JP2014073519A - Aluminum brazing sheet and blazing method using the same - Google Patents

Abstract

An aluminum brazing sheet for adding Mg to a constituent material of a brazing sheet and brazing without using a flux in an inert gas atmosphere, and a brazing method using the brazing sheet.
One or both surfaces of an aluminum core material are clad with an Al—Si brazing material, and the surface of the brazing material after the brazing heat is applied to a region of 10% or more of the total surface area of the brazing material. In an inert gas atmosphere furnace controlled to an oxygen concentration of 10 ppm or less and a dew point of −35 ° C. or less, from 540 ° C. to 570 ° C. for 3 minutes or more and less than 45 minutes. Then, the temperature is raised to 580 to 615 ° C. and brazing is performed.
[Selection figure] None

Description

  The present invention relates to an aluminum brazing sheet, in particular, an aluminum brazing sheet in which a core material or a brazing material contains Mg, and a brazing method using the brazing sheet. Hereinafter, aluminum includes an aluminum alloy.

  Brazing joining is widely used as a joining method for parts having many fine joints such as aluminum heat exchangers and machine parts. In order to braze and join aluminum, it is essential to break the oxide film covering the material surface and bring the molten brazing material into contact with the base material or the molten brazing material. The method of brazing by breaking the oxide film is roughly divided into a method of brazing using flux and a method of brazing without flux by heating in vacuum, both of which have been put into practical use. .

  Regarding the method of using the flux, the method of using a chloride-based flux was initially performed, but in order to maintain the corrosion resistance, it is necessary to remove the flux residue after brazing. Most of the methods switched to the joining method in nitrogen gas using the fluoride-based flux. Currently, the vast majority of automotive heat exchangers are brazed using fluoride-based fluxes. However, brazing with a fluoride-based flux has a problem that it cannot be applied to parts such as food, medical, and electronic equipment because the flux residue remains after brazing. There has also been a problem of clogging due to flux residues.

  For brazing without flux, a vacuum brazing method in which heating is performed in a vacuum furnace was developed and was temporarily applied instead of brazing with a chloride flux. However, there is also a problem with productivity and brazing stability, so the transition to brazing with fluoride-based flux has made rapid progress. There have been several development examples so far for brazing without using a flux in nitrogen gas without using an expensive vacuum furnace. For example, a VAW method has been developed in which a trace amount of elements such as Bi and Be are added to a brazing material, an etching treatment with acid or alkali is performed as a pretreatment before brazing, and heating is performed in an inert gas such as nitrogen gas. Although it has been put to practical use in some heat exchangers and electronic parts, it is rarely implemented at present because the range of application is limited due to instability of bonding and the cost burden of the etching process becomes a problem. Borg Warner method in which brazing material is Ni-plated and bonded in inert gas, and KD method in which dew point is strictly controlled at -60 ° C or less and KD method for bonding in inert gas were proposed. Has not yet been put to practical use.

  Similar to vacuum brazing, when Mg is added to the brazing material, it becomes possible to join to some extent even by heating in nitrogen gas, but there is a limit to the bondability in heating in an inert gas atmosphere where active evaporation of Mg cannot be expected. The fillet formation is unstable and the gap filling ability is poor. A method of brazing and heating by adding Mg to the core material instead of the brazing material and controlling the oxygen concentration in the inert gas to a very low level has been proposed, but the difference from the case of adding Mg to the brazing material is ambiguous. Therefore, it is not possible to exert the effect of stably forming the fillet.

As described above, by using a material in which Mg is added to the brazing material or the core material, a certain degree of joining is possible even in an inert gas atmosphere, but Mg also has an action contrary to brazing properties. For example, when aluminum containing Mg is heated in the atmosphere, Mg oxide (Al ₂ MgO ₄ .MgO) is generated on the surface of aluminum particularly in a high temperature range of 450 ° C. or higher. This is an oxide produced when Mg in aluminum reacts with oxygen in the atmosphere. Even when heated in an inert gas atmosphere, if the oxygen concentration or dew point in the inert gas is high, Mg reacts with oxygen and water vapor in the atmospheric gas to produce MgO on the surface of the oxide film, which causes a decrease in the wettability of the wax.

