A welding method for crosswise intersecting welds of aluminum-magnesium alloy thin ribbed plates

Abstract

The application discloses a welding method for cross-over welds of aluminum-magnesium alloy thin ribbed plates, which comprises the following steps: (1) four aluminum-magnesium alloy thin ribbed plates with the same material and thickness are prepared, two of which are welded by FSW (friction stir welding) with single-sided welding and double-sided forming, the welding position is flat position, the groove is I-shaped groove, the gap is 0-1 mm, and a first test plate is obtained; the other two plates are welded by FSW with single-sided welding and double-sided forming according to the same process, and a second test plate is obtained; (2) the first test plate and the second test plate are welded by MIG (metal inert gas) welding along the direction perpendicular to the FSW weld, the welding position is flat position, the groove is welded by symmetric single V-shaped groove, the single-side angle of the groove is 20-22.5 degrees, and the bottom gap is 0-1 mm. The welding method can guarantee that the yield strength of the joint is not less than 198 Mpa, the tensile strength is not less than 320 Mpa, the appearance of the weld meets the quality requirements, and the internal X-ray detection is not less than the I-class standard.

Description

A welding method for cross-shaped weld seams in aluminum-magnesium alloy thin strip stiffeners. Technical Field

[0001] This invention relates to the field of aluminum alloy welding technology, specifically to a hybrid welding method of FSW welding and MIG welding for flat butt cross welds of extruded high-strength corrosion-resistant aluminum-magnesium alloy thin strip stiffeners. Background Technology

[0002] Aluminum alloys are widely used in ships due to their low specific gravity, good corrosion resistance, and ease of processing. With increasing demands for ship speed, loading capacity, and structural weight, the need for high-strength, corrosion-resistant aluminum alloys is becoming increasingly urgent. For example, patent document CN112553512A discloses an aluminum-magnesium alloy sheet with high thermal stability, weldability, and corrosion resistance. This alloy sheet has a thickness of 1.0–4.0 mm, and its composition and weight percentage are: Mg 4.0%–4.9%, Zr 0.05%–0.12%, Er 0.05%–0.26%, Zn 0.01%–0.15%, unavoidable impurities <0.5%, and the balance being Al. Wide-width stiffened aluminum alloy plates can effectively reduce hull weight and welding workload while ensuring hull strength, and have wide applications in ships. Currently, there are two types of wide-width stiffened plates in China, one of which is made by splicing narrow-width extruded stiffened plates using FSW welds. During the actual ship construction process, connections with stiffening plates are inevitable, which will inevitably lead to the situation where the weld of friction stir welding (FSW) is joined with the weld of other fusion welding.

[0003] When FSW welds intersect with other fusion welds, defects such as porosity are highly likely to occur at the intersection, creating weak points in the overall weld quality. For high-strength, corrosion-resistant aluminum-magnesium alloy thin plates with a magnesium content of 5.5%–6.5%, the porosity and cracking sensitivity at the intersection of FSW welds and other fusion welds is even greater. Furthermore, the addition of Er, a microalloying element, to domestically produced high-strength, corrosion-resistant aluminum-magnesium alloys leads to Al3Er precipitation, further complicating weldability. Precipitation of weld metallurgical porosity, Al3Er pinning, joint softening, and corrosion performance are difficult to control. Currently, there is no suitable hybrid welding method combining FSW and MIG welding for flat butt joint cross-shaped welds on high-strength, corrosion-resistant aluminum-magnesium alloy thin plates. Summary of the Invention

[0004] The purpose of this invention is to provide a welding method for cross-shaped welds of aluminum-magnesium alloy thin strip stiffeners. This method combines friction stir welding (FSW) and gas metal arc welding (MIG) for cross-shaped welds of extruded high-strength corrosion-resistant aluminum-magnesium alloy thin strip stiffeners in a flat position. This overcomes the problems of porosity, cracks, joint softening, and insufficient corrosion resistance that occur when FSW welds intersect with other fusion welds in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A welding method for cross-shaped weld seams in aluminum-magnesium alloy thin strip stiffeners according to the present invention is characterized by comprising the following steps:

[0007] (1) Four aluminum-magnesium alloy thin strip stiffeners of the same material and thickness were used. Two of them were subjected to single-sided welding and double-sided forming FSW welding. The welding position was flat, the bevel was I-type bevel, and the gap was 0-1mm to obtain the first test plate. The other two were subjected to single-sided welding and double-sided forming FSW welding according to the same process to obtain the second test plate.

