JP2012050992A - Fluxless brazing method of aluminum material, aluminum brazing sheet for fluxless brazing, and aluminum alloy brazing material for fluxless brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable fluxless brazing under atmospheric pressure without using flux and vacuum equipment.SOLUTION: An Al-Si system brazing material has a composition which contains 0.1 to 5.0% of Mg, 3 to 13% of Si and 0.001 to 1.0% of Ca, and whose remaining part is composed of inevitable impurities, an aluminum clad material 1 is used at which the Al-Si system brazing material 3 in which an Si particulate whose diameter is not smaller than 1.75 μm among particulates which are preferably not smaller than 0.8 μm in circular equivalent diameters exists at not smaller 25% in a number ratio on the outermost surface of a member which is joined by brazing, and a member to be brazed and a contact/adhesion part 5 are joined using the Al-Si brazing material 3 at temperatures of 559 to 620°C in a non-oxide atmosphere not accompanying pressure reduction. Thus, the fluxless brazing under the atmosphere pressure is enabled without using the flux and the vacuum equipment, and also an inhibition factor is not caused even if Mg is added to a constituent to be brazed other than the brazing material.

Description

  The present invention relates to a fluxless brazing method for an aluminum material that can be brazed without using a flux in a non-oxidizing atmosphere, an aluminum alloy brazing sheet for fluxless brazing, and an aluminum alloy brazing material for fluxless brazing.

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 moisture is contained in the atmosphere. The atmosphere inside the furnace can be brazed by the getter action combined with oxygen 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 flux-less brazing under a non-oxidizing atmosphere and atmospheric pressure by placing an Mg-containing material on a brazed member or other part and covering the brazed material. is doing. However, in this technology, it is essential to cover, and it is necessary to prepare covers for each product size, it is necessary to prepare the number of pieces used in mass production, and further maintenance of the cover is required. There is a problem that it takes time and cost in mass production. Moreover, there is also a problem that the temperature rise rate of the brazed object is lowered by covering, and the productivity is lowered.

  To solve the above problem, Patent Document 2 proposes a mechanism in which a brazing member (cover) heated in the brazing furnace in advance is used to cover the brazed member in the furnace, thereby improving the decrease in the heating rate. Yes. However, in this method, it is necessary to provide a mechanism for controlling the operation of the windbreaker in the furnace, and there is a problem that it takes cost and labor to introduce and maintain equipment.

  On the other hand, as a fluxless brazing that does not require a cover, in Patent Document 3, Mg is added to a brazing material of a clad material, and the inside of the heat exchanger tube formed by the clad material is set to atmospheric pressure in an inert atmosphere. A fluxless brazing method has been proposed below.

  Similarly, as a method that does not require a cover, Patent Document 4 proposes a method in which a brazing material surface is clad with an antioxidant layer and the clad material is laminated to enable brazing in an air atmosphere. is there.

  In Patent Document 5, if the surface of the core material is clad with a brazing material made of an Al—Si—Mg alloy, and the surface of the material is acid-washed before brazing and the thickness of the oxide film is 20 mm or less, There is a proposal that enables fluxless brazing in an oxidizing atmosphere.

JP-A-9-85433 JP 2006-175500 A Japanese Patent No. 4037477 Japanese Patent No. 3701847 Japanese Patent Laid-Open No. 10-180489

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.
Further, in the technique proposed in Patent Document 4, 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, and the material cost is low. There is a problem that it becomes high, and there is a problem of versatility that the core is limited to a laminated structure.
Furthermore, the method disclosed in Patent Document 5 has a problem that the process management of the acid cleaning becomes complicated and the cost for the acid cleaning process increases.

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 improvement is necessary.
Therefore, there is a strong demand for a method capable of obtaining a good brazing state even when brazing is performed in an atmosphere having a slightly high oxygen concentration.

  In view of such problems, the present invention does not generate new operation costs such as introduction and operation costs such as flux application process and vacuum equipment, sub-material costs such as a cover used at the time of brazing, and material acid cleaning, and The development has been progressed with the aim of finding a fluxless brazing method of an aluminum material capable of general-purpose fluxless brazing under atmospheric pressure regardless of the shape of a heat exchanger or the like.

  And the present inventors have found that brazing is significantly improved even in an atmosphere having a higher oxygen concentration than before by adding Ca to the Al—Si—Mg-based brazing material, and the present invention has been completed. Is.

