US3659944A

US3659944A - Apparatus for continuous spectral analysis of molten substances

Info

Publication number: US3659944A
Application number: US118303A
Authority: US
Inventors: Milan Bojic
Original assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Current assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Priority date: 1970-02-27
Filing date: 1971-02-24
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02
Also published as: FR2080243A5; CA924928A; GB1292015A; ZA711184B; SE372344B

Abstract

Apparatus for direct and continuous spectrometric analysis of molten metals has a riser which draws a continuous stream of molten metal from a furnace in response to actuation of an electromagnetic pump. The stream flows through a spark chamber which contains a sill or barrier over which the metal must flow to rise to a predetermined level at a desired distance from a first electrode which is connected with one pole of a spark generator. The other pole of the spark generator is connected with a second electrode which dips into the stream of molten metal in the chamber with attendant generation of a spark between the exposed surface of the stream and the first electrode. The light or radiation which is generated by the spark is directed into a spectrometer by way of a horizontal or vertical tube. Such tube further serves to admit into the spark chamber a stream of inert gas which evacuates metallic vapors developing in the chamber in response to generation of the spark.

Description

0 United States Patent [151 3,659,944 Bojic 1 May 2, 1972 [54] APPARATUS FOR CONTINUOUS Primary Examiner-Ronald L. Wibert SPECTRAL ANALYSIS OF MOLTEN Assistant Examiner-V. P. McGraw SUBSTANCES Attorney-Michael S. Striker [72] Inventor: Milan Bojic, Metz, France 57 ABSTRACT Assigfleei 1mm"! de Recherche de la sldmll'flie Apparatus for direct and continuous spectrometric analysis of Francoise Germam-en-Layet France molten metals has a riser which draws a continuous stream of [22] Filed: Feb. 24, 1971 molten metal from a furnace in response to actuation of an electromagnetic pump. The stream flows through a spark PP 113,303 chamber which contains a sill or barrier over which the metal must flow to rise to a predetermined level at a desired distance [30] Foreign Appncauon p n from a first electrode which is connected with one pole of a spark generator. The other pole of the spark generator is con- 1970 France "7007139 nected with a second electrode which dips into the stream of molten metal in the chamber with attendant generation of a [52] US. Cl. "356/86, 356/74, 356/246 spark between the exposed surface f the sream and the first [51] "G013 'g 'g 2 electrode. The light or radiation which is generated by the [58] M Search spark is directed into a spectrometer by way of a horizontal or R I Cited vertical tube. Such tube further serves to admit into the spark [5 6] e erences chamber a stream of inert gas which evacuates metallic vapors UNITED STATES PATENTS glevelloping in the chamber in response to generation of the ar 3,602,595 8/1971 Dahlquist et al ..356/86 p 10 Claims, 3 Drawing Flgures s am ems/same 125 JfiHTAOHETE/P Jofit'rafi 22/ 1 5 225 y i ,1

l 7 i i 25 nnnnnnnnnnnn Patented May 2, 1972 2 Sheets-Sheet 1 FIG. I

Patented May 2, 1972 2 Sheets-Sheet 2 APPARATUS FOR CONTINUOUS SPECTRAL ANALYSIS OF MOLTEN SUBSTANCES CROSS-REFERENCE TO RELATED APPLICATIONS The apparatus of the present invention constitutes an improvement over and a further development of apparatus which are disclosed in the copending applications Ser. Nos. 95,568 filed Dec. 7, 1970 and 110,998 filed Jan. 29, 1971 by Milan Bojic et al. and owned by the assignee of the present application.

BACKGROUND OF THE INVENTION The present invention relates to apparatus for the examination of molten metals, alloys and/or other substances which melt at elevated temperatures. More particularly, the invention relates to improvements in apparatus for spectrometric examination or analysis of molten materials, such as iron, steel or aluminum alloys.

The aforementioned copending applications of Bojic et al. disclose apparatus for direct spectrometric analysis of molten materials, i.e., apparatus which can analyze samples of molten material upon withdrawal from a furnace or directly in the interior of a furnace. This renders it possible to complete the examination with a minimum of delay. Rapid completion of analysis is desirable when the samples are taken from molten material which undergoes a refining or other treatment so that its composition is likely to change before the examination of a sample is completed. Molten material is examined by producing a spark between the surface of molten metal and an electrode with attendant generation of light or radiation, and by thereupon subjecting such light or radiation to a spectrometric analysis.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved apparatus for direct and continuous spectrometric analysis of molten metals and/or other molten materials in such a way that the results of the analysis are available practically without any delay.