  For this reason, many fluxless brazing methods in an inert gas, such as the VAW method, strictly control the oxygen concentration and dew point in the atmosphere. On the other hand, for the purpose of suppressing the formation of Mg oxide, a method of limiting the amount of Mg added to the brazing material and raising the temperature in a short time has been proposed, but the fillet forming ability equivalent to brazing using a flux is proposed. The actual situation is that it has not been realized and the application range is limited to a laminated heat exchanger or the like mainly composed of surface bonding. Thus, in the method of brazing without using a flux in an inert gas such as nitrogen gas using a material in which Mg is added to the brazing material or the core material, there is a problem in the ability to form a fillet, Therefore, fluxless brazing in inert gas is limited to applications such as laminated heat exchangers that are all composed of surface joints and are given sufficient pressure, and have fins and headers. Currently, it is hardly used in general heat exchangers for automobiles that require a stable fillet forming ability.

JP 2011-025276 A

In order to study the action of Mg in the case of brazing without flux in an inert gas such as nitrogen gas using a material to which Mg is added, Si: 10% (mass%, the same applies hereinafter) ) And a brazing sheet clad on one side of an aluminum core containing Mg: 0.8% as a sample, in a nitrogen atmosphere having an oxygen concentration of 16 ppm and a dew point of −40 ° C. After raising the temperature to 4 ° C. in 4 minutes and then heating to 595 ° C. to melt the wax, the oxide film was peeled off from the sample and observed with a TEM (transmission electron microscope). As a result, a black rectangular substance was observed. , was the structural analysis of this material, primarily spinel Mg oxide, i.e., Al ₂ MgO _4, the oxide film this oxide covers the brazing material surfaces (mainly amorphous Shitsusan Film _{(Al 2 O} 3) oxide film to be formed in) is to weaken the effect of Mg is mainly spinel Mg in the amorphous oxide film of the braze surface _(Al 2 _{O 3)} It has been found that this is brought about by forming an Mg oxide composed of an oxide (Al ₂ MgO ₄ ) to weaken the oxide film.

  As a result of further testing and examination, when using brazing sheets in which Mg is added to brazing material and core material, brazing without using flux in an inert gas such as nitrogen gas, spinel-type Mg In order to form an oxide, weaken the oxide film on the surface of the brazing material, and improve the brazing property, the addition site and amount of Mg in the brazing sheet, the heating temperature and heating time in brazing, oxygen in heating We found the management of concentration and dew point to be important.

  The present invention has been made on the basis of the above knowledge, and its purpose is to add Mg to a brazing material and a core material, and braze an aluminum brazing sheet for brazing without using a flux in an inert gas atmosphere, Another object of the present invention is to provide a brazing method that enables stable fillet formation using the aluminum brazing sheet.

  An aluminum brazing sheet according to claim 1 for achieving the above object is a brazing sheet for brazing without using a flux in an inert gas atmosphere, and is formed of Al-Si on one or both sides of an aluminum core. A brazing material is clad, and a spinel-type Mg oxide is formed in the form of dots or planes in a region of 10% or more of the total surface area of the brazing material on the brazing material surface after the brazing heat is applied. .

  An aluminum brazing sheet according to claim 2 is the aluminum brazing sheet according to claim 1, wherein the aluminum core material is made of an aluminum alloy in which the Mg content is limited to 0.6% or less, and the Al-Si brazing material is Si: 6-13% and Mg: 0.2 to 0.6% is contained, the balance is aluminum and inevitable impurities, and the brazing material is clad on the core material with a thickness of 15 μm or more.

  The aluminum brazing sheet according to claim 3 is the aluminum brazing sheet according to claim 1, wherein the aluminum core material is made of an aluminum alloy containing Mg: 0.4 to 1.2%, and the Al-Si brazing material is Si: 6 to 13%. And Mg: 0.05 to 0.2%, the balance being aluminum and inevitable impurities, the brazing material being clad on the core material with a thickness of 15 to 60 μm.

  The aluminum brazing sheet according to claim 4 is the method according to claim 3, wherein an intermediate material containing Mg: 0.4 to 1.2% is interposed between the aluminum core material and the Al-Si brazing material. It is characterized by.

