JPH08143998A - Heat exchanger fin material made of aluminum alloy, having high fatigue strength after brazing - Google Patents

Abstract

PURPOSE: To produce a heat exchanger fin material made of Al alloy, having high fatigue strength after brazing. CONSTITUTION: This heat exchanger fin material made of Al alloy has a composition, consisting of, by weight, 0.5-1.5% Si, 0.3-2.5% Mn, one or more kinds among 0.6-1.5% Fe, 0.01-0.3% Cr, 0.01-0.3% Ti, 0.01-0.3% Zr, 0.01-0.3% V, and 0.01-0.7% Cu, and the balance Al with inevitable impurities and further containing, if necessary, one or more kinds among 0.01-1% Mg, 0.1-3% Zn, 0.005-0.1% In, and 0.05-0.2% Sn, and also has a structure where fine primary- crystal Si is concentratedly crystallized in the sheet thickness central part and the precipitation of inter-metallic compound is inhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger fin material made of Al alloy which has a brazing material invasion suppressing effect during brazing, and therefore has a very small decrease in fatigue strength due to brazing material penetration.

[0002]

2. Description of the Related Art Conventionally, Al is generally used for automobiles, for example.
An alloy heat exchanger is used, and this Al alloy heat exchanger is formed from a brazing sheet obtained by clad a brazing material of an Al-Si alloy on one surface of a core material of various Al alloys. It is manufactured by brazing and assembling a tube material and a fin material of various Al alloys via the brazing material. In general, the conventional Al alloy heat exchanger fin material is (a) a semi-continuous casting method of an Al alloy molten metal having a predetermined composition, for example, thickness: 500 mm x width:
It is cast into an ingot having a size of 1000 mm, and this ingot has a dendritic structure in which primary Si is distributed in the matrix.
A homogenization treatment is performed at a temperature of 0 ° C. for 4 to 12 hours to eliminate the dendritic structure and to precipitate an intermetallic compound, so that the primary crystal Si and the precipitated intermetallic compound are present in the matrix. (C) The ingot after the homogenization treatment is subjected to hot rolling to obtain a hot-rolled sheet having a plate thickness of 5 to 6 mm. (D) The above hot-rolled sheet requires cold rolling and According to the above, batch-type intermediate annealing is performed in the atmosphere at a temperature of 300 to 400 ° C. for 1 to 5 hours, and the above-mentioned primary crystal Si is added.
Has a fine structure, and has a structure in which a large amount of finely divided intermetallic compounds are uniformly deposited in the base material. Plate thickness: 70 to 150 μm
It is also known that a cold-rolled thin plate of m is manufactured by the above basic steps (a) to (d).

[0003]

On the other hand, in recent years, the weight and size of the Al alloy heat exchanger have been remarkably reduced, and along with this, the fin material constituting the heat exchanger tends to be thin. However, the above conventional Al alloy heat exchanger fin material is
As described above, since the fine primary Si and the precipitated intermetallic compound have a structure in which a large amount is dispersed and distributed in the matrix, the primary Si and the precipitated intermetallic compound act as nuclei for recrystallization during brazing. However, it has a fine recrystallized structure, but such a fine recrystallized structure has a large number of crystal grain boundaries, and the proportion of the brazing material penetrating from the crystal grain boundaries during brazing increases. Therefore, the fatigue strength of the fin material in which such a brazing material has penetrated through the crystal grain boundaries is remarkably lowered, and therefore, in the above conventional Al alloy heat exchanger fin material, if the thickness is reduced, Since the penetration of the brazing filler metal from the crystal grain boundaries reaches the central portion and the fatigue strength is remarkably lowered, it is not possible to achieve a sufficiently thin wall thickness.

[0004]

