JPS63266103A - Welding process for turbine diaphragm - Google Patents

Abstract

PURPOSE:To dispense with any correction work after welding by welding the whole section of a nozzle blade after putting an end face of the nozzle blade and a plate surface of a partition plate both in order, while machining a joining plane of the partition plate and, after fitting it in both inner and outer rings, welding the nozzle blade and the partition plate as well as these inner and outer rings together. CONSTITUTION:A turbine diaphragm is made up of being welded at weld zones 3 and 4 in the following process that a lot of holes are installed each to both sides of a ring partition plate 1 to be externally fitted in an inner ring 6 and a ring partition plate 1' to be internally fitted in an outer ring 7 and each double end of many nozzle blades 2 is inserted into each of these holes. In this case, first of all, an end face of each nozzle blade and a plate surface of these partition plates 1 and 1' are trued up in line, and electron beam welding takes place over the whole surface of sectional form of each nozzle blade 2. Next, a surface where these partition plate 1 and 1' come into contact with both inner and outer rings 6 and 7 is machined, and these partition plates 1 and 1' are fitted each in the inner ring 6 and the outer ring 7. Afterward, each nozzle blade 2 and these partition plates 1 and 1' are joined together with these inner and outer rings 6 and 7 by means of the said electron beam welding.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of welding a turbine diaphragm formed from an inner ring and an outer ring via a nozzle blade and a partition plate, in which all joints are welded by electron beam welding. The present invention relates to a welding method for a turbine diaphragm suitable for fixing the diaphragm.

[Prior art].

Regarding the technique of constructing a turbine diaphragm by electron beam welding, Japanese Patent Publication No. 53-32441 is known. Welding of the partition plate and the nozzle blade by this known technique involves welding the circumferential grooves on the side facing the inner ring and outer ring of the partition plate, and each true hole provided in the partition plate with a 1 mm seal, and then layer welding. After filling the hole and circumferential groove with welded metal, the inside and outside Il! are fixed using electron beam welding.

[Problem that the invention seeks to solve]

When a turbine diaphragm is constructed using electron beam welding according to the above-mentioned known technology, residual strain in the nozzle blade is large, and correction after welding requires a great deal of time and effort. Furthermore, even if the external shape is modified, the residual stress of welding is not removed, so there are concerns about reliability.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide the most efficient method of welding a turbine diaphragm, which does not cause deformation due to welding and does not require correction work.

[Means for solving problems]

In order to achieve the above object, the present invention uses electron beam welding, which can control the melting range to a minimum, when joining the nozzle blades and the partition plate. facing, similar to welding (as u work,
The partition plate and the nozzle blade end surface are set on the same plane and joined.

In the conventional method, the nozzle was fixed at the center of the true hole of the partition plate thickness, and then the nozzle end face was welded by TIG welding. For this reason, the blade end surface is filled with weld metal from the middle of the true hole to the end surface. In the present invention, the true hole end of the partition plate and the nozzle blade end are made on the same plane, and are only melted and fixed for electron beam welding, and no build-up is performed.

Furthermore, since it can be carried out in one pass, the amount of heat input is small and welding deformation and shrinkage are reduced.

On the other hand, when using the electron beam welding method, it is possible to join the partition plate to the blade shape, but if the partition is provided with an annular groove etc. and assembled with the inner and outer shafts, there will be no contact with the partition plate on the blade cross section. Unwelded areas will occur. Therefore, in the present invention, the blade cross section and the partition plate are uniformly melted and fixed by electron beam welding.

Based on the above-mentioned principle, the welding method of the present invention has a specific configuration for practical application of the welding method. This method is applied to a diaphragm welding method in which a number of holes into which nozzle blades are inserted are provided in a row on both sides of the diaphragm, and both ends of each of the number of nozzle blades are inserted into holes provided in both partition plates and welded. The end of the nozzle blade is inserted into the hole of the partition plate, the end surface of the nozzle blade is almost aligned with the plate surface of the partition plate, and the entire cross-sectional shape of the nozzle blade is joined by electron beam welding, so that the partition plate is aligned with the inner ring. After processing the surface that contacts the outer ring, the partition plate is fitted to the inner and outer rings, and then the nozzle blades, the partition plate, and the inner and outer recesses are fixed by electron beam welding.

[Effect]

In the welding method having the above configuration, since the nozzle blade end surface and the partition plate surface are welded so as to be aligned, there is no need to fill the gap with build-up. For this reason, there are few old metal layers,
Heat input is also small. Therefore, welding distortion is small, and distortion correction after welding is not necessary.

Further, as well as having little welding distortion, residual stress is also low, and a highly reliable turbine diaphragm can be obtained.

〔Example〕

FIG. 1 is a schematic explanatory diagram comparing an embodiment of the present invention and a conventional example.

A indicates a location welded using the conventional technique, and b indicates a location welded using the method of the present invention.

FIG. 2(A) shows the AA cross section of the conventional example a, and FIG. 2(B) shows the BB cross section of the embodiment.

When welding by conventional technology, generally one end of the nozzle blade 2 is inserted halfway into a hole provided in the partition plate 1, and the end surface of the nozzle blade is positioned halfway between the depth of the hole and the thickness of the partition plate. In this state, welding is performed along the line where the nozzle blade 2 and the partition plate 1 are in contact (along the outline of the cross-sectional shape of the nozzle blade 2). FIG. 3(A) is an explanatory diagram schematically depicting a welded portion in a conventional example.

