Aluminium-Semi-Continuous Casting Technic, State of the Art

摘要

The first patent concerning semi-continuous casting of aluminium billets, applicated by the former VAW/Germany, took place at Germany in 1936 (Figure 1). Since then many different ideas for designing casting devices followed. Finally the development focussed on the idea of lowering a casting table. To lower a casting table, the plate may be moved with a thread spindle drive, a rope system or with a hydraulic cylinder. Here the development focussed on using a hydraulic cylinder. To guide the casting table with high accuracy, usually a guiding systems with rails at the pit walls was installed. Due to problems caused by metal particles in the cooling water, sticking between bearing shoe and rail, the guiding system is now mostly implemented into the casting cylinder. The size of casting machines varies from 2 t to about 120 t metal weight per cast. The number of moulds depends on the billet or slab size and may be anywhere in the range from 1 to 144 pieces. Typical Mould No.'s for billet moulds are 12, 24, 48, 72 and 96 to match a good mould pattern. The cast length varies in the range of about 3'000 mm up to 7'000 mm, in single cases even up to more than 10'000 mm. The billet sizes are between 3" and 14". A typical billet diameter is 7", but also diameters up to 28" are of interest for forging ingots. The geometry of the cast product may be round (extrusion billets) or rectangular (rolling slabs) or even show an elliptical or t-formed shape. Many modern casting machines allow the cast of billets and slabs with the same machine. All wrought aluminium alloys are VDC-castable. About 70% of casted alloys is AA 6xxx, but also 1xxx, 3xxx and 7xxx are of interest. New demands of the automotive industry request casting of tin-containing alloys (tin is exchanging lead in the futures). Moulds for casting such special alloys are under development. In the following description, typical design properties of state-of-the-art aluminium-semi-continuous casting machines - or better said: Vertical Direct Chilled (VDC) Casting Machines will be discussed.