JPH062063A - Al alloy sheet excellent in hardenability in coating/ baking - Google Patents

Abstract

PURPOSE:To provide the objective Al allay sheet excellent in hardenability in baking/coating. CONSTITUTION:The objective Al alloy sheet has a compsn. contg., by weight, 0.3 to 0.6% Mg, 0.3 to 1% Si, 0.001 to 0.5% Be, 0.005 to 0.05% Ti and 0.001 to 0.01% B and furthermore contg., as necessary, one or <=two kinds among 0.05 to 1% Cu, 0.05 to 2% Zn, 0.01 to 0.6% Mn, 0.01 to 0.2% Cr and 0.01 to 0.2% Zr, and the balance Al with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy sheet material excellent in so-called paint bake hardenability, in which the strength is remarkably improved by a paint baking treatment carried out after molding when it is used as an automobile body sheet. It is a thing.

[0002]

2. Description of the Related Art Conventionally, for example, an Al alloy body of an automobile is generally made of an Al alloy plate material such as AA6063 or 6061 containing Mg and Si as main alloying components, which is subjected to solution hardening treatment, In a state where the Al alloy plate material is flattened by straightening it as necessary, it is processed into a predetermined body shape by press molding and then coated, and then, for example, in air, at a temperature of about 200 ° C. It is well known that it is manufactured by carrying out a paint baking treatment under the condition of holding for 20 minutes.

[0003]

However, the above AA6
In conventional Al alloy sheet materials such as 063 and 6061, the temperature rises after standing at room temperature after solution hardening treatment, that is, natural age hardening occurs, and this strength increase is proportional to the standing time. Considering the deterioration of molding processability, not only is there a time constraint on the molding process, but with the development of various paints in recent years, the baking temperature of this tends to decrease. There is also a case where paint baking is performed, but such low temperature baking cannot provide sufficient strength.

[0004]

Therefore, the present inventors have
From the above viewpoints, as a result of research to develop an Al alloy sheet material having excellent paint bake hardenability, which has high strength even when the paint bake treatment is performed at a low temperature, the result is% by weight.
(Hereinafter,% indicates% by weight), Mg: 0.3 to 0.8%, Si: 0.3 to 1
%, Be: 0.001-0.5%, Ti: 0.005-
0.05%, B: 0.001 to 0.01%, and, if necessary, Cu: 0.05 to 1%, Zn: 0.05 to 2
%, Mn: 0.01 to 0.6%, Cr: 0.01 to
0.2%, Zr: 0.01 to 0.2%, one or two or more of which are contained, and the rest has a composition of Al and inevitable impurities. The research results show that it exhibits excellent moldability and that it has high strength by coating baking treatment at a relatively low temperature.

The present invention was made on the basis of the above research results, and the reason why the composition of the Al alloy sheet material is limited as described above will be described below. (A) Mg and Si Both of these components have the effect of improving the strength after coating baking treatment in the coexisting state, but their content is M
If g: less than 0.3% and Si: less than 0.3%, the desired excellent coating bake hardenability cannot be secured, while the content exceeds Mg: 0.8% and Si: 1%. Since it becomes difficult to perform the forming process performed after the solution hardening treatment, the content of Mg: 0.3 to 0.8
%, Si: 0.3 to 1%, respectively.

(B) Be Be component has an effect of suppressing natural age hardening after solution hardening and providing high strength in coating baking at low temperature, that is, an effect of improving coating baking hardenability. However, if the content is less than 0.001%, the desired effect on the above-mentioned action cannot be obtained, while if the content exceeds 0.5%, the above-mentioned action does not show a further improving effect. The content was set to 0.001 to 0.5%, preferably 0.001 to 0.1%.

(C) Ti and B Both of these components have the function of refining the crystal grains in the coexisting state and improving the formability after the solution hardening treatment, but their contents are Ti: 0. If less than 0.005% and B: less than 0.001%, the desired effect of improving moldability cannot be obtained. On the other hand, if the content exceeds Ti: 0.05% and B: 0.01%, the molding processability is reduced. The ductility, which is indispensable to
i: 0.005-0.05%, B: 0.001-0.0
It was set at 1%.

(D) Cu and Zn Since these components have the effect of improving the coating bake hardenability, they are contained as necessary, but their contents are Cu: less than 0.05% and Zn, respectively. : 0.0
If it is less than 5%, the desired improving effect on the above-mentioned action cannot be obtained, while the contents are Cu: 1% and Zn: 2%, respectively.
If the content exceeds the above range, the moldability will be deteriorated. Therefore, the content of Cu: 0.05 to 1%,
Zn: It was set to 0.05 to 2%.

