JP3253823B2 - Method for producing high strength and high heat resistant fin material made of aluminum alloy for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al--Si--Mg alloy in the form of a bare material (bare material) or a brazing sheet core material for use as a fin of various heat exchangers such as condensers for automobile coolers and evaporators. The present invention relates to an aluminum alloy fin material which is used after being subjected to vacuum brazing using a brazing material, and in particular, vacuum brazing to prevent deformation and buckling of the fin when assembling the heat exchanger when the plate thickness is reduced. The present invention relates to a method of manufacturing a fin material for a heat exchanger, which has improved strength (original plate strength) and improved buckling resistance due to high temperature during vacuum brazing.

[0002]

2. Description of the Related Art Generally, Al alloy heat exchangers have been widely used as heat exchangers for radiators, intercoolers, evaporators, condensers, oil coolers and the like of automobiles. In such an Al alloy heat exchanger, it is usual to assemble a tube, a core plate, or a pipe through which a temperature medium (working fluid) such as water flows with a fin material made of an aluminum alloy. As the fin material in this case, a brazing sheet, that is, used as a laminated plate in which a skin material made of an aluminum alloy brazing material is previously applied to one or both surfaces of an aluminum alloy core material, or used as a bare bare material Things are going on.

[0003] Among the heat exchangers, in a laminated evaporator generally brazed by a vacuum brazing method, a 4003 brazing material is added to a core material made of 3003 alloy.
A brazing sheet clad with 4 alloy or 4104 alloy is used as a core plate, and as a fin material to be vacuum brazed to this core plate,
Al-Mn-Zn-In alloy or Al-Mn-Z
Generally, an n-Sn alloy is used. In these fin material alloys, In and Sn are added in order to make the potential of the fin lower than that of the core plate constituting the temperature medium passage (refrigerant passage) and to exert a sacrificial anode effect on the core plate. In addition, Zn is also added in a large amount for the sacrificial anode effect.

[0004]

SUMMARY OF THE INVENTION Conventionally used in a vacuum-brazed laminated evaporator as described above is A
l-Mn-Zn-In alloy or Al-Mn-Zn-Sn
A fin material made of a system alloy has a problem that the production cost must be increased because Sn or In is added. Also, this type of fin material contains a large amount of Zn. However, if a large amount of Zn is added, the amount of Zn evaporated during vacuum brazing increases, and the inside of the brazing furnace is contaminated. It is necessary to increase the number of times of cleaning, and there is a problem that the running cost is increased. Furthermore, since In and Sn added to this kind of fin material are elements that are hardly added to aluminum alloys for general use, such as scrap of this kind of fin material and debris during the manufacturing process, etc. When reused as a return material, it cannot be used for other general purposes, and therefore, it is necessary to avoid mixing this type of fin material return material with common aluminum alloy return material. There is also a problem that requires strict return material management.

In recent years, Al-Mn-Cu-based alloys and Al-Mn-Cu-Ti-based alloys, which have better corrosion resistance than 3003 alloy, are often used as the core plate of the laminated evaporator. . In the case of the core plate alloys of these systems, since Cu is added in an amount of about 0.2 to 0.8%, the potential of the core plate itself becomes 300%.
Therefore, the potential of the fin material is sufficiently lower than that of the core plate without using In, Sn or a large amount of Zn as a fin material brazed to the core plate. , It is possible to sufficiently exhibit the sacrificial anode effect of the fin material on the core plate. Therefore, when alloys of these systems are used for the core plate, they do not contain Sn or In as the fin material and It is possible to use a 3003 alloy that does not contain a large amount of Zn.

