Análise de defeito de fundição em componente de ferro fundido nodular obtido por moldagem Cold Box

Abstract

The presence of defects is a frequent problem in the manufacturing process of metal products by foundry, because depending on the type and quantity, they make the final application of the workpiece unfeasible and, most of the time, it causes financial loss to the manufacturers. When defects appear, the professional in this area should be able to identify and understand their cause, to act in a corrective manner under this. A very common defect of the castings is the pores or voids, and its origin may be a consequence of the contraction of the metal during solidification or resulting from gases. In this study a defect occurred in a nodular cast iron piece FE42012 class of the company Fundição e Metalúrgica Tiger, obtained by the Cold Box process, named Cage, in order to collaborate with the identification of the type, the cause and possible solution for this. For this, the solidification of the part was studied by means of the foundry software Click2Cast, used to simulate the solidification mode of the parts and analysis of defects, together with calculations of the modules and contraction for evaluation of the feed channels and sizing of the risers, and together with macroscopic and microscopic visual analyses to identify the defect. With the development of the work, it was possible to identify that the defect originated during the solidification process of the cast iron, due to its contraction, caused by an inefficient feeder specified in the mold design. Through the calculations performed in parallel with the analysis in the software it was possible to predict the need to modify the diameter and height of the riser and make modifications in the region where the metal from the riser transfers to the part, in order to prolong the time solidification in this region. A new model was tested, analyzed by the Click2Cast software, which indicated a decrease in the porosity probability of 100% to less than 3% compared to the original model.