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The planar flow casting process has drawn increasing attention because of its noticeable advantages including short process, low energy consumption and low cost. However, this process has its limits in that the high melting point and viscosity of silicon steel melt lead to poor formability, which will deteriorate the surface quality of the ribbons. Phosphorus can effectively lower the melting point and viscosity of silicon steel, improving the formability of non-oriented silicon steel ribbons prepared by planar flow casting. Therefore, this paper systematically investigates the effects of phosphorus content on the surface quality, microstructure and magnetic/mechanical properties of Fe–3%Si ribbons prepared with the planar flow casting. The results show that as phosphorus content increases, the surface quality of ribbons significantly improves and the average grain size of Fe–3%Si ribbons decreases. The magnetic induction of the Fe–3%Si ribbons decreases, while the iron loss first increases, then falls, and goes up again. After annealing at 925 °C for 30 min, the magnetic induction of the phosphorus-containing ribbons significantly increased and the iron loss decreased. The enhanced magnetic induction is mainly attributed to the suppression of unfavorable orientation grain growth. Meanwhile, phosphorus and Fe–P precipitated phases increase the resistivity and the eddy current loss reduces. When the phosphorus content is 0.5%, the magnetic properties of the annealed ribbons are optimal, with a magnetic induction of 1.60 T and iron loss of 16.59 W/kg. The tensile strength, hardness and elongation of the Fe–3%Si ribbons before annealing both increase with the increase of phosphorus content.

This paper systematically studies the effect of quenching temperature on the microstructure evolution and the relationship between the microstructure and mechanical properties of air-cooled TRIP steel prepared with C–Si–Mn hot-rolled sheet. The results indicate that when the quenching temperature is lower than (200 °C) or close to (250 °C) the Ms temperature, the martensite transformation mainly occurs during quenching or at early stage of air cooling. When the quenching temperature reaches 300 °C, lathy bainite begins to form. As the quenching temperature increases, the morphology of bainite is transformed from lathy to granular. Bainite transformation during air cooling can promote the C enrichment in austenite, thus improving the thermal stability of the austenite. However, martensite transformation also occurs during subsequent air cooling, and the start temperature of martensite transformation first decreases and then increases with the increase of quenching temperature from 300 °C to 450 °C. The yield and tensile strength of TRIP specimens first decrease and then increase, while the retained austenite content, elongation and product of strength and elongation (PSE) first increase and then decrease. When the quenching temperature is 400 °C, the best elongation and PSE are obtained. The best elongation of 400TRIP specimen is mainly attributed to its highest content and suitable mechanical stability of retained austenite, which is favorable for the expansion of the TRIP effect range. The TRIP specimens prepared with hot-rolled sheet all exhibit ultra-high tensile strength (over 1050 MPa), which is related to the ultrafine ferrite grains, martensite transformation during air cooling and TRIP effect of retained austenite.

Using the planar flow casting method to prepare ultra-thin silicon steel ribbons is an eco-friendly and efficient production method. However, the poor wettability between silicon steel and copper result in difficulties in formability by planar flow casting, which limits its application in production of silicon steel ultra-thin ribbons. The process parameters of planar flow casting are the key factors affecting the formability and magnetic properties of non-oriented silicon steel ribbons, in which the wheel speed determines the solidification rate of the silicon steel melt, which has an important influence on the surface quality and magnetic properties of silicon steel ultra-thin ribbons. Therefore, in this paper, the effect of wheel speed on microstructures and magnetic properties of Fe-3.0 wt %Si alloy are systematically investigated. The results indicate that as the wheel speed increases, the grain size and thickness gradually decrease. When the wheel speed is between 10 and 15 m/s, the surface of the ribbons is relatively flat. As the wheel speed increases, the surface quality of ribbons gradually deteriorates. The ribbons were in fragment with the wheel speed of 35 m/s. Compared with the ribbons before annealing, the magnetic induction B50 increased significantly and the iron losses P1.0/400 decreased sharply at 400 Hz after annealing. The magnetic induction of the ribbons after annealing with the wheel speed of 10 m/s reaches to 1.628 T as the wheel speed is 10 m/s with the corresponding iron loss is 16.171 W/kg. The lower lamination factor and micropores of the ribbons may cause the poorer magnetic properties.

Active front-end converters are part of high power installations for regenerative energy systems, feeding the regenerated energy into the utility. Under the island mode operation of the regenerative energy system, the load characteristics are difficult to detect, and the change of the load characteristics will cause the corresponding resonance. V/f control is usually used to ensure the harmonic quality. At high switching frequency, it has a good control effect. However, high switching frequency causes high switching loss. In order to reduce the switching loss, it will produce more harmonic distortion. Furthermore, the commonly used modulation strategies in this case face the problem of low real-time performance. Therefore, in order to avoid the harm caused by circuit resonance under the condition of reducing the switching frequency, this paper proposes a specific harmonic suppression algorithm with high real-time performance, which can be used as an optional control algorithm in the island operation state of power system. At the same time, aiming at the difficulty of adjusting the weight factors, this paper proposes a weight factor automatic tuner, which automatically adjusts the weight factors according to the harmonic component.

The microstructure evolution and precipitation behavior of hot-rolled Ti–Mo–V micro-alloyed high-strength steel processed at different final rolling temperatures (FRT) and coiling temperatures (CT) were investigated. The results indicated that the decrease of FRT (880 °C–820 °C) promoted the ferrite refinement and strain-induced precipitation in austenite, but it also led to the decrease of pearlite content, which finally led to a slight difference in properties, and CT obviously changed the phase component, grain size, and precipitation behavior. Appropriate reduction of the CT (650 °C–600 °C) could promote the precipitation of (Ti, Mo, V)C and refine ferrite grains, thus improving strength. As the CT further lowered to 550 °C, the precipitation hardening effect would be seriously lessened owing to the significant reduction of (Ti, Mo, V)C volume fraction, finally resulting in the loss of strength. The optimum mechanical properties were attained for the FRT850-CT600 sample, and the ultimate tensile strength (UTS), yield strength (YS), and total elongation (TE) were 908 MPa, 848 MPa, and 21.5 %, respectively, with precipitation hardening up to 383.51 MPa.