Browsing by Author "Raji, N. A."

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The effect of full annealing on the microstructure and mechanical properties of cold draw low carbon steel
(2013-06) Raji, N. A.; Oluwole, O. O.
The aim of this work is to determine the mechanical properties of cald drawn low carbon steel subjected to full annealing. The specimens were slowly heated up to a temperature of 900 followed by soaking treatment of 60 minutes under this temperature in a muffle furnance. Tensile, charpy and brinnel hardness tests were conducted to determine the yield strengths, tensile strengths, impact strengths and hardness of the annealed steel. The yield strength, tensile strength, hardness and toughness of the nail are greater in the non-treated nails when compared to the fully annealed nails at 60 minutes soaking time. The microstructure analysis showed that rate of grain nucleation and recrystalization increased with increasing degree of cold-drawn deformation. Grain growth was observed at higher degree of deformation leading into reduction in the mechanical properties of the material. It is evident from the resulting mechanical properties of the nails and the microstructure analysis that desired properties of the nails could be obtained by controlling the microstructure evolution of the low carbon steel in annealing.
Effect of soaking time on the machinical properties of anealed cold-drawn low carbon steel
(Scientific Research, 2012-08) Raji, N. A.; Oluwole, O. O.
The paper presents the results of investigation on the effect of soaking time on the yield strength, ductility and hardness properties of annealed cold-drawn low carbon steel. The low carbon steel cold-drawn at 40% deformation was annealed at 900 deg Celsius for soaking times of 10, 20, 30, 40, 50 and 60 minutes. Tensile, charpy and Brinnel hardness tests were conducted to determine the yield strengths, tensile strengths, impact strengths, ductility and hardness of the an- nealed steel with increasing soaking time. The yield strength, tensile strength, hardness and impact strength of the steel showed a continuous drop in value with increasing soaking time up to 60 minutes with a steep drop between 30 and 40 minutes. Ductility values followed the same decreasing trend up to 40 minutes soaking time after which the values started increasing again till 60 minutes soaking time. There was a linear relationship between the tensile strength and hardness of the material for different soaking times. This linear relationship was also observed for yield strength and hardness of the material.
Mechanical Properties of cold-drawn low carbon steel for nail manufacture: experimental observation
(Maxwell Scientific Organization, 2013-01) Raji, N. A.; Oluwole, O. O.
"The objective of this study is to investigate the influence of service situation on the mechanical properties of plain nails manufactured from low carbon steel. The influence of the degree of cold drawing on the mechanical properties and strain hardening of the material is investigated by tensile test experimentation. The stress-strain relationships of the cold-drawn low carbon steel were investigated over the 20, 25, 40 and 55% degree of drawn deformation for the manufacture of 4, 3, 2½ and 2 inches nails, respectively. The true stress-strain curves were analyzed to obtain the yield strength and tensile strength of the cold drawn steel. It is shown that the yield strength, tensile strength, hardness and toughness of the low carbon steel reduce with increasing degree of cold-drawn deformation. The micrographs of the deformed samples obtained using optical microscope shows that the grain structure elongates in the direction of the drawing operation and misorientation of the grains set in at 40 and 55% degree of deformation. The difference in yield strength was attributed to the strain hardening, resulting from the different degrees of drawn deformation."
Phase field simulation for recrystallization kinetics of cold-drawn 0.12wt%C steel in full annealing
(2014-03) Raji, N. A.; Oluwole, O. O.
The importance of recrystallization kinetics in metal process cannot be over emphasized in providing information as to the control of microstructure of materials for purpose of improving or impacting desired mechanical properties in processed materials. In this study, 0.12wt% C steel cold drawn between 20% - 55% were graduallyheateduptoatemperatureof900°C followed bysoakingtreatment between 600 seconds and 3600 seconds in a Gallenkomp® mufflefurnace model SVL-1009 with voltage regulation of 220 V, 50 Hz of temperature range 300°C - 1000°C. The influence of the annealing process on the strength and impact toughness properties of the annealed steel were evaluated from tensile and charpy-impact tests conducted on the annealed steel. A phase field method is used to describe the recrystallization kinetics of the annealed cold drawn 0.12wt%C steel for the different degrees of cold drawn deformation. The experimental data obtained from the tensile and charpy-impact test were used as input data for the phase field simulation of the recrystallization process. The results show that the yield strength of the annealed cold drawn 0.12wt% C steel increases with increasing soaking time within the range of 600 sec.– 3600 sec. for the 20% cold drawn steel, between 600 sec.- 2400 sec. for the 25% and between 600 sec.-1800 sec. for the 40% and 55% cold drawn steel. The treatment increased the impact toughness of the steel for the 20%-40% cold drawn deformation but loses its toughness for the 55% cold drawn steel. The tensile strength however reduces for all the cold drawn steel irrespective of the degree of deformation. The simulation results show that reformation of grains in cold drawn 0.12wt%C steel depends on the degree of cold drawn deformation and the soaking time of annealing. The response of the mechanical properties of the annealed cold drawn 0.12wt% C steel therefore depends on the degree of cold deformation and soaking time of annealing