JPS6069212A - Manufacture of nozzle box for steam turbine - Google Patents

Abstract

PURPOSE:To improve the safety for creep and fatigue destruction by a method wherein a nozzle box is divided into plural parts, and each part is manufactured by forging, then assembled by welding. CONSTITUTION:A nozzle box 100 is divided into an upper part 101 and a lower part 102 in circumferential direction, each part is manufactured by forging, then assembled into an integral structure by a welding 111. For each divided part manufactured by said process, the forging having the high-temperature strength and high reliablity can be selected. Therefore, the safety for creep and fatigue destruction can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the method of using a nozzle box for a steam turbine.

A nozzle box is provided at the steam inlet of the steam turbine, and the introduced high-temperature, high-pressure steam is ejected to the rotor blades to provide rotational force to the rotor. First, let's talk about the structure of the inlet of the steam turbine.
This will be explained with reference to FIGS. 1 and 2.

In these figures, 11 is an outer casing chamber, 21 is a float chamber, and the main steam inlet pipe 12 welded to the outer casing chamber 11 is connected to the nozzle box 10 welded to the float chamber 21 inside the turbine.
It is inserted into 0. A nozzle block 31 is provided at the tip of the nozzle hook 100. This nozzle box 100 has a complicated structure as shown in FIG. 2 in order to flow steam introduced through the main steam inlet pipe 12 to the nozzle block 31. Note that FIG. 2 is a sectional view taken along the line T in FIG. 1. Further, the flow of steam is indicated by an arrow 5o.

The steam ejected from the nozzle block 31 at high speed applies rotational force to the rotor 41 by applying it to the rotor blades 32a embedded in the rotor 41. Furthermore, the speed of the steam is increased again by the stationary blades 33 attached to the blade ring 34, and the steam is transferred to the next moving blade 32b.
A rotational force is applied to the rotor 41.

By the way, since the nozzle box 100 is located at the inlet of the steam turbine, it is exposed to the highest pressure and highest temperature steam. Therefore, it is necessary to be sufficiently safe against creep or fatigue fracture due to internal pressure stress and thermal stress, and it is also necessary that creep or plastic deformation be small. Therefore, the conventional nozzle box 100 has 2+
It was manufactured using Cr-MO steel.

However, in recent years, in order to improve the thermal efficiency of thermal power plants, so-called ultra-super high temperature steam that uses high temperature and pressure steam has been developed.
(High Pressure Plan) As USC is planned, the turbine inlet steam temperature in this case will increase from the conventional 560°C to 59°C.
The temperature ranges from 0℃ to 650℃.

The material for the nozzle box 100 that will be exposed to such temperatures is conventional 2-Cr-M.

The problem is that steel lacks high-temperature strength. Austenitic steel is a candidate for replacing this material. However, among austenitic steels, SUS
304 cast steel lacks high-temperature strength, so if this material is used, it must be made very thick.
Although 5US316 cast steel has a certain level of high-temperature strength, it has a high possibility of embrittlement, which leaves some concerns. Also,
If 5US316 forged steel is used, the high-temperature strength is sufficient, but the complicated shape of the nozzle box 100 causes difficulties in machining.

The present invention was made based on these circumstances, and
The object is to provide a method for manufacturing a nozzle box for a steam turbine that uses a material that has high temperature strength but can be machined.

Embodiments of the present invention will be described in detail below with reference to FIGS. 3 and 4.

In the present invention, the nozzle box is divided into several parts in the radial and circumferential direction, each of the divided parts is manufactured by forging, which is then machined and each part is welded. It is characterized by being assembled into one nozzle box.

That is, FIG. 3 is a sectional view showing the completed state of the first embodiment of the present invention, in which the nozzle box 100 is divided into two parts, an upper part 101 and a T part 102 in the circumferential direction, and the nozzle box 100 is divided into two parts, an upper part 101 and a T part 102, by welding. It is assembled in one piece. 111 is a welding part. FIG. 4 shows a cross section taken along line A'-fV in FIG. 3 (3).

In this example, 5US316 is used as the nozzle box material.
The upper part 101 and the lower part 102 are each manufactured by forging using forged materials, and then machined as necessary.
One nozzle box 100 is completed by joining by welding.

Next, another embodiment of the present invention shown in FIG. 5 will be described. In this embodiment, the nozzle box 100 is divided into three parts in the radial direction, a right part 103, a center part 104, and a left part 105, which are assembled integrally through welded parts 112 and 113, respectively. . In this embodiment, 2Cr-MO forged steel material was used as the nozzle box material, but in this case as well, the three parts of the right part 103, the center part 104, and the left part 105 were The nozzle box 100 is manufactured by forging, and then machined as required, and then welded to each part to complete one nozzle box 100.

As described above, in the present invention, machining is facilitated by dividing each part into parts, so that complex structures can be easily manufactured.

In addition, it is possible to select a forged product with high temperature strength and reliability, and by using a forged product, a nozzle box that is resistant to creep and fatigue fracture and resistant to creep deformation can be obtained. Furthermore, since there is little fear of high-temperature embrittlement and excellent high-temperature strength, there is provided an extremely useful method for producing a steam turbine nozzle that exhibits various effects such as no need to increase the wall thickness.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the structure of the inlet of a steam turbine, Fig. 2 is a cross-sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a nozzle box manufactured according to the first embodiment of the present invention. FIG. 4 is a sectional view taken along the line ■-4 in FIG. 3, and FIG. 5 is a cross-sectional view showing the completed state of the nozzle box manufactured according to the second embodiment of the present invention. %be. 100... Nozzle box, 101... Upper part, 102...
・Bottom part, 103... Right part, 104... Center part, 105
...Left part, 111-113...Welding part. Figure 1 Mouth 1 1:・・・・・・・・・・・・・・・[]jIj;1
11' Figure a Figure 5

Claims (1)

[Claims] There is a process of forging the parts of a steam turbine nozzle box that are divided into multiple parts in the radial or circumferential direction, a process of machining each part manufactured by forging, and a process of welding each machined part. A method of manufacturing a nozzle box for a steam turbine, comprising the steps of assembling it into a desired shape.