JP2013111634A - Method of brazing aluminum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of brazing aluminum material having excellent fillet forming ability equal to or higher than a conventional brazing method using a fluoride flux and capable of using a bonded member consisting of an Mg added aluminum alloy effective for thinning and strength enhancement.SOLUTION: In the method of brazing aluminum material of bonding a brazed member 4 consisting of the aluminum material by brazing it with an Al-Mg-Si based brazing filler metal 3 containing Mg of 0.2-5.0% and Si of 3-13% in mass%, the excellent fillet forming ability is obtained by performing brazing with the Al-Mg-Si based brazing filler metal 3 by arranging a composition 5 containing a silicon compound which is liquefied at normal temperature at least on a bonded part surface 4a of the brazed member 4, and use of the bonded member consisting of an Mg added aluminum alloy effective for thinning and strength enhancement is allowed by not using the fluoride flux.

Description

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

  In brazing fields such as automotive heat exchangers, brazing is currently performed using a non-corrosive fluoride-based flux such as Nocolok (registered trademark) flux in an inert gas atmosphere such as nitrogen gas. Or, a method of adding 0.5 to 1.5% by mass of Mg to the brazing material and brazing in a vacuum atmosphere has become the mainstream.

However, in the construction method using the above-described fluoride-based flux, when an Mg-added aluminum alloy effective for increasing the strength of the thin wall is used for a member to be joined, MgF ₂ is caused by the reaction between the fluoride-based flux and Mg in the alloy. As a result, the flux is inactivated, and as a result, there is a problem that the brazing property is remarkably lowered.

On the other hand, a fluxless brazing method that is performed under atmospheric pressure in consideration of mass productivity is also being developed. However, these fluxless brazing methods employ special methods such as surface treatment, material specifications, and brazing method, and many have problems in cost and quality stability. For this reason, the fluxless brazing method performed under atmospheric pressure has not yet been put into practical use.
In order to solve the problem of the above fluxless brazing method, Patent Document 1 includes decompression without generating equipment introduction costs and process costs by keeping the amount of Mg added to the brazing material within an appropriate range. Methods have been proposed that allow brazing without the use of flux under no atmosphere.

Japanese Patent No. 4547032

  However, in the brazing method described in Patent Document 1, the fillet forming ability at the brazed joint is not as high as that obtained by the conventional brazing method using a fluoride-based flux. For this reason, in order to obtain the stable mass-production quality, there exists a problem that it is necessary to limit a junction part shape.

  The present invention has been made against the background of the above circumstances, and has an excellent fillet forming ability equivalent to or better than a brazing method using a conventional fluoride flux, and is effective in increasing the thickness and strength of an aluminum-added aluminum alloy It aims at providing the brazing method of the aluminum material which can use the to-be-joined member which consists of.

  That is, among the brazing methods of the aluminum material of the present invention, the first present invention is an Al—Mg—Si based brazing containing 0.2 to 5.0% Mg and 3 to 13% Si by mass%. An aluminum material brazing method for brazing and joining a member to be joined made of an aluminum material with a material, wherein a composition containing a silicon compound that is liquid at normal temperature is disposed at least on the surface of the joined portion of the member to be joined. And brazing with the Al—Mg—Si brazing material.

According to the first aspect of the present invention, the composition containing the silicon compound that is liquid at room temperature is disposed on at least the surface of the joint portion of the member to be joined before brazing. It becomes a film that covers the surface of the member while causing thermal decomposition, and functions as an antioxidant film that suppresses oxidation of the surface of the member, which is a brazing inhibiting element. On the other hand, by adding Mg to the brazing material, the decomposition action of the member surface oxide film by Mg can be obtained.
Here, in the brazing temperature rising process when Mg is not added to the brazing material, the member oxidation suppression effect by the silicon compound at room temperature and the member surface due to the difference in thermal expansion between the material and the oxide film in the temperature rising process Cracking of the oxide film occurs, and the new surface of the member generated in the cracked part exhibits brazing wettability, resulting in brazing. Depending on the shape of the part, the wettability is insufficient and good bonding cannot be obtained. However, when Mg is added to the brazing material, the decomposition action of the member surface oxide film by Mg is added here, so that the brazing wettability of the member surface is improved and a good joining state can be obtained regardless of the shape of the applied joint portion. Become.
Furthermore, since the silicon compound is a liquid at room temperature, process management is easy, and since it does not become a fluoride-based residue after brazing, uniform surface treatment can be obtained, and a flux removal process is not required. In addition to the silicon compound that is liquid at room temperature, the composition may contain an organic resin binder (for example, an acrylic resin-based or urethane-based binder), a surfactant, and the like in order to improve paintability. Moreover, as a solvent at the time of coating, it is sufficient if compatibility with the liquid silicon compound used at normal temperature is obtained. For example, an organic solvent such as ethanol or methanol, water, or the like may be used. Moreover, the coating process may use a drying process for fixing the coating film on the surface of the member. The drying conditions are not particularly limited, but appropriate drying conditions may be used depending on the silicon compound used. For example, the conditions are such that the atmosphere is maintained in a drying furnace at about 200 ° C. for 3 minutes.
In the Mg-added Al—Si brazing material used in the present invention, it is sufficient that Mg is added, and other general impurity element concentrations are not particularly limited. In addition, the Al—Mg—Si brazing material may contain Zn in an amount of 0.1 to 5.0% by mass.

