Note: Descriptions are shown in the official language in which they were submitted.
B~CKGROUND OF THh~ INVENTION
(l) FIELD OF THE INVENTION
The present invention relates to an improved
process of providing a metallic article such as a ferrous
strip with a coating such as a zinc coating and more partic~
ularly to a "dipless" metallizing process without dipping
the article into a molten metallizing bath and to an apparatus
for carrying out said process.
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(2) DESCRIPTION OF THE PRIOR ART
Modern galvanizing procedures, in spite of recent
improvementsl can still be considered in outda-ted inheritance ~ -
of the original hot dip galvanizing in which the article to be -~ :
coated was submerged~ while still cold, in a heated zinc pot,
thereby passing through a layer of a flux which floats on the
molten zinc bath and cleans the article to be coated of any
dirt and moisture.
Before galvanizing takes place, the article had to
be heated to about the melting point of the zinc. Such heat~
ing, of course, takes some time. During heating a bri-ttle
layer of a ferro~zinc aIloy was formed on the interface
between the article and the zinc layer~ Said ferro-zinc alloy
layer caused the zinc coating to readily flake and peel off
the article, thus diminishing considerably the anti-corrosive
propert.ies of the galvanized article.
In spite of vast improvements as they are achieved
by recent modifications of the known processes, the sheet
material~ usually in the form of a continuous strip; is still
passed through a molten zinc bath after it has been preheated
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and under the protection o~ a non~o~idi~ing atmosphere.
Thus, it is no more necessary to keep the strip in the
molten zinc in order to heat it. However, on account of
merely geometrical considerations, the strip must remain in
contact with the molten zinc for a longer period of time than
required for purely metallurgical consideratlon. As a result
of such a prolonged contact of strip and zinc a brittle ferro- :
zinc alloy of greater thickness than desired is formed.
Formation of the ferro-zinc alloy is prevented, at leas-t
partly, by the addition of ~luminum or the like to the zinc
bath. Such addition, however, reduces to some extent the
ductility of the zinc coating in comparison to the ductility
of a non-alloyed zinc coating.
It follows that the duration of contact between the
article and the zinc bath is determined by the use o~E a zinc
bath provided with a sinking drum as well as by the dimensions
of such a drum.
` SIIM~RY OF T~IE INVENTION
It is one object of the present invention to over-
come the disadvantages of the heretofore used hot dip galvaniz-
ing or other metallizing process and to provide a dipless
process whereby contact of the ferrous article with the zinc -
is of such a short duration that formation of the ferro-zinc
alloy layer can be kept under control without having to add
aluminum to the spelter.
Another object of the present invention is to
provide a simple and effective apparatus to carry out said
dipless galvanizing or metallizing process.
~ further ob~ect of the present invention ~s to
provide a pure zinc coaked ferrous strip or article with an ~ :
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intermediate ferro-zinc alloy layer o~ optimum minimum thick--
ness.
Other objects of the present invention and advanta-
geous features thereof will become apparent as the description
proceeds.
In principle the process according to the present
invention comprises instantaneous application of molten metal,
i.e. fluid zinc to the heated article, i.e. the hot strip,
followed immediately thereafter by exposing the zinc-coated
article or strip to the action of a hot, non-oxidizing gas
blast which removes excess zinc and limits the thickness of
the zinc coating. Preferably immediately thereafter the zinc-
coated article or strip is rapidly cooled to a temperature
below the melting point of the zinc by exposing it to the
action of a cooling blast, for instance, by means of jets of
a coollng fluid.
According to another embodiment of the present
invention a pair of rollers is provided between the appli-
cation of molten zinc to the article and the hot gas blast.
