JP2016179494A - Aluminum material brazing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize appropriate brazing using an Al-Si-Mg base brazing material during brazing.SOLUTION: A method of brazing aluminum materials with each other by using a cladding material obtained by bonding an Al-Si-Mg brazing material containing, by mass%, 0.2-3.0% of Mg and 3-12% of Si to an aluminum alloy core material, in which an organic resin consisting only of C, H, and O is interposed at least in a bonded portion between the Al-Si-Mg based brazing material and the aluminum bonded member before brazing, and a surface of the bonded portion is protected from the atmosphere with a carbide film obtained by the organic resin as a barrier during brazing heating.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for brazing an aluminum material using an Al-Si-Mg brazing material.

Currently, in the brazing field including automotive heat exchangers, the construction method using nocolok flux is the mainstream, but Mg-added aluminum alloys that are effective in increasing the thickness and strength of the flux are the flux deactivation reactions. There is a problem that it cannot be used due to (formation of MgF ₂ ).
On the other hand, fluxless (no flux) brazing method has been proposed in consideration of mass productivity, but special surface treatment, material specifications, brazing method, etc. have been adopted. There are problems with cost and quality stability, and it has not yet been put into practical use.
On the other hand, in Patent Document 1, a fluxless method using an Al—Si—Mg alloy brazing material is proposed.

Japanese Patent No. 4547032

  However, even in Patent Document 1, the fillet forming ability of the joint does not have an advantage over the conventional nocolock flux, and it is necessary to limit the applied product shape in order to obtain stable mass production quality. . With such a background, it is strongly desired to develop a brazing method that can use an Mg-added aluminum alloy that is effective for increasing the thickness and strength, and that has a fillet forming ability equal to or higher than that of the conventional Nocolok brazing method. Is the situation.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a brazing method for an aluminum material that can be satisfactorily brazed using an Al—Si—Mg brazing material.

That is, in the brazing method for an aluminum material according to the present invention, the first embodiment is an Al—Si—Mg based brazing material containing 0.2 to 3.0% Mg and 3 to 12% Si in mass%. Is a method of brazing aluminum materials using a clad material bonded to an aluminum alloy core material,
At least at the joint between the Al—Si—Mg-based brazing material and the aluminum member to be joined, an organic resin consisting only of C, H, O is interposed before brazing, and is obtained by the organic resin at the time of brazing addition heat. It is characterized by using a carbide film to barrier the surface of the joint from the atmosphere and not using a flux for removing oxides.

In another aspect of the invention of the brazing method for an aluminum material, in the present invention of the above aspect, the organic resin is interposed in the joint in an amount of 0.1 to 5 g / m ² with a number average molecular weight of 300 to 60,000. It is characterized by that.

  Another form of the invention of the brazing method for an aluminum material is characterized in that, in the present invention of the above form, the carbide film evaporates before reaching the melting point of the brazing material in the brazing temperature rising process.

  In another aspect of the invention of the brazing method for an aluminum material, the organic resin is an epoxy resin, a mixture of an epoxy resin and another resin, or an epoxy group or an epoxy ring. It is characterized by being a resin.

  In another aspect of the invention of the brazing method for an aluminum material, in the present invention of the above form, the Al-Si-Mg-based brazing material contains 0.02 to 0.3% Bi in mass%. Features.

  Next, the contents defined in the present invention will be described. In addition, all component amounts are shown in mass%.

<Brazing material>
Si: 3 to 12%
When Si is contained in Al, its melting point is lowered, and a molten brazing material necessary for joining is generated at a temperature equal to or higher than the eutectic temperature at the time of brazing temperature rise. Further, on the Si particles existing on the surface of the brazing material, the growth of a dense oxide film of aluminum is suppressed, and a defective portion of the oxide film is generated. If the Si content is less than 3%, these effects cannot be obtained sufficiently. If the Si content exceeds 12%, the brazing filler metal strength becomes too high and the rollability deteriorates, making it impossible to produce a clad rolled material. . For this reason, it is preferable that content of Si shall be 3 to 12%. For the same reason, the Si content is more preferably set to a lower limit of 5.0% and an upper limit of 11.0%.

Mg: 0.2-3.0%
Mg acts on a dense oxide film (A1 ₂ O ₃ film) generated on the surface of the material in the brazing temperature rising process to decompose the oxide film, thereby improving the wettability and fluidity of the brazing. However, if the Mg content is less than 0.2%, the oxide film cannot be sufficiently decomposed. If it exceeds 3.0%, the brazing filler metal strength becomes too high and the rollability deteriorates, and the clad rolling It becomes difficult to produce the material. Further, since MgO grows thick and the decomposition action of the oxide film is lowered, the wettability of the molten braze is lowered, and it becomes difficult to obtain sufficient bonding. For this reason, the content of Mg is preferably 0.2 to 3.0%. For the same reason, the Mg content is more preferably 0.25% for the lower limit and 2.0% for the upper limit.

