JPS60234780A - Method for fitting of sleeve onto revolving shaft - Google Patents

Abstract

PURPOSE:To form a coating layer for preventing seizure to the bearing part of a revolving shaft such as a turbine rotor with the powerful tightening force equal to the tightening force of a shrinkage fit in the stage of forming said layer to said bearing part by enclosing the bearing part with a sleeve having a two-split construction and subjecting the sleeve and bearing part to rolling under heating after tack welding. CONSTITUTION:The two-split sleeves 20 made of a low alloy steel having the inside diameter larger by about 1-5mm. from the outside diameter of a bearing journal part 11 made of a 12% Cr steel of the turbine rotor, etc. and 5-20mm. thickness are butted at a groove 21 to the outside circumference of the part 11 in the stage of forming the coating layer consisting of a low alloy steel for preventing seizure to the part 11. The groove 21 is build-up-welded by arc welding 23 to form the sleeves 20 into an annular shape; further the one end face of the sleeve 20 is tack-welded 25 to the bearing journal 11 of the rotor shaft. A spacing ring 30 sliding together with the sleeve during rolling is inserted to the other side face of the sleeve 20 and thereafter the sleeve 20 is heated to 400-550 deg.C by a high-frequency induction coil 40 and is rolled to coat powerfully the sleeve 20 to the part 11. The seizure preventive layer is thus formed.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for fitting a sleeve to form a coating layer on the surface of a predetermined portion of a rotating shaft such as a turbine rotor. This is what I did.

[Prior art and its problems]

In general, bearing journals of rotating shafts such as turbine rotors made of alloy steel base material have the problem of preventing seizure, and to solve this problem, a structure in which the base of the rotating shaft is surrounded by a coating layer of low alloy steel has been developed. This structure will be explained using the turbine rotor shown in FIG. In recent years, with the increase in efficiency and capacity of steam turbines, high temperatures and
Turbine designs that can withstand high stress are required, and the rotor material for high-pressure turbines and medium-pressure turbines must be changed from low-alloy steel such as chrome-molybdenum-vanadium steel to high-alloy steel such as 12% chromium-based steel. It's becoming necessary. On the other hand, when 12% chrome steel is used as the rotor material, the base l of the 12% chrome steel is surrounded by the coating layer 2 of low alloy steel in the area surrounded by the dashed line in FIG. This coating layer 2 is formed by welding low-alloy steel to the surface of the base 1, but it is necessary to perform stress relief annealing to remove uneven residual stress that occurs when the low-alloy steel is welded. , when performing this stress relief annealing, 12%
Compared to chrome steel, which has a small coefficient of thermal expansion, low-alloy steel has a large coefficient of thermal expansion. Again, large residual stresses were generated, which required sophisticated techniques for stress relief annealing. In addition, the coating layer 2 may be fitted with a sleeve of low alloy steel instead of being welded, but in this case. It becomes impossible to form the large-diameter coupling portion 3 at the shaft end integrally with the rotor material. For this reason, the coupling portion 3 has a fitted structure, which may impair reliability in terms of strength and vibration.

[Purpose of the invention]

In view of the above-mentioned points, the present invention provides a simple method for forming a coating layer with a tightening force similar to that of firing without impairing the strength of the large-diameter camp ring portion at the end of the shaft. The purpose of the present invention is to provide a method for fitting a sleeve into the sleeve.

[Key points of the invention]

According to the present invention, the above-mentioned object is a method for fitting a sleeve to form a coating layer on the surface of a predetermined portion of a rotating shaft such as a turbine rotor, in which the inner diameter of the sleeve is set to be smaller than the outer diameter of the shaft portion. A step of dividing the sleeve in the axial direction by machining it into a large size, a step of abutting the divided sleeves against each other on the outer periphery of the shaft portion and welding them into an annular shape, and a step between the annular sleeve and the shaft portion. Temporarily welding one end surface of the sleeve to the shaft portion with substantially uniform gaps, and inserting a spacing ring capable of supporting the end of the sleeve into the gap on the other end surface of the sleeve. a step of heating the temporarily secured sleeve to a predetermined temperature; a step of rolling the heated sleeve in the axial direction until it comes into close contact with the shaft portion; and processing both end surfaces of the rolled sleeve. This is achieved by including the step of finishing the outer diameter to a predetermined size.

