JP3234511B2 - Method of manufacturing Al alloy plate for high speed forming and method of high speed forming of Al alloy plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an Al alloy sheet for high-speed forming and a method for forming an Al alloy sheet at a high speed. A suitable for high-speed molding such as
1. Field of the Invention The present invention relates to a method for manufacturing a 1-alloy plate and a high-speed forming method for the plate. In this specification, the content of the additional element in the Al alloy means mass%, but this is simply described as%.

[0002]

2. Description of the Related Art In many cases, an automobile outer panel, a chassis for home electric appliances, and the like are formed into products by baking and coating after forming the plate. Al-Mg-Si (-Cu) alloys have relatively good corrosion resistance and moldability, and age harden (bake hard, BH) by heating such as baking coating. There is. Further, in the case of a product having a shape that is difficult to form, an Al-Mg-based alloy that is more excellent in formability than a Δl-Mg-Si (-Cu) -based alloy is generally used.

[0003] In recent years, the weight and size of automobiles and home electric appliances have been further reduced, and as a result, the weight and thickness of parts and the complexity of shapes have been advanced, and materials having high strength and excellent moldability have been developed by automakers. It has been demanded by home appliance manufacturers. In order to meet such demands, a technique has been disclosed in which the properties are improved by defining an alloy composition or a special manufacturing method (for example, Japanese Patent Application Laid-Open No. HEI 5-11283).
9, JP-A-5-112840). However, in these techniques, the evaluation of the plate is performed by a normal tensile test, Erichsen test, etc., and these evaluations show that the strain rate of the material is lower than that of a press forming method that is often practiced industrially. This was a test, and so to say, the alloy composition and the manufacturing method were defined by an indirect evaluation method.

When the strain rates are actually compared, the rate of increase in strain at the time of tensile strength measurement in a tensile test (JIS Z 2241) is 80% / min or less, and the strain rate is 1.3 × 10 ^{− 2} s ⁻¹ or less. The punch speed in the Erichsen test (JIS Z 2247) is 5
Assuming that the Erichsen value is about 10 mm and the elongation at the fractured portion is about 30%, the strain rate in that region is 1.0 × 10 ⁻² s ⁻¹ or less. The strain rate during actual press molding differs depending on the drive system of the press machine. However, in the case of a mechanical drive system (such as a crank press) that is superior in terms of initial capital investment cost and productivity compared to a hydraulic drive system, the average It is considered that the punching stroke speed is 100 mm / s or more and the molding height is about 100 mm to 500 mm, and the strain rate at the risk of fracture such as the shoulder of the punch is 5 × 10 ⁻² s ⁻¹ or more. Can be Therefore, depending on the material, although the formability is excellent in the region where the strain rate is low, the formability may be inferior in the region where the strain rate is close to actual press molding. The effect of the strain rate on the formability is not so large in the case of Al-Mg-based alloys which have been frequently used as conventional forming alloys, and it is problematic to evaluate by low strain rate tests in predicting the formability. I never did.

[0005] Recently, Al-Mg-Si (-Cu)
The problem that the formability of a system alloy is reduced in a high strain rate region has been recognized, and a technique for defining the alloy composition in order to avoid this problem has been disclosed (JP-A-8-18884).
2). However, in this technique, the alloy composition is determined by simply changing the alloy composition and evaluating the high-speed overhang property, and high-speed drawability, which is important when molding an automobile body sheet or the like, has not been studied.

[0006]

As described above, Al-
In an Al-Mg-Si (-Cu) -based alloy that has a possibility to achieve both higher strength and formability than a Mg-based alloy, the formability in a high strain rate region tends to be lower than that in a low strain rate region. Therefore, even if alloys are developed by evaluating the formability by conventional tensile tests and Erichsen tests, there is a problem that it is difficult to form with a crank press or the like which is excellent in cost and productivity. . Against this background, rather than evaluating formability by indirect methods such as conventional low-strain-rate tensile tests and Erichsen tests, it is necessary to understand the deformation behavior of materials during high-speed molding, and to provide a mechanical support. There is a demand for a technique for improving the actual press formability of an Al-Mg-Si (-Cu) -based alloy that is originally superior in strength in terms of strength by performing evaluation using the above method. An object of the present invention is to find a method for producing an Al alloy sheet suitable for high-speed forming, and to find a high-speed forming method for an Al alloy sheet.

