Electrode for plasma ARC torch.

摘要

An electrode (14) for a plasma arc torch (10) and a method of fabricating the same are disclosed, and wherein the electrode (14) includes a copper holder (16) having a lower end which mounts an emissive insert (28) which acts as the cathode terminal for the arc during operation. Where a torch (10) is used in an oxidizing atmosphere, the copper holder (16) tends to oxidize, and the arc tends to attach to the oxidized copper rather than the insert (28), which results in the rapid destruction of the holder (16). To prevent this destruction, a sleeve (32) of silver or other metal having a relatively high work function is provided, and which is positioned to surround the insert (28) and form an annular ring (35) on the lower end surface (20) of the holder and thus to surround the exposed end face of the emissive insert (28). The annular ring (35) serves to prevent arcing from the copper holder (16), and so that the arc is maintained on the insert (28).