JPS6369954A - Stretcher leveling method for high-tensile aluminum alloy plate - Google Patents

Abstract

PURPOSE:To prevent the occurrence of stretcher strain and also to shorten the length of aging time in the following stage, by heating an age-hardening high-tensile Al alloy plate at a temp. in a specific range for a period having specific relations with the above temp. at the time of subjecting the above Al alloy plate to stretcher leveling after solution heat treatment. CONSTITUTION:An age-hardening high-tensile Al alloy, e.g., metal plate of 2000 or 7000 type is first subjected to solution heat treatment in order to allow solute atoms such as Cu, Zn, Mg, etc., to enter into solid solution. Since thermal strain occurs at this time, stretcher leveling is carried out by means of a stretcher, etc., and, prior to the above leveling, the above Al alloy plate is subjected to heating treatment at a temp. T( deg.C) of 250-750 deg.C for a time (t)(hr) satisfying an inequality. By this heat treatment, the concentration of the solute atoms existing in solid solution in the plate matrix is lowered and, as a result, formation of GP zone is inhibited and repetition of multiple yield can also be inhibited during tensile deformation, so that prevention of stretcher strain can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a tensile straightening method for high-strength aluminum alloy plates.

[Prior art] Age-hardening high-strength aluminum alloy, such as 2000
7000 series materials (hereinafter, solution treatment is performed to dissolve solute atoms such as high-strength aluminum).

The above solution treatment conditions vary slightly depending on the product, but the temperature for the 2000 series is 470-530℃, 7
For the 000 series, the temperature is generally 450 to 500°C. Also,
The treatment time varies depending on the thickness of the plate, but is usually 0.1 to 5 hours.

However, when the material is a plate, thermal distortion occurs during this solution treatment, so tensile straightening is performed using a stretcher or the like to remove distortions such as warps and waves on the plate and flatten it.Usually, the tension is The tensile force is such that the permanent elongation of the plate is about 0.5%.

After the tensile straightening as described above, finishing processing, room temperature aging treatment, or tempering treatment is performed as necessary, and the material is supplied as a processed material for the next process.

By the way, as described above, when tensile straightening is performed after solution treatment, stretcher strutsine (stripes on the plate surface that occurs during stretcher straightening) occurs on the plate surface.

Conventionally, the following techniques are known as stretcher prevention techniques.

■Technology for performing roller level processing on mild steel plates.

■Technology for tensile pre-processing for mild steel plates.

■Technology for increasing room temperature aging time and high-speed molding or low-temperature molding.

The above is from “Plasticity and Processing J voJ115, No. 162 (
1974-7) P526 to P534.

[Problems to be Solved by the Invention] The conventional technique for preventing stretcher strain of high-strength aluminum alloy plates as described above has the following problems.

■ Roller level processing or tension pre-processing techniques cannot prevent stretcher strain on aluminum alloy plates.

■With techniques such as increasing the aging time at room temperature, it is difficult to control the temperature and processing speed, and it is difficult to maintain the same conditions in each process.

As a result, there are many variations between products, making it impossible to manufacture uniform products without stretcher strain, and productivity is also poor.

In view of the above-mentioned circumstances, the present invention has discovered an effective tensile straightening method for controlling stretcher strain marks on high-strength aluminum alloy plates, and has developed the present invention based on this method.

[Means for Solving the Problems] The above problem arises in the method of tensile straightening a plate made of an age-hardening high-strength aluminum alloy after solution treatment, in which the high-strength aluminum alloy plate is A method for tensile straightening a high-strength aluminum alloy plate, characterized by heat treatment for a time t (hours) satisfying t≧-0.51T+42.75-6 set 1 at a temperature T (℃) of 25℃ or higher and 75℃ or lower. solved by.

The present invention targets age-hardening high-strength aluminum alloys. Examples of such alloys include:

Examples include 2000 series and 7000 series high strength aluminum alloys.

In the present invention, the solution treatment conditions are not limited to the solution treatment conditions.The solution treatment conditions differ somewhat depending on the product, but the temperature is, for example, 470-530℃ for the 2000 series, 700℃
For 0 series, the temperature is generally 450 to 500°C. Further, although the treatment time varies depending on the thickness of the plate, it is usually carried out for 0.1 to 5 hours. Of course, the above conditions are merely examples, and the scope of the present invention is not limited by these conditions.

In the present invention, the high-strength aluminum alloy plate is heated at a temperature T ('O
), t≧-0.51T+42.75...The heat treatment is performed for a time t (hours) that satisfies formula 1.

If the heating temperature is less than 25℃, a stretcher or a
Strain occurs.

