U.S. patent application number 10/577957 was filed with the patent office on 2007-09-27 for stainless steel strip coated with a metallic layer.
This patent application is currently assigned to SANDVIK AB. Invention is credited to Hakan Holmberg.
Application Number | 20070224439 10/577957 |
Document ID | / |
Family ID | 29707841 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070224439 |
Kind Code |
A1 |
Holmberg; Hakan |
September 27, 2007 |
Stainless Steel Strip Coated with a Metallic Layer
Abstract
A coated high strength stainless steel strip product with a
dense and evenly distributed metallic layer on one side or both
sides of said strip is provided. Said layer consists of essentially
pure gold, copper, nickel, cobalt, molybdenum, silver, tin or
tungsten or alloys of at least 2 of these metals, the thickness of
said layer is preferably maximally 15 .mu.m, the tolerance of said
layer is maximally +/-30% of the layer thickness, the Cr content of
the steel strip substrate is at least 10%, and that the layer has
such a good adhesion so that the coated steel strip can be
uniaxially stretched to fracture by tensile testing without showing
any tendency to peeling, flaking or the like. The metal-coated
strip product is suitable for use in applications that are load
carrying and is able to transfer electrical currents to a
contacting surface without an electrical conductivity drop at the
interface between the surfaces.
Inventors: |
Holmberg; Hakan; (Gavle,
SE) |
Correspondence
Address: |
DRINKER BIDDLE & REATH (DC)
1500 K STREET, N.W.
SUITE 1100
WASHINGTON
DC
20005-1209
US
|
Assignee: |
SANDVIK AB
Sandviken
SE
S-811 81
|
Family ID: |
29707841 |
Appl. No.: |
10/577957 |
Filed: |
November 3, 2004 |
PCT Filed: |
November 3, 2004 |
PCT NO: |
PCT/SE04/01603 |
371 Date: |
March 22, 2007 |
Current U.S.
Class: |
428/548 |
Current CPC
Class: |
C23C 14/022 20130101;
Y10T 428/12028 20150115; C22C 38/40 20130101; C23C 14/562 20130101;
G03B 5/06 20130101; C23C 14/16 20130101; B32B 15/013 20130101 |
Class at
Publication: |
428/548 |
International
Class: |
B22F 7/02 20060101
B22F007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2003 |
SE |
0302903-2 |
Claims
1. A coated stainless steel strip product with a dense and evenly
distributed layer on one side or both sides of said strip wherein
said layer consists essentially of one or several of the metals
gold, copper, nickel, molybdenum, cobalt, silver, tin or tungsten,
that the wherein a thickness of said layer is preferably maximally
15 .mu.m, wherein a tolerance of said layer is maximally +/-30% of
the layer thickness, wherein a Cr content of the steel strip
substrate is at least 10%, and wherein the layer has an adhesion to
the strip that the coated steel strip, under uniaxial stretching to
fracture by tensile testing, does not show any tendency to peeling
or flaking.
2. Product according to claim 1 wherein the thickness of the strip
substrate is between 0.015 mm and 3.0 mm.
3. Product according to claim 1, wherein said strip includes a
substrate of austenitic stainless steel, or duplex stainless steel,
or hardenable martensitic chromium steel, or precipitation
hardenable stainless steel, or maraging steel with a minimum
tensile strength of 1000 MPa in the cold rolled or heat treated
condition.
4. Product according to claim 1, wherein the layer has a
multi-layer constitution of up to 10 layers.
5. Product according to claim 4 wherein each individual layer has a
thickness of between 0.05 to 15 .mu.m.
6. Product according to claim 4 wherein each individual layer has a
thickness of between 0.05 to 11 .mu.m.
7. Product according to claim 4 wherein each individual layer has a
thickness of between 0.05 to 5 .mu.m.
8. Product according to claim 5, wherein the layer has a
multi-layer constitution of individual layers of different metallic
coatings.
9. Product according to claim 8, wherein the layer consists of
alloys of at least 2 elements selected from the group consisting of
gold, copper, nickel, molybdenum, cobalt, silver, tin and
tungsten.
10. A product according to claim 1, wherein the product is suitable
for use in load carrying applications where a low contact
resistance at the surface is advantageous.
11. A product according to claim 1, wherein the product is suitable
for the production and use of spring elements is in switches,
connectors, or metallic domes.
