JPH0543973A - High heat conductivity aluminum alloy sacrificial fin material for low temperature brazing and its production - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high thermal conductivity aluminum alloy sacrificial fin material for low temperature brazing, which has high strength and thermal conductivity after brazing and is used for heat exchangers for automobiles, and a method for manufacturing the same. [Constitution] Zr 0.03 to 0.30 wt% is contained, and further Zn 0.3 to 2.0 wt% and In 0.03 to 0.3 wt%
%, Sn 0.03 to 0.3 wt%, one or two or more, and the balance being Al and inevitable impurities, and the total of the inevitable impurities being 0.6 wt% or less from an Al alloy ingot When manufacturing a fin material by rolling, the final cold rolling rate is set to 20 to 80% without heating at a temperature higher than 520 ° C. in all manufacturing steps, and high thermal conductivity for low temperature brazing. Manufacturing method of aluminum alloy sacrificial fin material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductive aluminum alloy sacrificial fin material, and more particularly to a high thermal conductive aluminum alloy sacrificial fin material for low temperature brazing for brazing at a temperature of 500 ° C. or lower. In particular, it is used as a fin for radiators, heaters, condensers, etc. of heat exchangers for automobiles.

[0002]

2. Description of the Related Art Most heat exchangers for automobiles use Al and Al alloys and are manufactured by a brazing method. Usually, Al-Si type brazing material is used for brazing, and therefore brazing is performed at a high temperature of about 600 ° C. In a heat exchanger such as a radiator, for example, as shown in FIG. 1, thin fins (2) processed into a corrugated shape are integrally formed between a plurality of flat tubes (1), and both ends of the flat tubes (1) are Opened in the space consisting of the header (3) and the tank (4), the high temperature refrigerant is sent from the space on one tank side to the space on the other tank (4) side through the flat tube (1). , Tubes (1) and fins
In the part (2), the refrigerant that has exchanged heat and becomes a low temperature is circulated again. By the way, in recent years, heat exchangers have been in the direction of weight reduction and downsizing, and therefore thinning of materials has been desired. However, when the conventional material is thinned, the strength and the thermal conductivity become insufficient due to the decrease in the thickness of the material.
For this reason, studies have been conducted on increasing the strength of the fin material and improving the thermal conductivity, but sufficient results that satisfy both requirements have not been obtained. This is because brazing that heats up to around 600 ° C is used as the final process of the product, so the mechanism of strength improvement such as heat hardening cannot be used, and the elements added to the alloy during brazing re-dissolve and heat transfer This is because it inhibits Further, when the tube material, the tank material, the header material, and the like are thinned, the fin material is required to have a sufficient sacrificial effect for corrosion resistance as a heat exchanger.

[0003]

SUMMARY OF THE INVENTION In view of this, the present invention is directed to developing a fin material having high strength and high thermal conductivity after brazing, in which brazing is performed at a low brazing temperature instead of conventional brazing. The present invention has been accomplished on the assumption that the problem can be solved by developing a fin material suitable for the above. Here, brazing with a low brazing temperature is a brazing method developed in recent years because of a growing demand for a lower brazing temperature for the purpose of reducing the brazing cost. By lowering the brazing temperature, various advantages such as reduction of brazing time, reduction of heat quantity, reduction of cost of brazing furnace, and improvement of durability of brazing furnace are produced.
As a brazing filler metal currently brazed at a low temperature, if the melting point is 500 ° C. or lower, for example, pure Zn, Zn-0 to
28 wt% Al, Zn-Al system, Zn-Cd system, Sn-Z
There are n type, Sn-Pb type and the like. However, considering the corrosion resistance of the heat exchanger after brazing, the Zn-Al brazing material is the most effective. That is, the present invention is directed to a fin material that is suitable for the brazing method, has excellent thermal conductivity and strength after brazing, and can be thinned, and a method for manufacturing the fin material. , Zr 0.03 to 0.30
wt%, Zn 0.3-2.0 wt%, In
One or more of 0.03 to 0.3 wt% and Sn 0.03 to 0.3 wt% are contained, and the balance is Al and inevitable impurities, and the total of the inevitable impurities is 0.6 wt% or less. A high heat conductive aluminum alloy sacrificial fin material for low temperature brazing, comprising: Zr 0.03 to 0.30 wt%; and Zn.
0.3-2.0 wt%, In0.03-0.3 wt%, Sn
One or more of 0.03 to 0.3 wt% is contained, and the balance is Al and unavoidable impurities, and the total of the unavoidable impurities is 0.6 wt% or less. In producing a fin material by using a high heat conductive aluminum alloy for low temperature brazing, the final cold rolling rate is 20 to 80% without heating to a temperature higher than 520 ° C. in all manufacturing steps. A method for manufacturing a sacrificial fin material, wherein the invention according to claim 3 is Zr0.03.
〜0.30wt%, Zn0.3〜2.0wt
%, In 0.03 to 0.3 wt%, Sn 0.03 to 0.3
One or two or more of the wt% are contained, and the balance is Al and inevitable impurities, and the total of the inevitable impurities is 0.6 wt.
% To produce a fin material by rolling from an Al alloy ingot, the final cold rolling rate is 20% or more,
A method for producing a high-thermal-conductivity aluminum alloy sacrificial fin material for low-temperature brazing, which comprises performing precipitation treatment at a plate thickness of the final fin material at 300 ° C to 420 ° C.

