JP2003105471A - Aluminum alloy sheet, and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for producing an aluminum alloy which has excellent formability and coating/baking hardenability, and is suitable as an automobile outer board. SOLUTION: An aluminum alloy ingot containing, by weight, 0.2 to 0.5% Fe, 0.4 to 1.5% Si and 0.2 to 1.0% Mg is subjected to homogenizing treatment at >=500 deg.C, and is thereafter subjected to cooling treatment at a cooling rate of >=100 deg.C/h. By the control of the cooling rate, solution treatment time can be reduced, and the structural properties that the maximum diameters of Si and Mg2 Si. compounds reaches <=10 μm, and the number of Si and Mg2 Si compounds having a grain diameter of 2 to 10 μm reaches <=1,000 pieces/mm<2> can be obtained. After that, the ingot is subjected to hot rolling at 300 to 500 deg.C, and is successively subjected to cold rolling, solution treatment, quenching, heat treatment (preaging treatment) and reversion treatment under prescribed conditions, so that the aluminum alloy sheet having excellent formability and coating/baking hardenability, and applicable as the automobile outer board can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate, and more particularly to a technique for producing an aluminum alloy plate suitable for transportation vehicle members, particularly automobile outer plates, using aluminum alloy scrap as a raw material.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for weight reduction of vehicle bodies from the viewpoint of improving fuel efficiency of automobiles, and steel sheets are being replaced with aluminum alloys as materials used for automobile outer panels. (1) Formability, (2)
Shape freezeability (characteristic that shape is accurately formed during press working), (3) dent resistance, (4) corrosion resistance, (5) product surface quality, etc. are required. In order to meet this requirement, a 5000 series alloy (Al-Mg) having excellent formability is used as an outer panel for automobiles.
Type alloy), and excellent in formability and paint bake hardening 6
000 series alloy (Al-Mg-Si series alloy) is used. However, although the 5000 series alloy is excellent in strength and ductility and exhibits good formability, when the amount of Mg added is increased, the hot workability deteriorates, and SS marks (stretcher strain marks) are generated during forming. In some cases, the appearance becomes poor and the appearance may deteriorate. Also, 6000
Although the type alloy has excellent formability and the strength is increased by performing the baking treatment for coating, and excellent dent resistance, the cost is higher than that of the cold-rolled steel sheet and the range of use is limited. In order to reduce the cost of the 6000 series alloy, it is effective to utilize the scrap aluminum sash and scrap aluminum alloy collected from the scrap car. However, many of these aluminum alloy scraps have iron joined, and an increase in the amount of iron in the alloy cannot be avoided as recycling proceeds,
It is necessary to reduce the influence of the increased Fe element on the formability and the like.

Therefore, conventionally, for example, Japanese Patent Laid-Open No. 2001-31
Japanese Patent Publication No. 29 discloses an aluminum alloy technique in which various characteristics such as formability and corrosion resistance are not deteriorated even when impurities such as iron are contained in the aluminum alloy to some extent. In the technique described in this publication, the formability is improved by performing intermediate annealing in a continuous annealing furnace and refining the crystal grain structure after the solution treatment. However, the intermediate annealing causes processing costs, lowers productivity, and lowers material yield, which is disadvantageous in terms of cost. Further, for example, Japanese Unexamined Patent Application Publication No. 2000-160272 discloses an aluminum alloy technique capable of exhibiting good formability even when impurities such as iron are contained in the aluminum alloy to some extent. However, the technique described in this publication increases the solidification rate during casting,
Since the e-type crystallized substance is made finer, it is premised on the production by a thin plate continuous casting method, and the production by DC casting is difficult, so that it is not suitable for mass production and there is a problem in productivity.
Further, as for the characteristics of products, there is a problem that only the press formability is focused on, and the bending workability required for automobile outer panels is not taken into consideration.

[0004]

Therefore, the inventors of the present invention intend to realize an aluminum alloy plate having good formability even if the aluminum alloy contains impurities such as iron to some extent. Diligently studied the technology. As a result, the inventors of the present invention suitably set the composition of the alloy, the treatment conditions of the homogenization treatment and the cooling treatment, and the like, so that the aluminum alloy sheet suitable for the automobile outer panel is excellent in the formability and the paint bake hardenability. Succeeded in finding that.
An object of the present invention is to provide an aluminum alloy technology which is suitable for automobile outer panels and has excellent moldability and paint bake hardenability.

