JPS5837076B2 - Atsui Tab Zaino Yousetsu Hohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of welding a turbine diaphragm, and more particularly, to a method of welding a thick plate member surrounding a turbine diaphragm using high energy density beam welding.

Currently, there are two types of high-energy-density beam welding that can achieve deep penetration into welds: electron beam welding, which uses the kinetic energy of electrons, and laser welding, which uses the thermal energy of light.These welding methods can be used to weld metal parts. When performing welding, there is a limit to the welding depth of one pass, which is one welding, depending on the capacity of the welding machine.

Therefore, if the metal member plate thickness t is large, the maximum welding capacity pmm
When welding a metal member with a thickness of t ) 2 p using a welding machine, various measures are required.

As a conventional method, an electron beam welding method for thick plate metal members will be described with reference to FIGS. 1 to 3.

In the figure, electron beam welding is indicated by an arrow (FBW).

In Fig. 1a, between joint surfaces 5a and 5b formed on thick metal members 1a and 1b that require fixing, a metal of the same material as the metal members 1a and 1b is used, and the welding capacity is within the welding capacity of the welding machine. An electron beam welded portion 2 is formed by sandwiching the filler plate 3 between these metal members 1a and 1b and performing electron beam welding on the three members.

Subsequently, as shown in FIGS. 1b and 1c, there is a welding method in which another filler plate 3 is inserted above the welded area and the electron beam welding procedure is repeated to weld the metal members 1a and Ib.

In addition, as shown in FIG. 2, the metal members 1a and 1b are joined by a
, 5b at both ends of the metal members 1a, lb to form grooves 6 of appropriate size. One pass of electron beam welding is performed from both sides from below to form the electron beam welded part 2, and then as shown in FIG. 2b,
(2) A filler plate 4 made of the same metal as the metal member and having a bonding surface 6b on its outer surface and having the same shape as the groove 6 is fitted into the groove 6, and electron beam welding is performed on both bonding surfaces 6a and 6b. There is a welding method in which metal members ia and Ib are welded together by welding.

Further, as shown in FIG. 3, by forming uneven joint surfaces 7a at both ends of the joint surfaces 5a and sb of the metal members 1a and y1b, a rectangular groove 7 of an appropriate size is formed. The metal members 1a, 1 are attached to the planar joint surface 5a5b.
One pass of electron beam welding is performed from both above and below b to form an electron beam welded part 2, and then, as shown in FIG. There is a welding method in which a rectangular prism filler plate 8 having a surface 7b is fitted and electron beam welding is performed on both joining surfaces 7a and 7b to weld the metal members 1a and Ib.

However, in general, high energy density welding such as electron beam welding and laser welding can provide welds with deep penetration, but the precision of the weld groove, which is the joint surface, usually needs to be maintained at 0.2 mm or less.

In other words, high energy density welding melts the metal on both sides of the joint surface in a very thin area and joins the two, so if the gap between the two joint surfaces is uneven, welding defects will occur locally. .

Therefore, in the above-mentioned conventional method for welding thick plate members, multiple passes of electron beam welding are performed on the joint surfaces, which requires a weld opening to remove the thermal deformation caused by the previous welding pass and the excess buildup of the weld surface bead. Re-processing of the tip is required each time.

Further, a filling plate made of the same material as the metal members to be joined is required.

Furthermore, in electron beam welding, spiking defects with blowholes or voids are likely to occur at the tip of the weld, so as the number of welding passes in electron beam welding increases, Welding defects will increase.

Conventionally, attempts have been made to use electron beam welding to weld turbine diaphragms because it causes less thermal distortion than other welding methods, but as turbines become larger, the thickness of the members that make up the diaphragm has to be reduced. may become large and exceed the capability of the electron beam welding machine.

An object of the present invention is to weld a turbine diaphragm having a thick plate member that exceeds the penetration capacity of high energy density beam welding by using high energy density An object of the present invention is to provide a welding method using beam welding.

