US3490289A

US3490289A - Apparatus for taking samples from a bath of molten material

Info

Publication number: US3490289A
Application number: US719943A
Authority: US
Inventors: Francois Mangin
Original assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Current assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Priority date: 1967-04-10
Filing date: 1968-04-09
Publication date: 1970-01-20
Anticipated expiration: 1987-01-20
Also published as: BE713342A; GB1173864A; FR1527039A; LU55820A1; DE1773164A1; NL6804931A

Description

F. MANGIN Jan. 20, 1970 APPARATUS FOR TAKING SAMPLES FROM A BATH OF MOLTEN MATERIAL 2 Sheets-Sheet 1 Filed April 9, 1968 Qtb tbbuqfl \wm mu 2 2 I 0 w mu Jan.20, 1910 'F.MANGIN' 3,490,289

APPARATUS FOR TAKING SAMPLES FROM A BATH'OF MOLTEN MATERIAL Filed April 9, 1968 2 Sheets-Sheet B amend-19f! Frw mfg Hwy-.

United States Patent .0 F

3,490,289 APPARATUS FOR TAKING SAMPLES FROM A BATH OF MOLTEN MATERIAL Francois Mangin, Metz, France, assignor to Institut de Recherches de la Siderurgie Francaise, Saint-Germainen-Laye, France Filed Apr. 9, 1968, Ser. No. 719,943 Claims priority, application France, Apr. 10, 1967, 102,044, Patent 1,527,039 Int. Cl. G01n U1!) US. Cl. 73-423 14 Claims ABSTRACT OF THE DISCLOSURE An elongated metal tube is mounted on a support that is movable between an extended position in which one end of the metal tube extends into a bath of molten material, and a retracted position in which the end is withdrawn from the bath when the molten material has solidified within the end. A cutting device is provided for cutting ofl. at least the end portion of the tube with the solidified material therein. A shifting device moves the movable support relative to the tube to bring the movable support in position relative to the cut end of the tube to move the tube to the extended position. Thus, the cut-off end portion with the material therein may be used as a sample and the tube is again open and ready to receive a new sample during its next movement to its extended position.

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for taking samples from a bath of molten material, especially molten metal, such as pig iron or molten steel. Various devices are known in the art for taking samples from such a metal bath. In the art of metallurgy it .is often desired to take for instance during refining of metal, such as the refining of cast iron, samples from the molten metal baths, in order to properly control the refining process. The withdrawal of samples from the metal baths usually is carried out manually and relatively slow and the samples thus withdrawn are not immediately available for analysis and quite often also contain certain flaws. In addition, in order to manually withdraw samples from the hot metal bath, the operator will be required to approach the bath very closely in order to plunge the instrument serving to withdraw a sample from the bath into the latter, which, due to the extremely high temperature surrounding the bath, will make this operation a rather disagreeable one.

It is an object of the present invention to provide for an apparatus for withdrawing samples from a bath of molten material which avoids the difficulties and inconveniences connected with withdrawing of samples from a bath with means known in the art.

It is an additional object of the present invention to provide an apparatus of the aforementioned kind which can be operated fully automatic, and which provides samples directly usable for analysis, especially for spectrographic analysis thereof.

SUMMARY OF THE INVENTION With these objects in view, the apparatus according to the present invention for taking samples from a bath of 3,490,289 Patented Jan. 20, 1970 molten material mainly comprises support means, an elongated metal tube mounted on the support means movable between an extended position in which one end portion of the metal tube extends into the bath of molten material so that part of the molten material may penetrate in the end portion of the tube and a retracted position in which the end portion is withdrawn from the bath, means cooperating with the tube for moving the latter from the withdrawn to the extended position and from the extended to the retracted position after the material received in the end portion of the tube has solidified therein, and means adjacent the end portion of the tube, in the retracted position of the latter, for cutting off at least the end portion of the tube with the solidified material therein so that the cut-off end portion with the material therein may be used as a sample for analysis and so that the tube is again opened at the cut-off end so as to be ready to receive a new sample during its next movement from the retracted to the extended position.

