JPS616244A - High strength alloy for forming having fine grain and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a high strength alloy for forming having fine grains and hardenable by air-cooling by adding specified amounts of Mg, Zn and Cu as essential components and a specified amount of one or more among Mn, Cr, Zr and V to Al. CONSTITUTION:The composition of an alloy is composed of, by weight, 3.5-5% Mg, 2.1-3.5% Zn and 0.05-0.6% Cu as essential components, 0.05-0.6% one or more among 0.05-0.4% Mn, 0.05-0.25% Cr, 0.05-0.25% Zr and 0.05-0.25% V, and the balance Al with impurities. The alloy is homogenized at 400-520 deg.C, hot worked at 350-500 deg.C, cold worked at >=30% rate, subjected to soln. heat treatment at 430-530 deg.C, and hardened at >=5 deg.C/sec cooling rate.

Description

DETAILED DESCRIPTION OF THE INVENTION Industry - Second Field of Application The present invention relates to a high-strength forming alloy and a manufacturing method.

Conventional technology Conventionally, high-strength alloys with a tensile strength of 40k (around 1/11112) include JIS2014 alloy, 2017 alloy, and 202
4 alloys are known. These alloys are widely used as high-strength structural materials, but since they are heat-treatable alloys, quenching and tempering treatments are required to impart high strength. Needed. Therefore, there is a problem in that the heat treatment cost is high, including the removal of quenching distortion.

Problems to be Solved by the Invention The present invention aims to provide a low-cost, high-strength forming aluminum alloy that does not require water quenching and can be quenched even by air cooling.

Means for Solving the Problems The present invention provides M(13.5 to 5.0%, Zn2.1 to 3.0%).
5%, Cu 0.05-0.6% as essential components, M
n 0.05-0.40%, Q r 0.05-0.2
5%, Zr 0.05-0.25%, V 0.05-0.
It is an aluminum alloy containing 0.05 to 0.6% of one or more of 25% aluminum and the remainder consisting of aluminum and impurities.

Such alloys have high strength, fine grains,
It becomes possible to obtain a high-strength alloy plate for forming that has excellent forming processability and can be hardened by air quenching at a reduced cost.

The reasons for limiting each additive element are shown below.

Mi): Mill mainly increases the strength of the alloy and is in the range of 3.5 to 5.0%. When it is less than 3.5%, strength and formability are insufficient, and when it exceeds 5.0%, hot workability is extremely reduced.

';ln: Zn coexists with M(I) to impart aging properties to the alloy, making it possible to improve strength through room temperature aging after quenching, and should be in the range of 2.1 to 3.5%. If it is less than 2.1%, the strength will not be improved sufficiently, and if it exceeds 3.5%, the strength will increase significantly, but not only will the elongation decrease and formability decrease, but the hot Workability is significantly reduced.

(:, U: (:, Like Zn, U imparts aging properties to the alloy and has the effect of improving strength through room temperature aging after quenching. If it is less than 0.05%, there is no effect of improving strength. If the amount exceeds 0.6%, the strength will increase significantly or hot workability and moldability will decrease.

Mn, Cr, Zr, V: These elements precipitate as fine intermetallic compounds during the homogenization treatment of the ingot, and are effective in making recrystallized grains finer and improving strength. When the amount added is less than the lower limit, the above effect is not sufficient, and when the total amount added exceeds the upper limit, there is a problem that the hardenability decreases and a huge intermetallic compound crystallizes.

In addition, in the present invention, as with general aluminum alloys, addition of Ti at 0.2% or less and 30°01% or less is effective in refining the casting structure and improving hot workability and quality.

In order to obtain excellent performance with the alloy of the present invention, the following manufacturing steps are taken.

The ingot is soaked in one or multiple stages at 400 to 520°C to homogenize the ingot structure. When the temperature is below the lower limit, the homogenization effect is insufficient, and high strength and fine crystal grains cannot be obtained.

If the temperature exceeds the upper limit, there is a risk of eutectic melting.

