In recent years, the quality of the vacuum interrupter has been greatly improved, thanks to the introduction of new technologies, new processes, new materials, the path of technological innovation. This was reflected in the use of large vacuum furnace, with a closed row of processes, using low-carbon content stainless steel bellows, with copper - ceramic seal replaced Kovar - ceramic seal, as little as possible with and without cutting and so on.
A process to improve the vacuum seal row of vacuum interrupter, the effective activation of getter, gas internal parts more thoroughly than is conducive to long-term maintenance of the vacuum, but also conducive to storage leak detection method using a vacuum leak detected off slow arc chamber. A closure schedule greatly simplifies the process the structure of the vacuum interrupter, vacuum sealed to reduce the weld, reducing the possibility of leakage. Process to a large extent a closed row of human factors eliminated, improved product quality consistency. Consequent, a closed row of interrupter technique not only improves the quality, while significantly improving the production efficiency and reduce production costs.
Vacuum interrupters are used stainless steel bellows. Previously used stainless steel grades for lCr18Ni9Ti, are commonly used grades for OCr18Ni9 or 304L. 1Crl8Ni9Ti stainless steel, high carbon content, 0.1% or so. These carbon-saturated at room temperature to solution in austenite. When 1Cr18Ni9Ti stainless steel is heated to 550 ~ 800 ℃, the supersaturation of carbon to form chromium carbide precipitation at grain boundaries. Chromium carbides on the grain boundary and the acid reaction is easy to cause pitting and intergranular corrosion.
However, chromium carbide precipitation temperature is just right includes the vacuum interrupter brazing temperature brazing interrupter which will result in 1Crl8Ni9Ti stainless chromium carbide precipitation, which is capacity cause in the course of leakage of the vacuum interrupter gas. The 304L stainless steel OCrl8Ni9 or the carbon content of less than 0.03%, when the carbon content is close to the solubility of carbon in austenite, and thus does not cause heating of chromium carbide precipitation, which can avoid intergranular corrosion and Pitting corrosion, greatly reduces the possibility of leakage.
Bellows manufacturing process general there are two: First, thin-walled stainless steel drawing made directly through the bellows hydroforming (seamless bellows); the second is the first stainless steel sheet used by micro-arc welded thin-walled tube, and then bellows made by hydroforming (straight welding bellows). Now both the production of seamless bellows, also can produce welded bellows directly, can ensure the mechanical life of 10,000 times.
Copper - ceramic seal replaced Kovar - ceramic seal, can greatly reduce the chronic leakage rate. Kovar easily result in grain coarsening after heat treatment, stamping easily lead to small cracks, while cutting solder can easily penetrate the grain boundaries, grain boundary into the solder may be opening up the grain boundaries, resulting in chronic leak. The copper will not be similar and, therefore, copper - ceramic seal the interrupter to prevent the chronic leakage, greatly improve the reliability of the vacuum interrupter.
Because use of these new techniques, new materials, so that vacuum interrupter or vacuum due to leakage caused by the failure rate dropped from 0.3% to 0.1%, or even down to 0.03%. This can not be said that the vacuum interrupter of tremendous progress in manufacturing technology.
