JP2007092101A - Aluminum alloy clad material excellent in surface joinability on sacrificial anode material surface, and heat-exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy clad material which can suitably be used as an aluminum alloy-made heat exchanger, especially a tube material, header plate material in the heat exchanger for automobile and gives excellent corrosion resistance by displaying sufficient corrosion preventive effect as a sacrificial anode material and has excellent surface joinability by brazing on the sacrificial anode material surface. <P>SOLUTION: In the aluminum alloy clad material cladded with the sacrificial anode material, the sacrificial anode material is composed of 0.5-5% Zn, 0.1-<0.4% Fe, 0.01-1.2% Si, 0.1-2.0% Mn and the balance Al with inevitable impurities, and if heating the aluminum clad material under conditions of 50°C/min temperature-raising speed till heating to 400°C and within 30min as reaching time till heating to 595°C, a crystal grain size on the surface of the sacrificial anode material is 0.08-0.20mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aluminum alloy clad material excellent in surface bondability by brazing of a sacrificial anode material surface, in particular, a radiator or a heater bonded by brazing using a fluoride flux in an inert gas atmosphere or vacuum brazing. The present invention relates to an aluminum alloy clad material for a heat exchanger that is suitably used as a material for a fluid passage component such as a tube and header of an aluminum alloy heat exchanger such as the above, and a heat exchanger in which a tube formed from the clad material is assembled.

  A heat exchanger made of aluminum alloy for automobiles such as a radiator, for example, includes a tube serving as a passage for a working fluid (refrigerant), fins disposed between the tubes, and a header. As a tube material and header plate material of such an automobile heat exchanger, an aluminum of a two-layer structure in which an Al—Mn alloy such as JIS A3003 is used as a core and an Al—Si alloy brazing material is clad on one side of the core is used. Alloy clad material, aluminum alloy clad material with a three-layer structure in which brazing material is clad on both sides of the core material, or brazing material is clad on one side of the core material and Al—Zn alloy or Al—Zn—Mg type on the other side A three-layer aluminum alloy clad material clad with an alloy sacrificial anode material is used.

  When manufacturing an aluminum alloy heat exchanger, the cladding material Al-Si brazing material is used when the tube is joined by joining the outer surface of the tube and the fin, joining the tube and the header plate, or brazing the clad plate. Clad for brazing joints. For these brazings, inert gas atmosphere brazing using a fluoride flux and vacuum brazing are applied.

  Sacrificial anode material of aluminum alloy clad material with a three-layer structure is used on the inner surface side of the tube, for example, and exerts sacrificial anode action in contact with the working fluid, preventing the occurrence of pitting corrosion and crevice corrosion of the core material, and the outer surface of the tube The fin material joined to the surface exhibits a sacrificial anodic action during use to prevent the occurrence of pitting corrosion of the core material.

  Conventionally, as shown in FIG. 1, a radiator or a heater is formed by bending and welding a clad plate material 4 in which a brazing material 6 is clad on one surface of a core material 5 and a sacrificial anode material 7 is clad on the other surface ( The welded portion W) is made into a flat tube 1 and assembled to a header plate and then brazed integrally (hereinafter referred to as a welding mold). However, in recent years, as shown in FIGS. In many cases, the tube shapes 2 and 3 are formed without being welded only by bending, and are assembled to the header plate and then integrally brazed (hereinafter referred to as a brazing die).

  In the brazing mold shown in FIGS. 2 and 3, in the case of brazing with an inert gas atmosphere, the air on the inner surface of the tube remains without being completely replaced by the inert gas during brazing. That is, the joining surface of the sacrificial anode material 7 and the brazing material 6, and in FIG. 3, brazing joining of the B portion, that is, the joining end surface of the T-shaped bending end of the tube 3 and the sacrificial anode material 7 is performed. Insufficient wetting and spreading on the surface of the sacrificial anode material may be insufficient.

