High-corrosion-resistance and low-porosity MIG welding method for 5xxx high-magnesium rare earth aluminum alloy plate

Abstract

The invention relates to a high-corrosion-resistance low-porosity MIG welding method for 5xxx high-magnesium rare earth aluminum alloy plates, two 5xxx high-magnesium aluminum alloy thick plates with the same material and thickness are welded, the welding position is the transverse position, a groove is an asymmetric V-shaped groove, the single-edge angle of one side of the groove is 20-35 degrees, the single-edge angle of the other side of the groove is 40-50 degrees, and the bottom gap is 0-2 mm; before MIG welding of the front face, the back face of the 5xxx high-magnesium aluminum alloy thick plate is fixed through a 1-2-degree reversible deformation fixing reinforcing row in the welding direction so as to prevent welding deformation, facilitate bubble overflow in the welding process, improve the welding quality and guarantee the welding effect and the flatness of the surface after welding. And a welding gun is adopted for welding along the asymmetric v-shaped groove, and after welding is finished, the reversible deformation fixing reinforcing row is dismounted. By means of the method, it can be guaranteed that the yield strength of the welded joint is not lower than 198 Mpa, the tensile strength is not lower than 333 Mpa, the welding process is simple and rapid, repeated welding is not needed, the welded joint cannot be softened, and the corrosion resistance of the welded joint is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy material welding, and specifically to a high corrosion resistant and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plates, and in particular to a high corrosion resistant and low porosity MIG welding method for thick 5xxx high magnesium rare earth aluminum alloy plates. Background Art

[0002] Aluminum alloys are widely used in ships due to their low specific gravity, good corrosion resistance, and easy processing. With the increasing requirements for ship speed, loading capacity, and structural weight, the demand for high-strength and corrosion-resistant aluminum alloys has become more urgent. 5xxx high-magnesium rare earth aluminum alloys have the advantages of high strength and good corrosion resistance, making them a very promising lightweight and high-strength material for improving ship technical capabilities.

[0003] When high-magnesium rare earth aluminum alloy is melt welded, the higher magnesium content makes the aluminum alloy welding more resistant to thermal cracking and has a higher porosity sensitivity problem, especially in horizontal position welding, because the shielding of the upper test plate is extremely unfavorable for the overflow of bubbles. At the same time, with the increase of magnesium content and the addition of rare earth elements, the evaporation of magnesium is intensified, the burning is serious, and the second phase precipitation increases, resulting in reduced corrosion resistance of the joint. In addition, for thick aluminum alloy plates, the multi-layer and multi-pass welding process causes multiple thermal cycles to act on the welded joints, causing the welded joints to soften significantly. At present, there is no MIG welding method with high corrosion resistance and low porosity for thick 5xxx high-magnesium rare earth aluminum alloy plates. Summary of the invention

[0004] The object of the present invention is to provide an improved MIG welding method with high corrosion resistance and low porosity for 5xxx high magnesium rare earth aluminum alloy plates, which can overcome the problems of porosity, cracks, joint softening, insufficient corrosion resistance, etc. that occur during horizontal melting welding of large thickness 5xxx high magnesium rare earth aluminum alloy plates in the prior art.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is: a MIG welding method for 5xxx high-magnesium rare earth aluminum alloy plates with high corrosion resistance and low porosity, characterized in that: the welding method is as follows: two 5xxx high-magnesium aluminum alloy thick plates of the same material and thickness are welded, the welding position is a horizontal position, the groove is an asymmetric V-shaped groove, the single-side angle of the groove is 20-35° on one side and 40-50° on the other side, and the bottom gap between the two 5xxx high-magnesium aluminum alloy thick plates is 0-2mm; before performing front MIG welding, the back side of the 5xxx high-magnesium aluminum alloy thick plate is fixed along the welding direction with a 1-2° anti-deformation fixed reinforcement row to prevent welding deformation and facilitate bubble overflow during welding; during welding, a welding gun is used to weld along the asymmetric V-shaped groove, and a wire brush is used to grind the weld after each layer is welded, and a milling cutter is used to clean the oxide film on the weld surface. After welding, the anti-deformation fixed reinforcement row is removed to complete the welding work.

