US3891429A - Method for selective decarburization of alloy steels - Google Patents

Method for selective decarburization of alloy steels Download PDF

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Publication number
US3891429A
US3891429A US367839A US36783973A US3891429A US 3891429 A US3891429 A US 3891429A US 367839 A US367839 A US 367839A US 36783973 A US36783973 A US 36783973A US 3891429 A US3891429 A US 3891429A
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United States
Prior art keywords
fuel oil
melt
oxygen
tuyere
carbon
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Expired - Lifetime
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US367839A
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English (en)
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Gordon L Cox
Olin E Williams
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Raymond Kaiser Engineers Inc
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Koppers Co Inc
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Priority to US367839A priority Critical patent/US3891429A/en
Priority to CA190,834A priority patent/CA1005234A/en
Priority to DE19742405737 priority patent/DE2405737B2/de
Priority to FR7409282A priority patent/FR2232600B1/fr
Priority to JP49063822A priority patent/JPS5021918A/ja
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Publication of US3891429A publication Critical patent/US3891429A/en
Assigned to RAYMOND KAISER ENGINEERS INC., A CORP OF OHIO reassignment RAYMOND KAISER ENGINEERS INC., A CORP OF OHIO ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KOPPERS COMPANY, INC.
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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
    • C21C7/068—Decarburising
    • C21C7/0685—Decarburising of stainless steel
    • 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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/42—Constructional features of converters
    • C21C5/46—Details or accessories
    • C21C5/48—Bottoms or tuyéres of converters

