JP2000317676A - Filler metal for welding of al-zn-mg-cu base alloy and heat treatment of welding material using the filler metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide good welded joint efficiency and excellent toughness, weld crack resistance and stress corrosion crack resistance by incorporating specific ratios of Zn, Mg, Cu, Sc, Cr, V, Ti and Ag into the above filler metal and the balance consists of substantially Al and inevitable impurities. SOLUTION: This filler metal is for welding of an Al-Zn-Mg-Cu base alloy containing, by weight %, 5 to 8 Zn, 1 to 3 Mg, 2 to 4 Cu, 0.03 to 3.0 Sc, 0.05 to 0.2 Cr, 0.01 to 0.5 V, 0.005 to 0.2 Ti and 0.03 to 2 Ag and the balance consisting substantially of Al and inevitable impurities. The Al-Zn-Mg-Cu base alloy base metal having tensile strength of >=500 N/mm2 is welded by using the filler metal and is heat treated. The heat treatment conditions comprise holding for >=1 minute at 450 to 490 deg.C, under which a solution heat treatment is carried out and hardening is carried out at a cooling rate of 250 to 400 deg.C/second. The base metal is then subjected to an artificial aging treatment by holding for 5 to 72 hours at 110 to 180 deg.C after holding for >=24 hours at 10 to 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a steel sheet having a tensile strength of 500.
N / mm ² or more Al-Zn-Mg-Cu (JIS7
000 series) and a heat treatment method for a weld material welded using the filler material, the welded joint (weld bead portion) having a weld crack resistance and a stress corrosion crack resistance. It is excellent in toughness, and the joint efficiency of the welded joint with overfilling is 80% or more (the tensile strength is 400 N / mm ² or more).

[0002]

2. Description of the Related Art Aluminum has properties such as light weight, good electrical heat conductivity, non-magnetic properties, high corrosion resistance, and high strength obtained by alloying. Aluminum is used in a wide range of fields such as civil engineering, construction, vehicles, ships, and aircraft. Demand is growing. Aluminum and aluminum alloys are classified as follows in JIS. A1000 series: pure aluminum (non-heat treated type) A2000 series: Al-Cu based alloy (heat treated type) A3000 series: Al-Mn based alloy (non heat treated type) A4000 series: Al-Si based alloy (non heat treated type) A5000 series ... Al-Mg based alloy (non-heat treatment type) A6000 series ... Al-Mg-Si based alloy (heat treatment type) A7000 series ... Al-Zn-Mg- (Cu) based alloy (heat treatment type)

Among these alloys, Al-Mg based alloys (for example, A5052 alloy, A5083 alloy), Al-Mg-
Si alloy (e.g. A6063 alloy, A6061 alloy), Al-Zn-Mg-based alloy (e.g. A7N01 alloy, A7003 alloy) In the weldable material, often used as a welded construction material since there tensile strength even 400 N / mm ² near Have been. And, for welding these materials, JIS
Based on the selection guideline of base material and filler metal of Z3232 "Aluminum welding standard", A5356 alloy, A5
An Al-Mg based alloy filler such as 183 alloy is used.

However, since the Al-Mg alloy filler metal is a non-heat-treatable alloy, it is not limited to the case where the base material is a non-heat-treatable alloy, but also after the base metal is welded with a heat-treatable alloy (A7N01 alloy or the like). Even in the case of heat treatment, no significant improvement in welding strength can be expected, and the tensile strength of all welded joints is less than 400 N / mm ² .

[0005] A7N11 alloy filler material for A7N01 alloy was previously registered in JISZ3232-1969 as a filler material for 7000 series (Al-Zn-Mg) alloys. A (especially weld cracking resistance) is A
Since it is inferior to the l-Mg alloy filler metal and the tensile strength of the welded joint is not different from that of the Al-Mg alloy filler metal, the registration was deleted and the 7000 alloy filler metal is not present in JIS.