[0008] (2) The first test plate and the second test plate are joined together and double-sided MIG welding is performed in a direction perpendicular to the FSW weld. The welding position is flat, and the bevel is a symmetrical single V-shaped bevel. The angle of the bevel is 20 to 22.5° and the bottom gap is 0 to 1 mm.

[0009] The FSW welding has a stirring head rotation speed of 1000-1400 rpm, a welding speed of 200-400 mm / min, a shoulder press-in depth of 0.08-0.18 mm, and an inclination angle of 2-3°; the MIG welding has a welding voltage of 15-23V, a welding current of 80-96A, and a shielding gas flow rate of 20-35L / min.

[0010] The thickness of the aluminum-magnesium alloy thin strip is 3-4 mm;

[0011] The mass fraction of the chemical composition of the aluminum-magnesium alloy thin strip is as follows: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.1%, Mn: 0.7%~1.3%, Mg: 5.5%~6.5%, Zn: ≤0.2%, Zr: 0.02%~0.12%, Er: 0.10%~0.25%, with the balance being Al and unavoidable impurities;

[0012] The welding wire used in the MIG welding has the following chemical composition by mass fraction: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.05%, Mn: 0.8%–1.1%, Mg: 5.5%–6.5%, Zn: ≤0.2%, Zr: 0.02%–0.12%, Er: 0.10%–0.25%, with the balance being Al and unavoidable impurities; the welding wire diameter is 1.0 mm or 1.2 mm, preferably 1.2 mm.

[0013] When welding is performed at an ambient humidity of ≤85%, the heat input of the MIG welding process is 2.4 to 3.3 KJ / cm, and no preheating is required.

[0014] More preferably, the stirring head of the FSW welding has a rotation speed of 1400 rpm, a welding speed of 200 mm / min, a shoulder indentation depth of 0.1–0.15 mm, and an inclination angle of 2.5°; the MIG welding voltage is 18–20 V, the welding current is 81–93 A, the shielding gas flow rate is 25–30 L / min, and the welding heat input is 2.4–3.3 KJ / cm.

[0015] Preferably, in step (2), before performing the front-side MIG welding, a reinforcing strip is first installed on the reverse side of the first and second test plates along the weld direction parallel to the FSW welding. After the front-side welding is completed, the reinforcing strip is removed to prevent the aluminum alloy sheet from deforming during welding.

[0016] The welding method of this invention, in which the weld seam of FSW welding and MIG welding intersect at a 90° cross shape, ensures that the yield strength of the cross-welded joint is not less than 198 MPa and the tensile strength is not less than 320 MPa. After bending or back bending 180° with a 24mm diameter mandrel, no cracks or other defects with a length not exceeding 3mm appear on the surface of the weld joint. After welding, the appearance inspection of the aluminum alloy cross-welded joint meets the quality requirements, with no significant surface defects. The X-ray flaw detection rating of the weld seam meets the standard requirement of not less than Class I in NB / T47013. The corrosion morphology of the cross-welded joint of aluminum-magnesium alloy thin strip stiffener plate in a flat position obtained by the method of this invention meets the requirement of not less than Class PB in ASTM G66. The spalling corrosion and intergranular corrosion rate of the weld seam meet the requirements of ASTM G67, not exceeding 4 mg / cm. 2 . Attached Figure Description

[0017] Figure 1 is a schematic diagram of the arrangement of FSW welds and MIG welds; in the figure, 1-FSW weld of the first test plate, 2-FSW weld of the second test plate, 3-first test plate, 4-second test plate, 5-MIG weld.

[0018] Figure 2 is a schematic diagram of the position of the reinforcing bar during MIG welding; in the figure, 6-MIG weld, 7-FSW weld, 8-reverse side of test plate, 9-reinforcing bar.

