INFLUENCE OF HEATING RATE ON THE DECARBU- RIZED ANNEALING MICROSTRUCTURE AND TEXTURE IN LOW-CARBON NON-ORIENTED ELECTRICAL STEEL
XIA Dongsheng, YANG Ping(), XIE Li, MAO Weimin
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083
Cite this article:
XIA Dongsheng, YANG Ping, XIE Li, MAO Weimin. INFLUENCE OF HEATING RATE ON THE DECARBU- RIZED ANNEALING MICROSTRUCTURE AND TEXTURE IN LOW-CARBON NON-ORIENTED ELECTRICAL STEEL. Acta Metall Sin, 2014, 50(12): 1437-1445.
The present work investigates the effect of heating rate on the evolution of decarburized microstructures and textures in low-carbon electrical steels within the inter-critical temperature region. The results show that heating rate has a significant effect on both the final microstructures and textures during the process of decarburization annealing. The ''nucleation'' sites of columnar grains are determined by the heating rate. Slow heating rate would have the ''nuclei'' formed within a certain range of the surface layer, and finally leading to a fine-grained layer near the sample surface. By comparison, a complete columnar microstructure is acquired under the rapid heating condition. Strong g-fiber and relatively weak a-fiber components were obtained at the slow heating rate. In contrast, g-fiber texture is greatly weakened and a-fiber component slightly strengthened under the rapid heating condition, and a relatively strong {001}<120> texture is formed at the same time. The experimental results prove that the final decarburized textures are mainly dependent upon the texture component of recrystallized grains in the ''nucleation'' sites.
Fig.2 Decarburized microstructures in low-carbon electrical steels under different processing conditions (ND and RD denote the normal direction and rolling direction of the sample, respectively)
(a) H1DA2: 25 ℃/s, 900 ℃, 2 min
(b) H1DA2: 25 ℃/s, 900 ℃, 15 min
(c) H1DA3: 11 ℃/s, 900 ℃, 6 min
(d) H1DA3: 11 ℃/s, 900 ℃, 15 min
(e) H1DA1: 25 ℃/s, 780℃, 15 min
Fig.3 EBSD maps (a, b) and corresponding orientation distribution functions (ODFs) (c, d) at φ2=45° section under heating rates of 11 ℃/s (H1DA3) (a, c) and 25 ℃/s (H1DA2) (b, d)
Fig.4 Statistics for recrystallized textures in the surface layer at different heating rates
Fig.5 Partially recrystallized microstructure at slow heating rate
Fig.6 Schematic of temperature profiles within the samples under different heating conditions (T, as Y axis, is the temperature at a certain depth in the sample during the heating process, and 2x/h, as X axis, shows a certain depth along the sample′s ND; Ts is the temperature at the sample′s surface; T0 is the critical temperature for the formation of columnar nuclei; S and R denote the slow and rapid heating conditons, respectively; DR and DS are the critical depth in the sample for the formation of columnar ''nuclei'' at the critical temperature T0 under rapid and slow heating conditions, respectively)
Fig.7 Statistics for certain fiber-textures under slow (a) and rapid (b) heating rates
Fig.8 EBSD maps, (110) pole figure and corresponding φ2=45° section ODF for the H2DA2 samples
(a) partially recrystallized
(b) (110) pole figure for the appointed grain in Fig.8a
(c) after decarburization annealing
(d) φ2=45° section ODF of Fig.8c
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