Silver-Tungsten Carbide-Carbon Contact Material

Electric contacts are the core components of low-voltage electrical appliances. They take on the task of switching on and off the circuit in various control switches. They are widely used in military, aviation, aerospace and industrial control fields. The electrical properties of silver-based contact materials have a vital impact on the long life and high reliability of various electronic control systems.

Silver-tungsten carbide-carbon contact material is a new generation of contact material to replace traditional AgC₅. It has excellent weldability and is widely used in automatic switches, large capacity circuit breakers, plastic case circuit breakers and some other switches. Silver-tungsten carbide-carbon contact mainly utilizes the good conductivity and thermal conductivity of Ag and the high WC. Melting point, high hardness and good wear resistance. It can withstand strong arc corrosion, has good weldability and wear resistance, and achieves the effect of silver saving.

At present, the pairing of AgWC₁₂C₃ and AgW50 is often used as asymmetric and reasonable pairing contacts of circuit breakers in AgWC-C electrical contact materials. However, one of the main drawbacks of electrical contacts containing WC materials is the poor oxidation resistance, which makes it difficult to meet the high reliability and electromagnetic compatibility requirements of the fourth generation low voltage electrical appliances. In order to overcome the shortcomings and shortcomings of the existing technology, some scholars have proposed a preparation method of silver tungsten carbide carbon series electrical contact materials. The process includes:

(1)Ag powder and tungsten carbide, zirconium carbide solid solution and graphite were wet mixed with 0.3% Ni and 0.7% B at 85:12:3 ratio for 6 hours, the ratio of sphere to material was 1:1, vacuum drying, pelletizing in hydrogen atmosphere at 700 ℃ for 4 hours, and the fluidity of the powder was good. Among them, tungsten carbide and zirconium carbide solid solution were tungsten carbide and graphite. The ratio of zirconium carbide is 8:2.

(2)The granulated powder was compacted into 7.5 x 7.5 x 3.5 mm compact with initial pressure of 150 MPa.

(3)The compacts were sintered in hydrogen atmosphere at 880 ℃ for 4 hours.

(4)The sintered green body was repressed under 250 MPa pressure with a thickness of 2.8 mm.

(5)After repression, the green body was annealed at 500 ℃ in hydrogen atmosphere for 2 hours.

(6)The annealed green body was repressed under 560 MPa pressure to produce 7.5 x 7.5 x 2.5 mm product.

(7)The silver tungsten carbide zirconium carbide graphite contacts were ground, polished and dried.

The physical properties of the prepared AgWC_9.6ZrC_2.4C₃ contacts are as follows: density 9.69g/cm³, resistivity 3.05.cm, hardness 626MPa, high temperature oxidation resistance, welding resistance and arc burning resistance, which meet the requirements of high reliability and electromagnetic compatibility of the fourth generation low voltage electrical appliances.

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