Vacuum arc remelting of Alloy 718
Vacuum arc remelting (VAR) is the principal secondary melting process used to produce ingots for almost all wrought Alloy 718 applications. We will attempt, with this paper, to summarize our previous work along with other unpublished work as it applies to VAR of Alloy 718. Successful application for a particular alloy/ingot diameter combination is believed to be dependent on achieving quasisteady thermal/solutal conditions at the solidification interfaces. Local thermal environment is strongly influenced by fluid flows which in turn are driven by global temperature gradients (convection) and magnetohydrodynamic (MHD) forces created by the arc's current distribution. Quasisteady conditions are enhanced when the metal vapor arc is stabilized in the diffuse mode where it provides optimal melting efficiency, macrouniform heating, and axisymmetrical fluid flows in the molten pool atop the ingot. Furnace conditions of low ambient gas pressures (<0.01 torr) and short electrode gaps (<10 mm) stabilize the diffuse mode. A transition from convective to magnetically dominant fluid flow occurs in the pool atop the ingot between 6.6 and 7.6 kA for production size ingots. Constricted arcs are stabilized at elevated ambient gas pressures and electrode gaps. Under these arc conditions fluid flows become unsymmetrical with respect to the ingot axis, ''shelf'' forms on portions of the ingot periphery, and melting efficiency is decreased. 19 refs., 13 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6195796
- Report Number(s):
- SAND-89-0676C; CONF-890646-2; ON: DE89009069
- Country of Publication:
- United States
- Language:
- English
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Metal vapor plasma behavior during vacuum arc remelting of alloy 718
Metal vapor plasma behavior during vacuum arc remelting of alloy 718
Related Subjects
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360104 -- Metals & Alloys-- Physical Properties
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
ARC FURNACES
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
ELECTRIC FURNACES
ELECTRODES
ENERGY TRANSFER
FLUID FLOW
FURNACES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HEAT TRANSFER
INCONEL 718
IRON ALLOYS
MASS TRANSFER
MATERIALS
MELTING
MOLYBDENUM ALLOYS
NIOBIUM ALLOYS
PHASE TRANSFORMATIONS
SOLIDIFICATION
TITANIUM ADDITIONS
TITANIUM ALLOYS
VACUUM MELTING