METAL TRANSFER DURING VACUUM CONSUMABLE ARC REMELTING

An investigation was conducted to determine how metal is transferred during vacuum consumable arc remelting. The transfer mode was found to be dependent on arc length for the electrode sizes (0.10 to 0.20 m diam) and electrical parameters studied (1.9 to 3 kA and 25 V). At short arc lengths ≤0.03 m, metal transfer was found to occur when liquid metal spikes hanging from the cathode form a low resistance bridge (drop short) by touching the anode and then subsequently rupture. The formation and rupture of these molten metal bridges was confirmed with electrical resistance measurements. During the bridge lifetime (0.0003 to 0.020 s) the arc was extinguished and all of the electrical power was directed through the molten bridge. At long arc lengths (>0.1 m) the spikes separate before touching the anode. Experimental observations concerning the coalescence of molten material at the cathode tip were made and they were found to be in agreement with theories on liquid instabilities. A review of pertinent literature concerning vacuum arcs was conducted and this along with general information on vacuum consumable arc re-melting are included as background information. © 1979 American society for metals and the metallurgical society of aime.