JPS6365744B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing high-strength aluminum alloy sheets, which improves the toughness of high-strength aluminum alloy sheets without particularly restricting impurities and provides excellent formability with less anisotropy. It is something to do. [Prior Art] In general, structural members of transport aircraft, rockets, etc. are required to have excellent strength, and materials for fuel tanks, engine hoods, etc. must maintain sufficient strength and toughness from low to high temperatures. It is also required to have excellent weldability. Therefore, high-strength aluminum alloy plates made of AA2219 and AA2419 shown in Table 1 are used for these members.

[Problem that the invention seeks to solve]

The above alloy plate has a wide Cu content range of 5.8 to 6.8 wt% (hereinafter wt% is simply abbreviated as %) and has a relatively high concentration. This has the disadvantage that intermetallic compounds with low toughness are formed in the structure, reducing the toughness of the entire alloy plate. In addition, the above-mentioned forming process has strong anisotropy, and when stress is applied in a direction perpendicular to the rolling direction during forming, cracks are likely to occur in the rolling direction, which reduces formability. Furthermore, controlling impurities as in AA2419 described above in order to improve toughness requires the use of expensive high-purity ingots, which increases the price of high-strength aluminum alloy plates, which is economically disadvantageous. [Means for Solving the Problems] In view of this, as a result of various studies, the present invention has been developed to improve toughness beyond that obtained by regulating impurities, without particularly regulating impurities in alloy components, and to improve anisotropy. We have developed a manufacturing method for high-strength aluminum alloy sheets with low elasticity and excellent formability.Cu5.8~
6.3, Mn0.20~0.40%, V0.05~0.15wt%, Zr0.10
~0.25wt%, Ti0.02~0.10wt%, Si0.20wt% or less, Fe0.30wt% or less, Mg0.02wt% or less, balance Al
The alloy ingot is homogenized at 450 to 535°C, then hot rolled in a direction perpendicular to the casting direction, and then cold rolled in a direction perpendicular to the casting direction. That is, the present invention specifically limits the Cu content to 5.8 to 6.3% in AA2219, melts and casts it according to a conventional method, homogenizes the obtained ingot at 450 to 535°C, and then Hot rolled in a direction perpendicular to the In this homogenization process, the ingot is heated to 450-535℃ for 18-60℃.
After time treatment, hot rolling or ingot
After homogenizing for a short time at 450 to 535°C, hot rolling is performed, and during the rolling, reheating is performed at least once to 450 to 535°C, and the period from homogenization to the end of hot rolling is 450
Hold at ~535 °C for 18-60 hours. After hot working in this manner, cold rolling is performed in a direction perpendicular to the casting direction to obtain a desired size. [Function] In the present invention, the Cu content is adjusted to the above AA2219 and
The reason for limiting the Cu content to 5.8 to 6.3%, which is lower than that of AA2419, is because if the Cu content exceeds 6.3%, Cu that cannot be dissolved in the matrix tends to form, which creates intermetallic compounds and reduces toughness. It is. Next, we limited the homogenization temperature of the ingot to 450 to 535°C to prevent the risk of reducing the strength of the alloy plate by lowering Cu, which contributes most to strengthening the alloy plate. Therefore, by homogenizing the ingot at a higher temperature than before, Cu, which is present in many compounds that crystallize during casting, is sufficiently dissolved in the matrix together with other component elements, thereby preventing a decrease in strength. This is to improve toughness by finely dispersing compounds in the structure.
If the temperature exceeds 540℃, eutectic melting occurs, so 535℃
is the highest temperature in practical use, and a sufficient homogenization effect cannot be expected below 450°C. In addition, the homogenization treatment time is 18 to 60 hours, or the period from homogenization treatment to the end of hot rolling is reheated to 450 to 535℃.
Holding for 60 hours is because if it is held for less than 18 hours, it is not enough for the solute elements to diffuse and form a solid solution, and after 60 hours, the component elements are sufficiently dissolved in the matrix, so holding it for a longer time is meaningless. It's for a reason. Next, the reason why the ingot is hot-rolled in a direction perpendicular to the direction of the ingot after the above-mentioned homogenization treatment is to reduce anisotropy and provide excellent formability. That is, in the DC casting method commonly used for casting aluminum alloys, the molten metal is cooled and solidified in an annular cooling mold, and the solidified portion is continuously lowered to obtain an ingot. Therefore, solidification of the ingot starts from its periphery and solidification progresses in a direction perpendicular to the casting direction (the direction in which the ingot descends). The present inventors discovered that anisotropy occurs in the ingot during this solidification process. Furthermore, when the ingot is rolled, the crystal structure becomes flat and elongated in the rolling direction, and rolling the ingot in the casting direction further promotes anisotropy. When stress is applied, cracks are likely to occur along the rolling direction.
Therefore, by rolling the ingot in a direction perpendicular to the casting direction, the anisotropy is reduced and an alloy plate with excellent formability is obtained. [Example] An alloy having the composition shown in Table 2 was cast by DC casting to form an ingot with a thickness of 400 mm, and this was made into an ingot with a thickness of 10 mm per side.
After face cutting, hot rolling was performed under the conditions shown in Table 3 to obtain a 10 mm thick plate, and then cold rolling was performed to reduce the thickness.
Finished on a 6.5mm plate. The formability of the high-strength aluminum alloy sheets manufactured in this way in the hardened state was evaluated using the Erichsen value, and the toughness in the hardened state and the state artificially aged to the maximum strength (T6 state) was evaluated as UP/E.
It was evaluated based on the value. In addition, the mechanical properties in the T6 state were evaluated by a tensile test. These results are shown in Table 4. The quenching conditions were 535°C for 60 minutes, and the artificial aging conditions were 190°C for 36 hours.

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〔Effect of the invention〕

As described above, according to the present invention, the toughness of a high-strength aluminum alloy plate can be improved and the anisotropy can be reduced without particularly restricting impurities.

Claims (1)

[Claims] 1 Cu5.8-6.3wt%, Mn0.20-0.40wt%, V0.05
~0.15wt%, Zr0.10~0.25wt%, Ti0.02~0.10wt
%, Si0.20wt% or less, Fe0.30wt% or less,
An alloy ingot consisting of less than 0.02wt% Mg and the balance Al.
A method for producing a high-strength aluminum alloy sheet, which comprises homogenizing at 450 to 535°C, followed by hot rolling in a direction perpendicular to the casting direction, and then cold rolling in a direction perpendicular to the casting direction. 2. The method for producing a high-strength aluminum alloy plate according to claim 1, wherein the ingot is homogenized at 450 to 535°C for 18 to 60 hours and then hot rolled. 3 Reheat to 450 to 535℃ during hot rolling, and then heat to 450 to 535℃ between soaking and the end of hot rolling.
A method for manufacturing a high-strength aluminum alloy plate according to claim 1, which is maintained for 18 to 60 hours.