Continuous and semi-continuous casting of premium industrial aluminium alloys

In order to compete in the market, the Norwegian Aluminium industry is continuously seeking new profitable product segments that require superior competence levels and excellent quality of base metal. In order to be in position to efficiently bring new aluminium solutions to the market, a good understanding of the relation between alloy composition, casting process, casting defects and properties is crucial for further processing and final product performance. In this project, we have established experimental as well as numerical frameworks with new and improved modelling tools linking alloy composition and process conditions to nucleation and grain size, macrosegregation and hot tearing and precipitation. Advanced methods have been used to in-situ analyse grain nucleation, growth and the role of grain refiners. The latter has been studied under homogeneous and as well in the presence of thermal gradients. Extension of the grain growth and transport model from globular grains to describe also dendritic grains has been carried out. Nucleation modelling accounted for solute suppressed nucleation. Moreover, the ability to handle new alloys has also been extended by allowing for a direct link to thermodynamic databases. The possibilities of models for the cooling stage of homogenization heat treatments have been extended to multicomponent alloys accounting for particle size distribution. For the study of macrosegergation formation, a comprehensive model for solute transport has been developed accounting for several transport mechanisms including grain transport and grain morphology. 3D applications of such modelling have been developed and compared to industrial castings. The importance of grain morphology during transport and sedimentation has been demonstrated. Recently the role of forced convection as a mean to re-suspend equiaxed grains has been analysed. A framework for the hot cracking problem, both experimentally as well as through modelling, in addition to a strategy for extracting semi-solid properties for the mushy zone constitutive model has been established. The use non-destructive methods such as micro-CT for hot tearing analysis provide detailed information. The role of grain-size on the semi-solid mechanical behaviour has been studied both by experimentally and modelling using the phase field method. An approach for estimating solid mechanical properties based on chemical composition has been finalised. The industry is also continuously improving melt distributor systems, mould technology, casting equipment and addressing several casting processes (DC casting, twin-roll casting, belt & wheel casting. In this respect, we have extended our process simulator with new physics for example meniscus formation and metal level variations and large deformations, and particle flow. Finally, there has been focus in order to provide the industrial partners with user friendly and CPU efficient tools. Work to increase the efficiency of 3D macrosegregation simulations by exploiting GPU's has been demonstrated. Examples of use from industry are also shared during each project meeting.

The work has increased the R&D groups' knowledge base on solidification and casting and has been central for maintaining the national competence. The knowledge has been implemented in modelling tools and experimental methods that will constitute the basis for future research on alloy development, optimisation of casting processes and development of new casting technology. Two PhD candidates have been educated. The project has resulted in 17 journal papers, 7 conference papers and presentations. Strategic, international collaboration has been strengthened and new collaborations have been initiated. Project results are already used within several new research projects for Norwegian industry. 1 to 2 BIA project applications and at least 1 to 2 EU project applications in 2018-2019 rely on the tools developed in PRIMAL. Part of the competence is of high relevance to Si production, Weldsim has also been used for additive manufacturing and tools are also used by international industry.

In order to compete in the market, the Norwegian Aluminium industry is continuously seeking new profitable product segments which require superior competence levels and excellent quality of base metal. The focus on recycling also brings new challenges in terms of impurities and trace elements. The industry is also continuously improving melt distributor systems, mold technology, casting equipment and addressing several casting processes (DC casting, twin-roll casting, belt & wheel casting). In order to be in position to efficiently bring new holistic aluminium solutions to the market, a good understanding of the relation between alloy composition, casting process, casting defects and properties is crucial for further processing and final product performan ce. The goal of the project is to develop new knowledge systematised in the form of modelling tools describing phenomena, mechanisms and alloy aspects that are critical for the development of Aluminium alloys with targeted properties based on continuous and semi-continuous aluminium casting processes. The final aim is to provide the basis for innovative (alloys and products) and robust current and novel casting processes (rapid prototyping, productivity, cast product soundness).