(E) Mn, Cr, and Zr These components are contained as necessary because they have the effect of further improving the moldability, but their contents are
If Mn: less than 0.01%, Cr: less than 0.01%, and Zr: less than 0.01%, the desired effect cannot be obtained for the above-mentioned action, while the content of each is M.
n: 0.6%, Cr: 0.2%, and Zr: 0.2%
Even if it exceeds the limit, the moldability will decrease,
The contents of Mn: 0.01 to 0.6% and Cr: 0.
It was set to 01 to 0.2% and Zr: 0.01 to 0.2%. In addition, Cr: 0.05-0.15%, Cr: 0.
05-0.15%, and Zr: 0.05-0.15%
Is desirable.

[0010]

EXAMPLES Next, the Al alloy sheet material of the present invention will be specifically described by way of examples. After smelting Al alloys having the component compositions shown in Tables 1 and 2 in a normal low-frequency induction melting furnace and making an ingot by the semi-continuous casting method, 530
Homogenizing treatment is carried out at a predetermined temperature within the range of up to 550 ° C for 12 hours, and then hot rolling and cold rolling are performed under normal conditions to obtain a plate material having a thickness of 1 mm. Invention Al alloy plate materials 1 to 26 and conventional Al alloy plate materials 1 and 2 were manufactured.

[0011]

[Table 1]

[0012]

[Table 2]

Next, the various Al alloy sheet materials obtained as a result were subjected to solution hardening treatment of water quenching after being immersed in a salt bath heated to a predetermined temperature within the range of 530 to 560 ° C. for 30 seconds. In addition, after being left at room temperature for 1 week, it was immersed in an oil bath heated to 240 ° C. for 10 seconds, subjected to heat treatment of water quenching and left at room temperature for 1 week. At this point, the proof stress was measured by a tensile test. The proof stress at the time of standing at room temperature for 1 month after the heat treatment was measured, and subsequently, a plastic strain of 2% corresponding to the strain received during the molding process of the automobile body (panel) was applied by tension, The proof stress was measured by heating at 170 ° C., which is a low-temperature coating baking condition, for 20 minutes. The results of these measurements are shown in Table 3.

[0014]

[Table 3]

[0015]

From the results shown in Tables 1 to 3, the present invention A
The l alloy plate materials 1 to 26 have extremely low strength increase due to natural age hardening as compared with the conventional Al alloy plate materials 1 and 2 corresponding to AA6063 and 6061, and further have higher strength after coating baking treatment. Is clear. As described above, the Al alloy sheet material of the present invention has a low natural age hardening after the solution hardening treatment, which alleviates the restriction over time of the forming process, and is high in the coating baking treatment at a low temperature. Since it has strength, it has optimum properties as a body sheet for automobiles, for example.

Claims (4)

[Claims] 1. By weight%, Mg: 0.3 to 0.8%, Si: 0.3 to 1
%, Be: 0.001-0.5%, Ti: 0.005-
0.05%, B: 0.001 to 0.01%, and the balance being Al and unavoidable impurities.
Alloy plate material. 2. By weight%, Mg: 0.3 to 0.8%, Si: 0.3 to 1
%, Be: 0.001-0.5%, Ti: 0.005-
0.05%, B: 0.001-0.01%, and further Cu: 0.05-1%, Zn: 0.05-2
%, An Al alloy sheet material having excellent paint bake hardenability, characterized in that it has a composition comprising Al and unavoidable impurities. 3. By weight%, Mg: 0.3-0.8%, Si: 0.3-1
%, Be: 0.001-0.5%, Ti: 0.005-
0.05%, B: 0.001-0.01%, and further Mn: 0.01-0.6%, Cr: 0.01-
0.2%, Zr: 0.01 to 0.2%, one or two or more of which are contained, and the rest has a composition of Al and inevitable impurities. Excellent Al alloy plate material. 4. By weight%, Mg: 0.3-0.8%, Si: 0.3-1
%, Be: 0.001-0.5%, Ti: 0.005-
0.05%, B: 0.001-0.01%, and further Cu: 0.05-1%, Zn: 0.05-2
%, One or two of Mn: 0.01 to 0.6%, Cr: 0.01 to
0.2%, Zr: 0.01 to 0.2%, one or two or more of which are contained, and the rest has a composition of Al and inevitable impurities. Excellent Al alloy plate material.