JPS60147501A - Turbine rotor - Google Patents

Abstract

PURPOSE:To enhance the reliability and life to turbine as well as simply reclaim a rotor by a method in which the padding of a material whose thermal expansion coefficient is smaller than the base material of the rotor is provided on the surface of the turbine rotor. CONSTITUTION:A surface 19 as shown by surface contours 19a and 19b is provided for the surface of the rotor 13 in the high- and medium pressure stage 1 in high- and medium pressure steam turbines. The basal portion of a disc, as shown by a round mark A, is shaped into a circular arc form with an intention of relieving the concentration of stress. In this case, the surface contours 19a and 19b and the circular arc-shaped portion are made of paddings 18a-18c of a proper thickness formed from the contour 20, as shown by the oblique line. The material of the padding is high-Cr steels such as 12 Cr-steel, etc., in the case where the base material of the rotor 13 is a low-Cr steel such as Cr-Mo-V steels, etc., having a smaller thermal expansion coefficient than the base material of the rotor 13.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a turbine rotor used in a high-pressure or intermediate-pressure steam turbine. The present invention relates to a turbine rotor configured to do so.

[Background of the invention]

In recent years, in order to efficiently meet the increasing demand for raw power, steam turbine completion equipment has become significantly larger in capacity. Along with this, in order to compensate for the critical difference between day and night, power generation equipment, which has traditionally been operated as a pace road, is being required to start and stop frequently and change its load.

As a result of the above-mentioned start-up and stoppage and load changes, stress concentration occurs in the turbine rotor (hereinafter referred to as rotor) with a recommended stress of 4-1-1, especially at the root of the rotor's disk. Therefore, in order to improve the life span of the rotor, it is necessary to completely improve the strength of the steel rotor, especially the surface strength of the disk root. There is also a need for a means for appropriately regenerating the rotor when it becomes fatigued due to direct use of the turbine for a long period of time. However, in the prior art, there was a drawback that the reliability and life of the rotor were further deteriorated even though there were no effective means.

That is, FIG. 1 shows a steam flow path of a typical four-flow type steam turbine. Steam 5 from the boiler first passes through high pressure stage 1, is heated again in boiler 51, and passes through medium pressure stage 2.
to go into. Afterwards, it passes through a crossover pipe 3, passes through a low-pressure stage 4, and is led to a condenser.

In this steam turbine, thermal stress is generated in the turbine rotor due to changes in steam temperature when starting, stopping, or changing load. Here, the entire thermal stress generation process will be explained with reference to FIGS. 2(a) and 2(b).

Figure 2 (a) shows time on the horizontal axis, al:! lqI]
Figure 2 shows the temperature in and around the rotor, and Figure 2 <b) also shows the time on the 3rd sleeve and the stress generated on the rotor on the 4th and 1st. Both cases show the case of cold engine and startup.

As shown in FIG. 2(,l), when the turbine is started, the first stage 1 steam temperature 1w6 of the rotor rises like a circular line from a state of approximately room temperature. Also, the rotor surface temperature 7 is indicated by a dotted line.
1st stage 1 wheat steam temperature is slightly delayed from 6, and rises in the same way. Also, the rotor center hole temperature 8 rises approximately 471 degrees from the rotor surface temperature 1/7 in a rectangular shape indicated by a point 'lJ4'. From the start until the turbine stops, each of the above-mentioned temperatures passes in parallel to the center-to-center axis and at the same temperature. When the turbine is stopped, - first, the first steam temperature 6 decreases to approximately room temperature, and then the rotor surface temperature 7 and the rotor center hole temperature 8 decrease in the same way, one after the other.

Figure 2 (b) shows the stress generated in the rotor due to the degree change shown in Figure 2 (a), where the rotor surface stress [O] is the compressive stress as shown by the point 2 gland. Meanwhile, the rotor center hole stress 9 becomes a tensile stress, and the rotor surface stress 10 occurs at the root of the disk of the rotor, resulting in a compressive stress that exceeds the minus yield point 12t. Therefore, residual stress 11 remains even after starting. Further, when the turbine is stopped, as shown in the figure, the rotor surface stress 1o becomes a tensile stress and an expansion stress, and the rotor center hole stress 9 becomes a compressive stress.

