Patent ID: 7331757

Claim:
A turbine shaft oriented in an axial direction, comprising: a first flow region; a second flow region that adjoins the first flow region in an axial direction; a first material in the first flow region; and a second material in the second flow region, the second material joined to the first material through at least one weld joint, wherein the first material comprises a heat-resistant steel having undergone a tempering process and the second material comprises a steel which is tough at low temperatures and wherein the first material is characterized by a low stability during the tempering process relative to 1 CrMoV steel, wherein: the first material includes 0.20-0.24% by weight of C, ≦0.20% by weight of Si, 0.60-0.80% by weight of Mn, ≦0.010% by weight of P, ≦0.007% by weight of S, 2.05-2.20% by weight of Cr, 0.80-0.90% by weight of Mo, 0.70-0.80% by weight of Ni, 0.25-0.35% by weight of V and 0.60-0.70% by weight of W, and the second material includes 0.22-0.32% by weight of C, ≦0.15% by weight of Si, 0.15 to 0.40% by weight of Mn, ≦0.010% by weight of P, ≦0.007% by weight of S, 1.20-1.80% by weight of Cr, 0.25-0.45% by weight of Mo, 3.40-4.00% by weight of Ni, 0.05-0.15% by weight of V.