[0005]

In order to solve the above problems, the aluminum alloy plate of the present invention is constructed as described in claims 1-6. The method for producing an aluminum alloy plate of the present invention is as described in claims 7 to 14.
The invention according to each of these claims is a molding that can be applied as an automobile outer plate by appropriately setting the treatment conditions such as homogenization treatment and cooling treatment after the additive element in the aluminum alloy has a predetermined composition. It is a technology that makes it possible to realize an aluminum alloy technology that has excellent properties and paint bake hardenability. The present invention basically relates to a 6000 series alloy (Al-Mg-Si series alloy) used in so-called T4 tempering (solution treatment, quenching, normal temperature aging).

The aluminum alloy plate according to claim 1 is
It contains Al, main additive elements and impurities. The main additive elements include Si and Mg, and the impurities include Fe. This Fe is inevitably mixed as a raw material from, for example, aluminum alloy scrap. The present invention is intended to broadly include cases in which aluminum alloy scrap recovered from waste aluminum sashes, scrapped automobiles, etc. is used as a raw material or a part thereof, and cases where elements other than Al are positively added to the raw material. To do. Aluminum alloy scrap is a 6000 series alloy (Al-Mg-Si
Type alloys) Si and M more than scrap and 6000 type alloys
It is possible to use pure aluminum alloy scrap having a small amount of alloying elements such as g. Further, from the viewpoint of cost reduction, the higher the scrap compounding ratio, the more desirable.

Further, the aluminum alloy plate according to claim 1 contains Fe: 0.2 to 0.5% (weight%, hereinafter the same), and Si: 0.4 to 1.5 as a main additive element. %,
Mg: 0.2-1.0% is contained. Fe is an element inevitably mixed from the raw material scrap, and the preferable range is 0.2 to 0.5%. If the Fe content is less than 0.2%, the proportion of new ingots used as a raw material becomes high, which is disadvantageous in terms of cost. Also, the amount of Fe is 0.5%
If it is contained in excess of 1, the amount of crystallization of the Al-Fe-Si-based compound will increase and the formability will decrease. Si
Forms a Mg ₂ Si compound in the presence of Mg, or precipitates as a fine Si phase to improve strength and impart high paint bake hardenability. A preferable content range of Si is 0.4 to 1.5%, and if it is less than 0.4%, its effect is not sufficiently obtained and formability is deteriorated, and if it exceeds 1.5%, it is contained. Crystallization or precipitation of a coarse supersaturated Si phase, which is not solid-solved, occurs in the solution treatment, resulting in deterioration of formability and corrosion resistance. Si
The more preferable content range of is 0.6 to 1.3%,
The most preferable Si content range is 0.8 to 1.2%. Mg coexists with Si to form a Mg ₂ Si compound to improve the strength. The preferable content range of Mg is 0.2 to
If it is less than 0.2%, the effect cannot be sufficiently obtained, and if it exceeds 1.0%, the yield strength in T4 tempering becomes high, and the moldability and shape fixability are improved. Will be reduced. A more preferable content range of Mg is 0.3 to 0.
8%, and the most preferable Mg content range is 0.4 to
It is 0.6%.

In the aluminum alloy plate according to claim 1, the maximum diameters of Si and Mg ₂ Si compounds are 10 μm.
Below, the number of Si and Mg ₂ Si compounds having a diameter of ₂ to 10 μm is 1000 / mm ² or less. Such an aluminum alloy plate can be obtained by subjecting an aluminum alloy ingot having the above composition to a predetermined homogenizing treatment, cooling treatment, hot rolling, cold rolling, solution treatment and the like. In particular, in the cooling treatment after the homogenization treatment, the cooling rate is preferably 100 ° C./h or more. A more preferable cooling rate after the homogenization treatment is 20.
It is 0 ° C / h or more. By controlling such a cooling rate, the maximum diameters of Si and Mg ₂ Si compounds are 10
Si and Mg ₂ Si having a particle size of ₂ μm or less and ₂ μm or less
A texture property in which the number of compounds is 1000 / mm ² or less can be obtained. By providing such a texture property, the moldability and the paint baking hardenability are improved, and even when the Fe content is increased by recycling, after applying 10% tensile deformation, 180 ° close bending (inward bending No crack occurs at a radius of 0 mm), and the aluminum alloy plate can be flat-hem processed. The aluminum alloy plate having such performance can be suitably used especially as an automobile outer plate. As described above, according to the invention described in claim 1, it is possible to realize an aluminum alloy sheet which is applicable as an automobile outer panel and has excellent formability and paint bake hardenability.

