Microstructure Evolution and its Influence onTensileBehavior of Process Annealed Cold Drawn 0.12wt% C Steel

This work studied the effect of grain size evolution of cold drawn 0.12wt% C steel subjected to process annealing on tensile behavior. 20%, 25%, 40% and 55% cold drawn 0.12wt% C steel were subjected to annealing comprising of slow heating-up to various temperature ranging from 500oC to 700oC at interval of 50oC followed by soaking treatment for 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes under each of the temperature in a muffle furnace. These samples were submitted tooptical microscopy analysis and to tensile test. After annealing at 650oC and soaked for 10 minutes, the dislocation defects were annihilated in the 25% cold drawn samples. Grain coarsening is observed for the annealed steel at soaking time of 20 minutes to 30 minutes after which grain growth commenced at annealing temperature above 650oC at soaking time of 40 minutes for the 25%, 40% and 55% cold drawn samples. Fine grains of the microstructure were observed for all the annealed samples between the temperature range 500 o C-650 o C.The yield strength of the annealed samples increases compared to the non-treated samples thus improving the ductility of the steel. A better improvement of the yield strength is observed for the annealing temperature of 500 o C and 550 o C at soaking time of 10 minutes and 30 minutes for all the cold drawn samples except for the annealed 25% cold drawn steel whose yield strength is below the yield strength of the non-treated samples. Index Terms-annealing,cold drawn, deformation, grain size, microstructure, tensile strength, yield strength, steel