The gist of the present invention is to form a plurality of nozzle blade fitting holes at predetermined intervals on the U-shaped bottom surface of a pair of partition plates having a U-shaped cross section when welding thick plate members constituting a turbine diaphragm. The nozzle blade is inserted into the fitting hole, the nozzle blade and the partition plate are temporarily fixed by welding, the inside of the U-shape of the partition plate is welded with weld metal, and the plate is welded by machining. A joint surface corresponding to the joint surface formed on the inner ring or outer ring is formed across the surface of the metal part and the surface of the partition plate, and grooves are formed at both ends of the joint surface of the partition plate and the joint surface of the outer ring or inner ring. is formed, the joining surfaces of the partition plate and the outer ring and the inner ring are butted together and high energy density beam welding is performed, and then overlay welding is performed on the groove portion.

FIG. 4 shows a diagram of the principle of welding thick plate metal members.

In FIG. 4, joint surfaces 5a and 5b are formed on thick metal members 1a and 1b, respectively, which require fixing.

Grooves 9 for arc welding are also formed at the upper and lower ends of the joint surfaces 5a and sb by abutting both the metal members 1a and lb.

Planar joint surfaces 5a and sb formed on the metal member
The size of the welding area may be determined according to the maximum penetration ability of the welded part by the welding machine that performs electron beam welding.

In Fig. 4, electron beam welding is performed on metal members 1a and 1b.
Since welding is performed from both above and below, the dimensions of the joint surfaces 5a and sb may be within twice the maximum penetration capacity of the welding machine.

The metal members to be joined are shaped into the above-mentioned shape, and the joining surfaces 5a and sb of the metal members 1ayib are first butted against each other, and electron beam welding is performed from both above and below to form the electron beam welded portion 2. take shape

Next, arc welding is performed on the groove portions 9 at the ends of the joint surfaces 5a, 5b, and the weld metal portion 10 is formed by building up and filling the weld metal.

Through the above steps, the thick metal members 1a and Ib are fixed.

The above welding method effectively combines electron beam welding, which can achieve deep penetration welding, and arc welding, which does not require great groove precision and provides stable quality of the welded part, for multilayer welding of thick plate materials. It's a method.

Next, an embodiment in which the present invention is applied to a method of welding a diaphragm of a steam turbine will be described.

As shown in FIG.
3 and the outer ring 14 by welding.

The welding method will be explained in detail below with reference to FIG.

The annular partition plate 12 made of mild steel or heat-resistant alloy steel is
A recess 12a is formed so that its cross section is U-shaped, and a plurality of openings 12b having the same cross-sectional shape as the nozzle blade 11 made of 12Cr steel are bored in the bottom surface of the recess 12a.

Then, the end of the nozzle blade 11 is inserted into the opening 12b of the partition plate 12, and the weld metal 15 is seal-welded from the recess 12 side of the partition plate to temporarily fix the two.

Next, the inner ring 13 and the outer ring 14 are inserted into the recess 12a of the partition plate 12.
The partition plate 12 and the nozzle blade 11 are reliably fixed by overlay welding a weld metal 16 made of the same material as mild steel or heat-resistant alloy steel.

Thereafter, the outer surface of the weld metal 16 is machined to form a joint surface 17b that is flush with the partition plate.

In addition, the inner ring 13 and the outer ring 14 also have a partition plate 12 and a weld metal 1.
A joint surface 17a to be welded to a joint surface 17b shaped as 6
The joining surfaces 17a and 17b are joined by electron beam welding from both above and below, but the metal members to be joined are thick. This exceeds the welding machine's penetration ability, making it impossible to join with one pass of welding.

FIG. 6 shows a case where the thicknesses of the outer ring 14 and the partition plate 12 exceed the penetration capacity of the welding machine.

