JP5498213B2 - Aluminum alloy clad material for high-strength heat exchangers with excellent brazeability - 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) High-strength heat with excellent brazing properties suitable for pipe materials for connecting cladding plates and header plate materials, including those in which the cladding material is bent and tube-shaped by welding or brazing) The present invention relates to an aluminum alloy clad material for an exchanger.

  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). The tube material or header plate material of such an automobile radiator or heater has a two-layer structure in which an Al—Mn alloy such as JIS A3003 is used as a core material and an Al—Si alloy brazing material is clad on one side of the core material. An aluminum alloy clad material having a three-layer structure in which a brazing material is clad on one surface of a core material and a sacrificial anode material of an Al-Zn alloy or an Al-Zn-Mg alloy is clad on the other surface It 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 for piping materials connecting between heat exchangers for automobiles, an Al-Mn alloy such as JIS A3003 is used as a core material, and a sacrificial anode material of Al-Zn alloy such as JIS A7072 is clad on the inner surface or the inner and outer surfaces. Two-layer or three-layer clad tubes are used. The sacrificial anode material on the inner surface of the clad tube is in contact with the coolant during use and exerts a sacrificial anode effect to prevent the occurrence of pitting corrosion or crevice corrosion on the core material, and the outer sacrificial anode material is used in harsh environments. When used, the sacrificial anode effect is exhibited to prevent pitting corrosion or crevice corrosion occurring in the core material.

  As shown in FIG. 1, the radiator and the heater core are manufactured by bending and welding a brazing material 3 with a brazing material 3 on one side of a core material 2 and a sacrificial anode material 4 on the other side (welding part W). It was made by flattening the tube, assembling it to the header plate, and then brazing it integrally (welding type), but recently, as shown in FIGS. Thus, a method of manufacturing a tube by forming it into a tube shape and assembling it to a header plate and integrally brazing (brazing die) is performed.

  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. Since the corrosion resistance is reduced, a material structure has been proposed in which a large amount of Zn is added to the sacrificial anode material to ensure a potential difference from the core material and to ensure the sacrificial anode effect.

Also, a large amount of Mg is added to the sacrificial anode material, and Mg ₂ Si is finely precipitated at the interface between the sacrificial anode material and the core material, or 0.05 to 0.5% Mg is added to the core material to add to the core material. A material structure in which Mg ₂ Si is finely precipitated and further enhanced in strength has been proposed, but the addition of Mg to the sacrificial anode material is effective for the welding type, but for the brazing type, it is a sacrificial. There is a surface where the anode material and the braze are directly joined, and Mg reacts with the flux to form a compound such as MgF ₂ , which causes a problem that the function of the flux is impaired and a brazing defect occurs. When Mg is added to the core material, Mg is solid-phase diffused from the core material to the brazing material during brazing heating, and further, after the wax is melted, Mg is liquid-phase diffused through the molten braze, resulting in a large amount of Mg. However, since it 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.

  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 the combination thereof, even if a relatively high concentration of Mg was added to the core material, after the wax melted, the Mg diffused in the liquid phase through the molten solder, and the amount of Mg in the core material was reduced. In order to suppress the reduction, the Si concentration of the skin material is set to a specific low range, and in order to further reduce the liquid phase diffusion of Mg, it is necessary to control the dispersion state of Si by adding Sr. I found it preferable.

  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 to provide heat exchangers, particularly automotive heat exchanger tube materials, header plate materials, and piping materials. Another object of the present invention is to provide an aluminum alloy clad material for a high-strength heat exchanger that has excellent brazing properties and can be suitably used as a 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 clad with the skin material 1 on one surface of the core material and the skin material 2 on the other surface. A clad aluminum alloy clad material, wherein the core material is Mn: 0.8-2.0%, Si: 0.2-2.0%, Mg: 0.2-1.5% by mass%. It is an Al—Mn—Si—Mg-based aluminum alloy containing the balance aluminum and unavoidable impurities, and the skin material 1 contains Si: 2.5 to 6.0%, from the balance aluminum and unavoidable impurities. And the skin material 2 is one or two of Zn: 0.5 to 10%, In: 0.001 to 0.1%, and Sn 0.001 to 0.1%. Contains more than seeds, the balance aluminum and unavoidable Characterized in that an aluminum alloy consisting of impurities. Hereinafter, all alloy component values are indicated by mass%.

  The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 2 is characterized in that, in claim 1, the skin material 1 is Si: 2.5 to 6.0%, Sr: 0.005 to 0 It is an Al—Si-based aluminum alloy containing 1% and the balance being aluminum and inevitable impurities.

  The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 3 is the core material according to claim 1 or 2, further comprising: Cu: 1.2% or less, Fe: 2.0% or less, Contains one or more of 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 is characterized by doing.

  The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 4 is characterized in that, in any one of claims 1 to 3, 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 5 is any one of claims 1 to 4, wherein the skin material 2 further comprises Mn: 1.8% or less, Fe: 2 0.0% or less, Si: 2.0% or less, Ni: 2.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, Ti: 0.35% or less, Cu: 0.2 % Or less of 1% or less.

  ADVANTAGE OF THE INVENTION According to this invention, it is the aluminum for heat exchangers which has the high intensity | strength and the outstanding brazing property, and can be used conveniently as a raw material of a heat exchanger, especially the tube material of a heat exchanger for automobiles, a header plate material, and a piping material. An alloy cladding material is provided.

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.

When the brazing material is, for example, an Al-10% Si alloy brazing material of a general brazing material, as described above, after the brazing melt, Mg is liquid phase diffused through the molten brazing, so that a large amount of Mg is reaches 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.

