JPH06212371A - Production of high strength aluminum alloy fin material for forming - Google Patents

Abstract

PURPOSE:To produce a high strength Al alloy fin material for forming by subjecting an Al alloy ingot having a specified compsn. constituted of Si, Fe, Mn, Ti and Al to specified homogenizing treatment, hot rolling, cold rolling and skinpass annealing. CONSTITUTION:An Al alloy ingot contg., by weight, <=0.1% Si, 0.10 to 1.0% Fe, 0.10 to 0.50% Mn and 0.01 to 0.15% Ti, and the balance Fe with inevitable impurities is subjected to homogenizng treatment of executing holding at 400 to 500 deg.C for 1 to 30hr. After that, thin ingot is subjected to hot rolling, and, at this time, the draft is regulated in such a manner that the rolling to the sheet thickness finished with the hot rolling from 100mm sheet thickness is executed by >=7 passes. This hot rolled sheet is subjected to cold rolling, and, at this time, the draft in the final cold rolling is regulated to >=80%. The thin sheet obtd. by this is subjected to skinpass annealing at 250 to 320 deg.C to distribute intermetallic compounds having <=0.1mum diameter into the metallic structure by >=10 pieces/mum<3> bulk density. In this way, the high strength Al alloy fin material for forming capable of draw forming or the like even in the case of a thin one can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to draw molding, drawless molding or composite molding of both, that is, overhang processing,
The present invention relates to a method for producing a high-strength aluminum alloy fin material for forming, which is formed by performing all or a part of drawing, burring, ironing, and refiring and is used as a fin for a room air conditioner.

[0002]

2. Description of the Related Art Generally, an aluminum alloy fin for an air conditioner heat exchanger has a collar portion for mounting a heat exchange tube on a plate portion (1) as shown in FIGS. 1 (a) to 1 (d).
(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 plate shape. Draw molding (molding mainly for overhanging) is shown in Figure 2 (a) to (f)
As shown in, the process consists of overhanging (a), squeezing (b) to (d), punching, burring (e), and flare (f).
The overhanging process is central. Therefore, in the case of this draw forming, the fin material is required to have an excellent elongation, and normally, it is a thick material with a thickness of 0.12 mm or more and is tempered with an O material or H22. Is.
Also, when thin-walled materials with a thickness of 0.115 mm or less are draw-formed, problems such as deterioration of formability or insufficient strength occur, so it is very difficult to thin fins or form high-color height of thin-walled materials with current materials Met. In order to improve the above problems, drawless molding (molding mainly based on ironing) has been the mainstream of fin molding for several years. Drawless molding consists of punching-hole expansion (a), burring (b), ironing (c), and re-flare (d) as shown in Fig. 3 (a) to (d). Since it is used for forming thin fins, the fins can be made thinner (0.115 to 0.105) in low color height molding.
Thickness of around mm) is possible. In drawless molding, a semi-hard material of H24 to H26 is used because it has excellent ironing workability and requires some strength. However, it is still difficult to form a thin material having a thickness of 0.12 mm or less at a high color height, and the present situation is to use a thick material. Also, in the long-term press processing of drawless molding, a molding failure occurs due to die tool wear of the precoat (surface treatment) fins, which increases die / tool maintenance costs and lowers the viscosity of lubricating oil ( This is a serious problem such as frequent deterioration of moldability due to use of volatile oil). Therefore, it is strongly desired to maintain molding performance and reduce mold / tool maintenance costs compared to the current situation.

Recently, composite molding (hereinafter simply referred to as composite molding) in which the draw molding and the drawless molding are combined has been performed. As shown in Fig. 4, compound molding consists of the steps of overhanging (a), drawing (b), punching, burring (c), ironing (d) (e), and flare (f). This is a molding method in which ironing is performed after a certain color height is obtained, and the ironing rate can be made smaller than in drawless molding. However, with the aluminum alloy fin materials currently used, sufficient molding performance is not maintained and maintenance costs for molds and tools are not reduced by any of the molding methods.

