RESPONSE SURFACE OPTIMIZATION OF SOME PROPERTIES OF PROCESS ANNEALED LOW CARBON STEEL

Absract- In wire drawing process, the yield strength, tensile strength and impact toughness play major role in the structural reliability of the drawn wire. Low carbon steel wiresof 0.12wt% C are used for the manufacture of plain nails. Improved yield strength and impact toughness of the nails are often desire to avoid fracture failure andbuckling. In this study, polynomial modeling coupled with Response Surface Methodology was used to study the behavior of the tensile properties and impact toughness of cold drawn low carbon steel when annealed at various temperatures and soaking time. The Response Surface Methodology (RSM) was used to investigate the individual and interaction effect of annealing temperature and soaking time as independent variables on the yield strength, tensile strength and impact toughness properties of annealed cold drawn low carbon steel. The steel wire cold-drawn to 20% was annealed at various temperatures between 500oC-650oC for soaking time of between 10 minutes-60 minutes. The influence of the annealing temperature and soaking time on the yield strength, tensile strength and impact toughness were investigated by modeling the relationship using second order quadratic polynomials to develop the response surface plots and their respective contour plots. The RSM proposes models describing the influence of the annealing heat treatment parameters on the properties of the heat treated cold drawn wires. The model was able to account for the curvature of the response and the interaction of the independent variables in the response surface. The response surface methodology (RSM) was applied to optimize the annealing process parameters to attain the optimal values of the properties.The optimized values for the yield strength, tensile strength and impact toughness for the heat treated cold drawn wire were obtained as 678.90 MPa, 779.15 MPa and 42.65 J respectively. The optimization was achieved within the 95% confidence interval. Index Terms-Cold drawn, steel, annealing, temperature, time, yield strength, tensile strength, impact toughness, optimization, RSM, model