Since the Al—Zn—Mg—Cu alloy has a tensile strength of 500 N / mm ² or more, if a joint efficiency of 80% or more is obtained, the tensile strength of the joint will be 400 N / mm ² or more. , Its use is greatly expanded. However, Al-
A Zn-Mg-Cu-based alloy is inferior in welding crack resistance, and high joint strength cannot be expected even if welding can be performed without cracking. That is, an Al-Zn-Mg-Cu alloy is welded using the A7N11 alloy filler material, and a standard A7075-
T6 treatment (heating at 480 ° C and water cooling, then 24 hours at 125 ° C)
The joint has a tensile strength of 350
It is only about N / mm ² . Therefore, Al-Zn-
Mg-Cu based alloy structures are generally assembled using rivets and bolts.

Incidentally, filler metals for Al-Zn-Mg-Cu alloys are disclosed in JP-A-63-157792 and JP-A-5-208295, but they are used for repairing a molding die. It is mainly used for overlay welding. Therefore, the hardness of the welded joint is close to that of the base metal, the etching properties of mold polishing and drawing are the same between the bead and the base material, weld cracking resistance, photo-etching properties of welded joints, stress corrosion cracking resistance It is important to have excellent workability, and the joint is not required to have strength or toughness, and no heat treatment is performed after welding.

Japanese Patent Publication No. Hei 10-505282 discloses that a 7000 series alloy base material containing Sc is made of Al-Sc-Zr.
Alloy, Al-Mg-Sc-Ti alloy, Al-Cu-Sc
Although a method of welding with a filler material such as a -Zr alloy is disclosed, there is no description about an Al-Zn-Cu-Mg-based alloy base material and a filler material.

[0009]

As described above, Al-Z
A technique for welding an n-Mg-Cu alloy base material with a joint efficiency of 80% or more has not been realized so far. Therefore, the present inventors have developed Al-Zn having a tensile strength of 500 N / mm ² or more.
-Diligent research was conducted on the development of filler metal for welding Mg-Cu alloys. As a result, Al-Zn-Mg-Cu alloy
The inventors have found that the joint efficiency can be greatly improved by adding c, and have conducted further studies to complete the present invention. The present invention relates to a joint efficiency ([tensile strength of joint / tensile strength of base material]) of a welded joint with extra build when a 7000 series aluminum alloy containing Cu having a tensile strength of 500 N / mm ² or more is used as a base material. ) × 100%) is 80% or more (tensile strength is 400 N / mm ² or more), and a welded material capable of obtaining a welded joint excellent in toughness, weld cracking resistance and stress corrosion cracking resistance is obtained. An object of the present invention is to provide a heat treatment method for a welding material using an additive.

[0010]

According to the first aspect of the present invention,
Zn5 ~ 8wt%, Mg1 ~ 3wt%, Cu2 ~ 4wt%, S
c 0.03-3.0 wt%, Cr 0.05-0.2 wt%,
V0.01-0.5wt%, Ti0.005-0.2wt
%, 0.03 to 2 wt% of Ag, and the balance being Al and unavoidable impurities.
It is a filler metal for Cu-based alloy welding.

The invention according to claim 2 is characterized in that Zn 5 to 8 wt%,
Mg 1-3 wt%, Cu 2-4 wt%, Sc 0.03-3.
0 wt%, Cr 0.05-0.2 wt%, V0.01-0.
5 wt%, Ti 0.005 to 0.2 wt%, Ag 0.03 to
2wt%, Ni 0.03-1.0wt%, Zr
At least one selected from the group of 0.01 to 0.3 wt%
Seed, or B 0.0001 to 0.08 wt%, C0.00
At least one selected from the group of 02 to 0.1 wt%, or Ni 0.03 to 1.0 wt%, Zr 0.01 to 0.3
at least one selected from the group of wt% and B0.00
Al-Zn-Mg containing at least one member selected from the group consisting of 01 to 0.08 wt% and C 0.0002 to 0.1 wt%, the balance being Al and unavoidable impurities.
-A filler metal for welding Cu-based alloys.

According to a third aspect of the present invention, there is provided the method according to the third aspect, wherein
Mg 1-3 wt%, Cu 2-4 wt%, Sc 0.03-3.
0 wt%, Cr 0.05-0.2 wt%, V0.01-0.
5wt%, 0.005 ~ 0.2wt% Ti, Ni
At least one selected from the group consisting of 0.03 to 1.0 wt% and Zr 0.01 to 0.3 wt%, or B0.0001 to
At least one member selected from the group consisting of 0.08 wt% and C 0.0002 to 0.1 wt%, or Ni 0.03 to 1.0 wt%
%, At least one member selected from the group consisting of 0.01 to 0.3 wt% of Zr and 0.0001 to 0.08 wt% of Br, C0.
An Al-Zn-Mg-Cu alloy welding filler metal comprising at least one selected from the group of 0002 to 0.1 wt%, the balance being Al and unavoidable impurities.

