THE EFFECTS OF COPPER AND SECTION THICKNESS ON THE MORPHOLOGY OF GRAPHITE FLAKES IN GRAY CAST IRON
This research work investigated the effects of copper additions and section thickness on the morphology of graphite flakes in gray cast iron. Four samples of gray cast iron containing various amount of copper (0%-1.1%) were investigated. The section thickness varied from 10-75mm. Sand mould casting was adopted. The chemical composition, mechanical properties, graphite flake measurements and microstructural characterisation of each section of the casting were carried out with the aids of optical emission spectrometer, mechanical testing equipment and scanning electron microscope. The 0.8% Cu alloyed gray cast iron with section thickness of 10mm produced the highest tensile strength of 150.28 N/mm2, hardness value of 47.5 HRC and the lowest impact strength of 76.96 KJ/m2. However, the 1.1% Cu alloyed gray iron with 75mm section thickness had the least tensile strength of 58.36 N/mm2, hardness value of 40.1 HRC and the highest impact strength of 107.13 KJ/m2. The addition of copper up to 0.8% enhanced the pearlite phase and promoted the formation of ferrite when increased to 1.1%. The results of microstructural examination revealed that the morphology of the graphite flakes changes from fine and small flakes to coarse and long as the section thickness increases. The research showed that the developed type B (rosette graphite) graphite flake having 85.95µm length in the 1.1% Cu gray cast iron with 10mm section thickness gave a good combination of mechanical properties having 2.85% elongation, 111.41 N/mm2 tensile strength, 44.4 HRC hardness and 89.65 KJ/m2 impact strength.
|Keywords: Gray Iron, Copper, Casting, Graphite Flake And Microstructure|
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