US3653984A - Method for annealing silicon steel strip for use as material of electric machinery - Google Patents

Method for annealing silicon steel strip for use as material of electric machinery Download PDF

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Publication number
US3653984A
US3653984A US819876A US3653984DA US3653984A US 3653984 A US3653984 A US 3653984A US 819876 A US819876 A US 819876A US 3653984D A US3653984D A US 3653984DA US 3653984 A US3653984 A US 3653984A
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Prior art keywords
coil
annealing
steel strip
silicon steel
slurry
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US819876A
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English (en)
Inventor
Nobuo Urushiyama
Minoru Yosho
Takamitu Miyata
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Nippon Steel Corp
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Nippon Steel Corp
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
    • C21D1/70—Temporary coatings or embedding materials applied before or during heat treatment while heating or quenching
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire

Definitions

  • ABSTRACT Method for annealing silicon steel strip which has been coated with a slurry of such metal-hydroxides as are capable of forming a glassy film on the surface of said silicon steel strip, which has been wound into a coil, and which has been annealed in the desired atmosphere, thereby contracting the volume of the so applied metal-hydroxides, so as to produce a space between coil-layers.
  • the present invention relates, in general, to a method for annealing silicon steel strip, and more particularly, to a method for annealing silicon steel strip used for making electric machinery, which strip is wound into a coil, in a box or a batch-type furnace.
  • Silicon steel strip is generally wound into a coil so as to be subjected to annealing for such purposes as decarburizing and finishing-annealing.
  • a coil is so tightly wound that an effective atmospheric gas cannot enter between coil-layers, making necessary a longer time for annealing.
  • loose coil type methods according to which a space is produced between coil-layers, so that an atmospheric gas of high temperature can be driven through the space between coil-layers.
  • such loose coil there are available such methods as the one according to which metal wire is interposed between coil-layers and taken out just before the coil is charged into the annealing furnace, whereby there is formed a loose coil; the one according to which a coil is made with such metal wire or any other material that will produce a space between coil-layers, interposed between coillayers, and the thus formed loose coil is charged into the annealing furnace with said space-producing material; and the one according to which a coil is made with such combustible material as paper tape, interposed between coil-layers, and said combustible material is burned in the annealing furnace to produce a space between coil-layers, whereby there is formed a loose coil.
  • An object of the present invention is to provide a silicon steel strip annealing method developed to overcome the drawbacks of the conventional methods in which a loose coil is formed very easily and efficiently, and concurrently a film which is also useful as insulation, is formed on the surface of silicon steel strip.
  • Another object of the present invention is to provide a method for box or batch annealing of silicon steel strip.
  • Another object of the present invention is to provide a method for box or batch annealing, in which a glassy film is formed on the surface of silicon steel strip.
  • the present invention comprises a method for annealing silicon steel strip, which is characterized by applying a slurry of such metal-hydroxides as are capable of forming a glassy film by the reaction with SiO contained in the surface of silicon steel strip in the annealing atmosphere, winding the coated steel strip into a coil, annealing said coil in the desired annealing atmosphere to evaporate the combined water of the applied metal-hydroxides, thereby contracting the volume of said metal-hydroxide and producing a space between coil-layers, and annealing with an atmospheric gas flowing uniformly between coil-layers through the thus formed space from the lower end of said coil.
  • FIG. 1 is a diagrammatic view of an apparatus for applying the material for forming a film during the annealing according to the present invention.
  • FIG. 2 is a sectional view of a batch-type furnace for use in the annealing according to the present invention.
  • FIG. 3 is a plan view of an embodiment of the base plate of the apparatus for use in the annealing; according to the present invention.
  • FIG. 4 is a plan view of another embodiment of the base plate of FIG. 3.
  • FIG. 5A is a sectional view of. the coil-layers before the annealing according to the present invention.
  • FIG. 5B is a sectionalview of the coil-layers during or after the annealing according to the present invention.
  • a metalhydroxide which is capable of forming a glassy insulation film by a reaction with SiO contained in the surface of silicon steel strip, is applied to silicon steel strip; after this coating is dried, said steel strip is wound into a coil; the thus formed coil is charged into the annealing furnace and annealed in the desired annealing atmosphere, thereby causing dehydration of the applied metal-hydroxide to evaporate water completely to form a metal-oxide, againthereby contracting the volume of the original metal-hydroxide and producing a space between coil-layers.
  • the so-called loose coil is formed.
