US3909313A - Method for forming an electric insulating film having excellent punching property and heat resistance on an electrical steel sheet - Google Patents

Method for forming an electric insulating film having excellent punching property and heat resistance on an electrical steel sheet Download PDF

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Publication number
US3909313A
US3909313A US399625A US39962573A US3909313A US 3909313 A US3909313 A US 3909313A US 399625 A US399625 A US 399625A US 39962573 A US39962573 A US 39962573A US 3909313 A US3909313 A US 3909313A
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Prior art keywords
emulsion
insulating film
styrene
vinyl acetate
forming
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Expired - Lifetime
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US399625A
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English (en)
Inventor
Hirotada Kato
Kazuo Nakamura
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Nippon Steel Corp
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Nippon Steel Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/448—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from other vinyl compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/447—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from acrylic compounds
    • 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

Definitions

  • Example2 b Cl Com parafive Example 3 C (only A solution) so i Burr height 91) 2 4 6 8 l0 l2 l4 I5 l6 I8 20 22 24 Number of punchings (XlOlimes) METHOD FOR FORMING AN ELECTRIC INSULATING FILM HAVING EXCELLENT PUNCHING PROPERTY AND HEAT RESISTANCE ON AN ELECTRICAL STEEL SHEET
  • the present invention relates to a method for forming an electric insulating film having excellent punching property and heat resistance on the surface of an electrical steel sheet.
  • The'electrical steel sheet used herein includes all of so called silicon steels and low carbon steels usable for iron cores of electrical appliances.
  • the electric insulating filmcoated on'the electrical steel sheets is required to have excellent inter-layer resistance, film adhesion, corrosion resistance, weldability and punching properties in addition to electric insulating properties.
  • the punching property of the electrical steel sheet has an important influence on the dies for punching the sheet, and excellent punching property assures increased number of punchings per onedie and thus considerably elongates the life of the die.
  • the punching property can be improved to some degree by material improvement of the electrical sheet itself, but there is a limitation to the degree of improvement that can be effected by this alone.
  • FIG. 1 is a graph showing the relation between the additional amount of styrene resin and the punching property
  • FIG. 2 is a graph showing the relation between the burr height and number of punchings in the comparison I and Examples 2 and 3.
  • the present inventors have found that the punching property is largely influenced by the electric film formed on the surface of the electrical steel sheet and have conducted various extensive studies on the basis of the discovery, and have succeeded in developing film agents which make possible to increase the number of the punchings per one die to 2,500,000 that is, 5 to 30 times as compared with the conventional insulating film, and a method for forming the film.
  • the conventional film agent for example, an insulating film formed with a treating solution prepared by mixing divalent metal oxides with chromic acid anhydride shows the punching property as shown by the curve (a) in FIG. 2, where with about80,000 punchings, burrs reach 50p. of the allowable limit.
  • heat resistance is one of the important properties of the electric insulating film.
  • heat treatment of the electrical steel sheets is done in the piled form in order to remove the working strain and improve magnetic characteristics, and is usually done in a neutral or weak-reducing atmosphere, depending on the purposes of the treatment. In this case, heat resistance, namely, non-peeling of the insulating film is required.
  • generators for refrigerator compressors use freon gas if on the exposed edge surface of the iron core made by punching the electrical steel sheet, rust is formed and the rust strips off, it can get into the gas and clog the expansion valve. Further the exposed metal serves as a catalyst and decomposes the freon gas.
  • the punched edge surface is subjected to a blueing treatment. In this treatment also, it is required that the insulating film not peel off; powdering does not occur at the treating temperature between 400 and 600C, and the piled sheets do not adhere to each other. Thus an additional type of heat resistance is required.
  • one purpose of the present invention is to provide an electric insulating film for an electrical steel sheet, which film does not undergo thermal deterioration which cause the above troubles during the heat treatments, and which also possesses remarkably improved punching properties.
  • the steel plate sheet or strip to which the present insulating film is applied include silicon steel plates or low carbon iron plates containing very small amounts of silicon or containing no siliconwhich are generally used for electrical appliances, such as, generators and transformers.
  • the agent serves as a good solid lubricant and gives good punching property because of the small emulsion particles (0.1 to la).
