JPH059679A - Manufacture of thin aluminum alloy sheet for drawless fin excellent in ironability - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a thin aluminum alloy sheet for a drawless fin excellent in ironability and used as a fin for a room air conditioner by executing bulging, ironing and stretch-flanging. CONSTITUTION:This is a method for manufacturing a thin Al alloy sheet in which the number of intermetallic compounds with >=0.1mum diameter in the metallic structure before the forming is regulated to 5 pieces/mum<3> and specific resistance value is regulated to <=33.5nOMEGAm and excellent in ironability in which an alloy ingot contg., by weight, 0.01 to 0.15% Si, 0.10 to 0.40% Fe, 0.10 to 0.40% Mn and the balance Al with inevitable impurities is subjected to homogenizing treatment and hot rolling, and the obtd. hot rolled sheet is subjected to cold rolling at 50 to 90% draft, is subjected to precipitation treatment at 200 to 350 deg.C for >=2hr and is thereafter subjected to cold rolling at >=70% draft, and the obtd. thin sheet is subjected to temper annealing at 250 to 300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy thin plate for a drawless fin, which is excellent in ironing property and is used as a fin for a room air conditioner by subjecting it to overhanging, ironing and stretch-flange processing.

[0002]

2. Description of the Related Art Generally, an aluminum alloy fin for an air conditioner heat exchanger has a collar portion (for inserting a heat exchange tube in a plate portion (1) as shown in FIGS. 2) is formed, and is classified into a flat type (a), a louver type (b), a slit type (c), and a corrugated type (d) according to the shape of the plate portion. The molding method of the collar portion is classified into a draw method and a drawless method. Drawing method is shown in Figure 2.
As shown in (a) to (f), the process of overhanging (a), drawing (b) to (d), punching, burring (e), and flare (f) is the main process. Therefore, the fin material is required to have excellent elongation and is usually used for manufacturing a thick fin having a thickness of 0.13 mm or more. In addition, the drawless method is shown in Fig. 3 (a)-
As shown in (d), the process consists of punching, hole expansion (a), burring (b), ironing (c), and refraining (d), and ironing is the main process. Therefore, it is required that the fin material has excellent ironing workability.
It is used for manufacturing thin fins of less than mm.

Recently, it has been desired to reduce the weight of the heat exchanger from the viewpoint of energy saving and resource saving, and the aluminum alloy fins have been made thinner and lighter, and the drawless method has been widely used for manufacturing the fins. .. Molding defects that occur during molding of the drawless fins include ironing cracks that occur in the ironing process and flower cracks that occur in the flare process. In particular, ironing cracks are more likely to occur as the ironing rate becomes higher, and there is a problem that a product dimension above a specific height cannot be obtained. Further, all of these cracks impair the adhesion between the collar portion and the heat exchange tube, reduce the heat exchange characteristics, and impair the appearance of the molding fins.
Since the value as a product may be reduced, it is strongly desired to reduce these molding defects. In addition, since the corrugated type requires bulging, it requires high elongation at the same time as strength.However, the aluminum alloy sheet manufactured by the conventional ordinary manufacturing method does not provide sufficient strength and elongation, and There is a drawback that a product with good properties cannot be obtained.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, it has been found that if the fin material is microstructure-controlled by a precipitation treatment after hot rolling, the formability is improved. I found it. When a conventional hard aluminum material for drawless fins is used, in the ironing process during the drawless fin forming process, the dislocation structure formed by pre-processing recovers due to processing heat during ironing,
It has been found that when the ironing rate is large, that is, when the amount of heat generated by working is large, recovery subgrains are nonuniformly generated, and as a result, the fracture resistance of the material falls below the ironing force, and as a result, ironing cracks occur. Therefore, based on this knowledge, it is difficult to recover during ironing, that is, as a result of diligent study on a material having high high-temperature strength, as a result, cold rolling was performed on the obtained hot-rolled sheet at a reduction rate of 50 to 90%, After performing a precipitation treatment of maintaining the plate thickness at 200 to 350 ° C. for 2 hours or more, cold rolling is performed at a reduction rate of 70% or more, and the obtained thin plate is temper-annealed at a temperature in the range of 250 to 300 ° C. By applying the, the fine intermetallic compound is uniformly dispersed in the aluminum matrix of the aluminum alloy sheet before forming, and the effect of inhibiting the growth of recovery subgrains due to the heat generated during ironing can be obtained, and ironing is improved. We have obtained the knowledge that it will improve. Further, they have found that evenly dispersing the fine intermetallic compound improves the elongation value of the base plate itself. As a result of further studies, in addition to the above, by reducing the amount of solid solution in the aluminum matrix, work hardening during ironing forming is suppressed, ironing resistance is reduced, and as a result, ironing property is further improved. I found it.

