Abstract
More than three decades ago, at Fraunhofer IZFP, research activities that were related to the application of micromagnetic methods for nondestructive testing (NDT) of the microstructure and the properties of ferrous materials commenced. Soon, it was observed that it is beneficial to combine the measuring information from several micromagnetic methods and measuring parameters. This was the birth of 3MA—the micromagnetic multi-parametric microstructure and stress analysis. Since then, 3MA has undergone a remarkable development. It has proven to be one of the most valuable testing techniques for the nondestructive characterization of metallic materials. Nowadays, 3MA is well accepted in industrial production and material research. Over the years, several equipment variants and a wide range of probe heads have been developed, ranging from magnetic microscopes with µm resolution up to large inspection systems for in-line strip steel inspection. 3MA is extremely versatile, as proved by a huge amount of reported applications, such as the quantitative determination of hardness, hardening depth, residual stress, and other material parameters. Today, specialized 3MA systems are available for manual or automated testing of various materials, semi-finished goods, and final products that are made of steel, cast iron, or other ferromagnetic materials. This paper will provide an overview of the historical development, the basic principles, and the main applications of 3MA.
Highlights
The laboratory usually determines the quality-related material properties of ferrous materials.Here, several measuring techniques are available, allowing for the microstructure to be directly analyzed, e.g., by x-ray diffraction and optical or electron microscopy
This research project resulted in the construction of the so-called EM8101—the first prototype of a micromagnetic testing equipment that was developed at Fraunhofer IZFP
Calibration to hardness and residual stress was made with different steel grades from tool and Calibrationto tohardness hardnessand andresidual residualstress stresswas wasmade madewith withdifferent differentsteel steelgrades gradesfrom fromtool tooland and spring steels
Summary
The laboratory usually determines the quality-related material properties of ferrous materials. Critical material characteristics should be continuously and completely registered in order to monitor or even control the manufacturing processes with the aim of optimizing them in terms of quality, efficiency, and costs These objectives can only be achieved by the application of appropriate nondestructive testing (NDT) methods. The application of NDT in production has become an indispensable part of modern industry and characterizing materials in terms of microstructure, condition, and properties are important tasks for today’s techniques of production-integrated NDT [3]. In this context, the so-called “micromagnetic” methods are probably the most prominent representatives of such techniques. Micromagnetic methods allow for the nondestructive characterization of all ferromagnetic materials, showing magnetic interactions with the microstructure and stresses on a microscopic level
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