JP3480605B2 - Brazing method of aluminum alloy material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method having high joint strength in brazing aluminum alloy materials.

[0002]

2. Description of the Related Art A brazing method using a brazing material has heretofore been widely used as a method for joining materials to be joined without melting them as much as possible.

[0003]

However, when an aluminum alloy material is to be joined by brazing, aluminum oxide (Al ₂ O ₃ ) is firmly formed on the surface of the aluminum alloy material. Cannot be joined.

[0004]

In order to solve the above problems, the present invention provides a brazing method for joining materials to be joined made of an aluminum alloy material with a brazing material, wherein the brazing material is Mg.
Al alloy powder containing Al, and this brazing material is sandwiched between the joining surfaces of the materials to be joined and set in the furnace, then the pressure in the furnace is reduced and nitrogen gas is introduced to heat the furnace to a temperature near the melting point of the brazing material. To produce magnesium nitride (Mg ₃ N ₂ ). Then, the magnesium nitride was brought into contact with aluminum oxide (Al ₂ O ₃ ) on the joint surface of the material to be joined to reduce it, and then the material to be joined was pressure-bonded. Here, the brazing material is
For example, it contains 12% or more of Mg and has a lower melting point than the material to be joined.

[0005]

[Function] When a brazing material containing Mg is put into a furnace and nitrogen gas is injected and heated, magnesium nitride (Mg ₃ N ₂ ) is formed, and this magnesium nitride (Mg ₃ N ₂ ) is an aluminum alloy material. Surface oxide film (aluminum oxide Al ₂ O
₃ ) when contacted with oxygen, the oxygen O in the oxide film binds to Mg
O becomes O, oxygen O of Al ₂ O ₃ is deprived, and Al atoms are exposed on the surface.

The above reaction is represented by the following reaction formula. 3Mg + N ₂ = Mg ₃ N ₂ 2Mg ₃ N ₂ + 2Al ₂ O ₃ = 2AlN + 6Mg O + 2Al +
_{N 2 Mg3N 2 + 2Al 2 O} 3 + 3Mg = 2AlN + 6MgO + 2
Al In these equations, ΔG (Gibbs standard energy of formation) is negative and the reaction proceeds to the right, so Al is reduced.

As described above, brazing with high bonding strength is performed by melting the brazing material in a state where the Al atoms are exposed on the surface of the aluminum alloy material and performing pressure bonding.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of a furnace for carrying out the brazing method for an aluminum alloy material according to the present invention. A furnace body 1 has a heater 2 for heating the inside of the furnace and a material A to be joined made of the aluminum alloy material. , B are provided, and a gas introduction port 4 for introducing gas into the furnace and a suction port 5 for decompressing the inside of the furnace are opened on the side surface of the furnace body 1.

From the gas inlet 4, N ₂ (nitrogen)
Gas and Ar (argon) gas can be selectively supplied,
Further, a rotary pump 6 is connected to the suction port 5, and a crimping rod 8 which is movable up and down by a crimping drive device 7 is provided above the work table 3.

A specific example will be shown below. First, JIS-30
The aluminum alloy material of No. 03 is the materials to be joined A and B, and a predetermined amount of 50 wt% Mg-Al alloy powder, which is an Al alloy powder having a low melting point, is sandwiched between the joining surfaces of the two as a brazing material m. I set it like 1. Here, the brazing material m is 50 wt.
The particle size of the% Mg-Al alloy powder was 100 mesh or less.
In addition, as shown in FIG. 3, a schematic diagram of the atomic arrangement of the bonding surfaces of the materials A and B to be bonded at this time is such that aluminum oxide (Al ₂ O ₃ ) in which Al atoms and O atoms are strongly bonded is formed. It is in a broken state.

Next, the inside of the furnace is moved to 1 torr by the rotary pump 6.
Depressurize to 100% from the gas inlet 4 into the furnace
Injecting N ₂ gas to bring the pressure in the furnace to 1 atm,
100% N ₂ gas was continuously injected as a carrier gas at an injection rate of 1 liter per minute so that the atmosphere was not mixed into the furnace from the outside.

Then, the heater 2 in the furnace is operated in the nitrogen gas atmosphere as described above, and in the temperature treatment pattern as shown in FIG. 2, the temperature near the melting point of the brazing material m is raised at a temperature rising rate of 10 ° C./min. Heated to 450 ° C. and held for 30 minutes. Here, 450 ° C. is lower than the melting points (643 ° C.) of the materials to be joined A and B, and lower than the melting point (451 ° C.) of the brazing material m.

