JP3087090B2 - Bake hardening type surface treated aluminum alloy sheet excellent in formability and method for producing the same - 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 sheet mainly used as a lightweight material for automobiles, and more particularly to a bake hardening type surface-treated aluminum alloy sheet having excellent press formability and a method for producing the same.

[0002]

_2. Description of the Related Art Lightening of automobiles has been actively promoted from the viewpoints of energy saving, global environmental problems due to CO ₂ , etc. Among them, aluminum or aluminum is considered in terms of material reliability, workability, recycling and the like. Alloys have been in the limelight and are being used extensively in recent years.

[0003] However, aluminum alloy sheets have different characteristics as compared with steel sheets that have been frequently used in the past, and therefore have many problems when applied to automobile bodies. A typical example is press molding. Taking SPCC as an example of a steel sheet, the limit drawing LDR is 45% elongation and r value is 1.4.
Reaches 2.15, while the aluminum alloy plate
Taking SA A1822 as an example, elongation is 30%, r value is 0.7
And the LDR reaches only 1.8. Further, in the case of a bake hardening type aluminum alloy sheet whose strength is increased by the additional heat of paint baking after press forming, the formability is further lower, for example, JIS A
In 6009-T4, elongation is 25%, r value is 0.7, LD
R1.9. As described above, since the formability of the aluminum alloy sheet is remarkably inferior, application to an automobile body has been greatly restricted. That is, the application example of the aluminum alloy plate to the vehicle body panel is limited to a lightly processed member such as a hood, and cannot be applied to a more complicated member with a strong processing.

[0004] Since aluminum alloys have only recently been put into practical use as mass-produced products by press molding such as automobiles, no proposal or appropriate means for solving the above problems has been found, and these problems have been solved. At present, production is carried while holding the vehicle, and as a result, it has become difficult to achieve a reduction in body weight, which is a social requirement.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a bake hardening type which has significantly improved press formability as compared with conventional aluminum or aluminum alloy sheets, and can be manufactured easily, industrially, stably and economically. It is an object of the present invention to provide a surface-treated aluminum alloy sheet and a method for producing the same.

[0006]

As a result of intensive studies on the causes of the poor press formability of aluminum alloy sheets, especially bake hardening type aluminum alloy sheets, the material represented by the above-mentioned elongation characteristics is remarkably inferior to steel sheets. In addition, it has been found that the sliding properties of aluminum alloy plates are different from those of steel plates. That result of examining the surface pressure dependency of the coefficient of friction during sliding surface pressure dependence in the steel sheet as shown in FIG. 1 (eye
The surface pressure dependency (weight per unit area ) of the aluminum alloy plate was smaller than that of the aluminum alloy plate at which the difference between μ and ▲ at the application weight of 0 g / m ² was small.
( The difference between μ shown by ○ and ● when the amount is 0 g / m ² ) is very large. At low surface pressure side friction coefficient of the aluminum alloy plate is about the same as the friction coefficient of the steel sheet (eye
The difference between μ indicated by ○ and Δ when the applied weight is 0 g / m ² )
As the surface pressure increases, the friction coefficient of the aluminum alloy plate decreases and the difference from the steel plate increases (when the basis weight is 0 g / m ² ).
The difference between μ shown by ● and ▲) .

Based on this finding, the present invention has conducted intensive studies to improve the press formability of the aluminum alloy sheet, and as a result, has completed the present invention. That is, the present invention
By improving the elongation characteristics of the aluminum alloy sheet and simultaneously applying iron-based plating containing iron as a main component to the surface of the aluminum alloy sheet, the press formability is remarkably improved.

That is, according to the present invention, the elongation is 25% or more,
The difference between the friction coefficient when the friction coefficient is 0.13 or less and the surface pressure is 1 kgf / m ² and the friction coefficient when the surface pressure is 4 kgf / m ² is 0.0
A bake-hardening type surface-treated aluminum alloy sheet having excellent formability of 15 or less, wherein Mg and Si are made of Mg ₂ S
At least one plating layer is provided on the surface of a bake hardened aluminum alloy plate containing 0.4 wt% or more corresponding to i, and the outermost plating layer is an Fe-based plating layer, and the basis weight is
An object of the present invention is to provide a bake hardening type surface-treated aluminum alloy sheet excellent in formability, characterized in that the thickness is 5 to 50 g / m ² .

