JPH0463201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a Tenon regeneration method for a steam turbine impeller.

[Technical Background of the Invention] Generally, in a turbine impeller for a steam turbine, etc., a circumferential groove is formed in a single stage or in multiple stages in the radial direction on the outer periphery of a rotor disk. A device is used in which the movement in the radial direction is restricted by engaging a portion (referred to as a “portion”).

Figure 5 is an exploded partial view of the turbine impeller.
A plurality of grooves 2 extending on both front and rear sides are formed on the outer periphery of the rotor disk 1, and implanted portions 3' of the blades 3 are fitted in a hollow shape on the outer periphery of the rotor disk 1. A protrusion 4 formed on the opposing inner surface of the implanted portion 3' engages with the groove 2 of the rotor disk 1.

Incidentally, in the groove 2 forming portion of the rotor disk 1, one or more notches 5 are formed on the circumference, extending in the radial direction and having a width approximately equal to the thickness of the implanted portion 3'. After inserting the implanted part 3' of the blade 3 in the radial direction from the notch 5, the blade 3 is moved in the radial direction by sliding it in the circumferential direction and coupling it to the outer periphery of the rotor disk 1. is regulated.

In this way, a predetermined number of blades 3 are pressed against each other in the circumferential direction and assembled into an annular body. Then, in the final stage, the notch 5 has:
As shown in FIG. 6, a stopper blade 7 having a groove 6 matching the shape of the notch is engaged.

The engagement between the groove 6 of the stopper blade 7 and the notch 5 of the turbine disk 1 is a simple fit, unlike the case of the blade 3, and the movement of the rotor disk 1 in the radial direction is not restricted. As shown in FIG. 7 or 8, the stopper blade 7 is attached to the joint surface of the implanted part of the stopper blade 7 and the adjacent blades 3a, 3b or the adjacent blades 3c, 3d of the rotor disk 1. A pin hole 8 is provided in the thickness direction, into which a pin 9 is press-fitted, and a pin hole 1 is formed in the stopper blade 7 and the notch 5 that fits into the stopper blade 7 to pass through these.
This is done by providing a hole 0 and press-fitting the pin 11.

On the other hand, in FIG. 5, a protrusion (hereinafter referred to as a tenon) 12 is provided at the tip of the blade 3, and a protrusion (hereinafter referred to as a shroud) is formed through the tenon 12. 13 are pressed together and assembled into an annular body, as shown in Fig. 7, several blades are divided into several groups in the circumferential direction and fixed as one group, and various excitation sources including steam power are used. It is made to be able to resist.

FIG. 9 is an enlarged view showing the joint part of the shroud 13 with the blade 3, and the shroud 13 is fixed to the blade 3 by caulking the tenon 12 until it becomes a flat caulked part 12'. ing. The tenon 12 and the tenon caulking portion 12' resist steam force and high centrifugal force acting on the shroud 13.

The top of such a turbine impeller, more specifically the shroud 13 or the tenon 12,1
When damage occurs to the blade 2', if the damage is severe, it is normal to replace the blade with a new one, but if the damage is mild, a technique called shoulder-sliding the blade is used. The damaged blades are now being adopted and the damaged blades are being reused for restoration.

In the latter case, depending on the extent of the damage, the following steps are usually taken: First, if the damaged area is narrow and located close to the stop blade 7, the damaged blade is removed from the group including the stop blade and the damaged part is repaired.

To remove the blades, simply reverse the turbine impeller assembly procedure described above.
Since all the blades are arranged in groups as shown in FIG. 7, it is first necessary to separate all the blades to be extracted into individual blades.

For this purpose, the shroud 13 is usually cut using a grinder or the like as shown by the dashed line in FIG. From the blades separated in this way, the stopper blade 7 shown in FIG. Once the stopper blade 7 is removed, the remaining blades 3 (3a, 3
b, 3c...) can be easily removed from the notch 5 by sliding in the circumferential direction along the groove 2 in FIG.