When the strength and force are increased to the Tsubaki region and the heating time is prolonged, an intermediate phase is formed in the high-strength aluminum alloy plate due to the precipitation of intermetallic compounds, and age hardening progresses significantly, resulting in straightening. The heating temperature should not be more than 75℃, as it will be difficult to process.
Therefore, according to formula 1, the heating time should be within 30 hours.

In addition, the heating temperature is more preferably 30° C. or more and the heating time is more preferably 1 hour or more.

Stretcher strain can be prevented by reducing the concentration of solute atoms dissolved in the plate material by this preheating treatment, thereby suppressing the formation of GP zones during tensile deformation. In other words, since the repetition of multiple yielding is suppressed, stretcher m-strain can be prevented.

The conditions for tensile straightening after the above preliminary heat treatment are not particularly limited. For example, the tensile stress may be such that the permanent elongation of the plate is about 0.5%.

After tensile straightening, finishing processing, room-temperature aging treatment, or tempering treatment is performed as necessary. Normally, the treatment temperature for tempering treatment varies depending on the product, but for the 2000 series it is 150~2
00℃, 110-130℃ for 7000 series, processing time is 2
For the 000 series, it takes about 6 to 24 hours, and for the 7000 series, it takes about 20 to 30 hours. Such treatment achieves sufficient age hardening. Of course, the scope of the present invention is not limited by the aging treatment conditions and tempering treatment conditions.

[Embodiments of the invention] (First embodiment) 7 as a representative example of a 7000 series high strength aluminum alloy plate
A flat test piece of 4 x 1000 x 2000 mm was prepared using a 075 alloy plate.

The above test piece was immersed in a salt bath at about 470°C for 0.7 hours,
Thereafter, it was cooled with water and subjected to solution treatment.

After the solution treatment was completed, the test piece was transported into a furnace where the air temperature was maintained at approximately 50°C and held for 10 hours.The test piece was taken out of the furnace and stretched in the longitudinal direction of the plate using a stretcher. A tensile load was applied to the specimen until it reached approximately 1%, and the test piece was straightened.

The surface of the tensile straightened plate is flat and there is no distortion.
Stretcher strain was also not allowed.

Furthermore, when it was tempered by immersing it in oil at about 120°C, it was able to age harden in 24 hours. Almost no distortion of the board was observed.

(Example 2) As a representative example of 2000 series high strength aluminum alloy plate, 2
A flat test piece measuring 4 x 1000 x 2000 mm was prepared using a 024 alloy plate.

The above test piece was immersed in a salt bath at about 490°C, and then cooled with water to perform solution treatment. After the solution treatment, the test piece was immersed in a constant temperature bath in which the air temperature was maintained at approximately 60°C for 4 hours.

Thereafter, a tensile load was applied to the test piece using a stretcher until the elongation reached approximately 0.5% in the thickness direction, and the test piece was corrected.

The tensile straightened plate became flat, with no distortion, and no stretcher strain was observed.
Tempering treatment (T6) or tempering treatment after cold rolling (T8)
)Did.

In both cases, plates without distortion were obtained. Note that the aging time of the T4 treatment was 500 hr.

Although the examples have been shown above, it should be noted here that the temperature and time of the preheating treatment of the present invention are 30°C or higher, so it seems possible to leave the treatment in the atmosphere, but since the atmospheric temperature changes, Since the diffusion rate of solute atoms in the material also changes, the degree of occurrence of stretcher ψ strain differs, so the heat treatment time cannot be adjusted.

To prevent the occurrence of stretcher φ strain by the heat treatment of the present invention, the heating temperature must be kept constant for a long time of nearly 30 hours at a low temperature around 30°C, or 75°C.
At nearby high temperatures, the temperature is kept constant for a short period of about 30 minutes to complete the formation of the GP zone.

[Effects of the Invention] As explained above, by applying the tensile straightening method of the present invention, high-strength aluminum alloy plates with aging hardness, such as 2000 series and 7000 series high-strength aluminum alloy plates, can be produced. Not only can stretcher strain be prevented from occurring, but the time for post-process aging treatment (room temperature aging, tempering aging) can also be significantly shortened.

Claims (1)

[Scope of Claims] In a method of tensile straightening a plate made of an age-hardening high-strength aluminum alloy after solution treatment, the high-strength aluminum alloy plate is heated at a temperature T of 25°C or more and 75°C or less before the tensile straightening. A method for tensile straightening a high-strength aluminum alloy plate, which comprises heat-treating a high-strength aluminum alloy plate for a time t (hours) satisfying the following formula: t≧-0.51T+42.75 (°C).