JPH059673A - Manufacture of aluminum alloy fin material rxcellent in heat conductivity - Google Patents

Abstract

PURPOSE:To improve the brazability, high temp. buckling resistance and heat conductivity of a fin material for a heat exchanger. CONSTITUTION:As an aluminum alloy for a fin material, the one constituted of, by weight, 0.03 to 0.3% Zr, 0.03 to 0.3% Si as well as <=0.5% Zr and Si, 0.03 to 1.0% Fe, >=99.5% total content of Al and the above Fe and the balance Al with inevitable impurities is prepd. At the time of manufacturing a fin material for a heat exchanger by subjecting the above alloy to hot rolling, subsequent cold rolling and annealing, in the hot rolling, rolling from 120mm to a finish sheet thickness is executed by >=8 passes, and process annealing is executed at 320 to 450 deg.C at 20 to 85% final cold draft to manufacture an aluminum alloy fin material particularly excellent in heat conductivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy fin material having excellent heat conductivity, and is particularly used as a fin for radiators, heaters, condensers, etc. of heat exchangers for automobiles manufactured by brazing. It is something.

[0002]

2. Description of the Related Art Most heat exchangers for automobiles use Al and Al alloys and are manufactured by a brazing method. Brazing is usually A
An l-Si based brazing material is used, so brazing is performed at 60
It is performed at a high temperature of about 0 ° C. A heat exchanger such as a radiator has a plurality of flat tubes (1) as shown in FIG. 1, for example.
Thin fins (2) processed into a corrugated shape are integrally formed between the flat tubes (1), and both ends of the flat tube (1) are opened in a space formed by the header (3) and the tank (4). A high temperature refrigerant is sent from the space on the side of one tank through the inside of the flat tube (1) to the space on the side of the other tank (4), and heat is exchanged between the tubes (1) and fins (2) to become a low temperature refrigerant. To recycle.

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 thermal conductivity becomes insufficient as the material becomes thinner. Therefore, improvement of the thermal conductivity of the fin material has been studied, but sufficient results have not been obtained. For fin materials with improved thermal conductivity, this is 600 ° C as the final process of the product.
This is because the brazing material diffuses into the fin material or the fins are crushed during brazing that is heated to the vicinity.

[0004]

In view of this, the present invention has been made for a method of manufacturing a fin material which does not cause diffusion of the brazing during brazing, has excellent high temperature buckling property, and has high thermal conductivity. is there. That is, the present invention uses Zr: 0.03 to 0.3 wt.
%, Si: 0.03 to 0.3 wt%, the sum of Zr and Si contents is 0.5 wt% or less, Fe: 0.03 to 1.0 wt%, the sum of Al and Fe contents is 99.5 wt% or more, and the balance is unavoidable. In order to manufacture a fin material for a heat exchanger by performing hot rolling, cold rolling and annealing of an aluminum alloy ingot made of mechanical impurities, rolling from a sheet thickness of 120 mm to a hot rolling finished sheet thickness in hot rolling. At a plate thickness such that the final cold rolling rate is 20 to 85%, and the temperature is 320
The present invention provides a method for producing an aluminum alloy fin material having excellent thermal conductivity, which comprises performing intermediate annealing at a temperature of up to 450 ° C.

First, the composition of the aluminum alloy ingot used for producing the fin material of the present invention will be described. The aluminum alloy used in the present invention is Zr: 0.03 to 0.3 wt%,
Si: 0.03 to 0.3 wt% and the sum of the contents of Zr and Si is
It is 0.5 wt% or less, Fe: 0.03 to 1.0 wt%, the sum of the contents of Al and Fe is 99.5 wt% or more, and the balance consists of unavoidable impurities.

Zr is present as extremely fine dispersed particles of Zr-based intermetallic compound in the alloy structure of the formed fin material, and coarse recrystallized particles are generated in the fin material during brazing heating at 500 ° C. or less. This prevents the fins from softening. That is, the dispersed particles stabilize and refine the subgrains and pin dislocations. By such an action, coarse recrystallized grains elongated in the rolling direction are generated during the brazing heating, and the brazing diffusion and the high temperature buckling property deterioration during the brazing heating are prevented. If Zr is less than 0.03 wt%, the above action is insufficient. If Zr is added in excess of 0.30 wt%, cracking occurs during casting of the alloy, making it impossible to produce a fin material. Therefore, the Zr content is set to 0.03 to 0.3 wt%.

