JPH0747806B2 - High strength aluminum alloy extruded shape manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a structural material, industrial equipment, transportation or general use high-strength Al-Mg-Si alloy extruded profile.

[0002]

2. Description of the Related Art Extruded profiles of Al-Zn-Mg type alloys have good extrudability and weldability, and by applying heat treatment after extrusion, medium to high strength can be obtained. Widely used as a material alloy. Recently, aluminum alloy extruded shapes have been used for the purpose of reducing the weight of automobile bumpers, reinforcements, railway vehicles, etc., and these members are used in terms of strength, fracture toughness, extrudability, etc. Al-Zn-
Mg-based alloys such as JIS 7003 alloy are used.

[0003]

However, Al-Z
The n-Mg alloy has poor corrosion resistance and has a problem in stress corrosion cracking resistance.

According to the present invention, in order to solve the above problems,
Cu, or further Cr, M in 1-Mg-Si alloy
n, V, Zr containing alloy composition of a specific range,
Al-Zn-M was added to the billet heating method before extrusion.
Manufacture of high-strength Al-Mg-Si alloy extruded profiles that have the same extrudability as g-based alloy extruded profiles, and have good surface condition after extrusion, press hardenability, corrosion resistance, and corresponding corrosion cracking resistance. It is how to find a method.

[0005]

The present invention provides Mg: 0.4
~ 1.5%, Si: 0.4-1.3%, Cu: 0.05
~ 0.90%, or further Mn: 0.05 ~
0.50%, Cr: 0.05-0.30%, V: 0.0
5 to 0.30% and Zr: 0.05 to 0.30%, and an aluminum alloy ingot containing the remaining Al and impurities was homogenized at 520 to 560 ° C. for 6 to 10 hours. Then, after heating to 540 to 560 ° C, the temperature is lowered to 460 to 520 ° C which is the optimum extrusion temperature, and 460 to 52
A method for producing a high-strength aluminum alloy extruded profile, which comprises press-quenching after extrusion at 0 ° C.

The reasons for limiting the composition of the alloy and the processing conditions in the present invention are as follows.

Mg: Effective for improving strength. If it is less than 0.4%, the effect of press hardening is insufficient.
On the other hand, if it exceeds 1.5%, the extrudability becomes poor.

Similar to Si: Mg, it is effective in improving strength. If it is less than 0.4%, the effect of press hardening is insufficient. On the other hand, if it exceeds 1.3%, the extrudability becomes poor.

Cu: Effective for improving strength and refining crystal grains. If less than 0.05%, the effect is insufficient, and
If it exceeds 90%, the extrudability decreases and the corrosion resistance is impaired. Mn: has an effect of improving fracture toughness and suppressing coarsening of a recrystallized structure during extrusion. If it is less than 0.05%, its effect is insufficient, and if it exceeds 0.50%, press hardenability is deteriorated, which is not preferable.

Cr: Effective in improving fracture toughness and suppressing coarsening of recrystallized structure during extrusion. If it is less than 0.05%, the effect is insufficient, and if it exceeds 0.30%, a huge compound is formed to lower the extrudability and also the press hardenability, which is not preferable.

V, Zr: Effective for improving fracture toughness and suppressing coarsening of recrystallized structure during extrusion. If it is less than 0.05%, its effect is insufficient, and if it exceeds 0.30%, a huge compound is crystallized and extrudability is deteriorated, which is not preferable.

Homogenization treatment: Mg, S formed during casting
It has the function of reducing the crystallized substances and segregation of i, and finely precipitating the compound containing the transition metal, thereby refining the structure.
The extrudability is improved by aggregating the Al-Mg-Si eutectic compound and by uniformly distributing the Al-Mg-Si eutectic compound in the alloy.

If the homogenization temperature is lower than 520 ° C., the Al-Mg-Si eutectic compound formed during casting cannot be sufficiently infiltrated, and fine precipitation of the transition metal-containing compound is not possible. It is not preferable because it becomes sufficient and the effect of refining the structure is lost and the extrudability is reduced. Homogenization temperature is 56
When the temperature exceeds 0 ° C, the Al-Mg-Si-based eutectic compound can be sufficiently infiltrated, but fine precipitation of the compound containing a transition metal becomes coarse, the structure refining effect is lost, and extrudability is reduced, which is preferable. Absent. If the homogenization treatment time is less than 6 hours, the penetration of the Al-Mg-Si-based eutectic compound and the fine precipitation of the compound containing the transition metal are insufficient. It is not economical because there is little improvement effect.

Billet heating: Billet 540-560
After heating to ℃, Mg ₂ Si is fully infiltrated, then 4
By lowering the temperature to 60 to 520 ° C., the billet temperature is set to the optimum extrusion temperature with the best extrudability.

Extrusion temperature: When the extrusion temperature is less than 460 ° C., Mg ₂ Si aggregates during extrusion and the press-quenching effect by forced air cooling immediately after extrusion is insufficient. If the temperature exceeds 540 ° C, the effect of refining the recrystallized structure due to extrusion is lost, and the product surface is scratched, which is not preferable. In particular, when the trace elements such as Cr, Mn, V, and Zr are not present or are present in a small amount, the effect of refining the recrystallized structure due to the extrusion process is significantly lost.

After extrusion: After extrusion, a usual T5 treatment, that is, press quenching → tempering treatment is performed.

