Magnetic properties of melt quenched Ni–Fe alloy strips

The microstructure and magnetic properties of high permeability induction 79Ni–Fe alloy strips prepared by the melt drag casting process have been investigated to elucidate the effect of microstructure on their soft magnetic properties. The melt quenched and cold worked alloy strips were heat treated to control the microstructure. The microstructure of the melt quenched strip consist of directionally solidified grains that are inclined from the roll-contact side to the free-air side. A high permeability alloy, 79Ni–Fe alloy strip was well formed by the melt drag cast process using an alumina coated Cu–40Zn cast roll. The surface roughness of the cast strip can be controlled by about 30% cold rolling after the melt drag casting. Melt drag cast 79Ni–Fe alloy strip requires subsequent cold rolling of more than 30% and heat treatment at 1200 °C for 1 h for improving its magnetic property. The required cooling rate for adequate magnetic properties of 79Ni–Fe strips after heat treatment is below 5 °C/s. The present research demonstrated that 79Ni–Fe alloy strip was well formed by the melt drag cast process and the soft magnetic properties of the melt quenched strips could be improved by a combination of cold rolling and heat treatments with cold rolling after completion of the casting process.