[0007]

According to the present invention, as a result of various studies on the above-mentioned problems, it has been found that an Al-Al alloy having excellent strength and excellent high-speed press formability by using a crank press or the like.
A method for producing an Mg-Si-Cu-based alloy sheet and a high-speed forming method thereof have been developed.

[0008] That is, the invention of claim 1 for solving the above-mentioned problem is characterized in that Mg: 0.75 to 0.95% (mass).
%, The same applies hereinafter), Si: 0.45 to 0.95%, Cu:
1.3 to 1.7% is contained as an essential element, and Mn: 0.1 to 1.0%.
02-2.0%, Cr: 0.02-0.5%, Zr:
0.02 to 0.3%, one or more of Ti: 0.003 to 0.2%, Zn: 0 to 1.0%, and Fe as an impurity: 0.5% or less. The balance is substantially Al
After performing a solution treatment in the range of 500 ° C. or more and the melting temperature or less, the Al alloy plate is rapidly cooled to a temperature range of 40 ° C. to 175 ° C. at a cooling rate of 100 ° C./min or more. And then cooled to room temperature, or kept in a temperature range of 40 to 175 ° C. within 36 hours, and then cooled to room temperature.
By performing room temperature aging for not less than one week, as a characteristic of the plate, elongation is 30% or more in a tensile test with a strain rate of 5 × 10 ⁻² s ⁻¹ or more, and (tensile strength) ² /(0.2% proof stress). ) ≧ 480 (MPa).

According to a second aspect of the present invention, there is provided the method according to the second aspect, wherein Mg: 0.75-0.
95% (mass%, the same applies hereinafter), Si: 0.45 to
0.95%, Cu: 1.3-1.7% as essential elements, Mn: 0.02-2.0%, Cr: 0.02-
0.5%, Zr: 0.02-0.3%, Ti: 0.00
3 to 0.2%, and at least one of Zn: 0 to 1.
0%, Fe: 0.5% or less as an impurity, and the balance is substantially 500.
After performing the solution treatment in the range of not less than ℃ and melting temperature,
It is rapidly cooled to a temperature of 175 ° C. or less at a cooling rate of 00 ° C./min or more, and then reheated to 180 to 320 ° C.
After holding for 5 minutes, the sample was cooled to room temperature and then aged for 2 weeks or more at room temperature. As a property of the plate, the elongation was 30% in a tensile test at a strain rate of 5 × 10 ⁻² s ⁻¹ or more.
% Or more and (tensile strength) ² /(0.2% proof stress) ≧ 4
Al for high-speed molding characterized by being 80 (MPa)
This is a method for manufacturing an alloy plate.

According to a third aspect of the present invention, there is provided a method for manufacturing an Al alloy sheet for high-speed forming according to the first or second aspect.
The average punch stroke speed is 100
This is a high-speed forming method of an Al alloy plate, wherein high-speed forming at a speed of not less than mm / s is performed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Among the above-mentioned inventions, the inventions of claims 1 and 2 are Al alloy sheets for high-speed forming suitable for high-speed forming and excellent in curability (baked hard, BH) in baking coating. The invention of claim 3 relates to a high-speed molding method using the plate. Hereinafter, the respective inventions will be described in detail.

