Improvement of Texture and Magnetic Properties by Surface Effect Induced Transformation in Non‐Oriented Fe–0.82Si–1.37Mn Steel Sheets

Abstract

The potential of improving the magnetic properties of non‐oriented electrical steels has been gradually depleted by the conventional method, whereas the new process of α → γ → α transformation annealing can be used to further improve magnetic properties in the steel sheets with different chemical components. In present paper, compared with the recrystallized sheets of Fe–0.82%Si–1.37%Mn steel, the magnetic induction and iron loss are upgraded by surface effect induced transformation. Iron loss value P15/50 drops by about 40% and magnetic induction value B50 increases about 0.050T, mainly because of the decrease of the {111} texture component greatly. Besides, 0.35 mm thick cold‐rolled sheets are annealed under different transformation annealing parameters, and the results indicate that the process parameters have obvious effects on the formation of columnar grains. However, it is difficult to obtain the sharp {100} transformation texture as those of very low Si content or 3%Si alloys.

Application of Transformation Treatment to Commercial Low-Grade Electrical Steels under Different Processing Conditions

“…This demonstrates that transformation treatment can improve both grain size and texture, leading to an improvement in magnetic properties. However, in comparison with our previous laboratory-prepared electrical steels without Al and P [9][10][11][12], such transformation textures in this work are far from satisfactory.…”

“…Figure 7 shows the EBSD maps of finally transformation-treated sample 1# by 1 °C after direct cold rolling of columnar grains to 0.50 mm (80%). It is seen that und different processing parameters (C1 to C3), there is no obvious two layers of colum grain structure with {100} texture, which is related with surface-effect-indu transformation to ferrite, is formed as observed in our previous works [9][10][11][12]. microstructure is rather inhomogeneous and some grains grow, penetrating the s thickness to even 1 mm in size.…”

“…3 summarizes critical temperatures and contents of several steels with different compositions. When we compare the two industrial low-grade electrical steels used in this study 1#-2# with the 3 laboratory-prepared steels, namely, Fe-0.46%Mn, Fe-0.43%Si-0.50%Mn and Fe-0.82%Si-1.37%Mn [9][10][11][12], it is seen that the latter group shows much stronger {100} texture and the typical two layers of columnar grains in final sheets than the former group. The reasons lie in two folds.…”

“…A Zeiss Supra-55 SEM and EBSD Channel-5 system from Oxford Instruments (Abingdon, UK) are used to determine microstructure and grain orientations. To compare the influence of alloying elements Al, Mn and P on critical transformation temperatures, Thermo-Calc software is used to calculate phase diagrams of related steels in the condition of para-equilibrium, for both the steels in this study and those of laboratory-prepared steels without the addition of Al and P [9,11,12]. The transformation treatment parameters are listed in Table 2.…”

“…Our work [1] indicated that hot-rolled bands indeed show various microstructures depending on heating temperature. Our early work on the surface-effect-induced transformation to ferrite which is applied to laboratory-prepared electrical steels containing 0-1.37%Si revealed the good control of the third stage of transformation to ferrite in the final annealing stage and strong {100} texture could be produced successively with the typical two layers of columnar grains [9][10][11][12]. The magnetic properties are much improved.…”