JP2706310B2 - Aluminum alloy plate for automobile panel and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet for an automobile panel having excellent formability and used for an automobile panel, and a method for producing the same.

[Problems to be solved by conventional technology and invention]

Generally, steel plates are often used for automobile panels, but in recent years, aluminum alloys have been partially used for the purpose of weight reduction from the viewpoint of fuel saving.

Conventionally used aluminum alloys are adjusted in composition for the purpose of improving formability and strength, and finish annealing is performed by gradually raising the temperature in a box-type replacement gas atmosphere furnace and holding it in the furnace for a certain time. It is made of.

However, ductility represented by the strength and elongation of the material, that is, anisotropy occurs in the strength and elongation in the rolling direction and the direction perpendicular to it or in the direction of 45 °. Therefore, there is a need for an improvement in the shape of the spring due to the occurrence of the shape failure or the shape failure due to the spring pack.

[Means for solving the problem]

In view of this, as a result of various studies in view of this, although the anisotropy of strength and elongation cannot be eliminated by the conventional annealing method, the texture formed during rolling disappears due to the treatment at high temperature for a short time, and the anisotropy is reduced. By relaxing and increasing the rate of temperature rise during heat treatment, coarsening of recrystallized grains is suppressed, and the microscopic shape of the surface of the base plate also affects lubricating oil retention during molding, so-called average surface The inventors have found that there is an appropriate value for the roughness Ra, and as a result of further studies, have developed an aluminum alloy sheet for an automobile panel having excellent formability and a method for producing the same.

That is, one of the alloy sheets of the present invention contains Mg2 to 6 wt% (hereinafter, wt% is abbreviated as%), Mn0.05 to 0.5%, Zn0.001 to 0.3%,
An aluminum alloy plate comprising Fe and 0.2% or less in the impurities, the balance being Al and unavoidable impurities, and the maximum value of the anisotropy of the strength and elongation of the aluminum alloy plate depending on the rolling direction. The difference between the minimum values is within 15% of the maximum value, and the average surface roughness Ra is 0.1 to 2.0 μm.

Another one of the alloy sheets of the present invention is Mg2-6%, Mn0.05.
0.5%, Zn 0.001-0.3%, Cu 0.5% or less, Cr
0.3wt% or less, Ti0.3wt% or less, Zr0.3wt% or less, V0.3wt
% Or less, B 0.001 wt% or less, Ni0.5 wt% or less, containing at least one type, restricting the Fe content of impurities to 0.2% or less, aluminum alloy consisting of the balance of Al and unavoidable impurities A difference between the maximum value and the minimum value of the anisotropy in the rolling direction of the strength and elongation percentage of the aluminum alloy plate is within 15% of the maximum value, and the average surface roughness Ra is 0.1 to 2.0.
μm.

Further, the production method of the present invention, Mg2-6%, Mn0.05-0.5%,
Contains 0.001-0.3% of Zn, or Cu0.5% or less, Cr0.3
% Or less, Ti 0.3% or less, Zr 0.3% or less, V0.3% or less, B0.0
At least one type within the range of 01% or less and Ni 0.5% or less, the Fe content in impurities is regulated to 0.2% or less, and the balance A
After subjecting the alloy consisting of l and unavoidable impurities to soaking and hot rolling, intermediate annealing and cold rolling are performed, or the temperature is increased at a rate of 100 ° C / min or more without performing 400 to 600
The heat treatment is performed at a temperature of ° C.

(Operation)

The alloy sheet of the present invention has the above-mentioned structure, and the addition of Mg is for securing the strength. The content is limited to 2 to 6%. This is for reducing the corrosion cracking resistance. The addition of Mn is to ensure the same strength as Mg and to improve the stress corrosion cracking resistance. The content was limited to 0.05 to 0.5% by 0.05%.
If it is less than 0.5%, there is no effect, and if it exceeds 0.5%, an Al-Mn-Fe-based intermetallic compound is formed and ductility is reduced.
The addition of Zn is for improving ductility, and its content is 0.00
The reason for limiting the content to 1 to 0.3% is that if it is less than 0.001%, there is no effect, and if it exceeds 0.3%, it binds to Mg as a main element to form an intermetallic compound and lowers the strength. Also
Cu ≦ 0.5%, Cr ≦ 0.3%, Ti ≦ 0.3%, Zr ≦ 0.3%, V ≦ 0.
The reason for restricting the content to 3%, B ≦ 0.001%, Ni ≦ 0.5%, and Fe ≦ 0.2% is that if any of them exceeds the upper limit, the ductility is reduced.