(1) Al alloy plate used in the method of the present invention First, the reason why the alloy composition of the Al alloy plate used in the present invention is limited as described above will be described. Mg and Si
Both precipitate Mg ₂ Si and contribute to the improvement of high-speed formability. Further, Cu contributes to improvement in strength, ductility, and high-speed moldability. The added amount is 0.75 to 0.95, respectively.
%, 0.45 to 0.95%, and 1.3 to 1.7%, the reason is that in a high-speed tensile test of a plate manufactured by a manufacturing method described below, elongation ≧ 30%, (tensile strength Sa) ² /
(0.2% proof stress) ≧ 480 (MPa).

[0015] Zn is added as necessary for the purpose of improving the strength similarly to Cu. 0-1.0%
The reason is that if the upper limit is exceeded, the high-speed formability after the solution treatment is reduced and the quenching sensitivity is further increased. In addition, 0% here means the case where it is not added. Mn, Cr, Zr, and Ti each contain 1
Add more than seeds. The reason for limiting the amount of addition in each range is that the effect is small below the lower limit, and if it exceeds the upper limit, the high-speed formability after solution treatment is reduced, the compound with Si is easily formed, and age hardening is performed. This is to reduce the properties. Fe is generally contained as an impurity in an Al metal and forms a crystallized product of an Al—Fe system or a Δ1-Fe—Si system. If the content exceeds 0.5%, ductility and high-speed formability deteriorate. The content is desirably 0.5% or less. In addition, B, which is usually added as a refiner of the cast structure, does not impair the effects of the present invention as long as it is added in an amount of 0.1% or less.

The composition of the Al alloy used in the method of the present invention is as described above. The sheet according to the method of the present invention has a characteristic that the elongation is 30% or more in a tensile test at a strain rate of 5 × 10 ⁻² s ⁻¹ or more. And (tensile strength) ² /(0.2%
(Proof stress) ≧ 480 (MPa). If the elongation is less than 30%, the ductility is insufficient, and the stretchability during high-speed molding is poor. On the other hand (tensile strength) ² /
In the case of (0.2% proof stress) <480 (MPa), the inflow resistance of the flange portion is relatively high, or the strength is insufficient to withstand the material being pulled in by the punch.
Poor drawability during high speed molding.

The high-speed forming of an Al alloy sheet for high-speed forming means that the punch stroke speed in press forming or the like is 10 or more.
High-speed forming such as ⁰ mm / s or more (strain speed of 5 × 10 ⁻² s ⁻¹ or more) is meant. The Al alloy plate having the above features has excellent stretch formability and draw formability in high-speed forming, and also has excellent curability (bake hard, BH) in baking coating.

(2) Regarding the production method according to the invention of claim 1.2, the Al alloy plate having the alloy composition used in the method of the invention is:
It is manufactured by conventional semi-continuous casting, homogenization treatment, hot rolling, cold rolling or by direct casting and rolling. Before and after each step, a homogenizing heat treatment or an annealing treatment can be appropriately performed. First, the Al manufactured as described above is used.
The alloy plate is subjected to a solution treatment in a temperature range of not less than 500 ° C. and not more than a melting temperature, and then rapidly cooled to a temperature range of 40 to 175 ° C. at a cooling rate of 100 ° C./min or more. In this case, the temperature is rapidly cooled to 175 ° C. or less.

By the above-mentioned solution treatment, Si, Mg,
An additive element such as Cu is once dissolved in the matrix, and a fine reinforcing phase is precipitated during the subsequent baking heating, thereby improving the strength. The reason for setting the solution treatment temperature to 500 ° C. or higher is that if the temperature is lower than 500 ° C., the added element cannot be sufficiently solid-dissolved, and the strength improvement during baking coating is reduced. The first purpose of setting the cooling rate to 100 ° C./min or more is to suppress precipitation of coarse compounds during cooling to prevent a decrease in high-speed moldability.
If it is less than n, the solid solution amount of the additional element decreases, so that the strength in the subsequent baking coating step is not sufficiently increased, and the characteristics of the present alloy cannot be fully utilized.

