Note: Descriptions are shown in the official language in which they were submitted.
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Device Eor metering a gas contenk of liquid metal
and probe used therefor.
This invention relates to a device for metering
a gas content of liquid metal comprising a probe designed
for immersion into the liquid metal and having in its turn
a gas supply duct which terminates at the end of the probe
destined to be situated at the bottom, a gas collec-ting
portion for collecting the gas bubbling from the gas supply
duct through the metal, said portion being located opposite
the mouth of the gas supply duct and being provided with
a diaphragm allowing gas to pass but retaining liquid metal,
10 and a gas discharge duct connecting across the diaphragm
to the gas collecting portion, said device further including
a gas circuit having one end connected to the gas supply
duct of the probe and its other end to the gas discharge
duct of the probe, a gas detector mounted in said circuit
15 and means mounted in or on this circuit for allowing the
passage of gas through the circuit, through the gas
detector and the probe. -
The content of dissolved gases, and in particular
hydrogen, in liquid metal has an important effect on the
20 properties of the metal eventually obtained. A high
concentration of such gases leads not only to brittleness
of the metal but may also cause serious errors such as
flakes or blow holes.
Consequently, it is necessary in the case of
25 metal and especially steel, which has to meet high quality
requiremenks, to accurately follow the hydrogen content ~;
in the manufacturing process and more in particular during
refining and casting, so as to keep the gas content within
given limits.
Devices of the above type are mainly designed
for such a hydrogen content determination and intended for
replacing the conventional determination of the hydrogen
content, consisting in taking a sample from the liquid metal
and analyzing it in the laboratory. ~
With such devices, a small volume of carrier ~;
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gas can be bubbled through the liquid metal. This gas is
collected and is circulated several times in the closed
circuit until an equilibrium has established itself between
the gas in the metal and this carrier gas. Subsequently,
the gas content, and more in particular the hydrogen content,
is determined by means of the detector mounted in the gas
circuit.
A device of this type is known from British patent
821,821.
In the device disclosed in that patent, the probe,
however, is fixedly connected to the circuit and this probe
is designed for use in different successive measurements.
The probe should therefore be made of particular
material that is resistant to prolonged residence in a bath
15 of liquid metal, so that this probe is comparatively
expensive and in practice can only be used for metering
the hydrogen content in baths of metal having a relatively
low melting point.
Even in these cases, the life time is restricted
20 and replacing of the probe is rather time-consuming and
expensive.
Therefore, this probe has not found application
~or metering the hydrogen content, e.g. in li~uid metal.
It is an object of the present invention to
25 eliminate these drawbacks by providing a device for metering
a gas content of liquid metal that is comparatively
inexpensive in use and which can easily be rendered
suitable for metering said content in metal having a
relatively high melting point.
To that end, the device for metering a gas !
content of liquid metal comprises a lance through which
at least a part of the gas circuit extends, said lance
containing one portion of a quick-acting coupling
including two connectable portions, and the probe, at the
35 side remote from the collecting portion, and spaced from
said collecting portion~ containing the other portion of
the quick-acting couplingr said coupling, in coupled ~ ~
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position of the portions, ensuring a gastight connection
of the t~o above-mentioned ends of the gas circuit and the
gas supply duct and the gas discharge duct of the probe,
respectively.
The probe is accordingly designed as a disposable
probe, which is used only for one or at most a limited
number of measurements.
Consequently, the proble should be resistant
only to a relatively short residence time in the liquid
10 metal, so that it can also be designed for measurements
in metal having a high melting point and can be made from
relatively inexpensive materials.
In a particular embodiment of the present ~;
invention, the probe comprises a thermal protective device
15 surrounding the quick-acting coupling and the lance end
connecting to the probe.
This thermal protective device, too, should only
be resistant to liquid metal for a limited period of time
and can be made from inexpensive materials, such as baked
20 sand, cardboard and the like. The gases released by the
combustion, if any, of this protective device practically
do not affect the measurement, since this thermal protective
device is situated at a relatively large interspace from
the collecting portion.