As for aluminum alloy clad materials for heat exchangers, several studies have been made so far for the purpose of preventing corrosion in the vicinity of crystal grain boundaries such as intergranular corrosion of sacrificial anode materials. The recrystallized grains in the thickness direction of the material should be less than the thickness of the sacrificial anode material in the clad material (Patent Document 1), and the Zn content of the sacrificial anode material should be more than 6.0% and not more than 15.0% Although it has been proposed to have a component structure and the crystal grain size of the surface after brazing to be 100 to 700 μm (Patent Document 2), improvement of the brazing property of the sacrificial anode material surface has not been studied.
Japanese Patent Laid-Open No. 11-100608 JP 11-209837 A

  In order to solve the above problems, the inventors have studied the factors affecting the wettability of the sacrificial anode material surface. As a result, in particular, the crystal grain size of the sacrificial anode material has an effect on the wettability of the wax. The inventors have found that the wettability of the sacrificial anode material is improved by controlling the crystal grain size after brazing heating of the sacrificial anode material surface, and the surface bonding property by brazing of the sacrificial anode material surface is improved.

  The present invention has been made as a result of further examination and examination based on the above-mentioned knowledge, and its purpose is a heat exchanger, in particular, an automotive aluminum alloy heat exchanger such as a radiator or a heater mounted on a vehicle. The sacrificial anode material exhibits a sufficient anticorrosion effect to give excellent corrosion resistance, and has excellent surface joining by brazing the sacrificial anode material surface. The object is to provide an aluminum alloy clad material.

  An aluminum alloy clad material excellent in surface bondability by brazing a sacrificial anode material surface according to claim 1 for achieving the above object is an aluminum alloy clad material clad with a sacrificial anode material, and the sacrificial anode material Zn: 0.5 to 5%, Fe: 0.1 to less than 0.4%, Si: 0.01 to 1.2%, Mn: 0.1 to 2.0%, When the aluminum alloy clad material is heated under the condition that the temperature rising rate up to 400 ° C. is 50 ° C./min and the time required to reach 595 ° C. is within 30 minutes, the surface grain size of the sacrificial anode material is 0.08. It is ˜0.20 mm.

  The aluminum alloy clad material excellent in surface bondability by brazing the sacrificial anode material surface according to claim 2 is characterized in that the sacrificial anode material further comprises Cr: 0.02 to 0.3%, Zr: 0.00. It is characterized by containing one or more of 02 to 0.3% and Ti: 0.01 to 0.35%.

  The aluminum alloy clad material excellent in surface bondability by brazing the sacrificial anode material surface according to claim 3 is the sacrificial anode material according to claim 1 or 2, further comprising In: 0.001 to 0.05%, Sn: 0.001-0.05% of 1 type or 2 types are contained.

  The aluminum alloy clad material excellent in surface bondability by brazing of the sacrificial anode material surface according to claim 4 is obtained by clad the brazing material on one surface of the core material and the other surface on the other surface. It has a three-layer structure in which a sacrificial anode material is clad.

  The aluminum alloy clad material excellent in surface bonding property by brazing the sacrificial anode material surface according to claim 5 is manufactured by surface-bonding the sacrificial anode material surface by brazing in any one of claims 1 to 4. It is used as a tube material for heat exchangers.

  A heat exchanger according to claim 6 is formed by molding the aluminum alloy clad material according to any one of claims 1 to 4 into a heat exchanger tube, and assembling the formed tube, a fin and a header, and brazing them integrally. It is characterized by being joined.

  According to the present invention, a heat exchanger, particularly a heat exchanger made of aluminum alloy for automobiles such as a radiator or heater for automobiles joined by brazing using a fluoride flux in an inert gas atmosphere or vacuum brazing. Aluminum that can be used favorably as a tube material, header plate material, etc., and the sacrificial anode material provides excellent corrosion resistance by providing a sufficient anticorrosion effect, and also has excellent surface bonding by brazing the sacrificial anode material surface An alloy cladding material is provided.