  An aluminum brazing sheet according to claim 5 is the aluminum brazing sheet according to claim 1, wherein the aluminum core material is made of an aluminum alloy containing Mg: 0.4 to 1.2%, and the Al-Si brazing material is Si: 6 to 13%. The Mg content is limited to less than 0.05%, the balance is made of aluminum and unavoidable impurities, and the brazing material is clad on the core material with a thickness of 15 to 60 μm.

  The aluminum brazing sheet according to claim 6 is the method according to claim 5, wherein an intermediate material containing Mg: 0.4 to 1.2% is interposed between the aluminum core material and the Al-Si brazing material. It is characterized by.

  A brazing method according to claim 7 is a method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 2, wherein the oxygen concentration is 10 ppm or less and the dew point is −35 ° C. or less. The temperature is increased from 540 ° C. to 570 ° C. for 3 minutes to less than 45 minutes in a controlled inert gas atmosphere furnace, and then heated to 580 to 615 ° C. to perform brazing. .

  A brazing method according to claim 8 is a method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 3 or 4, wherein the oxygen concentration is 10 ppm or less, and the dew point is −35 ° C. The temperature is raised from 540 ° C. to 570 ° C. for 5 minutes to less than 45 minutes in an inert gas atmosphere furnace controlled as follows, and then the temperature is raised to 580 to 615 ° C. to perform brazing. And

  A brazing method according to claim 9 is a method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 5 or 6, wherein the oxygen concentration is 10 ppm or less, and the dew point is −35 ° C. The temperature is raised from 540 ° C. to 570 ° C. over a period of 7 minutes to less than 45 minutes in an inert gas atmosphere furnace controlled as follows, and then the temperature is raised to 580 to 615 ° C. to perform brazing. And

  According to the present invention, Mg is added to a brazing material and a core material, an aluminum brazing sheet for brazing at low cost without using a flux in an inert gas atmosphere, and stable fillet formation using the aluminum brazing sheet A brazing method is provided that enables The brazing method can be suitably used for brazing of an automotive heat exchanger or the like.

It is a figure which shows a gap filling test piece.

  In the present invention, as described above, the spinel-type Mg oxide is formed at the bonding interface to weaken the oxide film on the surface of the brazing material, thereby improving the brazing property. It has been found that the formation of spinel type Mg oxide becomes active at a temperature of 540 ° C. or higher, and it takes a certain amount of time to sufficiently weaken the oxide film. That is, in order to suppress the formation or reoxidation (growth of the oxide film) of MgO on the surface of the brazing material (the surface of the oxide film), it is desirable to rapidly heat and melt the braze in a short time. As long as the amount of Mg in the vicinity of the surface layer does not exceed the limit, it is possible to melt the wax without proceeding with the generation and reoxidation of MgO by heating in an atmosphere in which the oxygen concentration and dew point are kept low. It was recognized that

  Therefore, in a temperature range of 540 ° C. or higher, heating is performed over a period of time until the wax melts, thereby forming spinel-type Mg oxide in the oxide film and weakening the oxide film. A sufficiently brittle oxide film is easily broken when the wax is melted, and not only can it wet against the mating material, but the broken oxide film does not interfere with the fillet formation. As with brazing, fillet formation at the joint proceeds.

  The amount of spinel-type Mg oxide formed in the oxide film includes the amount of Mg contained in the brazing material, the amount of Mg diffusing from the core material or the intermediate material interposed between the core material and the brazing material, It is governed by four factors: heating temperature at the time of application and heating time. Regarding the amount of Mg, the amount of Mg contained in the brazing material, the core material or the intermediate material, which material is added with Mg, and the thickness of the brazing material to be clad are important.

The aluminum brazing sheet of the present invention can be divided into the following embodiments depending on which material is added with Mg.
(Embodiment 1): When adding Mg only to brazing filler metal (Claim 2)
(Embodiment 2): When adding Mg to brazing material and core material (Claim 3), when adding Mg to brazing material, intermediate material and core material (Claim 4)
(Embodiment 3): When adding Mg only to the core material (Claim 5), when adding Mg to the intermediate material and the core material (Claim 6)
As the core material, a known Al—Mn alloy or pure aluminum alloy is applied as the base alloy, and as the intermediate material, in addition to the known Al—Mn alloy or pure aluminum alloy, a sacrificial anode is used. An Al—Zn alloy having an effect is also applied.