[0004]

First, the alloy composition of the fin material of the present invention will be described. The fin material of the present invention is Zr 0.03 to 0.30 wt%
In addition, Zn 0.3-2.0 wt%, In0.0
1 out of 3 to 0.3 wt% and Sn 0.03 to 0.3 wt%
A fin material containing one or more kinds of Al, the balance being Al and inevitable impurities, and the total of the inevitable impurities being 0.6 wt% or less. Zr exists in the alloy as very fine dispersed particles and as solid solution Zr, and prevents fins from softening due to recrystallization of the fin material during brazing heating at 500 ° C. or less. That is, the dispersed particles make subgrains fine and stable, and the solid solution Zr pins dislocations.
Due to such an action, if the brazing heating is performed at 500 ° C. or less, high strength is exhibited even after brazing. Zr is 0.03wt%
If it is less than 0.3% by weight, the above action is insufficient, and if it is added in excess of 0.30% by weight, cracking occurs during casting of the alloy, making it impossible to manufacture a fin material. Therefore, the Zr content is determined to be 0.03 to 0.30 wt%. Zn, In, Sn
Has a function of making the electric potential of the fin material base, giving a sacrificial effect to the fin material, and enhancing the corrosion resistance of the heat exchanger. The amount of Zn is less than 0.3 wt%, In less than 0.03 wt%, Sn
If it is less than 0.03 wt%, the sacrificial effect is not sufficient, Zn exceeds 2.0 wt%, In exceeds 0.3 wt%, Sn
The effect does not change even if added in excess of 0.3 wt%, and conversely, the formability and heat conductivity of the fin material deteriorate. Therefore, Zn 0.3-2.0 wt%, In 0.03-0.3 wt%
%, Sn 0.03 to 0.3 wt%, or one or more of them. The above is the additional elements of the alloy fin material of the present invention. The balance is Al and inevitable impurities, and the inevitable impurities are Si, Fe, Mn,
There are Ti, Cr, etc., but if such unavoidable impurities are excessively present, the thermal conductivity of the fins decreases, so
The total amount of unavoidable impurities is defined as 0.6 wt% or less.