According to a fourth aspect of the present invention, the tensile strength is 500
The N / mm ² or more Al-Zn-Mg-Cu-based alloy matrix, a heat treatment method of welding weld material using any filler material according to claim 1, wherein the weld material 4
Solution treatment by holding at a temperature of 50 to 490 ° C. for 1 minute or more, and then quenching at a cooling rate of 250 to 400 ° C./sec.
Then, after maintaining at a temperature of 10 to 50 ° C. for 24 hours or more, 11
A heat treatment method for a welding material using the filler material, wherein the welding material is maintained at a temperature of 0 to 180 ° C. for 5 to 72 hours to perform an artificial aging treatment.

According to a fifth aspect of the present invention, the tensile strength is 500
The N / mm ² or more Al-Zn-Mg-Cu-based alloy matrix, a heat treatment method of welding weld material using any filler material according to claim 1, wherein the weld material 4
Solution treatment by holding at a temperature of 50 to 490 ° C. for 1 minute or more, and then quenching at a cooling rate of 250 to 400 ° C./sec.
Then, after holding at a temperature of 10 to 50 ° C. for 24 hours or more, 80
Hold at a temperature of １００100 ° C. for 5-20 hours, and further
A heat treatment method for a welding material using the filler metal, wherein the artificial aging treatment is performed at a temperature of 150 ° C. for 8 to 72 hours.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alloy composition of the filler metal of the present invention will be described below. Zn and Mg improve the tensile strength, weld cracking resistance and stress corrosion cracking resistance of the welded joint. Zn
And Mg content of 5 to 8 wt% and 1 to 3 wt%, respectively
If Zn is less than 5 wt% and Mg is less than 1 wt%, the target tensile strength cannot be obtained, and Zn is less than 8 wt%.
, The effect of improving the tensile strength saturates even if it is contained in excess, the weld cracking resistance, stress corrosion cracking resistance, and workability are reduced.
This is because workability and stress corrosion cracking resistance are reduced.

[0016] Cu improves the tensile strength and stress corrosion cracking resistance of the welded joint. The reason for limiting the Cu content to 2 to 4 wt% is that the effect is not sufficiently obtained if the content is less than 2 wt% or more than 4 wt%, and if it exceeds 4 wt%, the toughness also decreases. By the way, Cu has conventionally been regarded as an element that impairs the resistance to welding cracking, and it was common knowledge that it was not added to the filler metal. It has been found that the addition of an appropriate amount is useful for improving the tensile strength and weld cracking resistance of a welded joint with respect to an Al-Zn-Mg-Cu alloy base material.

Sc makes the crystal grains of the welded joint extremely fine, and improves tensile strength (particularly proof stress), toughness, and weld crack resistance. The effect is also seen in Zr or Ni, and Sc
When Zr and Ni are simultaneously added to the alloy, the effect is further improved. Each of the contents of Sc, Zr, and Ni is set to 0.03 to
3.0 wt%, 0.01-0.3 wt%, 0.03-1.0
The reason for specifying the wt% is that if the value is less than the specified value, the effect cannot be sufficiently obtained, and if the value exceeds the specified value, the welded joint becomes brittle and the tensile strength decreases.

[0018] Cr improves the stress corrosion cracking resistance of the welded joint. The reason for limiting the Cr content to 0.05 to 0.2 wt% is that if the content is less than 0.05 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.2 wt%, a giant compound is formed and the tensile strength is increased. And toughness is reduced.

V refines the crystal grains of the welded joint to improve toughness. The reason why the content of V is defined to be 0.01 to 0.5 wt% is that if the content is less than 0.01 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.5 wt%, the tensile strength and toughness decrease. Is

Ag improves the tensile strength, stress corrosion cracking resistance, and toughness of the welded joint. Ag content of 0.0
The reason for defining the content to be 3 to 2 wt% is that if the content is less than 0.03 wt%, the effect cannot be sufficiently obtained. If the content exceeds 2 wt%, not only the effect is saturated and the cost is increased, but also the toughness is reduced.
Thereby, workability is also reduced.