12. Method of manufacturing a coated stainless steel strip product
according to claim 1, comprising producing the coated stainless
steel strip product in a continuous roll-to-roll process included
in a strip production line using electron beam evaporation
comprising an etch chamber in-line.
13. Product according to claim 8, wherein the different metallic
coatings are selected from the group consisting of Ag, Ni, Mo, Co,
Au, Mo, W and Sn.
Description
[0001] The present invention relates to a method for manufacturing
a metal coated steel strip product in a roll-to-roll process and in
particular to a coated metallic substrate material suitable for
manufacturing high strength stainless steel products. This is
achieved by coating a metallic strip with an electrically
conductive layer, in accordance with claim 1.
BACKGROUND OF THE INVENTION
[0002] In many electronic devices such as telephones, remote
controls, computers, etc., springs and other formed metallic parts
are used for different functions. Hence, for electromagnetic
shielding (EMS) purposes, springs are used in so called "finger
stocks" as gaskets in removable sections in shielded boxes. In most
such products, several different requirements on the material are
at hand. For springs, the requirements are in general related to
the mechanical behavior such as force, relaxation resistance, and
fatigue resistance. However, as forming is generally involved, the
material must be able to be formed to requested shapes without any
cracking. Further, the ongoing miniaturization within this field
also puts increasing demands on tight geometrical tolerances of
components and parts in electronic devices. In addition to the
above, it is sometimes crucial to have well defined electrical
characteristics of such parts and components. This may involve
specific properties regarding electrical conductivity or contact
resistivity at interfaces within devices. Generally, when such
requirements are present, the solution is to choose a conductive
material such as copper or copper alloys, or alternatively to coat
a steel with a conductive layer. Copper and copper alloys are often
characterized by good electrical conductivity and good formability
but most of them are suffering from low mechanical strength, which
means that they are not suitable for applications that are highly
stressed, as for instance springs. Alloys of copper and beryllium
may be hardened to a tensile strength up to approximately 1400 MPa
but also this tensile strength level limits the spring force,
fatigue and relaxation resistance that can be achieved for spring
applications. Further, beryllium is a toxic metal, which may put
restrictions during manufacturing and use due to health
considerations. Finally, copper-beryllium alloys are costly and,
therefore, less expensive products are requested in many
applications.
[0003] Coating may be carried out by various methods that can be
divided into mechanical and chemical methods. These may also be
sub-divided into high and low temperature methods. Mechanical
methods may be exemplified by cladding, thermal by spraying or
painting. In this context, cladding is represented by roll bonding,
i.e., to bind two (or more) different materials by a rolling
process that is relatively simple and may be carried out with
different combinations of substrates and coatings. However,
cladding suffers from some technical disadvantages, which are
related to thickness tolerances and poor adhesion of the coated
layer. This often requires a post-bonding heat treatment in order
to obtain a diffusion zone between layers. If one (or several) of
the layers is/are stainless steel, then a good adhesion is even
more difficult to obtain due to the passive film at the stainless
surface. Further, roll bonding is a low speed process and is
limited in the possible combinations of base materials and
coatings.
[0004] There also exist numerous different deposition techniques
based on spraying methods with different names such as Thermal
Spray, High Velocity Oxide Fuel (HVOF), Plasma Spray, Combustion
Chemical Vapor Deposition (CCVD); however, the underlying method is
the same. The coating is sprayed onto a substrate and the material
is fed into the nozzle or "flame" from either a rod, wire, stock,
powdered material, liquid or gas. Spray techniques are most often
used to coat details and are not suitable for roll-to-roll
coatings, with high requirements on close tolerances and high
productivity.
[0005] Another method to coat a substrate is by hot dipping of the
product into a molten metal. Hot dipping is generally carried out
with coatings that have a low melting point, e.g., zinc, etc. For
coatings with higher melting points, such as nickel and copper, the
temperature of the molten metal is so high that it will often
affect the substrate material in a negative way. Further, to have
an accurate process control of such molten bath allowing close
tolerances on layer thickness, is difficult.
[0006] Electroplating is an electrochemical process in which the
coating is achieved by passing an electrical current through a
solution containing dissolved metal ions and the metal object to be
plated. The metal substrate serves as the cathode in an
electrochemical cell, attracting metal ions from the solution.
