[0001] The invention relates to a method for applying a metal coating or metal based coating
on a surface of a substrate. The invention also relates to an apparatus for applying
a metal coating or metal based coating on a surface of a substrate.
[0002] Metal coatings or metal based coatings (hereafter together referred to as metal coatings
unless indicated otherwise) are often applied by electroplating or dipping in a melt.
Especially for coating large surfaces, such as metal strips, hot dip coating is used
to apply a zinc or aluminium coating, or an alloy thereof, since electroplating is
more expensive and less practical on AHSS (advanced high strength steel) because of
hydrogen embrittlement. The metal strip, usually a steel strip, is first continuous
annealed and thereafter directly guided through a bath with molten metal. The coating
on the strip is relatively thick and has to be removed partly, for which gas knives
are used.
[0003] Hot dip coating however has the disadvantage that iron-aluminium alloy and oxide
pollutions in the metal bath build up to large quantities and lead to surface defects
in the coating. Moreover, the speed of coating is limited because when speed increases,
the amount of metal to be removed increases too. To do so, the gas flow of the gas
knives has to increase as well, which causes splashes, affecting the surface of the
coating. In addition, the coating thickness of the coating often varies due to strip
vibrations.
[0004] Other coating techniques have been developed, but these all have their disadvantages.
For instance, physical vapour deposition (PVD) requires much energy and needs a high
investment; PVD is therefore generally used for very thin coating layers. Thermal
spraying of zinc is known, but this is usually done to cover e.g. corners of profiled
products or welds. Typically thick layers are produced, having a poor quality; the
coating is porous and has an unattractive optical appearance.
A.Jaworek, Journal of Materials Sciences, vol. 42, n°1, pages 266-297, 2006, reviews electrospray methods and devices including liquid metal ion sources, used
for thin film deposition.
[0005] It is an object of the invention to provide a method for applying a metal coating
on a surface of a substrate (or a part of that surface), whereby the production speed
of the coating process can be increased.
[0006] It is another object of the invention to provide a method for applying a metal coating
on a surface of a substrate providing an improved surface quality compared to hot
dip coatings.
[0007] It is a further object of the invention to provide a method for applying a metal
coating on a surface of a substrate which coating can be thinner than usually applied
by hot dip coating.
[0008] It is yet another object of the invention to provide a method for applying a metal
coating on a surface of a substrate that has a better quality than a coating made
by hot dip coating.
[0009] Furthermore, it is an object of the invention to provide an apparatus that can be
used to implement the method according to the invention.
[0010] One or more of the objects of the invention are obtained by a method for applying
a metal coating or metal based coating on a surface of a substrate or a part of that
surface, wherein the surface of the substrate is electrically conductive, wherein
the surface of the substrate is provided with a temperature that is suitable for applying
the coating, wherein metal droplets are generated from a surface of a metal melt,
wherein an inert gas is present in the area of the metal melt and the droplets and
the surface of the substrate, and wherein a high voltage of between 1 and 30 kV is
applied between the metal melt and the surface of the substrate, whereby the metal
droplets impinge on the surface of the substrate to form a coating.
[0011] The inventors have found that a metal coating layer of good quality can be provided
when liquid metal droplets are generated from a melt and these droplets are pulled
towards the surface of the substrate. This surface has to be electrically conductive
so a high voltage can be applied between the metal melt and the surface. The droplets
will be electrically charged and thereby pulled to the surface; to be able to do so
over time, the electrical charge of the droplets has to be discharged by the electrically
conductive surface once the droplets impinge on the surface. The droplets must be
created and travel in an inert hot surrounding, otherwise the droplets will oxidise
and solidify. The surface of the substrate has to have a suitable temperature so the
droplets will stick on the surface and spread out by wetting. During their travel
to the surface the charges on the droplets will prevent coagulation of the droplets
and the droplets will be homogeneously dispersed in the inert gas as well.
[0012] By using the method according to the invention it is possible to apply a thin coating,
for instance a coating having a thickness between 1 and 5 µm, at a high speed, having
a smooth surface without defects, and having a constant thickness. It is also possible
to apply thicker coatings.