Next, the Al alloy plate is subjected to 40 to 175
Coiled in a temperature range of ° C. and then cooled to room temperature, or cooled to room temperature after being kept in a temperature range of 40 to 175 ° C. for 36 hours or less (the manufacturing method of claim 1). Alternatively, the Al alloy plate is heated at 180 to 320 ° C.
Then, the mixture is kept at 0 to 25 minutes and cooled to room temperature (the method of claim 2). These processes are performed
In any case, it is to increase the strength increase after painting baking heating.

Further, the Al alloy plate treated as described above is allowed to stand at room temperature for 2 weeks or more to allow natural aging to proceed, thereby increasing proof stress and tensile strength and improving high-speed formability. Improve. The amount of increase in proof stress and tensile strength due to aging at room temperature differs depending on the alloy composition, but is estimated to be about 20% each, and as a result, is an index of high-speed formability (tensile strength) ² /
The value of (0.2% proof stress) will increase by about 20%. The reason why the room temperature aging is set to two weeks or more is that the tensile strength is not sufficiently increased within two weeks, and the value of (tensile strength) ² /(0.2% proof stress) which is an index of high-speed moldability is used. This is because the increase is insufficient.

In the production method of the present invention, there is no particular limitation on the room temperature standing time from the solution treatment to the rapid cooling to the reheating treatment at 180 to 320 ° C. The effect is not impaired even if the reheating treatment is performed.

(3) The high-speed forming method according to the third aspect is characterized in that high-speed forming with an average punch stroke speed of 100 mm / s or more is performed using the Al alloy plate for high-speed forming manufactured as described above. Things. The purpose of this high-speed forming method is to provide a highly formable alloy sheet that can be formed by a low-cost and highly productive pressing method.
As described above, the average punch stroke speed is 100 mm /
When high-speed molding of s or more is performed, a mechanically driven press machine that is excellent in cost and productivity can be used. The strain rate at the time of molding varies greatly depending on the part of the material. However, when the molding height is about 100 mm to 500 mm, the strain rate at the fracture risk site such as the punch shoulder where the strain rate becomes the largest becomes large. The strain rate is 5 × 10
⁻² s ⁻¹ or more, and the Al composition
It is very effective to use an alloy plate. However, in general, the formability of an Al—Mg—Si (—Cu) -based alloy plate tends to deteriorate as the strain rate increases. Therefore, the alloy plate having the above-described alloy composition has a thickness of 5 × 10 ⁻² s. ^{Even in} a low strain rate region of less than ^-1 , sufficiently high formability is exhibited.

[0022]

Next, examples of the present invention (examples of the present invention) will be described in more detail together with comparative examples. An Al-Mg-Si-Cu alloy ingot having the composition shown in Table 1 was subjected to homogenization, hot rolling, cold rolling and the like by a conventional method to produce a 1 mm thick plate. Table 2 shows the details of the manufacturing conditions.

[0023]

[Table 1]

[0024]

[Table 2]

The plate manufactured as described above was subjected to a tensile test, a high-speed overhang test, and a high-speed deep drawing test. Table 3 shows the results. The tensile test was performed at two different tensile speeds. In both tests, a plate-shaped test piece having a parallel portion length of 16 mm was used, and the tensile speed was 10 mm / min.
(Initial strain rate: 1.04 × 10 ⁻² s ⁻¹ ) and 10
0 mm / min (initial strain rate: 1.04 × 10 ⁻¹ s)
^-1 ), and the tensile strength, proof stress, and elongation were measured. In addition, after heating under the conditions of Table 2 at 170 ° C. for 60 minutes to simulate a paint baking treatment after production, a tensile test at a normal tensile speed was performed, and bake hard (BH) properties were also evaluated. High speed overhang test is punch diameter φ50mm, blank diameter φ120mm, high speed deep drawing test is punch diameter φ40m
m, the blank diameter was 84 mm, and the cleaning oil was applied. The punching speed was 200 mm / s, and the breaking height (mm) was determined.

