Metal can either come directly from electrolysis (primary metal) or as cold, solid material meant for remelting. After filling of metal into, or remelting in, a holding or remelting furnace, the correct chemistry of the metal must be met by first measuring the chemistry, and thereafter if necessary, adding alloying elements. When the metal has reached the correct chemistry, it is important to remove oxides and dissolved hydrogen before casting. Removal of oxides is done first in the furnace by partly skimming of dross (mixture of metal and oxide on the melt surface) and settling on the furnace bottom, and in a later step by filtration in a mechanical filter. Hydrogen is often removed by gas purging in-line in the launder during casting. In addition to these removal processes, some grain refiner is most often added to the melt to obtain small and uniform grain sizes in the final cast product. It is also important to have good control and understanding of the actual casting process and the process parameters which influence the final cast product quality.
Increased recycling requires excellent cast house processes. Insight in the unit processes of recycling, that is collection, classification, liberation, sorting, pretreatment, blending and processes of the final residue must be combined with competence on specific cast house processes (e.g., degassing, filtration, dross handling and treatment, casting).
Projects spans from smaller scale projects (e.g., deciding the wetting angle between a liquid and solid), to larger value chain projects in recycling, research efforts from comprehensive, mechanistic studies of metal oxidation to estimation of the metal content in scrap. As a part of de-carbonisation strategies, we are also investigating the hydrogen content in the melt resulting from retrofit solutions for air gas-fired furnaces with hydrogen burners.
Our competence in refining and recycling of metals includes:
- Removal of dissolved impurities from molten metal
- Removal of inclusions from the melt
- Solidification and refining
- Remelting and addition of alloy components
- Principles of recycling of metals and pre-treatment before melting
We have an extensive international network. The competence is developed over decades together with NTNU through direct project with the industry and research projects financed by the Research Council of Norway in collaboration with national and international industry and universities.
We have access to unique infrastructure in terms of laboratories and modelling software including both thermodynamic software, microstructure, and process models. SINTEF and NTNU received funding for national research infrastructure for the transition to sustainable resource efficiency in metal production and recycling. This enables updating furnaces and molten metal quality equipment together with new techniques such as Laser Induced Breakdown Spectroscopy for liquid aluminium analysis.