Análisis de la influencia del tamaño de las agujas de la martensita en las propiedades mecánicas de los aceros AISI 4140 y AISI 4340.

Abstract

Technological advances and industrial development have led engineers to look for new alternatives on the use of materials, for this one of their main goals is to control their behaviour in the industry by modifying their properties. The following research work aims to analyse the influence of the size of martensite needles on the mechanical properties of AISI 4140 and AISI 4340, using a procedure that helps determine the length and distribution of martensite and its microstructure. To obtain different martensite needles it was necessary to temper the samples, after doing the metallographic analysis of the samples, it proceeds to calculate the grain size to determine the average diameter, which equals to the length of the main martensite needles, the same ones that grow from the edge on the edge of the austenite grains. After this, hardness and tensile tests were carried out, obtaining hardnesses of 45.8 HRC for a needle of 0.026 mm being the smallest and 60.2 HRC for a length of 0.0378 mm corresponding to the most considerable average length of the samples analysed and reaching a tensile strength of 1451.3MPa and 1589.74MPa. Concluding that the hardness increases as martensite needles grow, the opposite occurs with the results of tensile strength whose behaviour is independent of the martensitic microstructure, to extend the investigation into the influence of martensite needles on the properties mechanical steels, the recommendation is to obtain samples with needle lengths that vary considerably, considering that in this investigation the austenite grains range from 6.5 to 8.5.