US3575695A - Deoxidation method of molten steel - Google Patents

Deoxidation method of molten steel Download PDF

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Publication number
US3575695A
US3575695A US766542A US3575695DA US3575695A US 3575695 A US3575695 A US 3575695A US 766542 A US766542 A US 766542A US 3575695D A US3575695D A US 3575695DA US 3575695 A US3575695 A US 3575695A
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Prior art keywords
calcium
steel
molten steel
oxygen
inclusions
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US766542A
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English (en)
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Yoshio Miyashita
Katuhiko Nishikawa
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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

  • OCT-0N oxygen o 1 l l l I O Time after deoxidcnion with Al (minutes)
  • By increasing the yield of calcium in the molten steel floatation of some inclusions are rapidly accelerated and then those are easily separated, and the presence of harmful macro inclusions may be decreased in a great quantity.
  • This invention relates to a method of manufacturing steel having higher cleanliness by adding calcium or calcium allov to the molten steel and effectively improving yield of calcium. This eliminates some non-metallic inclusions from the molten steel and further effectively desulphurizes and degasses the steel.
  • Mn, Si, Al, Ti, and Cr have been widely used for the deoxidation of steel. Ordinarily, deoxidation is conducted in the ladle at the period of tapping. The amount of oxygen in a molten steel is generally higher than that being in equilibrium with metallic Mn,
  • Vacuum melting methods, vacuum degassing methods and electro slag methods are used in order to decrease inclusions in the steel. These all require complicated devices and are skilled work, which are therefore unsuitable for mass-production.
  • Mn, Si, or Al may be used in deoxidation without calcium.
  • concentration of total oxygen in the steel (the sum of free oxygen and oxide inclusions, and the oxygen found by oxygen analysis) is kept at a considerably high level. Because of inclusions not removable from the molten bath, it is difficult to keep the total oxygen stable below 0.004% no matter how much deoxidizer is added. Owing to various conditions at the time of deoxidation, inclusions that remain in steel tend to be unstable and create macro inclusions which are harmful to properties of steel.
  • FIG. 1 illustrates an embodiment of the invention
  • FIG. 2 shows graphs illustrating the decrease of oxygen in steel by using the present invention
  • FIGS. 3 and 4 are graphs illustrating the decrease in total oxygen with the addition of calcium at the time of Si-deoxidation
  • FIGS. 5 and 6 are graphs, similar to FIGS. 3 and 4, obtained from another series of tests (Al-deoxidation).
  • calcium alloy is added through hollow cylinder or tubing 3 to the lower part of the molten bath 5.
  • the calcium alloy is stored in tank 1 and its flow is controlled by adjusting valve 2 as gas is blown into said cylinder.
  • Refractory lining 4 surrounds cylinder or tubing 3, where it enters into the said bath 5.
  • the calcium rises to the surface rapidly and eliminates inclusions in said bath and prevents or decreases the occurences of macro-inclusions.
  • the requirement for preliminary deoxidation is to have the value of dissolving oxygen below the predetermined value of oxygen in steel. This matter must be conducted prior to calcium addition or during addition of calcium.
  • the calcium, melting point 1440 C. and boiling point 1440 0. when added to the lower part of the molten bath immediately liquifies or vaporises itself and as it rises to the surface, it melts into the bath, .thereby reacting with free oxygen and oxide inclusions. Inclusions reacting with added calcium rapidly rise to the surface as changes of its components are brought about and are eliminated so that the value of the total oxygen decreases surely.
  • a degree of reaction can be regulated at the time of addition to the molten bath.
  • Table 2 An analysis of the remaining calcium in steel is shown in Table 2 which is a comparison between a prior art addition of 0.1% calcium to the surface of 50 kg. molten bath, and an addition of the same amount made by the method of the present invention.
  • the calcium or calcium alloy required for the present invention may be a powder, granule or in small lump form. Besides the calcium or calcium alloy or calcium compound, magnesium, sodium or potassium or their alloys and compounds may be added.
  • the calcium or calcium alloy is usually added to ladle containing the molten steel but it can also be added to open hearth, converted, electric furnace or mould.
  • Inert gases like argon or nitrogen gas may be used when the calcium or calcium alloy is added.
  • nitrogen addition formation of nitrides can be effectively achieved.
