JP5632175B2 - Aluminum alloy clad material and heat exchanger for high-strength heat exchangers with excellent brazing properties - Google Patents

Description

  In particular, when manufacturing an aluminum alloy heat exchanger such as a radiator or a heater core by brazing using a flux containing a fluoride flux or a cesium compound in an inert gas atmosphere, the tube material (the structural member) A high strength aluminum alloy clad material for heat exchangers excellent in brazing suitable as a header plate material, and the aluminum alloy clad material. It relates to the heat exchanger used.

  2. Description of the Related Art An automobile heat exchanger, for example, a radiator, includes a tube and a header that have fins on the outer surface and whose inner surface serves as a passage for a working fluid (refrigerant). For such automobile radiators and heaters such as tube materials and header plate materials, an Al-Mn alloy such as JIS A3003 is used as a core material, and one or both surfaces of the core material are clad with an Al-Si alloy brazing material. Aluminum alloy clad with a three-layer structure in which a brazing material is clad on one surface of the core material and a sacrificial anode material of Al-Zn alloy or Al-Zn-Mg alloy is clad on the other surface The material is used.

  Aluminum alloy heat exchangers are often joined by brazing with an inert gas atmosphere using a fluoride flux or a cesium flux, and the Al-Si brazing filler metal is an aluminum alloy heat exchanger. When the tube is manufactured, it is clad for joining the tube and the fin, joining the tube and the header plate, or brazing when manufacturing the tube from the clad plate. The sacrificial anode material is used, for example, on the inner surface side of the tube, and exerts a sacrificial anode action in contact with the working fluid, thereby preventing the pitting corrosion and crevice corrosion of the core material.

  As shown in FIG. 1, the radiator and the heater core are manufactured by using a brazing material (a skin material 1 of the present invention to be described later) 3 on one side of a core material 2, and a brazing material 3 or a sacrificial anode material (a Skin material 2) Clad plate material 1 clad with 4 is bent and welded (welded portion W) to form a flat tube, assembled to the header plate, and then brazed together (welding die). However, in recent years, as shown in FIGS. 2 to 3, the clad plate 1 is manufactured by bending it into a tube shape without welding and assembling it to the header plate (brazing mold). Techniques are being implemented.

In recent years, with the demand for reducing the weight of automobiles, automobile heat exchangers are also required to be thinner from the viewpoint of energy saving and resource saving, and the thickness of tube materials has also been reduced. In order to reduce the thickness of the tube material, the core material contains a large amount of Mn, Cu, Si, etc. because it is necessary to further increase the strength and durability (fatigue life) of the material. There is a drawback that the corrosion resistance is lowered. A material structure in which 0.05 to 0.5% Mg is added to the core material to finely precipitate Mg ₂ Si in the core material and the strength is further increased is proposed, but when Mg is added to the core material, During brazing heating, Mg diffuses from the core material to the brazing material, and after the braze melts, Mg diffuses through the molten braze, resulting in a large amount of Mg reaching the brazing material surface layer. , to form a compound such as MgF ₂ reacts with the flux, the function of the flux is lost, there is a problem that brazing defects occur.

  To solve this problem, the amount of Mg added is limited to about 0.5% or less, or the ratio of the amount of Mn to the amount of Si in the core is limited to increase the amount of Mg. A material structure has also been proposed in which the amount of Mg diffused from the core material to the brazing material is reduced and no brazing defects occur even when the Mg content exceeds 0.5%. However, in any of these cases, the effect is not sufficient, and a reduction in brazeability cannot be denied. Furthermore, a material has been proposed in which an intermediate layer is provided between the core material and the brazing material to prevent Mg from diffusing from the core material to the surface layer of the brazing material, and brazing defects are suppressed. Is excellent, but there is a problem that the production cost is increased because the productivity of the material is reduced due to the provision of the intermediate layer.