Furthermore, the brazing method of the first aspect of the present invention is performed without using a fluoride-based flux without using a flux.
According to the first aspect of the present invention, by not using the fluoride flux, the flux inactivation due to the reaction between the fluoride flux and Mg in the aluminum alloy does not become a problem. Therefore, it is possible to use a member made of an Mg-added aluminum alloy that is effective for increasing the thickness and strength of the member to be joined, and meet the demand for future strength enhancement in the market.
In addition, as a to-be-joined member, it is not limited to what consists of said Mg addition aluminum alloy, A various aluminum material can be used.

  The method for brazing an aluminum material according to a second aspect of the present invention is characterized in that, in the first aspect of the present invention, the silicon compound is composed of one compound or a mixture of two or more selected from inorganic or organic compounds. .

  A brazing method for an aluminum material according to a third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the silicon compound is an organosilane compound.

  The brazing method for an aluminum material according to a fourth aspect of the present invention is characterized in that, in the third aspect of the present invention, the organosilane compound is a silane coupling agent.

  The aluminum material brazing method of the fifth aspect of the present invention is characterized in that, in any of the first to fourth aspects of the present invention, the composition containing the silicon compound contains sulfur.

  A brazing method for an aluminum material according to a sixth aspect of the present invention is characterized in that, in the fifth aspect of the present invention, the sulfur is supplied by a sulfur-containing silane coupling agent.

  The aluminum material brazing method according to a seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects of the present invention, the joining member is made of an Mg-added aluminum alloy.

  Hereinafter, the reasons for limitation in the present invention will be described. In addition, each component amount is shown by mass%.

1. Al—Mg—Si brazing material In the present invention, an Al—Mg—Si brazing material containing 0.2 to 5.0% Mg and 3 to 13% Si by mass is used as the brazing material. Note that the balance of the Al—Mg—Si brazing material can be made of Al and inevitable impurities. The action of each element in the Al—Mg—Si brazing filler metal and the reasons for limitation are as follows.

Mg: 0.2-5.0%
If the Mg content is less than 0.2%, the oxide film destruction effect on the brazed joint surface cannot be sufficiently obtained, and if it exceeds 5.0%, the effect is saturated and the workability of the aluminum material is difficult. . For this reason, Mg content shall be the said range.
The present technology using a composition containing a liquid silicon compound at room temperature can be brazed with fillet forming ability even when an Al—Si brazing material not containing Mg is used, but as in the present invention. By using a brazing material to which Mg is added, the aluminum surface oxide film destruction action by Mg becomes an auxiliary action, and a brazing state having better fillet forming ability is obtained.

Si: 3 to 13%
The content of Si is set to 3 to 13% as a proper content range that functions as a wax. If it is less than 3%, sufficient fluidity cannot be obtained because the amount of liquid phase produced is insufficient, and if it exceeds 13%, the primary crystal Si rapidly increases and the workability deteriorates and the brazing of the joint during brazing This is because erosion is remarkably accelerated.

