Composition to create heat-resistant welded insulating coatings for electrical steels

 

The invention relates to the field of electrical engineering, in particular to compositions for the manufacture of coatings for electrical steels for magnetic circuits of electrical machines and devices. The composition is prepared by adding an aqueous solution of polyvinyl alcohol at a temperature of 65-80oWith phosphoric acid, urea, ethanol, surfactants, with prolonged stirring, cooled to room temperature, add a pre-prepared alkali-alumino-Boro-silicate glass in the form of an aqueous suspension of chromium oxide (III). The composition is thoroughly mixed to achieve homogeneity and put on a strip of electrical steel, removing excess rubber roller. The drying is effected at 500-600oC for 30-60 C. a Significant predominance of inorganic components in the composition allows to obtain a uniform thickness of the heat-resistant coating with a high coefficient of electrical resistance, enabling welding package isolated steel plates coated on the side surface, which is the technical result of the proposed technical solution. table 1.

Isophasic steels for magnetic circuits of electrical machines and devices.

The aim of the invention is to provide a composition based on polyvinyl alcohol to obtain a heat-resistant coating for electrical steel having good insulating properties and allows to weld the outer edges of the packages insulated steel plates coated.

Known insulating compositions for the manufacture of coatings for electrical steels on the basis of phosphoric acid, butadiene-styrene latex,-butyrolactam or valerolactam, fraction of fatty alcohols C7-C12and water. The quality of the coverage provided by the introduction of faction fatty alcohols (Ed. mon. The USSR 1568081). Known mixture for insulation coating containing a latex of ethylene-propylene rubber, cellulose ether, neionogennye emulsifier, wax and stabilizer that protects from aging (Patent GDR 274512). The disadvantage of these compositions is their heterogeneity due to the insolubility of inorganic components in the water, leading to rapid stratification. The consequence of this is the non-uniformity of coating thickness and low-tech application process: the formation of traffic jams in transportation systems to the s deprived of compositions based on water-soluble polymers, in particular, polyvinyl alcohol (PVA). The use of PVA to obtain coatings can increase their dielectric properties and stampability.

The closest prototype is a composition to create a thermally stable insulating coatings for electrical steels on the basis of polyvinyl alcohol, phosphoric acid, urea, thiourea, boric anhydride, ethyl alcohol, glycerine, phthalic anhydride, surfactants (surface-active substance which is a mixture of mono - and diesters of phosphoric acid with polyfluorinated alcohol) and water (Patent RF 2161341).

The disadvantage of this composition is the limited thermal stability (only when heated in an inert atmosphere), as well as a low coefficient of resistivity isolation and poor weldability (impossibility of implementing welding package steel plates coated on the side surface). All these drawbacks the composition of the prototype associated with a high proportion of organic components in its composition.

The proposed composition contains, along with PVA, phosphoric acid, urea, ethanol, surfactants and water g/l alumino-Boro-silicate glass and chromium oxide (III).

Composition photosporno acid, urea, ethanol, surfactants, prolonged stirring, cooling to room temperature, add pre-cooked alumino-Boro-silicate glass in the form of an aqueous suspension of chromium oxide (III). The composition is thoroughly mixed to achieve homogeneity and put on a strip of electrical steel, removing excess rubber roller. The drying is performed at a temperature of 500-600oC for 30-60 sec.

Study of thermal stability of the coating, measuring resistance and testing the adhesion of coatings to metal produced according to GOST 21427-83. Coating thickness was measured on the device Deltascope. The drag coefficient was measured on the instrument CIS/C-2550 Interlaminar resistivity testr. Heat treatment of samples for testing thermal stability of the coatings produced in the atmosphere of nitrogen-hydrogen 95:5 and in the air. Properties of the obtained coatings was compared to the coating properties of the prototype (Patent RF 2161341). The weldability was evaluated by the possibility of obtaining monolithic (without shell) of the weld.

Formulations of the compositions and properties of the resulting insulating coating is shown in the table.

Example: To 800 ml heated to 80-85oWith deionized water were added 50 g of PVA and pen and slowly added to 15 g of orthophosphoric acid, 6 g CR2About3and 70 g alumino-Boro-silicate glass, crushed and pre-mixed with 30 g of deionized water. After stirring for 2 h to the resulting composition was added water up to a volume of 1 l and continued stirring. Applying the composition on a steel strip produced directly from the working tank with continuous stirring. The drying is carried out at a temperature of 540-560oC for 30-60 C. After drying, the measured thickness and the resistivity of the coating was subjected to heat treatment and re-measured the resistivity, and also investigated the strength of adhesion of the coating to the metal. Produced welding package steel plates coated on the side surface of the MIG (MiG welding in inert gas) and investigated g/l the quality of the weld.

Claims

Composition to create heat-resistant welded insulating coatings for electrical steels on the basis of polyvinyl alcohol, phosphoric acid, urea, ethanol, surfactants and water, characterized in that it further comprises alumino-Boro-silicate glass and the ACS is the 15 - 22

Urea 3 - 8

Ethyl alcohol 50 - 80

Surfactant 5 - 8

Alkali-alumino-Boro-silicate glass 70 - 90

Oxide chromium (III) 5 - 6

 

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