Therefore, the present inventors have
From the above-mentioned viewpoint, as a result of research to develop an Al alloy heat exchanger fin material in which the brazing material is less likely to penetrate from the crystal grain boundaries during brazing, (a) the Al alloy is represented by weight% ( Hereinafter,% indicates% by weight), Si: 0.5
~ 1.5%, Mn: 0.3-2.5%, Fe: 0.6-1.5%, Cr: 0.01-
0.3%, Ti: 0.01 to 0.3%, Zr: 0.
01-0.3%, V: 0.01-0.3%, C
u: 0.01 to 0.7%, one or more of them are contained, and Mg: 0.01 to if necessary.
1%, Zn: 0.1 to 3%, In: 0.005
~ 0.1%, Sn: 0.05-0.2%, 1 of
And an alloy containing at least two kinds, and the balance consisting of Al and unavoidable impurities, and (b) a molten metal of the above-specified Al alloy is thin plate continuous casting coil method (twin roll casting method) That is, the 3C method, more specifically, a method of supplying molten Al alloy from a refractory nozzle between a pair of water-cooled rolls is directly cast into a coil having a thickness of 4 to 10 mm, and the coil is quenched as described above. Therefore, the crystallization of the primary crystal Si is suppressed, and the primary crystal Si is also concentrated and crystallized in the central portion of the plate thickness, and the crystallization to other portions has substantially no structure, and (c) Then, the coil, without performing homogenization treatment and hot rolling, cold rolling,
For example, heating rate: 100 ° C / min or more, heating temperature: 45
Continuous annealing is performed under the conditions of 0 to 550 ° C. and holding time: 5 to 100 seconds to obtain a cold rolled coil having a plate thickness of 70 to 150 μm. The heat treatment made of Al alloy in the basic steps (a) to (c) above. When the fin material of the exchanger is manufactured, the resulting fin material has a structure in which fine primary crystal Si is crystallized intensively in the center part of the plate thickness by the above-mentioned 3C method, and precipitation of intermetallic compounds is suppressed (homogenized. Since the treatment, hot rolling, and batch type intermediate annealing are not performed, the precipitation of intermetallic compounds is remarkably suppressed over the entire plate thickness). The primary crystal Si is present in the center of the plate thickness, and the presence of precipitated intermetallic compounds is extremely small, so recrystallization during brazing is suppressed, and as a result, the crystal grains are relatively Hold a relatively large state, and in this state, through the grain boundaries The braze penetration is significantly less,
Further, the research results were obtained that, together with the fact that the fine primary crystal Si existing in the central portion of the plate thickness acts as a barrier for the penetration of the brazing filler metal, the reduction in fatigue strength is significantly suppressed.

The present invention has been made based on the above research results, and Si: 0.5 to 1.5%,
Mn: 0.3-2.5%, Fe: 0.6-
1.5%, Cr: 0.01 to 0.3%, Ti:
0.01-0.3%, Zr: 0.01-0.3%,
V: 0.01-0.3%, Cu: 0.01-0.
1% or 2 or more of 7%, and if necessary, Mg: 0.01 to 1%, Zn:
0.1-3%, In: 0.005-0.1%, Sn:
0.05 to 0.2%, one or more of which is contained, and the rest is composed of Al and unavoidable impurities, and fine primary crystal Si is crystallized intensively at the center of the plate thickness. The heat exchanger fin material made of Al alloy has a structure in which precipitation of intermetallic compounds is suppressed and retains high fatigue strength after brazing.

In the fin material of the present invention, the reason why the composition of the Al alloy constituting the fin material is limited as described above will be explained below. (A) Si As described above, in the fin material of the present invention, since the 3C method involving quenching is adopted in the manufacturing process, the crystallization of primary Si is suppressed and the primary Si Crystallization is mainly concentrated in the central part of the plate thickness. Therefore, Si
The components are solid-solved in the base material to improve the strength, and also exist as primary crystal Si in the center of the plate thickness to avoid becoming the nucleus of recrystallization during brazing, and thus the brazing material from the crystal grain boundary. Although it has the effect of suppressing the decrease in fatigue strength due to the intrusion of Al, if the content is less than 0.5%, the desired effect cannot be obtained, while if the content exceeds 1.5%, the melting point decreases. However, since the local melting occurs at the time of brazing, the content thereof is set to 0.5 to 1.5%, preferably 0.7 to 1.1%.

(B) Mn Similarly, in the fin material of the present invention, the homogenization treatment and hot rolling are not substantially performed in the manufacturing process, and the intermediate annealing during cold rolling is replaced with batch annealing. Since continuous annealing is adopted, Al-Mn compounds and Al-M
The precipitation of intermetallic compounds such as n-Si compounds is significantly suppressed. Therefore, the Mn component acts as a solid solution in the matrix to improve the high temperature strength, but if the content is less than 0.3%, the desired high temperature strength improving effect cannot be obtained, while the content is 2%. If it exceeds 0.5%, intermetallic compounds start to precipitate, which serves as nuclei for recrystallization during brazing, resulting in a fine recrystallized structure that promotes penetration of the brazing material and reduces fatigue strength. From that,
The content is 0.3 to 2.5%, preferably 1.0 to
It was set as 1.8.