  • the annealing of silicon steel strip carried out while an atmospheric gas is forced into said space is effective in the formation of a glassy film on the surface of the steel strip and in decarbonization and desulfurization of the steel strip.
  • metal-hydroxides which can be used in the method according to the present invention is magnesium hydroxide, as mentioned below.
  • the application the hydroxides of alkali earth metals and of other metals is not outside the scope of the present invention.
  • steps are taken to reduce the formation of hydrates to a minimum when making a slurry of an oxide of alkali earth metals according'to the conventional methods.
  • the volume contraction of the applied metal-hydroxides during annealing or other treatments is utilized, so that a slurry of said metal-oxide obtained by complete hydration, is applied to the surface of the silicon steel strip so that the volume of the applied metal-hydroxide is reduced on heating, and the thus produced space is utilized to carry out the effective annealing with an atmospheric gas flowing through the space;
  • the method of the present invention solves said problem of the generated water staying between coil-layers and improves the adherence, insulation and uniformness of the glassy film.
  • a slurry of magnesium hydroxide is applied to the silicon steel strip 4 which has been reduced to the final thickness and wound into a coil 3.
  • Magnesium hydroxide can be dehydrated to a volume of 0.54 that of its initial volume; however, such volume reduction is not as great is the magnesium oxide has not been hydrated sufficiently.
  • a comparison of the weight of a mixture of water and MgO after being dried at 1 10 C. to remove free water, with that which has been heated at 1,000 C. to remove combined water, reveals that the content of Mg(OI-l) in the mixture of water and MgO in the former case is reduced to 80 percent in the latter case, the temperature of water of both cases being 30 40 C. when measured.
  • the most appropriate water temperature for the hydration of MgO is between 30 and 40 C., to which range the water temperature must be adjusted.
  • the most appropriate mixing ratio between water and MgO is about 1 g. MgO for 10 cc. water.
  • a magnesium slurry l with a degree of high hydration preferably prepared as above is held in the container 2; the silicon steel strip 4 uncoiled from the coil 3, runs through said container 2; the volume of the applied material is adjusted by the roll 5. Then, the steel strip 4 is conveyed through the drying room 6, and dried to such an extent that only the free water is removed. After being dried, it is wound in a coil 7.
  • the volume of applied slurry of metal-hydroxide having a degree of hydration of 80 percent can be the low amount in the above range; the volume should be increased as the degree of hydration drops.
  • said magnesium hydroxide is heated by the annealing heat and decomposes and contracts as it give up combined water, thereby producing a space 15 as shown in FIG. 5B.
  • an atmospheric gas It is preferred that said annealing furnace 10 be a batch-type furnace in which it is possible to adjust the composition and pressure of an atmospheric gas, as shown in FIG. 2.
  • FIG. 4 is a plan view of another embodiment of the base plate.
  • the base plate of FIG. 4 is provided with an appropriate number of the gas supplying holes 14 and such a number of radial grooves 13, so that the supplied gas can be uniformly forced into the coil of the steel strip 4 placed on the plate from the bottom end of the coil.
  • the upper end of the center hollow of the coil be covered by a plate 16. Due to the supplied atmospheric gas, said magnesium hydroxide 8 decomposes and give up water in the form of steam, producing the space 15, as shown in FIG. 5B.
  • the volume of applied metal-hydroxides is, say, 18 g./m.”
  • a space of about 15 to p. is produced at a heating temperature between 500 and l,200 C., taking the expansion of the coil-layer into account.
  • an atmospheric gas can go through it very swiftly, making possible the annealing of the silicon steel strip 4 in a short time.
  • EXAMPLE MgO was mixed with water having a volume of three times as much as MgO at 30 C., and a slurry of magnesium hydroxide with a degree of hydration of 80 percent was obtained. This slurry was applied to silicon steel strip of the following specifications:
  • the volume of the slurry of magnesium hydroxide was adjusted by the roll to 20 g./m
  • the thus treated steel strip was dried at 250 C. for several minutes; then it was wound into a coil. Then, said coil was charged into the finishing annealing furnace and annealed at 1,150 C.
  • the annealing time was reduced to 30 to 40 percent, compared with the annealing time required by the conventional method.
  • a method of annealing silicon steel strip for decarburizing, finish annealing and the like which comprises the steps of applying a water slurry of a metal hydroxide in which the metal hydroxide has a large amount of combined water onto the surface of silicon steel strip in an amount of from 10 to 30 gm./m. for forming a glassy film on said strip surface, the metal hydroxide having a degree of hydration of about percent when it is applied in an amount of 10 gm./m.
  • metalhydroxide slurry is a slurry of the hydroxide of an alkali earth metal.
  • metalhydroxide slurry is a slurry of magnesium hydroxide made by mixing in water at a temperature between 30 and 40 C. at a mixing ratio of one gram MgO per 10 cc. water.
  • a method as claimed in claim 1 wherein said annealing furnace used in the annealing step to heat said coil is a boxtype furnace.
  • said annealing furnace used in the annealing step to heat said coil is a batchtype furnace which allows adjustment and feed of the atmospheric gas.

