JP2012061483A - Flux-less brazing method of aluminum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform flux-less brazing even in an internal space without requiring flux.SOLUTION: In this method, an AI-Si-based brazing material 3 containing, by mass, 3 to 13% of Si and 0.1 to 5.0% of Mg and a member 4 to be brazed are brought into contact with and adhere to each other, and brazing is performed in a non-oxide atmosphere not accompanying pressure reduction. Since the brazing is performed at the adhered face of a contact adhesion part by using the AI-Si-based brazing material 3 in a temperature range in which at least an actual temperature of AI-Si-based brazing material 3 reaches 400°C or higher while making the highest oxygen concentration in a brazing atmosphere not higher than 50 ppm, the flux-less brazing can stably be performed without requiring the flux, and favorable joining becomes possible even in a region such as the internal space of, for example, a heat exchanger.

Description

  The present invention relates to a fluxless brazing method of an aluminum material that can be brazed without using a flux.

Heat exchangers for automobiles, such as radiators and condensers, intercoolers, etc., and other heat exchangers and radiators manufactured from aluminum alloys, now use non-corrosive fluoride fluxes. The mainstream is a method of brazing or brazing under vacuum by adding about 0.5 to 1.5% by mass of Mg to the brazing material.
In the case of using the above-mentioned flux, most of the members to be brazed are processed by press molding or the like, and then put into a desired assembled state. Heat brazing in a non-oxidizing atmosphere such as In this case, there is a problem that the use of the flux itself, or the cost of installation and management of the coating process is required. In addition, it is known that a part of the flux evaporates during the brazing heating process and adheres to and accumulates on the inner wall of the furnace, and periodic furnace maintenance for removing the deposits also occurs as a necessary cost. . In recent years, with the promotion of weight reduction of automobiles, the heat exchangers for automobiles are also required to increase the thickness and strength of materials, and it is common to add Mg to aluminum alloys to increase the strength of aluminum materials. However, when brazing using a flux, Mg and the flux react to produce high melting point MgF ₂ , which may cause brazing inhibition or consume Mg in the material. However, there is a problem that the added Mg is not very useful for increasing the strength. That is, in flux brazing, there are limitations on the sites and amounts of Mg added in the product, and the current situation is that they cannot be actively used as a method for increasing the strength of materials.

  On the other hand, in vacuum brazing, Mg added to the brazing material evaporates from the material during the brazing temperature rising process, and at that time, the oxide film on the surface of the aluminum material, which is a brazing inhibiting factor, is destroyed, and in the atmosphere The atmosphere inside the furnace can be brazed by the getter action combined with moisture and oxygen. Although this method does not require the flux process control, there are problems that the vacuum furnace is an expensive facility and that the corresponding cost is required for the airtightness management of the furnace. In addition, in heat exchangers for automobiles, Zn is added for the purpose of ensuring the corrosion resistance of the product. However, there is a demerit that Zn is evaporated under vacuum heating, and sufficient Zn cannot be left in the product material. is there. Furthermore, since evaporated Mg and Zn accumulate on the inner wall of the furnace, periodic cleaning of the furnace is also required.

  On the other hand, fluxless brazing under atmospheric pressure has recently been proposed to solve the above problems. For example, Patent Document 1 proposes a method for brazing a lap joint of fluxless aluminum in the air by pulling out the metal plate from the pressure-bonded joint where a metal plate such as SUS is inserted after melting the brazing. However, in this technique, it is necessary to manage the drawing process of the metal plate, and there is a problem that the shape of the joint surface is limited.

  Patent Document 2 proposes a technique for performing fluxless brazing under a low oxygen concentration by covering a brazing object with a carbonaceous cover. However, this method has a problem that the process management of the cover is complicated.

  Patent Document 3 proposes a method in which Mg is added to a brazing material of a clad material, and the inner side of a heat exchanger tube formed of the clad material is fluxless brazed in an inert atmosphere under atmospheric pressure.

  Patent Document 4 proposes a technique in which the aluminum initial oxide film is reduced to 20 mm or less by pickling or the like, volatile oil is applied to suppress natural oxide film growth, and brazing is performed by the getter action of Mg.

  Patent Document 5 proposes a technique that secures brazability by providing an Mg diffusion delay layer outside the Mg-containing layer and gaining time for Mg to reach the aluminum surface.

