VACUUM INTERRUPTER WITH ARC-RESISTANT CENTER SHIELD
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority from and claims the benefit of L .
Patent Application Serial No. / ,92 , filed January 20, 4, which is
incorporated by reference herein.
BACKGROUND
Field
The disclosed concept pertains generally to vacuum circuit breakers
and other types of vacuum switchgear and related components, such as vacuum
interrupters and arc-resistant shields. n particular, the disclosed concept pertains to
new alloy compositions for use in constructing internal arc-resistant shields employed
in the vacuum interrupter chamber.
Backg n Infoxination
Vacuum interrupters are typically used to interrupt high voltage AC
currents. The interrupters include a generally cylindrical vacuum envelope
surrounding a pair of coaxial y aligned separable contact assemblies having opposing
contact surfaces. The contact surfaces abut one another in a closed circuit position
and are separated to open the circuit. Each electrode assembly is connected to a
current carrying terminal post extending outside the vacuum envelope and connecting
to an AC circuit.
An ar is typically formed between the contact surfaces when the
contacts are moved apart to the open circuit position. The arcing continues until the
current is interrupted. Metal from the contacts that is vaporized by the arc forms a
neutral plasma durin arcinu and condenses back onto the contacts and also onto a
vapor shield placed between the contact assemblies and the vacuum envelope after the
current is extinguished.
The vacuum envelope of the interrupter typical ly incl udes a ceramic
tubular insulating casing with metal end cap or seal covering each end. The
electrodes of the vacuum interrupter extend through the end caps into th vacuum
envelope. At least one of the end caps is r idly connected to the electrode and must
be able to withstand relatively high dynamic forces during operation of the
interrupter.
Vacuum interrupters are key components of vacuum-type switchgear.
It is typical for interrupters for vacuum-type circuit breakers using transverse
magnetic field contacts to include the vapor shield, e.g., internal arc shield or arcresistant
shield, that is resistant to heavy arcing to restrict the outward dissemination
of the arc and preserve the high voltage withstand of the interrupter after breaking the
fault current.
I is customary for the shield to be constructed of copper, stainless
steel, copper-chromium alloy or a combination thereof. In some cases, the shield may
be constructed of o e material in the arcing area and a second material may be used
for the remainder of the shield. The copper-chromi m alloy material may be used for
the highest fault current ratings because of its resistance to arc damage and its abi lit
to ho d off high voltages after the arcing has occurred. It is typical for the copperchromium
alloy to include about 10 to 25% by weight chromium and the balance
copper.
It is an object of the disclosed concept to develop new alloy
compositions for use i constructing arc-resistant shields for interna! use in vacuum
interrupters wherein th compositions are other than th conventional pure chromium
and copper alloys t is a further object to develop new alloy compositions wherein
the amount of chromium is present in a reduced amount as compared to known
copper-chromium compositions. I still a further obj ect chromium is absent from the
compositions. Chromium is expensive to obtai and therefore, reducing or
eliminating the presence of chromium will provide a lower cost alternative to the
conventional materials used in constructing arc-resistant shields. Further, it is
believed employing materials or elements other than pure chromium and copper can
result in alloy compositions which exhibit superior performance in arc-resistant
SUMMARY
These needs a others are met by embodiments of the disclosed
concept, which provide compositions and are-resistant shields constructed of these
compositions.
In an aspect, the disclosed concept provides an alloy composition for
constructing an arc-resistant shield positioned in a vacuum interrupter chamber. The
allo composition includes melting range of 0 C or greater between a solidiis
temperature and a li uid s temperature, the solidus temperature of 00X or greater, a
substantially multi-phase microstructure, and an ability to fbnn a substantially smooth
surface when rapidly cooled following arc melting.
The composition can include a first component and a second
component. The first component may include copper or a chemically compatible
element to copper. The second component may be selected from the group consisting
of iron, stainless steel, niobium, molybdenum, vanadium, chromium alloy, carbide,
and alloys and mixtures thereof. In certain embodiments, the composition includes
the copper component and ferrochrome. The ferrochrome may constitute about 70
weight percent chromium and about 30 weight percent iron.