Si has the function of promoting the precipitation of Zr compounds and increasing the strength of the fin material. However, the amount is 0.
If it is less than 03% by weight, its action is insufficient, and if it exceeds 0.3% by weight, solid solution Si is present in the fin and the thermal conductivity is lowered. Therefore, if Si is added, 0.3
wt% or less. Zr and Si are added as described above, but if the sum of their contents exceeds 0.5 wt%, the thermal conductivity decreases. Therefore, the total amount of Zr and Si added should be 0.5 wt% or less. Further, in the Al alloy according to the present invention, the sum of the contents of Al and Fe is 99.5 wt% or more. This is because if the sum is less than 99.5 wt%, the thermal conductivity will decrease.

Fe has the effect of increasing the strength of the fin material without impairing the thermal conductivity. This is because most of Fe exists in the precipitated state of Fe-based intermetallic compound. However, if the amount is less than 0.03 wt%, the effect is not sufficient,
If it exceeds 1.0 wt%, the formability will deteriorate and corrugation will not be possible. Therefore, the Fe content is 0.03 to 1.0 wt.
Defined as%.

In the Al alloy according to the present invention, Cu, Mg, Zn, Mn, Cr, Ti, B, etc., which usually come from Al ingot or are added in a trace amount for a certain purpose, are each 0.15.
If it is less than wt%, the object of the present invention is not impaired. Therefore, these elements are treated as inevitable impurities in the present invention.

Next, a method for manufacturing the Al alloy fin material of the present invention will be described. The production process of the present invention is a method for finely and densely distributing a Zr-based compound in forming a fin material from the above aluminum alloy, and hot rolling, cold rolling and annealing the ingot, When manufacturing the fin material for heat exchanger, in the hot rolling, the intermediate plate thickness 120m
It is characterized in that rolling from m to hot-rolled sheet thickness is performed with a number of passes of 8 or more, and the final cold rolling rate is 20 to 85%, and intermediate annealing is performed at a temperature of 320 to 450 ° C. And That is, the present method for producing a fin material is characterized in that the precipitation phase particles of the Zr-based intermetallic compound are finely and densely distributed to prevent the progress of recrystallization during brazing heating and prevent softening.

The alloy ingot used in the present invention may be manufactured by a usual DC casting method. The ingot produced by the DC casting method is sufficiently dissolved by using the alloy element of the present invention as a solute element. The homogenization treatment may be performed while also performing heating for hot rolling, and the temperature is usually about 450 ° C to 600 ° C.

The hot rolling is performed by an intermediate plate thickness of 120 m in the hot rolling.
Rolling from m to the end thickness of hot rolling is performed with 8 or more passes. That is, during the hot rolling process, Zr system and F
Precipitation of the e-system intermetallic compound occurs, but most of the precipitation occurs dynamically during the processing of the hot rolling pass, and the present invention is based on this that the fine precipitation phase described above occurs during hot rolling. I did so. In the present invention, the rolling pass of hot rolling from 120 mm to the thickness of the hot-rolled sheet is defined as 8 passes or more. In addition, 120 mm referred to here is an intermediate plate thickness of the hot rolled plate thickness and is a starting plate thickness determined to be 8 passes or more. Conventionally, hot rolling from 120 mm to the plate thickness after rolling is conventionally performed in 5 passes or 6 passes, but if it is less than 8 passes, the number of rolling passes is small and the amount of precipitation is small, and the precipitation phase is up to 0.02 μm. It does not grow and the effect of improving strength is insufficient. It is recommended that the temperature at 120 mm or less and the plate thickness after rolling is normally 350 to 440 ° C. This is because the dynamic precipitation of Zr-based and Fe-based intermetallic compounds easily progresses during this period. The end plate thickness of the hot rolling may be a plate thickness capable of implementing the cold rolling conditions of the present invention, and is not particularly limited,
Usually, it is about 2 mm to 10 mm. The hot rolling may be performed by two types of rolling mills different from hot rough rolling and hot finish rolling, or may be performed by one rolling mill.