Bi: 0.02-0.3%
Bi has a lower melting point due to coexistence with Mg, and exudation of wax occurs from a low temperature. Oxide film breaks up and breaks away from this site, improving the wettability of the molten wax and making it more stable. Since it becomes possible to obtain the joined state, it is contained if desired. In order to acquire the said effect | action, content of 0.02% or more is desirable, and an effect will become inadequate if it contains less than 0.02%. On the other hand, when it contains exceeding 0.3%, the rolling property of a brazing material will fall. For these reasons, the Bi content is preferably within the above range. For the same reason, it is more desirable to set the lower limit to 0.05% and the upper limit to 0.2%.

<Organic resin type>
The organic resin is composed only of C, H, and O, can form a carbide film during brazing heating, and can inhibit the growth of an oxide film on the surface of the aluminum material or the brazing material. In the present invention, the type of the organic resin is not limited, and any organic resin may be used as long as the object can be achieved. For example, an epoxy resin, a mixture of an epoxy resin and another resin, or a resin in which an epoxy group or an epoxy ring is polymerized is exemplified. Excellent paintability and economy by using epoxy resin.
<Molecular resin molecular weight>
The organic molecular weight is not limited in the present invention, but the number average molecular weight is preferably 300 to 60000.
If the number average molecular weight is less than 300, it decomposes and evaporates early in the brazing temperature rising process and the oxide film growth inhibiting action becomes insufficient. If the number average molecular weight exceeds 60,000, a residue is generated after the brazing material is melted. Impairs wet spread.
More preferably, the lower limit is 1000 and the upper limit is 10,000.
<Organic resin content>
Organic resin interposed amount is not particularly restricted but the present invention, the range of 0.1g ^{/ m 2} ~5g ^/ m 2 is desirable. If the intervening amount is 0.1 g / m ² , it decomposes and disappears early in the brazing temperature rising process, and the oxide film growth inhibiting action is insufficient, and if it is 5 g / m ² or more, a residue is generated after melting the brazing material. Impairs the wet spread of wax.
For the same reason, it is more desirable that the lower limit is 0.2 g / m ² and the upper limit is 3.0 g / m ² .

<Atmosphere>
Although the present invention can be brazed in the atmosphere, it is desirable to perform brazing in a non-oxidizing atmosphere such as an inert gas without reducing pressure or a reducing gas in order to further stabilize the joining state. The type of replacement gas to be used is not particularly limited in obtaining the joining of the aluminum material, but from the viewpoint of cost, the inert gas is nitrogen, argon, the reducing gas is hydrogen, ammonia, monoxide. It is preferred to use carbon. The oxygen concentration management range in the atmosphere is desirably 50 ppm or less. If it exceeds 50 ppm, the reoxidation of the brazing target member tends to proceed.

<Material of brazing target member>
As a brazing target member other than the brazing material, any commonly used aluminum material can be used without any problem.

  According to the present invention, the presence of an organic resin barriers the material surface to a high temperature range, suppresses the growth of the oxide film, and has an effect of obtaining good brazing properties without inhibiting the flow of the molten solder. .

It is the schematic which shows the state before brazing in one Embodiment of this invention. It is a figure which shows the brazing evaluation model in the Example of this invention.

Hereinafter, an embodiment of the present invention will be described.
As an aluminum alloy for brazing filler metal, it contains Mg: 0.2 to 3.0%, Si: 3 to 12% by mass, and optionally contains Bi: 0.02 to 0.3%, and the balance. Is prepared to a composition comprising Al and inevitable impurities. Moreover, as an aluminum alloy for core materials, it is 1 in mass%, Mn: 0.2-2.5%, Cu: 0.05-1.0%, Si: 0.1-1.2%, for example It contains seeds or two or more species, and the balance is prepared to be composed of Al and inevitable impurities.

Hot rolling and cold rolling are performed to obtain a clad material in which a brazing material is superposed on one or both surfaces of the core material and joined.
By passing through the said process, the aluminum alloy brazing sheet 1 for heat exchangers in which the aluminum alloy brazing material 3 was clad on one surface of the aluminum alloy core material 2 is obtained.
The aluminum alloy brazing sheet 1 can be used as a heat exchanger tube, header, tank, or the like.

  On the other hand, as the brazing object member 4, for example, an aluminum alloy containing Mg: 0.1 to 0.8% and Si: 0.1 to 1.2% by mass, with the balance being Al and inevitable impurities And processed into an appropriate shape.

In the aluminum alloy brazing sheet 1, the aluminum alloy brazing material 3 is located on the outermost surface, the average film thickness of the surface oxide film is 15 nm or less, and the average film thickness of the MgO film in the surface oxide film is 2 nm or less. Has been adjusted.
Moreover, the brazing object member 5 is adjusted so that the average film thickness of the surface oxide film is 15 nm or less and the MgO film thickness in the film is 2 nm or less at least on the bonding surface.
The surface oxide film can be adjusted by temperature and time during various heat treatments such as homogenization after casting, soaking before hot rolling, and annealing after cold rolling.

