In the present investigation, the effect of the annealing temperature in a nodular cast iron ASTM A536 on the hardness, impact resistance and microstructure in obtaining a ferritic nodular cast iron was studied. For this purpose we used square bars of 15 mm x 15 mm x 200 mm in length supplied by Fundición Laminar SAC - Lima, where the specimens were machined for the hardness test according to the ASTM E- 140 standard and for the impact test according to ASTM E23-98, which were annealed at temperatures of 800, 850, 900, 950 and 1000 ° C for a time of 25 hours with slow cooling inside the oven. The results show that when the annealing temperature is increased, the hardness decreases from 198.40 HB for supply (25°C) to 114.80 HB for 1000°C annealing temperature, and the impact resistance (J) increases as the temperature increases. annealed from 53.90 J for supply (25°C) up to 124.20 J ...