US2875113A - Method of decarburizing silicon steel in a wet inert gas atmosphere - Google Patents

Method of decarburizing silicon steel in a wet inert gas atmosphere Download PDF

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Publication number
US2875113A
US2875113A US696616A US69661657A US2875113A US 2875113 A US2875113 A US 2875113A US 696616 A US696616 A US 696616A US 69661657 A US69661657 A US 69661657A US 2875113 A US2875113 A US 2875113A
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Prior art keywords
silicon steel
decarburizing
carbon
inert gas
steel
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US696616A
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English (en)
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Elmore J Fitz
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General Electric Co
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General Electric Co
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Priority to US696616A priority Critical patent/US2875113A/en
Priority to CH6604358A priority patent/CH377867A/de
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/04—Decarburising

Definitions

  • the present invention relates to magnetic silicon steel for electrical uses, such as in transformers, motors and other electromagnetic apparatus, and more particularly to an improved process of producing decarburized silicon steel.
  • the silicon steel material to which the present invention relates normally contains about 3% silicon, but the silicon content may vary between 1% and 4%.
  • the carbon content of silicon steel ingots used as starting material for making electrical steel of the type herein concerned is generally. about 0.05% or less, with values of 0.020 to 0.030% carbon being typical. It is generally accepted that the lower the carbon content of processed silicon steel, the better are its ultimate magnetic properties. Even the above relatively small percentages of carbon will cause the watt loss of the final magnetic strip to be undesirably high if it is not further reduced in the course of processing themetal. The maximum amount of carbon tolerable from the standpoint of low Watt losses is now considered to be about 0.006%.
  • the conventional method of processing silicon steel material of the above type is to subject it to a series of rolling and heat treating (annealing) steps for reducing the material to strip formof desired gauge while'removing undesired impurities and internal strains therefrom.
  • annealing rolling and heat treating
  • the rolled material is usually subjected to a heat treatment of about 950 C. for softening the strip to facilitate further rolling and to relieve the strains therein.
  • the strip is subjected to a decarburizing treatment to reduce the carbon content to a minimum.
  • This treatment in the past, has been carried out in decarburizing atmospheres at a temperature of about 800 C., which was considered by the prior art to aiford the most eifective removal of the carbon in the shortest possible time. Temperatures higher than that range and particularly above 900 C. were found, using prior processes, to result either in less carbon removal or require longer heating periods, or both.
  • the decarburizing treatment has conventionally been carried out in a stage separate from the intermediate strain-relief anneal in which tempera.- tures well above 900 C. are most effective.
  • the decarburizing action produced in accordance withthe invention is effected chiefly by the moisture component of the present gas mixture and that the remaining gas component or components serve merely as diluents for the water vapor and should be inert'to the metal and its constituents.
  • reactive gases such as oxygen and hydrogen, and carbon bearing gases such, aswcarbon dioxide
  • a pure inert diluent gas h as n en i 1 3 51 as a vehicle for the decarbu'rizing water vapor While nitrogen is a particularly suitable inert as, especially from an economic standpoint, other inert types of gases such as argon, helium, krypton, neon and the like, or mixtures thereof, may alternatively be used where appropriate.
  • the proportion of water vapor used with the nitrogen or equivalent gas is not critical in the present invention, it having been found that substantially the same results iirterms of carbon removal are obtained whether the atmosphere is saturated with "moisture or contains only arelatively small proportion thereof.
  • successful ,decarburization has been accomplished with dew points as low as +40? F.
  • dew points above 35 F. since the process isthen lesssensitive to slight variations in surface preparation. Raising the dew point above 35 F. does not improve the efiicieney of the process but does offer the practical advantage of making it possible to add the desired water vapor to the pure inert gas by passing the latter through a water bath at room temperature, e.