Further, in the aluminum alloy plate according to the second aspect, Zn is contained and the content thereof is 0.5% or less. Zn is an element selectively contained in the aluminum alloy, but if contained in the range of 0.5% or less, it functions to improve the surface treatability. If the Zn content exceeds 0.5%, the corrosion resistance after coating will be reduced. The more preferable content range of Zn is 0.3% or less.

Further, in the aluminum alloy plate according to the third aspect, Cu is contained and the content thereof is 1.0% or less. Cu is an element selectively contained in the aluminum alloy, but if contained in the range of 1.0% or less, it functions to improve formability. The Cu content is 1.
If it exceeds 0%, the corrosion resistance after coating is deteriorated. The more preferable content range of Cu is 0.4 to 1.0%
And the most preferable Cu content range is 0.6 to 1.0.
%.

Further, in the aluminum alloy plate according to claim 4, in addition to the elements Fe, Si and Mg, Mn and C are further added.
It contains at least one trace element of r, V, and Zr. That is, Mn, Cr, and
It may contain either V or Zr, or may further contain a plurality of these as trace elements. And, those contents are Mn: 0.3% or less, Cr: 0.
3% or less, V: 0.2% or less, and Zr: 0.15% or less. Mn, Cr, V, and Zr are all elements that are selectively contained in the aluminum alloy, and all function to prevent roughening of the surface during molding by crystal grain refinement. The preferable content range of these is Mn: 0.3% or less,
Cr: 0.3% or less, V: 0.2% or less, Zr: 0.1
It is 5% or less, and when both are contained in excess of the upper limit,
Coarse intermetallic compounds are produced and the formability is reduced. The more preferable content range of these is Mn: 0.05 to
0.15%, Cr: 0.05 to 0.15%, V: 0.0
5 to 0.15%, Zr: 0.05 to 0.12%.

Further, in the aluminum alloy plate according to the fifth aspect, in addition to the elements Fe, Si and Mg, Ti and B are further added.
At least one of the elements is contained. That is,
It may contain either Ti or B, or may contain Ti and B. And, their content is Ti:
0.1% or less and B: 50 ppm (weight ppm, the same applies hereinafter) or less. Both Ti and B are elements selectively contained in the aluminum alloy, and function to refine the cast structure and improve the formability. The preferable content range of these is Ti: 0.1% or less, B: 5
If the content is in the range of 0 ppm or less and the content of each exceeds the upper limit, a coarse intermetallic compound is generated and the formability is deteriorated.

In the aluminum alloy plate described in claims 1 to 5, it is preferable that aluminum alloy scrap is used as a raw material as described in claim 6. That is, for example, an aluminum alloy scrap recovered from a waste aluminum sash or a waste automobile is used as a raw material or a part thereof. As a result, the aluminum alloy can be recycled and the manufacturing cost of the aluminum alloy plate can be reduced.