Definitions

  • Yeager I 5 7 ABSTRACT A method for selective de'carburization of crude, molten alloy steel by means of injecting into the bath, peripherally of a submerged tuyere, fuel oil which is maintained in the liquid state at least to the tuyerebath interface and simultaneously injecting a mixture of oxygen and vaporized fuel oil axially through said tuyere into the bath until the carbon-alloy equilibrium is reached, and thereafter adjusting the mixture so as to be rich in vaporized fuel oil and continuing said fuel oil enriched injection until the desired carbon level is reached and thereupon discontinuing fuel oil and gaseous mixture injections and purging undesired hydrogen from said bath by injecting both axially and peripherally of said tuyere an inert gas.
  • the present invention relates to a method for the production of ferro-alloy steels and, in particular, to a method for the selective decarhurization of high chromium steels and the like.
  • the present invention provides a method for cooling a submerged tuyere in a refining vessel and for reducing the partial pressure of carbon monoxide in the melt to obtain low carbon levels.
  • the method of the present invention provides a selective decarburization of a crude chromium alloy steel melt preferably prepared in an electric arc furnace.
  • the method comprises injecting a mixture of oxygen and vaporized fuel oil through the axial portion of a concentric tuyere for that period which is sufficient to achieve the theoretical carbon-chromiumtemperature equilibrium of the melt.
  • fuel oil maintained in the liquid state at least to the tuyere-bath interface, is injected into the refining vessel peripherally of the axial portion of the tuyere.
  • the volumetric ratio of vaporized fuel oil to oxygen in the gaseous mixture is increased to at least between 2:] and 6:] until the melt is decarburized to the desired carbon level.
  • the peripheral fuel oil injection and gas mixture injection are stopped when the desired end point is reached, and an inert gas, such as carbon dioxide, argon and the like, is injected for a short time into the melt to purge the melt of any residual hydrogen.
  • the present invention provides a process in which a high-carbon, high-chromium crude melt is prepared and deslagged in an electric arc furnace. Decarburization is carried out in a refining vessel having tuyeres submerged below the bath level and located, preferably, in the bottom thereof.
  • the tuyeres are of a double or concentric tube configuration in which a liquid hydrocarbon, preferably fuel oil, is injected into the molten bath through a space between the peripheral and axial tubes, and a mixture of oxygen and vaporized liquid hydrocarbon is injected through the central or axial tube.
  • the liquid hydrocarbon injected through the peripheral tube is maintained in the liquid state at least to the tuyere-bath interface.
  • the cracking may, under optimum conditions, provide preferential carbon donating residuum to the melt adjacent the tuyere.
  • the carbon residuum is believed to act as a protective film or insulator between the melt and the refractory, but whether or not any carbon residuum is deposited the cracking will preferentially donate carbon to and effect reduction of the ferric oxide which is known to have the greatest corrosive effect upon the lining. Accordingly, by preventing vaporization of the liquid hydrocarbon within the tuyere it is possible to both protect the tuyere tip and the adjacent refractory material, thus substantially reducing the rapid wear experienced when blowing pure oxygen into the molten bath.
  • the decarburization is carried out in three stages.
  • oxygen alone, or a mixture of oxygen and vaporized liquid hydrocarbon is injected into the bath through the axial tuyere. Where a gaseous mixture is used, the liquid hydrocarbon is vaporized upon addition to the oxygen to provide an oxygen to hydrocarbon vapor volumetric ratio of at least 3:1 or 4:1.
  • the second stage injection is commenced when the theoretical carbon-chromium-temperature equilibrium is reached as calculated upon the basis of the amount of oxygen injected in the first stage and an analysis of the melt.
  • the volume of vaporized hydrocarbon to oxygen is preferably about 3 to 4:1.
  • ratios that can be employed for second stage blowing range from 2:1 to about 6:1; but at the lower ratios, a higher percentage of chromium is oxidized than is generally preferred, and at the higher ratios the refining time is increased although very low carbon levels are achieved.
  • the second stage is continued until the desired carbon content in the melt is reached. At the desired end point, the flow of both the oxygen-hyd rocarbon mixture and the peripheral hydrocarbon cooling liquid is discontinued.
  • the liquid hydrocarbon in the oxygen stream acts as a diluent for the carbon monoxide formed during decarburization of the crude melt. It is believed that the molecules of the liquid hydrocarbon, fuel oil, upon vaporization in the oxygen stream within the tuyere, are activated by the high temperatures prevailing at the interface between the tuyere and molten bath. The hydrocarbon and oxygen combine to form peroxides which decompose to water and aldehyde. This combination and decomposition is in extremely rapid transformation and is believed to occur almost simultaneously. The aldehyde very rapidly thereafter is converted to carbon dioxide and water, the latter of which dissociates into hydrogen and oxygen. The carbon di oxide and the hydrogen from the dissociated water vapor act as diluents for the carbon monoxide formed in the melt during decarburization.
  • the amount of hydrocarbon required is substantially less than the amount of oxygen required even though the partial pressure of carbon monoxide does increase with increasing oxygen availability.
  • the amount of oxygen supplied is substantially the same as that heretofore required to equilibrate the carbon-chromium-temperature equilibrium relationship. Since a reduction in the carbon below equilibrium requires a shift in the equilibrium point by a reduction in the partial pressure of the carbon monoxide in the bath, the second stage involves a substantial increase in the volumetric ratios of vaporized liquid hydrocarbon to oxygen, for example, up to 6:1. It is preferred, however, that in the second stage the volumetric ratio of the vaporized liquid hydrocarbon to oxygen is 3:1.
  • Utilizing a liquid hydrocarbon both for oxygen dilution as well as a cooling agent for the submerged tuyere increases the availability of hydrogen for dissolution into the bath. Generally, a large portion of the available hydrogen becomes dissolved within the melt which if permitted to remain would render the heat unusable.
  • a third stage injection of an inert gas is used to flush the melt. This flushing also has the advantage of lowering the amount of oxygen dissolved therein.
  • FIG. 1 is a cross-sectional plan view of a tuyere for use with the present invention.
  • FIG. 2 is a sectional elevation taken along lines II-ll of FIG. 1 of said tuyere.
  • the method of selective decarburization of alloy steel is preferably carried out as a duplexing operation.
