Surface segregation and directionality of {110} grains in electrical steels containing Sn and Sb
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Surface Segregation and Directionality of {110} Grains in Electrical Steels Containing Sn and Sb N.H. HEO A repulsive segregation behavior between sulfur and tin or antimony was observed. Tin and antimony as well as sulfur governed the selective grain growth. In the tin- and the antimony-added strips, the deviation angle distributions between the 001 crystal direction of {110} grains and the rolling direction after final annealing were broad, compared to that in the strip without the solutes. This is due to a {110} cold-rolling texture with a deviation angle between the 001 crystal and the rolling directions that results in the initial annealing texture detrimental to the formation of sharp {110} 001 texture.
In alloy systems, a solute atom segregates to grain boundaries, in order to release the elastic strain energy arising from the atomic size difference between the solute and the solvent and to decrease the grain boundary energy. The much-studied phenomenon of temper brittleness in alloy steels is known to be caused by intergranular segregation of Sn, P, Sb, and As.[1,2,3] Sulfur segregates also to free surfaces as well as the grain boundaries and changes the surface energy in 3 pct Si-Fe alloy strips.[4,5] Electrical steels that are composed of {110} 001 Goss grains are widely used as pole-transformer cores in which the {110} plane is placed on the strip surface. The 001 crystal direction, which is the easy magnetization direction, is parallel to the rolling direction. The formation mechanism of the {110} 001 Goss texture in the alloy strips has been understood in light of the nucleation[6] and the surface-energy-induced selective growth.[5,6] The correlation between addition of tin or antimony, cold rolling texture, and directionality of the {110} grains was N.H. HEO, Senior Researcher, is with the Advanced Technology Center, Korea Electric Power Research Institute, Taejon 305-380, Korea. Contact e-mail: [email protected] Manuscript submitted July 9, 2004. VOLUME 36A, SEPTEMBER 2005—2555
Table I. Chemical Compositions of the Alloys (Weight Percent) Alloys Alloy-S Alloy-Sn Alloy-Sb
C
S
Mn
Sn
Sb
Al
Si
Fe
0.0029 0.0054 0.0026
0.0072 0.0069 0.0055
0.001 0.001 0.001
0.001 0.039 0.001
0.003 0.003 0.039
0.0042 0.0040 0.0
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