Direct Chill Casting of Magnesium using Hot-Top-Technology for Improved Casting Quality

LKR has a long history of direct chill casting of magnesium. Until recently a conventional mold design was used (i.e. Magnumcast). For the increased quality demands of the customers for extrusion and forging applications and furthermore for the production of newly developed alloys an improved die design had to be developed. This design allows for improved surface quality and smoothness. Therefore the billet can be extruded in "as cast" shape, which strong-ly decreases machining costs. Additionally, reduced sump depth results in a more homogene-ous grain size distribution and less macro segregation across the diameter. A further benefit of the new technology is a reduced technical complexity compared to the present state. This paper discusses the microstructural investigations made and the necessary steps for im-plementing the new technology in existing equipments.