JP2006015377A - Aluminum alloy brazing sheet for heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy brazing sheet for a heat exchanger, which has basic properties as a pipe material, such as corrosion resistance, brazing ability, strength characteristics and further has excellent slit cutting property, and of which all slit-cut strips can be formed into pipes under the same pipe production condition. <P>SOLUTION: The aluminum alloy brazing sheet has a three layer structure, which has a sacrificial anode material clad on one surface of a core material and has a solder material clad on the other surface of the core material. The core material is made of an Al-Mn alloy containing 0.05-1.2% Si, 0.05-1.0% Cu, 0.6-2.0% Mn, and 0.01-0.5% Fe. The sacrificial anode material is made of an Al-Zn alloy containing 0.5-6% Zn, 0.5-3% Mg, 0.05-1.2% Si, and 0.01-0.5% Fe. The difference between the hardness of the sacrificial anode material and the hardness of the solder material in the Micro-Vickers hardness is within 30% of the higher hardness of either the hardness of the sacrificial anode material or the hardness of the solder material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a case where an aluminum alloy brazing sheet for heat exchangers, in particular, a heat exchanger tube material for automobiles, such as a radiator, is formed by bending a strip material of a brazing sheet that has been cut into multiple slits, and pipe-formed by high frequency welding. It is related with the aluminum alloy brazing sheet for heat exchangers excellent in the slit cutting property used for.

  An automobile heat exchanger such as a radiator is composed of a plurality of flat tubes stacked, corrugated thin fins brazed between them, a header and a tank, and the flat tubes are made of an Al-Mn alloy such as JIS3003. A core material, one surface of the core material is clad with an Al—Si alloy brazing material such as JIS4045, and the other surface is a sacrificial anode material of an Al—Zn alloy or Al—Zn—Mg alloy such as JIS7072 The aluminum alloy brazing sheet with a three-layer structure clad is cut by multiple slits, the resulting strip is bent and formed by pipe-forming by high frequency welding, and the Al-Si brazing material is made of tubes and fins. The sacrificial anode material is in contact with the working fluid (refrigerant). To exert a sacrificial anode effect Te. As the brazing joint, normal flux brazing, inert gas atmosphere brazing using a fluoride-based flux or a cesium-based flux, or vacuum brazing is applied, and the brazing is performed by heating to a high temperature around 600 ° C. Is done.

  Conventionally, for a combination of a core material, a brazing material, and a sacrificial anode material in an aluminum alloy brazing sheet for a tube material of a heat exchanger, as an aluminum alloy composite material for brazing excellent in high-frequency weldability, for example, Mg: 0.2 %: Cr: 0.3% or less, Fe: 0.2% or less, Cu: more than 0.2% and 1.0% or less, Si: 0.3 to 1.3% The total content of Cu and Si is regulated to 1.5% or less, and further contains Mn: 0.3 to 1.5%, Ti: 0.02 to 0.3%, the balance Al and inevitable impurities Al-Si based brazing material on one side of the core material, Mg: 0.3-3%, Zn: more than 2.2% and 5% or less on the other side, the balance from Al and inevitable impurities A composite material made by cladding a sacrificial anode material has been proposed (patented) Document reference 1).

  In the above aluminum alloy composite material, the core material Si is 0.3 to 1.0%, Cu is more than 0.3% and 1.0% or less, Mn is 0.8 to 1.5%, The total content of Cu and Si is regulated to 1.3 to 1.6%, the Mg of the sacrificial anode material clad on the other surface is set to 2.0 to 3.0%, and Si: 0.1 to 1. The thing containing 0% is also proposed (refer patent document 2).

  When such an aluminum alloy composite material (brazing sheet) is subjected to multi-slit slit cutting and high-frequency welding is performed by a pipe making machine, the shape of the cut slit end face affects pipe forming properties. In general, the end face shape is required to be smooth with few burrs and sagging, but the shape characteristics change for each strip when continuously forming the strip material that has been cut into multiple strips. Further, since it is necessary to readjust pipe forming processing conditions such as roll adjustment, upset adjustment, and high-frequency output adjustment, it is desired that the shape change for each line is small.