  • Other additives aimed at the formation of nitrides can also be added along 'with the calcium or calcium alloy. In this case, the partial pressure of oxygen in the molten bath contacting nitrogen gas is kept at a very low level by calcium and nitrogen absorption in said bath is very effective.
  • the deoxidizing agent can be added without lowering the temperature.
  • the molten steel is stirred well as the calcium vaporizes and rises to the surface of said bath, thereby making composition of said bath uniform.
  • Any aimed composition of steel is possible to obtain easily as the amount of added calcium is small.
  • FIG. 2 contains curves 1, 2, 3 and 4.
  • O is the level of oxygen in the molten steel before deoxidation.
  • Curve 1 shows the behaviour of total oxygen, when deoxidation is effected in a normal manner at time T while curve 2 shows the behaviour of free oxygen under the same conditions.
  • curve 3 calcium has been added at time T and the total oxygen is shown on the curve 3, while the behaviour of the free oxygen under the same conditions is shown in curve 4.
  • FIGS. 3 and 4 show the behaviour of total oxygen in electrolytic iron, 1 kg., which has been melted in a high frequency furnace, with the temperature kept at 1600 C. and to which is added 0.05 calcium after it has been deoxidized with 0.3% silicon.
  • the total oxygen reaches a constant value of 0.015% approximately in one minute after calcium has been added. Under the same conditions but without calcium addition, it will also reach the set value of 0.015% in six to eight minutes after Si addition (see FIG. 4).
  • the metallic Si present was 0.10% and the equilibrating oxygen was 0.015%. Free oxygen at the period of Si deoxidation is shown to decrease in approximate equilibrium with metallic Si.
  • FIG. 4 shows an embodiment where calcium has been added to the bath after Si constituting the primary deoxidation product had almost risen to the surface of said bath and eliminated.
  • a constant value of total oxygen that is, about 0.015 is obtained in about six minutes. Accordingly, in the process of Si-deoxidation, an addition of calcium during Sideoxidation is desirable.
  • FIG. 5 shows that the total oxygen reaches 0.0016% and less if calcium addition has been made. Under the same conditions, but without calcium, it reaches about 0.004% but not less in 6 to 8 minutes after the aluminum addition (see FIG. 6).
  • the metallic Al was 0.14% and the equilibrating oxygen with Al is about 0.0001%.
  • fine particles formed in the primary deoxidation cannot rise to the surface of said bath even when the free oxygen decreases.
  • the value of total oxygen is thus kept at a considerably higher level than that of the free oxygen and does not decrease.
  • the oxygen value of 0.046% in one minute after Al addition most of it is A1 0 the primary deoxidation product. It rapidly rises to the surface of said bath and is eliminated, when calcium is added.
  • the value of the total oxygen tends to approach the value of free oxygen.
  • FIG. 6 shows an example where calcium addition is made to the molten steel where considerable A1 0 remains as the primary product. This figure indicates that oxygen rapidly decreases and the value of the total oxygen approaches the value of free oxygen.
  • FIGS. 3 to 6 show the results of small scale experiments with the molten steel of 1 kg., but the same or a similar effect is found when the amount of molten metal is increased to that of the scale of industrial production.
  • the method is eflective because the manner of addition keeps the amount of calcium escaping into the atmosphere as small as possible by keeping the contact period of calcium in liquid or vapor form longer after it has been added to the lower part of the molten bath. Accordingly, the more the amount of the molten steel, the longer the contact period. In some cases the static pressure of molten bath becomes higher than the vapor pressure of the calcium, thereby making the method more elfective. This has been confirmed in large scale tests.
  • the amount of deoxidizing element needed to keep free oxygen below 0.004% is, in the case of metallic Al about 0.0004%, and in the case of metallic Ti according to the work of Chipman et al. about 0.02%. That is to say, by adding calcium or calcium alloy to molten steel deoxidized preliminarily to make metallic Al 0.0004% and metallic Ti 0.02% the total oxygen can be decreased to below 0.004%. In this case, the composition of the inclusions change so that it prevents harmful macro in clusions in steel.
  • the improvement comprising blowing into said molten steel after the addition of said deoxidizer thereto about 0.05% by weight of said molten steel of at least one calcium additive selected from the group consisting of calcium and calcium alloys, said calcium additive being blown into the lower part of said vessel containing said molten steel by a blowing gas, whereby the amount and size of said nonmetallic inclusions in the steel are substantially reduced.