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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)
  • Chemical Treatment Of Metals (AREA)
  • Chemically Coating (AREA)
US819876A 1968-04-30 1969-04-28 Method for annealing silicon steel strip for use as material of electric machinery Expired - Lifetime US3653984A (en)

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JP2888868 1968-04-30

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US (1) US3653984A (enrdf_load_stackoverflow)
FR (1) FR2007295A1 (enrdf_load_stackoverflow)
GB (1) GB1266956A (enrdf_load_stackoverflow)
SE (1) SE357578B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3879234A (en) * 1971-12-22 1975-04-22 Merck & Co Inc Lithia-containing frit additives for MgO coatings
US3956029A (en) * 1973-06-07 1976-05-11 Nippon Steel Corporation Annealing separator for heat treatment of silicon steel sheets
US4113530A (en) * 1974-04-23 1978-09-12 Kawasaki Steel Corporation Method for forming a heat-resistant insulating film on a grain oriented silicon steel sheet
US4662954A (en) * 1985-08-13 1987-05-05 Allegheny Ludlum Corporation Method for improving base coating formation on silicon steel by controlling winding tension

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3503089A1 (de) * 1985-01-30 1986-07-31 Carl Prof. Dr.-Ing. 5100 Aachen Kramer Vorrichtung zur gleichmaessigen beaufschlagung einer planen flaeche mit einem gas

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492682A (en) * 1945-07-23 1949-12-27 Armco Steel Corp Processes of producing glass coated silicon steel
US2533351A (en) * 1946-11-22 1950-12-12 Armco Steel Corp Formation of glass film on silicon steel by strip annealing
GB892652A (en) * 1959-06-10 1962-03-28 Lee Wilson Stabilizer for opened coils of strip metal
US3037889A (en) * 1958-12-04 1962-06-05 United States Steel Corp Method and apparatus for annealing coils of strip metal
US3084081A (en) * 1957-12-30 1963-04-02 Armco Steel Corp Heat treatment of ferrous strip materials with separator coating
US3132056A (en) * 1961-05-19 1964-05-05 Gen Electric Insulating coating for magnetic sheet material and method for producing the same
US3331713A (en) * 1964-06-15 1967-07-18 Allegheny Ludlum Steel Method of forming an insulating coating on silicon-iron sheets

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492682A (en) * 1945-07-23 1949-12-27 Armco Steel Corp Processes of producing glass coated silicon steel
US2533351A (en) * 1946-11-22 1950-12-12 Armco Steel Corp Formation of glass film on silicon steel by strip annealing
US3084081A (en) * 1957-12-30 1963-04-02 Armco Steel Corp Heat treatment of ferrous strip materials with separator coating
US3037889A (en) * 1958-12-04 1962-06-05 United States Steel Corp Method and apparatus for annealing coils of strip metal
GB892652A (en) * 1959-06-10 1962-03-28 Lee Wilson Stabilizer for opened coils of strip metal
US3132056A (en) * 1961-05-19 1964-05-05 Gen Electric Insulating coating for magnetic sheet material and method for producing the same
US3331713A (en) * 1964-06-15 1967-07-18 Allegheny Ludlum Steel Method of forming an insulating coating on silicon-iron sheets

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3879234A (en) * 1971-12-22 1975-04-22 Merck & Co Inc Lithia-containing frit additives for MgO coatings
US3956029A (en) * 1973-06-07 1976-05-11 Nippon Steel Corporation Annealing separator for heat treatment of silicon steel sheets
US4113530A (en) * 1974-04-23 1978-09-12 Kawasaki Steel Corporation Method for forming a heat-resistant insulating film on a grain oriented silicon steel sheet
US4662954A (en) * 1985-08-13 1987-05-05 Allegheny Ludlum Corporation Method for improving base coating formation on silicon steel by controlling winding tension

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SE357578B (enrdf_load_stackoverflow) 1973-07-02
GB1266956A (enrdf_load_stackoverflow) 1972-03-15
FR2007295A1 (enrdf_load_stackoverflow) 1970-01-02

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