A method for the preparation of chromium - copper - contacts for vacuum switch and contacts made according to this method

摘要

A powdered metallurgical procedure for forming chromium copper contacts used in vacuum interrupters, wherein by adding a small amount of copper powder to the difficult-to-press chromium powder, superior pressed properties are attained and a resulting chromium compact having higher green strength is produced. By practicing the teaching of this invention, vacuum interrupter contacts can be pressed to complex shapes. It is desirable to have a vacuum interrupter contact having an approximately 50% chromium composition. The low compacting pressure necessary to produce a 40% to 60% chromium powder concentrations yields a compact having a very low green strength which cannot be ejected from a die without falling apart; by adding a small amount of copper powder to the chromium powder before pressing a compact having a much higher green strength, which can be readily handled, is obtained. Using the disclosed process a press to shape contact having a variable density can be attained. This process can be used to produce a desirable chromium compact having a high density on the peripheral areas which decreases to a lower density in the center contact area.