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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)
US766542A 1967-10-18 1968-10-10 Deoxidation method of molten steel Expired - Lifetime US3575695A (en)

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JP6660267 1967-10-18

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US (1) US3575695A (de)
BE (1) BE722596A (de)
DE (1) DE1803377B2 (de)
FR (1) FR1596638A (de)
GB (1) GB1206062A (de)
SE (1) SE361900B (de)
SU (1) SU367614A3 (de)

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3765875A (en) * 1970-07-23 1973-10-16 L Septier Inoculating alloy for cast irons
US3767380A (en) * 1970-05-29 1973-10-23 Lenin Kohaszati Muvek Process for the production of free-cutting carbon steels with special deoxidation
US3885957A (en) * 1972-03-01 1975-05-27 Thyssen Niederrhein Ag Method for the desulfurization of a steel melt
US3885956A (en) * 1974-05-21 1975-05-27 Rheinische Kalksteinwerke Method and composition for the treatment of ferrous melts and process for making the treating composition
US3891425A (en) * 1974-02-27 1975-06-24 Special Metals Corp Desulfurization of transition metal alloys
US3955966A (en) * 1974-03-06 1976-05-11 August Thyssen-Hutte Ag Method for dispensing a fluidizable solid from a pressure vessel
US3980469A (en) * 1973-04-28 1976-09-14 Thyssen Niederrhein Ag Hutten- Und Walzwerke Method of desulfurization of a steel melt
US3992195A (en) * 1974-04-20 1976-11-16 Thyssen Niederrhein Ag Hutten- Und Walzwerke Process for the production of steel with increased ductility
US4014684A (en) * 1973-11-27 1977-03-29 Foseco International Limited Manufacture of steel
US4014685A (en) * 1973-11-27 1977-03-29 Foseco International Limited Manufacture of steel
US4067730A (en) * 1974-04-20 1978-01-10 Thyssen Niederrhein Ag Hutten-Und Walzwerke Process for the production of steel with increased ductility
US4072511A (en) * 1976-11-26 1978-02-07 Harold Huston Method of producing silicon containing cast iron
US4073643A (en) * 1973-05-29 1978-02-14 Nippon Steel Corporation Continuously cast steel slabs for steel sheets having excellent workabilities and method for production thereof
US4232854A (en) * 1978-05-26 1980-11-11 Barbakadze Dzhondo F Method of introducing powdered reagents into molten metals and apparatus for effecting same
US4238227A (en) * 1979-06-27 1980-12-09 United States Steel Corporation Cleansing of steel by gas rinsing
US4251268A (en) * 1978-11-17 1981-02-17 Concast Ag Method of treating boron-containing steel
US4317678A (en) * 1980-09-26 1982-03-02 Union Carbide Corporation Process for continuous casting of aluminum-deoxidized steel
US4392887A (en) * 1981-12-04 1983-07-12 Arbed S.A. Method of desulfurizing an iron melt
US4435210A (en) 1982-02-12 1984-03-06 Showa Denko Kabushiki Kaisha Refining agent of molten metal and methods for producing the same
US4444590A (en) * 1983-03-28 1984-04-24 Esm Incorporated Calcium-slag additive for steel desulfurization and method for making same
USRE31676E (en) * 1982-09-29 1984-09-18 Thyssen Aktiengesellschaft vorm August Thyssen-Hutte AG Method and apparatus for dispensing a fluidizable solid from a pressure vessel
WO1985001518A1 (en) * 1983-10-03 1985-04-11 Union Carbide Corporation Process to control the shape of inclusions in steels
US4531972A (en) * 1983-03-15 1985-07-30 Vallourec Method for the fabrication of steels with high machinability
US4544405A (en) * 1983-09-02 1985-10-01 M.A.N. Maschinenfabrik Augsburg-Nurnberg Aktiengesellschaft Method of producing steels of great purity and low gas content in steel mills and steel foundries and apparatus therefor
US4891063A (en) * 1987-08-12 1990-01-02 L'air Liquide Process for stirring steel in a ladle with the aid of carbon dioxide
US4994108A (en) * 1988-07-18 1991-02-19 Kawasaki Steel Corporation Process for producing high cleanness extra low carbon steel
US5480127A (en) * 1994-02-11 1996-01-02 Leybold Durferrit Gmbh Apparatus for the melting and treatment of metal

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1069314A (en) * 1974-09-20 1980-01-08 Sumitomo Metal Industries, Ltd. Process for the addition of calcium to molten steel