[0013] According to a preferred embodiment the droplets have a diameter of at most 30 µm,
preferably a diameter of at most 20 µm. Droplets of a small size in a high density
spread out well on the surface of the substrate, and provide a coating with a uniform
thickness. The inventors expect that droplets having a diameter of 1 to 5 µm are most
preferred.
[0014] Preferably, the substrate is moving relative to the metal melt. In this way a coating
having a constant thickness is provided on the substrate while the droplets are generated
at a constant quantity, when the substrate is moving with a constant velocity. When
the velocity is changed, either the coating thickness changes and/or the quantity
of droplets has to be changed.
[0015] According to the invention the droplets are formed from the surface of the metal
melt by applying high-frequency ultrasonic energy to the metal melt. The high-frequency
ultrasonic energy excites the surface of the metal melt, whereby a standing wave is
formed on the surface, from which droplets are released when the amplitude is high
enough. The magnitude of the frequency determines the size and quantity of the droplets
that are formed.
[0016] Preferably the surface of the metal melt is formed at the end face of a nozzle tip.
When a standard (pressure) nozzle is used this nozzle usually has an entrance opening
to a cavity filled with molten metal. A transducer coupled to this cavity can provide
ultrasonic energy to the molten metal, whereby the surface of the molten metal will
vibrate and release droplets. Molten metal has to be fed into the cavity of the nozzle
continuously to keep the cavity filled. Usually the surface of the outlet opening
of the nozzle has a diameter of approximately 3 mm. Another embodiment uses a series
of coupled acoustic horns vibrating at resonance, whereby the molten metal covers
the end face of the last horn, which has a diameter of approximately 1 mm. This leads
to a monodisperse droplet distribution of diameters between 1 and 5 µm for MHz frequencies.
Reference is made to the article "Faraday instability-based micro droplet ejection
for inhalation drug delivery" by C.S. Tsai, R.W. Mao, S.K. Lin and S.C. Tsai, describing
the forming of water droplets.
[0017] According to a first preferred embodiment the temperature of the surface of the substrate
is higher then the melting temperature of the metal. The droplet impinging on the
surface of the substrate thus remains molten and will spread out well over that surface,
often increasing its diameter with approximately a factor ten compared to the diameter
of the original droplet.
[0018] According to a second preferred embodiment the temperature of the surface of the
substrate is lower then the melting temperature of the metal and the surface of the
substrate is heated to a temperature that is higher then the melting temperature of
the metal coating, after the metal coating has been applied. Using this method, the
droplet that impinged on the surface of the substrate will directly solidify on the
surface of the substrate, thus preventing bounce-off, and therefore not spread out
over that surface initially. Since the droplets impinge at random on the surface,
a locally uneven coating surface will be formed. To create a smooth, even surface
of the coating, the surface of the substrate has to be heated to a temperature that
is higher than the melting temperature of the metal coating, so the metal coating
will melt and a smooth surface is formed due to the interfacial (wetting) tension
between the coating and the surface of the substrate. Heating of the coating can be
performed in any suitable way, such as induction heating.
[0019] Preferably the metal coating is formed from a metal having a low melting point, such
as zinc, aluminium, tin, copper or an alloy thereof, wherein the alloying elements
are for instance aluminium or magnesium, or wherein the metal based coating is formed
from a metal coating with solid particles, for instance nano particles. It is expected
that the method according to the invention is very suitable for applying a zinc or
zinc based coating, since it is desired to produce zinc (alloy) coatings with a thickness
of less than 5 µm which are difficult to produce with hot dip coating. Moreover, the
coating velocity can be higher than the maximum practical velocity for hot dip coating,
and it is possible to apply a coating at only one side of the substrate. However,
the method is also perfectly suited to apply an aluminium, tin, copper or other metal
(alloy) coating. Furthermore, using the method of the invention it is possible to
apply a metal based coating by introducing solid particles in the metal melt. These
solid particles can for instance be nano particles or other small particles, which
are (very) small relative to the diameter of the droplets. In the method of the invention,
it is easier to introduce these solid particles in the coating, whereas using for
instance hot dip coating these particles will easily clog the molten metal bath.