  In the brazing sheet of each embodiment described above, the range of Mg content in the brazing material, and the brazing method using the brazing sheet of each embodiment, the results of experiments confirming the heating time from 540 ° C. to 570 ° C. are as follows: It is. Note that brazing is performed by brazing and joining after raising the temperature to 570 ° C. and then raising the temperature to 580 to 615 ° C.

  In the brazing sheet of Embodiment 1, since Mg is present in the vicinity of the brazing material surface layer from the beginning, the formation of the spinel-type Mg oxide in the oxide film proceeds relatively early. The preferable amount of Mg contained in the brazing filler metal is in the range of 0.2 to 0.6%. If it is less than 0.2%, the formation of spinel-type Mg oxide in the oxide film becomes slow, and the Mg content is 0. If it exceeds .6%, the formation of MgO on the surface of the oxide film proceeds, which causes the oxide film to be interrupted and to prevent wetting of the wax.

  In the brazing method using the brazing sheet of Embodiment 1, the preferred heating time from 540 ° C. to 570 ° C. is in the range of 3 minutes to less than 45 minutes. If it is less than 3 minutes, the formation area ratio of the spinel-type Mg oxide in the oxide film on the brazing material surface after brazing heating (after heating to 580 to 615 ° C., the same shall apply) is less than 10% of the entire brazing material surface, A sufficient fillet forming ability cannot be obtained. When the heating time from 540 ° C. to 570 ° C. is 45 minutes or more, when the brazing material thickness is 60 μm or less, the function as the brazing material is reduced due to Si diffusion into the core material, and sufficient gap filling properties cannot be obtained. . Even when the brazing material thickness exceeds 60 μm, since the brazing material surface is kept at a high temperature for a long time, the oxide film on the brazing material surface becomes dense, and the oxide film is difficult to be divided during the melting of the brazing material. In addition, the preferable range of the brazing material thickness is 15 μm or more. When the brazing material thickness is less than 15 μm, Si in the brazing material is the core material in the heating process for forming the spinel-type Mg oxide in the oxide film. Alternatively, it diffuses into the intermediate material, the amount of Si in the brazing material is reduced, and the function as the brazing material is likely to deteriorate.

  In the brazing sheet of Embodiment 2, the preferable amount of Mg contained in the brazing material is in the range of 0.05 to 0.2%, and the preferable amount of Mg contained in the core material and the intermediate material is 0.4 to 1. .2% range. When the amount of Mg in the brazing material is less than 0.05%, the formation of the spinel-type Mg oxide in the oxide film substantially depends on Mg diffusing from the core material or the intermediate layer. The preferable range of the thickness of the brazing material is 15 to 60 μm. In this case, Mg contained in the brazing material and Mg diffused from the core material or the intermediate material during the heating process are formed on the surface of the oxide film. Since the formation of the spinel-type Mg oxide proceeds, the upper limit value of the Mg content of the brazing material can be made lower than that in the first embodiment, and the core material and the intermediate material contain 0.4 to 1.2% of Mg. When contained, the upper limit of the Mg content of the brazing material is 0.2%.

  When the brazing material thickness is 60 μm or less and the Mg content of the core material and intermediate material is less than 0.4%, the formation of the spinel-type Mg oxide in the oxide film becomes slow, and the content exceeds 1.2%. Then, the formation of MgO on the surface of the oxide film proceeds, which causes the oxide film to be interrupted and the wetting of the wax to be hindered. Also, if the Mg content of the core material and intermediate material exceeds 1.2%, the amount of Mg that dissolves in the brazing material increases and the surface tension of the molten braze decreases, so that fillet formation is possible even if fillet formation is possible. It is inferior in nature and causes a practical problem.

  When the brazing material thickness is 15 μm or less, Si in the brazing material diffuses into the core material or intermediate material during the heating process to form the spinel-type Mg oxide in the oxide film, and the amount of Si in the brazing material decreases. In addition, the function as a brazing material is likely to deteriorate. When the brazing material thickness exceeds 60 μm, the formation of the spinel-type Mg oxide in the oxide film is mainly performed only by the Mg contained in the brazing material. Therefore, only the Mg content in the brazing material is the dominant factor. Become.

