Abstract: Precipitation behavior and evolution law of second-phase precipitates in high-grade non-oriented silicon steel with content of 2.5% silicon normalized at different temperatures were investigated by means of scanning electron microscopy, transmission electron microscopy and focused ion beam scanning electron microscopy. The results show that as the normalizing temperature increases from 850 ℃ to 1100 ℃, the micron-scale second-phase particles show the order of primary growth-precipitation-secondary growth-dissolution; When the normalizing temperature is lower than 920 ℃, the composite growth of AlN+MnS is dominant; then the number of small-sized MnS, AlN and their composite precipitates increases rapidly, reaching a peak at 950 ℃; When the normalizing temperature is further increased, the number of second-phase particles decreases rapidly and then slowly increases to equilibrium, and the large-size precipitates appear to partially dissolve. The nano-scale precipitates are mainly Cu₂S and Cu₂S+MnS composite precipitation. And when normalized at 950 ℃, 2.5%Si non-oriented silicon steel has the lowest iron loss.

Key words: 2.5%Si non-oriented silicon steel, normalizing temperature, second-phase