Patent ID: 8002910

Claim:
A heavy gauge seamless steel pipe characterized by the material of which it is manufactured being made up of basically of Fe and the following chemical composition expressed in % by weight of additional elements: C 0.06 to 0.13 Mn 1.00 to 1.30 Si 0.35 Max. P 0.015 Max. S 0.003 Max. Mo 0.1 to 0.2 Cr 0.10 to 0.30 V 0.050 to 0.10 Nb 0.020 to 0.035 Ni 0.30 to 0.45 Al 0.015 to 0.040 Ti 0.020 Max. N 0.010 Max. Cu 0.2 Max. and also the chemical composition with the following relation among the alloying elements: 0.5<(Mo+Cr+Ni)<1 (Mo+Cr+V)/5+(Ni+Cu)/15≦0.14; wherein the seamless steel pipe has a microstructure formed by re-heating to an austenitic temperature followed by water quenching and a tempering treatment that results in a microstructure having austenite grains with an average size from ASTM 10 to 20 microns.