Next, a method for manufacturing the alloy fin material of the present invention will be described. First, the first manufacturing method is the tempering symbol H1.
It is an n-type fin manufacturing method, and is manufactured by a step of homogenizing, hot rolling, cold rolling and annealing an Al alloy ingot having the above composition, and exceeds 520 ° C. in all manufacturing steps during that. The final cold rolling rate is set to 20 to 80% without heating to a temperature. This method for producing a fin material is characterized in that the precipitated phase particles containing Zr are finely and densely distributed to prevent the progress of recrystallization during brazing heating and prevent softening. When heating is performed at a temperature higher than 520 ° C. in the steps of homogenization treatment, hot rolling, cold rolling / annealing, precipitated particles become coarse and softening easily occurs during brazing heating. Also, the final cold rolling rate is
If it is less than 20%, the amount of work hardening is not sufficient and the strength is not improved, and if it exceeds 80%, the driving force for recrystallization increases, so that softening occurs during brazing heating. In addition, the process of the present invention only needs to satisfy the above, and an ingot produced by an ordinary water-cooled casting method may be used, and the subsequent homogenization treatment is performed at 520 ° C.
The heat treatment may be performed at the following temperature or may be performed only without heat treatment for hot rolling the ingot, and hot rolling may be performed by a conventional method. The obtained hot-rolled coil is cold-rolled to form a fin material, but is annealed in the middle to adjust the temper. It does not matter if annealing is performed more than once. The second manufacturing method of the present invention is manufactured by the steps of homogenizing, hot rolling, cold rolling and annealing an Al alloy ingot having the above composition, but the final cold rolling up to the plate thickness of the fin material. Rolling rate is 20% or more,
It is characterized in that the precipitation treatment is performed at a plate thickness of the final fin material at 300 ° C to 420 ° C. This manufacturing method is for manufacturing fins of the tempering symbol H2n type, and the characteristic is that the final precipitation treatment precipitates the second phase particles on the subgrain boundaries and stabilizes the subgrains. Especially. When a fin material having such stabilized sub-crystal grains is brazed and heated at 500 ° C. or less, the sub-crystal grain boundaries are pinned by the grains and therefore do not soften and have high strength even after brazing. .. Here, the precipitation treatment temperature is 300 ° C.
If it is less than 4, the precipitation does not occur sufficiently and the stabilizing effect is not obtained.
If it exceeds 20 ° C, the precipitation phase becomes coarse and the action of pinning the sub-grain boundaries is reduced. Therefore, the temperature of the precipitation treatment is 30
It is defined as 0 ° C to 420 ° C. The holding time is 0.5h
It may be about 6 hours. Here, the cold rolling is performed before performing the precipitation treatment in order to form the sub-crystal grains by the dislocation introduced by the rolling during the heating of the precipitation treatment and to cause the precipitation on the sub-crystal grains. However, if the cold rolling ratio is less than 20%, the amount of dislocations introduced is small, so that the sub-grains are not formed promptly during the precipitation treatment, and the precipitated grains do not occur on the sub-grain boundaries, so that the strength improving effect is obtained. Reduce.
In addition, precipitation treatment is performed with the final fin material plate thickness, and cold rolling is not performed thereafter.However, when cold rolling is performed after the precipitation treatment, new dislocations are introduced by cold rolling and brazing is performed. This is because a subcrystal is newly formed at the time of heating and the particles do not effectively function as a pin. The second manufacturing method of the present invention only needs to satisfy the above requirements, and an ingot produced by an ordinary water-cooled casting method may be used. The subsequent homogenization treatment may be performed at a temperature of 400 ° C. to 600 ° C. or may be performed only by heat treatment for hot rolling the ingot, and hot rolling may be performed by an ordinary method. The obtained hot-rolled coil is cold-rolled to have a fin material plate thickness, but it may be annealed halfway. The above is the method for producing the alloy fin material of the present invention, but when assembled as a heat exchanger, it is easiest to use it in combination with a tube material for a heat exchanger coated with a brazing material having a low melting point. In this case, the wax coating is a thermal spray method,
It is usually carried out by a method such as hot dip plating, electroplating or vapor deposition. The fin thickness of the present invention is 120 μm or less.

[0006]

EXAMPLES The present invention will be described in detail below with reference to examples. [Example 1] A composition shown in Table 1 was formed by water-cooling casting to a thickness of 40.
Aluminum alloy fin material (plate thickness 100 μ
m) was prepared. The obtained fin material was combined with the following tube material and header material to assemble the radiator shown in FIG. JISA3003 alloy is used as core material and J
Coil-shaped plate materials having plate thicknesses of 0.4 mm and 1.2 mm, in which ISA7072 alloy was clad at a ratio of 10%, were manufactured by a normal hot pressing method. Using this coiled plate material, Zn-11wt% Al (melting point 425 ° C) brazing material is plated on the opposite side of JISA7072 clad layer by hot-dip plating to a coiled plate material of 0.4mm thickness with a thickness of 20μm. The 1.2 mm coil-shaped plate material was plated to a thickness of 80 μm. In the case of a coil-shaped plate material having a plate thickness of 0.4 mm, slitting was performed according to the size of the electric resistance welded pipe to form a strip material having a width of 35.0 mm. Using the ERW 1 manufacturing apparatus, this strip was processed into an ERW pipe having a width of 16.0 mm and a thickness of 2.2 mm with a plating layer on the outer surface. In the case of a coil-shaped plate material having a plate thickness of 1.2 mm, a slitter having a width of 60 mm was used as a strip for a header. After degreasing, the assembled radiator was coated with a 10% concentration solution of a fluoride-based flux whose basic composition was AlF ₃ and CsF, and was inserted into a furnace in a nitrogen gas atmosphere with a dew point of −40 ° C. maintained at a temperature of 450 ° C. I brazed. At the same time, the fin material was heated, and the tensile strength and conductivity of the fin material after brazing and heating were measured. Here, the electrical conductivity is an index of thermal conductivity, and if the electrical conductivity of the fin is improved by 10% IACS, the thermal efficiency of the heat exchanger is improved by about 2%. As a conventional method for comparison, the core material is JISA3003 alloy and JISA
A similar radiator was assembled using the brazing sheet of the same structure in which 7072 alloy and JISA4343 alloy were hot-press bonded, and a 10% concentration solution of a fluoride-based flux having AlF ₃ and KF as a basic composition was applied at a temperature of 600 ° C. And brazing in the same furnace as above. At the same time, the fin material was heated, and the tensile strength and conductivity of the fin material after brazing and heating were measured. The results are shown in Table 3. In addition, we investigated the joining condition after brazing, and
A salt spray test according to ISZ2371 was carried out for 1000 hours. The pitting corrosion generated on the ERW tube material was judged to be equivalent to the conventional material, and to be inferior to the conventional material as x. These results are also shown in Table 3.

