JP2000034534A - Aluminum alloy for forming, having excellent chemical conversion treatment property, its manufacture, and transport equipment member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy for forming, excellent in property of chemical conversion treatment by zinc phosphate treatment, having superior corrosion resistance, particularly filiform corrosion resistance, and excellent in BH characteristic, a method of its manufacture, and a transport equipment member. SOLUTION: This aluminum alloy has a composition which consists of, by weight, 0.5-1.5% Si, 0.2-1.0% Mg, 0.05-<0.3% Zn, and the balance Al with impurities and in which the contents of Fe and Cu as impurities are limited to <=0.5% and <=0.05%, respectively. Further, one or >=2 kinds among <=0.3% Mn, <=0.3% Cr, <=0.2% V, and <=0.15% Zr can also be incorporated. A sheet of this aluminum alloy can be suitably used for automobile body sheet material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for forming and processing having excellent chemical conversion properties, particularly an aluminum alloy which can be suitably used as a member for transportation equipment such as a member for automobiles, a method for producing the same, and the use of the aluminum alloy. The present invention relates to transportation equipment members.

[0002]

2. Description of the Related Art From the viewpoint of reducing the weight of transportation equipment such as automobiles,
Attempts have been made to use various types of aluminum alloy materials.
Dent resistance, corrosion resistance, and product surface quality that does not cause roughening or ridging marks in press molding are required. To satisfy such characteristics, Al-Mg based (5000)
Alloys and Al-Mg-Si (6000 series) alloys have been developed, and many aluminum alloys for automotive outer panels have been developed. Of these alloys, the 6000 series alloys can satisfy the above characteristics in a well-balanced manner. It is attracting attention as a possible alloy material.

[0003] However, the 6000 series aluminum alloy has a problem that the zinc phosphate treatability is inferior.
Normally, in assembling an automobile body, a steel plate and an aluminum alloy plate are used in combination, and a body part made of a formed steel plate and an aluminum alloy plate is spot-welded, and then the entire body is subjected to a coating base treatment by zinc phosphate treatment, Painting is done. In this case, the aluminum alloy material is also subjected to zinc phosphate treatment similarly to the steel sheet. However, if the zinc phosphate treatment property is poor, the adhesion of the coating film tends to be insufficient, and the corrosion resistance, particularly the rust resistance, is inferior.

[0004] As a 6000 series aluminum alloy having improved zinc phosphate treatment properties to increase the adhesion of the coating film and to improve the rust resistance, Mg: 0.1-1.5%, Si: 0.3-2.5%, Z:
n: 0.3% to less than 0.5%, Cu: 0.5% or less, Fe: 0.5% or less, Mn: 0.8% or less, Cr: 0.3% or less, Zr: 0.2% or less, V: 0.2% or less An aluminum alloy containing one or more kinds and the balance of Al and inevitable impurities has been proposed (JP-A-6-6036).
No. 6), however, even with this aluminum alloy, the thread rust resistance under a severe corrosive environment is not always sufficient.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been developed to solve the above-mentioned conventional problems in aluminum alloys for transportation equipment, especially automobiles, and to provide a 6000 series aluminum alloy which solves the above-mentioned conventional problems. The purpose of this study was to review the characteristics of the aluminum-based alloys and to further review and study the relationship between the above-mentioned properties required for automotive outer panels and the component composition. It has excellent chemical conversion property by zinc treatment, good corrosion resistance, especially good thread rust resistance, and it can also improve strength and dent resistance by paint baking, making it suitable for transportation equipment such as automobiles. An object of the present invention is to provide an excellent aluminum alloy for forming and processing, a method for producing the same, and a member for a transportation device.

[0006]

According to the first aspect of the present invention, there is provided an aluminum alloy for forming and processing which has an excellent chemical conversion property, comprising: Si: 0.5 to 1.5%, Mg: 0.2.
1.01.0%, Zn: 0.05 or more and less than 0.3%, Fe as an impurity is limited to 0.5% or less, Cu is limited to 0.05% or less, and the balance consists of Al and impurities.

Further, the aluminum alloy according to the second and third aspects further comprises Mn: 0.3% or less and C
r: 0.3% or less, V: 0.2% or less, Zr: 0.15% or less.
0.1% or less, B: 50 ppm or less.