However, when the conventional 3003 alloy is used as a fin material, there is a problem that it cannot meet the recent demand for thinner fin materials. That is, in the case of a conventional general automotive heat exchanger fin material, for example, in the case of a brazing sheet core material, the plate thickness is generally about 0.16 mm. Therefore, there is a strong demand, and it is desired that the fin material for the heat exchanger be further reduced in thickness as compared with the conventional one, specifically, to about 0.03 to 0.1 mm. Therefore, in order to prevent deformation and buckling at the time of forming the fin material, it is required to further increase the strength of the base plate before brazing as compared with the conventional one, and buckling deformation at high temperature brazing. It is desired to improve heat resistance (high-temperature buckling resistance) in order to prevent cracking. However, in the case of a conventional 3003 alloy, if the thickness is reduced to about 0.03 to 0.1 mm, an attempt is made to increase the strength. If so, the high-temperature buckling resistance is reduced, so it is difficult to simultaneously prevent deformation of the fin material during the assembly of the heat exchanger, prevention of buckling and prevention of buckling due to high temperature during brazing, Eventually 0.0
It was practically difficult to reduce the thickness of the fin material to about 3 to 0.1 mm.

[0007] The present invention has been made in view of the above circumstances, and Al-Mn-Cu alloys and Al-Mn-Cu
-For laminated evaporators and radiators using a temperature medium passage such as a core plate made of a brazing sheet having a Ti-based alloy as a core material, or for a heat exchanger using an Al-Cu-based alloy extruded multi-hole tube as a temperature medium passage. As a fin material for vacuum brazing, the fin material strength (base plate strength) at the time of assembling the heat exchanger before brazing is high, and the buckling resistance due to the high temperature during brazing is excellent, as well as excellent high temperature buckling resistance. Low cost, low production cost and return material management
It is an object of the present invention to provide an aluminum alloy fin material that can be easily processed.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have conducted various experiments and studies, and as a result, the alloy components of the fin material have been appropriately adjusted based on an Al-Mn-Si alloy. At the same time, by appropriately selecting the fin material manufacturing process and appropriately setting the conditions of each step, the strength before brazing is high, the buckling deformation due to high temperature during brazing is small, and the manufacturing cost is also reduced. It is inexpensive and easy to control and treat the return material.Moreover, it has a sufficient sacrificial anode effect as a fin material and can provide sufficient corrosion resistance to the heat exchanger. The inventors have found that a fin material capable of easily coping with the problem can be obtained, and have accomplished the present invention.

More specifically, the method for producing a high-strength and high-heat-resistant fin material made of an aluminum alloy for a heat exchanger according to the present invention is described in US Pat.
n 1.0-2.0%, Si 0.2-0.8%, Cu0.
0.05-0.20%, Zn 0.2% or more and less than 0.5%, Fe is regulated to 0.3% or less, and the balance is A
4 for ingots of alloys consisting of
When the homogenization treatment is performed at 00 to 550 ° C. for 1 to 30 hours, and the hot rolling is further performed, the hot rolling start temperature is set to 40.
0 to 550 ° C. and the hot rolling end temperature is 300
° C or less, cold rolling is performed at a rolling rate of 50% or more after completion of hot rolling, then intermediate annealing is performed at a temperature range of 100 ° C or more and less than 300 ° C, and further cold-rolled at a rolling rate of 5 to 50%. Rolling is performed to obtain a fin material having a thickness of 0.03 to 0.10 mm and a tensile strength of 200 N / mm ² or more.

[0010]

First, the reasons for limiting the composition of the alloy according to the present invention will be described.

Mn: Mn is a basic alloy component of the fin material alloy used in the present invention, and forms fine Al-Mn-Si based intermetallic compound precipitates to form a base plate (a plate before brazing). ) And the strength after brazing are improved, and the moldability is also improved. Al-Mn-S
The i-type fine intermetallic compound also contributes to improvement in high-temperature buckling resistance by making recrystallized grains coarse during brazing. If the Mn content is less than 1.0%, these effects are not sufficient. On the other hand, if it exceeds 2.0%, a coarse intermetallic compound is generated at the time of casting, the rollability is deteriorated, and the production of a sheet material becomes difficult. . Therefore, the Mn content is set in the range of 1.0 to 2.0%.

