According to the functional requirements of low-voltage electrical appliances, selecting appropriate contacts and their preparation processes can optimize the design of low-voltage electrical appliances while achieving energy saving, environmental protection and other effects.

1. Rivet type contact

    Rivet-type contacts are mainly used in contactors and relays. They generally use pure Cu wire as the base material and Ag base wire as the working layer material. They are completed through processes such as wire debugging, forging, annealing, pickling and cleaning. Currently, the Ag base materials used in China include Ag, AgNi, AgCdO and AgSnO2.

2. Alloy internal oxidation method Ag metal oxide sheet contact tips

    The alloy internal oxidation method sheet contact tips are mainly used in contactors. At present, the alloy internal oxidation method contact tips used in China are mainly AgCdO and AgSnO2In2O3.

    The process flow is: alloy casting → alloy plate extrusion → composite complex silver hot rolling → cold rolling → annealing → stamping → internal oxidation of alloy → cleaning → finished product. This type of contact has uniform metallographic distribution, high hardness, low resistivity, good electrical conductivity, thermal conductivity, and good wear resistance and adhesion resistance.

3. Solid-phase sintering powder metallurgy contact tips

    Solid-phase sintering powder metallurgy contact tips are mainly used as static contacts in circuit breakers (molded case circuit breakers and frame circuit breakers). At present, the commonly used solid-phase sintering powder metallurgy contact tips in China include AgWC12C3 and AgNi30C3.

    The process flow is: powder mixing → powder granulation → initial compaction → compact sintering → compact compaction → cleaning → finished product. This type of contact has relatively low hardness and low resistivity. The material generally contains graphite powder with good adhesion resistance, which facilitates the circuit breaker to reliably break when encountering short-circuit current.

4. Infiltration method powder metallurgy contact tips

    Infiltration powder metallurgy contact tips are mainly used in movable contacts in circuit breakers. At present, the infiltration method powder metallurgy contact tips used in China include AgW50, AgWC40 and CuW70.

    The process flow is: skeleton powder mixing→powder granulation→initial pressing of the skeleton→skeleton sintering→skeleton infiltration→cleaning→finished product. The contacts generally contain refractory metal W or WC, which have high hardness, low resistivity, good electrical conductivity and resistance to electrical wear, so that the circuit breaker has a high short-circuit breaking capacity.  AgW has good electrical conductivity and is generally used for main contacts; CuW has good arc resistance and is generally used for arc contacts.

5. Extrusion powder metallurgy contact tips

    Extrusion powder metallurgy contact tips are mainly used as static contacts in small circuit breakers. At present, the extrusion method powder metallurgy contact tips used in China are mainly AgC.

    The main process is: powder mixing→powder ingot pressing→profile extrusion→contact cutting→contact decarburization→contact cutting→cleaning→finished product. The resistivity of AgC by extrusion method is very low, and the hardness is higher than that by powder method. The graphite fibers are arranged along the extrusion direction, and the graphite fibers in the contact are perpendicular to the working surface and parallel to the direction of the working current. The electrical performance of the contact with this structure is superior and more reliable.

——The content of the article comes from the Internet