The first component may be pure copper or a copper alloy, such as but
not limited to cupronickel, copper-tin, nickel-copper silver bearing copper, tin bronze
and aluminum bronze. The first component can also include nickel, silver, gold,
palladium, platinum, cobalt, rhodium, iridium, ruthenium, and alloys and mixtures
thereof
The carbide may be selected f om the group consisting of tungsten
carbide, chromium carbide, vanadium carbide, molybdenum carbide, niobium
carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide,
boron carbide, and silicon carbide.
n another aspect, the disclosed concept provides an arc -resistant shield
composed of an alloy material including a first component and a .second component.
The first component may include copper or a chemically compatible element to
copper. The second component may be selected fro the group consisting of iron,
stainless steel niobium molybdenum vanadium, chromium alloy, carbide, and their
alloys and mixtures. The arc-resistant shield is a internal component of a vacuum
interrupter.
In certain embodiments, the first component may include pure copper
or copper alloy. n other embodiments, t e first component may include nickel,
silver, gold, palladium, platinum, cobalt, rhodium, iridium, ruthenium, and alloys and
mixtures thereof.
In still another aspect, the disclosed concept provides a method for
preparing an arc-resistant shield located in a vacuum interrupter. The method
inc ludes obtaining a first component selected from the group consisting of pure
copper, copper alloy, chemically compatible element to copper and mixtures
thereof; obtaining a second component selected from the group consisting of iron,
stainless steel, niobium, molybdenum, vanadium, chromium alloy, carbide, an their
alioys a d mixtures; combining the first and second components to form a mixture,
shaping the mixture into a selected shape; and machining to form the arc-resistant
shield. The chromium alloy may be ierrochrome and the ferrochrome may be in the
form of a pre-a oyed chromium-iron powder. Further, the forming of the mixture
may b conducted by a technique selected from extruding, molding and combinations
thereof.
BRIEF DESCRIPTION O DRAWINGS
A full understanding of the disclosed concept can be gained from the
following description of the preferred embodiments when read i conjunction with the
accompanying drawing in which:
FIG. 1 is a sectional view of a vacuum interrupter including an arcresistant
shield, in accordance with the disclosed concept
DET AILED DESCRIPTION OF PREFERRED EMBODIMEN TS
The disclosed concept includes alloy compositions, methods of
prepar ing the compositions and methods of employing the compositions to prepare
arc-resistant shields for use i vacuum interrupters. Vacuum interrupters ar key
internal components of vacuum switch.gear, such as vacuum circuit breakers. The arcresistant
shields are traditionally constructed of copper, stainless steel or copperchromium
alloy particular, copper-chromium alloys are known materials for use
with highest fault current ratings because of their resistance to heavy arcing and their
ability to preserve the high voltage withstand of the interrupter after arcing has
occurred. Preferred copper-chromium alloys include from 10 to 25 weight percent
chromium and the balance copper based on total weight of the alloy composition.
One disadvantage of known copper-chromium alloys is the high cost associated with
them h particular, pure chromium is an expensive element and therefore, its
presence in an alloy composition can result in an expensive material. The cost of a
material may be lowered by reducing the amount of chromium or producing the
material in the absence of chromium. Thus, it is an object of this disclosed concept to
provide suitable alloy compositions that are useful i forming arc-resistant shields.
The alloy compositions should e capable of demonstrating resistance t ar damage
and holding off high voltages after arcing, while providing lower cost alternati ves to
traditional alloy compositions.
FIG. 1 shows a vacuum interrupter 10 having a cylindrical insulating
tube which, in combination with end seals 5 1 and 52, forms a vacuum envelope 50
The insulating tube supports a vapor shield 24 by means of a flange 25. An ar
resistant vapor shield 24 surrounds a first electrode assembly 20 and a second
electrode assembly 22 to prevent metal vapors from collecting on the insulating tube
1 an to prevent the arc from hitting the insulating tube 12. The insulating tube 12 is
preferably made of a ceramic material such as alumina, zirconta or other oxide
ceramics but mav also be alass. The first and second electrode assemblies 20 and 22.
respectively are longitudinally aligned within the vacuum envelope 50. The first
electrode assembly 20 includes a bellows 28, a first electrode contact 30, a first
terminal post , and a first vapor shield 32 The second electrode assembly 22
includes a second electrode contact 34, a second terminal post 35, and a second vapor
shield 36. While the vacuum envelope 50 show in FIG. 1 is part of the vacuum
interrupter 10, it i to be understood that the term "vacuum envelope" as used herein
is intended to include any sealed component having a ceramic to metal seal which
forms a substantially gas-tight enclosure. Such sealed enclosures may be maintained
a sub-atmospheric, atmospheric or super-atmospheric pressures during operation.