The moving means preferably include releasable clamping means for gripping the tube at a portion thereof spaced from the end portion and means for reciprocating the clamping means along a given stroke in longitudinal direction of the tube, whereby, after the end portion has been cut off, the tube may be advanced so that its new end is positioned the same distance from the bath as the previous, now cut-off end was, and then the clamping means be released and moved relative to the tube away from the neW end for a distance equal to the length of the cut-off portion and be reclamped in its new position.

In a preferred embodiment according to the present invention, the apparatus is also provided with automatic control means automatically controlling the clamping means, the moving means and the cut-off means in a predetermined sequenee and in such a manner that at the end of each sequence the tube end portion will again be in its original position, that is in the retracted position ready for being again extended with the end portion thereof into the bath of molten material.

The apparatus of the present invention may also include one or a plurality of the following features in combination with the above-mentioned features:

(a) The tube may be constituted by a plurality of tube sections screwed one to the end of the other;

(b) The apparatus may also include means for blowing a gas under pressure in the interior of the tube during movement of the tube from the retracted to the extended position and this blowing may be stopped after the lower extremity of the tube arrives at the predetermined zone of the liquid bath;

(0) The apparatus may also include means for providing a sub-atmospheric pressure in the interior of the tube during part of its movement into the bath;

((1) The support means of the apparatus may be provided with rollers or wheels so that the whole apparatus is movable and may be easily transported from one to another bath;

(e) The outer surface of the tube may be protected by a sheath of thermal insulation; and

(f) The means for reciprocating the releasable clamping means along a given stroke in longitudinal direction of the tube may be constituted by an endless belt driven by a reversible motor in one or the other direction.

As understood, the principle of the present invention mainly consists in plunging an end portion of a metal tube of predetermined wall thickness to a certain depth into a bath of molten material. The material forming the bath, which may be cast iron, steel or even molten glass, will penetrate into the end portion of the tube due to the hydrostatic pressure acting onto the bath surface, and the material in the interior of the tube will be cooled off by heat exchange with the cool tube wall and thus solidify in the tube. If the wall thickness of the tube is sufficiently large, the tube end portion may be maintained in the bath without melting during a time sufiicient to permit the material which has penetrated into the interior of the tube to solidify. After the material has solidified in the end portion of the tube, the latter is withdrawn from the bath and the tube end portion with the material therein is out off in at least one or a plurality of longitudinally spaced transverse planes to obtain in this way one or a plurality of samples which are representative of the composition of the bath at different levels.

The last out is taken at a place of the tube to which material has not penetrated so that after the cut the tube end is again open and so that material in the bath will again penetrate into the interior of the tube when the latter is again plunged into the bath.

All of the aforementioned operations are advantageously carried out in a fully automatic manner according to the predetermined sequence. Evidently, the tube is consumed after a series of such sequences have been carried out in succession. To facilitate the operation, it is preferred to manufacture the tube from a plurality of threadingly connected tube elements or at least to provide the tube at the end thereof opposite from the end portion to be plunged into the bath with a screw thread so that an additional tube may be connected to the first-mentioned tube after the latter has been consumed. In this way it is possible to carry out a series of operations of taking test samples from the bath in a simple and rapid manner without the necessity of disassembly of the apparatus.

The tube according to the present invention may also be surrounded at the outer surface thereof by a sheath of insulating material in order to assure that the tube material is heated up mainly by the material in the bath penetrating into the interior of the tube and not by the bath material surrounding the tube. In this way, the cooling and the solidification of the material penetrated into the interior of the tube is expedited and the time necessary for obtaining a sample reduced so that a series of samples may be quickly anal zed.

The present invention is especially adapted to obtain quickly samples from a bath of molten metal, especially from a bath of pig iron during the refining thereof.

