US3755126A - System for determining amount of an element dissolved in a molten metal - Google Patents

System for determining amount of an element dissolved in a molten metal Download PDF

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Publication number
US3755126A
US3755126A US00054937A US3755126DA US3755126A US 3755126 A US3755126 A US 3755126A US 00054937 A US00054937 A US 00054937A US 3755126D A US3755126D A US 3755126DA US 3755126 A US3755126 A US 3755126A
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tube
tip
probe
plug
compact
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US00054937A
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D Misener
D Faurschou
J Pope
R Hadden
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Canadian Patents and Development Ltd
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Canadian Patents and Development Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/411—Cells and probes with solid electrolytes for investigating or analysing of liquid metals

Definitions

  • a probe for determining the amount of dissolved gas, (e.g. oxygen) in a molten metal (e.g. steel). It includes a'disposable tip including three essential elements.
  • the first element is a solid electrolyte which reta'ins its ionic conduction properties and which does not exhibit substantial electronic conduction properties at the temperature of the molten metal.
  • the electrolyte is a compact which has been individually formed by a technique which includes first pressure compacting and then sintering a free flowing mixture of the solid electrolyte and a suitable fugitive binder and preferably also a small amount of a suitable high temperature binder.
  • the second element is a heat-resistant, substantially electrically non-conductive tube.
  • the compact which has a relative density, of about 70 percent, and which has an axial depression therein, is disposed and secured at one open end of the heat-resistant tube.
  • the third element is at least one electrically conductive metallic element in intimate electrical contact with the electrolyte.
  • the disposable tip' includes, and is disposed in, a fourth element, namely a plug which is formed of heat-resistant, substantially electrically non-conductive material, the plug being provided with a longitudinally extending aperture therethrough.
  • the'tip includes a fifth element, namely a tube formed of a structurally rigid, electrically conductive metal which secures the plug in one of its open ends.
  • the tube has a major portion of its length nondegradable in the molten metal being tested.
  • the tip is associated with a structurally rigid, heat-resistant, electrically conductive lance, to provide a mechanical assembly of the probe tip and the lance so that a component of the lance then is also in electrical contact with the electrically conductive metallic element which is in intimate electrical contact with the solid electrolyte, and also to provide the connection to a source of the reference gas.
  • This invention relates to an apparatus for the direct determination of a gas, e.g. oxygen dissolved in molten metals. It is more particularly directed to a probe for the direct determination of oxygen dissolved in molten metal. It also relates to components of such a probe.
  • a gas e.g. oxygen dissolved in molten metals.
  • half-cells include: stabilized zirconia tubes, closed at the immersion end, using air as the reference electrode; and a fused silica tube with -a stabilized zirconia disc tip as the solid electrolyte, sheathed by a sleeve sheath of graphite, and protected from contact with the slag by means of a metal disc.
  • An object of another aspect of the present invention is the provision of a gas half-cell probe for the direct determination of oxygen in iron, iron alloys, steel, nickel, nickel alloys, copper, or copper alloys in which the electrical lead or leads are firmly secured to the solid electrolyte.
  • An object'of another aspect of the present invention is the provision of a gas half-cell for the direct determination of oxygen in iron, ,iron alloys, steel, nickel, nickel alloys, copper, or copper alloys which is simple and economical to construct and is rugged and reliable in its operation.
  • An object of another aspect of this invention is to provide the apparatus with a heat-resistant, substantially electrical non-conductive tube which contains the electrolyte in which it is easy to develop an effective or adequate seal between the tube and the electrolyte.
  • An object of another aspect of this invention is to provide the apparatus with a heat-resistant, substantially. electrically nonconductive tube which contains the electrolyte which has minimal residual stresses developed therein.
  • An object of another aspect of this invention is to provide the apparatus with a solid electrolyte in a form which is a considerable improvement over the discs sliced from rods of zirconia as proposed heretofore.
  • An object of still another aspect of this invention is toprovide an apparatus with a reference electrode which is ambient, effectively well-buffered, and has an oxygen dissociation pressure relatively independent of temperature.
  • An object of yet another aspect of this invention is to provide an apparatus in which thermoelectric emfs are minimal.
  • An object of still another aspect of this invention is to provide an apparatus for the determination of oxygen in molten steel in which the output is not substantially subject to fluctuations of the level of carbon contents.
  • An object of yet another aspect of this invention is to provide an apparatus in which the thermal response time is optimized.
  • An object of another aspect of this invention is to provide an oxygen-probe apparatus in which the thermal shock resistance is high.
  • An object of yet another aspect of this invention is to provide an oxygen-probe apparatus in which there is good resistance to metal penetration.
  • An object of still another aspect of this invention is to provide an apparatus in which the electrical lead is fastened intimately to the electrolyte.
  • the tip also includes (d) a plug, formed of heat-resistant, substantially electrically non-conductive material and provided with a longitudinally extending aperture therethrough, whereby the tube (a) is disposed within the aperture in plug (d).
  • the plug (d) includes a first electrically conductive contact ring disposed within the aperture in plug (d), the ring being adapted to be in intimate electrical contact with the element and a second electrically conductive contact ring disposed within the aperture in plug (d) and electrically insulated from the first contact ring and further including an electrically conductive metallic trigger element extending outwardly beyond the exposed end of the plug (d), the trigger element being adapted to be in intimate electrical contact with the second contact ring.
  • the tip further includes (2), a tube formed of a structurally rigid, electrically conductive metal, having an outer surface for a major portion of its length, substantially non-distintegratable with respect to the molten metal being tested, the tube securing, at open open end thereof, the plug (d).