Ferrous and non-ferrous metal substrates are plated with a variety
of metals, including aluminum, brass, bronze, cadmium, copper,
chromium, iron, lead, nickel, tin, and zinc, as well as precious
metals, such as gold, platinum, and silver.
[0007] As the substrate acts as a cathode in the process and
thereby attracts the ions in the solution, it is difficult for flat
products to obtain an even layer distribution. Local variations in
current density will create an inhomogeneous deposition rate. A
well-known problem is the "dog bone" effect that means that the
thickness of the coating is often higher towards the edges of a
coated strip. Further, the method is characterized by not being
environmentally friendly as it involves electrolytes and costly
wastewater treatment. Electrochemical methods and dipping methods
also have the disadvantage that if a single sided coating is
requested, the surface that shall remain uncoated has to be masked
in some way prior to the coating. The masking then has to be
removed subsequent to the coating operation.
[0008] There are also some vapor deposition methods that can be
used for depositing metals. Most methods are batch-like processes,
but there are also some continuous processes. One example of a
roll-to-roll method making use of electron-beam deposition is
disclosed in WO 98/08986, which describes a method of manufacturing
ferritic stainless FeCrAl-steel strips, by bringing about an
aluminum coating of a substrate material in a roll-to-roll process.
However, the method described in this patent application is
optimized for a product suitable for use in a high temperature
corrosive environment, thus requiring a material with a good
high-temperature strength and also a good high-temperature
corrosion resistance, i.e., oxidation resistance. Moreover, this
patent application suggests that a homogenization annealing at a
temperature of 950-1150.degree. C. is made in connection to the
coating, in order to have the aluminum evenly distributed in the
ferrite. This means that the final product in this case is not a
coated product with an aluminum layer on the surface. Hence, it is
rather a FeCrAl strip product with a uniform distribution of the
alloying elements, including also aluminum. Further, this means
that there are no special requirements on an oxide free interface
and on a good adhesion of the layer.
[0009] Thus, all these conventional methods are suffering from
different disadvantages, which means that there is a need for a
development of a new product combining good mechanical properties
with excellent electrical characteristics and narrow geometrical
tolerances.
[0010] All processes based on batch-type production will always
increase the cost and it is therefore essential that the production
will be by a roll-to-roll process to decrease the cost.
[0011] Therefore, it is a primary object of the present invention
to provide a flexible metallic product with tailor-made physical
and mechanical characteristics suitable for further processing that
may be exemplified by, but not limited to, blanking, bending,
drilling, heat treatment etc.
[0012] Yet another object of the present invention is to provide a
flexible strip product, for springs and other products, that
requires a good electrical conductivity, made from a single- or
multilayered metallic strip that is inexpensive and which may be
produced in a continuous roll-to-roll process.
[0013] These and other objects have been attained in a surprising
manner by creating a coated steel product with the features
according to the characterizing clause of claim 1. Further
preferred embodiments are defined in the dependent claims.
BRIEF DESCRIPTION OF THE INVENTION
[0014] Thus, the above objects and further advantages are achieved
by applying one or more thin continuous, uniform, electrically
conductive layer(s) of a metal, such as nickel, silver, tin,
molybdenum, copper, tungsten gold or cobalt, on the top of a metal
stainless strip serving as substrate. The coating may be done on
one or both sides of the substrate strip. The metal layer should be
smooth and dense and have a good adhesion in order to allow for
further processing without the risk of flaking or peeling. The
final product, in form of a high strength strip steel with one or
two electrically conductive surfaces, is suitable for use in
electrical devices, in gaskets for electromagnetic shielding or for
any other purpose, where a high strength material with a low
contact resistance in the interface between the product according
to the invention and its contact point is requested.
[0015] The coated layer is deposited by means of the previously
known method electron beam evaporation (EB), in a roll-to-roll
process, to an evenly distributed layer with a thickness of
preferably less than 15 .mu.m. The substrate material should be a
stainless steel with a Cr content above 10% (by weight) and with a
strip thickness of usually less than 3 mm. The substrate material
should have a tensile strength of at least 1000 MPa, which can be
achieved by cold deformation or by thermal treatment such as
hardening from high temperature or by precipitation hardening at
lower temperatures. As a first step, the roll-to-roll process may
also include an etch chamber, in order to remove the oxide layer
that otherwise normally is present on a stainless steel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a schematic cross-section of a first embodiment
of the present invention, i.e., a substrate strip 2 with a coating
of an electrically conductive layer 1, 3 on one or both surfaces.