According to a fourth aspect of the present invention, there is provided a method for producing an aluminum alloy for forming and processing having excellent chemical conversion treatment properties, comprising forming an ingot of an aluminum alloy having the above composition by DC casting, hot rolling, and cold rolling in a conventional manner. After performing quenching and solution treatment and quenching in a temperature range of 120 ° C. or less, heat-treating at a temperature of 40 to 120 ° C. for 50 hours or less within 60 minutes after quenching, The manufacturing method 5 is characterized in that after the heat treatment, the heat treatment is further performed at a temperature of 180 to 260 ° C. for a time of 60 seconds or less.

According to a sixth aspect of the present invention, there is provided a method for producing an aluminum alloy, the ingot of the aluminum alloy having the above composition being formed by DC casting, subjected to hot rolling, cold rolling and solution treatment according to a conventional method, and after quenching, The heat treatment is performed at a temperature of 180 to 260 ° C. for a time of 60 seconds or less.

Further, according to a seventh aspect of the present invention, the aluminum alloy plate manufactured by the above-mentioned method is provided with an F ^- concentration of 350-8.
A zinc phosphate treatment is performed in a treatment solution containing 00 ppm.
3. A plate material of the aluminum alloy according to 3.

The significance of the alloy components in the present invention and the reasons for limiting them will be described. (1) Essential component Si forms Mg ₂ Si together with Mg, thereby increasing the strength and giving a strength improving effect (BH property) by baking paint. The preferable content range of Si is 0.5 to 1.5%, and
If it is less than 5%, BH property at the time of baking cannot be sufficiently obtained.
If the content exceeds 1.5%, the proof stress increases, the press formability and the shape freezing property (the shape of the press mold is accurately obtained during press forming) are deteriorated, and the corrosion resistance after painting is also reduced. S
A more preferred content of i is in the range of 0.8 to 1.3%.

[0012] Mg forms Mg ₂ Si together with Si, and functions to increase the strength and to impart BH properties by paint baking. The preferred content range is 0.2 to 1.0%,
If it is less than 0.2%, the BH property at the time of baking cannot be sufficiently obtained, and if it exceeds 1.0%, the proof stress after the solution treatment or the final heat treatment becomes high, and the formability and the shape freezing property decrease. Mg
Is more preferably from 0.3 to 0.7%.

[0013] Zn is an element that improves the zinc phosphate treatability and helps prevent rust. It also contributes to the improvement in BH properties. The preferable content of Zn is in the range of 0.05% or more and less than 0.3%, and the effect is small when the content is less than 0.05%.
%, The corrosion resistance of the material is reduced, and the rust resistance is degraded. In addition, since the proof stress increases due to the aging at room temperature, the amount of increase in the proof stress during baking of the paint decreases, and the moldability and the shape freezing property also deteriorate. A more preferred content range of Zn is 0.1 to
0.25%.

(Selective components) Mn and Cr function effectively to refine crystal grains and prevent roughening during molding. The preferred contents of Mn and Cr are both 0.3% or less (excluding 0%), and more preferably 0.02 to 0.3%.
Range. Below 0.02% the effect is small, 0.3
%, Coarse intermetallic compounds are likely to be formed, and moldability is reduced.

V and Zr also effectively function to refine crystal grains and prevent roughening during molding. The preferred contents of V and Zr are 0.2% or less and 0.
It is 15% or less (both do not include 0%), more preferably in the range of 0.02 to 0.2% and 0.02 to 0.15%, respectively. If it is less than 0.02%, the effect is small.
% And more than 0.15%, a coarse intermetallic compound is likely to be formed, and the moldability decreases.

[0016] Ti refines the ingot structure and improves the formability. The preferable content of Ti is 0.1% or less (excluding 0%), more preferably in the range of 0.005 to 0.1%. When the content is less than 0.005%, the effect is small. As a result, moldability tends to decrease.

B refines the ingot structure and improves the formability. The preferred content of B is 50 ppm or less (0 ppm
Is more preferably in the range of 1 to 50 ppm, and if it is less than 1 ppm, the effect is small, and if it exceeds 50 ppm, a coarse intermetallic compound is formed and the moldability tends to be lowered.

(Restriction of Impurities) Cu is an element which deteriorates the corrosion resistance and is therefore limited to 0.05% or less, preferably 0.02% or less. Fe is an element that lowers the formability, so it is limited to 0.5% or less, preferably 0.3% or less.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy for forming according to the present invention, which has excellent chemical conversion properties, is ingoted by ordinary DC casting, subjected to homogenization, hot rolling, and cold rolling according to a conventional method. It is manufactured by performing a solution treatment and a quenching and then performing a heat treatment.