[0006] Preferably, the welding voltage of MIG welding is 18V~22V, the welding current is 125~155A, the high energy pulse frequency is 4Hz~8Hz, the low energy pulse frequency is 100Hz~150Hz, the dry extension is 15~16mm, the welding gun is tilted upward by 5° during welding, and the shielding gas flow rate is 20~35L / min.

[0007] Furthermore, the MIG welding voltage is 20-22V, the welding current is 130-140A, the shielding gas flow rate is 25-30L / min, and the welding heat input is 6.5-8.7KJ / cm.

[0008] Furthermore, when the ambient humidity is ≤85%, the heat input of the MIG welding during the welding process is 5.5-9.4 KJ / cm, and no preheating is required.

[0009] Furthermore, the diameter of the welding wire used in MIG welding is 1.0 mm or 1.2 mm, and the preferred welding wire diameter is 1.2 mm.

[0010] Furthermore, the thickness of 5xxx high magnesium aluminum alloy thick plate is 18-25mm.

[0011] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects:

[0012] 1. The improvement scheme described in the present invention is to weld two 5xxx high-magnesium aluminum alloy thick plates of the same material and thickness, the welding position is a horizontal position, the groove is an asymmetric V-shaped groove, the single-side angle of the groove is 20-35° on one side and 40-50° on the other side, and the bottom gap between the two 5xxx high-magnesium aluminum alloy thick plates is 0-2mm; it can ensure that the yield strength of the welded joint after welding is not less than 198Mpa, the tensile strength is not less than 333Mpa, and after the core bending or back bending of 180° with a diameter of 6t (t is the plate thickness), there is no crack or other defects on the surface of the welded joint; the appearance inspection of the weld meets the quality requirements, there is no significant surface defect, and the internal X-ray flaw detection rating of the weld meets the requirements of not less than Class I in NB / T47013;

[0013] 2. In the technical solution of the present invention, before the front MIG welding, the back side of the 5xxx high magnesium aluminum alloy thick plate is fixed along the welding direction with a 1-2° anti-deformation fixed reinforcement row to prevent welding deformation and facilitate bubble overflow during welding, improve welding quality, and ensure welding effect and surface flatness after welding;

[0014] 3. The welding method of the present invention can complete the welding between two 5xxx high-magnesium aluminum alloy thick plates with only one welding. The welding process is simple and fast, and no repeated welding is required. It will not cause the weld joint to soften, and the corrosion resistance of the weld joint is improved. The exfoliation corrosion morphology of the horizontal position MIG welded joint of the thick 5xxx high-magnesium rare earth aluminum alloy plate obtained by this method meets the requirement of ASTM G66 of not less than N grade; the intergranular corrosion rate of the weld joint meets the index requirement of ASTM G67, which is 3.2-5.0 mg / cm 2 ;

[0015] 4. The process steps of the present invention are simple, the operation is convenient, the cost is low, it saves time and effort, and it is easy to promote and utilize. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of using an anti-deformation fixed reinforcement row in one embodiment of the present invention.

[0017] Figure 2 Schematic diagram of the structure of the MIG welding groove in one embodiment of the present invention.

[0018] Reference numerals:

[0019] 1 weld, the reverse side of 25xxx high magnesium aluminum alloy thick plate, 3 anti-deformation fixed reinforcement row, 45xxx high magnesium aluminum alloy thick plate, 5 asymmetric V-shaped groove. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention provides a high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate, which can be found in Figure 1 The difference between the present invention and the prior art is that the welding method is as follows: two 5xxx high magnesium aluminum alloy thick plates 4 of the same material and thickness are welded, the welding position is a horizontal position, the groove is an asymmetric V-shaped groove 5, the single-side angle of the groove is 20-35° on one side and 40-50° on the other side, and the bottom gap between the two 5xxx high magnesium aluminum alloy thick plates is 0-2mm.