  • emulsion resins such as, vinyl acetate emulsion using PVA protection colloids for paints, acrylic acid ester emulsion, or ethylene vinyl acetate emulsion are added to the chromic acid solution and the thus prepared treating solution is applied on the electrical steel plate, only poor heat resistance is obtained and the film peels off or powders during the heat treatment.
  • Another object of the present invention is to provide a method for formingan electric insulating film which has overcome the above defects.
  • the treating solution for forming the film according to the present invention may be prepared by adding styrene resin to a composition (A) containing one or more of chromic anhydride, chromate and bichromate.
  • salts of bivalent metals such as, magnesium, calcium and zinc, may be used.
  • an aqueous solution prepared by dissolving oxides of bivalent metals such as, MgO, CaO, ZnO; hydroxides, such as, Mg(OH) Ca(OI-I) and Zn(OH) or carbonates,'such as, MgCO CaCO and ZnCO in chromic anhydride in an amount less than their dissolution limit
  • This aqueous solution composition may be considered to be an aqueous solution of a mixture of chromic anhydride and chromate.
  • styrene resin As for the styrene resin to be added to the composition (A), styrene emulsion resin, styrene-acryl copolymer emulsion, and styrene vinyl acetate resin may be used.
  • styrene' is' contained in an amount of 50% or more as solid component. If the proportion of styrene is less than 50%, the heat resistance is poor so that the film will peel offor powder during the heat treatment.
  • the proportion of the styrene emulsion to the composition (A), for example, to chromic anhydride, is l to 35 parts to parts of chromium ions contained in the chromic anhydride.
  • the proportion of the styrene emulsion to the composition (A), for example, to chromic anhydride is l to 35 parts to parts of chromium ions contained in the chromic anhydride.
  • poor conductor-forming oxides such as, boric acid, colloidal silica, colloidal alumina, sodium silicate and potassium silicate may be added to the treating solution used in the present invention without deviating fromthe scope of the present invention.
  • the above oxides should be added in a range from 2 to 16 parts to 10 parts of the chromium ions in the composition (A).
  • the water-soluble saturated dicarboxylic acids having four or more carbon atoms used in the present invention are acids, such as, succinic acid, adipic acid, glutamic acid, and pimelic acid.
  • succinic acid adipic acid
  • glutamic acid glutamic acid
  • pimelic acid a carboxylic acid
  • the reducing force is so large that the reduction is effected in such a degree as to precipitate the inorganic substances and of the emulsion resin, thus damaging the stability of the solution, and result in a film having poor appearance,adhesion and heat resistance.
  • saturated carboxylic acids such as, oxalic acid having two carbon atoms
  • nonsaturated carboxylic acids such as, maleic acid
  • the stability of the solution is poor. Only when saturated carboxylic acids having 4 or more carbon atoms are used is the stability of the inorganic substances and the emulsion very excellent and a good film for an electrical steel sheet can be obtained.
  • Polyethylene glycols having about 200 to about 1000 molecular weight are most preferable for use in the present invention.
  • Ethylene glycol has so strong a reducing force that the solution stability is not obtained, and similarly polyhydric alcohols, such as, glycerine, amines, such as, triethanolamine, are not usable as they promote settlements of inorganic substances and of the emulsion resins.
  • the optimum proportion of the water-soluble saturated carboxylic acid having 4 or more carbon atoms and the polyethylene glycol is from 1 to 10 parts to 10 parts of the chromium ion. With less than 1 part, the reducing force is low and a large amount of hexavalent chromium remains in the film and the film dissolves in water. Even with more than 10 parts, the effects of the reducing agent will not change substantially.
  • the treating solution having the above composition may be applied on an electrical steel plate having suitable surface conditions by any of the conventional coating methods, such as, roll coating, brushing, spraying and immersion.
  • the coating amount of the treating solution it is most. desirable that the residual solid substance after the heating and baking is 0.5 to 5 g/m According to the present invention, the baking after the coating of the treating solution is done at a steel surface temperature of to 500C and the heating time for the baking is not specifically limited, but a heating time between 10 and 180 seconds will give good results.
  • the heating temperature is lower than 150C, no satisfactory baking is obtained and the film has no water-resistance and becomes viscous by absorption of water.
  • the heating temperature is higher than 500C, the film agent is decomposed and thus the film adhesion and the punching property become poor thus failing to obtain the desired results of the present invention.
  • the electric insulating film formed by the method of the present invention is excellent in both of the punching property and heat resistance, and the solution itself has good stability and can stand for long time.
  • the styrene emulsion resin is prepared by polymerization under the presence of an emulsifying agent (mainly a surface activating agent), and the stability of the emulsion resin in the treating solution of the present invention is influenced by the kind of the emulsifying agent to used.
  • an anionic activating agent for example, laulylic sodium sulfate
