JP2001355406A - Connecting structure of turbine moving blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability in strength of a loose tie connecting method of a moving blade of a turbine. SOLUTION: Metallic films 10 and 11 having Vickers hardness less than that of a tie wire 3 and a sleeve 4 are applied onto an outer face of the tie wire 3 and an inner face of the sleeve 4 in a loose tie wire connecting structure of the turbine moving blade 1 to lower the bearing caused by the partial contact of the sleeve 4 and the tie wire 3, and a relative sliding amount is reduced by increasing a coefficient of friction of a contact part, whereby the durability to fretting corrosion fatigue can be increased. On the contrary, the durability to fretting corrosion fatigue can be increased by improving the abrasion resistance by coating the metallic films 10 and 11 of high Vickers hardness, and increasing the relative sliding by lowering the coefficient of friction of the contact part. Further the durability to fretting corrosion fatigue can be increased by executing the surface curing treatment to the outer face of the tie wire 3 or the inner face of the sleeve 4 to improve the abrasion resistance, and increasing the relative sliding by lowering the coefficient of friction of the contact part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for connecting turbine blades.

[0002]

2. Description of the Related Art A moving blade of a steam turbine receives an exciting force due to a non-uniform flow of steam. When a natural frequency of the blade is equal to or close to an integral multiple of the rotation speed, the moving blade is generated. The resulting vibration stress increases, and the strength reliability of the blade decreases.

[0003] For this reason, in the moving blade design, the natural frequency of the moving blade is designed so as to be in an integral multiple of the rated rotation speed and at a ten-degree separation. However, in steam turbines of thermal power plants and nuclear power plants in recent years, the length of low-pressure stage rotor blades has been increased to improve plant efficiency and output. As the length of the blade increases, the natural frequency decreases and there are many vibration modes to avoid resonance. Therefore, it is important to secure sufficient detuning.

[0004] As one of the structures capable of obtaining excellent vibration characteristics, it is known that a plurality of blades are connected to each other by penetrating a blade hole in a turbine blade and passing a tie wire through the blade hole. I have. A structure of a loose tie wire connection system in which both ends of the tie wire are put in a sleeve and connected is disclosed in Japanese Patent Application Laid-Open No. 2-169802.

FIGS. 2 and 3 show the connection state of the moving blades by the loose tie wire connection method. A tie wire 3 is passed through a blade hole 2 provided through the rotor blade 1, and a damping effect on vibration is provided by a frictional force of a contact portion between the tie wire 3 and the blade hole 2.

[0006] The end of the tie wire 3 connecting the plurality of moving blades 1 is put in a hollow sleeve 4 and connected.
Since the tie wire 3 may be displaced or moved in the circumferential direction due to the vibration during operation or the torsional return force of the rotor blade, the sleeve 4 is not detached in response to such movement.
As shown in the figure, a through hole is provided at a substantially central portion of the sleeve 4,
The rivet 5 is passed through the hole, and the rivet 5 is fixed by caulking the head. The inner surface of the sleeve 4 and the outer surface of the tie wire 3 are used as machined.

[0007]

As shown in FIGS. 5 and 6, the centrifugal force 6 acting on the sleeve 4 during operation of the turbine is shown in FIG.
Due to the torsional return force 9 of the wing and the sleeve 4, the sleeve 4 and the tie wire 3 have 50M at the locations indicated by 7 in FIG. 5 and 8 in FIG.
When a high surface pressure of Pa or more is generated, and in addition to this, sufficient vibration stress is applied to generate fretting cracks due to the vibration of the moving blades, thereby causing fretting fatigue cracks on the inner surface of the sleeve 4 or the outer surface of the tie wire 3. Was found to occur.

When the fretting fatigue crack propagates, the fallen sleeve piece collides with the wing or casing to cause damage, or the connection state between the tie wire 3 and the sleeve 4 is impaired and the vibration mode changes to cause resonance. It is considered that the state approaches the state and the strength reliability decreases.