  That is, among the fluxless brazing methods for aluminum materials of the present invention, the first invention is mass%, Mg is 0.1 to 5.0%, Si is 3 to 13%, Ca: 0.001. A brazing method using an aluminum clad material in which an Al-Si brazing material containing ~ 1.0% is located on the outermost surface, and in a non-oxidizing atmosphere without decompression, the Al-Si brazing material The brazing member is brought into contact and in close contact, and the core material and the brazing member are joined to each other at the contact surface of the contact and adhering portion with the Al—Si brazing material at a heating temperature of 559 to 620 ° C. without flux. It is characterized by.

  The fluxless brazing method of the aluminum material of the second aspect of the present invention is the same as that of the first aspect of the present invention, wherein the Si particles contained in the Al—Si based brazing material have an equivalent circle diameter in the observation in the surface direction of the surface of the brazing material. The number of those having a diameter equivalent to a circle of 1.75 μm or more is 25% or more among those having a diameter of 0.8 μm or more.

  A fluxless brazing method for an aluminum material according to a third aspect of the present invention is the method according to the first or second aspect, wherein the Al—Si brazing material is further in mass% and Be is 0.0001 to 0.1. % Content.

  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 based brazing material further has Bi of 0.01% by mass. It is characterized by containing -1.0%.

  The fluxless brazing method for an aluminum material according to a fifth aspect of the present invention provides the fluxless brazing method according to any one of the first to fourth aspects of the present invention, wherein the Al—Si based brazing material further contains 0.1% by mass of Zn. It is characterized by containing ˜5.0%.

  An aluminum alloy brazing sheet for fluxless brazing according to a sixth aspect of the present invention is located on the outermost surface of the Al-Si brazing material according to any one of the first to fifth aspects of the present invention, which is clad by a core material. In a non-oxidizing atmosphere without pressure reduction, the Al—Si brazing material is brought into contact and contact with the brazed member, and the Al—Si brazing material is joined to the brazed member at the contact adhesion surface. As described above, it is characterized by being subjected to fluxless brazing.

  The aluminum alloy brazing material for fluxless brazing according to the seventh aspect of the present invention is, by mass, 0.1 to 5.0% Mg, 3 to 13% Si, and 0.001 to 1.0% Ca. It is characterized in that it contains Al and inevitable impurities, and is subjected to fluxless brazing in a non-oxidizing atmosphere without decompression.

  The aluminum alloy brazing filler metal for fluxless brazing according to the eighth aspect of the present invention is characterized in that, in the seventh aspect of the present invention, Be is further contained in an amount of 0.0001 to 0.1% by mass.

  The aluminum alloy brazing material for fluxless brazing according to the ninth aspect of the present invention is characterized in that in the seventh or eighth aspect of the present invention, Bi is further contained in an amount of 0.01 to 1.0% by mass.

  The aluminum alloy brazing filler metal for fluxless brazing according to the tenth aspect of the present invention is characterized in that in any of the seventh to tenth aspects of the present invention, Zn is further contained in an amount of 0.1 to 5.0% by mass. And

  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 and added with Mg and Ca is used.

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 oxide film (A1 ₂ 0 ₃ ) of aluminum on the surface of the material when brazing is applied, and has the effect of improving the bondability and the wettability of the wax. 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.

Ca: 0.001 to 1.0%
Ca reductively decomposes the Al and Mg oxide films formed on the surface of the brazing material to enable good brazing joining. If the Ca content is less than the lower limit, the effect is insufficient, and if the Ca content exceeds the upper limit, oxidation of the brazing filler metal surface is promoted and the bonding rate is lowered. For the same reason, it is desirable that the lower limit is 0.005% and the upper limit is 0.75%.

  The brazing material of the present invention may contain the above Si, Mg, Ca, and the other may be Al and inevitable impurities, and contains other components so as not to impair the action of the above Si, Mg, Ca. You may do. Below, the other component contained depending on necessity is demonstrated.

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 increases, so the content of Be is set in the above range. For the same reason, it is desirable that the lower limit is 0.0002% and the upper limit is 0.01%.

Bi: 0.01 to 1.0%
Bi suppresses re-oxidation of the material surface and improves the wetting and spreading property of the brazing material. If it is less than the lower limit, the effect is insufficient, and even if the upper limit is exceeded, no further effect can be obtained. For this reason, the above range is desirable for the Bi content.

Zn: 0.1 to 5.0%
Zn lowers the potential of the brazing material and has the effect of improving the corrosion resistance of the brazing sheet by the sacrificial anode effect, so it is optionally contained in the brazing material. 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%.

