JPS6024287A - Diffusion joining method of aluminum - Google Patents

Abstract

PURPOSE:To suppress the rate of plastic deformation by the exposed clean joint surfaces and to join diffusively joining members consisting of Al (alloy) by putting said joining member and Mg powder isolated by a wire net for preventing scattering into a retort and sealing the inside thereof to a vacuum then heating the retort and reducing away an Al oxide film by the Mg vapor generated by said heating. CONSTITUTION:A joining materials 2a, 2a having an Al2O3 film 2b and Mg powder 2c isolated by a wire net 2d for preventing scattering are charged into a retort 1 installed in a heating furnace 2. The retort 1 is then subjected to electron beam welding alpha and at the same time the inside thereof is evacuated. The materials 2a, 2a are heated to a prescribed temp. by a heater 3 and the film 2b is reduced away by the evaporated Mg in the retort 1 to expose the clean joint surfaces and thereafter the materials are pressurized with a press 4. The materials are in succession pressurized and soaked to join diffusively the materials 2a, 2a, by which said materials are united to one body. The diffusion joining of the joining materials to each other is thus made possible without using an insert metal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for diffusion bonding aluminum or aluminum alloys.

Conventionally, diffusion bonding of pure aluminum or aluminum alloys has not been performed. This is because a strong aluminum oxide film exists on the joint surface. The joining methods that have been used up until now include strongly pressurizing the members together (pressure welding method), or inserting a different material as an insert metal into the joint surface and utilizing a eutectic reaction (eutectic diffusion brazing method). The aluminum oxide film was mechanically destroyed or dissolved away to expose a clean joint surface.

However, the former method requires a large amount of plastic deformation and requires a lot of post-processing. On the other hand, the latter method generally uses a material other than aluminum as the insert metal, and therefore has drawbacks such as reduced corrosion resistance.

An object of the present invention is to develop a diffusion bonding method that eliminates the drawbacks of conventional methods, suppresses the amount of plastic deformation, and does not use insert metal.

In the method of the present invention, a joining member made of aluminum or an aluminum alloy and magnesium powder having a strong reducing power separated by a wire mesh for preventing magnesium scattering are placed in a retort, and the inside of the retort is evacuated by electron beam welding. This retort is set in a bonding device and heated. At this time, the magnesium in the retort evaporates, and the magnesium vapor reacts sufficiently with the oxide film of the aluminum bonding member to reduce and remove the oxide film, exposing a clean bonding surface and performing diffusion bonding.

The joining method according to the present invention is particularly useful for joining hollow, lightweight aluminum parts often used in aircraft, space equipment, and the like.

Next, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows the state a during diffusion bonding, and Figure 2 shows the bonding material (aluminum or aluminum alloy) in the retort,
It is a schematic diagram explaining the behavior of an oxide film and magnesium powder.

FIG. 2-(A) is a detailed view of the retort 1 when installed in the heating furnace 2 of FIG. 1, with the At,03 coating 2b. The bonding material 2a is put into the retort 1 together with the metal magnesium powder 2C, and the inside of the retort 1 is made into a vacuum β by electron beam welding α. 2d is a wire mesh that prevents the metallic magnesium powder 2C from scattering during evacuation during electron beam welding α.

The retort shown in FIG. 2-(A) is placed in a heating furnace 2 as shown in FIG. 1, and the bonding material is heated to a predetermined temperature by a heater 3. At this time, the magnesium in the retort 1 turns into vapor, reducing and removing the oxide film (AtxOs) 2t) present on the bonding surface as shown in FIG. 2-(B). γ indicates a state in which Aj,03 and Mf are reacting) After exposing a clean joint surface, pressure is applied with a press 4. Subsequently, pressure and soaking are carried out, and the bonding materials are diffusion bonded and integrated as shown in FIG. 2-(C). Diffusion bonding conditions vary depending on the type of bonding material, but using 7075 as an example, the conditions are: temperature 450-500°C, pressure 0.
5~1.5 kg7w? It is.

That is, in the present invention, by using magnesium, which has a strong reducing power, the reduction reaction of the following formula is caused to reduce aluminum oxide to aluminum, thereby performing diffusion bonding.

Although some of the MfO generated in -At 03+Mf -*-4Al+ MfO is dispersed from the bonding surface, most of it remains on the bonding surface.

The present invention enables the reduction reaction of the above formula to occur under certain diffusion bonding conditions, thereby removing the material that was conventionally mechanically destroyed by applying large plastic deformation by applying strong pressure, and which was removed by reaction with the insert metal. The aluminum oxide film can be removed by reducing or completely eliminating the disadvantages of conventional methods such as large plastic deformation and reduced corrosion resistance, thereby making it possible to diffusion bond aluminum 9m members.

[Brief explanation of drawings]

FIG. 1 shows an aspect of a heating furnace during diffusion bonding of the present invention,
FIG. 2 is a schematic diagram illustrating the behavior of the bonding material, AlI3 and magnesium powder in the retort in the heating furnace. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] In the diffusion bonding method for aluminum or aluminum alloy, aluminum bonding members and magnesium powder separated by a wire mesh to prevent magnesium scattering are placed in a retort,
The inside of the retort is vacuum sealed using electron beam welding, and the hindlimb retort is placed in a joining device and heated to generate magnesium vapor, which reduces and removes the aluminum oxide film on the joining surface. A diffusion bonding method for aluminum or aluminum alloy, characterized in that diffusion bonding is performed by exposing a clean bonding surface.