Accordingly, the present invention provides a measure for improving the strength reliability against fretting fatigue which may occur when the two members cause relative slip under a high surface pressure generated at the joint between the tie wire and the sleeve. To provide.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventors have eagerly worked to improve the strength reliability against fretting fatigue at the contact point between a tie wire and a sleeve where relative slip occurs under a high surface pressure. As a result of study, in order to increase the fretting fatigue strength, a method of increasing the friction coefficient of the contact part to reduce relative slip, and increasing the surface hardness to increase wear resistance,
In addition, it was concluded that measures to reduce fretting fatigue cracks by reducing the friction coefficient and increasing relative slip were effective, and at least one of the outer surface of the tie wire and the inner surface of the sleeve had excellent fretting resistance characteristics. It has been found that the strength reliability against fretting fatigue is improved in the state of being left.

A feature of the first means for improving the strength reliability against fretting fatigue is that at least one of the outer surface of the end of the tie wire and the inner surface of the sleeve has a higher fretting fatigue resistance than the tie wire or the sleeve. It means that the film was coated.

As the material of the coating, any of copper, lead, zinc, tin, cadmium, aluminum and silver can be adopted.

A feature of the second means is that at least one of the outer surface of the end of the tie wire and the inner surface of the sleeve is coated with TiN (titanium nitride).

Further, instead of TiN, chromium, nickel,
Either a tungsten compound or a phosphate may be coated.

Another feature of the third means is that at least one of the outer surface of the end of the tie wire and the inner surface of the sleeve is subjected to a surface hardening treatment.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a blade hole 2 is provided through a rotor blade 1 of a steam turbine. FIG.
Also in the case of the conventional example described above, the tie wire 3 is passed through the blade hole 2 of the moving blade 1 as in the conventional example described with reference to FIGS. It has an effect.

The end of the tie wire 3 connecting the plurality of rotor blades 1 is inserted into a hollow sleeve 4 to connect the tie wire 3 as shown in FIG. Since the tie wire 3 may be displaced or moved in the circumferential direction due to the vibration during operation or the torsional return force of the wing, the embodiment of the present invention may be used to prevent the sleeve 4 from coming off in response to such movement. As shown in FIG. 1, a through hole is provided at a substantially central portion of the sleeve 4, a rivet 5 is passed through the hole, and the rivet 5 is fixed by caulking.

In the first embodiment of the present invention, as shown in FIG.
The outer surface of the tie wire 3 and the inner surface of the sleeve 4 facing each other were coated with copper metal films 10, 11 having a Vickers hardness smaller than that of the material of the tie wire 3 by plating or thermal spraying. The metal film 10 applied to the outer surface of the tie wire 3 is widely applied so as to protrude outward from the end of the sleeve 4 as shown in FIG.

By forming such metal films 10 and 11 on the outer surface of the tie wire 3 and the inner surface of the sleeve 4, the coefficient of friction between the outer surface of the tie wire 3 and the inner surface of the sleeve 4 is increased to reduce the relative slip between the two. And fretting fatigue strength can be increased.

Generally, local plastic deformation occurring during the relative slippage and fretting process of the contact portion is accompanied by heat generation, and a rise in the temperature of the local portion adversely affects the generation of fatigue cracks. Since the copper thin film coated on each contact surface between the outer surface of the tie wire 3 and the inner surface of the sleeve 4 has a high thermal conductivity, it has an effect of dissipating heat at the contact portion and is useful for increasing fatigue strength.

In addition, a locally higher surface pressure is generated at a contact surface between the tie wire 3 and the sleeve 4 at the contact surface between them, and a fretting fatigue crack is easily generated at that portion, but the yield stress is smaller than that of the wing material. Due to the plastic deformation of the copper metal films 10 and 11, the contact between the two contact surfaces is reduced, and the peak value of the surface pressure is reduced.

Similar effects can be expected by using lead, zinc, tin, cadmium, aluminum, silver, or the like as a material for the metal film other than copper. Tie wire 3
When a material that is electrochemically lower than the material of the sleeve and the sleeve 4 is selected as the material of the metal coatings 10 and 11, if these metal coatings are coated on the tie wire 3 and the sleeve 4, the tie wire 3 and the sleeve 4 can be formed under a corrosive environment of wet steam. By selectively dissolving these coatings in the base material of the tie wire 3 and the sleeve 4, the material of the tie wire 3 and the sleeve 4 is protected from corrosion.