2. Composition containing a silicon compound that is liquid at normal temperature By disposing a silicon compound on the object to be brazed before brazing, it functions as an antioxidant film that covers the surface of the aluminum material while causing thermal decomposition during the brazing heat treatment process. To do. 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.
In addition, by using a liquid composition at room temperature, non-uniformity due to powder scattering into the work environment, powder particle size variation and aggregation caused by the use of powder powder at room temperature There is no problem with the application state.
Among silicon compounds, organosilane compounds are desirable, and among organosilane compounds, a silane coupling agent is more desirable.
In addition, since the organosilane compound does not become a fluoride-based residue after brazing, uniform surface treatment is obtained, and a flux removal step is not required. In addition to the silicon compound that is liquid at room temperature, the composition may contain an organic resin binder (for example, an acrylic resin-based or urethane-based binder), a surfactant, and the like in order to improve paintability. Moreover, as a solvent at the time of coating, it is sufficient if compatibility with the liquid silicon compound used at normal temperature is obtained. For example, an organic solvent such as ethanol or methanol, water, or the like may be used. Moreover, the coating process may use a drying process for fixing the coating film on the surface of the member. The drying conditions are not particularly limited, but appropriate drying conditions may be used depending on the silicon compound used. For example, the conditions are such that the atmosphere is maintained in a drying furnace at about 200 ° C. for 3 minutes.

3. Silane coupling agent 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 substrate), while the organic functional group that is the terminal group is an organic substance (such as an acrylic resin binder). Join. Therefore, when using a coating composition containing an organic binder, a silicon compound is evenly distributed on the surface of the member due to the coating uniformity of the organic binder, and a coating film having excellent handling properties and excellent adhesion can be obtained. Further, this distribution uniformity enables more stable joining by brazing. Examples of the silane coupling agent include dimethyldimethoxysilane, vinyltriethoxysilane, and 3-aminopropyltriethoxysilane.

4). Sulfur In the present invention, it is not essential to contain sulfur in a composition containing a silicon compound. However, when sulfur is added to the composition, the thermal decomposability of the composition is improved, which may cause a problem in appearance. It is possible to reduce the residue after attaching.
Also, sulfur can be added to the composition in any manner, but can be supplied by, for example, a sulfur-containing silane coupling agent. Examples of the sulfur-containing silane coupling agent include bis (triethoxysilylpropyl) tetrasulfide.

According to the method for brazing an aluminum material of the present invention, a composition containing a silicon compound that is liquid at room temperature is disposed on at least the surface of the bonded portion of the member to be bonded before brazing. Oxide film growth on the surface of the joint is suppressed, and further, an oxide film decomposition action by Mg added to the brazing material is added, so that a new surface appears on the material surface, and brazing using a conventional fluoride flux is performed. It becomes possible to obtain a joining state equivalent to or better than the method.
Further, according to the brazing method of the aluminum material of the present invention, the fact that the flux inactivation due to the reaction between the fluoride flux and Mg in the aluminum alloy becomes a problem by not using the fluoride flux. Therefore, it is possible to use a member made of an Mg-added aluminum alloy that is effective for increasing the thickness and strength of the member to be joined, and to meet future demands for increasing the strength of the wall in the market.

It is the schematic which shows the state before brazing in one Embodiment of this invention. (A) is the brazing evaluation model in this invention, (b) is a figure which shows the evaluation position about a junction part width | variety.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
In the brazing method of the present invention, an Al—Mg—Si brazing material containing 0.2 to 5.0% Mg and 3 to 13% Si by mass% is used. The Al—Mg—Si brazing material 3 and the core material 2 having the above composition range are overlapped and clad and rolled by a conventional method to obtain an aluminum clad material 1. The composition of the core material and the cladding rate are not particularly limited as the present invention.

  The aluminum clad material 1 is assembled so as to be in contact with the member to be brazed 4. At that time, a composition 5 containing a silicon compound that is liquid at room temperature is disposed on at least the joint surface 4a of the brazed member 4 in advance. The distribution method is not particularly limited as the present invention, and can be performed by coating, spraying, dipping, or other appropriate methods. Further, the region where the composition 5 containing the silicon compound is disposed may be at least a joint region with the member to be brazed, such as a range beyond the joint region (for example, the entire surface of the brazed member 4 or the like). ), Or only the joint surface 4a. In this example, the composition 5 is applied to the entire surface of the aluminum clad material 1. Moreover, in this example, the composition 5 is comprised only with the silane coupling agent.

The assembly is placed in a heating furnace and subjected to brazing. The atmosphere in brazing is not particularly limited, and an air atmosphere, an inert atmosphere, or the like can be selected. The heating temperature at the time of brazing is set to an appropriate temperature according to the type of brazing material.
In addition, as a brazing member, aluminum materials having various compositions can be used, and the present invention is not limited to a specific one. For example, an Mg-added aluminum alloy effective for increasing the thickness and strength Materials can be used.
The aluminum material joined by the brazing is satisfactorily brazed.