JP-A-8-174207 JP 2007-44713 A Japanese Patent No. 4037477 Japanese Patent No. 3556827 Japanese Patent No. 3701847

However, Patent Documents 3 to 5 that enable brazing under atmospheric pressure without requiring a cover also have the following problems.
In the method proposed in Patent Document 3, a flux is used to join the outer surface of the tube and the fin, and there is a problem that the disadvantages of using the flux are not completely eliminated.
Furthermore, the method disclosed in Patent Document 4 has a problem that the process management of the acid cleaning becomes complicated and the cost for the acid cleaning process increases.
Moreover, in the technique proposed in Patent Document 5, it is necessary to prepare a clad material in which an anti-oxidation layer is provided on the surface of the brazing material with respect to the material used for the conventional vacuum brazing or nocolok brazing, which reduces the material cost. There is a problem of becoming higher. In addition, products targeted by this technology are limited to laminated shapes, and there is a problem that they are not versatile for all brazed products.

In addition, fluxless brazing enables joining by the reductive decomposition action of the Al oxide film (Al ₂ O ₃ ) by Mg added to the brazing material. Therefore, in order to obtain a stable joining state, it is essential to add Mg to the brazing material and the brazed member. However, when oxygen in the atmosphere reacts with Mg to form an Mg oxide film (MgO), the joining is remarkably performed. Since the state deteriorates, it is difficult to obtain a stable joint. Conventionally, it is possible to join by optimizing the component components and brazing conditions, as well as the shape of the joint, the oxide film thickness of the member and the distribution density of the film defects, but depending on the shape and atmosphere of the joint It is difficult to obtain a sufficient bonding state, and the bonding state may become unstable. In particular, when the gas exchange with the external atmosphere is insufficient in the joint portion of the internal space of the heat exchanger, the temperature rises with the oxygen concentration being high, so that a joint failure is likely to occur. Therefore, it is necessary to take measures such as reducing the line speed during brazing and reducing the oxygen concentration inside the heat exchanger, and there is a problem that it is difficult to achieve both the bonding state and productivity.

  In view of such problems, the present invention does not require a new material cost such as a flux coating process, a secondary material cost such as a cover used during brazing, and a material acid cleaning, and it depends on the shape of the heat exchanger or the like. It is an object of the present invention to provide a fluxless brazing method of an aluminum material capable of non-general purpose fluxless brazing.

  That is, among the fluxless brazing methods for aluminum materials of the present invention, the first present invention is Al-Si containing, by mass%, Si: 3 to 13%, Mg: 0.1 to 5.0%. A method of bringing a brazing filler metal and a brazing member into close contact with each other and brazing in a non-oxidizing atmosphere without reducing pressure, wherein at least the actual temperature of the Al-Si brazing filler metal is 400 ° C or higher. The brazing atmosphere is characterized in that the maximum oxygen concentration in the brazing atmosphere is 50 ppm or less and brazing is performed on the adhesion surface of the contact adhesion portion with the Al—Si brazing material.

  The fluxless brazing method for an aluminum material according to the second aspect of the present invention is the inert gas containing 0.1% or more by volume of reducing gas or reducing gas in the brazing atmosphere in the first aspect of the present invention. Is replaced with an atmospheric gas, and at least in the temperature range where the actual temperature of the Al—Si brazing material is 400 ° C. or more, the maximum oxygen concentration in the brazing atmosphere is 50 ppm or less. To do.

A fluxless brazing method for an aluminum material according to the third aspect of the present invention includes an Al-Si brazing material containing Si: 3 to 13% and Mg: 0.1 to 5.0% by mass% and brazing. A method of brazing in a non-oxidizing atmosphere by bringing a member into close contact with each other, wherein the brazing atmosphere is reduced to 1-10 ⁻³ torr in a temperature range of less than 400 ° C. before or during brazing heat addition. Introducing a reducing gas or an inert gas containing a reducing gas in a volume ratio of 0.1% or more to replace the atmosphere gas to form a non-oxidizing atmosphere without depressurization, and at least the Al—Si type brazing In the temperature range where the actual temperature of the material is 400 ° C. or higher, the maximum oxygen concentration is set to 50 ppm or less in a brazing atmosphere, and brazing is performed on the adhesion surface of the contact adhesion portion with the Al—Si brazing material. Features.