In this embodiment, the case has been described in which both the outer surface of the tie wire 3 and the inner surface of the sleeve 4 are coated.
Alternatively, it is needless to say that the same effect can be expected even if the coating for forming the metal film 11 is performed only on the inner surface of the sleeve 4.

Further, in the case where the outer surface of the tie wire 3 is coated, only the region in contact with the sleeve 4 is coated. However, the coating region is further enlarged so that the contact region between the tie wire 3 and the wing hole 2 is increased. If the coating is also applied, the effect of increasing the fretting fatigue strength at the contact portion between the inner surface of the wing hole 2 and the outer surface of the tie wire 3 can be expected.

In this case, as shown in FIG. 7, the outer surface of the tie wire 3 may be coated with the metal coating 10, or the moving blade 1 and the sleeve 4 may be coated to reduce the cost of the coating material. May be selectively coated.

The coating thickness of the metal films 10, 11 is preferably between 10 μm and 150 μm. In general, as the film thickness increases, the fatigue strength against fretting increases. However, if the film thickness is too large, there is a problem that the production cost increases and the film is easily peeled.
After the coating is applied, it is preferable that the intersection between the tie wire 3 and the sleeve 4 is made a predetermined value by machining.

In this embodiment, the structure in which the tie wire 3 is passed through one place of the rotor blade 1 has been described. However, the same effect can be expected even if the tie wire 3 is passed through a plurality of places in the radial direction. Further, the structure in which the rivet 5 is fixed to the center of the sleeve 4 through the rivet 5 has been described. Can be expected.

Next, a second embodiment of the present invention will be described. The outer surface of the tie wire 3 and the inner surface of the sleeve 4 are coated with TiN (titanium nitride) films 10 and 11 having Vickers hardness greater than that of the material of the tie wire 3. The coverage of the coatings 10, 11 is shown in FIG.
Is the same as in the first embodiment.

By forming the coatings 10 and 11, the outer surface of the tie wire 3 and the inner surface of the sleeve 4
Adhesion between the surfaces is extremely small, and even if abrasive wear powder of a metal oxide is generated, the wear resistance is excellent, so that the surface is hardly scratched.

Further, the TiN films 10 and 11 reduce the friction coefficient between the tie wire 3 and the sleeve 4, so that the relative slip amount when receiving the vibration force from the moving blade 1 increases, so that the fretting occurs. Even if fatigue cracks occur, fatigue life can be increased by abrading them before the cracks propagate deeply.

Even if a film of chromium, nickel, tungsten compound or phosphate is formed as a film other than TiN, the same effect can be expected with a film that increases the hardness of the contact surface and increases the friction coefficient.

It is needless to say that the same effect can be expected even if coating is performed only on the outer surface of the tie wire 3 or only on the inner surface of the sleeve 4. In addition, when coating the outer surface of the tie wire 3 with the TiN material also in the contact area with the inner surface of the blade hole 2, the effect of increasing the fretting fatigue strength at the contact portion can be expected.

Even if the tie wire 3 is passed through a plurality of locations in the radial direction and the rivet 5 is not used,
Alternatively, a similar effect can be expected even in a structure using another fastening method such as a bolt instead of the rivet 5.

In the third embodiment of the present invention, at least one of the outer surface of the tie wire 3 and the inner surface of the sleeve 4 is subjected to a surface hardening treatment. By performing such a surface hardening treatment, the wear resistance is enhanced, and the friction coefficient at the contact portion between the outer surface of the tie wire 3 and the inner surface of the sleeve 4 is reduced to increase the relative slip, thereby increasing the strength against fretting fatigue. Can be increased. The range in which the surface hardening treatment is performed is the same as the range in which the metal coatings 10, 11 are applied as shown in FIG. 1 in the first embodiment.

The surface hardening treatment includes carburizing, nitriding,
Induction quenching, flame quenching and the like can be mentioned. By performing these surface hardening treatments, as described in the second embodiment, the effect of increasing the wear resistance and increasing the life with respect to fretting fatigue can be expected.

