JPS61155268A - Diffusion bonding method - 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 (Industrial Field of Application) The present invention relates to diffusion bonding, which prevents cracks from occurring in and around the joint in joining ceramics and ferrous metals.
This relates to a method for welding parts such as turbochargers for automobile parts.

(Prior Art) Regarding the diffusion bonding of ceramics and iron-based metals, there is a publication in JP-A-58-95670 titled ``Method for bonding silicon nitride ceramics and metals.''

This is a direct bonding method that joins a Cr-Ni-Fe-Mo-3i alloy and silicon nitride ceramics. It is disclosed that the method and metal are bonded together.

(Problems to be Solved by the Invention) However, in the case of direct bonding such as the above-mentioned bonding of ceramics and metal, the tensile strength is about 15 to 20'kg/yaku, and for parts that are subject to static loads. Although it can be used, rotating shafts that are used under high temperature and torque conditions due to frictional heat are more likely to break than the joint surfaces due to internal stress due to differences in thermal expansion coefficients, and the joint strength is reduced by 20 to 30% at high temperatures. There is a problem that the performance is degraded and reliability is lacking.

Therefore, the present invention can be used for a long period of time even when used as a rotating shaft of an automobile turbo in joining ceramics and ferrous metals, and has a tensile strength of at least 15 to 20.
To provide a joining method which does not cause damage to the joining part due to internal stress even if there is a difference in thermal expansion coefficients at kg/vs# or more, and does not reduce joining force even if a rotating shaft becomes high temperature due to frictional heat. The purpose is to

[Structure of the invention]

(Means to solve the problem) The technical measures taken to solve the above technical problem are:
In diffusion bonding of silicon nitride ceramics and iron-based metals, this is a diffusion bonding method in which a thin foil made of nickel, titanium, or molybdenum is inserted as an insert material between the two parts to be joined. In this joining process, the ceramic member has a conical end face, the metal member has a cup-shaped end face, and the insert material is cup-shaped and inserted and joined between the two members.

(Operation) The above means operates as follows. In other words, the coefficient of thermal expansion of the insert material inserted into the end face of the parts to be joined is approximately between that of ceramics and ferrous metals, so if they are joined using a diffusion bonding device, a joining reaction will occur actively.
The insert material diffuses between the atoms of the ceramic and iron-based metal, creating a strong bond, resulting in a tensile strength of 15 to 20K.
g/m, and even if the temperature of the rotating shaft rises due to rotational friction and there is a difference in thermal expansion coefficient, the insert 1 acts as a cushioning material for both parts, and there is no cracking or damage on the joint surface. There is no decrease in tensile strength at all.

In addition, when the joining end surfaces are tapered on one side and cup-shaped on the other, and a cup-shaped insert material is inserted and joined, the joining area increases, the centers of both parts match accurately, and the joining strength is further increased. It is.

(Example) Specific examples will be described below.

2 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 connected to the rod 5a by the heater 4.
, 5b to perform diffusion bonding.

The materials to be joined 2 are silicon nitride ceramics, 3 are ferrous metals such as nickel-chromium-molybdenum steel, and 10a and 10 are
b is an insert material made of nickel, titanium, and molybdenum, 10a is a flat plate, and 10b is cup-shaped.

The bonding method is to insert the insert material 10a into the ends of the bonding materials 2 and 3 in the diffusion bonding apparatus I, and perform bonding to obtain the bonding material 11.

Further, in joining the ceramic material 12 and the iron-based metal material 13, a tapered portion 12a and a cup portion 13a are formed, a cup-shaped insert 10b is inserted, and the joining material 14 is manufactured by joining by the diffusion bonding device 1.

Example 1 (Insert material: Ni foil) A test piece in the shape of a flat plate shown at 102 in Figure 2 was used, and silicon nitride ceramics (Si, 7N) was used as the material to be joined.
, f) and Ni-Cr-M.

Steel (SNCM≠Q) foils were pretreated with simple acetone degreasing and bonded at a bonding temperature of about 1100°C in a vacuum of about 10-4'Torr and a bonding pressure of about 1 kg/Ilm.
Diffusion bonding was performed for 0 minutes. Next, as a result of a tensile test of several test pieces, the tensile strength was 15 to 20 kg/in, and fracture occurred at the Si 3 % and Ni interface in all cases.

Next, the bonding material was subjected to a continuous high temperature durability test for 5 hours at a temperature of about 900° C. and 200,000 revolutions per minute, but no abnormality was observed in the bonded portion.

Example 2 (Insert cup material, Ti foil) The test piece was an insert material made of Ti foil with a thickness of 0.1 nm, and the other conditions were the same as in Example 1. As a result of several tensile tests, the tensile strength was 16-20 kg/Si
, N, and Ti interface.

Example-3 (insert material, Mo foil) The test piece was an insert material having a thickness of 0.1 Ill, and the other conditions were the same as in Example-1.

The tensile strength was 18-21 kg/m, and as a result of several tensile tests, fracture occurred at the S ia Ny and Mo interface.

〔Effect of the invention〕

The present invention has the following unique effects. In other words, in contrast to direct bonding, indirect bonding using an insert material allows the insert material to act as a buffer between dissimilar materials even if the bonded part becomes high temperature, adjusting the difference in thermal expansion coefficient and reducing tensile strength. There is no decrease in strength, it can be used for rotating shafts under high temperatures, and there is little variation, making it extremely reliable.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a diffusion bonding apparatus, and FIG. 2 is a cross-sectional view of an insert material, in which (A) is a flat plate and (B) is a cup-shaped one. FIG. 3 is a cross-sectional view of a round bar-shaped welding process; (a) is a cross-sectional view before welding, (b) is a cross-sectional view during welding, and (·) is a cross-sectional view after welding. Figure 4 is a diagram of the joining process for joining members with tapered and cup-shaped end faces, in which (a) is the preparation process, (b) is before joining, (c) is during joining, and (d) is a cross section after joining. It is a diagram. ■... Diffusion bonding device, 2... Ceramics. 3... Iron-based metal, 10a, 10b... Insert member

Claims (2)

[Claims] (1) In a method of joining ceramics and iron-based metals by diffusion welding using a diffusion welding device, an insert material made of a thin foil of nickel, titanium, or molybdenum is inserted between the diffusion joining materials and joined. Diffusion bonding method. (2) The ceramic is silicon nitride ceramic (
Si_3N_4), the metal is iron-based metal nickel.
The diffusion bonding method according to claim 1, which is made of chrome-molybdenum steel (SNCM40).