[0004]

The present inventors have obtained the following findings as a result of various investigations for solving the above problems. With the soft fin material used for conventional draw molding,
When the wall thickness is reduced to 0.12 mm or less, there is a problem that due to insufficient strength, buckling occurs when inserting the copper tube into the collar, impairing the adhesion between the collar and the heat exchange tube, and lowering the heat exchange performance. Get up. Further, the hard fin material used in the conventional drawless molding can be thinned because of its high strength, but its elongation value is low, so that high color height molding by draw molding is difficult. In drawless molding, ironing is the main focus, so it is difficult to significantly reduce problems such as lowering the viscosity of lubricating oil, deterioration of moldability associated with the precoat film, and tool wear during long-term pressing. As a means to solve the above, by draw molding,
If hard pre-coated fins of 0.12 mm or less can be formed, it is possible to suppress formability deterioration due to deterioration of lubricity and reduce maintenance costs due to tool wear. However, conventional hard materials have a low elongation value, especially plate thickness. With a thin-walled material having a thickness of 0.105 mm or less, a good molded product cannot be obtained by draw molding. In addition, with the use of volatile oil to omit washing after molding, recently, draw molding and drawless molding have been combined to achieve a certain color height by overhanging and drawing, and then ironing is performed. Since composite molding with a reduced ironing rate has also appeared, if composite molding can form hard pre-coated fins of 0.12 mm or less, it is possible to reduce the above-mentioned deterioration of moldability and maintenance costs due to tool wear. Although it is possible to reduce the amount, the conventional hard material has a low elongation value, and in particular, a thin product having a plate thickness of 0.105 mm or less cannot obtain a good molded product by composite molding. If a material that has the strength and moldability required for drawless molding and the elongation value and moldability required for draw molding can be obtained, draw molding as a thin fin of 0.12 mm or less,
Molding by drawless molding or composite molding is possible. By controlling the addition amounts of Si, Fe, Mn, and Ti, and the manufacturing process / conditions, it is possible to obtain a metallographic state within the scope of the claims of the present application and to obtain a material corresponding to the above.

The present invention is obtained from the above findings,
Si 0.1 wt% or less, Fe 0.10 to 1.0 wt%, Mn
0.10 to 0.50 wt%, Ti 0.01 to 0.15 wt%
Al alloy ingot containing Al and unavoidable impurities in the balance is subjected to homogenizing treatment by holding at a temperature of 400 to 500 ° C. for 1 to 30 hours, immediately followed by hot rolling, and then hot rolling. Rolling is performed from a plate thickness of 100 mm to a plate thickness after hot rolling with a reduction ratio of 7 passes or more, and then cold rolling is performed so that the reduction ratio of the final cold rolling is 80% or more. The thin sheet thus obtained is subjected to temper annealing at a temperature of 250 to 320 ° C., and an intermetallic compound having a diameter of 0.1 μm or less is distributed in the metal structure at a density of 10 or more / μm ³ or more. A method for producing a high-strength aluminum alloy fin material for use in automobiles.

[0006]

The function of the alloy composition and manufacturing conditions in the present invention will be described below. First, the reason why the alloy composition is limited as in the present invention will be described. The aluminum alloy fin material of the present invention has Si of 0.1 wt% (hereinafter simply referred to as%) or less, Fe of 0.10 to 1.0%, and Mn of 0.10 to 0.50.
%, Ti 0.01 to 0.15%, the balance consisting of Al and unavoidable impurities, and the intermetallic compound having a diameter of 0.1 μm or less in the metal structure before forming is made to have a number density of 1
It is characterized in that the number is 0 / μm ³ or more. S
Some of i, Fe, and Mn are solid-dissolved in aluminum and have the effect of increasing the strength of the fin material. In particular, Mn has the effect of improving the elongation value. Ti partially dissolves in aluminum and has a function of refining the structure. In particular, during temper annealing, it has an effect of uniformly promoting recovery and making the subgrain uniform and fine, and therefore has an effect of improving overhang and drawability. Further, Ti is said to have a function of improving local elongation of the material. In the fin forming process, particularly in the case of performing flange forming such as reflaring, the higher the local elongation, the higher the forming performance tends to be. Therefore, the Ti addition amount is specified in the present invention. Here, if the addition amount of Fe and Mn is less than 0.10%, not only the desired strength and elongation due to elemental solid solution cannot be obtained,
The amount of fine intermetallic compounds with a diameter of 0.1 μm or less is also reduced, and the function of suppressing the growth of recovery subgrains during temper annealing of the final plate is reduced, and as a result, an elongation value is secured. Inevitably, the strength is reduced, and the ironing property and the flare property in composite molding are also reduced. Furthermore, the subgrain distribution tends to be non-uniform,
Therefore, during draw forming, the overhanging property, drawability, etc. are actually deteriorated, and the strength is insufficient, resulting in a defective molded product. On the other hand, the addition amount of Si is more than 0.1%, the addition amount of Fe is more than 1.00%, and the addition amount of Mn is 0.5%.
When it is more than 0%, the intermetallic compound is coarsened to a value of 0.
The amount of fine intermetallic compounds of 1 μm or less is reduced, and the crystallized substances during casting are also coarsened. Therefore, during molding, the overhanging property and the drawability are deteriorated due to uneven deformation in the vicinity of the coarse crystallized substances. As a result, the molded product becomes defective. Therefore, the addition amount of Si is 0.1% or less, the addition amount of Fe is 0.10 to 1.0%,
The amount of Mn added needs to be 0.10 to 0.50%. If the addition amount of Ti is less than 0.01%, not only the effect of making the subgrain uniform and fine cannot be obtained, but also the moldability, particularly the overhanging property, the drawability, and the flare property cannot be further improved. On the other hand, the Ti addition amount is 0.1
If it exceeds 5%, coarse Ti-based compounds are distributed, and it becomes difficult to form uniform and fine subgrains. Therefore, the Ti addition amount is 0.01 to 0.15.
Must be%. There is no problem in adding a small amount of Zr, Cu, Y, Hf, etc. as other elements for the purpose of improving the balance between strength and elongation or improving moldability.

