JPH04333548A - Manufacture of high strength aluminum alloy extruded material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an extrusion processing method for difficult-to-process materials such as JIS 7075 series aluminum alloys containing Zn, Mg, and Cu. In particular, even if the extrusion speed is increased, tearing ( This relates to an extrusion processing method that does not generate defects such as microscopic scratches.

0002

[Prior Art] JIS 7075 series aluminum alloys are known as difficult-to-process materials because, when extruded, surface defects such as tearing (microscopic scratches) and abnormal structures with coarse crystal grains occur on the surface of the extruded material. and the extrusion speed is 1 m.
/min, which is extremely low, and poor productivity has become a problem.

0003

[Problems to be Solved by the Invention] Recently, the weight of aircraft parts, automobile parts, motorcycle parts, etc. has been reduced, and materials such as aluminum alloys and carbon fibers are increasingly being used. In order to further reduce the weight, it is necessary to increase the strength and reduce the wall thickness, and the use of shapes made of 7075 alloy material increases. Therefore, it was necessary to increase the extrusion speed and improve productivity. Therefore, the purpose of the present invention is to
This paper proposes an extrusion processing method that does not cause defects such as tearing (microscopic scratches) on the surface of the extruded material even if the extrusion speed is increased.

0004

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive research, it was found that defects such as tearing occur in the 7075 alloy material because it contains Zn, Mg, and Cu. It has been found that this is because the deformation resistance is increased by reacting with dislocations generated during extrusion, and also because the crystal grains on the surface of the extruded material become coarse.

That is, the occurrence of surface defects such as tearing and abnormal structures where crystal grains become coarse on the surface of extruded materials is due to the following reasons:
Solute atoms such as Zn, Mg, and Cu dissolved in solid solution react with dislocations generated during extrusion, work harden, and increase deformation resistance. In particular, the center of the extruded material becomes hard, and strain due to deformation becomes concentrated on the surface layer. As a result, shear bands are likely to be formed in the surface layer, and cracks occur along these shear bands, crystal grains coarsen, and an abnormal structure occurs.

The present invention has solved this problem, and its gist is that Zn: 4.0 to 8.0%, Mg: 1.0 to 3.0%
, Cu: 1.0 to 3.0%, and other Al and inevitable impurities. After homogenization heat treatment in a conventional manner, the aluminum alloy ingot was reheated to a temperature of 320 to 4.
After performing a precipitation treatment held at 20°C for 1 to 100 hours,
This is a method for producing a highly sensitive aluminum alloy extrusion material by extrusion processing at 320 to 420°C. Also, Ti: 0.005 to 0
．． 10%, Zr: 0.05-0.30%, Cr: 0.0
Mn: 5 to 0.30%, and Mn: 0.05 to 0.50%.

[0007]

[Function] Next, the function and effect of defining the composition of the aluminum alloy material used in the present invention will be explained. Zn: By containing Zn in combination with Mg and Cu, the strength as a structural material (tensile strength 45 kgf/
mm2 or more). However, 4.0
If it is less than 8.0%, this strength cannot be obtained, and if it exceeds 8.0%, casting cracks will occur, making manufacturing difficult.

Mg: Mg is necessary to obtain strength as a structural material (tensile strength of 45 kgf/mm 2 or more) by containing it in combination with Zn and Cu. However, this strength cannot be obtained with less than 1.0%, and 3.0%
Extrusion processing becomes difficult when it exceeds this.

Cu: Cu is necessary to obtain strength as a structural material (tensile strength of 45 kgf/mm 2 or more) by containing it in combination with Zn and Mg. However, this strength cannot be obtained with less than 1.0%, and 3.0%
Extrusion processing becomes difficult when it exceeds this.

[0010] Zr, Cr, Mn, Ti: Zr, Cr, M
Both n and Ti are elements necessary to refine the crystal grains of the extruded material, and Ti is less than 0.005%.Others have no effect when less than 0.05%, and Ti is 0.10%.
If it exceeds 0.30% for Zr and Cr,
When Mn exceeds 0.50%, huge crystallized substances are generated during casting, and the surface quality of the extruded material deteriorates.