[0020] According to a preferred embodiment the substrate is a moving strip, preferably a
moving metal strip, more preferably a moving steel strip. The method according to
the invention is very suitable for coating a metal or steel strip, in the same way
as a steel strip can be coated with zinc or aluminium by hot dip coating, directly
after the annealing line. The method according to the invention has the advantage
that coatings with practically any thickness can be applied, and that a very high
velocity of the strip can be used. Vibrations of the strip will not influence the
coating thickness, and the guiding of the strip is easier because no molten metal
bath is needed through which the strip has to be guided. No dross is formed in the
method according to the invention.
[0021] Preferably, the moving steel strip has a temperature of 350°C to 500°C when the metal
droplets consist of zinc or a zinc alloy. The strip thus has a temperature above the
melting temperature of zinc, or slightly below the melting temperature, but is thus
easy to heat above the melting temperature, as is described above.
[0022] According to a second aspect of the invention an apparatus for applying a metal coating
or metal based coating on a surface of a substrate or a part of that surface is provided,
the apparatus having a container for keeping an inert gas and for containing the surface
of the substrate to be coated, or a part of that surface, wherein means for generating
metal droplets from the surface of a metal melt are present in the container, and
wherein means to apply a high voltage of between 1 and 30 kV between the metal melt
and the surface of the substrate to be coated are present.
[0023] This apparatus can be used to implement the method according to the first aspect
of the invention as described above. The container is needed to keep the inert gas
in the area where the droplets are formed and travel and impinge on the surface of
the substrate. The high voltage is needed to pull the droplets to the surface of the
substrate.
[0024] It is possible that means are present to heat the surface of the substrate to be
coated. Whether these means are needed depends on the use that is made of the apparatus
according to the invention. When a steel strip has to be coated using the method of
the invention, and the apparatus is placed directly after the continuous annealing
line, it is possible that the strip has a temperature that is still high enough to
coat it, without use of additional heating means. This also depends on the coating
to be applied. If the apparatus is used as stand-alone equipment, a strip will have
to be heated before it can be coated using the method according to the invention and
heating means are needed for the apparatus.
[0025] According to a preferred embodiment the means for generating the metal droplets from
the surface of a metal melt are one or more nozzles, wherein the surface of the metal
melt is formed at the end face of a nozzle tip. The use thereof has been described
above.
[0026] According to the invention, means are present for applying high-frequency ultrasonic
energy to the surface of the metal melt. The forming of droplets using high-frequency
ultrasonic energy has been described above.
[0027] According to a preferred embodiment the container contains an entry gas lock system
and an outlet gas lock system for coating a moving substrate. The moving substrate,
for instance a steel strip or steel wire, can enter the container through the entry
gas lock system and leave the container after it has been coated and preferably after
the coating has solidified through the outlet gas lock system. The entry and outlet
gas lock systems are needed to keep the inert gas inside the container, while making
it possible to coat a moving substrate.
[0028] The invention will be elucidated with reference to an exemplary embodiment, as shown
schematically in the figures.
Fig. 1 shows, in a very schematic way and while leaving out several required parts,
an apparatus according to the invention for coating a moving strip using the method
according to the invention.
Fig. 2a shows, in a schematic way, a standard pressure nozzle as can be used in the
apparatus of Fig. 1, from the outside.
Fig. 2b shows in cross-section the pressure nozzle as schematically shown in Fig.
2a.
Fig. 3a shows, in a schematic way, another embodiment of nozzles placed in parallel,
which can be used in the apparatus shown in Fig. 1.
Fig. 3b shows one of the nozzles of Fig. 3a in more detail.
[0029] Figure 1 shows a moving metal strip 1 that is fed horizontally from for instance
an annealing furnace (not shown) and that is deflected in the vertical direction by
a guiding roll 2. Above the guiding roll 2 a container (not shown) is placed, having
an entry gas lock system in its lower part and an outlet gas lock system in its upper
part (also not shown), so the moving strip 1 can enter and exit, respectively, the
container. The gas lock systems are present so as to keep an inert gas inside the
container.