If the substrate is coated on both surfaces, then the coatings may
be of the same composition, or if so desired, of different
compositions. Also the thickness of the coating may be the same or
different for the two surfaces.
[0017] FIG. 2 shows a schematic cross-section of a second
embodiment of the present invention, i.e., a substrate strip 2 with
coatings of multiple layers (1,3,4 and 5,6, respectively) on one or
both surfaces.
[0018] FIG. 3 shows schematically a production line for the
manufacturing of a coated metal strip material according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The final product, in the form of a metal coated strip
material, is suitable for the use as load carrying parts that also
are characterized by providing a low contact resistance at the
interface. Examples of such applications are connectors and
switches. By applying a given force on the spring, it will contact
a surface and thus close an electrical circuit. At the point of
contact, where the current is transferred, it is important that the
contact resistance is low. Stainless steel is an increasingly used
material for spring applications. This is due to the attractive
combination of high mechanical strength and good formability,
allowing forming also rather complex spring geometries. High
strength stainless spring steels have in general superior
mechanical properties compared to non-ferrous materials. In the
context of spring properties, especially the fatigue and relaxation
resistance of high strength stainless steel are crucial for a long
lasting spring with a constant force throughout its service life.
However, stainless steel is characterized by a passive film on the
surface. This film consists of chromium oxide and has a
significantly lower electrical conductivity than the steel itself.
As a reference value, a stainless steel has an electrical
resistivity of 80-90.times.10.sup.-8 .OMEGA.m, depending on the
tensile strength. However, at the surface, the oxide
(Cr.sub.2O.sub.3), has a resistivity of approximately
1.3.times.10.sup.11 .OMEGA.m. If an oxide film is present at the
interface between two conductive surfaces, a drop in conductivity
will occur. This will decrease the efficiency in current
circulation in the circuit and thus decrease the performance.
[0020] To eliminate the problem of low conductivity in high
strength stainless steel, at least one of the strip surfaces is
coated with a metal layer that is less prone to form an oxide film
at the surface. The coated layer will thus allow for an oxide free
surface at the contact point, whereby the drop in electrical
conductivity at the interface is avoided. Depending on the
requirements, the coating may be of different metals. Silver,
copper, nickel, cobalt, gold, tungsten, tin and molybdenum are all
metals with a good electrical conductivity that may be deposited on
the surface by the method according to the invention. It is also of
vital importance that the coating is homogeneously distributed on
the surface and is not too thick compared to the substrate
thickness. A thick or an uneven layer will affect the spring
properties, as the bending force is proportional to the thickness
of a rectangular section raised to the third power. The thickness
of the layer is therefore preferably max 10% of the substrate
thickness. Moreover, the thickness of each coating layer is
preferably maximally 15 .mu.m, typically 0.05-15 .mu.m, preferably
0.05-10 .mu.m and even more preferably 0.05-5 .mu.m. If multiple
layers are to be deposited, then the total summarized thickness of
the coatings should not exceed 20% of the total thickness of the
coated strip. The thickness tolerance of the coated layer according
to the invention is very good. The variation in thickness of and
within each layer should not exceed +/-20% of the nominal thickness
of said layer. More preferably, the thickness variation should be
maximum +/-10% of the nominal thickness within each layer.
[0021] The coating should show a good adhesion to the substrate and
thus make subsequent manufacturing possible. The product according
to the invention shows an excellent adhesion between the coating
and the substrate. This is achieved by a pre-treatment operation of
the stainless strip by means of an ion etching in vacuum prior to
the deposition of the coating on the substrate. This allows for a
metal-metal contact with an oxide free interface that will give a
product that may be bent, blanked, slit or deep-drawn, the only
limit being set by the ductility of the substrate material.