Si: Si is also a basic alloying component of the fin material alloy used in the present invention, and produces fine Al-Mn-Si-based intermetallic compound precipitates to improve the strength of the original sheet and the strength after brazing. It is an element effective for improving the strength and improving the high-temperature buckling resistance through coarsening of recrystallized grains during brazing as described above. Si is effective for reducing the amount of solid solution of Mn to improve thermal conductivity, making the potential lower, and enhancing the sacrificial anode effect of the fin material. If the amount of Si is less than 0.2%, these effects cannot be sufficiently obtained. On the other hand, if the amount of Si exceeds 0.8%, penetration of the brazing filler metal, particularly Si, into the fin material during brazing (generally, There is a risk that erosion of the fins and deterioration of corrosion resistance due to erosion may occur. Therefore, the Si content is set in the range of 0.2 to 0.8%.

Cu: Cu is an element effective for improving the strength of the base plate and the strength after brazing. Cu content is 0.0
If it is less than 5%, these effects are small, while if it exceeds 0.2%, the potential of the fin material becomes noble and the sacrificial anode effect of the fin material is reduced. Therefore, the Cu content is set in the range of 0.05 to 0.2%.

Zn: Zn makes the potential of the fin material low,
It is an element effective for enhancing the sacrificial anode effect. Also Z
n may evaporate partially from the fin material during vacuum brazing and cause contamination of the vacuum brazing furnace, but when an Al-Si-Mg alloy is used as the brazing material,
Mg evaporating from the Al-Si-Mg-based brazing material reacts with Zn evaporating from the fin material to form a Mg-Zn compound and adhere to the furnace wall. In this case, the adhered substance made of the Mg—Zn compound can be removed more easily than the adhered substance of Mg or Zn, so that the cleaning time of the vacuum brazing furnace is shortened and the running cost is reduced. 0.2% Zn content
If it is less than 0.5%, these effects cannot be sufficiently obtained.
Then, the contamination of the vacuum brazing furnace becomes severe. Therefore, the Zn content is set in the range of 0.2% or more and less than 0.5%.

Fe: Fe is an element contained as an unavoidable impurity element or a positively added element even in a normal aluminum alloy, but if contained in an amount exceeding 0.3%, coarse Al-Mn-Fe alloys are formed. Crystallized intermetallic compounds are formed, recrystallized grains during brazing become too fine, and the high-temperature buckling resistance is significantly reduced. Therefore, in the case of the present invention, F
e must be restricted to 0.3% or less as an impurity.

Other than the above elements, unavoidable impurities other than Al and Fe may be used.

Next, the manufacturing process according to the present invention will be described.

Generally, fin materials for heat exchangers are prepared by melting and casting.
H1n hard tempered state by applying the process of homogenization processing → hot rolling → cold rolling → intermediate annealing → final cold rolling, that is, a product in which the mechanical properties have been adjusted to a predetermined range by work hardening. It is usually manufactured as And the intermediate annealing in this case is generally 320 to 4
Conditions at 50 ° C. for about 0.5 to 6 hours (for example,
129347) is usually applied, and when such intermediate annealing is applied, the material is completely recrystallized and a uniform recrystallized structure is obtained. However, in such a conventional H1n temper material manufacturing process, it is difficult to simultaneously satisfy both the strength of the base sheet before brazing and the high-temperature buckling resistance. Therefore, in the present invention, at the same time as adjusting the component composition of the alloy as described above, by appropriately setting the manufacturing process conditions, particularly the intermediate annealing conditions and the final cold rolling conditions, the original sheet strength and the high-temperature buckling resistance are improved. Both were able to improve. That is,
By adjusting the intermediate annealing temperature to less than 300 ° C. so as not to cause complete recrystallization, and further performing appropriate final cold rolling at a rolling reduction of 5 to 50%, the strength of the original sheet and the resistance to buckling at high temperatures are improved. It was possible to achieve. Each process will be described more specifically.

First, in the melting / casting step, a DC casting method (semi-continuous casting method) may be applied according to a conventional method.

