JPH07314129A - Vacuum brazing method - Google Patents

Abstract

PURPOSE:To prevent the harmful effect of the evapotranspiration of Mg, and to secure the excellent brazability in executing the brazing of Al alloy or dissimilar materials by the vacuum brazing method. CONSTITUTION:In the brazing of Al alloy and dissimilar materials, the Mg content of the Al alloy brazing filler metal and the Al alloy is regulated <=0.1wt.%, and the thickness of the oxide film of at least the brazed part is <=200Angstrom by the pickling before heating for the brazing, and these materials are heated under vacuum condition of <=10<-5>Torr, and the brazing is executed by suppressing the thickness of the oxide film to be below 200Angstrom during the heating. The brazing filler metal during the brazing has the stably excellent flowability to allow the excellent joining of the brazing filler metal. In addition, the staining due to the Mg evapotranspiration can be prevented, the brazed product with excellent surface glossiness can be obtained, and the cleaning of a vacuum furnace, etc., can be dispensed with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum brazing method for brazing Al alloy materials, Al alloy materials and different materials, or different materials under vacuum using Al alloy brazing materials.

[0002]

2. Description of the Related Art Conventionally, as a method of brazing an Al alloy material or a dissimilar material other than an Al alloy using an Al alloy brazing material, without using flux, 10 ^-4 Torr
A vacuum brazing method is known in which heating is performed in a vacuum atmosphere adjusted to a certain degree and bonding is performed. By the way, a stable oxide film of 300 Å or more is formed on the surface of an Al alloy brazing material or an Al alloy material in a generally controlled state, and it is necessary to destroy this film that inhibits the wetting of the brazing material during brazing. . In the normal brazing method, this film is destroyed by flux, but in the vacuum brazing method that does not use flux, A represented by JIS A4004 or A4104 is used.
1-Si-Mg based brazing filler metal is used, and the oxide film is destroyed by Mg contained in the brazing filler metal in an amount of about 1 to 2%. Therefore, in vacuum brazing, it is considered essential to contain Mg in the Al alloy brazing material and the brazing Al alloy material.

[0003]

However, since Mg contained in the brazing material or the Al alloy material for brazing evaporates vigorously during the brazing and contaminates the inside of the furnace, periodical cleaning of the furnace is required. However, there is a problem in that it is attached to the surface of the brazed product and impairs the appearance. On the other hand, the inventors of the present invention previously severely suppressed the Mg content in the material, and made the surface oxide film thickness of the brazing material or the Al alloy material for brazing thin before the brazing heat, A vacuum brazing method for preventing the contamination of Mg without impairing the brazing property has been proposed (name: “Method for manufacturing Al alloy brazing hollow structure”, etc .: 1992).
Application on December 9, 2012). However, it has been found that even if the oxide film is suppressed before the heat of brazing by this method, the oxide film grows by the heating during brazing, and as a result, the brazing property deteriorates in many cases. The present invention has been made in the background of the above circumstances, further improving the above proposal, while suppressing the oxide film thickness before brazing, by an oxide film that does not easily grow during brazing heat,
It is an object of the present invention to provide a vacuum brazing method capable of eliminating the harmful effects of Mg while stably maintaining good brazing properties.

[0004]

That is, the first invention of the vacuum brazing method of the present invention is to reduce the Mg contents of the Al alloy brazing material and the Al alloy material for brazing to 0.1% by weight or less, respectively. The oxide film thickness of at least each brazing part is regulated by acid treatment to 200 before brazing heat.
It is characterized in that it is set to Å or less, and these materials are heated under a vacuum of 10 ^-5 Torr or less, and the thickness of the oxide film during heating is suppressed to 200 Å or less, respectively, and the Al alloy materials are brazed to each other.

A second aspect of the present invention regulates the Mg contents of the Al alloy brazing material and the Al alloy material for brazing to 0.1 wt% or less, respectively, and performs an acid treatment to form an oxide film on at least the brazing portion. Thickness is 200Å before brazing heat
Below, these materials as well as other materials for brazing are heated under a vacuum of 10 ^-5 Torr or less, and the thickness of the oxide film during heating is controlled to 200 Å or less, respectively.
It is characterized in that an l alloy material and a dissimilar material are brazed.

A third aspect of the present invention regulates the Mg content of the Al alloy brazing material to 0.1% by weight or less, and at least makes the oxide film thickness of the brazing portion 200 Å or less before the brazing heat by acid treatment. The Al alloy brazing material and the dissimilar material for brazing are heated under a vacuum of 10 ^-5 Torr or less, and the thickness of the oxide film during heating is suppressed to 200 Å or less to braze the dissimilar materials. Characterize.

