Читать книгу Welding Metallurgy - Sindo Kou - Страница 28

Tungsten electrodes with about 2% ceria (CeO₂), thoria (ThO₂, somewhat radioactive), or lanthana (La₂O₃) have better electron emissivity, current‐carrying capacity, and resistance to contamination than pure tungsten electrodes [3]. As a result, arc starting can be easier and the arc more stable. The electron emissivity refers to the ability of the electrode tip to emit electrons. A lower electron emissivity implies that the electrode tip temperature must be higher to emit electrons and hence the risk of melting the tip is also higher.