Preparation And Soft Magnetic Properties Of Iron Powder Core And Fe-based Amorphous Powder Core

Soft magnetic powder cores have a wide range of applications in various inductordevices, power transformers and other fields. In this dissertation, the current research status ofmagnetic powder cores and its applications in the world were summarized. Fe and FeSiBbased soft magnetic cores were prepared. The effects of processing on the magnetic propertieswere investigated in detail.After completion of the market research for different soft magnetic materials companies,some representative corporations were selected to analyze the type, performance, applications,and development of their magnetic core products. Especially, based on the author’sengineering practical experience in Guangzhou Deloop Electronic Device Co. Ltd, thepreparation process of soft magnetic powder cores and production process of electronicdevices were introduced. The current development in soft magnetic powder cores industrywas discussed. In addition, the faced problems and the future trends of domestic powder coresindustry were analyzed.On the basis of the investigations on the research and development of soft magneticcores, iron powder cores and iron-based amorphous powder cores (Fe78Si9B13) werefabricated by powder metallurgy method. X-ray diffractometer (XRD), differential ScanningCalorimeter (DSC), scanning electronic microscopy (SEM), vibrating sample magnetometer(VSM), AC and DC soft magnetometers and other devices were employed to characterize themicro-structure and properties of the samples. The effects of pre-treatment for raw powdersand core preparation parameters on the permeability, power loss, coercivity, quality factor ofthe soft magnetic cores were investigated. The main research scope and the conclusions are asfollows:(1) Magnetic powder cores prepared by different processes have the constantpermeability between the frequencies of1kHz and100kHz. The soft magnetic properties areinfluenced by powder type, powder size, kind and quantity of coating agent, compactionpressure and annealing temperature.(2) For iron powder cores synthesis, adding2wt.%epoxy resin E-12as insulating bindercan lead to excellent magnetic properties. For the amorphous powder cores synthesis, increased magnetic permeability and reduced power loss can be obtained by employingSH-201high temperature silicone resin as the binder, and passivation treatment in thephosphate-acetone solution to form a uniform and dense passive film on the powders.(3) Different types of powders require different compaction pressures for coreconsolidation. Generally, a large pressure is necessary. Iron powders are relatively soft andeasy deformed. The optimized molding pressure is400MPa. For amorphous powders, acompaction pressure of1200MPa can lead to a density up to5.42g/cm~3. The coercivity canreach the lowest value of73.7A/m.(4) The cores prepared using the SH-201high temperature resistant silicone resin as thebinder can be heat treated at relatively high temperatures. It was found that heat treatment canincrease permeability and reduce core loss. Reasonably set heat treatment temperature for theamorphous powder cores can lead to high permeability, large quality factor, low coercivityand low core loss.(5) Through gradual optimization of the process conditions, the best preparation processconditions for the iron powder core include using2wt.%epoxy E-12as binder, particle size50μm-75μm, and molding pressure of400MPa. The initial permeability can reach83.1under50mT/50kHz. The effective permeability reaches approximately105, and unit mass loss is75w/kg. The optimal preparation conditions for amorphous FeSiB powder cores includepassivation in2wt.%phosphoric acid acetone solution, use of2wt.%organic SH-201siliconeresin as binder, compaction pressure of1200MPa, heat treatment at400℃for30min. Thesoft core exhibits an optimum permeability of26, minimum core loss of11.1W/kg at50mT/50kHz.