Further, according to the present invention, the difference between the coefficient of friction when the elongation is 25% or more, the coefficient of friction is 0.13 or less and the surface pressure is 1 kgf / m ² and the surface pressure is 4 kgf / m ² is 0.015.
When producing a bake-hardened surface-treated aluminum alloy sheet having excellent formability,
Annealed at 480 ° C. or higher temperatures an aluminum alloy plate containing more than 0.4 wt% in ₂ Si equivalent, then a single layer or two-layer outermost plating layer is Fe-plated basis weight 5 to 50 g / m ² An object of the present invention is to provide a method for producing a bake hardening type surface-treated aluminum alloy sheet having excellent formability, characterized by forming a plating layer comprising the above.

Further, the present invention provides that the difference in friction coefficient between the case where the elongation is 25% or more, the friction coefficient is 0.13 or less and the surface pressure is 1 kgf / m ² and the surface pressure is 4 kgf / m ² is 0.01.
When producing a bake-hardening type surface-treated aluminum alloy sheet having excellent formability of 5 or less, Mg and Si are converted to M
an aluminum alloy plate containing 0.4 wt% or more equivalent to g ₂ Si, forming a plating layer composed of a single layer or two or more layers in which the outermost plating layer is Fe-based plating with a basis weight of 5 to 50 g / m ² , Next, the present invention provides a method for producing a bake hardening type surface-treated aluminum alloy sheet having excellent formability, which is subjected to annealing at a temperature of 480 ° C. or higher.

[0011]

The present invention will be described below in more detail. The aluminum alloy plate as a material to be plated, which is one of the constituent elements of the present invention, contains Mg and Si as additive elements in an amount of 0.4 wt% or more, corresponding to Mg ₂ Si, for the reasons described later.

The iron-based plating containing iron as a main component, which is another component of the present invention, includes Fe plating and F
ep plating, Fe-C plating, Fe-B plating, Fe
-Zn alloy plating, Fe-Ni alloy plating, or other iron alloy plating. The iron-based plating needs to be on the outermost surface that comes into contact with the mold during press forming of the aluminum alloy plate. Therefore, the plating layer on the aluminum alloy plate may be a single layer or multiple layers, but the outermost layer plating is limited to iron-based plating in a single layer or two or more layers. In plating of two or more layers, the type of lower layer plating is not particularly limited, but iron or zinc is preferred. Also,
The means for plating may be any means such as electroplating, chemical plating, displacement plating, vapor deposition plating or cladding, and the means is not particularly limited.

When the above-described iron-based plating is applied to the outermost surface of an aluminum alloy plate and an effect of improving press formability is expected, as shown in FIG. 1, the basis weight of the iron-based plating is 5 g / m ^2.
As described above, the friction coefficient becomes 0.13 or less, and at the same time, the surface pressure dependency of the friction coefficient also becomes small. Also the basis weight is 50g
/ M ² , no further effect can be expected, and in addition, various materials and energy are wasted economically. Therefore, the preferred basis weight of the iron-based plating is 5 to 50 g / m ^2.
It is. Furthermore, even if the friction coefficient is 0.13 or less, if the elongation of the aluminum alloy sheet material is low (△: 22%), the improvement of the formability becomes insufficient as shown in FIG. Therefore, the elongation of the material is specified to be 25% or more (○: 26%, ●: 30%).

Further, bake hardenability is 180 ° C., a heating for 60 minutes, it is desirable that the strength change before and after heating is 7 kgf / mm ² or more, 0.4 wt in Mg ₂ Si in order that
% Must be contained. Mg ₂ Si at this time
Need to be dissolved during press molding and be precipitated as Mg ₂ Si during heating. As a means for dissolving Mg and Si, it is necessary to heat to a temperature of 480 ° C. or higher. May be before or after plating.

[0015]

Next, the present invention will be specifically described based on examples.

(Example 1) Mg 0.4 wt %, Si 0.8% (Al-0.63% M
g ₂ and Si-0.57% Si) aluminum alloy plate test piece containing, as a comparative material a material obtained by 450 ° C. annealing (22% elongation), 500 ° C. annealing (26% elongation), 55
An aluminum alloy plate (each having a thickness of 1.0 mm) annealed at 0 ° C. (elongation: 30%) was subjected to iron plating shown in Table 1. As comparative materials, Mg 0.2% and Si 0.4% (A
A material (elongation: 28%) obtained by annealing an aluminum alloy plate containing 1-0.31% Mg ₂ Si-0.28% Si) at 500 ° C. was similarly subjected to iron-based plating. For these materials, cup molding was performed at the same time as the coefficient of friction was measured. Table 1 shows the results. Further, regarding the bake hardenability, each test material was heated at 180 ° C. for 60 minutes, and the change in strength before and after heating was measured by a tensile test. Further, the effect of the weight of Fe-P plating and the surface pressure during sliding on the friction coefficient of the 560 ° C. annealed material is compared with the effect of the surface pressure on the friction coefficient of a steel plate (SPCC, plate thickness 1.0 mm). It is shown in FIG. FIG. 2 shows the effect of the basis weight of Fe-P plating on the cup forming height of the aluminum alloy plate.
FIG. 3 shows the effect of the annealing temperature on the elongation of the aluminum alloy plate (plate thickness: 1.0 mm).

