JP2018178170A - Thin wall fin material excellent in erosion resistance, manufacturing method of thin wall fin material excellent in erosion resistance, and manufacturing method of heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thin wall fin material excellent in erosion resistance, and a manufacturing method of the thin wall fin material excellent in erosion resistance.SOLUTION: A thin wall fin material excellent in erosion resistance consists of an aluminum alloy having a composition containing, by mass%, Mn:1.0 to 2.0%, Si:0.1 to 2.0%, Zn:0.1 to 3.0%, has sheet thickness of 0.06 nm or less, the melting point of 610°C to 645°C, average particle diameter of a recrystallized structure after a brazing heat treatment is 200 μm or more, average cross section distance of grain boundary, which is average grain boundary length (μm) of the cross section of the recrystallized grain after the brazing heat treatment/sheet thickness (μm) of the fin material, is 1.5 or more and recrystallization rate at 577°C during temperature rise after the brazing heat treatment is 97% or more.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a thin-walled fin material excellent in erosion resistance, a method of manufacturing a thin-walled fin material excellent in erosion resistance, and a method of manufacturing a heat exchanger.

An aluminum alloy is used for members for heat exchangers, such as a fin material and a tube material, and joining of each member is performed by brazing. In brazing, for example, a low melting point brazing material is provided between a tube material and a fin material, heating is performed to melt the brazing material, and the molten brazing material forms a fillet at the joint. .
However, if the erosion resistance of the fin material is low, there is a problem that the fin material is eroded during the heat addition to the brazing material, causing the fin material to buckle and the shape of the heat exchanger to collapse.
Then, the aluminum alloy material which adjusted content of various additional elements is proposed as an aluminum alloy material which improved erosion resistance.

For example, in Patent Document 1, Si: 0.7 to 1.3 wt%, Fe: more than 2.0 wt% and 2.8 wt% or less, Mn: more than 0.6 wt% and 1.2 wt% or less, Zn: 0. An aluminum alloy for fin material containing more than 02 wt% and 1.5 wt% or less has been proposed.
In Patent Document 2, Si: 0.3% or more and 1.2% or less, Fe: 0.05% or more and less than 0.7%, Mn: more than 0.8% and 2.0% or less, Zn: 0.5% An aluminum alloy containing not less than 4.0% and the like is described.
Patent Document 3 contains Si: 0.7 to 1.4 wt%, Fe: 0.5 to 1.4 wt%, Mn: 0.7 to 1.4 wt%, Zn: 0.5 to 2.5 wt%. Furthermore, an aluminum alloy fin material in which Mg as an impurity is limited to 0.05 wt% or less is described.
In Patent Document 4, an aluminum alloy laminate in which a sacrificial material is clad on at least one side of a core material, and the core material is Mn: 0.5 to 1.8 mass%, Si: 0.4 to 1.5 mass% In addition to Cu: 0.05 to 1.2% by mass, those containing at least one of Fe: 1.0% by mass or less and Ti: 0.3% by mass or less are described.
In Patent Document 5, Si: 0.6 to 1.6%, Fe: 0.5 to 1.2%, Mn: 1.2 to 2.6%, Zn: 0.4 to 3 in mass%. An aluminum alloy fin stock for heat exchangers is described which contains less than 0%, Cu: less than 0.2% and limits Mg as an impurity to less than 0.05%.

JP 2004-277756 A JP 2008-308761 A JP, 2012-211393, A JP, 2015-196859, A JP, 2015-218343, A

  By the way, there is a demand for weight reduction of heat exchangers, and it is necessary to reduce the thickness and increase the strength in order to realize the weight reduction, but for reducing the thickness and increasing the strength by thinning. The erosion resistance of the fin material may be lowered due to the increase of the additive element and the like. Therefore, an aluminum alloy material having both high strength and erosion resistance is required.

  The present invention has been made against the background described above, and an object thereof is to provide a thin fin material excellent in erosion resistance, a thin fin material excellent in erosion resistance, and a method of producing a heat exchanger. Do.

  That is, among the thin-walled fin materials having excellent erosion resistance according to the present invention, the first present invention is, by mass%, Mn: 1.0 to 2.0%, Si: 0.1 to 1.2%, Zn C .: made of an aluminum alloy having a composition containing 0.1 to 3.0%, the balance being Al and unavoidable impurities, the plate thickness is 0.06 mm or less, the melting point is 610.degree. C. to 645.degree. The average grain size of the recrystallized structure after 200 μm or more, the average grain boundary length (μm) of the section of recrystallized grain after brazing heat treatment / plate thickness (μm) of fin material as the average cross section distance of the grain boundary, The method is characterized in that the average cross-sectional distance is 1.5 or more, and the recrystallization ratio at 577 ° C. at the time of temperature elevation during brazing heat treatment is 97% or more.

