JPH0480107B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to an aluminum alloy for the fin material of a heat exchanger, such as a radiator or a car air conditioner, in which the fins and the material forming the working fluid passage are joined by brazing. This invention relates to an aluminum alloy for fin materials that has high thermal conductivity and excellent sacrificial anode effect. [Prior art] Heat exchangers such as radiators, air conditioners, intercoolers, and oil coolers for automobiles use Al-Cu alloys, Al-Mn alloys, and Al-Mn-
A working fluid passage constituent material such as a Cu-based alloy and a fin material made of an aluminum-based alloy are assembled by brazing. The fin material is required to have a sacrificial anode effect to prevent corrosion of the materials forming the working fluid passage, and also to have excellent high temperature resistance so that it will not be deformed by high temperature heating during brazing and will not corrode the solder. Buckling resistance is required. Adding Mn is effective in preventing deformation and wax corrosion during brazing.
Fin material is Al-Mn such as 3003 alloy and 3203 alloy.
alloys are used. In order to impart a sacrificial anode effect, there is also a method of electrochemically making the Al-Mn alloy less noble by adding Zn, Sn, In, etc. (for example, see Japanese Patent Application Laid-open No. 120455/1983). In order to further improve high-temperature buckling resistance (high-temperature sag resistance), a method of adding Cr, Ti, Zr, etc. (see, for example, Japanese Patent Application Laid-Open No. 118919/1983) has been proposed. [Problems to be Solved by the Invention] In recent years, there has been a strong demand for weight reduction and cost reduction of heat exchangers. It has become necessary to make materials thinner (such as materials). However, when the fin material is made thinner, the heat transfer cross-sectional area becomes smaller, which poses a problem in that heat exchange performance is impaired. In order to solve this problem, it is effective to increase the thermal conductivity of the fin material after brazing.
In the case of Al-Mn alloys, Mn is removed at high temperatures during brazing.
is dissolved in solid solution, resulting in a significant decrease in thermal conductivity. As a fin material with excellent thermal conductivity, Mn: 0.1-0.8%,
Aluminum alloys containing Zr: 0.02 to 0.2% and Si: 0.1 to 0.8% have also been proposed (Tokukō Sho 63-
In this case, since the amount of Mn is small, the strength after brazing is low, and the fins tend to collapse or deform during use. Furthermore, since the potential of the fin material is not base, the sacrificial anode effect is small. Also, Si:
Contains 0.03-0.3%, Fe: 0.05-0.6%, Zr: 0.01
Aluminum alloys containing one or two of Mn: ~0.4% and Mn: 0.01~0.3% have also been proposed (see JP-A-63-45352), but in this case, the potential of the fin material is not base; , the sacrificial anode effect is small.
In addition, pure aluminum (1050, 1070) has high thermal conductivity.
Attempts have also been made to use fin materials with Zn, Sn, In, Cr, Ti, Zr, etc. It is easy to fall down,
It hasn't really solved the problem. The present invention aims to fundamentally solve this problem. [Means for Solving the Problems] The present inventors investigated various aluminum alloys, and found that the thermal conductivity of We have discovered an aluminum alloy for fin materials that has significantly improved sacrificial anode effect and high-temperature buckling resistance, and completed the present invention. That is, in the present invention, Fe: 0.9 to 1.8%, Si: 0.2
~0.6%, Mn: 0.1~0.35%, Zr: 0.05~0.20%,
Aluminum for heat exchanger fin material with excellent post-brazing thermal conductivity and sacrificial anode effect, containing Zn: 0.5 to 2.0% or further Cu: 0.3% or less, with the remainder consisting of Al and unavoidable impurities. It is an alloy. The reasons for limiting each component in the present invention are as follows. Fe: Fe improves the strength of the alloy, that is, the strength of the fin material before brazing, as well as the strength after brazing. Since the alloy of the present invention contains Mn and Si, the strength improvement effect appears when Fe is 0.9% or more. If it is less than 0.9%, the effect is not sufficient.
On the other hand, if it exceeds 1.8%, coarse crystallized substances will be generated during casting, making it difficult to manufacture plate materials. Si: Si is Al-Mn-Si system or Al-Mn-Fe
-Generates Si-based compounds to reduce the amount of solid solution of Mn and improve thermal conductivity. If the content is less than 0.2%, the effect will not be sufficient, and if it exceeds 0.6%, the thermal conductivity will decrease. Mn: Like Fe, improves strength before and after brazing. It also improves high temperature buckling resistance and moldability. If it is less than 0.1%, the effect will not be sufficient, and if it exceeds 0.35%, the thermal conductivity will decrease. Zr: Zr improves high temperature buckling resistance. If it is less than the lower limit, the effect will not be sufficient, and if it exceeds the upper limit, the thermal conductivity after brazing will decrease. Zn: Zn makes the potential of the fin material less noble and gives it a sacrificial anode effect. In the case of the alloy of the present invention, since it contains Mn that makes the potential more noble, it has a content of 0.5% or more.
If the amount of Zn is low, the sacrificial anode effect will not be sufficient. If it exceeds 2.0%, not only the effect will be saturated, but also the self-corrosion resistance will deteriorate. Cu: Cu improves strength after brazing. 0.3%