The nozzle blade 2 is inserted into the partition plate 1 by a dimension Q1 to secure one dimension Q2, and the gap corresponding to the dimension Q2 is filled in many layers with the welded metal 5. Therefore, the amount of heat input is large, and the thermal strain is also large.

Further, as shown in FIG. 2(A), an unwelded portion 5a is formed.

The welding part a of this example shown in FIG. Electron beam welding is applied to the entire end surface of the nozzle blade 2, aligned with the plate surface. Second
As shown in FIG. 2(B), the welded portion 3 of this example has no unwelded portion (corresponding to 58 in FIG. 2(A)) unlike the conventional example, and has high welding reliability.

Furthermore, as can be easily understood from Fig. 3 (B), one-pass welding is possible using electron beam welding, and there is no need for multilayer metallization as in the conventional example shown in Fig. 3 (A). . Therefore, the amount of heat input is small, the residual stress of welding is small, and welding distortion is also small. Therefore, distortion correction after welding is not required, and welding reliability is high.

FIG. 4 is a front view of a turbine diaphragm constructed according to an embodiment of the method of the present invention.

Both ends of the large number of nozzle blades 2 are each partitioned F11.

1', this is fitted between the outer ring 7 and the inner width 6, and electron beam welding is performed.

The welding part 4 shown in FIG. 2(B) is a welding part for fixing the nozzle blade 2, the partition plate 1, and the inner part 6.

The welding method of the present invention can be applied even if the nozzle blade material and the partition plate material are different metals.

Table 1 below shows the elongation and aperture values as a result of a long-term tensile test at 550°C on Nozzle S (an EB welded joint of dissimilar metals between the material and the partition plate). .

Table 1 Tensile test load was conducted at 196 MPa. From this result, the nozzle blade material 12Cr heat-resistant steel and the partition plate, 2 1
The elongation and reduction of area values of /4 Cr-IMotll are comparable to the elongation of 16% and the reduction of area of 75%, which are the values of the 550°C high temperature tensile test of the same joint. but.

The elongation and reduction of area values in long-term tensile tests of Nb, V, and N-containing 12Cr heat-resistant steel and partition plates were significantly reduced. Therefore, for the same joint, the composition of the weld metal is 3% to 5%.
A similar test was conducted with a Cr filler rod added and joined by electron beam welding, and good results were obtained. This has made it possible to join the nozzle blade and the partition plate using electron beam welding using Nb, V, and N-containing 12Cr heat-resistant steel used in high-temperature parts.

FIG. 5 is a sectional view taken along the line CC in FIG. 4.

As in this example, a step 8 may be provided between the partition plate 1 and the inner ring 6, and a step 9 may be provided between the partition plate 1' and the outer ring 7. In this case as well, since the nozzle blades 2 are firmly welded to the partition plates 1 and 1', no problem arises in terms of strength.

The same effect can be achieved even if a fitting groove (not shown) is provided in place of the steps 8 and 9.

〔Effect of the invention〕

According to the method of the present invention, welding of the turbine diaphragm constituted by the nozzle blade, the partition plate, and the inner and outer widths,
This can be done with high precision without requiring distortion correction. Therefore, a high quality turbine diaphragm can be quickly and easily welded, and the manufacturing cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for comparing and explaining welding according to the prior art and welding according to the method of the present invention. 2(A) is a sectional view taken along the line AA in FIG. 1, and FIG. 2(B) is a sectional view taken along the line BB in FIG. 1. Figure 3 (8) is a schematic diagram showing the A-A cross section of Figure 1;
Figure (B) is a schematic diagram showing the BB cross section in Figure 1. FIG. 4 is a front view of a turbine diaphragm constructed by the method of the present invention, and FIG. 5 is a sectional view taken along the line CC. 1, 1'... Partition plate, 2... Nozzle blade, 3... Electron beam welding part between partition plate and nozzle blade, 4... Partition plate and inside. Electron beam i3 contact portion with external signal, 5... Welded metal by conventional technology, 6... Internal signal, 7... External signal.

Claims (1)

[Scope of Claims] 1. A large number of holes into which nozzle blades are inserted are arranged in both the annular partition plate that fits externally into the inner ring and the annular partition plate that fits internally into the outer ring. In a diaphragm welding method in which both ends of the nozzle blades are inserted into holes provided in both partition plates and welded, the ends of the nozzle blades are inserted into the holes of the partition plates, and the end faces of the nozzle blades are partitioned. Almost aligned with the plate surface of the plate, the entire cross-sectional shape of the nozzle blade was joined by electron beam welding, and after processing the surfaces where the partition plate contacts the inner and outer rings, the partition plate was fitted to the inner and outer rings. A method for welding a turbine diaphragm, comprising: fixing the nozzle blades, the partition plate, and the inner and outer rings by electron beam welding. 2. The nozzle blade is made of 12Cr heat-resistant steel containing niobium, vanadium, and nitrogen, and the electron beam welding is performed by adding a filler rod to improve the alloy composition of the molten part. A method for welding a turbine diaphragm according to claim 1. 3. The method for welding a turbine diaphragm according to claim 1, wherein the surface of the partition plate that contacts the inner ring and the outer ring is processed by providing at least one of a step and a fitting groove.