Japanese Patent No. 37772017 Japanese Patent No. 3217108 Japanese Patent Application No. 2007-037610 JP 2006-131923 A

  The inventors can achieve high strength equal to or higher than that of the above-described conventional tube material for the brazing-type radiator tube material, and in order to obtain excellent brazing properties, the core material and the skin material of the clad material As a result of testing and examining the composition and its combination, even if a relatively high concentration of Mg is added to the core material, the Mg diffuses in the liquid phase through the brazing filler metal after brazing and heating, and the amount of Mg in the core material is reduced. In order to suppress this, it has been found that it is important to set the Si concentration of the skin material to a specific low range. Further, it has been found that Mg liquid phase diffusion can be further reduced by adding Sr to control the dispersion state of Si.

  The present invention has been made on the basis of the above knowledge, and its purpose is to provide high strength and excellent brazing properties, and as a material for heat exchangers, in particular, tube materials and header plate materials for automotive heat exchangers. An object of the present invention is to provide an aluminum alloy clad material for a high-strength heat exchanger excellent in brazing that can be suitably used, and a heat exchanger using the aluminum alloy clad material.

The aluminum alloy clad material for a high-strength heat exchanger excellent in brazing according to claim 1 for achieving the above object is obtained by brazing using a flux containing a fluoride flux or a cesium compound in an inert gas atmosphere. In an aluminum alloy clad material , which is a clad material used when manufacturing an alloy heat exchanger , the skin material 1 is clad on one surface of the core material and the skin material 2 is clad on the other surface , In the same manner, the core material contains Mn: 0.8 to 2.0%, Si: 0.2 to 2.0%, Mg: 0.2 to 1.5%, and the balance aluminum and unavoidable impurities. an Al-Mn-Si-Mg series aluminum alloy comprising, cladding material 1 and cladding material 2, Si: 3.0 containing 6.0%, the balance being aluminum and unavoidable impurities Characterized in that it is a that Al-Si-based aluminum alloy. The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 2 is the core material according to claim 1, wherein the core material is Mn: 0.8 to 2.0%, Si: 0.2 to 2. It is characterized by being an Al-Mn-Si-Mg-based aluminum alloy containing 0%, Mg: more than 0.5% and 1.5% or less, and the balance aluminum and inevitable impurities.

High strength hot aluminum alloy clad material having excellent brazeability of claim 3, in claim 1 or 2, wherein the cladding material 1, Si: 3.0 ~6.0%, Sr : 0.005 It is an Al-Si-based aluminum alloy containing ~ 0.1% and the balance aluminum and unavoidable impurities, and the skin material 2 contains Si: 3.0 ~ 6.0%, and the balance aluminum and unavoidable It is characterized by being an Al—Si based aluminum alloy made of a general impurity.

High strength hot aluminum alloy clad material according to claim 4 excellent brazeability can Oite to claim 1, wherein the core further, Cu: 1.2% or less, Fe: 2 0.0% or less, Ti: 0.35% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 0.3% or less, B: 0.3% or less It contains 2 or more types.

The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 5 is any one of claims 1 to 4 , wherein the skin material 1 is further Fe: 2.0% or less, Ti: 0 0.3% or less, Zn: 2.0% or less, Cu: 1.0% or less, Na: 0.1% or less, Sb: 0.1% or less, Bi: 0.2% or less, Be: 0.1 % Or less of 1% or less.

The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 6 , in any one of claims 1 to 5 , the skin material 2 is further Sr: 0.005 to 0.1%, Fe: 2.0% or less, Ti: 0.3% or less, Zn: 10.0% or less, Cu: 1.0% or less, Na: 0.1% or less, Sb: 0.1% or less, Bi: It is characterized by containing one or more of 0.2% or less, Be: 0.1% or less, In: 0.1% or less, and Sn: 0.1% or less.

A heat exchanger according to a seventh aspect is characterized in that the aluminum alloy clad material according to any one of the first to sixth aspects is assembled and integrated by brazing.

  According to the present invention, an aluminum alloy clad material for a heat exchanger that has high strength and excellent brazing properties, and can be suitably used as a material for a heat exchanger, in particular, a tube material or a header plate material for an automotive heat exchanger. And a heat exchanger using the aluminum alloy clad material.