The first a d second electrode assemblies 20 an 22, respectively, are
axially movable with respect to each other for opening and closing the AC circuit.
The bellows 28 mounted on the first electrode assembly 20 seals the interior of the
vacuum envelope formed b the insulating tube 1.2 and end seals 5 1 and 52, while
pennitting movement of the first electrode assembly 20 from a closed position as
shown in FIG. 1 to an open circuit position (not shown). The first electrode contact
30 is connected to the generally cylindrical first terminal post which extends out of
the vacuum envelope 50 through a hole in the e d seal 5 . The first vapor shield 32 is
mounted on the first terminal post 3 1 in order to keep metal vapors off the bellows 28.
Likewise, the second electrode contact 34 is connected to the generally cylindrical
second terminal post 35 which extends through the end seal 52. The second vapor
shield 36 is mounted on the second terminal post 35 to protect the insulating tube 12
from metal vapors. The second terminal post 35 is rigidly and hermetically sealed to
the end seal 52 by means such as but not limited to, welding or brazing.
Preferably, said first an second electrode contacts 30 and 34,
respectively, are composed of an a oy composition. e.g., copper-chromium.
In accordance with certain embodiments of the disclosed concept
suitable alloy compositions for producing an arc-resistant shield demonstrate one or
more of the following characteristics or properties:
(i) melting range or interval wherein solid and liquid phases
simultaneously exist, e.g., a slurry, and wherein the melting range or interval is equal
to or greater than 1 0 C between solidus and liquidus temperatures;
(ii solidus temperature equal to or greater than 900°€;
(i ) .substantially multi-phase microstructure with at least two
phases; and
(iv ability to form a substantially smooth surfac when rapidly
cooled a i arc melting.
The disclosed concept relates to an alloy composition having a first
component and a second component. n certain e bodi ents the first component is
copper, including pure copper, copper alloy or mixtures thereof. n certain
embodiments, instead of or in addition to, the first component include any
compatible element. For example, an element that is chemically compatible to
copper. Tha is, an element that may serve as a replacement for copper. Suitable
compatible elements include but are not limited to nickel, silver, gold, palladium,
platinum, cobalt, rhodium, iridium, ruthenium, and alloys and mixtures thereof. The
second component ma include iron, stainless steel, niobium, molybdenum,
vanadium chromium, carbide and alloys and mixtures thereof. The carbide ay
include tungsten carbide, chromium carbide, vanadium carbide, molybdenum carbide,
niobium carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium
carbide, boron carbide and si ico carbide n certain embodiments, the second
component is chromium alloy.
Non-limiting examples of alloy compositions that are suitable for use
in the disclosed concept include a copper component with another component such as,
iron, stainless steel, niobium, molybdenum, vanadium, chromium, their alloys or
mixtures and carbide. certain embodiments of the disclosed concept, the alloy
compositions include copper-iron, copper-stainless steel, copper-niobium, coppermolybdenum,
copper-vanadium, copper-chromium alloy, copper-ferrochrome,
copper-ferrovanadium, copper-ferromobium, an copper-X-carbide wherein X
represents tungsten chromium vanadium, tantalum, molybdenum, niobium, silicon,
boron, or any common carbide former. Further, in certain embodiments, the copper
alloy can include euproniekel, copper-tin, nickel-copper, silver bearing copper, tin
bronze and aluminum bronze.
The disclosed concept relates to alloy compositions for producing the
arc-resistant shield that incl ude components other than pure chromium since the use
of pure chromium can result in a expensive material. In certain embodiments, the
compositions include copper, e.g., in the form of pure copper and/or copper alloy, and
a chromium alloy wherein the chromium alloy is ferrochrorne. The amount of each of
these components can vary. The ferrochrornema constitute from about 5 to about 60
weight percent based on total weight of the composition. The copper may constitute
the balance. The ferrochrorne component is chromium-iron alloy wherei the
amount of each of the chromium and iron can van The chromium may constitute
abou 70 weight percent and the iron may constitute about 30 weight percent based on
tota weight of the ferrochrome component.
In general, the alloy compositions of the disclosed concept ar
subjected to one or more of known powder metallurgy, extrusion, forging and casting
processes in order to form an arc-resistant shield. Traditional powder metallurgy
techniques include but are not limited to pressing and sintering, extrusion, e.g.,
binder-assisted extrusion, powder injection molding and powder forging. Extrusion
includes hot or cold extrusion and forging includes hot forging or cold forming.
