JP2017018959A - Brazing method of aluminum alloy member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brazing method of an aluminum alloy member capable of performing excellent brazing using an Mg-added aluminum alloy.SOLUTION: In a brazing method of an aluminum alloy member, an Al-Mg-Si-based brazing filler metal containing, by mass%, 0.2-3.0% Mg and 3-12% Si and the aluminum alloy member containing 0.1-0.8% Mg are used. A coating film is produced by a paint blended with a silane coupling agent and a water-soluble modified silicone oil at a junction of the aluminum alloy member and a member to be jointed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for brazing an aluminum alloy member.

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 (production of Mg fluoride, etc.) On the other hand, fluxless brazing performed under atmospheric pressure in consideration of mass productivity has been devised, but special surface treatment, material specifications, brazing method, etc. are adopted, and there are problems with cost and quality stability There is no real practical use. Further, in Patent Document 1, a fluxless method using an Al—Si—Mg alloy brazing material has been proposed. However, in Patent Document 1, the fillet forming ability of the joint is in contrast to the conventional Nocolok flux. In order to obtain stable mass production quality, it is necessary to limit the applied product shape. 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. .

  The present inventors have shown in Patent Document 2 that the Mg-added aluminum alloy can be satisfactorily brazed by disposing a silicon compound that is liquid at room temperature on the surface of the joint in Japanese Patent Application Laid-Open No. 2003-133620. In this technology, brown or grayish black residue is generated on the surface of the product after brazing, but it has been shown that the residue can be reduced by adding a compound containing sulfur to the paint.

Japanese Patent No. 4547032 JP 2013-111634 A

  However, the addition of a sulfur compound according to Patent Document 2 increases the cost of the coating film, and sulfur oxide generated by thermal decomposition during brazing becomes a problem in terms of working environment and natural environment, and is desirable as a measure for reducing residues. Absent.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide an aluminum alloy member brazing method that can effectively reduce residues and has no environmental problems.

The present inventors consider that by arranging the silane coupling agent coating film very thin and evenly on the surface of the joint, it is possible to eliminate good brazing properties, drastically reduce residues, and solve environmental problems, and examine the method. did. Silane coupling agents are made into paints using water or alcohol as a solvent after hydrolysis, but when they are applied very thinly and uniformly on an aluminum material, parts that are not applied due to repelling are generated, so a uniform coating film is obtained. I can't. The application wettability is improved by adding a surfactant or an organic resin binder to the paint, but the wettability is insufficient when an extremely thin film of about 0.01 g / m ² is formed. Addition of a large amount of surfactant, etc. improves coating wettability, but it cannot be used because residues such as surfactants deteriorate the wetting and spreading properties of the molten braze and the appearance quality after brazing. .

  The inventors of the present invention have found that coating wettability is dramatically improved by blending a specific silicone with a silane coupling agent, and an extremely thin and uniform coating film can be formed. By forming a film, the entire joint surface is barriered from the atmosphere, and growth of the oxide film during brazing is suppressed, so that the decomposition action of the oxide film by Mg added to the material is increased, and excellent wettability of the molten solder It has been found that it can be obtained, and the present invention has been completed.

  That is, among the aluminum alloy member brazing methods of the present invention, the invention of the first embodiment is Al-Mg-Si containing 0.2 to 3.0% Mg and 3 to 12% Si in mass%. Using a brazing filler metal and an aluminum alloy member containing 0.1 to 0.8% Mg by mass, at least at the joint between the aluminum alloy member and the member to be joined, a silane coupling agent and water-soluble A coating film is provided by a paint blended with a modified silicone oil.

The invention of the aluminum alloy member brazing method of the second aspect is characterized in that, in the invention of the above aspect, the amount of the coating film is 0.001 to 0.2 g / m ² .

  The invention of the aluminum alloy member brazing method of the third aspect is characterized in that, in the invention of the above aspect, the HLB value of the water-soluble modified silicone oil is 5 or more.

  The invention of the aluminum alloy member brazing method of the fourth aspect is characterized in that, in the invention of the above aspect, the water-soluble modified silicone oil is a side chain type polyether-modified silicone oil.

  The fifth aspect of the invention of the aluminum alloy member brazing method is characterized in that, in the aspect of the invention, the water-soluble modified silicone oil is an epoxy / polyether-modified silicone oil.

  The invention of the aluminum alloy member brazing method of the sixth aspect is characterized in that, in the invention of the above aspect, the blending ratio of the water-soluble modified silicone oil in the paint is 10% or less by mass%.

