Influência da grafita na formação de metal dobrado em cilindros de motores de combustão interna de ferro fundido cinzento e vermicular

Abstract

This study aimed to discuss the influence of graphite on formation of folded metal in the honing grooves of cylinder blocks of grey cast iron and compacted graphite iron, using image overlay technique, in order to assess the existence the relationship between folded metal and the presence, form and graphite distribution. Two regions of each cylinder were analyzed, in opposite quadrants that represent different wall thickness. Measurements of 3D topography were made by white light interferometry, in order to obtain topographic and 3D roughness parameters data, in addition to the metallographic preparations for identification of graphite. The quantification of folded metal was made with computational routine developed throughout this work. In terms of assessing of 3D roughness parameters, there are no significant differences between different cylinder thicknesses, or in regarding the use of two kinds of material. The tests showed the existence of different percentages of folded metal in relation to material and thickness variation. The morphology and the distribution of the graphite also showed significant differences when there was variation to the cylinder thickness, in addition to the obvious differences between the materials. The study showed that utilizing analyses of linear regressions and using the obtained data of image overlay, it is possible to verify that the graphite, although to manifest in different ways in relation to thickness and material variation as well as folded metal, it presents low correlation with the formation of folded metal, so we can see that other factors are most influential for occurrence to the folded metal.