The metal tubes utilized for the realization of the micropiles exist in different qualities of steel, with Chemical and mechanical characteristics thath can be guaranteed with a certification released by recognized control labs. 

They differ between the new steel ones St 52 type and the re-emplyment J55-K55-N80 steel ones that come from petrol research yards and are examined and inspected before their use.


Table n.1 illustrates the mechanical features of the different qualities of steel.