[0011] Precipitation treatment: In the precipitation treatment, Al, Zn, Mg
, Cu complex compounds (e.g. AlZnMg, MgZn2
, AlCuMg compound) is precipitated, and its size is reduced to 0.
．． Grow to 2-10 μm. This improves extrudability. If the precipitation treatment temperature is less than 320°C or no precipitation treatment is performed, the precipitates will be as fine as less than 0.2 μm (or the solute atoms of Zn, Mg, and Cu will be dissolved in solid solution), resulting in a decrease in extrudability. do. In the center of the extruded material, solute atoms dissolved in solid solution react with dislocations during extrusion, increasing deformation resistance. As a result, deformation concentrates on the surface layer of the extruded material, causing cracks and other problems, resulting in poor surface quality. to degrade. In the surface layer of the extruded material, solid-dissolved solute atoms form shear bands during extrusion, causing cracks and roughness on the surface, reducing extrudability. When the precipitation temperature exceeds 420°C, Al,
A composite compound of Zn, Mg, and Cu does not precipitate, resulting in poor extrudability. In addition, if the processing time is less than 1 hour, Al, Zn
, Mg, and Cu do not precipitate, resulting in poor extrudability. Even if the processing time exceeds 100 hours, Al,
The precipitation effect of the composite compound of Zn, Mg, and Cu remains unchanged. Even if the above precipitation treatment is performed, when the extrusion temperature is lower than 320° C., deformation resistance increases and extrudability is reduced. When the extrusion temperature exceeds 420° C., the precipitates coarsened by the precipitation treatment are likely to be solid-dissolved again, and the number of solid-dissolved solute atoms increases, resulting in a decrease in extrudability.

[0012] The homogenization treatment of the ingot performed prior to the precipitation treatment has the effect of decomposing the AlMgCu-based eutectic compound formed during casting and increasing the strength, and the transition metals such as Mn contained as other components. It has the effect of making the concentration distribution uniform and making the crystal grains finer.

[0013] If the treatment temperature is lower than 460°C, the AlMgCu-based eutectic compound formed during casting will not decompose, and the concentration distribution of the transition metal will not become uniform. When the temperature exceeds 500℃, the eutectic compound melts and easily diffused impurities such as hydrogen,
It will diffuse into this dissolved area. As a result, defects are more likely to occur in the extruded material. If the processing time is less than 1 hour,
The above effect cannot be obtained, and even after 50 hours, this effect is saturated and hardly changes.

[0014]

【Example】

Example 1 Al-4.0%Zn-2.8%Mg-1.3%Cu alloy was melted by a normal method, an ingot with a diameter of 200mm was cast, and then homogenized at 480°C for 10 hours. Thereafter, a precipitation treatment was performed under the conditions shown in Table 1, and the precipitated material was extruded to a diameter of 40 mm while changing the extrusion speed at 350 and 400° C. while observing the precipitates using a microscope. After extrusion, the surface properties of the extruded material were visually observed, and the extrusion speed at which the number of flaw defects was 1/cm2 or less was determined. These results are also listed in Table 1. As an evaluation criterion, the present invention was determined to have an extrusion speed of 1 m/min or more. That is, invention example No. 11
In samples 1 to 15, the size of the precipitate was 0.4 μm or more, and the extrusion speed was 1.4 m/min or more. However, comparative example No. No. 16 did not undergo precipitation treatment, so even when the size of the precipitates was 0.1 μm or less and the extrusion temperature was 400°C, the extrusion speed was 0.4 m.
/min. No. 17 has a precipitation treatment temperature of 3
As low as 00℃, No. On the other hand, 18 is as high as 450℃,
In all cases, the size of the precipitates was 0.1 μm or less and did not grow significantly, so the extrusion speed was as low as 0.4 m/min. No. In No. 19, the precipitation treatment temperature was 350° C., which was within the range of the invention, but the treatment time was as short as 0.5 hr, so the precipitates did not grow large, and the extrusion speed was as low as 0.5 m/min. Note) Regarding precipitates, coarse compounds of several μm are also precipitated by cooling after homogenization treatment, but in the precipitation treatment of the present invention,
This number is omitted because it is small compared to fine compounds.

