Vol 7, No 3 (2016) > Metalurgy and Material Engineering >

Effect of Plate Thickness and Casting Position on Skin Effect Formation in Thin Wall Ductile Iron Plate

Rianti Dewi Sulamet-Ariobimo, Johny Wahyuadi Soedarsono

 

Abstract:

In producing Thin Wall
Ductile Iron (TWDI) plate, special notice should be taken on the skin effect
formation. Skin effect is a rim of flake interdendritic graphite formed in the
surface. In a normal ductile iron casting, skin effect can be removed with
machining process. Unfortunately this procedure cannot be applied in TWDI due
to the thickness. This paper discusses the effect of casting design to the skin
effect formation. Vertical casting design is used in this work. Variations are
made in the thicknesses of the plate. The T1 model is equipped with 5 plates
with thicknesses of 1, 2, 3, 4, and 5 millimeters; while the T1-Mod is equipped
also with 5 plates, but with the same thickness, which is 1 mm. Skin
thicknesses, nodule count, and nodularity are measured by NIS Element software.
The result showed that skin effect formation is determined by magnesium content
and cooling rate. Skin effect thicknesses are determined by cooling rate and
the interaction area of molten metal with the mould. The presence of the skin
effect in similar thickness and position of plate improved nodule count. In the
same thickness, without the presence of the skin effect, the nodule count tends
to increase as the positions of the plates increase. In the design ranging from
1 to 5 mm plate thickness, the highest nodule count is 1284 nodule/mm2
gained by 1 mm plate thickness in 1st position and the lowest one is 512
nodule/mm2 gained by 5 mm plate thickness in 5th position. As for
the design of all 1 mm thickness where skin effect is not formed the highest
nodule count is 1689 nodule/mm2 gained by 1 mm plate thickness in
the 5th position and the lowest is 1113 nodule/mm2 gained by 1 mm
plate thickness in the 1st position (near the in gate). The highest nodule
count is 90 and the smallest is 85.

Keywords: Casting design; Cooling rate; Magnesium; Skin effect; Thin Wall Ductile Iron (TWDI)

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References


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