Usually, as shown in FIG. 1, the slit cutter is configured so that adjacent strips are arranged so that the direction in which the cutting blade enters is reversed, for example, odd-numbered strips are cut from the sacrificial anode material side, as shown in FIG. 1. Then, the even strips are cut from the brazing material side, and the direction of the burrs on the strip end faces are opposite to each other. In this case, if there is a large difference in the end face characteristics between the strip cut from the brazing filler metal side and the strip cut from the sacrificial anode material side, it becomes difficult to make a tube under the same conditions, and the production efficiency decreases. Become. From this point of view, conventional aluminum alloy brazing sheets for tube materials are not necessarily satisfactory.
JP-A-8-283891 JP-A-9-291328

  In order to solve the above-mentioned problems in the aluminum alloy brazing sheet for tube material that is multi-cut by a slit cutting machine, sent to a pipe making machine and welded at high frequency, the inventors have made the material characteristics and slits cut. As a result of testing and studying the relationship with the shape of the end face, the hardness of the material (brazing material or sacrificial anode material) on the face side where the cutting blade enters affects the shape characteristics of the slit end face, especially the surface roughness. I found.

  The present invention has been made as a result of further investigation based on the above knowledge, and its purpose is to bend the brazing sheet strip that has been subjected to multi-slit cutting and to perform pipe forming by high frequency welding. Aluminum alloy brazing sheet for tubes of heat exchangers used in certain cases, which has basic properties (corrosion resistance, brazing properties, strength properties) as a tube material and has excellent slit cutting properties and is cut Another object of the present invention is to provide an aluminum alloy brazing sheet for a heat exchanger capable of pipe-forming all the strip materials under the same conditions.

  An aluminum alloy brazing sheet for a heat exchanger according to claim 1 for achieving the above object is a three-layer aluminum alloy in which a sacrificial anode material is clad on one surface of a core material and a brazing material is clad on the other surface. Brazing sheet, core material: Si: 0.05-1.2%, Cu: 0.05-1.0%, Mn: 0.6-2.0%, Fe: 0.01-0 The sacrificial anode material is made of Zn: 0.5-6%, Mg: 0.5-3%, Si: 0.05-1.2%, Fe: 0 0.01-0.5% Al-Zn based alloy, and in micro Vickers hardness, the difference between the hardness of the sacrificial anode material and the hardness of the brazing material is, among the hardness of the sacrificial anode material and the hardness of the brazing material, It is characterized by being within 30% of the higher hardness.

  An aminium alloy brazing sheet for a heat exchanger according to claim 2 is the aluminium alloy brazing sheet according to claim 1, wherein the Al-Mn alloy of the core is further Cr: 0.03-0.3%, Zr: 0.03-0.3. %, Mg: One or more of 0.06 to 1.0% are contained.

  The aluminum alloy brazing sheet for a heat exchanger according to claim 3 is the aluminum alloy brazing sheet according to claim 1 or 2, wherein the sacrificial anode material further contains In: 0.005-0.1%, Sn: 0.01- It is characterized by containing one or two of 0.1%.

  According to the present invention, there is provided an aluminum alloy brazing sheet for a tube of a heat exchanger that is used when bending a strip material of a brazing sheet that has been cut into multiple slits and pipe-forming by high-frequency welding, Aluminum for heat exchangers that has basic properties such as corrosion resistance, brazing and strength properties as materials, and has excellent slit cutting properties, making it possible to tube-process all cut strips under the same conditions. An alloy brazing sheet is provided.

The composition of the aluminum alloy brazing sheet of the present invention and the reason for limitation will be described.
(Core material)
Mn: 0.6 to 2.0%
Mn functions to improve the corrosion resistance by improving the strength of the core material and making the potential of the core material noble and increasing the potential difference from the sacrificial anode material. The preferable content of Mn is in the range of 0.6 to 2.0%. If the content is less than 0.6%, the effect is small. If the content exceeds 2.0%, a coarse compound is produced during casting, and the rolling processability is low. It decreases and it becomes difficult to obtain a healthy plate (core material). A more preferable content range of Mn is more than 1.5% and 2.0% or less, and further excellent corrosion resistance can be achieved.