Distribution of Si particles: Equivalent circle diameter of 0.8 μm or more, 1.75 μm or more of number ratio is 25% or more Usually, a dense oxide film such as Al ₂ O ₃ is present on the aluminum material surface, In the brazing heat treatment process, this further grows and becomes a thick film. The general view is that the greater the thickness of the oxide film, the stronger the tendency to inhibit the destructive action of the oxide film. Due to the presence of coarse Si particles on the surface of the brazing material, a dense oxide film of aluminum does not grow on the surface of the coarse Si particles, and this site works as an oxide film defect on the surface of the aluminum material. That is, even if the oxide film on the surface of the aluminum material becomes a thick film during the brazing heat treatment, exudation of the brazing material from the Si particle portion occurs, and the oxide film destruction action and the breaking action proceed from this site, It improves the wettability of the molten solder and makes it possible to obtain a more stable joined state.
The term “Si particles” as used herein includes Si particles due to the composition of Si as a single component, and also includes, for example, Fe—Si compounds and Al—Fe—Si intermetallic compounds mainly composed of Fe—Si. Shall be. In the description of the present invention, these are referred to as Si particles for convenience.
Specifically, when the Si particles on the surface of the brazing material are regarded as equivalent circle diameters and the number of Si particles of 0.8 μm or more is counted and 25% or more of those having 1.75 μm or more are present, this effect is sufficiently obtained. It is done.
If the size of the Si particles on the surface of the brazing material is too small, the effect of acting as a defective portion of the oxide film becomes insufficient. Therefore, it is desirable that the number of Si particles of 1.75 μm or more is 25% or more of the number of Si particles of 0.8 μm or more. If it is less than 25%, the effect of acting as a defective portion of the oxide film becomes insufficient.
In addition, if there are excessively large Si particles, defects in the oxide film increase, but castability and rollability deteriorate, and die wear during cutting and pressing is promoted, so the upper limit is 50% or less. Is desirable.

The distribution of the Si particles can be controlled by thermal management when manufacturing the aluminum alloy brazing material.
For example, the size of the Si particles can be controlled by the solidification rate during casting, the temperature and time of the homogenization treatment, the maximum rolling rate during hot rolling, etc. Can be controlled.
That is, coarser Si particles are generated as the solidification rate during casting is slower, and finer Si particles are generated as the solidification rate is higher. Further, the faster the solidification rate, the larger the number of Si particles, and the slower the solidification rate, the smaller the number of Si particles.
Further, as the homogenization treatment is performed at a high temperature for a long time, coarse Si particles are generated, and when the homogenization treatment is performed at a low temperature for a short time, fine Si particles are obtained.
Moreover, as for the rolling reduction at the time of hot rolling, the compound is finely crushed as the rolling reduction at one time is larger.
By controlling these conditions in a complex manner, the distribution (size, number ratio) of Si can be changed even for the same component.

2. Core material The core material composition of the aluminum clad material used in the present invention is not particularly limited in obtaining a bond, but by realizing fluxless brazing, Mg addition aiming at high strength is actively added. Yes.
As a core component, what contains Si: 0.1-1.2% and Mg: 0.01-2.0% by mass ratio, and the remainder consists of Al and an unavoidable impurity are shown.
Moreover, by mass ratio, Mn: 0.2-2.5%, Cu: 0.05-1.0%, Si: 0.1-1.2%, Fe: 0.1-1.0%, Containing the balance Al and inevitable impurities.
As the core material component, one or more of Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, and Fe: 0.1 to 1.0% are contained. If desired, Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Bi: 0.01 to 1.0% One or two or more types are contained, and the balance is composed of Al and inevitable impurities. The action of each element and the reasons for limitation are as follows.

Si: 0.1-1.2%
In addition to improving the material strength by dissolving Si in a matrix with a simple substance of Si, in the present invention, the material strength is improved by precipitation of Mg ₂ Si obtained by a synergistic effect with the positive addition of Mg. This hardening by Mg ₂ Si precipitation contributes to a dramatic improvement in material strength by aging precipitation after brazing heat treatment. In an alloy design based on the conventional A3003 alloy or the like, it is dispersed as an Al—Mn—Si compound to improve the material strength. If the amount is less than the lower limit, the effect is insufficient. If the upper limit is exceeded, the melting point decreases and the core material melts, so the above range is desirable. In addition, the more preferable range of Si content is 0.3 to 1.0%. When positive inclusion of Si is not required due to inclusion of Mn or the like, it is allowed to contain less than 0.1% of Si as an impurity.