  In the brazing method using the brazing sheet of Embodiment 2, the preferred heating time from 540 ° C. to 570 ° C. is in the range of 5 minutes to less than 45 minutes. Formation of spinel-type Mg oxide in the oxide film proceeds relatively early, but for a while exceeding 540 ° C., that is, until Mg diffusing from the core material or intermediate material reaches the surface, Since the amount of spinel-type Mg oxide formed in the oxide film is small, the heating at 540 ° C. to 570 ° C. takes a long time compared to the brazing using the brazing sheet of Embodiment 1. When the heating time at 540 ° C. to 570 ° C. is less than 5 minutes, the formation area ratio of the spinel-type Mg oxide in the oxide film on the surface of the brazing material becomes less than 10% of the entire surface of the brazing material, and sufficient fillet forming ability is obtained. Absent. When the heating time at 540 ° C. to 570 ° C. is 45 minutes or more, the function as the brazing material is lowered when the brazing material thickness is 60 μm or less due to Si diffusion into the core material, and sufficient gap filling properties cannot be obtained. At the same time, since the surface of the brazing material is kept at a high temperature for a long time, the oxide film on the surface of the brazing material becomes dense, and the oxide film is difficult to be divided when the wax is melted.

  In the brazing sheet of Embodiment 3, the Mg content in the brazing material is limited to less than 0.05%, and the formation of the spinel-type Mg oxide in the oxide film proceeds by Mg diffusing from the core material or the intermediate material. The preferable amount of Mg contained in the core material and the intermediate material is in the range of 0.4 to 1.2%, and the preferable brazing material thickness is in the range of 15 to 60 μm. When the brazing material thickness is 60 μm or less and the Mg content of the core material and intermediate material is less than 0.4%, the formation of the spinel-type Mg oxide in the oxide film becomes slow, and the content exceeds 1.2%. Then, the formation of MgO on the surface of the oxide film proceeds, which causes the oxide film to be interrupted and the wetting of the wax to be hindered. Also, if the Mg content of the core material and intermediate material exceeds 1.2%, the amount of Mg that dissolves in the brazing material increases and the surface tension of the molten braze decreases, so that fillet formation is possible even if fillet formation is possible. It is inferior in nature and causes a practical problem.

  When the brazing material thickness is 15 μm or less, Si in the brazing material diffuses into the core material or intermediate material during the heating process to form the spinel-type Mg oxide in the oxide film, and the amount of Si in the brazing material decreases. In addition, the function as a brazing material is likely to deteriorate. When the brazing material thickness exceeds 60 μm, the formation of the spinel-type Mg oxide in the oxide film is mainly performed only by the Mg contained in the brazing material. Therefore, only the Mg content in the brazing material is the dominant factor. Become.

  In the brazing method using the brazing sheet of Embodiment 3, as described above, the Mg content in the brazing material is limited to less than 0.05%, and the formation of the spinel-type Mg oxide in the oxide film is the core material or Since the process proceeds by Mg diffusing from the intermediate material, the timing of starting the formation of the spinel-type Mg oxide in the oxide film is delayed as compared with the brazing using the brazing sheets of the first and second embodiments. However, weakening of the oxide film can be achieved by lengthening the heating time at 540 ° C. or higher. The preferable heating time from 540 ° C. to 570 ° C. is 7 minutes or more and less than 45 minutes. When the heating time is less than 7 minutes, the formation area ratio of the spinel-type Mg oxide in the oxide film on the surface of the brazing material is 10% of the entire surface of the brazing material. Thus, sufficient fillet forming ability cannot be obtained. When the heating time at 540 ° C. to 570 ° C. is 45 minutes or more, when the brazing material thickness is 60 μm or less, the function as the brazing material is lowered due to Si diffusion from the brazing material to the core material, and sufficient gap filling property is obtained. In addition, since the surface of the brazing material is kept at a high temperature for a long time, the oxide film on the surface of the brazing material becomes dense, and the oxide film is difficult to be divided when the wax is melted.