The preferred production conditions will be described. The homogenization treatment of the ingot is preferably performed at a temperature of 500 ° C. or more, and when the homogenization treatment is performed at a temperature of less than 500 ° C.,
Removal of ingot segregation and homogenization of the structure are not sufficient, and the solid solution of the Mg ₂ Si component contributing to the improvement of the strength is insufficient, which may lower the formability.

The cold rolling is desirably performed at a working ratio of 30% or more. If the degree of work is less than 30%, the crystal grains after the subsequent solution treatment will be coarse, and the skin tends to be rough. Decomposition of the hot-rolled structure is also likely to be insufficient, which is not preferable in terms of formability.

The solution treatment is preferably performed at a temperature of 500 ° C. or higher. When the solution treatment is performed at a temperature of less than 500 ° C., the solid solution of the precipitate becomes insufficient and sufficient strength and moldability may not be obtained. In addition, long-term treatment is required, which is not industrially preferable. The holding time is desirably 60 seconds or less, and if it exceeds 60 seconds, it is not preferable in terms of productivity.

After the solution treatment, quenching is performed. The cooling rate during quenching is not particularly specified, but is preferably 5 ° C./sec or more. In the first embodiment of the heat treatment after quenching, after quenching the alloy material to a temperature range of 120 ° C. or less, heat treatment is performed within 60 minutes at 40 to 120 ° C. for 50 hours or less (first time). (Step heat treatment) to improve paint bake hardenability. 40 ℃
If the temperature is lower than the above, the effect of improving the baking hardenability (BH property) is not sufficient, and if the temperature exceeds 120 ° C. or the time exceeds 50 hours, the moldability and the BH property may decrease.

In the second embodiment, after the above-described first-stage heat treatment, a second-stage heat treatment is further performed in a temperature range of 180 to 260 ° C. for 60 seconds or less. In the third embodiment, the second-stage heat treatment is performed directly after quenching without performing the first-stage heat treatment.

With respect to the aluminum alloy sheet produced by the above process, a zinc phosphate treatment liquid (F ^- concentration in the treatment liquid: 350 p
pm) to obtain a good chemical conversion property, but in order to obtain more excellent chemical conversion property and adhesion of the coating film in the coating process, the F ^- concentration must be reduced. The zinc phosphate treatment is preferably performed using a zinc phosphate treatment solution of 350 to 800 ppm. F ^- concentration 800p
If it exceeds pm, the zinc phosphate film becomes non-uniform and the adhesion tends to decrease.

[0026]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 An aluminum alloy having a composition shown in Table 1 was formed by DC casting, and the casting surface of the ingot was cut. Then
Homogenization treatment was performed at 550 ° C. for 8 hours, the temperature was lowered to a temperature of 420 ° C., hot rolling was started, and rolling was performed to a thickness of 4.5 mm. The end temperature of the hot rolling was 280 ° C. Next, cold rolling was performed to obtain a plate having a thickness of 1 mm.
A solution treatment was performed at 60 ° C. for 20 seconds, quenched in water at 20 ° C., and heat treated at a temperature of 100 ° C. for 4 hours within 10 minutes after quenching.

Using the obtained plate material as a test material, a tensile test and an Erichsen test were performed. Also, JIS Z237
1 was performed for 3 months, and the corrosion resistance was evaluated from the weight change before and after the test. Then, after 2% plastic deformation as simulated press working, zinc phosphate treatment (treatment solution: pH2.5~3.5, F ^- concentration 500p
pm), followed by electrodeposition coating, intermediate coating, and top coating according to the usual automotive member coating process,
For 20 minutes.

The coated test material is subjected to a tensile test, a cross cut to the base material of the aluminum alloy is performed on the test material, and a salt spray test according to JIS Z2371 is performed for 24 hours. It was left in the atmosphere for 2000 hours, and the maximum length of the thread rust generated from the cross cut portion was measured. The test results are shown in Table 2. The amount of zinc phosphate film was determined from the weight change before and after the treatment.

As can be seen from Table 2, all of the test materials according to the present invention were excellent in moldability and exhibited a molding height exceeding 10 mm in the Erichsen test. BH property after paint baking is also excellent. Sufficient film formation was also observed in the zinc phosphate treatment. Maximum thread rust length is 2mm
It shows excellent thread rust resistance at less than, and the material has excellent corrosion resistance.

