JP2873165B2 - Extruded Al-Mg-Si alloy with excellent bendability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Mg alloy having a high bending strength and a high bending strength, such as a side member and a bumper of an automobile.
It relates to an extruded Si-based alloy.

[0002]

2. Description of the Related Art Aluminum alloys have the advantages of being lighter and less rusty than iron.
It is widely used in the fields of various vehicles, ships and construction.

Incidentally, materials used for parts such as side members and bumpers of automobiles are required to have high strength and excellent bending workability. For this reason, conventionally, these parts include NP114 and SPCC
Etc. are used.

However, in recent years, there has been a strong demand for weight reduction of these parts, and automobile manufacturers are studying the use of extruded aluminum for these parts. In this case, since mechanical properties such as strength, corrosion resistance and workability are relatively excellent, Al-Mg-S
Attention has been paid to i-type (6000-type) alloys. Representative A
As the l-Mg-Si alloy, A6063 and A60
There are 61 alloys. A6063 alloy is used for building sashes and the like because of its excellent extrudability. Also, A60
Alloy 61 is a medium strength material and is used as a structural assembly material. Further, as a bumper material for automobiles, A70
03 alloy is used.

[0005]

However, when used as an automobile side member and a bumper,
A6063 alloy has a drawback of insufficient strength, and A6061 alloy has a drawback of poor bending workability. Further, the A7003 alloy has a problem that stress corrosion cracking may occur.

[0006] The present invention has been made in view of the above problems, and has excellent strength and bending workability, and has excellent bending properties suitable as a material for automobile parts such as side members and bumpers. An object of the present invention is to provide an extruded Mg-Si alloy.

[0007]

According to the first invention of the present application, an extruded Al-Mg-Si alloy having excellent bendability is made of Mg ₂
Si: 0.7 to 1.4% by weight, excess Si: 0.2 to 1.0% by weight, Cu: 0.1 to 1.0% by weight and T
i: 0.001 to 0.05% by weight, the balance being A
1 and unavoidable impurities, the average length of the Mg ₂ Si precipitate is 20 nm or less, and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is 2,000 / μm ² or more. I do.

In this case, Mn: 0.1 to 0.5
% By weight, Cr; 0.05-0.2% by weight and Zr;
It may contain at least one element selected from the group consisting of 0.05 to 0.2% by weight.

[0009]

[0010]

[0011]

Next, the reason for adding the components and the reason for limiting the composition of the extruded Al-Mg-Si alloy according to the present invention will be described.

Mg ₂ Si Mg ₂ Si is an intermetallic compound in which a weight ratio Mg: Si of Mg and Si is precipitated at a ratio of 1.73: 1 by performing an aging treatment after a solution treatment. There is an effect that the strength of the Al alloy is improved by the precipitation of the intermetallic compound.

However, the content of Mg ₂ Si is 0.7% by weight.
If it is less than 1, the strength is low, and if it exceeds 1.4% by weight, the solid solution becomes insufficient during the solution treatment, so that the effect of addition is saturated and the bendability of the Al alloy is deteriorated. Therefore, M
The g ₂ Si content is set to 0.7 to 1.4% by weight.

Excess Si Excess Si is added to the weight ratio of added Mg and Si (Mg /
When Si) is smaller than 1.73, a portion of Si greater than 1 / 1.73 of the weight of Mg is left without forming an intermetallic compound. This surplus Si is Mg ₂ Si
By finely dispersing the precipitate, there is an effect of improving strength and bendability. However, if the surplus Si content is less than 0.2% by weight, a sufficient strength improving effect cannot be obtained,
If it exceeds 1.0% by weight, the bendability deteriorates. Therefore, the surplus Si content is set to 0.2 to 1.0% by weight.

Ti Ti has an effect of making crystal grains in an Al alloy ingot fine. However, if the Ti content is less than 0.001% by weight, the effect is not sufficient, and if the Ti content exceeds 0.05% by weight, the effect is saturated. Therefore, the Ti content is set to 0.001 to 0.05% by weight.

