JP2002254167A - Brazing method and magnesium-containing aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out brazing using fluorine as flux, concerning the brazing of a magnesium-containing aluminum alloy. SOLUTION: On the joining face of the magnesium-containing aluminum alloy 12 with an other side part 10, a nickel layer is formed by nonelectlytic plating, and by using a fluorine-based compound as the flux, the flux is coated on the joining face under the pastelike state as shown by X, then the brazing is performed in a furnace which is under the nitrogen replacement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for brazing an aluminum alloy containing magnesium as a component thereof using a fluorine-based flux and a magnesium-containing aluminum alloy product.

[0002]

2. Description of the Related Art Although the oxide film formed on the surface of aluminum is strong and has excellent corrosion resistance, the wettability of brazing material is poor. Had been difficult. However, an aluminum alloy (Al-Si) brazing material using a chlorine-based compound as a brazing material has been provided, and according to this type of brazing material, the aluminum based on the chlorine-based flux contained therein is used. Since the oxide film on the surface can be easily decomposed, the wetting of the brazing material is remarkably improved, and as a result, brazing of aluminum or aluminum alloy can be performed.

However, chlorine-based fluxes are deliquescent and highly corrosive, so it is necessary to remove residual flux after brazing, and the rate of corrosion of the brazing furnace and jig is too fast. There is a problem that the working environment becomes poor.

[0004] Therefore, instead of brazing using a chlorine-based compound as a flux, brazing using a fluorine-based compound as a flux has been developed. In other words, brazing using a fluorine-based compound as a flux has the advantage that there is no problem of corrosion even if the flux remains after brazing and that there is no need for a vacuum furnace. In such a case, there is a situation that a brazing filler metal using a fluorine compound as a flux has been used.

[0005]

As described above, most of the brazing materials used recently have a fluorine compound as a flux. However, in the case of a brazing material having a fluorine compound as a flux, a magnesium-containing aluminum alloy is used. (Al-Mg-Si alloys such as the 6000th alloy in the JIS alloy designation for aluminum alloys) have the problem that brazing is difficult, especially when the magnesium content is 0.4%.
%, Brazing using a fluorine compound as a flux could hardly be employed. That is, when a magnesium-containing alloy is brazed with a fluorine-based compound by flux, magnesium in the alloy reacts with fluorine in the flux to produce a fluorine compound of magnesium (magnesium fluoride). The original function of the flux of removing the oxide film on the aluminum surface becomes insufficient. As a result, the wettability of the brazing material to the alloy surface becomes insufficient, and the joining degree of brazing is inevitably insufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to braze a magnesium-containing aluminum alloy part by using a fluorine compound as a flux.

[0007]

According to the first aspect of the present invention, there is provided a method for brazing parts, at least one of which is made of a magnesium-containing aluminum alloy, by using a fluorine-based compound as a flux. A metal layer having good adhesion to the alloy and good wettability of the brazing material is formed on the surface of the aluminum alloy component to be joined to the mating component, and then brazing is performed using the brazing material. A brazing method is provided.

The operation and effect of the first aspect of the invention will be described.
In a magnesium-containing aluminum alloy part, a metal layer is formed on a joint surface with a counterpart part, and then the aluminum alloy is brazed with a fluorine-based compound as a flux. The magnesium-containing alloy and the metal layer thereover are in a state of firm adhesion. Then, the magnesium in the magnesium alloy and the fluorine in the flux are cut off, the reaction between the fluorine in the flux and the magnesium in the alloy is prevented, and the oxide can be decomposed by the flux. On the other hand, brazing is performed on the metal layer on the magnesium-containing aluminum alloy, and the brazing property is good. And
Because of the good wettability of the brazing material to the metal layer, once the brazing material is in a molten state, it is instantaneously transmitted to the entire joint surface due to surface tension, and is applied to parts where corners of parts are difficult to braze. However, reliable brazing can be performed.

According to the second aspect of the present invention, the first aspect is provided.
In the invention described in (1), there is provided a brazing method, wherein the metal constituting the underlayer on the joint surface of the magnesium-containing aluminum alloy component with the mating component is nickel.

