VACUUM INDUCTION MELTING FURNACES

摘要

Vacuum induction furnaces comprising a crucible having a lining layer of bricks of sintered fusible lime, and surrounded by an insulated inductive heating coil present a problem of preventing metal break-out during use. This problem is overcome according to the invention by the provision of a crucible comprising three layers, namely progressing inwardly a heat-insulating ceramic layer, a rammed oxide layer and the said lining layer, the thickness of the said layers being selected so that in use the rammed oxide layer sinters in a zone adjacent the lining layer, the unsintered zone thus taking up movement due to contraction and expansion effects of the crucible in use.