[0030]

[Table 1] << Table Note >> B: ppm

[0031]

[Table 2] << Table Note >> Maximum rust length ◎: less than 1 mm ○: 1 to 2 mm Corrosion resistance ：: 3.5 g / m ² or less ：: 3.5 g / m ² or more and less than 4.5 g / m ² △: 4 g / m ² or more and less than 5 g / m ²

Comparative Example 1 An aluminum alloy having the composition shown in Table 3 was formed by DC casting, and the casting surface of the ingot was cut. Then
A homogenization treatment was performed at 550 ° C. for 8 hours.
After hot rolling and cold rolling were performed under the same conditions as in Example 1 to obtain a sheet material having a thickness of 1 mm, solution treatment was performed at 560 ° C. for 20 seconds, and quenching was performed in water at 20 ° C. as in Example 1. After one
Within 0 minutes, a heat treatment was performed at a temperature of 100 ° C. for 4 hours.

Using the obtained plate material as a test material, the properties of the material, the corrosion resistance of the material, and the properties after coating were evaluated in the same manner as in Example 1. Table 4 shows the results. In Table 3,
Those outside the conditions of the present invention are underlined. As shown in Table 4, the test material No. No. 8 has a high Zn content, so that the rust resistance after coating and the corrosion resistance of the material are inferior. Test material No. 9
Since the amount of Zn is too large, the rust resistance and the corrosion resistance of the material are inferior and the formability is poor.

Test material No. 10 has a small amount of Zn,
Poor zinc phosphate treatability. Test material No. 11 is S
Moldability is inferior due to high i content. Test material No. 12 has a large amount of Cu, so that the rust resistance after coating and the corrosion resistance of the material are not good. Test material No. 13 has a low Mg content and therefore has poor mechanical properties.

[0035]

[Table 3] << Table Note >> B: ppm

[0036]

[Table 4] "Table Note" Maximum yarn rust length ◎: less than 1mm ○: 1~2mm △: 2~4mm × : 4mm exceeds corrosion ◎: less than ^{3.5g / m 2 ○: 3.5g /} m 2 or more 4.5 g / Less than m ² Δ: 4 g / m ² or more and less than 5 g / m ² ×: 5 g / m ² or more

Example 2, Comparative Example 2 In the zinc phosphate treatment of No. 1 (plate material), the F ^- concentration in the zinc phosphate treatment solution was changed as shown in Table 5, and the zinc phosphate film amount was measured in the same manner as in Example 1. The coating and baking treatment were performed in the same manner as in Example 1, and the rust resistance was evaluated in the same manner as in Example 1. Table 5 shows the results.

[0038]

[Table 5]

As shown in Table 5, the F ^- concentration was 350 pp
No. m and a test material No. 14, 15, F ^- concentration is 300
Test material N chemically treated in a zinc phosphate treatment solution of ppm
o. As compared with No. 17, a sufficient zinc phosphate film was surely formed as a coating base, and excellent thread rust resistance was shown after coating.
Test material No. 16 F ^- is low density, the amount of zinc phosphate coating is inferior slightly even less filiform rust resistance. Test material No.
18, F zinc phosphate treatment solution ^- for the concentration is too high, easily zinc phosphate film is peeled off in a heterogeneous, filiform rust resistance is not slightly better.

Example 3 The test material No. of Example 1 was used. 1 and No. 5 ingots, 5
After homogenizing at 40 ° C. for 12 hours, hot rolling was started at a temperature of 460 ° C., and the hot rolling end temperature was set to 250 ° C., and the thickness was rolled to a thickness of 4.0 mm. Next, after performing cold rolling to obtain a plate material having a thickness of 1 mm, solution treatment was performed at 560 ° C. for 20 seconds, quenching was performed under the conditions shown in Table 6, and heat treatment was further performed.

Using the obtained plate material as a test material, a tensile test was performed to measure the proof stress. Further, after performing a 2% tensile deformation as a simulation of the press working, a coating treatment was performed in the same manner as in Example 1, a baking treatment was performed at 170 ° C. for 20 minutes, and the proof stress was measured. Table 6 shows the measurement results. As can be seen in Table 6, all of the test materials according to the present invention were:
The proof stress after painting was high and showed excellent BH properties.

