Browsing by Author "Akinlabi, Oyetunji"

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    Development of Martempered Ductile Iron by Step-Quenching Method in Warm Water
    (Daffodil International University, 2013-07) Akinlabi, Oyetunji; A. A, Barnabas; J.O.T, Adewara
    The evaluation of the suitability of warm water for interrupted quenching of ductile cast irons in the production of Martempered Ductile Iron (MDI) was carried out. Ductile cast irons used were normalized at a temperature of 850oC for 60 minutes. The normalized specimens were subsequently heat-treated in muffle furnace to a pre-determined temperature of 850oC for 30 minutes, then step-quenched in warm water maintained at temperature of 80oC for 40 seconds followed by tempering at different tempering temperatures (175oC-425oC) and times (30-180 minutes). Hardness test was used to evaluate the mechanical property while the metallographic examinations that produced different microstructures were used to evaluate the transformation behavior. The results showed that the developed MDI has a high average hardness value of 53Rc at the lowest transformation temperature, and 19.6Rc at the highest transformation temperature. Metallographic analysis showed that untempered martensite was obtained at holding temperature below 250oC, tempered martensite at 250oC to 325oC, tempered martensite at holding temperature of 350oC for short holding times, above which the specimen is over-tempered (depending on the holding time). This showed that warm water is a suitable quenchant for the production of MDI.
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    littleStudy On The Shear Strength Of Foundry Sand Cores Using Clay And Cassava Starch As Binder
    (Daffodil International University, 2013-07) Akinlabi, Oyetunji; S.O, Seidu,; A. I, Opaluwa
    Sand cores for casting intricate shapes were produced from Ojolofe silica sand using cassava starch and Iyoloko clay, Idah Kogi State Nigeria as binders. Various compositions (6 – 12% water 4 – 12% cassava starch and 5% Iyoloko clay) and Ojolofe silica sand were mixed to produce standard cores samples of two different types (green and baked). Cores samples were baked at different temperatures ranging from 90 and 200oC for 60 – 150 minutes. Determination of shear strengths was carried out on a large number of green and baked cores samples. Appropriate baking conditions and optimum core mixtures were established for cassava starch/clay bonded cores at 180oC and 2 hours respectively; and clay addition was found to increase both the green and baked strengths values. The optimum clay/starch core mixture with the best shear strength values was found to be core produced with 10% starch, 10% water and 5% clay. Their green and baked shear strength values were 31.1 KN/m2 and 498.1 KN/m2 respectively. These values were found to be adequate for production of strong sand cores using starch/clay as binders for non-ferrous and ferrous castings as collaborated by successfully casting of a T – joint pipe aluminum casting.