US3681972A - Process and device for determining the oxygen concentration in metal melts - Google Patents

Process and device for determining the oxygen concentration in metal melts Download PDF

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Publication number
US3681972A
US3681972A US44312A US3681972DA US3681972A US 3681972 A US3681972 A US 3681972A US 44312 A US44312 A US 44312A US 3681972D A US3681972D A US 3681972DA US 3681972 A US3681972 A US 3681972A
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melt
melting point
metal
oxygen
sample
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US44312A
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English (en)
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Bhaskar Chandra Mahanty
Gustav Mahn
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SALZGITTER HUETTENWERK AG
SALZGITTER HUTTENWERK AG
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SALZGITTER HUETTENWERK AG
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00Investigating or analyzing materials by the use of thermal means
    • G01N25/02Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
    • G01N25/04Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of melting point; of freezing point; of softening point
    • G01N25/06Analysis by measuring change of freezing point
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00Investigating or analyzing materials by the use of thermal means
    • G01N25/02Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
    • G01N25/04Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of melting point; of freezing point; of softening point
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/20Metals
    • G01N33/202Constituents thereof
    • G01N33/2022Non-metallic constituents
    • G01N33/2025Gaseous constituents
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/20Metals
    • G01N33/205Metals in liquid state, e.g. molten metals
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S73/00Measuring and testing
    • Y10S73/09Molten metal samplers
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T436/00Chemistry: analytical and immunological testing
    • Y10T436/20Oxygen containing
    • Y10T436/207497Molecular oxygen
    • Y10T436/209163Dissolved or trace oxygen or oxygen content of a sealed environment