[0007]

[Table 1]

[0008]

[Table 2]

[0009]

[Table 3]

As is clear from Table 3, the material sample No. of the present invention was obtained.
1 to 7 are conventional material sample Nos. Compared with No. 11, the bonding condition and corrosion resistance (results of salt spray test) are the same, and the tensile strength and conductivity are remarkably excellent. On the other hand, comparative material No. 1 containing no Zn, In, or Sn was added. No. 8 has a poor corrosion resistance, and the addition amount of Zr is less than the range of the present invention.
No. 9 has a small tensile strength. In addition, the comparative material No. 1 containing more unavoidable impurities than the range of the present invention. It can be seen that 10 has a low conductivity.

Example 2 Alloy No. 1 in Table 1 Table 2 from the ingot cast by the water-cooled casting with the composition shown in Figure 1 to a thickness of 400 mm.
The aluminum alloy fin material (plate thickness 1
00 μm) was prepared. Using the obtained fin material, a radiator was assembled in the same manner as in Example 1 and each characteristic was examined by the same method as in Example 1. The results are shown in Table 4.

[0012]

[Table 4]

As is apparent from Table 4, the material sample No. of the present invention manufactured by the manufacturing method of the present invention. Nos. 1 and 12 to 14 are conventional material sample Nos. Compared with No. 11, the tensile strength and the conductivity are remarkably excellent. On the other hand, the comparative material sample No. manufactured by the manufacturing method outside the scope of the manufacturing method of the present invention. The tensile strengths of Nos. 15 and 16 are slightly superior to the conventional materials, but are inferior to the materials of the present invention.

[0014]

As described above, the fin material of the present invention is 500
When brazing is performed at a low temperature of ℃ or less, the brazing property is not impaired, the strength is high, and the sacrificial effect is obtained. Further, the thermal conductivity is good, and a remarkable industrial effect is achieved.

[Brief description of drawings]

FIG. 1 is a perspective view of a partial cross section showing a radiator.

[Explanation of symbols]

 1 Flat tube 2 Fins 3 Header 4 Tank

Claims (3)

[Claims] 1. Containing Zr 0.03 to 0.30 wt%,
Zn 0.3-2.0 wt%, In 0.03-0.3
wt%, Sn 0.03 to 0.3 wt% 1 or 2
A high-thermal-conductivity aluminum alloy sacrificial fin material for low-temperature brazing, characterized in that it contains at least one kind and the balance is Al and inevitable impurities, and the total of the inevitable impurities is 0.6 wt% or less. 2. Zr 0.03-0.30 wt% is contained,
Zn 0.3-2.0 wt%, In 0.03-0.3
wt%, Sn 0.03 to 0.3 wt% 1 or 2
At the time of manufacturing a fin material by rolling from an Al alloy ingot containing at least one kind and the balance being Al and unavoidable impurities, and the total of the unavoidable impurities being 0.6 wt% or less, 520 ° C. in all manufacturing steps The final cold rolling rate is set to 20 to 80% without heating to a temperature higher than 100 ° C., and a method for producing a high thermal conductive aluminum alloy sacrificial fin material for low temperature brazing. 3. Zr 0.03-0.30 wt% is contained,
Zn 0.3-2.0 wt%, In 0.03-0.3
wt%, Sn 0.03 to 0.3 wt% 1 or 2
The final cold rolling rate when producing a fin material by rolling from an Al alloy ingot containing at least one species and the balance being Al and unavoidable impurities, and the total of these unavoidable impurities is 0.6 wt% or less. Is 20% or more, and the final fin plate thickness is 3
A method for producing a sacrificial fin material for a high-thermal-conductivity aluminum alloy for low-temperature brazing, which comprises performing precipitation treatment at 00 ° C to 420 ° C.