JPH0621328B2 - Method for manufacturing extruded material with excellent hollow extrudability - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an extruded material made of a high-strength aluminum alloy having a high specific elastic modulus which is excellent in hollow extrudability.

[Prior Art] As a high-strength aluminum alloy currently mainly used,
2xxxx system (Al-Cu system) alloy and 7xxx system (A
1-Zn-Mg-based alloy. Among these, C
Alloys containing a large amount of u and Mg have high deformation resistance during hot working and poor weldability during hollow extrusion. Therefore, the hollow extrusion is practically used only for some Al—An—Mg alloys such as 7NO1 alloy and 7003 alloy.

[Problems to be Solved by the Invention] The present invention relates to an alloy having a composition other than the alloy that is practically used for hollow extrusion described above, and a hollow extruded material having a high strength aluminum alloy having a high specific elastic modulus which is excellent in hollow extrusion. Is to be manufactured.

[Means for Solving the Problems] The present invention provides Li: 0.5 to 4.0%, Cu: 0.2 to 3.0%,
Mg: 0.2 to 2.0% as an essential component, or Zr: 0.05 to 0.30%, Cr: 0.05 to 0.30%, M
n: 0.05 to 1.0%, V: 0.05 to 0.30%, and at least one of them are cast, and after casting an alloy consisting of the remaining aluminum and impurities, homogenized at 480 to 550 ° C for 2 to 48 hours,
Then, it is a method for producing an extruded material having excellent hollow extrudability, which is characterized by performing hollow extrusion at 450 to 550 ° C.

Here, the reason for limiting the alloy composition is as follows.

Li: Li is effective in improving the strength of the alloy material. Furthermore L
The addition of i decreases the specific gravity and increases the elastic coefficient, and is therefore effective in reducing the density and increasing the elasticity of the alloy material. The above effect is not less than 1.5%, but more than 4.0%, it is difficult to cast, and it is difficult to remove the microsegregation during casting even by homogenization treatment, so that it is difficult to process and the weldability during hollow extrusion is poor. Further, ductility and toughness are reduced.

Cu, Mg: Cu and Mg are both effective in improving the strength of the alloy material. If the effect is less than the lower limit, the strength of the structure cannot be obtained, and if it exceeds the upper limit, the deformation resistance becomes large, hollow extrusion is difficult, and the weldability is poor.

Zr, Cr, Mn, V: These are precipitated as fine intermetallic compounds during homogenization treatment and suppress recrystallization of the alloy material,
In order to form fine crystal grains and improve the strength, they may be added alone or in plural. However, if these additive elements are added in excess of their upper limits, a huge intermetallic compound will crystallize during casting, resulting in defects in the subsequent plastic working. If it is less than the lower limit, the effect of refining the crystal grains is small.

In addition to the above essential components, the alloy of the present invention contains impurities such as Si and Fe. Also, in order to refine the casting structure,
Ti, B, etc. may be added. This effect is
If it is less than 0.005%, it is small, while if it is added more than 0.10%, a huge intermetallic compound is crystallized. 0 for B.
Addition of more than 02% also crystallizes large compounds.

The reasons for limiting the manufacturing conditions are as follows.

Homogenization treatment: It is necessary to raise the temperature to 480 ° C or higher in order to infiltrate the concentrated phase crystallized between dendrites during casting.
However, when the temperature exceeds 550 ° C, the eutectic melts easily and the oxidation becomes severe. This effect is insufficient if it is less than 2 hours, and the effect is not improved even if it exceeds 48 hours, which is not industrial.

Extrusion temperature: If it is less than 450 ° C, the deformation resistance during extrusion is large and hollow extrusion is difficult. On the other hand, if the temperature exceeds 550 ° C, the surface of the extruded material becomes rough and cracks easily occur, making it difficult to obtain a sound extruded material.