Ti, B, and C refine the crystal grains of the welded joint to prevent cracking of the welded joint. The effect is further improved when Ti and B or a combination of Ti and C are added rather than Ti alone. The contents of Ti, B, and C are respectively 0.005 to 0.2 wt%, 0.0001 to 0.08.
The reason for defining the wt% and 0.0002 to 0.1 wt% is that if the value is less than the specified value, the effect is not sufficiently obtained, and if the value exceeds the specified value, a huge compound is formed and the tensile strength is increased. This is because the hardness and the toughness decrease. Ti and B
Alternatively, when adding in a combination of Ti and C, the above effect is more efficiently exhibited if a larger amount of Ti is contained.

Next, the heat treatment method according to the present invention will be described. The heat treatment method includes a solution treatment step for homogenizing the solidified structure of the welded joint and dissolving the alloy element, a quenching step for bringing the solution treatment state to room temperature, and an artificial aging for precipitating the solid solution element. Consists of processing steps,
By this heat treatment, the tensile strength of the welded joint, weld crack resistance,
Improved stress corrosion cracking resistance, toughness, etc. In the present invention, the solution treatment step is performed at 450 to 490 ° C. for 1 minute or more, the quenching step is performed at a cooling rate of 250 to 400 ° C./sec, and the artificial aging step is performed at 10 to 50 ° C.
After holding at a temperature of at least 24 hours at a temperature of 110 to 180 ° C. for 5 to 72 hours, the effect is not sufficiently obtained even if any of the above specified values is below the lower limit,
If the upper limit value is exceeded, the low melting point compound present at the crystal grain boundaries may be melted in the solution treatment step, and in the artificial aging step, it becomes overaged and the target joint efficiency of 80% or more can be obtained. This is because the toughness also decreases and the toughness decreases. In the quenching step, quenching exceeding 400 ° C./sec is actually difficult.

The invention according to claim 5 is characterized in that the artificial aging treatment step is maintained at a temperature of 10 to 50 ° C. for 24 hours or more, and thereafter,
Hold at a temperature of 0 ° C. for 5-20 hours, and then 130-150
The invention is the same as the invention of claim 4 except that the treatment is carried out at a temperature of ° C. for 8 to 72 hours, and the reason for defining the conditions in the artificial aging treatment step is also the same as that of the invention of claim 4.

[0024]

The present invention will be described below in detail with reference to examples. (Example 1) The diameter of the composition specified in the present invention shown in Tables 1 and 2.
2mm round bar filler metal (No.1 ~ 49) and composition shown in Table 5
(No.1) 3mm thick Al-Zn-Mg-Cu alloy
(A7075P-T6 treated material, tensile strength 575 N / m
m ² ) Using a flat plate (base material), a fishbone crack test was performed to examine weld cracking resistance. Further, the Al alloy flat plate (but 5 mm thick) was subjected to MIG welding (butt welding) using a linear filler material having a diameter of 1.2 mm having the above composition,
Regarding the welded joint of the obtained welding material, stress corrosion cracking resistance, tensile strength, toughness (UPE, Unit Propagation En
ergy). Further, the workability of the filler material into a welding wire was examined.

(Comparative Example 1) Investigations (1) and (2) were carried out in the same manner as in Example 1 except that the fillers (Nos. 50 to 73) having a composition not specified in the present invention shown in Table 3 were used.

(Comparative Example 2) A conventional filler material (No.
74 to 82) were conducted in the same manner as in Example 1, except that the above-mentioned investigations were carried out.

In the fishbone type cracking test, a fishbone test piece 2 having notches 1 of various lengths was prepared using the above-mentioned alloy plate, and TIG welding was performed at the center of the test piece in the direction of the arrow to bead. 3 was formed, and the crack length 4 generated after welding was measured. The TIG welding uses a cerium-containing W rod having a diameter of 3.2 mm as an electrode rod, a welding current of 120 A, an arc voltage of 16 V, a welding speed of 60 cm / min,
The test was performed under the condition of an argon gas flow rate of 10 liter / min. The fishbone type crack test was performed five times, and the crack length 4 shown in FIG. 1 was measured with a vernier caliper to obtain an average value. Crack length 4
Was determined to be good (○) when the average value was 70 mm or less, and poor (X) when the average value exceeded 70 mm.