Cu Cu has the effect of improving strength and bendability by finely dispersing and depositing Mg ₂ Si precipitates. In the first invention of the present application, the Cu content is 0.1 to 1.0% by weight. If the Cu content is less than 0.1% by weight, Mg ₂
The effect of dispersing fine Si precipitates is insufficient and the strength is not sufficiently improved. If it exceeds 1.0% by weight, the strength is increased but the corrosion resistance of the Al alloy is reduced. For this reason, in the first invention of the present application, the Cu content is set to 0.1 to 1.0% by weight.

In the second invention of the present application, the Cu content is set to 0.4 to 2.5% by weight. By setting the Cu content to 0.4% by weight or more, the strength can be reliably ensured. If the Cu content exceeds 1% by weight, the corrosion resistance is reduced, but the strength is further improved. Therefore, when high strength is required, Cu
May be added in excess of 1% by weight. However, when the Cu content exceeds 2.5% by weight, the corrosion resistance is lower than that of the A7003 alloy conventionally used as a bumper material for automobiles. Therefore, in the second invention of the present application, the Cu content is set to 0.4 to 2.5% by weight.

Mn, Cr, Zr Mn, Cr, and Zr all have the effect of further improving strength and bending workability by refining crystal grains and forming a fiber structure. Add these elements,
By making the fiber structure a portion of 50% or more of the cross-sectional area of the extruded material, the strength and bending workability of the extruded material are significantly improved. However, when the Mn content is less than 0.1% by weight, when the Cr content is less than 0.05% by weight, and when the Zr content is less than 0.05% by weight, the effect of the addition is not sufficient. . When the Mn content exceeds 0.5% by weight, when the Cr content exceeds 0.2% by weight, and when the Zr content exceeds 0.2% by weight, the effect is only saturated. In addition, bending workability decreases. Therefore, the Mn content is 0.1 to 0.5% by weight,
The r content is 0.05 to 0.2% by weight, and the Zr content is 0.05 to 0.2% by weight.

The above-mentioned Mn, Cr and Zr are selective addition elements, and one of these elements may be used if necessary.
Seeds or two or more kinds may be added. However, when Mn, Cr or Zr is added, the Mn content must be 0.5% by weight or less, and the Cr and Zr content must be 0.2% by weight or less.

Next, the reasons for limiting the average length and density of the Mg ₂ Si precipitate will be described. In the first invention of the present application, the average length of the Mg ₂ Si precipitate is 20 nm or less, and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is 2,000.
Pieces / μm ² or more. The strength, ductility and bendability of an Al—Mg—Si based extruded material are greatly affected by the length and density of the Mg ₂ Si precipitate. By setting the average length of the Mg ₂ Si precipitate to 20 nm or less and the density of the precipitate having a diameter of 1.0 nm or more to 2000 pieces / μm ² or more, the strength, ductility and bendability of the Al alloy can be improved. . M
When the average length of the g ₂ Si precipitate exceeds 20 nm, ductility and bendability are significantly reduced, and when the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is less than 2000 / μm ² , the strength is reduced. descend. Accordingly, it is necessary that the average length of the Mg ₂ Si precipitate is 20 nm or less, and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is 2000 pieces / μm ² or more.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an Al-Mg-S according to the first invention of the present application
The i-type alloy extruded material will be specifically described in comparison with a comparative example out of the claims of the present invention.

First, A having the composition (% by weight) shown in Table 1 below
An alloy ingot (diameter: 155 mm) was melted by an ordinary method. The comparative material 13 is an Al alloy equivalent to 6061. Fe is an unavoidable impurity.

[0023]

[Table 1]

Next, these ingots were homogenized at a temperature of 540 ° C. for 4 hours. Then, after extruding each ingot under the conditions of an extrusion temperature of 530 ° C. and an extrusion speed of 10 m / min, the width was 54 mm and the height was 70 m by air cooling with a fan.
m, a hollow extruded material having an inner thickness of 2 mm was obtained.

Next, the obtained extruded material was cut into a predetermined length, and then held at a temperature of 555 ° C. for 1 hour to perform a solution treatment of quenching in water. Next, these were subjected to artificial aging treatment at a temperature of 170 ° C. for 6 hours to obtain test materials.

After cutting these test materials of the present example material and the comparative example material, the M of the (100) plane was observed with a transmission electron microscope.
The g ₂ Si precipitate was observed, and the average length of the Mg ₂ Si precipitate in the [100] and [010] directions and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more in the [001] direction were measured. The results are shown in Table 2 below. FIG. 1 shows a photograph taken by a transmission electron microscope (TEM).