It is sectional drawing which shows the tube shape of a welding type. It is sectional drawing which shows the Example of a brazing-type tube shape. It is sectional drawing which shows the other Example of the brazing-type tube shape. It is a figure which shows the gap filling test piece used by brazing property evaluation. Is a diagram showing the brazing of the filling length F _L after test of gap filling specimens.

In the present invention, when the skin material 1 is, for example, an Al-10% Si alloy brazing material, which is a general brazing material, as described above, after the brazing melts, Mg undergoes liquid phase diffusion through the melting brazing. Since a large amount of Mg reaches the surface layer of the brazing material and reacts with the flux to form a compound such as MgF _2, there is a problem that the function of the flux is impaired and a brazing defect occurs.

  In the present invention, the solid phase diffusion rate is higher than the liquid phase diffusion rate by reducing and optimizing the Si concentration of the skin material 1 and the skin material 2 and increasing the solid phase rate of the skin material 1 and the skin material 2. Since the ratio at which Mg diffuses in the liquid phase can be reduced significantly, and when the solid phase ratio of the skin material 1 and the skin material 2 is increased, the thickness of the skin material 1 and the skin material 2 due to melting is reduced. Since the decrease is suppressed, the distance from the core material to the skin material 1 and the skin material 2 surface layer is maintained, and the diffusion amount of Mg from the core material to the skin material 1 and the skin material 2 surface layer can be reduced, and brazing Can be improved.

  By simply reducing and optimizing the Si concentration of the skin material 1 and the skin material 2, the skin material 1 and the skin material 2 are partially melted locally due to the non-uniformity of the metal structure, and the Mg liquid phase is formed in the part. Diffusion may increase partially. In the present invention, Sr is added to the skin material 1 and the skin material 2 so that the dispersion state of the simple Si is made fine and uniform, and local melting is suppressed to diffuse Mg from the core material to the skin material 1 and the skin material 2 surface layer. By further reducing the amount, the brazing property can be further improved.

  In addition, since the brazing material 1 is disposed only on one side of the core material and the brazing material amount is insufficient and the brazing property is inferior, the present invention contains a reduced amount of Si on both sides of the core material. In order to improve the brazing property, the amount of brazing material is compensated to compensate for the shortage of brazing material and the amount of Mg diffused is also reduced.

The significance and reasons for limitation of the alloy components in the aluminum alloy clad material for heat exchanger according to the present invention will be described.
(Heartwood)
Si and Mg:
Si and Mg function to improve the strength of the core material by age hardening by fine precipitation of the compound Mg ₂ Si. The preferable content range of Si is 0.2 to 2.0%. If the content exceeds 2.0%, the melting point of the core material is lowered, and erosion along the grain boundaries is likely to occur during brazing. A more preferable range of Si is 0.4 to 0.8%.

  The preferable content range of Mg is 0.2 to 1.5%. If the content is less than 0.2%, the effect of improving the strength is not sufficient. Erosion along the grain boundary is likely to occur during application. A more preferable range is more than 0.5% and 1.5% or less, and a further more preferable range is more than 1.0% and 1.5% or less.

Mn:
Mn functions to improve the corrosion resistance by improving the strength of the core material and increasing the potential difference from the sacrificial anode material by making the potential of the core material noble. A preferable content range is 0.8 to 2.0%, and if the content is less than 0.8%, the effect is small. If the content exceeds 2.0%, a coarse compound is produced at the time of casting, and the rolling processability is impaired. As a result, it is difficult to obtain a sound plate material. A more preferable range of Mn is 1.0 to 1.7%.

Cu:
Cu functions to improve the anticorrosion effect by improving the strength of the core material, making the potential of the core material noble, and increasing the potential difference from the sacrificial anode material. Furthermore, Cu in the core material diffuses into the sacrificial anode material during brazing and forms a gentle concentration gradient. As a result, the potential on the core material side becomes noble and the potential on the surface side of the sacrificial anode material becomes base. A gentle potential distribution is formed in the sacrificial anode material, and the corrosion form is changed to a full corrosion type. The preferable content of Cu is 1.2% or less. If the content exceeds 1.2%, the melting point of the core material is lowered, and erosion along the grain boundaries is likely to occur during brazing. A more preferable range of Cu is 0.2 to 0.8%.

