JPH04173934A - Aluminum alloy fin material for vacuum brazing - Google Patents

Abstract

PURPOSE:To produce an Al alloy fin material for vacuum brazing having superior brazability, buckling resistance and strength by incorporating specified percentages of Si, Fe, Cu, Mn, Mg, Zn and Ca into Al. CONSTITUTION:An Al alloy fin material consisting of, by weight, 0.7-1.0% Si, 0.05-0.4% Fe, 0.1-0.2% Cu, 0.05-1.0% Mn, 0.05-1.0% Mg, 0.5-2.0% Zn, 0.01-0.5% Ca and the balance Al with inevitable impurities or further contg. <=0.25% Cr and/or <=0.25% Zr is prepd. This Al alloy fin material is fit for vacuum brazing and effective as the material of sacrificial fins and the evaporation of Zn is inhibited at the time of brazing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an aluminum alloy for hair fins used in heat exchangers manufactured by brazing properties, such as evaluators, heaters, condensers, evaporators, etc. The present invention provides a fin material for a heat exchanger that has excellent brazing properties, high and room temperature strength, and sacrificial effect in vacuum brazing.

[Conventional technology and its problems]

In general, aluminum alloy heat exchangers are widely used in radiators, heaters, air conditioner evaporators, condensers, etc. shown in Figure 1. These heat exchangers are basically a combination of tubes (2) through which a temperature medium such as water or fluorocarbon flows and fins (1).
Usually, they are joined by brazing methods such as FB (using chloride flux), NB (using fluoride flux), and VB method (brazing in vacuum) without using flux.

Fin materials for such heat exchangers include those used as so-called plating sheets clad with a brazing material and bare materials not covered with a brazing material. This pair fin material is JIS A 3003 (A j! -0,
15wt%Cu-1wt%Mn) or An-1wt%Mn
-1 wt% Zn alloy is used. (Hereinafter, wt% is simply abbreviated as %) These fin materials are usually corrugated and used, and are exposed to high temperatures of 600°C during brazing. As a result, the fins may buckle or have poor brazing properties, resulting in a loss of function as a heat exchanger. Furthermore, when brazing is performed by the VB method, which involves heating in a vacuum, problems often arise, such as the fact that Zn tends to evaporate and the effect as a sacrificial fin cannot be exerted. Particularly recently, in order to reduce the weight and cost of heat exchangers, it has been desired to make the fins even thinner. There has been a strong demand for materials that do not easily evaporate.

[Problem to be solved by the invention]

In view of this, as a result of various studies, the present invention has been developed as a bare material for fins, which has excellent brazing properties, buckling resistance at high temperatures, and strength after brazing, and is also effective as a sacrificial fin by suppressing Zn evaporation. We have developed an aluminum alloy suitable for certain types of vacuum brazing.

[Means for Solving the Problems] One of the alloys of the present invention contains 0.7 to 1.0 wt% Si, F
e0.05~0.4wt%, Cu0.1~0
．． 2wt%, Mn1. O ~ 1.8 wt%, Mg 0
．． 05-1.0 wt%, Zn 0.5-2.0-t%,
This is an aluminum alloy fin material for vacuum brazing that contains Ca 0.01~0.5wt% and the balance is Al and inevitable impurities.The other one is Si0.7~1.0w.
t%, Fe 0.05~0.4wt%, Cu 0.1~
0.2-t%, Mn 1.0-1.8wt%, Mg 0
．． 05-1.0iit%, Zn 0.5-2.0wt%
, contains 0.01 to 0.5 wt% of Ca, and further contains Cr 0
．． This is an aluminum alloy fin material for vacuum brazing, which contains Zr of 0.25 wt% or less, Zr of 0.25 wt% or less, and the remainder Affi and unavoidable impurities.

That is, the present invention utilizes the above-mentioned C, which has been conventionally used as bare material.
u, Mn, Si to aluminum alloy containing XZn,
By adding Mg, Fe, Ca, and further Cr and Zr, an aluminum alloy for fins is obtained which has excellent brazing properties, buckling resistance, and strength at room temperature, and further suppresses evaporation of Zn.

[Effect]

The effects of each component of the alloy of the present invention and the reason for limiting the amount thereof will be explained below.

