Novel Process for the Formation of Goss Grains by Concentrated Shear Strain on Surface in Inhibitor-Free Silicon Steel

Recent interest in sustainable development increased demand for efficient transformer to reduce energy consumption. In order to meet the high demand for efficient transformer, inefficient batch annealing manufacture for grain-oriented silicon steel, which is core material of transformer, should be improved. Therefore, novel process for achieving about 90% columnar Goss grains without an inhibitor in continuous line, which differs from the conventional batch process, is herein described. Fe-2.0%Si-C alloys were cold rolled and subsequently partially decarburized in a wet hydrogen gas and these steps are repeated several times. In this process, the sheet is divided into surface layer (alpha ferrite) and interior (pearlite-like structure + alpha ferrite). When two-layer sheet is cold rolled, {111} < 112 > is formed by concentrated shear strain and it is developed into Goss seed. During decarburization, Goss grains within surface layer grow inward as columnar grain, retaining the Goss texture of about 90%. Concentrated shear strain on surface layer was formed by large difference of strength between the surface and interior. By this difference, large stored energy difference between Goss and {111} < 112 >, {411} < 148 > is acquired, and this lead to the growth of Goss grains. Driving force for forming the Goss grains is concentrated shear strain on the surface layer. It has been verified that this novel process has a vast potential for making grain-oriented silicon steel by continuous process.