These rollers effect better distribution and spreading of the
zinc across the entire width of the strip; they will exclude
any effect of the hot gas blast on the apparatus and arrange-
ments for applying the zinc to the strip; they will cause
considerable stabilization of the moving strip thus resulting
in greater efficiency of the hot gas blast arrangementsO
The possible geometry of such a process limits the
length of contact between ferrous article and zinc to a few
inches, compared tc~ several feet as is the case for processes
using a zinc bath and a sinking drum~ Thus the duration of
the iron-zinc contact according to the present in~ention i9
several times shorter than that of the conventional methods.
,. .
In fact the duration of zinc-to-art~cle contact is limited
to less than a second.
As a result thereof, non-alloyed zinc can ~e used
in the process of the present invention thus improving the
corrosion resistance of the zinc coating ("pure" metal coating~
without undue growth of the brittle intermediate ferro-zinc
alloy layer, thus ensuring excellent adherence of the pure
zinc coating to the coated article or strip.
Several, but by no means limiting, ways of applying
zinc to the strip can be employed. For instance, molten zinc
can be poured onto the strip headers equipped with appropriate
nozzles through which molten zinc is discharged upon the strip,
for instance, i~ediately before it is passed between the above
mentioned rollers. According to another embodiment of the
15 present invention, the molten zinc is applied to the bodies of ~ -
the rollers and then applied ("printed") onto the strip as lt
contacts said rollers. As mentioned above the strip emerging
~rom said rollers undergoes a hot non-oxidizing gas blast
followed by a rapidly cooling blast outside of the coating
chamber. This blast does not have to be non-oxidizing. An air
blast or a water spray or the like are adequate means for cool-
ing the coated article.
In a preferredl but by no means limiting, embodiment
of the present invention, the strip emerging from a "snout" of
a pretreating device, such as a continuous furnace, is conducted
around a pulley and rises to the zone of the metallizing
process in a substantially vertical direction. The atmosphere
surrounding the pulley is substantially the same as is used in
the pretreating furnace.
The process chamber has an entry slo~ for the strip
by which i-t enters said chamber from the box which carries the ;
: .
strip deflecting pulley. The strip is then taken through
"reversed" wiper means contacting the strip under a vexy sli~ht
pressure. The purpose of these wiper means is to prevent any
excess zinc rolled off the strip by rollerc arranged after the
wiper means, from falling down onto the strip deflecting
pulley. The major part of the zinc removecl from the strip by
the rollers will run down onto the top faces of the wiper
means. If part of the zinc runs through the slot of the wiper
means, it will, by capillary action, run down the bottom face
of the wiper meansO As a result thereof, the rolled-off zinc
will drop to the bottom of the process chamber from where it
is returned to the zinc melting and de-oxidizing oven~
The molten zinc is supplied ko the zinc application
device from a zinc melting oven by means of a zinc pump.
Excess molten zinc which is partly removed by the rollers and
finally by subsequent hot blasting, drops to the bottom of the
process chamber, from where it is returned, by gravity, to
the zinc melting oven for further recirculation. Should any
zinc oxide have been formed on the way from the process chamber,
it will be de-oxidized to metallic zinc by the floating layer
of de-oxidizing agent provided on the molten z~nc surface of
the oven.
The zinc applying means are provided between the
reversed wiper means and the rollers which serve to remove
~5 most of the excess zinc from the coated strip. Thereafter,
the zinc coated strip is sub;ected to a hot blast of a non-
oxidizing gas which removes the remainder of the excess zinc. ~ -~
The coated strip passes then from the coating chamber through
a narrow slot into the surrounding atmosphere, where it under-
goes rapid cooling, i.e. ~uenching.
The combination of said guiding rollers and the
immediate quenching of the strip coating at the strip exit
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from the chamber permits to considerably reduce the non
guided portion o~ the coated strip, rendering it substantially
rigid, when it arrives at the hot blasting zone. Said guiding
distance is measured vertically from the bite of said rollers
and up to the point where, after being spray cooled, the zinc
coating has been sufficiently hard to be mechanically guided
by a pulley. Thereby, the strip is kept in a substantially
rigid condition so as to ensure optim~ per~ormance of the hot
blast. As a result thereof, the nozzles ~or the slot) of the
hot blasting unit can be placed much nearer to the strip
surface than is possible without the use of the rollers and
the rapid cooling means. Thi~ facty in its turn, will result
in a lower hot gas pressure and a lower gas consumption.
