US3130095A - Production of oriented silicon-iron sheets by secondary recrystallization - Google Patents

Production of oriented silicon-iron sheets by secondary recrystallization Download PDF

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Publication number
US3130095A
US3130095A US813289A US81328959A US3130095A US 3130095 A US3130095 A US 3130095A US 813289 A US813289 A US 813289A US 81328959 A US81328959 A US 81328959A US 3130095 A US3130095 A US 3130095A
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Prior art keywords
annealing
atmosphere
iron
silicon
grains
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US813289A
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Dale M Kohler
John M Jackson
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Armco Inc
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Armco Inc
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Priority to US813289A priority Critical patent/US3130095A/en
Priority to GB14658/60A priority patent/GB942399A/en
Priority to FR826752A priority patent/FR1256776A/fr
Priority to BE590764A priority patent/BE590764A/fr
Priority to CH550960A priority patent/CH433414A/de
Priority to DEA34653A priority patent/DE1292695B/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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
    • C21D8/1272—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1277—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
    • C21D8/1283—Application of a separating or insulating coating

Definitions

  • the invention has to do with the production of highly oriented silicon-iron in sheet form, and it will be described in connection with the manufacture of siliconiron having an orientation in which a (100) plane is parallel to the sheet surface, and more particularly one which can be described as a (100) [001] orientation by Millers indices. For convenience this orientation will hereinafter be designated as cubic texture.
  • FIG. 1 is a diagrammatic representation of an annealing furnace and an associated gas treating apparatus.
  • FIG. 2 is a chart showing the relationship of the concentration of an additive to the annealing atmosphere
  • FIG. 3 is an energy diagram.
  • a silicon-iron sheet stock in which the planes of the crystals are parallel with the sheet surfaces, the [001] direction being randomly oriented, may have permeabilities substantially equal in the straight grain and cross rolling directions, but will have a higher permeability than that of a sheet stock characterized by truly random orientation.
  • a silicon-iron sheet stock characterized by a high degree of cubic texture is especially useful in the electrical arts because while it may have a permeability in the straight grain direction which is as high as or higher than that characteristic of any other orientation, it also has a relatively high permeability in the cross grain direction.
  • the present invention is based on the discovery that the presence in the annealing atmosphere, during secondary recrystallization, of minute amounts of certain highly polar compounds greatly facilitates the growth of crystals or grains having certain orientations at the expense of grains having other orientations in the silicon-iron sheet stock.
  • the phenomenon of differential crystal growth is due to the fact that certain orientations constitute lower energy positions as respects others, those crystals or grains which occupy lower energy positions tending to grow at the expense of those in higher energy positions. It is possible to grow crystals during secondary recrystallization which have their (111) planes, or (100) planes or planes parallel to the surfaces of the sheet stock. In the preceding sentence crystals having the respective orientations have been mentioned in their normal descending order of surface energy.
  • the arrow 1 which may be regarded as indicating ascending values of surface energies, carries opposite it certain planes 2, 3 and 4 which are representative of surface energy levels for crystals respectively oriented with the (111), (100) and (110) planes parallel to the surfaces of the sheet.
  • the surface energy of grains having the (111) orientation may be lowered to the level 5
  • the surface energy of grains having the (110) orientation may be lowered to the level 6
  • the highly polar compounds thus far investigated include oxides of carbon, oxides of sulphur, and hydrogen sulfide. It is believed that other highly polar compounds may well be the equivalents of those just mentioned. For example, hydrogen selenide would presumably act in the same way as hydrogen sulfide. Sulfur and carbon,
