if(~,:~::'::c~igerian constructional steils, NST 37-2 and NST 60Mn, wereud~. ': h_eat· treated in various temperature ,, : quenching media of water,ud·.mineral oil and air .to ascertain ti ... :1ardness for manufacturingudpurpose. Results indicate that water seems to be the mostudefficient ouenching media where maximum hardness is required.udHowever, where hardness can be used for quenching. NST 60Hnudsteels, with higher Mn and C contents, showed greater hardness atudfast coolin~ rates. This greater hardness was due to the greaterudamount of martensitic transformation and precipitation hardening ofudcarbides (Fe 3C2.. ·The air-cooled samples did not show much increaseudin hardening because the steels transform more into ferrite withudvery little pearlite. The technological importance of theseudresults are discussed in this paper to help the local manufacturingudcompanies in adopting any of the quenching media above, which wouldudsuit their needs after the heat treatment. By so doing, the muchudneeded spare parts for machinery in Nigeria in particular, andudAfrica 1n general can be produced locally.
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