[Examples] Examples 1 to 4 and Comparative Examples 1 to 4 The alloys shown in Table 1 were melted and cast in an Ar atmosphere. After homogenizing the ingot under the conditions shown in the same table, it was externally cut into a φ6 ″ billet. Next, the ingot was preheated to the temperature shown in the same table, and one side of the outer periphery was 40 mm, Hollow extrusion was performed on a square pipe with a wall thickness of 3.5 mm.
After solution treatment at 40 ° C. for 40 minutes, water cooling, strain correction, and aging treatment at 190 ° C. for 24 hours were performed to obtain T 6 material.

Table 2 shows the results of the hollow weldability and the tensile test in the extrusion direction. The hollow weldability was determined by observing the microstructure of the welded section. Example No. In Nos. 1 to 4, hollow weldability was good, and a high-strength material having a tensile strength σ _B of T 6 material of about 45 kgf / mm ² was obtained. On the other hand, in Comparative Example 1, the hollow weldability is good, but the homogenization of the ingot is insufficient and the strength is low because the amounts of Cu and Mg are less than the lower limit values of the claims. In Comparative Example 2, since the amount of Mg exceeds the upper limit of the claimed range, hollow welding is insufficient and the extruded material is not sound. No tensile test was performed. In Comparative Example 3, since the amount of Li was large, surface oxidation was severe, and eutectic melting was observed in a part of the ingot due to the homogenization treatment at a temperature over 550 ° C.
A sound extruded material could not be obtained. Since Comparative Example 4 has a low extrusion temperature, the hollow weldability is poor.

Examples 5 to 9 and Comparative Examples 5 to 8 Extruded alloys shown in Table 3 were manufactured in the same process as in Example 1 and evaluated.

Table 4 shows hollow weldability and tensile test results in the extrusion direction. In Examples 5 to 9, the hollow weldability is good, and high strength materials having a tensile strength σ _B of the T 6 material of about 50 kgf / mm ² are obtained. However, in Comparative Example 5, since the amount of Mg is less than the lower limit value of the claimed range, the strength is lowered.

In Comparative Example 6, the amount of Li, and in Comparative Example 7, the amount of Cr and the amount of Zr exceeded the upper limits of the claims, respectively, so that a sound extruded material could not be obtained. In Comparative Example 8, the extrusion temperature was too low.
It was not possible to obtain a hollow extruded material with a large weld resistance and a good weld resistance.

Table 5 shows the existing JIS H 4100 7NO1 alloy (Al-4.5% Zn-
1.5% Mg-0.5% Mn) and the alloy of Example 7 having the highest strength among Examples 5 to 9 are compared in specific gravity and elastic modulus. The alloy of the present invention has a specific elastic modulus increased by nearly 20%, which is considered to be effective for thinning the frame material of a motorcycle, for example.

[Effects of the Invention] According to the present invention, it is possible to manufacture a high-strength profile excellent in hollow extrudability, which is optimal for manufacturing a frame of a two-wheeled vehicle, for example. Further, the addition of Li lowers the specific gravity and increases the elastic modulus, so that it is possible to obtain a material having a high specific elastic modulus. Therefore, the product can be made thin.

Claims (2)

[Claims] 1. Li: 1.5 to 4.0%, Cu: 0.2 to 3.0
%, Mg: 0.2-2.0% as an essential component, and after casting an alloy consisting of the remaining aluminum and impurities, 480-
Homogenize at 550 ℃ for 2-48 hours, then 450-550
A method for producing an extruded material having excellent hollow extrudability, which comprises performing hollow extrusion at ℃. 2. Li: 1.5 to 4.0%, Cu: 0.2 to 3.0
%, Mg: 0.2 to 2.0% as an essential component, Zr: 0.05 to 0.30%, Cr: 0.05 to 0.30%, Mn:
After casting an alloy containing 0.05 to 1.0% and V: 0.05 to 0.30%, and consisting of the remaining aluminum and impurities, homogenize at 480 to 550 ° C for 2 to 48 hours, and then 450 to 550. A method for producing an extruded material having excellent hollow extrudability, which comprises performing hollow extrusion at ℃.