Research On Improving Soft Magnetic Properties Of1J85Permalloy

As a typical soft magnetic permalloy,1J85alloy have properties of high initial permeability μo, high maximum permeability μm, high saturation flux density Bs and low coercivity Hc in weak magnetic field, with stable microstrucrure, low sensitivity exposed to external magnetic disturbances. This kind of permalloys are mainly used as magnetic core, magnetic conductor, magnetic shielding mask, shell of recording head, magnetic chip and transducer, which is worked in AC weak magnetic field. Magnetic property of1J85alloy produced in a company of Xi’an, can meet the national standard and customer’s requirements, but the performance is somewhat not high enough compared with those from some domestic and foreign manufacturers. So it is crucial to improve the magnetic properties and market competitiveness of1J85permalloy through analyzing possible factors which affect magnetic property, and proposing some processing measures for1J85alloy from the above company subsequently.On basis of the summary on theoretical knowledge of1J85alloy, this paper analyzed related factors which affect magnetic property, discussed function of certain chemical components of Ni, Mo, Si and Mn on magnetic properties with mathematical statistical methods. And then gas contents of1J85alloy from two company was compared. Impact of non-metallic inclusions and microstructure on the magnetic properties of1J85alloy were analyzed by means of thermodynamic calculation followed by experimental verification. The result showed that:(1) Effect of chemical component Ni, Mo, S and Mn on magnetic property of1J85alloy is not so obvious due to minor composition variation and less of statistical data.(2)[N],[H] and [O] gas content differences of two manufacturers were not significant, which were believed to have less influence to magnetic properties.(3) Thermodynamic calculation and experimental research showed that the possible non-metallic inclusion phases formed in1J85alloy were Al6Si2O3, Mn3Al2Si3O12and MgO-FeO-CaO multiple oxides combined with small amount of FeS and MnS. Content of non-metallic inclusions less than or equal to10μm were about74.65%to89.8%. It can be seen that magnetic properties of1J85alloy were deteriorated as the amount of non-metallic inclusions increasing. It is feasible adding SiCaBa alloy into the molten alloy to decrease amount of non-metallic inclusions, ensure residue inclusions ball-shaped through Ca treatment. Thus aim to reduce the harm effect of non-metallic inclusions.(4) With growth of grain size from75.5μm to151μm, the μo of1J85alloy increased from about58.13mH·m-1to126.8mH·m-1, the μm from about196mH-m-1to343.2mH-m-1due to less pinning of domain wall displacement. Large grain size is benefit to improve magnetic conductivity. Increasing amount of Mn and prolonging annealing time contribute to increase grain size.Influent factors affect magnetic properties were gained by maens of thermodynamic calculation and experimental research. And some feasible process improvement measures were proposed subsequently.