  The thin-walled fin material having excellent erosion resistance according to the second aspect of the present invention is characterized in that, in the first aspect of the present invention, Cu: 0.01 to 0.20%, Fe: 0.05 to 0.50 in mass%. %, Zr: at least one of 0.01 to 0.20%.

  In the thin-walled fin material excellent in the erosion resistance according to the third aspect of the present invention, in the first or the second aspect of the present invention, a long side parallel to the rolling direction of recrystallization grains after brazing heat treatment The average of the aspect ratio is 3.0 or more, where the side is an aspect ratio.

  The thin-walled fin material excellent in the erosion resistance according to the fourth aspect of the present invention has a 0.2% proof stress of at least 190 MPa and an elongation of 1.0 to 5.0% in any of the first to third aspects of the present invention. It is characterized by

  The method for producing a thin-walled fin material excellent in erosion resistance according to the fifth aspect of the present invention is the method for producing a thin-walled fin material excellent in erosion resistance according to any of the first to fourth aspects of the present invention. Of performing homogenization treatment on the aluminum alloy of the above, and in the homogenization treatment, when the temperature (.degree. C.) of the homogenization treatment is t and the time (hr) is T, the temperature t is less than 480.degree. In the case, the time T is in the range of −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86, and the temperature t is 480 ° C. or higher, the time T is −0.17 t + 86 ≦ T ≦ −0.0721 t + 39. It is characterized in that it is within the range of 137.

  The method of producing a thin-walled fin material excellent in erosion resistance according to a sixth aspect of the present invention is characterized in that, in the fifth aspect of the present invention, the temperature of the homogenization treatment is in the range of 400 to 500 ° C.

  The method for producing a thin-walled fin material excellent in erosion resistance according to a seventh invention of the present invention, in the fifth or sixth invention of the present invention, includes a cold rolling step, and the homogenization treatment in the cold rolling step It is characterized in that the intermediate annealing is performed at a lower temperature.

  The method for producing a thin-walled fin material excellent in erosion resistance according to the eighth invention is characterized in that, in any one of the fifth to seventh inventions, when brazing the thin-fin material after the homogenization treatment, It is characterized in that the temperature rising rate at the warm time is set to 300 ° C./min or less.

  The method for producing a heat exchanger according to the ninth aspect of the present invention comprises the step of subjecting an aluminum alloy having the above composition to homogenization treatment, in which the temperature (° C.) of the homogenization treatment is t, time (hour When hr) is T and temperature t is less than 480 ° C., time T is in the range of −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86 and temperature t is 480 ° C. or more The temperature T is in the range of −0.17t + 86 ≦ T ≦ −0.0721t + 39.137, and after the aluminum alloy after the homogenization treatment is formed into a thin fin, the temperature rising rate at the time of temperature rising is 300 ° C. / It is characterized in that it is incorporated into the heat exchanger by brazing heat treatment which is less than a minute.

  Hereinafter, the reasons for limitation of the components and the like in the present invention will be described. In addition, all content of each component has shown weight%.

Plate thickness: 0.06 mm or less In order to reduce the weight of the fin material, it is desirable to reduce the thickness of the fin material, but if the plate thickness exceeds 0.06 mm, the plate thickness is small as a thin fin material for heat exchangers. It is too thick and the mass of the heat exchanger becomes heavy. For this reason, the thickness of the fin material is determined in the above range.

Mn: 1.0 to 2.0%
Mn contributes to the strength and castability of the material. If the content of Mn is less than 1.0%, the strength of the fin material for heat exchangers is insufficient, and if the content of Mn exceeds 2.0%, a huge intermetallic compound is generated at the time of casting, and at the time of rolling It causes breakage. For this reason, let content of Mn be the said range.
In addition, as for Mn content, it is desirable to make a minimum 1.2% and an upper limit 1.8%.

Si: 0.1 to 1.2%
Si contributes to the strength and erosion resistance of the material. If the content of Si is less than 0.1%, the strength of the fin material for heat exchangers is insufficient, and if the content of Si exceeds 1.2%, the melting point of the material is lowered, and significant erosion occurs at the time of brazing. It occurs. Therefore, the content of Si is set to the above range.
In addition, as for Si content, it is desirable to make a lower limit 0.3% and an upper limit 1.0%.

Zn: 0.1 to 3.0%
Zn improves the corrosion resistance of the fin material by imparting a sacrificial anode effect to the fin material. When the content of Zn is less than the lower limit, the potential of the fin material becomes noble and the sacrificial anode effect does not work. When the content of Si exceeds the upper limit, the potential of the fin material becomes wrinkles and the self corrosion resistance is lowered. Therefore, the content of Zn is set to the above range.
In addition, as for content of Zn, it is desirable to set a minimum to 1.0% and an upper limit to 2.5%.