Another object of the invention is to provide an apparatus for direct and continuous spectrometric analysis of molten materials which can be used to examine the contents of existing furnaces for refining or other treatment of metals and/or alloys.

A further object of the invention is to provide an apparatus for continuous and direct spectrometric analysis of a stagnant or flowing bodies of molten material.

An additional object of the invention is to provide the apparatus with novel means for directing light from the point of electric spark discharge into a spectrometer, with novel means for evacuating metallic vapors which develop as a result of such discharge, and with novel means for controlling the spark discharge between a stationary electrode and a moving body of molten material.

In the above paragraph and in the following specification and claims the expression light" is intended to mean not only visible light but also invisible radiations, such as ultra-violet radiations.

The improved apparatus is particularly suited for continuous and direct spectrometric analysis of molten metals and comprises a housing which consists at least in part of refractory material and defines a preferably horizontal channelshaped spark chamber having an inlet opening and an outlet opening, an electromagnetic pump or other suitable means for circulating through the chamber a stream of molten material so that the stream fills only a portion of the chamber (i.e., that the material in the chamber has an exposed upper surface) and flows from the inlet opening toward and through the outlet opening, a barrier or other suitable means provided in the chamber (or regulating the operation of the circulating means) to maintain the upper surface of molten material at a predetermined first level, spark generator means having a first pole connected with the stream of molten material (for example, by way of an auxiliary electrode which dips into molten material in the spark chamber) and a second pole connected with a main electrode which extends into the spark chamber to a second level above the first level to produce between the tip of the second electrode and the upper surface of molten material in the chamber a spark with attendant generation of light, and means for directing at least a portion of such light from the spark chamber into a suitable spectrometer.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary partly schematic vertical sectional view of an apparatus which embodies one form of the inventron;

FIG. 2 is a horizontal sectional view as seen in the direction of arrows from the line A-A' of FIG. 1; and

FIG. 3 is a fragmentary vertical sectional view of a second apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 2, there is shown an apparatus for continuous and direct spectral analysis of a stream of molten material 100. Such material (e.g., an aluminum alloy) forms a bath in an industrial furnace 116 or another suitable source. The apparatus comprises a housing 1 which consists at least in part of refi'actory material (e.g., alumina) and defines a channel-shaped substantially horizontal spark chamber 2 having an inlet opening 3 at the end and an outlet opening 4 at the other end. When in use, the apparatus is mounted in such a way that the spark chamber 2 is located at a level above or laterally adjacent to the bath of molten material in the furnace 116. The means for circulating through the chamber 2 a continuous stream of molten material comprises a tubular riser 6 the upper end of which is fitted into the inlet opening 3 in the housing 1 and the lower end of which dips into the bath of molten material 100. The circulating means further comprises a suitable pump, such as an electromagnetic pump 7, which serves to cause a stream of molten material 100 to ascend in the riser 6 and to flow through the chamber 2 at such a rate that the chamber is only partially filled. The material of the stream is evacuated by way of the outlet opening 4 whence it can fiow back into the furnace 116 or into another receptacle. It is further clear that the circulating means of the apparatus can serve to draw a stream of molten material from a flowing body of such material, i.e., not necessarily from a furnace or vessel which contains a stagnant body of such material. The exact nature of refractory material which is used for the making of the housing I and other parts of the apparatus depends on the nature of molten material and on the temperatures which the refractory material must withstand when the apparatus is in use. Thus, it is clear that the refractory material which is used in an apparatus for the continuous analysis of a stream of Woods alloy or another material with a low melting point need not posses the same resistance to heating as the material which is used in an apparatus for the analysis of steel or other materials which melt at very high temperatures.

In accordance with a feature of the invention, the apparatus further comprises means for maintaining the exposed upper surface 19 of the stream of molten material in the spark chamber 2 at a predetermined level. Such level determining means comprises a barrier or sill 5 which can form an integral part of the housing 1 and extends transversely of the path of molten material in the chamber 2 to a level which is located at a predetermined distance from and below the level of the exposed surface 19 but above the

openings

3 and 4. Thus, if the pump 7 is caused to draw from the furnace l 16 molten material 100 at a constant rate, the stream of molten material which flows through the chamber 2 and over the topmost part of the barrier 5 can form above such topmost part a layer having a thickness which corresponds to the distance between the desired level of the exposed upper surface of the stream and the level of the topmost portion of the barrier 5.