The operation and effect of the second aspect of the present invention will be described. In the magnesium-containing aluminum alloy part, a nickel layer is formed as a base on a joint surface with a mating part. This nickel layer is formed by electroless plating. Can be performed very well. That is, an extremely thin underlayer having a thickness of 5 to 10 microns can be firmly formed on the surface of the magnesium-containing aluminum alloy. After that, the aluminum alloys are brazed using a fluorine-based compound flux.At this time, the magnesium in the magnesium alloy and the fluorine in the flux are cut off by the nickel layer on the magnesium-containing alloy, and Since the oxides are decomposed by the fluorine in the flux, the wettability of the brazing material is improved, and reliable brazing can be performed even at locations where brazing is difficult such as between corners of components.

According to the invention described in claim 3, according to claim 2
The present invention provides a brazing method characterized by performing electroless plating for forming a nickel underlayer on the surface of a magnesium-containing aluminum alloy.

The function and effect of the third aspect of the present invention will be described. The thinner the nickel underlayer, the better, as long as it achieves the function of blocking the magnesium-containing aluminum alloy as the ground and fluorine in the flux. Although it is possible to form a base layer having a very small thickness of 5 to 10 microns by electroless plating, but having high uniformity and little unevenness, the intended function can be efficiently achieved.

According to the fourth aspect of the present invention, there is provided a magnesium-containing aluminum alloy product obtained by brazing parts, at least one of which is made of a magnesium-containing aluminum alloy, with a fluorine compound as a flux. The aluminum-containing aluminum alloy part, which has a good adhesion to the alloy and a good wettability of the brazing material, is provided on the brazing joint surface with the counterpart part of the aluminum-containing aluminum alloy part. A magnesium-containing aluminum alloy product is provided, which is brazed to a counterpart component through an underlayer.

The function and effect of the invention of claim 4 will be described. When a base metal layer is provided on a joint surface of a magnesium-containing aluminum alloy part with a counterpart part, when brazing a fluorine-based compound as a flux,
Since the base metal layer blocks magnesium in the magnesium-containing aluminum alloy and fluorine in the flux, brazing properties are good, and it is possible to obtain a magnesium-containing aluminum alloy product in which the joining surfaces are brazed firmly. it can.

According to the invention set forth in claim 5, according to claim 4,
In the invention described in (1), a metal forming the underlayer is nickel, and a magnesium-containing aluminum alloy product is provided.

According to the fifth aspect of the invention, the metal constituting the base metal layer is made of nickel, so that an ultra-thin nickel layer is formed by electroless plating on the joint surface of the magnesium-containing aluminum alloy with the mating part. And a firmly brazed product of both components through the underlying nickel layer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the practice of the present invention, magnesium-containing aluminum alloys include Al-Mg-based (aluminum alloys of the 5000th JIS alloy name) and Al-Mg-Si-based (aluminum JI in alloys
Al-Zn-Mg-based alloys (in the JIS alloy designation of 7
Aluminum alloys for wrought materials such as 000th and monoliths.

A fluorine compound is used as the flux. Such a flux is mainly composed of an alkali metal chloride of the NaCl-KCl-LiCL system, and NaF, KF
And a small amount of a fluoride salt such as AlF3. Examples include products such as No. 30, No. 53 and No. 105 of ALCOA of the United States for brazing in a furnace in a nitrogen gas atmosphere. Although the melting temperature of the brazing material is close to that of the magnesium-containing aluminum alloy as the base material, the melting temperature is somewhat lower than that of the magnesium-containing aluminum alloy, and it is suitable for brazing in a furnace in a nitrogen gas atmosphere. It shows the attachment property. The composition of such brazing material is Al
-Si alloys are preferred, and JIS Z3263 contains various types (4343, 4045, 40
04, 4005, 4N04, 4104, 4N43, 4N45, 4145, 4047, etc.), and select the appropriate alloy number from among them. JIS Z326 is used in the practice of the present invention.
Alloy No. 4047 in 3 is particularly preferred. Further, as the properties of the brazing material, even if the brazing material is formed in a plate shape or a rod shape, a so-called brazing sheet in which the brazing material is clad on the surface (one surface or both surfaces) of the core material of the AL-Si alloy is used. Good. A paste made by mixing a powdery brazing material, a flux and a liquid binder can also be used.