  The seventh aspect of the invention of the aluminum alloy member brazing method is characterized in that, in the invention of the above aspect, the blending ratio of the water-soluble modified silicone oil in the paint is 2 to 5% by mass. .

  An eighth aspect of the invention of the aluminum alloy member brazing method is characterized in that, in the aspect of the invention, the silane coupling agent includes an epoxy silane coupling agent.

  According to the ninth aspect of the invention of the aluminum alloy member brazing method, in the invention of the above aspect, the brazing material and / or the aluminum alloy member further contains 0.02 to 0.3% Bi by mass%. It is characterized by containing.

  Below, the technical matter prescribed | regulated by this invention is demonstrated. In addition, when showing component content, all are shown by the mass%.

Al—Mg—Si brazing material Mg: 0.2 to 3.0%
Mg exhibits an oxide film destruction effect on the brazed joint surface and improves the brazeability, but if it is less than 0.2%, the oxide film destruction effect on the brazed joint surface cannot be sufficiently obtained, If the content exceeds 3.0%, the effect is saturated and the workability of the aluminum material becomes difficult, so the content is limited to the above range. For the same reason, it is desirable that the lower limit is 0.8% and the upper limit is 2.0%.

Si: 3 to 12%
The appropriate content range that functions as a brazing material is 3 to 12%. If it is less than 3%, sufficient fluidity cannot be obtained because the amount of liquid phase produced is insufficient, and if it exceeds 12%, the primary crystal Si increases rapidly and the workability deteriorates, and the brazing of the joint at the time of brazing Erosion is significantly accelerated.

Bi: 0.02-0.3%
Bi is contained in an amount of 0.02 to 0.3% as desired in order to improve the wettability by lowering the surface tension of the molten brazing filler metal. If the content is less than 0.02%, a sufficient effect cannot be obtained. If the content exceeds 0.3%, Bi that cannot be dissolved dissolves on the material surface during hot rolling or annealing (271 ° C. or more), and the material This is not preferable because it causes a reduction in surface quality of the surface. For the same reason, it is more desirable to set the lower limit to 0.05% and the upper limit to 0.2%.

Aluminum alloy member Mg: 0.1 to 0.8%
Mg is contained because it has the effect of improving the material strength. Moreover, it reacts with Si diffused from the brazing material during the brazing heat and forms Mg ₂ Si that improves the material strength. Furthermore, the effect of decomposing the oxide film reacts with the aluminum alloy member itself Al ₂ O ₃ oxide film can be obtained. If the amount is less than the lower limit, the effect is insufficient, and if the upper limit is exceeded, the melting point is lowered. Further, when mixed with Si diffused from the brazing material, the melting point is greatly lowered, so that it is susceptible to wax erosion.

Bi: 0.02-0.3%
Since Bi reduces the surface tension of the molten brazing material by diffusing into the brazing material, it improves the wet-spreading property of the molten brazing material. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, Bi, which cannot be solid-dissolved, dissolves on the surface of the material during hot rolling or annealing (271 ° C. or more), which is not preferable. For the same reason, it is more desirable to set the lower limit to 0.05% and the upper limit to 0.2%.

Silane coupling agent An anti-oxidation film that covers the aluminum material surface while causing thermal decomposition during the brazing heat treatment process by forming a coating film at least at the joint before brazing with a paint using a silane coupling agent. Function as. Thereby, the brazing wettability is ensured because the oxide film on the surface of the aluminum material is easily decomposed and divided in the process of raising the temperature of brazing.

  The alkoxy group that causes a dehydration condensation reaction at the terminal group of the silane coupling agent is bonded to the inorganic substance (aluminum base material), while the organic functional group that is the terminal group is bonded to the organic substance (such as an acrylic resin binder). In addition, the distribution uniformity enables more stable joining by brazing. Examples of the silane coupling agent include dimethyldimethoxysilane, vinyltriethoxysilane, and 3-aminopropyltriethoxysilane.