  • the steel surface is thoroughly cleaned prior to the decarburiaing treatment, especially for the "purpose of removing any. scale which may result from a prior hot-rolling stage.
  • the steel may be shot-blasted, pickled in an acid solution, e. g., hydrochloric and hydrofluoric acid mixture, and then washed in water.
  • the cleaning action should be sufliciently thorough to provide a clean, bright surface on the steel. Itis also desirable to remove any grease on the surface, and this may be accomplished, for example, by passing the material through a conventional vapor degreaser prior to its entrance into the decarburizing chamber.
  • Decarburization as carried out by the present process is particularly effective in the temperature range of 875 to 1025 C., which is in contrast with prior art teaching that best decarburization is achieved at a temperature of less than 875 C. Since the optimum temperature range for the stress-relief anneal is about 925 to 955 C., the present process is eminently suited for combination with the stress-relief anneal treatment in processing the silicon steel. , The time required for I maximum removal of carbon using the present process is of the order of minutes or less.
  • a silicon steel ingot containing about 3% silicon and .02% carbon is initially hot rolled to about .085 inch and after removal of the scale and other impurities by a pre-cleaning step, it is cold rolled to about .028 inch. Then the steel strip is subjected to a combined strain-relief anneal and decarburizing treatment in a pure wet nitrogen atmosphere at a temperature of about 925 to 955 C. for about four minutes. Thereafter, the decarburized strip is cold rolled to a gauge of .012-.0l4 inch. The material thus produced is ready for further refining and grain growth processes well known in the art.
  • the pre-cleaning step may be carried out immediately after the hot rolling stage as described, or it may be deferred until just prior to the combined strain-relief and decarburizing treatment.
  • silicon steel strip may be made with virtually the minimum detectable carbon content, and it may be effectively produced by the use of a decarburizing heat treatment having a relatively wide range of temperature as compared to the temperatures previously considered optimum in the prior art for reducing carbon to minimum levels.
  • a decarburizing heat treatment having a relatively wide range of temperature as compared to the temperatures previously considered optimum in the prior art for reducing carbon to minimum levels.
  • the invention of the combination of decarburizing and annealing steps using elevated temperatures of well above the 900 C. level which is opt1- mum for annealing purposes, thus enabling the elimination of the usual final decarburizing step, and in addition providing for carbon contents lower than obtained by any of the conventional decarburizing treatments in equivalent periods of time.
  • the method of treating silicon steel which comprises pre-cleaning the silicon steel, and heating the silicon steel at a temperature of 875-1025 C. in an atmosphere of pure wet inert gas.
  • the method of treating silicon steel which comprises pre-cleaning the silicon steel to provide a clean, bright surface thereon, and heating the silicon steel at a temperature of 8751025 C. in an atmosphere of pure inert gas containing water vapor.
  • the method of treating silicon steel which comprises pre-cleaning the silicon steel to provide a clean, bright surface thereon, and heating the silicon steel at a temperature of 925 C.9S5 C. in an atmosphere of pure nitrogen containing water vapor sufficient to provide a dew point of at least about 40 F.
  • decarburized silicon steel which comprises hot rolling silicon steel material to an intermediate gauge, cleaning the hot rolled silicon steel material to provide a clean, bright surface thereon, cold rolling the thus treated silicon steel material to a further reduced gauge, subjecting the silicon steel material to a temperature of 925 C.955 C. in an atmosphere of pure inert gas containing water vapor to provide a combined decarburization and stress-relief anneal, and cold rolling the thus treated material to final gauge.
  • the steps of pre-cleaning the silicon steel to provide a clean, bright surface thereon, and thereafter subjecting th chased i i Steel to a c mb n d strai and decarburizing treatment which comprises heating the silicon steel at a temperature of 925 C.955 C. in an atmosphere of pure inert gas containing water vapor sufiicient to provide a dew point of at least about -40 F.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
US696616A 1957-11-15 1957-11-15 Method of decarburizing silicon steel in a wet inert gas atmosphere Expired - Lifetime US2875113A (en)

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US696616A US2875113A (en) 1957-11-15 1957-11-15 Method of decarburizing silicon steel in a wet inert gas atmosphere
CH6604358A CH377867A (de) 1957-11-15 1958-11-11 Verfahren zur Entkohlung von Siliziumstahl

