Patent ID: 7435307

Claim:
A method of producing a Fe—Ni based permalloy, which comprises continuously casting an alloy comprising Ni: 30-85 wt %, C: not more than 0.015 wt %, Si: not more than 1.0 wt %, Mn: not more than 1.0 wt %, P: not more than 0.01 wt %, S: not more than 0.005 wt %, O: not more than 0.0060 wt %, Al: not more than 0.02 wt % and the remainder being Fe and inevitable impurities into a slab having a cast texture that an area ratio of equiaxed crystal is not more than 1% without electromagnetic agitation, and subjecting the cast slab to a homogenizing heat treatment and further to a hot rolling, wherein the homogenizing heat treatment is conducted at a temperature of 1100-1375° C. under a condition that Ni diffusion distance D Ni represented by the following equation is not less than 39: D Ni =( D t ) 1/2 μm wherein D: diffusion coefficient, D=D 0 ×exp(−Q/RT), D 0 : vibration number item=1.63×10 8 μm 2 ·s −1 Q: activation energy of Ni diffusion=2.79×10 5 J·mol −1 R: gas constant=8.31 J·mol −1 ·K −1 T: temperature K t: annealing time s.