JPH08252689A - Aluminum-lithium alloy filler metal - Google Patents

Abstract

PURPOSE: To provide a aluminum-lithium alloy filler metal which does not cause pin holes, cracks or other defects in the welding of the aluminum-lithium alloy, is excellent in the mechanical properties, and capable of forming a welded part having the tensile strength of >=300MPa and >=2% elongation at extremely low temperature. CONSTITUTION: This aluminum-lithium alloy filler metal has the composition consisting of 4-6.5% Cu, 0.1-0.9% Mg, 0.05-0.15% Ti, 0.4-1.0% Ag, 0.05-1.5% one kind of Mn, Cr and Zr if one kind is contained, or 0.05-l.5% in total thereof if two kinds are contained, <=0.09% Si, <=0.09% Fe, <=0.8cc/100gAl H2, and the balance Al with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-lithium alloy filler metal, and more particularly to an aluminum-lithium alloy filler metal used for welding an aluminum-lithium alloy containing several% of lithium.

[0002]

2. Description of the Related Art Aluminum-lithium alloys are expected to be structural materials for aviation and space because they have excellent specific strength and specific rigidity as compared with other aluminum alloys, and also liquid nitrogen, liquid hydrogen and liquid helium. Since it has excellent strength, elongation, fracture toughness at extremely low temperatures such as temperature, and high electrical resistance, it is a tank for superconducting magnets, a supporting tool, and a structural material provided in a place where a strong magnetic field acts, For example, it is expected as a fusion reactor material.

In order to use an aluminum-lithium alloy as the above-mentioned structural material, joining by welding is indispensable like other aluminum alloy materials, but the aluminum-lithium alloy has been conventionally used for welding general aluminum alloys. When welding is applied by using a welding wire, a common metal material, etc., used in the above, there is a problem that the elongation of the weld becomes low and blowholes are easily generated in the weld. Is required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems in aluminum-lithium alloy filler metal, and its object is to crack, pinhole, blow in the welded portion. It is possible to form welds with excellent strength characteristics without causing defects such as holes, and especially to form welds with excellent strength and ductility at extremely low temperatures such as liquid nitrogen, liquid hydrogen and liquid helium temperatures. It is to provide an aluminum-lithium alloy filler that can be used.

[0005]

The aluminum-lithium alloy filler material according to the present invention for achieving the above object comprises Cu: 4 to 6.5%, Mg: 0.1 to 0.9%, Ti: 0.05%.
.About.0.15%, Ag: 0.3 to 1.0%, Mn, C
When one of r and Zr is included, each is 0.05 to
When it contains 1.5% or 2 or more kinds, it is contained in a total amount of 0.05 to 1.5%, Si: 0.09% or less, Fe: 0.09% or less, H ₂ (hydrogen gas): 0.8 cc / 100 gAl or less, and the rest. The structural feature is that it is composed of Al and inevitable impurities.

[0006] Explaining the significance of the components contained in the aluminum-lithium alloy filler material composition of the present invention and the reason for limitation, Cu dissolves in the matrix of the weld zone and further forms a CuAl ₂ phase to form the weld zone. It is a main alloying element that improves mechanical properties. Preferred content is 4-6.5
%, And if it is less than 4%, weld cracking tends to occur, and if it exceeds 6.5%, the strength increases but the elongation decreases, and weld cracking easily occurs.

Mg forms a solid solution in the matrix and contributes to the strength improvement. The preferred content range is 0.1 to 0.9%,
If it is less than 0.9%, its effect is not sufficient, and if it exceeds 0.9%, Mg reacts with the moisture adhering to the material to be welded and the moisture in the welding atmosphere to generate hydrogen gas, which causes pinning in the weld zone. Holes are easily generated.

Ti has the effect of refining the structure of the weld and improving elongation. The preferred content range is 0.05 to 0.15%
If it is less than 0.05%, its effect is small, and if it exceeds 0.15%, a coarse TiAl ₃ compound is produced, and elongation is deteriorated. It should be noted that, similar to general aluminum alloys, Ti
The coexistence of 1/10 to 1/1 of the concentration of B makes it possible to more stably obtain the effect of refining the structure.