  Brazing heating when brazing is performed using the brazing sheets of Embodiments 1 to 3 is performed in an inert gas atmosphere furnace in which the oxygen concentration is controlled to 10 ppm or less and the dew point is −35 ° C. or less. The oxygen concentration and the dew point are adjusted by the flow rate of the inert gas flowing in the furnace, and both the oxygen concentration and the dew point are correlated with the gas flow rate. When the oxygen concentration exceeds 10 ppm or the dew point exceeds −35 ° C., the fillet forming ability decreases. This is particularly because the oxide film on the surface of the brazing material grows during the heating time at 540 ° C. or higher, and MgO is formed on the surface of the oxide film. The heating atmosphere at 540 ° C. or higher is more preferably an oxygen concentration of 10 ppm or less. Is 5 ppm or less, and the dew point is −35 ° C. or less, more preferably −45 ° C. or less.

  As described above, the brazing material of the brazing sheet, or the core material or intermediate material contains Mg, the heating rate is adjusted in an inert gas atmosphere with high purity, and the spinel Mg oxidation in the oxide film on the surface of the brazing material By promoting object formation and making the oxide film brittle, it is possible to promote division of the oxide film and improve fillet forming ability. According to the present invention, flux-free brazing of various types of heat exchangers that could not be put into practical use due to lack of fillet forming ability with conventional flux-free brazing in an inert gas atmosphere is possible, reducing costs. Improvements in the quality of the heat exchanger can also be realized.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects of the present invention. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Example 1 and Comparative Example 1
A single-sided brazing sheet (test material) having a thickness of 0.4 mm made of a brazing material based on an Al-10% Si alloy and a core material based on an Al-1.2% Mn alloy was prepared by a conventional method. Mg was appropriately added to the brazing material or the core material, and the thickness of the brazing sheet was 400 μm, and the thickness of the brazing material was 5 levels of 12 μm, 15 μm, 40 μm, 60 μm, and 70 μm. The degreased single-sided brazing sheet was used as a horizontal material, and was assembled into a gap-filling test piece shown in FIG. 1 using a 3003 alloy material having a thickness of 1 mm as a vertical material.

The nitrogen gas furnace is composed of a replacement chamber in which nitrogen gas is flowed, and a brazing chamber with an internal volume of 0.005 m ³ that is flowed with nitrogen gas and equipped with a heater. The oxygen concentration and dew point are determined by the amount of nitrogen gas fed into the brazing chamber. Adjusted. The temperature rises from 450 ° C to 540 ° C in 5 minutes, and after adjusting the temperature rise time from 540 ° C to 570 ° C at each level, the temperature is raised to 595 ° C in about 3 minutes and brazed. Joined.

  When the temperature of the gap filling test piece reached 595 ° C. in the brazing chamber, the test piece was transferred to the replacement chamber, cooled to 150 ° C. in the replacement chamber, and then taken out and cooled in the atmosphere. About the test piece after cooling, the formation area ratio of the spinel type Mg oxide in the oxide film with respect to the brazing material whole surface in the test material surface (brazing material surface) was calculated | required by FE-SEM (field emission scanning electron microscope). Further, the gap filling length was measured from the cooled test piece to evaluate the fillet forming ability, and the bonding stability was evaluated from the shape of the formed fillet. Tables 1 and 2 show the test materials, heating conditions (oxygen concentration, dew point), the formation area ratio of the spinel-type Mg oxide, the obtained gap filling length, and the fillet stability evaluation results.

  In the evaluation results, for a test material having a brazing filler metal thickness of 40 μm, a material with a gap filling length of 25 mm or more and a stable fillet shape is accepted (◯), and a gap filling length of less than 25 mm is a fillet shape. Was determined to be rejected (Δ to ×) depending on the degree. For a test material having a brazing filler metal thickness of 60 μm or more, a material having a gap filling length of 35 mm or more and a stable fillet shape is accepted (◯), and the gap filling length is less than 35 mm and the fillet shape is unstable. Depending on the degree, the product was rejected (Δ to ×). For the test materials having a brazing filler metal thickness of 12 μm and 15 μm, the one with a gap filling length of 10 mm or more and a stable fillet shape is accepted (O), and the gap filling length is less than 10 mm and the fillet shape is not good. A stable product was rejected (Δ to ×) depending on the degree.

