JPH0160689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a turbine rotor in which a coupling ring and a shaft are integrally formed, and in particular, the shaft is made of 10 to 14% chromium steel and has a journal sleeve on the outer periphery of the journal part. Regarding turbine rotors.

Conventionally, as a material for high and intermediate pressure rotors of steam turbines,
12% chromium steel is used because it has excellent creep properties at high temperatures. However, 12% chromium steel is
Bearing characteristics, especially friction characteristics, are very poor, and there is a risk that the bearing metal may seize and damage the journal part. It has a structure in which it is shrink-fitted to the journal part 2 of the rotor 1 made of chromium steel. In this case, since the coupling ring 5 has a larger diameter than the journal part 2, the coupling ring 5 must also have a shrink-fit structure, and the coupling ring 5 must be shrink-fitted after the sleeve 4 is shrink-fitted to the journal part 2.

However, since a large bending stress is applied to the shrink-fitted end of the coupling ring 5, there is a high risk that a crack 7 as shown in FIG. 1 will occur in the rotor 1. It is required to have an integral structure by machining.

In order to meet these two requirements, that is, to cover the outer surface of the journal part 2 with a low-alloy steel with good bearing properties and to make the coupling 5 integral with the rotor, it is necessary to use a metal with good bearing properties in the journal part 2. There are methods such as weld build-up and thermal spraying, but weld build-up tends to cause weld cracks, and thermal spraying has the disadvantage that the thermal sprayed part tends to peel off when the journal part is bent. Also in the journal section,
Although it is conceivable to integrate the split sleeves on the shaft and shrink-fit them, there is a problem in that the turbine rotor becomes elongated due to shrink-fitting or machining.

The present invention has been conceived in this regard, and its object is to provide a steam turbine rotor made of 10-14% chromium steel with an integral coupling, even if it uses a sleeve.
It is an object of the present invention to provide a turbine rotor of this type that does not increase the length of the turbine rotor.

The configuration of the present invention includes 10 integrated couplings.
In an annular journal sleeve that is attached to the journal part of a steam turbine rotor made of ~14% chromium steel, a step is provided on the outer peripheral surface of the journal part of the turbine rotor so that the outer diameter of the journal part differs from one another along the turbine axial direction. At the same time, a step is provided on the inner circumferential surface of the journal sleeve so that the inner diameters thereof are different from each other along the turbine axial direction so as to match the outer circumferential surface of the rotor journal part, and this journal sleeve is attached to the turbine rotor. The sleeve is attached to the outer periphery of the rotary journal, thereby allowing the sleeve to be easily attached to the rotary journal.

Next, a journal sleeve which is an embodiment of the present invention will be described with reference to the drawings. In Figure 2,
As shown in FIG. A half-shaped sleeve 10a divided into two,
10b. Further, on the outer circumferential surface of the journal part 2 of the turbine rotor 1, in advance, a minute groove is formed at the center along the turbine axis direction so that the outer circumferential surface near the coupling ring 5 has a smaller outer diameter than the outer circumferential surface of other parts. A step 2c is provided. The dimension of this step should be approximately 0.5 mm or more. Further, so that the journal sleeve 10 also matches the outer peripheral surface of the rotor journal part 2, the inner peripheral surface of the sleeve 10 near the coupling 5 has an inner diameter smaller than the inner peripheral surface of other parts. Along the line, a minute step 10c is provided exactly at the center. In addition, this journal sleeve 10 is
Low alloy steel with good bearing properties, e.g. Cr: 0.2 to 2.25
%, Mo: Bainitic steel containing 0.2 to 1% is used. Next, the attachment of this journal sleeve 10 to the rotor journal 2 will be explained.

First, as shown in FIG. 4, the sleeves 10a and 10b, which are divided into two parts in the circumferential direction, are welded together at the rotor part 1b, which is located between the journal part 2 and the coupling part 5 and has a smaller shaft diameter than the journal part. to form one ring shape. In the case of welding,
Since welding defects are likely to occur on the inner peripheral side of the sleeve and deformation occurs due to welding, the inner surface of the sleeve 10 is finished by machining after welding. This includes:
First, the cutting tool 7 is attached to the end of the rotor 1b, which is a rotor part that is close to the journal part 2 and has a smaller outer diameter than the journal part 2, using a cutting tool holder 8 and a fixing belt 9, and rotates together with the rotor. On the other hand, by moving the journal sleeve 10 toward the journal along the turbine axial direction, the inner circumferential surface of the sleeve 10 is formed with a minute step so that the diameter is small near the coupling ring 5 and the diameter is large near the journal 2. 10c.
The machining process is performed so that the inner diameter of the sleeve 10 has a certain shrinkage fit margin with respect to the outer diameter of the rotary journal portion 2. At this time, as shown in FIG. 5, the sleeve 10 overlaps with the small diameter side of the journal portion 2 by up to 1/2 of the length in the axial direction of the turbine. Therefore sleeve 1
After processing 0 from the journal side to 1/2,
Rotor 1b with bite 7 close to coupling 5
By attaching it to the end of the sleeve 10 and moving the sleeve 10 toward the coupling side while rotating the cutting tool 7 together with the rotor 1 as before, the inner circumferential surface of the sleeve 10 closer to the coupling will have a smaller diameter than that on the journal side. It is machined like this.
Also, during this machining, the rotor journal portion 2 is machined so as to have a certain shrink fit allowance with respect to the outer diameter thereof. After welding, the inner surface processed sleeve 10 is uniformly heated and shrink-fitted to the outer periphery of the journal part 2 on the rotor, and after removing the cutting tool from the rotor, the end part 2a of the journal part 2a in FIG. 2 is rolled. To prevent the sleeve 10 from coming off. After rolling, the outer periphery of the sleeve 10 made of low alloy steel may be finished by polishing.

