| 摘要 |
The cooling water can also contain an additive to promote electrode emission and ionisation in its light arc. The additives form a coating on the electrode surface, protecting it against lateral burning. The coating works by forming a sealed layer which prevents oxygen reaching the graphite, substances being present in the additive which are more easily oxidised than graphite and therefore primarily use up an oxygen which may be in contact with the electrode surface. Examples of the additives are silicon cpds. e.g. quartz, sodium silicate or calcium silicate. Oil or other hydrocarbon-based materials can also be added to the cooling water, or combinations of oil and silicon cpds. Concns. of additives must be between 0.1 o/o and 1 o/o and must be disoslved, in finely distributed form or as an emulsion. To stabilise the light arc, titnaium or boron cpds. are added, e.g. TiO2, B2O3 or TiB or TiB2. |
