Decarburization is a common adverse effect at manufacturing and processing of steel semi--products. A series of samples of various shapes, produced from spring steel 54SiCr6 (CSN 14260), was prepared and annealed at 800 • C at air atmosphere for 1, 4, 8, and 20 h. The decarburized layers that appeared on the surfaces were examined metallographically and magnetically by Magnetic Adaptive Testing (MAT). The magnetic tests proved an appreciable sensitivity, which depended on the samples shapes, on the way of measurement and on the surface treatment of the samples before the measurement.Careful weighing of the samples before and after the annealing and/or after the surface treatment proved to be a simple and reliable way for determination the thickness of the decarburized layer as well.
Topic of this work is to compare metalurgy of cast irons poured into sand moulds and into shell molds at IEG Jihlava company and from it following differencies in structures of thin- and thick-walled castings. This work is dealing with investigation and experimental measurement on surfaces and sections suitable thin- and thick-walled investment castings at IEG Jihlava. Cast irons with flake graphite (grey cast iron) and cast irons with spheroidal graphite (ductile cast iron). Both mechanical and physical properties are determined using calculations from as measured values of wall thicknesses L and Lu, Vickers hardness and remanent magnetism. Measurement results are discussed, findings are formulated and methods for castings metallurgical quality improvement are recommended finally.
Cast irons look like 'composites' made of a steel matrix and graphite filler. The standard description of matrix and graphite structure properties, e.g., after EN 945 is not satisfactory. Physical description of its structure can be better carried out using rigidity and hardness of matrix. The expression of this description in a plane using bidimensional vector of tension strength or yield strength offers new useful relations to manufacturing metallurgy. Mathematical models among physical and mechanical properties were derived by statistical analysis. The MAT method is developed for thin-wall castings. Magnetic adaptive testing (MAT) is shortly said magnetic hysteresis NDT method exploiting large datafile created by voltage impulse induced in detection coil winded onto specimen, in dependence on immediate value of magnetic field of specimen. It is combined with another way of testing by a device for remanent magnetism measurement and an ultrasound impulse device with probes placed onto surface of the measured object, together with wall-thickness tester for thick-wall castings. . He has published about 150 publications. From 1997 up to 2005, he was the Head of the Department of Magnetism of the Institute of Physics of AS of CR in Prague. His field of interest are temperature dependence of coercivity, modelling of coercivity, relation between domain wall coercivity, structure of the wall and structure of the material, characterisation of magnetisation processes and non-destructive testing of ferromagnetic construction materials. This paper is a revised and expanded version of a paper entitled 'Quantitative NDT structuroscopy of cast iron castings for vehicles (cars and locomotives)' presented at
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