Examples of the present invention will be described below.
An aluminum clad material in which an Al—Mg—Si brazing material having the composition shown in Table 1 (the balance is Al and inevitable impurities) and a core material of JIS A3003 was clad was prepared. The aluminum clad material was made of various composition brazing materials with a clad rate of 10%, and finished to a thickness of 0.25 mm with a temper equivalent to H14.
Further, a corrugated fin 7 obtained by corrugating a fin of an aluminum bare material (0.1 mm thickness) tempered to JIS A3005 alloy and H14 was prepared as a member to be brazed.

  A tube 8 having a width of 20 mm is manufactured using the aluminum clad material, and the tube 8 and the corrugated fin 7 are combined. As a brazing evaluation model, a tube having 15 steps and a length of 300 mm as shown in FIG. It was set as the core 6. At that time, the composition shown in Table 2 was applied to at least the joint portion between the tube 8 and the fin 7. At this time, a combination of methyl methacrylate as a binder and polyoxyalkylene alkyl ether as an activator was also evaluated.

  The core 6 coated with the composition was heated to 560 to 600 ° C. in a brazing furnace in a nitrogen atmosphere (oxygen content 50 ppm), and the brazing state was evaluated.

(1) Joining rate Joining rate was calculated | required by following Formula and the superiority or inferiority of the brazing property between each sample was evaluated.
Fin joint ratio (%) = (total brazing length of fin 7 and tube 8 / total contact length of fin 7 and tube 8) × 100
Those having a fin joint ratio after brazing of 95% or more were evaluated as ◎, those having 85% or more and less than 95% were evaluated as ○, and those having less than 85% were evaluated as ×, and the evaluation results are shown in Table 3.

(2) Joint width evaluation In order to confirm the improvement of fillet forming ability in the brazed joint, the joint width was evaluated. The width W of the joint portion between the fillet 9 and the tube 8 shown in FIG. 2B was measured for each sample at 20 points, and the superiority or inferiority of the brazed joint state was evaluated with the average value.
Those having a joint width of 0.7 mm or more were evaluated as “○”, and those having a joint width of less than 0.7 mm were evaluated as “×”.

(3) Surface treatment property A paint for forming an acrylic resin-based hydrophilic coating film was applied by dip coating to the brazed product obtained by brazing. After coating and drying, a part was cut out, and the amount of carbon on the surface was subjected to mapping analysis by EPMA (electron beam microanalysis) to confirm the adhesion state of the hydrophilic coating film. A site where the carbon content of the analysis site was 15% or more was judged as a hydrophilic coating film forming portion, and the adhesion area with respect to the analysis area was determined. Those having an adhesion rate of 95% or more were evaluated as “◎”, those having an adhesion rate of 90% or more and less than 95% were evaluated as “、”, and those having an adhesion rate of less than 90% were evaluated as “X”.

  As is clear from Table 3, all of the examples of the present invention showed good brazing properties, whereas the comparative example did not have sufficient fillet forming ability.

DESCRIPTION OF SYMBOLS 1 Aluminum clad material 2 Core material 3 Al-Mg-Si type | system | group brazing material 4 Brazed member 4a Joint surface 5 Composition containing a silicon compound 6 Core 7 Corrugated fin 8 Tube 9 Fillet W Joint width

Claims (7)

  Brazing of an aluminum material to be joined by brazing a joining member made of an aluminum material with an Al-Mg-Si brazing material containing 0.2 to 5.0% Mg and 3 to 13% Si in mass% A method comprising the steps of: brazing with an Al-Mg-Si brazing material by disposing a composition containing a silicon compound that is liquid at room temperature on at least the surface of the joint portion of the member to be joined. Brazing method of material.   The method for brazing an aluminum material according to claim 1, wherein the silicon compound is composed of one compound selected from inorganic or organic compounds or a mixture of two or more.   The method for brazing an aluminum material according to claim 1 or 2, wherein the silicon compound is an organosilane compound.   4. The method for brazing an aluminum material according to claim 3, wherein the organosilane compound is a silane coupling agent.   The method for brazing an aluminum material according to claim 1, wherein the composition containing the silicon compound contains sulfur.   The method for brazing an aluminum material according to claim 5, wherein the sulfur is supplied by a sulfur-containing silane coupling agent.   The said joining member consists of Mg addition aluminum alloys, The brazing method of the aluminum material in any one of Claims 1-6 characterized by the above-mentioned.

Images