  A fluxless brazing method for an aluminum material according to a fourth aspect of the present invention is the method according to any one of the first to third aspects of the present invention, wherein the Al-Si brazing material is clad by a core material on the outermost surface of the brazing sheet. It is located, The said core material and the said to-be-brazed member are joined by the said brazing, It is characterized by the above-mentioned.

  A fluxless brazing method for an aluminum material according to a fifth aspect of the present invention is the method according to any one of the first to third aspects, wherein the Al-Si brazing material is in the form of a sheet, It is arrange | positioned on both sides and the said to-be-brazed members are joined by the said brazing, It is characterized by the above-mentioned.

  Below, the reason for limitation of the component etc. which are prescribed | regulated by this invention is demonstrated below. In addition, each component amount is shown by mass%.

1. Brazing material In the present invention, a brazing material based on an Al-Si alloy is used, and Si and Mg are contained as essential components at the following contents.

Si: 3 to 13%
Si, when contained in Al, is a basic element that lowers its melting point and melts at a brazing temperature to form a predetermined joint. The appropriate content range that functions as a wax is 3 to 13%. 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 Erosion is significantly accelerated. The more preferable lower limit of the Si content is 6%, and the upper limit is 12%.
In addition, 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. That is, even if the oxide film on the surface of the aluminum material becomes a thick film during the brazing heat treatment, the brazing material oozes out from the periphery of the intermetallic compound, and the destruction and fragmentation of the oxide film proceeds from this site, Since the wettability of the molten solder is improved, a more stable joined state can be obtained.

Mg: 0.1-5.0%
Mg reduces and decomposes a dense aluminum oxide film (A1 ₂ 0 ₃ ) formed on the surface of the material during the heat of brazing, and has the effect of improving the bondability and the wettability of the braze. In the present invention, the Mg content for obtaining sufficient bonding is 0.1 to 5.0%. If the content is less than 0.1%, the effect of the present invention is not obtained by the effect of destroying the oxide film on the joint surface during brazing. If the content exceeds 5.0%, the effect is saturated and the workability of the aluminum material is difficult. Arise.
In the present invention, brazing properties can be ensured only by the oxide film breaking activity in the above Mg component range, but further, the Mg content is optimized and the effect of lowering the solidus temperature of the Al—Si—Mg brazing material is utilized. If this is the case, excellent brazing properties can be exhibited. The optimum Mg content in this case varies depending on the Si content. For example, when the Si content is 6 to 12%, the Mg content is preferably 0.75 to 1.5%. If it is this range, the melting | fusing point fall of solder | brazing | wax will fully be obtained and it will become possible to obtain a more favorable brazing property by the synergistic effect with the oxide film destruction effect by Mg. Specifically, brazing can be performed at the lowest solidus temperature of 559 ° C. or higher with an Al—Si—Mg alloy.

  The brazing filler metal of the present invention may contain the above Si and Mg, and the others may be Al and inevitable impurities, and may contain other components as long as the effects of the above Si and Mg are not impaired. May be. Below, the other component contained depending on necessity is demonstrated.

Zn: 0.1 to 5.0%
Zn has the effect of lowering the potential of the brazing material and improving the corrosion resistance of the brazing sheet or the like by the sacrificial anode effect, so it is contained in the brazing material as desired. The Zn content is preferably 0.1 to 5.0%. If it is less than 0.1%, the potential hardly changes, so that a sufficient corrosion resistance improving effect cannot be obtained. If it exceeds 5.0%, the corrosion rate increases remarkably. In addition, the more preferable minimum of Zn content is 0.5%, and an upper limit is 3.0%. Even when Zn is not actively added, the Zn may be contained as an inevitable impurity in an amount of less than 0.1%.

