US3860418A - Method of refining iron melts containing chromium - Google Patents

Method of refining iron melts containing chromium Download PDF

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Publication number
US3860418A
US3860418A US262718A US26271872A US3860418A US 3860418 A US3860418 A US 3860418A US 262718 A US262718 A US 262718A US 26271872 A US26271872 A US 26271872A US 3860418 A US3860418 A US 3860418A
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United States
Prior art keywords
carbon
oxygen
refining
melt
content
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Expired - Lifetime
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US262718A
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English (en)
Inventor
Erik Anders Ake Josefsson
Folke Karl Evald Johansson
Kurt Karl Axel Almqvist
Hoftsten Carl Fredrik Von
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stora Enso Oyj
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Stora Kopparbergs Bergslags AB
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Classifications

    • 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
    • C21C5/005—Manufacture of stainless steel

Definitions

  • the present invention relates to a method of refining carbon out of iron melts containing chromium.
  • the refining is performed with oxygen in an open vessel or ladle or converter in which the iron melt forms a bath.
  • the conditions for refining steel melts containing chromium to low C contents are substantially determined by the temperature and the partial pressure for CO.
  • One known method makes use of the latter principle in such a way that a mixture of argon and oxygen gas is blown through nozzles below the surface of the bath.
  • the proportion argonzoxygen increases gradually towards the end as the carbon content falls, and in this way low carbon contents can be achieved at reasonable refining temperatures without the chromium of the bath being oxidized to any great extent.
  • the surface of the bath is covered by a slag which takes up the silicon and the chromium which is oxidized.
  • the disadvantage with this method is that it requires a large quantity of expensive argon and special regulating and other equipment in order to maintain such conditions while the gas is being blown so that the nozzles are not quickly destroyed. Even with such precautions, maintenance, and replacement of the nozzles is a considerable expenditure.
  • a surprising result of the absence of slag from the surface of the bath during the refining process is that the production of smoke and dust is considerably less erred when compared to refining with a slag cover. This is also true at higher temperatures near l,900C.
  • Another advantage is that the attack on the refractory lining becomes milder since there is no floating slag which might attack the lining. Since the oxygen gas is supplied from above, even the corrosion problems connected with nozzles and the adjacent lining, in the methods in which oxygen gas is supplied below the surface of the melt, are eliminated.
  • the stirring can be produced in conventional manner either by so-called vibratory (shaking) ladle in which the melt is set in rotating movement in the refining vessci, or by blowing in inert gas, for example argon, krypton, xenon, helium, below the surface of the melt, suitably through openings or porous brick in the bottom or side walls of the refining vessel.
  • inert gas for example argon, krypton, xenon, helium
  • the slag-free surface of the bath is achieved by removing silicon, and other substances having greater affinity to oxygen than chromium, from the bath, suitably by oxidation and pre-slagging, and then drawing off all slag before the start of the carbon refining process.
  • the content of Si and similar substances, for example Al and V, should suitably be less than 0.05 percent. Due to the cooperation of the vigorous stirring and the bath surface free from slag at the start of the process, no noticeable new formation of slag takes place and the surface is kept slagfree.
  • argon gas supplied for stirring may also contribute to acquiring a low final carbon content by lowering the CO partial pressure at the gasemitting surfaces of the bath. This effect is more marked the larger the quantity of argon used in relation to the quantity of oxygen gas.
  • the refining is thus carried out with very small chromium losses right up to a well-defined end point when there is a steep decline in the CO content in the exhaust which is continuously analyzed indicating that the carbon refining process is ending and that further addition of oxygen substantially oxidizes the chromium in the bath.
  • the C content thus achieved is satisfactorily low and the steel can be finished by means of deoxidation and the addition of the required alloying substances, for example Mn and Si.
  • the amount of slag which may then occur on the surface of the bath is small in quantity and firm in consistency, and it may not be necessary to reduce it'completely in order to achieve a satisfactorily low oxygen content in the steel bath.
  • the steel melt may be tapped into a special completion vessel preferably after the refining, keeping back any slag.
  • the decrease in the ratio oxygenzinert gas can be
  • the carbon content in the low carboncontent range can be lowered still further in known manner by continued inert gas flushing without the supply of oxygen.
  • the steel refined in this way is deoxidized and alloyed I in the same way as described above.
  • molten pig iron and ferrochromium carbur have been used as raw materials for producing stainless steel.
  • pig iron, crude chromium and scrap which have been melted in electric arc furnaces and transferred to a vibratory ladle are all within the scope of the invention.
  • All silicon is preferably oxidized and all slag removed in the vibratory ladle before the carbon refining process is carried out according to the invention.
  • the required carbon content of 5 the steel prior to carbon refining according to the invention is dependent on the size of the charge, the temperature before blowing is started, and the specified final carbon content.
  • the refining was performed from a remarkably high carbon content. This was caused by the requirement of an extremely low carbon content in the finished steel and the very great heat loss caused by low charge weight in relation to the reaction heat.
  • the carbon refining according to the invention should start at at least 0.5 percent by weight C in the steel.
  • One of the advantages of the method is that it is possible to have a relatively high carbon content at the start of the refining, as an inexpensive crude chromium and FeCr carbur may then be used for the manufacture of stainless steel having a low C content.
  • the invention is exemplified here in the manufacture of chromium steel, but can also be used for the manufacture of other types of steel having a high chromium content, for example stainless steel containing Cr, Ni and possibly other alloying substances.
  • a method for refining carbon from an iron melt containing chromium comprising the steps of: maintaining said melt substantially free of surface slag, blowing oxygen gas from above onto said substantially slag free surface of said melt and subjecting said melt during carbon refining simultaneously to vigorous stirring by means of an inert gas being blown from under the surface of said melt as its surface is being kept substantially free of slag.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US262718A 1971-06-16 1972-06-14 Method of refining iron melts containing chromium Expired - Lifetime US3860418A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE07840/71A SE365546B (enrdf_load_stackoverflow) 1971-06-16 1971-06-16

