JPS63162902A - Manufacture of steam turbine nozzle box - Google Patents

Abstract

PURPOSE:To shorten the working time by dividing a nozzle box body into two parts through cutting and arranging an adjusting plate between the divided bodies and assembling them into an integral body. CONSTITUTION:A nozzle box body 1 having an integral ring structure is formed through forging. An inlet pipe 2 is welding-jointed onto the nozzle box body 1. Then, the nozzle box body 1 is divided into the upper and lower parts. An adjusting plate 6 is fixed between the divided bodies by a stop vis, and assembled integrally. Therefore, the intermediate working process for the welding process can be put together, and the working time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of manufacturing a steam turbine nozzle box disposed in a steam turbine for power generation or the like.

(Conventional technology) In recent years, problems such as a shortage of land for power plants have arisen due to the growth in electricity demand.In order to ensure a stable supply by increasing the power grid capacity, improvements in the reliability and performance of steam turbines have been developed. Improvement is desired.

For example, the steam conditions used are becoming higher pressure and temperature year by year, and ultra-high pressure and high temperature steam conditions such as 316 kg/aJ g and 566° C. are now being adopted.

In general, a steam turbine nozzle box is placed at the steam inflow part of a steam turbine, and has two functions: to efficiently flow the steam flowing into the turbine in the axial direction, and to prevent high-pressure, high-temperature steam from coming into direct contact with the rotor or casing. It is equipped with Therefore, the steam turbine nozzle box is
Since the steam turbine is constantly exposed to high pressure and high temperature steam as described above, in order to improve the reliability and performance of the steam turbine, it is necessary to improve the reliability and performance of the steam turbine nozzle box.

Conventionally, such a steam turbine nozzle box has a complex shape and a thick internal structure, so firstly, the nozzle box body with a top and bottom structure is manufactured by casting, and then each of these nozzle box bodies is made by casting. It is manufactured by repairing defects by welding, machining, and welding the parts that make up the steam flow path.

(Problems to be Solved by the Invention) However, in the above-described conventional method for manufacturing a steam turbine nozzle box, the nozzle box main body having a separate upper and lower structure is constructed by casting, and therefore there are the following problems.

In other words, it is difficult to change the wall thickness of each part of the nozzle box body depending on the stress level, and unnecessary wall thickness must be provided, resulting in decreased reliability due to increased thermal stress, and casting defects. There are many cases where welding requires time to repair and welding, and the heat treatment after welding causes a decrease in adhesion, resulting in a decrease in reliability. Furthermore, it takes a lot of time to separately weld a large number of parts constituting the steam passage to the nozzle box main body, which has a separate upper and lower structure. Due to the S-relic structure, the surface roughness is rough and disturbs the flow of steam, resulting in a decrease in performance.

The present invention has been made in response to such conventional circumstances,
The present invention aims to provide a method for manufacturing a steam turbine nozzle box that can significantly reduce machining time compared to conventional methods and that can manufacture a high-performance, highly reliable steam turbine nozzle box. .

(Means for Solving the Problem) That is, the present invention constructs a nozzle box main body having an integral ring structure by forging, and then attaches a nozzle box component made of rolled steel or forged steel to the nozzle box main body. The present invention is characterized in that the nozzle box body is joined by welding, and then the nozzle box body is cut into two parts, and an adjusting plate is disposed between these nozzle box bodies and assembled together.

(Function) In the method for manufacturing a steam turbine nozzle box of the present invention,
A nozzle box body with an integral ring structure is constructed by forging, and then nozzle box constituent members made of rolled steel or forged steel are welded to the nozzle box body, and after binding, the nozzle box body is cut. Divide into two,
An adjustment plate is arranged between these nozzle box bodies and assembled together.

Therefore, for example, rolled steel is used for nozzle box structural members such as partition plates and end blocks that have a relatively low stress level, and for other nozzle box structural members,
Thermal stress can be reduced by using, for example, Cr-Mo forged steel with a thickness that corresponds to the stress level, and the surface roughness can be made finer by using rolled steel or forged steel. This prevents the flow of steam from being disturbed.

