JPH09104940A - High-strength Al-Cu alloy with excellent weldability - Google Patents

Abstract

(57) [Abstract] [Problem] Aluminum for welded structure, which has high strength, excellent weldability and stress corrosion cracking resistance, and also excellent workability.
Provide alloy. SOLUTION: Cu 2-8 wt%, Sc 0.03-3.
0 wt%, Ti 0.005 to 0.2 wt%, B 0.0001 to 0.08 wt% at least one kind, Si 0.07 to 1.5 wt%, Fe
0.1-1.5 wt%, Mg 0.2-2.0 wt%, M
n0.01-1.5 wt%, Cr0.01-0.6 wt%, V0.01-0.5 wt%, Ni0.05-3.0
% By weight, Mo 0.01 to 0.5% by weight, Ag 0.03 to
1.0 wt%, Zr 0.01 to 0.25 wt%, rare earth element (one or more of La, Ce, Pr, Nd, Sm) 0.03 to 5.0 wt%, 1 of Or more than one kind, and is composed of the balance aluminum and unavoidable impurities and has high weldability and high strength Al-
Cu-based alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rolled material, an extruded material,
Regarding a high-strength aluminum alloy used for a welded structural material as a forging material, more specifically, a high-strength Al-Cu-based alloy capable of obtaining a tensile strength of 400 N / mm ² or more and having excellent weldability and stress corrosion cracking resistance It concerns alloys.

[0002]

2. Description of the Related Art In recent years, construction, vehicles, ships, aircrafts, etc. have become thinner and lighter, weldability has been achieved, tensile strength of 400 N / mm ² or more has been obtained, and stress corrosion cracking resistance has been excellent. The demand for high strength aluminum alloys is increasing. JIS 1000 series (pure aluminum), 300
0 series alloy (Al-Mn series alloy), 5000 series alloy (Al
-Mg-based alloy) has excellent weldability but low strength,
Tensile strength of 400 N / mm ² or more cannot be obtained. 600
The 0-based alloy (Al-Mg-Si-based alloy) easily causes microcracks in the heat-affected zone during welding, and has a tensile strength of 400 N /
mm ² or more cannot be obtained. Of the 7000 series alloys, Al-
A Zn-Mg-Cu alloy (A7075 etc.) has a tensile strength of 40.
0N / mm ² or more is obtained, but the weldability is poor. 7000
Al-Zn-Mg-based alloy (A7N01, A
7003 and other Cu-free alloys) have a tensile strength of 400 N
Although it is an alloy that can be welded at a rate of / mm ² or more, stress corrosion cracking may occur depending on the heat treatment method and heat treatment conditions. In order to prevent stress corrosion cracking, T6 treatment (2
Step aging) and T7 treatment are required. The 2000 series alloy (Al—Cu series alloy) has a strength of 400 N / mm ² or more and is excellent in stress corrosion cracking resistance but poor in weldability.
It is difficult to say that even the A2219 alloy, which is the only Al-Cu alloy that can be welded, has perfect weldability.

[0003]

Among the 2000 series alloys (Al-Cu series alloys) specified by JIS, there is A20.
14, A2017, A2020, A2219, etc.,
The tensile strength of each of these T6 materials is 400 N / mm ²
Therefore, stress corrosion cracking does not occur. However, A2
Other materials except 219 are seldom used as a welded structural material because weld cracking easily occurs. Al-
The relationship between the Cu content of the Cu-based alloy and the weld crack length is as shown in FIG. 1, and is the easiest to crack when Cu is 1 to 3 wt% (in the figure, cm is the composition of m).
is an abbreviation for etal). In A2219, Cu is added more than the peak value of this cracking, so cracking is relatively unlikely to occur, but in other alloys, C in the vicinity of this peak value is used.
Since the amount is u, weld cracking is likely to occur. But this A
Speaking of the fact that even 2219 has no problem with cracking, it actually belongs to one that is more susceptible to cracking than 5000 alloys such as A5083.