Cu: 0.05 to 1.0%
Cu functions to improve the corrosion resistance by improving the strength of the core material, making the potential of the core material noble, and increasing the potential difference with the sacrificial anode material and the potential difference with the brazing material. The preferable content of Cu is in the range of 0.05 to 1.0%. If the content is less than 0.05%, the effect is small. If the content exceeds 1.0%, the corrosion resistance of the core material is lowered, and the melting point is lowered. Thus, local melting is likely to occur during heat brazing.

Si: 0.05-1.2%
Si has the effect of improving the strength of the core material. The preferable content of Si is in the range of 0.05 to 1.2%. If the content is less than 0.05%, the effect is small. If the content exceeds 1.2%, the corrosion resistance of the core material decreases, and The melting point is lowered, and local melting tends to occur during brazing with heating.

Fe: 0.01 to 0.5%
Fe has the effect of improving the strength of the core material. The preferable content of Fe is in the range of 0.01 to 0.5%. If the content is less than 0.01%, the effect is small, and a high-purity aluminum ingot is used, resulting in high costs and practical problems. It is. If Fe exceeds 0.5%, the corrosion resistance of the core material is lowered.

Cr: 0.3% or less, Zr: 0.3% or less Cr and Zr control the structure and improve brazeability. However, when Cr and Zr exceed 0.3%, respectively, macrocrystals are formed during casting. A product is generated, workability is lowered, and it is difficult to produce a sound plate material.

Mg: 0.06 to 1%
Mg improves the strength of the core material. The preferable content of Mg is in the range of 0.06 to 1%, and if it is less than 0.06%, the effect is not sufficient, and if it exceeds 1%, it is contained in an inert gas atmosphere using a fluoride-based flux. When brazing with heat, Mg reacts with the fluoride-based flux at the time of brazing to produce Mg fluoride, reducing brazing properties and deteriorating the appearance of the brazed part.

(Sacrificial anode material)
Zn: 0.5-6%
Zn lowers the potential of the sacrificial anode material, exhibits the sacrificial anode effect on the core material, and prevents the occurrence of pitting corrosion and crevice corrosion of the core material. The preferable content of Zn is in the range of 0.5 to 6%. If the content is less than 0.5%, the effect is not sufficient. If the content exceeds 6%, the effect is saturated, and the effect is higher. Improvement cannot be expected, and the self-corrosion resistance of the sacrificial anode material decreases.

Mg: 0.5-3%
Mg functions to improve the strength and increases the hardness of the sacrificial anode material. The preferable content of Mg is in the range of 0.05 to 3%. If the content is less than 0.05%, the effect is not sufficient. If the content exceeds 3%, the melting point is lowered and local melting occurs during brazing. There is a fear.

Si: 0.05-1.2%
Si functions to improve the strength and increases the hardness of the sacrificial anode material. The preferable content of Si is in the range of 0.05 to 1.2%, and if it is less than 0.05%, the effect is not sufficient, and if it exceeds 1.2%, the melting point is lowered, and it is localized during brazing. May melt.

Fe: 0.01 to 0.5%
Fe functions to improve the strength and increases the hardness of the sacrificial anode material. The preferable content of Fe is in the range of 0.01 to 0.5%. If the content is less than 0.01%, the effect is small, and a high-purity aluminum ingot is used, resulting in high costs and practical problems. It is. When Fe exceeds 0.5%, the self-corrosion resistance of the sacrificial anode material is lowered.

In: 0.005 to 0.1%
In functions to suppress pitting corrosion and crevice corrosion by applying a sacrificial anode effect to the core material by lowering the potential of the sacrificial anode material and making the form of corrosion entirely corrosive. The preferable content of In is in the range of 0.005 to 0.1%. If the content is less than 0.005%, the effect is not sufficient, and if the content exceeds 0.1%, the effect is saturated. The improvement of the above effects cannot be expected, and the self-corrosion resistance of the sacrificial anode material is lowered, and the rolling workability is also lowered.

Sn: 0.01 to 0.1%
Sn functions to suppress the pitting corrosion and crevice corrosion by making the potential of the sacrificial anode material lower and imparting a sacrificial anode effect to the core material, making the form of corrosion entirely corrosive. The preferable content of Sn is in the range of 0.01 to 0.1%. If the content is less than 0.01%, the effect is not sufficient, and if the content exceeds 0.1%, the effect is saturated. The improvement of the above effects cannot be expected, and the self-corrosion resistance of the sacrificial anode material is lowered, and the rolling workability is also lowered.

