Evidence for the effectiveness of stress coatings in altering magnetic properties of commercially produced grain-oriented 3% silicon-iron (invited)

Commercially produced 0.27 mm samples from 3% silicon-iron heats of TRAN-COR H ( ) were treated with varying weights of CARLITE and CARLITE 3 coatings in the laboratory. On a relative basis, the CARLITE and CARLITE 3 coatings are considered to produce low and high amounts of tensile stress, respectively, in the rolling direction of grain-oriented 3% silicon-iron. Effects on magnetic properties of Epstein samples at various inductions were compared both in the flat condition and after forcing flat samples previously annealed on a 45" radius. CARLITE 3 coatings consistently produced lower core loss and reduced sensitivity to bending stresses. An optimum coating weight, lower than commercial practice, was indicated from the data on core loss. A detrimental effect, proportional to coating weight, was found for exciting power and B8permeability. Also, several heats of grain-oriented 3% silicon-iron ( ) were split between CARLITE and CARLITE 3 coatings on production equipment. CARLITE 3 coatings improved core losses and harmed exciting power. Model transformer core (corelet) results verified the core loss improvement found in Epstein samples.