The resulting "stability" of the travelling strip
in the coating chamber also permits to provide narrowing of
the strip exit slot therefrom~ A narrow exit slot, of course,
allows to operate under a lower pressure of the non-oxidizing
atmosphere in the cGating chamber than heretofore possible.
As a result thereof, the gas consumption of the galvanizing
unit is considerably reduced.
The short exposure of the metal of the strip to the
molten zinc and the almost immediate cool;ng of the zinc coat-
ing which takes place when the strip exit~ from the coating
chamber render it possible to reduce considerably or to even
completely eliminate the addition of aluminum to the spelter.
When aluminum is added to the spelter, the hot blast
must be of a non-o~idizing composition or it must even be, for
practical reasons, slightly deoxidizing so as not to cause
oxidation of the added alumlnum. ~owever, ~hen proceedin~
according to the present invention, the time of contact of the
molten zinc with the strip is so short that addition of
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aluminum can be completely avoided. Therefore, superheated
steam can be used for hot blasting because it does not
oxidize molten zinc~ Such superheated steam is much cheaper
and simpler to produce than a non-oxidizing gas blast.
Besides, should air be mixed with the steam and should some zinc
oxide be formed, the de-oxidizing effect of the protective
layer provided on the zinc surface in the z:inc melting oven
will reduce any formed oxide to metallic zinc. It is, of
course, not possible to reduce the aluminum oxide portion of
conventional top-dross by the de-oxidizing layer in the 2inc
melting ovenO
In view of the fact that the coating of the metallic
article can consist of pure zinc when proceeding according to
the continuous hot coating process of the presen-t invention,
the resulting coating has the best imaginable anti-corrosive
properties. Since the coating consists of pure metal, no
galvanic effects between the basic zinc and its alloying
elements are encountered.
Another advantage of the process according to the
present invention is that the coatin~ of pure zinc is more ;~
flexible and ductile than that of its alloys, including alumi-
num-zinc alloys~ Thus the pure zinc coated strip can better
be subjected to stamping and~or drawing working than products
galvanized in the conventional manner. ~ack of aluminum
addition to the spelter avoids the unpleasant fea-ture oE
"conventional" continuous galvanizing, namely the formation of
"WHITE RUST" which is especially critical in damp a-tmospheres
and which is a direct result of the aluminum added to -the
spelter. Chromate surface treatment baths, or similar, are
used to prevent the formation o~ white rust~ Obviously the
present process does not need any such extra treatment.
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While the process according to the present inven-
tion has been described hereinabo~e with respect to galvaniz-
ing ~errous articles such as stee] strips, lt is, of course,
also possible to use said process for applying coatln~s of
other metals to metallic articles. Thus the process can be
used~ for instance, for coating articles and especially strip
with aluminum, tin or tern alloy, or others. Of course,
other metallic articles than ferrous articles such as copper
strips can also be metallized by the process o~ the present
invention.
Likewise, instead of pouring the molten metal through
nozzles upon the metallic article or strip or applying it to
the article or strip by means, for instance, it can also be
applied thereto by other means, ~or instance, by forcing a
stream of molten zinc by gravity upon the strip or by any other
suitable means. In principle, the molten coating metal is
applied to the metallic article by projecting or gently pouring
it thereon in the form of a continuous stream.
