CA1330719C - Device for metering a gas content of liquid metal and probe used therefor - Google Patents

Abstract

ABSTRACT

The device comprises a probe with a gas supply pipe terminating at the lower end of the probe, a gas collecting portion for collecting the gas bubbling from the supply pipe through the metal, which portion is provided with a diaphragm allowing gas to pass but re-taining liquid metal, and a gas discharge pipe connecting over the diaphragm to the gas collecting portion. A
gas circuit connects with one end to the gas supply pipe and with its other end to the gas discharge pipe.
A gas detector and a pump are mounted in this circuit.
A lance through which at least a part of the gas circuit extends, contains the one portion of a quick-acting coupling with two connectable portions,while the probe contains the other portion of the coupling. Said coupling can ensure a gas-tight connection of the two above-mentioned ends of the gas circuit and the gas supply pipe,and the gas discharge pipe of the probe,respectively.

Description

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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 :

- 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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1330~19 g 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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1330~19 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.

Claims (47)

1.- An apparatus for measuring a gas content of liquid metal, said apparatus comprising a probe for being immersed in the liquid metal, said probe including a gas supply line which debouches at an end of the probe, a gas collection section for collecting a gas flowing out of the gas supply line, said gas collection section being positioned for receiving the gas flowing from the debouchement of the gas supply line and being provided with a diaphragm permeable for gas but impermeable for liquid metal, a gas removal line in fluid communication with the gas collection section, a gas circuit having a first end in fluid communication with the gas supply line of the probe and a second end in fluid communication with the gas removal line of the probe, at least one gas detector in fluid communication with said circuit, gas moving means in fluid communication with said circuit for moving gas through the circuit, the gas detector and the probe, a lance through which at least a section of the gas circuit extends, and a quick-connection coupling having two parts which can be coupled to each other, said lance containing one part of said quick-connection coupling, said probe containing the other part of the quick-connection coupling, said quick-connection coupling providing in the coupled state, a gastight connection of the gas supply line and the gas removal line to the first and second ends of the gas circuit.

2.- The apparatus of claim 1, further including a thermal shield surrounding the quick-connection coupling and an end of the lance adjacent to the probe.

3.- The apparatus of claim 2, wherein the thermal shield includes at least one tube of resin-bonded sand and at least one concentric tube of paperboard surrounding the quick-connection coupling.

4.- The apparatus of claim 2, wherein said thermal shield includes an innermost tube of paperboard positioned within a thin outermost tube of paperboard such that a space is formed therebetween, said space being filled with resin-bonded sand to thereby form a middle tube.

5.- The apparatus of claim 1, wherein said quick-connection coupling includes coupling means for coupling the two parts thereof detachably to each other, said coupling means incuding resilient legs on one part and a collar on the other part of the quick-connection coupling.

6.- The apparatus of claim 1, wherein the gas supply line and the gas removal line of the probe are concentrically positioned outwardly of the quick-connection coupling.

7.- The apparatus according to claim 6, wherein said quick-connection coupling couples the supply and gas removal lines to the gas circuit regardless of a relative angular position of one part of said quick-connection coupling with respect to the other part of said quick-connection coupling.

8.- The apparatus of claim 6, wherein the gas removal line includes a tube, said tube connecting the collection section to the quick-connection coupling part of the probe.

9.- The apparatus of claim 6, wherein the first and second ends of the gas circuit extend generally parallel to each other and the quick-connection coupling contains a junction of said parallel ends to the supply and gas removal lines.

10.- The apparatus according to claim 7, wherein the part of the quick-connection coupling on the probe includes an axial conduit and at least one adjacently situated conduit, said part of the quick-connection coupling on said lance includes an axial conduit and an adjacently situated channel and in the coupled condition of said parts both said axial conduits connect to each other and an annular space which is completely separated from said axial conduits couples the adjacently situated conduit to the adjacently situated channel.

11.- The apparatus of claim 1, wherein one part of the quick-connection coupling includes two sealing rings for providing a gastight connection of both quick-connecting coupling parts in the coupled condition.

12.- The apparatus of claim 1, further including opening means for opening the gas circuit and connecting a section thereof which communicates with the gas removal line to the open atmosphere.

13.- The apparatus of claim 12, further including a source of inert gas and a second supply line between said source and the gas circuit, said opening means being comprised of a stopcock having one position, wherein the gas circuit is closed and another position wherein the section of the gas circuit in fluid communication with the gas removal line is open to the atmosphere and connects another section of the gas circuit in fluid communication with the gas supply line of the probe to said second supply line between said source and gas circuit.

