Thin strip continuous casted non-oriented electrical steel has a unique advantage of high magnetic induction. However, under the circumstance of thin strip continuous casting, influencing factors and the physical metallurgy mechanisms of the non-oriented electrical steel remain unclear. The Basic Research on the Inclusions and Precipitates of the Non-oriented Silicon Steel under the Flexible Regulation of the Integration of Solidification, Cooling and Heat Treatment, a key project from Iron and Steel Joint Research Foundation undertaken by RAL, is centered on the twin roll strip casting, subsequent rolling and heat treatment process. It focuses on the control and precipitation of silicon particles in the second phase as well as the research on the mechanisms in which they impact on the finished iron loss. Significant progress was made in the research.
(1) In the process of thin strip continuous casting, primary precipitation has a tremendous impact on iron loss. In non-oriented silicon steel casting strip, AIN or AIN + MnS-based composite precipitation are of principality; the size and volume of the particle grow with the increasing superheat; coarse precipitates formed through high superheat are closely connected with the liquid solid core and its growth.
(2) The secondary precipitation in normalizing heat treatment process is essential to further reduce iron loss. By promoting precipitation and coarsening of the particle, normalizing heat treatment can effectively resolve the bottleneck problem of supersaturated strip casting and issues concerning numerous precipitations, pinning the grain boundaries and damaging the iron loss after the process in the second phase of the solid solution.
(3) By strengthening the organization regulation of coagulation and normalizing heat treatment, the magnetic properties of non-oriented silicon steel can be greatly improved. The results demonstrated that, to adopt the optimized technology of organizational control, Fe-1.3% Si non-oriented electrical steel’s lowest iron loss value (P15 / 50) reaches 4.07W/kg, with its magnetic induction (B50) of over 1.77T. Compared with the direct cold rolled annealing strip with less-often heat treatment, its iron loss has decreased by 0.5-1.0W/kg. If compared with the same grade, Baosteel B50A600, P15 / 50 has decreased by about 0.23W/kg, while B50 improved by 0.06T and above. This achievement broke through the technical limitations in the development of high-quality non-oriented silicon steel during casting process. It blazed new trails for the production of ultra-low iron loss, high magnetic non-oriented electrical steel.