Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a method of and an
apparatus for treating a metallic workpiece. More particularly
this invention concerns the immersive treatment of a metal strand
in a vessel.
It is frequently necessary to treat a metal workpiece
either physically, chemically, or thermally in a body of fluid
held in a vessel, Such a process is used for rinsing, pickling,
patenting, or similarly treating the workpiece.
When a workpiece that is being continually produced,
such as a steel strand or a wire in a rolling mill, is to be
immersively treated it is often necessary to provide an extremely
large and complicated device through which this workpiece is
passed and in which it spends enough time to undergo the neces-
sary treatment, Thus complicated baths and guides are necessary
in order to hold the workpiece immersed for a sufficiently long
period of time in the treatment bath. This problem is consider-
ably complicated when a high production speed is encountered, as
many rolling mills are capable of turning out wire at speeds in
excess of 30 meters per second so that the bath must contain 30
meters of workpiece for each second of treatment time desired.
It is~also known to treat workpieces by simply immer- r ,
sing them for a predetermined period of time in a bath. Such -
systems are rarely usable with continuously produced workpieces
and often are relatively inefficient because the fluid in the
vessel is not homogeneous, but tends to stratify and separate
so that different spots within the body of fluid will have dif- ~ -
ferent characteristics from other spots Thus in a plating or
patenting operation the finished workpiece will be unevenly
treated.
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It is therefore an object of the present invention to ;
provide an improved method of and app~ratus for treating a metal- - ;
lic workpiece with a treatment fluid.
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Another object of this invention is the provision of
an improved treatment system which allows a continuously produced
workpiece to be treated without interrupting its production.
Yet another object is to provide a treatment system
that gives very even results yet is simple to operate and inex-
pensive to set up and maintain.
A more specific object of this invention is to provide
an improved method of and apparatus for patenti~g steel wire
prior to drawing thereof.
These objects are attained according to the present
invention in a system where the metallic workpiece is lowered
into a body of treatment fluid in a vessel onto a support in the
vessel while maintaining predetermined characteristics of the
body of treatment fluid within predetermined ranges. Thereafter ;
the workpiece is held in the body on the support for a predeter-
mined period of time after which the support is raised to lift - - -
the workpiece entirely out of the body. The workpiece is then ~
picked off the support and the support is lowered back into the ~-
body ready to receive another workpiece. This system can operate -
very rapidly so as to treat a very large quantity of such work-
pieces within a relatively limited time, the unloading and re- '
loading operation belng very short.
The system according to the present invention has a
pair of such vessels so that while the support in the one body --
is being raised to allow the workpiece thereon to be picked off --
it the continuously arriving workpiece may be delivered to the - - -
other vessel. The rapid unloading time allows the support of the
first vessel to be back in position ready to receive another
~ workpiece before the second vessel is filled. With this arrange-
ment i$ is possible to work with a continuously arriving work-
piece, or in a batch-type operation. The changeover from the
one vessel to the other can take place when the one vessel is
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filled, or when a predetermined quantity of the continuously
arriving workpiece is charged into the first vessel Thus in
a wire-treatment apparatus when a predetermined volume of wire
has been delivered to the one vessel the wire is cut and the
next section is delivered to the other vessel.
The support according to the present invention is form-
ed of a plurality of bars or is at least formed with a plurality
of upwardly open slots so that times of the liftoff device may
slip under the workpiece on the support and lift it therefrom.
This liftoff fork may be carried on a turntable-type transport
system or an overhead-track arrangement so as to allow the treat-
ed workpiece to be carried off to the next treatment area.
With the system according to the present invention it
is only necessary to duplicate the vessel, the means for main- ~ -
taining the body within a predetermined set of parameters, and
the support in order to operate continuously. A common pickoff
and a common feed device for the workpiece may serve both such
arrangements when the vessels are placed adjacent one another.
This is best achieved by providing thè means for moving the two
supports between the two vessels, with the means for lowering -
the workpiece into the vessels being provided next to each other
to one side of the two vessels, and the pickoff arrangements
being provided movable at right angles to the feed arrangements.
The above and other objects, features, and advantages
will become more readily apparent from the following, reference
being made to the accompanying drawing in which: ~ -
Figure 1 is a vertical section through an installation
according to the present invention.
Figure 2 is a top view of the installation of Figure 1.
FigNre 3 is another vertical section through the
apparatu~ of Figure 1, taken at a right angle
to the section of Figure 1.
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The arrangement shown in Figures 1 to 3 is usable in
a steel mill for the patenting of wire, It comprises basically
a pair of like generally cylindrical vessels 1 each slightly
more than 4 meters deep and set in the floor next to each other.