FIG. 3 shows an outline of the rotor 13, and shows the high pressure stage IV.
The main steam S1 passes through C, and the reheated steam S, which is the main steam SI that has passed through, is reheated through the intermediate pressure stage 2. Due to these steams, thermal stress is generated as described above at the root A of the high pressure f7J stage disc of high pressure collapse 1 and the root B of the reheat stage 0 disc of medium pressure stage 2. , the above thermal stress also occurs in the rotor center hole 14.

Next, as shown in FIG.
The centrifugal response shown by the line 116 acts. Therefore, the resultant stress 17 (shown by a solid line) acts. On the rotor surface, the thermal stress 15 during start-up and stop is much larger than the stress 16 at the center of bloom, and the life span of the rotor surface is limited.
It is sufficient to consider low cycle fatigue based on the thermal stress 15 acting on the root of the I force I on r. Further, in the rotor center hole 14, low cycle fatigue due to thermal stress 15 and creep life due to centrifugal stress 16 may be reduced.

Regarding the above-mentioned lifespan management, there are official documents, for example,
a prior paker entitles v″
The Operation of Large Ste.
am Turbines t.

Lim1t Cyclie 'Pharma Cra
cking” by II P.

Tjmo to G, W Aarney (ASM
E Parker No. 67-WA/PWR, publ
However, in order to operate the turbine safely, it is necessary to manage the life of the rotor, and for this purpose, it is necessary to reduce the thermal stress caused by stress concentration at the base of the disk as much as possible. Needed. However, in the prior art, there is no simple and appropriate means, which causes a reduction in the reliability and life of the turbine. Furthermore, there was no suitable means for restoring the rotor which had suffered fatigue due to long-term use, which was a problem.

[Purpose of the invention]

At the end of Honto, I-j-ha Kime Haru Rou Δ斗＾晙ノff1l
The purpose of the l i2J Tamonode Ruri is to provide a turbine rotor that improves the reliability and life of the turbine and can be regenerated by a simple means.

[Summary of the Invention] In order to achieve the above object, the present invention features a turbine rotor in which the surface of the rotor is overlaid with a material having a lower coefficient of thermal expansion than the surface of the rotor. After welding overlay to the center of the stress nest and smoothing the core,
The turbine rotor is characterized by being formed by annealing.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

First, an outline of this embodiment will be explained.

As shown in FIG. 5, a surface portion 19 shown by surface contours (19a) and (19b) is formed on the surface of the rotor 130 of the high-pressure stage 1 (the same applies to the medium-pressure stage 2, but omitted hereinafter). , especially the base of the high-pressure first stage disc (indicated by circle A)
is formed in an arc shape to alleviate stress concentration. In this embodiment, the surface contour portions (19a) and (1gb) and the arcuate portion of the base of the high-pressure first-stage disk are formed by building up an appropriate thickness from the contour 20, as shown by diagonal lines in the figure.
Built-up parts 18a, 18b, and 18c are formed.

As the overlay material, the base material of the rotor 13 is Or-Mo-V.
In the case of JA μ-hole low chromium steel, it is preferable to use high chromium steel such as 12CrA. As is well known, 12Crjjli is a material that can be attached to Or-Mo-■ steel and has a small coefficient of thermal expansion. After the above-mentioned overlay, the surface strength can be improved by smoothing the surface. or,
Among the surface shapes of the rotor 13, the base of the high-pressure first-stage rotor disk is the area where stress is concentrated and easy to wear.
In particular, this portion is overlaid, finished into a smooth shape, and annealed to remove stress and strain, thereby forming a high-strength turbine rotor.

Next, this embodiment will be explained in detail.

First, the rationale will be described.

Generally, the thermal stress δT on the rotor surface is shown below.

Here, α is the thermal expansion coefficient of the rotor material, E is the longitudinal elastic modulus of the rotor, ν is the Poisson's ratio of the rotor, Ts is the average temperature of the rotor, and Ts is the surface temperature of the rotor.

From the above equation, the smaller the thermal expansion coefficient α of the rotor material, the smaller the thermal stress δte on the rotor surface.

As mentioned above, 12CrJ4 has a thermal expansion coefficient α that is 20% smaller than that of Cr-M OV steel. However, Ji:
zcrs is high chromium steel 0, the whole rotor 13 is 12Cr
Is it possible to make it with steel? ? Inferior. Therefore, the key point of this embodiment is to overlay only the required locations.