Publications (1)

Publication Number Publication Date
US3860418A true US3860418A (en) 1975-01-14

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US262718A Expired - Lifetime US3860418A (en) 1971-06-16 1972-06-14 Method of refining iron melts containing chromium

Country Status (3)

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US (1) US3860418A (enrdf_load_stackoverflow)
GB (1) GB1397449A (enrdf_load_stackoverflow)
SE (1) SE365546B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4066442A (en) * 1976-02-04 1978-01-03 Jean Saleil Method of making chrome steel in an electric arc furnace
FR2457902A1 (fr) * 1979-05-29 1980-12-26 Daido Steel Co Ltd Procede d'affinage d'acier fondu contenant du chrome
US4529442A (en) * 1984-04-26 1985-07-16 Allegheny Ludlum Steel Corporation Method for producing steel in a top oxygen blown vessel

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2820707A (en) * 1954-06-07 1958-01-21 Henry J Kaiser Company Converter
US3248211A (en) * 1964-09-18 1966-04-26 South African Iron & Steel Refining of iron
US3313619A (en) * 1961-03-24 1967-04-11 Lorraine Laminage Iron refining processes
US3323906A (en) * 1964-08-12 1967-06-06 Nat Steel Corp Method of steelmaking
US3567430A (en) * 1968-06-11 1971-03-02 Allegheny Ludlum Steel Method of removing lead from molten austenitic stainless steel
US3647418A (en) * 1964-12-11 1972-03-07 Lucas S Moussoulos HIGH-RECOVERY PRODUCTION OF RICH FeNi ALLOYS IN A CONVERTER

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2820707A (en) * 1954-06-07 1958-01-21 Henry J Kaiser Company Converter
US3313619A (en) * 1961-03-24 1967-04-11 Lorraine Laminage Iron refining processes
US3323906A (en) * 1964-08-12 1967-06-06 Nat Steel Corp Method of steelmaking
US3248211A (en) * 1964-09-18 1966-04-26 South African Iron & Steel Refining of iron
US3647418A (en) * 1964-12-11 1972-03-07 Lucas S Moussoulos HIGH-RECOVERY PRODUCTION OF RICH FeNi ALLOYS IN A CONVERTER
US3567430A (en) * 1968-06-11 1971-03-02 Allegheny Ludlum Steel Method of removing lead from molten austenitic stainless steel

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4066442A (en) * 1976-02-04 1978-01-03 Jean Saleil Method of making chrome steel in an electric arc furnace
FR2457902A1 (fr) * 1979-05-29 1980-12-26 Daido Steel Co Ltd Procede d'affinage d'acier fondu contenant du chrome
US4529442A (en) * 1984-04-26 1985-07-16 Allegheny Ludlum Steel Corporation Method for producing steel in a top oxygen blown vessel
EP0160376A3 (en) * 1984-04-26 1989-07-26 Allegheny Ludlum Steel Corporation Method for producing steel in a top oxygen blown vessel

Also Published As

Publication number Publication date
SE365546B (enrdf_load_stackoverflow) 1974-03-25
GB1397449A (en) 1975-06-11

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