Cu: 0.01 to 0.20%
Cu is optionally contained because it contributes to the strength and the erosion resistance of the material. If the content of Cu is less than 0.01%, the strength of the fin material for heat exchangers is insufficient, and if the content of Si exceeds 0.20%, the melting point of the fin material decreases, and the erosion is remarkable at the time of brazing Will occur. For this reason, it is desirable to make content of Cu into the said range.
The Cu content is more preferably 0.05% at the lower limit and 0.15% at the upper limit.

Fe: 0.05 to 0.50%
Fe is optionally contained to contribute to the strength and castability of the material. If the content of Fe is less than 0.05%, the strength of the heat exchanger fin material is insufficient, and if the content of Fe exceeds 0.50%, a huge intermetallic compound is generated at the time of casting, and at the time of rolling It causes breakage. For this reason, it is desirable to make content of Fe into the said range.
The Fe content is more preferably 0.10% at the lower limit and 0.30% at the upper limit.

Zr: 0.01 to 0.20%
Zr is optionally contained because it contributes to the erosion resistance and castability of the material. If the content of Zr is less than 0.01%, the aspect ratio of the recrystallized structure is reduced to cause erosion. When the content of Zr exceeds 0.20%, a huge intermetallic compound is generated at the time of casting, which causes breakage at the time of rolling. For this reason, it is desirable to make content of Zr into the said range.
The Zr content is more preferably 0.05% at the lower limit and 0.15% at the upper limit.

Melting point (solidus temperature): 610-645 ° C
Erosion resistance can be improved by raising the melting point of the fin material. If the melting point is less than 610 ° C., the melting point is too low, and significant erosion occurs regardless of the recrystallized grain size. If the melting point exceeds 645 ° C., the material can not contain the additional element, and a desired strength can not be obtained. Therefore, the melting point of the fin material is in the above range.

Average grain size of recrystallized structure after brazing heat treatment: 200 μm or more In order to improve the erosion resistance, it is necessary to suppress the progress of the erosion in the thickness direction of the fin material. Since erosion progresses from recrystallized grain boundaries, by increasing the recrystallized grain size and reducing the progress path of erosion, the erosion of the fin material at the time of brazing is suppressed, and excellent erosion resistance can be exhibited. it can.
When the grain size of the recrystallized structure is less than 200 μm, erosion proceeds from the grain boundaries, causing significant erosion. For this reason, let the average particle diameter of the recrystallized structure after brazing heat processing be the said range.

Average cross-sectional distance of grain boundaries to plate thickness of fin material after brazing heat treatment (average grain boundary length of section (μm) / plate thickness of fin material (μm)): 1.5 or more In order to improve the erosion resistance In addition, it is necessary to suppress the progress of erosion in the thickness direction of the fin material. Erosion progresses from the recrystallized grain boundaries, so by increasing the distance of grain boundaries with respect to the thickness of the fin material, it is difficult for the erosion to penetrate through the thickness of the fin material, and the erosion resistance can be greatly improved.
When the average sectional distance of grain boundaries with respect to plate thickness is less than 1.5, erosion penetrates the plate thickness due to the short grain boundary distance, resulting in significant erosion. For this reason, the average cross-sectional distance of the grain boundary with respect to the plate thickness is determined in the above range.
The grain boundary length is obtained by observing the cross section parallel to the rolling direction of the fin material at an arbitrary position and measuring the total length of 20 arbitrary grain boundaries penetrating the thickness of the fin material. (See Figure 3)
The grain boundary length indicates the length along the grain boundary.

Recrystallization ratio of fin material at 577 ° C. at brazing temperature: 97% or more At the time of brazing and melting in brazing heat treatment, if sub-grains remain in the fin material, the fin material suffers significant erosion. For this reason, it is desirable that recrystallization be almost completed by the time of wax melting (577 ° C.). Erosion from subgrain boundaries is thereby suppressed, and excellent erosion resistance can be exhibited.
When the recrystallization ratio of the fin material at 577 ° C. at the temperature of brazing is less than 97%, the erosion from the subgrain boundaries proceeds and significant erosion occurs. For this reason, let the recrystallization ratio of the fin material in 577 degreeC at the time of brazing temperature rising be the said range. In addition, it is more desirable that it is 99% or more.

