US3116179A - Production of non-oriented ferrous magnetic materials - Google Patents

Production of non-oriented ferrous magnetic materials Download PDF

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Publication number
US3116179A
US3116179A US58715A US5871560A US3116179A US 3116179 A US3116179 A US 3116179A US 58715 A US58715 A US 58715A US 5871560 A US5871560 A US 5871560A US 3116179 A US3116179 A US 3116179A
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United States
Prior art keywords
iron
atmosphere
annealing
carbon
hot
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Expired - Lifetime
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US58715A
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English (en)
Inventor
Victor W Carpenter
John M Jackson
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Armco Inc
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Armco Inc
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Publication date
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Priority to US58715A priority Critical patent/US3116179A/en
Priority to BE607960A priority patent/BE607960A/fr
Priority to SE9032/61A priority patent/SE304032B/xx
Priority to ES0270590A priority patent/ES270590A1/es
Priority to FR873971A priority patent/FR1309273A/fr
Priority to DE19611408931 priority patent/DE1408931A1/de
Priority to GB34765/61A priority patent/GB994080A/en
Application granted granted Critical
Publication of US3116179A publication Critical patent/US3116179A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/147—Alloys characterised by their composition
    • H01F1/14766—Fe-Si based alloys
    • H01F1/14775—Fe-Si based alloys in the form of sheets
    • H01F1/14783—Fe-Si based alloys in the form of sheets with insulating coating
    • 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
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following hot rolling
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1255—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest with diffusion of elements, e.g. decarburising, nitriding