Fe:
Fe improves the strength of the core material. A preferable content range is 2.0% or less, and when the content exceeds 2.0%, a coarse compound is produced at the time of casting, and rolling workability is impaired. As a result, it is difficult to obtain a sound plate material.

Ti:
Ti is divided into a high-concentration region and a low region in the thickness direction of the core material, and the layers are alternately distributed. As a result, the low-concentration region is preferentially corroded as compared to the high region. This prevents the progress of corrosion in the plate thickness direction, thereby improving the pitting corrosion resistance of the material. The preferable content range of Ti is 0.35% or less, and if it exceeds 0.35%, casting becomes difficult, and workability deteriorates, making it difficult to produce a sound material.

Cr, Zr, V, B:
Cr, Zr, V, and B suppress erosion during brazing heating by increasing the recrystallization temperature during brazing heating and increasing the crystal grain size of the core material. The preferable content ranges of these elements are all 0.3% or less, and even if each content exceeds 0.3%, the effect is saturated and further improvement effect cannot be expected.

(Skin 1 and Skin 2)
The skin material 1 is disposed on the outer surface side of the tube and joined to the fin, and the skin material 2 is disposed on the inner surface side of the tube and is in contact with the working fluid. Al-Si based alloys used as ordinary brazing filler metals are mostly in a liquid phase by brazing heating, and the thickness of the braze also decreases. Therefore, a large amount of Mg in the core material is dispersed in the brazing filler metal due to liquid phase diffusion. To reach. The skin material 1 and the skin material 2 are different from the Al-Si alloy used as the normal brazing material as described above, and by limiting the Si concentration to a low level within the brazing range, If the solid phase ratio is increased and the thickness of the skin material 1 and the skin material 2 is not reduced as much as possible, the distance from the core material to the skin material 1 surface layer and the skin material 2 surface layer can be increased, and Mg The liquid phase diffusion can be suppressed.

Si:
Si is limited to 3.0 to 6.0% for the above reason . If the content exceeds 6.0% , the diffusion amount of Mg increases and brazing properties are inhibited. A more preferable content range of Si is 3.0 to 4.0%.

Sr:
Sr makes the dispersion state of the simple Si fine and uniform, and suppresses local melting of the skin material 1 and the skin material 2. The preferable content range of Sr is 0.005 to 0.1%. If the content is less than 0.005%, the effect is small, and even if the content exceeds 0.1%, the effect is saturated. I can not expect. A more preferable range of Sr is 0.01 to 0.05%.

  In addition to the above, the skin material 1 includes Fe: 2.0% or less, Ti: 0.3% or less, Zn: 2.0% or less, Cu: 1.0% or less in a range not inhibiting the Mg diffusion suppressing effect. , Na: 0.1% or less, Sb: 0.1% or less, Bi: 0.2% or less, Be: 0.1% or less may be added. In addition, one or more of Ca: 1.0% or less, Li: 1.0% or less, In: 0.1% or less, Sn: 0.1% or less are added as necessary. Also good. If Zn is added in excess of 2.0%, the joint fillet between the tube and the fin is likely to be corroded, and the fin is likely to peel off.

  In addition to the above, the skin material 2 includes Fe: 2.0% or less, Ti: 0.3% or less, Zn: 10.0% or less, Cu: 1.0% or less in a range not inhibiting the Mg diffusion suppressing effect. Na: 0.1% or less, Sb: 0.1% or less, Bi: 0.2% or less, Be: 0.1% or less, In: 0.1% or less, Sn: 0.1% or less 1 type (s) or 2 or more types may be added. Moreover, 1 type or 2 types of Ca: 1.0% or less and Li: 1.0% or less may be added as needed. If Zn is added in excess of 10.0%, the amount of self-corrosion of the skin material 2 increases, and the strength as a tube material tends to decrease.