As described above, in the first embodiment,
A metal film having a lower Vickers hardness than the material of the tie wire 3 (zinc, copper, aluminum, lead, tin, cadmium, silver, etc.) on the outer surface of the tie wire 3 and the inner surface of the sleeve 4
Is coated by plating or thermal spraying, thereby increasing the friction coefficient between the two surfaces, suppressing the relative slip between the two, and increasing the fretting fatigue strength.

In the first embodiment, when a material having a high thermal conductivity, such as copper or silver, is selected as the material for the coating, the relative slip of the contact portion between the outer surface of the tie wire 3 and the inner surface of the sleeve 4, It has the effect of dissipating heat generated during the fretting process, and has the effect of increasing fatigue strength.

Further, in the first embodiment, the locally high surface pressure due to the contact between the tie wire 3 and the sleeve 4 is averaged by plastic deformation of the metal films 10 and 11 having a small yield stress, thereby reducing the peak surface pressure. It has the effect of lowering it and can be expected to have the effect of increasing the fretting fatigue life.

In the first embodiment, the rust preventive against corrosion is made by coating the metal coatings 10 and 11 with a material that is more electrochemically lower than the material of the tie wire 3 and the sleeve 4. It is effective and increases reliability in long-term use in a corrosive environment.

The outer surface of the tie wire 3 or the sleeve 4
In at least one of the inner surfaces of the second embodiment,
By coating a film (TiN, chromium, nickel, etc.) having a higher Vickers hardness than the material of the tie wire 3, and in the third embodiment, a surface hardening treatment (carburizing, nitriding, induction hardening, flame hardening, etc.) is performed. This has the effect of increasing the abrasion resistance of the contact portion and increasing the relative slip by reducing the friction coefficient of the contact portion, thereby increasing the strength against fretting fatigue.

As described above, in any of the embodiments, when a loose tie wire connection structure is adopted as the connection means of the turbine blade, damage due to fretting of the structure can be reduced.

[0042]

As described above, according to the present invention, it is possible to reduce damage caused by fretting of a loose tie wire connection structure when a structure of a loose tie wire connection system is adopted as a connection means of a turbine blade. Reliability is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a connection structure between a tie wire and a sleeve according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a connection relationship between a tie wire, a sleeve, and a moving blade.

FIG. 3 is a plan sectional view taken on line AA of FIG. 2;

FIG. 4 is a longitudinal sectional view of a conventional connection structure between a tie wire and a sleeve.

FIG. 5 is a longitudinal sectional view schematically showing deformation of a sleeve and a tie wire during steady operation.

FIG. 6 is a plan sectional view schematically showing deformation of a sleeve and a tie wire during a steady operation.

FIG. 7 is a longitudinal sectional view of a connection structure between a tie wire and a sleeve according to another embodiment of the present invention.

[Explanation of symbols]

1 ... rotor blade, 2 ... wing hole, 3 ... tie wire, 4 ... sleeve,
5 rivets, 10, 11 metal coatings.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Michihiro Goto 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Thermal and Hydropower Division, Hitachi, Ltd. F-term (Reference) 3G002 DA05 in the Thermal and Hydropower Division, Hitachi, Ltd.

Claims (5)

[Claims] 1. A turbine rotor blade coupling structure in which both ends of a tie wire passed through a blade hole of a turbine rotor blade are inserted into a sleeve, at least one of an outer surface of an end of the tie wire and an inner surface of the sleeve. And a coating having a higher fretting fatigue strength than the tie wire and the sleeve. 2. The method according to claim 1, wherein the material of the coating is copper, lead,
A connection structure for turbine blades, which is one of zinc, tin, cadmium, aluminum, and silver. 3. A turbine rotor blade coupling structure in which both ends of a tie wire passing through a blade hole of a turbine rotor blade are inserted into a sleeve, at least one of an outer surface of an end of the tie wire and an inner surface of the sleeve. A turbine rotor blade connection structure, characterized by being coated with TiN. 4. A connection structure for a turbine blade according to claim 3, wherein any one of chromium, nickel, tungsten compound and phosphate is coated instead of TiN. 5. A turbine rotor blade coupling structure in which both ends of a tie wire passed through a blade hole of a turbine rotor blade are inserted into a sleeve, at least one of an outer surface of an end of the tie wire and an inner surface of the sleeve. And a surface hardening treatment.