Effect of the Annealing Temperature on the Structure and Magnetic Properties of 2% Si Steel

To study the effect of the annealing temperature on the structure and magnetic properties of a 2%Si non-oriented steel cold rolled samples were submitted to final annealing in the temperature range of 540 °C to 980 °C in hydrogen atmosphere. The samples had received cold rolling reduction of 75% to a final thickness of 0.50 mm. Recovery and recrystallization resulted in significant improvement of magnetic properties, with decrease of iron loss (W1.5) and increase of polarisation (J50) and relative permeability (µ1.5). On further grain growth, after recrystallization, there was simultaneous decrease of iron loss, polarisation and relative permeability. Texture evolution on grain growth accounts for the observed decrease of J50 and µ1.5. The beneficial effect of increasing grain size on core loss overcomes the detrimental effect of texture resulting in decrease of W1.5

Effect of Sn on the oxide subscale structure formed on a 3% Si steel

Addition of tin in 3% Si steel is a method to improve magnetic properties since tin in steel is known as an element that segregates at grain boundaries, inhibits grain growth and has a dragging effect on grain boundary movement. However, tin is generally known as an element that has a harmful effect on surface coating properties. The oxide subscale formed on the decarburization annealing of a 3% Si steel containing tin was investigated by SEM, EDS, GDS and FTIR. The forsterite film was evaluated by SEM, EDS and GDS. The higher tin content decreased thickness, oxygen and fayalite/silica ratio in the subscale and resulted into a discontinuous forsterite film with poor oxidation resistance. After secondary coating the samples presented a reddish color due to the formation of iron oxide and poor dielectric property

Excess loss localization on the hysteresis curve

Two alloys of nonoriented electrical steel, with 2.45 and 3.3 %Si, respectively, had their magnetic properties characterized in an Epstein frame. Hysteresis curves for total, quasi-static, and parasitic losses were plotted and overlapped to identify the region where the anomalous loss happens. It was observed that most anomalous loss is from the domain wall movement’s region and a smaller contribution from nucleation and annihilation regions.IPTCAPE