Water-soluble modified silicone oil By adding water-soluble modified silicone oil to the hydrolyzed silane coupling agent solution, wettability by silicone is imparted, so that the wettability of the paint is improved. The wettability is low only with the silane coupling agent solution, and a thin and uniform coating film of 0.1 g / m ² or less cannot be formed on the material before brazing. The oxide film easily grows and it is difficult to obtain the destruction of the oxide film. As a result, the wetting and spreading of the molten solder is hindered, so that the brazing property is lowered. On the other hand, by forming a thin and uniform coating film by blending silicone, the growth of the oxide film is suppressed in the entire joining portion and the oxide film is easily destroyed, so that it is possible to ensure good brazing properties. Examples of the water-soluble silicone to be blended include side chain type polyether-modified silicone and epoxy / polyether-modified silicone.
The blending ratio is desirably 2% or more and 10% or less by mass ratio with respect to the paint. If it is less than 2%, the effect of improving wettability cannot be obtained, and if it is 10% or more, the brazing property and the appearance quality of the brazed product are deteriorated, causing a residue. Furthermore, the upper limit is desirably 5%.
In addition, the water-soluble modified silicone oil preferably has an HLB (Hydrophile-Lipophile Balance) value of 5 or more. When the HLB is less than 5, the coating property improving effect is insufficient.

Coating amount: 0.001 to 0.2 g / m ²
The amount of the coating film is preferably 0.001 to 0.2 g / m ² at least in the region of the coating film at the joint. If the amount is less than 0.001 g / m ² , the effect of suppressing oxidation is insufficient, and if it exceeds 0.2 g / m ² , the residue may impair the appearance of the product, or the flow of molten solder may be inhibited to inhibit fillet formation. Therefore, the above range is determined. For the same reason, it is desirable that the lower limit is 0.002 g / m ² and the upper limit is 0.1 g / m ² .

<Atmosphere>
In the present invention, it is desirable to perform brazing in a non-oxidizing atmosphere such as an inert gas or a reducing gas without reducing the pressure. 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 brazed member tends to proceed.
However, the present invention is not limited to a specific atmosphere.

<Members to be joined>
Any commonly used aluminum material can be used without any problem as a member to be brazed to the aluminum alloy member. In order to further stabilize the bonding state, it is desirable to use an aluminum material containing a predetermined amount of Mg or Bi. In addition, when the brazing material is supplied by the brazing sheet, Mg and Bi contained in the brazing material contribute to the joining, so that the core material of the brazing sheet has a stable joining state even if it does not contain Mg or Bi. can get.

  That is, according to the present invention, the growth of the oxide film on the surface of the joint portion is suppressed during the brazing heat treatment process, and further, a new surface appears on the surface of the material by adding an oxide film decomposition action by Mg added to the brazing material. As a result, it is possible to obtain a joining state equivalent to or higher than that of the conventional brazing method using a fluoride-based flux, and it is possible to reduce the residue and perform an operation with no environmental problems.

It is a figure which shows the state before brazing and the state after 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 contains Mg: 0.1-0.8% by mass%, and it prepares in the composition which remainder consists of Al and an unavoidable impurity.
In addition, the brazing material may additionally contain Fe, Cu, Mn, Ca, Li, Be, etc., and the aluminum alloy for the core material may additionally include Si, Cu, Mn, Fe, Mg, Bi etc. may be contained.

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, as shown in FIG. 1, 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 core material 2 corresponds to the aluminum alloy member of the present invention.
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. The brazing target member 4 corresponds to a member to be joined according to the present invention.

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. It is desirable to be adjusted to.
Moreover, as for the brazing object member 4, it is desirable that the average film thickness of the surface oxide film is adjusted to 15 nm or less and the MgO film thickness in the film is adjusted to 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 arranged such that the aluminum alloy brazing material 3 is interposed between the aluminum alloy core material 2 and the brazing target member. A coating film 5 containing a paint containing a silane coupling agent and a water-soluble modified silicone oil is formed. These are assembled into an aluminum alloy assembly for brazing. Thereby, the coating film 5 intervenes at least at the joint. The coating film 5 can be formed by application, 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. Application | coating is performed with respect to the junction part 6 at least. There is no problem in performing application beyond the joint 6.

  The assembly is disposed in a heating furnace that has a non-oxidizing atmosphere without reducing pressure. 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 590 to 610 ° C. to perform brazing.
Under brazing conditions, the coating film functions as a film up to about 400 ° C. and suppresses the growth of the oxide film, but when the Al—Si—Mg brazing material melts, it almost decomposes and leaves no residue. Good brazing can be performed without hindering the flow of the molten solder.
The above effect is that before the Al-Si-Mg brazing material is melted, the bonded portion is shielded from the atmosphere by the surface treatment agent and the growth of the oxide film is suppressed. It is thought that it was realized because it was not decomposed by the melting of Mg contained in the material and the joining member so as not to inhibit the flow of the molten solder.
Further, it is not necessary to use a fluoride-based flux for removing oxides, and the flux inactivation and residue due to the reaction between the fluoride-based flux and Mg in the aluminum alloy do not become a problem.

