Study On The Arc Eroding And Invalidation Mechanism Of CuW/CrCu Integrated Contact

Switches play transmitting and cutting electrical current role during the working electrical net as a hinge, the important role will be brought into effect by the key part in switches-arc contact. If the contacts have invalidated and could not accomplished the important role during the working electrical net, switches would detonate, which result in the paralysis of whole net linked by the switches, the higher the transmitting voltage of net is, the bigger the affected area is, therefore, in order to decrease or avoid the arc eroding and invalidation during the net working, it is necessary to study the arc eroding and invalidation mechanism of contacts, sequentially make the whole net stable. At present, the arc contacts in SFe switches is formed by the excellent property of electrical arc resistance of Cu W alloy and the eminent conductivity together with high elasticity of CrCu alloy, so-called CuW/CrCu integrated contact. In this paper, CuW/CrCu integrated contacts with 50%, 60%, 70% and 80% tungsten by weight were prepared by verticaT integrated sintering and infiltration technique, and the arc eroding and invalidation mechanism of contacts were analyzed in detail, the results were shown as following:The mechanism of arc eroding for CuW/CrCu integrated contact is different with the content of W.1. The mechanism of arc eroding for CuW60/CrCu integrated contact is the volatilization of Cu under the arc working, then the particles of W were worn off the matrix, this phenomena isn't formed continuous skeleton during the connecting and cutting. Such-and-such repeating resulted in the arc erosion of the contact, until invalidation.2. The arc erosion of CuW70/CrCu integrated contact is first from the even volatilization of the surface Cu, following by the formation of a W shell on the surface of W skeleton, then the shell flake off, after this, new arc erosion occur.3. The arc erosion of CuW80/CrCu integrated contact is primary forming the thicker shell and th\ shell flake off.4. When there are rich Cu defect in CuW/CrCu integrated contact, the arc eroding loss of the contact is first from the spraying of Cu, then the W skeleton flake off.The property of electrical arc resistance of CuW60 is the most bad one, CuW80 takes second place, and CuW70 is the best one in this test.There are three modes for the invalidation of CuW/CrCu integrated contact: splitting from the binding interface of CuW/CrCu; uneven distortion of contact finger and severe eroding loss. These invalidations are relative to the processing of preparing the contact directly, the products made in conventional and continuous powder metallurgy furnace are more easy invalidation than that of incontinuous one, and so we suggest avoiding this sintering method.1. The splitting from the binding interface of CuW/CrCu roots from the rich Cr and the oxidation of the binding interface, which leads to the higher thermal resistance in binding interface than normal, and the thermal stress enhanced. The extruded Cu is suggested to instead of casting Cu.2. The severe erosion is due to the bad skeleton intensity and isolated W particals, which results from the poor reduce of W surface oxidation. When the arc works, the capillaryIVis poor, so Cu is splitting greatly.3. The uneven distortion of contact finger is due to the uneven distribution of Cr along circle of the contact during infiltration.