The stress corrosion cracking resistance, tensile strength, and toughness (UPE) were measured for the Al-Zn-Mg-Cu shown in FIG.
MIG welding was performed by butt-joining two system alloy flat plates 6, and an examination was conducted using a heat-treated welding material (hereinafter referred to as a MIG welding material). In FIG. 2, 5 is a filler material (welding wire), 7 is a welding torch, 9 is an arc, 10 is a backing metal (made of copper), and 11 is an argon shielding gas. In the MIG welding, a welding current of 200 A, an arc voltage of 24 V, a welding speed of 60 cm / min,
The test was performed under the condition of an argon gas flow rate of 20 liter / min. The heat treatment is performed at 470 ° C. for 1 hour, after the solution treatment,
Water quenching at a cooling rate of 300 ° C./sec.
After holding for 00 hours, the coating was held at 120 ° C. for 24 hours under conditions of artificial aging.

The resistance to stress corrosion cracking can be determined by machining the MIG welding material into a strip-shaped test piece 12 shown in FIG. The test piece 12 was warped and attached to a stress applying jig 13 to apply a stress of 75% of the proof stress to the surface of the test piece 12, immersed in a boiling corrosive liquid for 30 minutes in this state, and checked for cracks in the immersed test piece 12. Examined. Those without cracks were judged as having good stress corrosion cracking resistance (○), and those with cracks were judged as poor (x). In FIGS. 3 (a) and (b), reference numeral 14 denotes a welded joint from which an extra bank is removed. The amount of warpage C (mm) of the test piece was C = (FL ² ) / 6.
It was determined by the equation of Et. In the formula, F is the stress applied to the surface of the test piece (75% of the proof stress of the test piece, N / mm ² ), L is the distance between the fulcrums at both ends (mm), and E is the elastic constant of the test piece (N / m ² ).
m ² ) and t are the thickness (mm) of the test piece. A solution prepared by dissolving 36 g of chromium trioxide, 30 g of potassium dichromate, and 3 g of sodium chloride in 1 liter of water was used as the above-mentioned corrosion liquid.

The tensile strength was determined according to JIS from the above MIG welding material.
No. 5 test piece of Z2201 was welded joint part (with extra height)
Cut out so that it is located in the center, and this is Amsler universal
Perform a tensile test using a testing machine based on JISZ2241
Solid. Tensile strength 460N / mm^Two(Joint efficiency 80%
Above) is good (○), tensile strength is 460 N / mm ^Two
Less than (joint efficiency less than 80%) is judged as defective (x)
did.

The toughness was determined by cutting out a test piece 15 having the shape shown in FIG. 4 from the MIG welding material, and pulling the test piece in the direction of the arrow with an Amsler universal testing machine to obtain a stress-displacement curve shown in FIG. UPE (the area of the hatched portion shown in FIG. 5) was determined. A UPE of 30 N · mm / mm ² or more was judged as good (○), and a UPE of less than 30 N · mm / mm ² was judged as poor (×). In FIG. 4, 16 is a welded joint, 17 is a notch, and 18 is a pin hole for hooking a chuck.

As for wire workability, a raw material blended so as to have a predetermined component is cast into a billet having a diameter of 219 mm by a semi-continuous casting method, and the billet is subjected to a first-stage heating (raising) for removing distortion of an ingot. Heat at a rate of 50 ° C./hour gradually and hold at 232 ° C. for 2 hours) and perform second-stage heating (holding at 460 ° C. for 16 hours) to eliminate segregation of components in the ingot, The rod was extruded into a rod having a diameter of 9 mm, and the rod was drawn into a rod having a diameter of 1.2 mm. The wire having a diameter of 4.8 mm and 2.4 mm in the middle of drawing was subjected to an annealing treatment at 360 ° C. for 1 hour. Those that did not break during wire drawing were evaluated as having good workability (O), and those that did break were evaluated as poor (x). The results are shown in Tables 6-9.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

[Table 8]

[0041]

[Table 9]

As is clear from Tables 6 to 9, the present invention
In Nos. 1 to 53, weld cracking and stress corrosion cracking did not occur, and the joint had high tensile strength, rich toughness, good wire workability, and was excellent overall. On the other hand, N
o. 54 to 77, and No. 78 to 86 of the conventional filler metal were inferior in any of the properties, and were generally inferior.

