OCCASO III. Iron peak and $\alpha$ elements of 18 open clusters.
  Comparison with chemical evolution models and field stars
  The study of open-cluster chemical abundances provides insights on stellar
nucleosynthesis processes and on Galactic chemo-dynamical evolution. In this
paper we present an extended abundance analysis of 10 species (Fe, Ni, Cr, V,
Sc, Si, Ca, Ti, Mg, O) for red giant stars in 18 OCCASO clusters. This
represents a homogeneous sample regarding the instrument features, method, line
list and solar abundances from confirmed member stars. We perform an extensive
comparison with previous results in the literature, and in particular with the
Gaia FGK Benchmark stars Arcturus and $\mu$Leo. We investigate the dependence
of [X/Fe] with metallicity, Galactocentric radius ($6.5<R_{\rm GC}<11$ kpc),
age ($0.3<Age<10$ Gyr), and height above the plane ($|z|<1000$ pc). We discuss
the observational results in the chemo-dynamical framework, and the radial
migration impact when comparing with chemical evolution models. We also use
APOGEE DR14 data to investigate the differences between the abundance trends in
$R_{\rm GC}$ and $|z|$ obtained for clusters and for field stars.