Further, the homogenization time is suitably 2 to 48 hours; if it is less than 2 hours, the homogenization effect will be insufficient, and if it exceeds 48 hours, the properties such as crystal grains, strength, and moldability will not improve.

It is desirable to carry out the dark processing during the homogenization treatment at a temperature of 350 to 500°C; below the lower limit, the deformation resistance is high and the hot part processing is vA! It is l. If the upper limit is exceeded, processing cracks may occur, which is not preferable.

The cold working degree of hot working corrosion is preferably 30% or more, and 30% or more is desirable.
If it is less than 5%, fine crystal grains cannot be obtained.

Final tempering is T4 treatment (solution treatment → quenching → room temperature aging)
It is desirable to carry out solution treatment at 430 to 530°C.

If the solution treatment temperature is below the lower limit, the strength will not be sufficient, and if it exceeds the upper limit, there is a risk of eutectic melting. Cooling after quenching does not require rapid cooling as in water quenching, and high strength can be achieved at a cooling rate of 5° C. or higher comparable to air quenching (10 to 10 b minutes).

Therefore, the invention alloy can be hardened at low cost in a continuous hardening furnace.

101 Examples and comparative examples will be described below.

Example 1 An alloy ingot (30 mm thick) having the composition shown in Table 1 was heated at 480°C for 16 hours, hot rolled at 420 to 460°C to 3u+, and then subjected to intermediate annealing at 360°C x 2 hours. After this, it was rolled into a 11BII plate by cold rolling. This 11II cold-rolled plate was solution treated at 480° C. for 2 minutes, then cooled by forced air cooling to room temperature at an average cooling rate of 30° C./sec, and various performances after aging at room temperature for 30 days were evaluated.

Various performances are shown in Table 2, and the invention alloy is 40k.

/l! It has a strength close to l12 and fine crystal grains, and has excellent elongation and Erichsen value, and excellent formability.

Comparative example alloys No. 12, No. 14 and No. 14 to 16 have high elongation and Erichsen value and excellent formability, but have low strength. Alloy No. 13 has high strength, but has low elongation and Erichsen value, and has problems with formability. Alloy No. 17 has poor hardenability and low strength.

Table 1 Chemical composition (%) of Examples Table 2 Various performances of 1uTJ plate 9 - Example 2 Each alloy shown in Table 1 was rolled to 1 ml under the manufacturing conditions shown in Table 3 and subjected to T4 treatment. Table 4 shows the various performances of the T4 plate aged for 30 days at room temperature after quenching.

Good performance was obtained only under the invention conditions (NOs 11 to 6), and good performance was not obtained under the comparative examples (1', lo, 7 to 12).

Manufacturing method f of Group 311111IIT4 plate [Table 4 1eml
The present invention provides an aluminum alloy with fine grains suitable for high-strength forming processing, which is excellent in quenching bamboo and can be processed at low cost in a continuous quenching furnace. be able to.

Claims (2)

[Claims] (1) Mg3.5-5.0%, Zn2.1-3.5%,
Cu10.05~0.6% is an essential component, Mn0.0
5-0.4%, Cr0.05-0.25%, Zr0.0
5 to 0.25%, V0.05 to 0.25%, and 0.05 to 0.6% of one or more of V0.05 to 0.25%, with the remainder consisting of aluminum and impurities, and is quenchable by air cooling. Alloy for high grain strength forming processing. (2) Mg3.5-5.0%, Zn2.1-3.5%,
Cu0.05-0.6% is an essential component, Mn0.05
~0.4%, Cr0.05~0.25%, Zr0.05
~0.25%, V0.05~0.25%, containing 0.05~0.6% of one or more of V0.05~0.25%, and the remaining aluminum and impurities after homogenization treatment at 400~520°C.
After hot working at 0 to 500℃, cold working by 30% or more,
A method for producing a fine-grained, high-strength forming alloy, which comprises solution treatment at 30 to 530°C and then quenching at a cooling rate of 5°C/sec or more.