JPS6147283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel rotor for a steam turbine and a method for manufacturing the same.

In recent years, 12% Cr steel, which has high high-temperature strength and toughness, has come to be used for steam turbine rotors. However, 12% Cr steel has poor bearing properties, particularly poor wear properties, and foreign matter such as dirt that gets into the bearing can cause sudden seizure of the bearing, damaging the rotor journal and bearing. Ta. For this reason, Japanese Patent Application Laid-Open No. 55-16744 discloses a rotor made of 12% Cr steel with a thermal sprayed layer formed by thermal spraying a metal with good bearing properties on the journal part, and a welded metal with good bearing properties on the journal part. 12% by overlay welding with a welding rod that produces metal and providing an overlay weld layer
A Cr steel rotor is shown.

Thermal spraying has a weak bond with the base material, and oxides and pores are formed, resulting in low tensile strength and toughness, and there is a risk of breakage.

For overlay welding, the metal to be overlaid must be selected based on the welding conditions with the base metal.
It is difficult to select a metal with excellent bearing properties. Therefore, there is a problem in that a metal must be selected that sacrifices bearing characteristics in relation to welding.

On the other hand, it is desirable for the steam turbine rotor to have a coupling that connects the generator with an integral structure because it is highly reliable in use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam turbine rotor with excellent bearing characteristics and a method for manufacturing the same, in which a rotor coupling that directly connects a steam turbine rotor and a generator is integrated.

The present invention comprises a body, a journal part having bearing parts at both ends of the body, and a coupling ring integrally formed on at least one of the journal parts, and is mainly made of high chromium steel having a martensitic structure. In the steam turbine rotor, the journal portion has the bearing portion and a portion having a smaller diameter than the bearing portion, and the bearing portion is made of a resistant chrome steel having higher bearing properties than the high chromium steel and a lower amount of chromium than the steel. A cylindrical sleeve made of steel and made up of a plurality of axially divided sleeves integrated by welding, which are fitted and fixed by the tightening force of the cylindrical sleeves. Found in turbine rotors.

For the sleeve, all bainitic steel containing 0.2 to 2.25% Cr and 0.2 to 1% Mo by weight is preferable as a low chromium steel with excellent bearing properties. Furthermore, this
All-bainitic steels containing 0.05-0.5% V are preferred.

For fitting and fixing, the arc-shaped sleeve is precisely machined with allowances for shrink fit or cold fit, and is welded and connected at the small diameter part of the rotor. When inserted into the journal part, it is shrink-fitted or cold-fitted.

Any other welding method such as arc welding or electron beam welding can be used for welding.

After welding, it is preferable to perform SR treatment in order to reduce residual stress in the welded area and improve toughness. During the SR treatment, it is undesirable for the inner surface of the sleeve and the surface of the journal portion to oxidize, so it is preferable to heat the sleeve in vacuum or in a non-oxidizing atmosphere.

After SR treatment, surface finishing is performed and then the parts are fitted together. SR treatment temperature 650~700℃, time 0.5~5hr
is preferred.

The high Cr steel of the rotor is C0.1~0.3% by weight, Si0.6
% or less, Mn0.4~1.5%, Ni1.2% or less, Cr8~13
%Mo0.5~1.5%, V0.05~0.3%, Nb0.02~0.15
%, preferably a forged steel having an entirely martensitic structure containing 0.04 to 0.1% N.

The number of divisions of the divided sleeve may be two, three, four, or more, but preferably two.

The cylindrical sleeve is preferably one in which the above-mentioned metal with high bearing properties is welded to the joining surfaces of the divided sleeves or the outer surface of the divided sleeves and then integrated by welding.

The present invention comprises a body, a journal part having bearing parts at both ends of the body, and a coupling ring integrally formed on at least one of the journal parts, and is mainly made of high chromium steel having a martensitic structure. In the method for manufacturing a rotor for a steam turbine, the journal portion includes the bearing portion having a predetermined diameter and a portion smaller in diameter than the bearing portion;
The journal portion with a small diameter is made of low chromium steel, which has higher bearing properties than the high chromium steel and has a lower chromium content than the steel, and is made of a plurality of sleeves divided in the axial direction, which are integrated by welding to form the journal. forming a cylindrical sleeve having a diameter larger than the diameter of the bearing part and smaller than the diameter of the bearing part, and then fitting the cylindrical sleeve to the bearing part by shrink fit or cold fit. A method of manufacturing rotors for steam turbines.

Example A test rotor made of the same material as the actual rotor material was used.
12% Cr forged steel was used. Its shape has an outer diameter of 254mm,
The length is 800mm. This is a tempered all-martensitic structure.

On the other hand, 1% Cr-0.5Mo forged steel was used as the sleeve material. The shape of the divided sleeve 1 is divided into two parts in the axial direction as shown in FIG. The dimensions are inner diameter 253.85mm, thickness 19mm, and length 300mm. In addition, a Y-shaped (angle: 60°, root face: 2 mm, root gap: none) welding groove 2 was turned by machining on the abutting surfaces of the split sleeves. It has an all-bainitic structure.

A sleeve having the shape described above was installed on the rotor journal and butt welded. The welding method is preheating and 250 to 300℃ between passes, and after the first pass is TIG welding to melt to the back of the groove, a commercially available coated arc welding rod for low alloy steel (diameter 3.2φ) is used.
Welded with.