Mg: 0.01-2.0%
When Mg is added simultaneously with Si, it precipitates as a fine intermetallic compound Mg ₂ Si after brazing and has the effect of significantly improving strength by age hardening. Moreover, it reacts with Si diffused from the brazing material during the brazing heat and has the same strength effect. Further, some of them diffuse into the brazing material and contribute to the action of inhibiting the oxide film destruction and oxide film growth on the surface of the brazing material. Below the lower limit, the effect is insufficient, and when the upper limit is exceeded, the melting point decreases and the core material melts. For this reason, the above range is desirable for the Mg content.

Mn: 0.2 to 2.5%
Mn crystallizes or precipitates as an intermetallic compound, and improves the strength after brazing. In addition, the corrosion resistance is improved by making the potential of the core material noble. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, workability such as rolling deteriorates. In addition, further effects cannot be obtained. For these reasons, the Mn content is preferably within the above range. In addition, the more preferable range of Mn content is 0.5 to 1.5%.

Cu: 0.05 to 1.0%
Cu is dissolved to improve the strength after brazing and to improve the corrosion resistance by making the potential of the core material noble. Below the lower limit, the effect is insufficient, and when the upper limit is exceeded, the melting point decreases and the core material melts. For this reason, the above range is desirable for the Cu content. In addition, the more preferable range of Cu content is 0.1 to 0.7%.

Fe: 0.1 to 1.0%
Fe crystallizes or precipitates as an intermetallic compound, and improves the strength after brazing. It also promotes recrystallization during final annealing and brazing. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, the corrosion rate becomes too fast. Further, the crystal grain size after the final annealing becomes too fine, and the erosion of the wax becomes remarkably large at the portion where the processing is not introduced at the time of molding. For these reasons, the above range is desirable for the Fe content. In addition, the more preferable range of Fe content is 0.2 to 0.5%.

Zr, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%
Zr, Ti or Cr is dispersed as a fine intermetallic compound after brazing to improve the strength. If it is less than the lower limit, the effect is insufficient, and if it exceeds the upper limit, the workability decreases. Therefore, the content of these components is preferably in the above range.

Bi: 0.01 to 1.0%
Bi suppresses re-oxidation of the material surface and improves the wetting and spreading property of the brazing material. If it is less than the lower limit, the effect is insufficient, and even if the upper limit is exceeded, no further effect can be obtained. For this reason, the above range is desirable for the Bi content.

3. Clad material In the clad material used in the present invention, it is sufficient that the Al-Si brazing material is clad on at least one side, and one side and a double sided clad material can be properly used. In the double-sided clad material, the both sides of the core material may be clad with a brazing material, the brazing material is clad on one side, and other materials such as a sacrificial material are clad on the other side. It may be a thing.

4). Material of Brazed Member As the brazed member other than the brazing material, any commonly used aluminum alloy can be used without any problem. Note that the brazing member may be clad with a brazing material.

5). Surface roughness of brazed member In carrying out the present invention, it is difficult to supply oxygen from the outside to the contact adhesion portion which is a junction portion by increasing the contact adhesion state of the junction portion. The ability to suppress oxidation of the material surface during the process is increased. The oxygen supply here does not mean oxygen in the air atmosphere, but indicates that oxygen is slightly contained in the non-oxidizing atmosphere. As a result of investigations by the present inventors, it has been found that if the surface roughness of both joining members in the joint portion is Ra 0.3 μm or less, better joining can be obtained, and more preferably, Ra 0.25 μm or less is stable. It was also found that a good bonding state can be obtained. When the surface roughness exceeds Ra 0.3 μm, brazing performance is lowered because sufficient airtightness cannot be obtained even if the pressure adhesion is increased.

6). 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.

7). In-furnace atmosphere In carrying out the present invention, the atmosphere in the furnace is changed to an inert gas or a non-oxidizing gas such as 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. The oxygen concentration management range in the atmosphere is preferably 5 to 500 ppm. If it is less than 5 ppm, there is no problem in the joining, but there is a concern that the manufacturing cost will increase, such as using a large amount of gas for managing the atmosphere. If the content exceeds 500 ppm, the reoxidation of the brazed member is likely to proceed, and in particular, it is not possible to sufficiently obtain a bond between the bare component member having no brazing material on the surface and the brazing material.

