In this investigation, the effect of the annealing time in an ASTM A536 nodular cast iron on the tensile strength, yield stress, ductility, hardness and microstructure was studied. For this reason, cylindrical bars with a diameter of 15 mm x 200 mm in length manufactured by the company Foundry to Laminate SAC - Lima were used. They were annealed at 880 ° C at times of 5, 10, 15, 20, 25, 30 and 35 hours with slow cooling (inside the furnace). The specimens were machined from the annealed bars, for the tensile test according to ASTM E8-98 and for the hardness test according to ASTM E-140. The experimental results show that the increase of the annealing time causes the tensile strength to decrease from 492.00 MPa for 5 hours to 312.00 MPa for 35 hours. The yield stress decreases from 334.70 MPa for 5 hours to 263.00 MPa for 35 hours and with respect to ductility, it increases from 8.10% fo...