The main purpose of this thesis is the determination of the chemical composition of Open Clusters (OCs) for the study of the chemical gradients in the Galactic disc with: Galactocentric radius, position above the plane, and age. High-resolution spectra of stars in 18 OCs have been collected during more than three years of observations to derive very accurate radial velocities, atmpospheric parameters and chemical abundances. A kinematic study of the OCs in the context of the Galactic disc has been done and also a computation of their orbits with different models. Effective temperatures, surface gravities and iron abundances have been computed using two different methodologies, which allows to do an exhaustive comparison of the behaviour of the methods. So far, Fe, Ni, Cr, Si, Ca, Ti, Mg and O abundances have been derived star-by-star, also obtaining mean cluster abundances and dispersions. These results have been analyzed under the point of view of the radial Galactocentric trends and the age-metallicity relation. In particular, NGC 6705 has been investigated in detail, obtaining an unexpected alpha-enhancement for its position and young age.