In the present invention, the fine intermetallic compound in the metal structure before forming is defined to have a diameter of 0.1 μm or less. The reason is that if the diameter is larger than 0.1 μm, the processed structure of the final plate is recovered during temper annealing. The effect of delaying the movement of the grain boundaries of the subgrains becomes smaller, and as a result, the strength must be reduced to secure the elongation value, and the subgrain distribution tends to become non-uniform. At the time of molding, the overhanging property, drawing property, and reflaring property are deteriorated, and the strength of the product is insufficient. Further, the distribution of intermetallic compounds having a diameter of 0.1 μm or less is set to a number density of 1
The reason for defining 0 or more / μm ³ or more is that if the number is less than 10 / μm ^3, it is difficult to obtain the above-mentioned effect, and therefore there is no effect of improving the overhanging property, drawability, flare property and strength.

Next, the manufacturing method of the present invention will be described.
The method for producing an aluminum alloy fin material of the present invention suppresses coarse precipitation during homogenization treatment and promotes precipitation of fine intermetallic compounds having a diameter of 0.1 μm or less during hot rolling or temper annealing. For that purpose, first, the ingot having the above alloy composition is subjected to a homogenizing treatment of holding at a temperature of 400 to 500 ° C. for 1 to 30 hours. If the homogenization temperature is less than 400 ° C, homogenization of the ingot structure will be insufficient and the solid solution amount of the additive element that was forced to form a solid solution during casting cannot be reduced, so work hardening occurs during ironing. It is easy to do and causes many molding cracks. In addition, the structure after hot rolling becomes non-uniform, and the overhanging property, drawability, and flare property during draw forming or composite forming deteriorate. On the other hand, if the homogenization treatment temperature exceeds 500 ° C., a sufficient solid solubility can be obtained, but the crystallized material is coarsely spheroidized, which adversely affects the moldability, which is not preferable. In particular, it becomes difficult to sufficiently deposit a fine intermetallic compound having a diameter of 0.1 μm or less, which suppresses the occurrence of recrystallization and improves the elongation value. It is not preferable because the refreshing property is deteriorated. If the holding time is less than 1 hour, many fine intermetallic compounds can be formed, but the amount of elemental solid solution cannot be reduced and ironing workability deteriorates. On the other hand, when it is held for more than 30 hours, the solid solution amount of the element is considerably reduced, but coarsening of precipitates is likely to occur, and many recrystallization nuclei are likely to be formed during temper annealing, so that formability is rather deteriorated. It is not preferable because

Hot rolling is performed immediately after the homogenization treatment.
In this hot rolling, it is necessary to carry out rolling from a plate thickness of 100 mm to a plate thickness after hot rolling at a reduction rate of 7 passes or more. If the number of passes is less than 7 passes, the amount of reduction per pass becomes large, so recovery between passes is repeated and recrystallization is repeated. As a result, old grains that tend to become recrystallization nuclei during temper annealing in the hot-rolled sheet after the final pass As a result, a large number of boundaries are generated, and the overhanging property, drawability, and flare property are significantly deteriorated during draw molding or composite molding.