Ag coexists with Cu and forms a solid solution, CuAl ₂
The mechanical properties are remarkably improved on the basis of adsorption to the phase, formation of the Ω phase, and the like. The preferable content is in the range of 0.3 to 1.0%, and if the content is less than 0.3%, the effect is insufficient and 1.0%.
If it exceeds, the decrease in elongation becomes large, which is not desirable.

Mn, Cr and Zr are combined with aluminum to form MnAl ₆ , CrAl ₇ and ZrAl _{3 respectively.}
Produce compounds such as crystal grains (including subgrains)
Has the effect of improving the elongation of the weld by inhibiting the movement of dislocations as well as refining. A preferable content range is 0.05 to 1.5% when one of Mn, Cr and Zr is contained, and a total amount of 0.05 to 1.5% when two or more of Mn, Cr and Zr are contained. is there. If the content is less than 0.05%, the effect is not sufficient and 1.5%
If it exceeds the range, primary crystals are formed with aluminum, and the mechanical properties of the weld, particularly elongation and toughness, are significantly deteriorated.

In the filler material of the present invention, Si and F
The content of e is 0.09% or less, more preferably 0.05
It is desirable to limit it to less than or equal to%. Si and Fe are inevitable impurities contained in the aluminum ingot,
If it is contained in a large amount, the elongation of the weld will be reduced.

The mixing of hydrogen gas (H ₂ ) into the welded portion is due to the hydrogen gas present in the aluminum-lithium alloy material serving as the filler metal and the welding base metal, and the moisture adhering to the surface. Although it occurs, it causes the formation of blowholes and pinholes in the weld metal, so it is preferable to limit the H ₂ concentration in the filler metal to 0.8 cc / 100 gAl or less by the melt treatment, and 0.6 cc / 100 gAl The following is more preferable.

The other unavoidable impurities contained in the filler metal of the present invention are preferably limited to 0.03% or less. In particular, the content of alkali metals such as Ca, Na, and K, and alkaline earth metals is liable to cause the grain boundary breakage of the welded portion, so it is desirable to limit the content to 10 ppm or less.

[0014]

In the filler metal of the present invention, a specific amount of Cu, M
By including g, improving the mechanical properties by the synergistic effect of Cu and Ag, improving the elongation by adding a specific amount of Ti and Mn, Cr or Zr, and limiting the content of Si, Fe and H ₂ . Improves the quality of the weld and, based on these combinations, does not cause defects such as pinhole formation and cracks in the aluminum-lithium alloy, has excellent mechanical properties, and has excellent strength and especially at extremely low temperatures. A weld having elongation can be formed.

[0015]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 Melting, casting, rolling, and wire drawing as usual in an aluminum-lithium alloy, Cu: 4.5%,
Mg: 0.5%, Ti: 0.10%, Ag: 1.0%, Mn: 1.0%,
Cr: 0.05%, Zr: 0.05%, Si: 0.08%, Fe: 0.0
An aluminum alloy welding line containing 8% of H ₂ : 0.10cc / 100g Al was prepared.

Using this welding line, Cu: 5.10%, L
i: 1.40%, Mg: 0.27%, Mn: 0.30%, Fe: 0.08
%. An aluminum-lithium alloy containing Si: 0.03%, Ti: 0.02%, and Zr0.14% is welded as base metal (thickness 6-10).
mm) was performed by MIG welding with an argon gas shield. After welding, it was observed whether or not giant compounds, pinholes, cracks, and coarse crystal grains were generated in the weld, but no defects or abnormal products were observed, and a very sound weld was obtained.

Comparative Example 1 Aluminum alloy welding wires having the compositions shown in Table 1 were prepared in the same manner as in Example 1, and the aluminum-lithium alloy having the same composition as in Example 1 was welded using these welding wires. As a base material, MIG welding was performed as in Example 1. In Table 1, those that do not satisfy the conditions of the present invention are underlined.

