Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAMIn the group Soft Magnetic Materials, innovative powder technologies are used to manufacture soft magnetic components with reduced losses or special property profiles. Different concepts are pursued depending on the requirements especially the frequency range. Common to all is the powder metallurgical manufacturing which enables the near-net-shape processing from a broad variety of materials. Mostly, iron-based alloy systems are analyzed. Depending on the concept, the components can be manufactured using a wide variety of processes. An important focus is the development of soft magnetic composites with inorganic coating for high frequency ranges.
Soft magnetic materials
© Fraunhofer IFAM Dresden
Soft magnetic materials
Powder metallurgical manufacturing processes for the production of soft magnetic components
3D Screen printed stator- and rotor sheet of a motor (PMSM).
Press with tool for toroidal cores
- Conventional Pressing (100 t) is used for manufacturing Soft Magnetic Composites especially for isotropic soft magnets with lowest losses at high frequencies.
- Additive manufacturing: IFAM provides binder-based and powder bed processes for the additive manufacturing of components. 3D screen printing is used to fabricate electrical steel sheets with customized composition and thickness. Thus, mechanical and magnetic properties can be adjusted. Electron beam melting is also used to manufacture soft magnetic components with special material compositions that cannot be produced by conventional means.
- Soft magnetic powder composites with special property profiles can be prepared by field-assisted sintering (FAST/SPS).
- In most cases, soft magnetic components need a heat treatment after manufacturing to achieve the best soft magnetic performance. A wide variety of furnaces are available for realizing the respective temperature profile in the desired atmosphere.
Characterization of soft magnetic components
Toroidal cores – unwounded and wounded for magnetic characterization
B-H-Curves with different frequencies
Strip tester for magnetic characterization
- Powder characterization: In the accredited laboratory, the incoming powder is comprehensively characterized and evaluated. This includes the determination of particle size distribution, morphology, bulk density, flowability, composition and much more.
- Structural characterization of the components: The generated test components can be extensively characterized to evaluate their structural properties. In this context, the correlation of the microstructure-property relationship is particularly essential, so that images of sample cross sections under the optical microscope or scanning electron microscope can provide informative insights. Due to the high influence of impurities, elemental analysis to determine the oxygen, carbon and nitrogen content is also an important tool.
- Magnetic characterization of the components: The characterization of the decisive soft magnetic parameters is carried out by recording B-H curves on strips or ring samples in a DC and AC field. In particular, the coercivity and permeability are decisive for drawing conclusions about the processing. The frequency-dependent losses and the electrical resistivity are further important parameters that can be determined.
- Mechanical characterization of the components: The components can be evaluated regarding their mechanical strength. Tensile or compression tests are used in adapted geometries. The determination of hardness values is also a common method for evaluating the mechanical properties.
Cross section soft magnetic composite (Differential interference contrast)
Cross section soft magnetic composite (Dark Field)
Cross section soft magnetic composite (Differential interference contrast)
The "Soft Magnetic Materials" working group of Dr. Inge Lindemann-Geipel researches the powder metallurgical production of application-relevant material concepts for the manufacture of loss-optimized soft magnetic components. Within the department Sintered and Composite Materials, the group has comprehensive know-how and the latest technologies in powder processing taking also generative manufacturing into account. The applications range from electromobility to modern energy converters in electrical machines.
The project "WeiMag" (600420) is funded internally through the Fraunhofer Attract program.