The aluminum alloy clad material of the present invention is characterized by the composition of the sacrificial anode material and the crystal grain size after brazing heating, and the composition and the reason for the limitation will be described.
(Sacrificial anode material)
Zn: 0.5 to 5.0%
Zn lowers the potential of the sacrificial anode material, exerts a sacrificial anode effect on the core material, and prevents the core material from pitting or crevice corrosion. The preferable content of Zn is in the range of 0.5 to 5.0%. If the Zn content is less than 0.5%, the effect is small, and if it exceeds 5.0%, the self-corrosion resistance of the sacrificial anode material Decreases. A more preferable content range of Zn is 1.5 to 5.0%. By setting the lower limit of the Zn content to 1.5%, a more excellent sacrificial anode effect can be exhibited.

Fe: Less than 0.1 to 0.4% Fe refines the crystal grains after brazing heating of the sacrificial anode material, and reduces the crystal grain size after brazing heating. If the Fe content exceeds 0.4%, the crystal grain size after brazing heating becomes too fine, melting occurs partly during brazing, and the self-corrosion resistance of the sacrificial anode material decreases. The preferable content of Fe is less than 0.4%, and if it is less than 0.1%, the effect is not sufficient. The more preferable content range of Fe is 0.1 to 0.3%.

Si: 0.01-1.2%
Si improves the strength of the sacrificial anode material, refines the crystal grains after brazing heating of the sacrificial anode material, and reduces the crystal grain size. If the Si content exceeds 1.2%, the melting point of the sacrificial anode material is lowered, and partial melting occurs during brazing, thereby reducing the sacrificial anode effect. If it is less than 0.01%, the bullion cost becomes high, which is not practically preferable. The more preferable content range of Si is 0.1 to 0.5%.

Mn: 0.1 to 2.0%
Mn improves the strength of the sacrificial anode material, refines the crystal grains after brazing heating of the sacrificial anode material, and reduces the crystal grain size. If the Mn content exceeds 2.0%, the self-corrosion resistance of the sacrificial anode material decreases. If it is less than 0.1%, the effect is not sufficient. A more preferable content range of Mn is 0.6 to 1.4%.

Cr: 0.02-0.3%, Zr: 0.02-0.3%, Ti: 0.01-0.35%
Cr, Zr, and Ti are divided into a high concentration region and a low concentration region in the thickness direction of the material, and these regions are alternately distributed in layers, and the low concentration region of each element is higher than the high region. Therefore, the corrosion form becomes layered, and therefore the progress of intergranular corrosion in the thickness direction is hindered to improve the pitting corrosion resistance of the material.

  The preferable content of Cr and Zr is in the range of 0.02 to 0.3%. If the content is less than 0.02%, the effect is not sufficient, and even if the content exceeds 0.3%, the effect is saturated. No further improvement can be obtained. A more preferable content range of Cr and Zr is 0.05 to 0.2%. The preferable content of Ti is in the range of 0.01 to 0.35%. When the content is less than 0.01%, the effect is small. When the content exceeds 0.35%, a coarse crystallized product is produced during casting. In addition, the processability is lowered, making it difficult to produce a sound material. A more preferable content range of Ti is 0.06 to 0.3%.

In: 0.001-0.05%, Sn: 0.001-0.05%
In and Sn lower the potential of the sacrificial anode material by adding a small amount, and prevent the occurrence of pitting corrosion and crevice corrosion of the core material by the sacrificial anode effect. The preferable contents of In and Sn are in the range of 0.001 to 0.05%. If the content is less than 0.001%, the effect is not sufficient. . A more preferable content range of In and Sn is 0.01 to 0.02%. In the present invention, the same effect can be obtained by adding one or more of V: 0.01 to 0.3%, B: 0.01 to 0.3%, and Cu: 0.2% or less.

  The aluminum alloy clad material according to the present invention has a three-layer clad material in which a brazing material is clad on one surface of a core material, a sacrificial anode material is clad on the other surface, and a two-layer clad material in which a sacrificial anode material is clad on one surface of the core material. It is applied to a clad material having a three-layer structure in which a sacrificial anode material is clad on both surfaces of a material and a core material. When applied to a clad material having a three-layer structure in which a brazing material is clad on one surface of the core material and a sacrificial anode material is clad on the other surface, the core material and the brazing material are usually put into practical use as shown below, for example. Aluminum alloys can be used.