Therefore, in the example of the present invention, planar joining surfaces 17a and 17b are formed on the outer ring 14 and the partition plate 12 within the penetration capability of electron beam welding by a welding machine, and Grooves 19 are formed at the ends of the joint surfaces 17a and 17b.

The shape of this groove portion 19 needs to be suitable for the groove shape when performing arc welding.

After doing so, the joint surface 17a of the outer ring 14 and the partition plate 12
and the joint surface 17b of the weld metal 16, and electron beam welding is performed from both above and below the joint surface to form an electron beam welded part 20, and the joint surface 17a,
Fix 17b.

Thereafter, by applying arc welding to the groove 19 formed between the outer ring 14 and the partition plate 12 and welding the weld metal 22, the partition plate 12 and the outer ring 14 are completely fixed, and the turbine diaphragm is The inner and outer rings and the nozzle blades are welded together.The reason why the inner and outer rings 13 and 14 and the nozzle blades 11 are welded by electron beam through the weld metal 16 is because the material of the nozzle blades 11 is 13Cr steel. The weld metal 15 for seal welding that temporarily fastens the nozzle blade 11 and the partition plate 12 often contains 4 to 6% Cr steel by melting Cr steel, and the inner and outer rings 13. When the material 14 is mild steel, if the outer ring material and the weld metal 15 are melted in equal amounts and electron beam welded, the Cr content of the electron beam weld increases, causing solidification cracking, etc. There is a high possibility that welding defects will occur.

Therefore, the weld metal 16 is further welded over the top of the weld metal 15 by seal welding to prevent an increase in the Cr content in the electron beam welded part.

Furthermore, the weld metal 16 and partition plate 16 that are electron beam welded to the inner and outer rings 13 and 14 are made of the same material as the inner and outer rings, since electron beam welding is performed on metals of different materials. This is to prevent the disadvantage that the beat, which is the electron beam welding part, is bent and an unwelded part is created.

According to the present invention, when welding a metal member of a turbine diaphragm made of a thick member using electron beam welding, it is possible to provide a welding method for a turbine diaphragm that has few welding defects in the welded part and has excellent welding workability. Become.

[Brief explanation of the drawing]

Figures 1 to 3 show a conventional welding method for performing electron beam welding on thick material members. 4 is an explanatory diagram showing a welding method in which electron beam welding is performed through a filling body, FIG. 4 is an explanatory diagram illustrating a welding method in which electron beam welding is applied to a thick plate member, and FIG. A schematic structural diagram showing a turbine diaphragm,
FIG. 6 is a partial sectional view taken along the line AA in FIG. 5 in which the present invention is applied to welding a turbine diaphragm. 1a, 1b...metal member, 2...electron beam metal part, 5a, sb...joint surface, 9...groove portion. 10
...Welded metal part, 11... Nozzle blade, 12... Partition plate, 12a... Recess, 12b... Opening, 13...
・Inner ring, 14... Outer ring, 'i 5, 1 6-...
Weld metal, 1 7a, 1 yb--joint surface, 19
... Groove section, 20... Electron beam welding section, 22...
・Welded metal.

Claims (1)

[Claims] 1. Drill a plurality of nozzle blade fitting holes at predetermined intervals in the U-shaped bottom of a pair of partition plates with a U-shaped cross section, insert the nozzle blades into the penalty blade fitting holes, and connect the nozzle blades and the partition. The plates are temporarily fixed by welding, and the inside of the U-shaped convex part of the partition plate is welded with weld metal to secure the nozzle blade and the partition plate, and the surface of the plate part and the partition plate are machined. , form a joint surface corresponding to the joint surfaces formed on the inner ring and the outer ring, and further form grooves at both ends of the joint surface of the partition plate and the outer ring, and form grooves on both ends of the joint surface of the partition plate and the outer ring. and a method for welding a turbine diaphragm, characterized in that the joint surfaces of the inner rings are butted together, high energy density beam welding is performed on both the butt surfaces, and then overlay welding is performed on the groove portion.