  In the present invention, among the components of the sacrificial anode material, the total content of Mg, Si and Fe is preferably in the range of 1.9 to 4.2%, and the total of Mg, Si and Fe in the sacrificial anode material By selecting the content of each component so that the content falls within this range and adjusting the hardness of the sacrificial anode material, it becomes easy to obtain excellent slit cutting performance by reducing the hardness difference between the sacrificial anode material and the brazing material. .

  The core material may contain, for example, 0.2% or less of Zn, 0.1% or less of V, B, or the like, if necessary, in order to improve the characteristics. May contain 0.2% or less of Cr, Zr, 0.1% or less of B, and the like.

(Brazing material)
Examples of the brazing material include commonly used Al-Si alloys such as JIS BA4343 (Al-7.5% Si), 4045 (Al-10% Si), 4047 (Al-12% Si), and the like. : Al-Si-Mg-Bi such as Al-Si-based alloy, Al-Si-Mg-based alloy containing 4 to 13%, 4104 (Al-10% Si-1.5% Mg-0.1% Bi) An Al-Si-Mg-Be-based alloy, an Al-Si-Mg-Bi-Be-based alloy, or the like is used. In order to improve the brazing property, one or more kinds of Bi, Be, Sr, Li, Na, etc. in a small amount, for example, 0.2% or less may be added to these brazing materials.

  The hardness of the sacrificial anode material and brazing material, which are the surfaces into which the cutting blade enters in slit cutting, affects the characteristics of the cutting end surface, such as the surface roughness of the slit-cut end surface, and the higher the hardness, the smaller the surface roughness tends to be. is there. In order to obtain a specific surface roughness, it is necessary to adjust pipe making conditions such as roll adjustment, upset amount, and high frequency output of the pipe making machine to optimum values, and the cutting end face characteristics of each strip differ. In that case, pipe making conditions must be set for each strip.

  As described above, in multi-strip cutting, strips cut from the sacrificial anode material side and strips cut from the brazing material side are alternately produced, but in the mass production line, both from the viewpoint of productivity It is desirable to make pipes under the same pipe making conditions, and for this purpose, the end face characteristics of the strip material cut from the sacrificial anode material side and the strip material cut from the brazing material side should be the same. It is important to adjust the hardness of the sacrificial anode material and the hardness of the brazing material as close as possible.

  In practice, in order to apply the same tube forming process conditions to each strip material that has been subjected to multiple slit cutting, in micro Vickers hardness, the difference between the hardness of the sacrificial anode material and the hardness of the brazing material is Within 30% of the higher of the hardness and the hardness of the brazing material, in other words, in the micro Vickers hardness, the lower of the sacrificial anode material hardness and the brazing material hardness, whichever is higher It is desirable that the hardness be 70% or more of the hardness, and when the hardness difference exceeds 30% of the higher hardness, the strip end face characteristics cut from the brazing material side and the sacrificial anode material side were cut. The difference from the end face characteristics of the strip material becomes too large, and it becomes difficult to make a pipe under the same pipe making conditions.

  The aluminum alloy brazing sheet of the present invention comprises an aluminum alloy constituting a core material, a sacrificial anode material and a brazing material, which is ingoted by, for example, continuous casting, and after homogenization treatment as necessary, for sacrificial anode material and brazing material Each aluminum alloy ingot is hot rolled to a predetermined thickness, and then the aluminum alloy ingot for the core material, the aluminum alloy for the sacrificial anode and the aluminum alloy for the brazing material are combined and hot rolled according to a conventional method. Thus, the clad material is produced by cold rolling, intermediate annealing, and cold rolling to obtain a predetermined thickness.

  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
An ingot obtained by ingoting a core material alloy having the composition shown in Table 1, a sacrificial anode material alloy having the composition shown in Table 2, and a brazing alloy having the composition shown in Table 3 by continuous casting. Among these, the ingots of the core material alloy and the sacrificial anode material alloy were subjected to a homogenization treatment.