Definitions

  • ABSTRACT The oxygen concentration in a metal melt, such as a steel melt, is determined by comparing the melting point temperature of a sample taken from the melt with the melting point temperature of the same metal but without any free oxygen, other impurities being taken into account. The difference is related to the oxygen concentration. This is preferably done by taking 23/230 253 PC two samples from the melt, fixing the free oxygen in one of them by a reducing agent and determining the [56] References cued difference between the melting point temperatures of UNITED STATES PATENTS the treated and untreated samples.
  • This invention relates generally to a process for determining the oxygen concentration in metal melts, and particularly steel melts. Metal melts are usually at temperatures above 1,500C and consequently, in the past, the samples for analysis first of all have had to be cooled down to room temperature before the analysis could be done.
  • a sample for example a steel sample
  • the sample which has been withdrawn in this way is rapidly cooled to room temperature, after which the surface layers, containing oxides and impurities, are cut away on a lathe.
  • the resultant cooled and cleaned sample is then melted again in a carbon boat under vacuum in a hot gas extraction apparatus at 1,600 to 1,800 C.
  • the oxygen escapes in the form of carbon monoxide mixed with nitrogen and hydrogen, and the gas mixture is fed to a gas analysis apparatus and the oxygen content determined.
  • the carbon monoxide content in the gas mixture can be determined by gas chromatography.
  • the carbon monoxide can be oxidized with oxygen to carbon dioxide on a platinum wire.
  • the carbon dioxide is passed through a solution of potassium hydroxide in a gas analysis apparatus and the oxygen content determined volumetrically.
  • the analysis can, if desired, be performed without using a hot extraction apparatus (vacuum extraction).
  • the sample is heated in a carbon boat and the carbon monoxide escaping is carried away in a current of argon.
  • the mixed gases are passed over palladium asbestos.
  • the carbon monoxide is oxidized to carbon dioxide, which is absorbed in a solution containing barium perchlorate and a little barium hydroxide. Barium carbonate is formed and the barium hydroxide consumed is replaced electrolytically from the barium perchlorate in the solution.
  • the oxygen content is calculated from the quantity of electric current consumed in the electrolytic process.
  • the present invention relates generally to a method and apparatus for determining the concentration of oxygen in metal melts such as steel melts. More particularly it relates to a new and useful method and apparatus by which this determinationcan be carried out quickly and at the place of the melt.
  • the solution to this problem is based on recognition of the fact that the melting point of a pure metal is lowered by the presence of impurities, for example the dissolved oxygen.
  • the lowering of the melting point depends on the natures and concentrations of the impurities, including the concentration of oxygen.
  • the oxygen concentration in a melt can therefore, in principle, be calculated from the lowering of the melting point.
  • a still further object of the invention is to provide a method and apparatus for measuring the melting point temperatures of two samples taken from the metal melt containing free oxygen, one of the samples having had its free oxygen fixed by the use of a reducing agent.
  • the lowering of the melting point of said metal due to the presence of oxygen is calculated as the difierence between the two melting points.
  • the oxygen concentration in the melt is read ofi from a calibration curve plotting oxygen concentration against temperaturedifierence. 7
  • An excess of the reducing agent added to the second sample is preferably used, to ensure that all the oxygen is eflectively fixed or stabilized.
  • a particularly suitable reducer is aluminum, because aluminum'oxide has a particularly high free reaction enthalpy, and the excess of aluminum required to stabilize the oxygen concentrations encountered in practice in steelmelts has only a negligible influence on the melting point of the steel, a 'fact which can be derived from the phase diagrams for iron and alul-loweve'r, to obtain precise results there should not be too great an excess of aluminum.
  • different reducing substances should be used, in each case the reducing agent having little, if any, influence on the melting point of the metal. In all cases the amount of reducing agent used should be only slightly in excess of the stoichiometric quantity.
  • An alternative method in accordance with the invention assumes that the specific lowering of the melting point temperature corresponding to the concentration, produced by each of the impurities in the metal, apart from the oxygen, is known. On this basis the total lowering of the melting point of the metal produced by all the impurities, other than oxygen, can be calculated once the impurities have been analyzed and quantitized. Any, further lowering of the melting point must be due to the concentration of oxygen. The melting point temperature of a sample of melt is therefore'measured and this substracted from the known melting point temperature of the metal in its pure form. From this value the calculated lowering due to the impurities other than oxygen is then substracted and the difference is the lowering of the melting point produced by the oxygen content.
  • the oxygen concentration in the melt can then be calculated using a known proportionality factor, or can be read off from the above mentioned calibration curve.
  • this method -assumes that a precise analysis has previously been made showing the concentrations of all the impurities other than oxygen in the melt.
  • the preferred method is therefore the first of the above alternatives, in which two samples of the melt are taken, and the oxygen concentration is obtained from the difference between the melting points of an untreated sample and a sample in which the oxygen has been fixed by a reducing agent.
  • Yet another object of the invention therefore is to provide for use in the preferred method a sampling lance having a pair of pans or receptacles at its lower end for withdrawing the two samples from the melt, each pan being equipped with a thermocouple element which is sensitive to temperature. Electric leads and compensation leads of the thermocouples are preferably led through a drilling passing upwards through the lance to means for determining the temperatures sensed by the thermocouples. Preferably this is connected to a temperature difference computer, which can itself be followed, if desired, by an indicating device which may indicate directly the oxygen concentration in the melt.