[0030] Figure 1 shows a small, closed bath 5 containing molten metal 6 at each side of the
metal strip 1. Each bath 5 has several outlet pipes 7 that are connected to nozzles
9. A valve 8 is present in each outlet pipe 7 to regulate the flow of molten metal
to each nozzle 9. The baths 5 with molten metal 6 are replenished with additional
molten metal at a moment in time and in a way as required, by means and measures that
are not shown here. To replenish molten metal in baths is as such known in the art.
[0031] Between the strip 1 and the molten metal 6 a high voltage is applied, of for instance
6 kV (6000 Volt). The molten metal has the high voltage relative to the strip 1, which
is connected to earth. Metal droplets are generated at the outlet openings of the
nozzles 9. These droplets are generated at the surface of the metal melt at the outlet
openings of the nozzle 9 by applying a high-frequency ultrasonic wave at the backside
of the nozzles 9. The means for generating the high-frequency ultrasonic waves are
not shown; the high frequency is for instance 3 MHz. The high-frequency ultrasonic
waves generate a standing wave at the surface of the metal melt in the outlet opening
of the nozzle 9, which standing waves produce droplets with an average diameter of
less then 20 µm.
[0032] Due to the high voltage between the molten metal 6 the droplets become charged and
are attracted towards the metal strip 1 and impinge thereon. When the metal strip
1 has a temperature that is higher than the melting temperature of the (molten) metal
6, the droplets remain molten and will spread out on the surface of the metal strip
1. In this way, a continuous, smooth, even metal coating will be formed on the strip
1, due to the interfacial (wetting) tension of the molten metal on the strip. The
droplets are shown in Figure 1 as a dark cloud in front of the nozzles 9.
[0033] The nozzles 9 shown in Figure 1 are depicted in more detail in Figures 2a and 2b.
Figure 2a shows a nozzle 9 having an outlet opening 10. Figure 2b shows that outlet
opening 10 is the outlet opening of a cavity 11, which can be filled through entrance
opening 12. The cavity 11 is filled with molten metal through entrance opening 12,
and at the outlet opening 10 the surface of the molten metal is formed. A transducer
13 behind the cavity 11 in the nozzle 9 is set to vibrate using high-frequency ultrasonic
energy, whereby the molten metal in the cavity 11 will vibrate. This vibration is
increased towards the outlet opening 10. At the surface of the molten metal in the
outlet opening 10 a standing wave is formed on the surface, from which droplets are
released when the amplitude is high enough. The magnitude of the frequency determines
the size and quantity of the droplets that are formed.
[0034] Instead of the nozzles 9 shown in Figure 1, 2a and 2b, it is also possible to use
another type of nozzle as shown in Figure 3a and 3b to generate droplets of the required
size. The nozzles 15 shown in Figure 3a use a series of three small horns 16 in series,
as shown in Figure 3b, which are induced to vibrate by high-frequency ultrasonic energy
generated in a transducer 17. The horns 16 increase the amplitude of the vibration,
such that the end face 18 of the last horn 16 has a high amplitude of a precise frequency.
The end face 18 of the nozzle 15 has a surface of for instance 1 mm
2. Molten metal is fed to the end face 18 of the nozzle 15 through a pipe 19. Due to
the precise frequency at the end face of the nozzle, droplets are formed within a
narrow diameter range between 1 and 5 µm. These diameters are very suitable to form
thin metal coatings in accordance with the invention.
[0035] It will be clear to the person skilled in the art that means have to be provided
to keep the molten metal 6 in the baths 5 at a required temperature, and also that
means can be needed to heat the steel strip before it enters the container, such that
the strip has the required temperature when the droplets impinge upon it, as described
hereinabove. It may also be necessary to use heating means after the coating has been
applied, to melt the coating consisting of impinged droplets, such that a smooth surface
of the coating is obtained. Further means for controlling the flow of molten metal
through the pipes 7 may be required, and also means to apply inert gas to the container.
[0036] Some droplets will become uncharged and float through the inert gas in the container,
therefore the container walls should have a temperature such that the droplets reaching
the container walls will remain liquid and flow downwards in the container, where
the molten metal can be tapped off.