  Subsequently, the ingot of the sacrificial anode material alloy and the brazing material alloy is hot-rolled to a predetermined thickness, and the hot-rolled plate and the core alloy ingot are hot-rolled together and clad ( A brazing sheet) was obtained. Thereafter, a coil of a brazing sheet (tempered H14, H24 or H26) having a thickness of 0.25 mm was obtained by cold rolling, intermediate annealing, and cold rolling. The composition of the brazing sheet was such that the clad rate of the sacrificial anode material and the brazing material was 10% or 15%.

  Using the obtained brazing sheet as a test material, the following methods were used: (1) Tensile strength of the material, (2) Tensile strength after brazing, (3) Micro Vickers hardness of the brazing material and sacrificial anode material and their differences (4) Brazing property, (5) Corrosion resistance, (6) Pipe-forming workability was evaluated. The results are shown in Table 4.

Tensile strength of material: A tensile test piece is taken from a test material and a tensile test is performed.
Tensile strength after brazing: Fluoride-based flux was applied to the test material, heated to a brazing temperature of 600 ° C (material temperature) for 3 minutes in a nitrogen gas atmosphere, and then a tensile test piece was collected. Perform a tensile test.
Hardness of brazing material and sacrificial anode material: The test material is filled with resin and the cross section is polished, and the hardness of the brazing material and sacrificial anode material is measured by a micro Vickers tester.

  Brazing: Applying a fluoride-based flux to the test material, heating it to a brazing temperature of 600 ° C (material temperature) for 3 minutes in a nitrogen gas atmosphere, then observing the cross section, and the brazing material is on the core material side Those that were not diffused were considered to have good brazing properties (◯).

Corrosion resistance: A fluoride-based flux was applied to a test material and heated to a brazing temperature of 600 ° C. (material temperature) in a nitrogen gas atmosphere, and then a corrosion test was performed under the following conditions.
Corrosion solution: Cl ⁻ : 100 ppm, SO ₄ ²⁻ : 100 ppm, HCO ₃ − ⁻ : 100 ppm, Cu ²⁺ : An aqueous solution containing 10 ppm Test method: After immersion in a corrosion solution heated to 80 ° C. for 8 hours, to room temperature The cycle of standing for 16 hours while allowing to cool was repeated for 12 weeks, and the maximum corrosion depth on the sacrificial anode material side was measured. The maximum corrosion depth was 0.02 mm or less.

Pipemaking workability: The test material coil was cut into four strips with a width of 34.8 mm using the slit cutter shown in FIG. (Meidensha Welded Pipe Line: High frequency welded pipe prototype test equipment, model RFG-120, transmission frequency 400 kHz). The pipe making test is performed after adjusting the pipe making conditions such as roll adjustment, upset amount, high frequency output, etc. so that it is optimal for odd-numbered strips (strips cut from the brazing filler metal side). Then, even-numbered strips (strips cut from the sacrificial anode material side) were formed. The manufactured pipes were evaluated by a pressure test, and those with a pressure strength of 30 kgf / cm ² or more were obtained for both odd and even strips (good), and those with less than 30 kgf / cm ² were poor (×). It was.

As seen in Table 4, the test material No. Nos. 1 to 33 all have excellent strength after brazing, and there is no difference in workability between the odd and even strips in pipe forming, both show a pressure strength of 30 kgf / cm ² or more, and the sacrificial anode material side The maximum corrosion depth of each has excellent corrosion resistance of 0.10 mm or less.

Comparative Example 1
A core material alloy having the composition shown in Table 5 and a sacrificial anode material alloy having the composition shown in Table 6 were ingoted by continuous casting, and the resulting ingot was homogenized. As the brazing material, an alloy ingot for brazing material having the composition shown in Table 3 was used.

  Subsequently, the ingot of the alloy for sacrificial anode material and the ingot of the alloy for brazing material are hot-rolled to a predetermined thickness, and the hot-rolled plate and the ingot of the core material alloy are hot-rolled together. A clad material (brazing sheet) was obtained. Thereafter, a coil of a brazing sheet (tempered H14, H24 or H26) having a thickness of 0.25 mm was obtained by cold rolling, intermediate annealing, and cold rolling. The composition of the brazing sheet was such that the clad rate of the sacrificial anode material and the brazing material was 10%. In Tables 5-6, those outside the conditions of the present invention are underlined.