Furthermore, with the apparatus of the present invention it is possible to take samples from a ladle of a furnace containing molten pig iron in such a manner that the sample is free of slag, usually forming on top of the molten pig iron. For this purpose, it is sufficient to blow into the interior of the tube, while the end portion thereof passes through the layer of slag forming on the molten pig iron, a neutral gas such as argon or nitrogene with a pressure at least equal to the hydrostatic pressure of this molten slag. This blowing is then stopped after the end of the tube reaches the metal below the slag layer. It is likewise possible to suck gas contained in the interior of the tube from the latter and to create in this way a pressure below atmospheric pressure in the interior of the tube to thus expedite penetration of the molten pig iron into the tube interior, and the sucking is interrupted after the pig iron has obtained a desired level in the interior of the tube. The aforementioned operation may also be carried out in a fully automatic manner, for instance with the aid of an electro valve operated automatically by a timer or other control device.

An additional reason renders the apparatus: of the present invention especially advantageous in siderurgical processes. As it is known, it is necessary in order to know for example the composition of the steel just before the latter is cast to calm or kill the steel sample taken from the molten steel bath in order to avoid the phenomenon of etfervescence occurring during solidification of the steel due to the fact that when the steel begins to solidify, the solubility of gases dissolved in the steel decreases and the excess gases are expelled from the metal, which will cause considerable variations in the composition of the metal. The apparatus according to the present invention permits a calming of the solidifying steel in an eflicient and simple manner. For this purpose it is sufiicient to dispose in the interior of the tube a reducing metal, for instance a rod or a band of aluminum.

The apparatus of the present invention provides also great advantages in that the apparatus may be integrated with automatic operations of a metallurgic process. The means for operating a furnace may be properly correlated at the most opportune moments with the operation of taking samples. For instance it is possible to control the openings of port holes of a furnace in such a manner that the port holes are opened at the exact moment the tube is plunged into the bath so that the tube may be plunged through one of the opened port holes into the interior of the bath so that the time the port hole is opened is re duced to a minimum.

The invention itself, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side view, partly in section, of the apparatus according to the present invention;

FIG. 1a is a partial longitudinal cross-section through a modified tube to be used in the apparatus as shown in FIG. 1; and

FIGS. 2a-2e are schematic views and showing some of the elements of the apparatus of FIG. 1 in successive positions these elements will assume during operation of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, and more specifically to FIG. 1, it will be seen that the apparatus according to the present invention includes support means which may comprise a frame having an upright 12 and an inclined longitudinal member 16 integrally connected to the upper end of the upright 12. Two pairs of roller means 5 are mounted on the upper downwardly inclined surface 6a of the member 6 and the pairs of roller means define between themselves an elongated path parallel to the surface 6a in which a metal tube 4 is guided for movement between a retracted position, as shown in full lines in FIG. 1, and an extended position shown in dotted lines in FIG. 1, in which the end portion 4a of the tube 4 extends into a metal bath 1, for instance a bath of molten cast iron contained in a furnace 2 and covered by a layer of slag 3. The metal tube preferably has an inner diameter of 25 millimeters and an outer diameter of 40 millimeters. Means cooperating with the tube 4 are provided for moving the tube in direction of its axis betwen a withdrawn position and an extended posi tion. The moving means for moving the tube 4 between the positions thereof preferably comprise releasable clamping means 7, schematically shown in FIG. 1, arranged and constructed for clamping the tube at a portion thereof spaced from the lower end portion. The clamping means 7 are fixedly connected at the lower end thereof to an endless belt 8 guided over an idling roller 9 and a driven roller 10, which are both mounted rotatable about parallel axes on the member 6. The driven roller 10 is driven by a reversible electro motor 11 likewise carried by the member 6. When the roller is rotated by the reversible motor 11 in the direction of the arrow a while the clamping means 7 are clamped on the outer surface of the tube, the latter will be moved from the retracted position, shown in full lines in FIG. 1, in the direction of the arrow b to the advanced position in which the end portion 4a of the tube is plunged into the metal bath 1. Rollers or wheels'12 are connected in a known manner to the base of the support means so that the apparatus may be moved along a supporting surface on rails 13 quickly toward and away from the furnace 2.

