TENSILE STRENGTH AND MICROSTRUCTURAL BEHAVIOUR OF MEDIUM CARBON STEEL QUENCHED IN SOME SELECTED MEDIA

Quenching effect of pap water, coconut water and spent engine oil (SPE) on the strength and microstructural behavior of medium carbon steel was studied. Prepared samples were first heat-treated in a muffle furnace to temperature of 840 and normalized in order to reduce the stresses that might have been induced during machining operations. The prepared samples were later heated to 730 , 760 and 790 and soaked for 30, 45 and 60 minutes, respectively using a muffle furnace and then quenched in different media. The control sample was only heated to 840 and normalized. A testometric M500-50AT model machine was used for the tensile test. M100 optical metallurgical microscope was used for the microstructural examination. An improved yield (YS) and ultimate tensile (UTS) strengths were observed in all the samples quenched in different media against the as-received samples. As-received samples tend to yield earlier at offset strain of about 0.07% which implies a drop in yield and ultimate tensile strength. SPE-quenched samples have better YS, UTS and percentage elongation than others. Quenched samples, irrespective of the heating temperature and soaking time has martensitic islands in matrix of ferrite phases. The quenching media proved effective in their application as quenching medi