  • the process is particularly well adapted for the production of steels having chromium content in excess of 5% and, preferably, from to 25%, with the carbon and silicon each present in amounts less than 1%.
  • the carbon content can be reduced to around 0.2% without any substantial oxidation and loss of chromium or other alloys.
  • an electric arc furnace is used to melt down scrap and alloy under dead melt conditions and to bring the melt temperature up to between l600 and l700C.
  • the molten metal is then tapped into a ladle, sampled and deslagged.
  • the deslagged crude hot metal is then transferred into a reaction or refining vessel.
  • the refining vessel can be a conventionally shaped Bessemer type converter adapted for rotation to facilitate charging, sampling and tapping.
  • the converter is rotatable about a pair of trunnions which are designed to permit the passage of oxygen and fuel oil conduits therethrough.
  • the bottom of the converter is fitted with a number of concentric tuyeres, for example, a [00 ton steel alloy converter would be provided with about five tuyeres.
  • tuyere 10 is representative of the type of tuyere preferred for use in the pres ent invention and includes an axial tube 11 and a concentrically aligned outer tube 12. Tuyere 10 is adapted to be mounted through refractory bottom 14 of the converter by mounting means 16. Axial tube 11 has a plurality of fluted passages 17 machined along the length of its outer surface. Passages 17 are designed to register with the inner surface of outer tube 12 to form a plurality of peripheral passages about the periphery of the axial tube for the peripheral injection of liquid hydrocarbon.
  • Outer tube 12 is provided with a number of grooves 18 machined along a portion of the inner surface and designed to register with the outer surface of inner tube 11, but not with the fluted passages 17.
  • Grooves 18 extend from the base of tube 12 to a position near the tip of tuyere 10, for example, within about one inch of the tuyere-bath interface.
  • the tip ends of grooves 18 are positioned to register with openings 19 which are angularly formed through axial tube 11 and provide for introduction of fuel oil from the grooves 18 into the oxygen stream in axial tube 11.
  • the inner diameter of axial tube 11 is preferably between 0.25 to 0.30 inches and is made of a high thermally conductive material such as copper or copper alloys.
  • Outer concentric tube 12, on the other hand, can be fabricated from any suitable material such as stainless or plain carbon steel.
  • the inner diameter of outer tube 12 and the outer diameter of inner tube 11 are essentially the same so that a tight nesting relationship therebetween is established to provide the appropriate sealing between passages 17 and grooves 18.
  • Passages 17 are connected to a source of fuel oil by means of line 21.
  • Elongated grooves 18 are connected at the base of tuyere 10 to line 22 that is connected to an independently regulatable source of fuel oil.
  • Axial tube 11 is connected to line 23 that is connected to a source of high pressure oxygen.
  • fuel oil is injected through line 21 and passages 17 peripherally of the axial oxygen tuyere. Pressure and/or flow rate in lines 21 and passages 17 is maintained to prevent the fuel oil from vaporizing before it reaches the tuyerebath interface. Premature vaporization can be detected by fluctuations in the flow meters on lines 21. Fuel oil in line 22, on the other hand, is maintained at a pressure and flow rate which provides both proper fuel oiloxygen vapor mixture ratio and preferably for vaporization of the fuel oil at the end of elongated grooves 18.
  • the tuyeres as well as the adjacent refractory lining 14 are protected from the rapid erosion of the bath. It is believed that both the heat of vaporization as well as the phenomena similar to cracking is used to absorb bath heat and to thereby cool the tuyere. Moreover, the cracked hydrocarbon fuel oil provides a carbonaceous layer or film in the area of the tuyere which either acts as a physical shield against the bath or preferably donates carbon to the ferric oxide.
  • the fuel oil is preferably maintained at a pressure of between and psi.
  • Oxygen supplied by line 23 and vaporized fuel oil from elongated groove 18 in tuyere 10 are injected into the bath through the axial tubes 11 of tuyere 10.
  • the total oxygen flow rate would, preferably, be about 1000 cubic feet of oxygen per hour per ton with 350 to 400 cubic feet of fuel oil per hour per ton of steel in the first stage. Since the first stage blow lasts until the theoretical carbon-chromium equilibrium point is reached, it is possible to blow in the first stage without the utilization of any fuel oil.
  • the second stage preferably utilizes approximately 1000 to I200 cubic feet of fuel oil per hour per ton of steel and about 300 to 400 cubic feet of oxygen.
  • Number 2 fuel oil, for example, injected into tuyere 10 at 100 psi will provide approximately 10 to l 1 cubic feet per gallon.
  • the second stage blow is ended when the desired carbon level has been reached.
  • the third stage blow of carbon dioxide or argon is utilized to stir the bath and remove any undesired hydrogen.
  • the third stage blow is from about I to 10 minutes and preferably about 3 minutes in duration, depending upon the amount of hydrogen dissolved in the bath.
  • a method of selective decarburization ofa chromium-alloy steel melt said decarburization being carried out in a refining vessel having at least one double tuyere submerged below the surface of the melt, said method comprising: injecting into said melt through a central tube of said tuyere a gas selected from the group consisting of oxygen and a mixture of oxygen and fuel oil for a period of time sufficient to reach the carbon-chromium-temperature equilibrium, while injecting, during the entire said period, fuel oil maintained in the liquid state to the tuyere-melt interface into said melt through said tuyere and peripherally of said central tube; injecting through said central tube into said melt a mixture of fuel oil and oxygen in a volumetric gas ratio offrom about 2:l to 6: l until said melt is decarburized, while continuing said peripheral flow of fuel oil into said melt; and thereafter discontinuing the injection of fuel oil and said mixture of fuel oil and oxygen, and injecting into said melt an inert gas to purge the
  • a method as set forth in claim 1 wherein said ratio of fuel oil to oxygen after equilibrium is 32L 4.
  • said inert gas is carbon dioxide.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
US367839A 1973-06-07 1973-06-07 Method for selective decarburization of alloy steels Expired - Lifetime US3891429A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US367839A US3891429A (en) 1973-06-07 1973-06-07 Method for selective decarburization of alloy steels
CA190,834A CA1005234A (en) 1973-06-07 1974-01-24 Method for selective decarburization of alloy steels
DE19742405737 DE2405737B2 (de) 1973-06-07 1974-02-07 Verfahren zum entkohlen von chromlegierungs-stahlschmelze
FR7409282A FR2232600B1 (enrdf_load_stackoverflow) 1973-06-07 1974-03-19
JP49063822A JPS5021918A (enrdf_load_stackoverflow) 1973-06-07 1974-06-05