As described above, in the conventional technique, the tensile strength is 4
It was very difficult to obtain an aluminum alloy having a stress corrosion cracking resistance and weldability of more than 00 N / mm ² and having excellent formability such as extrusion, rolling and forging. . INDUSTRIAL APPLICABILITY The present invention has a tensile strength of 400 N / mm ² or more, which is unsolvable by conventional techniques, and is satisfactory in all aspects of stress corrosion cracking resistance and weldability.
It is an object of the present invention to provide an Al-Cu based alloy material which is excellent in formability such as rolling and forging.

[0005]

As a result of various investigations in view of the above points, the present invention has a tensile strength of 400 N / mm ² or more and is satisfactory in all aspects of stress corrosion cracking resistance and weldability. Moreover, this is a high-strength aluminum alloy for welding which is excellent in formability such as extrusion, rolling and forging. That is, the present invention contains Cu 2 to 8 wt%, Sc 0.03 to 3.0 wt%, and Ti 0.005 to 0.2 wt%, B
At least one of 0.0001 to 0.08% by weight, Si0.07 to 1.5% by weight, Fe0.1 to 0.1% by weight
1.5 wt%, Mg 0.2-2.0 wt%, Mn 0.0
1 to 1.5% by weight, Cr 0.01 to 0.6% by weight, V
0.01-0.5 wt%, Ni 0.05-3.0 wt%, Mo 0.01-0.5 wt%, Ag 0.03-1.
0% by weight, Zr 0.01 to 0.25% by weight, rare earth element (one or more of La, Ce, Pr, Nd, Sm) 0.03 to 5.0% by weight, one of High strength Al-Cu excellent in weldability, characterized by containing two or more kinds and the balance aluminum and unavoidable impurities
It is a system alloy.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The role of additional elements and the reasons for limiting the content of the high-strength aluminum alloy for welding of the present invention will be described below. Cu contributes to the strength improvement of the present alloy and is an essential element for obtaining a tensile strength of 400 N / mm ² or more. If Cu is less than 2% by weight, sufficient strength cannot be obtained, and if it exceeds 8% by weight, weldability and workability deteriorate. Therefore, Cu is set to 2 to 8% by weight, but the most preferable range is 2.5 to 7.5% by weight. Sc has a remarkable effect of improving the weld cracking resistance, is the most important element for obtaining an Al-Cu alloy having excellent weldability, and also has the effect of improving the stress corrosion cracking resistance. It is also an essential element that contributes to the strength improvement of the present alloy and obtains a tensile strength of 400 N / mm ² or more. If the content of Sc is less than 0.03% by weight, its effect is small, and if it exceeds 3.0% by weight, the strength and workability may be deteriorated. Therefore, Sc is 0.03 to 3.0,
The most preferred range is 0.1 to 1.0% by weight.

Ti and B are elements that refine the structure and improve the weldability. Ti is 0.005% by weight
If it is less than 0.2%, the effect is small, and if it exceeds 0.2% by weight, a huge compound is generated, which may deteriorate toughness and workability. Therefore, Ti is set to 0.005 to 0.2% by weight, and the most preferable range is 0.008 to 0.1% by weight. If B is less than 0.0001% by weight, the effect of refining crystal grains is small, and if it exceeds 0.08% by weight, toughness and workability may be deteriorated. Therefore,
B is 0.0001 to 0.08% by weight.

Si, Fe, Mg, Mn, Cr, V, N
Each of i, Mo, Ag, Zr, and the rare earth element has an effect of improving strength, an effect of improving weldability, and an effect of improving stress corrosion cracking resistance, and one or more kinds thereof are added. Especially Mg,
Mn and Ag have a large effect of improving the strength, and Zr together with Sc makes the effect of improving the strength and weldability more remarkable. Content: Si: less than 0.07% by weight, F
e: less than 0.1% by weight, Mg: less than 0.2% by weight, M
n: less than 0.01% by weight, Cr: less than 0.01% by weight,
V: less than 0.01% by weight, Ni: less than 0.05% by weight,
If Mo: less than 0.01% by weight, Ag: less than 0.03% by weight, Zr: less than 0.01% by weight, and rare earth element (Misch metal): less than 0.03% by weight, the above effect is not obtained.