If the value exceeds , the potential of the fin material becomes noble and the sacrificial anode effect is impaired. Other elements may include Mg, Cr, Ti, etc. within a range that does not impair the effects of the alloy of the present invention. However, as the content of both increases, the thermal conductivity decreases, so Mg is 0.2% or less, Cr is 0.05% or less,
It is desirable that Ti be 0.05% or less. Mg is
In the case of fluoride flux brazing, it is even lower, i.e. 0.1%, as it reacts with the flux.
It is desirable to keep it below. Ti may be added as an alloying element for grain refinement during casting, or as an Al-Ti-B refiner, but it is desirable to keep it within the above range. [Example] Alloys No. 1 to 18 having the compositions shown in Table 1 were melted and cast, and subjected to homogenization treatment, hot rolling, cold rolling, intermediate annealing, and final cold rolling to form a 0.07 mm thick Fin material was obtained. In order to obtain the conditions for the obtained fin material after brazing, it was heated at 600°C for 3 minutes in nitrogen gas in the same way as during brazing, and then subjected to a tensile test.
Thermal conductivity was measured. Generally, there is a proportional relationship between the thermal conductivity and electrical conductivity of metals, so here we measured electrical conductivity (at 25°C) instead of thermal conductivity. In addition, in order to evaluate the sacrificial anode effect, the natural electrode potential was measured after immersion in a 3% NaCl aqueous solution adjusted to pH 3 for 8 hours. In addition, the fin material was corrugated, placed on a plate material with 3003 as the core material and 4045 as the skin material (brazing material), and fluoride flux brazing was performed to examine the brazing properties. In addition, a CASS test was conducted on the joint between the fin and the plate for one month based on JIS D0201, the maximum corrosion depth of the plate was measured, and the state of corrosion of the fin was observed. The results are also listed in Table 1. Alloys No. 1 to 5 according to the present invention have a tensile strength of
The material without Cu has a high electrical conductivity of 8.9 kgf/mm ² or more, and the material that contains Cu has a high electrical conductivity of 9.1 kgf/mm ² or more, and both have high electrical conductivity of 46% or more (the conventional material 3003
%) indicates high thermal conductivity. Furthermore, it has good brazing properties, and its natural electrode potential is in the range of -740 to -750V vs SCE, making it electrochemically base. In addition, the maximum corrosion depth of the plate material after the CASS test is small, less than 0.06 mm, and the sacrificial anode effect is excellent. Furthermore, the corrosion of the fins is also normal. On the other hand, comparative alloy No. 6 has a low tensile strength of 7.2 kgf/mm ² due to its low Fe content of 0.10%. No. 7 had a high Fe content of 2.10%, which caused coarse crystallization during casting, making it difficult to roll.
The test was interrupted. No. 8 has a low Si content of 0.09%, so its electrical conductivity is low at 42% IACS, and its thermal conductivity is low. No. 9 has a high Si content of 0.83%, so its electrical conductivity is low at 42% IACS, and its thermal conductivity is low. No. 10 has a low Mn content of 0.04%, so its tensile strength is low at 7.1 kgf/ ^mm2 . No. 11 has a high Mn content of 0.49%, so its electrical conductivity is low at 42% IACS, and its thermal conductivity is low. Because No. 12 had a low Zr content of 0.02%, buckling occurred in the fins during the brazing test. This is because the wax eroded into the fin material. No. 13 has a high Zr content of 0.25%, so its electrical conductivity is low at 42% IACS, and its thermal conductivity is low. No. 14 has a low Zn content of 0.3%, so the natural electrode potential is −700 mV vs SCE, which is electrochemically noble and inferior to the sacrificial anode effect. As a result, the maximum corrosion depth of the plate material increased to 0.41mm. In No. 15, the Zn content is as high as 2.5%, so the self-corrosion resistance of the fin material is poor, and the wear of the fins is significant. Since No. 16 has a high Cu content of 0.45%, the natural electrode potential is -690 mV vs SCE, which makes it electrochemically noble and inferior in sacrificial anode effect. As a result, the maximum corrosion depth of the plate material increased to 0.41mm. No. 17 is the case of the conventionally used 3003 alloy, which has a low electrical conductivity of 39% IACS and low thermal conductivity. Also, the natural electrode potential is −700mV vs SCE
It is electrochemically noble and inferior to the sacrificial anode effect. Therefore, the maximum corrosion depth of the plate material is also 0.42
It grew to mm. No. 18 is a case in which Zn is added to the conventionally used 3003 alloy. Due to the inclusion of Zn, the natural electrode potential becomes -740mV vs SCE, and the sacrificial anode effect is improved, but the electrical conductivity is 37%. IACS and low;
Low thermal conductivity.

[Table] [Effects of the Invention] According to the present invention, a fin material with excellent thermal conductivity, sacrificial anode effect, high temperature buckling resistance, and strength can be provided.
This makes it possible to make the fin material thinner, contributing to the weight and cost reduction of heat exchangers.

Claims (1)

[Claims] 1 Fe: 0.9 to 1.8% (weight %, same hereinafter), Si:
0.2~0.6%, Mn: 0.1~0.35%, Zr: 0.05~0.20
%, Zn: 0.5 to 2.0%, and the remainder consists of Al and inevitable impurities. An aluminum alloy for heat exchanger fin material having excellent post-brazing thermal conductivity and sacrificial anode effect. 2 Fe: 0.9~1.8%, Si: 0.2~0.6%, Mn: 0.1~
0.35%, Zr: 0.05~0.20%, Zn: 0.5~2.0%,
An aluminum alloy for heat exchanger fin material having excellent post-brazing thermal conductivity and sacrificial anode effect, containing Cu: 0.3% or less, with the remainder consisting of Al and unavoidable impurities.