This paper shows improvements made to a vertical type tandem twin roll caster and the appropriate casting conditions necessary to cast three-layer clad strips, the base strip of which has a lower solidification temperature than the overlay strip. In experiments, 4045 aluminum alloy was used for the base strip and 3003 aluminum alloy was used for the overlay strips. The roll speed was 30 m/min. By connecting the overlay strips to the base strip one at a time and cooling the base strip to between 450 and 530°C after applying the first overlay strip, a sound three-layer clad strip – defined as one in which the interfaces between strips are clear and do not separate during bending-to-failure tests – could be cast. The tensile shear testing between the base and second overlay strip was improved as the base-strip temperature was increased to 450-530°C range.
Strip casting using a side dam plate produces a vertical burr at the strip edge. In the present study, changing this vertical burr into a horizontal burr using a burr changer is proposed. The burr changer was placed inside the side dam plate. The burr changer was made from mild steel and an insulator sheet and cut along the shape of the roll. The burr changer was placed so as to prevent exhaustion of semisolid metal between the side dam plate and the roll-side surface. When the position of the burr changer was appropriate, the vertical burr changed into a horizontal burr. The horizontal burr was flat. The width of the horizontal burr was affected by the lowest position of the burr changer and became narrower as the lowest position of the burr changer approached the roll gap position.
The three layers clad strip was fabricated by a vertical type tandem twin roll caster for clad strip (VTTCC). The effect of the casting conditions of the base strip and the overlay strip on the interface between the base strip and the overlay strip was investigated. The temperature of the molten metal and roll-load were investigated casting conditions. Base strip was AA8079 and overlay strip was AA6022. The proper melt temperature of the overlay strip was around the liquidus line of the base strip. The proper roll-load, which was smaller than rolling, was existed.
The strip casting of Al-SiCp alloy was operated by a high speed twin roll caster. The content of SiCp was 20Vol% and 30Vol%. Both of Al-20Vol%SiCp and Al-30Vol%SiCp strips could be cast continuously at the speed up to 90m/min. The SiCp particle distributed uniformly. This was the effect of fine grain of the strip. The as-cast strip of Al-20Vol%SiCp could be cold rolled after homogenization. The as-cast strip of Al-30Vol%SiCp could be cold rolled after once hot rolling and annealing. The as-cast strip of Al-20Vol%SiCp could be coiled at the diameter of 460mm.
An Al-Mg strip without center segregation could be cast using a single-roll caster equipped with a scraper at speed of 40 m/min. The scraper was useful for flattening a free solidified surface and for cooling the solidification layer by pushing the solidification layer to the roll. Clad strips consisting of 1) an Al-Mn base strip and an Al-Mg overlay strip and 2) an Al base strip and an Al-Sn-Cu overlay strip could be cast using an unequal-diameter twin-roll caster equipped with a scraper at speeds of 30 m/min and 15 m/min, respectively. The base strip and overlay strip were strongly bonded at the interface between the base strip and the overlay strip. The elements of the overlay strip did not diffuse into the base strip. The scraper played two roles in the casting of the clad strip: prevention of the mixture of two kinds of molten metal and making the surface of the base strip a semisolid of high solid fraction.
Applying Crystallographic Orientation Analysis for Exploring Deformation Mechanism of 6.5 wt.% Si Electrical Strip During Twin-roll Thin Strip Casting Process