[0019] Figure 3 is a schematic diagram of the welding bevel for the flat butt joint FSW welding of the present invention; in the figure, 10-aluminum-magnesium alloy thin strip stiffener and 11-FSW weld flat position bevel.

[0020] Figure 4 is a schematic diagram of the flat butt joint MIG welding bevel of the present invention; in the figure, 12-aluminum-magnesium alloy thin strip stiffener and 13-MIG weld flat position bevel. Detailed Implementation

[0021] Those skilled in the art should recognize that this embodiment is only used to illustrate the present invention and is not intended to limit the present invention. Any changes or modifications to the embodiment within the scope of the present invention are within the scope of the claims of the present invention.

[0022] Example 1

[0023] 1. Welding materials

[0024] Base material: 4 pieces of O-state aluminum-magnesium alloy thin strip stiffener, 4mm thick, with the following chemical composition by mass fraction: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.1%, Mn: 0.7%~1.3%, Mg: 5.5%~6.5%, Zn: ≤0.2%, Zr: 0.02%~0.12%, Er: 0.10%~0.25%, with the balance being Al and unavoidable impurities.

[0025] The welding wire for MIG welding has a diameter of 1.2 mm and its chemical composition by mass fraction is as follows: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.05%, Mn: 0.8%~1.1%, Mg: 5.5%~6.5%, Zn: ≤0.2%, Zr: 0.02%~0.12%, Er: 0.10%~0.25%, with the balance being Al and unavoidable impurities.

[0026] Protective gas: Argon, purity ≥ 99.999%.

[0027] 2. Welding method: Weld at room temperature with an ambient temperature not less than 0℃. The welding process parameters are shown in Table 1.

[0028] (1) Two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW in a flat position. The bevel was type I, the gap was 0.8 mm, the stirring head rotation speed was 1400 rpm, the welding speed was 200 mm / min, the shoulder indentation depth was 0.08 mm, and the inclination angle was 2° to obtain the first test plate. The other two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW in the same process to obtain the second test plate.

[0029] (2) Butt the first test plate and the second test plate together and perform double-sided MIG welding in a direction perpendicular to the FSW weld. The welding position is flat. The weld arrangement is shown in Figure 1. The bevel adopts a symmetrical single V-shaped bevel with a bevel angle of 22.5° on one side and a bottom gap width of 1.0 mm. The welding voltage is 18V, the welding current is 81A, the shielding gas flow rate is 25L / min, and the welding heat input is 2.8KJ / cm. Before performing the MIG welding on the front side, a reinforcing strip is installed on the back side of the first test plate and the second test plate along the direction of the weld parallel to the FSW weld, as shown in Figure 2. The reinforcing strip is removed after the front welding is completed to prevent the aluminum alloy sheet from deforming during welding.

[0030] Table 1 Welding process parameters for Examples 1-3

[0031]

[0032]

[0033] Example 2

[0034] 1. The materials and shielding gas of the welding materials (base metal and welding wire) are the same as in Example 1, wherein the thickness of the base metal and the diameter of the welding wire are listed in Table 1.

[0035] 2. Welding method: Weld at room temperature with an ambient temperature not lower than 0℃. Other welding process parameters are shown in Table 1.

[0036] (1) Two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW welding in a flat position. The bevel was type I, the gap was 1.0 mm, the stirring head rotation speed was 1400 rpm, the welding speed was 200 mm / min, the shoulder indentation depth was 0.1 mm, and the inclination angle was 2.5° to obtain the first test plate. The other two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW welding in the same process to obtain the second test plate.

[0037] (2) Butt the first test plate and the second test plate together and perform double-sided MIG welding in a direction perpendicular to the FSW weld. The welding position is flat. The weld arrangement is shown in Figure 1. The bevel adopts a symmetrical single V-shaped bevel with a bevel angle of 22.5° on one side and a bottom gap width of 1.0 mm. The welding voltage is 19V, the welding current is 85A, the shielding gas flow rate is 28L / min, and the welding heat input is 3.0KJ / cm. Before performing the MIG welding on the front side, a reinforcing strip is installed on the back side of the first test plate and the second test plate along the weld direction parallel to the FSW weld, as shown in Figure 2. The reinforcing strip is removed after the front welding is completed to prevent the aluminum alloy sheet from deforming during welding.