[0018]

[Table 1]

When the generation of large compounds, pinholes, cracks, and coarse crystal grains in the welded portion when each test material was welded as a welding line was observed, Cu and Mn were found in the welding line of test material No. 1. , Ag content exceeds the upper limit of the present invention, a huge compound is produced, and pinholes are observed because the H ₂ content exceeds the upper limit. In test material No. 2, welding cracks were observed because the amounts of Cu and Ag were small. Test material
In No. 3, since the total content of Mn, Cr and Zr exceeded the upper limit, a huge primary crystal compound with aluminum was formed.

Even when the welding wire of test material No. 4 was used, the total content of Mn, Cr and Zr was the same as in test material No. 3.
Since it exceeds 1.5%, a huge compound is produced. In the test material No. 5, since the content of Ti was small, coarse crystal grains were generated, and a giant compound was also observed. In the test material No. 6, welding cracks were observed due to the small amount of Cu, and pinholes were also formed due to the large H ₂ content.

Example 2 In the same manner as in Example 1, aluminum alloy welding lines having the compositions shown in Table 2 were prepared, and using these welding lines, an aluminum-lithium alloy (thickness) having the same composition as in Example 1 was prepared. 6
.About.10 mm) was used as a welding base material and MIG welding was carried out in the same manner as in Example 1. Then, a tensile test piece was cut out from the welded portion and subjected to a tensile test at a liquid nitrogen temperature (77 K). As a result, excellent mechanical properties with a tensile strength of 300 MPa or more and an elongation of 2% or more were obtained in all the test materials. Almost no difference was observed depending on the thickness of the base metal.

[0022]

[Table 2] << Table Note >> Hydrogen gas (H ₂ ) content is 0.8cc / 100gAl or less

Comparative Example 2 Aluminum alloy welding lines having the compositions shown in Table 3 were prepared in the same manner as in Example 1, and using these welding lines, an aluminum-lithium alloy (plate having the same composition as in Example 1 was prepared. Thickness 6
.About.10 mm) as a welding base material, MIG welding was performed in the same manner as in Example 1, and after welding, tensile test pieces were sampled from the welded portion for each plate thickness in the same manner as in Example 2, and the liquid nitrogen temperature ( A tensile test was carried out at 77K). The results are shown in Table 4. In Table 3, those that do not satisfy the conditions of the present invention are underlined.

[0024]

[Table 3] << Table Note >> Hydrogen gas (H ₂ ) content is 0.8cc / 100gAl or less

[0025]

[Table 4]

As shown in Table 4, the test material No. 7 is S
Since the contents of i and Fe are large, the elongation rate is low. Test material No.8
Since the amount of Cu is too large, the elongation is low. Test material N
O.9 has a small amount of Si, and test material No. 10 has a small amount of elongation because the amount of Fe exceeds the upper limit. Test material No.11
Has a low Ag content, the test material No. 12 does not contain Mg, and the test material No. 13 does not contain Mg and has a small Ti content, so that both have low tensile strength.

[0027]

As described above, according to the present invention, in welding an aluminum-lithium alloy, pinholes, cracks, and other defects are not generated, and mechanical properties are excellent. Provided is a filler metal for aluminum-lithium alloy capable of forming a weld having the above tensile strength and an elongation of 2% or more.

Claims (1)

[Claims] 1. Cu: 4 to 6.5% (weight%, the same applies hereinafter),
Mg: 0.1-0.9%, Ti: 0.05-0.15%, Ag: 0.3-1.
0%, and one of Mn, Cr and Zr
When it contains seeds, it contains 0.05 to 1.5% respectively, and when it contains 2 or more kinds, it contains 0.05 to 1.5% in total. Si: 0.09% or less, Fe: 0.09% or less, H ₂ : 0.8 cc / 100 gAl or less. An aluminum-lithium alloy filler material, characterized in that the balance comprises Al and inevitable impurities.