The steel industry represents a sector of great importance in the production chain, being directly related to the economic development of the world. The straightening process, an important phenomenon of plastic deformation during steel production can bring changes in the results of mechanical properties. The goal of this study is to analyze the interaction between the variables involved in the natural strain ageing, straightening (manual and mechanical) and in the chemical composition (low and medium carbon steels) of the wire rod, being the variation of the mechanical properties - through the tensile test – and microstructural – from the microstructural characterization – the analysis parameters. The results indicate a trend towards an increase in the yield and resistance limits of the materials that were submitted to the straightening and strain aging process, and it is possible to notice the pattern, from the contour and response surface graphs, that the higher the levels of straightening and percentage of carbon, the higher the values of yield strength and resistance.