In the method for manufacturing an aluminum alloy plate according to the seventh aspect, the aluminum alloy ingot is processed by, for example, FIG.
As shown in FIG. 3, homogenization treatment, cooling treatment, hot rolling, cold rolling, solution treatment and the like are sequentially performed. Here, FIG. 1 is a diagram showing a processing flow of an aluminum alloy ingot according to an embodiment of the present invention. Hereinafter, description will be given with reference to FIG. This ingot of aluminum alloy contains F as an impurity.
e: containing 0.2 to 0.5%, as a main additive element,
It contains Si: 0.4 to 1.5% and Mg: 0.2 to 1.0%. This aluminum alloy ingot is obtained by ingoting the aluminum alloy having the above composition by a usual DC casting method. In the homogenization treatment, it is preferable to treat the aluminum alloy ingot at a temperature of 500 ° C. or higher. If the homogenization temperature is less than 500 ° C, the ingot segregation is not removed and the homogenization is not sufficient, and the solid solution of Mg and Si elements for improving the strength is insufficient, and the strength is lowered and the formability is lowered. I have something to do. When the homogenization process is completed, the aluminum alloy ingot is cooled. This cooling treatment is preferably performed at a cooling rate of 100 ° C./h or more. If the cooling rate is less than 100 ° C / h,
Precipitation and agglomeration of Si or Mg ₂ Si compound occur, so that a solution treatment for infiltrating this requires a long time, and productivity is lowered. In addition, since the amount of agglomerated Si and Mg ₂ Si compound is increased, the formability is lowered. By controlling the cooling rate after the homogenization treatment, the solution treatment time can be shortened, and the maximum diameter of Si and Mg ₂ Si compounds is 10 μm or less and the particle diameter is 2 to 2.
1000 μm of 10 μm Si and Mg ₂ Si compounds
It is possible to obtain a texture property of not more than the number of pieces / mm ² . A more preferable cooling rate is 200 ° C./h or more. The cooling rate in the normal process is 30 ° C./h or less. When the cooling process is completed, hot rolling is performed. When performing this hot rolling, cooling is performed to a predetermined temperature in the range of 300 to 500 ° C., and the hot rolling is started as it is, or when the temperature is once lowered to 300 ° C. or less, then 300 to 500 ° C.
The hot rolling may be started after reheating to a predetermined temperature in the range of ° C, and either process may be appropriately used. The hot rolling of the present invention is intended to broadly include these processes. This hot rolling is preferably started at a temperature of 300 to 500 ° C. If the temperature of hot rolling is less than 300 ° C, the deformation resistance becomes large and the rolling efficiency decreases. Fifty
When hot rolling is performed at a temperature higher than 0 ° C, coarsening of crystal grains occurs during rolling, and ridging marks are likely to occur. From the viewpoint of deformation resistance and work structure, a more preferable starting temperature range of hot rolling is 320 to 450 ° C. After hot rolling, cold rolling is performed to a predetermined thickness while sandwiching intermediate annealing if necessary, and then solution treatment and quenching are performed. A preferable solution treatment temperature is 500 ° C. or higher, and when the treatment temperature is lower than 500 ° C., solid solution of Mg and Si elements becomes insufficient, and sufficient strength and formability cannot be obtained,
Alternatively, in order to obtain the required strength and moldability, solution treatment for an extremely long time is required, which is not industrially preferable. Quenching after solution treatment is up to 120 ° C at 5 ° C / s
As described above, it is more preferable to cool at a cooling rate of 10 ° C./s or more. When this cooling rate (quenching rate) is slow, precipitation of solute elements occurs, which deteriorates the strength characteristics, coating bake hardenability and formability, and also reduces corrosion resistance. According to the present invention, the maximum diameter of Si and Mg ₂ Si compounds is 10 μm or less, and Si and M having a diameter of 2 to 10 μm.
It is possible to manufacture an aluminum alloy plate having a texture property in which the number of g ₂ Si compounds is 1000 / mm ² or less. As a result, the formability and paint bake hardenability are improved, and even if the Fe content increases due to recycling, cracking occurs after 180% close bending (inward bending radius 0 mm) after 10% tensile deformation. Without this, an aluminum alloy plate capable of flat hem processing can be realized. Aluminum alloy plate with such performance,
In particular, it can be suitably used as an automobile outer plate.
As described above, according to the invention described in claim 7, it is possible to realize an aluminum alloy plate which is applicable as an automobile outer plate and is excellent in formability and paint bake hardenability.

In the method of manufacturing an aluminum alloy sheet according to the eighth aspect, the solution-treated and quenched rolled sheet is further heat-treated. As the heat treatment, it is preferable to perform a pre-aging treatment of heating at a temperature of 40 to 120 ° C. for a time of 50 hours or less within 60 minutes after quenching. By performing this preliminary aging treatment, it is possible to improve the coating bake hardenability. At a heat treatment temperature of less than 40 ° C., the coating baking hardenability is not sufficiently improved, and at a heat treatment temperature of more than 120 ° C. or a heat treatment time of more than 50 hours, the moldability and the paint baking hardenability may decrease. The heat treatment here will be referred to as a preliminary aging treatment in the following description.

Further, in the method for manufacturing an aluminum alloy sheet according to the ninth aspect, the rolled sheet which has been subjected to the preliminary aging treatment is further subjected to the restoration treatment. Within 60 minutes after quenching, 170-230 ℃ within 3 days after performing a pre-aging treatment of heating at a temperature of 40-120 ℃ for a time within 50 h
It is preferable to perform the restoration process within 60 s at the temperature. By performing this restoration process, the paint baking hardenability can be further improved. At a restoration treatment temperature of lower than 170 ° C., the coating bake hardenability is not sufficiently improved, and at a restoration treatment temperature of higher than 230 ° C., the moldability and coating bake hardenability may decrease. Even in the conventional 6000 series aluminum alloy, the solution bake hardenability is improved by the solution heat treatment and the final heat treatment after quenching, but in the present invention, the cooling rate after the homogenization treatment is 100%. By setting the temperature to not less than ° C / h, the solid solution of the solute element during the solution heat treatment is promoted, and the effect of improving the coating baking hardenability becomes large.

Further, even when an element other than Fe, Si and Mg is contained as in the method for manufacturing an aluminum alloy plate according to claims 10 to 13, the content and treatment of Fe, Si and Mg are performed. By appropriately setting the conditions, the same effect as the manufacturing method according to the seventh aspect can be obtained.