The obtained ingot is subjected to a homogenization treatment (soaking heat treatment). This homogenization treatment is not only for the purpose of homogenizing the structure of the ingot, but also for the Al-Mn intermetallic compound (Al-Mn, Al-Mn-Fe, Al-Mn-Fe).
-Si, Al-Mn-Si, etc.) are finely precipitated to coarsen recrystallized grains during brazing, thereby improving high-temperature buckling resistance and enhancing strength after brazing. This is a process, and in order to improve the high-temperature buckling resistance and the strength after brazing, it is necessary to perform the homogenization treatment in the range of 400 to 550 ° C. for 1 to 30 hours. If the temperature of the homogenization treatment is lower than 400 ° C., the precipitation of the Al—Mn intermetallic compound is not sufficiently performed, so that the recrystallized grains during brazing become fine, and the high-temperature buckling resistance is significantly reduced. I will.
On the other hand, if the temperature exceeds 550 ° C., the precipitated Al—Mn intermetallic compound becomes coarse and the strength after brazing decreases, and at the same time, the recrystallized grains during brazing become fine and the high-temperature buckling resistance decreases. I do. If the homogenization time is less than 1 hour,
Because the precipitation of the Al-Mn intermetallic compound is not sufficient,
The effect of the homogenization treatment on the improvement of high-temperature buckling resistance and strength after brazing is small. On the other hand, even if the homogenization treatment is performed for more than 30 hours, the above-described effects are saturated, and it is only uneconomical in terms of energy consumption. After this homogenization treatment, hot rolling is performed as described later, but the homogenization treatment is also performed together with heating to obtain the required hot rolling start temperature, and immediately after the homogenization treatment, the hot rolling is performed. Rolling may be performed, or hot rolling may be performed by cooling once after the homogenization treatment and then heating again to the hot rolling start temperature.

In the hot rolling after the homogenization treatment, the starting temperature is set in the range of 400 to 530 ° C. in order to obtain good hot rolling property and good buckling resistance at high temperature and strength after brazing. Must be within. If the hot rolling start temperature is less than 400 ° C., the edge cracks during hot rolling become severe and rolling becomes difficult, while if the hot rolling starting temperature exceeds 530 ° C.,
As the strength after brazing decreases, the recrystallized grains after brazing become finer and the high-temperature buckling resistance decreases. Further, the end temperature in this hot rolling needs to be 300 ° C. or less. When the hot rolling end temperature exceeds 300 ° C,
During cooling of the hot-rolled coil after hot rolling, Al-Mn-based precipitates precipitate and become coarse, so that the strength after brazing is reduced and the high-temperature buckling resistance is reduced.

After hot rolling, cold rolling (primary cold rolling) is performed before intermediate annealing to obtain an intermediate sheet thickness. This primary cold rolling requires a rolling reduction of 50% or more. If the primary cold rolling reduction is less than 50%, the strength of the base sheet is not sufficiently improved, and the high-temperature buckling resistance is reduced.

The intermediate annealing after the primary cold rolling must be performed in a temperature range of 100 ° C. or more and less than 300 ° C., and the material must be annealed in a state where the material does not have a completely recrystallized structure. When the material is annealed at a high temperature of 300 ° C. or more, the material is completely recrystallized during the intermediate annealing.
In order to obtain a strength of ² mm2 or more, the final cold rolling reduction is 80
% Or more, but if the final cold rolling reduction is increased in this way, the high-temperature buckling resistance is reduced. On the other hand, when the intermediate annealing temperature is lower than 100 ° C., structural change hardly occurs, and the high-temperature buckling resistance is not improved. In addition, the holding time of the intermediate annealing is not particularly limited, but is usually preferably 10 hours or less and 0.5 hours or more. Even if it is held for more than 10 hours, only the softening gradually progresses, and there is no significant contribution to the improvement of the buckling resistance at high temperature. Therefore, only the production cost is increased. Is preferred. If the holding time of the intermediate annealing is less than 0.5 hour, the cold rolling property may not be sufficiently improved.