[0015]

[Table 1]

Example 2 An Al-8.0%Zn-1.1%Mg-1.1%Cu alloy was melted using a conventional method, and an ingot with a diameter of 200mm was cast. After the homogenization treatment, a precipitation treatment was performed under the conditions shown in Table 2, and the material subjected to the precipitation treatment was extruded to a diameter of 40 mm while changing the extrusion speed at 350 and 400° C. while observing the precipitates using a microscope. The test method and evaluation method are as in Example 1.
These results are also listed in Table 2. That is, invention example No. In Nos. 21 to 25, precipitates with a size of 0.3 μm or more were obtained, and extrusion processing speeds of 1.4 m/min or more were obtained. However, comparative example No. Since No. 26 did not undergo precipitation treatment, the size of the precipitates was 0.1 μm or less, and even when the extrusion temperature was 400° C., the extrusion temperature was as low as 0.3 m/min. No. 2
No. 7 has a low precipitation treatment temperature of 300°C. On the other hand, 28 is as high as 450℃, so the size of the precipitates is 0.1 in both cases.
The extrusion speed is 0.4 m because it does not grow large (less than μm).
/min. No. 29 has a precipitation treatment temperature of 3
Although it is within the range of the invention at 50°C, the precipitate does not grow large because the processing time is as short as 0.5 hr, and the extrusion speed is 0.5 m/min.
It became as low as min. Note) Regarding precipitates, coarse compounds of several μm are also precipitated by cooling after homogenization treatment, but in the precipitation treatment of the present invention,
This number is omitted because it is small compared to fine compounds.

[0017]

[Table 2]

Example 3 An Al-8.0%Zn-2.8%Mg-2.7%Cu alloy was melted using a conventional method, and an ingot with a diameter of 200mm was cast. After the homogenization treatment, a precipitation treatment was performed under the conditions shown in Table 3, and the material subjected to the precipitation treatment was extruded to a diameter of 40 mm while changing the extrusion speed at 350 and 400° C. while observing the precipitates using a microscope. The test method and evaluation method are as in Example 1.
These results are also listed in Table 3. That is, invention example No. In samples Nos. 31 to 35, the size of the precipitate was 0.5 μm or more, and the extrusion speed was 1.4 m/min or more. However, comparative example No. Since No. 36 was not subjected to precipitation treatment, the size of the precipitates was 0.1 μm, and even when the extrusion temperature was 400° C., the extrusion speed was as low as 0.4 m/min. No. No. 37 has a low precipitation treatment temperature of 300°C. 38 is 45 on the contrary
The temperature was as high as 0°C, and the size of the precipitates was 0.1 μm in both cases.
Since it did not grow significantly, the extrusion speed was as low as 0.4 m/min. No. No. 39 had a precipitation treatment temperature of 350° C., which was within the range of the invention, but because the treatment time was as short as 0.5 hr, the precipitates did not grow large, and the precipitation temperature was as low as 0.6 m/min. Note) Regarding precipitates, coarse compounds of several μm are also precipitated by cooling after homogenization treatment, but in the precipitation treatment of the present invention,
This number is omitted because it is small compared to fine compounds.

[0019]

[Table 3]

