US2871143A - Magnetic material provided with separator coating - Google Patents

Magnetic material provided with separator coating Download PDF

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Publication number
US2871143A
US2871143A US594707A US59470756A US2871143A US 2871143 A US2871143 A US 2871143A US 594707 A US594707 A US 594707A US 59470756 A US59470756 A US 59470756A US 2871143 A US2871143 A US 2871143A
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Prior art keywords
magnetic material
coating
refractory substance
refractory
separator coating
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Expired - Lifetime
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US594707A
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Jr Milan P Getting
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Allis Chalmers Corp
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Allis Chalmers Corp
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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
    • H01F1/16—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 in the form of sheets
    • H01F1/18—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 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
    • 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
    • C21D8/1277—Modifying the physical properties 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/90—Magnetic feature
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31678—Of metal
    • Y10T428/31703—Next to cellulosic

Definitions

  • This invention relates in general to magnetic sheet material employed in the manufacture of electrical ap-.
  • paratus such as transformers, and in particular to magnetic sheet material provided with a coating of a refractory substance bonded to the material by a heat decomposable binder.
  • the improved coated magnetic material may be used advantageously in manufacturing magnetic cores when the magnetic material must undergo various slitting, winding and forming operations subsequent to being coated and prior to receiving a high temperature anneal.
  • Electrical steel is sometimes supplied to the transformer manufacturer in a semifinished state in the form of large sheets or rolls.
  • the material is processed to a size convenient for the core manufacturing process, it is given a high temperature anneal which results in crystal growth in the preferred direction, further purification of the steel, and relief of any strains set up in the material during the manufacturing process.
  • the high temperature anneal the material is usually in the form of a rolled strip or in the form of stacked laminations depending on whether the steel is to be used in wound transformer cores or in stacked cores. In either case, the magnetic material is placed in the annealing furnace and heated in a multilayered assembly with relatively large surface contact between the layers.
  • One refractory substance or separator which is in common use is a substance consisting essentially of oxides of calcium and magnesium, although other substances have also been employed.
  • the refractory substance which is a powder like substance is applied to the magnetic material in a water slurry and then passed through an oven to evaporate the water. Because of the powdery nature of the refractory substance after the water has evaporated, it has a tendency to rub off quite easily during subsequent handling operations so that very little of the refractory substance is present during the high temperature anneal. It therefore becomes necessary with this arrangement to apply the coating immediately prior to the annealing operation which is a decided disadvantage. A further disadvantage is that in being rubbed off during the handling operation unpleasant and unhealthy working conditions are created.
  • the prior art has also suggested providing magnetic material with a separator coating comprising a refractory substance suspended in a heat decomposable binder such as an alkyd resin or cellulose acetate in suitable organic solvents. When the solvent evaporates, the resinous solvents.
  • a heat decomposable binder such as an alkyd resin or cellulose acetate
  • a third arrangement suggested in the prior art and similar to that just described employs a coating including a small amount of methyl cellulose as the heat decomp'osable binder for the refractory substance.
  • the cost of the methyl cellulose binder is substantially less than the cellulose acetate or alkyd resin binder.
  • magnetic material provided with a coating including methyl cellulose as the binder for the refractory substance, is slit into strips and these strips wound and formed into the shape they will take as a finished transformer core, a considerable amount of the refractory substance is brushed off.
  • magnetic material is provided with a separator coating comprising a refractory substance in a finely divided form bonded to the steel by a small amount of carboxymethyl hydroxyethyl cellulose. It has been found that such a coating adheres to the magneticmaterial during subsequent slitting, winding, and forming operations considerably better than any other coating suggested by the prior art.
  • Fig. 1 is a schematic view of apparatus suitable for carrying out the invention.
  • Fig. 2 is an enlarged cross section through a sheet of material prepared in accordance with the invention.
  • magnetic material in the microcrystalline state is coated with a slurry containing oarboxylmethyl hydroxyethyl cellulose, any known suitable refractory substance, and water.
  • suitable refractory substances are lime, dolomite, magnesium oxide, and silica, and various combinations of the above.
  • This slurry may be prepared by adding pounds of refractory substance, preferably a mixture of calcium oxide and magnesium oxide, 325 mesh, and 16.7 pounds of carboxymethyl hydroxyethyl cellulose to a suflicient amount of water to form a slurry.
  • Carboxyrnethyl hydroxyethyl cellulose sold by the Hercules Powder Cornp-any under the name CMHEC has been found quite satisfactory.
  • These ingredients are then ground together in a Wet ball mill for several hours until the refractory particles are thoroughly dispersed. It has been found that a suitable slurry is obtained when the specific gravity of the solution is substantially 1.07 and its viscosity is 18.5 seconds in a No. 2 Zahn cup.
  • the resulting solution may then be applied to magnetic material as the first step in handling the semiprocessed steel in a manner such as shown in Fig. 1.
  • the solution is applied to the steel as it is unrolled.
  • Any suitable means A may be employed for applying the coating to the material such as rubber doctor rolls or brushes.
  • the magnetic material is passed through an oven which causes the water in the solution to evaporate without harming the coating.
  • the resulting coating shown in Fig. 2 adheres to the magnetic material so that it may be freely handled in all types of slitting, Winding and forming operations which occur before the final anneal 3 without any substantial amount of the refractory substance rubbing 01?.
  • Magnetic sheet material having thereon a separator coating comprising a finely divided refractory oxide bonded to said material by carboxymethyl hydroxycthyl cellulose adhesive binder.
  • a continuous silicon steel strip having thereon an adherent coating comprising a refractory substance consisting essentially of calcium and magnesium oxide in a finely divided form and a small amount of carboxymethyl hydroxyethyl cellulose binder binding the refractory substance in intimate contact With the surface of said strip 4 to prevent said refractory substance from being subsequently rubbed as as said strip is mechanically processe prior to annealing.
  • a strip of steel in the microcrystalline state provided with a coating comprising a refractory substance in finelydivided form bonded to the surface of said material by carboxymethyl hydrox'yethyl cellulose.