Furthermore, in the present invention, it is preferable that an intermetallic compound or Si particles exist on the surface of the brazing material. Usually, a dense oxide film such as Al ₂ O ₃ is present on the surface of the aluminum material, and this further grows and becomes a thick film in the brazing heat treatment process. As the thickness of the oxide film increases, the tendency to inhibit the destruction of the oxide film becomes stronger. However, the presence of intermetallic compounds and Si particles on the brazing filler metal surface suppresses the growth of a dense oxide film of aluminum at the same site. A defect portion of the oxide film is generated. In other words, even if the oxide film on the surface of the aluminum material becomes thick during brazing heat treatment, the brazing material oozes out from the periphery of the intermetallic compound and Si particles, and the oxide film is broken or divided starting from this site. Since the wettability of the molten solder is improved, a more stable joined state can be obtained.
Therefore, in the present invention, if desired, one or more of Fe, Ni, and Mn are added to the brazing material, and Al—Fe, Al—Ni, Al—Mn, Al—Fe— (Mn, Ni), and Al— are added. A large number of Si- (Fe, Ni, Mn) -based intermetallic compounds are generated, the growth of the oxide film at the same site is suppressed, and the defect portion of the oxide film is formed, so that the joining rate can be remarkably improved.

Fe: 0.5 to 1.5%
The content of Fe is desirably 0.5 to 1.5%. If it is less than 0.5%, the amount of intermetallic compound produced is too small to obtain the above-mentioned effects sufficiently. On the other hand, if it exceeds 1.5%, the casting and rolling properties are remarkably lowered, and the corrosion of the brazing material is further reduced. Speed increases and corrosion resistance decreases. Note that the more preferable lower limit of the Fe content is more than 0.5%, and the upper limit is 1.0%.

Ni: 0.1 to 1.0%
The Ni content is preferably 0.1 to 1.0%. If the amount is less than 0.1%, the amount of intermetallic compound produced is too small to obtain a sufficient effect. If the amount exceeds 1.0%, the corrosion rate of the brazing material is remarkably increased and the corrosion resistance is lowered. In addition, the more preferable lower limit of Ni content is 0.3%, and the upper limit is 0.5%.

Mn: 0.3 to 1.7%
The Mn content is desirably 0.3 to 1.7%. If it is less than 0.3%, the production amount of intermetallic compounds is too small to obtain a sufficient effect, and if it exceeds 1.7%, the castability is lowered and the production becomes difficult. Note that the more preferable lower limit of the Mn content is 0.7%, and the upper limit is 1.5%.

Be: 0.0001 to 0.1%
Be suppresses the growth of an oxide film formed on the surface of the molten brazing during brazing, and a good bonding state can be obtained even when the oxygen concentration in the atmosphere is high. For this reason, the content of 0.0001% or more is necessary, and if the content is less than the lower limit, the above-described effect cannot be obtained sufficiently. On the other hand, if the upper limit is exceeded, the effect is saturated and the material cost is increased, so the content of Be is set in the above range. For the same reason, it is desirable that the lower limit is 0.002% and the upper limit is 0.01%.

Sr: 0.005 to 0.1%
Sr makes the brazing filler metal Si particles fine, uniformly disperses defective portions of the oxide film, and improves the stability of the bonding, so is contained as desired. If the Sr content is less than the lower limit, the effect is insufficient, while if the content exceeds the upper limit, the effect is saturated. Furthermore, if the upper limit is exceeded, a giant intermetallic compound is produced, and moldability and mold wear resistance are reduced.

Bi: 0.01-0.5%
Bi improves the wettability of the molten wax, and is therefore contained as desired. If the Bi content is less than the lower limit, the effect is insufficient. On the other hand, if the Bi content exceeds the upper limit, the effect is saturated and the material cost is increased.

Ca: 0.05 to 1.0%
Ca reduces and decomposes the Mg oxide film and improves the bonding state in brazing, so Ca is contained as desired. If it is less than the lower limit, the effect is insufficient. On the other hand, if the upper limit is exceeded, the oxidation of Ca is promoted and the bonding rate is lowered. For the same reason, it is desirable that the lower limit is 0.1% and the upper limit is 0.7%.

2. Material of Brazed Member Any generally used aluminum alloy can be used as the brazed member without any problem, and the present invention is not limited to a specific one. The brazing member may be clad with a brazing material, and the brazing member may be a bare member with no brazing material on the surface. The two brazed members that sandwich the brazing material sheet may be made of the same material, or may be made of different materials.