(Heartwood)
As the core material, an Al-Mn alloy represented by A3003, a higher strength Al-Si-Mn alloy, an Al-Cu-Mn alloy, an Al-Si-Cu-Mn alloy, or the like may be used. it can. Also, alloys obtained by adding Mg to the respective alloys can be used. The same effect can be obtained even if Ti, Zn, Cr, Zr, V, B, etc. are further contained in each alloy.

(Brazing material)
As the brazing material, a commonly used Al—Si alloy, for example, an Al—Si alloy containing Si: 6 to 13% is used. When the brazing performed to form a radiator or the like is vacuum brazing, an Al—Si—Mg alloy or the like is used. These Al—Si based alloys and Al—Si—Mg based alloys include Bi: 0.2% or less, Be: 0.1% or less, Ca: 1.0% or less, Li: 1, as necessary. 0.0% or less and Sr: 0.005 to 0.1% may be added.

(The crystal grain size of the surface of the sacrificial anode material when heated at a rate of temperature increase to 400 ° C. of 50 ° C./min and an arrival time of 595 ° C. within 30 minutes: 0.08 to 0.20 mm)
In the present invention, it is important that the crystal grain size on the surface of the sacrificial anode material is 0.08 to 0.20 mm when heated on the above heating conditions. The above heating conditions correspond to the conditions for brazing heating. If the crystal grain size of the surface of the sacrificial anode material is 0.08 to 0.20 mm under the above heating conditions, the sacrificial anode material after normal brazing heating is used. The crystal grain size of the surface can be set to about 0.08 to 0.20 mm.

  When the wax spreads to the surface of the sacrificial anode material, the grain boundary is preferentially a path through which the wax spreads, and then the wax wets and spreads inward from the crystal grain boundary. Therefore, when the crystal grain size is small, there are many routes for wetting and spreading, and the wax spreads uniformly. On the other hand, when the crystal grain size is large, there are few routes for wetting and spreading, the wetting and spreading of wax becomes non-uniform, and the wettability decreases. The crystal grain size of the sacrificial anode material with good brazing wettability is in the range of 0.08 to 0.20 mm when viewed from the surface of the sacrificial anode material, and when it exceeds 0.20 mm, the wetting and spreading properties are reduced. If this is 0.08 mm or less, this effect is saturated. A more preferable range of the crystal grain size is 0.08 to 0.15 mm.

  Production of the aluminum alloy clad material of the present invention, for example, the core material constituting the aluminum alloy clad material, the sacrificial anode material and the aluminum alloy constituting the brazing material, ingot by continuous casting, the ingot obtained, The core material is homogenized, the brazing material is homogenized as necessary, and then hot-rolled to a predetermined thickness. The sacrificial anode material is at a solidus temperature (° C.) × 0.7 or higher. After homogenization treatment, hot-roll to a predetermined thickness, then hot-roll in accordance with conventional methods by combining the aluminum alloy ingot for core material with the hot-rolled aluminum alloy for sacrificial anode and aluminum alloy for brazing material Then, a clad material is used, and then cold rolling, intermediate annealing at 350 ° C. or lower, and cold rolling at a workability of 20 to 35% are performed to obtain a predetermined thickness.

  In the present invention, the crystal grain size on the surface of the sacrificial anode material when heated at a rate of temperature increase to 400 ° C. of 50 ° C./min and an arrival time of 595 ° C. within 30 minutes is 0.08 to 0.005. In order to control to a range of 20 mm, the ingot of the sacrificial anode material is homogenized at a temperature equal to or higher than the solidus temperature of the sacrificial anode material (° C.) × 0.7 and the intermediate annealing temperature is 350 ° C. or less. It is effective to make the degree of cold rolling after intermediate annealing 20 to 35%.

  The aluminum alloy clad material of the present invention is molded into a tube shape shown in FIGS. 2 to 3, and a header made of an aluminum alloy fin and an aluminum alloy is assembled together with the tube, and brazed together to form a radiator and a heater. Such as automotive heat exchangers.

