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.