Residual Stress Distribution in Grain-oriented Silicon Steel

We investigated the residual stress distribution in a grain of laser-irradiated and gearrolled grain-oriented Fe-3%Si silicon steels by X-ray stress measurement method in order to clarify the effect of residual stresses on magnetic domain refining. Dotted cavity lines were formed by Nd:YAG laser with a power density of 3.3 mJ/pulse for the laserirradiated sample. By using a newly developed X-ray stress measurement method for a single crystal, the tensile residual stresses of 70-160 MPa were observed only in the vicinity of the laser-irradiated lines. After annealing at 1027 K for 2 hours in hydrogen, the residual tensile stresses were released and the domain-refining effect vanished. As for the gear-rolled sample, grooves of 0.1 mm wide and 0.015 mm deep were induced at 5 mm intervals. After annealing under the same condition, the residual stresses around the groove were released, whereas the refined magnetic domains were preserved. Therefore, the residual stresses should have no relevance to the domain-refining, which explains the tolerance to the thermal annealing for the gear-rolled ones. INTRODUCTION Grain-oriented Fe-3%Si steel, consisting of {110}<001> oriented large grains, is a soft magnetic material mainly used for transformer cores. In order to reduce the energy consumption in industries, the reduction in iron core loss has been strongly demanded. This has been achieved mainly by improving {110}<001> alignment, making the thinnergauge material and refining the magnetic domain spacing[1]. Pulse laser irradiation [2] and gear-rolling [3] techniques have been developed for the last purpose. It has been recognized that the gear-rolled samples have a greater heat-resistance than the laserCopyright ©JCPDS International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 402