After the intermediate annealing, 0.03 to 0.10 mm
Cold rolling (final cold rolling) is performed to the final sheet thickness of The rolling reduction in this final cold rolling needs to be 5% or more and 50% or less. When the final cold rolling reduction is less than 5%, it is difficult to achieve a value of 200 N / mm ² or more as the original plate strength. On the other hand, if the final cold rolling ratio exceeds 50%, the recrystallized grains during brazing become fine and the high-temperature buckling resistance decreases.

The fin material having a thickness of 0.03 to 0.10 mm obtained through the above-described process needs to have an original plate strength of 200 N / mm ² or more. If the strength of the base plate is less than 200 N / mm ² , in the case of a thin plate having a thickness of 0.03 to 0.10 mm, the occurrence rate of molding failure during the molding of the fin material increases, and the buckling of the fins when assembling the heat exchanger is reduced. This is likely to occur, and in any case, the product yield will decrease.

The fin material obtained as described above may be used as it is as a bare material in a heat exchanger, or may be used as a brazing sheet by clad with an Al-Si-Mg-based brazing material or the like. .

[0027]

【Example】

Example 1: Alloy No. 1 in Table 1 1 to No. Each alloy having the composition shown in FIG. 9 was melt-cast according to a conventional method, and the obtained ingot was subjected to a homogenizing treatment (soaking heat treatment), and subjected to hot rolling to obtain a sheet thickness of 2.0 to 2.5 mm. Was obtained.
Thereafter, primary cold rolling, intermediate annealing and final cold rolling were performed to obtain a bare fin material having a thickness of 0.070 mm. Temperature of the homogenization treatment (soaking heat treatment) in such a process,
Hot rolling start temperature, hot rolling end temperature, hot rolled up sheet thickness, sheet thickness during intermediate annealing (thickness after primary cold rolling), primary cold rolling rate until intermediate annealing, intermediate annealing temperature, The final cold rolling reduction is shown in Production Conditions A to Q in Table 2. In each case, the heating and holding time in the homogenization treatment was 10 hours, and the heating and holding time in the intermediate annealing was 5 hours.

Alloy No. of each component composition 1 to No. Using No. 9, a tensile test was performed on each fin material manufactured under any of the manufacturing conditions A to Q to measure the original plate strength (tensile strength). In addition, in order to examine the strength after brazing, a heat treatment equivalent to vacuum brazing at 600 ° C. for 3 minutes was performed in a vacuum of 5 × 10 ⁻⁵ Torr, and a tensile test was performed. Was measured.

Further, in order to evaluate the corrosion resistance as a heat exchanger, in particular, to evaluate the sacrificial anode effect of the fin material, the pitting potential of each fin material was examined. That is, generally, the fin material is brazed to a tube or a core plate for a temperature medium (working fluid) passage, and acts as a sacrificial anode effect on the temperature medium passage to prevent corrosion of the tube and the core plate. In order to exhibit the sacrificial anode effect of the fin material in this case, the pitting potential of the fin material is 30 m with respect to the temperature medium passage.
It is necessary to be lower than V. As a heat exchanger temperature medium passage material which is a target of the present invention, Cu is used in an amount of 0.1.
Al-Mn-Cu (-Ti) containing about 2 to 0.8%
The pitting potential of this alloy is -660.
The fin material must have a pitting potential of -690 mV or more in order to exert a sufficient sacrificial anode effect of the fin material on the temperature medium passage material. Therefore, in this embodiment, the corrosion resistance as a heat exchanger can be evaluated based on whether or not the pitting potential of the fin material is lower than -690 mV. The pitting potential was measured in a 2.67% AlCl ₃ aqueous solution.

Further, in order to evaluate the high-temperature buckling resistance during brazing, the amount of sag under the conditions corresponding to the fin material brazing was examined. That is, the sample was cut into a width of 20 mm and a length of 70 mm, and one end thereof was fixed with a jig to 60 m.
m, and heated in a vacuum of 5 × 10 ⁻⁵ Torr at 600 ° C. for 3 minutes to measure the amount of sag of the protruding tip.

