Mamoru Matsuo

Fabrication of 5052 Aluminum Alloy Thin Slab by Electromagnetic Casting and Mechanical Properties of Its Cold-Rolled Sheet

Effects of bottom block, spout shape and casting rate on thickness, outward appearance and structure of aluminum alloy slabs were evaluated in order to improve the electromagnetic casting process for manufacturing thin slabs. Furthermore, thin slabs of 5052 aluminum alloy were directly cold-rolled and tensile properties of the rolled sheets were evaluated. Slabs with a flat surface, fine microstructure and about 7mm in thickness are obtained by using a bottom block having a thickness of 6mm and a spout with cover. Even when cold rolling to a reduction of 75%, there is no surface defect. The cold-rolled sheet has tensile properties that satisfy the JIS requirements except for tensile strength of O-treated sheet, which has a value that is higher than that specified by JIS. However, the tensile properties are superior to those of the cold-rolled sheet obtained from DC hot plate.

Development of aluminum alloy sandwich panel using roll bonding and superplastic buldge forming.

The possibility of fabricating the metallic bonded truss structured aluminum board was studied by the combination of the roll bonding process and superplastic forming. Al–1.6%Mn alloy sheet was first pre-clad to the superplastic 5083 aluminum alloy sheet. These sheets were piled in three layers and then hot roll bonded. Here, the anti-bond coat was printed on both sides of the core sheet in striped pattern before hot roll bonding. These hot rolled bonded sheets were next subjected to cold rolling to obtain the superior superplasticity. The three layered roll bonded sheets were set between flat dies at superplastic temperature and the truss structured board was formed superplastically by applying the internal gas pressure to the un-bonded area with gradual opening of the flat dies. It was found that a higher pressure and a slower gap opening speed was desirable to obtain a flat surface board. As the results, the truss structured high rigidity board with flat surfaces was obtained.

Meniscus shape control of molten pure aluminum by electromagnetic force.

The fundamental phenomena of Electromagnetic Casting (EMC) were investigated. The magnetic flux density, current density and meniscus shape were measured under the electromagnetic force provided to the molten aluminum by 10 turns coil. The magnetic flux density in the coil without load is directly proportional to the voltage, reaching maximum 0.09 tesla. The induced current flows mainly inside of skin in the molten metal (skin effect), and the electric power consumed in the molten aluminum is about 2kW, and the electric power efficiency is about 10%. The meniscus height is directly proportional to square of the voltage, and the surface tension due to the strong oxide film effectively supports the molten aluminum. The meniscus height decreases when the screen is inserted. It decreases to 80% (Al), 70% (Brass), 50% (cast iron) and 45% (SUS) of the height prior to insertion and it is due to electric conductivity of screen.

Control of magnetic field by screen coil on electromagnetic casting.

Screen effect in Electromagnetic Casting (EMC) was continuously controlled over a wide range by replacing usually used metal screen with screen coil. The resistance of external coil with an insertable iron core was connected with condenser resonance circuit to obtain stronger electromagnetic fields. As a result, a maximum density of 0.13 T was obtained by this electromagnetic coil. By using this apparatus, the vertical side of levitated liquid metal is made more straight and the stable, vibrationless free meniscus is obtained. The area of horizontal cross section in the melt is also changed by altering the resistance of external coil, being influenced by number of turns and/or length of iron core insertion. This apparatus will contribute to the development of EMC.