  In the present invention, by reducing and optimizing the Si concentration of the skin material 1 and increasing the solid phase rate of the skin material 1, the solid phase diffusion rate becomes significantly smaller than the liquid phase diffusion rate. The liquid phase diffusion ratio can be reduced, and when the solid phase ratio of the skin material 1 is increased, a decrease in thickness due to melting of the skin material 1 is suppressed, so the distance from the core material to the skin material 1 surface layer Is held, the diffusion amount of Mg from the core material to the surface layer of the skin material 1 can be reduced, and the brazing property can be improved.

  By simply reducing and optimizing the Si concentration of the skin material 1, the skin material 1 may partially melt locally due to the non-uniformity of the metal structure, and the liquid phase diffusion of Mg may partially increase at that portion. is there. In the present invention, by adding Sr to the skin material 1 to make the dispersion state of simple Si fine and uniform, suppressing local melting and further reducing the amount of Mg diffused from the core material to the skin material 1 surface layer, The brazability can be further improved.

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 in the range of 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. The more preferable content 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 material 1)
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. Unlike the Al—Si alloy used as a normal brazing material as described above, the skin material 1 limits the solid phase ratio during brazing heating by limiting the Si concentration to a low level within the brazing range. If the thickness is increased and the thickness of the skin material 1 is not reduced as much as possible, the distance from the core material to the surface layer of the skin material 1 can be increased, and the liquid phase diffusion of Mg can be suppressed. .

Si:
Si is limited to 2.5 to 6.0% for the above reason. If it is less than 2.5%, there is no function as a brazing material, and if it exceeds 6.0%, the diffusion amount of Mg increases and brazing properties are inhibited. A more preferable range of Si is 3.0 to 4.5%, and a further preferable range is 3.0 to 4.0%.

Sr:
Sr makes the dispersion state of the single Si fine and uniform, and suppresses local melting of the skin material 1. 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.

(Skin material 2)
Zn, In and Sn:
Zn, In and Sn lower the potential of the skin material 2 and maintain the sacrificial anode effect on the core material. As a result, pitting corrosion and crevice corrosion of the core material are prevented. A preferable range of Zn is 0.5 to 10.0%, a preferable range of In is 0.001 to 0.1%, and a preferable range of Sn is 0.001 to 0.1%. A more preferable range of Zn is 1.5 to 5%, a more preferable range of In is 0.01 to 0.05%, and a more preferable range of Sn is 0.01 to 0.05%.

  In addition to the above components, the skin material 2 has Mn: 1.8% or less, Fe: 2.0% or less, Si: 2.0% or less, Ni: One or more of 2.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, Ti: 0.35% or less, Cu: 0.2% or less are added. Also good. Moreover, 1 type or 2 types of V: 0.3% or less and B: 0.3% or less may be added as needed.

  In the present invention, as described above, Si and Mg are added to the core material to increase the strength, while reducing and optimizing the Si concentration of the skin material 1 to increase the solid phase ratio of the skin material 1, The ratio of the liquid phase diffusion is decreased, and the decrease in thickness due to melting of the skin material 1 is suppressed as much as possible, thereby maintaining the distance from the core material to the skin material 1 surface layer, and the Mg from the core material to the skin material 1 surface layer. The brazing property is improved by reducing the amount of diffusion. Furthermore, Sr is added to the skin material 1 to make the dispersion state of single Si fine and uniform, suppress local melting, further reduce the amount of Mg diffused from the core material to the skin material 1 surface layer, and further improve the brazing property Let

  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.

  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 ingot obtained by ingoting a core material alloy having the composition shown in Table 1, an alloy for skin material 1 having the composition shown in Table 2, and an alloy for skin material 2 having the composition shown in Table 3 by continuous casting. Among them, the alloy for core material and the alloy for skin material 2 are homogenized, and the alloy for skin material 1 and the alloy for skin material 2 are hot-rolled to a predetermined thickness. 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 5.0 mm or more was determined to be good, and less than 5.0 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 39 according to the present invention were excellent in brazing property 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 5.0 mm.

1 Cladding material 2 Core material 3 Brazing material 4 Sacrificial anode material W Welded part

Claims (5)

An aluminum alloy clad material in which the skin material 1 is clad on one surface of the core material and the skin material 2 is clad on the other surface, and the core material is Mn: 0.8 to 2.0%, Si : 0.2-2.0%, Mg: 0.2-1.5%, Al-Mn-Si-Mg-based aluminum alloy consisting of the balance aluminum and unavoidable impurities, Si: 2.5-6.0% Al-Si-based aluminum alloy consisting of the balance aluminum and inevitable impurities, skin material 2 is Zn: 0.5-10%, In: 0.001 It is excellent in brazeability, characterized by being an aluminum alloy containing one or more of -0.1%, Sn0.001-0.1%, and the balance aluminum and inevitable impurities Aluminum alloy for high strength heat exchanger Rudd material. The skin material 1 is an Al—Si-based aluminum alloy containing Si: 2.5 to 6.0%, Sr: 0.005 to 0.1%, and remaining aluminum and inevitable impurities. The aluminum alloy clad material for a high-strength heat exchanger excellent in brazeability according to claim 1. 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 aluminum alloy clad for high-strength heat exchangers with excellent brazeability according to claim 1 or 2, characterized by containing one or more of 3% or less and B: 0.3% or less. Wood. 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 3, 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 further includes Mn: 1.8% or less, Fe: 2.0% or less, Si: 2.0% or less, Ni: 2.0% or less, Cr: 0.3% or less, Zr: The wax according to any one of claims 1 to 4, characterized by containing one or more of 0.3% or less, Ti: 0.35% or less, and Cu: 0.2% or less. Aluminum alloy clad material for high-strength heat exchangers with excellent adhesion.

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