Abstract: Effect of sprue/metal head height on mould filling,
microstructure and mechanical properties of TWDI casting is studied.
Results show that metal/sprue height of 50 mm is not sufficient to
push the melt through the gating channel, but as it is increased from
100-350 mm, proper mould filling is achieved. However at higher
heights between 200 mm and 350 mm, defects associated with
incomplete solidification, carbide precipitation and turbulent flow are
evident. This research shows that superior UTS, hardness, nodularity
and nodule count are obtained at 100 mm sprue height.
Abstract: Swedish truck industry is investigating the possibility
for implementing the use of Compacted Graphite Iron (CGI) in their
heavy duty diesel engines. Compared to the alloyed gray iron used
today, CGI has superior mechanical properties but not as good
machinability. Another issue that needs to be addressed when
implementing CGI is the inhomogeneous microstructure when the
cast component has different section thicknesses, as in cylinder
blocks. Thinner sections results in finer pearlite, in the material, with
higher strength. Therefore an investigation on its influence on
machinability was needed. This paper focuses on the effect that
interlamellar distance in pearlite has on CGI machinability and
material physical properties. The effect of pearlite content and
nodularity is also examined. The results showed that interlamellar
distance in pearlite did not have as large effect on the material
physical properties or machinability as pearlite content. The paper
also shows the difficulties of obtaining a homogeneous
microstructure in inhomogeneous workpieces.