Effect of Si addition on the magnetic properties of melt-quenched Ni–Fe alloy strip

A sheet manufacturing technology for 79Ni–Fe alloy, which is highly permeable and has soft magnetic properties, was developed based on the melt drag casting method. Melt drag strip was manufactured using the new 79Ni–Fe–Si alloy designed considering the strip forming ability and soft magnetic properties in the single-roll casting method. The microstructure and soft magnetic properties were measured based on following casting and heat treatment processes. Oxygen concentration within the air-heated molten 79Ni–Fe alloy decreased rapidly following the addition of a small quantity of Si to the existing 79Ni–Fe alloy. Moreover, the effect of enhancing the strip-forming ability was determined by increasing the liquidus line temperature and solidus line temperature interval of 79Ni–Fe alloy with the additional Si concentration. As a result of cold processing and proper heat treatment, the melt drag cast 79Ni–19Fe–2Si alloy exhibited excellent soft magnetic properties compared with the 79Ni–Fe alloy strip. Therefore, the forming ability of melt drag strip can be enhanced by adding a small quantity of Si to the traditional 79Ni–Fe alloy. Likewise, soft magnetic properties can be enhanced by reducing oxygen concentration within the molten metal.