Hot rolling and/or partial recrystallization of γ-austenite give rise to different types of transformed textures, thus affecting the final properties of the cold-rolled, and subsequently recrystallized sheets. The final texture in non-oriented electrical steels is influenced by all textures developed during the processing steps. There is an unexplored possibility of improving the magnetic properties of non-oriented electrical steels through texture control. The total time period for the isothermal annealing, with measurements, was 65 min. The AES measurements were performed after 5 min of annealing, in a 10-min sequence. Prior to the experiment at each annealing step, the specimen was cleaned by ion-etching. A Balzers QMS 200 quadrupole mass spectrometer (Balzers AG, Balzers, Principality of Liechtenstein) was used to analyze the residual gas during the experiments.
The typical pressure during the AES analysis was 10 −7 Pa, which increased to 10 −5 Pa during annealing at 950 ☌. The spectrometer was mounted on an ion-pumped ultra-high-vacuum chamber. The spectra were taken using a 10-kV electron-beam energy for the excitation of the Auger electrons and were recorded with a fixed retard ratio 4 of the analyzer. The temperature was monitored with a NiCr/Ni thermocouple that was attached to the specimen. The surface of the specimen metallographically prepared by grinding and polishing was subsequently cleaned using Ar-ion sputtering in order to obtain an appropriate surface. įor the in situ study of the segregation kinetics of surface active, residual elements in ultra-high vacuum (UHV) the specimen was resistively heated using an alternating current in the chamber of an Auger electron spectrometer (Microlab 310 F instrument, VG Scientific Ltd., East Grinstead, UK). In Fe-0.3 wt % Cu alloys, the presence of up to 0.1 wt % As did not induce grain-boundary cracking. As promotes internal oxidation and facilitates the grain-boundary oxidation at temperatures above 1000 ☌.
Surface cracking is most severe at 1050 ☌. It was also reported that As and (As + Cu) accelerate the oxidation of C–Mn steels and induce hot shortness. Moreover, As was found to segregate to the interface between the matrix and the oxide scale of the micro-alloyed steel. Macroscopic segregation studies showed that As segregated in regions near the top and bottom surfaces of the strip. In a micro-alloyed steel resulting from a compact strip production (CSP) process, As was found to segregate at the grain boundaries when the steel was annealed in the temperature range 950–1100 ☌. The effects of residual element As on the properties of steels are receiving more and more attention. The detected phenomenon of the As versus Sn site competition could be valuable for the texture design and surface engineering of silicon steels with a thermodynamically stable two-phase (α + γ) region.Īrsenic (As) can originate from several resources, such as complex iron ore, scrap steel, ferroalloys, and other furnace charges. The intensity of the As surface segregation in the temperature range 800–950 ☌ is proportional to the calculated amount of γ-austenite phase in the (α + γ) steel matrix. In spite of there being twice as much Sn compared to As in the bulk material, the As prevailed in the surface enrichments of the polycrystalline silicon steel at 950 ☌. These competing interactions are strongly time dependent. Attractive interactions between the segregands produced co-segregation, e.g., between Sn and Sb, whereas repulsive interactions resulted in site competition, e.g., between Sn and As. During annealing in the temperature range of 300–950 ☌, different kinds of interactions between the segregated residual elements were observed. The segregation kinetics of surface-active, residual elements are investigated in an in situ study of annealing scrap-based silicon electrical steel sheet where the arsenic (As) surface segregation is highlighted.