  • the tip also includes (f) a protective cover over the exposed poriton of the solid electrolyte compact (b), e.g. a fugitive cap or an extension of tube (e), the end of which has been closed over the solid electrolyte, preferably also including (g) an ablative covering over the protective cover to minimize deposition of slag therein.
  • a protective cover over the exposed poriton of the solid electrolyte compact (b), e.g. a fugitive cap or an extension of tube (e), the end of which has been closed over the solid electrolyte, preferably also including (g) an ablative covering over the protective cover to minimize deposition of slag therein.
  • a probe is pro vided for the direct determination of a dissolved gas in a molten metal, the probe comprising: (A) a tip including (a) a heat-resistant, substantially electrically nonconductive tube; (b) a solid electrolyte which retains its ionic conduction properties and which does not exhibit substantial electronic conduction properties at the temperature of the molten metal, the electrolyte being a compact which has been individually formed from the solid electrolyte and a suitable fugitive binder, the compact being disposed and secured at one open end of the heat-resistant tube (a), the electrolyte compact being inset in the tube (a) by an amount of at least onesixteenth inch, and protruding outwardly from the tube (a) by an amount of at least one-sixteenth inch; (c) at least one electrically conductive metallic element in intimate electrical contact with the electrolyte; (d) a plug, formed of heat-resistant, substantially electrically non-conductive material and provided with a
  • the probe tip may be any one of the variants as previously described hereinabove.
  • a solid electrolyte compact for use in a probe tip for the direct determination of a dissolved gas, e.g. oxygen in a molten metal, the electrolyte comprising an elongated compact which has been individually formed of solid oxide electrolyte which retains its ionic conduction properties and which does not exhibit substantial electronic conduction properties at the temperature of the molten metal, and a fugitive binder, the solid including a beaded wire-accepting depression axially therein.
  • a dissolved gas e.g. oxygen in a molten metal
  • the inventive concept represented in on embodiment resides in the use of pressure compacting techniques wherein powdered solid electrolyte, (e.g., lime-stabilizing zirconia powder), is intimately mixed with a particular fugitive binder (e.g. biphenyl, or an aqueous polyvinyl alcohol solution), as well as a high temperature binder ('e.g., biphenyl, or an aqueous polyvinyl alcohol solution), as well as a high temperature binder ('e.g.
  • a small amount, say, of the order of about 4 percent, of SiO, is then formed into particularly-sized granules (eg by screening the mixture formed of the stabilized zirconia and the biphenyl binder, or by spray drying a slurry of the stabilizing zir conia and the polyvinyl alcohol binder), is individually formed in a compression machine, e.g., an automatic pill-making machine, is baked andfinally is sintered to a substantially gas impermeable individually formed compact of controlled density and structure.
  • a compression machine e.g., an automatic pill-making machine
  • the electrolyte in compacted form proposed in accordance with all aspects of the invention possesses several advantages, which are essential in the production of commercially practical oxygen probes.
  • the specific advantages include:
  • thermocouple wires facilitates the intimate attachment of either a single electrical lead or a pair of thermocouple wires by means of embedding a bead of such metal in the electrolyte
  • Vycor is the trademark for a glass made by a process in which an article fabricated by conventional methods is chemically leached toremove substantially all of the ingredients except silica. When fired at high temperatures a transparentglass of high softening point and extremely low expansion coefficient is produced.) Vycor is only 96 percent silica and has a softening temperature of about l,530 C. which is almost 200 C. below that of quartz.
  • Air has the advantage of being ambient and effectively well-buffered both chemically and thermally so that the delivery system does not have to be flushed before use, or be absolutely gas-tight.
  • the electrolyte and the electrolyte-to-Vycor seal must, of course, be relatively impervious to molecular oxygen but need not be completely so because of the opposing ferro-static pressures, or the emf of the cell will be lowered. These latter two factors are more important when the reference has a high oxygen potential than when the reference has an oxygen potential close to that of the 'unknown.
  • the partial pressure of air is almost independent of temperature.
  • CO references are poorly buffered, difficult to handle, and have oxygen dissociation pressures quite dependent on temperature. The oxygen pressures in equilibrium with metal/- metal oxides, are similarly temperature dependent.
  • thermoelectric emfs are minimal. It is convenient to use a Pt-I3'Rh lead wire to the reference side of the solid electrolyte when the electrical lead to the'liquid steel is steel. The thermoelectric effects are dependent on temperature.
  • thermoelectric bias to the voltageof the'present probe is about +l millivolt regardless of localized heating of the probe and lance during immersion in steel.
  • the shape of the electrolyte compact is important since it is necessary to optimize thermal shock resistance, thermal response, and metal penetration.
  • Long thin cylinder or long conical shapes are preferred because they have better thermal shock resistance and strength than a thin disc in the end of a Vycor tube.
  • the use of a long cylinder facilitates the proper location and effective sealing of the electrolyte into the Vycor.
  • the resistance of the electrolyte to metal penetration" by diffusion can be controlled.
  • Metal penetration is an important consideration in use for steel, copper or nickel at high oxygen contents, e.g. 1,100 ppm in steel or 3,000 ppm in copper.
  • the minimum depth of inset isabout onesixteenth inch, and the minimum extent of protrusion is about one-sixteenth inch.
  • the protrusion would normally be about'one-eighth to one-fourth inch, depending on the outer geometry. of the electrolyte compact.
  • the size of the electrolyte compact is a major con trolling factor in the rate at which the cell reaches the temperature of the molten steel.
  • the electrolyte compact usually has a length to diameter ratio ranging from 4 to l.
  • the other major factor is the diameter and thickness of the Vycor tube.
  • the thermal mass and geometry control the thermal response time of the cell.