The alloy sheet of the present invention has the above composition, and particularly, the difference between the maximum value and the minimum value in the anisotropy in the rolling direction is 15% of the maximum value.
The difference between the maximum value and the minimum value is 15
%, Springback is likely to occur due to the direction of higher strength during molding. The difference between the maximum value and the minimum value of the elongation percentage in the anisotropy in the rolling direction is limited to within 15% of the maximum value, because the difference between the maximum value and the minimum value exceeds 15% of the maximum value. This is because wrinkles and uneven thickness sometimes occur. Further, the average surface roughness Ra is 0.1 to 2.0 μm
If it is less than 0.5 mm, the effect of retaining the lubricating oil is not sufficient, and problems such as cracking and seizure are likely to occur during molding. If it exceeds 2.0 μm, microscopic recesses on the surface are notched, causing cracking during molding. The control of the average surface roughness Ra depends on the method of polishing the roll, but the polishing may be performed by a grindstone, or a method of locally melting the roll surface by laser irradiation to form a conical, cylindrical or rectangular cylindrical dent. Alternatively, a chemical polishing treatment or the like may be used. Also, the surface of the base plate may be chemically etched.

Next, in the production method of the present invention, after performing soaking and hot rolling, without performing or performing intermediate annealing and cold rolling, the temperature is raised at a rate of 100 ° C / min or more to a temperature of 400 to 600 ° C. The heat treatment is performed to improve the formability. If the temperature rise rate is less than 100 ° C./min, the crystal grains may be coarsened at the time of temperature rise, causing inconvenience such as rough surface and cracks at the time of molding. This is because it is easy. If the heating temperature is lower than 400 ° C, the solution treatment effect is insufficient and the strength cannot be secured.If the heating temperature is higher than 600 ° C, not only the crystal grain coarsening and burning phenomenon may occur but also the moldability Leads to a decrease in The holding time is not particularly specified, but is preferably set within 10 minutes.

〔Example〕

A 500 mm thick ingot having the composition shown in Table 1 was soaked at 520 ° C for 4 hours, and then hot rolled to obtain a 5 mm thick plate. This was finished into a 1.0 mm thick plate by cold rolling. After subjecting this plate to a heat treatment under the conditions shown in Table 2, the proof stress, elongation anisotropy and overhang property were examined. The results are shown in Table 2.

The anisotropy of proof stress and elongation is the value in the direction where the maximum value was obtained by taking a JIS No. 5 test piece from the above plate in the direction of 0 °, 45 °, 90 ° with respect to the rolling direction and conducting a tensile test on this. And the ratio of the difference between the maximum value and the minimum value. For the overhang property, a 90 mm square plate was cut out from the above plate, and a predetermined lubricating oil was spray-coated to perform an overhang test.

As is clear from Tables 1 and 2, the alloy of the present invention (A
To H) produced by the method of the present invention (Nos. 1 to 8) were compared with comparative methods (Nos. 9 to 12) using alloys (I to L) other than the alloy composition of the present invention. It can also be seen that this is also excellent in the overhang property, which is the value of the formability evaluation index.

On the other hand, even in the case of the alloy (No. A) within the composition of the present invention, not only the anisotropy is increased but also the overhang property is inferior in the comparative method (Nos. 13 to 15) under different heat treatment conditions, Also, it can be seen that even in the case of the alloy (No. A) within the composition of the present invention, the overhanging property is inferior in the comparative method (No. 16) in which the surface roughness deviates.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide an aluminum alloy for an automobile panel having excellent moldability, and has an industrially remarkable effect such as enabling a reduction in the weight of an automobile.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C22F 1/00 686 8719-4K C22F 1/00 686A 691 8719-4K 691A 8719-4K 691B

Claims (3)

(57) [Claims] (1) Mg2-6 wt%, Mn0.05-0.5 wt%, Zn0.001-
An aluminum alloy sheet containing 0.3 wt% and the Fe content in impurities is controlled to 0.2 wt% or less, and the balance of Al and unavoidable impurities is different depending on the rolling direction of the strength and elongation of the aluminum alloy sheet. The difference between the maximum value and the minimum value of the anisotropy is within 15% of the maximum value, and the average surface roughness Ra is 0.1 to 2.0 μm
An aluminum alloy plate for an automobile panel, characterized in that: 2. Mg 2-6 wt%, Mn 0.05-0.5 wt%, Zn 0.001-
0.3wt%, Cu0.5wt% or less, Cr0.3wt% or less, T
i0.3wt% or less, Zr0.3wt% or less, V0.3wt% or less, B0.001w
t% or less, Ni0.5wt% or less, Fe0.2wt% or less, aluminum alloy plate consisting of the balance of Al and unavoidable impurities, the anisotropy of the strength and elongation of the aluminum alloy plate depending on the rolling direction An aluminum alloy plate for an automobile panel, wherein the difference between the maximum value and the minimum value of each property is within 15% of the maximum value, and the average surface roughness Ra is 0.1 to 2.0 μm. 3. Mg2-6 wt%, Mn0.05-0.5 wt%, Zn0.001-
0.3wt% or more, Cu0.5wt% or less, Cr0.3wt% or less, Ti0.3wt% or less, Zr0.3wt% or less, V0.3wt% or less, B
After restricting to 0.001wt% or less, Ni0.5wt% or less, and Fe0.2wt% or less, perform soaking and hot rolling on an alloy containing the balance of Al and unavoidable impurities, and then perform intermediate annealing and cold rolling. Manufacturing an aluminum alloy sheet for an automotive panel, wherein the temperature is raised at a rate of 100 ° C./min or more, heat-treated at a temperature of 400 to 600 ° C., and then the surface is roughened. Method.