In addition, since the nozzle box body has an integral ring structure, for example, machining of the inside of the nozzle box body, welding of the nozzle box components, etc. can be done all at once, reducing machining time and reducing the adhesion caused by heat treatment. can be prevented.

(Example) The method of the present invention will be described in detail below with reference to the drawings.

In the method for manufacturing a steam turbine nozzle box of this embodiment, first, a nozzle box body 1 having an integral ring structure as shown in FIGS. 1 and 2 is forged from, for example, Cr-Mo forged steel.

Next, the inlet pipe 2 is welded to the nozzle box body 1 at two places on the upper half and the lower half, and an end block 3 made of, for example, rolled steel and Nozzle box constituent members such as the partition plate 4 are welded and joined. Note that the nozzle ring 5 is
Finally, it is welded and joined to the nozzle box main body 1.

When welding and joining of the nozzle box main body 1 and the nozzle box constituent members such as the end block 3 and the partition plate 4 are completed in this way, the entire body is heat treated and machined. In this case, the nozzle box body 1 is machined into a perfect circle without cutting it into upper and lower halves.

Thereafter, as shown in FIG. 3, the nozzle box main body 1 is divided into upper and lower halves by the gold side or the like. Naturally, there will be structural gaps, but
The adjustment plates 6 are fixed on a horizontal surface with respective setscrews 7, and adjustments are made so that no structural gaps occur during assembly.

FIG. 4 shows a steam turbine nozzle box manufactured by the method described above, in which steam is introduced into the inlet pipe 2 from the direction of the arrow shown in the figure.
They each flow into the nozzle box main body 1 through the passageway and are discharged in the axial direction. Note that two inlet pipes 2 are normally installed in the upper half and two in the lower half.

The steam turbine nozzle box having the above configuration is installed within the casing 11 of the steam turbine, as shown in FIG. The steam coming out of the nozzle box body 1 flows into the blades 12, and the force converted into rotational energy is transmitted to the wheel 13 and transmitted to the generator via the rotor 14. Steam leakage on the other side is transmitted to the ground 15. This will be prevented.

In the method for manufacturing the steam turbine nozzle box of this embodiment with the above configuration, thermal stress is reduced by using rolled steel or the like for the nozzle box component members with low stress levels such as the partition plate 4 and the end block 3. In addition, by using rolled steel or forged steel, the surface roughness can be made finer and the flow of steam can be prevented from being disturbed.

In addition, since the nozzle box body 1 has an integral ring structure, processing of the grooves inside the nozzle box body 1, welding of the nozzle box components, etc. can be done all at once, reducing machining time and increasing the impact strength due to heat treatment. can be prevented from decreasing.

In this embodiment, the nozzle box main body 1 and the inlet pipe 2 are fixed together by welding, but the inlet pipe 2 and the nozzle box main body 1 may be forged together in advance.

[Effects of the Invention] As described above, in the method for manufacturing a steam turbine nozzle box of the present invention, materials can be used depending on the stress level, and thermal stress can be reduced. Further, since forged steel or rolled steel can be used, it is possible to prevent the surface roughness from becoming fine and disturbing the flow of steam.

Furthermore, since the welding process intermediate processing steps can be combined, heat treatment can be minimized, unnecessary reduction in striking force can be prevented, and processing efficiency can be improved.

Therefore, processing time can be significantly reduced compared to the conventional method, and a high-performance, highly reliable steam turbine nozzle box can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a front view of a steam turbine nozzle box for explaining the embodiment method of the present invention, FIG. 2 is a top view of FIG. 1, and FIG. 3 is a side view showing the main parts of the steam turbine nozzle box. FIG. 4 is a perspective view showing the steam turbine nozzle box, and FIG. 5 is a sectional view of the steam turbine. 1...Nozzle box body 2...Inlet pipe 3...End block 4...Partition plate Applicant Toshiba Corporation Patent attorney Nori Chika Yudo Hirofumi Mitsumata Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) Construct a nozzle box body with an integral ring structure by forging, then weld and join nozzle box constituent members made of rolled steel or forged steel to the nozzle box body, and then replace the nozzle box body with A method of manufacturing a steam turbine nozzle box, which comprises cutting the nozzle box into two parts, placing an adjusting plate between the nozzle box bodies, and assembling the nozzle box into one body.