A fourth invention is characterized in that, in the first to third inventions, the thickness of the oxide film is limited to 100 Å or less before the brazing heat is applied and 150 Å or less during the brazing heat.

The Al alloy material for brazing to be brazed in the present invention has other components except that Mg is 0.1% or less (desirably 0.05% or less) by weight. Is not limited. However, like Mg, it is desirable to contain as little elements as possible that evaporate during brazing.
It is desirable that n is 0.1% or less by weight%, and more desirably 0.05% or less. Further, it is desirable that the total amount of both is 0.1% or less, and further 0.05% or less.

As the constituent material of the different materials, any material other than the Al alloy may be used, and metallic materials and non-metallic materials are targeted. Materials that can be directly brazed include iron, nickel, titanium, stainless steel, and copper.
When the constituent material is made of stainless steel, ceramics or the like and the brazing property is not good, the material having good brazing property is coated on the surface by a method such as plating, thermal spraying or ion plating. Among the plating, electrolytic nickel plating and electroless nickel plating are excellent in brazing property of aluminum. In addition, the dissimilar materials include those having an Al alloy as a constituent material and a coating layer other than the Al alloy formed on the surface thereof for the purpose of decoration or the like. The point is that at least the brazing part is made of a material other than Al alloy.

As an example of the dissimilar material, stainless steel can be cited. Conventionally, a transition piece of stainless / aluminum alloy has been used in the fields of vacuum and heat exchange, the stainless steel is welded to the stainless steel, and the aluminum material is aluminum. Each of them was welded to the same material and joined to the same material. However, stainless / aluminum alloy transition pieces are usually manufactured by explosion welding / friction welding, which is very expensive, and the shape to be joined by explosion welding / friction welding is also limited to a certain extent. Since there is no restriction due to the shape, you can select any shape you like. Therefore, if the surface of stainless steel is nickel-plated (in the example, after nickel strike and then electro-nickel plating), it is cheap without placing insert materials on the surface of stainless steel or adopting other expensive ion plating methods. Vacuum brazing is possible with an easy method. It was also found that when nickel-phosphorus plating was applied instead of electric nickel plating, fine cracks were formed in the joint due to the effect of phosphorus. Therefore, it is desirable that the amount of phosphorus in the nickel plating be 0.1% or less.

Next, the brazing filler metal in the present invention is typically an Al-Si based one containing 5 to 15% by weight of Si, but the present invention is not limited to this. The point is that the Mg content may be regulated to 0.1% or less (desirably 0.05% or less). Further, like Mg, it is desirable to contain as little elements as possible that evaporate during brazing, and Zn added for the purpose of sacrificial anode action or the like is also preferably 0.1% or less by weight. The total amount of Mg and Zn is 0.1%.
Below, it is desirable to further regulate to 0.05% or less.

In addition, the brazing material is used as a brazing material,
Included are those provided as brazing sheets of Al alloy clad on one or both sides. Furthermore, a material in which an Al alloy brazing material is clad to a different material is also included.
In the brazing sheet, when the brazing material is clad on only one side, the other side may be left exposed and other members such as a sacrificial anode skin material may be clad.

The oxide film thickness of the brazing material and the Al alloy before the brazing heat is adjusted by acid treatment using nitric acid or sulfuric acid. The material to be treated is not necessarily the whole material, and at least the brazing part may be treated. This acid treatment is usually carried out by dipping, but it can also be carried out by coating or spraying. Prior to the acid treatment, pretreatment such as degreasing can be performed, and it is desirable to perform the acid treatment after the caustic treatment. After acid treatment,
Normally, the treated surface is washed, but it is desirable to wash with pure water in order to avoid deterioration and growth of the oxide film.

[0014]

[Function] Generally, an oxide film formed on the surface of an Al alloy when left in the air is a porous film, and oxygen molecules infiltrate through pores and cracks and actively contact with the Al alloy during the progress of oxidation. Therefore, the oxide film grows at a constant rate, and in particular, the thickness thereof is rapidly increased by heating. On the other hand, a thin oxide film that does not easily grow even when heated has very few film defects.
In other words, it is a dense oxide film having a high barrier property. In a dense oxide film, oxidation progresses by diffusion, so the growth of the film is slowed down and suppressed. The present inventors have found that a dense oxide film is not easily formed by leaving it in the atmosphere as described above, and can be obtained only by immersing the material in an acid, particularly nitric acid or sulfuric acid. Since the oxide film becomes a thin and dense passive film by the acid treatment, it is hard to be corroded by acid and the denseness is maintained.