Description

Jan. 27, 1959 M. P. GETTING, JR I 2,
MAGNETIC MATERIAL PROVIDED WITH SEPARATOR COATING Filed June 29, 1956 I Rubber Doctor Pol/s Ferrous Metal Evapofating Oven Insulating Film Comprising Carboxymeihy/ Hydroxyethy/ Ce/lu/ose and Refractory Substance Ferrous Metal iii '2 JAM/hm Want gwbbim jrl.
United States I Patent MAGNETIC MATERIAL PROVIDED WITH SEPARATOR COATING Milan P. Getting, Jr., Pittsburgh, Pa., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.
Application June 29, 1956, Serial No. 594,707
3 Claims. (Cl. 117-127) This invention relates in general to magnetic sheet material employed in the manufacture of electrical ap-.
paratus such as transformers, and in particular to magnetic sheet material provided with a coating of a refractory substance bonded to the material by a heat decomposable binder. The improved coated magnetic material may be used advantageously in manufacturing magnetic cores when the magnetic material must undergo various slitting, winding and forming operations subsequent to being coated and prior to receiving a high temperature anneal.
Electrical steel is sometimes supplied to the transformer manufacturer in a semifinished state in the form of large sheets or rolls. After the material is processed to a size convenient for the core manufacturing process, it is given a high temperature anneal which results in crystal growth in the preferred direction, further purification of the steel, and relief of any strains set up in the material during the manufacturing process. During the high temperature anneal the material is usually in the form of a rolled strip or in the form of stacked laminations depending on whether the steel is to be used in wound transformer cores or in stacked cores. In either case, the magnetic material is placed in the annealing furnace and heated in a multilayered assembly with relatively large surface contact between the layers. Due to the plasticity of the steel at the elevated temperatures associated with this anneal there is a tendency for the associated layers in the assembly to stick together and possibly even weld to one another. It, therefore, becomes necessary to have a refractory substance between adjacent layers during the high temperature anneal to avoid this sticking.
One refractory substance or separator which is in common use, is a substance consisting essentially of oxides of calcium and magnesium, although other substances have also been employed.
Various arrangements have been suggested in the prior art for applying a refractory separator coating to the magnetic material. In onesuggested arrangement, the refractory substance which is a powder like substance is applied to the magnetic material in a water slurry and then passed through an oven to evaporate the water. Because of the powdery nature of the refractory substance after the water has evaporated, it has a tendency to rub off quite easily during subsequent handling operations so that very little of the refractory substance is present during the high temperature anneal. It therefore becomes necessary with this arrangement to apply the coating immediately prior to the annealing operation which is a decided disadvantage. A further disadvantage is that in being rubbed off during the handling operation unpleasant and unhealthy working conditions are created.
The prior art has also suggested providing magnetic material with a separator coating comprising a refractory substance suspended in a heat decomposable binder such as an alkyd resin or cellulose acetate in suitable organic solvents. When the solvent evaporates, the resinous solvents.
lCC
component of the solution functions to bind the refractory substance to the steel. Whileunagnetic material provided with this type of coating has several advantages over magnetic material provided 'with a coating which is merely dusted on or applied in a water spray, it also has some serious disadvantages. The main disadvantage is tlhatthe cost on a commercial scale is relatively high because of the need of expensive organic Also, the use of organic solvents creates a serious fire hazard which is a decided disadvantage.
