2005 Volume 77 Issue 5 Pages 308-313
Recently, Rapid Prototyping has attracted considerable attention as a new manufacturing technology for metallic molds and parts. The optimum conditions to control the shape of castings produced by fused spinning deposition (FSD) method have been investigated for cylindrical and rectangular shaped hollow tube and solid specimens. In the present work, a double tube casting using two metallic materials, i.e., alloys having high melting point (Tm) and low melting point, was produced without welding. A cylindrical tube casting of Cu-20mass%Sn alloy (Tm = 1173 K) was prepared by sand mold casting, and set on the substrate of FSD apparatus. Then, Al-4mass%Cu alloy (Tm=923 K) was melted in a mullite tube with a small nozzle at the bottom. The molten aluminum alloy was cast on the outer surface of the copper alloy tube casting. It was found that the sufficient interface bonding between the aluminum alloy and copper alloy was obtained by using a refractory substrate with low thermal conductivity. Under a suitable condition, a part of the copper alloy casting was remelted and a reaction layer consisting of α phase, θ phase, δ phase and tin-rich phase was formed at the interface. When superheat of the molten aluminum alloy was increased, the reaction layer width was also increased. An excess heat capacity of the molten aluminum alloy leads to melting down and exfoliation of the aluminum alloy from the copper alloy casting by centrifugal force. A stable double tube casting was obtained when an optimal super heat of the molten aluminum alloy was chosen.