[Embodiments of the invention]

The present invention will be described below based on drawings showing embodiments. 2 to 5 show embodiments of the present invention, and in the figures, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted. A turbine rotor (hereinafter referred to as rotor shaft) made of 12% chromium steel that has been tempered. The base 11 of the ten bearing journals is cut to a predetermined size, and the base 11 is made of low alloy steel to match the dimensions of this base 11. Make sleeve 2°. At this time, the inner diameter of the sleeve 20 is 1 to 5 mm larger than the outer diameter of the base 11.
The diameter is about 5 to 20 inches, and the thickness in the radial direction is about 5 to 20 inches.
Cut it in the axial direction, divide it into two pieces, and make a bevel 21 on the cut surface. The two divided sleeves 2o are butted together at the outer periphery of the base 11, and the backing metal 22 is inserted into the gap between the base 11 of the rotor shaft and the sleeve 20, and then arc welding 23 is used to overlay the groove 21. The sleeve 2° is made into an annular shape, and the backing metal 22 is removed from the gap. This can prevent spatter from adhering to the rotor shaft or sleeve during welding. Next, as shown in FIGS. 4 and 5, the gap 24 between the sleeve 2° and the base 11 of the rotor shaft is kept approximately constant, and one end surface of the sleeve 20 is placed at the base of the rotor shaft. 11 is temporarily welded 25, and a spacing ring 30 that can slide on the base 11 of the rotor shaft while guiding the sleeve 20 when the sleeve 2o is rolled is inserted into the other end surface of the sleeve 20. Next, a coil 4o is placed on the outer circumferential side of the sleeve 20, and the sleeve 2o is heated to 400 to 550°C by high-frequency induction heating.
During heating, nitrogen gas is flowed into the gap 24 between the sleeve and the rotor shaft base to prevent the temperature rise of the rotor shaft base 11 and the oxidation of the inner diameter surface of the sleeve 20.
When the temperature rises uniformly, heating is stopped and the sleeve is rolled. A method of rolling this sleeve is shown in FIG.
This is carried out using a rolling roller 50 that can move in the axial direction of 0. First, the rotor shaft 10 is transferred to a device (not shown), and the rolling roller 50 intersects the axis of the rotor shaft 10. This intersection angle θ is approximately 306, and while rotating the turbine shaft 10 in the direction of arrow 51, the roller shaft 52 is sequentially lowered downward, and from the temporary welding 25 side of the sleeve,
It is sent in the direction of arrow 3, that is, in the axial direction of the sleeve 20. As a result, the roller 50 rotates in the direction of the arrow 54 when it hits the outer circumferential surface of the sleeve 20, and the sleeve 20, except for the ends on both sides, is not displaced toward its axis and is spaced apart in the direction of the arrow 53. It extends guided by the ring 30. This operation is continued until the inner diameter of the sleeve 20 comes into close contact with the outer diameter of the base 11 of the rotor shaft, and then the sleeve 20 is left until the temperature returns to room temperature. When the sleeve 20 returns to room temperature, it contracts corresponding to the temperature difference,
When tightened, a force is generated to form an integral structure with the base 11 of the rotor shaft. The rotor shaft 10 is transferred to a machine tool (not shown), and after cutting off the temporarily welded portion 25 of the sleeve and unnecessary parts on the spacing ring 30 side, the outer diameter is finished to a predetermined size and the fitting work of the sleeve 20 is completed.

【Effect of the invention】

As described above, the present invention eliminates the generation of residual stress due to heat by integrating the divided sleeves by welding and then applying warm rollers to tightly engage the sleeves with the rotor shaft. It is possible to provide a sleeve fitting method for a rotating shaft that can increase fatigue strength against repeated bending stress and form a coating layer on a bearing journal portion without impairing the strength of a large-diameter compaction portion at the shaft end.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway plan view of a turbine rotor showing a conventional example, and FIGS. 2 to 5 show embodiments of the present invention.
Fig. 2 is a plan view of the main part of the turbine rotor, Fig. 3 is a cross-sectional view of the main part of the turbine rotor showing the welding process of the sleeve, and Fig. 4 is a cross-sectional view of the main part of the turbine rotor showing the heating state of the sleeve. FIG. 5 is a sectional view taken along the line A-A in FIG. 4, and FIG. 6 is a plan view of the main parts of the turbine rotor showing the rolled state of the sleeve. lO: Turbine rotor, 20 sleeves, 25: Temporary fixing Fig. 2 zl Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Scope of Claims] 1) A method of fitting a sleeve onto the surface of a predetermined portion of a rotating shaft such as a turbine rotor, the sleeve being machined to have an inner diameter larger than an outer diameter of the shaft portion, and the sleeve being fitted onto the surface of a predetermined portion of a rotating shaft such as a turbine rotor a step of dividing the sleeve in the center direction; a step of abutting the divided sleeves against each other at the outer periphery of the shaft portion and welding them into an annular shape;
One end of the sleeve is temporarily welded to the shaft with a substantially uniform gap between the annular sleeve and the shaft, and the end of the sleeve is inserted into the gap on the other end of the sleeve. inserting a gap ring capable of supporting the
heating the temporarily secured sleeve to a predetermined temperature; rolling the heated sleeve in the axial direction until it comes into close contact with the shaft; and removing both end surfaces of the rolled sleeve. A method for fitting a rotating shaft into a sleeve, the method comprising: 2. A method for fitting a rotating shaft into a sleeve according to claim 1, wherein the base material of the rotating shaft is 12% chromium steel, and the base material of the sleeve is low alloy steel.