In the present investigation we studied the influence of the austenitization temperature on the tempering of a pearlitic gray cast iron was studied. For this purpose, bars of 30 mm diameter x 400 mm length were used; of which the test specimens were machined for the test. Length of 25 mm in diameter and 100 mm in length. Said test was carried out according to the ASTM A255-2014 standard and to evaluate the U or Grossmann curve, it used probes of 25 mm diameter x 50 mm in length. The test pieces were heated to the austenitization temperatures of 820, 860, 900, 940 and 980 ° C for a time of 1 hour, the Jominy test was carried out in quenching device for tests, according to ASTM A255 - 2014, and for the evaluation of the curve U the test pieces were tempered in oil. The results show that the austenitization temperature increases from 820 ° C to 900 ° C, the templering increases when the ...