US3645720A - Method of deoxidizing steel - Google Patents

Method of deoxidizing steel Download PDF

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Publication number
US3645720A
US3645720A US847053A US3645720DA US3645720A US 3645720 A US3645720 A US 3645720A US 847053 A US847053 A US 847053A US 3645720D A US3645720D A US 3645720DA US 3645720 A US3645720 A US 3645720A
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molten steel
value
deoxidizing agent
content
electromotive force
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Expired - Lifetime
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US847053A
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English (en)
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Ryochiro Imai
Yoshihiko Kawai
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JFE Engineering Corp
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Nippon Kokan Ltd
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing

Definitions

  • ABSTRACT In a steel manufacturing process an oxygen concentration cell is immersed in the molten steel bath, the maximum differentiated value of the electromotive force is detected and the detected maximum value is utilized as the control factor for adjusting the quantity of deoxidizing agent to be subsequently added into the molten steel bath.
  • This invention relates to a method of manufacturing steel wherein the deoxidizing process of the molten steel is improved.
  • a deoxidizing treatment is performed by adding a suitable deoxidizing agent to the molten steel in a ladle, such as aluminum, aluminum alloys, manganese, silicon, calcium and magnesium.
  • a suitable deoxidizing agent such as aluminum, aluminum alloys, manganese, silicon, calcium and magnesium.
  • the oxygen content of the molten steel is generally dependent upon the quantity of the deoxidizing agent, it is the common practice to add deoxidizing agent of a given weight per unit weight of said molten steel.
  • the desired degree of deoxidation cannot be provided or the degree of deoxidation varies every heating owing to such disturbing factors as oxidation by the atmosphere at the time of teeming, oxidation with oxidizing slag, or the oxidation caused by the slag adhering to the inside wall of ladle.
  • the control of the degree of oxidation is very difficult.
  • the control of adding said deoxidizing agent is also difficult and brings about final inequality of the added weight of said deoxidizing agent.
  • FIG. 1 illustrates theoretical characteristic curves helpful to explain the principle of this invention
  • FIG. 2 diagrammatically represents an apparatus utilized to carry out this invention
  • FIG. 3 is a diagram of essential components of the apparatus shown in FIG. 2;
  • FIG. 4 shows a modified embodiment of the apparatus utilized to carry out this invention
  • FIG. 5 shows characteristic curves obtained by carrying out this invention.
  • FIG. 6 is a statistical plot showing the soluble aluminum content of low-carbon aluminum-killed steels manufactured by the method of this invention.
  • the abscissa represents the time 2 (seconds) while the ordinate shows oxygen content (0)! (percent), aluminum content (A1)! (percent), and differentiated value of electromotive force Et with respect to time dE/dt(mV/sec.). From FIG. 1 it was found that the differentiated value of the electromotive force with respect to time, that is, dE/dt(mV/sec. reaches the maximum value when a predetermined quantity of aluminum is added in the molten steel as mentioned above, and when the oxygen content and aluminum content (A1)! reach a specific predetermined value (in the above example of calculation, (0): 0.0016 percent,
  • t represents the time from the maximum differentiated value to the stopping point of adding A1, (A1)max, the aluminum content corresponding to the maximum differentiated value, (O)max, the oxygen content corresponding to the maximum differentiated value, (A1)! the A1 content at the stopping point of adding Al, (0):" the oxygen content at the stopping point of adding A1, 1 the yield of added Al, and t", the delay time.
  • the invention is characterized by immersing an oxygen concentration cell in the molten steel, detecting differentiated value of electromotive force in the cell while adding deoxidizing agent to the molten steel and adjusting the added quantity of the deoxidizing agent to a predetermined value after the maximum differentiated value has been reached.
  • FIGS. 2 and 3 there is shown apparatus utilized to carry out this invention comprising a ladle 2 in which molten steel 1 is subjected to deoxidizing treatment, the molten steel having been subjected to preliminary deoxidizing treatment in the furnace.
  • An oxygen concentration cell 3 serving as a detecting element for deoxidizing rate is immersed in the molten steel 1.
  • the oxygen concentration cell 3 comprises a negative electrode 3a and a positive electrode 3b in the form of a bottom closed cylinder made of an electrolyte, the negative and positive electrodes are disposed in parallel and spaced apart a predetermined distance with thin lower ends immersed in the molten steel bath. Cooling gas such as air is introduced into the positive electrode 3b.
  • the electromotive force of the cell is amplified by a direct current amplifier 4 and then differentiated by a differentiating circuit 5, the output thereof being recorded and displayed by a recording meter 6.
  • a container type device 7 is used to add an aluminum wire acting as the deoxidizing agent into the ladle 2 at a definite rate and by a constant quantity (e.g., 0.008 kg./sec. t).
  • the start and stop operations of the supply device 7 are controlled by a time switch mechanism 8 which functions to automatically stop the supply device 7 after passing away of a specific time given by equation 4.
  • the operation of the apparatus is as follows.
  • Molten steel 1 which has been made in a furnace and subjected, or not subjected, to the preliminary deoxidation treatment is tapped into the ladle 2 to a level sufficient to immerse therein the oxygen concentration cell 3. Then supplying device 7 is started to add the A1 wire to the molten steel 1 at a predetermined speed and by a constant quantity. Simultaneously with the starting of supplying the aluminum wire the indicating recorder 6 is set into operation to record and display the differentiated value of the electromotive force in the cell 3 with respect to time.
  • the recording meter 6 When a predetermined interval has passed away after the starting of adding the aluminum wire, a rapid and large change takes place in the electromotive force of the cell 3. In response to this change, the recording meter 6 will record and indicate the characteristic point, that is, the maximum differentiated value of the electromotive force with respect to time. Once this peculiar point is noted, the time switch mechanism 8 is immediately set into operation. Thus, the time switch mechanism will stop the operation of the supplying device after passing away of a further predetermined period of time. In other words, supply of the aluminum wire is ceased when it has been further added by a predetermined quantity. Then, the molten steel is poured into ingot mold and cooled to obtain ingots of the desired aluminum-killed steel.
  • FIG. 5 is a plot of the measured value of changes in the differentiated value dE/dt of the electromotive force in the oxygen concentration cell and in Sol Al content of the abovedescribed embodiment.
  • the content of soluble aluminum was determined by analyzing the sample taken from the ladle during the course of adding the aluminum wire. From the result of measurement shown in FIG. 5 it was confirmed that at about 45 seconds after the start of adding aluminum wire the maximum differentiated value dE/dt was substantially coincident with said theoretical calculation. A predetermined time later (about 30 seconds) the incorporation of the aluminum wire was terminated to perform the desired degree of deoxidation. Further, it was possible to bring the Sol Al content to the desired level (0.035 percent).
  • the number of samples n was 1,432
  • the value of the center line Y was 43.9Xl0'percent
  • the standard deviation 5 was l0.5 l0"percent
  • the number of samples n was only 60
  • the value of the center line X was 35.6Xl0' percent
  • the standard deviation 8 was 4.4 l0' said center line being shown by dot and dash lines in FIG. 6.
  • FIG. 4 illustrates a modified apparatus for carrying out this invention.
  • a relay 9 is added to actuate the time switch mechanism when the recording meter 6 displays said peculiar point of maximum dE/a't.
  • the deoxidizing agent was added into the molten steel by a constant quantity and at a definite rate, and while such a method is advantageous, in certain cases, as far as the quantity can be controlled accurately, other adding means not including a timing mechanism can be used. Further, it is to be understood that the deoxidizing agent is not limited to aluminum wire, and that other various deoxidizing agents, as already pointed out, can also be used. Also the construction of the oxygen concentration cell is not limited to that illustrated in the drawing. Thus, it may be of any type so far as it can produce an electromotive force in response to the changes in the oxygen content in the molten steel.
  • an oxygen concentration value is detected as a function of its electromotive force and the detected value is utilized as the controlling factor to adjust quantity of the deoxidizing agent to be added.
  • a method of manufacturing steel characterized by immersing an oxygen concentration cell in a molten steel bath, detecting the differentiated value of the electromotive force in said cell with respect to time while adding a deoxidizing agent into said molten steel bath, detecting the maximum value of said differentiated value of said electromotive force, and regu lating the additional quantity of said deoxidizing agent to be added into said molten steel bath to a predetennined definite value after said differentiated value has reached said maximum value.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US847053A 1968-08-08 1969-08-04 Method of deoxidizing steel Expired - Lifetime US3645720A (en)