Casting includes vacuum induction melting, sand casting, and other conventional
casting methods.
n accordance with certain embodiments of the disclosed concept, each
of the copper and ferrochrome components may be in dry form, e.g., powder. In these
embodiments, the composition is prepared by mixing together copper powder an
ferrochrome powder. The ferrochrome powder constitutes a pre-alloyed chromiumiro
powder. The amounts of copper and ferrochrome, and the amounts of chromium
and ro can be within the weight ranges specified above. The copper and
ferrochrome powders may be atomized, chemically reduced, electrolytically formed,
ground or formed by any other know powder production process. The powder
morphology may be spherical, acicular, or irregular. The copper-ferrochrome powder
mixture is pressed to shape and sintered. The shaping and sintering can be conducted
in accordance with conventional shaping an sintering apparatus and processes known
in the art. The shaped, sintered article forms an arc -resistant shield. Optionally,
machining of the shaped, sintered artic le may be necessary to finalize the form of the
shield.
In a preferred method of fabricating the arc-resistant shield for the
vacuum circuit interrupter the steps of fabricating incl ude pouring a copperferrochrome
blend into a die cavity, tapping to level powder, applying a pressure of
about 80,000 to about 150,000 psi to form a shield, sintering the shield in a reducing
or vacuum furnace at a temperature of about 950° C to about 0 0° C for about 0.5 to
about 10 hours, and machining and forming a hollow shield.
in preferred method, the steps include initially prefabricating a
cylindrical shel l container or tube container of copper, or copper alloy, pouring
copper-ferrochrome powder, leveling by tapping or pressing, outgassing the container
containing the powder at a temperature of about 5 C to about 400° C, sealing the
container by welding a top cover of the container vacuum weld or welding the top;
evacuating through a port and seal, hoi extruding the co ainer a a temperature from
about 400° C to about 900° C removing the container and machining the shields.
another form of the method the container is hot isostatieaiSy pressed in the range of
about 700° C to about 80° between about ,000 psi to about 30,000 psi for
about 0.25 hours t about. 6 hours.
Various processes for the fabrication of the shield include the
following:
Process
. Pour a copper-ferroclirome blend into a die cavity a tap t
level powder;
2. Apply a pressure of about 80,000 to about 50,000 psi to
fabricate a shield pre-form;
3. Sinter in a reducing or vacuum furnace in range of about 950°
C to about 0° C for about 0.5 to about 10 hours; and
4. Machine the shield by boring out the center.
Process #2
. Same as Process # 1 except that a core is use in the die during
pressing to form a hollow tube pre-form;
2 . Sinter in reducing or vacuum furnace in a range of about 950°
C to about 00° C for about 0.5 to about 0 hours; and
3. Machme the shield.
Process #3
. Same as Processes # 1 a d #2 except that a rubber bag is used as
the die and a cold isostatic press is used to apply isostatic pressure i a range of about
60,000 psi to about 120,000 psi;
2. Sinter in a reducing or vacuum furnace in a range of about 950°
C to about 100° C for about 0.5 to about hours; and
Machine the shield.
Process #4
. Place a prefabricated copper or copper-ferrochrome pipe;
2. Plasma, laser deposit, thermal spray, or cold spray a layer of
copper-ferrochrome on the internal diameter of the pipe; an
3. chine the shield.
Process #
. Place a sacrificial or re-usable .mandrel;
2. Plasma, laser deposit, thermal spray, or cold spray a layer of
copper-ferrochrome o the outside diameter of the mandrel;
4. Remove the mandrel by machiniiig (or chemically f
sacrificial), or withdraw the mandrel from the deposited material if re-usable; and
3. Machine the shield.
Process #6
. Form slurry of copper powder, ferrochrome powder; and a
suitable liquid carrying agent (binder) that substantially solidifies when dried or
eentrifugaiiy separated;
2. Pour the slurry into a hollow pipe;
3. Spin the pipe to force the slurry against the inner diameter of
the pipe;