  • the emulsion resin readily settles in a short time.
  • Nonion activating agents for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene alkyl-aryl ether
  • nonionanion mixture activating agents for example, a mixture of polyoxyethylene noel phenol ether and dodecylbenzene sulfoninate
  • the vinyl acetate emulsions used in the present invention should be polymerized using nonion activating agents or nonion-anion mixture activating agents, and the vinyl acetate emulsions which are polymerized using high-moelcular protection colloids, such as, commercially available PVA and cellulose derivatives for paints, should be avoided.
  • high-moelcular protection colloids such as, commercially available PVA and cellulose derivatives for paints
  • the vinyl acetate emulsion resins in the EX M E 4 present invention means the vinyl acetate emulsion res- A treating solution having the following composmon: ins and the vinyl acetate-acryl copolymerizatlon emul- C I h t 75 K a ClUm C I'Omfl 8 sion prepared by using the above activating agents. Chromic h d d 12 The present invention will be more clear from the fol- 5 Boric acid 6 Kg 1 1 Succinic acid 4.5 Kg
  • a treating solution having the following composition: 40 Chromic anhydride 20 Kg Magnesium oxide 6 Kg Chromic anhydride 25 Kg 9 4 Kg Succmrc acid 4 Kg oxde 3 fi 40% vinyl acetate acryl copolymerization 1 g emulsion 30 Kg 2x 325 231 gsg zgg g g i L8 Kg (ratio of vinyl acetate to butyl a'crylate 7 3) l 35 K ater 300 Kg who of Style: m was left at ordinary temperatures for'one month and Water 4001 then heated at a sheet temperature of 300C, thereby a uniform and lustrous film was formed on the sheet in was left at ordinary temperatures for 15 days and then an amount of 2.1 g/m No gellation of the solution and coated by rolls on an electrical steel sheet and baked no settlement were observed.
  • the punching property at a sheet temperature of 300C, thereby a lustrous and test showed 1,600,000 times and the adhesion property uniform film'was formed on the steel sheet in an test showed less than 10 mm.
  • the corrosion resistance amount of 1.8 g/m No gellation of the solution and no and the heat resistance test were similar as those in settlement were observed. other examples.
  • Table 1 show the results obtained by coating the following solutions (1 (2) (3) by rolls on the steel sheet and heating at 300C to form a film in an amount of 2 g/m Solution (1) only the composition A the composition A 15 parts as solid of vinyl acetate emulsion (solid 50%) the composition A l0 parts as solid acrylic acid ester emulsion (solid 40%) Solution (3) cellent in the present invention.
  • a method for forming an insulating film having exmetal or a bichromate of a bivalent metal; 1 to 10 parts per ten parts on a weight basis of a reducing agent seemulsion containing 50% or more of styrene is a styrene emulsion, a styrene-acrylic copolymer emulsion or a styrene-vinyl acetate emulsion.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Electromagnetism (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Soft Magnetic Materials (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Organic Insulating Materials (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)
  • Manufacture Of Motors, Generators (AREA)
  • Paints Or Removers (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
US399625A 1972-09-29 1973-09-21 Method for forming an electric insulating film having excellent punching property and heat resistance on an electrical steel sheet Expired - Lifetime US3909313A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4183758A (en) * 1978-03-06 1980-01-15 Louis Schiffman Zinc chromium chromate pigment
FR2449134A1 (fr) * 1979-02-15 1980-09-12 Kawasaki Steel Co Procede pour former une pellicule dielectrique ayant une excellente aptitude au decoupage par poinconnage et une forte adhesion, meme apres recuit de detente des tensions dans l'air, sur les surfaces d'une tole d'acier electrique
US4966634A (en) * 1986-07-14 1990-10-30 Nihon Parkerizing Co., Ltd. Composition of the surface treatment for metal and the treatment method
EP0700059A1 (en) * 1993-02-08 1996-03-06 Kawasaki Steel Corporation Electromagnetic steel sheet having an electrically insulating coating with superior weldability
CN104212306A (zh) * 2014-09-17 2014-12-17 句容亿格纳米材料厂 一种绝缘纳米涂料及其制备方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2692279B2 (ja) * 1989-07-19 1997-12-17 日本鋼管株式会社 耐食性に優れた絶縁皮膜を電磁鋼板の表面に形成する方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3389006A (en) * 1964-05-18 1968-06-18 Armco Steel Corp Process for forming a refractory coating on silicon-iron stock
US3477881A (en) * 1964-02-24 1969-11-11 Yawata Seitetsu Kk Process for the formation of electric insulating coating on electric iron sheet
US3523837A (en) * 1967-11-06 1970-08-11 Westinghouse Electric Corp Non-reactive refractory separating coatings for electrical steels
US3562011A (en) * 1968-04-26 1971-02-09 Gen Electric Insulating coating comprising an aqueous mixture of the reaction product of chromium nitrate and sodium chromate,phosphoric acid and colloidal silica and method of making the same
US3649372A (en) * 1968-10-28 1972-03-14 Kawasaki Steel Co Reagent for forming an insulating coating on the surface of electrical steel sheets
US3785882A (en) * 1970-12-21 1974-01-15 Armco Steel Corp Cube-on-edge oriented silicon-iron having improved magnetic properties and method for making same
US3793073A (en) * 1970-09-17 1974-02-19 Nippon Steel Corp Electrical steel sheets and strips having excellent punching and welding characteristics for the use of a laminated iron core