[0022] Specifically, the magnesium content of 5xxx high-magnesium aluminum alloy is 6.0-6.2%wt, and the amount of rare earth element erbium added is not more than 0.25%wt. The thickness of 5xxx high-magnesium aluminum alloy thick plate is 18-25mm. Before the front MIG welding, the back side 2 of 5xxx high-magnesium aluminum alloy thick plate is fixed along the welding direction with 1-2° anti-deformation fixed reinforcement row 3 to prevent welding deformation and facilitate bubble overflow during welding; when welding, a welding gun is used to weld along the asymmetric V-shaped groove 5. After each layer is welded, the weld is polished with a wire brush, and the oxide film on the surface of the weld is milled with a milling cutter to prevent the oxide film from remaining in the next layer of weld to inhibit the generation of pores. After the welding is completed, the anti-deformation fixed reinforcement row is removed to complete the welding work.

[0023] The MIG welding process of double pulse CMT is adopted. The welding voltage of MIG welding is 18V~22V, the welding current is 125~155A, the high energy pulse frequency is 4Hz~8Hz, the low energy pulse frequency is 100Hz~150Hz, the dry extension is 15~16mm, the welding torch is tilted up by 5°, and the shielding gas flow rate is 20~35L / min. Furthermore, the MIG welding voltage is 20~22V, the welding current is 130~140A, the shielding gas flow rate is 25~30L / min, and the welding heat input is 6.5~8.7KJ / cm.

[0024] When the ambient humidity is ≤85%, the heat input of the MIG welding during the welding process is 5.5-9.4 KJ / cm, and no preheating is required.

[0025] The present invention is a MIG welding method with high corrosion resistance and low porosity for the horizontal position of rolled large-thickness 5xxx high-magnesium rare earth aluminum alloy plates. The method overcomes the problems of porosity, cracks, joint softening, insufficient corrosion resistance, etc. that occur during the horizontal melting welding of large-thickness 5xxx high-magnesium rare earth aluminum alloy plates in the prior art.

[0026] Example 1

[0027] 1. Welding materials

[0028] Base material: Two H112 state thick 5xxx high magnesium rare earth aluminum alloy plates are welded, with a thickness of 20mm.

[0029] MIG welding wire, diameter 1.2mm. Shielding gas: argon, purity ≥ 99.999%.

[0030] 2. Welding method:

[0031] Welding was performed at room temperature with an ambient temperature not less than 0°C. The welding process parameters are shown in Table 1. Two 5xxx high-magnesium rare earth aluminum alloy thick plates of the same material and thickness were welded in a horizontal position. The groove was an asymmetric V-shaped groove. The single-side angle of the groove was 25° on one side and 45° on the other side. The gap between the two 5xxx high-magnesium rare earth aluminum alloy thick plates was 1 mm.

[0032] The welding voltage is 21-22V, the welding current is 130-138A, the dry extension is 15mm, the welding torch is tilted upward by 5°, the high energy pulse frequency is 4Hz, the low energy frequency is 100Hz, the shielding gas flow rate is 30L / min, and the welding heat input is 6.5-7.5KJ / cm;

[0033] Before the front MIG welding, the reverse side of the test plate is fixed with a 1° anti-deformation reinforcement row along the welding direction, such as Figure 1 As shown, after each layer is welded, the weld is polished with a wire brush, and the oxide film on the weld surface is milled with a milling cutter to prevent the oxide film from remaining in the next layer of the weld to inhibit the generation of pores. After the front welding is completed, the reinforcement row is removed to prevent the aluminum alloy from welding deformation and facilitate the overflow of bubbles during the welding process.

[0034] Example 2

[0035] 1. The material and shielding gas of welding materials (parent metal and welding wire) are the same as those in Example 1, wherein the parent metal thickness and welding wire diameter are listed in Table 1.