Further, according to the method for manufacturing an aluminum alloy plate of the tenth to fourteenth aspects, the aluminum alloy can be recycled and the manufacturing cost of the aluminum alloy plate can be reduced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, examples of the present invention will be described in comparison with comparative examples, and the effects thereof will be demonstrated based on the examples. It should be noted that these examples are for explaining a preferred embodiment of the present invention, and the present invention is not limited thereby.

[Embodiment 1] Embodiment 1 will be described with reference to FIGS.
Will be described with reference to. Here, FIG. 2 is a diagram showing the compositions of the aluminum alloys A to M used in Example 1,
FIG. 3 shows the test material No. 1 according to the first embodiment. It is a figure which shows the evaluation result of 1-13. In Example 1, 50% or more of waste aluminum sash (aluminum alloy scrap) was used as a melting material, and aluminum alloys A to M having the chemical components shown in FIG. 2 were ingoted. Then, the aluminum alloy ingot thus obtained is homogenized at a temperature of 540 ° C. for 6 hours,
Then, it was cooled to room temperature (cooling treatment) at a cooling rate of 300 ° C./h. Then, this ingot is reheated to a temperature of 400 ° C., and hot rolling is started at this temperature to obtain a thickness of 4.0 mm.
(Hot rolling), and further cold rolling to obtain a cold rolled plate having a thickness of 1.0 mm. The cold-rolled sheet obtained by this cold rolling was subjected to solution treatment for 5 s at a temperature of 540 ° C., then quenched at a cooling rate of 30 ° C./s up to a temperature of 120 ° C., and 5 minutes after quenching. Later at 100 ° C for 3 hours
The preliminary aging treatment was performed. This pre-aged plate was used as a test material No. 1 to 13 (alloys A to M), by the following method, tensile properties, formability after 10 days from the preliminary aging treatment,
Evaluate corrosion resistance and paint bake hardenability to evaluate Si and Mg ₂
The number of Si compounds was counted. The evaluation result is shown in FIG.

The evaluation of each item shown in FIG. 3 was carried out as follows. 1) Tensile properties: JIS No. 5 tensile test pieces were molded, and the tensile strength, 0.2% proof stress and elongation were measured. 2) Moldability: An Erichsen test (EV) was performed, and those with a molding height of less than 10 mm were rejected. In addition, in order to evaluate the hemmability, after applying 10% tensile deformation, 1
Adhesion bending of 80 ° (inner bending radius 0 mm) was performed, and those having cracks on the surface were rejected regardless of the size of the cracks. Furthermore, 10% in the 90 ° direction to the rolling direction
After the tensile deformation was applied, electrodeposition coating was performed and the presence or absence of ridging marks was visually observed. 3) Corrosion resistance: The test material was subjected to zinc phosphate treatment with a commercially available chemical conversion treatment liquid and electrodeposition coating, and cross-cut to reach the aluminum base material. Thereafter, this test material was subjected to a salt spray test according to JIS Z 2371 for 24 hours, and then left in a humid atmosphere at 50 ° C.-95% for 1 month. The maximum thread rust length generated from the cross-cut portion at this time was measured, and the maximum thread rust length of 4 mm or less was accepted. 4) Coating baking hardening (BH property): Tensile deformation of 2% was applied, and 0.2% proof stress after heat treatment (BH) for 20 minutes at 170 ° C. was measured, and the proof stress was 200 MPa or more. The one was accepted. 5) Measurement of Si and Mg ₂ Si compound: The maximum diameter of the compound was measured by observing the structure of an optical microscope. 2-10 μm
For the distribution of diameter compounds, use an image analyzer to
A total area of 1 mm ² (1 mm ² ) was investigated under the condition of pixel = 0.25 μm. The Fe-based compound is distinguished from the Fe-based compound by the light and darkness of the compound, and the compound particles are previously confirmed by the point analysis.
The detection conditions were selected to the level at which the g ₂ Si compound was detected.

As shown in FIG. 3, the test material No. Nos. 1 to 13 all showed excellent BH properties exceeding 200 MPa in the BH property evaluation, and the moldability also exceeded the molding height of 10 mm in EV, cracking did not occur in the bending test, and ridging marks did not occur. No
It had good moldability, and had a maximum thread rust length of 4 mm or less, showing excellent corrosion resistance.