Further, the fin material is corrugated, and Al-1% Mn-0.5% Cu-0.10% Ti is used as a core material.
After placing on a brazing sheet having a thickness of 0.6 mm using an alloy and a brazing material of 4104 alloy and performing brazing and heating at 600 ° C. for 3 minutes in a nitrogen gas atmosphere, a brazing state was performed. Was micro-observed to examine the erosion property of the fin material by the molten solder during vacuum brazing.
Further, these vacuum brazed samples were subjected to a 720-hour CASS test to measure the maximum corrosion pit depth at the joint surface between the brazing sheet and the fin.

Table 3 shows the results of the above investigations.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

From Table 3, it can be seen that the fin material (Example of the present invention) obtained by satisfying the component composition conditions and the production process conditions specified in the present invention has a strength of the original plate greatly exceeding 200 N / mm ² and brazing. The strength afterwards is also 100N / m.
m ² , and the sag amount is 15 mm or less, the high temperature buckling resistance is excellent, and the spontaneous potential is certainly lower than -690 mV and has a sufficient sacrificial anode effect.
The CASS test revealed that the joint surface had a small corrosion depth, was excellent in corrosion resistance as a heat exchanger, and had little erosion of the brazing material during brazing.
On the other hand, Comparative Examples in which either the component composition conditions or the manufacturing process conditions were out of the ranges specified in the present invention were inferior in any of the above-mentioned performances.

[0037]

As is clear from the foregoing embodiments, the fin material for heat exchanger obtained by the method of the present invention has a high strength (base sheet strength) before brazing and a sheet thickness of 0.1 mm.
Deformation when assembling the heat exchanger,
There is very little buckling and excellent buckling resistance at high temperatures, and there is little risk of buckling due to high temperatures during brazing. In addition, the fin material obtained by the method of the present invention has a high strength after brazing, and has a sufficient sacrificial anode effect on these tubes and core plates after brazing to core plates and tubes as a heat exchanger. The erosion due to the brazing material can be extremely reduced. Furthermore, the fin material for a heat exchanger according to the present invention does not add a special element as an aluminum alloy additive element such as Sn or In, so that the material cost is not particularly increased, and the management and treatment of the return material is not required. Because it is easy and the Zn content is regulated to an appropriate amount, not only is the contamination of the vacuum brazing furnace small, but also when the brazing material made of an Al-Si-Mg alloy is used, the vacuum brazing is performed. Since the removal of contaminants from the furnace wall of the furnace is also facilitated, the cost required for cleaning the furnace does not increase. Therefore, when the fin material obtained by the method of the present invention is used for a heat exchanger, the fin material and the heat exchanger itself are not actually deteriorated or the cost is not increased without impairing various performances. By reducing the thickness of the fin material to 1 mm or less, the weight and cost of the heat exchanger can be reduced.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 686 C22F 1/00 686A 691 691B 694 694A

Claims (1)

(57) [Claims] 1. Mn 1.0-2.0% (% by weight, the same applies hereinafter), Si 0.2-0.8%, Cu 0.05-0.20
%, Zn 0.2% or more and less than 0.5%, and F
e is regulated to 0.3% or less, and the balance is 400 to 550 ° C. with respect to an ingot of an alloy including Al and unavoidable impurities.
In the hot rolling, the hot rolling start temperature is set to 400 to 550 ° C., the hot rolling end temperature is set to 300 ° C. or less, and 50% after hot rolling is completed. After performing cold rolling at the above rolling ratio, intermediate annealing is performed in a temperature range of 100 ° C. or more and less than 300 ° C., and further cold rolling is performed at a rolling ratio of 5 to 50%.
Within a and a tensile strength range plate thickness of 0.03~0.10mm is characterized in that to obtain 200 N / mm ² or more of the fin material, vacuum brazing using Al-Si-Mg based alloy brazing material Of high strength and high heat resistant fin material made of aluminum alloy for heat exchanger for heat treatment.