That is, according to the present invention, since the surface oxide film of the brazing material and the Al alloy material is regulated within a predetermined thickness before brazing and the film growth during heating is suppressed, Mg is not contained. Even if not included in the material, the wax has a stable and good flowability. Further, by controlling the brazing environment to a high vacuum of 10 ^-5 Torr or less, the brazing property is further improved and good brazing can be performed. Further, since there is no evaporation of Mg during the brazing or it can be almost ignored, it is possible to prevent the brazing atmosphere and the brazed product from being contaminated. The brazed product obtained has excellent surface gloss, with good bonding and no Mg remaining in the surface layer in the form of oxide or the like.

Next, the reasons for limiting the conditions in the present invention will be described. 1) Mg content: 0.1% or less When an Al alloy material or brazing material contains Mg in excess of 0.1%, it evaporates during brazing, so that the atmosphere (vacuum furnace) and brazed products Since it contaminates and loses the luster of the brazed product, the upper limit is made 0.1%. Further, when the content of Mg in the unavoidable impurities of the Al alloy material and the brazing material is set to 0.05% or less, the contamination of the brazed product is further reduced, the surface gloss is good, and the contamination of the furnace can be prevented. It is desirable to set it to 05%.

2) Oxide film thickness: 200 Å or less If the oxide film of Al alloy material or brazing material exceeds 200 Å, braze flow is significantly impaired and brazeability is reduced.
The upper limit is 00Å. For the same reason, it is desirable that the thickness of the coating film during the brazing heat be 150 Å or less. In addition, before the brazing heat is added, it is desirable to limit it to 100 Å or less in consideration of a slight film growth during heating.

3) Atmosphere: 10 ^-5 Torr or less In order to prevent the deterioration of the wettability of the braze due to almost no inclusion of Mg, the brazing is controlled by controlling the brazing atmosphere in addition to the control of the oxide film described above. Improve sex. Here, if the atmospheric pressure is lower than 10 ⁻⁵ Torr and the degree of vacuum is lower, the amount of minute water in the atmosphere increases and the brazing property deteriorates. For the same reason, it is more desirable to set the atmospheric pressure to 10 ⁻⁶ Torr or less.

[0019]

Example 1 Example 1 JIS A3003 alloy plate 1 with a thickness of 1 mm
And JIS A3003 alloy as core material
A brazing sheet 2 having a thickness of 0.5 mm, in which an l-Si alloy brazing material (JIS A4045) was clad at a thickness of 10% was prepared. The amounts of Mg contained in the JIS A3003 alloy and the JIS A4045 alloy used above were 0.01 and 0.02% by weight, respectively.

Regarding the above JIS A3003 alloy sheet 1, (1) solvent degreasing only, (2) degreasing in 10% caustic soda solution, followed by washing with water, (3) degreasing in 10% caustic soda solution, Immediately after washing with water, soak in 15% nitric acid, then wash with water, dry, (4) (3) shortened dipping time in nitric acid, (5) (3) change nitric acid to 15% sulfuric acid Those subjected to the same treatment were prepared, and the brazing sheet 2 was subjected to the treatment (3). Next, as shown in FIG. 1, the brazing sheet 2 was assembled between the alloy plates 1 and 1 in a standing state, and vacuum brazing was carried out at 600 ° C. for 5 minutes in an atmosphere of 10 ⁻⁶ Torr. The results of the brazing test of these test materials are shown in Table 1 together with the oxide film thickness of JISA3003 plate before and after brazing.
It was shown to. As is clear from Table 1, in the method of the present invention, the growth of the oxide film was suppressed even during brazing, and good brazing properties were obtained.

[0021]

[Table 1]

(Embodiment 2) Next, Embodiment 2 will be described below. The aluminum pipe 3 has a pipe shape obtained by cutting a brazing sheet clad with a JIS A3003 aluminum alloy and a JIS A4343 aluminum alloy brazing material, and the Mg and Zn contents are regulated to 0.01% each. As a pretreatment before brazing, the aluminum pipe 3 is immersed in a 10% NaOH solution at 60 ° C. for 30 seconds and then immersed in a 15% nitric acid solution for 1 minute to form a surface oxide film on the surface.
After adjusting to Å, it was washed with ion-exchanged pure water. Further, as a comparative example, an aluminum pipe having a surface oxide film adjusted to 120 Å was prepared by immersing in a 10% NaOH solution at 60 ° C. for 30 seconds and then washing with pure water without immersion in acid.