8). Brazing temperature In the present invention, brazing can be performed at the lowest solidus temperature of 559 ° C. of the brazing material Al—Si—Mg alloy, and naturally, the brazing temperature range by the conventional Al—Si brazing material is also used. Is possible. 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 explained above, according to the fluxless brazing method of the aluminum material of the present invention, the aluminum alloy brazing sheet for fluxless brazing and the aluminum alloy brazing material for fluxless brazing, no flux or vacuum equipment is required. Fluxless brazing at atmospheric pressure is possible, and a more stable joining state than before can be obtained easily and reliably. In addition, since heating is performed in an atmosphere without decompression, there is an advantage that Mg and Zn are hardly evaporated from the aluminum material, and the inner wall of the furnace is not contaminated.

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

Hereinafter, an embodiment of the present invention will be described.
Al-Si based brazing material containing at least 0.1 to 5.0% Mg, 3 to 13% Si, and Ca: 0.001 to 1.0% in mass% and a core material are ordinary methods. Can be manufactured. Both or another material such as a sacrificial material is overlapped and clad rolled. The clad rate of each layer is not specified as the present invention.

In the above brazing material, the distribution of Si particles is controlled by the solidification rate during casting, the temperature and time of the homogenization treatment, the maximum rolling rate during hot rolling, and the like.
By controlling these conditions in a complex manner, the distribution of Si particles (size, number ratio of coarse particles) is adjusted, and the number of Si particles having an equivalent circle diameter of 0.8 μm or more is 1.75 μm or more. The number of objects should be 25% or more.

  The composition of the core material is Si: 0.1 to 1.2%, Mg: 0.01 to 2.0%, Mn: 0.2 to 2.5%, Cu: 0.05 -1.0%, Si: 0.1-1.2%, Fe: 0.1-1.0%, or Si: 0.1-1.2%, Mg: 0.01- 2.0%, and Mn: 0.2 to 2.5%, Cu: 0.05 to 1.0%, Fe: 0.1 to 1.0%, or one or more of them Containing Zr: 0.01 to 0.3%, Ti: 0.01 to 0.3%, Cr: 0.01 to 0.5%, or more if desired. desirable.

As shown in FIG. 1, the aluminum clad material 1 obtained as described above 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 An oxide film of ˜500 mm 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 having a non-oxidizing atmosphere without decompression. The non-oxidizing atmosphere can be configured using an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen, ammonia or carbon monoxide, or a mixed gas thereof. The non-oxidizing atmosphere is not at reduced pressure during brazing addition heat, and is usually at atmospheric pressure. In addition, before obtaining a non-oxidizing atmosphere, you may include a pressure reduction process for the purpose of substitution. The heating furnace does not need to have a sealed space, and may have a brazing material carry-in port and a carry-out port. Even in such a heating furnace, the non-oxidizing atmosphere is maintained by continuously blowing the inert gas into the furnace. The non-oxidizing atmosphere preferably has an oxygen concentration of 5 to 500 ppm by volume. It brazes by heating at 559-620 degreeC under the said atmosphere. In brazing, the contact adhesion part 5 with the member to be brazed 4 is satisfactorily joined without flux.
The brazing material may be provided as a single material in addition to being provided as a clad material.

Examples of the present invention will be described below.
A core of the composition (the balance unavoidable impurities) consisting of an Al-Si brazing material having the composition shown in Tables 1 and 2 (the balance Al and inevitable impurities) and Al-0.5Mg-0.5Si-1.0Mn-0.3Fe An aluminum clad material was prepared by cladding the material with hot rolling and cold rolling. The solidification rate during casting of each alloy was controlled within a range of 0.1 to 2.0 ° C./sec, which is a general semi-continuous casting condition. In the brazing filler metal, the distribution of Si particles was controlled by variously changing the solidification speed and homogenization treatment conditions during casting and the maximum rolling rate during hot rolling.
In addition, the homogenization process was adjusted within the range of 300-595 degreeC x 1-48 hours, and the maximum rolling rate of hot rolling was adjusted within the range of 15-50%.
As the aluminum clad material, brazing materials and core materials having various compositions were selected and finished to a thickness of 0.5 mm with a brazing material clad rate of 10% and H14 equivalent tempering.

