JP2799114B2 - Aluminum alloy plate with excellent press workability - Google Patents

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 used for an automobile body.

[0002]

2. Description of the Related Art Recently, there has been an increasing need to reduce the weight of an automobile body due to global environmental problems, and the use of a high-strength steel sheet having a reduced thickness or the use of an aluminum alloy sheet having a low specific gravity has been studied. Has already been put into practical use. However, aluminum alloy sheets are particularly poor in mechanical properties compared to conventional thin steel sheets. For example, the r value, which is a deep drawing index that governs press workability, is 0.6 to
0.8, which is less than half that of a thin steel sheet, and the elongation El, which is one of the indices of overhang property, is as small as about 60 to 80% as compared with the conventional material. Therefore, the actual condition is that the parts to be used are limited to bonnets or the like that require only a slight processing.

On the other hand, for example, Japanese Patent Application Laid-Open No.
No. 452 discloses a method for producing an aluminum alloy sheet whose elongation El is improved by adding high Mg. In this method, it is also a necessary condition that impurities such as Fe and Si that generate intermetallic compounds and deteriorate elongation are reduced as much as possible. For that purpose, it is necessary to use expensive high-purity aluminum metal. However, even if such a method is used, the elongation is at most 40%, which is about 80% of the conventional thin steel sheet, and the r value which is an index value of deep drawing is hardly improved.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an aluminum alloy plate having good workability.

[0005]

Means for Solving the Problems The present inventors have conducted various studies on factors governing press workability and found an aluminum alloy plate having good workability. That is, according to the present invention, the surface roughness of an aluminum alloy plate containing 3 to 8 wt% of Mg or an aluminum alloy plate containing 0.5 to 3 wt% of Mg + Si is reduced to 0.1 to 0. 0 by cold rolling or skin pass. An object of the present invention is to provide an aluminum alloy plate excellent in press workability, characterized in that the thickness is adjusted to 6 μm and a solid lubricating film is applied to the surface thereof.

Hereinafter, the present invention will be described in more detail. First, the reasons for limiting the chemical components in the present invention will be described. One of the aluminum alloys targeted by the present invention is Mg
Is contained in an amount of 3 to 8 wt%, the lower limit of which is defined by the required strength of the automobile body,
If the amount of Mg is less than 3 wt%, the required strength cannot be obtained because the solid solution strengthening mechanism of Mg atoms cannot be sufficiently exhibited. In addition, the upper limit is limited due to manufacturing problems such as deterioration of workability (cracking) during casting and hot rolling.

On the other hand, another aluminum alloy targeted by the present invention is characterized by containing 0.5 to 3 wt% of Mg + Si. The above-mentioned materials are mainly used for the inner plate portion of the automobile body, and this material is mainly used for the outer plate portion. The biggest difference between the two is that when the latter is heated to a predetermined temperature after being strained, it exhibits a so-called bake hardening property in which the yield stress increases due to the effects of the added elements Mg and Si. This effect is imparted in the process of coating and subsequently baking a material that has been pressed on an automobile production line. During the press working, the softer one is more easily adapted to the shape of the mold and the elastic recovery is small, so that it is applied to the outer plate having a severe shape. However, since the required strength described above cannot be obtained, it is necessary to harden in the subsequent baking process. The amount of Mg + Si is 0.5 to 3% by weight from the viewpoint of securing the bake hardness and press workability.
Stipulated.

Next, the roughness of the material surface and the lubricant will be described below. First, the factors governing the press workability will be described. The two main factors are the mechanical properties of the material described above and the friction between the die and the material surface during the press working. As illustrated in FIG. 1, in actual press working, the punch 4 rises after sandwiching the thin sheet material 3 between the die 1 and the wrinkle retainer 2 with a predetermined wrinkle retainer load, and forms a part 5 as illustrated in FIG. 2. I do. As shown in FIG. 1, the material 3 is drawn along with the punch stroke between the die 1 and the wrinkle holder 2, and past the die shoulder. If the pull-in resistance at this time is higher than the breaking resistance of the material, the material breaks and a desired product cannot be obtained. Therefore, a material having a small pull-in resistance and a large breaking limit load, which is a breaking resistance of the material, has excellent press workability. Mechanical properties are also related to the mode of deformation of the material. For example, the larger the r value is, the greater the breaking limit load increases, and the lower the shrinkage flange deformation resistance under the die. Also, regardless of the deformation mode, the smaller the coefficient of friction between the mold and the material, the lower the draw-in resistance and the better the press workability. As described in the prior art, the mechanical properties cannot be expected to be significantly improved, and the focus here is on how the coefficient of friction with the mold can be reduced.

Factors related to friction include the surface roughness of the material and the lubricant. The result of examining the friction coefficient with this combination will be described below. The material used for the experiment was 1.
A 2 mm JIS5182 aluminum alloy plate,
Mg content is 4.5 wt%. The surface roughness (average roughness Ra) was adjusted to 0.2 to 1.2 μm by skin pass rolling. The lubricant is a low-viscosity (4 centistokes) washing oil (oil coat RL55, manufactured by Idemitsu Kosan Co., Ltd.) used in a normal press line of an automobile panel, and a solid lubricant (Kao) whose main component is solid wax. Kao Lube W2 manufactured by Co., Ltd.) was used. The same amount of cleaning oil as the press line was applied to the front and back surfaces of the material. Solid lubricants are
A range in which no uneven coating or peeling of the lubricating film occurs during pressing was selected, and 0.4 ± 0.1 g / m ² was applied per side.