  • FIG. 2 which plots the results of a series of anneals at 2200 F. (in a mufile) using samples 3 cm. wide, where parts per million of hydrogen sulfide in a dry hydrogen annealing atmosphere having a dew point of -50 F. are plotted against the percentage of transformation to the cubic texture.
  • the curve marked 8 represents a material having a thickness of 12 mils.
  • the curve in FIG. 2 is submitted only as representative or illustrative since the percentage of transformation can be affected by various factorsgand the concentration of hydrogen sulfide for optimum results will vary somewhat depending on the width of the material being annealed, the size of the charge,
  • the manner in which the highly polar substances are introduced into the annealing atmosphere may be varied.
  • the base silicon-iron stock itself contains sulfur, as much of this sulfur as migrates to the surface of the stock can combine with constituents of an annealing atmosphere to form a polar compound.
  • a high content of sulfur in silicon-iron sheet stock is undesirable for other reasons.
  • the transformation of the stock to cubic texture requires a high temperature secondary recrystallization varying in time with the thickness of the stock; and the proper sulfur content of the atmosphere should be maintained throughout the entire time of the transformation of the stock.
  • the highly polar compounds can be formed in the annealing atmosphere from constituents in an annealing separator located between silicon-iron sheets in a stack or between the convolutions of a coil.
  • an annealing separator which otherwise may consist of calcined magnesia, alumina or other suitable substances
  • a hydrogen annealing atmosphere may react with a hydrogen annealing atmosphere to provide desired quantities of hydrogen sulfide.
  • Calcium sulfide dissociates but slowly at the temperature of the secondary recrystallization (around 2200 F.) and can readily be apportioned in the annealing separator to maintain the desired concentration of hydrogen sulfide in the atmosphere. It is not preferred, however, to rely on a constituent of the annealing separator alone to maintain the concentration of polar compound in the annealing gas, since in many furnaces there is no assurance that all parts of the annealing atmosphere will be equally treated.
  • an annealing separator can provide or produce a content of polar compound in the annealing atmosphere
  • the atmosphere can be treated directly in the furnace used for the secondary recrystallization.
  • a boat or receptacle of treatment substance can be placed in the furnace in such position that the entering atmosphere will come into contact with it.
  • a substance which vaporizes, sublimes or decomposes so slowly at the temperatures of secondary recrystallization that an excess quantity of the polar compound will not be introduced into the atmosphere, while the desired quantity will be maintained throughout the treatment time.
  • calcium sulfide is an example of a material which may be used, as are certain other metal sulfides.
  • a furnace. for secondary recrystallization is shown at It and a boat containing a treatment substance has been indicated in dotted lines at 11.
  • FIG. 1 a preliminary or pretreatment furnace is indicated at 12 through which the annealing gas passes on its way to the furnace 10.
  • the atmosphere may be treated to the extent desired and at a desired temperature which may differ from the temperature for secondary recrystallization.
  • the furnace 12 may contain a quantity of ferrous sulfide which will decompose sufiiciently slowly at, say, 900 F., to treat the atmosphere. It will also be understood that the preheating of the atmosphere in the furnace 12 will increase the efl'iciency of operation of the furnace 10.
  • annealing atmospheres may be used.
  • Argon and helium as examples of inert gases, normally contain minute quantities of oxygen. If such gases are passed through the furnace 12 when it contains ferrous sulfide or other suitable sulfur bearing compounds slowly reactable with the oxygen at the temperatures involved, the emerging gases will contain minute quantities of sulfur oxides and will be suitable for use in the furnace 10 to obtain the desired transformation.
  • the furnace 12 contains some carbon in suitable form (preferably, though not necessarily, an activated form of charcoal) the emerging gases will contain minute amounts of carbon monoxide, and the transformation of the silicon iron will be improved. It has been found that a very slight oxidation of the silicon-iron in the furnace 10, contrary to expectations, does not interfere with the transformation. Oxygen or moisture if present in such amounts as to form a grey film on the sheet surface should be removed from the atmosphere. The dew point, to avoid such an amount of oxidation, should generally be lower than -40 F.