(C) Fe, Cr, Ti, Zr, V, and Cu Any of these components promotes crystallization of primary crystal Si to the center of the plate thickness and suppresses precipitation of intermetallic compounds. Has the effect of further improving the strength, but its content is Fe:
If less than 0.6%, and Cr, Ti, Zr, V, and Cu components are all less than 0.01%, the desired effect cannot be obtained, while the content of Fe: 1.5. %,
Cr, Ti, Zr, and V are all 0.3%, Cu
If the content of Fe exceeds 0.7%, the cold rolling property will decrease, so the content of Fe:
0.6-1.5%, Cr: 0.01-0.3%, Ti:
0.01-0.3%, Zr: 0.01-0.3%, V:
0.01-0.3%, and Cu: 0.01-0.7
%, More preferably Fe: 0.8 to 1.2%, Cr:
0.05 to 0.15%, Ti: 0.05 to 0.15%,
Zr: 0.05 to 0.15%, V: 0.05 to 0.15
%, And Cu: 0.05 to 0.5%.

(D) Mg Since the Mg component has the action of forming a solid solution in the matrix to further improve the strength, it is contained if necessary, but if the content is less than 0.01%, the desired strength is obtained. When the content exceeds 1%, the melting point is lowered,
Since local melting will occur during brazing, its content is 0.01 to 1%, preferably 0.05 to 0.
It was set at 3%.

(E) Zn, In, and Sn Any of these components has a function of forming a solid solution in the base material and making it electrochemically base, thereby ensuring the sacrificial anode effect on the pipe material. Therefore, the content of Zn is less than 0.1%.
If the In content is less than 0.005% and the Sn content is less than 0.05%, the potential drop is insufficient, and the desired sacrificial anode effect cannot be imparted.
%, In: 0.1%, and Sn: 0.2%, no further improvement effect appears in the above action, so the contents are Zn: 0.1-3% and In :, respectively. 0.0
05-0.1%, Sn: 0.05-0.2%, more preferably Zn: 1-2%, In: 0.01-0.
05% and Sn: 0.05 to 0.15%.

[0011]

EXAMPLES Next, the Al alloy heat exchanger fin material of the present invention will be specifically described by way of examples. Al alloy melts A to X having compositions shown in Tables 1 and 2, respectively, were prepared by an ordinary melting method, and these Al alloy melts were subjected to a 3C method (twin roll casting method) to obtain a roll diameter: 600 m
m, distance between rolls: 6 mm, melt temperature: 725 ° C., casting speed: 800 mm / min, thickness: 6 mm, directly cast into a coil, and then this coil is not subjected to homogenization treatment and hot rolling. When cold rolling was performed under normal conditions and the plate thickness reached 1.8 mm, the heating rate was 105 ° C / min.
, Temperature: 465 ° C., holding time: 20 seconds, cooling rate: 2
When the first intermediate continuous annealing was performed under the condition of 100 ° C / min, and further cold rolling was performed to reach a plate thickness of 0.2 mm, the heating rate: 3200 ° C / min, temperature: 540 ° C,
Holding time: 90 seconds, cooling rate: 450 ° C./min, the second intermediate continuous annealing was performed, and thereafter, the cold rolling was continued to a plate thickness of 50 μm.
24 were produced respectively.

For comparison purposes, Al alloy melts A to X having the same compositions shown in Tables 1 and 2 were used, and these were semi-continuously cast to have a thickness of 500 mm and a width of 1000 mm. Cast into an ingot, and in this ingot, in the atmosphere,
After performing homogenization treatment at a predetermined temperature within a range of 500 to 600 ° C. for 8 hours, hot rolling is performed under normal conditions to obtain a hot rolled sheet having a plate thickness of 6 mm. To
Cold-rolled under normal conditions, when the plate thickness becomes 1.8 mm and 0.2 mm, respectively, in the atmosphere, 300-40
The conventional fin materials 1 to 24 were manufactured by performing batch type intermediate annealing under the condition of maintaining at a predetermined temperature within a range of 0 ° C. for 3 hours and performing cold rolling to a plate thickness of 50 μm.

The fin materials 1 to 24 of the present invention obtained as a result
When observing the cross section in the thickness direction of the conventional fin materials 1 to 24 with a metallographic microscope, in the former, fine primary crystal Si was intensively crystallized in the center part of the plate thickness and almost no precipitation of intermetallic compounds was observed. However, the latter showed a structure in which a large amount of fine primary crystal Si and precipitated intermetallic compounds were dispersed and distributed over the entire surface.