After hot rolling, cold rolling / annealing is performed to obtain a predetermined product sheet thickness (for example, 0.06 mm), and the final cold rolling rate is set to 20 to 85%. When the final cold rolling rate is less than 20% or more than 80%, the brazing material diffuses into the core material during heating for brazing, and the high temperature buckling resistance decreases. Therefore, although the final cold rolling rate is set to 20 to 85%, the annealing before the final cold rolling is performed in a batch system and the annealing temperature is 320.
~ 450 ° C. Since annealing is performed in the presence of dislocations, diffusion progresses faster than in homogenization treatment. Therefore, the fine particles are precipitated during annealing, but
If it is lower than 20 ° C, it is difficult to precipitate, and if it exceeds 450 ° C, coarsening of particles occurs. The holding period of annealing is normally 0.
It takes about 5 to 6 hours. In addition, as long as the condition of the final cold rolling rate is satisfied, the annealing may be performed twice or more during the cold rolling.

[0014]

The present invention will be described in more detail with reference to the following examples.

Aluminum alloy fin materials (sheet thickness 60 μm) having the compositions shown in Table 1 were produced by the manufacturing methods shown in Tables 2 and 3. For the fin material, homogenization treatment, hot treatment, annealing conditions, etc. were changed. The hot rolling up to a plate thickness of 120 mm is performed under normal hot rolling conditions, and the number of rolling passes from the plate thickness of 120 mm to the hot rolling end plate thickness is as shown in Tables 2 and 3,
The rolling temperature was 440 ° C to 350 ° C. The obtained fin material was combined with the following tube material and header material, and FIG.
The radiator shown in was assembled. JIS tube material
A 3003 alloy as the core material, one side (inside the tube)
JIS A 7072 alloy on the other side (on the outside of the tube)
A coil-shaped plate material having a plate thickness of 0.4 mm in which JIS A 4343 alloy was clad at a ratio of 10% was manufactured by a usual method. The coiled plate material was slitted into a strip material having a size of 35.0 mm according to the size of the electric resistance welded pipe. This strip material was processed into an electric resistance welded pipe having a width of 16.0 mm and a thickness of 2.2 mm using a resistance welded pipe manufacturing apparatus. Further, a coil-shaped plate material having the same configuration and a plate thickness of 1.2 mm was produced and slitted to a width of 60 mm to obtain a strip material for a header.

The assembled radiator was coated with a 10% concentration solution of a fluoride-based flux, and the 60% in N ₂ gas was applied.
Brazing was performed by heating under the condition of 0 ° C. × 5 min. The degree of collapse of the resulting radiator fins was visually determined, and the degree of wax diffusion into the fins at the joint between the fins and the tube was evaluated by microstructure observation. At the same time, only the fin material was heated, and the conductivity of the fin material after brazing and heating was measured. The results are shown in Table 4. Here, the conductivity is an index of thermal conductivity, and if the conductivity of the fin is improved by 10% in IACS, the heat exchange rate of the heat exchanger is 2%.
Improve.

As is clear from the results shown in Table 4, the degree of crushing of the fins after brazing and the diffusion of the brazing material use the materials (No. 1, 2, 3, 5, 6, 8, 10) according to the method of the present invention. The radiator is good and is equivalent to the standard product using the conventional brazing sheet (No.12), but the conductivity after brazing is significantly better than the conventional example (No.12). I understand. Further, the fin material according to the method of the present invention,
Excellent in crushing of fins, diffusion of wax, and conductivity, but fin materials according to comparative examples (Nos. 4, 7, 9,
It can be seen that 11) is inferior in any of the characteristics.

[0018]

INDUSTRIAL APPLICABILITY As described above, the fin material according to the method of the present invention is excellent in any of the properties such as brazing property, high temperature buckling resistance, and thermal conductivity, and has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing a radiator with a part cut away.

[Explanation of symbols]

 1 Flat tube 2 Thin fin 3 Header 4 Tank

[Table 1]

[Table 2]

[Table 3]

[Table 4]

Claims (1)

[Claims] [Claim 1] Zr: 0.03 to 0.3 wt%, Si: 0.03 to 0.
3 wt% and the sum of Zr and Si contents is 0.5 wt% or less, F
e: 0.03 to 1.0 wt%, the sum of the contents of Al and Fe is 9
Hot-rolling aluminum alloy ingots with 9.5 wt% or more, the balance of which is unavoidable impurities, and then cold-rolling and annealing to produce fin materials for heat exchangers. The rolling up to the plate thickness after hot rolling is performed with 8 or more passes, and the final cold rolling rate is 20 to
A method for producing an aluminum alloy fin material having excellent thermal conductivity, which comprises performing intermediate annealing at a temperature of 320 to 450 ° C. at a plate thickness of 85%.