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3767380A (en) * 1970-05-29 1973-10-23 Lenin Kohaszati Muvek Process for the production of free-cutting carbon steels with special deoxidation
US3765875A (en) * 1970-07-23 1973-10-16 L Septier Inoculating alloy for cast irons
US3885957A (en) * 1972-03-01 1975-05-27 Thyssen Niederrhein Ag Method for the desulfurization of a steel melt
US3980469A (en) * 1973-04-28 1976-09-14 Thyssen Niederrhein Ag Hutten- Und Walzwerke Method of desulfurization of a steel melt
US4073643A (en) * 1973-05-29 1978-02-14 Nippon Steel Corporation Continuously cast steel slabs for steel sheets having excellent workabilities and method for production thereof
US4014685A (en) * 1973-11-27 1977-03-29 Foseco International Limited Manufacture of steel
US4014684A (en) * 1973-11-27 1977-03-29 Foseco International Limited Manufacture of steel
US3891425A (en) * 1974-02-27 1975-06-24 Special Metals Corp Desulfurization of transition metal alloys
US3955966A (en) * 1974-03-06 1976-05-11 August Thyssen-Hutte Ag Method for dispensing a fluidizable solid from a pressure vessel
US3992195A (en) * 1974-04-20 1976-11-16 Thyssen Niederrhein Ag Hutten- Und Walzwerke Process for the production of steel with increased ductility
US4067730A (en) * 1974-04-20 1978-01-10 Thyssen Niederrhein Ag Hutten-Und Walzwerke Process for the production of steel with increased ductility
US3885956A (en) * 1974-05-21 1975-05-27 Rheinische Kalksteinwerke Method and composition for the treatment of ferrous melts and process for making the treating composition
US4072511A (en) * 1976-11-26 1978-02-07 Harold Huston Method of producing silicon containing cast iron
US4232854A (en) * 1978-05-26 1980-11-11 Barbakadze Dzhondo F Method of introducing powdered reagents into molten metals and apparatus for effecting same
US4251268A (en) * 1978-11-17 1981-02-17 Concast Ag Method of treating boron-containing steel
US4238227A (en) * 1979-06-27 1980-12-09 United States Steel Corporation Cleansing of steel by gas rinsing
US4317678A (en) * 1980-09-26 1982-03-02 Union Carbide Corporation Process for continuous casting of aluminum-deoxidized steel
US4392887A (en) * 1981-12-04 1983-07-12 Arbed S.A. Method of desulfurizing an iron melt
US4435210A (en) 1982-02-12 1984-03-06 Showa Denko Kabushiki Kaisha Refining agent of molten metal and methods for producing the same
USRE31676E (en) * 1982-09-29 1984-09-18 Thyssen Aktiengesellschaft vorm August Thyssen-Hutte AG Method and apparatus for dispensing a fluidizable solid from a pressure vessel
US4531972A (en) * 1983-03-15 1985-07-30 Vallourec Method for the fabrication of steels with high machinability
US4444590A (en) * 1983-03-28 1984-04-24 Esm Incorporated Calcium-slag additive for steel desulfurization and method for making same
US4544405A (en) * 1983-09-02 1985-10-01 M.A.N. Maschinenfabrik Augsburg-Nurnberg Aktiengesellschaft Method of producing steels of great purity and low gas content in steel mills and steel foundries and apparatus therefor
EP0143276A1 (de) * 1983-10-03 1985-06-05 Union Carbide Corporation Verfahren zur Beeinflussung der Form von Einschlüssen in Stählen
WO1985001518A1 (en) * 1983-10-03 1985-04-11 Union Carbide Corporation Process to control the shape of inclusions in steels
JPS61500125A (ja) * 1983-10-03 1986-01-23 ユニオン　カ−バイド　コ−ポレ−シヨン 介在物がほぼ球形状の鋼の製造方法
JPH0133527B2 (de) * 1983-10-03 1989-07-13 Union Carbide Corp
US4891063A (en) * 1987-08-12 1990-01-02 L'air Liquide Process for stirring steel in a ladle with the aid of carbon dioxide
US4994108A (en) * 1988-07-18 1991-02-19 Kawasaki Steel Corporation Process for producing high cleanness extra low carbon steel
US5480127A (en) * 1994-02-11 1996-01-02 Leybold Durferrit Gmbh Apparatus for the melting and treatment of metal

Also Published As

Publication number Publication date
GB1206062A (en) 1970-09-23
FR1596638A (de) 1970-06-22
SU367614A3 (de) 1973-01-23
SE361900B (de) 1973-11-19
DE1803377B2 (de) 1976-07-15
DE1803377A1 (de) 1969-05-14
BE722596A (de) 1969-04-01

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