Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Magnetic permeability measures for the detection of heat treatments and anisotropy in a SAE 4340 steel
Submission Author:
Edgard Silva , PB
Co-Authors:
Edgard Silva, Arthuci Francis Pereira Lima, Carlos Eduardo Bezerra Lopes, Louise Gomes de Lima, Augusto Sérgio Oliveira Sampaio, João Pereira Leite, Josinaldo Leite
Presenter: Edgard Silva
doi://10.26678/ABCM.COBEM2021.COB2021-1386
Abstract
Microstructural variations result in changes in the magnetic properties of ferromagnetic materials and their mechanical properties. These lead to a change in the magnetic permeability of the materials and based on them non-destructive electromagnetic tests have been developed for this purpose. Among these, eddy currents and Magnetic Barkhausen Noise are used for this purpose. The latter performed in the region of irreversibility of the movement of the walls of the magnetic domains. In the present work, an electromagnetic test based on the application of field intensities in the region of magnetic reversibility is applied to detect the effect of heat treatments on a SAE 4340 steel, which has a high depth hardening capacity and has a wide application in the industry, such as in aerospace where it is used in aircraft landing gear. Four different heat treatments: an annealing at a temperature of 850 ºC, austenitization at 1000 ºC followed by cooling in the oven, in oil and in water were analyzed and compared with the condition as received from the material under study. A fixed magnetic field intensity was applied in the center of the circular samples, in order to analyze the value of the magnetic permeability for the applied treatments. The influence of treatments on the magnetic anisotropy of the steel under study was also analyzed. A fixed magnetic field strength was applied to treated circular samples, and these were rotated with steps from 45 to 360 degrees. The results of the electromagnetic tests were correlated with hardness measurements and optical microscopy. The analysis of the obtained magnetic permeability results shows that the test is able to differentiate the treatments, being sensitive to the variation in the amount of the ferrite constituent, which is ferromagnetic, as well as the presence of the martensite structure showing that it can be correlated with hardness measures. In addition, it was possible to verify the presence of a direction of easy magnetization, regardless of the microstructure of the heat treatment employed.
Keywords
Magnetic permeability measures, Heat treatments, anisotropy, microstructure anisotropy