Average aspect ratio of recrystallized grain size after brazing heat treatment (long side parallel to rolling direction / short side perpendicular to rolling direction): 3.0 or more Flatter than recrystallized grain is equiaxed One can delay the progress of the erosion in the thickness direction of the fin material and can exhibit excellent erosion resistance. The aspect ratio is indicated by the ratio of the long side parallel to the rolling direction of recrystallized grains and the short side perpendicular to the rolling direction.
If the aspect ratio of the recrystallized grain size is less than the lower limit, the recrystallized structure becomes an equiaxed grain, and erosion easily progresses from the grain boundary. For this reason, it is preferable to set the shape of recrystallized grain after brazing heat treatment to long side: short side = 3: 1 or more in aspect ratio.

0.2% proof stress before brazing heat treatment: 190 MPa or more Since thin-walled fin materials have a problem in formability, it is desirable to define the proof stress of the material before brazing heat treatment in order to improve the formability. When the 0.2% proof stress is less than 190 MPa, breakage easily occurs during corrugate molding. For this reason, it is desirable to make 0.2% proof stress before brazing heat treatment into the above-mentioned range. In addition, it is more preferable that it is 200 Mpa or more.

Elongation before brazing heat treatment: 1.0 to 5.0%
Since thin-walled fin materials have problems with formability, it is desirable to define the elongation of the material before brazing heat treatment in order to improve formability. When the elongation is less than 1.0%, fracture occurs during corrugate molding, and when it exceeds 5.0%, burrs are easily generated during corrugate molding. For this reason, it is desirable to make elongation of the material before brazing heat treatment into the above-mentioned range. In addition, it is still more desirable that it is 1.5 to 4.0%.

Homogenization process:
· Less than 480 ° C: -0.0721t + 39.137 ≦ TT -0.17t + 86 within the range 480 ° C or more: -0.17t + 86 ≦ TT -0.0721t + 39.137 within the range of homogenization in the fin material manufacturing process In the processing, when the temperature (° C.) is t and the time (hr) is T, the heat treatment condition is set such that the heat treatment time becomes shorter as the temperature becomes higher as the relationship between the temperature t and the time T satisfies the above equation. By doing this, coarsening of precipitates can be prevented, and structural features can be added to the fin material. However, performing the homogenization treatment for 18 hours or more is not desirable from the economical point of view, and when the heat treatment time is 1 hour, it is impossible to equalize heat in the coil.
In addition, it is desirable for the temperature of heat processing to be 400 degreeC-500 degreeC within the said range.

Intermediate annealing: at a lower temperature than the homogenization treatment By performing the intermediate annealing in cold rolling at a lower temperature than the homogenization treatment, coarsening of precipitates can be prevented.

Temperature rising rate of brazing heat treatment: 300 ° C./min or less By setting the upper limit of the temperature rising rate at the time of brazing, it is possible to suppress the refinement of the crystal grain size after recrystallization. Therefore, when performing the brazing heat treatment, it is desirable to set the temperature rising rate within the above range.

  According to the present invention, it is possible to obtain a thin fin material having excellent erosion resistance and a heat exchanger.

It is a schematic diagram which shows the temperature change of brazing heat processing in one Example of this invention. Similarly, it is a figure which shows the measuring method of the crystal grain size in the fin material after brazing heat processing. Similarly, it is a figure which shows the measuring method of the cross-sectional distance of the grain boundary with respect to the plate | board thickness of the fin material after brazing heat processing. It is a figure which similarly shows the calculation method of the aspect-ratio of the recrystallized grain in the fin material after brazing heat processing. Similarly, it is a figure which shows the favorable joining state after brazing. Similarly, it is a figure which shows the junction part in case the buckling has arisen to the fin material after brazing. Similarly, it is a figure which shows the relationship of the temperature and time of the homogenization process in a part of Example and a comparative example.

One embodiment of the thin fin material of the present invention and the method for producing the same will be described below.
Mn: 1.0 to 2.0%, Si: 0.1 to 1.2%, Zn: 0.1 to 3.0% by mass%, the balance comprising Al and unavoidable impurities, desired Aluminum alloy having a composition containing one or more of Cu: 0.01 to 0.20%, Fe: 0.05 to 0.50%, and Zr: 0.01 to 0.20% according to Melt and cast to obtain an aluminum alloy ingot. The method of obtaining the ingot is not particularly limited.

  The resulting aluminum alloy ingot is homogenized. In the homogenization treatment, when the temperature (° C.) of the homogenization treatment is t and the time (hr) is T, the time T is −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86 in the temperature range below 480 ° C. In the temperature range of 480 ° C. or more, the heat treatment conditions are set such that the heat treatment time becomes shorter as the temperature rises, with −0.17 t + 86 ≦ T ≦ −0.0721 t + 39.137. Thereby, coarsening of precipitates can be prevented, and structural features can be added to the fin material. The temperature is preferably 400 ° C. to 500 ° C., and the time is preferably 1 to 18 hours, and more preferably 3 to 10 hours.