  In the present invention, as described above, Si and Mg are added to the core material to increase the strength, and the Si concentration of the skin material 1 and the skin material 2 is reduced and optimized, thereby fixing the skin material 1 and the skin material 2. By increasing the phase ratio, decreasing the ratio of Mg in the liquid phase diffusion, and suppressing the decrease in thickness due to melting of the skin material 1 and the skin material 2 as much as possible, the core material to the skin material 1 surface layer and the skin material 2 By maintaining the distance to the surface layer and reducing the diffusion amount of Mg from the core material to the skin material 1 surface layer and the skin material 2 surface layer, the brazing property is improved. Further, Sr is added to the skin material 1 or the skin material 2 to make the dispersion state of the single Si fine and uniform, suppress local melting, and further increase the diffusion amount of Mg from the core material to the skin material 1 surface layer or the skin material 2 surface layer. Reduce and further improve brazing.

  The aluminum alloy clad material according to the present invention is produced by ingoting the core material alloy, the skin material 1 alloy, and the skin material 2 alloy by DC casting. For example, among the obtained ingots, the core material alloy and the skin material The alloy for 2 is homogenized, and the alloy for skin 1 and the alloy for skin 2 are hot-rolled to a predetermined thickness. Thereafter, the obtained clad material is cold-rolled, intermediate-annealed, and finally cold-rolled to obtain an aluminum alloy clad material (for example, H14) having a predetermined thickness.

  The heat exchanger according to the present invention is manufactured by assembling the aluminum alloy clad material of the present invention together with other members and brazing and integrating them.

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

Example 1
An alloy for core material having the composition shown in Table 1 by continuous casting, an alloy for skin material 1 having the composition shown in Table 2 and an alloy for skin material 2 shown in Table 3 are obtained. The alloy for skin material 1 and skin material 2 was hot-rolled to a predetermined thickness, and these and the ingot of the core material alloy were combined and hot-rolled to obtain a clad material.

  Subsequently, the obtained clad material was cold-rolled, intermediate-annealed, and cold-rolled to obtain a plate material (cladding material, grade H14) having a thickness of 0.20 mm. The clad configuration was such that the clad rate of the skin material 1 was 20% (thickness 0.040 mm), the clad rate of the skin material 2 was 20% (thickness 0.040 mm), and the remainder was the core material. Using the obtained clad material as a test material, brazing properties and strength were evaluated according to the following methods. The results are shown in Table 4.

  Note that the type, thickness, and clad rate of the clad material to be manufactured are not limited to those of the first embodiment, and may be appropriately adjusted according to the application, for example. For example, the plate thickness is 0.10 mm to 2.00 mm, and the cladding rate is about 2 to 30%.

(Evaluation of brazing)
Using the obtained clad plate material, as shown in FIG. 4, the end of the vertical plate is bent at a right angle, 5 g / m ^{2 of} fluoride flux is applied only to the vertical plate, and then combined as shown in FIG. A filling test piece was prepared, heated to 600 ° C. (material temperature) in nitrogen gas for 3 minutes, and the gap filling length (F _{L in} FIG. 5) of the gap filling test piece after heating was measured using a caliper, A gap filling length (F _L ) of 10 mm or more was determined to be good and less than 10 mm was determined to be defective. In addition, in FIG. 4, a numerical value shows length (unit mm).

(Strength evaluation)
Without applying a flux to the obtained clad material, it was heated in nitrogen gas to 600 ° C. (material temperature) for 3 minutes, and then a tensile test (JIS Z 2241) was performed. Less than 180 MPa was regarded as defective.

  As seen in Table 4, all of the test materials 1 to 30 according to the present invention were excellent in brazeability and had sufficient strength.

Comparative Example 1
The alloy for skin material 1 having the composition shown in Table 5 was ingot by continuous casting, the obtained ingot was hot-rolled to a predetermined thickness, and the ingot of the core material alloy ingot in Example 1 was used. The alloy for skin material 2 that was hot rolled to a predetermined thickness after ingot formation in Example 1 was combined and hot rolled to obtain a clad material.