Comparative Example 1 Comparative Example 1 will be described with reference to FIGS.
Will be described with reference to. Here, FIG. 4 is a diagram showing the compositions of the aluminum alloys N to Y used in Comparative Example 1,
5 is a test material No. 1 according to Comparative Example 1. It is a figure which shows the evaluation result of 14-25. In Comparative Example 1, waste aluminum sash (aluminum alloy scrap) was used as a melting material at 50%.
The aluminum alloys N to Y having the chemical components shown in FIG. Then, the ingot thus obtained is treated in the same treatment step as in Example 1 to obtain a thickness of 1.0.
mm cold rolled plate. The cold rolled sheet obtained by this cold rolling was subjected to solution treatment and quenching under the same conditions as in Example 1, and 5 minutes after quenching, a preliminary aging treatment was performed at 100 ° C. for 3 hours. This pre-aged plate was used as a test material No. 1
4 to 25 (alloys N to Y) were evaluated in the same manner as in Example 1 for tensile properties, formability, corrosion resistance and paint bake hardenability 10 days after the pre-aging treatment, and Si and M were evaluated.
The number of g ₂ Si compounds was counted. The evaluation result is shown in FIG.

As shown in FIG. 5, the test material No. 14
(Alloy N) had a large Fe content of 0.87%, and thus had poor bendability. Test material No. 15 (alloy O) has a Si content of 0.2
%, The EV value and BH property are poor. Test material N
o. 16 (alloy P) has a large Si content of 1.9%, so EV
Value, bendability and corrosion resistance are poor. Test material No. 17 (alloy Q) has a low BH property because the amount of Mg is as small as 0.1%.
Test material No. 18 (alloy R) has a large amount of Mg of 1.4% and thus has a poor EV value and bendability. Test material No. Since 19 (alloy S) has a large Cu content of 1.5%, bendability and corrosion resistance are poor. Test material No. 20 (alloy T) has a Zn content of 0.
Since it is as high as 8%, the corrosion resistance is poor. Test material No. 21-24
(Alloys U to X) have a large amount of Mn, Cr, V, and Zr, respectively (Mn: 0.5%, Cr: 0.5%, V: 0.3%,
Zr: 0.23%), so the EV value is inferior. Test material No. 25 (alloy Y) has a large amount of Ti and B (Ti:
0.3%, B: 73 ppm), and thus the EV value is inferior.

[Second Embodiment] A second embodiment will be described with reference to FIGS.
Will be described with reference to. Here, FIG. 6 shows the test material No. It is a figure which shows the processing conditions of 26-32, and FIG. 7 is a test material No. It is a figure which shows the evaluation result of 26-32. In Example 2, using the ingot of alloy A (see FIG. 2) used in Example 1, homogenization treatment, hot rolling, cold rolling, solution treatment, preliminary aging treatment and After restoration processing, the test material No. 26-3
2 was produced. At this time, the homogenization treatment time was 6 hours, the hot rolled thickness was 4.0 mm, the cold rolled thickness was 1.0 mm, and the pre-aging treatment time after quenching was 5 minutes. After the treatment, the number of days until the restoration treatment was 1 day.

This final heat-treated plate (preliminary aging-treated plate and restoration-treated plate) was used as a test material No. 26 to 32 (alloy A), by the same method as in Example 1, tensile properties 10 days after the final heat treatment (pre-aging treatment or restoration treatment),
The formability, corrosion resistance and paint bake hardenability were evaluated, and the numbers of Si and Mg ₂ Si compounds were counted. The evaluation result is shown in FIG. As shown in FIG. 7, the test material No. Nos. 26 to 32 all showed excellent BH properties exceeding 200 MPa in the evaluation of BH properties, and also regarding moldability, the molding height in EV exceeded 10 mm, cracks did not occur in the bending test, and ridging marks did not occur. No
It had good moldability, and had a maximum thread rust length of 4 mm or less, showing excellent corrosion resistance.

[Comparative Example 2] Comparative Example 2 is shown in FIGS.
Will be described with reference to. Here, FIG. 8 shows the test material No. 1 in Comparative Example 2. It is a figure showing the processing conditions of 33-41, and Drawing 9 shows test material No. 3 concerning comparative example 2. It is a figure which shows the evaluation result of 33-41. In Comparative Example 2, using the ingot of the alloy A (see FIG. 2) used in Example 1, homogenization treatment, hot rolling, cold rolling, solution treatment, preliminary aging treatment and After restoration processing, the test material No. 33-4
1 was produced. At this time, the homogenization treatment time was 6 hours, the hot rolled thickness was 4.0 mm, the cold rolled thickness was 1.0 mm, and the pre-aging treatment time after quenching was 5 minutes. After the treatment, the number of days until the restoration treatment was 1 day.