In addition, Si: 1.5% by weight, F
e: 1.5 wt%, Mg: 2.0 wt%, Mn: 1.5
% By weight, Cr: 0.6% by weight, V: 0.5% by weight, N
i: 3.0% by weight, Mo: 0.5% by weight, Ag: 1.0
If it is contained in an amount exceeding 5.0% by weight, Zr: 0.25% by weight, and rare earth element (Misch metal): 5.0% by weight, a huge crystallized substance may be generated, which may deteriorate toughness and workability.
Therefore, Si is 0.07 to 1.5% by weight and Fe is 0.1
~ 1.5 wt%, Mg 0.2-2.0 wt%, Mn 0.01-1.5 wt%, Cr 0.01-0.6 wt%, V 0.01-0. 0.5 wt%, Ni is 0.05 to
3.0 wt%, Mo 0.01-0.5 wt%, Ag 0.03-1.0 wt%, Zr 0.03-0.25
The weight% and the rare earth element are 0.03 to 5.0% by weight, but the most preferable ranges are Si: 0.08 to 1.2% by weight, Fe: 0.12 to 1.2% by weight, and Mg: 0.3 ~
1.8% by weight, Mn: 0.1 to 1.0% by weight, Cr:
0.05-0.4% by weight, V: 0.05-0.3% by weight, Ni: 0.1-2.0% by weight, Mo: 0.03-
0.3% by weight, Ag: 0.05 to 0.7% by weight, Zr:
0.05-0.2% by weight, rare earth element: 0.05-3.
0% by weight.

As rare earth elements, La, Ce, P
One or two or more of r, Nd, Sm and the like can be used, and the amount of any one of them or the total amount of two or more thereof is in the range of 0.03 to 5.0% by weight. It should be inside. As an alloy containing two or more kinds of these, for example, a misch metal containing Ce and La as main components (usually Ce 45 to 50% by weight, La 20 to 40% by weight,
The balance and other rare earth elements (made of Pr, Nd, Sm, etc.) can be used. Any one of the above rare earth elements or a misch metal exhibits the same effect, but the rare earth element alone is expensive, and it is economically advantageous to add it as a misch metal.

[0011]

Next, an embodiment of the present invention will be described. Table 1
To alloys of the present invention (invention alloy Nos. 1 to 110,
Comparative alloy No. 111-147, and conventional alloy No.
148 to 156) were cast into extrusion ingots (9 inch diameter) using a semi-continuous water-cooled casting device. 470 to this ingot
420-470 after homogenizing treatment at 490 ° C. for 12 hours
The mixture was heated to 0 ° C. and extruded into flat rectangular members each having a thickness of 10 mm and a width of 150 mm. At the time of extrusion processing, the flat material has a maximum extrusion speed (critical extrusion speed) at which it can be extruded without the occurrence of surface defects or cracks.
The evaluation was made in two stages, and the results are shown in Tables 7 to 10. The evaluation criteria are as follows. ○ ... Extrusion speed is A2219 limit extrusion speed (0.07
m / min) or higher. × ... Extrusion speed is A2219 limit extrusion speed (0.07
m / min) or less.

After each material was extruded, the Al--Cu alloy was solution-quenched at 490 to 530 ° C. for 1 hour and water-quenched.
The 1-Zn-Mg-based alloy and the Al-Zn-Mg-Cu-based alloy were water-quenched after solution treatment at 460 to 470 ° C for 1 hour. After that, the Al-Cu based alloy is 2 at 160 to 195 ° C.
The artificial aging treatment for 0 hours was performed using Al-Zn-Mg alloy, A
The l-Zn-Mg-Cu-based alloy is 24 at 120 to 130 ° C.
An artificial aging treatment of time was performed. A5083 is, after extrusion,
It annealed at 360 degreeC for 1 hour, and used for the following test.