Each of these vessels 1 is made of steel and is provided with
heating coils 4 that serve to heat a body of salt within it to
a temperature of between 450C and 600C, at which temperature
the salt melts and forms a liquid bath. Wire is delivered to
these vessels 1 at a speed between 30 meters/second and 60 meters/
second and at a temperature of approximately 800C. This wire
has a carbon content of below 0.3%. A pair of feed devices 5 is
provided connected to respective feeders 9 mounted on carriages
19 slidable along track 18 by means of cylinders 17. The tracks
18 are dlrectly in line with one another so that the carriages 19
and the feeders 9 may be pulled in opposite directions away from
the respective vessels 1. The feeders 9 feed the wire as it is - -
delivered into a helix and allow it to drop down into the res- ~-
pective vessels 1.
The salt bath is comprised of sodium nitrate which
melts at 308C. Other water-soluble alkali or earth-alkali salts
as well as mixtures thereof may also be employed.
The bath must be continuously cooled to maintain its
temperature within the range of 450C - 600C, since the wire
enters the bath at a substantially higher temperature. Each ves-
sel 1 is provided with a large-diameter riser pipe 12 which
terminates at its lower end near the bottom of the vessel 1 and
which extends up out of the vessel 1 and into a separation vessel
14. Extending vertically down to the center of each riser pipe
12 and terminating slightly above the lower end thereof is a ~`-
small-diameter pipe through which water or steam at a temperature
~u~tan~ia~y ~e~ow 4~C is intr~duced into the ~ath. On issuin~
~r~m the ~ottom of the pipe 20 the steam rises up and àny water
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vaporizes instantly in the bath and also rises in the tube 12,
entraining a portion of the bath in gas-lift pump fashion. Thus
molten sodium nitrate is pumped into the vessel 14 where it
separates from the water and flows back into the top of the bath
through a return pipe 13 that terminates at the top of the ves-
sel 1. This arrangement 12, 13, 14, 20 therefore serves not
only to cool the melt, but also circulates it from top to bottom
in the vessel so as to maintain the temperature in the vessel
relatively homogeneous. The amount of water or steam fed in
through the pipe 20 determines the temperature of the melt and
allows this temperature to be controlled within very close
parameters.
After separation in the vessel 14 the steam exits
through a pipe 22 and is fed to a condenser 26 and thence to a
vessel 25 in which the wire is rinsed after treatment. There- ~-
after the same water is passed through another cooler 27 and is
fed back into the vessel 1 so that very little of the salt is
lost, that portion which is carried off ~y the wire being re- -
covered from the rinse water.
Adjacent the bottom or sump 15 of each of the vessels 1
there is provided a vertically displaceable support 2 formed by
a plurality of parallel bars 23 together secured on a holder 6
that is vertically displaceable by means of a drive 11 into a
lower position indicated in solid lines in Figure 1 and an upper
position indicated to the right in dot-dash lines in Figure 1.
These bars 23 constituting the support 2 extend at right angles
to the tracks 18 and lie between a cylindrical upright array of
bar~ 16 that define with the bars 23 an upwardly open cage adapted
to receive a bundle B of wire. Each vessel 1 has an overall
depth H above the support 2 and the bundle B is formed such that
~ts top always lies in predetermined depth h underneath the sur-
face of the bath. This distance h is sufficient for the wire
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falling to the bundle B to take on the same temperature as the
bath No core is necessary for the bundle B since the wire
itself naturally forms a very neat cylindrical package resting
on the support 2 and confined by the cylindrical vertical array
of rods 16.
After a bundle B of desired size is formed the lifter
11 is actuated to ràise the support completely up out of the
bath, removing the bundle B totally from the salt. Thereupon
a fork 8 on a carriage 7 rollable acrcss tracks 24 perpendicular
~ to the tracks 18 is inserted between the bars 23. After the
fork 8 is fully underneath the bundle B the support 2 is lowered,
leaving this bundle B resting on the fork 8, Thereupon the
carriage 7 is withdrawn and another liftoff device 10 carried on
an overhead track 3 is used to pick the bundle B off the fork 8
and move it to the next stage, here a rinsing vessel 25 which
receives the water from the outlet 22.
In a system according to the present invention with
wire delivered at a rate of 40 meters/second it is possible to
form a bundle having a weight of 1400 kg. The device may operate
so rapidly that it takes only 40 seconds to lift a complete `
bundle out of the vessel 1 and lower the support 2 back in place
~o that more wire may be placed on top of it. In accordance with
this invention the two vessels are used with a single wire-making
string, with the wire being delivered to the one vessel until
the appropriately sized bundle B is formed and then being switch-
ed over to the other vessel during unloading. Obviously the
rapid cycling time makes it possible to operate this system
continuously even in a very high speed plant.
In addition it has been found that it is possible to
produce extremely high-quality patented wire, much better than
i8 obtained wlth the hitherto used lead-bath arrangements. This
lS due principally to the fact that the temperature is maintained
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within very close parameters in the bath and the wire rapidly
changes from its normally high temperature to its low temperature
as it crosses the austenitic point as is necessary in wire paten-
ting. In addition it is possible for this system to take up a
relatively reduced amount of space in an existing steel mill,
much less room being necessary than for the hitherto-used long
baths through which the wire is passed continuously.
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