14.- The apparatus according to claim 1, wherein the gas circuit further includes at least one filter coupled to the gas detector for filtering various gas components flowing through the gas circuit.

15.- The apparatus of claim 14, wherein the gas circuit includes a first gas detector, a filter for a first gas component, a second gas detector, and a second filter for a second gas component.

16.- A probe comprising a gas supply line which debouches J
at one end of the probe, a gas collection section for collecting gas flowing out of the gas supply line, said gas collection section being positioned for receiving the gas flowing from the debouchement of the gas supply line and including a diaphragm permeable for gas but impermeable for liquid metal, a gas removal line in fluid communication with the gas collection section, and a part of two-part quick-connection coupling mounted on another end of said probe for detachably receiving another part of said two-part quick-connection coupling mounted on an end of a lance.

17.- The probe of claim 16, in which the diaphragm is constructed of ceramic fibers bound with a binder.

18.- The probe of claim 16, in which the diaphragm is constructed of porous stone.

19.- The probe of claim 17, in which the diaphragm is generally bell-shaped to thereby form the gas collection section.

20.- The probe of claim 17, in which the gas collection section is formed by a section of a tube having the gas removal line and a disc-shaped diaphragm therein, said probe including a level detector positioned beneath the diaphragm in said section.

21.- A method for measuring a gas content of a bath of liquid metal, said method comprising the steps of :
providing a probe having a gas supply line and a gas removal line each having a lowermost end positioned proximate the other for being immersed in the bath;
sealing the lowermost end of at least one of the gas lines with a seal which opens immediately after immersion in the bath;
pumping carrier gas into the gas line having said sealed end;
immersing said probe in said bath of liquid metal such that said seal opens;
detecting a sudden pressure or flow-rate change in one of the gas lines;
passing carrier gas through the probe to thereby start a measurement cycle;
collecting the carrier gas in the course of the measurement cycle after exchanging with the bath the gas whose content is to be measured;
feeding the carrier gas through the gas removal line into a measuring apparatus, and measuring the gas content with said measuring apparatus.

22.- The method of claim 21, further comprising the step of calibrating said 'measuring apparatus upon detecting said sudden pressure or flow-rate change.

23.- The method of claim 21, wherein the step of passing carrier gas through the probe to start the measurement cycle comprises the steps of flushing the lines, feeding carrier gas through said lines, and allowing said carrier gas to escape into the open atmosphere.

24.- The method of claim 23, wherein the step of flushing the lines further comprises simultaneously feeding said carrier gas into the gas supply line and the gas removal line for allowing the carrier gas to escape into the bath.

25.- The method of claim 23, wherein the step of flushing the lines further comprises the steps of feeding carrier gas into one of the gas lines of the probe, removing the carrier gas through the other gas line in the probe and allowing the carrier gas to escape into the open atmosphere.

26.- The method of claim 23, wherein the step of flushing is carried out for 1 to 10 seconds.

27.- The method of claim 21, wherein the step of passing carrier gas through the probe to start a measurement cycle comprises the step of pumping the carrier gas in a closed circuit through the probe and the measuring apparatus.

28.- The method of claim 21, wherein the step of sealing the lowermost end of the gasline comprises the step of positioning a fusible stopper within the gas line, the stopper being of a type which melts upon immersion in the bath.

29.- The method of claim 28, wherein the step of sealing the lowermost end comprises the step of sealing the gas supply line with the fusible stopper.

30.- The method of claim 23, further comprising the steps of providing said lowermost end of said gas removal line with a gas collection section, said gas collection section being formed of said gas removal line and a disc-shaped diaphragm; and wherein the step of immersing said probe comprises the step of creating a carrier gas cushion beneath said diaphragm and maintaining said cushion during said measuring step to prevent contact of the metal with the diaphragm.

31.- The method of claim 23, further comprising the steps of filtering the carrier gas substances in the colloidal or gaseous state for removal of the surface-active substances in the carrier gas bubbles after passage through the metal.

32.-The method of claim 23, further comprising the step of adding a quantity of the gas component whose content in the metal is to be measured to the carrier gas for achieving a rapid equilibrium concentration of said gas component in the carrier gas.

33.- The method of claim 32, wherein the step of measuring further comprises the steps of :
feeding carrier gas into a closed circuit in fluid communication with the probe and a gas detector;
measuring the change of concentration of the gas component in the carrier gas after at least a circulation of the carrier gas through said circuit;
estimating an equilibrium concentration on the basis of a known, pre-programmed saturation curve;
adding the gas component to the carrier gas until the concentration of said component almost reaches' the estimated equilibrium concentration;
measuring the concentration change of said component after a subsequent circulation of the carrier gas;
estimating an equilibrium concentration in an analogous manner : and repeating one or more of the above steps until the estimated concentration is sufficiently accurate.