Definitions

  • the invention relates to the production of ferrous strip or sheet materials by a process which includes the basic steps of hot rolling the material to an intermediate gauge, decarburizing the material by annealing it with the hot mill scale still on its surfaces, cleaning the surfaces of the material, and then cold rolling it to gauge.
  • processes including these basic steps are particularly useful in the production of low carbon steels and silicon-iron sheets or strips for magnetic uses. Since the materials are usually non-oriented, they have numerous electrical uses, as for example in rotating electrical machinery and in certain types of transformers, in which uses core laminations are formed by stamping or diecutting. Consequently the die life of the material is of importance.
  • the chemistry of the material is not a limitation on the invention, excepting as to the carbon content; and the material may range from low carbon steels to silicon-iron alloys containing from about 0.5% to about 3.5% silicon. lt has long been known that annealing such materials in an intermediate gauge hot rolled condition with the hot mill scale or oxide still on their surfaces will result in an effective decarburization. The decarburization occurs through the interaction of the surface oxide with the carbon in the steel. When the intermediate hot rolled gauge is about 0.06 to .10 in.
  • a box anneal in the presence of the mill scale can be depended upon to reduce the carbon content to a value less than about .01% yas taught in U.S. Patent No. 2,236,519.
  • the mill scale is reduced or partially reduced, leaving on the surfaces of the stock a layer of substance which is exceedingly' difcult to remove either by abrasion or by pickling or both. But it is not practicable to leave this layer in place during the subsequent cold rolling not only because improper surface characteristics may be attained but also because the material will have a poor die life and will be unsuitable for punching.
  • lt is a fundamental object of the invention to provide a process including the basic steps set forth above, which will be devoid of the above defects.
  • coils of hot rolled ferrous material bearing the hot mill scale have been given box anneals, the air being generally liushed from the box, and the atmosphere remaining being that which is generated by the action of the carbon from the steel with the scale on the strip.
  • the decarburization is accompanied by a reduction of some or all of the iron oxide in the scale, leaving generally a dispersion of oxide in a matrix of iron, and in the case of siliconiron materials, a dispersion of silica or silicates along with iron oxide in a matrix of iron.
  • FIG. 1 is a diagram in which the ratio of hydrogen to water vapor in the annealing latmosphere is plotted against temperature.
  • FIG. 2 is a diagram in which the ratio 0f carbon dioxide to carbon monoxide is plotted against temperature in the ⁇ annealing operation.
  • one of the advantages of this invention is the provision of a box anneal which will be effective both for decarburization and for oxidation of the materials remaining upon the surfaces of the stock, so that this layer may be readily removed.
  • One of the objects of the invention is to accomplish both operations at a minimum of cost.
  • One way of accomplishing the objects of the invention is to control the atmosphere during the box anneal in such a way that it is oxidizing to carbon but reducing to iron. While the decarburization will 4take place whether the atmosphere be oxidizing, reducing, or neutral, the decarburization generally occurs in a lesser time if the atmosphere is initially controlled as indicated. When the decarburization is complete, the atmosphere may then be changed so as to oxidize the reduced scale layer on the strip.
  • Another way in which the objects of the invention can be accomplished is to control the atmosphere so that, while the steel will be decarburized, the surface layer of materials will remain in the oxidized form during the entire cycle. This also has been found to give a surface layer which is readily removed.
  • Coils may be wound with narrow corrugated metal strips located at their edges so as to separate the convolutions. Also coils may be wound with wire or nylon strands or the like between the convolutions, these intermediate members being removed before or after the coils have been annealed. The convolutions will then stand apart from each other so as to permit the annealing atmosphere to pass between them. Furthermore, it is possible so to design a box or furnace that the annealing atmosphere will be blown toward one end of each coil so as to pass continuously between the convolutions and keep all parts of the coil surfaces bathed in a substantially constant composition of atmosphere.
  • annealing atmosphere including air where constant oxidizing conditions are to be maintained.
  • gases including air where constant oxidizing conditions are to be maintained.
  • gases having a reducing potential will be used.
  • gases including partially coinbusted hydrocarbon gases, cracked ammonia and various mixtures of hydrogen, nitrogen and water vapor.
  • the reducing potential will normally he derived either from a hydrogentwater vapor ratio, or from a carbon dioxide: carbon monoxide ratio, or both.
  • varying hydrogen: water vapor ratios have been plotted in FIG. 1 against annealing temperatures.
  • the curves demark areas which are respectively designated as Fe, FeO and Fe304.
  • Fe the conditions shown on the chart are reducing toward, iron, while the other areas indicate conditions which are oxidizing toward iron in a greater or less degree.
  • FIG. 2 where the carbon dioxidezcarbon monoxide ratios have been plotted against temperature, like areas indicate conditions which are reducing or oxidizing toward iron.
  • the actual conditions of operation can be determined in accordance with the economics of the process. Ternperatures and atmospheres can be chosen such that decarburization is most rapid while scale formation is at a minimum. Preferred temperatures of operation lie between about l300 F. and 1600 F.
  • Example I Silicon-iron containing about 2.19% silicon and 0.029% carbon was decarburized for 2 hours at 1500 F. in a mixture of hydrogen, nitrogen and water vapor. The HQI/H2O ratio was 0.2. The nal carbon Content was 0.0054% and the surface was fully oxidized and readily blasted.
  • Example Il The same starting material was decarburized to 0.0069% carbon under the same conditions except that the liz/H2O ratio was 4.0. A layer of reduced iron remained on the surface of the material. Reheating for 2 hours at 1300 F. in an atmosphere having a Hz/HZO ratio of 0.2 caused the surface to be almost completely reoxidized. A similar treatment at l500 F. resulted in complete reoxidization. In commercial practice it is preferred to avoid a change in the fig/H2O or CO2/CO ratios during the decarburizing step by using a low Iig/H2O ratio and a high CO2/CO ratio throughout the anneal.
  • the anneal is carried on in those areas of FlGS. l and 2 denoted by the designations Fe() or Fe304. In these areas, the greater the oxidizing potential of the gas the lower the carbon will be in the finished product.
  • the invention has been disclosed in connection with a process involving the basic steps of hot rolling, decarburizing, and cold rolling, with an intermediate cleaning or pickling of the material between the decarburization step and the cold rolling step. It will be understood that the principles of the invention 4may be carried out in more elaborate processes, and that the spirit of the invention is not violated by the addition of other steps, either during the hot rolling, or more particularly following the cold rolling to a gauge which is either the final gauge or close to it. For example, the addition of final heat treatments to improve the magnetic qualities of the material may be practiced without departing from the invention. Also it is Within the purview of the invention to subject the decarburized and oxidized material to further hot rolling with or without subsequent cold rolling.
  • box annealing has been employed herein, it is to be understood that it is not confined to the use of a metal annealing box covering the coils of iaterial to be treated, the whole being enclosed in a furnace. It is intended to be construed broadly enough to include the use of a muffle furnace which serves in lieu of both the box and the exterior furnace elements in which the box is used.
  • muille furnaces may be electrically heated, or preferably heated by radiant tubes containing the products of combustion from burners. In some instances the products of burner combustion may be introduced directly into the muflle and may be so controlled as to give the desired effects upon the material being treated.
  • a process of producing low carbon ferrous strip 0r sheet materials consisting essentially of the steps of hot rolling ferrous material to an intermediate gauge, box annealing the material with the hot mill scale still on its surfaces whereby to effect solid state decarburization of the strip through the reaction of carbon therein with the iron oxide of the said hot rnill scale on the surfaces of the strip, cleaning the surfaces of the material and then cold rolling the material to gauge, wherein the hot rolled material is annealed in a single Inutile and in open coils all surfaces of which are bathed by an annealing atmosphere, and in which the annealing atmosphere is controlled so as to be oxidizing to iron at least at the end of the annealing treatment, whereby the material is decarburized and the product is left with a surface coating consisting substantially of oxides of iron which is easily removed by cleaning operations.
  • ferrous material has an initial carbon content not above about 0.10% and a final carbon content not in excess of about 0.01%.
  • ferrous material is a silicon-iron alloy containing from about .5% to about 3.5% silicon.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Electromagnetism (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
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US58715A 1960-09-27 1960-09-27 Production of non-oriented ferrous magnetic materials Expired - Lifetime US3116179A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US58715A US3116179A (en) 1960-09-27 1960-09-27 Production of non-oriented ferrous magnetic materials
BE607960A BE607960A (fr) 1960-09-27 1961-09-07 Fabrication de bandes ou de tôles en fer
SE9032/61A SE304032B (es) 1960-09-27 1961-09-11
ES0270590A ES270590A1 (es) 1960-09-27 1961-09-18 Procedimiento de obtenciën de flejes o planchas de materiales ferrosos de bajo contenido de carbono
FR873971A FR1309273A (fr) 1960-09-27 1961-09-22 Procédé d'obtention de matériaux ferreux en bandes ou feuilles à basse teneur en carbone
DE19611408931 DE1408931A1 (de) 1960-09-27 1961-09-23 Verfahren zur Herstellung von kohlenstoffarmen Eisenband oder-blech
GB34765/61A GB994080A (en) 1960-09-27 1961-09-27 The production of non-oriented ferrous magnetic materials