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

Example 1
Among the ingots obtained by ingot-making the alloy for core material having the composition shown in Table 1, the alloy for sacrificial anode material having the composition shown in Table 2, and the alloy for brazing material having the composition shown in Table 3 by continuous casting. The ingots of the core material alloy and the sacrificial anode material alloy were homogenized according to a conventional method. The homogenization temperature of the sacrificial anode material was set at 550 ° C. (solidus temperature (° C.) of sacrificial anode material × 0.7 or higher temperature).

  Next, the ingot of the alloy for sacrificial anode material and the alloy for brazing material is hot-rolled to a predetermined thickness, and the hot-rolled sheet and the ingot of alloy for core material (thickness 30 mm) are combined as a hot material. Rolling was performed to obtain a clad material having a three-layer structure (thickness: 3 mm). Thereafter, cold rolling, intermediate annealing (temperature 350 ° C.), and cold rolling with a workability of 30% were performed to obtain a plate material (cladding material) having a thickness of 0.20 mm. The structure of the clad material is 0.040 mm for the sacrificial anode material and 0.035 mm for the brazing material.

Using the obtained clad material as a test material, the crystal grain size of the surface (L-LT surface) of the sacrificial anode material is measured by the following method, and surface bondability and brazing wettability of the sacrificial anode material surface are measured. evaluated. The results are shown in Table 4.
(Measurement of crystal grain size)
Fluoride flux was applied to the clad material (test material) and heated to 595 ° C. (material temperature) in nitrogen gas. However, it heated at the temperature increase rate of 50 degree-C / min up to 400 degreeC. The time to reach a temperature of 595 ° C. was 20 minutes. The test material after heating was electropolished in a mixed solution of phosphoric acid 400 mL, sulfuric acid 100 mL and chromic anhydride 25 g for 1 to 3 minutes at a voltage of 30 V. Furthermore, pure water 500 mL, hydrofluoric acid 27 mL (46%), Electropolishing was performed at a voltage of 25 to 30 V for 45 to 60 seconds in a solution mixed with 11 g of boric acid. Thereafter, the polarization microstructure on the surface of the sacrificial anode material was photographed using an optical microscope, and the crystal grain size was measured by a comparative method. The standard grain size structure chart of ASTM (E112-61) was used for comparison.

(Evaluation of surface bondability by brazing the sacrificial anode material surface)
Using the obtained clad plate material, the end of the vertical plate was bent at a right angle, and after applying 5 g / m ^{2 of} fluoride flux only to the vertical plate, a gap filling test piece was prepared by combining as shown in FIG. Heated to 595 ° C. (material temperature) in gas. However, it heated at the temperature increase rate of 50 degree-C / min up to 400 degreeC. In FIG. 4, the numerical value indicates the length (unit: mm).
Void filling length of the gap filling test piece after heating F _{L (Figure} 5) was measured using calipers. In the evaluation of the surface bonding property by brazing, a gap filling length of 8.0 mm or more was evaluated as good (◯), and less than 8.0 mm was evaluated as defective (×).

(Evaluation of wax spreading on sacrificial anode material surface)
Using the obtained clad plate material, a 20 mm × 60 mm plate was cut out, and the end surfaces (all four surfaces) were cut by a shaper process to finish 15 mm × 55 mm. Without applying the flux, this plate was placed horizontally in the furnace with the sacrificial anode material facing up, and heated at a brazing temperature (material temperature) of 595 ° C. in nitrogen gas. However, it heated at the temperature increase rate of 50 degree-C / min up to 400 degreeC. A photograph of the sacrificial anode material surface after heating taken at a magnification of 16 using an optical microscope (negative-positive reversal photography) (FIG. 6) From above the average length L around the wax (for example, L = (L1 + L2) / 2 in FIG. 6) ) Was measured. In the evaluation of the wetting and spreading property of the wax, the average length L around the wax was 1.5 mm or more as good (◯), and less than 1.5 mm as bad (x).

  As seen in Table 4, the test material No. All of Nos. 1 to 25 were excellent in surface bondability by brazing of the surface of the sacrificial anode material, and wettability of the brazing.