  • Nitrogen is generally avoided as an annealing atmos phere for the reason that it appears to promote an indiscriminate grain growth, interfering with the desired transformation.
  • Hydrogen is entirely satisfactory and is preferred as an annealing atmosphere. It is cheaper than the inert gases; it is in itself a bright annealing medium; and it is readily freed from oxygen, Water vapor and like contaminants. If hydrogen is passed through the furnace 12 in contact with a sulfide such as ferrous sulfide, for example, it will pick up sulfur in the form of hydrogen sulfide. If the furnace 12 also contains carbon, the hydrogen will pick up carbon in some suitable form, although it is not clear just what that form is or whether it is the same in all instances.
  • a sulfide such as ferrous sulfide
  • a highor partial-vacuum anneal may be used and is meant to be included when annealing atmospheres are mentioned.
  • the highly polar compounds should be maintained in the furnace in such amounts that their partial pressures will be equivalent to those prevailing in the neutral or reducing atmospheres previously described, when the critical amounts of highly polarized compounds are present.
  • the partial pressure of hydrogen sulfide should be substantially within the range of 15 to 190 microns, which is the equivalent of 20 to 250 parts per million at atmospheric pressure, under the conditions prevailing for the determination of FIG. 2.
  • the highly polar compound shall exist in gaseous form in the annealing atmosphere prior to its sorption by the sheet surfaces.
  • sorption of a sulfur polar compound began at a temperature of about 950 F.
  • Hydrogen containing a highly polar sulfur compound was passed through the annealing furnace and burned in air upon its emergence therefrom, a content of sulfur in the annealing gas being indicated by a blue core in the flame.
  • the blue core disappeared.
  • the blue core reappeared in the flame when the material reached a temperature of about 1050 F., indicating that the sorption phenomenon was complete.
  • the blue core reappeared after a longer time of continued heating at rising temperature.
  • the content of highly polar compound in the annealing atmosphere should be maintained throughout the whole time of the secondary recrystalliza tion cycle necessary to produce the desired transformation. If this is not done, the transformation will be impeded.
  • Cir ulation of hydrogen without polar compound through the annealing mufllle will tend to remove polar compound which has been absorbed or adsorbed on the sheet surfaces, as can be determined by the persistence of the blue core for some time after the supply of polar compound has been cut off from the annealing gas.
  • WVhere sulfur treated annealing gas is used in accordance with the example throughout the secondary recrystallization cycle, tests have indicated that there is a very slight pickup of sulfur by the sheet stock, of the order of about 001%.
  • silicon-iron in the application is meant a ferrous metal containing substantially 2.5 to 4.0% silicon.
  • the metal should have a lngh degree of purity, by which is 6 meant freedom from carbon, nitrogen, oxygen, inclusions and the like. If the metal is open hearth metal, it will be decarburized in some suitable way. A decarburization in wet hydrogen as known in the art may be practiced, but if this is done, precautions should be taken to remove iron oxide and silica from the surfaces of the sheet stock. It is preferred to decarburize in a nonoxidizing atmosphere, e.g., dry hydrogen at a relatively high temperature of 1900 to 2200 F. as known in the art.
  • a siliconiron may be used containing from about 2.90 to 3.30% silicon, .007% or less carbon, from about .06 to .12% manganese, the remainder being substantially all iron with a total oxide content of .01% or less. Although some sulfur may be tolerated, it is preferred to have the metal low in sulfur.
  • the metal may be treated in various ways to provide a sheet product characterized by a sufiicient number of nuclei or grains having the cubic texture.
  • the starting material may be the highly oriented commercial silicon-iron characterized by a (110) [001] orientation, having a high permeability in the straight grain direction and a relatively low cross grain permeability.
  • Such material after a heat treatment in hydrogen at about 2200 F., is subjected to a cold rolling treatment producing a reduction of about 55 to 90%.
