Published Paper Details:

The CRNO steels are used as core materials in electrical motors and transformers. Key properties governing the efficiency of the components are low core loss and high permeability. 50C600 grade with Si % between 1.3 to 1.4 is one of the most common grades in India. Variation in permeability (B50) was found in this grade, with variation from 1.65 Tesla to 1.70 Tesla. Detailed investigation was carried out to find the factors affecting the permeability. The most notifying source was found to be average inclusion size. Inclusions deteriorate the magnetic property by pinning the motion of domain walls. Presence of inclusion above 10 ?m resulted in lower permeability. Subsequently use of diffuser in tundish was experimented for forced flotation of inclusions. Optimum gas flowrates were calculated mathematically and further adjusted with a series of experiments. Bubbling was kept normal and the back pressure was maintained constant during the sequence casting. Average inclusion size reduced from 12 ?m to less than 8 ?m in HR coils with the use of diffuser. In the coils having lower inclusions, average permeability improved from 1.68 Tesla to 1.7 Tesla in the coils produced with the use of diffusers.