Next, for the purpose of evaluating the fatigue strength after brazing, the above-mentioned various fin materials were cut into a size of width: 25 mm × length: 200 mm, and JIS Z3263BA4045 brazing material having 20 μm was superposed on both sides. And place it horizontally, and in this state in a nitrogen atmosphere, temperature: 61
After heating at 0 ° C for 5 minutes under the conditions equivalent to the brazing conditions, the parallel part width: 10 mm x parallel part length: 50
A test piece of mm was cut out, and a fatigue test was repeated in which stress: tension of 10 kgf / mm ² and no load were repeated at 30 Hz, and the number of repetitions until the test piece was broken was measured. The measurement results are shown in Tables 3 and 4. Also, in Tables 3 and 4,
The fatigue test results when the above brazing heat treatment was not performed are shown as "before brazing heat treatment".

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

From the results shown in Tables 3 and 4, all of the fin materials 1 to 24 of the present invention suppress recrystallization during brazing, and the crystal grains maintain a relatively coarse state. ,
Since the penetration of the brazing filler metal from the crystal grain boundaries is extremely small, the deterioration of the fatigue strength after brazing is extremely small, whereas the conventional fin materials 1 to 24 all have fine primary crystal Si and precipitated metal. The compound has a structure in which it is dispersed and distributed in a large amount in the matrix, and this primary crystal Si and precipitated intermetallic compound serve as nuclei for recrystallization during brazing to form a fine structure,
This result leads to an increase in the grain boundaries, which promotes the penetration of the brazing material from the grain boundaries, so that it is clear that the fatigue strength after brazing is significantly reduced. As described above, since the Al alloy heat exchanger fin material of the present invention is remarkably suppressed in the decrease in fatigue strength after brazing, it is possible to reduce the thickness of the heat exchanger fin material and reduce the weight of the heat exchanger. This greatly contributes to miniaturization.

Claims (4)

[Claims] 1. By weight%, Si: 0.5 to 1.5%, Mn: 0.3 to 2.5
%, Further, Fe: 0.6 to 1.5%, Cr: 0.01 to 0.
3%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.
3%, V: 0.01 to 0.3%, Cu: 0.01 to 0.
7%, one or more of them, and the balance consisting of Al and inevitable impurities, and fine primary crystal S
A heat exchanger fin material made of an Al alloy which retains high fatigue strength after brazing, characterized in that i has a structure in which precipitation of intermetallic compounds is suppressed in the central portion of the plate thickness. 2. By weight%, Si: 0.5-1.5%, Mn: 0.3-2.5
%, Mg: 0.01 to 1%, Fe: 0.6 to 1.5%, Cr: 0.01 to 0.
3%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.
3%, V: 0.01 to 0.3%, Cu: 0.01 to 0.
7%, one or more of them, and the balance consisting of Al and inevitable impurities, and fine primary crystal S
A heat exchanger fin material made of an Al alloy which retains high fatigue strength after brazing, characterized in that i has a structure in which precipitation of intermetallic compounds is suppressed in the central portion of the plate thickness. 3. By weight%, Si: 0.5-1.5%, Mn: 0.3-2.5
%, Fe: 0.6-1.5%, Cr: 0.01-0.
3%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.
3%, V: 0.01 to 0.3%, Cu: 0.01 to 0.
1% or 2 or more of 7%, and Zn: 0.1-3%, In: 0.005-
0.1%, Sn: 0.05 to 0.2%, one or more of them are contained, and the balance is composed of Al and unavoidable impurities, and fine primary crystal Si is the plate thickness center. Which has high fatigue strength after brazing, characterized by having a structure in which the precipitation of intermetallic compounds is suppressed in a concentrated area.
l Alloy heat exchanger fin material. 4. By weight%, Si: 0.5-1.5%, Mn: 0.3-2.5
%, Mg: 0.01-1%, Fe: 0.6-1.5%, Cr: 0.01-0.
3%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.
3%, V: 0.01 to 0.3%, Cu: 0.01 to 0.
1% or 2 or more of 7%, and Zn: 0.1-3%, In: 0.005-
0.1%, Sn: 0.05 to 0.2%, one or more of them are contained, and the balance is composed of Al and unavoidable impurities, and fine primary crystal Si is the plate thickness center. Which has high fatigue strength after brazing, characterized by having a structure in which the precipitation of intermetallic compounds is suppressed in a concentrated area.
l Alloy heat exchanger fin material.