That is, according to the present invention, Si0.01-0.
15% by weight, Fe 0.10 to 0.40% by weight, Mn0.
After homogenizing and hot rolling an alloy ingot containing 10 to 0.40% by weight and the balance Al and unavoidable impurities, a reduction ratio of 50 to 90% is applied to the obtained hot rolled sheet. After performing a cold rolling at 200 to 350 ° C. for 2 hours or more, a cold rolling at a rolling reduction of 70% or more,
The thin plate thus obtained is subjected to temper annealing at a temperature in the range of 250 to 300 ° C., and the intermetallic compound having a diameter of 0.1 μm or less in the metal structure of the thin plate before forming is made to have a number density of 5 /
A method for producing an aluminum alloy thin plate for drawless fins having excellent ironing workability, characterized in that the specific resistance value is ³ μm ³ or more and the specific resistance value is 33.5 nΩm or less.

Next, the reason why the component composition is limited as in the present invention will be explained. The aluminum alloy sheet of the present invention has a Si0.
It is characterized in that it has a composition including 01 to 0.15% by weight, 0.10 to 0.40% by weight of Fe, 0.10 to 0.40% by weight of Mn, and the balance Al and unavoidable impurities. The Si, Fe, and Mn components are partially solid-dissolved in aluminum, and in addition to the effect of increasing the strength of the thin plate, the alloy plate has an Al-Fe system having a diameter of about 1 to 10 µm,
It is an n-type and Al- (Fe, Mn) -Si type very hard intermetallic compound, which is uniformly dispersed and has the effect of preventing seizure with a tool during ironing and improving the ironing property. Further, the Mn component has an effect of improving the elongation value of the alloy thin plate. Here, the amount of Si added is less than 0.01% by weight,
Fe addition amount is less than 0.10% by weight, Mn addition amount is 0.1
If it is less than 0% by weight, not only the desired strength and elongation cannot be obtained, but also the number and size of the intermetallic compounds decrease, so that seizure frequently occurs and ironing property deteriorates. On the other hand, the Si addition amount is more than 0.15% by weight, and the Fe addition amount is 0.40% by weight.
If the amount of Mn added is more than 0.40% by weight, work hardening is likely to be promoted during ironing, and the intermetallic compound is coarsened, so that the intermetallic compound is removed during ironing and flare processing. Since the compound becomes the starting point of cracking, the moldability deteriorates. Therefore, Si is 0.
01-0.15 wt%, Fe addition amount is 0.10-0.4
It is necessary that the content of Mn is 0% by weight and the amount of Mn added is 0.10 to 0.40% by weight. In the present invention, the diameter of the intermetallic compound is defined as 0.1 μm or less because the diameter is 0.1 μm.
If it exceeds, the effect of delaying the movement of the sub-grain boundaries is reduced and recovery sub-grains are likely to occur. Even more was defined as the diameter 0.1μm and distribution of intermetallic compounds under diameter or less to the number density of 5 / [mu] m ³ or more, the above effect is difficult to obtain in less than 5 / [mu] m ^3,
Therefore, there is no ironing property improving effect. In addition,
The intermetallic compound has little effect even if it is unevenly distributed in the matrix, and it is more effective if it is dispersed uniformly. The present invention is characterized in that, in addition to the distribution of the fine intermetallic compounds described above, the specific resistance value of the metal structure before forming is specified to be 33.5 nΩm or less. This is a numerical representation of the solid solution amount of the additive element that governs work hardenability, and
This is because when the specific resistance value, which is an index of the amount of solid solution, is larger than 33.5 nΩm, work hardening is likely to occur and cracks are likely to occur during ironing. Therefore, the specific resistance value is 3
It should be 3.5 nΩm or less.