In an important embodiment of the present
invention, the quick-acting coupling comprises mechanical
means for interconnecting the two portions thereof.
In an effective embodiment of the present
invention, the gas supplylduct and the gas discharge duct
30 of the probe surround one another outside the portion of
the quick-coupling.
Preferably, the outer pipe includes a tube
connecting the collecting portion to the portion of the
quick-acting coupling of the probe.
In a special embodiment o~ the present invention
the diaphragm is made from ceramic fibres bonded together
with a binder. ;~
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Said diaphragm has a very low specific mass and
a very limited cooling effect on the molting metal so
that measuring is possible in molten metal the temperature ;.
of which is near to its solidification temperature.
In another important embodiment of the present
invention, the collecting portion and the diaphragm
are one and same piece.
In a preferred embodiment of the present invention,
the device comprises means for opening the gas circuit
and for placing its portion communicating with the gas
discharge pipe into communication with the free atmosphere.
In this embodiment, at the start of the measurement,
the carrier gas supplied to the gas circuit can be re~
turned to the atmosphere and the circulation proper
15 of the carrier gas in closed circuit over the probe, :
and hence the measu.rement proper, can be initiated only
after the first detection by the katharometer of impuri- ~
ties in the carr.ier gas. ~ ;
In an advantageous embodiment of the device according
to the invention it comprises in the gas circuit several
gas detectors and filters coupled thereon to retain ;:
different gascomponents from the carrier gas.
The present invention also relates to a probe :
designed for use in a device according to any one of
the preceding embodiments.
Other particulars and advantages of the present
invention will appear from the following description ~;
of a device ~or metering a gas content of liquid metal .~
and of a probe used therefor, according to the present :~-
invention; this des¢ription is given by way of example
only and is not intended to restrict the invention;
the reference numerals relate to the accompanying drawings.
Fig. 1 shows a block diagram of a device for metering ~: :
~ a gas content of liquid metal according to the present
: 35 invention;
Fig. 2 is a part-cross-sectional front view of
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a probe from the device shown in Fig. l;
Fig. 3 shows a detail from Fig. 2, but on a
larger scale, and showing in addition a part of the lance
connected to the probe;
Fig. 4 is a part-sectional front view of a probe
similar to that of Fig. 2 but relating to a different
embodiment of the probe;
Fig. 5 is a part-front view and part-sectional
view of a filter from the device shown in Fig. l;
Fig. 6 is a part-sectional front view of a probe
similar to that of Figs. 2 and 3 or 4 but relating to still
another embodiment of the probe.
In the different figures, the same reference
numerals relate to the same elements.
The device shown in Fig. 1 is a device for
metering the hydrogen content in liquid metal.
This device essentially consists of a probe 1
and a gas circuit 2 having both ends connected to the probe
and wherein, in the direction of flow of the gas indicated
20 by the arrow 3 in Fig. 1, there are mounted, successively, ~;~
a filter 4, a katharometer 5, a pump 6, a four-way valve 7
and a flow rate meter 8.
The probe 1 is a disposable probe and is `
detachably secured to a lance 11 through a quick-acting
25 coupling 9, 10, through which lance extend ends of the gas
aircuit 2, and is connected to these two ends of the
circuit 2 by means of the same quick-acting coupling 9, 10.
A bottle 12 containing nitrogen under pressure
is connected to the four;way valve 7 by means of a supply
30 duct 13.
Said four-way valve 7, in one position, closes ~``
the gas circuit 2, while supply duct 13 communicates with
; the free atmosphere. Naturally, bottle 12 is then closed.
In a different position, the four-way valve interrupts the
~ 35 gas circuit 2 and, on the one hand, establishes communication
; bstween supply duct 13 and the part of gas circuit 2
~ connected via the flow rate meter 8 to probe 1, and on the
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- 6 - 1 3 3 0 7 ~ 9
other hand, puts the part of gas circuit 2 coming from
pump 6 into communication with the free atmosphere.