As mentioned, one of the advantages of using spelter
without aluminum alloying is the possibility of using cheap
steam for the ho-t blast instead o~ more e~pensive neutral gas,
because steam does not oxidize molten zinc (but does, very
energetically, aluMinum~ However, it is not possible to have
steam of the blast mix with the stationary gas of the pre-
treating chamber o~ the furnace. A gas separating means have
to be provided, substantially according to the following lines:
as will be described in what ~ollows, a vertical separator is
to be located either before the zinc headers and the spreader
rolls or at the centerlines plane o~ these rolls. In -the first
case the not yet coated strip is exposed to the steam atmo-
sphere which is oxidizing to steel; but, for conditions of
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modern, high strip speed galvaniæing this exposure is of so
short a duration that ihis oxidation is not harmful. For
lower speed galvanizing, however, the duration is longer and
the gas-steam separation wall can be placed over and under
the spreader rolls, so ~hat no "rawl' strip is exposed to the
steam atmosphereO A possible particularity of such a seal con-
sists, for the lower roll, to dip it into a molten-æinc bath
which also collects the molten zinc overflow which has been
removed by the spreader rolls~ Conventional sealiny and wear
elements known to the man skilled in the art are to be used
at the split of the "wall" for the high speed type of coating
and on the upper roll of the described low speed coating.
Typical examples will be given in connection with the drawings.
In any case, in order to prevent any steam from getting into
the neutral gas zone by ]eaks, it is suggested to keep the
pressure in the neutral gas zone somewhat higher than in the
':steam" zone~
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages, and uses
of the present invention will become apparent ~rom a reading
o~ the following specification and claims taken in connection
with the attached drawings which form a part of the specifica-
tion and wherein:
Fig~ 1 is a vertical cross-sectional view of a dip-
less coating apparatus in which molten zinc is applied to the
rising strip which is then hot-blasted and quenched;
Fig~ 2 is a cross-sectional view of a similar dipless
coating apparatus in which strip movement stabiliæing and
excess zinc removing rollers are provided be~ween the zinc
applying means and the hot-blasting means;
Fig. 3 is a cross-sectional view o~ a similar dipless
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.
coating apparatus in which the molten zinc is applied to the
strip by means of a trough~ e distr~buting means;
Fig. 4 i5 a cross-sectional view of a dipless coat-
ing apparatus in which the molten zinc is applied to the strip
by means of the stabilizing rollers which are partly immersed
in an overflowing dipping bath, and
Fig. 5 is a cross-sectional view of a dipless coat-
ing apparatus similar to the apparatus of Fig. ~ in which the
molten zinc is poured on the rollers from a header and i9
applied to the strip by said rollers covered with the molten
zinc.
Fig. 6 is a cross-sectional view of a dipless coat-
ing apparatus in which the strip is passed through the coating
chamber in substantially horizontal direction and, after coat-
ing, is deflected upwardly for subsequent treatment.
Fig. 7 is cross-sectional view of a dipless coating ~-
apparatus similar to that of Fig. 6 in which the strip is
passed substantially horizontally through the coating chamber
and also through the subsequent treatment systems.
Fig. 8 is a cross-sectional view of a dipless coat-
ing apparatus enabling the use of steam for the hot blast -type,
recom~ended for lligh strip velocities.
Fig. 9 is a cross sectional view of a dipless coat-
ing apparatus enabling the use of steam for the hot blast
~5 type, recommended for lower strip velocitles.
Fig. 10 shows details of the gas tight seals,
applicable to both, the high speed and low speed, systems; it
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is a section according to X - Y of Figures 8 and 9.
1ike numerals in said drawings indicate li~e parts
3Q of the e~uipment.
:. '
DESCRIPTION OF THE P~EFERRED EMBODIMENTS
. . . ~
In said drawings, F~g. 1 demonstrates the principal
features of the present invention.
In said Fig. 1 strip 1 to be coated is passed from
the pretreating furnace (not shown) through snout 20 into
substantially gas-tight chamber 3 carrying strip deflecting
pulley 2. Said pulley 2 deflects strip 1 so that it is
conducted vertically upwardly into coating and processing
chamber 8 containing and enclosing the various elements of
the galvanizing process of the present invention. Strip 1
passes through orifice-like opening 21 into said chamber 8
and is then contacted by the pair of wipers 5. Strip 1 is
then contacted by a continuous stream of molten zinc 23
dispensed through headers 4 with nozzle -like openings.