Thereafter, a fin material is formed by cold rolling and intermediate annealing. The thickness of the fin material can be 0.02 mm to 0.06 mm for weight reduction. However, in the present invention, the thickness of the lower limit is not limited to the above. In addition, coarsening of a precipitate can be prevented by implementing intermediate | middle annealing once or twice or more at low temperature rather than the said homogenization process. However, in the present invention, intermediate annealing may not be performed.
According to the above process, an aluminum alloy fin material having a melting point of 610 ° C. to 645 ° C., a 0.2% proof stress of 190 MPa or more, an elongation of 1.0 to 5.0% and excellent formability can be obtained.

Then, a fin material can manufacture a heat exchanger by combining with other structural members (a tube, a header, etc.) and performing brazing as a structural member of a heat exchanger.
The conditions for brazing (brazing temperature, atmosphere, presence or absence of use of flux, type of brazing material, etc.) are not particularly limited, and can be carried out according to a conventional method. For example, brazing can be performed in a brazing furnace under an inert gas atmosphere such as nitrogen gas, and the oxygen concentration in the furnace can be 100 ppm or less.
In addition, it is desirable that the heat treatment for brazing be performed at a temperature rising rate of 300 ° C./min or less. By setting the upper limit of the temperature rising rate, it is possible to suppress the refinement of the crystal grain size after recrystallization. However, in the present invention, the range of the temperature rising rate is not limited to the above.
As the conditions of the brazing heat treatment, for example, the maximum temperature of brazing can be set to 590 to 600 ° C., and the heat treatment time of 577 ° C. or more can be set to 1 to 5 minutes. The optimal time is 2 minutes. Cooling is started after reaching the maximum temperature, and the cooling rate can be, for example, in the range of 550 ° C. to 300 ° C., and the cooling rate can be 20 to 150 ° C./min. The optimal cooling rate is 100 ° C./min. Fan cooling can be used to a temperature of 300 <0> C to 100 <0> C.

  Under the above conditions, the recrystallization ratio of the fin material at 577 ° C. at the temperature of brazing becomes 97% or more. For this reason, the erosion from the subgrain boundary at the time of brazing is suppressed, and excellent erosion resistance can be exhibited.

The fin material subjected to the brazing heat treatment has the following properties.
(Grain size)
The average grain size of the recrystallized structure after the brazing heat treatment is 200 μm or more. Erosion proceeds through grain boundaries as the main penetration path, so the large average grain size reduces the erosion path, suppresses erosion of the fin material during brazing, and exhibits excellent erosion resistance. be able to.

(Average cross-sectional distance of grain boundary to plate thickness)
The average cross-sectional distance of the grain boundary to the thickness of the fin material after brazing heat treatment (average grain boundary length of cross section (μm) / thickness of fin material (μm)) is 1.5 or more. Since the distance of grain boundaries with respect to the thickness of the fin material is large, the advancing distance of erosion is long, erosion is difficult to penetrate through the thickness of the fin material, and excellent erosion resistance can be exhibited. By limiting the homogenization treatment conditions, the precipitates are finely dispersed, and the pinning effect of the precipitates causes coarsening of recrystallized grains at the time of brazing. During recrystallization, the recrystallized grains are flattened under the influence of the old grain boundary extended by rolling, the distance of the grain boundary to the plate thickness becomes longer, and the average of the grain boundary to the plate thickness of the fin material after brazing The cross sectional distance is 1.5 or more. When the homogenization conditions are out of the specified range, coarsening / flattening of recrystallized grains does not occur during brazing, and the average cross-sectional distance of grain boundaries to the thickness of fin material after brazing is less than 1.5. Erosion resistance is reduced, and severe erosion occurs at the time of brazing.

(aspect ratio)
The average of the aspect ratio (long side parallel to the rolling direction / short side perpendicular to the rolling direction) of the recrystallized grain size after the brazing heat treatment is 3.0 or more. Since many of the recrystallized grains are flat grains, the progress of the erosion in the thickness direction of the fin material can be delayed, and excellent erosion resistance can be exhibited. By carrying out the intermediate annealing at a lower temperature than the homogenization treatment or not performing the intermediate annealing, coarsening of precipitates at the time of intermediate annealing is prevented, and the recrystallized grain at brazing is coarsened by the pinning effect by the precipitates. Turn During recrystallization, recrystallized grains are flattened under the influence of the old grain boundary extended by rolling, the distance of grain boundary to plate thickness becomes longer, and the aspect ratio of recrystallized grain size after brazing heat treatment (rolling The average of the long side parallel to the direction / short side perpendicular to the rolling direction is 3.0 or more. When the condition of the intermediate annealing is out of specification, coarsening / flattening of recrystallized grain does not occur at brazing, and the average aspect ratio of recrystallized grain size after brazing heat treatment becomes less than 3.0, and erosion resistance Sex is reduced, and severe erosion occurs at the time of brazing.

