Identificação e análise de defeito de fundição em coletor de freio motor

Abstract

Casting is a process of transformation consisting in pouring of a fused charge into a mold. In this process, during the solidification step, metal phase transformation occurs and then reduction in volume per unit mass to be considered in the design of moldes by the possibility of causing defects associated with contraction during the cooling. For gray cast iron, the effects of contraction are minimized by presence of graphite, less dense than the other phases. However, chemical compostion has an effect on the eutectoid reaction graphite formation. Therefore, product defects such as shrinkage and micro shrink hole caused when liquid metal has difficulty penetrating between dendrites formed in the solid-liquid interface, that stops the action of atmospheric pressure, require control parameters of the casting process, mainly in relation to feeding system, casting temperature and inoculation, to guarantee the efficiency to obtaining parts free from casting contraction defects. In this work, the shrinkage defect of an engine brake collector was identified and analyzed with defective section cut, photographic record, stereoscopy and micrography. Were listed probable causes of contraction that caused the porosity. With 3D plotting of part, was done riser sizing by modules rule, and the solidification simulation was carried out using Click2Cast software, making possible predict and evaluate a better design for collector feed system. With the development work, it was observed that onlt onde set of actions can prevent the appearance of defects identified in cast component, due to the large variability of the process. Ways to prevent the cause of scrap were recommended in order to avoid the occurrence of shrinkage in batches affected by process deviations.