  • the cell cannot generate the theoretical galvanic emf until the reference side of the electrolyte compact has reached the temperature of the molten metal whose oxygen content is being determined. Therefore, the cell should be as small as practicable toachieve an optimal thermal response time.
  • the electrical lead or leads must be fastened intimately to the electrolyte compact. Achieving good electrical contact is one of the difficult problems in working with solid electrolytes.
  • the solution provided by the present inventors is to mold a small diameter depression or valley in the electrolyte compact and to press fit the beaded end of the electrical lead or leads into the depression or valley.
  • the void structure and density of the electrolyte compacts are related aspects depending on how the compacts are made.
  • the compacts are preferably made from finely-divided lime-stabilized zirconia powder, asmall amount of a finely-divided high temperature binder, e.g., SiO, in an amount of the order of 4 percent by weight, and a fugitive binder, e.g., biphenyl or an aqueous solution of polyvinyl alcohol.
  • a fugitive binder e.g., biphenyl or an aqueous solution of polyvinyl alcohol.
  • One sequence of manufacture is bonding with polyvinyl alcohol, molding and sintering. This produces compacts with many fine dispersed voids.
  • Another sequence of manufacture is bonding with biphenyl using dry or moist heat, screening, molding under pressure, baking and sintering.
  • a third and preferred sequence is by forming a slurry of the zirconia powder, the high temperature binder and the fugitive binder, spray drying, pressing, baking and sintering. This procedure tends to produce intergranular void structures and it is important that these be controlled so that the compacts are sufficiently impervious to transport of molecular oxygen. ln all cases, the sintering parameters must be controlled to produce compacts having the required ionic conductivity and resistance to thermal shock, e.g. by a relative density of about 70 percent.
  • the probe includes a tube formed of a heat-resistant, nonmetallic, substantially electrically non conductive material.
  • suitable such materials include quartz or Vycor, especially Vycor code No. 7913.
  • the selection of an electrolyte is, of course, important.
  • the solid electrolyte which can be used in the probe of an aspect of the present invention must retain ionic conduction properties and must not exhibit electrical conduction properties in the usual temperature ranges of the molten metal. These are generally oxides of metals having a valence of four and which have a high enough melting point. Zirconia is compatible with air as a reference electrode. Zirconia is also a good ionic conductor to below 10 ppm oxygen in liquid steel.
  • Some other oxides which may be used include: stabilized zirconia, pure thoria, pure hafnia, and thoria or hafnia having added thereto such metallic oxides as lanthia, yttria and scandia.
  • a particularly suitable such zirconia is known by the Trade Mark of TAM-R. It is preferred that the solid electrolyte which should be used in forming the electrolyte compacts usually have a particle size of plus 80 to minus 400 mesh Tyler.
  • the solid electrolyte powder is first mixed with a suitable fugitive binder and preferably also a suitable high temperature binder.
  • suitable fugitive binders include biphenyl, and aqueous solutions of polyvinyl alcohol, polymethyl methacrylate, ethyl cellulose, zirconium nitrate in an alcohol and/or aqueous dispersion, and zirconyl nitrate in an alcoholic and/or aqueous dispersion.
  • a suitable high temperature binder is SiO,.
  • a heat-protective sheath is provided to protect the electrical lead or leads and also to prevent undesired electrical contact between the electrical leads.
  • suitable materials out of which to form such sheath include alumina, mullite, Alundum, quartz, and Vycor. (Alundum is the trademark for a line of fusedalumina refractory and abrasive products, having a fusion point 2,000 2,050 C.)
  • Suitable electrical lead wires include platinum, platinum/rhodium, tungsten, tungsten/rhenium, Chromel or Alumel. (Chromel is the trademark for an alloy of approximately 90 percent and 10 percent chromium, with carefully controlled minor ingredients. Alumel is the trademark product for an alloy consisting of about 94 percent nickel, with small, carefully controlled amounts of silicon, aluminum and manganese.) If a thermocouple pair of electrical wires is provided to measure the temperature of the electrolyte compact, it
  • thermocouple to measure the temperature of the electrolyte compact is platinum-platinum/rhodium.
  • Other thermocouples which may be used if the temperature conditions are low enough are tungstentungsten/rhenium and Chromel-Alumel. i
  • the solid electrolyte must have'on one face thereof a gas containing oxygen either in combined or uncombined form.
  • gases include air, CO/CO,, co,/o,, CO,/N,, N,/O,, 0,, H,O/H,, N 0, NO, N,O, and N0
  • the non-metallic, substantially electrically non-conductive tube be encased in a sheath.
  • the sheath is formed of an electrically conductive metal which may be the same or similar to the molten metal whose oxygen content is to be determined. If the metals are substantially different, an emf is produced by the thermocouple effect, and any readings must be corrected for such emf.
  • the sheath tube of the structurally rigid, electrically conductive metal is usually the same as the metal whose oxygen content is being determined. This may be iron, iron alloys, steel, nickel, nickel alloys, copper, or copper alloys.
  • the sheath tube has an exterior surface which is nondegradable by the molten metal whose dissolved oxygen content is being measured.
  • This may be a steel tube, for use in molten copper, but, usually it would take the form of heat-stable or protective, electrically nonconductive material, e.g. a suitable synthetic plas tics material or a refractory or ceramic material. Any such material which does not give off significant amounts of gases may be used. Examples include alumina, mullite, Alundum, cordierite, an asbestos fiber/cement composition, or a core sand.
  • Such core sand may be provided by silica sand bonded by a twostage binder which provides first a thermoplastic plastics material and then a thermoset plastics material.
  • a twostage binder which provides first a thermoplastic plastics material and then a thermoset plastics material.
  • a thermoset plastics material is the Novalak series of phenolic resins.