The reduction ratio of cold rolling to final cold rolling is 80%.
If less than 80%, it is 0.12
This is because when draw forming or composite forming a thin fin material having a thickness of 0 mm or less, strength is insufficient and problems such as buckling occur.

The fin material obtained by cold rolling has 25
By subjecting the fin material to temper annealing at a temperature of 0 to 320 ° C., the fin material secures the elongation value necessary for draw molding and the strength necessary for composite molding, and good swelling property, drawability, and flare property can be obtained. Moreover, the corrugated property is also improved. If the tempering temperature is less than 250 ° C, sufficient moldability cannot be obtained,
If the temperature exceeds 320 ° C., not only the strength is lowered, but also the elongation is lowered, and recrystallized grains are generated, which becomes the starting point and deteriorates the formability.

[0012]

EXAMPLES The present invention will now be described in more detail with reference to examples. Example 1 An Al alloy having the alloy composition shown in Table 1 was produced by water cooling casting. Ingot made by water cooling method (thickness 400m
After m) was machined on both sides by 10 mm on each side, homogenization treatment and hot rolling were carried out under the conditions shown in Table 2 to obtain a hot rolled sheet having a thickness of 6 mm. Cold rolled hot rolled sheet, thickness 0.115mm, 0.10
After forming a thin plate of 0 mm, it was subjected to temper annealing at a temperature of 250 to 320 ° C. to obtain a fin material for molding having a tensile strength of 10.0 to 15.0 kgf / mm ² . Table 3 shows the distribution state of the intermetallic compounds of the fin material thus obtained and the evaluation results of the formability. Here, for the distribution state of the intermetallic compound, the particle size of the 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. As for the formability test, first, the results of performing the limit value measurement of the color forming height by draw forming at plate thicknesses of 0.100 mm and 0.115 mm are shown. Next, as a result of evaluation by actual molding, using a fin material having a plate thickness of 0.105 mm, a collar height of 1.6
mm copper pipe fixing hole is overhanged using a draw forming die, continuously formed by drawing, up to the final processing of the reflare processing, and after obtaining 960 colors, cracks occur at the tip of the flare (curling) part. The evaluation was carried out by calculating the crack failure rate from the measurement of the number of holes and comparing it with the refresh failure crack failure rate when a fin material having a thickness of 0.130 mm of the current material was similarly formed. Similarly, using a composite molding die, continuous processing of overhanging, squeezing, ironing, and flare was performed, and after obtaining 960 colors, cracks occurred at the tip of the flare (curling) part. Evaluation was performed by calculating the defective rate and comparing it with the above-mentioned current material.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

As is clear from Table 3, the material sample N of the present invention
o. Nos. 1 to 11 are conventional material sample Nos. Compared with Nos. 22 and 23, it is possible to perform draw forming or composite forming with a thinner plate thickness, and particularly, the overhang formability and the flare formability by draw forming with a plate thickness of 0.100 mm are superior to conventional materials. Further, the material of the present invention is superior to the conventional material also in the limit value of the color forming height at the plate thickness of 0.115 mm. Compared with the conventional material, the present material has a large number of intermetallic compounds having a diameter of 0.1 μm or less. Therefore, in the material of the present invention, when the work structure of the final plate is temper-annealed, these fine compounds are It acts to delay the grain boundary migration of the recovered subgrains, thereby suppressing the generation of recrystallized nuclei, thus maintaining the strength required for composite molding of thin fins, and then, necessary for main molding. The overhang, draw formability, and ironing flare formability are also excellent. Therefore, even if the material of the present invention is thinned from 0.130 mm to 0.115 mm, as shown in Table 3, the current plate thickness (0.130 mm)
It is possible to secure the same or higher limit color height level. Further, even in composite molding, it is possible to maintain the flare moldability equal to or higher than the current material. On the other hand, comparative material sample No. outside the scope of the present invention. Nos. 12 to 21 are inferior to the material of the present invention in overhanging property, drawability, reflaring property in draw molding, and the flare property in composite molding, and the limit color height is at a level not higher than that of the material of the present invention. That is, Comparative Material Sample No. in which any one of Si, Fe, Mn and the content exceeds the upper limit. Nos. 12, 15, 16, and 20 have small intermetallic compounds having a diameter of 0.1 μm or less due to coarsening of intermetallic compounds, and also have large crystallized substances at the time of casting. In addition, the drawability and the refreshing property are deteriorated, resulting in a defective molded product. In addition, the comparative material sample No. In Nos. 17 and 18, since the Ti content exceeds the upper limit, a coarse Ti-based compound is distributed, and it becomes difficult to form uniform and fine subgrains. Sex decreases.