The apparatus of the present invention includes further means for cutting off the end portion 4a of the tube 4- after the end portion has been filled with material from the bath and the material has hardened in the end portion and after the tube has been retracted again so that its end portion is at its original position indicated at 4b. The means for cutting off the end portion of the tube may include a plurality of cutting discs or grinding

wheels

14, 14a and 14b arranged along a common axis parallel to the axis of the tube and driven'by a drive motor. The cutting

discs

14, 14a, and 14b, as well as the drive motor thereof, may be mounted on a bracket, which in turn is cornected to the member 6 in a known manner so that the discs may be moved from the position as shown in the drawing in which the peripheries of the discs are spaced from the outer surface of the tube 4 to a position in which the discs will cut through the tube and the material contained therein.

After the tube end portion has been cut off from the remainder of the tube, the clamping means and the tube are again moved in direction ofthe arrow b until the tube end abuts against an adjustable stop 15 connected to the lower end of the member 6 and which limits the downward movement of the tube in such a manner that the lower end of the tube will be at the same place as the lower end of the tube has been before cutting, as indicaed at 4b. Thereafter the clamping means 7 is released, the motor 11 reversed, arid the clamping means moved in o posite direction along the tube for a distance equal to the cut off end portion and reclamped in its new position. The stop means 15 is adjustable between the position shown in full lines in FIG. 1, in which a portion of the stop means extends into the path of the tube 4, and the position shown in dotted lines at 15a in which the stop means is removed from the path of the tube so that the latter can be advanced into the liquid bath 1. To adjust the position of the stop means 15, the latter may be turnably mounted for turning movement about an axis parallel to the tube axis, or the stop means 15 may be reciprocated in a direction normal to the axis of the tube 4.

The apparatus according to the present invention may also be provided with means for blowing a neutral gas into the interior of the tube during plunging of the latter into the molten material and also with means for providing a reduced pressure in the interior of the tube after the end portion of the same has been extended into the molten ma erial so as to expedite penetration of the molten material into the interior of the tube.

For this purpose the apparatus may be provided with a source of neutral gas, for instance a bottle 23 of nitrogene under pressure, and a vacuum pump 26, both mounted on the base of the support means as shown in FIG. 1. The bottle 23 and the vacuum pump 26 are connected respectively by

conduits

24 and 27 to a three position valve 20, which preferably is constructed in a Well known manner as an electro valve, and the latter is connected through a conduit 21 to a connection 16 carried by a support member 6, whereas the connection 16 is in turn connected by a flexible conduit 17 and a coupling sleeve 18 to the upper threaded end of the tube 4.

With this arrangement it is possible to prevent penetration of slag into the end portion of the tube 4 during plunging of the latter into the bath contained in the furnace 2 so as to obtain a sample free of slag. For this purpose it is only necessary to adjust the electro valve 20 in such a manner that, during plunging of the end portion of the tube 4 into the bath, nitrogene under compression is fed through the

valve openings

22 and 19 into the interior of the tube during the time the end portions traverse the layer of slag on top of the bath. The pressure of the gas in the interior of the tube will thus prevent penetration of any material into the tube end portion. Likewise it is possible to subsequently close the opening 22 of the valve after the end portion of the tube has penetrated in the liquid metal and to open subsequently thereto the valve opening 25 so as to connect the suction pump 26 with the tube interior to create an underpressure therein so that the liquid metal will rapidly enter into the tube end portion. This sequence is 0ptional, but the sequence will have certain advantages in that a rapid filling of the tube end portion with only metal will be obtained.

