| 摘要 |
Controlling the linear velocity of melt discharge from the discharge outlets of a melt distribution device so as to essentially negate reverse flow from the walls of the mold has been found to produce less oxides and less surface detects in an ingot, particularly an aluminum ingot. This discharge is controlled from the outset of the casting of an ingot because it has been found most defects occur within the initial phase of a cast. A melt distribution device, referred to as a "bag-in-a-bag", is provided which is a pressureless interiorly partitioned receptacle. The partitioning of the receptacle provides an outer bag and a melt-impermeable inner bag in which a pool of melt collects. The pool is deep enough to submerge the discharge end of a spout, to dissipate the kinetic energy of the incoming melt, and to distribute melt from a central zone to discharge zones on either side of the central zone. The discharge zones are provided with outlets through which the melt is discharged at a velocity in the range from about 40 in/min to about 100 in/min depending in part upon the drop rate and the size of the ingot to be cast. Desirable drop rates are in the range from about 2-10 in/min, preferably in the range from 3-7 in/min. A novel starting block is provided which confines the flow of melt so as to form a pool of melt in the center of the mold cavity before the rest of the ingot is cast.
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