Katharometer 5 is also of a known per se
construction and will not be described in more detail herein. `
This meter determines the hydrogen content of the inert
carrier gas by metering the thermal conductivity of the
gas.
The probe 1, as shown in Fig. 2, has at one end
a gas collecting portion formed by a bell 14 of porous
refractory brick and at the other end one portion 9 of the
above-mentioned quick-acting coupling 9, 10.
Bell 14 is oriented with its opening away from
the portion 9 and is kept spaced apart from portion 9 by `-
a quartz tube 15 to the ends of which bell 14 and portion 9
are secured by means of cement 16.
Extending axially through quartz tube 15 is a
quartz tube 17 which extends at one end into portion 9 and
at the other end through bell 14 and is secured to said
bell 14 with cement. ;--
Secured in the open end of quarts tube 17
projecting from bell 14, by means of cement 19, is one
leg of a narrower quartz tube 18 bent through 180. The
other leg of tube 18 is oriented with its open end towards
the opening of bell 14. Cement 19 provides a gas-tight
25 seal of tube 17 around tube 18. ~ ;
In quartz tube 15, quartz tube 17 is surrounded ~
by a tube 20 of Al 2 3 ~ -
The end of quartz tube 15 remote from bell 14
and especially the portion 9 of the quick-acting coupling
9, 10 are surrounded by a sleeve consisting of three tubes
surrounding and contacting each other, i.e. an inner tube 21 ;~
of cardboard, a central tube 22 of cardboard and an outer
tube 23 of resin-bonded sand.
Tubes 22, 23 of the sleeve are secured to quartz
tube 15 by means of cement 24.
Sleeve 21, 22, 23 extends at the end remove from ;
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bell 14 appreciably beyond the portion 9. The inside
diameter of the inner tube 21 corresponds with the outside
diameter of the lance 11, one end of which extends into
said sleeve when it is connected to probe 1.
Sleeve 21, 22, 23 forms a thermal protection
of this lower end of lance 11 and primarily of the quick-
acting coupling 9, 10.
As best shown in Fig. 3, the portion 9 of the
coupling 9, 10 comprises a body provided at the imrnersion
end, i.e. the end proximal to bell 14, with a collar 25
wherein quartz tube 15 is fixed and is provided centrally
with a bore 26 through which extends one end of quartz -
tube 17.
Extending through the body is an axial bore 27
which connects to bore 26 and, together with quartz tubes
17, 18 forms a gas supply pipe.
In addition to axial bore 27, four more bores 28
extend through the body of portion 9, which bores terminate
in the space between quartz tube 15 and quartz tube 17 and
which, together with the latter space, form a gas discharge
duct shut off at the immersion end by the porous bell 14
forming a diaphragm allowing the passage of gas but ~;
retaining liquid metal.
The diameter of the body o portion 9 of the
quick-acting coupling 9, 10, gradually decreases in the
direction away from quartz tube 15 in such a mar~ner t~t
three reentrant collars 29, 30, 31 are formed.
The inner tube 21 of sleeves 21, 22, 23 abuts
on the outermost collarl29 closest to quartz tube 15 and
also abuts on the exterior of the cylindrical part of
portion 9 located between collars 29 and 30.
The portion of the body having a smaller diameter
intermediate collars 30 and 31 is surrounded by an 0-ring
partly recessed therein.
The above bores 28 terminates in collar 30.
The cylindrical portion projecting from collar 30
is also surrounded by an 0-ring partly recessed therein.
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Collars 30, 31 and 0-rings 32, 33 coact with
part~ of the portion 10 of quick-acting coupling 9, 10,
said portion 10 forming a piece mounted on the end of
lance 11.