Next, the tensile strength, proof stress and elongation of the test materials of these examples and comparative examples were measured using JIS No. 13B test pieces. Table 2 also shows the results. next,
A bending test was performed on each test material of this example and a comparative example. FIG. 2 is a schematic diagram showing a bending test method (draw bending). Insert the core 1 into the inside of each test material 10,
Clamp type 2, pressure type 3, wiper (wrinkle prevention metal) 4
The test material 10 was bent by the bending die 5. Then, the bending state was evaluated by observing the crack state in the 180-degree bending test while keeping the bending radius of the bender constant.

[0028]

[Table 2]

The results are shown in Table 2. However, the case where cracks occurred was indicated by x, the case where there was no cracks but the skin was rough was indicated by △, and the case where neither cracks nor skin was found was indicated by ○. As can be seen from FIG. 1, the excess Si is 0.6% by weight,
Example alloy No. 2 containing 0.5% by weight of Cu has excess S
Compared with Comparative Example Alloy No. 10 containing no i and Comparative Example Alloy No. 12 containing no Cu, Mg ₂ Si precipitates are finely deposited at a high density.

Further, as is clear from Table 2, the alloys of Examples 1 to 7 each have an average length of Mg ₂ Si precipitates of 20 nm or less and 2000 or more per 1 μm ² . Since the Mg ₂ Si precipitates are dispersed and deposited at a high density, the strength is high and the ductility is excellent. These alloys also have good bendability.

On the other hand, Comparative Example Alloy No. 8 has a Mg ₂ Si content of less than 0.7% by weight, and Comparative Example Alloy No. 10 has a surplus Si content of less than 0.2% by weight. ₂ Si
The density of the precipitates is less than 2000 particles / μm ² , and the strength is reduced.

In Comparative Example Alloy No. 9, since the Mg ₂ Si content exceeded 1.4% by weight, the Mg ₂ Si precipitate became coarser than 20 nm, and the bendability was lowered.

In addition, since the excess Si content of the alloy of Comparative Example No. 11 exceeds 1.0% by weight, the ductility and the bendability are lowered.

Further, since the Cu content of Comparative Example Alloy No. 12 was less than 0.1% by weight, the length of the Mg ₂ Si precipitate exceeded 20 nm, and the bendability was reduced.

Further, the alloy of Comparative Example No. 13 (equivalent to 6061) has a Mg ₂ Si content exceeding 1.4% by weight.
Further, since the surplus Si content is less than 0.2% by weight, M
The length of the g ₂ Si precipitate exceeds 20 nm, and the bendability is reduced.

Next, the Al—Mg— according to the second invention of the present application is described.
The extruded Si-based alloy will be described in comparison with a comparative example out of the claims of the present invention. First, an Al alloy ingot having a composition (% by weight) shown in Table 3 below (diameter: 155 mm)
Was melted by an ordinary method. Note that Fe is an unavoidable impurity.

[0037]

[Table 3]

Next, these ingots were homogenized at a temperature of 540 ° C. for 4 hours. Then, after extruding each ingot under the conditions of an extrusion temperature of 530 ° C. and an extrusion speed of 10 m / min, the width was 54 mm and the height was 7 mm by cooling with a fan.
A hollow extruded material having a thickness of 0 mm and a thickness of 2 mm was obtained.

Next, these extruded materials were cut to a predetermined length, and then held at a temperature of 555 ° C. for 1 hour, and subjected to a solution treatment of quenching in water. These extruded materials were then
An artificial aging treatment was performed at a temperature of 0 ° C. for 6 hours to obtain a test material.

The crystal grains of each of the test materials of the present example material and the comparative example material were observed with an optical microscope. FIG. 3 is a photograph showing the crystal structure of Example Alloy Nos. 15 and 21.
As can be seen from FIG. 3, the alloy of Example No. 21 to which Mn, Cr and Zr are added has a fiber structure in most of the cross section, but the alloy of Example No. 21 to which these elements are not added. 15 does not have a fiber structure.