[0038] Welding was performed at room temperature with an ambient temperature not lower than 0℃. Other welding process parameters are shown in Table 1.

[0039] Example 3

[0040] 1. The materials and shielding gas of the welding materials (base metal and welding wire) are the same as in Example 1, wherein the thickness of the base metal and the diameter of the welding wire are listed in Table 1.

[0041] 2. Welding method: Weld at room temperature with an ambient temperature not lower than 0℃. Other welding process parameters are shown in Table 1.

[0042] (1) Two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW welding in a flat position. The bevel was type I, the gap was 1.0 mm, the stirring head rotation speed was 1000 rpm, the welding speed was 400 mm / min, the shoulder indentation depth was 0.18 mm, and the inclination angle was 3° to obtain the first test plate. The other two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW welding in the same process to obtain the second test plate.

[0043] (2) Butt the first test plate and the second test plate together and perform double-sided MIG welding in a direction perpendicular to the FSW weld. The welding position is flat. The weld arrangement is shown in Figure 1. The bevel adopts a symmetrical single V-shaped bevel with a bevel angle of 20° on one side and a bottom gap width of 1.0 mm. The welding voltage is 20V, the welding current is 93A, the shielding gas flow rate is 30L / min, and the welding heat input is 3.3KJ / cm. Before performing the front MIG welding, a reinforcing strip is installed on the reverse side of the first test plate and the second test plate along the weld direction parallel to the FSW weld, as shown in Figure 2. The reinforcing strip is removed after the front welding is completed to prevent the aluminum alloy sheet from deforming during welding.

[0044] Welding was performed at room temperature with an ambient temperature not lower than 0℃. Other welding process parameters are shown in Table 1.

[0045] Example 4

[0046] 1. The materials and shielding gas of the welding materials (base metal and welding wire) are the same as in Example 1, wherein the thickness of the base metal and the diameter of the welding wire are listed in Table 1.

[0047] 2. Welding method: Weld at room temperature with an ambient temperature not lower than 0℃. Other welding process parameters are shown in Table 1.

[0048] (1) Two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW in a flat position. The bevel was type I, the gap was 0.5 mm, the stirring head rotation speed was 1200 rpm, the welding speed was 300 mm / min, the shoulder indentation depth was 0.15 mm, and the inclination angle was 2.5° to obtain the first test plate. The other two aluminum-magnesium alloy thin strip stiffeners were subjected to single-sided welding and double-sided forming FSW in the same process to obtain the second test plate.

[0049] (2) Butt the first test plate and the second test plate together and perform double-sided MIG welding in a direction perpendicular to the FSW weld. The welding position is flat. The weld arrangement is shown in Figure 1. The bevel adopts a symmetrical single V-shaped bevel with a bevel angle of 20° on one side and a bottom gap width of 0.5mm. The welding voltage is 19V, the welding current is 88A, the shielding gas flow rate is 28L / min, and the welding heat input is 3.0KJ / cm. Before performing the MIG welding on the front side, a reinforcing strip is installed on the back side of the first test plate and the second test plate along the weld direction parallel to the FSW weld, as shown in Figure 2. The reinforcing strip is removed after the front welding is completed to prevent the aluminum alloy sheet from deforming during welding.

[0050] (3) Test Results

[0051] Welded joints were inspected according to GB / T2651-2008 and GB / T2653-2008, and tensile and bending properties were tested (the joints were tested using a 73mm diameter mandrel bend or a 180° back bend). The test results are shown in Table 2, and the results meet the standard requirements.

[0052] Table 2 Performance of welded joints in Examples 1-3

[0053]

[0054] Example 1: After welding, the X-ray flaw detection rating of the aluminum alloy welded joint met the Class I standard requirements in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint met the PB level in ASTM G66; the intergranular corrosion rate of the welded joint was 3.87 mg / cm³. 2 It meets the ASTM G67 standard of not exceeding 15 mg / cm³. 2 The indicator requirements.