A third arrangement suggested in the prior art and similar to that just described employs a coating including a small amount of methyl cellulose as the heat decomp'osable binder for the refractory substance. The cost of the methyl cellulose binder is substantially less than the cellulose acetate or alkyd resin binder. However, when magnetic material, provided with a coating including methyl cellulose as the binder for the refractory substance, is slit into strips and these strips wound and formed into the shape they will take as a finished transformer core, a considerable amount of the refractory substance is brushed off.
According to the present invention, magnetic material is provided with a separator coating comprising a refractory substance in a finely divided form bonded to the steel by a small amount of carboxymethyl hydroxyethyl cellulose. It has been found that such a coating adheres to the magneticmaterial during subsequent slitting, winding, and forming operations considerably better than any other coating suggested by the prior art.
It is therefore an object of the present invention to' provide magnetic materials having an improved separator coating.
Objects and advantages other than those mentioned abovewill be apparent from the following description.
Fig. 1 is a schematic view of apparatus suitable for carrying out the invention; and
Fig. 2 is an enlarged cross section through a sheet of material prepared in accordance with the invention.
In accordance with the present invention magnetic material in the microcrystalline state is coated with a slurry containing oarboxylmethyl hydroxyethyl cellulose, any known suitable refractory substance, and water. Some suitable refractory substances are lime, dolomite, magnesium oxide, and silica, and various combinations of the above.
This slurry may be prepared by adding pounds of refractory substance, preferably a mixture of calcium oxide and magnesium oxide, 325 mesh, and 16.7 pounds of carboxymethyl hydroxyethyl cellulose to a suflicient amount of water to form a slurry. Carboxyrnethyl hydroxyethyl cellulose sold by the Hercules Powder Cornp-any under the name CMHEC has been found quite satisfactory. These ingredients are then ground together in a Wet ball mill for several hours until the refractory particles are thoroughly dispersed. It has been found that a suitable slurry is obtained when the specific gravity of the solution is substantially 1.07 and its viscosity is 18.5 seconds in a No. 2 Zahn cup. The resulting solution may then be applied to magnetic material as the first step in handling the semiprocessed steel in a manner such as shown in Fig. 1. For example, if the semiprocessed steel is obtained in large rolls the solution is applied to the steel as it is unrolled. Any suitable means A may be employed for applying the coating to the material such as rubber doctor rolls or brushes. After being coated, the magnetic material is passed through an oven which causes the water in the solution to evaporate without harming the coating. The resulting coating shown in Fig. 2 adheres to the magnetic material so that it may be freely handled in all types of slitting, Winding and forming operations which occur before the final anneal 3 without any substantial amount of the refractory substance rubbing 01?.
While only one embodiment of the present invention has been described it Will be apparent to those skilled in the art that other modifications may be employed without departing from the spirit of'the invention or from the scope of the appended claims.
What is claimed is:
1. Magnetic sheet material having thereon a separator coating comprising a finely divided refractory oxide bonded to said material by carboxymethyl hydroxycthyl cellulose adhesive binder.
2. A continuous silicon steel strip having thereon an adherent coating comprising a refractory substance consisting essentially of calcium and magnesium oxide in a finely divided form and a small amount of carboxymethyl hydroxyethyl cellulose binder binding the refractory substance in intimate contact With the surface of said strip 4 to prevent said refractory substance from being subsequently rubbed as as said strip is mechanically processe prior to annealing. '1
3. A strip of steel in the microcrystalline state provided with a coating comprising a refractory substance in finelydivided form bonded to the surface of said material by carboxymethyl hydrox'yethyl cellulose.
References Cited in the file of this patent UNITED STATES PATENTS 1,789,477 Roseby l Ian. 20, 1931 1,940,707 Browne Dec. 26, 1933 2,426,445 Frisch et a1. Aug. 26, 1947 2,515,788 Morrill July 18, 1950 2,618,632 Klug Nov. 18, 1952 2,640,791 Barber June 2, 1953 2,641,556 Robinson June 9, 1953 2,739,085 McBride Mar. 20, 1956