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US58715A US3116179A (en) 1960-09-27 1960-09-27 Production of non-oriented ferrous magnetic materials

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US3116179A true US3116179A (en) 1963-12-31

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US (1) US3116179A (es)
BE (1) BE607960A (es)
DE (1) DE1408931A1 (es)
ES (1) ES270590A1 (es)
GB (1) GB994080A (es)
SE (1) SE304032B (es)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3926688A (en) * 1973-01-30 1975-12-16 Cockerill Method of manufacturing a flat steel product having an oxidation-resistant coating
US3932235A (en) * 1973-07-24 1976-01-13 Westinghouse Electric Corporation Method of improving the core-loss characteristics of cube-on-edge oriented silicon-iron
US4127429A (en) * 1976-07-05 1978-11-28 Kawasaki Steel Corporation Forsterite insulating films formed on surface of a grain-oriented silicon steel sheet having a high magnetic induction and a method of forming the same
US4173500A (en) * 1976-06-25 1979-11-06 Oiles Kogyo Kabushiki Kaisha Process for producing porous cast iron
DE19816200A1 (de) * 1998-04-09 1999-10-14 G K Steel Trading Gmbh Verfahren zur Herstellung eines Forsterit-Isolationsfilms auf einer Oberfläche von korn-orientierten, anisotropen, elektrotechnischen Stahlblechen

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011119395A1 (de) * 2011-06-06 2012-12-06 Thyssenkrupp Electrical Steel Gmbh Verfahren zum Herstellen eines kornorientierten, für elektrotechnische Anwendungen bestimmten Elektrostahlflachprodukts

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2236519A (en) * 1936-01-22 1941-04-01 American Rolling Mill Co Method of producing silicon steel sheet or strip
US2287467A (en) * 1940-01-03 1942-06-23 American Rolling Mill Co Process of producing silicon steel
US2455632A (en) * 1946-12-17 1948-12-07 American Steel & Wire Co Silicon electrical steel
US2533394A (en) * 1947-02-20 1950-12-12 Armco Steel Corp Method of obtaining large grain size in silicon steel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2236519A (en) * 1936-01-22 1941-04-01 American Rolling Mill Co Method of producing silicon steel sheet or strip
US2287467A (en) * 1940-01-03 1942-06-23 American Rolling Mill Co Process of producing silicon steel
US2455632A (en) * 1946-12-17 1948-12-07 American Steel & Wire Co Silicon electrical steel
US2533394A (en) * 1947-02-20 1950-12-12 Armco Steel Corp Method of obtaining large grain size in silicon steel

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3926688A (en) * 1973-01-30 1975-12-16 Cockerill Method of manufacturing a flat steel product having an oxidation-resistant coating
US3932235A (en) * 1973-07-24 1976-01-13 Westinghouse Electric Corporation Method of improving the core-loss characteristics of cube-on-edge oriented silicon-iron
US4173500A (en) * 1976-06-25 1979-11-06 Oiles Kogyo Kabushiki Kaisha Process for producing porous cast iron
US4127429A (en) * 1976-07-05 1978-11-28 Kawasaki Steel Corporation Forsterite insulating films formed on surface of a grain-oriented silicon steel sheet having a high magnetic induction and a method of forming the same
DE19816200A1 (de) * 1998-04-09 1999-10-14 G K Steel Trading Gmbh Verfahren zur Herstellung eines Forsterit-Isolationsfilms auf einer Oberfläche von korn-orientierten, anisotropen, elektrotechnischen Stahlblechen

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Publication number Publication date
BE607960A (fr) 1962-01-02
SE304032B (es) 1968-09-16
DE1408931A1 (de) 1969-05-08
ES270590A1 (es) 1962-02-16
GB994080A (en) 1965-06-02

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