INVESTIGATION ON THE MECHANICAL PROPERTIES OF CARBURIZED STEEL GRINDING MEDIA

Abstract

The study was performed to investigate the mechanical properties of carburized steel grinding media balls produced at the foundry shop of the Ajaokuta Steel Company Limited; the one tonne induction furnace was used for the casting of the steel balls.  The sand preparation process was carried out with the use of one tonne muller mixer. The stack mould technique was used for the making of the moulds. The materials used for the casting of 30mm grinding media balls were 15% chrome, steel scraps and pig iron which are required for the production of grinding media used in the quarries industries, cement factory, and mineral ores processing plant. The carburization process was carried out at the mechanical repairs and tool shop. The steel materials were subjected to various carburization time and temperatures with each holding period of 60 minutes, 120 minutes, 180 minutes, 240 minutes, and 300 minutes. The furnace temperatures were adjusted to the required temperature of 800^oC, 850^oC, 900^oC, 950^oC, and 1000^oC, with corresponding hardness values were 66, 69, 74, 80, 87 HRC respectively while the hardness value of un-carburized steel balls was 63.8HRC. The wear test was performed on the carburized and un-carburized samples in order to determine their values, time and temperature intervals were maintained within the range of 60 minutes and 50^oC respectively. The inverted Metallurgical Microscope was used to determine the microstructure of the samples before and after carburization. The SPECTRO analytical Instruments was used to determine the chemical compositions of steel samples before and after the carburization processes in order to determine the chemical compositions. The results obtained from the research work indicate that there were influences on the samples due to carburization processes.  The wear rate of the samples decreased with respect to time, the best surface hardness values was achieved when the samples was subjected to the highest temperature and it was observed that when the temperature was also increased there were increases in the diffusivity of carburization on the sample surfaces.