As a reference material, both the brazing material and the core material are not added with Mg, a brazing material thickness of 40 μm, a single-side brazing sheet with a plate thickness of 400 μm is produced, and a fluoride flux is applied in an amount of 3 g / m ² to obtain a horizontal material, 1 mm thick 3003 alloy material was assembled into a gap filling test piece shown in FIG. 1 using a vertical material, and the temperature was raised from 540 ° C. to 570 ° C. in 2 minutes, and then the temperature was raised to 595 ° C. and brazed and joined. . The oxygen concentration during brazing was 12 ppm, and the dew point was -35 ° C. The shape of the fillet formed on the test piece of the reference material was stable, and the filling length was 32 mm, which was a sufficiently practical level.

  As shown in Table 1, in all of the test materials 1 to 22 according to the present invention, the formation area ratio of the spinel-type Mg oxide in the oxide film on the surface of the brazing material is 10% or more of the entire surface of the brazing material, and the gap filling It was confirmed that the length and fillet shape were at acceptable levels.

  On the other hand, as shown in Table 2, the test materials (23, 24, 29, 30, 31, 35, 36, 37) and the heating conditions (oxygen concentration, dew point) whose Mg content does not satisfy the present invention are as follows. Test materials not satisfying the present invention (28, 34, 43), test materials not satisfying the present invention with heating time from 540 ° C. to 570 ° C. (26, 27, 32, 33, 41, 42), brazing material thickness It was confirmed that the test materials (25, 38, 39, 40) that were too thin or too thick did not reach the acceptable levels of the gap filling length and fillet shape.

  As a result of observing the surface of the cooled test material (horizontal material) with TEM and FE-SEM, the Mg content is insufficient (test materials 23, 29, 35), and the heating time from 540 ° C. to 570 ° C. In the short ones (test materials 26, 32, and 41), the formation area ratio of the spinel-type Mg oxide in the oxide film on the surface of the brazing material was less than 10% of the entire surface of the brazing material.

  In the case where the fillet forming ability was inferior due to the high oxygen concentration and dew point (test materials 28, 34, 43), the formation area ratio of the spinel-type Mg oxide exceeded 10% of the entire surface of the brazing material. (Test materials 28 and 34), it is presumed that the division of the oxide film was inhibited by the formation of MgO on the oxide film surface or the growth (densification) of the oxide film.

  Moreover, in the case where the Mg content is too high (test materials 24, 30, 31, 36, 37), in addition to the formation of MgO on the surface of the oxide film, the surface tension is reduced due to the increase in Mg in the molten braze, thereby causing a fillet shape. It is presumed that the result was inferior and the fillet-forming ability was inferior. When the heating time was too long (test materials 27, 33, and 42), the formation area ratio of the spinel-type Mg oxide exceeded 10% of the entire surface of the brazing filler metal. It is presumed that the formation of MgO on the surface results in insufficient splitting of the oxide film during melting of the wax, resulting in poor fillet forming ability.

  When the brazing material was too thin (test materials 25 and 38), the formation area ratio of the spinel-type Mg oxide exceeded 10% of the total surface of the brazing material, but due to diffusion of Si in the brazing material to the core material Fillet forming ability was inferior. When the brazing material was too thick (test materials 39 and 40), the formation area ratio of the spinel-type Mg oxide was less than 10% of the entire surface of the brazing material even when the heating time was lengthened, and the fillet forming ability was inferior. .

Example 2 and Comparative Example 2
A single-sided brazing sheet having a thickness of 0.4 mm comprising a brazing material based on an Al-10% Si alloy, a core material based on an Al-1.2% Mn alloy, and an intermediate material based on a pure aluminum alloy ( Test material) was prepared by a conventional method. Mg was appropriately added to the brazing material, the intermediate material, or the core material, the thickness of the brazing sheet was 400 μm, the thickness of the intermediate material was 40 μm, and the thickness of the brazing material was also 40 μm. The degreased single-sided brazing sheet is used as a horizontal material, and a 3003 alloy material having a thickness of 1 mm is used as a vertical material. The gap filling test piece shown in FIG. It brazed and joined as 595 degreeC.