In the friction test, as shown in FIG. 3, a tool 10 is pressed against the front and back surfaces of an aluminum alloy plate 12 with a predetermined surface pressure and P, and the end of the plate is gripped by a chuck 11 to be 25 mm / s.
Withdrawing at a speed of ec, the pulling load at this time, D, was measured with a load cell 13 connected to the back of the chuck. The friction coefficient μ was determined by μ = D / (2P). FIG. 4 shows that the solid lubricant was added to the material having the changed surface roughness by 0.4% per side.
The measurement results of the friction coefficient μ when g / m ² was applied and when the cleaning oil was applied are shown. The surface pressure P was 5 kgf / mm ² . When the surface roughness of the material is small, μ shows a very large value when the cleaning oil is used, but it turns out that when a solid lubricant is used, it shows a very small μ.

When the surface roughness increases, μ in the case of using a solid lubricant increases, and conversely, μ in the case of using a cleaning oil.
It can be seen that is reduced. When SRa exceeds 0.6 μm, μ of the cleaning oil and the solid lubricant show almost the same value, and the effectiveness of the solid lubricant is reduced. Therefore, when the surface roughness is 0.6
Applying a solid lubricant to a material having a size of not more than μm is effective for press workability. Also, the smaller the surface roughness, the more beautiful the surface after painting. Reducing the surface roughness of the material as shown in FIG. 4 sufficiently exerts the effect of the solid lubricant and is advantageous for press workability. However, scratches and the like occur on the surface due to handling of the material, and Since it is conspicuous, it may remain as a product surface defect. Further, if μ is reduced too much, the pull-in resistance described with reference to FIG. 1 may become too small, and conversely, defects such as wrinkles may occur. For the above reasons, a surface roughness of less than 0.1 μm is not preferred.

[0012]

EXAMPLES The effects of the present invention will be described below with reference to examples. (Example 1) Of the materials used in the above experiments, materials having surface roughnesses of 0.3 μm and 0.9 μm were used to mold inner plate parts of automobiles. The amount of the lubricant applied was the same as in the experiment, the wrinkle holding load was changed, and the evaluation was made based on the limit wrinkle holding load at which breakage occurred. Table 1 shows the results. ○ indicates that molding was possible without breakage, and X indicates that breakage occurred. In addition, △ indicates that some necking has occurred. In the case of the material of the present invention, it is possible to mold up to a wrinkle holding load of 17.5 tons, whereas the wrinkle holding load of a material having a large roughness is 7.5 tons. Further, when the cleaning oil was applied, cracking occurred even at 5 tons regardless of the roughness.

[0013]

[0014]

According to the present invention, by adjusting the surface roughness of an aluminum alloy plate having an appropriately selected content of Mg or Mg + Si and coating it with a solid lubricating film, an aluminum alloy plate having good press workability can be obtained. This is particularly preferred for application to automobile bodies and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a pressing step.

FIG. 2 is a perspective view of an example of a product obtained after pressing.

FIG. 3 is a view showing the entire friction test apparatus.

FIG. 4 is a graph showing the results of a friction test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Wrinkle holder 3 Thin plate material 4 Punch 5 Parts 10 Press tool for friction test 11 Chuck 12 Aluminum alloy plate 13 Load cell

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Hashiguchi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Headquarters, Kawasaki Steel Works (72) Inventor Yoshihiro Matsumoto Kawasaki, Chuo-ku, Chiba City, Chiba Prefecture No. 1, Kawasaki Steel Engineering Co., Ltd. (72) Inventor Kenichi Ogura 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Aluminum Industry Co., Ltd. (72) Inventor Susumu Yasunaga Taku, Saitama 1-4-1, Chuo, Honda R & D Co., Ltd. (72) Inventor Yoshihisa Saeki 1-4-1, Chuo, Wako, Saitama Pref. Honda R & D Co., Ltd. (72) Minoru Makita Wako, Saitama 1-4-1 Chuo-shi, Ichigo Honda R & D Co., Ltd. (72) Inventor Noboru Hayashi 1-4-1 Chuo Wako-shi, Saitama Pref. House (56) Reference Patent Sho 62-81221 (JP, A) JP flat 2-211902 (JP, A) (58 ) investigated the field (Int.Cl. ^6, DB name) B21B 1/22 - 1 / 28 B21B 3/00 B21D 22/20

Claims (2)

(57) [Claims] 1. An aluminum alloy sheet containing 3 to 8 wt% of Mg, the surface roughness of which is adjusted to 0.1 to 0.6 μm by cold rolling or skin pass, and a solid lubricating film is applied to the surface. Aluminum alloy plate with excellent press workability characterized by the following. 2. An aluminum alloy sheet containing 0.5% to 3% by weight of Mg + Si is adjusted to have a surface roughness of 0.1 to 0.6 μm by cold rolling or skin pass, and a solid lubricating film is applied to the surface. An aluminum alloy sheet with excellent press workability, characterized in that: