JPS63248587A - Turbine rotor and its build-up welding method - Google Patents

Abstract

PURPOSE:To locally give the heat of large capacity and to reduce residual stress by sticking the build-up metal having heat resistance and wear resistance to the build-up objective part of the base metal of a turbine rotor and integrally forming it with build-up welding by the projection of a laser beam. CONSTITUTION:A 12% chrome steel is used as the base metal for turbine rotor and the metal contg. <=0.5% C, <=2% Mn, <=3% Cr, <=1.0% Si, <=2.0% Mo and <=0.5% V in wt. % as a build-up metal. And, the build-up metal 2 is wound on a build-up objective part as the thin plate like metal 2a formed in a thin plate shape in advance or fed to the build-up objective part as a powdery metal 2b. Meantime, a laser beam 3 is projected on the thin plate like metal 2a or powdery metal 2b from the tip of a laser gun 4 after being focused to form a build-up welding zone. The build-up metal is then wound around the build-up objective part by forming it in a slender bar shape, the laser beam is projected and the build-up welding zone may be formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a turbine rotor of a steam turbine or the like and an overlay welding method for the same, and particularly to a method for overlay welding that reduces residual stress and thermal effects in the overlay weld. The present invention relates to a turbine rotor that can improve bearing characteristics and a method for overlay welding thereof.

(Prior Art) Generally, a turbine rotor made of a steel material containing a relatively large amount of chromium, which is a corrosion-resistant metal, such as a 12% chromium steel turbine rotor, deteriorates in bearing characteristics with long-term operation.

This deterioration of bearing characteristics is caused by the precipitation of chromium etc. from the rotor body parts, which causes a seizure phenomenon in the bearing, or by foreign matter getting into the bearing, causing abnormal wear and damage to the rotor's journal part and bearing surface. Caused by the occurrence of a phenomenon.

Conventionally, in order to prevent this galling phenomenon, a sleeve made of a steel material that is resistant to seizure and has excellent wear resistance, such as chromium-molybdenum steel or molybdenum-vanadium steel, is shrink-fitted onto the journal of the turbine rotor. It is fitted.

On the other hand, in recent years, attempts have been made to prevent the galling phenomenon by overlaying carbon steel or low alloy steel, which has excellent bearing properties as described above, on the surface of the journal portion.

(Problem to be Solved by the Invention) However, when the sleeve is fitted to the journal portion of the turbine rotor by shrink fitting, the sleeve and the turbine rotor, which are in contact with each other at the end surface of the sleeve, may be damaged due to rotational vibration. Abrasion occurs due to repeated relatively small slippage, and so-called fretting fatigue may cause a significant decrease in fracture strength.

In addition, when overlay welding by arc welding etc. is performed on the bearing part of the turbine rotor to form a protective layer, the heat input due to welding is large, so the rotor body parts are denatured over a wide range and the strength is increased. There is a problem in that a heat-affected zone is formed with reduced heat resistance, and residual stress due to heat is generated in the overlay weld, resulting in a reduction in the strength of the member.

Incidentally, it has been experimentally confirmed that the tensile residual stress on the surface of an overlay welded part by the conventional overlay welding method may reach 30 to 40 Ky f/-. It has been found that this residual stress cannot be easily alleviated by normal annealing operations, and this residual stress is a factor that promotes stress corrosion and reduces brittle strength of the turbine rotor.

In addition, in electro beam welding such as arc welding, the welding current forms a magnetic field around the arc, and this magnetic field deflects the arc from its normal direction to the side, preventing a uniform bead from being formed and reducing welding quality. This may require a great deal of effort to repair.

The present invention has been made in order to solve the above-mentioned problems, and the present invention has been made in order to solve the above-mentioned problems. The purpose is to provide a welding method.

[Structure of the invention]

(Means for Solving the Problems) A turbine rotor and an overlay welding method thereof according to the present invention attach an overlay metal having heat resistance and abrasion resistance to an overlay target portion of a turbine rotor, and It is characterized by being integrally formed by welding overlay metal to the target part by irradiating it with laser light.

(Function) According to the turbine rotor having the above configuration and the overlay welding method thereof, the overlay metal is first attached to the overlay target portion of the turbine rotor. As the overlay metal, a metal member having excellent heat resistance and wear resistance is formed into a thin plate shape or rod shape and used.

On the other hand, a laser beam oscillated from a laser beam oscillation device is focused by a condenser lens or the like and then irradiated onto the overlay metal.

The overlay metal irradiated with laser light melts and is integrally joined to the turbine rotor base material, completing overlay welding.

According to the above laser beam, it is possible to irradiate a large amount of heat locally to the part to be overlaid, so the width and depth of the heat affected zone of the base metal due to welding heat can be extremely minimized. can do.

Furthermore, laser light can be used by appropriately changing the width of the irradiation range and the shape of the irradiation.

Therefore, it is also possible to reduce the build-up thickness per pass (layer) as much as possible and form a build-up welded portion with a predetermined thickness by multiple passes. When welding is carried out using this so-called multilayer welding, each layer undergoes repeated local melting and solidification, and the amount of welding heat transferred is small, making it possible to disperse the weft heat input to the base metal. Become.

Therefore, the generation of residual stress in the overlay weld is suppressed, and the generation of a heat affected zone is limited to an extremely narrow area.

Furthermore, when laser light is used, unlike conventional electrobeam welding, there is no deterioration in welding quality due to so-called magnetic blowing. Therefore, this method is most suitable as an overlay welding method for members that may become magnetized, and contributes to improving the quality and reliability of turbine rotors.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings.

FIGS. 1A and 1B are perspective views showing a state in which the overlay welding method for a turbine rotor according to the present invention is being carried out.

When implementing this overlay method, first the turbine rotor 1
Overlay metal 2 is attached to the area to be overlaid on the outer peripheral surface. Here, as the overlay metal 2, a member having excellent heat resistance and wear resistance, such as carbon steel, chromium molybdenum steel, or chromium molybdenum vanadium steel, is used. The overlay metal 2 may be formed into a thin plate in advance and wrapped around the overlay target part as a thin plate metal 2a, as illustrated in FIG. 1(A), or as a powder as illustrated in FIG. shaped metal 2b
It is supplied to the part to be overlaid.

On the other hand, a laser beam 3 oscillated from a laser beam oscillation device (not shown) is focused by a condensing lens or the like, and then is irradiated from the tip of a laser gun 4 onto a thin metal plate 2a serving as a build-up metal 2. The thin metal plate 29 irradiated with the laser beam 3 is melted and joined integrally with the turbine rotor 1 to form the overlay weld portion 5 .

In addition, FIG. 1(B) shows powder metal 2 as overlay metal 2.
An example using b is shown. That is, the powdered metal 2b stored in the storage tank 6 is accompanied by an inert gas such as argon or helium, and delivered to the part to be overlaid, and at the same time, it is adhered and melted by the laser beam 3, and the overlay welding part 5 is deposited and melted by the laser beam 3. can also be formed.

Furthermore, although not shown, the operation of winding the overlay metal 2 formed into a thin rod shape around the overlay target part and the operation of irradiating the rolled overlay metal 2 with a laser beam 3 and melting it are repeated. It is also possible to form an overlay welded portion with a predetermined thickness.

FIGS. 2(A) and 2(B) are cross-sectional views showing the overlay welded portion 5 formed on the turbine rotor by the overlay welding method according to the present embodiment, and FIG.
A welding hole 7 is formed in advance on the journal portion of the holder, and an overlay welding portion 5 is formed inside the welding portion 5, which is finished flush with the journal portion.

On the other hand, FIG. 2<8) shows a state in which the overlay welded portion 5 is formed so as to protrude from the outer circumferential surface of the bearing portion of the turbine rotor 1 without performing groove processing.

When overlay welding is performed using conventional arc welding or the like, the molten pool is large and a large amount of welding heat input is added to the molten zone, and at the same time, a large heat-affected zone is formed in the periphery of the molten zone. but,
In overlay welding using a laser beam as in this example, it is possible to arbitrarily adjust the range, depth, and shape of the irradiation of the laser beam, which serves as a heat source, using a condenser lens or a reflecting mirror. Generally, the dimensional accuracy can be set strictly to about 0.1#.

Therefore, it is possible to perform overlay welding work with high dimensional accuracy in accordance with the shape of the overlay target part. In addition, the thin metal plate 2a
, powder metal 2b, or rod-shaped metal, the build-up metal 2 that can be easily applied can be appropriately selected to simplify the welding process.

Furthermore, since the human heat wave is locally limited, the residual ratio no.j of the build-up weld is significantly reduced, and the heat-affected zone is also limited to an extremely narrow range.

In addition, according to the turbine rotor and its overlay welding method of this embodiment, since a laser beam is used as a heating source instead of a welding current, welding quality deteriorates due to the magnetic blow phenomenon that occurs in the conventional method. There isn't. Therefore, repair work becomes unnecessary, and the build-up operation becomes simple, improving welding work efficiency.

Next, the effect of overlay welding performed by the overlay welding method of this embodiment will be explained with reference to the graphs of FIGS. 3 and 4.

Figure 3 shows a comparison of the residual stress on the surface of the overlay weld after performing overlay welding to a predetermined thickness by varying the overlay thickness t per layer (pass) and with the conventional overlay welding method. It is shown as follows.

In this example, the turbine rotor 1 is made of 12% chromium steel as a base material, and overlay metals I to Vl containing various chemical components as shown in Table 1 are shown in FIG. 1(B). Carbon dioxide gas (with an output of 3 kW) is supplied to the part to be overlaid in powder bed state.
CO2) Laser irradiation was performed to perform overlay welding. In addition,
The chemical components of the base material and overlay metals (1) to (2) of the turbine rotor 1 are shown in Table 1 below.

[Margin below]

In addition, the build-up thickness t per time is 1t5FHJ of 3M or less.
The total build-up thickness was 25 m, and the build-up metal ■ shown in the M1 table was used in a powder bed state, and the supply rate of the build-up metal ■ was set to 20 g/min. are doing. Furthermore, before overlay welding, the area to be overlaid is heated to 150°C.
Preheat at ~300℃, while after overlay welding, heat at 640℃
The annealing operation was carried out for about 1 hour.

As a result, as shown by the solid line in Figure 3, when the build-up thickness t per layer is 1M or less, the residual stress σ on the surface of the build-up weld is significantly reduced, compared to the case of the conventional method shown by the broken line. It was confirmed that the amount decreased to about 1/10.

Further, the thermal influence due to laser beam irradiation is small as shown in FIG. That is, FIG. 4 shows the distribution of the degree of influence of heat in the overlay weld and its surrounding area, understood as a change in the hardness (Hv) of the member. From the results shown in Figure 4, the part of the turbine rotor on the base metal side that is hardened due to welding heat input is 0.3# from the boundary between the base metal and the overlay weld.
The heat affected zone by the conventional method is from several M to several tens of M.
According to this embodiment, the thermal influence on 1 can be significantly reduced.

Furthermore, other overlay metals I, I[, IV shown in Table 1.

For V and Vl, the overlay thickness t per layer is 0°5#
III+, overlay welding was carried out in the same way, and changes in residual stress and hardness were measured. As a result, in weight %,
Overlay metal I containing up to 0.5% carbon, up to 2% manganese, up to 3% chromium, up to 1.0% silicon, up to 2.0% molybdenum, up to 0.5% vanadium , Il, IV, V, and Vl, the residual stress σ is 10Kyf/- or less, and the thickness of the hardened layer due to heat influence is extremely small, at maximum 0.5#, and the thickness of the hardened layer due to heat influence is extremely small, which is less than the base material of the turbine rotor. It was confirmed that the soundness of the plant was sufficiently maintained.