Excess zinc drops onto wipers 5 and is deflected from the strip
and collected in return conduit 6 from which the zinc is
returned into the zinc melting and regenerating oven (not - -
shown). The remainder of excess zinc on the zinc coated strip
is removed therefrom by the hot gas blast 22 supplied through
hot gas blast header 7. The zinc-coated stxip 1 from which
excess zinc has been removed passes through strip exit slot 9
of coating chamber 8 and is conducted to stabiliziny pulley
11 which in co-operation with strip deflecting pulley 2 stabi-
lize movement of the strip on travelling through coating
chamber 8. Immediately after coated strip 1 has left said
chamber 8 through exit slot g, it is rapidly cooled by exposure
to a spray of a cooling fluid 24 sprayed thereon by means of
header 10~ When operating as shown in Fig. 1~ the strip is
passed successively through reverse wipers 5, a stream of
molten zinc 23 applied by means of header 4, and hot gas blast
22 applied by means of header 7 all of them enclosed in
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~ , ~ . . '
processing chamber 8, and is then rapi~ly cooled by cooling
fluid spray 24.
The coating apparatus as illustrated in Fig. 2
differs rom that of Fig. 1 by providing between the appli-
cation o the molten zinc stream 23 and the hot gas blast
22, roller means 12 which remove the major part of excess
zinc from coated strip 1 passing therethrough. Said roller L
means 12 aid in urther stabili~ing the movement of strip 1
on its travel through coating chamber 8.
In Fig. 3 a modification of the means for applying
a continous stream of molten zinc to strip 1 is illustrated
while otherwise the apparatus is the same as shown in Fig. 2.
According to this modification the molten zinc 23 is poured : ~.
from header 4 onto deElecting and distributing spreader 13
which applies it to strip lo
Another means of applying the molten zinc to strip 1 ~
is illustrated in Fig. 4. According to said modification the ~ ~:
molten zinc 15 is supplied to pans 14 by means o header 4.
Rollers 12, as shown, dip into said pans 14 and carry along
the molten zinc for application to strip 1. The rollers 12 ~ -
are provided with elongated and inclined slots 17 which carry
a journal of the stabiliæing rollers 12 and thus assist in
exerting pressure between the rollers 12 but still permit to
readily shift the rollers so that a strip threading tool can ~.
be passed therebetween. Dipping pans 14 are provided with a
molten zinc overflow 16 allowing the molten zinc 15 in the
pans 14 to overflow onto and along the walls of coating chamber
8 and downwardly into the return conduit 6 from where it is
returned to the zinc melting oven (not shown).
Another modification of the means for applying
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.. , .. , ~ .
molten zinc to the strip 1 is illustrated in Fig. 5, whereby
the molten zinc stream 23 is supplied through header ~ to
deflector-distributor plate 18 which allows to evenly spread
the molten zinc over the surfaces of rollers 12 which apply
("print") the molten zinc onto the surface of strip 1. A
variancy of this consists of spraying the rollers 12 in an
anti-rotational direction from headers 4-~ preferably located
close to the rollers and to the mounting strip.
It will be noted that in the apparatus illustrated
by Figs. 2 to 5 inclusive in which strip stabilizing rollers
12 are used, the exit slots 9 can be made much more narrower
than in the apparatus illustrated by Fig. 1, where no stabi-
lizing rollers are used~ Since movement of the strip is
greatly enhanced by providing rollers 12 as shown in Fig. 2
to 5, the efficiency of the hot blast is considerably improved,
so that a reduced hot blast gas consumption is achieved.
Consequently, the hot gas blast headers 7 can be made smaller
than the headers 7 to Fig. 1, which shows no stabilizing
rollers.