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DE (1) DE1940489A1 (en))
FR (1) FR2015309B1 (en))
GB (1) GB1225580A (en))
SE (1) SE345691B (en))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4105507A (en) * 1970-08-27 1978-08-08 Asea Aktiebolag Method and system for instantaneously determining the oxygen activity in molten metals
US6350295B1 (en) 2001-06-22 2002-02-26 Clayton A. Bulan, Jr. Method for densifying aluminum and iron briquettes and adding to steel
CN115927948A (zh) * 2023-02-15 2023-04-07 福建鼎盛钢铁有限公司 一种薄板连铸连轧耐候钢冶炼方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2253574A (en) * 1938-01-11 1941-08-26 Bethlehem Steel Corp Method of controlling the deoxidation of steel
US2991684A (en) * 1955-08-02 1961-07-11 Max Planck Inst Eisenforschung Method of supervising metallurgical and metal melting processes
US3403090A (en) * 1964-05-06 1968-09-24 Yawata Iron & Steel Co Vessel for measuring oxygen content of a molten metal

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2253574A (en) * 1938-01-11 1941-08-26 Bethlehem Steel Corp Method of controlling the deoxidation of steel
US2991684A (en) * 1955-08-02 1961-07-11 Max Planck Inst Eisenforschung Method of supervising metallurgical and metal melting processes
US3403090A (en) * 1964-05-06 1968-09-24 Yawata Iron & Steel Co Vessel for measuring oxygen content of a molten metal

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Fitterer et al., The Rapid Determination of Oxygen in Commercial Steel With the Solid Electrolyte Probe, Journal of Metals, June 1968. *
Fitterer, G. R, (II), Further Development of the Electrolytic Method for the Rapid Determination of Oxygen in Liquid Steels, Journal of Metals, Sept. 1967. *
Fitterer, G. R. Progress in the Development of a Device for the Direct Determination of Oxygen in Liquid Steel, Journal of Metals, Aug. 1966. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4105507A (en) * 1970-08-27 1978-08-08 Asea Aktiebolag Method and system for instantaneously determining the oxygen activity in molten metals
US6350295B1 (en) 2001-06-22 2002-02-26 Clayton A. Bulan, Jr. Method for densifying aluminum and iron briquettes and adding to steel
CN115927948A (zh) * 2023-02-15 2023-04-07 福建鼎盛钢铁有限公司 一种薄板连铸连轧耐候钢冶炼方法
CN115927948B (zh) * 2023-02-15 2024-02-27 福建鼎盛钢铁有限公司 一种薄板连铸连轧耐候钢冶炼方法

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GB1225580A (en)) 1971-03-17
DE1940489A1 (de) 1970-09-03
FR2015309B1 (en)) 1973-03-16
FR2015309A1 (en)) 1970-04-24
SE345691B (en)) 1972-06-05

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