  According to this embodiment, it is possible to obtain a thin fin material excellent in erosion resistance. The obtained fin material is suitable as a material of a heat exchanger.

  An aluminum alloy having the composition shown in Tables 1 and 2 (the balance being Al and inevitable impurities) was melted to produce an aluminum alloy ingot. The obtained aluminum alloy ingot is subjected to homogenization treatment according to the temperature and holding time shown in Table 1 and Table 2, and after cold rolling and intermediate annealing, the plate thicknesses shown in Table 1 and Table 2 are obtained. The fin material which has it was produced. Intermediate annealing was performed under the temperature conditions shown in Table 1 and Table 2.

Also, in order to evaluate the brazeability of the obtained fin material, the fin material and a tube material (plate thickness 0.20 mm, 10% clad with 10% by mass Si brazing material) are combined to form a core. After applying 10 to 15 g / m ^{2 of} flux to the core, insert the core into a brazing furnace in which the oxygen concentration in the furnace is 100 ppm or less in a nitrogen gas atmosphere. Heating started. The maximum temperature of brazing is 595 ° C, heat treatment time of 577 ° C or more is 2 minutes, cooling is started after reaching the maximum temperature, and fan cooling is performed at 300 ° C to 100 ° C, 550 ° C to 300 ° C The cooling rate was controlled so that the cooling rate was 100 ° C./min.
In addition, when evaluating the crystal structure of the fin material after brazing heat treatment, brazing equivalent heat treatment was performed on the fin material alone without being combined with the tube material.
FIG. 1 is a schematic view showing a temperature change during brazing heat treatment. As shown in FIG. 1, the heat treatment time of 577 ° C. or higher was 2 minutes, and the maximum temperature was 595 ° C.

  0.2% proof stress, elongation, melting point, grain size, average cross sectional distance of grain boundary to fin plate thickness, and brazing rise for fin material before or after brazing heat treatment by the method shown below The recrystallization ratio at 577 ° C. when warm was measured, and the castability, formability, erosion resistance, durability, and corrosion resistance were evaluated. The measurement results and the evaluation results are shown in Table 3 and Table 4.

(0.2% proof stress)
The fin material before brazing equivalent heat treatment was milled to JIS No. 5 test piece shape, and 0.2% proof stress was measured by a tensile test.

(Growth)
The fin material before brazing equivalent heat treatment was milled to JIS No. 5 test piece shape, and the elongation was measured by a tensile test.

(Melting point)
The melting point of the fin material was obtained by collecting a DTA signal from room temperature to 700 ° C. by differential thermal analysis using Al ₂ O ₃ as a reference sample in a nitrogen atmosphere, and measuring the solidus temperature.

(Grain size)
The obtained fin material was subjected to the above-mentioned brazing heat treatment with the fin material alone, and then etching was performed with a mixed aqueous solution of hydrochloric acid, nitric acid, and hydrofluoric acid to expose the structure of the fin material surface. Thereafter, the tissue of the fin material was photographed with a CCD camera. The concentric circles were marked on the obtained photograph, the number of crystal grains cut into concentric circles was visually counted, and then the crystal grain size was determined by the following equation.
Crystal grain size = total number of concentric circles / number of crystal grains cut in concentric circles / measurement magnification (equation 1)
FIG. 2 is a view showing an example of a method of measuring the crystal grain size. As shown in FIG. 2, concentric circles C1, C2, C3, etc. are marked on the obtained photograph I, the number of crystal grains G on the concentric circles is counted, and the crystal grains cut concentrically with the circumference of the concentric circles are counted. The crystal grain size was calculated based on the number.

(Cross sectional distance of grain boundary to fin thickness)
After the above-mentioned brazing heat treatment was performed on the obtained fin material, the fin material was embedded in a resin in order to observe the cross-sectional structure of the fin material. After curing of the resin, it was finished by wet polishing to a buffing of 0.1 μm, and anodizing treatment was carried out by Barker's solution.
Thereafter, the cross-sectional structure of the fin material was observed using a metal optical microscope, the length of grain boundaries of 20 pieces was measured, and the average length of grain boundaries was determined. The cross-sectional distance of grain boundaries was measured by image analysis software at the time of cross-sectional observation with an optical microscope. Thereafter, the average cross-sectional distance of grain boundaries with respect to the thickness of the fin material was determined by the following equation.
Average cross-sectional distance of grain boundaries with respect to thickness of fin material = average grain boundary length of cross-section / plate thickness of fin material ... (Equation 2)
FIG. 3 is a view showing a method of measuring the sectional distance of grain boundaries with respect to the thickness of the fin material. As shown in FIG. 3, the cross section of the fin material was observed, and the grain boundary length of the grain boundary R viewed from the cross section of the fin material 1 was measured.