~s stated above, the claimed process permits,
according to another embodiment of the present invention, to
conduct the hot metallic article to pass substantially hori-
zon-tally throu~h coating chamber 3. Thus the procedure per-
mits to eliminate the wiper means 5 described hereinabove.
Fig. 6 illustrates in cross-sectional view this
procedure. In said Fig. 6 strip 1 to be coated is passed
from the pretreating furnace into chamber 3 which carries the
strip deflecting pulleys 2 and 2aO ~ulley 2a may e~en be
omitted~ Strip 1 passes then substantially horizontally,
3a pre~erably at a small angle downwardly, toward roller 12
which remove the major part of excess zinc from coated strip 1.
~aid rollers pre~erably deflect -the coated strip upwardly to
the hot blast means.
~hile passing ~r~m deflecting pulleys 2 and 2a
through coating chamber 3, khe strip ~s contacted by a
continuous stream of molten zinc 23 dispensed ~hrough headers
4 with nozzle-like openings. Preferably the upper header is
provided in the substantially horizontal part of the strip
while the lower header is provided underneath rollers 12.
Otherwise the procedure is the same as described hereinabove,
except that the wiper or deflecting means 5 are omitted.
Fig. 7 illustrates a further embodiment of the
present invention whereby the strip after coating is horizon-
tally conveyed past the hot gas blast header 7 through strip
exit slot 9 of coating chamber 3 to stabilizing pulleys 11
and lla. Between exit slot 9 and stabilizing pulleys 11 and
lla there are arranged two headers 24 spraying cooling fluid
upon the coated strip 1 so as to rapidly cool the same.
Coating chambers 3 in Fig. 6 and 7 are provided with
outlet 6 for excess molten coatlng metal. The angle of down-
ward inclination of strip 1 traveling through coating chamber
3 is indicated by a. Referring to Fig. 8; (30) is the
separator wall, of which (31) is its upper part and (32) its
lower part. The upper edge ~33) of (32) may be lined with
a wear strip (34), adjuskable vertically to compensate for
wear. It can be made of relatively soft material like asbes-
tos. The passing strip to be galvanized slightly presses
onto (33)~ The upper part (31) is slidable in the vertical
direction and presses onto strip (1), by ~ts weight, and there-
by onto the wear strip (34) or (32). It is shown as a soli~d
board maintained in position by appropriate guides on the
chamber walls and ceiling extension (35). As ~ill be de-
scribed in greater detail in Fig. 10, the upper part ~31)
of wall (30) is pressed against a machined pvrtion (42) of
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,1
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.
.
~t~
the side wall of the chamber 3 and of the ceiling extension
(35). The chamber is split and screwed together by appro-
priate flanges (36) on the substantlally vertical planes pass-
ing through the center lines of the deflecting pulle~s (2 &
S 2A) and spreading pinch rolls (12 & l~A). The whole system
(chamber, rolls, headers, etc.) is inclined somewhat from the
horizontal plane to prevent the molten zinc from flowing
"upstream" with regard to the movement of the strip, (1).
A bent part (37), forming a "rigidity rib" of the lower part
(35) of the separator wall 132), also forms a guide for the
strip during the threading of the furnace proper (not shown)
and of the metallizing chamber, (3). The pinch rolls (11 ~
llA) catch the quenched strip and deflect it, horizontally or
vertically for further processiny.
Fig. 9 showing the separator "on" the spreading
pinch rolls, (12 & 12A) of the likewise tilted metallizing
chamber (angle slope alpha~, is split on two substantially
horizontal planes of the upper and the lower deflector and
spreader pinch rolls and screwed toyether by flanges (38).
While the sealing off of the upper spreader pinch roll is
achieved by means similar to -those of the wall of the E'ig. 8.,
that of the lower roll is obtained by dipping it into a pure
zinc bath (39) contained in a tank (40). Zinc coming from
the headers (4) and partly removed by the spreader pinch rolls,
as well as that removed by the hot spray, falls into said tank
~40), overflows its lower edge (48~ and is conducted into the
zinc dump (not shown) by pipe (6).