[0037] The metal that can be applied as coating is the usual coating metal such as zinc,
aluminium, tin and copper, or alloys thereof, such as aluminium and magnesium for
zinc, and silicon for aluminium. However, also other metals and their alloys could
be used. The substrate to be coated will usually be a metal strip, preferably a steel
strip, such as a steel used for automotive purposes or for building purposes. However,
it is also possible to coat other substrates, as long as the surface of the substrate
to be coated is electrically conductive. It is also possible to coat other types of
substrates in the way as described above, such as metal wires and even metal pipes
(having a small diameter). It is also possible to coat a substrate with a metal coating
for instance larger diameter pipes and other long products in a semi-continuous way
using the method according to the invention, and using the apparatus according to
the invention after small modifications.
[0038] The metal coating described hereinabove also encompasses metal based coatings, wherein
solid particles are introduced in the molten metal that is deposited on the surface
of the substrate using the method according to the invention.
1. Method for applying a metal coating or metal based coating on a surface of a substrate
or a part of that surface, wherein the surface of the substrate is electrically conductive,
wherein the surface of the substrate is provided with a temperature that is suitable
for applying the coating, wherein metal droplets are generated from a surface of a
metal melt, wherein an inert gas is present in the area of the metal melt and the
droplets and the surface of the substrate, and wherein a high voltage of between 1
and 30 kV is applied between the metal melt and the surface of the substrate and the
droplets are formed from the surface of the metal melt by applying high-frequency
ultrasonic energy to the metal melt, whereby the metal droplets impinge on the surface
of the substrate to form a coating.
2. Method according to claim 1, wherein the droplets have a diameter of at most 30 µm,
preferably a diameter of at most 20 µm.
3. Method according to claim 1 or 2, wherein the substrate is moving relative to the
metal melt.
4. Method according to any one of the preceding claims, wherein the surface of the metal
melt is formed at the end face of a nozzle tip.
5. Method according to any one of claims 1 - 4, wherein the temperature of the surface
of the substrate is higher then the melting temperature of the metal.
6. Method according to any one of claims 1 - 4, wherein the temperature of the surface
of the substrate is lower then the melting temperature of the metal and the surface
of the substrate is heated to a temperature that is higher then the melting temperature
of the metal coating, after the metal coating has been applied.
7. Method according to any one of the preceding claims, wherein the metal coating is
formed from a metal having a low melting point, such as zinc, aluminium, tin, copper
or an alloy thereof, wherein the alloying elements are for instance aluminium or magnesium,
or wherein the metal based coating is formed from a metal coating with solid particles,
for instance nano particles.
8. Method according any one of the preceding claims, wherein the substrate is a moving
strip, preferably a moving metal strip, more preferably a moving steel strip.
9. Method according to any one of the preceding claims, wherein the moving steel strip
has a temperature of 350°C to 500°C when the metal droplets consist of zinc or a zinc
alloy.
10. Apparatus for applying a metal coating or metal based coating on a surface of a substrate
or a part of that surface, the apparatus having a container for keeping an inert gas
and for containing the surface of the substrate to be coated, or a part of that surface,
wherein means for generating metal droplets from the surface of a metal melt are present
in the container, wherein means to apply a high voltage of between 1 and 30 kV between
the metal melt and the surface of the substrate to be coated are present, and wherein
means are present for applying high-frequency ultrasonic energy to the surface of
the metal melt.
11. Apparatus according to claim 10, wherein means are present to heat the surface of
the substrate to be coated.
12. Apparatus according to claim 10 or 11, wherein the means for generating the metal
droplets from the surface of a metal melt are one or more nozzles, each having an
outlet opening for forming the surface of the metal melt, or the end faces of one
or more nozzle tips.
13. Apparatus according to any one of claims 10 - 12, wherein the container contains an
entry gas lock system and an outlet gas lock system for coating a moving substrate.