In this way, the sleeve 1 is divided into two in the circumferential direction.
0 are welded together to form an integral ring shape, and the outer surface of the rotary journal part 2 and the inner surface of the sleeve 4,
The part near the coupling ring has a smaller diameter than the other part near the turbine stage, and a step is provided so that the sleeve can be attached to the outer surface of these journal parts. During peripheral machining, the sleeve can be moved so that a part of the sleeve overlaps the journal part, so the length of the rotor shaft part 1b between the journal and the coupling ring may be at most the same length as the sleeve length. This prevents the turbine rotor from becoming longer due to mounting. Also,
Needless to say, the inner periphery of the sleeve can be machined well.

In the above embodiment, the number of steps provided on the outer surface of the rotary journal portion 2 is one, but a plurality of steps may be provided, and in that case, the number of steps provided on the inner surface of the sleeve 10 will also be multiple steps. Further, the step formed on the inner surface of the sleeve 10 may be processed before welding the sleeve divided in the inner circumferential direction, and in that case, the time used for processing the inner circumference of the sleeve after welding is the time required for cutting the welded part. Since it is only a finishing process, it will take even less time.

The material of the sleeve 10 is low alloy steel with good bearing properties, Cr: 0.2 to 2.25% by weight,
All-bainitic steel containing Mo: 0.2 to 1%, or bainitic steel further containing V: 0.05 to 0.5%, etc. may be used.

Compared to 12% chromium steel, low alloy steel has a thermal conductivity of approx.
This is because the temperature rise during rotor rotation is small because it is 30% higher, which has the advantage of being less likely to cause adhesive friction with the sleeve bearing. This has been confirmed by experiment. The experiment compared damage to the journal caused by the introduction of minute foreign objects during bearing lubrication between a rotor made of 12% chromium steel and a rotor made of chromium-molybdenum-vanadium low-alloy steel. be. Figures 6 and 7 show the journal surface roughness of a 12% chromium steel rotor and a low alloy steel rotor, respectively, after being rotated for a certain period of time after contamination with foreign matter. Steel rotor is 12% lower
It can be seen that the wear resistance is better than that of chrome steel.

The sleeves are brought into close contact with each other by rolling, but they may also be integrated by silver brazing. In this case, the close contact is increased and further contributes to preventing rotation of the sleeves. In addition, as a turbine rotor material made of chrome steel, in weight%, C: 0.1 to 0.3%, Si: 0.6
% or less, Mn: 0.4 to 1.5%, Ni: 1.2% or less, Cr:
10~14%, Mo: 0.5~1.5%, V: 0.05~0.3%,
Preferably, steel has a completely martensitic structure containing Nb: 0.02 to 0.15% and N: 0.04 to 0.1%.

According to the present invention, by providing a step in both the rotor journal part and the journal sleeve, it is possible to improve the efficiency of the turbine even when a 10-14% chromium steel turbine rotor with an integral coupling is used with a sleeve in the journal part. It is possible to avoid increasing the length of the rotor.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a 12% chromium steel rotor with a conventional sleeve and coupler shrink-fitted together, and Figure 2 is a chromium steel rotor equipped with a journal sleeve according to an embodiment of the present invention. 3 is a perspective view of the sleeve shown in FIG. 2, and FIG. 4 is a chromium steel rotor according to an embodiment of the present invention, showing the state of the sleeve before being attached to the rotor journal. FIG. 5 is a partial cross-sectional view of a chrome steel rotor showing the process of attaching a sleeve to the rotor journal, which is also an embodiment of the present invention, and FIGS. 6 and 7 are respectively 12%
FIG. 2 is a graph showing experimental data of surface roughness of a chrome steel journal and a low alloy steel journal. 1...12% chrome rotor, 2...Journal,
3...bearing, 5...coupling, 10...journal sleeve, 2c, 10c...step.

Claims (1)

[Scope of Claims] 1. A turbine rotor shaft made of 10 to 14% chromium steel, a coupling formed integrally with the rotor shaft at the end of the rotor shaft, and a coupling ring that is shrink-fitted to a journal portion of the rotor shaft. and a journal sleeve, wherein the journal sleeve is divided in the circumferential direction and fixed in a ring shape prior to shrink fitting to the journal, the outer peripheral surface of the journal part of the turbine rotor. A step is provided in the axial direction so that the outer diameter of the journal part is different in the axial direction, and an inner diameter is formed in the inner peripheral surface of the journal sleeve in the axial direction so as to match the outer peripheral surface of the journal part. 1. A turbine rotor in which a coupling ring and a shaft are integrally formed, characterized in that steps are provided with different heights, and the journal sleeve is shrink-fitted to the outer periphery of the journal portion of the turbine rotor. 2. Among the steps provided in the journal sleeve and the journal portion, the diameter of the step portion closer to the coupling ring is formed to be smaller than the diameter of the step portion of the other portions of the turbine rotor. A turbine rotor in which a coupling and a shaft according to claim 1 are integrally formed. 3. A turbine rotor in which a coupling and a shaft are integrally formed according to claim 1, wherein the journal sleeve is made of low alloy steel. 4 The low alloy steel contains 0.2 to 2.25% Cr and 0.2 to 2.25% Mo.
4. A turbine rotor in which a coupling and a shaft are integrally formed as claimed in claim 3, characterized in that the rotor is made of bainitic steel containing 1%.