[0036] 2. Welding method:

[0037] Two 5xxx high-magnesium rare earth aluminum alloy thick plates of the same material and thickness were welded, the welding position was horizontal, the groove was an asymmetric V-shaped groove, the single-side angle of the groove was 20° on one side and 40° on the other side, and the bottom gap between the two 5xxx high-magnesium rare earth aluminum alloy thick plates was 0 mm;

[0038] The welding voltage is 18-20V, the welding current is 130-138A, the dry extension is 15mm, the welding torch is tilted upward by 5°, the high energy pulse frequency is 5Hz, the low energy frequency is 120Hz, the shielding gas flow rate is 25L / min, and the welding heat input is 5.5-7KJ / cm;

[0039] Before the front MIG welding, the reverse side of the test plate is fixed with a 1° anti-deformation reinforcement row along the welding direction, such as Figure 1 As shown, after each layer is welded, the weld is polished with a wire brush, and the oxide film on the weld surface is milled with a milling cutter to prevent the oxide film from remaining in the next layer of the weld to inhibit the generation of pores. After the front welding is completed, the reinforcement row is removed to prevent the aluminum alloy from welding deformation and facilitate the overflow of bubbles during the welding process.

[0040] The welding was performed at room temperature with an ambient temperature not less than 0°C. The other welding process parameters are shown in Table 1.

[0041] Example 3

[0042] 1. The material and shielding gas of welding materials (parent metal and welding wire) are the same as those in Example 1, wherein the parent metal thickness and welding wire diameter are listed in Table 1.

[0043] 2. Welding method:

[0044] Two 5xxx high-magnesium rare earth aluminum alloy thick plates of the same material and thickness are welded, the welding position is horizontal, the groove is an asymmetric V-shaped groove, the single-side angle of the groove is 30° on one side and 45° on the other side, and the bottom gap between the two 5xxx high-magnesium rare earth aluminum alloy thick plates is 1 mm;

[0045] The welding voltage is 21-22V, the welding current is 135-145A, the dry extension is 16mm, the welding torch is tilted upward by 5°, the high energy pulse frequency is 7Hz, the low energy frequency is 130Hz, the shielding gas flow rate is 30L / min, and the welding heat input is 7-8.5KJ / cm;

[0046] Before the front MIG welding, the reverse side of the test plate is fixed with a 2° anti-deformation reinforcement row along the welding direction, such as Figure 1 As shown, after each layer is welded, the weld is polished with a wire brush, and the oxide film on the weld surface is milled with a milling cutter to prevent the oxide film from remaining in the next layer of the weld to inhibit the generation of pores. After the front welding is completed, the reinforcement row is removed to prevent the aluminum alloy from welding deformation and facilitate the overflow of bubbles during the welding process.

[0047] The welding was performed at room temperature with an ambient temperature not less than 0°C. The other welding process parameters are shown in Table 1.

[0048] Example 4

[0049] 1. The material and shielding gas of welding materials (parent metal and welding wire) are the same as those in Example 1, wherein the parent metal thickness and welding wire diameter are listed in Table 1.

[0050] 2. Welding method:

[0051] Two 5xxx high-magnesium rare earth aluminum alloy thick plates of the same material and thickness were welded in the horizontal position, the groove was an asymmetric V-shaped groove, the single-side angle of the groove was 35° on one side and 50° on the other side, and the bottom gap between the two 5xxx high-magnesium rare earth aluminum alloy thick plates was 2 mm;

[0052] The welding voltage is 21-22V, the welding current is 125-155A, the dry extension is 16mm, the welding torch is tilted upward by 5°, the high energy pulse frequency is 8Hz, the low energy frequency is 140Hz, the shielding gas flow rate is 30L / min, and the welding heat input is 7-9.4KJ / cm;

[0053] Before the front MIG welding, the reverse side of the test plate is fixed with a 2° anti-deformation reinforcement row along the welding direction, such as Figure 1 As shown, after each layer is welded, the weld is polished with a wire brush, and the oxide film on the weld surface is milled with a milling cutter to prevent the oxide film from remaining in the next layer of the weld to inhibit the generation of pores. After the front welding is completed, the reinforcement row is removed to prevent the aluminum alloy from welding deformation and facilitate the overflow of bubbles during the welding process.

[0054] Table 1 Welding process parameters of Examples 1 to 4

[0055]

[0056] Test results of 1-4 embodiments

[0057] According to GB / T2651-2008 and GB / T2653-2008, the welded joints were tested for tensile and bending properties (the joints were bent by 180° face or back bending with a diameter of 6t (t is the plate thickness)). The test results are shown in Table 2, which meet the standard requirements.