The plate material (material) before coating was treated with zinc phosphate at an F ^- concentration of 400 ppm in the treatment solution, and the amount of zinc phosphate film was measured from the weight change before and after the treatment. Lump) No. The test material according to 1 is 0.
6 to 0.7 g / m ² , test material (ingot) No. The test materials according to No. 5 were 0.8 to 0.9 g / m ² , and all showed good results.

Further, a salt spray test was conducted for 3 months in accordance with JIS Z2371 and the corrosion resistance was evaluated from the change in weight before and after the test.
o. In the test material according to No. 1, 1.8 to 2.6 g / m ² (corresponding to evaluation ◎), the test material (ingot) No. In the test materials according to No. 5, it was 3.7 to 4.2 g / m ² (corresponding to evaluation ○), and all showed good results.

[0044]

[Table 6]

Comparative Example 3 Test material No. 1 and No. The ingot No. 5 was homogenized, hot-rolled, and cold-rolled under the same conditions as in Example 3 to obtain a plate having a thickness of 1 mm, and then subjected to a solution treatment at 560 ° C. for 20 seconds. Hardening under the conditions shown in
Further heat treatment was performed.

Using the obtained plate material as a test material, coating treatment was performed in the same manner as in Example 3, and the proof stress after coating was measured and compared with the proof stress of the material. Table 7 shows the results. In addition,
In Table 7, those out of the conditions of the present invention are underlined. As shown in Table 7, all of the test materials subjected to the treatment deviating from the conditions of the present invention have low proof stress after painting and baking.
BH property is not enough.

[0047]

[Table 7]

[0048]

According to the present invention, an aluminum alloy for forming and processing which is excellent in chemical conversion treatment by zinc phosphate treatment, excellent in corrosion resistance, especially good in thread rust resistance, and excellent in BH property, its production method and transport equipment A member is provided. The plate material of the aluminum alloy according to the present invention is an automotive hood,
It is particularly suitably used as a member for fenders, trunk lids, roofs, doors and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 630 C22F 1/00 630K 631 631Z 686 686B 691 691B 691C 692 692B (72) Inventor Kaoru Ueda Tokyo 5-11-3 Shimbashi, Minato-ku, Tokyo F-term (reference) in Sumitomo Light Metal Industries, Ltd. 4K026 AA09 AA22 BA04 BB07 BB08 BB09 CA13 CA23 CA28 DA15 EA17

Claims (8)

[Claims] 1. An alloy containing Si: 0.5 to 1.5% (% by weight, the same applies hereinafter), Mg: 0.2 to 1.0%, Zn: 0.05 to less than 0.3%, Fe as an impurity of 0.5% or less, and Cu of 0.05 to 0.05%.
% Or less, and the balance consists of Al and impurities. 2. Mn: 0.3% or less (excluding 0%, the same applies hereinafter), Cr: 0.3% or less, V: 0.2% or less, Z:
2. The aluminum alloy for forming according to claim 1, which contains one or more kinds of r: 0.15% or less. 3. Ti: 0.1% or less, B: 50 ppm
The aluminum alloy for forming and processing excellent in chemical conversion treatment according to claim 1 or 2, comprising one or two of the following. 4. An ingot of the aluminum alloy according to any one of claims 1 to 3, which is ingot-formed by DC casting, and hot-rolled according to a conventional method.
After performing cold rolling and solution treatment, and quenching to a temperature range of 120 ° C. or lower, 40 to 1 within 60 minutes after quenching.
A method for producing an aluminum alloy for forming and processing excellent in chemical conversion treatment, wherein heat treatment is performed at a temperature of 20 ° C. for 50 hours or less. 5. The method according to claim 5, wherein after the heat treatment is performed, the temperature is further increased to a temperature of 180 to 260 ° C.
A method for producing an aluminum alloy for forming and processing having excellent chemical conversion properties, wherein the heat treatment is performed for a time of not more than seconds. 6. The ingot of the aluminum alloy according to claim 1 is ingot-formed by DC casting, and hot-rolled according to a conventional method.
Perform cold rolling and solution treatment, and after quenching,
A method for producing an aluminum alloy for forming and processing excellent in chemical conversion treatment, wherein a heat treatment is performed at a temperature of 260 ° C. for a time of 60 seconds or less. 7. An aluminum alloy sheet produced by the method of claim 4 to 6, F ^- excellent chemical conversion treatability, which comprises zinc phosphate treatment in the processing solution containing concentrations 350~800ppm Manufacturing method of aluminum alloy for forming. 8. A member for transportation equipment, comprising the aluminum alloy plate according to claim 1. Description: