The influence of annealing conditions on the internal oxidation and magnetic properties of silicon-aluminum bearing electrical steels

Abstract

Internal oxidation often occurs in electrical steels during decarburization anneals of sufficiently long time and high oxygen potential, resulting in deterioration of magnetic properties. Relationships between subscale thickness, anneal time, and effective oxygen potential of the anneal atmosphere were established for a Si-Al-bearing electrical steel. These kinetics are described by a Rhines diffusion equation modified to accommodate the oxygen potential. Electron microprobe and Auger spectroscopy confirmed the significance of solute element diffusion. Permeability at 1.5 T was found to decrease about 50 units for each micron of subscale thickness, while core loss remained essentially constant. SEM observations of the fine structure were used to estimate that the coercivity of the subscale is sufficiently high that this region is barely magnetized. Thus, the induction of the clean interior metal must be higher than the measured average value, resulting in reduced apparent permeability. Good agreement with observation was obtained.

Effect of Alloying Elements, Water Vapor Content, and Temperature on the Oxidation of Interstitial-Free Steels

“…Thus, Sb and B additions appear to decrease the amount of oxidation. This is in agreement with earlier work that proposed that the addition of Sb [32,33] and B [34] can suppress the internal oxidation of alloying elements due to their high segregation enthalpy. [35,36] Figure 15 shows the surface morphology for these four specimens; it can be seen that surface oxides appear to be more uniform on specimen 4, in which both B and Sb are present, and EDS results indicate that the ridges are rich in Mn, O, and P. Another important feature is that the grainboundary ridges are composed of coarse ridges and thin ridges.…”

Effect of stress relief annealing temperature and atmosphere on the magnetic properties of silicon steel

“…In the so called stress relief annealing deformed parts are recovered or recrystallized and residual stresses are relieved. However, interaction of the steel surface with the annealing atmosphere can cause nitration and/or oxidation of the metal [1][2][3][4]. In this work sheared samples of two silicon steel compositions were used to investigate the effect of annealing temperature and atmosphere on recovery of core loss (W 1.5 ).…”

Approach to saturation in textured soft magnetic materials

“…These parallel to the applied field direction. sample axes are numbered 1 (RD), 2 (TD), and 3 (ND), E int ϭ ϪMH ␣ и h xtal [4] respectively. All quantities associated with the polycrystal are calculated in this frame, e.g., the induction.…”

“…[4,5,6] Recent work on nonoriented influence of texture (crystallographic-preferred orientation) steels has demonstrated how sensitive the magnetic properon the magnetic properties of sheets of soft magnetic materities are to subtle variations in processing conditions. [2] Speals, such as iron.…”