The Substrate Strip to be Coated
[0022] The material that shall be coated should have a good general
corrosion resistance. This means that the material must have a
chromium content of at least 10% by weight, preferably minimum 12%
or more preferably minimum 13% or most preferably minimum 15%
chromium. Further, the material must be alloyed in a way that
allows for a high tensile strength of at least 1000 MPa, more
preferably a minimum of 1300 MPa or even more preferably minimum
1500 MPa, or most preferably a minimum of 1700 MPa. The mechanical
strength may be achieved by cold deformation such as for steels of
the ASTM 200 and 300 series, or by thermal hardening as for
hardenable martensitic chromium steels. Other suitable substrate
materials are precipitation hardenable (PH) steels of type 13-8PH,
15-5PH, 17-4PH or 17-7PH. Yet another group of suitable substrate
materials are stainless maraging steels that are characterized by a
low carbon and nitrogen containing martensitic matrix that is
hardened by the precipitation of substitutional atoms such as
copper, aluminum, titanium, nickel etc.
The Conductive Layer(s)
[0023] The material to be coated in the form of a thin layer film
on the substrate surface should be characterized by a good
electrical conductivity at room temperature, a thermodynamic
stability against oxide formation and a suitable modulus of
elasticity. The characteristics of the suitable elements are listed
below.
[0024] Silver has a very low electrical resistivity, approximately
1.47.times.10.sup.-8 .OMEGA.m, at room temperature. The free energy
for oxide formation for Ag.sub.2O at room temperature is
approximately .DELTA.G=-10.7 kJ which makes silver significantly
more stable against oxidation compared with the formation of
Cr.sub.2O.sub.3, as in stainless steel. As a reference value,
Cr.sub.2O.sub.3 has a free energy at room temperature of
approximately .DELTA.G=-1050 kJ. Silver has a modulus of elasticity
of approximately 79000 MPa that can be compared to the
180,000-220,000 MPa for different steel types. Silver is however
relatively expensive and sometimes cheaper alternatives are
required.
[0025] Copper has a low electrical resistivity of approximately
1.58.times.10.sup.-8 .OMEGA.m, a modulus of elasticity of
approximately 210,000 MPa and a free energy of .DELTA.G=-145 kJ and
.DELTA.G=-127 kJ for the formation of Cu.sub.2O and CuO
respectively. This combination of properties makes also copper a
suitable coating in the product according to the invention.
[0026] Nickel has a low electrical resistivity of approximately
6.2.times.10.sup.-8 .OMEGA.m, a modulus of elasticity of 200,000
MPa and a free energy of approximately .DELTA.G=-213 kJ for the
formation of NiO.
[0027] Gold has an electrical resistivity of approximately
2.times.10.sup.-8 .OMEGA.m, a modulus of elasticity of 80,000 MPa.
Gold is also extremely stable against oxidation. This makes gold in
many applications most suitable as an element for conductive
coatings. However, gold is expensive and alternatives are always
looked for due to the high alloy cost as well as re-cycling
costs.
[0028] Molybdenum has a low electrical resistivity of approximately
5.3.times.10.sup.-8 .OMEGA.m, a modulus of elasticity of 329,000
MPa and a free energy of approximately .DELTA.G=-668 kJ for the
formation of MoO.sub.3 and .DELTA.G=-533 kJ for the formation of
MoO.sub.2.
[0029] Cobalt has a low electrical resistivity of approximately
6.24.times..sub.10.sup.-8 .OMEGA.m, a modulus of elasticity of
209,000 MPa and a free energy of approximately .DELTA.G=-241 kJ for
the formation of CoO.
[0030] Tungsten has a low electrical resistivity of approximately
5.3.times.10.sup.-8 .OMEGA.m, a modulus of elasticity of 360,000
MPa and free energies of approximately .DELTA.G=-534 kJ and
.DELTA.G=-764 for the formation of WO.sub.2 and WO.sub.3,
respectively.
[0031] Tin has an electrical resistivity of approximately
10.times.10.sup.-8 .OMEGA.m and a modulus of elasticity of 50,000
MPa. The free energy to form SnO is approximately .DELTA.G=-534 kJ
at room temperature. Tin is also a relatively soft metal and is
easily deformed at the point of contact and may by this generate a
larger contact area at the interface. This may be utilized, e.g.,
in gasket springs for electromagnetic shielding.
Description of Coating Method
[0032] Advantageously, the coating method is integrated in a
roll-to-roll strip production line. In this roll-to-roll production
line, the first production step is an ion-assisted etching of the
metallic strip surface, in order to achieve good adhesion of the
first layer. The conductive layer is deposited by means of electron
beam evaporation (EB) in a roll-to-roll process. The formation of
multi-layers can be achieved by integrating several EB deposition
chambers in-line (see FIG. 3).