  • a protective cover e.g., a fugitive protective cap or a crimped extension of the tube of electrically conductive metal, is provided over the exposed portion of the solid electrolyte. This is to protect the electrolyte only while the probe tip is passing through slag before it contacts the molten metal whose oxygen content is to be determined.
  • the protective cover should be formed of material, e.g. which may be readily disintegrated or dissolved in the molten metal whose oxygen content is being determined, yet which is non-injurious to the metal whose oxygen content is being determined and does not appreciably disintegrate in the slag. Usually a cap formed of the same metal is used. Alternatively, any material which is disintegrated in the metal whose oxygen content is being determined but which does not give off substantial quantities of gas may be used.
  • the structurally rigid metallic tube may be extended over the probe tip, the overhang then being crimped to form the protective cover.
  • the crimped, integral cover may also be provided with a vent hole.
  • the protective cover may also preferably be provided with an ablative cover to minimize the slag from depositing directly on the protective cover which would thus delay the disintegration or dissolving of the protective cover in the molten metal, which, in turn, would delay the contact of the electrolyte with the mol- THE DRAWINGS 1.
  • FIG. 1 is a schematic illustration of a direct oxygen probe system according to one aspect of this invention
  • FIG. 2 is a central vertical sectional view of the probe tip and the probe-tip contacting portion of the probe lance of one aspect of this invention
  • FIG. 3 is a central vertical sectional view showing the structure of the throw-away probe including a futher aspect of the probe tip of the probe structure and the probe-tip contacting portion of the probe lance and also the disconnectable mounting between the probe and the lance and another aspect of this invention;
  • FIG. 4 is a central longitudinal section of a probe including a further aspect of the probe tip of the probe structure and the probe-tip contacting portion of the probe lance of'another aspect of this invention;
  • FIG. 5 is a central verticalsectional view of the probe tip of yet another aspect of the present invention.
  • FIG. 6 is a central vertical sectional view of the probe tip of the embodiment of FIG. Sand the lance connected thereto in the mechanical, electrical and reference gas senses;
  • FIG. 7 is a central vertical sectional view of a combined oxygen probe tip and thermocouple of yet another aspect of this invention.
  • FIG. 8 is an, enlarged cross-section of the electrolyte compact of the combined oxygen probe and thermocouple of FIG. 7;
  • FIG. 9 isa graph of Emf, mV andoxygen, ppm as ordinate versus time in minutes as abscissa to show the sequence of probe voltage and oxygenv results plotted to illustrate probe-to-probe variability; and FIG. Us a log-log graph of oxygen, ppm as ordinate versus silicon, weight percent as abscissa toshow the probe results versus silicon in electrolytic iron, the" reference isotherms being calculated. 2.
  • the embodimentof'the invention consists of a direct oxygen ,probe. 10' comprising a probe tip 11 and aprobelance 12.
  • Electrical wires 13 extend to an electrometer,,and if, asshown, it is desired to have arecord of'the values .ofxemf, a recorder 15 may be electrically connected to the probe bywire l6zand. to the electrometer by wire 1'7. Each ofthe electrometer and the recorder are grounded, as.at 18. The electrometer should,- haveav high impedance. Consequently, the electrometer maybe replaced by ahigh impedance amplifier.
  • the directoxygen probe 10 thus includes a probe lance l2which is formed of electrically conductive material, e.g., steel, gronded, as at 19. Itis also provided with a tube for the introduction of a-reference gas, e.g. oxygen or air, to the probe tip 11. Secured to the distal end 21 of the probe lance l2iby-means of an electrically conductive clamp 22 is a metal trigger rod Also secured to the distal end 21 of therprobe lance 12 is the probe tip 11.
  • a probe lance l2 which is formed of electrically conductive material, e.g., steel, gronded, as at 19. Itis also provided with a tube for the introduction of a-reference gas, e.g. oxygen or air, to the probe tip 11.
  • a metal trigger rod Also secured to the distal end 21 of therprobe lance 12 is the probe tip 11.
  • the probe tip includes a tube 51 formed of a heatresistant, substantially electrically non-conductive material, such as Vycor Code 7913. As also shown in FIG. 2, the probe-tip contacting portion of the probe lance is provided by a metal tip 50. Tube 51 includes a main portion 52, an auxiliary portion 53 of reduced diameter, and an apertured tip 54. Secured to the apertured tip 54 is the electrolyte compact 56. It is seen thatthe molded electrolyte compact 56 is in the form of an elongated cylinder coming to a point 57 and provided with a depression or valley 58 in its base. The solid electrolyte compact is, e.g.
  • the electrolyte being in the form of a compact of the solid oxide, e.g. the stabilized zirconia, and a fugitive binder, e.g. biphenyl and a small amount of a substantially nonfugitive binder, e.g. silica, individually formed by pressure-compacting techniques.
  • a fugitive binder e.g. biphenyl
  • a substantially nonfugitive binder e.g. silica
  • the metal tip 50 includes a substantially cylindrical base 63 terminating in a conical core 64 provided with a central bore 65 therein.
  • a ceramic tube 66 is secured within the bore 65.
  • the base 63 includes an internally threaded bore 70 which terminates in a shoulderf 69'. Slots 71 are provided to allow free return of air admit ted to the. interior of probe tip 51 from inlet tube 66 and back to the interior of the lance (not shown in FIG.' 2 but shown in FIG. 3').
  • the direct oxygen probe 311 is seen to consist of a probe lance 312 and a probe tip 313.
  • the probe tip 313 includes an outer, electrically conductive metal sheath 314, suitably formedof steel tubing, provided with a substantially cylindrical heat shield 315 thereon, suitably fonned of a' ceramic or refractory material as hereinbefore described.