  Subsequently, the obtained clad material was cold-rolled, intermediate-annealed, and cold-rolled to obtain a plate material (cladding material, grade H14) having a thickness of 0.20 mm. The clad configuration was such that the clad rate of the skin material 1 was 20% (thickness 0.040 mm), the clad rate of the skin material 2 was 20% (thickness 0.040 mm), and the remainder was the core material. Using the obtained clad material as a test material, brazing properties and strength were evaluated according to the same method as in the examples. The results are shown in Table 6.

As shown in Table 6, since the Al-Si alloy brazing material containing 10% Si used as a normal brazing material was used as the skin material 1, the test material 101 was melted during brazing heating. Then, since Mg diffused to the surface layer of the skin material 1, the brazing property was lowered, and the gap filling length (F _L ) was less than 10 mm. Since the test material 102 was not provided with the skin material 2, the brazing material was insufficient and the gap filling length (F _L ) was less than 10 mm.

1 Cladding material 2 Core material 3 Brazing material (skin material 1)
4 Sacrificial anode material (skin material 2)
W weld

Claims (7)

A clad material used when manufacturing an aluminum alloy heat exchanger by brazing using a flux containing a fluoride flux or a cesium compound in an inert gas atmosphere, and clad the skin material 1 on one side of the core material , in the aluminum alloy clad material obtained by cladding a cladding material 2 on the other side, by mass% (hereinafter the same), the core material, Mn: 0.8~2.0%, Si: 0.2~2.0%, Mg: An Al—Mn—Si—Mg-based aluminum alloy containing 0.2 to 1.5%, and remaining aluminum and inevitable impurities, and the skin material 1 and the skin material 2 are Si: 3.0 to An aluminum alloy for high-strength heat exchangers with excellent brazing characteristics, characterized in that it is an Al-Si-based aluminum alloy containing 6.0% and the balance aluminum and inevitable impurities Rudd material. The core material contains Mn: 0.8 to 2.0%, Si: 0.2 to 2.0%, Mg: more than 0.5% and 1.5% or less, and the remainder from aluminum and inevitable impurities The aluminum alloy clad material for a high-strength heat exchanger having excellent brazing properties according to claim 1, which is an Al—Mn—Si—Mg-based aluminum alloy. The skin material 1 is an Al—Si-based aluminum alloy containing Si: 3.0 to 6.0%, Sr: 0.005 to 0.1%, and remaining aluminum and inevitable impurities, The brazing property according to claim 1 or 2 , wherein the material 2 is an Al-Si-based aluminum alloy containing Si: 3.0 to 6.0%, the balance being aluminum and inevitable impurities. Excellent aluminum alloy clad material for high strength heat exchangers. The core material is further Cu: 1.2% or less, Fe: 2.0% or less, Ti: 0.35% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 0.00. The high-strength heat exchanger excellent in brazing property according to any one of claims 1 to 3, wherein the content of B is 0.3% or less, and B: 0.3% or less. Aluminum alloy clad material. The skin material 1 is further Fe: 2.0% or less, Ti: 0.3% or less, Zn: 2.0% or less, Cu: 1.0% or less, Na: 0.1% or less, Sb: The wax according to any one of claims 1 to 4 , comprising one or more of 0.1% or less, Bi: 0.2% or less, and Be: 0.1% or less. Aluminum alloy clad material for high-strength heat exchangers with excellent adhesion. The skin material 2 is further Sr: 0.005 to 0.1%, Fe: 2.0% or less, Ti: 0.3% or less, Zn: 10.0% or less, Cu: 1.0% or less Na: 0.1% or less, Sb: 0.1% or less, Bi: 0.2% or less, Be: 0.1% or less, In: 0.1% or less, Sn: 0.1% or less The aluminum alloy clad material for a high-strength heat exchanger having excellent brazing properties according to any one of claims 1 to 5 , characterized by containing one or more of the following. A heat exchanger, wherein the aluminum alloy clad material according to any one of claims 1 to 6 is assembled and integrated by brazing.

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