[0055] Example 2: After welding, the X-ray flaw detection rating of the aluminum alloy welded joint met the Class I standard requirements in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint met the PB level in ASTM G66; the intergranular corrosion rate of the welded joint was 4.55 mg / cm³. 2 It meets the ASTM G67 standard of not exceeding 15 mg / cm³.2 The indicator requirements.

[0056] Example 3: After welding, the X-ray flaw detection rating of the aluminum alloy welded joint met the Class I standard requirements in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint met the PB level in ASTM G66; the intergranular corrosion rate of the welded joint was 3.48 mg / cm³. 2 It meets the ASTM G67 standard of not exceeding 15 mg / cm³. 2 The indicator requirements.

[0057] Example 4: After welding, the X-ray flaw detection rating of the aluminum alloy welded joint met the Class I standard requirements in NB / T47013; in the exfoliation corrosion test of the welded joint, the corrosion morphology of the welded joint met the PB level in ASTM G66; the intergranular corrosion rate of the welded joint was 3.69 mg / cm³. 2 It meets the ASTM G67 standard of not exceeding 15 mg / cm³. 2 The indicator requirements.

[0058] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A welding method for cross-shaped weld seams in aluminum-magnesium alloy thin strip stiffeners, characterized in that, Includes the following steps: (1) Four aluminum-magnesium alloy thin strip stiffeners of the same material and thickness, the thickness of the aluminum-magnesium alloy thin strip stiffeners being 3-4 mm; two of them are subjected to single-sided welding and double-sided forming FSW welding, the welding position is flat, the bevel is an I-type bevel, and the gap is 0-1 mm, to obtain the first test plate; the other two are subjected to single-sided welding and double-sided forming FSW welding according to the same process, to obtain the second test plate; (2) The first test plate and the second test plate are butted together, and double-sided MIG welding is performed along the direction perpendicular to the FSW weld, the welding position is flat, the bevel is a symmetrical single V-type bevel, the single-sided angle of the bevel is 20-22.5°, and the bottom gap is 0-1 mm; the stirring head rotation speed of the FSW welding is 1000 The welding speed is 200-400 mm / min, the shoulder indentation depth is 0.08-0.18 mm, and the tilt angle is 2-3°. The MIG welding voltage is 18-20V, the welding current is 81-93A, the shielding gas flow rate is 25-30L / min, and the welding heat input is 2.4-3.3KJ / cm. The chemical composition of the aluminum-magnesium alloy thin strip is as follows: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.1%, Mn: 0.7%-1.3%, Mg: 5.5%-6.5%, Zn: ≤0.2%, Zr: 0.02%-0.12%, Er: 0.10%-0.25%, with the balance being Al and unavoidable impurities.

2. The welding method for cross-shaped weld seams of aluminum-magnesium alloy thin strip stiffeners according to claim 1, characterized in that, The welding wire used in the MIG welding has the following chemical composition by mass fraction: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.05%, Mn: 0.8%~1.1%, Mg: 5.5%~6.5%, Zn: ≤0.2%, Zr: 0.02%~0.12%, Er: 0.10%~0.25%, with the balance being Al and unavoidable impurities; the welding wire diameter is 1.0 mm or 1.2 mm.

3. The welding method for cross-shaped weld seams of aluminum-magnesium alloy thin strip stiffeners according to claim 1, characterized in that, Welding can be performed when the ambient humidity is ≤85%, and preheating is not required.

4. The welding method for cross-shaped weld seams of aluminum-magnesium alloy thin strip stiffeners according to claim 1, characterized in that, The stirring head for FSW welding rotates at 1400 rpm, the welding speed is 200 mm / min, the shoulder press-in depth is 0.1–0.15 mm, and the tilt angle is 2.5°.

5. The welding method for cross-shaped weld seams of aluminum-magnesium alloy thin strip stiffeners according to claim 1, characterized in that, In step (2), before performing the front-side MIG welding, a reinforcing strip is first installed on the reverse side of the first and second test plates along the weld direction parallel to the FSW welding. The reinforcing strip is removed after the front-side welding is completed.

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