  • a plug 316 (suitably formed of a ceramic. or refractory material 'by means of inwardly flared tips 317 on sheath 314. These tips 317 also provide electrical connection to ground the melt.
  • a fugitive cap 318 suitably formed of copper or steel is disposed protectively around'the end'of the oxygen probe 311. It is secured thereon by engagement of its inner open faces 319 with the'hexagonal (in crosssection) head 320 of plug 316.
  • Plug 316- is provided with-a central bore 321" within;
  • quartz tube 322 which is secured a quartz tube 322 of the probe'tip;
  • the configuration and construction of quartz tube 322 is substantially the same as that of tube 51- previously 'de-' scribed.
  • the quartz tube 322 contains at itsouter, parpact324is a platinum wire 326.
  • the lance 312 includes a structurally rigid, metallic,
  • electrically conductive tube 330 is disposed within, and in fixed longitudinal position within lance tube 330 is a metallic, electrically conductive inner tube 331, suitably formed of steel;
  • Inner tube 331 is provided with a flattenedportion 332 and disposed about the flattened portion isa clamp 333 secured in position by ring-like end--collars334.
  • the clamp 333 is adhesively secured'to the inside of tube 330 by means of a suitable silicone rubber adhesive 335, e.g. Dow Corning 40C, introduced by means of adhesive introduction holes 336 in tube 330.
  • the entire assembly is located in position adjacent a pin 337 depending downwardly from the interior of tube 330.
  • the other end of tube 331 is spaced within tube 330 by means of collar 338 mounted on a second flattened portion 339 of tube 331 and fitting within tube 330.
  • Metal tube 331 is provided with a truncated conical end 340 adapted to be in electrical contact at 329 with probe tip wire 326.
  • a ceramic gasconducting tube 3391 is secured to, and extends from, truncated conical end 340 of tube 331.
  • the open end of quartz tube 321 is retained by frictional contact with end 340.
  • the lance 312 is provided with an easily disengageable connection with the probe tip 313.
  • This consists of a knurled steel roller 341 eccentrically mounted on pin 342 between two brackets 343 welded, as at 344, to lance tube 330. Connection is provided by engagement of the knurled roller 341 with a knurled exposed circumferential face 345 of the probe tube 314.
  • the emf generated is measured between the platinum wire 326 and the sheath 314, by means (not shown) connected to the lance. Since tube 331 is in electrical contact only with platinum wire 326 at point 329, no substantial emf should be allowed to develop between wire 326 and tube 331. The emf generated at point 329 is low, and tends to compensate the Pt-l 3 Rd to molten metal (e.g. iron or steel) emf which is always generated if the wire 326 is Pt-13 Rh and the tube 331 is stainless steel.
  • molten metal e.g. iron or steel
  • the probe tip 313 is secured to the lance 312 by engagement of the knurled roller 341 with the knurled circumferential face 345 of the sheath 314, and engagement of the outer rim of the truncated conical end 340 of tube 331 with the inner face of the quartz tube 320.
  • a suitable gas e.g. air
  • the lance 312 and tip 313 combination is immersed in the molten metal, the cap 318 melts away and the molten metal contacts solid electrolyte compact 324. Within a few seconds, a stable emf reading is taken and the oxygen probe 311 is withdrawn.
  • the probe tip 313 may be discarded, or it may be used one or two times more.
  • the direct oxygen probe 411 is seen to consist of a probe lance 412 and a probe tip 413.
  • the probe tip 413 includes an outer, electrically conductive metal sheath 414, suitably formed of steel tubing, provided with a substantially cylindrical heat shield 415 thereon, suitably formed of a ceramic or refractory material as hereinbefore described.
  • a plug 416 (suitably formed of a ceramic or refractory material) on sheath 141.
  • a fugitive cap 418 suitably formed of copper or steel is disposed protectively around the end of the oxygen probe 411. it is secured thereon by engagement of its inner open faces 419 with the hexagonal (in cross-section) head 420 of plug 416.
  • Plug 416 is provided with a central bore 421 within which is secured a Vycor tube 422 of the probe tip by means of suitable adhesive 427.
  • Vycor tube 422 To Vycor tube 422 is fused the bullet-shaped electrolyte compact 424.
  • An electrical lead wire 426 is jammed into a depression 425 in the centre of the electrolyte compact 424.
  • the electrical lead wire 426 is connected to a metal collar 428 at the open other end of 416.
  • the lance 412 includes an outer, electrically conductive metal lance tube 430 suitably formed of steel tubing. Disposed within lance tube 430 is a ceramic coupling 433, which is secured to the interior thereof by 434. Ceramic coupling 433 is provided with a central well 435 in which is secured concentric metal tube 431. Tube 431 extends and is threadedly secured to, a truncated conical metal tip 440, within which is secured ceramic gas-conducting tube 439. Ceramic coupling 433 is also provided with a central, gas'conducting bore, communicating with the interior bore 438 of lance tube 430.
  • Truncated conical tip 440 is adapted to be in electrical contact at 429 with probe tip wire 426 by means of collar 428. The open end of plug 416 is retained by frictional contact with tip 440.
  • the emf generated is measured between the platinum wire 426 and the sheath 414, by means (not shown) connected to the lance. Since tube 431 is in electrical contact only with platinum wire 426 at point 429, no substantial emf should be allowed to develop between wire 426 and tube 431. The emf generated at point 429 is low, and tends to compensate the Pt] 3 Rd to molten metal.(e.g. iron or steel) emf which is always generated if the wire 426 is Pt-l 3 Rd and the tube 431 is stainless steel.
  • the probe tip 413 is secured to the lance 412 with engagement of the outer rim of the truncated conical tip 440 with the inner face of the plug 416.