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US367839A US3891429A (en) 1973-06-07 1973-06-07 Method for selective decarburization of alloy steels

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US (1) US3891429A (enrdf_load_stackoverflow)
JP (1) JPS5021918A (enrdf_load_stackoverflow)
CA (1) CA1005234A (enrdf_load_stackoverflow)
DE (1) DE2405737B2 (enrdf_load_stackoverflow)
FR (1) FR2232600B1 (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3992194A (en) * 1974-04-11 1976-11-16 Creusot-Loire Method and apparatus for use in the treatment of metals in the liquid state
US4138098A (en) * 1975-08-14 1979-02-06 Creusot-Loire Method of blowing smelting shaft furnaces and tuyeres used for said blowing
US4185683A (en) * 1978-01-18 1980-01-29 Artamonov Viktor L Electroslag remelting mould
US4360190A (en) * 1981-03-16 1982-11-23 Junichi Ato Porous nozzle for molten metal vessel
US4615730A (en) * 1985-04-30 1986-10-07 Allegheny Ludlum Steel Corporation Method for refining molten metal bath to control nitrogen
US4746361A (en) * 1987-04-03 1988-05-24 Inland Steel Company Controlling dissolved oxygen content in molten steel
US4890821A (en) * 1980-04-08 1990-01-02 Nixon Ivor G Metallurgical processes
US5431709A (en) * 1993-09-21 1995-07-11 Gas Research Institute Accretion controlling tuyere