This final heat-treated plate (preliminary aging-treated plate and restoration-treated plate) was tested as No. 33 to 41 (alloy A), in the same manner as in Example 1, tensile properties 10 days after the final heat treatment (pre-aging treatment or restoration treatment),
The formability, corrosion resistance and paint bake hardenability were evaluated, and the numbers of Si and Mg ₂ Si compounds were counted. The evaluation result is shown in FIG. As can be seen in FIG. 33 has a low homogenization treatment temperature of 450 ° C, and therefore EV
The value is low, the bendability is poor, and the BH property is also low. Test material No. 34 and No. 34. In No. 35, the cooling rate after the homogenization treatment is as small as 30 to 70 ° C./h, so that the bendability is poor and the BH property is also low. Test material No. Since No. 36 had a high hot rolling start temperature of 550 ° C., ridging marks were generated. Test material No. Since No. 37 has a solution treatment temperature as low as 470 ° C., its strength and EV value are low, and its BH property is also low. Test material No. 38 is the cooling rate after the solution treatment (quenching rate)
Of 1 ° C./s, the EV value, bendability and corrosion resistance are poor, and BH property is low. Test material No. No. 39 did not undergo the preliminary aging treatment, and thus had a low BH property. Test material No. 40
Has a high pre-aging treatment temperature of 140 ° C and a treatment time of 72
The EV value is low due to the long h. Test material No. In No. 41, the restoration processing temperature is as high as 250 ° C., so that the EV value is low.

As described above, according to the present embodiment, S
It is possible to obtain a textured aluminum alloy plate in which the maximum diameter of i and Mg ₂ Si compound is 10 μm or less and the number of Si and Mg ₂ Si compound is ₂ to 10 μm and the number is 1000 pieces / mm ² or less. The aluminum alloy sheet having such a texture property has improved formability and paint bake hardenability, and has an Fe content of 0.2 to 0.5 by recycling.
Even when it is increased to 10%, after applying 10% tensile deformation, cracks do not occur in 180 ° tight bending (inner bending radius 0 mm), and flat hem processing is possible. In addition, aluminum alloy scrap is used as a raw material, and even if the amount of impurities in Fe inevitably mixed in is high, it has excellent formability that allows flat hem and does not cause rough skin or ridging marks after forming, and shape fixability. The present invention provides an aluminum alloy sheet having excellent paint bake hardenability that achieves both high resistance and dent resistance, and also excellent in corrosion resistance, particularly in thread rust resistance, and a method for producing the same. The aluminum alloy plate is suitably used for transportation equipment members such as automobile hoods, fenders, trunk lids, roofs and doors, and enables gauge down of these members.

The present invention is not limited to the above-described embodiments, and various applications and modifications can be considered. For example, each of the following modes to which the above-described embodiment is applied can be implemented.

(A) In Examples 1 and 2 above, a case was described in which an ingot cooled to room temperature was reheated to 400 ° C. and then hot-rolled, but the temperature was in the range of 300 to 500 ° C. The ingot that has been cooled down to may be hot-rolled as it is.

(B) Further, in the above-mentioned Embodiments 1 and 2, the case where the waste aluminum sash as the aluminum alloy scrap is used as the raw material has been described, but for example, the waste automobile may be used as the raw material. Further, raw materials other than aluminum alloy scrap can be used.

[0033]

As described above, according to the present invention,
It is possible to realize an aluminum alloy technology having excellent formability and paint bake hardenability suitable for automobile outer panels.

[Brief description of drawings]

FIG. 1 is a diagram showing a processing flow of an aluminum alloy ingot according to an embodiment of the present invention.

2 is a diagram showing compositions of aluminum alloys A to M used in Example 1. FIG.

3 is a test material No. 1 according to Example 1. FIG. It is a figure which shows the evaluation result of 1-13.

4 is a diagram showing compositions of aluminum alloys N to Y used in Comparative Example 1. FIG.

5 is a test material No. according to Comparative Example 1. FIG. It is a figure which shows the evaluation result of 14-25.

6 is a test material No. 2 in Example 2. FIG. It is a figure which shows the processing conditions of 26-32.

7 is a test material No. 3 according to Example 2. FIG. It is a figure which shows the evaluation result of 26-32.

8 is a test material No. 3 in Comparative Example 2. FIG. It is a figure which shows the processing conditions of 33-41.

