Experiment Study On Welding Technique Of Cantctor In Circuit Breaker

In this paper, experimental study on welding method and welding procedure of contactor which is one of most important components in MCB(Miniature Circuit Breaker).Resistance brazing is the common method in welding the cantactor, but the intention of this paper is studied the welded joint quality of contact reaction soldering , optimizated the processing parameter, analysed the interface microscopic structure and then found the merits and drawbacks of contact reaction soldering and resistance brazing.The results show that: (1) The results of optimizing the parameters range of contact reaction soldering: welding time is from 230ms to 250ms; welding current is from 12kA to 12.4kA; welding pressure is from 1.5kN to 1.8kN. (2) Welding current has the largest influences on shearing force; welding pressure is the least one, welding time between them. With the welding current increasing, shearing force increases, when the welding current is 12.6kA, the shearing force is the maximum then begins to decline; Shearing force increases with the welding time increasing; Shearing force declines with the welding pressure increasing. (3) The silver and copper elements interdiffuse on the weld interface of contact reaction soldering, when the welding current is larger; the amount of reaction thickness is larger. When the welding time is longer, the reaction thickness is longer. At the same processing parameter, the elements diffusion amounts and reaction thickness is more than the length cutting directation's. (4)The microstructure of resistance brazing seam is complicated, the most black area that at the center of brazing seam is rich of phosphorus, which structure is a mechanical impurity of (Cu3P) and (Ag)+Cu3P eutectic structure. The structure of chrysanthemum crystals is (Cu) sosoloid, (Ag) + (Cu) divorced eutectic and Ag3Sn + (Cu). The shape of silver base sosoloid is columnar crystals, which is close to silver base metal. The nickel element in the brazing seam is in the (Cu, Ni) continuous solid-solution. The elements distribution of P and Ni has the same regularity. Ag element distribution has a reverse regularity with P, Ni and Cu, but has the same regularity with Sn.(5)The merits of contact reaction soldering has lower cost in production because it's not using solder and graphite electrode, the weakness of that is the welding equipment is more expensive than resistance brazing's. The shortcoming of resistance brazing is the microstructure of soldering seam that has a lot of eutectic structure and intermetallics, which is bad for the physical and mechanical property, because the fusing temperature of eutectic structure is low and the resistance is large, these propeties is bad for contactor's life length.