The riser 6 also consists of refractory material and its lower end is preferably sealed by a plug 29 of cardboard, wood or other material which disintegrates when the lower end portion of the riser penetrates into the body of molten material 100. The purpose of the plug 29 is to prevent slag which floats on the surface of certain molten materials from penetrating into the riser 6 while the apparatus is being moved to the position shown in FIG. 1. The plug 29 disintegrates when the lower end of the riser 6 descends below the layer of slag to insure that the molten material can ascend in the riser and can flow through the chamber 2 as soon as the pump 7 is started. This pump is mounted in a relatively thick refractory casing or shell 16 and surrounds the major portion of the riser 6. The windings 8 of the pump 7 are installed in circumferentially extending recesses or notches 9 of a laminated magnet 10 having a cruciform cross section. FIG. 2 shows that the four arms of the magnet 10 define longitudinally extending passages 11 for the circulation of a suitable coolant. The windings 8 consist of coiled wire which is not supported by a frame and is insulated in vacuo to insure satisfactory rigidity and resistance to heat at elevated temperatures. The coolant for the windings 8 of the pump 7 is preferably a gaseous fluid, e.g., nitrogen. The passages 11 communicate with each other by way of grooves 12 machined into the refractory shell 16. The upper ends of the passages 11 are connected with conduits 13 one of which admits fresh coolant and the other of which evacuates spent coolant. To further reduce the likelihood of overheating, the pump 7 is installed between an inner sleeve 14 and an outer sleeve 15 of thermally insulating material. The sleeve 14 surrounds the riser 6 and the sleeve 15 is surrounded by the shell 16. The wall thickness of the shell 16 depends on the temperature of the material 100. The windings 8 of the pump 7 are connected with a source of three-phase current by way of conductors (not shown) which extend through the conduits 13. The arrangement of windings 8 in a manner to produce a magnetic field which causes a column of molten material 100 to ascend in the riser 6 is well known in the art and forms no part of the invention. Each of a set of three windings 8 is connected with different phase of the energy source.

The apparatus further comprises a spark generator 121 which has two poles connected to conductors 21. One ofthese conductors 21 is connected with a vertical first or main electrode 17 consisting of silver or graphite and extending into the spark chamber 2 to a level at a predetermined distance from the level of the upper surface 19 of molten material 100 in the housing 1. The electrode 17 is surrounded by an insulator 18. The distance between the tip of the electrode 17 and the exposed surface l9 of molten material 100 in the chamber 2 is in the range of a few millimeters (for example, 6-8 mm). The other conductor 21 is connected with a second or auxiliary electrode consisting of cermet and extending through the top wall of the housing I and vertically across the chamber 2 to dip into the stream of molten material 100 which flows from the inlet opening 3 into the outlet opening 4 when the circuit of the pump 7 is completed.

The spark which is produced between the tip of the main electrode 17 and the surface 19 of the stream of molten material 100 generates light and at least a portion of such light is directed into a suitable spectrometer 123 by way of a mirror 22 and a tube 23 containing a system of lenses 24.

The tube 23 is further connected with a source 223 of inert gas (e.g., nitrogen or argon) which is admitted into the spark chamber 2 in the direction indicated by arrows to sweep the surface 19 of the stream of molten material 100 and to evacuate from the chamber 2 metallic vapors which develop as a result of the generation of a spark between the stream and the main electrode 17. The lenses 24 are mounted in the tube 23 with some clearance to define one or more gaps 25 through which the inert gas flows downwardly into the spark chamber 2. The inert gas, together with the metallic vapors, is caused to leave the chamber 2 by way of the outlet opening 4. The inert gas from the source 223 can be admitted at a certain pressure so that the pressure above the surface 19 of molten material in the chamber 2 is slightly above atmospheric pressure; nevertheless, it is not necessary to make the housing 1 gastight.

Additional inert gas can be supplied into the spark chamber 2 by way of a supply conduit 27 which is connected to the source 223 or to a separate source and is admitted into the chamber 2 by way of a ring-shaped orifice 26 surrounding the main electrode 17.

The cable 221 for the conductors 21 and conduits 13, 27 and the tube 23 are surrounded by a jacket 28 which defines a path for the circulation of a coolant and is preferably connected to the casing of the spectrometer 123.

The operation:

The entire apparatus is mounted on a suitable support which can cause the shell 16 to dip into the supply of molten material 100 in the furnace 116. The lower end of the riser 6 is sealed by the plug 29 which is caused to disintegrate after the riser penetrates through the layer of slag so that the molten material 100 rises and forms a stream which flows through the spark chamber 2 as soon as the circuit of the pump 7 is completed. The stream flows over the barrier 5 of the housing 1 so that its upper surface 19 remains at the desired distance from the tip of the main electrode 17. When the circuit of the

electrodes

17 and 20 is completed, the spark which develops between the electrode 17 and the surface 19 produces light which is reflected by the mirror 22 and passes through the optical system 24 in the tube 23 to be introduced into the spectrometer 123. The analysis can be completed within seconds so that the apparatus can furnish information concerning the nature of tested material practically without any delay.