[0026]

[Table 3]

As is evident from Table 3, the method (B, D) for producing an Al alloy sheet of the present invention has excellent high-speed tensile properties and, consequently, excellent high-speed formability (extension molding and drawing). It can be seen that there is no problem with the bake hard (BH) property. In contrast, Comparative Example (EK) which deviates from the composition specified by the method of the present invention or deviates from the production conditions of the present invention
It can be seen that the high-speed tensile properties are inferior even if the tensile properties are usually excellent, and the high-speed moldability also shows a low value.

[0028]

As described above, the Al for high-speed molding according to the present invention is described.
According to the alloy plate manufacturing method and the high-speed forming method, high strength
Al-M with high BH and excellent high-speed press formability
The present invention provides a g-Si-Cu-based alloy plate, a method for manufacturing the plate, and a high-speed forming technique, and has an industrially remarkable effect.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 691 C22F 1/00 691C 692 692A 694 694B (72) Inventor Yoshihiro Matsumoto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (72) Inventor Koichi Hashiguchi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Engineering Co., Ltd. (56) References JP-A-7-305135 (JP, A) JP-A-8 -269608 (JP, A) JP-A-8-188842 (JP, A) JP-A-8-31625 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22F 1/04- 1/057 C22C 21/00-21/18

Claims (3)

(57) [Claims] 1. Mg: 0.75 to 0.95% (mass)
%, The same applies hereinafter), Si: 0.45 to 0.95%, Cu:
1.3 to 1.7% is contained as an essential element, and Mn: 0.1 to 1.0%.
02-2.0%, Cr: 0.02-0.5%, Zr:
0.02 to 0.3%, one or more of Ti: 0.003 to 0.2%, Zn: 0 to 1.0%, and Fe as an impurity: 0.5% or less. The balance is substantially Al
After performing a solution treatment in the range of 500 ° C. or higher and the melting temperature or lower, the Al alloy plate is rapidly cooled to a temperature range of 40 ° C. to 175 ° C. at a cooling rate of 100 ° C./min or higher. And then cooled to room temperature or kept in a temperature range of 40 to 175 ° C. within 36 hours, and then cooled to room temperature.
By performing room temperature aging for not less than one week, as a characteristic of the plate, elongation is 30% or more in a tensile test with a strain rate of 5 × 10 ⁻² s ⁻¹ or more, and (tensile strength) ² /(0.2% proof stress). A method for producing an Al alloy sheet for high-speed forming, wherein ≧ 480 (MPa). 2. Mg: 0.75 to 0.95% (mass)
%, The same applies hereinafter), Si: 0.45 to 0.95%, Cu:
1.3 to 1.7% is contained as an essential element, and Mn: 0.1 to 1.0%.
02-2.0%, Cr: 0.02-0.5%, Zr:
0.02 to 0.3%, one or more of Ti: 0.003 to 0.2%, Zn: 0 to 1.0%, and Fe as an impurity: 0.5% or less. The balance is substantially Al
After performing a solution treatment in the range of 500 ° C. or higher and the melting temperature or lower, the aluminum alloy plate is rapidly cooled to a temperature of 175 ° C. or lower at a cooling rate of 100 ° C./min or higher, and then reheated to 180 to 320 ° C. After holding for 0 to 25 minutes and then cooling to room temperature, and then aging for 2 weeks or more at room temperature, the strain rate of 5 × 10 ⁻² s was obtained as a characteristic of the plate.
^In tensile test of ⁻¹ or more, elongation is 30% or more, and (tensile strength) ² /(0.2% proof stress) ≧ 480 (MPa)
A method for producing an A1 alloy sheet for high-speed forming. 3. The Al for high-speed molding according to claim 1 or 2.
A high-speed forming method of an Al alloy plate, wherein high-speed forming is performed at an average punch stroke speed of 100 mm / s or more using an Al alloy plate manufactured by the method for manufacturing an alloy plate.