Next, the mating material stainless steel pipe 4 to be brazed is SUS304 stainless steel cut into a pipe shape. The surface of the pipe is nickel-strike-treated and then electro-nickel plated. Ultrasonic cleaning was performed. Next, with the brazing material 3a side of the aluminum pipe 3 inside and the aluminum alloy 3b side outside, the aluminum pipe 3 and the stainless steel pipe 4 were butted against each other, clamped with a jig, and put into a vacuum brazing furnace. In the furnace, vacuum brazing was carried out at a vacuum degree of 10 ⁻⁶ Torr at 605 ° C. for 10 minutes. The oxide film thickness on the surface of the aluminum pipe of the obtained test material was measured, and the brazing property of the test material was evaluated. The results are shown in Table 2. As is clear from Table 2, even in the present example in which different materials were brazed, good brazing properties were obtained by the inventive method.

[0024]

[Table 2]

(Example 3) 1 mm thick JIS Class 1 Ti
The plates were assembled into a T shape, and a wire-shaped JIS A4045 brazing material having a diameter of 1 mm was arranged along the fillet portion. This JIS A4045 brazing filler metal has a Mg content of 0.01% by weight.
After the caustic treatment, it was immersed in 15% nitric acid and washed with pure water to adjust the surface oxide film to 50 Å. The above materials were placed in a vacuum furnace and vacuum brazed at 600 ° C. for 5 minutes in an atmosphere of 10 ⁻⁶ Torr.
It was confirmed that the obtained brazed product was well joined and there was no problem in brazing property. Also, the surface of the brazed part was excellent in gloss. The thickness of the oxide film after brazing of the brazing material was measured and found to be 55Å. Also,
Similar brazing tests were conducted on JIS Type 2 and Type 3 Ti plates, but good brazing properties were obtained.

[0026]

As described above, according to the vacuum brazing method of the present invention, M in the impurities of the brazing material and the Al alloy material is
Since the g content is 0.1% or less by weight and the oxide film thickness is 200 Å or less before and during the heat of brazing, a good brazing fluidity can be stably obtained.
The material for brazing is well joined, and further, contamination due to evaporation of Mg during brazing can be prevented, resulting in a well joined brazed article having sufficient surface gloss.
Moreover, since the brazing environment is prevented from being contaminated, it is not necessary to clean a device such as a vacuum furnace, and the work efficiency is improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is a perspective view of another embodiment of the present invention.

[Explanation of symbols]

1 Alloy plate 2 Brazing sheet 3 Aluminum pipe 4 Stainless steel pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toma Ken 85 Hiramatsu, Susono, Shizuoka Prefecture Mitsubishi Aluminum Co., Ltd.

Claims (4)

[Claims] 1. An Al alloy brazing material and an Al alloy material for brazing are each controlled to have a Mg content of 0.1% by weight or less, and at least the oxide film thickness of each brazing portion is brazed by acid treatment. Before the heat is applied, the pressure is set to 200 Å or less, these materials are heated under a vacuum of 10 ^-5 Torr or less, and the thickness of the oxide film during heating is 200
Å Vacuum brazing method characterized by brazing Al alloy materials to each other with the pressure kept below 2. The Mg content of the Al alloy brazing material and the Al alloy material for brazing are regulated to 0.1 wt% or less, respectively, and the oxide film thickness of at least the brazing part is brazed by acid treatment. Before applying heat, it should be 200 Å or less, and these materials and other materials for brazing should be 10 ^-5 Torr.
A vacuum brazing method characterized by heating under a vacuum of r or less and brazing an Al alloy material and a dissimilar material while suppressing the thickness of the oxide film during heating to 200 Å or less, respectively. 3. An Al alloy brazing material, the Mg content of which is regulated to 0.1% by weight or less, and at least the oxide film thickness of the brazing portion is made 200 Å or less before brazing heat by acid treatment. A vacuum characterized by heating a brazing material and a dissimilar material for brazing under a vacuum of 10 ^-5 Torr or less and brazing the dissimilar materials while suppressing the thickness of the oxide film during heating to 200 Å or less. Brazing method 4. The oxide film thickness is set to 1 before heat for brazing.
The method of vacuum brazing according to any one of claims 1 to 3, characterized in that it is limited to 00 Å or less and to 150 Å or less during heat applied by brazing.