A. when the marterial is poor conductive(such as irion,steel,stainless steel,nickel),the marterial of electrodes need to using high conductive(such as copper,alumina copper, chromium Zirconium copper),but,not using the red copper,as the strength of the red copper is too low at the high temperature.
B. When the marterial is high conductive(such as copper,aluminum,) the marterial of electrodes need to using poor conductive(such as tungsten, molybdenum,tungsten copper)