JPH01205889A - Joining method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of deformation by joining by performing vacuum diffusion welding on a continuous projection surrounding the periphery of the joining surface and further, performing diffusion welding on a remaining recessed part in the high-temperature hydrostatic pressure. CONSTITUTION:In joining an impeller of a centrifugal compressor, etc., for instance, the projection 2 is provided so as to surround the entire periphery of the surface to be joined to a main plate 5 on the tip of a vane 1 cut out by machining from a side plate 3 of the impeller. The main plate 5 is superposed on the side plate 3 and load is applied thereto from the outside and the projection 2 is joined by the vacuum diffusion welding method in the high temperature. Since a contact area of the projection is extremely small, the slight load applied from the outside will do and even if the vane 1 is inclined, the deformation is extremely slight and the recessed part remains as space 6 in a vacuum state. When the high hydrostatic pressure is then applied, although the stress to cause the deformation is not generated on the side plate 3, the main plate 5 and the vane 1, the internal force in the direction to crush acts on the vacuum space 6 of the recessed part and when the periphery is made in the high temperature, the remaining joining surface can be also welded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a joining method that is applied to, for example, the construction of impellers for centrifugal compressors and blowers.

[Conventional technology]

FIG. 2 is an explanatory diagram of a conventional welding method for joining centrifugal impellers. In the figure, the impeller is composed of a disk-shaped main plate 11 and a side plate 12, as shown in FIG. 2(a).
The blades 13 are formed integrally with the side plate 12 by cutting out the material of the side plate 12, as shown in FIG. 2(b). The main plate 11 and the side plate 12 are overlapped and shown in FIG.
), a welding groove is formed on the outside where the main plate 11 contacts the blade 13, and the two are welded from there, thereby integrating the blade part and the main plate 11. After welding, heat treatment appropriate to the material is applied to achieve the desired strength, and final finishing is performed.

[Problem to be solved by the invention]

In the joining method by welding as described above, a large amount of heat is input to the welded object, which deforms the welded object and loses initial processing accuracy. Furthermore, the heat generated during welding oxidizes the surface of the welded object, resulting in poor surface roughness. In order to prevent this, the surface is polished after welding to maintain a good surface roughness, but the inner surfaces of impellers, etc., are difficult to work with, making it impossible to obtain a perfect product, which also increases manufacturing costs.

To avoid this, vacuum diffusion welding is sometimes applied. FIG. 3 is an explanatory diagram of a conventional method of joining centrifugal impellers by vacuum diffusion welding. In the figure, this method allows joining when the blade 13 stands perpendicular to the side plate 12 as shown in FIG.
As shown in Figure (b), in recent high-performance centrifugal impellers, the blades 13 are inclined with respect to the side plate 12 to reduce fluid flow loss, and the blades 13 are bent due to the external load applied during diffusion welding. Due to the deformation shown by the broken line, compressive stress cannot be obtained uniformly on the bonding surfaces, making it impossible to bond.

[Means to solve the problem]

The joining method according to the present invention is aimed at solving the above problems, and involves providing continuous protrusions surrounding the joint surfaces, bringing the joint surfaces into contact with each other, and first performing vacuum diffusion welding on the projections. The method is characterized by performing diffusion bonding on the remaining recessed portions under high temperature and hydrostatic pressure.

[Effect]

That is, in the joining method according to the present invention, minute projections are provided all around the surfaces to be joined, vacuum diffusion welding is first performed on the projections, and the entire periphery of the area to be joined is sealed. Create a vacuum space inside. Next, by performing diffusion bonding using a so-called high-pressure treatment that applies hydrostatic pressure at high temperatures, even when the members are tilted to each other, uniform compressive stress is generated in the joint without deforming the joint, resulting in good results. It is possible to perform various types of joints.

Since the first vacuum diffusion welding involves only a small protrusion on the joint surface, a sufficiently high compressive stress can be generated with a small external load, and the welded part will not be deformed. In the subsequent diffusion bonding by high-temperature hydrostatic pressure treatment, the hydrostatic pressure produces an action that crushes the space existing in the remaining bonding surfaces, so that deformation of the bonded portion does not occur.

〔Example〕

An embodiment of the present invention will be described based on FIG.

FIG. 1 is an explanatory diagram of a method for joining impellers according to an embodiment of the present invention. In the figure, the blades 1 are formed by cutting out the side plate 3 of the impeller by machining, as shown in FIG. 1(a). FIG. 1(b) is a cross-sectional view taken along line bb in FIG. 1(a), and the tip of the blade 1 has a surface connected to the main plate 5 all around it, as shown in FIG. protrusion 2
is provided. This protrusion may be formed by electroplating as shown in FIG. 1(c) (or by attaching another material to the tip of the blade 1 to form a protrusion 2 at the tip corner. ), the tip of the blade 1 may be machined or etched to form a concave central portion, leaving the corner portions of the surfaces to be joined.

The side plate 3 with such blades l and the main plate 5 are shown in Figure 1 (
As shown in e), the blades are overlapped and a load is applied from the outside, and the corner portions, that is, the protrusions 2 of the entire circumference of the joining surface of the blade 1 are joined by vacuum diffusion welding at high temperature.

When vacuum diffusion welding 2 is performed in this way, the contact area of the protrusion is extremely small, so the load applied from the outside can be small. Therefore, even if the blade 1 is tilted, the deformation will be extremely small.

In this way, vacuum diffusion welding can be performed around the joint surface, so that the recess remains as a vacuum space 6. Next, when high hydrostatic pressure is applied as shown in Figure 1(f), stress that causes deformation is not generated in the side plate 3, main plate 5, and blade 1 based on the principle of hydrostatic pressure, but the vacuum space of the recess is not generated. An internal force acts on 6 in the direction of crushing it. In such a state, if the surrounding temperature is raised to high temperature, diffusion bonding can be performed on the remaining bonding surfaces.

〔Effect of the invention〕

The joining method according to the present invention is as described above, and there is no need to particularly apply a large amount of heat to the members to be joined, and since the entire member is kept at a uniform temperature, no deformation occurs due to joining. Even if they are not perpendicular to each other and are tilted, they can be joined.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a joining method according to an embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of a conventional joining method. 1...Blade, 2...Protrusion, 3...Side plate, 5...
Main plate, 6...space. Agent: Patent attorney Akira Sakama, 2 others, 42 wards (0-ri(no side 3) (b)

Claims (1)

[Claims] A continuous protrusion is provided surrounding the joint surface, the joint surfaces are brought into contact with each other, and vacuum diffusion welding is first performed on the protrusion.
Furthermore, the bonding method is characterized in that diffusion bonding is performed on the remaining recessed portions under high temperature and hydrostatic pressure.