The materials thus produced were subjected to a tensile test, a stress corrosion cracking test, and a welding cracking test, and the results are also shown in Tables 7-10. The test method is as shown below. (1) Tensile test (a) Test piece: JIS Z 2201 No. 5 test piece (b) Test method: An Amsler universal tester is used to perform a test based on JIS Z 2241. (C) Measured value: The tensile strength is measured and judged according to the following criteria. ○ ・ ・ Tensile strength 400N / mm ² or more × ・ ・ Tensile strength less than 400N / mm ²

(2) Stress corrosion cracking test (a) Test piece: JIS H 8711 No. 1 test piece Processed to a plate thickness of 3 mm. (B) Test method: Based on JIS H8711. Stress load: Load 75% of proof stress using No. 1 jig for test solution, immersion: 3.5% NaCl solution, alternate immersion (cycle: immersion for 10 minutes, drying for 50 minutes) for 100 days. (C) Evaluation: Observation of occurrence of stress corrosion cracking. ×: Cracking occurred within 30 days. ◯: No cracks occurred after 30 days.

(3) Weld crack test (a) Test piece: Fishbone type test piece shown in FIG. 2 Cut into a plate thickness of 3 mm. (B) Welding conditions: Welding method ... TIG filler metal ... not used Electrode rod ... W containing cerium, 3.2mmφ welding current ... 110A arc voltage ... 19V welding speed ...・ 30 cm / min Argon gas flow rate ... 10 liters / min (c) Crack evaluation: The crack length is measured and judged according to the following criteria. ◯: Cracking length is less than 50 mm × ... Cracking length is 50 mm or more

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

[Table 7]

[0023]

[Table 8]

[0024]

[Table 9]

[0025]

[Table 10]

As is clear from Tables 7 to 9, the alloy No. of the present invention. 1 to 110, tensile strength is 400 N / m
It is at least m ² , and is excellent in all of strength, extrusion processability, stress corrosion cracking resistance, and weldability. On the other hand, Tables 9 to 1
As is clear from No. 0, comparative alloy No. 111-14
7, and conventional alloy No. 148-156 are inferior in any of the above properties.

[0027]

As described above, the high strength Al-Cu of the present invention is used.
The alloys have a high tensile strength of 400 N / mm ² or more, and have good weldability despite being Al-Cu alloys that have been conventionally considered unsuitable as materials for welded structures. In addition, it is excellent in stress corrosion cracking resistance and workability (extrusion, rolling, forging, etc.), and has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the relationship between Cu content and weld crack length.

FIG. 2 is an explanatory plan view showing the shape (after welding) of a fishbone-shaped crack test piece. 1 ... Fishbone type crack test piece 1a ... Weld bead 1b ... Weld crack 1c ... Crack length 1d ... Welding direction ... Cut

Claims (1)

[Claims] 1. Cu 2 to 8% by weight, Sc 0.03 to 3.
0 wt%, Ti 0.005 to 0.2 wt%, B 0.0001 to 0.08 wt% at least one kind, Si 0.07 to 1.5 wt%, Fe
0.1-1.5 wt%, Mg 0.2-2.0 wt%, M
n0.01-1.5 wt%, Cr0.01-0.6 wt%, V0.01-0.5 wt%, Ni0.05-3.0
% By weight, Mo 0.01 to 0.5% by weight, Ag 0.03 to
1.0 wt%, Zr 0.01 to 0.25 wt%, rare earth element (one or more of La, Ce, Pr, Nd, Sm) 0.03 to 5.0 wt%, 1 of Or more than one kind, and is composed of the balance aluminum and unavoidable impurities and has high weldability and high strength Al-
Cu-based alloy.