The coolant which flows through the passages 11 between the arms of the magnet 10 and in the jacket 28 is circulated by suitable pumping means, not shown. The inert gas is caused to flow from the source 223, through the tube 23 and conduit 27 through the chamber 2, and through the outlet opening 4 to entrain metallic vapors which develop in response to generation of the spark.

FIG. 3 illustrates a portion of a modified apparatus wherein the construction of the housing 1 and of the parts in the shell 16 is preferably identical with the construction of the corresponding parts in the apparatus of FIGS. 1 and 2. The upright light-conducting tube 23 of HG. 1 is replaced with a substantially horizontal tube 230. The poles of the spark generator (not shown) are connected with the

respective electrodes

17, 20 by way of conductors 21a which extend lengthwise of the tube 230. The conductors 21a are preferably hollow metallic tubes which serve to admit into the spark chamber 2 streams of inert gas which escapes by way of the outlet opening 4 and entrains metallic vapors.

When the vertical tube 23 is replaced with a horizontal tube 23a, the latter is located nearer to the molten material in the furnace. Therefore, the tube 230 must be protected from heat and from drops of slag and/or molten material (as a result of splashing) by a tubular envelope 30 consisting of refractory material. This envelope 30 surrounds a cooling jacket 280 which directly surrounds the tube 230. The numeral 31 denotes separable couplings between those portions of conductors 21a and conduits 13 which are mounted in the housing 1 and the portions which are mounted in the interior of the envelope 30. The coupling 31 permit rapid detachment of the housing 1 and the attachment of a fresh or different housing.

An important advantage of the improved apparatus is that it facilitates continuous and direct analysis of a stream of molten material so that the results of the examination are available within seconds. This is particularly important in connection with the refining of metallic materials which undergo continuous changes so that even a relatively short delay between the taking of a sample and the completion of analysis would be likely to furnish misleading information. Since the apparatus is provided with means for circulating a stream of molten material, it is suited for continuous examination of a stagnant body of molten material as well as for continuous examination of molten material which is in motion.

The gas which is used to fill the chamber 2 above the exposed surface of the stream of molten material and to withdraw metallic vapors must be selected with a view to prevent undesirable reactions with the molten material and/or with the vapors. The electrode 17 is preferably adjustable so that the operators can change the length of the spark.

Without further analysis, the foregoing will 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 which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. Apparatus for direct spectrometric analysis of molten materials, particularly for continuous analysis of molten metals, comprising a housing consisting at least in part of refractory material and defining a spark chamber having an inlet opening and an outlet opening; means for circulating through said chamber a stream of molten material so that the stream fills a portion of said chamber and flows from said inlet opening to said outlet opening; means for maintaining the upper surface of molten material in said chamber at a predetermined first level; spark generator means having a first pole connected with the stream of molten material and a second pole; electrode means connected with said second pole and extending into said chamber to a second level above said first level to produce between said electrode means and the upper surface of molten material in said chamber a spark with attendant generation of light; spectrometer means; and means for directing at least a portion of said light from said chamber into said spectrometer means.

2. Apparatus as defined in claim 1, wherein said means for circulating comprises pump means arranged to circulate the molten material at a substantially constant rate and wherein said chamber is a substantially horizontal channel.

3. Apparatus as defined in claim 1, wherein said means for maintaining the upper surface of molten material in said chamber at said first level comprises a barrier extending into said chamber to a third level located below said first level and above said openings.

4. Apparatus as defined in claim 3, wherein said electrode means comprises at least one vertical electrode and said means for circulating comprises a riser having an upper end communicating with said inlet opening.

5. Apparatus as defined in claim 4, further comprising a source of molten material, said riser further having a lower end extending into the molten material in said source.

6. Apparatus as defined in claim 1, further comprising means for circulating an inert gaseous fluid through said chamber above said first level.

7. Apparatus as defined in claim 1, further comprising a source of molten material, said means for circulating comprising a riser having an upper end communicating with said inlet opening and a lower end dipping into molten material in said source, and electromagnetic pump means for causing said stream to ascend in said riser and to thereupon flow through said chamber to be evacuated from said housing by way of said outlet opening.

8. Apparatus as defined in claim 1, further comprising second electrode means connected with said first pole and dipping into molten material in said chamber.

9. Apparatus as defined in claim 1, wherein said means for directing light comprises an upright tube.

10. Apparatus as defined in claim 1, wherein said means for directing light comprises a substantially horizontal tube.