Measurement of ingot-crucible boundary conditions during vacuum arc remelting
This study is part of an ongoing program aimed at characterization of macrosegregation in vacuum consumable arc remelting. Such macrosegregation is attributed to fluid flow in the melt pool and the solidifying zone atop the ingot, so its prediction requires precise determination of the thermal conditions which shape these zones. These conditions in turn result from the complicated processes which fix the heat flux distribution between ingot and crucible wall. The experiments reported here attempt measurement of this flux distribution on the outside of the crucible wall, and calculation of the inside flux from that data. Measurements are made with an array of 40 stainless steel sheathed, electrically insulated, cromel/alumel thermocouples imbedded in the outside surface of the 203 mm ID copper crucible. In one melt two Ta sheathed, electrically insulated, W-5Re/W-26Re thermocouples were imbedded in the inside wall as well. Simultaneous measurements were made on total input power to the furnace, and by monitoring coolant flowrate and temperature rise, of total coolant power extracted. Major interest is on the 15 to 20 min. duration period of quasisteady melting conditions at constant melt current of 6 kA. Checks on ingot length (and thus, on meltrate) were obtained at intervals by driving the electrode down to the pool surface, causing a ram short. Results for two melts of U-6w/oNb give meltrates which agree to 7%, and indicate that about half the coolant power is heat deposited above the pool surface, and half below. The ingot-crucible contact extends from 50 to 75 cm below the pool surface. Measured inside temperature rises are compatible with inside temperature inferred by solving the inverse heat flow problem for the crucible wall, but noise levels preclude assigning significance to this agreement.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5044562
- Report Number(s):
- SAND-83-0150C; CONF-8307101-2; ON: DE84008851
- Country of Publication:
- United States
- Language:
- English
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