(Recrystallization rate at 577 ° C during brazing temperature rise)
Rapid cooling was performed when the material reached 577 ° C. during the brazing heat treatment, and the structure at 577 ° C. was frozen.
Then, after performing electrolytic polishing with a hydrofluoric acid aqueous solution, using EBSD (Electron BackScatter Diffraction (EBSD)), an area of 1000 μm × 100 μm is analyzed at an acceleration voltage of 15 kV for three fields of view, and a fin material The surface recrystallized grain rate was measured.

(Aspect ratio of recrystallized grain size)
After the above-mentioned brazing heat treatment was performed on the obtained fin material, etching was performed using a mixed aqueous solution of hydrochloric acid, nitric acid and hydrofluoric acid, and the texture of the fin material surface was removed. Thereafter, the tissue of the fin material was photographed with a CCD camera. With respect to the obtained photograph, the aspect ratio (long side parallel to the rolling direction, short side perpendicular to the rolling direction) of 20 crystal grains was measured on the display. The average was made into the aspect-ratio of the recrystallized grain after brazing.
FIG. 4 is a diagram showing a method of calculating an aspect ratio. As shown in the figure, measure the length of the long side parallel to the rolling direction of recrystallized grain G and the short side perpendicular to the rolling direction, calculate the aspect ratio of recrystallized grain size based on the measurement results, and average I asked.

<Evaluation method>
(Evaluation of castability)
When there was no cracking during casting or a huge intermetallic compound of 50 μm or more, the castability was judged to be good and described as ○, and subsequent rolling was difficult due to cracking during casting and a huge intermetallic compound. In the case, it was judged as bad and described as x.

(Evaluation of formability)
When the corrugating was possible, it was judged as ○, when the plate thickness was too thick to be difficult to form, or when breakage was caused and the corrugating was impossible, it was judged as x.

(Evaluation of erosion resistance)
After the above-mentioned brazing heat treatment was carried out, the obtained mini core was embedded in a resin, and after resin curing, it was finished to a buffing of 0.1 μm by wet polishing. Thereafter, anodizing treatment was carried out with Barker's solution, and the cross-sectional structure of the mini core was observed with a metal optical microscope.
There are 12 fin / tube joints in the mini core, and the brazability was evaluated based on how many of the 12 bucklings there are.

FIG. 5 shows a state in which the fin material 1 is well joined to the tube material 10, and FIG. 6 shows a joint state in which the fin material 1 has a buckling. Although the shape of the fin material is maintained as shown in FIG. 5 in a good bonding state, when the erosion is severe, the fin material is buckled as shown in FIG. 6 and heat is used when it is used as a heat exchanger. It will not be possible to maintain the shape of the exchanger.
If the number of buckling is 2 or less in 12 places, it is judged as good and marked as ○, and if the buckling is 3 to 12 in 12 places, it is judged as defective and is marked as × .

(Evaluation of durability (crushed fins))
A static pressure of 0.25 MPa was applied to determine how much fin collapse due to tube expansion occurred. It was judged as ○ if the collapse of the fin was 2% or less of the whole, and x if it exceeded 3%.

(Evaluation of corrosion resistance)
SST (continuous salt spray test) was performed to evaluate corrosion resistance. If there is no penetration in the tube material combined with the fin after 90 days, it is rated as ○ if penetration is seen in the tube material.

  As shown in Tables 1 to 4, in all of Examples 1 to 27 satisfying the definition of the present invention, good results were obtained in all of castability, formability, erosion resistance, durability, and corrosion resistance. However, in Comparative Examples 1 to 28 not having any one or more of the provisions of the present invention, good results were not obtained in at least one of formability, erosion resistance, durability, and corrosion resistance. More specifically, Comparative Examples 3, 11 and 13 have poor castability and can not be manufactured, Comparative Example 17 can not be economically manufactured, and Comparative Example 19 can not be manufactured because homogenization treatment can not be obtained by homogenization treatment. Further, in Comparative Example 1, the plate thickness is too thick and molding is difficult, in Comparative Examples 15 and 26, the material strength is low, and in Comparative Example 27, the elongation is low and fracture occurs, and in Comparative Example 28, the elongation is high. The moldability was poor because of the burrs. In Comparative Example 6, the potential difference with the tube was low, a through hole was generated in the tube, and in Comparative Example 7, the potential of the fin became too deep, and the fin quickly corroded and a through hole was generated in the tube. In the other comparative examples, the erosion resistance or the durability was poor.

