Estudo das propriedades da liga de ferro fundido nodular austemperado obtido a partir da liga SAE J434 - D5504

Abstract

In Brazil, despite the excellent conditions for the manufacture of austempered Nodular cast iron-ADI, there is insufficient production and low academic interest, and may be justified by the scarce knowledge of the engineers about the advantages Technical and economic characteristics of the material. In addition, a great lack of information about its mechanical behavior, restricting the application of the material even in the interest of the automobile and machinery industries. In view of this, it is observed the importance of studies that seek to identify the behavior of this material through analyses of its mechanical and microstructural properties. In this context, this study submitted a nodular cast iron alloy to the Austenipera process, and sought to identify the behavior of this material by analyzing the mechanical and microstructural properties before and after the heat treatment. Test specimens obtained by 24 Y-blocks of 25mm thickness were used, also leaked by three different fusions, for the composition of a nodular cast iron material of class SAE J434-D 5504. The process of heat treatment was divided into austenitization phase, maintained at 900 ° C for 2 hours, followed by the Austempera phase, maintained at a temperature of 290 °C also for 2 hours. Tensile, hardness and impact tests were performed. The microstructures were obtained with the aid of optical microscopy and image analysis, and the ausferritic matrix was identified without the presence of carbides, homogeneously throughout all the samples analyzed. The mechanical properties of the austeniated nodular cast iron, as expected, reached significantly better levels in relation to the gross Nodular Fusion, reaching Grade 3 classification in ASTM A 897/A897M-16 for the boundary properties of traction, increase of 195%, flow, increase of 242% and hardness, increase of 174%. However, for stretching and impact, the values were insufficient to reach a little lower than the minimum limit, which may be associated with the presence of type III graphites found.