4. D y the spun mixture;
5. Remove the solidified mixture from the pipe;
7. Sinter the eentrifugaiiy formed cylindrical powder mixture; and
8. Machine the shield from the cylindrical sintered part.
P cess #7
. Melt an appropriate mixture of copper and ferrochrome using
vacuum induction melt or other technique;
2 . Pour the melt into a mol with a central core;
3 . Break out the mold to remove the casting; and
4. Machine the casting to form a shield.
Process
. Me t a appropriate mixture of copper a d ferrochrome using
vacuum induction e!t o other technique;
2. Pour the melt into mold with a centrifugal caster and cast the
shield; and
3. Machine the shield.
Process
. Prepare a solid or cylindrical blank of copper and ferrochrome
by powder metallurgy sintering, powder metallurgy infiltration, or casting;
2. Heat the blank to a temperature at which it may he extruded;
3. Extrude the blank into a cylindrical shape, e.g., using an
extrusion press; and
4 . Machine the shield from the extruded cylindrical shape, if
necessary.
Process #10
. Mix dry copper and ferrochrome powder with a suitable plastic
binder system;
2 . Heat the powder/binder mixture to temperature at which it
may be molded;
3 Extrude or powder injection mold the powder/hinder mixture
into cylindrical shape;
4. Remove the plastic binder system by solvent process, thermal
process, or a combination thereof, such that the powder remains in its formed
cylindrical shape;
5. Sinter the cylindrical shape; and
6. Machine the shield, if necessary.
EXAMPLES
Example 1,
In one experiment, arc resistant shields were made by mixing 36 w %
high carbon ferrochrome powder and 64 wt% copper powder, pressing in a cylindrical
die, sintering the part, and machining the final shield shape. The composition of the
high carbon e oc rome powder was 67- t chromium. 8-9.5% carbon, with the
balance iron. The high carbon ferrochrome powder was ground to size o - 0 mesh.
The copper powder was water atomized pure copper, a a size of 140 mesh. Pressing
of the parts was performed with a dual-action powder compaction press. The tooling
elements used to press the cylindrical parts consisted of a hollow cylindric a upper
punch, hollow cylindrical lower punch, hollow cylindrical die body, and a solid
cylindrical core rod. Powder was fed into the cylindrical cavity using an automatic
powder shoe. Compaction was performed at pressures of 45,000 to 16,000 psi. Parts
were then vacimm sintered at 950 to 1 50°C for 6 hours and machined on a lathe to
final shape.
mple 2
another experiment, arc resistant shields were made by mixing 60 wt
% high carbon ierrochrome powder and 40 wt% copper powder, pressing n a
cylindrical die, sintering the part, and machining the final shield shape. The
composition of the high carbon ferrochrome powder was 67-71 wt% chromium, 8-
9 5% carbon, with the balance iron. The high carbon ferrochrome powder was ground
to a size o -100 mesh. The copper powder was water atomized pure copper, at a s ze
of -140 mesh . Pressing of the parts was performed with dual-ac tion powder
compaction press. The tooling elements used to press the cylindrical parts consisted of
a hollow cylindrical upper punch, hollow cylindrical lower punch, hollow cylindrical
die body, and a solid cylindrical core rod. Powder was fed into the cylindrical cavity
using an automatic powder shoe. Compaction was performed at pressures o 60,000 to
,000 psi Parts were then vacuum sintered at 950 to 050°C for 6 hours, and
machined on a lathe to final shape.
n another experiment, ar resistant shields were ade by mixing 36 wt
% o carbon ferroehrome powder and 64 t% copper powder, pressing in a
cylindrical die, sintering t e part, and machining the final shield shape. The
composition of the high carbon ferroehrome powder was 70 wt% chromium with the
balance iron. The high carbon ferroehrome powder was ground to size o -80 mesh.
The copper powder was water atomized pure copper, at a size o -140 mesh. Pressing
of the parts was performed wit a dual-action powder compaction press. The tooling
elements used to press the cylindrical parts consisted of a hollow cylindrical upper
punch, hollow cylindrical lower punch, hollow cyli drica die body, and a solid
cylindrical core rod. Powder was fed into the cylindrical cavity using an automatic
powde shoe. Compaction was performed at pressures of 43,000 to 000 psi. Parts
were then vacuum sintered at 950 to 50 C for 6 hours, and machined on a lathe to
fi n l shape.
In another experiment, arc resistant shields were made by mixing 60 wt
% low carbon ferroehrome powder and 40 wt copper powder pressing in a
cylindrical die, sintering the part, and machining the final shield shape. The
composition of the high carbon ferroehrome powder was 70 wt% chromium with the
balance iron. The high carbon ferroehrome powder was ground to a size o -80 mesh.
