Rapidly Solidified Metal Foils by Melt Overflow
- PDF / 1,199,665 Bytes
- 4 Pages / 417.6 x 639 pts Page_size
- 84 Downloads / 209 Views
RAPIDLY SOLIDIFIED METAL FOILS BY MELT OVERFLOW
THOMAS GASPAR-, LLOYD E. HACKHAN*, WOOD*** * Ribbon Technology Corporation, **
YOGESHWAR SAHAI**, Box 30758,
Gahanna,
Ohio State University, 11 Wjet 10ta Avenue, Open Universit?', Waltoa Hall, Hilton Keynes,
W.A.T. Orl
CLARK**
AND JOHN
43230
Colu:ibus, OH UK MK7 6AA
43210
ABSTRACT A single roller technique called melt overflow for direct casting metallic sheet, strip or foil is described. A simiple heat transfer nodel is developed to predict foil thickness frorn process parameters. The model agrees with thickness of Ti-6Ai-4V cast strip. Cooling rates as high as 10 K/s are estimated from measuremnents of secondary dendrite arm spacings in 7075 aluainuo alloys. Applications include magnesium-graphite composites. PROCESS DESCRIPTION Ribtec's melt overflow rapid solidification process is shown i3cnejiatically in Figure 1. Mol.ten metal overflows a reservoir onto the surface of a rotating chill block. The melt stream is not extruded through an orifice like melt spinning techniques, rather, the melt pool overflows a reservoir and is channeled by a runner or tundish to contact the moving chill surface. Rapidly soli:ifienntellic fiber, filaments, flakes, particuiate, foil, sheet and scrip can be cast depending on the surface geometry of Fit-. 1 Melt Overflow Process the chill block. Ribbon Technology Corporation operates a 200 pound steel equivalent air induction furnace and water-cooled chill block to cast netallic fiber, filanents, flakes, foils, sheet and strip by melt overflow. Tynically, the chill blocks are 23 cm (9 in) to 36 cm (14 in) diarieter and up to 30 cm (12 in) wide. Chill blocks have been fabricated from copper, brass or steel. Casting rates as high as 20 ni/s (66 ft/s) are used to cast fine fila-ients an(' fioer. Foil, sheet and strip products are cast at rates up to 10 ri/s (33 ft/s) depending on the thickness desired. HEAT TRANSFER MODEL The analysis of heat transfer, when molten metal comes in contact with a metallic chill surface, is very conwlicated. Molten metals do not normally "weld to the substrate, so a therial contict resistance exists at the solidified metal-mold interface. This resistance results in a larqe temperature drop at the interface. The thermal conductivity of the solidifying metal also contributes to the overall resistance to heat flow and results in a therial gradient wichin the solidifying foil. This Tmodel is based on the assuriptions that the interface resistance predominates over the resistance offered by the metal;the teti•perature in the water cooled copper mold and at the castinsurface is constant, To; the metal freezes as a plane at N=11 where the te ;perature is at the freezing point of the metal, Tm; and the teiperature profile within the solidifying
Mat. Res. Soc. Symp. Proc. Vol. 58. 1986 Materials Research Society
24
CHILL BLOCK
STRIP
metal layer is a linear function. Figure 2 presents a schematic diagram of the temperature profile in the solidifying foil. The solidified metal tenperature at the interface
Data Loading...