Next, the manufacturing method of the present invention will be described.
The present invention aims to promote the precipitation of fine intermetallic compounds having a diameter of 0.1 μm or less and to reduce the amount of solid solution. For that purpose, first, a homogenizing treatment is performed and hot rolling is performed. After that, it is necessary to perform cold rolling on the obtained hot-rolled sheet at a reduction rate of 50 to 90% and perform a precipitation treatment of holding at 200 to 350 ° C for 2 hours or more. Here, if the precipitation treatment temperature is less than 200 ° C., the effect is insufficient, and 3
When the temperature is higher than 50 ° C., the precipitated intermetallic compound becomes coarse, and recrystallized grains are generated depending on the temperature, which becomes a starting point of cracking, which rather deteriorates formability. Further, if the cold rolling ratio from the hot rolled plate to the plate to be subjected to the precipitation treatment is less than 50%, the dislocation density sufficient for precipitation at 200 to 350 ° C. cannot be obtained, so that the effect of the precipitation treatment is insufficient. If the above-mentioned cold rolling rate exceeds 90%, the final cold rolling rate after the precipitation treatment becomes low, which causes a problem that the strength as a drawless fin material is insufficient. The homogenization treatment may be performed according to a conventional method, but 500 to 620 ° C
At high temperature for a short time, preferably within 3 hours,
If the solid solution amount of the additional element before hot rolling is increased, the effect of the above precipitation treatment is great. The reason why cold rolling is performed at a rolling reduction of 70% or more is that the strength required as a drawless fin material is insufficient when the rolling reduction is lower than 70%. Further, by subjecting the obtained thin plate to temper annealing at a temperature in the range of 250 to 300 ° C., corrugation workability (protrudability) required as a corrugated type drawless fin material can be obtained. Here, if the tempering temperature is less than 250 ° C, sufficient formability cannot be obtained, and if tempering annealing is performed at a temperature higher than 300 ° C, recrystallized grains are generated, and this becomes a starting point of cracking, so rather formability Will deteriorate. Therefore, the obtained thin plate is
It is necessary to perform temper annealing at a temperature of 50 to 300 ° C.

[0008]

【Example】

[Example 1] An alloy ingot having the composition shown in Table 1 was produced by water cooling casting, and the ingot (thickness 400 mm) was formed on one side of 10 mm.
After performing double-sided surface cutting on each side, performing homogenizing treatment under the conditions shown in Table 2 and performing hot rolling, and then performing cold rolling on the hot rolled sheet,
After performing the precipitation treatment under the conditions shown in Table 2, cold rolling was further performed to form a thin plate having a thickness of 0.115 mm, and then 250
The tensile strength is 14.
A thin plate for a drawless fin having a weight of 0 to 15.5 kgf / mm ² was obtained. Table 3 shows the distribution state of the intermetallic compound of the fin material thus obtained, the specific resistance value and the formability evaluation result. Here, regarding the distribution state of the intermetallic compound, the particle diameter of the intermetallic compound and the number of the particles present in a given volume were measured using a transmission electron microscope. The particle diameter was the diameter of a circle having an area equal to the projected area of the particles. Regarding the electrical resistivity, the thin plate after temper annealing was measured using a double bridge based on JIS standard. Ironing processability is
With the drawless fin actual machine, the second with a diameter of 8.29 mm
Using an ironing die and a second ironing punch having a diameter of 8.24 mm, the ironing cracking failure rate was evaluated when 160 fin collar parts were molded under severe conditions with an ironing rate of 78%. The corrugation processability was evaluated by the presence or absence of cracks when 100 corrugated parts were molded with a drawless fin actual machine using a corrugated plate having a molding height of 1.3 mm.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