〔Effect of the invention〕

According to the turbine rotor and the overlay welding method thereof according to the present invention, the overlay metal is irradiated with a laser beam to melt the overlay metal to form an overlay welded portion on the turbine rotor that is the base material, Since a large amount of heat can be applied locally using a laser beam, the heat-affected zone of the base metal due to welding heat can be made extremely small, and the residual stress in the overlay weld can be greatly reduced. can be reduced.

Further, since the laser beam can be used by adjusting the irradiation range and the irradiation shape as appropriate, it is possible to perform overlay welding with high dimensional accuracy according to the dimensions and shape of the overlay target part. In particular, by setting the overlay thickness per layer small and performing overlay welding to a predetermined thickness using multiple layers, the enormous amount of heat to the overlay target area will be dispersed, reducing residual stress and heat-affected zone. can do.

Furthermore, according to the present invention, since the shrink-fit sleeve can be made unnecessary, corrosion and wear problems caused by fretting fatigue can be solved, and the residual stress generated in conventional overlay welding can be significantly reduced, resulting in excellent mechanical strength. A highly reliable turbine rotor can be provided.

[Brief explanation of the drawing]

Fig. 1 (A>, (B) is a perspective view showing a state in which overlay welding is being performed by the method of the present invention, and Fig. 2 (A), (B) is an overlay welded part of a turbine rotor according to the present invention. Figure 3 is a graph showing the relationship between the overlay thickness per layer and the residual stress on the surface of the overlay weld, and Figure 4 is a graph showing the distribution of member hardness around the overlay weld. Yes. 1... Turbine rotor, 2... Overlay metal, 2a...
- Thin plate metal, 2b... Powder metal, 3... Laser light, 4... Laser gun, 5... Overlay welding part, 6...
・Storage tank, 7... Welding groove, t... Thickness of build-up per one time, σ... Residual stress. Applicant's agent Hisashi Hatano - 16 = Figure 1 Figure 3 Boundary between the base material and the physical contact @i 1 S Lano! great fortune, d
(rnnl)Figure 4

Claims (1)

[Scope of Claims] 1. A build-up metal having heat resistance and wear resistance is attached to the part to be built up of the turbine rotor base material, and the build-up metal is built up to the part to be built up by laser beam irradiation. A turbine rotor characterized by being integrally welded. 2. The turbine rotor according to claim 1, wherein the turbine rotor base material is 12% chromium steel. 3. The turbine rotor according to claim 1, wherein the overlay metal is formed in advance into a thin plate shape or a rod shape. 4. Claim 1 in which the overlay metal is a powdered metal
Turbine rotor as described in section. 5. The overlay metal contains 0.5% or less carbon by weight,
Claim 1 comprising a metal member containing 2% or less manganese, 3% or less chromium, 1.0% or less silicon, 2.0% or less molybdenum, and 0.5% or less vanadium. turbine rotor. 6. Welding of a turbine rotor characterized by attaching a heat-resistant and wear-resistant overlay metal to the overlay target part of the turbine rotor, and performing overlay welding by irradiating the overlay metal with focused laser light. Mold welding method. 7. The overlay welding method for a turbine rotor according to claim 6, wherein the overlay target portion of the turbine rotor is preheated at a temperature of 150 to 300° C. for a predetermined period of time before overlay welding. 8. The overlay welding method for a turbine rotor according to claim 6, wherein the overlay welding is performed in a multi-layered overlay. 9. The overlay welding method for a turbine rotor according to claim 6, wherein the overlay target portion of the turbine rotor is annealed at a temperature of 500° C. or higher after overlay welding.