[0058] Table 2 Performance of welding joints in Examples 1 to 4

[0059]

[0060]

[0061] Among them, the X-ray flaw detection rating of the aluminum alloy welded joint after welding in Example 1 meets the requirements of Class I standard in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint meets the N level in ASTM G66; the intergranular corrosion rate index of the welded joint is 3.87 mg / cm 2 .

[0062] Example 2 After welding, the X-ray flaw detection rating of the aluminum alloy welded joint meets the requirements of Class I standard in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint meets the N level in ASTM G66; the intergranular corrosion rate index of the welded joint is 3.20 mg / cm 2 .

[0063] Example 3 After welding, the X-ray flaw detection rating of the aluminum alloy welded joint meets the requirements of Class I standard in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint meets the N level in ASTM G66; the intergranular corrosion rate index of the welded joint is 4.48 mg / cm 2 .

[0064] Example 4 After welding, the X-ray flaw detection rating of the aluminum alloy welded joint meets the requirements of the Class I standard in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint meets the N level in ASTM G66; the intergranular corrosion rate index of the welded joint is 5.00 mg / cm 2 .

[0065] The welding method of the present invention can ensure that the yield strength of the welded joint is not less than 198Mpa, the tensile strength is not less than 333Mpa, and after the core bend with a diameter of 6t (t is the plate thickness) is bent or back bent by 180°, there is no crack or other defects on the surface of the welded joint; the appearance inspection of the weld meets the quality requirements, there is no significant surface defect, and the internal X-ray flaw detection rating of the weld meets the standard requirements of not less than Class I in NB / T47013; the exfoliation corrosion morphology of the horizontal position MIG welded joint of the thick 5xxx high-magnesium rare earth aluminum alloy plate obtained by the method of the present invention meets the requirements of not less than Class N in ASTM G66; the intergranular corrosion rate of the welded joint meets the index requirements of ASTM G67, which is 3.2-5.0mg / cm 2 .

[0066] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to the above descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate, characterized in that: The welding method is as follows: two 5xxx high-magnesium aluminum alloy thick plates of the same material and thickness are welded, the welding position is a horizontal position, the groove is an asymmetric V-shaped groove, the single-side angle of the groove is 20-35° on one side and 40-50° on the other side, and the bottom gap between the two 5xxx high-magnesium aluminum alloy thick plates is 0-2mm; before performing front MIG welding, the back side of the 5xxx high-magnesium aluminum alloy thick plate is fixed along the welding direction with a 1-2° anti-deformation fixed reinforcement row to prevent welding deformation and facilitate bubble overflow during welding; when welding, a welding gun is used to weld along the asymmetric V-shaped groove, and a wire brush is used to grind the weld after each layer is welded, and a milling cutter is used to clean the oxide film on the weld surface. After welding is completed, the anti-deformation fixed reinforcement row is removed to complete the welding work.

2. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate according to claim 1, characterized in that: The welding voltage of MIG welding is 18V~22V, the welding current is 125~155A, the high energy pulse frequency is 4Hz~8Hz, the low energy pulse frequency is 100Hz~150Hz, the dry extension length is 15~16mm, the welding gun is tilted upward by 5° during welding, and the shielding gas flow rate is 20~35L / min.

3. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate according to claim 2, characterized in that: The MIG welding voltage is 20-22V, the welding current is 130-140A, the shielding gas flow rate is 25-30L / min, and the welding heat input is 6.5-8.7KJ / cm.

4. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate according to claim 1, characterized in that: When the ambient humidity is ≤85%, the heat input of MIG welding during welding is 5.5-9.4KJ / cm, and no preheating is required.

5. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate according to claim 1, characterized in that: The solid welding wire used in MIG welding has a diameter of 1.0 mm or 1.2 mm, and the preferred diameter is 1.2 mm.

6. A high corrosion resistance and low porosity MIG welding method for 5xxx high magnesium rare earth aluminum alloy plate according to claim 1, characterized in that: The thickness of 5xxx high magnesium aluminum alloy thick plate is 18-25mm.

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