Example 4 Al-6.2%Zn-2.4%Mg-2.3%Cu-0
．． A 12% Zr-0.05% Ti alloy was melted using a conventional method, and an ingot with a diameter of 200 mm was cast.
After homogenization treatment for hr, precipitation treatment was performed under the conditions shown in Table 4, and the precipitated material was examined with a microscope and the extrusion speed was changed at 350 and 400° C. to extrude it to a diameter of 40 mm. The test method and evaluation method were the same as in Example 1, and the results are also listed in Table 4. In other words, invention example No.
．． 41 to 45, the size of the precipitate was 0.5 μm or more, and the extrusion speed was 1.2 m/m.
More than in was obtained. However, comparative example No. 46 did not undergo precipitation treatment, so the size of the precipitates was 0.1μ
m, and even if the extrusion temperature is 400°C, the extrusion speed is 0.5
m/min. No. No. 47 has a low precipitation treatment temperature of 300°C. On the other hand, sample No. 48 had a high temperature of 450°C, and in both cases the precipitate size was 0.1 μm and did not grow large, so the extrusion speed was low at 0.5 m/min. No
．． No. 49 had a precipitation treatment temperature of 350° C., which was within the range of the invention, but because the treatment time was as short as 0.5 hr, the precipitates did not grow large, and the extrusion temperature was as low as 0.8 m/min. Note) Regarding precipitates, coarse compounds of several μm are also precipitated by cooling after homogenization treatment, but in the precipitation treatment of the present invention,
This number is omitted because it is small compared to fine compounds.

[0021]

[Table 4] Note) Regarding precipitates, several μ
Coarse compounds of m are also precipitated, but in the precipitation treatment of the present invention, this number is smaller than that of fine compounds, so they are omitted.

Example 5 Al-5.5%Zn-2.4%Mg-1.5%Cu-0
．． A 2% Cr-based alloy (7075) was melted in the usual manner, and an ingot with a diameter of 200 mm was cast, then heated at 460°C for 48 hours.
After the homogenization treatment, a precipitation treatment was performed under the conditions shown in Table 5, and extrusion was performed at 400° C. while changing the extrusion speed to a diameter of 40 mm. After extrusion, the surface properties of the extruded material were visually observed. The extrusion speed at which the number of flaw defects occurring on the surface of the extruded material was 1 flaw/cm2 or more was defined as the highest extrusion speed. The test method and evaluation method were the same as in Example 1, and the results are also listed in Table 5. That is, invention example No. 5
Nos. 1 to 54 yield precipitates with a size of 0.4 μm or more, and the extrusion speed is 1.2 m/min.
The above was obtained. However, comparative example No. No. 55 did not undergo precipitation treatment, so even when the size of the precipitates was 0.1 μm or less and the extrusion temperature was 400°C, the extrusion speed was 0.4
m/min. No. No. 56 has a low precipitation treatment temperature of 300°C. On the other hand, Sample No. 57 had a high temperature of 450° C., and the precipitate size was 0.1 μm or less and did not grow large in any case, so the extrusion speed was low at 0.4 m/min. No. No. 58 had a precipitation treatment temperature of 350° C., which was within the range of the invention, but the treatment time was as short as 0.5 hr, so the precipitates were not large and the extrusion speed was as low as 0.7 m/min. Note) Regarding precipitates, coarse compounds of several μm are also precipitated by cooling after homogenization treatment, but in the precipitation treatment of the present invention,
This number is omitted because it is small compared to fine compounds.

[0023]

[Table 5]

[0024]

[Effects of the Invention] As explained above, the present invention provides Al-Z
After homogenizing the n-Mg-Cu-based aluminum alloy ingot using a normal method and reheating it to perform precipitation treatment,
By extrusion processing, the extrusion speed can be increased without causing defects such as tearing on the surface of the extruded material, which is extremely effective industrially.

Claims (2)

[Claims] [Claim 1] Zn: 4.0 to 8.0% (weight %, the same applies hereinafter), Mg: 1.0 to 3.0%, Cu: 1.0 to 3
．． 0%, and other Al and other unavoidable impurities, is subjected to a homogenization heat treatment using a normal method, followed by a precipitation treatment in which it is reheated and held at 320 to 420°C for 1 to 100 hours. A method for producing a high-strength aluminum alloy extruded material, the method comprising: [Claim 2] The aluminum alloy ingot further contains Ti:
0.005-0.10% and Zr: 0.05-0.3
0%, Cr: 0.05~0.30%, Mn: 0.05~
The method for producing a high-strength aluminum alloy extruded material according to claim 1, which contains 0.50% of any one or two or more kinds.