In the present invention, prior to the brazing operation, an undercoating film forming process for the metal surface is performed on the joint surface with the counterpart component. As the metal coating, one having good adhesion to a magnesium-containing aluminum alloy and good wettability of the brazing material is a selection criterion, and nickel (Ni) is preferable as such a base metal, and nickel is preferable. Is preferably formed by electroless plating.
The thinner the base metal layer is, the more preferable it is. The thickness is at most about 10 microns, but it is as thin as several microns to 10 microns on the surface of a magnesium-containing aluminum alloy as a base material by electroless plating. It is possible to easily form a strong underlayer having a uniform thickness. The thickness of the nickel underlayer can be controlled by controlling the immersion time of the electroless plating solution. By forming a base layer of nickel on the joint surface of the magnesium-containing aluminum alloy, fluorine in the flux in the brazing material and magnesium in the magnesium-containing aluminum alloy are interrupted during brazing, and brazing is performed using nickel or the like. Since the flux is carried out on the base metal layer, the original function of the flux, which is the decomposition of oxides on the alloy surface by fluorine, is not impaired at all, and the brazing material is well wet on the nickel layer surface. The gap between the joint surfaces is instantaneously transmitted by capillary action, and the brazing material can be firmly adhered to the underlying metal layer by cooling. That is, in the present invention, the base metal layer is attached to the joining surface of the magnesium-containing aluminum alloy part, and the brazing material adheres to the base metal layer. In other words, the magnesium-containing aluminum alloy part is mediated by the base metal layer. This means that brazing is performed on the aluminum alloy part of the other party. Electroless plating is preferred as a method for forming the nickel layer, but an electroplating method can also be employed as long as a nickel coating as thin as several microns can be uniformly formed on the alloy surface. In addition, nickel is most preferable as the material of the base metal layer from the viewpoint that it can be formed to an extremely thin uniform thickness by electroless plating.However, as a metal other than nickel, chromium (Cr) or copper (Cu) or in some cases, Silver (Ag) and gold (Au) could also be used.

The metal coating such as nickel is formed on the joint surface of the magnesium-containing aluminum alloy. That is, when both components to be joined are magnesium-containing aluminum alloys, a metal coating such as nickel is formed on both joining surfaces. In addition, in the case of joining a magnesium-containing aluminum alloy and an aluminum alloy not containing magnesium, the formation of a metal coating such as nickel may be formed only on the joining surface of the magnesium-containing aluminum alloy, and the joining surface of the other party may be formed. No metal coating such as nickel is required.

As a brazing method, in-furnace brazing under a purge of an inert gas such as nitrogen (Nocoloc method of ALCAN, Canada) is preferred because of low cost and easy management and maintenance. That is, the magnesium-containing metal to be joined forms an extremely thin film of a metal such as nickel on the joining surface with the counterpart, and in this state, the joining surface is treated with a fluorine compound as a flux. As the processing of the brazing material, a paste brazing material obtained by kneading a powdery brazing material, a flux and a liquid binder may be applied, or a brazing sheet or a rod or a wire clad using a flux of a fluorine-based compound. A brazing filler metal may be applied to the joint surface. By replacing the inside of the furnace with nitrogen gas and heating the temperature of the aluminum alloy to be joined to a temperature higher than the melting point of the brazing material but lower than the melting point of the aluminum alloy, the brazing material is melted, and the molten brazing material is joined to the joining surface. The gap between them is instantaneously transmitted by the surface tension, and after being kept at that temperature for a certain period of time, the brazing material is solidified by lowering the furnace temperature, and the brazing is completed. When brazing,
The metal layer, such as nickel, on the surface of the magnesium-containing aluminum alloy blocks fluorine in the brazing filler metal flux from magnesium, so that the fluorine in the flux can effectively function to decompose oxides at the joint surface. it can. Therefore, since the oxide film on the surface is removed by the fluorine-containing flux, the wettability of the brazing material is improved, and good brazing can be performed. In addition,
In some cases, it is also possible to perform the brazing under vacuum instead of the brazing in a furnace with inert gas exchange.

