JPS58138204A - Steam turbine blade - Google Patents

Abstract

PURPOSE:To prevent erosion of deposited metal to deposit erosion preventing plate in such a way that the tip part of the erosion preventing plate is inserted into a recessed part which is formed at the straight upper part of the vane of a blade cover. CONSTITUTION:A recessed part 8 is formed at the straight upper part of a vane 1 to be continued to a vane 1 of a blade cover 7 which is incorporatively cut out of the vane, a boss 6a of an erosion preventing plate 6 is inserted into this recessed part 8 and they are welded together by welding metal 4b. Thus, since erodible part is covered with the erosion preventing plate 6, it will never be subject to erosion for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to steam turbine blades, particularly those having a K-shaped blade to prevent erosion at the tip of the blade.

[Technical background of the invention]

Among general steam turbine blades, those with a long blade section constituting the final stage, etc., have a leg section /'& that is inserted into the turbine disk integrally formed at the bottom of the blade, as shown in Figure 1. 2
In order to equalize the relative velocity of the steam at the blade root and the blade tip, the distance between the tips of the blade K and the tip of the blade L is correct, and in order to prevent the steam from flying out to the outer periphery, there is a The blade cover is cut out as one piece, and as shown in Fig. 3, both ends of the blade cover λ are welded to the ends of the blade cover λ of the adjacent blade to form a single rotor blade. Since the final stage and other stages operate in low-temperature, low-pressure immersed steam, the blades are susceptible to erosion due to the impact pressure of water droplets that have aggregated and coarsened moisture. For this purpose, an erosion prevention plate 3 made of a high-hardness alloy is attached to the tip of the blade 1 by welding.

This erosion prevention plate 3 is made of Kozasan chrome, 4! :11 Made of tungsten-cobalt alloy, its shape is as shown in Fig.
) As shown in (front view) and (b) (plan view), it has a plate shape with one side end bulged, and in order to weld this erosion prevention plate 3 to the blade lK, the steps shown in Figures 3 and 1 are as follows. As shown in FIG. 7, a welding groove 70 is provided along the outer periphery of the erosion prevention plate J, and as shown in FIG.
- Weld metal 1 made of nickel x91 chromium alloy is added, and weld metal ab made of the same composition as the corrosion prevention plate J is heaped up on the weld groove provided between the blade cover and the blade cover to increase its hardness. I have to.

[Problems with background technology]

However, when welding metal #b is heaped up and surface finishing is performed, part of welding metal pb is scraped off, resulting in variations in thickness. As a result, after many years of operation, the erosion part as shown in Figures 1 and 2! The occurrence of Vc is unavoidable, and even if the welded metal is made thicker, the blade cover 2 has a Vc
There are mass marketers who say that corrosion due to water droplets is unavoidable due to the use of chromium-rich steel.

[Purpose of the invention]

An object of the present invention is to provide a steam turpentine blade that can effectively prevent erosion after the blade is completed as described above.

[Structure of the invention]

In order to continuously achieve the above purpose, this launcher was designed by cutting 9 integrally from the wing.
A recess is formed in at least a part of the blade cover directly above the blade, and the tip of the blade cover is fitted into the recess, and the welding metal for welding the erosion prevention plate is placed directly under the blade cover. The main point is that the structure is designed to prevent exposure.

[Embodiments of the invention]

An example of the implementation of the present invention will be described below with reference to FIGS. 10 to 13.

Figure 1O (aJ is a front view of the erosion prevention plate t of the present invention, Figure 1O (b) is a view of the tip of the erosion prevention plate B viewed from the direction A, and the erosion prevention plate 6 is approximately Each plate is shaped like a plate, and a protrusion da is formed at its tip.

Fig. 1/ and Fig. 72 show the state in which the above-mentioned erosion prevention plate t is added to the blade/, and the blade cover 7 is formed with a recessed portion t which becomes a welding groove, and the four parts jK The protrusion 6a of the corrosion prevention plate A is fitted and welded with the weld metal pb as shown in FIG. 73.

In addition, the thickness of the blade cutter (-7) of the part forming the recess t is λ
~ jifJ is appropriate゛. If the step difference caused by the depression is raised with welded metal having the same composition as the erosion prevention plate 4, it is convenient to finish the blades of the blade group flush.

〔Effect of the invention〕

As described above, according to the main engine 1jlK, the blade cover cut out integrally from the wing is covered with the corrosion prevention plate directly above the wing, that is, the part that is susceptible to erosion, so that it is covered with the corrosion prevention plate. From this point of view, it is possible to eliminate areas where quality is likely to be uneven, and there is no erosion even after long-term operation.

[Brief explanation of the drawing]

The drawings show a conventional example and an example of the implementation of the present invention. Fig. 7 is a front view of a conventional turbine blade, Fig. 2 is a plan view of the same turbine blade as seen from one direction, and Fig. 3 is a conventional turbine blade. An enlarged view of the blade cover in Figure (aJ), i) Front view of the conventional blade cover, Figure φft) Figure 7 is a cross-sectional view taken along the line Vl-Vl in Figure 5, Figure 7 is a front view showing the welding groove with deposited metal, and Figure 7 shows the eroded part. Front view, Figure 2 shows the eroded area.
10(&) is a front view of the erosion prevention plate integrated in the present invention, and FIG. 10(b) is a flat ceramic viewed from the direct direction of the erosion prevention plate. The figure is a plan view showing the state in which the erosion prevention plate is welded to the present invention, FIG. 72 is a front view of the blade to which the erosion prevention plate is welded, and FIG. 13 is a perspective view showing the welded part. c... wing, 2.7... vane cover, 3.1... erosion prevention plate, da... protrusion of erosion prevention plate, r... recess.

Claims (1)

[Claims] In a turbine blade in which a blade cover is cut out at the tip of the blade and an erosion prevention plate is welded to the blade, a recess is formed in at least a part of the blade cover immediately above the blade, which is continuous with the blade; A steam turbine blade in which the tip of an erosion prevention plate is integrally fitted into a recess.