(Example 2) The composition of No. 2 shown in Table 5 (Defense Agency Standard NDSH4001B) was prepared using a linear filler material (No. 3) having a diameter of 1.2 mm and having the composition specified in the present invention shown in Table 1. BA6
0) 5 mm thick Al alloy flat plate (base metal) is butt-mig-welded, and this welded material is heat-treated under the conditions specified in the present invention shown in Table 10; Example 1 for tensile strength and toughness (UPE)
The investigation was performed in the same manner as described above. However, the judgment of tensile strength is 4
Those with 72 N / mm ² or more (joint efficiency 80% or more) are good (（), and the tensile strength is less than 472 N / mm ² (joint efficiency 8
(Less than 0%) was determined to be defective (x).

Comparative Example 3 The stress corrosion cracking resistance, tensile strength, and toughness were obtained in the same manner as in Example 2 except that the welded material was heat-treated under comparative heat treatment conditions not specified in the present invention shown in Table 11. (UPE) was examined.

Comparative Example 4 Stress corrosion cracking resistance, tensile strength, and toughness (UPE) were examined in the same manner as in Example 2 except that the welded material was heat-treated under the conventional conditions shown in Table 11. The results are shown in Tables 12 and 13.

[0046]

[Table 10]

[0047]

[Table 11]

[0048]

[Table 12]

[0049]

[Table 13]

As is clear from Tables 12 and 13, all of Nos. 87 to 105 of the present invention have no stress corrosion cracking.
High tensile strength (80% or more joint efficiency), toughness (UP
E) Rich and excellent overall. On the other hand, N
In all of O.106 to 121, stress corrosion cracking occurred, tensile strength was low, or toughness (UPE) was poor. In addition, in each of Nos. 122 and 123 heat-treated under the conventional conditions, the tensile strength of the joint was low. Therefore, it was inferior overall.

(Example 3) Using a linear filler material (No. 20) having a diameter of 1.2 mm and a composition specified in the present invention shown in Table 1, a No. 3 composition (Al-Zn-Mg) shown in Table 5 was used. -Cu alloy) thickness 5
butt welded aluminum alloy flat plate (base material)
This welded material was heat-treated under the conditions specified in the present invention shown in Table 14, and the stress-corrosion cracking resistance, tensile strength, and toughness (UPE) of the welded joint after the heat treatment were examined in the same manner as in Example 1. Was. However, the determination of the tensile strength was 460 N / mm ²
Those having the above (joint efficiency of 80% or more) were judged as good (（), and those having a tensile strength of less than 460 N / mm ² (joint efficiency of less than 80%) were judged as poor (×).

Comparative Example 6 The stress corrosion cracking resistance, tensile strength and toughness were determined in the same manner as in Example 3 except that the welded material was heat-treated under comparative heat treatment conditions outside the range specified in the present invention shown in Table 15. UPE).

Comparative Example 7 Stress corrosion cracking resistance, tensile strength, and toughness (UPE) were examined in the same manner as in Example 3 except that the welded material was heat-treated under the conventional conditions shown in Table 15. The results are shown in Tables 16 and 17.

[0054]

[Table 14]

[0055]

[Table 15]

[0056]

[Table 16]

[0057]

[Table 17]

As is clear from Tables 16 and 17, all of Nos. 124 to 152 of the present invention did not cause stress corrosion cracking.
High tensile strength, high toughness, and excellent overall. In contrast, Nos. 153 to 176 of the comparative examples and Nos. 177 and 178 of the conventional materials
In each case, the tensile strength of the joint was low, and overall was inferior.

[0059]

As described above, according to the present invention,
7000 including Cu with a tensile strength of 500 N / mm ² or more
Aluminum alloy (Al-Zn-Mg-Cu alloy)
The joint efficiency of a welded joint with extra swelling when using as a base metal is 80% or more, and a welded joint excellent in weld cracking resistance, stress corrosion cracking resistance, and toughness is obtained. Play.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a fishbone type crack test.