After welding the divided sleeves to form a cylindrical sleeve using the method described above, this was fitted and fixed onto the test rotor shaft. First, the presence or absence of defects in the welded portion was inspected by ultrasonic flaw detection and magnetic flaw detection. As a result, no welding defects were observed and the welding was good. Furthermore, after finishing the sleeve surface to a mirror finish, we conducted a bearing performance test on the sleeve. Babbitt metal was used for the bearings. The test results showed that the sleeve and bearing did not seize at all, and excellent bearing characteristics were obtained.

To fix the cylindrical sleeve 4 to the journal part 3 of the actual rotor, as shown in FIG. After preheating the sleeve, which has been divided into two parts in the direction, and welding them with a backing to form a cylindrical sleeve with an inner diameter smaller than the outer diameter of the journal part, the above-mentioned backing was removed, and then the surface was finished and heated to about 200℃. It can be obtained by holding it in place and fitting it into the journal part 2. 5 is coupling, 7
is a rotor blade, and 8 is a welded part. This rotor had excellent bearing properties.

The actual rotor has a weight of C0.16%, Si0.4%,
Mn0.7%, Ni0.5%, Cr10.8%, Mo1.0%, V0.2
%, Nb0.08%, N0.06%, balance Fe, and consists of an entirely martensitic structure that has been quenched and tempered.

FIG. 3 is a sectional view of a journal portion of a rotor according to another embodiment of the present invention. According to the method shown in FIG. 1, even if a welding defect such as insufficient penetration occurs in the back bead of the sleeve welded portion 8', it is difficult to repair the defect. In this case, the sleeve must be removed and a new sleeve must be welded, which is time consuming.

Therefore, as a countermeasure in the present invention, as shown in the figure, a sleeve in which the back surface of the welding groove is processed into a convex shape 9 is applied to each of the divided sleeves, while the roll side has a groove 10 into which the convex part of the sleeve can fit. It is intended to provide Using the sleeve and roll having such a shape, the convex portion 9 of the sleeve is pushed into the rotor groove 10 and fixed, and welded 8 with a high energy density beam. An example is shown in which electron beam welding is applied as this welding. According to this method, defects in the back bead of welding can be released to the convex portion 9 of the sleeve where no tensile stress in the circumferential direction is applied, and the method can be applied as is, so that the defects shown in FIG. 1 can be solved.
Further, the convex portion 9 is provided to protect the weld bead from penetrating the rotor surface.

4 and 5 show another embodiment of the present invention, in which overlay welding 11 is preliminarily applied to the groove surface or the groove surface and the entire outer surface of the split sleeve 1. Overlay welding only on the groove surface allows the SR treatment to be omitted after welding the split sleeve.
The purpose of overlay welding on the entire outer surface of the sleeve is to make the wear characteristics of the entire surface uniform by forming the outer surface of the sleeve only from welded metal. It is more preferable to perform SR treatment on these divided sleeves after overlay welding. The overlay material should have the same composition as the sleeve.

Furthermore, after welding to connect the split sleeves, it is preferable to apply peening to the welded portion to reduce residual stress in the welded portion.

As above. According to the present invention, it is possible to provide a journal portion of the sleeve made of a metal member with excellent bearing characteristics regardless of the rotor material. A high Cr steel steam turbine rotor having a martensitic structure is obtained.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the split sleeve of the present invention;
The figure is a configuration diagram of a rotor for a steam turbine according to the present invention, FIG. 3 is a sectional view of a rotor for a steam turbine to which a split sleeve according to another embodiment of the present invention is applied, and FIGS. FIG. 3 is a cross-sectional view of the split sleeve of the embodiment. 1... Split sleeve, 2... Welding groove, 3...
Journal part, 4... Cylindrical sleeve, 5... Coupling, 6... Smaller diameter portion of journal part, 7... Moving blade, 8, 8'... Welding part, 9... Convex part, 10... Groove, 11... Overlay welding part.

Claims (1)

[Scope of Claims] 1. A body, a journal part having bearings at both ends of the body, and a coupling formed integrally with at least one of the journal parts, and made of high chromium steel mainly having a martensitic structure. In the steam turbine rotor, the journal portion has the bearing portion and a portion having a smaller diameter than the bearing portion, and the bearing portion is made of low-grade steel having higher bearing properties than the high-chromium steel and having a lower chromium content than the steel. A cylindrical sleeve made of chromium steel and made up of a plurality of axially divided sleeves integrated by welding is fitted and fixed by the tightening force of the cylindrical sleeve. Rotor for steam turbine. 2. A steam turbine comprising a trunk, a journal part having bearing parts at both ends of the trunk, and a coupling ring integrally formed on at least one of the journal parts, and mainly made of high chromium steel having a martensitic structure. In the method for manufacturing a rotor for use in a rotor, the journal portion is formed into the bearing portion having a predetermined diameter and a portion smaller in diameter than the bearing portion, and the journal portion having the smaller diameter has higher bearing characteristics than the high chromium steel. A cylinder made of low chromium steel with a lower chromium content than the steel, which is made by integrating a plurality of sleeves divided in the axial direction by welding, and having a diameter larger than the diameter of the journal part and smaller than the diameter of the bearing part. 1. A method of manufacturing a rotor for a steam turbine, comprising forming a shaped sleeve, and then fitting the cylindrical sleeve to the bearing part by shrink fit or cold fit.