Figr 10 shows a possible embodiment of the seals of
the separating walls of the metall~zing chamber aga~nst the
side and upper panels of the metallizing chamber. (31) is the --
main plate, applied by its smoothed edge (~1) to a machined
~6-
,~
face (42) of the side pannel (43 & 3). Spxing (44)
forces plate (31) against (42), insuring gas tightness.
The smoothed side (47) of the plate (31) is sealed off by
strip (45), the latter being pressed towards (31) by spring
(46). Refering to Figs. 1 incl. 7, a man skilled in the art
will be able to apply the principle shown in Fi~s. 8, 9, and
10 to be Figures 2 incl. 7~ It will be noted that F~g.
(4 & 5) are appllcable to spreader rolls made of "zinc
wettable" materials, like iron or steel, the rest of the
figures may be applied to "zinc-unwettable" materials, like
silicone-carbon ceramic or composed materials.
~17~19~
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SUPPLEMENTARY DISCLOSURE
In the principal disclosure the invention is shown
in several aspects and shows a process and a system for
providing a metallic article with a metallic coating by causing
a continuous stream of the molten coating met:al to contact the
hot metallic article for a short period of time. Excess
coating metal is then removed from the coated metallic article
by subjecting it to the action of a hot gas blast. In a
preferred embodiment the coated article is subjected to the
action of a cooling ~last immediately after the hot gas blast
ing.
The hot gas blast provides a means for rapidly
removing excess coating metal from the metallic article. The
temperature of the hot blast should be hot enough to move
excess molten metal from the article, and this may happen when
the temperature of the hot blast is somewhat lower than or
higher than the melting point of the coating metal.
In this Supplementary Disclosure it is pointed out
that in many instances it is advantageous to use a hot blas~
gas temperature lower than the melting point of the coating
metal such as zinc. In this way the liquid coating metal is
prequenched or prechilled to some extent, thus hastening the
solidlfication of the coating when subsequently subjected to
a cooling blast. Under such conditions the time of contact
of the coated metal with the liquid coating metal is further
reduced and the coating process can be controlled more care~ully
and closely.
~ he temperature of the "cooler" hot blast may vary
according to such factors as -the speed with which the metallic
article is being galvanized in the system according to the
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.. . . .. .. . .. .
invention, the desired thickness of the coating, and the
condition of the raw material. The temperature o~ the hot
blast is preferably from 20 to 80C. below the melting point
of the coating material.
Thus the present invention provides a process of
providing a metallic article with a metallic coating, in
which the steps comprise causing a continuouC; stream of the
molten coating metal to contact the hot metallic article for
a short period of time, thereby coating the metallic article,
and removing excess coating metal from the coated metallic
article by subjecting it to the action of a hot, non-oxidizing
gas blast, said hot gas blast being at a temperature somewhat
lower, preferably between 20 and 80C. lower, than the melting
point of the coating rnetal. Preferably, the process also
includes the additional step of immediately after hot gas
blasting rapidly cooling the coated article by the action of
a cooling blast.
In another aspect the invention provides a system
for providing a metallic article with a metal coating, said
system comprising a coating chamber having an entrance opening
for the metallic article to be coated and an exit opening
or the metal coated article, said chamber being provided,
successively within and enclosed by said chamber; with means
for applying a continuous stream of molten metal to the
metallic article to be coated so as to uniformly and evenly
distribute the coating metal over tne surface of the hot
metallic article and to coat the same; and means for subjectin~
the coated metallic article to a hot gas blast at a te~perature
somewhat below preferably between 20 and 80C. below, the
melting point of the coating metal, so as to remove substan-
tially completely excess coating metal from the coated article,
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and, arranged following the exit opening of said coating
chamber; means for rapidly cooling the metal coated article,
said cooling means being provided outside the coating chamber.
ZO
SD-22
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