AgW30 soft annealed (+A)

Contact material. Silver tungsten materials are relatively rare in Europe, more commonly used in the US. With 20 to 80% W, they have the highest erosion resistance at medium to high switching capacities. This is especially true for high-W materials made by the soaking process. Abrasion and erosion are extremely low compared to other contact materials due to the high hardness and good arc resistance of such materials. However, the tendency to weld at startup is similarly unfavorable as silver-nickel. This relatively strong tendency to sweat must be compensated with design measures on the switching device or by using a non-symmetrical material pairing (mating contact piece of silver-graphite). The burnup is the smallest at a tungsten content of about 80%. Silver tungsten composites are preferred in the United States in low-voltage circuit breakers with rated currents up to 1000 A and short circuit switching currents up to 50,000 A. In addition, they are used in circuit breakers.