For the purpose of supplying useful information to manufacturing organizations, and of systematically examining the effects of temperature and time of annealing on the domestically produced low silicon steel electrical sheets, a series of experiments has been performed. The results show that the lowest obtainable values of core loss of samples box-annealed in its own atmosphere are approximately P10=2.3 watt kg, P15= 5.2 watt/kg, 30% lower than the permissible values set in ГOCT 802-41 for э1A.