METHOD OF MAKING ELECTRIC CONTACT AND COMPOSITE ELECTRIC CONTACT Russian patent published in 2020 - IPC H01H1/27 H01H1/04 

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical equipment, namely to methods of making electric graphite-silver composite contacts intended for use in various switching devices of automation. Technical result is achieved by the method involving alternate treatment of fine-grained compact graphite with liquid and silver-containing salt. Liquid used for graphite impregnation is an aqueous solution containing not more than 5 wt. % iron sulphate, after which contact is annealed in furnace at temperature of not less than 900 °C in reducing medium. Further, graphite is calcined at temperature of 450–500 °C in air medium for not more than 24 hours, as a result of catalytic oxidation, graphite base with transport porosity of 5–9 % is obtained, volumetric porosity of 9–14 %, compression strength of not less than 80 MPa, ash content of not more than 0.1 %, by which the required form of contact is given by mechanical treatment. Contact is heated to melting point of silver nitrate and placed in autoclave, in which rarefaction is created not less than -0.86 kgf/cm², after which autoclave is filled with melts of silver nitrate. Autoclave is pressurized not more than 50 kgf/cm², further contacting the impregnated silver nitrate is placed in a furnace and heated to a temperature above the melting point of silver, as a result, first, silver nitrate is decomposed to finely dispersed silver, and then it is melted into a monolithic structure on the contact surface.

EFFECT: technical result is creation of method of obtaining contact, characterized by low labour input, low share of loss of silver-containing salts, high degree of penetration of silver-containing salts into contact, which results in contact with stable transient electric resistance during the whole period of operation.

2 cl, 1 tbl, 5 ex