The composition of oxide layers on Fe-Si and their influence on magnetic properties

Iron alloys with 2.98 percent to 3.3 percent silicon and up to 0.84 percent aluminium were subjected to a two-stage final annealing treatment in a H2atmosphere (a tandem anneal treatment). The moisture content of the gas for the first stage at 850°C was varied between -3.6 ≤ 1g (H2O/H2) ≤ 0. Measurements were presented of the gain in weight by oxidation during the first stage and during the second annealing stage at a temperature of 1150°C, the moisture content of the gas being 1g (H2O/H2) = -2.1. It is shown that the composition of the oxide layers on these alloys varies from the first to the second annealing stage, and the annealing conditions, and consequently these oxide layers, affect magnetic properties such as coercive force.