  • a suitable gas e.g. air
  • the lance 412 and tip 413 combination is immersed in the molten metal, the cap 418 melts away and the molten metal contacts solid electrolyte compact 424. Within a few seconds, a stable emf reading is taken and the oxygen probe 411 is withdrawn.
  • the probe 513 includes an outer, electrically conductive metal sheath 514, suitably formed of steel tubing, provided with an outwardly flared tip 517 and further provided with a substantially cylindrical heat shield 515 thereon, suitably formed of a ceramic or refractory material as hereinbefore described.
  • a plug 516 (suitably formed of a ceramic or refractory material) by means of frictional engagement with the outwardly flared tips 517 on sheath 514.
  • a fugitive cap 518 suitably formed of copper or steel is disposed protectively around the end of the probe 513. It is secured by engagement of its inner open faces 519 with the head 520 of plug 516, and with the exposed end 533 of tube 514 by means of inwardly turned-in portion 534. The limit of seating of cap 518 is provided by partial shoulder 535.
  • Plug 516 is provided with a first central well 521 within which is secured a Vycor tube 522 of the probe tip.
  • the Vycor tube 522 contains, at its outer, partiallyv open, constricted end 523 a premoulded mass of sintered solid electrolyte compact 524. jammed into a depression 525 at the end of the solid electrolyte compact 524 is a platinum wire 526.
  • Plug 516 is also provided with a second central well 527, within which are secured, in axial spaced apart relationship to prevent electrical contact, an interior metal contact ring 528 and a terminal metal contact ring 529.
  • Each of contact rings 528 and 529 is longitudinally split to provide a radially outward spring effect to retain the contact rings in the central well 527.
  • Contact ring 528 is in electrical contact with wire 526, while contact ring 529 is in electrical contact, via lead 536 to trigger wire 537.
  • Plug 516 is also provided with a central bore 541 to place the interior of Vycor tube 522 which is in well 521 and well 527 17 gas through-flow communication with the interior 542 of tube 514.
  • FIG. 6 shows a variation of the embodiment of the probe of FIG. in combination with a lance. To the extent that the same reference numerals are used in FIG. 6 as in FIG. 5, the parts are identical, and will not be further described. Instead, however, of the fugitive metal cap 518, the embodiment of FIG. 6 provides a substantial extension 533 of the tube 514, which extension is inwardly formed at 643 to be crimped at 644.
  • the lance 612 includes an outer, electrically conduc tive metal lance tube 630, suitably formed of steel tubing. Disposed within tube 630 is a contact holder 638, held together by two flat clamps 639, suitably formed of polytetrafluorethylene or other heat stable electrically insulative material, by means of screw 640 through aperture 645 in tube 630. A central bore 646 is formed in contact holder 638 within which is secured first concentric inner metal tube 631 and second inner metal tube 632. An electrically conductive metal trigger contact 647 is disposed between tubes 631 and 632 within contact holder 638. Also extending through contact holder 638 is doubled-over wire loop contact 648.
  • the electrical lead wire 526 electrolyte compact 52 4 juncture By means of the bores of tubes 631 and 632, may be conducted to the electrical lead wire 526 electrolyte compact 52 4 juncture. Electrical contact to the electrical lead wire 526 is provided by electrical contact between interior metal collar 528and wire loop 648. Electrical contact between trigger contact tube 647 and terminal metal collar 529 is provided by spring steel strip carried'from. the contact holder 638 to the side (not: shown) of the lance via a ceramic insulated steel wire (not shown). The trigger wire is at a selected DC. voltage, e.g. 24 V. DC. The bath and the molten metal therein is grounded. A complete circuit is provided by the probe tip and probe, lance. As the cap melts, the trigger wire is shorted to ground which completes the electrical circuit. In essence, therefore, the trigger wire/molten metal together act as a one-time switch.
  • a selected DC. voltage e.g. 24 V. DC.
  • the lance 612 is provided with an easily disengageable connection with theprobe 613.
  • This consists of'a steel circular segment contact 649 mounted on a flat springsteel plate 650 secured to the interior of tube 630 and projectingthrough slot 651 therein. Connection is provided-by frictional engagement of the edge of contact 649 with the interior of tube'5l4. Contact 649 also provides electrical grounding between the probe and the lance.
  • the emf generated is measured between the platinum wire 526 and the sheath 514 by means (not shown) connected to the lance. Since tube 631 is in electrical contact only with platinum wire 526 at collar 528, no substantial emf should be allowed to develop between wire 528 and tube 631. The emf generated at collar 528 is low, and tends to compensate the Pt-l 3 Rd to molten metal (e.g. iron or steel) emf which is always generated if the wire 526 is Pt-l 3 Rd and the tube 631 is stainless steel.
  • molten metal e.g. iron or steel
  • FIGS. 5 and 6 have been modified to provide both an oxygen probe and a thermocouple. To the extent that the same reference numerals are used,'the parts are identical.
  • the platinum in contact with the zirconia when the oxygen emf is measured between the Pt-l3 Rh lead and the molten metal, it will be compensated by the Pt/Pt-l3 Rh temperature emf, which would then be in series with the oxygen cell.
  • the platinum/rhodium bead in the oxygen thermocouple probe assembly, the platinum/rhodium bead must be embedded in the zirconia.
  • the platinum bead for a thermocouple does not have to be attached directly to the platinum/rhodium bead. The two beads could be separated by a short length of platinum/rhodium wire, as long as there is no significant temperature difference between the two beads.
  • FIG. 8 One example of the bead structures is shown in FIG. 8.
  • the electrolyte compact 724 is provided with a depression 725 therein.