1. Verfahren zum Aufbringen eines Metallüberzugs oder metallischen Überzugs auf eine
Oberfläche eines Substrats oder einen Teil dieser Oberfläche, wobei die Oberfläche
des Substrats elektrisch leitend ist, wobei die Oberfläche des Substrats mit einer
Temperatur bereitgestellt wird, die zum Aufbringen des Überzugs geeignet ist, wobei
Metalltröpfchen von einer Oberfläche einer Metallschmelze erzeugt werden, wobei ein
Inertgas im Bereich der Metallschmelze und der Tröpfchen und der Oberfläche des Substrats
vorhanden ist, und wobei eine Hochspannung zwischen 1 und 30 kV zwischen der Metallschmelze
und der Oberfläche des Substrats angelegt wird und die Tröpfchen von der Oberfläche
der Metallschmelze durch ein Anwenden von hochfrequenter Ultraschallenergie auf die
Metallschmelze gebildet werden, wobei die Metalltröpfchen auf die Oberfläche des Substrats
aufprallen, um einen Überzug zu bilden.
2. Verfahren nach Anspruch 1, wobei die Tröpfchen einen Durchmesser von höchstens 30
µm, vorzugsweise einen Durchmesser von höchstens 20 µm aufweisen.
3. Verfahren nach Anspruch 1 oder 2, wobei sich das Substrat bezogen auf die Metallschmelze
bewegt.
4. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Oberfläche der Metallschmelze
an der Stirnfläche einer Düsenspitze gebildet wird.
5. Verfahren nach einem der Ansprüche 1 bis 4, wobei die Oberflächentemperatur des Substrats
höher als die Schmelztemperatur des Metalls ist.
6. Verfahren nach einem der Ansprüche 1 bis 4, wobei die Oberflächentemperatur des Substrats
niedriger als die Schmelztemperatur des Metalls ist und die Oberfläche des Substrats
auf eine Temperatur erwärmt wird, die höher als die Schmelztemperatur des Metallüberzugs
ist, nachdem der Metallüberzug aufgebracht wurde.
7. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Metallüberzug aus einem
Metall mit einem niedrigen Schmelzpunkt wie zum Beispiel Zink, Aluminium, Zinn, Kupfer
oder einer Legierung derselben gebildet wird, wobei die legierenden Elemente zum Beispiel
Aluminium oder Magnesium sind, oder wobei der metallische Überzug von einem Metallüberzug
mit Feststoffteilchen, zum Beispiel Nanoteilchen, gebildet wird.
8. Verfahren nach einem der vorhergehenden Ansprüche, wobei das Substrat ein beweglicher
Streifen, vorzugsweise ein beweglicher Metallstreifen, besonders bevorzugt ein beweglicher
Stahlstreifen ist.
9. Verfahren nach einem der vorhergehenden Ansprüche, wobei der bewegliche Stahlstreifen
eine Temperatur von 350 °C bis 500 °C aufweist, wenn die Metalltröpfchen aus Zink
oder einer Zinklegierung bestehen.
10. Vorrichtung zum Aufbringen eines Metallüberzugs oder metallischen Überzugs auf eine
Oberfläche eines Substrats oder einen Teil dieser Oberfläche, wobei die Vorrichtung
einen Behälter zum Aufbewahren eines Inertgases und zum Aufnehmen der Oberfläche oder
eines Teils dieser Oberfläche des zu beschichtenden Substrats aufweist, wobei Mittel
zum Erzeugen von Metalltröpfchen von der Oberfläche einer Metallschmelze in dem Behälter
vorhanden sind, wobei Mittel vorhanden sind, eine Hochspannung zwischen 1 und 30 kV
zwischen der Metallschmelze und der Oberfläche des zu beschichtenden Substrats anzulegen,
und wobei Mittel zum Anwenden von hochfrequenter Ultraschallenergie auf die Oberfläche
der Metallschmelze vorhanden sind.
11. Vorrichtung nach Anspruch 10, wobei Mittel vorhanden sind, die Oberfläche des zu beschichtenden
Substrats zu erwärmen.
12. Vorrichtung nach Anspruch 10 oder 11, wobei die Mittel zum Erzeugen der Metalltröpfchen
von der Oberfläche einer Metallschmelze eine oder mehrere Düsen, wobei jede eine Auslassöffnung
zum Bilden der Oberfläche der Metallschmelze aufweist, oder die Stirnflächen von einer
oder mehrerer Düsenspitzen sind.