The individual blades extracted in this way are
As shown in Figure 1, using an appropriate tool, first remove the tenon caulking part 12' and remove the shroud 13.
Then, by grinding or machining, a new tenon 14 is made as shown in FIG.
will be formed using a part of the effective part of the blade.

This is because the tenon 12' is shaved off as described above, so the tenon caulking part 1 is used when re-installing the rotor disk 1 and fitting and fixing the shrouds 13.
This is to ensure a caulking allowance equivalent to 2'. As a result, the height of the effective part of the new blade 15 is
Since the height is shortened by Δl from the original height l ₁ to l ₂ , the term "shoulder-slip" is usually used.

On the other hand, if the damage ranges over the entire circumference, it is necessary to lower the shoulders of all blades belonging to the turbine impeller. In this case, the method of separating the blades into individual blades as described above may be taken, but rather, the method of removing the shroud and tenon by removing the shroud and tenon by grinding the entire blade on a lathe is sometimes taken. There are many people.

That is, as shown in FIG. 13, first the cutting line a
Along b, the shroud 13 is shaved off from both sides, leaving a tenon width. At this time, the blade 3 can also be cut deeply by an amount corresponding to the shoulder sliding amount Δl shown in FIG. Then, along the cutting line,
If the tenon caulking portion 12' is removed, the remaining shroud 16 can be removed by a simple blow from the inside as shown in FIGS. 14 and 15. In this state, if the tops of the tenon 14 and blades 15 are finished using a grinder or the like as shown in FIG. 12, preparations for reassembly will be completed.

In this way, it is possible to repair only the top portion of the blade 3 without removing it. Of course, if manual work is done using a grinder or the like, the latter method of all-around repair can be applied to the former partial repair, and conversely, if it takes time and effort, the former method of separating into individual blades as described above can be applied. can also be applied to the latter all-around repair.

This shoulder-down technique is extremely effective for local repairs or as a temporary measure in emergencies, but as shown in Figure 12, the originally required effective blade length l ₁ is removed by the shoulder-down amount Δl. Because it is a translation,
It is inevitable that the efficiency of the blade will decrease.

In particular, when this technique is applied to the entire circumference of the rotor impeller, the effect cannot be ignored.
When applied to multiple stages of a steam turbine,
The steam turbine performance will be considerably deteriorated. For example, when the above technique is used for a 265 MW class intermediate pressure turbine, the heat consumption rate is 0.04.
There are also cases where the percentage decreases.

In order to avoid such performance deterioration, it is necessary to avoid the above-mentioned shoulder drop, that is, to compensate for the Tenon's removed amount 12' by some other method. For example, as shown in FIG. 16, Reshaping by Tenon's overlay welding is also partially used.

The reason why this method is not generally carried out is that even if a proper welding rod is used and proper welding and heat treatment are carried out, the remaining tenon 17 and the build-up part 18 are separated as shown in Fig. 16. Heat affected zone 1 due to welding between
9 and macroscopic welding defects (referred to as undercuts) are likely to occur at the welding start point 20a and end point 20b, so the tenon 12 must withstand long-term high loads including vibration components.
This is because the reliability is not sufficient.

In order to solve such problems, the present inventors first developed a tenon weld overlay to form a weld overlay on the residual tenon 12 remaining at the tip of the blade 3, as shown in FIG. In the method, a plate 25 having a through hole having a shape slightly larger than the outer circumference of the remaining tenon 12 is fitted onto the outer circumference of the remaining tenon 12, and the gap size between the outer circumference of the remaining tenon 12 and the inner circumference of the through hole is adjusted. is maintained at a predetermined value, and the said contact plate 2
5 is fixed, and then welding is carried out on the remaining tenon 12 in a space formed by the upper surface of the remaining tenon 12 and the inner surface of the through hole. , filed this application.