Mn improves the strength of the alloy. Its content is 1.0
The reason why it is limited to 1.8% is that below the lower limit, the effect is small, and above the upper limit, giant crystallized substances tend to form and the plastic workability is poor.

Cu functions to improve strength. Its content is 0.1
The reason why Zn is limited to ~0.2% is that if it is less than the lower limit, the effect will be insufficient, and if it exceeds the upper limit, the sacrificial effect of Zn will be reduced.

Mg works to improve the strength alone or in coexistence with Si. However, its content is 0.05~1.0%
The reason for this limitation is that below the lower limit, the effect is insufficient, and above the upper limit, the brazing properties deteriorate.

Fe improves strength and coarsens recrystallized grains to improve buckling resistance. Its content is 0.05~044
% because if it is less than the lower limit, the strength will not be improved enough, and if it exceeds the upper limit, the recrystallized grains will become finer and the buckling resistance will decrease.

Si acts to improve the strength alone or in coexistence with Mg. The content is limited to 0.7 to 1.0% because below the lower limit, the effect is small, and above the upper limit, the solidus temperature decreases and the buckling resistance decreases.

Zn functions to give the fin material a sacrificial anode effect. The reason why the content is limited to 0.5 to 2.0% is that below the lower limit, the effect is insufficient, and when exceeding the upper limit, the effect not only becomes saturated, but also self-corrosion resistance deteriorates. be.

Ca functions to suppress evaporation of Zn during brazing heat. However, the reason why the content was limited to 0.01 to 0.5% is that below the lower limit, the effect is insufficient, and beyond the upper limit, the effect not only becomes saturated, but also self-corrosion resistance decreases. It is.

Cr and Zr function to improve room temperature strength. The reason why the content is set to one or more of the following within the range of Cr 0.25% or less and Zr 0.25% or less is that if the upper limit is exceeded, large crystallized substances are likely to occur and undesirable workability is prevented. This is because it is inferior.

In addition to the above-mentioned additive elements, the alloy of the present invention may have Ti or B added in an amount of 0.25% or less for grain refinement during casting.

Note that the use of the alloy of the present invention is not limited to the pair fin material, but can also be used as any other member such as a tube or pipe material through which a heat medium flows, or a header material.

〔Example〕

An embodiment of the present invention will be described below.

Example 1 After homogenizing an alloy having the composition shown in Table 1, the alloy had a composition of 300 to 55
It was hot rolled at 0°C to form a plate material with a thickness of 3.5m+.

This was rolled to 0.14 m by cold rolling. Then, intermediate annealing was performed at 300 to 450°C, and cold rolling was performed to produce a heat-treated H-14 plate material with a thickness of 0.1 mm.

60° in vacuum for the plate material obtained in this way.
After heating to C, it was cooled at 100° (:/sin). Thereafter, a JISS No. test piece was prepared, and 30 days after heating, a tensile test was conducted to measure the tensile strength.

In addition, the evaluation of buckling resistance during brazing is as follows: Radius 22m, length 60
Cut out a test piece of the wall, and heat it to 600°C with one end sticking out for 50 cm and the other end fixed.The amount of droop of the front end at that time was measured, and the buckling resistance at high temperatures was determined by the size. evaluated. In addition, in this evaluation method, if the amount of droop is 15 or less, it means that there will be no problem when the actual radiator is brazed! Approved.

Regarding the evaporation of Zn during vacuum brazing, the same heating as above was performed and the amount of residual Zn was measured by chemical analysis. Note that if the amount of residual Zn is 0.3% or more, performance as a sacrificial fin can be obtained. Furthermore, if Cu is present in the alloy in an amount exceeding 0.2%, the potential becomes base and the effect as a sacrificial fin cannot be obtained, and if Zn is present in an amount exceeding 2.0%, the self-corrosion resistance will be poor. ing.

Furthermore, the brazing property was evaluated by corrugating the plate material and using a simulated core test piece shown in FIG. That is, after degreasing the test piece, it was heated at 600°C in a vacuum of 5 x 10-' Torr.
Brazing was performed by heating. The brazeability was evaluated based on the condition of the fillet, and a good one was evaluated as Q, and a poor one was evaluated as ×. The evaluation results are summarized in Table 2.