As is clear from Tables 1, 2, and 3, the alloy plate sample No. 1 to 7 are conventional alloy plate sample Nos. Compared to 13,
Excellent ironing and corrugating properties. This is because the precipitation treatment is carried out under the condition that the hot rolled plate is cold rolled by 50 to 90% at 200 to 350 ° C. for 2 hours or more. As a result, the conventional alloy plate sample No. Compared with No. 13, many fine intermetallic compounds having a diameter of 0.1 μm or less are uniformly present, and these fine intermetallic compounds suppress the growth of recovered subgrains during ironing, and as a result, Breaking resistance is increased. In addition, the alloy sheet of the present invention has a considerably reduced amount of the added element solid solution in the aluminum matrix before forming, the work hardening during ironing is suppressed, and the ironing force is also considerably reduced as compared with the conventional alloy sheet. On the other hand, comparative alloy plate sample No. out of the range of the alloy plate of the present invention. It can be seen that either the ironing property of 8 to 12 or the corrugating property is deteriorated. That is, Fe, Si, Mn
Comparative alloy plate sample No. with any of the contents exceeding the upper limit 9
The alloy cannot reduce the solid solution amount of the additional element before processing even if a thin plate is manufactured under a predetermined manufacturing condition, and the elongation value does not decrease, but it causes remarkable work hardening during ironing and frequently cracks. On the other hand, comparative alloy plate sample No. 1 having Fe, Si, or Mn content less than the lower limit. Since Nos. 11 and 12 have a small amount of fine intermetallic compounds and are easily recovered during ironing, ironing fracture is likely to occur under severe ironing conditions. In addition, the temperature of the precipitation treatment and the cold rolling ratio from the hot rolled plate to the plate subjected to the precipitation treatment were out of the range of the present invention. Nos. 8, 10 and 11 had a small amount of fine intermetallic compound and a large amount of solid solution, and therefore, improvement in ironing property and corrugation property was not observed. In particular, the comparative alloy plate sample No. 1
In No. 1, since the precipitation treatment temperature is high, the intermetallic compound is coarsened, and recrystallized grains are generated depending on the temperature, which becomes a starting point of cracking, which rather deteriorates formability.

Example 2 As shown in Table 3, the alloy plate sample No. of the present invention before temper annealing was used. 5 and comparative alloy plate sample No. 9, 11
Was subjected to temper annealing at a temperature shown in Table 4, and a tensile test and a formability test using a drawless fin actual machine were performed. The results are also shown in Table 4. The conditions of the moldability test are the same as those described in Example 1.

[0014]

[Table 4]

As is clear from Table 4, the alloy plate sample No. of the present invention. No. 5 was subjected to tempering annealing at 250 to 300 ° C. to obtain a comparative alloy plate sample No. The ironing property is excellent as compared with 9 and 11, and the corrugation property is also good. On the other hand, the tempering annealing temperature deviates from the range of the present invention. It can be seen that 5 ′ and 5 ″ have poor ironing and corrugating properties.

[0016]

INDUSTRIAL APPLICABILITY As described above, the fin material obtained according to the present invention has excellent ironing property and corrugation property in drawless fin formation, and has a remarkable effect that the defective rate can be remarkably reduced.

[Brief description of drawings]

1A to 1D are cross-sectional views showing a form of an aluminum fin of a heat exchanger, FIG. 1A is a flat type, FIG. 1B is a louver type, and FIG. 1C is a slit type. D) is a corrugated type.

2A to 2F are explanatory views showing a cross-sectional view of a fin forming method by a draw method.

3A to 3D are explanatory views showing a cross-sectional view of a fin forming method by a drawless method.

[Explanation of symbols]

 1 Plate 2 Color

Claims (1)

Claims 1. Si 0.01 to 0.15% by weight, Fe
The alloy ingot containing 0.10 to 0.40% by weight and Mn 0.10 to 0.40% by weight and obtained by performing homogenization treatment and hot rolling on the alloy ingot and the balance of Al and unavoidable impurities. Cold rolling the hot-rolled sheet at a reduction rate of 50 to 90%,
After performing a precipitation treatment of maintaining the plate thickness at 200 to 350 ° C. for 2 hours or more, cold rolling is performed at a reduction rate of 70% or more, and the obtained thin plate is temper-annealed at a temperature in the range of 250 to 300 ° C. And the diameter of the metal structure before forming of the thin plate is 0.1.
The number density of intermetallic compounds with a diameter of μm or less is 5 / μm ³
The method for producing an aluminum alloy thin plate for drawless fin excellent in ironing workability as described above, wherein the specific resistance value is 33.5 nΩm or less.