Effect of Hot Rolling Heating on Precipitated Phases of AlN and MnS in Non-oriented Silicon Steel

The precipitation of AlN and MnS has a significant impact on the magnetic properties of non-oriented silicon steel. Due to the influence of hot rolling heating process, the precipitation phase in non-oriented silicon steel is closely related to the effect achieved by non-normalization process. Taking the forging billet of 1.5% Si−0.3% Al non-oriented silicon steel as the research object, the thermodynamic software was used to calculate the possible precipitation phase in the steel. The hot rolling heating experiments were conducted on the experimental steel at different temperatures and holding times using a box type resistance furnace. The morphology and size of the precipitates, and sample grain size were characterized and analyzed with optical microscopy (OM) and scanning electron microscopy (SEM). The effects of hot rolling heating temperature and holding time on AlN and MnS precipitates in experimental steel were studied.The results show that the inclusions in the experimental steel are mainly AlN and MnS, when the heating temperature is 1 050 ℃, the holding time is extended from 1 h to 3 h, the proportion of precipitation phase of fine AlN and MnS (with a diameter of less than 1 μm) decreases from 33% to 19%, and the average grain size increases from 100.0 μm to 149.7 μm. When the holding time is 1 h, and the heating temperature is raised from 1 050 ℃ to 1 150 ℃, the proportion of precipitation phase of fine AlN and MnS decreases from 33% to 7%, and the average grain size increases from 100.0 μm to 124.3 μm. Without changing the other experimental conditions, increasing the hot rolling heating temperature and prolonging the holding time will result in increasing in the size of AlN and MnS precipitates and grains in the experimental steel, which is beneficial for achieving the normalization free production process of green and low-carbon non-oriented silicon steel.