  • the oxygen probe lead is provided by a platinum/platinum 13 rhodium wire 526.
  • the thermocouple lead is provided by a platinum wire 726.
  • the wires 526 and 726 are formed into a junction 736, and this junction is formed into a Pt-l3 Rh ball 737, which is jammed into depression 725 in the compact 724.
  • Wire 526 is in electrical contact with collar 528, while wire 726 extends around .plug 516 to be in electrical contact with collar 529.
  • ex pendable probes In one such system as tested, there is provided ex pendable probes, a tubular steel lance, a heavy-duty cable for air supply and electrical leads, plus control electronics and a chart recorder.
  • the probes have a tubular steel body coated with refractoryand are avail: able in two and 4-foot lengths.
  • the probes slip onto the lance.
  • Cardboard insulating tubes may also be slipped onto the lance for protection in open-hearth and basic oxygen vessels. I
  • FIG. 9 graphically shows the variability of a sequence of OXP results in mV and ppm oxygen.
  • FIG. 9 is of interest because it illustrates that iron is a very good solvent for oxygen. It is seen that oxygen was absorbed at a rate of about 6 ppm per minute.
  • FIG. 10 shows how the probe can be used to investigate deoxidation phenomena in ordinary melts.
  • Increments of ferrosilicon were added to two SO-lb. metls of electrolytic iron. minutes after each addition was made, and the melts were relatively uniform in oxygen, probe readings were taken.
  • the emf values were converted directly to theoretical oxygen values and plotted as crosses on a graph of log oxygen versus log silicon. These oxygen values were then corrected for the effect of silicon on the activity of the dissolved oxygen using the only interaction coefficients c reported in the literature.
  • c 0.02 and adjusted oxygen values, plotted as open circles, come into rather close agreement with the theoretical curve for l,600 C. The agreement is particularly good when it is considered that the melt temperature varied between l,590 and l,620 C.
  • FIG. shows the oxygensilicon equilibrium at l,500, l,600, l,700 and l,800
  • a heat resistant, substantially electrically nonconductive tube selected from the group consisting of quartz and a glass consisting essentially of about 96 percent silica;
  • a solid electrolyte selected from the group consisting of lime-stabilized zirconia, yttn'a stabilized thoria, magnesia-stabilized zirconia, thoria, hafnia, lanthia-stabilized thoria, scandia-stabilized thoria, lanthia-stabilized hafnia, yttria-stabilized hafnia, and scandia-stabilized hafnia, said electrolyte being a compact which has been individually formed by a technique including, first pressure compacting and then sintering from a free flowing intimate mixture, in fine granular form, of said solid electrolyte, and a fugitive binder selected from the group consisting of biphenyl, polyvinyl alcohol, an aqueous solution or dispersion of polymethyl methacrylate,
  • a plug formed of heat-resistant, substantially electrically non-conductive material selected from the group consisting of a ceramic material, alumina, mullite, and a fused alumina refractory material, said plug being provided with a longitudinally ex,- tending aperture therethrough, whereby said tube (a) is disposed within said aperture in said plug d 4.
  • the probe tip of claim 3 including in combination:
  • a tube formed of a structurally rigid, electrically conductive metal selected from the group consisting of iron, iron alloys, steel, nickel, nickel alloys, copper and copper alloys, having an outer surface for a major portion of its length substantially non-disintegratable with respect to the molten metal being tested, said tube securing, at one open end thereof, said plug (d).
  • the tip of claim 8 further including:
  • the tip of claim 3 including a first electrically conductive contact ring disposed within said aperture 17 in said plug (d), said ring being adapted to be in inti mate electrical contact with said element (c).
  • the tip of claim 15 including a sec'ond'electricall-y conductive contact ring disposed within said aperture in said plug (d) and electrically insulated from said first contact ring and further including an electrically conductive metallic trigger element extending outwardly beyond the exposed end of said plug (:1), said trigger element being adapted to be in intimate electrical con:- tact with said second, contact ring.
  • the probe as claimed in claim 28 said amount of at least about'one-sixteenth inch, and protrudes outwardly from said tube (a) byanarnou'nfof -at least about one-sixteenth inch.
  • said electrolyte compact is inset in said tube'(a) by an said tube being adapted mechanically to engage the heat-resistant tube (a) of tip (A) and also adapted to provide electrical connection with said electrically conductive metal element and iii. means for disengageably securing the lance (B) to the probe tip (A).
  • the probe of claim 30 including a protective cap over the exposed portion of the solid electrolyte compact.
  • the probe of claim 31 including an ablative covering over said protective cap to minimize deposition of slag therein.
  • said probe tip is one including: a first electrically conductive contact ring disposed within said aperture in plug (A) (d), said contact ring being adapted to be in intimate electrical contact with said element (A) (c); also including a second electrically conductive contact ring disposed within said aperture in plug (A) (d) and electrically insulated from said first contact ring; further including an electrically conductive metallic trigger element extending outwardly beyond the exposed end of said plug (A) (d), said trigger element being adapted to be in intimate electrical contact with said second contact ring; and wherein the electrical contact between the probe tip (A) and the probe lance (B) is provided by a spring wire contact loop in electrical contact with the first contact ring, and a spring steel strip in electrical contact with the second contact ring.
  • tube (ii) is secured in a plug of heat stable, substantially electrically non-conductive material selected from the group consisting of a ceramic material, alumina, mullite, and a fused alumina refractory material which is, in turn, secured within tube (1).
  • the means for securing the lance (B) to the probe tip (A) is a bayonnette-type, an expansion-collet type, a pressure-fit type, a push-on type, or a spring loaded internal frictional engagement type.