  In the above embodiment, the aluminum alloy core material and the aluminum alloy brazing material are clad and joined to the brazing member. However, a plate material made of an aluminum alloy brazing material is arranged between the brazing members. It is also possible to make joints.

The aluminum material which clad the Al-Si-Mg type | system | group brazing material of the composition shown in Table 1 (the remainder Al and an unavoidable impurity) and the core material of JISA3003 was prepared.
As the aluminum clad material, various composition brazing materials were made to have a clad rate of 10% and finished to a thickness of 0.25 mm with a temper equivalent to H14. Moreover, the corrugated fin 12 of the aluminum bear material (0.1 mm thickness) of JISA3005 alloy and H14 was prepared as a brazing object member.

  A tube 11 having a width of 20 mm is manufactured using the aluminum clad material, and the tube 11 and the corrugated fin 12 are combined. As a brazing evaluation model, a 15-stage tube having a length of 300 mm as shown in FIG. It was set to 10. At that time, the composition shown in Table 2 was applied to at least the joint between the tube and the fin. The said core which apply | coated the composition was heated to 600 degreeC in the brazing furnace in nitrogen atmosphere (oxygen content 50ppm), and the brazing state was evaluated.

O Brazing property and joining rate The joining rate was calculated | required with the following formula and the superiority / inferiority between each sample was evaluated.
Fin joint rate = (total brazing length of fin and tube / total contact length of fin and tube) × 100
The determination was made according to the following criteria, and the results are shown in Tables 3 and 4.
Fin joint ratio after brazing ◎: 98% or more, ○: 90% or more and less than 98%, Δ: 80% or more and less than 90%, ×: less than 80%

-Joint width evaluation The brazed joint state is not limited to the above-mentioned joint ratio, but in order to confirm the improvement of fillet forming ability, which is the object of the present invention, the width W of the joint part 13 as shown in FIG. 20 points were measured for each sample, and superiority or inferiority was evaluated based on the average value. The determination is based on the following criteria and shown in Tables 3 and 4.
A: 0.8 mm or more, B: 0.7 mm or more and less than 0.8 mm, Δ: 0.6 mm or more and less than 0.7 mm, X: less than 0.6 mm All the examples showed good brazing properties. On the other hand, in the comparative example, sufficient joining was not obtained.

  As described above, the present invention has been described based on the above-described embodiments and examples, but these can be appropriately changed without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Aluminum clad material 2 Core material 3 Al-Mg-Si type | system | group brazing material 4 Brazing member 5 Paint film 6 Joint part 10 Core 11 Corrugated fin 12 Tube

Claims (9)

  Al-Mg-Si brazing material containing 0.2 to 3.0% Mg and 3 to 12% Si in mass%, and aluminum containing 0.1 to 0.8% Mg in mass% An aluminum alloy characterized in that a coating film is provided by using a paint in which a silane coupling agent and a water-soluble modified silicone oil are blended at least in a joint portion between the aluminum alloy member and the member to be joined. Member brazing method. The aluminum alloy member brazing method according to claim 1, wherein the amount of the coating film is 0.001 to 0.2 g / m ² .   The aluminum alloy member brazing method according to claim 1 or 2, wherein the water-soluble modified silicone oil has an HLB value of 5 or more.   The aluminum alloy member brazing method according to claim 1, wherein the water-soluble modified silicone oil is a side chain type polyether-modified silicone oil.   3. The aluminum alloy member brazing method according to claim 1, wherein the water-soluble modified silicone oil is an epoxy / polyether-modified silicone oil.   The aluminum alloy member brazing method according to claim 1, wherein a blending ratio of the water-soluble modified silicone oil in the paint is 10% or less by mass%.   The aluminum alloy member brazing method according to any one of claims 1 to 6, wherein a blending ratio of the water-soluble modified silicone oil in the paint is 2 to 5% by mass.   The said silane coupling agent contains an epoxy-type silane coupling agent, The aluminum alloy member brazing method of any one of Claims 1-7 characterized by the above-mentioned.   The aluminum according to any one of claims 1 to 8, wherein the brazing material and / or the aluminum alloy member further contains 0.02 to 0.3% Bi by mass%. Alloy member brazing method.

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