squeeze casting: the future - International Specialised Skills Institute

The Australian ContextA Brief Description of the IndustrySqueeze casting was introduced by Ube Industries Ltd in 1976. Toyota Motor Corporation Ltdpresented their problem to Ube in 1975 because the carmaker was experiencing air leakage in itsaluminium wheels. Regardless of the casting process used, the wheels suffered from slow leaking overtime because of porosity in the aluminium.Toyota asked Ube for help to jointly develop an economical casting method by which aluminium wheelscould be cast to a density that would prevent leaking and using alloys that were heat-treatable in orderto maximise the alloy’s physical properties. The squeeze casting machine was the result.Squeeze casting is now considered a high integrity process because it imparts qualities to a metal thatare difficult to achieve with conventional die casting. This includes absence of porosity, improved wearresistance, and the ability to heat treat the component. Products manufactured on a worldwide basisusing this method include steering knuckles, pistons, engine mounts and wheels.What is Squeeze Casting?Squeeze casting is a die casting method based on slower continuous die filling and high metalpressures. Laminar die filling and squeezing, which is the application of pressure during solidification,ensures that the component is free from blowholes and porosity. This method produces heat-treatablecomponents that can also be used in safety-relevant applications and are characterised by their higherstrength and ductility when compared with conventional die cast components.How is Squeeze Casting Different from the Normal Die Casting Process?The die casting process is the high-speed injection of a molten metal alloy into a steel mould. Thisalloy then solidifies rapidly (solidification time varying from milliseconds to a few seconds) to form a netshaped component and is then extracted from the mould. During the die casting process the die isfilled at high speed, but during squeeze casting the filling process takes longer, from a half-a-second tothree seconds. This slower approach permits a die filling that is virtually free of gas entrapment.What are the Benefits of Squeeze Casting?Using this method it is possible to produce heat-treatable castings (not possible in conventional diecasting due to air entrapment). It has become known as ‘squeeze’ casting because the casting issqueezed in a controlled fashion under high pressure to complete the filling of the die.The applied pressure and instantaneous contact of molten metal with the die surface produces arapid heat transfer condition that yields a pore-free, fine-grained casting with mechanical propertiesapproaching those of a wrought product. Squeeze casting offers high metal yield, minimum gas orshrinkage, low porosity and an excellent surface finish, combined with lower operating costs.Squeeze casting decreases the percentage of porosity and increases density as well as grain size. Thisfine grain size improves the mechanical properties of the squeeze cast component.Another big advantage of squeeze casting is the possibility of using pre-forms (high-porosity bodiesmade from specially selected materials). By infiltrating these with molten metal under high pressure itis possible to further improve the properties of the aluminium through composites and, hence, createworking surfaces that are extremely hard wearing.Of the many casting techniques available, squeeze casting has greater potential to create lessdefective cast components. Since the as-fabricated components can be readily used in service(or require only minor post-fabrication treatment), squeeze casting is regarded as a net or near-netshape fabrication route.89