3. Initial oxide film thickness of brazing material and brazed member In carrying out the present invention, since it is not necessary to produce a material that suppresses the initial oxide film on the surface of the material in particular, it can usually be produced as a mass production coil material of aluminum. An aluminum material having an initial oxide film thickness of about 20 to 500 mm can be used. If it is less than 20 mm, acid cleaning or the like as shown in the prior art is necessary, and if it exceeds 500 mm, the oxide film destruction action by Mg cannot be sufficiently obtained, and it becomes difficult to obtain a good bonding state.

4). In-furnace atmosphere In carrying out the present invention, the atmosphere in the furnace is changed to a non-oxidizing gas such as an inert gas or a reducing gas, thereby reducing the oxygen concentration and dew point in the atmosphere and It is necessary to suppress oxidation. The type of replacement gas to be used is not particularly limited in obtaining bonding, but from the viewpoint of cost, nitrogen, argon, and hydrogen, ammonia, and carbon monoxide are used as the inert gas and the reducing gas, respectively. Is preferred. It is necessary to control the oxygen concentration in the atmosphere, and at least in the temperature range where the actual temperature of the Al—Si brazing material is 400 ° C. or higher, the maximum oxygen concentration in the brazing atmosphere needs to be 50 ppm or lower. . Therefore, in the temperature range below 400 ° C., the oxygen concentration is not necessarily required to be 50 ppm or less, and may be, for example, 500 ppm or less. If the oxygen concentration in the brazing atmosphere exceeds 50 ppm in a temperature range of 400 ° C. or higher, poor bonding is likely to occur in the heat exchanger internal space. Not enough. In the temperature range of 400 ° C. or higher, 3 ppm may be set as the lower limit. Even if it is less than 3 ppm, there is no problem in joining, but there is a concern that the manufacturing cost will increase, such as using a large amount of gas for the management of the atmosphere. In addition, you may make oxygen concentration 50 ppm or less in the temperature range below 400 degreeC.
Further, if the atmosphere is at least 400 ° C. and is not accompanied by reduced pressure, the evaporation of Mg and Zn from the aluminum material hardly occurs, and there is an advantage that the furnace wall and the like are not contaminated.
Here, the actual temperature of the Al—Si brazing material refers to the actual temperature of the brazing sheet or the brazing material single sheet. Therefore, the case where the temperature of the Al—Si brazing material does not reach the temperature even if the temperature of the atmosphere reaches the temperature does not reach the actual temperature here.

In order to reduce the oxygen concentration to 50 ppm or less, a method of purging the atmospheric gas by introducing a reducing gas or an inert gas into the brazing atmosphere as described above can be employed. In addition, when using an inert gas, what contains 0.1% or more of reducing gas by volume ratio is desirable. By containing 0.1% or more of reducing gas, oxygen and water vapor in the atmosphere are reduced, and it is possible to reduce the oxygen concentration and dew point significantly in a short time to a low oxygen concentration. In some cases, brazing time can be shortened, and productivity is remarkably improved. If the reducing gas is less than 0.1%, the effect is hardly obtained. In other words, the inert gas expels and replaces the original atmospheric gas, whereas the reducing gas has the effect of reducing the oxygen concentration more actively by reducing the oxygen and water vapor in the atmosphere. There is.
The purge is desirably performed in a temperature range below 400 ° C. in order to manage the oxygen concentration in a temperature range of 400 ° C. or higher.
In addition, the brazing atmosphere can be evacuated prior to the purge. By this evacuation, the oxygen concentration of the brazing atmosphere in the internal space of the heat exchanger where gas replacement is difficult to be performed can be surely reduced. The vacuuming is preferably adjusted to a pressure of 1 to 10 ⁻³ torr. If it is less than 10 ⁻³ torr, it takes time to evacuate, so that the productivity is lowered. If it exceeds 1 torr, the effect of lowering the oxygen concentration due to reduced pressure is hardly obtained.

5. Brazing temperature In the present invention, brazing can be performed at the lowest solidus temperature of 559 ° C. or higher of a brazing material sheet made of an Al—Si—Mg alloy. Ranges can also be used. Specifically, 559-620 degreeC is good. If it is less than 559 degreeC, the melting | fusing of a brazing cannot be obtained and brazing cannot be obtained. If it exceeds 620 ° C., the wax erosion becomes prominent, and there is a problem in maintaining the product shape. However, even in this temperature range, if the solidus temperature is low due to the alloy composition of the brazing, brazing erosion may become prominent. In this case, the brazing temperature suitable for the alloy composition within this temperature range. Is preferably selected.

