Heat treatment of turbo-generator and steam turbine rotors

Abstract

1. A forging reduction ratio of 4–6 for the barrel of steam turbine and turbo-generator rotors ensures uniform and high ductility properties and toughness throughout the whole section. The isotropy factors for specimens of the barrel are high (85–95%) and vary slightly between the surface and the center. 2. An increase in the reduction ratio at the journals of steam-turbine rotors to 11 and turbo-generators to 15 (compared with a barrel ratio of 4–6) causes an increase in ductility and toughness in the longitudinal sections and a considerable decline in the transverse specimens. As a result the isotropy factors for the metal of the journal, particularly in the middle, decline to a considerable extent, 3. Quenching of rotors made of 34KhN2M and 34KhN3M steels instead of normalizing, at a certain reduction of the absolute values of the ductility and toughness, increased the isotropy factor. 4. The hydrogen content in the central zone of the forgings (1–2 cm3/100 g) sharply reduces the ductility and elongation and compression isotropy factors. Prolonged soaking of the specimens at room temperature or at 450° for 4 or 6 hours increases the ductility of transverse specimens to satisfactory values, and also increases the isotropy factor. Hydrogen reduces the ductility of the metal in the transverse specimens to a greater extent than in the longitudinal ones. 5. Vacuuming the steel gives it high ductility and a high isotropy factor through the section of the part.