In this embodiment, the build-up parts 18a, 18b, and 18c are formed as described above on the parts of the rotor surface where thermal stress is large, and the surfaces of the build-up parts 18a, 18b, and 18c are connected to the rotor 1.
It is formed from a smooth finish that follows the shape of 3.

The prison, wall thickness, etc. of meat part A l & a, 18 b, 18 c depend on the 8th place of the turbine, the position and shape of the paragraph, etc.
It is set appropriately.

In this example, 120 rJ$t- was used for low chromium 44 Cr-Mo-V, but it is not limited to this, of course. Even if the base material of the rotor 13 is a low chromium steel other than Cr-MO-V steel, a high chromium steel with a correspondingly low thermal effect coefficient is appropriately set.

Next, one embodiment of the combined invention will be described. As mentioned above, the rotor 13 has a stressed portion such as the root of a stepped disc that is under pressure. This part is formed into an arc shape as shown in [C] above, but if the stepped shape is not sufficient, this part is further overlaid, finished into a smooth shape, and annealed. Out.

The strength of the joint can be improved by overlay finishing and annealing, leveling V&, and removing distortion. In this case, the overlay material may be the same as the base material of the rotor 13, or as mentioned above, it may be a material that has a lower shear coefficient than the base material.

Furthermore, the above-mentioned physical sensation is not only applicable to newly manufactured rotors 13, but also to the remanufacturing of rotors 13 whose surfaces have deteriorated due to fatigue due to use. In case of fatigue deterioration due to stress concentration, detect by all known means (magnetic flaw detection, color check, visual inspection, etc.), skin-cut this area, perform the above-mentioned overlay, refill, smooth finish, and then annealing. As a result, the rotor 13 with high strength is regenerated.

The above-mentioned overlaying technique is one that has been generally employed in the past, does not require highly sophisticated techniques, and can be easily implemented.

In the case of the above embodiment using chromium steel with a low thermal expansion coefficient, the thermal stress can be reduced by about 20%, and the service life can be significantly increased.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the reliability and life of the turbine can be greatly improved, and the rotor can be regenerated by a simple means.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram of a 4-flow steam turret; Fig. 2 (a) is a diagram showing temporal changes in steam temperature, rotor surface temperature, and rotor center hole temperature at startup, operation, and stop; Second
Figure (b) is a diagram showing the change in rotor stress generation over time corresponding to the temperature change in Figure 2 (a), Figure 3 is a cross-sectional view of the rotor near the pressure stage and the intermediate pressure stage, and Figure 4. 5 is a sectional view of the rotor when the turbine refrigerant is started, and FIG. 5 is a sectional view of the rotor showing an embodiment of the present invention. 1... High pressure stage, 2... Medium pressure stage, 6... Steam temperature after first immersion, 7... Rotor surface temperature, 8... Rotor center hole temperature, 9... Rotor center hole stress , lo... Rotor surface center force, 11... A residual stress, 12... Minus yield point, 13... Rotor, 14... Rotor center hole, 15... Thermal stress, 16... Centrifugal stress, 17...
Resultant stress, 18a. 18b, 18c... Overlay part, 19*face part, 19a. 19b... External contour, 20... Contour. Agent: Patent Attorney Masami Akimoto] Suri? figure time

Claims (1)

[Scope of Claims] 1. A turbine rotor in which a material having a smaller thermal expansion thread number than the base material of the rotor is overlaid on the surface of the rotor. 2. The turbine rotor according to claim 1, wherein the material is high chromium steel when the base material of the rotor is low chromium steel. 3. A turbine rotor formed by overlay welding on the stress concentration area on the surface of the rotor, and then smoothing the overlay by finishing fc stage and annealing. 4. The turbine rotor according to claim 3, wherein the stress concentration portion is a root of a disk of the rotor. 5. The turbine rotor according to claim 3, wherein the stress concentration portion is a skin-cut portion of the surface layer of the rotor whose strength is reduced by wave force. -17Q, Jbl-Li-J1%-'##1. n-J,
The turbine rotor according to claim 3, wherein the ridges are made of a small material. 7. The turbine rotor according to claim 6, wherein the material is high chromium steel when the base material of the rotor is low chromium steel.