SU301113A1 - METHOD OF MANUFACTURING A COMPOSITE ROTOR OF A POWERFUL TURBO-GENERATOR-PATENTNO-PHK ^ Y ^ FIRST LIBRARY - Google Patents

Description

The invention relates to power engineering, in particular to the manufacture of large rotors of turbo-generators.

Currently, the problem of power engineering is the creation of mosh turbogenerators, in particular nuclear power plant generators, which, at lower revolutions, have correspondingly increased torque and rotor dimensions.

One of the factors limiting the development of the production of ever larger turbo generators is the difficulty of producing rotor forgings.

For example, for nuclear power plant generators with a capacity of 500 mV, according to preliminary data, a forging of 200 tons and an ingot of 370 tons is required.

However, as the size of the ingot and forgings increases, the quality of the metal decreases, as liquation, gas saturation, content and dimensions of nonmetallic inclusions increase, the degree and uniformity of the hem decreases, and the hardenability during heat treatment deteriorates. In addition, the effect of defectoscopy and quality control of metal forgings is significantly reduced.

from pre-welded blanks, which will increase the weight of the forging to 140 tons. However, a further increase in the weight of the welded rotors is limited by the capabilities of the equipment for forging and heat treatment. At about the same level are the capabilities of world technology for the production of rotor forged whole forgings. Currently, a number of ways are known.

manufacturing composite rotors of powerful turbo-generators by coaxially connecting the annular sections between themselves and with one of the end sections by welding and tightening the rotor elements in the axial direction

Clicks.

The manufacture of generator rotors without the use of solid-forged blanks is based on the following two methods:

1. Assembly from separate parts with subsequent tightening by mechanical devices.

or preheated items.

2. Assembly from separate parts with the subsequent welding in an integral rotor.

Each of these methods has specific deficiencies, the value of which increases with the size of the rotors to such an extent that they cannot be successfully used for the manufacture of very large rotors. The disadvantages of precast rotors with central

The tightening is that the torque is transmitted only by the frictional forces between the joint parts. For high-power generators with large torques, the rotor joints closer to the drive coupling become unreliable, since the frictional force in these joints may be insufficient to transmit torque, especially in the case of a short circuit.

The disadvantages of prefabricated rotors with peripheral straps are that the peripheral straps are not applicable for bipolar rotors, and for large four-pole rotors the number of them becomes so large that they require increased manufacturing accuracy that can not be ensured by uniform loading. on metal-cutting machines used in generator construction. With uneven loading of the peripheral straps, there is a danger of loosening and vibrations of the elements of the assembled rotor or the destruction of the individual straps.

The disadvantages of welded rotors (for example, Brown-Bowery patent No. 150099 or E-Scher Visse No. 520324) are that existing methods of welding and testing of welded joints cannot guarantee the absence of defects, especially in the root of the seam . The likelihood of the occurrence of these defects increases with the size of the rotors. At the same time, the risk of these defects increases due to increased loads on the welded joints. Defects of welded joints, being stress concentrators, can develop under the action of cyclic tensile stresses arising at alternating bending. The possibility of developing defects is also enhanced by the fact that when welding high-strength rotary steels it is difficult to guarantee stable high ductility and toughness.

The aim of the invention is to prevent the development of welding defects with prolonged exposure to alternating bending moments. The proposed method is characterized in that the rotor elements are tightened in the axial direction after the welds are applied with a force that ensures that the compressive stress exceeds the bending stresses that occur when the rotor rotates.

The drawing shows a diagram of the composite rotor.

The rotor consists of a barrel-forming set of coaxially bonded annular sections / with centering lugs 2 on the tordovy surfaces. The sections are connected by circumferential welded grooves 3. The barrel is compressed with the end leading and driven sections and 5 connected by a stem rod 6 on the external end sides. Both end sections and the rod have in the axial part of the cavity,

the assembly forming a single channel 7 for connection to a source of heat carrier, for example, steam.

The master section 4 is rigidly connected to the adjacent section of the barrel by welding. The end of the driven section 5 is freely pressed against the end surface (barrel) and is connected to the rod by a screw thread.

To compress the welds 3, the driven section 5 is screwed onto the locally heated ground 6. At the same time, the temperature of the heat transfer medium must provide the specified compressive stresses of the welded joints during the subsequent cooling of the rod.

This opens up prospects for the application of the most progressive methods of metal smelting, in particular, electroslag and vacuum arc remelting, which radically improve the operational and technological properties of the metal.

In this drawing, all the joints of the rotor parts forming the barrel are connected by circumferential welds, except for the last joint (furthest from the lead section). It is possible to apply welded joints only at the first joints, the number of which, as well as the depth of the weld, are determined by the magnitude of the torques transmitted by the joints.

Calculations show that the required depth of the weld is usually small. Even for the first joint of a four-pole rotor with a capacity of 2000 mV, the depth of the schv is 100-150 mm. With such a relatively small weld depth, it becomes possible to use such advanced welding methods as electron beam welding in vacuum.

If necessary, the weld size of the first joint can be reduced by increasing the size of the first section, which correspondingly reduces the torque transmitted by the first joint.

For the purpose of unification, all welded joints may be the same (the same as the first, most loaded).

The prestressing force of the welds should ensure the creation of compressive stresses in them, which exclude the possibility of tensile stresses when subjected to a bending moment. To do this, the generated axial compressive stresses must exceed the calculated bending stresses due to the rotor's own weight. The welded-assembled design of the rotors allows this condition to be fulfilled with a large margin. For example, for a welded-assembled rotor of a generator with a capacity of 2000 mV, according to the scheme shown in the drawing, for the most loaded joints, preliminary compressive stresses can be created that are 5 times higher than the bending stresses.

of the ring sections between themselves and from one of the end sections by welding and tightening the rotor elements in the axial direction with strings, characterized in that, in order to prevent the development of welding defects during prolonged exposure to alternating bending moments, the rotor elements are tightened in the axial The machining is performed after welding is applied with a force that ensures that the compressive stress exceeds the bending stresses that occur when the rotor rotates.