The copper powder was water atomized pure copper, at a size o - 40 mesh. Pressing
of he parts was performed with dual-action powder compaction press. The tooling
elements used to press the cylindrical parts consisted of hollow cylindrical upper
punch, hollow cylindrical lower punch, hollow cylindrical die body, and a solid
cylindrical core rod. Powder was fed into the cylindrical cavity using an automatic
powder shoe. Compaction was performed at pressures of 50,000 to ,000 psi. Parts
were then vacuum sintered at 95 to 50 C for 6 hours, a d machined on a lathe to
inal shape.
While example systems, methods, and the like have been illustrated by
describing examples, and while the examples have been described n considerable
detail, it is not the intention of the applicants to restrict or in any way limit the scope
of the appended claims to such detail. t is, of course, not possible to describe every
conceivable combination of components or methodologies for purposes of describing
the systems, methods, and so o described herein. Therefore, the disclosed concept is
not limited to the specific details, the representative apparatus, and illustrative
examples shown and described. Thus, this application is intended to embrace
alieraiions. modifications, and variations that fall within the scope of the appended
claims.
W at is Claimed s:
! . An alloy composition for constructing an arc-resistant shield 24
positioned in a vacuum interrupter ( ) chamber, the ailoy composition comprising:
a melting range of 1 € or greater between a soii us temperature
and a liquidus temperature;
the soiidus temperature of 900°C or greater:
a substantially multi-phase microstruciure; and
an abilit t form a . substantially smooth surface when rapidly
cooled following arc -melting.
2 . The composition of claim 1 wherein the composition comprises two
components, comprising:
a fi rs component; and
a second component selected from the group consisting of iro ,
stainless steel, niobium, molybdenum, vanadium chromium ailoy, carbide, and alloys
and mixtures thereof.
3 . The composition of claim 2, wherein the first component is selected from
the group consisting of pure copper, copper ailoy, a chemically compatible element to
copper, and mixtures thereof
4 The composition of clai 3, wherein the copper a loy is c pronicke ,
copper-tin, nickel-copper, silver bearing copper, tin bronze, and aluminum bronze
5. The composition of claim 2, wherein the carbide is selected from the
group consisting of tungsten carbide, chromium carbide, vanadium carbide, molybdenum
carbide, niobium carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium
carbide, boron carbide, and silicon carbide.
6 The composition of claim 2, wherein the chromium alloy is ferrochrome.
7 The composition of claim 6, wherein the ferrochrome constitutes from
about 5 to about 60 weight percent based on total weight of the composition.
8 The composition of claim 6 wherem the e ochro e is in a form of prealloyed
powder.
9 . The composition of claim 6 wherein the ferrochrome constitutes from
about 70 weight percent chromium and about 30 weight percent iron based on total
weight of the ferrochrome component.
. The composition of claim 3. wherein the chemically compatible element is
selected from the group consisting of nickel, silver, gold, palladium, platinum, cobalt,
rhodium, iri dium ruthenium an alloys and mixtures thereof
. An arc-resistant shield (24) composed of an alloy material comprising;
a first component selected f om t group consisting of pure
copper, copper alloy, a chemically compatible element t copper, and mixtures thereof;
and
a second component; selected from the group consisting of iron ,
stainless steel, niobium, molybdenum, vanadium, chromium alloy, carbide, and alloys
and mixtures thereof
wherein, the arc-resistant shield (24) is an internal component of a vacuum
interrupter ( ).
12. A method for preparing an arc-resistant shield (24) located in a vacuum
switchgear chamber, the method compri sing:
obtaining a first component selected from the grou consisting of
pure copper, copper alloy, a chemically compatible element to copper, and mixtures
thereof;
obtaining a second component selected from the group consisting
of iron stainless steel, niobium, molybdenum, vanadi um, chromi um alloy, carbide, aad
alloys and mixtures thereof;
combining the first and second components to form a mixture;
shaping the mixture into a selected shape; and
machining to form the arc-resistant shield (24).
. The method of claim 2, wherein the chromium allo is ferrochrome.
14. The method of claim 3, wherein the ferrochrome is in a form of prealioyed
chromium-iron powder.
. The method of claim , wherein the forming of the mixture is conducted
by a technique selected from the group consisting of extruding, molding and
combinations thereof.