Casting of Aluminum Alloy Strand Using Two- and Three-Wheel Caster

Casting of a thin aluminum alloy strand was investigated using two-and three-wheel casters. Molten metal was poured through a launder into a trapezoidal groove in the lower wheel of the caster. In the two-wheel caster, the level of molten metal was lower than the height of the walls of the lower wheel groove, and a puddle was formed between the lower and upper wheels. As a result, it was possible to cast the strand without the formation of burrs. In the three-wheel caster, the level of molten metal was higher than the height of the walls of the lower wheel groove by effect of surface tension. However, with the use of a grooved first upper wheel, the molten metal became semisolid, and it was possible to cast the strand without burrs as this semisolid metal passed under the second upper wheel.

Feeding and Pore Formation in Semisolid Metal Casting

Semisolid casting can provide excellent castings, but the nature of the pore-forming mechanisms has not been properly clarified. In the current communication, it was suggested that hydrogen precipitated during slurry making might have a decisive role in the formation of both gas and shrinkage porosity. Intensive stirring at the end of the slurry making process may act as a degassing step. Without the intense shearing, structures of primary slurry particles form around the hydrogen pores, strongly affecting pore formation and feeding during the intensification stage.

Feeding and Pore Formation in Semisolid Metal Casting

Semisolid casting can provide excellent castings, but the nature of the pore-forming mechanisms has not been properly clarified. In the current communication, it was suggested that hydrogen precipitated during slurry making might have a decisive role in the formation of both gas and shrinkage porosity. Intensive stirring at the end of the slurry making process may act as a degassing step. Without the intense stirring, structures of primary slurry particles form around the hydrogen pores, strongly affecting pore formation and feeding during the intensification stage.

Changing from a Vertical Burr to a Horizontal Burr in the Vertical-Type High-Speed Twin-Roll Caster

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.

Burr Formation in Casting Using Vertical-Type High-Speed Twin-Roll Caster

The mechanism and region of burr formation in casting using a vertical-type high-speed twin-roll caster were investigated using a side-dam plate with a window. A383, an aluminum alloy typically used for casting due to its excellent fluidity at semisolid condition was used. The solid fraction of the semisolid metal ejected from the window was low. When solid metal was ejected from the window, no burr formed. The results suggest that a burr formed when the semisolid metal was ejected in gap between the side-dam plate and the side surface of a roll. The semisolid metal was ejected near the point where the semisolid metal on the two rolls met.

Rheoprocessing of Semisolid Aluminum Alloys

A semisolid metal processing technique is one of the newest metal casting technologies (less than 40 years). However, it has already proved itself as a commercially workable technology for the production of complex shape metallic components with improved mechanical properties and dimensional tolerances. The review of the commercially significant aluminum alloys and the specifics of their rheology are presented in this article.