  • the cold rolled material is annealed in hydrogen at a temperature of about 2200 to 2350 F., after which it is cold rolled with a reduction of about 75 to Such a material is also in a condition to provide a substantial number of grains having the cubic orientation upon primary recrystallization.
  • the strips were found to have about of their area transformed to cubic texture, and the magnetic permeability measured parallel to the rolling direction of the strip was 1836 at an induction of 10 kilogausses.
  • the primary recrystallization may be carried on as a separate step, but can be and preferably is combined with the secondary recrystallization, since the primary recrystallization occurs quite rapidly during the heating-up of the material in the final furnace.
  • the presence of the polar compound in the annealing atmosphere does not interfere with the primary recrystallization.
  • the phenomenon of secondary recrystallization starts to occur at temperatures around 1900 F. and higher and requires a length of time sufficient to permit the desired grain growth.
  • the nuclei or crystals characterized by cubic texture either originally extend through the thickness of the sheet stock as a result of the primary recrystallization, or they rapidly grow during secondary recrystallization so as to extend through the thickness of the sheet. Then they begin to grow laterally at the expense of adjacent grains or crystals having other and higher energy orientations.
  • the annealing atmosphere during the secondary recrystallization should be controlled so that it does not permit a harmful degree of carburization, nitriding, or oxidation; but it should contain a gaseous polar compound capable of lowering the surface energ of the crystals as hereinabove explained. Expedients such as electropolishing the stock, rolling it on polished rolls and the like may be practiced if desired but are not ordinarily necessary.
  • the sheet stock may be formed from vacuum melted material if desired; but it is an advantage of the invention that excellent silicon-iron sheet stock characterized by cubic orientation can be made from air melted metal such as produced in the open hearth or electric furnace.
  • nuclei or grains having the cubic texture orientation is meant not only grains precisely oriented in the (100) [001] position by Millers indices, but also grains departing from that orientation by no more than about 5 degrees.
  • the presence of the highly poiar compound in the annealing gas so greatly facilitates the transformation that in many instances satisfactory material may be made in a final heat treatment or secondary recrystallization step which is an open or continuous anneal as distinguished from a box anneal.
  • Materials may be made, of course, with difierent degrees of perfection of the cubic texture orientation; but for purposes of this application a sheet stock characterized by cubic texture orientation may be taken as one in which at least the majority of the surface area is composed of grains having a (100) [001] orientation by Millers indices.
  • carbon in gaseous form is employed along with some other highly polar compound such as hydrogen sulfide, it is usedin amounts generally less than the amounts of the other polar compound present, and may be used in such amounts as to be in equilibrium with a carbon content of about .005 in the silicon-iron.
  • a process of making silicon-iron sheets having a high proportion of cube-on-face grains comprising annealing cold rolled sheets of silicon-iron at a temperature of at least about 1900 F. in an atmosphere of dry hydrogen, said atmosphere containing a vapor of a sulfur containing compound which will dissociate at the annealing temperature to produce elemental sulfur, the partial pressure of said vapor being in the range of from 15 to microns of mercury, and continuing the annealing until substantially complete cube-on-face grain growth by secondary recrystallization takes place.
  • a process of making silicon-iron sheet stock characterized by cubic texture orientation which comprises providing a silicon-iron sheet stock characterized by a num ber of grains having a (100) [001] orientation, subjecting said stock to secondary recrystallization at an elevated temperature in an enclosure containing a highly polar substance comprising a compound of sulfur entrained in an annealing atmosphere in a concentration at the sheet surface of substantially 20 to 250 parts per million at atmospheric pressure when said enclosure is filled with said atmosphere, said annealing atmosphere other than said sulfur compound being chosen from the class consisting of argon, helium, and hydrogen at a pressure substantially no greater than atmospheric.