  • FIG. 1 is a graph plotting the oxygen concentration in a steel melt as a function of the difference between the melting points of reduced and unreduced samples from the melt in C (on the abscissa);
  • FIG. 2 is a diagrammatic picture of a concentration measuring apparatus
  • FIG. 3 is a modification of this apparatus.
  • the method of analysis of the-present invention can be applied in practice, for example, to a steel melt as follows.
  • a sample is withdrawn from the melt by means of a sampling device and its melting point is measured by observing the hesitation point on the cooling temperature curve, using a thermocouple and a temperature recorder.
  • a reference sample is taken from the melt and killed, i.e. its free oxygen is fixed or stabilized, for example by adding 0.2 percent of aluminum.
  • the melting-point of the reference sample is also measured.
  • the difference between the two melting points is calculated and the oxygen concentration in themelt is read off from the calibration curve shown in FIG. I. This method was used to make the following test.
  • FIG. 2 shows a device according to the invention which can be used for this purpose.
  • the device consists of a sampling lance 4 whose lower end is adapted for dipping into a metal melt and is provided with two sampling pans 5, 6 mounted next to each other.
  • Each sampling pan contains a thermocouple element 7, 8 whose leads are led up through a central drilling 9 in the lance 4 to a connection block 10, in which the thermocouple leads are connected over contacts 12, 13 to cables whose other ends are connected to a temperature determining and recording device 14, which is itself connected to a difference computer 14, which is followed by an indicator l6 calibrated to show oxygen concentrations directly.
  • a piece of a reducing agent 17 is introduced into one of the measuring pans 6, the quantity of reducing agent being sufficient to ensure complete reduction of the free oxygen in the sample entering this pan.
  • the sampling lance 4 is then dipped into the melt, so that both the measuring pans 5, 6 are filled at the same time.
  • the quantity of oxygen in the melt running into the measuring pan 6 is immediately captured by the reducing agent already present in this pan.
  • the sampling lance is then withdrawn from the melt and the two samples are allowed to cool. During the cooling the temperature of each sample decreases continuously down to the melting point, or freezing point of the sample. At this point the falling temperature curves of the two samples as measured by the device 14 hesitate indicating that the melting points have been reached.
  • the two melting points, or hesitation points are transmitted to the difference computer 15, which calculates the difference between them. This difference is transmitted to the indicating instrument 16, which is calibrated on the basis of the diagram shown in FIG. 1, so that it directly indicates the oxygen concentration in the melt.
  • the measuring pans can be mounted one above the other as represented in FIG. 3.
  • the method according to the invention for determining the oxygen concentrations of a melt used in conjunction with the device represented in the drawings is capable of delivering the desired analytical result in a period of time short enough to allow the result to be used in controlling the process.
  • An important point to observe is that the oxygen concentration is measured directly at the furnace or crucible containing the melt. A sample can therefore be taken just before tapping the furnace, allowing the quantity of reducing agents which need to be added to be calculated exactly. This makes it possible to dose the reducing agents preciselyto suit the precise oxygen concentration in the melt, so that there is obtained a final product of higher purity and better quality, which shows an analysis more precisely in agreement with the specified analysis.
  • the total melting point lowering produced by these substances in the steel is therefore 4.9 C, and this is added to the measured melting point of l,528 C to compensate for the influence of these substances.
  • the melting point lowering produced by the oxygen in the melt is therefore:
  • this temperature difference of 3.1 C corresponds to an oxygen concentration of approximately 0.042 percent oxygen in the sample.
  • any other substances present must also be allowed for although elements present only in traces may be neglected.
  • a process for determining the oxygen concentration in metal melts comprising the steps of taking a first sample from said metal melt containing free oxygen, determining the melting point temperature of said sample, taking a second sample from said metal melt containing free oxygen, adding to said second sample -a reducing agent which has little effect, if any, on the melting point of said metal to fix said free oxygen in said second sample, thereby to provide said metal containing no free oxygen, and determining the melting point temperature. of said treated second sample, the difference between the melting point temperatures of said first and second samples being directly related to the oxygen concentration in said metal melt.
  • a device for determining the oxygen concentration in metal melts comprising a sampling lance having an upper end, and a lower end adapted for dipping into a metal melt, a pair of measuring pans mounted on said lower end of said sampling lance, said pans being adapted to receive samples from the metal melts, one of said pans containing reducing means for its metal melt sample, a pair of thermocouple measuring elements located one in each of said measuring pans, conductors from said thermocouple elements leading to said upper end of said sampling lance, means for determining the temperatures measured by said thermocouple elements, and means connecting said conductors to said temperature determining means.
  • sampling lance is provided with a longitudinal drilling extending between said upper and lower ends and said conductors pass through said drilling.
  • thermocouple elements 7.
  • thermocouple elements further including means for computing the difference between the temperatures measured by said thermocouple elements and said temperature determining means, said computing means having an indicator device.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
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US44312A 1968-09-11 1970-06-08 Process and device for determining the oxygen concentration in metal melts Expired - Lifetime US3681972A (en)