  Moreover, the graph which plotted the relationship of the temperature and time of the homogenization process in Examples 17-20 and Comparative Examples 16-21, and the relationship of the temperature and time of the homogenization process in another Example is shown in FIG. . In FIG. 7, white circles indicate examples, and black circles indicate comparative examples. As shown in FIG. 7, in the temperature range of less than 480 ° C., the time T is in the range of −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86 in the temperature range of less than 480 ° C., 480 ° C. or more In Examples 17 to 20 in the temperature range of −0.17t + 86 ≦ T ≦ −0.0721t + 39.137, an aluminum alloy fin material having good characteristics was obtained, but the above range was exceeded. With regard to Comparative Examples 16 to 21, the erosion resistance is low in Comparative Examples 16, 18, 20 and 21, and Comparative Example 17 can not be economically manufactured, and Comparative Example 19 can not be manufactured because the soaking during homogenization treatment can not be obtained. And none of them gave good results.

1 fin material 2 fillet 10 tube material R grain boundary cross section C1, C2, C3 concentric circle

Claims (9)

  Composition containing, by mass%, Mn: 1.0 to 2.0%, Si: 0.1 to 1.2%, Zn: 0.1 to 3.0%, the balance being Al and unavoidable impurities Made of an aluminum alloy having a thickness of 0.06 mm or less, a melting point of 610.degree. C. to 645.degree. C., an average grain size of a recrystallized structure after brazing heat treatment of 200 .mu.m or more, and a recrystallized grain size after brazing heat treatment Average grain boundary length of cross section (μm) / thickness of fin material (μm) as average cross sectional distance of grain boundary, the average cross sectional distance is 1.5 or more, 577 ° C at the time of temperature rise at the time of brazing heat treatment A thin-walled fin material excellent in erosion resistance, characterized in that the recrystallization ratio in is 97% or more.   Containing one or more of Cu: 0.01 to 0.20%, Fe: 0.05 to 0.50%, and Zr: 0.01 to 0.20% by mass% The thin fin material excellent in the erosion resistance according to claim 1 characterized by the above.   The average of the aspect ratio is 3.0 or more, wherein the short side perpendicular to the long side / rolling direction parallel to the rolling direction of recrystallized grains after brazing heat treatment is an aspect ratio. The thin fin material which is excellent in the erosion resistance of 2 statement.   The thin fin material excellent in erosion resistance according to any one of claims 1 to 3, wherein 0.2% proof stress is 190 MPa or more and elongation is 1.0 to 5.0%. It is a manufacturing method of the thin fin material which is excellent in the erosion resistance in any one of Claims 1-4, Comprising:
A step of performing homogenization treatment on an aluminum alloy having the composition according to claim 1 or 2, wherein in the homogenization treatment, the temperature (° C) of the homogenization treatment is t and the time (hr) is T. When the temperature t is less than 480 ° C., the time T is in the range of −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86, and when the temperature t is 480 ° C. or more, the time T is −0. 17t + 86 ≦ T ≦ −0.0721t + 39.137, wherein the method for manufacturing a thin fin material excellent in erosion resistance.   The temperature of the said homogenization process exists in the range of 400-500 degreeC, The manufacturing method of the thin fin material which is excellent in the erosion resistance of Claim 5 characterized by the above-mentioned.   A thin-walled fin material excellent in erosion resistance according to claim 5 or 6, characterized in that it has a cold rolling step, and in the cold rolling step, intermediate annealing is performed at a temperature lower than the homogenization treatment. Manufacturing method.   The corrosion resistance according to any one of claims 5 to 7, characterized in that when the thin fin material after the homogenization treatment is brazed, the temperature rising rate at the time of temperature rising is set to 300 ° C / min or less. Method of thin fin material excellent in toughness.   A step of performing homogenization treatment on an aluminum alloy having the composition according to claim 1 or 2, wherein in the homogenization treatment, the temperature (° C) of the homogenization treatment is t and the time (hr) is T. When the temperature t is less than 480 ° C., the time T is in the range of −0.0721 t + 39.137 ≦ T ≦ −0.17 t + 86, and when the temperature t is 480 ° C. or more, the time T is −0. Heat treatment at a temperature rising rate of 300 ° C./min or less after forming the aluminum alloy after homogenization treatment into a thin-walled fin within the range of 17t + 86 ≦ T ≦ −0.0721t + 39.137 A method of manufacturing a heat exchanger characterized in that the heat exchanger is incorporated into the heat exchanger.

Images