Measurement of Si Particles For the prepared aluminum clad material, the outermost surface of the brazing material was polished with 0.1 μm abrasive grains, etched with 0.5% hydrofluoric acid aqueous solution for 60 seconds, and then EPMA (electron beam microanalyzer) from the surface direction. Particle size and number were measured by fully automatic particle analysis using Measurements were made at 5 arbitrary portions in an observation field corresponding to 250 μm square for each sample to obtain Si particle distribution (number ratio of 1.75 μm or more out of 0.8 μm or more). Indicated.
Further, a JIS A3003 alloy and a corrugated fin material made of H14-equivalent aluminum bare material (thickness: 0.1 mm) were prepared as brazing members.

Brazing property Using the aluminum clad material of the present invention, a flat electric sewn tube having a width of 20 mm was manufactured and combined with the corrugated fin to form a core shape. The core size was a tube with 15 steps and a length of 300 mm.
After performing the brazing heat treatment which heats the said core to 560-620 degreeC in nitrogen atmosphere (oxygen content 50ppm), brazing property was evaluated by measuring the joining rate of a tube and a fin. The bonding rate of the fins was obtained by the following formula, and the results are shown in Tables 1 and 2.
Fin joint rate = (total brazed joint length of fin and tube / total contact length of fin and tube) × 100 (%)

Material Strength The manufactured aluminum clad material (0.5 mm thickness) was used as a JIS No. 5 test piece, and subjected to a tensile test after brazing heat treatment under the above conditions and after aging treatment at 90 ° C. for 7 days. The obtained material strength measurements were evaluated, and the results are shown in Tables 1 and 2.

  The examples of the present invention showed better brazing properties than the conventional examples, whereas the comparative examples did not provide sufficient bonding. Further, in the examples, it was possible to achieve both high strength and brazability of the material, but the effect was not obtained with the comparative material.

DESCRIPTION OF SYMBOLS 1 Aluminum clad material 2 Core material 3 Al-Si type brazing material 4 Brazing member 5 Contact adhesion part

Claims (10)

  Aluminum clad material in which an Al-Si brazing material containing 0.1% to 5.0% Mg, 3% to 13% Si, and 0.001% to 1.0% Ca is located on the outermost surface in mass%. In which the Al-Si brazing material and the member to be brazed are brought into contact and contact with each other in a non-oxidizing atmosphere without decompression, and the Al-Si system is heated at a heating temperature of 559 to 620 ° C. A fluxless brazing method for an aluminum material, characterized in that the core material and the member to be brazed are joined to each other at the contact surface of the contact contact portion in a fluxless manner with a brazing material.   The Si particles contained in the Al—Si brazing material have a diameter corresponding to a circle equivalent diameter of 1.75 μm or more out of the number of diameters corresponding to a circle equivalent diameter of 0.8 μm or more in observation in the surface direction of the brazing filler metal. The method of fluxless brazing of an aluminum material according to claim 1, wherein the number of the aluminum materials is 25% or more.   The flux-less brazing method for an aluminum material according to claim 1 or 2, wherein the Al-Si brazing material further contains 0.0001 to 0.1% Be by mass%.   The flux-less brazing of an aluminum material according to any one of claims 1 to 3, wherein the Al-Si brazing material further contains 0.01 to 1.0% Bi by mass. Method.   The flux-less brazing of an aluminum material according to any one of claims 1 to 4, wherein the Al-Si brazing material further contains 0.1 to 5.0% by mass of Zn. Method.   The Al-Si brazing material according to any one of claims 1 to 5, wherein the Al-Si brazing material is clad on a core material and located on the outermost surface, and the Al-Si brazing material is used in a non-oxidizing atmosphere without depressurization. Fluxless brazing for use in fluxless brazing so as to be brought into contact and close contact with a member to be brazed and to be joined to the member to be brazed at the contact contact surface by the Al-Si brazing material Aluminum alloy brazing sheet.   In mass%, Mg contains 0.1 to 5.0%, Si contains 3 to 13%, Ca: 0.001 to 1.0%, the balance is made of Al and inevitable impurities, and is not accompanied by reduced pressure. An aluminum alloy brazing material for fluxless brazing, which is used for fluxless brazing in an oxidizing atmosphere.   The aluminum alloy brazing material for fluxless brazing according to claim 7, further comprising 0.0001 to 0.1% of Be by mass.   The aluminum alloy brazing material for fluxless brazing according to claim 7 or 8, further comprising 0.01 to 1.0% Bi by mass.   The aluminum alloy brazing material for fluxless brazing according to any one of claims 7 to 9, further comprising 0.1 to 5.0% by mass of Zn.

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