[0022]

1 to 3 show a heat sink as an electronic component to be brazed according to an embodiment of the present invention, which has a size of 150 mm × 250 mm × 20 mm. The heat sink includes a main body 10 and a lid 12. The main body 10 has a meandering rib 14. The lid 12 is attached to the main body 10, and is fastened with screws 13 to allow a cooling medium to pass through the rib 14. Meandering passage 16 is formed. Meandering passage 1
6 is connected at one end to an inlet port 18 on the side of the main body, and at the other end to an outlet port 20 on the side of the main body.

The main body 10 and the lid 12 are made of wrought Al-MG-Si aluminum alloy JIS6061 (melting temperature range: 582).
652652 ° C.).

Next, electroless plating of nickel was performed on the surfaces of the main body 10 and the lid 12. After the pretreatment such as degreasing, the main body 10 and the lid 12 for electroless plating,
It was immersed in an electroless plating solution containing Ni and P as main components (sold by Nippon Kanigen Co., Ltd. under the trade name (registered trademark) of “Summer”). The immersion time was set so that a nickel plating layer having a predetermined thickness was obtained, whereby a nickel underlayer having a thickness of 7.0 μm was formed on the front surface including the interconnecting surfaces of the main body 10 and the lid 12.

After the formation of the nickel underlayer, the main body 10 and the lid 12 were brazed. The flux used was a fluorine-based compound having a product number of 30 from ALCOA, USA. And brazing material
It was JIS4047 (solid layer temperature = 577 ° C: liquid layer temperature = 580 ° C), which is a Ni-Si brazing material. The brazing filler metal is available in a powder state containing a fluorine-based flux (trade name: F12 or F19 of Nice Co., Ltd.). Applied. FIG. 3 shows a state before the main body 10 and the lid 12 are combined, and a paste brazing material is applied to the joint surface of the main body 10 with the lid 12 as shown by an arrow X. Combine with the main body and fasten with screws 13.

Then, the brazing operation was performed in a furnace at 600 ° C. in which the main body 10 and the lid body 12 were combined and replaced with nitrogen gas. The temperature at the joint between the main body 10 and the lid 12 rises to the melting point of the brazing material, and becomes a complete liquid layer. When held in this state for 10 to 20 minutes, the brazing material wets the joint surface between the main body 10 and the lid 12 under surface tension. Next, the heating of the product was stopped, and the brazing material was solidified by cooling to complete the brazing of the main body 10 and the lid 12.

With respect to the heat sink obtained by brazing the joint surface between the main body 10 and the lid 12 as described above, the nitrogen gas (N 2) is used as a pressurizing body from the inlet port 18 toward the closed outlet port 20. Was introduced under a pressure of 8 kg / cm2, and the presence or absence of gas leakage from the brazing surface was checked, but no leakage of nitrogen gas was recognized.

[Brief description of the drawings]

FIG. 1 is a plan view of a heat sink as a magnesium-containing aluminum alloy product according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line II of FIG. 1;

FIG. 3 is a view for explaining a brazing process of a main body and a lid of the heat sink of FIGS. 1 and 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Body 12 ... Lid 14 ... Rib 16 ... Meandering passage 18 ... Inlet port 20 ... Outlet port

Claims (5)

[Claims] 1. A method of brazing parts, at least one of which is made of a magnesium-containing aluminum alloy, with an aluminum alloy brazing material using a fluorine compound as a flux, comprising: Forming a metal layer having good adhesion to the alloy and good wettability of the brazing material on the bonding surface of the underlayer, and then performing brazing using the flux and the brazing material. Method. 2. The brazing method according to claim 1, wherein the metal constituting the underlayer on the joint surface of the magnesium-containing aluminum alloy component with the mating component is nickel. . 3. The brazing method according to claim 2, wherein electroless plating is performed to form a nickel underlayer on the surface of the magnesium-containing aluminum alloy. 4. A magnesium-containing aluminum alloy product obtained by brazing parts at least one of which is made of a magnesium-containing aluminum alloy with an aluminum alloy brazing material containing a fluorine compound as a flux. The aluminum alloy part has a base layer of a metal having good adhesion to the alloy and good wettability of the brazing material on a brazing joint surface with a counterpart part, and the magnesium-containing aluminum alloy part is preferably A magnesium-containing aluminum alloy product, which is brazed to a counterpart part through an underlayer metal layer. 5. The magnesium-containing aluminum alloy product according to claim 4, wherein the metal forming the underlayer is nickel.