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE7501446L (enrdf_load_stackoverflow) * 1974-02-11 1975-08-12 Uss Eng & Consult
JPS5346887A (en) * 1976-10-12 1978-04-26 Okura Industrial Co Ltd Method of shrinkage wrapping
FR2448572B1 (fr) * 1979-02-09 1985-10-18 Pennsylvania Engineering Corp Procede d'obtention d'acier a basse teneur en carbone au convertisseur oxygene-argon
JPS5664968A (en) * 1979-11-01 1981-06-02 Akira Hirai Cellophane packed insecticidal tablet
JPS5665914A (en) * 1979-11-05 1981-06-04 Mitsubishi Heavy Ind Ltd Production of low carbon stainless steel
JPS5858218A (ja) * 1981-10-02 1983-04-06 Kawasaki Steel Corp 転炉の底吹き羽口

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986458A (en) * 1958-09-05 1961-05-30 Strategic Materials Corp Production of iron from ferrous slag materials
US3076703A (en) * 1958-04-28 1963-02-05 Arbed Manufacture of steel
US3330645A (en) * 1962-08-07 1967-07-11 Air Liquide Method and article for the injection of fluids into hot molten metal
US3706549A (en) * 1968-02-24 1972-12-19 Maximilianshuette Eisenwerk Method for refining pig-iron into steel
US3725041A (en) * 1970-09-25 1973-04-03 Allegheny Ludlum Ind Inc Deoxidizing metal
US3751242A (en) * 1969-04-02 1973-08-07 Eisenwerk Gmbh Sulzbach Rosenb Process for making chrimium alloys
US3817744A (en) * 1969-07-08 1974-06-18 Creusot Loire Method for cooling a tuyere of a refining converter

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3076703A (en) * 1958-04-28 1963-02-05 Arbed Manufacture of steel
US2986458A (en) * 1958-09-05 1961-05-30 Strategic Materials Corp Production of iron from ferrous slag materials
US3330645A (en) * 1962-08-07 1967-07-11 Air Liquide Method and article for the injection of fluids into hot molten metal
US3706549A (en) * 1968-02-24 1972-12-19 Maximilianshuette Eisenwerk Method for refining pig-iron into steel
US3751242A (en) * 1969-04-02 1973-08-07 Eisenwerk Gmbh Sulzbach Rosenb Process for making chrimium alloys
US3817744A (en) * 1969-07-08 1974-06-18 Creusot Loire Method for cooling a tuyere of a refining converter
US3725041A (en) * 1970-09-25 1973-04-03 Allegheny Ludlum Ind Inc Deoxidizing metal

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3992194A (en) * 1974-04-11 1976-11-16 Creusot-Loire Method and apparatus for use in the treatment of metals in the liquid state
US4138098A (en) * 1975-08-14 1979-02-06 Creusot-Loire Method of blowing smelting shaft furnaces and tuyeres used for said blowing
US4185683A (en) * 1978-01-18 1980-01-29 Artamonov Viktor L Electroslag remelting mould
US4890821A (en) * 1980-04-08 1990-01-02 Nixon Ivor G Metallurgical processes
US4360190A (en) * 1981-03-16 1982-11-23 Junichi Ato Porous nozzle for molten metal vessel
US4615730A (en) * 1985-04-30 1986-10-07 Allegheny Ludlum Steel Corporation Method for refining molten metal bath to control nitrogen
US4746361A (en) * 1987-04-03 1988-05-24 Inland Steel Company Controlling dissolved oxygen content in molten steel
US5431709A (en) * 1993-09-21 1995-07-11 Gas Research Institute Accretion controlling tuyere

Also Published As

Publication number Publication date
CA1005234A (en) 1977-02-15
FR2232600B1 (enrdf_load_stackoverflow) 1976-12-17
JPS5021918A (enrdf_load_stackoverflow) 1975-03-08
FR2232600A1 (enrdf_load_stackoverflow) 1975-01-03
DE2405737A1 (de) 1974-12-19
DE2405737B2 (de) 1977-01-13

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