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US813289A 1959-05-14 1959-05-14 Production of oriented silicon-iron sheets by secondary recrystallization Expired - Lifetime US3130095A (en)

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Application Number Priority Date Filing Date Title
US813289A US3130095A (en) 1959-05-14 1959-05-14 Production of oriented silicon-iron sheets by secondary recrystallization
GB14658/60A GB942399A (en) 1959-05-14 1960-04-26 The production of oriented silicon-iron sheets by secondary recrystallization
FR826752A FR1256776A (fr) 1959-05-14 1960-05-10 Procédé de fabrication de tôles de fer au silicium hautement orientées
BE590764A BE590764A (fr) 1959-05-14 1960-05-12 Préparation de fer au silicium fortement orienté
CH550960A CH433414A (de) 1959-05-14 1960-05-13 Verfahren zur Herstellung von Silicium-Eisen-Blech
DEA34653A DE1292695B (de) 1959-05-14 1960-05-14 Verfahren zur Erzeugung von Wuerfeltextur in Eisen-Silicium-Blechen

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3240638A (en) * 1964-10-21 1966-03-15 Westinghouse Electric Corp Use of silicon steel alloy having a critical sulfur range to insure cube-onface orientation
US3333992A (en) * 1964-06-29 1967-08-01 Armco Steel Corp Production of oriented silicon-iron using grain growth inhibitor during primary recrystallization heat treatment
US3333993A (en) * 1965-04-02 1967-08-01 Armco Steel Corp Production of thin, oriented siliconiron wherein grain growth inhibitor is added to primary recrystallization heat treatment atmosphere as function of mn content and final thickness
US3540948A (en) * 1967-12-18 1970-11-17 United States Steel Corp Method of producing cube-on-corner oriented electrical steel sheet
US4997493A (en) * 1987-11-27 1991-03-05 Nippon Steel Corporation Process for production of double-oriented electrical steel sheet having high flux density
EP0452153A3 (de) * 1990-04-12 1992-12-30 Nippon Steel Corporation Verfahren zum Herstellen doppeltorientierter Elektrobleche mit hoher magnetischer Flussdichte

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2192756A (en) * 1937-02-24 1940-03-05 Gen Electric Treatment of ferrous metal
US2227156A (en) * 1938-09-20 1940-12-31 Gen Electric Treatment of electrical apparatus
US2303343A (en) * 1941-01-14 1942-12-01 Carnegie Illinois Steel Corp Silicon steel electrical strip
US2455632A (en) * 1946-12-17 1948-12-07 American Steel & Wire Co Silicon electrical steel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2192756A (en) * 1937-02-24 1940-03-05 Gen Electric Treatment of ferrous metal
US2227156A (en) * 1938-09-20 1940-12-31 Gen Electric Treatment of electrical apparatus
US2303343A (en) * 1941-01-14 1942-12-01 Carnegie Illinois Steel Corp Silicon steel electrical strip
US2455632A (en) * 1946-12-17 1948-12-07 American Steel & Wire Co Silicon electrical steel

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3333992A (en) * 1964-06-29 1967-08-01 Armco Steel Corp Production of oriented silicon-iron using grain growth inhibitor during primary recrystallization heat treatment
US3240638A (en) * 1964-10-21 1966-03-15 Westinghouse Electric Corp Use of silicon steel alloy having a critical sulfur range to insure cube-onface orientation
US3333993A (en) * 1965-04-02 1967-08-01 Armco Steel Corp Production of thin, oriented siliconiron wherein grain growth inhibitor is added to primary recrystallization heat treatment atmosphere as function of mn content and final thickness
US3540948A (en) * 1967-12-18 1970-11-17 United States Steel Corp Method of producing cube-on-corner oriented electrical steel sheet
US4997493A (en) * 1987-11-27 1991-03-05 Nippon Steel Corporation Process for production of double-oriented electrical steel sheet having high flux density
EP0452153A3 (de) * 1990-04-12 1992-12-30 Nippon Steel Corporation Verfahren zum Herstellen doppeltorientierter Elektrobleche mit hoher magnetischer Flussdichte
US5346559A (en) * 1990-04-12 1994-09-13 Nippon Steel Corporation Process for manufacturing double oriented electrical steel sheet having high magnetic flux density

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GB942399A (en) 1963-11-20
DE1292695B (de) 1969-04-17
BE590764A (fr) 1960-09-01
CH433414A (de) 1967-04-15

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