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3105782A (en) * 1960-10-10 1963-10-01 Gen Electric Method of producing magnetic material
US3108912A (en) * 1960-10-05 1963-10-29 Gen Electric Magnetic material
US3149006A (en) * 1963-01-31 1964-09-15 William T Abel Prevention of embrittlement of metals
US3188246A (en) * 1961-12-04 1965-06-08 Armco Steel Corp Method of manufacturing drawing steel
US3201294A (en) * 1962-01-19 1965-08-17 Lysaght Australia Ltd Method of decarburizing electrical steel by using an oxide film
US3207639A (en) * 1960-02-16 1965-09-21 Mobius Hans-Eberhard Production of cube texture in sheets and strips of silicon and/or aluminum containing iron alloys
US3282747A (en) * 1964-04-13 1966-11-01 Westinghouse Electric Corp Annealing cube texture iron-silicon sheets
US4054471A (en) * 1976-06-17 1977-10-18 Allegheny Ludlum Industries, Inc. Processing for cube-on-edge oriented silicon steel
US4213804A (en) * 1979-03-19 1980-07-22 Allegheny Ludlum Industries, Inc. Processing for cube-on-edge oriented silicon steel
US4285742A (en) * 1979-11-29 1981-08-25 Boc Limited Heat treatment method
US4359351A (en) * 1979-10-23 1982-11-16 Air Products And Chemicals, Inc. Protective atmosphere process for annealing and or spheroidizing ferrous metals
US20090123651A1 (en) * 2005-10-14 2009-05-14 Nobuyoshi Okada Continuous Annealing and Hot Dip Plating Method and Continuous Annealing and Hot Dip Plating System of Steel sheet Containing Si

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010032919B4 (de) * 2010-07-30 2023-10-05 Air Liquide Deutschland Gmbh Verfahren und Vorrichtung zum Befeuchten eines brennbaren Gases

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1358810A (en) * 1919-04-04 1920-11-16 Westinghouse Electric & Mfg Co Process of treating magnetizable material
US2287467A (en) * 1940-01-03 1942-06-23 American Rolling Mill Co Process of producing silicon steel
US2534141A (en) * 1948-01-14 1950-12-12 Gen Electric Heat-treatment of cold rolled silicon steel strip

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1358810A (en) * 1919-04-04 1920-11-16 Westinghouse Electric & Mfg Co Process of treating magnetizable material
US2287467A (en) * 1940-01-03 1942-06-23 American Rolling Mill Co Process of producing silicon steel
US2534141A (en) * 1948-01-14 1950-12-12 Gen Electric Heat-treatment of cold rolled silicon steel strip

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3207639A (en) * 1960-02-16 1965-09-21 Mobius Hans-Eberhard Production of cube texture in sheets and strips of silicon and/or aluminum containing iron alloys
US3108912A (en) * 1960-10-05 1963-10-29 Gen Electric Magnetic material
US3105782A (en) * 1960-10-10 1963-10-01 Gen Electric Method of producing magnetic material
US3188246A (en) * 1961-12-04 1965-06-08 Armco Steel Corp Method of manufacturing drawing steel
US3201294A (en) * 1962-01-19 1965-08-17 Lysaght Australia Ltd Method of decarburizing electrical steel by using an oxide film
US3149006A (en) * 1963-01-31 1964-09-15 William T Abel Prevention of embrittlement of metals
US3282747A (en) * 1964-04-13 1966-11-01 Westinghouse Electric Corp Annealing cube texture iron-silicon sheets
US4054471A (en) * 1976-06-17 1977-10-18 Allegheny Ludlum Industries, Inc. Processing for cube-on-edge oriented silicon steel
US4213804A (en) * 1979-03-19 1980-07-22 Allegheny Ludlum Industries, Inc. Processing for cube-on-edge oriented silicon steel
US4359351A (en) * 1979-10-23 1982-11-16 Air Products And Chemicals, Inc. Protective atmosphere process for annealing and or spheroidizing ferrous metals
US4285742A (en) * 1979-11-29 1981-08-25 Boc Limited Heat treatment method
US20090123651A1 (en) * 2005-10-14 2009-05-14 Nobuyoshi Okada Continuous Annealing and Hot Dip Plating Method and Continuous Annealing and Hot Dip Plating System of Steel sheet Containing Si

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Publication number Publication date
CH377867A (de) 1964-05-31

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