The cutting

discs

14, 14a and 14b are preferably constituted by grinding wheels driven by common motor and they serve, as explained above, to cut through the tube end portion containing the solidified metal after the tube end portion has been retracted to the original position 4b. In this position of the tube the disc 14 is positioned relative to the tube in such a manner to cut through the tube adjacent to the stop 15, which during this cutting operation is held in the upper position as indicated in full lines in FIG. 1. The plug thus obtained is not utilized. This first cut is carried out as a precautionary matter to eliminate the extreme end portion of the tube, since the solidified material contained therein may have some flaws. The second cutting disc 14a cuts the tube in the region which likewise contains solidified metal to provide thus a sample free of flaws, the length of which is equal to the distance between the two planes of cutting of the cutting discs 14, 14a. This cut-off sample is dropped in a funnel not shown in the drawing and from there onto a transporting conveyor, likewise not shown, which transport the sample to a laboratory for analysis. This transporting conveyor may be of any type known, for instance a pneumatic transporting conveyor. At the same time the cutting disc 14b cuts the tube in the region where the tube is not filled with solidified metal. This provides again an open end at the lower end of the tube so that liquid metal may again penetrate thereinto during the next plunging of the end portion of the tube in the metal bath. Evidently, it is also possible to use more than three cutting discs, if it is desired to obtain more than one sample during each cycle of operation. Likewise, it may also be in certain cases unnecessary to blow nitrogene under pressure into the interior of the tube while the latter traverses the slag layer. In this case, the valve may be constructed and positioned in such a manner that the conduits 21 and 17 may be connected to the atmosphere. In this case the material in the bath will enter into the end portion of the tube, when the latter is plunged into the bath only due to the pressure acting on the bath surface. This permits to obtain a sample having a lower portion which will be representative of the metal in the bath and an upper portion which will be representative of the slag floating on the upper bath surface.

FIG. 1 illustrates at 7a the lower position of the clamping means 7, which position 7a corresponds to the position 4a of the end portion of the tube 4, while the upper position of the end portion is indicated at 4b. Likewise, FIG. 1 shows at 18a the lower position of the connecting sleeve 18 and the corresponding position 17a of the flexible tube 17.

The sequence of operations for taking samples from a bath of molten material with the apparatus of the present invention will now be described by means of FIGS. 2a2e.

FIG. 2a schematically illustrates the position of the tube 4 at the starting or retracted position in which the stop 15 is in its upper position and engages the lower end of the tube and blocks thereby its movement in downward direction. Subsequently thereto the stop is turned or withdrawn to the position a, the motor 11 is energized to rotate in counterclockwise direction as indicated by the arrow a in FIG. 1 and thereby the clamping means are moved from the upper position 7, as shown in FIG. 2a, to the lower position 7a, as indicated in FIG. 2b, while the tube held by the clamping means is simultaneously moved to its extended position, as indicated in FIG. 2b, in which the end portion of the tube reaches the position 4a and extends into the bath of molten material 1. The tube is maintained in this extended position for a predetermined time period sufiicient to let solidify the metal which has penetrated into the interior of the end portion of the tube. In order to maintain this time relatively short, it is necessary that the tube has a sufficient calorific capacity, that is that the tube must have a sufiicient mass of relatively cold material so as tocool and solidify the liquid metal penetrating into its ends portion. It is for this reason that the tube is preferably a steel tube with an inner diameter of millimeter and an outer diameter of 40 millimeter. On the other hand, in order to limit heat exchange between the tube and the mass of molten material surrounding the end portion of the tube at the outer surface thereof, the outer surface of the tube may be protected by a layer of refractory material as indicated in FIG. 1b in which the tube 4' consists of an inner steel tube 4 and an outer sheath 4 of refractory material.

The examples of the tube material given are to be considered as not limiting. The tube may also be formed from refractory steel or even from nearly pure iron.

