DEVELOPMENT OF (100) TEXTURE IN SILICON STEEL SHEETS BY REMOVAL OF MANGANESE AND DECARBURIZATION

An investigation has been made to develop (100) textures in silicon steel sheets utilizing isothermal austenite (gamma)-->alpha-ferrite(alpha) transformation and related processes. 2% silicon steel sheets containing 1% of manganese and 0.1% of carbon were vacuum-annealed and subsequently decarburized in a wet hydrogen-argon gas mixture. During the vacuum-annealing at the alpha/gamma duplex or gamma phase temperatures from 900 to 1 050 degrees C, a thin layer just below the sheet surface transforms to alpha, and a strong (100) texture develops in the layer. By the subsequent decarburization, the grains within the layer grow inward as columnar grains retaining the texture. The decarburized material with the columnar grain structure exhibits excellent soft-magnetic properties. The gamma-->alpha transformation occurring near the surface is due to the removal of manganese during the vacuum-annealing, and the selective driving force for forming the strong (100) texture is thought to reside in the anisotropy of surface energy.