According to the Tenon weld overlay method of the present invention,
The workability can be greatly improved, and a high quality overlay regenerated tenon can be obtained.
Therefore, repair by Tenon overlay welding can be used more widely.

On the other hand, in the prior art, as shown in FIG. 18, it is assumed that the remaining tenon part 12 is to be stretched to the maximum extent, so re-caulking is performed from the finished shape 44 after tenon overlay, and the top of the tenon is caulked. Part 12'
When the welding start point 20a or the welding end point 20b and the heat affected zone 19 are regenerated, the welding start point 20a or the welding end point 20b and the heat affected zone 19 will just coincide with the upper surface of the shroud 13 or its vicinity.

FIG. 19 is a diagram showing a general stress distribution at the joint between the tenons 12, 12' and the shroud 13. The shroud 13 has chamfered portions 13a and 13b around the tenon 12 fitting hole, and the blade 3. At the base of tenon 12 at the top of
12a are applied to each. When such a component rotates at a high rotational speed, shear stress is concentrated on the tenon 12' in contact with the chamfered portion 13b due to the centrifugal force of the shroud 13, and on the chamfered portion 13a,
This results in concentration of tensile stress due to the centrifugal force applied to the shroud 13 and the tenons 12, 12'. When we examine the general failure forms of such a bonded body, we find that there are many shear failures 47 of the chamfered portion 13b or tensile failures 48 of the Tenon 12, and although this does not always occur, generally It can be said that the chamfered portion 13b is in a slightly more severe condition than the chamfered portion 13a.

[Object of the Invention] The present invention has been made in response to the above-mentioned conventional circumstances, and aims to provide a tenon regeneration method for an impeller that can obtain a welded overlay tenon with high strength and reliability. be.

[Summary of the Invention] That is, the present invention has a tenon that extends from the tip surface of the blade at a required length, and when assembled as a group of blades, the tenon is inserted into each through hole bored in the shroud. In the impeller tenon regeneration method, in which the shroud is fixed to the tip surface of the blade by inserting the shroud and caulking the tip portions protruding from the shroud outer surface, each tenon is inserted from the caulking portion of the shroud outer surface to the middle of the shroud thickness or the shroud. The area away from the stress concentration area, which is located in the middle of the thickness minus the Tenon sink depth, is shaved off to maintain a width that roughly corresponds to the Tenon width in the forward and backward direction of the blade, and then the remaining portion of the Tenon is shaved off. It is characterized in that a tenon of a required length is formed on the tip surface of the blade by applying weld overlay to each blade in series.

[Embodiment of the Invention] An embodiment of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows an example of a reused blade to which the Tenon build-up welding method of the present invention is applied.As can be easily seen by comparing it with the stress distribution diagram in Figure 19, stress concentration occurs at the start of build-up. The part with the least degree of damage is selected. That is, the weld joint line 45 generated by overlay welding of the first layer and the heat affected zone 19 generated thereby are located at the chamfered portions 13a and 1.
It occurs approximately in the middle of section 3b, and is located at the safest location in terms of stress.

Furthermore, the undercuts that tend to occur at the welding start points 20a and 20b are minimized by the overlay welding method using the plate 25 shown in FIG. In order to do this, the tenon 12 is machined to have a large radius between the chamfered portions 13a and 13b of the shroud 13 using a grinder or the like.

FIG. 2 shows how to obtain a residual Tenon shape 12 that allows such Tenon overlay welding to be easily performed.
FIG. 3 is a diagram showing a processing method for disassembling a damaged rotor impeller. That is, the tip of the cutting edge for machining is located at approximately 1/2 of the thickness of the shroud 13 remaining after subtracting the dimensions of the chamfered portions 13a and 13b of the fitting hole of the tenon 12 of the shroud 13 from the thickness of the shroud 13. It is scraped off with a lathe or the like along the cutting line.