  • the probe of claim 29 including a second metallic element in electrical contact with said solid electrolyte compact, thereby to provide a thermocouple, whereby the probe may be used simultaneously to'determine the amount of gas dissolved in the molten metal and the temperature of said electrolyte compact.
  • CLAIM l3, COLUMN l6 Claim 13 shouldread 'as follows: 13. The tip of claim -8 wherein said protective cover is an extension of the tube (e) the end of which has been closed over the solid electrolyte compact (b) Signed and sealed this 23rd day of April 197M.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating And Analyzing Materials By Characteristic Methods (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)
US00054937A 1969-12-24 1970-07-15 System for determining amount of an element dissolved in a molten metal Expired - Lifetime US3755126A (en)

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BE (1) BE744850A (enrdf_load_stackoverflow)
DE (1) DE2003361A1 (enrdf_load_stackoverflow)
ES (1) ES383225A1 (enrdf_load_stackoverflow)
FR (1) FR2071555A5 (enrdf_load_stackoverflow)
GB (1) GB1278201A (enrdf_load_stackoverflow)
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1985002681A1 (en) * 1983-12-16 1985-06-20 Didier-Werke A. G. Carrier sleeves for measurement heads
US5561516A (en) * 1994-07-29 1996-10-01 Iowa State University Research Foundation, Inc. Casingless down-hole for sealing an ablation volume and obtaining a sample for analysis
US5789910A (en) * 1996-12-12 1998-08-04 R. Guthrie Research Associates Inc. Molten metal inclusion sensor probes
DE10161494A1 (de) * 2001-12-14 2003-07-17 Andion Gmbh Sensoreinheit, Messeinheit und Verfahren zu deren Betrieb
US20060096861A1 (en) * 2002-11-26 2006-05-11 Wilhelm Merkens Probe for determination of oxygen activity in metal melts and methods for its production
US20110308319A1 (en) * 2010-06-18 2011-12-22 Heraeus Electro-Nite International N.V. Measuring probes for measuring and taking samples with a metal melt
CN104324514A (zh) * 2014-11-28 2015-02-04 龚柱 制备浓缩液用的采样单元

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3784459A (en) * 1972-06-12 1974-01-08 Ford Motor Co Device for determining the activity of oxygen in molten metal
DE102014119079A1 (de) * 2014-12-18 2016-06-23 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Bezugselektrode und elektrochemischer Sensor

Citations (5)

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Publication number Priority date Publication date Assignee Title
GB934758A (en) * 1960-09-07 1963-08-21 United Steel Companies Ltd Improvements relating to the determination of the activity of oxygen or the activities of other ionic species in molten materials
FR1537804A (fr) * 1967-07-13 1968-08-30 Siderurgie Fse Inst Rech Bloc de mesure pour les piles destinées à mesurer l'activité de l'oxygène dans les métaux liquides
FR1556212A (enrdf_load_stackoverflow) * 1967-07-13 1969-02-07
US3616407A (en) * 1965-10-14 1971-10-26 Hoesch Ag Arrangement for determining the presence of an active element in a body of molten metal
US3619381A (en) * 1968-12-23 1971-11-09 George R Fitterer Determining oxygen content of materials

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB934758A (en) * 1960-09-07 1963-08-21 United Steel Companies Ltd Improvements relating to the determination of the activity of oxygen or the activities of other ionic species in molten materials
US3616407A (en) * 1965-10-14 1971-10-26 Hoesch Ag Arrangement for determining the presence of an active element in a body of molten metal
FR1537804A (fr) * 1967-07-13 1968-08-30 Siderurgie Fse Inst Rech Bloc de mesure pour les piles destinées à mesurer l'activité de l'oxygène dans les métaux liquides
FR1556212A (enrdf_load_stackoverflow) * 1967-07-13 1969-02-07
US3619381A (en) * 1968-12-23 1971-11-09 George R Fitterer Determining oxygen content of materials

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Title
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1985002681A1 (en) * 1983-12-16 1985-06-20 Didier-Werke A. G. Carrier sleeves for measurement heads
US5561516A (en) * 1994-07-29 1996-10-01 Iowa State University Research Foundation, Inc. Casingless down-hole for sealing an ablation volume and obtaining a sample for analysis
US5789910A (en) * 1996-12-12 1998-08-04 R. Guthrie Research Associates Inc. Molten metal inclusion sensor probes
DE10161494A1 (de) * 2001-12-14 2003-07-17 Andion Gmbh Sensoreinheit, Messeinheit und Verfahren zu deren Betrieb
US20060096861A1 (en) * 2002-11-26 2006-05-11 Wilhelm Merkens Probe for determination of oxygen activity in metal melts and methods for its production
US7578913B2 (en) * 2002-11-26 2009-08-25 Specialty Minerals (Michigan) Inc. Probe for determination of oxygen activity in metal melts and methods for its production
US20110308319A1 (en) * 2010-06-18 2011-12-22 Heraeus Electro-Nite International N.V. Measuring probes for measuring and taking samples with a metal melt
US8479579B2 (en) * 2010-06-18 2013-07-09 Heraeus Electro-Nite International N.V. Measuring probes for measuring and taking samples with a metal melt
CN104324514A (zh) * 2014-11-28 2015-02-04 龚柱 制备浓缩液用的采样单元
CN104324514B (zh) * 2014-11-28 2016-01-13 龚柱 制备浓缩液用的采样单元

Also Published As

Publication number Publication date
BE744850A (fr) 1970-07-01
DE2003361A1 (de) 1971-07-15
ES383225A1 (es) 1972-12-16
ZA707594B (en) 1971-08-25
FR2071555A5 (enrdf_load_stackoverflow) 1971-09-17
GB1278201A (en) 1972-06-21

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