Friction coefficient measurement test: Flat plate sliding, low-viscosity oil-lubricated cup molding: 50 mmφ cylindrical punch, blank diameter 100 mm, low-viscosity oil-lubricating, measuring the molding height to break

Tensile test: JIS Z2241 using a JIS No. 5 test piece specified in JIS Z2201
Based on, a tensile test is performed at a tensile speed of 10 mm / min,
The tensile strength and elongation were measured.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, the composition and steps of the bake hardening type surface treated aluminum alloy sheet are limited, and the press formability is remarkably improved by the combination of iron-based plating. As a result, the effect of increasing the production efficiency by reducing various troubles at the time of press molding and expanding the application range of the aluminum alloy plate to the complicated shape member can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect of surface pressure during sliding in comparison with the effect of surface pressure on the friction coefficient of a steel sheet.

FIG. 2 is a diagram showing the influence of the basis weight of Fe-P plating on the cup forming height of an aluminum alloy plate.

FIG. 3 is a diagram showing the effect of annealing temperature on elongation of an aluminum alloy plate.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Nobuo Totsuka, Inventor No. 1 Kawasaki-cho, Chiba-shi, Chiba Pref. Kawasaki Steel Corporation Research and Development Headquarters (72) Nobuyuki Morito No. 1, Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Koichi Hashiguchi 1 Kawasaki-cho Chiba City Chiba Prefecture Kawasaki Steel Corporation Research and Technology Headquarters (72) Inventor Yoshihiro Matsumoto Kawasaki-cho Chiba Chiba No. 1 Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Motohiro Nambae 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Industry Co., Ltd. (56) References JP-A-4-350195 (JP , A) 40th Anniversary Commemorative Committee Commemorative Publishing Subcommittee, “Structure and Properties of Aluminum” (Heisei 3-11-30), Japan Institute of Light Metals, p. 282, 293 (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 14/00-14/58 C23C 18/52 C23C 28/00 C25D 5/30

Claims (3)

(57) [Claims] (1) When the elongation is 25% or more, the friction coefficient is 0.13 or less and the surface pressure is 1 kgf / m ² , and the surface pressure is 4 kgf / m ^2.
2. A baking-hardened surface-treated aluminum alloy sheet having excellent formability and having a difference in friction coefficient of 0.015 or less in the case of No. ₂ , wherein 0.4 wt% of Mg and Si are equivalent to Mg ₂ Si.
The baking hardened aluminum alloy plate containing at least one plating layer is provided on the surface, and the outermost plating layer is Fe
A bake hardening type surface-treated aluminum alloy sheet having excellent formability, which is a system plating layer and has a basis weight of 5 to 50 g / m ² . ^2. A case where the elongation is 25% or more, the friction coefficient is 0.13 or less and the surface pressure is 1 kgf / m ² , and the surface pressure is 4 kgf / m ^2.
In producing a bake-hardening type surface-treated aluminum alloy sheet having excellent formability and having a difference in friction coefficient of 0.015 or less in the case of No. ₂ , Mg and Si are equivalent to Mg.
An aluminum alloy sheet containing 4 wt% or more is annealed at a temperature of 480 ° C or more, and then the outermost plating layer has a basis weight.
A method for producing a bake-hardening surface-treated aluminum alloy sheet having excellent formability, comprising forming a single layer or a plating layer composed of two or more layers, which is Fe-based plating of 5 to 50 g / m ² . 3. When the elongation is 25% or more, the friction coefficient is 0.13 or less and the surface pressure is 1 kgf / m ² , the surface pressure is 4 kgf / m ^2.
In producing a bake-hardening type surface-treated aluminum alloy sheet having excellent formability and having a difference in friction coefficient of 0.015 or less in the case of No. ₂ , Mg and Si are equivalent to Mg.
On an aluminum alloy plate containing 4 wt% or more, a plating layer composed of a single layer or two or more layers in which the outermost plating layer is an Fe-based plating having a basis weight of 5 to 50 g / m ² is formed, A method for producing a bake-hardened surface-treated aluminum alloy sheet having excellent formability, characterized by annealing at a temperature.