After the material has penetrated into the interior of the end portion of the tube and solidified therein, the tube is again withdrawn to the position as indicated in FIG. 20, that is to its original position shown in FIG. 2a. The only difference being is that the end portion 4b of the tube is filled with solidified metal. The grinding wheel 14 cuts the tube and the metal contained therein along the plane 28 to eliminate the extreme end portion of the tube in which the solidified metal contained therein may have some flaws. At the same time the grinding wheel 14a cuts the tube along the plane 29 which provides for a cut-off portion which is guided, as mentioned before, by a transporting mechanism to the laboratory for analysis. The samples thus produced may be subjected to an analysis, for example, to a spectographic analysis. Likewise, the grinding Wheel 14b simultaneously cuts the tube along the plane 31 at a place of the tube to which the metal has not penetrated. The thus provided new end 4c of the tube, shown in FIG. 2d, is again open and ready to be plunged again into the metal bath. FIG. 2e represents an intermediate position 7b of the clamping means 7. The clamping means 7 has to move the tube downwardly until its new end 4c contacts again the stop 15. After this position has been obtained, as shown in FIG. 2e, the clamping means are opened and again retracted by reversing the motor 11 until the clamping means 7 reaches its original position as shown in FIG. 2a, after which the clamping means is again tightened against the tube so that the apparatus is ready for the next cycle.

The above-described movements of the various elements, that is clamping and releasing the clamping means 7, movement of the tube between its retracted and its extended position, cutting off the tube end portion by the cutters 1444b, opening and closing of the electro valve 20, may be carried out according to the present invention in a fully automatic manner and in a predetermined sequence. For this purpose a programming or control device C of known construction may be provided and connected to the clamping means 7, the motor 11, the cutting means 14, 14a and 141), the stop 15 and the electro valve 20 as schematically indicated in FIG. 1. Such control devices or programmers are well known in the art, and the specific construction of the control device and the specific construction of the various components of the apparatus connected thereto so that they 8 can be operated by the control device do not form part of the present invention and therefore this arrangement is only schematically illustrated in FIG. 1. The movement of the various elements may be produced by solenoids or servomotors which are controlled by the control device C in a well known manner. It is also possible to connect an operating-mechanism for a door 32 of the furnace to the control device C in order to open the door at the moment the lower end of the tube approaches during its descent the opening in the furnace and to automatically close the door again after the tube has been withdrawn in upwards direction. Such an arrangement will result in a minimum heat loss during taking of samples. It is also possible to control the programmer C by signals obtainable from the interior of the furnace and indicating the state of operation taking place in the furnace. In this way it is possible to take samples at the most opportune moment of the furnace operation.

The apparatus according to the present invention has numerous advantages. The apparatus may be integrated with fully automatically carried out metallurgical operations. It may easily be placed adjacent to a furnace and it will permit to takesamples in rapid succession which are promptly available for analysis, for instance specto graphic analysis. The apparatus may be quickly provided with a new tube after one tube has been used up, since after the first tube becomes too short it is sufficient to release the coupling sleeve 18 and to screw a number of new tube elements to the upper end of the partlyused up tube and to rescrew afterwards the coupling sleeve onto the new upper extremity.

Finally, the apparatus is especially adapted topermit taking of samples free of any slag. It likewise permits to calm samples taken from an effervescent steel bath.

The use of the apparatus according to the present invention is not limited to taking samples of cast iron or steel, and evidently the apparatus may be used advantageously also in other fields where samples of molten material have to be taken.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of apparatus for taking samples from a bath of molten material differing from the types described above. 7

While the invention has been illustrated and described as embodied in an apparatus for taking samples from a bath of molten ferrous material, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoingwill so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characwhich said end portion is withdrawn from the bath; means cooperating with thetube for moving said tube from said retracted to said extended position and from the latter back to said retracted position after the materialreceived in said end portion has solidified therein; meansadjacent said end portions of said tube in said retracted position for cutting off at least said end portion of said tube with the solidified material therein; and means for subsequently shifting said moving means relative to said tube to bring said moving means in position relative to said cut end of the tube ready to move the latter to said extended position so that said cut-oil end portion with the material therein may be used as sample and so that the tube is again opened at its cut-ofi' end and ready to receive a new sample during its next movement to its extended position.

2. An apparatus as defined in claim 1, wherein said moving means includes releasable clamping means for gripping said tube at a portion thereof spaced from said end portion and means for reciprocating said clamping means along a given stroke in longitudinal direction of the tube, whereby, after the end portion has been cut off, the new end of the tube may again be moved to the position the tube end had before cutting and the clamping means be released and retracted for a distance equal to the length of the cut-off portion to be clamped again onto the tube so that the latter will be ready for the next cycle.

3. An apparatus as defined in claim 2 and including adjustable stop means on said support means for limiting advance of the tube after the tube end portion has been cut off.

4. An apparatus as defined in claim 3, wherein said support means includes a downwardly inclined portion and roller means on said portion and engaging said tube for guiding the same along a downwardly inclined path.

5. An apparatus as defined in claim 2, and including control means cooperating with said moving means, said cut-ofl? means, and said releasable clamping means for operating said means according to a predetermined sequence and in such a manner that the tube at the end of each sequence is in said retracted position.

6. An apparatus as defined in claim 1, wherein said tube is provided at the end thereof opposite said end portion with a screw thread for connecting thereto an additional tube after the first-mentioned tube has been substantially used up.

7. An apparatus as defined in claim 1, and including means connected to the end of the tube opposite said end portion for blowing a gas under pressure into the interior of said tube during dipping of said end portion into said bath and for releasing the gas pressure in the interior of the tube after said end portion has penetrated to a certain depth into said bath to permit material of the bath to penetrate into the tube only after the gas pressure has been released.

8. An apparatus as defined in claim 1, and including means connected to the end of the tube opposite said end portion for creating during part of the time said end portion extends into said bath a reduced pressure in the interior of said tube.

9. An apparatus as defined in claim 1, and including a source of compressed gas, a vacuum pump, a valve movable between three positions, tube means connecting said valve with said source of compressed gas, said vacuum pump, and the end of said tube opposite said end portion thereof in such a manner that in a first position of said valve the interior of said tube is connected to said source of gas under pressure, in a second position of said valve the interior of said tube communicates with said vacuum pump, and in a third position of said valve the interior of said tube communicates with the atmosphere.

10. An apparatus as defined in claim 9, wherein said valve is an electro valve, and including control means cooperating with said moving means and said electro valve for operating the latter and said moving means in timed sequence.

11. An apparatus as defined in claim 1, and including thermal insulating means fixed to and surrounding the outer surface of said metal tube.

12. An apparatus as defined in claim 1, wherein said moving means includes releasable clamping means for gripping said tube at a portion thereof spaced from said end portion and means cooperating with said clamping means for reciprocating the latter along a given stroke in longitudinal direction of said tube, said reciprocating means comprising an endless belt mounted on said support means and reversible motor means for moving said belt in one and in the opposite direction, said clamping means being fixed to a portion of said belt.

13. An apparatus as defined in claim 1, wherein said cut-off means comprises a plurality of cutting discs arranged along a common axis substantially parallel to that of said tube, a support mounted on said support means for supporting said discs rotatable about said common axis and movable between an inactive position in which said discs are disengaged from said end portion of said tube and an active position in which said discs will cut through said tube, and drive means connected to said discs for rotating the same.

14. An apparatus as defined in claim 1, wherein said support means are provided with rollers so as to be movable from one to another bath.

References Cited UNITED STATES PATENTS 3,255,634 6/1966 Cavalier.

3,298,069 1/1967 Acre.

3,313,159 4/1967 Vanderbeck.

3,315,529 4/ 1967 Feichtinger.

3,415,124 12/1968 Collins 73425.4

LOUIS R. PRINCE, Primary Examiner HARRY C. POST III, Assistant Examiner