As is clear from Tables 1 and 2, the alloy of the present invention has higher strength than the conventional alloy (and has good brazing properties, and does not cause buckling of the fins during brazing. Furthermore, the corrosion resistance was also good.

On the other hand, in comparison alloy No. 8, which is outside the composition range of the present alloy, the fins buckled during brazing, and in comparison alloy No. 9, the fins buckled during brazing, and the residual amount of Zn was low, resulting in poor corrosion resistance. .

Comparative alloy No. 7 had a small amount of Zn remaining after brazing and had poor corrosion resistance. Comparative alloy No.10 has 0 Cu in the alloy.
．． Since it contained 3%, the potential did not become base and the corrosion resistance was poor. The comparative alloy Ntl12 contained 2.5% Zn, and therefore had poor self-corrosion resistance.

Comparative alloy Sou 13 contained 1.25% Mg, so its brazing properties were poor. Furthermore, comparative alloys NCLII, N
[114 and No. 15 contain large amounts of Mn, Cr, and Zr, so the plastic workability was poor and it was not possible to process them into corrugated fins.In this way, comparative alloys that are outside the composition range of the present invention alloy have various It was not possible to satisfy all the performance requirements.

Example 2 Using the corrugated fin of the invention alloy fin 2 shown in Table 2, J
IS A 3003 alloy core material and JIS A4 on one side
A header material with a thickness of 1.6 mm consisting of a plating sheet clad with 343 brazing material and a JIS A 7072 sacrificial material at a ratio of 10% on the other side, and a tube material with a thickness of 0.4 mm were combined, as shown in Figure 1. I assembled the radiator shown. Furthermore, for comparison, a radiator was assembled in the same manner as above using corrugated fins made of conventional alloy Nα17. After degreasing the assembly with Freon, it was heated to 600°C in a vacuum of 5XIO-'Torr to perform brazing.

As a result of observing the radiator after brazing, there was no buckling of the fins in both cases and the brazing properties were good.

When the radiator after brazing was subjected to a pressure test with a resin tank attached, the tensile strength was 11.5 kg.
In a radiator using conventional alloy grade 17 corrugated fins, the tube was deformed and the fins were crushed at 5 kgf/c+4. On the other hand, the tensile strength is 17.2 kgf/
The radiator using corrugated fins of the present invention alloy size 2 did not deform even at 7 kgf/cnN.

Furthermore, the radiator after brazing was subjected to a CASS test for 720 hours to confirm the sacrificial effect of the fins. As a result, in a conventional radiator using fins with a remaining Zn content of 0.2%, the tubes could not be protected from corrosion, and through-pitting corrosion occurred in the tubes. On the other hand, in the case of a radiator using fins made of the alloy of the present invention, the remaining amount of Zn is 0.
．． 6%, pitting depth was shallow at 0.12 mm, and corrosion resistance was good.

[Effects of the Invention] As described above, the alloy of the present invention does not reduce formability as a heat exchanger fin material, has excellent buckling resistance, brazeability, and strength, and has Z
This has remarkable industrial effects such as suppressing the evaporation of n and making it possible to reduce the weight of the heat exchanger (thinner fins).

[Brief explanation of drawings]

FIG. 1 is a perspective view of a radiator, and FIG. 2 is a perspective view of a simulated core test piece. 1...Fin, 2...Tube, 3...
Header, 4...Resin tank, 5...Plate material. Patent applicant: Furukawa Aluminum Industry Co., Ltd. Figure 1 Figure 2

Claims (2)

[Claims] (1) Si0.7-1.0wt%, Fe0.05-0
．． 4wt%, Cu0.1-0.2wt%, Mn1.0-
1.8wt%, Mg0.05-1.0wt%, Zn0.
An aluminum alloy fin material for vacuum brazing, containing 5 to 2.0 wt% and 0.01 to 0.5 wt% of Ca, with the balance being Al and inevitable impurities. (2) Si0.7-1.0wt%, Fe0.05-0
．． 4wt%, Cu0.1-0.2wt%, Mn1.0-
1.8wt%, Mg0.05-1.0wt%, Zn0.
5 to 2.0 wt%, Ca0.01 to 0.5 wt%, and further contains any one or two types within the range of Cr0.25 wt% or less and Zr0.25 wt% or less, the balance being Al and unavoidable impurities. Aluminum alloy fin material for vacuum brazing consisting of.