Characterizing shrinkage porosity in gray cast iron using microstructure investigation

• The presence of shrinkage porosity in gray cast iron cylinder heads is a common reason for rejected castings. Therefore, an investigation was carried out to characterize the microstructure around these defects in order to achieve a better understanding of their origin. Cylinder heads from two different foundries, producing cylinder heads with different design, were examined. Despite the differences, shrinkage porosity was found to appear at similar positions. Color etsching technique was used to reveal the microstructure and the characteristic features of the porosity. Besides, also solidification simulation was used to compare thermal distribution at the positions of interest. The investigation shows that there are similarities, as well as differences, and these will be discussed in detail together with the characteristic features found. In both cases, the simulations shows a thermal center crossing the interface between mould and casting. This leads to a discussion of how the solidification is progressing and the importance of the solidification skin, or columnar zone, as well as the equiaxed zone on shrinkage porosity formation.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Publication and Content Type

ref (subject category)

kon (subject category)