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3477881A (en) * 1964-02-24 1969-11-11 Yawata Seitetsu Kk Process for the formation of electric insulating coating on electric iron sheet
US3389006A (en) * 1964-05-18 1968-06-18 Armco Steel Corp Process for forming a refractory coating on silicon-iron stock
US3523837A (en) * 1967-11-06 1970-08-11 Westinghouse Electric Corp Non-reactive refractory separating coatings for electrical steels
US3562011A (en) * 1968-04-26 1971-02-09 Gen Electric Insulating coating comprising an aqueous mixture of the reaction product of chromium nitrate and sodium chromate,phosphoric acid and colloidal silica and method of making the same
US3649372A (en) * 1968-10-28 1972-03-14 Kawasaki Steel Co Reagent for forming an insulating coating on the surface of electrical steel sheets
US3793073A (en) * 1970-09-17 1974-02-19 Nippon Steel Corp Electrical steel sheets and strips having excellent punching and welding characteristics for the use of a laminated iron core
US3785882A (en) * 1970-12-21 1974-01-15 Armco Steel Corp Cube-on-edge oriented silicon-iron having improved magnetic properties and method for making same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4183758A (en) * 1978-03-06 1980-01-15 Louis Schiffman Zinc chromium chromate pigment
FR2449134A1 (fr) * 1979-02-15 1980-09-12 Kawasaki Steel Co Procede pour former une pellicule dielectrique ayant une excellente aptitude au decoupage par poinconnage et une forte adhesion, meme apres recuit de detente des tensions dans l'air, sur les surfaces d'une tole d'acier electrique
US4966634A (en) * 1986-07-14 1990-10-30 Nihon Parkerizing Co., Ltd. Composition of the surface treatment for metal and the treatment method
EP0700059A1 (en) * 1993-02-08 1996-03-06 Kawasaki Steel Corporation Electromagnetic steel sheet having an electrically insulating coating with superior weldability
CN104212306A (zh) * 2014-09-17 2014-12-17 句容亿格纳米材料厂 一种绝缘纳米涂料及其制备方法

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Publication number Publication date
JPS4956200A (sv) 1974-05-31
BR7307592D0 (pt) 1974-08-22
JPS5219534B2 (sv) 1977-05-28

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