34.- The method of claim 32, wherein the step of measuring further comprises the steps of:
feeding carrier gas into a closed circuit in fluid communication with the probe and a gas detector;
varying the concentration of a gas component to be measured in the carrier gas before a complete circulation of the carrier gas around the circuit;
obtaining a concentration profile of the gas component to be measured as a function of time after said circulation of the carrier gas;
measuring an altered profile of concentration as a function of time; and comparing said altered profile with the preceding profile and, allowing for the delay resulting from the circulation time.

35.- A probe for measuring a gas content of a bath of liquid metal, said probe comprising a gas supply line having a lowermost end which debouches at an end of the probe and a gas removal line having a lowermost end for collecting carrier gas flowing out of the gas supply line, said lowermost end of said gas removal line being positioned proximate the lowermost end of the gas supply line, at least one of the gas lines being sealed by a seal removable during immersion of the probe into the liquid metal.

36.- The probe of claim 35, wherein the lowermost end of the gas supply line is sealed. I

37.- The probe of claim 35, wherein said seal is a fusible plug which melts during immersion into the liquid metal.

38.- The probe of claim 35, wherein said probe is disposable and includes means for detachably coupling the probe to a lance.

39.- A method for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, said method comprising the steps of:

providing a probe having a gas supply line and a gas removal line, each having a lowermost end positioned proximate the other;
immersing said lowermost ends in the liquid metal;
supplying a carrier gas to the gas supply line;
collecting said carrier gas after hydrogen gas has been exchanged with the bath;
feeding said hydrogen gas into the gas removal line of the probe to a gas detector;
measuring the hydrogen gas content; and drying the hydrogen gas before the end of the measuring.

40.- The method according to claim 39, wherein the step of measuring further comprises the step of circulating the hydrogen gas through a closed circuit, the probe, and the gas detector, said drying step of the gas being carried out during such circulation.

41.- An apparatus for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, said apparatus comprising a probe for immersion into the liquid metal, said probe including a gas supply line having an uppermost end and a lowermost end which debouches at an end of the probe and a gas removal line having an uppermost and a lowermost end for collecting gas flowing out of the gas supply line and for collecting hydrogen gas from the bath, the lowermost end of the said gas removal line being positioned proximate the lowermost end of the gas supply line, a gas circuit having one end in fluid communication with the gas supply line and another end in fluid communication with the gas supply line, said circuit including a gas detector and gas movement means for moving carrier gas through the circuit, the gas detector and the probe, and drying means for drying said carrier gas positioned within the gas supply line of the probe, the gas removal line of the probe, the gas circuit and the gas detector.

42.- The apparatus of claim 41, wherein the drying means is positioned within one of the gas lines.

43.- The apparatus of claim 41, wherein the probe is disposable and further including a lance, a quick-connection coupling for connecting said probe to said lance, part of said quick-connection coupling being installed on the probe and another part of the coupling being installed on the lance, said quick-connection coupling connected the gas supply line and the gas removal line of the probe to both ends of the gas circuit in a gastight manner, the drying means being disposed in one of the gaslines, the lowermost end of one of the gas lines in the probe being sealed in a moisture-tight manner by a first seal which is opened when the probe is immersed in the metal bath and an uppermost end of one of said gas lines in the probe being sealed in a moisture-tight manner by a second seal which is opened by coupling the parts of the quick-connection coupling to each other.

44.- The apparatus of claim 43, wherein the first and second seals seal said gas supply line of the probe.

45.- A throwaway probe for measuring a gas content, in particular a hydrogen content, of a bath of liquid metal with a low partial pressure of oxygen, said probe comprising a gas supply line having an uppermost and a lowermost end which debouches at an end of the probe, a gas removal line having an uppermost and a lowermost end for collecting a gas which flows out of the gas supply line, said lowermost end of said gas removal being positioned proximate the lowermost end of the gas supply line, and drying means positioned within one of the gas lines for drying said gas, one of said gas lines being closed at both ends in a moisture-tight manner by breakable seals.

46.- The throwaway probe of claim 45, wherein the gasline containing the drying means is closed at its lowermost end by a fusible stopper which melts at the temperature of the liquid metal.

47.- The throwaway probe of claim 45, wherein the gas line containing the drying means is closed at its uppermost end by an elastic stopper, said elastic stopper being piercable by a hollow needle.