More complex thin-wall castings were produced to show that the LDASC material could be used either on the mold or core surfaces.
The use of LDASC has significant control over the resulting microstructure and physical properties of thin-wall castings.
The effects of LDASC additions on ductile iron microstructure were shown most dramatically in the thin-wall manifold casting in the 0.079-in.
(2-mm) section and plotted against the volume percentage of LDASC in contact with the casting.
Researchers also have performed tensile tests on samples cut from thin-wall ductile iron castings produced with varying amounts of LDASC. They found a significant decrease in ultimate tensile strength (UTS) and yield strength and a corresponding increase in % elongation with increasing amounts of LDASC, as shown in Fig.
To address those difficulties, LDASC gate extensions were developed for thin-wall castings.
A series of specially designed thinwalled ductile iron castings were poured with varied levels of LDASC to evaluate the effects on the microstructure and hardness.
Binder levels were adjusted for blends of the material and lake sand with 8% binder by weight used with 100% LDASC.
Photomicrographs were taken in the thin sections 180 degrees from the flanges and showed the effects of reduced solidification and cooling rates with increased levels of LDASC. Higher amounts of the material in the mold facing reduced the percentage of carbides in the thin section and increased nodule size and ferrite levels.
The casting produced with a 100% LDASC mold and core was completely free of carbides and had a microstructure typical of a much heavier section.
The casting hardness decreased dramatically in the thin sections with increasing LDASC levels.
The 25% LDASC blends appeared to have minimal affect on structures and properties, but both the 50% blend and 100% LDASC had significant effects.