  About the test piece after cooling, the formation area ratio of spinel type Mg oxide was calculated | required by the same method as Example 1, and the gap filling length was measured from the test piece after cooling similarly to Example 1. The fillet forming ability was evaluated and the joining stability was evaluated from the shape of the formed fillet. Table 3 shows the evaluation results of the test material, heating conditions (oxygen concentration, dew point), the formation area ratio of the spinel-type Mg oxide, the obtained gap filling length, and fillet stability.

  As shown in Table 3, in all of the test materials 44 to 47 according to the present invention, the formation area ratio of the spinel-type Mg oxide in the oxide film on the surface of the brazing material is 10% or more of the entire surface of the brazing material, and the gap filling It was confirmed that the length and fillet shape were at acceptable levels.

  In contrast, since the test materials 48 and 50 have a low Mg content in the intermediate material, the formation area ratio of the spinel Mg oxide in the oxide film on the surface of the brazing material was less than 10% of the entire surface of the brazing material. . Moreover, since the test materials 49 and 51 have too much Mg content in the intermediate material, in addition to formation of MgO on the surface of the oxide film, the fillet shape is disturbed due to a decrease in surface tension due to an increase in Mg in the molten solder, and the fillet It is inferred that the formation ability was also inferior.

Claims (9)

A brazing sheet for brazing without using a flux in an inert gas atmosphere, comprising an aluminum (including an aluminum alloy, hereinafter the same) core material clad with an Al-Si brazing material on one side or both sides, An aluminum brazing sheet, characterized in that a spinel-type Mg oxide is formed in the shape of dots or planes in a region of 10% or more of the total surface area of the brazing material on the brazing material surface after the brazing heat. The aluminum core material is made of an aluminum alloy whose Mg content is limited to 0.6% (mass%, the same shall apply hereinafter) or less, and the Al—Si brazing material is Si: 6-13% and Mg: 0.2-0. The aluminum brazing sheet according to claim 1, comprising .6%, the balance being aluminum and inevitable impurities, wherein the brazing material is clad on the core material with a thickness of 15 μm or more. The aluminum core material is made of an aluminum alloy containing Mg: 0.4 to 1.2%, and the Al-Si brazing material contains Si: 6 to 13% and Mg: 0.05 to 0.2%. 2. The aluminum brazing sheet according to claim 1, wherein the brazing material is made of the balance aluminum and unavoidable impurities, and the core material is clad with a thickness of 15 to 60 [mu] m. The aluminum brazing sheet according to claim 3, wherein an intermediate material containing Mg: 0.4 to 1.2% is interposed between the aluminum core material and the Al-Si brazing material. The aluminum core material is made of an aluminum alloy containing Mg: 0.4 to 1.2%, the Al-Si brazing material contains Si: 6 to 13%, and Mg is limited to less than 0.05%. 2. The aluminum brazing sheet according to claim 1, wherein the brazing material is made of the balance aluminum and unavoidable impurities, and the core material is clad with a thickness of 15 to 60 [mu] m. The aluminum brazing sheet according to claim 5, wherein an intermediate material containing Mg: 0.4 to 1.2% is interposed between the aluminum core material and the Al—Si brazing material. A method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 2, wherein the oxygen concentration is controlled to 10 ppm or less and a dew point of -35 ° C or less. Then, after raising the temperature from 540 ° C. to 570 ° C. over a period of 3 minutes or more and less than 45 minutes, the temperature is raised to 580 to 615 ° C. and brazing is performed. A method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 3 or 4, wherein the inert gas atmosphere is controlled to have an oxygen concentration of 10 ppm or less and a dew point of -35 ° C or less. A brazing method characterized by performing brazing by raising the temperature from 540 ° C. to 570 ° C. in a furnace in a time of 5 minutes or more and less than 45 minutes and then raising the temperature to 580 to 615 ° C. A method of brazing without using a flux in an inert gas using the aluminum brazing sheet according to claim 5 or 6, wherein the inert gas atmosphere is controlled to have an oxygen concentration of 10 ppm or less and a dew point of -35 ° C or less. A brazing method characterized in that in a furnace, the temperature is raised from 540 ° C. to 570 ° C. in a time of 7 minutes or more and less than 45 minutes, and then the temperature is raised to 580 to 615 ° C. to perform brazing.

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