Comparative material sample No. whose manufacturing conditions are out of the range of the present invention 12, 13, 14, 15, 18, 19, 2
In Nos. 0 and 21, the drawability and drawability, or the flareability were deteriorated in the case of draw forming and composite forming with a plate thickness of 0.105 mm. In addition, even if the homogenization condition is appropriate, the comparative material sample No. In No. 19, a large number of old grain boundaries were formed, and sufficient effects of improving the overhanging property and the flare property were not obtained, and the formability was remarkably deteriorated. Even if the hot rolling conditions are appropriate, the homogenization treatment temperature is too low. In No. 21, the ingot structure is not sufficiently homogenized, the structure after hot rolling becomes nonuniform, work hardening easily occurs, and ironing property deteriorates. Comparative material sample No. whose homogenization temperature is too high 1
In No. 8, the amount of the solid solution element is greatly reduced, and actually, a large amount of coarse intermetallic compounds having a diameter of 0.1 μm or more are precipitated in the aluminum matrix. Therefore, when forming the thin fin, the overhanging property and the flare property are deteriorated.

Example 2 With respect to some samples of the present invention material and the comparative material shown in Table 3, bare plate performance for each temper annealing, specifically, tensile strength, elongation, Erichsen value, limit hole The expansion ratio was measured, and the results are shown in Table 4. As for the formability evaluation, as in the case of forming in Table 3, using a fin material with a plate thickness of 0.105 mm, an overhanging draw type draw mold and a compound forming mold were used for overhanging, drawing, hole expanding, ironing, and reflaring. Then, the evaluation was performed by comparing the defective ratio of the flare cracking of the fin material with the thickness of 0.130 mm of the current material.

[0019]

[Table 4]

As is apparent from Table 4, the material of the present invention has higher elongation value, Erichsen value, and limit hole expansion ratio without lowering the strength as compared with the comparative material. Excellent squeezing performance in molding,
The ironing performance and the refreshing performance are maintained.

[0021]

As described above, the fin material obtained by the present invention is excellent in overhanging property, drawability, ironing property, and reflaring property in draw molding and composite molding, and significantly reduces the molding crack defect rate. It has a remarkable effect of obtaining. It goes without saying that the fin material of the present invention can be applied to drawless molding. In particular, even a thin plate of 0.100 mm or the like can be color-molded to a height of 1.8 to 2.2 mm with a drawing mold, which makes it possible to significantly reduce the cost of equipment and materials.

[Brief description of drawings]

1 (a) to 1 (d) show the shapes of aluminum fins of a heat exchanger. (A) is a flat type, (B) is a louver type, (C) is a slit type,
(D) is a corrugated type.

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

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

4 (a) to 4 (f) are explanatory views showing cross-sectional views of a fin forming method by composite forming.

[Explanation of symbols]

 1 Plate part 2 Color part

Claims (1)

[Claims] 1. Si 0.1 wt% or less, Fe 0.10 to
1.0 wt%, Mn 0.10 to 0.50 wt%, Ti0.0
1 to 0.15 wt% with the balance being Al and inevitable impurities in an Al alloy ingot at a temperature of 400 to 500 ° C.
After carrying out the homogenizing treatment of holding for ~ 30 hours, hot rolling is immediately performed, and the hot rolling is performed at a reduction rate such that rolling from a sheet thickness of 100 mm to a sheet thickness after hot rolling is performed in 7 passes or more. Then, cold rolling is performed so that the rolling reduction of the final cold rolling is 80% or more, and the obtained thin plate is 250 to 320 ° C.
Temperature-annealed at a temperature of 0.1 μm in the metal structure
A method for producing a high-strength aluminum alloy fin material for molding, which comprises distributing the following intermetallic compound at a density of 10 or more per μm ³ .