As described above, according to the fluxless brazing method for aluminum material of the present invention, the Al—Si brazing containing Si: 3 to 13% and Mg: 0.1 to 5.0% in mass%. A method in which a brazing member and a brazing member are brought into contact and intimate contact, and brazing in a non-oxidizing atmosphere without decompression, at least in a temperature range where the actual temperature of the Al-Si brazing material is 400 ° C or higher, Since the maximum oxygen concentration in the brazing atmosphere is 50 ppm or less and brazing is performed on the adhesion surface of the contact adhesion portion with the Al-Si brazing material, flux-less brazing that does not require flux is possible, which is conventionally In addition, a stable joined state can be obtained easily and reliably.
Therefore, stable bonding can be performed even in the internal space of the heat exchanger, and there is an effect that both the bonding state and productivity can be achieved.

It is the schematic which shows the state before brazing in one Embodiment of this invention.

An embodiment of the present invention in which an Al—Si brazing material is clad will be described below.
An Al—Si brazing material containing 0.1 to 5.0% Mg and 3 to 13% Si and a core material can be manufactured by a conventional method, and both or a sacrificial material. Clad rolling with other materials. The production conditions in the clad rolling are not particularly limited.
Further, the cladding ratio of each layer is not specified as the present invention.
As the core material, Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, Mn: 0.2 to 2.5%, Cu: 0.05 to One containing 1.0%, Si: 0.1-1.2%, Fe: 0.1-1.0%, or Si: 0.1-1.2%, Mg: 0.01-2 0.0%, and further contains one or more of Mn: 0.2-2.5%, Cu: 0.05-1.0%, Fe: 0.1-1.0% Further, if desired, those containing one or more of Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, etc. Is desirable.

As shown in FIG. 1, the aluminum clad material 1 has the Al—Si brazing material 3 clad on one or both sides of the core material 2 positioned on the outermost surface, and an initial oxide film thickness of 20 to 500 mm. A film is formed.
The aluminum clad material 1 is assembled so that the Al-Si brazing material 3 is in close contact with a brazed member 4 such as a bare fin or a solid material connector, and preferably constitutes a heat exchanger assembly or the like. To do. Note that aluminum members having various compositions can be used as the member to be brazed, and the present invention is not limited to a specific one.

The assembly is placed in a heating furnace. The inside of the heating furnace (brazing atmosphere) is a non-oxidizing atmosphere during the brazing addition heat. The non-oxidizing atmosphere is configured using an inert gas such as nitrogen or argon, a reducing gas such as hydrogen, ammonia or carbon monoxide, or a mixed gas thereof.
The non-oxidizing atmosphere is generated by introducing a reducing gas or an inert gas containing a reducing gas into the heating furnace and purging the atmosphere gas. Thereby, in a brazing atmosphere, oxygen concentration is managed to 50 ppm or less. In addition, you may make it perform the process of pressure-reducing the inside of a heating furnace to 1-10 < ^-3 > torr prior to purge.
In the heating furnace, the purge is performed before or during the temperature increase, and in the temperature region where the actual temperature of the Al—Si brazing filler metal 3 is 400 ° C. or higher, the oxygen concentration is surely 50 ppm or lower.
Although the heating furnace may have a sealed space, the present invention does not require the heating furnace to be sealed, and may have a brazing material carry-in port and a carry-out port. Even in such a heating furnace, a non-oxidizing atmosphere is maintained by continuing to blow reducing gas or inert gas into the furnace. It brazes by heating at 559-620 degreeC under the said atmosphere. In brazing, the contact adhesion portion 5 between the core material 2 and the member to be brazed 4 is satisfactorily joined without flux in the internal space of the heat exchanger.
In the above description, the Al—Si brazing material has been described as being clad on the core material, but the brazing material may be used in the form of a sheet and sandwiched between brazed members. Good.