Claims (1)

1. MAGNETIC SHEET MATERIAL HAVING THEREON A SEPARATOR COATING COMPRISING A FINELY DIVIDED REFRACTORY OXIDE BONDED TO SAID MATERIAL BY CARBOXYMETHYL HYDROXYETHYL CELLULOSE ADHESIVE BINDER.
US594707A 1956-06-29 1956-06-29 Magnetic material provided with separator coating Expired - Lifetime US2871143A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3192619A (en) * 1961-06-13 1965-07-06 Hooker Chemical Corp Lubricant coating composition and method of cold forming metals
US3230212A (en) * 1960-04-27 1966-01-18 Frederick A H Rice Cross-linked cellulosic polymer
US3279896A (en) * 1960-10-26 1966-10-18 Itt Crucible seal
US3317513A (en) * 1960-04-27 1967-05-02 Frederick A H Rice Method for cross-linking cellulose compounds by intramolecular esterification
US3484344A (en) * 1965-05-10 1969-12-16 Ransburg Electro Coating Corp Production of electrically resistive coatings by anodic deposition from aqueous monoaluminum phosphate
US4540628A (en) * 1980-11-18 1985-09-10 John R. Koza Hydrophilic sheet and method of making
WO1999030335A1 (en) * 1997-12-11 1999-06-17 Krupp Vdm Gmbh Method for coating magnetic bands or sheet metal

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1789477A (en) * 1926-06-13 1931-01-20 Ass Telephone & Telegraph Co Magnet core
US1940707A (en) * 1931-06-02 1933-12-26 Vere B Browne Inorganic insulation for electrical sheets
US2426445A (en) * 1943-07-07 1947-08-26 Gen Electric Insulation for magnetic steel and the like
US2515788A (en) * 1945-10-22 1950-07-18 Gen Electric Process for coating magnetic materials
US2618632A (en) * 1949-04-05 1952-11-18 Hercules Powder Co Ltd Mixed cellulose ether and preparation thereof
US2640791A (en) * 1949-10-26 1953-06-02 Hercules Powder Co Ltd Coated paper
US2641556A (en) * 1953-06-09 Magnetic sheet material provided
US2739085A (en) * 1953-03-13 1956-03-20 Westinghouse Electric Corp Insulating coatings for magnetic sheets

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2641556A (en) * 1953-06-09 Magnetic sheet material provided
US1789477A (en) * 1926-06-13 1931-01-20 Ass Telephone & Telegraph Co Magnet core
US1940707A (en) * 1931-06-02 1933-12-26 Vere B Browne Inorganic insulation for electrical sheets
US2426445A (en) * 1943-07-07 1947-08-26 Gen Electric Insulation for magnetic steel and the like
US2515788A (en) * 1945-10-22 1950-07-18 Gen Electric Process for coating magnetic materials
US2618632A (en) * 1949-04-05 1952-11-18 Hercules Powder Co Ltd Mixed cellulose ether and preparation thereof
US2640791A (en) * 1949-10-26 1953-06-02 Hercules Powder Co Ltd Coated paper
US2739085A (en) * 1953-03-13 1956-03-20 Westinghouse Electric Corp Insulating coatings for magnetic sheets

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3230212A (en) * 1960-04-27 1966-01-18 Frederick A H Rice Cross-linked cellulosic polymer
US3317513A (en) * 1960-04-27 1967-05-02 Frederick A H Rice Method for cross-linking cellulose compounds by intramolecular esterification
US3279896A (en) * 1960-10-26 1966-10-18 Itt Crucible seal
US3192619A (en) * 1961-06-13 1965-07-06 Hooker Chemical Corp Lubricant coating composition and method of cold forming metals
US3484344A (en) * 1965-05-10 1969-12-16 Ransburg Electro Coating Corp Production of electrically resistive coatings by anodic deposition from aqueous monoaluminum phosphate
US4540628A (en) * 1980-11-18 1985-09-10 John R. Koza Hydrophilic sheet and method of making
WO1999030335A1 (en) * 1997-12-11 1999-06-17 Krupp Vdm Gmbh Method for coating magnetic bands or sheet metal

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