[0017]

【Example】

Example 1 An aluminum alloy billet composed of Mg 0.75%, Si 0.85%, Cu 0.75%, the remaining Al and impurities was agglomerated and homogenized at 540 ° C. for 8 hours, and then billet heaters shown in Table 1 were used. After being rapidly heated to the billet heating temperature shown in (1), it was cooled to the extrusion temperature shown in the same table in the billet cooling device, and press quenching was carried out by forced air cooling at the same time as extrusion processing. Furthermore, it was tempered at 175 ° C. for 8 hours to obtain a T5 treated material. In Table 1, the conventional method heats the billet and extrudes it at the same temperature without lowering the temperature, while the comparative example heats the billet and then lowers the temperature. However, at least one of the billet heating temperature and the extrusion temperature is an unsuitable temperature. A certain heating condition is shown.

[0018]

[Table 1] Table 2 shows the mechanical properties of T5 treated materials, and Table 3 shows other properties.
Are shown respectively. Extrusion H part in Table 2 is the initial extrusion part,
The extruded M part shows the middle extruding part, the extruding T part shows the final extruding part, and the extruding speed in Table 3 shows the maximum extruding speed of the billet under heating conditions. The strength of the T5 treated material according to the method of the present invention is about 95% when the strength of the T6 treated material is 100%, and σ _B = 341 to 366 MPa,
A high strength of σ _0.2 = 302 to 334 MPa was obtained, and the extrudability and the surface layer structure were also good. On the other hand, the conventional method No.
The T5 treated material of No. 1 has a large amount of coarse precipitates due to insufficient Mg ₂ Si penetration, and is about 80% when the strength of the T6 treated material is 100%, and σ _B = 283 to 318 Mpa, σ
_0.2 = 245 to 254 MPa, which was inferior to the method of the present invention. The T5 treated material of the conventional method No. 2 has sufficient Mg ₂ Si penetration and a relatively high strength, but since the extrusion temperature is high,
There were many scratches on the product surface, making it impossible to manufacture.

The conventional T5 treated materials of Nos. 3 and 4 are Mg ₂
溶入of insufficient coarse precipitates Si is large, strength Mg ₂
It was slightly inferior to the conventional method No. 2 in which Si was sufficiently infiltrated.

[0020]

[Table 2]

[0021]

[Table 3] Example 2 Mg 0.75%, Si 0.85%, Cu 0.75%, M
An aluminum alloy billet consisting of n0.08%, Cr0.06%, the remaining Al and impurities was agglomerated at 540 ° C.
After homogenizing for 8 hours, it is rapidly heated to the billet heating temperature shown in Table 1 with a billet heater, then cooled to the extrusion temperature shown in the table in the billet cooling device, and forced at the same time as the extrusion process. Press hardening was carried out by air cooling. Furthermore, it was tempered at 175 ° C. for 8 hours to obtain a T5 treated material. Table 4 shows the mechanical properties of the T5 treated material, and Table 5 shows other properties. The meanings of terms in Tables 4 and 5 are the same as those in Tables 2 and 3, respectively. The strength of the T5 treated material according to the method of the present invention is about 95% when the strength of the T6 treated material is 100%, and σ _B = 350 to 375 MPa, σ
_The target strength of _0.2 = 307 to 337 MPa was obtained, and the extrudability and the surface layer structure were also good. On the other hand, the T5 treated material according to the conventional method No. 1 has many coarse precipitates due to insufficient Mg ₂ Si penetration, and the strength is about 80% when the strength of the T6 treated material is 100%. _B =
290 to 321 MPa, σ _0.2 = 247 to 271 MPa
And was inferior to the method of the present invention. T5 according to conventional method No. 2
The treated material had sufficient Mg ₂ Si penetration and a relatively high strength, but the extrusion temperature was high, so the product surface had many scratches and could not be manufactured.

The T5 treated materials of the conventional methods No. 3 and 4 are Mg ₂
溶入of insufficient coarse precipitates Si is large, strength Mg ₂
It was slightly inferior to the conventional method No. 2 in which Si was sufficiently infiltrated.

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

The Al-Mg-Si alloy extruded profile obtained by the present invention has the same extrudability as the Al-Zn-Mg alloy extruded profile, and the surface condition after extrusion and press hardenability. ,
Good corrosion resistance and stress corrosion cracking resistance, σ _B ≧ 343M
Pa, σ _0.2 ≧ 294 Mpa, δ ≧ 8% Al-Z as an Al-Mg-Si based alloy profile having mechanical properties such as automobile bumper reinforcement, railway vehicles, etc.
It satisfies various characteristics in place of the n-Mg type alloy profile.

Claims (2)

[Claims] 1. Mg: 0.4 to 1.5% (weight, the same hereinafter), Si: 0.4 to 1.3%, Cu: 0.05 to 0.
An aluminum alloy ingot containing 90% and remaining Al and impurities is homogenized at 520 to 560 ° C for 6 to 10 hours, heated to 540 to 560 ° C, and then cooled to 460 to 520 ° C, which is the optimum extrusion temperature. Then 460-520
A method for producing a high-strength aluminum alloy extruded profile, which comprises press-quenching after extrusion at ℃. 2. Mg: 0.4 to 1.5%, Si: 0.4
.About.1.3%, Cu: 0.05 to 0.90%, and Mn: 0.05 to 0.50%, Cr: 0.05 to
0.30%, V: 0.05 to 0.30%, Zr: 0.0
5 to 0.30% of any one or more, and aluminum alloy ingots consisting of the remaining Al and impurities to 520 to 5
After homogenizing at 60 ° C. for 6 to 10 hours, 540 to 56
After heating to 0 ° C, the optimum extrusion temperature is 460-520 ° C.
A method for producing a high-strength aluminum alloy extruded shape material, which comprises cooling to 40 ° C., extruding at 460 to 520 ° C., and then quenching.