Next, the tensile strength, proof stress and elongation of the test materials of these examples and comparative examples were measured using JIS No. 13B test pieces. The results are shown in Table 4 below. Also,
A bending test was performed on each test material of this example and the comparative example by the method shown in FIG. Then, while keeping the bending radius of the bender constant, the state of cracking in 180-degree bending was observed to evaluate bending workability. The results are also shown in Table 4. However, the case where cracks occurred was indicated by x, the case where skin roughening occurred was indicated by Δ, and the case where neither cracking nor skin roughening was indicated by ○. Further, a salt water spray test for examining corrosion resistance was carried out by spraying salt water having a salt concentration of 5% by weight for 500 hours on each of the test materials of Examples and Comparative Examples. The results are also shown in Table 4. However, the case where the corrosion resistance was superior to that of the A7003 alloy was indicated by ○, and the case where the corrosion resistance was inferior was indicated by ×.

[0042]

[Table 4]

As is clear from Table 4, the alloy N of this example
Each of o.14 to 20 has high strength, and is excellent in bending property and corrosion resistance. Further, the alloys Nos. 21 and 22 of this example having a fiber structure by adding Mn, Cr and Zr have improved strength and good bending workability as compared with the recrystallized structure.

On the other hand, in Comparative Example Alloy No. 23, the Mg ₂ Si content was less than 0.7% by weight, and in Comparative Example Alloy No. 25, the excess Si content was less than 0.2% by weight. Even the strength is reduced.

The alloy of Comparative Example No. 24 has a Mg ₂ Si content exceeding 1.4% by weight, and the alloy of Comparative Example No. 26 has an excess Si content of exceeding 1.0% by weight. , The bendability is reduced.

Further, in Comparative Example Alloy No. 27, since the Cu content was less than 0.4% by weight, the bending workability was reduced.

Further, in Comparative Example Alloy No. 28, the Cu content exceeded 2.5% by weight, so that the corrosion resistance was reduced.

Further, Comparative Example Alloy Nos. 29 to 31
0.5% by weight and 0.2% by weight of Mn, Cr and Zr, respectively
And more than 0.2% by weight, the bending workability is reduced.

[0049]

As described above, according to the present invention, Al-
Mg-Si-based alloy extruded material has a predetermined composition, Mg ₂
Since the Si precipitates are finely and uniformly dispersed, the mechanical strength is high and the bendability is excellent. For this reason, the extruded Al-Mg-Si alloy according to the present invention is suitable for parts such as automobile side members and bumpers.

[Brief description of the drawings]

FIG. 1 is a metallographic photograph of the alloys of this example and a comparative example observed by a transmission electron microscope.

FIG. 2 is a schematic diagram showing a bending test method (draw bending).

FIG. 3 is a metallographic photograph of the alloy of this example observed by an optical microscope.

[Explanation of symbols]

 1; mandrel 2; clamp type 3; pressure type 4; wiper 5; bending type 10;

Continuation of the front page (56) References JP-A-6-212336 (JP, A) JP-A-6-25783 (JP, A) JP-A-5-279780 (JP, A) JP-A-5-171328 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C22C 21/06-21/18 C22F 1/04-1/057

Claims (2)

(57) [Claims] 1. Mg ₂ Si: 0.7 to 1.4% by weight;
Excess Si: 0.2 to 1.0% by weight, Cu: 0.1 to 1.0% by weight, and Ti: 0.001 to 0.05% by weight
, The balance consisting of Al and unavoidable impurities,
The average length of the g ₂ Si precipitate is 20 nm or less, and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is 200 nm.
An extruded material of Al-Mg-Si alloy excellent in bendability, characterized in that the extruded material is 0 / μm ² or more. 2. Mg ₂ Si: 0.7 to 1.4% by weight;
Excess Si: 0.2 to 1.0% by weight, Cu: 0.1 to 1.0% by weight, and Ti: 0.001 to 0.05% by weight
And Mn; 0.1 to 0.5% by weight, Cr;
0.05 to 0.2% by weight and Zr;
At least one element selected from the group consisting of 2% by weight, the balance being Al and unavoidable impurities;
The average length of the Mg ₂ Si precipitate is 20 nm or less, and the density of the Mg ₂ Si precipitate having a diameter of 1.0 nm or more is 20 nm or less.
An extruded Al-Mg-Si alloy material having excellent bendability, wherein the extruded material is at least 00 pieces / μm ² .