FIG. 3 shows the finished shape of the outer periphery of the rotor impeller obtained when the cutting method shown in FIG. SaS
It has been removed so that only about 1/2 of it remains,
Only both ends of the blade 3 in the front-rear direction remain in the Tenon caulked portion 12'. Therefore, in this state, the shroud 13 can be easily removed by lightly hitting it from the inside (the side of the blade 3). At this time, the height of the remaining tenon 12 is such that the tenon build-up welding shown in FIG. become.

As mentioned above, the reliability of the tenons 12, 12' which are welded overlayed as shown in FIG. It is clear from this.

Incidentally, in recent years, in order to reduce the amount of steam passing above the shroud 13 without passing through the effective part of the blade 3, a sunken tenon 12' has been increasingly adopted as shown in Fig. 4. , in such a case, the cutting line-line is from the shroud thickness S,
Needless to say, the thickness must be set near the center of the remaining thickness after subtracting not only the dimensions of the chamfered portions 13a and 13b but also the sinking depth r.

[Effects of the Invention] As described above, according to the method of the present invention, a high-strength, high-quality weld overlay regenerated tenon can be obtained. In particular, it is extremely effective when it is necessary to repair the blades around the entire circumference of the rotor impeller.

Therefore, it becomes possible to apply repair by Tenon welding over a wider range of areas, and it is possible to provide a blade repair method that does not reduce the performance of the Tenon part. These things greatly contribute to improving the operating rate of the steam turbine and maintaining economic efficiency.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the start position of overlay welding according to an embodiment of the method of the present invention, Fig. 2 is a diagram showing a tenon welded overlay by the method of the present invention, and Fig. 3 is a diagram showing the implementation of the method of the present invention. FIG. 4 is an explanatory diagram showing the finished shape of the outer periphery of the rotor impeller when the rotor impeller is machined. FIG.
The figure is an external view of the turbine impeller, Figure 6 is an external view of the stop blade, Figure 7 is a front view showing the assembly of the blade, Figure 8 is a vertical sectional view taken along line C-C in Figure 10, and Figure 6 is an external view of the stop blade. 9
The figure is a vertical cross-sectional view showing the joint between the shroud and the blade.
Figure 1 is an explanatory diagram showing the state in which Tenon has been removed.
Figure 2 is an explanatory diagram showing the shouldering of the blade, Figure 13 is an explanatory diagram showing the cutting of the tenon and shroud,
Figures 14 and 15 are explanatory diagrams showing the state of the Tenon and shroud after cutting, Figure 16 is an explanatory diagram showing the conventional Tenon weld overlay, and Figure 17 is the Tenon welding that the present inventor has already applied for. FIG. 18 is an explanatory diagram showing the overlaying method, FIG. 18 is an explanatory diagram showing a conventional residual Tenon, and FIG. 19 is an explanatory diagram showing the stress distribution of the Tenon. 1...Rotor disk, 3, 15...Blade, 5...
Notch, 12, 14... tenon, 13... shroud, 17... residual tenon, 19... heat affected zone,
20a...Welding start point, 20b...Welding end point,
25...Packing plate, 26...Hole, 30...Cooling plate.

Claims (1)

[Claims] 1 It has a tenon that extends from the tip surface of the blade at a required length, and when assembled as a blade group, the tenon is inserted into each through hole drilled in the shroud and protrudes from the outer surface of the shroud. In an impeller tenon regeneration method in which the shroud is fixed to the tip surface of the blade by caulking the respective tip portions, each tenon is attached from the caulking portion of the outer surface of the shroud to the intermediate thickness of the shroud or from the shroud thickness. The area away from the stress concentration area located in the middle of the area where the sinking depth is subtracted is shaved off while maintaining a width that approximately corresponds to the tenon width in the front-rear direction of the blade, and then welded to the remaining portion of the tenon. A method for regenerating a tenon of an impeller, comprising forming a tenon of a desired length on the tip surface of the blade by applying overlay to each blade.