Al— of the composition (residual Al and unavoidable impurities) shown in Tables 1 to 4 on both surfaces of the core material composed of Al—0.5Mg—0.5Si—1.0Mn—0.5Cu (remainder Al and unavoidable impurities) An aluminum clad material clad with a Si brazing material was prepared.
For the aluminum clad material, various composition brazing materials were finished with a brazing material clad rate of 10% and a tempered H14 equivalent tempered thickness of 0.5 mm.
Also, as a member to be brazed, fin material of H14 aluminum bare material (0.3 mm thickness for inner fin and 0.06 mm thickness for outer fin) made of Al-1.0Mn-0.15Cu-0.5Mg Two types were prepared.

Brazing property A flat ERW tube having a width of 30 mm is manufactured using the above aluminum clad material, and a corrugated fin of a bare material composed of Al-1.0Mn-0.15Cu-0.5Mg is used as an inner fin in the tube. The core was formed by combining outer fins of the same composition on the outside of the tube. The core was a 15-stage tube with a length of 300 mm, and a header plate and a tank, both having openings, were integrally brazed on both sides.
The core was heated to 600 ° C. in a brazing furnace using various gases while reducing the oxygen concentration in the atmosphere, and then cooled to room temperature.
For the brazing property, the joining ratios of the outer fin and the inner fin were determined by the following formulas, and the superiority or inferiority was evaluated by the joining ratio. The results are shown in Tables 1 to 4.
Fin joint ratio (%) = (total brazing length of fin and tube / total contact length of fin and tube) × 100

Oxygen concentration in the atmosphere The oxygen concentration in the atmosphere during the brazing heat treatment was continuously measured with an oxygen concentration meter, and the maximum oxygen concentration in the furnace at 400 ° C. or higher was measured. The results are shown in Tables 1 to 4.

  In the example, both the outer fin and the inner fin showed good brazing properties, whereas in the comparative example, sufficient bonding could not be obtained.

  As described above, the present invention has been described based on the above-described embodiment and examples. However, the present invention is not limited to the above description, and can be appropriately changed without departing from the scope of the present invention.

1 Aluminum clad material 2 Core material 3 Al-Si brazing material 4 Brazed member

Claims (5)

  Al-Si brazing material containing Si: 3 to 13% and Mg: 0.1 to 5.0% in mass% is brought into contact and close contact with the brazed member in a non-oxidizing atmosphere without pressure reduction. A method of brazing, wherein at least in the temperature range where the actual temperature of the Al—Si brazing material is 400 ° C. or more, the maximum oxygen concentration in the brazing atmosphere is 50 ppm or less, and the Al—Si brazing material is used. A fluxless brazing method for an aluminum material, characterized in that brazing is performed on the adhesion surface of the contact adhesion portion.   An inert gas containing 0.1% or more by volume of reducing gas or reducing gas is introduced into the brazing atmosphere to replace the atmosphere gas, and at least the actual temperature of the Al—Si brazing material is 400. 2. The fluxless brazing method for an aluminum material according to claim 1, wherein the maximum oxygen concentration in the brazing atmosphere is set to 50 ppm or less in the temperature range where the temperature is equal to or higher than 5 ° C. 3. A method of brazing in a non-oxidizing atmosphere by bringing an Al—Si brazing material containing 3% to 13% Si and Mg: 0.1% to 5.0% in mass% into contact with a brazed member. And after reducing the pressure to 1 to 10 ⁻³ torr in a temperature range of less than 400 ° C. before the brazing addition heat or at the time of the brazing addition heat, 0.1% by volume of reducing gas or reducing gas in the brazing atmosphere. At least in the above temperature range where the actual temperature of the Al—Si brazing material is 400 ° C. or higher, an inert gas containing at least% is introduced to replace the atmospheric gas to form a non-oxidizing atmosphere without decompression. A fluxless brazing method for an aluminum material, characterized in that brazing is performed on the adhesion surface of the contact adhesion portion with the Al-Si brazing material at a maximum oxygen concentration of 50 ppm or less in a brazing atmosphere.   The Al-Si brazing material is clad on a core material and located on the outermost surface of a brazing sheet, and the core material and the brazed member are joined by the brazing. The fluxless brazing method for an aluminum material according to any one of claims 1 to 3. The Al-Si brazing material is in a sheet form, is disposed between brazing materials, and joins the brazing materials by brazing. 4. A fluxless brazing method for an aluminum material according to any one of 3 above.

Images