Mg contained in the brazing material m by this heating
However, it sublimates (gasifies) as shown in FIG. 4 and immediately combines with the surrounding N ₂ gas to form magnesium nitride (Mg ₃ N ₂ ) around the joint surface as shown in FIG. Then, this magnesium nitride (Mg ₃ N ₂ ) comes into contact with the oxide film (Al ₂ O ₃ ) around the bonding surface and performs a reducing action as shown in FIG. That is, Mg atoms deprive O atoms of the oxide film (Al ₂ O ₃ ) to generate MgO, and Al atoms are exposed on the surface.

The amount of Mg contained in the brazing material m is 12%.
The above is preferable. The reason for this is that the mp (melting point) becomes 500 ° C. or less, and Mg easily sublimes.

After holding for 30 minutes in this way, the pressure inside the furnace was reduced to 1 torr by the rotary pump 6 again, and thereafter,
Ar (argon) gas, which is a rare gas, was injected from the gas inlet 4 to 1 atm. Then, the pressure-bonding drive device 7 is operated in this rare gas atmosphere, and the bonding surfaces of the materials A and B to be bonded are pressure-bonded at 1 kg / cm ² by the pressure-bonding rod 8 and 10 ° C. in that state.
The temperature was raised to 480 ° C. at a heating rate of / min and held for 30 minutes. Then, after the furnace was cooled to about 100 ° C. or lower, the materials A and B to be joined were taken out and air-cooled. Here, 480 ° C. is the melting point of the materials A and B to be joined (643
C.) or lower and the melting point of the brazing material m (451.degree. C.) or higher.

As a result, Al atoms are brazed in a state where they are exposed on the surface, and the bonding strength is improved as shown in the table below.

[0017]

[Table 1]

That is, in the comparative example, the same 50 wt% Mg-Al alloy powder as the brazing material m of the present invention was used as the brazing material m, and N ₂
This is a case where pressure bonding is performed after heating in an air atmosphere instead of a gas atmosphere. In this method, the reducing action by magnesium nitride (Mg ₃ N ₂ ) is not performed and the bonding strength is 2 k.
It was a weak gf / mm ^2, and even in the rupture test, the joint part (around the brazing material) broke. On the other hand, in the case of the present invention, the joining strength was improved to 11 kgf / mm ^2, and even in the breaking test, the joined parts (around the brazing material) did not break, and the materials to be joined A and B themselves broke.

In the above embodiment, Ar gas is used as a rare gas when pressure bonding is used.
He (helium), Ne (neon), Kr (krypton), Xe (xenon), and Rn (radon), which are elements of Group 0 of the periodic table, may be used.

[0020]

As described above, according to the present invention,
When brazing materials to be joined made of aluminum alloy materials, the brazing material is made of Al alloy powder containing Mg and heated to near the melting point of the brazing material under a nitrogen gas atmosphere to obtain magnesium nitride (Mg ₃ N ₂ ) is generated and aluminum nitride (Al ₂ O ₃ ) on the joint surface of the material to be joined is reduced with this magnesium nitride (Mg ₃ N ₂ ) to perform pressure joining, resulting in a dramatic increase in joining strength. Can be increased to

[Brief description of drawings]

FIG. 1 is a sectional view of a furnace for carrying out a brazing method for an aluminum alloy material according to the present invention.

FIG. 2 is a graph showing a processing pattern in the furnace.

FIG. 3 is a schematic diagram of the atomic arrangement on the surface of the material to be joined before Mg sublimates.

FIG. 4 is a schematic diagram showing a state where Mg is sublimated.

FIG. 5 is a schematic diagram showing a state in which sublimated Mg and N are bound together.

FIG. 6 is a schematic view showing a state in which Mg and O are bound and Al is exposed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Furnace main body, 2 ... Heater, 4 ... Gas inlet, 8 ... Crimping rod, A ... Joined material, B ... Joined material, m ... Brazing material.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuyoshi Sakuma 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture, within Honda Engineering Co., Ltd. (56) Reference JP-A-53-123354 (JP, A) JP-A 3-13294 (JP, A) JP-A-6-23583 (JP, A) JP-A-8-35025 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 1/00 -1/19

Claims (2)

(57) [Claims] 1. A brazing method for joining materials to be joined made of an aluminum alloy material with a brazing material, wherein the brazing method is a brazing material of Al alloy powder containing Mg. Sandwiching it in the furnace and setting it in the furnace, and after depressurizing the furnace, introducing nitrogen gas into the furnace and heating to near the melting point of the brazing material
₃ N ₂ ) is generated, and this magnesium nitride is brought into contact with aluminum oxide (Al ₂ O ₃ ) on the joint surface of the material to be bonded to reduce it, and the step of pressure-bonding the material to be bonded is performed. A method for brazing an aluminum alloy material, which comprises: 2. The brazing method for an aluminum alloy material according to claim 1, wherein the brazing material contains 12% or more of Mg and has a lower melting point than the material to be joined. Brazing method for alloy materials.