Comparative Example 1
An alloy for a sacrificial anode material having the composition shown in Table 5 was ingoted by continuous casting, and the resulting ingot was homogenized at a temperature of 550 ° C. Next, the ingot of the alloy for sacrificial anode material and the ingot of the alloy for brazing material ingoted in Example 1 were hot-rolled to a predetermined thickness, and these hot-rolled plates and the core material ingoted in Example 1 were hot rolled. An alloy ingot (thickness 30 mm) was hot-rolled as a laminated material to obtain a three-layer clad material (thickness 3 mm). Thereafter, a plate material (clad material) having a thickness of 0.20 mm was obtained by cold rolling, intermediate annealing (temperature: 500 ° C.), and cold rolling with a workability of 70%. The structure of the clad material is 0.080 mm for the sacrificial anode material and 0.035 mm for the brazing material.

  Using the obtained clad material as a test material, the crystal grain size (L-LT surface) of the surface of the sacrificial anode material was measured in the same manner as in Example 1, and the surface bondability by brazing the sacrificial anode material surface and the wetting spread of the brazing Sex was evaluated. The results are shown in Table 6.

  As shown in Table 6, since the test material 26 has a small Fe content, the crystal grain size of the sacrificial anode material is large, and the surface bonding property by brazing and the wetting and spreading property of the brazing are inferior. In the test material 27, the grain size of the sacrificial anode material is reduced due to the intermediate annealing temperature and the high degree of cold rolling after the intermediate annealing, and the evaluation of the surface bondability by brazing and the evaluation of the wetting spreadability of the brazing Local melting occurred in the sacrificial anode material upon heating.

It is sectional drawing which shows the Example of the tube for heat exchangers. It is sectional drawing which shows the other Example of the tube for heat exchangers. It is sectional drawing which shows the further another Example of the tube for heat exchangers. It is a figure which shows the test piece of the brazing property evaluation test of a sacrificial anode material surface. It is a figure which shows the gap filling condition of the wax after the test of FIG. It is a figure which shows the wetting spreading property test piece (before heating) of the sacrificial anode material surface, and the wetting spreading state (after heating) of the wax.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flat tube formed by bending and welding clad plate material 2 Example of tube formed only by bending clad plate material 3 Other embodiment of tube formed only by bending clad plate material 4 Clad plate material 5 Core material 6 Brazing material 7 Sacrificial anode material

Claims (6)

An aluminum alloy clad material clad with a sacrificial anode material, wherein the sacrificial anode material is Zn: 0.5 to 5% (mass%, the same shall apply hereinafter), Fe: 0.1 or more and less than 0.4%, Si: It contains 0.01 to 1.2%, Mn: 0.1 to 2.0%, and is composed of the balance Al and inevitable impurities. The aluminum alloy clad material is heated up to 400 ° C at a rate of 50 ° C / min. And brazing the sacrificial anode material surface, wherein the crystal grain size of the surface of the sacrificial anode material is 0.08 to 0.20 mm when heated under the condition that the time to reach 595 ° C. is within 30 minutes Aluminum alloy clad material with excellent surface bondability. The sacrificial anode material further contains one or more of Cr: 0.02-0.3%, Zr: 0.02-0.3%, Ti: 0.01-0.35%. The aluminum alloy clad material excellent in surface bondability by brazing the sacrificial anode material surface according to claim 1. 3. The sacrificial anode material further contains one or two of In: 0.001 to 0.05% and Sn: 0.001 to 0.05%. Aluminum alloy clad material with excellent surface bonding by brazing the sacrificial anode material surface. 4. The brazing of a sacrificial anode material surface according to claim 1, wherein the sacrificial anode material surface has a three-layer structure in which a brazing material is clad on one surface of the core material and a sacrificial anode material is clad on the other surface. Aluminum alloy clad material with excellent surface bondability. The surface joining property by brazing of the sacrificial anode material surface according to any one of claims 1 to 4, which is used as a tube material for a heat exchanger manufactured by surface joining of the sacrificial anode material by brazing. Excellent aluminum alloy clad material. The aluminum alloy clad material according to any one of claims 1 to 4 is formed into a heat exchanger tube, and the formed tube, a fin and a header are assembled and brazed together. Heat exchanger.

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