Said portion 10 is provided at its end with an
axial round bore 34 fitting the cylindrical part of portion 9
intermediate collars 30, 31 and has a small axial bore 35
terminating at one end at the bottom of bore 34 and at the
other end linking up with the end of gas circuit 2 down-
10 stream of flow rate meter 8.
Extending around bore 35 in portion 10 i 5 a duct
36 terminating at one end at the bottom of bore 35 and at
the other end linking up with the other end of gas circuit 2,
which just like the first end is mounted in this portion 10.
These two ends of the gas circuit therefore extend
through the metal lance 11.
In the smallest bore 35 of porti~ 10 of coupling
9, 10 there is provided a mechanical connecting piece 37
having four resilient legs 38 having thickened ends. When .:
20 lance 11 is pushed into sleeve 21, 22, 23, said four legs 38
click resiliently over the thickened head on the end of
the part of portion 9 projecting from collar 31.
When lance 11 has been pushed maximally into ~:
sleeve 21, 22, 23, as shown in Fig. 3, the thickened ends
25 of legs 38 catch behind on outwardly directed collar formed
adjacent a groove 47 in the end of the portion 9 of coupling `:
9, 10, projecting from collar 31.
The connecting piece 37 has a channel 39 so that
bore 35 remains in,communication with the end of circui,t,2
In the home position of lance 11, one end of
portion 10 abuts on collar 30 of portion 9 and the inner
wall of bore 34 abuts against 0-ring 32 in gastight
relationship.
The inner wall of bore 35 then has a gastight ~:
35 abutment against 0-ring 33.
:~ Probe 1 is thus connected mechanically but still
detachably to lance 11 through connecting piece 37, since, ~ .
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by exerting sufficient force, the legs 38 can be forced
apart in a resilient manner so as to cause them to slide
over the thickened end of portion 9.
The gas discharge duct 15, 28 of probe 1,
formed by tube 15, around tube 17, and bore 28, connects
in gastight fashion through duct 36 to one end of gas
circuit 2, while the gas supply duct 17, 18, 27 form~id
by tubes 17, 18 and bores 27, forms a gastight connection
via central bore 35 to the other end of the gas circuit 2.
In the coupled position of the quick-acting coupling 9,
10, a portion of bore 34 extending symmetrically around
portion 9 forms the connection between bores 28 in portion 9
and duct 36 in portion 10, while the axial bore 27 in -
portion 9 connects to channel 39 in portion 10 via bore 35.
lS Portion 10, consequently, may be coupled in any position
of portion 9 and lance 11 should thus not be pushed into ;
sleeve 21, 22, 23 in any predetermined position.
In a variant of the above-described embodiment,
the porous ball 14 is made from ceramic fibers bonded
together, instead of from porous brick.
The variant of probe 1 shown in Fig. 4 differs
only from the embodiment of the probe shown in Figs. 2,
3 in that the collecting portion is not formed by a bell 14
but b~ the immiersion end of the quartz tube 15 itself and
by the disc 40 of porous ceramic material which, at an
interspace from the open end of tube lS, shuts off said
tube around the axial quartz tube 17 and thus forms the `~
diaphragm allowing passage of the gas but no liquid metal,
and in that tube 2~0 of A120,~has been replaced by a mas!sl j,
of balls 41 filling the space around the axial tube 17 and
between disc 40 and portion 9 of quick-acting coupling 9,
10. These balls 41 do not impede the passage of gas so that ~-
the space between tube 15 and the central tube 17 still
forms part of the gas discharge duct of probe 1 terminating
l~ 35 at the porous disc 40. For simplicity's sake sleeve 21,
¦~ 22, 23 of probe 1 is not shown in Fig. 4. ~;~
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In both embodiments, exactly above the diaphragm,
i.e. above bell 14 or disc 40, tube 15 contains some grains
46 of a chemical element forming stable oxides, such as
chromiun, zinc, titanium, aluminum, zirconium, calcium,
magnesium, or an element of the lanthanides.