13. Vorrichtung nach einem der Ansprüche 10 bis 12, wobei der Behälter ein Einlassgassperrsystem
und ein Auslassgassperrsystem zum Überziehen eines beweglichen Substrats enthält.
1. Procédé permettant l'application d'un revêtement métallique ou d'un revêtement à base
de métaux sur une surface d'un substrat ou une partie de cette surface, ladite surface
du substrat étant électroconductrice, ladite surface du substrat étant fournie à une
température appropriée en vue de l'application du revêtement, des gouttelettes métalliques
étant produites à partir d'une surface d'un métal en fusion, un gaz inerte étant présent
dans la zone du métal en fusion et des gouttelettes et de la surface du substrat,
et une haute-tension comprise entre 1 et 30 kV étant appliquée entre le métal en fusion
et la surface du substrat et lesdites gouttelettes étant formées à partir de la surface
du métal en fusion en appliquant une énergie ultrasonore à haute fréquence sur le
métal en fusion, moyennant quoi les gouttelettes métalliques heurtent la surface du
substrat pour former un revêtement.
2. Procédé selon la revendication 1, lesdites gouttelettes possédant un diamètre inférieur
ou égal à 30 µm, de préférence un diamètre inférieur ou égal à 20 µm.
3. Procédé selon la revendication 1 ou 2, ledit substrat étant en déplacement par rapport
au métal en fusion.
4. Procédé selon l'une quelconque des revendications précédentes, ladite surface du métal
en fusion étant formée au niveau de la face d'extrémité d'un embout de buse.
5. Procédé selon l'une quelconque des revendications 1 à 4, ladite température de la
surface du substrat étant supérieure à la température de fusion du métal.
6. Procédé selon l'une quelconque des revendications 1 à 4, ladite température de la
surface du substrat étant inférieure à la température de fusion du métal et ladite
surface du substrat étant chauffée à une température supérieure à la température de
fusion du revêtement métallique, après que le revêtement métallique a été appliqué.
7. Procédé selon l'une quelconque des revendications précédentes, ledit revêtement métallique
étant formé à partir d'un métal à faible point de fusion, tel que le zinc, l'aluminium,
l'étain, le cuivre ou un alliage de ceux-ci, lesdits éléments d'alliage étant par
exemple de l'aluminium ou du magnésium, ou ledit revêtement à base de métaux étant
formé à partir d'un revêtement métallique avec des particules solides, par exemple
des nanoparticules.
8. Procédé selon l'une quelconque des revendications précédentes, ledit substrat étant
une bande en déplacement, de préférence une bande métallique en déplacement, idéalement
une bande d'acier en déplacement.
9. Procédé selon l'une quelconque des revendications précédentes, ladite bande d'acier
en déplacement possédant une température allant de 350°C à 500°C lorsque les gouttelettes
métalliques sont constituées de zinc ou d'un alliage de zinc.
10. Appareil destiné à l'application d'un revêtement métallique ou d'un revêtement à base
de métaux sur une surface d'un substrat ou d'une partie de cette surface, ledit appareil
possédant un récipient destiné à conserver un gaz inerte et destiné à contenir la
surface du substrat à revêtir ou une partie de cette surface, des moyens pour générer
des gouttelettes métalliques à partir de la surface d'un métal en fusion étant présents
dans le récipient, des moyens pour appliquer une haute tension comprise entre 1 et
30 kV entre le métal en fusion et la surface du substrat à revêtir étant présents,
et des moyens étant présents pour appliquer une énergie ultrasonore à haute fréquence
à la surface du métal en fusion.
11. Appareil selon la revendication 10, des moyens étant présents pour chauffer la surface
du substrat à revêtir.
12. Appareil selon la revendication 10 ou 11, lesdits moyens pour générer les gouttelettes
métalliques à partir de la surface d'un métal en fusion étant une ou plusieurs buses,
chacune possédant une ouverture de sortie pour former la surface du métal en fusion,
ou les faces d'extrémité d'un ou de plusieurs embouts de buses.
13. Appareil selon l'une quelconque des revendications 10 à 12, ledit récipient contenant
un système de verrouillage de gaz d'entrée et un système de verrouillage de gaz de
sortie pour revêtir un substrat en déplacement.