has low wastage of
electrode and high MRR (Material Removal Rate).
In
another experiment, researchers use copper (Cu), tungsten (W) and tungsten
copper (Cu-W) as electrode for tungsten carbide machining. The result shows
that tungsten copper (Cu-W) can remarkably improve the machining efficiency.
What’s more, the wastage of electrode is lower under the low voltage so that
Cu-W is the most ideal material for tungsten carbide machining. In addition,
the researchers also use different content of Cu and ZrB2 or TiSi as electrode
for EDM by PM (Powder Metallurgy). Compared with graphite, copper and tungsten
copper, TiSi/Cu has higher wastage of electrode, the machining surface is rough
and the efficiency is not so well so that it is not suitable used as electrode.
While ZrB2/Cu can be used as electrode, but the combining power between Cu-base
and ZrB2 is weak, and the content of ZrB2 will has an effect on EDM properties.
Besides
graphite, copper, and Cu-based alloy, Cu-based composite material is also a
kind of common materials of electrode.
3.
Cu-based Composite Material
Cu-based
composite electrode has good conductivity and thermo-plasticity and use air and
water as medium, which usually for EDM or polishing. It is composed of 60%-65%
solid carbon material (such as graphite powder, graphite slices or carbon
nano-tubes and other mixture) distributes thermoplastic matrix and soften over
and over again for molding. Compared with graphite and tungsten copper
electrode, it has many advantages, like low cost, available for complicated
shape and better efficiency, etc.
However,
due to its density is much lower than tungsten copper, the electrical
resistivity is higher and the wastage of electrode is increasing. This
composite material is under development, which requires that low electrical
resistivity, low coefficient of expansion, thermal cycling resistance,
excellent conductivity and good dimensional stability in liquid.
Besides
graphite, copper, and Cu-based alloy, Cu-based composite material, diamond is
also a common kind of material of electrode. However, due to the cost of diamond
is much higher than graphite and the size is limited, there are some scientists
do researches about that.
4.
Diamond
CVD
(Chemical Vapor Deposition) diamond, which mixed by carbon-containing gas and
oxygen was excitation-decomposition under the low standard atmospheric
pressure, and come into active diamond carbon atoms. They deposit at the matrix
and grow up to polycrystalline diamond (or monocrystalline diamond, mono like
diamond).
In
order to make it have the same properties of tungsten copper (such as
conductivity, electrical resistance), researchers add boron (B) during CVD,
which has excellent adsorption to oil medium in electrical discharge machining
(EDM). CVD diamond has high MRR (Material Removal Rate) and low wastage of
electrode, especially it can work in high current density under certain
condition, which Cu, graphite and tungsten copper is unavailable. In addition,
there is another kind of PCD (polycrystalline diamond), which has similarities
with CVD diamond and its cost is lower than CVD diamond so that it is a kind of
ideal material for electrode.
In
Micro- EDM, the electrode will increase the energy of spark in unit area, which
increase the wastage and decrease the precision of machining. If we change the
parameters to reduce the discharge energy unit area, the processing will be
longer and efficiency will decrease. Therefore, the choice of electrode
materials is also important for Micro-EDM, the common electrode materials are
tungsten (W), tungsten carbide (WC) and tungsten copper (W-Cu), etc. Drilling
and milling in Micro-EDM often uses tungsten (W) or tungsten carbide (WC) rod
or tube as the electrode of tools.
In
conclusion, we should choose different materials of electrode according to
different process parameters or different work-pieces. Therefore, learn some
methods, materials, shape, customer requirements and cost performance before we
choose electrode is significant to the quality of products. In addition,
tungsten copper and other new materials will promote the development of EDM
(Electrical discharge machining).
If you have any interest in our tungsten copper alloy products, please do not hesitated to contact us by Email:sales@chinatungsten.com or by telephone:86 592 5129696, we are at your service.
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