  The aluminum alloy brazing sheet 1 and the brazing target member 4 are disposed such that the aluminum alloy brazing material 3 is interposed between the aluminum alloy core material 2 and the brazing target member 4. An organic resin layer 5 made of an organic resin is formed thereon. These are assembled into an aluminum alloy assembly for brazing. As a result, the organic resin layer 5 is interposed at least at the junction. The organic resin layer 5 can be formed by coating, for example. The application may be performed on the surface of the aluminum alloy brazing material 3, may be performed on the surface of the brazing target member 4, or may be performed on both. As a coating method, the coating method is not particularly limited, and a spray method, a shower method, a flow coater method, a roll coater method, a brush coating method, a dipping method, and the like can be appropriately employed.

  The assembly is disposed in the heating furnace in the atmosphere or in a non-oxidizing atmosphere without decompression. The non-oxidizing atmosphere can be configured using an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen, ammonia or carbon monoxide, or a mixed gas thereof. The non-oxidizing atmosphere is not at reduced pressure during brazing heating and is usually at atmospheric pressure. In addition, before obtaining a non-oxidizing atmosphere, you may include a pressure reduction process for the purpose of substitution. The heating furnace does not need to have a sealed space, and may have a brazing material carry-in port and a carry-out port. Even in such a heating furnace, the non-oxidizing property is maintained by continuously blowing the inert gas into the furnace. The non-oxidizing atmosphere preferably has an oxygen concentration of 50 ppm or less by volume.

Under the above atmosphere, for example, heating is performed at a heating rate of 10 to 200 ° C./min, and heating is performed at 560 to 620 ° C. to perform brazing.
Under the brazing conditions, the thermal decomposition completion temperature of the organic coating becomes 400 ° C to 560 ° C, so that the material surface is barriered to a high temperature range to suppress the growth of the oxide film, but the Al-Si-Mg brazing material is melted. At this time, since there is almost no carbide residue, good brazing can be performed without hindering the flow of the molten solder.
In the above embodiment, the aluminum alloy core material and the aluminum alloy brazing material are clad and joined to the brazing target member. However, the brazing is performed by placing the aluminum alloy brazing material between the brazing target members. It is also possible to join.

Examples of the present invention will be described below.
The aluminum material which clad the Al-Si-Mg type | system | group brazing material of the composition shown in Table 1 and 2 (the remainder is Al and an unavoidable impurity) and the JIS A3003 aluminum alloy was prepared.
As the aluminum clad material, various composition brazing materials were made to have a clad rate of 10% and finished to a 0.25 mm tempered equivalent to H14. Further, a JIS A 3005 alloy, H14 aluminum bare material (0.1 mm thick) fin material was prepared as a brazing target member.
A tube 12 having a width of 20 mm is manufactured using the aluminum clad material, and the tube and the corrugated fin 11 are combined to form a core 10 having 15 stages of tubes and a length of 300 mm as shown in FIG. 2 as a brazing evaluation model. . At that time, the composition shown in Table 2 was applied at the application amount shown in Table 3 to at least the joint portion between the tube 12 and the fin 11. The said core which apply | coated the composition was heated to 560-600 degreeC in the brazing furnace in nitrogen atmosphere (oxygen content 50ppm), and the brazing state was evaluated.

○ Brazing property / joining rate The joining rate was calculated by the following formula, and the superiority or inferiority of each sample was evaluated.
Fin joint ratio = (total brazing length of fin and tube / total contact length of fin and tube) x 100 (%)
The determination was made according to the following criteria, and the results are shown in Table 3.
Fin joint ratio after brazing ◎: 95% or more, ○: 90% or more, Δ: 80% or more, ×: less than 80%

-Residue after brazing The residue after brazing was visually evaluated according to the following criteria.
○: No residue was found △: Sensitive residue was found (dotted in several places)
X: The residue was clearly recognized (present on almost the entire coated area)
While all of the examples showed good brazing properties, the comparative example did not provide sufficient bonding.

DESCRIPTION OF SYMBOLS 1 Aluminum clad material 2 Core material 3 Al-Mg-Si type brazing material 4 Brazing object member 5 Organic resin layer 10 Core 11 Corrugated fin 12 Tube

Claims (5)

Aluminum materials are brazed to each other using a clad material in which an Al-Si-Mg brazing material containing 0.2 to 3.0% Mg and 3 to 12% Si is bonded to an aluminum alloy core material. A way to
At least at the joint between the Al—Si—Mg-based brazing material and the aluminum member to be joined, an organic resin consisting only of C, H, O is interposed before brazing, and is obtained by the organic resin at the time of brazing addition heat. A method for brazing an aluminum material, characterized in that a carbide film is used to barrier the surface of the joint from the atmosphere and no flux is used to remove oxides. Wherein the organic resin as the number average molecular weight from 300 to 60,000, brazing method of the aluminum material according to claim 1, wherein the interposing said joint in an amount of 0.1-5 g / ^{m 2.}   3. The aluminum material brazing method according to claim 1, wherein the carbide film evaporates before reaching a melting point of the brazing material in a brazing temperature rising process.   The organic resin is an epoxy resin, a mixture of an epoxy resin and another resin, or a resin in which an epoxy group or an epoxy ring is polymerized. Method of brazing aluminum material.   The brazing of an aluminum material according to any one of claims 1 to 4, wherein the Al-Si-Mg-based brazing material contains 0.02 to 0.3% Bi by mass%. Method.

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