Nitrogen Without Oxygen : The effect of ferroalloys added after vacuum treatment on cleanliness of nitrogen-alloyed tool steel

Sammanfattning: Nitrogen-alloyed tool steel is made at Uddeholms AB by adding high-nitrogen ferroalloy after vacuum degassing where introduced impurities are hard to remove. In this thesis two types of high-nitrogen ferrochromium are compared, a solid version and a powder cored wire. They are examined in crossection and 16 samples from four charges are examined with Pulse Distribution Analysis as well as systematic microscopy of polished cross sections. The PDA results missed smaller spinel inclusions shown in previous research to be detrimental. The wire form shows promise but more charges need to be evaluated before a conclusion is drawn.