FIG. 2 is an explanatory diagram of butt welding.

FIG. 3A is an explanatory perspective view of a stress corrosion cracking test piece,
(B) is an explanatory view of a stress corrosion cracking resistance test.

FIG. 4 is a perspective view of a toughness test specimen.

FIG. 5 is an explanatory diagram of a method for obtaining UPE as an index of toughness from a stress-displacement curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Notch 2 Fishbone test piece 3 Bead 4 Cracking length 5 Filler material (welding wire) 6 Flat plate for stress corrosion cracking test (base material) 7 Welding torch 9 Arc 10 Backing metal (copper) 11 Argon shield Gas 12 Test piece for weld cracking resistance test 13 Stress applying jig 14 Welded joint part with extra slack removed 15 Test piece for toughness test 16 Welded joint part with notch 17 Notch 18 Pin hole for chucking

Claims (5)

[Claims] 1-5 wt% of Zn, 1-3 wt% of Mg, Cu
2-4 wt%, Sc 0.03-3.0 wt%, Cr0.05
~ 0.2wt%, V0.01 ~ 0.5wt%, Ti0.00
5 to 0.2 wt%, Ag 0.03 to 2 wt%, the balance A
and Al and unavoidable impurities.
A filler metal for welding Zn-Mg-Cu alloys. 2. 5 to 8 wt% of Zn, 1 to 3 wt% of Mg, Cu
2-4 wt%, Sc 0.03-3.0 wt%, Cr0.05
~ 0.2wt%, V0.01 ~ 0.5wt%, Ti0.00
5 to 0.2 wt%, Ag 0.03 to 2 wt%
i at least one selected from the group consisting of 0.03 to 1.0 wt% and Zr 0.01 to 0.3 wt%, or B0.0001
At least one member selected from the group consisting of Ni, 0.03 wt.
wt%, at least one selected from the group consisting of Zr 0.01-0.3 wt%, and B0.0001-0.08 wt%, C
A filler metal for welding Al-Zn-Mg-Cu alloys, comprising at least one selected from the group of 0.0002 to 0.1 wt%, the balance being Al and unavoidable impurities. 3. 5 to 8 wt% of Zn, 1 to 3 wt% of Mg, Cu
2-4 wt%, Sc 0.03-3.0 wt%, Cr0.05
~ 0.2wt%, V0.01 ~ 0.5wt%, Ti0.00
5 to 0.2 wt%, Ni 0.03 to 1.0 wt%
%, At least one selected from the group consisting of Zr 0.01 to 0.3 wt%, or B 0.0001 to 0.08 wt%, C
At least one selected from the group of 0.0002 to 0.1 wt%, or Ni 0.03 to 1.0 wt%, Zr0.01
At least one member selected from the group consisting of
0.0001 to 0.08 wt%, C 0.0002 to 0.1
at least one selected from the group of wt%, with the balance being Al
And Al-Z, comprising unavoidable impurities
A filler metal for welding n-Mg-Cu alloys. 4. Al having a tensile strength of 500 N / mm ² or more.
A method for heat treating a welded material obtained by welding a Zn-Mg-Cu-based alloy base material using any one of the filler materials according to claim 1, wherein the welded material is heated to a temperature of 450 to 490 ° C. For 1 minute or more for solution treatment, then 250-400
Quenching at a cooling rate of 10 ° C./sec, and then holding at a temperature of 10 to 50 ° C. for 24 hours or more,
A heat treatment method for a welded material using the filler metal, wherein the heat treatment is performed for 72 hours and an artificial aging treatment is performed. 5. Al having a tensile strength of 500 N / mm ² or more.
A method for heat-treating a welded material obtained by welding a Zn-Mg-Cu-based alloy base material using any one of the filler materials according to claims 1 to 3, wherein the welded material is heated to a temperature of 450 to 490C. For 1 minute or more for solution treatment, then 250-400
Quenching at a cooling rate of 10 ° C./sec, and then holding at a temperature of 10 to 50 ° C. for 24 hours or more,
Hold for 0 hours, and then at a temperature of 130-150 ° C. for 8-72
A heat treatment method for a welded material using the filler material, wherein the heat treatment is performed for artificial aging treatment.