  Using the obtained brazing sheet as a test material, by the same method as in Example 1, (1) Tensile strength of material, (2) Tensile strength after brazing, (3) Micro Vickers hardness of brazing material and sacrificial anode material And the difference between them, (4) brazeability, (5) corrosion resistance, and (6) tube-forming workability. The results are shown in Table 7. In Table 7, those outside the conditions of the present invention are underlined.

  Test material No. No. 32 has a large amount of Zn in the sacrificial anode material, so that the sacrificial anode material is quickly consumed and the corrosion resistance is lowered. Test material No. No. 33 has a small amount of Zn in the sacrificial anode material, so the sacrificial anode effect is not sufficient and the corrosion resistance is poor. Test material No. No. 34 has a large amount of Mg in the sacrificial anode material, so that it is difficult to produce a sacrificial anode material with poor rolling processability in the production of the sacrificial anode material. Test material No. No. 35 has a small amount of Mg in the sacrificial anode material, so that the difference between the hardness of the sacrificial anode material and the hardness of the brazing material is increased, resulting in a difference in the end face characteristics of the strip material.

  Test material No. Since No. 36 had a large amount of Si in the sacrificial anode material, local melting occurred during brazing heating. Test material No. No. 37 has a small amount of Si in the sacrificial anode material, so that the difference between the hardness of the sacrificial anode material and the hardness of the brazing material is increased, resulting in a difference in the end face characteristics of the strip material. Test material No. No. 38 has a large amount of Fe in the sacrificial anode material, so that the sacrificial anode material is quickly consumed in the corrosion resistance test, resulting in poor corrosion resistance.

  Test material No. Since No. 39 has a small amount of Mn in the core material, the strength after brazing is inferior. Test material No. Since No. 40 had a large amount of Mn in the core material, rolling processability was poor in the production of the brazing sheet, and a sound material could not be produced. Test material No. Since No. 41 had a large amount of Cu in the core material, local melting occurred during brazing heating. Test material No. Since 42 has a small amount of Cu in the core material, the potential difference from the sacrificial anode material is insufficient and the corrosion resistance is poor.

  Test material No. Since 43 had a large amount of Si in the core, local melting occurred during brazing heating. Test material No. No. 44 has a large amount of Fe in the core material, so the self-corrosion resistance of the core material is poor and the corrosion resistance is lowered. Test material No. No. 45 has the composition of the core material and the sacrificial anode material in accordance with the present invention. However, since the hardness difference between the sacrificial anode material and the brazing material is large, the tube-forming processability is inferior.

It is explanatory drawing of the slit cutter for multi-strip cutting. (The adjacent strips are configured so that the direction in which the cutting blade enters is reversed. For example, when the odd strip is cut from the sacrificial anode material side, the even strip is cut from the brazing filler metal side and Are opposite to each other)

Claims (3)

An aluminum alloy brazing sheet having a three-layer structure in which a sacrificial anode material is clad on one surface of a core material and a brazing material is clad on the other surface, and the core material is Si: 0.05 to 1.2% (mass) %, The same applies hereinafter), Cu: 0.05-1.0%, Mn: 0.6-2.0%, Fe: 0.01-0.5% containing Al-Mn alloy and sacrificed Al—Zn alloy containing anode material containing Zn: 0.5-6%, Mg: 0.5-3%, Si: 0.05-1.2%, Fe: 0.01-0.5% The difference between the hardness of the sacrificial anode material and the hardness of the brazing material is within 30% of the higher one of the hardness of the sacrificial anode material and the hardness of the brazing material in the micro Vickers hardness. An aminium alloy brazing sheet for heat exchangers. The Al—Mn-based alloy of the core material is one of Cr: 0.03 to 0.3%, Zr: 0.03 to 0.3%, Mg: 0.06 to 1.0%, or The aluminum alloy brazing sheet for a heat exchanger according to claim 1, comprising two or more kinds. The Al—Zn-based alloy of the sacrificial anode material further contains one or two of In: 0.005 to 0.1% and Sn: 0.01 to 0.1%. The aluminum alloy brazing sheet for heat exchangers according to claim 1 or 2.

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