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Application Number Priority Date Filing Date Title
DE19681798222 DE1798222B1 (de) 1968-09-11 1968-09-11 Verfahren zum bestimmen des sauerstoffgehalts von metall insbesondere stahlschmelzen

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BE (1) BE795847Q (fr)
DE (1) DE1798222B1 (fr)
FR (1) FR2066907A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3884680A (en) * 1971-08-31 1975-05-20 Metallurgie Hoboken Automatically controlling the oxygen content in copper and copper alloys
JPS5216990U (fr) * 1975-07-25 1977-02-05
US4046509A (en) * 1970-04-27 1977-09-06 Stig Lennart Backerud Method for checking and regulating the conditions of crystallization in the solidification of melts
US4098576A (en) * 1976-06-29 1978-07-04 National Steel Corporation Method for analyzing the latent gas content of metal samples
US4569237A (en) * 1984-04-16 1986-02-11 Electro-Nite Co. Method of sampling molten metal
US5319576A (en) * 1987-08-05 1994-06-07 General Signal Corporation Wireless data gathering system for molten metal processing

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2685483A1 (fr) * 1991-12-23 1993-06-25 Commissariat Energie Atomique Dispositif de solidification d'un materiau conducteur de l'electricite dope et de controle en continu de sa teneur en dopant.

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2303265A (en) * 1941-06-28 1942-11-24 Socony Vacuum Oil Co Inc Method for the determination of the content of isobutane in a mixture comprising essentially isobutane and nu-butane
US3403090A (en) * 1964-05-06 1968-09-24 Yawata Iron & Steel Co Vessel for measuring oxygen content of a molten metal
US3463005A (en) * 1966-07-12 1969-08-26 Leeds & Northrup Co Immersion molten metal sampler device
US3481201A (en) * 1967-10-02 1969-12-02 Richard A Falk Device for taking a molten sample
US3503259A (en) * 1967-06-27 1970-03-31 Westinghouse Electric Corp Direct sampler for use in basic oxygen furnaces and the like
US3559452A (en) * 1967-09-25 1971-02-02 Republic Steel Corp Thermal analysis of molten steel
US3574598A (en) * 1967-08-18 1971-04-13 Bethlehem Steel Corp Method for controlling basic oxygen steelmaking

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2303265A (en) * 1941-06-28 1942-11-24 Socony Vacuum Oil Co Inc Method for the determination of the content of isobutane in a mixture comprising essentially isobutane and nu-butane
US3403090A (en) * 1964-05-06 1968-09-24 Yawata Iron & Steel Co Vessel for measuring oxygen content of a molten metal
US3463005A (en) * 1966-07-12 1969-08-26 Leeds & Northrup Co Immersion molten metal sampler device
US3503259A (en) * 1967-06-27 1970-03-31 Westinghouse Electric Corp Direct sampler for use in basic oxygen furnaces and the like
US3574598A (en) * 1967-08-18 1971-04-13 Bethlehem Steel Corp Method for controlling basic oxygen steelmaking
US3559452A (en) * 1967-09-25 1971-02-02 Republic Steel Corp Thermal analysis of molten steel
US3481201A (en) * 1967-10-02 1969-12-02 Richard A Falk Device for taking a molten sample

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4046509A (en) * 1970-04-27 1977-09-06 Stig Lennart Backerud Method for checking and regulating the conditions of crystallization in the solidification of melts
US3884680A (en) * 1971-08-31 1975-05-20 Metallurgie Hoboken Automatically controlling the oxygen content in copper and copper alloys
JPS5216990U (fr) * 1975-07-25 1977-02-05
US4098576A (en) * 1976-06-29 1978-07-04 National Steel Corporation Method for analyzing the latent gas content of metal samples
US4569237A (en) * 1984-04-16 1986-02-11 Electro-Nite Co. Method of sampling molten metal
US5319576A (en) * 1987-08-05 1994-06-07 General Signal Corporation Wireless data gathering system for molten metal processing

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Publication number Publication date
DE1798222B1 (de) 1971-03-04
BE795847Q (fr) 1973-06-18
FR2066907A1 (fr) 1971-08-13

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