In particulax zinc, magnesium and calcium are appropriate,
since, at the temperatures used, they are in gaseous state
and are highly reactive. If the material of the diaphragm
contains unstable oxides, these elements prevent hydrogen
from the metal bath from being converted into water, which
would affect the measurement.
Instead of grains of these elements, a coating
of the element may be applied to a part of tube 15 or
tube 17.
In both embodiments, the unit formed by quartz ;~
tube 15 possibly with bell 14, the projecting end of quartz
tube 17 and quartz tube 18, may be surrounded by a cap of
metal which, for simplicity, is not shown in the drawings,
and which is attached to sleeve 21, 22, 23 and is surrounded
20 by a cap of cardboard, not shown in the figures either.
The cardboard cap prevents thatl during insertion
of probe 1 through a slag present on the liquid metal, the
slag adheres to the cap of metal, which avoids damage to `
probe 1 during its insertion through the slag.
During insertion, the cardboard cap is combusted,
while immediately after insertion, the metal cap melts,
after which the measurement can be effected in the following
manner.
As shown in Fig. 5, filter 4 comprises a tube 42
3~ closed onl one end and open at the other. The open end of
tube 42 connects to a portion 44 of the quick-acting
cou~pling, identical to the above portion 9 of coupling 9, 10.
Corresponding parts of portion 44 have been given the same
reference numeral as in portion 9.
A tube 43 open at both ends extends axially into
tube 42. One end of tube 43 terminates short of the closed
end of tube ~2 and its other end is secured in portion 44
and terminates in the axial bore 27 of portion 44. !'
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The space between tube 43 and tube 42, connecting
the bores 28 in portion 44, is filled with filter material
45.
Mounted in the gas circuit 2 is the second portion
5 of the quick-acting coupling, coacting with portion 44, -~
which second portion is identical to the above portion 10
of ~uick-acting coupling 9, 10.
For simplicity, this second portion is not shown
in the drawings.
Bore 35 and duct 39 of said second portion
connect to the portion of gas circuit 2 that directly
connects to probe 1, while duct 36 and bore 34 of said
second portion communicates with the portion of gas
circuit 2 that connects to katharometer 5.
In this manner, this quick-acting coupling,
similarly to coupling 9, lO,forms not only a quick
connection of the detachable filter to gas circuit 2, but
at the same time the transition from two coaxial ducts,
i.e. tube 42 and tube 43, to two parallel ducts, i.e. the
20 portions of gas circuit 2 on either side of filter 4. ~;
The embodiment of probe 1 shown in Fig. 6, differs
rom the embodiment shown in Figs. 2, 3 only in a different
construction of sleeve 21, 22, 23, forming the thermal
protection of quick-acting coupling 9, 10.
The inner tube 21, it is true, is also made of
cardboard, but the outer tube is a very thin tube of card-
board, while the central tube 22 is formed of resin-bonded
sand. -~
i The manufacture of this sleeve is rather easy.
30 It is sufficient to provide the sand with the resin between
sleeves 21 and 23 and to bake the whole in a furnace. The ;~
; outer sleeve 23 of cardboard protects the resin-bonded sand.
In another embodiment, said outer sleeve 23 is
made of tin, or even of synthetic plastics material instead
35 of cardboard. The outer sleeve 23 may or may not be covered ~ ~
with a non-splash cover. ~ ~;
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In performing a measurement, a probe 1 is mounted
on a lance 11 by means of a quick-acting coupling 9, 10,
i.e. said lance is pushed into sleeve 21, 22, 23 of probe 1.
The four-way valve 7 is placed in the positio~
5 wherein supply duct 13 connects to the gas circuit 2, so
that the bottle 12 is connected in the direction of probe 1
and probe 1 is immersed into the liquid metal.
Nitrogen bubbles from the quartz tube 18 and
is exhausted through the collecting portion, formed by
10 bell 14 or by the lower portion of quart~ tube 15l through
the diaphragm formed by said belL 14 or by disc 40, by
pump 6, which has meanwhile been actuated. This exhausted
gas escapes into the atmosphere at the four-way valve.
