Abstract:
Samples of grey cast iron of section sizes (15 mm, 20 mm, 25 mm, 30 mm and 35 mm) were produced with the same chemical composition. A rotary furnace was used to melt the charge. The charge was heated to 15500C and tapped into a preheated clay-graphite ladle at 15000C. Green moulding sand was used to prepare the mould. It was a plastic mixture of 80%Silicon sand, 10%clay (bentonite) 2% coal dust. The pattern used for the sand mould was made from hard wood and machined with woodworking lathe machine into cylindrical shape, 200 mm long and of various diameters: 17.2 mm, 22.5 mm, 27.5 mm, 33.0 mm and 38.5 mm. The moulds were prepared in moulding boxes by introducing plastic moulding sand and inserting the pattern into the moulding boxes. The prepared moulds were allowed to dry to eliminate moisture content before receiving the molten metal and the castings were subsequently obtained after 24 hours of solidification. A stainless wire brush was used to remove the sand that adheres to the casting after solidification. Abrasive wheel cutting machine was used to remove gates and risers. A lathe machine was used to machine the produced cast samples into standard test samples. The mechanical properties such as the hardness test result was observed to decrease from 36.00 HRC of test sample A to 33.40 HRC of test sample B due to the formation of graphite flakes in ferrite and pearlite. Test sample C was observed to possessed intermediate hardness 34.90 HRCwith both ferrite and pearlite matrix microstructure. Samples D and E were found to have 33.90HRC and 33.0 HRC respectively with graphite flakes extension in both matrices. Similarly, tensile strength was observed to decrease. Sample A had the highest yield strength (250.00 Mpa) with fine flakes while sample B has 199.20 Mpa. Sample C had intermediate yield strength of 220.70 Mpa. Samples D and E were found to be 201.00 and 198.20Mpa with flakes network in the matrices. However, impact toughness was found to increased from 5.07J/mm, 5.25 J/mm, 5.14 J/mm, 5.36 J/mm, and 5.58 J/mm for sample A, B, C, D and E respectively. The data generated from the experimental work is recommended for model development for the determination of mechanical properties of the produced grey cast iron from sand mould.
