JPS61222962A - Method of joining ceramics and metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention relates to a diffusion welding method for preventing the occurrence of cracks in joining ceramics and metals. It is used for parts.

(Prior art) For diffusion welding of ceramics and metals, see JP-A-58
-9567Or silicon nitride ceramic and metal bonding method” is published.

This Cr-Ni-Pe-Mo-5t alloy has good wettability with silicon nitride ceramics and the metal to be bonded, and produces silicon compounds of the alloy on the surface of the ceramic during fusion, thereby bonding the ceramic and the metal. It is disclosed that a strong bond is formed between the two.

However, there is a problem in that ceramics tend to crack due to internal stress caused by the difference in thermal expansion coefficients between ceramics and metals.

Therefore, the present invention solves the drawbacks of the above-mentioned prior art.
The technical objective is to develop a welding method that does not cause cracks in ceramics due to internal stress during diffusion welding, even if there is a difference in thermal expansion coefficient between ceramics and metals.

[Structure of the invention]

(Means for solving the problem) The technical means taken to solve the above technical problem is that in diffusion welding of ceramics and metal, both joint ends of the ceramic and metal are tapered, heated and pressurized. This is a diffusion welding method in which the material is press-fitted during the process and then held for a certain period of time to form a compound on the contact surface and join.

(Operation) The above technical means operates as follows. In other words, the hole shape of the tapered part on the metal side is the same as the tapered shape of the ceramic, and the size is such that the side surface of the ceramic and the inner surface of the metal come into contact, and the ceramic shaft is inserted into the tapered part of the metal hole.
Ceramics are heated and compressed and held for a certain period of time. Ceramics are extremely strong against compression pressure, and while compressive stress may once be present, tensile residual stress, which is harmful to ceramics, is reduced and cracking can be prevented.

In addition, the tapered shape of the platform makes press-fitting easier, and on the tapered side, the pressure from the metal due to press-fitting and the pressure from the outside also act on the contact surface, so there is enough press-fitting to spread. Furthermore, a diffusion phenomenon occurs not only on the taper bottom but also on the side surfaces, increasing the bonding area.

(Example) Hereinafter, the present invention will be explained based on examples.

1 is a diffusion welding device, 2 and 3 are objects to be joined, 4 is a heater, 5a and 5b are pressure rods, 6 is a heating power source, 7 is a vacuum pump, 8 is a compressor, and 9 is a cylinder. The objects 2 and 3 to be welded are diffusion welded by heating with a heater and applying pressure with a pressure rod.

The material 2 to be joined is silicon nitride ceramic, and 3 is a metal made of nickel, chromium, or molybdenum steel, and the end side of the joining material 2 has a taper 2a, and the end of the metal material has a tapered hole 3a.
The dimensions of the taper are the same, α is now 2 to 3 degrees. This joining material is joined by diffusion welding; (a) the workpiece is attached to a diffusion welding device; (b) heating and pressure are applied in a vacuum; the metal is softened by heating, and is then pressed into the tapered part with low pressure. be done.

(c) After press-fitting, the welding is completed by holding the press-in for a certain period of time to form a compound at high temperature on the contact surface.The above process welds the ceramic and the metal.

FIG. 4 shows an enlarged photograph of the joint. (A) is an enlarged view of the bottom part (A) of Fig. 2, and (B) is an enlarged view of the side part (B).
It is an enlarged view of. In each case, the white layer visible in the center was a diffusion layer, no cracks were observed, and a bonding strength of 20 to 22 kg/van'' was obtained.

10 is a turbo shaft and an impeller joined together by actual diffusion welding.

〔Effect of the invention〕

The present invention has the following unique effects. In other words, ceramics are bonded with a type of shrink fit effect in which compressive internal stress acts on them more than metals, so harmful tensile residual stress does not act on them and cracks do not occur in ceramics.

In addition, the tapered shape of the mounting table facilitates press-fitting and provides good coaxiality, and because pressure is applied to the tapered side surface in the normal direction to the axial pressure during diffusion bonding, diffusion phenomenon also occurs on the side surface. occurs and the joint area increases, so the strength increases.

On the other hand, as a trapezoid shape, for example, a straight type may be considered, but in this case initial setting is not easy and a single load is likely to be applied, and pressure is not applied to the side surface in the vertical direction compared to the axial direction in diffusion bonding. Because there is no such thing, diffusion reduction is unlikely to occur.

Furthermore, by making the length of the tapered part of the ceramic shorter than that of the metal, there is relief at the boundary, and no local tensile stress is applied to this part, so cracks do not occur.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the diffusion welding equipment, and Fig. 2 is a process diagram of this example, in which (a) is before welding, (b) is during welding, (
c) shows a cross-sectional view after joining. Figure 3 is a side view with a partial cross section of another modified embodiment, Figure 4 is an enlarged photograph of the joint, and (A) is A of Figure 2 (C).
Part, (b) indicates part B.

Claims (1)

[Claims] In a method of joining ceramics and metal by diffusion welding using a diffusion welding device, the end side surface of the ceramic is tapered, a tapered hole into which the ceramic is inserted and fitted is provided at the end of the metal, and the tapered side surface of the ceramic is formed. A method for joining ceramics and metal, in which the end surface and the side surface of a tapered hole in the metal are brought into contact with the end surface and joined by diffusion welding.