About ten seconds after the first detection of
15 impurities by katharometer 5, the four-way valve 7 is placed
in the other position shown in Fig. 1, either manually or
automatically.
The inert nitrogen gas present in gas circuit 2
is now circulated in this circuit by pump 6 through probe 1,
20 so that adjacent the collecting portion of this probe, when
the carrier gas bubbles through the liquid metal, an
exchange with the gases present in the liquid metal takes
place. After a short period, an equilibrium is approximated
and the signal from the katharometer becomes representative
of the concentration oE the gases, more in particular the
; hydrogen, dissolved in the liquid metal.
The measurement is very simple and quick. In
each measlurement,lonly the probe has to be replaced. The~
rest of the device can always be reused.
By virtue of the quick-acting coupling, -
replacement of the probe is very easy and can be performed
quickly~ Also the filter can be replaced quickly by the
coupling.
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By applying filters on the basis of zeolites, the
davices described hereinbefore may be used not only for
matering for instanca the hydrogan content but also for
simultaneously metering the content of other gaseous
components. To this end the katharometer in the device
shown in figure 1 is replaced by a number of in series
mounted katharometers, after each katharometer except
after the last one, a gaseous component to be metered
being filterad out of the gas.
The determination of the content of hydrogen, C0
and nitrogen of liquid matal takes place as follows. The
first katharom~ter meters the total partial pressure of
H2, C0 ~ ~2 and the carrier gas. Then the carrier gas
flows through a hydrogen filter on the basis of zeolites
where hydrogen is filtered out. Next the filtered gas flows
through a second katharometer which meters the total partial
pressure of CO,H2 and carrier gas. After a C0-filter
retaining the C0, a third katharometer meters the partial
pressure f ~2 and carrier gas. After filtering out N2 in
a third filter on the basis of zeolites, a fourth katharo-
meter metsrs the partial pressure of the carrier gas.
The partial pressure of each of the gaseous components
may be calculated by subtracting the metered results from
each other~ For in9tance, the diffarance between the
meaguring signals from the second and the third katharo-
meter give~ the C0 partial pressure.
The present invantion is by no means restricted
to the embodiments described above and many(alte~ations
on the embodiments described can be made within the scope ~;
of the present patent application, among other things as
regards form, composition, arrangement and number of the
parts employed for the realization of the present invention.
In particular,the different portions of the probe
need not necessarily be made of the above-described
materials. These materials depend among other things on
the matal bath wherein the measurement takes place.
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For instance, the diaphragm formed by the clock
or the disc need not necessarily be of porous brick. This
diaphragm may for instance alternatively be made of ceramic
fibers.
The outer tube of the probe need not necessarily
be made of quartz either. This tube may as well be made
of metal covered with a ceramic material. For measurement
in liquid copper, the tube may also be made of uncoated
steel.
In the embodiment wherein the lower portion of
the outer tube itself forms the collecting portion together
with the diaphragm, the entire tube may be made of porous
material, the upper end of which is provided with a gas-
tight and heat-resistant coating, and the lower end of which ',
15 forms a porous collecting portion together with the diaphragm.
The thermal protective device need not
necessarily consist of three concentric tubes. This thermal
protective device may for instance consist of a single sleeve
of resin-bonded sand or of cardboard.
The meter in the gas circuit need not
necessarily be a katharometer. Other detectors adapted to
meter a gas in the carrier gas can be used. For metering ,
CO~ C02 ~ SO2, and H2S, a meter based on infrared radiation
can be used, for example.
The mechanical coupling of the portions of the
quick-acting coupling need not necessarily be effected by
springing legs on the portion associated with the lance. ,~
The portion associated with the probe may be provided with
springing,,legs orl!may be,res,iliently deformable otherwise.
30 The coupling just has to permit a certain mechanical
connection, which can be undone by exerting suEficient
tractive force.