PREFERRED EMBODIMENT OF THE INVENTION
[0033] Two examples of embodiments of the invention will now be
described in more detail. One example is based on a silver coating
on a ASTM 301-type of steel with a chemical composition of max
0.12% C, max 1.5% Si, max 2% Mn, 16-18% Cr and 6-8% Ni with balance
Fe and residual elements that are present according to the
metallurgical method used. The second example is a nickel coating
on a modified ASTM 301-type of steel with a chemical composition of
max 0.12% C, max 1.5% Si, max 2% Mn, 16-18% Cr and 6-8% Ni,
0.5-1.0% Mo with balance Fe and residual elements that are present
according to the metallurgical method used.
[0034] Firstly, the substrate materials are produced by ordinary
metallurgical steel-making to a chemical composition as exemplified
above. They are then hot rolled down to an intermediate size, and
thereafter cold-rolled in several steps with a number of
recrystallization steps between said rolling steps, until a final
thickness of about 0.02-1 mm and a width of maximum 1000 mm are
attained. The surface of the substrate material is then cleaned in
a proper way to remove all oil residuals from the rolling.
[0035] Thereafter, the coating process takes place in a continuous
process line, starting with decoiling equipment. The first step in
the roll-to-roll process line can be a vacuum chamber or an
entrance vacuum lock followed by an etch chamber, in which
ion-assisted etching takes place in order to remove the thin oxide
layer on the surface of the stainless substrate material. The strip
then enters into the E-beam evaporation chamber(s) in which the
deposition of the desired layer takes place. A metal layer of
normally 0.05 up to 15 .mu.m is deposited, the preferred thickness
depending on the application. In the two examples described here, a
thickness of 0.2-1.5 .mu.m is deposited by using one E-beam
evaporation chamber.
[0036] After the EB evaporation, the coated strip material passes
through the exit vacuum chamber or exit vacuum lock before it is
coiled on to a coiler. The coated strip material can now, if
needed, be further processed by, for example, rolling or slitting,
to obtain the preferred final dimension for the manufacturing of
components.
[0037] The final product as described in the two examples, i.e., a
0.05 mm thick strip of ASTM 301 with a single sided 1.5 .mu.m
Ag-coating and a 0.07 mm thick strip of ASTM 301, modified with a
single sided 0.2 .mu.m Ni-coating, have a very good adhesion of the
coated layer and are thus suitable to be used in subsequent
manufacturing of components for high strength applications, e.g.,
for springs. The good adhesion of the layers is tested according to
standard tensile testing. From a substrate material of a stainless
steel strip that has been coated with a thin covering layer so as
to produce a coated strip product in accordance with the present
invention, tensile test specimens are produced according to
standard. Tensile testing of 4 specimens, for example according to
EN 10002-1, is thereafter carried out until fracture. After
testing, the fractured part of the specimen is investigated in an
optical microscope with a magnification of 50 times. Beside the
actual fracture from testing, no signs of flaking, peeling or any
other damage of the coated layer has been observed in any tested
specimen. The results from this test are presented in Table 1.
TABLE-US-00001 TABLE 1 Mechanical properties and adhesion of layer.
Proof Proof Tensile Visual Thick- strength strength stregth
examination ness, Rp 0.05%, Rp 0.2%, Rm, at 50 times Sample Mm MPa
MPa MPa magnification 301 + Ni 0.07 1659 2108 2120 No peeling or
flaking, 301Mod + 0.05 1445 1920 1945 No peeling or Ag flaking
[0038] The roll-to-roll electron beam evaporation process referred
to above is illustrated in FIG. 3. The first part of such a
production line is the uncoiler 13 within a vacuum chamber 14, then
the in-line ion assisted etching chamber 15, followed by a series
of EB evaporation chambers 16, the number of EB evaporation
chambers needed can vary from 1 up to 10 chambers, this to achieve
a multi-layered structure, if so desired. All the EB evaporation
chambers 16 are equipped with EB guns 17 and suitable crucibles 18
for the evaporation. After these chambers, comes the exit vacuum
chamber 19 and the recoiler 20 for the coated strip material, the
recoiler being located within vacuum chamber 19. The vacuum
chambers 14 and 19 may also be replaced by an entrance vacuum lock
system and an exit vacuum lock system, respectively. In the latter
case, the uncoiler 13 and the coiler 20 are placed in the open
air.
* * * * *