In the production of metals, the raw materials and ore will always contain some impurities. As an example, silicon contains impurity elements such as phosphorus and boron that may originate from the reductant materials, and titanium and aluminium that may originate from the ore (silicon oxide). Some of the impurities will always end up in the castings after the metal production. Con-trol of inclusions and dissolved elements is essential to achieve a satisfactory metal quality. In construction materials, mechanical properties lsuch as strength and fatigue, as well as porosity, depend on the content of dissolved impurities and inclusions. For a semi-conductor such as sili-con, also electrical properties such as resistivity and minority carrier lifetime depend on extremely small amounts of dissolved elements and inclusions. For a reactive metal such as aluminium, it is not only important to remove impurities, but also to reduce the formation of oxides and dross.

SINTEF has broad competence in refining, alloying, and melt treatment. These include:

• Measurement of impurity elements and inclusions in liquid and solid metals.
• Removal of impurity elements and inclusions from metals.
• Modeling and design of equipment for melt handling.
• Testing of equipment in water models.
• Alloying and controlled addition of elements.
• Laboratory scale testing of removal and alloying.
• Mathematical models for impurities during different stages of melt treatments.

Applications of this core competence

• Removal of dissolved elements in solar grade silicon by directional solidification.
• Removal of dissolved alkali elements from aluminium by chemical reactions.
• Removal of inclusions by filtration in mechanical filters and by flotation.
• Removal and addition of hydrogen in molten aluminium.
• Addition of silicon and magnesium to aluminium alloys.
• Modelling of the level of hydrogen in cast house, from holding furnaces to casting machine.

SINTEF’s Contact person: Dr Martin Syvertsen