9 is a test material No. 3 according to Comparative Example 2. FIG. It is a figure which shows the evaluation result of 33-41.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22F 1/00 630 C22F 1/00 630K 691 691B 691C 692 692A 692B 694 694B (72) Inventor Hideyuki Uto Tokyo Sumitomo Light Metal Industry Co., Ltd. 5-11-3 Shimbashi, Minato-ku (72) Inventor Tsutomu Furuyama 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (14)

[Claims] 1. An aluminum alloy plate comprising Al and other elements, containing Fe: 0.2 to 0.5 wt% as impurities,
As a main additive element, Si: 0.4 to 1.5% by weight, M
g: 0.2 to 1.0% by weight, the maximum diameter of Si and Mg ₂ Si compounds is 10 μm or less,
The number of Si and Mg ₂ Si compounds having a diameter of _{2 to} 10 μm is 1
An aluminum alloy plate characterized by being 000 pieces / mm ² or less. 2. The aluminum alloy plate according to claim 1, further comprising Zn, the content of which is 0.5% by weight or less. 3. The aluminum alloy plate according to claim 1 or 2, further containing Cu, and the content thereof is 1.0% by weight or less. 4. The aluminum alloy plate according to claim 1, further containing at least one of Mn, Cr, V, and Zr, the content of which is Mn: 0. 3% by weight or less, C
r: 0.3 wt% or less, V: 0.2 wt% or less, Zr:
An aluminum alloy plate characterized by being 0.15% by weight or less. 5. The aluminum alloy plate according to any one of claims 1 to 4, further containing at least one of Ti and B, and the content of Ti: 0.1% by weight or less. , B: 50 weight p
Aluminum alloy plate characterized by being pm or less. 6. The aluminum alloy plate according to any one of claims 1 to 5, wherein aluminum alloy scrap is used as a raw material. 7. A method for producing an aluminum alloy sheet, which comprises producing an aluminum alloy sheet from an aluminum alloy ingot containing Al and other elements, wherein Fe: 0.2 to 0.5 wt% is contained as an impurity. ,
As a main additive element, Si: 0.4 to 1.5% by weight, M
g: homogenizing an aluminum alloy ingot containing 0.2 to 1.0% by weight at a temperature of 500 ° C. or higher;
Cooling the aluminum alloy ingot to a temperature of 300 to 500 ° C. at a cooling rate of 00 ° C./h or more;
Hot rolling at a temperature of 0 to 500 ° C., and cold rolling the hot-rolled sheet, and then 5
Solution heat treated at a temperature of 00 ° C or higher, 5 ° C up to 120 ° C
Quenching at a cooling rate of / s or more, the maximum diameter of Si and Mg ₂ Si compound is 10 μm or less,
The number of Si and Mg ₂ Si compounds having a diameter of _{2 to} 10 μm is 1
A method for producing an aluminum alloy plate, characterized in that the number is 000 pieces / mm ² or less. 8. The method for manufacturing an aluminum alloy plate according to claim 7, further comprising a step of performing heat treatment at a temperature of 40 to 120 ° C. for 50 hours or more within 60 minutes after the quenching. And a method for manufacturing an aluminum alloy plate. 9. The method for manufacturing an aluminum alloy plate according to claim 8, further comprising the step of performing a restoration process within 60 seconds at a temperature of 170 ° C. to 230 ° C. within 3 days after the heat treatment. A method for manufacturing an aluminum alloy plate, comprising: 10. The method for manufacturing an aluminum alloy plate according to claim 7, wherein the aluminum alloy ingot further contains Zn and the content thereof is 0.5% by weight or less. A method of manufacturing an aluminum alloy plate, which is characterized in that 11. The method for manufacturing an aluminum alloy plate according to claim 7, wherein an aluminum alloy ingot containing Cu and having a content of 1.0 wt% or less is used. A method for manufacturing an aluminum alloy plate, comprising: 12. The method for manufacturing an aluminum alloy plate according to claim 7, further comprising at least one of Mn, Cr, V, and Zr, the content of which is Mn. : 0.3% by weight or less, C
r: 0.3 wt% or less, V: 0.2 wt% or less, Zr:
A method for producing an aluminum alloy plate, which comprises using an aluminum alloy ingot having a content of 0.15% by weight or less. 13. The method for manufacturing an aluminum alloy plate according to claim 7, further comprising at least one of Ti and B, the content of which is Ti: 0.1. Weight% or less, B: 50 weight p
A method for producing an aluminum alloy plate, which comprises using an aluminum alloy ingot having a thickness of pm or less. 14. The method for manufacturing an aluminum alloy plate according to claim 7, wherein aluminum alloy scrap is used as a raw material for the aluminum ingot, and a method for manufacturing an aluminum alloy plate. .